Naked-eye stereoscopic image display device and method for displaying a naked-eye stereoscopic image

Abstract

This naked-eye stereoscopic image display device comprises: an image display unit that displays a right-eye image and a left-eye image on a transmission-type image display surface in a time division manner; a projection unit that, with a plurality of point light sources which are arranged on an illumination arrangement face in a matrix shape and which turn on / off according to the time division, projects illumination light to the image display surface from the back face of the image display surface; and a light-collecting system array unit which includes a plurality of elemental light-collecting system regions arranged in a planar shape. The light-collecting system array unit is disposed between the image display surface and the illumination arrangement face. The distance between the light-collecting system array unit and the illumination arrangement face is approximately equal to the focal distance of the elemental light-collecting system regions. The light-collecting system array unit includes a common region, which is a region in which portions of adjacent elemental light-collecting system regions coexist, in a region extending from near the centers of the adjacent elemental light-collection system regions to near the boundary therebetween.

Description

[Technical Field]

[0001] The present invention relates to a naked-eye three-dimensional image display device and a naked-eye three-dimensional image display method. This application claims priority based on Japanese Patent Application No. 2020-202675, filed on December 7, 2020, the contents of which are incorporated herein by reference. [Background technology]

[0002] In recent years, there has been much research and development into naked-eye 3D image display devices, which are image display devices that allow users to view images in 3D without using glasses. A known example of a naked-eye 3D image display device is a time-division directional backlight type naked-eye 3D display that uses a lens array and a directional diffuser with vertical orientation to achieve uniform brightness on the image display surface (Patent Documents 1 and 2). Another known example of a naked-eye 3D image display device that does not use a directional diffuser is one in which a focusing array is arranged in front of the image display surface, with alternating prism units made of Fresnel lenses with lenses having different focal points for each groove, to make the joints between the element lenses of the lens array less noticeable (Patent Document 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-161035 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-153705 [Patent Document 3] Japanese Patent Application Laid-Open No. 2016-18108 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional time-sequential directional backlight autostereoscopic displays, such as those described in Patent Documents 1 and 2, use a directional diffuser with vertical orientation, which can prevent the viewer from seeing the stereoscopic image if they tilt their head relative to the image display surface. Furthermore, conventional time-sequential directional backlight autostereoscopic displays have a problem in that the directional diffuser increases crosstalk, where images for the right and left eyes mix, making it difficult to reduce the device's depth. Furthermore, the autostereoscopic image display device described in Patent Document 3 has a liquid crystal display located behind the lenses, which reduces the resolution of the displayed image. In a naked-eye stereoscopic image display device, it has been desired to present a high-resolution stereoscopic image by making the luminance of the image display surface uniform without using a directional diffuser.

[0005] The present invention has been made in consideration of the above points, and provides an autostereoscopic image display device and an autostereoscopic image display method that can present high-resolution stereoscopic images by making the brightness of the image display surface uniform without using a directional diffuser. [Means for solving the problem]

[0006] The present invention has been made to solve the above-mentioned problems, and one aspect of the present invention comprises an image display unit that displays an image for the right eye and an image for the left eye on a transmissive image display surface in a time-division manner, an illumination unit that irradiates illumination light onto the image display surface from behind the image display surface by a plurality of point light sources that are arranged in a matrix on an illumination arrangement surface and flash according to the time division, and a light converging system array unit having a plurality of element light converging system regions arranged in a plane, the light converging system array unit being arranged between the image display surface and the illumination arrangement surface, and the distance between the light converging system array unit and the illumination arrangement surface being approximately equal to the focal length of the element light converging system regions. Similarly, the light collecting optical system array section has a confluence region in which parts of the adjacent element light collecting optical system regions are mixed in a region from near the center to near the boundary of the adjacent element light collecting optical system regions, and the light collecting optical system array section is provided with a linear Fresnel lens array having a structure in which a plurality of linear Fresnel lenses are periodically arranged with the groove directions aligned with each other, and the linear Fresnel lens array is arranged with the groove direction aligned in the up and down direction, and the confluence region is a region in which parts of the adjacent linear Fresnel lenses are mixed in, and the position of the center of one of the adjacent linear Fresnel lenses and the position of the boundary of the other linear Fresnel lens are aligned in the up and down direction. In the direction in which the linear Fresnel lenses are adjacent to each other The overlapping regions are formed continuously by the overlapping prisms, and the width of the groove in the overlapping region is wider as the prism angle becomes gentler and narrower as the prism angle becomes steeper. This is an autostereoscopic image display device.

[0008] Furthermore, in one aspect of the present invention, in the above-mentioned naked-eye three-dimensional image display device, the focusing system array section includes two of the linear Fresnel lens arrays, and the two linear Fresnel lens arrays are arranged so as to be overlapped and orthogonal to the direction of the grooves of the linear Fresnel lenses included in the linear Fresnel lens array, and the element focusing system region is the portion where the orthogonal linear Fresnel lenses overlap.

[0009] In another aspect of the present invention, in the above-described naked-eye three-dimensional image display device, the meeting area is configured such that each portion of the linear Fresnel lens that constitutes the meeting area is alternately arranged for each groove of the linear Fresnel lens.

[0010] In addition, one aspect of the present invention is an autostereoscopic image display device as described above, further comprising an eye position detection unit that detects the positions of the eyes of the observers, and the illumination unit illuminates the directional backlight only in the vicinity of the left eyes of the one or more observers or only in the vicinity of the right eyes of the one or more observers in the area in front of the image display surface based on the positions of the left eyes or right eyes of the one or more observers detected by the eye position detection unit.

