An industrial lens

Abstract

The application discloses an industrial lens, which comprises a first lens group, a second lens group and a third lens group; the positions of the first lens group and the third lens group are fixed, and the position of the second lens group is floating; the first lens group comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens; the second lens group comprises a ninth lens; and the third lens group comprises a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, a fourteenth lens and a fifteenth lens. The second lens group is moved along an optical axis to realize focusing at different object distances; the first lens group and the third lens group are fixed and immovable, so that the influence of focusing at different object distances on resolution is reduced, and the image quality at each working distance is balanced. Furthermore, the number of lenses contained in each lens group is reasonably arranged, which is beneficial to the high-image-quality industrial lens.

Description

Technical Field

[0001] This invention relates to the field of optical device technology, and more particularly to an industrial lens. Background Technology

[0002] Short-throw industrial lenses have important applications in precision measurement and inspection, with their high resolution and low distortion enabling precise capture of changes in minute objects. In manufacturing, they are widely used in automated assembly and quality inspection processes to ensure consistent product quality. In security monitoring, they can be used for close-range monitoring and identification, helping to improve the accuracy and reliability of surveillance. In medical equipment, they are frequently used in microscopes, endoscopes, and other devices, aiding in accurate diagnosis. Even in emerging application areas, such as virtual reality and augmented reality technologies, they provide a wider field of view and a more realistic experience.

[0003] As the market demands increasingly higher quality industrial lenses for short focal lengths, industrial lenses that achieve high image quality have become a research hotspot. Summary of the Invention

[0004] This invention provides an industrial lens that achieves high image quality imaging performance.

[0005] This invention provides an industrial lens, comprising a first lens group, a second lens group, and a third lens group arranged sequentially along the optical axis from the object plane to the image plane; the positions of the first lens group and the third lens group are fixed, while the position of the second lens group can float along the optical axis;

[0006] The first lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens; the second lens group includes a ninth lens; and the third lens group includes a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, a fourteenth lens, and a fifteenth lens.

[0007] Optionally, the industrial lens has an optical length of TTL, a focal length of EFL, a maximum effective aperture of DM, an image size of IM, an aperture number of FNO, and a field of view of FOV.

[0008] Wherein, 17.5200≤TTL / EFL≤17.6500, 2.0400≤TTL / DM≤2.0600,

[0009] 3.0500≤IM / FNO≤3.0700, FOV≥96.3700.

[0010] Optionally, the first lens has a negative optical power; the second lens has a negative optical power; the third lens has a negative optical power; the fourth lens has a positive optical power; the fifth and sixth lenses are cemented together to form a first cemented lens, the first cemented lens having a negative optical power; the seventh and eighth lenses are cemented together to form a second cemented lens, the second cemented lens having a positive optical power; the ninth lens has a positive optical power; the tenth and eleventh lenses are cemented together to form a third cemented lens, the third cemented lens having a positive optical power; the twelfth, thirteenth, and fourteenth lenses are cemented together to form a fourth cemented lens, the fourth cemented lens having a negative optical power; and the fifteenth lens has a positive optical power.

[0011] Optionally, the fifth lens has an optical power of Φ5 and a refractive index of ND5; the sixth lens has an optical power of Φ6 and a refractive index of ND6.

[0012] Among them, -1.7900≤Φ5 / Φ6≤-1.1300, 1.2700≤ND6 / ND5≤1.3600.

[0013] Optionally, the Abbe number of the seventh lens is VD7, the Abbe number of the eighth lens is VD8, the Abbe number of the thirteenth lens is VD13, and the Abbe number of the fourteenth lens is VD14.

[0014] Among them, 1.9100≤|VD7 / VD8|≤2.9500, 4.6800≤VD13 / VD14≤5.3000.

[0015] Optionally, the industrial lens has an optical length of TTL, a focal length of EFL, a maximum effective aperture of DM, an image size of IM, a working F-number of FNO, and a field of view of FOV.

[0016] Wherein, 17.5200≤TTL / EFL≤17.6500, 2.0400≤TTL / DM≤2.0600,

[0017] 3.0500≤IM / FNO≤3.0700, FOV≥96.3700°.

[0018] Optionally, the refractive index Nd1 of the first lens satisfies Nd1≥1.9300.

[0019] Optionally, the industrial lens further includes an aperture stop, which is disposed in the optical path between the eleventh lens and the twelfth lens;

[0020] The optical power of the lens group formed by the ninth lens, the tenth lens and the eleventh lens is ΦZ1, the optical power of the lens group formed by the twelfth lens, the thirteenth lens and the fourteenth lens is ΦZ2, and the maximum optical distortion of the industrial lens is DISG.MAX;

[0021] Wherein, -0.9600≤ΦZ1 / ΦZ2≤-0.7500; 0≤|DISG.MAX|≤0.500%.

[0022] Optionally, the shape factor of the fourth lens is ξ4, and the minimum relative illumination of the industrial lens across the entire field of view is RI.MIN;

[0023] Among them, 6.0400≤|ξ4|≤12.1400; 84.2000%≤RI.MIN.

[0024] Optionally, the first lens includes a first object-side surface near the object surface and a first image-side surface near the image surface, wherein the first object-side surface is convex and the first image-side surface is concave.

[0025] The second lens includes a second object-side surface near the object plane and a second image-side surface near the image plane, wherein the second object-side surface is convex and the second image-side surface is concave.

[0026] The third lens includes a third object-side surface near the object plane and a third image-side surface near the image plane. The third object-side surface is concave, and the third image-side surface is concave.

[0027] The fourth lens includes a fourth object-side surface near the object plane and a fourth image-side surface near the image plane. The fourth object-side surface is concave, and the fourth image-side surface is convex.

[0028] The fifth lens includes a fifth object-side surface near the object plane and a fifth image-side surface near the image plane. The fifth object-side surface is concave, and the fifth image-side surface is convex.

[0029] The sixth lens 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 concave, and the sixth image-side surface is convex.

[0030] The seventh lens 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 or convex, and the seventh image-side surface is concave or convex.

[0031] The eighth lens includes an eighth object-side surface near the object plane and an eighth image-side surface near the image plane. The eighth object-side surface is either convex or concave, and the eighth image-side surface is convex.

[0032] The ninth lens includes a ninth object-side surface near the object plane and a ninth image-side surface near the image plane. The ninth object-side surface is convex, and the ninth image-side surface is either concave or convex.

[0033] The tenth lens includes a tenth object-side surface near the object plane and a tenth image-side surface near the image plane. The tenth object-side surface is convex, and the tenth image-side surface is concave.

[0034] The eleventh lens includes an eleventh object-side surface near the object plane and an eleventh image-side surface near the image plane. The eleventh object-side surface is convex, and the eleventh image-side surface is either concave or convex.

[0035] The twelfth lens includes a twelfth object-side surface near the object plane and a twelfth image-side surface near the image plane. The twelfth object-side surface is convex, and the twelfth image-side surface is concave.

[0036] The thirteenth lens includes a thirteenth object-side surface near the object plane and a thirteenth image-side surface near the image plane. The thirteenth object-side surface is convex, and the thirteenth image-side surface is convex.

[0037] The fourteenth lens includes a fourteenth object-side surface near the object plane and a fourteenth image-side surface near the image plane. The fourteenth object-side surface is concave, and the fourteenth image-side surface is either concave or convex.

[0038] The fifteenth lens includes a fifteenth object-side surface near the object plane and a fifteenth image-side surface near the image plane. The fifteenth object-side surface and the fifteenth image-side surface are both convex.

[0039] Optionally, the first lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens, the twelfth lens, the thirteenth lens, and the fourteenth lens are all glass spherical lenses;

[0040] Both the second lens and the fifteenth lens are glass aspherical lenses.

