Lens system

Abstract

The invention discloses a lens system. The lens system comprises a first lens group, a second lens group and a third lens group, the first lens group comprises a first lens with negative focal power and a second lens with negative focal power which are sequentially arranged from the object plane to the image plane along the optical axis; the second lens group comprises a third lens with positive focal power, a fourth lens with positive focal power, a fifth lens with negative focal power and a sixth lens with positive focal power which are sequentially arranged from the object plane to the image plane along the optical axis; the third lens group comprises a seventh lens with negative focal power and an eighth lens with positive focal power which are sequentially arranged from the object plane to the image plane along the optical axis; the focal power phi A of the first lens group, the focal power phi B of the second lens group, the focal power phi C of the third lens group and the focal power phi of the lens system meet the condition that phi A / phi is larger than or equal to-1.050 and smaller than or equal to-0.885. 1.185 < = phi B / phi < = 1.315; 0.065 < = phi C / phi < = 0.225. By reasonably matching the focal power of the three lens groups and the focal power of the eight lenses, light can be transited among different lens groups at a small deflection angle, the aberration of the system can be effectively controlled, and the ultra-high-definition imaging effect of the lens system is facilitated.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of optical devices, and in particular to a lens system. Background Art

[0002] Telephoto lenses offer greater magnification than short-focus lenses, holding significant potential for application in specific environments. Large-aperture, day / night parfocal telephoto lenses on the market are commonly used with sensors smaller than 1 / 2.7 inches, achieving a total optical length of less than 22.5mm. When paired with sensors larger than 1 / 1.8 inches, a telephoto lens can achieve a short overall length without achieving parfocality, or vice versa. Furthermore, compared to 1 / 2.7-inch sensors, 1 / 1.8-inch sensors require higher pixel counts, necessitating a higher resolution for the lens itself.

[0003] Therefore, how to achieve lens design that takes into account short, medium, long and long focal lengths and matches a 1 / 1.8-inch chip has become a research focus. Summary of the Invention

[0004] The present invention provides a lens system that realizes a lens design that takes into account short, medium, long and long focal lengths and matches a 1 / 1.8-inch chip.

[0005] An embodiment of the present invention provides a lens system comprising a first lens group, a second lens group, and a third lens group arranged in sequence from an object plane to an image plane along an optical axis;

[0006] The first lens group includes a first lens and a second lens arranged in sequence from the object plane to the image plane along the optical axis, the first lens is a negative power lens, and the second lens is a negative power lens;

[0007] The second lens group includes a third lens, a fourth lens, a fifth lens, and a sixth lens arranged in sequence along the optical axis from the object plane to the image plane, wherein the third lens has a positive optical power, the fourth lens has a positive optical power, the fifth lens has a negative optical power, and the sixth lens has a positive optical power;

[0008] The third lens group includes a seventh lens and an eighth lens arranged in sequence from the object plane to the image plane along the optical axis, the seventh lens has a negative optical power, and the eighth lens has a positive optical power;

[0009] The optical power of the first lens group is The optical power of the second lens group is The optical power of the third lens group is The optical power of the lens system is

[0010] in,

[0011] Optionally, the optical power of the first lens is The optical power of the second lens is The optical power of the third lens is The optical power of the fourth lens is The combined optical power of the fifth lens and the sixth lens is The optical power of the seventh lens is The optical power of the eighth lens is

[0012] in,

[0013] Optionally, the maximum effective diameter of the first lens is D1, the aperture of the lens system is Fno, and the maximum image circle radius of the lens system is Ymax;

[0014] Among them, 1.150≤D1 / (Fno*Ymax)≤1.450.

[0015] Optionally, the first lens includes a first object-side surface close to the object plane and a first image-side surface close to the image plane, the first object-side surface is convex, and the first image-side surface is concave;

[0016] The second lens includes a second object-side surface close to the object plane and a second image-side surface close to the image plane, the second object-side surface is concave, and the second image-side surface is convex;

[0017] The third lens comprises a third object-side surface close to the object plane and a third image-side surface close to the image plane, the third object-side surface is a convex surface, and the third image-side surface is a convex surface;

[0018] The fourth lens comprises a fourth object-side surface close to the object plane, and the fourth object-side surface is a convex surface;

[0019] The fifth lens comprises a fifth object-side surface close to the object plane and a fifth image-side surface close to the image plane, the fifth object-side surface is convex, and the fifth image-side surface is concave;

[0020] The sixth lens comprises a sixth object-side surface close to the object plane and a sixth image-side surface close to the image plane, the sixth object-side surface is a convex surface, and the sixth image-side surface is a convex surface;

[0021] The seventh lens element includes a seventh object-side surface close to the object plane and a seventh image-side surface close to the image plane, the seventh object-side surface is concave, and the seventh image-side surface is convex;

[0022] The eighth lens includes an eighth object-side surface close to the object plane and an eighth image-side surface close to the image plane, and both the eighth object-side surface and the eighth image-side surface include reverse curved surfaces.

[0023] Optionally, the full-aperture sagitta of the eighth object side is Sag8 A , the semi-caliber height is Sag8 B The full-aperture sagittal height of the eighth image side is Sag8 C , the semi-caliber height is Sag8 D ;

[0024] Among them, 0.555≤Sag8 B / Sag8 A ≤1.458;-4.515≤Sag8 C / Sag8 D ≤3.255.

[0025] Optionally, the fifth lens and the sixth lens are cemented together.

[0026] Optionally, the air gap length between the sixth lens and the seventh lens is d67, the thickness of the seventh lens is d7, and the thickness of the eighth lens is d8;

[0027] Among them, 0.285≤d67 / (d7+d8)≤0.615.

[0028] Optionally, the Abbe number of the fourth lens is VD4, the refractive index of the fifth lens is ND5, and the Abbe number of the sixth lens is VD6;

[0029] Among them, 65.520≤VD4≤98.165; 1.685≤ND5≤2.015; 65.520≤VD6≤98.165.

[0030] Optionally, the first lens, the second lens, the third lens, the seventh lens and the eighth lens are all plastic aspherical lenses, and the fourth lens, the fifth lens and the sixth lens are all glass spherical lenses.

[0031] Optionally, the lens system further includes an aperture, which is arranged in the optical path between the second lens and the third lens.

[0032] The lens system provided by the embodiment of the present invention includes three lens groups with a total of eight lenses. The number of lens groups and the number of lenses are reasonably set to ensure that the total length of the lens system is appropriate, which is conducive to realizing a miniaturized lens design. Furthermore, the optical power of the eight lenses is matched in a negative-negative-positive-positive-negative-positive-negative-positive manner, and the optical power of the first lens group is Refractive power of the second lens group Refractive power of the third lens group and the focal length of the lens system satisfy By rationally matching the three lens groups and the optical focal length of eight lenses, light can be transferred between different lens groups at a smaller deflection angle, which can effectively control the system aberration and help the lens system achieve ultra-high-definition imaging effects. A high-resolution day and night confocal lens system design with a focal length of about 7.6mm, an imaging target surface that can match a 1 / 1.8-inch chip, a total length of less than 22.5mm, and an aperture value of 1.28 has been realized.

