4K thermal stability DVR optical imaging system

Abstract

The invention discloses a 4K thermal stability DVR optical imaging system. The optical imaging system comprises a first lens, a second lens, a third lens, a diaphragm, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an optical filter, protective glass and an image surface which are arranged in a direction from an object side to an image side. According to the invention, by reasonably using the lenses with specific shapes and structures and limiting the focal power of each lens, the design of a large target surface is realized, the maximum target surface is greater than or equal to 9.56 mm, a 1 / 1.8 chip IMX728 can be matched, the design of a large aperture is F1.8, and the recording and identification of objects on two sides of a road in a dark environment can be realized; and the FOV is increased to 171 degrees, so that a large-angle picture can be shot, and the visual field range is expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of optical imaging, and specifically to a 4K thermally stable DVR optical imaging system. Background Art

[0002] With the rapid development of technology, automobiles have become an indispensable part of people's lives. More and more automobiles are equipped with in-vehicle driving recorders. After installing the driving recorder, it can record the video images and sounds of the entire driving process of the automobile, and can provide evidence for traffic accidents. Since the driving recorder needs to capture the states of the front or rear of the vehicle, whether there are scratches, collisions and other accidents, and also needs to capture the license plate numbers of the scratched vehicles, there are relatively high requirements for the clarity of the driving recorder.

[0003] At present, there are generally two major problems in the lens design of driving recorders: one is that the target surface is relatively small, and the other is that the aperture is relatively small. The problem of the relatively small target surface directly limits its inability to match large-target and high-pixel image sensor chips, affecting the clarity of the image and the ability to capture details. On the other hand, the relatively small aperture results in less light entering the lens. Especially in an environment with weak light, the insufficient light entering the lens makes the overall shooting effect darker, which not only affects the brightness performance of the picture, but also reduces the contrast and color saturation of the image to a certain extent, thus affecting the overall shooting quality of the driving recorder. Summary of the Invention

[0004] The present invention proposes a 4K thermally stable DVR optical imaging system, which takes into account the characteristics of a 4K thermally stable DVR optical imaging system with a large target surface, a large aperture, ultra-high definition pixels, athermalization, and purple fringe optimization.

[0005] A 4K thermally stable DVR optical imaging system sequentially includes, along the optical axis from the object surface to the image surface: a first lens, a second lens, a third lens, a fourth lens, a diaphragm, a fifth lens, a sixth lens, a seventh lens, a filter, a protective glass, and an image surface; The first lens is a meniscus lens with a negative optical power; the second lens is a concave-convex lens with a negative optical power; the third lens is a biconvex lens with a positive optical power; the fourth lens is a concave-convex lens with a positive optical power; the fifth lens is a biconvex lens with a positive optical power; the sixth lens is a biconcave lens with a negative optical power; the seventh lens is a biconvex lens with a positive optical power; Wherein, the ratio of the focal lengths of the first lens to the seventh lens to the focal length of the optical imaging system satisfies the following set relationship: 1.4 < |f1 / f| < 1.8, 9.8 < |f2 / f| < 10.4, 2.2 < |f3 / f| < 2.6, 4.0 < |f4 / f| < 4.4, 6.9 < |f5 / f| < 7.3, 1.4 < |f6 / f| < 1.8, 1.8 < |f7 / f| < 2.2, 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, f7 represents the effective focal length of the seventh lens, and f represents the effective focal length of the optical imaging system.

[0006] A further solution is that the focal length f5 of the fifth lens, the focal length f6 of the sixth lens, and the focal length f7 of the seventh lens of the optical imaging system satisfy: 0.8 < |(f5 + f6) / (f5 - f7)| < 1.5.

[0007] A further solution is that the Abbe numbers of the first lens, the second lens, the third lens, and the seventh lens are all greater than 40 and less than 50; the Abbe number of the fourth lens is greater than 53 and less than 58; the Abbe number of the fifth lens is greater than 80 and less than 85; the Abbe number of the sixth lens is greater than 20 and less than 25.

