WO2023097814A1 - 光学系统以及头戴显示设备 - Google Patents

光学系统以及头戴显示设备 Download PDF

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Publication number
WO2023097814A1
WO2023097814A1 PCT/CN2021/140041 CN2021140041W WO2023097814A1 WO 2023097814 A1 WO2023097814 A1 WO 2023097814A1 CN 2021140041 W CN2021140041 W CN 2021140041W WO 2023097814 A1 WO2023097814 A1 WO 2023097814A1
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Prior art keywords
lens
optical system
focal length
optical
glued
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Ceased
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PCT/CN2021/140041
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English (en)
French (fr)
Inventor
孙琦
赵博刚
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Goertek Optical Technology Co Ltd
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Goertek Optical Technology Co Ltd
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Application filed by Goertek Optical Technology Co Ltd filed Critical Goertek Optical Technology Co Ltd
Priority to JP2023526883A priority Critical patent/JP7485857B2/ja
Priority to US18/247,107 priority patent/US12572000B2/en
Priority to EP21957713.7A priority patent/EP4212945B1/en
Priority to KR1020237010506A priority patent/KR102865290B1/ko
Publication of WO2023097814A1 publication Critical patent/WO2023097814A1/zh
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
    • 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
    • G02B27/017—Head mounted
    • G02B27/0172—Head mounted characterised by optical features
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
    • G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
    • G02B13/002—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface
    • G02B13/0035—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface having three lenses
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B3/00—Simple or compound lenses
    • G02B3/02—Simple or compound lenses with non-spherical faces
    • G02B3/08—Simple or compound lenses with non-spherical faces with discontinuous faces, e.g. Fresnel lens
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B9/00—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or -
    • G02B9/12—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having three components only

Definitions

  • the present application relates to the technical field of optical imaging, and more specifically, the present application relates to an optical system and a head-mounted display device.
  • augmented reality Augmented Reality
  • virtual reality Virtual Reality
  • the core components of augmented reality technology and virtual reality technology are both display optical systems.
  • the quality of the display optical system will directly determine the quality of smart wearable devices.
  • a VR device In the existing related technologies, a VR device is taken as an example.
  • Existing VR devices mostly use a display optical system formed by a combination of a single-chip lens and a display screen (display).
  • the distance between the lens and the display screen will be relatively long, which leads to a large size of the VR device, which is not conducive to the miniaturization of the product, and may lead to poor user experience when wearing it.
  • the purpose of this application is to provide a new technical solution for an optical system and a head-mounted display device.
  • an optical system includes a third lens, a second lens and a first lens that are sequentially glued together along the propagation direction of the incident light;
  • Both surfaces of the cemented first lens and the second lens are Fresnel surfaces.
  • the refractive power of the first lens and the second lens are both positive, and the refractive power of the third lens is negative
  • the effective focal length f1 of the first lens and the effective focal length f of the optical system satisfy: 1.5 ⁇ f1/f ⁇ 2.22;
  • the effective focal length f2 of the second lens and the effective focal length f of the optical system satisfy: 1.5 ⁇ f2/f ⁇ 2.22;
  • the effective focal length f3 of the third lens and the effective focal length f of the optical system satisfy: -9 ⁇ f3/f ⁇ -5.
  • the effective focal length f1 of the first lens is: 30mm ⁇ f1 ⁇ 40mm;
  • the focal length f2 of the second lens is: 30mm ⁇ f2 ⁇ 40mm;
  • the focal length f3 of the third lens is: -180mm ⁇ f3 ⁇ -100mm;
  • the first lens, the second lens and the third lens are located on the same optical axis.
  • the effective focal length f of the optical system is: 18mm ⁇ f ⁇ 20mm.
  • the two glued Fresnel surfaces are glued and connected in the edge area by means of frame glue.
  • both the cemented surfaces of the second lens and the third lens are aspherical.
  • the two glued aspherical surfaces are glued and connected by any of the following methods:
  • the two aspherical surfaces are glued and connected by frame glue in the edge area;
  • the two aspheric surfaces are glued and connected by surface glue.
  • the first lens and the second lens, and the second lens and the third lens are glued together by light-transmitting optical glue, and the refractive index of the optical glue is 1.1 ⁇ 1.3.
  • a head-mounted display device is provided.
  • the head-mounted display device includes any one of the optical systems described above.
  • the embodiment of this application proposes a straight-through optical path structure design, through the bonding of three optical lenses, combined with the optimized design of the surface of the optical lens, the optical requirements of short focus, high light efficiency, and high resolution are realized, and the formed optical
  • the system can be applied, for example, in head-mounted display devices (eg, VR devices).
  • Fig. 1 is a schematic structural diagram of an optical system provided by an embodiment of the present application.
  • Fig. 2 is a schematic diagram of the imaging principle of the optical system provided in Embodiment 1 of the present application;
  • Fig. 3 is a spot diagram of the optical system provided by Embodiment 1 of the present application.
  • FIG. 4 is a field curvature and distortion diagram of the optical system provided in Embodiment 1 of the present application.
  • FIG. 5 is a dispersion diagram of the optical system provided in Embodiment 1 of the present application.
  • Fig. 6 is a schematic diagram of the imaging principle of the optical system provided in Embodiment 2 of the present application.
  • Figure 7 is a spot diagram of the optical system provided by Embodiment 2 of the present application.
  • Fig. 8 is a field curvature and distortion diagram of the optical system provided by Embodiment 2 of the present application.
  • FIG. 9 is a dispersion diagram of the optical system provided in Embodiment 2 of the present application.
  • Fig. 10 is a schematic diagram of the imaging principle of the optical system provided in Embodiment 3 of the present application.
  • Fig. 11 is a spot diagram of the optical system provided by Embodiment 3 of the present application.
  • Fig. 12 is a field curvature and distortion diagram of the optical system provided in Embodiment 3 of the present application.
  • Fig. 13 is the dispersion diagram of the optical system provided by Embodiment 3 of the present application.
  • an optical system is provided.
  • the optical system is a short-focus, high-efficiency, high-resolution straight-through optical system, which is suitable for use in electronic equipment, such as head mounted display (head mounted display, HMD), such as VR equipment (such as VR glasses or VR headset, etc.). It has a good application prospect.
  • An optical system provided by an embodiment of the present application includes a third lens 3, a second lens 2 and a first lens arranged in sequence along the propagation direction of incident light 1. Both surfaces of the cemented first lens 1 and the second lens 2 are Fresnel surfaces.
  • the optical system provided in the embodiment of the present application is designed with a straight-through optical path structure, and the overall optical path structure design is relatively simple, which makes the manufacture of the optical system relatively easy.
