Miniature dual-prism projection system for reflective illumination light source and near-eye display device

Abstract

The present application relates to the technical field of near-eye display, in particular to a micro double-prism projection system for reflecting illumination light source and a near-eye display device. The micro double-prism projection system comprises an illumination light source, an image source, a first prism and a second prism, the second prism is arranged between the first prism and the image source; the second prism is used for receiving the illumination light ray output by the illumination light source and reflecting the illumination light ray twice to the image source; the image source forms an image light ray after reflecting the illumination light ray, the image light ray is refracted by the second prism and then enters the first prism, and after twice reflection in the first prism, the image light ray is shot to an exit pupil position. In the present application, the illumination light path and the imaging light path share the second prism, the illumination light ray is shot to the image source after twice reflection by the second prism, the image light ray is refracted by the second prism, then realizes twice reflection by the first prism, and then is shot to the exit pupil position, realizing light path folding and greatly reducing the volume of the projection system.

Description

Technical Field

[0001] This invention relates to the field of near-eye display technology, and more specifically to a miniature biprism projection system and near-eye display device for reflecting illumination sources. Background Technology

[0002] Since the concepts of virtual reality (VR) and augmented reality (AR) were introduced, the market for near-eye display devices based on VR or AR modes has seen significant growth. Among the various hardware implementations of AR or VR technology, near-eye displays (NEDs) are the most effective and provide the best user experience. Because near-eye displays need to be worn on the head, their compact size and excellent display quality are particularly important.

[0003] Waveguide systems are currently the representative of thin and light solutions in near-eye display solutions. The thickness of waveguides is relatively thin, generally within 3mm. Waveguides need to be used in conjunction with projection systems. However, existing projection systems are usually large in size, and the size of the projection system directly restricts the overall size of the display module. Summary of the Invention

[0004] In view of this, embodiments of the present invention provide a miniature biprism projection system and a near-eye display device for reflecting illumination sources, in order to solve the technical problem of large size of projection systems in the prior art.

[0005] The technical solutions provided by the embodiments of the present invention are as follows:

[0006] In a first aspect, the present invention provides a miniature double-prism projection system for reflecting an illumination source. The system includes: an illumination source, an image source, a first prism, and a second prism. The second prism is disposed between the first prism and the image source, and the illumination light path and the imaging light path share the second prism. The second prism includes: a first incident surface, a second incident surface, a first reflecting surface, and a first beam-splitting surface. The four optical surfaces of the first incident surface, the second incident surface, the first reflecting surface, and the first beam-splitting surface intersect at an angle to form an irregular quadrangular prism. The first incident surface of the second prism is used to receive the illumination light output by the illumination source. After being reflected sequentially by the first reflecting surface and the first beam-splitting surface, the illumination light passes through the second incident surface and is directed towards the image source. The image source reflects the illumination light to form image light. The image light is transmitted through the second incident surface and the first beam-splitting surface of the second prism, is directed towards the first prism, and after being reflected twice in the first prism, is directed towards the exit pupil.

[0007] In one alternative implementation, the first incident surface, the second incident surface, the first reflecting surface, and the first beam-splitting surface are connected sequentially.

[0008] In one optional embodiment, the first prism includes: a second beam-splitting surface, a second reflective surface, and an exiting surface; the second beam-splitting surface is disposed close to the first beam-splitting surface, and the exiting surface is disposed close to the exit pupil position; the image light enters the first prism through the second beam-splitting surface; the second reflective surface is used to reflect the light entering the first prism back to the second beam-splitting surface; and the second beam-splitting surface is used to guide the light reflected by the second reflective surface to the exiting surface.

[0009] In one optional embodiment, the center rotation angles of the second incident surface and the second reflecting surface are the same, the exit surface and the second incident surface are symmetrical about the second beam splitter, the first reflecting surface and the second reflecting surface are symmetrical about the second beam splitter, and the angle between the second beam splitter and the aperture stop located at the exit pupil position satisfies a preset angle.

