Telecentric lens

Abstract

To provide a telecentric lens in a field of optical lens.SOLUTION: The telecentric lens is constituted of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens in order from an object side to an image side, and satisfies conditional expressions 1.980≤n2≤2.300, -0.600≤f8 / f≤-0.050, 0.600≤R4 / R3≤4.000, and 0.145≤NA*f / WD≤0.220. The telecentric lens has excellent optical performance and high magnification, and can meet precise detection needs of a machine vision system.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to the field of optical lenses, and in particular to telecentric lenses for industrial and machine vision detection applications. [Background technology]

[0002] With the development of industrial automation and the popularization of machine vision applications, industrial lenses are widely applied in fields such as defect detection, dimensional measurement, and security monitoring. Due to the unique technical advantage that the change in object distance does not affect the magnification of the image, telecentric lenses are widely applied in fields such as precision measurement and non-contact optical measurement. With the development of technology and the increasing diversification needs of users, when the system's requirements for imaging quality are becoming higher, the nine-piece lens structure gradually appears in the design of lenses. In order to meet the precise detection of machine vision systems, telecentric lenses with good optical performance and high magnification are in demand. Summary of the Invention [Problem to be solved by the invention]

[0003] SUMMARY OF THE PRESENT DISCLOSURE In view of the above problems, the present invention aims to provide a telecentric lens that can obtain good optical performance and high magnification, and can meet the precise detection requirements of machine vision systems. [Means for solving the problem]

[0004] In order to solve the above technical problem, an embodiment of the present invention provides a telecentric lens, which is composed of, in order from the object side to the image side, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens, When a focal length of the telecentric lens is f, a refractive index of the second lens is n2, a central radius of curvature of the object side surface of the second lens is R3, a central radius of curvature of the image side surface of the second lens is R4, a focal length of the eighth lens is f8, a working distance of the telecentric lens is WD, and a numerical aperture of the telecentric lens is NA, the following conditional formulas (1) to (4) are satisfied. 1.980≦n2≦2.300 (1) -0.600≦f8 / f≦-0.050 (2) 0.600≦R4 / R3≦4.000 (3) 0.145≦NA*f / WD≦0.220 (4)

[0005] Preferably, when the Abbe number of the third lens is v3 and the Abbe number of the fourth lens is v4, the following conditional expression (5) is satisfied. 50.000≦v4―v3≦80.000 (5)

[0006] Preferably, when the optical length of the telecentric lens is TTL, the following conditional expression (6) is satisfied: 2.000≦TTL / f≦5.000 (6)

[0007] Preferably, the first lens has positive refractive power, and an image side surface of the first lens is convex on a paraxial line, When the focal length of the first lens is f1, the central radius of curvature of the object side surface of the first lens is R1, the central radius of curvature of the image side surface of the first lens is R2, the axial thickness of the first lens is d1, and the optical length of the telecentric lens is TTL, the following conditional expressions (7) to (9) are satisfied. 0.54≦f1 / f≦1.95 (7) -0.50≦(R1+R2) / (R1−R2)≦4.01 (8) 0.04≦d1 / TTL≦0.06 (9)

[0008] Preferably, the object side surface of the second lens is a convex surface in a paraxial direction, and the image side surface of the second lens is a concave surface in a paraxial direction, When the focal length of the second lens is f2, the axial thickness of the second lens is d3, and the optical length of the telecentric lens is TTL, the following conditional expressions (10) and (11) are satisfied. -1.95≦f2 / f≦1.70 (10) 0.01≦d3 / TTL≦0.05 (11)

[0009] Preferably, the object side surface of the third lens is a paraxially convex surface, and the image side surface of the third lens is a paraxially concave surface, When the focal length of the third lens is f3, the central radius of curvature of the object side surface of the third lens is R5, the central radius of curvature of the image side surface of the third lens is R6, the axial thickness of the third lens is d5, and the optical length of the telecentric lens is TTL, the following conditional expressions (12) to (14) are satisfied. -0.44≦f3 / f≦3.20 (12) 1.44≦(R5+R6) / (R5−R6)≦8928.08 (13) 0.00≦d5 / TTL≦0.02 (14)

[0010] Preferably, the fourth lens has positive refractive power, an object side surface of the fourth lens is a convex surface on a paraxial line, and an image side surface of the fourth lens is a convex surface on a paraxial line, When the focal length of the fourth lens is f4, the central radius of curvature of the object side surface of the fourth lens is R7, the central radius of curvature of the image side surface of the fourth lens is R8, the axial thickness of the fourth lens is d7, and the optical length of the telecentric lens is TTL, the following conditional expressions (15) to (17) are satisfied. 0.18≦f4 / f≦0.35 (15) -0.35≦(R7+R8) / (R7-R8)≦-0.10 (16) 0.01≦d7 / TTL≦0.05 (17)

[0011] Preferably, the fifth lens has negative refractive power, an object side surface of the fifth lens is a paraxial concave surface, and an image side surface of the fifth lens is a paraxial concave surface, When the focal length of the fifth lens is f5, the central radius of curvature of the object side surface of the fifth lens is R9, the central radius of curvature of the image side surface of the fifth lens is R10, the axial thickness of the fifth lens is d9, and the optical length of the telecentric lens is TTL, the following conditional expressions (18) to (20) are satisfied. -0.25≦f5 / f≦-0.09 (18) 0.12≦(R9+R10) / (R9−R10)≦0.45 (19) 0.00≦d9 / TTL≦0.03 (20)

[0012] Preferably, the sixth lens has a positive refractive power, an object side surface of the sixth lens is a convex surface on a paraxial line, and an image side surface of the sixth lens is a convex surface on a paraxial line, When the focal length of the sixth lens is f6, the central radius of curvature of the object side surface of the sixth lens is R11, the central radius of curvature of the image side surface of the sixth lens is R12, the axial thickness of the sixth lens is d11, and the optical length of the telecentric lens is TTL, the following conditional expressions (21) to (23) are satisfied. 0.15≦f6 / f≦0.29 (21) -1.00≦(R11+R12) / (R11-R12)≦-0.33 (22) 0.01≦d11 / TTL≦0.06 (23)

