JP6637658B2 - Hologram display device - Google Patents

Description

  The present invention relates to a hologram display device.

  As a hologram display technique, a technique of displaying an interference fringe using a spatial light modulator (SLM) is known. In this case, the width of the viewing angle is approximately inversely proportional to the pixel pitch of the SLM as the display device. Therefore, in order to increase the viewing angle, it is necessary to reduce the pixel pitch of the SLM. The size of the screen to be displayed is proportional to the resolution (N × M) of the SLM. Therefore, in order to increase the screen size, it is necessary to increase the resolution of the SLM.

  The hologram display device requires a pixel pitch on the order of the wavelength of visible light (on the order of 1 μm) in order to display interference fringes. For example, in order to realize a screen size of 40 inches and a viewing angle of 30 degrees, when the wavelength of the reference light, the object light, and the illumination light for reproduction is 600 nm, an SLM having a pixel pitch of 1.2 μm and a resolution of 764000 × 430000 is required. Will be needed. However, since there is no ultra-high-definition SLM as described above, it is necessary to use a plurality of SLMs for realization, and it is difficult to put it to practical use at present.

In order to solve the above problem, a screen scanning hologram display device has been proposed. In the hologram display device, the modulated light from the SLM is reduced in the horizontal direction and enlarged in the vertical direction and projected on a display screen using an anamorphic optical system. In this way, by reducing in the horizontal direction, the apparent pixel pitch in the horizontal direction is reduced and the viewing angle in the horizontal direction is increased. Then, the modulated light projected on the display screen is scanned in the horizontal direction on the display screen to achieve a large screen and a wide viewing area in the horizontal direction (for example, see Patent Document 1).
[Patent Document 1] Japanese Patent Application Laid-Open No. 2010-8822

  In the conventional hologram display device, the viewing angle is about 15 degrees, and the viewing area is small.

  A hologram display device according to one embodiment of the present invention includes a spatial light modulator that receives a laser beam and modulates the laser beam based on hologram reproduction wavefront information, and forms an image by enlarging the modulated light modulated by the spatial light modulator. The modulated optical system is arranged on an image forming plane on which the modulated light is focused, and the modulated light is transmitted over time so that a visual field is formed in an entire circumferential area around the optical axis of the enlarged optical system. A deflecting optical system for deflecting by deflecting the deflection direction.

  The above summary of the present invention is not an exhaustive listing of all features of the present invention. Further, a sub-combination of these feature groups can also be an invention.

It is a lineblock diagram of a hologram display device in a 1st embodiment. FIG. 2 is an optical path diagram illustrating a configuration of an optical system according to the first embodiment. It is a figure explaining the difference of the observable area on the display screen in the conventional example and the observable area on the display screen in 1st Embodiment. FIG. 2 is an optical path diagram of an optical system of the hologram display device according to the first embodiment. It is a lineblock diagram of a hologram display device in a 2nd embodiment. It is an optical path diagram of the optical system of the hologram display device in the third embodiment. FIG. 7 is a flowchart illustrating a procedure for synchronizing rotation of a rotating screen and hologram display timing of a spatial light modulator. 3 is a photograph of a reproduced image obtained by a hologram display device as one example of the present invention.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all combinations of the features described in the embodiments are necessarily essential to the solution of the invention.

  FIG. 1 is a configuration diagram of the hologram display device according to the first embodiment. The hologram display device 100 according to the present embodiment includes a light source 102, a spatial light modulator 104, a projection lens 106, a single side band (SSB) filter 108, a rotating screen 110, a screen driving unit 120, and a control unit 130. In the following description, the side of the spatial light modulator 104 is the front side or the front side, and the side of the region 111 where the observer observes the reproduced image is the rear side along the rotation axis A indicated by the one-dot chain line. Or, it is called the back. For example, with respect to the projection lens 106, the side on which the spatial light modulator 104 is disposed is the front side or the front, and the side on which the rotating screen 110 is disposed is the rear side or the rear. In this embodiment, the optical axis of the projection lens 106 and the rotation axis A are the same.

  The light source 102 emits laser light that is coherent light. A semiconductor laser or the like is used for a light emitting unit of the light source 102. The light source 102 includes a collimator lens, and emits a beam emitted from the light emitting unit as parallel light. The spatial light modulator 104 is an electronic hologram display element that displays a hologram pattern. The light source 102 emits the coherent light to the spatial light modulator 104 as illumination light for reproducing a hologram. The spatial light modulator 104 emits modulated light obtained by modulating the intensity or phase of the laser light incident from the light source 102 according to the reproduction wavefront information of the hologram. Note that the reproduction wavefront information is information on a wavefront forming a reproduction image. The wavefront of the coherent light emitted from the light source 102 is modulated by a hologram pattern displayed on the spatial light modulator 104, and after passing through the SSB filter 108, is converted into the reproduction wavefront.

