Symmetrical double telecentric lens

Abstract

The utility model relates to a symmetrical double telecentric lens, and relates to the technical field of measurement and control instruments in accurate manufacturing. Comprising an incident lens group, an imaging lens group and a diaphragm. The diaphragm is arranged between the incident lens group and the imaging lens group, and the focal lengths of the incident lens group and the imaging lens group are the same; and the incident lens group and the imaging lens group at the two sides of the diaphragm are respectively provided with seven lenses with the same number. According to the invention, an object is imaged according to the object-image proportion of 1: 1 through a small number of lens groups, so that the vision is more visualized, the illusion of people or interpretation errors caused by image distortion due to an image magnification or reduction mode are reduced, the authenticity is improved, and people can easily distinguish detail features of the object on a large-target-surface sensor. The problems that the number of built-in lenses of an existing lens is large, the magnification and imaging stability are insufficient, and the requirement for high precision cannot be met are solved.

Description

Technical Field

[0001] The utility model relates to the technical field of measurement and control instruments in precision manufacturing, and particularly relates to a symmetric double telecentric lens. Background Art

[0002] With the rapid development of industrial automation, the market's requirements for the precision of product detection are constantly increasing. For example, in the fields of semiconductor and precision machinery manufacturing, higher standards are put forward for the detailed recognition of microstructures and complex workpieces.

[0003] However, many existing lenses on the market have a large number of built-in lenses and have deficiencies in magnification and imaging stability, unable to meet the high-precision requirements. Moreover, the large number of built-in lenses in existing lenses results in a large space occupation of the lens and an increase in manufacturing costs.

[0004] Regarding the above related technologies, there are problems that existing lenses have a large number of built-in lenses and deficiencies in magnification and imaging stability, and cannot meet the high-precision requirements. Content of the Utility Model

[0005] In view of the above deficiencies of the existing technology, the purpose of the present utility model is to provide a symmetric double telecentric lens, aiming to solve the problems that existing lenses have a large number of built-in lenses and deficiencies in magnification and imaging stability, and cannot meet the high-precision requirements.

[0006] A symmetric double telecentric lens provided by the present application adopts the following technical solution: A symmetric double telecentric lens, comprising:

[0007] An incident lens group;

[0008] An imaging lens group;

[0009] A diaphragm, disposed between the incident lens group and the imaging lens group, and the incident lens group and the imaging lens group have the same focal length;

[0010] The incident lens group includes a first convex lens, a second convex lens, a third convex lens, a fourth convex lens, a first concave lens, a second concave lens, and a third concave lens;

[0011] The first convex lens, the second convex lens, the third convex lens, the first concave lens, the second concave lens, the third concave lens, and the fourth convex lens are arranged in sequence, and the diaphragm is disposed close to the fourth convex lens;

[0012] The imaging lens group includes a fifth convex lens, a sixth convex lens, a seventh convex lens, an eighth convex lens, a fourth concave lens, a fifth concave lens, and a sixth concave lens;

[0013] The fifth convex lens, the sixth convex lens, the seventh convex lens, the fourth concave lens, the fifth concave lens, the sixth concave lens, and the eighth convex lens are arranged in sequence, and the diaphragm is arranged close to the eighth convex lens.

[0014] Optionally, the distance between the first convex lens and the second convex lens is 1 - 2 mm;

[0015] The distance between the second convex lens and the third convex lens is 6 - 7 mm;

[0016] The distance between the third convex lens and the first concave lens is 2 - 3 mm;

[0017] The distance between the first concave lens and the second concave lens is 9 - 10 mm;

[0018] The distance between the second concave lens and the third concave lens is 1 - 2 mm;

[0019] The distance between the third concave lens and the fourth convex lens is 1 - 2 mm;

[0020] The distance between the fourth convex lens and the diaphragm is 0.5 - 1 mm.

[0021] Optionally, the distance between the fifth convex lens and the sixth convex lens is 1 - 2 mm;

[0022] The distance between the sixth convex lens and the seventh convex lens is 6 - 7 mm;

[0023] The distance between the seventh convex lens and the fourth concave lens is 2 - 3 mm;

[0024] The distance between the fourth concave lens and the fifth concave lens is 9 - 10 mm;

[0025] The distance between the fifth concave lens and the sixth concave lens is 1 - 2 mm;

[0026] The distance between the sixth concave lens and the eighth convex lens is 1 - 2 mm;

[0027] The distance between the eighth convex lens and the diaphragm is 4 - 5 mm.

[0028] Optionally, the distance from the fifth convex lens to the image plane is 89 - 90 mm.

[0029] Optionally, the radius of curvature of the surface of the first convex lens facing away from the diaphragm is greater than or equal to 110 mm and less than or equal to 112 mm;

[0030] The radius of curvature of the first convex lens on the side close to the diaphragm is greater than or equal to -215 mm and less than or equal to -214 mm;

[0031] The radius of curvature of the second convex lens on the side away from the diaphragm is greater than or equal to 61 mm and less than or equal to 62 mm;

[0032] The radius of curvature of the second convex lens on the side close to the diaphragm is greater than or equal to -235 mm and less than or equal to -234 mm;

[0033] The radius of curvature of the third convex lens on the side away from the diaphragm is greater than or equal to 25 mm and less than or equal to 26 mm;

[0034] The radius of curvature of the third convex lens on the side close to the diaphragm is greater than or equal to 752 mm and less than or equal to 753 mm;

[0035] The radius of curvature of the fourth convex lens on the side away from the diaphragm is greater than or equal to 32 mm and less than or equal to 33 mm;

[0036] The radius of curvature of the fourth convex lens on the side close to the diaphragm is greater than or equal to -25 mm and less than or equal to -24 mm;

[0037] The radius of curvature of the first concave lens on the side away from the diaphragm is greater than or equal to -247 mm and less than or equal to -246 mm;

[0038] The radius of curvature of the first concave lens on the side close to the diaphragm is greater than or equal to 20 mm and less than or equal to 21 mm;

[0039] The radius of curvature of the second concave lens on the side away from the diaphragm is greater than or equal to -31 mm and less than or equal to -30 mm;

[0040] The radius of curvature of the second concave lens on the side close to the diaphragm is greater than or equal to -92 mm and less than or equal to -91 mm;

[0041] The radius of curvature of the surface of the third concave lens facing away from the diaphragm is greater than or equal to -55 mm and less than or equal to -54 mm;

[0042] The radius of curvature of the surface of the third concave lens facing the diaphragm is greater than or equal to 28 mm and less than or equal to 29 mm.

