An optical system

Abstract

The present application belongs to the field of optical imaging, and particularly relates to an optical system, comprising: a light source emitting light; a first prism oppositely arranged with the light source, the light emitted by the light source entering the first prism through a first optical surface; being incident to a second optical surface and being reflected on a total reflection film; being incident to a third optical surface and being reflected on the total reflection film; being emitted out of the first prism through a fourth optical surface; the first optical surface, the second optical surface, the third optical surface and the fourth optical surface are curved surfaces protruding outwardly away from the center of the first prism; the light enters a second prism after passing through the first prism; the light passes through the first optical surface, is incident to the second optical surface with an incident angle greater than arctan(1 / n), and is reflected on the second optical surface; is emitted to the third optical surface, is reflected by a light splitting film or a reflecting film, is incident to the second optical surface again, passes through the second optical surface and is emitted to an exit pupil, and forms a final image with a focal surface depth greater than 0.1 m.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging, and more specifically relates to an optical system. Background Technology

[0002] In recent years, with the rapid development of wearable display technologies such as augmented reality (AR) and virtual reality (VR), the demand for lightweight, thin, and wide-field-of-view visual optical systems has become increasingly urgent. Freeform surface optical elements, due to their asymmetry and high degree of design freedom, have become one of the key technologies for realizing compact optical systems. In existing technologies, visual optical systems based on freeform surface prisms often compress volume through optical path folding. However, constrained by traditional curved surface designs, the system focal length is relatively long, making it difficult to achieve a large field of view (e.g., a horizontal field of view ≥30°) on small-sized display screens. Furthermore, the long focal length design increases the axial dimensions of the optical system, contradicting the requirements of wearable devices for lightweight and miniaturization.

[0003] To address these issues, some solutions attempt to improve performance by increasing the number of optical elements or using complex curved surfaces. However, such designs not only significantly increase the difficulty of fabrication and assembly but may also lead to reduced system luminous efficiency and increased costs. For example, while using a combination of multiple spherical or aspherical lenses can shorten the focal length, it is difficult to balance aberration correction and volume control. On the other hand, while traditional single freeform prism systems can simplify the structure, their insufficient optical path unfolding length limits further improvement in the field of view.

[0004] Therefore, there is an urgent need for an optical system solution that can balance short focal length, large field of view, miniaturization, and manufacturing feasibility to meet the needs of wearable devices for high-performance visual optical systems. Summary of the Invention

[0005] The present invention is proposed based on the above-mentioned needs of the prior art. The technical problem to be solved by the present invention is to provide an optical system to improve performance.

[0006] To address the above problems, the technical solution provided by this invention includes:

[0007] An optical system is provided, comprising: a light source emitting light; a first prism disposed opposite to the light source, the first prism comprising: a first optical surface disposed opposite to the light source, wherein light emitted from the light source passes through the first optical surface and enters the first prism; a second optical surface disposed opposite to the first optical surface, wherein a total reflection film is disposed on the second optical surface, wherein light passing through the first optical surface is incident on the second optical surface and reflected on the total reflection film; a third optical surface disposed opposite to the second optical surface, wherein a total reflection film is disposed on the third optical surface, wherein light reflected from the second optical surface is incident on the third optical surface and reflected on the total reflection film; and a fourth optical surface disposed opposite to the third optical surface, wherein light reflected from the third optical surface exits onto the fourth optical surface and passes through the fourth optical surface and exits outside the first prism; wherein the first, second, third, and fourth optical surfaces are curved surfaces protruding outward from the center of the first prism; and a second prism disposed opposite to the first prism. The second prism is configured with mirrors facing each other. It includes: a first optical surface, positioned opposite to a fourth optical surface, through which light rays exiting the first prism enter the second prism. The first optical surface is a curved surface that is concave inwards towards the center of the second prism. A second optical surface, positioned opposite to the first optical surface, through which light rays passing through the first optical surface are incident at an angle greater than arctan(1 / n). The light rays are reflected on the second optical surface, where n is the refractive index of the second prism at 586 nm. The second optical surface is a curved surface that is concave inwards towards the center of the second prism. A third optical surface, positioned opposite to the second optical surface, has a beam-splitting film or a reflective film. Light rays reflected from the second optical surface exit the third optical surface, are reflected by the beam-splitting film or reflective film, and then re-enter the second optical surface, passing through it and exiting through the exit pupil to form a final image with a focal depth greater than 0.1 m. The third optical surface is a curved surface that protrudes outwards towards the center of the second prism.

