Optical imaging system and head-mounted display device

Abstract

Embodiments of the present application provide an optical imaging system and a head-mounted display device. The system comprises a first lens group, a first polarization device, a second lens group, and a second polarization device arranged in sequence. The second lens group has at least one reflection surface protruding towards the first polarization device, and comprises a first lens and a second lens. The first lens has a positive refractive power in a vicinity of an optical axis, and the second lens has a negative refractive power in a vicinity of the optical axis. The refractive index of the first lens is smaller than that of the second lens, and the Abbe number of the first lens is greater than that of the second lens. The system further comprises a first quarter-wave plate between the reflection surface of the second lens group and the first polarization device, and a second quarter-wave plate between the reflection surface of the second lens group and the second polarization device. The optical imaging system has high resolving power, thereby improving the resolution of the head-mounted display device and solving the problem of blurred imaging in vision of the head-mounted display device.

Description

Technical Field

[0001] This application relates to the field of optics, and more specifically, to an optical imaging system and a head-mounted display device. Background Technology

[0002] Head-mounted displays, such as virtual reality (VR) headsets, typically have a resolution of around 20 pixels per degree (PPD), while the human eye's resolution is generally around 60 PPD. The angular resolution of VR headsets is far lower than that of the human eye. This results in blurry visuals and a poor user experience.

[0003] To improve the resolution of head-mounted displays and address the issue of blurred visual imaging, higher pixel density displays, such as μ-organic light-emitting diode (μOLED) displays, can be used. However, the resolution of current optical imaging systems in head-mounted displays is generally around 20 line pairs / mm (lp / mm), which is only sufficient to resolve the larger pixel size of liquid crystal displays (LCDs). If the optical imaging system of a head-mounted display is to resolve μOLED displays, its resolution needs to be significantly improved. Summary of the Invention

[0004] This application provides an optical imaging system and a head-mounted display device. The optical imaging system has high resolution, which can improve the resolution of the head-mounted display device and solve the problem of blurry visual imaging in VR head-mounted display devices.

[0005] In a first aspect, an optical imaging system is provided, comprising: a first lens group, a first polarizing device, a second lens group, and a second polarizing device arranged sequentially; the second lens group having at least one reflective surface convex toward the first polarizing device; the second lens group including a first lens and a second lens; the portion of the first lens near the optical axis having positive optical power; the portion of the second lens near the optical axis having negative optical power; the refractive index of the first lens being less than the refractive index of the second lens; and the Abbe number of the first lens being greater than the Abbe number of the second lens; the optical imaging system further comprising a first quarter-wave plate and a second quarter-wave plate, the first quarter-wave plate being located between the reflective surface of the second lens group and the first polarizing device; and the second quarter-wave plate being located between the reflective surface of the second lens group and the second polarizing device. The first lens group is used to compensate for aberrations in unpolarized light; the first polarizing device is used to convert the aberration-compensated unpolarized light emitted from the first lens group into first linearly polarized light; the first quarter-wave plate is used to convert the first linearly polarized light emitted from the first polarizing device into first circularly polarized light; the second lens group is used to transmit the first circularly polarized light emitted from the first quarter-wave plate, and the reflecting surface of the second lens group is used to reflect the first circularly polarized light emitted from the second quarter-wave plate; the second quarter-wave plate is used to convert the first circularly polarized light emitted from the second lens group into first linearly polarized light, convert the first linearly polarized light emitted from the second polarizing device into first circularly polarized light, and convert the second circularly polarized light emitted from the second lens group into second linearly polarized light, wherein the second circularly polarized light is the light reflected from the reflecting surface of the second lens group when the first circularly polarized light emitted from the second quarter-wave plate strikes the reflecting surface of the second lens group; the second polarizing device is used to reflect the first linearly polarized light emitted from the second quarter-wave plate and transmit the second linearly polarized light emitted from the second quarter-wave plate.

[0006] In the optical imaging system provided in this application embodiment, on the one hand, by reasonably matching the optical power, Abbe number, and refractive index of the multiple lenses included in the second lens group, the second lens group can effectively correct chromatic aberration of the incident light. On the other hand, since the first polarizing device is located on the side of the first lens group away from the light source, the ghost image generated by birefringence of the first lens group can be eliminated using the principle of polarization. Furthermore, the first lens group is closer to the light source than the second lens group, and since the light incident on the first lens group is unpolarized, the first lens group does not need to control birefringence, allowing for a wide range of optical materials and greater design freedom; while the light incident on the second lens group is not unpolarized, the second lens group needs to control birefringence. Thus, this optical imaging system can eliminate the impact of increased operating temperature of the light source on the improvement of birefringence in the second lens group. Therefore, this optical imaging system has high resolution, thereby improving the resolution of the head-mounted display device and solving the problem of visually blurred images in head-mounted display devices.

[0007] In one feasible implementation, the absolute value of the sum of the first ratio and the second ratio is less than or equal to a first threshold, wherein the first ratio is the ratio of the optical power of the first lens to the Abbe number of the first lens, the second ratio is the ratio of the optical power of the second lens to the Abbe number of the second lens, and the first threshold is related to the optical power of the second lens group. In this way, the second lens group can achieve a higher chromatic aberration correction effect for incident light.

[0008] In one possible implementation, the optical imaging system further includes a third polarizing device located on the side of the second polarizing device away from the second lens group, the third polarizing device being used to absorb first linearly polarized light transmitted from the second polarizing device and to transmit second linearly polarized light emitted from the second polarizing device.

[0009] A third polarizing device is placed on the side of the second polarizing device away from the second lens group. In this way, the third polarizing device can absorb the first linearly polarized light emitted from the second polarizing device, thereby eliminating the ghosting produced by the first linearly polarized light.

[0010] In one possible implementation, the optical imaging system further includes a third lens group located on the side of the second polarizing device away from the second quarter-wave plate, the third lens group being used to transmit light emitted from the second polarizing device.

[0011] The light emitted from the second polarizing device is less dispersed, and the beams from different fields of view overlap more significantly. Therefore, the third lens group can correct aberrations that are independent of the field of view.

[0012] In one feasible embodiment, the second polarizing device is bonded to the third lens group. Alternatively, the second polarizing device is bonded to the third polarizing device, and the third polarizing device is bonded to the third lens group. This reduces the size and complexity of the optical imaging system.

[0013] In one possible implementation, the optical imaging system further includes a first substrate disposed on the side of the second polarizing device away from the second lens group, and the first substrate is bonded to the second polarizing device. Alternatively, the optical imaging system further includes a first substrate bonded to a third polarizing device, and the third polarizing device bonded to the second polarizing device. In this way, the surface of the second lens group near the second polarizing device can be configured as an aspherical surface of any shape, thereby increasing the design freedom of the optical imaging system.

[0014] In one feasible approach, the third lens group is made of optical resin. This effectively reduces the weight of the optical imaging system.

[0015] In one possible implementation, the optical imaging system further includes a display screen for emitting the unpolarized light.

[0016] In one possible embodiment, the optical imaging system further includes: a moving mechanism fixedly connected to the target structure, the moving mechanism being used to move the target structure along the direction of light transmission of the optical imaging system; wherein, the first lens group includes a first partial lens and a second partial lens, the first partial lens being located between the second partial lens and the display screen, the target structure including the display screen and the first partial lens; the target structure including the display screen and the first lens group; the target structure including the display screen, the first lens group, and the first polarizing device.

[0017] By incorporating a moving mechanism, the target structure is moved along the direction of light transmission in the optical imaging system, thereby adjusting the distance between the target structure and other structures in the optical imaging system, and ultimately adjusting the object distance. Based on the imaging relationship, if the object distance changes, the distance from the displayed image formed by the optical imaging system to the viewer's eye will also change accordingly. In this way, the optical imaging system can be adapted to people with different visual acuity.

[0018] In one feasible approach, the first polarizing device is bonded to the second lens group. Alternatively, the first polarizing device is bonded to the first quarter-wave plate, and the first quarter-wave plate is bonded to the second lens group. This reduces the size and complexity of the optical imaging system.