[0043] Optionally, the radius of curvature of the surface of the fifth convex lens facing away from the diaphragm is greater than or equal to -112 mm and less than or equal to -111 mm;

[0044] The radius of curvature of the surface of the fifth convex lens facing the diaphragm is greater than or equal to 214 mm and less than or equal to 215 mm;

[0045] The radius of curvature of the surface of the sixth convex lens facing away from the diaphragm is greater than or equal to -62 mm and less than or equal to -61 mm;

[0046] The radius of curvature of the surface of the sixth convex lens facing the diaphragm is greater than or equal to 234 mm and less than or equal to 235 mm;

[0047] The radius of curvature of the surface of the seventh convex lens facing away from the diaphragm is greater than or equal to -26 mm and less than or equal to -25 mm;

[0048] The radius of curvature of the surface of the seventh convex lens facing the diaphragm is greater than or equal to -753 mm and less than or equal to -752 mm;

[0049] The radius of curvature of the surface of the eighth convex lens facing away from the diaphragm is greater than or equal to -33 mm and less than or equal to -32 mm;

[0050] The radius of curvature of the surface of the eighth convex lens facing the diaphragm is greater than or equal to 24 mm and less than or equal to 25 mm;

[0051] The radius of curvature of the surface of the fourth concave lens facing away from the diaphragm is greater than or equal to 246 mm and less than or equal to 247 mm;

[0052] The radius of curvature of the fourth concave lens on the side close to the diaphragm is greater than or equal to -21 mm and less than or equal to -20 mm;

[0053] The radius of curvature of the fifth concave lens on the side away from the diaphragm is greater than or equal to 30 mm and less than or equal to 31 mm;

[0054] The radius of curvature of the fifth concave lens on the side close to the diaphragm is greater than or equal to 91 mm and less than or equal to 92 mm;

[0055] The radius of curvature of the sixth concave lens on the side away from the diaphragm is greater than or equal to 54 mm and less than or equal to 55 mm;

[0056] The radius of curvature of the sixth concave lens on the side close to the diaphragm is greater than or equal to -29 mm and less than or equal to -28 mm.

[0057] Optionally, the central thickness of the first convex lens is 5 - 6 mm;

[0058] The central thickness of the second convex lens is 7 - 8 mm;

[0059] The central thickness of the third convex lens is 7 - 8 mm;

[0060] The central thickness of the fourth convex lens is 7 - 8 mm;

[0061] The central thickness of the first concave lens is 2 - 3 mm;

[0062] The central thickness of the second concave lens is 1 - 2 mm;

[0063] The central thickness of the third concave lens is 1 - 2 mm.

[0064] Optionally, the central thickness of the fifth convex lens is 5 - 6 mm;

[0065] The central thickness of the sixth convex lens is 7 - 8 mm;

[0066] The central thickness of the seventh convex lens is 7 - 8 mm;

[0067] The central thickness of the eighth convex lens is 7 - 8 mm;

[0068] The central thickness of the fourth concave lens is 2 - 3 mm;

[0069] The central thickness of the fifth concave lens is 1 - 2 millimeters;

[0070] The central thickness of the sixth concave lens is 1 - 2 millimeters.

[0071] Optionally, the effective apertures of the lenses included in the incident lens group and the imaging lens group are both greater than 24 millimeters.

[0072] Optionally, the symmetric double telecentric lens includes a coaxial light system, the coaxial light system is arranged above the diaphragm, and the coaxial light system is used to emit parallel light to the diaphragm.

[0073] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0074] Seven lenses with the same quantity are respectively arranged in the incident lens group and the imaging lens group on both sides of the diaphragm. The incident lens group and the imaging lens group on both sides of the diaphragm in this patent application adopt a symmetric design. The distribution of the incident lens group and the imaging lens group makes the focal lengths on both sides of the diaphragm the same, achieving a magnification ratio of 1:1. The final image is exactly the same size as the object without any difference, with a particularly strong sense of reality.

[0075] This patent application uses a small number of lens groups to image an object at a 1:1 object-image ratio, making the vision more intuitive, reducing the misjudgment error caused by the illusion or image distortion due to image magnification or reduction, improving the authenticity, and making it easy for people to distinguish the detailed features of the object on a large target surface sensor. It solves the problems that the existing lenses have a large number of internal lenses and deficiencies in magnification and imaging stability, and cannot meet the high-precision requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0077] Figure 1 is a schematic structural diagram of the symmetric double telecentric lens configured with a coaxial light system in the embodiment of the present application;

[0078] Figure 2 is a schematic structural diagram of the symmetric double telecentric lens not configured with a coaxial light system in the embodiment of the present application;

[0079] Figure 3 is an MTF curve diagram of the symmetric double telecentric lens in the embodiment of the present application;

[0080] Figure 4 It is the spot diagram of the symmetric double telecentric lens in the embodiment of the present application;

[0081] Figure 5 It is the field curvature and distortion diagram of the symmetric double telecentric lens in the embodiment of the present application;

[0082] Figure 6 It is the relative illumination diagram of the symmetric double telecentric lens in the embodiment of the present application.

[0083] Description of reference numerals:

[0084] 1. Incident lens group; 11. First convex lens; 12. Second convex lens; 13. Third convex lens; 14. Fourth convex lens; 15. First concave lens; 16. Second concave lens; 17. Third concave lens; 2. Imaging lens group; 21. Fifth convex lens; 22. Sixth convex lens; 23. Seventh convex lens; 24. Eighth convex lens; 25. Fourth concave lens; 26. Fifth concave lens; 27. Sixth concave lens; 3. Aperture; 4. Coaxial light system; 41. Coaxial light condenser lens; 42. Coaxial light emitting light source. Detailed implementation manners

[0085] In order to enable those skilled in the art to better understand the solution of the present utility model, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0086] The following further elaborates on the present application with reference to the accompanying drawings of the specification.

[0087] The embodiment of the present application discloses a symmetric double telecentric lens.

[0088] As Figure 1 and Figure 2 shown, a symmetric double telecentric lens includes an incident lens group 1, an imaging lens group 2, and an aperture 3. The aperture 3 is disposed between the incident lens group 1 and the imaging lens group 2, and the focal lengths of the incident lens group 1 and the imaging lens group 2 are the same;

[0089] The incident lens group 1 includes a first convex lens 11, a second convex lens 12, a third convex lens 13, a fourth convex lens 14, a first concave lens 15, a second concave lens 16, and a third concave lens 17.

[0090] The first convex lens 11, the second convex lens 12, the third convex lens 13, the first concave lens 15, the second concave lens 16, the third concave lens 17, and the fourth convex lens 14 are arranged in sequence, and the aperture stop 3 is arranged close to the fourth convex lens 14; the imaging lens group 2 includes the fifth convex lens 21, the sixth convex lens 22, the seventh convex lens 23, the eighth convex lens 24, the fourth concave lens 25, the fifth concave lens 26, and the sixth concave lens 27.

