3D Image Display Device

Abstract

To provide a three-dimensional video display device that can display three-dimensional video having a wide depth range and high resolution.SOLUTION: A three-dimensional video display device 1 comprises: a beam emission unit 11 that emits, as beams for respective directions, beams in which brightness of three-dimensional video data in which a plurality of images for respective directions is two-dimensionally arranged is controlled for every pixel; a transmission type liquid crystal panel 12 that has a pixel pitch narrower than the beam emission unit 11, and transmits the beams for respective directions emitted from the beam emission unit 11 at transmittance for every controlled pixel; a first visual field control lens 131 that controls a visual field of the beam; a second visual field control lens 132; and a control unit 20 that controls the brightness of the three-dimensional video data and the transmittance of the transmission type liquid crystal panel 12 so as to minimize an error between the brightness for every pixel of the images for respective directions in input multi-viewpoint video data and the brightness for every pixel of the images for respective directions after passage through the second visual field control lens 132.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a three-dimensional image display device that displays three-dimensional images. [Background technology]

[0002] In recent years, a wide variety of three-dimensional image display devices have been proposed, including a two-lens system using 3D glasses. Among these, the light field method faithfully reproduces the group of light rays from an object, allowing it to present a natural three-dimensional image with parallax in both the horizontal and vertical directions to the observer without the need for special glasses (see Patent Document 1 and Non-Patent Documents 1-2). However, it is known that with the light field method, the resolution decreases as the depth of the 3D image is increased when the display screen is observed from a predetermined viewing distance. To display a high-resolution 3D image over a wide depth range, it is necessary to increase the angular density of the reproduced light rays, but the angular density of the light rays has a trade-off relationship with other display characteristic parameters such as the viewing angle and maximum number of pixels of the 3D image (see Non-Patent Literature 1).

[0003] Conventionally, viewpoint tracking technology has been proposed as a method to improve the display characteristics of 3D images (see Non-Patent Document 2). In this method, instead of narrowing the optical viewing angle in the direction of the viewpoint in a given frame, the angular density of light rays is increased, making it possible to display high-resolution 3D images over a wide depth range. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6598362 [Non-patent literature]

[0005] [Non-Patent Document 1] H. Hoshino, F. Okano, H. Isono, and I. Yuyama, “Analysis of resolution limitation of integral photography,” J. Opt. Soc. Am. A, vol. 15, no. 8, pp. 2059-2065 (1998). [Non-Patent Document 2] S. Hong, D. Shin, J.-J. Lee, and B.-G. Lee, “Viewing angle-improved 3D integral imaging display with eye tracking sensor,” J. Inf. Commun. Converg. Eng., vol. 12, no. 4, pp. 208-214 (2014). [Overview of the project] [Problems that the invention aims to solve]

[0006] As mentioned above, the angular density of light rays has a trade-off relationship with other display characteristics parameters such as the viewing angle and maximum number of pixels of the 3D image. Therefore, there is a problem in that increasing the angular density of light rays while maintaining other display characteristics would require an enormous amount of image information. Furthermore, conventional methods using gaze-tracking technology require designing the viewing angle of the 3D image to encompass both eyes of the viewer. Due to this constraint, it is difficult to significantly increase the angular density of light rays using methods that utilize gaze-tracking technology. Therefore, the object of the present invention is to provide a 3D image display device that can display high-resolution 3D images over a wide depth range by increasing the angular density of the regenerated light rays. [Means for solving the problem]

[0007] To solve the above problems, the three-dimensional video display device according to the present invention is a three-dimensional video display device that displays a three-dimensional video, and includes a light-emitting unit, a transmissive liquid crystal panel, a first viewing area control lens, a second viewing area control lens, and a control unit.

[0008] In such a configuration, the three-dimensional video display device emits, as light rays in different directions, light rays in which the luminance of three-dimensional video data in which a plurality of images in different directions are two-dimensionally arranged is controlled for each pixel by the light-emitting unit. This three-dimensional video data is data for displaying a three-dimensional video such as, for example, an elemental image group or a multi-viewpoint video. Then, the three-dimensional video display device allows the light rays in different directions to pass through at a transmittance for each controlled pixel by means of a transmissive liquid crystal panel that is disposed on the light-emitting side of the light rays of the light-emitting unit and has a pixel pitch smaller than that of the light-emitting unit.

[0009] Then, the three-dimensional video display device condenses the light rays onto the pixel positions of the three-dimensional video on the second viewing area control lens in the subsequent stage by means of a first viewing area control lens that is disposed in contact with the light-emitting side of the light rays of the transmissive liquid crystal panel. Then, the three-dimensional video display device diverges the condensed light rays in the front direction by means of a second viewing area control lens that is disposed at a distance from the first viewing area control lens by the focal length of the first viewing area control lens. Due to this divergence of the light rays, the observer can observe the three-dimensional video.

[0010] At this time, the three-dimensional video display device controls the luminance of the three-dimensional video data emitted by the light-emitting unit and the transmittance of the transmissive liquid crystal panel so as to minimize the error between the luminance for each pixel in different directions of the input multi-viewpoint video data and the luminance for each pixel in different directions after passing through the second viewing area control lens, by means of the control unit. As a result, the light rays in different directions emitted from the three-dimensional video display device become a plurality of light rays having different luminances, so that the angular density of the reproduced light rays can be increased.

[0011] Furthermore, in order to solve the above problems, the 3D image display device according to the present invention is a 3D image display device that displays a 3D image, and comprises a light ray emission unit having a display device and a liquid crystal lens array, a first field of view control lens, a second field of view control lens, and a control unit.

[0012] In this configuration, the 3D image display device uses a display device in the light ray emission unit to emit light rays in a time-division manner, switching between light rays in which the brightness of 3D image data, which is a 2D arrangement of multiple images for each direction, is controlled for each pixel, and light rays in which the brightness of 2D image data is controlled for each pixel, as light rays for each direction. The 3D image display device has a two-dimensional arrangement of liquid crystal lenses facing the light rays of the image in different directions. The liquid crystal lens array, positioned at a distance from the display device equal to the focal length of the liquid crystal lenses in lens state, allows the light rays of the display device to pass through while controlling the switching between lens state and transmission state.

[0013] The 3D image display device is positioned on the light-emitting side of the light-emitting section and uses a first field of view control lens to focus the light rays to the pixel positions of the 3D image on a subsequent second field of view control lens. The 3D image display device then uses a second field of view control lens, positioned at a distance equal to the focal length of the first field of view control lens, to diverge the focused light rays in a forward direction. This diverged light allows the observer to view a 3D image.