  • the optical system may further include a display 4, as shown in FIG. 2 , FIG. 6 and FIG. 10 .
  • the display screen 4 can be used to emit light in the light path structure, that is, the above-mentioned incident light.
  • a lens combination is designed in the optical system solution provided by the embodiment of the present application, and the lens combination includes, for example, three cemented optical lenses, as shown in Figure 1, Figure 2, Figure 6 and Figure 10, which It can be used to project the incident light (eg, emitted by the display screen 4 ) into the human eye 5 for imaging.
  • the optical system provided in the embodiment of the present application is based on the gluing design of three optical lenses, that is, the gluing of the first lens 1, the second lens 2 and the third lens 3 in the optical system can realize super Short focus, high light efficiency, high resolution optical structure design requirements. Moreover, based on the gluing of the three optical lenses, combined with the optimized design of the surface shape of each lens, it also helps to improve the imaging quality.
  • the imaging spot size of the optical system provided in the embodiment of the present application is ⁇ 50 ⁇ m in the 15° field of view, and ⁇ 88 ⁇ m in the full field of view.
  • the design of cementing the three lenses also reduces stray light in the optical system.
  • the cemented lens combination formed after gluing can be used as an optical component, which reduces the difficulty of assembling the optical component, and also reduces the risk of impurities between the lenses due to assembly, and can improve the yield rate.
  • the solution provided by the embodiment of the present application overcomes the long distance between the lens and the display screen brought about by the combination solution of the existing single-chip lens + display screen (display), which leads to a large size of the VR device, which is not conducive to the miniaturization of the product.
  • the problems of chemicalization and low light efficiency At the same time, it can also improve the defect of adopting the folded optical path, its processing difficulty and production cost are relatively low, and the straight-through optical structure is also simpler than the folded optical path.
  • a display screen 4 is provided in the optical system, and the display screen 4 is, for example, a 1.4inch Display, which realizes a 100-degree viewing angle.
  • the display screen 4 is, for example, a 1.4inch Display, which realizes a 100-degree viewing angle.
  • neither the conventional single-lens (1P) structure nor the double-lens (2P) structure is sufficient to distinguish this type of display screen. The reason is that:
  • the monolithic lens (1P) only has the optimization of the degree of freedom of the two surfaces, its converging ability is limited, and the aberration or chromatic aberration cannot be corrected.
  • the resolvable pixel size (imaging spot size) of the full field of view is about 80 ⁇ m ⁇ 100 ⁇ m, and more importantly, the purpose of short focus cannot be achieved.
  • the double-piece lens (2P) increases the freedom of lens surface optimization and can achieve short focus, it still has limitations in resolution and cannot meet the requirements for better imaging quality.
  • three optical lenses are used to glue together, which can not only achieve the purpose of short total optical length TTL, but also reduce the generation of stray light (for example, reduce the number of random reflections and radiation area of light in the air space, so that reduces the resulting stray light).
  • the solution of this application provides a short-focus optical path structure, which uses two glued Fresnel surfaces, which provides a larger focal power, and considering the influence of chromatic aberration, all The third lens 3 is matched to perform achromatization.
  • the Fresnel surface of the first lens 1 and the Fresnel surface of the second lens 2 include but are not limited to planar substrates.
  • the Fresnel surface of the first lens 1 and the Fresnel surface of the second lens 2 may also be curved substrates.
  • one of the Fresnel surfaces is a curved base, and the other Fresnel surface is a flat base.
  • the design of the curved substrate allows the lens to be thinner and lighter, thereby helping to reduce the overall mass of the optical system.
  • Those skilled in the art can properly adjust the base form of the Fresnel surface according to the specific situation, which is not specifically limited in this application.
  • the refractive powers of the first lens 1 and the second lens 2 are both positive, and the refractive power of the third lens 3 is negative.
  • the first lens 1 and the second lens 2 are both designed as positive lenses, and the third lens 3 is designed as a negative lens; the two positive lenses Can provide greater positive power, and the participation of negative lens can be used to eliminate chromatic aberration.
  • the two surfaces of the cemented first lens 1 and the second lens 2 are Fresnel surfaces.
  • the first lens 1 includes a first surface 11 and a second surface 12, and the second lens 2 includes a third surface 21 and a fourth surface 22.
  • the second surface 12 and the third surface 21 are glued together, and are all set as Fresnel surfaces, and the first surface 11 and the fourth surface 22 are aspherical (further , both surfaces are convex).
  • Anti-reflective coatings are respectively coated on the first surface 11 and the second surface 12 of the first lens 1 .
  • the reflected light can be reduced through the anti-reflection film, so as to increase the light transmission on the two surfaces of the first lens 1 Overrate.
  • a hardening coating may also be coated on the first surface 11 .
  • the first surface 11 of the first lens 1 is facing the outside, and it needs to avoid damages such as scratches and bruises, and the use of the first lens 1 can be improved by coating the hardened film. life. Coating a hardened film on the first surface 11 , that is, hardening the first surface 11 , can improve the hardness, strength, etc. of the first surface 11 . This is beneficial for improving the service life of the entire optical system.
  • the first lens 1 also has the following parameters.
  • the absolute value of the radius R 1 of the first surface 11 of the first lens 1 satisfies: 40mm ⁇ Abs(R 1 ) ⁇ 50mm; the radius R 1 of the second surface 12 of the first lens 1
  • the absolute value of the radius R 2 satisfies: 20mm ⁇ Abs(R 2 ) ⁇ 40mm; the absolute value of the conic coefficient K 1 of the first surface 11 and the second surface 12 satisfies: Abs(K 1 ) ⁇ 20.
  • the surface designs of the first surface 11 and the second surface 12 are different. Specifically, the outwardly facing first surface 11 is designed as an aspheric surface (such as a convex surface), and the second surface 12 is designed as a Fresnel surface, and the first lens formed by combining the Fresnel surface and the aspheric surface 1 Applied in the optical path structure, it helps to achieve the effect of short focus and high resolution.
  • the outwardly facing first surface 11 is designed as an aspheric surface (such as a convex surface)
  • the second surface 12 is designed as a Fresnel surface
  • the first lens formed by combining the Fresnel surface and the aspheric surface 1 Applied in the optical path structure it helps to achieve the effect of short focus and high resolution.
  • the conic coefficient (Coin Constant) of the first lens 1 namely
  • the value of K 1 is, for example, set at [-10, 10], and the radius R of the Fresnel surface of the first lens 1>23mm.
  • the second lens 2 includes a third surface 21 and a fourth surface 22, wherein the third surface 21 is designed as a Fresnel surface, and the fourth The surface 22 is designed as aspheric (eg convex).
  • an antireflection film is also coated on the third surface 21 and the fourth surface 22 .