[0013] Preferably, the seventh lens has a positive refractive power, When the focal length of the seventh lens is f7, the central radius of curvature of the object side surface of the seventh lens is R13, the central radius of curvature of the image side surface of the seventh lens is R14, the axial thickness of the seventh lens is d13, and the optical length of the telecentric lens is TTL, the following conditional expressions (24) to (26) are satisfied. 0.10≦f7 / f≦0.95 (24) -2.80≦(R13+R14) / (R13−R14)≦2.10 (25) 0.00≦d13 / TTL≦0.06 (26)

[0014] Preferably, the eighth lens has negative refractive power, and an object side surface of the eighth lens is concave in a paraxial direction. When the central radius of curvature of the object side surface of the eighth lens is R15, the central radius of curvature of the image side surface of the eighth lens is R16, the axial thickness of the eighth lens is d15, and the optical length of the telecentric lens is TTL, the following conditional expressions (27) and (28) are satisfied. -2.00≦(R15+R16) / (R15−R16)≦0.16 (27) 0.00≦d15 / TTL≦0.03 (28)

[0015] Preferably, the ninth lens has a positive refractive power, When the focal length of the ninth lens is f9, the central radius of curvature of the object side surface of the ninth lens is R17, the central radius of curvature of the image side surface of the ninth lens is R18, the axial thickness of the eighth lens is d17, and the optical length of the telecentric lens is TTL, the following conditional expressions (29) to (31) are satisfied. 0.64≦f9 / f≦2.97 (29) -32.02≦(R17+R18) / (R17−R18)≦2.00 (30) 0.01≦d17 / TTL≦0.08 (31)

[0016] Preferably, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens are all made of a glass material. Effect of the Invention

[0017] The beneficial effects of the present invention are as follows: The telecentric lens of the present invention has good optical performance and high magnification, which can meet the precise detection needs of machine vision systems. [Brief description of the drawings]

[0018] [Figure 1] 1 is a schematic diagram showing the structure of a telecentric lens according to a first embodiment of the present invention. [Diagram 2] 2 is a schematic diagram showing axial chromatic aberration of the telecentric lens shown in FIG. 1. [Diagram 3] 2 is a schematic diagram showing chromatic aberration of magnification of the telecentric lens shown in FIG. 1. [Figure 4] 2 is a schematic diagram showing the field curvature and distortion of the telecentric lens shown in FIG. 1. [Diagram 5] FIG. 5 is a schematic diagram showing the structure of a telecentric lens according to a second embodiment of the present invention. [Figure 6] 6 is a schematic diagram showing the axial chromatic aberration of the telecentric lens shown in FIG. 5. [Figure 7] 6 is a schematic diagram showing chromatic aberration of magnification of the telecentric lens shown in FIG. 5. [Figure 8] 6 is a schematic diagram showing the field curvature and distortion of the telecentric lens shown in FIG. 5. [Figure 9] FIG. 11 is a schematic diagram showing the configuration of a telecentric lens according to a third embodiment of the present invention. [Figure 10] 10 is a schematic diagram showing the axial chromatic aberration of the telecentric lens shown in FIG. [Figure 11] 10 is a schematic diagram showing chromatic aberration of magnification of the telecentric lens shown in FIG. 9. [Figure 12] 10A and 10B are schematic diagrams showing the field curvature and distortion of the telecentric lens shown in FIG. [Figure 13] FIG. 11 is a schematic diagram showing the structure of a telecentric lens according to a fourth embodiment of the present invention. [Figure 14] FIG. 14 is a schematic diagram showing axial chromatic aberration of the telecentric lens shown in FIG. [Figure 15] 14 is a schematic diagram showing chromatic aberration of magnification of the telecentric lens shown in FIG. 13. [Figure 16] 14 is a schematic diagram showing the field curvature and distortion of the telecentric lens shown in FIG. 13. [Figure 17] FIG. 13 is a schematic diagram showing the configuration of a telecentric lens according to a fifth embodiment of the present invention. [Figure 18]18 is a schematic diagram showing the axial chromatic aberration of the telecentric lens shown in FIG. 17. [Figure 19] 18 is a schematic diagram showing chromatic aberration of magnification of the telecentric lens shown in FIG. 17. [Figure 20] 18 is a schematic diagram showing the field curvature and distortion of the telecentric lens shown in FIG. 17. [Figure 21] FIG. 13 is a schematic diagram showing the configuration of a telecentric lens according to a sixth embodiment of the present invention. [Figure 22] FIG. 22 is a schematic diagram showing the axial chromatic aberration of the telecentric lens shown in FIG. 21. [Figure 23] FIG. 22 is a schematic diagram showing chromatic aberration of magnification of the telecentric lens shown in FIG. 21. [Figure 24] 22A to 22C are schematic diagrams showing the field curvature and distortion of the telecentric lens shown in FIG. 21. [Diagram 25] FIG. 13 is a schematic diagram showing the configuration of a telecentric lens according to a seventh embodiment of the present invention. [Figure 26] FIG. 26 is a schematic diagram showing the axial chromatic aberration of the telecentric lens shown in FIG. 25. [Figure 27] FIG. 26 is a schematic diagram showing chromatic aberration of magnification of the telecentric lens shown in FIG. 25. [Figure 28] 26 is a schematic diagram showing the field curvature and distortion of the telecentric lens shown in FIG. 25. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] In order to make the object, solution and advantages of the present invention clearer, the following describes in detail each embodiment of the present invention with reference to the drawings. However, in each embodiment of the present invention, many technical details are given so that the present invention can be well understood, but it should be understood by those skilled in the art that the present invention can be realized without the existence of various changes and modifications based on these technical details and each embodiment below.

