Optical element and device

Abstract

An optical element 20 comprises: a mirror array 24; and an optical surface 211 opposite to the mirror array 24. The mirror array 24 includes a mirror group 241 composed of a plurality of reflex mirrors 25 arranged in the X direction, and a mirror group 242 composed of a plurality of reflex mirrors 25 arranged in the X direction. The mirror group 241 and the mirror group 242 are lined up in the Y direction. The reflex mirrors 25 in the mirror group 241 extend in a W1 direction inclined with respect to the optical surface 211. The reflex mirrors 25 in the mirror group 242 extend in a W2 direction inclined with respect to the optical surface 211. The mirror group 241 and the mirror group 242 partially overlap each other in a V1 direction.

Description

Optical Elements and Instruments

[0001] The present invention relates to an optical element having a mirror array.

[0002] Display and imaging can be performed by controlling light using an optical element having a reflective optical system. Patent Document 1 discloses a light guide for a virtual image display device that guides image light from an image display element and emits it to display a virtual image, and that includes a retroreflection section that reverses the traveling direction of the image light guided within the light guide member of the light guide. Patent Document 2 also discloses that a light guide device used in a display device has multiple half mirrors between a first light guide and a second light guide.

[0003] JP 2018-132602 A JP 2019-066813 A

[0004] The technology of Patent Document 1 leaves room for improvement in terms of miniaturization of the light guide and improvement of optical performance. The technology of Patent Document 2 leaves room for improvement in terms of improvement of the optical performance of the light guide device. Therefore, an object of the present invention is to provide a technology that is advantageous for realizing an optical element that is small and has high optical performance.

[0005] A first means for solving the problem is an optical element having a mirror array and an optical surface facing the mirror array, wherein the mirror array includes a first mirror group consisting of a plurality of retroreflecting mirrors arranged in a first direction, and a second mirror group consisting of a plurality of retroreflecting mirrors arranged in the first direction, the first mirror group and the second mirror group being arranged side by side in a second direction intersecting the first direction, the plurality of retroreflecting mirrors of the first mirror group extending along a third direction intersecting the first direction and the second direction and inclined with respect to the optical surface, the plurality of retroreflecting mirrors of the second mirror group extending along a fourth direction intersecting the first direction and the second direction and inclined with respect to the optical surface, and the first mirror group and the second mirror group partially overlapping in a fifth direction perpendicular to the first direction and the third direction.

[0006] A second means for solving the problem is an optical element having a mirror array, a first optical surface facing the mirror array, and a second optical surface facing the mirror array, wherein the mirror array is arranged between the first optical surface and the second optical surface and includes a mirror group consisting of a plurality of retroreflecting mirrors arranged in a first direction, and the plurality of retroreflecting mirrors of the mirror group extend along a second direction that intersects the first direction and is inclined with respect to the first optical surface and the second optical surface.

[0007] A third means for solving the problems is an optical element having a mirror array and an optical surface facing the mirror array, wherein the mirror array includes a first light-transmitting mirror and a second light-transmitting mirror, wherein the first light-transmitting mirror extends along a first direction inclined with respect to the optical surface, and the second light-transmitting mirror extends along a second direction inclined with respect to the optical surface, and in a third direction intersecting the optical surface and the first direction, the first light-transmitting mirror is located between the second light-transmitting mirror and the optical surface, a first portion of the first light-transmitting mirror and a first portion of the second light-transmitting mirror overlap, a second portion of the first light-transmitting mirror does not overlap with the second light-transmitting mirror, and the second portion of the second light-transmitting mirror does not overlap with the first light-transmitting mirror, The mirror is characterized in that at least one of the following is satisfied: the reflectance of the first portion of the first light-transmitting mirror is lower than the reflectance of the second portion of the first light-transmitting mirror; and the reflectance of the first portion of the second light-transmitting mirror is lower than the reflectance of the second portion of the second light-transmitting mirror.

[0008] According to the present invention, it is possible to provide a technique that is advantageous for realizing a small optical element having high optical performance.

[0009] Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagram for explaining an optical element. Schematic diagrams for explaining an optical element. Schematic diagrams for explaining an optical element. Schematic diagrams for explaining an optical element. Schematic diagrams for explaining an apparatus. Schematic diagrams for explaining an apparatus. Schematic diagrams for explaining an apparatus.

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description and drawings, common reference numerals are used to designate components common to multiple drawings. Therefore, the common components will be described with mutual reference to multiple drawings, and descriptions of components with common reference numerals will be omitted as appropriate. Different components with the same name can be distinguished by adding "0", such as a first component and a second component.

[0011] 1A to 1D, an optical element 20 according to a first embodiment will be described. Fig. 1A is a cross-sectional view of the optical element 20 taken along the YZ plane, and Fig. 1B is a plan view of the optical element 20 taken along the XY plane.

[0012] The optical element 20 has a mirror array 24 and an optical surface 211 facing the mirror array 24. The optical surface 211 is an optical surface that is optically transmissive and / or optically reflective. An optical surface that is optically transmissive can be called a translucent surface, and an optical surface that is optically reflective can be called a reflective surface. The mirror array 24 includes a mirror group 241 and a mirror group 242. As shown in FIG. 1B , the mirror group 241 is made up of a plurality of retroreflecting mirrors 25 arranged in the X direction. In FIG. 1B , three of the six retroreflecting mirrors 25, namely, 251, 252, and 253, are given different reference numerals, but the retroreflecting mirrors 251, 252, and 253 are all examples of the retroreflecting mirror 25. As shown in FIG. 1B , the mirror group 242 is made up of a plurality of retroreflecting mirrors 25 arranged in the X direction. 1B, three of the six retroreflecting mirrors 25, 254, 255, and 256, are assigned different reference numerals, but the retroreflecting mirrors 251, 252, and 253 are all examples of the retroreflecting mirror 25. The mirror group 241 and the mirror group 242 are arranged side by side in the Y direction that intersects with the X direction. The Y direction is typically perpendicular to the X direction, but the Y direction may be inclined with respect to the X direction.

[0013] As shown in FIG. 1B , the multiple retroreflecting mirrors 25 of the mirror group 241 extend along a W1 direction intersecting the X and Y directions, so as to be inclined with respect to the optical surface 211. In other words, the W1 direction in which the multiple retroreflecting mirrors 25 of the mirror group 241 extend is inclined with respect to the optical surface 211. The W1 direction is typically perpendicular to the X direction, but the W1 direction may be inclined with respect to the X direction. The multiple retroreflecting mirrors 25 of the mirror group 242 extend along a W2 direction intersecting the X and Y directions, so as to be inclined with respect to the optical surface 211. In other words, the W2 direction in which the multiple retroreflecting mirrors 25 of the mirror group 242 extend is inclined with respect to the optical surface 211. The W2 direction is typically perpendicular to the X direction, but the W2 direction may be inclined with respect to the X direction. The W2 direction is typically parallel to the W1 direction, but the W2 direction may be inclined with respect to the W1 direction. Whether the W2 direction is parallel to the W1 direction or not, the W1 direction and the W2 direction can be collectively referred to as the W direction.

[0014] If a virtual plane along the X direction in which the retroreflecting mirrors 25 of the mirror group 241 are arranged and the W1 direction in which the mirror group 241 extends is defined as a modeled reflecting surface of the mirror group 241, the normal direction of this modeled reflecting surface can be defined as the V1 direction, which is orthogonal to the X direction and the W1 direction. If a virtual plane along the X direction in which the retroreflecting mirrors 25 of the mirror group 242 are arranged and the W2 direction in which the mirror group 242 extends is defined as a modeled reflecting surface of the mirror group 242, the normal direction of this modeled reflecting surface can be defined as the V2 direction, which is orthogonal to the X direction and the W2 direction. The V2 direction is typically parallel to the V1 direction, but the V2 direction may be inclined with respect to the V1 direction. Whether the V2 direction is parallel to the V1 direction or not, the V1 direction and the V2 direction can be collectively referred to as the V direction.

[0015] In the V1 direction, which is orthogonal to the X direction and the W1 direction, the mirror group 241 and the mirror group 242 partially overlap. In the V2 direction, which is orthogonal to the X direction and the W2 direction, the mirror group 241 and the mirror group 242 partially overlap. Figure 1A shows an overlapping area A1 between the mirror group 241 and the mirror group 242 in the V1 direction and / or the V2 direction.

[0016] It is preferable that the mirror group 241 and the mirror group 242 partially overlap in the Z direction perpendicular to the optical surface 211. Figures 1A and 1B show an overlapping region A2 between the mirror group 241 and the mirror group 242 in the Z direction. The Z direction is typically perpendicular to the X direction, but the Z direction may be inclined relative to the X direction. The Z direction is typically perpendicular to the Y direction, but the Z direction may be inclined relative to the Y direction. The optical surface 211 may be a curved surface, in which case the normal direction to the curved surface may be set to the Z direction, and the tangential directions tangent to the curved surface may be set to the X direction and the Y direction.

[0017] The direction in which the retroreflecting mirrors 25 are arranged (X direction) can be referred to as the arrangement direction. The direction in which the mirror groups 241, 242 are juxtaposed (Y direction) can be referred to as the juxtaposition direction. The direction perpendicular to the optical surface 211 (Z direction) can be referred to as the vertical direction. The direction in which the retroreflecting mirrors 25 extend (W direction) can be referred to as the extension direction. The direction perpendicular to the arrangement direction (X direction) and the extension direction (W direction) (V direction) can be referred to as the orthogonal direction.

[0018] The advantages of the mirror array 24 described above will be explained with reference to FIGS. 2A to 2D.

[0019] 2A , the mirror groups 241 and 242 are tilted relative to the optical surface 211, which allows the mirror group 24 to have both a retroreflection function and a reflection function toward the optical surface 211, thereby enabling the optical element 20 to be miniaturized in the Y direction. The mirror groups 241 and 242 are aligned in the W direction and shifted in the Z direction. This increases the thickness of the optical element 20 in the Z direction.

[0020] 2B, the mirror group 241 and the mirror group 242 are aligned in the Y direction, so the thickness of the optical element 20 in the Z direction can be reduced compared to the embodiment of Fig. 2A. However, stray light Lv in the V direction that passes between the mirror group 241 and the mirror group 242 is more likely to occur.

[0021] The configuration in Fig. 2C is a borderline example between an example in which the mirror group 241 and the mirror group 242 partially overlap in the V direction and an example in which the mirror group 241 and the mirror group 242 do not partially overlap in the V direction. The configuration in Fig. 2C can suppress stray light Lv in the V direction as in Fig. 2B. However, the configuration in Fig. 2D is prone to stray light Lz in the Z direction passing between the mirror group 241 and the mirror group 242.

[0022] The configuration in Fig. 2D is a borderline example between an example in which mirror group 241 and mirror group 242 partially overlap in the Z direction and an example in which mirror group 241 and mirror group 242 do not partially overlap in the Z direction. In the configuration in Fig. 2D, stray light Lz in the Z direction as in Fig. 2C can be suppressed.

[0023] 1C and 1D show examples of the shape of the mirror group 241 viewed from the W1 direction or the mirror group 242 viewed from the W2 direction. The retroreflecting mirror 25 will be described with reference to FIGS. 1C and 1D . Here, we focus on the X and V directions, which are orthogonal to the W direction. The angle of incidence of incident light incident in the S direction (incident direction) oblique to the V direction is defined as θa. θa is 10° or greater, preferably 20° or greater, and more preferably 30° or greater, and θa is 80° or less, preferably 70° or less, and more preferably 60° or less. The reflected light from the retroreflecting mirror 25 is reflected in the T direction (reflection direction) at an angle θb with respect to the V direction. Regarding the X-direction components of the incident and reflected light, if the angle θc between the S direction (incident direction) and the T direction (reflection direction) is smaller than 2×θa (θc<2×θa), it can be said that the retroreflecting mirror 25 has retroreflectivity in the X direction. In a non-retroreflecting mirror such as a plane mirror, the angle θc between the S direction (incident direction) and the T direction (reflecting direction) is θc = θa + θb, and θa = θb, resulting in θc = 2 × θa = 2 × θb. In the retroreflecting mirror 25, the angle θc between the S direction (incident direction) and the T direction (reflecting direction) is preferably smaller than θa (θc < θa), and more preferably smaller than θb / 2 (θc < θa / 2). In the examples of FIGS. 1C and 1D, θa = θb, and therefore θc = 0°, so θc is not shown. Because the retroreflecting mirror 25 extends in the W direction, the retroreflectivity of the retroreflecting mirror 25 in the W direction is weaker than the retroreflectivity in the X direction. Weak retroreflectivity in the X direction includes no retroreflectivity in the X direction. The strength of retroreflection in the X and W directions can be determined by decomposing the above-mentioned S and T directions into X and W direction components and evaluating the magnitude of the angle between the incident direction and the reflected direction in the X direction component and the angle between the incident direction and the reflected direction in the W direction component. The smaller the angle between the incident direction and the reflected direction in the directional component, the stronger the retroreflection can be evaluated.

[0024] In the example of FIG. 1C , the retroreflective mirror 25 includes a pair of reflective surfaces 25a, 25b that are non-parallel to each other and face each other in the X direction. Such a retroreflective mirror 25 can be called a triangular mirror. The angle formed by the pair of reflective surfaces 25a, 25b is, for example, 45° to 135°, and is typically 90°. A mirror in which the angle formed by the reflective surfaces 25a, 25b is 90°±10° can be called a right-angle mirror. The angle formed by the reflective surfaces 25a, 25b is not limited to a right angle, and may be an acute angle or an obtuse angle. The reflective surfaces 25a, 25b are formed by a reflector 26. The mirror group 241 includes a plurality of retroreflective mirrors 25 each including such a pair of reflective surfaces 25a, 25b, arranged in the X direction. Similarly, the mirror group 242 includes a plurality of retroreflective mirrors 25 each including such a pair of reflective surfaces 25a, 25b, arranged in the X direction. 1B and 1C, six retroreflecting mirrors 25 are arranged in the X direction. When viewed from the Z direction or the V direction, the boundaries between adjacent retroreflecting mirrors 25 are ridgelines 301a and 301b. The ridgelines 301a and 301b can be collectively referred to as ridgelines 301. The boundary between the reflecting surfaces 25a and 25b is the valley ridgeline 42. In FIG. 1B, the ridgelines 301a and 301b are indicated by dashed-dotted lines, and the valley ridgeline 42 is indicated by a dotted line. The reflecting surfaces 25a and 25b, the ridgelines 301a and 301b, and the valley ridgeline 42 extend along the W direction (W1 direction or W2 direction).

[0025] In the example of FIG. 1D , the retroreflecting mirror 25 includes a semicircularly curved reflective surface 25c and a semicircularly curved refracting surface 25d. A refracting body 28 is provided between the reflective surface 25c and the refracting surface 25d. The reflective surface 25c is formed by a reflector 26, and the refracting surface 25d is formed by a refracting body 28. The mirror group 241 includes a plurality of retroreflecting mirrors 25 each including a pair of the reflective surface 25c and the refracting surface 25d, arranged in the X direction. Similarly, the mirror group 242 includes a plurality of retroreflecting mirrors 25 each including a pair of the reflective surface 25c and the refracting surface 25d, arranged in the X direction. In FIGS. 1B and 1D , six retroreflecting mirrors 25 are arranged in the X direction. When viewed from the Z direction or the V direction, the boundaries between adjacent retroreflecting mirrors 25 are mountain ridgelines 301a and 301b. The bottom of the reflective surface 25c is the valley ridgeline 42. The reflecting surface 25c, the refracting surface 25d, the ridgelines 301a and 301b, and the valley ridgeline 42 extend along the W direction (W1 direction or W2 direction). The refracting body 28 is cylindrical and extends in the W direction.

[0026] In the retrorefractive mirror 25 of FIG. 1C or 1D , the reflector 26 can include a metal material (including an alloy) and / or a dielectric material. The reflector 26 may include multiple types of metal materials or dielectric materials, or the reflector 26 may be a dielectric multilayer film in which low-refractive index dielectric materials and high-refractive index dielectric materials are alternately stacked. Examples of low-refractive index dielectric materials include silicon oxide, magnesium fluoride, magnesium oxide, aluminum oxide, and aluminum fluoride. Examples of high-refractive index dielectric materials include silicon nitride, titanium oxide, hafnium oxide, zirconium oxide, tantalum oxide, and niobium oxide.

[0027] The retroreflective mirror 25 may be translucent. A retroreflective mirror 25 having translucency can transmit light of the same wavelength as the light reflected by the retroreflective mirror 25. For example, the reflector 26 of the retroreflective mirror 25 may reflect and transmit visible light. The optical characteristics of the retroreflective mirror 25 may be a reflectance of 5 to 95% and a transmittance of 5 to 95% for a specific wavelength. More preferably, the optical characteristics of the retroreflective mirror 25 are a reflectance of 10 to 90% and a transmittance of 10 to 90% for a specific wavelength. More preferably, the optical characteristics of the retroreflective mirror 25 are a reflectance of 25 to 75% and a transmittance of 25 to 75% for a specific wavelength. The specific wavelength is typically the wavelength of visible light, and may be, for example, any of the wavelengths in the range of 555±100 nm, 555±50 nm, or 555±10 nm. The translucent retroreflective mirror 25 can transmit light of a different wavelength from the light reflected by the retroreflective mirror 25. For example, the reflector 26 of the retroreflective mirror 25 can reflect visible light and transmit ultraviolet or infrared light. To realize the translucent retroreflective mirror 25, it is sufficient to adjust the light transmittance and light reflectance of the reflector 26, and to adjust the material and thickness of the reflector 26. The translucent retroreflective mirror 25 can be a one-way mirror, a half mirror, a bandstop filter, a bandpass filter, a dichroic mirror, or the like.

[0028] 1A and 1B, a base 201 having an optical surface 211 supports the reflectors 26 of the mirror array 24. The base 201 is a component that constitutes the optical element 20. The base 201 has a light-transmitting portion 27, which supports the reflectors 26 of the mirror array 24. Light that is incident on the retroreflector 25 and is retroreflected propagates within the base 201 (light-transmitting portion 27). Therefore, the base 201 (light-transmitting portion 27) may contain a light-transmitting material. The base 201 may have a portion located between the reflecting surface 25a and the reflecting surface 25b in the X direction. When the reflector 26 is a dielectric multilayer film, the refractive index of the high-refractive index dielectric material contained in the dielectric multilayer film of the reflector 26 is preferably higher than the refractive index of the light-transmitting portion 27, but may be lower than the refractive index of the light-transmitting portion 27. The refractive index of the low-refractive index dielectric material contained in the dielectric multilayer film of the reflector 26 is preferably lower than the refractive index of the light-transmitting portion 27, but may be higher than the refractive index of the light-transmitting portion 27. The light-transmitting material constituting the base 201 (light-transmitting portion 27) can be resin or glass. Examples of resins that can be used as light-transmitting materials include optical plastics such as acrylic resins, styrene resins, polyolefin resins, and polycarbonates. The refractive index of these resins is generally 1.45 to 1.60. Cycloolefin polymers are particularly suitable as the resin constituting the base 201. Cycloolefin polymers are suitable for improving the performance of the optical element 20, such as high transparency, light resistance, stability of the refractive index and Abbe number, low birefringence, low specific gravity, high heat resistance, and precision moldability.

