Optical system and head-mounted display apparatus

Abstract

Disclosed in the embodiments of the present disclosure are an optical system and a head-mounted display apparatus. In a specific implementation, the optical system comprises: an image source; a first prism having a first surface, a second surface and a third surface, wherein the first surface of the first prism is close to the image source; a second prism, wherein the second surface of the first prism is located on the side of the first prism away from the second prism, the third surface of the first prism is located on the side of the first prism close to the second prism, the second prism has a first surface, and the first surface of the second prism is close to the third surface of the first prism; a lens located on the side of the second prism away from the first prism, wherein a first included angle between the first surface of the second prism and the optical axis of the lens and a second included angle between the third surface of the first prism and the optical axis of the lens are both acute angles, and the first included angle is equal to the second included angle; a first film layer, which is located on the second surface of the first prism and can reflect and transmit light; and a second film layer, which is located on the side of the lens away from the second prism and can reflect light.

Description

Optical systems and head-mounted display devices

[0001] This disclosure claims priority to Chinese Patent Application No. CN202510147839.6, filed on February 10, 2025, entitled "Optical System and Head-Mounted Display Device", and to Chinese Patent Application No. CN202520210266.2, filed on February 10, 2025, entitled "Optical System and Head-Mounted Display Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to the field of optical imaging technology, and more particularly to an optical system and a head-mounted display device. Background Technology

[0003] Currently, head-mounted displays are being used more and more widely. Head-mounted displays can be used for content display. For example, they can be used to display movie footage, game images, web pages, etc. The optical system is a crucial component of head-mounted displays. Summary of the Invention

[0004] According to one aspect of the present disclosure, an optical system is provided, comprising: an image source; a first prism having a first surface, a second surface, and a third surface, the first surface of the first prism being close to the image source; a second prism having a second surface of the first prism located on the side of the first prism away from the second prism, and a third surface of the first prism located on the side of the first prism close to the second prism, the second prism having a first surface, the first surface of the second prism being close to the third surface of the first prism; and a lens located on the side of the second prism away from the first prism, wherein a first angle between the first surface of the second prism and the optical axis of the lens and a second angle between the third surface of the first prism and the optical axis of the lens are both acute angles. The first included angle is equal to the second included angle; the first film layer is located on the second surface of the first prism and can reflect and transmit light; the second film layer is located on the side of the lens away from the second prism and can reflect light; wherein, the light emitted from the image source enters the first prism from the first surface of the first prism, undergoes at least one total internal reflection in the first prism, is reflected by the first film layer, exits from the third surface of the first prism, enters the second prism from the first surface of the second prism, is reflected by the second film layer after passing through the second prism and the lens, and the light reflected by the second film layer passes sequentially through the lens, the first surface of the second prism, the third surface of the first prism and the second surface of the first prism, and exits through the first film layer.

[0005] In an optional example, the angle between the second surface of the first prism and the plane perpendicular to the optical axis of the lens is the third angle, and the angle between the first surface of the first prism and the third surface of the first prism is the fourth angle, then the fourth angle is greater than twice the third angle.

[0006] In an optional example, if the angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle, then the fourth angle is equal to the sum of the fifth angle and twice the third angle.

[0007] In an optional example, the angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle, and the absolute value of the difference between the sum of the fifth angle and twice the third angle and the fourth angle is less than or equal to 0.8 degrees.

[0008] In an optional example, if the angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle, then the ratio of twice the sum of the third and fifth angles to the complementary angle of the third angle is greater than 0.9.

[0009] In an optional example, the angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle. Then, the difference between twice the sum of the third and fifth angles and the complementary angle of the third angle is greater than negative 6 degrees.

[0010] In an optional example, the angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle, which is greater than 5 degrees and less than 15 degrees.

[0011] In the optional examples, the fifth included angle is greater than 5 degrees and less than 8 degrees, or the fifth included angle is greater than 8 degrees and less than 15 degrees.

[0012] In the optional example, the fifth included angle is greater than or equal to 7.5 degrees and less than or equal to 8 degrees.

[0013] In the optional example, the fifth included angle is greater than 8.1 degrees and less than 8.7 degrees.

[0014] In the optional example, the fifth included angle is greater than or equal to 8.7 degrees and less than or equal to 9.3 degrees.

[0015] In the optional example, the fifth included angle is greater than or equal to 9.4 degrees and less than or equal to 9.8 degrees.

[0016] In the optional example, the third included angle is greater than 20 degrees and less than 30 degrees.

[0017] In an optional example, the optical system further includes a compensator located near the second surface of the first prism. Light rays reflected by the second film layer pass through the first prism again and exit through the compensator.

[0018] In an optional example, the compensation element is a third prism, which has a first surface and a second surface. The first surface of the third prism is located on the side of the third prism away from the first prism, and the second surface of the third prism is located on the side of the third prism closer to the first prism. The light reflected by the second film layer passes through the first prism again, and then exits through the second surface and the first surface of the third prism.

[0019] In the optional example, the first prism, the second prism, and the third prism have the same refractive index.

[0020] In an optional example, the first surface of the third prism is curved.

[0021] In the optional example, the refractive index of the third prism is greater than or equal to 1.45 and less than or equal to 1.85.

[0022] In the optional example, the Abbe number of the third prism is greater than or equal to 40 and less than or equal to 80.

[0023] In an optional example, a portion of the second surface of the first prism near the image source has a groove that recesses into the interior of the first prism from that portion.

[0024] In an optional example, a portion of the second surface of the first prism near the image source is coated with black.

[0025] In an optional example, the second surface of the first prism has a rough surface in the region near the image source.

[0026] In an optional example, the lens has the same refractive index as the second prism.

[0027] In an optional example, the lens and the second prism are integrated as a single unit.

[0028] In an optional example, for a ray emitted from the image source that propagates along the optical axis of the lens, the optical path length traversed from its entry into the first prism at the first surface of the first prism to its first arrival at the second film layer is denoted as d, and the focal length of the lens is denoted as f. Then f / d is greater than or equal to 0.4 and less than or equal to 0.6.

[0029] In an optional example, the refractive index of the first prism is greater than or equal to 1.45 and less than or equal to 1.85.

[0030] In the optional example, the Abbe number of the first prism is greater than or equal to 40 and less than or equal to 80.

[0031] In an optional example, the first surface of the first prism is curved.

[0032] In an optional example, the refractive index of the second prism is greater than or equal to 1.45 and less than or equal to 1.85.

[0033] In the optional example, the Abbe number of the second prism is greater than or equal to 40 and less than or equal to 80.

[0034] In an optional example, the lens and the second prism are set separately, and the refractive index of the lens is greater than or equal to 1.4 and less than or equal to 1.95.

[0035] In an optional example, the lens has an Abbe number greater than or equal to 40 and less than or equal to 100.

[0036] In an optional example, the optical system of claim 1 further includes a first additional lens located between the image source and a first surface of the first prism; wherein light emitted from the image source enters the first prism after passing through the first additional lens.

[0037] In an optional example, the refractive index of the first additional lens is greater than or equal to 1.45 and less than or equal to 2.0.

[0038] In an optional example, the Abbe number of the first additional lens is greater than or equal to 15 and less than or equal to 100.

[0039] In an optional example, the second film is a semi-transparent and semi-reflective film, and the optical system further includes a second additional lens located on the side of the second film away from the lens.

[0040] According to another aspect of the present disclosure, a head-mounted display device is provided, comprising: a frame structure; and the aforementioned optical system, wherein the optical system is mounted on the frame structure.

