JP3391044B2 - Hologram manufacturing method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram manufacturing method for recording a hologram by multiple exposure. 2. Description of the Related Art When manufacturing a full-color hologram that emits reproduction light of a plurality of colors, a reference light of one wavelength is incident on one hologram recording material a plurality of times at different incident angles. A method for performing multiple exposures is known. In this method, since only one wavelength of reference light (one type of laser light) is used, multiple exposure can be performed with a small number of optical components. Since the wavelength has a great influence, there is a case where reproduction light of a desired wavelength (color) cannot be obtained, and there is a problem in maintaining quality when industrially producing a hologram. Therefore, three laser beams of red (R), green (G), and blue (B) are used to refer to three wavelengths (R, G, B) for one hologram recording material. A method of sequentially exposing light at different incident angles to perform multiple exposure has been developed, and for example, production of a hologram for a head-up display has been attempted by the multiple exposure. The hologram for a head-up display is used to reflect a color image radiated from a display unit with a hologram and project the image in front of a windshield, but enlarges the color image. There is a case where a concave mirror is recorded on a hologram in order to display it. In order to record the concave mirror on the hologram, the concave mirror is brought into close contact with the back side of the hologram recording material (the side opposite to the side on which the reference light of laser light is incident), and the laser light transmitted through the recording material is reflected by the concave mirror. There is a method in which light is reflected and re-incident on a recording material as object light for exposure. However, a concave mirror is closely attached to the back surface of such a hologram recording material, and three laser beams of red (R), green (G), and blue (B) are referred to. In the case where a so-called full-color Lippmann hologram in which light is sequentially incident from the surface side of the recording material at different incident angles to perform multiple exposure is manufactured, each of the R, G, and B reference lights is recorded at a different incident angle. , The reflection position of the concave mirror is also shifted by each reference light. For this reason, when a reproduction light (display light of a color image) is applied to the hologram when the hologram is used, and the reproduction light is selectively reflected to display a color image, there is a problem that a color shift occurs in the image. The present invention has been made in view of the above points, and has an optical reflection element adhered to the back surface of a hologram recording material, and a plurality of reference lights having different wavelengths are sequentially incident at different incident angles. It is an object of the present invention to provide a hologram manufacturing method capable of recording a hologram without causing a color shift in manufacturing a hologram to be subjected to multiple exposures. In order to achieve the above object, a method for producing a hologram according to the present invention is directed to a hologram recording material having an optical reflection element adhered to a back surface thereof. In the method of producing a hologram in which the reference light beams are sequentially incident at different incident angles and are subjected to multiple exposure, when performing multiple exposure by sequentially injecting each reference light at a predetermined incident angle from the surface side of the recording material, The exposure is performed by shifting the position of the reflection element by a predetermined distance calculated according to the incident angle of each reference light in the direction in which the incident angle of the reference light is changed. When manufacturing a hologram by multiple exposure, first, the position (distance from the reference position) of the optical reflection element at each exposure is calculated according to the incident angle of each reference light. Then, when performing multiple exposure by sequentially irradiating each reference light at a predetermined incident angle from the surface side of the recording material, the position of the optical reflective element is shifted by a predetermined distance calculated according to the incident angle of each reference light, Exposure is performed in such a manner as to shift the incident angle of the reference light. As described above, when each reference beam is incident upon multiple exposure, exposure is performed by shifting the position of the optical reflection element by the calculated distance in the direction in which each reference beam changes the incident angle. Thereby, the shift of the recording position of the optical reflection element due to the difference in the incident angle of each reference beam at each exposure is corrected, and the occurrence of color shift at the time of reproducing the hologram is prevented. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows that three reference beams having three wavelengths are sequentially incident at different incident angles, and are subjected to multiple exposure.
1 shows a schematic diagram of an optical system for recording a hologram. 1
Is a hologram recording material, which is formed by adhering dichromate gelatin containing a dye sensitizer such as methylene blue to a thickness of about 25 μm on the surface of a transparent substrate 2 such as soda glass. A concave mirror (spherical concave mirror) 3 is provided below the recording material 1 via a refractive index adjusting liquid (for example, silicone oil) 4.