[0029] In addition to the light-transmitting material that constitutes the light-transmitting portion 27, the base 201 may also include a coating material that covers the light-transmitting material that constitutes the light-transmitting portion 27. Various materials can be used as the coating material for the purposes of protection (scratch prevention, anti-fouling), anti-reflection, and reflection promotion, and a light-transmitting material or a light-blocking material can be used as the coating material. The coating material may be an inorganic material or an organic material. The coating material may also constitute the optical surface 211 of the base 201.

[0030] Here, the mirror array 24 is configured using the reflector 26, but the reflector 26 may be omitted and the mirror array 24 may be configured so that total reflection occurs on the inner surface of the base 201 (light-transmitting portion 27). In this case, the base 201 (light-transmitting portion 27) may function like a prism. The same can be said for the cover 202 (light-transmitting portion 37), which will be described later.

[0031] 1A and 1B, the behavior of a light ray L with respect to one retroreflecting mirror 25 including a pair of reflecting surfaces 25a and 25b will be described. For example, light ray L having a W1 direction component incident on the mirror group 241 is reflected by the reflecting surface 25b at the position of the white circle in FIGS. 1A and 1B with an X direction component. This light ray L propagates between the reflecting surfaces 25a and 25b and is incident on the reflecting surface 25a at the position of the black circle in FIGS. 1A and 1B. Since the light ray L has a W1 direction component, the positions of the white circle and the black circle are offset in the W1 direction. The light ray L is reflected by the reflecting surface 25a at the position of the black circle in FIGS. 1A and 1B with a W1 direction component. The same applies to the mirror group 242.

[0032] When the mirror group 241 does not have retroreflection in the W1 direction, the angle (incident angle) formed by the incident direction of light ray L with respect to the normal direction (V1 direction) of the modeled reflecting surface of the mirror group 241 is approximately the same as the angle (exit angle) formed by the exit direction of light ray L with respect to the normal direction (V1 direction) of the modeled reflecting surface of the mirror group 241. The angle formed by the incident direction of light ray L and the exit direction of light ray L is larger than the angle (incident angle) formed by the incident direction of light ray L with respect to the normal direction (V1 direction) of the modeled reflecting surface of the mirror group 241 and the angle (exit angle) formed by the exit direction of light ray L with respect to the normal direction (V1 direction) of the modeled reflecting surface of the mirror group 241. The same is true for the mirror group 242.

[0033] Here, an example is shown in which a typical light ray L is reflected in the Z direction by the reflecting surface 25a, but this is because setting a case in which the light ray L is perpendicularly incident on the optical surface 211 as a representative example is useful in designing and evaluating the optical element 20. However, when actually using the optical element 20, it is not essential that the light ray L is perpendicularly incident on the optical surface 211.

[0034] The mirror group 241 may have a non-facing surface (not shown) that does not face in the X direction a pair of reflecting surfaces 25 a, 25 b of at least one of the multiple retroreflecting mirrors 25 of the mirror group 241. In the V1 direction, it is preferable that the non-facing surface overlaps the mirror group 242. It is also preferable that the non-facing surface overlaps the mirror group 242 in the Z direction perpendicular to the optical surface 211.

[0035] The mirror group 242 may have a non-facing surface (not shown) that does not face in the X direction a pair of reflecting surfaces 25 a, 25 b of at least one of the multiple retroreflecting mirrors 25 of the mirror group 242. It is preferable that the non-facing surface overlaps the mirror group 241 in the V2 direction. It is also preferable that the non-facing surface overlaps the mirror group 241 in the Z direction perpendicular to the optical surface 211.

[0036] 1A, the W direction is indicated by a dotted line. The angle α formed by the W direction indicated by the dotted line and the optical surface 211 is preferably greater than 15° (α>15°), also preferably less than 60° (α<60°), and more preferably greater than 20° and less than 45° (20°<α<45°).

[0037] 1A shows an end 2412 of the mirror group 241 on the side of the mirror group 242 and an end 2411 of the mirror group 241 on the opposite side from the mirror group 242. Also, FIG. 1A shows an end 2421 of the mirror group 242 on the side of the mirror group 241 and an end 2422 of the mirror group 242 on the opposite side from the mirror group 241. In the V direction (V1 direction and / or V2 direction), it is preferable that the end 2421 of the mirror group 242 overlaps with the mirror group 241. In the V direction (V1 direction and / or V2 direction), it is preferable that the end 2412 of the mirror group 241 overlaps with the mirror group 241. In the Z direction, it is preferable that the end 2421 of the mirror group 242 overlaps with the mirror group 241. In the Z direction, it is preferable that the end 2412 of the mirror group 241 overlaps with the mirror group 241. This allows the mirror array 24 to appropriately reflect light incident on the vicinity of the end 2412 or the end 2421 .

[0038] In FIG. 1A , a two-dot chain line indicates a U direction perpendicular to the X direction, connecting an end 2412 of the mirror group 241 on the mirror group 242 side and an end 2421 of the mirror group 242 on the mirror group 241 side. The angle β that the U direction indicated by the two-dot chain line makes with the optical surface 211 is preferably greater than 45° and less than 135° (45°<β<135°), and more preferably greater than 60° and less than 120° (60°<β<120°). In order for the mirror group 241 and the mirror group 242 to overlap in the Z direction, the angle β is preferably greater than 90° (β>90°). Therefore, the angle β is preferably greater than 90° and less than 135° (90°<β<135°), and more preferably greater than 90° and less than 120° (90°<β<120°). Furthermore, the angle γ between the U direction indicated by the two-dot chain line and the W direction is preferably greater than 15° and less than 70° (15°<γ<70°). As can be seen from FIG. 1A, the angles α, β, and γ form the angles of a triangle, so α + β + γ = 180°. It is preferable that at least one, preferably two, and more preferably three of the following conditions be satisfied: α < β, α < γ, and γ < β. For example, α = 30°, β = 105°, and γ = 45°.

[0039] 1B , the multiple retroreflecting mirrors 25 of the mirror group 241 include a retroreflecting mirror 251, a retroreflecting mirror 252, and a retroreflecting mirror 253 located between the retroreflecting mirrors 251 and 252 in the X direction. In FIG. 1B , the width Na of the retroreflecting mirror 251 in the X direction, the width Nb of the retroreflecting mirror 252, and the width Nc of the retroreflecting mirror 253 in the X direction are all equal (Na = Nb = Nc). However, the width Na of the retroreflecting mirror 251 and the width Nb of the retroreflecting mirror 252 in the X direction may be greater than the width Nc of the retroreflecting mirror 253 in the X direction (Na > Nc and Nb > Nc). Alternatively, the width Na of the retroreflecting mirror 251 and the width Nb of the retroreflecting mirror 252 in the X direction may be smaller than the width Nc of the retroreflecting mirror 253 in the X direction (Na < Nc and Nb < Nc). Alternatively, the width Nc of the retroreflecting mirror 253 in the X direction may be between the width Na of the retroreflecting mirror 251 and the width Nb of the retroreflecting mirror 252 in the X direction (Na<Nc<Nb or Na>Nc>Nb).

[0040] The same applies to the multiple retroreflecting mirrors 25 of the mirror group 242. The multiple retroreflecting mirrors 25 of the mirror group 242 include a retroreflecting mirror 254, a retroreflecting mirror 255, and a retroreflecting mirror 256 located between the retroreflecting mirrors 254 and 255 in the X direction. In FIG. 1B , the width of the retroreflecting mirror 254 in the X direction, the width of the retroreflecting mirror 255, and the width of the retroreflecting mirror 255 in the X direction are all equal. However, the widths of the retroreflecting mirror 254 and the retroreflecting mirror 255 in the X direction may be larger or smaller than the width of the retroreflecting mirror 256 in the X direction. Alternatively, the width of the retroreflecting mirror 256 in the X direction may be between the widths of the retroreflecting mirror 254 and the retroreflecting mirror 255 in the X direction. The width of the retroreflecting mirror 25 in the X direction is, for example, 0.1 to 5.0 mm, for example, 0.5 to 2.5 mm.

[0041] 1B, the width Mb of the mirror group 242 in the X direction may be larger than the width Ma of the mirror group 241 in the X direction (Ma<Mb). By doing so, even if light traveling from the +Y direction to the -Y direction spreads in the X direction, it can be reflected over a wider range. The width Mb of the mirror group 242 in the X direction may be smaller than the width Ma of the mirror group 241 in the X direction (Mb<Ma). The width Mb of the mirror group 242 in the X direction may be equal to the width Ma of the mirror group 241 in the X direction (Ma=Mb).

[0042] 1B, the number of retroreflecting mirrors 25 arranged in each of the mirror groups 241 and 242 is six, but may be, for example, 10 to 100, or may be, for example, 15 to 60. The number of retroreflecting mirrors 25 in the mirror group 241 and the number of retroreflecting mirrors 25 in the mirror group 242 may be the same or different. The number of retroreflecting mirrors 25 in the mirror group 242 may be greater or smaller than the number of retroreflecting mirrors 25 in the mirror group 241.

[0043] The length Ea of the mirror group 241 in the W1 direction and the length Eb of the mirror group 242 in the W2 direction correspond to the range in which the mirror groups 241 and 242 provide non-retroreflection (weak retroreflection) in the W direction. The length Ea of the mirror group 241 in the W1 direction and the length Eb of the mirror group 242 in the W2 direction correspond to the lengths of the ridge lines 301 and valley ridge lines 42 of the retroreflection mirror 25. The length Ea of the mirror group 241 in the W1 direction and the length Eb of the mirror group 242 in the W2 direction can also be referred to as the extension distance of the retroreflection mirror 25. The length Ea of the retroreflection mirror 25 in the mirror group 241 in the W1 direction is preferably at least one time the width N (Na, Nb, Nc) of the retroreflection mirror 25 in the mirror group 241 in the X direction, and is preferably greater than the width N (Na, Nb, Nc) of the retroreflection mirror 25 in the mirror group 241 in the X direction. The length Ea of the retroreflecting mirror 25 of the mirror group 241 in the W1 direction can be two or more times, or three or more times, the width N (e.g., widths Na, Nb, Nc) of the retroreflecting mirror 25 of the mirror group 241 in the X direction. The length Ea of the retroreflecting mirror 25 of the mirror group 241 in the W1 direction can be ten or less times, nine or less times, or eight or less times, the width N (Na, Nb, Nc) of the retroreflecting mirror 25 of the mirror group 241 in the X direction. The length Ea of the retroreflecting mirror 25 of the mirror group 241 in the W1 direction can be more than ten times the width N (e.g., widths Na, Nb, Nc) of the retroreflecting mirror 25 of the mirror group 241 in the X direction, but because this leads to an increase in the size of the optical element 20, it is preferable that it be ten times or less.

[0044] The length Eb of the reflex mirror 25 of the mirror group 242 in the W2 direction is preferably at least one time the width N (Na, Nb, Nc) of the reflex mirror 25 of the mirror group 242 in the X direction, and is preferably greater than the width N of the reflex mirror 25 of the mirror group 242 in the X direction. The length Eb of the reflex mirror 25 of the mirror group 242 in the W2 direction can be at least two times, or at least three times, the width N of the reflex mirror 25 of the mirror group 242 in the X direction. The length Eb of the reflex mirror 25 of the mirror group 242 in the W2 direction may be ten times or less, or may be nine times or less, or eight times or less, the width N of the reflex mirror 25 of the mirror group 242 in the X direction. The length Eb of the reflex mirror 25 of the mirror group 242 in the W2 direction may be more than ten times the width N of the reflex mirror 25 of the mirror group 242 in the X direction, but because this leads to an increase in the size of the optical element 20, it is preferable that it be ten times or less.

[0045] The length Eb of the mirror group 242 in the W2 direction may be equal to the length Ea of the mirror group 241 in the W1 direction, or may be smaller than the length of the mirror group 241 in the W1 direction, or may be larger than the length of the mirror group 241 in the W1 direction. The length of the retroreflective mirror 25 in the W direction is, for example, 1 to 10 mm, e.g., 2 to 8 mm. The height difference of the retroreflective mirror 25 in the V direction (the height difference between the mountain ridge line 301 and the valley ridge line 42) is, for example, 0.07 to 3.5 mm, e.g., 0.35 to 1.75 mm.

[0046] As described with reference to FIGS. 1C and 1D , the mirror group 241 and the reflective area of ​​the mirror group 241 have a shape in which concave and convex portions are repeated in the X direction. Part of the concave portion is the valley ridge 42, and part of the convex portion is the mountain ridge 301 (mountain ridges 301a and 301b). The boundary between the concave portion and the convex portion can be set at a height in the V direction such that the height difference between the concave portion and the convex portion is half. In the example shown in FIG. 1B , in the V1 and V2 directions, the convex portion of the mirror group 241 overlaps with the convex portion of the mirror group 242, and the concave portion of the mirror group 241 overlaps with the concave portion of the mirror group 242. However, the convex portion of the mirror group 241 and the convex portion of the mirror group 242 can be shifted in the X direction, and the concave portion of the mirror group 241 and the concave portion of the mirror group 242 can also be shifted in the X direction. As a result, in the V1 and V2 directions, the concave portions of the mirror group 241 and the convex portions of the mirror group 242 may overlap, and the convex portions of the mirror group 241 and the concave portions of the mirror group 242 may overlap.

[0047] 3A to 3C, an optical element 20 according to a second embodiment will be described. Fig. 3A is a cross-sectional view of the optical element 20 in the Y-Z plane, Fig. 3B is a plan view of the optical element 20 in the X-Z plane, and Fig. 3C is a plan view of the optical element 20 in the X-Y plane.

[0048] The optical element 20 has a mirror array 24, an optical surface 211 facing the mirror array 24, and an optical surface 213 facing the mirror array 24. The mirror array 24 is disposed between the optical surface 211 and the optical surface 213. The optical surface 211 is an optical surface that is light-transmitting and / or light-reflective. The optical surface 213 is an optical surface that is light-transmitting and / or light-reflective. An optical surface that is light-transmitting can be referred to as a translucent surface, and an optical surface that is light-reflective can be referred to as a reflective surface. The mirror array 24 includes a mirror group 241. The mirror group 241 is disposed between the optical surface 211 and the optical surface 213. As shown in FIG. 1B , the mirror group 241 is composed of a plurality of retroreflecting mirrors 25 arranged in the X direction. In FIG. 1B , three of the six retroreflecting mirrors 25, 251, 252, and 253, are assigned different reference numerals, but the retroreflecting mirrors 251, 252, and 253 are all examples of the retroreflecting mirror 25. The optical surfaces 211 and 213 are aligned along the X direction and the Y direction intersecting the X direction. The Y direction is typically perpendicular to the X direction, but the Y direction may be inclined relative to the X direction. FIG. 3B shows the width Nx of the retroreflecting mirror 25 in the X direction. The width Nx of the retroreflecting mirror 25 in the X direction is the same as the width N (Na, Nb, Nc) of the retroreflecting mirror 25 in the mirror group 241 in the X direction described in the first embodiment.

[0049] As shown in FIG. 3A , the multiple retroreflecting mirrors 25 of the mirror group 241 extend along the W1 direction intersecting the X and Y directions, so as to be inclined with respect to the optical surface 211. In other words, the W1 direction in which the multiple retroreflecting mirrors 25 of the mirror group 241 extend is inclined with respect to the optical surface 211. The W1 direction is typically perpendicular to the X direction, but the W1 direction may be inclined with respect to the X direction. Also, as shown in FIG. 3A , the multiple retroreflecting mirrors 25 of the mirror group 241 extend along the W1 direction intersecting the X and Y directions, so as to be inclined with respect to the optical surface 213. In other words, the W1 direction in which the multiple retroreflecting mirrors 25 of the mirror group 241 extend is inclined with respect to the optical surface 213. The W1 direction is typically perpendicular to the X direction, but the W1 direction may be inclined with respect to the X direction. In this way, the plurality of retroreflecting mirrors 25 of the mirror group 241 extend along the W1 direction that intersects with the X direction and is inclined with respect to the optical surfaces 211 and 213 .

[0050] 3A , the W1 direction is indicated by a dotted line. The angle φ formed by the W1 direction indicated by the dotted line and the optical surface 211 is preferably greater than 15° (φ>15°), more preferably greater than 20° (φ>20°), preferably less than 60° (φ<60°), and more preferably less than 45° (φ<45°). The angle ψ formed by the W1 direction indicated by the dotted line and the optical surface 213 is preferably greater than 15° (ψ>15°), more preferably greater than 20° (ψ>20°), preferably less than 60° (ψ<60°), and more preferably less than 45° (ψ<45°). The angle φ formed by the W1 direction indicated by the dotted line and the optical surface 211 and the angle ψ formed by the W1 direction indicated by the dotted line and the optical surface 213 may be equal to or different from each other. The optical surfaces 211 and 213 can be parallel, but the optical surfaces 211 and 213 may also be non-parallel to each other.

[0051] A light-transmitting portion 27 is provided between the mirror array 24 and the optical surface 211. This allows light to propagate through the light-transmitting portion 27 between the optical surface 211 and the mirror array 24. A light-transmitting portion 37 is provided between the mirror array 24 and the optical surface 213. This allows light to propagate through the light-transmitting portion 37 between the optical surface 211 and the mirror array 24.

[0052] By disposing the mirror array 24 between the optical surface 211 and the optical surface 213, it is possible to utilize the propagation of light between the optical surface 211 and the mirror array 24 and the propagation of light between the optical surface 213 and the mirror array 24. Furthermore, by tilting the mirror array 24 with respect to the optical surfaces 211 and 213, it is possible to realize the propagation of light between the optical surface 211 and the mirror array 24 and the propagation of light between the optical surface 213 and the mirror array 24 in various directions, even while using the retroreflecting mirror 25. This allows for high optical performance to be achieved. For example, as shown in FIG. 3A , a light ray L incident on the mirror group 241 in the −Y direction from an oblique direction with respect to the optical surface 211 is reflected in the Z direction by the mirror group 241, enters the optical surface 211, transmits through the optical surface 211, and exits the optical element 20. The traveling direction of the light ray L may be opposite to that in the example of FIG. 3A , or a light ray incident on the optical surface 211 from outside the optical element 20 may be reflected by the mirror group 241. The light ray L may be, for example, a light ray propagating inside the optical element 20 (an internal light ray). Furthermore, for example, as shown in FIG. 3A , a light ray R incident on the mirror group 241 from the Z direction relative to the optical surface 213 may be reflected by the mirror group 241 toward the −Y side, obliquely relative to the optical surface 213. If the recursive mirror 25 is translucent, the light ray R traveling from the optical surface 213 toward the mirror group 241 may pass through the recursive mirror 25 and reach the optical surface 211. If the light ray R is, for example, a light ray incident on the optical surface 213 from outside the optical element 20 (an external light ray), the light ray R can be extracted from the optical surface 211. If both light ray R and light ray L are extracted from the optical surface 211, the light ray R and light ray L can be superimposed. For example, if the external light is natural light and the internal light is artificial light such as image light, the natural light and the artificial light can be superimposed. For example, XR technologies such as augmented reality (AR), virtual reality (VR), mixed reality (MR), and substitute reality (SR) can be realized by superimposing an image of real space (natural light) on an image of real space (artificial light). Alternatively, light ray L can be used for display, and light ray R can be used for imaging. Here, an example has been shown in which the mirror group 241 of the mirror array 24 faces the optical surface 211 and the optical surface 213. However, the mirror groups 242 and 243 described in the first embodiment may also face the optical surface 211 and the optical surface 213.