[0033] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 1 is a structural diagram of a lens system provided in Embodiment 1 of the present invention;

[0036] Figure 2 1 is a schematic diagram of a spherical aberration curve of a lens system provided in the first embodiment of the present invention;

[0037] Figure 3 1 is a schematic diagram of a light fan of a lens system provided in Embodiment 1 of the present invention;

[0038] Figure 4 1 is a schematic diagram of a field curvature distortion curve of a lens system provided in Example 1 of the present invention;

[0039] Figure 5 is a structural diagram of a lens system provided by Embodiment 2 of the present invention;

[0040] Figure 6 is a schematic diagram of a spherical aberration curve of a lens system provided in the second embodiment of the present invention;

[0041] Figure 7 Schematic diagram of a light fan of a lens system provided by the second embodiment of the present invention;

[0042] Figure 81 is a schematic diagram of a field curvature distortion curve of a lens system provided in a second embodiment of the present invention;

[0043] Figure 9 1 is a structural diagram of a lens system provided by Embodiment 3 of the present invention;

[0044] Figure 10 1 is a schematic diagram of a spherical aberration curve of a lens system provided in a third embodiment of the present invention;

[0045] Figure 11 Schematic diagram of a light fan of a lens system provided by the third embodiment of the present invention;

[0046] Figure 12 1 is a schematic diagram of a field curvature distortion curve of a lens system provided in a third embodiment of the present invention;

[0047] Figure 13 1 is a structural diagram of a lens system provided by a fourth embodiment of the present invention;

[0048] Figure 14 1 is a schematic diagram of a spherical aberration curve of a lens system provided by a fourth embodiment of the present invention;

[0049] Figure 15 1 is a schematic diagram of a light fan of a lens system provided by a fourth embodiment of the present invention;

[0050] Figure 16 1 is a schematic diagram of a field curvature distortion curve of a lens system provided by a fourth embodiment of the present invention;

[0051] Figure 17 1 is a structural diagram of a lens system provided by Embodiment 5 of the present invention;

[0052] Figure 18 1 is a schematic diagram of a spherical aberration curve of a lens system provided in a fifth embodiment of the present invention;

[0053] Figure 19 1 is a schematic diagram of a light fan of a lens system provided in a fifth embodiment of the present invention;

[0054] Figure 20 4 is a schematic diagram of a field curvature distortion curve of a lens system provided in Example 5 of the present invention. DETAILED DESCRIPTION

[0055] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0056] Example 1

[0057] Figure 1 FIG. 1 is a structural diagram of a lens system provided in the first embodiment of the present invention. Figure 1 As shown, the lens system provided by the embodiment of the present invention includes a first lens group S1, a second lens group S2 and a third lens group S3 arranged in sequence along the optical axis from the object plane to the image plane; the first lens group S1 includes a first lens 101 and a second lens 102 arranged in sequence along the optical axis from the object plane to the image plane, the first lens 101 is a negative optical focal length lens, and the second lens 102 is a negative optical focal length lens; the second lens group S2 includes a third lens 103, a fourth lens 104, a fifth lens 105 and a sixth lens 106 arranged in sequence along the optical axis from the object plane to the image plane, the optical focal length of the third lens 103 is positive, the optical focal length of the fourth lens 104 is positive, the optical focal length of the fifth lens 105 is negative, and the optical focal length of the sixth lens 106 is positive; the third lens group S3 includes a seventh lens 107 and an eighth lens 108 arranged in sequence along the optical axis from the object plane to the image plane, the optical focal length of the seventh lens 107 is negative, and the optical focal length of the eighth lens 108 is positive; the focal length of the first lens group S1 is The optical power of the second lens group S2 is The optical power of the third lens group S3 is The optical power of the lens system is

[0058] in,

[0059] like Figure 1 As shown, the lens system provided by the embodiment of the present invention includes three lens groups with a total of eight lenses with optical focal length. The arrangement of the eight lenses with optical focal length ensures that the number of lenses in the lens system is reasonably set. The lens volume will not be larger due to too many lenses, nor will the aberration of a single lens due to the large optical focal length caused by too few lenses be larger. While ensuring the miniaturization of the lens system, the imaging aberration is small and the imaging quality is high.

[0060] Furthermore, the focal power is equal to the difference between the convergence of the image plane beam and the convergence of the object plane beam, and it characterizes the ability of an optical system to deflect light. The larger the absolute value of the focal power, the stronger the ability to bend light, and the smaller the absolute value of the focal power, the weaker the ability to bend light. When the focal power is a positive number, the refraction of light is convergent; when the focal power is a negative number, the refraction of light is divergent. The focal power can be used to characterize a certain refractive surface of a lens (i.e., a surface of a lens), can be used to characterize a certain lens, and can also be used to characterize a system formed by multiple lenses (i.e., a lens group). In an embodiment of the present invention, the focal power of the first lens group S1 is negative, and the first lens group S1 includes a first lens 101 with a negative focal power and a second lens 102 with a negative focal power. The first lens 101 and the second lens 102 are the lenses in the optical lens that first adjust the incident light. The setting of their negative focal power can ensure that the light has a larger diameter before entering the aperture, increase the aperture of the optical lens, and enable the lens to still form a clear image under dim or dark conditions. The second lens group S2 has positive optical power and includes a third lens element 103 with positive optical power, a fourth lens element 104 with positive optical power, a fifth lens element 105 with negative optical power, and a sixth lens element 106 with positive optical power. The positive optical powers of the third and fourth lenses 103, 104 enable timely correction of the significant aberrations generated by the first and second lenses 101, 102. In particular, they significantly correct marginal aberrations of the optical lens, thereby improving the imaging resolution of the optical system. The fifth lens element 105 is a negative optical power lens, while the sixth lens element 106 is a positive optical power lens. Combined with the positive optical power of the third and fourth lenses 103, 104, the optical power of each subsequent lens in the optical path differs from that of the preceding lens, facilitating correction of aberrations. The third lens group S3 has positive power, and includes a seventh lens element 107 having negative power and an eighth lens element 108 having positive power. Combined with the negative power of the fifth lens element 105 and the positive power of the sixth lens element 106, the power of each subsequent lens in the optical path is different from that of the preceding lens, thereby further correcting aberrations.

[0061] Furthermore, the optical power of the first lens group Refractive power of the second lens group Refractive power of the third lens group and the focal length of the lens system satisfy The optical power of the first lens group S1, the second lens group S2 and the third lens group S3 in the lens system has a reasonable distribution ratio, which can make the light transition between different lens groups with a smaller deflection angle, effectively control the introduction of system aberrations, and facilitate the realization of ultra-high-definition imaging effects of the lens system.

[0062] In summary, the lens system provided by the embodiment of the present invention ensures that the total length of the lens system is appropriate by reasonably setting the number of lens groups and the number of lenses, which is conducive to realizing a miniaturized lens design. Furthermore, the focal power of the eight lenses is matched in a negative-negative-positive-positive-negative-positive-negative-positive manner, and the focal power of the first lens group is Refractive power of the second lens group Refractive power of the third lens group and the focal length of the lens system satisfy By rationally matching the three lens groups and the optical focal length of eight lenses, light can be transferred between different lens groups at a smaller deflection angle, which can effectively control the system aberration and help the lens system achieve ultra-high-definition imaging effects. A high-resolution day and night confocal lens system design with a focal length of about 7.6mm, an imaging target surface that can match a 1 / 1.8-inch chip, a total length of less than 22.5mm, and an aperture value of 1.28 has been realized.

