Display system

Abstract

To provide a display system capable of displaying three-dimensional images with a compact configuration.SOLUTION: In a display system S, a hologram data display device 1 includes an SLM array 10 and a DOE 11 that modulates the amplitude of light. A hologram data generation device 2 performs, prior to interference computation for causing object light and reference light to interfere with each other, a first propagation computation that propagates object light 25 generated from subject data 26 to a virtual SLM array 20 corresponding to the SLM array 10, a second propagation computation that propagates object light in SLM gap portions of the SLM array 20 to a virtual DOE 21 having a transmittance distribution configured to remove zero-order light inherently included in reproduction light that is corresponding to the DOE 11 and passes through the DOE 11, a first modulation computation that calculates object light obtained by modulating the object light in the SLM gap portions by the DOE 21, and a third propagation computation that propagates the modulated object light to the SLM array 20.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to holography, and more particularly to display systems. [Background technology]

[0002] Holography is a technology that records and reproduces the wavefront of light as interference fringes. In principle, 3D images reproduced by holography can faithfully reproduce the light from an actual subject. Therefore, 3D holographic images are said to be free from the so-called inconsistency between convergence and accommodation that is a problem with stereograms (two-eye three-dimensional displays).

[0003] Computer-generated holograms (hereafter referred to as CGH) are a method for generating hologram data, which is the basis for 3D images, through calculations. In CGH, the hologram is created by the interference of the wavefront (object light) from the subject with a reference light, rather than physically, through calculations. CGH is performed by calculating the propagation of the object light and the interference between the object light and the reference light, as well as generating hologram data that matches the modulation method and number of gray levels of the spatial light modulator (hereafter referred to as SLM) used for display.

[0004] The hologram data is displayed on the SLM. A 3D image is reproduced on the SLM by irradiating the SLM with the reference light used in generating the CGH as the reconstruction illumination light. The viewing angle of the 3D image (the angle at which the 3D image can be observed) θ VA is limited by the diffraction angle due to the pixel structure of the SLM and can be expressed as the following equation (1):

[0005] θ VA =2sin -1 [λ / (2p)] … Equation (1)

[0006] Here, λ is the wavelength of the reconstruction illumination light, and p is the pixel pitch of the SLM. From equation (1), it can be seen that narrowing the pitch of the SLM is necessary to widen the viewing area of ​​a 3D image. Also, to display a large 3D image, it is necessary to increase the area of ​​the SLM. Here, if the number of pixels in the width direction of the SLM is N, x , the number of pixels in the height direction is N y Then, the width W and height H of the SLM can be expressed by the following equations (2) and (3), respectively.

[0007] W=pN x … Formula (2) H=pN y … Formula (3)

[0008] Therefore, to display 3D images on a large screen with a wide viewing area, it is necessary to increase the number of pixels as well as narrowing the pixel pitch. In recent years, research has been conducted on SLMs with narrow pixel pitches and a large number of pixels in order to display holograms with a wide viewing area (see, for example, Patent Document 1). Research is also being conducted on arranging and applying multiple SLMs to achieve a large number of pixels in the entire hologram data display device (see, for example, Non-Patent Document 1). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 2019-144423 [Non-patent literature]

[0010] [Non-Patent Document 1] Jin Li et al., “Holobricks: modular coarse integral holographic displays”, Light: Science & Applications 11, 57 (2022) Summary of the Invention [Problem to be solved by the invention]

[0011] However, when using a single SLM to increase the number of pixels while narrowing the pixel pitch, it becomes difficult to arrange the circuits to drive the pixels as the number of pixels increases. Furthermore, the technology disclosed in Non-Patent Document 1 involves laying out a large optical system on a large workbench to eliminate gaps between SLMs. In other words, the conventional method of arranging multiple SLMs to increase the number of pixels across the entire display device requires an extremely large optical system.

[0012] The present invention has been made in view of the above problems, and an object of the present invention is to provide a display system that displays three-dimensional images with a compact configuration.

[0013] In order to solve the above problems, a display system according to the present invention comprises a hologram data display device having an SLM array with inter-SLM gaps between a plurality of SLMs, which are arranged spatial light modulators, and a diffractive optical element that is arranged at a distance from the SLM array and has a predetermined transmittance distribution and modulates the amplitude of light reproduced from hologram data displayed on the SLM array; and a hologram data generation device having a memory unit and a processing unit, which generates the hologram data by interference calculation that causes object light and reference light to interfere with each other, and the hologram data generation device generates the hologram data by an interference calculation that causes object light and reference light to interfere with each other, the hologram data generation device The following calculations are performed: a first propagation calculation that propagates light to the position of a virtual SLM array that corresponds to the SLM array; a second propagation calculation that propagates object light in the inter-SLM gap part of the virtual SLM array to the position of a virtual diffractive optical element that corresponds to the diffractive optical element and has a transmittance distribution that removes zero-order light that is originally contained in the reproduced light that passes through the diffractive optical element; a first modulation calculation that calculates object light obtained by modulating the object light in the inter-SLM gap part by the virtual diffractive optical element; and a third propagation calculation that propagates the object light modulated by the first modulation calculation to the position of the virtual SLM array.

[0014] According to this configuration, in the display system, the hologram data display device combines multiple SLMs and an amplitude modulation type diffractive optical element (hereinafter referred to as DOE) having a predetermined transmittance distribution. In addition, in the display system, the hologram data generator generates hologram data by performing calculations to propagate object light generated from object data and calculations to modulate the amplitude of the object light using a virtual DOE (diffractive optical element). The virtual DOE has a transmittance distribution that removes the zero-order light inherently contained in the reconstructed light passing through the DOE of the hologram data display device. As a result, the object light reconstructed from hologram data on the hologram data display device is equivalent to the object light modulated by the virtual DOE. On the hologram data display device, this reconstructed object light is modulated by a real DOE, and the modulated light is equivalent to the object light generated by calculation from the object data. Therefore, when the SLM array is observed through a real DOE on the hologram data display device, the 3D image that was the basis of the object data can be reproduced. Conventionally, when an observer observes an SLM array without a DOE, gaps between the SLMs are visible. On the other hand, when an observer looks at the SLM array through the DOE, the wavefront of the reconstructed light is scattered appropriately due to the DOE in front of the observer, allowing the observer to see a 3D image as if there were no gap between the SLMs.The display system does not require a large optical system as in conventional technology, so a large optical system is not required and the compact configuration makes it possible to hide the gap between the SLMs. [Effects of the Invention]

