WO2024247809A1 - Holographic projector device and control method - Google Patents

Abstract

A holographic projector device according to the present technology comprises: a light source; a spatial light modulation unit that performs spatial light modulation on light emitted from the light source; a projection unit that projects a reproduced image generated by the spatial light modulation unit; and a control unit that calculates a correction hologram for correcting deterioration in the reproduced image on the basis of a target image and deterioration element information indicating at least a resolution deterioration element of the reproduced image generated in a projection path from the light source to the projection unit, and performs control so that the spatial light modulation unit is driven according to a spatial light modulation pattern based on the calculated correction hologram.

Description

Holographic projector device and control method

This technology relates to a holographic projector device that projects images using holography technology and a control method for the same, and in particular to a technology for correcting degradation in the resolution of a reproduced image.

There is known a holographic projector device that projects an image using holography technology, which makes it possible to display 2D (two-dimensional) images and 3D (three-dimensional) images.
Some holographic projector devices are configured to form holograms using a spatial light modulator such as a liquid crystal panel. In this case, by changing the spatial light modulation pattern in the spatial light modulator, it is possible to change the hologram to be formed, and the displayed image can be changed. In other words, by changing the spatial light modulation pattern in the spatial light modulator, it is possible to switch still images to be displayed or to display moving images.

Note that the following Patent Document 1 can be cited as an example of related prior art. Patent Document 1 below discloses technology for increasing the resolution of a hologram image at the user's gaze point.

Japanese Patent Application Publication No. 10-326071

Here, in a holographic projector device, degradation in the resolution of the reconstructed image may occur along the projection path for projecting the reconstructed image.
However, in conventional holographic projector devices, no technology has been established to correct the degradation of resolution that occurs in the projection path. For example, it may be possible to use a high-resolution spatial light modulator in anticipation of the degradation of resolution, but in that case, the spatial light modulator to be used becomes expensive, making it difficult to reduce the price.

This technology was developed in light of the above circumstances, and aims to reduce the cost of holographic projector devices while suppressing degradation of resolution.

A holographic projector device according to the present technology includes a light source, a spatial light modulation unit that performs spatial light modulation on light emitted from the light source, a projection unit that projects a reconstructed image generated by the spatial light modulation unit, and a control unit that calculates a correction hologram for correcting degradation of the reconstructed image based on a target image and degradation element information that is information indicating at least resolution degradation elements of the reconstructed image that occur on the projection path from the light source to the projection unit, and controls the spatial light modulation unit to be driven by a spatial light modulation pattern based on the calculated correction hologram.
According to the above configuration, it is possible to perform resolution degradation correction taking into account the resolution degradation factors that actually occur in the projection path, and it is possible to realize appropriate resolution degradation correction. Furthermore, by performing resolution degradation correction, it is possible to use a spatial light modulator with a low resolution.

1 is a diagram showing an example of the configuration of a holographic projector device according to a first embodiment of the present technology. 1 is an explanatory diagram of the principle of hologram formation by spatial light phase modulation. FIG. 11 is an explanatory diagram of a measure against disclination. FIG. 2 is an explanatory diagram of various functions for implementing a degradation correction method according to a first embodiment. FIG. 11 is an explanatory diagram of an example of shift multiplexing display. 4 is a flowchart showing an example of a specific processing procedure to be executed to realize a degradation correction method according to a first embodiment. FIG. 13 is a diagram showing an example of the configuration of a holographic projector device according to a second embodiment. 1 is an explanatory diagram of the principle of hologram formation by spatial light amplitude modulation. FIG. 13 is a diagram showing an example of the configuration of a holographic projector device according to a third embodiment. FIG. 13 is an explanatory diagram of a degradation correction method according to a third embodiment. FIG. 13 is an explanatory diagram of various functions for realizing a degradation correction method according to a third embodiment. 13 is a flowchart showing an example of a specific processing procedure to be executed to realize a degradation correction method according to a third embodiment. FIG. 11 is an explanatory diagram of problems that may occur when the playback surface is uneven. 13 is an explanatory diagram of a case where a correction hologram is calculated assuming a reproduction surface having projections and recesses. FIG. FIG. 13 is an explanatory diagram of a modified holographic projector device.

Hereinafter, with reference to the accompanying drawings, embodiments of the present technology will be described in the following order.
1. First embodiment
[1-1. Device configuration example]
[1-2. Deterioration correction method as the first embodiment]
[1-3. Processing procedure]
<2. Second embodiment>
<3. Third embodiment>
4. Modifications
5. Summary of the embodiment
<6. This Technology>

1. First embodiment
[1-1. Device configuration example]
FIG. 1 is a diagram showing an example of the configuration of a holographic projector device 1 according to a first embodiment of the present technology.
Here, as an example, a holographic projector device that displays a 2D (two-dimensional) image is illustrated.

As shown in the figure, the holographic projector device 1 includes a light source 2, a beam expander 3, a collimator lens 4, a beam splitter 5, a spatial light modulation unit 6, a relay lens 7, a relay lens 8, an optical filter 9, a projection lens 10, a control unit 11, and a drive unit 12.

Light source 2 is provided as a light source for generating a reconstructed image. In a holographic projector device, it is preferable to use a coherent light source as the light source for the reconstructed image, and in this example, a semiconductor laser is used as light source 2.

The light emitted from the light source 2 is converted into divergent light by the beam expander 3 , and then converted into parallel light by the collimator lens 4 , and enters the beam splitter 5 .
The light incident on the beam splitter 5 from the light source 2 side in this manner is reflected by the selective reflection surface of the beam splitter 5 and enters the spatial light modulation unit 6 as shown in the figure.

The spatial light modulation unit 6 has a spatial light modulator and performs spatial light modulation on the incident light by the spatial light modulator. This spatial light modulation is for holographic projection, and a reconstructed image for realizing image display is generated by the spatial light modulation.
In this embodiment, the spatial light modulator in the spatial light modulation unit 6 is a spatial light phase modulator (hereinafter sometimes abbreviated as "phase modulator") that performs spatial light phase modulation on incident light. Specifically, a liquid crystal panel is used as the phase modulator. The liquid crystal panel is configured by two-dimensionally arranging a plurality of pixels in which the orientation state of the liquid crystal can be adjusted, and it is possible to perform spatial light phase modulation on the incident light independently for each pixel. In this example, for example, LCOS (Liquid Crystal On Silicon) is used as the liquid crystal panel.

In this example, the spatial light modulation unit 6 has a reflective spatial light modulator as the spatial light modulator. Therefore, the light that has been spatially modulated by the spatial light modulation unit 6 (spatial light phase modulation in this example) is emitted from the spatial light modulation unit 6 as reflected light from the reflective spatial light modulator (a reflective liquid crystal panel in this example).

The light emitted from the spatial light modulation unit 6 after spatial light modulation is incident again on the selective reflection surface of the beam splitter 5, passes through the selective reflection surface, and enters the relay lens system composed of the relay lens 7 and the relay lens 8.

In addition, by using, for example, a polarizing beam splitter as the beam splitter 5, it is possible to reduce the light loss associated with the reflection of the incident light from the light source 2 side and the transmission of the incident light from the spatial light modulation unit 6, thereby improving the efficiency of light utilization.

