Light guide plate device

Abstract

To achieve a light guide plate in which a deterioration in contrast of a formed image is not conspicuous.SOLUTION: A light guide plate (11) comprises: a plane of incidence on which light is incident; and a light path changing unit that is formed on a back face (11b) perpendicular to the plane of incidence and reflects the light and emits the light from an emission surface parallel to the back face. In a formed image (IA) formed by the light emitted from the emission surface, a surface image representing a surface includes nearby image formation parts (IA1) and a distant image formation part (IA2), and both ends of the surface image on a cross section perpendicular to the back face and perpendicular to an optical axis direction of a light source are included in the nearby image formation parts.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a light guide plate device for displaying a stereoscopic image in space.

Background Art

[0002] There is known a stereoscopic image display device that guides light incident from a light source inside and reflects the guided light by a reflecting member to form a stereoscopic image.

[0003] For example, in the technique disclosed in Patent Document 1, a light guide plate that guides light in a plane parallel to the emission surface, and an optical surface that receives the light guided by the light guide plate and emits the emitted light in a direction that substantially converges on one convergence point or convergence line in space or substantially diverges from one convergence point or convergence line in space are provided. And a plurality of light converging portions are formed along lines respectively predetermined in a plane parallel to the emission surface, the convergence points or convergence lines are different from each other among the plurality of light converging portions, and a stereoscopic image is formed in space by the collection of the plurality of convergence points or convergence lines.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technique disclosed in Patent Document 1, when displaying a plane image as a stereoscopic image, there is a problem that the deterioration of contrast is remarkable compared with a line image.

[0006] One aspect of the present invention aims to realize a light guide plate device in which deterioration of contrast and blurring of an imaged image are not noticeable.

Means for Solving the Problems

[0007] In order to solve the above problems, a light guide plate device according to an aspect of the present invention includes an incident surface on which light from a light source is incident, and an optical path changing portion that is formed at a predetermined position on the back surface perpendicular to the incident surface and reflects the light incident from the incident surface and guided to cause the light to be emitted from an emission surface parallel to the back surface. Among the imaging images formed by the light emitted from the emission surface, the surface image representing the surface is an image as a continuous surface including a near imaging portion whose imaging position is within a predetermined distance from the back surface and a far imaging portion whose imaging position is farther than the predetermined distance, and both ends of the surface image in a cross section perpendicular to the back surface and perpendicular to the optical axis direction of the light source are included in the near imaging portion.

[0008] In the above configuration, the light guide plate device forms an imaging image by the light that is incident from the incident surface, reflected by the optical path changing portion formed on the back surface, and emitted from the emission surface. Among the imaging images, the surface image representing the surface is an image as a continuous surface including a near imaging portion and a far imaging portion that are divided by the distance between the imaging position and the back surface.

[0009] Generally, in an imaging image, as the distance from the back surface increases, deterioration of contrast and blurring tend to be prominent. In other words, compared with the far imaging portion, the near imaging portion is less likely to show deterioration of contrast and blurring. Also, at the ends in a cross section parallel to the incident surface among the imaging images, deterioration of contrast and blurring are particularly likely to be prominent. In the above configuration, both ends of the surface image in a cross section perpendicular to the back surface of the light guide plate and perpendicular to the optical axis direction of the light source are included in the near imaging portion. Therefore, deterioration of contrast and blurring of the imaging image are not prominent.

[0010] In the light guide plate device according to an aspect of the present invention, the predetermined distance may be within 25% of the distance from the emission surface at the imaging position that is the farthest from the back surface among the far imaging portions.

[0011] In the light guide plate device according to one aspect of the present invention, the predetermined distance may be 50% or less of the average of the distances from the back surface at the imaging positions of the respective imaging regions of the imaged image.

[0012] In the light guide plate device according to one aspect of the present invention, the predetermined distance may be 12 mm on the light emission direction side from the back surface and 24 mm on the side opposite to the light emission direction from the back surface.

[0013] In the light guide plate device according to one aspect of the present invention, the predetermined distance may be 20% or less of the minimum value of the distance between the incident surface and the optical path changing portion.

[0014] In the light guide plate device according to one aspect of the present invention, the predetermined distance may be 20% or less of the longer one of the maximum length in the direction perpendicular to the incident surface and the maximum length in the direction parallel to the incident surface in the projection image region of the imaged image on the back surface.