[0010] In one optional embodiment, a polarizing beam splitter and a quarter-wave plate are disposed between the first beam splitter and the second beam splitter, with the polarizing beam splitter disposed close to the first beam splitter and the quarter-wave plate disposed close to the second beam splitter.

[0011] In one optional embodiment, the first incident surface, the second incident surface, and the exit surface are spherical, and the first reflecting surface is a freeform surface.

[0012] In one alternative embodiment, the system further includes a front lens disposed between the second prism and the image source, the front lens comprising a single lens, a positive-negative cemented lens, or a lens group.

[0013] In an alternative embodiment, the system further includes a collimating element and a homogenizing element disposed between the illumination source and the second prism.

[0014] In one alternative implementation, the image source is a non-self-emissive display screen.

[0015] In a second aspect, the present invention provides a near-eye display device, the device comprising a waveguide system and a miniature biprism projection system for reflecting an illumination source as described in the first aspect and any embodiment of the first aspect of the present invention, wherein the coupling end of the waveguide system is disposed at the exit pupil position of the miniature biprism projection system.

[0016] The technical solution of this invention has the following advantages:

[0017] The present invention provides a miniature biprism projection system and near-eye display device for reflecting illumination sources. Illumination light emitted from the illumination source is reflected twice by a second prism before being directed towards an image source. The illumination light is then reflected by the image source to form image light. The image source light passes through the second prism and undergoes two reflections in the first prism before exiting from the exit pupil. This miniature biprism projection system, through the rational arrangement of the optical surfaces of the second and first prisms, allows the illumination and imaging light paths to share the second prism and achieves optical path folding within the prism, significantly reducing the size of the projection system. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a three-dimensional cross-sectional view of a miniature double-prism projection system for reflecting illumination sources in an embodiment of the present invention;

[0020] Figure 2 This is a three-dimensional structural schematic diagram of a miniature double-prism projection system for reflecting illumination sources in an embodiment of the present invention;

[0021] Figure 3 This is a polarization path diagram of a miniature double-prism projection system for reflecting illumination sources in an embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of the imaging optical path of a miniature double-prism projection system for reflecting an illumination source in an embodiment of the present invention;

[0023] Figures 5(a) and 5(b) are image quality evaluation diagrams of the miniature biprism projection system used for reflective illumination light sources in an embodiment of the present invention;

[0024] Figure 6 This is a three-dimensional diagram of the near-eye display device in an embodiment of the present invention. Detailed Implementation

[0025] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0027] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0028] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] Example 1

[0030] This invention provides a miniature biprism projection system for reflecting illumination sources, such as... Figures 1 to 3 As shown, the system includes: an illumination source, an image source, a first prism 102, and a second prism 103. The second prism 103 is disposed between the first prism 102 and the image source; the illumination light path and the imaging light path share the second prism 103. The second prism 103 includes: a first incident surface S1, a second incident surface S4, a first reflecting surface S2, and a first beam-splitting surface S31. The first incident surface S1 of the second prism 103 receives the illumination light output by the illumination source. After being reflected sequentially by the first reflecting surface S2 and the first beam-splitting surface S31, the illumination light passes through the second incident surface S4 and is directed towards the image source. The image source reflects the illumination light to form image light. The image light passes through the second incident surface S4 and the first beam-splitting surface S31 of the second prism 103, is directed towards the first prism 102, and after being reflected twice in the first prism 102, is directed towards the exit pupil. An aperture stop 101 can be set at the exit pupil to precisely define the exit pupil size of the projection system.

[0031] Specifically, the illumination source can be an LED lamp 109 or similar device, and the image source is used for image display, such as a microdisplay 106. When the system is working, the light emitted from the illumination source passes through the second prism 103 and illuminates the image source, providing illumination for the non-self-emissive image on the image source. The illumination light is reflected by the image source to form image light, which then passes through the second prism 103 and the first prism 102 before being output from the exit pupil. In other words, the micro dual-prism projection system provided in this embodiment realizes the function of projecting the non-self-emissive image of the image source onto the projection surface.

