Method for improving ghost images of near-eye display and near-eye display

Abstract

The present invention provides a method for improving ghost images in a near-eye display and a near-eye display. The method for improving ghost images in a near-eye display comprises the following steps: Step S1: obtaining a micro-projector, and determining, based on the field of view of the micro-projector, a deflection angle θ required for ghost light reflected by the micro-projector after being incident on an optical waveguide structure to avoid the micro-projector; Step S2: determining, based on the deflection angle θ, the apex angle α of a wedge-shaped prism placed on the light-emitting side of the micro-projector; Step S3: determining, based on the apex angle α of the wedge-shaped prism, the thickness of the wedge-shaped prism, and then obtaining a wedge-shaped prism capable of deflecting the light emitted by the micro-projector by the angle θ. The present invention solves the problem of difficulty in improving ghost images in near-eye displays in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of near-eye display devices, and in particular to a method for improving ghost images of a near-eye display and a near-eye display. Background Art

[0002] With the continuous development and advancement of optical display devices, the field of near-eye displays has gradually attracted public attention. Existing near-eye displays generally consist of a micro-projector and an optical waveguide structure. Light emitted by the micro-projector is transmitted through the optical waveguide structure and ultimately reaches the human eye for image display. The final imaging effect of a near-eye display is crucial to its overall performance. However, currently common near-eye displays suffer from severe ghosting, resulting in poor imaging quality.

[0003] The ghost images of the imaging system in the near-eye display are mainly caused by the reflected light between the imaging lenses and the zero-order reflected light from the grating surface (see Figure 2). Figure 2 There are two common methods to improve ghost images (see attached Figure 3 ): One is to allow as much imaging light as possible to pass through the imaging element and reduce the proportion of reflected light. Generally, an anti-reflection film layer is used to reduce the proportion of reflected light in the imaging system of the micro-projector, but it cannot effectively improve the reflected light of the grating on the surface of the optical waveguide structure; the other is to increase the angle of the reflected light that causes the ghost image, so that it deviates from the imaging element or the ghost image caused by it is not within the imaging observation range. In this way, by tilting the micro-projector (see attached Figure 4 ) is used to adjust the angular relationship between the micro-projector and the optical waveguide structure to deflect the propagation direction of the light reflected from the grating surface so that it does not enter the micro-projector for secondary imaging. This method can effectively improve the ghost image caused by the reflection from the grating surface, but it has the following disadvantages: one is that it affects the overall appearance design of the device; the other is that it increases the difficulty of assembly and testing between the micro-projector and the optical waveguide structure.

[0004] That is to say, the near-eye display in the prior art has the problem of difficulty in improving ghost images. Summary of the Invention

[0005] The main purpose of the present invention is to provide a method for improving ghost images of a near-eye display and a near-eye display, so as to solve the problem of difficulty in improving ghost images in near-eye displays in the prior art.

[0006] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a method for improving ghost images of near-eye displays is provided, comprising the following steps: Step S1: obtaining a micro-projector, and obtaining, based on the field of view angle of the micro-projector, a deflection angle θ required for the micro-projector to avoid ghost light reflected after the micro-projector is incident on an optical waveguide structure; Step S2: obtaining, based on the deflection angle θ, the apex angle α of a wedge-shaped prism placed on the light-emitting side of the micro-projector; Step S3: obtaining, based on the apex angle α of the wedge-shaped prism, the thickness of the wedge-shaped prism, and then obtaining a wedge-shaped prism capable of deflecting the light emitted by the micro-projector at an angle θ.

[0007] Furthermore, the method for improving ghost images of a near-eye display further includes step S4 after step S3: adjusting the position of the wedge prism between the micro-projector and the optical waveguide structure so that the wedge prism can achieve a deflection angle θ.

[0008] Further, in step S4, the light incident surface of the wedge-shaped prism is adjusted to coincide with the exit pupil position of the micro-projector; or the wedge-shaped prism is adjusted to be located between the micro-projector and the exit pupil position of the micro-projector; or the wedge-shaped prism is adjusted to be located between the exit pupil position of the micro-projector and the optical waveguide structure.

