JP7770705B2 - Holographic optical element manufacturing apparatus and holographic optical element manufacturing method - Google Patents

Description

The present invention relates to a holographic optical element, a holographic optical element manufacturing apparatus and method for manufacturing the holographic optical element, and in particular to a holographic optical element equipped with a holographic diffraction grating, and a manufacturing apparatus and method for the same.

Holographic optical elements such as holographic diffraction gratings that use hologram technology and their manufacturing equipment have been put to practical use (e.g., Non-Patent Document 1). In particular, in recent years, various display devices such as transmissive head-mounted displays (hereinafter referred to as "HMDs") and head-up displays have been proposed to realize augmented reality (AR) (e.g., Patent Document 1). It is expected that the application of holographic optical elements to these types of display devices will enable the realization of high-quality, low-cost display devices that achieve a wide viewing angle.

Here, conventional holographic diffraction gratings are manufactured using a so-called two-beam interferometer, in which the exposure source beam emitted from a light source is split into S-polarized signal light and P-polarized reference light by a polarizing beam splitter (PBS). The signal light that passes through the PBS is then converted to S-polarized light by a λ/2 plate, the polarization direction of which is aligned, and the light is irradiated onto a recording medium made of a photosensitive material, causing the signal light and reference light to interfere with each other and exposing the resulting interference fringes onto the recording medium (see, for example, Non-Patent Document 1).

Sigma Koki Co., Ltd., "Grating exposure device" search [searched April 21, 2019], Internet URL: https://www.global-optosigma.com/jp/category/opt/opt07.html

Japanese Patent Application Laid-Open No. 2019-12259

However, holographic optical elements manufactured using the above-mentioned conventional two-beam interferometer generally function correctly only at the wavelength used for exposure; using a wavelength other than that used for exposure will result in a different function than intended. Therefore, to manufacture a holographic optical element that can achieve the intended function at wavelengths across the entire visible light range, it is necessary to perform wavelength-multiplexed exposure across the entire visible light range. However, the photosensitive material that makes up the recording medium is not sensitive to the entire visible light range, but is only sensitive to certain wavelengths. One possible method to achieve sensitivity across the entire visible light range is to use a recording medium that contains a mixture of multiple photosensitive materials. However, in this case, the wavelength of the exposure source beam must also be changed across the entire visible light range, necessitating very large-scale manufacturing equipment and making it difficult to reduce manufacturing costs.

The present invention was made in consideration of the circumstances described above, and its purpose is to provide a holographic optical element and a manufacturing apparatus therefor that can achieve the desired function across the entire visible light range and can be manufactured at low cost.

(1) In order to solve the above-mentioned problems, the holographic optical element of the present invention has a configuration in which multiple holographic diffraction gratings, each having a different grating spacing and grating curved surface, or multiple holographic diffraction gratings including diffraction planes with different orientations, are formed by overlapping each other.

As a result, the holographic optical element of the present invention can achieve the desired function across the entire visible light range, since multiple holographic diffraction gratings with different grating spacings and grating curves, or holographic diffraction gratings with diffraction planes oriented in different directions, each achieve the desired function for light of different wavelengths. Furthermore, multiple holographic diffraction gratings with different grating spacings and grating curves, or holographic diffraction gratings with diffraction planes oriented in different directions, can be formed by changing the relative angles at which the signal light and reference light are irradiated onto the recording medium, allowing them to be manufactured using a source beam of a single wavelength, thereby achieving low costs.

(2) In the above configuration, the multiple holographic diffraction gratings may have a layered structure in which layers with different refractive indices are stacked three-dimensionally.

With this configuration, the holographic optical element of the present invention can create a three-dimensional layer structure on a single recording medium by irradiating the signal light and reference light while changing the relative irradiation angle with respect to the recording medium, thereby achieving the desired function across the entire visible light range.

(3) Furthermore, the configuration described in claim 2 may have a different number of layers depending on the corresponding wavelength, and when parallel light of the corresponding wavelength is irradiated, the parallel light is diffracted and line-focused.

This configuration allows the holographic optical element of the present invention to function as an ideal cylindrical lens with uniaxial curvature, preventing the occurrence of aberrations that occur with conventional cylindrical lenses and improving focusing accuracy.

(4) In the configuration described in claim 3, the layer may have a shape that corresponds to the position where the diffracted light is focused and the direction of the diffracted light.

With this configuration, when the holographic optical element of the present invention is irradiated with parallel light of wavelengths corresponding to each layer, it can focus the parallel light so that line foci are formed at different positions. This allows the function of multiple cylindrical lenses to be achieved with a single holographic optical element, resulting in a low-cost, space-saving optical element.

(5) Furthermore, in the configuration described in claim 3 or 4, the layer may have a shape that, when irradiated with light diverging from the line focus, diffracts the light diverging from the line focus and generates parallel light having a direction corresponding to the position and direction of the line focus.

The shape of the layers that make up the holographic optical element of the present invention can be changed by changing the relative angle at which the signal light and reference light are irradiated onto the recording medium. This allows it to be manufactured using a source beam of a single wavelength without using large-scale manufacturing equipment, and this configuration improves the versatility of the optical element.

(6) The holographic optical element manufacturing apparatus of the present invention is a holographic optical element manufacturing apparatus for manufacturing a holographic optical element by exposing a recording medium made of a photosensitive material that is sensitive to a predetermined wavelength range, and includes a light source that emits an exposure source beam of a single wavelength, a beam splitter that splits the source beam into signal light and reference light, a signal light irradiation means that irradiates the recording medium with the signal light via a first optical path, and a reference light that irradiates the recording medium with the reference light via a second optical path, causing the signal light irradiated by the signal light irradiation means to interfere with the reference light, generating interference fringes, and exposing the generated interference fringes to the recording medium. an irradiation means, wherein the signal beam irradiation means has a signal beam irradiation angle adjustment means that adjusts the irradiation angle of the signal beam relative to the recording medium, and the reference beam irradiation means has a reference beam irradiation angle adjustment means that adjusts the irradiation angle of the reference beam relative to the recording medium, and the signal beam irradiation angle adjustment means adjusts the irradiation angle of the signal beam according to the interval between the generated interference fringes, and the reference beam irradiation angle adjustment means adjusts the irradiation angle of the reference beam relative to the recording medium according to the adjusted irradiation angle of the signal beam, thereby changing the interval between the interference fringes and generating multiple interference fringes each having a different interval, and multiplex-exposing the generated multiple interference fringes onto the recording medium.

With this configuration, the holographic optical element manufacturing apparatus of the present invention can multiplex-expose multiple holographic diffraction gratings, each with a different grating spacing and grating curved surface, or multiple holographic diffraction gratings with diffraction planes facing different directions, onto the recording medium by adjusting the relative irradiation angle of the signal beam and reference beam relative to the recording medium. Therefore, it is possible to expose holographic diffraction gratings compatible with multiple wavelengths using a source beam of a single wavelength. Therefore, the holographic optical element manufacturing apparatus of the present invention can achieve the desired functionality across the entire visible light range without employing a large-scale device configuration, and can manufacture holographic optical elements at low cost.

(7) Furthermore, in the configuration described in claim 6, the signal beam irradiation angle adjustment means may change the irradiation angle of the signal beam relative to the recording medium by a predetermined value, and the reference beam irradiation angle adjustment means may change the relative irradiation angle of the reference beam relative to the signal beam in accordance with the change in the irradiation angle of the signal beam relative to the recording medium, thereby generating a plurality of interference fringes with different intervals, and the generated plurality of interference fringes may be multiple-exposed onto the recording medium.

With this configuration, the relative irradiation angle of the signal light and reference light with respect to the recording medium is sequentially changed by a predetermined value to generate interference fringes with different spacing multiple times, and these interference fringes are then multiple-exposed to produce the holographic optical element of the present invention, which is composed of multiple holographic diffraction gratings each with a different grating spacing and grating curved surface, or multiple holographic diffraction gratings each with diffraction planes facing different directions, stacked one on top of the other.

(8) In the configuration described in claim 6 or 7, the signal light irradiation angle adjustment means may be configured to change the irradiation angle of the signal light with respect to the recording medium two-dimensionally or three-dimensionally.

With this configuration, the holographic optical element manufacturing apparatus of the present invention can change the angle of irradiation of the signal light onto the recording medium two-dimensionally or three-dimensionally, thereby enabling fine adjustment of the shape of the interference fringes exposed on the recording medium and manufacturing holographic optical elements that can realize various functions.

(9) Furthermore, in the configuration described in claim 8, a recording medium position adjustment means may be further provided that adjusts the position of the recording medium in accordance with the irradiation angle of the signal light adjusted by the signal light irradiation angle adjustment means.

With this configuration, the holographic optical element manufacturing apparatus of the present invention can adjust the position of the recording medium so that the signal light is irradiated at the desired position on the recording medium, even when the irradiation angle of the signal light is changed two-dimensionally or three-dimensionally, thereby enabling the holographic optical element of the present invention to be manufactured with high precision.

(10) Furthermore, in the configuration described in claim 9, the recording medium position adjustment means may include recording medium linear movement means that moves the recording medium linearly in a predetermined direction, and recording medium height adjustment means that moves the recording medium in a height direction, and the signal light irradiation angle adjustment means may adjust the position of the recording medium in accordance with the irradiation angle of the signal light adjusted by three-dimensionally changing the irradiation angle of the signal light with respect to the recording medium.

With this configuration, the holographic optical element manufacturing device of the present invention can move the recording medium in two axial directions. Therefore, even when the irradiation angle of the signal light onto the recording medium is changed three-dimensionally, the position of the recording medium can be precisely adjusted so that the signal light is irradiated onto the desired position on the recording medium, allowing for the manufacture of the holographic optical element of the present invention with high precision.

(11) Furthermore, in the configuration described in claim 9, the recording medium position adjustment means may include a recording medium plane movement means that moves the recording medium two-dimensionally within a predetermined plane, and a recording medium height adjustment means that moves the recording medium in a height direction, and the signal light irradiation angle adjustment means may adjust the position of the recording medium in accordance with the irradiation angle of the signal light adjusted by changing the irradiation angle of the signal light relative to the recording medium three-dimensionally.

With this configuration, the holographic optical element manufacturing apparatus of the present invention can adjust the position of the recording medium in three dimensions. Therefore, even when the irradiation angle of the signal light relative to the recording medium is changed in three dimensions, the position of the recording medium can be precisely adjusted so that the signal light is irradiated at the desired position on the recording medium, allowing for the manufacture of the holographic optical element of the present invention with high precision.

(12) Furthermore, in the configuration described in claim 9, the recording medium position adjustment means may include a recording medium plane movement means that moves the recording medium two-dimensionally within a predetermined plane, and a recording medium tilt angle change means that changes the tilt of the recording medium, and the signal beam irradiation angle adjustment means two-dimensionally changes the irradiation angle of the signal beam with respect to the recording medium, and the reference beam irradiation angle adjustment means adjusts the irradiation angle of the reference beam with respect to the recording medium in accordance with the adjusted irradiation angle of the signal beam, and the recording medium tilt angle change means changes the tilt of the recording medium in accordance with the irradiation angles of the signal beam and the reference beam, thereby three-dimensionally changing the relative irradiation angles of the signal beam and the reference beam with respect to the recording medium.

With this configuration, even if the holographic optical element manufacturing apparatus of the present invention employs a simple adjustment mechanism (such as the signal light rotation stage 115 described below) that can only change the signal light irradiation angle two-dimensionally as the signal light irradiation angle adjustment means, it can adjust the relative irradiation angle of the signal light and reference light with respect to the recording medium three-dimensionally by changing the tilt of the recording medium, while adjusting the signal light and reference light so that the signal light and reference light are irradiated at desired positions on the recording medium. This makes it possible to multiplex-expose multiple holographic diffraction gratings, each with different grating spacings and grating curves, or multiple holographic diffraction gratings with diffraction planes oriented in different directions, onto the recording medium, thereby enabling the holographic optical element of the present invention to be manufactured with high precision using a simple apparatus configuration.

(13) In addition, in the configuration described in claim 12, the recording medium position adjustment means may further include a recording medium height adjustment means that moves the recording medium in a height direction.

With this configuration, the holographic optical element manufacturing apparatus of the present invention can adjust the position of the recording medium in three dimensions while changing the tilt of the recording medium, thereby three-dimensionally adjusting the relative irradiation angle of the signal light and reference light with respect to the recording medium. This simplifies device setup and enables the manufacture of holographic optical elements with high precision.

(14) Furthermore, in the configuration described in any one of claims 6 to 13, the reference light irradiation means may have a cylindrical lens having a uniaxial curvature, and after the reference light is line-focused by the cylindrical lens, the reference light (cylindrical wave-like reference light) that spreads from the line focus may be irradiated onto the recording medium.

With this configuration, the holographic optical element manufacturing apparatus of the present invention can manufacture holographic optical elements that can achieve the same functionality as an ideal cylindrical lens with uniaxial curvature.

(15) The present invention also provides a method for manufacturing a holographic optical element, which involves irradiating a recording medium made of a photosensitive material sensitive to a predetermined wavelength range with signal light and reference light generated by splitting a single-wavelength source beam, each along a different optical path, causing the signal light and the reference light to interfere with each other, and exposing the recording medium to interference fringes generated by the interference. The method is configured to produce a holographic optical element by varying the relative irradiation angle of the signal light and the reference light with respect to the recording medium, thereby varying the spacing between the interference fringes and generating multiple interference fringes with different spacings, and then multiplex-exposing the generated multiple interference fringes onto the recording medium.

