Optical imaging lens, scanning display device and near-eye display device

Abstract

The embodiment of the application discloses an optical imaging lens, a scanning display device and a near-eye display device, and relates to the technical field of scanning display. The optical imaging lens can reasonably disperse the optical power of the system, slow down the aberration generated by the lens, achieve the purpose of correcting various aberrations, and realize clear imaging of the image surface on the basis of improving the field of view by reasonably optimizing the focal length, surface structure, refractive index and dispersion coefficient of the related lenses in the eight coaxial lenses of the optical imaging lens. The combination of aspherical lenses and spherical lenses and the reasonable use of single lenses and cemented lenses further ensure the large field of view of the optical imaging lens, strengthen the correction of various optical aberrations, realize clear imaging, and at the same time, further reduce the volume and weight of the optical imaging lens, so that the overall structure of the optical imaging lens can be more compact, and the production demand of miniaturization of the lens product is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of scanning display, in particular to an optical imaging lens, a scanning display device and a near-eye display device. BACKGROUND

[0002] Scanning display imaging as a new display technology can be used in various application scenarios such as projection display and near-eye display.

[0003] However, in the existing scanning display imaging system, there are high processing difficulty, high mass production cost, poor imaging quality, small field of view angle, and the like, which limits the application of scanning display imaging in the market, especially when it is applied to the near-eye display, the imaging effect and the field of view angle limit the performance requirements of high resolution in the near-eye display, thereby hindering the development of the near-eye display to the consumer market. SUMMARY

[0004] The present application aims to provide an optical imaging lens, a scanning display device and a near-eye display device to meet the requirements of large field of view angle, high imaging quality and small size in the near-eye display scenario.

[0005] The present application provides an optical imaging lens, which comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens arranged in sequence from a first side to a second side and sharing an optical axis, wherein the focal lengths of the first lens, the second lens, the third lens and the sixth lens are negative, positive, positive and positive respectively.

[0006] The first lens satisfies the following relationship: 1.7≤nd1≤2.0 and 17≤vd1≤23, wherein nd1 is the refractive index of the first lens, and vd1 is the dispersion coefficient of the first lens.

[0007] Further optionally, in the preferred embodiment of the present application, the first lens, the second lens, the third lens, the fourth lens, the sixth lens and the eighth lens are all spherical lenses.

[0008] The fifth lens and the seventh lens are both aspherical lenses.

[0009] Further optionally, in the preferred embodiment of the present application, the fourth lens and the sixth lens are both spherical cemented lenses.

[0010] Further optionally, in the preferred embodiment of the present application, the fourth lens and the sixth lens each comprise two sub-lenses, wherein the two sub-lenses of the fourth lens are arranged coaxially from the first side to the second side and the corresponding focal length positive-negative are positive and negative respectively; the two sub-lenses of the sixth lens are arranged coaxially from the first side to the second side and the corresponding focal length positive-negative are negative and positive respectively.

[0011] Further optionally, in the preferred embodiment of the present application, the second side surface of the sub-lens of the fourth lens close to the fifth lens is a concave surface; the first side surface of the fifth lens is a concave surface.

[0012] Further optionally, in the preferred embodiment of the present application, the focal lengths of the fourth lens, the fifth lens, the seventh lens and the eighth lens are negative, positive, positive and positive respectively;

[0013] The first lens and the optical imaging lens group have the following relationship: 0.7≤|f1 / f 总 |≤1.2, wherein f1 is the focal length of the first lens, f 总 is the total focal length of the optical imaging lens group;

[0014] The fourth lens close to the sub-lens of the fifth lens and the optical imaging lens group have the following relationship: 0.7≤|f 4-2 / f 总 |≤1, wherein f 4-2 is the focal length of the fourth lens close to the sub-lens of the fifth lens, f 总 is the total focal length of the optical imaging lens group.

[0015] Further optionally, in the preferred embodiment of the present application, the refractive index of the fourth lens close to the sub-lens of the fifth lens and the refractive index of the sixth lens close to the sub-lens of the fifth lens are both in [1.7, 2], and the dispersion coefficients are in [22, 28] and [18, 22] respectively.

[0016] The present application also provides a scanning display device, which comprises an optical fiber scanner and the optical imaging lens group described above, wherein the optical fiber scanner is used for scanning and emitting light of an image to be displayed, and the optical imaging lens group is used for magnifying and imaging the corresponding scanning surface of the light emitted by the optical fiber scanner and projecting the corresponding scanning surface.

[0017] The optical fiber scanner comprises an actuator and an optical fiber fixed on the actuator, and the part of the optical fiber beyond the actuator forms an optical fiber cantilever, which performs two-dimensional scanning under the driving of the actuator.

[0018] The embodiment of the present application also provides a near-eye display device, which is used as a head-mounted augmented reality device and comprises at least a near-eye display module and the scanning display device.

[0019] The embodiment of the present application also provides a near-eye display device, which is used as a head-mounted virtual reality device and comprises at least a near-eye display module and the scanning display device.

[0020] The technical solution in the embodiment of the present application can achieve the following technical effects:

[0021] In the embodiment of the present application, the focal lengths of the eight coaxial lenses are reasonably optimized, so that the optical power of the system is reasonably dispersed, the aberration generated by the lens is slowed down, the purpose of correcting various aberrations is achieved, and clear imaging of the curved surface on the image side is realized on the basis of improving the field of view.

[0022] Further, the overall structure of the optical imaging lens group is more compact through the reasonable number of lens combinations, which meets the production demand of miniaturization of the lens product; the correction of various optical aberrations is further strengthened through the combination of aspherical lenses and spherical lenses, and the reasonable use of single lenses and cemented lenses, clear imaging is realized, and at the same time, the volume and weight of the optical imaging lens group are further reduced.

[0023] Further, the refractive index, dispersion coefficient and surface structure of part of the eight coaxial lenses are limited and optimized, which further improves the field of view and imaging quality.

[0024] Other features and advantages of the present application will be described in the following description, and some will become apparent from the description, or will be understood by those skilled in the art through implementation of the technical solution of the present application. The purpose and other advantages of the present application can be achieved and obtained by the structure and / or process specifically pointed out in the specification, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0025] Other features, purposes and advantages of the present application will become more apparent by reading the detailed description of the non-limiting embodiments made with reference to the following drawings:

[0026] Figure 1a 、 1b is a structural schematic diagram of an illustrative scanning display system;

[0027] Figure 2a is a schematic diagram of the scanning output of the optical fiber scanner provided in the embodiment of the present application;

[0028] Figure 2b is a schematic diagram of a maximum effective half-aperture along a radial direction of a partial lens of an optical imaging lens provided by an embodiment of the present application;

[0029] Figure 3 is a structural schematic diagram of an optical imaging lens provided by an embodiment of the present application;

[0030] Figure 4 is an MTF curve diagram of the optical imaging lens in the embodiment of the present application;

[0031] Figure 5 is a field curvature distortion curve diagram of the optical imaging lens in the embodiment of the present application;

[0032] Figure 6 is a sagittal chromatic aberration diagram of the optical imaging lens in the embodiment of the present application.

[0033] Figure 7 is a structural schematic diagram of an optical imaging lens provided by an embodiment of the present application;

[0034] Figure 8 is an MTF curve diagram of the optical imaging lens in the embodiment of the present application;

[0035] Figure 9 is a field curvature distortion curve diagram of the optical imaging lens in the embodiment of the present application;

[0036] Figure 10 is a sagittal chromatic aberration diagram of the optical imaging lens in the embodiment of the present application.

[0037] Figure 11 is a structural schematic diagram of an optical imaging lens provided by an embodiment of the present application;

[0038] Figure 12 is an MTF curve diagram of the optical imaging lens in the embodiment of the present application;

[0039] Figure 13 is a field curvature distortion curve diagram of the optical imaging lens in the embodiment of the present application;

[0040] Figure 14 is a sagittal chromatic aberration diagram of the optical imaging lens in the embodiment of the present application.

[0041] Figure 15 is a structural schematic diagram of an optical imaging lens provided by an embodiment of the present application;

[0042] Figure 16 is an MTF curve diagram of the optical imaging lens in the embodiment of the present application;

[0043] Figure 17is a field curvature distortion curve diagram of the optical imaging lens set in Embodiment Four of the present application;

[0044] Figure 18 is a transverse chromatic aberration diagram of the optical imaging lens set in Embodiment Four of the present application;

[0045] Figure 19 is a structural schematic diagram of an optical imaging lens set provided in Embodiment Five of the present application;

[0046] Figure 20 is an MTF curve diagram of the optical imaging lens set in Embodiment Five of the present application;

[0047] Figure 21 is a field curvature distortion curve diagram of the optical imaging lens set in Embodiment Five of the present application;

[0048] Figure 22 is a transverse chromatic aberration diagram of the optical imaging lens set in Embodiment Five of the present application.

