Optical system and head-mounted display device

Abstract

Disclosed in the embodiments of the present disclosure are an optical system and a head-mounted display device. The specific implementation solution is that the optical system comprises: an image source; a first prism, having a first surface, a second surface and a third surface, the first surface of the first prism being arranged close to the image source, and the second surface of the first prism being arranged close to an eyebox of the optical system; a second prism, having a first surface and a second surface, the first surface of the second prism being arranged close to the eyebox of the optical system, and the second surface of the second prism being arranged close to the second surface of the first prism; a first lens, arranged close to the third surface of the first prism; and a semi-transparent and semi-reflective film, arranged on the 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 having a radius of curvature R1, the first surface of the second prism having a radius of curvature RL2, and the optical system satisfying: (R1 / RL2)×(NL2 / N1) being greater than or equal to 0.9 and less than or equal to 1.1, where NL2 represents the refractive index of the second prism, and N1 represents the refractive index of the first lens.

Description

Optical system and head-mounted display device

[0001] The present disclosure claims priority to the Chinese patent application No. CN202410852830.0, filed on June 27, 2024, and entitled "Optical system and head-mounted display device", the entire content of which is incorporated herein by reference. 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

[0003] At present, the head-mounted display device is applied more and more widely. The head-mounted display device can be used for content display. For example, the head-mounted display device can be used for displaying movie pictures, game pictures, web pages, etc. The optical system is an important component of the head-mounted display device. SUMMARY

[0004] Embodiments of the present disclosure provide an optical system and a head-mounted display device.

[0005] According to an 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 disposed close to the image source, the second surface of the first prism being disposed close to an eyebox 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 close to the eyebox of the optical system, the second surface of the second prism being disposed close 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 half-transmission half-reflection film, the half-transmission half-reflection film being disposed on a side of the first lens away from the third surface of the first prism; the first lens has a curvature radius R1 away from the surface of the first prism, the first surface of the second prism has a curvature radius RL2, the optical system satisfies (R1 / RL2)×(NL2 / N1) 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.

[0006] For example, the light emitted by the image source is incident from the first surface of the first prism, after at least one total reflection in the first prism, the light is emitted from the third surface of the first prism to the first lens, and the light reflected by the half-transmission half-reflection film passes through the first lens, the first prism and the second prism in turn, and is emitted from the first surface of the second prism to the eyebox of the optical system; the ambient light passing through the half-transmission half-reflection film passes through the first lens, the first prism and the second prism in turn, and is emitted from the first surface of the second prism to the eyebox of the optical system.

[0007] According to another aspect of the embodiments of the present disclosure, there is provided a head-mounted display device, comprising: a frame structure; and the optical system as described above, which is mounted to the frame structure. BRIEF DESCRIPTION OF DRAWINGS

[0008] FIG. 1 is a structural schematic diagram of an optical system according to some exemplary embodiments of the present disclosure.

[0009] FIG. 2 is a structural schematic diagram of an optical system according to some other exemplary embodiments of the present disclosure.

[0010] FIG. 3 is a structural schematic diagram of an optical system according to some further exemplary embodiments of the present disclosure.

[0011] FIG. 4 is a structural schematic diagram of an optical system according to some yet other exemplary embodiments of the present disclosure.

[0012] FIG. 5 is a schematic diagram of a modulation transfer function curve of an optical system according to some exemplary embodiments of the present disclosure.

[0013] FIG. 6 is a schematic diagram of a frame structure according to some exemplary embodiments of the present disclosure.

[0014] In the drawings, 10, an image source; 20, a first prism; 30, a second prism; 40, a first lens; 50, a semi-transparent mirror; 201, a first surface of the first prism; 203, a second surface of the first prism; 205, a third surface of the first prism; 301, a first surface of the second prism 30; 303, a second surface of the second prism 30; 100, a human eye; b1, a light ray emitted by the image source; b2, another light ray emitted by the image source; b3, still another light ray emitted by the image source; b4, an ambient light ray; 55, a second lens; 60, a polarization beam splitter; 70, a 1 / 4 wave plate. DETAILED DESCRIPTION

[0015] Hereinafter, 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, and are not all embodiments of the present disclosure, and it should be understood that the present disclosure is not limited to the exemplary embodiments described herein.

[0016] In the description of the present disclosure, the terms "upper", "lower", "left", "right", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and 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 particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present disclosure.

[0017] In the description of the disclosure, unless explicitly defined and limited, the terms "mounting", "connecting", "fixing" and the like should be understood in a broad sense, for example, can be fixedly connected, can be detachably connected, or integrally connected; can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in the disclosure can be understood according to the specific circumstances.

[0018] Exemplary summary

[0019] The 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 realize augmented reality (AR) effect, virtual reality (VR) effect, mixed reality (MR) effect, etc. The head-mounted display device can be in the form of glasses, a helmet, etc.

