Stereoscopic image display device and image generation device

Abstract

To provide a stereoscopic image display device that has a wide range capable of displaying a three-dimensional image and suppresses a contradiction of physiological factors in a three-dimensional view, and an image generation device.SOLUTION: A stereoscopic image display device 10 includes: a display unit 20 for successively displaying parallax images; a variable-focus lens unit 40 for forming virtual images Pa1, Pa2 of each of parallax images on each of display surfaces 102, 104; and a control unit 80 for distributing the luminance of a stereoscopic image Si to the luminance of parallax images according to a position of the stereoscopic image SI. The control unit 80 changes a distribution ratio for distributing the luminance of the stereoscopic image SI to the luminance of parallax images according to a distance between an observer and the stereoscopic image SI when the position of the stereoscopic image SI is a first position located between the shortest display surface and the longest display surface, and fixes a distribution ratio when the position of the stereoscopic image SI is a second position in which a distance from the observer is equal to or less than a distance between the observer and the shortest display surface, or when the position of the stereoscopic image SI is a third position in which the distance from the observer is equal to or more than a distance between the observer and the longest display surface.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a stereoscopic image display device and an image generation device.

Background Art

[0002] As a display device that displays a stereoscopic image (3D image) visible to the naked eye, a stereoscopic image display device using the DFD (Depth Fused 3D) method is known. For example, Patent Document 1 discloses a three-dimensional display device including a display device that displays a parallax image for the right eye and a parallax image for the left eye, a first bifocal lens provided in front of the observer's right eye, a second bifocal lens provided in front of the observer's left eye, and a synchronization device that switches the focal length of the first bifocal lens and the focal length of the second bifocal lens.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The three-dimensional display device of Patent Document 1 displays a parallax image for the right eye and a parallax image for the left eye on each of two virtual image planes. The three-dimensional display device of Patent Document 1 distributes the luminance ratio between the parallax image for the right eye and the parallax image for the left eye displayed on one virtual image plane and the parallax image for the right eye and the parallax image for the left eye displayed on the other virtual image plane according to the depth position of the three-dimensional stereoscopic image, thereby displaying a three-dimensional stereoscopic image between the two virtual image planes. As a result, the three-dimensional display device of Patent Document 1 suppresses the contradiction of physiological factors (binocular parallax, convergence, focus adjustment) in stereoscopic vision and reduces the observer's eye fatigue.

[0005] On the other hand, in the three-dimensional display device of Patent Document 1, since the stereoscopic image is displayed between two virtual image planes, the range in which the stereoscopic image can be displayed is narrow.

[0006] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a stereoscopic image display device and an image generation device that can display a stereoscopic image over a wide range and suppress contradictions in physiological factors in stereoscopic vision.

Means for Solving the Problems

[0007] To achieve the above object, a stereoscopic image display device according to a first aspect of the present disclosure includes: a display unit that sequentially displays parallax images that can be stereoscopically viewed; a variable focus lens unit that switches the focal length with respect to the display light of each of the parallax images and forms a virtual image of each of the parallax images on each of a plurality of display surfaces located in the depth direction as viewed from an observer; a control unit that distributes the luminance of the stereoscopic image to the luminance of the parallax images according to the position of the stereoscopic image formed from the virtual images of the parallax images, and includes: the control unit distributes the luminance of the stereoscopic image to the luminance of at least one of the parallax images; when the display surface having the shortest distance from the observer among the plurality of display surfaces is defined as the shortest display surface, and the display surface having the longest distance from the observer among the plurality of display surfaces is defined as the farthest display surface, the control unit when the position of the stereoscopic image is a first position located between the shortest display surface and the farthest display surface, changes a distribution ratio for distributing the luminance of the stereoscopic image to the luminance of the parallax images according to the distance between the observer and the stereoscopic image; when the position of the stereoscopic image is a second position where the distance from the observer is equal to or less than the distance between the observer and the shortest display surface, or a third position where the distance from the observer is equal to or greater than the distance between the observer and the farthest display surface, the distribution ratio is made constant.

[0008] A stereoscopic image display device according to a second aspect of the present disclosure includes: a display unit that sequentially displays two parallax images that can be stereoscopically viewed; a variable focus lens unit that switches the focal length with respect to the display light of each of the two parallax images and forms a virtual image of each of the parallax images on each of two display surfaces located in the depth direction as viewed from the observer; a control unit that distributes the luminance of the stereoscopic image to the luminance of the parallax images according to the position of the stereoscopic image formed from the virtual images of the parallax images; the control unit distributes the luminance of the stereoscopic image to the luminance of at least one of the parallax images; when the display surface of the two display surfaces that is closest to the observer is defined as the shortest display surface and the display surface of the two display surfaces that is farthest from the observer is defined as the farthest display surface, the control unit, when the position of the stereoscopic image is a first position located between the shortest display surface and the farthest display surface, changes a distribution ratio for distributing the luminance of the stereoscopic image to the luminance of the parallax images according to the distance between the observer and the stereoscopic image; when the position of the stereoscopic image is a second position where the distance from the observer is equal to or less than the distance between the observer and the shortest display surface, or a third position where the distance from the observer is equal to or greater than the distance between the observer and the farthest display surface, makes the distribution ratio constant.

[0009] An image generation device according to a third aspect of the present disclosure includes a luminance calculation unit that obtains a distribution ratio for distributing the luminance of the stereoscopic image to the luminance of the parallax images based on the position of the stereoscopic image to be displayed and the position of each of a plurality of display surfaces on which virtual images of the parallax images forming the stereoscopic image are respectively displayed; a parallax image generation unit that generates parallax image data representing the parallax images based on the distribution ratio obtained by the luminance calculation unit; when the display surface of the plurality of display surfaces that is closest to the observer is defined as the shortest display surface and the display surface of the plurality of display surfaces that is farthest from the observer is defined as the farthest display surface, the luminance calculation unit, When the position of the stereoscopic image is a first position located between the shortest display surface and the farthest display surface, the distribution ratio for distributing the luminance of the stereoscopic image to the luminance of the parallax image is changed according to the distance between the observer and the stereoscopic image. When the position of the stereoscopic image is a second position where the distance from the observer is equal to or less than the distance between the observer and the shortest display surface, or a third position where the distance from the observer is equal to or greater than the distance between the observer and the farthest display surface, the distribution ratio is made constant.

Advantages of the Invention

[0010] According to the present disclosure, a stereoscopic image can be displayed over a wide range, and contradictions in physiological factors in stereoscopic vision can be suppressed.

Brief Description of the Drawings

[0011]

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Mode for Carrying Out the Invention

[0012] Hereinafter, a stereoscopic image display device according to an embodiment will be described with reference to the drawings.

[0013] <Embodiment 1> With reference to FIGS. 1 to 14, a stereoscopic image display device 10 according to the present embodiment will be described. The stereoscopic image display device 10 is used, for example, as a head-mounted display.

[0014] (Overall Configuration) First, the overall configuration of the stereoscopic image display device 10 will be described. As shown in FIG. 1, the stereoscopic image display device 10 includes a display unit 20, a variable focus lens unit 40, and a control unit 80.

[0015] The display unit 20 sequentially displays a stereoscopically viewable first parallax image and a stereoscopically viewable second parallax image in a time-division manner. In the present embodiment, the display unit 20 emits the display light DL1 of the first parallax image and the second parallax image as polarized light whose polarization direction is a predetermined first direction. The display unit 20 includes a display device 20R for the right eye and a display device 20L for the left eye.

[0016] The variable focus lens unit 40 switches the focal length with respect to the display light DL1 of the first parallax image and the focal length with respect to the display light DL1 of the second parallax image, and forms virtual images of the first parallax image and the second parallax image respectively on the first display surface 102 and the second display surface 104 located in the depth direction as viewed from the observer. The virtual image Pa1 of the first parallax image and the virtual image Pa2 of the second parallax image form a stereoscopic image SI of a display object (for example, a three-dimensional object). In the present embodiment, the variable focus lens unit 40 includes a right-eye lens unit 40R and a left-eye lens unit 40L. The right-eye lens unit 40R corresponds to the right-eye display device 20R, and the left-eye lens unit 40L corresponds to the left-eye display device 20L. The first display surface 102 and the second display surface 104 will be described later.

[0017] The control unit 80 controls the brightness of the first parallax image (the virtual image Pa1 of the first parallax image) and the second parallax image (the virtual image Pa2 of the second parallax image) according to the position of the stereoscopic image SI. The control unit 80 generates first parallax image data representing the first parallax image and second parallax image data representing the second parallax image. In this specification, the control unit 80 functions as an image generation device. Further, the control unit 80 controls the display unit 20 and the variable focus lens unit 40.

[0018] In this specification, for ease of understanding, the left direction (the left direction of the paper surface) of the stereoscopic image display device 10 in FIG. 1 is defined as the +Z direction, the downward direction (the downward direction of the paper surface) is defined as the +X direction, and the direction perpendicular to the +X direction and the +Z direction (the front direction of the paper surface) is defined as the +Y direction for description.