  The hologram pattern can be generated by actually photographing with an image sensor. Further, the hologram pattern can be generated by computer simulation. The spatial light modulator 104 uses, for example, a spatial light modulator (MEMS-SLM) using MEMS (Micro Electro Mechanical Systems) or a spatial light modulator (LCOS-SLM) using LCOS (Liquid Crystal on Silicon). be able to.

  The hologram display device 100 shown in FIG. 1 uses a MEMS-SLM as an example of the spatial light modulator 104. Since the MEMS-SLM is a reflection type display device, the MEMS-SLM irradiates coherent light from the light source 102 to the inclined micro mirror surface from an oblique direction. When a transmission type ferroelectric liquid crystal is used, coherent light is irradiated from the back side, and when a reflection type LCOS-SLM is used, coherent light is irradiated from a position directly opposite the display surface. .

  The screen drive unit 120 rotates the rotating screen 110 around the rotation axis A in one direction. The screen drive unit 120 includes a motor 122, a rotation transmitting member 124, and a rotary encoder 126.

  The motor 122 rotates the rotary screen 110 around a rotation axis A that coincides with the optical axis of the projection lens 106 via the rotation transmission member 124. The rotation transmitting member 124 transmits the rotational force of the motor 122 to the rotating screen 110. As shown in FIG. 1, the rotation transmitting member 124 is, for example, a disk in which the rotation axis of the motor 122 and the center axis are aligned. The rotational force of the motor 122 is transmitted to the rotating screen 110 by pressing the cylindrical surface of the rotation transmitting member 124 against the circumferential surface of the rotating screen 110. Further, the rotation transmitting member 124 may be a gear. In this case, the rotation of the motor 122 may be transmitted to the rotation screen 110 by providing a tooth shape on the circumference of the rotation screen 110 and engaging with the rotation transmission member 124. The rotary encoder 126 detects the rotation of the motor 122 and transmits a pulse signal indicating the displacement of the rotation to the control unit 130.

  The control unit 130 mainly controls the operation of the light source 102, the spatial light modulator 104, and the motor 122. The control unit 130 includes a CPU 132 and an operation panel 134. In the present embodiment, the operation panel 134 is provided so that the user can operate near the hologram display device 100. However, the present invention is not limited to this. For example, another terminal device using a wired technology or a wireless technology is used. It may be configured to give an operation instruction from.

  The CPU 132 executes display control of the hologram display device 100 according to a hologram pattern to be displayed and an operation timing condition specified via the operation panel 134. The operation panel 134 is a display device including an input unit such as a touch panel, and receives input from an operator and displays menu items and the like. In the present embodiment, the control unit 130 functions as a control unit.

  The control unit 130 causes the spatial light modulator 104 to display a hologram pattern based on the reproduced wavefront information. The control unit 130 synchronizes the generation of the hologram pattern with the deflection direction of the screen lens 107 which changes with time according to the rotation of the motor 122. More specifically, the control unit 130 receives a pulse signal from the rotary encoder 126, and controls a hologram pattern to be displayed on the spatial light modulator 104 and a display timing of the hologram pattern according to the pulse signal. I do.

  The projection lens 106 is arranged behind the spatial light modulator 104. The projection lens 106 is a magnifying optical system that magnifies the modulated light emitted from the spatial light modulator 104 on a rotating screen 110 disposed behind and forms an image.

  The SSB filter 108 is disposed between the projection lens 106 and the rotating screen 110. More specifically, the SSB filter 108 is disposed on the rear focal plane of the projection lens 106, that is, on the Fourier plane. The SSB filter 108 removes a zero-order light and a conjugate image unnecessary for displaying a spatial hologram image.

  The rotating screen 110 is arranged on the image plane of the modulated light by the projection lens 106 and functions as a display screen for displaying a reproduced image. Further, the rotating screen 110 deflects the incident modulated light toward the observer who observes the reproduced image from a position shifted from the rotation axis A. In the present embodiment, the rotating screen 110 includes a screen lens 107 having a positive refractive power. The rotating screen 110 is preferably arranged such that the image plane of the modulated light by the projection lens 106 substantially coincides with the main plane on the front side of the screen lens 107. In the present embodiment, the rotating screen 110 and the screen driving unit 120 function as a deflection optical system.