As shown in the figure, the light incident on relay lens 7 is converted from parallel light to convergent light, focuses at a predetermined position, and then enters relay lens 8 in the form of diffused light. Relay lens 8 converts the incident diffused light into parallel light and emits it to projection lens 10.

An optical filter 9 is disposed between the relay lenses 7 and 8. The optical filter 9 transmits the first-order diffracted light at the position where the light emitted from the relay lens 7 is focused, and blocks other light (zeroth-order diffracted light, higher-order diffracted light, etc.). This removes noise light.

The projection lens 10 enlarges and projects the reproduced image incident via the relay lens 8 onto a projection target such as a screen S.
This makes it possible to display a 2D image on a projection target such as a screen S.

The control unit 11 is configured as a computer device equipped with a microcomputer having, for example, a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., and executes various processes related to image display in the holographic projector device 1.

The driving unit 12 is configured with a driving circuit for driving the spatial light modulator (in this example, a phase modulator) of the spatial light modulation unit 6. The driving unit 12 is configured to be able to individually drive each pixel of the spatial light modulator of the spatial light modulation unit 6.

As shown in the figure, a target image (a 2D image in this example) that is a display target image is input to the control unit 11. The control unit 11 controls the drive unit 12 based on this target image, thereby causing the spatial light modulation unit 6 to perform spatial light modulation for image display.
Specifically, the control unit 11 calculates a hologram (CGH: Computer Generated Hologram) for obtaining a reproduced image corresponding to the target image based on the target image, calculates a spatial light modulation pattern for the spatial light modulation unit 6 so that the calculated hologram is formed by spatial light modulation by the spatial light modulation unit 6, and controls the drive unit 12 so that spatial light modulation according to the spatial light modulation pattern is performed.
Here, the "spatial light modulation pattern" means information indicating the light modulation state for each pixel of the spatial light modulation unit 6 (spatial light modulator). Specifically, in this example, it is information indicating the drive signal value for each pixel of the spatial light modulation unit 6.

As described above, the control unit 11 controls the spatial light modulation pattern of the spatial light modulation unit 6 based on the target image, thereby realizing the display of a 2D image that reproduces the target image.

The principle of hologram formation by spatial light phase modulation will be explained with reference to Figure 2. For the sake of explanation, a case is shown here in which a transmissive modulator is used as the phase modulator in the spatial light modulation section 6, but the principle is the same when a reflective modulator is used.

In the figure, an example is shown in which the spatial light modulation unit 6 has pixels that modulate the phase of the incident light to a phase of 0 [rad] and pixels that modulate the phase to π [rad]. By performing spatial light phase modulation that imparts a phase distribution to the incident light in this way, spherical waves of different phases interfere with each other, and the interference causes the strengthening of light in a certain pattern. That is, an interference fringe (hologram) is formed in a certain pattern. At this time, the pattern of the hologram can be controlled by the pattern of the phase distribution given to the incident light in the phase modulator, that is, the spatial light modulation pattern of the phase modulator.

[1-2. Deterioration correction method as the first embodiment]
Here, it has been confirmed that in the holographic projector device, the resolution of the reproduced image is degraded in the projection path for projecting the reproduced image. In particular, when the noise light is removed using the optical filter 9 as in the above-mentioned holographic projector device 1, the resolution of the reproduced image is likely to be degraded. Specifically, when the noise light is removed in real space, a method is adopted in which the noise light is separated while narrowing the area of the original reproduced image, so that the image is displayed at a lower resolution than the resolution that can be displayed originally, resulting in resolution degradation. In addition, when a filter is used in the spatial frequency domain, the angular resolution contributing to the reproduced image is limited, which causes resolution degradation of the reproduced image due to this point.

Furthermore, when a liquid crystal panel is used as the spatial light modulator, the resolution of the reproduced image deteriorates due to measures taken against disclination of the liquid crystal panel.
Specifically, when a liquid crystal panel is used as a spatial light modulator, in order to suppress deterioration of the display image quality caused by disclination, a spatial light modulator with a large pixel pitch is used, or instead of writing information independently on a pixel-by-pixel basis (shown as "Px" in the figure) as in Figure 3A, a measure is taken in which the pixel pitch is artificially increased by writing the same information to multiple adjacent pixels (2 x 2 = 4 pixels or more) as illustrated in Figure 3B.
When the pixel pitch is actually increased as in the former case, the panel size increases, which reduces the number of pixels that can be produced during production and creates the issue of increased costs, making it difficult to increase the panel size. As a result, the number of pixels in the liquid crystal panel decreases, leading to a deterioration in the resolution of the reproduced image.
Moreover, in the latter case where the pixel pitch is artificially enlarged, the effective number of pixels decreases, resulting in degradation of the resolution of the reproduced image.

Therefore, in this embodiment, a method is adopted in which degradation correction of the reproduced image is performed using degradation element information, which is information indicating at least the resolution degradation elements of the reproduced image that occur on the projection path from the light source 2 to the projection unit (the part including at least the projection lens 10).
In this embodiment, the process for this deterioration correction is executed by the control unit 11 .

With reference to FIG. 4, various functions that the control unit 11 has for implementing the degradation correction method according to the first embodiment will be described.
4 shows the driving unit 12 shown in FIG. 1 together with the functional blocks of the control unit 11.

In this embodiment, the control unit 11 calculates a correction hologram for correcting the degradation of the reproduced image based on the target image and the above-mentioned degradation element information, and controls the spatial light modulation unit 6 to be driven by a spatial light modulation pattern based on the calculated correction hologram.
For this purpose, the control unit 11 in this embodiment has functions as a deteriorated image estimation unit F1, a multiplexing image generation unit F2, a correction hologram generation unit F3, a modulation pattern generation unit F4, and an output control unit F5 shown in the figure.

Here, in this embodiment, a method is adopted in which a plurality of reconstructed images are shift-multiplexed and displayed in order to correct degradation in resolution.
Here, the term "shift multiplexed display" as used in this specification refers to a display method in which multiple reconstructed images are superimposed on the reconstruction surface, and involves a shift (displacement) in the display position between the reconstructed images that is less than the pixel pitch.
By performing such shift multiplexing display, it is possible to realize a high-resolution image display using a low-resolution reconstructed image, that is, it is possible to realize the correction of resolution degradation based on the so-called super-resolution technology.

An example of shift multiplexing display in this embodiment will be described with reference to FIG.
Fig. 5A is a schematic diagram showing a plurality of reconstructed images used for the resolution degradation correction. As shown in Fig. 5A, in this example, four reconstructed images are generated as the reconstructed images used for the resolution degradation correction.
Then, as shown in Fig. 5B, these four reconstructed images are superimposed on the reconstruction surface, and at this time, a shift of less than the pixel pitch occurs in the image formation area between each reconstructed image. Specifically, in this example, a shift of half a pixel occurs. As shown in the figure, the image formation area of one of the four reconstructed images is used as a reference, and the remaining reconstructed image is shifted by half a pixel in the lateral direction (horizontal direction) (see the reconstructed image marked with ▲ in the figure), the remaining reconstructed image is shifted by half a pixel in the vertical direction (see the reconstructed image marked with ■ in the figure), and the remaining remaining reconstructed image is shifted by half a pixel in the diagonal direction (see the reconstructed image marked with × in the figure), thereby causing a shift of half a pixel in the image formation area between each reconstructed image.