[0091] The fifth convex lens 21, the sixth convex lens 22, the seventh convex lens 23, the fourth concave lens 25, the fifth concave lens 26, the sixth concave lens 27, and the eighth convex lens 24 are arranged in sequence, and the aperture stop 3 is arranged close to the eighth convex lens 24.

[0092] There are seven lenses with the same number on each of the incident lens group 1 and the imaging lens group 2 on both sides of the aperture stop 3. The incident lens group 1 and the imaging lens group 2 on both sides of the aperture stop 3 of this patent application adopt a symmetric design. The distribution of the incident lens group 1 and the imaging lens group 2 makes the focal lengths on both sides of the aperture stop 3 the same, achieving a magnification ratio of 1:1. The final image is exactly the same size as the object without any difference, with a particularly realistic sense.

[0093] This patent application forms an image of the object with a 1:1 object-image ratio through a small number of lens groups, making the vision more intuitive, reducing the misperception caused by the way of image magnification or reduction or the reading error caused by image distortion, improving the authenticity, and making it easy for people to distinguish the detailed features of the object on a large-target surface sensor. It solves the problems that the existing lenses have a large number of internal lenses and have deficiencies in magnification and imaging stability, and cannot meet the high-precision requirements.

[0094] The radius of curvature of the surface of the first convex lens 11 facing away from the aperture stop 3 is greater than or equal to 110 mm and less than or equal to 112 mm (i.e., 100 ≤ R1 convex back ≤ 112, where R1 convex back is the radius of curvature of the surface of the first convex lens 11 facing away from the aperture stop 3, and the unit of R1 convex back is mm).

[0095] The radius of curvature of the surface of the first convex lens 11 close to the aperture stop 3 is greater than or equal to -215 mm and less than or equal to -214 mm (i.e., -215 ≤ R1 convex close ≤ -214, where R1 convex close is the radius of curvature of the surface of the first convex lens 11 close to the aperture stop 3, and the unit of R1 convex close is mm).

[0096] The radius of curvature of the surface of the second convex lens 12 facing away from the aperture stop 3 is greater than or equal to 61 mm and less than or equal to 62 mm (i.e., 61 ≤ R2 convex back ≤ 62, where R2 convex back is the radius of curvature of the surface of the second convex lens 12 facing away from the aperture stop 3, and the unit of R2 convex back is mm).

[0097] The radius of curvature of the surface of the second convex lens 12 adjacent to the diaphragm 3 is greater than or equal to -235 mm and less than or equal to -234 mm (i.e., -235 ≤ R2adjacent ≤ -234, where R2adjacent is the radius of curvature of the surface of the second convex lens 12 adjacent to the diaphragm 3, and the unit of R2adjacent is mm).

[0098] The radius of curvature of the surface of the third convex lens 13 facing away from the diaphragm 3 is greater than or equal to 25 mm and less than or equal to 26 mm (i.e., 25 ≤ R3distant ≤ 26, where R3distant is the radius of curvature of the surface of the third convex lens 13 facing away from the diaphragm 3, and the unit of R3distant is mm).

[0099] The radius of curvature of the surface of the third convex lens 13 adjacent to the diaphragm 3 is greater than or equal to 752 mm and less than or equal to 753 mm (i.e., 752 ≤ R3adjacent ≤ 753, where R3adjacent is the radius of curvature of the surface of the third convex lens 13 adjacent to the diaphragm 3, and the unit of R3adjacent is mm).

[0100] The radius of curvature of the surface of the fourth convex lens 14 facing away from the diaphragm 3 is greater than or equal to 32 mm and less than or equal to 33 mm (i.e., 32 ≤ R4distant ≤ 33, where R4distant is the radius of curvature of the surface of the fourth convex lens 14 facing away from the diaphragm 3, and the unit of R4distant is mm).

[0101] The radius of curvature of the surface of the fourth convex lens 14 adjacent to the diaphragm 3 is greater than or equal to -25 mm and less than or equal to -24 mm (i.e., -25 ≤ R4adjacent ≤ -24, where R4adjacent is the radius of curvature of the surface of the fourth convex lens 14 adjacent to the diaphragm 3, and the unit of R4adjacent is mm).

[0102] The radius of curvature of the surface of the first concave lens 15 facing away from the diaphragm 3 is greater than or equal to -247 mm and less than or equal to -246 mm (i.e., -247 ≤ R1distant ≤ -246, where R1distant is the radius of curvature of the surface of the first concave lens 15 facing away from the diaphragm 3, and the unit of R1distant is mm).

[0103] The radius of curvature of the surface of the first concave lens 15 adjacent to the diaphragm 3 is greater than or equal to 20 mm and less than or equal to 21 mm (i.e., 20 ≤ R1adjacent ≤ 21, where R1adjacent is the radius of curvature of the surface of the first concave lens 15 adjacent to the diaphragm 3, and the unit of R1adjacent is mm).

[0104] The radius of curvature of the surface of the second concave lens 16 facing away from the diaphragm 3 is greater than or equal to -31 mm and less than or equal to -30 mm (i.e., -31 ≤ R2concave_back ≤ -30, where R2concave_back is the radius of curvature of the surface of the second concave lens 16 facing away from the diaphragm 3, and the unit of R2concave_back is mm).

[0105] The radius of curvature of the surface of the second concave lens 16 facing the diaphragm 3 is greater than or equal to -92 mm and less than or equal to -91 mm (i.e., -92 ≤ R2concave_near ≤ -91, where R2concave_near is the radius of curvature of the surface of the second concave lens 16 facing the diaphragm 3, and the unit of R2concave_near is mm).

[0106] The radius of curvature of the surface of the third concave lens 17 facing away from the diaphragm 3 is greater than or equal to -55 mm and less than or equal to -54 mm (i.e., -55 ≤ R3concave_back ≤ -54, where R3concave_back is the radius of curvature of the surface of the third concave lens 17 facing away from the diaphragm 3, and the unit of R3concave_back is mm).

[0107] The radius of curvature of the surface of the third concave lens 17 facing the diaphragm 3 is greater than or equal to 28 mm and less than or equal to 29 mm (i.e., 28 ≤ R3concave_near ≤ 29, where R3concave_near is the radius of curvature of the surface of the third concave lens 17 facing the diaphragm 3, and the unit of R3concave_near is mm).