[0009] Furthermore, the method for improving the ghost image of the near-eye display also includes a verification step S5 located after step S4, and the verification step S5 includes: step S51: lighting the micro-projector, obtaining the test camera and placing it at the lens-eye distance position, and calculating the first ghost image intensity I0; step S52: removing the wedge prism, restoring the micro-projector and the optical waveguide structure to their initial positions, lighting the micro-projector, placing the test camera at the lens-eye distance position, and calculating the second ghost image intensity I1; step S53: if the first ghost image intensity I0 is less than the second ghost image intensity I1, it proves that the ghost image is weakened.

[0010] Furthermore, in step S2, the field of view FOV of the micro-projector includes a horizontal field of view HFOV and a vertical field of view VFOV, and the deflection angle θ=min[HFOV, VFOV] / 2.

[0011] Furthermore, in step S3 , the deflection angle θ, the refractive index n of the wedge prism, and the apex angle α of the wedge prism satisfy the following relationship: θ=(n−1)*α.

[0012] Furthermore, in step S3 , the refractive index n of the wedge prism is adjusted to be within a range of greater than or equal to 1.3 and less than or equal to 2.1.

[0013] Furthermore, in step S3, the thickness of the wedge prism is adjusted to be within a range of greater than or equal to 0.2 mm and less than or equal to 4 mm.

[0014] According to another aspect of the present invention, a near-eye display is provided. The near-eye display is the above-mentioned near-eye display, and the near-eye display includes a micro-projector and a wedge-shaped prism and an optical waveguide structure arranged in sequence along the light output direction of the micro-projector. The wedge-shaped prism has a vertex angle α. The wedge-shaped prism can deflect the light emitted by the micro-projector, so that the ghost light reflected after passing through the optical waveguide structure avoids the micro-projector.

[0015] Furthermore, the wedge-shaped prism includes a light incident surface, a light emitting surface, a first side surface and a second side surface, one side of the light incident surface is connected to one side of the light emitting surface through the first side surface, and the other side of the light incident surface is connected to the other side of the light emitting surface through the second side surface, the first side surface and the second side surface are arranged in parallel, and the side where the light emitting surface is connected to the second side surface is inclined toward a direction close to the light incident surface, and the angle between the light emitting surface and the second side surface is the apex angle α of the wedge prism.

[0016] By applying the technical solution of the present invention, a method for improving ghost images of near-eye displays includes the following steps: Step S1: obtaining a micro-projector, and obtaining a deflection angle θ required for the micro-projector after the ghost image light reflected by the micro-projector after being incident on the optical waveguide structure is avoided according to the field of view of the micro-projector; Step S2: obtaining the apex angle α of the wedge-shaped prism placed on the light-emitting side of the micro-projector according to the deflection angle θ; Step S3: obtaining the thickness of the wedge-shaped prism according to the apex angle α of the wedge-shaped prism, and then obtaining a wedge-shaped prism that can deflect the light emitted by the micro-projector at the angle θ.

[0017] By adjusting the apex angle α and thickness of the wedge prism to match the deflection angle θ required for the ghost light to avoid the micro-projector, it is beneficial to ensure the accuracy of the ghost light avoiding the micro-projector, and further ensure that the ghost light reflected from the surface of the optical waveguide structure does not enter the micro-projector to participate in secondary imaging to form ghost images, thereby reducing ghost images and ensuring the final imaging quality of the optical waveguide structure. Compared with the method of directly tilting the micro-projector, the present application uses the apex angle α of the wedge prism to determine the deflection angle θ of the light coupled out of the micro-projector. During the module assembly and calibration process, there is no need to adjust the angle and position of the micro-projector, and there is no need to use angled structural parts, which reduces the difficulty of module assembly and testing. At the same time, it ensures that the ID design of the near-eye display is highly flexible and can maintain the relative position relationship between the micro-projector and the optical waveguide structure. In the optical system of the near-eye display, the wedge prism can also be used as a movable element for calibrating the binocular image during the assembly process, reducing the complexity of the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0019] Figure 1A flow chart showing a method for improving ghost images of a near-eye display according to an optional embodiment of the present invention;

