Ultra-short-focus large-target-surface compact low-light imaging optical system

Abstract

The invention discloses an ultra-short-focus large-target-surface compact low-light-level imaging optical system which comprises a first lens (1), a second lens (2), a third lens (3), a fourth lens (4), a fifth lens (5), a diaphragm (10), a sixth lens (6), a seventh lens (7), an eighth lens (8), a ninth lens (9) and a detector (11) which are sequentially and coaxially arranged from the object space to the image space. The low-illumination imaging effect is improved, large-target-surface high-resolution imaging is achieved, and both performance indexes and man-machine work efficiency are considered.

Description

Technical Field

[0001] The present invention relates to the technical field of optical systems, and specifically, to an ultra-short focal length, large target surface, and compact low-light imaging optical system. Background Art

[0002] Currently, optical lenses for fixed-focus and zoom televisions include visible light optical systems and near-infrared optical systems according to different working bands. The visible light optical system and the near-infrared optical system have their respective advantages and disadvantages. Among them, the visible light optical system has high imaging resolution and low cost, but the detection distance is limited in bad weather such as snow and fog; the near-infrared optical system has good fog penetration ability, but the cost is high and the resolution is limited. Therefore, fixed-focus and zoom televisions that combine visible light and near-infrared have become a research hotspot and have achieved good performance and wide applications, such as security, monitoring, aerial photography, and measurement.

[0003] However, at the present stage, fixed-focus and zoom televisions that combine visible light and near-infrared mainly adopt discrete optical systems, resulting in a more complex imaging optical system, lower registration accuracy between different spectral bands, and low effectiveness of mutual calibration. At the same time, fixed-focus and zoom television systems using confocal lenses generally have insufficient clarity at low illuminance, large defocus between infrared and visible light, and it is difficult to simultaneously meet the clarity requirements for imaging during the day and at night. Especially in high and low temperature environments, the clarity drops severely and the temperature drift is large, which cannot meet the requirements of vehicle-mounted, security, especially military application scenarios. Summary of the Invention

[0004] The purpose of the present invention is to provide an ultra-short focal length, large target surface, and compact low-light imaging optical system. This optical system adopts a confocal structure of visible light and near-infrared, improves the low-light imaging effect, realizes large target surface and high-resolution imaging, and takes into account performance indicators and ergonomics.

[0005] To achieve the above purpose, the present invention provides an ultra-short focal length, large target surface, and compact low-light imaging optical system. The imaging optical system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a diaphragm, a sixth lens, a seventh lens, an eighth lens, a ninth lens, and a detector coaxially arranged in sequence from the object side to the image side. Among them,

[0006] The focal length of the imaging optical system is f;

[0007] One side of the first lens facing the object side is convex, and the side facing the image side is concave. The focal length f L1 is set such that -2.18 ≤ f L1 / f ≤ -1.58;

[0008] Both sides of the second lens facing the object side and the image side are concave. The focal length f L2 is set such that -1.72 ≤ fL2 / f ≤ -1.32;

[0009] Both surfaces of the third lens facing the object side and the image side are convex, and its focal length is positive; one surface of the fourth lens facing the object side is concave, and the surface facing the image side is convex, and its focal length is negative; the third lens and the fourth lens are cemented to form the first doublet lens, and the focal length f of the first doublet lens C1 is set to 1.78 ≤ f C1 / f ≤ 2.08;

[0010] Both surfaces of the fifth lens facing the object side and the image side are convex, and its focal length f L5 is set to 1.18 ≤ f L5 / f ≤ 1.48;

[0011] Both surfaces of the sixth lens facing the object side and the image side are convex, and its focal length is positive; both surfaces of the seventh lens facing the object side and the image side are concave, and its focal length is negative; the sixth lens and the seventh lens are cemented to form the second doublet lens, and the focal length f of the second doublet lens C2 is set to -1.98 ≤ f C2 / f ≤ -1.68;

[0012] One surface of the eighth lens facing the object side is concave, and the surface facing the image side is convex, and its focal length f L8 is set to 3.22 ≤ f L8 / f ≤ 3.87;