[0015] In these configurations, a predetermined distance that defines the range of an image that becomes a nearby imaging portion is appropriately defined. Therefore, both ends in a cross section perpendicular to the back surface of the light guide plate and perpendicular to the optical axis direction of the light source are included in the nearby imaging portion for such a predetermined distance, so that deterioration of the contrast and blurring of the imaged image become less noticeable.

[0016] In the light guide plate device according to one aspect of the present invention, in the surface image, a cross section parallel to the incident surface of the surface image has an annular shape, and in the direction perpendicular to the emission surface, when the distance from the center of the annular shape to the farthest imaging position is defined as a first distance, the back surface may be present at a position within 20% of the first distance from the center of the annular shape in the direction perpendicular to the emission surface.

[0017] In the above configuration, many portions including both ends in the cross section of a surface image whose cross section parallel to the incident surface has an annular shape are included in the nearby imaging portion. Therefore, deterioration of the contrast of the imaged image can be made even less noticeable.

[0018] In the light guide plate device according to one aspect of the present invention, when the projected image of the surface image is viewed from a direction perpendicular to the emission surface, the length in the direction parallel to the incident surface of the projected image has a shape that is longer than the length in the direction perpendicular to the incident surface, and the distance from the emission surface of the imaging positions at both ends of the projected image in the direction parallel to the incident surface may be within the predetermined distance.

[0019] In the above configuration, in the projected image when the surface image included in the imaging image is viewed from a direction perpendicular to the emission surface, the length in the direction parallel to the incident surface is longer than the length in the direction perpendicular to the incident surface. When the imaging image includes such a surface image, deterioration of contrast and blurring are likely to be prominent. In such a surface image, by setting the distance from the emission surface of the imaging positions at both ends of the projected image in the direction parallel to the incident surface within the predetermined distance, deterioration of contrast and blurring can be made less prominent.

[0020] In the light guide plate device according to one aspect of the present invention, in the projected image when the surface image is viewed from a direction perpendicular to the emission surface, if the distance from the back surface at the imaging position farthest from the back surface among the distant imaging portions is defined as the second distance, the distance from the back surface of the imaging positions at both ends in the direction parallel to the incident surface may be within 30% of the second distance.

[0021] In the above configuration, many portions including both ends in the cross section perpendicular to the back surface of the light guide plate and perpendicular to the optical axis direction of the light source are included in the near imaging portion. Therefore, deterioration of contrast and blurring of the imaging image can be made even less prominent.

Advantages of the Invention

[0022] According to one aspect of the present invention, a light guide plate device in which deterioration of contrast of the imaging image is not prominent can be realized.

Brief Description of the Drawings

[0023]

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Figure 17

MODE FOR CARRYING OUT THE INVENTION

[0024] 〔Embodiment 1〕 Hereinafter, an embodiment according to one aspect of the present invention (hereinafter also referred to as "this embodiment") will be described with reference to the drawings. In the following, for convenience of explanation, there may be cases where the +X direction in FIG. 1 is the right direction, the -X direction is the left direction, the +Y direction is the upward direction, the -Y direction is the downward direction, the +Z direction is the front direction, and the -Z direction is the rear direction. Further, in the following, there may be cases where the +Y direction is described as the light incident direction and the +Z direction is described as the light emission direction.

[0025] §1 Application Example FIG. 1 is a perspective view showing a state in which the light guide plate 11 according to this embodiment is applied. First, an example of a scene to which the present invention is applied will be described with reference to FIG. 1. In FIG. 1, a display device 10 including a light guide plate 11 is shown displaying a three-dimensional image I, more specifically, a three-dimensional image I in the shape of a button (+Z-axis direction protruding shape) with the character "ON" displayed. As shown in FIG. 1, the display device 10 includes a light guide plate 11 (light guide plate device) and a light source 12.

[0026] The light guide plate 11 has a rectangular parallelepiped shape and is formed of a resin material having transparency and a relatively high refractive index. The material forming the light guide plate 11 may be, for example, polycarbonate resin, polymethyl methacrylate resin, glass, or the like. The light guide plate 11 includes an emission surface 11a that emits light, a back surface 11b that is parallel to the emission surface 11a and is on the opposite side of the emission surface 11a, and end surfaces 11c, 11d, 11e, and 11f that are the four side end surfaces. The end surface 11c is an incident surface through which light from the light source 12 enters the light guide plate 11. Hereinafter, the end surface 11c will also be referred to as the incident surface 11c. The end surface 11d is a surface on the opposite side of the end surface 11c. The end surface 11e is a surface on the opposite side of the end surface 11f. The light guide plate 11 spreads and guides the light from the light source 12 in a plane parallel to the emission surface 11a. The light source 12 is, for example, an LED (Light Emitting diode) light source.

