Volume hologram manufacturing method, volume hologram, and volume hologram manufacturing apparatus

Abstract

To produce a volume hologram capable of reproducing an image with good accuracy.SOLUTION: The method for manufacturing a volume hologram includes a step (S2) of attaching a recording material to a transmission-type interference-fringe forming member on which a computer-generated hologram is formed, and a step (S3) of recording the volume hologram on the recording material by irradiating the recording material with reproduction illumination light from the interference-fringe forming member side and irradiating the recording material with reference light from the recording material side (S4). The incident angle of the reproduction illumination light is 0 degree or more and 30 degrees or less. The incident angle of the reference light is greater than 0 degrees and less than or equal to 70 degrees.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a volume hologram, a volume hologram, and a volume hologram manufacturing apparatus. [Background technology]

[0002] Computer-generated holograms (CGHs) can reproduce non-existent objects or scenes represented by numerical data. However, in order to exhibit and view holograms under a white light source other than a laser light source, thin holograms are not suitable, and a method of recording computer-generated holograms on volume holograms (thick holograms) is required.

[0003] Patent Document 1 describes a technique for transferring a high-resolution master CGH made of a metal film onto a recording material as a volume hologram.

[0004] Patent Document 2 describes a technique in which a computer-generated hologram is irradiated with a reconstruction illumination light, and a hologram recording material is placed near the reconstructed image to record it as a reflection or transmission volume hologram. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-166300 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-145467 Summary of the Invention [Problem to be solved by the invention]

[0006] For example, by forming a relief with concaves and convexes corresponding to the phase modulation of the computer-generated hologram using lithography or laser processing, the computer-generated hologram can be realized as a phase-modulation hologram. However, if the angle of incidence of the reconstruction illumination light is large, it may not be possible to reconstruct the image accurately. This is because when the reconstruction illumination light is incident on the interference fringe-forming medium at an angle, the reconstruction illumination light passes through adjacent cells or is reflected by the concave and convex wall surfaces of the relief.

[0007] Furthermore, in the configuration shown in FIG. 15 of Patent Document 1, the reconstruction illumination light (82) illuminating the master CGH and the reference light (101) are the same light. Therefore, the reconstruction illumination light used to reconstruct the volume hologram must be irradiated at the same angle of incidence as the reconstruction illumination light used to record the volume hologram. However, with the technology of Patent Document 1, the reconstruction illumination light is incident at an angle, which may prevent accurate recording or reconstruction of the image. Similarly, with the technology of Patent Document 2, the reconstruction illumination light is incident at an angle, which may prevent accurate recording or reconstruction of the image.

[0008] An object of one aspect of the present invention is to provide a method for manufacturing a volume hologram in which a computer-generated hologram is recorded, which allows for accurate image reconstruction. [Means for solving the problem]

[0009] A method for manufacturing a volume hologram according to a first aspect of the present invention includes the steps of: attaching, directly or indirectly, a recording material capable of recording a volume hologram to a transmission-type interference fringe-forming medium on which a computer-generated hologram has been formed; and irradiating a reconstruction illumination light from the side of the interference fringe-forming medium to generate a reconstruction light from the interference fringe-forming medium, and simultaneously irradiating a reference light from the side of the recording material, thereby recording the interference fringes formed by the reconstruction light and the reference light as a volume hologram on the recording material, wherein the angle of incidence of the reconstruction illumination light on the optical axis of the interference fringe-forming medium is equal to or greater than 0 degrees and equal to or less than 30 degrees, and the angle of incidence of the reference light on the optical axis of the recording material is greater than 0 degrees and equal to or less than 70 degrees.

[0010] A volume hologram manufacturing method according to a second aspect of the present invention may be the method of the first aspect above, wherein a phase modulation hologram is formed in the interference fringe forming medium.

[0011] A volume hologram manufacturing method according to aspect 3 of the present invention may be a method in which, in the above-mentioned aspect 1, a phase modulation hologram having concaves and convexes corresponding to the interference fringes is formed on the interference fringe-forming medium.

