Display device and display method for animated holograms

Abstract

To provide an animation hologram display device and display method for irradiating, with reproduction light, an interference fringe forming medium in which an interference fringe corresponding to a plurality of frames are multiplexed by spatial division so as to reproduce the animation of each frame.SOLUTION: Provided is an animation hologram display device 1 for irradiating, with reproduction light, an interference fringe forming medium in which an interference fringe corresponding to a plurality of frames are multiplexed by spatial division so as to reproduce the animation of each frame, said device comprising an optical pattern filter 10 which is located close to an interference fringe forming medium 20, and a reproduction light source 30 for sequentially irradiating the interference fringe forming medium with rays of reproduction light differing in characteristics for each frame via the optical pattern filter. The optical pattern filter 10 is made to pass through or block the reproduction light for each region facing the interference fringe of each frame on the basis of the characteristic of the reproduction light. The optical pattern filter 10 may pass through or block the reproduction light on the basis of the direction of polarization of the reproduction light. The optical pattern filter 10 further may pass through or block the reproduction light on the basis of the wavelength of the reproduction light.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an animation hologram display device and a display method, and particularly to an animation hologram display device and a display method for reproducing an animation of each frame by irradiating a reproduction light onto an interference fringe forming medium in which interference fringes corresponding to a plurality of frames are spatially multiplexed.

Background Art

[0002] Analog holograms and omnidirectional parallax high-resolution computer-generated holograms can reproduce high-quality stereoscopic images that achieve both a wide viewing range and a large size by forming a fine interference fringe pattern on an interference fringe forming medium. However, due to the characteristic of recording a fixed interference fringe pattern on a single interference fringe forming medium, there is a feature that only still images can be reproduced and the reproduced image cannot be switched.

[0003] In Patent Document 1, in order to enable switching of a plurality of reproduced images using a single interference fringe forming medium, as shown in FIG. 12, a part of the interference fringe data of each of a plurality of holograms calculated by computer holography is extracted according to a predetermined spatial division pattern, and the interference fringe forming medium is generated by integrating the parts of each interference fringe data into one. A technique is disclosed.

[0004] If the interference fringe forming medium thus generated is sequentially irradiated while switching the pattern illumination (structured illumination) of the same pattern as the spatial division pattern of the interference fringe data as shown in FIG. 13, an animation hologram capable of switching a plurality of hologram reproduced images is realized.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0006] [Non-Patent Document 1] K. Matsushima and S. Nakahara: Extremely high-definition full-parallax computer-generated hologram created by the polygon-based method, App. Opt. 48, H54-H63 (2009). [Non-Patent Document 2] Kondo, Akiyasu; Matsushima, Kyoji: Hidden surface elimination of omnidirectional parallax CGH using silhouette approximation, IEICE Transactions D-II J87-D-II, 7, 1487-1495 (2004). [Non-Patent Document 3] K. Nakamoto, K. Matsushima: Exact mask-based occlusion processing in large-scale computer holography for 3D display, SPIE Digital Optical Technologies 2019, Munich, Germany, SPIE Proc. 11062, 1106204 (2019.6.24). [Non-Patent Document 4] A. Stein, Z. Wang, and J. Jr, "Computer-generated holograms: A simplified ray-tracing approach," Comput. Phys. 6, 389-392 (1992). [Non-Patent Document 5] H. Ando, ​​T. Sogawa and H. Gotoh, Appl. Phys. Lett. 73(1998)566. [Non-Patent Document 6] Color Animated Full-parallax High-definition Computer-generated Hologram,SIGGRAPH Asia 2022,2022 / 12. [Overview of the project] [Problems that the invention aims to solve]

[0007] Patent Document 1 switches between a spatial division pattern and structured illumination of the same pattern, but there is a problem that, due to the spread of light, the light from the structured illumination leaks out of the desired area, resulting in the superimposition of reconstructed images other than the desired hologram reconstructed image.

[0008] In addition, because the structured illumination needs to be precisely aligned with the spatial division pattern of the interference fringe-forming medium without any deviation, there are problems such as the time required for alignment and the inability to play the correct image if the structured illumination is misaligned due to some kind of impact.

