Display device

Abstract

To provide a display device configured so that the viewpoint pitch in three-dimensional image display in which the number of viewpoints is large can be made narrower than the viewpoint pitch in three-dimensional image display in which the number of viewpoints is small.SOLUTION: A display device 100 includes an image display unit 10, a first lens element 20, and a second lens element 30. The image display unit 10 includes a plurality of pixels, and displays parallax images corresponding to each of N1 viewpoints (N1 is an integer of 2 or greater) along a predetermined direction and parallax images corresponding to each of N2 viewpoints (N2 is an integer greater than N1) along the predetermined direction. When the parallax images corresponding to each of the N1 viewpoints are displayed on the image display unit 10, the first lens element 20 distributes light emitted from the plurality of pixels into the N1 viewpoints. When the parallax images corresponding to each of the N2 viewpoints are displayed on the image display unit 10, the second lens element 30 distributes light emitted from the plurality of pixels into each of the N2 viewpoints.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a display device. [Background technology]

[0002] Display devices that display flat images (2D images) and stereoscopic images (3D images) without the need for glasses are known. Furthermore, display devices that can switch the number of viewpoints when displaying stereoscopic images are also known. Display devices that can switch the number of viewpoints can display high-resolution stereoscopic images by reducing the number of viewpoints. Furthermore, display devices that can switch the number of viewpoints can impart motion parallax to stereoscopic images by increasing the number of viewpoints. For example, the image display device disclosed in Patent Document 1 includes an optical element whose refractive index distribution changes depending on the applied voltage, a voltage control unit that controls the voltage applied to the optical element so that the optical element acts as two Fresnel lenses with different numbers of stages, and a display unit that displays images.

[0003] In the image display device of Patent Document 1, the number of parallaxes (number of viewpoints) can be changed by changing the lens pitch of a Fresnel lens in an optical element. Furthermore, in Patent Document 1, when the lens pitch of the Fresnel lens in a first mode with a small number of parallaxes is Lp_1 and the lens pitch of the Fresnel lens in a second mode with a large number of parallaxes is Lp_2, the relationship Lp_1×m=Lp_2×n (n: an integer equal to or greater than 1, m: an integer greater than n) is satisfied. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5694556 Summary of the Invention [Problem to be solved by the invention]

[0005] When the number of viewpoints is small, it is desirable for the image display device to have a wider viewpoint pitch at the optimum viewing distance in order to prevent reverse viewing. On the other hand, when the number of viewpoints is large, it is desirable for the image display device to have a narrow viewpoint pitch in order to smooth motion parallax. The optimum viewing distance is the distance at which the viewpoint area is at its largest, and the viewpoint pitch is the width of the viewpoint area. The viewpoint pitch is determined by the optimum viewing distance, the pixel pitch, the distance between the lens and the pixel, and the refractive index of the lens. However, in the image display device of Patent Document 1, even if the lens pitch is switched by voltage control, the viewpoint pitch does not change because the distance between the lens and the pixel, the refractive index of the lens, etc. do not change.

[0006] The present disclosure has been made in consideration of the above circumstances, and aims to provide a display device that can make the viewpoint pitch in stereoscopic image display with a large number of viewpoints narrower than the viewpoint pitch in stereoscopic image display with a small number of viewpoints. [Means for solving the problem]

[0007] In order to achieve the above object, the display device of the present disclosure comprises: an image display unit having a plurality of pixels and displaying parallax images corresponding to N1 (N1 is an integer equal to or greater than 2) viewpoints along a predetermined direction, and parallax images corresponding to N2 (N2 is an integer greater than N1) viewpoints along the predetermined direction; a first lens element that overlaps the image display unit and that, when parallax images corresponding to the N1 viewpoints are displayed on the image display unit, distributes light emitted from the plurality of pixels that display the respective parallax images to the N1 viewpoints corresponding to the respective parallax images; a second lens element that overlaps the image display unit and that, when parallax images corresponding to the N2 viewpoints are displayed on the image display unit, distributes light emitted from the plurality of pixels that display the respective parallax images to the N2 viewpoints corresponding to the respective parallax images. 、 The viewpoint pitch of the N2 viewpoints is narrower than the viewpoint pitch of the N1 viewpoints. [Effects of the Invention]

[0008] According to the present disclosure, the viewpoint pitch in a stereoscopic image display with a large number of viewpoints can be made narrower than the viewpoint pitch in a stereoscopic image display with a small number of viewpoints. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing a cross section of a display device according to a first embodiment. [Figure 2] 1 is a top view showing pixels of an image display unit according to Embodiment 1. FIG. [Figure 3] 1 is a schematic diagram showing a stereoscopic image display (N1=2) on an XZ cross section including a center line of the display device perpendicular to the display surface according to the first embodiment. FIG. [Figure 4] FIG. 2 is a schematic diagram showing a cross section of a first lens element according to the first embodiment. [Figure 5] FIG. 3 is a top view showing a second substrate of the first lens element according to the first embodiment. [Figure 6] FIG. 4 is a schematic diagram illustrating the operation of the first lens element according to the first embodiment. [Figure 7] 1 is a schematic diagram showing a stereoscopic image display (N1=6) on an XZ cross section including a center line of the display device perpendicular to the display surface according to the first embodiment. FIG. [Figure 8] FIG. 3 is a schematic diagram showing a cross section of a second lens element according to the first embodiment. [Figure 9] FIG. 4 is a top view showing a fourth substrate of the second lens element according to the first embodiment. [Figure 10] 10 is a diagram showing values of lens pitch, viewpoint pitch, and optimum visible distance for Example 1, Example 2, Comparative Example 1, and Comparative Example 2 according to Embodiment 1. FIG. [Figure 11] FIG. 10 is a schematic diagram showing an optical model of stereoscopic image display at N1 viewpoints at the center of the display device according to the second embodiment. [Figure 12] FIG. 10 is a schematic diagram showing an optical model of stereoscopic image display from N2 viewpoints at the center of the display device according to the second embodiment. [Figure 13]FIG. 10 is a schematic diagram showing an optical model of stereoscopic image display at N1 viewpoints at the end of the display device in the +X direction according to the second embodiment. [Figure 14] FIG. 10 is a schematic diagram showing an optical model of stereoscopic image display from N2 viewpoints at the end of the display device in the +X direction according to the second embodiment. [Figure 15] FIG. 10 is a diagram showing values of lens pitch, viewpoint pitch, and optimum visible distance in Examples 3 and 4 according to the second embodiment. [Figure 16] FIG. 10 is a schematic diagram showing a cross section of a display device according to a third embodiment. [Figure 17] FIG. 11 is a schematic diagram showing an optical model of stereoscopic image display at N1 viewpoints at the center of the display device according to the third embodiment. [Figure 18] FIG. 11 is a schematic diagram showing an optical model of stereoscopic image display from N2 viewpoints at the center of the display device according to the third embodiment. [Figure 19] FIG. 11 is a schematic diagram showing an optical model of stereoscopic image display from N1 viewpoints at the −X direction end of the display device according to the third embodiment. [Figure 20] FIG. 10 is a diagram showing values of lens pitch, viewpoint pitch, and optimum visible distance in Example 5 according to Embodiment 3. [Figure 21] FIG. 10 is a schematic diagram showing a cross section of a display device according to a fourth embodiment. [Figure 22] FIG. 10 is a diagram showing values of lens pitch, viewpoint pitch, and optimum visible distance in Example 6 according to Embodiment 4. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a display device according to an embodiment will be described with reference to the drawings.