[0012] A volume hologram manufacturing method according to aspect 4 of the present invention may be a method in which, in any of aspects 1 to 3 above, the angle of incidence of the reproduction illumination light on the optical axis of the interference fringe forming medium is greater than 0 degrees and less than or equal to 20 degrees.

[0013] A volume hologram manufacturing method according to aspect 5 of the present invention may be a method in which, in any one of aspects 1 to 4 above, the incident angle of the reference light on the optical axis of the recording material is 30 degrees or more and 70 degrees or less.

[0014] A volume hologram manufacturing method according to a sixth aspect of the present invention may be the method of the first aspect above, wherein an amplitude modulation hologram is formed in the interference fringe forming medium.

[0015] A volume hologram manufacturing method according to a seventh aspect of the present invention may be a method in any one of the first to sixth aspects, in which the reconstruction illumination light incident on the interference fringe forming medium is a plane wave.

[0016] A volume hologram according to an eighth aspect of the present invention may be produced by the volume hologram production method in any one of the first to seventh aspects.

[0017] A volume hologram production apparatus according to a ninth aspect of the present invention comprises a transmission-type interference fringe forming medium on which a computer-generated hologram is formed, a recording material capable of recording a volume hologram and attached directly or indirectly to the interference fringe forming medium, and a light source that irradiates a reconstruction illumination light from the side of the interference fringe forming medium to generate a reconstruction light from the interference fringe forming medium and at the same time irradiates a reference light from the side of the recording material, wherein the incident angle of the reconstruction illumination light on the optical axis of the interference fringe forming medium is greater than or equal to 0 degrees and less than 30 degrees, and the incident angle of the reference light on the optical axis of the recording material is greater than 0 degrees and less than 70 degrees. [Effects of the Invention]

[0018] According to one aspect of the present invention, it is possible to produce a volume hologram in which a computer-generated hologram is recorded, which allows an image to be reconstructed with high accuracy. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 10 is a diagram showing an example of the arrangement of reconstruction illumination light when viewing a hologram. [Figure 2] 1 is a schematic diagram showing the configuration of a volume hologram producing apparatus according to an embodiment of the present invention. [Figure 3] FIG. 2 is a cross-sectional view showing a schematic configuration of a laminate. [Figure 4] FIG. 1 is a diagram showing a flow for manufacturing a volume hologram. [Figure 5] 1 is a schematic diagram showing the configuration of a volume hologram reproducing device according to an embodiment of the present invention; [Figure 6] FIG. 10 is a diagram showing a reconstructed image obtained by reconstructing a hologram device using laser light. [Figure 7] FIG. 10 is a diagram showing a reconstructed image of a hologram device reconstructed using white light. DETAILED DESCRIPTION OF THE INVENTION

[0020] In addition to the problems mentioned above, when the angle of incidence of the reconstruction illumination light for a computer-generated hologram (CGH) is set large, the spacing between interference fringes narrows. This makes it difficult to write the computer-generated hologram as a phase-modulation hologram or an amplitude-modulation hologram on the recording material using a writing device. Furthermore, the narrow spacing between the interference fringes increases the calculation time required to generate the computer-generated hologram.

[0021] On the other hand, when viewing a reconstructed image of a hologram, it may be preferable to set the incident angle of the reconstruction illumination light to a large value.

[0022] FIG. 1 shows an example of the arrangement of reconstruction illumination light when viewing a hologram. A hologram device 10 in which a volume hologram is formed is hung on a wall. An observer 21 views the hologram device 10 from the front. A light source 20 is placed, for example, on the ceiling, and irradiates the hologram device 10 with reconstruction illumination light 22 (second reconstruction illumination light). The reconstruction illumination light 22 may be white light or laser light. Because volume holograms have wavelength selectivity, they can also be reconstructed using white light.

[0023] In the example shown in 101, the light source 20 is located behind the observer 21, and the reconstruction illumination light 22 is incident on the hologram device 10 at a small angle of incidence. In this case, there is a possibility that the reconstruction illumination light 22 will be partially blocked by the observer 21.

