Optical device and near-eye display apparatus

Abstract

The embodiment of the utility model discloses an optical device and near-to-eye display equipment, the optical device comprises a projection light source, an optical isolator and a diffraction optical waveguide, the projection light source is used for emitting image light; the diffractive optical waveguide comprises a coupling grating; image light emitted by the projection light source passes through the optical isolator and then enters the coupling-in grating, and after being diffracted by the coupling-in grating, the image light returns to the optical isolator and cannot return to the projection light source. According to the technical scheme disclosed by the invention, the light rays diffracted and returned by the coupled grating can be prevented from entering the projection light source to form a ghosting image.

Description

Technical Field

[0001] This application relates to the field of augmented reality, and more particularly to an optical device and a near-eye display device. Background Technology

[0002] Optical waveguide display technology is one of the most challenging and complex problems in the field of augmented reality. Diffracting waveguides are a commonly used type of optical waveguide in optical waveguide display technology. Typically, image light emitted from a projection light source is incident on a coupling grating and undergoes diffraction. The first-order diffracted light is transmitted through total internal reflection in the diffracting waveguide to the output grating and then coupled out to the human eye, allowing the human eye to see the displayed image. At the same time, the reflected zero-order light is reflected back to the projection light source and reflected again before being incident on the coupling grating. After undergoing the same total internal reflection and coupling out, it is incident on the human eye, causing the human eye to see an artifact corresponding to the normal image, also known as a ghost image. The presence of ghost images seriously affects the display effect and impacts the user experience. Utility Model Content

[0003] To solve the above problems, this invention provides an optical device and a near-eye display device that can avoid forming ghost images.

[0004] Based on this, this application provides an optical device, including: a projection light source, an optical isolator, and a diffractive waveguide, wherein the projection light source is used to emit image light; the diffractive waveguide includes a coupling grating; the image light emitted from the projection light source passes through the optical isolator and then enters the coupling grating, and after being diffracted by the coupling grating, returns to the optical isolator and cannot return to the projection light source.

[0005] In practice, the optical isolator includes a first polarizer, an optical rotator, and a second polarizer. The polarization directions of the first polarizer and the second polarizer are at an angle of 45°. The optical rotator is used to rotate the polarization direction of the image light passing through the first polarizer to be consistent with the polarization direction of the second polarizer. The optical rotator is also used to rotate the polarization direction of the image light passing through the second polarizer to be perpendicular to the polarization direction of the first polarizer.

[0006] In practice, the polarization direction of the second polarizer is rotated 45° counterclockwise relative to the polarization direction of the first polarizer; the optical rotation element is a magneto-optical element, and the magnetic field direction of the magneto-optical element is along the direction from the first polarizer to the second polarizer, used to rotate the polarization direction of the image light incident on the magneto-optical element counterclockwise by 45°.

[0007] In practice, the image light emitted from the projection light source is incident on the optical rotator in a first polarization direction via the first polarizer, then on the second polarizer in a second polarization direction after passing through the optical rotator, and then on the coupling grating after being diffracted by the coupling grating. After being diffracted by the coupling grating, it returns to the second polarizer in a second polarization direction and then on the optical rotator in a second polarization direction. After passing through the optical rotator, it is incident on the optical rotator in a third polarization direction, which is perpendicular to the polarization direction of the first polarizer and is cut off by the first polarizer.

[0008] In practice, the projection light source is used to emit image light rays that are in a polarized state, the polarization direction of which is consistent with the polarization direction of the first polarizer; or, the projection light source is used to emit unpolarized image light rays.

[0009] In an implementable manner, the optical isolator includes a first wedge-shaped birefringent crystal, an optical rotator, and a second wedge-shaped birefringent crystal. The angle between the optical axes of the first and second wedge-shaped birefringent crystals is 45°. The optical rotator is used to rotate the polarization directions of the ordinary and extraordinary rays emitted from the first wedge-shaped birefringent crystal to be consistent with the polarization directions of the ordinary and extraordinary rays in the second wedge-shaped birefringent crystal. The optical rotator is also used to rotate the polarization directions of the ordinary and extraordinary rays emitted from the first wedge-shaped birefringent crystal to be perpendicular to the polarization directions of the ordinary and extraordinary rays in the first wedge-shaped birefringent crystal.