The holographic optical element and its manufacturing apparatus and method of the present invention can provide a holographic optical element that can achieve the desired function across the entire visible light range at low cost.

1 is a system configuration diagram showing the configuration of a manufacturing system for a holographic optical element according to a first embodiment of the present invention. 10A and 10B are diagrams for explaining interference fringes formed by interference between signal parallel light formed in the manufacturing apparatus of the first embodiment and cylindrical wave-like reference light spreading from a line focus. 10 is a graph showing the relationship between the rotation angle of the signal beam rotating stage and the wavelength when the exposure wavelength is 532 nm and the vertical angle is 10° in the manufacturing apparatus of the first embodiment. 10 is a graph showing the relationship between the rotation angle of the goniostage and the vertical angle when the exposure wavelength is 532 nm and the vertical angle is −10° to 10° in the manufacturing apparatus of the first embodiment. 10 is a diagram showing the resulting horizontal angle range of a signal collimated light in the manufacturing apparatus of the first embodiment. FIG. 10 is a graph showing the relationship between the rotation angle of the reference beam rotary stage and the wavelength when the exposure wavelength is 532 nm and the vertical angle is 10° in the manufacturing apparatus of the first embodiment. 1 is a flowchart (part 1) illustrating a process executed by an information processing device in the manufacturing system according to the first embodiment. 10 is a flowchart (part 2) illustrating the process executed by the information processing device in the manufacturing system of the first embodiment. FIG. 10 is a diagram (part 1) showing the changing state of the optical system of the manufacturing device when manufacturing a holographic diffraction grating corresponding to one wavelength in the manufacturing system of the first embodiment. FIG. 2 is a diagram (part 2) showing the changing state of the optical system of the manufacturing device when manufacturing a holographic diffraction grating corresponding to one wavelength in the manufacturing system of the first embodiment. 1A and 1B show an example of the three-dimensional structure of a holographic diffraction grating manufactured by the manufacturing system of the first embodiment, in which (A) and (B) show an example of the structure of a holographic diffraction grating when white parallel light is irradiated and the line focus is near the center of the holographic diffraction grating in the vertical direction of the drawing, and (C) and (D) show an example of the structure of a holographic diffraction grating when the line focus is toward the lower side of the holographic diffraction grating HG. FIG. 10 is a diagram (part 1) showing an example of the configuration of a head-mounted display using a holographic light guide plate in Modification 2 of the present invention. FIG. 10 is a diagram (part 2) showing an example of the configuration of a head-mounted display using a holographic light guide plate in Modification 2. FIG. 10 is a diagram (part 3) showing an example of the configuration of a head-mounted display using a holographic light guide plate in Modification 2. FIG. 10 is a system configuration diagram showing the configuration of a manufacturing system for a holographic optical element according to a second embodiment of the present invention. 10A and 10B are diagrams showing an example of a change in the state of an optical system of a manufacturing apparatus when a holographic diffraction grating is manufactured in a manufacturing system according to a second embodiment.

Embodiments of the present invention will now be described with reference to the drawings. The following embodiments are examples in which the present invention is applied to a holographic diffraction grating as a holographic optical element and to an apparatus for manufacturing such a holographic diffraction grating. However, the embodiments described below do not unduly limit the content of the present invention as defined in the claims, and not all of the configurations described in the present embodiments are necessarily essential components of the present invention.

[A] First Embodiment [A.1] Overall Configuration of Holographic Optical Element Manufacturing System 1A First, the configuration of a holographic optical element manufacturing system 1A (hereinafter referred to as "manufacturing system 1A") according to one embodiment of the present invention will be described using FIG. 1. FIG. 1 is a diagram showing the configuration of manufacturing system 1A according to this embodiment. In addition, in FIG. 1, the directions of the x, y, and z axes are indicated by arrows to define directions in x, y, and z space within manufacturing system 1A.

The manufacturing system 1A of this embodiment includes a manufacturing apparatus 10A including an optical system for recording (exposing) a holographic diffraction grating HG (described later) on a recording medium 124 (described later), and an information processing device 20 that is connected to the manufacturing apparatus 10A via a wired communication interface such as IEEE (Institute of Electrical and Electronics Engineers) 488 or a wireless interface such as IEEE 802.11a, b, g, n, or ac and that performs adjustment processing and the like related to a stage (described later) of the optical system in the manufacturing apparatus 10A. The manufacturing system 1A is for manufacturing a reflective volume holographic diffraction grating HG (hereinafter referred to as "holographic diffraction grating _HG ") that can achieve a desired function for light in the entire visible light range, using the recording medium 124 made of a photosensitive material that is sensitive only to light in a predetermined wavelength range and light of a single wavelength (for example, wavelength λ 0 ) to which the photosensitive material is sensitive (i.e., source beam SB in FIG. 1 ).

Here, as described above, when a holographic diffraction grating HG is formed on the recording medium 124 using a source beam SB of a single wavelength, the desired function cannot be realized for light of wavelengths (e.g., _λ1 , _λ2 , _λ3 , etc. ₎ other than the wavelength corresponding to the source beam SB (e.g., _λ0 when a source beam SB of wavelength λ0 is used), and it is difficult to manufacture a holographic diffraction grating HG that can achieve the desired function over the entire visible light range.

In general, the diffraction phenomenon in a diffraction grating follows the diffraction grating equation, and the following relationship holds for both transmission and reflection type diffraction gratings.

(1) In the case of a transmission diffraction grating,

(2) In the case of a reflective diffraction grating,

In these equations, α is the angle between the incident light and the normal to the diffraction grating (i.e., the angle of incidence), β is the angle between the diffracted light and the normal to the diffraction grating (i.e., the angle of diffraction), d is the grating spacing, λ is the wavelength, and m is the order of the diffracted light.

As described above, the diffraction of light at a diffraction grating for wavelength λ depends on the grating spacing d of the diffraction grating. Therefore, in order to achieve the desired function with white light having wavelengths across the entire visible light range, it is necessary to devise a structure for the holographic diffraction grating HG.

The manufacturing system 1A of this embodiment therefore performs multiple exposures of multiple holographic diffraction gratings, each with a different grating spacing d, onto the recording medium 124, thereby achieving the function of manufacturing a holographic diffraction grating HG that can achieve the desired function for light across the entire visible light range. The holographic diffraction grating HG manufactured by the manufacturing system 1A of this embodiment achieves the same function as a cylindrical lens: when white parallel light is incident, the parallel light is diffracted and line-focused, and when divergent light from the line-focused white light is incident, the divergent light is diffracted and generates parallel light. The manufacturing method and specific structure of the holographic diffraction grating HG manufactured by the manufacturing system 1A of this embodiment will be described in detail below.

[A.2] Specific Configuration of Manufacturing Apparatus 10A In order to manufacture the above-described holographic diffraction grating HG, manufacturing apparatus 10A of this embodiment has light source 111 formed of a single-wavelength laser, and is configured so that source beam SB is incident from light source 111 on beam splitter 112. Beam splitter 112 splits source beam SB incident from light source 111 into two beams, signal beam SL and reference beam RL, and causes signal beam SL to be incident on signal beam plane mirror 117 and reference beam RL to be incident on reference beam plane mirror 114.

In this manner, the signal light SL and reference light RL split by the beam splitter 112 are incident on the signal light plane mirror 117 and the reference light plane mirror 114. Therefore, (a) the beam splitter 112, (b) the signal light plane mirror 117, and (c) the reference light plane mirror 114 are configured so that their heights (i.e., their positions in the z-axis direction) are aligned. The beam splitter 112 may be configured, for example, using a half mirror to split the source beam SB so that the signal light SL and the reference light RL have a 1:1 intensity ratio. Alternatively, the beam splitter 112 may be configured with a PBS to split P-polarized light as the signal light SL and S-polarized light as the reference light RL depending on the polarization direction. In this case, a λ/2 plate (not shown) may be provided between the beam splitter 112 and the signal light plane mirror 117 to align the polarization directions of the signal light SL and the reference light RL. Furthermore, the wavelength of the source beam SB is arbitrary, and any wavelength may be used as long as the photosensitive material that makes up the recording medium 124 is sensitive to that wavelength.

The signal light plane mirror 117 reflects the signal light SL incident from the beam splitter 112 and makes it incident on the recording medium 124 as signal collimated light 118. This signal light plane mirror 117 is mounted on a goniostage 116 provided on the signal light rotation stage 115. By rotating the signal light rotation stage 115 around the z-axis, the angle of the signal light plane mirror 117 relative to the incident direction of the signal light SL can be changed, thereby changing the emission direction (i.e., reflection direction) of the signal collimated light 118 within the xy plane. Furthermore, by changing the tilt of the signal light plane mirror 117 with the goniostage 116, the emission direction of the signal collimated light 118 can be changed in the z-axis direction. For example, the signal light plane mirror 117, signal light rotation stage 115, and goniostage 116 of this embodiment work in conjunction with a stage drive circuit 130 and information processing device 20, which will be described later, to form the "signal light irradiation means" of the present invention, and the signal light rotation stage 115 and goniostage 116 work in conjunction with the stage drive circuit 130 and information processing device 20 to form the "signal light irradiation angle adjustment means" of the present invention.

With this configuration, the manufacturing apparatus 10A of this embodiment can change the emission direction of the signal light SL (i.e., the signal parallel light 118) reflected by the signal light plane mirror 117 to the intended direction in xyz space, thereby three-dimensionally changing the irradiation angle of the signal parallel light 118 with respect to the recording medium 124.

Generally, the vertical viewing angle (z-axis direction in FIG. 1) achieved when a holographic diffraction grating HG is used in a transmissive display panel (e.g., a display panel for a transmissive HMD or an optical combiner for a head-up display) depends on the amount of angular displacement in the z-axis direction when the signal collimated light 118 is irradiated onto the recording medium 124 during exposure of the holographic diffraction grating HG, and is approximately twice the amount of angular displacement in the z-axis direction. Therefore, when exposing the holographic diffraction grating HG on the recording medium 124 using the manufacturing system 1 of this embodiment, a transmissive display panel with a vertical viewing angle of approximately 20° can be achieved by displacing the angle of the signal collimated light 118 in the z-axis direction by approximately 10° using the goniostage 116.

On the other hand, if the emission direction of the signal collimated light 118 is changed in the z-axis direction using the goniostage 116, or if the signal light plane mirror 117 is rotated using the signal light rotation stage 115, it becomes difficult to make the signal collimated light 118 incident on the desired position on the recording medium 124. Therefore, in the manufacturing apparatus 10A of this embodiment, a height adjustment stage 126 is provided on the recording medium linear movement stage 125, and the recording medium 124 is placed on this height adjustment stage 126.

This linear movement stage 125 for the recording medium is configured to be able to move the recording medium 124 linearly in a predetermined direction (e.g., the y-axis direction) in the xy plane, and the height adjustment stage 126 is configured to be able to move the recording medium 124 in the z-axis direction (i.e., the height direction).When the signal light rotation stage 115 rotates the signal light plane mirror 117 or the goniostage 116 changes the inclination of the signal light plane mirror 117 to change the emission direction of the signal collimated light 118 three-dimensionally in the xyz space, the linear movement stage 125 for the recording medium and the height adjustment stage 126 are moved in conjunction with the signal light rotation stage 115 and the goniostage 116 to move the position of the recording medium 124 in the xyz space, and the position of the recording medium 124 is adjusted so that the signal collimated light 118 is irradiated at the desired position on the recording medium 124. The rotation angles of the signal beam rotation stage 115 and the goniostage 116 and the movement amount of the recording medium linear movement stage 125 during the manufacture of the holographic diffraction grating HG will be described in detail later. Furthermore, the recording medium linear movement stage 125 and height adjustment stage 126 of this embodiment work in conjunction with the stage drive circuit 130 and the information processing device 20 to constitute, for example, the "recording medium position adjustment means" of the present invention, and also work in conjunction with the stage drive circuit 130 and the information processing device 20 to constitute the "recording medium linear movement means" and "recording medium height adjustment means" of the present invention, respectively. Furthermore, in order to finely adjust the position of the recording medium 124, it is desirable to use a stage that can adjust the position of the recording medium 124 in two axial directions, the x-axis and the y-axis, as the recording medium linear movement stage 125, and to use this stage and the height adjustment stage 126 to adjust the position of the recording medium 124 in three axial directions, the x-axis, y-axis, and z-axis. However, this would complicate the device configuration and position adjustment. Therefore, to make the explanation easier to understand, this embodiment will be described assuming that the recording medium linear movement stage 125 is configured so that its position can be adjusted only in a specific direction (specifically the y-axis direction). The use of a stage that can be adjusted in two axial directions (the recording medium planar movement stage 140 described below) will be explained in the third embodiment.

The reference light plane mirror 114 then reflects the reference light RL incident from the beam splitter 112, causing it to enter the cylindrical lens system 122 as reference collimated light 119. This reference light plane mirror 114 is mounted on a reference light rotation stage 113, which is provided on a reference light linear translation stage 121. By rotating the reference light rotation stage 113 about the z-axis, the emission direction of the reference collimated light 119 can be changed within the xy plane. Note that, for example, the reference light rotation stage 113 and reference light linear translation stage 121 of this embodiment, in conjunction with the cylindrical lens linear translation stage 120, stage drive circuit 130, and information processing device 20, constitute the "reference light irradiation angle adjustment means" of the present invention.