[0011] <Embodiment 1> 1 to 10, a display device 100 according to this embodiment will be described. Display device 100 displays a planar image and a stereoscopic image. Furthermore, when displaying a stereoscopic image, display device 100 can switch the number of viewpoints between N1 (N1 is an integer equal to or greater than 2) and N2 (N2 is an integer greater than N1). As shown in FIG. 1, display device 100 includes image display unit 10, first lens element 20, and second lens element 30. For ease of understanding, the description herein will be made assuming that the rightward direction of display device 100 in FIG. 1 (the rightward direction on the paper) is the +X direction, the upward direction (the upward direction on the paper) is the +Z direction, and the direction perpendicular to the +X direction and the +Z direction (toward the depth of the paper) is the +Y direction.

[0012] In this embodiment, first lens element 20 and second lens element 30 are stacked in this order on display surface 10a of image display unit 10. When display device 100 displays a planar image, first lens element 20 and second lens element 30 do not function as lenses, and the planar image displayed on image display unit 10 is displayed. When display device 100 displays a stereoscopic image with N1 viewpoints, only first lens element 20 functions as a lens. When display device 100 displays a stereoscopic image with N2 viewpoints, only second lens element 30 functions as a lens.

[0013] The image display unit 10 of the display device 100 displays a planar image, parallax images corresponding to N1 (N1 is an integer equal to or greater than 2) viewpoints along the X direction, and parallax images corresponding to N2 (N2 is an integer greater than N1) viewpoints along the X direction. The image display unit 10 has a plurality of pixels 12 arranged in a matrix.

[0014] FIG. 2 shows a pixel 12 of the image display unit 10. As shown in FIG. 2, the pixel 12 is formed of a red (R) sub-pixel 12R, a green (G) sub-pixel 12G, and a blue (B) sub-pixel 12B aligned in the Y direction. The sub-pixels 12R, 12G, and 12B are repeatedly arranged in the Y direction, and sub-pixels 12R, 12G, and 12B of the same color are arranged in the X direction at a pixel pitch P (horizontal stripe arrangement). In this embodiment, when a stereoscopic image is displayed with N1 viewpoints, N1 pixels 12 adjacent in the X direction display parallax images corresponding to the N1 viewpoints. In this specification, the N1 pixels 12 adjacent in the X direction that display parallax images are referred to as first pixel units 14. If the pitch of the pixels 12 is P, the pitch of the first pixel units 14 is P×N1. Note that FIG. 2 shows first pixel units 14 where N1=2.

[0015] Furthermore, when a stereoscopic image is displayed with N2 viewpoints, N2 pixels 12 adjacent in the X direction display parallax images corresponding to the N2 viewpoints. In this specification, the N2 pixels 12 adjacent in the X direction that display parallax images are referred to as second pixel units 16. The pitch of the second pixel units 16 is P×N2. Note that FIG. 2 shows second pixel units 16 where N2=6. The image display unit 10 is, for example, an organic EL (Electro Luminescence) display panel.

[0016] First lens element 20 of display device 100 overlaps image display unit 10 and is disposed on the display surface 10a side of image display unit 10. When parallax images corresponding to the N1 viewpoints are displayed on image display unit 10, first lens element 20 distributes light emitted from pixels 12 included in first pixel unit 14 that displays the parallax images to the N1 viewpoints corresponding to the parallax images, as shown in FIG. 3. In FIG. 3, symbol H1 represents the distance between vertex Lt1 of the lens of first lens element 20 and pixel 12. Symbol J represents the center line of display device 100 that is perpendicular to display surface 101.

[0017] Specifically, when parallax images corresponding to the N1 viewpoints are displayed on the image display unit 10, the first lens element 20 functions as a lenticular lens array in which lenticular lenses extending in the Y direction are arranged in the X direction. Each lenticular lens of the first lens element 20 distributes light emitted from the first pixel units 14 that display the N1 parallax images adjacent in the X direction to the N1 viewpoints along the X direction. In this embodiment, the lens pitch Lp1 of the first lens element 20 in the X direction is set to be slightly smaller than the pitch P×N1 of the first pixel units 14. The focal length of the first lens element 20 is set to be approximately equal to the distance H1 between the vertex Lt1 of the lens and the pixel 12.