  • the anti-reflection coating is used to reduce reflected light, so as to increase the transmittance of light on both surfaces of the second lens 2 .
  • the second lens 2 also has the following parameters.
  • the absolute value of the radius R 3 of the third surface 21 of the second lens 2 satisfies: 20mm ⁇ Abs(R 3 ) ⁇ 30mm;
  • the absolute value of the radius R 4 satisfies: 50mm ⁇ Abs(R 4 ) ⁇ 90mm;
  • the absolute value of the conic coefficient K 2 of the third surface 21 and the fourth surface 22 satisfies: Abs(K 2 ) ⁇ 20.
  • the conic coefficient (Coin Constant) of the second lens 2 that is, The value of K 2 is designed to be [-10, 10], and the radius of the Fresnel surface of the second lens 2 is >23mm. This is basically the same as the first lens 1 .
  • both the first lens 1 and the second lens 2 have Fresnel surfaces.
  • the surface parameters Considering the processing of the lens surface, it is necessary to set the surface parameters within a certain range, otherwise there will be low processing accuracy or risk of tool breakage (this is because the processing of the tooth profile is more difficult, the smaller the sharp angle of the tooth profile, the lower the processing accuracy. the more difficult the inclination and movement).
  • the combination of aspheric surface (such as convex surface) + Fresnel surface can be used, based on different Refractive index & Abbe number material selection and coordination realize low dispersion and short focus of the optical path structure.
  • the third lens 3 includes a fifth surface 31 and a sixth surface 32; wherein, the fifth surface 31 and the fourth surface of the second lens 2 22 is also a glue setting, and the fifth surface 31 is an aspheric surface, so that an aspheric glue is formed between the third lens 3 and the second lens 2 .
  • the refractive power of the third lens 3 is negative.
  • the third lens 3 is a negative lens, which is thin in the middle and thick in the periphery, and has the ability to diverge light.
  • the third lens 3 can be used for achromatization in the entire optical path structure.
  • the third lens 3 can be, for example, a biconcave lens (that is, both surfaces are concave), or a plano-concave lens (that is, one surface is concave and the other surface is flat).
  • the fifth surface 31 is configured as a concave surface
  • the sixth surface 32 is configured as a plane or a concave surface.
  • both the fifth surface 31 and the sixth surface 32 are coated with an anti-reflective coating (Anti-Reflective coating, AR).
  • Anti-Reflective coating AR
  • the reflected light can be reduced through the anti-reflection film, so as to increase the light transmission on the two surfaces of the third lens 3 Overrate.
  • the third lens 3 also has the following parameters.
  • the absolute value of the radius R 6 of the sixth surface 32 of the third lens 3 satisfies: 200mm ⁇ Abs(R 6 ) ⁇ 500mm.
  • the sixth surface 32 is adjacent to the display screen 4 .
  • the optical system may include: a display screen 4, and the first lens 1, the second lens 2, and the third lens 3;
  • the incident light emitted by the display screen 4 enters the interior of the third lens 3 through the sixth surface 32 of the third lens 3 coated with an anti-reflection film, and the transmitted light through the third lens 3 is diverged and enters
  • both surfaces of the second lens 2 are also coated with an anti-reflection film, so that the light is converged after passing through the second lens 2, and then enters the first lens 1,
  • the first lens 1 is still a converging positive lens, and after being transmitted through the first lens 1 , the light enters the human eye 5 for imaging.
  • There is no optical path folding in the entire optical system and the surface of each lens is coated with an anti-reflection film, so that the light transmission efficiency is high.
  • the relationship between the effective focal length f 1 of the first lens 1 and the effective focal length f of the optical system is: 1.5 ⁇ f 1 /f ⁇ 2.22; the effective focal length f of the second lens 2
  • the relationship between the focal length f2 and the effective focal length f of the optical system is: 1.5 ⁇ f2 /f ⁇ 2.22; the relationship between the effective focal length f3 of the third lens 3 and the effective focal length f of the optical system is: : -9 ⁇ f 3 /f ⁇ -5.
  • the optical system provided in the embodiment of the present application has the characteristic of small effective focal length f value.
  • the effective focal length f 1 of the first lens 1 is: 30mm ⁇ f 1 ⁇ 40mm; the focal length f2 of the second lens 2 is: 30mm ⁇ f 2 ⁇ 40mm; The focal length f 3 of the three lenses 3 is: -180mm ⁇ f 3 ⁇ -100mm; the first lens 1 , the second lens 2 and the third lens 2 are located on the same optical axis.
  • the effective focal length f of the optical system is: 18mm ⁇ f ⁇ 20mm.
  • the effective focal length f of the optical system is: 19.0,mm-19.5mm.
  • the effective focal length f1 of the first lens 1 and the focal length f2 of the second lens 2 are both greater than the effective focal length f of the lens group.
  • the application provides a short-focus optical system. There is no optical path folding in the entire optical system, and it is a straight-through optical system that can achieve high-definition imaging.
  • the two glued Fresnel surfaces are glued and connected in the edge area by means of frame glue.
  • Both the first lens 1 and the second lens 2 have a Fresnel surface. Considering the base tooth structure of the Fresnel surface, it is preferable to connect the edge regions of the two lenses by gluing, so that The first lens 1 and the second lens 2 are closely attached together. The gluing of the two Fresnel surfaces is more reliable by using frame glue.
  • both the cemented surfaces of the second lens 2 and the third lens 3 are aspherical.
  • the convex surface of the second lens 2 is glued to the concave surface of the third lens 3 .
  • the two glued aspheric surfaces can be glued and connected by any of the following methods:
  • the two aspherical surfaces are glued and connected by frame glue in the edge area;
  • the two aspheric surfaces are glued and connected by surface glue.
  • the third lens 3 and the second lens 2 are also glued together.
  • the aspheric surface of the third lens 3 is glued to the aspheric surface of the second lens 2, that is, the aspheric surface is glued between the two lenses, and both kinds of glue can be used, but because the edge
  • the scheme of coating optical glue in the area and the effective diameter area makes the coverage area of the optical glue wider, so that the glue is firmer and more stable, but the yield rate will be lower than that of the lens skirt glue.
  • the refractive index of the optical glue 6 is set to 1.1-1.3.
  • the optical glue used when cementing the three lenses is preferably a low refractive index optical glue.
  • the second lens 2 is sandwiched between the first lens 1 and the third lens 3, and glued together with the first lens 1 and the third lens 3 set to form a cemented lens group.
  • the surface of the cemented second lens 2 and the first lens 1 is a Fresnel surface
  • the cemented surface of the second lens 2 and the third lens 3 is a Fresnel surface.
  • the surface is aspherical, so there is no need to consider the air gap between the lenses, which not only helps to achieve short focus, but also better eliminates stray light.
