Light guide element, observation optical system, and display device

Abstract

Disclosed are a light guide element, a viewing optical system, and a display device. The light guide element includes an expander configured to expand incident light and a light guide unit configured to guide the light expanded by the expander to an eye point. The expander includes a first reflector and a second reflector. Each of the first reflector and the second reflector has a plurality of reflective surfaces. In a first cross-section including the first reflector and the second reflector, the first reflector and the second reflector form angles having different signs with a first axis corresponding to a chief ray at a central viewing angle of the incident light. In each of the first reflector and the second reflector, a reflective surface closest to the light guide unit among the plurality of reflective surfaces is a partially reflective surface. The light reflected multiple times by at least one of the first reflector and the second reflector reaches the light guide unit.

Description

Technical Field

[0001] This disclosure relates to one or more embodiments of light guide elements, observation optical systems, and display devices. Background Technology

[0002] Observational optics systems with semi-reflective mirror-overlapping light guides are known for use in augmented reality (AR) glasses, etc. Typically, the image beam from the display element is small, and in order to ensure the size of the eye-tracking frame (EMB) over a wide field of view, the light guide has an extender (extension unit) configured to extend the image beam.

[0003] Japanese Patent Application Publication No. 2015-106105 discloses an expander configured to expand an image beam by introducing an image beam into a region where partially transmissive reflective surfaces and highly reflective reflective surfaces are arranged adjacent to each other and parallel to each other, and repeating reflection and transmission between them. Japanese Patent Application Publication No. 2023-103432 discloses an expander configured to expand an image beam by arranging a plurality of partially reflective surfaces at an angle relative to the surfaces within a waveguide having two parallel surfaces, and repeating total internal reflection at the surfaces and reflection from the partially reflective surfaces. Summary of the Invention

[0004] A light guide element according to one aspect of this disclosure includes an expander configured to amplify incident light and a light guide unit configured to guide the light amplified by the expander to an eyepoint. The expander includes a first reflector and a second reflector. Each of the first and second reflectors has a plurality of reflective surfaces. In a first cross-section including the first and second reflectors, the first and second reflectors form an angle with a first axis of the principal ray corresponding to the central viewing angle of the incident light, having an angle of different sign. In each of the first and second reflectors, the reflective surface closest to the light guide unit among the plurality of reflective surfaces is a partially reflective surface. Light reflected multiple times by at least one of the first and second reflectors reaches the light guide unit. An observation optical system and a display device, each having the aforementioned light guide element, also constitute another aspect of this disclosure.

[0005] The features of this disclosure will become clear from the following description of embodiments with reference to the accompanying drawings. The following description of embodiments will be given by way of example. Attached Figure Description

[0006] Figure 1 These are schematic diagrams of display devices according to each embodiment.

[0007] Figure 2A This is a schematic diagram of the light guide plate based on the comparative example.

[0008] Figure 2B and Figure 2C This is a schematic diagram of the light guide plate according to the first embodiment.

[0009] Figure 3A , Figure 3B , Figure 3C and Figure 3D The diagram illustrates the relationship between the arrangement angle of the mirror pair and the propagation of light, and explains the arrangement angle of the mirror pair in the first embodiment.

[0010] Figure 4A , Figure 4B and Figure 4C This is a schematic diagram of a light guide plate according to the second embodiment and an optical path diagram of light propagating inside the mirror pair in the first and second embodiments.

[0011] Figure 5A and Figure 5B This is a schematic diagram of a light guide plate and illustrates the effect of the light guide plate in the second embodiment.

[0012] Figure 6A This is a schematic diagram of a light guide plate according to the third embodiment.

[0013] Figure 6B , Figure 6C and Figure 6D An example of reflectivity and transmittance in the third embodiment is illustrated.

[0014] Figure 7A This is a schematic diagram of the light guide plate according to the fourth embodiment.

[0015] Figure 7B The diagram illustrates the optical path and the intensity of the extended beam in the thickness direction of the light guide plate in the third embodiment.