[0024] In the example shown in 102, light source 20 is positioned closer to hologram device 10 so that viewer 21 does not block reconstruction illumination light 22. In this case, the angle of incidence of reconstruction illumination light 22 onto hologram device 10 becomes larger. Considering the exhibition of hologram device 10, it is preferable to set the angle of incidence of reconstruction illumination light 22 larger. However, as mentioned above, setting the angle of incidence of reconstruction illumination light 22 larger causes the problems mentioned above, such as the inability to accurately record a volume hologram with conventional technology.

[0025] (Volume hologram recording) 2 is a schematic diagram showing the configuration of a volume hologram producing apparatus 1 of this embodiment. The volume hologram producing apparatus 1 includes a light source 2, a beam splitter 3, a first ND filter 4a, a second ND filter 4b, a first spatial filter 5a, a second spatial filter 5b, a first lens 6a, a second lens 6b, mirrors 7a and 7b, and a laminate 8. The laminate 8 includes a first substrate 13, a recording material 14, and an interference fringe forming medium 15.

[0026] The light source 2 is a light source that emits coherent light. The light source 2 is, for example, a laser light source that emits laser light. The light emitted from the light source 2 is incident on the beam splitter 3.

[0027] The beam splitter 3 splits the incident light into a reference light 11 and a first reconstructed illumination light 12 (reconstructed illumination light). The reference light 11 is incident on a first ND filter 4a. The first reconstructed illumination light 12 is incident on a second ND filter 4b.

[0028] The first ND filter 4a and the second ND filter 4b are filters that attenuate the intensity of light passing through them. The first ND filter 4a attenuates the intensity of the reference light 11. The second ND filter 4b attenuates the intensity of the first reconstructed illumination light 12. The first ND filter 4a and the second ND filter 4b can adjust the intensity ratio between the reference light 11 and the first reconstructed illumination light 12. The reference light 11 that passes through the first ND filter 4a is reflected by the mirror 7a and enters the first spatial filter 5a. The first reconstructed illumination light 12 that passes through the second ND filter 4b enters the second spatial filter 5b.

[0029] The first spatial filter 5a and the second spatial filter 5b are filters that remove unnecessary components of the incident light, thereby making the intensity distribution of the transmitted light a predetermined distribution (for example, a Gaussian distribution). The first spatial filter 5a adjusts the intensity distribution of the reference light 11. The second spatial filter 5b adjusts the intensity distribution of the first reconstructed illumination light 12. The reference light 11 that has passed through the first spatial filter 5a is incident on the first lens 6a. The first reconstructed illumination light 12 that has passed through the second spatial filter 5b is incident on the second lens 6b.

[0030] The first lens 6a collimates the reference light 11 into a parallel light (plane wave). The second lens 6b collimates the first reconstruction illumination light 12 into a parallel light (plane wave). The reference light 11 that has passed through the first lens 6a enters the stack 8 from one side of the stack 8. The first reconstruction illumination light 12 that has passed through the second lens 6b is reflected by the mirror 7b and enters the stack 8 from the other side of the stack 8.

[0031] 3 is a cross-sectional view showing a schematic configuration of the laminate 8. The first substrate 13 is a light-transmitting carrier that supports the recording material 14. For example, the first substrate 13 is a glass substrate.

[0032] The recording material 14 is a photosensitive material capable of recording a volume hologram (a so-called thick hologram). For example, a photopolymer or a silver halide film can be used as the material for the recording material 14. Because the photopolymer is soft, the recording material 14 is attached and fixed to the first substrate 13 here. The recording material 14 here is the one before the volume hologram is recorded.

[0033] Interference fringe forming medium 15 is a medium on which a transmission-type computer-generated hologram (so-called thin hologram) is formed. Here, a phase-modulation hologram is formed in interference fringe forming medium 15. Phase-modulation holograms are advantageous in that they have high diffraction efficiency and do not reproduce conjugate images. Interference fringe forming medium 15 has second substrate 15a and relief 15b. Second substrate 15a is a light-transmitting carrier that supports relief 15b. For example, second substrate 15a is a glass substrate.

