Low-cost large-target-surface ADAS optical imaging system

Abstract

The invention provides a low-cost large-target-surface ADAS optical imaging system. The optical system sequentially comprises a first lens, a diaphragm, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, an optical filter, protective glass and an image surface from an object surface to an image surface along an optical axis. The first lens E1 has proper negative focal power, the second lens E2 has certain positive focal power, the lens with the positive focal power and the lens with the negative focal power are matched, the large-target-surface effect of the lens is achieved, the long-focal-length lens structure is matched, the definition and details of imaging can be guaranteed on the large target surface, and imaging of a distant object on the large-target-surface sensor is larger and clearer; in addition, the optical design enables the width of the light beam entering the optical system to be larger, the large aperture design of the optical system is facilitated, the imaging effect is good, and objects on the two sides of the road can be recognized in the dark light environment.

Description

Technical Field

[0001] The present invention relates to the technical field of optical imaging, and particularly to a low-cost large-target-surface ADAS optical imaging system. Background Art

[0002] In this era of exponential and rapid development of technology, from the leap in the performance of intelligent chips, to the continuous improvement of sensor accuracy, to the ever-changing communication technology, numerous cutting-edge scientific and technological achievements are intertwined and converged. Driven by this powerful wave of technology, ADAS technology has gradually spread in the automotive field and related industries. It is no longer just a remarkable cutting-edge concept in the laboratory, but has gradually entered the lives of ordinary people, gradually descending from high-end models to mid- and low-end models, from a novelty configuration for a few technology pioneers to a common option for more and more consumers when purchasing a car, bringing a new experience of being more intelligent, safer, and more convenient for people's travel.

[0003] However, most of the current ADAS lenses have the following problems: the target surface and aperture are small, which limits the field of view and imaging quality, making it difficult to identify objects on both sides of the road in low-light environments. When the vehicle is in a turning state, there are serious safety hazards, increasing the risk of collisions between the vehicle and pedestrians and non-motor vehicles when turning. Summary of the Invention

[0004] The present invention proposes a low-cost large-target-surface ADAS optical imaging system, which combines the characteristics of low cost, large target surface, large aperture, ultra-high definition pixels, athermalization, and purple fringing optimization.

[0005] The above technical object of the present invention is achieved through the following technical solutions: A low-cost large-target-surface ADAS optical imaging system: Sequentially including, along the optical axis from the object surface to the image surface: a first lens, a diaphragm, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a filter, a protective glass, and an image surface; The first lens is a concavo-convex lens with a negative optical power; the second lens is a biconvex lens with a positive optical power; the third lens is a biconvex lens with a positive optical power; the fourth lens is a biconcave lens with a negative optical power; the fifth lens is a biconvex lens with a positive optical power; the sixth lens is a concavo-convex lens with a negative optical power; Wherein, the ratio of the focal lengths of the first lens to the sixth lens to the focal length of the optical imaging system satisfies the following set relationship: -2.1 < f1 / f < -1.1, 0.8 < f2 / f < 1.9, 1.1 < f3 / f < 2.3, -2.6 < f4 / f < -1.3, 1.0 < f5 / f < 2.2, -1.6 < f6 / f < -0.5; where f1 represents the effective focal length of the first lens, f2 represents the effective focal length of the second lens, f3 represents the effective focal length of the third lens, f4 represents the effective focal length of the fourth lens, f5 represents the effective focal length of the fifth lens, f6 represents the effective focal length of the sixth lens, and f represents the effective focal length of the optical imaging system; Wherein, the entrance pupil diameter EPD of the optical imaging system and the maximum holographic height IH corresponding to the maximum field of view angle satisfy: 1 < IH / EPD < 1.2.

[0006] Further, the Abbe numbers of the first lens, the fourth lens, and the fifth lens are all greater than 40 and less than 50; the Abbe number of the sixth lens is greater than 35 and less than 42; the Abbe numbers of the second lens and the third lens are both greater than 61 and less than 72.

[0007] Further, the distance L1 between the first lens and the second lens and the distance L2 between the second lens and the third lens satisfy: 2.7 < L2 - L1 < 3.1.