[0019] In one possible implementation, the optical imaging system further includes a second substrate disposed on the side of the first polarizer away from the first lens group, and the second substrate is attached to the first polarizer. Alternatively, the optical imaging system further includes a second substrate attached to the first quarter-wave plate, and the first quarter-wave plate is attached to the first polarizer. In this way, the surface of the second lens group near the first polarizer and the surface of the first lens group near the first polarizer can both be set as aspherical surfaces of arbitrary shapes, thereby not only increasing the design freedom of the optical imaging system, but also enabling the second lens group to achieve higher chromatic aberration correction.

[0020] In one feasible embodiment, the second polarizing device is bonded to the second lens group. Alternatively, the second polarizing device and the second quarter-wave plate are bonded together, and the second quarter-wave plate is bonded to the second lens group. This not only reduces the size and complexity of the optical imaging system but also avoids the existence of an air gap between the second lens group and the second polarizing device, which would prevent light reflected from the second polarizing device from reflecting at the air interface before the reflecting surface in the second lens group, forming a ghost image that enters the human eye.

[0021] In one possible implementation, the optical imaging system further includes a third substrate disposed on the side of the second polarizing device near the second lens group, the third substrate being bonded to the second polarizing device. Alternatively, the optical imaging system further includes a third substrate bonded to the second quarter-wave plate, and the second polarizing device being bonded to the second quarter-wave plate. In this way, the surface of the second lens group near the second polarizing device can be set as an aspherical surface of any shape, thereby not only increasing the design freedom of the optical imaging system, but also enabling the second lens group to achieve higher chromatic aberration correction, thus improving the image sharpness of the optical imaging system.

[0022] In one feasible approach, the first polarizing device is bonded to the first lens group. This can reduce the size and complexity of the optical imaging system.

[0023] In one possible implementation, the optical imaging system further includes a fourth substrate disposed on the side of the first polarizing device near the first lens group, and the fourth substrate is attached to the first polarizing device. In this way, the surface of the first lens group near the first polarizing device can be set as an aspherical surface of any shape, thereby not only increasing the design freedom of the optical imaging system, but also enabling the first lens group to achieve higher aberration correction effects, thus improving the image sharpness of the optical imaging system.

[0024] In one possible implementation, the optical imaging system further includes a third quarter-wave plate located between the first polarizing device and the first lens group, the third quarter-wave plate being used to transmit aberration-compensated unpolarized light emitted from the first lens group.

[0025] Since the third quarter-wave plate is positioned between the first lens group and the first polarizing device, the ghost image generated by the surface reflection of the first lens group can be eliminated.

[0026] In one feasible approach, the third quarter-wave plate is attached to the first lens group. Alternatively, the third quarter-wave plate is attached to the first polarizing device. This reduces the size and complexity of the optical imaging system.

[0027] In one possible implementation, the optical imaging system further includes a fifth substrate disposed on the side of the third quarter-wave plate away from the first polarizing device, the fifth substrate being attached to the third quarter-wave plate. In this way, the surface of the first lens group near the third quarter-wave plate can be configured as an aspherical surface of any shape, thereby not only increasing the design freedom of the optical imaging system, but also enabling the first lens group to achieve higher chromatic aberration correction, thus improving the image sharpness of the optical imaging system.

[0028] In one possible implementation, the slow axis direction of the third quarter-wave plate forms a 45-degree angle with the polarization direction that the first polarization device allows to transmit.

[0029] In one possible implementation, the slow axis direction of the first quarter-wave plate forms a 45-degree angle with the polarization direction that the first polarization device allows to transmit.

[0030] In one possible implementation, the slow axis direction of the second quarter-wave plate forms a 45-degree angle with the polarization direction that the second polarization device allows to transmit through.

[0031] In one possible implementation, the slow axis direction of the first quarter-wave plate forms a 90-degree angle with the slow axis direction of the second quarter-wave plate; the polarization direction that the first polarizing device allows to pass through forms a 90-degree angle with the polarization direction that the second polarizing device allows to pass through.

[0032] In one feasible manner, the reflectivity of the reflecting surface of the second lens group is 30%-70%.

[0033] In one feasible approach, the first lens group is made of optical resin.

[0034] Since the first lens group does not need to control birefringence, it is not limited by the birefringence properties of the material. The material of the first lens group can be any optical resin, which can effectively reduce the weight of the optical imaging system.

[0035] In one possible implementation, the second lens group is made of optical glass; or, the second lens group is made of optical resin in which the average birefringence path difference within the aperture is less than or equal to a second threshold, wherein the second threshold is 30 nm.

[0036] The larger the birefringence path difference, the greater the change in polarization state of polarized light after passing through the lens, resulting in a larger ghost image. In optical imaging systems, the second lens group needs to control birefringence. Therefore, choosing a material with a smaller birefringence path difference for the second lens group can reduce the ghost image introduced by the optical imaging system.

[0037] In one possible implementation, the side of the second lens group closest to the second polarizing device is a plane.

[0038] By making the side of the second lens group closest to the second polarizing device a plane, the second polarizing device can be well fitted to the second lens group. Alternatively, the second polarizing device can be well fitted to the second lens group via a second quarter-wave plate. This planar bonding method helps improve the yield of the optical imaging system 200 and reduce its cost.

[0039] In a second aspect, a head-mounted display device is provided, including an optical imaging system as described in the first aspect or any possible implementation thereof.

[0040] In one possible implementation, the head-mounted display device further includes a processor for displaying an image on the display screen to cause the display screen to emit the unpolarized light.

[0041] In one possible implementation, the head-mounted display device further includes: a memory for storing image data; when the image data is executed by the processor, the display screen displays the image.

[0042] The beneficial effects of the head-mounted display device mentioned in the second aspect above can be referred to the first aspect, and for the sake of brevity, they will not be repeated. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the structure of a head-mounted display device provided in an embodiment of this application.

[0044] Figure 2 This is a schematic diagram of the structure of an optical imaging system provided in an embodiment of this application.

[0045] Figure 3 This is a schematic diagram of another optical imaging system provided in an embodiment of this application.

[0046] Figure 4 This is a schematic diagram of the structure of another optical imaging system provided in the embodiments of this application.

[0047] Figure 5 This is a schematic diagram of the structure of another optical imaging system provided in the embodiments of this application.

[0048] Figure 6 This is an MTF curve of the optical imaging system provided in the embodiments of this application. Detailed Implementation

[0049] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0050] It should be noted that, in the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in this article is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone.

[0051] In the embodiments of this application, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of the embodiments of this application, "multiple" refers to two or more, and "at least one" and "one or more" refer to one, two, or more than two. The singular expressions "a," "an," "the," "the," "the," and "this" are intended to also include expressions such as "one or more," unless the context explicitly indicates otherwise.

[0052] The terms “including,” “comprising,” “having,” and variations thereof all mean “including but not limited to,” unless otherwise specifically emphasized.

[0053] In the description of the embodiments of this application, the terms "upper," "lower," "left," "right," "inner," "outer," and "vertical," etc., indicate orientations or positional relationships relative to the indicated placement of components in the accompanying drawings. It should be understood that these directional terms are relative concepts, used for relative description and clarification, and not to indicate or imply a specific orientation that the device or component must have, or its construction and operation in a specific orientation. They can change accordingly based on variations in the orientation of the components in the accompanying drawings, and therefore should not be construed as limiting this application. Furthermore, the term "vertical" in this application is not vertical in the strict sense, but rather within the permissible range of error.

[0054] In the embodiments of this application, the same reference numerals are used to denote the same component or part. For the same part in the embodiments of this application, only one part or component may be labeled with reference numerals in the figures. It should be understood that the reference numerals also apply to other identical parts or components. In addition, the various parts in the figures are not drawn to scale, and the dimensions and sizes of the parts shown in the figures are only exemplary and should not be construed as limiting this application.