[0016] Figure 7C and Figure 7D The diagram illustrates the optical path and the intensity of the extended beam in the thickness direction of the light guide plate in the fourth embodiment. Detailed Implementation

[0017] A detailed description of embodiments according to the present disclosure will now be given with reference to the accompanying drawings. Corresponding elements in the various figures will be designated by the same reference numerals, and repeated descriptions thereof will be omitted.

[0018] First Embodiment

[0019] First, refer to Figure 1 A display device 10 according to a first embodiment of the present disclosure is described. Figure 1 This is a schematic diagram of the display device 10. (For example...) Figure 1As shown in the figure above, the display device 10 includes a display element 13, a projection optical system (projection unit) 11, and a light guide plate (light guide element) 12 configured to guide an image beam from the projection optical system 11 to the observer's eye (an eye point corresponding to the pupil of the observer's eye) 15.

[0020] like Figure 1 As shown in the following figure (side view of light guide plate 12), the light beam entering the light guide plate 12 from the projection optics system 11 (incident light from the projection optics system 11) travels through the light guide plate 12 while being internally reflected along substantially the entire thickness direction (vertical direction in the side view) of the light guide plate 12. The angle of the light beam emitted from the light guide plate 12 in the width direction corresponds to the vertical direction, and the angle of the light beam emitted from the light guide plate 12 in the thickness direction corresponds to the horizontal direction.

[0021] The light guide plate 12 includes an expander 121 configured to expand light (incident light) from the projection optics system 11 having an image beam diameter P into light having a predetermined beam diameter EP, and an emitter (light guide unit) 122 configured to emit (extract) the light (image beam) expanded by the expander 121 from the light guide plate 12 and guide it to the observer's eye 15.

[0022] Next, refer to Figure 2A , Figure 2B and Figure 2C The function and effect of the light guide plate 12 according to this embodiment will be described below. In the following description, when the light guide plate 12 is viewed parallel to its surface, the direction of travel of the central viewing angle ray of the image beam (the principal ray at the central viewing angle of the incident light on the light guide plate 12) is defined as the X-axis direction (the direction of the first axis, the first direction). Here, the principal ray is the ray passing through the center of the aperture in the aperture stop (the ray passing through the center of the pupil). The direction orthogonal to the X-axis direction is the Y-axis direction (the direction of the second axis, the second direction), and the direction orthogonal to both the X-axis and Y-axis (the direction from the observer's eye 15 toward the light guide plate 12) is the Z-axis direction.

[0023] Figure 2A The diagram illustrates an expander 121 based on a comparative example light guide plate 112, in which a pair of adjacent parallel mirrors (two mirrors) are arranged at a predetermined angle relative to a first direction. The length L of the expander 121 required to expand light to a predetermined beam diameter EP is determined by the angle at which the mirror pair is arranged. Therefore, a projection optics system 111 can be deployed at the end of the light guide plate 112.

[0024] Figure 2B and Figure 2C This is a schematic diagram of the light guide plate 12 according to this embodiment. Figure 2B As shown, the expander 121 of the light guide plate 12 has adjacent parallel mirror groups (mirror units or mirror pairs) 1211 and 1212 arranged at two angles (first angle) α and angle (second angle) β relative to a first direction. Mirror group 1211 serves as a first reflector having multiple reflective surfaces, and mirror group 1212 serves as a second reflector having multiple reflective surfaces.

[0025] Here, angles α and β are angles opposite to each other in the propagation direction (first direction) of the principal ray at the central viewing angle of the incident light in a predetermined cross section (first cross section), that is, the incident direction (central axis) of the light passing through the center of the pupil. Here, as... Figure 2B As shown, the first cross section includes mirror groups 1211 and 1212 (including the first axis and the second axis). That is, mirror groups 1211 and 1212 form angles with opposite signs in the first cross section relative to the first axis corresponding to the principal ray at the central viewing angle of the incident light.

[0026] In each embodiment, the clockwise direction from the principal ray is defined as the positive direction, and the counterclockwise direction from the principal ray is defined as the negative direction. Angles α and β are set within a range satisfying the following inequality:

[0027] -90 < α

[0028] β < 0

[0029] 0 < α, β < 90.

[0030] That is, the absolute values ​​of angles α and β, |α| and |β| (°), respectively satisfy the following inequalities:

[0031] 0 < |α| and |β| < 90.