[0053] Third Embodiment An optical element 20 according to a third embodiment will be described with reference to Figures 4A to 4C-2. Figure 4A is a cross-sectional view of the YZ plane (VW plane) of the optical element 20. Figures 4B-1, 4B-2, 4C-1, and 4C-2 are cross-sectional views of the XV plane of the optical element 20.

[0054] The optical element 20 has a mirror array 24 and an optical surface 211 facing the mirror array 24. The optical surface 211 is an optical surface that is light-transmitting and / or light-reflective. An optical surface that is light-transmitting can be called a translucent surface, and an optical surface that is light-reflective can be called a reflective surface. In the example of FIG. 4A , the optical element 20 further has the mirror array 24 and an optical surface 213 facing the mirror array 24, and the mirror array 24 is disposed between the optical surface 211 and the optical surface 213, but the optical surface 213 need not be provided.

[0055] The mirror array 24 includes a light-transmitting mirror 257, a light-transmitting mirror 258, and a light-transmitting mirror 259. The light-transmitting mirror 257 extends along a W1 direction that is inclined with respect to the optical surface 211. The light-transmitting mirror 258 extends along a W2 direction that is inclined with respect to the optical surface 211. The light-transmitting mirror 259 extends along a W3 direction that is inclined with respect to the optical surface 211. The W1 direction, the W2 direction, and the W3 direction may be parallel to each other or may be non-parallel to each other.

[0056] Light-transmitting mirrors 257, 258, and 259 of mirror array 24 are composed of reflector 26. Light-transmitting portion 27 of base 201, which has optical surface 211, supports reflector 26. Light-transmitting portion 37 of cover 202, which has optical surface 213, covers reflector 26. Connection surface 43, indicated by a dashed line in Figures 4A to 4C-2, is the connection surface (boundary surface) between base 201 (light-transmitting portion 27) and cover 202 (light-transmitting portion 37).

[0057] In a configuration having multiple light-transmitting mirrors, some of the light passing through a light-transmitting mirror may be reflected by an adjacent light-transmitting mirror and reach the optical surface 211, or even reach an observer positioned on the optical surface 211 side. For example, some of the light beam L incident on the mirror array 24 is reflected by the light-transmitting mirror 257 and reaches the observer, while the remaining light passing through the light-transmitting mirror 257 is reflected by the light-transmitting mirror 258 and reaches the observer. As a result, the light intensity in the overlapping region where adjacent light-transmitting mirrors overlap as seen from the observer is greater than the light intensity in the non-overlapping region where adjacent light-transmitting mirrors do not overlap as seen from the observer. As a result, a distribution occurs in the light reaching the optical surface 211. Therefore, the reflector 26 is formed so that the reflectance in the overlapping region where the light-transmitting mirrors overlap as seen from the observer is lower than that in the non-overlapping region. This makes it possible to prevent local increases in light intensity in the overlapping region where the light-transmitting mirrors overlap. The portion where the reflectance is reduced is not limited to both ends of the leading end on the optical surface 211 side and the trailing end on the optical surface 213 side in the W direction of the translucent mirror, but may be one end.

[0058] The translucent mirror 257 has high-reflection portions 2621 and 2622 and low-reflection portions 261 and 263. The reflectance of the low-reflection portions 261 and 263 of the translucent mirror 257 is lower than the reflectance of the high-reflection portions 2621 and 2622 of the translucent mirror 257. The transmittance of the low-reflection portions 261 and 263 of the translucent mirror 257 is higher than the transmittance of the high-reflection portions 2621 and 2622 of the translucent mirror 257. In the W1 direction, the high-reflection portions 2621 and 2622 are located between the low-reflection portion 261 and the low-reflection portion 263. In the W1 direction, the high-reflection portion 2621 is located between the low-reflection portion 261 and the high-reflection portion 2622. In the W1 direction, the high-reflection portion 2622 is located between the low-reflection portion 263 and the high-reflection portion 2621. The highly reflective portion 2621 is located in the center of the translucent mirror 257 in the W1 direction, and the low reflective portions 261 and 263 are located at the ends of the translucent mirror 257 in the W1 direction. The highly reflective portion 2622 is located in the middle between the center and the ends of the translucent mirror 257 in the W1 direction.

[0059] The translucent mirror 258 has high-reflection portions 2651, 2652, and 2653 and low-reflection portions 264 and 266. The reflectance of the low-reflection portions 264 and 266 of the translucent mirror 258 is lower than the reflectance of the high-reflection portions 2651, 2652, and 2653 of the translucent mirror 258. The transmittance of the low-reflection portions 264 and 266 of the translucent mirror 258 is higher than the transmittance of the high-reflection portions 2651, 2652, and 2653 of the translucent mirror 258. In the W2 direction, the high-reflection portions 2651, 2652, and 2653 are located between the low-reflection portion 264 and the low-reflection portion 266. In the W2 direction, the high-reflection portion 2651 is located between the low-reflection portion 264 and the high-reflection portion 2652. In the W2 direction, the high-reflection portion 2653 is located between the low-reflection portion 266 and the high-reflection portion 2652. The high-reflection portion 2652 is located in the center of the translucent mirror 258 in the W2 direction, and the low-reflection portions 264 and 266 are located at the ends of the translucent mirror 258 in the W2 direction. The high-reflection portions 2651 and 2653 are located in the intermediate portions between the center and the ends of the translucent mirror 258 in the W2 direction.

[0060] The translucent mirror 259 has high-reflection portions 2681 and 2682 and low-reflection portions 267 and 269. The reflectance of the low-reflection portions 267 and 269 of the translucent mirror 259 is lower than the reflectance of the high-reflection portions 2681 and 2682 of the translucent mirror 259. The transmittance of the low-reflection portions 267 and 269 of the translucent mirror 259 is higher than the transmittance of the high-reflection portions 2681 and 2682 of the translucent mirror 259. In the W3 direction, the high-reflection portions 2681 and 2682 are located between the low-reflection portion 267 and the low-reflection portion 269. In the W3 direction, the high-reflection portion 2681 is located between the low-reflection portion 267 and the high-reflection portion 2682. In the W3 direction, the high-reflection portion 2682 is located between the low-reflection portion 269 and the high-reflection portion 2681. The highly reflective portion 2682 is located in the center of the translucent mirror 259 in the W3 direction, and the low reflective portions 267 and 269 are located at the ends of the translucent mirror 259 in the W3 direction. The highly reflective portion 2681 is located in the intermediate portion between the center and the ends of the translucent mirror 259 in the W3 direction.

[0061] The reflectance and transmittance of the high-reflection portions 2621, 2622, 2651, 2652, 2653, 2681, and 2682 and the low-reflection portions 261, 263, 264, 266, 267, and 269 can be adjusted by varying the structure of the reflector 26 in those portions. Typically, the thickness of the reflector 26 can be varied. For example, a typical thickness Ta of the high-reflection portions 2621, 2622, 2651, 2652, 2653, 2681, and 2682, represented by the high-reflection portion 2622, is smaller than a typical thickness Tb of the reflector 26 in the low-reflection portions 261, 263, 264, 266, 267, and 269, represented by the low-reflection portion 263. In addition to the thicknesses Ta and Tb, the reflectance and transmittance can also be adjusted by varying the refractive index of the reflector 26 or the layer structure of the reflector 26.

[0062] The light-transmitting mirror 257 is located between the light-transmitting mirror 258 and the optical surface 211 in the V1 direction intersecting the optical surface 211 and the W1 direction and / or in the V2 direction intersecting the optical surface 211 and the W2 direction.

[0063] In the V1 direction and / or V2 direction, the low-reflection portion 264 and the high-reflection portion 2622 overlap in an overlapping region Ab, and the low-reflection portion 263 and the high-reflection portion 2651 overlap in an overlapping region Ac. In the V1 direction and / or V2 direction, the low-reflection portion 261 and the high-reflection portion 2621 do not overlap with the translucent mirror 258, and are shown as non-overlapping regions Aa. In the V1 direction and / or V2 direction, the high-reflection portion 2652 does not overlap with the translucent mirror 257, and are shown as non-overlapping regions Ad.

[0064] The translucent mirror 258 is located between the translucent mirror 259 and the optical surface 211 in the V2 direction intersecting the optical surface 211 and the W2 direction and / or in the V3 direction intersecting the optical surface 211 and the W3 direction.

[0065] In the V2 and / or V3 directions, the low-reflection portion 267 and the high-reflection portion 2653 overlap in an overlapping region Ae, and the low-reflection portion 266 and the high-reflection portion 2681 overlap in an overlapping region Af. In the V2 and / or V3 directions, the low-reflection portion 269 and the high-reflection portion 2682 do not overlap with the translucent mirror 257, and are shown as non-overlapping regions Ag. In the V2 and / or V3 directions, the high-reflection portion 2652 does not overlap with the translucent mirror 259, and are shown as non-overlapping regions Ad.

[0066] In FIG. 4A, overlapping regions Ab, Ac, Ae, and Af and non-overlapping regions Aa, Ad, and Ag in the V1, V2, and V3 directions are shown separated by dashed dotted lines.

[0067] In the Z direction perpendicular to the optical surface 211, the low-reflection portion 263 and the low-reflection portion 264 overlap in an overlapping region Bb, and the low-reflection portion 266 and the low-reflection portion 267 overlap in an overlapping region Bd. In the Z direction, the low-reflection portion 261 and the high-reflection portions 2621 and 2622 do not overlap with the translucent mirror 258, and are shown as non-overlapping regions Ba. In the Z direction, the high-reflection portions 2651, 2652, and 2653 do not overlap with the translucent mirrors 257 and 258, and are shown as non-overlapping regions Bc.

[0068] 4A shows a typical light ray L incident on the mirror array 24. The light ray L is reflected by the mirror array 24, exits from the mirror array 24, and travels toward the optical surface 211. For example, the angle that the incident direction of the light ray L makes with respect to the V direction is approximately equal to the angle that the exit direction of the light ray L makes with respect to the V direction. If the inclination angle of the W direction with respect to the optical surface 211 is φ and the inclination angle of the incident direction of the light ray L with respect to the optical surface 211 is θ, and φ = θ, then the angle that the incident direction of the light ray L makes with respect to the V direction and the angle that the exit direction of the light ray L makes with respect to the V direction are approximately equal to the inclination angle φ and the inclination angle θ. The exit direction of the light ray L is perpendicular to the optical surface 211. In the Z direction perpendicular to the optical surface 211, the low-reflection portion 263 and the low-reflection portion 264 overlap in the overlap region Bb, and the low-reflection portion 266 and the low-reflection portion 267 overlap in the overlap region Bd, which is advantageous in reducing unevenness in the amount of reflected light when the mirror array 24 is observed from the Z direction.

[0069] If both of the reflective portions of the light-transmitting mirrors 257, 258, and 259 that overlap in the overlapping regions Ab, Ac, Ae, Af, Bb, and Bd are highly reflective, the reflection at the two overlapping highly reflective portions will be greater than the reflection at a single highly reflective portion in the non-overlapping regions Aa, Ad, Ag, Ba, Bc, and Be. For example, suppose the light-transmitting mirrors 257, 258, and 258 are half mirrors with a reflectance of 50% and a transmittance of 50% at their reflective portions, and incident light of intensity P is incident on the two overlapping reflective portions. Of the two overlapping reflective portions, 50% of the reflected light (intensity P / 2) is reflected by the first reflective portion. Furthermore, 50% of the transmitted light (intensity P / 2) that passes through the first reflective portion is reflected by the second reflective portion at 50% (intensity P / 4), and 50% of this transmitted light (intensity P / 8) passes through the first reflective portion and exits. Since the exiting light is the sum of the reflected light with intensity P / 2 and the transmitted light with intensity P / 8, the intensity of the exiting light is 5 / 8P light. Since the exiting light from the reflective portion in the non-overlapping region is only 50% reflected light (intensity P / 2) from one reflective portion, the exiting light from the overlapping region is 1.25 times that from the non-overlapping region. Therefore, by lowering the reflectivity of at least one of the two overlapping reflective portions, the difference in the exiting light between the overlapping region and the non-overlapping region can be reduced.

[0070] In this way, at least one of the portions of the translucent mirrors 257, 258, 259 that overlap each other in the overlapping regions Ab, Ac, Ae, Af, Bb, and Bd is a low-reflection portion, which makes it possible to prevent an extreme increase in reflection in the overlapping regions Ab, Ac, Ae, Af, Bb, and Bd of the mirror array 24, and to reduce unevenness in the amount of light reflected by the mirror array 24.

[0071] 4B-1 and 4B-2 show cases where the translucent mirrors 257, 258, and 259 are non-retroreflective mirrors. FIG. 4B-1 is an XV cross-sectional view of the high-reflection portions 2621, 2622, 2651, 2652, 2653, 2681, and 2682, and FIG. 4B-2 is an XV cross-sectional view of the low-reflection portions 261, 263, 264, 266, 267, and 269. The reflective surfaces 25f of the translucent mirrors 257, 258, and 259 serving as non-retroreflective mirrors are flat. The thicknesses Tb of the low-reflection portions 261, 263, 264, 266, 267, and 269 are smaller than the thicknesses Ta of the high-reflection portions 2621, 2622, 2651, 2652, 2653, 2681, and 2682. The relationship between the thickness Ta and the thickness Tb controls the high and low relationships between the reflectance and the transmittance.

[0072] 4C-1 and 4C-2 show cases where the translucent mirrors 257, 258, and 259 are retroreflecting mirrors. FIG. 4C-1 is an XV cross-sectional view of the high-reflecting portions 2621, 2622, 2651, 2652, 2653, 2681, and 2682, and FIG. 4C-2 is an XV cross-sectional view of the low-reflecting portions 261, 263, 264, 266, 267, and 269. The translucent mirrors 257, 258, and 259 serving as retroreflecting mirrors have a pair of reflective surfaces 25a and 25b that are non-parallel to each other and face each other in the forward X direction. The ends of the reflective surfaces 25a and 25b opposite the optical surface 211 form a valley ridge 42. Retroreflectivity will be described in detail in the fourth embodiment. The thickness Tb of the low-reflection portions 261, 263, 264, 266, 267, and 269 is smaller than the thickness Ta of the high-reflection portions 2621, 2622, 2651, 2652, 2653, 2681, and 2682. The relationship between the thickness Ta and the thickness Tb controls the high-low relationship between the reflectance and the transmittance.

[0073] The reflectance of the highly reflective portions 2621 and 2622 of the light-transmitting mirror 257 may be the same as or different from the reflectance of the highly reflective portions 2651, 2652, and 2653 of the light-transmitting mirror 258. In particular, if the reflectance of the highly reflective portions 2621 and 2622 of the light-transmitting mirror 257 is lower than the reflectance of the highly reflective portions 2651, 2652, and 2653 of the light-transmitting mirror 258, it is possible to increase the amount of light that passes through the light-transmitting mirror 257 and reaches the light-transmitting mirror 258. As a result, it is possible to reduce the difference between the amount of light reflected by the light-transmitting mirror 257 and the amount of light reflected by the light-transmitting mirror 258. For example, the thickness of the highly reflective portions 2621 and 2622 of the light-transmitting mirror 257 may be made smaller than the thickness of the highly reflective portions 2651, 2652, and 2653 of the light-transmitting mirror 258.

[0074] The reflectance of the highly reflective portions 2651, 2652, and 2653 of the light-transmitting mirror 258 may be the same as or different from the reflectance of the highly reflective portions 2681 and 2682 of the light-transmitting mirror 259. In particular, if the reflectance of the highly reflective portions 2651, 2652, and 2653 of the light-transmitting mirror 258 is lower than the reflectance of the highly reflective portions 2681 and 2682 of the light-transmitting mirror 259, it is possible to increase the amount of light that passes through the light-transmitting mirror 258 and reaches the light-transmitting mirror 259. As a result, it is possible to reduce the difference between the amount of light reflected by the light-transmitting mirror 258 and the amount of light reflected by the light-transmitting mirror 259. For example, the thickness of the highly reflective portions 2651, 2652, and 2653 of the light-transmitting mirror 258 may be made smaller than the thickness of the highly reflective portions 2681 and 2682 of the light-transmitting mirror 259.

[0075] The reflectance of the low-reflection portions 261, 263 of the light-transmitting mirror 257 may be the same as or different from the reflectance of the low-reflection portions 264, 266 of the light-transmitting mirror 258. In particular, if the reflectance of the low-reflection portions 261, 263 of the light-transmitting mirror 257 is lower than the reflectance of the low-reflection portions 264, 266 of the light-transmitting mirror 258, it is possible to increase the amount of light that passes through the light-transmitting mirror 257 and reaches the light-transmitting mirror 258. As a result, it is possible to reduce the difference between the amount of light reflected by the light-transmitting mirror 257 and the amount of light reflected by the light-transmitting mirror 258. For example, the thickness of the low-reflection portions 261, 263 of the light-transmitting mirror 257 may be made smaller than the thickness of the low-reflection portions 264, 266 of the light-transmitting mirror 258.

[0076] The reflectance of the low-reflection portions 264, 266 of the light-transmitting mirror 258 may be the same as or different from the reflectance of the low-reflection portions 267, 269 of the light-transmitting mirror 259. In particular, if the reflectance of the low-reflection portions 264, 266 of the light-transmitting mirror 258 is lower than the reflectance of the low-reflection portions 267, 269 of the light-transmitting mirror 259, it is possible to increase the amount of light that passes through the light-transmitting mirror 258 and reaches the light-transmitting mirror 259. As a result, it is possible to reduce the difference between the amount of light reflected by the light-transmitting mirror 258 and the amount of light reflected by the light-transmitting mirror 259. For example, the thickness of the low-reflection portions 264, 266 of the light-transmitting mirror 258 may be made smaller than the thickness of the low-reflection portions 267, 269 of the light-transmitting mirror 259.

[0077] In an embodiment in which the first embodiment and / or the second embodiment is combined with the third embodiment, each of the plurality of retroreflecting mirrors 25 of the mirror group 241 described in the first and second embodiments corresponds to the light-transmitting mirror 257 described in the third embodiment. In an embodiment in which the first embodiment and the third embodiment are combined, each of the plurality of retroreflecting mirrors 25 of the mirror group 242 described in the first embodiment corresponds to the light-transmitting mirror 258 described in the third embodiment.

[0078] 5A to 5D show Y-Z cross-sectional views of the optical element 20, similar to FIG. 4A. FIG. 5A shows an example in which low-reflection portions are provided at the tip ends of the light-transmitting mirrors 257, 258, and 259, and high-reflection portions are provided at the rear ends. The reflectance of the high-reflection portions and the reflectance of the low-reflection portions increase in the order of the light-transmitting mirrors 257, 258, and 259. FIG. 5B shows an example in which low-reflection portions are provided at the rear ends of the light-transmitting mirrors 257, 258, and 259, and high-reflection portions are provided at the tip ends. The reflectance of the high-reflection portions and the reflectance of the low-reflection portions increase in the order of the light-transmitting mirrors 257, 258, and 259. FIG. 5C shows an example in which low-reflection portions are provided at the rear ends of the light-transmitting mirrors 257, 258, and 259, and low-reflection portions are provided at the tip ends. The reflectance of the high-reflection portions and the reflectance of the low-reflection portions increase in the order of the light-transmitting mirrors 257, 258, and 259.