[0034] Relief 15b has projections and depressions corresponding to the interference fringes of the computer-generated hologram and is provided on second substrate 15a. The phase of first reconstruction illumination light 12 passing through relief 15b is modulated in accordance with the depth of the projections and depressions on the surface of relief 15b. Relief 15b constitutes a phase-modulation hologram. Relief 15b is made of, for example, photoresist.

[0035] (Volume hologram recording process) FIG. 4 shows the flow of manufacturing a volume hologram. First, a computer-generated hologram calculated by a computer is formed on interference fringe forming medium 15 (S1). For example, photoresist is provided on second substrate 15a. By using laser lithography, the photoresist is irradiated with laser light at an intensity corresponding to the unevenness of the interference fringes, and the depth to which the resist is removed by development can be adjusted. This allows the formation of relief 15b having unevenness corresponding to the interference fringes of the computer-generated hologram.

[0036] The recording material 14 is attached directly or indirectly to the interference fringe forming medium 15 (S2). Here, the recording material 14 is attached directly to the interference fringe forming medium 15, but this is not limiting. The recording material 14 may also be attached indirectly to the interference fringe forming medium 15 so that another light-transmitting object, for example, the first substrate 13, is located between the interference fringe forming medium 15 and the recording material 14. The relief 15b or the second substrate 15a may be in contact with the recording material 14. By fixing the recording material 14 to the interference fringe forming medium 15, the effects of minute vibrations that occur during hologram transfer can be suppressed.

[0037] Laser light is emitted from the light source 2, and the laminate 8 is simultaneously irradiated with the reference light 11 and the first reproduction illumination light 12. At this time, the reference light 11 is irradiated from the recording material 14 side of the interference fringe forming medium 15 (i.e., from the first substrate 13 side), and at the same time, the first reproduction illumination light 12 is irradiated from the interference fringe forming medium 15 side of the recording material 14 (S3).

[0038] First reconstruction illumination light 12 irradiated onto interference fringe forming medium 15 is diffracted by relief 15b of interference fringe forming medium 15, generating reconstruction light. The reconstructed image produced by this reconstruction light is created by a computer-generated hologram. Because interference fringe forming medium 15 is a transmissive type, the generated reconstruction light is irradiated onto recording material 14. Because the hologram formed on interference fringe forming medium 15 is a phase-modulation hologram, the intensity of the undiffracted light of first reconstruction illumination light 12 incident on recording material 14 is very small.

[0039] Meanwhile, reference light 11 is irradiated onto recording material 14 from the opposite side to first reconstruction illumination light 12. In recording material 14, the reference light 11 and the reconstruction light interfere with each other, forming interference fringes. Recording material 14 records the interference fringes formed by reference light 11 and the reconstruction light as a volume hologram (S4). Note that by exchanging first substrate 13 and recording material 14, volume holograms can be transferred to multiple recording materials 14 using a single interference fringe forming medium 15. Note that because the side of the recording material from which reference light 11 enters and the side from which reconstruction light exits are the same, the volume hologram formed on recording material 14 is a reflection hologram.

[0040] In this way, the computer-generated hologram can be transferred to the recording material 14 as a volume hologram. A reconstructed image can be reconstructed by irradiating the recording material 14 on which the volume hologram has been recorded with a second reconstruction illumination light from the same direction as the reference light 11 used for recording. That is, the incident angle α of the reference light becomes the incident angle of the second reconstruction illumination light when reconstructing the volume hologram. In this embodiment, the reference light 11 and the first reconstruction illumination light 12 used to record the volume hologram are incident from opposite sides. Therefore, the incident angle β of the first reconstruction illumination light 12 when recording the volume hologram can be made different from the incident angle α of the second reconstruction illumination light when subsequently reconstructing the volume hologram.