[0014] In this state, the 3D image display device, via its control unit, switches between the lens state and the transparency state of the liquid crystal lens array for each frame. The control unit then synchronizes the display of 3D image data on the display device when the lens state is active, and 2D image data when the transparency state is active. As a result, the brightness of each pixel passing through the liquid crystal lens array in the lens state, and the brightness of each pixel passing through the liquid crystal lens array in the transmission state are added together by time-division multiplexing. Furthermore, the 3D image display device controls the brightness of the 3D image data in the lens state emitted by the light ray emitter and the brightness of the 2D image data in the transmission state, by the control unit, in order to minimize the error between the brightness of each pixel in each direction of the input multi-view image data and the brightness of each pixel in each direction after passing through the second viewing range control lens. This results in multiple rays of light with different brightness levels being emitted from the 3D image display device in different directions, thereby increasing the angular density of the reproduced light rays. [Effects of the Invention]

[0015] According to the present invention, the angular density of the regenerated light rays emitted from the 3D image display device is increased. As a result, the present invention can display high-resolution 3D images over a wide depth range. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic perspective view showing a three-dimensional image display device according to an embodiment of the present invention. [Figure 2] This is a plan view showing the configuration of a three-dimensional image display device according to the first embodiment of the present invention. [Figure 3] This figure shows an example of the configuration of a light ray emission unit of a three-dimensional image display device according to the first embodiment of the present invention, where (a) is a plan view showing the configuration of an integral type light ray emission unit, and (b) is an enlarged view of a display device corresponding to one element lens in (a). [Figure 4] This is an explanatory diagram to illustrate the field of view control performed by field of view control lenses. [Figure 5] This diagram schematically shows the light rays when a transmissive liquid crystal panel is installed. [Figure 6] This diagram schematically shows the light rays when a transmissive liquid crystal panel is not provided. [Figure 7] This is a block diagram showing the configuration of the control unit of a three-dimensional image display device according to the first embodiment of the present invention. [Figure 8] This is an explanatory diagram illustrating the processing of the brightness error minimization unit in Figure 7. [Figure 9] This figure shows another example of the configuration of the light ray emission unit of a three-dimensional image display device according to the first embodiment of the present invention, and is a plan view showing the configuration of the light ray emission unit of a multi-view image projection system. [Figure 10] This is a plan view showing the configuration of a three-dimensional image display device according to a second embodiment of the present invention. [Figure 11] This is a block diagram showing the configuration of the control unit of a three-dimensional image display device according to a second embodiment of the present invention. [Figure 12] This is a plan view showing the configuration of a three-dimensional image display device according to the third embodiment of the present invention. [Modes for carrying out the invention]

[0017] Embodiments of the present invention will be described below with reference to the drawings. <First Embodiment> First, with reference to Figures 1 and 2, a three-dimensional image display device 1 according to the first embodiment of the present invention will be described.

[0018] The 3D image display device 1 displays a 3D image. This 3D image display device 1 displays a 3D image T that has parallax in the horizontal and vertical directions. As shown in Figure 1, the 3D image display device 1 comprises a display unit 10 and a control unit 20. As shown in Figure 2, the display unit 10 comprises a light ray emission unit 11, a transmissive liquid crystal panel 12, and two field of view control lenses 13 (a first field of view control lens 131 and a second field of view control lens 132).

[0019] The light ray emission unit 11 emits light rays as directional light rays, the brightness of which is controlled for each pixel of 3D video data arranged in a 2D array of multiple images for each direction. The light ray emission unit 11 can use a general light field type 3D video display device (for example, Patent Document 1, Non-Patent Documents 1, 2). The polarization state of the light emitted from the light emission unit 11 can be random polarization, circular polarization, or linear polarization. However, if the emitted light is linearly polarized and its polarization direction is perpendicular to the polarization transmission axis of the polarizer on the incident surface of the transmissive liquid crystal panel 12 (described later), the emitted light will be blocked by the polarizer. Therefore, when the emitted light is linearly polarized, the polarization direction should be configured so that it is not perpendicular to the polarization transmission axis of the polarizer on the incident surface of the transmissive liquid crystal panel 12.

[0020] In the most desirable configuration, the emitted light from the light emission unit 11 is linearly polarized, and its polarization direction is the same as the polarization transmission axis of the polarizer on the incident surface of the transmissive liquid crystal panel 12, thereby enabling the 3D image T displayed by the 3D image display device 1 to be displayed in the brightest possible light. For clarity, only the five pixels in the horizontal direction (x direction) of the light-emitting section 11 are shown in this diagram. The direction and brightness of the light emitted by the light ray emission unit 11 will be explained later.

[0021] Now, with reference to Figure 3, an example of the configuration of the light ray emission unit 11 will be described. Figure 3(a) shows an example in which the light ray emission unit 11 is configured as an integral type light ray emission unit 111. Figure 3(b) is an enlarged view of the display device 110 corresponding to one element lens 111a of the light ray emission unit 111. As shown in Figure 3(a), the light ray emission unit 111 comprises a display device 110 and an element lens array 111.

[0022] The display device 110 displays video data in which the brightness of the 3D video data is controlled for each pixel by the control unit 20, which will be described later. The 3D image data is a set of integral element images. The display device 110 uses a direct-view display device such as a liquid crystal display or an organic electroluminescent (OLED) display. For clarity, only the 50 pixels in the horizontal direction (x direction) of the pixels pe displayed by the display device 110 are shown in the illustration.

[0023] The element lens array 111 is an optical element in which minute element lenses (convex lenses) 111a are arranged in a two-dimensional array. The element lens array 111 arranges the element lenses 111a in a two-dimensional array facing the direction-specific images (element images) displayed on the display device 110, and the focal length f of the element lenses 111a a It is positioned at a distance from the display device 110. Generally, the size of the element lens 111a is about 1 mm, and the number of element lenses 111a constituting the element lens array 111 is several hundred or more in each direction. However, for the sake of clarity, only the five in the horizontal direction (x direction) are shown in this illustration. In other words, this example shows one element lens 111a associated with 10 horizontal pixels of the element image Ie displayed by the display device 110.

[0024] Furthermore, Figure 3(a) shows only the principal rays of the group of rays emitted from pixels pe facing the element lenses 111a at both ends in the horizontal direction and passing through the center of the element lenses 111a (lens center Lc). Also, in Figure 3(a), the principal ray traveling furthest downward (negative x-axis direction) is shown as a dashed line, and rays traveling in other directions are shown as dotted lines. As shown in Figure 3(b), the light rays from the pixel pe of the display device 110 illuminate the entire surface of the opposing element lens 111a, and are emitted in one direction as parallel light from the entire surface of the element lens 111a. The direction of this parallel light is the same as the direction connecting the position of the pixel pe and the lens center Lc.

[0025] As explained above, in the light ray emission unit 111, the number of element lenses 111a corresponds to the number of pixels in the light ray emission unit 111, and the number of pixels of the display device 110 facing one element lens 111a corresponds to the number of emission directions of the light ray emission unit 111. In the example shown in Figure 3(a), the light emission unit 111 emits images in 10 directions for each pixel, with 5 pixels in the horizontal direction (x direction) and a pixel aperture ratio of 100%. Returning to Figure 2, we will continue our explanation of the configuration of the 3D image display device 1.

[0026] The transmissive liquid crystal panel 12 is positioned on the light emission side of the light emission unit 11 and has a narrower pixel pitch than the light emission unit 11. It transmits light rays emitted from the light emission unit 11 in different directions with a controlled transmittance for each pixel. The pixels of the emitted 3D video data are the pixels of the display device 110 described in Figure 3. The transmissive liquid crystal panel 12 is positioned in close contact with the display surface of the light ray emission unit 11. The transmissive liquid crystal panel 12 is a typical liquid crystal panel in which a liquid crystal layer, alignment film, transparent electrode, color filter, polarizer, etc., are laminated (not shown in the figure). In Figure 2, the light emission unit 11 and the transmissive liquid crystal panel 12 are spaced apart for better visibility.