  As the screen lens 107, for example, an eccentric lens in which the optical axis OAs is eccentrically arranged with respect to the rotation axis A, an HOE (Holographic Optical Element), or the like can be used. As the eccentric lens, a spherical lens, an aspherical lens, a Fresnel lens, a DOE (Diffractive Optical Element) lens, or the like can be used. In the present embodiment, an eccentric spherical lens is used for the screen lens 107. The screen lens 107 deflects the incident modulated light in the eccentric direction of the optical axis OAs of the screen lens 107 with respect to the rotation axis A. The screen lens 107 is manufactured such that the outer circumference is a circle having a predetermined radius around the rotation axis A. The predetermined radius is, for example, 100 mm.

  The rotating screen 110 rotates around a rotation axis A that coincides with the optical axis of the projection lens 106. As a result, the rotating screen 110 deflects the incoming modulated light by changing the direction of deflection with time, thereby forming a viewing zone in the entire annular area around the optical axis of the projection lens 106.

  The rotating screen 110 in the present embodiment has a rotationally symmetric shape and rotates only in one direction. For this reason, even if the diameter is relatively large, it is easy to realize stable rotational scanning. That is, in the hologram display device 100 according to the present embodiment, it is relatively easy to enlarge the display screen of the reproduced image. In the following description, a plane orthogonal to the rotation axis A of the rotating screen 110 may be referred to as a scanning plane. A direction parallel to the scanning surface may be referred to as a horizontal direction, and a direction perpendicular to the scanning surface may be referred to as a vertical direction.

  Each light flux of the modulated light emitted from each point on the spatial light modulator 104 is once formed on the rotating screen 110 by the projection lens 106. Thereafter, these light beams overlap at a position separated by a distance L at which the reproduced image can be observed relatively large, and form a three-dimensionally closed, that is, localized, visual field. The region 111 is a region that is one section of the visual field localized at a position separated by a distance L from the rotating screen 110 along the rotation axis A.

  In the present embodiment, the modulated light emitted from the spatial light modulator 104 is enlarged and formed on the rotating screen 110 by the projection lens 106. That is, since the apparent pixel pitch on the rotating screen 110 is enlarged, the viewing angle is reduced. However, the hologram display device 100 changes the localization position of the visual field over time along the rotational scanning direction SD by rotating the rotating screen 110 around the rotation axis A. Thereby, as shown by the enlarged region 114, the viewing area of the hologram display device 100 is substantially enlarged to 360 degrees around the rotation axis A.

  Further, the control unit 130 synchronizes the generation of the hologram pattern with the rotation angle of the rotating screen 110 in order to generate a reproduced image that does not cause a sense of incongruity according to the observation position. As a specific synchronization method, a hologram pattern may be generated according to the rotation angle of the rotating screen 110. By synchronizing the rotation angle of the rotating screen 110 and the display of the hologram pattern, the observer can observe a reproduced image without any uncomfortable feeling according to the observation angle from an arbitrary position on the enlarged area 114.

  FIG. 2 is an optical path diagram illustrating the configuration of the optical system according to the first embodiment. FIG. 2 will be described first as a coaxial optical system in which the projection lens 106 and the screen lens 107a have a common optical axis OA in order to simplify the description. FIG. 2 shows modulated lights MLu and MLl emitted from both ends of the spatial light modulator 104 among the modulated lights emitted from each point on the spatial light modulator 104, and the propagation directions thereof are indicated by dotted lines. The same members as those shown in FIG. 1 are denoted by the same reference numerals, and overlapping description will be omitted.

  The projection lens 106 is arranged behind the spatial light modulator 104. As shown by the modulated lights MLu and MLl, the modulated light emitted from the spatial light modulator 104 has a spread angle corresponding to the pixel pitch of the spatial light modulator 104. As shown in FIG. 2, the propagation direction of the modulated light is substantially parallel to the optical axis OA. The projection lens 106 emits the modulated lights MLu and MLl incident from the spatial light modulator 104 toward the rear focal position F '.

  The modulated light beams MLu and MLl emitted from the projection lens 106 have zero-order light and a conjugate image removed by the SSB filter 108 disposed on the Fourier plane of the projection lens 106, and are once formed on the screen lens 107a.

  As represented by the modulated lights MLu and MLl, the luminous flux of each modulated light emitted from each point on the spatial light modulator 104 is a predetermined light beam orthogonal to the optical axis OA via the screen lens 107a. In the area on the surface, substantially all overlap each other to form a localized viewing area 112a (hatched area), which is a three-dimensionally closed viewing area.

  The SSB filter 108 and the region 111a have an optically conjugate relationship with the screen lens 107a. The screen lens 107a functions as a so-called field lens that guides the incident modulated light to an area 111a on a predetermined surface.