[0011] Another aspect of the present invention includes an image display step of displaying an image for the right eye and an image for the left eye on a transmissive image display surface in a time-division manner; an illumination step of irradiating illumination light onto the image display surface from behind the image display surface by a plurality of point light sources arranged in a matrix on an illumination arrangement surface and flashing in accordance with the time division; and a light-collecting system array step of converting the illumination light into approximately parallel light by a light-collecting system array having a plurality of element light-collecting system regions arranged in a plane, the light-collecting system array being arranged between the image display surface and the illumination arrangement surface, and the distance between the light-collecting system array and the illumination arrangement surface being equal to or less than the focal point of the element light-collecting system regions. The distance is approximately equal to the distance between the center of the adjacent element light-collecting system regions and the boundary of the adjacent element light-collecting system regions, and the light-collecting system array has a meeting region where parts of the adjacent element light-collecting system regions are mixed together, and the light-collecting system array includes a linear Fresnel lens array having a structure in which a plurality of linear Fresnel lenses are periodically arranged with the groove directions aligned with each other, and the linear Fresnel lens array is arranged with the groove direction aligned in the vertical direction, and the meeting region is where parts of the adjacent linear Fresnel lenses are mixed together, and the position of the center of one of the adjacent linear Fresnel lenses and the position of the boundary of the other linear Fresnel lens are aligned in the vertical direction. In the direction in which the linear Fresnel lenses are adjacent to each other The overlapping regions are formed continuously by the overlapping prisms, and the width of the groove in the overlapping region is wider as the prism angle is gentler and narrower as the prism angle is steeper. This is a method for displaying autostereoscopic images.

[0012] In addition, one aspect of the present invention is a method for displaying a naked eye stereoscopic image, further comprising an eye position detection step for detecting the eye positions of observers, wherein the illumination step illuminates, for one or more observers, only the vicinity of the left eyes of the one or more observers or only the vicinity of the right eyes of the one or more observers in the area in front of the image display surface with directional backlight, based on the positions of the left eyes or right eyes of the one or more observers detected by the eye position detection step. [Effects of the Invention]

[0013] According to the present invention, in a naked-eye three-dimensional image display device, the brightness of the image display surface can be made uniform without using a directional diffuser. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing an example of a configuration of a naked-eye three-dimensional image display device according to an embodiment of the present invention. [Figure 2] 3A and 3B are diagrams illustrating a first example of an illumination method for a directional backlight according to an embodiment of the present invention. [Figure 3] 6A and 6B are diagrams illustrating a second example of an illumination method for a directional backlight according to an embodiment of the present invention. [Figure 4] FIG. 1 is a diagram showing an example of a conventional linear Fresnel lens according to the present invention. [Figure 5] FIG. 1 is a diagram showing an example of a cross section of a conventional linear Fresnel lens according to the present invention. [Figure 6] FIG. 1 is a diagram illustrating an example of a cross section of a linear Fresnel lens according to an embodiment of the present invention. [Figure 7] FIG. 10 is a diagram illustrating an example of a cross section of a linear Fresnel lens according to a modified example of the embodiment of the present invention. [Figure 8] FIG. 2 is a diagram showing an example of a side view of a convex lens array according to an embodiment of the present invention. [Figure 9] FIG. 2 is a diagram showing an example of a top view of a convex lens array according to an embodiment of the present invention. [Figure 10]FIG. 10 is a diagram showing an example of the luminance of a backlight when a convex lens array according to an embodiment of the present invention is used. DETAILED DESCRIPTION OF THE INVENTION

[0015] (Embodiment) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. For convenience of explanation, the drawings show an XYZ Cartesian coordinate system, which is a three-dimensional Cartesian coordinate system. In the XYZ Cartesian coordinate system, the Y axis faces vertically upward. In the following description, a direction parallel to the Y axis is also referred to as the up-down direction. The direction of the Y axis is also referred to as the upward direction. The direction opposite to the direction of the Y axis is also referred to as the downward direction. The positive side of the Y axis direction is also referred to as the upper side, and the negative side of the Y axis direction is also referred to as the lower side. A direction parallel to the Z axis is also referred to as the depth direction. The positive side of the Z axis direction is also referred to as the front side, and the negative side of the Z axis direction is also referred to as the back side. A direction parallel to the X axis is also referred to as the left-right direction. The positive side of the X axis direction is also referred to as the right side, and the negative side of the X axis direction is also referred to as the left side.

[0016] [Configuration of image display device] 1 is a diagram showing an example of the configuration of a naked-eye three-dimensional image display device 1 according to this embodiment. The naked-eye three-dimensional image display device 1 is a naked-eye three-dimensional image display device that displays a right-eye image and a left-eye image in a time-division manner using a directional backlight, and displays a stereoscopic image that allows the image to be viewed in three dimensions.

[0017] The naked-eye three-dimensional image display device 1 includes an image display unit 11, an irradiation unit 12, a condensing optical system array unit 13, and a control device 14. The irradiation unit 12 includes an illumination arrangement control unit 121, a light source unit 122, and an eye position detection device 20. The image display unit 11, the condensing optical system array unit 13, the illumination arrangement control unit 121, and the light source unit 122 are provided in the naked-eye three-dimensional image display device 1 in this order from the front side to the back side. An observer P1 observes the image display unit 11 from the front side. The eye position detection device 20 is, for example, installed above the image display unit 11.