In this embodiment, the shift multiplexed display is performed by projecting the four reconstructed images as described above in a time-division manner. Specifically, the control unit 11 in this embodiment calculates a plurality of correction holograms for the shift multiplexed display, and controls the spatial light modulation unit 6 so that the correction holograms are formed in a time-division manner.
By forming a plurality of correction holograms for shift multiplexed display in this manner in a time-division manner, it becomes possible to realize a shift of the reconstructed image for shift multiplexed display by using these correction holograms.
Since the shifting of the reconstructed image is realized by time-division formation of the correction holograms, it becomes unnecessary to provide a shift device for shifting the position of the reconstructed image on the reconstruction surface when realizing shift multiplexed display.

For confirmation, in order to make the formation areas of each reconstructed image on the reconstruction surface different as shown in Figure 5B, the settings for which areas on the reconstruction surface are to be set as the target formation areas of the reconstructed images can be changed in the calculation of each correction hologram.

In FIG. 4, the functions from the degraded image estimation unit F1 to the correction hologram generation unit F3 are functions for generating multiple correction holograms to achieve the resolution degradation correction by the shift multiplexing display as described above.

The degraded image estimation unit F1 estimates a degraded image as an image in which the degradation indicated by the degradation element information has been applied to the target image, based on the target image and the degradation element information.
The specific procedure is as follows: first, a hologram that reproduces the target image is calculated as an undegraded hologram, then a degraded hologram is calculated based on the undegraded hologram and the degradation element information, and finally, the reconstructed image based on the degraded hologram is calculated as the degraded image.

　［式１］において、「Ｆ」はフーリエ変換、「Ｆ^－１」は逆フーリエ変換、「ｆ_ｘ」「ｆ_ｙ」は周波数領域の座標、「ｕ_１」はターゲット波面、「λ」は光の波長を意味する。 The undegraded hologram can be obtained by, for example, wavefront propagation calculation using the angular spectrum method. Specifically, it can be calculated as "Hologram" shown in the following [Equation 1].

In Equation 1, "F" denotes the Fourier transform, "F ^-1 " denotes the inverse Fourier transform, "f _x " and "f _y " denote coordinates in the frequency domain, "u ₁ " denotes the target wavefront, and "λ" denotes the wavelength of light.

In this embodiment, the degradation of the reproduced image is corrected by correcting the degradation of resolution caused by the optical filter 9 and the degradation that occurs in the liquid crystal panel of the spatial light modulation unit 6, specifically the degradation of the reproduced image caused by the disclination described above. Furthermore, in this example, the degradation of the reproduced image caused by optical aberration is also corrected. The optical aberration here can be, for example, lens distortion caused by the projection lens 10.

In this example, the degraded image is generated by reproducing the degradation of resolution caused by the optical filter 9, the degradation of the reconstructed image caused by disclination, and the degradation of the reconstructed image caused by optical aberration. Therefore, as the degradation element information, information on the degradation elements of the resolution caused by the optical filter 9, information on the degradation elements of the reconstructed image caused by disclination, and information on the degradation elements of the reconstructed image caused by optical aberration are prepared.
The information indicating the various degradation factors may be obtained in advance experimentally or by simulation calculation.

First, a degraded hologram is calculated based on the pre-degradation hologram and the degradation element information.
In this example, the degraded hologram is calculated by using information on the resolution degradation elements caused by the optical filter 9, information on the degradation elements of the reconstructed image caused by disclinations, and information on the degradation elements of the reconstructed image caused by optical aberration, all of which are prepared in advance as degradation element information, and imparting degradation due to these degradation elements to the pre-degraded hologram.

　［式２］において、「Ａ」「φ」は、［式１］の計算で求まった複素振幅ホログラムとしての劣化前ホログラムにおける振幅ホログラム、位相ホログラムを意味する。また、「ｄ」はディスクリネーションにより受ける表示パターンの帯域制限を意味する。この「ｄ」の情報が、ディスクリネーションに起因した再生像の劣化要素の情報に相当するものである。 Specifically, the amount of degradation caused by disclination can be calculated as a calculation to obtain "Hologram_Dl" in the following [Equation 2].

In [Equation 2], "A" and "φ" refer to the amplitude hologram and phase hologram of the pre-deterioration hologram as the complex amplitude hologram obtained by the calculation of [Equation 1]. Also, "d" refers to the band limitation of the display pattern caused by the disclination. This information on "d" corresponds to information on the degradation element of the reproduced image caused by the disclination.

　［式３］において、「Mask」は、周波数空間におけるホログラムの帯域制限を表す。なお［式３］における「Ａ」「φ」については、［式２］により「Hologram_Dl」として求めた複素振幅ホログラムにおける振幅ホログラム、位相ホログラムを用いる。
　［式３］における「Mask」の情報が、光学フィルタ９による解像度劣化要素の情報に相当する。 Furthermore, the calculation for imparting the degradation in resolution by the optical filter 9 can be performed as a calculation for obtaining "Hologram_Df" in the following [Equation 3].

In [Equation 3], "Mask" represents the band limit of the hologram in frequency space. Note that for "A" and "φ" in [Equation 3], the amplitude hologram and phase hologram in the complex amplitude hologram obtained as "Hologram_Dl" by [Equation 2] are used.
The “Mask” information in [Equation 3] corresponds to information on the resolution degradation factor caused by the optical filter 9 .

In addition, in this example, a calculation is performed to further add degradation of the reconstructed image due to optical aberration to the complex amplitude hologram as "Hologram_Df" obtained by [Equation 3]. This calculation can be performed in a similar manner to [Equation 2] and [Equation 3], using information on degradation factors of the reconstructed image due to optical aberration that has been prepared in advance, such as information indicating degradation factors as lens distortion caused by the projection lens 10.

In this example, a hologram obtained by adding various degradations indicated by the degradation element information to an undegraded hologram as described above is calculated as a degraded hologram.
The degraded image estimation unit F1 calculates the reconstructed image from this degraded hologram as a degraded image. The degraded image can be obtained by performing a wavefront propagation calculation for the degraded hologram in the same manner as in [Equation 1].

Note that the order in which the degradation of the resolution caused by the optical filter 9, the degradation of the reconstructed image caused by disclination, and the degradation of the reconstructed image caused by optical aberration is applied is not limited to the above order, and it is also possible to adopt other orders, such as, for example, degradation of the reconstructed image caused by optical aberration → degradation of the resolution caused by the optical filter 9 → degradation of the reconstructed image caused by disclination.

Here, the degradation element information, specifically in this example, information on the resolution degradation elements caused by the optical filter 9, information on the degradation elements of the reproduced image caused by disclination, and information on the degradation elements of the reproduced image caused by optical aberration, are stored in a memory (non-volatile memory) that can be read by the control unit 11. The memory may be provided within the holographic projector device 1. Alternatively, the memory may be provided in an external device (e.g., a cloud server, etc.).

The multiplexing image generation unit F2 generates, by calculation, multiple (four in this example) multiplexing images to be used for the shift multiplexing display described above, based on the difference between the degraded image obtained by the degraded image estimation unit F1 and the target image.
Specifically, by performing the shift multiplexing display described in FIG. 5, four images (having the same resolution as that of the target image) that can cancel the difference between the degraded image and the target image are calculated as images for multiplexing.
In addition, a calculation method used in a general super-resolution technique can be used for calculating a plurality of multiplexing images to be used in shift multiplexing display for correcting resolution degradation based on the difference between a degraded image and a target image. For example, the method disclosed in Reference 1 below can be used.