[0055] The head-mounted display device involved in the embodiments of this application can be a VR head-mounted display device, or it can also be called a VR headset, VR glasses, etc. The VR head-mounted display device can be an external head-mounted display device, an all-in-one head-mounted display device, or a mobile head-mounted display device, etc., and this application does not limit it in this regard.

[0056] For example, Figure 1 This is a schematic diagram of the structure of a head-mounted display device 100 provided in an embodiment of this application.

[0057] like Figure 1 As shown, the head-mounted display device 100 may include at least one processor 110, a memory 120, a communication interface 130, a communication bus 140, and an optical imaging system 150.

[0058] Processor 110 is the control center of the head-mounted display device 100. It can be a single processor or a collective term for multiple processing elements. In a specific implementation, as one embodiment, processor 110 may include a central processing unit (CPU) or multiple CPUs. Processor 110 may also be an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of this application, such as one or more digital signal processors (DSPs), or one or more field-programmable gate arrays (FPGAs).

[0059] In one example, if processor 110 is one or more CPUs, processor 110 can run or execute image data stored in memory 120 in head-mounted display device 100, so that the display screen included in optical imaging system 150 can display an image, so that optical imaging system 150 can present a virtual image of the image displayed on the display screen.

[0060] Optionally, in some embodiments, the head-mounted display device 100 may include other processors in addition to the processor 110. Each of these processors may be a single-core processor (CPU) or a multi-core processor (CPU). Here, a processor may refer to one or more devices, circuits, and / or processing cores for processing data (e.g., computer program instructions).

[0061] The memory 120 may be a read-only memory (ROM) or other type of static storage device capable of storing static information and instructions, random access memory (RAM) or other type of dynamic storage device capable of storing information and instructions, or electrically erasable programmable read-only memory (EEPROM), magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but is not limited thereto. The memory 120 may exist independently and be connected to the processor 110 via bus 140. The memory 120 may also be integrated with the processor 110.

[0062] The memory 120 is used to store image data and is controlled by the processor 110.

[0063] The optical imaging system 150 can be connected to the memory 120 and the processor 110 via the bus 140 to display the image content stored in the memory 120.

[0064] The communication interface 130 is used to communicate with other devices or communication networks. The communication interface 130 may include a receiving unit to implement the receiving function and a sending unit to implement the sending function.

[0065] The communication bus 140 can be an industry standard architecture (ISA) bus, a peripheral component (PCI) bus, or an extended industry standard architecture (EISA) bus. This bus can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 1 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0066] Figure 1 The device structure shown does not constitute a limitation on the head-mounted display device and may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0067] Alternatively, in some embodiments, the optical imaging system 150 may not include a display screen, and the display screen may be incorporated into the head-mounted display device 100.

[0068] To facilitate understanding, the technical terms used in this application will be explained and described below.

[0069] The optical axis refers to the light rays that pass through the center of each lens element in a lens assembly.

[0070] Light-transmitting aperture refers to the effective diameter of light entering the lens.

[0071] Birefringence occurs when ordinary light enters anisotropic materials (such as calcite, cotton fibers, and synthetic fibers). Besides surface reflection, the light entering the anisotropic material splits into two rays: one obeys the law of refraction and is called the ordinary ray (O ray); the other does not refract according to the law of refraction and is called the extraordinary ray (E ray). This phenomenon is called birefringence. The difference in refractive index between these two rays is called the birefringence. When polarized light passes through anisotropic materials, its polarization state changes due to the optical path difference between the O and E rays. The birefringence path difference is equal to the product of the birefringence and the thickness of the anisotropic material.

[0072] Aberrations refer to the differences between the actual image and the ideal image. Aberrations are mainly classified into spherical aberration, coma, field curvature, astigmatism, distortion, and chromatic aberration.

[0073] Aberrations are generally divided into two main categories: chromatic aberration and monochromatic aberration. Chromatic aberration, often simply called color aberration, arises because the refractive index of a lens material is a function of wavelength. It can be further divided into positional chromatic aberration and magnification chromatic aberration. Monochromatic aberration refers to aberrations that occur even with highly monochromatic light. Based on the effect produced, it is divided into two categories: blurring and distortion. The former includes spherical aberration, coma, and astigmatism. The latter includes field curvature and distortion.

[0074] A polarizer, also known as a light polarizer, is a type of optical filter. Polarizers are used to absorb or reflect light with one polarization direction while transmitting light with another orthogonally polarized direction. The transmittance of light is directly related to its polarization state. Polarizers are generally classified into absorptive polarizers and reflective polarizers (RP). Absorptive polarizers strongly absorb one of the orthogonally polarized components of incident linearly polarized light, while absorbing the other component weakly. Reflective polarizers can transmit linearly polarized light in a certain direction and reflect light with a polarization direction perpendicular to the transmitted direction. Absorptive polarizers can be, for example, dichroic polarizers, while reflective polarizers can be, for example, birefringence-based polarizing beam splitters.

[0075] Light waves are electromagnetic waves, composed of both electric and magnetic fields. Both are vectors perpendicular to the direction of light wave propagation. Light waves are deflected in these electric and magnetic fields, becoming polarized. When the light vector vibrates in only one fixed direction, this light is called linearly polarized light, also known as plane-polarized light. When both vectors rotate around themselves, the light wave is circularly polarized. Circularly polarized light is characterized by its light vector rotating at a certain frequency (left-handed or right-handed) within a plane perpendicular to the direction of light propagation. If the trajectory of the endpoint of the light vector is a circle, this light is called circularly polarized light.

[0076] When natural light (or unpolarized light) is incident on a polarizer, the outgoing light becomes linearly polarized. When linearly polarized light is incident on a polarizer, the outgoing light remains linearly polarized.

[0077] The polarization direction is also called the polarization direction or the polarization initiation direction. This is because there is a certain characteristic direction in the polarizer, called the polarization direction. The polarizer only allows light parallel to the polarization direction to pass through, while absorbing or reflecting light perpendicular to this direction.

[0078] A quarter-wave plate (1 / 4 wave plate) can also be called a 90° phase retardation plate. A quarter-wave plate is made of a birefringent material. When the light vector of linearly polarized light forms a ±45° angle with the fast or slow axis of the quarter-wave plate, the light passing through the quarter-wave plate is circularly polarized; conversely, when circularly polarized light passes through the quarter-wave plate, it becomes linearly polarized. The direction of the light vector with the slower propagation speed in the quarter-wave plate is called the slow axis direction of the quarter-wave plate.

[0079] A semi-transparent and semi-reflective film is a film that allows incident light to partially pass through and partially reflect. For example, a film with both 50% transmittance and 50% reflectance. Transmission is the phenomenon where incident light, after refraction, exits through an object. The object through which light is transmitted is transparent or translucent, such as glass or a color filter. If the transparent object is colorless, most light passes through it, except for a small amount reflected. To represent the degree to which light passes through an object, the ratio of the intensity of the transmitted light to the intensity of the incident light is typically used to characterize transmissivity. The ratio of the intensity of the reflected light to the intensity of the incident light is used to characterize reflectivity.

[0080] Focal length, also known as focal length, is a measure of the convergence or divergence of light in an optical imaging system. It refers to the vertical distance from the optical center of a lens or lens group to the focal plane when a scene at infinity is formed into a clear image on the focal plane.

[0081] A lens with a positive focal length is called a positive lens, meaning it has positive optical power. Positive lenses converge light, so they can also be called converging lenses.

[0082] A lens with a negative focal length is called a negative lens, meaning it has negative optical power. Negative lenses diverge light, so they can also be called diverging lenses.

[0083] The refractive index is the ratio of the speed of light in air to the speed of light in an optical material. The higher the refractive index of an optical material, the stronger its ability to refract incident light, and the thinner the lens.

[0084] The Abbe number, also known as the dispersion coefficient, measures the degree of light dispersion in a transparent medium and is an important indicator of the sharpness of a lens image. Generally speaking, the higher the refractive index of the medium, the more severe the dispersion, and the smaller the Abbe number; conversely, the lower the refractive index of the medium, the less severe the dispersion, and the larger the Abbe number.