[0027] The transmissive liquid crystal panel 12 is controlled by the control unit 20, which controls the voltage of each pixel, thereby changing the angle between the light distribution direction of the liquid crystal molecules and the polarizing plate, and thus controlling the transmittance. The pixel density of the transmissive liquid crystal panel 12 is made higher than the pixel density of the light ray emission unit 11. Figure 2 shows that 10 pixels pp of the transmissive liquid crystal panel 12 correspond to one pixel pr in the horizontal direction (x direction) of the light ray emission unit 11.

[0028] Thus, the pixel density of the transmissive liquid crystal panel 12 is higher than the pixel density of the light ray emission unit 11. Furthermore, the light rays that pass through the pixels pp of the transmissive liquid crystal panel 12 become luminance-modulated light rays from both the light ray emission unit 11 and the transmissive liquid crystal panel 12. As a result, the light ray emitted from one pixel pr of the light ray emission unit 11 travels as 10 parallel light ray beams with different brightness levels through the transmissive liquid crystal panel 12. The transmissive liquid crystal panel 12 illuminates the first field of view control lens 131 with transmitted light rays.

[0029] The field of view control lens 13 controls the field of view of light rays passing through the transmissive liquid crystal panel 12. The field of view control lens 13 comprises a first field of view control lens 131 and a second field of view control lens 132. The field of view control lens 131 and the field of view control lens 132 can each be made of a general convex lens, Fresnel lens, diffractive lens, etc. In this example, the field of view control lens 131 and the field of view control lens 132 are each made of convex lenses.

[0030] The field of view control lens 131 focuses the light rays from the transmissive liquid crystal panel 12 onto the field of view control lens 132. Here, the field of view control lens 131 focuses the light rays from each pixel pp emitting from the transmissive liquid crystal panel 12 in multiple directions onto the field of view control lens 132, according to their respective directions. The diameter of the field of view control lens 131 is greater than or equal to the display size of the light ray emission section 11. The field of view control lens 131 is positioned in contact with the light ray emission surface of the transmissive liquid crystal panel 12. Note that in Figure 2, the transmissive liquid crystal panel 12 and the field of view control lens 131 are spaced apart for better visibility of the diagram.

[0031] The field of view control lens 132 diverges the light rays focused by the field of view control lens 131 in the forward direction. Here, let Ψ be the viewing angle of the ray emission unit 11, and consider a polar coordinate system where the zx axis is the coordinate axis when the origin position of the xyz axes shown in Figure 2 is translated parallel to the center position of the display screen of the ray emission unit 11. If a ray is emitted from the ray emission unit 11 at a maximum angle of Ψ / 2, then the focal length of the viewing area control lens 131 is f v In this case, the light is refracted by the field of view control lens 131, and x = f on the field of view control lens 131. v It passes through the position tan(Ψ / 2). Therefore, the diameter of the field of view control lens 132 is 2f v It needs to be larger than tan(Ψ / 2). Note that the viewing angle of the ray emission unit 11 differs depending on the type of ray emission unit 11 (for example, Patent Document 1, Non-Patent Documents 1, 2), so the explanation is omitted here. The field of view control lens 132 receives the focal length f of the field of view control lens 131. vThey are positioned with a certain distance between them. The focal length of the field of view control lens 132 is the same as the focal length of the field of view control lens 131.

[0032] Here, referring to Figure 4, the field of view control by the field of view control lens 13 will be explained by illustrating the light rays. The pixel configuration of the light ray emission unit 11 and the transmissive liquid crystal panel 12 is the same as the configuration described in Figures 2 and 3. Here, only the principal rays are shown for the group of light rays emitted from pixels pp1 and pp50 at both ends of the transmissive liquid crystal panel 12 in the horizontal direction. In Figure 4, the principal ray traveling furthest downward (negative x-axis direction) is shown as a dashed line, and rays traveling in other directions are shown as dotted lines.

[0033] As explained in Figure 3, parallel light rays are emitted from each of the pixels pr of the light ray emission unit 11 in 10 directions in the horizontal direction. In other words, of the 10 rays emitted from pixel pr1 of the light ray emission unit 11 shown in Figure 4, for example, the ray whose brightness is modulated by pixel pp1 of the transmissive liquid crystal panel 12 is refracted by the first viewing range control lens 131 and emitted in the 10 directions. Similarly, for the other pixels, the ray emitted from the pixels of the light ray emission unit 11 and whose brightness is modulated by the transmissive liquid crystal panel 12 is refracted by the first viewing range control lens 131 and emitted in the 10 directions.

[0034] Here, the second field of view control lens 132 has a focal length f of the field of view control lens 131. v Because it is spaced apart from the field of view control lens 131, the light rays refracted by the field of view control lens 131 are focused at 10 different horizontal positions on the field of view control lens 132. The light rays focused onto the second field of view control lens 132 are further refracted by the field of view control lens 132 and diverge while spreading out in the positive z-axis direction at a predetermined field of view angle φ. Because the brightness of this divergent light is modulated by the pixels of the transmissive liquid crystal panel 12, the 10 light rays emitted by the 5 pixels (pr1, ..., pr5) of the light ray emission unit 11 have 50 steps of brightness variation within the viewing angle φ.

[0035] In other words, as shown in Figure 5, parallel light emitted in one direction from the pixel pr of the light ray emission unit 11 is luminance modulated by the 10 pixels pp of the transmissive liquid crystal panel 12 facing the pixel pr, and the light rays with different luminances are focused onto the light field control lens 132 by the viewing field control lens 131 and then diverged by the viewing field control lens 132.

[0036] This allows the observer to perceive the parallel light emitted from the pixel pr of the light-emitting unit 11 as 10 rays, and by using the focusing position on the field of view control lens 132 as the pixel pt of the 3D image display device 1, 50 viewpoints can be recognized at pixel pt.

[0037] For reference, if the transmissive liquid crystal panel 12 is omitted from the 3D image display device 1, as shown in Figure 6, the unidirectional parallel light emitted from the pixel pr of the light ray emission unit 11 is not subjected to brightness modulation, is focused onto the field of view control lens 132 by the field of view control lens 131, and then diverges by the field of view control lens 132. Note that only the principal ray of the unidirectional parallel light emitted from the pixel pr is shown in this illustration. As a result, the observer can only perceive the parallel light emitted from pixel pr of the light-emitting unit 11 as coming from one direction, and can only perceive five viewpoints due to the divergent light from pixel pt.

[0038] For the sake of simplicity, crosstalk between light rays emitted by the light ray emission unit 11 is ignored here, and the light ray emission unit 11 is described as emitting parallel light at discrete angular intervals. In this case, as shown in Figure 4, the light rays are focused at discrete positions on the second viewing range control lens 132, so the pixel aperture ratio of the displayed image of the 3D image display device 1 can be considered to be 0%.

[0039] However, since the light rays emitted from the 3D image display device 1 have crosstalk in the angular direction, they have a continuous brightness distribution. In this case, the light rays are emitted from continuous positions on the second viewing range control lens 132, and the pixel aperture ratio of the displayed image of the 3D image display device 1 becomes 100%. However, since the angular density of the light rays emitted from the viewing range control lens 132 does not change, the effects of the present invention are not affected even if there is crosstalk. When increasing the number of viewpoints (angular density) within the viewing angle by performing such brightness control, it is necessary to perform brightness control so that the reproduced 3D image T becomes the desired 3D image. This control will be described later with reference to Figure 7. Returning to Figure 2, we will continue our explanation of the configuration of the 3D image display device 1.