[0049] Icon: 100-processor; 110-laser group; 120-fiber scanning module; 130-transmission fiber; 140-light source modulation circuit; 150-scanning driving circuit; 160-combining unit; 121-scanning actuator; 121a-slow axis; 121b-fast axis; 122-fiber cantilever; 123-mirror group; 124-scanner package shell; 125-fixing member; 230-scanning curved surface; 240-imaging plane; 11-first lens; 12-second lens; 13-third lens; 14-fourth lens; 141, 142-fourth sub-lens; 15-fifth lens; 16-sixth lens; 161, 162-sixth sub-lens; 17-seventh lens; 18-eighth lens; 01-diaphragm; 02-scanning curved surface; 31-first lens; 32-second lens; 33-third lens; 34-fourth lens; 341, 342-fourth sub-lens; 35-fifth lens; 36-sixth lens; 361, 362-sixth sub-lens; 37-seventh lens; 38-eighth lens; 03-diaphragm; 04-scanning curved surface; 51-first lens; 52-second lens; 53-third lens; 54-fourth lens; 541, 542-fourth sub-lens; 55-fifth lens; 56-sixth lens; 561, 562-sixth sub-lens; 57-seventh lens; 58-eighth lens; 05-diaphragm; 06-scanning curved surface; 71-first lens; 72-second lens; 73-third lens; 74-fourth lens; 741, 742-fourth sub-lens; 75-fifth lens; 76-sixth lens; 761, 762-sixth sub-lens; 77-seventh lens; 78-eighth lens; 07-diaphragm; 08-scanning curved surface; 91-first lens; 92-second lens; 93-third lens; 94-fourth lens; 941, 942-fourth sub-lens; 95-fifth lens; 96-sixth lens; 961, 962-sixth sub-lens; 97-seventh lens; 98-eighth lens; 09-diaphragm; 10-scanning curved surface. DETAILED DESCRIPTION

[0050] The application will be further described below in conjunction with the drawings and examples. It should be understood that the specific examples described herein are intended to be illustrative only and are not intended to limit the scope of the application. In addition, it should be noted that only the parts of the drawings that are pertinent to the relevant application are shown for the sake of convenience.

[0051] Illustrative scanning display system

[0052] For the current scanning display imaging, it can be realized by Micro-Electro-Mechanical System (MEMS) or Fiber Scanning Display (FSD) device. The FSD scheme is a new type of scanning display imaging method, which realizes the scanning output of the image through the fiber scanner. In order to enable those skilled in the art to clearly understand the scheme of the present application, the brief principle of fiber scanning imaging and the corresponding system are described below.

[0053] As shown in Figure 1a , it is an illustrative scanning display system in the present application, which mainly includes:

[0054] The processor 100, the laser group 110, the fiber scanning module 120, the transmission fiber 130, the light source modulation circuit 140, the scanning driving circuit 150 and the beam combining unit 160. Among them,

[0055] The processor 100 can be a Graphics Processing Unit (GPU), a Central Processing Unit (CPU) or other chips or circuits with control function and image processing function, which is not specifically limited here.

[0056] When the system works, the processor 100 can control the light source modulation circuit 140 to modulate the laser group 110 according to the image data to be displayed. The laser group 110 contains multiple monochromatic lasers, which respectively emit light beams of different colors. As can be seen from FIG. 1, the laser group can specifically use Red (R), Green (G) and Blue (B) three-color lasers. The light beams emitted by each laser in the laser group 110 are combined into a laser beam by the beam combining unit 160 and coupled into the transmission fiber 130.

[0057] The processor 100 can also control the scanning driving circuit 150 to drive the fiber scanner in the fiber scanning module 120 to scan, so as to scan and output the light beam transmitted in the transmission fiber 130.

[0058] A beam of light output from a fiber optic scanner acts on a specific pixel on the surface of a medium, forming a light spot at that pixel, thus achieving scanning of that pixel location. Driven by the fiber optic scanner, the output end of the transmission fiber 130 sweeps along a specific scanning trajectory, causing the beam to move to the corresponding pixel location. During the actual scanning process, the beam output from the transmission fiber 130 forms a light spot with corresponding image information (such as color, grayscale, or brightness) at each pixel location. Within one frame, the beam traverses each pixel location at a sufficiently high speed to complete the scanning of one frame of the image. Due to the "visual persistence" characteristic of human vision, the human eye cannot perceive the movement of the beam at each pixel location, but instead sees a complete image frame.

[0059] Continue to refer to Figure 1b The specific structure of the fiber optic scanning module 120 includes: a scanning actuator 121, a fiber optic cantilever 122, a mirror assembly 123, a scanner housing 124, and a fixing member 125. The scanning actuator 121 is fixed to the scanner housing 124 by the fixing member 125. The transmission fiber 130 extends from the front end of the scanning actuator 121 to form the fiber optic cantilever 122 (also called the scanning fiber). During operation, driven by the scanning drive signal, the slow axis 121a (also called the first actuation part) of the scanning actuator 121 moves along the vertical direction (this vertical direction is parallel to the...). Figure 1a , 1b The Y-axis in the reference coordinate system (in this application, the vertical direction can also be referred to as the first direction) vibrates, and its fast axis 121b (also referred to as the second actuator) vibrates along the horizontal direction (this horizontal direction is parallel to the reference coordinate system). Figure 1a , 1b The X-axis in the reference coordinate system (in this application, this horizontal direction can also be referred to as the second direction) vibrates, driven by the scanning actuator 121. The front end of the fiber optic cantilever 122 performs a two-dimensional sweep along a preset trajectory and emits a light beam. The emitted light beam can then pass through the mirror assembly 123 to achieve scanning imaging. Generally, the structure composed of the scanning actuator 121 and the fiber optic cantilever 122 can be called a fiber optic scanner.

[0060] like Figure 2aAs shown in this embodiment, the motion trajectory of the optical fiber output end forms a scanning surface 230 through the movement of the fast and slow axes. After passing through the corresponding lens group 123, it is converted into an imaging plane 240 (when imaging is performed on a planar carrier, the image is a plane; it should be noted that in other embodiments of the present invention, the image formed after passing through the lens group 123 can correspond to the surface of the imaging carrier, that is, it can change with the shape of the carrier surface, as long as the image is clear). When applied to near-eye display devices such as augmented reality (AR) devices, the imaging plane 240 is coupled into the waveguide as the entrance pupil of the waveguide for imaging so that the human eye can view it.

[0061] To facilitate description and enable those skilled in the art to easily understand the solution of this application, it should be noted that the optical imaging lens assembly in this application (such as...) Figure 2a The lens group 123 shown serves as an eyepiece. Through the action of this optical imaging lens group, the scanning surface 230 can be converted into an imaging plane 240 (in practical applications, the direction of light transmission is from the scanning surface 230 to the imaging plane 240). Therefore, the side of the optical imaging lens group corresponding to the imaging plane 240 is referred to as the first side, and the side of the optical imaging lens group corresponding to the scanning surface 230 is referred to as the second side. In the following description, "first side" and "second side" will be used as references to describe the embodiment of the optical imaging lens group. Furthermore, in the description of the subsequent embodiments, such as for a certain lens in the optical imaging lens group, "the first side surface of the Xth lens" refers to the surface of the Xth lens facing the first side.

[0062] It should be further noted that in the field of projection, the image corresponding to the first side is a planar image, and the corresponding planar image carrier can be such as a projection screen, a screen, or a wall. The image corresponding to the second side is a curved image, that is, an arc-shaped scanning surface scanned by a fiber optic scanner or emitted by other image sources. In the application scenario of the camera field, the optical path is reversed in the field of projection. The first side generally corresponds to the object side that collects image information, and the second side generally corresponds to the image side that is captured and formed.

[0063] Optical imaging lens

[0064] The optical imaging lens in the embodiment of the present application comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens arranged in sequence on the same optical axis from the first side to the second side, wherein the focal lengths of the first lens, the second lens, the third lens and the sixth lens are negative, positive, positive and positive respectively. It should be noted that by arranging a reasonable number of lenses and limiting the focal lengths of the first lens to the third lens and the sixth lens, the optical power of the system can be reasonably dispersed, the aberration generated by the lens can be slowed down, the purpose of correcting various aberrations can be achieved, and clear imaging of the curved surface of the image can be realized on the basis of improving the field of view. In addition, it should be emphasized that limiting the focal lengths of the third lens and the sixth lens to be positive can strengthen the convergence ability of the curved image to balance the aberration.

[0065] Further, in the embodiment of the present application, preferably, the focal lengths of the fourth lens, the fifth lens, the seventh lens and the eighth lens are negative, positive, positive and positive respectively. It should be emphasized that in other embodiments of the present application, the positive and negative of the focal lengths of the fourth lens, the fifth lens, the seventh lens and the eighth lens are not limited as in the embodiment of the present application, which can be positive or negative.

[0066] Further preferably, in the embodiment provided by the present application, the first lens, the second lens, the third lens, the fourth lens, the sixth lens and the eighth lens are all spherical lenses; the fifth lens and the seventh lens are all aspherical lenses. Moreover, the fourth lens and the sixth lens are both spherical cemented lenses. It should be noted that by reasonably configuring and using aspherical lenses and spherical lenses for the eight lenses, and by reasonably using single lenses and cemented lenses, the correction of various optical aberrations is further strengthened, and clear imaging is realized on the basis of expanding the field of view. It should be emphasized that by limiting the lens surface structure of a reasonable position and number (the fifth lens and the seventh lens) of lenses to an aspherical surface structure, more control variables can be obtained to reduce aberration and reasonably reduce the number of lenses, so as to help the miniaturization or micro-miniaturization of the optical imaging lens on the basis of improving the image display quality. In addition, the aspherical lens defined above refers to the first side surface and the second side surface being aspherical surface structures, and it can be understood that the entire or part of the optical effective area of the lens surface is aspherical.