[0018] Furthermore, in this embodiment, the lens pitch Lp1 of the first lens element 20 is set slightly smaller than the pitch P×N1 of the first pixel units 14. Therefore, light emitted from the pixels 12 corresponding to the N1 viewpoints of the first pixel units 14 overlaps in the viewpoint region SR1 regardless of the positions of the first pixel units 14 in the image display unit 10. The viewpoint region SR1 refers to an area where the observer can observe only the parallax images corresponding to the respective viewpoints when the observer's right eye or left eye is positioned therein. In this specification, the distance in the +Z direction between the display surface 101 of the display device 100 and the observation surface S at which the width of the viewpoint region SR1 in the X direction is widest is defined as the optimal viewing distance OD1. In this specification, the width (period of the projected image) of the projected image of the pixels 12 projected onto the observation surface S at the optimal viewing distance OD1 is defined as the viewpoint pitch e1.

[0019] First lens element 20 is, for example, a liquid crystal lens that functions as a lenticular lens array. As shown in Fig. 4, first lens element (liquid crystal lens) 20 has first substrate 21, second substrate 22, first electrode 24, second electrodes 25 and 26, and liquid crystal 28. In this embodiment, second substrate 22 is disposed on display surface 10a of image display unit 10, as shown in Fig. 1.

[0020] The first substrate 21 and the second substrate 22 are light-transmitting. The first substrate 21 and the second substrate 22 are, for example, flat glass substrates. As shown in FIG. 4, the first substrate 21 and the second substrate 22 are bonded together with a sealant 29, and a liquid crystal 28 is sandwiched between them.

[0021] The first electrode 24 is formed in a rectangular shape from ITO (Indium Tin Oxide) on the first main surface 21a of the first substrate 21. The first electrode 24 faces comb-tooth portions 25a of the second electrode 25 and comb-tooth portions 26a of the second electrode 26, which will be described later. The first electrode 24 is connected to a control unit (not shown).

[0022] The second electrodes 25 and 26 are made of ITO and formed in a comb-like shape on the first main surface 22a of the second substrate 22. As shown in FIG. 5, the second electrodes 25 and 26 have comb-tooth portions 25a and 26a, respectively. The comb-tooth portions 25a extend in the +Y direction, and the comb-tooth portions 26a extend in the -Y direction. The comb-tooth portions 25a and 26a are arranged alternately and parallel to each other along the X direction. When the display device 100 is viewed from the +Z direction, the spacing between the center lines of the comb-tooth portions 25a is the lens pitch Lp1 of the first lens element 20 in the X direction, and the spacing between the center lines of the comb-tooth portions 25a and 26a is 1 / 2 of Lp1. The second electrodes 25 and 26, like the first electrode 24, are connected to a control unit.

[0023] The liquid crystal 28 is sandwiched between the first substrate 21 and the second substrate 22. The liquid crystal 28 is, for example, a positive nematic liquid crystal. The liquid crystal 28 is oriented in the X direction by an orientation film (not shown).

[0024] Here, the operation of first lens element 20 will be described. For example, when the control unit sets first electrode 24 and second electrodes 25, 26 to the same potential (for example, ground potential), no voltage is applied to liquid crystal 28, and liquid crystal 28 maintains its orientation in the X direction. In a state in which liquid crystal 28 maintains its orientation in the X direction, no lens effect is produced, and first lens element 20 does not function as a lenticular lens array.

[0025] Meanwhile, by separately controlling the voltage applied between the first electrode 24 and the second electrode 25 and the voltage applied between the first electrode 24 and the second electrode 26 of the second substrate, a quadratic curved potential is formed between the first substrate 21 and the second substrate 22. The molecules M of the liquid crystal 28 are oriented as shown in FIG. 6 by the quadratic curved potential thus formed. This change in the orientation of the liquid crystal 28 causes a refractive index distribution in the first lens element 20 that follows the quadratic curved potential, and the first lens element 20 functions as a lenticular lens array extending in the Y direction. The lens pitch of the formed lenticular lenses is Lp1, and the focal length of the formed lenticular lenses is approximately equal to the interval H1. As a result, the display device 100 can display a stereoscopic image from N1 viewpoints when parallax images corresponding to each of the N1 viewpoints are displayed on the image display unit 10.

[0026] Second lens element 30 of display device 100 is disposed on the display surface 10a side of image display unit 10. In this embodiment, second lens element 30 is disposed above first lens element 20.

[0027] When parallax images corresponding to the N2 viewpoints are displayed on image display unit 10, second lens element 30 distributes light emitted from pixels 12 included in second pixel unit 16 that displays the parallax images to the N2 viewpoints corresponding to the parallax images, as shown in Fig. 7. In Fig. 7, symbol H2 represents the distance between vertex Lt2 of the lens of second lens element 30 and pixel 12.

[0028] Specifically, when parallax images corresponding to the N2 viewpoints are displayed on the image display unit 10, the second lens element 30 functions as a lenticular lens array in which lenticular lenses extending in the Y direction are arranged in the X direction. Each lenticular lens of the second lens element 30 distributes light emitted from the second pixel units 16 that display the N2 parallax images adjacent in the X direction to the N2 viewpoints along the X direction. In this embodiment, the lens pitch Lp2 of the second lens element 30 in the X direction is set to be slightly smaller than the pitch P×N2 of the second pixel units 16. In addition, the focal length of the second lens element 30 is set to be approximately equal to the distance H2 between the vertex Lt2 of the lens and the pixel 12.

[0029] Furthermore, because the lens pitch Lp2 of the second lens element 30 is set slightly smaller than the pitch P×N2 of the second pixel units 16, light emitted from the pixels 12 corresponding to each of the N2 viewpoints of the second pixel units 16 overlaps in the viewpoint region SR2 regardless of the position of the second pixel units 16 in the image display unit 10. Similar to the viewpoint region SR1, the viewpoint region SR2 refers to an area where the observer can observe only the parallax images corresponding to each viewpoint when the observer's right eye or left eye is positioned therein. In this specification, the distance in the +Z direction between the display surface 101 of the display device 100 and the observation surface S at which the width of the viewpoint region SR2 in the X direction is widest is referred to as the optimal viewing distance OD2. In this specification, the width (period of the projected image) of the projected image of the pixels 12 projected onto the observation surface S at the optimal viewing distance OD2 is referred to as the viewpoint pitch e2.