[0079] In the embodiment shown in FIG. 4A , no reflector 26 is formed on the connecting surface 43, but a reflector 26 may be provided on the connecting surface 43 along the connecting surface 43. As shown in FIG. 5D , the reflector 26 on the connecting surface 43 also functions as a translucent mirror 278, 289. The mirror array 24 may include these translucent mirrors 278, 289. The translucent mirror 278, which is formed by the reflector 26 on the connecting surface 43 connecting the tip end of the translucent mirror 257 and the rear end of the translucent mirror 258, connects the translucent mirror 257 and the translucent mirror 258. The translucent mirror 289, which is formed by the reflector 26 on the connecting surface 43 connecting the tip end of the translucent mirror 258 and the rear end of the translucent mirror 259, connects the translucent mirror 258 and the translucent mirror 259. To avoid inhibiting light propagation between the light-transmitting mirror 257 and the light-transmitting mirror 258 in the Y direction, the reflectance of the reflector 26 on the connecting surface 43 is preferably lower than the reflectance of the high-reflection portions 2621, 2622, 2651, 2652, 2653, 2681, and 2682. Furthermore, the reflectance of the reflector 26 on the connecting surface 43 is preferably lower than the reflectance of the low-reflection portions 261, 263, 264, 266, 267, and 269. The reflector 26 on the connecting surface 43 can be made of a dielectric material selected from silicon oxide, magnesium fluoride, magnesium oxide, aluminum oxide, tantalum oxide, titanium oxide, zirconium oxide, niobium oxide, or a mixture thereof. The thickness Tc of the reflector 26 on the connecting surface 43 is preferably smaller than the thickness Ta of the high-reflection portion and smaller than the thickness Tb of the low-reflection portion. The reflector 26 on the connecting surface 43 farther from the light incident portion preferably has mirror characteristics with higher reflectivity and lower transmittance. This reduces the possibility of differences in brightness due to the angle of view of the displayed image.

[0080] Here, an example is shown in which three light-transmitting mirrors 257, 258, and 259 are arranged side by side in the Y direction, but the number of light-transmitting mirrors may be two, or four or more, as long as multiple light-transmitting mirrors are arranged so as to overlap each other.

[0081] Fourth Embodiment A display device 100 according to a fourth embodiment will be described with reference to FIGS. 6A and 6B. FIG. 6A is a schematic diagram of the display device 100. The display device 100 includes a projection unit 10 and an optical element 20. The optical element 20 in the fourth embodiment can be any of the optical elements 20 described in the first to third embodiments. For example, the direction connecting the viewer's left and right eyes will be referred to as the X direction (arrangement direction), the direction connecting the viewer's philtrum and the space between the eyebrows will be referred to as the Y direction (juxtaposition direction), and the direction perpendicular to the X and Y directions (the direction from the viewer's eye (pupil) 30 toward the optical element 20) will be referred to as the Z direction. The display device 100 can be used as AR (Augmented Reality) glasses.

[0082] The projection unit 10 has a display element 11 such as an OLED (organic light emitting diode) or an LCD (liquid crystal display), and a projection optical system 12. The projection optical system 12 has a free-form prism, achieving a wide acceptance angle and compact size. However, this embodiment is not limited to this, and the projection optical system 12 may be configured using a general optical system instead of the free-form prism. The optical element 20 is arranged to project a pupil EP conjugate with the exit pupil EP of the projection unit 10 (projection optical system 12) at the position of the viewer's eye 30 in a one-dimensional direction (for example, the horizontal direction (X direction)). Ｃ In this embodiment, the projection optical system 12 and the optical element 20 constitute an observation optical system that guides light from the display element 11 to the viewer's eye 30. The light beam incident from the projection optical system 12 into the optical element 20 fills the entire thickness of the optical element in the thickness direction of the optical element, and in the width direction of the optical element, a light beam having a light beam width narrower than the width of the optical element travels while being internally reflected within the optical element 20. Of the light beams emitted from the optical element, the light beam in the width direction of the optical element corresponds to the arrangement direction (X direction), and the light beam in the thickness direction of the optical element corresponds to the juxtaposition direction (Y direction).

[0083] In this embodiment, the ratio of the angle of view of the display device 100 in the horizontal direction (X direction) and the vertical direction (Y direction) is 16:9. ＣTherefore, the optical element 20 forms a pupil EP conjugate with the exit pupil EP in the horizontal direction. Ｃ However, this embodiment is not limited to this, and a pupil EP conjugate with the exit pupil EP is formed in the vertical direction (Y direction) instead of the horizontal direction. Ｃ It may be configured to form

[0084] In this embodiment, the state in which a pupil EPC conjugate with the exit pupil EP of the projection unit 10 is formed in the viewer's eye 30 is called "pupil conjugate." The optical element 20 has a mirror array 24 described later, and thereby forms a pupil EP conjugate with the exit pupil EP of the projection unit 10 in one dimensional direction (horizontal direction or vertical direction). Ｃ is formed on the observer's eye 30. This makes it possible to reduce wasted light that does not enter the observer's eye 30, and therefore to increase the proportion of light that reaches the observer's eye 30 out of the light projected from the projection unit 10 (the light utilization efficiency of the optical element 20).

[0085] In the case of a pupil conjugate configuration in one dimension (horizontal direction), it is preferable to configure the mirror array 24 so that light is incident at an angle other than perpendicular to the mirror array 24 and reflected in a different direction in a direction (vertical direction) that is not pupil conjugate with the mirror array 24. Ｃ can be located at a location different from the exit pupil EP.

[0086] As shown in FIG. 6B , the optical element 20 includes a light-guiding section 21, an incident section 22, and a mirror array 24. Image light from the projection section 10 shown in FIG. 6A is incident on the incident section 22. The light-guiding section 21 has a function of guiding the image light from the incident section 22 to the mirror array 24, and includes a folding mirror 23 in this example. The mirror array 24 is a reflecting section that retroreflects light from the projection optical system 12, and in this embodiment, includes a mirror group 241, a mirror group 242, and a mirror group 243. Each of the multiple retroreflecting mirrors 25 in the mirror group 241 corresponds to the light-transmitting mirror 257 described in the third embodiment. Each of the multiple retroreflecting mirrors 25 in the mirror group 242 corresponds to the light-transmitting mirror 258 described in the third embodiment. Each of the multiple retroreflecting mirrors 25 in the mirror group 243 corresponds to the light-transmitting mirror 259 described in the third embodiment. The exit pupil EP of the projection optical system 12 is formed inside the optical element 20 (at the base (tip) 22a of the entrance portion 22). Light from the projection optical system 12 shown in FIG. 6A is reflected by the mirror array 24 of the optical element 20, thereby forming a pupil EPC conjugate with the exit pupil EP of the projection portion 10 in the horizontal direction at the entire angle of view outside the optical element 20 (at the position of the viewer's eye 30). At this time, the optical surface 211 of the optical element 20 of the first embodiment can face the eye 30. The light reflected by the mirror array 24 passes through the optical surface 211 and can form an image (virtual image) outside the optical element 20.

[0087] The display device 100 of this embodiment uses the optical element 20, thereby enabling a thin display device 100 to be realized. Furthermore, the optical element 20 has a high light utilization efficiency (the proportion of light projected from the display element that reaches the viewer's eye). As a result, brightness sufficient for use in bright environments such as outdoors can be achieved, and battery weight can be reduced. Furthermore, the configuration of the optical element 20 can reduce degradation and brightness distribution in the image of the display element that reaches the viewer's eye, thereby providing a high-quality display device. In particular, by arranging a reflective mirror 25 in the optical element 20 to form a pupil conjugate, light utilization efficiency can be improved, thereby providing a bright display device 100. Although the mirror array 24, which is an array of reflective mirrors 25 (e.g., right-angle mirrors), has a three-dimensional structure, the use of the optical element 20 described in the first embodiment enables the display of a high-quality image. Therefore, a thin display device 100 with high light utilization efficiency and high image quality can be realized.

[0088] Fifth Embodiment Next, the configuration of an optical element 20 according to a fifth embodiment will be described with reference to FIGS. 7A to 10B. The optical element 20 according to the fifth embodiment can be the same as the optical elements 20 described in the first to fourth embodiments. FIG. 7A is a perspective view of the optical element 20, viewed mainly from the front surface, and FIG. 7B is a perspective view of the optical element 20, viewed mainly from the back surface. FIG. 8A is a YZ cross-sectional view of the optical element 20 taken along line II in FIG. 7A. FIG. 8B is an enlarged view of region II in FIG. 8A. FIG. 9A is a perspective view of a base 201 constituting the optical element 20, viewed mainly from the back surface, and FIG. 9B is a perspective view of the base 201 constituting the optical element 20, viewed mainly from the front surface. FIG. 10A is a perspective view of a cover 202 constituting the optical element 20, viewed mainly from the back surface, and FIG. 10B is a perspective view of the cover 202 constituting the optical element 20, viewed mainly from the front surface.

[0089] The optical element 20 is mainly composed of a base 201 and a cover 202. The base 201 has a front surface including an optical surface 211, a back surface opposite the front surface, and a side surface connecting the front surface and the back surface. The base 201 has a light guide section 21, an incident section 22, a mirror array 24, and a peripheral section 29. The mirror array 24 has a mirror group 241, a mirror group 242, and a mirror group 243. However, this embodiment is not limited to this, and the number of mirror groups included in the mirror array 24 may be two, four, or more. As described in the first embodiment, the reflecting surfaces 25a and 25b of the mirror array 24 are formed by a reflector 26. The surface roughness Ra (arithmetic mean roughness) of the reflecting surfaces 25a and 25b is preferably 50 nm or less, more preferably 25 nm or less, and may be 1 nm or more, or may be 5 nm or more.

[0090] The light-guiding unit 21 also has an optical surface 214 on a surface including the optical surface 211 facing the mirror array 24. The light-guiding unit 21 also has an optical surface 212 on a back surface opposite the surface on which the optical surface 214 is located. The optical surfaces 214 and 212 may be reflective surfaces of the light-guiding unit 21. The optical surfaces 214 and 212 may be reflective surfaces that reflect light by total reflection within the light-guiding unit 21. In this case, the optical surfaces 214 and 212 may also be light-transmitting surfaces. By using the optical surfaces 214 and 212 as light-transmitting surfaces, light that enters the optical surface 212 from the outside can be emitted from the optical surface 214. The side surface of the base 201 also includes an optical surface 215 that constitutes the folding mirror 23. The reflection at the folding mirror 23 may be reflection by a reflector disposed on the optical surface 215, or total reflection at the optical surface 215. The surface roughness Ra (arithmetic mean roughness) of the optical surfaces 211 to 215 is preferably 50 nm or less, more preferably 10 nm or less, and even more preferably 5 nm or less.

[0091] 7A and 9A , in the light guide section 21 and the peripheral section 29 around the mirror array 24, there are marks 81 from ejector pins of the mold used to mold the base 201 on the back surface opposite to the front surface including the optical surface 211 facing the mirror array 24. By providing the marks 81 on the back surface, the optical surfaces 211 and 214 on the front surface can be widened. The outer surface of the peripheral section 29 may be rougher than the optical surfaces 211 to 215, and the surface roughness Ra (arithmetic mean roughness) of the outer surface of the peripheral section 29 may be greater than 50 nm.

[0092] As shown in FIG. 8A , the cover 202 of the optical element 20 is a component that covers the mirror array 24 from the side opposite the optical surface 211. As shown in FIG. 8B , the cover 202 has an optical surface 213 and a padding portion 84. The optical surface 213 may be a light-transmitting surface. Like the optical surface 211, the optical surface 213 also faces the mirror array 24. As shown in FIG. 8B , the distance dt between the optical surfaces 211 and 213 is, for example, 1 to 10 mm, preferably 2 to 6 mm. When positioning the mirror array 24, it is advantageous to tilt the extension direction (W) of the retroreflecting mirror 25 toward the optical surfaces 211 and 213 and juxtapose the mirror groups 241, 242, and 243 in the Y direction in order to reduce the distance dt. The distance from the optical surface 211 to the reflector 26 may be, for example, 0.1 to 1.0 mm, preferably 0.25 to 0.75 mm. The distance from the optical surface 213 to the reflector 26 can be, for example, 0.1 to 1.0 mm, preferably 0.25 to 0.75 mm.

[0093] The distance between the optical surface 212 and the optical surface 214 is, for example, 1 to 10 mm, and preferably 2 to 6 mm. The distance between the optical surface 212 and the optical surface 214 can be 0.5 to 1.5 times, and preferably 0.75 to 1.25 times, the distance dt between the optical surface 211 and the optical surface 213. The maximum thickness of the base 201 in the Z direction is, for example, 1.5 to 5.0 times, and preferably 1.5 to 3.0 times, the distance between the optical surface 212 and the optical surface 214. The thickness of the base 201 in the Z direction can typically be greatest at the incident portion 22. The minimum thickness of the base 201 in the Z direction is, for example, 0.01 to 0.5 times, and preferably 0.05 to 0.5 times, the distance between the optical surface 212 and the optical surface 214. For example, the thickness of the base 201 in the Z direction can be smallest at the light-transmitting portion 27.

[0094] In the configuration of the optical element 20, the filling portion 84 is disposed to cover the mirror array 24, and the optical surface 213 is positioned alongside the optical surface 212. The filling portion 84 has an inverted uneven shape of the light-transmitting portion 27 so as to fit into the uneven shape of the light-transmitting portion 27, filling some of the gaps in the mirror array 24. An adhesive 245 is provided between the reflector 26 of the mirror array 24 and the cover 202. This adhesive 245 fixes the cover 202 to the base 201. The adhesive 245 fills the gaps between the filling portion 84 and the mirror array 24. If the reflector 26 is light-transmitting, using a light-transmitting material for the adhesive 245 can reduce light loss between the base 201 and the cover 202. The thickness of the adhesive 245 is, for example, 1 μm or more and, for example, 1 mm or less, for example, 10 to 100 μm. 10B , around the filling portion 84 of the cover 202, there are marks 82 from the ejector pins of the mold used to mold the cover 202. By providing the marks 82 on the surface opposite to the optical surface 213, the optical surface 213 can be made wider.

[0095] The cover 202 (filler 84) may contain a light-transmitting material. The filler 84 containing the light-transmitting material constitutes at least a portion of the light-transmitting portion 37 shown in Figures 3A to 3C and 4A to 4C-2. The filler 84 may have a portion located between the reflecting surface 25a and the reflecting surface 25b in the X direction. When the reflector 26 is a dielectric multilayer film, the refractive index of the high-refractive index dielectric material contained in the dielectric multilayer film of the reflector 26 is preferably higher than the refractive index of the filler 84, but may be lower than the refractive index of the filler 84. The refractive index of the low-refractive index dielectric material contained in the dielectric multilayer film of the reflector 26 is preferably lower than the refractive index of the filler 84, but may be higher than the refractive index of the filler 84. The light-transmitting material constituting the filler 84 may be resin or glass. Examples of resins that can be used as light-transmitting materials include optical plastics such as acrylic resins, styrene resins, polyolefin resins, and polycarbonates. The refractive index of these resins is generally 1.45 to 1.60. Cycloolefin polymer is particularly suitable as the resin that constitutes the cover 202. Cycloolefin polymer is suitable for improving the performance of the optical element 20, such as high transparency, light resistance, stability of the refractive index and Abbe number, low birefringence, low specific gravity, high heat resistance, and precision moldability.

[0096] It is not essential that light propagates between the optical surface 213 and the mirror array 24, and the cover 202 (filler 84) may be made of a light-shielding material. When the reflector 26 is translucent, the filler 84 is preferably translucent in order to propagate light transmitted through the reflector 26. By making the filler 84 translucent, for example, light can propagate from the translucent filler 84 to the translucent light-transmitting portion 27 via the translucent reflector 26.

[0097] In addition to the material (e.g., a light-transmitting material) that constitutes the filling portion 84, the cover 202 may also include a coating material that covers the material that constitutes the filling portion 84. The coating material may be an appropriate material for purposes such as protection (scratch prevention, anti-fouling, anti-fogging), anti-reflection, reflection promotion, and light blocking, and a light-transmitting material or a light-blocking material may be used. The coating material may be an inorganic material or an organic material. The coating material may also constitute the optical surface 213 of the cover 202.

[0098] Light (image light) from the projection optical system 12 enters the entrance unit 22 and travels while undergoing total reflection between the optical surface 214 and the optical surface 212. The light from the projection optical system 12 changes course at the optical surface 215 formed by the folding mirror 23, and travels toward the mirror array 24 while again undergoing total reflection between the optical surface 214 and the optical surface 212. The light from the projection optical system 12 then changes course at the mirror array 24, exits from the optical surface 211, and reaches the viewer's eye 30 located on the optical surface 211 side. By reaching the viewer's eye 30 via the mirror array 24, the light from the projection optical system 12 reaches the viewer's eye 30 at a pupil EP conjugate with the exit pupil EP of the projection unit 10 in the horizontal direction over the entire angle of view. Ｃ can be formed outside the optical element 20 (at the position of the observer's eye 30).

[0099] The mirror array 24 is disposed at an angle relative to the optical surfaces 211 and 213. That is, a valley ridge 42 formed by the reflecting surfaces 25a and 25b is inclined relative to the optical surfaces 211 and 213. In this embodiment, three mirror groups 241, 242, and 243 are disposed along the Y direction (the juxtaposition direction). The angles formed by the three mirror groups 241, 242, and 243 and the optical surface 211 are equal. Between the mirror group 241 and the mirror group 242 and between the mirror group 242 and the mirror group 243, there are connecting surfaces 43 connecting adjacent mirror arrays 24. The connecting surfaces 43 are formed by the base 201 (light-transmitting portion 27). The connecting surfaces 43 extend along the U direction described in the first embodiment. The angle formed between the connecting surfaces 43 and the optical surface 211 corresponds to the angle β described in the first embodiment. 1A, the connecting surface 43 connects an end 2412 of the mirror group 241 on the mirror group 242 side to an end 2421 of the mirror group 242 on the mirror group 241 side, perpendicular to the X direction. Note that although the connecting surface 43 can be covered with the reflector 26, in this example the connecting surface 43 is not covered with the reflector 26 and is in contact with the adhesive 245. That is, the adhesive 245 is in contact with the base 201 at the connecting surface 43 of the base 201.

[0100] The observation optical system of each embodiment has an optical element (pupil-conjugate optical element) that forms a pupil conjugate with the exit pupil of the projection unit at the position of the observer's eye, thereby achieving brightness that is usable in bright environments such as outdoors while reducing the battery weight. Therefore, each embodiment can provide a thin observation optical system, display device, and method for manufacturing an observation optical system that have high light utilization efficiency (the proportion of light that reaches the observer's eye out of the light projected by the projection unit).

[0101] Sixth Embodiment As the sixth embodiment, the configuration of the mirror array 24 will be described using first to sixth examples. For the optical element 20 including the mirror array 24 in the sixth embodiment, for example, the base 201 described in the fifth embodiment can be used. Therefore, for convenience, a case where the mirror array 24 is applied to the base 201 described in the fifth embodiment will be described, as shown in FIG. 11 . However, the optical element 20 to which the mirror array 24 of the sixth embodiment can be applied is not limited to the optical element 20 shown in the fifth embodiment.

