Optical phase modulation system and display device

Abstract

An optical phase modulation system of the present disclosure comprises: an illumination light projection unit that is configured to enable polarization control in which the directions of the polarization of light projected as illumination light are set to a first polarization direction and a second polarization direction different from the first polarization direction, and that is configured to enable the light in the first polarization direction and the light in the second polarization direction to be projected at mutually different timings and in mutually different directions; a phase modulation unit having a first area configured to enable phase modulation of the light in the first polarization direction from the illumination light projection unit, and a second area configured to enable phase modulation of the light in the second polarization direction from the illumination light projection unit; and a synchronization controller that synchronizes the timing at which the light in the first polarization direction and the light in the second polarization direction are projected from the illumination light projection unit and the timing of the phase modulation of the first and second areas of the phase modulation unit.

Description

Technical Field

[0001] The present disclosure relates to an optical phase modulation system and a display device.

Background Art

[0002] Generally, in a liquid crystal type optical phase modulation element, in order to ensure a phase modulation amount (0 to 2π) twice that of a liquid crystal type luminance modulation element, the thickness of the liquid crystal layer is doubled. As a principle characteristic of liquid crystal, the response speed is proportional to the square of the thickness of the liquid crystal layer. Therefore, the optical phase modulation element has a response speed four times slower than that of the luminance modulation element. On the other hand, a technique has been proposed in which two optical phase modulation elements having the same thickness as the luminance modulation element and a phase modulation amount of 0 to π are arranged in the optical path to realize a normal phase modulation amount (0 to 2π) while making the response speed equivalent to that of a normal luminance modulation element (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] When two optical phase modulation elements are arranged in the same optical path, the distance for arranging the two optical phase modulation elements becomes long. In addition, since the light incident on the second optical phase modulation element already has a non-planar phase, it becomes very difficult to control the phase surface, leading to a deterioration in image quality.

[0005] It is desirable to provide an optical phase modulation system and a display device that can improve the response speed of phase modulation while suppressing a deterioration in image quality.

[0006] An optical phase modulation system according to one embodiment of the present disclosure includes: an illumination light emission unit configured to control the polarization direction of light emitted as illumination light to a first polarization direction and a second polarization direction different from the first polarization direction, and configured to emit light in the first polarization direction and light in the second polarization direction at different timings and in different directions from each other; a phase modulation unit having a first region configured to perform phase modulation on light in the first polarization direction from the illumination light emission unit and a second region configured to perform phase modulation on light in the second polarization direction from the illumination light emission unit; and a synchronization control unit that synchronizes the timing of emission of light in the first polarization direction and light in the second polarization direction from the illumination light emission unit with the timing of phase modulation in the first region and the second region of the phase modulation unit.

[0007] A display device according to one embodiment of the present disclosure includes: an illumination light emission unit configured to control the polarization direction of light emitted as illumination light to a first polarization direction and a second polarization direction different from the first polarization direction, and configured to emit light in the first polarization direction and light in the second polarization direction at different timings and in different directions; a phase modulation unit having a first region configured to perform phase modulation on light in the first polarization direction from the illumination light emission unit and a second region configured to perform phase modulation on light in the second polarization direction from the illumination light emission unit; and an illumination light emission unit Polarization control in It includes a synchronization control unit that synchronizes the timing with the timing of phase modulation in the first and second regions of the phase modulation unit.

[0008] In an optical phase modulation system or display device according to one embodiment of the present disclosure, light with a first polarization direction and light with a second polarization direction are emitted from an illumination light emission unit at different timings, and the light with the first polarization direction and the light with the second polarization direction are phase-modulated in a first region and a second region of a phase modulation unit, respectively. At this time, the timing of emission of light with each polarization direction and the timing of phase modulation in each region are synchronized. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view showing an overview of a luminance modulation display device. [Figure 2] This is a cross-sectional view showing an overview of a luminance modulation display device. [Figure 3] This is a perspective view showing an overview of a phase modulation display device. [Figure 4] This is a cross-sectional view showing an overview of a phase modulation display device. [Figure 5] This is a cross-sectional view comparing the configuration of a liquid crystal type brightness modulation element and a liquid crystal type optical phase modulation element. [Figure 6] This is a schematic cross-sectional view showing one example configuration of an optical phase modulation system related to a comparative example. [Figure 7] Figure 6 is an explanatory diagram illustrating the challenges of the optical phase modulation system shown. [Figure 8] This is a configuration diagram showing an overview of the optical phase modulation system according to the first embodiment of this disclosure. [Figure 9] This is a schematic plan view showing one example of the configuration of the phase modulation section in the optical phase modulation system according to the first embodiment. [Figure 10] This is a schematic plan view showing one example of the configuration of the phase modulation unit and the illumination light emission unit in the optical phase modulation system according to the first embodiment. [Figure 11] This is an explanatory diagram showing an example of the driving state of the phase modulation unit in the optical phase modulation system according to the first embodiment. [Figure 12] This is an explanatory diagram showing an example of the rise time response speed of a liquid crystal type brightness modulation element and a liquid crystal type optical phase modulation element. [Figure 13] This is an explanatory diagram showing an example of the fall-side response speed between a liquid crystal type brightness modulation element and a liquid crystal type optical phase modulation element. [Figure 14] This is an explanatory diagram showing a first example of the driving state of an optical phase modulation element related to a comparative example. [Figure 15] This is an explanatory diagram showing a second example of the driving state of the optical phase modulation element according to the comparative example. [Figure 16]It is an explanatory diagram showing an example of the driving state of a phase modulation unit in an optical phase modulation system according to the first embodiment. [Figure 17] It is a cross-sectional view schematically showing a configuration example of an optical phase modulation system according to Modification 1. [Figure 18] It is a cross-sectional view schematically showing a configuration example of an optical phase modulation system according to Modification 2. [Figure 19] It is a cross-sectional view schematically showing a configuration example of an optical phase modulation system according to Modification 3. [Figure 20] It is a cross-sectional view schematically showing a first configuration example of a polarization beam splitter. [Figure 21] It is a perspective view schematically showing a second configuration example of a polarization beam splitter. [Figure 22] It is a cross-sectional view schematically showing a configuration example of an optical phase modulation system according to Modification 4. [Figure 23] It is a cross-sectional view schematically showing a configuration example of an optical phase modulation system according to Modification 5. [Figure 24] It is a cross-sectional view schematically showing a configuration example of an optical phase modulation system according to Modification 6. [Figure 25] It is a cross-sectional view schematically showing a configuration example of an optical phase modulation system according to Modification 7. [Figure 26] It is a cross-sectional view schematically showing a configuration example of an optical phase modulation system according to Modification 8. [Figure 27] It is a cross-sectional view schematically showing a configuration example of an optical phase modulation system according to Modification 9. [Figure 28] It is a cross-sectional view schematically showing a configuration example of an optical phase modulation system according to Modification 10.