[0013] Both surfaces of the ninth lens facing the object side and the image side are convex, and its focal length f L9 is set to 2.82 ≤ f L9 / f ≤ 3.12;

[0014] The f-number F# of the imaging optical system is 1.5 - 3;

[0015] From the object side surface of the first lens to the imaging surface is the total optical length TTL, which is set to 4.5 ≤ TTL / f ≤ 5.5;

[0016] From the image side surface of the ninth lens to the imaging surface is the back focal length BFL, which is set to 0.18 ≤ BFL / TTL ≤ 0.32.

[0017] Preferably, the air gap between the first lens and the second lens is 3-4 mm, the air gap between the second lens and the first doublet lens is 0.5-1 mm, the air gap between the first doublet lens and the diaphragm is 0.2-0.3 mm, the air gap between the diaphragm and the second doublet lens is 0.05-0.15 mm, and the air gap between the second doublet lens and the eighth lens is 1.4-1.5 mm; the air gap between the eighth lens and the ninth lens is 0.9-1 mm; the air gap between the ninth lens and the detector is 3.9-4 mm, and the air gap between the detector and its photosensitive surface is 0.05-0.15 mm.

[0018] Preferably, the first lens is a meniscus lens with a negative focal length, the second lens is a biconcave lens with a negative focal length, the fifth lens is a biconvex lens with a positive focal length, the eighth lens is a meniscus lens with a positive focal length, the ninth lens is a biconvex lens with a positive focal length, and the detector is a black silicon CMOS sensor.

[0019] Preferably, the curvature R of the object side surface of the first lens O1 is 17-20, and the curvature R of the image side surface S1 is 4-6; the curvature R of the object side surface of the second lens O2 is -15 to -11, and the curvature R of the image side surface S2 is 5-8; the curvature R of the object side surface of the third lens O3 is 9-13, and the curvature R of the image side surface S3 is -9 to -6; the curvature R of the object side surface of the fourth lens O4 is -9 to -6, and the curvature R of the image side surface S4 is -94 to -86; the curvature R of the object side surface of the fifth lens O5 is 6-9, and the curvature R of the image side surface S5 is -11 to -8; the curvature R of the object side surface of the sixth lens O6 is 14-18, and the curvature R of the image side surface S6 is -4 to -2; the curvature R of the object side surface of the seventh lens O7 is -4 to -2, and the curvature R of the image side surface S7 is 8-11; the curvature R of the object side surface of the eighth lens O8 is -23 to -20, and the curvature R of the image side surface S3 is -10 to -7; the curvature R of the object side surface of the ninth lens O9 is 11-14, and the curvature R of the image side surface S9 is -76 to -69.

[0020] Preferably, the refractive index of the first lens is between 1.7 and 1.8; the refractive index of the second lens is between 1.5 and 1.6; the refractive index of the third lens is between 1.7 and 1.8; the refractive index of the fourth lens is between 1.5 and 1.6; the refractive index of the fifth lens is between 1.6 and 1.7; the refractive index of the sixth lens is between 1.5 and 1.6; the refractive index of the seventh lens is between 1.7 and 1.8; the refractive index of the eighth lens is between 1.7 and 1.8; the refractive index of the ninth lens is between 1.7 and 1.8.

[0021] Preferably, the thickness of the first lens is 0.6 - 0.7 mm, the thickness of the second lens is 0.6 - 0.7 mm, the thickness of the third lens is 3.1 - 3.2 mm, the thickness of the fourth lens is 0.7 - 0.8 mm, the thickness of the fifth lens is 4.6 - 4.7 mm, the thickness of the sixth lens is 2.1 - 2.2 mm, the thickness of the seventh lens is 0.4 - 0.5 mm, the thickness of the eighth lens is 1.3 - 1.4 mm, and the thickness of the ninth lens is 2.0 - 2.1 mm.

[0022] Preferably, the first doublet lens is composed of heavy lanthanum flint glass and crown glass with a large difference in dispersion coefficient.