[0009] The object of the present invention is to solve the above technical problems and to provide an animation hologram display device and display method that can suppress light leakage outside the desired area and suppress quality degradation due to the superposition of different reconstructed images by placing an optical pattern filter in close proximity to the interference fringe forming medium in the animation hologram and switching the light corresponding to the filter characteristics using a variable reconstructive light source and control device. [Means for solving the problem]

[0010] To achieve the above objective, the present invention provides an animation hologram display device that reproduces each frame by irradiating a regenerative light onto an interference fringe forming medium in which interference fringes corresponding to multiple frames are spatially divided and multiplexed, wherein the device is provided with an optical pattern filter positioned close to the interference fringe forming medium and an illumination means that sequentially irradiates the interference fringe forming medium with regenerative light having different characteristics for each frame via the optical pattern filter, and the optical pattern filter is configured to transmit or block the regenerative light in each region facing the interference fringes of each frame based on its characteristics.

[0011] Note that the present invention can be realized not only as a display device for an animation hologram having the above-described characteristic configuration, but also as a method for displaying an animation hologram using such a characteristic process as steps.

Advantages of the Invention

[0012] According to the present invention, by arranging an optical pattern filter in proximity to the interference fringe forming medium and switching the light corresponding to the characteristics of the filter, it is possible to suppress light leakage to the outside of a desired region and suppress quality degradation due to the superposition of different reproduced images.

[0013] In addition, since the light applied to the interference fringe generation medium is switched with high precision by the optical pattern filter and the variable reproduction light source without using structured illumination, precise alignment of the light source, which was conventionally required, becomes unnecessary.

Brief Description of the Drawings

[0014] [Figure 1] It is a diagram schematically showing the configuration of an animation hologram display device to which the present invention is applied. [Figure 2] It is a diagram schematically showing the configuration of an animation hologram display device according to the first embodiment. [Figure 3] It is a diagram schematically showing a method for generating an analog hologram. [Figure 4] It is a diagram schematically showing the configuration of an animation hologram display device according to the second embodiment. [Figure 5] It is a diagram showing an arrangement example (No. 1) of a plurality of reproduction light sources in the second embodiment. [Figure 6] It is a diagram showing an arrangement example (No. 2) of a plurality of reproduction light sources in the second embodiment. [Figure 7] It is a chart listing combinations of the types of the optical pattern filter and the reproduction light source and the method for controlling the light source. [Figure 8] It is a diagram showing an application example of the present invention to a reflection hologram. [Figure 9]This is a diagram showing an application example of the present invention to a transmissive hologram. [Figure 10] This is a diagram showing an example in which the reproduction light is temporarily extinguished during the transition of frame switching. [Figure 11] This is a diagram showing an example in which the polarization direction of the reproduction light is rotated during the transition of frame switching. [Figure 12] This is a diagram showing a conventional example in which interference fringes spatially divided for each frame are integrated into one by multiplexing. [Figure 13] This is a diagram showing a conventional example in which an animation is reproduced by irradiating a single interference fringe obtained by integrating the interference fringes of each frame with reproduction light having a unique irradiation pattern for each frame.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram schematically showing the configuration of the main part of an animation hologram display device 1 to which the present invention is applied, and configurations unnecessary for the description of the present invention are omitted from the illustration here.

[0016] The animation hologram display device 1 sequentially irradiates an interference fringe forming medium 20 in which interference fringes corresponding to a plurality of frames to be reproduced are spatially division multiplexed with reproduction light having different characteristics, for example, polarization direction and wavelength, from a reproduction light source 30 while switching to reproduce each frame. In the present embodiment, the number of reproduced frames is "2", and the case where interference fringes 21 corresponding to frame 1 and interference fringes 22 corresponding to frame 2 are spatially division multiplexed in a lattice pattern in the interference fringe forming medium 20 will be described as an example.

[0017] On the light source side of the interference fringe forming medium 20, an optical pattern filter 10 that transmits or blocks reproduction light based on its characteristics is disposed in proximity for each region facing the interference fringes of each frame.

[0018] The optical pattern filter 10 has the same pattern as the arrangement pattern of each interference fringe in the interference fringe forming medium 20. The region 11 opposite the interference fringe 21 of frame 1 is provided with a filter function that transmits the regenerated light of frame 1 but blocks the regenerated light of frame 2, and the region 12 corresponding to the interference fringe 22 of frame 2 is provided with a filter function that transmits the regenerated light of frame 2 but blocks the regenerated light of frame 1. The optical pattern filter 10 is fixed in close contact to the light source side of the interference fringe forming medium 20, for example by adhesive, with each pattern precisely positioned.