[0020] The optical system is an important component of the head-mounted display device. The optical system can also be referred to as an optical machine. The optical system can be used to emit light of a display picture of the head-mounted display device, and process the light so that the light is projected to the eyes of a user wearing the head-mounted display device, thereby enabling the user to see the display picture. Therefore, in order to ensure the user's experience, it is necessary to reasonably design the optical system.

[0021] Exemplary structure

[0022] Some exemplary embodiments of the disclosure provide an optical system. For example, as shown in FIGS. 1 to 4, the optical system provided by the embodiments of the disclosure can include an image source 10, a first prism 20, a second prism 30, a first lens 40, and a semi-transparent semi-reflective film 50. The first prism 20 can have a first surface 201, a second surface 203, and a third surface 205. The first surface 201 of the first prism 20 can be disposed close to the image source 10. The second surface 203 of the first prism 20 can be disposed close to an eyebox of the optical system. The second prism 30 can have a first surface 301 and a second surface 303. The first surface 301 of the second prism 30 can be disposed close to the eyebox of the optical system. The second surface 303 of the second prism 30 can be disposed close to the second surface 203 of the first prism 20. The first lens 40 can be disposed close to the third surface 205 of the first prism 20. The semi-transparent semi-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.

[0023] In some optional embodiments of the present disclosure, the image source 10 can be configured to emit light rays of a display image. 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), and the like. For example, the image source 10 can be an OLED display screen.

[0024] In some optional embodiments of the present disclosure, the first prism 20 can be configured 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 eyebox 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.

[0025] It can be understood that the eyebox of the optical system can be a region in which a human eye (for example, the human eye 100 in FIGS. 3 and 4) can move, and in which the human eye 100 can see a clear and complete display image. The eyebox of the optical system can also be referred to as an Eye Box or EB. The size of the eyebox of the optical system is an important design index in the optical system.

[0026] In some optional embodiments of the present disclosure, the second prism 30 can be configured to serve as a compensating mirror for observing the external environment and to compensate for the optical path difference of light rays emitted from different light-emitting positions on the image source 10 after the light rays propagate in the first prism 20, so that the optical paths of the light rays emitted from different light-emitting positions are substantially 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 flat surface. The first surface 301 and the second surface 303 of the second prism 30 can intersect.

[0027] In some optional embodiments of the present disclosure, the first lens 40 can be used to provide optical power to achieve a large field of view. 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-transmission half-reflection film 50 can be disposed on the side of the first lens 40 away from the third surface 205 of the first prism 20. The half-transmission half-reflection film 50 can transmit light and reflect light. The half-transmission half-reflection film 50 can be disposed by bonding or the like.

[0028] It should be noted that the light emitted by the image source 10 can be incident on the first surface 201 of the first prism 20, after at least one total reflection in the first prism 20, the light is emitted from the third surface 205 of the first prism 20 to the first lens 40, and the light reflected by the half-transmission half-reflection film 50 passes through the first lens 40, the first prism 20 and the second prism 30 in turn, and is emitted from the first surface 301 of the second prism 30 to the eyebox of the optical system. The ambient light passing through the half-transmission half-reflection film 50 passes through the first lens 40, the first prism 20 and the second prism 30 in turn, and is emitted from the first surface 301 of the second prism 30 to the eyebox of the optical system.

[0029] 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, after at least one total reflection in the first prism 20, the light is emitted from the third surface 205 of the first prism 20 to the first lens 40, and the light reflected by the half-transmission half-reflection film 50 passes through the first lens 40, the first prism 20 and the second prism 30 in turn, and is emitted from the first surface 301 of the second prism 30 to the eyebox of the optical system. The ambient light passing through the half-transmission half-reflection film 50 passes through the first lens 40, the first prism 20 and the second prism 30 in turn, and is emitted from the first surface 301 of the second prism 30 to the eyebox of the optical system.

[0030] In an optional example, as shown in FIG. 4, the light rays emitted by the image source 10 can include a light ray b1, a light ray b2, and a light ray b3. The light ray b1 can be incident on the first surface 201 of the first prism 20 to enter the first prism 20. Next, the light ray b1 can propagate to the third surface 205 of the first prism 20 and undergo total 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 propagating to the second surface 203 of the first prism 20 can undergo reflection and exit from the third surface 205 of the first prism 20 to the first lens 40. Then, the semi-transparent and semi-reflective film 50 can reflect the light ray b1 so that the light ray b1 is adjusted to have a horizontal leftward propagation direction. In this way, the light ray b1 with the adjusted propagation direction can pass through the second prism 30 after passing through the first prism 20 again and exit from the first surface 301 of the second prism 30 to the eyebox of the optical system. The propagation paths of the light rays b2 and b3 can be understood with reference to the description of the propagation path of the light ray b1 and will not be repeated here.

[0031] As can be seen, 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, the light rays can undergo one total reflection and one reflection in the first prism 20, which not only prolongs the optical path of the optical system, but also avoids the problem of excessively large volume of the first prism 20 and excessively large degree of divergence of the light rays caused by too many times of total reflection and reflection in the first prism 20.