[0027] On the back surface 11b of the light guide plate 11, a plurality of light path changing portions including a light path changing portion 13a, a light path changing portion 13b, and a light path changing portion 13c are formed. Hereinafter, the plurality of light path changing portions including the light path changing portion 13a, the light path changing portion 13b, and the light path changing portion 13c may be collectively referred to as the light path changing portion 13. The light path changing portion 13 is formed at a predetermined position on the back surface 11b perpendicular to the incident surface 11c, and reflects the light incident from the incident surface 11c and guided thereby to emit it from the emission surface 11a parallel to the back surface 11b. The light path changing portion 13 is formed substantially continuously in the X-axis direction as a predetermined position. Specifically, as shown in FIG. 1, the light path changing portion 13a, the light path changing portion 13b, and the light path changing portion 13c are respectively formed along the line La, the line Lb, and the line Lc. Here, the line La, the line Lb, and the line Lc are straight lines substantially parallel to the X-axis direction. Any light path changing portion 13 is formed substantially continuously along a straight line parallel to the X-axis direction. In other words, the light path changing portion 13 is formed along a line predetermined in advance within a plane parallel to the back surface 11b. At each position in the X-axis direction of the light path changing portion 13, the light projected from the light source 12 and guided by the light guide plate 11 is incident. The light path changing portion 13 substantially converges the light incident at each position of the light path changing portion 13 to a fixed point corresponding to each light path changing portion 13. FIG. 1 shows a state in which a plurality of lights reflected by the light path changing portion 13a, the light path changing portion 13b, and the light path changing portion 13c as a part of the light path changing portion 13 converge.

[0028] Specifically, the light from each position of the optical path changing unit 13a converges at the fixed point PA that forms a part of the stereoscopic image I. Therefore, the wavefront of the light from the optical path changing unit 13a becomes the wavefront of the light emitted from the fixed point PA. The light from each position of the optical path changing unit 13b converges at the fixed point PB that forms a part of the stereoscopic image I. Therefore, the wavefront of the light from the optical path changing unit 13b becomes the wavefront of the light emitted from the fixed point PB. The same applies to the light from each position of the optical path changing unit 13c as the light from each position of the optical path changing units 13a and 13b. In this way, the light from each position of any optical path changing unit 13 substantially converges at the fixed point corresponding to each optical path changing unit 13. Thereby, any optical path changing unit 13 can provide a wavefront of light as if the light is emitted from the corresponding fixed point. The fixed points corresponding to each optical path changing unit 13 are different from each other, and a stereoscopic image I recognized by the user is formed in space (more specifically, in the space on the emission surface 11a side from the light guide plate 11) by a collection of a plurality of fixed points respectively corresponding to the optical path changing units 13.

[0029] §2 Configuration Example FIG. 2 is a perspective view showing a configuration example of the light guide plate 11 according to the configuration example of the present embodiment. FIG. 3 is a cross-sectional view of the light guide plate 11 shown in FIG. 2 in a cross-section parallel to the incident surface 11c. In the examples shown in FIGS. 2 and 3, a stereoscopic image IA (imaging image) recognized by the user is formed in space by the light emitted from the light guide plate 11. Hereinafter, for simplicity, not only the region located in front of the back surface 11b of the stereoscopic image IA (that is, the real image), but also the region located behind the back surface 11b of the stereoscopic image IA (that is, the virtual image) will be expressed as "formed". That is, in the light guide plate 11 in FIGS. 2 and 3, a plurality of optical path changing units 13 are formed on the back surface 11b of the light guide plate 11 so as to display the stereoscopic image IA.

[0030] As shown in FIGS. 2 and 3, the stereoscopic image IA is a planar image having a strip shape. The planar image referred to here represents a plane, and on the plane where the image is formed, it refers to an image in which the density of imaging points per unit area is 30% or more. Also, the planar image refers to an image in which the full width at half maximum with respect to the brightest point is greater than 2 mm. Therefore, the planar image may include, in addition to an image in which the entire surface is filled, for example, an image with hatching applied thereto.