[0108] The radius of curvature of the surface of the fifth convex lens 21 facing away from the diaphragm 3 is greater than or equal to -112 mm and less than or equal to -111 mm (i.e., -112 ≤ R5convex_back ≤ -111, where R5convex_back is the radius of curvature of the surface of the fifth convex lens 21 facing away from the diaphragm 3, and the unit of R5convex_back is mm).

[0109] The radius of curvature of the surface of the fifth convex lens 21 facing the diaphragm 3 is greater than or equal to 214 mm and less than or equal to 215 mm (i.e., 214 ≤ R5convex_near ≤ 215, where R5convex_near is the radius of curvature of the surface of the fifth convex lens 21 facing the diaphragm 3, and the unit of R5convex_near is mm).

[0110] The radius of curvature of the surface of the sixth convex lens 22 facing away from the diaphragm 3 is greater than or equal to -62 mm and less than or equal to -61 mm (i.e., -62 ≤ R6convex_back ≤ -61, where R6convex_back is the radius of curvature of the surface of the sixth convex lens 22 facing away from the diaphragm 3, and the unit of R6convex_back is mm).

[0111] The radius of curvature of the sixth convex lens 22 on the side close to the diaphragm 3 is greater than or equal to 234 mm, and the radius of curvature of the sixth convex lens 22 on the side close to the diaphragm 3 is less than or equal to 235 mm (i.e., 234 ≤ R6adjacent ≤ 235, where R6adjacent is the radius of curvature of the sixth convex lens 22 on the side close to the diaphragm 3, and the unit of R6adjacent is mm).

[0112] The radius of curvature of the seventh convex lens 23 on the side away from the diaphragm 3 is greater than or equal to -26 mm, and the radius of curvature of the seventh convex lens 23 on the side away from the diaphragm 3 is less than or equal to -25 mm (i.e., -26 ≤ R7distant ≤ -25, where R7distant is the radius of curvature of the seventh convex lens 23 on the side away from the diaphragm 3, and the unit of R7distant is mm).

[0113] The radius of curvature of the seventh convex lens 23 on the side close to the diaphragm 3 is greater than or equal to -753 mm, and the radius of curvature of the seventh convex lens 23 on the side close to the diaphragm 3 is less than or equal to -752 mm (i.e., -753 ≤ R7adjacent ≤ -752, where R7adjacent is the radius of curvature of the seventh convex lens 23 on the side close to the diaphragm 3, and the unit of R7adjacent is mm).

[0114] The radius of curvature of the eighth convex lens 24 on the side away from the diaphragm 3 is greater than or equal to -33 mm, and the radius of curvature of the eighth convex lens 24 on the side away from the diaphragm 3 is less than or equal to -32 mm (i.e., -33 ≤ R8distant ≤ -32, where R8distant is the radius of curvature of the eighth convex lens 24 on the side away from the diaphragm 3, and the unit of R8distant is mm).

[0115] The radius of curvature of the eighth convex lens 24 on the side close to the diaphragm 3 is greater than or equal to 24 mm, and the radius of curvature of the eighth convex lens 24 on the side close to the diaphragm 3 is less than or equal to 25 mm (i.e., 24 ≤ R8adjacent ≤ 25, where R8adjacent is the radius of curvature of the eighth convex lens 24 on the side close to the diaphragm 3, and the unit of R8adjacent is mm).

[0116] The radius of curvature of the fourth concave lens 25 on the side away from the diaphragm 3 is greater than or equal to 246 mm, and the radius of curvature of the fourth concave lens 25 on the side away from the diaphragm 3 is less than or equal to 247 mm (i.e., 246 ≤ R4distant ≤ 247, where R4distant is the radius of curvature of the fourth concave lens 25 on the side away from the diaphragm 3, and the unit of R4distant is mm).

[0117] The radius of curvature of the fourth concave lens 25 on the side close to the diaphragm 3 is greater than or equal to -21 mm, and the radius of curvature of the fourth concave lens 25 on the side close to the diaphragm 3 is less than or equal to -20 mm (i.e., -21 ≤ R4adjacent ≤ -20, where R4adjacent is the radius of curvature of the fourth concave lens 25 on the side close to the diaphragm 3, and the unit of R4adjacent is mm).

[0118] The radius of curvature of the surface of the fifth concave lens 26 facing away from the diaphragm 3 is greater than or equal to 30 mm and less than or equal to 31 mm (i.e., 30 ≤ R5 concave back ≤ 31, where R5 concave back is the radius of curvature of the surface of the fifth concave lens 26 facing away from the diaphragm 3, and the unit of R5 concave back is mm).

[0119] The radius of curvature of the surface of the fifth concave lens 26 facing the diaphragm 3 is greater than or equal to 91 mm and less than or equal to 92 mm (i.e., 91 ≤ R5 concave near ≤ 92, where R5 concave near is the radius of curvature of the surface of the fifth concave lens 26 facing the diaphragm 3, and the unit of R5 concave near is mm).

[0120] The radius of curvature of the surface of the sixth concave lens 27 facing away from the diaphragm 3 is greater than or equal to 54 mm and less than or equal to 55 mm (i.e., 54 ≤ R6 concave back ≤ 55, where R6 concave back is the radius of curvature of the surface of the sixth concave lens 27 facing away from the diaphragm 3, and the unit of R6 concave back is mm).

[0121] The radius of curvature of the surface of the sixth concave lens 27 facing the diaphragm 3 is greater than or equal to -29 mm and less than or equal to -28 mm (i.e., -29 ≤ R6 concave near ≤ -28, where R6 concave near is the radius of curvature of the surface of the sixth concave lens 27 facing the diaphragm 3, and the unit of R6 concave near is mm).

[0122] Meanwhile, the central thickness of the first convex lens 11 is 5 - 6 mm. The central thickness of the second convex lens 12 is 7 - 8 mm. The central thickness of the third convex lens 13 is 7 - 8 mm. The central thickness of the fourth convex lens 14 is 7 - 8 mm. The central thickness of the first concave lens 15 is 2 - 3 mm. The central thickness of the second concave lens 16 is 1 - 2 mm. The central thickness of the third concave lens 17 is 1 - 2 mm. The central thickness of the fifth convex lens 21 is 5 - 6 mm. The central thickness of the sixth convex lens 22 is 7 - 8 mm. The central thickness of the seventh convex lens 23 is 7 - 8 mm. The central thickness of the eighth convex lens 24 is 7 - 8 mm. The central thickness of the fourth concave lens 25 is 2 - 3 mm. The central thickness of the fifth concave lens 26 is 1 - 2 mm. The central thickness of the sixth concave lens 27 is 1 - 2 mm.