[0032] 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, the number of times of total reflection in the first prism 20 before the light rays exit from the third surface 205 of the first prism 20 to the first lens 40 can not be limited to one, and the number of times of reflection in the first prism 20 can also not be limited to one. For example, after one total 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 total reflection can occur again at the third surface 205 of the first prism 20 and one reflection can occur again at the second surface 203 of the first prism 20, and then the light rays exit from the third surface 205 of the first prism 20 to the first lens 40.

[0033] In some optional embodiments of the present disclosure, ambient light can pass through the semi-transparent and semi-reflective film 50 and enter the first lens 40. Next, the ambient light can enter the first prism 20 from the third surface 205 of the first prism 20, 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 exit from the first surface 301 of the second prism 30 to the eyebox of the optical system. In an optional example, the ambient light can include a light ray b4 in FIG. 4.

[0034] It can be seen that, in the optical system provided by the embodiments of the present disclosure, 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, by cooperation of the image source 10, the first prism 20, the second prism 30, the first lens 40 and the semi-transparent semi-reflective film 50. In this way, the human eye 100 can see the display picture provided by the image source 10, and the head-mounted display device can normally display content to meet the use requirements of the user, for example, to meet the viewing requirements of the user. 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 requirement of the user to understand the external environment.

[0035] In some optional embodiments of the present disclosure, as shown in FIG. 3 and FIG. 4, the optical system can further include a second lens 55. The second lens 55 can be arranged between the image source 10 and the first surface 201 of the first prism 20. 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 second lens 55.

[0036] In some optional embodiments of the present disclosure, the second lens 55 can belong to a positive lens. For example, the second lens 55 can be a double-convex lens as shown in FIG. 3. For another example, the second lens 55 can be a plano-convex lens as shown in FIG. 4.

[0037] In the embodiments of the present disclosure, the light emitted by the image source 10 can first pass through the second lens 55, and then be incident from the first surface 201 of the first prism 20. The second lens 55 can be a non-spherical 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.

[0038] In some optional embodiments of the present disclosure, as shown in FIG. 2, a polarization beam splitting film 60 can be arranged between the second surface 203 of the first prism 20 and the second surface 303 of the second prism 30. A 1 / 4 wave plate 70 can be arranged between the first lens 40 and the third surface 205 of the first prism 20.

[0039] As shown in FIG. 2, the polarization beam splitting film 60 can be attached to the second surface 203 of the first prism 20 and the second surface 303 of the second prism 30, respectively. 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 can be spaced apart from the first lens 40 by a certain distance. The 1 / 4 wave plate 70 can also be spaced apart from the third surface 205 of the first prism 20 by a certain distance.

[0040] Due to the arrangement of the polarization splitting film 60, when the light emitted by the image source 10 propagates to the polarization splitting film 60 through total reflection at the third surface 205 of the first prism 20, the polarization splitting film 60 can partially reflect the light, and the light reflected by the polarization splitting film 60 can be polarized light. The polarized light can exit from the third surface 205 of the first prism 20 and reach the half-transmission half-reflection film 50 after passing through the 1 / 4 wave plate 70 and the first lens 40 to be reflected by the half-transmission half-reflection film 50. Then, the polarized light passes through the first lens 40 and the 1 / 4 wave plate 70 again. Due to the two times of passing through the 1 / 4 wave plate 70, the polarization direction of the polarized light can change. When the polarized light reaches the polarization splitting film 60 through the 1 / 4 wave plate 70, the polarized light can be directly transmitted from the polarization splitting film 60 to enter the human eye 100 after passing through the second prism 30.

[0041] In this way, the light emitted by the image source 10 is incident on the polarization splitting film 60 during the propagation in the first prism 20, the first type of linearly polarized light is reflected by the polarization splitting film 60, is transmitted by the third surface 205 of the first prism 20, passes through the 1 / 4 wave plate 70 to convert the first type of linearly polarized light into the first type of circularly polarized light, is transmitted by the first lens 40 and reflected by the half-transmission half-reflection film 50 to convert the first type of circularly polarized light 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 to enter the first prism 20 and be transmitted by the polarization splitting film 60. Through the cooperation of the polarization 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, so that the human eye 100 can see the display picture provided by the image source 10.

[0042] In some optional embodiments of the present disclosure, a compensation lens can be arranged on the side of the second prism 30 away from the first prism 20 to compensate for the deformation of the ambient light caused by the first lens 40. 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 compensation lens, and the human eye 100 can see the ambient image without deformation.

[0043] In some optional embodiments of the present disclosure, the first surface 301 of the second prism 30 can be arranged as a curved surface, for example, as an aspherical surface. In this way, the first lens 40 does not need to be provided with an additional compensation lens. The ambient light can enter the human eye 100 without deflection after passing through the first lens 40, the first prism 20 and the second prism 30, and the optical system can be simplified.