[0010] In practice, the optical axis of the second wedge-shaped birefringent crystal is rotated 45° counterclockwise relative to the optical axis of the first wedge-shaped birefringent crystal; the optical rotation element is a magneto-optical element, and the magnetic field direction of the magneto-optical element is along the direction from the first wedge-shaped birefringent crystal to the second wedge-shaped birefringent crystal, used to rotate the polarization direction of the image light incident on the magneto-optical element counterclockwise by 45°.

[0011] In practice, the unpolarized image light emitted from the projection light source, after passing through the first wedge-shaped birefringent crystal, is emitted as ordinary and extraordinary light rays and then incident on the optical rotator. After passing through the optical rotator, the polarization direction of the ordinary light is consistent with the polarization direction of the ordinary light in the second wedge-shaped birefringent crystal, and the polarization direction of the extraordinary light is consistent with the polarization direction of the extraordinary light in the second wedge-shaped birefringent crystal. After passing through the second wedge-shaped birefringent crystal, the light rays are combined into a single beam and then incident on the coupling grating. The image light rays that return to the second wedge-shaped birefringent crystal after diffraction by the coupling grating, after passing through the second wedge-shaped birefringent crystal, are emitted as ordinary and extraordinary light rays and then incident on the optical rotator. After passing through the optical rotator, the polarization direction of the ordinary light is consistent with the polarization direction of the extraordinary light in the first wedge-shaped birefringent crystal, and the polarization direction of the extraordinary light is consistent with the polarization direction of the ordinary light in the first wedge-shaped birefringent crystal. After passing through the first wedge-shaped birefringent crystal, the light rays continue to be emitted as ordinary and extraordinary light rays.

[0012] In an implementable manner, the first wedge-shaped birefringent crystal includes a first surface and a second surface disposed opposite to each other, and the second wedge-shaped birefringent crystal includes a third surface and a fourth surface disposed opposite to each other; wherein, the first surface and the fourth surface are wedge-shaped surfaces, and along the direction from the first wedge-shaped birefringent crystal to the second wedge-shaped birefringent crystal, the image light passes sequentially through the first surface, the second surface, the third surface and the fourth surface, the first surface and the fourth surface are parallel, and the second surface and the third surface are parallel.

[0013] A near-eye display device, wherein the near-eye display device comprises the optical element described in any of the preceding claims.

[0014] The optical device and near-eye display device provided in this application add an optical isolator between the projection light source and the coupling grating of the diffractive waveguide. The optical isolator allows unidirectional light transmission by changing the polarization direction of the light. In this way, the image light emitted from the projection light source can pass through the optical isolator as the incident light of the coupling grating, while the light reflected back by the diffraction of the coupling grating can no longer pass through the optical isolator, or even if it does pass through the optical isolator, the state of the light is changed and it cannot return to the projection light source. Thus, the reflected image light can be prevented from being incident on the projection light source, thereby effectively reducing or even avoiding unwanted ghosting images. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of an optical device in one embodiment of this application;

[0017] Figure 2 This is a schematic diagram of the optical path of an optical isolator in an embodiment of this application;

[0018] Figure 3 This is a schematic diagram of the optical path of the optical isolator in another embodiment of the present application;

[0019] Attached image labels:

[0020] 100: Projection light source;

[0021] 200: Optical isolator; 211: First polarizer; 220: Optical rotator; 231: Second polarizer; 212: First wedge-shaped birefringent crystal; 232: Second wedge-shaped birefringent crystal;

[0022] 300: Diffractive waveguide; 310: Coupled grating. Detailed Implementation

[0023] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] The technical solution of this application will be described in detail below with reference to specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0025] According to one aspect of the present invention, an optical device is provided, comprising: a projection light source, an optical isolator, and a diffractive waveguide, wherein the projection light source is used to emit image light; the diffractive waveguide includes a coupling grating; the image light emitted from the projection light source passes through the optical isolator and then enters the coupling grating, and after being diffracted by the coupling grating, returns to the optical isolator and cannot return to the projection light source.