[0102] [First Example] A first example of the sixth embodiment will be described with reference to Figures 12A to 12D. Figures 12A to 12D are front views of the base 201. Figure 12A is a YZ cross-sectional view of the base 201 along the juxtaposition direction. Figure 12B is an XY cross-sectional view of the base 201 along line VV in Figure 12A. Figure 12C is a front view of Figure 12A as seen from the Z direction. Figure 12D is a front view showing only one retroreflecting mirror 25 from Figure 12C.

[0103] The mirror array 24 is configured by arranging multiple pairs of retroreflecting mirrors 25, each consisting of a reflective surface 25a and a reflective surface 25b, in the arrangement direction (X direction). The reflective surfaces 25a and 25b are arranged perpendicular to each other, forming a right-angle mirror. Three mirror groups 241, 242, and 243 are arranged along the juxtaposition direction (Y direction). The mirror groups 241, 242, and 243 are arranged at an angle with respect to the optical surface 211. That is, the valley ridge 42 of the retroreflecting mirror 25, formed by the reflective surfaces 25a and 25b, is inclined with respect to the optical surface 211. The valley ridges 42 of the three mirror groups 241, 242, and 243 form equal angles with the optical surface 211. Furthermore, the mountain ridges 301 formed by adjacent retroreflecting mirrors 25 in the arrangement direction are also inclined with respect to the optical surface 211. The angles formed by the mountain ridge lines 301 of the three mirror groups 241, 242, and 243 and the optical surface 211 are equal, and the valley ridge lines 42 are parallel to the mountain ridge lines 301. Between the mirror groups 241 and 242, and between the mirror groups 242 and 243, there are connecting surfaces 43 that connect adjacent mirror arrays 24. In Figures 12A to 12D, the mountain ridge lines 301 are indicated by dashed lines, and the valley ridge lines 42 are indicated by dotted lines.

[0104] Light from the projection optical system 12 enters through the incident section 22 and travels while undergoing total reflection between the optical surfaces 211 and 212. The light from the projection optical system 12 changes course at the folding mirror 23 and travels toward the mirror array 24 while again undergoing total reflection between the optical surfaces 211 and 212. A light ray L21 that travels near the mirror array 24 is reflected by the optical surface 211. The light ray L22 reflected by the optical surface 211 is retroreflected by the reflecting surfaces 25a and 25b as a light ray L23, changes course as a light ray L24, and reaches the viewer's eye 30 on the optical surface 211 side. Light with different angles of view is retroreflected by one of the retroreflecting mirrors 25 of the mirror groups 241, 242, and 243, respectively, to form an image at the position of the viewer's eye 30.

[0105] Because the retroreflective mirror 25 has a three-dimensional structure, there is an area A21 on the retroreflective mirror 25 that cannot be retroreflected. In other words, when viewed from the observer's eye 30, an image cannot be displayed in area A21, and it is missing. The reason why light ray L24 is not emitted from area A21 is because there is no paired reflective surface 25a or reflective surface 25b at a position where light ray L22 is reflected to light ray L23. Therefore, the mirror array 24 is arranged to overlap in the juxtaposition direction to cover area A21 where retroreflection is not possible. In other words, the mirror group 241 and the mirror group 242, and the mirror group 242 and the mirror group 243 overlap in area A22 when viewed from the Z direction.

[0106] When viewed from a vector D perpendicular to the valley ridge 42 of the retroreflecting mirror 25 and perpendicular to the arrangement direction, the mirror group 241 and the mirror group 242, and the mirror group 242 and the mirror group 243 overlap.

[0107] By arranging the mirror arrays 24 in an overlapping manner and covering the non-reflecting area A21 described below, a high-quality image without any defects can be formed at the position of the observer's eye 30. As a result, the connecting surface 43 becomes an undercut.

[0108] The mirror groups 241, 242, and 243 are arranged at an inclination of 30 degrees with respect to the optical surface 211. The angles between the valley ridges 42 of the three mirror groups 241, 242, and 243 and the optical surface 211 are all equal and within a range of more than 20 degrees and less than 45 degrees. The angles between the mountain ridges 301 of the three mirror groups 241, 242, and 243 and the optical surface 211 are all equal and within a range of more than 20 degrees and less than 45 degrees, and the valley ridges 42 and the mountain ridges 301 are parallel. The connecting surface 43 is inclined within a range of more than 0 degrees and less than 45 degrees with respect to the optical surface 211, forming an undercut shape. The retroreflecting mirrors 25 are arranged at a pitch of 0.5 to 3 mm in the arrangement direction and at a pitch of 3 to 10 mm in the juxtaposition direction. The mirror groups 241 and 242, and the mirror groups 242 and 243 overlap within a range of 0.1 to 3 mm in the juxtaposition direction when viewed from the Z direction.

[0109] For mirror groups 241, 242, and 243, the distance dc from the optical surface 211 to the tip of ridge line 301 on the optical surface 211 side can be 0.1 to 1.0 mm. For mirror groups 241, 242, and 243, the distances dc from the optical surface 211 to the tip of ridge line 301 on the optical surface 211 side may be the same (the difference is 0.1 mm or less).

[0110] A vector A is parallel to the normal to the optical surface 211 and points from the optical surface 211 toward the retroreflecting mirror 25. A vector B is parallel to the valley ridge 42 of the retroreflecting mirror 25 and points away from the optical surface 211. In this case, the angle θ between the vectors A and B is ＡＢ is 45°<θ ＡＢ It is desirable that the angle θ is less than 70°. ＡＢ If the angle θ is less than 45°, the light ray L22 reflected by the optical surface 211 will not reach the viewer's eye 30 on the optical surface 211 side as in the case of L24 after being retroreflected by the retroreflecting mirror 25, and the number of optically invalid light rays may increase. ＡＢ If the angle θ exceeds 70 degrees, the light rays will not be totally reflected by the optical surface 211, and the number of light rays that are not optically valid may increase. ＡＢ <70° can mean the same as 20°<α<45° shown in FIG.

[0111] A vector C is parallel to the perpendicular to the connecting surface 43 and points away from the optical surface 211. In this case, the angle θ between the vectors A and C is ＡＣ is 45°<θ ＡＣ It is desirable that the angle θ is less than 90°. ＡＣ If the angle θ is less than 45 degrees, the undercut of the connecting surface 43 becomes too large, making it difficult to mold the resin with high precision. ＡＣ If the angle exceeds 90 degrees, the undercut shape will no longer be formed, the area A22 where the retroreflecting mirrors overlap in the juxtaposition direction will disappear, and the area A21 where the adjacent retroreflecting mirrors 25 cannot retroreflect will no longer be covered. ＡＣ <90° can mean the same as 90°<β<135° shown in FIG.

[0112] Also, the angle θ between vector B and vector C ＡＢ is 105°<θ ＡＢ It is desirable that the angle θ is less than 160°. ＡＢ If the angle θ is less than 105 degrees, the tip of the retroreflecting mirror 25 in the juxtaposition direction will be too acute, making it difficult to mold the retroreflecting mirror 25 with high precision by resin molding. ＡＢ If θ exceeds 160°, the undercut shape will no longer be formed, the area A22 where the retroreflecting mirrors overlap in the juxtaposition direction will disappear, and the area A21 where the adjacent retroreflecting mirrors 25 cannot retroreflect will no longer be covered. ＡＢ <160° can mean the same as 15°<γ<70° shown in FIG.

[0113] The light ray L24 that is retroreflected by the retroreflecting mirror 25 and travels to the viewer's eye 30 may be inclined, for example, at an angle in the range of 0° to 50° with respect to the Z direction perpendicular to the optical surface 211. The light ray L24 may also be inclined at an angle in the range of 0° to 30° with respect to the Y direction. The magnitude of the inclination varies depending on the location on the mirror array 24, and the greater the inclination, the wider the viewing angle of the displayed image.

[0114] Second Example A second example of the sixth embodiment will be described with reference to Figures 13A to 13D. Figure 13A is a YZ cross-sectional view of the base 201 along the juxtaposition direction. Figure 13B is an XY cross-sectional view of the base 201 along line VI-VI in Figure 13A. Figure 13C is a front view of Figure 13A as seen from the Z direction. Figure 13D is a front view showing only one set of retroreflecting mirrors 25 from Figure 13C. A description of the aspects that may be the same as in the first example will be omitted, and the following description will focus on the differences from the first example.

[0115] Since undercuts are difficult to fabricate in resin molded products, a configuration without undercut shapes is generally preferable. As a comparative example of such a case, an example will be described in which the mirror arrays 24 are not overlapped in the Z direction, and the mirror groups 241 and 242, and the mirror groups 242 and 243 are arranged so as to be in contact when viewed from the Z direction. In this case, the connecting surface 43 is perpendicular to the optical surface 211.

[0116] In this arrangement, the non-retroreflecting area A11 of the retroreflecting mirror 25 does not overlap with the mirror group 241 in the Z direction. Therefore, when an observer observes from the Z direction, depending on the size of area A11, an image cannot be displayed on the screen and a missing area may be visible. To reduce the visibility of area A11, the angle of incidence on the mirror array 24 can be adjusted so that light is reflected in a direction inclined from the Z direction.

[0117] Third Example A third example will be described with reference to Figures 14A to 14D. Figure 14A is a YZ cross-sectional view of the base 201 along the juxtaposition direction. Figure 14B is an XY cross-sectional view of the base 201 along line VII-VII in Figure 14A. Figure 14C is a front view of Figure 14A as seen from the Z direction. Figure 14D is a front view showing only one set of retroreflecting mirrors 25 from Figure 14C. A description of the aspects that may be the same as in the first example will be omitted, and the following description will focus on the differences from the first example.

[0118] In contrast to the first embodiment, the end of the retroreflective mirror 25 in the juxtaposition direction extends only toward the optical surface 211. To prevent the extended retroreflective mirror 25 from coming too close to the optical surface 211, the end of the retroreflective mirror 25 facing the optical surface 211 is cut, forming a non-facing surface 302. The non-facing surface 302 is an extension of the ridge line 301. The distance df of the non-facing surface 302 from the optical surface 211 may be 0.1 to 1.0 mm. The non-facing surface 302 may be a surface extending along the X direction. Therefore, the non-facing surface 302 does not face, in the X direction, a pair of reflecting surfaces 25a, 25b of at least one retroreflective mirror of the multiple retroreflective mirrors 25 in the mirror group 242. Here, the non-facing surface 302 may be a surface extending along the Y direction, but the non-facing surface 302 may also be inclined with respect to the Y direction. In the Z direction perpendicular to the optical surface 211 , the non-opposing surface 302 overlaps the mirror group 243 .

[0119] Extending the recursive mirror 25 increases the area of ​​the recursive mirror 25. This makes it possible to display an image in a wider area with the same number of recursive mirrors 25, which is effective in widening the viewing angle of the display device. Alternatively, it makes it possible to display an image in the same area with a fewer number of recursive mirrors 25, which is effective in improving the brightness of the display device.

[0120] As in the first embodiment, the mirror arrays 24 are arranged to overlap in the juxtaposition direction so as to cover the non-retroreflecting area A41 of the retroreflecting mirror 25. That is, the mirror groups 241 and 242, and the mirror groups 242 and 243, overlap in area A42 when viewed from the Z direction. By overlapping the mirror arrays 24 to cover the non-retroreflecting area A41, a high-quality image without any defects can be formed at the position of the observer's eye 30.

[0121] Furthermore, by extending the end of the reflective mirror 25 in the juxtaposition direction toward the optical surface 211, the area of ​​the reflective mirror 25 can be enlarged while facilitating processing when manufacturing it by resin molding.

[0122] [Fourth Example] A fourth example of the sixth embodiment will be described with reference to Figures 15A to 15D. Figure 15A is a YZ cross-sectional view of the base 201. Figure 15B is an XY cross-sectional view of the base 201 taken along line VI-VI in Figure 15A. Figure 15C is a front view of Figure 15A as seen from the Z direction. Figure 15D is a front view showing only one set of retroreflecting mirrors 25 from Figure 15C. A description of the aspects that may be the same as in the third example will be omitted, and the following description will focus on the differences from the third example.

[0123] Unlike the third embodiment, the end of the retroreflecting mirror 25 in the extension direction is extended opposite the optical surface 211. The end of the retroreflecting mirror 25 in the extension direction is cut so that the extended retroreflecting mirror 25 does not come too close to the optical surface 211 or the optical surface 213 (not shown). As in the fourth embodiment, a non-facing surface 302 is formed at the end of the mirror group 242 close to the optical surface 211 (the end on the mirror group 243 side). Furthermore, a non-facing surface 302 is formed at the end of the mirror group 242 opposite the optical surface 211 (the end on the mirror group 241 side). The non-facing surfaces 302 and 303 are on extensions of the mountain ridge line 301. The non-facing surface 303 can be a surface along the X direction. Therefore, the non-facing surface 303 does not face a pair of reflecting surfaces 25 a and 25 b of at least one retroreflecting mirror of the multiple retroreflecting mirrors 25 of the mirror group 242 in the X direction. Here, the non-opposing surface 303 can be a surface along the Y direction, but the non-opposing surface 303 may also be inclined with respect to the Y direction. In the Z direction perpendicular to the optical surface 211, the non-opposing surface 303 overlaps the mirror group 241.

[0124] Extending the recursive mirror 25 increases the area of ​​the recursive mirror 25. This makes it possible to display an image in a wider area with the same number of recursive mirrors 25, which is effective in widening the viewing angle of the display device. Alternatively, it makes it possible to display an image in the same area with a fewer number of recursive mirrors 25, which is effective in improving the brightness of the display device.

[0125] As in the first embodiment, the mirror arrays 24 are arranged to overlap in the juxtaposition direction so as to cover the non-retroreflecting area A31 of the retroreflecting mirror 25. That is, the mirror groups 241 and 242, and the mirror groups 242 and 243, overlap in the area A32 when viewed from the Z direction. By overlapping the mirror arrays 24 to cover the non-retroreflecting area A31, a high-quality image with reduced defects can be formed at the position of the observer's eye 30.

[0126] Fifth Example A fifth example of the sixth embodiment will be described with reference to Figures 16A to 16D. Figure 16A is a YZ cross-sectional view of the base 201. Figure 16B is an XY cross-sectional view of the base 201 taken along line VI-VI in Figure 16A. Figure 16C is a front view of Figure 16A as viewed from the Z direction. Figure 16D is a front view of Figure 16C showing only one set of retroreflecting mirrors 25. A description of the aspects that may be the same as in the fourth example will be omitted, and the following description will focus on the differences from the fourth example.

[0127] Mirror group 241 and mirror group 242, and mirror group 242 and mirror group 243 are arranged with a phase shift. As a result, the concave portions of mirror group 241 overlap with the convex portions of mirror group 242, and the convex portions of mirror group 241 overlap with the concave portions of mirror group 242. The concave portions of mirror group 242 overlap with the convex portions of mirror group 243, and the convex portions of mirror group 242 overlap with the concave portions of mirror group 243. This makes it possible to more efficiently cover area A31 where retroreflection is not possible.

[0128] Placing the non-retroreflective areas described in Examples 1 to 5 in the overlapping areas Ab, Ac, Ae, Af, Bb, and Bd described in the third embodiment is effective in reducing the visibility of the non-retroreflective areas. Also, placing the low-reflection portions described in the third embodiment in the non-retroreflective areas is effective in reducing the visibility of the non-retroreflective areas.

[0129] Sixth Example A sixth example of the sixth embodiment will be described with reference to Figures 17A to 17C. Figure 17A is a YZ cross-sectional view of the base 201, and also a VW cross-sectional view. Figure 17B is a perspective view of the base 201 with the cover 202 removed, observed from the direction of the arrow in Figure 17A. Points A to G in Figure 17A correspond to the boundaries A to G in Figure 7B. Figure 17C is an XV cross-sectional view perpendicular to the W direction.

[0130] The structure shown in Figures 17A and 17B may be the same as that of the third example of the sixth embodiment shown in Figures 14A to 14D, and therefore a detailed description thereof will be omitted. Note that, in Figure 17A, the mirror array 24 is viewed from the rear side, and therefore the peaks and valleys appear reversed compared to the previous description. That is, in Figure 17A, the valley-like portions that are concave toward the back of the page are the mountain ridgelines 301a and 301b when the mirror array 24 is viewed from the optical surface 211. Furthermore, the mountain-like portions that are toward the front of the page are the valley ridgelines 42 when the mirror array 24 is viewed from the optical surface 211.

[0131] 17B , the width of mirror group 242 in the X direction is greater than the width of mirror group 241 in the X direction. Furthermore, the width of mirror group 243 in the X direction is greater than the width of mirror group 242 in the X direction. This allows for appropriate reflection of light spreading from the front stage (mirror group 241) to the rear stage (mirror group 243).

[0132] The mirror group 241 has 27 retroreflecting mirrors 25 arranged therein, the mirror group 242 has 29 retroreflecting mirrors 25 arranged therein, and the mirror group 243 has 31 retroreflecting mirrors 25 arranged therein.

[0133] 17B, ​​the length of mirror group 242 in the W direction is greater than the length of mirror group 241 in the W direction. Furthermore, the length of mirror group 243 in the W direction is greater than the length of mirror group 242 in the W direction. The length of mirror group 242 in the Y direction is greater than the length of mirror group 241 in the Y direction. Furthermore, the length of mirror group 243 in the Y direction is greater than the length of mirror group 242 in the Y direction. This allows for appropriate reflection of light as it spreads from the front stage (mirror group 241) to the rear stage (mirror group 243). The lengths of mirror groups 241, 242, and 243 in the W direction may be distributed in the range of 4 to 8 mm, for example.

[0134] As shown in Figures 17B and 17C, the mirror array 24 is configured by arranging multiple pairs of retroreflecting mirrors 25, each consisting of a reflecting surface 25a and a reflecting surface 25b, in the X direction. The central axis M of the mirror array 24 in the X direction, which is the arrangement direction, is shown. The mirror array 24 can be symmetrical in the X direction with the central axis M as the axis of symmetry. The reflecting surfaces 25a and 25b are arranged perpendicular to each other, and the retroreflecting mirror 25 forms a right-angle mirror. The reflecting surface 25a is the reflecting surface of the retroreflecting mirror 25 on the side of the central axis M. The reflecting surface 25b is the reflecting surface of the retroreflecting mirror 25 on the opposite side from the central axis M.

[0135] 17B , the phases of the recesses and protrusions in mirror group 241 are shifted from the phases of the recesses and protrusions in mirror group 242. Similarly, the phases of the recesses and protrusions in mirror group 242 are shifted from the phases of the recesses and protrusions in mirror group 243. That is, for example, on central axis M, valley ridge 42 of mirror group 241, mountain ridge 301 of mirror group 242, and valley ridge 42 of mirror group 243 are aligned. Furthermore, in the Y direction, the recesses of mirror group 241, the protrusions of mirror group 242, and the recesses of mirror group 243 are aligned. As a result, in the V direction and the Z direction, the recesses of mirror group 241 and the protrusions of mirror group 242 overlap, and the protrusions of mirror group 242 and the recesses of mirror group 243 overlap. Furthermore, in the Y direction, the protrusions of mirror group 241, the recesses of mirror group 242, and the protrusions of mirror group 243 are aligned. As a result, in the V direction and the Z direction, the convex portions of mirror group 241 overlap with the concave portions of mirror group 242, and the concave portions of mirror group 242 overlap with the convex portions of mirror group 243. By doing so, it is possible to increase the area of ​​the region where retroreflection is not possible at the front end of the rear mirror group in the Y direction and the rear end of the front mirror group in the Y direction overlap.