[0044] In some optional embodiments of the present disclosure, the first lens 40 can have a curvature radius R1 away from the surface of the first prism 20. The first surface 301 of the second prism 30 can have a curvature radius RL2. The optical system can satisfy: (R1 / RL2) x (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 30, and N1 represents the refractive index of the first lens 40.

[0045] That is, (R1 / RL2) x (NL2 / N1) can be limited within the range of [0.9, 1.1]. For example, (R1 / RL2) x (NL2 / N1) can be 0.9, 0.95, 0.97, 1.0, 1.03, 1.05, 1.1, and the like, which will not be listed one by one here.

[0046] The first surface 301 of the second prism 30 participates in the optical path of the image source light and the ambient light. The parameters of the first surface 301 of the second prism 30 have an influence on both the image light and the ambient light. It is found through research that limiting (R1 / RL2) x (NL2 / N1) within the range of [0.9, 1.1] can compensate for the influence of the first lens 40 on the ambient light, while being able to take into account the imaging performance of the optical system for the image source light.

[0047] In some optional embodiments of the present disclosure, the light rays of the light rays emitted by the image source 10 that propagate along the optical axis of the optical system pass through a preset optical path length d in the first prism 20 when passing through the first prism 20 for the first time. The optical system can 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.

[0048] It should be noted that the optical system is a system composed of multiple optical elements in a certain order. For the optical system, the optical axis is the line connecting the optical centers of the optical elements in the optical system, and each optical element is arranged along the optical axis.

[0049] The light rays of the light rays emitted by the image source 10 that propagate along the optical axis of the optical system are incident from the first surface 201 of the first prism 20, the light rays that propagate along the optical axis of the optical system are emitted from the third surface 205 of the first prism 20, and the actual propagation distance of the light rays emitted by the image source 10 that propagate along the optical axis of the optical system in the first prism 20 is represented as a target distance. The target distance can be converted into the corresponding distance of the light rays propagating in a vacuum, and the corresponding distance obtained by the conversion 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, and the like, which will not be listed one by one here.

[0050] It is found through research that limiting f / d in the range of [0.4, 0.5] is conducive to achieving a larger eye relief (ER) and a larger eye box (EB) through a smaller volume of the optical system. The smaller volume is conducive to ensuring miniaturization and light weight of the optical system. The larger eye box is conducive to taking into account users with different pupil distances. The larger eye relief can allow a user who wears glasses (for example, myopia glasses) to use the head-mounted display device without taking off the glasses.

[0051] 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). Alternatively, the distance between the human eye 100 and the first surface 301 of the second prism 30 in FIGS. 3 and 4 can be taken as the eye relief. The eye relief can be generally set to 15 mm.

[0052] In some optional embodiments of the present disclosure, the light rays in the light rays emitted by the image source 10 that propagate along the optical axis of the optical system pass through a preset optical path length d in 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 sagittal height SAGL. The optical system can satisfy that the ratio SAGL / L of the surface sagittal 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 greater than or equal to 0.05 and less than or equal to 0.1.

[0053] It should be noted that the target path in the above can be taken as the actual length L corresponding to the preset optical path length d. The ratio SAGL / L of the surface sagittal 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 can be limited in 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, and the like, which will not be listed one by one here.

[0054] It is found through research that limiting SAGL / L in the range of [0.05, 0.1] is conducive to controlling the chief ray angle (CRA), the field curvature, and the pupil shift distortion of the optical system, thereby being conducive to ensuring the imaging quality of the optical system.

[0055] In some optional embodiments of the present disclosure, the optical system can satisfy that the ratio fL1 / f of the focal length fL1 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 1.8.

[0056] 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 in the range of [1.8, +∞). In this case, fL / f can be a finite value, for example, 1.8, 2, 3, 4, 5, 10, 20, etc., which are not listed one by one here. In this case, the first surface 201 of the first prism 20 can be a curved surface. Alternatively, fL / f can also tend to infinity. In this case, the first surface 201 of the first prism 20 can be a plane.

[0057] By limiting fL / f in the range of [1.8, +∞), the rationality of the parameters of the first surface 201 of the first prism 20 is ensured to ensure the imaging quality of the optical system. In addition, in the case where 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 aspheric surface. Through the aspheric surface, the field curvature and the pupil shift distortion can be corrected to further ensure the imaging quality of the optical system, while not significantly increasing the difficulty of lens processing.

[0058] In some optional embodiments of the present disclosure, the light rays of the light rays emitted by the image source 10 that propagate along the optical axis of the optical system pass through a preset optical path length d in the first prism 20 when passing through the first prism 20 for the first time. The second lens 55 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 55, and N2 represents the refractive index of the second lens 55.

[0059] That is, the ratio T×N2 / d 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 can be limited in 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 one by one here.

[0060] It is found through research that by limiting T×N2 / d in the range of [0.1, 0.2], the pupil shift distortion of the optical system can be controlled, and the entire optical system can realize a larger field of view angle in a smaller volume. In this way, the miniaturization, lightness and field of view range of the optical system can be taken into account.