[0031] However, the stereoscopic image IA may be an image including a planar image and an image different from the planar image, for example, a line image. The line image referred to here means an image in which the full width at half maximum with respect to the brightest point is 2 mm or less. The description of the stereoscopic image IA in the following explanation also applies to the planar image when the stereoscopic image IA includes a planar image and an image different from the planar image.

[0032] As shown in FIG. 3, the stereoscopic image IA is an image as a continuous plane including a near imaging portion IA1 whose imaging position is within a predetermined distance d from the back surface 11b of the light guide plate 11 and a far imaging portion IA2 whose imaging position is farther than the predetermined distance d. The predetermined distance d will be described later.

[0033] As shown in FIG. 3, both ends of the stereoscopic image IA in a cross section perpendicular to the back surface 11b and perpendicular to the optical axis direction of the light source 12 are included in the near imaging portion IA1. In the image formed by the light guide plate 11, as the distance from the back surface 11b to the imaging position increases, deterioration of contrast and blurring tend to become prominent. In other words, in the near imaging portion IA1, deterioration of contrast and blurring are less prominent compared to the far imaging portion IA2. Also, deterioration of contrast and blurring are particularly prominent at the ends in a cross section parallel to the incident surface 11c among the images formed by the light guide plate 11. In the stereoscopic image IA, both ends in a cross section perpendicular to the back surface 11b and perpendicular to the optical axis direction of the light source 12 are included in the near imaging portion IA1. Therefore, according to the light guide plate 11, deterioration of contrast and blurring of the stereoscopic image IA become less prominent.

[0034] In addition, in this configuration example, when the projected image of the stereoscopic image IA is viewed from a direction perpendicular to the emission surface 11a, the length in the direction parallel to the incident surface 11c is longer than the length in the direction perpendicular to the incident surface 11c. In such a stereoscopic image IA, deterioration of contrast and blurring are likely to be prominent. In such a stereoscopic image IA, by setting the distance from the emission surface 11a to the imaging positions at both ends of the projected image in the direction parallel to the incident surface 11c within a predetermined distance d, deterioration of contrast and blurring of the stereoscopic image IA become less prominent.

[0035] §3 Operation Example Next, as an operation example of the light guide plate 11 according to the configuration example of the present application, a specific example of the predetermined distance d will be described below.

[0036] The predetermined distance d may be within 25% of the distance from the back surface 11b at the imaging position farthest from the back surface 11b in the stereoscopic image IA. Further, the predetermined distance d may be 50% or less of the average of the distances from the back surface 11b at the imaging positions of each imaging region of the stereoscopic image IA. Further, the predetermined distance d may be 12 mm on the light emission direction side from the back surface 11b and 24 mm on the side opposite to the light emission direction from the back surface 11b.

[0037] Further, the predetermined distance d may be 20% or less of the minimum value of the distance between the incident surface 11c and the optical path changing unit 13. The shorter the distance between the incident surface 11c and the optical path changing unit 13, the greater the spread of the light incident on the optical path changing unit 13. Therefore, for example, deterioration of contrast and blurring due to a change in the viewing point are likely to occur. By determining the predetermined distance d as described above according to the minimum value of the distance between the incident surface 11c and the optical path changing unit 13, deterioration of contrast and blurring of the stereoscopic image IA formed by the light guide plate 11 having the optical path changing unit 13 can be made less prominent.

[0038] Further, the predetermined distance d may be 20% or less of the longer one of the maximum length in the direction perpendicular to the incident surface 11c and the maximum length in the direction parallel to the incident surface 11c in the projected image region of the stereoscopic image IA on the back surface 11b.

[0039] In these configurations, a predetermined distance d that defines the range of the image that becomes the vicinity imaging portion IA1 is appropriately defined. Therefore, both ends of the planar image in a cross-section perpendicular to the back surface 11b and perpendicular to the optical axis direction of the light source 12 are included in the vicinity imaging portion IA1 for such a predetermined distance d, so that the deterioration of the contrast and the blurring of the stereoscopic image IA become less noticeable.

[0040] In addition, in the optical path changing portion 13 where the imaging position is on the front side of the back surface 11b, the spread of the reflected light in the left-right direction is larger compared to the optical path changing portion 13 where the imaging position is on the rear side of the back surface 11b. For this reason, in the region of the stereoscopic image IA on the front side of the back surface 11b, the light reflected by the plurality of optical path changing portions 13 is more likely to be seen as overlapping compared to the region on the rear side of the back surface 11b. As a result, blurring of the stereoscopic image IA and a decrease in the design quality of the stereoscopic image IA due to such blurring are likely to occur.