[0015] The present invention provides the following excellent effects. The display system according to the present invention can display three-dimensional images on a large screen by increasing the number of spatial light modulators arranged in the SLM array of the hologram data display device. In addition, the display system can also achieve a wider viewing zone by increasing the number of spatial light modulators arranged in the SLM array of the hologram data display device and applying spatial light modulators with narrow pixel pitches. Therefore, the display system can display 3D images with a wide viewing area and a large screen with a compact configuration. Furthermore, the hologram data generating device of the display system is capable of generating hologram data with a compact configuration that allows the three-dimensional image that is the basis of the subject data to be reproduced on the hologram data display device side. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic diagram showing an overview of processing performed by a hologram data display device and a hologram data generation device according to an embodiment of the present invention. [Figure 2] 1 is a block diagram showing an example of the configuration of a hologram data display device and a hologram data generation device according to an embodiment of the present invention. [Figure 3] (a) is a schematic diagram of a DOE, and (b) is a schematic diagram of a virtual DOE. [Figure 4] FIG. 2 is a schematic diagram showing the flow of processing in the display system according to the first embodiment. [Figure 5] FIG. 10 is a schematic diagram showing the flow of processing in a display system according to a second embodiment. [Figure 6] FIG. 11 is a schematic diagram showing the flow of processing in a display system according to a third embodiment. [Figure 7] FIG. 10 is a schematic diagram showing the flow of processing in a display system according to a fourth embodiment. [Figure 8] 10(a) to 10(c) are schematic diagrams showing the conditions of the verification experiment. [Figure 9] 10(a) to 10(c) are schematic diagrams showing the conditions of the verification experiment. [Figure 10] FIG. 10 is a diagram showing playback results in a verification experiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of a display system, a hologram data generating device, and a hologram data display device according to the present invention will be described in order. (First embodiment) [Display system overview] 1, the display system S includes a hologram data display device 1 and a hologram data generation device 2. The hologram data display device 1 includes an SLM array 10 and a DOE (diffractive optical element) 11. The SLM array 10 is a multiplicity of SLMs (Spatial Light Modulators) 10 i There is an inter-SLM gap between them, and it displays hologram data 3. The DOE 11 is arranged at a distance from the SLM array 10, has a predetermined transmittance distribution, and modulates the amplitude of light reproduced from the hologram data 3 displayed on the SLM array 10. Note that i is an identifier of the SLM, and i=1, 2, ... The hologram data generating device 2 generates hologram data 3 by performing an interference calculation to cause interference between object light and reference light, and is realized by a general computer equipped with a storage unit and a processing unit. Before the interference calculation, the hologram data generation device 2 performs a first propagation calculation, a second propagation calculation, a first modulation calculation, and a third propagation calculation. The first propagation calculation is a calculation process for propagating the object beam 25 generated from the subject data 26 to the position of the virtual SLM array 20. Here, the virtual SLM array 20 corresponds to the SLM array 10, and is composed of a plurality of virtual SLMs (spatial light modulators) 20 arranged two-dimensionally. i It has. The second propagation calculation is a calculation process in which the object light in the gap between the SLMs of the virtual SLM array 20 is propagated to the position of the virtual DOE 21. Here, the virtual DOE 21 corresponds to the DOE 11, and has a transmittance distribution that removes the zero-order light that is originally contained in the reconstructed light that passes through the DOE 11. The first modulation calculation is a calculation process for calculating object light obtained by modulating the object light in the gap between the SLMs by the virtual DOE 21 . The third propagation calculation is a calculation process in which the object light modulated by the first modulation calculation is propagated at the position of the virtual SLM array 20.

[0018] [Configuration example of a hologram data display device] An example of the configuration of a hologram data display device will be described with reference to Fig. 2 (and also with reference to Fig. 1 as appropriate). Fig. 2 is a block diagram showing a display system S including a hologram data display device 1 and a hologram data generation device 2. The hologram data display device 1 shown in Fig. 2 includes an SLM array 10, a DOE 11, and a light source 12.

[0019] The SLMs that make up the SLM array 10 can be SLMs that are commonly used in holography. The SLM is, for example, a liquid crystal display device. When using a liquid crystal display device as the SLM, it is preferable to use a narrow pixel pitch of, for example, several μm or less in order to achieve a wide viewing angle. The number of SLMs in the SLM array 10 may be more than one, and is not limited to the number shown in the figure (i=1 to 4) or the arrangement shown in the figure (two in the width direction and two in the height direction). Each SLM 10 that makes up the SLM array 10 i The SLMs do not all need to have the same specifications, and for example, SLMs with different numbers of pixels or pixel pitches may be arranged. i There is no need for all of them to have the same specifications.

[0020] Light reconstructed from hologram data 3 displayed on the SLM array 10 is incident on the DOE 11. The DOE 11 modulates the light reconstructed by irradiating the SLM array 10 displaying the hologram data 3 with reference light 23 as reconstruction illumination light 13. The DOE 11 modulates the amplitude of reconstruction light 14 reconstructed from hologram data 3 generated in advance by calculation using a virtual DOE 21.

[0021] The DOE 11 is an optical element that utilizes the diffraction phenomenon of light to convert (modulate) incident light into a pre-designed pattern. The DOE 11 is an amplitude modulation type that allows or blocks light depending on the area. The areas of the DOE 11 that allow light to pass are called transmissive areas, while the areas that do not allow light to pass are called opaque areas. In this embodiment, the smallest unit of area with different light intensities on the surface of the DOE 11 is called a pixel. For example, by distributing the pixels of the transmissive area and the pixels of the opaque area in the DOE 11 in the same ratio, the input light can be modulated so that half of the light passes through. Furthermore, by setting the number of pixels in the opaque area to three times the number of pixels in the transmissive area, the input light can be modulated so that one-quarter of the light passes through. DOE functions include a multifocal lens function and a diffusion screen function. DOEs are available in types that transmit incident light and types that reflect it.

[0022] The space between the SLM array 10 and the DOE 11 can be, for example, free space (air). Alternatively, a light-transmitting member made of a material that transmits visible light, such as glass or resin, can be placed between the SLM array 10 and the DOE 11 to integrate the SLM array 10 and the DOE 11. Integrating the SLM array 10 and the DOE 11 in this way can prevent the positional relationship between the SLM array 10 and the DOE 11 from shifting.