[0061] In some optional embodiments of the present disclosure, the focal length f2 of the second lens 55 can be greater than or equal to 10 mm and less than or equal to 30 mm.

[0062] That is, the focal length f2 of the second lens 55 can be limited in the range of [10 mm, 30 mm]. For example, f2 can be 10 mm, 12 mm, 15 mm, 18 mm, 20 mm, 21 mm, 24 mm, 26 mm, 28 mm, 30 mm, etc., which are not listed one by one here.

[0063] It is found through research that limiting f2 in the range of [10mm, 30mm] can not only control the chief ray angle and field curvature of the optical system, but also correct the field curvature and chromatic aberration, thereby being conducive to ensuring the imaging quality of the optical system.

[0064] In some optional embodiments of the present disclosure, the refractive index N2 of the second lens 55 can be greater than or equal to 1.4 and less than or equal to 2.

[0065] That is, the refractive index N2 of the second lens 55 can be limited in 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 the like, which will not be listed one by one here. By limiting the refractive index N2 of the second lens 55 in the range of [1.4, 2.0], the second lens 55 can effectively correct the field curvature and pupil shift distortion, which is conducive to the overall optical design of the optical system, thereby being conducive to ensuring the imaging quality of the optical system.

[0066] In some optional embodiments of the present disclosure, the Abbe number AB2 of the second lens 55 can be greater than or equal to 15 and less than or equal to 90.

[0067] That is, the Abbe number AB2 of the second lens 55 can be limited in the range of [15, 90]. For example, AB2 can be 15, 20, 25, 30, 45, 60, 70, 80, 90, and the like, which will not be listed one by one here.

[0068] By limiting the Abbe number AB2 of the second lens 55 in the range of [15, 90], it is conducive to effectively correcting the field curvature and pupil shift distortion by the second lens 55, which is conducive to the overall optical design of the optical system, thereby being conducive to the imaging quality of the optical system.

[0069] In some optional embodiments of the present disclosure, the focal length fL1 of the first surface 201 of the first prism 20 can be greater than or equal to 25 millimeters.

[0070] That is, the focal length fL1 of the first surface 201 of the first prism 20 can be limited in the range of [25mm, +∞). Then, fL1 can be a finite value, for example, 25mm, 35mm, 40mm, 45mm, 55mm, 60mm, 80mm, 100mm, and the like, which 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. Alternatively, fL can tend to infinity. In this case, the first surface 201 of the first prism 20 can be a plane.

[0071] By limiting fL1 in the range of [25mm, +∞), the field curvature and the pupil shift distortion can be corrected without significantly increasing the difficulty of lens processing, so as to ensure the imaging quality of the optical system. In addition, in the case that 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 aspheric surface. The field curvature and the pupil shift distortion can be corrected by the aspheric surface, so as to further ensure the imaging quality of the optical system.

[0072] In some optional embodiments of the present disclosure, the refractive index NL1 of the first prism 20 can be greater than or equal to 1.5 and less than or equal to 1.8.

[0073] That is, the refractive index NL1 of the first prism 20 can be limited in the range of [1.5, 1.8]. For example, NL1 can be 1.5, 1.6, 1.7, 1.8, and the like, which will not be listed one by one here.

[0074] By limiting the refractive index NL1 of the first prism 20 in 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 eyebox and the eye relief and ensuring the imaging quality of the optical system.

[0075] In some optional embodiments of the present disclosure, the Abbe number ABL1 of the first prism 20 can be greater than or equal to 15 and less than or equal to 60.

[0076] That is, the Abbe number ABL1 of the first prism 20 can be limited in the range of [15, 60]. For example, ABL1 can be 15, 20, 30, 40, 50, 60, and the like, which will not be listed one by one here.

[0077] By limiting the Abbe number ABL1 of the first prism 20 in the range of [15, 60], it is beneficial to ensure the rationality of the parameters of the first prism 20, thereby being beneficial to ensure the imaging quality of the optical system.

[0078] In some optional embodiments of the present disclosure, the included angle a between the second surface 203 of the first prism 20 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.

[0079] That is, the included 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 in the range of [20°, 30°]. For example, a can be 20°, 23°, 25°, 26°, 28°, 30°, and the like, which will not be listed one by one here.

[0080] It is found through research that the included angle a is related to the eye box, the eye relief and the volume of the optical system. By limiting the included angle a in the range of [20°, 30°], the light emitted by the image source 10 can propagate along the set route and finally enter the eye box of the optical system, avoiding the adverse effects caused by too large or too small values of the included angle a. For example, the light emitted by the image source 10 can perform one total reflection and one reflection in the first prism 20 when passing through the first prism 20 for the first time.

[0081] In some optional embodiments of the present disclosure, the refractive index NL2 of the second prism 30 can be greater than or equal to 1.5 and less than or equal to 1.8.

