Linear fresnel lens and transmissive autostereoscopic image display device

Abstract

To provide a linear Fresnel lens having an interlaced structure corresponding to optical see-through display using a transmission type display, and a transmission type naked eye stereoscopic video display device using the same.SOLUTION: A linear Fresnel lens in which a plurality of linear prisms, which are lens elements extending in a first direction, are arranged along a second direction orthogonal to the first direction, wherein the linear prisms have a compound groove structure in which a groove structure in a right region from a center portion of the linear Fresnel lens to the vicinity of one end portion is overlapped with a groove structure in a left region from the center portion to the vicinity of the other end portion, and a flat portion that transmits light without bending the light is formed between the linear Fresnel lenses adjacent to each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a linear Fresnel lens having a convex structure and a transmission-type autostereoscopic image display device using the same. [Background technology]

[0002] In recent years, research and development has been conducted on naked-eye 3D image display devices, which are image display devices that allow any image to be viewed in 3D without the use of glasses specifically designed for 3D viewing. One example of such 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 that is oriented in the vertical direction (see, for example, Patent Documents 1 and 2).

[0003] As another type of naked-eye 3D image display device using a lens array, a multi-viewpoint 3D display is known that displays an array of elemental images that can be seen from different viewpoints for each elemental lens that makes up the lens array (see, for example, Patent Documents 3 and 4).Furthermore, a naked-eye 3D image display device is known in which a focusing system array in which prism units of adjacent Fresnel lenses are alternately arranged at the ends of the elemental lenses is disposed in front of the image display surface to make the joints between the elemental lenses of the lens array less noticeable (see, for example, Patent Document 5).

[0004] However, the time-division directional backlight type autostereoscopic displays described in Patent Documents 1 and 2 have a problem in that a plurality of people cannot simultaneously view a stereoscopic image from unique viewpoints.

[0005] Furthermore, the naked-eye 3D image display devices described in Patent Documents 3 and 4 have the problem that the seams between the element lenses become noticeable, resulting in a decrease in image quality. The naked-eye 3D image display device described in Patent Document 5 alleviates this problem, but has another problem in that the continuity of the seams is insufficient, and there is a demand for displaying more natural 3D images.

[0006] For this reason, for example, Patent Document 6 discloses a naked-eye three-dimensional image display device that uses a linear Fresnel lens having an intersecting groove structure in which a groove structure in a right region from the center to near one end of the linear Fresnel lens is overlapped with a groove structure in a left region from the center to near the other end, thereby making the joints between multiple element lenses less noticeable and enabling the display of three-dimensional images that reproduce smooth motion parallax with uniform brightness. [Prior art documents] [Patent documents]

[0007] [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. 2008-15121 [Patent Document 4] Japanese Patent Application Laid-Open No. 2009-8722 [Patent Document 5] Japanese Patent Application Laid-Open No. 2016-18108 [Patent Document 6] Japanese Patent Publication No. 2024-010522 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the naked-eye stereoscopic image display device described in Patent Document 6 cannot display stereoscopic images corresponding to optical see-through display using a transmissive display, and there has been a demand for a naked-eye stereoscopic image display device that can perform optical see-through display over a wide angle of view.

[0009] The present invention has been made in view of the above-mentioned problems, and aims to provide a linear Fresnel lens having a convex structure that is compatible with optical see-through display using a transmissive display, and a transmissive naked-eye 3D image display device using the same. [Means for solving the problem]

[0010] In order to solve the above problems, the linear Fresnel lens and the transmission-type autostereoscopic image display device according to one embodiment of the present invention propose the following means. (1) A linear Fresnel lens according to a first aspect of the present invention is a linear Fresnel lens in which a plurality of linear prisms, which are lens elements extending in a first direction, are arranged along a second direction perpendicular to the first direction, and the linear prisms have an interdigitated structure in which an inclined structure in a left region from the center to the vicinity of the other end is superimposed on an inclined structure in a right region from the center to the vicinity of the other end of the linear Fresnel lens, and flat portions are formed between adjacent linear prisms that allow light to pass through without being bent.

[0011] (2) A second aspect of the present invention is the linear Fresnel lens of the first aspect, wherein the linear prisms are formed intermittently along the first direction.

