3D image display device

Abstract

To provide a small three-dimensional image display device.SOLUTION: A three-dimensional image display device 1 includes a projection display device 10, a diffusion screen 12 in which microlenses that can switch between the transmission state and the lens state are arranged two-dimensionally, a first collimating lens 13 that can switch between the lens state and the transmission state, an imaging lens 14 that is arranged for each viewpoint image v and can switch between the lens state and the transmission state, and a mirror 15 that reflects the light of each viewpoint image v condensed by the imaging lens 14 as reflected light.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a three-dimensional image display device that displays three-dimensional images by projecting a multi-viewpoint image made up of a plurality of viewpoint images. [Background technology]

[0002] A wide variety of 3D image display methods have been proposed, including the two-eye method using 3D glasses. For example, a 3D image display method has been proposed in which a display device projects multiple viewpoint images from the back of a display screen in a superimposed manner to reproduce a high-density group of light rays (Patent Documents 1 and 2).

[0003] Conventional technology does not require special glasses and can reproduce natural 3D images with horizontal and vertical parallax. Conventional technology also makes it possible to display 3D images on a large screen by using a projection display device such as a projector as the display device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-62295 A [Patent Document 2] JP 2020-60711 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the above-mentioned conventional technology, the size in the depth direction (depth size) is large because the housing size of the projection type display device and the projection distance from the projection type display device to the display optical system are long. Furthermore, in the conventional technology, the image of each viewpoint is enlarged by the imaging lens in the display optical system and projected onto the diffusion screen, so the distance between the imaging lens and the diffusion screen is also long, and the depth size is large. For these reasons, the depth size of the entire display device is large in the conventional technology.

[0006] The depth size will be specifically described below with reference to Fig. 10. As shown in Fig. 10, the display device 9 includes a plurality of projection-type display devices 90 and a display optical system 91. The display optical system 91 includes a collimator lens 92, an imaging lens 93, and a diffusion screen 94. In addition, in Fig. 10, the multi-viewpoint image V and the observer α are illustrated, and light rays are illustrated with dotted arrows. Hereafter, the X-axis direction represents the horizontal direction, the Y-axis direction represents the vertical direction, and the Z-axis direction represents the depth direction.

[0007] The projection display device 90 is disposed at a focal length f1 of the collimator lens 92. The projection display device 90 projects a multi-viewpoint image V in which a plurality of viewpoint images v are arranged two-dimensionally. The imaging lenses 93 are arranged two-dimensionally to correspond to each viewpoint image v. The light beam of the multi-viewpoint image V is converted into parallel light by the collimator lens 92, and is output as a single viewpoint image v by the imaging lens 93. The light beam of each viewpoint image v is then collected at a focal length f2 of the imaging lens 93, and then enlarged and projected onto the diffusion screen 94. Note that d5 is the distance between the collimator lens 92 and the imaging lens 93, and d6 is the distance between the collection surface of the viewpoint image v by the imaging lens 93 and the diffusion screen 94.

[0008] The diffusion screen 94 slightly diffuses the discrete light beams incident thereon, and emits them as a group of light beams with a continuous luminance distribution. As shown in Fig. 11, a lens array 95 in which minute convex lenses 95a are arranged two-dimensionally can be used as the diffusion screen 94. Note that the lens size of the lens array 95 needs to be smaller than the light beam of one pixel of the viewpoint image v incident on the diffusion screen 94.

[0009] Here, the diffusion angle θ d is expressed by the following formula (1), and it is preferable to set it to the same angular interval as the light beam of the incident viewpoint image v. d is the lens pitch of the lens array 95, f d is the focal length of the lens array 95.

[0010]

number

[0011] As described above, the display device 9 allows the observer α to perceive a three-dimensional image because the high-density light beams emitted from the diffusion screen 94 form an optical image in space. Furthermore, the display device 9 can increase the display size of the three-dimensional image by increasing the number of pairs of the projection display device 90 and the display optical system 91.

[0012] On the other hand, in the display device 9, in principle, it is necessary to superimpose a plurality of viewpoint images v at a certain point on the diffusion screen 94. Therefore, in the display device 9, it is necessary to increase the distance between the imaging lens 93 and the diffusion screen 94, which increases the depth size of the display optical system 91. Furthermore, in the display device 9, the projection type display device 90 is disposed behind the display optical system 91, which increases the housing size and projection distance (focal length f1) of the projection type display device 90, and therefore the depth size.

[0013] Another configuration example of the conventional technology will be described below with reference to Fig. 12. As shown in Fig. 12, the display device 9A further includes two condenser lenses 96 and 97 as a display optical system 91A.

[0014] The condenser lens 96 is disposed at a focal length f2 of the imaging lens 93. The condenser lens 96 collects the light of the viewpoint images v at a predetermined position on the diffusion screen 94, so that all the viewpoint images v are projected onto the same area of ​​the diffusion screen 94. The condenser lens 97 collects the light of each viewpoint image v at the optimum viewing distance L where the observer α is positioned. For example, the condenser lens 97 is disposed at the focal length f3 of the condenser lens 96.

[0015] Here, the optimum viewing distance L is expressed by the following formula (2): where f4 is the focal length of the condenser lens 97, and f3≧f4.

[0016]

number

[0017] In the display device 9A, the observer α can perceive a three-dimensional image even if the observer α is far from the optimum viewing distance L. Furthermore, in the display device 9A, the viewing angle of the three-dimensional image can be expanded by increasing the number of pairs of the projection display device 90 and the display optical system 91A.