[0023] The light source 12 irradiates the SLM array 10 displaying the hologram data 3 with a reconstruction illumination light 13. The light source 12 may be an external device to the hologram data display device 1, but it may also be provided internally in the hologram data display device 1. The light source 12 may be a light source that is generally used in holography. There are no particular limitations on the wavelength of the light source, and it may be visible light. The light source 12 is, for example, a laser beam.

[0024] The hologram data display device 1 can include a synchronization device 17 and a control unit 18 as needed. The synchronizer 17 outputs a synchronization signal to the SLM array 10 and the light source 12 to synchronize the display timing of the hologram data 3 displayed on the SLM array 10 with the irradiation timing of the light source 12, for example.

[0025] The control unit 18 outputs operational instructions to, for example, the SLM array 10 and the light source 12. The control unit 18 can also receive the hologram data 3 from the hologram data generation device 2, store the hologram data 3, and output the hologram data 3 to the SLM array 10. The control unit 18 is realized, for example, by a general computer including a storage unit and a processing unit. The processing unit operates based on a hologram data display program stored in the storage unit. The hologram data display program is a program that causes the computer to function as the hologram data display device 1. The control unit 18 may be incorporated into, for example, a liquid crystal display device and used as an SLM that constitutes the SLM array 10. Note that in hologram data reproduction, known hologram reproduction means may be used for all processes except for modulating the reproduction light using the DOE 11.

[0026] [Configuration example of hologram data generation device] Next, an example of the configuration of the hologram data generating device 2 will be described with reference to FIG. 2 (and also with reference to FIG. 1 as appropriate). The hologram data generator 2 generates hologram data 3 to be displayed on the SLM array 10 of the hologram data display device 1 by calculation. The hologram data generation device 2 is realized by a general computer including a storage unit and a processing unit, such as a personal computer. For example, the hologram data generation device 2 shown in FIG. 2 includes a CPU 51, a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, an HDD (Hard Disk Drive) 54, an input / output interface 55, a communication interface 56, and a media interface 57.

[0027] CPU 51 operates based on a hologram data generation program stored in ROM 52 or HDD 54, and executes the hologram data generation program loaded into RAM 53. The hologram data generation program is a program for causing a computer to function as hologram data generation device 2. Input / output interface 55 is connected to input devices 61 such as a mouse and keyboard, and output devices 62 such as a display. Media interface 57 writes data to and reads data from recording medium 64, such as a semiconductor memory.

[0028] The generated hologram data can be transmitted to the hologram data display device 1 via a network 63. It is also possible to record the hologram data on a recording medium 64 and read the recording medium 64 in the hologram data display device 1.

[0029] [Display system layout example] Next, an example of the arrangement of the display system will be described with reference to FIG. 1 (referring to FIG. 1 as needed). As shown in FIG. 1, in the hologram data display device 1, the DOE 11 is positioned at a distance z from the SLM array 10 in the z direction. D The position of the DOE 11 is set to the z direction with the position of the SLM array 10 as the reference (position 0). D Let's say. In the hologram data generating device 2, the position of the virtual SLM array 20 in the z direction is taken as the reference (position 0), and the position of the virtual DOE 21 is also taken as the z direction. D Let's say. The distance from the position of the SLM array 10 to the position of the DOE 11 is z D (When the distance is expressed including the propagation direction, +z D ) The distance from the position of the virtual DOE 21 to the position of the virtual SLM array 20 is also z D (When the distance is expressed including the propagation direction, -z D ) In addition, the position of the object light 25 is z OSimilarly, the position of the reconstructed light 15 is z O In other words, the distance from the position of the SLM array 10 to the position of the reconstructed light 15 is z O (When the distance is expressed including the propagation direction, +z O ), and the distance from the position of the object beam 25 to the position of the virtual SLM array 20 is z O (When the distance is expressed including the propagation direction, -z O )

[0030] Here, the position of the reconstruction light 15 (and the position of the object light 25) z O can be set to a desired value depending on the depth at which the three-dimensional video 16 is to be displayed. Also, the virtual position of DOE21 (and the position of DOE11) z D can be set to a desired value depending on the image quality of the 3D image 16 to be displayed. Note that the 3D image to be reproduced may have a reduced brightness in the area corresponding to the gap between the SLMs, resulting in brightness unevenness. However, when the position z of the virtual DOE 21 is D By adjusting the position z of the virtual DOE 21, it is possible to eliminate uneven brightness. D Regardless of this, it is also possible to reduce brightness unevenness by performing a process in advance to increase the brightness of areas in a 3D image where the brightness is low (such as areas corresponding to the gaps between SLMs).

[0031] 1, the reference numerals of the components of the hologram data display device 1 are in the tens range, and the reference numerals of the components of the hologram data generation device 2 are in the twenties range. Furthermore, the ones digit of the reference numerals of the components of the hologram data generation device 2 that correspond to the components of the hologram data display device 1 corresponds to the ones digit of the reference numerals of the components of the hologram data display device 1. 1, the reconstructed beams 14 and 15 and the object beams 24 and 25 are shown schematically as wavefronts of light. The three-dimensional image 16 is not limited to the illustrated cylinder or rectangular parallelepiped, and may have any other three-dimensional shape as long as it has the same shape as the subject data 26 that is the basis of the three-dimensional image 16.

[0032] [Processing in the display system] Next, the processing in the display system will be described with reference to FIG. 1 (and also with reference to FIGS. 2 to 4 as appropriate), focusing mainly on the processing by the hologram data generating device 2. The calculation for generating the hologram data 3 by the hologram data generating device 2 is complementary to the hologram reconstruction process. The DOE 11 included in the hologram data display device 1 is, for example, an amplitude binary modulation (hereinafter, the transmittance distribution of the DOE 11 is referred to as A D In the case of (x, y), negative modulation is not possible, so the transmitted light contains zero-order light. In Figure 3(a), the transmitting area is indicated by a square and the light-blocking area is indicated by a black square. Furthermore, (x, y) represent spatial coordinates.