[0085] The optical imaging system provided in the embodiments of this application will now be described in detail with reference to the specific accompanying drawings. This optical imaging system can be as described above. Figure 1 The optical imaging system 150 shown.

[0086] Figure 2 This is a schematic diagram of the structure of an optical imaging system 200 provided in an embodiment of this application.

[0087] like Figure 2 As shown, the optical imaging system 200 includes a first lens group 210, a first polarizing device 220, a second lens group 230, a second polarizing device 240, a first quarter-wave plate 250, and a second quarter-wave plate 260. Along the direction from the light source to the human eye, the first lens group 210, the first polarizing device 220, the second lens group 230, and the second polarizing device 240 are arranged sequentially. The second lens group 230 has at least one reflective surface convex to the first polarizing device 220. The first quarter-wave plate 250 is located between the reflective surface of the second lens group 230 and the first polarizing device 220, and the second quarter-wave plate 260 is located between the reflective surface of the second lens group 230 and the second polarizing device 240. The light source can also be referred to as an image source. Thus, the first lens group 210 is positioned closer to the light source, i.e., closer to the image display side. The second polarizing device 240 is positioned closer to the human eye. The first lens group 210, the first polarizing device 220, the second lens group 230, and the second polarizing device 240 will be described in detail below.

[0088] It should be noted that if the second lens group 230 has multiple reflecting surfaces protruding towards the first polarizing device 220, then the first quarter-wave plate 250 can be located between any one of the reflecting surfaces of the second lens group 230 and the first polarizing device 220. Furthermore, the second quarter-wave plate 260 is located between the last reflecting surface of the second lens group 230 and the second polarizing device 240. The last reflecting surface of the second lens group 230 is the last reflecting surface in the second lens group 230 along the direction from the light source to the human eye.

[0089] (1) First lens group 210

[0090] This application embodiment does not limit the number of lenses included in the first lens group 210. For example, the first lens group 210 may include one or more lenses. Furthermore, this application embodiment does not limit the type of lenses included in the first lens group 210. For example, the type of lenses included in the first lens group 210 may include at least one of the following: convex lenses, concave lenses, and other aspherical lenses.

[0091] In the optical imaging system 200, since the light incident on the first lens group 210 is natural light (or unpolarized light), the first lens group 210 does not need to control birefringence. Therefore, on the one hand, the first lens group 210 is not limited by the birefringence properties of the material, and the range of materials that can be selected for the first lens group 210 is relatively wide; for example, the material of the first lens group 210 can be any optical resin. This not only increases the design freedom of the first lens group 210 but also effectively reduces the weight of the optical imaging system 200. On the other hand, generally, increased temperature causes lens expansion, increasing birefringence. Since the first lens group 210 is closer to the light source than the second lens group 230, the effect of increased light source operating temperature on the second lens group 230 (which requires birefringence control) can be eliminated, thus preventing any impact on the birefringence of the optical imaging system 200.

[0092] Furthermore, since the natural light emitted by the light source is relatively dispersed, that is, the beams of different fields of view emitted by the light source are significantly separated, in the optical imaging system 200, the first lens group 210 is placed on the side of the light source close to the natural light, and the first lens group 210 can correct field-related aberrations.

[0093] It should be noted that the natural light or unpolarized light involved in the embodiments of this application is not necessarily completely unpolarized light in the strict sense; it may have a small degree of polarization. For example, light with a polarization degree less than or equal to 0.2 can be called unpolarized light.

[0094] (2) First polarization device 220

[0095] The first polarizing device 220 is an absorptive polarizer that has the function of both blocking and transmitting incident light. For example, in the optical imaging system 200, the first polarizing device 220 can transmit first linearly polarized light (such as longitudinal light) and absorb second linearly polarized light (such as transverse light).

[0096] In some embodiments, the first polarization device 220 may be disposed on a separate substrate.

[0097] In some embodiments, the optical imaging system 200 further includes a fourth substrate disposed on the side of the first polarizing device 220 near the first lens group 210, and the fourth substrate is attached to the first polarizing device 220. In this way, the surface of the first lens group 210 near the first polarizing device 220 can be configured as an aspherical surface of any shape, thereby not only increasing the design freedom of the optical imaging system 200, but also enabling the first lens group 210 to achieve higher aberration correction effects, thus improving the image sharpness of the optical imaging system 200.

[0098] In some embodiments, the optical imaging system 200 further includes a second substrate disposed on the side of the first polarizing device 220 away from the first lens group 210, and the second substrate is attached to the first polarizing device 220.

[0099] In this embodiment, if the first quarter-wave plate 250 is disposed between the plurality of lenses included in the second lens group 230, then one side of the second substrate is attached to the first polarizing device 220, and whether the other side is attached to other components is not limited. If the first quarter-wave plate 250 is disposed between the second lens group 230 and the first polarizing device 220, then one side of the second substrate is attached to the first polarizing device 220, and the other side is attached to the first quarter-wave plate 250.

[0100] In some embodiments, the optical imaging system 200 further includes a second substrate, which is bonded to a first quarter-wave plate 250, and the first quarter-wave plate 250 is bonded to a first polarizing device 220. That is, one side of the first quarter-wave plate 250 is bonded to the second substrate, and the other side is bonded to the first polarizing device 220.

[0101] In an embodiment where the optical imaging system 200 includes a second substrate, the surface of the second lens group 230 near the first polarizing device 220 can be set as an aspherical surface of any shape. This not only enhances the design freedom of the optical imaging system 200, but also enables the second lens group 230 to achieve a higher chromatic aberration correction effect, thereby improving the clarity of the image formed by the optical imaging system 200.

[0102] For example, the first polarizing device 220 can be mounted on a separate substrate by adhesive bonding.

[0103] In some embodiments, in order to reduce the size and complexity of the optical imaging system 200, the first polarizing device 220 can be directly attached to its adjacent components.

[0104] For example, the side of the first polarizing device 220 closest to the first lens group 210 is attached to the first lens group 210. Alternatively, the side of the first polarizing device 220 closest to the second lens group 230 is attached to the second lens group 230. Or, the side of the first polarizing device 220 closest to the first quarter-wave plate 250 is attached to the first quarter-wave plate 250, in which case the side of the first quarter-wave plate 250 closest to the second lens group 230 is attached to the second lens group 230.

[0105] It should be noted that if the first quarter-wave plate 250 is disposed among the multiple lenses included in the second lens group 230, the side of the first polarizing device 220 closest to the second lens group 230 is in contact with the second lens group 230. If the first quarter-wave plate 250 is disposed between the second lens group 230 and the first polarizing device 220, one side of the first quarter-wave plate 250 is in contact with the first polarizing device 220, and the other side is in contact with the second lens group 230.

[0106] For example, the first polarizing device 220 can be directly bonded to its adjacent components by adhesive bonding.

[0107] Since the first polarizing device 220 is located on the side of the first lens group 210 away from the light source, the ghost image generated by the birefringence of the first lens group 210 can be eliminated using the principle of polarization. Specifically, the ghost image introduced by the birefringence of the first lens group 210 can be caused by the direct transmission rather than reflection of natural light when it first passes through the second polarizing device 240.

[0108] In some embodiments, the polarization direction that the first polarizing device 220 allows to pass through forms a 45-degree angle with the slow axis direction of the first quarter-wave plate 250.

[0109] In some embodiments, the polarization direction that the first polarization device 220 allows to pass through forms a 90-degree angle with the polarization direction that the second polarization device 240 allows to pass through.

[0110] (3) Second lens group 230

[0111] The reflective surface of the second lens group 230 provides the main converging capability of the optical imaging system 200, and the edge rays begin to travel closer to the optical axis after passing through the reflective surface of the second lens group 230.

[0112] For example, the reflectivity of the reflecting surface of the second lens group 230 is 30%-70%. For instance, the reflectivity of the reflecting surface of the second lens group 230 is 30%-70% for the first circularly polarized light emitted from the first quarter-wave plate 250.