[0018] On the other hand, in the display device 9A, the viewpoint image v is enlarged and projected onto the diffusion screen 94, so the distance between the condenser lens 96 and the diffusion screen 94 becomes long, and the depth size of the display optical system 91 becomes large. Furthermore, in the display device 9A, the housing size and the projection distance (focal length f1) of the projection type display device 90 increase, and the depth size becomes large.

[0019] Therefore, an object of the present invention is to provide a small-sized three-dimensional image display device. [Means for solving the problem]

[0020] In order to solve the above problems, the three-dimensional image display device of the present invention is a three-dimensional image display device that displays a three-dimensional image by projecting a multi-viewpoint image composed of a plurality of viewpoint images, and is configured to include a projection means, a diffusion means, a first collimating lens, an imaging lens, and a reflection means.

[0021] According to this configuration, the projection means projects a multi-viewpoint image. The diffusing means is composed of microlenses that can be switched between a transmission state in which the light of the multi-viewpoint image projected by the projection means is transmitted, and a lens state in which the reflected light from the opposite side of the projection means is diffused. The first collimator lens is switchable between a lens state in which the light of the multi-viewpoint image transmitted by the diffusing means is output as parallel light, and a transmission state in which the first collimator lens transmits the reflected light from the opposite side of the diffusing means. The imaging lens is arranged for each viewpoint image, and is switchable between a lens state in which the parallel light emitted by the first collimating lens is collected as light for the viewpoint image, and a transmission state in which the reflected light from the opposite side of the first collimating lens is transmitted. The reflecting means reflects the light of each viewpoint image collected by the imaging lens as reflected light. The microlenses, first collimator lens and imaging lens of the diffusing means are composed of polarizing diffractive lenses whose focal length changes whether positive or negative depending on the polarization direction, and convex lenses arranged for each polarizing diffractive lens. The projection means includes a polarizing plate that outputs light of the multi-viewpoint image in a predetermined first polarization direction. The diffusion means is in a transmissive state for the light of the multi-viewpoint image projected by the projection means in a first polarization direction, and is in a lens state for the light reflected by the reflection means in a second polarization direction opposite to the first polarization direction. The first collimator lens is in a lens state for the light of the multi-viewpoint image transmitted by the diffusing means in the first polarization direction, and is in a transmitting state for the reflected light reflected by the reflecting means in the second polarization direction. The imaging lens is in a lens state for the parallel light emitted by the first collimator lens in the first polarization direction, and is in a transmission state for the reflected light reflected by the reflecting means in the second polarization direction. The reflecting means inverts the first polarization direction to a second polarization direction when reflecting the light of each viewpoint image collected by the imaging lens as reflected light.

[0022] That is, the 3D image display device employs a lens / transmission switching lens that can switch between a lens state and a transmission state as the diffusion means, the first collimating lens, and the imaging lens. This allows the 3D image display device to realize a reflective configuration that folds back light rays in the depth direction, and the depth size can be reduced to about half compared to conventional technology. Effect of the Invention

[0023] According to the present invention, a small-sized three-dimensional image display device can be provided. [Brief description of the drawings]

[0024] [Figure 1] 1A and 1B are explanatory diagrams for explaining the operating principle of the lens / transmission switching lens in the first embodiment, where (a) shows the lens state and (b) shows the transmission state. [Diagram 2] FIG. 2 is an explanatory diagram for explaining switching between the lens state and the transmission state when circularly polarized light is used in the first embodiment, where (a) shows the lens state and (b) shows the transmission state. [Diagram 3] FIG. 2 is an explanatory diagram for explaining switching between a lens state and a transmission state when linearly polarized light is used in the first embodiment, where (a) shows the lens state and (b) shows the transmission state. [Figure 4]FIG. 1 is a schematic diagram of a three-dimensional image display device according to a first embodiment, in which (a) shows a state before a light ray is incident on a mirror, and (b) shows a state after the light ray is reflected by the mirror. [Diagram 5] 10A and 10B are schematic diagrams illustrating the configuration of a three-dimensional image display device according to a second embodiment, in which (a) shows the state before a light ray is incident on a mirror, and (b) shows the state after the light ray is reflected by the mirror. [Figure 6] 11A and 11B are schematic diagrams illustrating the configuration of a three-dimensional image display device according to a third embodiment, in which (a) shows the state before a light ray is incident on a mirror, and (b) shows the state after the light ray is reflected by the mirror. [Figure 7] FIG. 13 is a schematic diagram of a three-dimensional image display device according to a fourth embodiment, in which (a) shows the state up until a light ray is incident on a mirror, and (b) shows the state after the light ray is reflected by the mirror. [Figure 8] 13A and 13B are explanatory diagrams illustrating the operating principle of the focal length switching lens in the fifth embodiment, where (a) shows a state in which the focal length is long, and (b) shows a state in which the focal length is short. [Figure 9] FIG. 13 is a schematic diagram of a three-dimensional image display device according to a fifth embodiment, in which (a) shows the process up until a light ray is incident on a mirror, and (b) shows the light ray after it is reflected by the mirror. [Figure 10] FIG. 1 is a schematic diagram illustrating a configuration of a conventional display device. [Figure 11] FIG. 1 is an explanatory diagram illustrating a diffusion screen in the prior art. [Figure 12] FIG. 1 is a schematic diagram illustrating a configuration of a conventional display device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, each embodiment of the present invention will be described with reference to the drawings. However, each embodiment described below is intended to embody the technical idea of ​​the present invention, and unless otherwise specified, the present invention is not limited to the following. In addition, the same symbols are used for the same means, and the description may be omitted.

