Optical system and head-mounted display device

Abstract

The embodiment of the utility model discloses an optical system and head-mounted display equipment. According to the specific implementation scheme, the optical system comprises an image source; the first prism is provided with a first surface, a second surface and a third surface, the first surface of the first prism is arranged close to the image source, and the second surface of the first prism is arranged close to an eye box of the optical system; the second prism is provided with a first surface and a second surface, the first surface of the second prism is arranged close to an eye box of the optical system, and the second surface of the second prism is arranged close to the second surface of the first prism; the first lens is arranged close to the third surface of the first prism; the semi-transparent and semi-reflective film is arranged on one side, far away from the third surface of the first prism, of the first lens; the surface, away from the first prism, of the first lens has the curvature radius R1, the first surface of the second prism has the curvature radius RL2, and the optical system meets the conditions that (R1 / RL2) * (NL2 / N1) is larger than or equal to 0.9 and smaller than or equal to 1.1, NL2 represents the refractive index of the second prism, and N1 represents the refractive index of the first lens.

Description

Technical Field

[0001] The present disclosure relates to the field of optical imaging technologies, and particularly to an optical system and a head-mounted display device. Background Art

[0002] Currently, head-mounted display devices are increasingly widely used. Head-mounted display devices can be used for content display. For example, head-mounted display devices can be used to display movie scenes, game scenes, web pages, etc. An optical system is an important component of a head-mounted display device. Summary of the Utility Model

[0003] Embodiments of the present disclosure provide an optical system and a head-mounted display device.

[0004] According to one aspect of the embodiments of the present disclosure, there is provided an optical system, including: 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 disposed close to the image source, and the second surface of the first prism is disposed close to the eye box of the optical system; a second prism having a first surface and a second surface, wherein the first surface of the second prism is disposed close to the eye box of the optical system, and the second surface of the second prism is disposed close to the second surface of the first prism; a first lens disposed close to the third surface of the first prism; a semi-transmissive semi-reflective film disposed on a side of the first lens away from the third surface of the first prism; the surface of the first lens away from the first prism has a radius of curvature R 1 , and the first surface of the second prism has a radius of curvature RL 2 , and the optical system satisfies: (R 1 / RL 2 )×(NL 2 / N 1 ) is greater than or equal to 0.9 and less than or equal to 1.1, NL 2 represents the refractive index of the second prism, and N 1 represents the refractive index of the first lens.

[0005] For example, light rays emitted from the image source enter from the first surface of the first prism, undergo at least one total internal reflection in the first prism, and then exit from the third surface of the first prism to the first lens. The light rays reflected by the semi-transmissive semi-reflective film sequentially pass through the first lens, the first prism, and the second prism, and exit from the first surface of the second prism to the eye box of the optical system; the ambient light passing through the semi-transmissive semi-reflective film sequentially passes through the first lens, the first prism, and the second prism, and exits from the first surface of the second prism to the eye box of the optical system.

[0006] According to another aspect of the embodiments of the present disclosure, there is provided a head-mounted display device, including: a frame structure; the above optical system, and the optical system is mounted on the frame structure. Description of the Drawings

[0007] Figure 1 It is a schematic structural diagram of an optical system provided by some exemplary embodiments of the present disclosure.

[0008] Figure 2 It is a schematic structural diagram of an optical system provided by some other exemplary embodiments of the present disclosure.

[0009] Figure 3 It is a schematic structural diagram of an optical system provided by some further exemplary embodiments of the present disclosure.

[0010] Figure 4 It is a schematic structural diagram of an optical system provided by some other exemplary embodiments of the present disclosure.

[0011] Figure 5 It is a schematic diagram of the modulation transfer function curve of the optical system in some exemplary embodiments of the present disclosure.

[0012] Figure 6 It is a schematic diagram of the frame structure in some exemplary embodiments of the present disclosure.

[0013] In the figure, 10 is the image source; 20 is the first prism; 30 is the second prism; 40 is the first lens; 50 is the semi-transmissive and semi-reflective film; 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; 301 is the first surface of the second prism 30; 303 is the second surface of the second prism 30; 100 is the human eye; b1 is the light ray emitted by the image source; b2 is another light ray emitted by the image source; b3 is still another light ray emitted by the image source; b4 is the ambient light; 55 is the second lens; 60 is the polarization beam splitter film; 70 is the quarter-wave plate. Detailed implementation manners

[0014] Next, exemplary embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments of the present disclosure. It should be understood that the present disclosure is not limited by the exemplary embodiments described herein.

[0015] In the description of the present disclosure, the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present disclosure and simplifying the description, rather than indicating or implying that the device referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present disclosure.

[0016] In the description of the present disclosure, unless otherwise clearly specified and defined, terms such as "installation", "connection", "fixation", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0017] Exemplary Overview

[0018] A head-mounted display device can also be referred to as a head-mounted display (HMD) or a head-mounted display. The head-mounted display device can be used to achieve augmented reality (AR) effects, virtual reality (VR) effects, mixed reality (MR) effects, etc. The head-mounted display device can be presented in the form of glasses, helmets, etc.

[0019] The optical system is an important part of the head-mounted display device. The optical system can also be referred to as an optical-mechanical system. The optical system can be used to emit the light of the display screen of the head-mounted display device and process the light so that the light is projected onto the eyes of the user wearing the head-mounted display device, enabling the user to see the display screen. Therefore, in order to ensure the user experience, it is necessary to reasonably design the optical system.