[0008] A further solution is that the optical imaging system satisfies the following conditional expressions: 0.30 < Nd6 - Nd5 < 0.50; 50 < Vd5 - Vd6 < 65; -4.5 < f5 / f6 < -3.5; where, Nd5 represents the refractive index of the fifth lens, Nd6 represents the refractive index of the sixth lens, Vd5 represents the Abbe number of the fifth lens, Vd6 represents the Abbe number of the sixth lens, f5 represents the focal length of the fifth lens, and f6 represents the focal length of the sixth lens.

[0009] A further solution is that the curvature radius R1 of the object side surface of the first lens and the curvature radius R2 of the image side surface of the first lens satisfy: 0.5 < (R1 - R2) / (R1 + R2) < 1.0.

[0010] A further solution is that the entrance pupil diameter EPD of the optical system and the maximum holographic height IH corresponding to the maximum field of view angle satisfy: 4.5 < IH / EPD < 5.5.

[0011] A further solution is that the maximum holographic height IH of the optical imaging system satisfies the following conditions: IH ≥ 9.56 mm; the maximum field of view angle of the optical imaging system: FOV ≥ 171°.

[0012] A further solution is that the aperture of the optical imaging system: F / NO = 1.8.

[0013] A further solution is that the maximum full-image height IH of the optical imaging system and the effective focal length f of the optical imaging system satisfy the following condition: 2.3 mm ≤ IH / f ≤ 2.8 mm.

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

[0015] In summary, the present invention has the following beneficial effects: The present invention discloses a 4K thermal-stable DVR optical imaging system, especially a 4K thermal-stable DVR optical imaging system that takes into account a large target surface, a large aperture, ultra-high definition pixels, athermalization, and purple fringing optimization. The optical imaging system includes a first lens, a second lens, a third lens, a diaphragm, a fourth lens, a fifth lens, a sixth lens, a seventh lens, a filter, a protective glass, and an image plane arranged in the direction from the object side to the image side. By reasonably using lenses with specific shape structures and defining the optical power of each lens, the present invention realizes a large target surface design, with a maximum target surface ≥ 9.56 mm, which can match a 1 / 1.8 chip IMX728. The large aperture design of F1.8 can record and identify objects on both sides of the road in low-light environments; the FOV is increased to 171 degrees, enabling the capture of large-angle images and enhancing the field of view. The combination of 5G + 2GM spherical and aspherical surfaces in the present invention optimizes the high and low temperature drift compensation of the entire optical imaging system, and the operating temperature can range from -40 degrees to 95 degrees, greatly improving the application of this product in complex temperature scenarios. The use of low-dispersion materials and a two-piece glass aspherical design optimizes the purple fringing of the lens, with the lens purple fringing less than 3 um, improving the problem of image quality degradation in the captured images caused by severe purple fringing overflow in most lenses. Description of the Drawings

[0016] Figure 1Schematic diagram of the structure of a 4K thermally stable DVR optical imaging system according to an embodiment of the present invention; Figure 2 MTF analysis diagram of the optical imaging system provided by an embodiment of the present invention at 20°C in visible light; Figure 3 Defocus curve diagram of the optical imaging system provided by an embodiment of the present invention at 20°C in visible light; Figure 4 Defocus curve diagram of the optical imaging system provided by an embodiment of the present invention at -40°C in visible light; Figure 5 Defocus curve diagram of the optical imaging system provided by an embodiment of the present invention at 95°C in visible light; Figure 6 Field curvature diagram of the optical imaging system provided by an embodiment of the present invention in visible light; Figure 7 F-THETA distortion diagram of the optical imaging system provided by an embodiment of the present invention in visible light; Figure 8 Relative illuminance diagram of the optical imaging system provided by an embodiment of the present invention in visible light; Figure 9 Axial chromatic aberration diagram of the optical imaging system provided by an embodiment of the present invention at wavelengths from 435nm to 656nm; Figure 10 Standard spot diagram of the optical imaging system provided by an embodiment of the present invention in visible light. Detailed implementation manners

[0017] The embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the 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 drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0018] 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. is based on the orientation or positional relationship shown in the drawings, and is 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 therefore should not be construed as limiting the present invention.