・Reference 1: “Image Enhancement in Projectors via Optical Pixel Shift and Overlay” Behzad Sajadi, Duy Qoc-Lai, Alex T.Ihler, M.Gopi, Aditi Majumder: Department of Computer Science University of Califronia, Irvine

The correction hologram generating unit F3 generates, by calculation, a hologram for obtaining the multiplexing image as a reproduced image, as a correction hologram, for each multiplexing image calculated by the multiplexing image generating unit F2.
Conversion from a multiplexed image to a correction hologram can be performed by wavefront propagation calculations such as those shown in the above [Equation 1], in the same manner as the conversion from a target image to an undegraded hologram described above.

The modulation pattern generating unit F4 generates, by calculation, a spatial light modulation pattern for the spatial light modulating unit 6 for forming each correction hologram obtained by the correction hologram generating unit F3.
In this embodiment, since spatial light phase modulation is performed as the spatial light modulation, only a phase hologram is extracted from the correction hologram as a complex amplitude hologram.
Specifically, assuming that the correction hologram is obtained as “ _u2 (x' ^{, y')” shown in the following [Equation 4], phase distribution information on the phase modulation surface of the spatial light modulation unit 6 is obtained by extracting “e iφ(x', y')} ” in [Equation 4].

The modulation pattern generation unit F4 obtains the above-mentioned phase distribution information for each correction hologram, and then calculates, for each correction hologram, a drive signal value for each pixel of the phase modulator to realize the phase distribution indicated by the phase distribution information on the phase modulation plane. The drive signal value for each pixel of the phase modulator calculated in this way for each correction hologram is information on the spatial light modulation pattern for each correction hologram.

The output control unit F5 outputs the information on the spatial light modulation pattern for each correction hologram generated by the modulation pattern generating unit F4 to the driving unit 12 in a time-division manner.
This drives the phase modulator of the spatial light modulation unit 6 to form four correction holograms for shift multiplexing display in a time-division manner. As a result, reconstructed images corresponding to the four multiplexing images for correcting various degradations such as resolution are displayed in a time-division shift multiplexing manner, thereby achieving correction of various degradations in the displayed image.

For confirmation, when performing shift multiplexing display in a time-division manner as in this embodiment, the display cycle of the multiplexing images is set to a sufficiently fast cycle that takes into account the visual integration effect.

In this embodiment, a phase modulator is used as a spatial light modulator for holographic projection, which can improve the efficiency of light utilization when displaying an image. As described above with reference to Fig. 2, when a phase modulator is used, a hologram can be formed by adjusting the phase of incident light, so there is no need to block the incident light, and the efficiency of light utilization can be improved.
By improving the light utilization efficiency, it is possible to achieve a higher contrast for the displayed image and a reduction in the power consumption of the light source 2 .

Furthermore, in this embodiment, since pixel position shifting in shift multiplexed display is performed by spatial light modulation, there is no need to provide a shift device for shifting pixel positions (for example, a device for vibrating a spatial light modulator, etc.).
When a shift device is used, a transition period occurs until the pixel position is completely shifted, during which an image cannot be displayed, resulting in low efficiency. When the pixel position is shifted by spatial light modulation as in this embodiment, such a transition period does not occur, improving efficiency.
In addition, if the shift device is not required, the width of the pixel position shift does not depend on the shift device, and the display density can be improved. Therefore, it is possible to realize high-precision correction of resolution degradation, such as a quarter-pixel shift.

In addition, in this embodiment, the deterioration caused by disclination of the liquid crystal panel is also corrected, which makes it possible to eliminate the need to use a liquid crystal panel with a large pixel pitch to deal with disclination, or to use a liquid crystal panel with a pixel number four or more times the number of pixels of the reproduced image.
Therefore, the holographic projector device 1 can be made smaller and less expensive.

Furthermore, in this embodiment, the deterioration caused by optical aberrations such as lens distortion is also corrected, which eliminates the need to use expensive lenses with an aberration correction function, thereby enabling the holographic projector device 1 to be manufactured at a low price.

[1-3. Processing procedure]
FIG. 6 is a flowchart showing an example of a specific processing procedure to be executed by the control unit 11 in order to realize the degradation correction method according to the first embodiment described above.
When a moving image is displayed, the control unit 11 executes the process shown in Fig. 6 for each frame image, which constitutes the moving image, as a target image. When a still image is displayed, the control unit 11 may repeatedly execute the process shown in Fig. 6 for a common target image.

First, in step S101, the control unit 11 calculates a hologram that reproduces the target image as an undegraded hologram. That is, the undegraded hologram is calculated based on the target image using the above-mentioned [Equation 1].

In step S102 following step S101, the control unit 11 calculates a degraded hologram based on the pre-degraded hologram and the degradation element information. Specifically, in this example, based on information on resolution degradation elements caused by the optical filter 9 (the above-mentioned "Mask") stored in the memory as degradation element information, information on degradation elements of the reproduced image caused by disclination (the above-mentioned "d"), and information on degradation elements of the reproduced image caused by optical aberration, a process is performed to impart resolution degradation caused by the optical filter 9, degradation of the reproduced image caused by disclination, and degradation of the reproduced image caused by optical aberration to the pre-degraded hologram, thereby calculating a degraded hologram.
In addition, the specific calculation method for imparting deterioration has already been explained, so a duplicate explanation will be avoided.

In step S103 following step S102, the control unit 11 calculates the reconstructed image from the degraded hologram as the degraded image. That is, as described above, the degraded image is calculated from the degraded hologram by wavefront propagation calculation.

In step S104 following step S103, the control unit 11 calculates a multiplexing image for degradation correction based on the difference between the calculated degraded image and the target image, and then in the following step S105, calculates a hologram (correction hologram) for each multiplexing image. The calculation method for the multiplexing image and the calculation method for the correction hologram have already been explained, so a duplicate explanation will be avoided.

In step S106 following step S105, the control unit 11 calculates a spatial light modulation pattern for forming a hologram for each correction hologram. That is, as described above, a phase hologram is extracted for each correction hologram to obtain information on the phase distribution on the phase modulation plane, and then the drive signal value for each pixel of the phase modulator to realize the phase distribution is calculated as the spatial light modulation pattern.

In step S107 following step S106, the control unit 11 outputs the calculated spatial light modulation pattern in a time-division manner. That is, information on the calculated spatial light modulation pattern for each correction hologram is output to the drive unit 12 in a time-division manner.

After executing the process of step S107, the control unit 11 ends the series of processes shown in FIG.

<2. Second embodiment>
Next, a second embodiment will be described.
In the second embodiment, a hologram for displaying an image is formed by spatial light amplitude modulation rather than spatial light phase modulation.

FIG. 7 is a diagram showing an example of the configuration of a holographic projector device 1A according to the second embodiment.
In the following description, parts that are similar to parts that have already been described will be given the same reference numerals and description thereof will be omitted.

Holographic projector device 1A differs from holographic projector device 1 as the first embodiment in that spatial light modulation unit 6A is provided instead of spatial light modulation unit 6, and control unit 11A is provided instead of control unit 11.