  The region 111a on the predetermined surface is set at a position where the observer can easily observe the reproduced image. Note that, depending on the residual aberration of the projection lens 106 and the screen lens 107a, the positions where the respective luminous fluxes of the modulated light emitted from the screen lens 107a overlap may differ depending on the image height. It is sufficient that they substantially overlap.

  Considering that the reconstructed wavefront of the hologram enters the human eye through the pupil, the size of the region 111a can be reduced to about the size of the pupil. The pupil diameter of a human varies depending on the brightness of the surrounding environment, and is said to be 2 to 8 mm on average. Thus, in the present embodiment, substantial wavefront reproduction can be realized by the region 111a having a size that includes a circle having a diameter of 2 mm or more.

  As shown in FIG. 2, the localized visual field 112a gradually expands from EP1, which is closer to the screen lens 107a, and gradually narrows through the region 111a to reach EP2, which is farther from the screen lens 107a. It is represented as a closed space area. The observer can observe the entire reproduced image formed in the vicinity of the rotating screen 110a, which is a display screen, at least in the localized visual field 112a.

  FIG. 3 is a diagram for explaining the difference between the observable area on the display screen in the conventional example and the observable area on the display screen in the first embodiment. In particular, FIG. 3 is a diagram showing a cross section in a plane orthogonal to the display screen. In FIG. 3B, the display screen can be regarded as a main plane on the rear side of the screen lens 107.

  FIG. 3A is a diagram illustrating a visible region on a display screen of a hologram display device in a conventional example. FIG. 3A shows modulated lights MLu and MLl emitted from both ends of the display screen 410 among modulated lights emitted from respective points on the display screen 410, and the propagation directions thereof are indicated by alternate long and short dash lines.

  In the hologram display device in the conventional example, the propagation directions of the modulated lights emitted from the respective points on the display screen 410 at the viewing angle α are parallel to each other as shown by the modulated lights MLu and MLl. Therefore, in FIG. 3A, the observer can observe only a partial area of the display screen 410 as shown in the observable area OBA1. Note that the width of the observable area OBA1 is d + Lα, where L is the distance from the display screen 410 to the pupil of the observation eye E, and d is the pupil diameter of the observation eye E.

  FIG. 3B is a diagram illustrating a visible region on the display screen of the hologram display device according to the present embodiment. For the sake of simplicity, the description will be made as a coaxial optical system similar to that of FIG. In FIG. 3B, of the modulated light emitted from each point on the rotating screen 110a, modulated light MLu and MLl emitted from both ends of the rotating screen 110a are shown, and the propagation directions thereof are indicated by dashed lines.

  In FIG. 3B, the modulated lights MLu and MLl are directed at a viewing zone angle β toward the pupil of the observation eye E of the observer located at a distance L from each point on the rotating screen 110 a as the display screen. Is emitted. Then, as shown by the modulated lights MLu and MLl, the luminous fluxes of the respective modulated lights emitted from the rotating screen 110a substantially completely overlap each other in the region 111a, and a localized visual field is formed. To form Therefore, in FIG. 3B, the observer can observe the entire reproduced image formed near the rotary screen 110a as shown in the observable area OBA2.

  In the conventional hologram display device, the propagation directions of the modulated lights emitted from the display screen are parallel to each other and the viewing angles are the same, so that there is substantially no region where all the light beams of the respective modulated lights overlap. . That is, the conventional hologram display device does not localize the viewing zone. On the other hand, in the hologram display device according to the present embodiment, substantially all of the light beams of the respective modulated lights are overlapped in the region 111a by the configuration of the projection lens 106 and the rotating screen 110a as shown in FIG. This localizes the viewing zone. As described above, the hologram display device according to the present embodiment can observe the entire reproduced image at a position closer to the display screen as compared with the conventional hologram display device by localizing the viewing zone. .

  FIG. 4 is an optical path diagram of an optical system of the hologram display device according to the first embodiment. The same members as those shown in FIGS. 1 and 2 are denoted by the same reference numerals, and overlapping description will be omitted.

  In FIG. 4, the optical axis OAs of the screen lens 107 is parallel eccentric by a distance R in a direction orthogonal to the rotation axis A. The reproduced light imaged on the screen lens 107 is deflected in the screen lens 107 toward an area 111 that is in an optically conjugate relationship with the SSB filter 108, and substantially overlaps and a localized visual field 112. To form In FIG. 2, the coaxial optical system has been described. However, by using an eccentric lens for the screen lens 107, the screen lens 107 is localized in the direction from the rotation axis A (the optical axis OA in FIG. 2) to the optical axis OAs of the screen lens 107. The visualized area can be displaced.