[0012] (3) A third aspect of the present invention is the linear Fresnel lens of the first or second aspect, wherein a light-shielding film is formed on a part of the flat portion.

[0013] (4) A fourth aspect of the present invention is a cross-sectional structure in the linear Fresnel lens of any one of the first to third aspects, in which the convoluted structure has a triangular symmetrical peak or valley formed at the center in a cross section of the linear Fresnel lens perpendicular to the first direction, and when the center is a peak or valley, triangular peaks are formed on both sides of the peak or valley, with the slopes closer to the peak or valley being gentler than those on the farther side.

[0014] (5) A transmissive naked-eye 3D image display device according to aspect 5 of the present invention comprises a light-transmitting image display unit that displays, on an image display surface, elemental images that can be observed from a number of different viewpoint positions, and a focusing optical system array unit that is arranged on the front side from which the projection light of the image display unit is emitted, and the focusing optical system array unit comprises first and second linear Fresnel lenses that are formed by stacking two linear Fresnel lenses according to any one of aspects 1 to 4 so that the first directions are perpendicular to each other.

[0015] (6) A sixth aspect of the present invention is a transmissive naked-eye 3D image display device according to the fifth aspect, further comprising a shutter display disposed between the image display unit and the linear Fresnel lens, and the shutter display switches in a time-division manner between a first operating mode in which, when the elemental image is displayed, light is blocked from passing through areas other than the overlapping portions of the linear prisms of the first and second linear Fresnel lenses, and a second operating mode in which, when all of the projection light from the image display unit is transmitted, light is blocked from passing through at the positions where the linear prisms are formed.

[0016] (7) A seventh aspect of the present invention is a transmissive naked-eye three-dimensional image display device according to the fifth aspect, wherein a mask layer is further formed adjacent to the first linear Fresnel lens or the second linear Fresnel lens, and the mask layer is a light-blocking material formed in a shape that suppresses the transmission of light in an area where the linear prism-forming portion of the first linear Fresnel lens overlaps with the flat portion of the second linear Fresnel lens, and in an area where the flat portion of the first linear Fresnel lens overlaps with the linear prism-forming portion of the second linear Fresnel lens. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a linear Fresnel lens having a convex structure that is compatible with optical see-through display using a transmissive display, and a transmissive naked-eye three-dimensional image display device using the same. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view showing an example of a conventional linear Fresnel lens. [Figure 2] FIG. 1 is a cross-sectional view showing an example of a cross section of a conventional linear Fresnel lens. [Figure 3] FIG. 1 is an explanatory diagram illustrating the configuration of a linear Fresnel lens according to a first embodiment of the present invention. [Figure 4] FIG. 1 is a cross-sectional view showing an example of a cross section of a linear Fresnel lens according to a first embodiment of the present invention. [Figure 5] FIG. 1 is a cross-sectional view showing a linear Fresnel lens according to a second embodiment of the present invention. [Figure 6] 1 is a schematic diagram showing a basic configuration of a transmission-type naked-eye three-dimensional image display device according to one embodiment of the present invention. [Figure 7] 10 is a photograph showing an example of an image to be displayed on an image display unit. [Figure 8] 1 is a plan view of a convex lens array according to an embodiment of the present invention, as viewed from the side. [Figure 9] 1 is a plan view of a convex lens array according to an embodiment of the present invention as viewed from above. [Figure 10] FIG. 5 is a schematic diagram showing regions constituting element lenses and transmission regions when two linear Fresnel lenses shown in FIG. 4 are stacked. [Figure 11] FIG. 10 is an explanatory diagram showing an example of the configuration of a light-shielding mask. [Figure 12] FIG. 6 is a schematic diagram showing regions constituting element lenses and transmission regions when two linear Fresnel lenses shown in FIG. 5 are stacked. [Figure 13] FIG. 10 is an explanatory diagram showing the state of odd-numbered frames in time-division display when a shutter display is used. [Figure 14] FIG. 10 is an explanatory diagram showing the state of even-numbered frames in time-division display when a shutter display is used. [Figure 15] 1 is a cross-sectional view showing a design example of a linear Fresnel lens. [Figure 16] FIG. 10 is an enlarged perspective view of a main part showing a modified example (stereoscopic display glasses) of the transmission type naked eye three-dimensional image display device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a linear Fresnel lens and a transmission-type naked-eye 3D image display device according to one embodiment of the present invention will be described with reference to the drawings. Note that the following embodiment is specifically described to provide a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. Furthermore, the drawings used in the following description may show essential parts enlarged for convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may not necessarily be the same as those in reality.