[0008] Further, the refractive index n1 of the first lens satisfies: 1.73 < n1 < 1.9, the refractive index n4 of the fourth lens satisfies: 1.73 < n4 < 1.9, the refractive index n5 of the fifth lens satisfies: 1.73 < n5 < 1.9, and the refractive index n6 of the sixth lens satisfies: 1.73 < n6 < 1.9.

[0009] Further, the focal length f of the optical imaging system and the maximum holographic height IH corresponding to the maximum field of view angle satisfy: 1.3 < f / IH < 1.8.

[0010] Further, the third lens and the fourth lens form a cemented lens.

[0011] Further, the aperture stop ST0 is disposed between the first lens and the second lens.

[0012] Further, the maximum holographic height IH of the optical imaging system satisfies the following condition: IH ≥ 9.688 mm; the aperture of the optical imaging system satisfies the following condition: F / NO = 1.6.

[0013] Further, the effective focal length f of the optical imaging system satisfies the following condition: 15.30 mm ≤ f ≤ 15.38 mm.

[0014] In a further solution, the surface of the first lens facing the object side is concave, and the surface facing the image side is convex; the absolute value of the radius of curvature of the surface of the second lens facing the object side is less than the absolute value of the radius of curvature of the surface of the second lens facing the image side; the absolute value of the radius of curvature of the surface of the third lens facing the object side is less than the absolute value of the radius of curvature of the surface of the third lens facing the image side; the surface of the fourth lens facing the object side is a concave surface with a platform, and the surface facing the image side is concave; the surface of the fifth lens facing the object side is convex, and the surface facing the image side is convex; the surface of the sixth lens facing the object side is concave, and the surface facing the image side is convex.

[0015] In summary, the present invention has the following beneficial effects: The present invention provides a low-cost large-target ADAS optical imaging system, especially an ADAS optical imaging system that takes into account low cost, large target, large aperture, ultra-high definition pixels, athermalization, and purple edge optimization. The optical imaging system includes a first lens, a diaphragm, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a filter, a protective glass, and an image plane arranged in the direction from the object side to the image side. The present invention adopts a 5G+1GM structure design, designs ultra-high definition pixels in a cost-effective manner, and reduces the product cost. It can be paired with a large-target 8MPixel 1 / 1.8 chip; the present invention designs an aperture of F1.6, which can realize the recognition of objects on both sides of the road in low-light environments; the present invention uses low-dispersion materials to design and optimize purple edges, improving the imaging quality of the lens; the present invention adopts an athermalization design, realizes thermal drift compensation, and the operating temperature can range from -50°C to 105°C, greatly improving the application of the product in other complex temperature scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic structural diagram of the optical imaging system provided by the embodiment of the present invention; Figure 2 It is an MTF analysis diagram of the optical imaging system provided by the embodiment of the present invention at 20°C in visible light; Figure 3 It is a defocus curve diagram of the optical imaging system provided by the embodiment of the present invention at 20°C in visible light; Figure 4 It is a defocus curve diagram of the optical imaging system provided by the embodiment of the present invention at -50°C in visible light; Figure 5 It is a defocus curve diagram of the optical imaging system provided by the embodiment of the present invention at 105°C in visible light; Figure 6 It is an F-THETA distortion diagram of the optical imaging system provided by the embodiment of the present invention; Figure 7 It is a relative illuminance curve diagram of the optical imaging system provided by the embodiment of the present invention in visible light; Figure 8 The field curvature diagram of the optical imaging system provided by the embodiment of the present invention in visible light; Figure 9 The standard spot diagram of the optical imaging system provided by the embodiment of the present invention in visible light.