[0008] By employing a freeform prism structure with a total reflection film and a beam splitter, combined with an optical path folding design, the system focal length is shortened, achieving a large field of view (diagonal field of view ≥35°) while significantly reducing the system size. The configuration of the total reflection film and the beam splitter optimizes the light transmission path, ensuring efficient coupling of light to the human eye to form a virtual image with a focal plane depth greater than 1 meter, meeting the application requirements of lightweight and wearable devices.

[0009] Preferably, when a beam-splitting film is disposed on the third optical surface, the optical system further includes a third prism, wherein one surface of the third prism is complementary to the third optical surface and is disposed in close contact.

[0010] By adding a third prism to the third optical surface and combining it with a beam splitter, the system's perspective function is enhanced, allowing external light to merge with the display light path to achieve augmented reality (AR) effects while maintaining the clarity and contrast of the displayed content.

[0011] Preferably, the spectral ratio of the spectral film is 1:1.

[0012] The beam splitter uses a 1:1 beam splitting ratio to balance the energy distribution of transmitted and reflected light, ensuring uniformity of brightness in the displayed image, reducing light energy loss, and improving the system's optical efficiency.

[0013] Preferably, a coordinate system is formed with the exit pupil center as the origin O, the direction towards the second prism and coinciding with the optical axis as the Z-axis, the direction perpendicular to the Z-axis and upward as the Y-axis, and the direction perpendicular to the ZOY plane as the X-axis. The distance between the first optical surface and the origin O ranges from 18.8 mm to 22.8 mm, the Y-axis eccentricity ranges from 8 mm to 14 mm, and the tilt angle with the XOY plane ranges from 46° to 56°. The distance between the second optical surface and the origin O ranges from 14 mm to 19 mm, the Y-axis eccentricity ranges from 1 mm to 5 mm, and the tilt angle with the XOY plane ranges from ±5°. The distance between the third optical surface and the origin O ranges from 20 mm to 24 mm, the Y-axis eccentricity ranges from -2 mm to +2 mm, and the tilt angle with the XOY plane ranges from -32° to -22°.

[0014] By limiting the position, eccentricity range, and tilt angle of each optical surface of the second prism in the coordinate system, the propagation path of light can be precisely controlled, effectively correcting off-axis aberrations (such as coma and astigmatism), improving imaging quality, and ensuring the compactness of the system structure.

[0015] Preferably, the Z-eccentricity range of the first optical surface is 25mm to 31mm, the Y-eccentricity range is 19mm to 26mm, and the tilt angle with respect to the XOY plane is -46° to -36°; the Z-eccentricity range of the second optical surface is 18mm to 25mm, the Y-eccentricity range is 17mm to 25mm, and the tilt angle with respect to the XOY plane is -16° to -6°; the Z-eccentricity range of the third optical surface is 25mm to 31mm, the Y-eccentricity range is 19mm to 26mm, and the tilt angle with respect to the XOY plane is 27° to 37°; the Z-eccentricity range of the fourth optical surface is 20mm to 26mm, the Y-eccentricity range is 12mm to 18mm, and the tilt angle with respect to the XOY plane is 45° to 55°.

[0016] Further define the geometric parameters of each optical surface of the first prism, optimize the optical path folding design, reduce stray light interference, reduce system distortion (e.g., optical distortion <8%), and ensure the stability and sharpness of the virtual image surface.

[0017] Preferably, the Z-eccentricity range of the light-emitting surface of the light source is 29mm to 36mm, the Y-eccentricity range is 12mm to 18mm, and the tilt angle with the XOY plane is -27° to -18°.