[0020] [Linear Fresnel Lens: First Embodiment] First, a linear Fresnel lens suitable for the transmission type naked eye three-dimensional image display device of this embodiment will be described. Figure 1 is a perspective view showing an example of a conventional linear Fresnel lens. The conventional linear Fresnel lens L10 is configured by arranging multiple columnar prisms in a direction perpendicular to the height direction. In this linear Fresnel lens L10, the prisms are formed to extend linearly.

[0021] Figure 2 shows a cross section S10 of a conventional linear Fresnel lens L10. The cross section S10 is obtained by dividing a cylindrical convex lens in a direction perpendicular to the optical axis and reducing the thickness, leaving only the portion near the surface.

[0022] FIG. 3 is a cross-sectional view showing a linear Fresnel lens according to the first embodiment of the present invention. The linear Fresnel lens L1 of this embodiment has a cross section S1 that is symmetrical ( FIG. 3(c)). Note that the cross section S1 may also be asymmetrical. This linear Fresnel lens L1 is designed by dividing a linear Fresnel lens LR, which is the basis of the design, into a linear Fresnel lens L2 in a right region from the center N1 to near one end N2, and a linear Fresnel lens L3 in a left region from the center N1 to near the other end N3, in a cross section S2 that is perpendicular to the extension direction of the slope structure (the depth direction in FIG. 3) ( FIG. 3(a)).

[0023] Then, the linear Fresnel lens L2 and the linear Fresnel lens L3 are overlapped over the entire width (FIG. 3(b)). The inclined shapes of the linear Fresnel lens L2 and the linear Fresnel lens L3 are combined to form a plurality of interdigitated structures (linear prisms) C1 that form lens elements.

[0024] Furthermore, flat portions F1 that transmit light are formed between adjacent concentric structures (linear prisms) C1, resulting in a linear Fresnel lens L1 in which concentric structures (linear prisms) C1 and flat portions F1 are alternately arranged and continuously extend in the first direction, which is the depth direction in FIG. 3 (FIG. 3(d)).

[0025] Such a convoluted structure (linear prism) C1 is a structure obtained by combining the inclined shape of the linear Fresnel lens L2, which is the right region of the linear Fresnel lens LR, and the inclined shape of the linear Fresnel lens L3, which is the left region of the linear Fresnel lens LR. The flat portion F1 is formed in a structure that allows incident light to pass through as is without being refracted.

[0026] As shown in FIG. 4, in the intersecting structure C1 of the linear Fresnel lens L1 of this embodiment, the columnar prisms (inclined shape) that make up the linear Fresnel lens L2 and the columnar prisms (inclined shape) that make up the linear Fresnel lens L3 are alternately arranged with flat portions F1 interposed between them.

[0027] With this arrangement, the directions of the inclined structure of linear Fresnel lens L2 and the inclined structure of linear Fresnel lens L3 are aligned with each other. In practice, it is desirable to set the width of each of the interdigitated structures (linear prisms) C1 to a value that is sufficiently small (approximately tens to hundreds of micrometers) relative to the width of linear Fresnel lens L1.

[0028] As shown in cross section S1, in the overlapping structure (linear prism) C1, the columnar prisms that respectively constitute the linear Fresnel lens L2 and the linear Fresnel lens L3 may be arranged alternately in a back-to-back orientation with the bases of the prisms aligned.

[0029] In cross section S1, a triangular, symmetrical mountain is formed in the center of the convoluted structure (linear prism) C1. The slope of the mountain formed in the center of the convoluted structure C1, in the portion formed by the linear Fresnel lens L2, becomes gentler as you move from the left side to the right side of the convoluted structure C1. On the other hand, the slope of the mountain, in the portion formed by the linear Fresnel lens L3, becomes steeper as you move from the left side to the right side of the convoluted structure C1.