[0019] Figure 2 is a schematic diagram showing the configuration of the main parts of the animation hologram display device 1 according to the first embodiment of the present invention, where the same reference numerals as above represent the same or equivalent parts. This embodiment is characterized in that it employs a light source (variable regenerative light source) 30A with variable polarization direction and wavelength as the regenerative light source 30.

[0020] In this embodiment, we focus on the polarization direction as a characteristic of light, and the optical pattern filter 10 is constructed by spatially dividing and multiplexing two types of linear polarization filters, whose polarization directions are mutually orthogonal, in a grid-like manner, similar to interference fringes.

[0021] As the optical pattern filter 10, for example, a photonic crystal polarizing element capable of freely forming polarization directions in units of 1 μm can be used. However, any filter can be used as long as it can transmit and block linearly polarized regenerated light in opposing regions by cutting and pasting a polarizing film according to the spatial division pattern.

[0022] Furthermore, although this embodiment uses an optical pattern filter for linear polarization, an optical pattern filter in which right-circular polarization or left-circular polarization patterns are arranged to match the spatial division pattern may also be used. When circular polarization is used, even if the optical axis of the regenerating light source 30A is tilted with respect to the vertical axis of the interference fringe forming medium 20, light can be transmitted and blocked normally, which has the advantage of increasing the degree of freedom in the installation of the regenerating light source 30A.

[0023] The optical pattern filter 10 does not need to be a single filter; it may be a structure that combines multiple filters or optical elements. For example, if you want to combine a linearly polarized light source with a circularly polarized polarizing element, it is desirable to use an optical pattern filter that combines a circularly polarized polarizing element with a pattern similar to the spatial division pattern and a quarter-wave plate.

[0024] Furthermore, if we focus on wavelength as a characteristic of light, a color filter may be used instead of a polarizing element. For example, when switching between two types of reconstructed images with different wavelengths of the reconstructed light source 30A used for reconstruction, such as frame 1 being a monochromatic red reconstructed image and frame 2 being a monochromatic blue reconstructed image, a color filter can be used as an optical pattern filter.

[0025] The interference fringe forming medium 20 can be formed by spatially dividing and multiplexing two frames of interference fringes calculated by computer holography using a 3D model as input, using the same method as in Figure 12. Such interference fringes are formed by treating the polygons included in the 3D polygon mesh model to be reproduced as surface light sources, as disclosed in Non-Patent Literature 1, and performing optical wave propagation calculations from each surface light source to the interference fringe forming medium 20.

[0026] In this process, in order to display the 3D model with correct hidden surface removal, the silhouette method disclosed in Non-Patent Document 2 or the surface mask method disclosed in Non-Patent Document 3 are adopted as hidden surface removal methods for the polygon method. Light waves are shielded using a mask, and the propagation of light waves to the interference fringe forming medium 20 is calculated while considering the shielding relationship.

[0027] Furthermore, when using a point cloud model instead of a polygon mesh model as input for calculations, the point source method disclosed in Non-Patent Document 4 is adopted, and the propagation calculation is performed by treating the point cloud as a point source.

[0028] Interference calculations are performed on the light wave distribution of the 3D model, called object light, which has been calculated for propagation, by adding a reference light with the same position and wavelength as the regenerated light source during regeneration on a computer. The amplitude distribution or phase distribution obtained by the interference calculation is spatially multiplexed onto the quantized interference fringe data, and then an interference fringe forming medium 20 is generated using lithography techniques with a laser writing device or electron beam writing device, or other microfabrication techniques.

[0029] In this embodiment, a computer-generated hologram is used as the interference fringe; however, an analog hologram may also be used, which is obtained by generating light interference using a real object as the subject and recording the resulting interference fringe.

[0030] Figure 3 schematically illustrates the method for generating an analog hologram. First, the object light L1 and reference light L2 of frame 1 are recorded on the interference fringe recording material 50 through a mask 51 with the same pattern as a pre-designed spatial division pattern, thereby generating only the interference fringes of frame 1.