[0067] Further specifically preferably, in the embodiments of the present application, the fourth lens and the sixth lens each have two sub-lenses as spherical cemented lenses. Preferably, the two sub-lenses of the fourth lens are arranged co-axially from the first side to the second side and have positive and negative focal lengths respectively; and the two sub-lenses of the sixth lens are arranged co-axially from the first side to the second side and have negative and positive focal lengths respectively. It should be noted that by limiting the positive and negative of the focal lengths of the corresponding sub-lenses of the fourth lens and the sixth lens, chromatic aberration and spherical aberration can be well eliminated, which is crucial for aberration correction of the entire imaging lens. Of course, in some embodiments of the present application, the positive and negative of the focal lengths of the two sub-lenses of the fourth lens can also be negative, and the two sub-lenses of the sixth lens can also be arranged to be positive. It should be emphasized that in other embodiments of the present application, the number of corresponding sub-lenses of the fourth lens and the sixth lens is not limited to the number provided in the embodiments of the present application, and can also be other numbers of sub-lenses, such as 3 or 4, which can be flexibly set according to actual design needs.

[0068] Further, in the optical imaging lens provided in the embodiments of the present application, the second side surface of the sub-lens of the fourth lens close to the fifth lens is a concave surface, and the first side surface of the fifth lens is also a concave surface. It should be noted that by limiting the two opposite surfaces of the fourth lens and the fifth lens (i.e. the second side surface of the sub-lens of the fourth lens close to the fifth lens and the first side surface of the fifth lens) to be concave, a larger image field curvature can be generated to cooperate with the curvature of the image surface, thereby achieving good aberration correction effect.

[0069] In addition, it should be noted that the first side surface being convex means that the first side surface forms a convex shape towards the first side direction of the optical imaging lens; the first side surface being concave means that the first side surface forms a concave shape towards the first side direction of the optical imaging lens; the second side surface being convex means that the second side surface forms a convex shape towards the second side direction of the optical imaging lens; and the second side surface being concave means that the second side surface forms a concave shape towards the second side direction of the optical imaging lens.

[0070] Further, in some embodiments, the surface type of the lens is not entirely concave or convex, and the surface type of the lens can be a composite curved surface, or the near-optical axis part is a curved surface and the edge part is not a curved surface; especially, when the lens surface is convex and the position of the convex surface is not defined, it means that the convex surface can be located at the near-optical axis of the lens surface; similarly, when the lens surface is concave and the position of the concave surface is not defined, it means that the concave surface can be located at the near-optical axis of the lens surface.

[0071] Further, in the optical imaging lens provided in the embodiments of the present application, the first lens and the optical imaging lens have the following relationship: 0.7≤|f1 / f 总|≤1.2, where f1 is the focal length of the first lens, f 总 This represents the total focal length of the optical imaging lens group; additionally, the sub-lens of the fourth lens closest to the fifth lens has the following relationship with the optical imaging lens group: 0.8 ≤ |f 4-2 / f 总 |≤1.5, where f 4-2 f is the focal length of the sub-lens of the fourth lens that is closest to the fifth lens. 总 The focal length is the total focal length of the optical imaging lens group. It should be noted that by defining the focal length ratio between the first lens and the total focal length of the optical imaging lens group, and by defining the focal length ratio between the sub-lens of the fourth lens (close to the fifth lens) and the total focal length of the optical imaging lens group, the optical power of the system is reasonably distributed and configured, thereby further enhancing the correction of various aberrations and improving the field of view and image quality. Additionally, if the location of the lens focal length is not defined in this embodiment, it means that the focal length of the lens can be the focal length of the lens near the optical axis. It should be emphasized that prior to this invention, existing optical imaging lens groups for projection displays could not achieve a balance between image quality and a large field of view; that is, they typically reduced image quality while increasing the field of view, and could not achieve a large field of view while maintaining image quality. The invention of this application achieves high-quality image output while improving the field of view and miniaturization by defining and rationally configuring the corresponding features (focal length, spherical and aspherical, single lens and cemented lens, and surface structure, etc.) of the corresponding lenses among the eight lenses.

[0072] Furthermore, it should be noted that the first lens provided in this embodiment of the invention satisfies the following relationship: 1.7≤nd1≤2.0, and 17≤vd1≤23, where nd1 is the refractive index of the first lens and vd1 is the dispersion coefficient of the first lens. Additionally, preferably, the refractive indices of the sub-lenses of the fourth lens and the sixth lens near the fifth lens are both in the range [1.7, 2], and the dispersion coefficients are in the ranges [22, 28] and [18, 22], respectively. It is important to emphasize that by optimizing the refractive index design of the relevant sub-lenses of the first, fourth, and sixth lenses, the dispersion coefficients of the corresponding lenses can be reasonably controlled, thereby ensuring image quality and a large field of view.

[0073] Furthermore, in order to achieve a balance between image quality and wide field of view performance in the optical imaging lens assembly of the present invention, and to ensure that both are in their optimal state, the preferred embodiment of the present invention has the following limitations: First, it should be noted that, please refer to... Figure 2b and combination Figure 3The maximum effective half-aperture of the third lens in the radial direction is Y1, the maximum effective half-apertures of the opposite two surfaces of the fourth lens and the fifth lens in the radial direction are the same and are Y2, and the maximum effective half-aperture of the seventh lens in the radial direction is Y3; wherein Y1 and Y2 have the following relationship: 1<=Y1 / Y2<=1.4; Y2 and Y3 have the following relationship: 1.4<=Y3 / Y2<=1.7.

[0074] Further, in a possible implementation, the connection between the eight lenses can be interval connection or adhesion, which will be determined according to actual application requirements, and is not limited here.

[0075] Further optionally, in a possible implementation, the first lens to the eighth lens are made of plastic or glass. It should be noted that the first lens to the eighth lens made of plastic can effectively reduce the production cost. Compared with glass material, the cost of plastic material lens is one-twentieth to one-tenth of the cost of glass material, so it is very beneficial to low-cost mass production. In addition, the plastic material lens can usually be injection molded, which has low processing difficulty and can be easily processed into various surface structures that meet aspheric surfaces. At the same time, the plastic material can also reduce the weight of the lens as a whole, which is beneficial to the lightweight product design. When using glass material, the refractive index of glass material is higher and wider, which has an advantage in correcting lens aberration. The expansion coefficient of glass material is much smaller, which is beneficial to precise assembly. In addition, due to the characteristics of high temperature resistance, ultraviolet resistance, and acid and alkali resistance of glass, the service life and performance stability of the lens group have strong advantages. It should be emphasized that in other embodiments of the present application, the plastic and glass materials provided in the embodiments of the present application are not limited to the two materials, and other materials that can be used to make lenses can also be used.

[0076] It should be further noted that the optical imaging lens group disclosed in the embodiments of the present application can optionally be provided with at least one diaphragm, which can be located before the first lens (first side), between the lenses, or after the eighth lens (second side). The diaphragm can be an aperture diaphragm or a field diaphragm, which can be used to reduce stray light and help improve image display quality.

[0077] Example One

[0078] Figure 3 A structure diagram of an optical imaging lens group provided in an embodiment of the present application. The optical imaging lens group includes from the first side (also known as the side where the diaphragm 01 in the first lens is located) to the second side (also known as the side where the diaphragm 01 in the eighth lens is located). Figure 3 Figure 3 ​The first lens 11, the second lens 12, the third lens 13, the fourth lens 14, the fifth lens 15, the sixth lens 16, the seventh lens 17 and the eighth lens 18 are arranged in sequence on the same axis of the scanning surface 02.

[0079] In the embodiment, there is a gap between each two adjacent lenses among the first lens 11, the second lens 12, the third lens 13, the fourth lens 14, the fifth lens 15, the sixth lens 16, the seventh lens 17 and the eighth lens 18, and the first lens 11, the second lens 12, the third lens 13, the fifth lens 15, the seventh lens 17 and the eighth lens 18 are six single non-adhesive lenses. The fourth lens 14 is a glued lens composed of two sub-lenses, and the corresponding two sub-lenses are the fourth sub-lens 141 and the fourth sub-lens 142 from the first side to the second side; the sixth lens 16 is also a glued lens composed of two sub-lenses, and the corresponding two sub-lenses are the sixth sub-lens 161 and the sixth sub-lens 162 from the first side to the second side.

[0080] The focal lengths of the first lens 11 to the eighth lens 18 from the first side to the second side are negative, positive, positive, negative, positive, positive, positive and positive in sequence, wherein the focal lengths of the fourth sub-lens 141 and the fourth sub-lens 142 included in the fourth lens 14 are positive and negative respectively, and the focal lengths of the sixth sub-lens 161 and the sixth sub-lens 162 included in the sixth lens 16 are negative and positive respectively.

[0081] The first side surface and the second side surface of the first lens 11 are both concave at the near optical axis;

[0082] The first side surface of the second lens 12 is concave at the near optical axis, and the second side surface is convex.

[0083] The first side surface and the second side surface of the third lens 13 are both convex;

[0084] The first side surface and the second side surface of the fourth sub-lens 141 in the fourth lens 14 are both convex, and the first side surface and the second side surface of the fourth sub-lens 142 are both concave;

[0085] The first side surface of the fifth lens 15 is concave at the near optical axis, and the second side surface is convex at the near optical axis;

[0086] The first side surface and the second side surface of the sixth sub-lens 161 in the sixth lens 16 are both concave, and the first side surface and the second side surface of the sixth sub-lens 162 are both convex;

[0087] The first side surface of the seventh lens 17 is convex at the near optical axis, and the second side surface is concave at the near optical axis;

[0088] The first side surface of the eighth lens 18 is convex, and the second side surface is concave at the near optical axis.