[0063] For further reference, Figure 1 As shown, the lens system used in the embodiment of the present invention may also include an aperture STO and a filter 109. The aperture STO is disposed in the optical path between the second lens 102 and the third lens 103, and the filter 109 is disposed in the optical path between the eighth lens 108 and the image plane. The aperture STO can adjust the propagation direction of the light beam, which is beneficial for improving imaging quality. Furthermore, in this lens system, the aperture STO disposed in the optical system can limit the beam size and control the amount of light passing through the lens, which is beneficial for reducing the aperture value and achieving a large aperture. The filter 109 can filter out stray light and improve the imaging effect.

[0064] Furthermore, the optical lens provided by embodiments of the present invention may further include a protective glass and an imaging sensor. The protective glass may be disposed on the image side of the filter, and the imaging sensor may be disposed on the image side of the protective glass. The protective glass protects the optical system, and the imaging sensor captures images, thereby enabling the optical system to function properly.

[0065] Based on the above embodiment, the optical power of the first lens 101 is The optical power of the second lens 102 is The optical power of the third lens 103 is The optical power of the fourth lens 104 is The combined optical power of the fifth lens 105 and the sixth lens 106 is The optical power of the seventh lens 107 is The optical power of the eighth lens 108 is in, Reasonable setting of the optical power values ​​of each lens or lens group can effectively control the trend of light, reduce the field curvature and spherical aberration of the optical system, and at the same time reduce the tolerance sensitivity of the lens system and improve the image quality of the optical system.

[0066] Based on the above embodiment, the maximum effective diameter of the first lens 101 is D1, the aperture of the lens system is Fno, and the maximum image circle radius of the lens system is Ymax; wherein,

[0067] 1.150≤D1 / (Fno*Ymax)≤1.450. By limiting the maximum image circle and aperture size of the optical imaging system, the purpose of limiting the optical effective diameter of the first lens 101 can be achieved, thereby ensuring that the optical system meets the requirement of miniaturization.

[0068] On the basis of the above embodiment, the first lens 101 includes a first object-side surface close to the object plane and a first image-side surface close to the image plane, the first object-side surface is convex, and the first image-side surface is concave; the second lens 102 includes a second object-side surface close to the object plane and a second image-side surface close to the image plane, the second object-side surface is concave, and the second image-side surface is convex; the third lens 103 includes a third object-side surface close to the object plane and a third image-side surface close to the image plane, the third object-side surface is convex, and the third image-side surface is convex; the fourth lens 104 includes a fourth object-side surface close to the object plane, the fourth object-side surface is convex; the fifth lens 10 The sixth lens element 106 includes a sixth object-side surface near the object plane and a sixth image-side surface near the image plane, the sixth object-side surface is convex, and the sixth image-side surface is concave. The seventh lens element 107 includes a seventh object-side surface near the object plane and a seventh image-side surface near the image plane, the seventh object-side surface is concave, and the seventh image-side surface is convex. The eighth lens element 108 includes an eighth object-side surface near the object plane and an eighth image-side surface near the image plane, both of which include anti-curved surfaces.

[0069] Specifically, the object-side surface of the lens can be understood as the surface of the lens close to the object plane, and the image-side surface of the lens can be understood as the surface of the lens close to the image plane.

[0070] The object-side surface of the first lens 101 is convex, and the image-side surface is concave. This means that the object-side surface of the first lens 101 is convex toward the object plane near the optical axis, while the image-side surface is concave toward the image plane near the optical axis. In other words, the first lens 101 has a convex-concave structure. The convex object-side surface of the first lens maximizes the convergence of light entering the system, while the concave image-side surface allows light to enter the system at a smaller deflection angle, facilitating a larger aperture and minimized aberrations.

[0071] The object-side surface of the second lens 102 is concave, and the image-side surface is convex. This means that the object-side surface of the second lens 102 is concave toward the object plane near the optical axis, while the image-side surface is convex toward the image plane near the optical axis. In other words, the second lens 102 has a concave-convex structure. This effectively controls the trajectory of light, reduces field curvature and spherical aberration of the optical system, and improves image quality.

[0072] The object-side surface and image-side surface of the third lens element 103 are convex. This means that the object-side surface of the third lens element 103 is convex toward the object plane near the optical axis, while the image-side surface is convex toward the image plane near the optical axis. In other words, the third lens element 103 has a biconvex structure. The fact that both sides of the third lens element 103 are convex and have positive optical power effectively controls the smooth entry of light into the optical system, reduces spherical aberration, and improves imaging quality.

[0073] The object-side surface of the fourth lens 104 is a convex surface, which can be understood as the object-side surface of the fourth lens 104 is convex toward the object plane at a position near the optical axis, and the surface shape toward the image side surface is not limited.

[0074] The object-side surface of the fifth lens element 105 is convex, and the image-side surface is concave. This means that the object-side surface of the fifth lens element 105 is convex toward the object plane near the optical axis, while the image-side surface is concave toward the image plane near the optical axis. In other words, the fifth lens element 105 has a convex-concave structure. The object-side surface of the sixth lens element 106 is convex, and the image-side surface is convex. This means that the object-side surface of the sixth lens element 106 is convex toward the object plane near the optical axis, while the image-side surface is convex toward the image plane near the optical axis. In other words, the sixth lens element 106 can have a biconvex structure. The matching surface shapes of the fifth and sixth lenses 105, 106 facilitate the cementation of the fifth and sixth lenses 105, 106. Furthermore, the configuration of the surface profiles of the fifth lens element 105 and the sixth lens element 106, combined with their focal power configuration, not only helps balance various aberrations generated by light passing through the aperture, thereby improving the imaging quality of the lens system; it also helps increase the aperture, ensuring clear imaging even in low-light conditions, and meeting the all-weather monitoring requirements of surveillance equipment.

[0075] The object-side surface of the seventh lens element 107 is concave, and the image-side surface is convex. This means that the object-side surface of the seventh lens element 107 is concave toward the object plane near the optical axis, while the image-side surface is convex toward the image plane near the optical axis. In other words, the second lens element 102 has a concave-convex structure. The concave object-side surface of the seventh lens element 107 effectively controls the trajectory of light, allowing it to enter the eighth lens element 108 at a smaller deflection angle, thereby effectively reducing system tolerances.

[0076] The object-side surface and the image-side surface of the eighth lens 108 both include reverse curved surfaces, and the full-aperture sag height of the eighth object-side surface is Sag8. A , the semi-caliber height is Sag8 B The full-aperture height of the eighth image is Sag8. C , the semi-caliber height is Sag8 D ; Among them, 0.555≤Sag8 B / Sag8 A ≤1.458;

[0077] -4.515≤Sag8 C / Sag8 D ≤3.255. The object side surface and the image side surface of the eighth lens 108 are both provided with anti-curved surfaces and the relationship between the full-aperture sag and the half-aperture sag of the object side surface and the image side surface is further provided, so as to ensure that the eighth lens 108 can effectively control the trend of light, raise the height of light, and achieve the design effect of large target surface imaging. In addition, the seventh lens 107 cooperates with the eighth lens 108, which can not only improve the smoothness of light transmission, thereby reducing the probability of various aberrations while reducing the tolerance sensitivity of the lens system, thereby improving the assembly yield of the lens system. Furthermore, the seventh lens 107 cooperates with the eighth lens 108 to compress the light beam, thereby reducing the divergence angle of the main light, so as to adapt to the CRA (main light angle) curve requirements of the photosensitive chip located on the image plane, and improve the matching degree with the photosensitive chip.

