Light guide element and observation optical system and display device having the same

Abstract

To provide a light guide element for realizing an observation optical system that is compact and can secure a wide eye-motion box. [Solution] The light guide element is a light guide element that guides light from a display element to the observer's eye, and comprises a prism into which light from the display element is incident, and an expanding portion that expands the diameter of the light beam from the prism, and each of the expanding portions has first to third surfaces perpendicular to the intersection surface of the light guide element that intersects with the observer's line of sight direction and parallel to the direction of propagation of the light incident on the expanding portion, the third surface being a partially reflective surface positioned between the first and second surfaces, and the light incident on the expanding portion propagates while being reflected by the intersection surface and the first and second surfaces.

Description

Technical Field

[0001] The present invention relates to a light guide element.

Background Art

[0002] Conventionally, an observation optical system has been provided with a light guide plate including an enlarging portion that enlarges the image light beam diameter (Patent Documents 1, 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the configuration of Patent Document 1, since the light beam diameter in the direction perpendicular to the thickness direction of the light guide plate is not enlarged, if the image display element is lengthened in the direction perpendicular to the thickness direction in order to secure a wide eye motion box, the projection optical system becomes large, and as a result, the observation optical system becomes large.

[0005] In the configuration of Patent Document 2, although the light beam diameter in the thickness direction and the direction perpendicular to the thickness direction is enlarged, two projection optical systems are required, and the observation optical system becomes large.

[0006] An object of the present invention is to provide a light guide element for realizing an observation optical system that can secure a small and wide eye motion box.

Means for Solving the Problems

[0007] One aspect of the present invention is a light guide element that guides light from a display element to the observer's eye, comprising a prism into which light from the display element is incident, and an expanding portion that expands the diameter of the light beam from the prism, wherein the expanding portion each has first to third surfaces perpendicular to the intersection surface of the light guide element that intersects with the observer's line of sight and parallel to the direction of propagation of the light incident on the expanding portion, the third surface being a partially reflective surface positioned between the first and second surfaces, and the light incident on the expanding portion propagates while being reflected by the intersection surface and the first and second surfaces. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a light guide element for realizing an observation optical system that can secure a small and wide eye motion box. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of the display device according to the first embodiment. [Figure 2] This is an explanatory diagram of the light guide plate of the first embodiment. [Figure 3] This is an explanatory diagram of the light guide plate of the second embodiment. [Figure 4] This is an explanatory diagram of the light guide plate of the third embodiment. [Figure 5] This is an explanatory diagram of the light guide plate of the fourth embodiment. [Figure 6] This is an explanatory diagram of the light guide plate according to the fifth embodiment. [Modes for carrying out the invention]

[0010] The embodiments of the present invention will be described in detail below with reference to the drawings. In each figure, the same reference numerals are used for the same components, and redundant explanations are omitted. [First Embodiment] Figure 1 is a schematic diagram of the display device of this embodiment, as seen from the observer's side. The display device is, for example, AR (Augmented Reality) glasses. The display device has a display element that displays an image and an observation optical system that guides the image light beam from the image to the observer's eye. The observation optical system has a projection optical system arranged in the direction perpendicular to the plane of the paper (direction as seen from the observer's side, direction of the observer's line of sight) and a light guide plate (light guide element) 12 that guides the image light beam projected by the projection optical system to the eye.

[0011] The light guide plate 12 has a prism section 121 that causes the image light beam to travel through the light guide plate 12 while internally reflecting, an magnification section 122 that magnifies the incident image light beam, and an extraction section 123 that extracts the magnified image light beam (magnified light beam) outside the light guide plate 12 and guides it to the eye. In the light beam emitted from the light guide plate 12, the angle of the light beam in the width direction of the light guide plate 12 (direction perpendicular to the line of sight) represents the vertical direction, and the angle of the light beam in the thickness direction of the light guide plate 12 (line of sight) represents the horizontal direction.

[0012] The function and effects of the light guide plate 12 of this embodiment will be described below with reference to Figure 2. Figure 2 is an explanatory diagram of the light guide plate 12 of this embodiment. Figure 2(a) shows the structure of the prism section 121 and the magnifying section 122. Figures 2(b) and 2(c) are schematic diagrams of the optical path of the image light beam. Figure 2(b) is a view from the side of arrow A1 in Figure 2(a). Figures 2(d) and 2(e) are schematic diagrams of the light guide plate 12.

