Optical system and head-mounted display device

Abstract

Disclosed are an optical system and a head-mounted display device. The optical system comprises: an image source (10); a first prism (20), having a first surface (201), a second surface (203), and a third surface (205), the first surface (201) being arranged close to a first additional lens (15); a lens (30), arranged close to the third surface (205), the second surface (203) of the first prism (20) being away from the lens (30); and a reflective film (40), arranged on the side of the lens (30) away from the third surface (205). Light emitted by the image source (10) enters the first surface (201) of the first prism (20), and exits from the third surface (205) to the lens (30) after undergoing at least one total reflection in the first prism (20). Among the light emitted by the image source (10), the light propagating along the optical axis of the optical system travels by a preset optical path length d in the first prism (20) when passing through the first prism (20) for the first time. The light reflected by the reflective film (40) passes through the first prism (20) again and then exits. The ratio f / d of the system focal length f of the optical system to d is greater than or equal to 0.45 and less than or equal to 0.60.

Description

Optical systems and head-mounted display devices

[0001] This disclosure claims priority to the Chinese patent application filed with the Patent Office of China on January 31, 2024, with application number CN202410140167.1 and invention name “Optical system and head-mounted display device”, and the Chinese patent application filed with the Patent Office of China on February 5, 2024, with application number CN202410166394.1 and invention name “Optical system and head-mounted display device”, the entire contents of which are incorporated by reference into this disclosure. Technical Field

[0002] The present disclosure relates to the field of optical imaging technology, and in particular to an optical system and a head-mounted display device. Background Art

[0003] Head-mounted display devices are increasingly being used. They can be used to display content, such as movies, games, and web pages. The optical system is a crucial component of these devices. Summary of the Invention

[0004] According to one aspect of an embodiment of the present disclosure, an optical system is provided, comprising: an image source; a first prism, the first prism having a first surface, a second surface and a third surface, the first surface of the first prism being arranged close to a first lens; a lens, the lens being arranged close to the third surface of the first prism, and the second surface of the first prism being away from the lens; a reflective film, the reflective film being arranged on a side of the second lens away from the third surface of the first prism; wherein, light emitted by the image source is incident from the first surface of the first prism, undergoes at least one total reflection in the first prism, and is emitted from the third surface of the first prism to the second lens, and light emitted by the image source that propagates along the optical axis of the optical system passes through a preset optical path length d in the first prism when passing through the first prism for the first time; the light reflected by the reflective film passes through the first prism again and then is emitted; the optical system satisfies: a ratio f / d of the system focal length f of the optical system to the preset optical path length d is greater than or equal to 0.45 and less than or equal to 0.60.

[0005] According to another aspect of an embodiment of the present disclosure, a head-mounted display device is provided, including: a frame structure; and the above-mentioned optical system, wherein the optical system is installed on the frame structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The above and other purposes, features and advantages of the present disclosure will become more apparent by describing the embodiments of the present disclosure in more detail in conjunction with the accompanying drawings. The accompanying drawings are used to provide a further understanding of the embodiments of the present disclosure and constitute a part of the specification. Together with the embodiments of the present disclosure, they are used to explain the present disclosure and do not constitute a limitation of the present disclosure. In the drawings, the same reference numerals generally represent the same components or steps;

[0007] FIG1 is a schematic structural diagram of an optical system provided by some exemplary embodiments of the present disclosure;

[0008] FIG2 is a schematic structural diagram of an optical system provided by some other exemplary embodiments of the present disclosure;

[0009] FIG3 is a schematic structural diagram of an optical system provided by some further exemplary embodiments of the present disclosure;

[0010] FIG4 is a schematic structural diagram of an optical system provided by yet other exemplary embodiments of the present disclosure;

[0011] FIG5 is a schematic structural diagram of an optical system provided by yet other exemplary embodiments of the present disclosure;

[0012] FIG6 is a schematic diagram of a modulation transfer function curve of an optical system in some exemplary embodiments of the present disclosure;

[0013] FIG7 is a schematic structural diagram of an optical system provided by some exemplary embodiments of the present disclosure;

[0014] FIG8 is a schematic structural diagram of an optical system provided by some other exemplary embodiments of the present disclosure;

[0015] FIG9 is a schematic structural diagram of an optical system provided by some further exemplary embodiments of the present disclosure;

[0016] FIG10 is a schematic structural diagram of a first prism in some exemplary embodiments of the present disclosure;

[0017] FIG11 is a schematic structural diagram of an optical system provided by yet other exemplary embodiments of the present disclosure;

[0018] FIG12 is a schematic diagram of a modulation transfer function curve of an optical system in some exemplary embodiments of the present disclosure;

[0019] FIG. 13 is a schematic diagram of a frame structure in some exemplary embodiments of the present disclosure. DETAILED DESCRIPTION

[0020] Below, the exemplary embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments of the present disclosure, and it should be understood that the present disclosure is not limited to the exemplary embodiments described herein.

[0021] In the description of the present disclosure, the terms "up", "down", "left", "right", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the device referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on the present disclosure.

[0022] In the description of this disclosure, unless otherwise specified or limited, the terms "installed," "connected," and "fixed" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; and they may refer to direct connections or indirect connections through an intermediary. Those skilled in the art will understand the specific meanings of these terms in this disclosure based on specific circumstances.

[0023] Exemplary Overview

[0024] Head-mounted displays (HMDs) are also called head-mounted displays (HMDs). They can be used to achieve augmented reality (AR), virtual reality (VR), and mixed reality (MR). They can take the form of glasses, helmets, and more.

[0025] The optical system is a crucial component of a head-mounted display (HMD). This system, also known as an optical engine, generates and processes the light that produces the HMD's display image, ensuring it reaches the user's eyes and allows them to see the image. Therefore, to ensure a seamless user experience, a well-designed optical system is essential.

[0026] Exemplary Structure

[0027] Some exemplary embodiments of the present disclosure provide an optical system. The optical system provided by the embodiments of the present disclosure may include an image source 10, a first prism 20, a lens 30, and a reflective film 40. The first prism 20 may have a first surface 201, a second surface 203, and a third surface 205. The first surface 201 of the first prism 20 may be disposed proximate to the image source 10. The second surface 203 of the first prism 20 may be disposed proximate to the eyebox of the optical system. The lens 30 may be disposed proximate to the third surface 205 of the first prism 20. The second surface 203 of the first prism 20 is distal to the lens 30. The reflective film 40 may be disposed on a side of the lens 30 distal to the third surface 205 of the first prism 20.

[0028] Some exemplary embodiments of the present disclosure provide an optical system. For example, as shown in Figures 1, 2, 3, and 4, the optical system provided by embodiments of the present disclosure may include an image source 10, a first lens 15, a first prism 20, a second lens 30, and a reflective film 40. The first lens 15 may be disposed near the image source 10. The first prism 20 may have a first surface 201, a second surface 203, and a third surface 205. The first surface 201 of the first prism 20 may be disposed near the first lens 15. The second surface 203 of the first prism 20 may be disposed near the eye box of the optical system. The second lens 30 may be disposed near the third surface 205 of the first prism 20. The reflective film 40 may be disposed on a side of the second lens 30 away from the third surface 205 of the first prism 20.