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The description will be made in the following order. 0. Comparative Example and Background (Figs. 1 to 7) 1. First Embodiment 1.1 Configuration and Operation (Figs. 8 to 16) 1.2 Variations (Figures 17-28) 1.3 Effects 2. Other Embodiments

[0011] <0. Comparative Examples and Background> (Display devices using luminance modulation, and display devices using phase modulation) Figures 1 and 2 show an overview of a luminance modulation display device. A typical projection display device (projector) configuration, as shown in Figures 1 and 2, involves irradiating a light intensity modulation element 501 with uniform illumination light emitted from a light source 500 to perform light intensity modulation and generate an image, which is then projected onto a screen 50 through a projection lens.

[0012] Typically, LCDs (Liquid Crystal Displays) or DMDs (Digital Micro-mirror Devices) are used as the light intensity modulation element 501. Liquid crystal projectors, in particular, offer good color reproduction and high image quality. In liquid crystal projectors, the liquid crystal panel is used as a light shutter. Figures 1 and 2 show an example in which a transmissive liquid crystal panel is used as the light intensity modulation element 501. The liquid crystal panel has a structure in which a liquid crystal layer 513 containing multiple liquid crystal molecules 514 is sandwiched between a pair of substrates 502 and 503. When the light intensity modulation element 501 is a transmissive liquid crystal panel, a polarizer 521 is positioned in the direction of light incidence, and an analyzer 522 is positioned in the direction of light emission. The polarizer 521 emits polarized light from the incident light L11 that is polarized in a predetermined polarization direction. In the case of a luminance modulation display device, one pixel of the light intensity modulation element 501 corresponds to one pixel of the final displayed image. When the light intensity modulation element 501 is a liquid crystal panel, when displaying dark areas of the image, the illumination light must be blocked by the liquid crystal panel, resulting in unused light and a significant decrease in the efficiency of light utilization.

[0013] In contrast, there is a technology that uses a Spatial Light Modulator (SLM) as a diffraction element to generate illumination light, thereby distributing a portion of the light illuminating low-brightness pixel areas to high-brightness areas as a phase-modulation display device.

[0014] Figures 3 and 4 show an overview of a phase modulation display device. Figures 3 and 4 show an example in which a reflective diffractive element is used as the optical phase modulation element 1. In a phase modulation display device, for example, a reconstructed image is projected onto a screen 50 by irradiating the optical phase modulation element 1 with uniform illumination light emitted from a light source 500 to perform phase modulation. Phase modulation display devices are highly efficient because they use light diffraction. In the case of a phase modulation display device, one pixel of the optical phase modulation element 1 does not necessarily correspond to one pixel of the final displayed image, and it is possible to make multiple pixels in the optical phase modulation element 1 correspond to one pixel of the displayed image. Since it is possible to construct one pixel of the final displayed image using multiple pixels in the optical phase modulation element 1, it is also characterized by the stability of the pixel display even if a pixel defect occurs in the optical phase modulation element 1. Furthermore, color display is also possible, and a technique has been disclosed in which illumination light of the three primary colors R (red), G (green), and B (blue) is generated using different optical phase modulation elements 1 for each color.

[0015] As the optical phase modulation element 1, a liquid crystal type optical phase modulation element can also be used. By calculating a phase distribution pattern (phase hologram) corresponding to the desired reconstructed image and displaying it on the liquid crystal type optical phase modulation element, the desired reconstructed image can be obtained.

[0016] (Liquid crystal type brightness modulation element and liquid crystal type optical phase modulation element) Figure 5 shows a comparison of the configuration of a liquid crystal type brightness modulation element (Figure 5(A)) and the configuration of a liquid crystal type optical phase modulation element (Figure 5(B)).

[0017] Figure 5 shows an example of a reflective configuration. Both the luminance modulation element and the optical phase modulation element have a configuration in which liquid crystal molecules 613 are sealed between two opposing substrates 601 and 602. On substrate 601, a pixel electrode (transparent electrode) 611 is provided on the liquid crystal layer side, and substrate 60 2 In this configuration, a pixel electrode (reflective electrode) 612 is provided on the liquid crystal layer side.

[0018] Generally, in liquid crystal type optical phase modulation elements, the thickness of the liquid crystal layer (cell gap) d is doubled to ensure twice the phase modulation amount (0 to 2π) compared to liquid crystal type luminance modulation elements. As a fundamental characteristic of liquid crystals, the response speed is proportional to the square of the liquid crystal layer thickness. Therefore, optical phase modulation elements have a response speed four times slower than luminance modulation elements. For this reason, in phase modulation display devices, optical phase modulation elements are usually used with the understanding that image quality will be degraded, or measures such as turning off the lights are taken, but in that case, the frame rate, image quality, and brightness will decrease.

