Light guide element, observation optical system, and display device

Abstract

To provide a small light guide element capable of reducing ghosting. [Solution] The light guide element (12) has an magnifying section (121) that magnifies incident light from the projection section (11) and a light guide section (122) that guides the light magnified by the magnifying section to the eye point. The magnifying section has first and second reflecting sections (1211, 1212), each of the first and second reflecting sections having multiple reflecting surfaces. In a first cross-section including the first and second reflecting sections, the first and second reflecting sections are at angles of different signs with respect to a first axis corresponding to the principal ray in the central field of view of the incident light. In each of the first and second reflecting sections, the reflecting surface closest to the light guide section among the multiple reflecting surfaces is a partial reflecting surface, and light that has been reflected multiple times by at least one of the first and second reflecting sections reaches the light guide section.

Description

Technical Field

[0001] The present invention relates to a light guide element, an observation optical system, and a display device.

Background Art

[0002] Conventionally, an observation optical system using a half-mirror laminated light guide plate and used in AR (Augmented Reality) glasses or the like is known. Generally, the image light beam from the display element is small, and in order to secure the size of the EMB (Eye Motion Box) in a wide viewing angle range, the light guide plate has an enlarged portion that enlarges the image light beam.

[0003] Patent Document 1 discloses an enlarged portion that enlarges an image light beam by making the image light beam incident on a region where a partially transmissive reflection surface and a highly reflective reflection surface are arranged adjacent to each other in parallel and repeating reflection and transmission therebetween. Patent Document 2 discloses an enlarged portion that enlarges an image light beam by arranging a plurality of partial reflection surfaces having an angle with respect to the surface in a waveguide having two parallel surfaces and repeating total reflection on the surface and reflection on the partial reflection surfaces.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] A light guide element that is small and can reduce the generation of ghosts is desired.

Means for Solving the Problems

[0006] A light guide element as one aspect of the present invention comprises an magnifying section that magnifies incident light from a projection section, and a light guide section that guides the light magnified by the magnifying section to an eye point, wherein the magnifying section has first and second reflecting sections, each of the first and second reflecting sections has a plurality of reflecting surfaces, and in a first cross-section including the first and second reflecting sections, the first and second reflecting sections are at angles of different signs with respect to a first axis corresponding to the principal ray in the central field of view of the incident light, and in each of the first and second reflecting sections, the reflecting surface closest to the light guide section among the plurality of reflecting surfaces is a partial reflecting surface, and the light that has been reflected multiple times by at least one of the first and second reflecting sections reaches the light guide section. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a light guide element that is small and capable of reducing the occurrence of ghosting. [Brief explanation of the drawing]

[0008] [Figure 1] These are schematic diagrams of the display devices in each embodiment. [Figure 2(a)] This is a schematic diagram of a light guide plate as a comparative example. [Figure 2(b)] This is a schematic diagram of the light guide plate in the first embodiment. [Figure 2(c)] This is a schematic diagram of the light guide plate in the first embodiment. [Figure 3] This diagram shows the relationship between the arrangement angle of the mirror pair and the propagated light, as well as an explanatory diagram of the arrangement angle of the mirror pair in the first embodiment. [Figure 4] This diagram shows a schematic representation of the light guide plate in the second embodiment, and optical path diagrams of light propagating inside the mirror pair in the first and second embodiments. [Figure 5] This is a schematic diagram of the light guide plate and an explanatory diagram of the effect of the light guide plate in the second embodiment. [Figure 6(a)] This is a schematic diagram of the light guide plate in the third embodiment. [Figure 6(b)]An example of reflectance and transmittance in the third embodiment. [Figure 6(c)] An example of reflectance and transmittance in the third embodiment. [Figure 6(d)] An example of reflectance and transmittance in the third embodiment. [Figure 7(a)] A schematic diagram of a light guide plate in the fourth embodiment. [Figure 7(b)] A diagram showing an optical path diagram in the thickness direction of the light guide plate and the intensity of the expanded light beam in the third embodiment. [Figure 7(c)] A diagram showing an optical path diagram in the thickness direction of the light guide plate and the intensity of the expanded light beam in the fourth embodiment. [Figure 7(d)] A diagram showing an optical path diagram in the thickness direction of the light guide plate and the intensity of the expanded light beam in the fourth embodiment.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each figure, the same members are denoted by the same reference numerals, and overlapping descriptions are omitted.