[0033] The zero-order light is light that passes through the DOE 11 without being modulated, and unless some ingenuity is taken, gaps in the SLM array 10 will be visible when observing the reconstructed light, just as in the case where no DOE is applied. Therefore, a virtual DOE 21 that corresponds to the DOE 11 has a transmittance distribution A as shown in Figure 3(b). D The average value μ of (x,y) D Transmittance distribution A with subtraction of D - (x, y) is given to remove the zero-order light. By giving the virtual DOE 21 such a transmittance distribution, negative modulation becomes possible, and the virtual DOE 21 operates as a virtual phase modulation element. In Figure 3(b), the area where the phase modulation is π modulation is indicated by a ■ symbol, and the area where the phase modulation is unmodulated is indicated by a square symbol. Note that the amplitude is also uniformly modulated by the virtual DOE 21, but since this is processed within the computer, it does not affect the hologram data 3.

[0034] Therefore, in this embodiment, the hologram data generation device 2 performs calculation processing assuming that the transmittance distribution of the virtual DOE 21 is a transmittance distribution obtained by uniformly subtracting the average value from the transmittance distribution of the DOE 11 included in the hologram data display device 1. In short, the hologram data generation device 2 calculates A shown in the following equation (4).D - The modulation is calculated by using (x, y) as the transmittance distribution of the virtual DOE 21.

[0035] A D - (x,y)=A D (x,y)-μ D … Formula (4)

[0036] That is, the hologram data generation device 2 can modulate the phase of the light incident on the virtual DOE 21. Therefore, the object light (reconstructed light) in the gap between the SLMs can be widely incident beyond the gap of the SLM array 10.

[0037] As shown in FIG. 4, in this embodiment, the hologram data generation device 2 generates object light 25 from subject data 26 that forms the basis of the three-dimensional image 16 (object light generation: step S1). Note that, because the DOE 11 of the hologram data display device 1 is amplitude binary modulated, the reproduced light 14 contains zero-order light, i.e., light that passes through the DOE 11 as is. Utilizing this characteristic, the hologram data generation device 2 first performs a calculation to propagate the object light 25 to the position of the virtual SLM array 20 (first propagation calculation: step S2). This propagation distance is calculated as -z O Then, the hologram data generating device 2 performs a calculation to propagate the object light 25a in the gap between the SLMs to the position of the virtual DOE 21 (second propagation calculation: step S3a). This propagation distance is calculated as z D Then, the hologram data generation device 2 uses the above-mentioned formula (4) to calculate the object light 24a obtained by modulating the object light 25a in the gap between the SLMs by the virtual DOE 21 (first modulation calculation: step S4a). Then, the hologram data generation device 2 performs a calculation to propagate the object light 24a modulated in step S4a back to the position of the virtual SLM array 20 (third propagation calculation: step S5a). This propagation distance is -z D is.

[0038] The modulated object light 24a is called "modulated" because it is uniformly amplitude modulated, but with regard to phase modulation, it contains a π-modulated component and a non-phase-modulated component.

[0039] Then, the hologram data generating device 2 causes the object light 24a modulated by the virtual DOE 21 to interfere with the reference light 23 to calculate the hologram data 3 (interference step: step S6). Note that when generating the hologram data from the interference fringes of the object light and the reference light, each SLM 10 constituting the SLM array 10 of the hologram data display device 1 i Calculations are performed according to specifications such as the number of pixels, pixel pitch, and modulation method (see Figure 1).

[0040] On the other hand, in the hologram data display device 1, hologram data 3 is displayed on an SLM array 10, and the SLM array 10 is irradiated with reconstruction illumination light 13 emitted from a light source 12, thereby reconstructing the displayed hologram data 3. The reconstructed light is projected over a predetermined distance z D By propagating only a certain distance (see Figure 1), reconstructed light 14 modulated by the virtual DOE 21 applied when generating the hologram data is obtained. Here, the component of reconstructed light 14 corresponding to object light 24a modulated on the hologram generation side is selectively transmitted by DOE 11 only in the region where the phase is not modulated by the virtual DOE 21 (region with no phase modulation, marked "□"). On the other hand, the region of reconstructed light 14 where the phase is π-modulated by the virtual DOE 21 on the hologram generation side (marked "■") is selectively shielded. In other words, DOE 11 acts as a light-shielding mask (amplitude mask) for the phase modulation by the virtual DOE 21. By operating in this way, DOE 11 removes the phase modulation introduced by the virtual DOE 21. When the reconstructed light modulated by DOE 11 is transmitted over a predetermined distance (z O -z D ) (see FIG. 1), a reconstructed beam 15 is obtained, and a three-dimensional image 16 is reproduced.

[0041] 4, the reference light 23 is illustrated as being irradiated perpendicularly to the hologram surface, but it may be irradiated non-perpendicularly as shown in Fig. 1. Similarly, the irradiation direction of the reconstruction illumination light 13 may be either perpendicular or non-perpendicular as long as it is the same as the direction of the reference light 23.

[0042] Furthermore, when generating hologram data 3, known hologram generation processes may be applied to the hologram data generation process other than the calculation process, except for the calculation of modulating object light using virtual DOE 21. For example, ray-to-wavefront conversion technology may be used in step S1, where object light 25 is generated from subject data 26. Furthermore, in step S6 (when generating phase hologram data), the hologram data may be optimized using a Fourier iteration method or an error diffusion method.

[0043] When the hologram data 3 generated by the hologram data generating device 2 is displayed by the hologram data display device 1, the two devices may be directly connected, or may be connected via a recording medium on which the hologram data 3 is written. Alternatively, the hologram data 3 may be transferred via broadcasting or transmission, either wired or wirelessly.

[0044] [Effects of the display system] In the hologram data display device 1 and hologram data generation device 2 having the configuration shown in FIG. 1, desired reconstructed light 15 can be obtained by designing a DOE 11 (real) and a virtual DOE 21 (virtual). The observer observes the hologram from the side where the 3D image 16 is placed (the right side in FIG. 1), with the DOE 11 as the reference in FIG. 1. That is, the observer views the 3D image 16 through the DOE 11, so even if the gap between the SLMs is large enough to be visible to the naked eye, it can be concealed. If the DOE 11 were not located in front of the observer, the gap between the SLMs would be visible, and the quality of the 3D image 16 would be significantly degraded. Furthermore, since unwanted light (such as high-order diffracted light and zero-order light) is modulated by passing through or reflecting off the DOE 11, the unwanted light can be made less noticeable to the observer compared to the desired reconstructed light 15. As shown in FIG. 1, the display system S according to this embodiment does not require a large-scale optical system as in the prior art, and therefore can conceal the gap between the SLMs with a compact configuration.