  • the materials of the first lens 1 and the second lens 2 are the same, and both are COP materials; the third lens 3 is made of OKP materials or EP materials.
  • first lens 1 , the second lens 2 and the third lens 3 are not limited to the materials mentioned above, and other materials such as PMMA material, glass material, etc. are also included.
  • the central thickness h 1 of the first lens 1 is: 2mm ⁇ h 1 ⁇ 4mm; the central thickness h2 of the second lens 2 is: 3mm ⁇ h 2 ⁇ 5mm; The central thickness h 3 of the third lens 3 is: 2mm ⁇ h 3 ⁇ 4mm.
  • each lens will not be too thick, which is also beneficial to reduce the weight of the entire optical path structure.
  • Embodiment 1 provides an optical system.
  • Table 1 shows structural parameters in the optical system
  • FIG. 2 shows the structure of the optical system.
  • Table 1 lists the optical surface number (Surface) numbered sequentially from the human eye 5 (diaphragm) to the display screen 4, the curvature (C) of each optical surface on the optical axis, and the number of optical surfaces from the human eye 5 (diaphragm) The distance (T) between each optical surface and the next optical surface on the optical axis of the display screen 4, and even-order aspheric coefficients ⁇ 2 , ⁇ 3 , ⁇ 4 .
  • the aspheric coefficient can satisfy the following equation:
  • z is the coordinate along the optical axis
  • Y is the radial coordinate in units of lens length
  • C is the curvature (1/R)
  • K is the cone coefficient (Coin Constant)
  • ⁇ i is the height
  • the coefficient of the second term, 2i is the order of Aspherical Coefficient (the order of Aspherical Coefficient).
  • the smoothness of field curvature is considered, and the spherical coefficient of no high-order term is up to 4th order.
  • the effective focal length f 19.248mm.
  • the maximum spot size is the maximum field of view 1.0F, and its maximum value is ⁇ 88 ⁇ m;
  • the RGB wavelengths of field curvature in the T&S direction are all ⁇ 1.5mm, and the maximum distortion is ⁇ 37% at the maximum field of view;
  • the maximum dispersion of RGB is at the position of the field of view of 0.9F, the entire RGB is 450nm to 630nm, and the LCA is 170nm.
  • Embodiment 2 provides an optical system, and Table 2 is used to show structural parameters in the optical system, and FIG. 6 shows the structure of the optical system.
  • the effective focal length f 19.28mm.
  • the maximum spot size is the maximum field of view 1.0F, and its maximum value is ⁇ 76 ⁇ m;
  • the RGB wavelengths of field curvature in the T&S direction are all ⁇ 1.2mm, and the maximum distortion is ⁇ 35% at the maximum field of view;
  • the maximum RGB dispersion is at the 0.9F field of view position, the entire RGB is 450nm to 630nm, and the LCA is 155nm.
  • Embodiment 3 provides an optical system, and Table 3 is used to show structural parameters in the optical system, and FIG. 10 shows the structure of the optical system.
  • the maximum spot size is the maximum field of view 1.0F, and its maximum value is ⁇ 70 ⁇ m;
  • the RGB wavelengths of field curvature in the T&S direction are all ⁇ 1.0mm, and the maximum distortion is ⁇ 34% at the maximum field of view;