[0010] (First Embodiment) First, referring to FIG. 1, the display device 10 in the first embodiment of the present invention will be described. FIG. 1 is a schematic diagram of the display device 10. As shown in the upper diagram in FIG. 1, the display device 10 includes a display element 13, a projection optical system (projection unit) 11, and a light guide plate (light guide element) 12 that guides the image light beam from the projection optical system 11 to the observer's eye (eye point corresponding to the pupil of the observer's eye) 15.

[0011] As shown in the lower diagram in FIG. 1 (side view of the light guide plate 12), the light beam (incident light from the projection optical system 11) incident on the inside of the light guide plate 12 from the projection optical system 11 travels while internally reflecting on the inside of the light guide plate 12 in substantially the entire thickness direction (vertical direction in the side view) of the light guide plate 12. The light beam emitted from the light guide plate 12 has an angle of the light beam in the width direction of the light guide plate as the vertical direction and an angle of the light beam in the thickness direction of the light guide plate as the horizontal direction.

[0012] The light guide plate 12 has an enlarging portion 121 that enlarges the light (incident light) with an image light beam diameter P from the projection optical system 11 into light with a predetermined light beam diameter EP, and an extraction portion (light guiding portion) 122 that extracts the light (image light beam) enlarged by the enlarging portion 121 to the outside of the light guide plate 12 and guides it to the observer's eye 15.

[0013] Next, referring to FIGS. 2(a), 2(b), and 2(c), the functions and effects of the light guide plate 12 in the present embodiment will be described. In the following description, when observing the light guide plate 12 parallel to the surface of the light guide plate 12, the traveling direction of the central angular ray of the image light beam (the principal ray of the central angular aperture of the incident light on the light guide plate 12) is taken as the X-axis direction (the direction of the first axis, the first direction). Here, the principal ray is a ray passing through the aperture center of the aperture stop (a ray passing through the pupil center). Also, the direction perpendicular to the X-axis direction is the Y-axis direction (the direction of the second axis, the second direction), and the direction orthogonal to the X-axis and Y-axis (the direction from the observer's eye 15 to the light guide plate 12) is the Z-axis direction.

[0014] FIG. 2(a) is a schematic view of a light guide plate 112 as a comparative example, showing an enlarging portion 121 in which an adjacent pair of parallel mirrors (two mirrors) arranged at a predetermined angle with respect to the first direction is disposed. The length L of the enlarging portion required to enlarge to the predetermined light beam diameter EP is determined by the angle at which the mirror pair is disposed. For this reason, the projection optical system 111 needs to be disposed at the end of the light guide plate 112.

[0015] On the other hand, FIGS. 2(b) and 2(c) are schematic views of the light guide plate 12 in the present embodiment. As shown in FIG. 2(b), the enlarging portion 121 of the light guide plate 12 has adjacent parallel mirror groups (mirror pairs) 1211 and 1212 disposed at two angles (the first angle) α and angle (the second angle) β with respect to the first direction. The mirror group 1211 is a first reflecting portion having a plurality of reflecting surfaces, and the mirror group 1212 is a second reflecting portion having a plurality of reflecting surfaces.

[0016] Here, angles α and β are angles that, in a predetermined cross-section (the first cross-section), are opposite to each other with respect to the direction of incidence of the principal rays of the central field of view of the incident light (the first direction), i.e., the direction of incidence of the light passing through the center of the pupil (the central axis). Here, the first cross-section is the cross-section containing the mirror groups 1211 and 1212 (the cross-section containing the first axis and the second axis), as shown in Figure 2(b). That is, in the first cross-section, the mirror groups 1211 and 1212 form angles with different signs with respect to the first axis corresponding to the principal rays of the central field of view of the incident light.

[0017] In each embodiment, clockwise rotation is considered the positive direction and counterclockwise rotation the negative direction with respect to the principal ray. The angles α and β (°) are set within the range that satisfies the conditions -90 < α, β < 0 and 0 < α, β < 90. That is, the absolute values ​​of angles α and β, respectively, |α| and |β| (°), are 0 < |α| and |β| < 90. Preferably, the absolute values ​​of angles α and β are less than 45° (0 < |α| < 45 and 0 < |β| < 45).