[0018] The position parameters of the light-emitting surface of the light source (Z / Y eccentricity and tilt angle) are designed to match the prism optical path to avoid the incident angle of light deviating from the design range, thereby improving the light energy utilization rate and suppressing the generation of ghost images.

[0019] Preferably, the focal length of the first prism and the second prism is no greater than 13mm, and the focal depth of the final image is in the range of 100mm to 100000mm.

[0020] By limiting the prism focal length to ≤13mm and combining it with the focal plane depth range (100mm~100000mm), the system combines short focal length characteristics with adjustable virtual image depth, making it suitable for diverse scenarios such as near-eye displays and AR / VR.

[0021] Preferably, when viewed from the exit pupil position, the diagonal field of view of the optical system is not less than 35°; wherein the horizontal field of view should be at least greater than 30°; and the exit pupil diameter of the system should be not less than 7 mm.

[0022] The design with a diagonal field of view ≥35° and a horizontal field of view ≥30° expands the user's field of vision and enhances the sense of immersion; the exit pupil diameter ≥7mm adapts to different users' interpupillary distances and enhances wearing comfort.

[0023] Preferably, the first optical surface, the second optical surface, and the third optical surface are all aspherical, and the material of the second prism is moldable low-melting-point glass or injection-molded optical resin material.

[0024] The second prism uses an aspherical optical surface and low-melting-point glass / optical resin material, which simplifies the manufacturing process (such as molding or injection molding), reduces production costs, and ensures the accuracy of the optical surface shape and the stability of the system.

[0025] Preferably, the first optical surface, the second optical surface, the third optical surface and the fourth optical surface are all aspherical, and the material of the first prism is moldable low-melting-point glass or injection-molded optical resin material.

[0026] The aspherical design and low-cost material selection of the first prism further reduce system complexity and manufacturing costs, while the freeform surface correction of off-axis aberrations achieves a balance between high performance and lightweight design.

[0027] Compared with existing technologies, this invention shortens the focal length by arranging the four optical surfaces of the first prism to protrude away from the prism center. Simultaneously, a reflective or beam-splitting film is attached to the first prism to shorten the system's focal length through optical path folding, thereby increasing the field of view while reducing the overall size. Furthermore, by establishing a coordinate system to clarify the relative positions of each optical element and surface, off-axis aberrations are effectively corrected, improving image quality, reducing stray light interference, and minimizing system distortion, thus meeting user needs as much as possible. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of this specification. For those skilled in the art, other drawings can be obtained based on these drawings.

[0029] Figure 1 This is a schematic diagram of the optical path structure of the optical system in an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of light transmission during viewing by a viewer in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the optical system in the coordinate system according to an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram showing the angle of incidence when light enters the second prism from the first prism in an embodiment of the present invention;

[0033] Figure 5 This is a partial structural diagram of the third prism and the second prism in an embodiment of the present invention;

[0034] Figure 6 This is a schematic diagram of an optical system according to one embodiment of the present invention;

[0035] Figure 7 This is a schematic diagram of the sampling field-of-view MTF curve of an optical system under one embodiment of the present invention;

[0036] Figure 8 This is a schematic diagram of the distortion grid of an optical system under one embodiment of the present invention;

[0037] Figure 9 This is a schematic diagram of an optical system according to another embodiment of the present invention;

[0038] Figure 10 This is a schematic diagram of the sampling field-of-view MTF curve of the optical system under another embodiment of the present invention;

[0039] Figure 11 This is a schematic diagram of the distortion grid of an optical system under another embodiment of the present invention.

[0040] Figure label:

[0041] 1. Light source; 2. First prism; 3. Second prism; 4. First optical surface; 5. Second optical surface; 6. Third optical surface; 7. Fourth optical surface; 8. First optical surface; 9. Second optical surface; 10. Third optical surface; 11. Exit pupil; 12. Flat panel display; 13. Flat glass; 14. Third prism. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. 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.

[0043] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the term "connected" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral connection; it can refer to a mechanical connection or an electrical connection; it can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the present invention according to the specific circumstances.