[0020] Figure 2 A schematic diagram illustrating sources of ghost images in a near-eye display in the prior art;

[0021] Figure 3 A schematic diagram showing a method for improving ghost images in a near-eye display in the prior art is shown;

[0022] Figure 4 A schematic diagram showing how a near-eye display in the prior art uses a tilted micro-projector to improve ghost images;

[0023] Figure 5 A schematic structural diagram of a near-eye display according to an optional embodiment of the present invention is shown;

[0024] Figure 6 Schematic diagram showing three positions of a wedge-shaped prism in a near-eye display of the present invention;

[0025] Figure 7 A comparison diagram of the optical paths of the near-eye display of the present invention and the prior art is shown;

[0026] Figure 8 FIG. 1 is a state diagram showing the method for improving ghost images of a near-eye display according to the present invention in the verification step S5 .

[0027] The above drawings include the following reference numerals:

[0028] 10. Micro-projector; 11. Exit pupil position; 20. Wedge-shaped prism; 21. Light incident surface; 22. Light exit surface; 23. First side surface; 24. Second side surface; 30. Optical waveguide structure; 31. Waveguide plate; 32. Incoupling grating; 33. Outcoupling grating; 34. Protective glass; 40. Test camera. DETAILED DESCRIPTION

[0029] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0030] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by ordinary technicians in the technical field to which this application belongs.

[0031] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity direction; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above directional words are not used to limit the present invention.

[0032] In order to solve the problem of difficulty in improving ghost images in near-eye displays in the prior art, the present invention provides a method for improving ghost images of a near-eye display and a near-eye display.

[0033] like Figures 1 to 8 As shown, the method for improving the ghost image of the near-eye display includes the following steps: Step S1: obtaining the micro-projector 10, and obtaining the deflection angle θ required for the micro-projector 10 so that the ghost light reflected by the micro-projector 10 after being incident on the optical waveguide structure 30 can avoid the micro-projector 10 according to the field of view of the micro-projector 10; Step S2: obtaining the vertex angle α of the wedge-shaped prism 20 placed on the light-emitting side of the micro-projector 10 according to the deflection angle θ; Step S3: obtaining the thickness of the wedge-shaped prism 20 according to the vertex angle α of the wedge-shaped prism 20, and then obtaining the wedge-shaped prism 20 that can deflect the light emitted by the micro-projector 10 by the angle θ.

[0034] By adjusting the top angle α and thickness of the wedge prism 20 to match the deflection angle θ required for the ghost light to avoid the micro-projector 10, it is beneficial to ensure the accuracy of the ghost light avoiding the micro-projector 10, and further ensure that the ghost light reflected from the surface of the optical waveguide structure 30 will not enter the micro-projector 10 to participate in secondary imaging to form ghost images, thereby reducing ghost images and ensuring the final imaging quality of the optical waveguide structure 30. Compared with the method of directly tilting the micro-projector 10, the present application uses the top angle α of the wedge-shaped prism 20 to determine the deflection angle θ of the light coupled out of the micro-projector 10. During the module assembly and calibration process, there is no need to adjust the angle and position of the micro-projector 10, and there is no need to use angled structural parts, which reduces the difficulty of module assembly and testing. At the same time, it ensures that the ID design of the near-eye display is highly flexible, and the relative position relationship between the micro-projector 10 and the optical waveguide structure 30 can be maintained; in the optical system of the near-eye display, the wedge-shaped prism 20 can also be used as an active element for binocular image calibration during the assembly process, reducing process complexity.

[0035] like Figure 7 As shown, the lines with arrows represent light rays, the solid lines with arrows represent light rays used for imaging, and the dotted lines with arrows represent ghost light rays.