[0020] Exemplary Structure

[0021] Some exemplary embodiments of the present disclosure provide an optical system. For example, as Figures 1 to 4 shown, the optical system provided by the embodiments of the present disclosure may include an image source 10, a first prism 20, a second prism 30, a first lens 40, and a semi-transmissive semi-reflective film 50. 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 close to the image source 10. The second surface 203 of the first prism 20 may be disposed close to the eyebox of the optical system. The second prism 30 may have a first surface 301 and a second surface 303. The first surface 301 of the second prism 30 may be disposed close to the eyebox of the optical system. The second surface 303 of the second prism 30 may be disposed close to the second surface 203 of the first prism 20. The first lens 40 may be disposed close to the third surface 205 of the first prism 20. The semi-transmissive semi-reflective film 50 may be disposed on a side of the first lens 40 away from the third surface 205 of the first prism 20.

[0022] In some alternative embodiments of the present disclosure, an image source 10 can be used to emit light for a display screen. The image source 10 can include, but is not limited to, an Organic Light Emitting Diode (OLED) image source, a Liquid Crystal image source, a Liquid Crystal on Silicon (LCOS) image source, a Micro Electro Mechanical System (MEMS) image source, a Digital Micromirror Device (DMD), etc. For example, the image source 10 can be an OLED display screen.

[0023] In some alternative embodiments of the present disclosure, a first prism 20 can be used to extend the optical path of an optical system. The first surface 201 of the first prism 20 can face 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 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 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.

[0024] It can be understood that the eye box of the optical system can be the movable area of a human eye (such as Figure 3 , Figure 4 the human eye 100 therein), within which the human eye 100 can see a clear and complete display screen. The eye box of the optical system can also be referred to as EyeBox or EB. The size of the eye box of the optical system is an important design index in the optical system.

[0025] In some alternative embodiments of the present disclosure, a second prism 30 can be used as a compensation mirror for assisting in observing the external environment and is used to compensate for the optical path difference generated after the light rays emitted from different light-emitting positions on the image source 10 propagate in the first prism 20, so that the optical paths of the light rays emitted from different light-emitting positions are basically the same, thereby reducing image distortion and improving the imaging quality of the optical system. The first surface 301 of the second prism 30 can be a curved surface. The second surface 303 of the second prism 30 can be a plane. The first surface 301 and the second surface 303 of the second prism 30 can intersect. The second surface 303 of the second prism 30 can intersect with the second surface 203 of the first prism 20.

[0026] In some alternative embodiments of the present disclosure, the first lens 40 can be used to provide optical power to achieve a relatively large field of view angle. The first lens 40 can also be used to correct field curvature to improve imaging resolution. The first lens 40 can be opposite to the third surface 205 of the first prism 20. A half-transmissive and half-reflective film 50 can be disposed on a side of the first lens 40 away from the third surface 205 of the first prism 20. The half-transmissive and half-reflective film 50 can both transmit light and reflect light. The half-transmissive and half-reflective film 50 can be disposed by means of bonding or the like.

[0027] It should be noted that the light emitted from the image source 10 can enter from the first surface 201 of the first prism 20, and after at least one total internal reflection in the first prism 20, it exits from the third surface 205 of the first prism 20 to the first lens 40. The light reflected by the half-transmissive and half-reflective film 50 sequentially passes through the first lens 40, the first prism 20, and the second prism 30, and exits from the first surface 301 of the second prism 30 to the eye box of the optical system. The ambient light passing through the half-transmissive and half-reflective film 50 sequentially passes through the first lens 40, the first prism 20, and the second prism 30, and exits from the first surface 301 of the second prism 30 to the eye box of the optical system.

[0028] In some alternative embodiments of the present disclosure, after the light emitted from the image source 10 enters from the first surface 201 of the first prism 20, it can be totally internally reflected by the third surface 205 of the first prism 20 and then reflected by the second surface 203 of the first prism 20 in sequence within the first prism 20, and then exits from the third surface 205 of the first prism 20 to the first lens 40. The light exiting to the first lens 40 can propagate to the half-transmissive and half-reflective film 50. The half-transmissive and half-reflective film 50 can reflect the light propagating to it to adjust the light propagation direction. The light with the adjusted propagation direction can sequentially pass through the first lens 40, the first prism 20, and the second prism 30, and exit from the first surface 301 of the second prism 30 to the eye box of the optical system.

[0029] In an alternative example, such as Figure 4As shown, the light rays emitted by the image source 10 may include light ray b1, light ray b2, and light ray b3. Light ray b1 may be incident on the first surface 201 of the first prism 20 to enter the first prism 20. Next, 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 towards the second surface 203 of the first prism 20. The light ray b1 that propagates to the second surface 203 of the first prism 20 may be reflected and exit from the third surface 205 of the first prism 20 to the first lens 40. Thereafter, the semi-transmissive and semi-reflective film 50 may reflect the light ray b1 so that the propagation direction of the light ray b1 is adjusted to horizontally leftward. In this way, after the light ray b1 with the adjusted propagation direction passes through the first prism 20 again, it may pass through the second prism 30 and exit from the first surface 301 of the second prism 30 to the exit pupil of the optical system. The propagation paths of light ray b2 and light ray b3 may refer to the relevant description of the propagation path of light ray b1 and will not be elaborated here.

[0030] It can be seen that after the light rays emitted by the image source 10 enter the first prism 20 from the first surface 201 of the first prism 20, they can undergo one total internal reflection and one reflection within the first prism 20, which can not only extend the optical path of the optical system but also avoid the problems of excessive volume of the first prism 20 and excessive divergence of light rays caused by too many times of total internal reflection and reflection within the first prism 20.