[0044] Throughout the text, the terms “top,” “bottom,” “above,” “below,” and “on top” refer to the relative positions of components of the device, such as the relative positions of the top and bottom substrates within the device. It is understood that the device is multifunctional and independent of its spatial orientation.

[0045] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. These embodiments do not constitute a limitation on the embodiments of the present invention.

[0046] This embodiment provides an optical system, such as Figures 1-3 As shown.

[0047] The optical system includes a light source 1, a first prism 2, and a second prism 3.

[0048] Light source 1 emits light to serve as the light source for the optical system.

[0049] Furthermore, the light source 1 includes a flat panel display 12 and a flat glass 13, with the flat glass 13 positioned in front of the flat panel display 12 to protect the light-emitting surface from damage.

[0050] A first prism 2 is disposed opposite to the light source 1. The first prism 2 includes a first optical surface 4, a second optical surface 5, a third optical surface 6, and a fourth optical surface 7. The first optical surface 4, the second optical surface 5, the third optical surface 6, and the fourth optical surface 7 are curved surfaces that protrude outwards from the center of the first prism 2, thereby effectively shortening the focal length and increasing the field of view.

[0051] The first optical surface 4 is positioned opposite to the light source 1, and the light emitted by the light source 1 is transmitted through the first optical surface 4 and enters the first prism 2.

[0052] The second optical surface 5 is disposed opposite to the first optical surface 4, and a total reflection film is disposed on the second optical surface 5, so that light incident on the second optical surface 5 is reflected on the surface. Light transmitted through the first optical surface 4 is emitted towards the second optical surface 5 and reflected by the total reflection film.

[0053] The third optical surface 6 is disposed opposite to the second optical surface 5, and a total reflection film is also disposed on the third optical surface 6 to reflect light incident on the third optical surface 6. Light reflected by the second optical surface 5 is incident on the third optical surface 6 and emitted under the action of the total reflection film.

[0054] The fourth optical surface 7 is positioned opposite to the third optical surface 6. Light reflected from the third optical surface 6 is projected through the fourth optical surface 7 and output to the outside of the first prism 2.

[0055] Since this optical system is an off-axis system, all the aforementioned surfaces are described using freeform surfaces to correct off-axis aberrations. To reduce the manufacturing difficulty of the system, the material of the first prism 2 can be moldable low-melting-point glass or injection-molded optical resin.

[0056] The second prism 3 is disposed opposite to the first prism 2. The second prism 3 includes a first optical surface 8, a second optical surface 9, and a third optical surface 10. The first optical surface 8 and the second optical surface 9 are curved surfaces that are concave inward toward the center of the second prism 3, and the third optical surface 10 is a curved surface that protrudes outward toward the center of the second prism 3, so as to correct aberrations to a certain extent.

[0057] The first optical surface 8 is positioned opposite to the fourth optical surface 7. Light rays projected through the fourth optical surface 7 will be incident on the first optical surface 8 and then enter the second prism 3.

[0058] The second optical surface 9 is positioned opposite the first optical surface 8. Light rays passing through the first optical surface 8 are incident on the second optical surface 9 at an angle that satisfies the condition for total internal reflection, such as... Figure 4 As shown, the incident angle is greater than arctan(1 / n), causing the light to be reflected on the second optical surface 9, where n is the refractive index of the second prism 3 under 586nm light.

[0059] The third optical surface 10 is disposed opposite to the second optical surface 9, and a beam-splitting film or a reflective film is disposed on the third optical surface 10.

[0060] The beam splitter allows a portion of the incident light to continue propagating in the form of transmission, and allows another portion of the incident light to continue propagating in the form of reflection. The specific ratio of reflected light to transmitted light is determined by its own specific beam splitting ratio.

[0061] The light reflected from the second optical surface 9 is emitted to the third optical surface 10. After being reflected by the beam splitter or reflective film, it is emitted to the second optical surface 9 again. At this time, the incident angle of the light is less than or equal to arctan(1 / n). The light passes through the second optical surface 9 and is emitted to the exit pupil 11, finally forming a final image with a focal depth greater than 0.1m.

