Optical system and display apparatus

Abstract

An optical system and a display apparatus. The optical system comprises: a lens component, comprising at least two lenses, and the at least two lenses comprising a first surface, a second surface, a third surface and a fourth surface which are sequentially arranged in an optical axis direction of the lens component; a transflective film, provided on the side of the fourth surface away from the third surface; a polarization reflective layer, provided on the side of the third surface away from the fourth surface; a phase retardation film, located on the side of the fourth surface away from the transflective film; and an adhesive layer, comprising an adhesive-layer lens, at least one of the first surface and the second surface being a Fresnel surface, and the adhesive layer being bonded between the second surface and the third surface. The adhesive layer bonded between the second surface and the third surface comprises the adhesive-layer lens, reflection of light rays by means of the adhesive-layer lens and the Fresnel surface can achieve color aberration correction, and the light rays will not pass through the Fresnel surface during returning processes, thus reducing stray light.

Description

Optical system and display device

[0001] This application claims priority to Chinese Patent Application No. 202311865201.3 filed on December 29, 2023, and the contents of the above-mentioned Chinese patent application disclosure are hereby incorporated by reference in their entirety as a part of this application. Technical Field

[0002] At least one embodiment of the present disclosure relates to an optical system and a display device. Background Art

[0003] With the rapid development of virtual reality (VR) technology, head-mounted displays (HMDs) have become increasingly popular among various display devices due to their high immersiveness, portability, and hands-free operation. As a key component of VR devices, the performance of HMDs is a key factor affecting both imaging quality and cost. Summary of the Invention

[0004] At least one embodiment of the present disclosure provides an optical system and a display device.

[0005] At least one embodiment of the present disclosure provides an 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 the optical axis direction of the lens assembly; a transflective film, disposed on a side of the fourth surface away from the third surface; a polarizing reflective layer, disposed on a side of the third surface away from the fourth surface; a phase delay film, located on a side of the fourth surface away from the transflective film; and an adhesive layer, comprising 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.

[0006] For example, according to at least one embodiment of the present disclosure, the distance between two intersection points of the first surface and the second surface with the optical axis is a first distance; and the ratio of the center thickness of the glue layer lens to the first distance is 1 / 6 to 2.

[0007] For example, according to at least one embodiment of the present disclosure, the center thickness of the gel layer lens is 0.5 mm to 3 mm.

[0008] 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 focal length of the first lens and the optical focal length of the glue layer lens is positive, and the other is negative.

[0009] 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 glue layer lens to the dispersion coefficient of the glue layer lens is a second ratio; the sum of the first ratio and the second ratio is less than 0.

[0010] 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 glue layer lens, the refractive index of the second lens is less than the refractive index of the glue layer lens, and the refractive index of the first lens is less than or equal to the refractive index of the second lens.

[0011] 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 glue layer lens, the dispersion coefficient of the second lens is greater than the dispersion coefficient of the glue layer lens, and the dispersion coefficient of the first lens is greater than or equal to the dispersion coefficient of the second lens.

[0012] 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 glue layer lens, and the refractive index of the first lens is greater than the refractive index of the second lens.

[0013] For example, according to at least one embodiment of the present disclosure, the dispersion coefficient of the first lens is smaller than the dispersion coefficient of the glue layer lens, and the dispersion coefficient of the first lens is smaller than the dispersion coefficient of the second lens.

[0014] For example, according to at least one embodiment of the present disclosure, the ratio of the center thickness to the edge thickness of the first lens is a third ratio, and the ratio of the center 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.

[0015] 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.

[0016] For example, according to at least one embodiment of the present disclosure, the second surface is a convex surface, and the center thickness of the glue layer lens is smaller than the edge thickness.

[0017] 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 smaller than the absolute value of the radius of curvature of the third surface.

[0018] For example, according to at least one embodiment of the present disclosure, the second surface is a convex surface, and a ratio of a radius of curvature of the second surface to an effective focal length of the optical system is -0.5 to -2.

[0019] For example, according to at least one embodiment of the present disclosure, the second surface is a concave surface, and the center thickness of the glue layer lens is greater than the edge thickness.

[0020] For example, according to at least one embodiment of the present disclosure, the distance between the two intersection points of the first surface and the second surface with the optical axis is a first distance; the distance between the two intersection points of the third surface and the fourth surface with the optical axis is a second distance; and the ratio of the second distance to the first distance is 2 to 4.

[0021] For example, according to at least one embodiment of the present disclosure, a ratio of the first distance to the effective focal length of the optical system is 0.1 to 0.3, and a ratio of the second distance to the effective focal length of the optical system is 0.5 to 0.7.

[0022] 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 curvature radius of the first surface to the effective focal length of the optical system is -40 to -50, and the cone coefficient of the first surface is -10 to 0.

[0023] 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 curvature radius of the third surface to the effective focal length of the optical system is -3 to -4, and the cone coefficient of the third surface is -10 to -1.

[0024] For example, according to at least one embodiment of the present disclosure, the fourth surface is convex, the ratio of the curvature radius 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.

[0025] 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 also includes a fifth surface opposite to the third surface, and the third lens also includes a sixth surface located between the fifth surface and the fourth surface; the fifth surface and the sixth surface have the same surface shape; wherein, one of the optical focal length of the first lens and the optical focal length of the glue 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 glue layer lens.

[0026] At least one embodiment of the present disclosure provides a display device, comprising the optical system described in any of the above embodiments. 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, rather than limiting the present disclosure.

[0028] FIG1 is an optical system provided in an example of at least one embodiment of the present disclosure.

[0029] FIG. 2A is a point diagram of the optical system shown in FIG. 1 .

[0030] FIG. 2B is a graph showing how the diffuse spot size of the optical system shown in FIG. 1 changes with the field of view angle.

[0031] FIG. 2C is a diagram of vertical chromatic aberration of the optical system shown in FIG. 1 .

[0032] FIG. 2D is a distortion diagram of the optical system shown in FIG. 1 .

[0033] FIG3 is an optical system provided in an example of at least one embodiment of the present disclosure.

[0034] FIG4A is a schematic diagram of light deflection of a single lens.

[0035] FIG4B is a schematic diagram of light deflection in an example of at least one embodiment of the present disclosure.

[0036] 5 to 9 illustrate optical systems provided by different examples in at least one embodiment of the present disclosure.

[0037] FIG10 is a display device provided as an example in at least one embodiment of the present disclosure. DETAILED DESCRIPTION

[0038] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0039] Unless otherwise defined, technical or scientific terms used in this disclosure should have the ordinary meanings understood by people with ordinary skills in the field to which this disclosure belongs. The words "first", "second" and similar terms used in this disclosure do not indicate any order, quantity or importance, but are simply used to distinguish different components. The words "include" or "comprising" and similar terms mean that the elements or objects preceding the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0040] The features such as "perpendicular", "parallel" and "same" used in this disclosure include the features such as "perpendicular", "parallel" and "same" in the strict sense, as well as the cases where "approximately perpendicular", "approximately parallel" and "approximately the same" include certain errors, taking into account the errors associated with the measurement and the measurement of specific quantities (that is, the limitations of the measurement system), and are expressed as being within the acceptable deviation range for a specific value determined by a person of ordinary skill in the art. The "center" in the embodiments of the present disclosure can include a position strictly at the geometric center and a position approximately at the center of a small area around the geometric center. For example, "approximately" can mean within one or more standard deviations, or within 10% or 5% of the value.