[0078] By rationally setting the concave and convex surface shapes of each lens, it is possible to ensure that each lens modulates the light emission angle. In addition, for a cemented lens, at least two adjacent lenses can be cemented together. On the other hand, the distance between adjacent lenses can be reduced, which is conducive to the design of a small-volume lens system.

[0079] Based on the above embodiment, the fifth lens 105 and the sixth lens 106 are cemented together.

[0080] Specifically, the bonding of different lenses can be understood as the image side surface of the preceding lens and the object side surface of the following lens in the optical path being bonded together and having the same surface shape. Figure 1 As shown, the fifth lens 105 and the sixth lens 106 are cemented together, which can be understood as the image-side surface of the fifth lens 105 and the object-side surface of the sixth lens 106 being in contact with each other.

[0081] Cemented lenses can be used to minimize or eliminate chromatic aberration. Using cemented lenses in lens systems improves image quality and reduces reflection loss of light energy, thereby enhancing image clarity. Furthermore, cementing eliminates the air gap between the two lenses, making the overall optical system more compact and meeting the requirements of system miniaturization. Furthermore, cementing lenses reduces sensitivity to tolerances such as tilt and deflection that can occur during lens unit assembly.

[0082] Based on the above embodiment, the air gap between the sixth lens 106 and the seventh lens 107 has a length of d67, the thickness of the seventh lens 107 has a thickness of d7, and the thickness of the eighth lens 108 has a thickness of d8; wherein 0.285≤d67 / (d7+d8)≤0.615. Properly controlling the air gap between the sixth lens 106 and the seventh lens 107, as well as the sum of the thicknesses of the seventh lens 107 and the eighth lens 108, can effectively control both the lateral length and distortion of the system, thereby improving optical imaging performance.

[0083] Based on the above embodiment, the Abbe number of the fourth lens 104 is VD4, the refractive index of the fifth lens 105 is ND5, and the Abbe number of the sixth lens 106 is VD6; wherein, 65.520≤VD4≤98.165; 1.685≤ND5≤2.015; and 65.520≤VD6≤98.165.

[0084] Specifically, the Abbe number is an index used to indicate the dispersion ability of a transparent medium. The greater the dispersion, the smaller the Abbe number; conversely, the less dispersion, the larger the Abbe number. The refractive index is a coefficient that indicates the ability of a transparent medium to deflect light. A higher refractive index indicates a stronger refraction of incident light; a lower refractive index indicates a weaker refraction. The rational combination of materials for the fourth lens element 104 and the cemented lens effectively reduces spherical aberration, coma, astigmatism, field curvature, positional chromatic aberration, and chromatic aberration of magnification across the entire lens system, improving final image quality and chromatic aberration correction. The fourth lens element 104 and the sixth lens element 106 are designed using low-dispersion materials, optimizing the purple fringing effect at the edges of objects and near-infrared imaging, better reproducing the true image. This also provides thermal compensation for the entire optical system, stabilizing thermal drift at high and low temperatures and ensuring resolution requirements at both high and low temperatures.

[0085] Based on the above embodiment, the first lens 101 , the second lens 102 , the third lens 103 , the seventh lens 107 and the eighth lens 108 are all plastic aspherical lenses, and the fourth lens 104 , the fifth lens 105 and the sixth lens 106 are all glass spherical lenses.

[0086] Specifically, aspheric lenses are characterized by a continuously varying curvature from the lens center to the lens periphery. Unlike spherical lenses, which have a constant curvature from the lens center to the lens periphery, aspheric lenses have a better curvature radius characteristic, with the advantages of improving distortion and astigmatism. The first lens 101, the second lens 102, the third lens 103, the seventh lens 107, and the eighth lens 108 are all plastic aspheric lenses. The use of plastic aspheric lenses facilitates the manufacturing process of aspheric lenses, and the lower cost of aspheric lenses can reduce the cost of the optical system.

[0087] Spherical lenses are characterized by a constant curvature from the center to the periphery, ensuring simple lens configuration. Furthermore, because glass lenses have a low coefficient of thermal expansion and excellent stability, the fourth, fifth, and sixth lenses 104, 105, and 106 are all glass spherical lenses. Glass spherical lenses offer greater thermal stability, ensuring good resolution over a wide temperature range even when handling a wide range of optical powers. Furthermore, the wider range of glass materials available, with relatively flexible choices of refractive index and Abbe number, allows for a certain degree of control over higher-order aberrations and chromatic aberrations, meeting the demands of complex operating conditions.

[0088] Therefore, in the lens system provided by the embodiment of the present invention, a mixed combination of glass spherical lenses and plastic aspherical lenses can be used, which can effectively control the cost of the lens system while ensuring the optical performance of the lens system; at the same time, the lens materials have a mutual compensation effect, which can ensure that it can still be used normally in high and low temperature environments.

[0089] As a feasible implementation method, the parameters of each lens in the lens system are described below.

[0090] Table 1 Optical design values ​​of the lens system in Example 1

[0091]

[0092] Table 2 Design values ​​of optical physical parameters of lens system

[0093]

[0094]

[0095] The surface numbers in Table 2 are numbered according to the order of the lens surfaces. "1" represents the object-side surface of the first lens, "2" represents the image-side surface of the first lens, and so on. STO represents the aperture stop. The radius of curvature represents the degree of curvature of the corresponding lens surface. A positive value indicates that the surface is curved toward the image plane, while a negative value indicates that the surface is curved toward the object plane. "INF" indicates that the surface is flat and has an infinite radius of curvature. The thickness represents the axial distance from the center of the current surface to the next surface. The refractive index represents the light-bending ability of the material between the current and next surfaces. A blank space represents the current position as air with a refractive index of 1. The Abbe number represents the dispersion properties of the material between the current and next surfaces. k represents the conic coefficient of the aspheric surface.

[0096] In an embodiment of the present invention, the aspheric lens of the lens system satisfies the following formula:

[0097]

[0098] Wherein, Z is the axial distance from the curved surface at a position perpendicular to the optical axis at a height r to the vertex of the surface along the optical axis; c represents the curvature at the vertex of the aspheric surface; A, B, C, D, E, F, and G are the high-order aspheric coefficients of the corresponding aspheric surface of the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders.

[0099] Table 3 Aspheric coefficients of lens system

[0100]

[0101]

[0102] Among them, -6.043800E-03 means -6.043800*10 -3 , the remaining parameters can be expressed in this way.

[0103] This embodiment meets the following parameters:

[0104] Focal length: f=7.514mm;

[0105] Field of view angle: DFOV = 67.32°;

[0106] Total optical length: TTL = 21.96mm.

[0107] Figure 2This is a schematic diagram of the spherical aberration curve of a lens system provided in Example 1 of the present invention. The vertical direction represents the normalized aperture, with 0 representing the optical axis and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of imaging of the system (436nm, 486nm, 546nm, 588nm, 656nm, and 850nm, respectively). Figure 2 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.04mm, +0.04mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide-spectrum applications.

