Infrared optical lens for image matching

Abstract

The invention relates to the technical field of infrared optical lenses, in particular to an infrared optical lens for image matching. According to the infrared optical lens for image matching, in a limited space range, a four-piece structure is adopted, germanium and chalcogenide glass are matched, an aspheric surface and a diffraction surface are adopted to complete optical passive athermalization from-45 DEG C to + 80 DEG C, f is 4.5 mm, D / F is 1.0, a 640 * 512 and 12-micron detector is adapted, the field angle 2w is 95.2 degrees, and distortion is controlled within 3%.

Description

Technical Field

[0001] The invention relates to the technical field of infrared optical lenses, and in particular to an infrared optical lens for image matching. Background Art

[0002] With the development of modern technology, due to the long range and high hit rate of aircraft outside the defense zone, as the demand scenarios increase, it is currently proposed to achieve navigation silence in a certain range segment and use guidance optics to achieve image matching. Therefore, the infrared optical lens of the optical cabin of the outside defense zone seeker has a large field of view and small distortion, and at the same time, the volume and weight should be small, and the window area should be small. The technical problem to be solved by this patent is to achieve a large field of view, small distortion, small volume and light weight of the infrared optical lens within a limited space.

[0003] In the existing public technology, CN103543515B provides a solution that uses 5 lenses and 5 aspherical surfaces to achieve a focal length of 4mm, a field of view angle greater than 90°, and a distortion of less than 5%; CN111061044B provides a solution that uses 4 lenses and 5 aspherical surfaces to achieve a focal length of 4.28mm, a horizontal field of view angle of 91.5°, and a distortion of 41%. CN201310445384.3 provides a solution that uses 2 lenses, two aspherical surfaces, and one diffraction surface, with a focal length of 3.5mm, a field of view angle of 58°, and a distortion of about 20%.

[0004] It can be seen that the long-wave uncooled infrared lens in the prior art has disadvantages such as a large number of glass sheets at the same focal length and large distortion. Summary of the invention

[0005] In view of this, the present invention provides an infrared optical lens for image matching, which can use a four-piece optical structure to achieve an effective field of view angle of 95°, control the distortion to less than 3%, and complete optical athermalization at -45°C to 80°C.

[0006] To achieve the above purpose, the technical solution of the present invention is as follows:

[0007] An infrared optical lens for image matching comprises four lenses and an aperture; wherein the optical powers of the four lenses are arranged in the order of negative-negative-positive-positive, the first lens and the fourth lens each comprise a surface adopting a high-order aspheric surface, and the lens surface is curved toward the aperture; the second lens adopts a double aspheric surface structure, and the third lens adopts a double convex lens, and both surfaces are spherical; the aperture is placed in the center but in front of the entrance pupil.

[0008] Among them, the aperture is between the second mirror and the third mirror, L aperture position / L total length = 0.45, L entrance pupil / L total length = 0.2.

[0009] Among them, the materials of the four lenses are germanium-germanium-chalcogenide glass-germanium.

[0010] Among them, the optical power ratio of the first mirror, the second mirror, the third mirror and the fourth mirror is approximately 1.4:5:1:1.7.

[0011] The four lenses are made of three pieces of germanium and one piece of chalcogenide glass; the chalcogenide glass is immediately behind the aperture, and the chalcogenide glass is a double convex lens; the germanium glass can be a diffraction surface.

[0012] Among them, the optical power ratio of the first mirror and the fourth mirror is about 1:1.2, and the optical power ratio of the second mirror and the third mirror is about 5:1.

[0013] Beneficial effects:

[0014] 1. The infrared optical lens of the present invention adopts a 4-piece structure within a limited space. Germanium and chalcogenide glass are matched and aspheric and diffractive surfaces are used to achieve -45°C to +80°C optical passive athermalization, and achieve f=4.5mm, D / F=1.0, adapt to 640×512, 12-micron detectors, field of view 2w=95.2°, and distortion is controlled within 3%.

[0015] 2. The design of the infrared optical lens of the present invention with the aperture diaphragm placed in the center but the entrance pupil placed in front reduces the effective area of ​​the large field of view lens window; the total length of the infrared optical lens is controlled within 45 mm.

[0016] 3. The infrared optical lens of the present invention adopts a design in which the aperture is centered but the entrance pupil is placed in front, 0.55≥L aperture position / L total length≥0.45, and L entrance pupil / L total length≤0.2. The aperture is centered, which is beneficial to correcting lens astigmatism, coma, and magnification chromatic aberration; satisfying this condition is more conducive to controlling system distortion. This entrance pupil position can also greatly reduce the effective area of ​​the lens window, thereby reducing the window area of ​​the out-of-zone guidance optical cabin. Reducing the window area on the necessary number of windows can reduce its electromagnetic radiation area, and at the same time is beneficial to increasing its shell rigidity and facilitating the stealth design of the shell.

[0017] 4. The present invention adopts three pieces of germanium and one piece of chalcogenide glass; the chalcogenide glass is placed right behind the aperture, and the chalcogenide glass adopts a double convex lens; the germanium glass can adopt a diffraction surface; the overall optical power sequence of "negative-negative-positive-positive" is adopted, and the optical power ratio of the first mirror to the fourth mirror is about 1:1.2, and the optical power ratio of the second mirror to the third mirror is about 5:1; finally, optical athermalization is achieved at -45°C to 80°C, and the distortion is controlled at about 3%.

