WO2023071032A1 - 一种短焦折叠光学系统以及虚拟现实显示设备 - Google Patents

一种短焦折叠光学系统以及虚拟现实显示设备 Download PDF

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Publication number
WO2023071032A1
WO2023071032A1 PCT/CN2022/081707 CN2022081707W WO2023071032A1 WO 2023071032 A1 WO2023071032 A1 WO 2023071032A1 CN 2022081707 W CN2022081707 W CN 2022081707W WO 2023071032 A1 WO2023071032 A1 WO 2023071032A1
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light
lens
optical system
focus
short
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PCT/CN2022/081707
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English (en)
French (fr)
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张雪冰
庞斌
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广州视源电子科技股份有限公司
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Publication of WO2023071032A1 publication Critical patent/WO2023071032A1/zh

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/01—Head-up displays

Definitions

  • the present application relates to the technical field of virtual reality display devices, for example, to a short-focus folding optical system and a virtual reality display device.
  • the volume, weight, and display resolution (definition) of related virtual reality display devices on the market are not satisfactory, mainly due to the design scheme of the virtual reality optical system, which determines the final quality of the virtual reality display device.
  • the current design of the optical system of virtual reality is not reasonable enough, and the image light is not enough to turn back in the optical system, so that the length (thickness) of the optical system cannot be reduced. Displays the size and weight of the device.
  • the purpose of this application is to provide a short-focus folding optical system to solve the shortcomings and deficiencies in the related art.
  • a short-focus folding optical system of the present application comprising: a display unit and a light folding unit;
  • the display unit is used to emit circularly polarized image light toward the light folding unit; the light folding unit is used to fold and transmit the image light to human eyes;
  • the light folding unit includes a first lens, a second lens, a first quarter-wave plate and a reflective polarizer; the first lens and the second lens are arranged in sequence along the image light emitting direction, and the first Both the first lens and the second lens have a light incident surface facing the display unit and a light exit surface facing away from the display unit, and a semi-transparent and semi-reflective film is arranged on the light incident surface or the light exit surface of the first lens; Both the first quarter-wave plate and the reflective polarizer are located on the side of the first lens facing away from the display unit, and they are arranged in sequence along the direction in which the image light is emitted; the circular polarization state When the image light passes through the first quarter-wave plate for the first time, it is transmitted and transformed into the image light in the first linear polarization state; the reflective polarizer is used to reflect the light in the first linear polarization state and transmit the light in the second linear polarization state status light.
  • the light folding unit includes a first lens, a second lens, a first quarter-wave plate and a reflective polarizer, which utilize light Polarization characteristics, so that the image light is reflected and refracted multiple times in the light folding unit, and the length (thickness) of the optical system can be shortened by increasing the number of times the image light turns back, and at the same time, the number of optical lenses used can be reduced to achieve a small size , light weight and high resolution advantages.
  • the semi-transparent and semi-reflective film is disposed on the light incident surface of the first lens, and the first quarter-wave plate is disposed on the light exit surface of the first lens,
  • the reflective polarizer is disposed on the light incident surface of the second lens.
  • the light incident surface of the first lens is a convex surface, and the light exit surface is a plane;
  • the light-incident surface of the second lens is convex, and the light-exit surface is concave.
  • the semi-transparent and semi-reflective film is disposed on the light exit surface of the first lens
  • the reflective polarizer is disposed on the light incident surface of the second lens
  • the first The quarter-wave plate is disposed on a side of the reflective polarizer facing away from the second lens.
  • the light incident surfaces of the first lens and the second lens are convex, and the light exit surfaces are concave.
  • the semi-transparent and semi-reflective film is disposed on the light incident surface of the first lens, and the first quarter-wave plate is disposed on the light exit surface of the second lens,
  • the reflective polarizer is disposed on a side of the first quarter-wave plate facing away from the second lens.
  • the light-incident surfaces of the first lens and the second lens are convex, and the light-exit surfaces are flat.
  • the light folding unit further includes an absorbing polarizer for absorbing light in a first linear polarization state and transmitting light in a second linear polarization state, and the first four The quarter-wave plate, reflective polarizer and absorbing polarizer are sequentially arranged along the image light emission direction.
  • the display unit includes a display device and a second quarter-wave plate, the display device is used to emit image light in a second linear polarization state to the second quarter-wave plate , when the image light in the second linear polarization state passes through the second quarter-wave plate, it is transmitted and transformed into the image light in the circular polarization state.
  • the present application also provides a virtual reality display device, which includes a spectacle frame and the above-mentioned short-focus folding optical system; the spectacle frame forms an optical system cavity, and the short-focus folding optical system is arranged in the optical system cavity Inside.
  • Figure 1 is one of the structural schematic diagrams of the short-focus folding optical system of the present application.
  • FIG. 2 is a schematic structural diagram of the display unit of the present application.
  • FIG. 3 is a schematic structural view of the short-focus folding optical system of Embodiment 1 of the present application.
  • FIG. 4 is another structural schematic diagram of the short-focus folding optical system of Embodiment 1 of the present application.
  • FIG. 5 is a schematic structural view of a display device of the present application.
  • FIG. 6 is a graph of the modulation transfer function MTF corresponding to the short-focus folded optical system of Embodiment 1 of the present application.
  • FIG. 7 is a schematic structural view of the short-focus folding optical system of Embodiment 2 of the present application.
  • FIG. 8 is another structural schematic diagram of the short-focus folding optical system of Embodiment 2 of the present application.
  • FIG. 9 is a graph of the modulation transfer function MTF corresponding to the short-focus folding optical system of Embodiment 2 of the present application.
  • FIG. 10 is a schematic structural view of the short-focus folding optical system of Embodiment 3 of the present application.
  • Fig. 11 is another structural schematic diagram of the short-focus folding optical system of Embodiment 3 of the present application.
  • FIG. 12 is a curve diagram of a modulation transfer function (MTF) corresponding to the short-focus folded optical system of Embodiment 3 of the present application.
  • MTF modulation transfer function
  • first and second are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features, that is, limited to “first”, “second Two” features may explicitly or implicitly include one or more of these features. Also, unless otherwise specified, "plurality” means two or more.
  • the present application provides a short-focus folding optical system, including a display unit 10 and a light folding unit 20 .
  • the display unit 10 is used for emitting the image light 101 in a circularly polarized state toward the light folding unit 20 , and the light folding unit 20 is used for folding the image light 101 to the human eye 30 .