[0030] In addition, the width of the linear Fresnel lens L2's intersection structure (linear prism) C1 is wider for prisms with gentler angles and narrower for steeper angles. This increases the effect of making the brightness uniform and also has the benefit of bringing the tips of the prisms closer together. A group of linear Fresnel lenses is formed by arranging such linear Fresnel lenses L1 adjacent to each other on the left and right.

[0031] [Linear Fresnel Lens: Second Embodiment] FIG. 5 is a cross-sectional view showing a linear Fresnel lens according to a second embodiment of the present invention. While the convex structure (linear prism) C1 of the first embodiment shown in FIG. 4 is formed to extend continuously along the first direction, the linear Fresnel lens L11 of this embodiment has a plurality of convex structures (linear prisms) C11 formed intermittently along the first direction X, and flat portions F11 are also formed between each of the convex structures (linear prisms) C11.

[0032] That is, in the linear Fresnel lens L11 according to the second embodiment, flat portions F11 that extend continuously along the first direction X are formed between the adjacent convex structures (linear prisms) C11 that are arranged along the second direction Y, and flat portions F11 are also formed between the adjacent convex structures (linear prisms) C11 in the first direction X.

[0033] A transmission-type naked-eye three-dimensional image display device according to one embodiment of the present invention will be described. FIG. 6 is a schematic diagram showing the basic configuration of the transmission-type naked-eye three-dimensional video display device of this embodiment. The transmissive autostereoscopic video display device 10 of this embodiment is of a coarse integral imaging type. An image for coarse integral imaging is displayed on a visible light transmissive image display unit 11 controlled by a display controller 16.

[0034] As the image display unit 11, for example, a transmissive liquid crystal display panel, which is a transmissive color image display device, or a transmissive OLED (organic light emitting diode) display panel or the like can also be used.

[0035] The image display unit 11 of this embodiment includes 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 surface D1 of the image display unit 11 includes a plurality of pixel sets, each of which is made up of a predetermined number of pixels that simultaneously display multi-viewpoint images, arranged in a matrix. FIG. 7 shows an example of an image (element image) displayed on the image display unit 11 when the number of element lenses E1 of a convex lens array A1, which will be described later, is 11×6.

[0036] The light-collecting system array 12 is disposed in front of the viewer 15 on the front side of the transmissive image display unit 11. The light-collecting system array 12 includes a convex lens array A1. The convex lens array A1 includes a plurality of element lenses E1 arranged in a plane. The element lenses E1 are an example of an element light-collecting system region.

[0037] In this embodiment, the element light collecting system area is realized by the intersections of linear Fresnel lenses stacked vertically and horizontally. The array-shaped element lens area is realized by the intersections of linear prisms constituting a linear Fresnel lens group in which multiple linear Fresnel lenses are arranged parallel to each other in the vertical direction (first direction) and linear prisms constituting a linear Fresnel lens group in which multiple linear Fresnel lenses are arranged parallel to each other in the horizontal direction (first direction).

[0038] The distance between the image display unit 11 and the convex lens array A1 is set to be slightly shorter than the focal length of each of the plurality of element lenses E1. This results in a virtual image formation state. In this embodiment, element images corresponding to each element lens E1 are enlarged and formed as virtual images 14 on the back side of the transmissive image display unit 11. An observer 15 observes the virtual images 14 through the transmissive image display unit 11 as a distant three-dimensional image.

[0039] In a virtual image formation state such as that of this embodiment, the elemental image is enlarged, and therefore the viewing area can be enlarged compared to a conventional lens array method that uses an infinite imaging state in which the distance between the image display unit and the convex lens array is equal to the focal length of the elemental lens E1.

[0040] In addition to this embodiment, a configuration in which a plurality of transmissive image display surfaces are stacked as the image display unit can also be used, for example, as shown in Fig. 12 of the above-mentioned Patent Document 3. Furthermore, any multi-viewpoint naked-eye three-dimensional video display device that includes an elemental image display unit having a display surface that displays a plurality of elemental images side by side and a display controller that controls the display, and a light-collecting system array unit including an array made up of a plurality of elemental light-collecting system regions, and that presents each elemental image to the viewer through the light-collecting system array unit, can be used as the configuration of the transmissive naked-eye three-dimensional video display device 10 of the present invention.