[0018] The image light beam reaches the extraction section 122 after reflecting multiple times between the two mirrors that make up the mirror group 1211 or the mirror group 1212. The width of each mirror surface of the mirror groups 1211 and 1212 is approximately the same as the thickness of the light guide plate 12. In addition, the distance A between the two mirrors that make up each of the mirror groups 1211 and 1212 in the second direction is less than or equal to half the image light beam diameter P.

[0019] The multiple reflective surfaces constituting each of the mirror groups 1211 and 1212 have different reflectances. In this embodiment, the multiple reflective surfaces include a first surface with a first reflectance and a second surface with a second reflectance lower than the first reflectance. That is, mirror group 1211 has a mirror (reflective surface) 1211a with a first reflectance and a mirror 1211b with a second reflectance. Similarly, mirror group 1212 has a mirror 1212a with a first reflectance and a mirror 1212b with a second reflectance.

[0020] Of the two mirrors 1211a and 1211b that make up the mirror group 1211, The mirror furthest from the extraction section 122 (the furthest mirror) has a reflective surface with a reflectivity of 90% or more. Similarly, of the two mirrors 1212a and 1212b that make up the mirror group 1212, the mirror furthest from the extraction section 122 (the furthest mirror) has a reflective surface with a reflectivity of 90% or more. On the other hand, of the two mirrors 1211a and 1211b that make up the mirror group 1211, the mirror 1211a that is closer to the extraction section 122 (i.e., the mirror closest to the extraction section 122) is a partially reflective surface (partially transmissive reflective surface). Similarly, of the two mirrors 1212a and 1212b that make up the mirror group 1212, the mirror 1212b that is closer to the extraction section 122 (i.e., the mirror closest to the extraction section 122) is a partially reflective surface (partially transmissive reflective surface). As a result, the image light beam is reflected multiple times at each of the mirror groups 1211 and 1212, and the light beam diameter is expanded as it travels in the first direction. With this configuration, the length L of the expansion section 121 in the first direction required to expand to a predetermined light beam diameter EP can be shortened compared to the case where only one mirror group (mirror pair) is provided, as in the comparative example shown in Figure 2(a).

[0021] The reflective surfaces (mirrors 1211a, 1212a) are surfaces with a light reflectance of 90% or more. Preferably, the reflective surfaces have a reflectance of 95% or more. On the other hand, the partially reflective surfaces (mirrors 1211b, 1212b) are surfaces with a lower reflectance than the reflective surfaces (mirrors 1211a, 1212a), and have a reflectance of less than 95%. Preferably, the partially reflective surfaces have a reflectance of 3% or more and less than 90%. More preferably, the partially reflective surfaces have a reflectance of 5% or more and less than 80%. These points also apply to each embodiment described later. The partially reflective surface only needs to be a transmissive reflective surface in part, and may be a configuration in which only a part of the surface is a transmissive reflective surface or a configuration in which all of the surface is a transmissive reflective surface.

[0022] In this embodiment, the position of the projection optical system 11 can be arbitrarily adjusted according to the lengths of the two mirror groups 1211 and 1212. Therefore, as shown in Figure 2(c), the projection optical system 11 can be positioned to match the projection system arrangement area specified in the display device 10 from a design perspective. In other words, this embodiment improves the degree of freedom in the arrangement of the projection optical system 11.

[0023] Here, let |φ|(°) be the angle of the angle-of-view rays included in the image luminous flux with respect to the first direction. In this case, it is preferable that the angles α and β(°) satisfy the following conditions (1-1) and (1-2).

[0024] |α|-|φ| / 2<45 … (1-1) |β|-|φ| / 2<45 … (1-2) Furthermore, the angle at which the angle of the angle of the field-of-view rays included in the image beam with respect to the first direction is maximized (maximum angle) is |φ M Let |(°). In this case, it is more preferable that the angles α and β(°) satisfy the following conditions (2-1) and (2-2).

[0025] |α|-|φ M | / 2<45 … (2-1) |β|-|φ M | / 2<45 … (2-2) Figures 3(a) to 3(c) show the relationship between the arrangement angle of the mirror pair and the propagated light in this embodiment. Figure 3(d) is an explanatory diagram of the arrangement angle of the mirror pair in this embodiment. If conditions (2-1) and (2-2) are not satisfied, as shown in Figure 3(a), some of the light rays incident on the partial reflective surface undergo total internal reflection at the side surface of the light guide plate 12, resulting in light rays propagating at an angle φ' different from the original angle of view light rays. The light rays that reach the extraction section 122 in this state are guided to the observer's eye 15 as ghosts, which degrades the image quality of the displayed image and is therefore undesirable.