[0123] The distance between the first convex lens 11 and the second convex lens 12 is 1 - 2 mm. The distance between the second convex lens 12 and the third convex lens 13 is 6 - 7 mm. The distance between the third convex lens 13 and the first concave lens 15 is 2 - 3 mm. The distance between the first concave lens 15 and the second concave lens 16 is 9 - 10 mm. The distance between the second concave lens 16 and the third concave lens 17 is 1 - 2 mm. The distance between the third concave lens 17 and the fourth convex lens 14 is 1 - 2 mm. The distance between the fourth convex lens 14 and the aperture stop 3 is 0.5 - 1 mm.

[0124] The distance between the fifth convex lens 21 and the sixth convex lens 22 is 1 - 2 mm. The distance between the sixth convex lens 22 and the seventh convex lens 23 is 6 - 7 mm. The distance between the seventh convex lens 23 and the fourth concave lens 25 is 2 - 3 mm. The distance between the fourth concave lens 25 and the fifth concave lens 26 is 9 - 10 mm. The distance between the fifth concave lens 26 and the sixth concave lens 27 is 1 - 2 mm. The distance between the sixth concave lens 27 and the eighth convex lens 24 is 1 - 2 mm. The distance between the eighth convex lens 24 and the aperture stop 3 is 4 - 5 mm.

[0125] Specifically, the incident lens group 1 is arranged on the left side of the aperture stop 3, and the imaging lens group 2 is arranged on the right side of the aperture stop 3. The symmetric double telecentric lens of the present application is, in the direction of the optical path transmission (the direction of the optical path transmission is the Figure 1 direction from left to right in the figure), successively the incident lens group 1, the aperture stop 3, and the imaging lens group 2. The incident lens group 1 and the imaging lens group 2 are completely symmetric systems.

[0126] Specifically expanded as: the first convex lens 11, the second convex lens 12, the third convex lens 13, the first concave lens 15, the second concave lens 16, the third concave lens 17, the fourth convex lens 14, the aperture stop 3, the eighth convex lens 24, the sixth concave lens 27, the fifth concave lens 26, the fourth concave lens 25, the seventh convex lens 23, the sixth convex lens 22, and the fifth convex lens 21.

[0127] In this embodiment, the surface of the lens close to the light source incident is hereinafter referred to as the front surface, and the surface of the lens away from the light source incident is hereinafter referred to as the rear surface.

[0128] The radius of curvature of the front surface of the first convex lens 11 is 111.162 mm, the radius of curvature of the rear surface is -214.124 mm, the central thickness of the first convex lens 11 is 5.18 mm, the material of the first convex lens 11 is H-FK61B, the refractive index of its material is 1.497, the dispersion coefficient is 81.60542, and the effective aperture of the first convex lens 11 is Φ48 mm.

[0129] The radius of curvature of the front surface of the second convex lens 12 is 61.228 mm, the radius of curvature of the rear surface is -234.467 mm, the central thickness of the second convex lens 12 is 7.363 mm, the material is H-ZPK7, the refractive index of the material is 1.56907, the dispersion coefficient is 71.30425, the effective aperture of the second convex lens 12 is Φ47.2 mm. Among them, the distance between the front surface of the second convex lens 12 and the rear surface of the first convex lens 11 is 1.611 mm.

[0130] The radius of curvature of the front surface of the third convex lens 13 is 25.995 mm, the radius of curvature of the rear surface is 752.683 mm, the central thickness of the third convex lens 13 is 7.922 mm, the material is H-FK95N, the refractive index of the material is 1.43780, the dispersion coefficient is 94.523389, the effective aperture of the third convex lens 13 is Φ35 mm. Among them, the distance between the front surface of the third convex lens 13 and the rear surface of the second convex lens 12 is 6.892 mm.

[0131] The radius of curvature of the front surface of the first concave lens 15 is -246.915 mm, the radius of curvature of the rear surface is 20.430 mm, the central thickness of the first concave lens 15 is 2.08 mm, the material is H-K51, the refractive index of the material is 1.523074, the dispersion coefficient is 58.608589, the effective aperture of the first concave lens 15 is Φ32 mm. Among them, the distance between the front surface of the first concave lens 15 and the rear surface of the third convex lens 13 is 2.056 mm.

[0132] The radius of curvature of the front surface of the second concave lens 16 is -30.84 mm, the radius of curvature of the rear surface is -91.471 mm, the central thickness of the second concave lens 16 is 1.693 mm, the material is H-TF3L, the refractive index of the material is 1.6134, the dispersion coefficient is 44.107022, the effective aperture of the second concave lens 16 is Φ24 mm. Among them, the distance between the front surface of the second concave lens 16 and the rear surface of the first concave lens 15 is 9.376 mm.

[0133] The radius of curvature of the front surface of the third concave lens 17 is -54.915 mm, the radius of curvature of the rear surface is 28.149 mm, the central thickness of the third concave lens 17 is 1.684 mm, the material is H-LAK7A, the refractive index of the material is 1.713, the dispersion coefficient is 53.83297, the effective aperture is Φ24 mm. Among them, the distance between the front surface of the third concave lens 17 and the rear surface of the second concave lens 16 is 1.906 mm.

[0134] The radius of curvature of the front surface of the fourth convex lens 14 is 32.397 mm, the radius of curvature of the rear surface is -24.1426 mm, the central thickness of the fourth convex lens 14 is 7.255 mm, the material is H-ZPK7, the refractive index of the material is 1.56907, the dispersion coefficient is 71.30425, the effective aperture of the fourth convex lens 14 is Φ26 mm. Among them, the distance between the front surface of the fourth convex lens 14 and the rear surface of the third concave lens 17 is 1.491 mm.

[0135] The front surface of the diaphragm 3 is a plane, and the rear surface is also a plane. The central thickness of the diaphragm 3 is 25.4 mm, the material is H-K9L, the refractive index of the material is 1.516802, the dispersion coefficient is 64.230624, the effective aperture of the diaphragm 3 is Φ25.4 mm. Among them, the distance between the front surface of the diaphragm 3 (i.e., the side of the diaphragm 3 close to the fourth convex lens 14) and the rear surface of the fourth convex lens 14 is 0.629 mm.

[0136] It should be noted that as Figure 1 shown, when the coaxial optical system 4 is not required to be configured in the system, the diaphragm 3 can be made into a cylindrical lens or a tetrahedral lens.

[0137] As Figure 2 shown, when the system needs to be configured with the coaxial optical system 4 for illumination, the diaphragm 3 can be designed to be composed of two right-angled prisms glued together with inclined surfaces. A semi-transparent and semi-reflective film is coated on the inclined surface of a single prism for illuminating the object and participating in the imaging system to improve the illuminance of the image plane.

