Optical system and display device

Abstract

The invention discloses an optical system and a display device. An optical system includes a projection unit configured to project light from a display element to form a first pupil, and a light guide element configured to guide light from the projection unit to an eye point. The light guiding element includes a reflector configured to form a second pupil at an eye point. The reflector includes a plurality of reflective surface pairs, each reflective surface pair consisting of a first reflective surface and a second reflective surface. A predetermined inequality is satisfied.

Description

Technical Field

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

[0002] Observational optical systems with light guides, such as semi-reflective mirror stacked light guides or diffractive light guides, are conventionally known and used in augmented reality (AR) glasses, etc. Regarding light guide elements for virtual image display devices, which guide image light from a display element and emit it to display a virtual image, Japanese Patent Application Publication No. 2024-65027 discloses a pupil conjugate light guide that improves optical utilization efficiency by using a recursive mirror to collect a widely diffused beam of light from a projection unit onto the observer's pupil. Regarding light guides that guide image light from a display element to an observer, PCT International Publication No. WO 2019 / 120839 discloses an optical deflector that couples the image light to be guided and diffuses it within the light guide member of the light guide. Summary of the Invention

[0003] One or more embodiments of an optical system according to one or more aspects of this disclosure may include a projection unit configured to project light from a display element to form a first pupil, and a light guide element configured to guide light from the projection unit to an eye point. The light guide element includes a reflector configured to form a second pupil at the eye point. The reflector includes a plurality of pairs of reflective surfaces, each pair consisting of a first reflective surface and a second reflective surface. In a first cross-section including the normal to each of the first and second reflective surfaces, the following inequality is satisfied with respect to the principal ray at the central viewing angle:

[0004] 0 ≤ |α| ≤ 20

[0005] 0 ≤ |β| ≤ 20

[0006] Where α(°) is the angle between the light incident on the first reflecting surface and the second reflecting surface, and β(°) is the angle between the light reflected from the second reflecting surface and the first reflecting surface. Alternatively, the following inequality is satisfied:

[0007] 50 ≤ |θ| ≤ 70

[0008] Wherein, θ (°) is the angle between the first reflective surface and the second reflective surface. According to one or more other aspects of this disclosure, one or more display devices may include one or more optical systems.

[0009] 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 is provided by way of example. Attached Figure Description

[0010] Figure 1 This is a perspective view of the display device according to the first embodiment.

[0011] Figure 2 It is a perspective view illustrating the positional relationship of each optical element in the first embodiment.

[0012] Figure 3 This is a cross-sectional view of the projection unit in each embodiment.

[0013] Figure 4A and Figure 4B This is a cross-sectional view of the image extractor in each embodiment.

[0014] Figure 5A and Figure 5B This is a cross-sectional view of the pupil reconstruction mirror in each embodiment.

[0015] Figure 6A , Figure 6B , Figure 6C , Figure 6D and Figure 6E The mirror pairs in each embodiment and the mirror pairs in the comparative examples are described.

[0016] Figure 7A and Figure 7B These are cross-sectional views of the pupil reconstruction mirror in each embodiment and the pupil reconstruction mirror in the comparative example.

[0017] Figure 8A and Figure 8B The diagram illustrates the relationship between the angle formed by the mirror pair and the ratio of the reflected light beam in each embodiment.

[0018] Figure 9A , Figure 9B and Figure 9C These are cross-sectional views of mirror pairs according to variations of each embodiment.

[0019] Figure 10 This is a perspective view of the observation optical system according to the second embodiment.

[0020] Figure 11A , Figure 11B and Figure 11C This is a cross-sectional view of the pupil reconstruction mirror according to the third embodiment.

[0021] Figure 12A , Figure 12B and Figure 12C This is a cross-sectional view of the pupil reconstruction mirror according to the fourth embodiment.

[0022] Figure 13A and Figure 13B This is a cross-sectional view of the pupil reconstruction mirror according to the fifth embodiment.

[0023] Figure 14A and Figure 14B This is a cross-sectional view of the pupil reconstruction mirror according to the sixth embodiment. Detailed Implementation

[0024] 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 denoted by the same reference numerals, and repeated descriptions thereof will be omitted.

[0025] First Embodiment

[0026] First, refer to Figure 1 The display device 100 according to this embodiment is described. Figure 1 This is a perspective view of the display device 100. The display device 100 includes a display element 190 and an optical system (observation optical system) that guides light from the display element 190 to an eye point (the pupil in the eye of the observer 300) 170.

[0027] The display device 100 also includes a light guide plate (light guide element) 110, a projection unit 120, a first pupil (exit pupil) 130 formed by the projection unit 120, a folding (or rewinding) mirror 140, a pupil reconstruction mirror (reflector) 150, and an image extractor (extractor, light guide unit) 160. The folding mirror 140 is a deflecting element that, with respect to the principal ray at the central viewing angle, causes light from the projection unit 120 to be incident parallel to the mirror surface of the second mirror of the pupil reconstruction mirror 150, and is deployed to allow light from the first pupil 130 to enter the pupil reconstruction mirror 150 at a desired angle. However, in this embodiment, the folding mirror 140 is not necessary. For example, instead of providing a folding mirror 140, the position of the first pupil 130 can be adjusted so that light from the first pupil 130 enters the pupil reconstruction mirror 150 directly.