[0108] Figure 3 This is a schematic diagram of the light fan of a lens system provided in the first embodiment of the present invention. The light fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis is the beam diameter, and the vertical axis is the vertical axis aberration. The most ideal curve is a straight line that coincides with the horizontal axis, indicating that all light rays are focused on the same point on the image plane, and the corresponding interval on the vertical axis of the curve is the maximum diffusion range of the light beam on the ideal image plane. The light fan diagram can not only reflect the monochromatic aberration of different wavelengths, but also indicate the size of the vertical axis chromatic aberration. Figure 3 It can be seen that the system's wavelengths in each field of view (436nm, 486nm, 546nm, 588nm, 656nm and 850nm) are all well aligned with the horizontal axis, indicating that the vertical axis aberration of the system at each wavelength is well corrected. At the same time, there is no obvious dispersion at each wavelength, indicating that the system's chromatic aberration is also well corrected, thereby ensuring that the optical system can achieve high-resolution imaging requirements.

[0109] Figure 4 : is a schematic diagram of a field curvature distortion curve of a lens system provided in the first embodiment of the present invention. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature, and the unit is mm; the vertical coordinate represents the normalized image height, and there is no unit; Figure 4 It can be seen that the lens provided in this embodiment effectively controls field curvature from light with a wavelength of 436nm to light with a wavelength of 850nm. That is, when imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal coordinate represents the degree of distortion in %, and the vertical coordinate represents the normalized image height in no unit. Figure 4 It can be seen that the maximum distortion of the lens provided in this embodiment is 8.6508%.

[0110] In summary, the lens system provided by the embodiments of the present invention adopts a 3G5P structure, and its optical power is negative-negative-positive-positive-negative-positive-negative-positive. The optical power, shape, and position layout of each lens are reasonable, realizing a high-resolution day and night confocal lens system design with a focal length of approximately 7.514 mm, an imaging target surface that can match a 1 / 1.8-inch chip, a total length of less than 22.5 mm, and an aperture value of 1.28.

[0111] Example 2

[0112] Figure 5 FIG. 1 is a structural diagram of a lens system provided in the second embodiment of the present invention. Figure 5 As shown, the lens system provided by Example 2 of the present invention includes a first lens group S1, a second lens group S2 and a third lens group S3 arranged in sequence along the optical axis from the object plane to the image plane; the first lens group S1 includes a first lens 101 and a second lens 102 arranged in sequence along the optical axis from the object plane to the image plane, the first lens 101 is a negative optical focal length lens, and the second lens 102 is a negative optical focal length lens; the second lens group S2 includes a third lens 103, a fourth lens 104, a fifth lens 105 and a sixth lens 106 arranged in sequence along the optical axis from the object plane to the image plane, the optical focal length of the third lens 103 is positive, the optical focal length of the fourth lens 104 is positive, the optical focal length of the fifth lens 105 is negative, and the optical focal length of the sixth lens 106 is positive; the third lens group S3 includes a seventh lens 107 and an eighth lens 108 arranged in sequence along the optical axis from the object plane to the image plane, the optical focal length of the seventh lens 107 is negative, and the optical focal length of the eighth lens 108 is positive; the focal length of the first lens group S1 is The optical power of the second lens group S2 is The optical power of the third lens group S3 is The optical power of the lens system is

[0113] in,

[0114] Other parameters are the same as those in the first embodiment and will not be described again here.

[0115] As another feasible implementation, specific parameters in the lens system are described below.

[0116] Table 4 Optical design values ​​of the lens system in Example 2

[0117]

[0118] Table 5 Design values ​​of optical physical parameters of lens system

[0119]

[0120]

[0121] The surface numbers in Table 5 are numbered according to the order of the lens surfaces. "1" represents the object-side surface of the first lens, "2" represents the image-side surface of the first lens, and so on. STO represents the aperture stop. The radius of curvature represents the degree of curvature of the corresponding lens surface. A positive value indicates that the surface is curved toward the image plane, while a negative value indicates that the surface is curved toward the object plane. "INF" indicates that the surface is flat and has an infinite radius of curvature. The thickness represents the axial distance from the center of the current surface to the next surface. The refractive index represents the light-bending ability of the material between the current and next surfaces. A blank space represents the current position as air with a refractive index of 1. The Abbe number represents the dispersion properties of the material between the current and next surfaces. k represents the conic coefficient of the aspheric surface.

[0122] In an embodiment of the present invention, the aspheric lens of the lens system satisfies the following formula:

[0123]

[0124] Wherein, Z is the axial distance from the curved surface at a position perpendicular to the optical axis at a height r to the vertex of the surface along the optical axis; c represents the curvature at the vertex of the aspheric surface; A, B, C, D, E, F, and G are the high-order aspheric coefficients of the corresponding aspheric surface of the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders.

[0125] Table 6 Aspheric coefficients of lens system

[0126]

[0127] Among them, -5.989996E-03 means -5.989996*10 -3 , the remaining parameters can be expressed in this way.

[0128] This embodiment meets the following parameters:

[0129] Focal length: f=7.612mm;

[0130] Field of view angle: DFOV = 66.20°;

[0131] Total optical length: TTL = 22.45mm.

[0132] Figure 6This is a schematic diagram of the spherical aberration curve of a lens system provided by Example 2 of the present invention. The vertical direction represents the normalized aperture, with 0 representing the optical axis and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset relative to the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of imaging of the system (436nm, 486nm, 546nm, 588nm, 656nm, and 850nm, respectively). Figure 6 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.04mm, +0.04mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide-spectrum applications.

[0133] Figure 7 This is a schematic diagram of the light fan of a lens system provided in the second embodiment of the present invention. The light fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis is the beam diameter, and the vertical axis is the vertical axis aberration. The most ideal curve is a straight line that coincides with the horizontal axis, indicating that all light rays are focused on the same point on the image plane, and the corresponding interval on the vertical axis of the curve is the maximum diffusion range of the light beam on the ideal image plane. The light fan diagram can not only reflect the monochromatic aberration of different wavelengths, but also indicate the size of the vertical axis chromatic aberration. Figure 7 It can be seen that the system's wavelengths in each field of view (436nm, 486nm, 546nm, 588nm, 656nm and 850nm) are all well aligned with the horizontal axis, indicating that the vertical axis aberration of the system at each wavelength is well corrected. At the same time, there is no obvious dispersion at each wavelength, indicating that the system's chromatic aberration is also well corrected, thereby ensuring that the optical system can achieve high-resolution imaging requirements.

[0134] Figure 8 : This is a schematic diagram of a field curvature distortion curve of a lens system provided by the second embodiment of the present invention. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature, and the unit is mm; the vertical coordinate represents the normalized image height, and there is no unit; Figure 8 It can be seen that the lens provided in this embodiment effectively controls field curvature from light with a wavelength of 436nm to light with a wavelength of 850nm. That is, when imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal coordinate represents the degree of distortion in %, and the vertical coordinate represents the normalized image height in no unit. Figure 8 It can be seen that the maximum distortion of the lens provided in this embodiment is 9.8545%.

[0135] In summary, the lens system provided by the embodiments of the present invention adopts a 3G5P structure, and its optical power is negative-negative-positive-positive-negative-positive-negative-positive. The optical power, shape, and position layout of each lens are reasonable, realizing a high-resolution day and night confocal lens system design with a focal length of approximately 7.612 mm, an imaging target surface that can match a 1 / 1.8-inch chip, a total length of less than 22.5 mm, and an aperture value of 1.28.