[0030] Similar to first lens element 20, second lens element 30 is a liquid crystal lens that functions as a lenticular lens array. As shown in FIG. 8, second lens element (liquid crystal lens) 30 has third substrate 31, fourth substrate 32, third electrode 34, fourth electrodes 35 and 36, and liquid crystal 38. In this embodiment, as shown in FIG. 1, fourth substrate 32 is disposed on first substrate 21 of first lens element 20. Since third substrate 31, fourth substrate 32, and liquid crystal 38 of second lens element 30 are similar to first substrate 21, second substrate 22, and liquid crystal 28 of first lens element 20, only third electrode 34 and fourth electrodes 35 and 36 will be described.

[0031] The third electrode 34 is formed in a rectangular shape from ITO on the first main surface 31a of the third substrate 31. The third electrode 34 faces comb-tooth portions 35a of the fourth electrode 35 and comb-tooth portions 36a of the fourth electrode 36, which will be described later. The third electrode 34 is connected to a control unit (not shown).

[0032] The fourth electrodes 35 and 36 are made of ITO and formed in a comb-like shape on the first main surface 32a of the fourth substrate 32. As shown in FIG. 9 , the fourth electrodes 35 and 36 have comb-tooth portions 35a and 36a, respectively. The comb-tooth portions 35a extend in the +Y direction, and the comb-tooth portions 36a extend in the −Y direction. The comb-tooth portions 35a and 36a are arranged alternately and parallel to each other along the X direction. When the display device 100 is viewed from the +Z direction, the spacing between the center lines of the comb-tooth portions 35a is the lens pitch Lp2 of the second lens element 30 in the X direction, and the spacing between the center lines of the comb-tooth portions 35a and 36a is ½ of Lp2. The fourth electrodes 35 and 36, like the third electrode 34, are connected to a control unit.

[0033] When the control unit sets the third electrode 34 and the fourth electrodes 35 and 36 to the same potential, no voltage is applied to the liquid crystal 38, and therefore no lens effect is produced in the second lens element 30. Therefore, the second lens element 30 does not function as a lenticular lens array. On the other hand, by separately controlling the voltage applied between the third electrode 34 and the fourth electrode 35 and the voltage applied between the third electrode 34 and the fourth electrode 36, the second lens element functions as a lenticular lens array extending in the Y direction, similar to the first lens element 20. The lens pitch of the formed lenticular lenses is Lp2, and the focal length of the formed lenticular lenses is approximately equal to the interval H2. As a result, when parallax images corresponding to each of the N2 viewpoints are displayed on the image display unit 10, the display device 100 can display a stereoscopic image from N2 viewpoints.

[0034] In this embodiment, the lens pitch Lp2 of the second lens element 30 in the X direction satisfies the condition of the following formula (1).

[0035]

number

[0036] By satisfying the condition of formula (1), the viewpoint pitch e2 in stereoscopic image display with N2 (N2>N1) viewpoints can be made narrower than the viewpoint pitch e1 in stereoscopic image display with N1 (an integer equal to or greater than 2) viewpoints. For example, if image display unit 10 is a 6.9-inch WQHD (Wide Quad High Definition) display with a pixel pitch P of 60 μm and a diagonal resolution of 6.9 inches, and first lens element 20 has the following conditions: N1=2, H1=0.5 mm, Lp1=119.9 μm, OD1=399 mm, and e1=71.9 mm, and the distance H2 between lens vertex Lt2 of second lens element 30 and pixel 12 is H2=1.5 mm, then by satisfying the condition of formula (1), the viewpoint pitch e2 can be made narrower than the viewpoint pitch e1, as shown in examples 1 and 2 of Figure 10. On the other hand, as shown in Comparative Examples 1 and 2 in FIG. 10, when Lp1×(N2 / N1)=Lp2 is satisfied, the viewpoint pitch e2 cannot be made narrower than the viewpoint pitch e1.

[0037] Furthermore, as shown in Fig. 10, by satisfying the condition of formula (1), it is possible to reduce the difference between the optimal viewing distance OD2 for stereoscopic image display from N2 viewpoints and the optimal viewing distance OD1 for stereoscopic image display from N1 viewpoints. This reduces the amount of movement of the viewer in the Z direction when the number of viewpoints is changed.

[0038] The values of the viewpoint pitch e2, the optimum viewing distance OD2, etc. shown in Fig. 10 can be obtained from an optical model. Generally, the optimum viewing distances OD1 and OD2 depend on the size of the image display unit 10. For example, if the size of the image display unit 10 is 4 to 13 inches diagonally, the optimum viewing distances OD1 and OD2 are preferably 150 mm to 750 mm. If the size of the image display unit 10 is 14 to 30 inches diagonally, the optimum viewing distances OD1 and OD2 are preferably 250 mm to 1300 mm.

[0039] As described above, when displaying a stereoscopic image, display device 100 can switch the number of viewpoints between N1 (an integer equal to or greater than 2) and N2 (N2>N1), and the viewpoint pitch e2 when displaying a stereoscopic image with N2 viewpoints can be made narrower than the viewpoint pitch e1 when displaying a stereoscopic image with N1 viewpoints. In other words, the viewpoint pitch when displaying a stereoscopic image with a large number of viewpoints can be made narrower than the viewpoint pitch when displaying a stereoscopic image with a small number of viewpoints. Furthermore, when the number of viewpoints is switched, the difference between the optimal viewing distance OD1 and the optimal viewing distance OD2 can be reduced.

[0040] <Embodiment 2> In embodiment 1, the lens pitch Lp2 of second lens elements 30 satisfies the condition of formula (1), but in this embodiment, the interval H2 and lens pitch Lp2 of second lens elements 30 each satisfy the conditions of formulas (2) and (3) below, respectively. The other configurations of this embodiment are the same as those of embodiment 1. Note that if the conditions of formulas (2) and (3) are satisfied, the condition of formula (1) is also satisfied.