[0089] In the present embodiment, the focal length of the first lens 11 and the fourth lens 14 in the optical imaging lens group satisfies the following relationship:

[0090] 0.7≤|f1 / f 总 |≤1.2, 0.8≤|f 4-2 / f 总 |≤1.5, where f1 is the focal length of the first lens, f 4-2 is the focal length of the sub-lens of the fourth lens 14 close to the fifth lens 15, that is, the focal length of the fourth sub-lens 142, and f 总 is the total focal length of the optical imaging lens group. It should be noted that the specific focal length value of each lens is shown in Table 1:

[0091] Table 1: Focal length parameter table of each lens in the optical imaging lens group

[0092] Lens Focal length Lens focal length / total lens focal length First lens 11 -2.86 -1.11 Second lens 12 7.17 2.78 Third lens 13 3.82 1.48 Fourth lens 14 -12.02 -4.66 Fourth sub-lens 141 3.9 1.51 Fourth sub-lens 142 -2.21 -0.86 Fifth lens 15 61.18 23.71 Sixth lens 16 40.01 15.51 Sixth sub-lens 161 -6.69 -2.59 Sixth sub-lens 162 11.05 4.28 Seventh lens 17 9.1 3.53 Eighth lens 18 64.08 24.84

[0093] The refractive index and dispersion coefficient of the first lens 11, the fourth sub-lens 142, and the sixth sub-lens 161 in the optical imaging lens group satisfy the following conditions, respectively:

[0094] The refractive index and dispersion coefficient of the first lens 11 are 1.92 and 20.9, respectively; the refractive index and dispersion coefficient of the fourth sub-lens 142 are 1.85 and 23.8, respectively, and the refractive index and dispersion coefficient of the sixth sub-lens 161 are 1.92 and 20.9, respectively.

[0095] The optical imaging lens group provided by the embodiment one has a total focal length of 2.58 mm and a field of view angle of 28 degrees. The radius of curvature, thickness parameter, refractive index, and dispersion coefficient of each lens in the imaging of the scanning curved surface 02 are shown in Table 2:

[0096] Table 2: Structure parameter of the optical imaging lens group in embodiment one

[0097]

[0098]

[0099] It should be noted that Table 1 and Table 2 are the detailed structure data of the optical imaging lens group in embodiment one, wherein the units of the radius of curvature, thickness, and focal length are all millimeters, and the surfaces 0-20 in Table 2 represent the surfaces from the first side to the second side in order; the optical surface with a radius of curvature of "infinity" in the imaging plane means a plane.

[0100] Further, the conic coefficient and aspheric coefficient of the surfaces corresponding to the fifth lens 15 and the seventh lens 17 (both are aspheric lenses) are shown in Table 3:

[0101] Table 3. Conicity and asphericity data of the aspherical lens surface in Example 1.

[0102] Surface k A4 A6 A8 A10 A12 A14 A16 11 -7.5E-01 1.6E-01 -5.4E-02 6.4E-02 -4.9E-02 2.6E-02 -9.3E-03 2.9E-03 12 -1.2E+00 4.5E-04 -1.4E-03 1.1E-03 -1.8E-04 -1.1E-04 4.6E-05 -3.0E-06 16 -6.9E-01 -6.3E-03 -1.4E-03 -1.5E-04 8.3E-04 -5.2E-04 1.4E-04 -1.4E-05 17 -1.1E+00 -4.1E-02 2.5E-03 6.5E-03 -5.9E-03 2.4E-03 -4.6E-04 3.4E-05

[0103] Table 3 shows the conic coefficient and aspheric coefficient data in Example 1, where k is the conic coefficient in the aspheric curve equation, and A4 to A16 represent the 4th to 16th order aspheric coefficients of each surface.

[0104] Additionally, please refer to the following: Figure 2b and Figure 3 In this embodiment, the maximum effective half-aperture Y1 of the third lens along the radial direction, the maximum effective half-aperture Y2 of the two opposite surfaces of the fourth and fifth lenses along the radial direction, and the maximum effective half-aperture Y3 of the seventh lens along the radial direction satisfy the following relationship: Y1 / Y2=1.47, Y3 / Y2=1.8.

[0105] Furthermore, tests showed that when the image light corresponding to the scanning surface is projected using the aforementioned optical imaging lens group, its optical transfer function curve is as follows: Figure 4 As shown, the field distortion curve is as follows: Figure 5 As shown, the vertical axis color difference curve is as follows: Figure 6 As shown; among them, the Modulation Transfer Function (MTF) curve represents the overall resolution level of an optical system, the Field Curve Distortion curve represents the F-Tan (theta) distortion magnitude (percentage) under different field angles, and the Vertical Chromatic Aberration curve represents the magnitude of chromatic aberration in the direction perpendicular to the axial direction.

[0106] Depend on Figures 4-6 Observations show that the optical imaging lens group in Example 1 has good imaging resolution, small optical system distortion and chromatic aberration across the entire field of view. Therefore, the optical imaging lens group can clearly image the scanning surface image of the fiber optic scanner and has good imaging effect.

[0107] Of course, in practical applications, the optical imaging lens assembly may also include a display element, a housing, etc. The display element can be set on the second side of the optical imaging lens assembly, and the optical imaging lens assembly can be installed in the housing. This allows the curved image formed by the image source (such as a fiber optic scanner) to be imaged onto a flat carrier, thus achieving clear imaging.

[0108] Example Two

[0109] Figure 7 This is a schematic diagram of an optical imaging lens assembly provided in an embodiment of the present invention. The optical imaging lens assembly includes a first side (i.e., Figure 7the side where the scan surface 04 is located in the first embodiment) to the second side (i.e., the side where the diaphragm 03 is located in the first embodiment) is sequentially arranged with a first lens 31, a second lens 32, a third lens 33, a fourth lens 34, a fifth lens 35, a sixth lens 36, a seventh lens 37, and an eighth lens 38. Figure 7

[0110] In the first embodiment, each two adjacent lenses among the first lens 31, the second lens 32, the third lens 33, the fourth lens 34, the fifth lens 35, the sixth lens 36, the seventh lens 37, and the eighth lens 38 has a gap, and the first lens 31, the second lens 32, the third lens 33, the fifth lens 35, the seventh lens 37, and the eighth lens 38 are six single non-bonded lenses. The fourth lens 34 is a bonded lens composed of two sub-lenses, and the corresponding two sub-lenses from the first side to the second side are the fourth sub-lens 341 and the fourth sub-lens 342, respectively. The sixth lens 36 is also a bonded lens composed of two sub-lenses, and the corresponding two sub-lenses from the first side to the second side are the sixth sub-lens 361 and the sixth sub-lens 362, respectively.

[0111] The focal lengths of the first lens 31 to the eighth lens 38 from the first side to the second side are negative, positive, positive, negative, positive, positive, positive, and negative, respectively. Among them, the focal lengths of the fourth sub-lens 341 and the fourth sub-lens 342 included in the fourth lens 34 are positive and negative, respectively, and the focal lengths of the sixth sub-lens 361 and the sixth sub-lens 362 included in the sixth lens 36 are negative and positive, respectively.

[0112] The first side surface and the second side surface of the first lens 31 are both concave at the near optical axis;

[0113] The first side surface of the second lens 32 is concave at the near optical axis, and the second side surface is convex.

[0114] The first side surface and the second side surface of the third lens 33 are both convex;

[0115] The first side surface and the second side surface of the fourth sub-lens 341 in the fourth lens 34 are both convex, and the first side surface and the second side surface of the fourth sub-lens 342 are both concave;

[0116] The first side surface of the fifth lens 35 is concave at the near optical axis, and the second side surface is convex at the near optical axis;

[0117] The first side surface of the sixth sub-lens 361 in the sixth lens 36 is convex, and the second side surface is concave, and the first side surface and the second side surface of the sixth sub-lens 362 are both convex;

[0118] The first side surface of the seventh lens 37 is convex at the near optical axis, and the second side surface is concave at the near optical axis;

[0119] ​The first side surface of the eighth lens 38 is convex, and the second side surface is concave at the near optical axis.

[0120] In the embodiment, the focal lengths of the first lens 31 and the fourth lens 34 in the optical imaging lens satisfy the following relationship:

[0121] 0.7≤|f1 / f 总 |≤1.2, 0.8≤|f 4-2 / f 总 |≤1.5, where f1 is the focal length of the first lens, f 4-2 is the focal length of the fourth sub-lens 342 close to the fifth lens 35, i.e., the focal length of the fourth sub-lens 342, and f 总 is the total focal length of the optical imaging lens. It should be noted that the specific focal length of each lens is shown in Table 4:

[0122] Table 4: Focal length parameter table of each lens in the optical imaging lens

[0123] Lens Focal length Lens focal length / total lens focal length First lens 31 -2.53 -0.99 Second lens 32 6.38 2.50 Third lens 33 3.61 1.41 Fourth lens 34 -12.10 -4.75 Fourth sub-lens 341 5.74 2.25 Fourth sub-lens 342 -3.01 -1.18 Fifth lens 35 -16.14 -6.33 Sixth lens 36 22.04 8.64 Sixth sub-lens 361 -15.40 -6.04 Sixth sub-lens 362 22.90 8.98 Seventh lens 37 6.01 2.36 Eighth lens 38 -23.16 -9.08

[0124] The refractive index and dispersion coefficient of the first lens 31, the fourth sub-lens 342, and the sixth sub-lens 361 in the optical imaging lens satisfy the following conditions, respectively:

[0125] The refractive index and dispersion coefficient of the first lens 31 are 1.95 and 17.9, respectively; the refractive index and dispersion coefficient of the fourth sub-lens 342 are 1.78 and 25.7, respectively, and the refractive index and dispersion coefficient of the sixth sub-lens 361 are 1.92 and 18.89, respectively.