[0041] The industrial lens provided in this embodiment of the invention features a second lens group that can float along the optical axis, ensuring focusing at different working distances and achieving clear imaging at different object distances. Furthermore, the second lens group includes only a ninth lens, meaning only one lens performs floating focusing; fewer floating lenses result in higher lens stability. Additionally, the first and third lens groups remain fixed, thus reducing the impact of different object distances on resolution and ensuring balanced image quality at various working distances, achieving a high-quality imaging performance industrial lens.

[0042] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the structure of an industrial lens at the optimal object distance provided in Embodiment 1 of the present invention;

[0045] Figure 2 This is a schematic diagram of a Ray Fan for an industrial lens at the optimal object distance, provided in Embodiment 1 of the present invention;

[0046] Figure 3 This is a schematic diagram of the field curvature distortion curve of an industrial lens at the optimal object distance, provided in Embodiment 1 of the present invention.

[0047] Figure 4 This is a schematic diagram of the MTF curve of an industrial lens at the optimal object distance, provided in Embodiment 1 of the present invention.

[0048] Figure 5 This is a schematic diagram of axial chromatic aberration of an industrial lens at the optimal object distance, provided in Embodiment 1 of the present invention.

[0049] Figure 6 This is a schematic diagram of the vertical chromatic aberration of an industrial lens at the optimal object distance, provided in Embodiment 1 of the present invention.

[0050] Figure 7 This is a schematic diagram of the structure of an industrial lens at the optimal object distance according to Embodiment 2 of the present invention;

[0051] Figure 8This is a schematic diagram of a Ray Fan for an industrial lens at the optimal object distance, provided in Embodiment 2 of the present invention;

[0052] Figure 9 This is a schematic diagram of the field curvature distortion curve of an industrial lens at the optimal object distance, provided in Embodiment 2 of the present invention.

[0053] Figure 10 This is a schematic diagram of the MTF curve of an industrial lens at the optimal object distance, provided in Embodiment 2 of the present invention.

[0054] Figure 11 This is a schematic diagram of axial chromatic aberration of an industrial lens at the optimal object distance, provided in Embodiment 2 of the present invention.

[0055] Figure 12 This is a schematic diagram of the vertical chromatic aberration of an industrial lens at the optimal object distance, provided in Embodiment 2 of the present invention.

[0056] Figure 13 This is a schematic diagram of the structure of an industrial lens at the optimal object distance provided in Embodiment 3 of the present invention;

[0057] Figure 14 This is a schematic diagram of a Ray Fan for an industrial lens at the optimal object distance, provided in Embodiment 3 of the present invention;

[0058] Figure 15 This is a schematic diagram of the field curvature distortion curve of an industrial lens at the optimal object distance, provided in Embodiment 3 of the present invention.

[0059] Figure 16 This is a schematic diagram of the MTF curve of an industrial lens at the optimal object distance, provided in Embodiment 3 of the present invention;

[0060] Figure 17 This is a schematic diagram of axial chromatic aberration of an industrial lens at the optimal object distance, provided in Embodiment 3 of the present invention.

[0061] Figure 18 This is a schematic diagram of the vertical chromatic aberration of an industrial lens at the optimal object distance, provided in Embodiment 3 of the present invention. Detailed Implementation

[0062] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0063] Example 1

[0064] Figure 1 This is a schematic diagram of the structure of an industrial lens at the optimal object distance according to Embodiment 1 of the present invention, as shown below. Figure 1 As shown, the industrial lens provided in this embodiment of the invention includes a first lens group S1, a second lens group S2, and a third lens group S3 arranged sequentially along the optical axis from the object plane to the image plane; the positions of the first lens group S1 and the third lens group S3 are fixed, while the position of the second lens group S2 can float along the optical axis; the first lens group S1 includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107, and an eighth lens 108; the second lens group S2 includes a ninth lens 109; and the third lens group S3 includes a tenth lens 110, an eleventh lens 111, a twelfth lens 112, a thirteenth lens 113, a fourteenth lens 114, and a fifteenth lens 115.

[0065] Specifically, the industrial lens provided in this embodiment of the invention includes a first lens group S1, a third lens group S3, and a second lens group S2 located between the first lens group S1 and the third lens group S3 along the optical axis. The first lens group S1 and the third lens group S3 can both be understood as lenses with fixed positions, while the second lens group S2 can be understood as a lens group whose position changes. The second lens group S2 moves between the first lens group S1 and the third lens group S3. The focal length of the industrial lens is adjusted by changing the position of the second lens group S2 to ensure that the industrial lens can focus at different object distances, guaranteeing clear imaging at various object distances. Furthermore, since the positions of the first lens group S1 and the third lens group S3 remain fixed, the aberration changes caused by the movement of the second lens group S2 at different working distances are mitigated by the fixed positions of the first lens group S1 and the third lens group S3, maintaining symmetry. This ensures that the image quality is balanced at each working distance, guaranteeing image quality.

[0066] Furthermore, the first lens group S1 includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107, and an eighth lens 108; the second lens group S2 includes a ninth lens 109; and the third lens group S3 includes a tenth lens 110, an eleventh lens 111, a twelfth lens 112, a thirteenth lens 113, a fourteenth lens 114, and a fifteenth lens 115. In other words, the first lens group S1 includes eight lenses, the second lens group S2 includes one lens, and the third lens group S3 includes six lenses. This means that the industrial lens includes fourteen fixed lenses, with only one lens floating. This single floating lens enables floating focusing. The small number of floating lenses results in high stability for the industrial lens, ensuring high image quality.

[0067] In summary, the industrial lens provided by this invention features a second lens group that can float along the optical axis, ensuring focusing at different working distances and achieving clear imaging at different object distances. Furthermore, the second lens group includes only a ninth lens, meaning only one lens performs floating focusing, resulting in high lens stability due to the small number of floating lenses. Additionally, the first and third lens groups remain fixed, reducing the impact of different object distances on resolution and ensuring balanced image quality across working distances, thus achieving a high-quality industrial lens. Moreover, the arrangement of fifteen lenses ensures a reasonable number of lenses in the optical system, preventing excessive lens size or excessive aberrations caused by a single lens bearing too much power. This approach ensures both miniaturization of the optical system and low imaging aberrations, resulting in high image quality.

[0068] Based on the above embodiments, continue to refer to Figure 1 As shown, the industrial lens provided in this embodiment of the invention also includes an aperture stop 116 and a filter 117. The aperture stop 116 can adjust the propagation direction of the light beam, which is beneficial for improving image quality. Furthermore, in this industrial lens, the aperture stop 116 is located in the optical path between the eleventh lens 111 and the twelfth lens 112, meaning the aperture stop 116 is located within the optical system. This allows for a smaller aperture value, achieving a large aperture. The filter 117 is located in the optical path between the fifteenth lens 115 and the image plane, which can filter out stray light and improve imaging performance.

[0069] Furthermore, the industrial lens provided in this embodiment of the invention may also include a protective glass and an image acquisition element. The protective glass may be disposed on the image-side of the filter, and the image acquisition element may be disposed on the image-side of the protective glass. The optical system is protected by the protective glass, and images are acquired by the image acquisition element, thus enabling the optical system to perform its normal imaging function.