[0023] Preferably, the second doublet lens is composed of heavy flint glass and heavy crown glass with a large difference in dispersion coefficient.

[0024] According to the above technical solution, the present invention coaxially arranges the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the aperture stop, the sixth lens, the seventh lens, the eighth lens, the ninth lens, and the detector in sequence from the object side to the image side, which has a simple structure and is an ultra-wide-angle imaging objective lens without special materials; it covers both visible light and near-infrared dual bands, combines a large relative aperture and a large-target CMOS sensor, and achieves a good low-light imaging effect. In addition, based on the optical imaging principle, an optical design software can be used to repeatedly modify the structure of the imaging optical system to achieve the optimized design of aberration, and finally achieve large-target high-resolution imaging while ensuring that the imaging quality meets the best requirements.

[0025] Other features and advantages of the present invention will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and are used to explain the present invention together with the following specific implementation, but do not constitute a limitation to the present invention. In the drawings:

[0027] Figure 1 is a schematic structural diagram of an ultra-short focal length large-target compact low-light imaging optical system provided by the present invention;

[0028] Figure 2 It is the modulation transfer function curve graph in the embodiment of the ultra-short focal length, large target surface, and compact low-light imaging optical system provided by the present invention;

[0029] Figure 3 It is the modulation transfer function curve graph at -45 °C in the embodiment of the ultra-short focal length, large target surface, and compact low-light imaging optical system provided by the present invention;

[0030] Figure 4 It is the modulation transfer function curve graph at 60 °C in the embodiment of the ultra-short focal length, large target surface, and compact low-light imaging optical system provided by the present invention;

[0031] Figure 5 It is the spot diagram of the embodiment of the ultra-short focal length, large target surface, and compact low-light imaging optical system provided by the present invention;

[0032] Figure 6 It is the field curvature and distortion graph of the embodiment of the ultra-short focal length, large target surface, and compact low-light imaging optical system provided by the present invention.

[0033] Description of reference numerals

[0034] 1 - First lens 2 - Second lens

[0035] 3 - Third lens 4 - Fourth lens

[0036] 5 - Fifth lens 6 - Sixth lens

[0037] 7 - Seventh lens 8 - Eighth lens

[0038] 9 - Ninth lens 10 - Diaphragm

[0039] 11 - Detector Detailed implementation manners

[0040] The following will describe the detailed implementation manners of the present invention in conjunction with the accompanying drawings. It should be understood that the detailed implementation manners described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0041] In the present invention, unless otherwise stated, the directional terms such as "front, back", etc. included in the terms only represent the directions of the terms in the normal use state, or the common names understood by those skilled in the art, and should not be regarded as a limitation to the terms.

[0042] See Figure 1, the present invention provides an ultra-short focal length and large target surface compact low-light imaging optical system. The imaging optical system includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a diaphragm 10, a sixth lens 6, a seventh lens 7, an eighth lens 8, a ninth lens 9, and a detector 11 that are coaxially arranged in sequence from the object side to the image side. Among them,

[0043] The focal length of the imaging optical system is f;

[0044] One side of the first lens 1 facing the object side is convex, and the side facing the image side is concave. The focal length f L1 is set to -2.18 ≤ f L1 / f ≤ -1.58;

[0045] Both sides of the second lens 2 facing the object side and the image side are concave. The focal length f L2 is set to -1.72 ≤ f L2 / f ≤ -1.32;

[0046] Both sides of the third lens 3 facing the object side and the image side are convex, and the focal length is positive; one side of the fourth lens 4 facing the object side is concave, and the side facing the image side is convex, and the focal length is negative; the third lens 3 and the fourth lens 4 are cemented to form a first doublet lens. The focal length f C1 is set to 1.78 ≤ f C1 / f ≤ 2.08;

[0047] Both sides of the fifth lens 5 facing the object side and the image side are convex. The focal length f L5 is set to 1.18 ≤ f L5 / f ≤ 1.48;