  • the light folding unit 20 includes a first lens 21, a second lens 22, a first quarter-wave plate 23 and a reflective polarizer 24;
  • the emitting direction is arranged in sequence, and the first lens 21 and the second lens 22 both have a light incident surface (light incident surface 211 of the first lens 21, light incident surface 221 of the second lens 22) towards the display unit 10 and Back to the light exit surface of the display unit 10 (the light exit surface 212 of the first lens 21, the light exit surface 222 of the second lens 22), the light incident surface 211 or the light exit surface 212 of the first lens 21 is provided with a semi-transparent Semi-reflective film 25, the semi-transparent and semi-reflective film 25 has the functions of reflection and transmission to incident light, that is, when incident light passes through the semi-transparent and semi-reflective film, part of the light penetrates, and part of the light is reflected back, and the semi-transparent and semi-reflective film
  • the transmittance ratio of the reflective film can be designed according to requirements. In the
  • Both the first quarter-wave plate 23 and the reflective polarizer 24 are located on the side of the first lens 21 facing away from the display unit 10 , and they are arranged in sequence along the direction in which the image light is emitted.
  • the reflective polarizer 24 is used to reflect light in the first linear polarization state and transmit light in the second linear polarization state, wherein the light in the first linear polarization state is linearly polarized light in the first polarization direction, and the light in the second linear polarization state Light is the linearly polarized light in the second polarization direction, the first polarization direction and the second polarization direction are orthogonal, in this application, the first polarization direction is defined as the S direction, the second polarization direction is the P direction, and the S direction is perpendicular to the P direction Therefore, the light in the first linear polarization state can also be called S-polarized light, and the light in the second linear polarization state can be called P-polarized light similarly.
  • the first quarter-wave plate 23 can convert linearly polarized light into circularly polarized light, or convert circularly polarized light into linearly polarized light.
  • Those skilled in the art should understand the characteristics of the quarter-wave plate, namely: When the S-polarized light passes through the quarter-wave plate at a certain angle, it will be converted into circularly polarized light, and when the circularly polarized light passes through the quarter-wave plate at a certain angle again, it will be converted into P-polarized light ;Similarly, when the P polarized light passes through the quarter-wave plate at a certain angle, it will be converted into circularly polarized light, and when the circularly polarized light passes through the quarter-wave plate at a certain angle again, it will be transformed For S polarized light.
  • the display unit 10 includes a display device 11 and a second quarter-wave plate 12, and the display device 11 is used to emit image light 101' in a second linear polarization state to The second quarter-wave plate 12, when the image light 101 ′ in the second linear polarization state passes through the second quarter-wave plate 12, it is transmitted and transformed into the image light 101 in the circular polarization state .
  • the image light 101 in the circular polarization state passes through the first quarter-wave plate 23 for the first time, it is transmitted and transformed into the image light in the first linear polarization state.
  • the light folding unit 20 includes a first lens 21, a second lens 22, a first quarter-wave plate 23 and a reflective polarizer 24 , which utilizes the polarization characteristics of light to cause the image light to undergo multiple reflections and refractions in the light folding unit 20, shorten the length (thickness) of the optical system by increasing the number of times the image light turns back, and also reduce the number of optical lenses used Quantity, to achieve the advantages of small size, light weight and high resolution.
  • the short-focus folding optical system uses a high-resolution display unit 10. After being enlarged by the light folding unit 20, because the light folding unit 20 has high resolution, it can still display the display details of the original image without loss. The resolution of the original image.
  • the setting positions of the semi-transparent and semi-reflective film 25, the first quarter-wave plate 23 and the reflective polarizer 24 can have multiple options, and different setting positions will make the propagation path of the image light slightly different, combined below
  • the accompanying drawings illustrate various embodiments of the present application in detail.
  • FIG. 3 includes the propagation route of the image light.
  • the semi-transparent and semi-reflective film 25 is arranged on the light incident surface 211 of the first lens 21, and the first The quarter wave plate 23 is disposed on the light emitting surface 212 of the first lens 21 , and the reflective polarizer 24 is disposed on the light incident surface 221 of the second lens 22 .
  • the short-focus folding optical system enters the image light of the human eye 30, and its propagation in the light folding unit 20 and the polarization direction change process are as follows:
  • the display unit 10 emits circularly polarized image light 101 toward the light folding unit 20, and the circularly polarized image light 101 is partially transmitted through the semi-transparent and semi-reflective film 25 sequentially, and passes through the first
  • a lens 21 is transmitted through the first quarter-wave plate 23 to be transmitted and transformed into image light 101A in the first linear polarization state, and the image light 101A in the first linear polarization state passes through the reflective polarizer in turn 24 is reflected, is transmitted through the first quarter-wave plate 23 and transformed into an image light in a circularly polarized state, is transmitted through the first lens 21, and is partially reflected through the semi-transparent and semi-reflective film 25,
  • the image light 101B is transmitted through the first lens 21 again, transmitted through the first quarter-wave plate 23 and transformed into the image light 101B of the second linear polarization state, transmitted through the reflective polarizer 24, and finally passed through the
  • the second lens 22 enters the human eye 30 after being transmitted.
  • the human eyes 30 can see the virtual image displayed by
  • the image light is reflected and transmitted multiple times in the light folding unit 20 , and the light folding unit 20 makes the image light continuously folded and propagated, so as to shorten the length (thickness) of the optical system.
  • the light folding unit 20 further includes an absorbing polarizer 26 for absorbing light in the first linear polarization state and transmitting light in the second linear polarization state.
  • the first quarter-wave plate 23 , reflective polarizer 24 and absorbing polarizer 26 are sequentially arranged along the image light emission direction.
  • the absorbing polarizer 26 can just absorb the image light in the first linear polarization state passing through the reflective polarizer 24 , through this arrangement, the stray light of the optical device can be reduced, and the contrast of the entire display screen can be improved.
  • the absorbing polarizer 26 described in this embodiment can be arranged between the reflective polarizer 24 and the second lens 22, and can also be arranged on one side of the light-emitting surface 222 of the second lens 22, for example, as shown in FIG. 4 As shown, in this embodiment, the absorbing polarizer 26 is arranged between the reflective polarizer 24 and the second lens 22 for bonding.
  • the light incident surface 211 of the first lens 21 is a convex surface
  • the light exit surface 212 is a plane
  • the light incident surface 221 of the second lens 22 is a convex surface
  • the light exit surface 222 is a concave surface, so that the image light It can propagate in a reasonable route in the light folding unit 20 .
  • the light incident surface 211 of the first lens 21, the light incident surface 221 of the second lens 22 and the light exit surface 222 of the second lens 22 can all be spherical surfaces, free curved surfaces or other curved surfaces.
  • the light incident surface 211 of the first lens 21 , the light incident surface 221 of the second lens 22 and the light exit surface 222 of the second lens 22 are all aspheric surfaces, which can significantly improve the resolution of the optical system.