[0026] (First embodiment) [Operation principle of lens / transmission switching lens] As described above, the 3D image display device 1 (FIG. 4) according to the first embodiment employs the lens / transmission switching lens 100 that is switchable between a lens state and a transmission state. Therefore, the operating principle of the lens / transmission switching lens 100 will be described with reference to FIG. 1, and then the configuration of the 3D image display device 1 will be described.

[0027] As shown in Fig. 1, the lens / transmission switching lens 100 includes a polarizing diffractive lens 110 and a convex lens 120. In order to make the drawing easier to see, Fig. 1 illustrates three lens / transmission switching lenses 100 arranged in the horizontal direction.

[0028] The polarized diffractive lens 110 is a lens whose focal length changes positive or negative depending on the polarization direction. For example, the polarized diffractive lens 110 can be made of a periodically oriented liquid crystal polymer (Optica, Vol. 2, No. 11, pp. 958-964, November 2015). Since the polarized diffractive lens 110 is a type of diffractive optical element, the diffraction angle changes depending on the wavelength in principle, and chromatic aberration may occur. Therefore, in order to prevent chromatic aberration, it is preferable to use a polarized diffractive lens 110 having wavelength selectivity with the same diffraction angle for each wavelength of RGB.

[0029] The convex lens 120 is disposed for each polarizing diffractive lens 110, and is, for example, a general convex lens. Here, the convex lens 120 is disposed after the polarizing diffractive lens 110. Note that the lens / transmission switching lens 100 may use a thinner diffractive lens (not shown) instead of the convex lens 120.

[0030] Here, the focal length of the convex lens 120 is f. The focal length of the polarizing diffractive lens 110 when a right-handed circularly polarized light beam is incident is +f, and the focal length of the polarizing diffractive lens 110 when a left-handed circularly polarized light beam is incident is -f. As shown in FIG. 1(a), when right-handed circularly polarized parallel light beam is incident on the lens / transmission switching lens 100, the focal lengths of the polarizing diffractive lens 110 and the convex lens 120 are added together, and the focal length of the lens / transmission switching lens 100 becomes f / 2. Therefore, the lens / transmission switching lens 100 is in a lens state and functions as a convex lens that focuses light at its focal length f / 2.

[0031] On the other hand, consider the case where left-handed circularly polarized parallel light is incident on the lens / transmission switching lens 100, as shown in FIG. 1(b). In this case, because the focal length of the polarized diffractive lens 110 is negative, the lens action is cancelled out between the polarized diffractive lens 110 and the convex lens 120. Therefore, the lens / transmission switching lens 100 is in a transmitting state, and the incident light is transmitted without being refracted. In this way, the lens / transmission switching lens 100 can switch between a lens state and a transmitting state depending on the polarization direction of the light beam.

[0032] Next, a method of using the lens / transmission switching lens 100 in the three-dimensional image display device 1 will be described with reference to Fig. 2. In Fig. 2, the lens / transmission switching lens 100 is shown by a solid line when in the lens state, and by a dashed line when in the transmission state. In Fig. 2, the lens / transmission switching lens 100, which is composed of the polarized diffractive lens 110 and the convex lens 120, is shown as a single convex lens to make the drawing easier to see.

[0033] 2, the lens / transmission switching lens 100 uses circularly polarized light to switch between the lens state and the transmission state depending on the incident direction of a light beam. As described above, the lens / transmission switching lens 100 is in the lens state when a right-handed circularly polarized light beam is incident thereon, and in the transmission state when a left-handed circularly polarized light beam is incident thereon. Furthermore, the lens / transmission switching lens 100 does not change the polarization direction of the incident light and the outgoing light.

[0034] 2(a), consider the case where a right-handed circularly polarized light beam is incident on the lens / transmission switching lens 100 from the right side of the drawing. In this case, since the lens / transmission switching lens 100 is in a lens state, the incident light beam is focused at the focal length and then diverges, and reaches the mirror 130. At this time, the polarization direction of the light beam remains right-handed circularly polarized.

[0035] Next, as shown in Fig. 2(b), the light is reflected by mirror 130, reversing the polarization direction from right-handed circularly polarized light to left-handed circularly polarized light. Then, the left-handed circularly polarized light enters lens / transmission switching lens 100 from the left side of the drawing. In this case, since lens / transmission switching lens 100 is in a transmission state, the reflected light from mirror 130 is transmitted as is. In this way, lens / transmission switching lens 100 can switch between a lens state and a transmission state depending on the incident direction of the light.

[0036] As shown in Fig. 3, the lens / transmission switching lens 100 can also use linearly polarized light instead of circularly polarized light. Here, the lens / transmission switching lens 100 is in a lens state when a horizontally polarized light beam is incident thereon, and in a transmitting state when a vertically polarized light beam is incident thereon. In addition, a quarter-wave plate 140 is disposed between the lens / transmission switching lens 100 and the mirror 130. This quarter-wave plate 140 converts linearly polarized light into circularly polarized light.

[0037] 3(a), consider the case where a horizontally polarized light beam is incident on the lens / transmission switching lens 100 from the right side of the drawing. In this case, because the lens / transmission switching lens 100 is in a lens state, the incident light beam is focused at the focal length, and then converted to right-handed circularly polarized light by the quarter-wave plate 140. After being focused at the focal length, the light beam diverges before reaching the mirror 130.

[0038] 3(b), the light is reflected by mirror 130, thereby inverting the polarization direction of the light from right-handed circularly polarized light to left-handed circularly polarized light. The reflected light from mirror 130 is then converted to vertically polarized light by quarter-wave plate 140, and then enters lens / transmission switching lens 100 from the left side of the drawing. In this case, since lens / transmission switching lens 100 is in a transmitting state, the reflected light from mirror 130 is transmitted as is.