[0126] The total focal length of the optical imaging lens provided in the second embodiment of the present application is 2.58 mm, and the field of view angle is 28 degrees. The curvature radius, thickness parameter, refractive index, and dispersion coefficient of each lens in the imaging of the scanning curved surface 04 are shown in Table 5:

[0127] Table 5: Structure parameter of the optical imaging lens in the second embodiment

[0128]

[0129] It should be noted that Table 4 and Table 5 are detailed structure data of the optical imaging lens in the second embodiment, wherein the units of the curvature radius, thickness, and focal length are all millimeters, and the surfaces 0-20 in Table 5 represent the surfaces from the first side to the second side in order; the optical surface with a curvature radius of "infinity" in the imaging plane means a plane.

[0130] Further, the aspheric conic coefficients of the surfaces corresponding to the fifth lens 35 and the seventh lens 37 (both are aspheric lenses) are shown in Table 6:

[0131] Table 6. Conicity and asphericity data of the aspherical lens surface in Example 2.

[0132] Surface k A4 A6 A8 A10 A12 A14 A16 11 -9.83E-01 6.19E-02 -2.18E-02 -9.85E-04 3.42E-02 -5.23E-02 3.47E-02 -8.51E-03 12 -1.10E+00 -2.14E-02 1.43E-02 -1.15E-02 7.37E-03 -3.01E-03 6.84E-04 -6.44E-05 16 -9.81E-01 -1.45E-02 8.92E-03 -6.56E-03 4.10E-03 -1.64E-03 3.49E-04 -2.96E-05 17 -5.03E+00 -1.23E-03 -1.35E-02 1.48E-02 -1.04E-02 4.09E-03 -7.93E-04 5.82E-05

[0133] Table 6 shows the conic coefficient and aspheric coefficient data in Example 2, where k is the conic coefficient in the aspheric curve equation, and A4 to A16 represent the 4th to 16th order aspheric coefficients of each surface.

[0134] Additionally, please refer to the following: Figure 2b and Figure 7 In this embodiment, the maximum effective half-aperture Y1 of the third lens along the radial direction, the maximum effective half-aperture Y2 of the two opposite surfaces of the fourth and fifth lenses along the radial direction, and the maximum effective half-aperture Y3 of the seventh lens along the radial direction satisfy the following relationship: Y1 / Y2=1.37, Y3 / Y2=1.7.

[0135] Furthermore, tests showed that when the image light corresponding to the scanning surface is projected using the aforementioned optical imaging lens group, its optical transfer function curve is as follows: Figure 8 As shown, the field distortion curve is as follows: Figure 9 As shown, the vertical axis color difference curve is as follows: Figure 10 As shown; among them, the Modulation Transfer Function (MTF) curve represents the overall resolution level of an optical system, the Field Curve Distortion curve represents the F-Tan (theta) distortion magnitude (percentage) under different field angles, and the Vertical Chromatic Aberration curve represents the magnitude of chromatic aberration in the direction perpendicular to the axial direction.

[0136] Depend on Figures 8-10 Observations show that the optical imaging lens group of Example 2 has good imaging resolution and small optical system distortion and chromatic aberration across the entire field of view. Therefore, the optical imaging lens group can clearly image the scanning surface image of the fiber optic scanner and has good imaging effect.

[0137] Of course, in practical applications, the optical imaging lens assembly may also include a display element, a housing, etc. The display element can be set on the second side of the optical imaging lens assembly, and the optical imaging lens assembly can be installed in the housing. This allows the curved image formed by the image source (such as a fiber optic scanner) to be imaged onto a flat carrier, thus achieving clear imaging.

[0138] Example Three

[0139] Figure 11 This is a schematic diagram of an optical imaging lens assembly provided in an embodiment of the present invention. The optical imaging lens assembly includes a first side (i.e., Figure 11 From the side where aperture 05 is located (to the second side, that is,Figure 11 The first lens 51, the second lens 52, the third lens 53, the fourth lens 54, the fifth lens 55, the sixth lens 56, the seventh lens 57 and the eighth lens 58 are sequentially arranged on the same axis of the scanning surface 06.

[0140] In the embodiment, there is a gap between each two adjacent lenses among the first lens 51, the second lens 52, the third lens 53, the fourth lens 54, the fifth lens 55, the sixth lens 56, the seventh lens 57 and the eighth lens 58, and the first lens 51, the second lens 52, the third lens 53, the fifth lens 55, the seventh lens 57 and the eighth lens 58 are six single non-bonding lenses. The fourth lens 54 is a bonded lens composed of two sub-lenses, and the corresponding two sub-lenses are the fourth sub-lens 541 and the fourth sub-lens 542 from the first side to the second side; the sixth lens 56 is also a bonded lens composed of two sub-lenses, and the corresponding two sub-lenses are the sixth sub-lens 561 and the sixth sub-lens 562 from the first side to the second side.

[0141] The focal lengths of the first lens 51 to the eighth lens 58 from the first side to the second side are negative, positive, positive, negative, positive, positive, negative and positive in sequence, wherein the focal lengths of the fourth sub-lens 541 and the fourth sub-lens 542 included in the fourth lens 54 are negative and negative respectively, and the focal lengths of the sixth sub-lens 561 and the sixth sub-lens 562 included in the sixth lens 56 are positive and positive respectively.

[0142] The first side surface and the second side surface of the first lens 51 are both concave at the near optical axis;

[0143] The first side surface and the second side surface of the second lens 52 are both convex.

[0144] The first side surface and the second side surface of the third lens 53 are both convex.

[0145] The first side surface of the fourth sub-lens 541 in the fourth lens 54 is concave at the near optical axis, and the second side surface is convex, and the first side surface and the second side surface of the fourth sub-lens 542 are both concave;

[0146] The first side surface of the fifth lens 55 is concave at the near optical axis, and the second side surface is convex at the near optical axis;

[0147] The first side surface of the sixth sub-lens 561 in the sixth lens 56 is convex, and the second side surface is concave, and the first side surface and the second side surface of the sixth sub-lens 562 are both convex;

[0148] The first side surface of the seventh lens 57 is convex at the near optical axis, and the second side surface is concave at the near optical axis;

[0149] The first side surface of the eighth lens 58 is convex, and the second side surface is concave at the near optical axis.

[0150] In the embodiment, the focal length of the first lens 51 and the fourth lens 54 in the optical imaging lens group satisfies the following relationship:

[0151] 0.7≤|f1 / f 总 |≤1.2, 0.8≤|f 4-2 / f 总 |≤1.5, where f1 is the focal length of the first lens, f 4-2 is the focal length of the sub-lens of the fourth lens 54 close to the fifth lens 55, that is, the focal length of the fourth sub-lens 542, and f 总 is the total focal length of the optical imaging lens group. It should be noted that the specific focal length value of each lens is shown in Table 7:

[0152] Table 7: Focal length parameter table of each lens in the optical imaging lens group

[0153] Lens Focal length Lens focal length / total lens focal length First lens 51 -1.94 -0.70 Second lens 52 3.18 1.15 Third lens 53 2.90 1.05 Fourth lens 54 -2.41 -0.87 Fourth sub-lens 541 -5.55 -2.01 Fourth sub-lens 542 -2.76 -1.00 Fifth lens 55 6.23 2.25 Sixth lens 56 7.32 2.65 Sixth sub-lens 561 22.90 8.28 Sixth sub-lens 562 27.08 9.79 Seventh lens 57 -2.36 -0.85 Eighth lens 58 2.04 0.74

[0154] The refractive index and dispersion coefficient of the first lens 51, the fourth sub-lens 542, and the sixth sub-lens 561 in the optical imaging lens group satisfy the following conditions respectively:

[0155] The refractive index and dispersion coefficient of the first lens 51 are 1.96 and 19.4 respectively; the refractive index and dispersion coefficient of the fourth sub-lens 542 are 1.82 and 22.4 respectively, and the refractive index and dispersion coefficient of the sixth sub-lens 561 are 1.89 and 20.2 respectively.

[0156] The optical imaging lens group provided in the third embodiment of the present application has a total focal length of 2.58 mm and a field of view angle of 28 degrees. The radius of curvature, thickness parameter, refractive index, and dispersion coefficient of each lens in the optical imaging lens group for imaging the scanning curved surface 06 are shown in Table 8:

[0157] Table 8: Structure parameter of the optical imaging lens group in the third embodiment

[0158]

[0159]

[0160] It should be noted that Table 7 and Table 8 are detailed structure data of the optical imaging lens group in the third embodiment, wherein the units of the radius of curvature, thickness, and focal length are all millimeters, and the surfaces 0-20 in Table 8 represent the surfaces from the first side to the second side in order; the optical surface with a radius of curvature of "infinity" in the imaging plane means a plane.