[0031] In some embodiments, after the light rays emitted by the image source 10 enter the first prism 20 from the first surface 201 of the first prism 20, before exiting from the third surface 205 of the first prism 20 to the first lens 40, the number of times of total internal reflection experienced within the first prism 20 may not be limited to one, and the number of times of reflection experienced within the first prism 20 may also not be limited to one. For example, after one total internal reflection occurs at the third surface 205 of the first prism 20 and one reflection occurs at the second surface 203 of the first prism 20, one more total internal reflection may occur at the third surface 205 of the first prism 20 and one more reflection may occur at the second surface 203 of the first prism 20, and then it exits from the third surface 205 of the first prism 20 to the first lens 40.

[0032] In some alternative embodiments of the present disclosure, ambient light may pass through the semi-transmissive and semi-reflective film 50 and enter the first lens 40. Next, the ambient light may enter the first prism 20 from the third surface 205 of the first prism 20 in sequence, exit from the second surface 203 of the first prism 20 and enter the second prism 30 from the second surface 303 of the second prism 30, and then may exit from the first surface 301 of the second prism 30 to the exit pupil of the optical system. In an alternative example, the ambient light may include Figure 4 light ray b4 therein.

[0033] It can be seen that in the optical system provided by the embodiments of the present disclosure, through the cooperative use of the image source 10, the first prism 20, the second prism 30, the first lens 40, and the semi-transmissive and semi-reflective film 50, the light emitted by the image source 10 can enter the eyebox of the optical system, and the ambient light can enter the eyebox of the optical system. In this way, the human eye 100 can see the display screen provided by the image source 10, and the head-mounted display device can normally display content to meet the user's usage requirements, such as meeting the user's movie-watching requirements. In addition, when the user wears the head-mounted display device, the ambient light can enter the human eye 100, and the human eye 100 can see the ambient image to meet the user's need to understand the external environment.

[0034] In some alternative embodiments of the present disclosure, such as Figure 3 , Figure 4 shown, the optical system may further include a second lens 55. The second lens 55 may be disposed between the image source 10 and the first surface 201 of the first prism 20. The light emitted by the image source 10 may be incident on the first surface 201 of the first prism 20 after passing through the second lens 55.

[0035] In some alternative embodiments of the present disclosure, the second lens 55 may be a positive lens. For example, the second lens 55 may be Figure 3 shown biconvex lens. For another example, the second lens 55 may be Figure 4 shown plano-convex lens.

[0036] In the embodiments of the present disclosure, the light emitted by the image source 10 may first pass through the second lens 55 and then be incident on the first surface 201 of the first prism 20. The second lens 55 may be an aspherical lens. In this way, by using the second lens 55, the field curvature, pupil swim, and chromatic aberration can be corrected to ensure the imaging quality of the optical system.

[0037] In some alternative embodiments of the present disclosure, such as Figure 2 shown, a polarization beam splitter film 60 may be disposed between the second surface 203 of the first prism 20 and the second surface 303 of the second prism 30. A quarter-wave plate 70 may be disposed between the first lens 40 and the third surface 205 of the first prism 20.

[0038] Such as Figure 2As shown, the polarization beam splitting film 60 can be respectively attached to the second surface 203 of the first prism 20 and the second surface 303 of the second prism 30. The polarization beam splitting film 60 can be bonded to at least one of the second surface 203 of the first prism 20 and the second surface 303 of the second prism 30. The 1 / 4 wave plate 70 and the first lens 40 can be separated by a certain distance. The 1 / 4 wave plate 70 and the third surface 205 of the first prism 20 can also be separated by a certain distance.

[0039] Due to the setting of the polarization beam splitting film 60, when the light emitted by the image source 10 propagates to the polarization beam splitting film 60 through total reflection at the third surface 205 of the first prism 20, the polarization beam splitting film 60 can partially reflect the light, and the light reflected by the polarization beam splitting film 60 can be polarized light. The polarized light can exit from the third surface 205 of the first prism 20, and after passing through the 1 / 4 wave plate 70 and the first lens 40, it reaches the semi-transmissive semi-reflective film 50 and is reflected by the semi-transmissive semi-reflective film 50. Then, the polarized light will pass through the first lens 40 and the 1 / 4 wave plate 70 again. Since the polarized light passes through the 1 / 4 wave plate 70 twice, the polarization direction of the polarized light can change. When the polarized light passes through the 1 / 4 wave plate 70 and reaches the polarization beam splitting film 60, the polarized light can directly transmit through the polarization beam splitting film 60 and enter the human eye 100 after passing through the second prism 30.

[0040] In this way, the light emitted by the image source 10 is incident on the polarization beam splitting film 60 during the propagation in the first prism 20. The first type of linearly polarized light is reflected by the polarization beam splitting film 60, transmitted through the third surface 205 of the first prism 20, and then passes through the 1 / 4 wave plate 70, so that the first type of linearly polarized light is converted into the first type of circularly polarized light. After passing through the first lens 40 and being reflected by the semi-transmissive semi-reflective film 50, the first type of circularly polarized light is converted into the second type of circularly polarized light, and is converted into the second type of linearly polarized light when passing through the 1 / 4 wave plate 70 again, enters the first prism 20 and is transmitted through the polarization beam splitting film 60. By the combined use of the polarization beam splitting film 60 and the 1 / 4 wave plate 70, the light emitted by the image source 10 can propagate along the required path and finally enter the eyebox of the optical system, thus ensuring that the human eye 100 can see the display picture provided by the image source 10.

[0041] In some alternative embodiments of the present disclosure, a compensating lens can be provided on the side of the second prism 30 away from the first prism 20 to compensate for the deformation caused by the first lens 40 to the ambient light, so that the ambient light can enter the human eye 100 without deflection after passing through the first lens 40, the first prism 20, the second prism 30 and the compensating lens, and the human eye 100 can see a non-deformed ambient image.