[0036] like Figure 5 and Figure 7As shown, based on the field of view FOV of the micro-projector 10, it is confirmed that the ghost light reflected by the micro-projector 10 after entering the optical waveguide structure 30 can avoid the deflection angle θ required by the micro-projector 10. In step S2, the field of view FOV of the micro-projector 10 includes the field of view angle HFOV in the horizontal direction and the field of view angle VFOV in the vertical direction, and the deflection angle θ = min[HFOV, VFOV] / 2. This setting is conducive to ensuring a high degree of matching between the deflection angle θ and the field of view angle of the micro-projector 10, thereby effectively eliminating ghost images. By utilizing the polarization performance of the wedge prism 20, the out-coupled light of the micro-projector 10 is deflected to a set angle, so that the reflected light on the surface of the coupling-in grating 32 of the optical waveguide structure 30 grazes out of the optical waveguide structure 30 at a certain angle and does not enter the micro-projector 10 to participate in secondary imaging to form ghost images.

[0037] Specifically, based on the size of the angle θ, we can determine the vertex angle α of the wedge prism 20. In step S3, the deflection angle θ, the refractive index n of the wedge prism 20, and the vertex angle α of the wedge prism 20 satisfy the following relationship: θ = (n-1) * α. The wedge prism 20 is then brought into the simulation modeling of the micro-projector 10, and the optimal thickness of the wedge prism 20 is optimized. In step S3, the refractive index n of the wedge prism 20 is adjusted to be within a range of greater than or equal to 1.3 and less than or equal to 2.1. In step S3, the thickness of the wedge prism 20 is adjusted to be within a range of greater than or equal to 0.2 mm and less than or equal to 4 mm. The thickness value of the wedge prism 20 is obtained by optimizing the optical structure parameters of the micro-projector 10. Different micro-projectors 10 need to be used with wedge prisms 20 of different thicknesses. Selecting a wedge prism 20 of appropriate thickness can avoid the addition of the wedge prism 20 affecting the imaging performance of the micro-projector 10, such as adding additional aberrations and chromatic aberrations, and ensure that the addition of the wedge prism 20 only changes the projection angle of the micro-projector 10, but does not guarantee the normal use effect of the micro-projector 10.

[0038] like Figure 6 As shown, the method for improving ghost images in near-eye displays also includes step S4, which is located after step S3: adjusting the position of the wedge prism 20 between the micro-projector 10 and the optical waveguide structure 30 so that the wedge prism 20 can achieve a deflection angle θ. In step S4, the light incident surface 21 of the wedge prism 20 is adjusted to coincide with the exit pupil position 11 of the micro-projector 10; or the wedge prism 20 is adjusted to be between the micro-projector 10 and the exit pupil position 11 of the micro-projector 10; or the wedge prism 20 is adjusted to be between the exit pupil position 11 of the micro-projector 10 and the optical waveguide structure 30. Based on the design requirements of the optical waveguide structure 30, the wedge prism 20 is placed at a position determined after joint optimization simulation of the wedge prism 20 and the micro-projector 10, to avoid disrupting the matching relationship between the exit pupil of the micro-projector 10 and the coupling grating 32 of the optical waveguide structure 30 and introducing new optical aberrations.

[0039] like Figure 6 As shown, the placement of the wedge prism 20 needs to be determined by optimizing the optical structure of the micro-projector through simulation. The position of the wedge prism 20 can be such that the light incident surface 21 of the wedge prism 20 coincides with the exit pupil position 11 of the micro-projector 10; or the wedge prism 20 is located between the last lens of the micro-projector 10 and the exit pupil position 11, in which case the distance between the wedge prism 20 and the last lens of the micro-projector 10 is greater than or equal to 0 mm and less than or equal to 5 mm; or the wedge prism 20 is located between the exit pupil position 11 of the micro-projector 10 and the surface of the optical waveguide structure 30, in which case the distance between the wedge prism 20 and the optical waveguide structure 30 is greater than or equal to 0 mm and less than or equal to 5 mm. Appropriately selecting the placement of the wedge prism 20 can prevent the addition of the wedge prism 20 from affecting the imaging performance of the micro-projector 10, such as adding additional aberrations and chromatic aberrations, and ensure that the addition of the wedge prism 20 only changes the projection angle of the micro-projector 10.