[0032] In one optional embodiment, the first incident surface S1, the second incident surface S4, the first reflecting surface S2, and the first beam-splitting surface S31 of the second prism 103 are connected sequentially. By reasonably setting the position and shape of the first incident surface S1, the second incident surface S4, the first reflecting surface S2, and the first beam-splitting surface S31, the transmission optical path of the illumination light in the second prism 103 is cross-folded, thereby reducing the volume of the second prism 103. Specifically, the first beam-splitting surface S31 is located between the first reflecting surface S2 and the first incident surface S1, and the second incident surface S4 is located between the first reflecting surface S2 and the first incident surface S1. The four optical surfaces intersect at an angle to form an irregular quadrangular prism. Furthermore, the positions of the four optical surfaces satisfy the following: the illumination light rays that pass through the first incident surface S1 and are incident on the first reflecting surface S2 are reflected by the first reflecting surface S2 and then incident on the first beam-splitting surface S31 and reflected by the first beam-splitting surface S31. The illumination light rays that are reflected by the first beam-splitting surface S31 pass between the first incident surface S1 and the first reflecting surface S2 and are incident on the second incident surface S4. This achieves the folding of the illumination light path within the second prism 103.

[0033] The miniature double-prism projection system for reflecting illumination sources provided in this embodiment illuminates the image source after being reflected twice by the second prism. The illumination light is then reflected by the image source to form image light. The image light passes through the second prism and is reflected twice in the first prism before exiting from the exit pupil, thus achieving light path folding and greatly reducing the size of the projection system.

[0034] In one alternative implementation, such as Figure 3As shown, the first prism 102 includes a second beam-splitting surface S32, a second reflecting surface S5, and an exiting surface S6 arranged sequentially. The second beam-splitting surface S32 is positioned close to the first beam-splitting surface S31, and the second beam-splitting surface S32 and the first beam-splitting surface S31 have the same surface shape, preferably planar; the exiting surface S6 is positioned close to the exit pupil. The illumination light enters the first prism 102 through the second beam-splitting surface S32, and the second reflecting surface S5 reflects the light entering the first prism back to the second beam-splitting surface S32. The second beam-splitting surface S32 guides the light reflected by the second reflecting surface S5 to the exiting surface S6. Specifically, the illumination light output from the illumination source shines on the image source after passing through the second prism. After being reflected by the image source, it forms image light. The image light is transmitted through the second prism and the second beam-splitting surface S32 of the first prism and enters the first prism. The image light entering the first prism is reflected by the second reflecting surface to the second beam-splitting surface S32, and after being reflected by the second beam-splitting surface S32, it exits from the exit pupil position through the exit surface.

[0035] In one optional embodiment, to achieve a compact design for the first and second prisms and to accommodate the folding of the illumination and image light paths, the center rotation angles of the second incident surface S4 and the second reflecting surface S5 are the same. The exit surface S6 and the second incident surface S4 are symmetrical about the second beam-splitting surface S32, and the first reflecting surface S2 and the second reflecting surface S5 are symmetrical about the second beam-splitting surface S32. The angle between the second beam-splitting surface S32 and the aperture stop 101 located at the exit pupil position satisfies a preset angle. The consistent center rotation angles mean that the rotation angles of the second incident surface and the second reflecting surface relative to the projection system coordinate system are the same, i.e., the central principal planes of the second incident surface and the second reflecting surface are parallel to each other. Furthermore, the symmetry of the exit surface and the second incident surface about the second beam-splitting surface S32, and the symmetry of the first reflecting surface and the second reflecting surface about the second beam-splitting surface S32, can be approximately symmetrical in actual configuration. Additionally, the angle between the second beam-splitting surface S32 and the aperture stop can be between 50° and 60°, thereby enabling the first and second prisms to form a five-faceted biprism system. In practical applications, the angle between the second beam splitter S32 and the aperture can be 55°.