[0062] Since this optical system is an off-axis system, all the aforementioned surfaces are described using freeform surfaces to correct off-axis aberrations. To reduce the manufacturing difficulty of the system, the material of the second prism 3 can be moldable low-melting-point glass or injection-molded optical resin.

[0063] Furthermore, when a beam-splitting film is disposed on the third optical surface 10, such as Figure 5 As shown, a third prism 14 can be added to the optical system as a compensating mirror. One surface of the third prism 14 is fitted to the third optical surface 10 to achieve perspective without distortion, meaning that external light can pass through the third prism 14 and the second prism 3 and exit through the exit pupil 11. Furthermore, the beam splitter has a splitting ratio of 1:1. This configuration allows light emitted from the light source 1 to enter through the exit pupil 11 and see the final image, while also allowing external light to pass through the second prism 3 and see the external environment at the exit pupil 11, providing a good visual perspective experience.

[0064] Furthermore, such as Figure 3 As shown, to describe the position of each optical surface of the optical system, a coordinate system is established with the center of the exit pupil 11 as the origin O, the direction towards the second prism 3 and coinciding with the optical axis as the Z-axis, the direction perpendicular to the Z-axis and upward as the Y-axis, and the direction perpendicular to the ZOY plane as the X-axis.

[0065] The distance between the first optical surface 8 and the origin O ranges from 18.8 mm to 22.8 mm, the Y-eccentricity ranges from 8 mm to 14 mm, and the tilt angle with the XOY plane ranges from 46° to 56°.

[0066] The distance between the second optical surface 9 and the origin O ranges from 14mm to 19mm; the Y-eccentricity ranges from 1mm to 5mm; and the tilt angle (Alpha angle) with the XOY plane ranges from ±5°.

[0067] The distance between the third optical surface 10 and the origin O ranges from 20mm to 24mm, the Y-eccentricity ranges from -2mm to +2mm, and the tilt angle with the XOY plane ranges from -32° to -22°.

[0068] The Z-eccentricity range of the first optical surface 4 is 25mm to 31mm, the Y-eccentricity range is 19mm to 26mm, and the tilt angle with the XOY plane ranges from -46° to -36°.

[0069] The Z-eccentricity range of the second optical surface 5 is 18mm to 25mm, the Y-eccentricity range is 17mm to 25mm, and the tilt angle with the XOY plane ranges from -16° to -6°.

[0070] The Z-eccentricity range of the third optical surface 6 is 25mm to 31mm, the Y-eccentricity range is 19mm to 26mm, and the tilt angle with the XOY plane ranges from 27° to 37°.

[0071] The Z-eccentricity range of the fourth optical surface 7 is 20mm to 26mm, the Y-eccentricity range is 12mm to 18mm, and the tilt angle with the XOY plane ranges from 45° to 55°.

[0072] The Z-eccentricity range of the light-emitting surface of light source 1 is 29mm to 36mm, the Y-eccentricity range is 12mm to 18mm, and the tilt angle with the XOY plane ranges from -27° to -18°.

[0073] The aforementioned relative positions allow the optical system to achieve optimal performance while maintaining focal depth and field of view. The focal length of the freeform prism in this system is no greater than 13mm; the focal depth range is 100mm to 100,000mm; when viewed from the exit pupil 11, the diagonal field of view of the displayed optical path is no less than 35°; the horizontal field of view should be at least greater than 30°; and the diameter of the exit pupil 11 should be no less than 7mm.

[0074] The following will describe in detail a possible implementation of this embodiment so that this disclosure is sufficient and complete, and fully conveys the concept of this patent to those skilled in the art.

[0075] like Figure 6The optical system shown, with the optical system parameter characteristics provided in Table 1, the freeform surface coefficients provided in Table 2, and the aspherical coefficients provided in Table 3, forms a system field of view of 35°, an exit pupil diameter of 7mm, a final image focal depth of 2m, and a focal length of 13mm.

[0076] Table 1 Optical System Parameters

[0077]

[0078] Wherein, 101 represents the final image, 102 represents the exit pupil 11, 103 is the second optical surface 9, 104 is the third optical surface 10, 105 is the first optical surface 8, 106 is the fourth optical surface 7, 107 is the third optical surface 6, 108 is the second optical surface 5, 109 is the first optical surface 4, 110 is the light-emitting surface of the flat panel display 12, and 111 is the flat glass 13.