[0070] Based on the above embodiments, the optical power of the first lens 101 is negative; the optical power of the second lens 102 is negative; the optical power of the third lens 103 is negative; the optical power of the fourth lens 104 is positive; the fifth lens 105 and the sixth lens 106 are cemented together to form a first cemented lens, and the optical power of the first cemented lens is negative; the seventh lens 107 and the eighth lens 108 are cemented together to form a second cemented lens, and the optical power of the second cemented lens is positive; the optical power of the ninth lens 109 is positive; the tenth lens 110 and the eleventh lens 111 are cemented together to form a third cemented lens, and the optical power of the third cemented lens is positive; the twelfth lens 112, the thirteenth lens 113 and the fourteenth lens 114 are cemented together to form a fourth cemented lens, and the optical power of the fourth cemented lens is negative; the optical power of the fifteenth lens 115 is positive.

[0071] Specifically, optical power is equal to the difference between the convergence of the image-side beam and the convergence of the object-side beam; it characterizes the ability of an optical system to deflect light. The larger the absolute value of the optical power, the stronger its ability to bend light; the smaller the absolute value, the weaker its ability to bend light. When the optical power is positive, the refraction of light is converging; when the optical power is negative, the refraction of light is diverging.

[0072] In the industrial lens provided in this embodiment of the invention, the first lens 101, the second lens 102, and the third lens 103 serve as the lenses that first adjust the incident light. Their negative optical power setting ensures that the light has a larger aperture before entering the aperture stop, thus increasing the aperture of the industrial lens. A larger aperture results in a larger amount of light entering the lens, enabling clear imaging even in dim or dark conditions. In this embodiment of the invention, the aperture number (FNO) of the industrial lens can be 1.9, satisfying the large aperture setting of an industrial lens.

[0073] Furthermore, the positive optical power setting of the fourth lens 104 can promptly correct the large aberrations produced by the first lens 101, the second lens 102, and the third lens 103, especially the edge aberrations of industrial lenses, thereby improving the imaging resolution of the optical system.

[0074] Furthermore, the fifth lens 105 and the sixth lens 106 have opposite optical powers and are cemented together to form a first cemented lens with negative optical power; the seventh lens 107 and the eighth lens 108 have opposite optical powers and are cemented together to form a second cemented lens with positive optical power; the tenth lens 110 and the eleventh lens 111 are cemented together to form a third cemented lens with positive optical power; and the twelfth lens 112, the thirteenth lens 113, and the fourteenth lens 114 are cemented together to form a fourth cemented lens with negative optical power. Cemented lenses can be used to minimize or eliminate chromatic aberration. In industrial lenses, the use of cemented lenses can improve image quality and reduce light energy reflection loss, thereby improving the sharpness of the lens image. In addition, the cementation of the lenses eliminates the air gap between the two lenses, making the overall optical system compact and meeting the requirements for system miniaturization. Furthermore, the cementation of the lenses reduces tolerance sensitivity issues such as tilting / eccentricity that occur during the assembly of lens units. For example, the fifth lens 105 and the sixth lens 106 can be bonded together using a spacer or glue; the seventh lens 107 and the eighth lens 108 can be bonded together using a spacer or glue; the tenth lens 110 and the eleventh lens 111 can be bonded together using a spacer or glue; and the twelfth lens 112, the thirteenth lens 113, and the fourteenth lens 114 can be bonded together using a spacer or glue. Furthermore, the first cemented lens, the second cemented lens, the ninth lens 109, the third cemented lens, the fourth cemented lens, and the fifteenth lens 115 are arranged in a negative-positive-positive-positive-negative-positive configuration, with a combination of positive and negative optical powers, which is beneficial for aberration correction.

[0075] Based on the above embodiment, the fifth lens 105 has an optical power of Φ5 and a refractive index of ND5; the sixth lens 106 has an optical power of Φ6 and a refractive index of ND6; wherein -1.7900≤Φ5 / Φ6≤-1.1300, 1.2700≤ND6 / ND5≤1.3600. The fifth lens 105 and the sixth lens 106 are two lenses with positive and negative polarities, and the refractive indices of the two lenses differ significantly. When the above conditions are met, spherical aberration can be effectively corrected, and the imaging quality during detection can be improved.

[0076] Based on the above embodiments, the Abbe number of the seventh lens 107 is VD7, the Abbe number of the eighth lens 108 is VD8, the Abbe number of the thirteenth lens 113 is VD13, and the Abbe number of the fourteenth lens 114 is VD14; wherein, 1.9100≤|VD7 / VD8|≤2.9500, 4.6800≤VD13 / VD14≤5.3000. The seventh lens 107 and the eighth lens 108 are cemented together, and the thirteenth lens 113 and the fourteenth lens 114 are also cemented together. When the difference in the Abbe number of the lenses in the cemented lens group is large, it can effectively correct the chromatic aberration of the system, improve the imaging quality, and make the detection effect of the industrial lens clearer and more accurate.

[0077] Based on the above embodiments, the industrial lens has a total optical length of TTL, a focal length of EFL, a maximum effective aperture of DM, an image size of IM, a working F-number of FNO, and a field of view of FOV; wherein, 17.5200≤TTL / EFL≤17.6500, 2.0400≤TTL / DM≤2.0600,

[0078] 3.0500≤IM / FNO≤3.0700, FOV≥96.3700°.

[0079] Specifically, TTL represents the distance from the front end of the first lens 101 to the image plane, and DM represents the maximum effective aperture of the lens. To ensure a constant image height, a shorter overall length results in a smaller maximum effective aperture and a correspondingly smaller volume. Therefore, setting 2.0400≤TTL / DM≤2.0600 allows for a larger image height while reducing volume. Furthermore, EFL represents the overall focal length of the lens, and FOV represents the field of view. Large-aperture line-scan industrial lenses are typically bulky and require many lenses for aberration correction. Therefore, setting 17.5200≤TTL / EFL≤17.6500 and FOV≥96.3700° ensures good aberration correction and image quality even at a large field of view. Further, IM represents the image plane size, and FNO represents the working aperture number. For the same image plane size, a smaller working aperture number results in a larger aperture, allowing more light in and producing brighter and sharper images. Therefore, setting 3.0500≤IM / FNO≤3.0700 within this range ensures good brightness and clarity in the image. This invention achieves high-quality imaging on a large target surface using only 15 lenses, minimizing cost and size while keeping the total length within 90.01mm and guaranteeing clear resolution.

[0080] Based on the above embodiments, the refractive index Nd1 of the first lens 101 satisfies Nd1≥1.9300. As the foremost lens of the industrial lens, the high refractive index of the first lens 101 is beneficial for the design of short focal length lenses, making the incident light at large angles tend to flatten more quickly. While ensuring the maximum range of information collected from the object under test, it reduces the number of lenses and meets the lightweight design requirements of industrial lenses.

[0081] Based on the above embodiments, continue to refer to Figure 1 As shown, the industrial lens also includes an aperture stop 116, which is disposed in the optical path between the eleventh lens 111 and the twelfth lens 112; the optical power of the lens group formed by the ninth lens 109, the tenth lens 110 and the eleventh lens 111 is ΦZ1, and the optical power of the lens group formed by the twelfth lens 112, the thirteenth lens 113 and the fourteenth lens 114 is ΦZ2; the maximum optical distortion of the industrial lens is DISG.MAX; where -0.9600≤ΦZ1 / ΦZ2≤-0.7500; 0≤|DISG.MAX|≤0.500%.

[0082] Specifically, setting the aperture stop 116 can adjust the propagation direction of the light beam, which is beneficial to improving image quality. Furthermore, in this scanning lens, the aperture stop 116 is positioned in the optical path between the eleventh lens 111 and the twelfth lens 112, meaning the aperture stop STO is located within the optical system. This allows for a smaller aperture value, achieving a larger aperture. Further, the ninth lens 109 to the fourteenth lens 114 form a symmetrical structure centered on the aperture stop 116, with opposite optical powers and similar absolute values ​​in the two lens groups, i.e., -0.9600≤ΦZ1 / ΦZ2≤-0.7500. This effectively corrects the system's optical distortion, reduces the impact of imaging distortion, and keeps the maximum system optical distortion within ±0.5%, reducing field curvature and better reflecting the actual value of the measured object, resulting in more accurate data obtained from industrial testing.