  If the distance of the region 111 from the rotation axis A is D, and the paraxial image magnification of the screen lens 107 is Ms, the relationship of D = Ms × R is satisfied. As the rotating screen 110 rotates about the rotation axis A, the localized viewing area 112 is displaced with time, and an annular viewing area having a radius D around the rotation axis A is formed. Therefore, the observer can observe the reproduced image from the direction of 360 degrees around the rotation axis A reproduced in the vicinity of the rotating screen 110.

  FIG. 5 is a configuration diagram of the hologram display device according to the second embodiment. The hologram display device 200 according to the second embodiment has a diffusion plate 212 in addition to the members constituting the hologram display device 100 according to the first embodiment. The same members as those shown in FIG. 1 are denoted by the same reference numerals, and overlapping description will be omitted.

  The rotating screen 210 according to the present embodiment includes a screen lens 107 having a positive refractive power and a diffusion plate 212. The diffusion plate 212 is provided on the surface of the screen lens 107, and diffuses the modulated light in a plane direction determined by the rotation axis A and the direction in which the modulated light is deflected. In other words, the diffusion plate 212 diffuses the modulated light in a fan-shaped manner with the emission position as the center in a plane including the rotation axis A and the optical axis OAs of the screen lens 107. Further, the diffusion plate 212 rotates integrally with the screen lens 107. Therefore, even if the rotating screen 210 rotates around the rotation axis A, the diffusion plate 212 always diffuses the modulated light in the vertical direction. Therefore, a wide viewing area is formed in the vertical direction, and a reproduced image reproduced in the vicinity of the rotating screen 210 from various heights can be favorably observed.

  As the diffusion plate 212, a lenticular lens, a holographic diffuser, or the like including a large number of cylindrical lenses can be used. In the present embodiment, a lenticular lens is used for the diffusion plate 212. At this time, the lenticular lens is arranged such that one of the two orthogonal axes of the cylindrical lens having no curvature is orthogonal to the plane including the rotation axis A and the optical axis OAs of the screen lens 107. By arranging the lenticular lens in this manner, the modulated light can be diffused in a fan shape centered on the emission position in a plane including the rotation axis A and the optical axis OAs of the screen lens 107.

  Further, even with a holographic diffuser having similar diffusion characteristics, the viewing zone can be expanded in the vertical direction.

  The region 211 indicates a region that is one cross section of the localized visual field. As indicated by the region 211, the localized viewing zone is expanded by the diffusion action of the diffusion plate 212. In addition, the rotational scanning of the rotating screen 210 substantially enlarges the viewing area in the rotational scanning direction as shown in the enlarged area 214. The observer can observe the entire reproduced image formed in the vicinity of the rotating screen 210 as a display screen from an arbitrary position on the enlarged area 214.

  FIG. 6 is an optical path diagram of an optical system of the hologram display device according to the third embodiment. The same members as those shown in FIG. 1 are denoted by the same reference numerals, and overlapping description will be omitted.

  In the present embodiment, a screen mirror 307 is used as the rotating screen 310. The screen mirror 307 is an eccentric concave mirror in which the central axis CA is eccentric with respect to the rotation axis A. The screen mirror 307 is arranged on the image plane of the modulated light by the projection lens 106. The screen mirror 307 forms a localized viewing zone 312 at a position away from the rotation axis A on the side where the projection lens 106 is disposed.

  An elliptical mirror can be used for the screen mirror 307. The screen mirror 307 is arranged such that the SSB filter 108 and the region 311 have an optically conjugate relationship with respect to the screen mirror 307. That is, in FIG. 6, when the SSB filter 108 is disposed at the first focal point Fm1 of the screen mirror 307, the region 311 is formed at the second focal point Fm2. By rotating the rotating screen 310 around the rotation axis A, an annular viewing zone is formed around the rotation axis A, as in the first embodiment and the second embodiment.

  Note that a diffusing plate may be provided on the surface of the screen mirror 307 to diffuse the modulated light in a plane direction determined by the rotation axis A and the direction of deflection of the modulated light. Thereby, the visual field in the vertical direction can be enlarged. As in the second embodiment, a lenticular lens, a holographic diffuser, or the like can be used as the diffusion plate.

  In the present embodiment, the screen mirror 307 is used as the reflection-type rotating screen, but it may be configured by combining a lens and a mirror. Further, an eccentric lens or a diffusion plate having a reflection surface formed by depositing silver or aluminum on one optical surface may be used. In this case, the rotating screen may be rotated by a motor through a shaft attached to a rotating shaft on the opposite side of the screen.

  FIG. 7 is a flowchart illustrating a procedure for synchronizing the rotation of the rotating screen and the hologram display timing of the spatial light modulator. In the description of this flow, the hologram display device 100 according to the first embodiment will be described. This flow is started, for example, when the CPU 132 receives a hologram display command from the user via the operation panel 134.