[0018] The image display unit 11 has a transmissive image display surface D1 on which a plurality of display elements are arranged in a matrix. The image display unit 11 is configured to include, for example, a transmissive liquid crystal display (LCD). The image display unit 11 displays an image for the right eye and an image for the left eye on the image display surface D1 in a time-division manner.

[0019] The irradiation unit 12 irradiates the image display surface D1 with illumination light from the back surface of the image display surface D1. Specifically, the irradiation unit 12 is an irradiation device that irradiates each of the pixels arranged on the image display surface D1 with illumination light in response to a request from the control device 14. The illumination arrangement control unit 121 includes an illumination arrangement surface D2 that variably controls the arrangement of illumination light, which is irradiated onto the image display surface D1 from the rear of the image display surface D1, relative to the image display surface D1. A plurality of illumination arrangement control elements are arranged in a matrix on the illumination arrangement surface D2. The illumination arrangement control unit 121 includes, for example, a transmissive LCD.

[0020] The light source unit 122 irradiates illumination light onto the back surface of the illumination arrangement surface D2. The light source unit is, for example, a backlight using LEDs (Light Emitting Diodes). The light source unit irradiates illumination light of white or one of three colors, red, green, and blue, onto each of a plurality of illumination arrangement control elements arranged in a matrix on the illumination arrangement surface D2. Each of the plurality of illumination arrangement control elements irradiates illumination light of the color of the irradiated illumination light onto the image display surface D1. The plurality of illumination arrangement control elements are an example of a plurality of point light sources arranged in a matrix on the illumination arrangement surface and flashing in accordance with time division.

[0021] The light source unit may be a backlight using other light sources instead of an LED. Furthermore, the illumination arrangement control unit 121 may be provided with a self-luminous dot matrix LED display device having a function of emitting illumination light, instead of a transmissive LCD and a light source unit. The illumination arrangement control section 121 may be a liquid crystal panel capable of displaying color images (that is, a color liquid crystal panel), or may be a liquid crystal panel capable of displaying only black and white images (that is, a monochrome liquid crystal panel).

[0022] The condensing optical system array unit 13 is disposed between the image display surface D1 and the illumination arrangement surface D2. The condensing optical system array unit 13 converts the illumination light incident from the irradiation unit 12 into parallel light and emits it toward the image display surface D1. In other words, the condensing optical system array unit 13 generates directional backlight. The condensing optical system array unit 13 includes a convex lens array A1.

[0023] The convex lens array A1 includes a plurality of lens elements E1 arranged in a plane. The lens elements E1 are an example of an element light-collecting system region. The distance between the illumination arrangement surface D2 and the convex lens array A1 is approximately equal to the focal length of each of the lens elements E1. Therefore, when illumination light emitted from the irradiation unit 12 enters the light-collecting system array unit 13, the illumination light is collimated and emitted toward the image display surface D1. Therefore, illumination light emitted from the intersection of the illumination arrangement surface D2 and a line segment connecting the eye of the observer P1 to the center of the lens elements E1 is converted by the light-collecting system array unit 13 into directional light rays that enter the right or left eye of the observer P1. When there are multiple observers, the number of intersections of the illumination arrangement surface D2 and the line segment connecting the eye to the center of the lens elements E1 increases accordingly. Therefore, by increasing the number of positions on the illumination arrangement surface D2 where illumination light is irradiated, light rays are incident on the eyes of all observers. The focal lengths of the plurality of element lenses E1 are common to each other.

[0024] The eye position detection device 20 detects the eye position of the viewer P1. The eye position detection device 20 is installed above the image display unit 11 and captures an image including the face of the viewer P1 on the front side of the device. The eye position detection device 20 detects the eye position of the viewer P1 from the captured image using image recognition technology or the like. The eye position detection device 20 outputs information indicating the detected eye position of the viewer P1 (for example, coordinates in a three-dimensional Cartesian coordinate system) to the control device 14. The eye position detecting device 20 may output the captured image to the control device 14. In this case, the control device 14 detects the eye position of the viewer P1 from the image captured by the eye position detecting device 20 using image recognition technology or the like.

[0025] The control device 14 controls the entire autostereoscopic image display device 1. The control device 14 displays an image for the right eye and an image for the left eye on the image display surface D1 based on a time-division pattern. The control device 14 also controls a plurality of illumination arrangement control elements arranged on the illumination arrangement surface D2 based on the position of the eyes of the viewer P1 and the time-division pattern.

[0026] The control device 14 controls the plurality of illumination arrangement control elements to switch between positions on the illumination arrangement surface D2 to be illuminated with illumination light and positions not to be illuminated with illumination light in each time-division frame. Here, the control device 14 determines the positions on the illumination arrangement surface D2 to be illuminated with illumination light based on the position of the eyes of the viewer P1. In this way, the control device 14 switches whether the directional backlight is incident on the right eye or the left eye of the viewer P1. When an image for the right eye is displayed on the image display surface D1 based on the time-division pattern, the control device 14 causes the directional backlight to be incident on the right eye of the viewer P1. On the other hand, when an image for the left eye is displayed on the image display surface D1 based on the time-division pattern, the control device 14 causes the directional backlight to be incident on the left eye of the viewer P1. In this way, the autostereoscopic image display device 1 realizes stereoscopic viewing with the naked eye.

[0027] 2 and 3, a description will be given of a method of illuminating the directional backlight in the autostereoscopic image display device 1. Illuminating the directional backlight is also referred to as projecting the directional backlight. Fig. 2 is a diagram showing a first example of a directional backlight irradiation method according to this embodiment. The autostereoscopic image display device 1 shown in Fig. 2 has the same configuration as the autostereoscopic image display device 1 shown in Fig. 1. In Fig. 2, the autostereoscopic image display device 1 irradiates a backlight R2 as a directional backlight toward the front side (positive side in the direction of the Z axis) of the image display surface D1. Fig. 2 shows, as an example, a case where two observers, observer P2-1 and observer P2-2, each observe the image display surface D1 from the front side.

