Athermal lens for visible light imaging

Abstract

The invention relates to an athermalization lens for visible light imaging, and relates to the field of optical elements. Comprising a first lens with a convex object-side surface, a second lens with a convex object-side surface, a third lens with a convex object-side surface, a fourth lens with a concave object-side surface, a fifth lens with a convex object-side surface, a sixth lens with a convex object-side surface and a seventh lens with a convex object-side surface, all the lenses are glass spherical lenses, all the lenses except the fourth lens and the fifth lens are arranged at intervals, the light output end side of the seventh lens is provided with an imaging side, and the optical system has the advantages that the optical system can achieve high-quality clear imaging at low cost in a wide temperature range without a compensation mechanism.

Description

Technical Field

[0001] This invention relates to the field of optical element technology, and in particular to a thermalized lens for visible light imaging. Background Technology

[0002] With the development of optical lens technology, the market demands for optical lenses are becoming increasingly stringent. Temperature changes can cause the optimal image plane of an optical system to deviate, reducing image quality and affecting lens performance. The urgent need for stable imaging performance across all temperatures in outdoor, automotive, aviation, and security applications is a necessary development for optical systems to cope with complex thermal environments. An anechoic lens is a lens that can effectively reduce or eliminate changes in parameters such as focal length and image plane position caused by temperature variations within a certain temperature range, thereby maintaining relatively stable image quality. To achieve the anechoic effect, anechoic lenses typically require a special temperature compensation structure, which is not only complex and costly, but also inefficient to assemble, increasing the overall weight and size of the lens and making it inconvenient to use.

[0003] Therefore, to address the above shortcomings, there is a need to provide a thermal-free lens for visible light imaging. Summary of the Invention

[0004] (a) Technical problems to be solved The technical problem to be solved by this invention is how to reduce costs while ensuring high-quality imaging.

[0005] (II) Technical Solution To address the aforementioned technical problems, this invention provides a thermal-free lens for visible light imaging, comprising a first lens with a convex object side, a second lens with a convex object side, a third lens with a convex object side, a fourth lens with a concave object side, a fifth lens with a convex object side, a sixth lens with a convex object side, and a seventh lens with a convex object side, arranged sequentially along the light propagation direction. All lenses are glass spherical lenses, and all lenses except the fourth and fifth lenses, which are cemented together, are arranged at intervals. The seventh lens has an imaging side on its light output end.

[0006] As a further explanation of the present invention, preferably, the first lens has positive optical power, the second lens has negative optical power, the third lens has positive optical power, the fourth lens has negative optical power, the fifth lens has positive optical power, the sixth lens has negative optical power, and the seventh lens has positive optical power.

[0007] As a further explanation of the present invention, preferably, the front and rear surface curvatures of the first lens are 30.349 and 321.202, respectively; the front and rear surface curvatures of the second lens are 25.214 and 13.500, respectively; the front and rear surface curvatures of the third lens are 16.288 and 50.767, respectively; the front and rear surface curvatures of the fourth lens are -325.106 and 17.720, respectively; the front and rear surface curvatures of the fifth lens are 17.720 and 29.334, respectively; the front and rear surface curvatures of the sixth lens are 21.379 and 292.143, respectively; and the front and rear surface curvatures of the seventh lens are 9.134 and 6.555, respectively.

[0008] As a further explanation of the present invention, preferably, the center thickness of the first lens is 4.500 mm; the center thickness of the second lens is 1.983 mm; the center thickness of the third lens is 3.000 mm; the center thickness of the fourth lens is 1.846 mm; the center thickness of the fifth lens is 2.777 mm; the center thickness of the sixth lens is 2.500 mm; and the center thickness of the seventh lens is 2.708 mm.

[0009] As a further explanation of the present invention, preferably, the center-to-center distance between the first lens and the second lens is 0.640 mm; the center-to-center distance between the second lens and the third lens is 0.722 mm; the center-to-center distance between the third lens and the fourth lens is 3.50 mm; the center-to-center distance between the fifth lens and the sixth lens is 10.602 mm; the center-to-center distance between the sixth lens and the seventh lens is 0.501 mm; and the center distance between the seventh lens and the imaging side is 14.311 mm.