[0019] (Display unit) The display unit 20 of the stereoscopic image display device 10 sequentially displays the first parallax image and the second parallax image in a time-division manner based on the image signal supplied from the control unit 80. In the present embodiment, the display unit 20 emits the display light DL1 of the first parallax image and the second parallax image as polarized light whose polarization direction is a predetermined first direction. The display light DL1 of the first parallax image and the second parallax image is incident on the variable focus lens unit 40. Also, the predetermined first direction is the X direction.

[0020] The display unit 20 includes a right-eye display device 20R located in front of the observer's right eye (+Z side) and a left-eye display device 20L located in front of the observer's left eye (+Z side). The right-eye display device 20R displays a right-eye image, and the left-eye display device 20L displays a left-eye image. The display light of the right-eye image is incident on the observer's right eye. The display light of the left-eye image is incident on the observer's left eye. One right-eye image and one left-eye image form one parallax image.

[0021] In this embodiment, the first right-eye image PR1 displayed on the right-eye display device 20R and the first left-eye image PL1 displayed on the left-eye display device 20L form a first parallax image. Also, the second right-eye image PR2 displayed on the right-eye display device 20R and the second left-eye image PL2 displayed on the left-eye display device 20L form a second parallax image. That is, the right-eye display device 20R and the left-eye display device 20L synchronously display the first right-eye image PR1 and the first left-eye image PL1 at the same time, and display the second right-eye image PR2 and the second left-eye image PL2 at the same time.

[0022] Also, the display light DL1 of the first right-eye image PR1 and the second right-eye image PR2 is incident on the right-eye lens unit 40R of the variable focus lens unit 40. The display light DL1 of the first left-eye image PL1 and the second left-eye image PL2 is incident on the left-eye lens unit 40L of the variable focus lens unit 40.

[0023] As shown in FIG. 2, the right-eye display device 20R includes a right-eye liquid crystal display panel 22R and a light source unit 32. The left-eye display device 20L includes a left-eye liquid crystal display panel 22L and a light source unit 32. Since the configurations of the right-eye display device 20R and the left-eye display device 20L are the same, the right-eye display device 20R will be taken as an example to explain the right-eye display device 20R and the left-eye display device 20L.

[0024] The liquid crystal display panel 22R for the right eye modulates the light emitted from the light source unit 32 and sequentially displays the first right-eye image PR1 and the second right-eye image PR2 in a time-division manner. The liquid crystal display panel 22R for the right eye is, for example, a transmissive TN (Twisted Nematic) liquid crystal panel that is actively matrix-driven by TFT (Thin Film Transistor).

[0025] As shown in FIG. 3, the liquid crystal display panel 22R for the right eye includes pixels P arranged in a matrix, a gate driver 23G, and a data driver 23D. The gate driver 23G sequentially selects the pixels P row by row and performs a line sequential scan in the -Y direction. The data driver 23D supplies a voltage corresponding to the image signal to each of the selected pixels P and writes the image signal to each of the pixels P. The image signal is a signal for displaying the first right-eye image PR1 or the second right-eye image PR2. In addition, the liquid crystal display panel 22R for the right eye includes a polarizing plate, liquid crystal, and the like.

[0026] Note that in FIG. 3, only a part of the pixels P arranged in the matrix is shown. Also, the liquid crystal display panel 22L for the left eye of the left-eye display device 20L modulates the light emitted from the light source unit 32 and sequentially displays the first left-eye image PL1 and the second left-eye image PL2 in a time-division manner.

[0027] The light source unit 32 is, for example, a direct-type backlight provided on the back surface (+Z side) of each of the liquid crystal display panel 22R for the right eye and the liquid crystal display panel 22L for the left eye. The light source unit (backlight) 32 includes, not shown, an LED (Light emitting diode) element, a reflection sheet, a diffusion sheet, and the like.

[0028] (Variable focus lens unit) As shown in FIG. 1, the variable focus lens unit 40 of the stereoscopic image display device 10 includes a right-eye lens unit 40R and a left-eye lens unit 40L. The right-eye lens unit 40R is disposed between the right-eye display device 20R and the observer's right eye. The left-eye lens unit 40L is disposed between the left-eye display device 20L and the observer's left eye.

[0029] The right-eye lens unit 40R switches the focal length with respect to the display light DL1 of the first right-eye image PR1 and the focal length with respect to the display light DL1 of the second right-eye image PR2 in synchronization with the display of the right-eye liquid crystal display panel 22R, and forms the first right-eye image PR1 and the second right-eye image PR2 as virtual images on the first display surface 102 and the second display surface 104, respectively. The left-eye lens unit 40L switches the focal length with respect to the display light DL1 of the first left-eye image PL1 and the focal length with respect to the display light DL1 of the second left-eye image PL2 in synchronization with the display of the left-eye liquid crystal display panel 22L, and forms the first left-eye image PL1 and the second left-eye image PL2 as virtual images on the first display surface 102 and the second display surface 104, respectively. Thereby, a virtual image Pa1 of the first parallax image is formed on the first display surface 102, and a virtual image Pa2 of the second parallax image is formed on the second display surface 104.

[0030] The right-eye lens unit 40R and the left-eye lens unit 40L each have a polarization switching unit 50 and a polarization bifocal lens 60. The polarization switching unit 50 switches the polarization direction of the display light DL1 emitted from the display unit 20 to a predetermined first direction and a predetermined second direction and emits it. The polarization bifocal lens 60 is a lens whose focal length with respect to the emitted light emitted from the polarization switching unit 50 differs depending on the polarization direction of the emitted light.

[0031] The polarization switching unit 50 of the right-eye lens unit 40R switches the polarization direction of the display light DL1 emitted from the right-eye display device 20R between a predetermined first direction (X direction) and a predetermined second direction based on a switching signal supplied from the control unit 80. The switching signal is synchronized with the image signal supplied to the display unit 20 (right-eye liquid crystal display panel 22R). In the present embodiment, the predetermined second direction is the Y direction.

[0032] Specifically, when the first right-eye image PR1 is being displayed on the right-eye liquid crystal display panel 22R, the polarization switching unit 50 maintains the polarization direction of the display light DL1 incident from the right-eye liquid crystal display panel 22R in the X direction and emits it. On the other hand, when the second right-eye image PR2 is being displayed on the right-eye liquid crystal display panel 22R, the polarization switching unit 50 switches the polarization direction of the display light DL1 incident from the right-eye liquid crystal display panel 22R to the Y direction and emits it.

[0033] The polarization switching unit 50 is, for example, a TN liquid crystal element with a twist angle of 90°. As shown in FIG. 4, the polarization switching unit (TN liquid crystal element) 50 includes a liquid crystal 52, two light-transmissive substrates 54a and 54b that sandwich the liquid crystal and have electrodes 53 for applying a voltage to the liquid crystal, and an alignment film (not shown) for aligning the liquid crystal. The light-transmissive substrate 54a and the light-transmissive substrate 54b are bonded together by a sealing material 56. When an OFF-level switching signal is supplied to the polarization switching unit 50, it rotates the polarization direction of the display light DL1 by 90° and emits the display light DL2 with the polarization direction in the Y direction. On the other hand, when an ON-level switching signal is supplied to the polarization switching unit 50, the liquid crystal 52 aligns perpendicular to the light-transmissive substrates 54a and 54b, and the polarization switching unit 50 maintains the polarization direction of the display light DL1 in the X direction and emits the display light DL2. The display light DL2 emitted from the polarization switching unit 50 enters the polarization bifocal lens 60.

[0034] The polarization bifocal lens 60 of the right-eye lens unit 40R is a lens in which the focal length with respect to the light emitted from the polarization switching unit 50, that is, the display light DL2 emitted from the polarization switching unit 50, differs depending on the polarization directions (X direction and Y direction) of the display light DL2. The polarization bifocal lens 60 forms the first right-eye image PR1 and the second right-eye image PR2 as virtual images on the first display surface 102 and the second display surface 104, respectively, as seen by the observer. The first display surface 102 and the second display surface 104 are virtual display surfaces located at different positions in the depth direction (+Z direction) as seen by the observer. In the present embodiment, as shown in FIG. 1, the first display surface 102 and the second display surface 104 are located farther from the display unit 20 than the observer. Also, the first display surface 102 is located closer to the observer (-Z side) than the second display surface 104. The first display surface 102 of the present embodiment corresponds to the shortest display surface, and the second display surface 104 of the present embodiment corresponds to the farthest display surface.

[0035] The polarization bifocal lens 60 is, for example, a liquid crystal lens. The polarization bifocal lens (liquid crystal lens) 60 includes, as shown in FIG. 5, a first light-transmissive substrate 61, a second light-transmissive substrate 62, and liquid crystal 64.

[0036] The first light-transmissive substrate 61 and the second light-transmissive substrate 62 are, for example, glass substrates. The first light-transmissive substrate 61 has a Fresnel lens 66 made of resin on the first main surface 61a facing the second light-transmissive substrate 62. The first light-transmissive substrate 61 and the second light-transmissive substrate 62 are bonded together by a sealing material 67 to sandwich the liquid crystal 64. The liquid crystal 64 is, for example, a nematic liquid crystal having positive refractive index anisotropy (Δn = ne - no > 0, ne: extraordinary ray refractive index, no: ordinary ray refractive index). The liquid crystal 64 is aligned in the Y direction by an alignment film (not shown).