[0161] Further, the conic coefficients and aspheric coefficients of the corresponding surfaces of the fifth lens 55 and the seventh lens 57 (both are aspheric lenses) are shown in Table 9 below:

[0162] Table 9: Conic coefficients and aspheric coefficients of the surfaces of the aspheric lenses in Example 3

[0163] Surface k A4 A6 A8 A10 A12 A14 A16 11 -9.06E-01 2.82E-02 7.00E-02 -2.42E-02 4.35E-02 -5.16E-02 2.57E-02 -4.82E-03 12 -1.66E+00 -4.48E-02 1.66E-02 -8.28E-03 7.33E-03 -3.04E-03 6.71E-04 -6.89E-05 16 9.39E-02 2.62E-02 -1.25E-02 -4.29E-04 3.54E-03 -1.96E-03 4.82E-04 -4.90E-05 17 -1.43E+00 8.33E-02 1.40E-02 -1.08E-02 3.34E-03 1.23E-02 -8.69E-03 1.88E-03

[0164] Table 9: Conic coefficients and aspheric coefficients of the surfaces of the aspheric lenses in Example 3, wherein k is the conic coefficient in the aspheric curve equation, and A4 to A16 represent the 4th to 16th order aspheric coefficients of the surfaces.

[0165] In addition, please refer to Figure 2b and Figure 11 , the maximum effective half aperture Y1 of the third lens along the radial direction, the maximum effective half aperture Y2 of the two surfaces of the fourth lens and the fifth lens along the radial direction, and the maximum effective half aperture Y3 of the seventh lens along the radial direction satisfy the following relationship: Y1 / Y2 = 1.28, Y3 / Y2 = 1.53.

[0166] Further, when the image light corresponding to the scanning surface of the optical fiber scanner is projected by using the optical imaging lens group, the Modulation Transfer Function (MTF) curve is as shown in Figure 12 , the field curvature distortion curve is as shown in Figure 13 , and the sagittal chromatic aberration curve is as shown in Figure 14 ; wherein the Modulation Transfer Function (MTF) curve represents the comprehensive resolution level of an optical system, the field curvature distortion curve represents the F-Tan(theta) distortion value (percentage) under different field angles, and the sagittal chromatic aberration curve represents the size of the chromatic aberration perpendicular to the axial direction.

[0167] As can be seen from Figures 12-14 , the optical imaging lens group of Example 3 has good imaging resolution, small optical system distortion and small chromatic aberration in the full field of view, so the optical imaging lens group can clearly image the scanning surface image of the optical fiber scanner, and all have good imaging effect.

[0168] Of course, in actual application, the optical imaging lens group can also include display elements, a housing, etc., the display elements can be arranged on the second side of the optical imaging lens group, and the optical imaging lens group can be installed in the housing, so that the curved surface image scanned by the image source (such as an optical fiber scanner) can be imaged on a flat carrier, achieving clear imaging.

[0169] Example Four

[0170] Figure 15A structural schematic diagram of an optical imaging lens provided by an embodiment of the present application. The optical imaging lens comprises a first lens 71, a second lens 72, a third lens 73, a fourth lens 74, a fifth lens 75, a sixth lens 76, a seventh lens 77 and an eighth lens 78 arranged in sequence on an optical axis from a first side (i.e., a side where a stop 07 in Figure 15 is located) to a second side (i.e., a side where a scanning surface 08 in Figure 15 is located).

[0171] In the embodiment, each two adjacent lenses among the first lens 71, the second lens 72, the third lens 73, the fourth lens 74, the fifth lens 75, the sixth lens 76, the seventh lens 77 and the eighth lens 78 has a gap, and the first lens 71, the second lens 72, the third lens 73, the fifth lens 75, the seventh lens 77 and the eighth lens 78 are six single non-bonding lenses. The fourth lens 74 is a bonded lens composed of two sub-lenses, and the corresponding two sub-lenses from the first side to the second side are a fourth sub-lens 741 and a fourth sub-lens 742 respectively; the sixth lens 76 is also a bonded lens composed of two sub-lenses, and the corresponding two sub-lenses from the first side to the second side are a sixth sub-lens 761 and a sixth sub-lens 762 respectively.

[0172] The focal lengths of the first lens 71 to the eighth lens 78 from the first side to the second side are negative, positive, positive, positive, positive, positive, negative and positive in sequence, wherein the focal lengths of the fourth sub-lens 741 and the fourth sub-lens 742 included in the fourth lens 74 are positive and negative respectively, and the focal lengths of the sixth sub-lens 761 and the sixth sub-lens 762 included in the sixth lens 76 are negative and positive respectively.

[0173] The first side surface and the second side surface of the first lens 71 are both concave at the near optical axis;

[0174] The first side surface and the second side surface of the second lens 72 are both convex.

[0175] The first side surface of the third lens 73 is concave at the near optical axis, and the second side surface is convex;

[0176] The first side surface and the second side surface of the fourth sub-lens 741 in the fourth lens 74 are both convex, and the first side surface and the second side surface of the fourth sub-lens 742 are both concave;

[0177] The first side surface of the fifth lens 75 is concave at the near optical axis, and the second side surface is convex at the near optical axis;

[0178] The first side surface and the second side surface of the sixth sub-lens 761 in the sixth lens 76 are both concave, and the first side surface and the second side surface of the sixth sub-lens 762 are both convex;

[0179] The first side surface of the seventh lens 77 is convex at the near optical axis, and the second side surface is concave at the near optical axis;

[0180] The first side surface of the eighth lens 78 is convex, and the second side surface is concave at the near optical axis.

[0181] In the embodiment, the focal length of the first lens 71 and the fourth lens 74 in the optical imaging lens group satisfies the following relationship:

[0182] 0.7≤|f1 / f 总 |≤1.2, 0.8≤|f 4-2 / f 总 |≤1.5, where f1 is the focal length of the first lens, f 4-2 is the focal length of the sub-lens of the fourth lens 74 close to the fifth lens 75, that is, the focal length of the fourth sub-lens 742, and f 总 is the total focal length of the optical imaging lens group. It should be noted that the specific focal length value of each lens is shown in Table 10:

[0183] Table 10: Focal length parameter table of each lens in the optical imaging lens group

[0184] Lens Focal length Lens focal length / total lens focal length First lens 71 -1.98 -0.70 Second lens 72 3.01 1.06 Third lens 73 12.15 4.29 Fourth lens 74 19.90 7.03 Fourth sub-lens 741 3.66 1.29 Fourth sub-lens 742 -2.83 -1.00 Fifth lens 75 4.38 1.55 Sixth lens 76 11.41 4.03 Sixth sub-lens 761 -17.03 -6.02 Sixth sub-lens 762 9.21 3.25 Seventh lens 77 -2.48 -0.87 Eighth lens 78 1.81 0.64

[0185] The refractive index and dispersion coefficient of the first lens 71, the fourth sub-lens 742, and the sixth sub-lens 761 in the optical imaging lens group satisfy the following conditions respectively:

[0186] The refractive index and dispersion coefficient of the first lens 71 are 1.78 and 21.4 respectively; the refractive index and dispersion coefficient of the fourth sub-lens 742 are 1.9 and 27.1 respectively, and the refractive index and dispersion coefficient of the sixth sub-lens 761 are 1.83 and 21.6 respectively.

[0187] The total focal length of the optical imaging lens group provided by the fourth embodiment of the present application is 2.58mm, and the field of view angle is 28 degrees. The curvature radius, thickness parameter, refractive index, and dispersion coefficient of each lens in the optical imaging lens group for imaging the scanning curved surface 08 are shown in Table 11:

[0188] Table 11: Structure parameters of the optical imaging lens group in the fourth embodiment

[0189]

[0190]

[0191] It should be noted that Table 10 and Table 11 are detailed structure data of the optical imaging lens set of Example 4, wherein the units of the curvature radius, the thickness and the focal length are millimeters, and the surfaces 0-20 in Table 11 represent the surfaces from the first side to the second side in sequence; the optical surface with the curvature radius of "infinity" in the imaging plane means a plane.

[0192] Further, the conic coefficients and aspheric conic coefficients of the surfaces corresponding to the fifth lens 75 and the seventh lens 77 (both are aspheric lenses) are shown in Table 12 below:

[0193] Table 12 is the conic coefficients and aspheric coefficients data of the surfaces of different lenses in Example 4.

[0194] Surface k A4 A6 A8 A10 A12 A14 A16 11 -9.69E-01 6.51E-02 3.83E-02 -2.30E-02 4.47E-02 -5.37E-02 2.70E-02 -4.99E-03 12 -1.81E+00 -2.00E-02 1.53E-02 -7.08E-03 7.45E-03 -3.20E-03 6.67E-04 -6.24E-05 16 -6.75E-01 5.42E-02 -2.09E-02 1.51E-03 4.48E-03 -2.00E-03 3.54E-04 -2.26E-05 17 -1.51E+00 2.09E-01 -1.20E-01 5.20E-02 1.77E-02 3.09E-04 -1.21E-02 3.86E-03

[0195] Table 12 is the conic coefficients and aspheric coefficients data in Example 4, wherein k is the conic coefficient in the aspheric curve equation, and A4 to A16 represent the 4th to 16th order aspheric coefficients of each surface.

[0196] In addition, please refer to Figure 2b and Figure 15 , the maximum effective half aperture Y1 of the third lens in the radial direction, the maximum effective half aperture Y2 of the two surfaces of the fourth lens and the fifth lens in the radial direction, and the maximum effective half aperture Y3 of the seventh lens in the radial direction satisfy the following relationship: Y1 / Y2 = 1.31, Y3 / Y2 = 1.5.

[0197] Further, it is tested that when the image light corresponding to the projection scanning surface is projected by using the above optical imaging lens set, the modulation transfer function (MTF) curve is as shown in Figure 16 , the field curvature distortion curve is as shown in Figure 17 , and the axial chromatic aberration curve is as shown in Figure 18 ; wherein the modulation transfer function (MTF) curve represents the comprehensive resolution level of an optical system, the field curvature distortion curve represents the F-Tan(theta) distortion size value (percentage) under different field angles, and the axial chromatic aberration curve represents the size of the chromatic aberration perpendicular to the axial direction.