[0031] Next, the object light L1 and reference light L2 of frame 2 are recorded on the interference fringe recording material 50 via a mask 52 with the reverse pattern of the mask 51, and the interference fringes of frame 2 are added, thereby generating an interference fringe forming medium 20 with interference fringes for two frames.

[0032] Returning to Figure 2, the polarization direction of the variable regenerative light source 30A is controlled by the control device 40. The control device 40 may play an animation by automatically switching the polarization direction of the variable regenerative light source 30A at a preset update frequency, or it may be equipped with an input device such as an input button so that the polarization direction can be switched at any time.

[0033] If a linear polarization filter with two orthogonal polarization directions is used as the optical pattern filter 10, then the variable regenerative light source 30A should be a light source capable of switching and outputting linearly polarized light in two orthogonal directions. Specifically, it can be configured using a light source with linear polarization characteristics, such as a conventional laser diode.

[0034] Furthermore, if a circularly polarized filter is used for the optical pattern filter 10, the variable regenerative light source 30A should use a laser capable of switching between circular and polarized light, such as the spin-controlled semiconductor laser disclosed in Non-Patent Document 5 or a linearly polarized laser combined with a quarter-wave plate. Alternatively, even if a special polarizing laser is not used, a polarizing element can be placed on the light source side and switched to create the variable regenerative light source 30A.

[0035] The control device 40 adjusts the polarization direction of the regenerated light to a first polarization direction when regenerating the animation of frame 1. This direction allows the light to be transmitted in the region of the optical pattern filter 10 opposite the interference fringes of frame 1 (opposing region) and blocked in other regions. As a result, the regenerated light illuminates the interference fringes of frame 1 but not the interference fringes of frame 2, so that only frame 1 can be regenerated.

[0036] When playing the animation of frame 2, the polarization direction of the playback light is rotated by 90° to a second polarization direction in the optical pattern filter 10, synchronized with the switching timing of the playback frames. This direction transmits light in the region opposite frame 2 and blocks it in other regions. As a result, when playing frame 2, the playback light illuminates the interference fringes of frame 2 but not the interference fringes of frame 1, allowing only frame 2 to be played.

[0037] Such a control device 40 can be configured by implementing applications (programs) that realize each of the functions detailed below on one or more general-purpose computers or servers equipped with a CPU, ROM, RAM, bus, interface, etc. Alternatively, it can be configured as a dedicated machine or single-function machine in which part of the application is implemented in hardware or software.

[0038] Figure 4 is a schematic diagram showing the configuration of the main parts of the animation hologram display device 1 according to the second embodiment of the present invention, where the same reference numerals as above represent the same or equivalent parts.

[0039] This embodiment is characterized by having two light sources 30B and 30C whose polarization directions are mutually orthogonal as the regenerating light source 30. In the optical pattern filter 10, two types of linear polarization filters with mutually orthogonal polarization directions are spatially divided and multiplexed in a grid pattern similar to interference fringes. The switching between the regenerating light sources 30B and 30C is controlled by the control device 40.

[0040] The regeneration light source 30B emits regenerated light with a first polarization direction that is transmitted in the region opposite to the interference fringes of frame 1 of the optical pattern filter 10 (opposing region) and blocked in other regions. The regeneration light source 30C emits regenerated light with a second polarization direction that is transmitted in the region opposite to frame 2 of the optical pattern filter 10 and blocked in other regions.

[0041] When playing back frame 1, the control device 40 turns on the playback light source 30B and turns off the playback light source 30C. As a result, the playback light from the playback light source 30B illuminates the interference fringes of frame 1, but not the interference fringes of frame 2, so that only frame 1 can be played back.

[0042] Furthermore, when playing back frame 2, the control device 40 switches the playback light source 30B off and the playback light source 30C on in synchronization with the switching timing of the playback frames. As a result, when playing back frame 2, the playback light from the playback light source 30C is irradiated onto the interference fringes of frame 2, but not onto the interference fringes of frame 1, so that only frame 2 can be played back.

[0043] Figures 5 and 6 show an example of the arrangement of the two regenerative light sources 30B and 30C in the second embodiment.

[0044] In the example shown in Figure 5, one regeneration light source 30B and the other regeneration light source 30C are arranged so that the optical axes of their respective regeneration beams are aligned via a half-mirror 60 and irradiated onto the interference fringe forming medium 20 via an optical pattern filter 10.