[0013] The magnified section 122 has two parallel mirror surfaces (first surface, second surface) 1221, 1222 and a partially reflective mirror surface (partially reflective surface, third surface) 1223 arranged at intervals d that divide the distance D between the mirror surfaces 1221, 1222 equally. Each mirror surface is perpendicular to the surface 12a of the light guide plate 12, which is the intersecting surface that intersects with the observer's line of sight, represented by arrow A2, and is parallel to the direction of propagation of light incident on the magnified section 122, represented by arrow A3. The length of each mirror surface in the line of sight direction is the same as the thickness T of the light guide plate 12.

[0014] As shown in Fig. 2(b), the prism section 121 has a first prism 1211 including a first structure 1211a that propagates certain angular rays of the incident image light beam in the line-of-sight direction at an angle of ±α. The first structure 1211a reflects the light from the display element so that the light incident on the enlarging section 122 travels while being reflected by the surface 12a of the light guide plate 12. Also, as shown in Fig. 2(c), the prism section 121 has a second prism 1212 including a second structure 1212a that is incident on the mirror surfaces 1221, 1222 at an angle of ±β, and the light beam diameter in the arrangement direction of each mirror surface represented by arrow A4 of the light incident on the enlarging section 122 becomes d. The second structure 1212a reflects the light from the display element so that the light incident on the enlarging section 122 travels while being reflected by the mirror surfaces 1221, 1222.

[0015] By adopting such a configuration, as shown in Fig. 2(d), the light beam diameter P of the image light beam in the direction perpendicular to the line-of-sight direction can be enlarged to the light beam diameter EP.

[0016] Here, the lengths L1, L2, L3 in the traveling direction of the light incident on each of the enlarging section 122 of the mirror surfaces 1221, 1222 and the partial reflection mirror surface 1223 preferably satisfy the following formula (1).

[0017]

Equation

[0018] Also, the transmittance and reflectance of the partial reflection mirror surface 1223 with respect to the light from the display element are preferably 50% each.

[0019] By setting such lengths and characteristics, unevenness in the light intensity in the enlarged light beam can be suppressed.

[0020] Furthermore, if the angle β is smaller than the critical angle of the light guide plate 12, at least one of the mirror surfaces 1221 and 1222 may be the outer surface of the light guide plate 12, as shown in Figure 2(e). By doing so, when the light guide plate 12 of this embodiment is applied to an eyeglass-type device, the magnifying section 122 can be housed in the temples, thereby improving the design.

[0021] As described above, according to the configuration of this embodiment, the light beam diameter is expanded in the line of sight direction and in the direction perpendicular to the line of sight direction inside the light guide plate 12, making it possible to realize an observation optical system that can secure a small and wide eye motion box. [Second Embodiment] The basic configuration of the display device in this embodiment is the same as in Embodiment 1. In this embodiment, only the configurations that differ from the first embodiment will be described, and the common configurations will not be described.

[0022] Figure 3 is an explanatory diagram of the light guide plate 12 of this embodiment. The enlarged portion 122 has the configuration of the first embodiment (first enlarged portion), and a configuration including mirror surfaces 2211, 2212 that are parallel to each other, and a partially reflective mirror surface 2223 that is arranged at intervals 2d that equally divide the distance 4d between the mirror surfaces 2221, 2222 (second enlarged portion). By arranging the configuration including the two mirror surfaces and the partially reflective mirror surface in this manner, it is possible to further enlarge the light beam diameter.

[0023] Furthermore, as shown in Figure 3(b), a configuration including mirror surfaces 2231, 2232 and a partially reflective mirror surface 2233 arranged at an interval d / 2 that equally divides the distance d between the mirror surfaces 2231, 2232 may be arranged before the configuration of the first embodiment. This makes it possible to further reduce the luminous flux diameter P required to obtain the desired luminous flux diameter EP.

[0024] As described above, the configuration of this embodiment makes it possible to further increase the optical beam diameter and further miniaturize the projection optical system compared to the first embodiment.

[0025] In this embodiment, we have described a case where two configurations, each including two mirror surfaces and a partially reflective mirror surface, are arranged in a series. However, three or more such configurations may be arranged. [Third Embodiment] The basic configuration of the display device in this embodiment is the same as in Embodiment 1. In this embodiment, only the configurations that differ from the first embodiment will be described, and the common configurations will not be described.

[0026] Figure 4 is an explanatory diagram of the light guide plate 32 of this embodiment. Figure 4(a) is a schematic diagram of the optical path of the image light beam. Figure 4(b) is a schematic diagram of the light guide plate 32. Figure 4(c) shows the light intensity distribution of the magnified light beam when the transmittance of the partial reflective mirror surface 3223 is constant. Figure 4(d) shows the light intensity distribution of the magnified light beam when the transmittance of the partial reflective mirror surface 3223 changes.