[0198] It can be observed from Figures 16-18 that the imaging resolution of the optical imaging lens set of Example 4 is good in the full field of view, the optical system distortion and the chromatic aberration are small, so the optical imaging lens set can clearly image the scanning surface image of the fiber scanner, and all have good imaging effect.

[0199] Of course, in practical applications, the optical imaging lens group can also include display elements, housings, etc., the display elements can be arranged on the second side of the optical imaging lens group, and the optical imaging lens group can be installed in the housing, that is, the curved image scanned by the image source (such as a fiber scanner) can be imaged on a planar carrier to achieve clear imaging.

[0200] Example Five

[0201] Figure 19 A structural schematic diagram of an optical imaging lens group provided by an embodiment of the present application. The optical imaging lens group includes first lens 91, second lens 92, third lens 93, fourth lens 94, fifth lens 95, sixth lens 96, seventh lens 97 and eighth lens 98 arranged in order on the same optical axis from the first side (that is, the side on which the diaphragm 09 in the above embodiment is located) to the second side (that is, the side on which the scanning curved surface 10 in the above embodiment is located). Figure 19 Figure 19

[0202] In the present embodiment, each two adjacent lenses among the first lens 91, the second lens 92, the third lens 93, the fourth lens 94, the fifth lens 95, the sixth lens 96, the seventh lens 97 and the eighth lens 98 have a gap, and the first lens 91, the second lens 92, the third lens 93, the fifth lens 95, the seventh lens 97 and the eighth lens 98 are six single non-adhesive lenses. The fourth lens 94 is a cemented lens composed of two sub-lenses, and the corresponding two sub-lenses are the fourth sub-lens 941 and the fourth sub-lens 942 from the first side to the second side; the sixth lens 96 is also a cemented lens composed of two sub-lenses, and the corresponding two sub-lenses are the sixth sub-lens 961 and the sixth sub-lens 962 from the first side to the second side.

[0203] The focal lengths of the first lens 91 to the eighth lens 98 from the first side to the second side are negative, positive, positive, positive, positive, positive, negative and positive in order, wherein the focal lengths of the fourth sub-lens 941 and the fourth sub-lens 942 included in the fourth lens 94 are positive and negative respectively, and the focal lengths of the sixth sub-lens 961 and the sixth sub-lens 962 included in the sixth lens 96 are negative and positive respectively.

[0204] The first side surface and the second side surface of the first lens 91 are both concave at the near optical axis;

[0205] The first side surface and the second side surface of the second lens 92 are both convex.

[0206] The first side surface of the third lens 93 is concave at the near optical axis, and the second side surface is convex;

[0207] ​​The first side surface and the second side surface of the fourth sub-lens 941 in the fourth lens 94 are both convex, and the first side surface and the second side surface of the fourth sub-lens 942 are both concave;

[0208] The first side surface of the fifth lens 95 is concave at the near optical axis, and the second side surface is convex at the near optical axis;

[0209] The first side surface and the second side surface of the sixth sub-lens 961 in the sixth lens 96 are both concave, and the first side surface and the second side surface of the sixth sub-lens 962 are both convex;

[0210] The first side surface of the seventh lens 97 is convex at the near optical axis, and the second side surface is concave at the near optical axis;

[0211] The first side surface of the eighth lens 98 is convex, and the second side surface is concave at the near optical axis.

[0212] In the embodiment, the focal length of the first lens 91 and the fourth lens 94 in the optical imaging lens group satisfies the following relationship:

[0213] 0.7≤|f1 / f 总 |≤1.2, 0.8≤|f 4-2 / f 总 |≤1.5, where f1 is the focal length of the first lens, f 4-2 is the focal length of the sub-lens of the fourth lens 94 close to the fifth lens 95, that is, the focal length of the fourth sub-lens 942, and f 总 is the total focal length of the optical imaging lens group. It should be noted that the specific focal length value of each lens is shown in Table 13:

[0214] Table 13 Focal length parameter table of each lens in the optical imaging lens group

[0215] Lens Focal length Lens focal length / total lens focal length First lens 91 -2.83 -1.05 Second lens 92 4.74 1.75 Third lens 93 7.65 2.83 Fourth lens 94 22.83 8.45 Fourth sub-lens 941 4.10 1.52 Fourth sub-lens 942 -3.80 -1.41 Fifth lens 95 5.88 2.18 Sixth lens 96 23.76 8.80 Sixth sub-lens 961 -17.03 -6.31 Sixth sub-lens 962 11.75 4.35 Seventh lens 97 -9.32 -3.45 Eighth lens 98 6.34 2.35

[0216] The refractive index and the dispersion coefficient of the first lens 91, the fourth sub-lens 942, and the sixth sub-lens 961 in the optical imaging lens group satisfy the following conditions respectively:

[0217] The refractive index and the dispersion coefficient of the first lens 91 are 1.79 and 23 respectively; the refractive index and the dispersion coefficient of the fourth sub-lens 942 are 1.72 and 24 respectively, and the refractive index and the dispersion coefficient of the sixth sub-lens 961 are 1.77 and 21.8 respectively.

[0218] The total focal length of the optical imaging lens group is 2.58 mm, and the field of view angle is 28 degrees. The radius of curvature, thickness parameter, refractive index, and dispersion coefficient of each lens in the optical imaging lens group for imaging the scanning curved surface 10 are shown in Table 14:

[0219] Table 14 Structure parameters of the optical imaging lens set in Example Five

[0220]

[0221] It is to be noted that Table 13 and Table 14 are detailed structure data of the optical imaging lens set in Example Five, wherein the units of the curvature radius, the thickness and the focal length are millimeters, and the surfaces 0-20 in Table 14 represent the surfaces from the first side to the second side in sequence; the optical surface with the curvature radius of "infinity" in the imaging plane means a plane.

[0222] Further, the conic coefficients and aspheric coefficients of the surfaces corresponding to the fifth lens 95 and the seventh lens 97 (both are aspheric lenses) are shown in Table 15 as follows:

[0223] Table 15 Conic coefficients and aspheric coefficients of the surfaces of the aspheric lenses in Example Five

[0224] Surface k A4 A6 A8 A10 A12 A14 A16 11 -1.06E+00 8.34E-02 2.36E-02 -3.28E-02 5.08E-02 -5.02E-02 2.39E-02 -4.39E-03 12 -1.58E+00 -2.26E-02 1.38E-02 -8.06E-03 7.33E-03 -3.26E-03 7.23E-04 -6.72E-05 16 -5.11E-01 5.29E-02 -1.64E-02 -3.02E-04 4.32E-03 -1.84E-03 3.24E-04 -1.81E-05 17 -5.21E+00 1.35E-01 -7.26E-02 2.82E-02 -1.63E-03 2.82E-03 -3.58E-03 9.62E-04

[0225] Table 15 is the conic coefficients and aspheric coefficients data in Example Five, wherein k is the conic coefficient in the aspheric curve equation, and A4 to A16 represent the 4th to 16th order aspheric coefficients of each surface.

[0226] In addition, please refer to Figure 2b and Figure 19 , the maximum effective half aperture radius Y1 of the third lens in the radial direction, the maximum effective half aperture radius Y2 of the two surfaces of the fourth lens and the fifth lens in the radial direction, and the maximum effective half aperture radius Y3 of the seventh lens in the radial direction satisfy the following relationship: Y1 / Y2 = 1.36, Y3 / Y2 = 1.41.

[0227] Further, it is tested that when the image light corresponding to the projection scanning surface is projected by using the above optical imaging lens set, the optical transfer function curve is as shown in Figure 20 , the field curvature distortion curve is as shown in Figure 21 , and the axial chromatic aberration curve is as shown in Figure 22 ; wherein the optical transfer function curve (Modulation Transfer Function, MTF) represents the comprehensive resolution level of an optical system, the field curvature distortion curve represents the F-Tan(theta) distortion size value (percentage) under different field angles, and the axial chromatic aberration curve represents the size of the chromatic aberration perpendicular to the axial direction.

[0228] from Figures 20-22It can be observed that the optical imaging lens group of Example Five has good imaging resolution, small optical system distortion and small chromatic aberration in the full field of view range, and thus the optical imaging lens group can clearly image the curved surface image scanned by the fiber scanner, and both have good imaging effects.

[0229] Of course, in actual applications, the optical imaging lens group can further include a display element and a housing, and the display element can be arranged on the second side of the optical imaging lens group. The optical imaging lens group can be installed in the housing, so that the curved surface image scanned by the image source (such as the fiber scanner) can be imaged on a planar carrier to achieve clear imaging.

[0230] Scanning display device

[0231] The optical imaging lens group described above can be combined with a fiber scanner (or a corresponding fiber scanning module) to form a scanning display device in the embodiments of the present application (such as Figure 1a , 1b The optical imaging lens group is arranged on the light path of the fiber scanner), and the first side of the optical imaging lens group faces the scanning direction of the fiber scanner. Preferably, the optical imaging lens group is coaxial with the central optical axis of the fiber scanner. Of course, the structure and general principle of the fiber scanner can refer to the foregoing Figure 1a , 1b The corresponding content will not be described in detail here.

[0232] Near-eye display device

[0233] In the present application, the scanning display device can be further applied to a near-eye display device, and can be combined with a near-eye display module to form a near-eye display device in the embodiments of the present application, and can be used as a head-mounted AR device (such as AR glasses). The scanning display device is arranged in the near-eye display module.