[0028] As described above, the control device 14 included in the autostereoscopic image display device 1 switches whether the directional backlight is incident on the right eye or the left eye of the observer P2-1 based on the position of the observer P2-1's eyes. When displaying an image for the right eye on the image display surface D1, the control device 14 causes the directional backlight to be incident on the right eye of the observer P2-1 based on a time-division pattern. In the directional backlight irradiation method shown in FIG. 2, the control device 14 irradiates the backlight R2 on the vicinity of the right eye of the observer P2-1 and on a region on the front side of the image display surface D1 excluding the vicinity of the left eye of the observer P2-1. When displaying an image for the left eye on the image display surface D1, the control device 14 causes the directional backlight to be incident on the left eye of the observer P2-1 based on a time-division pattern, as in the case of displaying an image for the right eye. In the directional backlight illumination method shown in FIG. 2, the control device 14 illuminates the backlight R2 near the left eye of the viewer P2-1 and the area on the front side of the image display surface D1 excluding the area near the right eye of the viewer P2-1.

[0029] When the backlight R2 is incident on the right and left eyes of the observer P2-2, the control device 14 irradiates the backlight R2 in the same way as when the backlight R2 is incident on the right and left eyes of the observer P2-1. In other words, when displaying an image for the right eye on the image display surface D1, the control device 14 irradiates the backlight R2 to the vicinity of the right eye of the observer P2-1, the vicinity of the right eye of the observer P2-2, and an area on the front side of the image display surface D1 excluding the vicinity of the left eye of the observer P2-1 and the vicinity of the left eye of the observer P2-2.

[0030] 2, when displaying an image for the right eye on image display surface D1, control device 14 irradiates with directional backlight an area on the near side (i.e., the front) of image display surface D1, including the area near the viewer's right eye, excluding the area near the viewer's left eye. Also, when displaying with directional backlight irradiation method shown in Fig. 2, when displaying an image for the left eye on image display surface D1, control device 14 irradiates with directional backlight an area on the near side (i.e., the front) of image display surface D1, including the area near the viewer's left eye, excluding the area near the viewer's right eye. In other words, in the directional backlight illumination method shown in Figure 2, the control device 14 illuminates the directional backlight to all areas of the front surface of the image display surface D1 except for the area near the left eye or the area near the right eye of one or more observers, based on the position of each of the left eyes or right eyes of the one or more observers detected by the eye position detection device 20.

[0031] Fig. 3 is a diagram showing a second example of a directional backlight illumination method according to this embodiment. In the directional backlight illumination method shown in Fig. 3, the control device 14 illuminates the directional backlight only near the left eye of a viewer or only near the right eye of the viewer. Fig. 3 shows, as an example, a case in which two viewers, viewer P3-1 and viewer P3-2, each view image display surface D1 from the front side.

[0032] The control device 14 irradiates the backlight R3-1 as a directional backlight only near the left eye of the viewer P3-1 or only near the right eye of the viewer P3-1. When displaying an image for the right eye on the image display surface D1, the control device 14 irradiates the backlight R3-1 only near the right eye of the viewer P3-1. When displaying an image for the left eye on the image display surface D1, the control device 14 irradiates the backlight R3-1 only near the left eye of the viewer P3-1. Similarly, the control device 14 irradiates the backlight R3-2 as a directional backlight only near the left eye of the viewer P3-2 or only near the right eye of the viewer P3-2. When displaying an image for the right eye on the image display surface D1, the control device 14 irradiates the backlight R3-2 only near the right eye of the viewer P3-2. When displaying an image for the left eye on the image display surface D1, the control device 14 irradiates the backlight R3-2 only near the left eye of the viewer P3-2.

[0033] 3, the control device 14 applies directional backlight only to the vicinity of the left eye or the vicinity of the right eye of one or more observers within the area on the front surface of the image display surface D1, based on the positions of the left eye or the right eye of one or more observers, respectively, detected by the eye position detection device 20. The eye position detection device 20 is an example of an eye position detection unit that detects the positions of the observers' eyes.

[0034] The illumination method of the directional backlight shown in Fig. 2 described above requires a luminous flux proportional to the square of the size of the image display surface D1. As a result, when the size of the image display surface D1 is enlarged, the power of the light source (i.e., the power consumption of the light source unit 122 shown in Fig. 1), which accounts for the majority of the display power, increases in proportion to the square of the size. The illumination method of the directional backlight shown in Fig. 2 is, so to speak, similar to the illumination light illumination method in conventional displays (in other words, the image projection method).

[0035] On the other hand, in the directional backlight illumination method shown in Fig. 3, the directional backlight is illuminated only near the left eye or only near the right eye of the viewer, so the power of the light source increases in proportion to an increase in the number of viewers, but the power consumption of the light source can be significantly reduced compared to the directional backlight illumination method shown in Fig. 2. In other words, in the directional backlight illumination method shown in Fig. 3, the power consumption of the light source can be significantly reduced compared to when the directional backlight is illuminated to the entire area in front of the image display surface D1 except for the area near the left eye or the area near the right eye of the viewer.

[0036] 4 to 10, the configuration of the convex lens array A1 will be described in detail. The convex lens array A1 includes a plurality of linear Fresnel lenses. Before describing the linear Fresnel lenses included in the convex lens array A1, a conventional linear Fresnel lens will first be described.