Here, to determine the focusing position of the diffracted light relative to the direction of the incident plane wave, it is necessary to control the direction of the signal light SL and the position of the line focus 127. Therefore, in the manufacturing apparatus 10A of this embodiment, a configuration is adopted in which the reference light rotation stage 113 is mounted on the reference light linear movement stage 121. When the recording medium linear movement stage 125 is moved to match the direction of the signal collimated light 118, the reference light linear movement stage 121 is moved in the xy plane accordingly, so that the signal light plane mirror 117 and the reference light plane mirror 114 are moved to positions symmetrical with respect to the recording medium 124. The rotation angle of the reference light rotation stage 113 and the movement amount of the recording medium linear movement stage 125 during manufacturing of the holographic diffraction grating HG will be described in detail later.

The cylindrical lens system 122 may be, for example, a single lens with a uniaxial curvature, or a combination of multiple similar lenses. When the reference collimated light 119 reflected by the reference light plane mirror 114 is incident on the cylindrical lens system 122, the cylindrical lens system 122 focuses the reference collimated light 119 and irradiates the recording medium 124 with cylindrical wave-like reference light 123. At this time, the cylindrical wave-like reference light 123 is first focused linearly at the back focal position of the cylindrical lens system 122 to form a line focus 127, and then diverges again before being irradiated with the recording medium 124. While the cylindrical lens system 122 can be constructed using a general cylindrical lens, using a general cylindrical lens may result in aberrations that may prevent the cylindrical wave-like reference light 123 from being focused accurately linearly. Therefore, it is preferable to use a lens with the above-described shape. In this embodiment, the cylindrical lens system 122 is installed at the same height as the reference light plane mirror 114 so that the reference collimated light 119 from the reference light plane mirror 114 is irradiated at the desired position on the cylindrical lens system 122. That is, in the manufacturing apparatus 10A of this embodiment, the heights of (a) the beam splitter 112, (b) the signal beam plane mirror 117, (c) the reference beam plane mirror 114, and (d) the cylindrical lens system 122 are all set to the same height.

Here, if the tilt of the signal light plane mirror 117 is adjusted using the goniostage 116 and the height of the recording medium 124 is adjusted accordingly using the height adjustment stage 126, the recording medium 124 will be displaced in the vertical direction (z-axis direction) relative to the installation position of the cylindrical lens system 122. However, since the cylindrical wave-like reference light 123 is irradiated onto the recording medium 124 with a sufficient divergence angle from the line focus 127 behind the cylindrical lens system 122, the cylindrical wave-like reference light 123 is maintained in a state where it is reliably irradiated onto the recording medium 124, even when the height of the recording medium 124 is adjusted in accordance with changes in the tilt of the signal light plane mirror 117.

At this time, if the recording medium 124 is positioned above the line focus 127, the cylindrical wave-like reference beam 123 is irradiated onto the recording medium 124 from below in the z-axis direction and is reflected upward by the recording medium 124. Also, at this time, the signal beam plane mirror 117 is tilted upward by the goniostage 116, so the signal parallel beam 118 is also irradiated onto the recording medium 124 from below in the z-axis direction and is reflected upward.

In contrast, when the recording medium 124 is positioned below the line focus 127, the cylindrical wave-like reference beam 123 is irradiated onto the recording medium 124 from above in the z-axis direction downward, and is reflected downward by the recording medium 124. At this time, the signal beam plane mirror 117 is tilted downward by the goniostage 116, so the signal parallel beam 118 is also irradiated onto the recording medium 124 from above in the z-axis direction downward, and is reflected downward.

In addition, in this embodiment, the cylindrical lens system 122 is placed on a cylindrical lens linear movement stage 120, and is configured so that the position of the cylindrical lens system 122 can be moved within the xy plane by the cylindrical lens linear movement stage 120 in conjunction with the rotation of the reference light rotation stage 113. In this embodiment, the reference light plane mirror 114, reference light rotation stage 113, cylindrical lens linear movement stage 120, reference light linear movement stage 121, and cylindrical lens system 122 work in conjunction with the stage drive circuit 130 and information processing device 20 to constitute, for example, the "reference light irradiation means" of the present invention.

In the manufacturing apparatus 10A of this embodiment, when the reference light plane mirror 114 is rotated around the z-axis by the reference light rotation stage 113, the emission direction of the reference parallel light 119 changes within the xy plane. However, with the above configuration, the cylindrical lens system 122 can be moved to a desired position within the xy plane, so that the reference parallel light 119 can be irradiated onto a desired position on the cylindrical lens system 122 while maintaining a constant distance between the reference light plane mirror 114 and the cylindrical lens system 122.

Furthermore, when the cylindrical lens system 122 moves in accordance with the rotation of the reference light plane mirror 114, the focusing position of the cylindrical wave-like reference light 123 (i.e., the position of the line focus 127) changes in the x-axis or y-axis direction, and the irradiation position of the divergent light from the line focus 127 on the recording medium 124 changes. For this reason, the manufacturing apparatus 10A of this embodiment employs a configuration in which the recording medium linear movement stage 125 moves parallel to the cylindrical lens linear movement stage 120, and adjustments are made so that the divergent light from the line focus 127 is irradiated at the desired position on the recording medium 124.

With this configuration, the manufacturing apparatus 10A of this embodiment can adjust the position so that the signal collimated light 118 and the cylindrical wave-like reference light 123 spreading from the line focus 127 are always irradiated at the desired position on the recording medium 124, even when the orientations of the signal light plane mirror 117 and the reference light plane mirror 114 are changed using the signal light rotation stage 115, goniostage 116, and reference light rotation stage 113, thereby reliably exposing the recording medium 124 to the interference fringes generated by the signal collimated light 118 and the cylindrical wave-like reference light 123.

The signal beam rotation stage 115, goniostage 116, reference beam rotation stage 113, cylindrical lens linear translation stage 120, reference beam linear translation stage 121, recording medium linear translation stage 125, and height adjustment stage 126 are automated stages equipped with stepping motors or piezoelectric actuators (not shown). Under the control of the information processing device 20, they adjust the angles of the reference beam plane mirror 114 and the signal beam plane mirror 117, or adjust the positions of the reference beam plane mirror 114, cylindrical lens system 122, and recording medium 124 in the xy plane based on drive signals supplied from the stage drive circuit 130 via control lines (not shown). Note that the wavelength range of visible light is within the range of approximately 400 to 700 nm, and the longest wavelength is approximately twice the shortest wavelength. Therefore, it is sufficient for the reference beam rotation stage 113, signal beam rotation stage 115, and goniostage 116 to be rotatable within a range of approximately 10 to 20°. Furthermore, the specific configurations of the signal light rotation stage 115, gonio stage 116, linear movement stage 125, and height adjustment stage 126 are the same as those of conventional automatic stages, so details will be omitted.

The recording medium 124 is formed by applying a photosensitive material sensitive to the wavelength of the source beam SB to a predetermined thickness on a flat substrate made of a highly transmittance material such as glass, or by consisting solely of a photosensitive material of a predetermined thickness. When irradiated with the signal parallel beam 118 and the cylindrical wave-like reference beam 123, the recording medium records the interference fringes produced by the interference between the two.

Based on control signals supplied from the information processing device 20, the stage driving circuit 130 generates driving signals and supplies them to each stage 113, 115, 116, 120, 121, 125, and 126 to adjust the angle of the reference beam plane mirror 114 and the signal beam plane mirror 117, or to adjust the positions of the reference beam plane mirror 114, cylindrical lens system 122, and recording medium 124 in the xy plane. The driving signals supplied by the stage driving circuit 130 to each stage 113, etc., may take any format; for example, a configuration may be adopted in which a PWM (pulse wide modulation) format driving signal is supplied to drive a motor or the like mounted on each stage 113, 115, 116, 120, 121, 125, and 126.

The information processing device 20 is a device such as a PC (personal computer), and when manufacturing a holographic diffraction grating HG using the manufacturing device 10A, it executes processing to control the operation of each stage and outputs control signals to the stage driving circuit 130 according to the processing results.

In this embodiment, the stage drive circuit 130 is configured to drive the signal beam rotation stage 115, goniostage 116, reference beam rotation stage 113, cylindrical lens linear translation stage 120, reference beam linear translation stage 121, recording medium linear translation stage 125, and height adjustment stage 126 based on control signals supplied from the information processing device 20. Adjusting the positions and angles of these stages changes the relative illumination angles of the signal collimated beam 118 and cylindrical wave-like reference beam 123 with respect to the recording medium 124, as well as the optical paths and optical path lengths of the signal beam SL and reference beam RL. This changes the spacing of the interference fringes formed by the signal collimated beam 118 and the cylindrical wave-like reference beam 123 expanding from the line focus 127 on the recording medium 124, generating multiple interference fringes with different spacings, and multiplexing the generated multiple interference fringes onto the recording medium 124. With this configuration, the manufacturing system 1A of this embodiment exposes multiple holographic diffraction gratings with different grating spacings onto the recording medium 124 while superimposing them. The extent and manner in which each stage is moved to achieve the grating spacing corresponding to each holographic diffraction grating will be described in detail later.

[A.3] Manufacturing principle of holographic diffraction grating HG in manufacturing apparatus 10A Next, the manufacturing principle of holographic diffraction grating HG in manufacturing system 1A of this embodiment will be described using Figures 1 and 2. Note that Figure 2 is a diagram for explaining interference fringes formed by interference between signal parallel light 118 formed in manufacturing apparatus 10A of this embodiment and cylindrical wave-like reference light 123 spreading from line focus 127.

First, when an arbitrary point on line focus 127 is defined as point 2 in xyz space, consider line 3, which is an arbitrary line in signal collimated light 118 within plane 1 (not shown) that includes point 2 and has the line of line focus 127 as its normal (see FIG. 2). Also, in xyz space, consider intersection 7 between line 4 extending from point 2 and line 6, which extends from an arbitrary point 5 on line 3 and is one of the perpendicular lines to line 3, as shown in FIG. 2. When the position of point 5 is changed while maintaining the orientation of line 6, point 7 moves on curve 9 such that the value (hereinafter referred to as "value 8") obtained by dividing the difference between the distance between point 2 and point 7 and the distance between point 5 and point 7 by the wavelength remains constant. When the value 8 is changed, another curve 9' (not shown) is drawn, but each curve 9 included in the group of all curves 9, 9', 9", 9'", 9"", ... drawn when the value 8 is changed multiple times indicates a curve that is in phase with the interference fringes generated by the signal parallel light 118 generated from the source beam SB of a predetermined wavelength _λ0 and the cylindrical wave-like reference light 123 spreading from the line focus 127.

Now, consider drawing the same group of curves 9, 9', 9", 9'", 9"", ... at different wavelengths λ'. By changing the orientation of lines 4 and 6 in the depth direction of plane 1, the same group of curves can be drawn at different wavelengths. This shows that even when a source beam SB of a wavelength λ' different from _λ0 is used, interference fringes corresponding to wavelength _λ0 can be formed simply by changing the orientations of lines 4 and 6. In other words, this shows that interference fringes corresponding to a plurality of wavelengths can be formed using a source beam SB of a single wavelength simply by adjusting the orientations of lines 4 and 6. Note that, in this case, if plane 1 is displaced in a direction perpendicular to plane 1, the locus drawn by point 2 will coincide with line focus 127, and the plane drawn by line 3 will coincide with a portion of the signal collimated light 118.

Furthermore, since straight line 4 in Figure 2 is part of the cylindrical wave-like reference light 123 spreading from an arbitrary point 2 on the line focus 127, the direction of straight line 4 can be changed by rotating the reference light plane mirror 114 using the reference light rotation stage 113. On the other hand, straight line 6 in Figure 2 is parallel to the direction of the signal collimated light 118, so the direction of straight line 6 can be changed by changing the direction of the signal light plane mirror 117 using the signal light rotation stage 115 and goniostage 116.

In light of the above, the manufacturing apparatus 10A of this embodiment employs a method in which the reference beam rotation stage 113 rotates the reference beam plane mirror 114 to adjust the orientation of line 4, and the signal beam rotation stage 115 and goniostage 116 change the orientation of the signal beam plane mirror 117 to adjust the orientation of line 6, thereby changing the relative irradiation angle of the cylindrical wave-like reference beam 123 and signal parallel beam 118 expanding from the line focus 127 with respect to the recording medium 124. This generates multiple interference fringes with different intervals using a single-wavelength source beam SB, and the generated multiple interference fringes are then multiple-exposed onto the recording medium 124.