[0028] The light guide plate 110 directs light from the projection unit 120 to the eye point 170 of the observer 300. That is, the light guide plate 110 is configured to... Figure 1 A second pupil 171 is formed at the position of the pupil (eye point 170) of the observer 300 in the z direction. The second pupil 171 is a reconstruction of the first pupil 130.

[0029] Projection unit 120 projects light from display element 190 to form a first pupil 130. A light beam entering light guide plate 110 from the first pupil 130 formed by projection unit 120 is filled in a region equal to the thickness of light guide plate 110 in the thickness direction of light guide plate 110. In the thickness direction of light guide plate 110, beams with a width smaller than the width of light guide plate 110 travel inside light guide plate 110, while being internally reflected. The direction of travel of this beam varies according to the viewing angle, and therefore the beam travels from the first pupil 130 with a diffusion corresponding to the viewing angle. The light traveling while being internally reflected is deflected by folding mirror 140 and enters pupil reconstruction mirror 150.

[0030] The pupil reconstruction mirror 150 is deployed outside the perspective area, and its reflectivity can be 80% or higher, or 90% or higher. Using the pupil reconstruction mirror 150, a reflectivity higher than that of a semi-reflective mirror can be achieved.

[0031] The light entering the pupil reconstruction mirror 150 is deflected in the x-direction and reflected at different angles to form a second pupil 171. Before the second pupil 171 is formed, the reflected light is extracted (guided) by the image extractor 160 to the outside of the light guide plate 110, and the second pupil 171 is formed at the position of the observer 300's eye point 170.

[0032] Therefore, in this embodiment, the pupil reconstruction mirror 150 forms a second pupil 171 at the eye point 170, and the image extractor 160 extracts light to the outside of the light guide plate 110 (guiding the light from the pupil reconstruction mirror 150 to the eye point). In this embodiment, the pupil reconstruction mirror 150 and the image extractor 160 are configured as separate entities.

[0033] Now for reference Figure 2 The following describes the positional relationship of the optical elements that realize pupil reconstruction. Now assume that A1 (mm) is the equivalent air distance from the position of the pupil reconstruction mirror 150 to the position of the first pupil 130 formed by the projection unit 120, and A2 (mm) is the equivalent air distance from the position of the pupil reconstruction mirror 150 to the position of the eye point 170. The eye point 170 is the position where the second pupil 171 is formed. The eye point 170 is positioned, for example, at a distance of approximately 12mm to 18mm from the emitting surface of the light guide plate 110 (making the interpupillary distance 12mm to 18mm). However, this embodiment is not limited to this example and can be varied depending on the size of the display device 100, whether it is compatible with vision correction glasses, etc.

[0034] Now assume L1a is the distance from the center of the first pupil 130 inside the light guide plate 110 to the center of the folding mirror 140, and L1b is the distance from the position of the folding mirror 140 inside the light guide plate 110 to the position of the pupil reconstruction mirror 150. In this embodiment, the position of the pupil reconstruction mirror 150 is the center of the pupil reconstruction mirror 150 corresponding to the eye height of the observer 300. This position can also be the position where the principal ray at the central viewing angle reaches the image extractor 160. N is the refractive index of the light guide plate 110 for the d-line. In this case, the air equivalent distance A1 is expressed as:

[0035] A1 = (L1a / N) + (L1b / N).

[0036] The equivalent air distance A2 is expressed as:

[0037] A2 = (L2a / N) + L2b

[0038] Wherein, L2a is the distance from the position of the pupil reconstruction mirror 150 inside the light guide plate 110 to the center position of the image extractor 160, and L2b is the air distance from the exit surface of the light guide plate 110 to the eye point 170.

[0039] In this embodiment, in order to reconstruct the first pupil 130 formed by the projection unit 120 at the eye point 170 (to achieve pupil reconstruction), the relationship between the air equivalent distances A1 and A2 can satisfy the following inequality (1):

[0040] 0.5 < A2 / A1 < 2.0(1)

[0041] When A2 / A1 becomes greater than the upper limit of inequality (1), a pupil is formed in front of the observer 300's eye to prevent viewing the image at a wide angle (while the visible field of view narrows). On the other hand, when A2 / A1 becomes lower than the lower limit of inequality (1), a pupil is formed behind the observer 300's eye to prevent viewing the image at a wide angle (while the visible field of view narrows). Regarding distance L1b, when the light guide plate 110 includes multiple recursive mirrors, inequality (1) can be satisfied for distances L1b to all (e.g., three) recursive mirrors (e.g., distance to the center of a single recursive mirror).

[0042] Inequality (1) can be replaced by the following inequality (1a):

[0043] 0.6 < A2 / A1 < 1.5(1a)

[0044] Inequality (1) can be replaced by the following inequality (1b):

[0045] 0.8 < A2 / A1 < 1.2(1a)

[0046] Now for reference Figure 3 The following will provide a description of the function of the projection unit 120. Figure 3 This is a cross-sectional view of the projection unit 120. The projection unit 120 includes a display element 190 such as an organic light-emitting diode (OLED) and a projection optical system. The projection optical system includes a freeform prism 201, achieving a wide reception angle and a compact size. However, this embodiment is not limited to this example, and the projection unit 120 may use a general optical system instead of the freeform prism 201.