[0045] From the perspective of recording object beam 25, if all of the light from a given object point constituting subject data 26 reaches a narrow region called the inter-SLM gap (e.g., a cross-shaped region in Figure 1), it is impossible to record or reconstruct this object point. On the other hand, modulation using the virtual DOE 21 allows the light from the given object point to extend beyond the inter-SLM gap (e.g., the cross-shaped region) and be widely incident on the virtual SLM array 20. In this case, because the virtual SLM array 20 has an inter-SLM gap, some hologram data 3 will be lost in the display system. However, due to the redundancy of holography, the recorded object point can be reconstructed, albeit with some degradation due to the loss. To ensure redundancy in the gap position of the SLM array 10, it is preferable to separately measure and adjust the gap position and width. Furthermore, increasing the number of pixels in the SLM can improve the PSNR (Peak Signal-to-Noise Ratio) of the reconstructed image.

[0046] (Second embodiment) Next, a display system according to a second embodiment will be described with reference to FIG. The display system according to the second embodiment includes a hologram data display device 201 and a hologram data generating device 202. In Fig. 5, to indicate that it is the second embodiment, the reference numerals of the components of each device are indicated by numbers in the 200 range. Furthermore, the last two digits of the reference numerals of the components of each device correspond to the reference numerals of the components shown in Fig. 1.

[0047] 5, hologram data generation device 202 generates object beam 225 from subject data 226 (step S1) and performs calculations to propagate object beam 225 to the position of virtual SLM array 220 (step S2). Then, hologram data generation device 202 performs calculations to propagate object beam 225a in the inter-SLM gap to the position of virtual DOE 221 (step S3a). Then, hologram data generation device 202 calculates object beam 224a obtained by modulating object beam 225a in the inter-SLM gap by virtual DOE 221 (step S4a). Then, hologram data generation device 202 performs calculations to propagate modulated object beam 224a again to the position of virtual SLM array 220 (step S5a).

[0048] The second embodiment differs from the first embodiment in that the hologram data generating device 202 further performs some additional calculation processes in the calculation process before the interference step (step S6). The hologram data generating device 202 is a virtual SLM 20 i (See FIG. 1) is calculated to propagate the object beam 225b of the SLM units arranged in the virtual DOE 221 (fourth propagation calculation: step S3b). This propagation distance is calculated as z D is. The hologram data generating device 202 then calculates whether the object light 225b of the SLM unit is transmitted through the transmittance distribution A of the DOE 211 of the hologram data display device 201. D The object light 224b modulated by (x, y) is calculated (second modulation calculation: step S4b). Then, the hologram data generating device 202 performs a calculation to propagate the object beam 224b modulated in step S4b to the position of the virtual SLM array 220 again (fifth propagation calculation: step S5b). This propagation distance is calculated as -z D is. The modulated object light 224b is uniformly amplitude modulated, and the transparent regions (□) are recorded, but the light-shielding regions (■) are not recorded as a hologram.

[0049] In this embodiment, hologram data generation device 202 superimposes modulated object beam 224a and modulated object beam 224b together, and then hologram data generation device 202 causes the superimposed object beam to interfere with reference beam 223 to calculate hologram data 203 (step S6). Here, the method of superimposing the modulated object light 224a and the modulated object light 224b can be, for example, weighted addition, space division multiplexing, time division multiplexing, etc. In the following, as an example, the modulated object light 224a and the modulated object light 224b are described as being weighted and added.

[0050] Meanwhile, in hologram data display device 201, hologram data 203 is displayed on SLM array 210, and reconstruction illumination light 213 emitted from light source 212 is irradiated onto SLM array 210, thereby reconstructing the displayed hologram data 203. Reconstruction light 14 modulated by virtual DOE 221 propagates to DOE 211. Here, of the component of reconstruction light 214 corresponding to modulated object light 224a, only the region □ where the phase is unmodulated is selectively transmitted by DOE 211, while the region (■) where the phase is π-modulated is selectively blocked.

[0051] In addition, the component of the reconstructed light 214 corresponding to the modulated object light 224b has the same transmittance distribution A as the DOE 211 in the hologram data generating device 202. D The DOE 211 is modulated by (x, y). Therefore, light that reaches the transparent regions (□) of the DOE 211 is reproduced, but light that reaches the light-shielding regions (■) of the DOE 211 is not reproduced. The reproduced light modulated by the DOE 211 then propagates to the position of the object data 226 (reproduced light 215), and a three-dimensional image 216 is reproduced.

[0052] Although the second embodiment requires more calculation time than the first embodiment, like the first embodiment, it does not require a large-scale optical system as in the prior art, and therefore can conceal the gap between the SLMs with a compact configuration. Furthermore, while the first embodiment reconstructs light that reaches the light-shielding region (■) of the actual DOE, the second embodiment does not reconstruct light that reaches the light-shielding region (■) of the actual DOE 211. Therefore, the second embodiment has the effect of increasing the utilization efficiency of incident light (reconstruction illumination light) in hologram data.

[0053] (Third embodiment) Next, a display system according to a third embodiment will be described with reference to FIG. The display system according to the third embodiment includes a hologram data display device 301 and a hologram data generating device 302. In Fig. 6, the reference numerals of the components of each device are indicated by numbers in the 300 range to indicate that this is the third embodiment. The last two digits of the reference numerals of the components of each device correspond to the reference numerals of the components shown in Fig. 1. Below, descriptions of the same configuration as in Fig. 4 will be omitted as appropriate.

[0054] This embodiment can be applied to either the first or second embodiment already described, as long as hologram data can be generated using a multi-wavelength reference light instead of a single wavelength. Below, the third embodiment will be described with respect to differences from the first or second embodiment.

[0055] The hologram data generating device 302 generates hologram data by using multiple wavelengths of the reference light. j is a time-division multi-wavelength reference light 323 j Here, j is an identifier for identifying the wavelength of light. For example, when three colors of light are emitted, j may be set to 1, 2, 3. As an example, the reference light 323 j is assumed to be light of the three RGB colors. Here, j corresponds to the three RGB colors, and j is set to R, G, B.