[0029] In order to facilitate the distinction of components, the first lens 15 will be referred to as the first additional lens 15 , and the second lens 30 will be referred to as the lens 30 hereinafter.

[0030] In some optional embodiments of the present disclosure, image source 10 can be used to emit light for displaying images. Image source 10 may include, but is not limited to, an organic light emitting diode (OLED) image source, a liquid crystal (LCS) image source, a liquid crystal on silicon (LCOS) image source, a microelectromechanical system (MEMS) image source, a digital micromirror device (DMD), and the like. For example, image source 10 may be an OLED display screen.

[0031] In some optional embodiments of the present disclosure, the first prism 20 can be used to extend the optical path of the optical system. The first surface 201 of the first prism 20 can be opposite to the image source 10. The first surface 201 and the second surface 203 of the first prism 20 can both be located on the side of the third surface 205 of the first prism 20 close to the eye box of the optical system. The first surface 201 and the second surface 203 of the first prism 20 can both be located on the side away from the lens 30. The first surface 201 and the second surface 203 of the first prism 20 can intersect. The first surface 201 and the third surface 205 of the first prism 20 can intersect. The second surface 203 and the third surface 205 of the first prism 20 can intersect. If the first surface 201, the second surface 203, and the third surface 205 of the first prism 20 are all planes, the first prism 20 can be a triangular prism.

[0032] It is understood that the eye box of an optical system can be the movable area of ​​a human eye (e.g., human eye 100 in Figures 1-2, 7-8), within which the human eye 100 can see a clear and complete display image. The eye box of an optical system can also be called an eye box or EB. The size of the eye box of an optical system is an important design parameter in the optical system.

[0033] In some optional embodiments of the present disclosure, such as the embodiments shown in FIGS. 1 to 6 , the optical system may have a first additional lens 15 .

[0034] The first additional lens 15 can be disposed between the image source 10 and the first surface 201 of the first prism 20. Optionally, the first additional lens 15 can be an aspheric lens. Thus, the first additional lens 15 can correct for field curvature, pupil swim, and chromatic aberration to ensure the imaging quality of the optical system.

[0035] In some optional embodiments of the present disclosure, the first additional lens 15 can be a positive lens. For example, as shown in Figures 1 and 2 , the first additional lens 15 can be a biconvex lens. For another example, as shown in Figures 3 and 4 , the first additional lens 15 can be a plano-convex lens. This allows the surface of the first additional lens 15 to be more regular, making it easier to manufacture.

[0036] In some optional embodiments of the present disclosure, the lens 30 can be used to correct field curvature and provide optical power to achieve a larger field of view angle. The lens 30 can be opposite to the third surface 205 of the first prism 20. A reflective film 40 can be provided on the side of the lens 30 away from the third surface 205 of the first prism 20 by bonding or other means. The reflective film 40 can be used to fully reflect or partially reflect light. If the reflective film 40 is used to partially reflect light, the reflective film 40 can be a semi-transparent and semi-reflective film.

[0037] It should be noted that in the embodiments shown in Figures 1 to 6, the light emitted by the image source 10 can be incident from the first surface 201 of the first prism 20 after passing through the first additional lens 15, and after at least one total reflection occurs in the first prism 20, it is emitted from the third surface 205 of the first prism 20 to the lens 30. The light reflected by the reflective film 40 passes through the first prism 20 again and is emitted, for example, to the eye box of the optical system.

[0038] It should be noted that in the embodiments shown in Figures 7 to 12, the light emitted by the image source 10 can be incident on the first surface 201 of the first prism 20, and after at least one total reflection occurs in the first prism 20, it is emitted from the third surface 205 of the first prism 20 to the lens 30. The light reflected by the reflective film 40 passes through the first prism 20 again and is emitted, for example, to the eye box of the optical system.

[0039] The reflective film 40 can reflect light that propagates toward it to adjust its direction of propagation. For example, as shown in Figures 1 to 3, 7, and 8, the reflective film 40 can adjust the direction of light propagation from horizontally rightward to horizontally leftward. In this way, the light with the adjusted direction of propagation can be emitted after passing through the first prism 20 again, for example, toward the eye box of the optical system.

[0040] As can be seen, in the optical system provided by the embodiments of the present disclosure, the coordinated use of the image source 10, the first prism 20, the lens 30, and the reflective film 40 allows light emitted by the image source 10 to enter the eye box of the optical system. This allows the human eye 100 to see the display provided by the image source 10. Consequently, the head-mounted display device can display content normally, meeting the user's needs, such as viewing a movie.

[0041] In some embodiments of the present disclosure, such as those shown in Figures 1 to 12 , the first surface 201 of the first prism 20 can be a flat surface or a curved surface. The second surface 203 and the third surface 205 of the first prism 20 can both be flat surfaces. Curving the first surface 201 of the first prism 20 facilitates correction of field curvature and pupillary distortion of the optical system.

[0042] In some optional embodiments of the present disclosure, the light emitted by the image source 10 can be incident on the first surface 201 of the first prism 20, and then be totally reflected by the third surface 205 of the first prism 20 and reflected by the second surface 203 of the first prism 20 in the first prism 20, and then emitted from the third surface 205 of the first prism 20.

[0043] In an optional example, as shown in Figures 1 to 3 and 7 to 8, the light emitted by the image source 10 may include a light ray b1. The light ray b1 may be incident on the first surface 201 of the first prism 20 to enter the first prism 20. Next, the light ray b1 may propagate to the third surface 205 of the first prism 20 and undergo total internal reflection at the third surface 205 of the first prism 20 to propagate toward the second surface 203 of the first prism 20. The light ray b1 that has propagated to the second surface 203 of the first prism 20 may be reflected and emitted from the third surface 205 of the first prism 20 to the lens 30.

[0044] In another optional example, as shown in Figures 4 and 9, the light emitted by the image source 10 may include light b2, light b3, and light b4. Similar to light b1, any of light b2, light b3, and light b4 may first undergo total internal reflection at the third surface 205 of the first prism 20, then be reflected at the second surface 203 of the first prism 20, and then be emitted from the third surface 205 of the first prism 20 to the lens 30.

[0045] It is understood that total internal reflection refers to the phenomenon in which light is reflected without refraction when it travels from a denser medium to a less dense medium. The critical angle at which total internal reflection occurs is related to the refractive index of the denser medium and the refractive index of the less dense medium.

[0046] In this way, after the light emitted by the image source 10 enters the first prism 20 from the first surface 201 of the first prism 2, it can undergo one total reflection and one reflection in the first prism 20, which not only extends the optical path of the optical system, but also avoids the problem of too many total reflections and reflections in the first prism 20 resulting in an excessively large volume of the first prism 20 and excessive light divergence.