[0040] like Figure 8 As shown, the method for improving ghost images of a near-eye display further includes a verification step S5 located after step S4, and the verification step S5 includes:

[0041] Step S51: Light up the micro-projector 10, obtain the test camera 40 and place it at the designed eye-relief distance, and calculate the first ghost image intensity I0;

[0042] Step S52: Remove the wedge prism 20, restore the micro-projector 10 and the optical waveguide structure 30 to their initial positions, light up the micro-projector 10, place the test camera 40 at the designed eye-relief distance, and calculate the second ghost image intensity I1;

[0043] Step S53: Comparing I0 and I1. If the first ghost intensity I0 is less than the second ghost intensity I1, the ghost image is reduced. This proves that the method can effectively improve the ghost image. At the same time, the difference between I1 and I0 is calculated to determine or monitor the ghost image improvement.

[0044] It should be noted that eye-relief is generally defined in optical design as the distance from the human eye's exit pupil to the outermost lens of the imaging system. When the human eye moves freely within the eye-relief distance, it can observe a complete image. When the position of the human eye exceeds the designed eye-relief, the image observed by the human eye is incomplete. This is why the test camera 40 is placed at the eye-relief position.

[0045] The present invention also provides a near-eye display, which is the above-mentioned near-eye display. The near-eye display includes a micro-projector 10 and a wedge-shaped prism 20 and an optical waveguide structure 30 arranged in sequence along the light-emitting direction of the micro-projector 10. The wedge-shaped prism 20 has a vertex angle α. The wedge-shaped prism 20 can deflect the light emitted by the micro-projector 10, so that the ghost light reflected after passing through the optical waveguide structure 30 avoids the micro-projector 10.

[0046] Specifically, the wedge-shaped prism 20 includes a light incident surface 21, a light emitting surface 22, a first side surface 23 and a second side surface 24. One side of the light incident surface 21 is connected to one side of the light emitting surface 22 through the first side surface 23, and the other side of the light incident surface 21 is connected to the other side of the light emitting surface 22 through the second side surface 24. The first side surface 23 and the second side surface 24 are arranged in parallel, and the side where the light emitting surface 22 is connected to the second side surface 24 is inclined toward a direction close to the light incident surface 21. The angle between the light emitting surface 22 and the second side surface 24 is the apex angle α of the wedge-shaped prism 20.

[0047] Specifically, the optical waveguide structure 30 of the near-eye display includes a waveguide plate 31 and an in-coupling grating 32 and an out-coupling grating 33 spaced apart on the waveguide plate 31. The in-coupling grating 32 and the out-coupling grating 33 are located on the side of the waveguide plate 31 away from the micro-projector 10. The optical waveguide structure 30 also includes a protective glass 34, which covers the surface of the waveguide plate 31 having the in-coupling grating 32 and the out-coupling grating 33. The micro-projector emits collimated light of specific requirements. When this collimated light reaches the wedge-shaped prism 20, due to the angular deflection function of the wedge-shaped prism 20, the collimated light is deflected at a specific angle when it is coupled out of the wedge-shaped prism 20. The deflected projected light is coupled into the in-coupling grating 32 of the optical waveguide structure 30, where it is diffracted. The diffracted light is then transmitted through total internal reflection within the waveguide plate 31 to the out-coupling grating 33. It is then diffracted out of the waveguide plate 31 by the out-coupling grating 33 and projected into the human eye to form a virtual image. The addition of the wedge prism 20 can prevent the projected light of the micro-projector 10 from being reflected by the coupling grating 32 of the optical waveguide structure 30 and re-entering the micro-projector 10 to form a secondary image and a ghost image.

[0048] Obviously, the embodiments described above are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0049] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, tasks, devices, components and / or combinations thereof.

[0050] It should be noted that the terms "first," "second," and the like in the specification and claims of this application and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein.