[0113] For example, such as Figure 2 and Figure 3 As shown, the optical imaging system 200 also includes a semi-transparent and semi-reflective coating 310, which is located on the reflective surface of the first lens 231 near the first polarizing device 220. Here, the reflectivity of the reflective surface of the second lens group 230 is about 50%.

[0114] Typically, a semi-transparent and semi-reflective film 310 can be formed on the reflective surface of the second lens group 230 by coating.

[0115] For example, the second lens group 230 may include M positive lenses and N negative lenses. The chromatic aberrations of the M positive lenses and N negative lenses may cancel each other out or almost cancel each other out.

[0116] For example, such as Figure 2 and Figure 3 As shown, the second lens group 230 includes a first lens 231 and a second lens 232. The first lens 231 has positive optical power near the optical axis, and the second lens 232 has negative optical power near the optical axis. Furthermore, the refractive index of the first lens 231 is less than that of the second lens 232, and the Abbe number of the first lens 231 is greater than that of the second lens 232.

[0117] Thus, under the condition that the first quarter-wave plate 250 is located between the reflecting surface of the second lens group 230 and the first polarizing device 220, the first quarter-wave plate 250 can be disposed between the multiple lenses included in the second lens group 230, or the first quarter-wave plate 250 can be disposed between the second lens group 230 and the first polarizing device 220.

[0118] Similarly, the second quarter-wave plate 260 can be disposed between multiple lenses included in the second lens group 230, provided that it is located between the reflecting surface of the second lens group 230 and the second polarizing device 240. The second quarter-wave plate 260 can also be disposed between the second lens group 230 and the second polarizing device 240.

[0119] In some embodiments, the chromatic aberrations of the M positive lenses and N negative lenses can cancel each other out or almost cancel each other out. This can be understood as the absolute value of the sum of the target ratios corresponding to each lens of the second lens group 230 being less than or equal to a first threshold. Here, the target ratio is the ratio of optical power to Abbe number.

[0120] The first threshold is related to the total optical power of the second lens group 230.

[0121] For example, the first threshold can be satisfy:

[0122]

[0123] Where i = 1, 2, ..., M; j = 1, 2, ..., N; The total optical power of the second lens group is 230. Let be the optical power of the i-th positive lens; Let be the optical power of the j-th negative lens.

[0124] For example, the optical power and Abbe number of M positive lenses and N negative lenses satisfy:

[0125]

[0126] Among them, v i v' is the Abbe number of the i-th positive lens; j Let be the Abbe number of the j-th negative lens; T is the first threshold.

[0127] Thus, the optical power and Abbe number of the first lens 231 and the second lens 232 satisfy the following:

[0128]

[0129] in, The optical power of the first lens 231; The optical power of the second lens 232; v i v' is the Abbe number of the first lens 231; j This is the Abbe number of the second lens 232.

[0130] The optical power of a lens is the reciprocal of its focal length. Therefore, the optical power of the i-th positive lens... satisfy:

[0131]

[0132] Where, n i d is the refractive index of the i-th positive lens; i r is the center thickness of the i-th positive lens; 1i r is the radius of the side of the i-th positive lens closest to the first lens group 210; 2i Let be the radius of the side of the i-th positive lens that is away from the first lens group 210.

[0133] The optical power of the j-th negative lens satisfy:

[0134]

[0135] Where, n j d is the refractive index of the j-th negative lens; j r is the center thickness of the j-th negative lens; 1j r is the radius of the side of the j-th negative lens closest to the first lens group 210; 2j Let be the radius of the side of the j-th negative lens that is away from the first lens group 210.

[0136] The Abbe number v of the i-th positive lens i satisfy:

[0137]

[0138] Where, n di nFi n Ci are the refractive indices of the i-th positive lens at the helium yellow line, hydrogen blue line, and hydrogen red line of the Fraunhofer spectrum, respectively.

[0139] The Abbe number v' of the j-th negative lens j satisfy:

[0140]

[0141] Where, n dj n Fj n Cj are the refractive indices of the j-th negative lens at the helium yellow line, hydrogen blue line, and hydrogen red line of the Fraunhofer spectrum, respectively.

[0142] In this way, by reasonably matching the optical power and refractive index of M positive lenses and N negative lenses, the second lens group 230 can effectively correct chromatic aberration of the incident light. This, in turn, can improve the resolution of the optical imaging system 200, that is, improve the clarity of the image formed by the optical imaging system 200.

[0143] For example, if there are no other components between two adjacent lenses in the second lens group 230, and there is no gap between the two adjacent lenses, then the two adjacent lenses can be bonded together by adhesive bonding. For example, as Figure 2 As shown, the first lens 231 can be bonded to the second lens 232 by adhesive bonding.

[0144] In the optical imaging system 200, since the light incident on the second lens group is not unpolarized, the second lens group 230 needs to control birefringence. Because a larger birefringence path difference results in a greater change in the polarization state of polarized light after passing through the lens, a larger ghost image is introduced. Therefore, to reduce the ghost image introduced by the optical imaging system 200, the material of the second lens group 230 is chosen to have a smaller birefringence path difference. For example, the material of the second lens group 230 can be optical glass. Alternatively, the material of the second lens group 230 can be an optical resin material whose average optical birefringence path difference within the aperture is less than or equal to a second threshold. Alternatively, the material of the second lens group 230 can be an optical resin material whose optical birefringence path difference within part or all of the aperture is less than or equal to the second threshold. The second threshold can be 30 nm.

[0145] In some embodiments, the lenses of the second lens group 230 are arranged in pairs adjacent to each other along the direction from the light source to the human eye. That is, there are no other components between any two adjacent lenses in the second lens group 230 along the direction from the light source to the human eye.

[0146] For example, such as Figure 2 As shown, the second lens 232 and the first lens 231 are arranged adjacent to each other.

[0147] In some embodiments, along the direction from the light source to the human eye, the lenses included in the second lens group 230 are not arranged in pairs adjacent to each other. That is, along the direction from the light source to the human eye, there are other components between adjacent lenses in the second lens group 230.

[0148] For example, such as Figure 3 As shown, a first quarter-wave plate 250 exists between the second lens 232 and the first lens 231.

[0149] This application does not limit the arrangement order of the M positive lenses and N negative lenses included in the second lens group 230.

[0150] For example, such as Figure 2 As shown, the second lens 232 can be located on the side of the first lens 231 that is away from the first polarizing device 220. For example, as Figure 3 As shown, the second lens 232 can be located on the side of the first lens 231 that is close to the first polarizing device 220.

[0151] (4) Second polarization device 240

[0152] The second polarizing device 240 is a reflective polarizer that can transmit linearly polarized light in a certain direction and reflect light whose polarization direction is perpendicular to the direction of transmission. For example, in the optical imaging system 200, the second polarizing device 240 can transmit second linearly polarized light and reflect first linearly polarized light.

[0153] In some embodiments, the second polarization device 240 may be disposed on a separate substrate.

[0154] In some embodiments, the optical imaging system 200 further includes a third substrate disposed on the side of the second polarizer 240 near the second lens group 230, and the third substrate is attached to the second polarizer 240.

[0155] In this embodiment, if the second quarter-wave plate 260 is disposed between the plurality of lenses included in the second lens group 230, then one side of the third substrate is attached to the second polarizing device 240, and whether the other side is attached to other components is not limited. If the second quarter-wave plate 260 is disposed between the second lens group 230 and the second polarizing device 240, then one side of the third substrate is attached to the second polarizing device 240, and the other side is attached to the second quarter-wave plate 260.

[0156] In some embodiments, the optical imaging system 200 further includes a third substrate, which is bonded to the second quarter-wave plate 260, and the second polarizing device 240 is bonded to the second quarter-wave plate 260. That is, one side of the second quarter-wave plate 260 is bonded to the third substrate, and the other side is bonded to the second polarizing device 240.

[0157] In the embodiment where the second polarizing device 240 is disposed on a separate substrate, the surface of the second lens group 230 near the second polarizing device 240 can be set as an aspherical surface of any shape, thereby not only improving the design freedom of the optical imaging system 200, but also enabling the second lens group 230 to achieve a higher chromatic aberration correction effect, thereby improving the clarity of the image formed by the optical imaging system 200.

