Optical system and display device

Abstract

An optical system and a display device, the optical system comprising: a lens assembly comprising at least two lenses, the at least two lenses comprising a first surface, a second surface, a third surface and a fourth surface arranged in sequence along an optical axis direction of the lens assembly; the transflective film is arranged on the side, away from the third surface, of the fourth surface; the polarization reflection layer is arranged on the side, away from the fourth surface, of the third surface; the phase delay film is located on the side, away from the transflective film, of the fourth surface; the adhesive layer comprises an adhesive layer lens; wherein at least one of the first surface and the second surface is a Fresnel surface, and the glue layer is glued between the second surface and the third surface. The glue layer glued between the second surface and the third surface comprises the glue layer lens, light rays are refracted through the glue layer lens and the Fresnel surface, chromatic aberration can be corrected, the light rays do not pass through the Fresnel surface in the returning process, and stray light is reduced.

Description

Technical Field

[0001] At least one embodiment of the present disclosure relates to an optical system and a display device. Background Art

[0002] With the rapid development of virtual reality (VR) technology, among many display devices, head-mounted displays (HMDs) are favored by people because of their high immersion, portability, and hands-free features. As one of the important components of virtual reality devices, the performance of head-mounted displays is a key factor affecting the imaging quality and cost of virtual reality devices. Summary of the Invention

[0003] At least one embodiment of the present disclosure provides an optical system and a display device.

[0004] At least one embodiment of the present disclosure provides an optical system, including: a lens assembly including at least two lenses, the at least two lenses including a first surface, a second surface, a third surface, and a fourth surface arranged in sequence along the optical axis direction of the lens assembly; a transmissive-reflective film disposed on a side of the fourth surface away from the third surface; a polarization reflection layer disposed on a side of the third surface away from the fourth surface; a phase retardation film located on a side of the fourth surface away from the transmissive-reflective film; and a glue layer including a glue layer lens; wherein at least one of the first surface and the second surface is a Fresnel surface, and the glue layer is glued between the second surface and the third surface.

[0005] For example, according to at least one embodiment of the present disclosure, the distance between two intersection points where the first surface and the second surface intersect with the optical axis is a first distance; the ratio of the central thickness of the glue layer lens to the first distance is 1 / 6 to 2.

[0006] For example, according to at least one embodiment of the present disclosure, the central thickness of the glue layer lens is 0.5 mm to 3 mm.

[0007] For example, according to at least one embodiment of the present disclosure, the at least two lenses include a first lens and a second lens arranged along the optical axis direction, the first lens includes the first surface and the second surface, and the second lens includes the third surface and the fourth surface; one of the optical power of the first lens and the optical power of the glue layer lens is positive, and the other is negative.

[0008] For example, according to at least one embodiment of the present disclosure, the ratio of the optical power of the first lens to the dispersion coefficient of the first lens is a first ratio, and the ratio of the optical power of the adhesive layer lens to the dispersion coefficient of the adhesive layer lens is a second ratio; the sum of the first ratio and the second ratio is less than 0.

[0009] For example, according to at least one embodiment of the present disclosure, the refractive index of the first lens is less than the refractive index of the adhesive layer lens, the refractive index of the second lens is less than the refractive index of the adhesive layer lens, and the refractive index of the first lens is less than or equal to the refractive index of the second lens.

[0010] For example, according to at least one embodiment of the present disclosure, the dispersion coefficient of the first lens is greater than the dispersion coefficient of the adhesive layer lens, the dispersion coefficient of the second lens is greater than the dispersion coefficient of the adhesive layer lens, and the dispersion coefficient of the first lens is greater than or equal to the dispersion coefficient of the second lens.

[0011] For example, according to at least one embodiment of the present disclosure, the refractive index of the first lens is greater than the refractive index of the adhesive layer lens, and the refractive index of the first lens is greater than the refractive index of the second lens.

[0012] For example, according to at least one embodiment of the present disclosure, the dispersion coefficient of the first lens is less than the dispersion coefficient of the adhesive layer lens, and the dispersion coefficient of the first lens is less than the dispersion coefficient of the second lens.

[0013] For example, according to at least one embodiment of the present disclosure, the ratio of the central thickness to the edge thickness of the first lens is a third ratio, and the ratio of the central thickness to the edge thickness of the second lens is a fourth ratio; at least one of the third ratio and the fourth ratio is greater than 1 and less than 3.

[0014] For example, according to at least one embodiment of the present disclosure, the second surface is a planar Fresnel surface or a curved Fresnel surface.

[0015] For example, according to at least one embodiment of the present disclosure, the second surface is a convex surface, and the central thickness of the adhesive layer lens is less than the edge thickness.

[0016] For example, according to at least one embodiment of the present disclosure, the second surface is a convex surface, and the absolute value of the radius of curvature of the second surface is less than the absolute value of the radius of curvature of the third surface.

[0017] For example, according to at least one embodiment of the present disclosure, the second surface is a convex surface, and the ratio of the radius of curvature of the second surface to the effective focal length of the optical system is -0.5 to -2.

[0018] For example, according to at least one embodiment of the present disclosure, the second surface is a concave surface, and the central thickness of the adhesive layer lens is greater than the edge thickness.

[0019] For example, according to at least one embodiment of the present disclosure, the distance between two intersection points where the first surface and the second surface intersect with the optical axis is a first distance; the distance between two intersection points where the third surface and the fourth surface intersect with the optical axis is a second distance; the ratio of the second distance to the first distance is 2 to 4.

[0020] For example, according to at least one embodiment of the present disclosure, the ratio of the first distance to the effective focal length of the optical system is 0.1 to 0.3, and the ratio of the second distance to the effective focal length of the optical system is 0.5 to 0.7.

[0021] For example, according to at least one embodiment of the present disclosure, the first surface is a plane; or the first surface is a convex surface, the ratio of the radius of curvature of the first surface to the effective focal length of the optical system is -40 to -50, and the conic coefficient of the first surface is -10 to 0.

[0022] For example, according to at least one embodiment of the present disclosure, the third surface is a plane; or the third surface is a concave surface, the ratio of the radius of curvature of the third surface to the effective focal length of the optical system is -3 to -4, and the conic coefficient of the third surface is -10 to -1.

[0023] For example, according to at least one embodiment of the present disclosure, the fourth surface is a convex surface, the ratio of the radius of curvature of the fourth surface to the effective focal length of the optical system is -2 to -3, and the conic coefficient of the fourth surface is -10 to -1.

[0024] For example, according to at least one embodiment of the present disclosure, the at least two lenses include a first lens, a second lens, and a third lens arranged in sequence along the optical axis direction; the first lens includes the first surface and the second surface, the second lens includes the third surface, and the third lens includes the fourth surface; the second lens further includes a fifth surface opposite to the third surface, and the third lens further includes a sixth surface located between the fifth surface and the fourth surface; the surface profiles of the fifth surface and the sixth surface are the same; wherein, one of the optical power of the first lens and the optical power of the adhesive layer lens is positive and the other is negative; and / or, the dispersion coefficient of at least one of the first lens and the second lens is different from the dispersion coefficient of the adhesive layer lens.

[0025] At least one embodiment of the present disclosure provides a display device including the optical system described in any of the above embodiments.

[0026] The optical system and display device provided by at least one embodiment of the present disclosure provide attachment positions for the transflective film, the polarized reflective layer and the phase delay film by setting a lens assembly of at least two lenses, so that the light can be folded back between the transflective film and the polarized reflective layer. The adhesive layer glued between the second surface and the third surface includes an adhesive layer lens, which can refract the light together with the Fresnel surface to correct chromatic aberration. In addition, after the light is emitted from the polarized reflective layer and enters the Fresnel surface, the light will not pass through the Fresnel surface during the folding process, thereby reducing stray light. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present disclosure, but are not intended to limit the present disclosure.

[0028] Figure 1 An optical system is provided as an example in at least one embodiment of the present disclosure.

[0029] Figure 2A for Figure 1 Spot diagram of the optical system shown.

[0030] Figure 2B for Figure 1 A graph showing the variation of the diffuse spot size with the field of view angle for the optical system shown.

[0031] Figure 2C for Figure 1 Vertical axial chromatic aberration diagram of the optical system shown.

[0032] Figure 2D for Figure 1 Distortion diagram of the optical system shown.

[0033] Figure 3 An optical system is provided as an example in at least one embodiment of the present disclosure.

[0034] Figure 4A Schematic diagram of light deflection of a single lens.

[0035] Figure 4B The diagram is a light deflection diagram of an example of at least one embodiment of the present disclosure.

[0036] Figures 5 to 9 An optical system is provided for different examples in at least one embodiment of the present disclosure.

[0037] Figure 10 A display device is provided as an example in at least one embodiment of the present disclosure. DETAILED DESCRIPTION

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present disclosure. Apparently, the described embodiments are some but not all of the embodiments of the present disclosure. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present disclosure without creative efforts shall fall within the scope of protection of the present disclosure.

[0039] Unless otherwise defined, the technical terms or scientific terms used in the present disclosure shall have the ordinary meanings understood by those of ordinary skill in the art to which the present disclosure pertains. The terms "first", "second", and the like used in the present disclosure do not denote any order, quantity, or importance, but are only used to distinguish different components. The terms such as "comprising" or "including" mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items.

[0040] The features such as "vertical", "parallel", and "same" used in the present disclosure include the strictly defined features such as "vertical", "parallel", and "same", as well as the cases with certain errors such as "substantially vertical", "substantially parallel", and "substantially same". Considering the measurement and the errors associated with the measurement of a specific quantity (i.e., the limitations of the measurement system), it means within the acceptable deviation range for a specific value determined by those of ordinary skill in the art. The "center" in the embodiments of the present disclosure may include the position strictly located at the geometric center and the position of the approximate center within a small area around the geometric center. For example, "substantially" can mean within one or more standard deviations, or within 10% or 5% of the value.