[A. 4] Method for Adjusting the Signal Light Rotation Stage 115 and the Goniostage 116 Next, with reference to Figures 3 to 5, the relationship between the rotation angles of the signal light rotation stage 115 and the goniostage 116 in the manufacturing system 1A of this embodiment and the signal collimated light 118 will be explained, and a method for adjusting the signal light rotation stage 115 and the goniostage 116 will be explained. 3 is a graph showing the relationship between the rotation angle of the signal light rotation stage 115 and wavelength when the exposure wavelength (i.e., the wavelength of the source beam SB) is 532 nm and the vertical angle θ _v , which is the angle at which the optical axis is changed in a plane parallel to the plane 1, is 10°. FIG. 3 also shows the relationship between the rotation angle of the signal light rotation stage 115 and wavelength when the horizontal angle θ _h , which is the angle at which the optical axis is changed in a plane perpendicular to the plane 1 and parallel to the line focus 127, is 75°, 60°, 45°, 30°, and 15°, and also shows by shading the driving range of the signal light rotation stage 115 when the horizontal angle of the diffracted light is set to match the horizontal angle θ _h = 30° of the signal light over the entire range of the corresponding wavelength λ, 400 nm to 700 nm. 4 is a diagram showing the relationship between the rotation angle of the goniostage 116 for matching the vertical angle _θv of the signal light with the vertical angle of the diffracted light. In FIG. 4, the relationship between the rotation angle of the goniostage 116 and the vertical angle θv is shown when (a) λ=700 nm and the horizontal angle _θh =15°, and when (b) λ=400 nm and the horizontal angle _θh =60°. The driving range of the goniostage 116 is indicated by shading when the angle is set to match the vertical angle _θv of the signal light, _θv =-10° to 10°, over the entire range of the corresponding wavelength λ of the diffracted light, 400 to 700 nm. 5 is a diagram showing the range of horizontal angles of signal collimated light 118 that changes when the horizontal angle of the diffracted light is set to match the horizontal angle θ _h and vertical angle θ _v of the signal light over the entire range of corresponding wavelengths λ. Similar to FIG. 3, FIG. 5 shows the relationship between the horizontal angle of the corresponding wavelength λ and the wavelength when the vertical angle θ _v is set to 10° and the horizontal angle θ _h is set to 75°, 60°, 45°, 30°, and 15°. The range of horizontal angle θ h of the signal light that changes when the signal light rotation stage 115 and the goniostage 116 are driven so that the horizontal angle of the diffracted light over the entire range of corresponding wavelengths λ, 400 nm to 700 nm _{, is 30° is indicated by a hatched pattern. It can also be seen that, for example, when the horizontal angle θ h of} the signal light is changed from 15° to 60°, the range of horizontal angles of the diffracted light over the entire range of corresponding wavelengths λ, 400 nm to 700 nm, becomes approximately 20° to 40°.

First, the coordinates of the reference point in the recording medium 124 in the xyz space are ( _x0 , _y0 , _z0 ), the coordinates of the reference point in the line focus 127 are ( _x1 , _y1 , _z1 ), the coordinates of the rotation center in the signal light plane mirror 117 are ( _x2 , _y2 , _z2 ), the coordinates of the reference point in the cylindrical lens system 122 are ( _x3 , _y3 , _z3 = _z1 ), the coordinates of the rotation center in the reference light plane mirror 114 are ( _x4 , _y4 , _z4 = _z1 ), and the coordinates of the reference point in the beam splitter 112 are ( _x5 , _y5 , _z5 = z1 _). ), the propagation direction vector of the signal beam SL is set to √2/2(1,1,0), the propagation direction vector of the reference beam RL is set to √2/2(-1,1,0), the normal vector of the signal beam plane mirror 117 when the rotation angle of the signal beam rotation stage 115 and the goniostage 116 is set to 0° is set to (1,0,0), the normal vector of the reference beam plane mirror 114 when the rotation angle of the reference beam rotation stage 113 is set to 0° is set to (-1,0,0), and also when y ₁ = y ₂ , the optical path length l _x in the x-axis direction and the optical path length l _z in the z-axis direction from the rotation center of the signal beam plane mirror 117 to the reference point on the recording medium 124 are expressed by the following equations 3 and 4, respectively.

Furthermore, the optical path length d is defined by the following equations 5 to 7, which show the difference between the optical path length in the x direction (i.e., x ₀ -x ₁ ) between the reference point coordinates (x ₁ , y ₁ , z ₁ ) on the line focus 127 and the reference point coordinates (x ₀ , y ₀ , z ₀ ) on the recording medium 124 and the above l _z .

Here, d indicates a fixed condition for determining curve 9, and represents the projection of the optical path difference onto plane 1. In this case, the optical path length l, which is normalized as 1 when the projection of the optical path difference from the rotation center ( _x2 , _y2 , _z2 ) of the signal light plane mirror 117 to the reference point ( _x0 , _y0 , _z0 ) of the recording medium 124 onto plane 1, can be calculated using the following equations 8 and 9.

Here, z' is a parameter for moving point 5 on line 3, and when z'=0, it indicates the rotation center ( _x2 , _y2 , _z2 ) of signal light plane mirror 117. In addition, if y= _y0 is set at this time, positions x and z through which curve 9 formed by any surface at y= _y0 passes are each expressed by the following equation 10, and the curved surface is uniform in the y direction.

Here, when the z-axis rotation angle of the reference light plane mirror 114 by the reference light rotating stage 113 is Δφ ₁ , the z-axis rotation angle of the signal light plane mirror 117 by the signal light rotating stage 115 is Δφ ₂ , and the rotation angle of the goniostage 116 is Δθ, the direction vector of the signal parallel light 118 is expressed by equation 11, while the direction vector of the cylindrical wave-like reference light 123 spreading from the line focus 127 is expressed by equation 12.

Furthermore, if it is desired to generate interference fringes for a wavelength different from that of the source beam SB used for exposure, the cylindrical wave-like reference light 123 and signal parallel light 118 from the line focus 127 must be rotated around the rotation axis shown in Equation 13 below.

Here, when the direction of the signal collimated light 118 is changed to the direction expressed by Equations 14 and 15, it is necessary to change the rotation angle _Δφ2 of the signal light rotation stage 115 in accordance with Equation 16, and it is also necessary to change the rotation angle Δθ of the goniostage 116 in accordance with Equation 17.

Therefore, in the manufacturing system 1A of this embodiment, the information processing device 20 calculates the rotation angles _Δφ2 and Δθ of the signal beam rotation stage 115 and the goniostage 116 based on the above-mentioned formulas 16 and 17, and supplies a control signal to the stage driving circuit 130 so that the angles of the signal beam rotation stage 115 and the goniostage 116 are set to these angles, thereby adjusting the angles of the signal beam rotation stage 115 and the goniostage 116.

In this case, in manufacturing system 1A, when the vertical angle _θv is 10° and the horizontal angle _θh is 75°, 60°, 45°, 30°, or 15°, the relationship between the rotation angle _Δφ2 of signal beam rotation stage 115 and the wavelength is shown by the curves corresponding to each horizontal angle _θh in FIG. 3 . Therefore, the rotation angle _Δφ2 of signal beam rotation stage 115 is adjusted so that it falls on the corresponding curve in accordance with the wavelength corresponding to the holographic diffraction grating to be manufactured.

In addition, in manufacturing system 1A, the relationship shown in FIG. 4 holds between the rotation angle Δθ of goniostage 116 and the vertical angle _θv of the signal light when the corresponding wavelength range is 400 to 700 nm and the vertical angle of the diffracted light is set to -10° to 10°. Therefore, depending on the corresponding wavelength of the holographic diffraction grating to be manufactured, the rotation angle _Δθ of goniostage 116 is adjusted so that the signal light lies on a corresponding wavelength line (not shown) between the line λ=400 nm, _θh =60° and the line λ=700 nm, θh=15°.

Here, as shown in FIG. 5 , the inventors' simulation experiments have shown that when the signal light rotation stage 115 and the goniostage 116 are driven so that θ _h is within a range of 15° to 60°, for example, the angular range of θ _h of diffracted light in the corresponding wavelength λ range of 400 nm to 700 nm is an angular range of approximately 20° between 20° and 40°. Therefore, by changing the rotation angles of the signal light rotation stage 115 and the goniostage 116 within this angular range, it is possible to manufacture a holographic diffraction grating HG having desired characteristics.

Furthermore, as shown in Figure 4, for the goniostage 116, by displacing the angle of the signal light plane mirror 117 within an angle range of about 10° (approximately -7° to 7°), a holographic diffraction grating HG with the desired characteristics can be manufactured.

If, within this angle range, the goniostage 116 is used to displace the irradiation angle of the signal collimated light 118 in the z-axis direction while exposing interference fringes onto the recording medium 124 to produce a holographic diffraction grating HG, a transmissive display panel using the produced holographic diffraction grating HG can ensure a viewing angle of approximately 20° in the vertical direction.

In addition, when considering exposing a holographic diffraction grating for diffracting parallel light with a corresponding wavelength range of 400 to 700 nm, a vertical angle θ _v =10°, and a horizontal angle θ _h =30° with a source beam SB of 532 nm wavelength, the inventor's simulation results show that, within the corresponding wavelength range of 400 to 700 nm, the driving ranges of the signal beam rotation stage 115 and the reference beam rotation stage 113 are as shown by the shaded areas in Figures 3 and 6, and the driving range of the goniostage 116 is between the lines of λ=400 nm, θ _h =60° and λ=700 nm, θ _h =15° at θ _v =10° in Figure 4 (approximately 5° to 7°). Therefore, when the stages 115 and goniostage 116 are driven within the shaded area in FIG. 3 and the range of approximately 5° to 7°, the horizontal angle range of the signal collimated light 118 is approximately 20° to 40°, as shown by the shaded area in FIG. 5 . This means that, at a wavelength of 532 nm, a diffraction grating is multiplexed to diffract collimated light within a horizontal angle range of approximately 20° to 40°. If it is desired to diffract collimated light with angles within this range for all light with wavelengths from 400 to 700 nm, attention should be paid to the upper limit (40°) of the shortest wavelength (400 nm) and the lower limit (20°) of the longest wavelength (700 nm) in FIG. 5 . The curve intersects with the curve for θ _h = 60° near the upper limit (40°) of the shortest wavelength (400 nm), and with the curve for θ _h = 60° near the lower limit (20°) of the longest wavelength (700 nm). Therefore, the horizontal angle range of the diffracted light is approximately 20° to 40°, and if the angle range of the signal collimated light 118 with a wavelength of 532 nm is determined so as to satisfy this value, it will be approximately 15° to 60°, which determines the corresponding drive range of each of the stages 113, 115, and 116. Furthermore, the drive range of each of the stages 113, 115, and 116 can be determined in a similar manner for other vertical angles.

[A. 5] Method for Adjusting the Reference Beam Rotation Stage 113 Next, using FIG. 6 , we will explain the relationship between the cylindrical wave-like reference beam 123 spreading from the line focus 127 in the manufacturing system 1A of this embodiment and the rotation angle of the reference beam rotation stage 113, and also explain the method for adjusting the reference beam rotation stage 113. Note that FIG. 6 is a graph showing the relationship between the rotation angle _{Δφ 1} of the reference beam rotation stage 113 and the corresponding wavelength when the wavelength of the source beam SB is 532 nm and the vertical angle θ v is 10°. This figure shows the relationship between the rotation angle and wavelength when the horizontal angle θ _h is 75°, 60°, 45°, 30°, and 15°. Also, in FIG. 6 , the driving range of each reference beam rotation stage 113 when θ _h = 30° is indicated by shading.

In the manufacturing apparatus 10A of this embodiment, in order to change the direction of the optical axis of the cylindrical wave-like reference light 123 spreading from the line focus 127 to the direction shown by Equations 18 to 20, it is necessary to change the rotation angle Δφ ₁ of the reference light rotation stage 113 in accordance with Equation 21.

Therefore, in the manufacturing system 1A of this embodiment, a configuration is adopted in which the information processing device 20 calculates the rotation angle _Δφ1 of the reference beam rotation stage 113 according to Equation ₂₁ , and supplies a control signal to the stage driving circuit 130 so that the rotation angle of the reference beam rotation stage 113 is set to the rotation angle Δφ1, thereby adjusting the angle of the reference beam rotation stage 113.

In this case, in manufacturing system 1A, when vertical angle _θv is 10° and horizontal angle _θh is 75°, 60°, 45°, 30°, or 15°, the relationship between rotation angle _Δφ1 of reference beam rotation stage 113 and the wavelength satisfies the curves corresponding to each horizontal angle _θh in Figure 6. Therefore, rotation angle _Δφ1 of reference beam rotation stage 113 is adjusted so that it falls on the corresponding curve depending on the wavelength of the holographic diffraction grating to be manufactured. With this configuration, manufacturing apparatus 10A of this embodiment can adjust the direction of cylindrical wave-like reference beam 123 spreading from line focus 127 to the direction shown by Equations 18 to 20. As shown in FIG. 6, the horizontal angle range of the reference beam rotation stage 113 is also approximately 10°, that is, from 3° to 13°. Therefore, by adjusting the horizontal angle of each of the signal beam rotation stage 115, the goniostage 116, and the reference beam rotation stage 113 within a range of approximately 10° to 20°, a holographic diffraction grating HG that achieves the desired function can be manufactured.

[A.6] Exposure Method When manufacturing a holographic diffraction grating HG using the manufacturing system 1A of this embodiment, first, the relative position of line focus 127 with respect to recording medium 124 is determined, and then the direction of diffracted light generated when light is irradiated onto the manufactured holographic diffraction grating HG is determined in order to set the characteristics of the holographic diffraction grating HG manufactured by the manufacturing system 1A. For example, if the horizontal angle θ _h and vertical angle θ _v of the diffracted light in holographic diffraction grating HG are determined according to the following equations 22 and 23, the direction of signal collimated light 118 is determined according to equation 24. The direction of the diffracted light can be set by an operator using the information processing device 20.

From this, by determining the reference direction (u ₂ , 0, w ₂ ) and the rotation axis (n _x , _ny , _nz ) shown in equation 13, the angle θ ₀ of the diffracted light viewed from this reference direction can be calculated using equation 25.

The wavelength of the source beam SB used for exposure is set to λ ₀ , and the signal parallel light 118 and the cylindrical wave-like reference light 123 spreading from the line focus 127 are superimposed and irradiated onto the recording medium 124, thereby exposing interference fringes on the recording medium 124.

When a holographic diffraction grating HG manufactured using this method is irradiated with cylindrical wave-like reference light 123 expanding from a line focus 127, light having the same optical axis as the signal collimated light 118 is diffracted. On the other hand, when light having the same optical axis as the signal collimated light 118 but traveling in the opposite direction is irradiated onto the diffraction grating, the light is focused on the same straight line as the line focus 127.