[0036] It should be noted that the second beam-splitting surface S32 of the first prism 102 and the first beam-splitting surface S31 of the second prism 103 are adjacent surfaces of the two prisms. Since the two surfaces have the same shape and are fitted together, it can be understood that the second beam-splitting surface S32 of the first prism 102 and the first beam-splitting surface S31 of the second prism are approximately coincident. Therefore, the exit surface S6 and the second incident surface S4 are also symmetrical about the first beam-splitting surface S31, the first reflecting surface S2 and the second reflecting surface S5 are also symmetrical about the first beam-splitting surface S31, and the angle between the first beam-splitting surface S31 and the aperture stop 101 set at the exit pupil position also satisfies the above-mentioned preset angle.

[0037] By setting the surfaces of the first and second prisms in this manner, the entire system can be quickly assembled.

[0038] In one optional embodiment, a polarizing beam splitter (PBS) film and a quarter-wave plate (QWP) film are disposed between the first beam splitter surface S31 and the second beam splitter surface S32. The polarizing beam splitter film is disposed closer to the first beam splitter surface S31, and the quarter-wave plate film is disposed closer to the second beam splitter surface S32. The QWP film can change the polarization state of light, and the PBS film can achieve the reflection of a first polarized light and the transmission of a second polarized light. The first polarized light can be either P-polarized light or S-polarized light. The following explanation uses the example of the PBS film achieving the reflection of S-polarized light and the transmission of P-polarized light.

[0039] Specifically, such as Figure 3As shown, when the illumination light (which is S-polarized light) from the illumination source enters the second prism 103 and is reflected by the first reflecting surface S2 to the first beam-splitting surface S31, the PBS film can reflect the light. The reflected light then illuminates the image source through the second incident surface S4. The image source uses liquid crystal display technology (Liquid Crystal). In non-self-emissive displays such as onSilicon (LCOS), when light shines on the image source, the image source changes the polarization direction of the linearly polarized light while reflecting the light. Thus, after reflection by the image source, the S-polarized light is converted into P-polarized light and re-enters the second prism 103. At this time, the P-polarized light can pass through the PBS film on one side of the first beam splitter S31. Then, when passing through the QWP film, the polarization state is changed, that is, from P-polarized light to right-hand circularly polarized light or left-hand circularly polarized light (the direction of left-hand or right-hand rotation is related to the angle of QWP adhesion) and enters the first prism 102. The circularly polarized light entering the first prism is reflected by the second reflecting surface S5 and the rotation direction is changed again. After the reflected circularly polarized light shines on the second beam splitter S32, it passes through the QWP film and the polarization state becomes S-polarized light. The S-polarized light is reflected by the PBS film to the exit surface S6 and exits from the exit pupil position.

[0040] In one optional embodiment, the first incident surface S1, the second incident surface S4, the second reflecting surface S5, and the exit surface S6 are spherical surfaces, the first beam-splitting surface S31 and the second beam-splitting surface S32 are planar surfaces, and the first reflecting surface S2 is a freeform reflecting surface. Specifically, except for the beam-splitting surface of the film, the first reflecting surface, and the second reflecting surface, all other surfaces can be transmissive surfaces, and their surface shape can be spherical.

[0041] In one alternative implementation, such as Figures 1 to 3 As shown, the system further includes a front lens, disposed between the second prism 103 and the image source, wherein the illumination optical path and the imaging optical path share the second prism 103 and the front lens. The front lens may be a single lens, a positive-negative cemented lens, or a lens group. Figure 1 In the embodiment shown, the front lens includes a positive-negative cemented lens consisting of a first lens 104 and a second lens 105. The first lens 104 and the second lens 105 are made of glass with different refractive indices and are cemented together to eliminate chromatic aberration.

[0042] The system further includes a collimating element and a light-diffusing element, disposed between the illumination source and the second prism. The collimating element may be a total internal reflection lens 108, and the light-diffusing element may be a compound eye array 107.

[0043] Specifically, a total internal reflection lens 108 and a compound eye array 107 are arranged between the illumination source and the first incident surface S1 of the second prism 103. The total internal reflection lens is used to collimate the beam output from the illumination source, and the compound eye array is used to achieve uniform illumination of the beam. Meanwhile, to ensure that the light input to the second prism 103 is S-polarized light, the illumination source can be a polarized light source, or a polarizing element can be arranged between the illumination source and the second prism to make the beam output from the illumination source S-polarized light.