  Upon receiving a hologram display command from the user, the CPU 132 starts rotating the rotating screen 110 (step S101). Specifically, the rotating screen 110 is rotated by driving the motor 122. The CPU 132 monitors a change in the rotation speed of the motor 122 from an output signal indicating the rotation speed of the motor 122 received from the rotary encoder 126. Then, the CPU 132 waits until the rotation speed of the motor 122 reaches a predetermined rotation speed and the rotation operation is stabilized. Here, the predetermined number of rotations is determined from a predetermined frame rate for displaying a stereoscopic image.

  In the hologram display device 100 according to the present embodiment, one three-dimensional image is generated every time the rotating screen 110 makes one rotation. Therefore, assuming that the display frame rate of the stereoscopic image is f (Hz), the number of rotations of the rotating screen 110 is 60 f (rpm). In the present embodiment, if the radius of the rotation transmitting member 124 is r1, the radius of the rotating screen 110 is r2, the number of rotations of the rotating screen 110 is m, and the number of rotations of the motor 122 is n, n = (r2 / r1) × m It has the relationship The CPU 132 calculates the rotation speed n of the motor 122 from the relational expression. In addition, the display frame rate f of the predetermined stereoscopic image is, for example, 30 Hz.

  When receiving a hologram display command from the user, the CPU 132 starts displaying light from the light source 102 and displaying a hologram pattern of the spatial light modulator 104.

  When determining that the operation of the motor 122 is stabilized, the CPU 132 detects the rotation angle of the rotating screen 110 from the output signal from the rotary encoder 126 (Step S102). The rotation angle is a rotation angle of the direction of deflection of the viewing zone by the screen lens 107 from a predetermined reference direction. The predetermined reference azimuth is, for example, an azimuth in which a reproduced image in front of a three-dimensional image to be reproduced can be observed.

  Next, the CPU 132 switches the hologram pattern display to be displayed on the spatial light modulator 104 in order to project a corresponding reproduced image on the rotating screen 110 according to the detected rotation angle of the rotating screen 110 (step S103). . Specifically, when the rotation angle is 0 degrees, the timing of displaying the hologram pattern of the spatial light modulator 104 is controlled so that the observation image from the front of the stereoscopic image to be reproduced is always displayed. By performing such control, the attitude of the three-dimensional image can always be kept constant. In other words, the modulated light for reproducing the image on the right side of the stereoscopic image is always projected on the rotating screen 110 for the observation position on the right side of the reproduced stereoscopic image, and the stereoscopic image is always projected for the observation position on the back side. The modulated light for reproducing the image on the back of the projector is projected on the rotating screen 110.

  Further, if the display frame rate of the hologram pattern of the spatial light modulator 104 is fh, it is fh / f hologram patterns during one rotation of the rotating screen 110, based on the relationship with the display frame rate f of the three-dimensional image described above. Is displayed. For example, assuming that the display frame rate fh of the hologram pattern of the spatial light modulator 104 is 30 kHz and the display frame rate f of the stereoscopic image is 30 Hz, 1000 hologram patterns are applied to the spatial light modulator while the rotating screen 110 rotates once. Displayed at 104.

  The screen lens 107 forms an area 111 which is a projection image of the aperture at a position conjugate with the aperture of the fixed SSB filter 108. Since the SSB filter 108 has a rectangular opening, the region 111 formed by the screen lens 107 has a rectangular shape. Further, since the SSB filter 108 is fixed, the region 111 formed in a direction orthogonal to the long side of the rectangular opening is formed such that the long side is parallel to the direction of the rotational scanning. On the other hand, the region 111 formed in a direction orthogonal to the short side of the rectangular opening is formed such that the short side is parallel to the direction of the rotational scanning.

  Thus, the product of the length of the short side of the region 111 and the number of hologram patterns displayed during one rotation of the rotating screen 110 is set to be larger than the length of the scanning circumference. Accordingly, the regions 111 formed for each hologram pattern overlap each other, and a continuous viewing area is formed on the scanning circumference.

  The CPU 132 determines whether or not there has been a termination instruction from the user (step S104). If there is no end instruction from the user (NO in step S104), the process proceeds to step S102 to continue the synchronous control of the rotation of the rotating screen 110 and the display timing of the hologram pattern displayed on the spatial light modulator 104.

  If there is a termination instruction from the user (YES in step S104), CPU 132 stops the light emission of light source 102 and the display of the hologram pattern of spatial light modulator 104. Further, the CPU 132 stops driving the motor 122, stops rotation of the rotating screen 110, and ends all operations of the hologram display device 100.