[0017] Figure 10 The sagittal chromatic aberration diagram of the optical imaging system provided by the embodiment of the present invention at a wavelength of 435 - 656 nm. Detailed implementation manners

[0018] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0019] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

[0020] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0021] In the present invention, unless otherwise clearly specified and defined, the terms "mounted", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] Such as Figure 1As shown in the figure, the present invention provides a low-cost large target surface ADAS optical imaging system. The optical imaging system includes a first lens E1, a diaphragm ST0, a second lens E2, a third lens E3, a fourth lens E4, a fifth lens E5, a sixth lens E6, a filter IR, a protective glass CG, and an image plane IMA arranged in the direction from the object side to the image side. Among them, the first lens E1 to the sixth lens E6 are all glass lenses. The second lens E2 is an aspherical glass lens, and the first lens E1, the third lens E3, the fourth lens E4, the fifth lens E5, and the sixth lens E6 are all spherical glass lenses. Compared with the traditional ADAS optical imaging system that requires a 7G or even 8G design, the optical imaging system of the present application has a lower cost.

[0023] Specifically, the first lens E1 is a concave-convex lens with a negative optical power; the second lens E2 is a biconvex lens with a positive optical power; the third lens E3 is a biconvex lens with a positive optical power; the fourth lens E4 is a biconcave lens with a negative optical power; the fifth lens E5 is a biconvex lens with a positive optical power; the sixth lens E6 is a concave-convex lens with a negative optical power.

[0024] Among them, the ratio of the focal lengths of the first lens E1 to the sixth lens E6 to the focal length of the optical imaging system satisfies the following set relationship: -2.1 < f1 / f < -1.1, 0.8 < f2 / f < 1.9, 1.1 < f3 / f < 2.3, -2.6 < f4 / f < -1.3, 1.0 < f5 / f < 2.2, -1.6 < f6 / f < -0.5; where f1 represents the effective focal length of the first lens E1, f2 represents the effective focal length of the second lens E2, f3 represents the effective focal length of the third lens E3, f4 represents the effective focal length of the fourth lens E4, f5 represents the effective focal length of the fifth lens E5, f6 represents the effective focal length of the sixth lens E6, and f represents the effective focal length of the optical imaging system.

[0025] It should be noted that the effective focal length f of the optical imaging system, the focal length f1 of the first lens E1, and the focal length f2 of the second lens E2 satisfy: -2.1 < f1 / f < -1.1, 0.8 < f2 / f < 1.9, 15.30mm ≤ f ≤ 15.38mm. Meeting the above range can make the first lens E1 have an appropriate negative optical power and the second lens E2 have a certain positive optical power, so that the light rays are first diverged by the first lens E1 with negative optical power and then converged by the subsequent second lens E2 with positive optical power. The combination of positive and negative optical power lenses is conducive to the lens achieving a large target surface effect. With the long focal length lens structure, the clarity and details of the image can be guaranteed on the large target surface, making the images of distant objects larger and clearer on the large target surface sensor.

[0026] In a further solution, the Abbe numbers of the first lens E1, the fourth lens E4, and the fifth lens E5 of the optical imaging system are all greater than 40 and less than 50; the Abbe number of the sixth lens E6 is greater than 35 and less than 42; the Abbe numbers of the second lens E2 and the third lens E3 are both greater than 61 and less than 72. Meeting the above ranges, the second lens E2 and the third lens E3 adopt low-dispersion materials, and the first lens E1, the fourth lens E4, and the fifth lens E5 are selected with materials having similar Abbe numbers. Their refraction laws for light of different wavelengths are relatively similar, which can make the dispersion effects generated by different lenses compensate each other, thereby effectively reducing chromatic aberration. This can ensure that light in a relatively wide wavelength range from ultraviolet to infrared can be focused and imaged in a more similar manner, resulting in higher color fidelity of the image, more natural and real color transition, and improved imaging quality.

[0027] Preferably, for the spacing distance L1 (mm) between the first lens E1 and the second lens E2 of the optical lens, and the spacing distance L2 (mm) between the second lens E2 and the third lens E3, it satisfies: 2.7 < L2 - L1 < 3.1. A larger lens spacing distance can increase the distance that light travels between the lenses. Appropriately increasing the lens spacing can make the light propagation path more flexible, facilitating the correction of chromatic aberration, spherical aberration, coma aberration, etc., improving the imaging quality and making the image clearer and more accurate; at the same time, a larger spacing can provide better thermal compensation when the temperature changes, maintaining the stability of the optical performance.