[0138] At this time, the symmetric double telecentric lens further includes a coaxial optical system 4. The coaxial optical system 4 is arranged above the diaphragm 3, and the coaxial optical system 4 can emit parallel light to the diaphragm 3. The coaxial optical system 4 includes a coaxial optical condenser lens 41 and a coaxial optical light-emitting light source 42. The coaxial optical condenser lens 41 is arranged between the coaxial optical light-emitting light source 42 and the diaphragm 3. The coaxial optical light-emitting light source 42 can emit light to the diaphragm 3 in the form of parallel light through the coaxial optical condenser lens 41.

[0139] As Figure 1 and Figure 2 shown, the radius of curvature of the front surface of the eighth convex lens 24 is 24.1426 mm, the radius of curvature of the rear surface is -32.397 mm, the central thickness of the eighth convex lens 24 is 7.255 mm, the material is H-ZPK7, the refractive index of the material is 1.56907, the dispersion coefficient is 71.30425, the effective aperture of the eighth convex lens 24 is Φ26 mm. Among them, the distance between the front surface of the eighth convex lens 24 and the rear surface of the diaphragm 3 (i.e., the side of the diaphragm 3 close to the eighth convex lens 24) is 4.199 mm.

[0140] The front surface curvature radius of the sixth concave lens 27 is -28.149 mm, the rear surface curvature radius is 54.915 mm, the central thickness of the sixth concave lens 27 is 1.684 mm, the material is H-LAK7A, the refractive index of the material is 1.713, the dispersion coefficient is 53.83297, the effective aperture of the sixth concave lens 27 is Φ24 mm. Among them, the distance between the front surface of the sixth concave lens 27 and the rear surface of the eighth convex lens 24 is 1.419 mm.

[0141] The front surface curvature radius of the fifth concave lens 26 is 91.471 mm, the rear surface curvature radius is 30.84 mm, the central thickness of the fifth concave lens 26 is 1.693 mm, the material is H-TF3L, the refractive index of the material is 1.6134, the dispersion coefficient is 44.107022, the effective aperture of the fifth concave lens 26 is Φ24 mm. Among them, the distance between the front surface of the fifth concave lens 26 and the rear surface of the sixth concave lens 27 is 1.906 mm.

[0142] The front surface curvature radius of the fourth concave lens 25 is -20.430 mm, the rear surface curvature radius is 246.915 mm, the central thickness of the fourth concave lens 25 is 2.08 mm, the material is H-K51, the refractive index of the material is 1.523074, the dispersion coefficient is 58.608589, the effective aperture of the fourth concave lens 25 is Φ32 mm. Among them, the distance between the front surface of the fourth concave lens 25 and the rear surface of the fifth concave lens 26 is 9.376 mm.

[0143] The front surface curvature radius of the seventh convex lens 23 is -752.683 mm, the rear surface curvature radius is -25.995 mm, the central thickness of the seventh convex lens 23 is 7.922 mm, the material is H-FK95N, the refractive index of the material is 1.43780, the dispersion coefficient is 94.523389, the effective aperture of the seventh convex lens 23 is Φ35 mm. Among them, the distance between the front surface of the seventh convex lens 23 and the rear surface of the fourth concave lens 25 is 2.056 mm.

[0144] The front surface curvature radius of the sixth convex lens 22 is 234.467 mm, the rear surface curvature radius is -61.228 mm, the central thickness of the sixth convex lens 22 is 7.363 mm, the material is H-ZPK7, the refractive index of the material is 1.56907, the dispersion coefficient is 71.30425, the effective aperture of the sixth convex lens 22 is Φ47.2 mm. Among them, the distance between the front surface of the sixth convex lens 22 and the rear surface of the seventh convex lens 23 is 6.892 mm.

[0145] The front surface curvature of the fifth convex lens 21 is 214.1241 mm, the rear surface curvature radius is -111.162 mm, the central thickness of the fifth convex lens 21 is 5.18 mm, the lens material is H-FK61B, the refractive index of the material is 1.497, the dispersion coefficient is 81.60542, and the effective aperture of the fifth convex lens 21 is Φ48 mm. Among them, the distance between the front surface of the fifth convex lens 21 and the rear surface of the sixth convex lens 22 is 1.611 mm.

[0146] It should be noted that the distance from the fifth convex lens 21 to the image plane is 89 - 90 mm. In this embodiment, the distance from the rear surface of the fifth convex lens 21 to the image plane is 89.903 mm, and the diameter of the image plane is 29.72 mm.

[0147] Through the above lens design of the symmetric double telecentric lens of the present application, the focal length values of the incident lens group 1 and the imaging lens group 2 are as follows: the focal length of the incident lens group 1 is 81.7605 mm, and the focal length of the imaging lens group 2 is also 81.7605 mm, realizing the complete symmetry of the symmetric double telecentric lens.

[0148] The focal length value of the optical system is 285.896 mm. Among them, the focal length value of the optical system is the focal length value obtained after the combination of the above 14 lenses.

[0149] After applying this symmetric double telecentric lens to an optical system (the optical system includes a symmetric double telecentric lens and all necessary components related thereto, such as a light source, a filter, an image processor, etc. These systems are usually used in applications that require high-precision measurement, such as the measurement of precision mechanical components, the measurement of electronic components, etc. For example, in the present application, the symmetric double telecentric lens is used in cooperation with a camera), the F value of the optical system (the F value is the FNo. value, which is a parameter indicating the light passing ability of the lens) can be adjusted to 5.4 through the aperture 3. Then, the combination of the long focal length and the large aperture of the optical system can be achieved, and the image plane of the incident lens group 1 is located at the front focal plane position of the imaging lens group 2, and the optical system can meet the effect of an imaging magnification of 1.

[0150] Specifically, as Figure 1 、 Figure 3 、 Figure 4 、 Figure 5 and Figure 6 shown, actual numerical detection is carried out on the symmetric double telecentric lens, and its optical design indicators include: optical system diagram, modulation transfer function (MTF) curve diagram, spot diagram, field curvature and distortion diagram, relative illumination diagram.

[0151] Among them, as Figure 1 and Figure 2As shown in the figure, it can be seen from the optical system diagram that the optical structure design of the symmetric double telecentric lens of this application is completely symmetric, achieving a magnification ratio of 1:1, with the imaging being exactly the same size as the object without any difference, and having a particularly realistic sense.

[0152] As Figure 3 shown, it can be seen from the MTF curve graph that the imaging resolution obtained by the optical system using the double telecentric lens and the diffraction limit design method is: MTF@0.3 = 180 (line pairs per millimeter (lp / mm)). The imaging resolutions of different colors are very close to the diffraction limit and have reached the requirements of high-definition resolution. Among them, MTF@0.3 = 180 (lp / mm) means that the value of MTF at 0.3 is 180 lp / mm.