[0026] In this application, the optical isolator only allows light to be transmitted unidirectionally in its original state. Specifically, the optical isolator allows image light emitted from the projection light source to pass through and be incident on the coupling grating, while the light rays diffracted back by the coupling grating are not allowed to pass through the optical isolator and return to the projection light source in their original state.

[0027] Specifically, refer to Figure 1 The image light emitted from the projection light source 100 (shown by the solid blue line) passes through the optical isolator 200 and then enters the coupling grating 310 of the diffraction waveguide 300. The light rays diffracted back by the coupling grating 310 (shown by the solid red line) are either blocked or broken into multiple large-angle light rays after returning to the optical isolator 200, and cannot return to the projection light source (shown by the dashed red line) in their original state.

[0028] In one implementable embodiment, the optical isolator includes a first polarizer, an optical rotator, and a second polarizer. The polarization directions of the first polarizer and the second polarizer are at an angle of 45°. The optical rotator is used to rotate the polarization direction of the image light passing through the first polarizer to be consistent with the polarization direction of the second polarizer, and the optical rotator is used to rotate the polarization direction of the image light passing through the second polarizer to be perpendicular to the polarization direction of the first polarizer.

[0029] Specifically, the polarization direction of the second polarizer is rotated 45° counterclockwise compared to the polarization direction of the first polarizer; the optical rotator is a magneto-optical element, and the magnetic field direction of the magneto-optical element is along the direction from the first polarizer to the second polarizer, used to rotate the polarization direction of the image light incident on the magneto-optical element counterclockwise by 45°. Alternatively, the polarization direction of the second polarizer is rotated 45° clockwise compared to the polarization direction of the first polarizer; the optical rotator is a magneto-optical element, and the magnetic field direction of the magneto-optical element is along the direction from the second polarizer to the first polarizer, used to rotate the polarization direction of the image light incident on the magneto-optical element clockwise by 45°.

[0030] The optical rotator is a magneto-optical element. Light travels through a transparent medium within a magnetic field, the direction of which may be the same as or opposite to the direction of light propagation. When the magnetic field direction is the same as the direction of light propagation, the optical rotator rotates the polarization direction of the light by 45° counterclockwise (towards the direction of light propagation) when the light enters the optical rotator. When the magnetic field direction is opposite to the direction of light propagation, the optical rotator rotates the polarization direction of the light by 45° clockwise (towards the direction of light propagation) when the light enters the optical rotator. Furthermore, if light passes through the optical rotator and then, after reflection, re-enters the optical rotator, the rotation angle of the polarization direction is the sum of the two rotation angles, rather than canceling each other out.

[0031] In practice, the image light emitted from the projection light source is incident on the optical rotator in a first polarizer with a first polarization direction, then on the second polarizer with a second polarization direction after passing through the optical rotator, and then on the coupling grating after passing through the second polarizer. After being diffracted by the coupling grating, it returns to the second polarizer with a second polarization direction and then on the optical rotator in a second polarization direction after passing through the second polarizer. After passing through the optical rotator, it is incident on the optical rotator in a third polarization direction after passing through the optical rotator. The third polarization direction is perpendicular to the polarization direction of the first polarizer and is blocked by the first polarizer.