[0079] Among the above surfaces, the surfaces that constitute the freeform surface satisfy the following equation: c is the reciprocal of the radius of curvature, r is the radial distance from a point on the surface, and k is the quadratic surface constant. i These are the coefficients of higher-order terms. The surfaces constituting the aspherical surface satisfy the equation: 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 A i These are the coefficients of higher-order terms.

[0080] Table 2 Freeform Surface Coefficients

[0081]

[0082] Table 3 Aspherical coefficients

[0083]

[0084]

[0085] like Figure 7 As shown, the MTF of each sampling field of view obtained based on the above implementation method is higher than 0.2 at 30 lp / mm, indicating that the system imaging quality is excellent. Here, the horizontal axis represents the sampling frequency of the image space, the vertical axis represents the contrast ratio, and F1 to F9 are the sampling fields of view used to evaluate the system display quality. Figure 8 As shown, the ideal state of no distortion is compared with the actual state after processing by the visual optical system, and it is found that the optical distortion is less than 8% and the imaging quality is good.

[0086] Another feasible implementation of this embodiment will be provided in detail below to make this disclosure sufficient and complete, and to fully convey the concept of this patent to those skilled in the art.

[0087] like Figure 9 The optical system shown, with the optical system parameter characteristics provided in Table 4, the freeform surface coefficients provided in Table 5, and the aspherical coefficients provided in Table 6, forms a system with a field of view of 35°, an exit pupil diameter of 7mm, a final image focal depth of 2m, and a focal length of 9.5mm.

[0088] Table 4 Optical System Parameters

[0089]

[0090]

[0091] Wherein, 201 represents the final image, 202 represents the exit pupil 11, 203 is the second optical surface 9, 204 is the third optical surface 10, 205 is the first optical surface 8, 206 is the fourth optical surface 7, 207 is the third optical surface 6, 208 is the second optical surface 5, 209 is the first optical surface 4, 210 is the light-emitting surface of the flat panel display 12, and 211 is the flat glass 13.

[0092] Among the above surfaces, the surfaces that constitute the freeform surface satisfy the following equation: c is the reciprocal of the radius of curvature, r is the radial distance from a point on the surface, and k is the quadratic surface constant. i These are the coefficients of higher-order terms. The surfaces constituting the aspherical surface satisfy the equation: 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 A i These are the coefficients of higher-order terms.

[0093] Table 5 Freeform Surface Coefficients

[0094]

[0095]

[0096] like Figure 10 As shown, the MTF of each sampling field of view obtained based on the above implementation method is higher than 0.2 at 30 lp / mm, indicating that the system imaging quality is excellent. Here, the horizontal axis represents the sampling frequency of the image space, the vertical axis represents the contrast ratio, and F1 to F9 are the sampling fields of view used to evaluate the system display quality. Figure 11 As shown, the ideal state of no distortion is compared with the actual state after processing by the visual optical system, and it is found that the optical distortion is less than 6% and the imaging quality is good.