[0041] In a near-eye display optical system, especially in some head-mounted display optical systems that use 4K high-definition displays with an inch-level or smaller size in combination with a large field of view, low dispersion is one of the prerequisites for ensuring imaging clarity and improving the immersive experience. In some optical systems, digital chromatic aberration correction can be used in the later stage to reduce the impact of the inherent chromatic aberration of the optical system on optical performance. In the research, the inventors of the present application found that compared with the method of digital chromatic aberration correction, by using optical design methods to eliminate chromatic aberration in the early R & D stage of the optical system, the chromatic aberration problem can be more fundamentally solved.

[0042] At least one embodiment of the present disclosure provides an optical system, including: a lens assembly including at least two lenses, the at least two lenses including a first surface, a second surface, a third surface, and a fourth surface arranged in sequence along the optical axis direction of the lens assembly; a transmissive-reflective film disposed on a side of the fourth surface away from the third surface; a polarization reflection layer disposed on a side of the third surface away from the fourth surface; a phase retardation film located on a side of the fourth surface away from the transmissive-reflective film; and an adhesive layer including an adhesive layer lens; wherein at least one of the first surface and the second surface is a Fresnel surface, and the adhesive layer is bonded between the second surface and the third surface.

[0043] At least one embodiment of the present disclosure provides a display device including the above optical system.

[0044] The optical system and the display device provided by at least one embodiment of the present disclosure provide an attachment position for the transmissive-reflective film, the polarization reflection layer, and the phase retardation film by providing a lens assembly including at least two lenses, so that light can be refolded between the transmissive-reflective film and the polarization reflection layer. The adhesive layer bonded between the second surface and the third surface includes an adhesive layer lens, which can correct chromatic aberration by jointly refracting light with the Fresnel surface. In addition, after the light exits from the polarization reflection layer and enters the Fresnel surface, the light does not pass through the Fresnel surface during the refolding process, reducing stray light.

[0045] The optical system and the display device will be described below with reference to the accompanying drawings and through some embodiments.

[0046] Figure 1 This is the optical system provided by an example in at least one embodiment of the present disclosure.

[0047] Reference Figure 1 , at least one embodiment of the present disclosure provides an optical system, the optical system including a lens assembly 100, the lens assembly 100 including a transmissive-reflective film 200, a polarization reflection layer 300, a phase retardation film 400, and an adhesive layer. The lens assembly 100 includes at least two lenses. For example, as Figure 1 shown, the lens assembly 100 can be composed of two lenses, namely a lens 110 and a lens 120. For example, the adhesive layer is a light-transmissive adhesive layer.

[0048] As Figure 1 shown, the at least two lenses include a first surface 101, a second surface 102, a third surface 103, and a fourth surface 104 arranged in sequence along the optical axis OA direction of the lens assembly 100. For example, a side of the first surface 101 away from the fourth surface 104 is the light-emitting side of the optical system. For example, when the optical system is applied to a display device, the display screen can be located on a side of the fourth surface 104 of the optical system away from the first surface 101, and the light emitted by the display screen enters from the fourth surface 104 and exits from the first surface 101.

[0049] like Figure 1 As shown, the transflective film 200 is disposed on a side of the fourth surface 104 away from the third surface 103. The polarizing reflective layer 300 is disposed on a side of the third surface 103 away from the fourth surface 104. The phase delay film 400 is located on a side of the fourth surface 104 away from the transflective film 200. For example, the light incident on the lens assembly 100 after being transmitted by the transflective film 200 is configured to be folded back between the transflective film 200 and the polarizing reflective layer 300, and to be emitted from the polarizing reflective layer 300, thereby forming a folded light path through the polarizing reflective layer 300, the transflective film 200, and the phase delay film 400.

[0050] like Figure 1 As shown, the adhesive layer includes an adhesive layer lens 130, and the adhesive layer is glued between the second surface 102 and the third surface 103. For example, the adhesive layer has viscosity, so that it can be glued between the second surface 102 and the third surface 103. In addition, the adhesive layer also includes an adhesive layer lens 130 located between the second surface 102 and the third surface 103, and the adhesive layer lens is a lens formed by the adhesive layer, so that the light can be refracted when it is incident on the adhesive layer lens 130 or when it is emitted from the adhesive layer lens 130, so as to correct chromatic aberration.

[0051] like Figure 1 As shown, at least one of the first surface 101 and the second surface 102 is a Fresnel surface. A Fresnel surface refers to a non-smooth surface on one side of two opposing surfaces of a Fresnel lens. For example, the first surface 101 and the second surface 102 may be two opposing surfaces of a lens, and the lens may be a Fresnel lens. A Fresnel lens is also known as a spiral lens. One side of the Fresnel lens is a smooth surface, and the other side is divided into a plurality of concentric circular patterns (also known as Fresnel bands). These patterns can change the degree of refraction of light, so that the thickness of the Fresnel lens can be effectively reduced in the case of a short focal length.

[0052] For example, refer to Figure 1 , the second surface 102 can be set as a Fresnel surface. For example, the adhesive layer can be made of a material with lower hardness. By setting the Fresnel surface to be bonded to the adhesive layer, on the one hand, the bonding strength between the adhesive layer and the lenses on both sides of the adhesive layer can be improved, and on the other hand, the adhesive layer can buffer the external stress to prevent the toothed structure of the Fresnel surface from being damaged. In addition, by setting the second surface 102 as a Fresnel surface, the toothed structure of the Fresnel surface can be used to reduce the amount of adhesive layer material between the second surface 102 and the third surface 103, thereby reducing costs. Moreover, when the first surface 101 is a smooth surface (no Fresnel surface is set), it is easy to attach the film layer. For example, an anti-reflection film can be attached to the first surface 101.

[0053] For example, in other examples, the first surface may be set as a Fresnel surface (not shown in the figure). For example, in other examples, both the first surface and the second surface may be set as Fresnel surfaces (not shown in the figure). The present disclosure does not limit this.

[0054] The optical system provided by the present disclosure provides attachment positions for the transflective film, the polarized reflective layer and the phase delay film by setting a lens assembly of at least two lenses, so that the light can be folded back between the transflective film and the polarized reflective layer. The adhesive layer glued between the second surface and the third surface includes an adhesive layer lens, which can refract the light together with the Fresnel surface to correct the chromatic aberration. At the same time, the Fresnel surface is conducive to improving the degree of design freedom, and the light enters the Fresnel surface after being emitted from the polarized reflective layer. The light will not pass through the Fresnel surface during the folding process, thereby reducing stray light.

[0055] In some optical systems, a Fresnel surface can be introduced into the return path of the light, and different optical materials can be used on both sides of the Fresnel surface. For example, a Fresnel surface can be introduced between the transflective film and the polarized reflective layer, so as to use the different refractive indices and dispersion coefficients of different optical materials, combined with the refractive effect of the Fresnel surface, to jointly correct the chromatic aberration.

[0056] For example, the material of the adhesive layer may include optical adhesive. For example, the material of the lens assembly may include optical grade transparent inorganic polymer or glass. Thus, the adhesive layer lens is made of different materials from the lenses on both sides thereof, and the chromatic aberration can be corrected by the difference in refractive index and dispersion coefficient of different materials. For example, the material of the adhesive layer may also include silicone material, and the better fluidity of the silicone material is more conducive to the process.

[0057] For example, refer to Figure 1 , the optical system further includes a linear polarization film 500, which is disposed on a side of the polarization reflection layer 300 away from the transflective film 200. For example, the adhesive layer can be glued between the linear polarization film 500 and the second surface 102. For example, the linear polarization film 500 can be a linear polarizer or a polarizer. For example, the optical axis OA of the linear polarization film 500 coincides with the optical axis OA of the polarization reflection layer 300, such as the linear polarization film 500 can be used to further filter other stray light, and only polarized light (such as s-linear polarized light) passing through the linear polarization film 500 is allowed to enter the human eye. For example, the linear polarization film can adopt a three-layer laminated structure, and the middle layer in the three-layer laminated structure can be polyvinyl alcohol (PVA) with added dichroic molecules, and at least one layer on both sides of the middle layer in the three-layer laminated structure can be triacetate (TAC). For example, the surface of the linear polarization film facing the air is anti-reflective treated. For example, the surface of the linear polarization film facing the air can be attached to a moth-eye film.

[0058] For example, refer to Figure 1, the transmissive-reflective film 200 is configured to transmit part of the light and reflect the other part of the light. For example, the transmittance of the transmissive-reflective film can be 50%, and the reflectance can be 50%. For example, the transmittance of the transmissive-reflective film can be 60%, and the reflectance can be 40%. For example, the transmittance of the transmissive-reflective film can be 65%, and the reflectance can be 35%. The optical system provided by the present disclosure is not limited thereto, and the transmittance and reflectance of the transmissive-reflective film can be set according to product requirements. For example, the transmissive-reflective film can be deposited on the fourth surface.

[0059] For example, referring to Figure 1 , the function of the polarization reflection layer 300 is as follows: there is an optical axis OA direction in the plane of the film layer, and the transmittance of the polarization component (such as s-line polarized light) of the incident light parallel to the optical axis OA direction is greater than the transmittance of the polarization component (such as p-line polarized light) perpendicular to the optical axis OA direction, and the reflectance of the polarization component (such as s-line polarized light) parallel to the optical axis OA direction is less than the reflectance of the polarization component (such as p-line polarized light) perpendicular to the optical axis OA direction. For example, the transmittance of the polarized light parallel to the optical axis direction of the polarization reflection layer is not less than 85%, such as not less than 90%, such as not less than 95%, such as not less than 98%; the reflectance of the polarized light perpendicular to the optical axis direction of the polarization reflection layer is not less than 85%, such as not less than 90%, such as not less than 95%, such as not less than 98%.