The spatial light modulation section 6A has a spatial light amplitude modulator (hereinafter sometimes abbreviated as "amplitude modulator") as a spatial light modulator.
In this example, a reflective liquid crystal panel is used as the amplitude modulator. In this case, the liquid crystal panel is configured to be capable of adjusting the amplitude of incident light for each pixel. Specifically, the liquid crystal panel is configured to be capable of adjusting the degree of blocking of incident light for each pixel.

The principle of hologram formation by spatial light amplitude modulation will be explained with reference to Figure 8. For the sake of explanation, a case is shown in which a transmissive modulator is used as the amplitude modulator in the spatial light modulation section 6A, but the principle is similar when a reflective modulator is used.

The figure shows an example in which the spatial light modulation section 6A has pixels that display white (lowest light blocking) and pixels that display black (highest light blocking). By performing spatial light amplitude modulation in this way, the spherical waves from pixels through which light is not blocked (white pixels) interfere with each other, and the interference creates a certain pattern of reinforcement of the light, forming interference fringes (hologram) in the required pattern. At this time, the hologram pattern can be controlled by the pattern of the amplitude distribution imparted to the incident light in the amplitude modulator, in other words, the spatial light modulation pattern of the amplitude modulator.

The control unit 11A has functions similar to those of the degraded image estimation unit F1, the multiplexing image generation unit F2, the correction hologram generation unit F3, the modulation pattern generation unit F4, and the output control unit F5 of the control unit 11. However, the control unit 11A differs from the control unit 11 in that the modulation pattern generation unit F4 performs a conversion process corresponding to the case where an amplitude modulator is used to convert the correction hologram into a spatial light modulation pattern.
Specifically, for a correction hologram as a complex amplitude hologram obtained by the form shown in [Equation 4] above, amplitude distribution information on the amplitude modulation plane of the spatial light modulation unit 6A is obtained by extracting the amplitude hologram " _a2 (x',y')". In this case, the modulation pattern generation unit F4 obtains the above-mentioned amplitude distribution information for each correction hologram, and then calculates, for each correction hologram, a drive signal value for each pixel of the amplitude modulator for realizing the amplitude distribution indicated by the amplitude distribution information on the amplitude modulation plane. This allows for obtaining information on the spatial light modulation pattern for each correction hologram that corresponds to the case where an amplitude modulator is used.

Furthermore, in the second embodiment, when correcting degradation caused by disclination of a liquid crystal panel, the degraded image estimation unit F1 applies degradation to the pre-degraded hologram not according to the above-mentioned [Equation 2], but according to the following [Equation 5].

By employing a technique for forming a hologram by spatial light amplitude modulation as in the second embodiment, it is possible to use an amplitude modulation type spatial light modulator that is generally used for image display as the spatial light modulator.

<3. Third embodiment>
In the third embodiment, the deterioration correction of the reconstructed image is performed only on a part of the image region, such as a region of interest as an image region that is attracting the user's attention.

FIG. 9 is a diagram showing an example of the configuration of a holographic projector device 1B according to the third embodiment.
The difference from the holographic projector device 1 shown in FIG. 1 is that a control unit 11B is provided instead of the control unit 11.

The control unit 11B controls the spatial light modulation unit so that a correction hologram is formed only in a specified partial image area of the reconstructed image.
Specifically, in this example, attention area designation information is input to the control unit 11B. This attention area designation information is information that designates the user's attention area, that is, the image area in the displayed image that the user is paying attention to.

Here, the attention area may be determined based on the result of estimating the user's line of sight, face direction, etc. based on an image captured by a camera installed inside or outside the holographic projector device 1B. Alternatively, the attention area may be specified by a user operation.
In the former case, it is assumed that the process of estimating the user's gaze direction, face orientation, etc. and the process of setting the attention area based on the estimation result are performed outside the control unit 11B. In this case, information indicating the attention area set outside is input to the control unit 11B as attention area designation information.
The above estimation process and the process of setting the area of interest based on the estimation result may be performed by the control unit 11B itself. Alternatively, only the estimation process may be performed outside the control unit 11B, and the process of setting the area of interest based on the estimation result may be performed by the control unit 11B.
In the latter case, it is possible that the control unit 11B performs a process of setting the region of interest based on a user operation. In this case, information on the operation performed by the user to specify the region of interest is input to the control unit 11B as region of interest specification information.

In addition, it is possible to identify the region of interest by image analysis of the target image. For example, an artificial intelligence model that has undergone machine learning such as deep learning can be used to infer the region of interest from the input image.

In this example, the control unit 11B calculates multiple multiplexing images to be used for shift multiplexing display, and calculates a correction hologram for each multiplexing image, for only the attention area specified by the attention area designation information.

FIG. 10 is an explanatory diagram of a degradation correction method according to the third embodiment.
First, as indicated by <1> in the figure, the control unit 11B calculates an entire hologram from the target image. This process is a process of calculating an undegraded hologram from the target image, similar to the process in step S101 above. In the second embodiment, the undegraded hologram for the entire target image is referred to as an entire hologram.

Furthermore, the control unit 11B generates a multiplexing image of the attention area based on the target image, as indicated by <2> in the figure.
Then, as shown by <3> in the figure, the control unit 11B converts each multiplexing image for the region of interest into a hologram to obtain a plurality of correction holograms.
Then, the control unit 11B synthesizes the correction hologram generated in <3> with the whole hologram calculated in <1> above. This synthesis with the whole hologram is performed for each correction hologram.
Thereafter, each composite hologram is converted into a spatial light modulation pattern, and the spatial light modulation pattern for each composite hologram is output to the driving unit 12 in a time-division manner.
This makes it possible to realize degradation correction limited to the region of interest.

FIG. 11 is an explanatory diagram of the functions of the control unit 11B.
As shown in the figure, control unit 11B differs from control unit 11 in that it has the function of a degraded image estimation unit F1B instead of the degraded image estimation unit F1, that it has the function of a multiplexing image generation unit F2B instead of the multiplexing image generation unit F2, and that it has the additional functions of an overall hologram calculation unit F6 and a synthesis unit F7.

The degraded image estimation unit F1B generates a degraded image for the attention area based on the target image, the degradation element information, and the attention area designation information.
The process performed by this deteriorated image estimation unit F1B is similar to the process performed by the deteriorated image estimation unit F1, except that the image region to be processed is limited to the region of interest, and therefore a duplicated description will be avoided.

The multiplexing image generating unit F2B generates a multiplexing image of the attention area by calculation based on the deteriorated image for the attention area obtained by the deteriorated image estimating unit F1B, the target image, and the attention area designation information.
Specifically, the image for multiplexing generating unit F2B generates an image for multiplexing of the region of interest based on the difference between the image of the region of interest in the target image and the deteriorated image of the region of interest obtained by the deteriorated image estimating unit F1B. This process is similar to the process of the image for multiplexing generating unit F2, except that the image region to be processed is limited to the region of interest, so a duplicated description will be avoided.

In this case, the correction hologram generation unit F3 converts each multiplexing image of the area of interest generated by the multiplexing image generation unit F2B into a hologram, thereby obtaining each correction hologram for the area of interest (see <3> in Figure 10).