[0010] As a further explanation of the present invention, preferably, the material of the first lens is H-ZK11; the material of the second lens is H-ZLAF53B; the material of the third lens is H-LAF3B; the material of the fourth lens is H-ZF7LAGT; the material of the fifth lens is H-LAF3B; the material of the sixth lens is H-LAF3B; and the material of the seventh lens is H-ZLAF53B.

[0011] As a further explanation of the present invention, preferably, the total length of the lens system is 50mm, the effective focal length is 40mm, the F number is 2, and the full field of view is 2ω=8.9°.

[0012] As a further explanation of the present invention, preferably, the anechoic temperature range of the lens is -40°C to 60°C.

[0013] (III) Beneficial Effects The above-described technical solution of the present invention has the following advantages: This invention employs an optimized double-Gaussian structure and high-refractive-index materials to effectively reduce optical system aberrations. This results in an MTF greater than 0.3 across the entire field of view within the range of -40℃ to 60℃, achieving a resolution suitable for 3.45μm detector pixels, under conditions of F-number 2, aperture 20mm, and focal length 40mm. Furthermore, all lenses used in the lens are made of glass spherical lenses, offering low cost and high performance-to-price ratio. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the lens distribution of the present invention; Figure 2 This is the MTF plot of the present invention at -40°C; Figure 3 This is the MTF plot of the present invention at 20°C; Figure 4 This is the MTF diagram of the present invention at 60°C.

[0015] In the diagram: 1. First lens; 2. Second lens; 3. Third lens; 4. Fourth lens; 5. Fifth lens; 6. Sixth lens; 7. Seventh lens; 8. Imaging side. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] A thermal-free lens for visible light imaging, such as Figure 1 As shown, the lens includes a first lens 1 with a convex object side, a second lens 2 with a convex object side, a third lens 3 with a convex object side, a fourth lens 4 with a concave object side, a fifth lens 5 with a convex object side, a sixth lens 6 with a convex object side, and a seventh lens 7 with a convex object side, arranged sequentially along the direction of light propagation. The seventh lens 7 has an imaging side 8 on its light output end.

[0018] like Figure 1As shown, all lenses are glass spherical lenses. The front and rear surface curvatures of the first lens 1 are 30.349 and 321.202, respectively; the front and rear surface curvatures of the second lens 2 are 25.214 and 13.500, respectively; the front and rear surface curvatures of the third lens 3 are 16.288 and 50.767, respectively; the front and rear surface curvatures of the fourth lens 4 are -325.106 and 17.720, respectively; the front and rear surface curvatures of the fifth lens 5 are 17.720 and 29.334, respectively; the front and rear surface curvatures of the sixth lens 6 are 21.379 and 292.143, respectively; and the front and rear surface curvatures of the seventh lens 7 are 9.134 and 6.555, respectively.

[0019] like Figure 1 As shown, the first lens 1 has positive optical power and a center thickness of 4.500 mm; the second lens 2 has negative optical power and a center thickness of 1.983 mm; the third lens 3 has positive optical power and a center thickness of 3.000 mm; the fourth lens 4 has negative optical power and a center thickness of 1.846 mm; the fifth lens 5 has positive optical power and a center thickness of 2.777 mm; the sixth lens 6 has negative optical power and a center thickness of 2.500 mm; and the seventh lens 7 has positive optical power and a center thickness of 2.708 mm.

[0020] like Figure 1 As shown, all lenses except the fourth lens 4 and the fifth lens 5 are cemented together and arranged at intervals. The center-to-center interval between the first lens 1 and the second lens 2 is 0.640 mm; the center-to-center interval between the second lens 2 and the third lens 3 is 0.722 mm; the center-to-center interval between the third lens 3 and the fourth lens 4 is 3.50 mm; the center-to-center interval between the fifth lens 5 and the sixth lens 6 is 10.602 mm; the center-to-center interval between the sixth lens 6 and the seventh lens 7 is 0.501 mm; and the center-to-center distance between the seventh lens 7 and the imaging side 8 is 14.311 mm.

[0021] Furthermore, the material of the first lens 1 is H-ZK11; the material of the second lens 2 is H-ZLAF53B; the material of the third lens 3 is H-LAF3B; the material of the fourth lens 4 is H-ZF7LAGT; the material of the fifth lens 5 is H-LAF3B; the material of the sixth lens 6 is H-LAF3B; and the material of the seventh lens 7 is H-ZLAF53B. The system uses only four lens materials, greatly reducing the complexity of the lens manufacturing process and lowering costs.