[0158] For example, the second polarizing device 240 can be disposed on a separate substrate by adhesive bonding.

[0159] In some embodiments, in order to reduce the size and complexity of the optical imaging system 200 and to avoid an air gap between the second lens group 230 and the second polarizing device 240, such that light reflected from the second polarizing device 240 is reflected at the air interface before the reflecting surface 310 in the second lens group 230 to form a ghost image that enters the human eye, the second polarizing device 240 can be directly attached to its adjacent components.

[0160] In some embodiments, if the second quarter-wave plate 260 is disposed between the plurality of lenses included in the second lens group 230, then the second polarizing device 240 is attached to the second lens group 230.

[0161] In some embodiments, if the second quarter-wave plate 260 is disposed between the second lens group 230 and the second polarizing device 240, then one side of the second quarter-wave plate 260 is attached to the second lens group 230 and the other side is attached to the second polarizing device 240.

[0162] Alternatively, in order to reduce the cost of the optical imaging system 200, improve the yield of the optical imaging system 200, and ensure that the second polarizing device 240 can fit well with the second lens group 230, the side of the second lens group 230 close to the second polarizing device 240 can be set as a plane.

[0163] For example, the second polarizing device 240 can be directly bonded to its adjacent components by adhesive bonding.

[0164] In some embodiments, the polarization direction that the second polarizing device 240 allows to pass through forms a 45-degree angle with the slow axis direction of the second quarter-wave plate 260.

[0165] In some embodiments, the slow axis direction of the first quarter-wave plate 250 forms a 90-degree angle with the slow axis direction of the second quarter-wave plate 260.

[0166] Below, in conjunction with Figures 2 to 3 The optical path of the optical imaging system 200 is described in detail.

[0167] like Figure 2 The optical imaging system 200 shown has the following optical path:

[0168] (a): After natural light ① is incident on the first lens group 210, the first lens group 210 performs aberration compensation on it and emits the aberration-compensated natural light ①.

[0169] (b): After the aberration-compensated natural light ① emitted from the first lens group 210 enters the first polarization device 220, the first polarization device 220 transmits the first linearly polarized light ② from the natural light ①.

[0170] (c): After the first linearly polarized light ② transmitted from the first polarizing device 220 enters the first quarter-wave plate 250, the first quarter-wave plate 250 converts the first linearly polarized light ② into the first circularly polarized light ③ and emits it.

[0171] (d): After the first circularly polarized light ③ emitted from the first quarter-wave plate 250 enters the second lens group 230, the second lens group 230 refracts the first circularly polarized light ③ emitted from the first quarter-wave plate 250 and then emits the refracted first circularly polarized light ③.

[0172] (e): After the first circularly polarized light ③ emitted from the second lens group 230 enters the second quarter-wave plate 260, the second quarter-wave plate 260 converts the first circularly polarized light ③ into the first linearly polarized light ② and emits it.

[0173] (f): The first linearly polarized light ② emitted from the second quarter-wave plate 260 enters the second polarization device 240, and the second polarization device 240 reflects the first linearly polarized light ②.

[0174] (g): After the first linearly polarized light ② reflected from the second polarizing device 240 enters the second quarter-wave plate 260, the second quarter-wave plate 260 converts the first linearly polarized light ② into the first circularly polarized light ③ and emits it.

[0175] (h): After the first circularly polarized light ③ emitted from the second quarter-wave plate 260 enters the second lens group 230, since the second lens group 230 has a reflective surface that protrudes towards the first polarizing device 220, the second lens group 230 can reflect the first circularly polarized light ③ and convert it into second circularly polarized light ④.

[0176] (i): The second circularly polarized light ④ emitted from the second lens group 230 enters the second quarter-wave plate 260, and the second quarter-wave plate 260 converts the second circularly polarized light ④ into the second linearly polarized light ⑤ and emits it.

[0177] (j): The second linearly polarized light ⑤ emitted from the second quarter-wave plate 260 enters the second polarization device 240, and the second polarization device 240 transmits the second linearly polarized light ⑤. At this time, the second linearly polarized light ⑤ is orthogonal to the first linearly polarized light ②.

[0178] like Figure 3 The optical imaging system 200 shown has the following optical paths in sequence: (a), (b), (c'), (d'), (e'), (e), (f), (g), (h'), (i), (j). (a), (b), (e), (f), (g), (i), and (j) are described above and will not be repeated here. (c'), (d'), (e'), and (h') will be described in detail below.

[0179] (c'): The first linearly polarized light ② transmitted from the first polarizing device 220 enters the second lens 232 of the second lens group 230, and the second lens 232 refracts the first linearly polarized light ② and emits the refracted first linearly polarized light ②.

[0180] (d'): After the first linearly polarized light ② emitted from the second lens 232 enters the first quarter-wave plate 250, the first quarter-wave plate 250 converts the first linearly polarized light ② into the first circularly polarized light ③ and emits it.

[0181] (e'): After the first circularly polarized light ③ emitted from the first quarter-wave plate 250 enters the first lens 231 of the second lens group 230, the first lens 231 refracts the first circularly polarized light ③ emitted from the first quarter-wave plate 250 and then emits the refracted first circularly polarized light ③.

[0182] (h'): After the first circularly polarized light ③ emitted from the second quarter-wave plate 260 enters the first lens 231 of the second lens group 230, since the first lens 231 has a reflective surface that protrudes toward the first polarizing device 220, the first lens 231 of the second lens group 230 can reflect the first circularly polarized light ③ and convert it into second circularly polarized light ④.

[0183] In some embodiments, such as Figure 4 As shown, the optical imaging system 200 also includes a display screen 280. The display screen 280 is used to emit natural light, i.e., unpolarized light.

[0184] In this embodiment, the display screen 280 can be understood as a light source or image source of the optical imaging system 200. The natural light emitted by the display screen 280 can be understood as the natural light emitted by the image displayed on the display screen 280.

[0185] In some embodiments, since the second polarizing device 240 may not be able to completely reflect the first linearly polarized light emitted from the second quarter-wave plate 260, some of the first linearly polarized light may be transmitted through the second polarizing device 240. Therefore, the optical imaging system 200 further includes a third polarizing device located on the side of the second polarizing device 240 away from the second lens group 230. The third polarizing device is used to absorb the first linearly polarized light transmitted from the second polarizing device 240 and to transmit the second linearly polarized light emitted from the second polarizing device 240. In this case, the third polarizing device can be an absorptive polarizer. In this way, the third polarizing device can absorb the first linearly polarized light emitted from the second polarizing device 240, thereby eliminating the ghosting caused by the first linearly polarized light.

[0186] In some embodiments, such as Figure 4 As shown, the optical imaging system 200 may further include a third lens group 270. The third lens group 270 is disposed on the side of the second polarizing device 240 away from the second quarter-wave plate 260, and is used to transmit light emitted from the second polarizing device 240.

[0187] This application embodiment does not limit the number of lenses included in the third lens group 270. For example, the third lens group 270 may include one or more lenses. Furthermore, this application embodiment does not limit the type of lenses included in the third lens group 270. For example, the type of lenses included in the third lens group 270 may include convex lenses and / or concave lenses and / or other aspherical lenses.

[0188] In the optical imaging system 200, since the third lens group 270 is close to the human eye, the light emitted from the second polarizing device 240 is not so dispersed, and the beams from different fields of view overlap more. Therefore, the third lens group 270 can correct aberrations that are not related to the field of view, such as spherical aberration.

[0189] In some embodiments, the optical imaging system 200 further includes a first substrate.

[0190] In some embodiments, the first substrate is disposed on the side of the second polarizing device 240 away from the second lens group 230, and the first substrate is attached to the second polarizing device 240.

[0191] In some embodiments, the first substrate is bonded to the third polarizing device, and the third polarizing device is bonded to the second polarizing device 240. That is, one side of the third polarizing device is bonded to the first substrate, and the other side is bonded to the second polarizing device 240.