[0032] refer to Figure 2 The image light emitted from the projection light source (shown by the blue solid line) is incident on the optical rotator 220 with the first polarizer 211 (polarization direction 0°) in the first polarization direction (0°). After passing through the optical rotator 220, the polarization direction is rotated counterclockwise by 45° and incident on the second polarizer 231 (polarization direction 45°) in the second polarization direction (45°). After passing through the second polarizer 231, it is incident on the coupling grating. The light rays that return after diffraction by the coupling grating (shown by the red solid line) retain their polarization direction and return to the second polarizer 231 with the second polarization direction (45°). After passing through the second polarizer 231, they are incident on the optical rotator 220 with the second polarization direction (45°). After passing through the optical rotator 220, the polarization direction is rotated counterclockwise again by 45° and incident on the first polarizer 211 with the third polarization direction (90°). The third polarization direction (90°) is perpendicular to the polarization direction (0°) of the first polarizer 211 and is cut off by the first polarizer 211. In this way, the returned image light will no longer be incident on the projection light source, which can effectively reduce or even avoid unwanted ghosting images.

[0033] In the above embodiments, the projection light source can be used to emit image light rays that are in a polarized state, and the polarization direction of the image light rays is consistent with the polarization direction of the first polarizer; or, the projection light source can be used to emit unpolarized image light rays.

[0034] In another possible implementation, the optical isolator includes a first wedge-shaped birefringent crystal, an optical rotator, and a second wedge-shaped birefringent crystal. The angle between the optical axes of the first and second wedge-shaped birefringent crystals is 45°. The optical rotator is used to rotate the polarization directions of the ordinary and extraordinary rays emitted from the first wedge-shaped birefringent crystal to align with the polarization directions of the ordinary and extraordinary rays emitted from the second wedge-shaped birefringent crystal. The optical rotator is also used to rotate the polarization directions of the ordinary and extraordinary rays emitted from the first wedge-shaped birefringent crystal to be perpendicular to the polarization directions of the ordinary and extraordinary rays emitted from the first wedge-shaped birefringent crystal. In this case, the projection light source is used to emit unpolarized image light.

[0035] Specifically, the optical axis of the second wedge-shaped birefringent crystal is rotated 45° counterclockwise compared to the optical axis of the first wedge-shaped birefringent crystal; the optical rotator is a magneto-optical element, and the magnetic field of the magneto-optical element is directed along the direction from the first wedge-shaped birefringent crystal to the second wedge-shaped birefringent crystal, used to rotate the polarization direction of the image light incident on the magneto-optical element counterclockwise by 45°. Alternatively, the optical axis of the second wedge-shaped birefringent crystal can be rotated 45° clockwise compared to the optical axis of the first wedge-shaped birefringent crystal; the optical rotator is a magneto-optical element, and the magnetic field of the magneto-optical element is directed along the direction from the second wedge-shaped birefringent crystal to the first wedge-shaped birefringent crystal, used to rotate the polarization direction of the image light incident on the magneto-optical element clockwise by 45°.

[0036] In practice, the unpolarized image light emitted from the projection light source passes through the first wedge-shaped birefringent crystal, where ordinary and extraordinary rays are emitted and incident on the optical rotator. After passing through the optical rotator, the polarization direction of the ordinary ray is consistent with that of the ordinary ray in the second wedge-shaped birefringent crystal, and the polarization direction of the extraordinary ray is consistent with that of the extraordinary ray in the second wedge-shaped birefringent crystal. The light then passes through the second wedge-shaped birefringent crystal and is combined into a single beam before being incident on the coupling grating. The image light that returns to the second wedge-shaped birefringent crystal after diffraction by the coupling grating passes through the second wedge-shaped birefringent crystal, where ordinary and extraordinary rays are emitted and incident on the optical rotator. After passing through the optical rotator, the polarization direction of the ordinary ray is consistent with that of the extraordinary ray in the first wedge-shaped birefringent crystal, and the polarization direction of the extraordinary ray is consistent with that of the ordinary ray in the first wedge-shaped birefringent crystal. The light then passes through the first wedge-shaped birefringent crystal and continues to be emitted as ordinary and extraordinary rays, with the deviation between them further increasing.