  • the maximum dispersion of RGB is the maximum position of the field of view, the entire RGB is 450nm to 630nm, and the LCA is 155nm.
  • the first lens 1 and the second lens 2 provide positive refractive power
  • the third lens 3 provides negative refractive power.
  • the effective focal length of the first lens 1 and the second lens 2 is between 30 mm and 40 mm
  • the effective focal length f3 of the third lens 3 is -100 ⁇ -180 mm
  • the effective focal length f of the optical system formed is Between 19.0 and 19.5mm.
  • the embodiment of this application provides a short-focus optical system, but it does not involve folding optical path:
  • a head-mounted display device is provided.
  • the head-mounted display device includes any one of the optical systems described above.
  • the head-mounted display device is, for example, a VR device.

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Abstract

一种光学系统以及头戴显示设备；其中，光学系统包括沿入射光的传播方向依次胶合设置的第三透镜（3）、第二透镜（2）和第一透镜（1）；第一透镜（1）和第二透镜（2）胶合的两个面均为菲涅尔面。提供了一种短焦、高光效及高解析力的直透式光路结构设计，通过三个光学镜片胶合的设计还有助于减少杂散光。

Description

光学系统以及头戴显示设备
本申请要求于2021年11月30日提交中国专利局、申请号为202111450383.9、发明名称为“光学系统以及头戴显示设备”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
本申请涉及光学成像技术领域，更具体地，本申请涉及一种光学系统以及头戴显示设备。
背景技术
近年来，增强现实(Augmented Reality，AR)技术及虚拟显现实(Virtual Reality，VR)技术等在智能穿戴设备中得到了应用，并快速发展起来。增强现实技术和虚拟现实技术的核心部件均是显示光学系统。显示光学系统显示效果的好坏将直接决定着智能穿戴设备的质量。
在现有的相关技术中，以VR设备为例。现有的VR设备大多采用单片式透镜+显示屏幕(display)组合形成的显示光学系统。然而，基于光路成像要求，透镜距离显示屏幕会比较远，这就导致VR设备的尺寸较大，这不利于产品的小型化，可能会导致用户佩戴时的使用体验不佳。此外，在目前的VR设备中，还有采用折叠光路的方案，该方案虽然可以实现VR设备的小型化、轻量化，但却存在制作成本较高、光效低(＜25％)且存在鬼影的问题。
发明内容
本申请的目的在于提供的一种光学系统以及头戴显示设备的新技术方案。
根据本申请的一个方面，提供了一种光学系统。所述光学系统包括沿入射光的传播方向依次胶合设置的第三透镜、第二透镜和第一透镜；
所述第一透镜和所述第二透镜胶合的两个面均为菲涅尔面。
可选地，所述第一透镜和所述第二透镜的光焦度均为正，所述第三透镜的光焦度为负
可选地，所述第一透镜的有效焦距f1与所述光学系统的有效焦距f满足：1.5＜f1/f＜2.22；
所述第二透镜的有效焦距f2与所述光学系统的有效焦距f满足：1.5＜f2/f＜2.22；
所述第三透镜的有效焦距f3与所述光学系统的有效焦距f满足：-9＜f3/f ＜-5。
可选地，所述第一透镜的有效焦距f1为：30mm≤f1≤40mm；
所述第二透镜的焦距f2为：30mm≤f2≤40mm；
所述第三透镜的焦距f3为：-180mm≤f3≤-100mm；
所述第一透镜、所述第二透镜及所述第三透镜位于同一光轴上。
可选地，所述光学系统的有效焦距f为：18mm≤f≤20mm。
可选地，两个胶合的所述菲涅尔面是在边缘区域通过框胶的方式胶合连接。
可选地，所述第二透镜和所述第三透镜胶合的两个面均为非球面。
可选地，两个胶合的所述非球面通过如下任一种方式胶合连接：
两个所述非球面在边缘区域通过框胶的方式胶合连接；
两个所述非球面之间通过面胶的方式胶合连接。
可选地，所述第一透镜和所述第二透镜之间、所述第二透镜与所述第三透镜之间分别通过透光的光学胶胶合，所述光学胶的折射率为1.1～1.3。
根据本申请的另一个方面，提供了一种头戴显示设备。
所述头戴显示设备包括如上任一种所述的光学系统。
本申请的有益效果在于：
本申请实施例提出了一种直透式光路结构设计，通过三片光学镜片胶合，再结合光学镜片的面型优化设计，实现了短焦、高光效、高解析力的光学要求，形成的光学系统可应用于例如头戴显示设备(如，VR设备)中。
通过以下参照附图对本申请的示例性实施例的详细描述，本申请的其它特征及其优点将会变得清楚。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一部分附图，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据提供的附图获得其他的附图。
图1是本申请实施例提供的光学系统的结构示意图；
图2是本申请实施例1提供的光学系统的成像原理示意图；
图3是本申请实施例1提供的光学系统的点列图；
图4是本申请实施例1提供的光学系统的场曲和畸变图；
图5是本申请实施例1提供的光学系统的色散图；
图6是本申请实施例2提供的光学系统的成像原理示意图；
图7是本申请实施例2提供的光学系统的点列图；
图8是本申请实施例2提供的光学系统的场曲和畸变图；
图9是本申请实施例2提供的光学系统的色散图；
图10是本申请实施例3提供的光学系统的成像原理示意图；
图11是本申请实施例3提供的光学系统的点列图；
图12是本申请实施例3提供的光学系统的场曲和畸变图；
图13是本申请实施例3提供的光学系统的色散图.
附图标记说明：
1、第一透镜；2、第二透镜；3、第三透镜；4、显示屏幕；5、人眼；6、光学胶；
11、第一表面；12、第二表面；
21、第三表面；22、第四表面；
31、第五表面；32、第六表面。
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描述，显然，所描述的实施例仅仅是本申请一部分实施例，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。