[0041] In addition to this embodiment, as shown in FIG. 16, a transmission-type naked-eye three-dimensional image display device may also be a pair of three-dimensional display glasses (transmission-type naked-eye three-dimensional image display device) 30. The stereoscopic display glasses 30 are, for example, eyeglass-type transmission-type naked-eye stereoscopic image display devices worn in front of the observer's eyes, and include a transmission-type image display unit 11 and a light-collecting optical array 12 molded to fit the shape of the frame. Furthermore, a display controller 16 may be formed in the temple portion.

[0042] In this way, even with the stereoscopic display glasses (transmissive naked-eye stereoscopic image display device) 30, the observer can observe a virtual image 14, which is an enlarged image of the image on the image display unit 11 and projected in front of the stereoscopic display glasses 30, as a stereoscopic image via the image display unit 11 and the focusing array 12.

[0043] Next, a detailed description will be given of the configuration of the convex lens array A1 that constitutes the light-collecting system array 12. The convex lens array A1 includes a plurality of linear Fresnel lenses L1 as shown in the above-described embodiment.

[0044] 8 and 9 show the details of the configuration of the convex lens array A1 shown in FIG. 1. FIG. 7 shows a side view, and FIG. 8 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 so as to be overlapped in the depth direction (Z-axis direction). The horizontal lens array A11 and the vertical lens array A12 may have the same shape.

[0045] The horizontal lens array A11 and the vertical lens array A12 each have a plurality of linear Fresnel lenses L1 shown in Fig. 1 periodically arranged with the directions of their concentric structures (linear prisms) C1 aligned to one another. Such a plurality of linear Fresnel lenses L1 periodically arranged with the directions of their concentric structures (linear prisms) C1 aligned to one another means that linear Fresnel lenses L1 formed by overlapping and combining the concentric structure (linear prism) C1 of a linear Fresnel lens L2 and the concentric structure (linear prism) C1 of a linear Fresnel lens L3 shown in Fig. 3 in one area on one surface are repeatedly arranged adjacent to one another on the left and right.

[0046] In this embodiment, the convex structure (linear prism) C1 of the linear Fresnel lens L2 or the convex structure (linear prism) C1 of the linear Fresnel lens L3 constituting the linear Fresnel lens L1 corresponds to the element lens E1. In each of the horizontally oriented lens array A11 and the vertically oriented lens array A12, the linear Fresnel lens L1 corresponds to the element lens of the lens array. Here, the linear Fresnel lens L1 is entirely constituted by the convex structure C1, as described in FIG. 4 .

[0047] In the convex lens array A1, the horizontal lens array A11 and the vertical lens array A12 are overlapped with each other so that the groove directions of the linear Fresnel lenses included therein are orthogonal to each other. In the convex lens array A1, the element lens E1 is the overlapping portion of the linear Fresnel lens L1 included in the horizontal lens array A11 and the linear Fresnel lens L1 included in the vertical lens array A12.

[0048] The overlapping portions of these linear Fresnel lenses L1 are formed by overlapping the forming portions of the meeting structures (linear prisms) C1 of the linear Fresnel lenses L1 included in the horizontal lens array A11 and the forming portions of the meeting structures (linear prisms) C1 of the linear Fresnel lenses L1 included in the vertical lens array A12.

[0049] Next, the overlap structure of the two linear Fresnel lenses L1 described above will be further explained. The convex lens array A1 shown in FIGS. 8 and 9 is formed by stacking two linear Fresnel lenses L1 shown in FIG. 4, and the lenses are stacked so that the extension directions of their respective intersecting structures (linear prisms) C1 are perpendicular to each other.

[0050] FIG. 10 is a schematic diagram showing the regions that constitute the element lens E1 when two linear Fresnel lenses L1 shown in FIG. 4 are stacked together, and the transmission region. When the convex lens array A1 is viewed in a plan view along the overlapping direction of the two linear Fresnel lenses L1, the region where the formation position of the convex structure (linear prism) C1 of one linear Fresnel lens L1 overlaps with the formation position of the convex structure (linear prism) C1 of the other linear Fresnel lens L1 is defined as the lens region. The region where the formation position of the flat portion F1 of one linear Fresnel lens L1 overlaps with the formation position of the flat portion F1 of the other linear Fresnel lens L1 is defined as the transmissive region. Furthermore, the region where the formation position of the convex structure (linear prism) C1 of the two linear Fresnel lenses L1 overlaps with the formation position of the flat portion F1 is defined as the non-transmissive region.