[0019] In addition, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, 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 of" means two or more unless otherwise specifically defined.

[0020] In the present invention, unless otherwise clearly specified and defined, terms such as "mounted", "connected", "coupled", "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 components or the interaction relationship between two components. 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.

[0021] As Figure 1 shown, the present invention provides a 4K thermally stable DVR optical imaging system, which includes a first lens E1, a second lens E2, a third lens E3, a stop STO, a fourth lens E4, a fifth lens E5, a sixth lens E6, a seventh lens E7, an infrared filter IR, a protective glass CG, and an image plane IMA arranged in the direction from the object side to the image side. The first lens E1 is a meniscus lens with a negative focal power; the second lens E2 is a concave-convex lens with a negative focal power; the third lens E3 is a biconvex lens with a positive focal power; the fourth lens E4 is a concave-convex lens with a positive focal power; the fifth lens E5 is a biconvex lens with a positive focal power; the sixth lens E6 is a biconcave lens with a negative focal power; the seventh lens E7 is a biconvex lens with a positive focal power.

[0022] It should be noted that the present invention adopts a 5G + 2GM design, that is, five glass spherical lenses and two glass aspherical lenses. The aspherical lenses can better control the refraction and focusing of light, reduce aberration and chromatic aberration, improve the imaging quality and resolution. At the same time, the combination of spherical and aspherical lenses optimizes the compensation of temperature drift at high and low temperatures, ensuring that the picture remains clear when the lens works at high and low temperatures, and has more cost advantages and higher cost performance.

[0023] Among them, the ratio of the focal lengths of the first lens E1 to the seventh lens E7 to the focal length of the optical imaging system satisfies the following set relationship: 1.4 < |f1 / f| < 1.8, 9.8 < |f2 / f| < 10.4, 2.2 < |f3 / f| < 2.6, 4.0 < |f4 / f| < 4.4, 6.9 < |f5 / f| < 7.3, 1.4 < |f6 / f| < 1.8, 1.8 < |f7 / f| < 2.2, 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, f7 represents the effective focal length of the seventh lens E7, and f represents the effective focal length of the optical imaging system.

[0024] In this embodiment, the third lens E3 of the optical imaging system adopts an aspherical design. The effective focal length f of the optical imaging system, the focal length f1 of the first lens E1, and the focal length f3 of the third lens E3 satisfy: -1.8 < f1 / f < -1.4, 2.2 < f3 / f < 2.6. Meeting the above ranges can make the first lens E1 have an appropriate negative optical power, and the third lens E3 have a certain positive optical power, so that the light rays are first diverged by the negative optical power first lens E1 and then converged by the subsequent positive optical power third lens E3, increasing the field of view angle; at the same time, the aspherical lens can correct problems such as spherical aberration of the spherical lens. Using the aspherical lens can better control the propagation path of the light rays, reduce aberration, and improve the imaging quality, thereby achieving a larger field of view angle.

[0025] In addition, the focal length f5 of the fifth lens E5, the focal length f6 of the sixth lens E6, and the focal length f7 of the seventh lens E7 of the optical imaging system satisfy: 0.8 < |(f5 + f6) / (f5 - f7)| < 1.5; meeting the above range can expand the width of the light beam when the large-angle light rays pass through the sixth lens E6 and the seventh lens E7. In this process, the light rays can be fully and efficiently transmitted to the imaging surface, thereby expanding the maximum target surface of the optical imaging system.

[0026] Among them, the Abbe numbers of the first lens E1, the second lens E2, the third lens E3, and the seventh lens E7 are all greater than 40 and less than 50; the Abbe number of the fourth lens E4 is greater than 53 and less than 58; the Abbe number of the fifth lens E5 is greater than 80 and less than 85; the Abbe number of the sixth lens E6 is greater than 20 and less than 25.