[0041] For this reason, for example, as described in the above example, “it may be 12 mm on the light emission direction side from the back surface 11b and 24 mm on the side opposite to the light emission direction from the back surface 11b”, the predetermined distance d on the light emission direction side may be made shorter than the predetermined distance d on the side opposite to the light emission direction. By setting the predetermined distance d in this way, it is possible to suppress the blurring of the stereoscopic image IA particularly on the front side of the back surface 11b and the decrease in the design quality of the stereoscopic image IA due to such blurring.

[0042] FIG. 16 is a diagram for explaining a method of deriving the depth D to the point P0 where the stereoscopic image IE is imaged on the rear side of the light guide plate 11. The stereoscopic image IE has a substantially cubic shape. With reference to FIG. 16, a method of deriving the depth D to the point P0 will be described.

[0043] To derive the depth D to point P0, the three-dimensional image IE is viewed from two viewpoints E1 and E2. The viewpoints E1 and E2 respectively correspond to the left eye and the right eye of the user who views the three-dimensional image IE. Let the point P0 projected onto the light-emitting surface 11a of the light guide plate 11 as viewed from the viewpoint E1 be point P1. Also, let the point P0 projected onto the light-emitting surface 11a of the light guide plate 11 as viewed from the viewpoint E2 be point P2. When the distance between the points P1 and P2 is L1 and the angle between the viewpoints E1 and E2 with respect to the point P0 is Δθ, the depth D = L1 / Δθ.

[0044] FIG. 17 is a diagram for explaining a method of calculating the depth D by image analysis. In FIG. 17, the light guide plate 11 and the three-dimensional image IE viewed from the viewpoint E1 are indicated by reference numeral 171, and the light guide plate 11 and the three-dimensional image IE viewed from the viewpoint E2 are indicated by reference numeral 172. Also, an image obtained by superimposing the images of reference numerals 171 and 172 is indicated by reference numeral 173. With reference to FIG. 17, a method of calculating the depth D by image analysis will be described.

[0045] When calculating the depth D by image analysis, an arbitrary point on the light-emitting surface 11a is specified as point P3. The point P3 may be an arbitrary point included in the three-dimensional image IE imaged on the light-emitting surface 11a. Also, the point P3 may be a point marked on the light-emitting surface 11a that is not included in the three-dimensional image IE. The position of such a point P3 on the light-emitting surface 11a is constant regardless of the position of the viewpoint.

[0046] In image analysis, as shown in reference numeral 173, the images shown in reference numerals 171 and 172 are superimposed so that the points P3 coincide with each other. Since the position of the point P3 on the light-emitting surface 11a is constant regardless of the position of the viewpoint, the distance between the points P1 and P2 in the image shown in reference numeral 173 is equal to the distance L1 shown in FIG. 16. Therefore, as described above, the depth D can be calculated as D = L1 / Δθ.

[0047] §4 Modification As described above, the embodiments of the present invention have been described in detail. However, the description up to this point is merely an exemplification of the present invention in every aspect. Needless to say, various improvements and modifications can be made without departing from the scope of the present invention. For example, the following changes are possible. In the following, the same reference numerals are used for the same components as in the above embodiment, and the description of the same points as in the above embodiment is omitted as appropriate. The following modification examples can be combined as appropriate.

[0048] <4.1> FIG. 4 is a perspective view showing a first modification example of the light guide plate 11. FIG. 5 is a cross-sectional view of the light guide plate 11 shown in FIG. 4 in a cross-section parallel to the incident surface 11c.

[0049] As shown in FIGS. 4 and 5, the light guide plate 11 according to this modification example forms a three-dimensional image IB (imaging image). The three-dimensional image IB is a surface image whose cross-section parallel to the incident surface 11c has an annular shape. However, the three-dimensional image IB may be an image including a surface image and an image different from the surface image, for example, a line image. The description of the three-dimensional image IB in the following explanation is also applicable to the surface image in the case where the three-dimensional image IB includes a surface image and an image different from the surface image.