[0041] The technical solutions of this disclosure will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0042] The above and other objects, features, and advantages of this disclosure will become more apparent from the more detailed description of the embodiments thereof in conjunction with the accompanying drawings. The drawings are provided to further illustrate the embodiments of this disclosure and form part of the specification. They are used together with the embodiments of this disclosure to explain the disclosure and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps;

[0043] Figure 1 is a schematic diagram of the structure of an optical system provided by some exemplary embodiments of this disclosure;

[0044] Figure 2 is a schematic diagram of the structure of an optical system provided by some other exemplary embodiments of the present disclosure;

[0045] Figure 3-1 is a schematic diagram of the structure of an optical system provided in some exemplary embodiments of the present disclosure;

[0046] Figure 3-2 is a schematic diagram of the structure of an optical system provided by some exemplary embodiments of the present disclosure;

[0047] Figure 4 is a schematic diagram of the structure of an optical system provided by some exemplary embodiments of the present disclosure;

[0048] Figure 5 is a schematic diagram of the structure of an optical system provided by some exemplary embodiments of the present disclosure;

[0049] Figure 6 is a schematic diagram of the structure of an optical system provided by some exemplary embodiments of the present disclosure;

[0050] Figure 7 is a schematic diagram of the structure of an optical system provided by some exemplary embodiments of the present disclosure;

[0051] Figure 8 is a schematic diagram of the structure of an optical system provided by some exemplary embodiments of the present disclosure;

[0052] Figure 9-1 is a schematic diagram of the structure of an optical system provided by some exemplary embodiments of the present disclosure;

[0053] Figure 9-2 is a schematic diagram of the structure of an optical system provided by some exemplary embodiments of the present disclosure;

[0054] Figure 10-1 is a schematic diagram of the effect of an optical system provided by some exemplary embodiments of the present disclosure;

[0055] Figure 10-2 is a schematic diagram of the effect of an optical system provided by some other exemplary embodiments of the present disclosure;

[0056] Figure 10-3 is a schematic diagram of the effect of the optical system provided in some exemplary embodiments of the present disclosure;

[0057] Figure 11-1 is a schematic diagram of the structure of an optical system provided by some exemplary embodiments of the present disclosure;

[0058] Figure 11-2 is a schematic diagram of the structure of an optical system provided by some exemplary embodiments of the present disclosure;

[0059] Figure 11-3 is a schematic diagram of the structure of an optical system provided by some exemplary embodiments of the present disclosure;

[0060] Figures 11-4 are schematic diagrams of the structure of an optical system provided by some exemplary embodiments of the present disclosure;

[0061] Figure 12 is a schematic diagram of the framework structure in some exemplary embodiments of this disclosure.

[0062] In the diagram, 10 is the image source; 20 is the first prism; 30 is the second prism; 40 is the lens; 45 is the first coating layer; 50 is the second coating layer; 201 is the first surface of the first prism; 203 is the second surface of the first prism; 205 is the third surface of the first prism; 207 is the groove; 100 is the human eye; 301 is the first surface of the second prism; V is the light ray incident on the first prism from its first surface; 60 is the third prism; 601 is the first surface of the third prism; 603 is the second surface of the third prism; 70 is the first auxiliary lens; 80 is the second auxiliary lens; Z is the axis; ∠R1 is the angle between the first surface of the second prism and the optical axis of the lens; ∠R2 is the angle between the third surface of the first prism and the optical axis of the lens. Angle; U1, center thickness of one optical system; U2, center thickness of another optical system; P, position to which the first common edge needs to be moved; ∠A, angle between the second surface of the first prism and the target plane; ∠C, angle between the first surface and the third surface of the first prism; ∠B, angle between the third surface of the first prism and the target plane; ∠Q, angle between the first surface of the second prism and the target plane; ∠E, angle between the light ray incident from the first surface of the first prism and the third surface of the first prism; ∠R3, angle between the normal of the image source and the optical axis of the lens; ∠R4, angle between the second surface of the first prism and the optical axis of the lens; 90, frame structure. Detailed Implementation

[0063] Hereinafter, exemplary embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present disclosure, and not all embodiments of the present disclosure, and it should be understood that the present disclosure is not limited to the exemplary embodiments described herein.

[0064] In the description of this disclosure, the terms "upper," "lower," "left," "right," 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 this disclosure and simplifying the description, and are not intended to indicate or imply that the device 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 this disclosure.

[0065] In the description of this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," "fixing," etc., 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 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 this disclosure according to the specific circumstances.

[0066] Exemplary Overview

[0067] Head-mounted displays, also known as head-mounted displays (HMDs) or head-mounted devices, can be used to achieve augmented reality (AR), virtual reality (VR), and mixed reality (MR) effects. They can take the form of glasses, helmets, or other similar devices.

[0068] The optical system is a crucial component of head-mounted display devices. It can also be called an optomechanical system. The optical system emits light and processes it, directing the light into the eye socket. When a user wears the head-mounted display, their eyes are positioned within the eye socket, light is projected onto their eyes, and the user sees the displayed image. Therefore, to ensure a superior user experience, it is essential to design the optical system effectively.

[0069] Exemplary Structure

[0070] This disclosure provides an optical system through several exemplary embodiments. The optical system provided by the embodiments of this disclosure may include an image source, a prism, and a lens.

[0071] For example, as shown in FIG1, the optical system provided by the embodiments of the present disclosure may include an image source 10, a first prism 20 and a lens 40.

[0072] In some optional embodiments of this disclosure, the image source 10 can be used to emit light for displaying an image. The image source 10 may include, but is not limited to, an organic light-emitting diode (OLED) image source, a liquid crystal (LCD) image source, a liquid crystal on silicon (LCOS) image source, a microelectromechanical system (MEMS) image source, a digital micromirror device (DMD), etc. For example, the image source 10 can be an OLED display screen.

[0073] In some optional embodiments of this disclosure, the first prism 20 can be used to extend the optical path of an optical system. The first prism 20 may have a first surface 201, a second surface 203, and a third surface 205. For example, the first surface 201 and the second surface 203 of the first prism 20 may intersect, as may the first surface 201 and the third surface 205, and the second surface 203 and the third surface 205. The first surface 201, the second surface 203, and the third surface 205 of the first prism 20 may all be planes, and the first prism 20 may be a triangular prism. In an optional example, the first surface 201 and the second surface 203 of the first prism 20 may be perpendicular, and the first prism 20 may be a right-angle prism.

[0074] Understandably, the "intersection" or "angle" described in this disclosure can refer to two elements actually intersecting or forming an actual angle between them. If two elements do not actually intersect or do not form an angle between them, the non-actually existing parts of the extended parts can still intersect or form an angle after the two elements extend along their respective directions, satisfying the relevant limitations in the embodiments of this disclosure.

[0075] In some embodiments, the first surface 201 of the first prism 20 may also be curved to facilitate optimization of field curvature and pupil shift distortion.

[0076] In some alternative embodiments of this disclosure, lens 40 can be used to provide optical power and correct aberrations. The first surface 201 of the first prism 20 can be close to the image source 10. The second surface 203 of the first prism 20 can be located on the side of the first prism 20 away from lens 40. The third surface 205 of the first prism 20 can be located on the side of the first prism 20 close to lens 40. For example, the first surface 201 of the first prism 20 can be opposite to the image source 10. Both the first surface 201 and the second surface 203 of the first prism 20 can be located on the side of the first prism 20 close to the eyepiece of the optical system.