[0040] The control unit 20 controls the brightness of the 3D video data emitted by the light ray emission unit 11 and the transmittance of the transmissive liquid crystal panel 12 so as to minimize the error between the brightness of each pixel in the image for each direction of the input multi-view video data and the brightness of each pixel for each direction after passing through the second viewing range control lens 132. The control unit 20 receives multi-viewpoint video data for displaying a 3D image T, generates 3D video data with modulated brightness to be output to the light ray emission unit 11, and also generates panel display video data to be displayed on the transmissive liquid crystal panel 12. Multi-view video data can be obtained by placing a typical 3D model, generated using 3DCG production software or volumetric capture technology, into a virtual space and rendering it using oblique projection. Here, the number of pixels, pixel density, and viewing direction of each multi-view video are assumed to be the same as those of the 3D video T.

[0041] Now, with reference to Figure 7 (and Figures 2 and 3 as appropriate), the configuration of the control unit 20 will be explained. The control unit 20 includes a specification value storage unit 21, a brightness image generation unit 22, a brightness error minimization unit 23, a brightness image conversion unit 24, and a transmittance conversion unit 25.

[0042] The specification value storage unit 21 stores the specification values ​​of each component that makes up the 3D image display device 1, and can be configured using a general storage medium such as semiconductor memory. The specification value storage unit 21 stores in advance the specification values ​​of each part that makes up the 3D image display device 1, such as the number of pixels in the horizontal and vertical directions of the display device 110 of the light ray emission unit 11, the number and focal length of element lenses 111a in the horizontal and vertical directions of the element lens array 111, and the focal length of the viewing range control lens 13.

[0043] Furthermore, the specification value storage unit 21 stores correspondence tables between pixel values ​​and brightness values ​​in the display device 110, and correspondence tables between transmittance and pixel values ​​in the transmissive liquid crystal panel 12, etc. A table showing the correspondence between pixel values ​​and brightness values ​​is, for example, a table that pre-associates the values ​​of each 8-bit 256-level RGB channel (pixel values) with the optical brightness (brightness values). The table of correspondence between transmittance and pixel value is a table that pre-associates the transmittance of the transmissive liquid crystal panel 12 (e.g., 0 to 0.3) with the pixel value of the transmissive liquid crystal panel 12 (e.g., 0 to 255 (8-bit, 256 gradations)). Here, for example, transmittance "0" corresponds to pixel value "0", and transmittance "0.3" corresponds to pixel value "255", so the transmittance increases in proportion to the pixel value.

[0044] The luminance image generation unit 22 generates a luminance image from multi-view image data for displaying a three-dimensional image T. The luminance video generation unit 22 receives multi-view video data, refers to a correspondence table between pixel values ​​and luminance values ​​stored in the specification value storage unit 21, and generates a luminance video by converting the pixel values ​​to luminance values. The luminance image generation unit 22 outputs the luminance value of each pixel in the multi-view video data to the luminance error minimization unit 23. If the multi-view video data is a luminance video, the luminance image generation unit 22 outputs the input multi-view video data as is, as the luminance value of the pixels, to the luminance error minimization unit 23. For the sake of simplicity, here we will represent the brightness of a pixel in multi-view video data corresponding to the horizontal (x-direction) viewing direction θ and the pixel position (x-coordinate) as V(x,θ).

[0045] The luminance error minimization unit 23 generates 3D video data and panel display video data that minimize the error between the luminance for each viewing direction and pixel position input from the luminance video generation unit 22 and the luminance for each viewing direction and pixel position displayed as a 3D video T via the display unit 10 (light ray emission unit 11, transmissive liquid crystal panel 12, and viewing range control lens 13).

[0046] Here, with reference to Figure 8, the processing of the brightness error minimization unit 23 will be explained in detail. Note that Figure 8 has the same pixel configuration as Figure 4. Also, for the sake of simplicity, the explanation will be given in only one direction (z-direction). I(x,θ) is the brightness of the light rays emitted from the pixel position (x) in the x-direction of the pixel pr (element lens array 111 in Figure 3) of the light ray emission unit 11 at an angle θ which is the angle between the pixel and the z-axis passing through the lens centers Lc1 and Lc2 of the field of view control lenses 131 and 132. The transmittance of the pixel position (x) in the x-direction of the transmissive liquid crystal panel 12 is denoted as T(x). The brightness (reproduced light ray brightness) at the angle θ at the position of pixel pt of the x-coordinate of the 3D image display device 1, which is the light-gathering position on the field of view control lens 132, is denoted as L(x,θ). Note that the angle θ indicates the direction of light propagation, and the range of θ is -90° < θ < 90°. In the diagram, the z direction is θ = 0°, the positive x-axis direction is θ = 90°, and the negative x-axis direction is θ = -90°.

[0047] In this case, the light rays (with brightness I(x,θ)) emitted in the θ direction from the pixel position x of the pixel pr of the light ray emission unit 11 are luminance-modulated by the transmittance T(x) at the pixel position x of the transmissive liquid crystal panel 12 and emitted from the viewing range control lens 132. Then, at all angles θ, by minimizing the error between L(x,θ) emitted from the viewing range control lens 132 and the brightness V(x,θ) of the pixel corresponding to the horizontal (x-direction) viewing direction θ and pixel position (x-coordinate) of the multi-view image data, the 3D image T becomes the desired 3D image to be reproduced. In other words, L(x,θ), I(x,θ), and T(x) are related by the following equation (1).

[0048]

number

[0049] Therefore, the luminance error minimization unit 23 calculates I(x',θ') and T(x') using the following equation (2) as the objective function of the least squares method. Note that equation (2) can be calculated using a general least squares optimization algorithm.

[0050]

number

[0051] Returning to Figure 7, we will continue the explanation of the configuration of the control unit 20. The luminance error minimization unit 23 outputs the calculated luminance I(x′,θ′) of the pixel position for each viewing direction to the luminance video conversion unit 24. Furthermore, the brightness error minimization unit 23 outputs the calculated transmittance T(x') for each pixel position to the transmittance conversion unit 25.

[0052] The luminance video conversion unit 24 converts the luminance I(x′,θ′) of the pixel position for each viewing direction, calculated by the luminance error minimization unit 23, into 3D video data. The luminance image conversion unit 24 generates three-dimensional image data, i.e., a group of elemental images, by referring to a correspondence table of pixel values ​​and luminance values ​​stored in the specification value storage unit 21 and the positional relationship between the pixels pe of the display device 110 of the light ray emission unit 11 and the elemental lens array 111, and converting the luminance of the pixel positions for each viewing direction into pixel values. The luminance image conversion unit 24 displays the generated elemental image group as three-dimensional image data on the light ray emission unit 11.

[0053] The transmittance conversion unit 25 converts the transmittance for each pixel position calculated by the brightness error minimization unit 23 into panel display video data. The transmittance conversion unit 25 generates panel display video data by referring to the correspondence table between pixel values and transmittance stored in the specification value storage unit 21 and converting the transmittance for each pixel position into the pixel value for each pixel position. The transmittance conversion unit 25 displays the generated panel display video data on the transmissive liquid crystal panel 12.

[0054] With the configuration described above, the three-dimensional video display device 1 can emit light rays with the luminance modulated for each pixel of the transmissive liquid crystal panel 12 in different directions for the three-dimensional video data (element image group). Thus, since the three-dimensional video display device 1 can increase the angular density of the three-dimensional video T, it can display a three-dimensional video T with high resolution within a wide depth range.