[0041] In near-eye display optical systems, especially in some head-mounted display optical systems that use 4K high-definition display screens of inch level or smaller size combined 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 correction of chromatic aberration can be used in the later stage to reduce the impact of the inherent chromatic aberration of the optical system on the optical performance. In the study, the inventors of this application found that compared with the method of using digital correction of chromatic aberration, the chromatic aberration problem can be solved more fundamentally by using optical design methods to eliminate chromatic aberration in the early research and development stage of the optical system.

[0042] At least one embodiment of the present disclosure provides an 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 the optical axis direction of the lens assembly; a transflective film, disposed on a side of the fourth surface away from the third surface; a polarizing reflective layer, disposed on a side of the third surface away from the fourth surface; a phase delay film, located on a side of the fourth surface away from the transflective film; and an adhesive layer, comprising 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-mentioned optical system.

[0044] At least one embodiment of the present disclosure provides an optical system and display device that, by providing a lens assembly comprising at least two lenses, provides attachment locations for a transflective film, a polarizing reflective layer, and a phase retardation film, enabling light to be refracted between the transflective film and the polarizing reflective layer. The adhesive layer bonded between the second and third surfaces includes an adhesive lens that, together with the Fresnel surface, refracts light to correct chromatic aberration. Furthermore, after exiting the polarizing reflective layer and entering the Fresnel surface, light does not pass through the Fresnel surface during the refracting process, thereby reducing stray light.

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

[0046] FIG1 is an optical system provided in an example of at least one embodiment of the present disclosure.

[0047] Referring to FIG1 , at least one embodiment of the present disclosure provides an optical system comprising a lens assembly 100, which includes a transflective film 200, a polarizing reflective layer 300, a phase retarder film 400, and an adhesive layer. The lens assembly 100 includes at least two lenses. For example, as shown in FIG1 , the lens assembly 100 can be composed of two lenses, lens 110 and lens 120. For example, the adhesive layer is a light-transmitting adhesive layer.

[0048] As shown in FIG1 , at least two lenses include a first surface 101, a second surface 102, a third surface 103, and a fourth surface 104, arranged sequentially along the optical axis OA of the lens assembly 100. For example, the side of the first surface 101 facing away from the fourth surface 104 serves as the light-emitting side of the optical system. For example, when the optical system is used in a display device, the display screen may be located on the side of the fourth surface 104 of the optical system facing away from the first surface 101, with light emitted from the display screen entering through the fourth surface 104 and exiting through the first surface 101.

[0049] As shown in FIG1 , the transflective film 200 is disposed on the side of the fourth surface 104 away from the third surface 103. The polarizing reflective layer 300 is disposed on the side of the third surface 103 away from the fourth surface 104. The phase retarder film 400 is located on the side of the fourth surface 104 away from the transflective film 200. For example, light incident on the lens assembly 100 after being transmitted through the transflective film 200 is configured to be folded back between the transflective film 200 and the polarizing reflective layer 300 and emitted from the polarizing reflective layer 300, thereby forming a folded optical path through the polarizing reflective layer 300, the transflective film 200, and the phase retarder film 400.

[0050] As shown in FIG1 , the adhesive layer includes an adhesive lens 130, which is bonded between the second surface 102 and the third surface 103. For example, the adhesive layer has adhesive properties, enabling bonding between the second surface 102 and the third surface 103. Furthermore, the adhesive layer includes an adhesive lens 130 located between the second surface 102 and the third surface 103. The adhesive lens is formed using the adhesive layer. This utilizes the material difference between the adhesive lens 130 and the lens to refract light when it enters or exits the adhesive lens 130, thereby correcting chromatic aberration.

[0051] As shown in Figure 1, at least one of the first surface 101 and the second surface 102 is a Fresnel surface. A Fresnel surface refers to the non-smooth surface of the two opposing surfaces of a Fresnel lens. For example, the first surface 101 and the second surface 102 may be opposing surfaces of a lens, in which case the lens may be a Fresnel lens. A Fresnel lens, also known as a threaded lens, has a smooth surface on one side and a plurality of concentric circular patterns (also known as Fresnel zones) on the other side. These patterns can change the degree of refraction of light, effectively reducing the thickness of the Fresnel lens at short focal lengths.

[0052] For example, referring to Figure 1 , the second surface 102 can be configured as a Fresnel surface. For example, the adhesive layer can be made of a material with a relatively low hardness. By providing a Fresnel surface bonded to the adhesive layer, the adhesive layer can improve the bonding strength between the lens and the adhesive layer on either side. Furthermore, the adhesive layer can buffer external stresses, preventing damage to the serrated structure of the Fresnel surface. Furthermore, configuring the second surface 102 as a Fresnel surface can reduce the amount of adhesive material used between the second surface 102 and the third surface 103 through the serrated structure of the Fresnel surface, thereby reducing costs. Furthermore, when the first surface 101 is smooth (no Fresnel surface is provided), it can facilitate the attachment of a film layer. For example, an anti-reflective film can be attached to the first surface 101.

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

[0054] The optical system disclosed herein utilizes a lens assembly comprising at least two lenses, providing attachment locations for a transflective film, a polarizing reflective layer, and a phase retardation film, enabling light to be refracted between the transflective film and the polarizing reflective layer. The adhesive layer bonded between the second and third surfaces includes an adhesive lens that, together with the Fresnel surface, refracts light to correct chromatic aberration. Furthermore, the Fresnel surface enhances design freedom, and after exiting the polarizing reflective layer and entering the Fresnel surface, light does not pass through the Fresnel surface during the refracting process, reducing stray light.

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

[0056] For example, the adhesive layer can be made of optical adhesive. For example, the lens assembly can be made of an optically transparent inorganic polymer or glass. Thus, the adhesive layer lens is made of a different material than the lenses on either side, allowing for chromatic aberration correction by exploiting differences in refractive index and dispersion coefficient between the materials. For example, the adhesive layer can also be made of silicone, whose superior fluidity facilitates processing.

[0057] For example, referring to FIG1 , the optical system further includes a linear polarizing film 500, which is disposed on a side of the polarizing reflective layer 300 away from the transflective film 200. For example, an adhesive layer can be bonded between the linear polarizing film 500 and the second surface 102. For example, the linear polarizing film 500 can be a linear polarizer or a polarizer. For example, the optical axis OA of the linear polarizing film 500 coincides with the optical axis OA of the polarizing reflective layer 300. The linear polarizing film 500 can be used to further filter out other stray light, allowing only polarized light (such as s-polarized light) that passes through the linear polarizing film 500 to enter the human eye. For example, the linear polarizing film can have a three-layer laminate structure, in which the middle layer can be polyvinyl alcohol (PVA) with added dichroic molecules, and at least one layer on either side of the middle layer in the three-layer laminate structure can be triacetate (TAC). For example, the surface of the linear polarizing film facing the air is treated with anti-reflection treatment. For example, the surface of the linear polarizing film facing the air can be attached to a moth-eye film.