[0042] In some alternative embodiments of the present disclosure, the first surface 301 of the second prism 30 may be provided as a curved surface, for example, an aspherical surface. In this way, there is no need to provide an additional compensating lens for the first lens 40. After the ambient light passes through the first lens 40, the first prism 20, and the second prism 30, it can enter the human eye 100 without deflection. The optical system can be simplified.

[0043] In some alternative embodiments of the present disclosure, the surface of the first lens 40 away from the first prism 20 may have a radius of curvature R 1 . The first surface 301 of the second prism 30 may have a radius of curvature RL 2 . The optical system may satisfy: (R 1 / RL 2 ) × (NL 2 / N 1 ) is greater than or equal to 0.9 and less than or equal to 1.1, where NL 2 represents the refractive index of the second prism 30, and N 1 represents the refractive index of the first lens 40.

[0044] That is, (R 1 / RL 2 ) × (NL 2 / N 1 ) can be restricted within the range of [0.9, 1.1]. For example, (R 1 / RL 2 ) × (NL 2 / N 1 ) can be 0.9, 0.95, 0.97, 1.0, 1.03, 1.05, 1.1, etc., and will not be listed one by one here.

[0045] The first surface 301 of the second prism 30 participates in the optical path of both the image source light and the ambient light. The parameters of the first surface 301 of the second prism 30 have an impact on both the image light and the ambient light. Through research, it is found that restricting (R 1 / RL 2 ) × (NL 2 / N 1 ) within the range of [0.9, 1.1] can compensate for the influence of the first lens 40 on the ambient light, and at the same time can take into account the imaging performance of the optical system for the image source light.

[0046] In some alternative embodiments of the present disclosure, for the light rays emitted by the image source 10 and propagating along the optical axis of the optical system, when passing through the first prism 20 for the first time, they pass through a preset optical path length d within the first prism 20. The optical system may satisfy: the 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 0.4 and less than or equal to 0.5.

[0047] It should be noted that the optical system is a system composed of various optical elements combined in a certain order. For the optical system, the optical axis is the 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.

[0048] Among the light rays emitted by the image source 10, the light rays along the optical axis of the optical system are incident from the first surface 201 of the first prism 20 and exit from the third surface 205 of the first prism 20. The actual propagation path of the light rays emitted by the image source 10 along the optical axis of the optical system within the first prism 20 is denoted as the target path. Then, the target path can be converted into the corresponding path of the light rays propagating in a vacuum, and the obtained corresponding path can be used as the preset optical path length d. The ratio f / d of the system focal length f of the optical system to the preset optical path length d can be limited within the range of [0.4, 0.5]. For example, f / d can be 0.425, 0.450, 0.475, 0.480, 0.490, 0.50, etc., which will not be listed one by one here.

[0049] Through research, it is found that limiting f / d within the range of [0.4, 0.5] is beneficial to achieving a larger eye relief (ER) and a larger eye box (EB) through an optical system with a smaller volume. A smaller volume is beneficial to ensuring the miniaturization and light weight of the optical system. A larger eye box is beneficial to accommodating users with different pupil distances. A larger eye relief allows users who are already wearing glasses (such as myopia glasses) to use the head-mounted display device without removing the glasses.

[0050] It should be noted that the eye relief (ER) is an important design index in the optical system. The eye relief can refer to the distance from the human eye to the plane of the first optical element placed in the optical system (which can be considered as the optical element closest to the human eye). Optionally, Figure 3 、 Figure 4 the distance between the human eye 100 and the first surface 301 of the second prism 30 in can be used as the eye relief. The eye relief can usually be set to 15 mm.

[0051] In some alternative embodiments of the present disclosure, among the light rays emitted by the image source 10, the light rays propagating along the optical axis of the optical system pass through the preset optical path length d within the first prism 20 when passing through the first prism 20 for the first time. The first surface 201 of the first prism 20 can be a curved surface. The first surface 201 of the first prism 20 can have a surface sag SAGL. The optical system can satisfy that 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 is greater than or equal to 0.05 and less than or equal to 0.1.

[0052] It should be noted that the target distance in the above text 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 within the range of [0.05, 0.1]. For example, SAGL / L can be 0.05, 0.06, 0.07, 0.08, 0.098, 0.1, etc., and will not be listed one by one here.

[0053] Through research, it is found that limiting SAGL / L within the range of [0.05, 0.1] is beneficial to controlling the chief ray angle (CRA), field curvature, and pupil shift distortion of the optical system, thereby being beneficial to ensuring the imaging quality of the optical system.

[0054] In some alternative embodiments of the present disclosure, the optical system may satisfy that the focal length fL of the first surface 201 of the first prism 20 1 and the system focal length f of the optical system, the ratio fL 1 / f is greater than or equal to 1.8.

[0055] 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 within the range of [1.8, +∞). Then, fL / f can be a finite value, such as 1.8, 2, 3, 4, 5, 10, 20, etc., and will not be listed one by one here. In this case, the first surface 201 of the first prism 20 can be a curved surface. Or, fL / f can also approach infinity. In this case, the first surface 201 of the first prism 20 can be a plane.

[0056] By limiting fL / f within the range of [1.8, +∞), it is beneficial to ensure the rationality of the parameters of the first surface 201 of the first prism 20 to ensure the imaging quality of the optical system. In addition, when the first surface 201 of the first prism 20 is a curved surface, the first surface 201 of the first prism 20 can be an aspherical surface. The field curvature and pupil shift distortion can be corrected by the aspherical surface to further ensure the imaging quality of the optical system, and at the same time, the lens processing difficulty is not significantly increased.

[0057] In some alternative embodiments of the present disclosure, for the light rays emitted by the image source 10 and propagating along the optical axis of the optical system, when passing through the first prism 20 for the first time, they pass through the preset optical path length d within the first prism 20, and the second lens 55 satisfies: T×N 2 / d is greater than or equal to 0.1 and less than or equal to 0.2, where T represents the thickness of the second lens 55, and N 2 represents the refractive index of the second lens 55.