[0039] [Configuration of 3D image display device] The configuration of the three-dimensional image display device 1 according to the first embodiment will be described with reference to FIG. The three-dimensional image display device 1 displays a three-dimensional image by projecting a multi-viewpoint image V composed of a plurality of viewpoint images v. As shown in Fig. 4, the three-dimensional image display device 1 includes a projection type display device (projection means) 10 and a display optical system 11. The display optical system 11 includes a diffusion screen (diffusion means) 12, a first collimator lens 13, an imaging lens 14, and a mirror (reflection means) 15.

[0040] This three-dimensional image display device 1 has a configuration optically equivalent to that of the display device 9 in Fig. 10. Also, the diffusion screen 12, the first collimator lens 13, and the imaging lens 14 are switchable between a lens state and a transmission state, similar to the lens / transmission switching lens 100 in Figs.

[0041] In this embodiment, the 3D image display device 1 switches between the lens state and the transmission state using circularly polarized light (see Figs. 1 and 2). In this embodiment, right-handed circularly polarized light is the first polarization direction described in the claims, and left-handed circularly polarized light, which is opposite to the right-handed circularly polarized light, is the second polarization direction.

[0042] The projection display device 10 is, for example, a general projector that projects a multi-viewpoint image V. The projection display device 10 also includes a polarizing plate 10a that emits the light of the multi-viewpoint image V as right-handed circularly polarized light.

[0043] The mirror 15 reflects the light of each viewpoint image v focused by the imaging lens 14 as reflected light. At this time, when the mirror 15 reflects the light of each viewpoint image v focused by the imaging lens 14 as reflected light, the mirror 15 inverts the right-handed circularly polarized light to left-handed circularly polarized light. For example, the mirror 15 is disposed at a distance equivalent to f1+(d5+f2+d6) / 2 in FIG. 10 from the projection display device 10 so that the center of the mirror 15 coincides with the optical axis of the projection display device 10.

[0044] The diffusion screen 12 is composed of microlenses that can be switched between a transmission state in which the light of the multi-viewpoint image V projected by the projection display device 10 is transmitted and a lens state in which the light reflected from the opposite side of the projection display device 10 is diffused (see FIG. 11). Specifically, the diffusion screen 12 is in a transmission state for the light of the multi-viewpoint image V projected by the projection display device 10 with right-handed circular polarization. On the other hand, the diffusion screen 12 is in a lens state for the light reflected by the mirror 15 with left-handed circular polarization. That is, the diffusion screen 12 is in a transmission state for the light beam incident from the right side of the drawing and in a lens state for the light beam incident from the left side of the drawing. For example, the diffusion screen 12 is placed at a distance equivalent to f1 in FIG. 10 from the projection display device 10, that is, at the focal length f1 of the first collimator lens 13, so that the center of the diffusion screen 12 is on the optical axis of the projection display device 10.

[0045] The first collimator lens 13 switches between a lens state in which the light of the multi-viewpoint image V transmitted by the diffusion screen 12 is output as parallel light, and a transmission state in which the light reflected from the opposite side of the diffusion screen 12 is transmitted. Specifically, the first collimator lens 13 is in a lens state for the light of the multi-viewpoint image V transmitted by the diffusion screen 12 with right-handed circular polarization. On the other hand, the first collimator lens 13 is in a transmission state for the reflected light reflected by the mirror 15 with left-handed circular polarization. That is, the first collimator lens 13 is in a lens state for the light beam incident from the right side of the drawing, and in a transmission state for the light beam incident from the left side of the drawing. For example, the first collimator lens 13 is disposed adjacent to the diffusion screen 12 at a distance corresponding to f1 in FIG. 10 from the projection display device 10, that is, at the focal length f1 of the first collimator lens 13, so that the center of the first collimator lens 13 is on the optical axis of the projection display device 10. However, in order to simplify the explanation, the diffusion screen 12 and the first collimator lens 13 are shown separated from each other in FIG.

[0046] The imaging lens 14 is arranged for each viewpoint image v, and switches between a lens state in which the parallel light emitted by the first collimator lens 13 is condensed as the light of the viewpoint image v, and a transmission state in which the reflected light from the opposite side of the first collimator lens 13 is transmitted. Specifically, the imaging lens 14 is in a lens state for the parallel light emitted by the first collimator lens 13 with right-handed circular polarization. On the other hand, the imaging lens 14 is in a transmission state for the reflected light reflected by the mirror 15 with left-handed circular polarization. That is, the imaging lens 14 is in a lens state for the light beam incident from the right side of the drawing, and in a transmission state for the light beam incident from the left side of the drawing. For example, four imaging lenses 14 are arranged vertically, and are arranged at a distance equivalent to f1+d5 in FIG. 10 from the projection display device 10 so that the centers of the four imaging lenses 14 are on the optical axis of the projection display device 10.

[0047] <3D image display> Hereinafter, the display of three-dimensional images by the three-dimensional image display device 1 will be described. 4(a), it is assumed that the projection display device 10 projects the light of the multi-viewpoint image V with right-handed circular polarization. In this case, the light of the multi-viewpoint image V passes through the diffusion screen 12 in a transmissive state, is converted to parallel light by the first collimator lens 13 in a lens state, and enters the imaging lens 14. The parallel light of the multi-viewpoint image V is then condensed by the imaging lens 14 at a focal length f2 as the light of each viewpoint image v, and then becomes divergent light and reaches the mirror 15.