[0058] For example, referring to Figure 1 , the transflective film 200 is configured to transmit some light and reflect another portion of light. For example, the transflective film may have a transmittance of 50% and a reflectance of 50%. For example, the transflective film may have a transmittance of 60% and a reflectance of 40%. For example, the transflective film may have a transmittance of 65% and a reflectance of 35%. The optical system provided herein is not limited to this, and the transmittance and reflectance of the transflective film may be configured based on product requirements. For example, the transflective film may be coated on the fourth surface.

[0059] For example, referring to FIG1 , the polarizing reflective layer 300 functions as follows: an optical axis OA exists within the plane of the film layer, the transmittance of the polarization component of the incident light parallel to the optical axis OA (e.g., s-polarized light) is greater than the transmittance of the polarization component perpendicular to the optical axis OA (e.g., p-polarized light), and the reflectivity of the polarization component parallel to the optical axis OA (e.g., s-polarized light) is less than the reflectivity of the polarization component perpendicular to the optical axis OA (e.g., p-polarized light). For example, the transmittance of polarized light parallel to the optical axis of the polarizing reflective layer is not less than 85%, such as not less than 90%, such as not less than 95%, such as not less than 98%; and the reflectivity of polarized light perpendicular to the optical axis of the polarizing reflective 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 FIG1 , the polarizing reflective layer 300 is configured to reflect linearly polarized light of one characteristic and transmit linearly polarized light of another characteristic. The polarizing reflective layer 300 can be disposed on a side of the third surface 103 away from the fourth surface 104 , and the phase retarder film 400 can be disposed between the polarizing reflective layer 300 and the transflective film 200 . For example, the polarizing reflective layer can also be referred to as a polarizing beam splitter film. For example, the polarizing reflective layer can also include a multilayer reflective polarizer (Advanced Polarizer Film, APF). For example, the polarizing reflective layer can also include an IQPS (Image Quality Polarizer Standard) film or an IQPE (Image Quality Polarizer Enhanced) film.

[0061] For example, the polarizing reflective layer is a cholesteric liquid crystal layer (not shown in the figure), and the phase retarder film is disposed on the side of the cholesteric liquid crystal layer away from the transflective film. For example, cholesteric liquid crystals can reflect circularly polarized light and transmit circularly polarized light. Referring to the aforementioned principle of folded optical paths, the cholesteric liquid crystal layer is disposed between the phase retarder film and the transflective film. A wave plate can be disposed on the display surface side of the display screen located on the 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 transflective film. After passing through the transflective film, the polarization state of the right-handed circularly polarized light remains unchanged. After passing through the cholesteric liquid crystal layer, the right-handed circularly polarized light is reflected back to the transflective film, where a first reflection occurs; the right-handed circularly polarized light is reflected at the transflective film, where a second reflection occurs. Due to 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 the cholesteric liquid crystal layer and reaches the phase delay film, where it is converted into s-polarized light. The s-linearly polarized light then passes through the linear polarization film and is emitted to the human eye.

[0062] For example, referring to FIG1 , the phase retarder film 400 is configured to convert the transmitted light between a circularly polarized state and a linearly polarized state. For example, the phase retarder film can be a quarter-wave plate. For example, the phase retarder film 400 can have the following characteristics: within the plane of the film layer, there exists a direction with the lowest refractive index and a direction with the highest refractive index, which are respectively the fast axis and the slow axis. After passing through the phase retarder film, the phase of polarized light parallel to the slow axis is delayed by 1 / 4 wavelength compared to polarized light parallel to the fast axis after passing through the phase retarder film. For example, the angle between the slow axis of the phase retarder film and the optical axis of the polarizing reflective layer is 45 degrees.

[0063] For example, referring to Figure 1 , the material of the phase retarder film 400 can include a liquid crystal polymer. Phase retarder films made of liquid crystal polymers are relatively thinner, with film thicknesses ranging from 1μm to 5μm. Thinner phase retarder films are more adaptable to curved surfaces, allowing them to more easily conform to the surface shape, reducing the possibility of wrinkles when attached to the curved surface, which could affect phase retarder accuracy and optical performance. Furthermore, phase retarder films made of liquid crystal polymers experience less optical shift when attached to a curved surface. Liquid crystal polymers are cross-linked systems, with molecules linked by chemical bonds and a high modulus. When a phase retarder film made of this material is stretched after attachment, only elastic deformation occurs, without strong optical anisotropy effects such as molecular stretching and rearrangement. Therefore, phase retarder films made of liquid crystal polymers are suitable for attachment to surfaces with a small radius of curvature. This flexibility in curvature radius also makes it easier to meet requirements for clarity, distortion, and dispersion, contributing to better image quality in 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 transflective film, a polarizing reflective layer, and a phase retardation film. The arrangement of the transflective film, the polarizing reflective layer, and the phase retardation film can be referred to in the above examples and will not be further described here. Thus, the second optical element can achieve light refraction.

[0065] For example, the adhesive layer lens can be glued between the first optical element and the second optical element. It is understandable that, depending on the different setting positions of the polarizing reflective layer, phase delay film or other film layers, the adhesive layer can be glued between the second surface and different film layers. For example, when no linear polarizing film is provided in the second optical element, and the phase delay film is provided between the polarizing reflective layer and the third surface, the adhesive layer can be glued between the polarizing reflective layer and the second surface. For example, when no linear polarizing film is provided in the second optical element, and the phase delay film is provided on the side of the polarizing reflective layer (for example, the polarizing reflective layer is a cholesteric liquid crystal layer) away from the transflective film, the adhesive layer can be glued between the phase delay film and the second surface. For example, when a linear polarizing film is provided in the second optical element, the adhesive layer can be glued between the second surface and the linear polarizing film.

[0066] For example, referring to Figure 1 , when the optical system is applied to a display device, the principle of folding the optical path is as follows: a wave plate can be provided on the light-emitting side of the display screen's display surface, located on the side of the fourth surface 104 facing away from the first surface 101. Image light emitted from the display surface is converted to right-handed circularly polarized light after passing through the wave plate. The polarization state of the right-handed circularly polarized light remains unchanged after passing through the transflective film 200. This light enters the phase retarder film 400 after transmission. The right-handed circularly polarized light incident on the phase retarder film 400 is converted to p-linearly polarized light. The p-linearly polarized light is reflected back to the phase retarder film 400 by the polarizing reflective layer 300, where the first reflection occurs. Subsequently, the p-linearly polarized light is converted to right-handed circularly polarized light after passing through the phase retarder film 400. This right-handed circularly polarized light then passes through the transflective film 200 and is reflected there, where the second reflection occurs. Due to 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 reaches the phase retarder film 400 after being transmitted, and becomes s-linearly polarized light after passing through the phase retarder film 400. The s-linearly polarized light then passes through the polarizing reflective layer 300 and is emitted toward the exit pupil, such as the human eye.