[0032] The absolute values ​​of angles α and β can be less than 45°; that is, the following inequality can be satisfied:

[0033] 0 < |α| < 45

[0034] 0 < |β| < 45.

[0035] The image beam reaches the emitter 122 after being reflected multiple times between the two mirrors constituting mirror group 1211 or 1212. The width of each mirror in mirror group 1211 or 1212 is approximately the same as the thickness of light guide plate 12. The distance A in the second direction between the two mirrors constituting each mirror group 1211 or 1212 is less than half the diameter P of the image beam.

[0036] Each mirror assembly 1211 or 1212 has multiple reflective surfaces with different reflectivities. In this embodiment, the multiple reflective surfaces include a first surface having a first reflectivity and a second surface having a second reflectivity lower than the first reflectivity. That is, mirror assembly 1211 includes a mirror (reflective surface) 1211a having a first reflectivity and a mirror 1211b having a second reflectivity. Similarly, mirror assembly 1212 includes a mirror 1212a having a first reflectivity and a mirror 1212b having a second reflectivity.

[0037] Of the two mirrors 1211a and 1211b constituting mirror group 1211, the mirror farther (or furthest) from the emitter 122 has a reflective surface with a reflectivity of 90% or higher. Similarly, of the two mirrors 1212a and 1212b constituting mirror group 1212, the mirror farther (or furthest) from the emitter 122 has a reflective surface with a reflectivity of 90% or higher.

[0038] On the other hand, in the two mirrors 1211a and 1211b constituting mirror group 1211, the mirror 1211a closer to the transmitter 122 (i.e., the mirror closest to the transmitter 122) is a partially reflective surface (partially transmissive reflective surface). Similarly, in the two mirrors 1212a and 1212b constituting mirror group 1212, the mirror 1212b closer to the transmitter 122 (i.e., the mirror closest to the transmitter 122) is also a partially reflective surface (partially transmissive reflective surface). Therefore, the image beam is reflected multiple times by each of mirror groups 1211 and 1212, expanding its beam diameter as it travels in the first direction. Due to this configuration, as in... Figure 2A Compared to using only a single mirror group (mirror pair) as shown in the comparative example, the length L of the expander 121 for expanding the beam to a predetermined beam diameter EP in the first direction can be shorter.

[0039] Reflective surfaces (such as mirrors 1211a and 1212a) are surfaces with a light reflectivity of 90% or higher. A reflective surface can also be a surface with a reflectivity of 95% or higher. On the other hand, partially reflective surfaces (such as mirrors 1211b and 1212b) are surfaces with a lower reflectivity than the reflective surfaces (such as mirrors 1211a and 1212a), i.e., surfaces with a reflectivity of less than 95%. A partially reflective surface can be a surface with a reflectivity of 3% or more but less than 90%. A partially reflective surface can be a surface with a reflectivity of 5% or more but less than 80%. These points apply similarly to the following embodiments. A partially reflective surface is sufficient as long as at least a portion of the surface is a transmissive reflective surface, and it can be configured such that only a portion of the surface is a transmissive reflective surface, or that the entire surface is a transmissive reflective surface.

[0040] In this embodiment, the position of the projection optical system 11 can be arbitrarily adjusted according to the lengths of the two mirror groups 1211 and 1212. Therefore, as Figure 2C As shown, the projection optical system 11 can be deployed in the projection system arrangement area specified by the display device 10 from a design perspective. In other words, this embodiment can increase the degree of freedom in positioning the projection optical system 11.

[0041] Angles α and β (°) can satisfy the following inequalities (1-1) and (1-2):

[0042] |α| - |φ| / 2 < 45(1-1)

[0043] |β| - |φ| / 2 < 45(1-2)

[0044] Where |φ| (°) is the angle of the view ray contained in the image beam relative to the first direction.

[0045] Angles α and β (°) can satisfy the following inequalities (2-1) and (2-2):

[0046] |α|-|φ M | / 2 < 45(2-1)

[0047] |β|-|φ M | / 2 < 45(2-2)

[0048] Where |φ M | (°) is the maximum angle between the viewpoint ray contained in the image beam and the first direction.