[0019] In liquid crystal luminance modulation elements, it is sufficient to ensure retardation Δnd = π for any wavelength λ, whereas in phase modulation liquid crystal elements, it is necessary to ensure retardation Δnd = 2π for any wavelength λ. Generally, the rise time response speed of a nematic liquid crystal is expressed by the following equation (1), and the fall time response speed is expressed by the following equation (2). In equations (1) and (2), γ1 is rotational viscosity, ε0 ​​is the permittivity of vacuum, Δε is the dielectric anisotropy, d is the cell gap, V is the applied voltage, and V th It is rotational viscosity.

[0020]

number

[0021]

number

[0022] According to equations (1) and (2), if the thickness of the liquid crystal layer is doubled to ensure a retardation of 2π, both the rise response speed and the fall response speed will be 2 2 This slows down the response time by four times. As a result, the possibility of applying liquid crystal type optical phase modulation elements to applications such as field sequential holographic displays that require high-speed response, or ranging technologies such as LiDAR (Light Detection and Ranging), is limited.

[0023] To address the response speed issues described above, Patent Document 1 (Japanese Patent Application Publication No. 2014-66869) proposes a technique that achieves a normal phase modulation amount (0 to 2π) while maintaining a response speed equivalent to that of a normal luminance modulation element by arranging two optical phase modulation elements with the same thickness as a luminance modulation element in the optical path, each with a phase modulation amount of 0 to π.

[0024] Figure 6 shows an overview of an optical phase modulation system according to the technology described in Patent Document 1 as a comparative example. This optical phase modulation system comprises a first optical phase modulation element 121 with a phase modulation amount of 0 to π and a second optical phase modulation element 122 with a phase modulation amount of 0 to π, both of which are reflective liquid crystal type optical phase modulation elements. A polarizing beam splitter 130, a first quarter-wave plate 141, and a second quarter-wave plate 142 are arranged between the first optical phase modulation element 121 and the second optical phase modulation element 122. In this optical phase modulation system, first, the incident light Lin to the polarizing beam splitter 130 is phase-modulated by the first optical phase modulation element 121 after passing through the first quarter-wave plate 141. First optical phase modulation element 121 The light phase-modulated by the first optical phase modulator is phase-modulated by the second optical phase modulator 122 after passing through the first quarter-wave plate 141, the polarizing beam splitter 130, and the second quarter-wave plate 142. The light phase-modulated by the second optical phase modulator 122 is then emitted as output light Lout after passing through the second quarter-wave plate 142 and the polarizing beam splitter 130.

[0025] Figure 7 illustrates the challenges of the optical phase modulation system shown in Figure 6. In the optical phase modulation system shown in Figure 6, since two optical phase modulation elements 121 and 122 are used in the same optical path, a distance Da is required to position the optical element 120 between the optical phase modulation elements 121 and 122. Therefore, even if the wavefront Wa of the incident light Lin is planar, the wavefront Wb at the stage when it is incident on the second optical phase modulation element 122 is no longer planar, making it extremely difficult to control the phase plane. Calculating the phase pattern to be displayed on each optical phase modulation element also becomes difficult.

[0026] <1. First Embodiment> [1.1 Configuration and Operation] (Overview of the optical phase modulation system) Figure 8 shows an overview of the optical phase modulation system according to the first embodiment of this disclosure.

[0027] The optical phase modulation system according to the first embodiment comprises a phase modulation unit 20, an illumination light emission unit 21, and a synchronization control unit 22.

[0028] Figure 9 schematically shows one example configuration of the phase modulation unit 20. Figure 10 schematically shows one example configuration of the phase modulation unit 20 and the illumination light emission unit 21.

[0029] The phase modulation unit 20 has a first region 31 configured to perform phase modulation on light with a first polarization direction (e.g., P polarization) from the illumination light emission unit 21, and a second region 32 configured to perform phase modulation on light with a second polarization direction (e.g., S polarization) from the illumination light emission unit 21.

[0030] Figure 9 shows an example in which the phase modulation section 20 is composed of a single liquid crystal optical phase modulation element 30 having a first region 31 and a second region 32. For example, positions A and A' in the phase modulation section 20 in Figure 8 correspond to positions A and A' in the optical phase modulation element 30 in Figure 9. For example, the optical phase modulation element 30 has an effective pixel region and a peripheral region 33. The optical phase modulation element 30 has a structure in which the effective pixel region is divided into a first region 31 and a second region 32. In the optical phase modulation element 30, the orientation of the liquid crystal molecules 41 is different in the first region 31 and the second region 32. In the example configuration in Figure 9, the effective pixel region is divided into left and right halves, and the left divided region is designated as the first region 31, with the orientation of the liquid crystal molecules 41 parallel to the long side of the optical phase modulation element 30. On the other hand, the right-hand divided region is designated as the second region 32, and the orientation of the liquid crystal molecules 41 is set perpendicular to the long side of the optical phase modulation element 30. This makes it possible to perform phase modulation for P-polarized light in the first region 31, and phase modulation for S-polarized light in the second region 32. Note that the method and shape of dividing the effective pixel region are not limited to the configuration example in Figure 9, and other methods and shapes of division are also possible.

[0031] Furthermore, the phase modulation unit 20 may be configured with a first optical phase modulation element 30A and a second optical phase modulation element 30B, as shown in the configuration example in Figure 10. In this case, the overall orientation of the effective pixel region in the first optical phase modulation element 30A may be the same as that of the first region 31 of the optical phase modulation element 30 described above. Also, the overall orientation of the effective pixel region in the second optical phase modulation element 30B may be the same as that of the second region 32 of the optical phase modulation element 30 described above. This may enable the first optical phase modulation element 30A (first region 31) to perform phase modulation for P-polarized light. Also, the second optical phase modulation element 30B (second region 32) may be enabled to perform phase modulation for S-polarized light.

[0032] The illumination light emission unit 21 is configured to control the polarization direction of the light emitted as illumination light between a first polarization direction (e.g., P polarization) and a second polarization direction different from the first polarization direction (e.g., S polarization). Furthermore, the illumination light emission unit 21 is configured to emit light in the first polarization direction and light in the second polarization direction at different timings and in different directions.