[0041] The incident angle β is the angle of incidence of the optical axis of the first reconstruction illumination light 12 with respect to the interference fringe forming medium 15. The optical axis corresponds to the center line of the light beam. The incident angle β is the angle between the traveling direction of the first reconstruction illumination light 12 and the perpendicular line to the interference fringe forming medium 15. To accurately reconstruct the hologram of the interference fringe forming medium 15, it is preferable that the incident angle β is small. For example, the incident angle β may be greater than 0 degrees and less than 30 degrees. For example, if the incident angle β is less than 20 degrees, the reconstructed image can be reconstructed more accurately. The incident angle β of the first reconstruction illumination light 12 may be greater than 0 degrees. This allows the non-diffracted light of the first reconstruction illumination light 12 to be slightly tilted to prevent the non-diffracted light from being emitted in the front direction of the recording material 14 (toward the observer during reconstruction). This prevents the non-diffracted light from overlapping with the reconstructed image positioned in the perpendicular line to the recording material 14 during reconstruction.

[0042] The incident angle α is the angle of incidence of the optical axis of the reference beam 11 relative to the recording material 14. The incident angle α is the angle formed by the traveling direction of the reference beam 11 relative to the normal to the recording material 14. Because the reference beam 11 is independent of the interference fringe forming medium 15, in this embodiment, the incident angle α can be set within a wide range. For example, the incident angle α may be greater than 0 degrees and equal to or less than 70 degrees. The incident angle α may also be equal to or greater than 30 degrees. In this case, the viewing direction of the observer 21 (the front direction of the recording material 14) is made different from the direction in which the second reconstruction illumination light is irradiated, thereby preventing the second reconstruction illumination light from being blocked by the observer 21.

[0043] (Volume hologram reconstruction) 5 is a schematic diagram showing the configuration of a volume hologram reconstructing device 30 of this embodiment. The volume hologram reconstructing device 30 includes a light source 20, a beam splitter 3, a first ND filter 4a, a first spatial filter 5a, a first lens 6a, a mirror 7a, a hologram device 10, and a light-shielding plate 24. Here, an example configuration in which the optical path of the first reconstruction illumination light 12 of the volume hologram producing device 1 is blocked by the light-shielding plate 24 will be described.

[0044] Light source 20 emits light containing the wavelength of the light emitted by light source 2. Light source 20 may be the same laser light source as light source 2, or may be a white light source that emits white light, such as an LED. Because volume holograms have wavelength selectivity, reconstructed light 23 is generated by light contained in the white light and having the wavelength used during recording.

[0045] The beam splitter 3 splits the incident light into two. One of the split lights is the second reconstruction illumination light 22. The other split light, which corresponds to the first reconstruction illumination light 12 in the volume hologram production apparatus 1, is not required for reconstruction. The light shielding plate 24 blocks the other split light. The beam splitter 3 and the light shielding plate 24 may be omitted.

[0046] The second reconstruction illumination light 22 passes through the first ND filter 4 a, the first spatial filter 5 a, and the first lens 6 a, and is incident on the hologram device 10.

[0047] Hologram device 10 includes first substrate 13 and recording material 14. Hologram device 10 is obtained by removing interference fringe-forming medium 15 from laminate 8 used during recording. Here, recording material 14 has already had a volume hologram recorded on it. Second reconstruction illumination light 22 is incident on hologram device 10 at an incident angle α. This causes recording material 14 to generate reconstruction light 23 that reconstructs reconstruction image 33. Because recording material 14 constitutes a reflection-type hologram, reconstruction light 23 is diffracted toward the incident side of second reconstruction illumination light 22 (toward observer 21). This allows observer 21 to observe reconstruction image 33 created by a computer-generated hologram through hologram device 10.

[0048] (Example) FIG. 6 shows a reconstructed image of hologram device 10 reconstructed using a laser beam. Hologram device 10 was fabricated using volume hologram fabrication apparatus 1. Hologram device 10 was reconstructed using volume hologram reconstructor 30. The second reconstruction illumination beam 22 was the same laser beam as used during recording. Using the same interference fringe-forming medium 15, volume holograms were recorded and reconstructed by setting the incident angle α of reference beam 11 to 30 degrees, 50 degrees, and 70 degrees. The incident angle α of second reconstruction illumination beam 22 was also the same as the incident angle α of reference beam 11. The images shown in FIG. 6 were captured by a camera of reconstructed image 33 when the incident angle α was 30 degrees, 50 degrees, and 70 degrees, respectively. The incident angle β of first reconstruction illumination beam 12 was set to 0 degrees. First reconstruction illumination beam 12 was a plane wave.