[0060] For example, referring to Figure 1 , the polarization reflection layer 300 is configured to reflect linearly polarized light of one characteristic and transmit linearly polarized light of another characteristic; the polarization reflection layer 300 can be disposed on the side of the third surface 103 away from the fourth surface 104, and the phase retardation film 400 can be disposed between the polarization reflection layer 300 and the transmissive-reflective film 200. For example, the polarization reflection layer can also be referred to as a polarization beam splitter film. For example, the polarization reflection layer can further include a multilayer film reflective polarizer (Advanced Polarizer Film, APF). For example, the polarization reflection layer can further include an IQPS (Image Quality Polarizer Standard) film or an IQPE (ImageQuality Polarizer Enhanced) film.

[0061] For example, the polarization reflection layer is a cholesteric liquid crystal layer (not shown in the figure), and the phase retardation film is disposed on a side of the cholesteric liquid crystal layer away from the transmissive and reflective film. For example, cholesteric liquid crystal can reflect circularly polarized light and transmit circularly polarized light. Referring to the aforementioned folding optical path principle, the cholesteric liquid crystal layer is disposed between the phase retardation film and the transmissive and reflective film. A wave plate can be disposed on the display surface side of the display screen on a side of the second lens away from the first lens. The image light emitted from the display screen is converted into right-handed circularly polarized light after passing through the wave plate. The right-handed circularly polarized light is incident on the transmissive and reflective film, and the polarization state of the right-handed circularly polarized light remains unchanged after passing through the transmission of the transmissive and reflective film. The right-handed circularly polarized light is reflected back to the transmissive and reflective film after passing through the cholesteric liquid crystal layer, and the first reflection occurs here; the right-handed circularly polarized light is reflected at the transmissive and reflective film, and the second reflection occurs here. Due to the half-wave loss, the reflected light is changed from right-handed circularly polarized light to left-handed circularly polarized light. The left-handed circularly polarized light reaches the phase retardation film after passing through the cholesteric liquid crystal layer and is converted into s-polarized light by the phase retardation film. Then, the s-linearly polarized light is transmitted through the linear polarization film and emitted to the human eye.

[0062] For example, referring to Figure 1 , the phase retardation film 400 is configured such that the transmitted light realizes the conversion between the circular polarization state and the linear polarization state. For example, the phase retardation film can be a quarter-wave plate. For example, the phase retardation film 400 can have the following characteristics: there is a direction with the lowest refractive index and a direction with the highest refractive index in the film layer plane, which are the fast axis and the slow axis respectively. The phase of the polarized light parallel to the slow axis is delayed by 1 / 4 wavelength after passing through the phase retardation film compared with the polarized light parallel to the fast axis after passing through the phase retardation film. For example, the angle between the slow axis of the phase retardation film and the optical axis of the polarization reflection layer is 45 degrees.

[0063] For example, referring to Figure 1 , the material of the phase retardation film 400 can include liquid crystal polymer. The film thickness of the phase retardation film of the liquid crystal polymer material is relatively thinner, which can reach 1 μm to 5 μm. The thinner phase retardation film has a higher degree of adaptation to the curved surface, can be more easily shaped according to the surface shape of the curved surface, and reduces the possibility of generating wrinkles when fitting with the curved surface, which affects the phase retardation accuracy and optical performance. Moreover, the optical offset generated after the phase retardation film made of liquid crystal polymer material is attached to the curved surface is smaller. The liquid crystal polymer is a cross-linked system, and the molecules are connected by chemical bonds, and the modulus is relatively high. When the phase retardation film of this material is stretched after being attached, only elastic deformation occurs, and strong optical anisotropic effects such as molecular stretching and rearrangement do not occur. Therefore, the phase retardation film made of liquid crystal polymer material is suitable for fitting with the surface shape of a small radius of curvature. Such a degree of freedom of the radius of curvature is also more likely to meet the index requirements such as clarity, distortion, and dispersion, which is beneficial to obtaining better image quality of the optical system.

[0064] For example, the optical system may include a first optical element and a second optical element. The first optical element may include a first surface and a second surface, and the second optical element may include a third surface and a fourth surface. The second optical element may further include a beam splitter film, a polarization reflection layer, and a phase retardation film. The arrangement of the beam splitter film, the polarization reflection layer, and the phase retardation film may refer to the foregoing examples and will not be elaborated here. Thus, the return of light can be achieved through the second optical element.

[0065] For example, the cemented lens may be cemented between the first optical element and the second optical element. It can be understood that, according to the different setting positions of the polarization reflection layer, the phase retardation film, or other film layers, the cement layer may be cemented between the second surface and different film layers. For example, when the linear polarization film is not provided in the second optical element and the phase retardation film is provided between the polarization reflection layer and the third surface, the cement layer may be cemented between the polarization reflection layer and the second surface. For example, when the linear polarization film is not provided in the second optical element and the phase retardation film is provided on the side of the polarization reflection layer (for example, the polarization reflection layer is a cholesteric liquid crystal layer) away from the beam splitter film, the cement layer may be cemented between the phase retardation film and the second surface. For example, when the linear polarization film is provided in the second optical element, the cement layer may be cemented between the second surface and the linear polarization film.

[0066] For example, referring to Figure 1 , when the optical system is applied to a display device, the principle of the folded optical path is as follows: A wave plate may be provided on the light-emitting side of the display surface of the display screen on the side of the fourth surface 104 away from the first surface 101. The image light emitted from the display surface is converted into right-handed circularly polarized light after passing through the wave plate, and the polarization state of the right-handed circularly polarized light remains unchanged after passing through the beam splitter film 200. This light enters and, after passing through, reaches the phase retardation film 400. The right-handed circularly polarized light incident on the phase retardation film 400 is converted into p-linearly polarized light, and the p-linearly polarized light is reflected back to the phase retardation film 400 by the polarization reflection layer 300, and the first reflection occurs here. Then, the p-linearly polarized light is converted into right-handed circularly polarized light after passing through the phase retardation film 400. This right-handed circularly polarized light passes through and reaches the beam splitter film 200, and is reflected at the beam splitter film 200, and the second reflection occurs here. Due to the half-wave loss, the reflected light changes from right-handed circularly polarized light to left-handed circularly polarized light. The left-handed circularly polarized light passes through and reaches the phase retardation film 400, becomes s-linearly polarized light after passing through the phase retardation film 400, and then the s-linearly polarized light passes through the polarization reflection layer 300 and is emitted towards the exit pupil, such as the human eye.

[0067] The above-mentioned folded optical path can change the polarization state of the light propagating between the polarization reflection layer 300 and the transmissive and reflective film 200, realizing the folding of the light, so that the focal length of the original optical system, which is increased due to the setting of the above-mentioned polarization reflection layer 300, phase retardation film 400 and transmissive and reflective film 200, such as two reflections, is folded, thus greatly compressing the space required between the human eye and the optical system, and making the optical system smaller, thinner and lighter.

[0068] Figure 2A For Figure 1 the spot diagram of the optical system shown. Figure 2B For Figure 1 the curve graph of the spot size of the optical system shown changing with the field angle.

[0069] Refer to Figure 2A , the spot diagram refers to a dispersion pattern that is formed by a large number of light rays emitted from a point after passing through an optical system. Due to aberration, the intersection points of these light rays with the image plane are no longer concentrated at the same point but are scattered within a certain range, and it can be used to evaluate the imaging quality of the optical system. Figure 2A In , taking the first set of values on the left vertical axis as an example, 0.00 represents the normalized field of view in the X direction, 1.00 represents the normalized field of view in the Y direction, 0.000 represents the field angle in the X direction, and 45.00 represents the field angle in the Y direction. Figure 2A In , taking the first set of values on the right vertical axis as an example, RMS represents the root mean square of the radius from the dispersion points of the spot to the centroid of the spot (or the center of the spot), and 100% represents the diameter of the spot. Figure 2A It is usually used to evaluate the clarity of the entire field of view of the optical system, that is, when the human eye pupil is at the entrance pupil position on the optical axis OA and is looking at the center of the lens (i.e., the zero field of view), the imaging clarity of the entire field of view that can be covered by the peripheral vision, which is also called the transient mode. In addition to considering the clarity of the entire field of view in the transient mode, for wearers of, for example, head-mounted displays, the fixation point clarity is one of the more important optical indicators. The fixation point clarity refers to the clarity of the picture within a certain angular range that can be directly seen (rather than seen by peripheral vision) when the eyes turn up, down, left, and right.

[0070] In the fixation point mode, when the eyeball rotates by a certain angle, the pupil deviates from the center of the optical axis OA. It has a certain deviation in the Z direction and Y direction of the optical axis OA, and the chief ray passing through the pupil center has a certain angle with the Z axis. For example, the range of this angle is ±35 degrees. The setting of this angle range takes into account the observation habits of the human eye. To see the objects in front beyond 35 degrees from the center of the human eye, people will actively turn their heads instead of strenuously rotating their eyeballs. Refer to Figure 2B , Figure 2Bshows the relationship between the fixation point clarity and the fixation angle. The blur spot in the central visual field is much smaller than one pixel, and the diameter of the blur spot when the human eye rotates to 20 degrees is less than 5 micrometers. From Figure 2B it can be seen that the blur spot of the optical system of the present disclosure is small, and the resolution of the optical system is high. In summary, it can be known that the optical system provided by at least one embodiment of the present disclosure can image clearly.