[0037] FIG. 4 is a diagram showing an example of a conventional linear Fresnel lens L10. The linear Fresnel lens L10 is composed of multiple columnar prisms arranged in a direction perpendicular to the height direction. In the linear Fresnel lens L10, linear grooves are formed by adjacent prisms. FIG. 5 shows a cross section S10 of the conventional linear Fresnel lens L10. The cross section S10 is obtained by dividing a columnar convex lens in a direction perpendicular to the optical axis and reducing the thickness, leaving only the portion near the surface.

[0038] 6 is a diagram showing an example of a cross section S1 of the linear Fresnel lens L1 according to this embodiment. The cross section S1 is bilaterally symmetric. However, the cross section S1 may also be bilaterally asymmetric. The linear Fresnel lens L1 is formed by arranging a linear Fresnel lens L2 and a linear Fresnel lens L3 adjacent to each other on the left and right sides with an intersecting region C1 between them. Both the linear Fresnel lens L2 and the linear Fresnel lens L3 have the same shape as the conventional linear Fresnel lens L10. A right region P2, which is the right half region from the center of the linear Fresnel lens L2, and a left region P3, which is the left half region from the center of the linear Fresnel lens L3, overlap each other. In other words, the center position of the linear Fresnel lens L2 coincides with the position of the left boundary of the linear Fresnel lens L3, and the center position of the linear Fresnel lens L3 coincides with the position of the right boundary of the linear Fresnel lens L2.

[0039] The meeting region C1 is provided in the region where the right region P2 and the left region P3 overlap. In other words, the meeting region C1 is provided in the region from the center to the boundary between the adjacent linear Fresnel lens L2 and linear Fresnel lens L3. The meeting region C1 is a region where a portion included in the right region P2 of the linear Fresnel lens L2 and a portion included in the left region P3 of the linear Fresnel lens L3 are mixed.

[0040] 6, in the meeting region C1, the columnar prisms that make up the linear Fresnel lens L2 included in the right region P2 and the columnar prisms that make up the linear Fresnel lens L3 included in the left region P3 are alternately arranged for each groove of the linear Fresnel lens L2 and the linear Fresnel lens L3. With this arrangement, the grooves of the linear Fresnel lens L2 and the grooves of the linear Fresnel lens L3 are aligned in the same direction. In practice, it is desirable to set the width of each prism arranged in the meeting region C1 to a value that is sufficiently small (approximately tens to hundreds of micrometers) relative to the width of the linear Fresnel lens L1.

[0041] As shown in the cross section S1, in the meeting area C1, the columnar prisms that respectively constitute the linear Fresnel lens L2 and the linear Fresnel lens L3 are alternately arranged back-to-back with the bases of the prisms aligned. In the cross section S1, a triangular, symmetrical mountain is formed in the center of the meeting region C1. The slope of the mountain formed in the center of the meeting region C1 becomes steeper as you move from the left side to the right side of the meeting region C1 in the portion formed by the right region P2 of the linear Fresnel lens L2. On the other hand, the slope of the mountain becomes gentler as you move from the left side to the right side of the meeting region C1 in the portion formed by the left region P3 of the linear Fresnel lens L3.

[0042] The overlapping positions of the linear Fresnel lens L2 and the linear Fresnel lens L3 may be shifted from that shown in FIG. 6 to form a triangular symmetrical valley in the center of the meeting region C1 in the cross section S1. Also, as shown in Figure 7(B), the lens width in the converging region may be wider for prisms with gentler angles and narrower for steeper angles. This increases the effect of uniforming the brightness and also has the benefit of bringing the prism tips closer together. For comparison, Figure 7(A) shows the lens configuration in the converging region before the lens width is made wider for prisms with gentler angles and narrower for steeper angles.

[0043] As described above, the linear Fresnel lens L1 is formed by arranging the linear Fresnel lens L2 and the linear Fresnel lens L3 adjacent to each other on the left and right. Since the linear Fresnel lens L1 has the meeting region C1, the boundary between the linear Fresnel lens L2 and the linear Fresnel lens L3 is less noticeable than when the meeting region C1 is not provided.

[0044] 8 and 9 show the details of the configuration of the convex lens array A1 shown in FIG. 1. FIG. 8 shows a side view, and FIG. 9 shows a top view. The convex lens array A1 includes a horizontal lens array A11 and a vertical lens array A12. The horizontal lens array A11 and the vertical lens array A12 are arranged overlapping each other in the depth direction (Z-axis direction). The horizontal lens array A11 and the vertical lens array A12 have the same shape.

[0045] The horizontal lens array A11 and the vertical lens array A12 each include a plurality of linear Fresnel lenses L1, as described in FIG. 6, periodically arranged with the grooves aligned. The plurality of linear Fresnel lenses L1 periodically arranged with the grooves aligned means, in other words, that a linear Fresnel lens L2 and a linear Fresnel lens L3 are repeatedly arranged adjacent to each other on the left and right sides with a meeting region C1 formed therebetween. In this embodiment, the linear Fresnel lens L2 or the linear Fresnel lens L3 constituting the linear Fresnel lens L1 corresponds to the element lens E1. In each of the horizontal lens array A11 and the vertical lens array A12, the linear Fresnel lens L1 corresponds to the element lens of the lens array. Here, the linear Fresnel lens L1 is constituted by the meeting region C1 as described in FIG. 6.