[0051] Of these three regions, the convex lens array A1 has element lenses E1 formed by the lens regions. The transmission region is a region through which visible light is transmitted as is without being significantly refracted.

[0052] In the convex lens array A1 of this embodiment, a configuration is provided to shield the non-transmitting regions among these three regions. As shown in Fig. 11, in this embodiment, for example, a light-shielding mask M1 may be provided that is patterned to shield only the non-transmitting regions among the above-mentioned three regions.

[0053] Such a light-shielding mask M1 may be formed either outside one of the linear Fresnel lenses L1 of the convex lens array A1, outside the other linear Fresnel lens L1, or between the one and the other linear Fresnel lenses L1.

[0054] As a result, when the convex lens array A1 is viewed in a plane along the overlapping direction of the two linear Fresnel lenses L1, the convex lens array A1 is formed to consist of a lens area that constitutes the element lens E1 and a transparent area that transmits visible light.

[0055] By combining a convex lens array A1 consisting of two linear Fresnel lenses L1 configured as described above with a light-shielding mask M1, it is possible to realize a transmission-type naked-eye three-dimensional image display device 10 in which a virtual image 14, which is enlarged and focused on the back side of the image display unit 11, can be observed by an observer 15 through the transmission-type image display unit 11 as a three-dimensional image located at a distance, as shown in FIG.

[0056] FIG. 12 is a schematic diagram showing the regions that constitute the element lens E1 when two linear Fresnel lenses L11 shown in FIG. 5 are stacked together, and the transmission region. In the linear Fresnel lens L11 shown in FIG. 5, flat portions F11 extending continuously along the first direction X are formed between the adjacent convex structures (linear prisms) C11 arranged along the second direction Y, and flat portions F11 are also formed between each adjacent convex structure (linear prism) C11 in the first direction X.

[0057] When two linear Fresnel lenses L11 having this configuration are stacked in directions perpendicular to each other to form a convex lens array A1, when the convex lens array A1 is viewed in a plane along the overlapping direction of the two linear Fresnel lenses L11, as shown in FIG. 12, only two regions are formed: a lens region where the formation position of the meeting structure (linear prism) C1 of one linear Fresnel lens L11 and the formation position of the meeting structure (linear prism) C1 of the other linear Fresnel lens L11 overlap; and a transmissive region where the formation position of the flat portion F1 of one linear Fresnel lens L1 and the formation position of the flat portion F1 of the other linear Fresnel lens L1 overlap.

[0058] Therefore, when a convex lens array A1 is formed by stacking two linear Fresnel lenses L11 as shown in Figure 5, there is no overlapping portion between the linear prism C1 and the flat portion F11 as shown in Figure 10, so it is possible to realize a transmissive naked-eye three-dimensional image display device 10 that allows a three-dimensional image (virtual image) at a distance to be observed through the transmissive image display unit 11 without forming a light-shielding mask.

[0059] Furthermore, when the convex lens array A1 is formed by stacking two linear Fresnel lenses L11 shown in FIG. 5 in mutually orthogonal directions, a shutter display can also be used to reduce noise in time-division display.

[0060] Fig. 13 is an explanatory diagram showing the state of odd-numbered frames in time-division display when a shutter display is used, and Fig. 14 is an explanatory diagram showing the state of even-numbered frames in time-division display. In this embodiment, for example, a transmissive monochrome liquid crystal panel 21 is provided as a shutter display between the image display unit 11 and the convex lens array A1. The transmissive monochrome liquid crystal panel 21 may be configured to switch any region between a transmissive display (for example, a visible light transmittance of 90% or more) and a black display (for example, a visible light transmittance of 10% or less).

[0061] Then, for example, in odd-numbered frames of the time-division display shown in FIG. 13, the transmissive monochrome liquid crystal panel 21 is controlled so that the lens areas where the overlapping structures (linear prisms) C1 are displayed in a transmissive manner, and the transmissive areas where the flat portions F11 are displayed in a black manner (light-blocking manner) (first operating mode).