[0041]

number

number

[0042] By satisfying the conditions of formula (2) and formula (3), the viewpoint pitch e2 in stereoscopic image display from N2 viewpoints can be made narrower than the viewpoint pitch e1 in stereoscopic image display from N1 viewpoints. Furthermore, the difference between the optimal viewing distance OD2 in stereoscopic image display from N2 viewpoints and the optimal viewing distance OD1 in stereoscopic image display from N1 viewpoints can be eliminated. In other words, the optimal viewing distance OD1 and the optimal viewing distance OD2 can be made equal. Formulas (2) and (3) will be described below with reference to FIGS. 11 to 15.

[0043] First, we will explain formula (2). Fig. 11 shows an optical model (XZ cross section) of stereoscopic image display from N1 viewpoints at the center of display device 100. In stereoscopic image display from N1 viewpoints, pixels 12 with pixel pitch P are projected via first lens element 20 onto observation surface S located at optimum viewing distance OD1 at viewpoint pitch e1, and therefore the following formulas (2-1), (2-2), and (2-3) hold. Here, n represents the refractive index of display device 100.

[0044]

number

number

number

[0045] When θ1 and φ1 are sufficiently small, they can be approximated as sinθ1=tanθ1 and sinφ1=tanφ1, and therefore the following equation (2-4) can be obtained from equations (2-1) to (2-3).

[0046]

number

[0047] 12 shows an optical model (XZ cross section) of stereoscopic image display from N2 viewpoints at the center of display device 100. In stereoscopic image display from N2 viewpoints, pixels 12 with pixel pitch P are projected via second lens element 30 onto observation surface S located at optimum viewing distance OD2 at viewpoint pitch e2, and therefore the following equations (2-5), (2-6), and (2-7) hold.

[0048]

number

number

number

[0049] When θa and φa are sufficiently small, they can be approximated as sinθa=tanθa and sinφa=tanφa, and therefore the following equation (2-8) can be obtained from equations (2-5) to (2-7).

[0050]

number

[0051] Since the optimum visibility distance OD1 and the optimum visibility distance OD2 are equal, equation (2) can be obtained from equations (2-4) and (2-8).

[0052] Next, equation (3) will be explained. Fig. 13 shows an optical model (XZ cross section) of stereoscopic image display from N1 viewpoints at the end of display device 100 in the +X direction. In stereoscopic image display from N1 viewpoints, lens pitch Lp1 of first lens element 20 is set to be slightly smaller than pitch P × N1 of first pixel unit 14, and therefore equations (3-1), (3-2), and (3-3) below hold. n represents the refractive index of display device 100, and m1 represents the number of lenticular lenses in first lens element 20 from the center of display device 100 to the end of display device 100 in the +X direction.

[0053]

number

number

number

[0054] When θ2 and φ2 are sufficiently small, they can be approximated as sinθ2=tanθ2 and sinφ2=tanφ2, so the following equation (3-4) can be obtained from equations (3-1) to (3-3).

[0055]

number

[0056] 14 shows an optical model (XZ cross section) of stereoscopic image display from N2 viewpoints at the end of display device 100 in the +X direction. In stereoscopic image display from N2 viewpoints, lens pitch Lp2 of second lens element 30 is set to be slightly smaller than pitch P×N2 of second pixel unit 16, and therefore the following equations (3-5), (3-6), and (3-7) hold. n represents the refractive index of display device 100, and m2 represents the number of lenticular lenses in second lens element 30 from the center of display device 100 to the end of display device 100 in the +X direction.

[0057]

number

number

number

[0058] When θb and φb are sufficiently small, they can be approximated as sinθb=tanθb and sinφb=tanφb, and therefore the following equation (3-8) can be obtained from equations (3-5) to (3-7).

[0059]

number

[0060] Since the optimum visibility distance OD1 is equal to the optimum visibility distance OD2, equation (3) can be obtained from equations (2), (3-4), and (3-8).

[0061] For example, if image display unit 10 is a 6.9-inch diagonal WQHD (Wide Quad High Definition) display with a pixel pitch P of 60 μm, then as shown in Examples 3 and 4 of FIG. 15, by satisfying the conditions of Equation (2) and Equation (3), viewpoint pitch e2 can be made narrower than viewpoint pitch e1, and optimal viewing distance OD1 can be made equal to optimal viewing distance OD2 (conditions for first lens element 20: N1=2, H1=0.5 mm, Lp1=119.9 μm, OD1=399 mm, e1=71.9 mm).

[0062] As described above, by satisfying the conditions of formulas (2) and (3), the viewpoint pitch e2 in stereoscopic image display from N2 viewpoints can be made narrower than the viewpoint pitch e1 in stereoscopic image display from N1 viewpoints. Furthermore, the optimum viewing distance OD1 in stereoscopic image display from N1 viewpoints can be made equal to the optimum viewing distance OD2 in stereoscopic image display from N2 viewpoints.

[0063] <Embodiment 3> In embodiments 1 and 2, the first lens element 20 and the second lens element 30 are arranged on the display surface 10a side of the image display unit 10, but the first lens element 20 may also be arranged on the side opposite the display surface 10a side of the image display unit 10.

[0064] As shown in FIG. 16 , display device 100 of this embodiment includes image display unit 10, first lens element 20, second lens element 30, and light source unit 310. In this embodiment, first lens element 20 is disposed on the side opposite display surface 10a of image display unit 10. Second lens element 30 is disposed on the display surface 10a side of image display unit 10. In this embodiment, as in the first embodiment, when display device 100 displays a planar image, first lens element 20 and second lens element 30 do not function as lenses, and the planar image displayed on image display unit 10 is displayed. When display device 100 displays a stereoscopic image with N1 viewpoints, only first lens element 20 functions as a lens. When display device 100 displays a stereoscopic image with N2 viewpoints, only second lens element 30 functions as a lens.

[0065] The image display unit 10 of this embodiment is, for example, a transmissive liquid crystal display panel. Other configurations of the image display unit 10 of this embodiment are the same as those of the image display unit 10 of the first embodiment.