[0048] 4(b), the polarization direction of the light of the viewpoint image v reflected by the mirror 15 is inverted from right-handed circular polarization to left-handed circular polarization. The reflected light of the viewpoint image v then passes through the imaging lens 14 and the first collimator lens 13 in a transmitting state, and is diffused by the diffusion screen 12 to become a light beam with a continuous luminance distribution, and is displayed as a three-dimensional image.

[0049] [Actions and Effects] As described above, the 3D image display device 1 according to the first embodiment employs the lens / transmission switching lens 100 (FIG. 1) that can switch between a lens state and a transmission state as the diffusion screen 12, the first collimator lens 13, and the imaging lens 14. This allows the 3D image display device 1 to realize a reflective configuration that folds back light rays in the depth direction, and the depth size can be reduced to about half that of the conventional technology.

[0050] Furthermore, in the 3D image display device 1, the projection display device 10 can be placed on the observer α side, so the space can be shared between the projection distance and the viewing distance of the projection display device 10. This allows the entire 3D image display device 1 to be made smaller.

[0051] The three-dimensional image display device 1 may use linearly polarized light to switch between the lens state and the transmission state (see FIG. 3). Furthermore, the three-dimensional image display device 1 includes a plurality of projection-type display devices 10, and a display optical system 11 is arranged for each projection-type display device 10, thereby making it possible to enlarge a three-dimensional image (not shown).

[0052] Second embodiment [Configuration of 3D image display device] With reference to FIG. 5, the configuration of a three-dimensional image display device 1A according to the second embodiment will be described with respect to the differences from the first embodiment. As shown in FIG. 5, a three-dimensional image display device 1A differs from the first embodiment in that a first collimator lens 13A is a decentered lens.

[0053] The three-dimensional image display device 1A includes a projection type display device 10 and a display optical system 11A. The display optical system 11A includes a diffusion screen 12, a first collimating lens 13A, an imaging lens 14, and a mirror 15. Note that each of the means other than the first collimating lens 13A is similar to that of the first embodiment, and therefore description thereof will be omitted.

[0054] In an actual installation environment, the projection display device 10 may be placed off the optical axis of the first collimator lens 13A, for example by placing the projection display device 10 directly on the ground. In this case, the 3D image display device 1A projects the multi-viewpoint image V upward toward the first collimator lens 13A. As a result, the viewing area of ​​the 3D image shifts upward by the same amount as the projection angle of the multi-viewpoint image V. In order to adjust the amount of shift in the viewing area, the 3D image display device 1A uses the first collimator lens 13A.

[0055] As shown in Fig. 5(a), the first collimator lens 13A is in a lens state for the light of the multi-viewpoint image V transmitted by the diffusion screen 12 as right-handed circularly polarized light, and functions as a decentered lens. On the other hand, as shown in Fig. 5(b), the first collimator lens 13A is in a transmissive state for the light reflected by the mirror 15 as left-handed circularly polarized light. For example, the first collimator lens 13A is disposed so that the projection display device 10 is spaced apart by the focal length f1 of the first collimator lens 13A.

[0056] Here, the amount of shift in the viewing zone is equal to the angle between the line segment connecting the lens center c1 of the first collimator lens 13A and the projection lens center c2 of the projection display device 10 and the ground plane. For example, to set the amount of shift in the viewing zone to 0, as shown in Fig. 5(a), the optical axis of the first collimator lens 13A and the optical axis of the projection lens of the projection display device 10 are made to coincide with each other, and the above-mentioned line segment is made parallel to the ground plane.

[0057] [Actions and Effects] As described above, the three-dimensional image display device 1A according to the second embodiment can be reduced in depth to about half that of the conventional technology, similarly to the first embodiment. Furthermore, in the three-dimensional image display device 1A, the viewing zone can be controlled by the decentered first collimator lens 13A, so the projection-type display device 10 can be disposed at a position other than the optical axis of the first collimator lens 13A. As a result, in the three-dimensional image display device 1A, even when the observer α views the image near the center of the three-dimensional image display device 1A, the projection-type display device 10 is unlikely to get in the way of the observer α.

[0058] Third embodiment [Configuration of 3D image display device] With reference to FIG. 6, the configuration of a three-dimensional image display device 1B according to the third embodiment will be described with respect to the differences from the first embodiment. As shown in FIG. 6, the three-dimensional image display device 1B differs from the first embodiment in that a first condenser lens 16 and a second condenser lens 17 are added.

[0059] The three-dimensional image display device 1B includes a projection display device 10 and a display optical system 11B. The display optical system 11B includes a diffusion screen 12, a first collimator lens 13, an imaging lens 14, a mirror 15, a first condenser lens 16, and a second condenser lens 17.

[0060] This three-dimensional image display device 1B has a configuration optically equivalent to that of the display device 9A in Fig. 12. The first condenser lens 16 and the second condenser lens 17 are switchable between a lens state and a transmission state, similar to the lens / transmission switching lens 100 in Fig. 1. Note that each unit other than the first condenser lens 16 and the second condenser lens 17 is similar to that in the first embodiment, and therefore a description thereof will be omitted.

[0061] The first condenser lens 16 switches between a transmission state in which it transmits the light of the multi-viewpoint image V transmitted by the diffusion screen 12 as right-handed circularly polarized light, and a lens state in which it collects the light reflected by the mirror 15 as left-handed circularly polarized light. As shown in Fig. 6(a), the first condenser lens 16 is in a transmission state for light rays incident from the right side of the drawing. On the other hand, as shown in Fig. 6(b), the first condenser lens 16 is in a lens state for light rays incident from the left side of the drawing, and collects the light reflected from the mirror 15 at the optimal viewing distance L where the observer α is located.