[0153] As Figure 4 shown, the three spot diagrams are the RMS radii (radius of the blur spot) under different image-side fields of view. Among them, the RMS radius is an important optical parameter used to quantitatively reflect the size of the actual blur spot in the system.

[0154] It can be seen from the spot diagram that the size of the spot size (the size of the points in the spot diagram) in the inner field of view is less than 3 μm, and it is only greater than 7 μm at the outer edge field of view. Therefore, the symmetric telecentric lens of this application has a high imaging effect and quality, and the existing 3-μm pixels of the sensor are sufficient to achieve a completely distinguishable state.

[0155] As Figure 5 shown, the one on the left is the field curvature diagram, and the one on the right is the distortion diagram. It can be seen from the field curvature diagram that: the field curvature changes of the meridian and sagittal lines within the entire field of view are both within 0.05, belonging to a small-field curvature optical system in the machine vision system.

[0156] Similarly, it can be seen from the distortion diagram that the distortion of the entire system in each field of view is less than 0.01% and can be regarded as a distortion-free system. In this way, there is no impact or change on the imaging of the object, and its application range or precision measurement, etc. can be expanded.

[0157] As Figure 6 shown, it can be seen from the relative illuminance diagram that the relative illuminance at the center and edge of the imaging image plane of the optical system of the symmetric double telecentric lens of this application is almost the same, indicating that the illuminance uniformity of its image plane is highly consistent, and there will be no situation of bright center and dark edge, improving the accuracy of alignment and interpretation.

[0158] It can be seen from the above structure of the symmetric double telecentric lens and the actual data detection that the structure of this application has the following effects:

[0159] 1. In all the lenses (i.e., 14 lenses) of the symmetric double telecentric lens of the present application, the effective aperture of the lens is greater than Φ24 mm, meeting the requirements of large target surface imaging.

[0160] 2. The F value of the optical system (the F value is the FNo. value, which is a parameter representing the light passing ability of the lens) can reach 5.4 through the aperture 3, and the focal length value of the optical system can reach 285.896 mm. Among them, the focal length value of the optical system is the focal length value obtained after combining the above 14 lenses, belonging to a typical long focal length and large aperture optical system (a long focal length and large aperture optical system needs to meet a large focal length and a small F number), and can achieve the effect of uniform brightness of the object surface and the image surface.

[0161] 3. The symmetric double telecentric lens of the present application is composed of 14 lenses and the aperture 3. The 14 lenses cooperate with each other to eliminate the influence of various aberrations on imaging, improve the imaging quality, and achieve the effect of high resolution.

[0162] 4. Adopting the optical design idea of the double telecentric lens enables the incident lens group 1 to image the object surface on the position surface of the aperture 3, and at the same time, the position of the aperture 3 is at the front focal plane position of the imaging lens group 2, sharing the advantages of object-side telecentricity and image-side telecentricity, improving the brightness uniformity of the object surface and the image surface, and at the same time, also improving the alignment accuracy of the object surface and the discrimination accuracy of the image surface, further improving the monitoring level of precision testing and ultra-small components.

[0163] 5. Adopting the design idea of diffraction limit greatly improves the resolution of the optical system, making it a high-definition resolution lens. Among them, the diffraction limit means that due to the diffraction characteristics of light, traditional imaging, focusing, and transmission methods are limited by wavelength and aperture, resulting in the inability to achieve higher resolution and smaller spatial dimensions. The design idea of diffraction limit is a strategy adopted by designers to break through this limitation.

[0164] 6. Using lenses with a larger aperture to improve the imaging resolution and obtain a larger range of object surface measurement or monitoring to expand the application range of the lens.

[0165] 7. The coaxial light system 4 can be assisted to increase the brightness of the object surface and the image surface, thereby improving the uniformity of resolution, reducing alignment and reading judgment errors, and being able to adapt to applications in darker scenes.

[0166] The symmetric double telecentric lens needs to be used in cooperation with a camera. The maximum size of the camera's sensor can support 1.8 inches, and the symmetric double telecentric lens of the present application can be compatible with cameras of smaller inches.

[0167] That is, the symmetric double telecentric lens of the present application can achieve high-resolution effects of large target surface and high magnification.

[0168] In summary, by adopting the structure of the symmetric double telecentric lens of the present application, an amplification factor of 1:1 can be achieved, which can truly reflect the actual situation of the object without the illusion error caused by human factors. At the same time, by using a large-aperture objective lens, a long focal length, and a large aperture 3-hole, the resolution ability of the lens for object details is improved. The design concept of diffraction limit and telecentric lens is used to improve the lens, making the brightness and resolution of the entire picture uniform, improving the accuracy to meet the high-definition requirements of the resolution, and improving the alignment accuracy and reducing the reading error. The auxiliary coaxial light system 4 can improve the resolution and the brightness of the object image plane by one level, and can meet the shooting use of the sensors of any camera with a size of less than 1.8 inches, with a wide application. The completely symmetric structure design, all of which are single lenses, is simple to process and low in cost.

[0169] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0170] It should be noted that the present utility model takes a symmetric double telecentric lens as an example to introduce the specific structure and working principle of the present utility model. However, the application of the present utility model is not limited to a symmetric double telecentric lens, and can also be applied to the production and use of other similar workpieces.

[0171] It should be understood that the present utility model is not limited to the precise structure already described and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present utility model is only limited by the appended claims.

[0172] The above are only the preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present utility model shall be included in the protection scope of the present utility model.

Claims

1. A symmetric double telecentric lens, characterized in that, Comprising: An incident mirror group; An imaging mirror group; A diaphragm, disposed between the incident mirror group and the imaging mirror group, and the incident mirror group and the imaging mirror group have the same focal length; The incident mirror group includes a first convex lens, a second convex lens, a third convex lens, a fourth convex lens, a first concave lens, a second concave lens, and a third concave lens; The first convex lens, the second convex lens, the third convex lens, the first concave lens, the second concave lens, the third concave lens, and the fourth convex lens are arranged in sequence, and the diaphragm is disposed close to the fourth convex lens; The imaging mirror group includes a fifth convex lens, a sixth convex lens, a seventh convex lens, an eighth convex lens, a fourth concave lens, a fifth concave lens, and a sixth concave lens; The fifth convex lens, the sixth convex lens, the seventh convex lens, the fourth concave lens, the fifth concave lens, the sixth concave lens, and the eighth convex lens are arranged in sequence, and the diaphragm is disposed close to the eighth convex lens.