[0067] The folded optical path can change the polarization state of light propagating between the polarizing reflective layer 300 and the transflective film 200, thereby folding the light. This causes the original focal length of the optical system to be folded due to, for example, two additional reflections caused by the provision of the polarizing reflective layer 300, the phase delay film 400, and the transflective film 200. This greatly reduces the space required between the human eye and the optical system, thereby making the optical system smaller and thinner.

[0068] Fig. 2A is a spot diagram of the optical system shown in Fig. 1. Fig. 2B is a graph showing how the diffuse spot size of the optical system shown in Fig. 1 changes with the field of view angle.

[0069] Referring to Figure 2A, a spot diagram refers to the pattern of scattered light rays emitted from a single point. After passing through an optical system, due to aberrations, their intersections with the image plane no longer converge at the same point, but rather form a diffuse pattern distributed over a certain range. This pattern can be used to evaluate the imaging quality of an optical system. In Figure 2A, 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 of view angle in the X direction, and 45.00 represents the field of view angle in the Y direction. In Figure 2A, 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 diffusion point to the centroid (or center) of the diffuse spot, and 100% represents the diameter of the diffuse spot. Figure 2A is typically used to evaluate the full-field clarity of an optical system. This refers to the image clarity across the entire field of view covered by the peripheral vision when the human pupil is at the entrance pupil position on the optical axis OA and looking at the center of the lens (i.e., zero field of view). This is also known as the transient mode. In addition to considering full-field clarity in transient mode, gaze point clarity is an even more important optical indicator for wearers of head-mounted displays. Gaze point clarity refers to the image clarity within a specific angle range that the eye can directly see (not just peripheral vision) as it moves up, down, left, or right.

[0070] In the gaze point mode, the eyeball rotates a certain angle, and the pupil deviates from the center of the optical axis OA. It deviates a certain amount from the optical axis OA in the Z and Y directions, and the main light passing through the center of the pupil has a certain angle with the Z axis. For example, the range of the angle is ±35 degrees. The range of the angle is set taking into account the observation habits of the human eye. In order to see the objects in front that are more than 35 degrees beyond the center of the human eye, people will actively turn their heads instead of laboriously turning their eyeballs. Referring to Figure 2B, Figure 2B shows the relationship between the clarity of the gaze point and the gaze angle. The diffuse spot of the central field of view is much smaller than a pixel, and the diameter of the diffuse spot when the human eye rotates to 20 degrees is less than 5 microns. As can be seen from Figure 2B, the diffuse 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 seen that the optical system provided by at least one embodiment of the present disclosure can form clear images.

[0071] FIG2C is a diagram of the vertical chromatic aberration of the optical system shown in FIG1 . Referring to FIG2C , the diagram of the vertical chromatic aberration represents the height difference of each wavelength relative to the center wavelength at different image heights on the imaging surface. The horizontal axis represents the vertical chromatic aberration value of each wavelength relative to the center wavelength, and the vertical axis represents the normalized field of view angle. As shown in FIG2C , R light is red light, G light is green light, and B light is blue light. R light and B light are located at the two ends of the sensitive area of ​​the human eye, and G light is located in the middle close to the spectrum line to which the human eye is most sensitive. As can be seen from FIG2C , the absolute value of the vertical chromatic aberration of B light and R light is controlled within 0.05 mm, and the absolute value of the vertical chromatic aberration of B light and G light is controlled within 0.025 mm. It can be seen that, for example, the optical system shown in FIG1 can excellently correct the chromatic aberration of the edge field of view and the secondary spectrum of the entire image surface.

[0072] Figure 2D is a distortion diagram for the optical system shown in Figure 1. Referring to Figure 2D , the distortion diagram reflects the differences in image plane position for sharp images in different fields of view. As shown in Figure 2D , the maximum absolute value of distortion is within 35%. This demonstrates that the optical system provided by at least one embodiment of the present disclosure can effectively correct distortion and meet high-quality imaging requirements. Furthermore, distortion correction can be pre-processed in software.

[0073] FIG3 is an optical system provided in an example of at least one embodiment of the present disclosure.

[0074] The difference between the optical system shown in FIG3 and the optical system shown in FIG1 is that the second surface 102 and the adhesive layer lens 130 in the optical system shown in FIG3 are different from the second surface 102 and the adhesive layer lens 130 in the optical system shown in FIG1. ​​Of course, the optical system shown in FIG3 may also have other differences from the optical system shown in FIG1, such as the number of lenses, etc., and the present disclosure does not limit this. For example, the number of lenses in the optical system shown in FIG3 may be different from or the same as the number of lenses in the optical system shown in FIG1. ​​The transflective film 200, polarizing reflective layer 300, phase delay film 400, and linear polarizing film 500 in the optical system shown in FIG3 may have the same features as the transflective film 200, polarizing reflective layer 300, phase delay film 400, and linear polarizing film 500 in the optical system shown in FIG1, and will not be repeated here.

[0075] For example, the adhesive layer lens 130 shown in FIG1 is a concave lens. In the optical system shown in FIG1 , the adhesive layer lens 130 can be made of optical adhesive. For example, the adhesive layer lens 130 shown in FIG3 is a convex lens. When the adhesive layer lens 130 is a convex lens, the center thickness of the adhesive layer lens 130 is greater than the edge thickness, requiring more material. In the optical system shown in FIG3 , the adhesive layer lens 130 can be made of optical-grade silicone material, thereby reducing costs and facilitating processing. For example, the center thickness of the adhesive layer lens 130 can be the distance between the two intersection points where two opposite surfaces of the adhesive layer lens 130 intersect with the optical axis OA. For example, the second surface 102 shown in FIG1 is a convex surface. For example, the second surface 102 shown in FIG3 is a concave surface.

[0076] With reference to Figures 1 and 3, in some examples, the distance between the two intersection points of the first surface 101 and the second surface 102 with the optical axis OA is a first distance D1, and the ratio of the center 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 center thickness d of the adhesive layer lens 130 to the first distance D1, the adhesive layer can be made to fill the space 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 made to fill the serrations of the Fresnel surface, thereby providing a surface shape complementary to that of the second surface 102 on the side of the adhesive layer lens bonded to the second surface 102.

[0077] For example, referring to FIG1 , the ratio of the center thickness d of the glue layer lens 130 to the first distance D1 may be 1 / 6 to 1 / 4. For example, referring to FIG1 , the ratio of the center thickness d of the glue layer lens 130 to the first distance D1 may be 1 / 4 to 1 / 2. For example, referring to FIG3 , the ratio of the center thickness d of the glue layer lens 130 to the first distance D1 may be 1 / 2 to 2.

[0078] In some optical systems, the adhesive layer used to bond two lenses together is typically thin, typically ranging in thickness from tens to several dozen microns. Referring to Figures 1 and 3 , in some examples, the center thickness d of the adhesive layer lens 130 can be 0.5 mm to 3 mm. Providing a thicker adhesive layer allows the adhesive layer to fill the space 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 fill the serrations of the Fresnel surface. For example, referring to Figure 1 , the center thickness d of the adhesive layer lens 130 can be 0.5 mm to 0.8 mm. For example, referring to Figure 1 , the center thickness d of the adhesive layer lens 130 can be 0.8 mm to 1 mm. For example, referring to Figure 3 , the center thickness d of the adhesive layer lens 130 can be 1 mm to 1.5 mm. For example, referring to Figure 3 , the center thickness d of the adhesive layer lens 130 can be 1.5 mm to 2 mm. For example, referring to Figure 3 , the center thickness d of the adhesive layer lens 130 can be 2 mm to 2.5 mm. For example, referring to FIG. 3 , the center thickness d of the gel layer lens 130 may be 2.5 mm to 3 mm.