[0058] That is, the ratio T×N of the product of the thickness of the second lens 55 and the refractive index of the second lens 55 to the preset optical path length 2 / d can be limited within the range of [0.1, 0.2]. For example, T×N 2 / d can be 0.1, 0.12, 0.15, 0.16, 0.17, 0.18, 0.2, etc., and will not be listed one by one here.

[0059] Through research, it is found that by limiting T×N 2 / d within the range of [0.1, 0.2], it is beneficial to control the pupil shift distortion of the optical system and enable the entire optical system to achieve a larger field of view angle within a smaller volume. In this way, the miniaturization, lightweight, and field of view range of the optical system can be taken into account.

[0060] In some alternative embodiments of the present disclosure, the focal length f of the second lens 55 2 can be greater than or equal to 10 millimeters and less than or equal to 30 millimeters.

[0061] That is, the focal length f of the second lens 55 2 can be limited within the range of [10mm, 30mm]. For example, f2 can be 10mm, 12mm, 15mm, 18mm, 20mm, 21mm, 24mm, 26mm, 28mm, 30mm, etc., and will not be listed one by one here.

[0062] Through research, it is found that by limiting f 2 within the range of [10mm, 30mm], not only can the chief ray angle and field curvature of the optical system be controlled, but also the field curvature and chromatic aberration can be corrected, which is beneficial to ensuring the imaging quality of the optical system.

[0063] In some alternative embodiments of the present disclosure, the refractive index N of the second lens 55 2 can be greater than or equal to 1.4 and less than or equal to 2.

[0064] That is, the refractive index N of the second lens 55 2 can be limited within the range of [1.4, 2.0]. For example, N 2 can be 1.4, 1.5, 1.6, 1.7, 1.8, 2.0, etc., and will not be listed one by one here. By limiting the refractive index N of the second lens 55 2 within the range of [1.4, 2.0], the second lens 55 can effectively correct the field curvature and pupil shift distortion, which is beneficial to the overall optical design of the optical system, and thus beneficial to ensuring the imaging quality of the optical system.

[0065] In some alternative embodiments of the present disclosure, the Abbe number AB of the second lens 55 2It can be greater than or equal to 15 and less than or equal to 90.

[0066] That is, the Abbe number AB of the second lens 55 2 can be restricted within the range of [15, 90]. For example, AB 2 can be 15, 20, 25, 30, 45, 60, 70, 80, 90, etc., and will not be listed one by one here.

[0067] By restricting the Abbe number AB of the second lens 55 2 within the range of [15, 90], it is beneficial to effectively correct field curvature and pupil shift distortion by using the second lens 55, which is beneficial to the overall optical design of the optical system, and thus beneficial to the imaging quality of the optical system.

[0068] In some alternative embodiments of the present disclosure, the focal length fL of the first surface 201 of the first prism 20 1 can be greater than or equal to 25 millimeters.

[0069] That is, the focal length fL of the first surface 201 of the first prism 20 1 can be restricted within the range of [25mm, +∞). Then, fL 1 can be a finite value, such as 25mm, 35mm, 40mm, 45mm, 55mm, 60mm, 80mm, 100mm, etc., and will not be listed one by one here. In this case, the first surface 201 of the first prism 20 can be a curved surface. Or, fL can approach infinity. In this case, the first surface 201 of the first prism 20 can be a plane.

[0070] By making fL 1 restricted within the range of [25mm, +∞), field curvature and pupil shift distortion can be corrected without significantly increasing the lens processing difficulty to ensure the imaging quality of the optical system. Additionally, when the first surface 201 of the first prism 20 is a curved surface, the first surface 201 of the first prism 20 can be an aspherical surface. The field curvature and pupil shift distortion can be corrected by the aspherical surface to further ensure the imaging quality of the optical system.

[0071] In some alternative embodiments of the present disclosure, the refractive index NL of the first prism 20 1 can be greater than or equal to 1.5 and less than or equal to 1.8.

[0072] That is, the refractive index NL of the first prism 20 1 can be restricted within the range of [1.5, 1.8]. For example, NL 1 can be 1.5, 1.6, 1.7, 1.8, etc., and will not be listed one by one here.

[0073] By restricting the refractive index NL of the first prism 20 1 within the range of [1.5, 1.8], it is beneficial to reduce the volume of the optical system, while meeting the design specifications of the eye box and eye relief and ensuring the imaging quality of the optical system.

[0074] In some alternative embodiments of the present disclosure, the Abbe number ABL of the first prism 20 1 can be greater than or equal to 15 and less than or equal to 60.

[0075] That is to say, the Abbe number ABL of the first prism 20 1 can be restricted within the range of [15, 60]. For example, ABL 1 can be 15, 20, 30, 40, 50, 60, etc., and will not be listed one by one here.

[0076] By restricting the Abbe number ABL of the first prism 20 1 within the range of [15, 60], it is beneficial to ensure the rationality of the parameters of the first prism 20, and thus beneficial to ensure the imaging quality of the optical system.

[0077] In some alternative embodiments of the present disclosure, the angle a between the second surface 203 and the third surface 205 of the first prism 20 can be greater than or equal to 20 degrees and less than or equal to 30 degrees.

[0078] That is to say, the angle a between the second surface 203 and the third surface 205 of the first prism 20 can be restricted within the range of [20°, 30°]. For example, a can be 20°, 23°, 25°, 26°, 28°, 30°, etc., and will not be listed one by one here.