[0048] Both sides of the sixth lens 6 facing the object side and the image side are convex, and the focal length is positive; both sides of the seventh lens 7 facing the object side and the image side are concave, and the focal length is negative; the sixth lens 6 and the seventh lens 7 are cemented to form a second doublet lens. The focal length f C2 is set to -1.98 ≤ f C2 / f ≤ -1.68;

[0049] One side of the eighth lens 8 facing the object side is concave, and the side facing the image side is convex. The focal length f L8 is set to 3.22 ≤ f L8 / f ≤ 3.87;

[0050] Both sides of the ninth lens 9 facing the object side and the image side are convex. The focal length f L9 is set to 2.82 ≤ f L9 / f ≤ 3.12;

[0051] The f-number F# of the imaging optical system is 1.5 - 3;

[0052] In the imaging optical system, the optical surface on the object side of the lens is called the object side surface, and the optical surface on the image side is the imaging surface. The optical total length TTL from the object side surface of the first lens 1 to the imaging surface is set such that 4.5 ≤ TTL / f ≤ 5.5;

[0053] The back focal length BFL from the image side surface of the ninth lens 9 to the imaging surface is set such that 0.18 ≤ BFL / TTL ≤ 0.32.

[0054] By the above technical solution, the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, the aperture stop 10, the sixth lens 6, the seventh lens 7, the eighth lens 8, the ninth lens 9 and the detector 11 are coaxially arranged in sequence from the object side to the image side, which is a simple-structured ultra-wide-angle imaging objective without special materials; it covers both visible light and near-infrared bands, combines a large relative aperture and a large target surface CMOS sensor, and achieves a good low-light imaging effect. In addition, based on the optical imaging principle, the structure of the imaging optical system can be repeatedly modified using optical design software to optimize the aberration design, and finally high-resolution imaging with a large target surface is achieved while ensuring that the imaging quality meets the best requirements, as follows.

[0055] In this embodiment, in order to better control the distance between the lenses and optimize the air gap, preferably, the air gap between the first lens 1 and the second lens 2 is 3 - 4 mm, the air gap between the second lens 2 and the first doublet lens is 0.5 - 1 mm, the air gap between the first doublet lens and the aperture stop 10 is 0.2 - 0.3 mm, the air gap between the aperture stop 10 and the second doublet lens is 0.05 - 0.15 mm, the air gap between the second doublet lens and the eighth lens 8 is 1.4 - 1.5 mm; the air gap between the eighth lens 8 and the ninth lens 9 is 0.9 - 1 mm; the air gap between the ninth lens 9 and the detector 11 is 3.9 - 4 mm, and the air gap between the detector 11 and its photosensitive surface is 0.05 - 0.15 mm.

[0056] In this embodiment, in order to facilitate the processing of lenses of various shapes and simplify the manufacturing difficulty, preferably, the first lens 1 is a meniscus lens with a negative focal length, the second lens 2 is a biconcave lens with a negative focal length, the fifth lens 5 is a biconvex lens with a positive focal length, the eighth lens 8 is a meniscus lens with a positive focal length, the ninth lens 9 is a biconvex lens with a positive focal length, and the detector 11 is a black silicon CMOS sensor.

[0057] In this embodiment, preferably, the curvature R of the object side surface of the first lens 1 O1 is 17 - 20, and the curvature R of the image side surface S1 is 4 - 6; the curvature R of the object side surface of the second lens 2 O2is from -15 to -11, such as the lateral curvature R S2 is from 5 to 8; the object-side curvature R of the third lens 3 O3 is from 9 to 13, and the image-side curvature R S3 is from -9 to -6; the object-side curvature R of the fourth lens 4 O4 is from -9 to -6, and the image-side curvature R S4 is from -94 to -86; the object-side curvature R of the fifth lens 5 O5 is from 6 to 9, and the image-side curvature R S5 is from -11 to -8; the object-side curvature R of the sixth lens 6 O6 is from 14 to 18, and the image-side curvature R S6 is from -4 to -2; the object-side curvature R of the seventh lens 7 O7 is from -4 to -2, and the image-side curvature R S7 is from 8 to 11; the object-side curvature R of the eighth lens 8 O8 is from -23 to -20, and the image-side curvature R S3 is from -10 to -7; the object-side curvature R of the ninth lens 9 O9 is from 11 to 14, and the image-side curvature R S9 is from -76 to -69.