[0071] Figure 2C is Figure 1 the vertical chromatic aberration diagram of the optical system shown. Referring to Figure 2C , the vertical chromatic aberration diagram represents the height difference of each wavelength relative to the central wavelength at different image heights on the imaging surface. The horizontal axis represents the vertical chromatic aberration value of each wavelength relative to the central wavelength, and the vertical axis represents the normalized field angle. As Figure 2C shown, the R light is red light, the G light is green light, and the B light is blue light. The R light and the B light are at both ends of the human eye sensitive region, and the G light is located near the spectral line that is the most sensitive to the human eye. From Figure 2C it can be seen that the absolute value of the vertical chromatic aberration between the B light and the R light is controlled within 0.05 mm, and the absolute value of the vertical chromatic aberration between the B light and the G light is controlled within 0.025 mm. Thus, it can be known that the optical system shown in, for example, Figure 1 can excellently correct the chromatic aberration of the edge field of view and the secondary spectrum of the entire image plane.

[0072] Figure 2D is Figure 1 the distortion diagram of the optical system shown. Referring to Figure 2D , the distortion diagram reflects the difference in the image plane positions where clear images are formed in different fields of view. As shown in Figure 2D , the absolute value of the maximum distortion is within 35%. Thus, it can be known that the optical system provided by at least one embodiment of the present disclosure can preferably correct the distortion and meet the requirements of high-quality imaging. In addition, the distortion correction can be pre-processed in software.

[0073] Figure 3 is the optical system provided by an example in at least one embodiment of the present disclosure.

[0074] Figure 3 The difference between the optical system shown and Figure 1 the optical system shown is that Figure 3 the second surface 102 and the adhesive layer lens 130 in the optical system shown are different from Figure 1 the second surface 102 and the adhesive layer lens 130 in the optical system shown. Of course, Figure 3 the difference between the optical system shown and Figure 1 the optical system shown may also have other differences, such as the number of lenses, etc. The present disclosure does not limit this. For example, Figure 3 the number of lenses in the optical system shown can be the same as Figure 1The number of lenses in the shown optical system can be different or the same. Figure 3 The beam splitter film 200, polarization reflection layer 300, phase retardation film 400, and linear polarizing film 500 in the shown optical system can be Figure 1 the same as those in the shown optical system and will not be elaborated here.

[0075] For example, Figure 1 the shown adhesive layer lens 130 is a concave lens. In Figure 1 the shown optical system, an optical adhesive can be used to make the adhesive layer lens 130. For example, Figure 3 the shown adhesive layer lens 130 is a convex lens. When the adhesive layer lens 130 is a convex lens, the central thickness of the adhesive layer lens 130 is greater than the edge thickness, and more materials are required. In Figure 3 the shown optical system, an optical grade silicone material can be used to make the adhesive layer lens 130, thereby reducing costs and facilitating processing. For example, the central thickness of the adhesive layer lens 130 can be the distance between two intersection points where the two opposite surfaces of the adhesive layer lens 130 intersect with the optical axis OA. For example, Figure 1 the shown second surface 102 is a convex surface. For example, Figure 3 the shown second surface 102 is a concave surface.

[0076] Referring to Figure 1 and Figure 3 , in some examples, the distance between the two intersection points where the first surface 101 and the second surface 102 intersect with the optical axis OA is the first distance D1, and the ratio of the central thickness d of the adhesive layer lens 130 to the first distance D1 can be 1 / 6 to 2. By setting the ratio of the central thickness d of the adhesive layer lens 130 to the first distance D1, the adhesive layer can be filled between the second surface 102 and the third surface 103. For example, when the second surface 102 is a Fresnel surface, the adhesive layer can be filled with the tooth-shaped structure of the Fresnel surface, and thus the surface of the adhesive layer lens that is glued to the second surface 102 has a surface shape complementary to the second surface 102.

[0077] For example, referring to Figure 1 , the ratio of the central thickness d of the adhesive layer lens 130 to the first distance D1 can be 1 / 6 to 1 / 4. For example, referring to Figure 1 , the ratio of the central thickness d of the adhesive layer lens 130 to the first distance D1 can be 1 / 4 to 1 / 2. For example, referring to Figure 3 , the ratio of the central thickness d of the adhesive layer lens 130 to the first distance D1 can be 1 / 2 to 2.

[0078] In some optical systems, the adhesive layer used to bond two lenses is usually a relatively thin layer, and the thickness of the adhesive layer is usually from a dozen micrometers to dozens of micrometers. Refer to Figure 1 and Figure 3 , in some examples, the central thickness d of the adhesive layer lens 130 can be 0.5 mm to 3 mm. By setting a thicker adhesive layer, the adhesive layer can be filled between the second surface 102 and the third surface 103. For example, when the second surface 102 is a Fresnel surface, the adhesive layer can be filled with the tooth-shaped structure of the Fresnel surface. For example, refer to Figure 1 , the central thickness d of the adhesive layer lens 130 can be 0.5 mm to 0.8 mm. For example, refer to Figure 1 , the central thickness d of the adhesive layer lens 130 can be 0.8 mm to 1 mm. For example, refer to Figure 3 , the central thickness d of the adhesive layer lens 130 can be 1 mm to 1.5 mm. For example, refer to Figure 3 , the central thickness d of the adhesive layer lens 130 can be 1.5 mm to 2 mm. For example, refer to Figure 3 , the central thickness d of the adhesive layer lens 130 can be 2 mm to 2.5 mm. For example, refer to Figure 3 , the central thickness d of the adhesive layer lens 130 can be 2.5 mm to 3 mm.

[0079] Refer to Figure 1 and Figure 3 , in some examples, at least two lenses include a first lens 110 and a second lens 120 arranged along the optical axis OA direction. The first lens 110 includes a first surface 101 and a second surface 102, and the second lens 120 includes a third surface 103 and a fourth surface 104. For example, the lens assembly 100 can be composed of the first lens 110 and the second lens 120.

[0080] Refer to Figure 1 and Figure 3 , for example, after the first lens 110 and the second lens 120 are formed by injection molding, one of the lenses (for example, the first lens 110) can be placed in the limit circle of the mold and then filled with glue. A step portion can be provided in the limit circle to limit the amount of glue poured while limiting the lens, preventing the amount of glue from being too much or too little. Taking the second surface 102 of the first lens 110 as a Fresnel surface as an example, when filling with glue, it is necessary to ensure that the colloid fills the tooth gaps of the tooth-shaped structure on the Fresnel surface. Then, the other lens (for example, the second lens 120) can be placed on the step portion of the limit circle and pressure can be applied so that the excess colloid can be discharged from the glue discharge hole opened on the limit circle. At the same time, the glue discharge hole can also be used to discharge the gas inside the colloid. After discharging the excess colloid, the bonding and fixing can be achieved by heating or ultraviolet irradiation.

[0081] Refer to Figure 1 andFigure 3 In some examples, the distance between two intersection points where the first surface 101 and the second surface 102 intersect the optical axis OA is the first distance D1, and the distance between two intersection points where the third surface 103 and the fourth surface 104 intersect the optical axis OA is the second distance D2. For example, the first distance D1 is the central thickness of the first lens 110, and the second distance D2 is the central thickness of the second lens 120. The ratio of the second distance D2 to the first distance D1 can be 2 to 4. For example, the ratio of the second distance D2 to the first distance D1 can be 2.5 to 3.5. For example, the ratio of the second distance D2 to the first distance D1 can be 3.

[0082] Reference Figure 1 and Figure 3 In some examples, the ratio of the first distance D1 to the effective focal length of the optical system can be 0.1 to 0.3. For example, the ratio of the first distance D1 to the effective focal length of the optical system can be 0.15 to 0.25. For example, the ratio of the first distance D1 to the effective focal length of the optical system can be 1.2. In some examples, the ratio of the second distance D2 to the effective focal length of the optical system can be 0.5 to 0.7. For example, the ratio of the second distance D2 to the effective focal length of the optical system can be 0.55 to 0.65. For example, the ratio of the second distance D2 to the effective focal length of the optical system can be 0.6.

[0083] Reference Figure 1 and Figure 3 In some examples, one of the optical powers of the first lens 110 and the cemented lens 130 is positive, and the other is negative. Thus, by setting the optical powers of the first lens 110 and the cemented lens 130 to be positive and negative values with respect to each other, chromatic aberration can be corrected.

[0084] Figure 4A is a schematic diagram of the light deflection of a single lens. Figure 4B is a schematic diagram of the light deflection of an example in at least one embodiment of the present disclosure. Hereinafter, taking the light of the incident optical system undergoing one refraction as an example, chromatic aberration correction will be described.

[0085] Figure 4A shows the situation where light is deflected in a single lens. As Figure 4A shown, the single lens L is a convex lens, with the side away from the target surface S0 being the light incident side, that is, light enters the single lens L from Figure 4A the left side and exits the single lens L to the target surface S0 after refraction. After white light (such as the solid line shown in Figure 4A ) is incident on the single lens L, the white light is dispersed and decomposed into monochromatic lights with different wavelengths. Figure 4A The red light R with a longer wavelength is indicated by a dashed line, and the blue light B with a shorter wavelength is indicated by a dotted line. AsFigure 4A It can be known that the wavelength of blue light B is shorter and the wavelength of red light R is longer. After passing through the single lens L, it is difficult to converge on the target surface S0.