[0037] refer to Figure 3The image light emitted from the projection light source is split into ordinary light (o-ray) and extraordinary light (e-ray) after passing through the first wedge-shaped birefringent crystal 212 (0° in the optical axis direction) and then enters the optical rotator 220. After passing through the optical rotator 220, the polarization direction is rotated 45° counterclockwise and then enters the second wedge-shaped birefringent crystal 232 (45° in the optical axis direction). At this time, the polarization direction of the ordinary light (o-ray) is exactly the same as the polarization direction of the ordinary light (o-ray) in the second wedge-shaped birefringent crystal 232, and the polarization direction of the extraordinary light (e-ray) is exactly the same as the polarization direction of the extraordinary light (e-ray) in the second wedge-shaped birefringent crystal 232. Therefore, the ordinary light (o-ray) and the extraordinary light (e-ray) are combined into a single beam after passing through the second wedge-shaped birefringent crystal 232 and enter the coupling grating. The image light rays returning after diffraction by the coupled grating are split into ordinary (o-ray) and extraordinary (e-ray) rays after passing through the second wedge-shaped birefringent crystal 232 (optical axis direction 45°), and then incident on the optical rotator 220. After passing through the optical rotator 220, the polarization direction is rotated counterclockwise by 45° before entering the first wedge-shaped birefringent crystal 212 (optical axis direction 0°). At this time, the polarization direction of the ordinary (o-ray) ray is exactly the same as the polarization direction of the extraordinary (e-ray) ray in the first wedge-shaped birefringent crystal 232, and the polarization direction of the extraordinary (e-ray) ray is exactly the same as the polarization direction of the ordinary (o-ray) ray in the second wedge-shaped birefringent crystal 232. Therefore, they continue to emerge as ordinary and extraordinary rays, and the deviation between them further increases. At this time, by adjusting the tilt angle of the wedge surfaces of the first and second wedge-shaped birefringent crystals, the light transmission direction can be deviated and cannot return to the projection light source, which can effectively reduce or even avoid unwanted ghosting images.

[0038] It should be noted that the aforementioned Figure 1 The direction of light transmission in the image shown in Figure 3 is for illustrative purposes only.

[0039] In practice, the first wedge-shaped birefringent crystal includes a first surface and a second surface disposed opposite to each other, and the second wedge-shaped birefringent crystal includes a third surface and a fourth surface disposed opposite to each other; wherein the first surface and the fourth surface are wedge-shaped surfaces, and along the direction from the first wedge-shaped birefringent crystal to the second wedge-shaped birefringent crystal, the image light passes through the first surface, the second surface, the third surface and the fourth surface in sequence, the first surface and the fourth surface are parallel, and the second surface and the third surface are parallel.

[0040] According to another aspect of the present invention, an embodiment of the present invention provides a near-eye display device, which includes: the optical element provided in any of the foregoing embodiments.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this utility model.

Claims

1. An optical device, characterized in that, include: The projection light source, optical isolator, and diffractive waveguide are provided. The projection light source is used to emit image light rays. The diffractive waveguide includes a coupling grating. The image light rays emitted from the projection light source pass through the optical isolator and are then incident on the coupling grating. After being diffracted by the coupling grating, the light rays return to the optical isolator and cannot return to the projection light source.

2. The optical device according to claim 1, characterized in that, The optical isolator includes a first polarizer, an optical rotator, and a second polarizer. The polarization directions of the first polarizer and the second polarizer are at an angle of 45°. The optical rotator is used to rotate the polarization direction of the image light passing through the first polarizer to be consistent with the polarization direction of the second polarizer. The optical rotator is also used to rotate the polarization direction of the image light passing through the second polarizer to be perpendicular to the polarization direction of the first polarizer.

3. The optical device according to claim 2, characterized in that, The polarization direction of the second polarizer is rotated 45° counterclockwise compared to the polarization direction of the first polarizer; the optical rotation element is a magneto-optical element, and the magnetic field direction of the magneto-optical element is along the direction from the first polarizer to the second polarizer, used to rotate the polarization direction of the image light incident on the magneto-optical element counterclockwise by 45°.