[0077] Understandably, the eyebox of an optical system can be an area where the human eye (e.g., eye 100 in Figure 1) can move, within which the human eye 100 can see the display image. The eyebox of an optical system can also be called an Eye Box or EB. The dimensions of the eyebox are an important design parameter in an optical system.

[0078] In some optional embodiments of this disclosure, as shown in FIG1, the optical system provided by the embodiments of this disclosure may further include film layers, such as a first film layer 45 and a second film layer 50. The first film layer 45 may be located on the second surface 203 of the first prism 20 and is capable of reflecting and transmitting light. The first film layer 45 may be a semi-reflective film without beam splitting capability, or a polarizing beam splitting film. The first film layer 45 may be disposed on the second surface 203 of the first prism 20 by means of bonding, coating, etc. The second film layer 50 may be located on the side of the lens 40 away from the first prism 20 and is capable of reflecting light. The second film layer 50 may be used for total internal reflection or partial reflection of light, thus, the second film layer 50 may be a total internal reflection film or a semi-reflective film. The second film layer 50 may be disposed on the side of the lens 40 away from the first prism 20 by means of bonding, coating, etc.

[0079] It should be noted that the light emitted from image source 10 can enter the first prism 20 from its first surface 201. After undergoing at least one total internal reflection within the first prism 20, it is reflected by the first film layer 45 and exits from the third surface 205 of the first prism 20. After passing through lens 40, it is reflected by the second film layer 50. The light reflected by the second film layer 50 then passes sequentially through lens 40, the third surface 205 of the first prism 20, and the second surface 203 of the first prism 20, before exiting through the first film layer 45. The light exiting through the first film layer 45 can enter the eyepiece of the optical system.

[0080] In the optical system provided by the embodiments of this disclosure, through the coordinated use of the image source 10, the first prism 20, the lens 40, the first film layer 45, and the second film layer 50, the light emitted by the image source 10 can enter the eye chamber of the optical system. Thus, the human eye 100 can see the display image provided by the image source 10. Therefore, the head-mounted display device can display content normally to meet the user's needs, such as the user's movie-watching needs.

[0081] In some optional embodiments of this disclosure, as shown in Figures 2, 3-1, and 3-2, the optical system provided by the embodiments of this disclosure may include a second prism 30 in addition to the image source 10, the first prism 20, the lens 40, the first film layer 45, and the second film layer 50. The second surface 203 of the first prism 20 may be located on the side of the first prism 20 away from the second prism 30. The third surface 205 of the first prism 20 may be located on the side of the first prism 20 closer to the second prism 30. The second prism 30 may have a first surface 301. The first surface 301 of the second prism 30 may be close to the third surface 205 of the first prism 20. The first surface 301 of the second prism 30 may be planar. The first surface 301 of the second prism 30 and the third surface 205 of the first prism 20 may be opposite each other and have a gap.

[0082] In some optional embodiments of this disclosure, the lens 40 may be located on the side of the second prism 30 away from the first prism 20. The lens 40 and the second prism 30 may be a single piece, as shown in Figures 2 and 3-2. Alternatively, the lens 40 and the second prism 30 may be separate components, as shown in Figure 3-1. If the lens 40 and the second prism 30 are a single piece, it can be understood that one surface of the second prism 30 is curved, and the portion constituting the lens 40 and the portion constituting the second prism 30 may be integrally injection molded. If the lens 40 and the second prism 30 are separate components, the lens 40 and the second prism 30 may be injection molded separately and fixed together by means of bonding or other methods. Furthermore, the surface of the lens 40 away from the second prism 30 may be spherical or aspherical. For example, the surface of the lens 40 away from the second prism 30 may be a rotationally symmetric aspherical surface.

[0083] It should be noted that the light emitted from the image source 10 can enter the first prism 20 from the first surface 201, undergo at least one total internal reflection within the first prism 20, be reflected by the first film layer 45, exit from the third surface 205 of the first prism 20, and enter the second prism 30 from the first surface 301. After passing through the second prism 30 and the lens 40, it is reflected by the second film layer 50. The light reflected by the second film layer 50 passes sequentially through the lens 40, the first surface 301 of the second prism 30, the third surface 205 of the first prism 20, and the second surface 203 of the first prism 20, and exits through the first film layer 45.

[0084] In some optional embodiments of this disclosure, light rays incident on the first prism 20 from the first surface 201 (e.g., light ray V in FIG. 2) may first undergo total internal reflection at the third surface 205 of the first prism 20, then undergo reflection at the second surface 203 of the first prism 20 (which may be reflected by the first film layer 45), and then exit from the third surface 205 of the first prism 20 and enter the second prism 30 from the first surface 301. Of course, the number of times total internal reflection occurs within the first prism 20 before exiting from the third surface 205 of the first prism 20 is not limited to one, and the number of times reflection occurs within the first prism 20 is also not limited to one. For example, after a total internal reflection occurs at the third surface 205 of the first prism 20 and a reflection occurs at the second surface 203 of the first prism 20, a total internal reflection can occur again at the third surface 205 of the first prism 20 and a reflection can occur again at the second surface 203 of the first prism 20, after which the light exits from the third surface 205 of the first prism 20.

[0085] Light rays emitted from the third surface 205 of the first prism 20 can enter the second prism 30 through the first surface 301. The light rays entering the second prism 30 can propagate to the second film layer 50 after passing through the second prism 30 and lens 40 in sequence. The second film layer 50 can reflect the light rays to adjust their propagation direction. For example, referring to Figure 2, the second film layer 50 can adjust the propagation direction of the light rays from horizontal to right to horizontal to left. Thus, the light rays with the adjusted propagation direction can pass sequentially through lens 40, the first surface 301 of the second prism 30, the third surface 205 of the first prism 20, the second surface 203 of the first prism 20, and the first film layer 45, until they reach the eyepiece of the optical system.

[0086] In the optical system provided by the embodiments of this disclosure, through the coordinated use of the image source 10, the first prism 20, the second prism 30, the lens 40, the first film layer 45, and the second film layer 50, the light emitted by the image source 10 can enter the eye box of the optical system. Thus, the human eye 100 can see the display image provided by the image source 10. Therefore, the head-mounted display device can normally display content to meet the user's needs, such as meeting the user's movie-watching needs.

[0087] In some optional embodiments of this disclosure, the optical system may further include a compensation element. The compensation element can compensate for the deflection of light within the first prism 20, and also provide optical path compensation to compensate for the optical path difference caused by light emitted from different emission positions on the image source 10 propagating within the first prism 20, ensuring that the optical paths of light emitted from different emission positions are substantially the same. The compensation element can be located close to the second surface 203 of the first prism 20. Light reflected by the second film layer 50 passes through the first prism 20 again and exits through the compensation element. For example, the light emitted from the image source 10 can propagate along the following target path: first prism 20 → first film layer 45 → first prism 20 → second prism 30 → lens 40 → second film layer 50 → lens 40 → second prism 30 → first prism 20 → first film layer 45 → compensation element → eyebox of the optical system.

[0088] In this way, with the addition of the compensation element, the light emitted from image source 10 can enter the eye chamber of the optical system. Thus, the human eye 100 can see the display image provided by image source 10. In addition, with the addition of the compensation element, it is also beneficial to ensure that the optical path of light emitted from different light-emitting positions is basically the same, and it is also beneficial to compensate for the deflection of light within the first prism 20, thereby improving the imaging quality of the optical system.

[0089] In some optional embodiments of this disclosure, as shown in Figures 2 to 5, the compensation element can be a third prism 60. The third prism 60 may have a first surface 601 and a second surface 603. The first surface 601 of the third prism 60 may be located on the side of the third prism 60 away from the first prism 20. The second surface 603 of the third prism 60 may be located on the side of the third prism 60 closer to the first prism 20. Light reflected by the second film layer 50 passes through the first prism 20 again, and then exits through the second surface 603 and the first surface 601 of the third prism 60.