[0026] On the other hand, when conditions (2-1) and (2-2) are satisfied, as shown in Figure 3(b), no light rays undergo total internal reflection at the side surface of the light guide plate 12, and therefore no ghosting occurs. If it is difficult to satisfy conditions (2-1) and (2-2) due to size constraints of the light guide plate 12, etc., it is preferable to make the side surface of the light guide plate 12 (at least a part of the side surface of the light guide plate 12), excluding the incident portion of the image light beam, a light-shielding surface, as shown in Figure 3(c). With such a configuration, it is possible to absorb light that undergoes total internal reflection and suppress the generation of ghosting.

[0027] In this embodiment, it is preferable that angles α and β are equal to each other. The length L(L) of the magnification section 121 necessary to magnify the light (incident light) with an image beam diameter P from the projection optical system 11 to light with a predetermined beam diameter EP is α , L β ) is the angle φ M This depends on α and β. If angles α and β are not equal, as shown in Figure 3(d), light reaches the side of the light guide plate 12 before it reaches the extraction section 122, resulting in absorbed or totally reflected light (waste light). This leads to a decrease in the propagation efficiency of the image light beam, which is undesirable.

[0028] According to this embodiment, it is possible to provide a compact light guide element, observation optical system, and display device while suppressing the generation of ghosting. The conditions described in this embodiment can also be applied to the embodiments described later.

[0029] (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to Figures 4(a) to (c) and Figures 5(a) and (b). Figure 4(a) is a schematic diagram of the light guide plate (light guide element) 42 in this embodiment. Figure 4(b) is an optical path diagram of light propagating inside the mirror group 1211 (1212) in the first embodiment. Figure 4(c) is an optical path diagram of light propagating inside the mirror group 4211 (4212) in this embodiment. Figure 5(a) is a schematic diagram of a light guide plate (light guide element) 52 as a modified example of this embodiment. Figure 5(b) is an explanatory diagram of the effect of the light guide plate 52.

[0030] In the first embodiment, a configuration was described in which each of the mirror groups 1211 and 1212 has only one partial reflective surface (partially transmissive reflective surface). However, in this embodiment, a configuration is described in which each of the mirror groups has multiple partial reflective surfaces in at least one of the first or second directions.

[0031] First, the light guide plate 42 in this embodiment will be described with reference to Figure 4(a). The light guide plate 42 has an enlarged section 421 and an extraction section 422. The enlarged section 421 has a group of mirrors (first reflective section) 4211 and a group of mirrors (second reflective section) 4212 arranged at angles α and β opposite to each other with respect to the first direction. The mirror group 4211 has three adjacent parallel mirrors (reflective surfaces) 4211a, 4211b, and 4211c along the first direction. Similarly, the mirror group 4212 has three adjacent parallel mirrors (reflective surfaces) 4212a, 4212b, and 4212c along the first direction. Of the three mirrors 4211a, 4211b, and 4211c, the two mirrors 4211b and 4211c, excluding the mirror 4211a, which is furthest from the extraction section 422, are partially transparent reflective surfaces. Similarly, of the three mirrors 4212a, 4212b, and 4212c, the two mirrors 4212b and 4212c, excluding the mirror 4212a which is furthest from the extraction section 422, are partially transmissive reflective surfaces.

[0032] In this embodiment, mirror groups 4211 and 4212 each have three mirrors, but they may have four or more mirrors. Even in this case, all of the mirrors except the one furthest from the extraction section 422 are partially transparent reflective surfaces.

[0033] Figure 4(b) shows the optical path of a light beam in which the angle of the field-of-view rays included in the image light beam with respect to the first direction is φ, when only one partially transparent reflective surface is arranged as in the first embodiment. In this way, for light rays other than the central field of view, gaps are created in the magnified light beam, and gaps of a similar size are also created in the light beam guided to the observer's eye 15. As the angle φ increases, the gaps widen and become noticeable to the observer, leading to a decrease in image quality.