[0079] Through research, it is found that the angle a is related to the eye box, eye relief, and the volume of the optical system. Restricting the angle a within the range of [20°, 30°] can enable the light rays emitted by the image source 10 to propagate along the set route and finally enter the eye box of the optical system, avoiding the adverse effects caused by the angle a being too large or too small. For example, when the light rays emitted by the image source 10 pass through the first prism 20 for the first time, they can undergo one total internal reflection and one reflection within the first prism 20.

[0080] In some alternative embodiments of the present disclosure, the refractive index NL of the second prism 30 2 can be greater than or equal to 1.5 and less than or equal to 1.8.

[0081] That is to say, the refractive index NL of the second prism 30 2 can be restricted within the range of [1.5, 1.8]. For example, NL 2It can be 1.5, 1.6, 1.7, 1.8, etc., and will not be listed one by one here. Optionally, NL 2 is the same as NL in the above text 1 and their specific values can be the same or different.

[0082] By restricting the refractive index NL of the second prism 30 2 within the range of [1.5, 1.8], it is beneficial to effectively compensate for the optical path difference generated after the light rays emitted from different light-emitting positions on the image source 10 propagate in the first prism 20, thereby being beneficial to ensuring the imaging quality of the optical system. At the same time, it can meet the design index of the eye relief.

[0083] In some optional embodiments of the present disclosure, the Abbe number ABL of the second prism 30 2 can be greater than or equal to 15 and less than or equal to 60.

[0084] That is to say, the Abbe number ABL of the second prism 30 2 can be restricted within the range of [15, 60]. For example, ABL 2 can be 15, 20, 30, 40, 50, 60, etc., and will not be listed one by one here. Optionally, ABL 2 is the same as ABL in the above text 1 and their specific values can be the same or different.

[0085] By restricting the Abbe number ABL of the second prism 30 2 within the range of [15, 60], it is beneficial to effectively compensate for the optical path difference generated after the light rays emitted from different light-emitting positions on the image source 10 propagate in the first prism 20, thereby being beneficial to ensuring the imaging quality of the optical system. At the same time, it can meet the design index of the eye relief.

[0086] In some optional embodiments of the present disclosure, the focal length f of the first lens 40 1 can be greater than or equal to 10 millimeters and less than or equal to 20 millimeters.

[0087] That is to say, the focal length f of the first lens 40 1 can be restricted within the range of [10mm, 20mm]. For example, f 1 can be 10mm, 12mm, 14mm, 15mm, 18mm, 20mm, etc., and will not be listed one by one here.

[0088] By restricting f 1 within the range of [10mm, 20mm], it can provide sufficient optical power for the optical system to achieve a larger field of view angle, and at the same time can effectively correct the field curvature, thereby being beneficial to ensuring the imaging quality of the optical system.

[0089] In some alternative embodiments of the present disclosure, the refractive index N of the first lens 40 1 may be greater than or equal to 1.45 and less than or equal to 1.75.

[0090] That is to say, the refractive index N of the first lens 40 1 can be limited within the range of [1.45, 1.75]. For example, N 1 can be 1.45, 1.55, 1.6, 1.7, 1.75, etc., which will not be enumerated one by one here.

[0091] By limiting the refractive index N of the first lens 40 1 within the range of [1.45, 1.75], it is beneficial to the overall optical design of the optical system, thus helping to ensure the imaging quality of the optical system.

[0092] In some alternative embodiments of the present disclosure, the Abbe number AB of the first lens 40 1 may be greater than or equal to 40 and less than or equal to 80.

[0093] That is to say, the Abbe number AB of the first lens 40 1 can be limited within the range of [40, 80]. For example, AB 1 can be 40, 45, 50, 55, 60, 70, 80, etc., which will not be enumerated one by one here.

[0094] Optionally, the first lens 40 may have an aspherical surface, and the field curvature and pupil shift distortion can be corrected by the aspherical surface to ensure the imaging quality of the optical system.

[0095] By limiting AB 1 within the range of [40, 80], it is beneficial to the overall optical design of the optical system, thus helping to ensure the imaging quality of the optical system.

[0096] In some alternative embodiments of the present disclosure, the field of view angle FOV of the optical system may be greater than or equal to 40 degrees and less than or equal to 80 degrees.

[0097] That is to say, the field of view angle FOV of the optical system can be limited within the range of [40°, 80°]. For example, FOV can be 40°, 50°, 60°, 70°, 80°, etc., which will not be enumerated one by one here. In this way, in the embodiments of the present disclosure, the user can see a clear picture within the field of view range of greater than or equal to 40 degrees and less than or equal to 80 degrees, and the field of view range is relatively large.

[0098] In some alternative embodiments of the present disclosure, the volume V of the optical system may be less than or equal to 10 cubic centimeters.

[0099] That is, the volume V of the optical system can satisfy the following formula: V ≤ 10 cc. For example, V can be 5 cc, 6 cc, 7 cc, 8 cc, 9 cc, 10 cc, etc., and will not be listed one by one here. In this way, in the embodiments of the present disclosure, the optical system has a small volume and a compact structure, which is beneficial to ensuring the miniaturization and light weight of the optical system.

[0100] In some alternative embodiments of the present disclosure, the size of the eye box at a preset suitable eye distance can satisfy at least one of the following two items:

[0101] 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;

[0102] The diameter DIA of the eye box is greater than 6 mm.

[0103] That is, the length LEN of the eye box can be limited within the range of [8 mm, 25 mm]. The height HEI of the eye box can be limited within the range of [3 mm, 10 mm]. For example, LEN can be 8 mm, 10 mm, 15 mm, 20 mm, 25 mm, etc., and HEI can be 3 mm, 5 mm, 6 mm, 9 mm, 10 mm, etc., and will not be listed one by one here. In addition, the diameter DIA of the eye box can be 6 mm, 6.5 mm, 7 mm, 8 mm, etc., and will not be listed one by one here. In this way, the optical system can have a larger eye box, which is beneficial to accommodating users with different pupil distances.