[0192] In this embodiment, the surface of the third lens group 270 near the second polarizing device 240 can be set as an aspherical surface of any shape. This not only increases the design freedom of the optical imaging system 200, but also allows the third lens group 270 to achieve a higher aberration correction effect, thereby improving the image clarity of the optical imaging system 200.

[0193] In some embodiments, to reduce the size and complexity of the optical imaging system 200, the third lens group 270 and the second polarizing device 240 can be directly bonded together. Alternatively, the third lens group 270 can be bonded to the second polarizing device 240 via the third polarizing device, that is, one side of the third polarizing device is bonded to the third lens group 270, and the other side is bonded to the second polarizing device 240.

[0194] The third lens group 270 can correct the aberrations of the light transmitted from the second polarizing device 240 and then project the corrected light into the human eye to form a display image.

[0195] In the optical imaging system 200, since the third lens group 270 also does not need to control birefringence, it is not limited by the birefringence properties of the material, and the range of materials that can be selected for the third lens group 270 is relatively wide. For example, any optical resin material can be chosen for the third lens group 270. Therefore, not only can the design freedom of the third lens group 270 be improved, but the weight of the optical imaging system 200 can also be effectively reduced.

[0196] For ease of description, the optical imaging system 200 excluding the third lens group 270 is referred to as Scheme 1, and the optical imaging system 200 including the third lens group 270 is referred to as Scheme 2. Compared to Scheme 2, the second lens group 230 is closer to the human eye in Scheme 1. Therefore, under the same field of view (FOV), the light output aperture of the head-mounted display device corresponding to Scheme 1 is smaller than that of Scheme 2. Thus, Scheme 1 can achieve the goal of a small light output aperture and a large FOV.

[0197] In some embodiments, such as Figure 4 As shown, the optical imaging system 200 may further include a third quarter-wave plate 290. The third quarter-wave plate 290 is located between the first polarizing device 220 and the first lens group 210. The third quarter-wave plate 290 is used to transmit aberration-compensated unpolarized light emitted from the first lens group 210.

[0198] Since the third quarter-wave plate 290 is disposed between the first lens group 210 and the first polarizing device 220, the ghost image generated by the surface reflection of the first lens group 210 can be eliminated.

[0199] In some embodiments, the slow axis direction of the third quarter-wave plate 290 forms a 45-degree angle with the polarization direction that the first polarizing device 220 allows to pass through.

[0200] In some embodiments, the optical imaging system 200 further includes a fifth substrate disposed on the side of the third quarter-wave plate 290 away from the first polarizing device 220, and the fifth substrate is attached to the third quarter-wave plate 290. In this way, the surface of the first lens group 210 near the third quarter-wave plate 290 can be set as an aspherical surface of any shape, thereby not only increasing the design freedom of the optical imaging system 200, but also enabling the first lens group 210 to achieve a higher chromatic aberration correction effect, thus improving the image sharpness of the optical imaging system 200.

[0201] In some embodiments, in order to reduce the size and complexity of the optical imaging system 200, the third quarter-wave plate 290 can be directly attached to its adjacent first lens group 210 or first polarizing device 220.

[0202] Below, in conjunction with Figure 4 The optical path of the optical imaging system 200 is described in detail.

[0203] like Figure 4 The optical imaging system 200 shown has the following optical paths in sequence: (a”), (a), (b”), (c”), (d) to (j), (l). For (a”), (d) to (j), please refer to the description above; they will not be repeated here. Below, (a”), (b”), (c”), and (l) will be described in detail.

[0204] (a”): Display screen 280 emits natural light ①.

[0205] It should be understood that, in cases such as Figure 4 In the optical imaging system 200 shown, the natural light ① described in (a) is emitted by the display screen 280.

[0206] (b”): The aberration-compensated natural light ① emitted from the first lens group 210 enters the third quarter-wave plate 290 and is emitted by the third quarter-wave plate 290.

[0207] (c”): After the natural light ① emitted from the third quarter-wave plate 290 enters the first polarization device 220, the first polarization device 220 transmits the first linearly polarized light ② from the natural light ①.

[0208] (l): The third lens group 270 transmits light emitted from the second polarizing device 240.

[0209] Because the focal length range of the eyes of nearsighted individuals differs from that of normal-vision individuals, in order to ensure that the optical imaging system 200 can be applied to different groups of people, in some embodiments, such as... Figure 4 As shown, the optical imaging system 200 also includes a moving mechanism 300. This moving mechanism 300 is fixedly connected to the target structure and is used to move the target structure along the direction of light transmission in the optical imaging system 200, thereby adjusting the distance between the target structure and other structures in the optical imaging system 200, and thus adjusting the object distance. Depending on the imaging relationship, if the object distance changes, the distance from the displayed image formed by the display screen 280 through the optical imaging system 200 to the human eye will also change accordingly.

[0210] In some embodiments, if the first lens group 210 includes a first partial lens and a second partial lens, then the target structure includes the display screen 280 and the first partial lens.

[0211] In some embodiments, the target structure includes a display screen 280 and a first lens group 210.

[0212] In some embodiments, such as Figure 5 As shown, the target structure includes a display screen 280, a first lens group 210, and a first polarizing device 220.

[0213] In some embodiments, the moving mechanism 300 includes an inner lens and an outer lens, with the target structure disposed in the inner lens and other structures disposed in the outer lens. Thus, the inner and outer lenses, through a threaded structure, allow for adjustment of the distance between the target structure and other structures.

[0214] Alternatively, the target structure can be sealed within the inner lens. This isolates the target structure from dust, preventing dust from falling onto the display screen 280 and thus avoiding the image of dust entering the human eye.

[0215] For example, in order to reduce the weight of the optical imaging system 200, the external lens may be the frame of the head-mounted display device 100.

[0216] In some embodiments, the moving mechanism 300 may include a motor, and the motor is connected to the target structure.

[0217] For example, the motor can be controlled by software, buttons, voice, or other means.

[0218] In this way, the user can move the target structure along the direction of light transmission of the optical imaging system 200 through the moving mechanism 300, thereby adjusting the distance between the target structure and other structures to adjust the object distance, so as to cover users with different vision using the head-mounted display device 100 including the optical imaging system 200.

[0219] Specifically, when the user has normal vision, the mobile mechanism 300 can adjust the distance between the target structure and other structures to a first distance; when the user is nearsighted, the mobile mechanism 300 can adjust the distance between the target structure and other structures to a second distance; and when the user is farsighted, the mobile mechanism 300 can adjust the distance between the target structure and other structures to a third distance. The third distance > the first distance > the second distance.

[0220] For example, such as Figure 5 As shown, when the target structure A includes a display screen 280, a first lens group 210, and a first polarizing device 220, and the user has normal vision, the moving mechanism 300 can adjust the distance between the target structure A and the second lens group 230 to such a position. Figure 5 As shown in (a) above, when the user is nearsighted, the moving mechanism 300 can adjust the distance between the target structure A and the second lens group 230 to, for example, L1. Figure 5 L2 is shown in (b) of the diagram. Where L2 is less than L1.

[0221] It should be understood that Figures 2 to 5 The structure of each component in the device shown and the connection relationship between the components are only illustrative. The structure of any replaceable component that performs the same function as each component is within the protection scope of the embodiments of this application.

[0222] Typically, the modulation transfer function (MTF) reflects the resolving power of an optical imaging system. The following section combines... Figure 6 The resolution of the optical imaging system 200 provided in the embodiments of this application will be described.

[0223] Figure 6 The MTF (Mean Transmission Factor) curves of the optical imaging system 200 are shown at 0°, 10°, 20°, and 25° fields of view. Specifically, T1 represents the radial (tangential) MTF curve of the optical imaging system 200 at 0° field of view, and S1 represents the sagittal MTF curve. T2 represents the radial MTF curve of the optical imaging system 200 at 10° field of view, and S2 represents the sagittal MTF curve. T3 represents the radial MTF curve of the optical imaging system 200 at 20° field of view, and S3 represents the sagittal MTF curve. T4 represents the radial MTF curve of the optical imaging system 200 at 25° field of view, and S4 represents the sagittal MTF curve. Figure 6 (a) is a graph of the MTF of the optical imaging system 200 when the user has normal vision. Figure 6 (b) in the figure shows the MTF curve of the optical imaging system 200 when the user is nearsighted. Figure 6 (a) and Figure 6 In (b) of the diagram, the horizontal axis represents the spatial frequency in cycles per mm, and the vertical axis represents the MTF.