[0033] The illumination light emission unit 21 includes, for example, a polarization rotation element that controls the polarization direction of light to a first polarization direction and a second polarization direction, and an optical path branching element that branches the optical path of light in the first polarization direction and the optical path of light in the second polarization direction.

[0034] The synchronous control unit 22 synchronizes the timing of the emission of light in a first polarization direction and light in a second polarization direction from the illumination light emission unit 21 with the timing of phase modulation in the first region 31 and the second region 32 of the phase modulation unit 20. The synchronous control unit 22 also synchronizes the timing of the emission of light in a first polarization direction from the illumination light emission unit 21 with the timing of phase modulation of light in a first polarization direction in the first region 31. Furthermore, it synchronizes the timing of the emission of light in a second polarization direction from the illumination light emission unit 21 with the timing of phase modulation of light in a second polarization direction in the second region 32.

[0035] In the configuration example shown in Figure 10, the illumination light emission unit 21 includes a light source 60, a polarization rotation element 61, a polarization beam splitter (PBS) 62, and a mirror 63. The polarization rotation element 61 is an element capable of electrically rotating the polarization direction of light, and is, for example, a liquid crystal element (e.g., a ferroelectric liquid crystal element). The polarization beam splitter 62 is an optical path splitting element that splits the optical path of light in a first polarization direction and the optical path of light in a second polarization direction. The light source 60 is, for example, a laser light source that emits linearly polarized light.

[0036] In the configuration example shown in Figure 10, linearly polarized light from the light source 60 is incident as incident light Lin to the polarization rotation element 61. The polarization rotation element 61 controls the polarization direction of the incident light Lin to P-polarized and S-polarized light and emits it. The P-polarized light is incident on the first region 31 (first optical phase modulation element 30A) of the phase modulation unit 20 via the polarization beam splitter 62 and mirror 63, and phase modulation is performed in the first region 31. The S-polarized light is incident on the second region 32 (second optical phase modulation element 30B) of the phase modulation unit 20 via the polarization beam splitter 62, and phase modulation is performed in the second region 32. The P-polarized and S-polarized light after phase modulation are emitted in the same direction, forming a reconstructed image according to the phase modulation pattern.

[0037] The synchronous control unit 22 synchronizes the timing of polarization control by the polarization rotation element 61 with the timing of phase modulation in the first region 31 and the second region 32 of the phase modulation unit 20. The illumination light emitted from the polarization rotation element 61 illuminates either the first region 31 or the second region 32 of the phase modulation unit 20, depending on its polarization direction. The synchronous control unit 22 controls the polarization rotation element 61 to rotate the polarization direction of the illumination light in accordance with the response completion time of the liquid crystal in each of the first region 31 and the second region 32. As a result, the phase modulation pattern is displayed alternately in each of the first region 31 and the second region 32.

[0038] Figure 11 shows an example of the driving state (liquid crystal response state) of the phase modulation unit 20 in the optical phase modulation system shown in Figure 10. In Figure 11, the horizontal axis represents time, and the vertical axis represents retardation. In Figure 11, an example is shown in which the retardation value is alternately displayed as 1.0 and 0 in the first region 31 (first optical phase modulation element 30A) and the second region 32 (second optical phase modulation element 30B).

[0039] As described above, in the optical phase modulation system according to the first embodiment, by alternately using the first region 31 and the second region 32 of the phase modulation unit 20, it is possible to drive the liquid crystal at twice the speed of the conventional system as a whole. At this time, noise light generated from the pixel region in the refresh state among the first region 31 and the second region 32 has its linear polarization direction switched to a direction in which no in-plane phase distribution occurs, so ideally it becomes all zero-order light, and can be easily removed by installing a spatial filter for zero-order light cut after the phase modulation unit 20. Furthermore, even in applications where a static reproduced image is continuously output, the linear polarization direction rotates by 90° within each frame, so it is possible to reduce the degradation of image quality due to speckle.

[0040] (Regarding the liquid crystal response speed of the phase modulation unit 20) Figure 12 shows an example of the rise time response speed of a liquid crystal luminance modulation element and a liquid crystal optical phase modulation element. Figure 13 shows an example of the fall time response speed of a liquid crystal luminance modulation element and a liquid crystal optical phase modulation element.

[0041] Let's summarize the current state of response speed, which this technology attempts to solve. As mentioned above, liquid crystal type optical phase modulation elements need to ensure twice the retardation compared to liquid crystal type luminance modulation elements. This results in the problem of slower response speed. Figures 12 and 13 show an example of the response speed when the thickness of the liquid crystal layer in a liquid crystal type optical phase modulation element is changed to twice the thickness of the liquid crystal layer in a liquid crystal type luminance modulation element. According to the theoretical formulas (1) and (2) above, increasing the thickness of the liquid crystal layer slows down the response speed in both rising and falling states. When outputting a desired reproduced image using a liquid crystal type optical phase modulation element, a large deviation from the ideal phase distribution in the transient state is a problem. easy This can be imagined, and this deviation in phase distribution leads to a decrease in diffraction efficiency and a deterioration in image quality.

[0042] Figure 14 shows a first example of the driving state of the optical phase modulation element according to the comparative example.

[0043] Let's consider the response of a liquid crystal when attempting 100Hz drive with a conventional liquid crystal type optical phase modulation element. Figure 14 shows the behavior of the liquid crystal response for 8 frames. Since it is driven at 100Hz, 1 frame = 10ms. Here, we consider the case where the desired retardation value of 1.0 and 0 are displayed alternately every 10ms. Here, we consider the VA (Vertical Alignment) mode, in which the rotation angle of the nematic liquid crystal is controlled by the vertical electric field mode. First, a voltage of a certain magnitude is applied at t=0ms, and at t≈7ms, it reaches 90% of the target retardation value. Then, at t=10ms, it switches to the next frame, Frame2, and the voltage application stops, so the liquid crystal transitions to the tilt angle of the liquid crystal that realizes the next phase distribution due to the anchoring energy of the alignment film. At this time, the retardation value from 0ms when the voltage application starts until approximately 7ms when the desired retardation value is achieved differs greatly from the target value, and it is obvious that the target phase distribution has not been realized. This can lead to a decrease in diffraction efficiency and a degradation of the image quality of the reconstructed image.