For example, to provide the above function for an arbitrary wavelength λ, the information processing device 20 calculates the direction of the signal collimated light 118 based on equation 26 so that equation 26 is satisfied.

Next, in the manufacturing system 1A of this embodiment, the information processing device 20 calculates the rotation angle Δφ2 of the signal light rotation stage 115 according to the above-mentioned equation 16, and calculates the rotation angle Δθ of the goniostage 116 according to the equation 17, so that the signal parallel light 118 is irradiated in the direction calculated by equation ₂₆ .

Then, in order to align the angles of the signal beam rotation stage 115 and the goniostage 116 with the rotation angle _Δφ2 of the signal beam rotation stage 115 and the rotation angle Δθ of the goniostage 116 calculated in this manner, the information processing device 20 outputs a control signal to the stage driving circuit 130 to change the rotation angle of the signal beam rotation stage 115 to the calculated _Δφ2 as described above, and change the rotation angle of the goniostage 116 to Δθ.

Next, the information processing device 20 sets the direction of the cylindrical wave-like reference light 123 spreading from the line focus 127 shown in Equation 12 as u ₁ = -u ₂ , v ₁ = v ₂ , and w ₁ = -w _2. At this time, the cylindrical wave-like reference light 123 spreading from the line focus 127 can be rotated in the opposite direction to the signal collimated light 118. That is, if the direction of the signal collimated light 118 is θ ₁ and the direction of the cylindrical wave-like reference light 123 is θ ₂ , then θ ₁ = -θ ₂ can be set. To achieve this, the information processing device 20 calculates the rotation angle Δφ ₁ of the reference light rotation stage 113 according to Equation 21.

After calculating the rotation angle _Δφ1 of the reference beam rotation stage 113 in this manner, the information processing device 20 outputs a control signal to the stage driving circuit 130 to change the rotation angle of the reference beam rotation stage 113 to _Δφ1 .

Next, the information processing device 20 executes processing to adjust the positions of the recording medium linear movement stage 125, height adjustment stage 126, cylindrical lens linear movement stage 120, and reference light linear movement stage 121. At this time, the information processing device 20 calculates the movement distances of the recording medium linear movement stage 125, height adjustment stage 126, cylindrical lens linear movement stage 120, and reference light linear movement stage 121, respectively, using the following method, and adjusts the positions of the linear movement stages 120, 121, 125, and height adjustment stage 126 based on the calculated values.

(1) Method of Adjusting Recording Medium Linear Movement Stage 125 and Height Adjustment Stage 126 With regard to the recording medium linear movement stage 125, the information processing device 20 calculates Δy ₀ shown in Equation 27-1, and then outputs a control signal to the stage driving circuit 130 to move the position of the recording medium linear movement stage 125 in the y-axis direction by Δy ₀ , and with regard to the height adjustment stage 126, calculates Δz ₀ shown in Equation 27-2, and then outputs a control signal to the stage driving circuit 130 to move the height of the height adjustment stage 126 in the z-axis direction by Δz ₀ .

(2) Method of Adjusting the Cylindrical Lens Linear Translation Stage 120 Furthermore, with regard to the cylindrical lens linear translation stage 120, the information processing device 20 calculates _Δy3 shown in Equation 28, and then outputs a control signal to the stage driving circuit 130 to move the position of the recording medium linear translation stage 125 in the y-axis direction by _Δy3 .

(3) Method for Adjusting Reference Beam Linear Moving Stage 121 In response to this, the information processing device 20 calculates _Δx4 shown in Equation 29 for the reference beam linear moving stage 121, and then outputs a control signal to the stage driving circuit 130 to move the position of the recording medium linear moving stage 125 by _Δx4 in the x-axis direction and by _Δy4 in the y-axis direction.

When the position adjustment of each stage 113, 115, 120, 125, 126, and 121 is completed by the above method, in manufacturing apparatus 10A, the optical system is moved to an arrangement state, for example, as shown in Figure 9, and signal parallel light 118 and cylindrical wave-like reference light 123 spreading from line focus 127 are irradiated onto recording medium 124 at a relative irradiation angle determined by the arrangement state, and interference fringes generated by the interference of the two light beams 118 and 123 are exposed onto recording medium 124. As a result, a holographic diffraction grating corresponding to one wavelength (for example, λ ₁ ) is formed on recording medium 124.

[A.7] Operations during manufacturing of holographic diffraction grating HG in manufacturing system 1A Next, the operations during manufacturing of holographic diffraction grating HG in manufacturing system 1A of this embodiment will be described using Figures 7 to 10. Figures 7 and 8 are flowcharts showing the processing executed by information processing device 20 in manufacturing system 1A of this embodiment, and Figures 9 and 10 are diagrams showing the changes in the optical path system of manufacturing apparatus 10A when exposing two types of holographic diffraction gratings with different grating spacings.

First, in manufacturing system 1A of this embodiment, an operator determines the relative position of line focus 127 with respect to recording medium 124 and the direction of diffracted light generated when a predetermined light is irradiated onto holographic diffraction grating HG manufactured by manufacturing system 1A, and inputs the necessary information into information processing device 20. In order to expose a holographic diffraction grating corresponding to one wavelength _λ1 in the visible light range onto recording medium 124, information processing device 20 sets λ to the shortest wavelength _λ1 in the visible light range (e.g., 400 nm) (step S1).

Next, the information processing device 20 determines the direction of the signal collimated light 118 according to equation 26 above (step S2).

Once the direction of the signal collimated light 118 has been determined in this manner, the information processing device 20 calculates the rotation angles _Δφ2 and Δθ of the signal light rotation stage 115 and the goniostage 116 based on the determined direction and on the above-mentioned equations 16 and 17 (step S3), and supplies a control signal to the stage driving circuit 130 based on the calculated rotation angles _Δφ2 and Δθ to adjust the rotation angles of the signal light rotation stage 115 and the goniostage 116 to the calculated rotation angles _Δφ2 and Δθ (step S4).

Next, the information processing device 20 calculates the rotation angle _Δφ1 of the reference beam rotation stage 113 based on the above equation 21 (step S5), and supplies a control signal to the stage driving circuit 130 based on the calculated rotation angle _Δφ1 to adjust the rotation angle of the reference beam rotation stage 113 to the calculated rotation angle _Δφ1 (step S6).

Next, the information processing device 20 executes a process of calculating the movement amounts of the linear movement stages 120, 121, and 125 and the height adjustment stage 126 (step S7). At this time, the information processing device 20 calculates the movement amount _Δy0 of the recording medium linear movement stage 125 based on the above equation 27-1, and calculates the movement amount _Δz0 of the height adjustment stage 126 based on equation 27-2. At this time, the information processing device 20 also calculates the movement amount _Δy3 of the cylindrical lens linear movement stage 120 based on equation 28, and further calculates the movement amounts _Δx4 and _Δy4 of the reference beam linear movement stage 121 based on equation 29 (step S7).

After calculating the values of _Δy0 , _Δz0 , _Δy3 , _Δx4 , and _Δy4 in this manner, the information processing device 20 outputs a control signal to the stage driving circuit 130 based on the calculated movement amounts _Δy0 , _Δy3 , _Δx4 , and _Δy4 to (1) move the recording medium linear movement stage 125 in the y-axis direction by Δy0, (2) move the height adjustment stage 126 in the height direction (z-axis direction) by _Δz0 , (3) move the cylindrical lens linear movement stage 120 in the y-axis direction by _Δy3 , and (4) move the reference light linear movement stage 121 in the x-axis direction _{by Δx4} and in the y-axis direction by _Δy4 , thereby adjusting the positions of the recording medium 124, the reference light plane mirror 114, and the cylindrical lens system 122 to the corresponding positions (step S8).

When the optical system of manufacturing apparatus 10A reaches a state matching the exposure of the holographic diffraction grating corresponding to wavelength _λ1 through the above procedure, information processing apparatus 20 outputs a control signal to light source 111 to irradiate source beam SB for a predetermined exposure time, thereby generating interference fringes corresponding to wavelength _λ1 and exposing recording medium 124 to the holographic diffraction grating corresponding to wavelength _λ1 (step S9).

Next, the information processing device 20 determines whether exposure of the holographic diffraction gratings corresponding to all interference fringes to be multiple-exposed on the recording medium 124 is complete (step S10). If it determines that exposure is not complete (step S10: No), it sets λ _n = λ _n-1 + Δλ to change the wavelength to be exposed by Δλ (step S11). For example, when exposure of the holographic diffraction grating corresponding to wavelength λ ₁ is complete, it sets λ _n = λ ₁ + Δλ. Note that the specific value of Δλ is arbitrary and may be set to, for example, 10 nm. The key is to set an appropriate value depending on the wavelength at which the function of the holographic diffraction grating HG is desired to be realized.

In this way, when λ _n = λ _n-1 + Δλ is set in step S11, the information processing device 20 returns the process to step S2 and repeats the processes of steps S2 to S9 to expose a holographic diffraction grating corresponding to the next wavelength (for example, λ ₁ + Δλ) onto the recording medium 124.

Then, the information processing device 20 determines whether exposure of the holographic diffraction gratings corresponding to all wavelengths has been completed (step S10), and repeats the processing of steps S2 to S11 described above until exposure of the holographic diffraction gratings corresponding to all wavelengths has been completed, ending the processing once exposure of the holographic diffraction gratings corresponding to all wavelengths has been completed.

At this time, in the optical system of the manufacturing apparatus 10A of this embodiment, the positions and angles of the reference beam plane mirror 114, signal beam plane mirror 117, cylindrical lens system 122, and recording medium 124 change to match the wavelength of the holographic diffraction grating to be exposed, as shown in Figures 9 and 10, and as the state of the optical system changes, a holographic diffraction grating corresponding to that state is exposed onto the recording medium 124.

In the manufacturing system 1A of this embodiment, by performing this process, multiple holographic diffraction gratings, each with a different grating spacing and each achieving the desired function for a different wavelength, are multiplexed and exposed onto the recording medium 124.

As described above, the manufacturing system 1A of this embodiment is configured to split a single-wavelength source beam SB into a signal beam SL and a reference beam RL by a beam splitter 112, and irradiate each of these beams onto a recording medium 124 via different optical paths. The cylindrical wave-like reference beam 123 expanding from a line focus 127 interferes with the signal parallel beam 118, generating interference fringes that are then exposed to the recording medium 124, thereby manufacturing a holographic diffraction grating HG.

The manufacturing system 1A of this embodiment is configured to perform multiple exposures of multiple holographic diffraction gratings, each with a different grating spacing, on the recording medium 124 while changing the relative angle at which the signal collimated beam 118 and the cylindrical wave-like reference beam 123 are irradiated onto the recording medium 124 by adjusting the rotation angles of the reference beam rotation stage 113, the signal beam rotation stage 115, and the goniostage 116. With this configuration, the manufacturing system 1A of this embodiment can manufacture a holographic diffraction grating HG that can achieve the desired function across the entire visible light range using a single-wavelength source beam SB. As a result, the manufacturing system 1A of this embodiment can manufacture a holographic diffraction grating HG that can achieve the desired function across the entire visible light range at low cost, without the need to provide the manufacturing apparatus 10A with a light source that emits source beams SB of multiple wavelengths and optical systems for those wavelengths.

[A.8] Structure of Holographic Diffraction Grating HG Manufactured by Manufacturing System 1A of the Present Embodiment Next, a specific structure of the holographic diffraction grating HG manufactured by the manufacturing system 1A of the present embodiment will be described with reference to FIG. 11 . Note that FIG. 11 illustrates an example of the three-dimensional structure of the holographic diffraction grating HG manufactured by the manufacturing system 1A of the present embodiment. (A) and (B) show examples of the structure of holographic diffraction gratings HG1 and HG2 when irradiated with white parallel light and line-focused near the center of the holographic diffraction grating HG in the vertical direction (i.e., the z-axis direction) of the drawing, and (C) and (D) show examples of the structure of holographic diffraction gratings HG3 and HG4 when line-focused toward the bottom of the holographic diffraction grating HG (note that in this specification, each of the holographic diffraction gratings HG1 to HG4 will be referred to as the "holographic diffraction grating HG" unless otherwise specified). Furthermore, the combinations of (A) and (B) and the combinations of (C) and (D) each illustrate examples of the structure of holographic diffraction gratings HG corresponding to different wavelengths.

(1) Example of structure when white parallel light is focused near the center of the holographic diffraction grating HG As shown in Figures 11(A) and 11(B), the holographic diffraction gratings HG1 and 2 in this case have multiple parabolic cylindrical layers stacked along a cross section in the vertical direction (i.e., the z-axis direction) (i.e., the cross section seen in the foreground in each of Figures 11), with the center of each holographic diffraction grating HG1 and 2 as the center, presenting a layer structure reminiscent of the growth rings of a tree stump. Each layer has a different refractive index and is nearly identical in shape, and similar interference fringes are continuously formed across the entire surface of each layer.

In particular, when focusing white parallel light near the center, this function is achieved by forming a three-dimensional structure in which layers having approximately parabolic cylindrical shapes with different curvatures are stacked on top of each other at the focusing position (i.e., a position a predetermined distance away from the center of the holographic diffraction gratings HG1 and HG2 in the z direction).