[0056] That is, the reference beam 323 shown in the figure j is the first reference beam 323 R and the second reference beam 323 G and the third reference beam 323 B The hologram data 303 shown in the figure is a generalized representation. j is the first hologram data 303 R and second hologram data 303 G and the third hologram data 303 B Similarly, in the illustrated hologram data generating device 302, the object beam 325 j , modulated object beam 324 j , hologram data 303 j is the reference beam 323 j The figure shows a generalized representation of the RGB three colors corresponding to the

[0057] On the other hand, the hologram data display device 301 includes a light source 312 in addition to the SLM array 310 and the DOE 311. j and a synchronizer 317. light source 312 j is a time-division multiple-wavelength reconstruction illumination light 313 for the SLM array 310. j The illustrated light source 312 is switched to emit light. j is the first light source 312 R and the second light source 312 G and the third light source 312 B The first light source 312 is a generalized R is the wavelength λ corresponding to red R and the second light source 312 G is the wavelength λ corresponding to green G and the third light source 312 B is the wavelength λ corresponding to blue B It emits light.

[0058] light source 312 iFor example, the light source element may be configured by providing red light source elements, green light source elements, and blue light source elements in a predetermined periodic arrangement. Each light source element may be, for example, a semiconductor laser. In the illustrated hologram data display device 301, the reconstructed illumination light 313 j , modulated regenerated light 314 j , regeneration light 315 j , 3D video 316 j is light source 312 j The figure shows a generalized representation of the RGB three colors corresponding to the

[0059] The synchronizer 317 synchronizes the reconstructed illumination light 313 j Wavelength and hologram data 303 j The synchronizer 317 synchronizes the switching timing between the SLM array 310 and the light source 312. j The SLM array 310 outputs a synchronization signal for each wavelength according to the time. j Switch between the two. Light source 312 j In accordance with the synchronization signal, the reconstructed illumination light 313 corresponding to each wavelength is generated according to time. j Switch and fire.

[0060] Specifically, the light source 312 j is the first wavelength λ R and the second wavelength λ G and the third wavelength λ B That is, the SLM array 310 emits light of the first wavelength λ R First hologram data 303 according to R When the light source 312 is displayed, j is the first wavelength λ R The SLM array 310 also emits light of a second wavelength λ G Second hologram data 303 according to G When the light source 312 is displayed, j is the second wavelength λ G Furthermore, the SLM array 310 emits light of a third wavelength λ BThird hologram data 303 according to B When the light source 312 is displayed, j is the third wavelength λ B As a result, the hologram data display device 301 displays a color three-dimensional image 316 j can be presented to the observer.

[0061] In the third embodiment, a three-color light source 312 j and a synchronization device 317, but as with the first embodiment, there is no need to install a large-scale optical system as in the prior art, and therefore the gap between the SLMs can be hidden with a compact configuration.

[0062] (Fourth embodiment) Next, a display system according to a fourth embodiment will be described with reference to FIG. The display system according to the fourth embodiment includes a hologram data display device 401 and a hologram data generating device 402. In Fig. 7, to indicate the fourth embodiment, the reference numerals of the components of each device are indicated by numbers in the 400 range. The last two digits of the reference numerals of the components of each device correspond to the reference numerals of the components shown in Fig. 1. Below, explanations of the same configuration as in Fig. 6 will be omitted as appropriate.

[0063] This embodiment can be applied to any of the first to third embodiments already described, provided that hologram data can be generated using a multi-wavelength reference light instead of a single wavelength and that the data can be displayed in a spatially divided manner. Below, the fourth embodiment will be described with respect to the differences from the third embodiment.

[0064] A color filter 419 is arranged on the DOE 411 that constitutes the hologram data display device 401. As an example, the reference light 423 jis assumed to be light of three RGB colors. Here, j=R, G, B specifically corresponding to the three RGB colors. In this case, color filters 419 of the three RGB colors arranged in a predetermined periodic array are arranged on the DOE 411. As the color filters, general filters made of known materials can be used. The color filters can be arranged in a general manner such as the Bayer method. Note that color filters can also be arranged on the SLM array 410 instead of the DOE 411.

[0065] Alternatively, the color filter itself may be used as the DOE 411. That is, the DOE 411 constituting the hologram data display device 401 has a transmittance distribution A D (x, y) is the characteristic (Σ j A Dj (x,y) where A Dj (x, y) indicates the transmittance distribution for each RGB color of the color filter. For example, A DR (x, y) is the wavelength λ R The transmittance distribution for the wavelength λ R Only the wavelength λ is blocked. G ,λ B Similarly, light of A is transmitted. DG (x, y) is the wavelength λ G Only the wavelength λ is blocked. B ,λ R The light of A is transmitted. DB (x, y) is the wavelength λ B Only the wavelength λ is blocked. R ,λ G Light passes through.

[0066] In the following, this embodiment is assumed to be applied to, for example, either the first or second embodiment. In this case, the hologram data generating device 402 generates the reference light 423, which is multi-wavelength by time division. j Each hologram data 403 generated by j By multiplexing the hologram data 403 kHere, the identifier k indicates that the hologram data is multiplexed. Specifically, the hologram data 403 k is the first wavelength λ R First hologram data 403 according to R and the second wavelength λ G Second hologram data 403 according to G and the third wavelength λ B Third hologram data 403 according to B and are multiplexed.

[0067] The illustrated reference beam 423 j is the first reference beam 423 R and the second reference beam 423 G and the third reference beam 423 B Similarly, in the illustrated hologram data generating device 402, the object beam 425 j , modulated object beam 424 j is the reference beam 423 j The figure shows a generalized representation of the RGB three colors corresponding to the

[0068] On the other hand, in the hologram data display device 401, the light source 412 of three colors of RGB is k is the multiplexed hologram data 403 k Based on this assumption, the SLM array 410 is subjected to the multiplexing of the RGB three-color reconstructed illumination light 413 k In the illustrated hologram data display device 401, modulated reconstructed light 414 k indicates the multiplexed RGB triad. Modulated regenerated light 414 k is spatially divided into a first wavelength λ by a color filter 419 disposed in the DOE 411. R and the second wavelength λ G and the third wavelength λ B It should be noted that the reconstructed light 415 shown in the figure can be separated into the reconstructed light 415 and the reconstructed light 415. j and 3D video 416 j shows a generalized representation of spatially divided RGB triads.