An overall hologram calculation unit F6 obtains an overall hologram by performing calculations to convert the target image into a hologram.
The synthesis unit F7 synthesizes the correction hologram for the region of interest obtained by the correction hologram generation unit F3 with the whole hologram obtained by the whole hologram calculation unit F6. As described above, synthesis with the whole hologram is performed for each correction hologram. In other words, in this example, four correction holograms are generated, and four synthesized holograms, each of which has a different correction hologram, are obtained.

In this case, the modulation pattern generating unit F4 converts each composite hologram obtained by the combining unit F7 into a spatial light modulation pattern.
In this case, the output control unit F5 outputs the spatial light modulation pattern for each composite hologram obtained by the modulation pattern generation unit F4 to the drive unit 12 in a time-division manner.

FIG. 12 is a flowchart showing an example of a specific processing procedure executed by the control unit 11B to realize the degradation correction method according to the third embodiment described above.
In addition, with regard to the process shown in Figure 12, similar to the process shown in Figure 6 above, when a moving image is displayed, the frame images that make up the moving image are used as target images, and the process shown is executed for each frame image, and when a still image is displayed, the process shown is executed repeatedly for a common target image.

First, in step S101, control unit 11B calculates a hologram that reproduces the target image as a pre-deterioration hologram (whole hologram). This process corresponds to the process described above as whole hologram calculation unit F6.

In response to executing the process of step S101, the control unit 11B advances the process to step S201.
In step S201, the control unit 11B calculates a degraded hologram for the attention area based on the undegraded hologram of the attention area, the degradation element information, and the attention area designation information. That is, based on the attention area designation information, an undegraded hologram of the attention area is obtained by converting the image of the attention area in the target image into a hologram, and a degraded hologram of the attention area is obtained by performing a process of adding various degradations to the undegraded hologram of the attention area using the degradation element information.

In step S202 following step S201, the control unit 11B calculates a degraded image of the attention area based on the calculated degraded hologram.
Then, in step S203 following step S202, the control unit 11B calculates a multiplexing image of the attention area based on the difference between the deteriorated image of the attention area and the image of the attention area in the target image, and further in the following step S204, calculates a hologram of the multiplexing image (correction hologram). The processes of steps S203 and S204 correspond to the processes of the multiplexing image generating unit F2B and the correction hologram generating unit F3 described above, respectively.

In step S205 following step S204, the control unit 11B performs a synthesis process of the entire hologram (hologram before deterioration) and the correction hologram. That is, this is a process of synthesizing the entire hologram as the hologram before deterioration calculated in step S101 with each correction hologram calculated in step S204. As described above, synthesis with the entire hologram is performed for each correction hologram.

In step S206 following step S205, the control unit 11B converts each composite hologram into a spatial light modulation pattern, and in the subsequent step S207, outputs the spatial light modulation patterns in a time-division manner.

After executing the process of step S207, the control unit 11B ends the series of processes shown in FIG. 12.

The technique of performing degradation correction only on a part of an image region as in the third embodiment can also be applied to the case where an amplitude modulator is used as the spatial light modulator as in the second embodiment.

4. Modifications
Although various embodiments according to the present technology have been described above, the present technology is not limited to the specific examples described above, and various modified configurations may be adopted.
For example, in the above, the calculation of the correction hologram is based on the assumption that the reconstruction surface is a two-dimensional plane, but it is also possible to calculate the correction hologram based on the assumption that the reconstruction surface has projections and recesses.

For example, as shown in FIG. 13, the actual playback surface may not be a two-dimensional plane indicated by "I" in the figure, but may instead be a surface with relatively large projections and recesses. In this case, particularly when it is assumed that a light diffusion element such as a microlens array, HOE (Holographic Optical Element), DOE (Diffractive Optical Element), etc. is placed on the playback surface to improve the viewing angle characteristics, if hologram calculations are performed assuming a two-dimensional plane as the playback surface, the imaging positions of the light rays of the playback image will not coincide with the positions of the diffusion elements, i.e., defocusing will occur with respect to the diffusion elements, and the diffusion elements will not properly diffuse the light, resulting in failure to improve the viewing angle characteristics.

As a result, as shown in Figure 14, the correction hologram is calculated assuming that the reconstruction surface is an uneven surface. Specifically, three-dimensional information showing the uneven shape of the reconstruction surface is measured in advance, and the measured three-dimensional information is used as the three-dimensional information of the assumed reconstruction surface in the calculation of the correction hologram.

FIG. 15 is a diagram for explaining holographic projector device 1C that calculates a correction hologram using three-dimensional information on the reproduction surface as described above. Specifically, it is a functional explanatory diagram of control unit 11C that holographic projector device 1C has. Note that the configuration of holographic projector device 1C other than control unit 11C is similar to that of holographic projector device 1 described in the first embodiment, for example, and therefore redundant explanation will be avoided.

Control unit 11C differs from control unit 11 in that it has a correction hologram generating unit F3C instead of correction hologram generating unit F3.
The three-dimensional information of the actually measured reproduction surface is input to the correction hologram generating unit F3C as the reproduction surface three-dimensional information. Here, the reproduction surface three-dimensional information may be stored in a memory that can be read by the control unit 11C, similar to the degradation element information.

The correction hologram generating unit F3C uses the coordinate information indicated by the reproduction plane three-dimensional information as the coordinate information of the reproduction plane assumed in the calculation of the correction hologram.
This makes it possible to calculate an appropriate correction hologram for correcting degradation in resolution when the actual reconstruction surface has irregularities. In particular, when the above-mentioned diffusion element is disposed on the reconstruction surface, it becomes possible to make the focusing position of each light beam of the reconstruction image coincide with the position of the diffusion element, thereby improving the viewing angle characteristics.

In the explanation so far, we have given an example of displaying 2D images, but this technology can also be suitably applied to displaying 3D images.

Furthermore, the present technology can also be suitably applied to the display of color images.
For example, a possible configuration could be to provide a spatial light modulator for each of the colors R (red), G (green), and B (blue), generate a correction hologram for each color based on a target image and a degraded image, and perform shift multiplexing display using the generated correction holograms.
Alternatively, for a single-panel spatial light modulator, a spatial light modulation area can be defined for each color, and each of these spatial light modulation areas can be regarded as a spatial light modulator for each color, and a correction hologram can be generated based on a target image and a degraded image for each color, and a shift multiplexed display can be performed using the generated correction hologram.
If the above-described configuration is adopted as a configuration for displaying a color image, it becomes possible to simultaneously display the reconstructed images of the respective colors instead of in a time-division manner, thereby making it possible to suppress color breakup.
If color breaks can be ignored, it is possible to adopt a configuration in which shift multiplexed display using correction holograms generated for each color is performed in a time-division manner.

In addition, in the explanation so far, an example has been given of a case where resolution degradation correction is performed using shift multiplexing display, but it is also possible to realize resolution degradation correction by, for example, generating a correction hologram that cancels the difference between the target image and the degraded image and forming the correction hologram using a spatial light modulation unit. In this case, the correction hologram may be generated by, for example, calculating a blur function for each pixel of the degraded image, multiplying the pixel value for each pixel of the target image by the inverse function of the blur function to generate a correction image, and generating a hologram that reproduces the correction image.

In addition, in the explanation so far, an example has been given in which a semiconductor laser is used as the light source 2, but it is also possible to use a light emitting element other than a semiconductor laser, such as an LED (Light Emitting Diode), as the light source 2.