[0028] Preferably, for the refractive index n1 of the first lens E1, it satisfies: 1.73 < n1 < 1.9; for the refractive index n4 of the fourth lens E4, it satisfies: 1.73 < n4 < 1.9; for the refractive index n5 of the fifth lens E5, it satisfies: 1.73 < n5 < 1.9; for the refractive index n6 of the sixth lens E6, it satisfies: 1.73 < n6 < 1.9. The first lens E1, the fourth lens E4, the fifth lens E5, and the sixth lens E6 adopt high-refractive-index materials. High-refractive-index materials can make the light focus more precisely, improving the imaging quality of the lens; at the same time, high-refractive-index materials can make the light deflection ability stronger. When designing a complex optical imaging system, using its characteristics can achieve the same optical function with fewer lenses, thereby reducing the overall number of lenses in the lens and lowering the cost.

[0029] Preferably, the present invention adopts a 5G + 1GM design. Aspherical lenses can better control the refraction and focusing of light, reduce aberration and chromatic aberration, improve the imaging quality and resolution. One aspherical lens can replace the functions of multiple spherical lenses, which can reduce the number of lenses, simplify the structure of the optical imaging system, and reduce the complexity and cost of the lens.

[0030] Preferably, the focal length f of the present optical imaging system and the maximum holographic height IH corresponding to the maximum field of view angle satisfy: 1.3 < f / IH < 1.8; satisfying the above range is beneficial to balancing the relationship between the focal length of the optical imaging system and the maximum holographic height, and is beneficial for the optical lens to achieve a large target surface design.

[0031] Preferably, the entrance pupil diameter EPD of the present optical imaging system and the maximum holographic height IH corresponding to the maximum field of view angle satisfy: 1 < IH / EPD < 1.2; satisfying the above range can make the beam width entering the optical imaging system larger, which is beneficial for the large aperture design of the optical imaging system, has a good imaging effect, and can realize the recognition of objects on both sides of the road in low light environments.

[0032] Preferably, in the above optical imaging system provided by the embodiment of the present invention, the maximum holographic height IH of the optical imaging system satisfies the following condition: IH ≥ 9.688 mm.

[0033] Preferably, in the above optical imaging system provided by the embodiment of the present invention, the aperture of the optical imaging system: F / NO = 1.6.

[0034] Preferably, in the above optical imaging system provided by the embodiment of the present invention, the effective focal length f of the optical imaging system satisfies the following condition: 15.30 mm ≤ f ≤ 15.38 mm.

[0035] Preferably, the surface S1 of the first lens E1 facing the object side is concave, and the surface S2 facing the image side is convex; the surface S4 of the second lens E2 facing the object side is a large convex surface, and the surface S5 facing the image side is a small convex surface, that is, the absolute value of the radius of curvature of the surface S4 of the second lens E2 facing the object side is less than the absolute value of the radius of curvature of the surface S5 of the second lens E2 facing the image side; the surface S6 of the third lens E3 facing the object side is a large convex surface, and the surface where the third lens E3 and the fourth lens E4 are cemented is S7; the surface S8 of the fourth lens E4 facing the image side is concave; the surface S9 of the fifth lens E5 facing the object side is convex, and the surface S10 facing the image side is convex; the surface S11 of the sixth lens E6 facing the object side is concave, and the surface S12 facing the image side is convex.

[0036] This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications without creative contributions to this embodiment according to needs after reading this specification, but as long as it is within the scope of the claims of the present invention, it is protected by the patent law.

[0037] Among them, the parameters of each lens in this embodiment are listed in Table 1 below in sequence, and the aspheric coefficients of the lenses are shown in Table 2 below.

[0038] Table 1 Physical Parameters of Each Lens

[0039] Table 2 Aspherical Coefficients of the Lenses

[0040] The aspherical coefficients satisfy the following equation:

[0041] Where z is the aspherical sag, c is the aspherical paraxial curvature, y is the lens aperture, k is the conic coefficient, a4 is the 4th-order aspherical coefficient, a6 is the 6th-order aspherical coefficient, a8 is the 8th-order aspherical coefficient, a10 is the 10th-order aspherical coefficient, a12 is the 12th-order aspherical coefficient, a14 is the 14th-order aspherical coefficient, and a16 is the 16th-order aspherical coefficient.