[0027] The light guide plate 32 has a prism section 321 that causes the image light beam to travel through the light guide plate 32 while internally reflecting, an magnification section 322 that magnifies the incident image light beam, and an extraction section 323 that extracts the magnified image light beam outside the light guide plate 12 and guides it to the eye.

[0028] The magnification section 322 has partial reflective mirror surfaces 3221, 3223, and a mirror surface 3222. Each mirror surface is parallel and arranged at intervals corresponding to the diameter of the image light beam incident on the magnification section 322. Preferably, the reflectance and transmittance of the partial reflective mirror surface 3223 are 50% each. With this configuration, as shown in Figure 4(b), it is possible to reduce the area of ​​the magnification section 322 required to obtain the desired light beam diameter EP.

[0029] Furthermore, it is preferable that the reflectivity of the partial reflective mirror surface 3221 be set such that the transmittance increases as the distance from the incident position to the magnification section 322 increases. When the transmittance is constant, the amount of light transmitted through the partial reflective mirror surface 3221 decreases as the distance from the incident position increases, resulting in greater intensity unevenness within the magnified luminous beam, as shown in Figure 4(c). On the other hand, when the transmittance changes, the intensity unevenness within the magnified luminous beam can be reduced. The change in transmittance can be achieved with a single type of coating, for example, by defining it by the area ratio of the mirror-coated portion to the uncoated portion of the mirror surface.

[0030] As described above, the configuration of this embodiment makes it possible to enlarge the luminous beam diameter while reducing the area required for the enlarged portion. [Fourth Embodiment] In the first to third embodiments, a configuration was described in which only the luminous flux diameter of the image luminous beam perpendicular to the line of sight is enlarged. However, in this embodiment, a configuration is described in which the luminous flux diameter of the image luminous beam in the line of sight is also enlarged. The basic configuration of the display device in this embodiment is the same as in Embodiment 1. In this embodiment, only the configurations that differ from the first embodiment will be described, and the common configurations will not be described.

[0031] Figure 5 is an explanatory diagram of the light guide plate 12 of this embodiment. Figure 5(a) is a perspective view of an enlarged section of this embodiment. Figures 5(b) and 5(c) are schematic diagrams of the optical path of the image light beam of this embodiment.

[0032] The enlarged portion 122 has two parallel mirror surfaces 5221 and 5222, a partially reflective mirror surface 5223 arranged at intervals d that divide the distance D between the mirror surfaces 5221 and 5222 equally, and a partially reflective mirror surface (fourth surface) 5224 arranged at intervals t that divide the thickness T of the light guide plate 12 equally.

[0033] As shown in Figure 5(b), the prism section 121 has a first prism 5211 that propagates a certain angle of light ray of the incident image light beam in the line of sight direction at an angle of ±α. The prism section 121 also has a second prism 5212 that is incident on the mirror surfaces 5221 and 5222 at an angle of ±β, and the diameter of the light beam incident on the magnification section 122 is d.

[0034] By adopting this configuration, the diameter of the image light beam can be expanded in the line of sight direction, making it possible to reduce the diameter of the light beam required to fill the entire thickness of the light guide plate 12.

[0035] Here, it is preferable that the lengths L1, L2, and L3 in the direction of propagation of light incident on the respective enlarged portions 122 of the mirror surfaces 5221, 5222, and the length L4 in the line of sight direction of the partially reflective mirror surface 5224 satisfy the following equation (2).

[0036]

number

[0037] Furthermore, it is preferable that the transmittance and reflectance of the partially reflective mirror surfaces 5223 and 5224 are 50%, respectively.

[0038] By setting the length and characteristics in this way, it is possible to suppress unevenness in light intensity in the expanded luminous beam.

[0039] As described above, according to the configuration of this embodiment, the light beam can be expanded in two dimensions simultaneously inside the light guide plate 12. [Fifth Embodiment] In the first to fourth embodiments, the description assumed that the width of the mirror surface of the magnified portion in the line of sight direction was equal to the thickness of the light guide plate. However, in this embodiment, the configuration of the magnified portion when the width of the mirror surface is narrower than the thickness of the light guide plate will be described. Such a magnified portion is applied, for example, when it is not possible to form mirrors in the entire line of sight direction due to manufacturing constraints or the like.