[0090] Optionally, the first surface 601 and the second surface 603 of the third prism 60 can both be planar, as shown in Figures 2, 3-1, and 3-2. Alternatively, the first surface 601 of the third prism 60 can be curved, and the second surface 603 of the third prism 60 can be planar, as shown in Figures 4 and 5. The first surface 601 and the second surface 603 of the third prism 60 can intersect. The first film layer 45 can be a polarizing beam splitter located between the second surface 603 of the third prism 60 and the second surface 203 of the first prism 20. A quarter-wave plate can be disposed between the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30. The polarizing beam splitter and the quarter-wave plate can be used in conjunction to ensure that the light emitted from the image source 10 propagates along the target path described above.

[0091] After being reflected by the second film layer 50, the light passes through the first prism 20 again, and can exit from the second surface 203 of the first prism 20 and enter the third prism 60 from the second surface 603 of the third prism 60. Then it exits from the first surface 601 of the third prism 60 and continues to the eye box of the optical system.

[0092] Thus, with the third prism 60 as the compensation element, the light emitted from the image source 10 can enter the eye chamber of the optical system. Consequently, the human eye 100 can see the display image provided by the image source 10. Furthermore, the third prism 60 helps ensure that the optical path of light emitted from different light-emitting positions is essentially the same, and it helps compensate for the deflection of light within the first prism 20, improving the imaging quality of the optical system. Moreover, the third prism 60 has a simple surface shape, making it easy to manufacture.

[0093] In some alternative embodiments of this disclosure, as shown in Figures 4 to 8, the optical system may further include a first auxiliary lens 70. The first auxiliary lens 70 may be located between the image source 10 and the first surface 201 of the first prism 20. Light emitted from the image source 10 may enter the first prism 20 after passing through the first auxiliary lens 70.

[0094] Optionally, the first additional lens 70 can be a positive lens. For example, the first additional lens 70 can be a plano-convex lens. As another example, the first additional lens 70 can be a biconvex lens.

[0095] Due to the arrangement of the first auxiliary lens 70, the light emitted from the image source 10 can first pass through the first auxiliary lens 70, and then enter the first prism 20 from the first surface 201 of the first prism 20. The first auxiliary lens 70 can be an aspherical lens, which is beneficial for correcting aberrations and ensuring the imaging quality of the optical system.

[0096] In some embodiments of this disclosure, at least one of the image source 10 and the first additional lens 70 may be movable relative to the first prism 20 for diopter adjustment.

[0097] In some alternative embodiments of this disclosure, the second film layer 50 may be a semi-transparent, semi-reflective film. As shown in Figures 5, 7, and 8, the optical system may further include a second auxiliary lens 80. The second auxiliary lens 80 may be located on the side of the second film layer 50 away from the lens 40.

[0098] Optionally, the second additional lens 80 and the second film layer 50 can be attached together. Alternatively, a gap may exist between the second additional lens 80 and the second film layer 50.

[0099] Here, the second auxiliary lens 80 can be used as a compensating lens for the lens 40. Since the second auxiliary lens 80 is located on the side of the second film layer 50 away from the lens 40, light from the external environment (also called ambient light) can pass sequentially through the second auxiliary lens 80, the second film layer 50, the lens 40, the second prism 30, the first prism 20, and the third prism 60, until it reaches the eyepiece of the optical system. In this way, ambient light can enter the human eye 100 without deflection, allowing the user to see an undistorted environmental image when observing the external environment while wearing a head-mounted display device.

[0100] In some embodiments, the first surface 601 of the third prism 60 may be a curved surface, such as a concave surface, which can effectively compensate for the optical power of the lens 40. In this case, it is not necessary to additionally provide a second auxiliary lens 80 as a compensating lens for the lens 40.

[0101] In some optional embodiments of this disclosure, as shown in Figures 8, 9-1, and 9-2, a portion of the second surface 203 of the first prism 20 near the image source 10 may have a groove 207. The groove 207 may be recessed from this portion of the region (hereinafter referred to as the target region) toward the interior of the first prism 20.

[0102] Optionally, the common edge of the first surface 601 and the second surface 603 of the third prism 60 can be represented as the first common edge. The target region can be located on the second surface 203 of the first prism 20, between the first surface 201 and the first common edge. The groove 207 can be a V-shaped groove.

[0103] It should be noted that light rays emanating from the edge region of image source 10 (e.g., the lower left edge region of image source 10 in Figures 2 to 9-2), after entering the first prism 20 from its first surface 201, may directly project onto the target region of the second surface 203 of the first prism 20 (i.e., not first projected onto the third surface 205 of the first prism 20 according to the designed optical path). If the light rays directly projected onto the target region of the second surface 203 of the first prism 20 subsequently reach the eyebox of the optical system along with the normal optical path, it may cause ghosting, compromising the imaging quality of the optical system. Research has shown that by providing a groove 207 in a portion of the second surface 203 of the first prism 20 near the image source 10, the propagation path of the light rays directly projected onto the target region of the second surface 203 of the first prism 20 can be altered, preventing the light rays from reaching the eyebox of the optical system. For example, this prevents the light rays from satisfying the total internal reflection condition (e.g., not satisfying the condition that the angle of incidence is greater than or equal to the critical angle), thereby helping to eliminate ghosting and ensuring the imaging quality of the optical system.

[0104] In some alternative embodiments of this disclosure, a portion of the second surface 203 of the first prism 20 near the image source 10 may be coated with black. For example, the groove wall of the recess 207 may be coated with black.

[0105] Optionally, the groove walls of the groove 207 can be coated with black using a coating process. In this way, light directly projected onto the target area of ​​the second surface 203 of the first prism 20 will be absorbed, preventing total internal reflection, which helps to eliminate ghosting and ensure the imaging quality of the optical system.

[0106] In some alternative embodiments of this disclosure, a portion of the second surface 203 of the first prism 20 near the image source 10 may be a rough surface. For example, the groove wall of the groove 207 may be a rough surface.

[0107] Optionally, the groove wall of the groove 207 can have a large surface roughness. In this way, the light directly projected onto the target area of ​​the second surface 203 of the first prism 20 will undergo diffuse reflection instead of total internal reflection, which helps to eliminate ghosting and ensure the imaging quality of the optical system.

[0108] In some optional embodiments of this disclosure, the first included angle between the first surface 301 of the second prism 30 and the optical axis of the lens 40, and the second included angle between the third surface 205 of the first prism 20 and the optical axis of the lens 40, can both be acute angles, and the first included angle can be equal to the second included angle. In this document, the first included angle being equal to the second included angle can be understood as the two included angles being equal or substantially the same.

[0109] Optionally, the optical axis of lens 40 can be represented as axis Z in Figure 2. The first surface 301 of the second prism 30 can be tilted relative to the optical axis of lens 40, such that the first included angle between the first surface 301 of the second prism 30 and the optical axis of lens 40 is an acute angle. The third surface 205 of the first prism 20 can be tilted relative to the optical axis of lens 40, such that the second included angle between the third surface 205 of the first prism 20 and the optical axis of lens 40 is an acute angle. The tilt angle of the third surface 205 of the first prism 20 relative to the optical axis of lens 40 can be the same as the tilt angle of the first surface 301 of the second prism 30 relative to the optical axis of lens 40. The tilt angle of the third surface 205 of the first prism 20 relative to the optical axis of lens 40 can be characterized by the first included angle between the first surface 301 of the second prism 30 and the optical axis of lens 40. The first included angle can be seen in ∠R1 in Figure 2. The inclination of the first surface 301 of the second prism 30 relative to the optical axis of the lens 40 can be characterized by a second included angle between the third surface 205 of the first prism 20 and the optical axis of the lens 40, which can be seen in Figure 2 as ∠R2. Here, both ∠R1 and ∠R2 can be located between 0 degrees and 90 degrees, and ∠R1 and ∠R2 can be equal.