[0047] In this embodiment, the projection unit 120 forms a first pupil 130 inside the light guide plate 110, and folds the pupil when light enters the head 202, thereby filling the light beam propagating inside the light guide plate 110 without gaps. Due to this configuration, the light beam is extracted by the image extractor 160 without any light beam leakage, and a good image can be provided to the observer 300.

[0048] Next, we will refer to Figure 4A and Figure 4B Describe image extractor 160 (160a, 160b). Figure 4A This is a cross-sectional view of the image extractor 160 (160a) in this embodiment. Figure 4B This is a cross-sectional view of the image extractor 160 (160b) according to a modified example of this embodiment.

[0049] like Figure 4A As shown, the image extractor 160 (160a) in this embodiment has an insert mirror 162. Since the insert mirror 162 is deployed in the perspective region, from the viewpoint of the transmittance of the AR glass, the transmittance of the insert mirror 162 can be 80% or higher, or 90% or higher. The insert mirror 162 is deployed without gaps in the line of sight of the observer 300 and can extract light for the observer 300 without any beam leakage.

[0050] like Figure 4B As shown, the image extractor 160b can be formed by applying a diffraction grating or hologram to the surface 163 of the light guide plate 110. Due to this configuration, the diffraction grating or hologram can be deployed without gaps in the viewing direction of the observer 300. In this modified example, from the viewpoint of transmittance, the transmittance of the perspective can be 80% or higher, or 90% or higher.

[0051] In either configuration, in this embodiment, the optical paths before and after the pupil reconstruction mirror 150 are separate. Therefore, the image extractor 160 can fill the viewer's line of sight without gaps and can provide the viewer 300 with a good image.

[0052] Next, we will refer to Figure 5A and Figure 5B The configuration of the pupil reconstruction mirror 150 in this embodiment is described. Figure 5A and Figure 5B This is a cross-sectional view of the pupil reconstruction mirror 150.

[0053] Figure 5A from Figure 1 The first pupil 130, the pupil reconstruction mirror 150, and the eyepoint 170 (second pupil 171) were extracted. The pupil reconstruction mirror 150 includes multiple mirror groups (multiple pairs of reflective surfaces). Each of the multiple mirror groups is a mirror pair (pair of reflective surfaces) 210 that includes a first mirror (first reflective surface) and a second mirror (second reflective surface) (opposite to or adjacent to each other).

[0054] A predetermined section of the normal to the mirror surface, including both the first and second mirrors (first section: Figure 5A and Figure 5B In the cross section shown, θ (°) is the angle between the first mirror and the second mirror. The pupil reconstruction mirror 150 includes a mirror group in which a plurality of mirror pairs 210 are arranged in the planar direction of the light guide plate 110, and each mirror pair 210 has two mirrors arranged relative to each other at an angle θ.

[0055] In this embodiment, the mirror pair 210 consists of two mirrors of the same length ( Figure 5B The angle θ between mirrors 210a and 210b in (b2) is set to 60 degrees, and multiple mirror pairs 210 are arranged along the line segment connecting the ends of the mirrors. Figure 5A and Figure 5B The example shown has θ as 60 degrees. However, this embodiment is not limited to this example, and multiple mirror groups may include at least two mirror groups that satisfy the inequalities 50 ≤ |θ| ≤ 70 or 55 ≤ |θ| ≤ 65.

[0056] Light from the first pupil 130 travels in a diffusion angle ±φ corresponding to the central viewing angle, based on the direction of travel of the central viewing angle. In this embodiment, the angle φ has angular information in the vertical direction, and the viewing angle in the vertical direction at the eye point 170 can be represented as 2Nφ using the refractive index N of the light guide plate 110. This diffused light with ±φ is reflected twice by the surface of the mirror pair 210 constituting the pupil reconstruction mirror 150, and is simultaneously converged and reflected to form the second pupil 171.

[0057] Figure 5BThe illustration shows how a beam of light from the central viewing angle and a field of view beam diffused vertically at an angle φ is reflected by the pupil reconstruction mirror 150. Mirror pairs 210 are arranged such that the first mirror and the second mirror face each other. The mirrors of the first and second mirrors are arranged such that light at the central viewing angle is incident parallel to the mirror of the second mirror and reflected parallel to the mirror of the first mirror.

[0058] Light incident on the pupil reconstruction mirror 150 at the center viewing angle is reflected twice by the mirror surface (first reflecting surface) 210a of the first mirror and the mirror surface (second reflecting surface) 210b of the second mirror, thereby changing its path in the horizontal direction.

[0059] Figure 5B Figure (b1) illustrates the reflection of light that has entered the pupil reconstruction mirror 150 from the light that has diffused ±φ relative to the central viewing angle. The dashed lines in the figure indicate the direction of light travel at the central viewing angle. The light diffused at an angle φ relative to the central viewing angle is reflected twice by the mirror surface (first reflecting surface) 211a of the first mirror and the mirror surface (second reflecting surface) 211b of the second mirror, thereby changing its path in the converging direction at an angle φ relative to the central viewing angle.