[0086] Figure 4B It shows the situation where the light rays are deflected in the optical system when the optical power of lens L1 and the optical power of lens L2 in the lens assembly are positive and negative with respect to each other. As Figure 4B shown, taking the side away from the target surface S0 as the light incident side, that is, the light rays enter the lens assembly from Figure 4B the left side and are refracted and then exit the lens assembly to the target surface S0. After white light (such as Figure 4B the solid line shown) is incident on the lens assembly, the white light is dispersed and decomposed into monochromatic lights with different wavelengths. Figure 4B The red light R with a longer wavelength is indicated by a dashed line, and the blue light B with a shorter wavelength is indicated by a dotted line. By setting the optical power of lens L1 and the optical power of lens L2 to be positive and negative, the deflection angles of the red light R and the blue light B are changed, and finally the red light R and the blue light B can converge on the target surface S0.

[0087] For example, referring to Figure 4B , lens L1 is a convex lens with a positive optical power, and lens L2 is a concave lens with a negative optical power. After the incident light is dispersed when entering lens L1, the blue light B with a relatively shorter wavelength is more deflected towards the optical axis OA than the red light R. Since the optical power of lens L2 is negative, after the light rays exit from lens L2, the red light R and the blue light B can converge on the target surface S0, thereby achieving the purpose of correcting chromatic aberration.

[0088] For example, referring to Figure 1 , the first lens 110 can be a convex lens, and the adhesive layer lens 130 can be a concave lens, so that the optical power of the first lens 110 is positive and the optical power of the adhesive layer lens 130 is negative, thereby correcting chromatic aberration. Moreover, for the concave lens of the adhesive layer lens 130, the amount of the adhesive layer material used is less. For example, the second surface 102 of the first lens 110 is a Fresnel surface, and the adhesive layer glues the Fresnel surface and the second lens 120 together, so as to reduce the amount of the adhesive layer through the tooth-shaped structure of the Fresnel surface, thereby reducing the cost. In addition, setting the first lens 110 as a convex lens and the adhesive layer lens 130 as a concave lens at the same time can also make the optical system thinner and lighter.

[0089] For example, referring to Figure 3 , the first lens 110 can be a concave lens, and the adhesive layer lens 130 can be a convex lens, so that the optical power of the first lens 110 is negative and the optical power of the adhesive layer lens 130 is positive, thereby correcting chromatic aberration. Moreover, the central thickness of the convex lens of the adhesive layer lens 130 is thicker, which can ensure that there is an adhesive layer between the center of the first lens 110 and the center of the second lens 120.

[0090] In some examples, referring to Figure 1 , the ratio of the optical power of the first lens 110 to the dispersion coefficient of the first lens 110 is the first ratio, and the ratio of the optical power of the adhesive layer lens 130 to the dispersion coefficient of the adhesive layer lens 130 is the second ratio. The sum of the first ratio and the second ratio is less than 0. Thus, chromatic aberration can be corrected by combining the positive and negative optical powers of the first lens 110 and the adhesive layer lens. At the same time, at least part of the optical power of the second lens 120 can be offset by the optical power margin of the first lens 110 and the adhesive layer lens, making the correction effect of chromatic aberration better.

[0091] In some examples, referring to Figure 1 , the refractive index of the first lens 110 is less than the refractive index of the adhesive layer lens 130, the refractive index of the second lens 120 is less than the refractive index of the adhesive layer lens 130, and the refractive index of the first lens 110 is less than or equal to the refractive index of the second lens 120. By setting the first lens 110, the second lens 120, and the adhesive layer lens 130 to have different refractive indices, the deflection angles of light rays of different wavelengths (such as red light and blue light) after white light dispersion can be changed, so that light rays of different wavelengths can converge after exiting from the lens assembly 100, thereby correcting chromatic aberration. Moreover, the refractive index of the first lens 110 can be relatively close to the refractive index of the second lens 120, and the deflection of light occurs in the first lens 110 and the second lens 120 with a relatively small refractive index difference. The reflection loss of light is less than 2% of the reflection loss at the lens-air interface, improving the optical efficiency.

[0092] Since the same transparent medium has a refractive index difference for light of different wavelengths, and white light is composed of various colors of light with different wavelengths, the transparent medium will disperse when refracting white light. The dispersion coefficient (also known as the Abbe number) is an index used to represent the dispersion ability of a transparent medium and is used to measure the degree of light dispersion of the transparent medium. Generally speaking, the greater the refractive index of the medium, the more serious the dispersion and the smaller the Abbe number; conversely, the smaller the refractive index of the medium, the less serious the dispersion and the larger the Abbe number.

[0093] In some examples, referring to Figure 1 , the dispersion coefficient of the first lens 110 is greater than the dispersion coefficient of the adhesive layer lens 130, the dispersion coefficient of the second lens 120 is greater than the dispersion coefficient of the adhesive layer lens 130, and the dispersion coefficient of the first lens 110 is greater than or equal to the dispersion coefficient of the second lens 120. By setting the first lens 110, the second lens 120, and the adhesive layer lens 130 to have different dispersion coefficients, the deflection angles of light rays of different wavelengths (such as red light and blue light) after white light dispersion can be changed, so that light rays of different wavelengths can converge after exiting from the lens assembly 100, thereby correcting chromatic aberration.

[0094] For example, referring toFigure 1 The dispersion coefficient of the first lens 110 can be set to be much larger than that of the adhesive lens 130, the dispersion coefficient of the second lens 120 can be set to be much larger than that of the adhesive lens 130, and the dispersion coefficient of the first lens 110 is set to be greater than or equal to that of the second lens 120.

[0095] In some examples, referring to Figure 3 the refractive index of the first lens 110 is greater than that of the adhesive lens 130, and the refractive index of the first lens 110 is greater than that of the second lens 120. By setting the first lens 110, the second lens 120, and the adhesive lens 130 to have different refractive indices, the deflection angles of light rays of different wavelengths (such as red light and blue light) after white light dispersion can be changed, so that light rays of different wavelengths can converge after exiting from the lens assembly 100, thereby correcting chromatic aberration.

[0096] For example, referring to Figure 3 the refractive index of the first lens 110 can be set to be greater than that of the adhesive lens 130. At the same time, the refractive index of the second lens 120 is set to be relatively close to that of the adhesive lens 130 to facilitate the correction of chromatic aberration.

[0097] In some examples, referring to Figure 3 the dispersion coefficient of the first lens 110 is less than that of the adhesive lens 130, and the dispersion coefficient of the first lens 110 is less than that of the second lens 120. By setting the first lens 110, the second lens 120, and the adhesive lens 130 to have different dispersion coefficients, the deflection angles of light rays of different wavelengths (such as red light and blue light) after white light dispersion can be changed, so that light rays of different wavelengths can converge after exiting from the lens assembly 100, thereby correcting chromatic aberration.

[0098] For example, referring to Figure 3 the dispersion coefficient of the first lens 110 can be set to be much less than that of the adhesive lens 130. At the same time, the dispersion coefficient of the second lens 120 is set to be relatively close to that of the adhesive lens 130 to facilitate the correction of chromatic aberration.

[0099] For example, referring to Figure 1 or Figure 3 the dispersion coefficient of the first lens 110 can be 50 - 60. For example, the dispersion coefficient of the first lens can be 54 - 56. For example, the dispersion coefficient of the adhesive lens 130 can be 30 - 40. For example, the dispersion coefficient of the adhesive lens can be 34 - 36. For example, the dispersion coefficient of the second lens can be 50 - 60. For example, the dispersion coefficient of the second lens can be 55 - 57. For example, the dispersion coefficient of the second lens can be 56.5.

[0100] For example, referring to Figure 1 or Figure 3 , the refractive index of the first lens 110 can be 1.4 to 1.5. For example, the refractive index of the first lens can be 1.41 to 1.49. For example, the refractive index of the first lens can be 1.42 to 1.48. For example, the refractive index of the first lens can be 1.45. For example, the refractive index of the second lens 120 can be 1.5 to 1.6. For example, the refractive index of the second lens can be 1.54 to 1.56. For example, the refractive index of the first lens can be 1.49 and the refractive index of the second lens can be 1.54. For example, the refractive index of the adhesive layer lens can be 1.5 to 1.6. For example, the refractive index of the adhesive layer lens can be 1.53 to 1.57.

[0101] For example, referring to Figure 1 or Figure 3 , after the light exits from the second lens 120, the refractive index of the external air can be 1.52 and the dispersion coefficient can be 64.

[0102] In some examples, referring to Figure 1 or Figure 3 , the ratio of the central thickness to the edge thickness of the first lens 110 is a third ratio, and the ratio of the central thickness to the edge thickness of the second lens 120 is a fourth ratio; at least one of the third ratio and the fourth ratio is greater than 1 and less than 3. For example, the ratio of the central thickness to the edge thickness of the first lens can be 1 to 3. For example, the ratio of the central thickness to the edge thickness of the first lens can be 2 to 2.5. For example, the ratio of the central thickness to the edge thickness of the second lens 120 can be 1 to 3. For example, the ratio of the central thickness to the edge thickness of the second lens can be 2 to 2.5. By setting the proportional relationship between the central thickness and the edge thickness of each of the above lenses, it is beneficial to ensure the injection molding of each lens.

[0103] In some examples, the first surface can be a plane. For example, referring to Figure 1 , the second surface 102 can be set as a convex surface, so that the first lens 110 is a convex lens and at the same time the adhesive layer lens 130 is a concave lens, thereby correcting chromatic aberration. For example, referring to Figure 3 , the second surface 102 can be set as a concave surface, so that the first lens 110 is a concave lens and at the same time the adhesive layer lens 130 is a convex lens, thereby correcting chromatic aberration.

[0104] Figure 5 This is the optical system provided by an example in at least one embodiment of the present disclosure.