[0027] As an improvement, the optical imaging system satisfies the following conditional expressions: 0.30 < Nd6 - Nd5 < 0.50; 50 < Vd5 - Vd6 < 65; -4.5 < f5 / f6 < -3.5; Among them, Nd5 represents the refractive index of the fifth lens E5, Nd6 represents the refractive index of the sixth lens E6, Vd5 represents the Abbe number of the fifth lens E5, Vd6 represents the Abbe number of the sixth lens E6, f5 represents the focal length of the fifth lens E5, and f6 represents the focal length of the sixth lens E6. By satisfying the above conditional expressions, through the reasonable distribution and balance of the optical power and dispersion relationship of the fifth lens E5 and the sixth lens E6, and at the same time using a low-dispersion material for the fifth lens E5, the chromatic aberration of the system can be effectively corrected, the imaging quality can be improved, the deflection angle of light in the lens can be effectively reduced, the sensitivity of lens production can be lowered, and the yield of the product can be increased.

[0028] As an improvement, the curvature radius R1 of the object side surface of the first lens E1 and the curvature radius R2 of the image side surface of the first lens E2 satisfy: 0.5 < (R1 - R2) / (R1 + R2) < 1.0. By satisfying the above range, the curvature radius of the object side surface and the image side surface of the first lens E1 are defined, making the refraction and propagation of light in the lens more reasonable to achieve an ultra-wide-angle effect.

[0029] As an improvement, the entrance pupil diameter EPD of the present optical system and the maximum holographic height IH corresponding to the maximum field of view angle satisfy: 4.5 < IH / EPD < 5.5; by satisfying the above range, the beam width of the light beam incident on the optical system can be made larger, which is beneficial to the large-aperture design of the optical system and can also achieve clear imaging in a low-light environment.

[0030] 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 ≥ 9.56 mm.

[0031] Preferably, in the above optical imaging system provided by the embodiment of the present invention, the maximum field of view angle of the optical imaging system: FOV ≥ 171°.

[0032] Preferably, in the above optical imaging system provided by the embodiment of the present invention, the aperture of the optical imaging system: F / NO = 1.8.

[0033] 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 and the effective focal length f satisfy the following conditions: 2.3 mm ≤ IH / f ≤ 2.8 mm. By satisfying the above range, while ensuring a large target surface of the optical system, the depth of field can be optimized, and the imaging quality of the optical imaging system can be guaranteed.

[0034] Preferably, the surface S1 of the first lens E1 facing the object side is convex, and the surface S2 facing the image side is concave; the surface S3 of the second lens E2 facing the object side is concave, and the surface S4 facing the image side is convex; the surface S5 of the third lens E3 facing the object side is a small convex surface, and the surface S6 facing the image side is a large convex surface; the surface S8 of the fourth lens E4 facing the object side is concave, and the surface S9 facing the image side is convex; the surface S10 of the fifth lens E5 facing the object side is a convex surface with a platform, and the surface S11 facing the image side is convex; the surface S11 of the sixth lens E6 facing the object side is a small concave surface, and the surface S12 facing the image side is a large concave surface; the surface S13 of the seventh lens E7 facing the object side is a large convex surface, and the surface S14 facing the image side is a small convex surface.

[0035] This specific embodiment is only an explanation of the present invention and is not a limitation thereof. After reading this specification, those skilled in the art can make modifications to this embodiment without creative contributions as needed, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

[0036] Among them, the parameters of each lens in this embodiment are listed in Table 1 below, and the aspheric coefficients of the lenses are shown in Table 2 below.