[0058] In this embodiment, preferably, the refractive index of the first lens 1 is between 1.7 and 1.8; the refractive index of the second lens 2 is between 1.5 and 1.6; the refractive index of the third lens 3 is between 1.7 and 1.8; the refractive index of the fourth lens 4 is between 1.5 and 1.6; the refractive index of the fifth lens 5 is between 1.6 and 1.7; the refractive index of the sixth lens 6 is between 1.5 and 1.6; the refractive index of the seventh lens 7 is between 1.7 and 1.8; the refractive index of the eighth lens 8 is between 1.7 and 1.8; the refractive index of the ninth lens 9 is between 1.7 and 1.8.

[0059] In this embodiment, preferably, the thickness of the first lens 1 is 0.6 - 0.7 mm, the thickness of the second lens 2 is 0.6 - 0.7 mm, the thickness of the third lens 3 is 3.1 - 3.2 mm, the thickness of the fourth lens 4 is 0.7 - 0.8 mm, the thickness of the fifth lens 5 is 4.6 - 4.7 mm, the thickness of the sixth lens 6 is 2.1 - 2.2 mm, the thickness of the seventh lens 7 is 0.4 - 0.5 mm, the thickness of the eighth lens 8 is 1.3 - 1.4 mm, and the thickness of the ninth lens 9 is 2.0 - 2.1 mm.

[0060] In this embodiment, two cemented lenses are designed in the ultra-short focal length large target surface compact low-light imaging optical system. In this embodiment, the first doublet is composed of heavy lanthanum flint glass and crown glass with large difference in dispersion coefficient, and the second doublet is composed of heavy flint glass and heavy crown glass with large difference in dispersion coefficient. In this way, the chromatic aberration is effectively reduced by the effective cooperation of the dispersion coefficients. At the same time, the refractive index difference between the glasses on both sides of the cemented surface also corrects the monochromatic aberration, especially improving the high-order aberration characteristics of the optical system.

[0061] In addition, the field curvature of the imaging optical system can be corrected by relying on the structural change of the fifth lens 5; the spherical aberration can be corrected by bending and deforming the first lens 1, the second lens 2, the eighth lens 8 and the ninth lens 9; the astigmatism can be corrected by changing the air gap between the lenses; in addition, the quasi-symmetry before and after the aperture 10 can reduce the incident angle on the lens surface, which is beneficial to the balance of high-order aberrations.

[0062] In the actual design and adjustment process, based on the optical imaging principle, using optical design software, according to the combined lens power formula: Φ = Φ1 + Φ2 - dΦ1Φ2, the curvature, material and thickness of each lens are modified, the focal length of each lens is adjusted (Φ in the formula is the reciprocal of the focal length), and the distance between the lens groups (d in the formula) is repeatedly modified and adjusted and combined for calculation. Without the help of aspherical surfaces and special materials, in a specific embodiment, an imaging optical system for a 2 / 3-inch large target surface CMOS sensor with a field of view of 112°×63°, a focal length of 6.9 mm, an overall optical length of 28 mm, F2.5, a wide wavelength band of 450 nm - 900 nm, a distortion not greater than 35%, a high resolution of 1920×1080 and a pixel size of 5 μm is finally obtained.