[0049] Figure 3A , Figure 3B and Figure 3C The diagram illustrates the relationship between the mirror arrangement angle and the propagating light in this embodiment. Figure 3D The mirror arrangement angle in this embodiment is explained. In cases where inequalities (2-1) and (2-2) are not satisfied, such as... Figure 3A As described above, a portion of the light incident on the partially reflective surface is totally reflected by the side surface of the light guide plate 12 and becomes light propagating at an angle φ' different from the original viewing angle. The light reaching the emitter 122 is guided to the observer's eye 15 as ghosting light, which may reduce the quality of the displayed image.

[0050] On the other hand, under the condition that inequalities (2-1) and (2-2) are satisfied, such as Figure 3B As shown, no light is totally reflected by the side surface of the light guide plate 12, therefore no ghosting light is produced. In cases where inequalities (2-1) and (2-2) are difficult to satisfy due to the size limitations of the light guide plate 12, as... Figure 3CAs shown, the side surface of the light guide plate 12 (at least a portion of the side surface of the light guide plate 12) other than the incident portion of the image beam can be a light-shielding surface. This configuration can absorb totally internally reflected light and suppress the occurrence of ghosting.

[0051] In this embodiment, angles α and β can be equal to each other. The length L(L) of the expander 121 required to expand the light (incident light) from the projection optics system 11 having an image beam diameter P into light having a predetermined beam diameter EP is... α L β It depends on the angle φ M α and β. When angles α and β are not equal, such as... Figure 3D As shown, the light will reach the side surface of the light guide plate 12 before reaching the emitter 122, and become absorbed or totally reflected light (waste light). This may reduce the propagation efficiency of the image beam.

[0052] This embodiment can provide a light guide element, an observation optical system, and a display device with reduced size and the ability to suppress ghosting. The conditions described in this embodiment also apply to the embodiments described later.

[0053] Second Embodiment

[0054] Next, we will refer to Figure 4A , Figure 4B , Figure 4C , Figure 5A and Figure 5B A second embodiment of this disclosure is described. Figure 4A This is a schematic diagram of the light guide plate (light guide element) 42 according to this embodiment. Figure 4B The diagram illustrates the optical path of light propagating inside the mirror assembly 1211 (1212) in the first embodiment. Figure 4C The diagram illustrates the optical path of light propagating inside the mirror assembly 4211 (4212) in this embodiment. Figure 5A This is a schematic diagram of a light guide plate (light guide element) 52 according to a modified example of this embodiment. Figure 5B This explains the effect of the light guide plate 52.

[0055] In the first embodiment, each mirror group 1211 and 1212 has only one partially reflective surface (partially transmissive reflective surface). On the other hand, in this embodiment, each mirror group has multiple partially reflective surfaces in at least one of the first and second directions.

[0056] First, refer to Figure 4AThe light guide plate 42 in this embodiment is described. The light guide plate 42 includes an expander 421 and an emitter 422. The expander 421 includes a mirror group (first reflector) 4211 and a mirror group (second reflector) 4212 arranged on opposite sides of a first direction at angles α and β. The mirror group 4211 has three adjacent parallel reflective mirrors (reflective surfaces) 4211a, 4211b, and 4211c along the first direction. Similarly, the mirror group 4212 has three adjacent parallel reflective mirrors (reflective surfaces) 4212a, 4212b, and 4212c along the first direction. Of the three reflective mirrors 4211a, 4211b, and 4211c, except for the reflective mirror 4211a which is farthest from the emitter 422, the two reflective mirrors 4211b and 4211c are partially transmissive reflective surfaces. Similarly, among the three reflectors 4212a, 4212b and 4212c, except for reflector 4212a which is farthest from transmitter 422, the other two reflectors 4212b and 4212c are partially transmissive reflective surfaces.

[0057] In this embodiment, although each mirror group 4211 and 4212 includes three mirrors, each of them may have four or more mirrors. Even in this case, all mirrors except the one furthest from the transmitter 422 are partially transmissive reflective surfaces.