  • the aspheric surface type expression is:
  • z is the sagittal height of the aspheric surface
  • k is the quadratic surface coefficient
  • c is the curvature
  • a 4 ⁇ A 16 are the non-spherical Higher order coefficients for the sphere.
  • the material of the first lens 21 and the second lens 22 can be optical plastic or optical glass.
  • the first lens 21 is made of optical glass
  • the second lens 22 is made of optical plastic.
  • the display unit 10 includes a display device 11 and a second quarter-wave plate 12, the display device 11 is used to emit image light in a second linear polarization state to the second quarter-wave plate 12, as a
  • the display device 11 is LCoS or TFT-LCD, the image light emitted by it is linearly polarized light, and the linearly polarized light can be set as the image light in the second linearly polarized state.
  • the display device 11 includes Micro-OLED or LED111, and an absorbing polarizing film 112, the absorbing polarizing film 112 is used to absorb the light, the light in the second linearly polarized state is transmitted, because the light emitted by the Micro-OLED or LED111 is non-polarized light, when the image light 101 ′′ emitted by the Micro-OLED or LED111 passes through the absorbing polarizing film 112, it will be transmitted as The image light 101 ′ in the second linear polarization state meets the usage requirements.
  • FIG. 6 is a graph of the modulation transfer function (MTF) corresponding to the short-focus folded optical system of Embodiment 1.
  • the modulation transfer function (MTF) is used to represent the ability of the optical system to transmit information of different spatial frequencies, that is, the resolving power. The higher the resolving power of the optical system, the higher the corresponding spatial frequency, which can match the display device 11 with corresponding pixel density.
  • the field angle of the optical system corresponding to this embodiment is 70 degrees, the focal length is 21.5 mm, the image height is 12.7 mm, the eye relief (Eye Relief) is 17 mm, and the eye box (Eye box) is 10 mm.
  • the minimum MTF value of all viewing angles at a spatial frequency of 50lp/mm is 0.28.
  • a spatial frequency of 50 lp/mm corresponds to a display device 11 with a pixel size of 10 um and a pixel density PPI of 2540, which belongs to a high-resolution display device. Therefore, the resolving power of the short-focus folding optical system of this embodiment can at least match a high-resolution display device with a pixel density PPI of 2540.
  • the short-focus folding optical system can be designed to zoom, that is, the distance of the displayed image can be changed.
  • zoom that is, the distance of the displayed image can be changed.
  • the display unit 10 is set to be movable relative to the first lens 21, and the display unit 10 is moved mechanically while other optical devices are fixed, which changes the object distance of the optical system (display unit 10 to distance between the first lenses 21 ), so that the image distance of the optical system can be correspondingly changed, that is, the distance from the image light magnified by the light folding unit 20 to the human eye 30 .
  • the first lens 21 is movably disposed between the display unit 10 and the second lens 22 , and the first lens 21 is moved mechanically while other optical components are fixed.
  • This solution changes the focal length of the optical system, and also changes the object distance, thus correspondingly changing the image distance of the optical system.
  • the first lens 21 is set as a liquid crystal lens or a liquid lens, and the overall focal length of the optical system is changed by changing the focal length of the liquid crystal lens or liquid lens.
  • This solution changes the focal length of the liquid crystal lens or liquid lens by applying voltage.
  • the zoom speed of this solution is faster, and it can focus according to the focus distance of the human eye 30. To adjust the focal length in real time to realize the dynamic adjustment of the virtual image distance.
  • the main difference between this embodiment and Embodiment 1 is the setting positions of the semi-transparent and semi-reflective film 25, the first quarter-wave plate 23 and the reflective polarizer 24, as shown in Figure 7, which includes image light
  • the transmission route, the semi-transparent and semi-reflective film 25 in this embodiment is arranged on the light-emitting surface 212 of the first lens 21, and the reflective polarizer 24 is arranged on the light-incident surface 221 of the second lens 22 , the first quarter-wave plate 23 is disposed on a side of the reflective polarizer 24 facing away from the second lens 22 .
  • the short-focus folding optical system enters the image light of the human eye 30, and its propagation in the light folding unit 20 and the polarization direction change process are as follows:
  • the display unit 10 emits the image light 101 in the circularly polarized state toward the light folding unit 20 , and the image light 101 in the circularly polarized state is transmitted through the first lens 21 sequentially, and passes through the semi-transparent and semi-reflective film 25 Partially transmitted through the first quarter-wave plate 23 and transformed into image light in the first linearly polarized state, the image light in the first linearly polarized state is reflected by the reflective polarizer 24 in turn, The image light 101C that is transmitted and transformed into a circularly polarized state through the first quarter-wave plate 23 is partially reflected by the semi-transparent and semi-reflective film 25, and passes through the first quarter-wave plate 23 again.
  • the image light 101B transformed into the second linear polarization state by transmission is transmitted through the reflective polarizer 24 , finally transmitted through the second lens 22 and enters the human eye 30 .
  • the human eyes 30 can see the virtual image displayed by the display unit 10, achieving the effect of virtual reality.
  • the image light is reflected and transmitted multiple times in the light folding unit 20 , and the light folding unit 20 makes the image light continuously folded and propagated, so as to shorten the length (thickness) of the optical system.
  • the absorbing polarizer 26 in this embodiment can be arranged between the reflective polarizer 24 and the second lens 22, or can be arranged on one side of the light-emitting surface of the second lens 22, For example, as shown in FIG. 8 , the absorbing polarizer 26 of this embodiment is arranged between the reflective polarizer 24 and the second lens 22 for bonding.
  • the light-incident surfaces of the first lens 21 and the second lens 22 are convex, and the light-exit surfaces are concave, that is, the first lens 21 and the second lens 22 are both meniscus lenses, so that the image The light can travel in a reasonable route in the light folding unit 20 .
  • the light incident surface 211 and the light exit surface 212 of the first lens 21, the light incident surface 221 and the light exit surface 222 of the second lens 22 may be spherical surfaces, free curved surfaces or other curved surfaces.
  • the light incident surface 211 and the light exit surface 212 of the first lens 21, and the light incident surface 221 and the light exit surface 222 of the second lens 22 are all aspherical, which can significantly improve the resolution of the optical system.
  • the expression of the aspheric surface type is the same as that in Embodiment 1, so it will not be repeated.
  • both the first lens 21 and the second lens 22 are made of optical plastic with a relatively low birefringence index.
  • optical glass may also be used for the first lens 21 and the second lens 22 .