[0051] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for improving ghost images of a near-eye display, characterized in that: The steps include: Step S1: obtaining a micro-projector (10), and obtaining, based on the field of view angle of the micro-projector (10), a deflection angle θ required for ghost light reflected by the micro-projector (10) after being incident on the optical waveguide structure (30) to avoid the micro-projector (10); Step S2: obtaining the vertex angle α of the wedge prism (20) placed on the light-emitting side of the micro-projector (10) according to the deflection angle θ; the field of view angle FOV of the micro-projector (10) includes a horizontal field of view angle HFOV and a vertical field of view angle VFOV, and the deflection angle θ=min[HFOV, VFOV] / 2; Step S3: The thickness of the wedge-shaped prism (20) is obtained according to the apex angle α of the wedge-shaped prism (20), and then the wedge-shaped prism (20) is obtained that can achieve the deflection angle θ of the light emitted by the micro-projector (10); the deflection angle θ, the refractive index n of the wedge-shaped prism (20), and the apex angle α of the wedge-shaped prism (20) satisfy the following relationship: θ=(n-1)*α.

2. The method for improving ghost images of a near-eye display according to claim 1, wherein: The method for improving ghost images of a near-eye display further includes step S4 after step S3: The position of the wedge-shaped prism (20) between the micro-projector (10) and the optical waveguide structure (30) is adjusted so that the wedge-shaped prism (20) can achieve the deflection angle θ.

3. The method for improving ghost images of a near-eye display according to claim 2, wherein: In step S4, Adjusting the light incident surface (21) of the wedge-shaped prism (20) to coincide with the exit pupil position (11) of the micro-projector (10); or Adjusting the wedge-shaped prism (20) to be located between the micro-projector (10) and the exit pupil position (11) of the micro-projector (10); or The wedge-shaped prism (20) is adjusted to be located between the exit pupil position (11) of the micro-projector (10) and the optical waveguide structure (30).

4. The method for improving ghost images of a near-eye display according to claim 2, wherein: The method for improving ghost images of a near-eye display further includes a verification step S5 after step S4, wherein the verification step S5 includes: Step S51: lighting up the micro-projector (10), acquiring the test camera (40) and placing it at the eyepiece distance, and calculating the first ghost image intensity I0; Step S52: removing the wedge prism (20), restoring the micro-projector (10) and the optical waveguide structure (30) to their initial positions, lighting the micro-projector (10), placing the test camera (40) at the eyepiece distance, and calculating the second ghost image intensity I1; Step S53: If the first ghost image intensity I0 is less than the second ghost image intensity I1, it is proved that the ghost image is reduced.

5. The method for improving ghost images of a near-eye display according to claim 1, wherein: In step S3, the refractive index n of the wedge prism (20) is adjusted to be within a range of greater than or equal to 1.3 and less than or equal to 2.

1.

6. The method for improving ghost images of a near-eye display according to claim 1, wherein: In step S3, the thickness of the wedge prism (20) is adjusted to be within a range of greater than or equal to 0.2 mm and less than or equal to 4 mm.

7. A near-eye display, characterized in that: The near-eye display is the near-eye display according to any one of claims 1 to 6, comprising a micro-projector (10) and a wedge-shaped prism (20) and an optical waveguide structure (30) sequentially arranged along a light-emitting direction of the micro-projector (10), wherein the wedge-shaped prism (20) has a vertex angle α, and the wedge-shaped prism (20) is capable of deflecting light emitted by the micro-projector (10), so that ghost light reflected after passing through the optical waveguide structure (30) avoids the micro-projector (10).

8. The near-eye display according to claim 7, wherein: The wedge-shaped prism (20) comprises a light incident surface (21), a light emitting surface (22), a first side surface (23) and a second side surface (24); one side of the light incident surface (21) is connected to one side of the light emitting surface (22) via the first side surface (23); the other side of the light incident surface (21) is connected to the other side of the light emitting surface (22) via the second side surface (24); the first side surface (23) and the second side surface (24) are arranged in parallel; the side where the light emitting surface (22) is connected to the second side surface (24) is inclined in a direction close to the light incident surface (21); and the angle between the light emitting surface (22) and the second side surface (24) is the vertex angle α of the wedge-shaped prism (20).

Images