[0136] Example 3

[0137] Figure 9 FIG. 1 is a schematic structural diagram of a lens system provided in the third embodiment of the present invention at an optimal object distance. Figure 9 As shown, the lens system provided by the third embodiment of the present invention includes a first lens group S1, a second lens group S2 and a third lens group S3 arranged in sequence along the optical axis from the object plane to the image plane; the first lens group S1 includes a first lens 101 and a second lens 102 arranged in sequence along the optical axis from the object plane to the image plane, the first lens 101 is a negative optical focal length lens, and the second lens 102 is a negative optical focal length lens; the second lens group S2 includes a third lens 103, a fourth lens 104, a fifth lens 105 and a sixth lens 106 arranged in sequence along the optical axis from the object plane to the image plane, the optical focal length of the third lens 103 is positive, the optical focal length of the fourth lens 104 is positive, the optical focal length of the fifth lens 105 is negative, and the optical focal length of the sixth lens 106 is positive; the third lens group S3 includes a seventh lens 107 and an eighth lens 108 arranged in sequence along the optical axis from the object plane to the image plane, the optical focal length of the seventh lens 107 is negative, and the optical focal length of the eighth lens 108 is positive; the focal length of the first lens group S1 is The optical power of the second lens group S2 is The optical power of the third lens group S3 is The optical power of the lens system is

[0138] in,

[0139] Other parameters are the same as those in the first embodiment and will not be described again here.

[0140] As another feasible implementation, specific parameters in the lens system are described below.

[0141] Table 7 Optical design values ​​of the lens system in Example 3

[0142]

[0143]

[0144] Table 8 Design values ​​of optical physical parameters of lens system

[0145]

[0146] The surface numbers in Table 8 are numbered according to the order of the lens surfaces. "1" represents the object-side surface of the first lens, "2" represents the image-side surface of the first lens, and so on. STO represents the aperture stop. The radius of curvature represents the degree of curvature of the corresponding lens surface. A positive value indicates that the surface is curved toward the image side, while a negative value indicates that the surface is curved toward the object side. "INF" indicates that the surface is flat and has an infinite radius of curvature. The thickness represents the axial distance from the center of the current surface to the next surface. The refractive index represents the light-bending ability of the material between the current and next surfaces. A blank space represents the current position as air with a refractive index of 1. The Abbe number represents the light-dispersion properties of the material between the current and next surfaces. k represents the conic coefficient of the aspheric surface.

[0147] In an embodiment of the present invention, the aspheric lens of the lens system satisfies the following formula:

[0148]

[0149] Wherein, Z is the axial distance from the curved surface at a position perpendicular to the optical axis at a height r to the vertex of the surface along the optical axis; c represents the curvature at the vertex of the aspheric surface; A, B, C, D, E, F, and G are the high-order aspheric coefficients of the corresponding aspheric surface of the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders.

[0150] Table 9 Aspheric coefficients of lens system

[0151]

[0152] Among them, -5.878553E-03 means -5.878553*10 -3 , the remaining parameters can be expressed in this way.

[0153] This embodiment meets the following parameters:

[0154] Focal length: f=7.550mm;

[0155] Field of view angle: DFOV = 67.32°;

[0156] Total optical length: TTL = 22.43mm.

[0157] Figure 10This is a schematic diagram of the spherical aberration curve of a lens system provided by Example 3 of the present invention. The vertical direction represents the normalized aperture, with 0 representing the optical axis and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset from the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of imaging of the system (436nm, 486nm, 546nm, 588nm, 656nm, and 850nm, respectively). Figure 10 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.09mm, +0.09mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide-spectrum applications.

[0158] Figure 11 This is a schematic diagram of the light fan of a lens system provided in the third embodiment of the present invention. The light fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis is the beam diameter, and the vertical axis is the vertical axis aberration. The most ideal curve is a straight line that coincides with the horizontal axis, indicating that all light rays are focused on the same point on the image plane, and the corresponding interval on the vertical axis of the curve is the maximum diffusion range of the light beam on the ideal image plane. The light fan diagram can not only reflect the monochromatic aberration of different wavelengths, but also indicate the size of the vertical axis chromatic aberration. Figure 11 It can be seen that the system's wavelengths in each field of view (436nm, 486nm, 546nm, 588nm, 656nm and 850nm) are all well aligned with the horizontal axis, indicating that the vertical axis aberration of the system at each wavelength is well corrected. At the same time, there is no obvious dispersion at each wavelength, indicating that the system's chromatic aberration is also well corrected, thereby ensuring that the optical system can achieve high-resolution imaging requirements.

[0159] Figure 12 : is a schematic diagram of a field curvature distortion curve of a lens system provided in Example 3 of the present invention. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature, and the unit is mm; the vertical coordinate represents the normalized image height, and there is no unit; Figure 12 It can be seen that the lens provided in this embodiment effectively controls field curvature from light with a wavelength of 436nm to light with a wavelength of 850nm. That is, when imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal coordinate represents the degree of distortion in %, and the vertical coordinate represents the normalized image height in no unit. Figure 12 It can be seen that the maximum distortion of the lens provided in this embodiment is 8.3911%.

[0160] In summary, the lens system provided by the embodiments of the present invention adopts a 3G5P structure, and its optical power is negative-negative-positive-positive-negative-positive-negative-positive. The optical power, shape, and position layout of each lens are reasonable, realizing a high-resolution day and night confocal lens system design with a focal length of approximately 7.550 mm, an imaging target surface that can match a 1 / 1.8-inch chip, a total length of less than 22.5 mm, and an aperture value of 1.28.

[0161] Example 4

[0162] Figure 13 FIG. 4 is a structural diagram of a lens system provided by a fourth embodiment of the present invention at an optimal object distance. Figure 13 As shown, the lens system provided by Example 4 of the present invention includes a first lens group S1, a second lens group S2 and a third lens group S3 arranged in sequence along the optical axis from the object plane to the image plane; the first lens group S1 includes a first lens 101 and a second lens 102 arranged in sequence along the optical axis from the object plane to the image plane, the first lens 101 is a negative optical focal length lens, and the second lens 102 is a negative optical focal length lens; the second lens group S2 includes a third lens 103, a fourth lens 104, a fifth lens 105 and a sixth lens 106 arranged in sequence along the optical axis from the object plane to the image plane, the optical focal length of the third lens 103 is positive, the optical focal length of the fourth lens 104 is positive, the optical focal length of the fifth lens 105 is negative, and the optical focal length of the sixth lens 106 is positive; the third lens group S3 includes a seventh lens 107 and an eighth lens 108 arranged in sequence along the optical axis from the object plane to the image plane, the optical focal length of the seventh lens 107 is negative, and the optical focal length of the eighth lens 108 is positive; the focal length of the first lens group S1 is The optical power of the second lens group S2 is The optical power of the third lens group S3 is The optical power of the lens system is

[0163] in,

[0164] Other parameters are the same as those in the first embodiment and will not be described again here.

[0165] As another feasible implementation, specific parameters in the lens system are described below.