[0037] Table 1 Physical parameters of each lens

[0038] Table 2 Aspheric coefficients of lenses

[0039] The aspheric coefficients satisfy the following equation:

[0040] Among them, z is the aspheric sag, c is the aspheric paraxial curvature, the curvature is the reciprocal of the radius of curvature, y is the lens aperture, k is the conic coefficient, a4 is the 4th-order aspheric coefficient, a6 is the 6th-order aspheric coefficient, a8 is the 8th-order aspheric coefficient, a10 is the 10th-order aspheric coefficient, and a12 is the 12th-order aspheric coefficient.

[0041] Specifically, the R values and thicknesses of the surfaces of each lens in this embodiment are shown in Table 1, and the aspheric parameters are shown in Table 2.

[0042] Specifically, in this embodiment, the R values (Radius of curvature), thicknesses (Thickness), refractive indices (Index), Abbe numbers (ABB), and effective focal lengths of the lenses (EFL-E) of each lens surface are shown in Table 1, and the aspheric parameters are shown in Table 2. In Table 1, Surf represents the mirror surface number, InFInITY represents infinity. In Table 2, R1 represents the radius of curvature of the corresponding lens surface facing the object side, and R2 represents the radius of curvature of the corresponding lens surface facing the image side. A positive radius of curvature indicates that the mirror surface bends towards the object surface side, and a negative radius of curvature indicates that the mirror surface bends towards the image surface side.

[0043] Among them, the effective focal length of the optical imaging system provided in Table 1 is 3.63 mm, the full image height is 9.56 mm, the maximum field of view angle is 171 degrees, and the aperture F / NO is 1.8. In Table 1, mirror surface numbers 1 and 2 successively represent the two mirror surfaces of lens 1 along the light incident direction, mirror surface numbers 3 and 4 successively represent the two mirror surfaces of lens 2 along the light incident direction, mirror surface numbers 5 and 6 successively represent the two mirror surfaces of lens 3 along the light incident direction, mirror surface numbers 8 and 9 successively represent the two mirror surfaces of lens 4 along the light incident direction, mirror surface number 10 represents the mirror surface of lens 5 facing the object side, mirror surface number 11 represents the cemented surface of lens 5 and lens 6, mirror surface number 12 represents the mirror surface of lens 6 facing the image side, and mirror surface numbers 13 and 14 successively represent the two mirror surfaces of lens 7 along the light incident direction.

[0044] In the embodiment of the present invention, Figure 2 is a graph of the modulation transfer function (MTF) in the visible light band, which represents the comprehensive resolution ability of the optical imaging system. In the figure, the horizontal axis 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. It should be particularly noted that 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 and the stronger the ability to restore the real image; from Figure 2 it can be seen that in the imaging area near the center in 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 is represented as the field curvature graph. From Figure 6 it can be known that the field curvature value is controlled between -0.12 mm and 0.12 mm. The smaller the field curvature value is, the better the imaging quality of the lens; Figure 7It is represented as an F-THETA distortion diagram. The smaller the F-THETA distortion, the smaller the compression amount of the imaging picture edge; Figure 8 It is represented as a relative illuminance diagram. The higher the relative illuminance, the higher the overall brightness of the captured picture; Figure 9 It is represented as a lateral chromatic aberration diagram. The smaller the lateral chromatic aberration, the better the color restoration of the imaging picture and the better the purple fringing optimization; Figure 10 It is represented as a standard spot diagram.

Claims

1. A 4K thermally stable DVR optical imaging system, characterized by: The optical axis includes, from the object plane to the image plane, a first lens, a second lens, a third lens, a fourth lens, an aperture, a fifth lens, a sixth lens, a seventh lens, a filter, a protective glass and an image plane; The first lens is a meniscus lens with negative focal power; the second lens is a concave-convex lens with negative focal power; the third lens is a biconvex lens with positive focal power; the fourth lens is a concave-convex lens with positive focal power; the fifth lens is a biconvex lens with positive focal power; the sixth lens is a biconcave lens with negative focal power; the seventh lens is a biconvex lens with positive focal power; The ratio of the focal lengths of the first to seventh lenses to the focal length of the optical imaging system satisfies the following setting relationship: 1.4<|f1 / f|<1.8, 9.8<|f2 / f|<10.4, 2.2<|f3 / f|<2.6, 4.0<|f4 / f|<4.4, 6.9<|f5 / f|<7.3, 1.4<|f6 / f|<1.8, 1.8<|f7 / f|<2.2, wherein 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, f7 represents the effective focal length of the seventh lens, and f represents the effective focal length of the optical imaging system.