[0110] Figures 10-1, 10-2, and 10-3 all show two optical systems. In any of these three figures, the optical system on the right side presents a configuration where the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30 are both tilted relative to the optical axis of the lens 40, and the tilt angle of the third surface 205 of the first prism 20 relative to the optical axis of the lens 40 is the same as the tilt angle of the first surface 301 of the second prism 30 relative to the optical axis of the lens 40. The optical system on the left side presents a configuration where the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30 are not tilted relative to the optical axis of the lens 40 (i.e., ∠R1 and ∠R2 are essentially right angles). Furthermore, the thickness (center thickness) of the optical system on the left side along the optical axis of the lens 40 can be represented as U1, and the thickness (center thickness) of the optical system on the right side along the optical axis of the lens 40 can be represented as U2, where U1 and U2 are the same. It should be noted that Figure 10-1 illustrates the direction of light emitted from a point in the right half of the image source 10 in Figures 2 to 9-2; Figure 10-2 illustrates the direction of light emitted from a point in the left half of the image source 10 in Figures 2 to 9-2; and Figure 10-3 illustrates the direction of light emitted from both a point in the left half of the image source 10 in Figures 2 to 9-2 and a point in the right half of the image source 10. The dashed lines in the figures represent the optical axis of the optical system.

[0111] The eyebox of the optical system needs to cover the light from all areas of the image source 10 to ensure a good user experience. In Figure 10-3, the bold vertical line indicates the size of the eyebox of the optical system in this cross-section. By comparing the two optical systems, it can be seen that, with the same center thickness and achieving the same field of view, the size of the eyebox of the optical system on the left is smaller than that of the optical system on the right. Therefore, in the embodiments of this disclosure, by making the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30 both inclined relative to the optical axis of the lens 40, and making the inclination of the third surface 205 of the first prism 20 relative to the optical axis of the lens 40 consistent with the inclination of the first surface 301 of the second prism 30 relative to the optical axis of the lens 40, it is beneficial to achieve a larger eyebox with the same center thickness and the same field of view. Furthermore, observation shows that if the size of the eyebox of the optical system on the right side is to be reduced to the size of the eyebox of the optical system on the left side, the first common edge (i.e., the common edge of the first surface 601 and the second surface 603 of the third prism 60) mentioned above can be moved to position P in Figure 10-1. Obviously, if the first common edge is moved to position P, the center thickness U2 of the optical system on the right side will also be reduced accordingly. Therefore, in the embodiments of this disclosure, by making the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30 both inclined relative to the optical axis of the lens 40, and making the inclination of the third surface 205 of the first prism 20 relative to the optical axis of the lens 40 consistent with the inclination of the first surface 301 of the second prism 30 relative to the optical axis of the lens 40, it is also beneficial to achieve a smaller center thickness with the same field of view and the same size eyebox, thereby facilitating the miniaturization and weight reduction of the optical system.

[0112] In some optional embodiments of this disclosure, the angle between the second surface 203 of the first prism 20 and the plane perpendicular to the optical axis of the lens 40 is the third angle, and the angle between the first surface 201 of the first prism 20 and the third surface 205 of the first prism 20 is the fourth angle. The fourth angle can be greater than twice the third angle.

[0113] For ease of description, the plane perpendicular to the optical axis of lens 40 can be referred to as the target plane. The angle between the second surface 203 of the first prism 20 and the target plane (i.e., the third angle) can be represented as ∠A as shown in Figure 2. The angle between the third surface 205 of the first prism 20 and the target plane (i.e., the fifth angle hereinafter) can be represented as ∠B as shown in Figure 2. The angle between the first surface 201 and the third surface 205 of the first prism 20 (i.e., the third angle) can be represented as ∠C as shown in Figure 2.

[0114] In some alternative embodiments of this disclosure, ∠C ≠ 2∠A. For example, ∠C > 2∠A.

[0115] Optionally, the common edge of the second surface 203 and the third surface 205 of the first prism 20 can be referred to as the second common edge. The target plane can be a plane passing through the second common edge and perpendicular to the axis Z in Figure 2.

[0116] Understandably, when a prism has a sharp point, two adjacent surfaces extend to touch each other, forming a practical common edge. When a prism does not have a sharp point, meaning two adjacent surfaces do not extend to touch each other but terminate at different points, the common edge can be the edge formed by the two adjacent surfaces theoretically extending to touch each other.

[0117] In the case where the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30 are not tilted relative to the optical axis of the lens 40, as described above, ∠C = 2∠A. By setting ∠C ≠ 2∠A, the optical system provided by the embodiments of this disclosure can be clearly distinguished from the optical system in this case. For example, in the optical system provided by the embodiments of this disclosure, the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30 are both tilted relative to the optical axis of the lens 40, and the tilt angle of the third surface 205 of the first prism 20 relative to the optical axis of the lens 40 can be consistent with the tilt angle of the first surface 301 of the second prism 30 relative to the optical axis of the lens 40. This is advantageous for achieving a larger eyebox with the same center thickness and the same field of view, and for achieving a smaller center thickness with the same field of view and the same size eyebox, thereby facilitating the miniaturization and weight reduction of the optical system.

[0118] In some alternative embodiments of this disclosure, the fourth included angle can be equal to the sum of the fifth included angle and twice the third included angle. That is, ∠C = 2∠A + ∠B.

[0119] In some alternative embodiments of this disclosure, the absolute value of the difference between the sum of the fifth included angle and twice the third included angle and the fourth included angle is less than or equal to 0.8 degrees. That is, |∠C-(2∠A+∠B)|≤0.8°.

[0120] Optionally, |∠C-(2∠A+∠B)| can be equal to 0, meaning that ∠C and (2∠A+∠B) can be the same. Of course, ∠C and (2∠A+∠B) can also be different but sufficiently close, meaning that ∠C and (2∠A+∠B) can be essentially the same. For example, |∠C-(2∠A+∠B)| can be equal to 0.1°, 0.2°, 0.7°, etc., which will not be listed here.

[0121] By using the constraint that |∠C-(2∠A+∠B)|≤0.8°, ∠C can be made to be the same as or substantially the same as (2∠A+∠B). Research has shown that having ∠C the same as or substantially the same as (2∠A+∠B) is beneficial in ensuring that, for the optical system provided in the embodiments of this disclosure, the light emitted from image source 10 propagates along the target path described above.

[0122] In some alternative embodiments of this disclosure, the ratio of twice the sum of the third and fifth included angles to the complementary angle of the third included angle is greater than 0.9. That is, 2(∠A+∠B) / (90°-∠A)>0.9.

[0123] In some optional embodiments of this disclosure, the difference between twice the sum of the third and fifth included angles and the complementary angle of the third included angle is greater than -6 degrees. That is, 2(∠A+∠B)-(90°-∠A)>-6°. 2(∠A+∠B)-(90°-∠A)>-6° can also be transformed into 3∠A+∠2B-90°>-6°.