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

[0080] Referring to Figures 1 and 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 limiting ring of the mold and then glue is poured. A step portion can be provided in the limiting ring to limit the amount of glue poured while limiting the lens, preventing too much or too little glue. Taking the second surface 102 of the first lens 110 as a Fresnel surface as an example, when pouring glue, it is necessary to ensure that the colloid fills the inter-tooth gaps of the tooth-shaped structure on the Fresnel surface. Afterwards, the other lens (for example, the second lens 120) can be placed on the step portion of the limiting ring, and pressure is applied so that excess colloid can be discharged from the glue discharge hole opened on the limiting ring. At the same time, the glue discharge hole can also be used to discharge the gas inside the colloid. After the excess colloid is discharged, it can be glued and fixed by heating or ultraviolet irradiation.

[0081] With reference to Figures 1 and 3, in some examples, the distance between the two intersection points of the first surface 101 and the second surface 102 with the optical axis OA is a first distance D1, and the distance between the two intersection points of the third surface 103 and the fourth surface 104 with the optical axis OA is a second distance D2. For example, the first distance D1 is the center thickness of the first lens 110, and the second distance D2 is the center 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] 1 and 3 , in some examples, the ratio of the first distance D1 to the effective focal length of the optical system may be 0.1 to 0.3. For example, the ratio of the first distance D1 to the effective focal length of the optical system may be 0.15 to 0.25. For example, the ratio of the first distance D1 to the effective focal length of the optical system may be 1.2. In some examples, the ratio of the second distance D2 to the effective focal length of the optical system may be 0.5 to 0.7. For example, the ratio of the second distance D2 to the effective focal length of the optical system may be 0.55 to 0.65. For example, the ratio of the second distance D2 to the effective focal length of the optical system may be 0.6.

[0083] Referring to Figures 1 and 3 , in some examples, the optical power of the first lens 110 or the optical power of the adhesive layer lens 130 is positive, while the other is negative. Thus, by setting the optical power of the first lens 110 and the optical power of the adhesive layer lens 130 to positive and negative values, chromatic aberration can be corrected.

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

[0085] Figure 4A illustrates the deflection of light in a single lens. As shown in Figure 4A, the single lens L is a convex lens, with the side away from the target surface S0 as the light incident side, that is, the light enters the single lens L from the left side of Figure 4A and is emitted from the single lens L to the target surface S0 after refraction. After the white light (the solid line shown in Figure 4A) enters the single lens L, the white light is dispersed and decomposed into monochromatic lights of different wavelengths. Figure 4A uses a short dash line to indicate the red light R with a longer wavelength and a dotted line to indicate the blue light B with a shorter wavelength. As can be seen from Figure 4A, the wavelength of the blue light B is shorter and the wavelength of the red light R is longer, which will make it difficult to converge on the target surface S0 after passing through the single lens L.

[0086] Figure 4B illustrates the deflection of light in the optical system when the focal power of lens L1 and the focal power of lens L2 in the lens assembly are positive and negative. As shown in Figure 4B, the side away from the target surface S0 is the light incident side, that is, the light enters the lens assembly from the left side of Figure 4B and is emitted from the lens assembly to the target surface S0 after refraction. After white light (the solid line shown in Figure 4B) enters the lens assembly, the white light is dispersed and decomposed into monochromatic lights of different wavelengths. Figure 4B shows the red light R with a longer wavelength as a short dash line and the blue light B with a shorter wavelength as a dotted line. By setting the focal power of lens L1 and the focal power of lens L2 to one positive and one negative, the deflection angles of red light R and blue light B change, and ultimately the red light R and blue light B can converge on the target surface S0.

[0087] For example, referring to Figure 4B , lens L1 is a convex lens with positive power, while lens L2 is a concave lens with negative power. After incident light enters lens L1 and is dispersed, the shorter-wavelength blue light B deviates further toward the optical axis OA than the red light R. Because lens L2 has a negative power, upon exiting lens L2, the red light R and blue light B converge on target surface S0, thereby 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. Furthermore, the adhesive layer lens 130 being a concave lens requires less adhesive layer material. For example, the second surface 102 of the first lens 110 is a Fresnel surface, and the adhesive layer bonds the Fresnel surface to the second lens 120. The toothed structure of the Fresnel surface reduces the amount of adhesive layer required, thereby reducing costs. Furthermore, configuring the first lens 110 as a convex lens and the adhesive layer lens 130 as a concave lens can also make the optical system thinner and lighter.

[0089] For example, referring to FIG3 , the first lens 110 can be a concave lens, and the adhesive layer lens 130 can be a convex lens. This allows the optical power of the first lens 110 to be negative and the optical power of the adhesive layer lens 130 to be positive, thereby correcting chromatic aberration. Furthermore, the center thickness of the convex adhesive layer lens 130 is thicker, ensuring that an adhesive layer is provided between the center of the first lens 110 and the center of the second lens 120.

[0090] In some examples, referring to FIG. 1 , the ratio of the optical power of the first lens 110 to the Abbe number of the first lens 110 is a first ratio, and the ratio of the optical power of the adhesive layer lens 130 to the Abbe number of the adhesive layer lens 130 is a second ratio. The sum of the first ratio and the second ratio is less than 0. Thus, chromatic aberration can be corrected using the combined positive and negative optical powers of the first lens 110 and the adhesive layer lens. Simultaneously, the residual optical power of the first lens 110 and the adhesive layer lens can offset at least a portion of the optical power of the second lens 120, resulting in a more effective correction of chromatic aberration.

[0091] In some examples, referring to FIG1 , the refractive index of the first lens element 110 is less than that of the adhesive lens 130, the refractive index of the second lens element 120 is less than that of the adhesive lens 130, and the refractive index of the first lens element 110 is less than or equal to that of the second lens element 120. By setting the first lens element 110, the second lens element 120, and the adhesive lens 130 to different refractive indices, the deflection angles of light of different wavelengths (e.g., red light and blue light) after dispersion of white light can be varied, allowing light of different wavelengths to converge after exiting the lens assembly 100, thereby correcting chromatic aberration. Furthermore, the refractive index of the first lens element 110 can be relatively close to that of the second lens element 120. Light is deflected in the first and second lens elements 110, 120, where the refractive index difference is smaller. Light reflection loss is less than 2% of the reflection loss at the lens-air interface, thereby improving optical efficiency.

[0092] Because the same transparent medium has different refractive indices for light of different wavelengths, and white light is composed of various colors of light at different wavelengths, dispersion occurs when a transparent medium refracts white light. The dispersion coefficient (also known as the Abbe number) is an index used to indicate the dispersion capacity of a transparent medium and measures the degree of light dispersion within the medium. Generally speaking, the greater the medium's refractive index, the greater the dispersion and the smaller the Abbe number; conversely, the smaller the medium's refractive index, the less dispersion and the larger the Abbe number.