[0047] In some embodiments, after the light emitted by the image source 10 enters the first prism 20 from the first surface 201 of the first prism 2, the number of total internal reflections experienced within the first prism 20 before being emitted from the third surface 205 of the first prism 20 to the lens 30 may not be limited to one, and the number of reflections experienced within the first prism 20 may not be limited to one. For example, after a total internal reflection occurs once at the third surface 205 of the first prism 20 and a reflection occurs once at the second surface 203 of the first prism 20, the light may undergo another total internal reflection at the third surface 205 of the first prism 20 and another reflection at the second surface 203 of the first prism 20 before being emitted from the third surface 205 of the first prism 20 to the lens 30.

[0048] In some optional embodiments of the present disclosure, as shown in Figures 1 to 3, 7 to 8, the optical system may further include a second prism 50. The second prism 50 may have a first surface 501 and a second surface 503. The first surface 501 of the second prism 50 may be disposed near the eye box of the optical system. The first surface 501 of the second prism 50 may be away from the first prism 20. The second surface 503 of the second prism 50 may be disposed near the second surface 203 of the first prism 20. The light reflected by the reflective film 40 passes through the first prism 20 again, the second surface 503 of the second prism 50, and the first surface 501 of the second prism 50, and then exits, for example, to the eye box of the optical system.

[0049] When the light emitted by the image source 10 passes through the first prism 20, the light from different positions on the light-emitting surface of the image source 10 will pass through different parts of the first prism 20, resulting in differences in their optical paths. The second prism 50 can compensate for this optical path difference.

[0050] As shown in Figures 1 to 3, 7 to 8, the first surface 501 and the second surface 503 of the second prism 50 can both be planes. The first surface 501 and the second surface 503 of the second prism 50 can intersect. The second surface 503 of the second prism 50 can be aligned with the second surface 203 of the first prism 20. Alternatively, the second prism 50 can be a triangular prism.

[0051] After the light emitted by the image source 10 is reflected by the reflective film 40, the reflected light can pass through the first prism 20 to reach the second surface 503 of the second prism 50 and enter the second prism 50. Thereafter, the light can be emitted from the first surface 501 of the second prism 50, for example, to the eye box of the optical system.

[0052] Thus, with the introduction of the second prism 50, light emitted by the image source 10 can enter the eyebox of the optical system. Thus, the human eye 100 can see the display provided by the image source 10. Furthermore, the second prism 50 can compensate for the optical path differences caused by light emitted from different light-emitting locations on the image source 10 after propagating through the first prism 20, ensuring that the optical paths of light emitted from different light-emitting locations are substantially the same, thereby reducing image distortion and improving the imaging quality of the optical system.

[0053] 5 and 11 , a polarizing film 52 may be disposed between the second surface 203 of the first prism 20 and the second surface 503 of the second prism 50 . A quarter wave plate 55 may be disposed between the lens 30 and the third surface 205 of the first prism 20 .

[0054] As shown in Figures 5 and 11, the polarizing beam splitter film 52 can be attached to the second surface 203 of the first prism 20 and the second surface 503 of the second prism 50, respectively. Alternatively, the polarizing beam splitter film 52 can be bonded to at least one of the second surface 203 of the first prism 20 and the second surface 503 of the second prism 50. The quarter-wave plate 55 and the lens 30 can be separated by a certain distance. The quarter-wave plate 55 and the third surface 205 of the first prism 20 can also be separated by a certain distance.

[0055] Due to the provision of the polarizing beam splitter film 52, when light emitted from the image source 10 propagates to the polarizing beam splitter film 52 via total internal reflection at the third surface 205 of the first prism 20, the polarizing beam splitter film 52 can partially reflect the light, and the light reflected by the polarizing beam splitter film 52 can be polarized light. The polarized light can be emitted from the third surface 205 of the first prism 20 and, after passing through the quarter-wave plate 55 and the lens 30, reach the reflective film 40 to be reflected by the reflective film 40. Thereafter, the polarized light will pass through the lens 30 and the quarter-wave plate 55 again. Because the polarized light passes through the quarter-wave plate 55 twice, the polarization direction of the polarized light can change. When the polarized light passes through the quarter-wave plate 55 and reaches the polarizing beam splitter film 52, the polarized light can directly transmit through the polarizing beam splitter film 52 and enter the human eye 100 after passing through the second prism 50.

[0056] Thus, light emitted by the image source 10 is incident on the polarization beam splitter film 52 while propagating within the first prism 20. The first type of linearly polarized light is reflected by the polarization beam splitter film 52, transmitted through the third surface 205 of the first prism 20, and then passes through the quarter-wave plate 55, where it is converted into the first type of circularly polarized light. After passing through the lens 30 and reflecting from the reflective film 40, the first type of circularly polarized light is converted into the second type of circularly polarized light. Upon passing through the quarter-wave plate 55 again, the light is converted into the second type of linearly polarized light, enters the first prism 20, and is transmitted by the polarization beam splitter film 52. Through the coordinated use of the polarization beam splitter film 52 and the quarter-wave plate 55, the light emitted by the image source 10 can propagate along the desired path and ultimately enter the eye box of the optical system, thereby ensuring that the human eye 100 can see the display image provided by the image source 10.

[0057] 2 to 3 , 7 to 8 , the optical system may further include a second additional lens 60 . The second additional lens 60 may be located on a side of the lens 30 away from the first prism 20 .

[0058] Here, the second additional lens 60 can be attached to the reflective film 40 provided on the lens 30. Alternatively, the second additional lens 60 and the reflective film 40 can be bonded. Of course, the second additional lens 60 and the reflective film 40 can also be separated by a certain distance.

[0059] In an optional example, the second additional lens 60 can be used as a compensator for the lens 30 to compensate for the surface shape of the lens 30. As shown in Figures 2-3, 7-8, and 7-9, a light ray e1 may be present in the external environment. The light ray e1 may sequentially pass through the second additional lens 60, the reflective film 40, the lens 30, the first prism 20, and the second prism 50, ultimately entering the eye box of the optical system. In this way, light from the external environment can enter the human eye 100 without deflection, allowing the user to observe the external environment while wearing the head-mounted display device and viewing an undistorted image of the environment.

[0060] In some optional embodiments of the present disclosure, light emitted by the image source 10 that propagates along the optical axis of the optical system travels a preset optical path length d within the first prism 20 when passing through the first prism 20 for the first time. For example, in the embodiments shown in Figures 1 to 6 , the optical system may satisfy the following conditions: the ratio f / d of the optical system's focal length f to the preset optical path length d is greater than or equal to 0.475 and less than or equal to 0.6. For example, in the embodiments shown in Figures 7 to 12 , the optical system may satisfy the following conditions: the ratio f / d of the optical system's focal length f to the preset optical path length d is greater than or equal to 0.45 and less than or equal to 0.60.