以下对至少一个示例性实施例的描述实际上仅仅是说明性的，决不作为对本申请及其应用或使用的任何限制。
对于相关领域普通技术人员已知的技术、方法和设备可能不作详细讨论，但在适当情况下，所述技术、方法和设备应当被视为说明书的一部分。
在这里示出和讨论的所有例子中，任何具体值应被解释为仅仅是示例性的，而不是作为限制。因此，示例性实施例的其它例子可以具有不同的值。
应注意到：相似的标号和字母在下面的附图中表示类似项，因此，一旦某一项在一个附图中被定义，则在随后的附图中不需要对其进行进一步讨论。
下面结合附图1至图13对本申请实施例提供的光学系统以及头戴显示设备进行详细描述。
根据本申请实施例的一个方面，提供了一种光学系统。所述光学系 统为一种短焦、高光效、高解析力的直透式光学系统，其适合应用于电子设备中，例如头戴显示设备(head mounted display，HMD)，如VR设备(如VR眼镜或者VR头盔等)。其具有良好的应用前景。
本申请实施例提供的一种光学系统，如图1、图2、图6和图10所示，其包括沿入射光的传播方向依次设置的第三透镜3、第二透镜2和第一透镜1；所述第一透镜1和所述第二透镜2胶合的两个面均为菲涅尔面。
本申请实施例提供的光学系统，其为直透式光路结构设计，整个光路结构设计较为简单，这使得光学系统的制作较为容易。
所述光学系统还可以包括显示屏幕(display)4，如图2、图6和图10所示。所述显示屏幕4在光路结构中可用于发射光线，即上述的入射光。
也就是说，在本申请实施例提供的光学系统方案中设计了一透镜组合，该透镜组合例如包括三个胶合设置的光学镜片，如图1、图2、图6和图10所示，其能够用于将所述入射光(例如由显示屏幕4发出)投射到人眼5中进行成像。
本申请实施例提供的光学系统，基于三个光学镜片的胶合设计，即将光学系统中的所述第一透镜1、所述第二透镜2及所述第三透镜3的进行胶合，能够实现超短焦、高光效、高解析的光学结构设计要求。并且，基于三个光学镜片的胶合，再结合各透镜的面型优化设计，还有助于提高成像质量。
进一步来说，本申请实施例提供的光学系统的成像光斑尺寸(spot size)在15°视场内＜50μm，在全视场下＜88μm。
将三个透镜进行胶合的设计还可减少光学系统的杂散光。
并且，胶合后所形成的胶合透镜组合可作为一个光学组件，这样减少了光学组件的组装难度、也减少了镜片之间因组装而产生杂质的风险，可提升良品率。
综合比较，本申请实施例提供的方案克服了现有单片式透镜+显示屏幕(display)的组合方案带来的透镜距离显示屏幕较远，导致VR设备的尺寸较大，不利于产品的小型化及光效低的问题。同时，也能够改善采用折叠光路的缺陷，其加工难度及生产成本都比较低，直透式光学结构也比折叠光路简单。
例如，如图1和图2所示，在所述光学系统中设置有一显示屏幕4，该显示屏幕4例如为1.4inch Display，实现了100度视场角。而在此基础上，常规的单片式透镜(1P)结构或者双片式透镜(2P)结构均不足以分辨该类型的显示屏幕。究其原因在于：
单片式透镜(1P)仅存在两个表面的面型自由度的优化，其汇聚能力有限，而且像差或者色差无法校正，全视场可分辨的像素大小(成像光斑尺寸spot size)约为80μm～100μm，而更重要的是无法达到短焦的目的。
双片式透镜(2P)虽然增加了透镜表面面型优化的自由度，可实现短焦，但仍存在解析力的限制，也无法达到较佳的成像质量要求。
在本申请实施例方案中，采用三个光学镜片胶合，既能够达到短光学总长TTL的目的，又能够减少杂散光的产生(例如，减少了光线在空气间隔的杂乱反射次数和辐射面积，从而减少了导致的杂散光)。
本申请的方案提供了一种短焦光路结构，其中采用了两个胶合的菲涅尔面，这提供了较大的光焦度(focal power)，而考虑到色差的影响，还采用了所述第三透镜3配合来进行消色差。
需要说明的是，在本申请实施例提供的方案中，所述第一透镜1的菲涅尔面和所述第二透镜2的菲涅尔面包括但不限于为平面基底。
也就是说，所述第一透镜1的菲涅尔面和所述第二透镜2的菲涅尔面还可以为曲面基底。又例如，其中的一个菲涅尔面为曲面基底，而另一个菲涅尔面为平面基底。曲面基底的设计可使透镜更加轻薄，从而有助于减轻光学系统的总质量。本领域技术人员可以根据具体情况适当调整菲涅尔面的基底形式，本申请在此不作具体限定。
在本申请的一些例子中，所述第一透镜1和所述第二透镜2的光焦度均为正，所述第三透镜3的光焦度为负。
可以理解的是，在本申请实施例提供的光学系统中，所述第一透镜1和所述第二透镜2均设计为正透镜，所述第三透镜3设计为负透镜；两个正透镜可以提供较大的正光焦度，而负透镜的参与可用来消除色差。
如图1、图2、图6和图10所示，所述第一透镜1和所述第二透镜2胶合的两个表面均为菲涅尔面。
也就是说，在光路结构中设计具有两个相邻设置的菲涅尔面，并且这两个菲涅尔面是胶合设置的。这一设计能够实现光路结构的低色散和短焦，还可以减少杂散光，这使得形成的光学系统具有光效高的特点。
在本申请的一些例子中，如图1所示，所述第一透镜1包括第一表面11和第二表面12，所述第二透镜2包括第三表面21和第四表面22，在整个光学系统中，所述第二表面12与所述第三表面21为胶合设置，且均设置为菲涅尔面，所述第一表面11和所述第四表面22均为非球面(进一步地，这两个表面均为凸面)。
可选的是，本申请的实施例中设计：在所述第一透镜1的第一表面11和第二表面12上分别镀有增透膜(Anti-Reflective coating，AR)。
在所述第一透镜1的两个表面上分别镀有增透膜之后，可通所述增透膜来减少反射光，以此来增加光线在所述第一透镜1两个表面上的透过率。
可选的是，在所述第一透镜1的第一表面11上除了镀有所述增透膜之外，在所述第一表面11上还可以镀上硬化膜。
这是因为：所述第一透镜1的第一表面11是面向外部的，其需要避免划伤、碰伤等损伤，通过镀上所述硬化膜之后就能够提高所述第一透镜1的使用寿命。在所述第一表面11上镀硬化膜，即对所述第一表面11进行硬化处理，以此就能够提高所述第一表面11的硬度、强度等。这对于 提高整个光学系统的使用寿命是有利的。
当然，本申请实施例中并不限于在所述第一透镜1的第一表面11上镀硬化膜，还可以在所述第一透镜1的第二表面12上镀有硬化膜，本领域技术人员可以根据具体需要灵活调整，本申请在此不做具体限制。
此外，本申请实施例中，所述第一透镜1还具有如下参数。
在本申请的一些例子中，所述第一透镜1的第一表面11的半径R 1的绝对值满足：40mm≤Abs(R 1)≤50mm；所述第一透镜1的第二表面12的半径R 2的绝对值满足：20mm≤Abs(R 2)≤40mm；所述第一表面11和所述第二表面12的圆锥系数K 1的绝对值满足：Abs(K 1)≤20。
其中，所述第一表面11与所述第二表面12的面型设计不同。具体地，朝向外的所述第一表面11被设计为非球面(例如凸面)，所述第二表面12被设计为菲涅尔面，利用菲涅尔面和非球面组合形成的第一透镜1应用于光路结构中，其有助于实现短焦、高分辨的效果。
本申请的实施例中，在对所述第一透镜1的面型优化之后，考虑到加工难度及成本，更为优选的是，将所述第一透镜1的圆锥系数(Coin Constant)，即K 1值例如设计在[-10，10]，并且，所述第一透镜1的菲涅尔面的半径R>23mm。