[0060] Figure 5B Figure (b3) illustrates the reflection of light rays that have entered the lower mirror pair 212 of the pupil reconstruction mirror 150 in a diffused viewing angle. As shown in (b1), light diffused at an angle φ relative to the central viewing angle is reflected twice by the mirror surface (first reflecting surface) 212a of the first mirror and the mirror surface (second reflecting surface) 212b of the second mirror, thereby changing its path in the converging direction at an angle φ relative to the central viewing angle. Therefore, the pupil reconstruction mirror 150, including the mirror pair 210 with the same angle between them, can converge the expanded field-of-view beam while maintaining the angular information (angle φ) relative to the central viewing angle, and can form a second pupil 171.

[0061] In this embodiment, α (°) is the angle between the light incident on the first mirror and the surface of the second mirror, and β (°) is the angle between the light reflected from the second mirror and the surface of the first mirror. Then, Figure 5B The illustration shows the state where α=0 and β=0. However, this embodiment is not limited to this example. For example, the mirrors can be arranged such that the inequalities 0 ≤ |α| ≤ 20 and 0 ≤ |β| ≤ 20 are satisfied for the principal ray at the central viewing angle.

[0062] Now for reference Figure 6A , Figure 6B , Figure 6C , Figure 6D and Figure 6E This will provide a description of the relationship between the angles of the incident and reflected light relative to the mirror and the beam width. Figure 6AThe diagram illustrates a configuration where mirrors are arranged such that light incident on mirror 210a of the first mirror is parallel to mirror 210b of the second mirror, and light reflected from mirror 210b of the second mirror is parallel to mirror 210a of the first mirror. In this configuration, the angle θ between the mirror pairs 210 is 60°. L is the opening of the mirror pair 210, and D is the beam width on the effective mirror surface used for reflection.

[0063] like Figure 6A As shown, light enters parallel to the mirror surface 210b of the second mirror and can strike the entire mirror surface 210a of the first mirror, thus allowing for a large effective mirror surface. In this case, the triangle (oblique angle portion) formed by the light incident on the opening L and the beam width (effective diameter) D on the effective mirror surface is an isosceles triangle with two sides L. Therefore, as shown in equation (2), the beam width D is represented by the angle θ between the mirror pairs 210:

[0064] D = L * sin(θ / 2) * 2(2)

[0065] exist Figure 6A In this configuration, the beam width D is the same length as the opening L of the mirror pair 210. The light reflected and emitted from the mirror surface 210b of the second mirror is parallel to the mirror surface 210a of the first mirror. Therefore, light can be reflected without being obstructed by the mirror surface 210a of the first mirror.

[0066] Figure 6B The illustration shows a comparative example where mirrors are arranged such that φ = 45°, where φ is the angle of light relative to each mirror. In this configuration, the angle θ between the mirror pairs is 30°. When light is incident at an angle on the second mirror, as in this configuration, the shadow projected by the second mirror blocks the light from entering, thus reducing the beam width D on the effective mirror surface. In this case, the beam width D is D = L * sin(30 / 2) * 2 = 0.52L, which is half the effective diameter at θ = 60°.

[0067] Figure 6C The illustration shows a comparative example where the light angle φ is set at the same level as... Figure 6B The mirrors are positioned in opposite directions, and the mirrors are arranged such that φ = 30°. In this configuration, the angle θ between the mirror pairs is 80°. Light incident at this angle strikes not only the mirror of the first mirror but also the mirror of the second mirror, generating stray light and preventing all light entering the opening L from being properly reflected. Therefore, beam leakage occurs at all viewing angles, resulting in a degraded image quality across the entire viewing angle.

[0068] Figure 6D and Figure 6E The illustration shows that in Figure 6A and Figure 6BThe image shows the beam width on the mirror surface under the incident conditions when light is incident at an angle (viewing angle) φ relative to the central viewing angle. In this case, it can be understood that... Figure 6A Compared to the beam width D in the image, the beam width on the mirror is reduced by w. The reduction w is expressed using the angle (angular offset) φ as follows (3):

[0069] w ≈ L * cos φ(3)

[0070] In other words, it can be understood that the reduction in beam width w is determined by the angle (angular offset) φ, and is independent of the angle θ. Since the beam leakage ratio is w / D, the larger the beam width D without beam leakage, the smaller the effect of beam leakage. The beam width D is maximized when the light incident on the first mirror is parallel to the second mirror and the light reflected from the second mirror is parallel to the first mirror, i.e., when θ = 60°. Therefore, the optimal arrangement of mirror pair 210 is θ = 60°.

[0071] Figure 7A and Figure 7B The diagram illustrates the reflection when multiple mirror pairs are arranged. Figure 7A The comparative example is illustrated, in which the angle between the pairs of mirrors of the pupil reconstruction mirror 151 is 30 degrees ((a1) to (a3)). Figure 7B Comparative examples are illustrated, where the angle between the pairs of mirrors of the pupil reconstruction mirror 150 is 60 degrees ((b1) to (b3)). Each figure illustrates the reflection of the beam traveling at the central viewing angle and at an angle ±φ away from the central viewing angle.