FIG. 8 is a photograph of a reproduced image obtained by the hologram display device as one embodiment of the present invention. In the hologram display device of this embodiment, a DMD (Digital Micromirror Device: Discovery ^™ 4100 manufactured by Texas Instruments), which is a MEMS-SLM, was used as the spatial light modulator. The spatial light modulator has a resolution of 1024 × 768 and a pixel pitch of 13.68 μm. The frame rate is 22.727 kHz. In addition, a semiconductor laser having an oscillation wavelength of 635 nm was used as a light source of illumination light for image reproduction.

Projection lens, the magnification _{M p} was 5.71. Therefore, the pixel pitch on the screen lens is expanded to 78.1 μm. The size of the display screen on the screen lens is enlarged to 80 × 60 mm ² (3.94 inches diagonally).

  The rotating screen of this embodiment is a reflection type screen. An off-axis Fresnel lens was used as the screen lens. The screen lens has a diameter of 100 mm, and the eccentricity of the optical axis, that is, the distance between the rotation axis and the optical axis is 172 mm.

  As a vertical diffusion plate, a lenticular lens having an aluminum coating on the plane side was used, and the cylindrical surface was arranged close to the rear of the Fresnel lens with the Fresnel lens side. The focal length of the Fresnel lens was 700 mm. The modulated light transmitted through the Fresnel lens is reflected by the aluminum coating applied to the plane side of the lenticular lens, and passes twice through the Fresnel lens. Therefore, the effective focal length of the screen lens is 350 mm.

  A shaft was attached to the back side of the reflection surface of the rotating screen so that the rotation axis of the rotating screen substantially coincided with the axis. Then, the rotating screen was rotated via the shaft using a servomotor. In addition, a rotary encoder was used to acquire a display hologram update signal to be transmitted to the DMD. The rotary encoder generates 800 pulses per rotation of the rotating screen in order to set the frame rate of stereoscopic display to approximately 30 Hz.

  The rotation speed of the servomotor was set to 1704 rpm, and the frame rate for stereoscopic display was set to 28.4 Hz. Therefore, the number of hologram patterns generated during one rotation of the rotating screen is 800.

  FIGS. 8A and 8B are photographs of reconstructed images of different objects taken from different angles. Specifically, FIG. 8A shows a ring (a height 70 mm from the screen), a character “TUAT” (a height 90 mm from the screen), and “3D”, each having a different height from the screen. Is a photograph of a reproduced image of a symbol composed of characters (height from the screen: 110 mm) taken from four directions of different angles: 0, 90, 180, and 270 degrees. FIG. 8B is a photograph of a reproduced image of the airplane taken from four directions of different angles of 0 °, 90 °, 180 °, and 270 °.

  The direction of the reproduced stereoscopic image changed according to the observation position. The three-dimensional images of the symbols are formed from objects of different heights, and the relative positions of the respective objects have changed according to the observation position. Since the relative distance between the ring, “3D” and “TUAT” changes according to the observation angle, it can be seen that the object is stereoscopically viewed. In addition, the reproduced image had smooth motion parallax. Multiple observers were able to observe stereoscopic images reproduced simultaneously from different directions around the rotating screen.

  The hologram display device described above includes, for example, (1) watching sports from a 360-degree favorite direction, (2) highly reliable Internet shopping, (3) a conference surrounding images, (4) medical images, and simulation. As a result, it can be used for visualizing design drawings. Further, since different videos can be displayed depending on the observation position, it is possible to display different video contents for each user.

  In the above description, each of the projection lens 106 and the screen lens 107 is described as a single convex lens. However, the projection lens 106 and the screen lens 107 may be composed of a plurality of lenses from the viewpoint of aberration correction.

  In the above description, the screen lens 107 and the screen mirror 307 have a positive refractive power, but may have a negative refractive power.

  In the above description, an elliptical mirror is used as the screen mirror 307, but the shape is not limited to an elliptical surface. For example, a spherical surface, a paraboloid, or a hyperboloid may be used. Further, it may be a free-form surface.

  In the above description, the screen lens 107 and the screen mirror 307 have been described as being arranged on the image forming plane on which the modulated light is formed by the projection lens 106. However, the screen lens 107 and the screen mirror 307 do not need to partially or entirely coincide with the image plane of the modulated light by the projection lens 106, and are disposed substantially near the image plane. It should just be.

  The residual aberration of the projection lens 106, the screen lens 107, and the screen mirror 307, for example, distortion may be compensated by changing the hologram pattern displayed on the spatial light modulator 104.

  In the above description, the diffusion plate 212 has been described as being disposed on the surface of the screen lens 107 and the screen mirror 307. However, the diffusion plate 212 does not need to partially or entirely coincide with the screen lens 107 and the screen mirror 307, and may be disposed substantially near the screen lens 107 and the screen mirror 307. .