  • Fig. 9 is the modulation transfer function MTF curve diagram corresponding to the short-focus folding optical system of embodiment 2, the field angle of the optical system corresponding to this embodiment is 90 degrees, the focal length is 19.1 mm, and the image height is 14 mm , the eye relief is 14mm, and the eye box is 8mm.
  • the minimum MTF value of all field angles at a spatial frequency of 70lp/mm is 0.16.
  • a spatial frequency of 70 lp/mm corresponds to a pixel size of the display device 11 of 7.14um and a pixel density PPI of 3556, which belongs to a high-resolution display device. Therefore, the resolving power of the short-focus folding optical system of this embodiment can at least match a high-resolution display device with a pixel density PPI of 3556.
  • the main difference between this embodiment and Embodiment 1 is the setting positions of the semi-transparent and semi-reflective film 25, the first quarter-wave plate 23 and the reflective polarizer 24, as shown in Figure 10, which includes image light
  • the semi-transparent and semi-reflective film 25 is arranged on the light incident surface 211 of the first lens 21, and the first quarter-wave plate 23 is arranged on the second lens 22.
  • the reflective polarizer 24 is disposed on a surface of the first quarter wave plate 23 facing away from the second lens 22 .
  • the short-focus folding optical system enters the image light of the human eye 30, and its propagation in the light folding unit 20 and the polarization direction change process are as follows:
  • the display unit 10 emits an image light 101 in a circularly polarized state toward the light folding unit 20, and the image light 101 in a circularly polarized state is partially transmitted through the semi-transparent and semi-reflective film 25 sequentially, and passes through the first lens.
  • the reflective polarizer 24 is reflected and transmitted through the first quarter-wave plate 23 and transformed into a circularly polarized image light 101C, which is transmitted through the second lens 22, transmitted through the first lens 21, and passed through the
  • the semi-transparent and semi-reflective film 25 is partially reflected, transmitted through the first lens 21 again, transmitted through the second lens 22 again, and transformed into the second linear polarization state through the first quarter-wave plate 23 again
  • the image light 101B finally enters the human eye 30 after being transmitted through the reflective polarizer 24 .
  • the human eyes 30 can see the virtual image displayed by the display unit 10, achieving the effect of virtual reality.
  • the image light is reflected and transmitted multiple times in the light folding unit 20 , and the light folding unit 20 makes the image light continuously folded and propagated, so as to shorten the length (thickness) of the optical system.
  • the above setting method is a setting method of this embodiment.
  • the first quarter-wave plate 23 in this embodiment can be set on the second lens 22 on the light incident surface of the second lens 22.
  • the reflective polarizer 24 is arranged on the light exit surface of the second lens 22.
  • the first quadrant described in this embodiment One of the wave plates 23 can also be arranged on the light incident surface of the first lens 21, and at this time, the reflective polarizer 24 is arranged on the light exit surface of the second lens 22. Both of these arrangements are optional.
  • the propagation of the image light in the light folding unit 20 and the process of changing the polarization direction can be deduced with reference to the above process, and will not be described in detail here.
  • the absorbing polarizer 26 in this embodiment can only be disposed on the side of the reflective polarizer 24 facing away from the second lens 22 .
  • the light-incident surfaces of the first lens 21 and the second lens 22 are convex, and the light-exit surfaces are flat, that is, the first lens 21 and the second lens 22 are plano-convex lenses, so that the image light It can propagate in a reasonable route in the light folding unit 20 .
  • Both the light incident surface 211 of the first lens 21 and the light incident surface 221 of the second lens 22 can be a spherical surface, a free-form surface or other curved surfaces, for example, the light incident surface of the first lens 21 described in this embodiment 211 and the light incident surface 221 of the second lens 22 are both aspherical, which can significantly improve the resolution of the optical system.
  • the expression of the aspheric surface type is the same as that in Embodiment 1, so it will not be repeated.
  • both the first lens 21 and the second lens 22 are made of optical plastic with a relatively low birefringence index.
  • optical glass may also be used for the first lens 21 and the second lens 22 .
  • Fig. 12 is the modulation transfer function MTF graph corresponding to the short-focus folded optical system of embodiment 3, the field angle of the optical system corresponding to this embodiment is 70 degrees, the focal length is 22.9 mm, and the image height is 15.5 mm, the Eye Relief is 15mm, and the Eye box is 8mm.
  • the minimum MTF value of all viewing angles at a spatial frequency of 40lp/mm is 0.18.
  • a spatial frequency of 40 lp/mm corresponds to a pixel size of the display device 11 of 12.5 um and a pixel density of PPI of 2032, which belongs to the high-resolution display device 11 . Therefore, the resolving power of the short-focus folding optical system of this embodiment can at least match the high-resolution display device 11 with a pixel density PPI of 2032.
  • the propagation paths of the image light in the light folding unit are different, but all of them can make the image light be reflected and transmitted multiple times, increase the number of return times of the image light, thereby shortening
  • the length (thickness) of the optical system can reduce the number of optical lenses used, and has the advantages of small size, light weight and high resolution.
  • the present application also provides a virtual reality display device, which includes a spectacle frame and the above-mentioned short-focus folding optical system; the spectacle frame forms an optical system cavity, and the short-focus folding optical system is arranged in the optical system cavity Inside.
  • the virtual reality display device may be a head-mounted display device, a wearable display device, etc., which include all the technical effects of the above-mentioned short-focus folding optical system, and will not be repeated here.