[0020] (First embodiment) Referring to the drawings, the present invention provides a telecentric lens 10. FIG. 1 shows a telecentric lens 10 according to a first embodiment of the present invention, and the telecentric lens 10 includes nine lenses. Specifically, the telecentric lens 10 includes, in order from the object side to the image side, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, a dichroic prism BS, a diaphragm S1, a seventh lens L7, an eighth lens L8, and a ninth lens L9. An optical element such as an optical filter may be provided between the ninth lens L9 and an image surface Si.

[0021] In this embodiment, the object plane OBJ and the image plane Si are arranged so that the light rays are incident from the left side and the light incidence direction is from left to right. In an alternative embodiment, the light rays may be incident from the right side, i.e., the object plane OBJ and the image plane Si are arranged so that the light incidence direction is from right to left.

[0022] If the refractive index of the second lens L2 is defined as n2, the conditional formula 1.980≦n2≦2.300 is satisfied, the range of the refractive index of the second lens L2 is specified, a high refractive index material is used, and the tip diameter can be effectively controlled.

[0023] If the focal length of the telecentric lens 10 is defined as f and the focal length of the eighth lens L8 is defined as f8, then the conditional formula -0.600≦f8 / f≦-0.050 is satisfied. The ratio between the focal length f of the eighth lens L8 and the focal length of the telecentric lens 10 is specified. By appropriately allocating the optical focal length of the telecentric lens 10, the telecentric lens 10 has excellent imaging quality and low sensitivity.

[0024] If the central radius of curvature of the object side surface of the second lens L2 is defined as R3 and the central radius of curvature of the image side surface of the second lens L2 is defined as R4, the conditional formula 0.600≦R4 / R3≦4.000 is satisfied, which defines the shape of the second lens L2 and, within the range of the conditional formula, can reduce the degree of deflection of a light ray passing through the lens. This is advantageous for correcting the astigmatism and distortion of the telecentric lens 10, and the distortion aberration is |Distortion|≦0.04%, which meets the high-precision detection requirements of the machine vision system.

[0025] If the working distance of the telecentric lens (i.e., the axial distance from the object surface to the object side surface of the first lens L1) is defined as WD, and the numerical aperture of the telecentric lens is defined as NA, then the conditional formula 0.145≦NA*f / WD≦0.220 is satisfied, which specifies the conditions that the numerical aperture and resolution of the telecentric lens 10 must satisfy, and within the range of the conditional formula, the telecentric lens 10 has a relatively larger numerical aperture and stronger resolution.

[0026] When the distance from the object side surface of the first lens L1 of the telecentric lens 10 of the present invention to the observed object, the optical length, the numerical aperture, the focal length, the central radius of curvature of the object side surface and the central radius of curvature of the image side surface of the associated lenses satisfy the above-mentioned relational expressions, the telecentric lens 10 can have good optical performance and high magnification, and can meet the precise detection of the machine vision system, wherein the magnification can reach 3x.

[0027] The telecentric lens 10 of the present invention adopts an object-side telecentric design, and by arranging two sets of cemented achromatic lenses in the front group, the primary chromatic aberration can be effectively corrected. By rationally combining and composing the refractive power and materials of each optical lens, the aperture stop is arranged on the image-side focal plane of the optical system, and the incidence is located at infinity of the optical system, so that it can be ensured that the telecentric lens 10 has the same optical magnification within the depth of field even if the object distance changes. This realizes the object-side telecentric function of the telecentric lens 10, and provides the most accurate principle guarantee for visual applications that need to accurately calibrate and calculate the proportional relationship of the object image to meet the design requirements of high resolution, low distortion and elimination of chromatic aberration.

[0028] If the Abbe number of the third lens L3 is defined as v3 and the Abbe number of the fourth lens L4 is defined as v4, then the conditional formula 50.000≦v4-v3≦80.000 is satisfied, the difference between the Abbe number of the fourth lens L4 and the Abbe number of the third lens L3 is specified, and within the range of the conditional formula, the chromatic aberration of the system can be effectively corrected so that the chromatic aberration is |LC|≦2 μm.

[0029] If the optical length of the telecentric lens 10 is defined as TTL, then the conditional expression 2.000≦TTL / f≦5.000 is satisfied, and the overall length of the lens can be effectively controlled within the range of the conditional expression.

[0030] In this embodiment, the first lens L1 is made of a glass material, the second lens L2 is made of a glass material, the third lens L3 is made of a glass material, the fourth lens L4 is made of a glass material, the fifth lens L5 is made of a glass material, the sixth lens L6 is made of a glass material, the seventh lens L7 is made of a glass material, the eighth lens L8 is made of a glass material, and the ninth lens L9 is made of a glass material.

[0031] In this embodiment, the object side surface of the first lens L1 is a paraxially convex surface, and the image side surface of the first lens L1 is a paraxially convex surface, and the first lens L1 has a positive refractive power. In other optional embodiments, the object side surface and the image side surface of the first lens L1 may be arranged in other concave-convex distribution conditions, and the first lens L1 may have a negative refractive power.

[0032] If the focal length of the first lens L1 is defined as f1, the condition 0.54≦f1 / f≦1.95 is satisfied, and the refractive power is reasonably distributed, so that the system has excellent imaging quality and low sensitivity.

[0033] If the central radius of curvature of the object side surface of the first lens L1 is defined as R1 and the central radius of curvature of the image side surface of the first lens L1 is defined as R2, then the conditional formula -0.50≦(R1+R2) / (R1-R2)≦4.01 is satisfied, and by rationally controlling the shape of the first lens L1, the first lens can effectively correct the system spherical aberration.

[0034] If the axial thickness of the first lens L1 is defined as d1, the condition 0.04≦d1 / TTL≦0.06 is satisfied, which is advantageous for controlling the lens thickness and overall lens length.

[0035] In this embodiment, the object side surface of the second lens L2 is a paraxially convex surface, and the image side surface of the second lens L2 is a paraxially concave surface, and the second lens L2 has a positive refractive power. In other optional embodiments, the object side surface and the image side surface of the second lens L2 may be arranged in other concave-convex distribution conditions, and the second lens L2 may have a negative refractive power.