[0045] When reproducing frame 1, as shown in Figure (a), the regeneration light from the regeneration light source 30B passes through the half mirror 60 and reaches the optical pattern filter 10, and irradiates the interference fringe forming medium 20. When reproducing frame 2, as shown in Figure (b), the regeneration light from the regeneration light source 30C is reflected by the half mirror 60 and reaches the optical pattern filter 10, and irradiates the interference fringe forming medium 20.

[0046] In the example shown in Figure 6, two regeneration light sources 30B and 30C are positioned so that their regeneration light directly illuminates the interference fringe forming medium 20 via the optical pattern filter 10. The on / off switching of each regeneration light source 30B and 30C is synchronized with the frame switching. In this case, when calculating or recording the interference fringes corresponding to each frame, the position of the reference light is set according to the position of the light source for each frame, thereby allowing the regeneration image of each frame to be reproduced in the same position.

[0047] Figure 7 is a diagram that lists the combinations of the types of optical pattern filters 10 and regenerative light sources 30 and the control methods for the light sources 30.

[0048] When the optical pattern filter 10 is configured with a combination of a circular polarizing filter and a quarter polarizer, the regenerated light is converted to circular polarization by the quarter polarizer before reaching the circular polarizing filter. Similarly, when the optical pattern filter 10 is configured with a combination of a linear polarizing filter and a quarter polarizer, the regenerated light is converted to circular polarization by the quarter polarizer before reaching the linear polarizing filter.

[0049] In this embodiment, if a linearly polarizing filter is used as the optical pattern filter 10, it can be applied to both a reflective hologram, which allows observation of the reflected light 71 of the regenerated light 70 as shown in Figure 8, and a transmissive hologram, which allows observation of the transmitted light 72 of the regenerated light 70 as shown in Figure 9. If a circularly polarizing filter is used as the optical pattern filter 10, it can only be applied to a transmissive hologram because the direction of rotation is reversed by reflection.

[0050] Figures 10 and 11 schematically show a method for controlling the playback light during frame switching transitions. If linear polarization is used, in both the first and second embodiments, as shown in Figure 10, the variable playback light source 30A may be turned off for a short time during the switching of polarization direction when switching playback frames, thereby instantly switching to the other image. Furthermore, in the first embodiment, for smoother switching, the polarization direction may be gradually rotated as shown in Figure 11, so that the transmission ratio of the two images is gradually changed.

[0051] Furthermore, according to each of the above embodiments, it is possible to suppress light leakage outside the desired area in the animation hologram and suppress quality degradation due to the superposition of different reproduced images. Moreover, since the precise alignment of light sources that was previously required is no longer necessary, it becomes possible to contribute to Goal 9, "Build resilient infrastructure and promote inclusive and sustainable industrialization," and Goal 11, "Make cities inclusive, safe, resilient and sustainable," which are led by the United Nations. [Explanation of Symbols]

[0052] 1…Animation hologram display device, 10…Optical pattern filter, 20…Interference fringe forming medium, 21…Interference fringe corresponding to frame 1, 22…Interference fringe corresponding to frame 2, 30, 30A, 30B, 30C…Regenerated light source, 11…Area of ​​the optical pattern filter opposite the interference fringe of frame 1, 12…Area of ​​the optical pattern filter opposite the interference fringe of frame 2, 60…Half mirror, 70…Regenerated light, 71…Reflected light, 72…Transmitted light

Claims

1. In an animation hologram display device that reproduces each frame by irradiating a regenerative light onto an interference fringe forming medium in which interference fringes corresponding to multiple frames are spatially divided and multiplexed, An optical pattern filter placed in close proximity to the interference fringe forming medium, The system comprises illumination means that sequentially irradiates the interference fringe forming medium with regenerated light having different characteristics for each frame via the optical pattern filter, The optical pattern filter is provided with a filtering function in which the characteristics of the reproduced light transmitted or blocked are fixedly different for each region facing the interference fringes of each frame, and the reproduced light is transmitted or blocked based on these characteristics, characterized in that the optical pattern filter is provided with a filtering function in which the characteristics of the reproduced light are fixedly different for each region facing the interference fringes of each frame, and the display device for an animation hologram is characterized in that the reproduced light is transmitted or blocked based on these characteristics.