[0050] In this modification example, as shown in FIG. 5, in the direction perpendicular to the exit surface 11a (in the Y-axis direction), the distance from the center C of the annular shape of the three-dimensional image IB to the farthest imaging position of the three-dimensional image IB is defined as the first distance R1. At this time, in the direction perpendicular to the exit surface 11a, the back surface 11b may exist at a distance d1 within 20% of the first distance R1 from the center C of the annular shape. That is, d1 < 0.2 × R1 may be satisfied.

[0051] According to the light guide plate 11 shown in FIG. 5, many portions including both ends of the surface image whose cross-section parallel to the incident surface 11c has an annular shape are included in the vicinity imaging portion IA1 (see FIG. 3). Therefore, it is possible to further make the deterioration of the contrast of the three-dimensional image IA less noticeable.

[0052] <4.2> FIG. 6 is a perspective view showing a second modified example of the light guide plate 11. As shown in FIG. 6, the light guide plate 11 according to this modified example forms a stereoscopic image IC (imaging image). The stereoscopic image IC has a cylindrical shape with an opening formed at an end. In such a stereoscopic image IC, the rear side of the stereoscopic image IC may be a surface image similar to the front side, or a surface image with a lower gradation value than the front side. Further, the rear side of the stereoscopic image IC may be a line image of only the outline. Even when the rear side of the stereoscopic image IC is represented by any of the above images, by forming the stereoscopic image IC such that both ends in a cross section perpendicular to the back surface 11b and perpendicular to the optical axis direction of the light source 12 are included in the nearby imaging portion IA1, the deterioration of the contrast of the stereoscopic image IC becomes less noticeable.

[0053] <4.3> FIG. 7 is a view for explaining a third modified example of the light guide plate 11. As shown in FIG. 7, the light guide plate 11 according to this modified example forms a stereoscopic image IB. The shape of the stereoscopic image IB is as described with reference to FIGS. 4 and 5.

[0054] In this modified example, as shown in FIG. 7, in the projection image when viewed from a direction where the stereoscopic image IB is on the emission surface 11a parallel Let the distance from the back surface 11b at the imaging position farthest from the back surface 11b be the second distance R2. At this time, the distance d2 from the back surface 11b at both end portions in the X direction (direction parallel to the incident surface 11c) of the imaging position may be within 30% of the second distance R2. That is, d2 < 0.3×R2 may be satisfied.

[0055] According to the light guide plate 11 shown in FIG. 7, many portions including both ends of the surface image in a cross section perpendicular to the back surface 11b and perpendicular to the optical axis direction of the light source 12 are included in the nearby imaging portion IA1 (see FIG. 3). Therefore, the deterioration of the contrast of the stereoscopic image IB can be made even less noticeable.

[0056] <4.4> FIG. 8 is a diagram for explaining a fourth modification example of the light guide plate 11. FIG. 9 is a cross-sectional view of the three-dimensional image ID (imaging image) shown in FIG. 8 in a cross-section parallel to the incident surface 11c. However, the three-dimensional image ID may be an image including a planar image and an image different from the planar image, for example, a line image.

[0057] As shown in FIGS. 8 and 9, the light guide plate 11 according to this modification example forms a three-dimensional image ID. The three-dimensional image ID is a planar image having a shape in which a cross-section parallel to the incident surface 11c is bent rearward from both ends in the X-axis direction. In other words, the shape of the cross-section parallel to the incident surface 11c of the three-dimensional image ID shown in FIGS. 8 and 9 is different from the three-dimensional image IB shown in FIG. 7 and is not an annular shape.

[0058] As shown in FIG. 9, in the projection image when the three-dimensional image ID is viewed from a direction perpendicular to the emission surface 11a, the distance d2 may be within 30% of the second distance R2. Thereby, also in the light guide plate 11 shown in FIG. 9, the deterioration of the contrast of the three-dimensional image ID can be further made less conspicuous.

[0059] <4.5> A display device 10A, which is a modification example of the display device 10, will be described below.

[0060] FIG. 10 is a perspective view of the display device 10A. As shown in FIG. 10, the display device 10A includes a light source 12 and a light guide plate 15. The light guide plate 15 is a modification example of the light guide plate 11 described above.

[0061] FIG. 11 is a cross-sectional view showing the configuration of the optical path changing portion 16 provided in the light guide plate 15. FIG. 12 is a plan view showing the configuration of the light guide plate 15. FIG. 13 is a perspective view showing the configuration of the optical path changing portion 16 provided in the light guide plate 15.