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Abstract

一种短焦折叠光学系统以及虚拟现实显示设备，短焦折叠光学系统包括：显示单元(10)和光线折叠单元(20)；显示单元(10)用于朝光线折叠单元(20)发出圆偏振状态的图像光线(101)；光线折叠单元(20)用于将图像光线(101)折叠传播至人眼(30)；光线折叠单元(20)包括第一透镜(21)、第二透镜(22)、第一四分之一波片(23)和反射型偏振片(24)，利用光的偏振特性，使得图像光线(101)在光线折叠单元(20)中进行多次反射和折射，通过增加图像光线(101)的折返次数来缩短光学系统的长度，同时还可以减少使用的光学镜片的数量，实现体积小、重量轻以及高解析力的优点。

Description

一种短焦折叠光学系统以及虚拟现实显示设备
本申请要求于2021年10月26日提交国家知识产权局、申请号为202111246774.9、发明名称为“一种短焦折叠光学系统以及虚拟现实显示设备”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及虚拟现实显示设备技术领域，例如涉及一种短焦折叠光学系统以及虚拟现实显示设备。
背景技术
市面上相关虚拟现实显示设备的体积、重量，以及显示分辨率(清晰度)都不够令人满意，主要是受制于虚拟现实光学系统的设计方案，虚拟现实光学系统决定了虚拟现实显示设备的最终形态，目前虚拟现实的光学系统设计不够合理，图像光线在光学系统中折返不足，使得光学系统的长度(厚度)无法降低，此类光学系统的体积较大，重量较大，不利于减少虚拟现实显示设备的体积和重量。
发明内容
本申请的目的在于提供一种短焦折叠光学系统，以解决相关技术中的缺点与不足。
本申请的一种短焦折叠光学系统，包括：显示单元和光线折叠单元；
所述显示单元用于朝所述光线折叠单元发出圆偏振状态的图像光线；所述光线折叠单元用于将所述图像光线折叠传播至人眼；
所述光线折叠单元包括第一透镜、第二透镜、第一四分之一波片和反射型偏振片；所述第一透镜和第二透镜沿所述图像光线发出方向依次布置，所述第一透镜和第二透镜均具有朝向所述显示单元的入光面以及背向所述显示单元的出光面，所述第一透镜的入光面或出光面上设置有半透半反膜；所述第一四分之一波片和反射型偏振片均位于所述第一透镜背向所述显示单元的一侧，且两者沿所述图像光线发出方向依次布置；所述圆偏振状态的图像光线首次经过所述第一四分之一波片时，被透射变换为第一线偏振状态的图像光线；所述反射型偏振片用于反射第一线偏振状态的光和透射第二线偏振状态的光。
本申请实施例的短焦折叠光学系统，通过设置所述光线折叠单元，所述光线折叠单元包括第一透镜、第二透镜、第一四分之一波片和反射型偏振片，其利用光的偏振特性，使得图像光线在光线折叠单元中进行多次反射和折射，通过增加图像光线的折返次数来缩短光学系统的长度(厚度)，同时还可以减少使用的光学镜片的数量，实现体积小、重量轻以及高 解析力的优点。
在一可选实施例中，所述半透半反膜设置于所述第一透镜的入光面上，所述第一四分之一波片设置于所述第一透镜的出光面上，所述反射型偏振片设置于所述第二透镜的入光面上。
在一可选实施例中，所述第一透镜的入光面为凸面，出光面为平面；
所述第二透镜的入光面为凸面，出光面为凹面。
在一可选实施例中，所述半透半反膜设置于所述第一透镜的出光面上，所述反射型偏振片设置于所述第二透镜的入光面上，所述第一四分之一波片设置于所述反射型偏振片背向所述第二透镜的一面上。
在一可选实施例中，所述第一透镜和第二透镜的入光面均为凸面，出光面均为凹面。
在一可选实施例中，所述半透半反膜设置于所述第一透镜的入光面上，所述第一四分之一波片设置于所述第二透镜的出光面上，所述反射型偏振片设置于所述第一四分之一波片背向所述第二透镜的一面上。
在一可选实施例中，所述第一透镜和第二透镜的入光面均为凸面，出光面均为平面。
在一可选实施例中，所述光线折叠单元还包括吸收型偏振片，所述吸收型偏振片用于吸收第一线偏振状态的光和透射第二线偏振状态的光，所述第一四分之一波片、反射型偏振片和吸收型偏振片沿所述图像光线发出方向依次布置。
在一可选实施例中，所述显示单元包括显示装置和第二四分之一波片，所述显示装置用于发出第二线偏振状态的图像光线至所述第二四分之一波片，所述第二线偏振状态的图像光线经过所述第二四分之一波片时，被透射变换为所述圆偏振状态的图像光线。
本申请还提供一种虚拟现实显示设备，其包括眼镜架和上述的短焦折叠光学系统；所述眼镜架形成一光学系统容腔，所述短焦折叠光学系统设置于所述光学系统容腔内。
为了更好地理解和实施，下面结合附图详细说明本申请。
附图说明
图1为本申请短焦折叠光学系统的其中一种结构示意图；
图2为本申请显示单元的结构示意图；
图3为本申请实施例1的短焦折叠光学系统的结构示意图；
图4为本申请实施例1的短焦折叠光学系统的另一个结构示意图；
图5为本申请显示装置的其中一种结构示意图；
图6为本申请实施例1的短焦折叠光学系统对应的调制传递函数MTF曲线图；
图7为本申请实施例2的短焦折叠光学系统的结构示意图；
图8为本申请实施例2的短焦折叠光学系统的另一个结构示意图；
图9为本申请实施例2的短焦折叠光学系统对应的调制传递函数MTF曲线图；
图10为本申请实施例3的短焦折叠光学系统的结构示意图；
图11为本申请实施例3的短焦折叠光学系统的另一个结构示意图；
图12为本申请实施例3的短焦折叠光学系统对应的调制传递函数MTF曲线图。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请的一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
需要理解的是，在本申请的描述中，术语“中心”、“上”、“下”、“前”、“后”、“左”、“右”、“竖直”、“水平”、“顶”、“底”、“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请和简化描述，而不是指示或暗示所指的装置或元件具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请的限制。术语“第一”、“第二”仅用于描述目的，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量，也即，限定有“第一”、“第二”的特征可以明示或者隐含地包括一个或者更多个该特征。此外，除非另有说明，“多个”的含义是两个或两个以上。
需要说明的是，在本申请的描述中，除非另有明确的规定和限定，术语“设置”、“相连”、“连接”、“空心”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通。对于本领域的普通技术人员而言，可以具体情况理解上述术语在本申请中的具体含义。