[0018] 5. The present invention is applicable to guided optical cabins, airborne optoelectronic systems, vehicle-mounted optoelectronic equipment, power monitoring systems, airport monitoring systems, etc., where the systems have requirements on the field of view, distortion, volume, weight, etc. of uncooled infrared optical lenses. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of an embodiment of an infrared optical lens for image matching according to the present invention.

[0020] Figure 2 The figure is a distortion diagram of an infrared optical lens embodiment for image matching according to the present invention.

[0021] Figure 3 MTF diagram of an infrared optical lens embodiment for image matching of the present invention (20°C)

[0022] Figure 4 MTF diagram of the infrared optical lens embodiment for image matching of the present invention (-45°C)

[0023] Figure 5 MTF diagram of an infrared optical lens embodiment for image matching of the present invention (80°C)

[0024] Among them, 1-the first mirror, 2-the second mirror, 3-the third mirror, 4-the fourth mirror, 5-the aperture, and 6-the window. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0026] The present invention provides an infrared optical lens for image matching, comprising 4 lenses and an aperture. The focal powers of the 4 lenses are arranged in a negative-negative-positive-positive order, and the materials are germanium-germanium-chalcogenide glass-germanium; the focal power ratio of the first mirror, the second mirror, the third mirror and the fourth mirror is about 1.4:5:1:1.7, and the first mirror and the fourth mirror both include a high-order aspheric surface, and the lens surface is bent toward the aperture; the second mirror adopts a double aspheric structure and effectively compresses the range of light, and the third mirror adopts a double convex lens, and both surfaces are spherical. The aperture is centered but the entrance pupil is placed in front. Specifically, the aperture is between the second mirror and the third mirror, L aperture position / L total length = 0.45, L entrance pupil / L total length = 0.2.

[0027] In this embodiment, 0.55≥L aperture position / L total length≥0.45, and L entrance pupil / L total length≤0.2, and the centering of the aperture is beneficial to correcting the lens astigmatism, coma, and magnification chromatic aberration; satisfying this condition is more conducive to controlling system distortion; satisfying the above-mentioned entrance pupil position can also greatly reduce the effective area of ​​the lens window, thereby reducing the window area of ​​the out-of-zone guidance optical cabin, and reducing the window area based on the necessary number of windows can reduce its electromagnetic radiation area, while helping to increase the rigidity of its outer shell and facilitate the stealth design of the outer shell.

[0028] Specifically, the infrared optical lens of this embodiment is as follows: Figure 1As shown, the four lenses use three germanium and one chalcogenide glass; the chalcogenide glass is immediately behind the aperture, and the chalcogenide glass uses a double convex lens; the germanium glass can use a diffraction surface; the overall "negative-negative-positive-positive" optical focal length is arranged, and the optical focal length ratio of the first lens and the fourth lens is about 1:1.2, and the optical focal length ratio of the second lens and the third lens is about 5:1; finally, the optical athermalization is completed at -45℃~80℃, MTF≥0.35@42lp / mm, and the distortion is ≤3%. This implementation example has a focal length of f=4.5mm, a relative aperture D / F=1.0, an adapted detector of 640×512, 12 microns, a working band of 8~12 microns, and a field of view angle of 2w=95.2°.

[0029] In summary, the present invention adopts a 4-piece structure within a limited space, and germanium and chalcogenide glass are matched and aspheric and diffractive surfaces are used to complete -45℃~+80℃ optical passive athermalization, and achieve f=4.5mm, D / F=1.0, adapt to 640×512, 12 micron detector, field of view angle 2w=95.2°, and distortion is controlled within 3%; at the same time, the design of centered aperture but front entrance pupil reduces the effective area of ​​the large field of view lens window; the total length of the lens is less than 45mm. The present invention is suitable for guided optical cabins, airborne optoelectronic systems, vehicle-mounted optoelectronic equipment, power monitoring systems, airport monitoring systems, etc., and the systems have field of view, distortion, volume, weight and other requirements for non-cooled infrared optical lenses. The present invention is suitable for guided optical cabins, airborne optoelectronic systems, vehicle-mounted optoelectronic equipment, power monitoring systems, airport monitoring systems, etc., and the systems have field of view, distortion, volume, weight and other requirements for non-cooled infrared optical lenses.

[0030] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An infrared optical lens for image matching, characterized in that: It includes 4 lenses and an aperture; the optical powers of the 4 lenses are arranged in the order of negative-negative-positive-positive, the first mirror and the fourth mirror each contain a high-order aspheric surface, and the lens surface is curved toward the aperture; the second mirror adopts a double aspheric structure, and the third mirror adopts a double convex lens, both surfaces are spherical; the aperture is centered but in front of the entrance pupil.

2. The infrared optical lens according to claim 1, characterized in that: The aperture is between the second mirror and the third mirror, L aperture position / L total length = 0.45, L entrance pupil / L total length = 0.

2.

3. The infrared optical lens according to claim 1 or 2, characterized in that: The materials of the four lenses are germanium-germanium-chalcogenide glass-germanium.

4. The infrared optical lens according to claim 3, characterized in that: The optical power ratio of the first mirror, the second mirror, the third mirror and the fourth mirror is approximately 1.4:5:1:1.

7.

5. The infrared optical lens according to claim 3, characterized in that: The four lenses are made of three pieces of germanium and one piece of chalcogenide glass; the chalcogenide glass is immediately behind the aperture, and the chalcogenide glass is a double convex lens; the germanium glass can be a diffraction surface.

6. The infrared optical lens according to claim 4 or 5, characterized in that: The optical power ratio of the first mirror and the fourth mirror is about 1:1.2, and the optical power ratio of the second mirror and the third mirror is about 5:1.

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