And a prism 5 for adjusting the angle of light incident on the recording material 1 via the refractive index adjusting liquid 4 is disposed on the transparent substrate 2. As will be described later, the position of the concave mirror 3 at the time of exposure is adjusted so as to be shifted by a predetermined distance in the inclination direction of each reference light, that is, in the horizontal direction in the drawing. Light sources include red (R), green (G), and blue (B).
A laser oscillator that emits each of the three laser beams is used, and the laser beams emitted from the laser oscillators are collimated by a lens (not shown). So that
The optical system is configured. The wavelengths of the red (R), green (G), and blue (B) reference lights LR, LG, and LB are, for example, LR: wavelength 64
7.1 nm, LG: wavelength 514.5 nm, LB: wavelength 4
It is set to 76.2 nm. Using such an optical system, multiplex exposure of the hologram is performed by sequentially irradiating each reference light at different incident angles. For example, the first exposure is performed by irradiating a red reference light LR. In this case, the second exposure of the green reference light LG and the third exposure of the blue reference light L
At the time of incidence B, exposure is performed by shifting the position of the concave mirror 3 by a predetermined distance in the direction in which each reference beam changes the incident angle, that is, rightward in FIG. The amount of displacement of the concave mirror 3 during the second exposure and the third exposure (distance shifted from the first exposure) is calculated as follows. That is, as shown in FIG. 1, assuming that the center position of the concave mirror 3 is Pc, a perpendicular line is extended upward from the center position Pc at the time of the first exposure as a reference, and the intersection with the surface of the recording material 1 is Po, Let H be the thickness of the concave mirror 3 at the center position. Each of the R, B, and G reference beams LR, L
B and LG enter as shown in FIG.
When the angles of reflection when reflected by c, that is, the angles of re-entry to the recording material 1 are θr, θb, and θg, and the intersections of the reflected light and the surface of the recording material 1 are Rp, Bp, and Gp, respectively. The distance L1 between the point Po and the point Rp is L1 = H · ta
nθr, the distance L2 between the point Po and the point Bp is L2 = H · t
anθb, the distance L3 between the point Po and the point Gp is L3 = H ·
tan θg. Therefore, when the first exposure is used as a reference, the concave mirror 3 is shifted to the right in FIG. 1 by the distance (L3-L1) during the second exposure, and the concave mirror 3 is moved to the distance (L2-L) during the third exposure. Exposure is performed by shifting to the right by L1) (FIG. 2). The exposed recording material 1 is subjected to a predetermined developing and fixing process, dried at a high temperature, and sealed to complete a hologram. Next, a specific example when the above-mentioned hologram is actually manufactured is described. When the hologram is reproduced, three types of target reproduction light wavelengths are defined as λr = 611 nm, λb = 452 nm, and λg = 54.
3 nm, and the emission and incidence angles θ of the reproduction light are θ = 33.
When the angle is set to 5 °, the angles of incidence θr, θb, and θg on the recording material 1 at the time of exposure are θr = 9.375 from a predetermined arithmetic expression.
°, θb = 11.12 °, and θg = 28.01 °. If the thickness H of the concave mirror 3 is H = 12 mm, the distance L1 between the point Po and the point Rp is L1 = 12 ×
tan 9.375 = 1.981 mm, and the distance L2 between the point Po and the point Bp is L2 = 12 × tan 11.12 = 2.35.
9 mm, the distance L3 between the point Po and the point Gp is L3 = 12 × t
an28.01 = 6.383 mm. Therefore, when the first exposure is used as a reference, the distance (L3-L) by which the concave mirror 3 is displaced during the second exposure.