[0066] The light source unit 310 functions as a backlight for the image display unit (transmissive liquid crystal display panel) 10. The light source unit 310 is disposed on the opposite side of the image display unit 10 from the display surface 10a side. The light source unit 310 includes an LED (Light Emitting Diode) element, a diffusion sheet, etc., which are not shown.

[0067] First lens element 20 of the present embodiment overlaps image display unit 10 and is disposed between image display unit 10 and light source unit 310. When parallax images corresponding to the N1 viewpoints are displayed on image display unit 10, first lens element 20 of the present embodiment distributes light emitted from light source unit 310, thereby distributing light emitted from pixels 12 included in first pixel unit 14 that displays the parallax images, to the N1 viewpoints corresponding to the parallax images. This allows display device 100 of the present embodiment to display a stereoscopic image from the N1 viewpoints.

[0068] In first lens element 20 of the present embodiment, lens pitch Lp1 is set to be slightly larger than pitch P×N1 of first pixel units 14. Other configurations of first lens element 20 of the present embodiment are similar to the configurations of first lens element 20 of the first embodiment.

[0069] Second lens element 30 of this embodiment overlaps image display unit 10 and is disposed on the display surface 10a side of image display unit 10. Lens pitch Lp2 of second lens element 30 of this embodiment satisfies the condition of formula (4) below. By satisfying the condition of formula (4), the viewpoint pitch e2 in stereoscopic image display from N2 (N2>N1) viewpoints can be made narrower than the viewpoint pitch e1 in stereoscopic image display from N1 (an integer equal to or greater than 2) viewpoints. The other configurations of second lens element 30 of this embodiment are the same as the configurations of second lens element 30 of embodiment 1. Note that if the condition of formula (4) is satisfied, the condition of formula (1) is also satisfied.

[0070]

number

[0071] Here, we will explain equation (4). First, we will find the viewpoint pitch e1. Fig. 17 shows an optical model (XZ cross section) of stereoscopic image display from N1 viewpoints at the center of display device 100 of this embodiment. In stereoscopic image display from N1 viewpoints, pixels 12 with a pixel pitch P are projected by first lens element 20 onto observation surface S located at optimum viewing distance OD1 at a viewpoint pitch e1, and therefore the following equations (4-1), (4-2), and (4-3) hold. Here, n represents the refractive index of display device 100.

[0072]

number

number

number

[0073] When θ3 and φ3 are sufficiently small, they can be approximated as sinθ3=tanθ3 and sinφ3=tanφ3, and therefore the following equation (4-4) can be obtained from equations (4-1) to (4-3).

[0074]

number

[0075] Next, the viewpoint pitch e2 is calculated. Fig. 18 shows an optical model (XZ cross section) of stereoscopic image display from N2 viewpoints at the center of display device 100 of this embodiment. Since pixels 12 with pixel pitch P are projected via second lens element 30 onto observation surface S located at optimal viewing distance OD2 at viewpoint pitch e2, the following equations (4-5), (4-6), and (4-7) hold.

[0076]

number

number

number

[0077] When θ4 and φ4 are sufficiently small, they can be approximated as sinθ4=tanθ4 and sinφ4=tanφ4, and therefore the following equation (4-8) can be obtained from equations (4-5) to (4-7).

[0078]

number

[0079] Next, the optimum viewing distance OD1 is calculated. Fig. 19 shows an optical model (XZ cross section) of stereoscopic image display from N1 viewpoints at the -X direction end of display device 100 of this embodiment. In stereoscopic image display from N1 viewpoints, lens pitch Lp1 of first lens element 20 is set slightly larger than pitch P × N1 of first pixel unit 14, and therefore the following equations (4-9), (4-10), and (4-11) hold.

[0080]

number

number

number

[0081] When θ5 and φ5 are sufficiently small, they can be approximated as sinθ5=tanθ5 and sinφ5=tanφ5, and therefore the following equation (4-12) can be obtained from equations (4-9) to (4-11).

[0082]

number

[0083] Next, the optimum visibility distance OD2 is calculated. According to an optical model similar to the optical model shown in Fig. 13 of the second embodiment, the optimum visibility distance OD2 is expressed by the following formula (4-13).

[0084]

number

[0085] When the viewpoint pitch e2 is narrower than the viewpoint pitch e1, the following formula (4-14) is established from formulas (4-4) and (4-8): The following formula (4-15) can be obtained from formulas (4-12) to (4-14).

[0086]

number

number

[0087] Furthermore, since second lens element 30 distributes the light emitted from N2 pixels 12, lens pitch Lp2 satisfies the following formula (4-16): Formula (4) can be obtained from formulas (4-15) and (4-16).

[0088]

number

[0089] For example, if image display unit 10 is a 6.9-inch WQHD (Wide Quad High Definition) display with a pixel pitch P of 60 μm, then by satisfying the condition of equation (4), as shown in Example 5 of FIG. 20, viewpoint pitch e2 can be made narrower than viewpoint pitch e1 (first lens element 20: conditions N1=2, H1=0.5 mm, Lp1=119.9 μm, OD1=399 mm, e1=72.1 mm). In addition, the difference between optimal viewing distance OD1 and optimal viewing distance OD2 can be reduced.

[0090] As described above, in this embodiment, by satisfying the condition of formula (4), the viewpoint pitch e2 in stereoscopic image display from N2 viewpoints can be made narrower than the viewpoint pitch e1 in stereoscopic image display from N1 viewpoints. Furthermore, the difference between the optimal viewing distance OD1 and the optimal viewing distance OD2 can be made smaller. In this embodiment, the second lens element 30, the image display unit 10, and the first lens element 20 are stacked in this order as seen by the viewer. Therefore, the distance H1 between the vertex Lt1 of the first lens element 20 and the pixel 12 and the distance H2 between the vertex Lt2 of the second lens element 30 and the pixel 12 can be set regardless of the thickness of the other lens elements. Furthermore, the overlay accuracy of the first lens element 20, the second lens element 30, and the image display unit 10 can be improved.