[0105] Figure 5 The optical system shown is different from the optical system shown in Figure 1 in that Figure 5 the first surface 101 in the optical system shown is different fromFigure 1 is different from the first surface 101 in the optical system shown. Of course, Figure 5 the optical system shown and Figure 1 there may also be other differences in the optical system shown, such as the number of lenses, etc., and the present disclosure does not limit any of these. For example, Figure 5 the number of lenses in the optical system shown may be different from Figure 1 the number of lenses in the optical system shown, or may be the same. Figure 5 The beam splitter film 200, polarization reflection layer 300, phase retardation film 400, and linear polarization film 500 in the optical system shown may have the same characteristics as Figure 1 the beam splitter film 200, polarization reflection layer 300, phase retardation film 400, and linear polarization film 500 in the optical system shown, and will not be elaborated herein.

[0106] In some examples, referring to Figure 5 , the first surface 101 may be a convex surface. For example, the second surface 102 may be set as a convex surface, such that the first lens 110 is a convex lens, and at the same time, the adhesive layer lens 130 is a concave lens, thereby correcting chromatic aberration.

[0107] For example, the first surface 101 may be an aspherical surface, such as can be represented by the following numerical formula:

[0108]

[0109] For example, in the above formula, the height of the aspherical surface in the direction perpendicular to the optical axis OA is Y, and the distance from the vertex of the aspherical surface to the projection of the point on the aspherical surface with height Y on the optical axis OA is z, that is, z is the coordinate in the direction of the optical axis OA; C is the curvature (the reciprocal of the radius of curvature R), k is the conic constant, α i is the coefficient of each higher-order term, and 2i is the order of the aspherical coefficient.

[0110] When actually optimizing the reasonable configuration of the parameters of the lens assembly, the values of the radius of curvature, conic constant, height, and aspherical coefficient of each lens in the lens assembly are put into the above numerical formula, and through optical simulation calculations, various optimized parameters capable of correcting the aberration of each lens in the lens assembly are obtained. Through the optimization process, the preferred values of the radius of curvature, thickness along the optical axis OA, effective aperture, and conic constant of each lens in the lens assembly are obtained.

[0111] Referring to Figure 5The ratio of the radius of curvature of the first surface 101 to the effective focal length of the optical system can be -40 to -50, and the conic coefficient of the first surface 101 can be -10 to 0. For example, the ratio of the radius of curvature of the first surface to the effective focal length of the optical system can be -42 to -48. For example, the ratio of the radius of curvature of the first surface to the effective focal length of the optical system can be -44 to -46. For example, the ratio of the radius of curvature of the first surface to the effective focal length of the optical system can be -45. For example, the conic coefficient of the first surface can be -9 to -0.5. For example, the conic coefficient of the first surface can be -8 to -2. For example, the conic coefficient of the first surface can be -6 to -4. For example, the conic coefficient of the first surface can be -5.

[0112] Of course, in some other examples, the first surface can also be set as a concave surface. By changing the surface shape parameters of the second surface, the first lens can be made a convex lens or a concave lens, and correspondingly, the adhesive layer lens can be made a concave lens or a convex lens. As long as the optical power of the first lens and the optical power of the adhesive layer lens can be made positive and negative of each other by setting the surface shape parameters of each surface, the present disclosure does not limit this.

[0113] In some examples, referring to Figure 1 、 Figure 3 and Figure 5 , the second surface 102 is a curved Fresnel surface. For example, the second surface 102 can be a convex Fresnel surface (referring to Figure 1 、 Figure 5 ), or it can also be a concave Fresnel surface (referring to Figure 3 ), and the present disclosure does not limit this.

[0114] In some examples, referring to Figure 1 or Figure 5 , the second surface 102 is a convex surface, and the central thickness of the adhesive layer lens 130 is less than the edge thickness. When the second surface 102 is set as a convex surface, by setting the central thickness of the adhesive layer lens 130 to be less than the edge thickness, the adhesive layer lens 130 can be made to form a concave lens, so as to cooperate with the convex lens first lens 110 to correct chromatic aberration.

[0115] In some examples, referring to Figure 1 or Figure 5 , the second surface 102 is a convex surface, and the absolute value of the radius of curvature of the second surface 102 is less than the absolute value of the radius of curvature of the third surface 103. Thus, the curvature of the third surface 103 is smaller, while the curvature of the second surface 102 is larger, so that the adhesive layer lens 130 filled between the second surface 102 and the third surface 103 is thinner in the middle and thicker at the edges, so as to form a concave lens.

[0116] The surface profile of the curved Fresnel surface can be approximated as the surface profile of an aspherical surface, such as the surface profile formula of the aforementioned aspherical surface can be referred to. In some examples, referring to Figure 1 or Figure 5 , the second surface 102 is a convex surface, and the ratio of the radius of curvature of the second surface 102 to the effective focal length of the optical system can be -0.5 to -2. For example, the radius of curvature of the second surface 102 refers to the radius of curvature of the Fresnel surface including the toothed structure. For example, the second surface 102 of the Fresnel surface can be approximated as a smooth and toothless spherical surface or aspherical surface, and the curvature of this spherical surface or aspherical surface is the curvature of the Fresnel surface. For example, the tooth width or tooth height of the second surface 102 can be assumed to be infinitesimal. For example, the ratio of the radius of curvature of the second surface 102 to the effective focal length of the optical system can be -1 to -1.4. For example, the ratio of the radius of curvature of the second surface 102 to the effective focal length of the optical system can be -1.25.

[0117] In some examples, referring to Figure 3 , the second surface 102 is a concave surface, and the central thickness of the adhesive layer lens 130 is greater than the edge thickness. When the second surface 102 is set as a concave surface, by setting the central thickness of the adhesive layer lens 130 to be greater than the edge thickness, the adhesive layer lens 130 can be formed into a convex lens, so as to cooperate with the first lens 110 with concave lens characteristics to correct chromatic aberration.

[0118] Figure 6 This is the optical system provided by an example in at least one embodiment of the present disclosure.

[0119] Figure 6 The optical system shown is different from the optical system shown in Figure 1 in that Figure 6 the second surface 102, the adhesive layer lens 130, and the third surface 103 in the optical system shown are different from the second surface 102, the adhesive layer lens 130, and the third surface 103 in the optical system shown in Figure 1 . Of course, Figure 6 the optical system shown and the optical system shown in Figure 1 may also have other differences, such as the number of lenses, etc., and the present disclosure does not limit this. For example, Figure 6 the number of lenses in the optical system shown can be different from or the same as the number of lenses in the optical system shown in Figure 1 . Figure 6 The dichroic mirror 200, the polarization reflection layer 300, the phase retardation film 400, and the linear polarization film 500 in the optical system shown can have the same characteristics as the dichroic mirror 200, the polarization reflection layer 300, the phase retardation film 400, and the linear polarization film 500 in the optical system shown in Figure 1 , and will not be elaborated here.

[0120] In some examples, referring toFigure 6 , the second surface 102 is a planar Fresnel surface. For example, the second surface 102 can be set as a planar Fresnel surface. At the same time, by setting the third surface 103 as a convex surface, the adhesive layer lens 130 between the second surface 102 and the third surface 103 can be made into a concave lens, thereby correcting chromatic aberration. For example, a phase retardation film 400 can be attached to the side of the third surface 103 away from the fourth surface 104. By setting the third surface 103 as a convex surface, it is also beneficial to the attachment of the phase retardation film 400 and reduces the probability of attachment wrinkles. For example, the second surface can also be set as a convex Fresnel surface while the third surface is set as a convex surface to make the adhesive layer lens a concave lens, and the present disclosure does not limit this.

[0121] For example, after discretizing a continuous surface, a spherical curvature or an aspherical curvature obtained by discretization can be superimposed, so as to obtain a curved Fresnel surface with a curved surface as the base surface (for example, refer to Figure 1 , Figure 3 and Figure 5 ). For example, a continuous surface can be discretized to obtain a planar Fresnel surface with a plane as the base surface (for example, refer to Figure 6 ). Thus, the radius of curvature of the Fresnel surface in the optical system has a large adjustment space, so that the dispersed light can be better deflected and converged. Moreover, by adjusting the slope of the Fresnel surface, the deflection ability of the second surface to light is enhanced, which can not only achieve an ultra-short focal length, but also improve the correction effect of chromatic aberration and enhance the clarity.

[0122] For example, by comprehensively considering the light deflection situation in the optical system and the surface shape parameters of each surface in the lens assembly, parameters such as the draft angle, tooth width, and tooth height of the Fresnel surface can be obtained. Thus, through the surface shape design of the Fresnel surface, the stray light that may be generated on the backlight surface of the Fresnel surface can be reduced, and the visual effect can be improved.

[0123] Refer to Figure 1 , Figure 3 , Figure 5, in some examples, the third surface 103 may be a concave surface, the ratio of the radius of curvature of the third surface 103 to the effective focal length of the optical system may be -3 to -4, and the conic coefficient of the third surface 103 may be -10 to -1. For example, the ratio of the radius of curvature of the third surface 103 to the effective focal length of the optical system may be -3.2 to -3.9. For example, the ratio of the radius of curvature of the third surface 103 to the effective focal length of the optical system may be -3.4 to -3.6. For example, the ratio of the radius of curvature of the third surface 103 to the effective focal length of the optical system may be -3.5. For example, the conic coefficient of the third surface 103 may be -8 to -2. For example, the conic coefficient of the third surface 103 may be -6 to -4. For example, the conic coefficient of the third surface 103 may be -5.

[0124] Figure 7 This is the optical system provided by an example in at least one embodiment of the present disclosure.