[0082] That is, the refractive index NL2 of the second prism 30 can be limited in the range of [1.5, 1.8]. For example, NL2 can be 1.5, 1.6, 1.7, 1.8, and the like, which will not be listed one by one here. Optionally, the specific value of NL2 can be the same as or different from NL1 in the above.

[0083] By limiting the refractive index NL2 of the second prism 30 in the range of [1.5, 1.8], the optical path difference caused by the light emitted by different light-emitting positions on the image source 10 after propagating in the first prism 20 can be effectively compensated, thereby helping to ensure the imaging quality of the optical system, and at the same time, the design index of the eye relief can be met.

[0084] In some optional embodiments of the present disclosure, the Abbe number ABL2 of the second prism 30 can be greater than or equal to 15 and less than or equal to 60.

[0085] That is, the Abbe number ABL2 of the second prism 30 can be limited in the range of [15, 60]. For example, ABL2 can be 15, 20, 30, 40, 50, 60, and the like, which will not be listed one by one here. Optionally, the specific value of ABL2 can be the same as or different from ABL1 in the above.

[0086] By limiting the Abbe number ABL2 of the second prism 30 in the range of [15, 60], the optical path difference caused by the light emitted by different light-emitting positions on the image source 10 after propagating in the first prism 20 can be effectively compensated, thereby helping to ensure the imaging quality of the optical system, and at the same time, the design index of the eye relief can be met.

[0087] In some optional embodiments of the present disclosure, the focal length f1 of the first lens 40 can be greater than or equal to 10 millimeters and less than or equal to 20 millimeters.

[0088] That is, the focal length f1 of the first lens 40 can be limited in the range of [10mm, 20mm]. For example, f1 can be 10mm, 12mm, 14mm, 15mm, 18mm, 20mm, and the like, which are not listed one by one here.

[0089] By limiting f1 in the range of [10mm, 20mm], the optical system can be provided with sufficient optical power to achieve a larger field of view, while effectively correcting field curvature, thereby facilitating the guarantee of the imaging quality of the optical system.

[0090] In some optional embodiments of the present disclosure, the refractive index N1 of the first lens 40 can be greater than or equal to 1.45 and less than or equal to 1.75.

[0091] That is, the refractive index N1 of the first lens 40 can be limited in the range of [1.45, 1.75]. For example, N1 can be 1.45, 1.55, 1.6, 1.7, 1.75, and the like, which are not listed one by one here.

[0092] By limiting the refractive index N1 of the first lens 40 in the range of [1.45, 1.75], the overall optical design of the optical system is facilitated, thereby facilitating the guarantee of the imaging quality of the optical system.

[0093] In some optional embodiments of the present disclosure, the Abbe number AB1 of the first lens 40 can be greater than or equal to 40 and less than or equal to 80.

[0094] That is, the Abbe number AB1 of the first lens 40 can be limited in the range of [40, 80]. For example, AB1 can be 40, 45, 50, 55, 60, 70, 80, and the like, which are not listed one by one here.

[0095] Optionally, the first lens 40 can have an aspherical surface, which can correct field curvature and pupil shift distortion to guarantee the imaging quality of the optical system.

[0096] By limiting AB1 in the range of [40, 80], the overall optical design of the optical system is facilitated, thereby facilitating the guarantee of the imaging quality of the optical system.

[0097] In some optional embodiments of the present disclosure, the field of view FOV of the optical system can be greater than or equal to 40 degrees and less than or equal to 80 degrees.

[0098] That is, the field of view FOV of the optical system can be limited in the range of [40°, 80°]. For example, the FOV can be 40°, 50°, 60°, 70°, 80°, and the like, which are not listed one by one here. In this way, in the embodiments of the present disclosure, the user can see a clear picture in a field of view range greater than or equal to 40 degrees and less than or equal to 80 degrees, and the field of view range is larger.

[0099] In some optional embodiments of the present disclosure, the volume V of the optical system can be less than or equal to 10 cubic centimeters.

[0100] That is, the volume V of the optical system can satisfy the following formula: V≤10cc. For example, V can be 5cc, 6cc, 7cc, 8cc, 9cc, 10cc, and the like, which are not listed one by one here. In this way, in the embodiments of the present disclosure, the volume of the optical system is small, and the structure is compact, which is beneficial to ensure the miniaturization and light weight of the optical system.

[0101] In some optional embodiments of the present disclosure, an optical system is provided, which includes: 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 the image source, the second surface of the first prism being arranged close to an eyebox 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 a curved surface arranged close to the eyebox of the optical system, the second surface of the second prism being arranged close to the second surface of the first prism; a first lens, the first lens being arranged close to the third surface of the first prism, the surface of the first lens away from the first prism being a curved surface; a half-transmission half-reflection film, the half-transmission half-reflection film being arranged on the 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 in the first prism, the light is emitted from the third surface of the first prism to the first lens, and the light reflected by the half-transmission half-reflection film passes through the first lens, the first prism and the second prism in turn, and is emitted from the first surface of the second prism to the eyebox of the optical system; the ambient light passes through the half-transmission half-reflection film, the first lens, the first prism and the second prism in turn, and is emitted from the first surface of the second prism to the eyebox of the optical system; the volume V of the optical system is less than or equal to 10 cubic centimeters.