[0091] <Embodiment 4> In the third embodiment, first lens element 20 is arranged on the side opposite to display surface 10a of image display unit 10. First lens element 20 may be arranged on the side of display surface 10a of image display unit 10, and second lens element 30 may be arranged on the side opposite to display surface 10a of image display unit 10.

[0092] As shown in FIG. 21 , display device 100 of this embodiment includes image display unit 10, first lens element 20, second lens element 30, and light source unit 310. In this embodiment, first lens element 20 is disposed on the display surface 10a side of image display unit 10. Second lens element 30 is disposed on the opposite side of image display unit 10 from display surface 10a. The configurations of image display unit 10 and light source unit 310 of this embodiment are similar to those of image display unit 10 and light source unit 310 of Embodiment 3. Furthermore, first lens element 20 of this embodiment is similar to first lens element 20 of Embodiment 1. Here, second lens element 30 of this embodiment will be described.

[0093] Second lens element 30 of the present embodiment overlaps image display unit 10 and is disposed between image display unit 10 and light source unit 310. When parallax images corresponding to the N2 viewpoints are displayed on image display unit 10, second lens element 30 of the present embodiment distributes light emitted from light source unit 310, thereby distributing light emitted from pixels 12 included in second pixel unit 16 that displays the parallax images, to the N2 viewpoints corresponding to the parallax images. This allows display device 100 of the present embodiment to display a stereoscopic image from the N2 viewpoints.

[0094] In this embodiment, by satisfying the condition of formula (5), the viewpoint pitch e2 in stereoscopic image display from N2 (N2>N1) viewpoints can be made narrower than the viewpoint pitch e1 in stereoscopic image display from N1 (an integer equal to or greater than 2) viewpoints. The other configurations of second lens element 30 in this embodiment are the same as those of second lens element 30 in embodiment 1.

[0095]

number

[0096] Here, equation (5) will be explained. According to an optical model similar to the optical model shown in Fig. 18 of the third embodiment, the viewpoint pitch e1 is expressed by the following equation (5-1).

[0097]

number

[0098] Furthermore, according to an optical model similar to the optical model shown in FIG. 17 of the third embodiment, the viewpoint pitch e2 is expressed by the following formula (5-2).

[0099]

number

[0100] Furthermore, according to an optical model similar to the optical model shown in Fig. 13 of the second embodiment, the optimum visibility distance OD1 is expressed by the following formula (5-3): According to an optical model similar to the optical model shown in Fig. 19 of the third embodiment, the optimum visibility distance OD2 is expressed by the following formula (5-4):

[0101]

number

number

[0102] When the viewpoint pitch e2 is narrower than the viewpoint pitch e1, the following formula (5-5) is established from formulas (5-1) and (5-2): The following formula (5-6) can be obtained from formulas (5-3) to (5-5).

[0103]

number

number

[0104] Furthermore, since second lens element 30 distributes the light emitted from N2 pixels 12, lens pitch Lp2 satisfies the following formula (5-7): Formula (5) can be obtained from formulas (5-6) and (5-7).

[0105]

number

[0106] For example, if image display unit 10 is a 6.9-inch WQHD (Wide Quad High Definition) display with a pixel pitch P of 60 μm, then by satisfying the condition of equation (5), as shown in Example 6 of FIG. 22, viewpoint pitch e2 can be made narrower than viewpoint pitch e1 (first lens element 20: conditions N1=2, H1=0.5 mm, Lp1=119.9 μm, OD1=400 mm, e1=71.9 mm). In addition, the difference between optimal viewing distance OD1 and optimal viewing distance OD2 can be reduced.

[0107] As described above, in this embodiment, by satisfying the condition of formula (5), the viewpoint pitch e2 in stereoscopic image display with N2 viewpoints can be made narrower than the viewpoint pitch e1 in stereoscopic image display with N1 viewpoints. Furthermore, the difference between the optimal viewing distance OD1 and the optimal viewing distance OD2 can be made smaller. In this embodiment, the first lens element 20, the image display unit 10, and the second lens element 30 are stacked in this order from the viewer's perspective. Therefore, the distance H1 between the vertex Lt1 of the first lens element 20 and the pixel 12 and the distance H2 between the vertex Lt2 of the second lens element 30 and the pixel 12 can be set regardless of the thickness of the other lens elements. Furthermore, the overlay accuracy of the first lens element 20, the second lens element 30, and the image display unit 10 can be improved. Furthermore, the first lens element 20, which functions as a lenticular lens in stereoscopic image display with a small number of viewpoints (N1), is positioned on the viewer side. Therefore, the light emitted from first lens element 20 is not disturbed by other members, and a high-definition stereoscopic image can be displayed with a small number of viewpoints.

[0108] <Regarding formula (1)> The formula (1) in the first embodiment can be obtained from an optical model similar to the optical model for stereoscopic image display in the second embodiment.

[0109] Specifically, the following formula (1-1) is obtained from formula (2-4), and the following formula (1-2) is obtained from formula (2-5).

[0110]

number

number

[0111] In order to make the viewpoint pitch e2 in stereoscopic image display from N2 (N2>N1) viewpoints narrower than the viewpoint pitch e1 in stereoscopic image display from N1 (an integer greater than or equal to 2) viewpoints (e1>e2), the following equation (1-3) must be satisfied from equations (1-1) and (1-2).

[0112]

number

[0113] On the other hand, the following formula (1-4) is obtained from formula (3-4), and the following formula (1-5) is obtained from formula (3-5).

[0114]

number

number

[0115] The following formula (1-6) is obtained from formulas (1-3) to (1-5).

[0116]

number

[0117] Furthermore, the lens pitch Lp2 of the second lens element 30 satisfies the formula (4-16), similarly to the third embodiment. Therefore, the formula (1) can be obtained from the formulas (1-6) and (4-16).

[0118] <Modification> Although the embodiments have been described above, various modifications can be made to the present disclosure without departing from the spirit and scope of the present disclosure.

[0119] For example, the image display unit 10 is not limited to an organic EL display panel, and the image display unit 10 in the first and second embodiments may be a transmissive liquid crystal display panel.