[0044] Next, let's consider the falling edge response in Frame 2. Figure 14 shows that the voltage application stops at t=20ms and settles roughly at the target retardation value at t≈18ms. At this time, similar to Frame 1, the transient response has a significant impact for about 8ms after the applied voltage changes, causing image quality degradation. Similarly, each time a frame is switched, the transient response has a strong impact, leading to a decrease in diffraction efficiency and image quality degradation, which is a challenge.

[0045] Figure 15 shows a second example of the driving state of the optical phase modulation element according to the comparative example.

[0046] To address the above problem explained using Figure 14, applying the same voltage to the liquid crystal layer every two frames extends the time during which the target retardation value can be stably obtained, minimizing the impact of the liquid crystal's transient response on the reproduced image. Furthermore, by turning off the light source in the transient response region, the impact on image quality degradation of the reproduced image can be further reduced. However, in this case, the light utilization efficiency decreases, and LiDAR and Field... Do There are challenges, such as limitations on its applicability to applications requiring high-speed operation, like sequential holographic displays.

[0047] Figure 16 shows an example of the driving state of the phase modulation unit 20 in the optical phase modulation system according to the first embodiment.

[0048] In the optical phase modulation system according to the first embodiment, the above problems can be solved by alternately using the first region 31 and the second region 32 of the phase modulation unit 20. As shown in the example in Figure 16, for example, by introducing the concept of a Sub-Frame, which divides each 20ms frame into time for using the first region 31 and time for using the second region 32, it is possible to prevent a decrease in diffraction efficiency and deterioration of the reproduced image quality due to the effects of transient response. Figure 16 shows an example in which the retardation value in the first region 31 is alternately displayed as 1.0 and 0, and the retardation value in the second region 32 is alternately displayed as 0.9 and 0.1. For example, in Frame 1, by using the second region 32 from t=0 to 10ms and the first region 31 from t=10 to 20ms, each region has sufficiently passed the transient response during the effective time for actually displaying the reproduced image, and a stable retardation value is achieved. By incorporating the concept of Sub-Frame driving in subsequent frames, it is possible to reduce the effects of transient response and prevent a decrease in the quality of the reproduced image. As a side effect, since the final reproduced image will consist of linearly polarized light that is orthogonal to each other by half, it is also possible to reduce the effects of speckle-induced degradation of the reproduced image.

[0049] [1.2 Variant] (Variation 1) Figure 17 schematically shows one example configuration of an optical phase modulation system according to Modification Example 1.

[0050] In the optical phase modulation system according to Modification 1, the illumination light emission unit 21 further includes a mirror 71 compared to the configuration example shown in Figure 10. Also, compared to the configuration example shown in Figure 10, a polarizing beam splitter (PBS) 72 is positioned on the light emission side from the phase modulation unit 20.

[0051] In the optical phase modulation system according to Modified Example 1, linearly polarized light from the light source 60 is incident as incident light Lin to the polarization rotation element 61. The polarization rotation element 61 controls the polarization direction of the incident light Lin to P-polarized and S-polarized light and emits it. The P-polarized light is incident on the first region 31 (first optical phase modulation element 30A) of the phase modulation unit 20 via the polarization beam splitter 62 and mirror 63, and phase modulation is performed in the first region 31. The S-polarized light is incident on the second region 32 (second optical phase modulation element 30B) of the phase modulation unit 20 via the polarization beam splitter 62 and mirror 71, and phase modulation is performed in the second region 32. The P-polarized and S-polarized light after phase modulation are emitted in the same direction via the polarization beam splitter 72, forming a reconstructed image according to the phase modulation pattern.

[0052] The optical phase modulation system according to this modified example 1 has a configuration that makes it easier to lay out the optical system after the phase modulation unit 20 compared to the configuration example shown in Figure 10.

[0053] Other configurations and operations are the same as those shown in the example configuration in Figure 10.

[0054] (Modification 2) Figure 18 schematically shows one example configuration of an optical phase modulation system according to Modification Example 2.

[0055] The optical phase modulation system according to Modification Example 2 is configured such that the phase modulation unit 20 is composed of a single optical phase modulation element 30 as shown in Figure 9, compared to the configuration example shown in Figure 10.

[0056] Other configurations and operations are the same as those shown in the example configuration in Figure 10.

[0057] (Variation 3) Figure 19 schematically shows one example configuration of an optical phase modulation system according to Modification Example 3.

[0058] The optical phase modulation system according to Modification 3 uses a polarization spectrometer 64 instead of a polarization beam splitter 62 as an optical path branching element that branches the optical path of light in the first polarization direction and the optical path of light in the second polarization direction, compared to the configuration example shown in Figure 10.

[0059] Figure 20 schematically shows a first configuration example of the polarization spectrometer 64. Figure 21 schematically shows a second configuration example of the polarization spectrometer 64. The polarization spectrometer 64 may be, for example, a metasurface polarization spectrometer 81 as shown in Figure 20. Alternatively, the polarization spectrometer 64 may be, for example, a polarization prism 82 as shown in Figure 21.

[0060] In the optical phase modulation system according to Modified Example 3, linearly polarized light from the light source 60 is incident as incident light Lin to the polarization rotation element 61. The polarization rotation element 61 controls the polarization direction of the incident light Lin to P-polarized and S-polarized light and emits it. The P-polarized light is incident on the first region 31 (first optical phase modulation element 30A) of the phase modulation unit 20 via the polarization spectrometer 64, and phase modulation is performed in the first region 31. The S-polarized light is incident on the second region 32 (second optical phase modulation element 30B) of the phase modulation unit 20 via the polarization spectrometer 64, and phase modulation is performed in the second region 32. The P-polarized and S-polarized light after phase modulation are emitted in the same direction, forming a reconstructed image according to the phase modulation pattern.