请参阅图1，本申请提供一种短焦折叠光学系统，包括显示单元10和光线折叠单元20。
所述显示单元10用于朝所述光线折叠单元20发出圆偏振状态的图像光线101，所述光线折叠单元20用于将所述图像光线101折叠传播至人眼30。
所述光线折叠单元20包括第一透镜21、第二透镜22、第一四分之一波片23和反射型偏振片24；所述第一透镜21和第二透镜22沿所述图像光线101发出方向依次布置，所述第一透镜21和第二透镜22均具有朝向所述显示单元10的入光面(第一透镜21的入光面211、 第二透镜22的入光面221)以及背向所述显示单元10的出光面(第一透镜21的出光面212、第二透镜22的出光面222)，所述第一透镜21的入光面211或出光面212上设置有半透半反膜25，所述半透半反膜25对入射光具有反射和透过的功能，也即入射光穿过半透半反膜时部分光穿透过来，部分光被反射回去，半透半反膜的透反比可以根据需求进行设计，在本申请实施例中半透半反膜25的透反比可以为1：1，此时光学系统的光能利用率最高。
所述第一四分之一波片23和反射型偏振片24均位于所述第一透镜21背向所述显示单元10的一侧，且两者沿所述图像光线发出方向依次布置。
所述反射型偏振片24用于反射第一线偏振状态的光和透射第二线偏振状态的光，其中，第一线偏振状态的光即第一偏振方向的线偏振光，第二线偏振状态的光即第二偏振方向的线偏振光，第一偏振方向和第二偏振方向正交，在本申请中定义第一偏振方向为S方向，第二偏振方向为P方向，S方向与P方向正交，因此，第一线偏振状态的光也可以称之为S偏振光，第二线偏振状态的光同理可以称为P偏振光。
所述第一四分之一波片23能够将线偏振光变换为圆偏振光，或者将圆偏振光变换为线偏振光，本领域技术人员应该理解四分之一波片的特性，即：当S偏振光以一定角度穿过四分之一波片时，会被变换为圆偏振光，而该圆偏振光再次以一定角度经过四分之一波片时，会被变换为P偏振光；同理，当P偏振光以一定角度穿过四分之一波片时，会被变换为圆偏振光，而该圆偏振光再次以一定角度经过四分之一波片时，会被变换为S偏振光。
如图2所示，在一实施例中，所述显示单元10包括显示装置11和第二四分之一波片12，所述显示装置11用于发出第二线偏振状态的图像光线101’至所述第二四分之一波片12，所述第二线偏振状态的图像光线101’经过所述第二四分之一波片12时，被透射变换为所述圆偏振状态的图像光线101。当所述圆偏振状态的图像光线101首次经过所述第一四分之一波片23时，被透射变换为第一线偏振状态的图像光线。
本申请的短焦折叠光学系统，通过设置所述光线折叠单元20，所述光线折叠单元20包括第一透镜21、第二透镜22、第一四分之一波片23和反射型偏振片24，其利用光的偏振特性，使得图像光线在光线折叠单元20中进行多次反射和折射，通过增加图像光线的折返次数来缩短光学系统的长度(厚度)，同时还可以减少使用的光学镜片的数量，实现体积小、重量轻以及高解析力的优点。该短焦折叠光学系统采用高分辨率的显示单元10，经过光线折叠单元20放大后，由于所述光线折叠单元20具有高解析力，因此仍然可以显示出原有图像的显示细节，不会损失原有图像的分辨率。
其中，半透半反膜25、第一四分之一波片23和反射型偏振片24的设置位置可以有多种选择，不同的设置位置会使得图像光线的传播路径略有不同，下面结合附图对本申请的各 个实施例进行详细说明。
实施例1
如图3所示，图3中包含了图像光线的传播路线，在本实施例中，所述半透半反膜25设置于所述第一透镜21的入光面211上，所述第一四分之一波片23设置于所述第一透镜21的出光面212上，所述反射型偏振片24设置于所述第二透镜22的入光面221上。
本实施例短焦折叠光学系统进入人眼30的图像光线，其在光线折叠单元20中传播以及偏振方向变化过程如下：
如图3所示，显示单元10朝所述光线折叠单元20发出圆偏振状态的图像光线101，所述圆偏振状态的图像光线101依次经过半透半反膜25被部分透射，经过所述第一透镜21被透射，经过所述第一四分之一波片23被透射变换为第一线偏振状态的图像光线101A，该第一线偏振状态的图像光线101A依次经过所述反射型偏振片24被反射，经过所述第一四分之一波片23被透射变换为圆偏振状态的图像光线，经过所述第一透镜21被透射，经过所述半透半反膜25被部分反射，再次经过所述第一透镜21被透射，再次经过所述第一四分之一波片23被透射变换为第二线偏振状态的图像光线101B，经过所述反射型偏振片24被透射，最后经过所述第二透镜22被透射后进入人眼30。从而使人眼30看到显示单元10所显示的虚拟图像，达到虚拟现实的效果。
由上可知，图像光线在光线折叠单元20中进行了多次反射和透射，光线折叠单元20使得图像光线不断地折叠传播，以此缩短光学系统的长度(厚度)。
由于实际使用中，反射型偏振片24对S偏振光的反射率并不是100％，因此在图像光线传播过程中，仍然会有少量的第一线偏振状态的图像光线会透过反射型偏振片24后进入人眼30，此部分图像光线为杂散光，会降低整个显示画面的对比度。因此，如图4所示，在一实施例中，所述光线折叠单元20还包括吸收型偏振片26，所述吸收型偏振片26用于吸收第一线偏振状态的光和透射第二线偏振状态的光，所述第一四分之一波片23、反射型偏振片24和吸收型偏振片26沿所述图像光线发出方向依次布置。吸收型偏振片26刚好可以吸收透过反射型偏振片24的第一线偏振状态的图像光线，通过此种设置可以减少光学装置的杂散光，提高整个显示画面的对比度。
本实施例所述吸收型偏振片26可以设置在所述反射型偏振片24和第二透镜22之间，也可以设置在第二透镜22的出光面222的一侧，例如，如图4所示，本实施例吸收型偏振片26设置在所述反射型偏振片24和第二透镜22之间，以便贴合。
在本实施例中，所述第一透镜21的入光面211为凸面，出光面212为平面，所述第二 透镜22的入光面221为凸面，出光面222为凹面，以使得图像光线可以在光线折叠单元20内以合理的路线传播。所述第一透镜21的入光面211、第二透镜22的入光面221和第二透镜22的出光面222均可以是球面、自由曲面或其他面型的曲面，可选的，在本实施例中，所述第一透镜21的入光面211、第二透镜22的入光面221和第二透镜22的出光面222均为非球面面型，可以显著提高光学系统的分辨率。所述非球面面型表达式为：
Figure PCTCN2022081707-appb-000001
上式中，z为非球面面型的矢高，r为非球面的半径，即r＝sqrt(x 2+y 2)，k为二次曲面系数，c为曲率，A 4～A 16为非球面的高次项系数。