[0055] (Display characteristics of three-dimensional video) Next, referring to FIG. 4, the display characteristics of the three-dimensional video T displayed by the three-dimensional video display device 1 will be described. Here, let the maximum number of pixels of the light ray emitting unit 11, the display device 110 of the light ray emitting unit 11, the transmissive liquid crystal panel 12, and the three-dimensional video display device 1 be N [[ID=____]] I , N [[ID=____]] E , N [[ID=____]] T , N [[ID=____]] L respectively. Also, let the number of light ray emission directions of the light ray emitting unit 11 and the number of viewpoints of the three-dimensional video display device 1 be M [[ID=____]] I , M [[ID=____]] L respectively.

[0056] [[ID=...]] Each condensing point on the viewing field control lens 131 of the three-dimensional video display device 1 becomes a pixel pt of the three-dimensional video T. Therefore, the maximum number of pixels N [[ID=____]] L = M [[ID=____]] I . Also, from the pixel pt of the three-dimensional video display device 1, light rays with the luminance modulated for each pixel of the transmissive liquid crystal panel 12 are emitted in different directions. Considering the traveling direction of this light ray as the viewpoint direction, the number of viewpoints M [[ID=____]] L = N [[ID=____]] T . Also, the viewing angle φ of the three-dimensional video T displayed by the three-dimensional video display device 1 is represented by the following formula (3).

[0057]

number

[0058] Here, D is the display size of the light ray emission unit 11, f v This is the focal length of the field of view control lens 13 (131,132). As can be seen from equation (3), the 3D image display device 1 controls the viewing angle φ of the 3D image T using the focal length f of the viewing area control lens 13. v It can be adjusted by [this method]. Furthermore, the angular density ω of the light rays displayed by the 3D image display device 1 is expressed by the following equation (4).

[0059]

number

[0060] As can be seen from equation (4), the 3D image display device 1 has a number of pixels N in the transmissive liquid crystal panel 12. T By increasing the angular density of light rays ω, the angular density ω can be easily improved. In this way, by increasing the angular density, the light field type 3D image display device 1 can display a high-resolution 3D image T over a wide depth range when viewed by an observer from a predetermined viewing distance of the display screen.

[0061] In equation (2) above, even after optimization, L(x,θ) still has an error with respect to V(x,θ). However, this error is due to the number of pixels (N) of the display image of the light ray emission unit 11. I The more you increase ), the smaller it can be made. However, M I =N L =N E / N I Because of the relationship, N I Increasing the number of emission directions (M) of the light emission unit 11 will increase I ) decreases, and the maximum number of pixels (N) of the 3D video display device 1 decreases. LThis would result in a decrease in performance. Therefore, the 3D image display device 1 should be designed taking this trade-off into consideration.

[0062] In order to display a 3D image T with overall good characteristics, the number of pixels (N) in the light ray emission unit 11 is I The number of pixels (N) of the transmissive liquid crystal panel 12 relative to ) T The ratio of ) that is, N T / N I It is preferable to set this to about 10 to 20. Furthermore, as in the 3D image display device 1C (Figure 12) described later, it is preferable to configure the field of view control lenses 13C to be tiled with respect to the transmissive liquid crystal panel 12, and to set the number of pixels of the transmissive liquid crystal panel 12 facing one field of view control lens 13 to several hundred pixels.

[0063] The three-dimensional image display device 1 according to the first embodiment of the present invention has been described above. The three-dimensional image display device 1 according to the first embodiment of the present invention uses integral type light ray emission units 11, 111, which are one type of light field system. However, the three-dimensional image display device 1 may also use a multi-view image projection type light ray emission unit.

[0064] (Modified version of the light-emitting section) Here, with reference to Figure 9, an example of the configuration of the light ray emission units 11 and 112 of the multi-view image projection system will be described.

[0065] As shown in Figure 9, the light ray emission unit 112 comprises a projector 112, a collimator lens 113, an imaging lens array 114, two condenser lenses 115 (1151, 1152), and a diffusion screen 116.

[0066] The projector 112 projects video data, in which the brightness of the 3D video data is controlled for each pixel by the control unit 20, as video light. In this case, the 3D video data is multi-view video from a multi-view projection system. The projector 112 projects image light from a multi-view projection system onto the collimator lens 113. For the sake of clarity, the number of pixels in the horizontal direction (x direction) of the projected image is assumed to be 50 pixels.

[0067] The collimator lens 113 converts the image light emitted from the projector 112 into parallel light, and is composed of a typical convex lens or the like. The collimator lens 113 is positioned at a focal length f from the light source of the projector 112. b They are arranged with a certain amount of space between them. The collimator lens 113 illuminates the imaging lens array 114 with parallel light.

[0068] The imaging lens array 114 is an optical element in which imaging lenses (convex lenses) 114a are arranged in a two-dimensional array in opposition to the image light corresponding to each viewpoint image Vi of the multiview image emitted from the collimator lens 113. The imaging lens array 114 arranges imaging lenses in a two-dimensional array in opposition to the light rays of directional images (each viewpoint image constituting the multiview image), and focuses the image light corresponding to each viewpoint image Vi of the multiview image emitted from the collimator lens 113 onto the surface of the first condenser lens 1151 and images it onto the surface of the second condenser lens 1152. Here, the imaging lens array 114 is shown with only 10 lenses in the horizontal direction (x direction), facing each viewpoint image Vi of the multi-view image projected from the collimator lens 113. Note that in Figure 9, the viewpoint images Vi and the imaging lenses 114a are spaced apart to make the path of the light rays easier to understand, but they may also be connected without being spaced apart.

[0069] The condenser lens 115 controls the field of view of the light rays imaged by the imaging lens array 114. The condenser lens 115 comprises a first condenser lens 1151 and a second condenser lens 1152. The condenser lenses 1151 and 1152 can be made of general convex lenses, Fresnel lenses, diffractive lenses, etc. In this example, the condenser lens 1151 is a convex lens and the condenser lens 1152 is a plano-convex lens.

[0070] The condenser lens 1151 directs the light rays formed by each of the imaging lenses 114a of the imaging lens array 114 to the same predetermined range on the condenser lens 1152. In other words, the condenser lens 1151 superimposes the viewpoint image Vi formed by the imaging lens 114a onto the same predetermined range on the condenser lens 1152. The condenser lens 1151 directs the light rays from the imaging lens array 114 to the focal length f of the imaging lens 114a. c They are arranged with a certain amount of space between them.

[0071] The condenser lens 1152 converts the light rays of the directional images (viewpoint images Vi) superimposed from the condenser lens 1151 into directional parallel light. In other words, the condenser lens 1152 emits the superimposed viewpoint images Vi as light rays with discrete angular intervals for each viewpoint. Furthermore, the condenser lens 1152 is connected to the condenser lens 1151 at a focal length f d They are spaced apart by this amount. Also, the focal length of condenser lens 1152 is the same as the focal length of condenser lens 1151 (f d ) Light rays emitted from the condenser lens 1152 at discrete angular intervals for each viewpoint are projected onto the diffusion screen 116.

[0072] The diffusion screen 116 diffuses the light rays incident from the condenser lens 1152. The diffusion screen 116 interpolates between light rays by diffusing the light rays incident at discrete angular intervals in the horizontal and vertical directions.