(2) Example of structure when white parallel light is focused downward on the holographic diffraction grating HG. In this case, the holographic diffraction gratings HG3 and HG4 have a structure in which multiple parabolic cylindrical layers, each having a roughly identical shape along the vertical cross section, are stacked one on top of the other, as shown in FIGS. 11(C) and 11(D).

In this case, however, the focusing position is below the holographic diffraction gratings HG3 and HG4, so the shape of each layer differs from the case where the light is focused near the center as described above, and the center of the parabolic cylindrical layer is shifted below the holographic diffraction gratings HG3 and HG4 so that the white collimated light is focused below the holographic diffraction grating HG. Furthermore, because each layer has a shape that forms part of a roughly cylindrical shape, each layer functions as a cylindrical lens, and the holographic diffraction grating HG as a whole functions as a cylindrical lens with a uniaxial curvature.

The holographic diffraction grating HG of this embodiment, which has the above structure, has a layer shape corresponding to any focusing position, and as the number of layers changes, the corresponding wavelength changes. When the number of layers is large (for example, holographic diffraction gratings HG1 and 3 in the example shown in FIG. 11), focusing characteristics for light on the short wavelength side are realized, and when the number of layers is small (for example, holographic diffraction gratings HG2 and HG4 in the example shown in FIG. 11), focusing characteristics for light on the long wavelength side are realized. In the manufacturing system 1A of this embodiment, holographic diffraction gratings corresponding to multiple interference fringes corresponding to different wavelengths are multiplexed and a holographic diffraction grating HG having a stacked structure of multiple layers, as shown in FIG. 11, is manufactured.

With this configuration, the holographic diffraction grating HG manufactured by the manufacturing system 1A of this embodiment is configured so that when white parallel light is incident from the same direction as the optical axis of the signal parallel light 118, the light is focused on the line focus 127, and when white light is incident from the same direction as the cylindrical wave-like reference light 123 spreading from the line focus 127, light having the same optical axis as the signal parallel light 118 is diffracted. In other words, the holographic diffraction grating HG manufactured by the manufacturing system 1A of this embodiment achieves the same function as a cylindrical lens with a uniaxial curvature. Note that a method for manufacturing holographic diffraction gratings HG with different layer shapes (i.e., holographic diffraction gratings HG with different focusing positions) will be described in the section on Variation Example 3.

[B] Modification [B. 1] Modification 1
In the first embodiment, the manufacturing apparatus 10A and the information processing apparatus 20 are configured as separate devices and are connected to each other by wire or wirelessly. However, the manufacturing apparatus 10A may be provided with a control unit including a CPU (Central Processing Unit) and ROM/RAM, and the control unit may perform the same functions as the information processing apparatus 20. In this case, an operation unit including a keyboard or the like may be provided, and the control unit may execute the same processes as those shown in FIGS. 7 and 8 while setting the direction of diffracted light in the holographic diffraction grating HG to be manufactured in response to input operations made by an operator on the operation unit. With this configuration, the manufacturing apparatus 10A alone can manufacture a holographic diffraction grating HG that exhibits the desired function across the entire visible light range.

[B.2] Modification 2
In the above embodiment, the case of manufacturing a holographic diffraction grating HG has been described as an example, but the present invention can also be applied to the manufacture of a light guide plate having a holographic diffraction grating HG.

In this case, the recording medium 124 is placed in a transparent substrate, and the holographic diffraction grating HG is multiple-exposed onto the recording medium 124 in the substrate. In this case, a prism is placed on the first height adjustment stage 126 together with the recording medium 124, and the prism is used to irradiate the signal collimated light 118 and the cylindrical wave-like reference light 123 onto the recording medium 124. Other configurations and operations are the same as those in the first embodiment, so details will be omitted.

The holographic light guide plate HGLP manufactured using this method can be used as an optical combiner in a transmissive HMD or head-up display. For example, Figures 12 to 14 show an example configuration in which this holographic light guide plate HGLP is used in a transmissive HMD 30.

As shown in Figure 12, a see-through HMD 30 using this holographic light guide plate HGLP has a prism-shaped light entrance portion LE at the end of the holographic light guide plate HGLP, and uses a configuration in which image light VL is irradiated from this light entrance portion LE by a projector P.

The image light VL emitted from the projector P is repeatedly totally reflected at the boundary surfaces of the holographic light guide plate HGLP, traveling through the holographic light guide plate HGLP and reaching its edge. During this process of repeated total reflection, the image light VL is diffracted by the holographic diffraction grating HG formed inside the holographic light guide plate HGLP and enters the user's eye EY. Furthermore, external light OL passes through the holographic light guide plate HGLP and enters the user's eye EY as is. As a result, the user sees the external scenery and the information (text, images, colors, etc.) displayed by the image light VL superimposed on each other, and the user perceives this information as a virtual image.

Here, the see-through HMD 30 focuses the image light VL from the projector P at infinity using a lens L, thereby showing a virtual image from infinity to the user's eye EY. A certain distance is required between the user's eye EY and the see-through HMD 30, and to provide a wide FOV (Field Of View), the area (eyebox) where the image light VL guided through the holographic light guide plate HGLP is reflected toward the eye EY must be widened. As shown in Figure 13, if a diffractive optical element functioning as a plane mirror is constructed inside the holographic light guide plate HGLP using an existing method, it is easy to widen the eyebox because the diffractive optical element simply reflects a portion of the image light VL in the guided direction. However, widening the eyebox in a direction perpendicular to the guided direction requires two-stage diffraction or another function.

By adopting the method of this modification, it is possible to fabricate a holographic diffraction grating HG that functions as a curved mirror within a holographic light guide plate HGLP, as shown in Figure 14. In this case, a method can be used in which the image light VL from the projector P is imaged horizontally with infinity using a cylindrical lens CL to form an image in a direction perpendicular to the horizontal axis. The light spreads vertically around the pixel position and also within the wave guide. Thus, by fabricating a holographic light guide plate HGLP having a holographic diffraction grating HG that functions as a curved mirror, as shown in Figure 14, using the method of this modification (i.e., a method of fabricating a holographic light guide plate HGLP by mounting a prism together with a recording medium 124 on a height adjustment stage 126), it is possible to spread the light vertically within the wave guide. Furthermore, the light spread within the wave guide is diffracted into parallel light with a vertical angle corresponding to the vertical pixel position due to the diffraction characteristics of the holographic diffraction grating HG, enabling the fabrication of a see-through HMD 30 with a wide eyebox, a wide FOV, and high practicality.

[B.3] Modification 3
In the above embodiment, a configuration was adopted in which a plurality of interference fringes, each with a different grating interval, are generated to achieve the desired function for light across the entire visible light range, and the holographic diffraction grating HG is manufactured by multiple-exposing the plurality of interference fringes onto the recording medium 124. However, a plurality of holographic diffraction gratings HG that each achieve a different function may also be multiple-exposed onto the recording medium 124. For example, a configuration may be adopted in which holographic diffraction gratings HG with different light-focusing positions, such as holographic diffraction gratings HG1 and 2 and holographic diffraction gratings HG3 and 4 in FIG. 11 , are multiple-exposed onto the recording medium 124.

In this case, when the operator determines the diffraction direction of the diffracted light before starting the process of FIG. 7, the operator sets the direction of the diffracted light to match the focusing position, and then exposes the holographic diffraction grating HG (e.g., holographic diffraction grating HG1 or 2) onto the recording medium 124 using this setting. After the exposure of the holographic diffraction grating HG is complete, the direction of the diffracted light corresponding to the new focusing position is set again to expose a holographic diffraction grating HG with a different focusing position (e.g., holographic diffraction grating HG3 or 4), and the holographic diffraction grating HG corresponding to this diffracted light direction is once again exposed onto the recording medium 124. Thereafter, the direction of the diffracted light corresponding to each focusing position is repeatedly reset, generating multiple interference fringes, and the generated multiple interference fringes are multiple-exposed onto the recording medium 124.

In this case, a holographic diffraction grating HG is manufactured that has a structure in which multiple holographic diffraction gratings HG with different layer shapes depending on the focusing position are multiplexed, as shown in Figure 11.

In this modified example, the holographic diffraction grating HG may be multiple-exposed with different focusing positions for only some wavelengths, or the holographic diffraction grating HG may be multiple-exposed with different focusing positions for the entire visible light range.

If you want to give the holographic diffraction grating HG the property of focusing only light of certain wavelengths at different positions, you can fix the value of λ in Equation 26 to that wavelength, change the direction of the diffracted light, generate interference fringes multiple times, and perform multiple exposures on the holographic diffraction grating HG.

On the other hand, if you want to have the ability to focus light across the entire visible light range at different focusing positions, you can repeat the processes in Figures 7 and 8 above each time you reset the direction of the diffracted light, and multiple holographic diffraction gratings HG corresponding to those focusing positions can be multiplexed and exposed onto the recording medium 124.

[B.4] Modification 4
In the above embodiment, an example of a structure in which multiple parabolic cylindrical layers that function as grating surfaces are formed within the recording medium 124 as shown in FIG. 11 has been described. However, even if a configuration is adopted in which multiple diffraction planes, each having a different refractive index and each oriented in a different direction, are exposed on the recording medium 124, it is possible to achieve the same function as the holographic diffraction grating HG configured as shown in FIG. 11 .

In this case, the manufacturing apparatus 10A does not need to be provided with a cylindrical lens system 122; instead, the reference parallel light 119 is irradiated directly onto the recording medium 124, and the irradiation angles of the reference parallel light 119 and the signal parallel light 118 are changed while causing them to interfere with each other, and the resulting multiple interference fringes are exposed onto the recording medium 124.

Furthermore, multiple holographic diffraction gratings HG corresponding to each wavelength may be configured to be formed two-dimensionally on the surface of the recording medium 124.

[C] Second Embodiment [C.1] Configuration of Manufacturing System 1B of Second Embodiment Next, a second embodiment of a holographic optical element manufacturing apparatus according to the present invention will be described using FIG. 15. FIG. 15 is a system configuration diagram showing the configuration of manufacturing system 1B of this embodiment. In addition, in FIG. 15, components similar to those in FIG. 1 are designated by the same reference numerals. Therefore, unless otherwise specified, components in FIG. 15 designated by the same reference numerals as those in FIG. 1 will be described as having the same configuration and function as those in the first embodiment and performing the same operations.

The manufacturing apparatus 10B constituting the manufacturing system 1B of this embodiment employs a configuration in which the beam splitter 112 is configured using a PBS and splits P-polarized light into signal light SL and S-polarized light into reference light RL depending on the polarization direction. Furthermore, the manufacturing apparatus 10B of this embodiment employs a configuration in which a λ/2 plate (not shown) is provided between the beam splitter 112 and the signal light plane mirror 117, and the signal light SL is irradiated onto the signal light plane mirror 117 while the reference light RL is irradiated onto the reference light plane mirror 114 while aligning the polarization directions of the signal light SL and the reference light RL. Note that the beam splitter 112 in the manufacturing apparatus 10B of this embodiment may also be configured using a half mirror.

Furthermore, the manufacturing apparatus 10B of this embodiment employs a configuration in which a slit member (not shown) is added between the cylindrical lens system 122 and the recording medium 124. The cylindrical wave-like reference light 123 generated after passing through the cylindrical lens system 122 forms a line focus 127 as it passes through a slit portion provided in this slit member, and is then irradiated onto the recording medium 124 while expanding from the slit portion (i.e., the line focus 127). With this configuration, the manufacturing apparatus 10B of this embodiment is able to create a narrow line focus 127, thereby improving the accuracy with which the cylindrical wave-like reference light 123 is irradiated onto the recording medium 124.

In the manufacturing apparatus 10B of this embodiment, as in the manufacturing apparatus 10A of the first embodiment, a plane mirror 114 for reference light is provided on the optical path of the reference light RL branched by the beam splitter 112, and this plane mirror 114 for reference light is mounted on a rotation stage 113 for reference light provided on a linear movement stage 121 for reference light.By linearly moving the linear movement stage 121 for reference light within the xy plane and rotating the rotation stage 113 for reference light along the z axis, the irradiation direction of the reference parallel light 119 can be adjusted within the xy plane. Furthermore, in the manufacturing apparatus 10B of this embodiment, a cylindrical lens system 122 mounted on a cylindrical lens linear movement stage 120 is arranged on the optical path of the reference collimated light 119, and this cylindrical lens linear movement stage 120 can be driven in conjunction with the reference light linear movement stage 121 and the reference light rotation stage 113 to adjust the position of the cylindrical lens system 122 to match the irradiation direction of the reference collimated light 119. However, since the optical path configuration on the reference light RL side is the same as that of the manufacturing apparatus 10A of the first embodiment, details will be omitted.

Here, the manufacturing apparatus 10A of the first embodiment above employs a configuration in which a goniostage 116 is provided on a signal light rotation stage 115, and a signal light plane mirror 117 is placed on this goniostage 116. The signal light rotation stage 115 is rotated about the z-axis, and the goniostage 116 is used to adjust the tilt of the signal light plane mirror 117, thereby three-dimensionally changing the irradiation angle of the signal collimated light 118 with respect to the recording medium 124. Furthermore, the manufacturing apparatus 10A of the first embodiment employs a configuration in which the recording medium 124 is placed on a height adjustment stage 126 provided on a recording medium linear movement stage 125, and the position of the recording medium 124 is adjusted by the recording medium linear movement stage 125 and height adjustment stage 126 to match the irradiation angle of the signal collimated light 118, thereby irradiating the signal collimated light 118 at a desired position on the recording medium 124.