[0136] 17B and 17C, the widths of the multiple retroreflecting mirrors 25 constituting the mirror group 241 (the distance between the ridge lines 301a and 301b) are non-uniform. Specifically, the farther the retroreflecting mirror 25 is from the central axis M in the X direction, the wider the retroreflecting mirror 25. Therefore, the widths of the retroreflecting mirrors 25 at both ends in the X direction are greater than the widths of the retroreflecting mirrors 25 near the central axis M in the X direction. This allows for appropriate reflection of the spread of light in the X direction from the central axis M toward both ends. The widths of the retroreflecting mirrors 25 in the X direction may be distributed within a range of 0.5 to 1.5 mm, for example.

[0137] 17C , the distances from the optical surface 211 to the valley ridgelines 42 of the multiple retroreflecting mirrors 25 constituting the mirror group 241 are non-uniform. Specifically, the farther a retroreflecting mirror 25 is from the central axis M in the X direction, the greater the distance from the valley ridgeline 42 to the optical surface 211. For example, the distance he from the optical surface 211 to the valley ridgeline 42 farther from the central axis M is greater than the distance hd from the optical surface 211 to the valley ridgeline 42 closer to the central axis M. The same is true for the mirror groups 242 and 243.

[0138] In the VX cross-sectional view of the mirror group 241 shown in Figure 17C, the ridge lines 301 of the multiple retroreflecting mirrors 25 that make up the mirror group 241 can have the same distance ha from the optical surface 211 (for example, the difference is 0.1 mm or less). Figure 17C shows that the ridge lines 301 are aligned along a straight line (the distances ha are the same). The same is true for the mirror groups 242 and 243. The distance ha can be, for example, 0.25 to 0.75 mm.

[0139] In this way, the retroreflecting mirror 25 is configured so that the difference in height between the ridge lines 301 and the valley ridge lines 42 increases as it moves outward from the central axis M. This allows appropriate retroreflection to be achieved in relation to the spread of light. Note that it is also possible to make the distances of the valley ridge lines 42 from the optical surface 211 uniform, while making the distances of the ridge lines 301 from the optical surface 211 non-uniform. However, making the distances of the ridge lines 301 closest to the optical surface 211 uniform from the optical surface 211 is advantageous in terms of size reduction and molding accuracy.

[0140] 17C, the retroreflecting mirror 25 includes a reflecting surface 25e that is inclined relative to the reflecting surface 25b. In this example, the reflecting surface 25e is arranged perpendicular to the arrangement direction (X direction) of the retroreflecting mirrors 25, in other words, along the V direction. The normal direction of the reflecting surface 25e is parallel to the arrangement direction (X direction) of the retroreflecting mirrors 25. The reflecting surfaces 25a and 25e are non-parallel to each other and face each other in the X direction. In this way, by providing the reflecting surface 25e, it is possible to reduce the gap between the light beams reflected by the mirror array 24.

[0141] In the V-X cross-sectional view of the mirror group 241 shown in FIG. 17C, the reflective surfaces 25e of the multiple reflex mirrors 25 constituting the mirror group 241 have non-uniform lengths in the V direction. Specifically, the farther a reflex mirror 25 is from the central axis M in the X direction, the greater the length of the reflective surface 25e in the V direction. For example, the V direction lengths ha-hc of the reflective surfaces 25e farther from the central axis M are greater than the V direction lengths ha-hb of the reflective surfaces 25e closer to the central axis M. The same is true for the mirror groups 242 and 243. By making the V direction lengths of the reflective surfaces 25e non-uniform in this way, it is possible to further reduce gaps in the light beams reflected by the mirror array 24. This reduces the resulting shading in the displayed image, enabling high-quality images to be displayed.

[0142] Seventh Embodiment As a seventh embodiment, a method for manufacturing an optical element 20 will be described with reference to FIGS. 7A to 10. FIG.

[0143] 9A and 9B, a base 201 having a light-guiding portion 21, an incident portion 22, and a light-transmitting portion 27 is formed by injection molding. During the injection molding, an ejector pin mark 81 is formed as shown in FIG.

[0144] 10A and 10B, a cover 202 having a filling portion 84 similar in shape to the mirror array 24 is formed by injection molding. During injection molding, ejector pin marks 82 are formed as shown in Fig. 10B. The material for the cover 202 is preferably a thermoplastic optical resin such as PMMA, polycarbonate, or cycloolefin polymer (cyclic olefin-based resin).

[0145] In the third formation step, a reflector 26 (see FIG. 8B ) is formed on the light-transmitting portion 27 of the base 201 formed in the first formation step by an appropriate method, such as physical vapor deposition (e.g., vapor deposition or sputtering), chemical vapor deposition, or liquid phase deposition (e.g., plating). If the base 201 has multiple retroreflecting mirrors, the characteristics (transmittance and reflectance characteristics) of the reflectors 26 can be made different for each retroreflecting mirror in order to adjust the brightness according to the angle of view of the displayed image (so that the brightness of the displayed image seen by the observer is constant). For example, the reflectance of the reflector 26 formed in the rear mirror group can be made higher than the reflectance of the reflector 26 in the front mirror group. Furthermore, the transmittance of the reflector 26 formed in the rear mirror group can be made lower than the transmittance of the reflector 26 in the front mirror group. For example, the reflectance of the reflectors 26 of the mirror group 243 can be higher than the reflectance of the reflectors 26 of the mirror group 241 , and the transmittance of the reflectors 26 of the mirror group 243 can be lower than the transmittance of the reflectors 26 of the mirror group 241 .

[0146] In the fourth formation step, the base 201 formed in the third formation step and the cover formed in the second formation step are bonded together with an adhesive such as an ultraviolet-curable resin to form the optical element 20. At this time, the mirror array 24 and the filling portion 84 are bonded together to form the optical element 20 as shown in FIGS. 7A and 7B. The ultraviolet-curable resin serves as the adhesive 245 (see FIG. 8B) described above. According to this embodiment, the optical element 20 is manufactured by bonding two molded products (the base 201 and the cover 202), so that the optical element 20 can be manufactured with both mass productivity and high optical performance.

[0147] The second forming step may be performed before the first forming step, or after the third forming step as long as it is before the fourth forming step, or may be performed simultaneously with the first forming step or the third forming step.

[0148] As another manufacturing method for the optical element 20, instead of the third formation step, the reflector 26 may be formed on the cover 202 formed in the second step. The cover 202 can also be considered as a component (base) that supports the reflector 26, and the base 201 as a component (cover) that covers the reflector 26 (mirror array 24). If the cover 202, which is smaller in size than the base 201, is used as a base for forming the reflector 26, it becomes easier to form the cover 202 with high precision and it becomes possible to form a large number of films at once. Furthermore, the cover 202 has fewer optical surfaces than the base 201, which means that there are fewer areas (optical surfaces) where the reflector 26 should not be formed, which are protected during the formation of the reflector 26, making it easier to form the reflector 26.

[0149] As another method for manufacturing the optical element 20, insert molding may be performed in which one of the base 201 and the cover 202 is placed in a mold as an insert, and the other of the base 201 and the cover 202 is injection molded into the mold. In this case, the adhesive 245 can be omitted, and one of the first and second forming steps can be integrated into the fourth forming step.

[0150] A specific example of the fourth forming step will be described with reference to FIGS. 18A to 18D.

[0151] 18A shows the state after the third formation step described above. The base 201 is preferably made of a thermoplastic optical resin, such as PMMA, polycarbonate, or cycloolefin polymer (a cyclic olefin-based resin). A reflector 26 is formed on the light-transmitting portion 27 of the base 201 by vapor deposition or sputtering. The light-transmitting portion 27 is preferably made of a thermoplastic optical resin, such as PMMA, polycarbonate, or cycloolefin polymer (a cyclic olefin-based resin). The reflector 26 can be a total reflection mirror or a half mirror. The reflector 26 is made of a material selected from silicon oxide, magnesium fluoride, magnesium oxide, aluminum oxide, tantalum oxide, titanium oxide, zirconium oxide, niobium oxide, or a mixture thereof, and the reflectivity is controlled by the film thickness and film configuration.

[0152] 18B illustrates the next step after that of FIG. 18A, in which adhesive 244 is applied onto reflector 26. An energy ray curable resin is used as adhesive 244, and for example, an ultraviolet curable resin is applied. The ultraviolet curable resin is preferably an acrylic resin, an epoxy resin, or a mixture thereof. Adhesive 244 is also applied to connecting surface 43.

[0153] FIG. 18C illustrates the next step after FIG. 18B , in which the cover 202 is placed on the adhesive 244. The cover 202 is preferably molded from the same material as the base 201 to suppress refraction of transmitted light. Even if the base 201 and cover 202 are made of different materials, it is preferable that the difference in refractive index between the base 201 (transparent portion 27) and the cover 202 (transparent portion 37, filling portion 84) be less than 0.01. When combining the cover 202 and reflector 26 via adhesive 244, if there is a gap between the cover 202 and reflector 26, the gap may refract or scatter reflected and transmitted light, affecting optical performance. Therefore, it is desirable to fill the space between the reflector 26 and the cover 202 with adhesive 244. If a UV-curable resin is used for the adhesive 244, the cover 202 and the reflector 26 of the base 201 are sealed with the adhesive 244. Then, the cover 202 is cured by irradiating it with ultraviolet light from the optical surface 213 thereof.

[0154] FIG. 18D shows the state in which adhesive 244 has hardened to form adhesive 245. If adhesive 245 is made of a different material than base 201 (translucent portion 27) and cover 202 (translucent portion 37), a large difference in refractive index between translucent portion 27 and translucent portion 37 will result in increased refraction of light passing through translucent portion 37, translucent reflector 26, and adhesive 245. Therefore, the thickness of adhesive 245 may be 1 μm or more, but is preferably 1 mm or less. For example, taking into consideration the ease of application of adhesive 244, the thickness of adhesive 245 can be set to 10 to 100 μm, e.g., 50 μm. Furthermore, the difference in refractive index between adhesive 245 and base 201 (translucent portion 27) is preferably less than 0.25, more preferably 0.01 or less. Furthermore, the difference in refractive index between adhesive 245 and cover 202 (translucent portion 37) is preferably less than 0.25, more preferably 0.01 or less. This can reduce the influence of refraction caused by sealing with adhesive 245 .

[0155] As another manufacturing method, as shown in FIGS. 19A to 19D, the structure of the optical element 20 is shown when the cover 202 is formed without using the adhesive material 245.

[0156] In the step shown in FIG. 19A, similarly to FIG. 18A, a reflector 26 is formed on a light-transmitting portion 27 of a substrate 201 by vapor deposition or sputtering.

[0157] 19B, a fluid resin 248 is disposed on the reflector 26 by a method such as coating. The fluid resin 248 is typically an uncured photocurable resin, but may also be a molten thermoplastic resin or an uncured thermosetting resin.

[0158] In the process shown in Figure 19C, in order to form optical surface 213 on the surface of resin 248, a mold 300 manufactured with the surface shape of optical surface 213 is abutted against resin 248, and the surface shape of mold 300 is transferred to resin 248.

[0159] 19D , energy rays (light) are irradiated onto resin 248 to harden resin 248. At this time, if mold 300 is opaque, the energy rays for hardening are irradiated onto resin 248 from the optical surface 211 side, passing through light-transmitting portion 27. By hardening resin 248, cover 202 is formed, which has filling portion 84, light-transmitting portion 37, and optical surface 213. FIG. 19D shows the state in which mold 300 is released after resin 248 has hardened.

[0160] In addition, in the process of applying and hardening the resin 248, the process may be carried out in multiple steps, taking into consideration dimensional changes and internal stresses caused by hardening shrinkage.

[0161] 20A and 20B are diagrams showing light rays propagating through the inside of the light-transmitting portion 27 of the base 201 by the reflecting surfaces 25a and 25b of the retroreflecting mirror 25. When the light rays passing through the inner surface of the light-transmitting portion 27 reach the reflecting surface 25a of the base 201, the light rays are reflected by the reflector 26 on the surface of the light-transmitting portion 27. The reflected light is then reflected by the reflecting surface 25b and emitted toward the optical surface 211 (not shown). At this time, the light rays arrive after being reflected once by the reflecting surfaces 25a and 25b, so the perpendicularity of the reflecting surfaces 25a and 25b must be formed with high precision.

[0162] 20A, if the inner surface of the light-transmitting portion 27 is configured to reflect light, the reflected light can be reflected without being affected by the film thickness distribution that occurs in the reflector 26 or the adhesive 245 or by the refractive index of each. Because the retroreflecting mirror 25 can be molded with a right-angled retroreflecting shape, the squareness is highly accurate and manufacturing variations are small. Therefore, by adopting the configuration of this embodiment, an optical element 20 with high optical performance can be obtained.

[0163] In contrast, in the example shown in Figure 20B, the reflector 26 is formed on the filling portion 84 and then bonded to the base 201 with an adhesive 245. The surfaces of the reflecting surfaces 25a and 25b are defined not by a mold but by the surface of the reflector 26 at the time of film formation. Minute irregularities may occur on the film-formed surface of the reflector 26, and if such irregularities exist on the reflecting surfaces 25a and 25b, the reflection accuracy at the reflecting surfaces 25a and 25b may be inferior to that in the example shown in Figure 20A. In addition, the thickness of the adhesive 245 and the attachment error between the base 201 and the cover 202 (and the reflector 26) may also have an effect.

[0164] Therefore, in order to obtain a high-precision optical element 20, the structure and manufacturing method of FIG. 20A are preferable to those of FIG. 20B.

[0165] Eighth Embodiment As an eighth embodiment, an apparatus EQP including an optical element 20 will be described with reference to FIGS. 8A and 8B . In this embodiment, an example of an apparatus EQP including a display device DSPL is shown as shown in FIG. 21A . The display device 100 of the fourth embodiment described above can be applied to the display device DSPL. The optical system OPT included in the display device DSPL is an observation optical system that guides light from the display element 11 to the viewer's eye 30, and can include the projection optical system 12 described in the fourth embodiment in addition to the optical element 20. The optical element 20 described in the first to seventh embodiments can be applied to this embodiment.

[0166] The optical system of the device EQP has a projection optical system 12 that projects light from a display element 11, and an optical element 20 that guides the light from the projection optical system 12 to the observer's eye, and the optical element 20 can be configured to form a pupil outside the optical element 20 that is conjugate with the exit pupil of the projection optical system 12.

[0167] The device EQP may include at least one of a control device CTRL, a communication device IF, an imaging device IS, and an audio device AUDIO. The control device CTRL controls the display device DSPL. may be a DSP or an ASIC. The control device CTRL may include a processing unit, which may be configured to perform computing using artificial intelligence. The control device CTRL may also include a power supply unit and may supply power to the display device DSPL and the imaging device IS. The communication device IF communicates (transmits / receives) signals including information to be displayed in the display area of ​​the display element 11. The communication device IF has wireless communication and / or wired communication functions. The communication device IF may have only a receiving function without a transmitting function. The optical system OPT projects the image displayed on the display element 11 onto a screen or the retina. The optical system OPT may include a lens, a prism, or a mirror. The device EQP including the display device DSPL may also include an imaging device IS. In the equipment EQP, an image captured by the imaging device IS can be displayed on the display device DSPL. The equipment EQP having the imaging device IS may be a camera or an information device with a camera.

[0168] The imaging device IS captures an image. The image captured by the imaging device IS can be displayed in the display area of ​​the display element 11. The imaging device IS can be a CMOS image sensor that photoelectrically converts light captured from outside the device EQP. The audio device AUDIO can include a microphone that inputs sound from outside the device EQP and / or a speaker that outputs sound. In particular, the imaging device IS and the audio device AUDIO can be omitted as appropriate depending on the specifications of the device EQP and the user's requests.

[0169] The device EQP is also suitable for electronic devices such as information terminals with display functions (e.g., smartphones and wearable devices) and cameras (e.g., interchangeable lens cameras, compact cameras, video cameras, and surveillance cameras). The device EQP may also be transportation equipment such as vehicles, ships, and aircraft. Alternatively, the device EQP may be medical equipment such as ophthalmic equipment, measuring equipment such as distance sensors, or office equipment such as copiers.

[0170] The device EQP including the display device DSPL may be a mobile device such as a smartphone, a mobile PC, or a tablet. The device EQP including the display device DSPL may be a wearable device. A wearable device is a type of mobile device. The optical element 20 can be applied to wearable devices such as smart glasses, a head-mounted display (HMD), and a goggle-type display.

[0171] FIG. 21B shows an example of a head-mounted display HMD as an example of the device EQP. The head-mounted display HMD includes a wearing mechanism WR for using the device EQP as a head-mounted display. The wearing mechanism WR is a band, strap, or the like. The optical element 20 can be worn on the user's head by the wearing mechanism WR. The head-mounted display HMD is provided with multiple display devices DSPL so that the user can observe images with both eyes. The head-mounted display HMD also includes multiple image capture devices IS so that distance information can be acquired. The display devices DSPL and image capture devices IS are housed in a housing HS. By positioning a microphone of the audio device AUDIO near the user's mouth, sound emitted from the user's mouth can be input to the microphone. By positioning speakers of the audio device AUDIO near the user's ears, sound directed toward the user's ears can be output from the speakers.

[0172] FIG. 21C is a schematic diagram illustrating an eyeglass-type head-mounted display HMD as an example of a wearable device EQP. The head-mounted display HMD is an eyeglass-type device and has an eyeglass-type frame FR. The head-mounted display HMD may include, for example, the projection unit 10 described in the fourth embodiment and an optical element 20 having an incident unit onto which light from the projection unit 10 is incident. The frame FR includes a rim or bridge that holds the optical element 20, as well as temples and nose pads that are worn over the ears. The optical element 20 can be worn on the user's head using attachment means WR such as temples or nose pads.

[0173] The image capturing device IS may include a photographing lens for forming an image on an image sensor. The image capturing device IS is provided on the outer surface of the temple of the eyeglasses. The image is displayed via an optical element 20.

[0174] The head-mounted display HMD may have a communication unit (not shown), and the head-mounted display HMD and other devices may communicate with each other via wired and / or wireless communication via the communication unit. The head-mounted display HMD may have two display devices DSPL, one for the left eye and one for the right eye. The head-mounted display HMD may have two image capture devices IS, one for the left eye and one for the right eye. The timing of image capture and display can be set arbitrarily for each of the image capture devices IS and display devices DSPL for the left eye and the right eye. Specifically, this may involve capturing images at the same time and displaying them at different times, or capturing images at different times and displaying them at the same time. The image capture device IS and display device DSPL may be located at different positions, or may be located so that they overlap in the line of sight.

[0175] The present invention is not limited to the above-described embodiments, and many modifications are possible within the technical concept of the present invention. Furthermore, the effects described in the embodiments are merely a list of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments.

[0176] The above-described embodiments can be modified as appropriate without departing from the spirit and scope of the present invention. For example, multiple embodiments can be combined. Furthermore, some aspects of at least one embodiment can be deleted or replaced.

[0177] Furthermore, new matters may be added to at least one embodiment. The disclosure of this specification includes not only what is explicitly described in this specification, but also all matters that can be understood from this specification and the drawings attached hereto.