2. A 4K thermally stable DVR optical imaging system according to claim 1, characterized in that: The focal length f5 of the fifth lens, the focal length f6 of the sixth lens and the focal length f7 of the seventh lens of the optical imaging system satisfy: 0.8<|(f5+f6) / (f5-f7)|<1.

5.

3. The 4K thermally stable DVR optical imaging system according to claim 1, characterized in that: The Abbe coefficients of the first lens, the second lens, the third lens and the seventh lens are all greater than 40 and less than 50; the Abbe coefficient of the fourth lens is greater than 53 and less than 58; the Abbe coefficient of the fifth lens is greater than 80 and less than 85; and the Abbe coefficient of the sixth lens is greater than 20 and less than 25.

4. A 4K thermally stable DVR optical imaging system according to claim 3, characterized in that: The optical imaging system satisfies the following conditions: 0.30<Nd6-Nd5<0.50; 50<Vd5-Vd6<65; -4.5<f5 / f6<-3.5; Among them, Nd5 represents the refractive index of the fifth lens, Nd6 represents the refractive index of the sixth lens, Vd5 represents the Abbe number of the fifth lens, Vd6 represents the Abbe number of the sixth lens, f5 represents the focal length of the fifth lens, and f6 represents the focal length of the sixth lens.

5. The 4K thermally stable DVR optical imaging system according to claim 1, characterized in that: The radius of curvature R1 of the object side of the first lens and the radius of curvature R2 of the image side of the first lens Satisfies: 0.5<(R1-R2) / (R1+R2)<1.

0.

6. The 4K thermally stable DVR optical imaging system according to claim 1, characterized in that: The entrance pupil diameter EPD of the optical system and the maximum total image height IH corresponding to the maximum field angle satisfy: 4.5<IH / EPD<5.

5.

7. A 4K thermally stable DVR optical imaging system according to claim 1 or 3, characterized in that: The maximum total image height IH of the optical imaging system satisfies the following conditions: IH≥9.56mm; the maximum field of view angle of the optical imaging system: FOV≥171°.

8. A 4K thermally stable DVR optical imaging system according to claim 1 or 3, characterized in that: The aperture of the optical imaging system is: F / NO=1.

8.

9. A 4K thermally stable DVR optical imaging system according to claim 1 or 3, characterized in that: The maximum total image height IH of the optical imaging system and the effective focal length f of the optical imaging system satisfy the following condition: 2.3mm≤IH / f≤2.8mm.

10. The 4K thermally stable DVR optical imaging system according to claim 1, characterized in that: The first lens has a convex surface facing the object side, and a concave surface facing the image side; the second lens has a concave surface facing the object side, and a convex surface facing the image side; the third lens has a convex surface facing the object side and a convex surface facing the image side, and the absolute value of the radius of curvature of the surface of the third lens facing the object side is greater than the absolute value of the radius of curvature of the surface facing the image side; the fourth lens has a concave surface facing the object side, and a convex surface facing the image side; the fifth lens has a convex surface with a platform facing the object side, and the surface facing the image side is convex; the sixth lens has a concave surface facing the object side and a concave surface facing the image side, and the absolute value of the radius of curvature of the surface of the sixth lens facing the object side is greater than the absolute value of the radius of curvature of the surface facing the image side; the seventh lens has a convex surface facing the object side and a convex surface facing the image side, and the absolute value of the radius of curvature of the surface of the seventh lens facing the object side is less than the absolute value of the radius of curvature of the surface facing the image side.

Images