[0036] If the focal length of the second lens L2 is defined as f2, the conditional formula −1.95≦f2 / f≦1.70 is satisfied, and the refractive power is reasonably distributed, so that the system has excellent imaging quality and low sensitivity.

[0037] If the axial thickness of the second lens L2 is defined as d2, the conditional expression 0.01≦d3 / TTL≦0.05 is satisfied, which is advantageous for controlling the lens thickness and overall lens length.

[0038] In this embodiment, the object side surface of the third lens L3 is a paraxial convex surface, and the image side surface of the third lens L3 is a paraxial concave surface, and the third lens L3 has a negative refractive power. In other optional embodiments, the object side surface and the image side surface of the third lens L3 may be arranged in other concave-convex distribution situations, and the third lens L3 may have a positive refractive power.

[0039] If the focal length of the third lens L3 is defined as f3, the conditional formula -0.44≦f3 / f≦3.20 is satisfied, and the refractive power is reasonably distributed, so that the system has excellent imaging quality and low sensitivity.

[0040] If the central radius of curvature of the object side surface of the third lens L3 is defined as R5 and the central radius of curvature of the image side surface of the third lens L3 is defined as R6, then the conditional formula 1.44≦(R5+R6) / (R5-R6)≦8928.08 is satisfied, which defines the shape of the third lens L3. Within the range defined by the conditional formula, the degree of refraction of light passing through the lens can be mitigated, and aberration can be effectively reduced.

[0041] If the axial thickness of the third lens L3 is defined as d5, the conditional expression 0.00≦d5 / TTL≦0.02 is satisfied, which is advantageous for controlling the lens thickness and overall lens length.

[0042] In this embodiment, the object side surface of the fourth lens L4 is a paraxial convex surface, and the image side surface of the fourth lens L4 is a paraxial convex surface, and the fourth lens L4 has a positive refractive power. In other optional embodiments, the object side surface and the image side surface of the fourth lens L4 may be arranged in other concave-convex distribution conditions, and the fourth lens L4 may have a negative refractive power.

[0043] If the focal length of the fourth lens L4 is defined as f4, then the conditional formula 0.18≦f4 / f≦0.35 is satisfied, which specifies the ratio of the focal length f4 of the fourth lens L4 to the system focal length f. Within the range of the conditional formula, this is advantageous for improving the performance of the optical system.

[0044] If the central radius of curvature of the object side surface of the fourth lens L4 is defined as R7 and the central radius of curvature of the image side surface of the fourth lens L4 is defined as R8, the conditional expression -0.35≦(R7+R8) / (R7-R8)≦-0.10 is satisfied, which defines the shape of the fourth lens L4. Within the range defined by the conditional expression, it is possible to alleviate the degree of deflection of light rays passing through the lens, and effectively reduce aberration.

[0045] If the axial thickness of the fourth lens L4 is defined as d7, the conditional expression 0.01≦d7 / TTL≦0.05 is satisfied, which is advantageous for controlling the lens thickness and the overall lens length.

[0046] In this embodiment, the object side surface of the fifth lens L5 is a paraxial concave surface, and the image side surface of the fifth lens L5 is a paraxial concave surface, and the fifth lens L5 has a negative refractive power. In other optional embodiments, the object side surface and the image side surface of the fifth lens L5 may be arranged in other concave-convex distribution conditions, and the fifth lens L5 may have a positive refractive power.

[0047] If the focal length of the fifth lens L5 is defined as f5, then the conditional formula -0.25≦f5 / f≦-0.09 is satisfied, which specifies the ratio of the focal length f5 of the fifth lens L5 to the focal length f of the system, and is advantageous for improving the performance of the optical system.

[0048] If the central radius of curvature of the object side surface of the fifth lens L5 is defined as R9 and the central radius of curvature of the image side surface of the fifth lens L5 is defined as R10, the conditional formula 0.12≦(R9+R10) / (R9-R10)≦0.45 is satisfied, which defines the shape of the fifth lens L5. Within the range defined by the conditional formula, it is possible to reduce the degree of deflection of light passing through the lens, and effectively reduce aberration.

[0049] If the axial thickness of the fifth lens L5 is defined as d9, the conditional expression 0.00≦d9 / TTL≦0.03 is satisfied, which is advantageous for controlling the lens thickness and the overall lens length.

[0050] In this embodiment, the sixth lens L6 has a paraxially convex object side surface and a paraxially convex image side surface, and the sixth lens L6 has a positive refractive power. In other optional embodiments, the object side surface and the image side surface of the sixth lens L6 may be arranged in other concave-convex distribution conditions, and the sixth lens L6 may have a negative refractive power.

[0051] If the focal length of the sixth lens L6 is defined as f6, then the conditional formula 0.15≦f6 / f≦0.29 is satisfied, which specifies the ratio of the focal length f6 of the sixth lens L6 to the focal length f of the system. Within the range of the conditional formula, this is advantageous for improving the performance of the optical system.

[0052] If the central radius of curvature of the object side surface of the sixth lens L6 is defined as R11 and the central radius of curvature of the image side surface of the sixth lens L6 is defined as R12, the conditional formula -1.00≦(R11+R12) / (R11-R12)≦-0.33 is satisfied, which defines the shape of the sixth lens L6. Within the range defined by the conditional formula, it is possible to reduce the degree of deflection of light passing through the lens, and effectively reduce aberration.

[0053] If the axial thickness of the sixth lens L6 is defined as d11, the condition 0.01≦d11 / TTL≦0.06 is satisfied, which is advantageous for controlling the lens thickness and the overall lens length.

[0054] In this embodiment, the seventh lens L7 has a paraxially concave object side surface and a paraxially convex image side surface, and the seventh lens L7 has a positive refractive power. In other optional embodiments, the object side surface and the image side surface of the seventh lens L7 may be arranged in other concave-convex distribution conditions, and the seventh lens L7 may have a negative refractive power.