[0166] Table 10: Optical design values ​​of the lens system in Example 4

[0167]

[0168]

[0169] Table 11 Design values ​​of optical physical parameters of lens system

[0170]

[0171] The surface numbers in Table 11 are numbered according to the order of the lens surfaces. "1" represents the object-side surface of the first lens, "2" represents the image-side surface of the first lens, and so on. STO represents the aperture stop. The radius of curvature represents the degree of curvature of the corresponding lens surface. A positive value indicates that the surface is curved toward the image plane, while a negative value indicates that the surface is curved toward the object plane. "INF" indicates that the surface is flat and has an infinite radius of curvature. The thickness represents the axial distance from the center of the current surface to the next surface. The refractive index represents the light-bending ability of the material between the current and next surfaces. A blank space represents the current position as air with a refractive index of 1. The Abbe number represents the dispersion properties of the material between the current and next surfaces. k represents the conic coefficient of the aspheric surface.

[0172] In an embodiment of the present invention, the aspheric lens of the lens system satisfies the following formula:

[0173]

[0174] Wherein, Z is the axial distance from the curved surface at a position perpendicular to the optical axis at a height r to the vertex of the surface along the optical axis; c represents the curvature at the vertex of the aspheric surface; A, B, C, D, E, F, and G are the high-order aspheric coefficients of the corresponding aspheric surface of the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders.

[0175] Table 12 Aspheric coefficients of lens system

[0176]

[0177]

[0178] Among them, -5.766005E-03 means -5.766005*10 -3 , the remaining parameters can be expressed in this way.

[0179] This embodiment meets the following parameters:

[0180] Focal length: f=7.560mm;

[0181] Field of view angle: DFOV = 67.32°;

[0182] Total optical length: TTL = 22.42mm.

[0183] Figure 14This is a schematic diagram of the spherical aberration curve of a lens system provided by Example 4 of the present invention. The vertical direction represents the normalized aperture, with 0 representing the optical axis and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset from the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of imaging by the system (436nm, 486nm, 546nm, 588nm, 656nm, and 850nm, respectively). Figure 14 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.09mm, +0.09mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide-spectrum applications.

[0184] Figure 15 This is a schematic diagram of the light fan of a lens system provided in the fourth embodiment of the present invention. The light fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis is the beam diameter, and the vertical axis is the vertical axis aberration. The most ideal curve is a straight line that coincides with the horizontal axis, indicating that all light rays are focused on the same point on the image plane, and the corresponding interval on the vertical axis of the curve is the maximum diffusion range of the light beam on the ideal image plane. The light fan diagram can not only reflect the monochromatic aberration of different wavelengths, but also indicate the size of the vertical axis chromatic aberration. Figure 15 It can be seen that the system's wavelengths in each field of view (436nm, 486nm, 546nm, 588nm, 656nm and 850nm) are all well aligned with the horizontal axis, indicating that the vertical axis aberration of the system at each wavelength is well corrected. At the same time, there is no obvious dispersion at each wavelength, indicating that the system's chromatic aberration is also well corrected, thereby ensuring that the optical system can achieve high-resolution imaging requirements.

[0185] Figure 16 Schematic diagram of a field curvature distortion curve of a lens system provided by the fourth embodiment of the present invention. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature, and the unit is mm; the vertical coordinate represents the normalized image height, and there is no unit; Figure 16 It can be seen that the lens provided in this embodiment effectively controls field curvature from light with a wavelength of 436nm to light with a wavelength of 850nm. That is, when imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal coordinate represents the degree of distortion in %, and the vertical coordinate represents the normalized image height in no unit. Figure 16 It can be seen that the maximum distortion of the lens provided in this embodiment is 8.6935%.

[0186] In summary, the lens system provided by the embodiments of the present invention adopts a 3G5P structure, and its optical power is negative-negative-positive-positive-negative-positive-negative-positive. The optical power, shape, and position layout of each lens are reasonable, realizing a high-resolution day and night confocal lens system design with a focal length of approximately 7.560 mm, an imaging target surface that can match a 1 / 1.8-inch chip, a total length of less than 22.5 mm, and an aperture value of 1.28.

[0187] Example 5

[0188] Figure 17 FIG. 5 is a structural diagram of a lens system provided by the fifth embodiment of the present invention at an optimal object distance. Figure 17 As shown, the lens system provided by Example 5 of the present invention includes a first lens group S1, a second lens group S2 and a third lens group S3 arranged in sequence along the optical axis from the object plane to the image plane; the first lens group S1 includes a first lens 101 and a second lens 102 arranged in sequence along the optical axis from the object plane to the image plane, the first lens 101 is a negative optical focal length lens, and the second lens 102 is a negative optical focal length lens; the second lens group S2 includes a third lens 103, a fourth lens 104, a fifth lens 105 and a sixth lens 106 arranged in sequence along the optical axis from the object plane to the image plane, the optical focal length of the third lens 103 is positive, the optical focal length of the fourth lens 104 is positive, the optical focal length of the fifth lens 105 is negative, and the optical focal length of the sixth lens 106 is positive; the third lens group S3 includes a seventh lens 107 and an eighth lens 108 arranged in sequence along the optical axis from the object plane to the image plane, the optical focal length of the seventh lens 107 is negative, and the optical focal length of the eighth lens 108 is positive; the focal length of the first lens group S1 is The optical power of the second lens group S2 is The optical power of the third lens group S3 is The optical power of the lens system is

[0189] in,

[0190] Other parameters are the same as those in the first embodiment and will not be described again here.

[0191] As another feasible implementation, specific parameters in the lens system are described below.

[0192] Table 13 Optical design values ​​of the lens system in Example 5

[0193]

[0194] Table 14 Design values ​​of optical physical parameters of lens system

[0195]

[0196]

[0197] The surface numbers in Table 14 are numbered according to the order of the lens surfaces. "1" represents the object-side surface of the first lens, "2" represents the image-side surface of the first lens, and so on. STO represents the aperture stop. The radius of curvature represents the degree of curvature of the corresponding lens surface. A positive value indicates that the surface is curved toward the image side, while a negative value indicates that the surface is curved toward the object side. "INF" indicates that the surface is flat and has an infinite radius of curvature. The thickness represents the axial distance from the center of the current surface to the next surface. The refractive index represents the light-bending ability of the material between the current and next surfaces. A blank space represents the current position as air with a refractive index of 1. The Abbe number represents the dispersion properties of the material between the current and next surfaces. k represents the conic coefficient of the aspheric surface.

[0198] In an embodiment of the present invention, the aspheric lens of the lens system satisfies the following formula:

[0199]

[0200] Wherein, Z is the axial distance from the curved surface at a position perpendicular to the optical axis at a height r to the vertex of the surface along the optical axis; c represents the curvature at the vertex of the aspheric surface; A, B, C, D, E, F, and G are the high-order aspheric coefficients of the corresponding aspheric surface of the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth orders.

[0201] Table 15 Aspheric coefficients of lens system

[0202]

[0203] Among them, -5.893622E-03 means -5.893622*10 -3 , the remaining parameters can be expressed in this way.

[0204] This embodiment meets the following parameters:

[0205] Focal length: f=7.570mm;

[0206] Field of view angle: DFOV = 67.32°;

[0207] Total optical length: TTL = 22.42mm.