[0061] It should be noted that an optical system is a system composed of multiple optical elements in a certain order. For an optical system, the optical axis is a line connecting the optical centers of each optical element in the optical system in sequence, and each optical element is arranged along the optical axis.

[0062] The light emitted by the image source 10 along the optical axis of the optical system is incident from the first surface 201 of the first prism 20, and the light propagating along the optical axis of the optical system is emitted from the third surface 205 of the first prism 20. The actual propagation distance of the light emitted by the image source 10 along the optical axis of the optical system in the first prism 20 is expressed as the target distance. The target distance can be converted into the corresponding distance of the light propagating in a vacuum, and the corresponding distance obtained by conversion can be used as the preset optical path length d.

[0063] For example, in the embodiments shown in Figures 1 to 6, the ratio f / d of the optical system's focal length f to the preset optical path length d can be limited to the range of [0.475, 0.60]. For example, f / d can be 0.475, 0.480, 0.50, 0.52, 0.54, 0.57, 0.60, etc., which are not listed here one by one.

[0064] For example, in the embodiments shown in Figures 7 to 12 , the ratio f / d of the optical system's focal length f to the preset optical path length d can be limited to the range of [0.45, 0.60]. For example, f / d can be 0.45, 0.46, 0.50, 0.52, 0.54, 0.57, 0.60, etc., which are not listed here one by one.

[0065] Research has found that limiting f / d to the range of [0.45, 0.60] and [0.475, 0.60] in the above-mentioned embodiments facilitates achieving a larger eye relief (ER) and a larger eye box (EB) using a smaller optical system. A smaller system size helps ensure the miniaturization and lightweighting of the optical system. A larger eye box facilitates accommodating users with different pupil distances. A larger eye relief allows users who already wear glasses (e.g., myopia glasses) to use the head-mounted display device without removing them. Limiting f / d to the range of [0.45, 0.60] also facilitates correction of field curvature and pupil shift distortion.

[0066] It should be noted that eye relief (ER) is an important design parameter in optical systems. It can be defined as the distance from the human eye to the plane containing the first optical element in the optical system (considered to be the optical element closest to the eye). Alternatively, the distance between the human eye 100 and the first surface 501 of the second prism 50 in Figures 1 to 3, 7, and 8 can serve as the ER.

[0067] In some optional embodiments of the present disclosure, the first additional lens 15 may satisfy: T×N2 / d is greater than or equal to 0.1 and less than or equal to 0.2, where T represents the thickness of the first additional lens 15 and N2 represents the refractive index of the first additional lens 15.

[0068] That is, the ratio T×N2 / d, the product of the thickness of the first additional lens 15 and the refractive index of the first additional lens 15, to the predetermined optical path length d, can be limited to the range of [0.1, 0.2]. For example, T×N2 / d can be 0.1, 0.12, 0.15, 0.16, 0.17, 0.18, 0.2, etc., which are not listed here one by one.

[0069] Research has found that limiting T×N² / d to the range of [0.1, 0.2] is beneficial for controlling pupil distortion in the optical system and enabling the entire optical system to achieve a larger field of view within a smaller volume. This balances miniaturization, lightweighting, and field of view.

[0070] In some optional embodiments of the present disclosure, the focal length f2 of the first additional lens 15 may be greater than or equal to 15 mm and less than or equal to 35 mm.

[0071] That is, the focal length f2 of the first additional lens 15 can be limited to the range of [15 mm, 30 mm]. For example, f2 can be 15 mm, 18 mm, 20 mm, 21 mm, 24 mm, 26 mm, 28 mm, 30 mm, etc., which are not listed here one by one.

[0072] Research has found that limiting f2 to the range of [15mm, 30mm] can not only control the chief ray angle (CRA) and field curvature of the optical system, but also correct field curvature and chromatic aberration, thereby helping to ensure the imaging quality of the optical system.

[0073] In some optional embodiments of the present disclosure, the focal length f1 of the lens 30 may be greater than or equal to 10 mm and less than or equal to 20 mm.

[0074] That is, the focal length f1 of the lens 30 can be limited to the range of [10 mm, 20 mm]. For example, f1 can be 10 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 18 mm, 20 mm, etc., which are not listed here one by one.

[0075] By limiting f1 to the range of [10mm, 20mm], sufficient optical power can be provided to the optical system to achieve a larger field of view, while effectively correcting field curvature, thereby ensuring the imaging quality of the optical system.

[0076] For example, in the embodiments shown in Figures 1 to 6, in some optional implementations of the present disclosure, the ratio fL / f of the focal length fL of the first surface 201 of the first prism 20 to the system focal length f of the optical system may be greater than or equal to 2.

[0077] That is, the ratio fL / f of the focal length fL of the first surface 201 of the first prism 20 to the system focal length f of the optical system can be limited to the range of [2, +∞). Then, fL / f can be a finite value, such as 2, 3, 4, 5, 10, 20, etc., which are not listed here. In this case, the first surface 201 of the first prism 20 can be a curved surface. Alternatively, fL / f can also approach infinity. In this case, the first surface 201 of the first prism 20 can be a flat surface.

[0078] By limiting fL / f to the range of [2, +∞), it is helpful to ensure the rationality of the parameters of the first surface 201 of the first prism 20, thereby ensuring the imaging quality of the optical system. In addition, if the first surface 201 of the first prism 20 is a curved surface, the first surface 201 of the first prism 20 can be aspherical. The aspherical surface can correct field curvature and pupil distortion, further ensuring the imaging quality of the optical system, while not significantly increasing the difficulty of lens manufacturing.

[0079] In some optional embodiments of the present disclosure, the focal length fL of the first surface 201 of the first prism 20 is greater than or equal to 40 mm.

[0080] That is, the focal length fL of the first surface 201 of the first prism 20 can be limited to the range of [40 mm, +∞). Then, fL can be a finite value, such as 40, 45, 55, 60, 80, 100, etc., which are not listed here. In this case, the first surface 201 of the first prism 20 can be a curved surface. Alternatively, fL can approach infinity. In this case, the first surface 201 of the first prism 20 can be a flat surface.

[0081] By limiting fL to the range of [40mm, +∞), field curvature and pupil distortion can be corrected without significantly increasing the difficulty of lens manufacturing, thereby ensuring the imaging quality of the optical system. Furthermore, if the first surface 201 of the first prism 20 is curved, the first surface 201 of the first prism 20 can be aspherical. Using an aspherical surface, field curvature and pupil distortion can be corrected, further ensuring the imaging quality of the optical system.

[0082] In some optional embodiments of the present disclosure, the first additional lens 15 can be a plano-convex lens, and the focal length fL of the first surface 201 of the first prism 20 can be limited to the range [40 mm, +∞). This reduces the manufacturing difficulty of the first additional lens 15 and helps ensure the imaging quality of the optical system. Referring to Figure 3, the first additional lens 15 is a plano-convex lens, with the convex surface of the plano-convex lens facing the first surface 201 of the first prism 20.