[0055] If the focal length of the seventh lens L7 is defined as f7, then the conditional formula 0.10≦f7 / f≦0.95 is satisfied, which specifies the ratio of the focal length f7 of the seventh lens L7 to the focal length f of the system, and is advantageous for improving the performance of the optical system within the range of the conditional formula.

[0056] If the central radius of curvature of the object side surface of the seventh lens L7 is defined as R13 and the central radius of curvature of the image side surface of the seventh lens L7 is defined as R14, then the conditional formula -2.80≦(R13+R14) / (R13-R14)≦2.10 is satisfied. This conditional formula defines the shape of the seventh lens L7, and within the range defined by the conditional formula, the degree of deflection of light passing through the lens can be alleviated, and aberration can be effectively reduced.

[0057] If the axial thickness of the seventh lens L7 is defined as d13, the conditional expression 0.00≦d13 / TTL≦0.06 is satisfied, which is advantageous for controlling the lens thickness and the overall lens length.

[0058] In this embodiment, the object side surface of the eighth lens L8 is a paraxial concave surface, and the image side surface of the eighth lens L8 is a paraxial concave surface, and the eighth lens L8 has a negative refractive power. In other optional embodiments, the object side surface and the image side surface of the eighth lens L8 may be arranged in other concave-convex distribution situations, and the eighth lens L8 may have a positive refractive power.

[0059] If the central radius of curvature of the object side surface of the eighth lens L8 is defined as R15 and the central radius of curvature of the image side surface of the eighth lens L8 is defined as R16, then the conditional formula -2.00≦(R15+R16) / (R15-R16)≦0.16 is satisfied. This conditional formula defines the shape of the eighth lens L8, and within the range defined by the conditional formula, the degree of deflection of light passing through the lens can be alleviated, and aberration can be effectively reduced.

[0060] If the axial thickness of the eighth lens L8 is defined as d15, the conditional expression 0.00≦d15 / TTL≦0.03 is satisfied, which is advantageous for controlling the lens thickness and the overall lens length.

[0061] In this embodiment, the object side surface of the ninth lens L9 is a paraxially convex surface, and the image side surface of the ninth lens L9 is a paraxially convex surface, and the ninth lens L9 has a positive refractive power. In other optional embodiments, the object side surface and the image side surface of the ninth lens L9 may be arranged in other concave-convex distribution conditions, and the ninth lens L9 may have a negative refractive power.

[0062] If the focal length of the ninth lens L9 is defined as f9, then the conditional formula 0.64≦f9 / f≦2.97 is satisfied, which specifies the ratio of the focal length f9 of the ninth lens L9 to the focal length f of the system, and is advantageous for improving the performance of the optical system within the range of the conditional formula.

[0063] If the central radius of curvature of the object side surface of the ninth lens L9 is defined as R17 and the central radius of curvature of the image side surface of the ninth lens L9 is defined as R18, then the conditional formula -32.02≦(R17+R18) / (R17-R18)≦2.00 is satisfied. This conditional formula defines the shape of the ninth lens L9, and within the range defined by the conditional formula, the degree of deflection of light passing through the lens can be alleviated, and aberration can be effectively reduced.

[0064] If the axial thickness of the ninth lens L9 is defined as d17, the condition 0.01≦d17 / TTL≦0.08 is satisfied, which is advantageous for controlling the lens thickness and the overall lens length.

[0065] The telecentric lens 10 of the present invention will be described below using examples. The symbols used in each example indicate the following: The focal length, axial distance, central radius of curvature, and axial thickness are all in mm.

[0066] TTL: Optical length (the axial distance from the object side of the first lens L1 to the image plane) in mm.

[0067] Preferably, an inflection point and / or a stationary point may be further set on the object side and / or image side of the lens to meet the demand for high quality imaging, and a specific embodiment is given below.

[0068] Table 1 shows design data of the telecentric lens 10 according to the first embodiment of the present invention.

[0069] [Table 1]

[0070] The meanings of the symbols are as follows: S1: Aperture OBJ: object plane BS: Dichroic prism Gn: nth lens R: Radius of curvature of the center of the optical surface R1: The central radius of curvature of the object side of the first lens L1 R2: Radius of curvature of the center of the image side of the first lens L1 R3: The central radius of curvature of the object side of the second lens L2 R4: Radius of curvature of the center of the image side of the second lens L2 R5: The central radius of curvature of the object side of the third lens L3 R6: The central radius of curvature of the image side of the third lens L3 R7: The central radius of curvature of the object side of the fourth lens L4 R8: The central radius of curvature of the image side of the fourth lens L4 R9: The central radius of curvature of the object side of the fifth lens L5 R10: Radius of central curvature of the image side of the fifth lens L5 R11: The central radius of curvature of the object side of the sixth lens L6 R12: Radius of curvature of the center of the image side of the sixth lens L6 R13: The central radius of curvature of the object side of the seventh lens L7 R14: Radius of curvature of the center of the image side of the seventh lens L7 R15: Radius of curvature of the center of the object side of the eighth lens L8 R16: Radius of curvature of the center of the image side of the eighth lens L8 R17: The central curvature radius of the object side of the ninth lens L9 R18: Radius of curvature of the center of the image side of the ninth lens L9 d: Axial thickness of the lens or axial distance between lenses dOBJ(WD): The axial distance from the object plane OBJ to the object side of the first lens L1 d1: Axial thickness of the first lens L1 d2: The axial distance from the image side surface of the first lens L1 to the object side surface of the second lens L2 d3: Axial thickness of the second lens L2 d4: The axial distance from the image side surface of the second lens L2 to the object side surface of the third lens L3 d5: Axial thickness of the third lens L3 d6: The axial distance from the image side surface of the third lens L3 to the object side surface of the fourth lens L4 d7: Axial thickness of the fourth lens L4 d8: The axial distance from the image side surface of the fourth lens L4 to the object side surface of the fifth lens L5 d9: Axial thickness of the fifth lens L5 d10: the axial distance from the image side surface of the fifth lens L5 to the object side surface of the sixth lens L6 d11: Axial thickness of the sixth lens L6 d11-BS: The axial distance from the image side of the sixth lens L6 to the object side of the dichroic prism BS dBS: Axial thickness of dichroic prism BS dBS-S1: Axial distance from the image side of the dichroic prism BS to the aperture stop S1 dS1-13: Axial distance from aperture S1 to the image side of the seventh lens L7 d13: Axial thickness of the seventh lens L7 d14: Axial distance from the image side surface of the seventh lens L7 to the object side surface of the eighth lens L8 d15: Axial thickness of the eighth lens L8 d16: The axial distance from the image side surface of the eighth lens L8 to the object side surface of the ninth lens L9 d17: Axial thickness of the ninth lens L9 d18: Axial distance from the image side of the ninth lens L9 to the image plane Si nd: Refractive index of d line nd1: refractive index of the d line of the first lens L1 nd2: refractive index of the d line of the second lens L2 nd3: refractive index of the d line of the third lens L3 nd4: Refractive index of the d line of the fourth lens L4 nd5: refractive index of the d line of the fifth lens L5 nd6: Refractive index of the d line of the sixth lens L6 nd7: Refractive index of the d line of the seventh lens L7 nd8: Refractive index of the d line of the eighth lens L8 nd9: refractive index of the d line of the ninth lens L9 vd: Abbe number v1: Abbe number of the first lens L1 v2: Abbe number of the second lens L2 v3: Abbe number of the third lens L3 v4: Abbe number of the fourth lens L4 v5: Abbe number of the fifth lens L5 v6: Abbe number of the sixth lens L6 v7: Abbe number of the seventh lens L7 v8: Abbe number of the eighth lens L8 v9: Abbe number of the ninth lens L9