[0063] The following Table 1 provides the optical parameters of the optical system to illustrate the optical performance and size of the optical system of the present invention:

[0064]

[0065]

[0066] The optical performance of the above specific embodiment is as Figures 2 to 4 shown, where Figure 2 is the MTF curve of this embodiment at room temperature, which is used to evaluate the image resolution ability of the optical system. At a spatial frequency of 100 lp / mm, the MTF values of all fields are above 0.35, which can easily meet the high-definition requirements of 2 million pixels. Figure 3 is the MTF curve of this embodiment at -45°C, Figure 4This is the MTF curve of this embodiment at 60°C, which is used to evaluate the athermalization effect of the optical system. It can be seen that under high and low temperature environmental conditions, the change amount of the MTF value is less than 5%, and it hardly affects the imaging effect. Therefore, under high and low temperature environments, this embodiment can still maintain a very good imaging effect. Figure 5 This is the spot diagram of this embodiment. It can be seen from the spot diagram that the points where the light rays of each aperture band and field of view pass through this imaging optical system and are focused on the image plane are basically controlled within 1 pixel size, indicating that it has excellent resolution ability in different fields of view. Figure 6 This is the distortion and field curvature diagram of this embodiment. It can be seen from the field curvature curve that the maximum field curvature change does not exceed 20μm. And this embodiment is an ultra-short focal length imaging optical system, indicating that it has a very good imaging effect within the depth of field range. And it can be seen from the distortion curve that the maximum F-Tan(θ) distortion is not greater than 35%. Combining with electronic distortion correction, it is completely possible to achieve a distortion-free imaging effect for a large field of view.

[0067] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0068] In addition, it should be noted that, among the various specific technical features described in the above specific embodiments, without conflict, they can be combined in any appropriate way. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0069] In addition, any combination can be made between various different embodiments of the present invention, as long as it does not violate the idea of the present invention, it should also be regarded as the content disclosed by the present invention.

Claims

1. An ultra-short-focus, large-target-area, compact low-light-level imaging optical system, characterized in that: The imaging optical system comprises a first lens (1), a second lens (2), a third lens (3), a fourth lens (4), a fifth lens (5), an aperture (10), a sixth lens (6), a seventh lens (7), an eighth lens (8), a ninth lens (9) and a detector (11) which are coaxially arranged in sequence from the object side to the image side, wherein: The focal length of the imaging optical system is f; The first lens (1) has a convex surface facing the object side and a concave surface facing the image side, and a focal length f L1 Set to -2.18≤f L1 / f≤-1.58; The second lens (2) has two concave surfaces facing the object side and the image side, and a focal length f L2 Set to -1.72≤f L2 / f≤-1.32; The third lens (3) has two convex surfaces facing the object side and the image side, and has a positive focal length; the fourth lens (4) has a concave surface facing the object side and a convex surface facing the image side, and has a negative focal length; the third lens (3) and the fourth lens (4) are glued together to form a first double glued lens, and the focal length of the first double glued lens is f C1 Set to 1.78≤f C1 / f≤2.08; The fifth lens (5) has convex surfaces on both the object side and the image side, and a focal length of f L5 Set to 1.18≤f L5 / f≤1.48; The sixth lens (6) has two convex surfaces facing the object side and the image side, and has a positive focal length; the seventh lens (7) has two concave surfaces facing the object side and the image side, and has a negative focal length; the sixth lens (6) and the seventh lens (7) are glued together to form a second double glued lens, and the focal length of the second double glued lens is f C2 Set to -1.98≤f C2 / f≤-1.68; The eighth lens (8) has a concave surface facing the object side and a convex surface facing the image side, and a focal length f L8 Set to 3.22≤f L8 / f≤3.87; The ninth lens (9) has convex surfaces on both the object side and the image side, and a focal length f L9 Set to 2.82≤f L9 / f≤3.12; The aperture number F# of the imaging optical system is 1.5-3; The total optical length TTL from the object side of the first lens (1) to the imaging surface is set to 4.5≤TTL / f≤5.5; The back focal length BFL from the image side surface of the ninth lens (9) to the imaging surface is set to 0.18≤BFL / TTL≤0.

32.