[0073] In the light emission unit 112 described above, the projector 112 irradiates the collimator lens 113 with multi-view image projection light (multi-view image) whose brightness for each pixel has been modulated by the control unit 20. The image light irradiated onto the collimator lens 113 becomes parallel light and irradiates the imaging lens array 114. The imaging lens array 114 focuses the illuminated image light onto the condenser lens 1151, with each imaging lens 114a converging on the condenser lens 1151. In this configuration, the image light is focused by the 10 imaging lenses 114a onto 10 different positions on the condenser lens 1151.

[0074] The condenser lens 1151 refracts the image light from each focused position and superimposes it onto the condenser lens 1152. The condenser lens 1152 refracts the superimposed image light from 10 images and emits it as parallel light in 10 directions. The diffusion screen 116 slightly diffuses the parallel light rays incident at discrete angular intervals from 10 directions, converting the angular brightness distribution of the light rays into continuous rays.

[0075] In this light-emitting unit 112, the number of pixels in the projected image from the projector 112 that enters one imaging lens 114a becomes the number of pixels in the displayed image of the light-emitting unit 112. Also, in the light-emitting unit 112, the number of imaging lenses 114a becomes the number of emission directions of the light-emitting unit 112. Therefore, in the example shown in Figure 9, the light ray emitter 112 emits images with 5 pixels in the horizontal direction (x direction) and a pixel aperture ratio of 100% in 10 directions for each pixel. In Figure 9, the light ray that travels in the downward direction (negative x-axis direction) among the group of light rays emitted from the diffusion screen 116 is shown as a dashed line, and the light rays that travel in other directions are shown as dotted lines.

[0076] <Second Embodiment> Next, with reference to Figures 1 and 10, a three-dimensional image display device 1B according to a second embodiment of the present invention will be described.

[0077] The 3D image display device 1B, like the 3D image display device 1, displays a 3D image. This 3D image display device 1B displays a 3D image T that has parallax in the horizontal and vertical directions.

[0078] As shown in Figure 1, the 3D image display device 1B comprises a display unit 10B and a control unit 20B. As shown in Figure 10, the display unit 10B comprises a light ray emission unit 11B and two field of view control lenses 13 (131, 132). The field of view control lenses 13 have the same configuration as those of the 3D image display device 1, so their description is omitted. The light ray emission unit 11B emits images with different brightness levels in multiple directions using time-division multiplexing. The light ray emission unit 11B comprises a display device 110 and a liquid crystal lens array 117.

[0079] The display device 110 emits light rays as directional light rays, with the brightness of each pixel controlled, which are 3D video data arranged in a two-dimensional array of multiple images for each direction. The display device 110 switches between displaying 3D video data, in which the brightness of the 3D video data is controlled pixel by pixel by the control unit 20B (described later), and 2D video data, which is a brightness image. The 3D video data is an integral-type set of elemental images. Note that the display device 110 is the same as the display device 110 described in Figure 3. Here, for clarity, only the 50 pixels in the horizontal direction (x direction) displayed by the display device 110 are shown in the illustration.

[0080] The liquid crystal lens array 117 is an array of liquid crystal lenses 117a arranged in a two-dimensional array, which switch between a lens state and a transmission state. The liquid crystal lens array 117 is located at the focal length f of the liquid crystal lens 117a from the display surface of the display device 110. a They are arranged with a certain amount of space between them. The liquid crystal lens 117a functions as a convex lens in its lens state. In its transparent state, the liquid crystal lens 117a functions as a glass plate.

[0081] The liquid crystal lens 117a of the liquid crystal lens array 117 is switched between lens state and transmission state by the control unit 20B, which will be described later. Furthermore, known liquid crystal lenses can be used to switch between the lens state and the transmission state in this manner. For example, the liquid crystal lenses described in the following references 1 and 2 can be used.

[0082] (Reference 1) J. Kim, J. Kim, JH Na, B. Lee, and SD Lee, "Liquid crystal-based square lens array with tunable focal length," Opt. Express, vol. 22, no. 3, pp. 3316-3324 (2014). (Reference 2) F. Chu, YQ Guo, YX Zhang, W. Duan, HL Zhang, LL Tian, ​​L. Li, and QH Wang, "Four-mode 2D / 3D switchable display with a 1D / 2D convertible liquid crystal lens array," Opt. Express, vol. 29, no. 23, pp. 37464-37475 (2021).

[0083] In lens mode, the liquid crystal lens array 117 functions as an integral element lens array that displays the element image group shown by the display device 110 as a three-dimensional image T. In its transparent state, the liquid crystal lens array 117 displays the two-dimensional image shown by the display device 110 directly.

[0084] The control unit 20B switches the lens state and transmission state of the liquid crystal lens array 117 frame by frame, and displays 3D video data on the display device 110 in sync when it is in the lens state, and 2D video data when it is in the transmission state. As a result, the brightness of each pixel passing through the liquid crystal lens array 117 in each direction when it is in the lens state and the brightness of each pixel passing through the liquid crystal lens array 117 in the transmission state are added together by time-division multiplexing. Furthermore, the control unit 20B controls the brightness of the 3D video data in the lens state emitted by the light ray emission unit 11B and the brightness of the 2D video data in the transmission state, in order to minimize the error between the brightness of each pixel in each direction of the input multi-view video data and the brightness of each pixel in each direction after passing through the second viewing range control lens 132. The control unit 20B receives multi-viewpoint video data for displaying a 3D image T, generates 3D and 2D video data for each frame with modulated brightness to be output to the display device 110 of the light ray emission unit 11B, and controls the switching of the lens state and transmission state of the liquid crystal lens array 117 in synchronization with the frame.

[0085] Now, with reference to Figure 11, the configuration of the control unit 20B will be described. The control unit 20B includes a specification value storage unit 21B, a brightness image generation unit 22, a brightness error minimization unit 23B, a brightness image conversion unit 24B, and a transparency switching unit 26. The luminance image generation unit 22 has the same configuration as the control unit 20 described in Figure 7, so its description is omitted.

[0086] The specification value storage unit 21B stores the specification values ​​of each component that constitutes the 3D image display device 1B, and can be configured using a general storage medium such as semiconductor memory. The specification value storage unit 21B has pre-stored specification values ​​for each component of the 3D image display device 1B, such as the number of pixels in the horizontal and vertical directions of the display device 110 of the light ray emission unit 11B, the number and focal lengths of the liquid crystal lenses 117a in the horizontal and vertical directions of the liquid crystal lens array 117, and the focal length of the viewing range control lens 13. Furthermore, the specification value storage unit 21B stores a correspondence table between pixel values ​​and brightness values ​​in the display device 110. Since this correspondence table is the same as the contents stored in the specification value storage unit 21 of the control unit 20 described in Figure 7, its explanation is omitted.

[0087] The luminance error minimization unit 23B generates frame-by-frame 3D video data and 2D video data that minimize the error between the luminance for each viewing direction and pixel position input from the luminance video generation unit 22 and the luminance for each viewing direction and pixel position displayed as a 3D video T via the display unit 10B (light ray emission unit 11B and viewing range control lens 13). The luminance error minimization unit 23B switches between outputting the generated 3D video data and 2D video data to the luminance video conversion unit 24B for each frame. Specifically, the luminance error minimization unit 23B outputs 3D video data to the luminance video conversion unit 24B at odd-numbered frame display timings, and outputs 2D video data to the luminance video conversion unit 24B at even-numbered frame display timings, switching this process for each frame. Furthermore, the luminance error minimization unit 23B instructs the transmission switching unit 26 (switching instruction) on the timing of this switching. This frame switching is performed at a speed where flicker is not perceived (for example, every 1 / 120th of a second).