[0234] The near-eye display module can include a light source, a processing control circuit, a wearable frame structure, a waveguide, and the like. The image light beam output by the light source enters the scanning display device, is scanned by the fiber scanner in the scanning display device, and is output to the optical display lens group. The scanning curved surface (which can refer to the scanning curved surface 02 in Figure 3 and the corresponding scanning curved surface 230 in Figure 2a ) of the fiber scanner is converted into an imaging plane (which can refer to the imaging plane 240 in Figure 2a ) after the optical display lens group, and the imaging plane is coupled into the waveguide as an entrance pupil surface of the waveguide, and then is expanded and coupled out by the waveguide to enter the human eye.

[0235] As another possible implementation, the scanning display device can further be configured into the near-eye display module as the near-eye display device in the embodiments of the present application, and used as a head-mounted VR device (e.g., a VR helmet / glasses). The scanning display device is arranged in the near-eye display module.

[0236] In the embodiments of the present application, by reasonably optimizing the focal lengths of the five coaxial lenses of the optical imaging lens group, the optical power of the system can be reasonably dispersed, the aberration generated by the lens can be slowed down, the purpose of correcting various aberrations can be achieved, and clear imaging of the image surface can be achieved on the basis of improving the field of view; by limiting and optimizing the refractive index, the dispersion coefficient and the surface structure of the five coaxial lenses, the imaging quality and the field of view are further improved; by limiting and optimizing the five coaxial lenses to be aspherical surface structures, the imaging quality is further improved, and the overall structure of the optical imaging lens group is more compact, which meets the production requirements of miniaturization of the lens product.

[0237] The above are only preferred embodiments of the present application, and each embodiment is only used to illustrate the technical solutions of the present application but not to limit the present application, and any technical solution obtained by logical analysis, reasoning or effective experiment according to the concept of the present application should be within the scope of the present application.

[0238] Each embodiment in the present application is described in a progressive manner, and the same or similar parts between each embodiment can be referred to each other, and each embodiment mainly describes the difference from other embodiments.

[0239] The expressions "first", "second", "the first" or "the second" used in various embodiments of the present disclosure can modify various components regardless of order and / or importance, but these expressions do not limit the corresponding components. The above expressions are only configured for the purpose of distinguishing the elements from other elements. For example, the first lens and the second lens represent different lenses, although both are lenses.

Claims

1. An optical imaging lens system, characterized in that, The optical imaging lens group comprises, sequentially from a first side to a second side, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens, wherein the first side of the optical imaging lens group corresponds to a planar image, the second side of the optical imaging lens group corresponds to a curved surface image, and the first lens, the second lens, the third lens and the sixth lens correspond to negative, positive, positive and positive focal lengths, respectively. The first lens satisfies the following relationship: 1.7≤nd1≤2.0 and 17≤vd1≤23, wherein nd1 is the refractive index of the first lens, and vd1 is the dispersion coefficient of the first lens.

2. The optical imaging lens according to claim 1, wherein, The first lens, the second lens, the third lens, the fourth lens, the sixth lens and the eighth lens are all spherical lenses. The fifth lens and the seventh lens are both aspherical lenses.

3. The optical imaging lens according to claim 2, wherein, The fourth lens and the sixth lens are both spherical cemented lenses.

4. The optical imaging lens according to claim 3, wherein, The fourth lens and the sixth lens each comprise two sub-lenses, wherein the two sub-lenses of the fourth lens are arranged coaxially from a first side to a second side and correspond to positive and negative focal lengths, respectively; and the two sub-lenses of the sixth lens are arranged coaxially from a first side to a second side and correspond to negative and positive focal lengths, respectively.

5. The optical imaging lens according to claim 4, wherein, The second side surface of the sub-lens of the fourth lens close to the fifth lens is a concave surface; and the first side surface of the fifth lens is a concave surface.

6. The optical imaging lens according to claim 4, wherein, The focal lengths of the fourth lens, the fifth lens, the seventh lens and the eighth lens are negative, positive, positive and positive, respectively. The first lens and the optical imaging lens group have the following relationship: 0.7≤|f1 / f 总 |≤1.2, wherein f1 is a focal length of the first lens, and f 总 is a total focal length of the optical imaging lens group. The fourth lens has a sub-lens close to the fifth lens, and the optical imaging lens set has the following relationship: 0.8≤|f 4-2 / f 总 |≤1.5, wherein f 4-2 is a focal length of the sub-lens of the fourth lens close to the fifth lens, and f 总 is a total focal length of the optical imaging lens set.

7. The optical imaging lens according to claim 4, wherein, The refractive indices of the sub-lens of the fourth lens close to the fifth lens and the sub-lens of the sixth lens close to the fifth lens are both in [1.7, 2], and the dispersion coefficients are in [22, 28] and [18, 22], respectively.

8. A scanning display device, characterized by The optical imaging lens group comprises, sequentially from a first side to a second side, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens, wherein the first side of the optical imaging lens group corresponds to a planar image, the second side of the optical imaging lens group corresponds to a curved surface image, the first lens, the second lens, the third lens and the sixth lens correspond to negative, positive, positive and positive focal lengths, respectively; The first lens satisfies the following relationship: 1.7≤nd1≤2.0 and 17≤vd1≤23, wherein nd1 is the refractive index of the first lens, and vd1 is the dispersion coefficient of the first lens.

9. A near-eye display device, comprising: The first lens, the second lens, the third lens, the fourth lens, the sixth lens and the eighth lens are all spherical lenses; 10. A near-eye display device, comprising: The fifth lens and the seventh lens are both aspherical lenses. The fourth lens and the sixth lens are both spherical cemented lenses. The fourth lens and the sixth lens each comprise two sub-lenses, wherein the two sub-lenses of the fourth lens are arranged coaxially from a first side to a second side and correspond to positive and negative focal lengths, respectively; and the two sub-lenses of the sixth lens are arranged coaxially from a first side to a second side and correspond to negative and positive focal lengths, respectively. The second side surface of the sub-lens of the fourth lens close to the fifth lens is a concave surface; and the first side surface of the fifth lens is a concave surface. The focal lengths of the fourth lens, the fifth lens, the seventh lens and the eighth lens are negative, positive, positive and positive, respectively; The refractive indices of the sub-lens of the fourth lens close to the fifth lens and the sub-lens of the sixth lens close to the fifth lens are both in [1.7, 2], and the dispersion coefficients are in [22, 28] and [18, 22], respectively. The optical imaging lens group comprises, sequentially from a first side to a second side, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens, wherein the first side of the optical imaging lens group corresponds to a planar image, the second side of the optical imaging lens group corresponds to a curved surface image, the first lens, the second lens, the third lens and the sixth lens correspond to negative, positive, positive and positive focal lengths, respectively; The first lens satisfies the following relationship: 1.7≤nd1≤2.0 and 17≤vd1≤23, wherein nd1 is the refractive index of the first lens, and vd1 is the dispersion coefficient of the first lens. The first lens, the second lens, the third lens, the fourth lens, the sixth lens and the eighth lens are all spherical lenses; The fifth lens and the seventh lens are both aspherical lenses. The fourth lens and the sixth lens are both spherical cemented lenses. The fourth lens and the sixth lens each comprise two sub-lenses, wherein the two sub-lenses of the fourth lens are arranged coaxially from a first side to a second side and correspond to positive and negative focal lengths, respectively; and the two sub-lenses of the sixth lens are arranged coaxially from a first side to a second side and correspond to negative and positive focal lengths, respectively. The second side surface of the sub-lens of the fourth lens close to the fifth lens is a concave surface; and the first side surface of the fifth lens is a concave surface. The focal lengths of the fourth lens, the fifth lens, the seventh lens and the eighth lens are negative, positive, positive and positive, respectively; The refractive indices of the sub-lens of the fourth lens close to the fifth lens and the sub-lens of the sixth lens close to the fifth lens are both in [1.7, 2], and the dispersion coefficients are in [22, 28] and [18, 22], respectively. The optical imaging lens group comprises, sequentially from a first side to a second side, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens, wherein the first side of the optical imaging lens group corresponds to a planar image, the second side of the optical imaging lens group corresponds to a curved surface image, the first lens, the second lens, the third lens and the sixth lens correspond to negative, positive, positive and positive focal lengths, respectively; The first lens satisfies the following relationship: 1.7≤nd1≤2.0 and 17≤vd1≤23, wherein nd1 is the refractive index of the first lens, and vd1 is the dispersion coefficient of the first lens. The first lens, the second lens, the third lens, the fourth lens, the sixth lens and the eighth lens are all spherical lenses; The fifth lens and the seventh lens are both aspherical lenses. The fourth lens and the sixth lens are both spherical cemented lenses. The fourth lens and the sixth lens each comprise two sub-lenses, wherein the two sub-lenses of the fourth lens are arranged coaxially from a first side to a second side and correspond to positive and negative focal lengths, respectively; and the two sub-lenses of the sixth lens are arranged coaxially from a first side to a second side and correspond to negative and positive focal lengths, respectively. The second side surface of the sub-lens of the fourth lens close to the fifth lens is a concave surface; and the first side surface of the fifth lens is a concave surface. The focal lengths of the fourth lens, the fifth lens, the seventh lens and the eighth lens are negative, positive, positive and positive, respectively; The refractive indices of the sub-lens of the fourth lens close to the fifth lens and the sub-lens of the sixth lens close to the fifth lens are both in [1.7, 2], and the dispersion coefficients are in [22, 28] and [18, 22], respectively.

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