第一透镜21和第二透镜22的材质可以采用光学塑料，也可以采用光学玻璃。在一实施例中，第一透镜21采用光学玻璃，第二透镜22采用光学塑料。
所述显示单元10包括显示装置11和第二四分之一波片12，所述显示装置11用于发出第二线偏振状态的图像光线至所述第二四分之一波片12，作为一种可选地实施方式，所述显示装置11为LCoS和TFT-LCD，其出射的图像光线是线偏振光，该线偏振光可以被设置为第二线偏振状态的图像光线。如图5所示，作为另一种可选地实施方式，所述显示装置11包括Micro-OLED或LED111、和一吸收型偏振膜112，吸收型偏振膜112用于吸收第一线偏振状态的光，透射第二线偏振状态的光，由于Micro-OLED或LED111发出的光线是非偏振光，当Micro-OLED或LED111发出的图像光线101”经过所述吸收型偏振膜112时，则会被透射为第二线偏振状态的图像光线101’，以满足使用要求。
请参阅图6，图6为实施例1的短焦折叠光学系统对应的调制传递函数MTF曲线图，调制传递函数MTF用来表征光学系统对不同空间频率信息的传递能力，即解析力。光学系统的解析力越高，其对应的空间频率也越高，就可以匹配相应像素密度的显示装置11。
本实施例对应的光学系统的视场角为70度，焦距为21.5mm，图像高度为12.7mm，出瞳距(Eye Relief)为17mm，眼盒(Eye box)为10mm。所有视场角在空间频率50lp/mm下的MTF值最小为0.28。空间频率50lp/mm对应显示装置11的像素尺寸为10um，像素密度PPI为2540，属于高分辨率显示装置。因此，本实施例的短焦折叠光学系统的解析力至少可以匹配像素密度PPI为2540的高分辨率显示装置。
另外，为了满足近视用户在不佩戴近视镜的情况下，能够看清采用上述短焦折叠光学系统所显示的虚拟图像，可以对短焦折叠光学系统进行变焦设计，即可以改变显示图像的距离。当近视用户使用时，可以通过调节显示图像的远近来看清图像细节。
上述短焦折叠光学系统的变焦设计方案的实施方式有以下三种：
第一种，显示单元10被设置为可相对于第一透镜21移动，通过采用机械方式移动显示单元10，其他光学器件固定不动，这种方式改变了光学系统的物距(显示单元10到第一透镜21的间距)，这样就可以相应地改变光学系统的像距，即经过光线折叠单元20放大后的图像光线到人眼30的距离。
第二种，第一透镜21可移动地设置于所述显示单元10和第二透镜22之间，通过采用机械方式移动第一透镜21，其他光学器件固定不动。这种方案改变了光学系统的焦距，同时也改变了物距，如此相应地改变了光学系统的像距。
第三种，第一透镜21设置为液晶透镜或液体透镜，通过改变液晶透镜或液体透镜的焦距来改变光学系统的整体焦距。这种方案通过采用施加电压的方式来改变液晶透镜或液体透镜的焦距，与上述两种采用机械式移动光学器件的方案相比，该方案的变焦速度更快，可以根据人眼30的聚焦远近来实时调整焦距，实现虚像距离的动态调整。
实施例2
本实施例与实施例1的主要区别在于半透半反膜25、第一四分之一波片23和反射型偏振片24的设置位置，如图7所示，图7中包含了图像光线的传播路线，本实施例所述半透半反膜25设置于所述第一透镜21的出光面212上，所述反射型偏振片24设置于所述第二透镜22的入光面221上，所述第一四分之一波片23设置于所述反射型偏振片24背向所述第二透镜22的一面上。
本实施例短焦折叠光学系统进入人眼30的图像光线，其在光线折叠单元20中传播以及偏振方向变化过程如下：
如图7所示，显示单元10朝所述光线折叠单元20发出圆偏振状态的图像光线101，所述圆偏振状态的图像光线101依次经过第一透镜21被透射，经过半透半反膜25被部分透射，经过所述第一四分之一波片23被透射变换为第一线偏振状态的图像光线，该第一线偏振状态的图像光线依次经过所述反射型偏振片24被反射，经过所述第一四分之一波片23被透射变换为圆偏振状态的图像光线101C，经过所述半透半反膜25被部分反射，再次经过所述第一四分之一波片23被透射变换为第二线偏振状态的图像光线101B，经过所述反射型偏振片24被透射，最后经过所述第二透镜22被透射后进入人眼30。从而使人眼30看到显示单元10所显示的虚拟图像，达到虚拟现实的效果。
由上可知，图像光线在光线折叠单元20中进行了多次反射和透射，光线折叠单元20使得图像光线不断地折叠传播，以此缩短光学系统的长度(厚度)。
与实施例1类似地，本实施例所述吸收型偏振片26可以设置在所述反射型偏振片24 和第二透镜22之间，也可以设置在第二透镜22的出光面的一侧，例如，如图8所示，本实施例吸收型偏振片26设置在所述反射型偏振片24和第二透镜22之间，以便贴合。
在本实施例中，所述第一透镜21和第二透镜22的入光面均为凸面，出光面均为凹面，即第一透镜21和第二透镜22都是弯月透镜，以使得图像光线可以在光线折叠单元20内以合理的路线传播。所述第一透镜21的入光面211和出光面212、第二透镜22的入光面221和出光面222均可以是球面、自由曲面或其他面型的曲面，可选的，本实施例所述第一透镜21的入光面211和出光面212、第二透镜22的入光面221和出光面222均为非球面面型，可以显著提高光学系统的分辨率。所述非球面面型表达式与实施例1相同，故不赘述。
本实施例第一透镜21和第二透镜22均采用双折射系数较低的光学塑料。可选地，第一透镜21和第二透镜22也可以采用光学玻璃。
请参阅图9，图9为实施例2的短焦折叠光学系统对应的调制传递函数MTF曲线图，本实施例对应的光学系统的视场角为90度，焦距为19.1mm，图像高度为14mm，出瞳距(Eye Relief)为14mm，眼盒(Eye box)为8mm。所有视场角在空间频率70lp/mm下的MTF值最小为0.16。空间频率70lp/mm对应显示装置11的像素尺寸为7.14um，像素密度PPI为3556，属于高分辨率显示装置。因此，本实施例的短焦折叠光学系统的解析力至少可以匹配像素密度PPI为3556的高分辨率显示装置。
实施例3
本实施例与实施例1的主要区别在于半透半反膜25、第一四分之一波片23和反射型偏振片24的设置位置，如图10所示，图10中包含了图像光线的传播路线，本实施例所述半透半反膜25设置于所述第一透镜21的入光面211上，所述第一四分之一波片23设置于所述第二透镜22的出光面222上，所述反射型偏振片24设置于所述第一四分之一波片23背向所述第二透镜22的一面上。
本实施例短焦折叠光学系统进入人眼30的图像光线，其在光线折叠单元20中传播以及偏振方向变化过程如下：