1) is 6.383-1.981 = 4.4 mm, and the displacement distance (L2-L1) of the concave mirror 3 during the third exposure is
2.359-1.981 = 0.4 mm. As described above, for example, when the first exposure is performed by irradiating the red reference light LR, when the green reference light LG to be exposed secondly is incident, the blue light to be exposed thirdly is exposed. When the reference light LB is incident, the position of the concave mirror 3 is shifted by a distance (L3-
L1) and the distance (L2−L1), the exposure is performed, so that the shift of the recording position of the concave mirror 3 due to the difference in the incident angle of the reference light at each exposure is corrected, and the color shift at the time of reproducing the hologram is corrected. Occurrence is prevented. In the above embodiment, the hologram is recorded using a spherical concave mirror. However, other optical reflecting elements such as a parabolic concave mirror and an elliptical concave mirror can be used. In addition, the prism 5 for adjusting the incident light angle is not necessarily required as long as each reference light can be incident at a predetermined incident angle. As described above, three laser beams of red (R), green (G), and blue (B) are used to perform multiple exposure while changing the incident angle of each laser beam (reference beam). Holograms manufactured to record concave mirrors are used, for example, in head-up display devices for vehicles. FIG. 3 is a schematic structural view of the head-up display device. The hologram 10 manufactured as described above is used by being enclosed in a windshield 12 or adhered to the inside. As described above, this hologram 10 has an enlarged display function by recording a concave mirror,
It has a diffraction characteristic of reflecting only light of a specific wavelength (red, green, blue) incident at a specific incident angle. Reference numeral 13 denotes a display for displaying a meter or the like.
A display device for projecting an image, such as a liquid crystal display or a fluorescent display tube, is built in the display 13 together with a light source. Further, an optical reflection element 11 is arranged in front of the display 13 so as to be inclined so as to reflect the light emitted from the display 13 toward the hologram 10 of the windshield 12. The optical reflection element 11 is configured to reflect only light of a specific wavelength (for example, green light) emitted from the display unit 13. For example, it reflects only light of a specific wavelength incident at a specific angle. A hologram manufactured as described above, or a dichroic mirror composed of a dichroic filter and a reflecting mirror that transmits only light of a specific wavelength is used. In such a head-up display device, display light (for example, green) of a meter or the like radiated from the display 13 impinges on the optical reflection element 11 and the optical reflection element 1
The green display light reflected at 1 is incident on the hologram 10 on the windshield at a predetermined incident angle. Then, the display light reflected and diffracted from the hologram 10 is emitted toward the driver's eyes, and the driver visually recognizes a display image of a meter or the like as a virtual image in front of the windshield 12. On the other hand, the natural light from the sun, that is, the background image of the display image is also transmitted from the front of the windshield 12 to the hologram 1.
0 passes through and enters the driver's eyes. For this reason, if the hologram 10 has the property of reflecting and diffracting only green light, only the green light is reflected by the hologram, so that light obtained by removing green light from the spectrum of natural light is transmitted to the driver. As a result, a phenomenon in which the background image appears to be purple, which is a complementary color of green, tends to occur. However, if the hologram 10 having the diffraction characteristic of reflecting only the three primary colors of red, green and blue is attached to the windshield 12 as described above, the wavelength characteristic of the transmitted light shown in FIG. As shown in the graph (C), the transmitted light in which natural light from the outside passes through the hologram 10 and enters the driver's eyes has a spectrum from which the three primary colors of red, green, and blue have been removed. The background is not stained with a complementary color (purple) of the image (green), and unnatural coloring can be prevented from occurring in the field of view seen through the hologram 10.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an optical system during hologram recording according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing the incident state of each reference light and the position of a concave mirror during multiple exposure. FIG. 3 is a schematic configuration diagram of a head-up display device. FIG. 4 is a graph of wavelength characteristics of natural light (A), a graph of diffraction efficiency of a hologram (B), and a graph of wavelength characteristics of transmitted light (C). [Description of Signs] 1-recording material, 2-transparent substrate, 3-concave mirror, 4-refractive index adjusting liquid, LR, LB, LG-reference light.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masahiro Higuchi 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-3-223807 (JP, A) JP-A-3-3 188481 (JP, A) JP-A-64-44977 (JP, A) JP-A-3-273276 (JP, A) JP-A-3-168681 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03H 1/00-5/00

Claims (1)

(57) [Claims 1] A plurality of reference lights having different wavelengths are sequentially incident at different incident angles on a hologram recording material having an optical reflection element adhered to the back surface. In the method of manufacturing a hologram for multiple exposure, when performing multiple exposure by sequentially irradiating each reference light at a predetermined incident angle from the surface side of the recording material, the position of the optical reflection element is set to the incident angle of each reference light. A method for manufacturing a hologram, characterized in that exposure is performed by shifting the incident angle of the reference light by a predetermined distance calculated accordingly in a direction of changing the incident angle.