[0049] A phase modulation hologram having a relief 15b was formed on an interference fringe forming medium 15. The size of the interference fringe forming medium 15 was 26 mm × 26 mm. The computer-generated hologram formed on the interference fringe forming medium 15 was 32768 × 32768 pixels. The size of one pixel was 0.8 μm × 0.8 μm. A reconstructed image 33 having a height of 12.5 mm was set at a depth of 50 mm in the direction perpendicular to the interference fringe forming medium 15. The wavelength of the reference beam 11 was 640 nm. The intensity ratio between the reference beam 11 and the first reconstruction illumination beam 12 was 1:1. The exposure time during recording was 14 seconds, and the exposure dose on the recording material 14 was 15 mJ / cm. 2 The thickness of the recording material 14 was 16 μm.

[0050] With hologram device 10 where the incidence angle α was 30 degrees and 50 degrees, a sufficiently bright reconstructed image 33 could be observed. With hologram device 10 where the incidence angle α was 70 degrees, the reconstructed image 33 was also observable, but it was darker than with 30 degrees or 50 degrees. However, with both incidence angles α, the computer-generated hologram was reconstructed with high accuracy. Note that because the incidence angle β was set to 0 degrees, non-diffracted light was superimposed on the reconstructed image 33. This non-diffracted light can be prevented from superimposing on the reconstructed image 33 by slightly tilting the incidence angle β.

[0051] Fig. 7 shows a reconstructed image of hologram device 10 reconstructed using white light. The images shown in Fig. 7 were taken with a camera of reconstructed image 33 when the incident angle α was 30 degrees, 50 degrees, and 70 degrees. The hologram device 10 used was the same as that used in Fig. 6. Only second reconstruction illumination light 22 was white light emitted from a white LED light source.

[0052] When reconstructed with white light, the reconstructed image 33 was darker than when reconstructed with laser light. Nevertheless, a bright reconstructed image 33 could be observed with white light for hologram device 10 with an incident angle α of 30 degrees and 50 degrees. Even with hologram device 10 with an incident angle α of 70 degrees, the reconstructed image 33 could be observed with white light, but it was darker than with 30 degrees or 50 degrees. If the reconstructed image 33 is dark, some effort will be required, such as darkening the environment in which hologram device 10 is exhibited. Furthermore, because white light has a broadband spectrum, the reconstructed image 33 was slightly blurred compared to reconstruction with laser light.

[0053] In this way, it was possible to produce hologram device 10, in which a computer-generated hologram was recorded, which could accurately reconstruct an image, using volume hologram production apparatus 1. Furthermore, it was possible to accurately reconstruct reconstructed image 33 from hologram device 10 using laser light or white light.

[0054] The hologram can be reconstructed with reconstruction illumination light having the same angle of incidence as the reference light. According to this embodiment, the reference light 11 can be made to have a large angle of incidence, so that the hologram can be reconstructed with reconstruction illumination light (second reconstruction illumination light 22) having a large angle of incidence.

[0055] Furthermore, according to this embodiment, the first reconstruction illumination light 12 can be incident on the interference fringe forming medium 15 at an angle close to perpendicular. This prevents an increase in the spatial frequency of the interference fringes (prevents the spacing between the interference fringes from narrowing). Furthermore, in a phase modulation CGH, light can easily reach deep areas of the relief. As a result, images can be recorded and reproduced with high precision.

[0056] Furthermore, since the hologram formed by transferring the CGH to the recording material 14 is a volume hologram, it has wavelength selectivity and can reproduce a reproduced image even with broadband illumination such as white light.

[0057] (Variation) It should be noted that the reference light 11 incident on the recording material 14 does not have to be a plane wave. The reference light 11 may be, for example, a spherical wave. For example, the wavefront and incident angle α of the reference light 11 may be set to match the second reconstruction illumination light 22 of the light source 20 when the hologram device 10 is exhibited. It should be noted that the reference light 11 may be a plane wave, and the second reconstruction illumination light 22 may be a spherical wave.