[0102] In some optional embodiments of the present disclosure, the size of the eyebox at the preset eye relief can satisfy at least one of the following two conditions:

[0103] The length LEN of the eyebox is greater than or equal to 8 millimeters and less than or equal to 25 millimeters, and the height HEI of the eyebox is greater than or equal to 3 millimeters and less than or equal to 10 millimeters;

[0104] The diameter DIA of the eyebox is greater than 6 millimeters.

[0105] That is, the length LEN of the eyebox can be limited in the range of [8mm, 25mm]. The height HEI of the eyebox can be limited in 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., which are not listed one by one here. In addition, the diameter DIA of the eyebox can be 6mm, 6.5mm, 7mm, 8mm, etc., which are not listed one by one here. In this way, the optical system can have a larger eyebox, which is conducive to taking into account users with different pupil distances.

[0106] In some optional embodiments of the present disclosure, the optical system can satisfy the following conditions: (1) (R1 / RL2) x (NL2 / N1) = 1.07; (2) the ratio of the system focal length f of the optical system to the preset optical path length d f / d = 0.447; (3) the ratio of the face form sagittal 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 SAGL / L = 0.076; (4) the ratio of the focal length fL1 of the first surface 201 of the first prism 20 to the system focal length f of the optical system fL1 / f = 1.938; (5) the ratio of the product of the thickness T of the second lens 55 and the refractive index N2 of the second lens to the preset optical path length d T x N2 / d = 0.124; (6) the focal length f2 of the second lens 55 is 19.8mm; (7) the focal length fL1 of the first surface 201 of the first prism 20 is 26.4mm; (8) the included angle a between the second surface 203 of the first prism 20 and the third surface 205 of the first prism 20 is 27.75°; (9) the focal length f1 of the first lens 40 is 14.11mm; (10) the field of view FOV of the optical system is 54°; (11) the volume V of the optical system is 8cc; (12) the eyebox of the optical system is 20mm x 10mm. The optical system is designed according to the reverse optical path, and satisfies the following Table 1 and Table 2.

[0107] Table 1

[0108] Table 2

[0109] In some optional embodiments of the present disclosure, the optical system can satisfy the following conditions: (1) (R1 / RL2) x (NL2 / N1) = 1.04; (2) the ratio of the system focal length f of the optical system to the preset optical path length d f / d = 0.45; (3) the ratio of the surface form sagittal 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 SAGL / L = 0.064; (4) the ratio of the focal length fL1 of the first surface 201 of the first prism 20 to the system focal length f of the optical system fL1 / f = 3.51; (5) the ratio of the product of the thickness T and the refractive index N2 of the second lens 55 to the preset optical path length d T x N2 / d = 0.147; (6) the focal length f2 of the second lens 55 is 19.33; (7) the focal length fL1 of the first surface 201 of the first prism 20 is 45.73 mm; (8) the included angle a between the second surface 203 of the first prism 20 and the third surface 205 of the first prism 20 is 27.75°; (9) the focal length f1 of the first lens 40 is 13.91 mm; (10) the field of view FOV of the optical system is 56°; (11) the volume V of the optical system is 8 cc; (12) the eyebox of the optical system is 20 mm x 10 mm. The optical system is designed according to the reverse light path and satisfies the following Table 3 and Table 4.

[0110] Table 3

[0111] Table 4

[0112] For Table 2 and Table 4, “S3” can refer to the surface with surface number 3, “S6” can refer to the surface with surface number 6, “S11” can refer to the surface with surface number 11, and “S12” can refer to the surface with surface number 12.

[0113] 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 for describing 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 FIG. 5. The horizontal axis in FIG. 5 can represent spatial frequency, the vertical axis can represent contrast, the solid line can represent the meridional direction, and the dashed line can represent the sagittal direction. As shown in FIG. 5, the optical system has good resolving power in different field directions, and the overall imaging quality is high.

[0114] In summary, the optical system provided by the embodiments of the present disclosure can achieve a larger field of view in a smaller volume, effectively control the chief ray angle, effectively correct field curvature, pupil shift distortion and chromatic aberration, and thus ensure the imaging quality.

[0115] Some example embodiments of the present disclosure also provide a head-mounted display device. The head-mounted display device can include the frame structure 600 shown in FIG. 6 and the optical system in any of the above embodiments. The optical system can be mounted on the frame structure.

[0116] In some optional embodiments of the present disclosure, the frame structure 600 can be a structure capable of supporting and accommodating the optical system. For example, the frame structure 600 can include a spectacle frame, a headband, etc.