[0034] On the other hand, Figure 4(c) shows the optical path when multiple partially transparent reflective surfaces are arranged, as in this embodiment. Because the reflected light from the partially transparent reflective surface closer to the extraction section 422 travels through an optical path that fills the gaps, the light beam can be expanded without creating gaps even when the angle φ is large.

[0035] As described above, in this embodiment, the plurality of mirrors constituting the mirror groups 4211 and 4212 each include at least three mirrors arranged along the first direction. Furthermore, each of the plurality of mirrors, except for the mirror furthest from the extraction section 422, is a partially reflective surface.

[0036] Next, with reference to Figure 5(a), a modified example of this embodiment, the light guide plate 52, will be described. The light guide plate 52 has an enlarged section 521 and an extraction section 522. The enlarged section 521 has a group of mirrors (first reflective section) 5211 and a group of mirrors (second reflective section) 5212 arranged at angles α and β opposite to each other with respect to the first direction. The mirror group 5211 has six adjacent parallel mirrors (reflective surfaces) along the second direction. Similarly, the mirror group 5212 has six adjacent parallel mirrors (reflective surfaces) along the second direction. Of the six mirrors in each of the mirror groups 5211 and 5212, the other five mirrors, excluding the mirror 5211a (5212a) furthest from the incident part of the image light beam, are partially transparent reflective surfaces. With this configuration, as shown in Figure 5(b), the length L of the enlarged section 121 in Figure 2(b) is shortened, making it possible to miniaturize the light guide plate 52.

[0037] In this modified example, mirror groups 5211 and 5212 each have six mirrors, but it is sufficient to have three or more mirrors. Even in this case, all mirrors except the one furthest from the incident part of the image light beam are partially transparent reflective surfaces.

[0038] As described above, in this modified example, the plurality of mirrors constituting the mirror groups 5211 and 5212 each include at least three mirrors arranged along a second direction perpendicular to the first direction. Furthermore, each of the plurality of mirrors, except for the mirror furthest from the incident light source in the magnification section 521, is a partial reflecting surface.

[0039] In this embodiment, the effects of arranging multiple partial reflective surfaces in the first direction or the second direction were explained separately, but it is also possible to obtain both effects simultaneously by arranging multiple partial reflective surfaces in both the first and second directions. In this way, by arranging multiple partially transmissive reflective surfaces, it is possible to provide a compact light guide element, observation optical system, and display device while suppressing the occurrence of ghosting even in a wide field of view.

[0040] (Third embodiment) Next, a third embodiment of the present invention will be described with reference to Figures 6(a) to 6(d). Figure 6(a) is a schematic diagram of the light guide plate (light guide element) 62 in this embodiment. Figures 6(b) to 6(d) are examples of the reflectance and transmittance of the partial reflective surface (partially transmissive reflective surface) of the mirror group in this embodiment. This embodiment differs from the first and second embodiments in that the transmittance and reflectance of the partial reflective surface change between each mirror, within the same mirror surface, or both, depending on the position of the partial reflective surface.

[0041] First, the light guide plate 62 in this embodiment will be described with reference to Figure 6(a). The light guide plate 62 has an enlarged section 621 and an extraction section 622. The enlarged section 621 has a group of mirrors (first reflecting section) 6211 and a group of mirrors (second reflecting section) 6212 arranged at angles α and β opposite to each other with respect to the first direction. Each of the mirror groups 6211 and 6212 has a plurality of adjacent parallel mirrors along the first and second directions, respectively. The distance between two adjacent mirrors (mirror spacing) is set to be less than or equal to half of the incident image light beam diameter P. However, this embodiment is not limited to this, and the mirror spacings in the first and second directions may be different from each other.

[0042] In each of the mirror groups 6211 and 6212, all mirrors except for mirror Mb, which is furthest from the incident portion of the image light beam in the second direction, are partially reflective surfaces (partially transmissive reflective surfaces). The transmittance and reflectance of the partially reflective surfaces are set to vary between each mirror, within the same mirror surface, or both, depending on their position within the magnification section 621. The changes in transmittance and reflectance can be achieved with a single type of coating, for example, by defining the area ratio of the mirror-coated portion to the uncoated portion on the mirror surface.