[0124] Through geometric derivation, it can be seen that 2(∠A+∠B) can be equal to the angle between the normal of image source 10 and the optical axis of lens 40, and the angle between the normal of image source 10 and the optical axis of lens 40 can be represented as ∠R3 in Figure 2. Furthermore, 90°-∠A can be equal to the angle between the second surface 203 of the first prism 20 and the optical axis of lens 40, and the angle between the second surface 203 of the first prism 20 and the optical axis of lens 40 can be represented as ∠R4 in Figure 2. Research has shown that limiting ∠A and ∠B to 2(∠A+∠B) / (90°-∠A)>0.9 and 3∠A+∠2B-90°>-6° helps to keep rays that might form ghosting as far away as possible from the effective display screen, thus ensuring the imaging quality of the optical system.

[0125] In some optional embodiments of this disclosure, the fifth included angle can be greater than 5 degrees and less than 15 degrees. That is, ∠B can be greater than 5° and less than 15°. In other words, ∠B can be limited to the range of (5°, 15°). For example, ∠B can be 6°, 7°, 8°, 9°, 10°, 11°, 12°, 13°, 14°, etc., which will not be listed here.

[0126] Research has shown that limiting ∠B to the range of (5°, 15°) helps to ensure the rationality of the parameters of the first prism 20, thereby helping to ensure the imaging quality of the optical system.

[0127] In some optional embodiments of this disclosure, the fifth included angle can be greater than 5 degrees and less than 8 degrees, or greater than 8 degrees and less than 15 degrees. That is, ∠B can be greater than 5° and less than 8°, or ∠B can be greater than 8° and less than 15°. In other words, ∠B can be limited to the range of (5°, 8°)∪(8°, 15°). For example, ∠B can be 6°, 7°, 9°, 10°, 11°, 12°, 13°, 14°, etc., which will not be listed here.

[0128] In some optional embodiments of this disclosure, the fifth included angle can be greater than or equal to 7.5 degrees and less than or equal to 8 degrees. That is, ∠B can be greater than or equal to 7.5° and less than or equal to 8°. In other words, ∠B can be limited to the range of [7.5°, 8°]. For example, ∠B can be 7.5°, 7.7°, 7.8°, 7.9°, 8°, etc., which will not be listed here.

[0129] In some optional embodiments of this disclosure, the fifth included angle can be greater than 8.1 degrees and less than 8.7 degrees. That is, ∠B can be greater than 8.1° and less than 8.7°. In other words, ∠B can be limited to the range of (8.1°, 8.7°). For example, ∠B can be 8.2°, 8.3°, 8.4°, 8.5°, 8.6°, etc., which will not be listed here.

[0130] In some optional embodiments of this disclosure, the fifth included angle can be greater than or equal to 8.7 degrees and less than or equal to 9.3 degrees. That is, ∠B can be greater than or equal to 8.7° and less than or equal to 9.3°. In other words, ∠B can be limited to the range of [8.7°, 9.3°]. For example, ∠B can be 8.7°, 8.8°, 8.9°, 9.1°, 9.2°, 9.3°, etc., which will not be listed here.

[0131] In some optional embodiments of this disclosure, the fifth included angle can be greater than or equal to 9.4 degrees and less than or equal to 9.8 degrees. That is, ∠B can be greater than or equal to 9.4° and less than or equal to 9.8°. In other words, ∠B can be limited to the range of [9.4°, 9.8°]. For example, ∠B can be 9.4°, 9.5°, 9.6°, 9.7°, 9.8°, etc., which will not be listed here.

[0132] In some optional embodiments of this disclosure, the third included angle can be greater than 20 degrees and less than 30 degrees. That is, ∠A can be greater than 20° and less than 30°. In other words, ∠A can be limited to the range of (20°, 30°). For example, ∠A can be 21°, 23°, 24°, 25°, 27°, 28°, 29°, etc., which will not be listed here.

[0133] Research has shown that limiting ∠A to the range of (20°, 30°) helps to ensure the rationality of the parameters of the first prism 20, thereby helping to ensure the imaging quality of the optical system.

[0134] In some alternative embodiments of this disclosure, the angle between the third surface 205 of the first prism 20 and the target plane may be equal to the angle between the first surface 301 of the second prism 30 and the target plane.

[0135] Optionally, the angle between the third surface 205 of the first prism 20 and the target plane can be equal to ∠B as shown in Figure 2, and the angle between the first surface 301 of the second prism 30 and the target plane can be equal to ∠Q in Figure 2. Therefore, ∠Q = ∠B. In this case, the third surface 205 of the first prism 20 and the first surface 301 of the second prism 30 can be parallel to each other.

[0136] Research has shown that if ∠Q = ∠B, then ∠R2 = ∠R1, and ∠C = 2∠A + ∠B. This ensures that, for the optical system provided in the embodiments of this disclosure, the light emitted from image source 10 propagates along the target path described above.

[0137] By observing Figure 2, we can see that ∠R1 = 90° - ∠Q = 90° - ∠B. Assuming that the angle between the light ray incident from the first surface 201 of the first prism 20 and the third surface 205 of the first prism 20 is represented by ∠E in Figure 2, then through geometric derivation, we know that ∠R1 = 2∠A + ∠E, and ∠C + ∠E = 90°. Therefore, 90° - ∠B = 2∠A + ∠E. Since ∠C + ∠E = 90°, we can then have ∠C + ∠E - ∠B = 2∠A + ∠E, thus obtaining ∠C = 2∠A + ∠B.

[0138] Of course, the structure of the optical system provided in the embodiments of this disclosure is not limited to the structure shown in Figures 1 to 9-2.

[0139] For example, the structure of the optical system provided in the embodiments of this disclosure can also be seen in Figures 11-1 or 11-2. As shown in Figures 11-1 and 11-2, the first surface 601 of the third prism 60 can be a plane, and the surface of the second additional lens 80 near the external environment can be a curved surface. By setting the surface of the second additional lens 80 near the external environment as a curved surface, such as a convex or concave surface, it is beneficial to compensate for external light, thereby enabling the user to see an undistorted environmental image.

[0140] For example, the structure of the optical system provided in the embodiments of this disclosure can be seen in Figures 11-3 or 11-4. As shown in Figures 11-3 and 11-4, the first surface 601 of the third prism 60 can be curved, and the surface of the second additional lens 80 near the external environment can also be curved; for example, both can be a free combination of convex and concave surfaces. By setting the first surface 601 of the third prism 60 to be curved, it is beneficial to achieve a larger eyebox at the same field of view, while also improving aberrations. By setting the surface of the second additional lens 80 near the external environment to be curved, it is beneficial to compensate for external light, thereby allowing the user to see an undistorted environmental image.

[0141] In some alternative embodiments of this disclosure, the refractive indices of the first prism 20, the second prism 30, and the third prism 60 may be the same.

[0142] Here, the fact that the refractive indices of the first prism 20, the second prism 30, and the third prism 60 are the same can be understood as the three having the same or essentially the same refractive indices.

[0143] Research has shown that by setting the refractive indices of the first prism 20, the second prism 30, and the third prism 60 to be consistent, it can be ensured that when the first surface 301 of the second prism 30 is tilted relative to the optical axis of the lens 40, and the third surface 205 of the first prism 20 is tilted relative to the optical axis of the lens 40, and the tilt angle of the third surface 205 of the first prism 20 relative to the optical axis of the lens 40 is consistent with the tilt angle of the first surface 301 of the second prism 30 relative to the optical axis of the lens 40, the light emitted by the image source 10 propagates along the target path described above through the same optical path.