[0044] Example 2

[0045] This embodiment provides a miniature double-prism projection system for reflecting illumination sources, such as... Figures 1 to 3 As shown, the system includes a microdisplay 106, an LED lamp 109, an aperture 101, a first prism 102, a second prism 103, a first lens 104 of a cemented doublet lens group, a second lens 105 of a cemented doublet lens group, a compound eye array 107, and a total internal reflection lens 108. The second prism includes a first incident surface S1, a second incident surface S4, a first reflecting surface S2, and a first beam-splitting surface S31 connected in sequence; the first prism includes a second beam-splitting surface S32, a second reflecting surface S5, and an exit surface S6 arranged in sequence. The microdisplay 106 is a non-self-emissive display screen such as Liquid Crystal on Silicon (LCOS). This projection system includes an illumination light path and an imaging light path. The illumination optical path includes an LED lamp 109, a compound eye array 107, a total internal reflection lens 108, a second prism 103, and a cemented doublet lens group, while the imaging optical path includes a microdisplay 106, a cemented doublet lens group, a second prism 103, and a first prism 102.

[0046] In practical applications, this projection system operates according to the following process:

[0047] The LED lamp 109 emits illumination light, which is collimated by the total internal reflection lens 108 and homogenized by the compound eye array 107. The light then enters the second prism 103 through the first incident surface S1. The light entering the second prism 103 is S-polarized light. The polarizing element can be located at the first incident surface S1 or at any position before reaching the first incident surface S1. In this embodiment, the polarizing element is located on the light-emitting surface of the total internal reflection lens 108. After entering the second prism, the illumination light is reflected by the first reflecting surface S2 and then incident on the first beam splitting surface S31. A PBS film and a QWP film are disposed between the first beam splitting surface S31 and the second beam splitting surface S32. The PBS film is attached to the second prism side, and the QWP film is attached to the first prism side. The function of the PBS film is to reflect S-polarized light and transmit P-polarized light. Therefore, the illumination light is reflected by the first beam splitting surface S31, then exits through the second incident surface S4, passes through the doublet lens group, and is directed towards the microdisplay 106. The illumination light is reflected by the microdisplay 106 to form the image light. The image light passes through the doublet lens group again and enters the second prism from the second incident surface S4. For the LCOS display screen, the pixel image with imaging information can rotate the polarization state of the incident light by 90°. At this time, the polarization state of the light is P-polarized light. When it is incident on the first beam splitter S31, according to the functional characteristics of the PBS, the image light passes through the PBS film and becomes right-handed or left-handed circularly polarized light after passing through the QWP. The direction of rotation is related to the angle of the QWP. After the circularly polarized light is reflected by the second reflecting surface S5, the rotation direction changes to left-handed or right-handed circularly polarized light, which is opposite to the rotation direction of the polarization state before reflection. When the opposite polarization state is incident on the QWP of the beam splitter again, the polarization state becomes S-polarized light. At this time, according to the functional characteristics of the PBS, the image light is reflected and exits from the exit surface S6 of the first prism and exits from the exit pupil.

[0048] Specifically, when the projection system operates according to the above workflow, for the illumination light path, after the light is reflected by the first reflecting surface S2, it is reflected again by the first beam-splitting surface S31. Since the surface of the first beam-splitting surface S31 is covered with a PBS film, there are certain requirements for the incident angle of the light. By optimizing the surface shape of the first reflecting surface S2, the incident angle of the light on the PBS film can be controlled. In this embodiment, the incident angle range of the principal rays at the center of each field of view on the PBS film is 30-35°. This angle range is relatively small, and the illumination light has higher reflection efficiency, which can improve the light efficiency and brightness uniformity. Among them, each field of view in the principal rays at the center of each field of view represents a different angle of light emission. Since the system has a certain pupil size, the light emitted from each angle is not a simple line but a cylinder. The central principal ray refers to the center position of this cylinder.