[0088] Now, with reference to Figure 10, the processing of the luminance error minimization unit 23B will be explained in detail. I′(x,θ) is the luminance (emitted ray luminance) of the light rays emitted from the pixel position x on the liquid crystal lens array 117 of the light ray emission unit 11B in odd-numbered frames, traveling in the direction of the angle θ which is the angle with the z axis passing through the lens centers Lc1 and Lc2 of the field of view control lenses 131 and 132. In even-numbered frames, it is assumed that light rays with a uniform brightness distribution in the angular direction are emitted from each pixel of the display device 110 of the light ray emission unit 11B, and the brightness of the light ray emitted from pixel position x is denoted as A(x).

[0089] Here, when the brightness of light rays from consecutive frames is added together by time-division multiplexing, the brightness of the light ray propagating in the direction of angle θ emitted from the pixel position x on the viewing range control lens 132 (reconstructed light ray brightness) is denoted as L′(x,θ). In this case, the light rays of odd-numbered frames (luminance I'(x',θ')) emitted in the θ' direction from the pixel position x' on the liquid crystal lens array 117 of the light ray emission unit 11B, and the light rays of even-numbered frames (luminance A(x'')) emitted from the pixel position x'' on the display device 110 are added together and emitted in the direction of angle θ from the pixel position x on the viewing range control lens 132. The relationship between x, θ, x', x'', and θ' will be described later.

[0090] Then, at all pixel positions x and angles θ, by minimizing the error between L′(x,θ) emitted from the viewing range control lens 132 and the brightness V(x,θ) of the pixel corresponding to the horizontal (x-direction) viewing direction θ and pixel position (x-coordinate) of the input multi-view video data, the 3D image T becomes the desired 3D image to be reproduced. In other words, L′(x,θ), I′(x,θ), and A(x) are related by the following equation (5).

[0091]

number

[0092] Therefore, the luminance error minimization unit 23B replaces L(x,θ) in equation (2) with L′(x,θ), and then uses equation (2) as the objective function of the least squares method to calculate I′(x′,θ′) and A(x″). Returning to Figure 11, we will continue the explanation of the configuration of the control unit 20B.

[0093] The luminance error minimization unit 23B outputs the calculated luminance I′(x′,θ′) of the pixel position for each viewing direction to the luminance video conversion unit 24B at the display timing of odd frames. Furthermore, the brightness error minimization unit 23B outputs the calculated brightness A(x″) for each pixel position to the brightness video conversion unit 24B at the display timing of even frames. Then, the brightness error minimization unit 23B instructs the transparency switching unit 26 to set the liquid crystal lens array 117 to lens state at the display timing of odd-numbered frames. Furthermore, the brightness error minimization unit 23B instructs the transparency switching unit 26 to set the liquid crystal lens array 117 to a transparent state at the display timing of even-numbered frames.

[0094] The luminance image conversion unit 24B converts the brightness of each pixel in the luminance image generated by the luminance error minimization unit 23B into a pixel value. The luminance image conversion unit 24B converts to a pixel value by referring to a correspondence table between pixel values ​​and luminance values ​​stored in the specification value storage unit 21B. In addition, the luminance image conversion unit 24B converts the luminance I′(x′,θ′) into an element image group (3D image data) by referring to the positional relationship between the pixels of the display device 110 and the liquid crystal lens array 117 stored in the specification value storage unit 21B.

[0095] When the luminance error minimization unit 23B receives a luminance I′(x′,θ′), the luminance image conversion unit 24B converts the luminance of the pixel position into a pixel value, thereby generating a set of elemental images (3D image data) for displaying the 3D image T. When a luminance A(x″) is input from the luminance error minimization unit 23B, the luminance video conversion unit 24B generates two-dimensional video data by converting the luminance of the pixel position into a pixel value. The luminance video conversion unit 24B displays the converted video data (3D video data or 2D video data) on the display device 110 of the light ray emission unit 11. The transparency switching unit 26 switches between the lens state and the transparency state of the liquid crystal lens array 117 based on instructions from the brightness image conversion unit 24B.

[0096] With the configuration described above, the 3D image display device 1B can emit light rays in different directions by modulating the brightness of the light rays of the 3D image data (element image group) through time-division multiplexing. In this way, the 3D image display device 1B can increase the angular density of the 3D image T, and thus can display a high-resolution 3D image T over a wide depth range.

[0097] Furthermore, while the 3D image display device 1 attenuates the brightness of light rays using the transmissive liquid crystal panel 12, the 3D image display device 1B displays a 3D image T with high angular density by adding the brightness of light rays through time-division multiplexing. Therefore, when the maximum transmittance of the pixels of the transmissive liquid crystal panel 12 is less than 50%, the 3D image display device 1B can display a brighter 3D image than the 3D image display device 1 in Figure 2.

[0098] <Third Embodiment> Next, with reference to Figures 1 and 12, a three-dimensional image display device 1C according to a third embodiment of the present invention will be described. The 3D image display device 1C, like the 3D image display device 1, displays a 3D image. This 3D image display device 1C displays a 3D image T that has parallax in the horizontal and vertical directions.

[0099] As shown in Figure 1, the 3D image display device 1C comprises a display unit 10C and a control unit 20. As shown in Figure 12, the display unit 10C comprises a light ray emission unit 11, a transmissive liquid crystal panel 12, and a field of view control lens 13C (first field of view control lens 13C1, second field of view control lens 13C2).

[0100] The display unit 10C differs from the display unit 10 described in Figure 2 only in the configuration of the field of view control lens 13C. In the display unit 10 described in Figure 2, each of the two field of view control lenses 13 (131, 132) is composed of a single lens. In the display unit 10C, each of the two field of view control lenses 13C (13C1, 13C2) is configured by arranging multiple lenses in the horizontal and vertical directions. This example shows two first field-of-view control lenses 13C1 arranged horizontally (x-direction) and two second field-of-view control lenses 13C2 arranged horizontally (x-direction).

[0101] In this way, the 3D image display device 1C can use lenses with a small aperture as the field of view control lenses by arranging multiple units of each of the two field of view control lenses 13C (13C1, 13C2). Therefore, the 3D image display device 1C can reduce errors in the direction of light propagation due to aberrations in the viewing range control lens, thereby improving the display quality of the 3D image T.

[0102] Here, the number of first field of view control lenses 13C1 and second field of view control lenses 13C2 are N, respectively. P The number of emission directions of the light ray emission unit 11 is M I Therefore, the maximum number of pixels N in the 3D image T is... L is, N L =M I N P Thus, in the 3D image display device 1C, the number of viewing range control lenses 13C is newly added as a parameter that affects the display characteristics. As a result, the 3D image display device 1C can be designed with greater flexibility. Furthermore, when D′ is the display size corresponding to the size of one lens of the viewing range control lens 13C of the light ray emission unit 11, the viewing angle φ′ of the 3D image T is expressed by the following equation (6).