[0058] Figure 4B The illustration shows the optical path of a beam containing spectral rays at an angle φ relative to a first direction, where only a partially transmissive and reflective surface is provided, as in the first embodiment. Therefore, gaps appear in the extended beam for rays other than the central spectral angle, and equally sized gaps also appear in the beam guided to the observer's eye 15. As the angle φ increases, the gaps increase and become more noticeable to the observer, leading to a decrease in image quality.

[0059] on the other hand, Figure 4C The diagram illustrates the optical path in the case where multiple partially transmissive and reflective surfaces are provided, as in this embodiment. Since the light reflected by the partially transmissive and reflective surfaces closer to the emitter 422 travels along the optical path that fills the gaps, the beam can be extended without creating gaps, even as the angle φ increases.

[0060] As shown above, in this embodiment, the plurality of mirrors constituting each mirror group 4211 and 4212 includes at least three mirrors arranged along a first direction. All of the plurality of mirrors except for the mirror furthest from the transmitter 422 are partially reflective surfaces.

[0061] Next, refer to Figure 5AThe light guide plate 52 according to a modified embodiment will be described below. The light guide plate 52 includes an expander 521 and an emitter 522. The expander 521 includes a mirror group (first reflecting mirror) 5211 and a mirror group (second reflecting mirror) 5212 arranged at angles α and β relative to a first direction on opposite sides of each other. The mirror group 5211 has six adjacent parallel reflecting mirrors (reflective surfaces) arranged along a second direction. Similarly, the mirror group 5212 has six adjacent parallel reflecting mirrors (reflective surfaces) along the second direction. Of the six reflecting mirrors in each mirror group 5211 and 5212, the other five reflecting mirrors, except for the reflecting mirror 5211a (5212a) farthest from the incident portion of the image beam, are partially transmissive reflective surfaces. Figure 5B As shown, this configuration can reduce Figure 2B The length L of the expander 121 and the size of the light guide plate 52.

[0062] In this variant, each mirror group 5211 and 5212 has six mirrors, but it may also have three or more mirrors. Even in this case, all mirrors except the one furthest from the incident portion of the image beam are partially transmissive reflective surfaces.

[0063] As described above, in this modified example, the plurality of mirrors constituting each mirror group 5211 and 5212 includes at least three mirrors arranged along a second direction orthogonal to the first direction. All of the plurality of mirrors except for the mirror furthest from the incident portion of the incident light from the expander 521 are partially reflective surfaces.

[0064] This embodiment has discussed the effects of arranging multiple partially reflective surfaces in either the first or second direction. Placing multiple partially reflective surfaces in both the first and second directions can achieve both effects simultaneously. Therefore, placing multiple partially transmissive reflective surfaces can provide light guide elements, observation optical systems, and display devices with reduced size even at wide viewing angles and can suppress ghosting.

[0065] Third Embodiment

[0066] Next, we will refer to Figure 6A , Figure 6B , Figure 6C and Figure 6D A third embodiment of this disclosure is described. Figure 6A This is a schematic diagram of the light guide plate (light guide element) 62 according to this embodiment. Figure 6B , Figure 6C and Figure 6DThe illustration shows an example of the reflectivity and transmittance of a portion of the reflective surface (partially transmissive reflective surface) of the mirror assembly in this embodiment. This embodiment differs from the first and second embodiments in that the transmittance and reflectivity of the partial reflective surface vary between mirrors, within the same mirror surface, or on both, depending on the location of the partial reflective surface.

[0067] First, refer to Figure 6A The light guide plate 62 according to this embodiment will be described. The light guide plate 62 includes an expander 621 and an emitter 622. The expander 621 has a mirror group (first reflector) 6211 and a mirror group (second reflector) 6212 arranged on opposite sides of a first direction at angles α and β. Each mirror group 6211 and 6212 has a plurality of adjacent parallel reflectors along each of the first and second directions. The distance between two adjacent reflectors (mirror distance) is set to be less than half the diameter P of the incident image beam. However, this embodiment is not limited to this example, and the mirror distances in each of the first and second directions may be different.

[0068] In each mirror group 6211 and 6212, all mirrors except for the mirror Mb, which is furthest from the incident portion of the image beam in the second direction, are partially reflective surfaces (partially transmissive reflective surfaces). The transmittance and reflectance of the partially reflective surfaces are set to vary between mirrors, within the same mirror surface, or both, depending on their position within the expander 621. The variation in transmittance and reflectance can be achieved, for example, by defining it as the area ratio between the mirror-coated portion and the uncoated portion on the mirror surface using a single type of coating.