[0061] Other configurations and operations are the same as those shown in the example configuration in Figure 10.

[0062] (Modification 4) Figure 22 schematically shows one example configuration of the optical phase modulation system according to Modification 4.

[0063] Variation 4 The optical phase modulation system relating to this system is a modified example 3 shown in Figure 19, in which the phase modulation unit 20 is composed of a single optical phase modulation element 30 shown in Figure 9.

[0064] The other configurations and operations are the same as those of Modification 3 shown in Figure 19.

[0065] (Variation 5) Figure 23 schematically shows one example configuration of the optical phase modulation system according to Modification Example 5.

[0066] The optical phase modulation system according to Modification 5 is configured such that the first optical phase modulation element 30A and the second optical phase modulation element 30B are reflective optical phase modulation elements, compared to the configuration example shown in Figure 10.

[0067] Other configurations and operations are the same as those shown in the example configuration in Figure 10.

[0068] (Experimental variation 6) Figure 24 schematically shows one example configuration of the optical phase modulation system according to Modification 6.

[0069] The optical phase modulation system according to Modification 6 is configured such that the first optical phase modulation element 30A and the second optical phase modulation element 30B are reflective optical phase modulation elements, compared to Modification 3 shown in Figure 19.

[0070] The other configurations and operations are the same as those of Modification 3 shown in Figure 19.

[0071] (Example 7) Figure 25 schematically shows one example configuration of the optical phase modulation system according to Modification Example 7.

[0072] In the optical phase modulation system according to Modified Example 7, the illumination light emission unit 21 includes a light source 90, a rotating quarter-wave plate 91, a polarizing beam splitter (PBS) 62, and a mirror 65. Furthermore, the optical phase modulation system according to Modified Example 7 has a phase modulation unit 20 composed of one optical phase modulation element 30 as shown in Figure 9. It is also possible to configure the phase modulation unit 20 with a first optical phase modulation element 30A and a second optical phase modulation element 30B, similar to the configuration example shown in Figure 10.

[0073] The light source 90 is a circularly polarized light source that emits circularly polarized light. The rotating quarter-wave plate 91 is a polarization rotation element that can mechanically rotate the polarization direction of light, and is a rotating quarter-wave plate equipped with a mechanical rotation mechanism. The polarization beam splitter 62 is an optical path splitting element that splits the optical path of light with a first polarization direction (P polarization) and the optical path of light with a second polarization direction (S polarization).

[0074] In the optical phase modulation system according to Modified Example 7, circularly polarized light from the light source 90 is incident as incident light Lin to the rotating quarter-wave plate 91. The rotating quarter-wave plate 91 controls the polarization direction of the incident light Lin to P-polarized and S-polarized light and emits it. The P-polarized light is incident on the first region 31 of the phase modulation unit 20 via the polarizing beam splitter 62, and phase modulation is performed in the first region 31. The S-polarized light is incident on the second region 32 of the phase modulation unit 20 via the polarizing beam splitter 62 and the mirror 65, and phase modulation is performed in the second region 32. The P-polarized and S-polarized light after phase modulation are emitted in the same direction, forming a reconstructed image according to the phase modulation pattern.

[0075] The synchronous control unit 22 synchronizes the timing of polarization control by the rotating quarter-wave plate 91 with the timing of phase modulation in the first region 31 and the second region 32 of the phase modulation unit 20. The illumination light emitted from the rotating quarter-wave plate 91 illuminates either the first region 31 or the second region 32 of the phase modulation unit 20, depending on its polarization direction. The synchronous control unit 22 controls the rotating quarter-wave plate 91 to rotate the polarization direction of the illumination light in accordance with the response completion time of the liquid crystal in each of the first region 31 and the second region 32. As a result, the phase modulation pattern is displayed alternately in each of the first region 31 and the second region 32.

[0076] The optical phase modulation system according to this modified example 7 has a configuration that can improve the efficiency of optical utilization.

[0077] (Variation 8) Figure 26 schematically shows one example configuration of the optical phase modulation system according to Modification Example 8.

[0078] In the optical phase modulation system according to Modified Example 8, the illumination light emission unit 21 includes a light source 60, a galvanometer mirror 92, a mirror 93, and a half-wave plate 94. Furthermore, the optical phase modulation system according to Modified Example 8 has a phase modulation unit 20 composed of one optical phase modulation element 30 as shown in Figure 9. It is also possible to configure the phase modulation unit 20 with a first optical phase modulation element 30A and a second optical phase modulation element 30B, similar to the configuration example shown in Figure 10.

[0079] The light source 60 is, for example, a laser light source that emits P-polarized light as linearly polarized light. The galvanometer mirror 92 is an optical path switching element that switches the optical path of the illumination light between a first optical path and a second optical path different from the first optical path. The half-wave plate 94 is a polarization conversion element placed on the second optical path that converts the polarization direction of the light from the first polarization direction (P-polarization) to the second polarization direction (S-polarization).

[0080] In the optical phase modulation system according to Modified Example 8, linearly polarized (P-polarized) light from the light source 60 is incident on the galvanometer mirror 92 as incident light Lin. The galvanometer mirror 92 switches the optical path depending on whether the illumination light is incident on the first region 31 or the second region 32 of the phase modulation unit 20. When the galvanometer mirror 92 switches to the first optical path, P-polarized light is incident on the first region 31 of the phase modulation unit 20 as illumination light, and phase modulation is performed in the first region 31. When the galvanometer mirror 92 switches to the second optical path, P-polarized light is incident on the half-wave plate 94 via the mirror 93 and converted to S-polarized light. The S-polarized light is incident on the second region 32 of the phase modulation unit 20, and phase modulation is performed in the second region 32. The P-polarized light and S-polarized light after phase modulation are emitted in the same direction, forming a reconstructed image according to the phase modulation pattern.