[0083] Based on the above embodiments, the shape factor of the fourth lens 104 is ξ4, and the minimum relative illumination of the industrial lens across the entire field of view is RI.MIN; where 6.0400≤|ξ4|≤12.1400; 84.2000%≤RI.MIN.

[0084] Specifically, the shape factor, as a parameter affecting the basic optical performance of a lens, can be adjusted by changing the lens's curvature, aperture, and material. The fourth lens 104 uses a high refractive index material and has a positive optical power. Located at a position where light rays converge, it has a large shape factor, which can optimize the system's focusing ability and imaging quality. When the lens at this position meets the above conditions, it can more effectively correct aberrations and improve imaging quality and relative illumination.

[0085] Based on the above embodiments, the first lens 101 includes a first object-side surface near the object plane and a first image-side surface near the image plane, wherein 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 near the object plane and a second image-side surface near the image plane, wherein the second object-side surface is convex and the second image-side surface is concave; the third lens 103 includes a third object-side surface near the object plane and a third image-side surface near the image plane, wherein the third object-side surface and the third image-side surface are both concave; the fourth lens 104 includes a fourth object-side surface near the object plane and a fourth image-side surface near the image plane, wherein the fourth object-side surface is concave. The fourth image-side surface is convex; the fifth lens 105 includes a fifth object-side surface near the object plane and a fifth image-side surface near the image plane, the fifth object-side surface being concave and the fifth image-side surface being convex; the sixth lens 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 being concave and the sixth image-side surface being convex; the seventh lens 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 being either concave or convex, and the seventh image-side surface being either concave or convex; the eighth lens 108 includes an eighth object-side surface near the object plane and an eighth image-side surface near the image plane, the fifth object-side surface being concave or convex, and the sixth image-side surface being convex or concave; The eighth object-side surface is either convex or concave, and the eighth image-side surface is convex; the ninth lens 109 includes a ninth object-side surface near the object plane and a ninth image-side surface near the image plane, the ninth object-side surface being convex and the ninth image-side surface being either concave or convex; the tenth lens 110 includes a tenth object-side surface near the object plane and a tenth image-side surface near the image plane, the tenth object-side surface being convex and the tenth image-side surface being concave; the eleventh lens 111 includes an eleventh object-side surface near the object plane and an eleventh image-side surface near the image plane, the eleventh object-side surface being convex and the eleventh image-side surface being either concave or convex; the twelfth lens 112 includes a twelfth object-side surface near the object plane. The 12th object-side surface and the 13th image-side surface are both convex and concave. The 14th object-side surface and the 15th image-side surface are both concave and convex. The 15th object-side surface and the 16th image-side surface are both convex and concave.

[0086] Specifically, the object-side surface of a lens can be understood as the surface of the lens closest to the object plane, and the image-side surface can be understood as the surface of the lens closest to the image plane. The object-side surface of the first lens 101 is convex, and the image-side surface is concave; the object-side surface of the second lens 102 is also convex, and the image-side surface is concave. This can be understood as the object-side surfaces of both the first lens 101 and the second lens 102 convex towards the object plane near the optical axis, and the image-side surfaces of both lenses concave towards the image plane near the optical axis. In other words, both the first lens 101 and the second lens 102 are lenses with a convex-concave structure. Furthermore, both the first lens 101 and the second lens 102 can be meniscus negative lenses. The surface shape of the first lens 101, combined with its optical power parameters, and the surface shape of the second lens 102, combined with its optical power parameters, can converge light rays from a large field of view into the system as much as possible, which is beneficial for improving the field of view of the optical system. The object-side surface of the third lens 103 is concave, and the image-side surface is also concave. This can be understood as the object-side surface of the third lens 103 being concave towards the object plane near the optical axis, and the image-side surface being concave towards the image plane near the optical axis. In other words, the third lens 103 is a double-concave lens. The object-side surfaces of the fourth lens 104, fifth lens 105, and sixth lens 106 are all concave, and the image-side surfaces are all convex. This can be understood as the object-side surfaces of the fourth lens 104, fifth lens 105, and sixth lens 106 being concave towards the object plane near the optical axis, and the image-side surfaces being convex towards the image plane near the optical axis. In other words, the fourth lens 104, fifth lens 105, and sixth lens 106 are all concave-convex lenses. The object-side surface of the seventh lens 107 is concave or convex, and the image-side surface is also concave or convex. This can be understood as the object-side surface of the seventh lens 107 being concave or convex towards the object surface near the optical axis, and the image-side surface being concave or convex towards the image surface near the optical axis. In other words, the seventh lens 107 can be a biconvex lens, a concave-convex lens, or a convex-concave lens. Example 1 uses a biconvex lens as an example. The object-side surface of the eighth lens 108 is concave or convex, and the image-side surface is convex. This can be understood as the object-side surface of the eighth lens 108 being concave or convex towards the object surface near the optical axis, and the image-side surface being convex towards the image surface near the optical axis. In other words, the eighth lens 108 can be a concave-convex or biconvex lens. Example 1 uses a concave-convex lens as an example. The object-side surface of the ninth lens 109 is convex, and the image-side surface is either concave or convex. This can be understood as the object-side surface of the ninth lens 109 convex towards the object plane near the optical axis, while the image-side surface is concave or convex towards the image plane near the optical axis. In other words, the ninth lens 109 can be a lens with a convex-concave or biconvex structure. Example 1 uses a lens with a biconvex structure as an example for illustration.The tenth lens 110 has a convex object-side surface and a concave image-side surface. This can be understood as the object-side surface of the tenth lens convex towards the object plane near the optical axis, while the image-side surfaces are all concave towards the image plane near the optical axis. Therefore, the tenth lens 110 is a lens with a convex-concave structure. The eleventh lens 111 has a convex object-side surface and either a concave or convex image-side surface. This can be understood as the object-side surface of the eleventh lens convex towards the object plane near the optical axis, while the image-side surfaces are all concave or convex towards the image plane near the optical axis. Therefore, the eleventh lens 111 can be a lens with a convex-concave or biconvex structure. Example 1 uses a lens with a convex-concave structure as an example. The twelfth lens 112 has a convex object-side surface and a concave image-side surface. This can be understood as the object-side surface of the twelfth lens convex towards the object plane near the optical axis, while the image-side surfaces are all concave towards the image plane near the optical axis. Therefore, the twelfth lens 112 is a lens with a convex-concave structure. The thirteenth lens 113 has a convex object-side surface and three convex image-side surfaces. This can be understood as the thirteenth lens having an object-side surface that convexes towards the object plane near the optical axis, and image-side surfaces that convex towards the image plane near the optical axis. Therefore, the thirteenth lens 113 is a biconvex lens. The fourteenth lens 114 has a concave object-side surface and either a concave or convex image-side surface. This can be understood as the fourteenth lens having an object-side surface that is concave towards the object plane near the optical axis, and image-side surfaces that are either concave or convex towards the image plane near the optical axis. Therefore, the fourteenth lens 114 is a biconcave or concave-convex lens. Example 1 uses a biconcave fourteenth lens as an example. The fifteenth lens 115 has a convex object-side surface and a convex image-side surface. This can be understood as the fifteenth lens having an object-side surface that convex towards the object plane near the optical axis, and image-side surfaces that convex towards the image plane near the optical axis. Therefore, the fifteenth lens 115 is a biconvex lens. By rationally setting the concave and convex surfaces of each lens, cemented lenses can achieve cemented settings of at least two adjacent lenses. On the other hand, it can also reduce the spacing between adjacent lenses, which is beneficial for achieving small-volume industrial lens designs.