[0069] The variations in transmittance and reflectance of some reflective surfaces will now be described. First, as... Figure 6B As shown, within the expander 621, the reflectivity can be altered to decrease along the first direction. That is, the reflectivity of the partially reflective surface can decrease as the distance from the projection optical system 11 increases in the first direction.

[0070] Since many regions of the extended beam (a beam with a predetermined beam diameter EP) utilize light reflected near the incident portion of the image beam, increasing the reflectivity near the incident portion can reduce the difference in light intensity between the regions utilizing transmitted light and those utilizing transmitted light. On the other hand, decreasing the reflectivity near the emitter 622 can increase the amount of light reaching the emitter 622.

[0071] For similar reasons, in the case of providing multiple partially reflective surfaces, such as Figure 6CAs shown, the reflectivity can decrease as the distance from the reflector Mb increases. That is, the multiple reflectors include a first portion of the reflective surface and a second portion of the reflective surface closer to the emitter 622 than the first portion of the reflective surface, and the reflectivity of the first portion of the reflective surface can be higher than the reflectivity of the second portion of the reflective surface. In the case of providing multiple reflective surfaces, as... Figure 6D As shown, within the same mirror surface, the reflectivity can decrease with increasing distance from the incident portion of the image beam. That is, the reflectivity of each of the first and second partial reflective surfaces can decrease with increasing distance from the projection optical system 11. By combining these various results, the variations in transmittance and reflectivity of the partial reflective surfaces can achieve a more effective result.

[0072] Therefore, by varying the transmittance and reflectance of a portion of the reflective surface between mirrors, within the same mirror, or both, depending on the position within the expander 621, the beam can be expanded and inhomogeneities suppressed.

[0073] Fourth embodiment

[0074] Next, we will refer to Figure 7A , Figure 7B , Figure 7C and Figure 7D A fourth embodiment of this disclosure is described. Figure 7A This is a schematic diagram of the light guide plate (light guide element) 72 according to this embodiment. Figure 7B The diagram illustrates the optical path and the intensity of the extended beam in the thickness direction of the light guide plate 62 according to the third embodiment. Figure 7C and Figure 7D The diagram illustrates the optical path and the intensity of the extended beam in the thickness direction of the light guide plate 72 according to this embodiment.

[0075] The first to third embodiments assume that the width of the reflector in the expander along the thickness direction of the light guide plate is equal to the thickness of the light guide plate. On the other hand, this embodiment will discuss the configuration of the expander when the width of the reflector is narrower than the thickness of the light guide plate. For example, such expanders are used when it is impossible to form a reflector along the entire thickness direction due to manufacturing limitations such as the use of injection molding.

[0076] First, refer to Figure 7AThe light guide plate 72 according to this embodiment will be described. The light guide plate 72 includes an expander 721 and an emitter 722. The expander 721 includes mirror groups 7211 and 7212 arranged at angles α and β on opposite sides in a first direction. Each mirror group 7211 and 7212 has a plurality of adjacent parallel mirrors along each of the first and second directions. The distance (mirror distance) between two adjacent mirrors in each of the first and second directions is set to α. However, this embodiment is not limited to this example, and the mirror distances in each of the first and second directions may be different.

[0077] In the direction of the thickness D of the light guide plate 72, the width d of each reflector (partial reflective surface) is less than the width D of the light guide plate 72. The distance a can satisfy the following inequality (3):

[0078] a ≤ A·d / D(3)

[0079] Where A is the distance between each reflector in the third embodiment.

[0080] Figure 7B The diagram illustrates the light path of light incident on the expander 621 in the third embodiment when viewed from the thickness direction of the light guide plate 62. On the other hand, Figure 7C and Figure 7D The diagram illustrates the light path of light incident on the expander 721 in this embodiment when viewed from the thickness direction of the light guide plate 72. Figure 7C The diagram illustrates the case where a = A, and Figure 7D The diagram illustrates the case where a = A·d / D.