[0071] Fig. 2 and Fig. 3 are schematic diagrams showing the axial chromatic aberration and lateral chromatic aberration of light having wavelengths of 660 nm, 546 nm, and 460 nm, respectively, after passing through the telecentric lens 10 according to the first embodiment. Fig. 4 is a schematic diagram showing the field curvature and distortion aberration of light having wavelength of 546 nm after passing through the telecentric lens 10 according to the first embodiment, where the field curvature S in Fig. 4 is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0072] Table 8 below shows values ​​corresponding to the parameters defined by various numerical values ​​and conditional expressions in each of the first, second, third, fourth, fifth, sixth and seventh embodiments.

[0073] As shown in Table 8, the first embodiment satisfies each of the conditional expressions.

[0074] In this embodiment, the entrance pupil diameter of the telecentric lens is 4633.628 mm, the image height of the full field of view is 18.5 mm, and the numerical aperture is 0.13, which has good optical performance and high magnification, and can meet the precise detection of the machine vision system.

[0075] Second embodiment The second embodiment is basically the same as the first embodiment, and the symbols have the same meanings as in the first embodiment, so only the differences will be described below.

[0076] Table 2 shows design data of the telecentric lens 20 according to the second embodiment of the present invention.

[0077] [Table 2]

[0078] Fig. 6 and Fig. 7 are schematic diagrams showing the axial chromatic aberration and lateral chromatic aberration of light having wavelengths of 660 nm, 546 nm, and 460 nm, respectively, after passing through the telecentric lens 20 according to the second embodiment. Fig. 8 is a schematic diagram showing the field curvature and distortion aberration of light having wavelength of 546 nm after passing through the telecentric lens 20 according to the second embodiment, where the field curvature S in Fig. 8 is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0079] Table 8 below shows values ​​corresponding to the parameters defined by various numerical values ​​and conditional expressions in each of the first, second, third, fourth, fifth, sixth and seventh embodiments.

[0080] As shown in Table 8, the second embodiment satisfies each of the conditional expressions.

[0081] In this embodiment, the entrance pupil diameter of the telecentric lens is 5000.248 mm, the image height in the full field of view is 18.5 mm, and the field angle in the diagonal direction is 0.01°, providing good optical performance.

[0082] Third embodiment The third embodiment is basically the same as the first embodiment, and the symbols have the same meanings as in the first embodiment, so only the differences will be described below.

[0083] In this embodiment, the seventh lens L7 has an object side surface that is convex on the paraxial direction, and the ninth lens L9 has an image side surface that is concave on the paraxial direction.

[0084] Table 3 shows design data of the telecentric lens 30 according to the third embodiment of the present invention.

[0085] [Table 3]

[0086] Fig. 10 and Fig. 11 are schematic diagrams showing the axial chromatic aberration and the chromatic aberration of magnification after light of wavelengths 660 nm, 546 nm, and 460 nm has passed through the telecentric lens 30 according to the third embodiment. Fig. 12 is a schematic diagram showing the field curvature and distortion aberration after light of wavelength 546 nm has passed through the telecentric lens 30 according to the third embodiment, where the field curvature S in Fig. 12 is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0087] Table 8 below shows values ​​corresponding to the parameters defined by various numerical values ​​and conditional expressions in each of the first, second, third, fourth, fifth, sixth and seventh embodiments.

[0088] As shown in Table 8, the third embodiment satisfies each of the conditional expressions.

[0089] In this embodiment, the entrance pupil diameter of the telecentric lens is 3592.504 mm, the image height in the full field of view is 18.5 mm, and the angle of view in the diagonal direction is 0.03°, providing good optical performance.

[0090] (Fourth embodiment) The fourth embodiment is basically the same as the first embodiment, and the symbols have the same meanings as in the first embodiment, so only the differences will be described below.

[0091] In this embodiment, the seventh lens L7 has an object side surface that is convex paraxially.

[0092] Table 4 shows design data for the telecentric lens 40 according to the fourth embodiment of the present invention.