[0087] Based on the above embodiments, the first lens 101, the third lens 103, the fourth lens 104, the fifth lens 105, the sixth lens 106, the seventh lens 107, the eighth lens 108, the ninth lens 109, the tenth lens 110, the eleventh lens 111, the twelfth lens 112, the thirteenth lens 113, and the fourteenth lens 114 are all glass spherical lenses; the second lens 102 and the fifteenth lens 115 are both glass aspherical lenses.

[0088] Specifically, by setting the second lens 102 and the fifteenth lens 115 to be aspherical lenses, off-axis aberrations, including field curvature, coma, and astigmatism, can be corrected. The first lens 101, third lens 103, fourth lens 104, fifth lens 105, sixth lens 106, seventh lens 107, eighth lens 108, ninth lens 109, tenth lens 110, eleventh lens 111, twelfth lens 112, thirteenth lens 113, and fourteenth lens 14 are all glass spherical lenses. Using an optical structure of 13 glass spherical lenses and 2 glass aspherical lenses better corrects chromatic aberration and other aberrations, improves image quality, and reduces processing costs, achieving a higher cost-performance ratio. The materials of the glass spherical lenses and glass aspherical lenses are various types of glass known to those skilled in the art; this embodiment of the invention does not elaborate on or limit their use.

[0089] As a feasible implementation method, the parameters of each lens in the industrial lens will be explained next.

[0090] Table 1. Optical design values ​​for an industrial lens in Example 1.

[0091] Scope of protection Example 1 lower limit upper limit TTL / EFL 17.6451 17.5200 17.6500 TTL / DM 2.0454 2.0400 2.0600 IM / FNO 3.0617 3.0500 3.0700 EFL 5.1006 5.1000 5.1400 TTL 90.0000 89.9900 90.0100 FOV 96.8057 96.3700 96.8100 ND1 1.9722 1.9300 2.0800 |VD7 / VD8| 2.9412 1.9100 2.9500 VD13 / VD14 5.2947 4.6800 5.3000 ND6 / ND5 1.2906 1.2700 1.3600 Φ5 / Φ6 -1.1534 -1.7900 -1.1300 ΦZ1 / ΦZ2 -0.9523 -0.9600 -0.7500 |DISG.MAX| 0.4927％ 0.4900％ 0.5000％ |ξ4| 6.1367 6.0400 12.1400 RI.MIN 84.2088％ 84.2000％ 86.1000％ Φ1 -0.0156 -0.0220 -0.0150 Φ2 -0.0438 -0.0440 -0.0400 Φ3 -0.0457 -0.0540 -0.0300 Φ4 0.0108 0.0090 0.0180 Φ5-6 -0.0013 -0.0110 -0.0010 Φ7-8 0.0114 0.0110 0.0230 Φ9 0.0293 0.0160 0.0300 Φ10-11 0.0097 0.0090 0.0270 Φ12-14 -0.0402 -0.0530 -0.0400 Φ15 0.1060 0.1010 0.1070

[0092] Table 2 Design values ​​of optical physical parameters for industrial lenses

[0093]

[0094]

[0095] The surface numbers in Table 2 are assigned according to the surface sequence of each lens. "OBJ" represents the object surface, "2" represents the object-side surface of the first lens, "3" represents the image-side surface of the first lens, and so on. The radius of curvature represents the degree of curvature of the corresponding lens surface; a positive value indicates that the surface bends towards the image surface, and a negative value indicates that the surface bends towards the object surface. "Infinite" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance between the current surface and the next surface. The refractive index represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air, and the refractive index is 1. The Abbe number represents the dispersion characteristics of the material between the current surface and the next surface. Half-aperture indicates half the aperture size of the current surface. When the spacing between the 15th surface is 0.138 mm and the spacing between the 18th surface is -0.138 mm, it is possible to focus to an object distance of infinity. When the spacing between the 15th surface is 4.793 mm and the spacing between the 18th surface is -4.793 mm, it is possible to focus to an object distance of 50 mm.

[0096] Table 3. Design values ​​for the aspherical coefficient of industrial lenses.

[0097]

[0098] The K value in Table 2 represents the magnitude of the conic coefficient of the aspherical surface.

[0099] 1.406197E-04 represents 1.406197 * 10 -4 All other parameters can be represented in this way.

[0100] Furthermore, the aspherical conic coefficients can be defined using the following aspherical formula, but are not limited to the following representations:

[0101]

[0102] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the conic coefficient; and AE are the coefficients of the 4th, 6th, 8th, 10th, and 12th order terms of the aspherical polynomial.

[0103] Figure 2 This is a Ray Fan diagram of an industrial lens at optimal object distance, provided in Embodiment 1 of the present invention. The Ray Fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis represents the beam aperture, and the vertical axis represents the transverse aberration. The ideal curve is a straight line coinciding with the horizontal axis, indicating that all rays converge at the same point on the image plane. The interval corresponding to the vertical axis of the curve is the maximum dispersion range of the beam on the ideal image plane. The Ray Fan diagram can reflect not only monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 2 It can be seen that the system closely approximates the horizontal axis at each wavelength in each field of view, indicating that the transverse aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the optical system can achieve the high-resolution imaging requirements.

[0104] Figure 3 This is a schematic diagram of the field curvature distortion curve of an industrial lens at the optimal object distance, provided in Embodiment 1 of the present invention. In the coordinate system on the left side of the figure, the horizontal axis represents the magnitude of the field curvature in mm; the vertical axis represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; Figure 3 As can be seen, the lens provided in this embodiment effectively controls field curvature, meaning that during imaging, the difference in image quality between the center and the periphery is small, resulting in good consistency. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit. Figure 3 As can be seen, the distortion of the lens provided in this embodiment has been well corrected, with optical distortion less than ±0.5%.

[0105] Figure 4This is a schematic diagram of the MTF curve of an industrial lens at the optimal object distance according to Embodiment 1 of the present invention. The horizontal axis represents spatial frequency, which refers to the number of black and white line pairs per 1mm. The vertical axis represents the modulation modulus (M' / M), where M refers to the grating modulation degree before imaging, and M' refers to the grating modulation degree after imaging. Therefore, 0 ≤ M' / M ≤ 1. The MTF curve represents the resolving power of the optical system for objects at different frequencies in different fields of view, meridional, and sagittal directions. It reflects the degree of image quality after the object passes through the optical system. The higher the MTF, the higher the image quality of the lens. Figure 4 It can be seen that the image quality of the lens of the present invention is higher than 0.3MTF for 200pl / mm from the center field of view to the edge field of view, and the imaging has excellent resolution.

[0106] Figure 5 This is a schematic diagram of the axial chromatic aberration of an industrial lens at the optimal object distance, provided in Embodiment 1 of the present invention. The vertical direction represents the normalized 0-field pupil plane, where 0 represents the pupil center, and the vertical vertex represents the pupil vertex. The horizontal direction represents the axial chromatic aberration at different wavelengths (specifically 460nm, 530nm, and 620nm), in millimeters (mm). As shown in the figure, the axial chromatic aberration of the entire pupil of the lens of the present invention is less than 19μm, resulting in excellent image sharpness.

[0107] Figure 6 This is a schematic diagram of the transverse chromatic aberration of an industrial lens at the optimal object distance, provided in Embodiment 1 of the present invention. In the diagram, the vertical direction represents the field of view angle, 0 represents the field of view angle incident parallel to the optical axis, and the vertex of the vertical direction represents the maximum half-field of view angle. As shown in the figure, at each wavelength (specifically 460nm, 530nm, and 620nm), the transverse chromatic aberration from the center field of view to the edge field of view of the lens is less than 1.1μm, resulting in higher imaging quality.