[0081] If this value becomes higher than the upper limit of inequality (3), such as Figure 7C As shown, compared to when the width of the mirror equals its thickness, the number of reflections by the mirror decreases. In this case, the amount of transmitted light is large, the amount of reflected and spread light is small, and the non-uniformity of the spread beam increases.

[0082] On the other hand, such as Figure 7D As shown, when the mirror distance is set to satisfy inequality (2), all light rays are reflected at least the same number of times as when the mirror width is equal to the thickness, and the light intensity non-uniformity of the extended beam can be suppressed. Therefore, reducing the distance between multiple partially reflecting surfaces can suppress intensity non-uniformity and extend the beam.

[0083] In each embodiment, the extender and the emitter can have the same integrally formed surface. That is, there is no air layer or the like between the extender and the emitter, and the surfaces of the extender and the emitter are connected. Since such a structure can be achieved, for example, by injection molding using two molds, the light guide plate can be manufactured more easily.

[0084] Each embodiment can provide a light guide element, an observation optical system, and a display device with reduced size and the ability to suppress ghosting.

[0085] While this disclosure has been described with reference to embodiments, it should be understood that this disclosure is not limited to the disclosed embodiments. The scope of the following claims should be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. A light guide element, comprising: Extender, the extender being configured to extend the incident light; as well as A light guide unit, configured to guide light expanded by the expander to the eyepoint. The extender is characterized in that it includes a first reflector and a second reflector. Each of the first reflector and the second reflector has multiple reflective surfaces. In the first cross-section including the first reflector and the second reflector, the first reflector and the second reflector form angles with different signs with the first axis of the principal ray corresponding to the central viewing angle of the incident light. In each of the first and second reflectors, the reflective surface closest to the light guide unit among the plurality of reflective surfaces is a partially reflective surface, and Light reflected multiple times by at least one of the first reflector and the second reflector reaches the light guide unit.

2. The light guide element according to claim 1, characterized in that, The plurality of reflective surfaces includes a first surface and a second surface with different reflectivities.

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

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

5. The light guide element according to claim 1, characterized in that, The absolute value of the first angle of the first reflector relative to the first axis and the angular value of the second angle of the second reflector relative to the first axis are equal to each other.

6. The light guide element according to claim 1, characterized in that, The following inequalities are satisfied: |α|-|φ| / 2 < 45 |β|-|φ| / 2 < 45 Wherein, α (°) is the first angle of the first reflector relative to the first axis, β (°) is the second angle of the second reflector relative to the first axis, and φ (°) is the angle of the incident light relative to the first axis.

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

8. The light guide element according to claim 1, characterized in that, The plurality of reflective surfaces includes at least three reflective surfaces arranged along the first axis. Each of the plurality of reflective surfaces, except for the reflective surface furthest from the light guide unit, is a partial reflective surface.

9. The light guide element according to claim 1, characterized in that, The plurality of reflective surfaces includes at least three reflective surfaces arranged along a second direction orthogonal to the first axis. Each of the plurality of reflective surfaces, except for the reflective surface furthest from the incident portion of the incident light in the expander, is a partially reflective surface.

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

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

12. The light guide element according to claim 1, characterized in that, The reflectivity of the partially reflective surface decreases as the distance of the projection unit emitting the incident light along the first axial distance increases.

13. The light guide element according to claim 1, characterized in that, The plurality of reflective surfaces includes a first reflective surface and a second reflective surface, wherein the second reflective surface is closer to the light guide unit than the first reflective surface. The reflectivity of the first part of the reflective surface is higher than that of the second part of the reflective surface.

14. The light guide element according to any one of claims 1 to 13, characterized in that, The plurality of reflective surfaces includes a first reflective surface and a second reflective surface, wherein the second reflective surface is closer to the light guide unit than the first reflective surface. Wherein, the reflectivity of the first part of the reflective surface and the reflectivity of the second part of the reflective surface decrease as the distance from the projection unit that outputs the incident light increases.

15. An observation optical system, comprising: The light guide element according to any one of claims 1 to 14; as well as A projection unit that outputs incident light.

16. A display device, comprising: The observation optical system according to claim 15; as well as Display element.

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