[0043] Here, we will explain the changes in transmittance and reflectance of the partially reflective surface. First, as shown in Figure 6(b), it is preferable that the reflectance within the magnified portion 621 decreases along the first direction. That is, it is preferable that the reflectance of the partially reflective surface decreases as the distance from the projection optical system 11 in the first direction increases.

[0044] In many regions of the expanded luminous beam (luminous beam with a predetermined luminous beam diameter EP), the light reflected near the incident end of the image luminous beam is used. Therefore, by increasing the reflectivity near the incident end, the difference in light intensity between the region using transmitted light and the region using the incident end can be suppressed. On the other hand, by decreasing the reflectivity near the extraction section 622, the amount of light reaching the extraction section 622 can be increased.

[0045] When multiple partial reflective surfaces are provided, for similar reasons, it is preferable that the reflectivity decreases as the distance from the mirror Mb increases, as shown in Figure 6(c). That is, the multiple mirrors include a first partial reflective surface and a second partial reflective surface closer to the extraction section 622 than the first partial reflective surface, and it is preferable that the reflectivity of the first partial reflective surface is higher than that of the second partial reflective surface. Furthermore, when multiple partial reflective surfaces are provided, within the same mirror surface, it is preferable that the reflectivity decreases as the distance from the incident section of the image light beam increases, as shown in Figure 6(d). That is, it is preferable that the reflectivity of the first partial reflective surface and the second partial reflective surface decreases as the distance from the projection optical system 11 increases. In addition, a higher effect can be obtained by setting the combined result of the changes in transmittance and reflectivity of the partial reflective surfaces.

[0046] In this way, by changing the transmittance and reflectance of the partial reflective surface depending on its position within the magnification section 621, between each mirror, within the same mirror surface, or both, the light beam can be magnified while suppressing unevenness.

[0047] (Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to Figures 7(a) to 7(d). Figure 7(a) is a schematic diagram of the light guide plate (light guide element) 72 in this embodiment. Figure 7(b) is a diagram relating to the optical path in the thickness direction and the intensity of the luminous beam after expansion of the light guide plate 62 in the third embodiment. Figures 7(c) and 7(d) are diagrams relating to the optical path in the thickness direction and the intensity of the luminous beam after expansion of the light guide plate in this embodiment.

[0048] In the first to third embodiments, the width of the mirror in the magnification portion relative to the thickness direction of the light guide plate was described on the premise that it was equal to the thickness of the light guide plate. On the other hand, in this embodiment, the configuration of the magnification portion when the width of the mirror is narrower than the thickness of the light guide plate will be described. Such a magnification portion is applied when, for example, a manufacturing method such as injection molding is used, and it is not possible to form a mirror along the entire thickness direction due to manufacturing constraints.

[0049] First, with reference to Figure 7(a), the light guide plate 72 in this embodiment will be described. The light guide plate 72 has an enlarged section 721 and an extraction section 722. The enlarged section 721 has mirror groups 7211 and 7212 arranged at angles α and β opposite to each other with respect to the first direction. Each of the mirror groups 7211 and 7212 has a plurality of adjacent parallel mirrors along the first and second directions, respectively. The distance between two adjacent mirrors in the first and second directions (mirror spacing) is set to a. However, this embodiment is not limited to this, and the mirror spacings in the first and second directions may be different from each other.

[0050] In the direction of the thickness D of the light guide plate 72 (thickness direction), the width d of each mirror (partial reflective surface) is smaller than the thickness D of the light guide plate 72. Here, if the distance between each mirror in the third embodiment is A, it is preferable that the distance a satisfies the following condition (2).

[0051] a ≤ A·d / D … (2) Figure 7(b) shows the optical path of a light ray incident on the magnified section 621, observed from the thickness direction of the light guide plate 62, in the third embodiment. On the other hand, Figures 7(c) and 7(d) show the optical path of a light ray incident on the magnified section 721, observed from the thickness direction of the light guide plate 72, in this embodiment. Figure 7(c) shows the case where a=A, and Figure 7(d) shows the case where a=A·d / D.

[0052] When the upper limit of condition (2) is exceeded, as shown in Figure 7(c), the number of times the light is reflected by the mirror decreases compared to the case where the width of the mirror is equal to its thickness. In this case, the amount of light transmitted is large, and the amount of light reflected and amplified is small, resulting in greater unevenness in the amplified light beam, which is undesirable.