[0093] In some examples, referring to FIG1 , the Abbe coefficient of the first lens 110 is greater than the Abbe coefficient of the adhesive layer lens 130, the Abbe coefficient of the second lens 120 is greater than the Abbe coefficient of the adhesive layer lens 130, and the Abbe coefficient of the first lens 110 is greater than or equal to the Abbe 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 Abbe coefficients, the deflection angles of light rays of different wavelengths (e.g., red light and blue light) after the white light is dispersed can be changed, so that light rays of different wavelengths can converge after exiting the lens assembly 100, thereby correcting chromatic aberration.

[0094] For example, referring to Figure 1, the dispersion coefficient of the first lens 110 can be set to be much larger than the dispersion coefficient of the glue layer lens 130, the dispersion coefficient of the second lens 120 can be set to be much larger than the dispersion coefficient of the glue layer lens 130, and the dispersion coefficient of the first lens 110 can be set to be greater than or equal to the dispersion coefficient of the second lens 120.

[0095] In some examples, referring to FIG3 , 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 of different wavelengths (e.g., red light and blue light) can be changed after the white light is dispersed, so that light of different wavelengths can converge after exiting the lens assembly 100, thereby correcting chromatic aberration.

[0096] For example, referring to FIG3 , the refractive index of the first lens 110 can be set to be greater than the refractive index of the adhesive layer lens 130 , and the refractive index of the second lens 120 can be set to be close to the refractive index of the adhesive layer lens 130 to facilitate correction of chromatic aberration.

[0097] In some examples, referring to FIG3 , the Abbe coefficient of the first lens 110 is smaller than the Abbe coefficient of the adhesive lens 130, and the Abbe coefficient of the first lens 110 is also smaller than the Abbe coefficient of the second lens 120. By setting the first lens 110, the second lens 120, and the adhesive lens 130 to have different Abbe coefficients, the deflection angles of light of different wavelengths (e.g., red light and blue light) can be changed after the white light is dispersed, so that light of different wavelengths can converge after exiting the lens assembly 100, thereby correcting chromatic aberration.

[0098] For example, referring to FIG3 , the dispersion coefficient of the first lens 110 can be set to be much smaller than the dispersion coefficient of the adhesive layer lens 130 , and at the same time, the dispersion coefficient of the second lens 120 can be set to be relatively close to the dispersion coefficient of the adhesive layer lens 130 to facilitate correction of chromatic aberration.

[0099] For example, referring to FIG1 or FIG3 , the Abbe number of the first lens 110 may be 50 to 60. For example, the Abbe number of the first lens may be 54 to 56. For example, the Abbe number of the adhesive layer lens 130 may be 30 to 40. For example, the Abbe number of the adhesive layer lens may be 34 to 36. For example, the Abbe number of the second lens may be 50 to 60. For example, the Abbe number of the second lens may be 55 to 57. For example, the Abbe number of the second lens may be 56.5.

[0100] For example, referring to FIG1 or FIG3 , the refractive index of the first lens 110 may be 1.4 to 1.5. For example, the refractive index of the first lens may be 1.41 to 1.49. For example, the refractive index of the first lens may be 1.42 to 1.48. For example, the refractive index of the first lens may be 1.45. For example, the refractive index of the second lens 120 may be 1.5 to 1.6. For example, the refractive index of the second lens may be 1.54 to 1.56. For example, the refractive index of the first lens may be 1.49, and the refractive index of the second lens may be 1.54. For example, the refractive index of the glue layer lens may be 1.5 to 1.6. For example, the refractive index of the glue layer lens may be 1.53 to 1.57.

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

[0102] In some examples, referring to FIG1 or FIG3 , the ratio of the center thickness to the edge thickness of the first lens 110 is a third ratio, and the ratio of the center 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 center thickness to the edge thickness of the first lens may be 1 to 3. For example, the ratio of the center thickness to the edge thickness of the first lens may be 2 to 2.5. For example, the ratio of the center thickness to the edge thickness of the second lens 120 may be 1 to 3. For example, the ratio of the center thickness to the edge thickness of the second lens may be 2 to 2.5. By setting the proportional relationship between the center thickness and the edge thickness of each of the above lenses, it is helpful to ensure the injection molding of each lens.

[0103] In some examples, the first surface can be a plane. For example, referring to FIG1 , the second surface 102 can be configured as a convex surface, such that the first lens element 110 is a convex lens and the adhesive layer lens 130 is a concave lens, thereby correcting chromatic aberration. For example, referring to FIG3 , the second surface 102 can be configured as a concave surface, such that the first lens element 110 is a concave lens and the adhesive layer lens 130 is a convex lens, thereby correcting chromatic aberration.

[0104] FIG. 5 shows an optical system provided in an example of at least one embodiment of the present disclosure.

[0105] The difference between the optical system shown in FIG5 and the optical system shown in FIG1 is that the first surface 101 in the optical system shown in FIG5 is different from the first surface 101 in the optical system shown in FIG1. ​​Of course, the optical system shown in FIG5 may also have other differences from the optical system shown in FIG1, such as the number of lenses, etc., and the present disclosure does not limit this. For example, the number of lenses in the optical system shown in FIG5 may be different from or the same as the number of lenses in the optical system shown in FIG1. ​​The transflective film 200, polarizing reflective layer 300, phase delay film 400, and linear polarizing film 500 in the optical system shown in FIG5 may have the same features as the transflective film 200, polarizing reflective layer 300, phase delay film 400, and linear polarizing film 500 in the optical system shown in FIG1, and will not be repeated here.

[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 to a convex surface, so that the first lens 110 is a convex lens and the gel layer lens 130 is a concave lens, thereby correcting chromatic aberration.

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

[0108] For example, in the above formula, the height of the aspheric surface along the direction perpendicular to the optical axis OA is Y, the distance between the aspheric vertex and the projection of the aspheric surface at a height of Y on the optical axis OA is z, that is, z is the coordinate along the optical axis OA; C is the curvature (the inverse of the curvature radius R), k is the conic constant, α i is the coefficient of each higher-order term, and 2i is the order of Aspherical Coefficient.

[0109] When optimizing the proper configuration of lens assembly parameters, the curvature radius, conic coefficient, height, and aspheric coefficient of each lens element in the lens assembly are incorporated into the aforementioned numerical formulas, and optical simulations are performed to obtain the optimized parameters that can correct the aberrations of each lens element in the lens assembly. The optimization process yields the preferred values ​​for the curvature radius, thickness along the optical axis OA, effective aperture, and conic coefficient of each lens element in the lens assembly.

[0110] 5 , the ratio of the radius of curvature of the first surface 101 to the effective focal length of the optical system may be -40 to -50, and the conic coefficient of the first surface 101 may 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 may 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 may 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 may be -45. For example, the conic coefficient of the first surface may be -9 to -0.5. For example, the conic coefficient of the first surface may be -8 to -2. For example, the conic coefficient of the first surface may be -6 to -4. For example, the conic coefficient of the first surface may be -5.