[0049] like Figure 4The diagram shows the design of the imaging optical path. In this embodiment, the imaging optical path adopts a coaxial system. The design concept is a reverse design, that is, it is assumed that the light rays are emitted from the exit pupil and incident on the microdisplay 106 in the reverse direction along the imaging optical path. This helps to perform image quality analysis within the field of view. In the imaging optical path design, the optically effective surfaces are the second beam-splitting surface S32, the second reflecting surface S5, and the exit surface S6 of the first prism 102; the second incident surface S4 and the first beam-splitting surface S31 of the second prism 103; and the first surface S7, the second surface S8, and the third surface S9 of the two lenses in the positive-negative cemented doublet lens group. According to this imaging optical path, the incident angle of the main ray on the microdisplay 106 can be effectively controlled. At this time, the incident angle of the field rays at the center of each field of view on the microdisplay 106 is less than 0.5°, and the brightness uniformity is good. The relevant parameters of the optically effective surfaces are shown in Table 1 below:

[0050] Table 1 Parameters of each optical surface in the imaging optical path

[0051]

[0052] Since the illumination optical path generally does not have imaging quality design requirements, in addition to the parameter data in Table 1 above, for the first incident surface S1 and the first reflecting surface S2, the first incident surface S1 is a sphere with a radius of curvature of 25.676, and the first reflecting surface S2 is a freeform reflecting surface, where the freeform surface parameters satisfy the following equations.

[0053]

[0054] In the formula, c is the reciprocal of the radius of curvature, r is the radial distance from a point on the surface, k is the quadratic surface constant, and C j These are the polynomial coefficients.

[0055] The Y-radius of the first reflecting surface S2 is 19.4119, k is 0, and C... j The polynomial coefficients are shown in Table 2 below:

[0056] Table 2. Coefficients of the freeform surface expression for the first reflecting surface S2

[0057]

[0058]

[0059] Based on the projection system structure and related parameters, the overall optical parameters of the projection system are shown in Table 3 below:

[0060] Table 3 System parameters of the projection system

[0061] parameter numerical values Remark Field of view 40° diagonal field of view focal length 9.07mm Exit pupil diameter 3.6mm Exit pupil distance 0.3mm Three-dimensional volume parameters 16mm*11mm*7mm

[0062] In addition, the image quality of the imaging optical path in the projection system can be evaluated. Figures 5(a) and 5(b) show the image quality evaluation diagrams of the imaging optical path. Figure 5(a) is the MTF (Modulation Transfer Function) diagram, where the horizontal axis is the spatial frequency in line pairs per millimeter (lp / mm) and the vertical axis is the modulation transfer function. It can be seen from Figure 5(a) that the MTF is >0.4 at 120 lp / mm, indicating good imaging quality. Figure 5(b) is the distortion diagram, where the horizontal axis is the horizontal FOV (field of view) and the vertical axis is the vertical FOV. It can be seen from Figure 5(b) that the overall optical distortion is less than 3%.

[0063] Example 3

[0064] This embodiment also provides a near-eye display device, which includes a waveguide system and the miniature biprism projection system for reflecting illumination light sources described in the above embodiment. The coupling end of the waveguide system is located at the exit pupil position of the miniature biprism projection system, and an aperture stop 101 is provided at the coupling end. Wherein, as... Figure 6 The image shown is a 3D diagram of a near-eye display device, where 201 is a miniature dual-prism projection system and 202 is a waveguide system. In this embodiment, the waveguide system can be a waveguide element with pupil expansion function, such as an array waveguide, a holographic waveguide, or an embossed grating waveguide.

[0065] The micro projection system and near-eye display device provided by the present invention share a second prism (and a front lens) for the imaging optical path and the illumination optical path, and the first prism and the second prism share a surface with a beam splitting function. The overall system uses two reflective surfaces and two beam splitting surfaces to fold the optical path, which greatly reduces the size of the projection system.

[0066] While exemplary embodiments and their advantages have been described in detail, those skilled in the art can make various changes, substitutions, and modifications to these embodiments without departing from the spirit of the invention and the scope of protection defined by the appended claims. Such modifications and variations all fall within the scope defined by the appended claims. For other examples, those skilled in the art should readily understand that the order of process steps can be changed while remaining within the scope of the invention.