[0062] The light guide plate 15 is a member that guides the light (incident light) incident from the light source 12. The light guide plate 15 is formed of a resin material that is transparent and has a relatively high refractive index. As the material for forming the light guide plate 15, for example, polycarbonate resin, polymethyl methacrylate resin, etc. can be used. In this modification example, the light guide plate 15 is formed of polymethyl methacrylate resin. The light guide plate 15 includes an emission surface 15a, a back surface 15b, and an incident surface 15c as shown in FIG. 11.

[0063] The emission surface 15a is a surface that emits the light guided inside the light guide plate 15 and whose optical path is changed by the optical path changing portion 16 described later. The emission surface 15a constitutes the front surface of the light guide plate 15. The back surface 15b is a surface parallel to the emission surface 15a and is the surface on which the optical path changing portion 16 described later is disposed. The incident surface 15c is a surface on which the light emitted from the light source 12 is incident into the light guide plate 15.

[0064] The light emitted from the light source 12 and incident on the light guide plate 15 from the incident surface 15c is totally reflected at the emission surface 15a or the back surface 15b and is guided inside the light guide plate 15.

[0065] As shown in FIG. 11, the optical path changing portion 16 is formed on the back surface 15b inside the light guide plate 15 and is a member for changing the optical path of the light guided inside the light guide plate 15 and emitting it from the emission surface 15a. A plurality of optical path changing portions 16 are provided on the back surface 15b of the light guide plate 15.

[0066] As shown in FIG. 12, the optical path changing portion 16 is provided along a direction parallel to the incident surface 15c. As shown in FIG. 13, the optical path changing portion 16 has a triangular pyramid shape and includes a reflection surface 16a that reflects (totally reflects) the incident light. The optical path changing portion 16 may be, for example, a recess formed on the back surface 15b of the light guide plate 15. Note that the optical path changing portion 16 is not limited to the triangular pyramid shape. As shown in FIG. 12, a plurality of optical path changing portion groups 17a, 17b, 17c... each composed of a plurality of optical path changing portions 16 are formed on the back surface 15b of the light guide plate 15.

[0067] FIG. 14 is a perspective view showing the arrangement of the optical path changing units 16. As shown in FIG. 14, in each of the optical path changing unit groups 17a, 17b, 17c..., the reflecting surfaces 16a of the plurality of optical path changing units 16 are arranged on the back surface 15b of the light guide plate 15 such that the angles with respect to the light incident direction are different from each other. Thereby, each of the optical path changing unit groups 17a, 17b, 17c... changes the optical path of the incident light and causes it to be emitted from the emission surface 15a in various directions.

[0068] Next, a method for forming the three-dimensional image I by the light guide plate 15 will be described with reference to FIG. 15. Here, a case will be described in which a three-dimensional image I as a planar image is formed on a three-dimensional image forming surface P, which is a plane perpendicular to the emission surface 15a of the light guide plate 15, by the light whose optical path is changed by the optical path changing unit 16.

[0069] FIG. 15 is a perspective view showing a method for forming the three-dimensional image I by the light guide plate 15. Here, a case will be described in which a hatched ring mark is formed as the three-dimensional image I on the three-dimensional image forming surface P.

[0070] In the light guide plate 15, as shown in FIG. 15, for example, the light whose optical path is changed by each optical path changing unit 16 of the optical path changing unit group 17a intersects the three-dimensional image forming surface P at lines La1 and La2. Thereby, a line image LI, which is a part of the three-dimensional image I, is formed on the three-dimensional image forming surface P. The line image LI is a line image parallel to the XZ plane. In this way, the line images LI of the lines La1 and La2 are formed by the light from a large number of optical path changing units 16 belonging to the optical path changing unit group 17a. Note that the light for forming the images of the lines La1 and La2 only needs to be provided by at least two optical path changing units 16 in the optical path changing unit group 17a.

[0071] Similarly, the light whose optical path is changed by each optical path changing unit 16 of the optical path changing unit group 17b intersects the three-dimensional image forming surface P at lines Lb1, Lb2, and Lb3. Thereby, a line image LI, which is a part of the three-dimensional image I, is formed on the three-dimensional image forming surface P.

[0072] In addition, the light whose optical path is changed by each optical path changing unit 16 in the optical path changing unit group 17c intersects the three-dimensional image formation plane P at lines Lc1 and Lc2. As a result, a line image LI which is a part of the three-dimensional image I is formed on the three-dimensional image formation plane P.