[0093] [Table 4]

[0094] Fig. 14 and Fig. 15 are schematic diagrams showing the axial chromatic aberration and lateral chromatic aberration of light having wavelengths of 660 nm, 546 nm, and 460 nm, respectively, after passing through the telecentric lens 40 according to the fourth embodiment. Fig. 16 is a schematic diagram showing the field curvature and distortion aberration of light having wavelength of 546 nm after passing through the telecentric lens 40 according to the fourth embodiment, where the field curvature S in Fig. 16 is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0095] Table 8 below shows values ​​corresponding to the parameters defined by various numerical values ​​and conditional expressions in each of the first, second, third, fourth, fifth, sixth and seventh embodiments.

[0096] As shown in Table 8, the fourth embodiment satisfies each of the conditional expressions.

[0097] In this embodiment, the entrance pupil diameter of the telecentric lens is 3820.700 mm, the image height in the full field of view is 18.5 mm, and the angle of view in the diagonal direction is 0.02°, providing good optical performance.

[0098] Fifth embodiment The fifth embodiment is basically the same as the first embodiment, and the symbols have the same meanings as in the first embodiment, so only the differences will be described below.

[0099] In this embodiment, the seventh lens L7 has a paraxially convex object side surface, the seventh lens L7 has a paraxially concave image side surface, and the ninth lens L9 has a paraxially concave object side surface.

[0100] Table 5 shows design data for the telecentric lens 50 according to the fifth embodiment of the present invention.

[0101] [Table 5]

[0102] Fig. 18 and Fig. 19 are schematic diagrams showing the axial chromatic aberration and lateral chromatic aberration of light having wavelengths of 660 nm, 546 nm, and 460 nm, respectively, after passing through the telecentric lens 50 according to the fifth embodiment. Fig. 20 is a schematic diagram showing the field curvature and distortion aberration of light having wavelength of 546 nm after passing through the telecentric lens 50 according to the fifth embodiment, where the field curvature S in Fig. 20 is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0103] Table 8 below shows values ​​corresponding to the parameters defined by various numerical values ​​and conditional expressions in each of the first, second, third, fourth, fifth, sixth and seventh embodiments.

[0104] As shown in Table 8, the fifth embodiment satisfies each of the conditional expressions.

[0105] In this embodiment, the entrance pupil diameter of the telecentric lens is 25971.381 mm, the image height in the full field of view is 18.5 mm, and the field angle in the diagonal direction is 0.00°, providing good optical performance.

[0106] Sixth embodiment The sixth embodiment is basically the same as the first embodiment, and the symbols have the same meanings as in the first embodiment, so only the differences will be described below.

[0107] In this embodiment, the first lens L1 has an object side surface that is concave paraxially, the eighth lens L8 has an image side surface that is convex paraxially, the ninth lens L9 has an object side surface that is concave paraxially, the second lens L2 has negative refractive power, and the third lens L3 has positive refractive power.

[0108] Table 6 shows design data for the telecentric lens 60 according to the sixth embodiment of the present invention.

[0109] [Table 6]

[0110] Fig. 22 and Fig. 23 are schematic diagrams showing the axial chromatic aberration and the chromatic aberration of magnification after light of wavelengths 660 nm, 546 nm, and 460 nm has passed through the telecentric lens 30 according to the sixth embodiment. Fig. 24 is a schematic diagram showing the field curvature and distortion aberration after light of wavelength 546 nm has passed through the telecentric lens 20 according to the sixth embodiment, where the field curvature S in Fig. 24 is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0111] Table 8 below shows values ​​corresponding to the parameters defined by various numerical values ​​and conditional expressions in each of the first, second, third, fourth, fifth, sixth and seventh embodiments.

[0112] As shown in Table 8, the sixth embodiment satisfies each of the conditional expressions.

[0113] In this embodiment, the entrance pupil diameter of the telecentric lens is 2624.704 mm, the image height in the full field of view is 18.5 mm, and the angle of view in the diagonal direction is 0.03°, providing good optical performance.

[0114] Seventh embodiment

[0115] The seventh embodiment is basically the same as the first embodiment, and the symbols have the same meanings as in the first embodiment, so only the differences will be described below.

[0116] Table 7 shows design data for the telecentric lens 70 according to the seventh embodiment of the present invention.

[0117] [Table 7]

[0118] Fig. 26 and Fig. 27 are schematic diagrams showing the axial chromatic aberration and lateral chromatic aberration of light having wavelengths of 660 nm, 546 nm, and 460 nm, respectively, after passing through the telecentric lens 70 according to the seventh embodiment. Fig. 28 is a schematic diagram showing the field curvature and distortion aberration of light having wavelength of 546 nm after passing through the telecentric lens 70 according to the seventh embodiment, where the field curvature S in Fig. 28 is the field curvature in the sagittal direction, and T is the field curvature in the tangential direction.

[0119] Table 8 below shows values ​​corresponding to the parameters defined by various numerical values ​​and conditional expressions in each of the first, second, third, fourth, fifth, sixth and seventh embodiments.

[0120] As shown in Table 8, the seventh embodiment satisfies each of the conditional expressions.

[0121] In this embodiment, the entrance pupil diameter of the telecentric lens is 4516.334 mm, the image height in the full field of view is 18.5 mm, and the angle of view in the diagonal direction is 0.02°, providing good optical performance.

[0122] [Table 8]

[0123] The above is merely an embodiment of the present invention, and those skilled in the art may make modifications without departing from the spirit of the present invention, all of which are within the scope of protection of the present invention.