[0022] like Figure 1 As shown, the lens system has a total length of 50mm, an effective focal length of 40mm, an F-number of 2, and a full field of view of 2ω = 8.9°. This invention optimizes the system using an evaluation function, such as... Figure 2 As shown, the MTF of the optical system at 145 lp / mm is greater than 0.3 at -40℃. Figure 3 As shown, at 20℃ and 145 lp / mm, the MTF is greater than 0.3, as... Figure 4 As shown, the MTF is greater than 0.3 at 145 lp / mm at 60℃.

[0023] In summary, this invention designs an athermal visible light lens comprising eight lenses and one cemented doublet lens group, effectively reducing optical system aberrations by employing an optimized double Gaussian structure and high-refractive-index materials. This allows the lens to achieve an MTF greater than 0.3 across the entire field of view within the temperature range of -40℃ to 60℃, under conditions of F-number 2, aperture 20mm, and focal length 40mm, enabling it to match detector pixels of 3.45μm.

[0024] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An athermalized lens for visible light imaging, characterized in that: It comprises first lens (1) with convex object side, second lens (2) with convex object side, third lens (3) with convex object side, fourth lens (4) with concave object side, fifth lens (5) with convex object side, sixth lens (6) with convex object side and seventh lens (7) with convex object side, all lenses are glass spherical lenses, all lenses are arranged apart from each other except that fourth lens (4) and fifth lens (5) are cemented, and seventh lens (7) is provided with imaging side (8) on the light output end side.

2. An athermalized lens for visible light imaging according to claim 1, characterized in that: First lens (1) has positive focal power, second lens (2) has negative focal power, third lens (3) has positive focal power, fourth lens (4) has negative focal power, fifth lens (5) has positive focal power, sixth lens (6) has negative focal power, and seventh lens (7) has positive focal power.

3. An athermalized lens for visible light imaging according to claim 2, characterized in that: The front and back surface curvatures of first lens (1) are 30.349 and 321.202 respectively, the front and back surface curvatures of second lens (2) are 25.214 and 13.500 respectively, the front and back surface curvatures of third lens (3) are 16.288 and 50.767 respectively, the front and back surface curvatures of fourth lens (4) are -325.106 and 17.720 respectively, the front and back surface curvatures of fifth lens (5) are 17.720 and 29.334 respectively, the front and back surface curvatures of sixth lens (6) are 21.379 and 292.143 respectively, and the front and back surface curvatures of seventh lens (7) are 9.134 and 6.555 respectively.

4. An athermalized lens for visible light imaging according to claim 3, characterized in that: The center thickness of first lens (1) is 4.500mm, the center thickness of second lens (2) is 1.983mm, the center thickness of third lens (3) is 3.000mm, the center thickness of fourth lens (4) is 1.846mm, the center thickness of fifth lens (5) is 2.777mm, the center thickness of sixth lens (6) is 2.500mm, and the center thickness of seventh lens (7) is 2.708mm.

5. An athermalized lens for visible light imaging according to claim 4, characterized in that: The center distance between first lens (1) and second lens (2) is 0.640mm, the center distance between second lens (2) and third lens (3) is 0.722mm, the center distance between third lens (3) and fourth lens (4) is 3.50mm, the center distance between fifth lens (5) and sixth lens (6) is 10.602mm, the center distance between sixth lens (6) and seventh lens (7) is 0.501mm, and the center distance between seventh lens (7) and imaging side (8) is 14.311mm.

6. An athermalized lens for visible light imaging according to claim 5, characterized in that: The material of first lens (1) is H-ZK11, the material of second lens (2) is H-ZLAF53B, the material of third lens (3) is H-LAF3B, the material of fourth lens (4) is H-ZF7LAGT; The material of fifth lens (5) is H-LAF3B, the material of sixth lens (6) is H-LAF3B, and the material of seventh lens (7) is H-ZLAF53B.

7. An athermalized lens for visible light imaging according to claim 6, characterized in that: The total length of lens system is 50mm, the effective focal length is 40mm, the F number is 2, and the full field angle 2ω is 8.9°.

8. An athermalized lens for visible light imaging according to claim 7, characterized in that: The temperature range of the athermalization of the lens is -40°C to 60°C.

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