[0103]

number

[0104] In the 3D image display device 1C, in order to ensure that the pixel positions of the 3D image T are equally spaced across the entire display screen, it is preferable to make the viewing angle φ′ of the 3D image display device 1C the same as the viewing angle Ψ of the light ray emission unit 11. Furthermore, in this configuration, the 3D image display device 1C is configured by replacing the first field of view control lens 131 and the second field of view control lens 132 of the 3D image display device 1 with multiple lenses instead of a single lens each. Similarly, the first field of view control lens 131 and the second field of view control lens 132 of the 3D image display device 1B (see Figure 10) may be configured by replacing each of them from a single lens to multiple lenses.

[0105] (Design example) Here, as an example of the design of the 3D image display device 1C shown in Figure 12, an example of design values ​​is shown. Here, the light ray emission unit 11 is an integral type light ray emission unit 111 (Figure 3), and the design values ​​are shown only for the horizontal direction (x direction). The display device 110 constituting the light ray emission unit 11 has 4000 pixels, a pixel pitch of 100 μm, the element lens array 111 has 400 element lenses 111a, a lens pitch of 1 mm, and a focal length f a Let this be 2.836 mm. At this time, the number of pixels in the display image of the light ray emission unit 11 is 400 pixels, the number of emission directions is 10, the viewing angle is 20 degrees, and the angular density of light rays is 0.5 rays / degree.

[0106] Next, the transmissive liquid crystal panel 12 constituting the 3D image display device 1C has 4000 pixels and a pixel pitch of 100 μm. Also, the number of lenses in the viewing range control lens 13C is 40 sets, the lens pitch is 10 mm, and the focal length is f v Let this be 28.36 mm. At this time, the number of pixels in the displayed image of the 3D image display device 1C is 400 pixels, the number of viewpoints is 100 directions, the viewing angle is 20 degrees, and the angular density of light rays is 0.05 rays / degree. When comparing the light ray emission unit 11 and the 3D image display device 1C, the number of pixels in the displayed image and the viewing angle are the same, but the 3D image display device 1C can reproduce light rays with an angular density 10 times higher.

[0107] Although embodiments of the present invention have been described above, the present invention is not limited to these embodiments and includes design modifications and the like that do not depart from the spirit of the present invention. For example, to simplify the explanation, we have used an example where we only increase the angular density in the horizontal direction (x direction). However, the present invention can similarly increase the angular density in the vertical direction (y-direction).

[0108] Specifically, the pixel position x and line of sight direction θ in equations (1) and (5) are replaced with pixel position (x,y) and line of sight direction (θx,θy), respectively. Brightness control can then be performed by taking into account the vertical pixel position y and the vertical line of sight direction θy. For example, instead of equation (1), we can use equation (7) below.

[0109]

number

[0110] Then, the luminance error minimization unit 23 (Figure 7) can calculate I(x',y',θx',θy') and T(x',y') using the following equation (8) as the objective function of the least squares method. The same applies to equation (5).

[0111]

number

[0112] 1,1B,1C 3D Image Display Device 10,10B,10C Display section 11,11B Light beam emission part 110 Display Devices 111-element lens array 112 Projectors 113 Collimator lens 114 Imaging lens array 1151 First condenser lens 1152 Second condenser lens 116 Diffusion Screen 117 Liquid Crystal Lens Array 12. Transmissive LCD Panel 131 First field of view control lens 132 Second field of view control lens 20,20B Control Unit 21, 21B Specification Value Storage Unit 22 Brightness Image Generation Unit 23,23B Brightness Error Minimization Section 24,24B Brightness Video Conversion Unit 25 Transmittance conversion unit 26 Transparency switching section

Claims

1. A three-dimensional image display device that displays three-dimensional images, A light ray emission unit emits light rays as directional light rays, with the brightness of each pixel controlled, from 3D video data arranged in a 2D array of multiple images for each direction. A transmissive liquid crystal panel having a pixel pitch narrower than the light-emitting section, which transmits light rays emitted from the light-emitting section in different directions with a controlled transmittance for each pixel, A first field of view control lens that focuses light rays transmitted through the aforementioned transmissive liquid crystal panel onto a subsequent second field of view control lens, A second field of view control lens is positioned at a distance from the first field of view control lens equal to the focal length of the first field of view control lens, and the focused light rays are diverged in the forward direction. A control unit controls the brightness of the three-dimensional video data in the light emission unit and the transmittance of the transmissive liquid crystal panel in order to minimize the error between the brightness of each pixel in the image for each direction of the input multi-view video data and the brightness of each pixel for each direction after passing through the second viewing range control lens. A three-dimensional image display device characterized by having the following features.

2. The aforementioned light ray emission unit is, A display device that displays video data in which the brightness of the aforementioned three-dimensional video data is controlled for each pixel, An element lens array is formed by arranging element lenses in a two-dimensional array opposite to the aforementioned images for each direction, and positioning them at a distance from the display device equal to the focal length of each element lens, The three-dimensional image display device according to claim 1, characterized by comprising the above.

3. The aforementioned light ray emission unit is, A projector that projects video data, in which the brightness of the aforementioned three-dimensional video data is controlled for each pixel, as video light, A collimator lens that converts the image light emitted from the projector into parallel light, An imaging lens array is provided, which is arranged on the side of the collimator lens where parallel light is emitted, and imaging lenses are arranged in a two-dimensional array facing the light rays of the image for each direction. A first condenser lens is positioned at a distance from the imaging lens array equal to the focal length of the imaging lens, and superimposes the light rays of the image for each direction onto the second condenser lens. A second condenser lens having the same focal length as the first condenser lens and positioned at a distance equal to its focal length from the first condenser lens, which converts the light rays of the image for each direction into parallel light for each direction, A diffusion screen is positioned in contact with the light ray emission side of the second condenser lens and diffuses the parallel light in each direction into light rays with a continuous brightness distribution in the angular direction, The three-dimensional image display device according to claim 1, characterized by comprising the above.

4. A three-dimensional image display device that displays three-dimensional images, A display device that switches between and displays three-dimensional video data in which the brightness of each pixel in each direction is controlled for multi-view video data arranged in a two-dimensional array of multiple images in different directions, and two-dimensional video data in which the brightness of each pixel in the multi-view video data is controlled for multi-view video data; and a light ray emission unit comprising a liquid crystal lens array in which liquid crystal lenses are arranged in a two-dimensional array facing the light rays of the images in each direction, and which are controlled to switch between lens state and transmission state, and which are positioned at a distance from the display device equal to the focal length of the liquid crystal element lenses in the lens state, A first field of view control lens is positioned on the light emission side of the light emission unit and focuses the light beam onto a subsequent second field of view control lens, A second field of view control lens is positioned at a distance from the first field of view control lens equal to the focal length of the first field of view control lens, and the focused light rays are diverged in the forward direction. A control unit controls the brightness of the three-dimensional video data in the lens state and the brightness of the two-dimensional video data in the transmission state in the light ray emission unit, so as to minimize the error between the brightness of each pixel in each direction passing through the liquid crystal lens array in the lens state and the brightness of each pixel passing through the liquid crystal lens array in the transmission state, obtained by time-division multiplexing, and the brightness of each pixel in each direction after passing through the second field of view control lens. A three-dimensional image display device characterized by having the following features.

5. The three-dimensional image display device according to any one of claims 1 to 4, characterized in that the first field of view control lens and the second field of view control lens are each arranged in multiples in the horizontal and vertical directions.

Images