[0067] Furthermore, the scope of this invention is not limited to the processes, mechanisms, manufacturing methods, material compositions, means, methods, and steps of the specific embodiments described in the specification. From the disclosure of this invention, those skilled in the art will readily understand that any existing or future processes, mechanisms, manufacturing methods, material compositions, means, methods, or steps that perform substantially the same function or obtain substantially the same results as the corresponding embodiments described in this invention can be applied according to this invention. Therefore, the appended claims are intended to include these processes, mechanisms, manufacturing methods, material compositions, means, methods, or steps within their scope of protection.

Claims

1. A miniature biprism projection system for reflecting illumination sources, characterized in that, The system includes: an illumination source, an image source, a first prism, and a second prism; The second prism is disposed between the first prism and the image source. The illumination optical path and the imaging optical path share the second prism. The second prism includes: a first incident surface facing the illumination source, a second incident surface facing the image source, a first reflecting surface and a first beam splitting surface. The first incident surface, the second incident surface, the first reflecting surface and the first beam splitting surface are connected in sequence. The four optical surfaces of the first incident surface, the second incident surface, the first reflecting surface and the first beam splitting surface are inclined and intersected to form an irregular quadrangular prism. The first incident surface of the second prism is used to receive the illumination light output by the illumination source. After being reflected by the first reflecting surface and the first beam splitting surface in sequence, the illumination light passes through the second incident surface and is directed towards the image source. The image source reflects the illumination light to form image light, which is transmitted through the second incident surface and the first beam splitting surface of the second prism, and then shines on the first prism. After being reflected twice in the first prism, it shines on the exit pupil. The first prism includes: a second beam-splitting surface, a second reflecting surface, and an exiting surface; The second beam-splitting surface is positioned close to the first beam-splitting surface, and the exit surface is positioned close to the exit pupil. The image light enters the first prism through the second beam-splitting surface. The second reflective surface is used to reflect the light entering the first prism back to the second beam-splitting surface, and the second beam-splitting surface is used to guide the light reflected by the second reflective surface to the exit surface. The exit surface and the second incident surface are symmetrical about the first beam-splitting surface, and the first reflecting surface and the second reflecting surface are symmetrical about the first beam-splitting surface.

2. The miniature biprism projection system for reflecting illumination sources according to claim 1, characterized in that, The center rotation angles of the second incident surface and the second reflecting surface are the same. The exit surface and the second incident surface are symmetrical about the second beam splitter. The first reflecting surface and the second reflecting surface are symmetrical about the second beam splitter. The angle between the second beam splitter and the aperture stop located at the exit pupil position satisfies a preset angle.

3. The miniature biprism projection system for reflecting illumination sources according to claim 1, characterized in that, A polarizing beam splitter and a quarter-wave plate are disposed between the first beam splitter and the second beam splitter, with the polarizing beam splitter disposed close to the first beam splitter and the quarter-wave plate disposed close to the second beam splitter.

4. The miniature biprism projection system for reflecting illumination sources according to claim 1, characterized in that, The first incident surface, the second incident surface, and the exit surface are all spherical, and the first reflecting surface is a freeform surface.

5. The miniature biprism projection system for reflecting illumination sources according to claim 1, characterized in that, The system further includes a front lens disposed between the second prism and the image source, the front lens comprising a single lens, a positive-negative cemented lens, or a lens group.

6. The miniature biprism projection system for reflecting illumination sources according to claim 1, characterized in that, The system further includes a collimating element and a light-diffusing element, disposed between the illumination source and the second prism.

7. The miniature biprism projection system for reflecting illumination sources according to claim 1, characterized in that, The image source is a non-self-emissive display screen.

8. A near-eye display device, characterized in that, The device includes a waveguide system and a miniature biprism projection system for reflecting an illumination source as described in any one of claims 1-7, wherein the coupling end of the waveguide system is disposed at the exit pupil position of the miniature biprism projection system.

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