[0117] In the embodiments of the present disclosure, the installation of the optical system can be reliably achieved through the provision of the frame structure 600. Through the cooperation of various optical elements in the optical system, the human eye 100 in FIGS. 3 and 4 can see the display picture provided by the image source 10 to meet the use requirements of the user, and in addition, the human eye 100 can also see the external environment.

[0118] It should be noted that the various optional embodiments and optional embodiments disclosed above can be flexibly selected and combined as needed to achieve the corresponding functions and effects, and the present disclosure does not enumerate one by one.

[0119] The basic principles of the present disclosure are described above in combination with specific embodiments, but it should be noted that the advantages, advantages, effects, etc. mentioned in the present disclosure are only examples and are not limiting, and these advantages, advantages, effects, etc. cannot be considered as the must-have of each embodiment of the present disclosure. In addition, the specific details disclosed above are only for the purpose of example and for the purpose of understanding, and are not limiting, and the above details do not limit the present disclosure to be implemented with the above specific details.

[0120] Each of the embodiments in the specification is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be mutually referred to.

[0121] Those skilled in the art can make various modifications and variations 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 modifications and variations.

Claims

1. An optical system, comprising: Image source; A first prism has a first surface, a second surface, and a third surface. 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 eyepiece of the optical system. The second prism has a first surface and a second surface, the first surface of the second prism being disposed close to the eyebox of the optical system, and the second surface of the second prism being disposed close to the second surface of the first prism. A first lens is disposed near the third surface of the first prism; A semi-transparent and semi-reflective film is disposed on the side of the first lens away from the third surface of the first prism; The light emitted from the image source enters from the first surface of the first prism, undergoes at least one total internal reflection within the first prism, and exits from the third surface of the first prism to the first lens. After being reflected by the semi-transparent and semi-reflective coating, the light 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. Ambient light sequentially passes through the semi-transparent and semi-reflective coating, 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. The first lens has a radius of curvature R1 on the surface away from the first prism, the second prism has a radius of curvature RL2 on its first surface, the first lens has a refractive index N1, the second prism has a refractive index NL2, and the optical system satisfies that (R1 / RL2)×(NL2 / N1) is greater than or equal to 0.9 and less than or equal to 1.

1.

2. The optical system according to claim 1, wherein, When the light emitted from the image source passes through the first prism for the first time, the light propagating along the optical axis of the optical system travels through a preset optical path length d within the first prism. The optical system satisfies the following condition: the ratio of the system focal length f of the optical system to the preset optical path length d, f / 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 or 2, wherein, When the light emitted from the image source passes through the first prism for the first time, the light propagating along the optical axis of the optical system travels a preset optical path length d within the first prism. The first surface of the first prism is curved and has a surface profile sagitta SAGL. The optical system satisfies the following: the ratio of the surface profile sagitta SAGL of the first surface of the first prism to the actual length L corresponding to the preset optical path length d, SAGL / L, is greater than or equal to 0.05 and less than or equal to 0.

1.

4. The optical system according to any one of claims 1 to 3, wherein, The optical system satisfies the following condition: the ratio of the focal length fL1 of the first surface of the first prism to the system focal length f of the optical system, fL1 / f, is greater than or equal to 1.

8.

5. The optical system according to any one of claims 1 to 4, further comprising: A second lens is disposed between the image source and the first surface of the first prism; The light emitted from the image source, after passing through the second lens, enters from the first surface of the first prism.

6. The optical system according to claim 5, wherein, When the light emitted from the image source passes through the first prism for the first time, the light propagating along the optical axis of the optical system travels through a preset optical path length d within the first prism. The second lens satisfies the following condition: 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 second lens and N2 represents the refractive index of the second lens.

7. The optical system according to claim 5 or 6, wherein, 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 any one of claims 5 to 7, wherein, The refractive index N2 of the second lens is greater than or equal to 1.4 and less than or equal to 2, and the Abbe number AB2 of the second lens is greater than or equal to 15 and less than or equal to 90.

9. The optical system according to any one of claims 1-8, wherein, The focal length fL1 of the first surface of the first prism is greater than or equal to 25 mm.

10. The optical system according to any one of claims 1-9, wherein, The refractive index NL1 of the first prism is greater than or equal to 1.5 and less than or equal to 1.8, and the Abbe number ABL1 of the first prism is greater than or equal to 15 and less than or equal to 60.

11. The optical system according to any one of claims 1-10, wherein, The refractive index NL2 of the second prism is greater than or equal to 1.5 and less than or equal to 1.8, and the 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 any one of claims 1-11, wherein, The focal length f1 of the first lens is greater than or equal to 10 mm and less than or equal to 20 mm.

13. The optical system according to any one of claims 1-2, wherein, The refractive index N1 of the first lens is greater than or equal to 1.45 and less than or equal to 1.75, and the Abbe number AB1 of the first lens is greater than or equal to 40 and less than or equal to 80.

14. The optical system according to any one of claims 1-13, wherein, The volume V of the optical system is less than or equal to 10 cubic centimeters.

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

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