[0072] When comparing under the same angular change Figure 7A and Figure 7B At that time, it is understandable that although the beam escape rate does not change significantly, the overall beam ratio is larger at θ=60°. This is because, as... Figure 7A and Figure 7B As shown, for light at the central viewing angle, the size of the beam reflected from a pair of mirrors is larger at θ=60° than at θ=30°.

[0073] Figure 8A and Figure 8B This is a graph plotting the relationship between the angle θ between the mirror pairs and the fill rate of the reflected beam relative to the central viewing angle. Figure 8A In the diagram, the horizontal axis represents the angle (°) relative to the central viewing angle, and the vertical axis represents the ratio of the reflected beam. Figure 8B In the diagram, the horizontal axis represents the angle (°) relative to the center viewpoint, and the vertical axis represents the beam ratio after reflection (based on 60°).

[0074] Recently, AR glasses with typically wide viewing angles have a diagonal viewing angle of 50 degrees or more. If the display aspect ratio is 4:3, the refractive index of the light guide plate is N=1.5, the viewing angle information in the horizontal direction is set to the propagation angle in the thickness direction, and the viewing angle information in the vertical direction is set to the planar direction, then the viewing angle beam propagating within the light guide plate 110 is approximately ±10° in the planar direction. Based on the above information, Figure 8A and Figure 8B The diagram illustrates an angular range of ±10°. When θ is 60° or less (dashed curve plotted with black dots), it can be understood that the beam fill rate decreases significantly as the viewing angle moves away from the central viewing angle, reaching its maximum at 60°. Conversely, when θ is greater than 60° (dashed curve plotted with black triangles), beam leakage occurs even at the central viewing angle, but the rate gradually decreases because beam leakage is less likely to occur when θ is less than 60°.

[0075] In this embodiment, the range of angle θ can be appropriately selected according to the intended use of the AR glasses. For example, to achieve uniform display across a wide viewing angle, such as in a monitor, beam leakage from the center viewing angle to the high viewing angle range must be suppressed. In this case, a range of 60 < θ ≤ 70 can be used, which can further suppress beam leakage towards the high viewing angle side. The mirrors are arranged such that the angle of light incident on the first mirror relative to the mirror of the second mirror is within 20° or 15°, and the angle of light reflected from the second mirror relative to the mirror of the first mirror is within 20° or 15°.

[0076] A range of 60 < θ ≤ 65 can be used because this range can suppress the effects of beam leakage even near the central viewing angle. In this case, the mirrors are arranged such that the angle between the light incident on the first mirror and the mirror of the second mirror is within 7.5°, and the angle between the light reflected from the mirror of the second mirror and the mirror of the first mirror is within 7.5°.

[0077] When the display is primarily in the center of the screen, such as in navigation, it is necessary to minimize beam leakage near the center viewing angle. In this case, a range of 50 ≤ θ ≤ 60 can be used, which suppresses beam leakage at the center viewing angle and limits the impact on the higher viewing angle side to approximately 10% of θ=60. In this case, the mirrors are arranged such that the angle of light incident on the first mirror relative to the second mirror is within 20° or 15°, and the angle of light reflected from the second mirror relative to the first mirror is also within 20° or 15°.

[0078] A range of 55 ≤ θ ≤ 60 can be used because image quality degradation can be suppressed even at higher viewing angles. In this case, the mirrors are arranged such that the angle of light incident on the first mirror relative to the second mirror is within 7.5°, and the angle of light reflected from the second mirror relative to the first mirror is also within 7.5°.

[0079] Now for reference Figure 9A , Figure 9B and Figure 9C A description of a modified example of the mirror pair constituting the pupil reconstruction mirror according to this embodiment will be given. Figure 9A This is a cross-sectional view of mirror pair 210 in this embodiment. Figure 9B This is a cross-sectional view of mirror pair 213 in the first modified example. Figure 9C This is a cross-sectional view of mirror pair 214 in the second variation.

[0080] like Figure 9B Like mirror pair 213, as long as the angle θ is maintained, the direction of light reflection does not change even if the mirror pair is tilted φ. This arrangement can be used in the variations described below to further reduce beam leakage. Figure 9C Similar to mirror pair 214, mirror pairs do not need to touch each other. A pupil reconstruction mirror can be similarly implemented as long as vertices are formed on the line segments of the reflecting mirrors and the angle between them is θ. Therefore, in this embodiment, the arrangement and length of the mirror pairs are unrestricted as long as the angle θ between them is fixed.

[0081] Second Embodiment

[0082] Next, we will refer to Figure 10 A second embodiment of this disclosure is described. Figure 10 This is a perspective view of the optical system (observation optical system) according to this embodiment. The first embodiment has discussed a configuration where a viewing beam emitted from the first pupil 130 enters the pupil reconstruction mirror 150 at an appropriate angle using a folding mirror 140. On the other hand, this embodiment will discuss a configuration where light from the first pupil 131 enters the pupil reconstruction mirror directly without using a folding mirror.