2. The display device for an animated hologram according to claim 1, characterized in that the optical pattern filter transmits or blocks the regenerated light based on its polarization direction.

3. The optical pattern filter has different polarization patterns for each region opposite to the interference fringes of each frame. The display device for an animation hologram according to claim 2, characterized in that the illumination means irradiates regenerated light with a polarization direction that is transmitted by the polarization pattern of the region opposite to the interference fringes of the frame to be reproduced and blocked by the polarization pattern of the region opposite to the interference fringes of the frame not to be reproduced.

4. The display device for an animated hologram according to claim 1, characterized in that the optical pattern filter transmits or blocks the regenerated light based on its wavelength.

5. The optical pattern filter has different colors for each region opposite to the interference fringes of each frame. The display device for an animation hologram according to claim 4, characterized in that the illumination means irradiates regenerated light of a wavelength that is transmitted by the color of the region opposite to the interference fringes of the frame to be reproduced and blocked by the color of the region opposite to the interference fringes of the frame not to be reproduced.

6. The display device for an animation hologram according to claim 2 or 3, characterized in that the illumination means rotates the polarization direction of the playback light to a predetermined angle for each frame being played back.

7. The illumination means includes a plurality of light sources that selectively irradiate regenerated light with different polarization directions, The display device for an animation hologram according to claim 2 or 3, characterized in that, for each frame being played back, one corresponding light source is turned on and the other light sources are turned off.

8. The display device for an animation hologram according to claim 6, characterized in that the illumination means linearly polarizes the polarization direction of the reproduced light in one direction with a different angle for each frame.

9. The display device for an animation hologram according to claim 7, characterized in that the illumination means linearly polarizes the polarization direction of the reproduced light in one direction with a different angle for each frame.

10. The display device for an animation hologram according to claim 7, characterized in that the illumination means circularly polarizes the polarization direction of the reproduced light in a different rotational direction for each frame.

11. The display device for an animated hologram according to any one of claims 1 to 5, characterized in that the illumination means temporarily interrupts the emission of light during the transition between frames to be played back.

12. The display device for an animation hologram according to claim 6, characterized in that the illumination means continuously changes the polarization direction during the transition of frames to be played back.

13. In a method for displaying an animated hologram, in which interference fringes corresponding to multiple frames are spatially divided and multiplexed, and regenerative light with different polarization directions is sequentially irradiated onto an interference fringe forming medium to regenerate each frame, An optical pattern filter is placed in close proximity to the interference fringe forming medium. The polarization direction of the playback light is rotated to a predetermined angle for each frame being played back. The optical pattern filter is characterized in that it transmits or blocks the regenerated light in each region opposite to the interference fringes of each frame based on its characteristics.

14. In a method for displaying an animated hologram, in which interference fringes corresponding to multiple frames are spatially divided and multiplexed, and regenerative light with different polarization directions is sequentially irradiated onto an interference fringe forming medium to regenerate each frame, An optical pattern filter is placed in close proximity to the interference fringe forming medium. From among multiple light sources that emit regenerative light with different polarization directions, one light source corresponding to each frame being regenerated is turned on, and the other light sources are turned off. The optical pattern filter is characterized in that it transmits or blocks the regenerated light in each region opposite to the interference fringes of each frame based on its characteristics.

15. In a method for displaying an animated hologram, in which interference fringes corresponding to multiple frames are spatially divided and multiplexed, and regenerative light of different wavelengths is sequentially irradiated onto an interference fringe forming medium to regenerate each frame, An optical pattern filter is placed in close proximity to the interference fringe forming medium. The wavelength of the playback light is varied for each frame being played back. The optical pattern filter is characterized in that it transmits or blocks the regenerated light in each region opposite to the interference fringes of each frame based on its characteristics.

16. In a method for displaying an animated hologram, in which interference fringes corresponding to multiple frames are spatially divided and multiplexed, and regenerative light of different wavelengths is sequentially irradiated onto an interference fringe forming medium to regenerate each frame, An optical pattern filter is placed in close proximity to the interference fringe forming medium. From among multiple light sources that emit regeneration light of different wavelengths, one light source corresponding to each frame being regenerated is turned on, and the other light sources are turned off. The optical pattern filter is characterized in that it transmits or blocks the regenerated light based on its wavelength for each region opposite to the interference fringes of each frame.

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