[0144] In some optional embodiments of this disclosure, the refractive index of the third prism 60 can be greater than or equal to 1.45 and less than or equal to 1.85. That is, the refractive index of the third prism 60 can be limited to the range of [1.45, 1.85]. For example, the refractive index of the third prism 60 can be 1.45, 1.55, 1.65, 1.75, 1.85, etc., which will not be listed here.

[0145] Research has shown that limiting the refractive index of the third prism 60 to the range of [1.45, 1.85] is beneficial for effectively compensating for the optical path difference caused by the light emitted from different light-emitting positions on the image source 10 after propagating within the first prism 20, thereby helping to ensure the imaging quality of the optical system.

[0146] In some optional embodiments of this disclosure, the refractive index of the third prism 60 can be greater than or equal to 1.45 and less than 1.547, or the refractive index of the third prism 60 can be greater than 1.547 and less than or equal to 1.85. That is, the refractive index of the third prism 60 can be limited to the range of [1.45, 1.547) ∪ (1.547, 1.85]. For example, the refractive index of the third prism 60 can be 1.45, 1.52, 1.54, 1.546, 1.55, 1.65, 1.75, 1.85, etc., which will not be listed here.

[0147] In some optional embodiments of this disclosure, the Abbe number of the third prism 60 can be greater than or equal to 40 and less than or equal to 80. That is, the Abbe number of the third prism 60 can be limited to the range of [40, 80]. For example, the Abbe number of the third prism 60 can be 40, 50, 60, 70, 80, etc., which will not be listed here.

[0148] Research has shown that limiting the Abbe number of the third prism 60 to the range of [40, 80] is beneficial for effectively compensating for the optical path difference caused by light emitted from different light-emitting positions on the image source 10 after propagating within the first prism 20, thereby helping to ensure the imaging quality of the optical system.

[0149] In some optional embodiments of this disclosure, the refractive indices of lens 40 and second prism 30 may be the same. Here, the same refractive index of lens 40 and second prism 30 can be understood as the refractive indices of the two being identical or substantially identical.

[0150] In some optional embodiments of this disclosure, if the refractive indices of the lens 40 and the second prism 30 are the same, the lens 40 and the second prism 30 can be a single piece. In this way, the lens 40 and the second prism 30 can be integrally formed. Because the lens 40 and the second prism 30 are integrally formed, their edge thickness (e.g., the left edge thickness in Figures 2, 3-2 to 9-2) is increased compared to the lens 40 alone. The larger edge thickness helps reduce processing difficulty and facilitates mass production.

[0151] In some optional embodiments of this disclosure, for the light rays emitted from the image source 10 that propagate along the optical axis of the lens 40, the optical path length traversed from the moment the light rays enter the first prism 20 at the first surface 201 of the first prism 20 until they first reach the second film layer 50 is denoted as d, and the focal length of the lens 40 is denoted as f. Then, f / d can be greater than or equal to 0.4 and less than or equal to 0.6. That is, f / d can be limited to the range of [0.4, 0.6]. For example, f / d can be 0.4, 0.45, 0.5, 0.51, 0.52, 0.54, 0.57, 0.6, etc., which will not be listed here one by one.

[0152] Research has shown that limiting f / d to the range of [0.4, 0.6] facilitates achieving a larger eye relief (ER) and a larger eye box (EB) with a smaller optical system. Limiting f / d to the range of [0.4, 0.6] also helps in the correction of field curvature and pupil shift distortion.

[0153] It should be noted that eye relief (ER) is an important design parameter in optical systems. Eye relief can be defined as the distance from a preset eye position to the plane on which the first optical element in the optical system is placed (which can be considered the optical element closest to the preset eye position). Taking Figures 2, 3-1, and 3-2 as examples, the distance between the human eye 100 and the first surface 601 of the third prism 60 can be used as the eye relief.

[0154] In some optional embodiments of this disclosure, the refractive index of the first prism 20 can be greater than or equal to 1.45 and less than or equal to 1.85. That is, the refractive index of the first prism 20 can be limited to the range of [1.45, 1.85]. For example, the refractive index of the first prism 20 can be 1.45, 1.5, 1.6, 1.7, 1.8, 1.85, etc., which will not be listed here.

[0155] Research has shown that limiting the refractive index of the first prism 20 to the range of [1.45, 1.85] helps to ensure the rationality of the parameters of the first prism 20, thereby helping to ensure the imaging quality of the optical system.

[0156] In some alternative embodiments of this disclosure, the refractive index of the first prism 20 is greater than or equal to 1.45 and less than 1.547, or the refractive index of the first prism 20 is greater than 1.547 and less than or equal to 1.85.

[0157] That is, the refractive index of the first prism 20 can be limited to the range of [1.45, 1.547)∪(1.547, 1.85]. For example, the refractive index of the first prism 20 can be 1.45, 1.457, 1.542, 1.546, 1.549, 1.6, 1.7, 1.8, 1.85, etc., which will not be listed here.

[0158] In some optional embodiments of this disclosure, the Abbe number of the first prism 20 can be greater than or equal to 40 and less than or equal to 80. That is, the Abbe number of the first prism 20 can be limited to the range of [40, 80]. For example, the Abbe number of the first prism 20 can be 40, 50, 60, 70, 80, etc., which will not be listed here.

[0159] Research has shown that limiting the Abbe number of the first prism 20 to the range of [40, 80] helps to ensure the rationality of the parameters of the first prism 20, thereby helping to ensure the imaging quality of the optical system.

[0160] In some optional embodiments of this disclosure, the refractive index of the second prism 30 can be greater than or equal to 1.45 and less than or equal to 1.85. That is, the refractive index of the second prism 30 can be limited to the range of [1.45, 1.85]. For example, the refractive index of the second prism 30 can be 1.45, 1.5, 1.6, 1.7, 1.8, 1.85, etc., which will not be listed here.

[0161] Research has shown that limiting the refractive index of the second prism 30 to the range of [1.45, 1.85] helps to ensure the rationality of the parameters of the second prism 30, thereby helping to ensure the imaging quality of the optical system.

[0162] In some alternative embodiments of this disclosure, the refractive index of the second prism 30 may be greater than or equal to 1.45 and less than 1.547, or the refractive index of the second prism 30 may be greater than 1.547 and less than or equal to 1.85.

[0163] That is, the refractive index of the second prism 30 can be limited to the range of [1.45, 1.547)∪(1.547, 1.85]. For example, the refractive index of the second prism 30 can be 1.45, 1.5, 1.52, 1.54, 1.545, 1.6, 1.7, 1.8, 1.85, etc., which will not be listed here.

[0164] In some optional embodiments of this disclosure, the Abbe number of the second prism 30 can be greater than or equal to 40 and less than or equal to 80. That is, the Abbe number of the second prism 30 can be limited to the range of [40, 80]. For example, the Abbe number of the second prism 30 can be 40, 50, 60, 70, 80, etc., which will not be listed here.

[0165] Research has shown that limiting the Abbe number of the second prism 30 to the range of [40, 80] helps to ensure the rationality of the parameters of the second prism 30, thereby helping to ensure the imaging quality of the optical system.

[0166] In some optional embodiments of this disclosure, the lens 40 and the second prism 30 can be separately disposed, and the refractive index of the lens 40 can be greater than or equal to 1.4 and less than or equal to 1.95. That is, if the lens 40 and the second prism 30 are separately disposed, the refractive index of the lens 40 can be different from that of the second prism 30, and can be limited to the range of [1.4, 1.95]. For example, the refractive index of the lens 40 can be 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 1.95, etc., which will not be listed here.