[0040] The basic configuration of the display device in this embodiment is the same as in Embodiment 1. In this embodiment, only the configurations that differ from the first embodiment will be described, and the common configurations will not be described.

[0041] Figure 6 is an explanatory diagram of the light guide plate 12 of this embodiment. Figure 6(a) is a perspective view of the enlarged section 122.

[0042] The enlarged section 122 has mirror surfaces 6221, 6222 that are parallel to each other, and a plurality of partially reflective mirror surfaces 6223, 6224, 6225 arranged at intervals p that divide the distance D between the mirror surfaces 6221, 6222 equally. The width t of the partially reflective mirror surfaces 6223, 6224, 6225 in the line of sight direction is narrower than the thickness T of the light guide plate 12. In this case, it is preferable that the interval p between the partially reflective mirrors satisfies the following condition (3) using the interval d of the first embodiment.

[0043]

number

[0044] Figure 6(b) shows the optical path of a light ray incident on the magnifying section 122, as observed from the prism section 121 side, in the first embodiment. Figures 6(c) and 6(d) show the optical path of a light ray incident on the magnifying section 122, as observed from the prism section 121 side, when it travels the same distance as the light ray in Figure 5(b), in this embodiment. Figure 6(c) is for the case p=d, and Figure 6(d) is for the case p=(t×d) / T.

[0045] As shown in Figure 6(c), if condition (3) is not satisfied, the number of times light is reflected by the partially reflective mirror surface is less than the thickness T of the light guide plate 12, because the width of the partially reflective mirror surface is less than the thickness T of the light guide plate 12. In such cases, the amount of light in the region that should be reflected and magnified is reduced, resulting in uneven light intensity in the magnified luminous flux, which is undesirable. On the other hand, as shown in Figure 6(d), if condition (3) is satisfied, all light rays are reflected at least as many times as when the width of the partially reflective mirror surface is equal to the thickness T of the light guide plate 12, thus suppressing uneven light intensity in the magnified luminous flux. In this way, even when the width of the partially reflective mirror surface is narrow with respect to the line of sight, the luminous flux can be magnified while suppressing uneven light intensity in the magnified luminous flux by narrowing the spacing between the partially reflective mirror surfaces.

[0046] Each embodiment disclosed includes the following configuration: (Composition 1) A light guide element that guides light from a display element to the observer's eye, A prism into which light from the display element is incident, It has an expanding section that expands the diameter of the light beam from the prism, Each of the magnified portions comprises a first to third surface perpendicular to the intersecting surface of the light guide element that intersects with the observer's line of sight, and parallel to the direction of propagation of light incident on the magnified portion. The third surface is a partially reflective surface located between the first and second surfaces. A light guide element characterized in that light incident on the enlarged portion propagates while being reflected by the intersecting surface and the first and second surfaces. (Configuration 2) The light guide element according to configuration 1, characterized in that the prism comprises a first prism including a first structure that reflects light from the display element such that light incident on the magnifying portion propagates while being reflected by the intersecting surface, and a second prism including a second structure that reflects light from the display element such that light incident on the magnifying portion propagates while being reflected by the first and second surfaces. (Composition 3) When the lengths of the first to third surfaces in the direction of travel are L1, L2, and L3, respectively, the distance between the first and second surfaces is D, and the angle at which the light incident on the enlarged portion is incident on the first and second surfaces is β,

[0047]

number

[0048] A light guide element according to configuration 1 or 2, characterized by satisfying the following conditional expression. (Composition 4) A light guide element according to any one of configurations 1 to 3, characterized in that the transmittance and reflectance of the third surface to light from the display element are each 50%. (Composition 5) The third surface is positioned such that it is at equal distances from the first and second surfaces. The light guide element according to any one of configurations 1 to 4, characterized in that the distance between the first and third surfaces is equal to the diameter of the light beam incident on the enlarged portion in the direction in which the first to third surfaces are arranged. (Composition 6) The magnification section comprises a first magnification section and a second magnification section into which light from the first magnification section is incident. The light guide element according to configuration 5, characterized in that the distance between the third surfaces of the first and second enlarged portions is equal to the diameter of the light beam in the arrangement direction of the light incident on the second enlarged portion. (Composition 7) A light guide element according to any one of configurations 1 to 6, characterized in that one of the first and second surfaces is a partially reflective surface. (Composition 8) The light guide element according to any one of configurations 1 to 7, characterized in that the enlarged portion comprises a fourth surface that is parallel to the intersecting surface and is a partially reflective surface. (Composition 9) The prism reflects light from the display element such that light incident on the magnified portion travels while being reflected by the intersecting surface. When L4 is the length of the fourth surface in the line of sight direction, T is the length of the light guide element in the line of sight direction, and α is the angle at which light from the display element is incident on the intersecting surface,