[0111] Of course, in other examples, the first surface can be set as a concave surface, and by changing the surface parameters of the second surface, the first lens can be made convex or concave, and the adhesive layer lens can be made concave or convex accordingly. As long as the surface parameters of each surface can be set so that the optical power of the first lens and the optical power of the adhesive layer lens are positive or negative, this disclosure is not limited to this.

[0112] In some examples, referring to Figures 1, 3, and 5, the second surface 102 is a curved Fresnel surface. For example, the second surface 102 can be a convex Fresnel surface (see Figures 1 and 5) or a concave Fresnel surface (see Figure 3), and this disclosure is not limited thereto.

[0113] In some examples, referring to FIG. 1 or FIG. 5 , second surface 102 is convex, and the center thickness of gel layer lens 130 is smaller than the edge thickness. When second surface 102 is convex, by setting the center thickness of gel layer lens 130 to be smaller than the edge thickness, gel layer lens 130 can be formed into a concave lens, thereby cooperating with first lens element 110, which is a convex lens, to correct chromatic aberration.

[0114] In some examples, referring to FIG. 1 or FIG. 5 , second surface 102 is convex, and the absolute value of the radius of curvature of second surface 102 is smaller than the absolute value of the radius of curvature of third surface 103. Thus, the curvature of third surface 103 is smaller, while the curvature of second surface 102 is larger. As a result, the gel layer lens 130 between second surface 102 and third surface 103 is thinner in the middle and thicker at the edges, forming a concave lens.

[0115] The surface shape of the curved Fresnel surface can be approximated as an aspherical surface, as can be seen from the aforementioned aspherical surface shape formula. 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 a Fresnel surface including a toothed structure. For example, the second surface 102 of the Fresnel surface can be approximated as a smooth, toothless spherical or aspherical surface, and the curvature of the spherical 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.

[0116] In some examples, referring to FIG3 , the second surface 102 is concave, and the center thickness of the adhesive layer lens 130 is greater than the edge thickness. When the second surface 102 is concave, by setting the center 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, thereby cooperating with the first lens element 110, which has concave lens properties, to correct chromatic aberration.

[0117] FIG6 is an optical system provided in an example of at least one embodiment of the present disclosure.

[0118] The difference between the optical system shown in FIG6 and the optical system shown in FIG1 is that the second surface 102, the adhesive lens 130, and the third surface 103 in the optical system shown in FIG6 are different from the second surface 102, the adhesive lens 130, and the third surface 103 in the optical system shown in FIG1. ​​Of course, the optical system shown in FIG6 may also have other differences from the optical system shown in FIG1, such as the number of lenses, etc., and the present disclosure does not limit this. For example, the number of lenses in the optical system shown in FIG6 may be different from or the same as the number of lenses in the optical system shown in FIG1. ​​The transflective film 200, the polarizing reflective layer 300, the phase delay film 400, and the linear polarizing film 500 in the optical system shown in FIG6 may have the same features as the transflective film 200, the polarizing reflective layer 300, the phase delay film 400, and the linear polarizing film 500 in the optical system shown in FIG1, and no further details will be given here.

[0119] In some examples, referring to FIG6 , the second surface 102 is a planar Fresnel surface. For example, the second surface 102 can be set as a planar Fresnel surface, and 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 a concave lens, thereby correcting chromatic aberration. For example, the phase retarder 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, the attachment of the phase retarder film 400 can be facilitated, reducing the probability of wrinkles during attachment. For example, the second surface can also be set as a convex Fresnel surface, while the third surface can also be set as a convex surface, so that the adhesive layer lens is a concave lens. This disclosure is not limited to this.

[0120] For example, a continuous curved surface can be discretized and then a discretized spherical or aspheric curvature can be superimposed to obtain a curved Fresnel surface with a curved base surface (for example, see Figures 1, 3, and 5). For example, a continuous curved surface can be discretized to obtain a planar Fresnel surface with a planar base surface (for example, see Figure 6). As a result, the radius of curvature of the Fresnel surface in the optical system has a large adjustment range, thereby better deflecting and converging dispersed light. Moreover, the adjustable slope of the Fresnel surface enhances the light deflection capability of the second surface, enabling ultra-short focus while improving chromatic aberration correction and enhancing clarity.

[0121] For example, by comprehensively considering the light deflection in the optical system and the surface parameters of each lens assembly, parameters such as the draft angle, tooth width, and tooth height of the Fresnel surface can be determined. This allows the design of the Fresnel surface to reduce stray light that may be generated by the backlight side of the Fresnel surface, thereby improving visual effects.

[0122] With reference to Figures 1, 3, and 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.

[0123] FIG. 7 is an optical system provided in an example of at least one embodiment of the present disclosure.

[0124] The difference between the optical system shown in FIG7 and the optical system shown in FIG1 is that the adhesive layer lens 130 and the third surface 103 in the optical system shown in FIG7 are different from the adhesive layer lens 130 and the third surface 103 in the optical system shown in FIG1. ​​Of course, the optical system shown in FIG7 may also have other differences from the optical system shown in FIG1, such as the number of lenses, etc., and the present disclosure does not limit this. For example, the number of lenses in the optical system shown in FIG7 may be different from or the same as the number of lenses in the optical system shown in FIG1. ​​The transflective film 200, polarizing reflective layer 300, phase delay film 400, and linear polarizing film 500 in the optical system shown in FIG7 may have the same features as the transflective film 200, polarizing reflective layer 300, phase delay film 400, and linear polarizing film 500 in the optical system shown in FIG1, and will not be repeated here.

[0125] In some examples, referring to FIG7 , third surface 103 can be a plane. When third surface 103 is a plane, second surface 102 can be configured as a convex surface, thereby making adhesive layer lens 130 between second surface 102 and third surface 103 a concave lens. Thus, concave adhesive layer lens 130 can cooperate with convex first lens element 110 to correct chromatic aberration.

[0126] With reference to Figures 1, 3, and 5 to 7, in some examples, the fourth surface 104 is a convex surface, the ratio of the radius of curvature of the fourth surface 104 to the effective focal length of the optical system may be -2 to -3, and the conic coefficient of the fourth surface 104 may 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 may 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 may 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 may be -2.5. For example, the conic coefficient of the fourth surface 104 may be -8 to -2. For example, the conic coefficient of the fourth surface 104 may be -6 to -3. For example, the conic coefficient of the fourth surface 104 may be -5.

[0127] Combined with the above example, for example, the high-order 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 high-order 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 high-order 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 high-order 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.

[0128] FIG8 is an optical system provided in an example of at least one embodiment of the present disclosure.

[0129] The difference between the optical system shown in FIG8 and the optical system shown in FIG1 is that the number of lenses in the optical system shown in FIG8 is different from the number of lenses in the optical system shown in FIG1. ​​Of course, the optical system shown in FIG8 and the optical system shown in FIG1 may also have other differences, such as the surface shape of each surface, the optical focal length of the adhesive lens 130, etc., and the present disclosure does not limit this. For example, the surface parameters of each surface shape in the optical system shown in FIG8 may be different from or the same as the surface parameters of each surface shape in the optical system shown in FIG1. ​​The transflective film 200, polarizing reflective layer 300, phase delay film 400, and linear polarizing film 500 in the optical system shown in FIG8 may have the same features as the transflective film 200, polarizing reflective layer 300, phase delay film 400, and linear polarizing film 500 in the optical system shown in FIG1, and will not be repeated here.