[0125] Figure 7 The optical system shown is different from Figure 1 the optical system shown in that Figure 7 the cemented lens 130 and the third surface 103 in the optical system shown are different from Figure 1 the cemented lens 130 and the third surface 103 in the optical system shown. Of course, Figure 7 the optical system shown may also have other differences from Figure 1 the optical system shown, such as the number of lenses, etc., and the present disclosure does not limit this. For example, Figure 7 the number of lenses in the optical system shown may be different from Figure 1 the number of lenses in the optical system shown, or may be the same. Figure 7 The dichroic mirror 200, polarization reflection layer 300, phase retardation film 400, and linear polarization film 500 in the optical system shown may have the same characteristics as Figure 1 the dichroic mirror 200, polarization reflection layer 300, phase retardation film 400, and linear polarization film 500 in the optical system shown, and will not be elaborated here.

[0126] In some examples, referring to Figure 7 , the third surface 103 may be a flat surface. When the third surface 103 is a flat surface, the second surface 102 may be set as a convex surface, so that the cemented lens 130 between the second surface 102 and the third surface 103 is a concave lens. Thus, the cemented lens 130 of the concave lens can cooperate with the first lens 110 of the convex lens to correct chromatic aberration.

[0127] Referring to Figure 1 , Figure 3 , Figures 5 to 7, in some examples, the fourth surface 104 is a convex surface, and the ratio of the radius of curvature of the fourth surface 104 to the effective focal length of the optical system can be -2 to -3, and the conic coefficient of the fourth surface 104 can be -10 to -1. For example, the ratio of the radius of curvature of the fourth surface 104 to the effective focal length of the optical system can be -2.2 to -2.8. For example, the ratio of the radius of curvature of the fourth surface 104 to the effective focal length of the optical system can be -2.4 to -2.6. For example, the ratio of the radius of curvature of the fourth surface 104 to the effective focal length of the optical system can be -2.5. For example, the conic coefficient of the fourth surface 104 can be -8 to -2. For example, the conic coefficient of the fourth surface 104 can be -6 to -3. For example, the conic coefficient of the fourth surface 104 can be -5.

[0128] Combined with the foregoing examples, for example, the higher-order term coefficients of the first surface 101 satisfy: α4 = 6.0E-06, α6 = 6.1E-08, α8 = -5.2E-10, α 10 = 1.3E-12, α 12 = 8.2E-16, α 14 = -7.6E-18. For example, the higher-order term coefficients of the second surface 102 satisfy: α4 = -1.9E-05, α6 = 8.0E-08, α8 = 1.7E-10, α 10 = -4.6E-13, α 12 = -3.93E-15. For example, the higher-order term coefficients of the third surface 103 satisfy: α4 = 7.5E-06, α6 = 4.8E-08, α8 = -2.9E-10, α 10 = -1.6E-12, α 12 = 2.2E-14, α 14 = -9.8E-17. For example, the higher-order term coefficients of the fourth surface 104 satisfy: α4 = -5.5E-06, α6 = 1.8E-09, α8 = 7.7E-11, α 10 = -5.9E-13, α 12 = 2.4E-15, α 14 = -6.4E-18.

[0129] Figure 8 The optical system provided by an example in at least one embodiment of the present disclosure.

[0130] Figure 8 The shown optical system and Figure 1 The shown optical system are different in that Figure 8 The number of lenses in the shown optical system and Figure 1 The number of lenses in the shown optical system are different. Of course, Figure 8 The shown optical system and Figure 1The optical system shown may also have other differences, such as the surface shape of each surface, the optical power of the adhesive lens 130, etc. The present disclosure does not limit any of these. For example, Figure 8 The surface shape parameters of each surface in the optical system shown may be different from Figure 1 the surface shape parameters of each surface in the optical system shown, or may be the same. Figure 8 The beam splitter film 200, polarization reflection layer 300, phase retardation film 400, and linear polarization film 500 in the optical system shown may be the same as Figure 1 the beam splitter film 200, polarization reflection layer 300, phase retardation film 400, and linear polarization film 500 in the optical system shown, and the same features are not described herein again.

[0131] In some examples, referring to Figure 8 , at least two lenses include a first lens 110, a second lens 120, and a third lens 140 arranged in sequence along the optical axis OA direction. For example, the adhesive lens 130 is located between the first lens 110 and the second lens 120. For example, the lens assembly 100 may be composed of the first lens 110, the second lens 120, and the third lens 140. The first lens 110 includes a first surface 101 and a second surface 102, the second lens 120 includes a third surface 103, the third lens 140 includes a fourth surface 104, the second lens 120 further includes a fifth surface 105 opposite to the third surface 103, and the third lens 140 further includes a sixth surface 106 located between the fifth surface 105 and the fourth surface 104. For example, the third surface 103 and the fifth surface 105 are two opposite surfaces of the second lens 120 on the optical axis OA. For example, the fourth surface 104 and the sixth surface 106 are two opposite surfaces of the third lens 140 on the optical axis OA. The surface shapes of the fifth surface 105 and the sixth surface 106 are the same so that the second lens 120 and the third lens 140 are fitted together.

[0132] By providing the second lens 120 and the third lens 140, more film attachment positions can be provided. For example, the phase retardation film 400 can be provided between the fifth surface 105 and the sixth surface 106.

[0133] Such as Figure 8 shown, one of the optical powers of the first lens 110 and the adhesive lens 130 is positive, and the other is negative. For example, the optical power of the first lens 110 can be positive, that is, the first lens 110 is a convex lens, and the optical power of the adhesive lens 130 can be negative, that is, the adhesive lens 130 is a concave lens. Thus, chromatic aberration can be corrected jointly by the first lens 110 and the adhesive lens 130.

[0134] Such as Figure 8As shown, the dispersion coefficient of at least one of the first lens 110 and the second lens 120 is different from that of the adhesive lens 130. For example, the dispersion coefficient of the first lens 110 can be different from that of the adhesive lens 130. For example, the dispersion coefficient of the second lens 120 can be different from that of the adhesive lens 130. Thus, chromatic aberration can be corrected by the difference in dispersion coefficients. For example, the refractive index of at least one of the first lens 110 and the second lens 120 can also be different from that of the adhesive lens 130, so as to correct chromatic aberration by the difference in refractive indices.

[0135] Figure 9 This is an optical system provided by an example in at least one embodiment of the present disclosure.

[0136] Figure 9 The optical system shown is different from Figure 8 the optical system shown in that Figure 9 the fifth surface 105 and the sixth surface 106 in the optical system shown are different from Figure 8 the fifth surface 105 and the sixth surface 106 in the optical system shown. Of course, Figure 9 the optical system shown can also be different from Figure 8 the optical system shown in other aspects, such as the surface shape of each surface, the optical power of the adhesive lens 130, etc., and the present disclosure does not limit this. For example, Figure 9 the surface shape parameters of each surface in the optical system shown can be different from Figure 8 the surface shape parameters of each surface in the optical system shown, or can be the same. Figure 9 The beam splitter 200, the polarization reflection layer 300, the phase retardation film 400, and the linear polarizing film 500 in the optical system shown can have the same characteristics as Figure 8 the beam splitter 200, the polarization reflection layer 300, the phase retardation film 400, and the linear polarizing film 500 in the optical system shown, and will not be elaborated here.

[0137] For example, referring to Figure 8 , both the fifth surface 105 and the sixth surface 106 can be flat surfaces. For example, referring to Figure 9 , both the fifth surface 105 and the sixth surface 106 are curved surfaces. For example, both the fifth surface 105 and the sixth surface 106 are convex surfaces. For example, both the fifth surface 105 and the sixth surface 106 are curved away from the third surface 103, so that the difference between the central thickness and the edge thickness of the second lens 120 is small, and the difference between the central thickness and the edge thickness of the third lens 140 is small, thereby reducing the processing difficulty.

[0138] Figure 10 This is a display device provided by an example in at least one embodiment of the present disclosure.

[0139] Such asFigure 10 As shown, at least one embodiment of the present disclosure provides a display device, including the optical system of any of the above embodiments. For example, the display device further includes a display screen 10, and the display screen 10 is located on the side of the fourth surface 104 away from the first surface 101. Since the display device according to the embodiments of the present disclosure includes at least one of the above optical systems, it also has corresponding beneficial technical effects, which will not be elaborated here. It can be understood that Figure 10 the display screen 10 shown, in cooperation with an optical system such as Figure 1 , Figure 3 , Figures 5 to 9 can form different display devices. For example, the display surface of the display screen 10 is located on the focal plane of the light incident side of the optical system.

[0140] For example, referring to Figures 1 to 10 , the ratio of the total optical length (TTL) of the optical system to the effective focal length can be 0.85 to 1. For example, the ratio of the total optical length of the optical system to the effective focal length can be 0.9 to 0.95. The total optical length refers to the distance between the highest point on the first surface 101 of the lens assembly 100 along the optical axis OA and the center of the display screen 10. The highest point on the first surface 101 includes the edge sag of the lens assembly 100 on the side where the first surface 101 is located.

[0141] For example, referring to Figures 1 to 10 , the field of view angle of the optical system can be greater than 90°. For example, the field of view angle is the full field of view angle. For example, the field of view angle of the optical system can be but is not limited to 90°, 92°, 94°, 96°, 98°, 100°. For example, calculated with an effective aperture that can achieve a field of view angle of 100°, the weight of the binocular lens is less than 20 g.

[0142] For example, referring to Figures 1 to 10 , the exit pupil distance (EPD) of the optical system can be 12 mm to 20 mm. For example, the exit pupil distance is the distance from the vertex of the last surface of the optical system to the intersection of the exit pupil plane and the optical axis. For example, the exit pupil distance can be 14 mm to 18 mm. For example, the exit pupil distance can be 15 mm. The optical system provided by the present disclosure has a relatively large exit pupil distance, which can meet the needs of myopic users wearing glasses.