[0037] When the display light DL2 of the first right-eye image PR1 whose polarization direction is the X direction is incident on the polarization bifocal lens 60, since the nematic liquid crystal having a positive refractive index anisotropy is oriented in the Y direction, the focal length of the polarization bifocal lens 60 with respect to the display light DL2 is long, and the virtual image of the first right-eye image PR1 is formed on the first display surface 102. On the other hand, when the display light DL2 of the second right-eye image PR2 whose polarization direction is the Y direction is incident on the polarization bifocal lens 60, the focal length of the polarization bifocal lens 60 with respect to the display light DL2 is short, and the virtual image of the second right-eye image PR2 is formed on the second display surface 104.

[0038] The configuration of the polarization switching unit 50 of the left-eye lens unit 40L and the polarization bifocal lens 60 is the same as the configuration of the polarization switching unit 50 of the right-eye lens unit 40R and the polarization bifocal lens 60. The polarization switching unit 50 of the left-eye lens unit 40L switches the polarization direction of the display light DL1 emitted from the left-eye display device 20L to a predetermined first direction and a predetermined second direction. The polarization bifocal lens 60 of the left-eye lens unit 40L forms the first left-eye image PL1 and the second left-eye image PL2 respectively as virtual images on the first display surface 102 and the second display surface 104 as seen by the observer.

[0039] The observer views the virtual image Pa1 of the first parallax image and the virtual image Pa2 of the second parallax image that are sequentially displayed in a time-division manner, and recognizes the stereoscopic image SI of the display target. The brightness of the first parallax image (the virtual image Pa1 of the first parallax image) and the second parallax image (the virtual image Pa2 of the second parallax image) is controlled according to the position of the stereoscopic image SI. The position of the stereoscopic image SI and the brightness of the first parallax image and the second parallax image will be described later.

[0040] (Control unit) The control unit 80 of the stereoscopic image display device 10 generates first parallax image data representing a first parallax image and second parallax image data representing a second parallax image based on three-dimensional object data representing a display target input from an external device (not shown). In generating the first parallax image data and the second parallax image data, the control unit 80 distributes the luminance of the stereoscopic image SI to the luminance of the first parallax image and the luminance of the second parallax image according to the position of the stereoscopic image SI. Further, the control unit 80 controls the display unit 20 and the variable focus lens unit 40.

[0041] First, the relationship between the position of the stereoscopic image SI and the luminance of the first parallax image and the second parallax image will be described. In the present embodiment, as shown in FIGS. 6 to 8, the position of the stereoscopic image SI is described on the assumption that the stereoscopic image SI is formed on a straight line S2 extending in the depth direction (+Z direction) as viewed from the observer, from an intermediate point M1 of a straight line S1 connecting the viewpoints of the right eye and the left eye. Further, the position of the intermediate point M1 is taken as the position of the observer, and the distance between the observer and the stereoscopic image SI is taken as L. The distance between the observer and the intersection of the first display surface 102 and the straight line S2 (hereinafter referred to as the distance between the observer and the first display surface 102) is taken as L1. The distance between the observer and the intersection of the second display surface 104 and the straight line S2 (hereinafter referred to as the distance between the observer and the second display surface 104) is taken as L2. Further, on the straight line S2, the position between the first display surface 102 (shortest display surface) and the second display surface 104 (farthest display surface) is taken as the first position, the position where the distance from the observer is equal to or less than the distance L1 between the observer and the first display surface 102 (shortest display surface) is taken as the second position, and the position where the distance from the observer is equal to or greater than the distance L2 between the observer and the second display surface 104 (farthest display surface) is taken as the third position.

[0042] As shown in FIG. 6, when forming the stereoscopic image SI at the first position (L1 < L < L2), similar to the stereoscopic image display device using the DFD method, as shown in FIG. 9, the control unit 80 changes the distribution ratio DR for distributing the luminance of the stereoscopic image SI to the luminance of the first parallax image and the luminance of the second parallax image according to the distance L between the observer and the stereoscopic image SI (i.e., the position of the stereoscopic image). For example, when the luminance of the stereoscopic image SI is set to 1 and the stereoscopic image SI is formed in the middle between the first display surface 102 and the second display surface 104, the control unit 80 sets the distribution ratio DR for the luminance of the first parallax image and the luminance of the second parallax image to 0.5:0.5. As the position where the stereoscopic image SI is formed approaches the first display surface 102 from the middle between the first display surface 102 and the second display surface 104, the control unit 80 increases the ratio of the luminance distributed to the first parallax image. As the position where the stereoscopic image SI is formed approaches the second display surface 104 from the middle between the first display surface 102 and the second display surface 104, the control unit 80 increases the ratio of the luminance distributed to the second parallax image.

[0043] Also, when the luminance of the stereoscopic image SI is SIL, the luminance of the first parallax image is LP1, and the luminance of the second parallax image is LP2, for example, the luminance LP1 of the first parallax image is represented by the following formula (1), and the luminance LP2 of the second parallax image is represented by the following formula (2).

[0044]

Equation

[0045] When the stereoscopic image SI is located at the first position, the virtual images Pa1 of the first parallax image and Pa2 of the second parallax image are sequentially displayed on the first display surface 102 and the second display surface 104, respectively. Since the luminance of the stereoscopic image SI is distributed to the luminance of the first parallax image and the luminance of the second parallax image according to the distance L between the observer and the stereoscopic image SI, the observer perceives that the focus of the eyes is located at the position of the stereoscopic image SI. Also, the observer perceives that the distance between the stereoscopic image SI due to parallax and convergence and the distance between the stereoscopic image SI due to the focus of the eyes are consistent. Therefore, the stereoscopic image display device 10 can suppress the contradiction of physiological factors in stereoscopic vision and display the stereoscopic image SI.

[0046] As shown in FIG. 7, when the stereoscopic image SI is formed at the second position (L ≦ L1), as shown in FIG. 9, the control unit 80 distributes the luminance of the stereoscopic image SI to the luminance of the first parallax image and the luminance of the second parallax image, and makes the distribution ratio DR constant regardless of the distance L between the observer and the stereoscopic image SI. The luminance of the stereoscopic image SI is distributed to the luminance of the first parallax image and the luminance of the second parallax image with the distribution ratio DR being constant, and the stereoscopic image display device 10 can display the stereoscopic image SI with the correct luminance due to binocular parallax.

[0047] Also, when the stereoscopic image SI is formed at the second position, it is preferable that the control unit 80 makes the ratio of the luminance of the first parallax image, which has a virtual image displayed on the first display surface 102 with a shorter distance from the observer, to be equal to or greater than the ratio of the luminance of the second parallax image. Thereby, the stereoscopic image display device 10 can match the position of the stereoscopic image SI due to parallax and the position of the stereoscopic image SI due to the luminance ratio between the first parallax image and the second parallax image.

[0048] As shown in FIG. 8, when the stereoscopic image SI is formed at the third position (L ≧ L2), as shown in FIG. 9, the control unit 80 distributes the luminance of the stereoscopic image SI to the luminance of the first parallax image and the luminance of the second parallax image, and makes the distribution ratio DR constant regardless of the distance L between the observer and the stereoscopic image SI. By making the distribution ratio DR constant, the stereoscopic image display device 10 can display the stereoscopic image SI with the correct luminance.

[0049] When forming the stereoscopic image SI at the third position, it is preferable that the control unit 80 makes the ratio of the luminance of the second parallax image, which is displayed as a virtual image on the second display surface 104 with a long distance from the observer, to be equal to or greater than the ratio of the luminance of the first parallax image. Thereby, the stereoscopic image display device 10 can align the position of the stereoscopic image SI due to parallax and the position of the stereoscopic image SI due to the luminance ratio between the first parallax image and the second parallax image.

[0050] When the stereoscopic image SI is located at the second position, it is preferable that the distance L between the observer and the stereoscopic image SI and the distance L1 between the observer and the first display surface 102 satisfy the following formula (3). Also, when the stereoscopic image SI is located at the third position, it is preferable that the distance L between the observer and the stereoscopic image SI and the distance L2 between the observer and the second display surface 104 satisfy the following formula (4). By these, the stereoscopic image display device 10 can suppress the contradiction of physiological factors in stereoscopic vision and display the stereoscopic image SI. Hereinafter, the reasons for these will be explained.

[0051]

Number

[0052] The relationship between the distance Da perceived by eye focus adjustment and the distance Dv perceived by convergence is generally represented as shown in FIG. 10. In FIG. 10, on the straight line S3 passing through the origin with a slope of 1, the distance Da perceived by eye focus adjustment and the distance Dv perceived by convergence coincide. The further away from the straight line S3, the higher the degree of discomfort of the observer. Note that the unit D is the reciprocal of meter (1 / m).

[0053] Regarding the relationship between the distance Da perceived by focusing adjustment and the distance Dv perceived by convergence, there is a region called Percival’s zone of comfort where the degree of discomfort of the observer is low (described in, for example, Journal of Vision, 2008, 8, 1 - 30). Based on Percival’s zone of comfort, if the difference between the distance Da perceived by focusing adjustment and the distance Dv perceived by convergence is within 0.3 D, the degree of discomfort obtained by the observer is low, and the contradiction of physiological factors in stereoscopic vision can be suppressed.