[0069] In the fourth embodiment, a three-color light source 412 k Although the SLMs are provided with a color filter 419, no synchronization device is required, and the gap between the SLMs can be hidden with a compact configuration.

[0070] The display system, hologram data generating device, and hologram data display device according to the embodiments of the present invention have been described above, but the scope of the present invention is not limited to these descriptions and should be broadly interpreted based on the claims. It goes without saying that various changes and modifications based on these descriptions are also included in the scope of the present invention.

[0071] For example, the hologram data generation device 2 may perform pre-interference calculation processing and interference calculation processing by regarding the transmittance distribution of the virtual DOE 21 as having the inverse characteristics of the transmittance distribution of the DOE 11 included in the hologram data display device 1. Here, the inverse characteristics refer to optical characteristics that cancel out the positive optical characteristics of the DOE 11, assuming that the DOE 11 has a positive characteristic. For example, assume that a certain light (L) is incident in a positive direction on a DOE 11 of a certain type (transmissive and phase modulation type), and the phase distribution is modulated by the DOE 11, resulting in the emission of light (M). In this case, if the modulated light (M) is incident in a negative direction on a virtual DOE 21 of the same type (transmissive and phase modulation type) with the inverse characteristics, ideally the phase distribution of the DOE 11 is canceled out, resulting in the emission of the original light (L). When the positive characteristic is expressed by a function, vector, matrix, complex number, or the like, the inverse characteristic corresponds to its inverse function, inverse vector, inverse matrix, complex conjugate, or the like.

[0072] In this case, virtual DOE 21 has the inverse characteristics of real DOE 11 arranged in hologram data display device 1, so that at hologram data display device 1, object light (reconstructed light 14) from which hologram data 3 is reconstructed is light equivalent to object light 24 modulated by virtual DOE 21. At hologram data display device 1, light obtained by modulating this reconstructed object light by real DOE 11 is light equivalent to object light 25 generated by calculation from object data 26. Therefore, when SLM array 10 is observed at hologram data display device 1 through real DOE 11, it is possible to reconstruct 3D image 16, which is the basis of object data 26. Therefore, by displaying hologram data 3 at hologram data display device 1, 3D image 16 corresponding to object data 26 can be displayed on a large screen with a wide viewing area, in a compact configuration.

[0073] Specifically, the hologram data generating device 2 uses A shown in the following equation (5) or (6) instead of the above equation (4). D - The modulation may be calculated by using (x, y) as the transmittance distribution of the virtual DOE 21.

[0074] A D - (x,y)=[1-A D (x,y)]-μ D … Formula (5) A D - (x,y)=[A D (x,y)-μ D ] * … Formula (6)

[0075] In equation (6), * denotes a complex conjugate. By doing so, the unmodulated and π-modulated regions of the modulated reproduced light 14 are inverted, and the π-modulated regions are transmitted by the DOE 11 (the unmodulated regions are blocked). However, since the light is uniformly π-modulated, this does not affect the 3D image 16. Up to now, the actual DOE 11 has been described as a transmission type DOE, but it may also be a reflection type DOE.

[0076] Also, for example, the hologram data generating device 2 may include a virtual SLM 20 arranged in a virtual SLM array 20. i The distance between the SLMs 10 arranged in the SLM array 10 included in the hologram data display device 1 is i It is also possible to perform pre-interference calculation processing and interference calculation processing separately, assuming that the gap length is larger than the gap length by a predetermined value. In this way, redundancy for the gap position of the SLM array 10 can be ensured without having to separately measure and adjust the gap position and width of the SLM array 10.

[0077] A verification experiment conducted to verify the effectiveness of the display system will be described below with reference to FIG. An experimental system was constructed, hologram data 203 was generated by calculation corresponding to the hologram data generating device 202 of the display system according to the second embodiment, and a reconstructed image (three-dimensional video 216) was observed by optical reconstruction of the hologram data 203. In the experiment, a reflective SLM was used to simulate the SLM array 210 of the hologram data display device 201. This reflective SLM has a width direction pixel count N x is 3840, the number of pixels in the height direction is N y is 2160 and the pixel pitch p is 3.74 μm.

[0078] Additionally, an actual DOE 211 for the hologram data display device 201 was fabricated. A metal film was laminated on a substrate, and resist was uniformly applied to the metal film. Next, a pattern of a transparent region was written using a laser writing device. At this time, the transmittance distribution was set to uniform random numbers, and the size of the transparent region (□) that forms the minimum structure was set to 3.74 × 3.74 μm. Using the resist remaining only in the region corresponding to the light-shielding region as a mask, the metal film corresponding to the transparent region was etched. Next, the remaining resist was removed, leaving only the metal film corresponding to the light-shielding region.

[0079] Furthermore, the object data 226 was set to the alphabet "N," and the hologram data generating device 202 generated hologram data 203 (hereinafter referred to as CGH) as follows. In the propagation calculation step (step S2), as shown in FIG. 8(a), the complex amplitude distribution of the object light (object light 225i on the SLM array surface) at position z0+z1 relative to the SLM array 220 is set to U(x, y, z0+z1). Also, the distance of the back propagation of the object light 225 to the SLM array 220 is (z O +z1). 8(b), the propagation calculation step (step S3a) was set to a propagation distance (z0) of object beam 225a in the inter-SLM gap to DOE 221. That is, DOE 221 was located at position z0. In the modulation step (step S4a), the object light 224a obtained by modulating the object light 225a in the gap between the SLMs by the virtual DOE 21 was calculated using the above-mentioned formula (4). In the propagation calculation step (step S5a), the distance of back propagation of modulated object beam 224a to SLM array 220 was assumed to be (z0), as shown in Fig. 9(a). In addition, the complex amplitude distribution of object beam 225a in the inter-SLM gap portion, which has been phase-modulated by virtual DOE 221, on the array surface of virtual SLM array 220 was assumed to be U1(x, y).

[0080] In the fourth propagation calculation (step S3b), as shown in FIG. 8(c), the propagation distance of object light 225b of the SLM unit to the position of DOE 221 was assumed to be (z0). In the second modulation calculation (step S4b), the object light 225b of the SLM part has a transmittance distribution A D The object beam 224b modulated by (x, y) was calculated. 9(b), the distance of back propagation of modulated object beam 224b to the position of SLM array 220 was assumed to be (z0). In addition, the complex amplitude distribution of object beam 225b of the SLM section modulated by the actual DOE 211 on the array plane of the virtual SLM array 220 was assumed to be U2(x, y). Furthermore, the complex amplitude distribution U(x, y) obtained by weighting and adding the complex amplitude distribution U1(x, y) and the complex amplitude distribution U2(x, y) is defined by the following equation (7).