[0053] On the other hand, as shown in Figure 7(d), if the mirror spacing is set to satisfy condition (2), all light rays are reflected at least as many times as when the width of the mirror is equal to its thickness, thus suppressing unevenness in the light intensity of the magnified luminous beam. In this way, by narrowing the spacing between multiple partial reflective surfaces, the luminous beam can be magnified while suppressing unevenness in intensity.

[0054] In each embodiment, preferably, the enlarged portion and the extraction portion have the same surface formed integrally. That is, there is no layer of air or other material between the enlarged portion and the extraction portion, and the surface of the enlarged portion and the surface of the extraction portion are connected. Since such a structure can be realized, for example, by injection molding using two molds, it becomes possible to manufacture the light guide plate more easily.

[0055] According to each embodiment, it is possible to provide a compact light guide element, an observation optical system, and a display device that can reduce the occurrence of ghosting.

[0056] Each embodiment of the disclosure includes the following configuration and method. (Composition 1) A magnifying unit that amplifies the incident light from the projection unit, It has a light guide section that guides the light amplified by the aforementioned magnification section to the eye point, The enlarged portion has first and second reflective portions, Each of the first and second reflective sections has a plurality of reflective surfaces, In the first cross-section including the first and second reflectors, the first and second reflectors form angles with different signs of sign with respect to a first axis corresponding to the principal ray in the central field of view of the incident light. In each of the first and second reflective sections, the reflective surface closest to the light guide among the plurality of reflective surfaces is a partially reflective surface. A light guide element characterized in that light reflected multiple times by at least one of the first and second reflecting portions reaches the light guide portion. (Configuration 2) The light guide element according to configuration 1, characterized in that the plurality of reflective surfaces include first and second surfaces having different reflectances from each other. (Composition 3) The light guide element according to configuration 1 or 2, characterized in that the reflective surface furthest from the light guide portion among the plurality of reflective surfaces has a reflectivity of 90% or more. (Composition 4) The light guide element according to any one of configurations 1 to 3, characterized in that the absolute value of the first angle of the first reflecting portion with respect to the first axis and the absolute value of the second angle of the second reflecting portion with respect to the first axis are less than 45°. (Composition 5) The light guide element according to any one of configurations 1 to 4, characterized in that the absolute value of the first angle of the first reflecting portion with respect to the first axis and the absolute value of the second angle of the second reflecting portion with respect to the first axis are equal to each other. (Composition 6) When the first angle of the first reflecting portion with respect to the first axis is α(°), the second angle of the second reflecting portion with respect to the first axis is β(°), and the angle of the incident light with respect to the first axis is φ(°), |α|-|φ| / 2<45 |β|-|φ| / 2<45 A light guide element according to any one of configurations 1 to 5, characterized in that it satisfies the following conditional expression. (Composition 7) The light guide element according to any one of configurations 1 to 6, characterized in that at least a portion of the side surface of the enlarged portion is a light-shielding surface. (Composition 8) The plurality of reflective surfaces include at least three reflective surfaces arranged along the first axis, The light guide element according to any one of configurations 1 to 7, characterized in that each of the multiple reflective surfaces, excluding the reflective surface furthest from the light guide portion, is a partial reflective surface. (Composition 9) The plurality of reflective surfaces include at least three reflective surfaces arranged along a second direction perpendicular to the first axis, The light guide element according to any one of configurations 1 to 8, characterized in that each of the multiple reflective surfaces, excluding the reflective surface furthest from the incident portion of the incident light in the enlarged portion, is a partial reflective surface. (Composition 10) The light guide element according to any one of configurations 1 to 9, characterized in that the width of the partial reflective surface in the thickness direction of the light guide element is smaller than the thickness of the light guide element. (Composition 11) The light guide element according to any one of configurations 1 to 10, characterized in that the magnifying portion and the light guide portion have the same surface formed integrally. (Composition 12) The light guide element according to any one of configurations 1 to 11, characterized in that the reflectance of the partial reflective surface decreases as the distance from the projection unit on the first axis increases. (Composition 13) The multiple reflective surfaces include a first partial reflective surface and a second partial reflective surface that is closer to the light guide than the first partial reflective surface. The light guide element according to any one of configurations 1 to 11, characterized in that the reflectance of the first partial reflective surface is higher than the reflectance of the second partial reflective surface. (Composition 14) The multiple reflective surfaces include a first partial reflective surface and a second partial reflective surface that is closer to the light guide than the first partial reflective surface. The light guide element according to any one of configurations 1 to 11, characterized in that the reflectance of the first partial reflective surface and the second partial reflective surface decreases as the distance from the projection unit increases. (Composition 15) An observation optical system characterized by having a light guide element according to any one of configurations 1 to 14 and the projection unit. (Composition 16) A display device characterized by having a light guide element according to any one of configurations 1 to 14, a projection unit, and a display element.