[0083] The optical system according to this embodiment includes a light guide plate 111, a projection unit 121, a first pupil 131 formed by the projection unit 121, a pupil expansion system 180 for expanding the first pupil 131, a pupil reconstruction mirror 150, and an image extractor 160. The light emitted from the first pupil 131 is pre-set such that the central viewing angle beam is at an optimal angle relative to the pupil reconstruction mirror 150. Subsequently, the pupil expansion system 180 expands the pupil diameter while maintaining the propagation angle of the viewing angle beam.

[0084] A pupil expansion system 180 is used to enlarge the observer's eye socket and includes, for example, at least one semi-reflective mirror to expand the beam diameter by reflecting the beam multiple times using the semi-reflective mirror. The position of the first pupil 131 of the expanded viewing angle beam is located at a different position than before expansion. In this embodiment, a virtual first pupil is formed near the intersection 132 between the principal ray of the central viewing angle beam and the extrapolation line of the first pupil 131. The air equivalent distance A1' calculated to achieve pupil reconstruction is expressed as A1' = L3 / N, where L3 is the distance between the intersection 132 and the center of the pupil reconstruction mirror 150.

[0085] Because the first embodiment provides a folding mirror, the size of the light guide plate increases in the y-direction. On the other hand, in the case where light from the first pupil directly enters the pupil reconstruction mirror as in this embodiment, the deflection of the folding mirror can be omitted. This configuration prevents the size of the light guide plate from increasing in the y-direction, allowing it to remain within a size suitable for eyeglasses.

[0086] Third Embodiment

[0087] Next, we will refer to Figure 11A , Figure 11B and Figure 11C The third embodiment according to this disclosure is described. The pupil reconstruction lens 152 according to this embodiment is a variation of the pupil reconstruction lens 150 according to the first embodiment. Figure 11A , Figure 11B and Figure 11C This is a cross-sectional view of the pupil reconstruction mirror 152 according to this embodiment. Figure 11A , Figure 11B and Figure 11C The illustration shows the reflection when the mirrors are arranged such that the angle between the light incident on the first mirror and the mirror of the second mirror is 15° and the angle between the light reflected from the mirror of the second mirror and the mirror of the first mirror is 15°.

[0088] In this configuration, the angle between the mirror pairs is θ = 50°, and Figure 11A , Figure 11B and Figure 11C The illustration shows the reflection of a beam of light traveling at a central viewing angle and an angle ±φ off-center from the central viewing angle. The pupil reconstruction mirror 152 has multiple pairs of mirrors arranged along the dashed line segment 152s connecting the mirror ends. (As shown from...) Figure 8B The graph shows that even at θ=50 degrees, the beam fill rate remains at approximately 90% compared to θ=60 degrees.

[0089] Fourth embodiment

[0090] Next, we will refer to Figure 12A , Figure 12B and Figure 12CThe fourth embodiment according to this disclosure is described. The pupil reconstruction lens 153 according to this embodiment is a variation of the pupil reconstruction lens 150 according to the first embodiment. Figure 12A , Figure 12B and Figure 12C This is a cross-sectional view of the pupil reconstruction mirror 153 according to this embodiment. Figure 12A , Figure 12B and Figure 12C The illustration shows the reflection when the mirrors are arranged such that the angle between the light incident on the first mirror and the mirror of the second mirror is 15° and the angle between the light reflected from the mirror of the second mirror and the mirror of the first mirror is 15°.

[0091] In this configuration, the angle between the mirror pairs is θ = 70 degrees, and Figure 12A , Figure 12B and Figure 12C The illustration shows the reflection of a beam traveling at a central viewing angle and an angle ±φ off-center from the central viewing angle. The pupil reconstruction mirror 153 has multiple pairs of mirrors arranged along the dashed line segment 153s connecting the mirror ends. In this configuration, as shown in the reference... Figure 6C As stated above, even for a beam with a central viewing angle, the incident light enters both mirror pairs, producing stray light from abnormal reflections and beam leakage in the reflected light. However, for a beam with a viewing angle, the beam is approximately the same as when θ = 60 degrees.

[0092] Fifth embodiment

[0093] Next, we will refer to Figure 13A and Figure 13B The fifth embodiment according to this disclosure is described. The pupil reconstruction lens 155 according to this embodiment is a variation of the pupil reconstruction lens 150 according to the first embodiment. Figure 13A and Figure 13B This is a cross-sectional view of the pupil reconstruction mirror 155 according to this embodiment. Figure 13B The diagram shows... Figure 13A A magnified view of a portion of it.

[0094] The pupil reconstruction mirror 150 according to the first embodiment has a configuration in which the mirror pairs are arranged in a straight line along the line segment connecting the mirror ends. On the other hand, the mirror pairs 215 of the pupil reconstruction mirror 155 according to this embodiment are arranged such that the principal ray of each field-of-view beam from the first pupil 134 is parallel to the mirror surface 215b of the second mirror, and the light reflected from the mirror surface 215b of the second mirror is parallel to the mirror surface 215a of the first mirror. More specifically, the mirror pairs incident on the view beams at an angle φ offset from the center view beam are arranged with an inclination of φ. This indicates that the inclination angle of the mirror pairs increases with increasing φ, and in the case of arranging multiple mirror pairs, the mirror pairs are arranged to draw curved surfaces, unlike the linear arrangement in the first embodiment.