[0108] In summary, the industrial lens provided in this embodiment of the invention adopts an all-glass 15G structure. Through the combination of lens materials and the reasonable allocation of the optical power of each element, and using an intermediate group focusing method, it achieves focusing from 50mm to infinity. At the optimal object distance, it can achieve a high-resolution industrial lens design with low distortion and a large target area. The system focal length is 5mm, the maximum aperture is F1.9, the optimal object distance is 150mm, the maximum optical distortion is <0.5%, and the image quality can reach 200pl / mm >0.3MTF.

[0109] Example 2

[0110] Figure 7 This is a schematic diagram of the structure of an industrial lens at the optimal object distance according to Embodiment 2 of the present invention, as shown below. Figure 7As shown, the industrial lens provided in Embodiment 2 of the present invention includes a first lens group S1, a second lens group S2, and a third lens group S3 arranged sequentially from the object plane to the image plane along the optical axis; the positions of the first lens group S1 and the third lens group S3 are fixed, while the position of the second lens group S2 can float along the optical axis; the first lens group S1 includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107, and an eighth lens 108; the second lens group S2 includes a ninth lens 109; the third lens group S3 includes a tenth lens 110, an eleventh lens 111, a twelfth lens 112, a thirteenth lens 113, a fourteenth lens 114, and a fifteenth lens 115.

[0111] The difference between Embodiment 2 and Embodiment 1 is that the object-side surface of the seventh lens is concave, the image-side surface of the eleventh lens is convex, and the image-side surface of the fourteenth lens is convex.

[0112] Other parameters are the same as in Example 1, and will not be repeated here.

[0113] As another feasible implementation method, the specific parameters in industrial lenses are explained below.

[0114] Table 4. Optical design values ​​for a fixed-focus lens in Example 2.

[0115] Scope of protection Example 2 lower limit upper limit TTL / EFL 17.6022 17.5200 17.6500 TTL / DM 2.0515 2.0400 2.0600 IM / FNO 3.0581 3.0500 3.0700 EFL 5.1127 5.1000 5.1400 TTL 89.9950 89.9900 90.0100 FOV 96.6232 96.3700 96.8100 ND1 1.9393 1.9300 2.0800 |VD7 / VD8| 1.9596 1.9100 2.9500 VD13 / VD14 5.2943 4.6800 5.3000 ND6 / ND5 1.3571 1.2700 1.3600 Φ5 / Φ6 -1.3107 -1.7900 -1.1300 ΦZ1 / ΦZ2 -0.8269 -0.9600 -0.7500 |DISG.MAX| 0.4947％ 0.4900％ 0.5000％ |ξ4| 12.1330 6.0400 12.1400 RI.MIN 84.5525％ 84.2000％ 86.1000％ Φ1 -0.0213 -0.0220 -0.0150 Φ2 -0.0403 -0.0440 -0.0400 Φ3 -0.0304 -0.0540 -0.0300 Φ4 0.0100 0.0090 0.0180 Φ5-6 -0.0052 -0.0110 -0.0010 Φ7-8 0.0116 0.0110 0.0230 Φ9 0.0242 0.0160 0.0300 Φ10-11 0.0216 0.0090 0.0270 Φ12-14 -0.0522 -0.0530 -0.0400 Φ15 0.1018 0.1010 0.1070

[0116] Table 5 Design values ​​of optical physical parameters for industrial lenses

[0117]

[0118]

[0119] The surface numbers in Table 5 are assigned according to the surface sequence of each lens. "OBJ" represents the object surface, "2" represents the object-side surface of the first lens, "3" represents the image-side surface of the first lens, and so on. The radius of curvature represents the degree of curvature of the corresponding lens surface; a positive value indicates that the surface bends towards the image surface, and a negative value indicates that the surface bends towards the object surface. "Infinite" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance between the current surface and the next surface. The refractive index represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air, and the refractive index is 1. The Abbe number represents the dispersion characteristics of the material between the current surface and the next surface. Half-aperture indicates half the aperture size of the current surface. When the spacing between the 15th surface is 0.148 mm and the spacing between the 18th surface is -0.148 mm, it is possible to focus to an object distance of infinity. When the spacing between the 15th surface is 5.617 mm and the spacing between the 18th surface is -5.617 mm, it is possible to focus to an object distance of 50 mm.

[0120] Table 6. Design values ​​for the aspherical coefficient of industrial lenses.

[0121]

[0122] The K value in Table 6 represents the magnitude of the conic coefficient of the aspherical surface.

[0123] 1.543630E-04 means 1.543630 * 10 -4 All other parameters can be represented in this way.

[0124] Furthermore, the aspherical conic coefficients can be defined using the following aspherical formula, but are not limited to the following representations:

[0125]

[0126] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the conic coefficient; and AE are the coefficients of the 4th, 6th, 8th, 10th, and 12th order terms of the aspherical polynomial.

[0127] Figure 8 This is a Ray Fan diagram of an industrial lens at the optimal object distance, provided in Embodiment 2 of the present invention. The Ray Fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis represents the beam aperture, and the vertical axis represents the transverse aberration. The ideal curve is a straight line coinciding with the horizontal axis, indicating that all light rays converge at the same point on the image plane. The interval corresponding to the vertical axis of the curve is the maximum dispersion range of the beam on the ideal image plane. The Ray Fan diagram can reflect not only monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 8 It can be seen that the system closely approximates the horizontal axis at each wavelength in each field of view, indicating that the transverse aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the optical system can achieve the high-resolution imaging requirements.

[0128] Figure 9 This is a schematic diagram of the field curvature distortion curve of an industrial lens at the optimal object distance, provided in Embodiment 2 of the present invention. In the coordinate system on the left side of the figure, the horizontal axis represents the magnitude of the field curvature, in mm; the vertical axis represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; Figure 9 As can be seen, the lens provided in this embodiment effectively controls field curvature, meaning that during imaging, the difference in image quality between the center and the periphery is small, resulting in good consistency. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit. Figure 9As can be seen, the distortion of the lens provided in this embodiment has been well corrected, with optical distortion less than ±0.5%.

[0129] Figure 10 This is a schematic diagram of the MTF curve of an industrial lens at the optimal object distance, provided in Embodiment 2 of the present invention. The horizontal axis represents spatial frequency, which refers to the number of black and white line pairs per 1mm. The vertical axis represents the modulation modulus (M' / M), where M refers to the grating modulation degree before imaging, and M' refers to the grating modulation degree after imaging. Therefore, 0 ≤ M' / M ≤ 1. The MTF curve represents the resolving power of the optical system for objects at different frequencies in different fields of view, meridional, and sagittal directions. It reflects the degree of image quality after the object passes through the optical system. The higher the MTF, the higher the image quality of the lens. Figure 10 It can be seen that the image quality of the lens of the present invention is higher than 0.38MTF for 200pl / mm from the center field of view to the edge field of view, and the imaging has excellent resolution.

[0130] Figure 11 This is a schematic diagram of the axial chromatic aberration of an industrial lens at the optimal object distance, provided in Embodiment 2 of the present invention. The vertical direction represents the normalized 0-field pupil plane, where 0 represents the pupil center, and the vertical vertex represents the pupil vertex. The horizontal direction represents the axial chromatic aberration at different wavelengths (specifically 460nm, 530nm, and 620nm), in millimeters (mm). As shown in the figure, the axial chromatic aberration of the entire pupil of the lens of the present invention is less than 9μm, resulting in excellent image sharpness.