如图10所示，显示单元10朝所述光线折叠单元20发出圆偏振状态的图像光线101，所述圆偏振状态的图像光线101依次经过半透半反膜25被部分透射，经过第一透镜21被透射，经过第二透镜22被透射，经过所述第一四分之一波片23被透射变换为第一线偏振状态的图像光线，该第一线偏振状态的图像光线依次经过所述反射型偏振片24被反射，经过所述第一四分之一波片23被透射变换为圆偏振状态的图像光线101C，经过第二透镜22被透射，经过第一透镜21被透射，经过所述半透半反膜25被部分反射，再次经过第一透镜21被透 射，再次经过第二透镜22被透射，再次经过所述第一四分之一波片23被透射变换为第二线偏振状态的图像光线101B，最后经过所述反射型偏振片24被透射后进入人眼30。从而使人眼30看到显示单元10所显示的虚拟图像，达到虚拟现实的效果。
由上可知，图像光线在光线折叠单元20中进行了多次反射和透射，光线折叠单元20使得图像光线不断地折叠传播，以此缩短光学系统的长度(厚度)。
上述设置方式为本实施例一种设置方式，当然，作为一种可选地设置方式(图未示出)，本实施例所述第一四分之一波片23可以设置在第二透镜22的入光面上，此时反射型偏振片24则设置在第二透镜22的出光面上，作为另一种可选地设置方式(图未示出)，本实施例所述第一四分之一波片23还可以设置在第一透镜21的入光面上，此时反射型偏振片24则设置在第二透镜22的出光面上，此两种设置方式均为可选方案，其图像光线在光线折叠单元20中传播以及偏振方向变化过程可以参照上述过程进行推理得出，此处不作赘述。
与实施例1不同的是，如图11所示，本实施例所述吸收型偏振片26只可设置于所述反射型偏振片24背向所述第二透镜22的一侧。
在本实施例中，所述第一透镜21和第二透镜22的入光面均为凸面，出光面均为平面，即第一透镜21和第二透镜22都是平凸透镜，以使得图像光线可以在光线折叠单元20内以合理的路线传播。所述第一透镜21的入光面211和第二透镜22的入光面221均可以是球面、自由曲面或其他面型的曲面，例如，本实施例所述第一透镜21的入光面211和第二透镜22的入光面221均为非球面面型，可以显著提高光学系统的分辨率。所述非球面面型表达式与实施例1相同，故不赘述。
本实施例第一透镜21和第二透镜22均采用双折射系数较低的光学塑料。可选地，第一透镜21和第二透镜22也可以采用光学玻璃。
请参阅图12，图12为实施例3的短焦折叠光学系统对应的调制传递函数MTF曲线图，本实施例对应的光学系统的视场角为70度，焦距为22.9mm，图像高度为15.5mm，出瞳距(Eye Relief)为15mm，眼盒(Eye box)为8mm。所有视场角在空间频率40lp/mm下的MTF值最小为0.18。空间频率40lp/mm对应显示装置11的像素尺寸为12.5um，像素密度PPI为2032，属于高分辨率显示装置11。因此，本实施例的短焦折叠光学系统的解析力至少可以匹配像素密度PPI为2032的高分辨率显示装置11。
本申请以上各个实施例对应的光学系统，其图像光线在光线折叠单元中的传播路径均有所不同，但是均可以使得图像光线得到多次反射和透射，增加图像光线的折返次数，以此缩短光学系统的长度(厚度)，从而可以减少使用的光学镜片的数量，具有体积小、重量轻以及高解析力的优点。
本申请还提供一种虚拟现实显示设备，其包括眼镜架和上述的短焦折叠光学系统；所述眼镜架形成一光学系统容腔，所述短焦折叠光学系统设置于所述光学系统容腔内。该虚拟现实显示设备可以是头戴式显示设备、穿戴式显示设备等等，其包含上述短焦折叠光学系统的所有技术效果，在此不再赘述。
以上所述实施例仅表达了本申请的几种实施方式，其描述较为详细，但并不能因此而理解为对本申请专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。

Claims (10)

  1. 一种短焦折叠光学系统，其中，包括：
    显示单元和光线折叠单元；
    所述显示单元用于朝所述光线折叠单元发出圆偏振状态的图像光线；所述光线折叠单元用于将所述图像光线折叠传播至人眼；
    所述光线折叠单元包括第一透镜、第二透镜、第一四分之一波片和反射型偏振片；所述第一透镜和第二透镜沿所述图像光线发出方向依次布置，所述第一透镜和第二透镜均具有朝向所述显示单元的入光面以及背向所述显示单元的出光面，所述第一透镜的入光面或出光面上设置有半透半反膜；所述第一四分之一波片和反射型偏振片均位于所述第一透镜背向所述显示单元的一侧，且两者沿所述图像光线发出方向依次布置；所述圆偏振状态的图像光线首次经过所述第一四分之一波片时，被透射变换为第一线偏振状态的图像光线；所述反射型偏振片用于反射第一线偏振状态的光和透射第二线偏振状态的光。
  2. 根据权利要求1所述的短焦折叠光学系统，其中：
    所述半透半反膜设置于所述第一透镜的入光面上，所述第一四分之一波片设置于所述第一透镜的出光面上，所述反射型偏振片设置于所述第二透镜的入光面上。
  3. 根据权利要求2所述的短焦折叠光学系统，其中：
    所述第一透镜的入光面为凸面，出光面为平面；
    所述第二透镜的入光面为凸面，出光面为凹面。
  4. 根据权利要求1所述的短焦折叠光学系统，其中：
    所述半透半反膜设置于所述第一透镜的出光面上，所述反射型偏振片设置于所述第二透镜的入光面上，所述第一四分之一波片设置于所述反射型偏振片背向所述第二透镜的一面上。
  5. 根据权利要求4所述的短焦折叠光学系统，其中：
    所述第一透镜和第二透镜的入光面均为凸面，出光面均为凹面。
  6. 根据权利要求1所述的短焦折叠光学系统，其中：
    所述半透半反膜设置于所述第一透镜的入光面上，所述第一四分之一波片设置于所述第二透镜的出光面上，所述反射型偏振片设置于所述第一四分之一波片背向所述第二透镜的一面上。
  7. 根据权利要求6所述的短焦折叠光学系统，其中：
    所述第一透镜和第二透镜的入光面均为凸面，出光面均为平面。
  8. 根据权利要求1-7任一项所述的短焦折叠光学系统，其中：
    所述光线折叠单元还包括吸收型偏振片，所述吸收型偏振片用于吸收第一线偏振状态的光和透射第二线偏振状态的光，所述第一四分之一波片、反射型偏振片和吸收型偏振片沿所述图像光线发出方向依次布置。
  9. 根据权利要求1-7任一项所述的短焦折叠光学系统，其中：
    所述显示单元包括显示装置和第二四分之一波片，所述显示装置用于发出第二线偏振状态的图像光线至所述第二四分之一波片，所述第二线偏振状态的图像光线经过所述第二四分之一波片时，被透射变换为所述圆偏振状态的图像光线。
  10. 一种虚拟现实显示设备，其中，包括：
    眼镜架和如权利要求1-9任一项所述的短焦折叠光学系统；所述眼镜架形成一光学系统容腔，所述短焦折叠光学系统设置于所述光学系统容腔内。
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