[0046] In the convex lens array A1, the horizontally oriented lens array A11 and the vertically oriented lens array A12 are arranged to overlap with the groove directions of the linear Fresnel lenses included therein being orthogonal to each other. In the convex lens array A1, the element lens E1 is the portion where the linear Fresnel lenses L1 included in the horizontally oriented lens array A11 and the linear Fresnel lenses L1 included in the vertically oriented lens array A12 overlap. This overlapping portion is formed by the overlapping region C1 of the linear Fresnel lenses L1 included in the horizontally oriented lens array A11 and the overlapping region C1 of the linear Fresnel lenses L1 included in the vertically oriented lens array A12.

[0047] In this embodiment, the meeting region C1 is a region from the center of adjacent lens elements E1 to the boundary between the adjacent lens elements E1, where parts of the adjacent lens elements E1 are mixed together. That is, the light-collecting system array unit 13 has the meeting region C1, which is a region from the center of adjacent lens elements E1 to the boundary between the adjacent lens elements E1, where parts of the adjacent lens elements E1 are mixed together.

[0048] Next, referring to FIG. 10, the luminance of the backlight when the convex lens array A1 is used will be described. The luminance of the backlight when the convex lens array A1 is used is the luminance on the image display surface D1 when illumination light from the irradiation unit 12 is irradiated onto the image display unit 11 via the convex lens array A1. FIG. 10 is a diagram showing an example of the luminance of the backlight when the convex lens array A1 according to this embodiment is used. FIGS. 10(A), (B), and (C) are diagrams for explaining a linear Fresnel lens array in which conventional linear Fresnel lenses are arranged as a comparative example with this embodiment. FIGS. 10(D), (E), and (F) are diagrams for explaining the convex lens array A1 according to this embodiment.

[0049] In Figure 10(A), two linear Fresnel lens arrays are stacked on top of each other with the grooves of the linear Fresnel lenses orthogonal to each other to form a convex lens array. A conventional linear Fresnel lens is placed next to each of the two linear Fresnel lens arrays. The arrangement of linear Fresnel lenses shown in Figure 10(A) is equivalent in terms of backlight luminance distribution to an arrangement of spherical lenses arranged in a grid pattern as shown in Figure 10(B). The arrangement of linear Fresnel lenses shown in Figure 10(A) corresponds to a lens array with spherical lenses as element lenses. When the linear Fresnel lens array shown in Figure 10(A) is used, the backlight luminance distribution reflects the shape of the spherical lenses, as shown in Figure 10(C), and is not uniform. With the conventional linear Fresnel lens L10, the periphery tends to be darker than the center, meaning that with the conventional linear Fresnel lens L10, there is a difference in brightness between the center and the periphery.

[0050] FIG. 10(D) shows the arrangement of linear Fresnel lenses in the convex lens array A1. The arrangement of linear Fresnel lenses shown in FIG. 10(D) is optically equivalent to the arrangement of spherical lenses arranged in a grid pattern with overlapping portions as shown in FIG. 10(E). In the convex lens array A1, the area formed by multiple spherical lenses overlapping each other from the center to the boundary corresponds to an element lens. When the linear Fresnel lenses shown in FIG. 10(D) (i.e., the convex lens array A1) are used, the brightness of the backlight becomes more uniform than when the spherical lenses do not overlap each other, as shown in FIG. 10(F).

[0051] In the present embodiment, an example has been described in which the convex lens array A1 includes a horizontally oriented lens array A11 and a vertically oriented lens array A12, which are stacked with the grooves of the linear Fresnel lenses orthogonal to each other. However, this is not limiting. The convex lens array A1 may include only the vertically oriented lens array A12. In other words, the convex lens array A1 may include only a linear Fresnel lens array, with the grooves of the linear Fresnel lenses arranged vertically. However, in order to enable stereoscopic viewing even when the viewer P1 tilts his / her head with respect to the image display surface D1, it is preferable that the convex lens array A1 include the horizontally oriented lens array A11 and the vertically oriented lens array A12, which are stacked with the grooves of the linear Fresnel lenses orthogonal to each other.

[0052] In this embodiment, an example has been described in which the meeting region C1 is formed by overlapping a right region P2, which is the right half region from the center of the linear Fresnel lens L2, and a left region P3, which is the left half region from the center of the linear Fresnel lens L3, which are adjacent to each other on the left and right sides, to form the linear Fresnel lens L1. That is, in this embodiment, the meeting region C1 is the entire region of the linear Fresnel lens L1, and the meeting region C1 forms element lenses, but this is not limited to this. The meeting region C1 may also be formed by overlapping a right region from near the center to near the boundary of the linear Fresnel lens L2 and a left region from near the center to near the boundary of the linear Fresnel lens L3. However, to achieve uniform brightness, it is preferable that the meeting region C1 be formed over the entire region of the linear Fresnel lens L1.

[0053] In the present embodiment, an example has been described in which the meeting region C1 is configured by alternately arranging the portions of the linear Fresnel lens that make up the meeting region C1 for each groove of the linear Fresnel lens, but this is not limiting. The meeting region C1 may also be configured by alternately arranging the portions of the linear Fresnel lens that make up the meeting region C1 in units of length that are narrower or wider than the width of the groove of the linear Fresnel lens.