[0062] Here, the first condenser lens 16 may be disposed between the diffusion screen 12 and the first collimator lens 13. For example, the first condenser lens 16 is disposed adjacent to the diffusion screen 12 so that f3 = 2 d1 + d2 is satisfied. Here, f3 represents the focal length of the second condenser lens 17, d1 represents the distance between the mirror 15 and the second condenser lens 17, and d2 represents the distance between the first condenser lens 16 and the second condenser lens 17.

[0063] The second condenser lens 17 switches between a lens state in which it collects the light of each viewpoint image v collected by the imaging lens 14 with right-handed circular polarization, and a transmission state in which it transmits the light reflected by the mirror 15 with left-handed circular polarization. As shown in Fig. 6(a), the second condenser lens 17 is in the lens state for light rays incident from the right side of the drawing, and collects the light of the viewpoint image v on the central half surface of the mirror 15. On the other hand, as shown in Fig. 6(b), the second condenser lens 17 is in the transmission state for light rays incident from the left side of the drawing.

[0064] Here, the second condenser lens 17 may be disposed between the imaging lens 14 and the mirror 15. For example, the second condenser lens 17 is disposed at a focal length f2 of the imaging lens 14. The second condenser lens 17 may also be disposed adjacent to the imaging lens 14 (not shown).

[0065] [Actions and Effects] As described above, the 3D image display device 1B according to the third embodiment can reduce the depth size to about half that of the conventional technology, similar to the first embodiment. Furthermore, the 3D image display device 1B can control the viewing area of ​​the 3D image and efficiently use limited light information.

[0066] The three-dimensional image display device 1B can also employ a decentered first collimator lens 13A (FIG. 5) in the same manner as in the second embodiment. Furthermore, in the three-dimensional image display device 1B, the various means of the display optical system 11B, except for the mirror 15, may be disposed adjacent to each other.

[0067] (Fourth embodiment) [Configuration of 3D image display device] With reference to FIG. 7, the configuration of a three-dimensional image display device 1C according to the fourth embodiment will be described with respect to the differences from the first embodiment. As shown in FIG. 7, a three-dimensional image display device 1C differs from the first embodiment in that a second collimator lens 18 and a third condenser lens 19 are added.

[0068] The three-dimensional image display device 1C includes a projection display device 10 and a display optical system 11C. The display optical system 11C includes a diffusion screen 12, an imaging lens 14, a mirror 15, a second collimator lens 18, and a third condenser lens 19.

[0069] Here, the second collimator lens 18 and the third condenser lens 19 are general convex lenses or diffractive lenses, rather than the lens / transmission switching lens 100. Note that each unit other than the second collimator lens 18 and the third condenser lens 19 is similar to that of the first embodiment, and therefore description thereof will be omitted.

[0070] The second collimator lens 18 outputs the light of the multi-viewpoint image V transmitted through the diffusion screen 12 as parallel light. The second collimator lens 18 also outputs the light reflected by the mirror 15 to the diffusion screen 12. Here, the second collimator lens 18 is disposed after the diffusion screen 12 in place of the first collimator lens 13. For example, the second collimator lens 18 is disposed so that the projection type display device 10 is separated therefrom by a focal length f1 of the second collimator lens 18.

[0071] The third condenser lens 19 focuses the light of each viewpoint image v focused by the imaging lens 14 onto the central half surface of the mirror 15. The third condenser lens 19 also focuses the light reflected by the mirror 15 onto the second collimator lens 18.

[0072] Here, the third condenser lens 19 may be placed between the imaging lens 14 and the mirror 15. For example, the third condenser lens 19 is placed near the imaging lens 14 so that f3=2·d3+d4 with respect to the mirror 15. Note that f3 is the focal length of the third condenser lens 19, d3 is the distance between the focusing surface of the viewpoint image v formed by the imaging lens 14 and the mirror 15, and d4 is the distance between the focusing surface of the viewpoint image v formed by the imaging lens 14 and the third condenser lens 19. When the imaging lens 14 and the third condenser lens 19 are placed adjacent to each other, d4=f2.

[0073] <3D image display> The display of three-dimensional images by the three-dimensional image display device 1C will be described below. As shown in Fig. 7(a), it is assumed that the projection display device 10 projects the light of the multi-viewpoint image V with right-handed circular polarization. In this case, the light of the multi-viewpoint image V passes through the diffusion screen 12 in a transmissive state, is converted into parallel light by the second collimator lens 18, and enters the imaging lens 14. The parallel light of the multi-viewpoint image V is then emitted by the imaging lens 14 as the light of each viewpoint image v. The light of each viewpoint image v is then condensed onto the central half of the mirror 15 by the third condenser lens 19.

[0074] 7(b), the polarization direction of the light of the viewpoint image v reflected by the mirror 15 is inverted from right-handed circularly polarized light to left-handed circularly polarized light. The reflected light of the viewpoint image v is then converted into parallel light by the third condenser lens 19 and enters the second collimator lens 18. After that, this parallel light is condensed by the second collimator lens 18 and the diffusion screen 12 to the focal length f1 (optimum viewing distance) of the second collimator lens 18.

[0075] In FIG. 7(b), the parallel light emitted by the third condenser lens 19 travels in a different direction for each viewpoint image v. Therefore, when the distance between the third condenser lens 19 and the second collimator lens 18 is long, the light of the viewpoint image v is projected onto the second collimator lens 18 while being slightly shifted in the travel direction. As a result, a phenomenon occurs in which the display area of ​​the 3D image continuously shifts depending on the viewing area of ​​the 3D image. To prevent this phenomenon, in the 3D image display device 1C, the diffusion screen 12, the imaging lens 14, the second collimator lens 18, and the third condenser lens 19 may be disposed adjacent to each other.