In contrast, in the manufacturing apparatus 10B of this embodiment, the signal light plane mirror 117 is placed directly on the signal light rotation stage 115, and the goniostage 116 is omitted. As a result, in the manufacturing apparatus 10B of this embodiment, the signal light rotation stage 115 changes the irradiation angle of the signal collimated light 118 only two-dimensionally within the same plane, and does not change it in the z-axis direction. Note that the signal light rotation stage 115 of this embodiment works in conjunction with the stage drive circuit 130 and the information processing device 20 to constitute, for example, the "signal light irradiation angle adjustment means" of the present invention.

In particular, in the manufacturing apparatus 10B of this embodiment, instead of the linear motion stage 125 for recording medium, which can move the position of the recording medium 124 in a predetermined direction (e.g., the y-axis direction), a planar motion stage 140 for recording medium is provided, which can move the position of the recording medium 124 two-dimensionally within the xy plane (i.e., in the biaxial directions of the x-axis and y-axis). A goniostage 150 for recording medium is provided on this planar motion stage 140 for recording medium, and the recording medium 124 is placed on this goniostage 150 for recording medium, thereby eliminating the height adjustment stage 126. The specific configuration of the planar motion stage 140 for recording medium is the same as that of the linear motion stage 125 for recording medium, except that, like the linear motion stage 125, it is configured to be linearly movable in two axial directions using a piezoelectric actuator or stepping motor.

In the manufacturing apparatus 10B of this embodiment, the recording medium goniostage 150 is used to change the tilt of the recording medium 124 relative to the signal collimated light 118 and cylindrical wave-like reference light 123, so that the recording medium goniostage 150 alone achieves functionality equivalent to the combination of the goniostage 116 and height adjustment stage 126 in the first embodiment. For example, the recording medium planar movement stage 140 and recording medium goniostage 150 of this embodiment cooperate with the stage drive circuit 130 and information processing device 20 to constitute the "recording medium planar movement means" and "recording medium tilt angle change means" of the present invention. Furthermore, the specific configuration of the recording medium goniostage 150 is the same as the goniostage 116 of the first embodiment, except for the object to be adjusted.

As in the first embodiment, the manufacturing apparatus 10B of this embodiment also produces a holographic diffraction grating HG (see FIG. 11) that functions similarly to a cylindrical lens: when white parallel light is incident, the parallel light is diffracted and line-focused, while when divergent light from the line-focused white light is incident, the divergent light is diffracted and generates parallel light. For example, when signal parallel light 118 is incident on the holographic diffraction grating HG manufactured by the manufacturing apparatus 10B of this embodiment, the signal parallel light 118 diffracted by the holographic diffraction grating HG is line-focused in a form that coincides with the line focus 127, while when cylindrical wave-like reference light 123 diverging from the line focus 127 is incident on the holographic diffraction grating HG, the parallel light generated by diffraction has the same optical axis as the signal parallel light 118.

When manufacturing such a holographic diffraction grating HG, the recording medium goniostage 150 adjusts the tilt of the recording medium 124 to change the relative tilt of the recording medium 124 with respect to the signal collimated light 118 and cylindrical wave-like reference light 123 (i.e., changes the relative irradiation angle of the signal collimated light 118 and cylindrical wave-like reference light 123 with respect to the recording medium 124), allowing the recording medium goniostage 150 alone to achieve functionality equivalent to the combination of the goniostage 116 and height adjustment stage 126 in the manufacturing apparatus 10A of the first embodiment. As described above, in the manufacturing apparatus 10B of this embodiment, the irradiation direction of the signal collimated light 118 is not changed in the z-axis direction, and the irradiation angle of the signal collimated light 118 is changed only two-dimensionally within the same plane. Therefore, even if the height adjustment stage 126 is omitted, the recording medium planar movement stage 140 alone can irradiate the signal collimated light 118 and cylindrical wave-like reference light 123 at desired positions on the recording medium 124.

[C. 2] Adjustment Method of Each Stage Next, a method of adjusting each stage in the manufacturing apparatus 10B of this embodiment having the above-described configuration will be described.

First, in the manufacturing apparatus 10B of this embodiment, when the rotation angle of the reference light rotation stage 113 is Δφ ₁ , the rotation angle of the signal light rotation stage 115 is Δφ ₂ , and the tilt rotation angle of the recording medium goniostage 150 is Δθ ₂ , the direction vector of the signal parallel light 118 is expressed by the following equation 30, which is different from equation 11 in the first embodiment.

At this time, the value of the rotation angle Δφ ₂ of the signal beam rotation stage 115 is expressed by the following equation 31, which is different from equation 16 in the first embodiment.

At this time, the rotation angle Δθ ₂ of the recording medium goniostage 150 is expressed by the following equation 32.

Furthermore, at this time, (1) the movement amount Δy ₀ in the y-axis direction of the planar movement stage 140 for the recording medium is expressed by Equation 27-1, as in the first embodiment, while (2) the movement amount Δx ₀ in the x-axis direction is expressed by Equation 33 below.

In the manufacturing apparatus 10B of this embodiment, the information processing device 20 calculates Δφ ₂ , Δθ ₂ , Δx ₀ and Δy ₀ based on the above relationships, and based on the calculation results, adjusts the angles of the signal light rotation stage 115 and the recording medium goniostage 150 to Δφ ₂ and Δθ ₂ , and moves the recording medium planar movement stage 140 by Δx ₀ in the x-axis direction and Δy ₀ in the y-axis direction.

In this embodiment, the method for calculating the rotation angle _Δφ1 of the reference beam rotation stage 113 is the same as in the first embodiment, and is calculated based on the above formula 21. Also, in this embodiment, as in the first embodiment, (i) the movement amount _Δy3 of the cylindrical lens linear movement stage 120 is calculated based on formula 28, and (ii) the movement amounts _Δx4 and _Δy4 of the reference beam linear movement stage 121 are calculated based on formula 29. Then, as in the first embodiment, the information processing device 20 adjusts the angles and positions of the stages 113, 115, 120, 121, 140, and 150 in cooperation with the stage driving circuit 130 based on the calculation results.

When the adjustment of each stage 113, 115, 120, 121, 140, and 150 is completed by the above method, in the manufacturing apparatus 10B of this embodiment, the optical system is arranged, for example, as shown in Fig. 15, and the signal parallel light 118 and the cylindrical wave-like reference light 123 spreading from the line focus 127 are irradiated onto the recording medium 124 at a relative irradiation angle determined by this arrangement, and interference fringes generated by the interference of the two light beams 118 and 123 are exposed onto the recording medium 124. As a result, a holographic diffraction grating corresponding to one wavelength (for example, λ ₁ ) is formed on the recording medium 124.

[C.3] Operations during Manufacturing of Holographic Diffraction Grating HG in Manufacturing System 1B Next, the operations during manufacturing of holographic diffraction grating HG in manufacturing system 1B of this embodiment will be described. However, since manufacturing system 1B of this embodiment also manufactures holographic diffraction grating HG based on processes basically similar to those shown in Figures 7 and 8, the following description will focus on the differences between the processes executed in manufacturing system 1B of this embodiment and the first embodiment. However, since this embodiment employs a configuration in which goniostage 116 and height adjustment stage 126 are omitted as described above and their functions are replaced by recording medium goniostage 150, the references to goniostage 116 in Figures 7 and 8 should be read as recording medium goniostage 150.

First, in the manufacturing system 1B of this embodiment, the information processing device 20 sets λ to the shortest wavelength (e.g., 400 nm) in the visible light region, _λ1 , in step S1, in order to expose a holographic diffraction grating corresponding to one wavelength _λ1 in the visible light region onto the recording medium 124.

Next, the information processing device 20 determines the direction of the signal collimated light 118 according to equation 26 (step S2). Note that the processing of steps S1 and S2 is the same as in the first embodiment.

In particular, in this embodiment, unlike the first embodiment, the information processing device 20 calculates the rotation angle _Δφ2 of the signal beam rotation stage 115 and the rotation angle _Δθ2 of the recording medium goniostage 150 based on the above-mentioned equations 31 and 32 in step S3, and then supplies a control signal to the stage drive circuit 130 based on the calculated rotation angles _Δφ2 and _Δθ2 in step S4 to adjust the rotation angles of the signal beam rotation stage 115 and the recording medium goniostage 150 to the calculated rotation angles _Δφ2 and _Δθ2 , and then adjusts the angle of the reference beam rotation stage 113 by processing similar to that in the first embodiment (steps S5 and S6).

In this embodiment, the information processing device 20 calculates the movement amount _Δy3 of the cylindrical lens linear movement stage 120 and the movement amounts _Δx4 and _Δy4 of the reference light linear movement stage 121 in step S7, as in the first embodiment (step S7).

However, in this embodiment, unlike the first embodiment, the information processing device 20 is configured to execute processing to calculate the movement amount of the recording medium planar movement stage 140 in step S7 in addition to calculating the movement amounts of the linear movement stages 120 and 121. At this time, the information processing device 20 calculates the movement amount _Δy0 of the recording medium planar movement stage 140 in the y-axis direction based on the above equation 27-1, and calculates the movement amount _Δx0 of the recording medium planar movement stage 140 in the x-axis direction based on equation 33. Note that, since the manufacturing apparatus 10B of this embodiment is configured to omit the height adjustment stage 126, the information processing device 20 is configured to omit the processing to calculate the movement amount _Δz0 of the height adjustment stage 126 in step S7.

After calculating the values of _Δx0 , _Δy0 , _Δy3 , _Δx4 , and _Δy4 in this manner, in this embodiment, unlike the first embodiment, the information processing device 20 outputs a control signal to the stage driving circuit 130 in step S8 based on the movement amounts _Δx0 , _Δy0 , _Δy3 , _Δx4 , and _Δy4 calculated in step S7, and (1) moves the recording medium planar movement stage 140 in the x-axis direction by _Δx0 and in the y-axis direction by _Δy0 , and (2) moves the cylindrical lens linear movement stage 120 in the y-axis direction by _Δy3 , and (3) moves the reference beam linear movement stage 121 in the x-axis direction by _Δx4 and in the y-axis direction by _Δy4 , thereby adjusting the positions of the recording medium 124, the reference beam plane mirror 114, and the cylindrical lens system 122 to the corresponding positions. In the manufacturing apparatus 10B of this embodiment, the height adjustment stage 126 is omitted, and therefore the height of the height adjustment stage 126 is not adjusted in step S8.

Once the optical system of manufacturing apparatus 10B is in a state that matches the exposure of the holographic diffraction grating corresponding to wavelength _λ1 through the above procedure, information processing apparatus 20 outputs a control signal to light source 111 to irradiate source beam SB for a predetermined exposure time, thereby generating interference fringes corresponding to wavelength _λ1 and exposing recording medium 124 to the holographic diffraction grating corresponding to wavelength _λ1 (step S9).

Next, the information processing device 20 determines whether exposure of the holographic diffraction gratings corresponding to all interference fringes to be multiplexed on the recording medium 124 (i.e., holographic diffraction gratings corresponding to all wavelengths) is complete (step S10). If it determines that exposure is not complete (step S10: No), it sets λ _n = λ _n-1 + Δλ to change the wavelength to be exposed by Δλ (step S11), returns the process to step S2, and repeats steps S2 to S9 to expose a holographic diffraction grating corresponding to the next wavelength (e.g., λ ₁ + Δλ) on the recording medium 124.

Then, the information processing device 20 determines whether exposure of the holographic diffraction gratings corresponding to all wavelengths has been completed (step S10), and repeats the processing of steps S2 to S11 described above until exposure of the holographic diffraction gratings corresponding to all wavelengths has been completed, ending the processing once exposure of the holographic diffraction gratings corresponding to all wavelengths has been completed. Note that the operations in steps S9 to S11 described above are the same as in the first embodiment, so details will be omitted.

At this time, in the optical system of the manufacturing apparatus 10 of this embodiment, the positions and angles of the reference beam plane mirror 114, signal beam plane mirror 117, cylindrical lens system 122, and recording medium 124 are changed to match the wavelength of the holographic diffraction grating to be exposed, as shown in Figures 15 and 16, for example, and holographic diffraction gratings corresponding to this state (i.e., holographic diffraction gratings each having a different grating spacing and corresponding to a different wavelength) are sequentially exposed onto the recording medium 124, resulting in a holographic diffraction grating HG that achieves the desired function across the entire visible light range being exposed onto the recording medium 124.

With the above configuration, the manufacturing apparatus 10B of this embodiment achieves the functions of the goniostage 116 and height adjustment stage 126 using the recording medium goniostage 150 alone, while adjusting the relative irradiation angles of the signal collimated light 118 and the cylindrical wave-like reference light 123 spreading from the line focus 127 relative to the recording medium 124 using the recording medium goniostage 150, allowing for multiple exposure of multiple holographic diffraction gratings, each with different grating spacings, onto the recording medium 124. This simplifies the apparatus configuration and enables the low-cost manufacture of holographic diffraction gratings HG that can achieve the desired function across the entire visible light range.

In particular, assuming that adjustments will be made to the equipment when actually manufacturing the holographic diffraction grating HG, it is desirable for the laser light (i.e., signal light SL, signal collimated light 118, reference light RL, reference collimated light 119, etc.) to pass within the same plane as much as possible. For example, checking whether the laser light is traveling in a specified direction can be performed by first comparing the height from a reference position between two points separated by as much distance as possible. However, in a configuration such as the first embodiment, which combines the height adjustment stage 126 and goniostage 116 to adjust the irradiation angle of the signal collimated light 118 and cylindrical wave-like reference light 123 relative to the recording medium 124, the height in the z-axis direction through which the laser light passes changes, making it difficult to establish a reference position and potentially requiring severe adjustments. On the other hand, when the method of this embodiment is adopted, the center of the laser light always passes within the same plane, which facilitates adjustments when actually manufacturing the holographic diffraction grating HG.