[0054] [summary] As described above, the autostereoscopic image display device 1 according to this embodiment includes the image display section 11, the irradiation section 12, and the condenser array section 13. The image display unit 11 displays an image for the right eye and an image for the left eye on a transmissive image display surface D1 in a time-division manner. The illumination unit 12 irradiates illumination light onto the image display surface D1 from behind the image display surface D1 using a plurality of point light sources (in this embodiment, illumination arrangement control elements) that are arranged in a matrix on the illumination arrangement surface D2 and blink in accordance with the time division. The condenser array unit 13 has a plurality of element condenser regions (in this embodiment, element lenses E1) arranged in a plane. The condensing system array section 13 is arranged between the image display surface D1 and the illumination arrangement surface D2, and the distance between the condensing system array section 13 and the illumination arrangement surface D2 is approximately equal to the focal length of the element condensing system area (in this embodiment, element lens E1). The light collecting system array unit 13 has a confluence region C1 that is a region from near the center to near the boundary of adjacent element light collecting system regions (element lens E1 in this embodiment, that is, linear Fresnel lens L2 or linear Fresnel lens L3). The confluence region C1 is a region where parts of the adjacent element light collecting system regions (in this embodiment, right region P2 of linear Fresnel lens L2 and left region P3 of linear Fresnel lens L3) are mixed together.

[0055] With this configuration, the naked-eye stereoscopic image display device 1 of this embodiment can average out the difference in brightness between near the center and near the boundary of the element light-collecting system area, so that the naked-eye stereoscopic image display device can present high-resolution stereoscopic images by making the brightness of the image display surface uniform without using a directional diffuser. Conventional naked-eye stereoscopic image display devices (see, for example, Patent Document 3) have a problem in that the resolution of the presented image is reduced because a liquid crystal display is placed behind the lenses. The naked-eye stereoscopic image display device 1 according to this embodiment can present a stereoscopic image with higher resolution than when a liquid crystal display is placed behind the lenses.

[0056] Furthermore, conventional naked-eye 3D image display devices using directional backlights use a vertical directional diffuser, which makes crosstalk, a phenomenon in which images for the right and left eyes are mixed together, more likely to occur. The naked-eye 3D image display device 1 does not require a vertical directional diffuser, so the occurrence of crosstalk can be suppressed. Furthermore, because the naked-eye 3D image display device 1 does not require a vertical directional diffuser, the thickness in the depth direction can be thinner than when such a directional diffuser is provided. Furthermore, the naked-eye 3D image display device 1 consumes less power than when a vertical directional diffuser is provided.

[0057] Furthermore, in the naked eye three-dimensional image display device 1 according to this embodiment, the light collecting system array unit 13 includes a linear Fresnel lens array (in this embodiment, a vertically oriented lens array A12) having a structure in which a plurality of linear Fresnel lenses (in this embodiment, a linear Fresnel lens L2 and a linear Fresnel lens L3) are periodically arranged with the groove directions aligned with one another. The linear Fresnel lens array (in this embodiment, a vertically oriented lens array A12) is arranged with the grooves of the linear Fresnel lenses oriented in the vertical direction. The meeting area C1 is configured by a mixture of portions of adjacent linear Fresnel lenses (in this embodiment, a linear Fresnel lens L2 and a linear Fresnel lens L3). With this configuration, the naked eye three-dimensional image display device 1 according to this embodiment can make the brightness of the image display surface uniform by using a linear Fresnel lens without using a vertical directional diffuser.

[0058] Furthermore, in the naked eye three-dimensional image display device 1 according to this embodiment, the light collecting system array unit 13 includes two linear Fresnel lens arrays (in this embodiment, a horizontal lens array A11 and a vertical lens array A12). The two linear Fresnel lens arrays (in this embodiment, the horizontal lens array A11 and the vertical lens array A12) are arranged to be overlapped with the groove directions of the linear Fresnel lenses (in this embodiment, the linear Fresnel lens L2 and the linear Fresnel lens L3) included in the linear Fresnel lens arrays being orthogonal to each other. The element light collecting system region (in this embodiment, the element lens E1) is the portion where the orthogonal linear Fresnel lenses (in this embodiment, the linear Fresnel lens L2 or the linear Fresnel lens L3 included in the horizontal lens array A11 and the linear Fresnel lens L2 or the linear Fresnel lens L3 included in the vertical lens array A12) are overlapped.

[0059] With this configuration, the autostereoscopic image display device 1 according to this embodiment allows stereoscopic viewing even when the viewer P1 tilts his / her head relative to the image display surface D1. Conventional autostereoscopic image display devices using directional backlights use a vertical (vertical direction in this embodiment) directional diffuser, which diffuses illumination light only in the vertical direction, and the fields of view for the viewer's right and left eyes are only extended in the vertical direction. Therefore, when the viewer P1 tilts his / her head relative to the image display surface D1, stereoscopic viewing may become impossible.

[0060] Furthermore, in the naked eye stereoscopic image display device 1 according to this embodiment, the meeting area C1 is configured such that each portion of the linear Fresnel lens (in this embodiment, the linear Fresnel lens L2 and the linear Fresnel lens L3) that constitutes the meeting area is alternately arranged in each groove of the linear Fresnel lens. With this configuration, in the naked eye three-dimensional image display device 1 according to this embodiment, the meeting area C1 can be configured by utilizing the grooves of the linear Fresnel lens, and therefore the meeting area C1 can be easily formed.

[0061] In this embodiment, an example in which linear Fresnel lenses are used in the convex lens array A1 has been described, but this is not limiting. Ordinary rotationally symmetric Fresnel lenses may be used as the element lenses constituting the convex lens array A1. When rotationally symmetric Fresnel lenses are used as the element lenses, for example, the Fresnel lenses are arranged in a lattice pattern so that adjacent Fresnel lenses overlap each other, with the boundary of one lens touching the center of the other semicircle. The above-described meeting area may be formed in the area where adjacent Fresnel lenses overlap each other.