[0120] The arrangement of the pixels 12 of the image display unit 10 is not limited to a horizontal stripe arrangement. The arrangement of the pixels 12 may be a vertical stripe arrangement, a delta arrangement, etc. Furthermore, the colors of the pixels 12 are not limited to three, red, green, and blue, but may be four colors.

[0121] First lens element (liquid crystal lens) 20 may include an insulating layer, a dielectric layer, or the like on first electrode 24 and second electrodes 25 and 26. Second lens element (liquid crystal lens) 30 may include an insulating layer, a dielectric layer, or the like on third electrode 34 and fourth electrodes 35 and 36. Furthermore, first lens element (liquid crystal lens) 20 and second lens element (liquid crystal lens) 30 may be other types of liquid crystal GRIN (Gradient Index) lenses.

[0122] In the first and second embodiments, the first lens element 20 and the second lens element 30 are stacked on the display surface 10a of the image display unit 10 in the order of the first lens element 20, the second lens element 30. The first lens element 20 and the second lens element 30 may also be stacked on the display surface 10a of the image display unit 10 in the order of the second lens element 30, the first lens element 20.

[0123] Although the preferred embodiments have been described above, the present disclosure is not limited to such specific embodiments, and the present disclosure includes the inventions described in the claims and their equivalents. [Explanation of symbols]

[0124] 10 image display section, 12 pixel, 12R, 12G, 12B sub-pixel, 14 first pixel unit, 16 second pixel unit, 20 first lens element, 21 first substrate, 21a first main surface of first substrate, 22 second substrate, 22a first main surface of second substrate, 24 first electrode, 25, 26 second electrode, 25a, 26a comb tooth portion, 28 liquid crystal, 29 sealing material, 30 second lens element, 31 third substrate, 31a first main surface of third substrate, 32 fourth substrate, 32a first main surface of fourth substrate, 34 third electrode, 35, 36 fourth electrode, 35a, 36a comb tooth portion, 38 liquid crystal, 100 display device, 101 display surface, e1, e2 viewpoint pitch, Lp1, Lp2 lens pitch, Lt1, Lt2 lens vertex, H1, H2 Distance between the vertex of the lens and the pixel, J Center line of the display device, M Molecular, m1, m2 Number of lenticular lenses, OD1, OD2 Optimum viewing distance, P Pixel pitch, S Observation surface, SR1, SR2 Viewing area, θ1, θ2, θ3, θ4, θ5, θa, θb, φ1, φ2, φ3, φ4, φ5, φa, φb Angle

Claims

1. an image display unit having a plurality of pixels and displaying parallax images corresponding to N1 (N1 is an integer equal to or greater than 2) viewpoints along a predetermined direction, and parallax images corresponding to N2 (N2 is an integer greater than N1) viewpoints along the predetermined direction; a first lens element that overlaps the image display unit and that, when parallax images corresponding to the N1 viewpoints are displayed on the image display unit, distributes light emitted from the plurality of pixels that display the respective parallax images to the N1 viewpoints corresponding to the respective parallax images; a second lens element that overlaps the image display unit and that, when parallax images corresponding to the N2 viewpoints are displayed on the image display unit, distributes light emitted from the plurality of pixels that display the respective parallax images to the N2 viewpoints corresponding to the respective parallax images, a viewpoint pitch among the N2 viewpoints is narrower than a viewpoint pitch among the N1 viewpoints; Display device.

2. An image display unit having a plurality of pixels and displaying a parallax image corresponding to each of N1 (N1 is an integer equal to or greater than 2) viewpoints along a predetermined direction, and a parallax image corresponding to each of N2 (N2 is an integer greater than N1) viewpoints along the predetermined direction; a first lens element that overlaps the image display unit and that, when parallax images corresponding to the N1 viewpoints are displayed on the image display unit, distributes light emitted from the plurality of pixels that display the respective parallax images to the N1 viewpoints corresponding to the respective parallax images; a second lens element that overlaps the image display unit and that, when parallax images corresponding to the N2 viewpoints are displayed on the image display unit, distributes light emitted from the plurality of pixels that display the respective parallax images to the N2 viewpoints corresponding to the respective parallax images, the second lens element is disposed on a display surface side of the image display unit, When the lens pitch of the first lens element is Lp1, the lens pitch of the second lens element is Lp2, and the pixel pitch of the plurality of pixels in the predetermined direction is P, [Equation 1] fulfill, Display device.

3. the first lens element is disposed on a display surface side of the image display unit, When the distance between the vertex of the lens of the first lens element and the pixel is H1, the viewpoint pitch of the N1 viewpoints is e1, the distance between the vertex of the lens of the second lens element and the pixel is H2, and the viewpoint pitch of the N2 viewpoints is e2, [Equation 2] [Equation 3] fulfill, The display device according to claim 2 .

4. the first lens element is disposed on a side opposite to a display surface side of the image display unit, [Equation 4] fulfill, The display device according to claim 2 .

5. An image display unit having a plurality of pixels and displaying a parallax image corresponding to each of N1 (N1 is an integer equal to or greater than 2) viewpoints along a predetermined direction, and a parallax image corresponding to each of N2 (N2 is an integer greater than N1) viewpoints along the predetermined direction; a first lens element that overlaps the image display unit and that, when parallax images corresponding to the N1 viewpoints are displayed on the image display unit, distributes light emitted from the plurality of pixels that display the respective parallax images to the N1 viewpoints corresponding to the respective parallax images; a second lens element that overlaps the image display unit and that, when parallax images corresponding to the N2 viewpoints are displayed on the image display unit, distributes light emitted from the plurality of pixels that display the respective parallax images to the N2 viewpoints corresponding to the respective parallax images, the first lens element is disposed on a display surface side of the image display unit, the second lens element is disposed on a side opposite to a display surface side of the image display unit, When the lens pitch of the first lens element is Lp1, the lens pitch of the second lens element is Lp2, and the pixel pitch of the pixels in the predetermined direction is P, [Equation 5] fulfill, Display device.

Images