[0130] In some examples, referring to FIG8 , at least two lenses include a first lens 110, a second lens 120, and a third lens 140, arranged sequentially along the optical axis OA. For example, the glue layer lens 130 is located between the first lens 110 and the second lens 120. For example, the lens assembly 100 may include 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 also includes a fifth surface 105 opposite the third surface 103, and the third lens 140 also 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 opposing surfaces of the second lens 120 along the optical axis OA. For example, the fourth surface 104 and the sixth surface 106 are two opposing surfaces of the third lens 140 along the optical axis OA. The fifth surface 105 and the sixth surface 106 have the same surface shape so that the second lens 120 and the third lens 140 can be bonded together.

[0131] By providing the second lens 120 and the third lens 140 , more film attachment locations can be provided. For example, the phase delay film 400 can be provided between the fifth surface 105 and the sixth surface 106 .

[0132] As shown in Figure 8 , one of the optical power of the first lens 110 and the optical power of the adhesive layer lens 130 is positive, and the other is negative. For example, the optical power of the first lens 110 can be positive, meaning that the first lens 110 is a convex lens, while the optical power of the adhesive layer lens 130 can be negative, meaning that the adhesive layer lens 130 is a concave lens. Thus, chromatic aberration can be corrected by both the first lens 110 and the adhesive layer lens 130.

[0133] As shown in FIG8 , the Abbe number of at least one of the first lens 110 and the second lens 120 is different from the Abbe number of the adhesive layer lens 130. For example, the Abbe number of the first lens 110 and the adhesive layer lens 130 may be different. For example, the Abbe number of the second lens 120 and the adhesive layer lens 130 may be different. Thus, chromatic aberration can be corrected by utilizing the difference in Abbe number. For example, the refractive index of at least one of the first lens 110 and the second lens 120 may be different from the refractive index of the adhesive layer lens 130, thereby correcting chromatic aberration by utilizing the difference in refractive index.

[0134] FIG. 9 is an optical system provided in an example of at least one embodiment of the present disclosure.

[0135] The optical system shown in FIG9 differs from the optical system shown in FIG8 in that the fifth surface 105 and the sixth surface 106 in the optical system shown in FIG9 are different from the fifth surface 105 and the sixth surface 106 in the optical system shown in FIG8 . Of course, the optical system shown in FIG9 may also differ from the optical system shown in FIG8 in other ways, such as the surface shape of each surface, the optical power of the adhesive lens 130, etc., and this disclosure does not limit this. For example, the surface parameters of each surface shape in the optical system shown in FIG9 may be different from or the same as the surface parameters of each surface shape in the optical system shown in FIG8 . The transflective film 200, polarizing reflective layer 300, phase retarder film 400, and linear polarizing film 500 in the optical system shown in FIG9 may have the same features as the transflective film 200, polarizing reflective layer 300, phase retarder film 400, and linear polarizing film 500 in the optical system shown in FIG8 , and will not be further described here.

[0136] For example, referring to FIG8 , the fifth surface 105 and the sixth surface 106 can both be planar. For example, referring to FIG9 , the fifth surface 105 and the sixth surface 106 can both be curved. For example, the fifth surface 105 and the sixth surface 106 can both be convex. For example, the fifth surface 105 and the sixth surface 106 can both be curved toward a side away from the third surface 103 , thereby reducing the difference between the center thickness and the edge thickness of the second lens 120 and the difference between the center thickness and the edge thickness of the third lens 140, thereby reducing processing difficulty.

[0137] FIG10 is a display device provided as an example in at least one embodiment of the present disclosure.

[0138] As shown in Figure 10, 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 also 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 embodiment of the present disclosure includes at least one of the above-mentioned optical systems, it also has corresponding beneficial technical effects, which will not be described in detail here. It can be understood that the display screen 10 shown in Figure 10 can form different display devices in conjunction with the optical systems shown in Figures 1, 3, and 5 to 9. For example, the display surface of the display screen 10 is located in the focal plane of the light incident side of the optical system.

[0139] 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 along the optical axis OA from the highest point on the first surface 101 of the lens assembly 100 in the optical system to the center of the display screen 10. The highest point on the first surface 101 includes the edge sagittal height of the lens assembly 100 on the side where the first surface 101 is located.

[0140] For example, referring to Figures 1 to 10 , the field of view of the optical system can be greater than 90°. For example, the field of view is the full field of view. For example, the field of view of the optical system can be, but is not limited to, 90°, 92°, 94°, 96°, 98°, or 100°. For example, based on an effective aperture capable of achieving a field of view of 100°, the binocular lens can weigh less than 20g.

[0141] 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 large exit pupil distance, which can meet the needs of myopic users wearing glasses.

[0142] For example, referring to Figures 1 to 10 , the ratio of the effective aperture to the effective focal length of the lens assembly 100 can be 2.3 to 2.7. The effective aperture of the lens assembly described above refers to the effective aperture through which light can pass, i.e., the maximum aperture through which light can pass. 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.

[0143] For example, referring to Figures 1 to 10, the ratio of the distance between the aperture (e.g., the human eye) and the first surface 101 on the optical axis OA in the optical system 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.

[0144] For example, referring 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 on the optical axis OA in the optical system to the effective focal length is less than -80.

[0145] For example, referring to Figures 1 to 10 , the ratio of the distance between the display surface and the image plane of the display screen 10 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 and the image plane of the display screen 10 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 and the image plane of the display screen 10 on the optical axis OA to the effective focal length is 0.08.

[0146] For example, referring 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.

[0147] For example, the display screen may 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), and the like.

[0148] For example, if the display screen is a liquid crystal display screen, the pixel size is about twenty micrometers. For example, if the display screen is an organic light emitting diode display screen, the pixel size is about several micrometers.

[0149] For example, the display device may be a virtual reality display device. For example, the virtual reality display device may be a display device using an ultra-short-throw folded optical path.

[0150] For example, the display device may be a near-eye display device, and the near-eye display device may be a wearable VR helmet, VR glasses, etc., but the embodiments of the present disclosure are not limited thereto.

[0151] There are a few points to note:

[0152] (1) The drawings of the embodiments of the present disclosure only involve structures related to the embodiments of the present disclosure, and other structures can refer to general designs.

[0153] (2) In the absence of conflict, features in the same embodiment and different embodiments of the present disclosure may be combined with each other.

[0154] The foregoing description is merely an exemplary embodiment of the present disclosure and is not intended to limit the scope of protection of the present disclosure. The scope of protection of the present disclosure is determined by the appended claims.

Claims

1. An optical system, comprising: A lens assembly including at least two lenses, where the at least two lenses include 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 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 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 or 2, 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 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 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 or 5, 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 any one of claims 4 to 6, 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 any one of claims 4-9, 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 1-10, 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 1-15, wherein, 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.

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 1-17, 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 1-18, 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 1-19, 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 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.

22. 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 profiles 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.

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