[0097] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An optical system, characterized in that, include: A light source, which emits light; A first prism, positioned opposite to the light source, comprises: A first optical surface is positioned opposite to the light source, and light emitted from the light source passes through the first optical surface and enters the first prism. A second optical surface is disposed opposite to the first optical surface. A total reflection film is disposed on the second optical surface. Light rays passing through the first optical surface are incident on the second optical surface and reflected on the total reflection film. A third optical surface is disposed opposite to the second optical surface. A total reflection film is disposed on the third optical surface. Light rays reflected from the second optical surface are incident on the third optical surface and reflected on the total reflection film. The fourth optical surface is set opposite to the third optical surface. Light reflected by the third optical surface is emitted towards the fourth optical surface and passes through the fourth optical surface to exit the first prism. The first optical surface, the second optical surface, the third optical surface, and the fourth optical surface are curved surfaces that protrude outwards away from the center of the first prism; A second prism, disposed opposite to the first prism, comprises: The first optical surface is set opposite to the fourth optical surface. Light rays emitted from the first prism enter the second prism through the first optical surface. The first optical surface is a curved surface that is concave inward toward the center of the second prism. The second optical surface is set opposite to the first optical surface. Light rays passing through the first optical surface are incident on the second optical surface at an angle greater than arctan(1 / n). The light rays are reflected on the second optical surface, where n is the refractive index of the second prism under 586nm light. The second optical surface is a curved surface that is concave inward toward the center of the second prism. The third optical surface is disposed opposite to the second optical surface. A beam-splitting film or a reflective film is disposed on the third optical surface. The light reflected from the second optical surface is emitted towards the third optical surface. After being reflected by the beam-splitting film or the reflective film, it is emitted again towards the second optical surface, passes through the second optical surface and is emitted out of the exit pupil, forming a final image with a focal depth greater than 0.1m. The third optical surface is a curved surface that protrudes outward toward the center of the second prism.

2. The optical system according to claim 1, characterized in that, When a beam-splitting film is disposed on the third optical surface, the optical system further includes a third prism, wherein one surface of the third prism is complementary to the third optical surface and is disposed in close contact.

3. The optical system according to claim 2, characterized in that, The spectral splitting ratio of the spectral splitting film is 1:

1.

4. The optical system according to claim 1, characterized in that, A coordinate system is formed with the exit pupil center as the origin O, the direction towards the second prism and coinciding with the optical axis as the Z-axis, the direction perpendicular to the Z-axis and upward as the Y-axis, and the direction perpendicular to the ZOY plane as the X-axis. The distance between the first optical surface of the second prism and the origin O ranges from 18.8 mm to 22.8 mm, the Y-axis eccentricity ranges from 8 mm to 14 mm, and the tilt angle with the XOY plane ranges from 46° to 56°. The distance between the second optical surface and the origin O ranges from 14mm to 19mm; the Y-eccentricity ranges from 1mm to 5mm; and the tilt angle with the XOY plane ranges from ±5°. The distance between the third optical surface and the origin O ranges from 20mm to 24mm, the Y-eccentricity ranges from -2mm to +2mm, and the tilt angle with the XOY plane ranges from -32° to -22°.

5. The optical system according to claim 4, characterized in that, The Z-eccentricity range of the first optical surface of the first prism is 25mm to 31mm, the Y-eccentricity range is 19mm to 26mm, and the tilt angle with the XOY plane ranges from -46° to -36°. The Z-eccentricity range of the second optical surface is 18mm to 25mm, the Y-eccentricity range is 17mm to 25mm, and the tilt angle with the XOY plane ranges from -16° to -6°. The Z-eccentricity range of the third optical surface is 25mm to 31mm, the Y-eccentricity range is 19mm to 26mm, and the tilt angle with the XOY plane ranges from 27° to 37°. The Z-eccentricity range of the fourth optical surface is 20mm to 26mm, the Y-eccentricity range is 12mm to 18mm, and the tilt angle with the XOY plane ranges from 45° to 55°.

6. The optical system according to claim 4, characterized in that, The Z-eccentricity range of the light-emitting surface is 29mm to 36mm, the Y-eccentricity range is 12mm to 18mm, and the tilt angle with the XOY plane ranges from -27° to -18°.

7. The optical system according to claim 1, characterized in that, The combined focal length of the first and second prisms is no greater than 13mm, and the focal depth of the final image ranges from 100mm to 100,000mm.

8. The optical system according to claim 1, characterized in that, When viewed from the exit pupil position, the diagonal field of view of the optical system should be no less than 35°; the horizontal field of view should be at least greater than 30°; and the exit pupil diameter of the system should be no less than 7 mm.

9. The optical system according to claim 1, characterized in that, The first, second, and third optical surfaces are all aspherical, and the material of the second prism is moldable low-melting-point glass or injection-molded optical resin material.

10. The optical system according to claim 1, characterized in that, The first, second, third, and fourth optical surfaces are all aspherical, and the material of the first prism is moldable low-melting-point glass or injection-molded optical resin material.

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