[0083] In some optional embodiments of the present disclosure, at least one of the surface of the first additional lens 15 and the first surface 201 of the first prism 20 may satisfy: [SAG(φ1)-SAG(φ2)] / [SAG(φ2)-SAG(φ3)]>1, φ1>φ2>φ3, φ1-φ2=φ2-φ3, φ1, φ2, φ3 all represent values ​​in the effective path, SAG(φ1) represents the sag corresponding to φ1, SAG(φ2) represents the sag corresponding to φ2, and SAG(φ3) represents the sag corresponding to φ3.

[0084] Generally speaking, an optical element such as a lens may include an effective diameter portion and a portion located at the edge for installation and fixation, and the effective diameter portion may participate in imaging.

[0085] For the first surface 201 of the first prism 20, when the effective diameter is φ1, the sag of the first surface 201 of the first prism 20 can be expressed as SAG(φ1); when the effective diameter is φ2, the sag of the first surface 201 of the first prism 20 can be expressed as SAG(φ2); and when the effective diameter is φ3, the sag of the first surface 201 of the first prism 20 can be expressed as SAG(φ3). Since [SAG(φ1)-SAG(φ2)] / [SAG(φ2)-SAG(φ3)]>1, φ1>φ2>φ3, φ1-φ2=φ2-φ3. In this way, the change in pupil distortion can be reduced, the imaging quality can be guaranteed, and the processing difficulty of the lens can be reduced.

[0086] Optionally, the surface of the first additional lens 15 may also satisfy the above-mentioned relationship between the effective diameter and the sag. For example, the convex surface of the first additional lens 15 in Figure 3 satisfies the above-mentioned relationship between the effective diameter and the sag, which can reduce the change of pupil distortion, ensure imaging quality, and reduce the difficulty of lens processing.

[0087] In some optional embodiments of the present disclosure, the refractive index N2 of the first additional lens 15 may be greater than or equal to 1.4 and less than or equal to 2.0.

[0088] That is, the refractive index N2 of the first additional lens 15 can be limited to the range of [1.4, 2.0]. For example, N2 can be 1.4, 1.5, 1.6, 1.7, 1.8, 2.0, and so on, which are not listed here. By limiting the refractive index N2 of the first additional lens 15 to the range of [1.4, 2.0], the first additional lens 15 can effectively correct field curvature and pupil shift distortion, which is beneficial to the overall optical design of the optical system, thereby helping to ensure the imaging quality of the optical system.

[0089] In some optional embodiments of the present disclosure, the Abbe number AB2 of the first additional lens 15 may be greater than or equal to 15 and less than or equal to 90.

[0090] That is, the Abbe number AB2 of the first additional lens 15 can be limited to the range of [15, 90]. For example, AB2 can be 15, 20, 25, 30, 45, 60, 70, 80, 90, etc., which are not listed here one by one.

[0091] By limiting the Abbe number AB2 of the first additional lens 15 to the range of [15, 90], the first additional lens 15 can effectively correct field curvature and pupil distortion, which is beneficial to the overall optical design of the optical system and thus to the imaging quality of the optical system.

[0092] In some optional embodiments of the present disclosure, the refractive index N1 of the lens 30 may be greater than or equal to 1.45 and less than or equal to 1.75.

[0093] That is, the refractive index N1 of the lens 30 may be limited to the range of [1.45, 1.75]. For example, N1 may be 1.45, 1.50, 1.55, 1.60, 1.70, 1.75, etc., which are not listed here one by one.

[0094] By limiting the refractive index N1 of the lens 30 to the range of [1.45, 1.75], it is beneficial to the overall optical design of the optical system, thereby facilitating the guarantee of the imaging quality of the optical system.

[0095] In some optional embodiments of the present disclosure, the Abbe number AB1 of the lens 30 may be greater than or equal to 40 and less than or equal to 80.

[0096] That is, the Abbe number AB1 of the lens 30 can be limited to the range of [40, 80]. For example, AB1 can be 40, 45, 50, 55, 60, 70, 80, etc., which are not listed here one by one.

[0097] Optionally, the lens 30 may have an aspheric surface, which can correct field curvature and pupil distortion to ensure the imaging quality of the optical system.

[0098] By limiting AB1 to the range of [40, 80], it is beneficial to the overall optical design of the optical system, thereby helping to ensure the imaging quality of the optical system.

[0099] In some optional embodiments of the present disclosure, the angle a between the second surface 503 of the first prism 50 and the third surface 205 of the first prism 20 may be greater than or equal to 1 / 2 of the complementary angle of the critical angle for total internal reflection of light within the first prism 20 .

[0100] Here, the critical angle at which light is totally reflected in the first prism 20 can be determined based on the refractive index of the first prism 20 and the refractive index of air. Assuming that the critical angle at which light is totally reflected in the first prism 20 is represented by C, the angle a can satisfy the following equation: a≥(90°-C) / 2.

[0101] By setting the angle a to be greater than or equal to (90° - C) / 2, light emitted from image source 10 can propagate along a predetermined path and ultimately enter the eyebox of the optical system, thereby avoiding the adverse effects of setting an angle a too small. For example, when light emitted from image source 10 first passes through first prism 20, it can undergo one total internal reflection and one reflection within first prism 20.

[0102] In some optional embodiments of the present disclosure, the angle a between the second surface 503 of the first prism 50 and the third surface 205 of the first prism 20 may be greater than or equal to 20 degrees and less than or equal to 30 degrees.

[0103] That is, the angle a between the second surface 203 of the first prism 20 and the third surface 205 of the first prism 20 can be limited to the range of [20°, 30°]. For example, a can be 20°, 23°, 25°, 26°, 28°, 30°, etc., which are not listed here one by one.

[0104] In some embodiments, a may be further restricted to be within the range of [25°, 30°].

[0105] Research has found that angle a is related to the eye box, eye relief, and optical system volume. Limiting angle a to the range of [20°, 30°] allows light emitted by image source 10 to propagate along a predetermined path and ultimately enter the eye box of the optical system, avoiding the adverse effects of excessively large or small angle a. For example, when light emitted by image source 10 first passes through first prism 20, it can undergo a total internal reflection and a single reflection within first prism 20.

[0106] In some optional embodiments of the present disclosure, the refractive index NL1 of the first prism 20 may be greater than or equal to 1.5 and less than or equal to 1.8.

[0107] That is, the refractive index NL1 of the first prism 20 can be limited to the range of [1.5, 1.8]. For example, NL1 can be 1.5, 1.6, 1.7, 1.8, etc., which are not listed here one by one.