[0042] Specifically, in this embodiment, the R values and thicknesses of the surfaces of each lens are shown in Table 1, and the aspherical parameters are shown in Table 2.

[0043] Specifically, in this embodiment, the R values (Radius curvature radius), thicknesses (Thickness), refractive indices (Index), Abbe numbers (ABB), and effective focal lengths of the lenses (EFL-E) of the surfaces of each lens are shown in Table 1, and the aspherical parameters are shown in Table 2. In Table 1, Surf represents the mirror surface number, InFInITY represents infinity. In Table 2, R1 represents the curvature radius of the surface of the corresponding lens facing the object side, and R2 represents the curvature radius of the surface of the corresponding lens facing the image side. A positive curvature radius indicates that the mirror surface bends towards the object surface side, and a negative curvature radius indicates that the mirror surface bends towards the image surface side.

[0044] Among them, the effective focal length of the optical imaging system provided in Table 1 is 15.34 mm, the maximum full image height is 9.688 mm, and the aperture F / NO is 1.6. In Table 1, the mirror surface numbers 1 and 2 represent the two mirror surfaces of the first lens E1 along the light incident direction in sequence, the mirror surface numbers 4 and 5 represent the two mirror surfaces of the second lens E2 along the light incident direction in sequence, the mirror surface number 6 represents the mirror surface of the third lens E3 facing the object side, the mirror surface number 7 represents the cemented surface of the third lens E3 and the fourth lens E4, the mirror surface number 8 represents the mirror surface of the fourth lens E4 facing the image side, the mirror surface numbers 9 and 10 represent the two mirror surfaces of the fifth lens E5 along the light incident direction in sequence, and the mirror surface numbers 11 and 12 represent the two mirror surfaces of the sixth lens E6 along the light incident direction in sequence.

[0045] In the embodiment of the present invention, Figure 2It is a modulation transfer function (MTF) curve graph in the visible light band, representing the comprehensive resolution ability of an optical imaging system. The horizontal axis in the graph represents the spatial frequency, unit: cycles per millimeter (cycles / mm), and the vertical axis represents the value of the modulation transfer function (MTF). The value of MTF is used to evaluate the imaging quality of the lens, and the value range is 0 - 1. In particular, the optical transfer function is a relatively accurate, intuitive and common way to evaluate the imaging quality of an optical imaging system. The higher and smoother its curve is, the better the imaging quality of the system is, and the stronger the ability to restore the real image is; From Figure 2 it can be seen that in the imaging area near the center of the visible light band, MTF > 0.7, and the imaging quality is good. From Figure 3 the defocus curve graph, it can be seen that the MTF concentration of this lens is good, which is convenient for focusing. From Figure 4 And Figure 5 it can be seen that the defocus curves at high temperature and low temperature both meet high resolution, the change amount of the defocus curve focus is small, and there is no defocus in high and low temperature environments; Figure 6 It is represented as an F-THETA distortion graph. The smaller the F-THETA distortion is, the smaller the compression amount of the imaging picture edge is; Figure 7 It is represented as a relative illumination graph. The higher the relative illumination is, the higher the overall brightness of the photographed picture is; Figure 8 It is represented as a field curvature graph. From Figure 8 it can be known that the field curvature value is controlled between -0.035mm and 0.035mm. The smaller the field curvature value is, the better the imaging quality of the lens is; Figure 9 It is the standard spot diagram of the visible light wavelength in the invention embodiment; Figure 10 It is represented as a lateral chromatic aberration graph. The smaller the lateral chromatic aberration is, the better the color restoration degree of the imaging picture is, and the better the purple edge optimization is.