在本申请的一些例子中，如图1所示，所述第二透镜2包括第三表面21和第四表面22，其中，所述第三表面21设计为菲涅尔面，所述第四表面22设计为非球面(例如凸面)。
可选的是，在所述第三表面21和第四表面22上也镀有增透膜。
其中，通过所述增透膜来减少反射光，以此来增加光线在所述第二透镜2两个表面上的透过率。
此外，本申请实施例中，所述第二透镜2还具有如下参数。
在本申请的一些例子中，所述第二透镜2的第三表面21的半径R 3的绝对值满足：20mm≤Abs(R 3)≤30mm；所述第二透镜2的第四表面22的半径R 4的绝对值满足：50mm≤Abs(R 4)≤90mm；所述第三表面21和所述第四表面22的圆锥系数K 2的绝对值满足：Abs(K 2)≤20。
本申请的实施例中，在对所述第二透镜2的面型优化之后，考虑到加工难度及成本，更为优选的是，将所述第二透镜2的圆锥系数(Coin Constant)，即K 2值设计在[-10，10]，并且所述第二透镜2的菲涅尔面的半径>23mm。这与所述第一透镜1基本是相同的。
需要说明的是，所述第一透镜1和所述第二透镜2均具有菲涅尔面。考虑到镜片面型的加工，需要将面型参数设定到某一范围内，否则会出现加工精度低或者断刀风险(这是因为齿形加工困难大，齿形的锐角越小，加工的倾角和动作越困难)。也正因为如此，设定圆锥系数K值较为优选地范围为[-10，10]，且各透镜的菲涅尔面的R值在23mm以上。
在本申请实施例的方案中，对于所述第一透镜1和所述第二透镜2， 即两个正透镜，均可利用非球面(例如凸面)+菲涅尔面组合的方式，基于不同折射率&阿贝数材料选择及配合，实现了光路结构的低色散及短焦。
在本申请的一些例子中，如图1所示，所述第三透镜3包括第五表面31和第六表面32；其中，所述第五表面31与所述第二透镜2的第四表面22也为胶合设置，所述第五表面31为非球面，这样，所述第三透镜3与所述第二透镜2之间就形成了非球面胶合的形式。
例如，所述第三透镜3的光焦度为负。
在本申请的方案中设计，所述第三透镜3为负透镜，其为中间薄而周边厚的透镜，其具有发散光的能力。所述第三透镜3在整个光路结构中可用以进行消色差。
所述第三透镜3例如可以为双凹透镜(即两个表面均为凹面)，也可以为平凹透镜(即一个表面为凹面，另一个表面为平面)。
较为优选的是，所述第五表面31设置为凹面，所述第六表面32设置为平面或者凹面。这样，所述第三透镜3的凹面就能与所述第二透镜2的凸面很好地胶合在一起，形成非球面胶合。
可选的是，在所述第五表面31和所述第六表面32上均镀有增透膜(Anti-Reflective coating，AR)。
在所述第三透镜3的两个表面上分别镀有增透膜之后，可通所述增透膜来减少反射光，以此来增加光线在所述第三透镜3两个表面上的透过率。
此外，本申请实施例中，所述第三透镜3还具有如下参数。
在本申请的一些例子中，所述第三透镜3的第六表面32的半径R 6的绝对值满足：200mm≤Abs(R 6)≤500mm。
其中，所述第六表面32与所述显示屏幕4为相邻设置。
在本申请一个具体的例子中，如图1所示，所述光学系统可包括：显示屏幕4，以及所述第一透镜1、所述第二透镜2和所述第三透镜3；所述显示屏幕4发射出的入射光经过镀有增透膜的所述第三透镜3的第六表面32进入到所述第三透镜3内部，经所述第三透镜3的传递光线被发散后进入到所述第二透镜2，所述第二透镜2的两个表面也均镀有增透膜，这样，光线经所述第二透镜2后进行汇聚，然后进入至所述第一透镜1，所述第一透镜1仍为汇聚的正透镜，经所述第一透镜1的光线传输后，再进入到人眼5进行成像。整个光学系统中并无光路折叠，且各透镜的表面均镀有增透膜，光线传递效率高。
在本申请的一些例子中，所述第一透镜1的有效焦距f 1与所述光学系统的有效焦距f满足的关系为：1.5＜f 1/f＜2.22；所述第二透镜2的有效焦距f 2与所述光学系统的有效焦距f满足的关系为：1.5＜f 2/f＜2.22；所述第三透镜3的有效焦距f 3与所述光学系统的有效焦距f满足的关系为：-9＜f 3/f＜-5。
本申请实施例提供的光学系统具有有效焦距f值小的特点。
在本申请的一些例子中，所述第一透镜1的有效焦距f 1为：30mm≤f 1≤40mm；所述第二透镜2的焦距f 2为：30mm≤f 2≤40mm；所述第三透镜3的焦距f 3为：-180mm≤f 3≤-100mm；所述第一透镜1、所述第二透镜2及所述第三透镜2位于同一光轴上。
在本申请的一些例子中，所述光学系统的有效焦距f为：18mm≤f≤20mm。
进一步地，所述光学系统的有效焦距f为：19.0,mm～19.5mm。
其中，所述第一透镜1的有效焦距f 1和所述第二透镜2的焦距f 2均大于所述透镜组的有效焦距f。本申请提供的是一种短焦光学系统。整个光学系统中并无光路折叠，是一种直透式的光学系统，能够实现高清成像。
本申请实施例提供的方案中，不同透镜之间的胶合方式有两种：
(1)仅对透镜的边缘区域进行胶合，从而使得胶合的透镜形成紧密贴合，此时，透镜的有效径区域无胶，这种方式为框胶的方式；
(2)在透镜的边缘区域和有效径区域全部涂布光学胶，从而使胶合在一起的透镜形成紧密贴合，这种方式为面胶的方式。
在本申请的一些例子中，两个胶合的所述菲涅尔面是在边缘区域通过框胶的方式胶合连接。
所述第一透镜1和所述第二透镜2均具有菲涅尔面，考虑到菲涅尔面的基底齿形结构，优选的是，将这两个透镜的边缘区域通过胶合连接，从而使所述第一透镜1和所述第二透镜2紧密贴合在一起。两个菲涅尔面的胶合采用框胶的方式可靠性更高。
在本申请的一些例子中，所述第二透镜2与所述第三透镜3胶合的两个表面均为非球面。
例如，所述第二透镜2的凸面与所述第三透镜3的凹面胶合设置。
在本申请的一些例子中，两个胶合的所述非球面可通过如下任一种方式胶合连接：
两个所述非球面在边缘区域通过框胶的方式胶合连接；
两个所述非球面之间通过面胶的方式胶合连接。
在本申请中，所述第三透镜3与所述第二透镜2也为胶合设置。
具体地，所述第三透镜3的非球面与所述第二透镜2的非球面胶合连接，也即该两个透镜之间为非球面胶合，两种胶合方式均可使用，但是因为在边缘区域和有效径区域内全部涂布光学胶的方案使得光学胶的覆盖区域更广，这样胶合的牢固更高、稳定性更好，但良品率相对于透镜裙边胶合的方案来说会偏低一些。本领域技术人员可以根据具体需要，灵活选择透镜之间的胶合方式。
在本申请的一些例子中，所述第一透镜1和所述第二透镜2之间，所述第二透镜2与所述第三透镜3之间均通过透光的光学胶6胶合，所述光学胶6的折射率设置为1.1～1.3。
为了不影响所述入射光的传播路径或者偏折规律等，在胶合三个透镜时采用的光学胶优选为低折射率的光学胶。
本申请实施例提供的光学系统，所述第二透镜2夹设在所述第一透镜1与所述第三透镜3之间，并与所述第一透镜1、所述第三透镜3胶合设置，以形成胶合透镜组。对于形成的所述胶合透镜组来说：所述第二透镜2与所述第一透镜1相胶合的面均为菲涅尔面，所述第二透镜2与所述第三透镜3胶合的面为非球面，各个透镜之间无需更多的考虑空气间隔的问题，不仅有助于实现短焦，还能更好地实现杂散光的消除。
在本申请的一些例子中，所述第一透镜1和所述第二透镜2的材质相同，且均为COP材料；所述第三透镜3为OKP材料或者EP材料。
在本申请实施例提供的方案中，对于各透镜(即所述第一透镜1、所述第二透镜2及所述第三透镜3)，在材料选择上，基于短焦和色差的考虑，选择高折射率及高低阿贝数的材料组合进行优化设计。