2. The ultra-short focus, large target surface, compact low-light-level imaging optical system according to claim 1, characterized in that: The air gap between the first lens (1) and the second lens (2) is 3-4 mm, the air gap between the second lens (2) and the first double-cemented lens is 0.5-1 mm, the air gap between the first double-cemented lens and the diaphragm (10) is 0.2-0.3 mm, the air gap between the diaphragm (10) and the second double-cemented lens is 0.05-0.15 mm, the air gap between the second double-cemented lens and the eighth lens (8) is 1.4-1.5 mm; the air gap between the eighth lens (8) and the ninth lens (9) is 0.9-1 mm; the air gap between the ninth lens (9) and the detector (11) is 3.9-4 mm, and the air gap between the detector (11) and its photosensitive surface is 0.05-0.15 mm.

3. The ultra-short focus large target area compact low light imaging optical system according to claim 2, characterized in that: The first lens (1) is a meniscus lens with a negative focal length, the second lens (2) is a biconcave lens with a negative focal length, the fifth lens (5) is a biconvex lens with a positive focal length, the eighth lens (8) is a meniscus lens with a positive focal length, the ninth lens (9) is a biconvex lens with a positive focal length, and the detector (11) is a black silicon CMOS sensor.

4. The ultra-short focus large target area compact low light imaging optical system according to claim 3, characterized in that: The object side curvature R of the first lens (1) is O1 is 17 to 20, like the side curvature R S1 is 4 to 6; the object side curvature R of the second lens (2) O2 -15~-11, like the side curvature R S2 The object side curvature R of the third lens (3) is 5 to 8. O3 is 9 to 13, like the side curvature R S3 The object side curvature R of the fourth lens (4) is -9 to -6. O4 -9 to -6, like the side curvature R S4 The object side curvature R of the fifth lens (5) is -94 to -86. O5 6 to 9, like the side curvature R S5 The object side curvature R of the sixth lens (6) is -11 to -8. O6 is 14 to 18, like the side curvature R S6 The object side curvature R of the seventh lens (7) is -4 to -2. O7 -4 to -2, like the side curvature R S7 The object side curvature R of the eighth lens (8) is 8 to 11. O8 -23~-20, like the side curvature R S3 The object side curvature R of the ninth lens (9) is -10 to -7. O9 is 11 to 14, like the side curvature R S9 It is -76 to -69.

5. The ultra-short focus large target area compact low light imaging optical system according to claim 4, characterized in that: The refractive index of the first lens (1) is between 1.7 and 1.8; the refractive index of the second lens (2) is between 1.5 and 1.6; the refractive index of the third lens (3) is between 1.7 and 1.8; the refractive index of the fourth lens (4) is between 1.5 and 1.6; the refractive index of the fifth lens (5) is between 1.6 and 1.7; the refractive index of the sixth lens (6) is between 1.5 and 1.6; the refractive index of the seventh lens (7) is between 1.7 and 1.8; the refractive index of the eighth lens (8) is between 1.7 and 1.8; and the refractive index of the ninth lens (9) is between 1.7 and 1.

8.

6. The ultra-short focus large target area compact low light imaging optical system according to claim 5, characterized in that: The thickness of the first lens (1) is 0.6-0.7 mm, the thickness of the second lens (2) is 0.6-0.7 mm, the thickness of the third lens (3) is 3.1-3.2 mm, the thickness of the fourth lens (4) is 0.7-0.8 mm, the thickness of the fifth lens (5) is 4.6-4.7 mm, the thickness of the sixth lens (6) is 2.1-2.2 mm, the thickness of the seventh lens (7) is 0.4-0.5 mm, the thickness of the eighth lens (8) is 1.3-1.4 mm, and the thickness of the ninth lens (9) is 2.0-2.1 mm.

7. The ultra-short focus, large target surface, compact low-light-level imaging optical system according to any one of claims 1 to 6, characterized in that: The first double cemented lens is composed of heavy lanthanum flint glass and crown glass with large dispersion coefficient differences.

8. The ultra-short focus, large target surface, compact low-light-level imaging optical system according to any one of claims 1 to 6, characterized in that: The second double cemented lens is composed of heavy flint glass and heavy crown glass with large dispersion coefficient differences.

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