[0076] [Actions and Effects] As described above, the three-dimensional image display device 1C according to the fourth embodiment can be reduced in depth size to about half that of the conventional technology, similarly to the first embodiment. Furthermore, the three-dimensional image display device 1C is useful when the projection display device 10 is placed near the viewer α, since the projection distance of the projection display device 10 can be made equal to the optimum viewing distance (focal length f1).

[0077] Furthermore, the three-dimensional image display device 1C has one less condenser lens than the three-dimensional image display device 1B in FIG. 6, making the configuration simpler. Furthermore, in the three-dimensional image display device 1C, since the second collimator lens 18 and the third condenser lens 19 are not the lens / transmission switching lens 100 (Figure 1), the decrease in light amount due to the diffraction efficiency of the polarizing diffractive lens 110 is suppressed, and the efficiency of light utilization can be increased.

[0078] In addition, since the three-dimensional image display device 1C has only one second collimator lens 18, it is not possible to arrange multiple sets of projection-type display devices 10 and display optical systems 11C. For this reason, the three-dimensional image display device 1C is particularly useful when using a single high-definition projection-type display device 10.

[0079] Fifth embodiment [Operation principle of focal length switching lens] A 3D image display device 1D according to the fifth embodiment (FIG. 9) differs from the first embodiment in that it uses a focal length switching lens that can switch the focal length. Therefore, the operation principle of the focal length switching lens will be explained first, and then the configuration of the 3D image display device 1D will be explained.

[0080] As shown in FIG. 8, the focal length switching lens 200 switches focal length based on the same principle as the lens / transmission switching lens 100 in FIG.

[0081] Since the configurations of the polarized diffractive lens 210 and the convex lens 220 are the same as those in Fig. 1, detailed description thereof will be omitted. Also, in Fig. 8, three focal length switching lenses 200 arranged in the horizontal direction are illustrated for ease of viewing the drawing.

[0082] Here, the focal length of the polarizing diffractive lens 210 is ±f g , the focal length of the convex lens 220 is f c (However, |f g |>f cAs shown in FIG. 8(a), when right-handed circularly polarized light is incident on the focal length switching lens 200, the focal length f a On the other hand, as shown in FIG. 8B, in the case of the focal length switching lens 200, when left-handed circularly polarized light is incident, the focal length f b becomes shorter.

[0083]

number

[0084] In this way, the focal length switching lens 200 can switch the focal length according to the polarization direction of the light. Note that the focal length switching lens 200 can also use linearly polarized light instead of circularly polarized light.

[0085] [Configuration of 3D image display device] With reference to FIG. 9, the configuration of a three-dimensional image display device 1D according to the fifth embodiment will be described with respect to the points that differ from the first embodiment. As shown in FIG. 9, a three-dimensional image display device 1D differs from the first embodiment in that a fourth condenser lens 20 is added.

[0086] The three-dimensional image display device 1D includes a projection display device 10 and a display optical system 11D. The display optical system 11D includes a diffusion screen 12, a first collimator lens 13, an imaging lens 14, a mirror 15, and a fourth condenser lens 20.

[0087] Here, the fourth condenser lens 20 is a focal length switching lens. Note that the other elements than the fourth condenser lens 20 are the same as those in the first embodiment, and therefore the description thereof will be omitted.

[0088] The fourth condenser lens 20 has a focal length f a , and the mirror 15 is set to have a focal length f so that the light reflected by the mirror 15 as left-handed circularly polarized light is focused on the diffusion screen 12. aShorter focal length f b The focal length f a is the first focal length as claimed, and the focal length f b is the second focal length.

[0089] As shown in FIG. 9(a), the fourth condenser lens 20 has a focal length of f a 9B, the fourth condenser lens 20 has a focal length of f b As a result, the light reflected from the mirror 15 is focused onto the outer periphery of the diffusion screen 12 .

[0090] Here, the fourth condenser lens 20 may be disposed between the imaging lens 14 and the mirror 15. For example, the fourth condenser lens 20 is arranged at a focal distance of f a = 2 d3 + d4. Note that d3 represents the distance between the focusing surface of the viewpoint image v formed by the imaging lens 14 and the mirror 15, and d4 represents the distance between the focusing surface of the viewpoint image v formed by the imaging lens 14 and the fourth condenser lens 20. Furthermore, when the imaging lens 14 and the fourth condenser lens 20 are positioned adjacent to each other, d4 = f2.

[0091] <3D image display> The display of three-dimensional images by the three-dimensional image display device 1D will be described below. As shown in Fig. 9(a), it is assumed that the projection display device 10 projects the light of the multi-viewpoint image V with right-handed circular polarization. In this case, the light of the multi-viewpoint image V passes through the diffusion screen 12 in a transmissive state, is converted into parallel light by the first collimator lens 13, and enters the imaging lens 14. The parallel light of the multi-viewpoint image V is then emitted by the imaging lens 14 as the light of each viewpoint image v. The light of each viewpoint image v is then condensed onto the central half of the mirror 15 by the fourth condenser lens 20.

[0092] Next, as shown in FIG. 9(b), the light of the viewpoint image v reflected by the mirror 15 is inverted in polarization direction from right-handed circular polarization to left-handed circular polarization. The reflected light of the viewpoint image v is then incident on the diffusion screen 12 by the fourth condenser lens 20 and condensed at the optimum viewing distance L. At this time, in the above-mentioned formula (2), f3=f a , f4=f b By substituting the above, the optimal viewing distance L can be calculated.