[0108] In the embodiment of the present disclosure, by limiting the refractive index NL1 of the first prism 20 to the range of [1.5, 1.8], it is beneficial to reduce the volume of the optical system while meeting the design indicators of the eye box and the eye distance and ensuring the imaging quality of the optical system.

[0109] In some optional embodiments of the present disclosure, the Abbe number ABL1 of the first prism 20 is greater than or equal to 15 and less than or equal to 60.

[0110] That is, the Abbe number ABL1 of the first prism 20 can be limited to the range of [15, 60]. For example, ABL1 can be 15, 20, 30, 40, 50, 60, etc., which are not listed here one by one.

[0111] By limiting the Abbe number ABL1 of the first prism 20 to the range of [15, 60], the parameters of the first prism 20 are rationally maintained, thereby facilitating the improvement of the imaging quality of the optical system. In the embodiments shown in Figures 7 to 12 , the volume of the optical system is further reduced while meeting the design specifications for the eye box and eye relief, and ensuring the imaging quality of the optical system.

[0112] In some optional embodiments of the present disclosure, the refractive index NL2 of the second prism 50 is greater than or equal to 1.5 and less than or equal to 1.8.

[0113] That is, the refractive index NL2 of the second prism 50 can be limited to the range of [1.5, 1.8]. For example, NL2 can be 1.5, 1.6, 1.7, 1.8, etc., which are not listed here. Optionally, the specific value of NL2 can be the same as or different from the specific value of NL1 mentioned above.

[0114] In the embodiment of the present disclosure, by limiting the refractive index NL2 of the second prism 50 to the range of [1.5, 1.8], it is beneficial to effectively compensate for the optical path difference generated by the light emitted from different light-emitting positions on the image source 10 after propagating in the first prism 20, thereby ensuring the imaging quality of the optical system and, at the same time, being able to meet the design indicators of the eye distance.

[0115] In some optional embodiments of the present disclosure, the Abbe number ABL2 of the second prism 50 is greater than or equal to 15 and less than or equal to 60.

[0116] That is, the Abbe number ABL2 of the second prism 50 can be limited to the range of [15, 60]. For example, ABL2 can be 15, 20, 30, 40, 50, 60, etc., which are not listed here. Optionally, the specific value of ABL2 can be the same as or different from the specific value of ABL1 mentioned above.

[0117] By limiting the Abbe number ABL2 of the second prism 50 to the range of [15, 60], it is beneficial to effectively compensate for the optical path difference generated by the light emitted from different light-emitting positions on the image source 10 after propagating in the first prism 20, thereby ensuring the imaging quality of the optical system and, at the same time, meeting the design indicators of the eye distance.

[0118] In some optional embodiments of the present disclosure, the field of view (FOV) of the optical system may be greater than or equal to 40 degrees and less than or equal to 80 degrees.

[0119] That is, the optical system's field of view (FOV) can be limited to the range of [40°, 80°]. For example, the FOV can be 40°, 50°, 60°, 70°, 80°, and so on, which are not listed here. Thus, in the embodiments of the present disclosure, users can see a clear image within a field of view greater than or equal to 40 degrees and less than or equal to 80 degrees, resulting in a wide field of view.

[0120] In some optional embodiments of the present disclosure, for example, the volume V of the optical system shown in Figures 1 to 6 can be less than or equal to 10 cubic centimeters. That is, the volume V of the optical system can satisfy the following equation: V ≤ 10 cc. For example, V can be 5 cc, 6 cc, 7 cc, 8 cc, 9 cc, 10 cc, etc., which are not listed here.

[0121] In some optional embodiments of the present disclosure, for example, the volume V of the optical system shown in Figures 7 to 12 can be less than or equal to 7 cubic centimeters. That is, the volume V of the optical system can satisfy the following equation: V ≤ 7 cc. For example, V can be 4 cc, 5 cc, 6 cc, 7 cc, etc., which are not listed here.

[0122] Thus, in the embodiment of the present disclosure, the optical system has a small volume and a compact structure, which is conducive to ensuring the miniaturization and lightweight of the optical system.

[0123] In some optional embodiments of the present disclosure, the size of the eye box at the preset eye relief satisfies any of the following sizes:

[0124] The length LEN of the eye box is greater than or equal to 8 mm and less than or equal to 25 mm, and the height HEI of the eye box is greater than or equal to 3 mm and less than or equal to 10 mm;

[0125] The diameter DIA of the eye box is greater than 6 mm.

[0126] That is, the length LEN of the eyebox can be limited to the range of [8mm, 25mm]. The height HEI of the eyebox can be limited to the range of [3mm, 10mm]. For example, LEN can be 8mm, 10mm, 15mm, 20mm, 25mm, etc., and HEI can be 3mm, 5mm, 6mm, 9mm, 10mm, etc., not listed here. Furthermore, the diameter DIA of the eyebox can be 6mm, 6.5mm, 7mm, 8mm, etc., not listed here. This allows the optical system to have a larger eyebox, which is beneficial for users with different pupil distances.

[0127] For example, in the embodiments shown in FIGS. 7 to 12 , the first prism 20 may include a plano-convex lens 207 and a triangular prism 209 .

[0128] A plano-convex lens 207 may be formed on one surface of the triangular prism 209. The convex surface of the plano-convex lens 207 may constitute the first surface 201 of the first prism 20. The other surfaces of the triangular prism 209 may constitute the second surface 203 and the third surface 205 of the first prism 20, respectively.

[0129] Here, the plano-convex lens 207 and the triangular prism 209 are two independent optical elements. For example, the plano-convex lens 207 and the triangular prism 209 can be formed separately. As shown in Figure 4, the plano-convex lens 207 can have an upper surface and a lower surface. The upper surface of the plano-convex lens 207 can be convex, and the lower surface of the plano-convex lens 207 can be flat. The triangular prism 209 can have an upper left surface, a lower left surface, and a right surface. The lower surface of the plano-convex lens 207 and the upper left surface of the triangular prism 209 can be attached and fixedly connected. Optionally, the lower surface of the plano-convex lens 207 and the upper left surface of the triangular prism 209 can be bonded. The plano-convex lens 207 and the triangular prism 209 can be combined to form the first prism 20. The upper surface of the plano-convex lens 207 can serve as the first surface 201 of the first prism 20. The lower left surface of the triangular prism 209 can serve as the second surface 203 of the first prism 20. The right surface of the triangular prism 209 may serve as the third surface 205 of the first prism 20 .

[0130] In this way, by assembling the separately formed plano-convex lens 207 and prism 209, the lens molding process can be simplified. Furthermore, since the convex surface of the plano-convex lens 207 serves as the first surface 201 of the first prism 20, the first surface 201 of the first prism 20 can be aspherical. This aspherical surface can correct for field curvature and pupil distortion, ensuring the imaging quality of the optical system and thus improving the user experience. Compared to lenses with other free-form surfaces, aspherical surfaces are less difficult to manufacture.