[0073] The positions of the line images LI in the X-axis direction formed by each of the optical path changing unit groups 17a, 17b, 17c... are different from each other. In the light guide plate 15, by reducing the distance between the optical path changing unit groups 17a, 17b, 17c..., the distance of the line images LI in the X-axis direction formed by each of the optical path changing unit groups 17a, 17b, 17c... can be reduced. As a result, in the light guide plate 15, by integrating a plurality of line images LI formed by the light whose optical path is changed by each optical path changing unit 16 in the optical path changing unit groups 17a, 17b, 17c..., substantially the three-dimensional image I which is a planar image is formed on the three-dimensional image formation plane P.

[0074] Note that the three-dimensional image formation plane P may be a plane perpendicular to the X-axis, a plane perpendicular to the Y-axis, or a plane perpendicular to the Z-axis. Also, the three-dimensional image formation plane P may be a plane not perpendicular to the X-axis, Y-axis, or Z-axis. Further, the three-dimensional image formation plane P may be a curved surface instead of a plane. That is, the light guide plate 15 can form the three-dimensional image I on an arbitrary surface (plane and curved surface) in space by the optical path changing unit 16. Also, a three-dimensional image can be formed by combining a plurality of planar images.

[0075] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

Explanation of Reference Numerals

[0076] 11, 15 Light guide plate (light guide plate device) 12 Light source 11a, 15a Exit surface 11b, 15b Back surface 11c, 15c Incident surface 13, 13a, 13b, 13c, 16 Optical path changing section d Predetermined distance d2 Distance I, IA, IB, IC, ID Stereoscopic image (imaging image) IA1 Nearby imaging part IA2 Distant imaging part R1 First distance R2 Second distance

Claims

1. An incident surface on which light from a light source is incident, and an optical path changing unit formed at a predetermined position on the back surface perpendicular to the incident surface, which reflects the light incident from the incident surface and guided, and emits the light from an emission surface parallel to the back surface, Among the imaging images formed by the light emitted from the emission surface, the surface image representing the surface is an image as a continuous surface including a near imaging portion where the imaging position is within a predetermined distance from the back surface and a far imaging portion where the imaging position is farther than the predetermined distance, Both ends of the surface image in a cross section perpendicular to the back surface and perpendicular to the optical axis direction of the light source when viewed from a direction perpendicular to the emission surface are included in the near imaging portion, The surface image has an annular shape in a cross section parallel to the incident surface of the surface image, When the distance from the center of the annular shape to the farthest imaging position in the direction perpendicular to the emission surface is defined as the first distance, in the direction perpendicular to the emission surface, the back surface exists at a position within 20% of the first distance from the center of the annular shape. A light guide plate device.

2. The light guide plate device according to claim 1, wherein the predetermined distance is within 25% of the distance from the emission surface at the imaging position farthest from the back surface among the far imaging portions.

3. The light guide plate device according to claim 1, wherein the predetermined distance is 50% or less of the average of the distances from the back surface at the imaging positions of the respective imaging regions of the imaging image.

4. The light guide plate device according to claim 1, wherein the predetermined distance is 12 mm on the light emission direction side from the back surface and 24 mm on the side opposite to the light emission direction from the back surface.

5. The light guide plate device according to claim 1, wherein the predetermined distance is 20% or less of the minimum value of the distance between the incident surface and the optical path changing unit.

6. The light guide plate device according to claim 1, wherein the predetermined distance is 20% or less of the longer one of the maximum length in the direction perpendicular to the incident surface and the maximum length in the direction parallel to the incident surface in the projection image region of the imaging image on the back surface.

7. The projection image when the surface image is viewed from a direction perpendicular to the emission surface has a shape in which the length in the direction parallel to the incident surface is longer than the length in the direction perpendicular to the incident surface, The light guide plate device according to claim 1, wherein the distances from the emission surface at the imaging positions of both end portions of the projection image in the direction parallel to the incident surface are within the predetermined distance.

8. In the projection image when the front surface image is viewed from a direction parallel to the exit surface, among the distant imaging portions, if the distance from the back surface at the imaging position farthest from the back surface is defined as the second distance, the distance from the back surface of the imaging positions at both ends in the direction parallel to the incident surface is within 30% of the second distance. The light guide plate device according to claim 1.

Images