[0208] Figure 18This is a schematic diagram of the spherical aberration curve of a lens system provided by Example 5 of the present invention. The vertical direction represents the normalized aperture, with 0 representing the optical axis and the vertical vertex representing the maximum pupil radius; the horizontal direction represents the offset from the ideal focus, in millimeters (mm). The different linear curves in the figure represent different wavelengths of imaging by the system (436nm, 486nm, 546nm, 588nm, 656nm, and 850nm, respectively). Figure 18 It can be seen that the axial aberrations at different wavelengths are all controlled within the range of (-0.09mm, +0.09mm), indicating that the spherical aberration of this fixed-focus lens at each wavelength is well controlled and can meet the needs of wide-spectrum applications.

[0209] Figure 19 This is a schematic diagram of the light fan of a lens system provided in Example 5 of the present invention. The light fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis is the beam diameter, and the vertical axis is the vertical axis aberration. The most ideal curve is a straight line that coincides with the horizontal axis, indicating that all light rays are focused on the same point on the image plane, and the corresponding interval on the vertical axis of the curve is the maximum diffusion range of the light beam on the ideal image plane. The light fan diagram can not only reflect the monochromatic aberration of different wavelengths, but also indicate the size of the vertical axis chromatic aberration. Figure 19 It can be seen that the system's wavelengths in each field of view (436nm, 486nm, 546nm, 588nm, 656nm and 850nm) are all well aligned with the horizontal axis, indicating that the vertical axis aberration of the system at each wavelength is well corrected. At the same time, there is no obvious dispersion at each wavelength, indicating that the system's chromatic aberration is also well corrected, thereby ensuring that the optical system can achieve high-resolution imaging requirements.

[0210] Figure 20 : is a schematic diagram of a field curvature distortion curve of a lens system provided by Example 5 of the present invention. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature, and the unit is mm; the vertical coordinate represents the normalized image height, and there is no unit; Figure 20 It can be seen that the lens provided in this embodiment effectively controls field curvature from light with a wavelength of 436nm to light with a wavelength of 850nm. That is, when imaging, the difference in image quality between the center and the periphery is small. In the coordinate system on the right, the horizontal coordinate represents the degree of distortion in %, and the vertical coordinate represents the normalized image height in no unit. Figure 20 It can be seen that the maximum distortion of the lens provided in this embodiment is 8.7295%.

[0211] In summary, the lens system provided by the embodiments of the present invention adopts a 3G5P structure, and its optical power is negative-negative-positive-positive-negative-positive-negative-positive. The optical power, shape, and position layout of each lens are reasonable, realizing a high-resolution day and night confocal lens system design with a focal length of approximately 7.570 mm, an imaging target surface that can match a 1 / 1.8-inch chip, a total length of less than 22.5 mm, and an aperture value of 1.28.

[0212] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A lens system, characterized in that: comprising a first lens group, a second lens group, and a third lens group arranged in sequence from the object plane to the image plane along the optical axis; The first lens group includes a first lens and a second lens arranged in sequence from the object plane to the image plane along the optical axis, the first lens is a negative power lens, and the second lens is a negative power lens; The second lens group includes a third lens, a fourth lens, a fifth lens, and a sixth lens arranged in sequence along the optical axis from the object plane to the image plane, wherein the third lens has a positive optical power, the fourth lens has a positive optical power, the fifth lens has a negative optical power, and the sixth lens has a positive optical power; The third lens group includes a seventh lens and an eighth lens arranged in sequence from the object plane to the image plane along the optical axis, the seventh lens has a negative optical power, and the eighth lens has a positive optical power; The focal power of the first lens group is φ A , the optical power of the second lens group is φ B , the focal length of the third lens group is φ C , the focal power of the lens system is φ; Among them, -1.050≤φ A / φ≤-0.885;1.185≤φ B / φ≤1.315;0.065≤φ C / φ≤0.

225.

2. The lens system according to claim 1, wherein: The optical power of the first lens is φ1, the optical power of the second lens is φ2, the optical power of the third lens is φ3, the optical power of the fourth lens is φ4, the combined optical power of the fifth lens and the sixth lens is φ56, the optical power of the seventh lens is φ7, and the optical power of the eighth lens is φ8; Among them, -0.515≤φ1 / φ≤-0.405, -0.505≤φ2 / φ≤-0.415, 0.655≤φ3 / φ≤0.785, 0.485≤φ4 / φ≤0.585, 0.095≤φ56 / φ≤0.450, -0.750≤φ7 / φ≤-0.465, 0.585≤φ8 / φ≤0.

685.

3. The lens system according to claim 1, wherein: The maximum effective diameter of the first lens is D1, the aperture of the lens system is Fno, and the maximum image circle radius of the lens system is Ymax; Among them, 1.150≤D1 / (Fno*Ymax)≤1.

450.

4. The lens system according to claim 1, wherein: The first lens includes a first object-side surface close to the object plane and a first image-side surface close to the image plane, the first object-side surface is convex, and the first image-side surface is concave; The second lens includes a second object-side surface close to the object plane and a second image-side surface close to the image plane, the second object-side surface is concave, and the second image-side surface is convex; The third lens comprises a third object-side surface close to the object plane and a third image-side surface close to the image plane, the third object-side surface is a convex surface, and the third image-side surface is a convex surface; The fourth lens comprises a fourth object-side surface close to the object plane, and the fourth object-side surface is a convex surface; The fifth lens comprises a fifth object-side surface close to the object plane and a fifth image-side surface close to the image plane, the fifth object-side surface is convex, and the fifth image-side surface is concave; The sixth lens comprises a sixth object-side surface close to the object plane and a sixth image-side surface close to the image plane, the sixth object-side surface is a convex surface, and the sixth image-side surface is a convex surface; The seventh lens element includes a seventh object-side surface close to the object plane and a seventh image-side surface close to the image plane, the seventh object-side surface is concave, and the seventh image-side surface is convex; The eighth lens includes an eighth object-side surface close to the object plane and an eighth image-side surface close to the image plane, and both the eighth object-side surface and the eighth image-side surface include reverse curved surfaces.

5. The lens system according to claim 4, wherein: The full-aperture sagitta of the side of the eighth object is Sag8 A , the semi-caliber height is Sag8 B The full-aperture sagittal height of the eighth image side is Sag8 C , the semi-caliber height is Sag8 D ; Among them, 0.555≤Sag8 B / Sag8 A ≤1.458;-4.515≤Sag8 C / Sag8 D ≤3.

255.

6. The lens system according to claim 4, wherein: The fifth lens and the sixth lens are cemented together.

7. The lens system according to claim 1, wherein: The air gap between the sixth lens and the seventh lens has a length of d67, the thickness of the seventh lens is d7, and the thickness of the eighth lens is d8; Among them, 0.285≤d67 / (d7+d8)≤0.

615.

8. The lens system according to claim 1, wherein: The Abbe number of the fourth lens is VD4, the refractive index of the fifth lens is ND5, and the Abbe number of the sixth lens is VD6; Among them, 65.520≤VD4≤98.165; 1.685≤ND5≤2.015; 65.520≤VD6≤98.

165.

9. The lens system according to claim 1, wherein: The first lens, the second lens, the third lens, the seventh lens, and the eighth lens are all plastic aspherical lenses, and the fourth lens, the fifth lens, and the sixth lens are all glass spherical lenses.

10. The lens system according to claim 1, wherein: The lens system further includes an aperture, which is arranged in the optical path between the second lens and the third lens.

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