[0178] In addition, with regard to the specific numerical ranges exemplified in this specification, the notation "e to f" (e and f are numbers) means e or more and / or f or less. Furthermore, when a range of i to j and a range of m to n are both listed for the specific numerical ranges exemplified (i, j, m, and n are numbers), the set of lower and upper limits is not limited to the set of i and j or the set of m and n. For example, it is also possible to consider a combination of multiple sets of lower and upper limits. In other words, when a range of i to j and a range of m to n are both listed, it is also possible to consider the range of i to n or the range of m to j, as long as there is no contradiction. Furthermore, "e or more" means either e or greater than e (exceeding e), and it is also possible to adopt a value greater than e without adopting e. Furthermore, "f or less" means either f or smaller than f (less than f), and it is also possible to adopt a value smaller than f without adopting f.

[0179] The disclosure of this specification also includes the following:

[0180] [Item A1] An optical element having a mirror array and an optical surface facing the mirror array, wherein the mirror array includes: a first mirror group consisting of a plurality of retroreflecting mirrors arranged in a first direction; and a second mirror group consisting of a plurality of retroreflecting mirrors arranged in the first direction, wherein the first mirror group and the second mirror group are arranged side by side in a second direction intersecting the first direction, wherein the plurality of retroreflecting mirrors of the first mirror group extend along a third direction that intersects the first direction and the second direction and is inclined with respect to the optical surface, wherein the plurality of retroreflecting mirrors of the second mirror group extend along a fourth direction that intersects the first direction and the second direction and is inclined with respect to the optical surface, and wherein the first mirror group and the second mirror group partially overlap in a fifth direction that is perpendicular to the first direction and the third direction.

[0181] [Item A2] The optical element according to item A1, wherein the first mirror group and the second mirror group partially overlap in a direction perpendicular to the optical surface.

[0182] [Item A3] The optical element according to item A1 or A2, wherein each of the plurality of retroreflecting mirrors of the first mirror group and the plurality of retroreflecting mirrors of the second mirror group includes a pair of reflective surfaces that are non-parallel to each other and face each other in the first direction.

[0183] [Item A4] The optical element according to item A3, wherein the first mirror group has non-opposing surfaces that do not face the pair of reflecting surfaces of at least one of the plurality of recursive mirrors of the first mirror group in the first direction, and the non-opposing surfaces overlap the second mirror group in a direction perpendicular to the optical surface.

[0184] [Item A5] The optical element according to any one of items A1 to A4, wherein the angle formed between the third direction and the optical surface is greater than 20° and smaller than 45°.

[0185] [Item A6] The optical element according to any one of items A1 to A5, wherein a direction connecting an end of the first mirror group on the side of the second mirror group and an end of the second mirror group on the side of the first mirror group, perpendicular to the first direction, forms an angle with the optical surface that is greater than 90° and smaller than 135°.

[0186] [Item A7] The optical element according to any one of items A1 to A6, wherein a direction connecting an end of the first mirror group on the side of the second mirror group and an end of the second mirror group on the side of the first mirror group, perpendicular to the first direction, forms an angle with a third direction that is greater than 15° and smaller than 70°.

[0187] [Item A8] The optical element described in any one of items A1 to A7, wherein the plurality of retroreflective mirrors of the first mirror group include a first retroreflective mirror, a second retroreflective mirror, and a third retroreflective mirror positioned between the first retroreflective mirror and the second retroreflective mirror in the first direction, and the width of the first retroreflective mirror and the width of the second retroreflective mirror in the first direction are greater than the width of the third retroreflective mirror in the first direction.

[0188] [Item A9] The optical element according to any one of items A1 to A8, wherein the width of the second mirror group in the first direction is greater than the width of the first mirror group in the first direction.

[0189] [Item A10] The optical element described in any one of items A1 to A9, wherein the reflective area of ​​the first mirror group has a shape in which concave portions and convex portions are repeated in the first direction, the second mirror group has a shape in which concave portions and convex portions are repeated in the first direction, and the concave portions of the first mirror group and the convex portions of the second mirror group overlap in the fifth direction, and the convex portions of the first mirror group and the concave portions of the second mirror group overlap.

[0190] [Item A11] The optical element according to any one of items A1 to A10, wherein a substrate having the optical surface supports a reflector of the mirror array.

[0191] [Item A12] The optical element according to Item A11, wherein the substrate is made of at least a resin.

[0192] [Item A13] The optical element according to item A12, wherein the resin is a cycloolefin polymer.

[0193] [Item A14] The optical element according to any one of items A11 to A13, wherein the base has a surface including the optical surface, a back surface opposite to the surface, and a side surface connecting the surface and the back surface, and the back surface has a mark of an ejector pin of a mold.

[0194] [Item A15] The optical element according to any one of items A11 to A14, wherein the base has a front surface including the optical surface, a back surface opposite to the front surface, and a side surface connecting the front surface and the back surface, and the side surface includes the optical surface.

[0195] [Item A16] The optical element according to any one of items A11 to A15, wherein the reflector includes a dielectric material.

[0196] [Item A17] The optical element according to any one of items A11 to A16, wherein the reflector has light-transmitting properties.

[0197] [Item A18] The optical element according to any one of items A11 to A17, further comprising a component covering the mirror array from the opposite side of the mirror array from the optical surface.

[0198] [Item A19] The optical element according to item A18, wherein an adhesive is provided between the reflector and the component.

[0199] [Item A20] The optical element according to item A18 or A19, wherein the optical surface of the base is a first optical surface, and the component has a second optical surface facing the mirror array.

[0200] [Item A21] The optical element according to any one of items A1 to A20, including an incident section on which light is incident, and a light guide section that guides the light from the incident section to the mirror array.

[0201] [Item A22] The optical element according to item A21, wherein the light guide portion includes a reflective surface that reflects the light by total reflection.

[0202] [Item A23] An apparatus comprising the optical element according to any one of items A1 to A22, and a display element that displays an image formed by light incident on the optical element.

[0203] [Item A24] A device comprising the optical element according to any one of items A1 to A22 and a mounting means for mounting the optical element on a user's head.

[0204] [Item A25] The device according to item A23 or A24, further comprising an imaging element that captures an image to be displayed on the display element.

[0205] [Item B1] An optical element having a mirror array, a first optical surface facing the mirror array, and a second optical surface facing the mirror array, wherein the mirror array is arranged between the first optical surface and the second optical surface and includes a mirror group consisting of a plurality of retroreflecting mirrors arranged in a first direction, and the plurality of retroreflecting mirrors of the mirror group extend along a second direction that intersects the first direction and is inclined with respect to the first optical surface and the second optical surface.

[0206] [Item B2] The optical element according to item B1, wherein the length in the second direction of each of the plurality of retroreflecting mirrors of the mirror group is at least twice the width in the first direction of each of the plurality of retroreflecting mirrors.

[0207] [Item B3] The optical element according to item B1 or B2, wherein the length in the second direction of each of the plurality of retroreflecting mirrors of the mirror group is 10 times or less the width in the first direction of each of the plurality of retroreflecting mirrors.

[0208] [Item B4] The optical element according to any one of items B1 to B3, wherein the plurality of retroreflecting mirrors are translucent.

[0209] [Item B5] The optical element according to any one of items B1 to B4, wherein the distance between the first optical surface and the second optical surface is 1 mm or more and 10 mm or less.

[0210] [Item B6] The optical element according to any one of items B1 to B5, wherein a base having the first optical surface supports a reflector of the mirror array.

[0211] [Item B7] The optical element according to item B6, wherein the component having the second optical surface covers the mirror array from the side opposite to the first optical surface with respect to the mirror array.

[0212] [Item B8] The optical element according to item B7, wherein an adhesive is provided between the reflector and the component.

[0213] [Item B9] The optical element according to item B7 or B8, wherein the adhesive is in contact with the substrate.

[0214] [Item B10] The optical element according to item B8 or B9, wherein the thickness of the adhesive is 1 μm or more and 1 mm or less, and / or the difference between the refractive index of the adhesive and the refractive index of the component is less than 0.25.

[0215] [Item B11] The optical element according to any one of Items B7 to B10, wherein the substrate and the component are made of the same material, and / or the difference between the refractive index of the substrate and the refractive index of the component is less than 0.01.

[0216] [Item B12] The optical element according to any one of Items B6 to B11, wherein the base is made of at least a resin.

[0217] [Item B13] The optical element according to item B12, wherein the reflector contains an inorganic material, and the inorganic material is in contact with the resin.

[0218] [Item B14] The optical element according to item B12 or B13, wherein the resin is a cycloolefin polymer.

[0219] [Item B15] An optical element according to any one of items B6 to B14, wherein a component having the second optical surface covers the mirror array from the opposite side of the mirror array from the first optical surface, and the component is made of at least a cycloolefin polymer.

[0220] [Item B16] The optical element according to any one of items B1 to B15, wherein each of the plurality of retroreflecting mirrors of the mirror group includes a pair of reflective surfaces that are non-parallel to each other and face each other in the first direction.

[0221] [Item B17] The optical element according to any one of items B1 to B16, wherein an angle formed between the second direction and the first optical surface is greater than 15° and less than 45°, and an angle formed between the second direction and the second optical surface is greater than 15° and less than 45°.

[0222] [Item B18] An optical element described in any one of items B1 to B17, wherein the mirror group is a first mirror group, the mirror array is arranged between the first optical surface and the second optical surface, and includes a second mirror group consisting of a plurality of retroreflecting mirrors arranged in the first direction, the plurality of retroreflecting mirrors of the second mirror group extend along a third direction that intersects the first direction and is inclined relative to the first optical surface and the second optical surface, and the first mirror group and the second mirror group are arranged side by side in a fourth direction that intersects the first direction.

[0223] [Item B19] The optical element according to any one of items B6 to B15, wherein the base has a surface including the first optical surface, a back surface opposite the surface, and a side surface connecting the surface and the back surface, and the back surface has a mark of an ejector pin of a mold.

[0224] [Item B20] The optical element according to any one of items B6 to B16, wherein the base has a surface including the first optical surface, a back surface opposite the surface, and a side surface connecting the surface and the back surface, and the side surface includes an optical surface.

[0225] [Item B21] The optical element according to any one of items B1 to B20, comprising an incident section on which light is incident, and a light guiding section that guides the light from the incident section to the mirror array.

[0226] [Item B22] The optical element according to item B21, wherein the light guide portion includes a reflective surface that reflects the light by total reflection.

[0227] [Item B23] A device comprising the optical element according to any one of items B1 to B22, and a display element that displays an image formed by light incident on the optical element.

[0228] [Item B24] A device comprising the optical element according to any one of items B1 to B22 and a mounting means for mounting the optical element on a user's head.

[0229] [Item B25] The device according to item B23 or B24, further comprising an imaging element that captures an image to be displayed on the display element.

[0230] [Item C1] An optical element having a mirror array and an optical surface facing the mirror array, wherein the mirror array includes a first light-transmitting mirror and a second light-transmitting mirror, wherein the first light-transmitting mirror extends along a first direction inclined with respect to the optical surface, and the second light-transmitting mirror extends along a second direction inclined with respect to the optical surface, and in a third direction intersecting the optical surface and the first direction, the first light-transmitting mirror is located between the second light-transmitting mirror and the optical surface, a first portion of the first light-transmitting mirror and a first portion of the second light-transmitting mirror overlap, a second portion of the first light-transmitting mirror does not overlap with the second light-transmitting mirror, and the second portion of the second light-transmitting mirror does not overlap with the first light-transmitting mirror, an optical element that satisfies at least one of the following conditions: a reflectance of the first portion of the first light-transmitting mirror is lower than a reflectance of the second portion of the first light-transmitting mirror; and a reflectance of the first portion of the second light-transmitting mirror is lower than a reflectance of the second portion of the second light-transmitting mirror.

[0231] [Item C2] The optical element according to item C1, wherein the first portion of the first light-transmitting mirror and the first portion of the second light-transmitting mirror overlap in a direction perpendicular to the optical surface.

[0232] [Item C3] The optical element according to item C1 or C2, wherein the reflectance of the second portion of the second light-transmitting mirror is higher than the reflectance of the second portion of the first light-transmitting mirror.

[0233] [Item C4] The optical element according to any one of Items 1C to C3, wherein the first light-transmitting mirror and the second light-transmitting mirror are retroreflecting mirrors.

[0234] [Item C5] The optical element according to any one of items C1 to C4, wherein each of the first light-transmitting mirror and the second light-transmitting mirror includes a pair of reflecting surfaces that are non-parallel to each other and face each other in the first direction.

[0235] [Item C6] The optical element according to item C5, wherein the first light-transmitting mirror has non-opposing surfaces that do not face the pair of reflecting surfaces of the first light-transmitting mirror in the first direction, and the non-opposing surfaces overlap the second light-transmitting mirror in a direction perpendicular to the optical surface.

[0236] [Item C7] The optical element described in any one of items C1 to C6, wherein the mirror array includes: a first mirror group consisting of a plurality of retroreflective mirrors arranged in a fourth direction intersecting the first direction; and a second mirror group consisting of a plurality of retroreflective mirrors arranged in the fourth direction, the first mirror group and the second mirror group being arranged side by side in a fifth direction intersecting the fourth direction, the plurality of retroreflective mirrors of the first mirror group extending along the first direction, the plurality of retroreflective mirrors of the second mirror group extending along the second direction, at least one of the plurality of retroreflective mirrors of the first mirror group being the first translucent mirror, and at least one of the plurality of retroreflective mirrors of the second mirror group being the second translucent mirror.

[0237] [Item C8] The optical element according to item C7, wherein the plurality of retroreflective mirrors of the first mirror group include a first retroreflective mirror, a second retroreflective mirror, and a third retroreflective mirror positioned between the first retroreflective mirror and the second retroreflective mirror in the fourth direction, and the width of the first retroreflective mirror and the width of the second retroreflective mirror in the fourth direction are greater than the width of the third retroreflective mirror in the fourth direction.

[0238] [Item C9] The optical element according to item C7 or C8, wherein the width of the second mirror group in the fourth direction is greater than the width of the first mirror group in the fourth direction.

[0239] [Item C10] The optical element described in any one of items C7 to C9, wherein the reflective area of ​​the first mirror group has a shape in which concave portions and convex portions are repeated in the fourth direction, and the second mirror group has a shape in which concave portions and convex portions are repeated in the fourth direction, and the concave portions of the first mirror group and the convex portions of the second mirror group overlap in the third direction, and the convex portions of the first mirror group and the concave portions of the second mirror group overlap.

[0240] [Item C11] The optical element according to any one of items C1 to C10, wherein a substrate having the optical surface supports a reflector of the mirror array.

[0241] [Item C12] The optical element according to item C11, wherein the substrate is made of at least a resin.

[0242] [Item C13] The optical element according to item C12, wherein the resin is a cycloolefin polymer.

[0243] [Item C14] The optical element according to any one of items C11 to C13, wherein the base has a surface including the optical surface, a back surface opposite to the surface, and a side surface connecting the surface and the back surface, and the back surface has a mark of an ejector pin of a mold.

[0244] [Item C15] The optical element according to any one of items C11 to C14, wherein the base has a surface including the optical surface, a back surface opposite to the surface, and a side surface connecting the surface and the back surface, and the side surface includes the optical surface.

[0245] [Item C16] The optical element according to any one of items C11 to C15, wherein the reflector includes a dielectric material.

[0246] [Item C17] The optical element according to any one of items C1 to C16, wherein the mirror array includes a translucent mirror that connects the first translucent mirror and the second translucent mirror.

[0247] [Item C18] The optical element according to any one of items C11 to C17, further comprising a component covering the mirror array from the opposite side of the mirror array from the optical surface.

[0248] [Item C19] The optical element according to Item C18, wherein an adhesive is provided between the reflector and the component.

[0249] [Item C20] The optical element according to item C18 or C19, wherein the optical surface of the base is a first optical surface, and the component has a second optical surface facing the mirror array.

[0250] [Item C21] The optical element according to any one of items C1 to C20, comprising an incident section on which light is incident, and a light guiding section that guides the light from the incident section to the mirror array.

[0251] [Item C22] The optical element according to item C21, wherein the light guide portion includes a reflective surface that reflects the light by total reflection.

[0252] [Item C23] An apparatus comprising the optical element according to any one of items C1 to C22, and a display element that displays an image formed by light incident on the optical element.

[0253] [Item C24] An apparatus comprising the optical element according to any one of items C1 to C22 and a mounting means for mounting the optical element on a user's head.

[0254] [Item C25] The device according to item C23 or C24, further comprising an imaging element that captures an image to be displayed on the display element.

[0255] [Item D1] An optical element having a mirror array and a first optical surface facing the mirror array, wherein the mirror array includes: a first mirror group consisting of a plurality of retroreflecting mirrors arranged in a first direction; and a second mirror group consisting of a plurality of retroreflecting mirrors arranged in the first direction, wherein the first mirror group and the second mirror group are arranged side by side in a second direction intersecting the first direction, wherein the plurality of retroreflecting mirrors of the first mirror group extend along a third direction that intersects the first direction and the second direction and is inclined with respect to the first optical surface, wherein the plurality of retroreflecting mirrors of the second mirror group extend along a fourth direction that intersects the first direction and the second direction and is inclined with respect to the first optical surface, and wherein the first mirror group and the second mirror group partially overlap in a fifth direction that is perpendicular to the first direction and the third direction.

[0256] [Item D2] The optical element according to item D1, wherein the first mirror group and the second mirror group partially overlap in a direction perpendicular to the first optical surface.

[0257] [Item D3] The optical element according to item D1 or D2, wherein each of the plurality of retroreflecting mirrors of the first mirror group and the plurality of retroreflecting mirrors of the second mirror group includes a pair of reflective surfaces that are non-parallel to each other and face each other in the first direction.

[0258] [Item D4] The optical element according to item D3, wherein the first mirror group has non-opposing surfaces that do not face the pair of reflecting surfaces of at least one of the plurality of recursive mirrors of the first mirror group in the first direction, and the non-opposing surfaces overlap the second mirror group in a direction perpendicular to the first optical surface.

[0259] [Item D5] The optical element according to any one of items D1 to D5, wherein the angle formed between the third direction and the first optical surface is greater than 20° and smaller than 45°.

[0260] [Item D6] The optical element described in any one of items D1 to D5, wherein a direction connecting an end of the first mirror group on the side of the second mirror group and an end of the second mirror group on the side of the first mirror group, perpendicular to the first direction, forms an angle with the first optical surface that is greater than 90° and smaller than 135°.

[0261] [Item D7] An optical element according to any one of items D1 to D6, wherein a direction connecting an end of the first mirror group on the side of the second mirror group and an end of the second mirror group on the side of the first mirror group perpendicular to the first direction forms an angle greater than 15° and smaller than 70° with respect to a third direction.

[0262] [Item D8] The optical element described in any one of items D1 to D7, wherein the plurality of retroreflective mirrors of the first mirror group include a first retroreflective mirror, a second retroreflective mirror, and a third retroreflective mirror located between the first retroreflective mirror and the second retroreflective mirror in the first direction, and the width of the first retroreflective mirror and the width of the second retroreflective mirror in the first direction are greater than the width of the third retroreflective mirror in the first direction.

[0263] [Item D9] The optical element according to any one of items D1 to D8, wherein the width of the second mirror group in the first direction is greater than the width of the first mirror group in the first direction.

[0264] [Item D10] An optical element described in any one of items D1 to D9, wherein the reflective area of ​​the first mirror group has a shape in which concave portions and convex portions are repeated in the first direction, the second mirror group has a shape in which concave portions and convex portions are repeated in the first direction, and the concave portions of the first mirror group and the convex portions of the second mirror group overlap in the fifth direction, and the convex portions of the first mirror group and the concave portions of the second mirror group overlap.