[0049]

number

[0050] The light guide element according to configuration 8, characterized in that it satisfies the following conditional expression. (Composition 10) A light guide element according to any one of configurations 1 to 9, characterized in that, in the line of sight direction, the length of the third surface is shorter than the length of the light guide element. (Composition 11) The third surface includes multiple surfaces, When the distance between the third surfaces is p, the length of the third surface in the line of sight direction is t, the length of the light guide element in the line of sight direction is T, and the diameter of the light beam incident on the enlarged portion in the direction of arrangement of the first to third surfaces is d,

[0051]

number

[0052] The light guide element according to configuration 10, characterized in that it satisfies the following conditional expression. (Composition 12) A light guide element described in any one of configurations 1 to 11, An observation optical system characterized by having a projection optical system that projects light from a display element onto a light guide element. (Composition 13) The observation optical system described in configuration 12, A display device characterized by having a display element.

[0053] Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its gist. [Explanation of Symbols]

[0054] 12 Light guide elements 121 Prism section 122 Enlarged section 1221 Mirror surface (first surface or second surface) 1222 Mirror surface (second surface or first surface) 1223 Partially reflective mirror surface (third surface)

Claims

1. A light guide element that guides light from a display element to the observer's eye, A prism into which light from the display element is incident, It has an expanding section that expands the diameter of the light beam from the prism, Each of the magnified portions comprises a first to third surface perpendicular to the intersecting surface of the light guide element that intersects with the observer's line of sight, and parallel to the direction of propagation of light incident on the magnified portion. The third surface is a partially reflective surface located between the first and second surfaces. The light guide element is characterized in that light incident on the enlarged portion propagates while being reflected by the intersecting surface and the first and second surfaces.

2. The light guide element according to claim 1, wherein the prism comprises a first prism including a first structure that reflects light from the display element such that light incident on the magnifying portion propagates while being reflected by the intersecting surface, and a second prism including a second structure that reflects light from the display element such that light incident on the magnifying portion propagates while being reflected by the first and second surfaces.

3. The lengths of the first to third surfaces in the direction of travel are each L. １ , L ２ , L ３ When D is the distance between the first and second surfaces, and β is the angle at which the light incident on the enlarged portion is incident on the first and second surfaces, The light guide element according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

4. The light guide element according to claim 1 or 2, characterized in that the transmittance and reflectance of the third surface to light from the display element are each 50%.

5. The third surface is positioned such that it is at equal distances from the first and second surfaces. The light guide element according to claim 1 or 2, characterized in that the distance between the first and third surfaces is equal to the diameter of the light beam incident on the enlarged portion in the direction in which the first to third surfaces are arranged.

6. The magnification section comprises a first magnification section and a second magnification section into which light from the first magnification section is incident. The light guide element according to claim 5, characterized in that the distance between the third surfaces of the first and second enlarged portions is equal to the diameter of the light beam in the arrangement direction of the light incident on the second enlarged portion.

7. The light guide element according to claim 1 or 2, characterized in that one of the first and second surfaces is a partially reflective surface.

8. The light guide element according to claim 1 or 2, characterized in that the enlarged portion comprises a fourth surface that is parallel to the intersecting surface and is a partially reflective surface.

9. The prism reflects light from the display element such that light incident on the magnified portion travels while being reflected by the intersecting surface. When L4 is the length of the fourth surface in the line of sight direction, T is the length of the light guide element in the line of sight direction, and α is the angle at which light from the display element is incident on the intersecting surface, The light guide element according to claim 8, characterized in that it satisfies the following conditional expression.

10. The light guide element according to claim 1 or 2, characterized in that, in the line of sight direction, the length of the third surface is shorter than the length of the light guide element.

11. The third surface includes multiple surfaces, When the distance between the third surfaces is p, the length of the third surface in the line of sight direction is t, the length of the light guide element in the line of sight direction is T, and the diameter of the light beam incident on the enlarged portion in the direction of arrangement of the first to third surfaces is d, The light guide element according to claim 10, characterized in that it satisfies the following conditional expression.

12. A light guide element according to claim 1 or 2, An observation optical system characterized by having a projection optical system that projects light from a display element onto a light guide element.

13. The observation optical system according to claim 12, A display device characterized by having a display element.

Images