Furthermore, in the above explanation, an example has been given in which a reflective liquid crystal panel is used as a spatial light modulator for forming a hologram, but it is also possible to use a reflective spatial light modulator other than a liquid crystal panel.
For example, when using a phase modulator as in the first embodiment, it is possible to use a mirror using MEMS (Micro Electro Mechanical Systems), specifically, a MEMS mirror configured so that the height of the mirror surface can be adjusted for each pixel.
Furthermore, when an amplitude modulator is used as in the second embodiment, it is possible to use a DMD (Digital Micro Mirror Device).
It is also possible to use a transmissive spatial light modulator instead of a reflective spatial light modulator.

5. Summary of the embodiment
As described above, the holographic projector device (1, 1A, 1B, 1C) as an embodiment includes a light source (2), a spatial light modulation unit (6, 6A) that performs spatial light modulation on light emitted from the light source, a projection unit (relay lenses 7, 8, projection lens 10) that projects a reconstructed image generated by the spatial light modulation unit, and a control unit (11, 11A, 11B, 11C) that calculates a correction hologram for correcting degradation of the reconstructed image based on a target image and degradation element information that is information indicating at least resolution degradation elements of the reconstructed image that occur on the projection path from the light source to the projection unit, and controls the spatial light modulation unit to be driven by a spatial light modulation pattern based on the calculated correction hologram.
According to the above configuration, it is possible to perform resolution degradation correction that takes into account the resolution degradation factors that actually occur in the projection path, and it is possible to realize appropriate resolution degradation correction. Furthermore, by performing resolution degradation correction, it is possible to use a spatial light modulator with a low resolution.
Therefore, it is possible to suppress degradation of resolution while reducing the cost of the holographic projector device.

Furthermore, the holographic projector device according to the embodiment includes an optical filter (9) that applies optical filtering to the reconstructed image, and the degradation element information includes information on resolution degradation elements caused by the optical filter.
This makes it possible to correct the degradation in resolution in cases where the optical filter causes a degradation in resolution.

Furthermore, in the holographic projector device according to the embodiment, the optical filter is an optical filter that removes noise light.
An optical filter that removes noise light can cause degradation of the resolution of the reconstructed image.
Therefore, it is preferable to perform the resolution degradation correction taking into consideration the resolution degradation factor caused by the optical filter.

Furthermore, in a holographic projector device as an embodiment, the spatial light modulation section performs spatial light modulation using a liquid crystal panel, and the degradation factor information includes information on degradation factors of the reproduced image that occur in the liquid crystal panel.
This makes it possible to correct the degradation of the reconstructed image in the case where a degradation factor of the reconstructed image occurs in the liquid crystal panel used for spatial light modulation.

In the holographic projector device according to the embodiment, the degradation factor information includes information on degradation factors of the reproduced image caused by disclinations in the liquid crystal panel.
This makes it possible to correct the degradation of the reproduced image caused by disclination, and eliminates the need to use a liquid crystal panel with a large pixel pitch to deal with disclination, or to use a liquid crystal panel with a number of pixels four or more times the number of pixels of the reproduced image.
Therefore, the holographic projector device can be made smaller and cheaper.

Furthermore, in the holographic projector device according to the embodiment, the degradation element information includes information indicating degradation elements caused by optical aberrations occurring in the reconstructed image.
This makes it possible to calculate a corrective hologram that can not only correct degradation in resolution, but also correct degradation in the reconstructed image caused by optical aberrations, such as lens distortion in a projection lens system.
Therefore, the quality of the displayed image can be improved.

Furthermore, in a holographic projector device as an embodiment, the control unit controls the spatial light modulation unit so that degradation is corrected by a method of shifting and multiplexing a plurality of reconstructed images to be displayed.
By performing shift multiplexing display, it is possible to realize a high-resolution image display using a low-resolution reconstructed image, that is, it is possible to realize the correction of resolution degradation based on the so-called super-resolution technology.

In the holographic projector device according to the embodiment, the control unit controls the spatial light modulation unit so that a plurality of correction holograms for shift multiplexed display are formed in a time-division manner.
By forming a plurality of correction holograms for shift multiplexed display in a time-division manner as described above, it is possible to realize a shift of the reconstructed image for shift multiplexed display by using these correction holograms.
Since the shift of the reconstructed image is realized by time-division formation of the correction hologram, there is no need to provide a shift device for shifting the position of the reconstructed image on the reconstruction surface when realizing shift multiplexed display. This makes it possible to reduce the number of parts required to correct resolution degradation, and to reduce the size, weight, and cost of the holographic projector device.

Furthermore, in the holographic projector device of the embodiment, the control unit calculates a hologram that reproduces the target image as an undegraded hologram, calculates a degraded hologram based on the undegraded hologram and the degradation element information, calculates a reconstructed image from the degraded hologram as a degraded image, calculates a plurality of multiplexing images to be used for shift multiplexing display based on the difference between the calculated degraded image and the target image, calculates a hologram as a correction hologram for obtaining the multiplexing image as a reconstructed image, and controls the spatial light modulation unit so that the correction hologram for each calculated multiplexing image is formed in a time-division manner.
By forming a correction hologram for each multiplexed image in a time-division manner as described above, the correction holograms realize the shifting of the reconstructed image for shift multiplexed display.
Therefore, when realizing shift multiplexed display, there is no need to provide a shift device for shifting the position of the reproduced image on the reproduction surface, and the number of parts required to achieve resolution degradation correction can be reduced, making it possible to make the holographic projector device smaller, lighter, and less expensive.

Furthermore, in the holographic projector devices (1, 1B, 1C) as the embodiments, the spatial light modulation section performs spatial light phase modulation as the spatial light modulation.
By generating a reconstructed image by spatial light modulation, it is possible to improve the efficiency of light utilization in image display, thereby enabling the contrast of the displayed image to be increased and the power consumption of the light source to be reduced.

In addition, in the holographic projector device (same as 1B) as an embodiment, the control unit (same as 11B) controls the spatial light modulation unit so that a correction hologram is formed only in a specified partial image area in the reproduced image.
This makes it possible to perform calculation processing for correcting degradation in resolution only on a portion of the image area that particularly requires correction, such as an image area that the user is paying attention to.
Therefore, the calculation processing load required for correcting degradation in resolution can be reduced.

Furthermore, in the holographic projector device according to the embodiment, the control unit (11C) calculates a correction hologram by assuming a reproduction surface having projections and recesses.
This makes it possible to calculate an appropriate correction hologram for correcting degradation in resolution in cases where the actual reproduction surface has projections and recesses.

In addition, the control method as an embodiment is a control method for a holographic projector device that includes a light source, a spatial light modulation unit that performs spatial light modulation on the light emitted from the light source, and a projection unit that projects a reconstructed image generated by the spatial light modulation unit, and the control method calculates a correction hologram for correcting degradation of the reconstructed image based on a target image and degradation element information that is information indicating at least resolution degradation elements of the reconstructed image that occur on the projection path from the light source to the projection unit, and controls the spatial light modulation unit to be driven by a spatial light modulation pattern based on the calculated correction hologram.
With such a control method, it is possible to obtain the same functions and effects as the holographic projector device according to the above-described embodiment.