[0054] Therefore, when the stereoscopic image SI is located at the second position, it is preferable that the difference between the reciprocal of the distance L between the observer and the stereoscopic image SI and the reciprocal of the distance L1 between the observer and the first display surface 102 is less than 0.3 (Equation (3)). Also, when the stereoscopic image SI is located at the third position, it is preferable that the difference between the reciprocal of the distance L2 between the observer and the second display surface 104 and the reciprocal of the distance L between the observer and the stereoscopic image SI is less than 0.3 (Equation (4)). Furthermore, regarding the distance L1 between the observer and the first display surface 102 and the distance L2 between the observer and the second display surface 104, the following Equation (5) can be obtained from Equation (3) and Equation (4).

[0055]

Equation

[0056] As described above, not only when the stereoscopic image SI is located at the first position between the first display surface 102 and the second display surface 104, but also when the stereoscopic image SI is located at a distance equal to or less than the distance L1 between the observer and the first display surface 102 (when the stereoscopic image SI is located at the second position) and when the stereoscopic image SI is located at a distance equal to or greater than the distance L2 between the observer and the second display surface 104 (when the stereoscopic image SI is located at the third position), the stereoscopic image display device 10 can display the stereoscopic image SI while suppressing the contradiction of physiological factors in stereoscopic vision.

[0057] Next, the configuration of each part of the control unit 80 will be described. As shown in FIG. 11, the control unit 80 includes a storage unit 82, a luminance calculation unit 84, a parallax image generation unit 86, a display image generation unit 88, a display driving unit 92, and an optical driving unit 94.

[0058] The storage unit 82 of the control unit 80 stores programs for causing the luminance calculation unit 84, the parallax image generation unit 86, the display image generation unit 88, the display driving unit 92, and the optical driving unit 94 to function. Further, the storage unit 82 stores various data such as display surface data, viewpoint data, the distance L1 between the observer and the first display surface 102, and the distance L2 between the observer and the second display surface 104. The display surface data is coordinate data representing the positions of the first display surface 102 and the second display surface 104 in the display space (three-dimensional space) for displaying the stereoscopic image SI. The viewpoint data is coordinate data representing the position of the observer's viewpoint in the display space.

[0059] The luminance calculation unit 84 of the control unit 80 obtains a distribution ratio DR for distributing the luminance of the stereoscopic image SI to the luminance of the first parallax image and the luminance of the second parallax image based on the position of the stereoscopic image SI and the positions of the first display surface 102 and the second display surface 104. Specifically, the luminance calculation unit 84 obtains a distribution ratio DR for distributing the luminance of the stereoscopic image SI to the luminance of the first parallax image and the luminance of the second parallax image based on the three-dimensional object data representing the display target, the display surface data, and the viewpoint data. The luminance calculation unit 84 outputs the obtained distribution ratio DR to the parallax image generation unit 86. The three-dimensional object data includes coordinate data representing the position of the display target in the display space, color data representing the color of the display target, and luminance data representing the luminance of the display target.

[0060] The luminance calculation unit 84 first determines the distance L between the observer and the stereoscopic image SI from the coordinate data of the display target, the display surface data, and the viewpoint data. When L1 < L < L2, the luminance calculation unit 84 determines that the stereoscopic image SI is located at the first position, and obtains a distribution ratio DR according to the distance L between the observer and the stereoscopic image SI. For example, when the stereoscopic image SI is formed in the middle of the first display surface 102 and the second display surface 104, the luminance calculation unit 84 sets the distribution ratio DR for distributing the luminance of the stereoscopic image SI to the luminance of the first parallax image and the luminance of the second parallax image to 0.5:0.5. When L ≤ L1, the luminance calculation unit 84 determines that the stereoscopic image SI is located at the second position, and sets the distribution ratio DR to be constant regardless of the distance L between the observer and the stereoscopic image SI. For example, the luminance calculation unit 84 sets the distribution ratio DR to 0.6:0.4. Further, when L2 ≤ L, the luminance calculation unit 84 determines that the stereoscopic image SI is located at the third position, and sets the distribution ratio DR to be constant regardless of the distance L between the observer and the stereoscopic image SI. For example, the luminance calculation unit 84 sets the distribution ratio DR to 0.3:0.7. When the position of the stereoscopic image SI is at the second position or the third position, the ratio of distribution to the luminance of the first parallax image and the ratio of distribution to the luminance of the second parallax image are preferably greater than zero as in the present embodiment.

[0061] The parallax image generation unit 86 of the control unit 80 generates first parallax image data representing the first parallax image and second parallax image data representing the second parallax image based on the distribution ratio DR obtained by the luminance calculation unit 84. Specifically, the parallax image generation unit 86 generates the first parallax image data and the second parallax image data from the three-dimensional object data, the display surface data, and the distribution ratio DR obtained by the luminance calculation unit 84. The luminance of the first parallax image and the luminance of the second parallax image are distributed from the luminance of the stereoscopic image SI according to the position of the stereoscopic image SI as described above. The parallax image generation unit 86 outputs the first parallax image data and the second parallax image data to the display image generation unit 88.

[0062] The display image generation unit 88 of the control unit 80 generates first right-eye image data representing a first right-eye image PR1 to be displayed on the right-eye display device 20R and first left-eye image data representing a first left-eye image PL1 to be displayed on the left-eye display device 20L from the first parallax image data. Further, the display image generation unit 88 generates second right-eye image data representing a second right-eye image PR2 to be displayed on the right-eye display device 20R and second left-eye image data representing a second left-eye image PL2 to be displayed on the left-eye display device 20L from the second parallax image data. The display image generation unit 88 outputs the first right-eye image data, the first left-eye image data, the second right-eye image data, and the second left-eye image data to the storage unit 82 (frame memory) and stores them in the storage unit 82. Hereinafter, the first right-eye image data, the first left-eye image data, the second right-eye image data, and the second left-eye image data are collectively referred to as display image data.

[0063] The display driving unit 92 of the control unit 80 sequentially reads the display image data from the storage unit 82 and generates a first right-eye image signal for displaying the first right-eye image, a first left-eye image signal for displaying the first left-eye image, a second right-eye image signal for displaying the second right-eye image, and a second left-eye image signal for displaying the second left-eye image. Hereinafter, the first right-eye image signal, the first left-eye image signal, the second right-eye image signal, and the second left-eye image signal are collectively referred to as image signals.

[0064] The display driving unit 92 supplies the image signals to the display unit 20 together with a synchronization signal. Specifically, the display driving unit 92 supplies the first right-eye image signal and the second right-eye image signal to the right-eye liquid crystal display panel 22R of the right-eye display device 20R, and supplies the first left-eye image signal and the second left-eye image signal to the left-eye liquid crystal display panel 22L of the left-eye display device 20L. Further, the display driving unit 92 supplies the synchronization signal to the optical driving unit 94.

[0065] In the present embodiment, the display driving unit 92 supplies the image signals to the right-eye liquid crystal display panel 22R and the left-eye liquid crystal display panel 22L at a cycle of 120 Hz (period of one frame: 8.4 ms). The right-eye liquid crystal display panel 22R and the left-eye liquid crystal display panel 22L perform line sequential scanning (i.e., writing to the pixel P) at a cycle of 120 Hz.

[0066] Taking the case where the stereoscopic image SI is formed at the third position (L2 ≤ L) as an example, the polarities of the voltages written to each of the image signal and the pixel P will be described. Note that the cases where the stereoscopic image SI is formed at the first position and the cases where the stereoscopic image SI is formed at the second position are the same as the case where the stereoscopic image SI is formed at the third position.

[0067] As shown in FIG. 12, the display driving unit 92 alternately supplies the first right-eye image signal and the second right-eye image signal to the right-eye liquid crystal display panel 22R one frame at a time, and the right-eye liquid crystal display panel 22R sequentially displays the first right-eye image and the second right-eye image. In this case, it is preferable that the polarity of the voltage written to each pixel P of the right-eye liquid crystal display panel 22R is inverted for each writing (for each frame). Specifically, in the pixel circuit shown in FIG. 13, the display driving unit 92 inverts the magnitude relationship between the potential Vcom of the common electrode of the right-eye liquid crystal display panel 22R and the potential Vpi on the TFT side of the right-eye liquid crystal display panel 22R for each writing (FIG. 12). Thereby, the image burn-in of the right-eye liquid crystal display panel 22R can be suppressed.

[0068] On the other hand, the display driving unit 92 supplies the first left-eye image signal to the left-eye liquid crystal display panel 22L in synchronization with the first right-eye image signal, and supplies the second left-eye image signal to the left-eye liquid crystal display panel 22L in synchronization with the second right-eye image signal. The left-eye liquid crystal display panel 22L sequentially displays the first left-eye image and the second left-eye image. The first left-eye image and the first right-eye image are displayed simultaneously, and the second left-eye image and the second right-eye image are displayed simultaneously. Similar to the pixel P of the right-eye liquid crystal display panel 22R, it is preferable that the polarity of the voltage written to each pixel P of the left-eye liquid crystal display panel 22L is inverted for each writing.