Although the second embodiment described above employs a configuration in which the height adjustment stage 126 is omitted, it is also possible to provide the height adjustment stage 126 on the recording medium planar movement stage 140, and then provide the recording medium goniostage 150 on which the recording medium 124 is placed. In this case, the method for adjusting the height adjustment stage 126 is the same as in the first embodiment. A configuration may be adopted in which the movement amount _Δz0 of the height adjustment stage 126 is calculated in step S7 based on Equation 27-2, and the height of the height adjustment stage 126 is adjusted in step S8 based on the calculation result. In the method of the second embodiment described above, the angle of the signal collimated light 118 in the z-axis direction must be adjusted during initial setup, which can make the initial setup difficult. However, with this configuration, the angle of the signal collimated light 118 in the z-axis direction does not need to be adjusted during initial setup, which can simplify the setup of the device.

[D] Third embodiment In the manufacturing apparatus 10A of the first embodiment described above, the height adjustment stage 126 on which the recording medium 124 is placed is provided on a linear movement stage 125 for the recording medium, and this linear movement stage 125 for the recording medium moves the position of the recording medium 124 in a predetermined direction (for example, the y-axis direction), while the height adjustment stage 126 moves the recording medium 124 in the z-axis direction, thereby adopting a configuration in which the recording medium 124 can be moved in two axial directions in accordance with the three-dimensional irradiation angle of the signal parallel light 118.

In contrast, in this embodiment, the planar movement stage 140 for the recording medium used in the second embodiment is used instead of the linear movement stage 125 for the recording medium, and a height adjustment stage 126 on which the recording medium 124 is placed is provided on this planar movement stage 140 for the recording medium, thereby adopting a configuration in which the position of the recording medium 124 can be adjusted in the three axes of x, y, and z.

In this embodiment, the amount of movement Δy ₀ in the y-axis direction of the planar moving stage 140 for recording medium is expressed by the above formula 27-1, and the amount of movement Δx ₀ in the x-axis direction is expressed by the above formula 33, which is the same as in the second embodiment, and the amount of movement Δz ₀ in the z-axis direction of the height adjustment stage 126 is expressed by the above formula 27-2, which is the same as in the first embodiment.

7 and 8. In other words, in this embodiment, the information processing device 20 also executes the same processes as steps S1 to S6 in the first embodiment to adjust the angles of the signal beam rotary stage 115, the goniostage 116, and the reference beam rotary stage 113 to match the exposure of the holographic diffraction grating corresponding to _λ1 .

8, the information processing device 20 calculates (1) the movement amount of the linear movement stages 120 and 121, (2) the movement amount of the height adjustment stage 126, and (3) the movement amount of the recording medium planar movement stage 140. At this time, the information processing device 20 (a) calculates the movement amount _Δy0 of the recording medium planar movement stage 140 in the y-axis direction based on the above equation 27-1, (b) calculates the movement amount _Δx0 of the recording medium planar movement stage 140 in the x-axis direction based on equation 33, and (c) calculates the movement amount _Δz0 of the height adjustment stage 126 based on equation 27-2. At this time, the information processing device 20 also (d) calculates the movement amount _Δy3 of the cylindrical lens linear movement stage 120 based on equation 28, and (e) further calculates the movement amounts _Δx4 and _Δy4 of the reference beam linear movement stage 121 based on equation 29.

Having calculated the values of _Δx0 , Δy0, _Δz0 , _Δy3 , _{Δx4 , and Δy4 in} this manner, in step S8 the information processing device 20 of this embodiment outputs a control signal to the stage driving circuit 130 based on the movement amounts _Δx0 , _Δy0 , _Δy3 , _Δx4 , and _Δy4 calculated in step S7, to (1) move the recording medium planar movement stage 140 by _Δx0 in the x-axis direction and by _Δy0 in the y-axis direction, and (2) move the height adjustment stage 126 by _Δz0 . Also in step S8, the information processing device 20 (3) moves the cylindrical lens linear movement stage 120 by _Δy3 in the y-axis direction, and (4) moves the reference beam linear movement stage 121 by _Δx4 in the x-axis direction and _Δy4 in the y-axis direction, thereby adjusting the positions of the recording medium 124, the reference beam plane mirror 114, and the cylindrical lens system 122 to the corresponding positions.

When the optical system of the manufacturing apparatus 10 reaches a state matching the exposure of the holographic diffraction grating corresponding to the predetermined wavelength _λ1 by the above method, the information processing apparatus 20 outputs a control signal to the light source 111 to irradiate the source beam SB for a predetermined exposure time, thereby generating interference fringes corresponding to the wavelength _λ1 , and exposing the holographic diffraction grating corresponding to the wavelength _λ1 onto the recording medium 124 (step S9).

Then, the information processing device 20 determines whether exposure of the holographic diffraction gratings corresponding to all interference fringes to be multiple-exposed on the recording medium 124 has been completed (step S10). The information processing device 20 repeats the above steps S2 to S11 until exposure of the holographic diffraction gratings corresponding to all interference fringes (i.e., holographic diffraction gratings corresponding to all wavelengths) has been completed, and ends the process when exposure of the holographic diffraction gratings corresponding to all wavelengths has been completed. Note that the operations in the above steps S9 to S11 are the same as in the first embodiment, so details will be omitted.

At this time, in the optical system of the manufacturing apparatus 10 of this embodiment, the positions and angles of the reference beam plane mirror 114, signal beam plane mirror 117, cylindrical lens system 122, and recording medium 124 are changed to match the wavelength of the holographic diffraction grating to be exposed, and the holographic diffraction grating corresponding to this state is sequentially exposed onto the recording medium 124, resulting in a holographic diffraction grating HG that achieves the desired function across the entire visible light range being exposed onto the recording medium 124.

As described above, according to this embodiment, the position of the recording medium 124 can be adjusted in the three axes of x, y, and z. This makes it possible to adjust the position of the recording medium 124 with high precision according to the irradiation angle of the signal collimated light 118, thereby enabling the holographic diffraction grating HG to be manufactured with high precision.

1, 1A, 1B... Manufacturing system, 10, 10A, 10B... Manufacturing apparatus, 111... Light source, 112... Beam splitter, 113... Rotating stage for reference light, 114... Plane mirror for reference light, 115... Rotating stage for signal light, 116... Gonio stage, 117... Plane mirror for signal light, 118... Signal parallel light, 119... Reference parallel light, 120... Linear movement stage for cylindrical lens, 121... Linear movement stage for reference light, 122... Cylindrical lens, 123... Cylindrical wave-like reference light, 124... Recording Medium, 125...linear movement stage for recording medium, 126...height adjustment stage, 127...line focus, 130...stage drive circuit, 140...planar movement stage for recording medium, 150...goniostage for recording medium, 20...information processing device, SL...signal light, RL...reference light, 30...HMD, VL...image light, OL...external light, P...projector, HGLP...holographic light guide plate, HG...holographic diffraction grating, LE...light incident portion, L...lens, CL...cylindrical lens

Claims (9)

1. A holographic optical element manufacturing apparatus for manufacturing a holographic optical element by exposing a recording medium made of a photosensitive material having sensitivity to a predetermined wavelength range, comprising:
a light source that emits an exposure source beam of a single wavelength;
a beam splitter that splits the source beam into a signal beam and a reference beam;
a signal light irradiation means for irradiating the signal light onto the recording medium via a first optical path;
a reference light irradiating means for irradiating the recording medium with the reference light via a second optical path, thereby causing interference between the signal light irradiated by the signal light irradiating means and the reference light to generate interference fringes, and exposing the generated interference fringes to the recording medium;
and
The signal light irradiation means
a signal light irradiation angle adjusting means for three-dimensionally adjusting the irradiation angle of the signal light with respect to the recording medium, and changing the irradiation angle of the signal light with respect to the recording medium three-dimensionally by a predetermined value in accordance with the interval of the interference fringes to be generated;
The reference light irradiation means
(1) A reference beam irradiation angle adjusting means for adjusting the irradiation angle of the reference beam with respect to the recording medium is provided, and (2) a cylindrical lens having a curvature on one axis is provided, and after the reference beam is line-focused by the cylindrical lens, the irradiation angle of the reference beam spreading from the line focus with respect to the storage medium is adjusted in accordance with a change in the irradiation angle of the signal beam with respect to the recording medium, and the reference beam after the irradiation angle adjustment is irradiated onto the recording medium, and the relative irradiation angle of the reference beam with respect to the signal beam is changed , thereby forming a layer in which a plurality of layered interference fringes, each having a parabolic cylindrical shape with a different curvature , are three-dimensionally stacked. a holographic optical element manufacturing apparatus for manufacturing a holographic optical element, the apparatus comprising: a holographic optical element that, when irradiated with parallel light of a corresponding wavelength, diffracts the parallel light and produces a line focus; a holographic optical element that diffracts the parallel light and produces a line focus when irradiated with the parallel light of a corresponding wavelength ... of a corresponding wavelength and produces a line focus when irradiated with the parallel light of a corresponding wavelength; a holographic optical element that diffracts the parallel light of a corresponding wavelength and produces a line focus when irradiated with the parallel light of a corresponding wavelength; The holographic optical element manufacturing apparatus of claim 1, further comprising a recording medium position adjustment means for adjusting the position of the recording medium in accordance with the irradiation angle of the signal light adjusted by the signal light irradiation angle adjustment means. The recording medium position adjusting means
a linear moving means for moving the recording medium linearly in a predetermined direction;
a recording medium height adjusting means for moving the recording medium in a height direction;
Equipped with
The signal light irradiation angle adjustment means
3. The holographic optical element manufacturing apparatus according to claim 2, wherein the position of the recording medium is adjusted in accordance with the irradiation angle of the signal light adjusted by changing the irradiation angle of the signal light with respect to the recording medium in three dimensions. The recording medium position adjusting means
a recording medium plane moving means for moving the recording medium two-dimensionally within a predetermined plane;
a recording medium height adjusting means for moving the recording medium in a height direction;
Equipped with
The signal light irradiation angle adjustment means
3. The holographic optical element manufacturing apparatus according to claim 2, wherein the recording medium position adjustment means adjusts the position of the recording medium in accordance with the irradiation angle of the signal light adjusted by three-dimensionally changing the irradiation angle of the signal light with respect to the recording medium. The recording medium position adjusting means
a recording medium plane moving means for moving the recording medium two-dimensionally within a predetermined plane;
a recording medium tilt angle changing means for changing the tilt of the recording medium;
Equipped with
The signal light irradiation angle adjustment means
The irradiation angle of the signal light with respect to the recording medium is changed two-dimensionally, and
The reference beam irradiation angle adjusting means
adjusting an irradiation angle of the reference beam with respect to the recording medium in accordance with the adjusted irradiation angle of the signal beam;
The recording medium tilt angle changing means
3. The holographic optical element manufacturing apparatus according to claim 2, wherein the tilt of the recording medium is changed in accordance with the irradiation angles of the signal light and the reference light, thereby changing the relative irradiation angles of the signal light and the reference light with respect to the recording medium in three dimensions. The recording medium position adjusting means
6. The holographic optical element manufacturing apparatus according to claim 5, further comprising a recording medium height adjustment means for moving the recording medium in a height direction. A method for manufacturing a holographic optical element, comprising: irradiating a recording medium made of a photosensitive material having sensitivity to a predetermined wavelength region with signal light and reference light, each of which is generated by splitting a source beam of a single wavelength, along different optical paths, thereby causing the signal light and the reference light to interfere with each other, and exposing the recording medium to interference fringes generated by the interference, thereby manufacturing a holographic optical element, the method comprising:
The irradiation angle of the signal light with respect to the recording medium is changed three-dimensionally by a predetermined value increments according to the intervals of the generated interference fringes, and the reference light is line-focused by a cylindrical lens having a curvature on one axis. Then, the irradiation angle of the reference light spreading from the line focus with respect to the recording medium is adjusted in accordance with the change in the irradiation angle of the signal light with respect to the recording medium, and the reference light after the irradiation angle adjustment is irradiated onto the recording medium, thereby causing interference between the reference light and the signal light whose angle has been adjusted three-dimensionally , and a plurality of layered interference fringes each having a parabolic cylindrical shape with a different curvature are three-dimensionally stacked. a method for manufacturing a holographic optical element, the method comprising: generating a plurality of interference fringes exhibiting a layer structure while changing the spacing between the layers; multiplexing the plurality of interference fringes onto the recording medium to form a plurality of holographic diffraction gratings each having a different grating spacing and grating curved surface, the plurality of holographic diffraction gratings having a layer structure in which layers each having a different refractive index are stacked three-dimensionally; and having a different number of layers according to a corresponding wavelength, the method comprising manufacturing a holographic optical element that, when irradiated with parallel light of the corresponding wavelength, diffracts the parallel light and line-focuses the light. The holographic optical element manufacturing method described in claim 7, wherein the recording medium is moved three-dimensionally in accordance with the irradiation angle of the signal light adjusted by changing the irradiation angle of the signal light relative to the recording medium three-dimensionally, and the signal light is irradiated at a desired position on the recording medium. 9. The method for manufacturing a holographic optical element according to claim 8, wherein the relative irradiation angles of the signal beam and the reference beam with respect to the recording medium are changed three-dimensionally by changing the position and tilt of the recording medium according to the irradiation angle of the signal beam.