It should be noted that the effects described in this specification are merely examples and are not limiting, and other effects may also be obtained.

<6. This Technology>
The present technology can also be configured as follows.
(1)
A light source;
a spatial light modulation unit that performs spatial light modulation on the light emitted from the light source;
a projection unit that projects a reproduced image generated by the spatial light modulation unit;
a control unit that calculates a correction hologram for correcting degradation of the reconstructed image based on a target image and degradation element information that is information indicating at least a resolution degradation element of the reconstructed image that occurs on a projection path from the light source to the projection unit, and controls the spatial light modulation unit to be driven by a spatial light modulation pattern based on the calculated correction hologram.
(2)
an optical filter that performs optical filtering on the reconstructed image;
The holographic projector device according to (1), wherein the degradation element information includes information on a resolution degradation element caused by the optical filter.
(3)
The holographic projector device according to (2), wherein the optical filter is an optical filter that removes noise light.
(4)
the spatial light modulation unit performs the spatial light modulation using a liquid crystal panel;
The holographic projector device according to any one of (1) to (3), wherein the degradation factor information includes information on degradation factors of the reproduced image that occur in the liquid crystal panel.
(5)
The holographic projector device according to (4), wherein the degradation element information includes information on degradation elements of the reproduced image caused by disclinations of the liquid crystal panel.
(6)
The holographic projector device according to any one of (1) to (5), wherein the degradation element information includes information indicating a degradation element caused by optical aberration occurring in the reconstructed image.
(7)
The control unit is
The holographic projector device according to (1) above, wherein the spatial light modulation unit is controlled so that the deterioration is corrected by a method of shifting and multiplexing a plurality of reconstructed images to be displayed.
(8)
The control unit is
The holographic projector device according to (7) above, wherein the spatial light modulation unit is controlled so that a plurality of the correction holograms for the shift multiplexed display are formed in a time division manner.
(9)
The control unit is
Calculating a hologram that reproduces the target image as a pre-deterioration hologram;
calculating a degraded hologram based on the pre-degraded hologram and the degradation element information;
A reconstructed image based on the degraded hologram is calculated as a degraded image;
calculating a plurality of multiplexing images to be used in the shift multiplexing display based on the calculated difference between the deteriorated image and the target image;
calculating, for each of the calculated multiplexing images, a hologram for obtaining the multiplexing image as a reproduced image as the correction hologram;
The holographic projector device according to (8) above, wherein the spatial light modulation unit is controlled so that the correction hologram for each of the calculated multiplexed images is formed in a time-division manner.
(10)
The holographic projector device according to any one of (1) to (9), wherein the spatial light modulation unit performs spatial light phase modulation as the spatial light modulation.
(11)
The control unit is
The holographic projector device according to any one of (1) to (10), further comprising: controlling the spatial light modulation unit so that the correction hologram is formed only for a specified partial image region in the reconstructed image.
(12)
The control unit is
The holographic projector device according to any one of (1) to (11), wherein the calculation of the correction hologram is performed by assuming a reconstruction surface having projections and recesses.
(13)
A control method for a holographic projector device including a light source, a spatial light modulation unit that performs spatial light modulation on light emitted from the light source, and a projection unit that projects a reproduced image generated by the spatial light modulation unit, comprising:
A control method comprising: calculating a correction hologram for correcting degradation of the reconstructed image based on a target image and degradation element information, which is information indicating at least a resolution degradation element of the reconstructed image that occurs on a projection path from the light source to the projection unit; and controlling the spatial light modulation unit to be driven by a spatial light modulation pattern based on the calculated correction hologram.

1, 1A, 1B, 1C Holographic projector device 2 Light source 3 Beam expander 4 Collimator lens 5 Beam splitter 6, 6A Spatial light modulation section 7, 8 Relay lens 9 Optical filter 10 Projection lens 11, 11A, 11B, 11C Control section 12 Driving section S Screen F1, F1A Degraded image estimation section F2, F2B Multiplexing image generation section F3, F3C Correction hologram generation section F4 Modulation pattern generation section F5 Output control section F6 Overall hologram calculation section F7 Synthesis section

Claims (13)

A light source;
a spatial light modulation unit that performs spatial light modulation on the light emitted from the light source;
a projection unit that projects a reproduced image generated by the spatial light modulation unit;
a control unit that calculates a correction hologram for correcting degradation of the reconstructed image based on a target image and degradation element information that is information indicating at least a resolution degradation element of the reconstructed image that occurs on a projection path from the light source to the projection unit, and controls the spatial light modulation unit to be driven by a spatial light modulation pattern based on the calculated correction hologram. an optical filter that performs optical filtering on the reconstructed image;
The holographic projector device according to claim 1 , wherein the degradation factor information includes information on a resolution degradation factor caused by the optical filter. The holographic projector device according to claim 2 , wherein the optical filter is an optical filter for removing noise light. the spatial light modulation unit performs the spatial light modulation using a liquid crystal panel;
2. The holographic projector device according to claim 1, wherein the degradation factor information includes information on degradation factors of the reproduced image that occur in the liquid crystal panel. The holographic projector device according to claim 4 , wherein the degradation element information includes information on degradation elements of the reproduced image caused by disclinations of the liquid crystal panel. The holographic projector device according to claim 1 , wherein the degradation element information includes information indicating a degradation element caused by optical aberration occurring in the reconstructed image. The control unit is
The holographic projector according to claim 1 , wherein the spatial light modulation unit is controlled so that the deterioration is corrected by a method of shifting and multiplexing a plurality of reconstructed images to be displayed. The control unit is
The holographic projector device according to claim 7 , wherein the spatial light modulation unit is controlled so that a plurality of the correction holograms for the shift multiplexed display are formed in a time-division manner. The control unit is
Calculating a hologram that reproduces the target image as a pre-deterioration hologram;
calculating a degraded hologram based on the pre-degraded hologram and the degradation element information;
A reconstructed image based on the degraded hologram is calculated as a degraded image;
calculating a plurality of multiplexing images to be used in the shift multiplexing display based on the calculated difference between the deteriorated image and the target image;
calculating, for each of the calculated multiplexing images, a hologram for obtaining the multiplexing image as a reproduced image as the correction hologram;
The holographic projector device according to claim 8 , wherein the spatial light modulation unit is controlled so that the correction hologram for each of the calculated multiplexed images is formed in a time-division manner. The holographic projector device according to claim 1 , wherein the spatial light modulation section performs spatial light phase modulation as the spatial light modulation. The control unit is
2. The holographic projector device according to claim 1, wherein the spatial light modulation unit is controlled so that the correction hologram is formed only in a specified partial image region of the reproduced image. The control unit is
The holographic projector device according to claim 1 , wherein the correction hologram is calculated by assuming a reconstruction surface having projections and recesses. A control method for a holographic projector device including a light source, a spatial light modulation unit that performs spatial light modulation on light emitted from the light source, and a projection unit that projects a reproduced image generated by the spatial light modulation unit, comprising:
A control method comprising: calculating a correction hologram for correcting degradation of the reconstructed image based on a target image and degradation element information, which is information indicating at least a resolution degradation element of the reconstructed image that occurs on a projection path from the light source to the projection unit; and controlling the spatial light modulation unit to be driven by a spatial light modulation pattern based on the calculated correction hologram.

Images