2. The symmetrical double telecentric lens according to claim 1, wherein The distance between the first convex lens and the second convex lens is 1 - 2 millimeters; The distance between the second convex lens and the third convex lens is 6 - 7 millimeters; The distance between the third convex lens and the first concave lens is 2 - 3 millimeters; The distance between the first concave lens and the second concave lens is 9 - 10 millimeters; The distance between the second concave lens and the third concave lens is 1 - 2 millimeters; The distance between the third concave lens and the fourth convex lens is 1 - 2 millimeters; The distance between the fourth convex lens and the diaphragm is 0.5 - 1 millimeter.

3. The symmetrical double telecentric lens according to claim 2, wherein The distance between the fifth convex lens and the sixth convex lens is 1 - 2 millimeters; The distance between the sixth convex lens and the seventh convex lens is 6 - 7 millimeters; The distance between the seventh convex lens and the fourth concave lens is 2 - 3 millimeters; The distance between the fourth concave lens and the fifth concave lens is 9 - 10 millimeters; The distance between the fifth concave lens and the sixth concave lens is 1 - 2 millimeters; The distance between the sixth concave lens and the eighth convex lens is 1 - 2 millimeters; The distance between the eighth convex lens and the diaphragm is 4 - 5 millimeters.

4. The symmetric double telecentric lens according to claim 3, wherein The distance from the fifth convex lens to the image plane is 89 - 90 millimeters.

5. The symmetric double telecentric lens according to claim 4, wherein The radius of curvature of the surface of the first convex lens facing away from the diaphragm is greater than or equal to 110 millimeters and less than or equal to 112 millimeters; The radius of curvature of the surface of the first convex lens facing the diaphragm is greater than or equal to -215 millimeters and less than or equal to -214 millimeters; The radius of curvature of the surface of the second convex lens facing away from the diaphragm is greater than or equal to 61 millimeters and less than or equal to 62 millimeters; The radius of curvature of the surface of the second convex lens facing the diaphragm is greater than or equal to -235 millimeters and less than or equal to -234 millimeters; The radius of curvature of the third convex lens on the side away from the diaphragm is greater than or equal to 25 mm and less than or equal to 26 mm; The radius of curvature of the third convex lens on the side close to the diaphragm is greater than or equal to 752 mm and less than or equal to 753 mm; The radius of curvature of the fourth convex lens on the side away from the diaphragm is greater than or equal to 32 mm and less than or equal to 33 mm; The radius of curvature of the fourth convex lens on the side close to the diaphragm is greater than or equal to -25 mm and less than or equal to -24 mm; The radius of curvature of the first concave lens on the side away from the diaphragm is greater than or equal to -247 mm and less than or equal to -246 mm; The radius of curvature of the first concave lens on the side close to the diaphragm is greater than or equal to 20 mm and less than or equal to 21 mm; The radius of curvature of the second concave lens on the side away from the diaphragm is greater than or equal to -31 mm and less than or equal to -30 mm; The radius of curvature of the second concave lens on the side close to the diaphragm is greater than or equal to -92 mm and less than or equal to -91 mm; The radius of curvature of the third concave lens on the side away from the diaphragm is greater than or equal to -55 mm and less than or equal to -54 mm; The radius of curvature of the third concave lens on the side close to the diaphragm is greater than or equal to 28 mm and less than or equal to 29 mm.

6. The symmetrical double telecentric lens according to claim 5, characterized in that, The radius of curvature of the fifth convex lens on the side away from the diaphragm is greater than or equal to -112 mm and less than or equal to -111 mm; The radius of curvature of the fifth convex lens on the side close to the diaphragm is greater than or equal to 214 mm and less than or equal to 215 mm; The radius of curvature of the sixth convex lens on the side away from the diaphragm is greater than or equal to -62 mm and less than or equal to -61 mm; The radius of curvature of the sixth convex lens on the side close to the diaphragm is greater than or equal to 234 mm and less than or equal to 235 mm; The radius of curvature of the seventh convex lens on the side away from the diaphragm is greater than or equal to -26 mm and less than or equal to -25 mm; The radius of curvature of the seventh convex lens on the side close to the diaphragm is greater than or equal to -753 mm and less than or equal to -752 mm; The radius of curvature of the eighth convex lens on the side away from the diaphragm is greater than or equal to -33 mm and less than or equal to -32 mm; The radius of curvature of the eighth convex lens on the side close to the diaphragm is greater than or equal to 24 mm and less than or equal to 25 mm; The radius of curvature of the fourth concave lens on the side away from the diaphragm is greater than or equal to 246 mm and less than or equal to 247 mm; The radius of curvature of the fourth concave lens on the side close to the diaphragm is greater than or equal to -21 mm and less than or equal to -20 mm; The radius of curvature of the fifth concave lens on the side away from the diaphragm is greater than or equal to 30 mm and less than or equal to 31 mm; The radius of curvature of the fifth concave lens on the side close to the diaphragm is greater than or equal to 91 mm and less than or equal to 92 mm; The radius of curvature of the sixth concave lens on the side away from the diaphragm is greater than or equal to 54 mm and less than or equal to 55 mm; The radius of curvature of the sixth concave lens on the side close to the diaphragm is greater than or equal to -29 mm and less than or equal to -28 mm.

7. The symmetrical double telecentric lens according to claim 6, wherein The central thickness of the first convex lens is 5 - 6 mm; The central thickness of the second convex lens is 7 - 8 mm; The central thickness of the third convex lens is 7 - 8 mm; The central thickness of the fourth convex lens is 7 - 8 mm; The central thickness of the first concave lens is 2 - 3 mm; The central thickness of the second concave lens is 1 - 2 mm; The central thickness of the third concave lens is 1 - 2 mm.

8. The symmetrical double telecentric lens according to claim 7, characterized in that, The central thickness of the fifth convex lens is 5 - 6 mm; The central thickness of the sixth convex lens is 7 - 8 mm; The central thickness of the seventh convex lens is 7 - 8 mm; The central thickness of the eighth convex lens is 7 - 8 mm; The central thickness of the fourth concave lens is 2 - 3 mm; The central thickness of the fifth concave lens is 1 - 2 mm; The central thickness of the sixth concave lens is 1 - 2 mm.

9. The symmetric double telecentric lens according to claim 1, wherein The effective apertures of the lenses included in the incident lens group and the imaging lens group are both greater than 24 mm.

10. The symmetric double telecentric lens according to claim 1, wherein The symmetry The symmetric double telecentric lens includes a coaxial optical system, and the coaxial optical system is arranged above the diaphragm, The coaxial optical system is used to emit parallel light to the diaphragm.

Images