Claims

1. A low-cost large target surface ADAS optical imaging system, characterized in that: Along the optical axis from the object surface to the image surface, it successively includes: a first lens, a diaphragm, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a filter, a protective glass, and an image surface; The first lens is a concave-convex lens with a negative optical power; the second lens is a biconvex lens with a positive optical power; the third lens is a biconvex lens with a positive optical power; the fourth lens is a biconcave lens with a negative optical power; the fifth lens is a biconvex lens with a positive optical power; the sixth lens is a concave-convex lens with a negative optical power; Wherein, the ratio of the focal lengths of the first lens to the sixth lens to the focal length of the optical imaging system satisfies the following set relationship: -2.1 < f1 / f < -1.1, 0.8 < f2 / f < 1.9, 1.1 < f3 / f < 2.3, -2.6 < f4 / f < -1.3, 1.0 < f5 / f < 2.2, -1.6 < f6 / f < -0.5; where f1 represents the effective focal length of the first lens, f2 represents the effective focal length of the second lens, f3 represents the effective focal length of the third lens, f4 represents the effective focal length of the fourth lens, f5 represents the effective focal length of the fifth lens, f6 represents the effective focal length of the sixth lens, and f represents the effective focal length of the optical imaging system; Wherein, the entrance pupil diameter EPD of the optical imaging system and the maximum holographic height IH corresponding to the maximum field of view angle satisfy: 1 < IH / EPD < 1.

2.

2. The low-cost large target surface ADAS optical imaging system according to claim 1, characterized in that: The Abbe numbers of the first lens, the fourth lens, and the fifth lens are all greater than 40 and less than 50; the Abbe number of the sixth lens is greater than 35 and less than 42; the Abbe numbers of the second lens and the third lens are both greater than 61 and less than 72.

3. The low-cost large target surface ADAS optical imaging system according to claim 1, characterized in that: The spacing distance L1 between the first lens and the second lens and the spacing distance L2 between the second lens and the third lens satisfy: 2.7 < L2 - L1 < 3.

1.

4. A low-cost large-field-of-view ADAS optical imaging system according to claim 1, characterized in that: The refractive index n1 of the first lens satisfies: 1.73 < n1 < 1.9, the refractive index n4 of the fourth lens satisfies: 1.73 < n4 < 1.9, the refractive index n5 of the fifth lens satisfies: 1.73 < n5 < 1.9, and the refractive index n6 of the sixth lens satisfies: 1.73 < n6 < 1.

9.

5. A low-cost large-field-of-view ADAS optical imaging system according to claim 1, characterized in that: The focal length f of the optical imaging system and the maximum holographic height IH corresponding to the maximum field of view angle satisfy: 1.3 < f / IH < 1.

8.

6. The low-cost large-field-of-view ADAS optical imaging system according to claim 1, characterized in that: The third lens and the fourth lens form a cemented lens.

7. A low-cost large-field-of-view ADAS optical imaging system according to claim 1, characterized in that: The diaphragm ST0 is arranged between the first lens and the second lens.

8. The low-cost large-target-surface ADAS optical imaging system according to claim 1 or 2, characterized in that: The maximum holographic height IH of the optical imaging system satisfies the following condition: IH ≥ 9.688 mm; the aperture of the optical imaging system satisfies the following condition: F / NO = 1.

6.

9. A low-cost large-field-of-view ADAS optical imaging system according to claim 1 or 2, characterized in that: The effective focal length f of the optical imaging system satisfies the following condition: 15.30 mm ≤ f ≤ 15.38 mm.

10. A low-cost large-field-of-view ADAS optical imaging system according to claim 1 or 2, characterized in that: One side of the first lens facing the object side is concave, and the side facing the image side is convex; the absolute value of the radius of curvature of one side of the second lens facing the object side is less than the absolute value of the radius of curvature of the side of the second lens facing the image side; the absolute value of the radius of curvature of one side of the third lens facing the object side is less than the absolute value of the radius of curvature of the side of the third lens facing the image side; one side of the fourth lens facing the object side is a concave surface with a platform, and the side facing the image side is concave; one side of the fifth lens facing the object side is convex, and the side facing the image side is convex; one side of the sixth lens facing the object side is concave, and the side facing the image side is convex.

Images