需要说明的是，所述第一透镜1、所述第二透镜2和所述第三透镜3并不限于采用上述材料，还可以采用其他材料例如PMMA材料、玻璃材料等也在包含在内。
在本申请的一些例子中，所述第一透镜1的中心厚度值h 1为：2mm≤h 1≤4mm；所述第二透镜2的中心厚度h 2为：3mm≤h 2≤5mm；所述第三透镜3的中心厚度h 3为：2mm≤h 3≤4mm。
各透镜的厚度不会过厚，这也有利于降低整个光路结构的重量。
实施例1
实施例1提供了一种光学系统，采用表1示出光学系统中的结构参数，图2示出了该光学系统的结构。
表1中分别列出由人眼5(光阑)到显示屏幕4依序编号的光学面号码(Surface)、在光轴上各光学面的曲率(C)、从人眼5(光阑)到显示屏幕4的光轴上各光学面与后一光学面的距离(T)，及偶次非球面系数α 2、α 3、α 4。
其中，非球面系数可以满足如下的方程：
Figure PCTCN2021140041-appb-000001
式(1)中：z是沿光轴方向的坐标，Y为以透镜长度单位为单位的径向坐标，C是曲率(1/R)，K为圆锥系数(Coin Constant)，αi是各高次项的系数，2i是非球面的高次方(the order of Aspherical Coefficient)，本申请的方案设计中考虑到场曲的平缓，无高次项球面系数至4阶。
表1
Figure PCTCN2021140041-appb-000002
根据上述的实施例1可知：
所述第一透镜1的有效焦距f 1＝31.128mm；所述第二透镜2的有效焦距f 2＝35.81mm；所述第三透镜3的有效焦距f 3＝-124.804mm；所述光学系统的有效焦距f＝19.248mm。
通过如下参数反应实施例1的光学系统的性能好坏：
如图3所示，spot size最大处为最大视场1.0F，其最大值＜88μm；
如图4所示，T&S方向场曲RGB波长均＜1.5mm，最大畸变为最大视场处＜37％；
如图5所示，RGB最大色散为0.9F视场位置，整个RGB 450nm～630nm，LCA为170nm。
实施例2
实施例2提供了一种光学系统，采用表2示出光学系统中的结构参数，图6示出了该光学系统的结构。
表2
Figure PCTCN2021140041-appb-000003
Figure PCTCN2021140041-appb-000004
根据上述的实施例2可知：
所述第一透镜1的有效焦距f 1＝31.59mm；所述第二透镜2的有效焦距f 2＝33.63mm；所述第三透镜3的有效焦距f 3＝-106.77mm；所述光学系统的有效焦距f＝19.28mm。
通过如下参数反应实施例2的光学系统的性能好坏：
如图7所示，spot size最大处为最大视场1.0F，其最大值＜76μm；
如图8所示，T&S方向场曲RGB波长均＜1.2mm，最大畸变为最大视场处＜35％；
如图9所示，RGB最大色散为0.9F视场位置，整个RGB 450nm～630nm，LCA为155nm。
实施例3
实施例3提供了一种光学系统，采用表3示出光学系统中的结构参数，图10示出了该光学系统的结构。
表3
Figure PCTCN2021140041-appb-000005
根据上述的实施例3可知：
所述第一透镜1的有效焦距f 1＝31.1mm，所述第二透镜2的有效焦距f 2＝37.65mm，所述第三透镜3的有效焦距f 3＝-168.8mm，所述光学系统的有效焦距f＝19.07mm。
通过如下参数反应实施例3的光学系统的性能好坏：
如图11所示，spot size最大处为最大视场1.0F，其最大值＜70μm；
如图12所示，T&S方向场曲RGB波长均＜1.0mm，最大畸变为最大视场处＜34％；
如图13所示，RGB最大色散为视场最大位置，整个RGB450nm～630nm，LCA为155nm。
基于上述的三个实例可以看出，所述第一透镜1和所述第二透镜2提供正光焦度，所述第三透镜3提供负光焦度。所述第一透镜1和所述第二透镜2的有效焦距在30mm～40mm之间，所述第三透镜3的有效焦距f 3为-100～-180mm，组成的光学系统的有效焦距f为19.0～19.5mm之间。
本申请实施例提供了一种短焦光学系统，但其中并不涉及折叠光路：
(1)通过三个光学镜片胶合形成胶合透镜组，实现了超短焦效果；胶合之后的透镜组可作为一个光学元件来使用，减少了与结构件组装的难度，还减少了镜片之间因组装产生杂质的风险，提升了良品率；
(2)将两个菲涅尔面胶合及两个非球面胶合，可以减少杂散光。
根据本申请的另一个方面，提供了一种头戴显示设备。
所述头戴显示设备包括如上任一种所述的光学系统。
所述头戴显示设备例如为VR设备。
上文实施例中重点描述的是各个实施例之间的不同，各个实施例之间不同的优化特征只要不矛盾，均可以组合形成更优的实施例，考虑到行文简洁，在此则不再赘述。
虽然已经通过例子对本申请的一些特定实施例进行了详细说明，但是本领域的技术人员应该理解，以上例子仅是为了进行说明，而不是为了限制本申请的范围。本领域的技术人员应该理解，可在不脱离本申请的范围和精神的情况下，对以上实施例进行修改。本申请的范围由所附权利要求来限定。

Claims (10)

  1. 一种光学系统，其特征在于，包括沿入射光的传播方向依次胶合设置的第三透镜(3)、第二透镜(2)和第一透镜(1)；
    所述第一透镜(1)和所述第二透镜(2)胶合的两个面均为菲涅尔面。
  2. 根据权利要求1所述的光学系统，其特征在于，所述第一透镜(1)和所述第二透镜(2)的光焦度均为正，所述第三透镜(3)的光焦度为负
  3. 根据权利要求1所述的光学系统，其特征在于，所述第一透镜(1)的有效焦距f1与所述光学系统的有效焦距f满足：1.5＜f1/f＜2.22；
    所述第二透镜(2)的有效焦距f2与所述光学系统的有效焦距f满足：1.5＜f2/f＜2.22；
    所述第三透镜(3)的有效焦距f3与所述光学系统的有效焦距f满足：-9＜f3/f＜-5。
  4. 根据权利要求1所述的光学系统，其特征在于，所述第一透镜(1)的有效焦距f1为：30mm≤f1≤40mm；
    所述第二透镜(2)的焦距f2为：30mm≤f2≤40mm；
    所述第三透镜(3)的焦距f3为：-180mm≤f3≤-100mm；
    所述第一透镜(1)、所述第二透镜(2)及所述第三透镜(3)位于同一光轴上。
  5. 根据权利要求1所述的光学系统，其特征在于，所述光学系统的有效焦距f为：18mm≤f≤20mm。
  6. 根据权利要求1所述的光学系统，其特征在于，两个胶合的所述菲涅尔面是在边缘区域通过框胶的方式胶合连接。
  7. 根据权利要求1所述的光学系统，其特征在于，所述第二透镜(2)和所述第三透镜(3)胶合的两个面均为非球面。
  8. 根据权利要求7所述的光学系统，其特征在于，两个胶合的所述非球面通过如下任一种方式胶合连接：
    两个所述非球面在边缘区域通过框胶的方式胶合连接；
    两个所述非球面之间通过面胶的方式胶合连接。
  9. 根据权利要求1所述的光学系统，其特征在于，所述第一透镜(1)和所述第二透镜(2)之间、所述第二透镜(2)与所述第三透镜(3)之间分别通过透光的光学胶(6)胶合，所述光学胶(6)的折射率为1.1～1.3。
  10. 一种头戴显示设备，其特征在于：包括：
    如权利要求1-9中任意一项所述的光学系统。
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