4. The optical device according to claim 2, characterized in that, The image light emitted from the projection light source is incident on the optical rotator in a first polarization direction via the first polarizer. After passing through the optical rotator, it is incident on the second polarizer in a second polarization direction, and after passing through the second polarizer, it is incident on the coupling grating. After being diffracted by the coupling grating, it returns to the second polarizer in a second polarization direction, and after passing through the second polarizer, it is incident on the optical rotator in a second polarization direction. After passing through the optical rotator, it is incident on the first polarizer in a third polarization direction. The third polarization direction is perpendicular to the polarization direction of the first polarizer and is cut off by the first polarizer.

5. The optical device according to claim 2, characterized in that, The projection light source is used to emit image light rays that are in a polarized state, and the polarization direction of the image light rays is consistent with the polarization direction of the first polarizer; or, the projection light source is used to emit unpolarized image light rays.

6. The optical device according to claim 1, characterized in that, The optical isolator includes a first wedge-shaped birefringent crystal, an optical rotator, and a second wedge-shaped birefringent crystal. The angle between the optical axes of the first and second wedge-shaped birefringent crystals is 45°. The optical rotator is used to rotate the polarization directions of the ordinary and extraordinary rays emitted from the first wedge-shaped birefringent crystal to be consistent with the polarization directions of the ordinary and extraordinary rays in the second wedge-shaped birefringent crystal. The optical rotator is also used to rotate the polarization directions of the ordinary and extraordinary rays emitted from the first wedge-shaped birefringent crystal to be perpendicular to the polarization directions of the ordinary and extraordinary rays in the first wedge-shaped birefringent crystal.

7. The optical device according to claim 6, characterized in that, The optical axis of the second wedge-shaped birefringent crystal is rotated 45° counterclockwise relative to the optical axis of the first wedge-shaped birefringent crystal; the optical rotation element is a magneto-optical element, and the magnetic field direction of the magneto-optical element is along the direction from the first wedge-shaped birefringent crystal to the second wedge-shaped birefringent crystal, which is used to rotate the polarization direction of the image light incident on the magneto-optical element counterclockwise by 45°.

8. The optical device according to claim 6, characterized in that, The unpolarized image light emitted from the projection light source passes through the first wedge-shaped birefringent crystal and is incident on the optical rotator. After passing through the optical rotator, the polarization direction of the ordinary light is consistent with the polarization direction of the ordinary light in the second wedge-shaped birefringent crystal, and the polarization direction of the extraordinary light is consistent with the polarization direction of the extraordinary light in the second wedge-shaped birefringent crystal. The light then passes through the second wedge-shaped birefringent crystal and is combined into a single beam before being incident on the coupling grating. The image light rays that return to the second wedge-shaped birefringent crystal after being diffracted by the coupled grating, are emitted from the second wedge-shaped birefringent crystal as ordinary and extraordinary rays, and then incident on the optical rotator. After passing through the optical rotator, the polarization direction of the ordinary ray is consistent with the polarization direction of the extraordinary ray in the first wedge-shaped birefringent crystal, and the polarization direction of the extraordinary ray is consistent with the polarization direction of the ordinary ray in the first wedge-shaped birefringent crystal. After being incident on the first wedge-shaped birefringent crystal and passing through the first wedge-shaped birefringent crystal, they continue to be emitted as ordinary and extraordinary rays.

9. The optical device according to claim 6, characterized in that, The first wedge-shaped birefringent crystal includes a first surface and a second surface disposed opposite to each other, and the second wedge-shaped birefringent crystal includes a third surface and a fourth surface disposed opposite to each other; wherein, the first surface and the fourth surface are wedge-shaped surfaces, and along the direction from the first wedge-shaped birefringent crystal to the second wedge-shaped birefringent crystal, the image light passes through the first surface, the second surface, the third surface and the fourth surface in sequence, the first surface and the fourth surface are parallel, and the second surface and the third surface are parallel.

10. A near-eye display device, characterized in that, The near-eye display device is an optical device as described in any one of claims 1-9.

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