[0131] Figure 12 This is a schematic diagram of the transverse chromatic aberration of an industrial lens at the optimal object distance, provided in Embodiment 2 of the present invention. In the diagram, the vertical direction represents the field of view angle, 0 represents the field of view angle incident parallel to the optical axis, and the vertex of the vertical direction represents the maximum half-field of view angle. As shown in the figure, at each wavelength (specifically 460nm, 530nm, and 620nm), the transverse chromatic aberration from the center field of view to the edge field of view of the lens is less than 0.9μm, resulting in higher imaging quality.

[0132] In summary, the industrial lens provided in this embodiment of the invention adopts an all-glass 15G structure. Through the combination of lens materials and the reasonable allocation of the optical power of each element, and using an intermediate group focusing method, it achieves focusing from 50mm to infinity. At the optimal object distance, it can achieve a high-resolution industrial lens design with low distortion and a large target area. The system focal length is 5mm, the maximum aperture is F1.9, the optimal object distance is 150mm, the maximum optical distortion is <0.5%, and the image quality can reach 200pl / mm > 0.38MTF.

[0133] Example 3

[0134] Figure 13This is a schematic diagram of the structure of an industrial lens at the optimal object distance according to Embodiment 3 of the present invention, as shown below. Figure 13 As shown, the industrial lens provided in Embodiment 3 of the present invention includes a first lens group S1, a second lens group S2, and a third lens group S3 arranged sequentially from the object plane to the image plane along the optical axis; the positions of the first lens group S1 and the third lens group S3 are fixed, while the position of the second lens group S2 can float along the optical axis; the first lens group S1 includes a first lens 101, a second lens 102, a third lens 103, a fourth lens 104, a fifth lens 105, a sixth lens 106, a seventh lens 107, and an eighth lens 108; the second lens group S2 includes a ninth lens 109; and the third lens group S3 includes a tenth lens 110, an eleventh lens 111, a twelfth lens 112, a thirteenth lens 113, a fourteenth lens 114, and a fifteenth lens 115.

[0135] The difference between Embodiment 3 and Embodiment 1 is that the image-side surface of the seventh lens is concave, the object-side surface of the eighth lens is convex, the image-side surface of the ninth lens is concave, and the image-side surface of the eleventh lens is convex.

[0136] Other parameters are the same as in Example 1, and will not be repeated here.

[0137] As another feasible implementation method, the specific parameters in industrial lenses are explained below.

[0138] Table 7. Optical design values ​​for a fixed-focus lens in Example 3.

[0139] Scope of protection Example 3 lower limit upper limit TTL / EFL 17.5290 17.5200 17.6500 TTL / DM 2.0427 2.0400 2.0600 IM / FNO 3.0673 3.0500 3.0700 EFL 5.1343 5.1000 5.1400 TTL 89.9990 89.9900 90.0100 FOV 96.3739 96.3700 96.8100 ND1 2.0734 1.9300 2.0800 |VD7 / VD8| 1.9190 1.9100 2.9500 VD13 / VD14 4.6815 4.6800 5.3000 ND6 / ND5 1.2722 1.2700 1.3600 Φ5 / Φ6 -1.7859 -1.7900 -1.1300 ΦZ1 / ΦZ2 -0.7583 -0.9600 -0.7500 |DISG.MAX| 0.4926％ 0.4900％ 0.5000％ |ξ4| 6.0441 6.0400 12.1400 RI.MIN 86.0924％ 84.2000％ 86.1000％ Φ1 -0.0175 -0.0220 -0.0150 Φ2 -0.0405 -0.0440 -0.0400 Φ3 -0.0530 -0.0540 -0.0300 Φ4 0.0174 0.0090 0.0180 Φ5-6 -0.0101 -0.0110 -0.0010 Φ7-8 0.0221 0.0110 0.0230 Φ9 0.0164 0.0160 0.0300 Φ10-11 0.0266 0.0090 0.0270 Φ12-14 -0.0521 -0.0530 -0.0400 Φ15 0.1046 0.1010 0.1070

[0140] Table 8 Optical Design Values ​​of Various Lenses in Industrial Lenses

[0141]

[0142]

[0143] The surface numbers in Table 8 are assigned according to the surface sequence of each lens. "OBJ" represents the object surface, "2" represents the object-side surface of the first lens, "3" represents the image-side surface of the first lens, and so on. The radius of curvature represents the degree of curvature of the corresponding lens surface; a positive value indicates that the surface bends towards the image surface, and a negative value indicates that the surface bends towards the object surface. "Infinite" indicates that the surface is flat and the radius of curvature is infinite. The thickness represents the central axial distance between the current surface and the next surface. The refractive index represents the ability of the material between the current surface and the next surface to deflect light. A blank space indicates that the current position is air, and the refractive index is 1. The Abbe number represents the dispersion characteristics of the material between the current surface and the next surface. Half-aperture indicates half the aperture size of the current surface. When the spacing between the 15th surface is 0.131 mm and the spacing between the 18th surface is -0.131 mm, it is possible to focus to an object distance of infinity. When the spacing between the 15th surface is 5.986 mm and the spacing between the 18th surface is -5.986 mm, it is possible to focus to an object distance of 50 mm.

[0144] Table 9. Design values ​​for the aspherical coefficient of industrial lenses.

[0145]

[0146] The K value in Table 9 represents the magnitude of the conic coefficient of the aspherical surface.

[0147] 1.565131E-04 means 1.565131 * 10 - 4. All other parameters can be represented in this way.

[0148] Furthermore, the aspherical conic coefficients can be defined using the following aspherical formula, but are not limited to the following representations:

[0149]

[0150] Where z is the axial sagitta in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature; k is the conic coefficient; and AE are the coefficients of the 4th, 6th, 8th, 10th, and 12th order terms of the aspherical polynomial.

[0151] Figure 14 This is a Ray Fan diagram of an industrial lens at optimal object distance, provided in Embodiment 3 of the present invention. The Ray Fan diagram is one of the most commonly used evaluation methods in modern optical design. The horizontal axis represents the beam aperture, and the vertical axis represents the transverse aberration. The ideal curve is a straight line coinciding with the horizontal axis, indicating that all rays converge at the same point on the image plane. The interval corresponding to the vertical axis of the curve is the maximum dispersion range of the beam on the ideal image plane. The Ray Fan diagram can reflect not only monochromatic aberrations of different wavelengths but also the magnitude of transverse chromatic aberration. Figure 14It can be seen that the system closely approximates the horizontal axis at each wavelength in each field of view, indicating that the transverse aberration of each wavelength is well corrected. At the same time, there is no obvious dispersion of each wavelength, indicating that the chromatic aberration of the system is also well corrected, thus ensuring that the optical system can achieve the high-resolution imaging requirements.

[0152] Figure 15 This is a schematic diagram of the field curvature distortion curve of an industrial lens at the optimal object distance, provided in Embodiment 3 of the present invention. In the coordinate system on the left side of the figure, the horizontal axis represents the magnitude of the field curvature, in mm; the vertical axis represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; Figure 15 As can be seen, the lens provided in this embodiment effectively controls field curvature, meaning that during imaging, the difference in image quality between the center and the periphery is small, resulting in good consistency. In the coordinate system on the right, the horizontal axis represents the magnitude of distortion, expressed as a percentage; the vertical axis represents the normalized image height, which has no unit. Figure 15 As can be seen, the distortion of the lens provided in this embodiment has been well corrected, with optical distortion less than ±0.5%.