[0069] The optical drive unit 94 of the control unit 80 generates a switching signal based on the synchronization signal supplied from the display drive unit 92. The optical drive unit 94 supplies the switching signal to the right-eye lens unit 40R and the polarization switching unit 50 of the right-eye lens unit 40R. In the present embodiment, when the first right-eye image is displayed on the right-eye liquid crystal display panel 22R and the first left-eye image is displayed on the left-eye liquid crystal display panel 22L, the optical drive unit 94 sets the switching signal to the ON level and supplies it to the polarization switching unit 50.

[0070] FIG. 14 shows the hardware configuration of the control unit 80. The control unit 80 includes a CPU (Central Processing Unit) 95, a ROM (Read Only Memory) 96, a RAM (Random Access Memory) 97, and an input / output interface 98. The CPU 95, the ROM 96, the RAM 97, and the input / output interface 98 are connected by a bus 99. The CPU 95 executes various processes. The ROM 96 stores programs and data. The RAM 97 stores data. The input / output interface 98 inputs and outputs signals between the CPU 95, the display unit 20 (the right-eye liquid crystal display panel 22R and the left-eye liquid crystal display panel 22L), the variable focus lens unit 40 (the polarization switching unit 50), and an external device. The functions of the control unit 80 are realized by the CPU 95 executing the programs stored in the ROM 96.

[0071] As described above, even when the stereoscopic image display device 10 forms the stereoscopic image SI at a position closer to the observer than the position of the first display surface 102 or at a position farther from the observer than the position of the second display surface 104, the contradiction of physiological factors in stereoscopic vision can be suppressed. Therefore, the stereoscopic image display device 10 can display the stereoscopic image SI over a wide range and suppress the contradiction of physiological factors in stereoscopic vision.

[0072] <Embodiment 2> In Embodiment 1, when forming the stereoscopic image SI at the second position (L≦L1), the stereoscopic image display device 10 distributes the luminance of the stereoscopic image SI to the luminance of the first parallax image and the luminance of the second parallax image at a ratio of 0.6:0.4. Also, when forming the stereoscopic image SI at the third position (L2≦L), the stereoscopic image display device 10 distributes the luminance of the stereoscopic image SI to the luminance of the first parallax image and the luminance of the second parallax image at a ratio of 0.3:0.7.

[0073] When forming the stereoscopic image SI at the second position or the third position, the distribution ratio DR for distributing the luminance of the stereoscopic image SI to the luminance of the first parallax image and the luminance of the second parallax image is arbitrary.

[0074] For example, when forming the stereoscopic image SI at the second position or the third position (L≦L1, L2≦L), as shown in FIG. 15, the stereoscopic image display device 10 (control unit 80) may distribute the luminance of the stereoscopic image SI to the luminance of the first parallax image and the luminance of the second parallax image at a ratio of 0.5:0.5. Further, when forming the stereoscopic image SI at the second position or the third position (L≦L1, L2≦L), as shown in FIGS. 16 and 17, the stereoscopic image display device 10 (control unit 80) may set one of the ratio for distributing to the luminance of the first parallax image and the ratio for distributing to the luminance of the second parallax image to zero. In other words, the stereoscopic image display device 10 (control unit 80) may distribute the luminance of the stereoscopic image SI (all of the luminance) to the luminance of one parallax image.

[0075] <Embodiment 3> In Embodiment 1, the display driving unit 92 of the control unit 80 alternately supplies the first right-eye image signal and the second right-eye image signal to the liquid crystal display panel 22R for the right eye one frame at a time, and alternately supplies the first left-eye image signal and the second left-eye image signal to the liquid crystal display panel 22L for the left eye one frame at a time. The display driving unit 92 may continuously supply the same image signal to the liquid crystal display panel 22R for the right eye and the liquid crystal display panel 22L for the left eye twice.

[0076] In this embodiment, the display driving unit 92 supplies the image signal to the liquid crystal display panel 22R for the right eye and the liquid crystal display panel 22L for the left eye at a period of 240 Hz (the period of one frame: 4.2 ms). The liquid crystal display panel 22R for the right eye and the liquid crystal display panel 22L for the left eye write to the pixel P at a period of 240 Hz.

[0077] Taking the case of forming the stereoscopic image SI at the third position (L2 ≤ L) as an example, the polarities of the voltage written to each of the image signal and the pixel P will be described. As shown in FIG. 18, the display driving unit 92 supplies the first right-eye image signal to the liquid crystal display panel 22R for the right eye twice continuously, and then supplies the second right-eye image signal to the liquid crystal display panel 22R for the right eye twice continuously. Then, the liquid crystal display panel 22R for the right eye displays the first right-eye image by two consecutive frames, and then displays the second right-eye image by two consecutive frames. In this case, it is preferable that the polarity of the voltage written to each pixel P of the liquid crystal display panel 22R for the right eye is inverted for each write (for each frame). Specifically, as in the first embodiment, the display driving unit 92 reverses the magnitude relationship between the potential Vcom of the common electrode of the liquid crystal display panel 22R for the right eye and the potential Vpi on the TFT side of the liquid crystal display panel 22R for each write in the pixel circuit shown in FIG. 13 (FIG. 18).

[0078] Similar to the liquid crystal display panel 22R for the right eye, the display driving unit 92 supplies the first left-eye image signal to the liquid crystal display panel 22L for the left eye twice continuously, and then supplies the second left-eye image signal to the liquid crystal display panel 22L for the left eye twice continuously. The liquid crystal display panel 22L for the left eye displays the first left-eye image by two consecutive frames, and then displays the second left-eye image by two consecutive frames. It is also preferable that the polarity of the voltage written to each pixel P of the liquid crystal display panel 22L for the left eye is inverted for each write (for each frame).

[0079] Thereby, the stereoscopic image display device 10 can further suppress the image sticking of the displays of the liquid crystal display panel 22R for the right eye and the liquid crystal display panel 22L for the left eye.

[0080] <Embodiment 4> In Embodiment 1, the polarities of the voltages written to the pixels P of the liquid crystal display panel 22R for the right eye and the liquid crystal display panel 22L for the left eye are inverted for each writing (for each frame). The display driving unit 92 may make the polarities of the voltages written to the pixels P of the liquid crystal display panel 22R for the right eye and the liquid crystal display panel 22L for the left eye the same in the sequential display of consecutive images, and may invert the polarities of the voltages written to the pixels P of the liquid crystal display panel 22R for the right eye and the liquid crystal display panel 22L for the left eye in the sequential display of the next consecutive images.

[0081] In this embodiment, the display driving unit 92 supplies the image signals to the liquid crystal display panel 22R for the right eye and the liquid crystal display panel 22L for the left eye at a 120 Hz cycle (the period of one frame: 8.4 ms), similar to Embodiment 1. The liquid crystal display panel 22R for the right eye and the liquid crystal display panel 22L for the left eye perform writing to the pixels P at a 120 Hz cycle.

[0082] Taking the case of forming the stereoscopic image SI at the third position (L2 ≦ L) as an example, the image signal and the polarities of the voltages written to the pixels P will be described. As shown in FIG. 19, the display driving unit 92 continuously supplies the first right-eye image signal and the second right-eye image signal to the liquid crystal display panel 22R for the right eye, and the liquid crystal display panel 22R for the right eye sequentially displays the first right-eye image and the second right-eye image in consecutive frames. In the sequential display of the consecutive first right-eye image and the second right-eye image, the display driving unit 92 makes the polarities of the voltages written to the pixels P of the liquid crystal display panel 22R for the right eye the same. Then, in the sequential display of the next consecutive first right-eye image and the second right-eye image, the display driving unit 92 inverts the polarities of the voltages written to the pixels P of the liquid crystal display panel 22R for the right eye.

[0083] The display driving unit 92 supplies the first left-eye image signal and the second left-eye image signal to the left-eye liquid crystal display panel 22L continuously, similar to the right-eye liquid crystal display panel 22R. The left-eye liquid crystal display panel 22L sequentially displays the first left-eye image and the second left-eye image in consecutive frames. In the sequential display of the consecutive first left-eye image and second left-eye image, the display driving unit 92 makes the polarities of the voltages written to each pixel P of the left-eye liquid crystal display panel 22L the same, and in the sequential display of the next consecutive first left-eye image and second left-eye image, it inverts the polarities of the voltages written to each pixel P of the left-eye liquid crystal display panel 22L.

[0084] Thus, the stereoscopic image display device 10 can suppress image burn-in on the right-eye liquid crystal display panel 22R and the left-eye liquid crystal display panel 22L.

[0085] <Embodiment 5> In Embodiment 1, the virtual image Pa1 of the first parallax image is displayed on the first display surface 102, and the virtual image Pa2 of the second parallax image is displayed on the second display surface 104. The stereoscopic image display device 10 may display each of the virtual images of three or more parallax images on each of three or more display surfaces.