[0143] For example, referring to Figures 1 to 10 , the ratio of the effective aperture of the lens assembly 100 to the effective focal length can be 2.3 to 2.7. The effective aperture of the above lens assembly refers to the effective light passing aperture, such as the maximum aperture through which light can pass through the lens assembly, and this aperture is determined by the maximum luminous flux of the lens assembly. For example, the ratio of the effective aperture to the effective focal length can be 2.4 to 2.6. For example, the ratio of the effective aperture to the effective focal length can be 2.5.

[0144] For example, referring toFigures 1 to 10 The ratio of the distance between the aperture (such as the human eye) in the optical system and the first surface 101 on the optical axis OA to the effective focal length is 0.7 to 1.5. For example, the ratio of the distance between the aperture and the first surface on the optical axis OA to the effective focal length is 0.8 to 1.4. For example, the ratio of the distance between the aperture and the first surface on the optical axis OA to the effective focal length is 0.9 to 1.3. For example, the ratio of the distance between the aperture and the first surface on the optical axis OA to the effective focal length is 1 to 1.2. For example, the ratio of the distance between the aperture and the first surface on the optical axis OA to the effective focal length is 1.1.

[0145] For example, refer to Figures 1 to 10 The effective aperture of the aperture is 4 mm. For example, the ratio of the distance between the object plane and the aperture in the optical system on the optical axis OA to the effective focal length is below -80.

[0146] For example, refer to Figures 1 to 10 The ratio of the distance between the display surface of the display screen 10 and the image plane on the optical axis OA to the effective focal length is 0.03 to 0.12. For example, the ratio of the distance between the display surface of the display screen 10 and the image plane on the optical axis OA to the effective focal length is 0.06 to 0.09. For example, the ratio of the distance between the display surface of the display screen 10 and the image plane on the optical axis OA to the effective focal length is 0.08.

[0147] For example, refer to Figures 1 to 10 The ratio of the distance between the fourth surface 104 and the display surface of the display screen 10 on the optical axis OA to the effective focal length is 0.05 to 0.3. For example, the ratio of the distance between the fourth surface 104 and the display surface of the display screen 10 on the optical axis OA to the effective focal length is 0.06 to 0.2. The ratio of the distance between the fourth surface 104 and the display surface of the display screen 10 on the optical axis OA to the effective focal length is 0.1.

[0148] For example, the display screen can be any type of display screen, such as a liquid crystal display screen, an organic light-emitting diode display screen, an inorganic light-emitting diode display screen, a quantum dot display screen, a projector (such as an LCOS micro-projector), etc.

[0149] For example, the display screen is a liquid crystal display screen, and the pixel size is about twenty-something micrometers. For example, the display screen is an organic light-emitting diode display screen, and the pixel size is about a few micrometers.

[0150] For example, the display device can be a virtual reality display device. For example, the virtual reality display device can be a display device using an ultra-short focal length folding optical path.

[0151] For example, the display device can be a near-eye display device, and the near-eye display device can be a wearable VR helmet, VR glasses, etc., and the embodiments of the present disclosure are not limited thereto.

[0152] The following points need to be explained:

[0153] (1) In the accompanying drawings of the embodiments of the present disclosure, only the structures related to the embodiments of the present disclosure are involved, and other structures can refer to the general design.

[0154] (2) Without conflict, the features in the same embodiment and different embodiments of the present disclosure can be combined with each other.

[0155] The above are only exemplary embodiments of the present disclosure, rather than being used to limit the protection scope of the present disclosure. The protection scope of the present disclosure is determined by the appended claims.

Claims

1. An optical system, comprising: a lens assembly including at least two lenses, the at least two lenses including a first surface, a second surface, a third surface, and a fourth surface arranged in sequence along the optical axis direction of the lens assembly; a dichroic mirror film provided on a side of the fourth surface away from the third surface; a polarization reflection layer provided on a side of the third surface away from the fourth surface; a phase retardation film located on a side of the fourth surface away from the dichroic mirror film; and an adhesive layer including an adhesive layer lens; wherein at least one of the first surface and the second surface is a Fresnel surface, and the adhesive layer is bonded between the second surface and the third surface.

2. The optical system according to claim 1, wherein The distance between two intersection points of the first surface and the second surface intersecting with the optical axis is a first distance; The ratio of the central thickness of the adhesive layer lens to the first distance is 1 / 6 to 2.

3. The optical system according to claim 1, wherein, The central thickness of the adhesive layer lens is 0.5 mm to 3 mm.

4. The optical system according to any one of claims 1-3, wherein, The at least two lenses include a first lens and a second lens arranged along the optical axis direction, the first lens including the first surface and the second surface, and the second lens including the third surface and the fourth surface; One of the optical power of the first lens and the optical power of the adhesive layer lens is positive, and the other is negative.

5. The optical system according to claim 4, wherein, The ratio of the optical power of the first lens to the dispersion coefficient of the first lens is a first ratio, and the ratio of the optical power of the adhesive layer lens to the dispersion coefficient of the adhesive layer lens is a second ratio; The sum of the first ratio and the second ratio is less than 0.

6. The optical system according to claim 4, wherein, The refractive index of the first lens is less than the refractive index of the adhesive layer lens, the refractive index of the second lens is less than the refractive index of the adhesive layer lens, and the refractive index of the first lens is less than or equal to the refractive index of the second lens.

7. The optical system according to claim 4, wherein, The dispersion coefficient of the first lens is greater than the dispersion coefficient of the adhesive layer lens, the dispersion coefficient of the second lens is greater than the dispersion coefficient of the adhesive layer lens, and the dispersion coefficient of the first lens is greater than or equal to the dispersion coefficient of the second lens.

8. The optical system according to claim 4, wherein, The refractive index of the first lens is greater than the refractive index of the adhesive layer lens, and the refractive index of the first lens is greater than the refractive index of the second lens.

9. The optical system according to claim 4, wherein, The dispersion coefficient of the first lens is less than the dispersion coefficient of the adhesive layer lens, and the dispersion coefficient of the first lens is less than the dispersion coefficient of the second lens.

10. The optical system according to claim 4, wherein, The ratio of the central thickness to the edge thickness of the first lens is a third ratio, and the ratio of the central thickness to the edge thickness of the second lens is a fourth ratio; At least one of the third ratio and the fourth ratio is greater than 1 and less than 3.

11. The optical system according to any one of claims 1-3, wherein, The second surface is a planar Fresnel surface or a curved Fresnel surface.

12. The optical system according to claim 11, wherein, The second surface is a convex surface, and the central thickness of the adhesive layer lens is less than the edge thickness.

13. The optical system according to claim 11, wherein, The second surface is a convex surface, and the absolute value of the radius of curvature of the second surface is less than the absolute value of the radius of curvature of the third surface.

14. The optical system according to claim 11, wherein, The second surface is a convex surface, and the ratio of the radius of curvature of the second surface to the effective focal length of the optical system is -0.5 to -2.

15. The optical system according to claim 11, wherein, The second surface is a concave surface, and the central thickness of the adhesive layer lens is greater than the edge thickness.

16. The optical system according to any one of claims 1-3, wherein, The distance between two intersection points where the first surface and the second surface intersect the optical axis is a first distance; The distance between two intersection points where the third surface and the fourth surface intersect the optical axis is a second distance; The ratio of the second distance to the first distance is 2 to 4.

17. The optical system according to claim 16, wherein, The ratio of the first distance to the effective focal length of the optical system is 0.1 to 0.3, and the ratio of the second distance to the effective focal length of the optical system is 0.5 to 0.

7.

18. The optical system according to any one of claims 1-3, wherein, The first surface is a plane; or The first surface is a convex surface, the ratio of the radius of curvature of the first surface to the effective focal length of the optical system is -40 to -50, and the conic coefficient of the first surface is -10 to 0.

19. The optical system according to any one of claims 1 to 3, wherein, The third surface is a plane; or The third surface is a concave surface, the ratio of the radius of curvature of the third surface to the effective focal length of the optical system is -3 to -4, and the conic coefficient of the third surface is -10 to -1.

20. The optical system according to any one of claims 1-3, wherein, The fourth surface is a convex surface, the ratio of the radius of curvature of the fourth surface to the effective focal length of the optical system is -2 to -3, and the conic coefficient of the fourth surface is -10 to -1.

21. The optical system according to any one of claims 1-3, wherein, The at least two lenses include a first lens, a second lens, and a third lens arranged in sequence along the optical axis direction; The first lens includes the first surface and the second surface, the second lens includes the third surface, and the third lens includes the fourth surface; The second lens further includes a fifth surface opposite to the third surface, and the third lens further includes a sixth surface located between the fifth surface and the fourth surface; the surface types of the fifth surface and the sixth surface are the same; Wherein, one of the optical power of the first lens and the optical power of the adhesive layer lens is positive, and the other is negative.

22. The optical system according to any one of claims 1 to 3, wherein, The at least two lenses include a first lens, a second lens, and a third lens arranged in sequence along the optical axis direction; The first lens includes the first surface and the second surface, the second lens includes the third surface, and the third lens includes the fourth surface; The second lens further includes a fifth surface opposite to the third surface, and the third lens further includes a sixth surface located between the fifth surface and the fourth surface; the surface types of the fifth surface and the sixth surface are the same; Wherein, the dispersion coefficient of at least one of the first lens and the second lens is different from the dispersion coefficient of the adhesive layer lens.

23. A display device, comprising the optical system according to any one of claims 1-22.

Images