[0131] In some embodiments, the plano-convex lens 207 and the triangular prism 209 may be different parts of the first prism 20, making the first prism 20 a separate optical element. For example, the first prism 20 having a curved first surface 201 may be directly obtained through an integral molding process. This helps improve the assembly efficiency of the optical system.

[0132] In some optional embodiments of the present disclosure, the first surface 201 of the first prism 20 may have a focal length fL. The optical system may satisfy: a ratio fL / f of the focal length fL of the first surface 201 of the first prism 20 to the system focal length f of the optical system is greater than or equal to 0.5 and less than or equal to 2.

[0133] That is, the ratio fL / f of the focal length fL of the first surface 201 of the first prism 20 to the system focal length f of the optical system can be limited to the range of [0.5, 2]. For example, fL / f can be 0.5, 0.7, 0.8, 1, 1.3, 1.6, 1.9, 2, etc., which are not listed here one by one.

[0134] In related technologies, some parameters of an optical system may constrain each other. For example, increasing the field of view (FOV) of an optical system can easily increase the system's volume. Research has found that limiting fL / f to the range of [0.5, 2] facilitates achieving a larger FOV within a smaller volume. This approach achieves both miniaturization and lightweighting of the optical system while maintaining a wider FOV.

[0135] In some optional embodiments of the present disclosure, the first surface 201 of the first prism 20 may be a curved surface. The first surface 201 of the first prism 20 may have a surface sag height SAGL. The optical system may satisfy the following requirement: a ratio SAGL / L of the surface sag height SAGL of the first surface 201 of the first prism 20 to an actual length L corresponding to a preset optical path length d is greater than or equal to 0.05 and less than or equal to 0.15.

[0136] As shown in FIG. 4 , the surface sag SAGL of the first surface 201 of the first prism 20 may refer to the distance sag of the vertices of the first surface 201 .

[0137] It should be noted that the target distance mentioned above can be used as the actual length L corresponding to the preset optical path length d. The ratio SAGL / L of the surface sag SAGL of the first surface 201 of the first prism 20 to the actual length L corresponding to the preset optical path length d can be limited to the range of [0.05, 0.15]. For example, SAGL / L can be 0.05, 0.07, 0.08, 0.098, 0.11, 0.13, 0.14, 0.15, etc., which are not listed here one by one.

[0138] Through research, it is found that limiting SAGL / L to the range of [0.5, 2] is beneficial to controlling the chief ray angle (CRA), field curvature and pupil distortion of the optical system, thereby ensuring the imaging quality of the optical system.

[0139] In some optional embodiments of the present disclosure, the focal length fL of the first surface 201 of the first prism 20 may be greater than or equal to 5 mm and less than or equal to 30 mm.

[0140] That is, the focal length fL of the first surface 201 of the first prism 20 can be limited to the range of [5 mm, 30 mm]. For example, fL can be 5 mm, 8 mm, 9 mm, 10 mm, 15 mm, 18 mm, 20 mm, 25 mm, 28 mm, 30 mm, etc., which are not listed here one by one.

[0141] By limiting fL to the range of [5mm, 30mm], it is helpful to ensure the rationality of the parameters of the first surface 201 of the first prism 20, so that the first surface 201 can effectively correct field curvature and pupil distortion to ensure the imaging quality of the optical system.

[0142] In some optional embodiments of the present disclosure, the optical system shown in Figures 1 to 6 can meet the following conditions: (1) the system focal length of the optical system is 10.84 mm; (2) the field of view angle FOV of the optical system is 57°; (3) the focal length f1 of the lens 30 is 12.25 mm; (4) the refractive index N1 of the lens 30 is 1.509; (5) the Abbe number AB1 of the lens 30 is 56.32; (6) the focal length f2 of the first additional lens 15 is 15.3 mm; (7) the first additional lens 15 is 15.3 mm; (8) the focal length f3 of the first additional lens 15 is 15.3 mm; (9) the focal length f4 of the first additional lens 15 is 15.3 mm; (10) the focal length f5 of the first additional lens 15 is 15.3 mm; (11) the focal length f6 of the first additional lens 15 is 15.3 mm; (12) the focal length f7 of the first additional lens 15 is 15.3 mm; (13) the focal length f8 of the first additional lens 15 is 15.3 mm; (14) the focal length f9 of the first additional lens 15 is 15.3 mm; (15) the focal length f1 of the first additional lens 15 is 15.3 mm; (16) the focal length f1 of the first additional lens 15 is 15.3 mm; (17) the focal length f1 of the first additional lens 15 is 15.3 mm; (18) the focal length f1 of the first additional lens 15 is 15.3 mm; (19) the focal length f2 of the first additional lens 15 is 15.3 mm; (20) the focal length f1 of the first additional lens 15 is 10.8 mm; (21) the focal length The refractive index N2 of the lens 15 is 1.77; (8) the Abbe number AB2 of the first additional lens 15 is 50; (9) the ratio f / d of the system focal length f of the optical system to the preset optical path length d is 0.460; (10) the ratio f2 / f of the focal length f2 of the first additional lens 15 to the system focal length f of the optical system is 1.411; (11) the ratio T×N2 / d of the product of the thickness of the first additional lens 15 and the refractive index of the first additional lens 15 to the preset optical path length d is 0.18.

[0143] It should be noted that, excluding the surface of the second prism 50, the light emitted by the image source 10 can reach the human eye 100 after passing through 14 surfaces in sequence. Therefore, these 14 surfaces can be numbered in the direction opposite to the path of the light. These 14 surfaces can satisfy the following Tables 1 and 2:

[0144] Table 1

[0145] Table 2

[0146] Among them, "S6" in Table 2 may refer to the surface with surface number 6, and "S12" in Table 2 may refer to the surface with surface number 12.

[0147] In some optional embodiments of the present disclosure, the optical system shown in Figures 7 to 12 can meet the following conditions: (1) the system focal length f of the optical system is 11.5 mm; (2) the field of view angle FOV of the optical system is 63°; (3) the focal length f1 of the lens 30 is 11.9 mm; (4) the refractive index N1 of the lens 30 is 1.494; (5) the Abbe number AB1 of the lens 30 is 58.13; (6) the focal length fL of the first surface 201 of the first prism 20 is 18.4 mm; (7) the first prism 2 0 is 1.639; (8) the Abbe number ABL1 of the first prism 20 is 23.34; (9) the ratio f / d of the system focal length f of the optical system to the preset optical path length d is 0.46; (10) the ratio fL / f of the focal length fL of the first surface 201 of the first prism 20 to the system focal length f of the optical system is 1.6; (11) the ratio SAGL of the surface sag height SAGL of the first surface 201 of the first prism 20 to the actual length L corresponding to the preset optical path length d is 0.098.