[0095] In this configuration, because the light path lengths of the light entering the upper and lower parts of the pupil reconstruction mirror 155 are different, the arrangement is not a perfect arc, but rather a line 155s whose curvature flattens as it approaches the bottom. For the mirror pairs outside the principal ray of the maximum viewing angle beam, no further tilting is required, so they can be arranged such that they are linearly aligned while maintaining the tilt at the maximum viewing angle. That is, the mirror pairs can include curved or linearly aligned portions, or both.

[0096] In this embodiment, the tilt (or orientation) of each of the plurality of lens groups in the first cross-section varies depending on their position. Furthermore, in the first cross-section, each of the plurality of lens groups has an arc shape with its center close to the first pupil (an arc shape that bulges out in a direction away from the first pupil). In this embodiment, the plurality of lens groups need not be arc-shaped. For example, the curvature can vary depending on the position of the lens groups. The plurality of lens groups may include lens groups arranged such that the curvature is zero.

[0097] As described above, the pupil reconstruction mirror 155 can have a fixed angle θ formed by the mirror pair in the pupil reconstruction mirror 155, and pupil reconstruction can be achieved even if the tilt of the mirror pair is changed. In addition, by making one of the mirrors in the mirror pair parallel to each viewpoint beam, the angular relationship between the mirror pair and the viewpoint beam can be consistent with the angular relationship at the central viewpoint, and beam leakage is unlikely to occur.

[0098] Sixth Embodiment

[0099] Next, we will refer to Figure 14A and Figure 14B The sixth embodiment of this disclosure is described. The pupil reconstruction lens 156 according to this embodiment is a variation of the pupil reconstruction lens 150 according to the first embodiment. Figure 14A and Figure 14B This is a cross-sectional view of the pupil reconstruction mirror 156 according to this embodiment.

[0100] The first to fifth embodiments have discussed pupil reconstruction mirrors in which multiple mirror pairs are arranged on a single straight line or curve. On the other hand, the pupil reconstruction mirror 156 according to this embodiment has two pupil reconstruction mirrors (mirror groups): pupil reconstruction mirror (first mirror group) 156a and pupil reconstruction mirror (second mirror group) 156b.

[0101] The mirror pair of the pupil reconstruction mirror 156a has the characteristic of reflecting only S-polarized light, and only reflects the S-polarized light of the unpolarized incident light toward the image extractor. On the other hand, the mirror pair of the pupil reconstruction mirror 156b has the characteristic of reflecting only P-polarized light, and reflects the P-polarized light that has passed through the pupil reconstruction mirror 156a toward the image extractor. Since the light reflected by the pupil reconstruction mirror 156a is only P-polarized light, it passes through the pupil reconstruction mirror 156a without being reflected. As a result, although beam leakage occurs in a single pupil reconstruction mirror 150, beam leakage is reduced in the pupil reconstruction mirror 156 which has two mirror groups.

[0102] In this embodiment, multiple mirror groups include a first mirror group (first reflecting surface pair) arranged in a first row and a second mirror group (second reflecting surface pair) arranged in a second row within a first cross section including the normal of the first and second mirrors. For example, the first mirror group reflects S-polarized light, and the second mirror group reflects P-polarized light. This embodiment arranges two pupil reconstruction mirrors with different deflection characteristics and can compensate for inherent beam leakage. In this embodiment, the number of pupil reconstruction mirrors is not limited to two; three or more pupil reconstruction mirrors can be arranged.

[0103] To achieve an optical system with high light utilization efficiency, each embodiment may have the following characteristics: the angle α (°) between the light incident on the first mirror and the surface of the second mirror, and the angle β (°) between the light reflected from the second mirror and the surface of the first mirror, may satisfy the following inequality:

[0104] 0 ≤ |α| ≤ 20

[0105] 0 ≤ |β| ≤ 20.

[0106] They can satisfy the following inequalities:

[0107] 0 ≤ |α| ≤ 15

[0108] 0 ≤ |β| ≤ 15.

[0109] They can satisfy the following inequalities:

[0110] 0 ≤ |α| ≤ 7.5

[0111] 0 ≤ |β| ≤ 7.5.

[0112] They can satisfy the following equation:

[0113] α = 0

[0114] β = 0.

[0115] The reflectivity of the mirror pair of the pupil reconstruction mirror can be three times or more than that of the image extractor. In the first section, the following inequality can be satisfied:

[0116] 0 ≤ |γ| ≤ 10.

[0117] Wherein, γ is the angle (°) between the direction of light traveled by the pupil reconstruction mirror and the direction from the pupil reconstruction mirror (e.g., the center position) toward the image extractor (e.g., the center position).

[0118] The following inequalities can be satisfied:

[0119] 0 ≤ |γ| ≤ 5.

[0120] To achieve an optical system with high light utilization efficiency, each condition must be met for the principal ray at the central viewing angle. Each condition must be satisfied for the principal ray at the total viewing angle. Each condition must be satisfied for all rays from the projection unit 120.

[0121] In each embodiment, in order to achieve an optical system with high light utilization efficiency, the angle (°) between the first mirror and the second mirror in the first cross section can satisfy the following inequality:

[0122] 50 ≤ |θ| ≤ 70.