[0167] Research has shown that when the lens 40 and the second prism 30 are set separately, limiting the refractive index of the lens 40 to the range of [1.4, 1.95] helps to ensure the rationality of the parameters of the lens 40, thereby helping to ensure the imaging quality of the optical system.

[0168] In some optional embodiments of this disclosure, the Abbe number of lens 40 can be greater than or equal to 40 and less than or equal to 100. That is, the Abbe number of lens 40 can be limited to the range of [40, 100]. For example, the Abbe number of lens 40 can be 40, 50, 60, 70, 80, 90, 100, etc., which will not be listed here.

[0169] Research has shown that limiting the Abbe number of lens 40 to the range of [40, 100] helps to ensure the rationality of the parameters of lens 40, thereby helping to ensure the imaging quality of the optical system.

[0170] In some optional embodiments of this disclosure, the refractive index of the first additional lens 70 can be greater than or equal to 1.45 and less than or equal to 2.0. That is, the refractive index of the first additional lens 70 can be limited to the range of [1.45, 2.0]. For example, the refractive index of the first additional lens 70 can be 1.45, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, etc., which will not be listed here.

[0171] Research has shown that limiting the refractive index of the first additional lens 70 to the range of [1.45, 2.0] helps to ensure the rationality of the parameters of the first additional lens 70, thereby helping to ensure the imaging quality of the optical system.

[0172] In some optional embodiments of this disclosure, the Abbe number of the first additional lens 70 can be greater than or equal to 15 and less than or equal to 100. That is, the Abbe number of the first additional lens 70 can be limited to the range of [15, 100]. For example, the Abbe number of the first additional lens 70 can be 15, 20, 30, 40, 50, 60, 80, 90, 100, etc., which will not be listed here.

[0173] Research has shown that limiting the Abbe number of the first additional lens 70 to the range of [15, 100] helps to ensure the rationality of the parameters of the first additional lens 70, thereby helping to ensure the imaging quality of the optical system.

[0174] This disclosure also provides a head-mounted display device through some exemplary embodiments. The head-mounted display device may include the frame structure 90 shown in FIG12 and the optical system in any of the above embodiments. The optical system may be mounted on the frame structure 90.

[0175] In some alternative embodiments of this disclosure, the frame structure 90 may be a structure capable of supporting and accommodating the optical system. For example, the frame structure 90 may include, but is not limited to, eyeglass frames, headbands, etc.

[0176] In the embodiments of this disclosure, the optical system can be reliably installed through the frame structure 90. Through the cooperation of the various optical elements in the optical system, the human eye 100 can see the display image provided by the image source 10, thus meeting the user's needs. In some embodiments, the human eye 100 can also see the external environment.

[0177] It should be noted that the various optional embodiments and implementation methods disclosed above can be flexibly selected and combined as needed to achieve the corresponding functions and effects, and this disclosure does not list them all.

[0178] The basic principles of this disclosure have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this disclosure are merely examples and not limitations, and should not be considered as essential features of each embodiment of this disclosure. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the scope of this disclosure to the necessity of employing the aforementioned specific details for implementation.

[0179] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0180] Various modifications and variations can be made to this disclosure without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this disclosure and their equivalents, this disclosure is also intended to include such modifications and variations.

Claims

1. An optical system, comprising: Image source; A first prism, having a first surface, a second surface, and a third surface, wherein the first surface of the first prism is close to the image source; The second prism has a second surface of the first prism located on the side of the first prism away from the second prism, and a third surface of the first prism located on the side of the first prism closer to the second prism. The second prism has a first surface, and the first surface of the second prism is close to the third surface of the first prism. A lens is located on the side of the second prism away from the first prism. The first surface of the second prism is inclined relative to the optical axis of the lens, and the third surface of the first prism is inclined relative to the optical axis of the lens. The inclination of the third surface of the first prism relative to the optical axis of the lens is the same as the inclination of the first surface of the second prism relative to the optical axis of the lens. A first film layer, located on the second surface of the first prism, is capable of reflecting and transmitting light; The second film layer, located on the side of the lens away from the second prism, is capable of reflecting light; The light emitted from the image source enters the first prism from the first surface of the first prism, undergoes at least one total internal reflection within the first prism, is reflected by the first film layer, exits from the third surface of the first prism, and enters the second prism from the first surface of the second prism. After passing through the second prism and the lens, it is reflected by the second film layer. The light reflected by the second film layer passes sequentially through the lens, the first surface of the second prism, the third surface of the first prism, and the second surface of the first prism, and exits through the first film layer.

2. The optical system according to claim 1, wherein, The first angle between the first surface of the second prism and the optical axis of the lens and the second angle between the third surface of the first prism and the optical axis of the lens are both acute angles, and the first angle is equal to the second angle. The angle between the second surface of the first prism and the plane perpendicular to the optical axis of the lens is the third angle, and the angle between the first surface of the first prism and the third surface of the first prism is the fourth angle. The fourth angle is greater than twice the third angle.

3. The optical system according to claim 2, wherein, If the angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle, then the fourth angle is equal to the sum of the fifth angle and twice the third angle.

4. The optical system according to claim 2, wherein, The angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle. The absolute value of the difference between the sum of the fifth angle and twice the third angle and the fourth angle is less than or equal to 0.8 degrees.

5. The optical system according to claim 2, wherein, If the angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle, then the ratio of twice the sum of the third angle and the fifth angle to the complementary angle of the third angle is greater than 0.

9.

6. The optical system according to claim 2, wherein, The angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle. The difference between twice the sum of the third angle and the fifth angle and the complementary angle of the third angle is greater than negative 6 degrees.

7. The optical system according to claim 2, wherein, The angle between the third surface of the first prism and the plane perpendicular to the optical axis of the lens is the fifth angle, which is greater than 5 degrees and less than 15 degrees.

8. The optical system according to claim 1, further comprising: A compensating element is located near the second surface of the first prism. Light rays reflected by the second film layer pass through the first prism again, then through the compensating element, and finally exit. A first additional lens is located between the image source and the first surface of the first prism, wherein light emitted from the image source enters the first prism after passing through the first additional lens; A second additional lens is located on the side of the second film layer away from the lens, wherein the second film layer is a semi-transparent and semi-reflective film.

9. The optical system according to claim 8, wherein, The compensation element is a third prism, which has a first surface and a second surface. The first surface of the third prism is located on the side of the third prism away from the first prism, and the second surface of the third prism is located on the side of the third prism closer to the first prism. After being reflected by the second film layer, the light passes through the first prism again, and then exits through the second surface and the first surface of the third prism.

10. The optical system according to claim 9, wherein, The first prism, the second prism, and the third prism have the same refractive index.

11. The optical system according to claim 1, wherein, The second surface of the first prism has a groove in a portion of its surface near the image source, and the groove is recessed into the interior of the first prism from this portion of its surface.

12. The optical system according to claim 1 or 11, wherein, The portion of the second surface of the first prism near the image source is coated with black, and the portion of the second surface of the first prism near the image source is a rough surface.

13. The optical system according to claim 1, wherein, The lens and the second prism have the same refractive index, and the lens and the second prism are integral parts.

14. The optical system according to claim 1, wherein, For the light rays emitted from the image source that propagate along the optical axis of the lens, the optical path length traversed from the moment it enters the first prism from its first surface to the moment it first reaches the second film layer is denoted as d, and the focal length of the lens is denoted as f. Then f / d is greater than or equal to 0.4 and less than or equal to 0.

6.

15. A head-mounted display device, comprising: Framework structure; The optical system as described in any one of claims 1-14, wherein the optical system is mounted on the frame structure.

Images