[0093] In addition, since the distance between the fourth condenser lens 20 and the diffusion screen 12 is increased, the light of the viewpoint image v does not irradiate the same area of ​​the diffusion screen 12. Therefore, by disposing the fourth condenser lens 20 and the diffusion screen 12 adjacent to each other, it is possible to irradiate the light of the viewpoint image v to the same area of ​​the diffusion screen 12.

[0094] [Actions and Effects] As described above, the three-dimensional image display device 1D according to the fifth embodiment can be reduced in depth to about half that of the prior art, similarly to the first embodiment. Furthermore, the three-dimensional image display device 1D has one less condenser lens than the three-dimensional image display device 1B in FIG. 6, making the configuration simpler.

[0095] As in the second embodiment, the three-dimensional image display device 1D can also employ a decentered first collimator lens 13A (FIG. 5).

[0096] Although each embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiments, and also includes design modifications and the like within the scope of the present invention that do not deviate from the gist of the present invention. For example, in the three-dimensional image display device according to each embodiment, the arrangement of the optical elements may be changed as long as the temporal order in which the optical elements act is not changed. [Explanation of symbols]

[0097] 1,1A~1D 3D image display device 9,9A display device 10 Projection display device (projection means) 11,11A~11D Display optical system 12 Diffusion screen (diffusion means) 13,13A First collimating lens 14 Imaging Lens 15 Mirror (reflection means) 16 First condenser lens 17 Second condenser lens 18 Second collimating lens 19 Third condenser lens 20 4th condenser lens 90 Projection display device 91,91A Display optical system 92 Collimating Lens 93 Imaging Lens 94 Diffusion Screen 95 Lens Array 95a Convex lens 96,97 Condenser Lens 100 Lens / Transparent Switching Lens 110 Polarized Diffractive Lenses 120 Convex Lens 130 Mirror 140 1 / 4 wave plate 200 Focal length switching lens 210 Polarized Diffractive Lenses 220 Convex Lens V Multi-perspective video v Point of view video α Observer

Claims

1. A three-dimensional image display device that displays a three-dimensional image by projecting a multi-viewpoint image composed of a plurality of viewpoint images, a projection means for projecting the multi-viewpoint image; A diffusion means configured with a micro lens capable of switching between a transmission state in which light of the multi-viewpoint image projected by the projection means is transmitted and a lens state in which reflected light from the opposite side of the projection means is diffused; a first collimator lens capable of switching between a lens state in which the light of the multi-viewpoint image transmitted through the diffusion means is output as parallel light and a transmission state in which the light reflected from the opposite side of the diffusion means is transmitted; an imaging lens arranged for each of the viewpoint images, switchable between a lens state in which the parallel light emitted by the first collimator lens is condensed as light for the viewpoint image and a transmission state in which reflected light from an opposite side of the first collimator lens is transmitted; a reflecting means for reflecting the light of each viewpoint image collected by the imaging lens as the reflected light; Equipped with The microlenses, the first collimator lens and the imaging lens of the diffusing means are each composed of a polarizing diffractive lens whose focal length changes depending on the polarization direction, and a convex lens arranged for each of the polarizing diffractive lenses, the projection means includes a polarizing plate that outputs light of the multi-viewpoint image in a predetermined first polarization direction; the diffusion means is in a transmissive state with respect to the light of the multi-viewpoint image projected by the projection means in the first polarization direction, and is in a lens state with respect to the light reflected by the reflection means in a second polarization direction opposite to the first polarization direction, the first collimator lens is in a lens state with respect to the light of the multi-viewpoint image transmitted by the diffusion means in the first polarization direction, and is in a transmission state with respect to the reflected light reflected by the reflection means in the second polarization direction, the imaging lens is in a lens state with respect to the parallel light emitted in the first polarization direction from the first collimator lens, and in a transmission state with respect to the reflected light reflected in the second polarization direction from the reflecting means, The three-dimensional image display device is characterized in that the reflection means inverts the first polarization direction to the second polarization direction when reflecting the light of each viewpoint image focused by the imaging lens as the reflected light.

2. The three-dimensional image display device according to claim 1 , wherein the first collimator lens is a decentered lens.

3. a first condenser lens that is disposed between the diffusion means and the first collimator lens and is switchable between a transmission state in which the diffusion means transmits light of the multi-viewpoint image transmitted in the first polarization direction and a lens state in which the reflection means collects reflected light reflected in the second polarization direction; a second condenser lens that is disposed between the imaging lens and the reflecting means and is switchable between a lens state in which the imaging lens focuses light of each viewpoint image focused in the first polarization direction and a transmission state in which the reflecting means transmits reflected light in the second polarization direction; The three-dimensional image display device according to claim 1 , further comprising:

4. a second collimator lens that is disposed after the diffusion means in place of the first collimator lens and that outputs the light of the multi-viewpoint image transmitted by the diffusion means as parallel light; a third condenser lens disposed between the imaging lens and the reflecting means, for focusing the light of each viewpoint image focused by the imaging lens onto the reflecting means and focusing the reflected light reflected by the reflecting means onto the second collimating lens; The three-dimensional image display device according to claim 1 , further comprising:

5. a fourth condenser lens, which is disposed between the imaging lens and the reflecting means and is switchable between a first focal length at which the imaging lens focuses the light of each viewpoint image focused in the first polarization direction on the reflecting means and a second focal length shorter than the first focal length so as to focus the reflected light reflected in the second polarization direction by the reflecting means on the diffusing means; The three-dimensional image display device according to claim 1 , further comprising:

Images