[0153] Figure 16 This is a schematic diagram of the MTF curve of an industrial lens at the optimal object distance, provided in Embodiment 3 of the present invention. The horizontal axis represents spatial frequency, which refers to the number of black and white line pairs per 1mm. The vertical axis represents the modulation modulus (M' / M), where M refers to the grating modulation degree before imaging, and M' refers to the grating modulation degree after imaging. Therefore, 0 ≤ M' / M ≤ 1. The MTF curve represents the resolving power of the optical system for objects at different frequencies in different fields of view, meridional, and sagittal directions. It reflects the degree of image quality after the object passes through the optical system. The higher the MTF, the higher the image quality of the lens. Figure 16 It can be seen that the image quality of the lens of the present invention is higher than 0.34MTF at 200pl / mm from the center field of view to the edge field of view, and the imaging has excellent resolution.

[0154] Figure 17 This is a schematic diagram of axial chromatic aberration of an industrial lens at the optimal object distance, provided in Embodiment 3 of the present invention. The vertical direction represents the normalized 0-field pupil plane, where 0 represents the pupil center, and the vertical vertex represents the pupil vertex. The horizontal direction represents the axial chromatic aberration at different wavelengths (specifically 460nm, 530nm, and 620nm), in millimeters (mm). As shown in the figure, the axial chromatic aberration of the entire pupil of the lens of the present invention is less than 9μm, resulting in excellent image sharpness.

[0155] Figure 18This is a schematic diagram of the transverse chromatic aberration of an industrial lens at the optimal object distance, provided in Embodiment 3 of the present invention. In the diagram, the vertical direction represents the field of view angle, 0 represents the field of view angle incident parallel to the optical axis, and the vertex of the vertical direction represents the maximum half-field of view angle. As shown in the figure, at each wavelength (specifically 460nm, 530nm, and 620nm), the transverse chromatic aberration from the center field of view to the edge field of view of the lens is less than 0.8μm, resulting in higher imaging quality.

[0156] In summary, the industrial lens provided in this embodiment of the invention adopts an all-glass 15G structure. Through the combination of lens materials and the reasonable allocation of the optical power of each element, and using an intermediate group focusing method, it achieves focusing from 50mm to infinity. At the optimal object distance, it can achieve a high-resolution industrial lens design with low distortion and a large target area. The system focal length is 5mm, the maximum aperture is F1.9, the optimal object distance is 150mm, the maximum optical distortion is <0.5%, and the image quality can reach 200pl / mm > 0.34MTF.

[0157] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. An industrial lens, characterized in that, It includes a first lens group, a second lens group, and a third lens group arranged sequentially along the optical axis from the object plane to the image plane; the positions of the first lens group and the third lens group are fixed, while the position of the second lens group can float along the optical axis. The first lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens; the second lens group includes a ninth lens; the third lens group includes a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, a fourteenth lens, and a fifteenth lens; the industrial lens includes fifteen lenses with optical power. The first lens has a negative optical power; the second lens has a negative optical power; the third lens has a negative optical power; the fourth lens has a positive optical power; the fifth and sixth lenses are cemented together to form a first cemented lens, which has a negative optical power; the seventh and eighth lenses are cemented together to form a second cemented lens, which has a positive optical power; the ninth lens has a positive optical power; the tenth and eleventh lenses are cemented together to form a third cemented lens, which has a positive optical power; the twelfth, thirteenth, and fourteenth lenses are cemented together to form a fourth cemented lens, which has a negative optical power; and the fifteenth lens has a positive optical power. The first lens includes a first object-side surface near the object plane and a first image-side surface near 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 near the object plane and a second image-side surface near the image plane, wherein the second object-side surface is convex and the second image-side surface is concave. The third lens includes a third object-side surface near the object plane and a third image-side surface near the image plane. The third object-side surface is concave, and the third image-side surface is concave. The fourth lens includes a fourth object-side surface near the object plane and a fourth image-side surface near the image plane. The fourth object-side surface is concave, and the fourth image-side surface is convex. The eighth lens includes an eighth object-side surface near the object plane and an eighth image-side surface near the image plane. The eighth object-side surface is either convex or concave, and the eighth image-side surface is convex. The ninth lens includes a ninth object-side surface near the object plane and a ninth image-side surface near the image plane. The ninth object-side surface is convex, and the ninth image-side surface is either concave or convex. The tenth lens includes a tenth object-side surface near the object plane and a tenth image-side surface near the image plane. The tenth object-side surface is convex, and the tenth image-side surface is concave. The thirteenth lens includes a thirteenth object-side surface near the object plane and a thirteenth image-side surface near the image plane. The thirteenth object-side surface is convex, and the thirteenth image-side surface is convex. The fifteenth lens includes a fifteenth object-side surface near the object plane and a fifteenth image-side surface near the image plane. The fifteenth object-side surface is convex, and the fifteenth image-side surface is convex. The optical power of the fifth lens is Φ5, and the optical power of the sixth lens is Φ6, wherein -1.7900≤Φ5 / Φ6≤-1.1300; The optical power of the lens group formed by the ninth lens, the tenth lens and the eleventh lens is ΦZ1, and the optical power of the lens group formed by the twelfth lens, the thirteenth lens and the fourteenth lens is ΦZ2, wherein -0.9600≤ΦZ1 / ΦZ2≤-0.7500.

2. The industrial lens according to claim 1, characterized in that, The refractive index of the fifth lens is ND5; the refractive index of the sixth lens is ND6; Wherein, -1.2700≤ND6 / ND5≤1.3600.

3. The industrial lens according to claim 1, characterized in that, The Abbe number of the seventh lens is VD7, the Abbe number of the eighth lens is VD8, the Abbe number of the thirteenth lens is VD13, and the Abbe number of the fourteenth lens is VD14. Among them, 1.9100≤|VD7 / VD8|≤2.9500, 4.6800≤VD13 / VD14≤5.3000.

4. The industrial lens according to claim 1, characterized in that, The industrial lens has an optical length of TTL, a focal length of EFL, a maximum effective aperture of DM, an image size of IM, a working F-number of FNO, and a field of view of FOV. Among them, 17.5200≤TTL / EFL≤17.6500, 2.0400≤TTL / DM≤2.0600, 3.0500≤IM / FNO≤3.0700, and FOV≥96.3700°.

5. The industrial lens according to claim 1, characterized in that, The refractive index Nd1 of the first lens satisfies Nd1≥1.9300.

6. The industrial lens according to claim 1, characterized in that, The industrial lens also includes an aperture stop, which is disposed in the optical path between the eleventh lens and the twelfth lens; The maximum optical distortion of the industrial lens is DISG.MAX; Where 0 ≤ |DISG.MAX| ≤ 0.500%.

7. The industrial lens according to claim 1, characterized in that, The fifth lens includes a fifth object-side surface near the object plane and a fifth image-side surface near the image plane. The fifth object-side surface is concave, and the fifth image-side surface is convex. The sixth lens 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 concave, and the sixth image-side surface is convex. The seventh lens 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 or convex, and the seventh image-side surface is concave or convex. The eleventh lens includes an eleventh object-side surface near the object plane and an eleventh image-side surface near the image plane. The eleventh object-side surface is convex, and the eleventh image-side surface is either concave or convex. The twelfth lens includes a twelfth object-side surface near the object plane and a twelfth image-side surface near the image plane. The twelfth object-side surface is convex, and the twelfth image-side surface is concave. The fourteenth lens includes a fourteenth object-side surface near the object plane and a fourteenth image-side surface near the image plane. The fourteenth object-side surface is concave, and the fourteenth image-side surface is either concave or convex.

8. The industrial lens according to claim 1, characterized in that, The first lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the eleventh lens, the twelfth lens, the thirteenth lens, and the fourteenth lens are all glass spherical lenses; Both the second lens and the fifteenth lens are glass aspherical lenses.

Images