[0265] [Item D11] An optical element having a mirror array, a first optical surface facing the mirror array, and a second optical surface facing the mirror array, wherein the mirror array is arranged between the first optical surface and the second optical surface and includes a mirror group consisting of a plurality of retroreflecting mirrors arranged in a first direction, and the plurality of retroreflecting mirrors of the mirror group extend along a second direction that intersects the first direction and is inclined with respect to the first optical surface and the second optical surface.

[0266] [Item D12] The optical element according to item D11, wherein the length in the second direction of each of the plurality of retroreflecting mirrors of the mirror group is at least twice the width in the first direction of each of the plurality of retroreflecting mirrors.

[0267] [Item D13] The optical element according to item D11 or D12, wherein the length in the second direction of each of the plurality of retroreflecting mirrors of the mirror group is 10 times or less the width in the first direction of each of the plurality of retroreflecting mirrors.

[0268] [Item D14] The optical element according to any one of items D1 to D13, wherein the plurality of retroreflecting mirrors are translucent.

[0269] [Item D15] The optical element according to any one of items D11 to D14, wherein the distance between the first optical surface and the second optical surface is 1 mm or more and 10 mm or less.

[0270] [Item D16] An optical element described in any one of items D11 to D14, wherein a base having the first optical surface supports a reflector of the mirror array, and a component having the second optical surface covers the mirror array from the side opposite the first optical surface with respect to the mirror array.

[0271] [Item D17] The optical element according to item D16, wherein the substrate and the component are made of the same material, and / or the difference between the refractive index of the substrate and the refractive index of the component is 0.01 or less.

[0272] [Item D18] The optical element according to any one of items D11 to D14, wherein each of the plurality of retroreflecting mirrors of the mirror group includes a pair of reflective surfaces that are non-parallel to each other and face each other in the first direction.

[0273] [Item D19] The optical element according to any one of items D11 to D14, wherein the angle formed between the second direction and the first optical surface is greater than 15° and less than 45°, and the angle formed between the second direction and the second optical surface is greater than 15° and less than 45°.

[0274] [Item D20] An optical element described in any one of items D11 to D14, wherein the mirror group is a first mirror group, the mirror array is arranged between the first optical surface and the second optical surface, and includes a second mirror group consisting of a plurality of retroreflecting mirrors arranged in the first direction, the plurality of retroreflecting mirrors of the second mirror group extending along a third direction that intersects the first direction and is inclined relative to the first optical surface and the second optical surface, and the first mirror group and the second mirror group are arranged side by side in a fourth direction that intersects the first direction.

[0275] [Item D21] An optical element having a mirror array and a first optical surface facing the mirror array, wherein the mirror array includes a first light-transmitting mirror and a second light-transmitting mirror, wherein the first light-transmitting mirror extends along a first direction inclined with respect to the first optical surface, and the second light-transmitting mirror extends along a second direction inclined with respect to the first optical surface, and in a third direction intersecting the first optical surface and the first direction, the first light-transmitting mirror is located between the second light-transmitting mirror and the first optical surface, a first portion of the first light-transmitting mirror and a first portion of the second light-transmitting mirror overlap, a second portion of the first light-transmitting mirror does not overlap with the second light-transmitting mirror, and the second portion of the second light-transmitting mirror does not overlap with the first light-transmitting mirror, an optical element that satisfies at least one of the following conditions: a reflectance of the first portion of the first light-transmitting mirror is lower than a reflectance of the second portion of the first light-transmitting mirror; and a reflectance of the first portion of the second light-transmitting mirror is lower than a reflectance of the second portion of the second light-transmitting mirror.

[0276] [Item D22] The optical element according to item D21, wherein the first portion of the first light-transmitting mirror and the first portion of the second light-transmitting mirror overlap in a direction perpendicular to the first optical surface.

[0277] [Item D23] The optical element according to item D21 or D22, wherein the reflectance of the second portion of the second light-transmitting mirror is higher than the reflectance of the second portion of the first light-transmitting mirror.

[0278] [Item D24] The optical element according to any one of items D21 to D23, wherein the first light-transmitting mirror and the second light-transmitting mirror are retroreflecting mirrors.

[0279] [Item D25] The optical element according to any one of items D21 to D24, wherein each of the first light-transmitting mirror and the second light-transmitting mirror includes a pair of reflecting surfaces that are non-parallel to each other and face each other in the first direction.

[0280] [Item D26] The optical element according to item D25, wherein the first light-transmitting mirror has non-opposing surfaces that do not face the pair of reflecting surfaces of the first light-transmitting mirror in the first direction, and the non-opposing surfaces overlap the second light-transmitting mirror in a direction perpendicular to the first optical surface.

[0281] [Item D27] The optical element described in any one of items D21 to D27, wherein the mirror array includes: a first mirror group consisting of a plurality of retroreflecting mirrors arranged in a fourth direction intersecting the first direction; and a second mirror group consisting of a plurality of retroreflecting mirrors arranged in the fourth direction, the first mirror group and the second mirror group being arranged side by side in a fifth direction intersecting the fourth direction, the plurality of retroreflecting mirrors of the first mirror group extending along the first direction, the plurality of retroreflecting mirrors of the second mirror group extending along the second direction, at least one of the plurality of retroreflecting mirrors of the first mirror group being the first translucent mirror, and at least one of the plurality of retroreflecting mirrors of the second mirror group being the second translucent mirror.

[0282] [Item D28] The optical element according to any one of items D1 to D27, wherein a substrate having the first optical surface supports a reflector of the mirror array.

[0283] [Item D29] The optical element according to item D28, wherein the substrate is made of at least a resin.

[0284] [Item D30] The optical element according to item D29, wherein the resin is a cycloolefin polymer.

[0285] [Item D31] The optical element according to item D29 or D30, wherein the reflector contains an inorganic material, and the inorganic material is in contact with the resin.

[0286] [Item D32] The optical element described in any one of Items D28 to D31, wherein the base has a surface including the first optical surface, a back surface opposite the surface, and a side surface connecting the surface and the back surface, and the back surface has a mark of an ejector pin of a mold.

[0287] [Item D33] The optical element according to any one of items D28 to D32, wherein the base has a surface including the first optical surface, a back surface opposite the surface, and a side surface connecting the surface and the back surface, and the side surface includes an optical surface.

[0288] [Item D34] The optical element according to any one of items D28 to D33, wherein the reflector includes a dielectric material.

[0289] [Item D35] The optical element according to any one of items D21 to D27, wherein the mirror array includes a translucent mirror that connects the first translucent mirror and the second translucent mirror.

[0290] [Item D36] The optical element according to any one of items D28 to D36, further comprising a component covering the mirror array from the side opposite to the first optical surface with respect to the mirror array.

[0291] [Item D37] The optical element according to Item D36, wherein the substrate is made of at least a cycloolefin polymer, and the component is made of at least a cycloolefin polymer.

[0292] [Item D38] The optical element according to item D36, wherein an adhesive is provided between the reflector and the component.

[0293] [Item D39] The optical element according to item D38, wherein the thickness of the adhesive is 1 μm or more and 1 mm or less, and / or the difference between the refractive index of the adhesive and the refractive index of the component is less than 0.25.

[0294] [Item D40] The optical element according to any one of items D36 to D39, wherein the component has a second optical surface facing the mirror array.

[0295] [Item D41] The optical element according to any one of items D1 to D40, comprising an incident section on which light is incident, and a light guiding section that guides the light from the incident section to the mirror array.

[0296] [Item D42] The optical element according to item D41, wherein the light guide includes a reflective surface that reflects the light by total reflection.

[0297] [Item D43] A device comprising the optical element according to any one of items D1 to D42, and a display element that displays an image formed by light incident on the optical element.

[0298] [Item D44] A device comprising the optical element according to any one of items D1 to D42 and a mounting means for mounting the optical element on a user's head.

[0299] [Item D45] The device according to item D43 or D44, comprising an imaging element that captures an image to be displayed on the display element.

[0300] Furthermore, the disclosure of this specification includes the complement of each individual concept described in this specification. In other words, if this specification contains a statement that "A is B," it can be said that this specification discloses "A is not B," even if it omits a statement that "A is not B." This is because a statement that "A is B" presupposes that the case in which "A is not B" is taken into consideration.

[0301] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0302] This application claims priority based on Japanese Patent Application No. 2022-173225 filed on October 28, 2022, Japanese Patent Application No. 2023-103414 filed on June 23, 2023, Japanese Patent Application No. 2023-107672 filed on June 30, 2023, and Japanese Patent Application No. 2023-110813 filed on July 5, 2023, the entire contents of which are incorporated herein by reference.

[0303] 24 Mirror array 211 Optical surface 213 Optical surface 20 Optical element 25 Retroreflecting mirror 241 Mirror group 242 Mirror group 257 Light-transmitting mirror 258 Light-transmitting mirror 259 Light-transmitting mirror

Claims

1. a mirror array; a first optical surface facing the mirror array; An optical element having The mirror array a first mirror group consisting of a plurality of retroreflecting mirrors arranged in a first direction; a second mirror group consisting of a plurality of retroreflecting mirrors arranged in the first direction, the first mirror group and the second mirror group are arranged side by side in a second direction intersecting the first direction, the plurality of retroreflecting mirrors of the first mirror group extend along a third direction that intersects the first direction and the second direction and is inclined with respect to the first optical surface, the plurality of retroreflecting mirrors of the second mirror group extend along a fourth direction that intersects the first direction and the second direction and is inclined with respect to the first optical surface, an optical element, wherein the first mirror group and the second mirror group partially overlap in a fifth direction that is perpendicular to the first direction and the third direction;

2. The optical element according to claim 1 , wherein the first mirror group and the second mirror group partially overlap in a direction perpendicular to the first optical surface.

3. The optical element according to claim 1 , wherein each of the plurality of retroreflecting mirrors of the first mirror group and the plurality of retroreflecting mirrors of the second mirror group includes a pair of reflective surfaces that are non-parallel to each other and face each other in the first direction.

4. the first mirror group has non-opposing surfaces that do not face the pair of reflecting surfaces of at least one of the plurality of retroreflecting mirrors of the first mirror group in the first direction, The optical element according to claim 3 , wherein the non-opposing surface overlaps the second mirror group in a direction perpendicular to the first optical surface.

5. The optical element according to claim 1 , wherein the angle formed between the third direction and the first optical surface is greater than 20° and smaller than 45°.

6. 3. The optical element according to claim 2, wherein a direction connecting an end of the first mirror group on the side of the second mirror group and an end of the second mirror group on the side of the first mirror group, perpendicular to the first direction, forms an angle with the first optical surface that is greater than 90° and smaller than 135°.

7. 3. The optical element according to claim 2, wherein a direction connecting an end of the first mirror group on the side of the second mirror group and an end of the second mirror group on the side of the first mirror group, perpendicular to the first direction, forms an angle with a third direction that is greater than 15° and smaller than 70°.

8. the plurality of retroreflecting mirrors of the first mirror group include a first retroreflecting mirror, a second retroreflecting mirror, and a third retroreflecting mirror located between the first retroreflecting mirror and the second retroreflecting mirror in the first direction; The optical element according to claim 2 , wherein the width of the first retroreflecting mirror and the width of the second retroreflecting mirror in the first direction are greater than the width of the third retroreflecting mirror in the first direction.

9. The optical element according to claim 1 , wherein a width of the second mirror group in the first direction is greater than a width of the first mirror group in the first direction.

10. a reflection region of the first mirror group has a shape in which recesses and protrusions are repeated in the first direction, and the second mirror group has a shape in which recesses and protrusions are repeated in the first direction, 2. The optical element according to claim 1, wherein in the fifth direction, the concave portions of the first mirror group and the convex portions of the second mirror group overlap, and the convex portions of the first mirror group and the concave portions of the second mirror group overlap.

11. a mirror array; a first optical surface facing the mirror array; a second optical surface facing the mirror array; An optical element having the mirror array is disposed between the first optical surface and the second optical surface and includes a mirror group consisting of a plurality of retroreflecting mirrors arranged in a first direction; An optical element, characterized in that the plurality of retroreflecting mirrors of the mirror group extend along a second direction that intersects the first direction and is inclined with respect to the first optical surface and the second optical surface.

12. 12. The optical element according to claim 11, wherein the length in the second direction of each of the plurality of retroreflecting mirrors in the mirror group is at least twice the width in the first direction of each of the plurality of retroreflecting mirrors.

13. 13. The optical element according to claim 12, wherein the length in the second direction of each of the plurality of retroreflecting mirrors in the mirror group is 10 times or less the width in the first direction of each of the plurality of retroreflecting mirrors.

14. The optical element according to claim 1 , wherein the plurality of retroreflecting mirrors are optically transparent.

15. The optical element according to claim 11 , wherein the distance between the first optical surface and the second optical surface is not less than 1 mm and not more than 10 mm.

16. a substrate having the first optical surface supporting a reflector of the mirror array; The optical element according to claim 11 , wherein the component having the second optical surface covers the mirror array from the side opposite to the first optical surface with respect to the mirror array.

17. the substrate and the component are made of the same material; and / or 17. The optical element according to claim 16, wherein the difference between the refractive index of the substrate and the refractive index of the component is 0.01 or less.

18. The optical element according to claim 11 , wherein each of the plurality of retroreflecting mirrors of the mirror group includes a pair of reflective surfaces that are non-parallel to each other and face each other in the first direction.

19. an angle formed between the second direction and the first optical surface is greater than 15° and smaller than 45°; The optical element according to claim 11 , wherein the angle formed between the second direction and the second optical surface is greater than 15° and smaller than 45°.

20. The mirror group is a first mirror group, the mirror array includes a second mirror group that is disposed between the first optical surface and the second optical surface and that is composed of a plurality of retroreflecting mirrors that are arranged in the first direction; the plurality of retroreflecting mirrors of the second mirror group extend along a third direction that intersects with the first direction and is inclined with respect to the first optical surface and the second optical surface; The optical element according to claim 11 , wherein the first mirror group and the second mirror group are arranged side by side in a fourth direction that intersects with the first direction.

21. a mirror array; a first optical surface facing the mirror array; An optical element having The mirror array a first light-transmitting mirror; a second optically transmissive mirror; the first light-transmitting mirror extends along a first direction inclined with respect to the first optical surface, the second light-transmitting mirror extends along a second direction inclined with respect to the first optical surface, the first light-transmitting mirror is located between the second light-transmitting mirror and the first optical surface in a third direction intersecting the first optical surface and the first direction, a first portion of the first light-transmitting mirror overlaps with a first portion of the second light-transmitting mirror, a second portion of the first light-transmitting mirror does not overlap with the second light-transmitting mirror, the second portion of the second light-transmitting mirror does not overlap with the first light-transmitting mirror, and a third portion of the first light-transmitting mirror overlaps with a third portion of the second light-transmitting mirror, an optical element that satisfies at least one of the following conditions: a reflectance of the first portion of the first light-transmitting mirror is lower than a reflectance of the second portion of the first light-transmitting mirror, a reflectance of the second portion of the second light-transmitting mirror, and a reflectance of the third portion of the first light-transmitting mirror; and a reflectance of the first portion of the second light-transmitting mirror is lower than a reflectance of the second portion of the first light-transmitting mirror, a reflectance of the second portion of the second light-transmitting mirror, and a reflectance of the third portion of the second light-transmitting mirror.

22. 22. The optical element according to claim 21, wherein the first portion of the first light-transmitting mirror and the first portion of the second light-transmitting mirror overlap in a direction perpendicular to the first optical surface.

23. 22. The optical element according to claim 21, wherein the reflectivity of the second portion of the second light-transmitting mirror is higher than the reflectivity of the second portion of the first light-transmitting mirror.

24. 22. The optical element according to claim 21, wherein the first optically transmissive mirror and the second optically transmissive mirror are retroreflecting mirrors.

25. 22. The optical element according to claim 21, wherein each of the first light-transmitting mirror and the second light-transmitting mirror includes a pair of reflective surfaces that are non-parallel to each other and face each other in the first direction.

26. the first light-transmitting mirror has non-opposing surfaces that do not face the pair of reflecting surfaces of the first light-transmitting mirror in the first direction, 26. The optical element according to claim 25, wherein the non-opposing surface overlaps the second light-transmitting mirror in a direction perpendicular to the first optical surface.

27. The mirror array a first mirror group including a plurality of retroreflecting mirrors arranged in a fourth direction intersecting the first direction; a second mirror group consisting of a plurality of retroreflecting mirrors arranged in the fourth direction, the first mirror group and the second mirror group are arranged side by side in a fifth direction intersecting the fourth direction, the plurality of retroreflecting mirrors of the first mirror group extend along the first direction, the plurality of retroreflecting mirrors of the second mirror group extend along the second direction, at least one of the plurality of retroreflecting mirrors in the first mirror group is the first light-transmitting mirror, 22. The optical element according to claim 21, wherein at least one of the plurality of retroreflecting mirrors in the second mirror group is the second light-transmitting mirror.

28. 22. The optical element of claim 1, 11 or 21, wherein a substrate having the first optical surface supports a reflector of the mirror array.

29. 29. The optical element according to claim 28, wherein the substrate is made of at least a resin.

30. 30. The optical element according to claim 29, wherein the resin is a cycloolefin polymer.

31. 30. The optical element according to claim 29, wherein the reflector includes an inorganic material, and the inorganic material is in contact with the resin.

32. 29. The optical element according to claim 28, wherein the substrate has a surface including the first optical surface, a back surface opposite the surface, and a side surface connecting the surface and the back surface, and the back surface has a mark of an ejector pin of a mold.

33. 29. The optical element according to claim 28, wherein the substrate has a surface including the first optical surface, a back surface opposite the surface, and a side surface connecting the surface and the back surface, the side surface including an optical surface.

34. 30. The optical element of claim 28, wherein the reflector comprises a dielectric material.

35. 22. The optical element according to claim 21, wherein the mirror array includes a translucent mirror connecting the first translucent mirror and the second translucent mirror.

36. 29. The optical element according to claim 28, further comprising a component covering the mirror array from the side opposite the first optical surface with respect to the mirror array.

37. the substrate is made of at least a cycloolefin polymer, 37. The optical element of claim 36, wherein the component is made of at least a cycloolefin polymer.

38. 37. The optical element of claim 36, wherein an adhesive is provided between the reflector and the component.

39. The adhesive has a thickness of 1 μm or more and 1 mm or less, and / or 39. The optical element of claim 38, wherein the difference between the refractive index of the adhesive and the refractive index of the component is less than 0.

25.

40. 37. The optical element of claim 36, wherein the component has a second optical surface facing the mirror array.

41. 22. The optical element according to claim 1, comprising: an incident portion on which light is incident; and a light guiding portion that guides the light from the incident portion to the mirror array.

42. 42. The optical element of claim 41, wherein the light guide includes a reflective surface that reflects the light by total internal reflection.

43. 22. An apparatus comprising: the optical element according to claim 1, 11, or 21; and a display element that displays an image formed by light incident on the optical element.

44. 22. An apparatus comprising the optical element according to claim 1, 11 or 21, and a mounting means for mounting the optical element on a user's head.

45. 44. The device of claim 43, further comprising an imaging element that captures an image to be displayed on the display element.