[0123] Angle θ (°) can satisfy the following inequality:

[0124] 55 ≤ |θ| ≤ 65.

[0125] Angle θ (°) can satisfy the following equation:

[0126] θ = 60.

[0127] It may include at least two mirror groups (mirror pairs) that satisfy each inequality. The angle between the direction of the angle bisector of the mirror group and the direction of travel of the projected light may be 90° - |θ|.

[0128] Each embodiment can provide an optical system and a display device, each with high light utilization efficiency and capable of forming a good image with minimal beam leakage (light loss).

[0129] While this disclosure describes exemplary embodiments, it should be understood that this disclosure is not limited to exemplary embodiments. The scope of the following claims should be given the broadest possible description to cover all such modifications and equivalent structures and functions.

[0130] Each embodiment can provide an optical system with high light utilization efficiency.

Claims

1. An optical system comprising: A projection unit configured to project light from a display element to form a first pupil; as well as A light guide element configured to guide light from the projection unit to the eyepoint. The light guide element is characterized in that it includes a reflector configured to form a second pupil at the eye point. The reflector includes multiple pairs of reflective surfaces, each pair consisting of a first reflective surface and a second reflective surface. In a first cross-section including the normal of each of the first and second reflective surfaces, the following inequality is satisfied with respect to the principal ray at the central viewing angle: 0 ≤ |α| ≤ 20 0 ≤ |β| ≤ 20 Wherein, α(°) is the angle between the light incident on the first reflective surface and the second reflective surface, and β(°) is the angle between the light reflected by the second reflective surface and the first reflective surface.

2. The optical system according to claim 1, characterized in that, The following inequalities are satisfied: 0 ≤ |α| ≤ 7.5 0 ≤ |β| ≤ 7.5。 3. The optical system according to claim 1, characterized in that, The following inequalities are satisfied: α = 0 β = 0。 4. The optical system according to claim 1, characterized in that, The inequality is satisfied for the principal ray at the overall viewing angle.

5. The optical system according to claim 1, characterized in that, The inequality is satisfied for all light rays from the projection unit.

6. The optical system of claim 1, further comprising a light guide unit configured to guide light from the reflector to the eyepoint. Its features are, The reflectivity of each reflective surface pair is three times or more the reflectivity of the light guide unit.

7. The optical system according to claim 1, characterized in that, The light guide element has a deflection element that, with respect to the central viewing angle, causes the light from the projection unit to be incident parallel to the second reflective surface.

8. The optical system of claim 1, further comprising a light guide unit configured to guide light from the reflector to the eyepoint. Its features are, The following inequalities are satisfied: 0 ≤ |γ| ≤ 10 Wherein, γ is the angle (°) between the direction of light traveled by the reflector in the first cross section and the direction from the reflector toward the light guide unit.

9. The optical system according to claim 1, characterized in that, The following inequalities are satisfied: 0.5 < A2 / A1 < 2.0 Wherein, A1 (mm) is the equivalent air distance from the reflector to the first pupil, and A2 (mm) is the equivalent air distance from the reflector to the eye point.

10. The optical system according to claim 1, characterized in that, The projection unit forms the first pupil inside the light guide element.

11. The optical system according to claim 1, characterized in that, The tilt of each of the plurality of reflective surface pairs varies depending on its position in the first cross section.

12. The optical system according to claim 11, characterized in that, Each of the plurality of reflective surface pairs has an arc shape in the first cross section with its center located on the side closest to the first pupil.

13. The optical system according to claim 11, characterized in that, The plurality of reflective surface pairs includes reflective surface pairs arranged such that the curvature is zero.

14. The optical system according to any one of claims 1 to 13, characterized in that, The plurality of reflective surface pairs in the first cross section includes a first reflective surface pair arranged in a first row and a second reflective surface pair arranged in a second row.

15. The optical system according to claim 14, characterized in that, The first reflective surface reflects S-polarized light, and the second reflective surface reflects P-polarized light.

16. An optical system comprising: A projection unit configured to project light from a display element to form a first pupil; as well as A light guide element configured to guide light from the projection unit to the eyepoint. The light guide element is characterized in that it includes a reflector configured to form a second pupil at the eye point. The reflector includes multiple pairs of reflective surfaces, each pair consisting of a first reflective surface and a second reflective surface. In a first cross-section including the normal to each of the first and second reflective surfaces, the following inequality is satisfied: 50 ≤ |θ| ≤ 70 Wherein, θ (°) is the angle between the first reflective surface and the second reflective surface.

17. The optical system according to claim 16, characterized in that, The angle between the direction of the angle bisector of each pair of reflecting surfaces and the direction of propagation of the projected light is 90° - |θ|.

18. The optical system according to claim 16, characterized in that, The tilt of each of the plurality of reflective surface pairs in the first cross section varies depending on its position.

19. The optical system according to any one of claims 16 to 18, characterized in that, The plurality of reflective surface pairs in the first cross section includes a first reflective surface pair arranged in a first row and a second reflective surface pair arranged in a second row.

20. A display device, comprising: The optical system according to any one of claims 1 to 19; as well as Display unit.

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