Claims

1. A telecentric lens, The optical system is constituted by, in order from the object side to the image side, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens, a focal length of the telecentric lens being f, a refractive index of the second lens being n2, a central radius of curvature of the object side surface of the second lens being R3, a central radius of curvature of the image side surface of the second lens being R4, a focal length of the eighth lens being f8, a working distance of the telecentric lens being WD, and a numerical aperture of the telecentric lens being NA, the following conditional expressions (1) to (4) are satisfied: 1.980≦n2≦2.300 (1) -0.600≦f8 / f≦-0.050 (2) 0.600≦R4 / R3≦4.000 (3) 0.145≦NA*f / WD≦0.220 (4)

2. 2. The telecentric lens according to claim 1, wherein the following conditional expression (5) is satisfied, where v3 is the Abbe number of the third lens and v4 is the Abbe number of the fourth lens: 50.000≦v4−v3≦80.000 (5)

3. 2. The telecentric lens according to claim 1, wherein the following conditional expression (6) is satisfied, where TTL is an optical length of the telecentric lens: 2.000≦TTL / f≦5.000 (6)

4. the first lens has a positive refractive power, and an image side surface of the first lens is convex on a paraxial line; The telecentric lens according to claim 1, characterized in that the following conditional expressions (7) to (9) are satisfied when a focal length of the first lens is f1, a central radius of curvature of an object-side surface of the first lens is R1, a central radius of curvature of an image-side surface of the first lens is R2, an axial thickness of the first lens is d1, and an optical length of the telecentric lens is TTL. 0.54≦f1 / f≦1.95 (7) -0.50≦(R1+R2) / (R1-R2)≦4.01 (8) 0.04≦d1 / TTL≦0.06 (9)

5. an object side surface of the second lens is a paraxially convex surface, and an image side surface of the second lens is a paraxially concave surface; The telecentric lens according to claim 1, characterized in that the following conditional expressions (10) and (11) are satisfied when the focal length of the second lens is f2, the axial thickness of the second lens is d3, and the optical length of the telecentric lens is TTL. −1.95≦f2 / f≦1.70 (10) 0.01≦d3 / TTL≦0.05 (11)

6. an object side surface of the third lens is a paraxially convex surface, and an image side surface of the third lens is a paraxially concave surface, The telecentric lens according to claim 1, characterized in that the following conditional expressions (12) to (14) are satisfied when a focal length of the third lens is f3, a central radius of curvature of an object-side surface of the third lens is R5, a central radius of curvature of an image-side surface of the third lens is R6, an axial thickness of the third lens is d5, and an optical length of the telecentric lens is TTL. −0.44≦f3 / f≦3.20 (12) 1.44≦(R5+R6) / (R5-R6)≦8928.08 (13) 0.00≦d5 / TTL≦0.02 (14)

7. the fourth lens has positive refractive power, an object side surface of the fourth lens is a convex surface on a paraxial line, and an image side surface of the fourth lens is a convex surface on a paraxial line, The telecentric lens according to claim 1, characterized in that the following conditional expressions (15) to (17) are satisfied when a focal length of the fourth lens is f4, a central radius of curvature of an object-side surface of the fourth lens is R7, a central radius of curvature of an image-side surface of the fourth lens is R8, an axial thickness of the fourth lens is d7, and an optical length of the telecentric lens is TTL. 0.18≦f4 / f≦0.35 (15) -0.35≦(R7+R8) / (R7-R8)≦-0.10 (16) 0.01≦d7 / TTL≦0.05 (17)

8. the fifth lens has negative refractive power, an object side surface of the fifth lens is a paraxial concave surface, and an image side surface of the fifth lens is a paraxial concave surface; The telecentric lens according to claim 1, characterized in that the following conditional expressions (18) to (20) are satisfied when a focal length of the fifth lens is f5, a central radius of curvature of an object-side surface of the fifth lens is R9, a central radius of curvature of an image-side surface of the fifth lens is R10, an axial thickness of the fifth lens is d9, and an optical length of the telecentric lens is TTL. −0.25≦f5 / f≦−0.09 (18) 0.12≦(R9+R10) / (R9-R10)≦0.45 (19) 0.00≦d9 / TTL≦0.03 (20)

9. the sixth lens has positive refractive power, an object side surface of the sixth lens is a convex surface on a paraxial line, and an image side surface of the sixth lens is a convex surface on a paraxial line, The telecentric lens according to claim 1, characterized in that the following conditional expressions (21) to (23) are satisfied when a focal length of the sixth lens is f6, a central radius of curvature of an object side surface of the sixth lens is R11, a central radius of curvature of an image side surface of the sixth lens is R12, an axial thickness of the sixth lens is d11, and an optical length of the telecentric lens is TTL. 0.15≦f6 / f≦0.29 (21) -1.00≦(R11+R12) / (R11-R12)≦-0.33 (22) 0.01≦d11 / TTL≦0.06 (23)

10. the seventh lens has a positive refractive power, The telecentric lens according to claim 1, characterized in that the following conditional expressions (24) to (26) are satisfied when a focal length of the seventh lens is f7, a central radius of curvature of a surface of the seventh lens on the object side is R13, a central radius of curvature of a surface of the seventh lens on the image side is R14, an axial thickness of the seventh lens is d13, and an optical length of the telecentric lens is TTL. 0.10≦f7 / f≦0.95 (24) -2.80≦(R13+R14) / (R13-R14)≦2.10 (25) 0.00≦d13 / TTL≦0.06 (26)

11. the eighth lens has negative refractive power, and an object side surface of the eighth lens is a paraxial concave surface; The telecentric lens according to claim 1, characterized in that, when a central radius of curvature of an object-side surface of the eighth lens is R15, a central radius of curvature of an image-side surface of the eighth lens is R16, an axial thickness of the eighth lens is d15, and an optical length of the telecentric lens is TTL, the following conditional expressions (27) and (28) are satisfied. -2.00≦(R15+R16) / (R15-R16)≦0.16 (27) 0.00≦d15 / TTL≦0.03 (28)

12. the ninth lens has a positive refractive power, The telecentric lens according to claim 1, characterized in that the following conditional expressions (29) to (31) are satisfied when a focal length of the 9th lens is f9, a central radius of curvature of an object side surface of the 9th lens is R17, a central radius of curvature of an image side surface of the 9th lens is R18, an axial thickness of the 8th lens is d17, and an optical length of the telecentric lens is TTL. 0.64≦f9 / f≦2.97 (29) -32.02≦(R17+R18) / (R17-R18)≦2.00 (30) 0.01≦d17 / TTL≦0.08 (31)

13. 2. The telecentric lens according to claim 1, wherein the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, and the ninth lens are all made of a glass material.

Images