[0104] In some alternative embodiments of the present disclosure, the optical system can satisfy the following conditions: (1) (R 1 / RL 2 ) × (NL 2 / N 1 ) = 1.07; (2) the ratio f / d of the system focal length f of the optical system to the preset optical path length d = 0.447; (3) 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 = 0.076; (4) the ratio fL 1 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 1 / f = 1.938; (5) the ratio T×N 2 / d of the product of the thickness of the second lens 55 and the refractive index of the second lens to the preset optical path length d = 0.124; (6) the focal length f 2 of the second lens 55 is 19.8 mm; (7) the focal length fL 1= 26.4 mm; (8) The included angle α between the second surface 203 and the third surface 205 of the first prism 20 is 27.75°; (9) The focal length f of the first lens 40 1 = 14.11 mm; (10) The field of view angle FOV of the optical system is 54°; (11) The volume V of the optical system is 8 cc; (12) The exit pupil of the optical system is 20 mm × 10 mm. The optical system is designed according to the reverse optical path and satisfies Tables 1 and 2 as follows.

[0105] Table 1

[0106]

[0107]

[0108] Table 2

[0109]

[0110] In some alternative embodiments of the present disclosure, the optical system may satisfy the following conditions: (1) (R 1 / RL 2 ) × (NL 2 / N 1 ) = 1.04; (2) The ratio f / d of the system focal length f of the optical system to the preset optical path length d is 0.45; (3) 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 is 0.064; (4) The ratio fL 1 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 fL 1 / f = 3.51; (5) The ratio T×N 2 / d of the product of the thickness of the second lens 55 and the refractive index of the second lens to the preset optical path length d is 0.147; (6) The focal length f 2 of the second lens 55 is 19.33; (7) The focal length fL 1 of the first surface 201 of the first prism 20 is 45.73 mm; (8) The included angle α between the second surface 203 and the third surface 205 of the first prism 20 is 27.75°; (9) The focal length f 1 of the first lens 40 is 13.91 mm; (10) The field of view angle FOV of the optical system is 56°; (11) The volume V of the optical system is 8 cc; (12) The exit pupil of the optical system is 20 mm × 10 mm. The optical system is designed according to the reverse optical path and satisfies Tables 3 and 4 as follows.

[0111] Table 3

[0112] Surface Number Surface Type Radius of Curvature Thickness Refractive Index Abbe Number Tilt Angle 1 Virtual Image Infinity -5000 2 Infinity 15.00 3 Aspherical -41.22 7.00 1.544 56.00 4 Spherical Infinity 0.20 5 Lens Infinity 2.80 1.589 61.25 6 Reflective Surface -44.28 -2.80 7 Infinity -0.20 8 Spherical Infinity -3.70 1.544 56.00 9 Reflective Plane Infinity 3.70 1.544 56.00 27.75° 10 Reflective Plane Infinity -8.20 1.544 56.00 0° 11 Aspherical 25.00 -0.5 -55.5° 12 Aspherical -15.00 -2.4 1.773 49.62 13 Spherical Infinity -0.5 14 Image Plane

[0113] Table 4

[0114]

[0115] For Table 2 and Table 4, "S3" may refer to the surface with surface number 3, "S6" may refer to the surface with surface number 6, "S11" may refer to the surface with surface number 11, and "S12" may refer to the surface with surface number 12.

[0116] Through experiments, the Modulation Transfer Function (MTF) curve of the optical system can be obtained. It can be understood that the MTF curve is a curve describing the performance of the optical system and can be used to evaluate the ability of the optical system to restore contrast. Optionally, the MTF curve of the optical system can be as Figure 5 shown. Figure 5 In the horizontal axis can represent the spatial frequency, the vertical axis can represent the contrast, the solid line can represent the meridional direction, and the dashed line can represent the sagittal direction. From Figure 5 it can be seen that the optical system has good resolving power in different field directions and the overall imaging quality is high.

[0117] In summary, by using the optical system provided by the embodiments of the present disclosure, a large field of view can be achieved with a small volume, and the chief ray angle can be effectively controlled, and the field curvature, pupil shift distortion, and chromatic aberration can be effectively corrected, so as to ensure the imaging quality.

[0118] Some exemplary embodiments of the present disclosure also provide a head-mounted display device. The head-mounted display device may include Figure 6 the frame structure 600 shown in and the optical system in any of the above embodiments. The optical system may be installed in the frame structure.

[0119] In some alternative embodiments of the present disclosure, the frame structure 600 may be a structure capable of supporting and accommodating the optical system. For example, the frame structure 600 may include a glasses frame, a headband, etc.

[0120] In the embodiments of the present disclosure, through the setting of the frame structure 600, the installation of the optical system can be reliably realized. Through the cooperation of the various optical elements in the optical system, it can enable Figure 3 , Figure 4 the human eye 100 in to see the display picture provided by the image source 10 to meet the user's usage requirements. In addition, it can also enable the human eye 100 to see the external environment.

[0121] It should be noted that the various disclosed optional embodiments and optional implementation manners can be flexibly selected and combined according to needs to achieve corresponding functions and effects, and the present disclosure will not list them one by one.

[0122] The basic principles of the present disclosure have been described above in conjunction with specific embodiments. However, it should be pointed out that the advantages, benefits, effects, etc. mentioned in the present disclosure are only examples and not limitations, and it cannot be considered that these advantages, benefits, effects, etc. are essential for each embodiment of the present disclosure. In addition, the above-disclosed specific details are only for the purpose of illustration and easy understanding, rather than limitations. These details do not limit the present disclosure to necessarily adopt the above specific details to be implemented.