[0086] In this embodiment, as shown in FIG. 20, the stereoscopic image display device 10 forms a stereoscopic image SI by displaying the virtual image Pa1 of the first parallax image, the virtual image Pa2 of the second parallax image, and the virtual image Pa3 of the third parallax image on the first display surface 102, the second display surface 104, and the third display surface 106, respectively. The stereoscopic image display device 10 of this embodiment includes a display unit 20, a variable focus lens unit 40, and a control unit 80, similar to the stereoscopic image display device 10 of Embodiment 1.

[0087] The display unit 20 of the present embodiment sequentially displays the first parallax image, the second parallax image, and the third parallax image in a time-division manner. The first parallax image, the second parallax image, and the third parallax image are parallax images capable of stereoscopic viewing. The display unit 20 emits the display light DL1 of the first parallax image, the second parallax image, and the third parallax image as polarized light whose polarization direction is a predetermined first direction (X direction). Similar to the first embodiment, the display unit 20 of the present embodiment includes a display device 20R for the right eye and a display device 20L for the left eye.

[0088] The display device 20R for the right eye sequentially displays the first right-eye image PR1, the second right-eye image PR2, and the third right-eye image PR3 in a time-division manner. The display device 20L for the left eye sequentially displays the first left-eye image PL1, the second left-eye image PL2, and the third left-eye image PL3 in a time-division manner. The first right-eye image PR1 and the first left-eye image PL1 form the first parallax image. The second right-eye image PR2 and the second left-eye image PL2 form the second parallax image, and the third right-eye image PR3 and the third left-eye image PL3 form the third parallax image. Other configurations of the display device 20R for the right eye and the display device 20L for the left eye are the same as those of the display device 20R for the right eye and the display device 20L for the left eye in the first embodiment.

[0089] The variable focal length lens unit 40 of the present embodiment switches the focal length with respect to the display light DL1 of the first parallax image, the focal length with respect to the display light DL1 of the second parallax image, and the focal length with respect to the display light DL1 of the third parallax image, and forms each of the first parallax image, the second parallax image, and the third parallax image as a virtual image on each of the first display surface 102, the second display surface 104, and the third display surface 106 located in the depth direction as viewed from the observer. In the present embodiment, as shown in FIG. 20, the first display surface 102, the second display surface 104, and the third display surface 106 are located in the order of the first display surface 102, the second display surface 104, and the third display surface 106 from the observer side. The first display surface 102 of the present embodiment corresponds to the shortest display surface, and the third display surface 106 of the present embodiment corresponds to the farthest display surface.

[0090] The variable focus lens unit 40 of this embodiment has a right-eye lens unit 40R and a left-eye lens unit 40L, similar to Embodiment 1. The right-eye lens unit 40R is disposed between the right-eye display device 20R and the observer's right eye, and the left-eye lens unit 40L is disposed between the left-eye display device 20L and the observer's left eye.

[0091] The right-eye lens unit 40R of this embodiment is a liquid crystal lens 600. The liquid crystal lens 600 changes the focal length with respect to polarized light having a polarization direction in a predetermined first direction according to the applied voltage. Specifically, the liquid crystal lens 600 changes the focal length with respect to the display light DL1 emitted from the display unit 20 based on the switching signal supplied from the control unit 80. As shown in FIGS. 21 and 22, the liquid crystal lens 600 has a third light-transmissive substrate 610, a fourth light-transmissive substrate 620, and liquid crystal 630.

[0092] The third light-transmissive substrate 610 is, for example, a flat glass substrate. The third light-transmissive substrate 610 and the fourth light-transmissive substrate 620 are bonded together by a sealing material 615. The third light-transmissive substrate 610 and the fourth light-transmissive substrate 620 sandwich the liquid crystal 630. The third light-transmissive substrate 610 has a first electrode 612 and an alignment film (not shown).

[0093] The first electrode 612 of the third light-transmissive substrate 610 is formed in a rectangular shape on the first main surface 610a of the third light-transmissive substrate 610. The first electrode 612 faces the second electrode 622 of the fourth light-transmissive substrate 620, which will be described later. The first electrode 612 is connected to the control unit 80.

[0094] The alignment film of the third light-transmissive substrate 610 is provided on the first electrode 612. The alignment film aligns the liquid crystal 630 in the X direction. The alignment film is, for example, a polyimide alignment film subjected to a rubbing treatment.

[0095] The fourth light-transmissive substrate 620 is a flat glass substrate, similar to the third light-transmissive substrate 610. The fourth light-transmissive substrate 620 has two second electrodes 622 and an alignment film (not shown).

[0096] The second electrodes 622 of the fourth light-transmissive substrate 620 are respectively disposed at the +X side end and the -X side end of the first main surface 620a of the fourth light-transmissive substrate 620. Each of the second electrodes 622 extends in the Y direction and is connected to the control unit 80.

[0097] The alignment film of the fourth light-transmissive substrate 620 is provided on the first main surface 620a and the second electrodes 622. Similar to the alignment film of the third light-transmissive substrate 610, the alignment film aligns the liquid crystal 630 in the X direction.

[0098] The liquid crystal 630 is a nematic liquid crystal having positive dielectric anisotropy and positive refractive index anisotropy. The liquid crystal 630 is aligned in the X direction in a state where no voltage is applied.

[0099] In the liquid crystal lens 600, by applying a voltage between the first electrode 612 and the second electrode 622, a quadratic curve-shaped potential is formed between the two second electrodes 622 when viewed in the XZ cross-section. The liquid crystal 630 aligns along the formed quadratic curve-shaped potential. The liquid crystal lens 600 acts as a lens on the display light DL1 emitted from the display unit 20 due to the alignment of the liquid crystal 630 along the quadratic curve-shaped potential. The focal length of the liquid crystal lens 600 depends on the value of the applied voltage.

[0100] In this embodiment, when a predetermined first voltage is applied between the first electrode 612 and the second electrode 622, the liquid crystal lens 600 forms the first right-eye image PR1 on the first display surface 102 by switching the focal length with respect to the display light DL1 to the first focal length. Also, when a predetermined second voltage (the first voltage < the second voltage) is applied between the first electrode 612 and the second electrode 622, the liquid crystal lens 600 forms the second right-eye image PR2 on the second display surface 104 by switching the focal length with respect to the display light DL1 to the second focal length. Further, when a predetermined third voltage (the second voltage < the third voltage) is applied between the first electrode 612 and the second electrode 622, the liquid crystal lens 600 forms the third right-eye image PR3 on the third display surface 106 by switching the focal length with respect to the display light DL1 to the third focal length.

[0101] The left-eye lens unit 40L of this embodiment is also a liquid crystal lens 600, similar to the right-eye lens unit 40R. The left-eye lens unit 40L forms the first left-eye image PL1, the second left-eye image PL2, and the third left-eye image PL3 as virtual images on the first display surface 102, the second display surface 104, and the third display surface 106, respectively, as viewed from the observer.

[0102] The control unit 80 of this embodiment controls the display unit 20 and the variable focus lens unit 40. The control unit 80 generates first parallax image data, second parallax image data, and third parallax image data representing the third parallax image based on three-dimensional object data input from an external device (not shown). In generating the first parallax image data, the second parallax image data, and the third parallax image, the control unit 80 distributes the luminance of the stereoscopic image SI to the luminance of the first parallax image, the luminance of the second parallax image, and the luminance of the third parallax image according to the position of the stereoscopic image SI.

[0103] Here, the distribution of the luminance of the stereoscopic image SI and the polarity of the voltage written to each pixel P will be described. Other configurations of the control unit 80 are the same as those of the control unit 80 in Embodiment 1.

[0104] First, the distribution of the luminance of the stereoscopic image SI will be described. In this embodiment, as shown in FIGS. 23 to 26, the distance between the observer and the intersection of the third display surface 106 and the straight line S2 (hereinafter referred to as the distance between the observer and the third display surface 106) is defined as L3. Further, on the straight line S2, the position between the first display surface 102 (the shortest display surface) and the third display surface 106 (the farthest display surface) is defined as the first position, the position where the distance from the observer is less than or equal to the distance L1 between the observer and the first display surface 102 (the shortest display surface) is defined as the second position, and the position where the distance from the observer is greater than or equal to the distance L3 between the observer and the third display surface 106 (the farthest display surface) is defined as the third position. The distance L between the observer and the stereoscopic image SI, the distance L1 between the observer and the first display surface 102, etc. are the same as those in Embodiment 1.

[0105] As shown in FIGS. 23 and 24, when forming the stereoscopic image SI at the first position (L1 < L < L3), the control unit 80 (luminance calculation unit 84), similar to the DFD method stereoscopic image display device, as shown in FIG. 27, according to the distance L between the observer and the stereoscopic image SI, changes the distribution ratio DR for distributing the luminance of the stereoscopic image SI to the luminance of the first parallax image, the luminance of the second parallax image, and the luminance of the third parallax image. In the present embodiment, when forming the stereoscopic image SI between the first display surface 102 and the second display surface 104 (FIG. 23), the control unit 80 sets the ratio for distributing to the luminance of the third parallax image to zero, and as the position where the stereoscopic image SI is formed approaches the first display surface 102, increases the ratio for distributing to the luminance of the first parallax image, and as the position where the stereoscopic image SI is formed approaches the second display surface 104, increases the ratio for distributing to the luminance of the second parallax image. Further, when forming the stereoscopic image SI between the second display surface 104 and the third display surface 106 (FIG. 24), the control unit 80 sets the ratio for distributing to the luminance of the first parallax image to zero, and as the position where the stereoscopic image SI is formed approaches the second display surface 104, increases the ratio for distributing to the luminance of the second parallax image, and as the position where the stereoscopic image SI is formed approaches the third display surface 106, increases the ratio for distributing to the luminance of the third parallax image.