[0081] The synchronization control unit 22 synchronizes the timing of the optical path switching by the galvanometer mirror 92 with the timing of the phase modulation in the first region 31 and the second region 32 of the phase modulation unit 20. As a result, the phase modulation patterns are displayed alternately in the first region 31 and the second region 32, respectively.

[0082] The optical phase modulation system according to this modified example 8 has a configuration that can improve the efficiency of optical utilization. Furthermore, it has a configuration that allows polarization control using only general optical elements.

[0083] (Extreme variation 9) Figure 27 schematically shows one example configuration of the optical phase modulation system according to Modification 9.

[0084] The optical phase modulation system according to Modification 9 differs from Modification 7 shown in Figure 25 in that a nematic liquid crystal element 95 is used as the polarization rotation element instead of a rotating quarter-wave plate 91.

[0085] In the optical phase modulation system according to Modified Example 9, circularly polarized light from the light source 90 is incident on the nematic liquid crystal element 95 as incident light Lin. The nematic liquid crystal element 95 controls the polarization direction of the incident light Lin to P-polarization and S-polarization and emits it. The synchronization control unit 22 synchronizes the timing of polarization control by the nematic liquid crystal element 95 with the timing of phase modulation in the first region 31 and the second region 32 of the phase modulation unit 20.

[0086] Other configurations and operations are the same as those shown in Modification 7 in Figure 25.

[0087] (Variation 10) Figure 28 schematically shows one example configuration of an optical phase modulation system according to modified example 10.

[0088] The optical phase modulation system according to Modification 10 differs from Modification 7 shown in Figure 25 in that it uses a ferroelectric liquid crystal element 96 instead of a rotating quarter-wave plate 91 as the polarization rotation element. Furthermore, instead of a light source 90 that emits circularly polarized light, it uses a light source 60 that emits linearly polarized P-polarized light.

[0089] In the optical phase modulation system according to modified example 10, P-polarized light from the light source 60 is incident on the ferroelectric liquid crystal element 96 as incident light Lin. The ferroelectric liquid crystal element 96 controls the polarization direction of the incident light Lin to P-polarized and S-polarized light before emitting it. The synchronization control unit 22 synchronizes the timing of polarization control by the ferroelectric liquid crystal element 96 with the timing of phase modulation in the first region 31 and the second region 32 of the phase modulation unit 20.

[0090] Other configurations and operations are the same as those shown in Modification 7 in Figure 25.

[0091] [1.3 Effects] As described above, according to the optical phase modulation system of the first embodiment, the illumination light emission unit 21 emits light in a first polarization direction and light in a second polarization direction at different timings, and the light in the first polarization direction and the light in the second polarization direction are phase-modulated in the first region 31 and the second region 32 of the phase modulation unit 20, respectively. At this time, the timing of emission of light in each polarization direction and the timing of phase modulation in each region are synchronized. This makes it possible to improve the response speed of phase modulation while suppressing the deterioration of image quality.

[0092] According to the optical phase modulation system of the first embodiment, the delay in response speed when using an optical phase modulation element with a phase modulation amount of 0 to 2π can be improved by alternately using two regions of the phase modulation unit 20. In this case, it is possible to increase the frame rate without degradation of image quality or reduction in brightness (efficiency). Furthermore, since the light incident on the two regions of the phase modulation unit 20 maintains the wavefront (plane) from the illumination light, it is possible to easily calculate a phase pattern for displaying an arbitrary distribution.

[0093] The effects described herein are merely illustrative and not limiting, and other effects may also exist. The same applies to the effects of other embodiments described later.

[0094] <2. Other Embodiments> The technology described herein is not limited to the embodiments described above and can be modified in various ways.

[0095] For example, this technology can also take the following configuration. According to this technology, which has the following configuration, light with a first polarization direction and light with a second polarization direction are emitted from the illumination light emission unit at different timings, and the light with the first polarization direction and the light with the second polarization direction are phase-modulated in the first and second regions of the phase modulation unit, respectively. At that time, the timing of emission of light with each polarization direction and the timing of phase modulation in each region are synchronized. This makes it possible to improve the response speed of phase modulation while suppressing the degradation of image quality.