[0057] 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]

[0058] 11 Projection optical system (projection section) 12. Light guide plate (light guide element) 121 Enlarged section 122 Extraction section (light guide section) 1211 Mirror group (first reflector) 1212 Mirror group (second reflector)

Claims

1. A magnifying unit that amplifies the incident light from the projection unit, It has a light guide section that guides the light amplified by the aforementioned magnification section to the eye point, The enlarged portion has first and second reflective portions, Each of the first and second reflective sections has a plurality of reflective surfaces, In the first cross-section including the first and second reflectors, the first and second reflectors form angles with different signs of sign with respect to a first axis corresponding to the principal ray in the central field of view of the incident light. In each of the first and second reflective sections, the reflective surface closest to the light guide section among the plurality of reflective surfaces is a partially reflective surface. A light guide element characterized in that light reflected multiple times by at least one of the first and second reflecting portions reaches the light guide portion.

2. The light guide element according to claim 1, characterized in that the plurality of reflective surfaces include first and second surfaces having different reflectances from each other.

3. The light guide element according to claim 1, characterized in that the reflective surface furthest from the light guide portion among the plurality of reflective surfaces has a reflectivity of 90% or more.

4. The light guide element according to claim 1, characterized in that the absolute value of the first angle of the first reflecting portion with respect to the first axis and the absolute value of the second angle of the second reflecting portion with respect to the first axis are less than 45°.

5. The light guide element according to claim 1, characterized in that the absolute value of the first angle of the first reflecting portion with respect to the first axis and the absolute value of the second angle of the second reflecting portion with respect to the first axis are equal to each other.

6. When the first angle of the first reflecting portion with respect to the first axis is α (°), the second angle of the second reflecting portion with respect to the first axis is β (°), and the angle of the incident light with respect to the first axis is φ (°), |α|-|φ| / 2<45 |β|-|φ| / 2<45 The light guide element according to claim 1, characterized in that it satisfies the following condition.

7. The light guide element according to claim 1, characterized in that at least a portion of the side surface of the enlarged portion is a light-shielding surface.

8. The plurality of reflective surfaces include at least three reflective surfaces arranged along the first axis, The light guide element according to claim 1, characterized in that each of the multiple reflective surfaces, excluding the reflective surface furthest from the light guide portion, is a partial reflective surface.

9. The plurality of reflective surfaces include at least three reflective surfaces arranged along a second direction perpendicular to the first axis, The light guide element according to claim 1, characterized in that each of the multiple reflective surfaces, excluding the reflective surface furthest from the incident portion of the incident light in the enlarged portion, is a partial reflective surface.

10. The light guide element according to claim 1, characterized in that the width of the partial reflective surface in the thickness direction of the light guide element is smaller than the thickness of the light guide element.

11. The light guide element according to claim 1, characterized in that the magnified portion and the light guide portion have the same surface formed integrally.

12. The light guide element according to claim 1, characterized in that the reflectance of the partial reflective surface decreases as the distance from the projection portion on the first axis increases.

13. The multiple reflective surfaces include a first partial reflective surface and a second partial reflective surface that is closer to the light guide than the first partial reflective surface. The light guide element according to claim 1, characterized in that the reflectance of the first partial reflective surface is higher than the reflectance of the second partial reflective surface.

14. The multiple reflective surfaces include a first partial reflective surface and a second partial reflective surface that is closer to the light guide than the first partial reflective surface. The light guide element according to claim 1, characterized in that the reflectance of the first partial reflective surface and the second partial reflective surface decreases as the distance from the projection unit increases.

15. An observation optical system characterized by having a light guide element according to any one of claims 1 to 14 and the projection unit.

16. A display device characterized by having an observation optical system as described in claim 15 and a display element.

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