[0062] Furthermore, in addition to linear Fresnel lenses or rotationally symmetric Fresnel lenses, zone plates may be used as element lenses in the light-collecting optical system array 13. When zone plates are used as element lenses, for example, the zone plates are arranged in a lattice pattern so that adjacent zone plates overlap each other, with the boundary of one being in contact with the center of the semicircle of the other. In the overlapping region of adjacent zone plates, a pattern of light-transmitting and light-blocking regions is formed, which is an area having the periodicity or regularity of both adjacent zone plates, as an intersecting region. [Industrial Applicability]

[0063] The naked eye stereoscopic image display device 1 according to this embodiment is suitable for use in a three-dimensional display for medical purposes or a head-up display for an automobile.

[0064] One embodiment of the present invention has been described in detail above with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes and the like are possible within the scope that does not deviate from the gist of the present invention. [Explanation of symbols]

[0065] 1...naked-eye stereoscopic image display device, 11...image display section, 12...illumination section, 13...light-collecting system array section, D1...image display surface, D2...illumination arrangement surface, E1...element lens, L1, L2, L3...linear Fresnel lens, C1...intersection area

Claims

1. an image display unit that displays an image for the right eye and an image for the left eye on a transmission-type image display surface in a time-division manner; an illumination unit that irradiates illumination light onto the image display surface from behind the image display surface using a plurality of point light sources that are arranged in a matrix on the illumination arrangement surface and that flash in accordance with the time division; a light-collecting optical system array unit having a plurality of element light-collecting optical system regions arranged in a plane; Equipped with the light-collecting optical system array unit is disposed between the image display surface and the illumination arrangement surface, and a distance between the light-collecting optical system array unit and the illumination arrangement surface is substantially equal to a focal length of the element light-collecting optical system area; the light-collection-system array section has a confluence region in a region from near the center of the adjacent element light-collection system regions to near the boundary of the adjacent element light-collection system regions, where parts of the adjacent element light-collection system regions are mixed together, the light-collecting optical system array unit includes a linear Fresnel lens array having a structure in which a plurality of linear Fresnel lenses are periodically arranged with groove directions aligned with each other, The linear Fresnel lens array is arranged with the grooves oriented in a vertical direction, the meeting region is configured so that portions of the adjacent linear Fresnel lenses are mixed together, and the position of the center of one of the adjacent linear Fresnel lenses and the position of the boundary of the other linear Fresnel lens coincide with each other in the direction in which the linear Fresnel lenses are adjacent to each other, thereby making the meeting region continuous; The width of the groove in the meeting region is wider as the prism angle is gentler, and narrower as the prism angle is steeper. Naked-eye stereoscopic image display device.

2. the light-collecting optical system array unit includes two linear Fresnel lens arrays, The two linear Fresnel lens arrays are arranged so as to be overlapped with each other and orthogonal to the direction of the grooves of the linear Fresnel lenses included in the linear Fresnel lens array, The element light-collecting system area is a portion where the orthogonal linear Fresnel lenses overlap. The naked eye three-dimensional image display device according to claim 1 .

3. The meeting area is configured such that the portions of the linear Fresnel lens that make up the meeting area are alternately arranged for each groove of the linear Fresnel lens. The naked eye three-dimensional image display device according to claim 2 .

4. further comprising an eye position detection unit for detecting the position of the viewer's eye; The illumination unit illuminates, with directional backlight, only the vicinity of the left eye or the vicinity of the right eye of one or more observers within a region in front of the image display screen, based on the positions of the left eye or the right eye of one or more observers detected by the eye position detection unit.

4. The naked eye three-dimensional image display device according to claim 1, claim 2 or claim 3.

5. an image display step of displaying an image for the right eye and an image for the left eye on a transmission type image display surface in a time-division manner; an illumination step of irradiating the image display surface with illumination light from behind the image display surface by a plurality of point light sources arranged in a matrix on the illumination arrangement surface and flashing in accordance with the time division; a light-collecting system array step for substantially collimating the illumination light by a light-collecting system array having a plurality of element light-collecting system regions arranged in a plane; and the light-collecting optical array is disposed between the image display surface and the illumination placement surface, and a distance between the light-collecting optical array and the illumination placement surface is approximately equal to a focal length of the element light-collecting optical area; the light-collection array has a confluence region in a region from near the center of the adjacent element light-collection regions to near the boundary of the adjacent element light-collection regions, where parts of the adjacent element light-collection regions are mixed together, the light-collecting optical system array includes a linear Fresnel lens array having a structure in which a plurality of linear Fresnel lenses are periodically arranged with groove directions aligned with each other, The linear Fresnel lens array is arranged with the grooves oriented in a vertical direction, the meeting region is configured so that portions of the adjacent linear Fresnel lenses are mixed together, and the position of the center of one of the adjacent linear Fresnel lenses and the position of the boundary of the other linear Fresnel lens coincide with each other in the direction in which the linear Fresnel lenses are adjacent to each other, thereby making the meeting region continuous; The width of the groove in the meeting region is wider as the prism angle is gentler, and narrower as the prism angle is steeper. A method for displaying naked-eye stereoscopic images.

6. further comprising an eye position detecting step of detecting the position of the observer's eye; The illumination step illuminates, with a directional backlight, only a vicinity of the left eye or a vicinity of the right eye of one or more observers within a region in front of the image display surface, based on the positions of the left eye or the right eye of one or more observers detected in the eye position detection step. The method for displaying a naked eye three-dimensional image according to claim 5.

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