  In the above description, an example in which the rotating screen 110 is rotated by the motor 122 via the rotation transmitting member 124 has been introduced. However, when a reflection type screen such as the screen mirror 307 is used, the motor 122 is installed on the back side of the rotating screen so that the rotating axis A and the rotating axis of the motor 122 coincide with each other. Alternatively, the rotating screen may be rotated.

  In the above description, an example in which an ellipsoidal mirror is used as the reflective rotary screen has been introduced, but a MEMS mirror array may be used. In this case, without turning the screen, the reflecting surface of the micromirror constituting the MEMS mirror array can be deflected with time to displace the position of the localized visual field with time. The deflection optical system can be configured without including the screen drive unit 120.

  In the above description, the rotary encoder 126 detects the rotation angle and the number of rotations of the motor 122 with the slit disk attached to the rotation shaft of the motor 122. However, as another configuration, the rotary encoder 126 may provide a slit disc on the holding frame of the screen lens 107 and directly detect the rotation angle and the rotation speed of the rotating screen 110.

  In the above description, as a method of synchronizing the generation of the hologram pattern and the rotation angle of the rotating screen 110 in order to generate a reproduced image without a sense of incongruity according to the observation position, Generated pattern. However, the rotation angle of the rotating screen 110 may be controlled in synchronization with the timing of generating a hologram pattern by the spatial light modulator 104.

  In the above description, the configuration in which the central axis of the spatial light modulator 104 substantially coincides with the optical axis of the projection lens 106 has been described, but the optical axis of the projection lens 106 is deviated from the central axis of the spatial light modulator 104. You may care. Further, the optical axis of the projection lens 106 may be eccentric with respect to the rotation axis of the rotating screen. Also in this case, the modulated light emitted from the spatial light modulator 104 is formed into an enlarged image on the rotating screen 110 disposed behind.

  In the above description, since only one light source is used in the hologram display device, a single color display is performed. By using an RGB light source in the hologram display device, color display can be realized in a time-division manner. Alternatively, color display can be realized by using three hologram display devices and using each light source as an RGB light source.

  As described above, the present invention has been described using the embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. It is apparent to those skilled in the art that various changes or improvements can be made to the above embodiment. It is apparent from the description of the appended claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.

100, 200 hologram display device, 102 light source, 104 spatial light modulator, 106 projection lens, 107, 107a screen lens, 108 SSB filter, 110, 110a, 210, 310 rotating screen, 111, 111a, 211, 311 area, 112 , 112a, 312 localized viewing zone, 114, 214 enlarged area, 120 screen drive unit, 122 motor, 124 rotation transmitting member, 126 rotary encoder, 130 control unit, 132 CPU, 134 operation panel, 212 diffuser , 307 screen mirror, 410 display screen

Claims (10)

A spatial light modulator that injects laser light and modulates the laser light based on reproduction wavefront information of a hologram;
Magnifying optical system for magnifying the modulated light modulated by the spatial light modulator to form an image,
The modulated light is deflected with time so that the modulated light is arranged on an image plane on which the modulated light is focused, and a visual field is formed in an entire circumferential area around the optical axis of the magnifying optical system. A deflection optical system for changing the direction and deflecting the light,
A hologram display device, comprising: a filter disposed on a focal plane of the magnifying optical system on the side of the deflection optical system , the filter configured to cut a zero-order light of the modulated light and a conjugate image.   The hologram display device according to claim 1, wherein the deflection optical system includes an eccentric lens rotated around the optical axis.   The hologram display device according to claim 2, wherein a diffusion plate that diffuses the modulated light in a plane direction determined by the optical axis and the deflection direction is provided on a surface of the eccentric lens.   The hologram display device according to claim 1, wherein the deflection optical system includes an eccentric concave mirror rotated around the optical axis.   The hologram display device according to claim 4, wherein a diffusion plate for diffusing the modulated light in a surface direction determined by the optical axis and the deflection direction is provided on a surface of the eccentric concave mirror.   The hologram display device according to claim 3, wherein the diffusion plate is configured by a lenticular lens.   The hologram display device according to claim 3, wherein the diffusion plate includes a holographic diffuser.   The hologram display device according to claim 1, wherein the spatial light modulator is a MEMS spatial light modulator. A control unit that displays a pattern based on the reproduced wavefront information on the MEMS spatial light modulator,
The hologram display device according to claim 8, wherein the control unit synchronizes the generation of the pattern with the deflection direction.   The hologram display device according to any one of claims 1 to 9, wherein the viewing zone has a size including at least a circle having a diameter of 2 mm or more.