[0224] Depend on Figure 6 As shown in (a), at a spatial frequency of 100 cycles / mm, the MTF values ​​of the optical imaging system 200 at 0°, 10°, 20°, and 25° fields of view are all above 0.2. Figure 6 As shown in (b), at a spatial frequency of 100 cycles / mm, the MTF values ​​of the optical imaging system 200 at 0° field of view, 10° field of view, 20° field of view, and 25° field of view are all above 0.3.

[0225] Therefore, the optical imaging system 200 provided in this application has high resolution, imaging rate, and system resolution, resulting in good imaging performance. Furthermore, it can improve the resolution of the head-mounted display device 100, solving the problem of blurred visual imaging in the head-mounted display device 100.

[0226] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An optical imaging system, characterized in that, include: The first lens group, the first polarizing device, the second lens group, and the second polarizing device are arranged in sequence. The second lens group has at least one reflective surface that protrudes toward the first polarizing device. The second lens group includes a first lens and a second lens. The portion of the first lens near the optical axis has positive optical power, and the portion of the second lens near the optical axis has negative optical power. The refractive index of the first lens is less than that of the second lens, and the Abbe number of the first lens is greater than that of the second lens. The optical imaging system further includes a first quarter-wave plate and a second quarter-wave plate, wherein the first quarter-wave plate is located between the reflecting surface of the second lens group and the first polarizing device, and the second quarter-wave plate is located between the reflecting surface of the second lens group and the second polarizing device. The first lens group is used to compensate for aberrations in unpolarized light. The first polarization device is used to convert aberration-compensated unpolarized light emitted from the first lens group into first linearly polarized light; The first quarter-wave plate is used to convert the first linearly polarized light emitted by the first polarization device into first circularly polarized light. The second lens group is used to transmit the first circularly polarized light emitted from the first quarter-wave plate, and the reflecting surface of the second lens group is used to reflect the first circularly polarized light emitted from the second quarter-wave plate; The second quarter-wave plate is used to convert the first circularly polarized light emitted from the second lens group into the first linearly polarized light, to convert the first linearly polarized light emitted from the second polarizing device into the first circularly polarized light, and to convert the second circularly polarized light emitted from the second lens group into the second linearly polarized light. The second circularly polarized light is the light reflected from the reflecting surface of the second lens group when the first circularly polarized light emitted from the second quarter-wave plate is incident on the reflecting surface of the second lens group. The second polarization device is used to reflect first linearly polarized light emitted from the second quarter-wave plate and to transmit second linearly polarized light emitted from the second quarter-wave plate.

2. The optical imaging system according to claim 1, characterized in that, The absolute value of the sum of the first ratio and the second ratio is less than or equal to a first threshold, wherein the first ratio is the ratio of the optical power of the first lens to the Abbe number of the first lens, the second ratio is the ratio of the optical power of the second lens to the Abbe number of the second lens, and the first threshold is related to the optical power of the second lens group.

3. The optical imaging system according to claim 1, characterized in that, The optical imaging system further includes a third polarizing device located on the side of the second polarizing device away from the second lens group. The third polarizing device is used to absorb first linearly polarized light transmitted from the second polarizing device and to transmit second linearly polarized light emitted from the second polarizing device.

4. The optical imaging system according to claim 1, characterized in that, The optical imaging system also includes: A third lens group is located on the side of the second polarizing device away from the second quarter-wave plate, and the third lens group is used to transmit light emitted from the second polarizing device.

5. The optical imaging system according to claim 4, characterized in that, The second polarizing device is attached to the third lens group; or, The second polarizing device is bonded to the third polarizing device, and the third polarizing device is bonded to the third lens group; or, The optical imaging system further includes a first substrate, which is disposed on the side of the second polarizing device away from the second lens group, and the first substrate is attached to the second polarizing device; or... The optical imaging system further includes a first substrate, which is bonded to a third polarizing device, and the third polarizing device is bonded to a second polarizing device.

6. The optical imaging system according to claim 4, characterized in that, The material used for the third lens group is optical resin.

7. The optical imaging system according to claim 1, characterized in that, The optical imaging system also includes: A display screen for emitting the unpolarized light.

8. The optical imaging system according to claim 7, characterized in that, The optical imaging system also includes: A moving mechanism is fixedly connected to a target structure, and the moving mechanism is used to drive the target structure to move along the direction of light transmission of the optical imaging system. The first lens group includes a first part lens and a second part lens, the first part lens is located between the second part lens and the display screen, and the target structure includes the display screen and the first part lens; Alternatively, the target structure may include the display screen and the first lens group; Alternatively, the target structure may include the display screen, the first lens group, and the first polarizing device.

9. The optical imaging system according to claim 1, characterized in that, The first polarizing device is bonded to the second lens group; or... The first polarizing device is bonded to the first quarter-wave plate, and the first quarter-wave plate is bonded to the second lens group; or... The optical imaging system further includes a second substrate, which is disposed on the side of the first polarizing device away from the first lens group, and the second substrate is attached to the first polarizing device. or, The optical imaging system further includes a second substrate, which is bonded to the first quarter-wave plate, and the first quarter-wave plate is bonded to the first polarizing device.

10. The optical imaging system according to claim 1, characterized in that, The second polarizing device and the second lens group are bonded together; or, The second polarizing device and the second quarter-wave plate are bonded together, and the second quarter-wave plate is bonded to the second lens group; The optical imaging system further includes a third substrate, which is disposed on the side of the second polarizing device near the second lens group, and the third substrate is attached to the second polarizing device. or, The optical imaging system further includes a third substrate, which is bonded to the second quarter-wave plate, and the second polarizing device is bonded to the second quarter-wave plate.

11. The optical imaging system according to claim 1, characterized in that, The first polarizing device is attached to the first lens group; or... The optical imaging system further includes a fourth substrate, which is disposed on the side of the first polarizing device close to the first lens group, and the fourth substrate is attached to the first polarizing device.

12. The optical imaging system according to claim 1, characterized in that, The optical imaging system also includes: A third quarter-wave plate is located between the first polarizing device and the first lens group, and the third quarter-wave plate is used to transmit aberration-compensated unpolarized light emitted from the first lens group.

13. The optical imaging system according to claim 12, characterized in that, The third quarter-wave plate is attached to the first lens group; or... The third quarter-wave plate is attached to the first polarizing device; or, The optical imaging system further includes a fifth substrate, which is disposed on the side of the third quarter-wave plate away from the first polarizing device, and the fifth substrate is attached to the third quarter-wave plate.

14. The optical imaging system according to claim 1, characterized in that, The reflectivity of the reflecting surface of the second lens group is 30%-70%.

15. The optical imaging system according to claim 1, characterized in that, The first lens group is made of optical resin.

16. The optical imaging system according to claim 1, characterized in that, The second lens group is made of optical glass; or, The material used for the second lens group is an optical resin with an average birefringence path difference within the light-transmitting aperture that is less than or equal to a second threshold, where the second threshold is 30 nm.

17. The optical imaging system according to any one of claims 1 to 16, characterized in that, The side of the second lens group closest to the second polarizing device is a plane.

18. A head-mounted display device, characterized in that, Includes the optical imaging system as described in any one of claims 1 to 17.

19. The head-mounted display device according to claim 18, characterized in that, The head-mounted display device also includes: A processor for displaying images on a display screen to cause the display screen to emit the unpolarized light.

20. The head-mounted display device according to claim 19, characterized in that, The head-mounted display device also includes: Memory, used to store image data; When the image data is executed by the processor, the display screen displays the image.

Images