[0123] Each embodiment in this specification is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.

[0124] Those skilled in the art can 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 equivalent technologies, the present disclosure also intends to include these changes and modifications.

Claims

1. An optical system, characterized in that: include: Image source; a first prism, wherein the first prism has a first surface, a second surface, and a third surface, the first surface of the first prism being disposed close to the image source, and the second surface of the first prism being disposed close to an eye box of the optical system; a second prism, the second prism having a first surface and a second surface, the first surface of the second prism being disposed proximate to an eye box of the optical system, and the second surface of the second prism being disposed proximate to the second surface of the first prism; a first lens, the first lens being disposed close to the third surface of the first prism; a semi-transparent and semi-reflective film, wherein the semi-transparent and semi-reflective film is arranged on a side of the first lens away from the third surface of the first prism; Wherein, the light emitted by the image source is incident from the first surface of the first prism, and after at least one total reflection occurs in the first prism, it is emitted from the third surface of the first prism to the first lens, and the light reflected by the semi-transparent and semi-reflective film passes through the first lens, the first prism and the second prism in sequence, and is emitted from the first surface of the second prism to the eye box of the optical system; the ambient light passing through the semi-transparent and semi-reflective film passes through the first lens, the first prism and the second prism in sequence, and is emitted from the first surface of the second prism to the eye box of the optical system; The surface of the first lens away from the first prism has a curvature radius R1, the first surface of the second prism has a curvature radius RL2, and the optical system satisfies: (R1 / RL2)×(NL2 / N1) is greater than or equal to 0.9 and less than or equal to 1.1, NL2 represents the refractive index of the second prism, and N1 represents the refractive index of the first lens.

2. The optical system according to claim 1, characterized in that Among the light rays emitted by the image source and propagating along the optical axis of the optical system, the light rays pass through a preset optical path length d in the first prism when passing through the first prism for the first time, and 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 0.4 and less than or equal to 0.

5.

3. The optical system according to claim 1, characterized in that Among the light rays emitted by the image source and propagating along the optical axis of the optical system, the light rays pass through a preset optical path length d in the first prism when passing through the first prism for the first time. The first surface of the first prism is a curved surface, and the first surface of the first prism has a surface sag SAGL. The optical system satisfies: a ratio SAGL / L of the surface sag SAGL of the first surface of the first prism to an actual length L corresponding to the preset optical path length d is greater than or equal to 0.05 and less than or equal to 0.

1.

4. The optical system according to claim 1, characterized in that The optical system satisfies: a ratio fL1 / f of a focal length fL1 of a first surface of the first prism to a system focal length f of the optical system is greater than or equal to 1.

8.

5. The optical system according to claim 1, characterized in that Also includes: a second lens, the second lens being disposed between the image source and the first surface of the first prism; Wherein, the light emitted by the image source is incident from the first surface of the first prism after passing through the second lens.

6. The optical system according to claim 5, characterized in that The light emitted by the image source and propagating 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, and the second lens satisfies: T×N2 / d is greater than or equal to 0.1 and less than or equal to 0.2, T represents the thickness of the second lens, and N2 represents the refractive index of the second lens.

7. The optical system according to claim 5, characterized in that The focal length f2 of the second lens is greater than or equal to 10 mm and less than or equal to 30 mm.

8. The optical system according to claim 5, characterized in that A refractive index N2 of the second lens is greater than or equal to 1.4 and less than or equal to 2.

9. The optical system according to claim 5, characterized in that The Abbe number AB2 of the second lens is greater than or equal to 15 and less than or equal to 90.

10. The optical system according to any one of claims 1 to 9, characterized in that: The focal length fL1 of the first surface of the first prism is greater than or equal to 25 mm.

11. The optical system according to any one of claims 1 to 9, characterized in that: The refractive index NL1 of the first prism is greater than or equal to 1.5 and less than or equal to 1.

8.

12. The optical system according to any one of claims 1 to 9, characterized in that: The Abbe number ABL1 of the first prism is greater than or equal to 15 and less than or equal to 60.

13. The optical system according to any one of claims 1 to 9, characterized in that: 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.

14. The optical system according to any one of claims 1 to 9, characterized in that: The refractive index NL2 of the second prism is greater than or equal to 1.5 and less than or equal to 1.

8.

15. The optical system according to any one of claims 1 to 9, characterized in that: The Abbe number ABL2 of the second prism is greater than or equal to 15 and less than or equal to 60.

16. The optical system according to any one of claims 1 to 9, characterized in that: The focal length f1 of the first lens is greater than or equal to 10 mm and less than or equal to 20 mm.

17. The optical system according to any one of claims 1 to 9, characterized in that: The refractive index N1 of the first lens is greater than or equal to 1.45 and less than or equal to 1.

75.

18. The optical system according to any one of claims 1 to 9, characterized in that: The Abbe number AB1 of the first lens is greater than or equal to 40 and less than or equal to 80.

19. The optical system according to any one of claims 1 to 9, characterized in that: 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.

20. The optical system according to any one of claims 1 to 9, characterized in that: The volume V of the optical system is less than or equal to 10 cubic centimeters.

21. The optical system according to any one of claims 1 to 9, characterized in that: The size of the eye box at the preset eye relief satisfies at least one of the following two items: 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; The diameter of the eye box DIA is greater than 6 mm.

22. The optical system according to any one of claims 1 to 9, characterized in that: A polarization splitter film is disposed between the second surface of the first prism and the second surface of the second prism, and a quarter wave plate is disposed between the first lens and the third surface of the first prism.

23. A head mounted display device, characterized in that: include: A frame structure and an optical system as claimed in any one of claims 1 to 22, wherein the optical system is mounted on the frame structure.

Images