[0062] Also, for example, in the even-numbered frames of the time-division display shown in FIG. 14, the transmissive monochrome liquid crystal panel 21 is controlled so that the lens areas where the intersecting structures (linear prisms) C1 overlap each other are displayed in black (light-blocking display), and the transmissive areas where the flat portions F11 overlap each other are displayed in transmissive display (second operation mode).

[0063] In this way, by using a shutter display such as a transmissive monochrome liquid crystal panel 21 and controlling the shading of the lens area and transmissive area of ​​the convex lens array A1 at a high refresh rate in a time-division display, flickering of a distant three-dimensional image (virtual image) can be suppressed through the transmissive image display unit 11, thereby obtaining a clear display image.

[0064] Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Example]

[0065] The linear Fresnel lens of the first embodiment described above was actually designed. An example of a linear Fresnel lens design is shown in Figure 15. The linear Fresnel lens shown in Figure 15 is an example in which the pitch of the element prism pairs is 0.24 mm and the focal length is 15 mm. Note that Figure 15 shows only half the cross section in the left-right direction. [Industrial Applicability]

[0066] According to the transmission-type naked-eye 3D image display device of the present invention, when applied to, for example, a medical 3D display, it is possible to display a clearer 3D image in space than conventional 3D images, contributing to more accurate observation and treatment. Furthermore, when applied to a head-up display for an automobile, it is possible to display various information necessary for driving as a clear 3D image, contributing to improved operability when driving an automobile. Therefore, the present invention has industrial applicability. [Explanation of symbols]

[0067] 10...Transmission type naked eye 3D image display device 11...Image display section 12...Light-concentrating array 14...Virtual image (image plane) 15...Observer A1...Convex lens array C1...Meander structure (linear prism) L1...Linear Fresnel lens

Claims

1. A linear Fresnel lens in which a plurality of linear prisms, which are lens elements extending in a first direction, are arranged along a second direction perpendicular to the first direction, the linear prism has a convoluted structure in which a sloped structure in a right region from the center to the vicinity of one end of the linear Fresnel lens is superimposed on a sloped structure in a left region from the center to the vicinity of the other end, A linear Fresnel lens, wherein flat portions that transmit light without bending it are formed between adjacent linear prisms.

2. The linear Fresnel lens according to claim 1 , wherein the linear prisms are formed intermittently along the first direction.

3. 3. The linear Fresnel lens according to claim 1, wherein a light-shielding film is formed on a part of the flat portion.

4. 3. The linear Fresnel lens according to claim 1, wherein the convoluted structure has a cross-sectional structure in which a triangular symmetrical peak or valley is formed at the center in a cross section of the linear Fresnel lens perpendicular to the first direction, and when the center is a peak or valley, triangular peaks are formed on both sides of the peak or valley, with slopes closer to the peak or valley being gentler than those on the farther side.

5. a light-transmitting image display unit that displays elemental images observed from a number of different viewpoint positions side by side on an image display surface; a light-collecting optical system array unit disposed on the front side from which projection light of the image display unit is emitted, 10. A transmission-type naked-eye three-dimensional image display device, wherein the light-collecting optical system array section has first and second linear Fresnel lenses formed by stacking two linear Fresnel lenses according to claim 1 so that the first directions are orthogonal to each other.

6. a shutter display is further disposed between the image display unit and the linear Fresnel lens; 6. The transmissive naked-eye three-dimensional video display device according to claim 5, wherein the shutter display switches in a time-division manner between a first operating mode in which, at the timing of displaying the elemental images, the shutter display blocks light transmission in areas other than the overlapping portions of the linear prisms of the first and second linear Fresnel lenses, and a second operating mode in which, at the timing of transmitting all of the projection light from the image display unit, the shutter display blocks light transmission at positions where the linear prisms are formed.

7. a mask layer is further formed adjacent to the first linear Fresnel lens or the second linear Fresnel lens; 6. The transmissive naked-eye three-dimensional image display device according to claim 5, wherein the mask layer is a light-blocking material formed in a shape that suppresses light transmission in an area where a portion of the linear prism of the first linear Fresnel lens overlaps with the flat portion of the second linear Fresnel lens, and in an area where the flat portion of the first linear Fresnel lens overlaps with the portion of the linear prism of the second linear Fresnel lens.

Images