[0106] When the stereoscopic image SI is located at the first position, similar to Embodiment 1, the observer perceives that the focus of the eye is located at the position of the stereoscopic image SI. Further, the observer perceives that the distance between the stereoscopic image SI due to parallax and convergence and the distance between the stereoscopic image SI due to the focus of the eye are consistent. Therefore, the stereoscopic image display device 10 can suppress the contradiction of physiological factors in stereoscopic vision and display the stereoscopic image SI.

[0107] As shown in FIG. 25, when forming the stereoscopic image SI at the second position (L≦L1), as shown in FIG. 27, the control unit 80 distributes the luminance of the stereoscopic image SI to the luminance of the first parallax image, the luminance of the second parallax image, and the luminance of the third parallax image, and makes the distribution ratio DR constant regardless of the distance L between the observer and the stereoscopic image SI. In this embodiment, the distribution ratio DR for distributing to the luminance of the first parallax image, the luminance of the second parallax image, and the luminance of the third parallax image is set to 1.0:0.0:0.0. Also in this embodiment, since the distribution ratio DR is constant, the stereoscopic image display device 10 can display the stereoscopic image SI with the correct luminance. Further, it is preferable that the control unit 80 makes the ratio of distributing to the luminance of the first parallax image in which the virtual image is displayed on the first display surface 102 equal to or greater than the ratio of distributing to the luminance of the second parallax image and the luminance of the third parallax image.

[0108] Furthermore, similar to Embodiment 1, it is preferable that the distance L between the observer and the stereoscopic image SI and the distance L1 between the observer and the first display surface 102 satisfy Equation (3). Thereby, the stereoscopic image display device 10 can suppress the contradiction of physiological factors in stereoscopic vision.

[0109] As shown in FIG. 26, when forming the stereoscopic image SI at the third position (L≧L3), as shown in FIG. 27, the control unit 80 distributes the luminance of the stereoscopic image SI to the luminance of the first parallax image, the luminance of the second parallax image, and the luminance of the third parallax image, and makes the distribution ratio DR constant regardless of the distance L between the observer and the stereoscopic image SI. In this embodiment, the distribution ratio DR for distributing to the luminance of the first parallax image, the luminance of the second parallax image, and the luminance of the third parallax image is set to 0.0:0.0:1.0.

[0110] Also in this embodiment, since the distribution ratio DR is constant, the stereoscopic image display device 10 can display the stereoscopic image SI with the correct luminance due to binocular parallax. Further, it is preferable that the control unit 80 makes the ratio of distributing to the luminance of the third parallax image in which the virtual image is displayed on the third display surface 106 equal to or greater than the ratio of distributing to the luminance of the first parallax image and the luminance of the second parallax image.

[0111] Furthermore, the distance L between the observer and the stereoscopic image SI and the distance L3 between the observer and the third display surface 106 preferably satisfy the following formula (6) (however, L ≥ L2). Thereby, similar to the first embodiment, the stereoscopic image display device 10 can suppress the contradiction of physiological factors in stereoscopic vision.

[0112]

Number

[0113] Next, taking the liquid crystal display panel 22R for the right eye as an example, the polarity of the voltage written to each pixel P will be described. In the present embodiment, the control unit 80 (display driving unit 92) supplies an image signal to the liquid crystal display panel 22R for the right eye at a period of 180 Hz (period of one frame: 5.6 ms). The liquid crystal display panel 22R for the right eye writes to the pixel P at a period of 180 Hz.

[0114] Here, taking the case where the stereoscopic image SI is formed at the first position (L1 < L < L3, between the first display surface 102 and the second display surface 104) as an example, the image signal and the polarity of the voltage written to each pixel P will be described.

[0115] As shown in FIG. 28, the control unit 80 (display driving unit 92) sequentially supplies the first right-eye image signal, the second right-eye image signal, and the third right-eye image signal for displaying the third right-eye image to the liquid crystal display panel 22R for the right eye one frame at a time, and the liquid crystal display panel 22R for the right eye sequentially displays the first right-eye image, the second right-eye image, and the third right-eye image. In this case, the polarity of the voltage written to each pixel P of the liquid crystal display panel 22R for the right eye is inverted for each writing (for each frame). Thereby, the stereoscopic image display device 10 can suppress the burn-in of the display of the liquid crystal display panel 22R for the right eye.

[0116] In this embodiment, in particular, since the number of display surfaces is odd (three), the polarity of the voltage written in the display of the first right-eye image and the polarity of the voltage written in the display of the next first right-eye image are inverted. Also, the polarity of the voltage written in the display of the second right-eye image and the polarity of the voltage written in the display of the next second right-eye image, and the polarity of the voltage written in the display of the third right-eye image and the polarity of the voltage written in the display of the next third right-eye image are also inverted. Therefore, the stereoscopic image display device 10 can more effectively suppress burn-in of the display on the liquid crystal display panel 22R for the right eye. Similar to the display on the liquid crystal display panel 22R for the right eye, the stereoscopic image display device 10 can more effectively suppress burn-in of the display on the liquid crystal display panel 22L for the left eye.

[0117] As described above, the stereoscopic image display device 10 of this embodiment displays the virtual image Pa1 of the first parallax image, the virtual image Pa2 of the second parallax image, and the virtual image Pa3 of the third parallax image on the first display surface 102, the second display surface 104, and the third display surface 106, respectively, to display the stereoscopic image SI. Even when the stereoscopic image display device 10 of this embodiment forms the stereoscopic image SI at a position closer to the observer than the position of the first display surface 102 or at a position farther from the observer than the position of the third display surface 106, it can suppress the contradiction of physiological factors in stereoscopic vision. Therefore, the stereoscopic image display device 10 of this embodiment can also display the stereoscopic image SI over a wide range and suppress the contradiction of physiological factors in stereoscopic vision. Furthermore, since the number of display surfaces is odd, the stereoscopic image display device 10 can more effectively suppress burn-in of the displays on the liquid crystal display panel 22R for the right eye and the liquid crystal display panel 22L for the left eye.

[0118] <Modification Example> Although the embodiment has been described, the present disclosure can be variously modified without departing from the gist. Hereinafter, there may be cases where the first to third parallax images are referred to as parallax images, the first to third right-eye images PR1 to PR3 are referred to as right-eye images, and the first to third left-eye images PL1 to PL3 are referred to as left-eye images.

[0119] In the embodiment, the right-eye display device 20R and the left-eye display device 20L of the display unit 20 include a liquid crystal display panel (right-eye liquid crystal display panel 22R, left-eye liquid crystal display panel 22L) and a light source unit 32, but the configurations of the right-eye display device 20R and the left-eye display device 20L are not limited thereto. For example, the right-eye display device 20R and the left-eye display device 20L may include a self-luminous display panel and a polarizing plate. The self-luminous display panel is, for example, an organic EL (Electro Luminescence) display panel that is actively matrix-driven by a TFT.

[0120] In the embodiment, the display unit 20 includes a right-eye display device 20R and a left-eye display device 20L. The display unit 20 may display a parallax image by one display device. For example, as shown in FIG. 29, the display unit 20 may include a display device 200 that sequentially displays a first right-eye image PR1, a second right-eye image PR2, a first left-eye image PL1, and a second left-eye image PL2 in a time-division manner. The display device 200 includes a liquid crystal display panel 202 and a light source unit 32. In this case, the right-eye lens unit 40R and the left-eye lens unit 40L include a liquid crystal shutter 204 that blocks the display light DL1 emitted from the display device 200. The liquid crystal shutter 204 of the right-eye lens unit 40R blocks the display light DL1 of the left-eye image based on a shielding signal from the control unit 80. Also, the liquid crystal shutter 204 of the left-eye lens unit 40L blocks the display light DL1 of the right-eye image based on a shielding signal from the control unit 80. The right-eye lens unit 40R and the left-eye lens unit 40L switch the focal length according to the right-eye image or the left-eye image displayed on the display device 200.

[0121] Also, as shown in FIG. 30, the display unit 20 may include a display device 210 using a parallax barrier method or a lenticular lens method. For example, the display device 210 spatially separates the parallax image displayed on the liquid crystal display panel 214 into a right-eye image and a left-eye image by the lenticular lens 212. The display light DL1 of the right-eye image enters the right-eye lens unit 40R, and the display light DL1 of the left-eye image enters the left-eye lens unit 40L.

[0122] The polarization switching unit 50 of the variable focus lens unit 40 is not limited to a TN liquid crystal element. The polarization switching unit 50 may be a PLZT (Lead Lanthanum Zirconate Titanate) element, an element utilizing the Faraday effect, or the like.