[0058] First reconstruction illumination light 12 incident on interference fringe forming medium 15 does not have to be a plane wave. First reconstruction illumination light 12 may be, for example, a spherical wave. However, from the viewpoint of accurately reconstructing a computer-generated hologram of interference fringe forming medium 15, first reconstruction illumination light 12 is preferably a plane wave.

[0059] The interference fringe forming medium 15 does not have to be a phase modulation hologram, but may be a transmission type amplitude modulation hologram, which is a computer generated hologram, formed in the interference fringe forming medium 15.

[0060] A transmission type spatial light modulator may be used as interference fringe forming medium 15. A computer generated hologram may be directly displayed (formed) by the spatial light modulator.

[0061] It is also possible to omit some optical elements in the volume hologram producing apparatus 1 and the volume hologram reconstructing apparatus 30. For example, the first ND filter 4a, the second ND filter 4b, the first spatial filter 5a, and / or the second spatial filter 5b may be omitted.

[0062] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0063] 1. Volume hologram production device 2, 20 light sources 5a First spatial filter 5b Second spatial filter 8 Laminate 10 Hologram Device 11 Reference light 12 First reconstruction illumination light (reconstruction illumination light) 13 First board 14 Recording material 15 Interference fringe forming medium 15a Second board 15b Relief 22 Second reconstruction illumination light (reconstruction illumination light) 23 Regeneration light 24 Shade 30 Volume hologram reconstruction device 33 Reconstructed image

Claims

1. a step of directly or indirectly attaching a recording material capable of recording a volume hologram to a transmission type interference fringe forming medium on which a computer-generated hologram has been formed; a step of irradiating a reproducing illumination light from the side of the interference fringe forming medium to generate a reproducing light from the interference fringe forming medium, and simultaneously irradiating a reference light from the side of the recording material, thereby recording an interference fringe formed by the reproducing light and the reference light on the recording material as a volume hologram, an incident angle of the reproduction illumination light on the optical axis of the interference fringe forming medium is equal to or greater than 0 degrees and equal to or less than 30 degrees; A method for manufacturing a volume hologram, wherein the incident angle of the reference light on the optical axis of the recording material is greater than 0 degrees and is not more than 70 degrees.

2. The method for producing a volume hologram according to claim 1 , wherein a phase modulation hologram is formed in the interference fringe forming medium.

3. The method for producing a volume hologram according to claim 1, wherein the interference fringe forming medium has a phase modulation hologram formed thereon, the phase modulation hologram having concaves and convexes corresponding to the interference fringes.

4. 2. The method for producing a volume hologram according to claim 1, wherein the angle of incidence of the reproduction illumination light on the optical axis of the interference fringe forming medium is greater than 0 degrees and is equal to or smaller than 20 degrees.

5. The method for producing a volume hologram according to claim 1 , wherein an incident angle of the reference light on the optical axis of the recording material is equal to or greater than 30 degrees and equal to or less than 70 degrees.

6. The method for producing a volume hologram according to claim 1 , wherein an amplitude modulation hologram is formed in the interference fringe forming medium.

7. The method for producing a volume hologram according to claim 1 , wherein the reconstruction illumination light incident on the interference fringe forming medium is a plane wave.

8. A volume hologram produced by the method for producing a volume hologram according to any one of claims 1 to 7.

9. a transmission type interference fringe forming medium on which a computer-generated hologram is formed; a recording material capable of recording a volume hologram, attached directly or indirectly to the interference fringe forming medium; a light source that irradiates a reproduction illumination light from the side of the interference fringe forming medium to generate a reproduction light from the interference fringe forming medium, and at the same time irradiates a reference light from the side of the recording material, an incident angle of the reproduction illumination light on the optical axis of the interference fringe forming medium is equal to or greater than 0 degrees and equal to or less than 30 degrees; A volume hologram producing apparatus, wherein the incident angle of the reference light on the optical axis with respect to the recording material is greater than 0 degrees and not more than 70 degrees.

Images