[0096] (1) An illumination light emitting unit is configured to control the polarization direction of light emitted as illumination light to a first polarization direction and a second polarization direction different from the first polarization direction, and is configured to emit light in the first polarization direction and light in the second polarization direction at different timings and in different directions from each other. A phase modulation unit having a first region configured to perform phase modulation on light in a first polarization direction from the illumination light emission unit, and a second region configured to perform phase modulation on light in a second polarization direction from the illumination light emission unit, A synchronization control unit synchronizes the timing of the emission of light in the first polarization direction and light in the second polarization direction from the illumination light emission unit with the timing of phase modulation in the first region and the second region of the phase modulation unit. Equipped with Optical phase modulation system. (2) The synchronization control unit, The timing of the emission of light in the first polarization direction from the illumination light emission unit is synchronized with the timing of the phase modulation of the light in the first polarization direction in the first region, and the timing of the emission of light in the second polarization direction from the illumination light emission unit is synchronized with the timing of the phase modulation of the light in the second polarization direction in the second region. The optical phase modulation system described in (1) above. (3) The phase modulation unit is A first optical phase modulation element having the first region, A second optical phase modulation element having the second region and including The optical phase modulation system described in (1) or (2) above. (4) The phase modulation unit includes one optical phase modulation element having a first region and a second region. The optical phase modulation system described in (1) or (2) above. (5) The illumination light emission unit is, A polarization rotation element that controls the polarization direction of light to the first polarization direction and the second polarization direction, An optical path branching element that branches the optical path of light in the first polarization direction and the optical path of light in the second polarization direction. It has, The synchronization control unit synchronizes the timing of the polarization control by the polarization rotation element with the timing of the phase modulation in the first and second regions of the phase modulation unit. An optical phase modulation system as described in any one of (1) through (4) above. (6) The polarization rotation element is an element capable of electrically rotating the polarization direction of light. The optical phase modulation system described in (5) above. (7) The polarization rotation element is a liquid crystal element. The optical phase modulation system described in (6) above. (8) The polarization rotation element is an element capable of mechanically rotating the polarization direction of light. The optical phase modulation system described in (5) above. (9) The polarization rotation element is a rotating waveplate equipped with a mechanical rotation mechanism. The optical phase modulation system described in (8) above. (10) The optical path splitting element is a polarizing beam splitter. An optical phase modulation system as described in any one of (5) through (9) above. (11) The optical path branching element is a polarization spectrometer. An optical phase modulation system as described in any one of (5) through (9) above. (12) The illumination light emission unit is, An optical path switching element that switches the optical path of the illumination light between a first optical path and a second optical path different from the first optical path, A polarization conversion element is arranged on the second optical path and converts the polarization direction of light from the first polarization direction to the second polarization direction. It has, The synchronization control unit synchronizes the timing of the optical path switching by the optical path switching element with the timing of the phase modulation in the first and second regions of the phase modulation unit. An optical phase modulation system as described in any one of (1) through (4) above. (13) The illumination light emission unit has a light source that emits linearly polarized light. An optical phase modulation system as described in any one of (1) through (12) above. (14) The illumination light emission unit has a light source that emits circularly polarized light. An optical phase modulation system as described in any one of (1) through (12) above. (15) An illumination light emitting unit is configured to control the polarization direction of light emitted as illumination light to a first polarization direction and a second polarization direction different from the first polarization direction, and is configured to emit light in the first polarization direction and light in the second polarization direction at different timings and in different directions from each other. A phase modulation unit having a first region configured to perform phase modulation on light in a first polarization direction from the illumination light emission unit, and a second region configured to perform phase modulation on light in a second polarization direction from the illumination light emission unit, A synchronization control unit that synchronizes the timing of polarization control in the illumination light emission unit with the timing of phase modulation in the first and second regions of the phase modulation unit. Equipped with Display device.

[0097] This application claims priority based on Japanese Patent Application No. 2021-194909, filed with the Japan Patent Office on November 30, 2021, and all contents of that application are incorporated herein by reference.

[0098] Those skilled in the art will understand that various modifications, combinations, subcombinations, and changes can be conceived depending on design requirements and other factors, and that these fall within the scope of the attached claims and their equivalents.

Claims

1. An illumination light emission unit is configured to control the polarization direction of light emitted as illumination light to a first polarization direction and a second polarization direction different from the first polarization direction, and is configured to emit light in the first polarization direction and light in the second polarization direction at different timings and in different directions from each other. A phase modulation unit having a first region configured to perform phase modulation on light in a first polarization direction from the illumination light emission unit, and a second region configured to perform phase modulation on light in a second polarization direction from the illumination light emission unit, A synchronization control unit synchronizes the timing of the emission of light in the first polarization direction and light in the second polarization direction from the illumination light emission unit with the timing of phase modulation in the first region and the second region of the phase modulation unit. Equipped with Optical phase modulation system.

2. The synchronization control unit, The timing of the emission of light in the first polarization direction from the illumination light emission unit is synchronized with the timing of the phase modulation of the light in the first polarization direction in the first region, and the timing of the emission of light in the second polarization direction from the illumination light emission unit is synchronized with the timing of the phase modulation of the light in the second polarization direction in the second region. The optical phase modulation system according to claim 1.

3. The phase modulation unit is A first optical phase modulation element having the first region, A second optical phase modulation element having the second region and including The optical phase modulation system according to claim 1.

4. The phase modulation unit includes one optical phase modulation element having a first region and a second region. The optical phase modulation system according to claim 1.

5. The illumination light emission unit is, A polarization rotation element that controls the polarization direction of light to the first polarization direction and the second polarization direction, An optical path branching element that branches the optical path of light in the first polarization direction and the optical path of light in the second polarization direction. It has, The synchronization control unit synchronizes the timing of the polarization control by the polarization rotation element with the timing of the phase modulation in the first and second regions of the phase modulation unit. The optical phase modulation system according to claim 1.

6. The polarization rotation element is an element capable of electrically rotating the polarization direction of light. The optical phase modulation system according to claim 5.

7. The polarization rotation element is a liquid crystal element. The optical phase modulation system according to claim 6.

8. The polarization rotation element is an element capable of mechanically rotating the polarization direction of light. The optical phase modulation system according to claim 5.

9. The polarization rotation element is a rotating waveplate equipped with a mechanical rotation mechanism. The optical phase modulation system according to claim 8.

10. The optical path splitting element is a polarizing beam splitter. The optical phase modulation system according to claim 5.

11. The optical path branching element is a polarization spectrometer. The optical phase modulation system according to claim 5.

12. The illumination light emission unit is, An optical path switching element that switches the optical path of the illumination light between a first optical path and a second optical path different from the first optical path, A polarization conversion element is arranged on the second optical path and converts the polarization direction of light from the first polarization direction to the second polarization direction. It has, The synchronization control unit synchronizes the timing of the optical path switching by the optical path switching element with the timing of the phase modulation in the first and second regions of the phase modulation unit. The optical phase modulation system according to claim 1.

13. The illumination light emission unit has a light source that emits linearly polarized light. The optical phase modulation system according to claim 1.

14. The illumination light emission unit has a light source that emits circularly polarized light. The optical phase modulation system according to claim 1.

15. An illumination light emission unit is configured to control the polarization direction of light emitted as illumination light to a first polarization direction and a second polarization direction different from the first polarization direction, and is configured to emit light in the first polarization direction and light in the second polarization direction at different timings and in different directions from each other. A phase modulation unit having a first region configured to perform phase modulation on light in a first polarization direction from the illumination light emission unit, and a second region configured to perform phase modulation on light in a second polarization direction from the illumination light emission unit, A synchronization control unit that synchronizes the timing of polarization control in the illumination light emission unit with the timing of phase modulation in the first region and the second region of the phase modulation unit. Equipped with Display device.

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