[0148] It should be noted that the light emitted by the image source 10 can reach the human eye 100 after passing through 12 surfaces in sequence. Therefore, these 12 surfaces can be numbered in the direction opposite to the path of the light. These 12 surfaces can meet the following Tables 3 and 4:

[0149] Table 3

[0150] Table 4

[0151] In Table 2, "S6" may refer to the surface numbered 6, and "S11" may refer to the surface numbered 11. The surface numbered 6 may be the surface of the lens 30 away from the first prism 20. The surface numbered 11 may be the first surface 201 of the first prism 20.

[0152] On this basis, the modulation transfer function (MTF) curve of the optical system can be obtained. It can be understood that the MTF curve is a curve that describes the performance of the optical system and can be used to judge the ability of the optical system to restore contrast. Optionally, the MTF curve of the optical system can be as shown in Figures 6 and 12. The horizontal axis in Figures 6 and 12 can represent the spatial frequency, the vertical axis can represent the contrast, the solid line can represent the meridian direction, and the dotted line can represent the sagittal direction. It can be seen from Figures 6 and 12 that the optical system has good resolving power in different field of view directions and the overall imaging quality is high.

[0153] In summary, the optical system provided by the embodiments of the present disclosure can achieve a large field of view in a small size, effectively control the chief ray angle, and effectively correct field curvature, pupil shift distortion, and chromatic aberration, thereby ensuring image quality. The optical system provided by the embodiments shown in Figures 7 to 12 can also achieve a larger eye box and eye relief.

[0154] Some exemplary embodiments of the present disclosure further provide a head-mounted display device. The head-mounted display device may include a frame structure 70 shown in FIG13 and an optical system according to any of the above embodiments. The optical system may be mounted on the frame structure.

[0155] In some optional embodiments of the present disclosure, the frame structure 70 may be a structure capable of supporting and accommodating an optical system. For example, the frame structure 70 may include a glasses frame, a headband, and the like.

[0156] In the embodiments of the present disclosure, the provision of the frame structure 70 enables reliable installation of the optical system. The coordination of the various optical elements in the optical system enables the human eye 100 in Figures 1 to 3, 7, and 8 to see the display provided by the image source 10, thereby meeting the user's needs. In some embodiments, the human eye 100 can also see the external environment.

[0157] It should be noted that the various optional embodiments and optional implementation methods disclosed above can be flexibly selected and combined as needed to achieve corresponding functions and effects, and this disclosure does not list them one by one.

[0158] The basic principles of the present disclosure have been described above in conjunction with specific embodiments. However, it should be noted that the advantages, strengths, and effects mentioned in this disclosure are merely illustrative and not restrictive, and should not be construed as necessarily possessed by each embodiment of the present disclosure. Furthermore, the specific details disclosed above are provided for illustrative purposes and to facilitate understanding, rather than as limitations. These details do not limit the present disclosure to necessarily being implemented using these specific details.

[0159] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0160] Those skilled in the art may make various changes and modifications to the present disclosure without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present disclosure and their equivalents, the present disclosure is intended to include these modifications and variations.

Claims

1. An optical system comprising: Image source; a first prism, wherein the first prism has a first surface, a second surface, and a third surface, and the first surface of the first prism is disposed close to the image source; a lens, wherein the lens is disposed adjacent to the third surface of the first prism, and the second surface of the first prism is away from the lens; a reflective film, the reflective film being arranged on a side of the lens away from the third surface of the first prism; The light emitted by the image source is incident on the first surface of the first prism, undergoes at least one total internal reflection within the first prism, and then is emitted from the third surface of the first prism to the lens. The light emitted by the image source that propagates along the optical axis of the optical system travels a preset optical path length d within the first prism when it passes through the first prism for the first time. The light reflected by the reflective film passes through the first prism again and then is emitted. The optical system satisfies: a ratio f / d of the system focal length f of the optical system to the preset optical path length d is greater than or equal to 0.45 and less than or equal to 0.

60.

2. The optical system according to claim 1 further includes a first additional lens, which is arranged close to the image source. After passing through the first additional lens, the light emitted by the image source is incident from the first surface of the first prism. The optical system satisfies: a ratio f / d of the system focal length f of the optical system to the preset optical path length d is greater than or equal to 0.475 and less than or equal to 0.

6.

3. The optical system according to claim 2, wherein: The first additional lens satisfies: T×N2 / d is greater than or equal to 0.1 and less than or equal to 0.2, where T represents the thickness of the first additional lens and N2 represents the refractive index of the first additional lens.

4. The optical system according to claim 2, wherein: At least one of the surface of the first additional lens and the first surface of the first prism satisfies the following conditions: [SAG(φ1)-SAG(φ2)] / [SAG(φ2)-SAG(φ3)]>1, φ1>φ2>φ3, φ1-φ2=φ2-φ3, φ1, φ2, φ3 all represent effective diameters, SAG(φ1) represents the sag corresponding to φ1, SAG(φ2) represents the sag corresponding to φ2, and SAG(φ3) represents the sag corresponding to φ3.

5. The optical system according to claim 2, wherein: A ratio fL / f of a focal length fL of a first surface of the first prism to a system focal length f of the optical system is greater than or equal to 2.

6. The optical system according to claim 2, wherein: The refractive index N2 of the first additional lens is greater than or equal to 1.4 and less than or equal to 2.0, and the Abbe number AB2 of the first additional lens is greater than or equal to 15 and less than or equal to 90.

7. The optical system according to claim 1 or 2, wherein: The refractive index N1 of the lens is greater than or equal to 1.45 and less than or equal to 1.75, and the Abbe number AB1 of the lens is greater than or equal to 40 and less than or equal to 80.

8. The optical system according to claim 1 or 2, wherein: An included angle a between the second surface of the first prism and the third surface of the first prism is greater than or equal to 20 degrees and less than or equal to 30 degrees.

9. The optical system according to claim 1 or 2, wherein: A refractive index NL1 of the first prism is greater than or equal to 1.5 and less than or equal to 1.8, and an Abbe number ABL1 of the first prism is greater than or equal to 15 and less than or equal to 60.

10. The optical system according to claim 1 or 2, wherein: The optical system further comprises: The second prism has a first surface and a second surface. The first surface of the second prism is far away from the first prism, and the second surface of the second prism is arranged close to the second surface of the first prism. After being reflected by the reflective film, the light passes through the first prism again, the second surface of the second prism, and the first surface of the second prism and then is emitted.

11. The optical system according to claim 10, wherein: A refractive index NL2 of the second prism is greater than or equal to 1.5 and less than or equal to 1.8, and an Abbe number ABL2 of the second prism is greater than or equal to 15 and less than or equal to 60.

12. The optical system according to claim 1 or 2, wherein: The optical system further comprises: A second additional lens is located on a side of the lens away from the first prism.

13. The optical system according to claim 1 or 2, wherein: The field of view (FOV) of the optical system is greater than or equal to 40 degrees and less than or equal to 80 degrees.

14. The optical system according to claim 2, wherein: The volume V of the optical system is less than or equal to 10 cubic centimeters.

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

Images