[0081] U(x,y)=(1-α)U1(x,y)+αU2(x,y) … Equation (7)

[0082] Here, α (0≦α≦1) represents a weighting coefficient. Using Equation (7), the weighting coefficient α was changed from 0 to 1, and CGHs were generated by calculation.

[0083] The generated CGH was displayed on a reflective SLM, and the displayed CGH was irradiated with reconstruction illumination light 213 from a light source 212 and observed through the fabricated DOE 211. At this time, the central strip in the vertical direction of the reflective SLM (number of pixels in the width direction N x is 3840, the number of pixels in the height direction is N y A mask was placed so that the reconstruction illumination light 213 would not hit the area (region 540 pixels) of the CGH. As a result, the part of the CGH that was not hit by the reconstruction illumination light 213 became a defect. As shown in FIG. 9(c), the defect introduced into part of the generated CGH (3840 pixels × 540 pixels) simulated a gap in the SLM array 210. The wavelength λ of the reconstruction illumination light 213 was set to 632.8 nm.

[0084] Figure 10 shows the results of recapturing the optical images reconstructed from each CGH generated by varying the weighting coefficient α from 0 to 1. Note that the light appearing on the right side of each optical image (N) is the zeroth-order light of the SLM. When α=1, only the complex amplitude distribution U2(x,y) of object beam 225b in the SLM section is recorded and reproduced, which indicates that a defect occurs in the portion corresponding to the inter-SLM gap. On the other hand, when α=0.2, the complex amplitude distribution U1(x,y) of object beam 225a in the inter-SLM gap and the complex amplitude distribution U2(x,y) of object beam 225b in the SLM section are reproduced with approximately the same brightness, indicating that the reproduced image of the inter-SLM gap can be interpolated. From the above, the effectiveness of the display system of this embodiment has been demonstrated by optical reproduction. [Explanation of symbols]

[0085] S Display System 1,201,301,401 Hologram data display device 2,202,302,402 Hologram data generator 3,203,303 j ,403 k hologram data 10 i SLM (Spatial Light Modulator) 10,210 SLM array 11,211 DOE (diffractive optical element) 12,212 light sources 13,213 Reconstruction Light 14,214 Modulated reconstructed light 15,215 Regeneration light 16,216 3D images 17,317 Synchronous Devices 18 Control Unit 20 i ,201,202SLM (Virtual Spatial Light Modulator) 20,220 SLM array (virtual SLM array) 21,221 DOE (Virtual Diffractive Optical Element) 23,223 Reference light 24 Modulated object beam 24a,224a Modulated object beam 224b Modulated object beam 25,225 object light 25a, 225a Object beam in the gap between the SLMs 225b Object beam of SLM 26,226 subject data 419 Color Filter

Claims

1. a hologram data display device comprising: an SLM array having inter-SLM gaps between a plurality of SLMs, each of which is a spatial light modulator arranged; and a diffractive optical element, which is disposed at a distance from the SLM array and has a predetermined transmittance distribution and modulates the amplitude of light reproduced from hologram data displayed on the SLM array; a hologram data generating device having a storage unit and a processing unit, and configured to generate the hologram data by interference calculation for causing interference between an object beam and a reference beam, The hologram data generation device performs the following before the interference calculation: a first propagation calculation for propagating object light generated from subject data to a position of a virtual SLM array corresponding to the SLM array; a second propagation calculation for propagating the object light in the gap between the SLMs of the virtual SLM array to the position of a virtual diffractive optical element that corresponds to the diffractive optical element and has a transmittance distribution that removes zero-order light that is originally included in the reproduced light that passes through the diffractive optical element; a first modulation calculation for calculating object light obtained by modulating the object light in the inter-SLM gap portion by the virtual diffractive optical element; a third propagation calculation for propagating the object light modulated by the first modulation calculation to the position of the virtual SLM array; A display system characterized by performing the above.

2. The hologram data generating device further a fourth propagation calculation for propagating object light from the SLM units arranged in the virtual SLM array to the position of the virtual diffractive optical element; a second modulation calculation for calculating object light modulated by the transmittance distribution of the diffractive optical element of the hologram data display device; 2. The display system according to claim 1, further comprising: a fifth propagation calculation for propagating the object light modulated by the second modulation calculation to the position of the virtual SLM array.

3. The display system described in claim 1 or claim 2, characterized in that the hologram data generating device performs calculations assuming that the length between the virtual spatial light modulators arranged in the virtual SLM array is longer by a predetermined value than the length between the spatial light modulators arranged in the SLM array provided in the hologram data display device.

4. The display system described in claim 1 or claim 2, characterized in that the hologram data generating device performs calculations assuming that the transmittance distribution of the virtual diffractive optical element is a transmittance distribution obtained by uniformly subtracting the average value from the transmittance distribution of the diffractive optical element provided in the hologram data display device.

5. The display system described in claim 1 or claim 2, characterized in that the hologram data generating device performs calculations assuming that the transmittance distribution of the virtual diffractive optical element has the inverse characteristics of the transmittance distribution of the diffractive optical element provided in the hologram data display device.

6. the hologram data generating device generates the hologram data using a reference light having multiple wavelengths obtained by time division; The hologram data display device comprises: a light source that switches and irradiates the SLM array with multi-wavelength reconstruction illumination light in a time-division manner; 3. The display system according to claim 1, further comprising a synchronization device that synchronizes switching timing between the wavelength of the reproduction illumination light and the hologram data.

7. the hologram data generating device generates the hologram data using a reference light having multiple wavelengths obtained by time division; 3. The display system according to claim 1, wherein the hologram data display device has a color filter disposed on the diffractive optical element or the SLM array.

8. the hologram data generating device generates the hologram data using a reference light having multiple wavelengths obtained by time division; 3. The display system according to claim 1, wherein the diffractive optical element of the hologram data display device has a transmittance distribution obtained by superimposing transmittance distributions for the respective RGB colors of a color filter.

Images