[0123] Furthermore, the configurations of the right-eye lens unit 40R and the left-eye lens unit 40L are not limited to one set of polarization switching unit 50 and polarization bifocal lens 60, or liquid crystal lens 600. For example, the right-eye lens unit 40R and the left-eye lens unit 40L may be liquid lenses utilizing electro-wetting, whose focal length changes according to the applied voltage. Furthermore, in Embodiment 5, the right-eye lens unit 40R and the left-eye lens unit 40L may switch the focal length in three steps by two sets of polarization switching units 50 and polarization bifocal lenses 60.

[0124] The stereoscopic image display device 10 may display each virtual image of a plurality of parallax images on each of a plurality of display surfaces. In particular, when the number of display surfaces is an odd number of 3 or more, as in Embodiment 5, the stereoscopic image display device 10 can further suppress image burn-in.

[0125] In Embodiment 1, the three-dimensional object data is input from an external device to the control unit 80, and the display surface data and the viewpoint data are stored in the storage unit 82. At least one of the display surface data and the viewpoint data may be input from the external device to the control unit 80 together with the three-dimensional object data.

[0126] The control unit 80 may be included in an independent device including a CPU, a RAM, a ROM, and the like.

[0127] As described above, the preferred embodiments have been explained, but the present disclosure is not limited to such specific embodiments, and the present disclosure includes the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0128] 10 Stereoscopic image display device, 20 Display unit, 20R Right-eye display device, 20L Left-eye display device, 22R Right-eye liquid crystal display panel, 22L Left-eye liquid crystal display panel, 23D Data driver, 23G Gate driver, 32 Light source unit, 40 Variable focus lens unit, 40R Right-eye lens unit, 40L Left-eye lens unit, 50 Polarization switching unit, 52 Liquid crystal, 53 Electrodes, 54a, 54b Translucent substrates, 56 Sealing material, 60 Polarization bifocal lens, 61 First translucent substrate, 61a First main surface of the first translucent substrate, 62 Second translucent substrate, 64 Liquid crystal, 66 Fresnel lens, 67 Sealing material, 80 Control unit, 82 Memory unit, 84 Luminance calculation unit, 86 Parallax image generation unit, 88 Display image generation unit, 92 Display drive unit, 94 Optical drive unit, 95 CPU, 96 ROM, 97 RAM, 98 Input / output interface, 99 Bus, 102 First display surface, 104 Second display surface, 106 Third display surface, 200 Display device, 202 Liquid crystal display panel, 204 Liquid crystal shutter, 210 Display device, 212 Lenticular lens, 214 Liquid crystal display panel, 600 Liquid crystal lens, 610 Third translucent substrate, 610a First main surface of the third translucent substrate, 612 First electrode, 615 Sealing material, 620 Fourth translucent substrate, 620a First main surface of the fourth translucent substrate, 622 Second electrode, 630 Liquid crystal, SI Stereoscopic image, DL1, DL2 Display light, P Pixel, Pa1 Virtual image of the first parallax image, Pa2 Virtual image of the second parallax image, Pa3 Virtual image of the third parallax image, PR1 First right-eye image, PR2 Second right-eye image, PR3 Third right-eye image, PL1 First left-eye image, PL2 Second left-eye image, PL3 Third left-eye image, DR Distribution ratio, S1, S2, S3 Straight lines, M1 Intermediate point, SIL, LP1, LP2 Luminance, L, L1, L2, L3, Da, Dv Distances, Vcom, Vpi Potentials

Claims

1. A display unit that sequentially displays parallax images capable of stereoscopic viewing, A variable focus lens unit that switches the focal length for the display light of each of the parallax images and forms a virtual image of each of the parallax images on each of a plurality of display surfaces located in the depth direction as viewed from the observer, A control unit that distributes the luminance of the stereoscopic image formed from the virtual images of the parallax images to the luminance of the parallax images, and comprising: The control unit distributes the luminance of the stereoscopic image to the luminance of at least one of the parallax images, When the display surface having the shortest distance from the observer among the plurality of display surfaces is defined as the shortest display surface, and the display surface having the longest distance from the observer among the plurality of display surfaces is defined as the farthest display surface, The control unit, When the position of the stereoscopic image is a first position located between the shortest display surface and the farthest display surface, changes the distribution ratio for distributing the luminance of the stereoscopic image to the luminance of the parallax images according to the distance between the observer and the stereoscopic image, When the position of the stereoscopic image is a second position where the distance from the observer is equal to or less than the distance between the observer and the shortest display surface, or a third position where the distance from the observer is equal to or greater than the distance between the observer and the farthest display surface, makes the distribution ratio constant, A stereoscopic image display device.

2. A display unit that sequentially displays two parallax images capable of stereoscopic viewing, A variable focus lens unit that switches the focal length for the display light of each of the two parallax images and forms a virtual image of each of the parallax images on each of two display surfaces located in the depth direction as viewed from the observer, A control unit that distributes the luminance of the stereoscopic image formed from the virtual images of the parallax images to the luminance of the parallax images, and comprising: The control unit distributes the luminance of the stereoscopic image to the luminance of at least one of the parallax images, When the display surface having the shortest distance from the observer among the two display surfaces is defined as the shortest display surface, and the display surface having the longest distance from the observer among the two display surfaces is defined as the farthest display surface, The control unit, When the position of the stereoscopic image is a first position located between the shortest display surface and the farthest display surface, changes the distribution ratio for distributing the luminance of the stereoscopic image to the luminance of the parallax images according to the distance between the observer and the stereoscopic image, When the position of the stereoscopic image is at a second position where the distance from the observer is less than or equal to the distance between the observer and the shortest display surface, or at a third position where the distance from the observer is greater than or equal to the distance between the observer and the farthest display surface, the distribution ratio is made constant. Stereoscopic image display device.

3. When the position of the stereoscopic image is at the second position or the third position, the ratio of distribution to the luminance of the parallax image is greater than zero. The stereoscopic image display device according to claim 1 or 2.

4. The display unit includes a liquid crystal display panel that sequentially displays any one of the parallax image, the right-eye image that forms each of the parallax images, and the left-eye image that forms each of the parallax images. When the images are displayed on the liquid crystal display panel by two consecutive frames, the polarity of the voltage written to each pixel of the liquid crystal display panel is inverted for each writing. The stereoscopic image display device according to claim 1 or 2.

5. The display unit includes a liquid crystal display panel that sequentially displays any one of the parallax image, the right-eye image that forms each of the parallax images, and the left-eye image that forms each of the parallax images. When each of the images is sequentially displayed on the liquid crystal display panel by each of consecutive frames, in the display of the consecutive images, the polarity of the voltage written to the pixels of the liquid crystal display panel is the same, and when the next consecutive images are displayed, the polarity of the voltage written to the pixels of the liquid crystal display panel is inverted. The stereoscopic image display device according to claim 1 or 2.

6. The number of the plurality of display surfaces is an odd number of 3 or more. The display unit includes a liquid crystal display panel that sequentially displays any one of the parallax image, the right-eye image that forms each of the parallax images, and the left-eye image that forms each of the parallax images. When each of the images is sequentially displayed on the liquid crystal display panel by each of consecutive frames, the polarity of the voltage written to the pixels of the liquid crystal display panel is inverted for each frame. The stereoscopic image display device according to claim 1.

7. When the position of the stereoscopic image is the second position, the control unit displays one of the parallax images on the shortest display surface, and displays the other one of the parallax images on another display surface other than the shortest display surface, and controls the ratio of the luminance distributed to the parallax image displayed on the shortest display surface to be equal to or greater than the ratio of the luminance distributed to the parallax image displayed on the other display surface. When the position of the stereoscopic image is the third position, the control unit displays one of the parallax images on the farthest display surface, and displays the other one of the parallax images on another display surface other than the farthest display surface, and controls the ratio of the luminance distributed to the parallax image displayed on the farthest display surface to be equal to or greater than the ratio of the luminance distributed to the parallax image displayed on the other display surface. The stereoscopic image display device according to claim 1 or 2.

8. A luminance calculation unit that obtains a distribution ratio for distributing the luminance of the stereoscopic image to the luminance of the parallax image based on the position of the stereoscopic image to be displayed and the position of each of a plurality of display surfaces on which virtual images of the parallax images forming the stereoscopic image are displayed. A parallax image generation unit that generates parallax image data representing the parallax image based on the distribution ratio obtained by the luminance calculation unit. Among the plurality of display surfaces, the display surface with the shortest distance from the observer is defined as the shortest display surface, and the display surface with the longest distance from the observer among the plurality of display surfaces is defined as the farthest display surface. The luminance calculation unit is When the position of the stereoscopic image is the first position located between the shortest display surface and the farthest display surface, the distribution ratio for distributing the luminance of the stereoscopic image to the luminance of the parallax image is changed according to the distance between the observer and the stereoscopic image. When the position of the stereoscopic image is the second position where the distance from the observer is less than or equal to the distance between the observer and the shortest display surface, or the third position where the distance from the observer is greater than or equal to the distance between the observer and the farthest display surface, the distribution ratio is made constant. Image generation device.

Images