Low-distortion athermalization correctable short-wave infrared optical system and lens

Abstract

The invention discloses a low-distortion athermalization correctable short-wave infrared optical system and a lens, and belongs to the technical field of optics. According to the system, an optical lens is additionally arranged at the rear end to serve as a correction lens to achieve image correction in an external field environment; passive athermalization under wide-temperature and vacuum conditions is realized through focal power distribution and material matching of each optical lens; all the lenses are set to be spherical surfaces, so that the influence of aspheric surface processing errors on system index precision, processing cost and system installation and adjustment is avoided; the system adopts a positive-negative-positive-negative-negative five-lens focal power configuration. The positive-negative-positive-negative lenses are located at the front end, and the last negative lens is located at the rear end. The five lens materials are zinc sulfide, a chalcogenide material, single crystal barium fluoride, single crystal calcium fluoride and a chalcogenide material in sequence; the correction lens is located at the rear end of the last negative lens. The short-wave infrared optical system can solve the problems that an existing short-wave infrared optical system is large in imaging distortion, or athermalization is not achieved, or image correction under the external field application condition cannot be achieved.

Description

Technical Field

[0001] The present invention belongs to the field of optical technology, and in particular relates to a low-distortion athermal correctable short-wave infrared optical system and lens. Background Art

[0002] Shortwave infrared systems play an important role in many application fields, including military fields such as night vision, reconnaissance and surveillance, remote sensing, infrared imaging guidance and optoelectronic countermeasures, as well as in spectroscopy, non-destructive testing, industrial multispectral imaging analysis, and resource remote sensing.

[0003] Chinese patent CN104297899B discloses a large-field-of-view passively athermalized short-wave infrared optical system. This system utilizes three infrared crystal materials (ZnSe, ZnS, and BaF2) and six lenses to achieve optical passive athermalization for a large-field-of-view, high-resolution short-wave infrared optical system. An aspheric lens assembly is introduced to correct for spherical aberration and coma. The system achieves a resolution of 0.9-2.5 μm, an F# of 1.4, a 45° field of view, a 70 mm optical system length, a 24.7 mm focal length, 3% distortion, and an MTF >0.6 @ 20 lp / mm. The detector is 640 x 512, 25 μm.

[0004] Chinese patent CN118671947A discloses a high-quality, ultra-large aperture short-wave infrared optical system. This system utilizes eleven glass lenses, achieving an F# of up to 0.9. It maintains clear imaging in temperatures ranging from -40°C to +80°C, meeting the requirements of detectors with 4µm pixels. It boasts an MTF > 0.25 @ 120lp / mm and a distortion of 2.5%. This addresses the issue of existing short-wave infrared optical systems, which generally have resolutions below 10µm pixels, a maximum aperture of F1.4, and limited light intake, resulting in low detection sensitivity and making them unsuitable for complex detection environments.

[0005] Chinese patent CN109324392B discloses a medium- and short-wavelength, wide-band infrared optical system and remote sensing optical equipment. The system utilizes a straight-tube, single-shot imaging system with four spherical lenses (ZnS, IG4, and MgF2). It operates in the 1.5-5µm wavelength range, has a focal length of 60mm, an F#3 aperture, a field of view of 11.8°, and pixel sizes of 640 x 512 x 15µm. The MTF exceeds 0.45 at 33lp / mm.

[0006] The 2020 doctoral dissertation "Multi-band Short-wave Infrared Camera Optical System Design and Imaging Quality Evaluation" designed a 640*512*25um, 0.9-1.7um band, -40~+40℃, resolution 100m@528Km, focal length 132mm, field of view 9°, F#4, distortion 1%, size 50*130mm, glass material, MTF>0.7@20lp / mm (normal temperature and pressure).

[0007] A paper titled "A high-resolution short-wave infrared passive athermal optical system with a wide temperature range" was published in the journal "Laser and Optoelectronics Progress" in 2012. The paper provides a system with an operating band of 0.9 to 1.7 μm, a resolution of 640*512*25 μm, a clear aperture of 20 mm, a total system length of 55 mm, an MTF of >0.6@20lp / mm at all temperatures from -40 to +60°C, and uses 6 lenses (ZnSe, BaF2), consisting of spherical + aspherical + diffraction surfaces.

[0008] The above existing technologies all realize short-wave infrared optical systems, but some of them have relatively large system distortion, some have special surface shapes that make processing or assembly difficult, and some do not consider image correction for field applications. Summary of the Invention

[0009] The present invention aims to solve one of the technical problems in the above-mentioned related art at least to a certain extent.

[0010] To this end, the purpose of the present invention is to provide a low-distortion athermalized correctable short-wave infrared optical system that can solve the problems of existing short-wave infrared optical systems such as large imaging distortion, failure to achieve athermalization, or inability to achieve image correction under field application conditions.

[0011] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0012] An embodiment of the present invention provides a low-distortion, athermalized, correctable short-wave infrared optical system, which has low-distortion, high-resolution imaging capabilities over a wide temperature range and under normal pressure and vacuum conditions; the system comprises:

[0013] By adding an optical lens at the back end, image correction can be achieved in outdoor environments;

[0014] Through the distribution of optical power and the matching of materials of each optical lens, passive athermalization is achieved under wide temperature and vacuum conditions;

[0015] By setting all lenses to spherical, the impact of aspheric surface processing errors on system accuracy, processing costs, and system assembly and adjustment is avoided;

[0016] Image correction in an outdoor environment is achieved by introducing a detachable and switchable optical lens as a correction lens at the rear end.

[0017] In addition, the low-distortion athermal correctable short-wave infrared optical system according to the present invention may also have the following additional technical features:

[0018] In some of the embodiments, the system uses a five-lens optical power configuration of positive-negative-positive-negative-negative;

[0019] Among them, the four lenses of positive-negative-positive-negative are located at the front end, and the last negative lens is located at the back end.

[0020] In some embodiments, the optical lens added at the rear end is located behind the rear negative lens.

[0021] In some embodiments, the four lenses at the front end are:

[0022] The first lens is a biconvex lens with positive optical power;

[0023] The second lens is a meniscus lens with negative optical power and the concave surface facing forward;

[0024] The third lens is a biconvex lens with positive optical power;

[0025] The fourth lens is a biconcave lens with negative optical power;

[0026] The lens at the rear is:

[0027] The fifth lens is a meniscus lens with negative optical power, and its concave surface faces forward.

[0028] In some embodiments, the first lens is made of zinc sulfide, and the optical power is: 0.009 < optical power absolute value < 0.012;

[0029] The second lens is made of chalcogenide material, and the optical power is: 0.004<absolute value of optical power<0.006;

[0030] The third lens is made of single crystal barium fluoride material, and the optical power is: 0.01<absolute value of optical power<0.03;

[0031] The fourth lens is made of single crystal calcium fluoride, and the optical power is: 0.01<absolute value of optical power<0.02.

[0032] In some embodiments, the fifth lens is made of a chalcogenide material, and has a focal power of 0.003 < absolute value of focal power < 0.006.

[0033] In some of the embodiments, a stop is provided at the front end of the five lenses.

[0034] In some embodiments, the overall focal length of the optical system is 107.1 mm, and the distortion is better than 0.3%.

[0035] In some embodiments, the optical system operates in a wavelength range of 1-2.5 μm.

[0036] In some of the embodiments, the optical system further comprises a focal plane;

[0037] The focal plane is arranged behind the optical lens added at the rear end, and the distance between the focal plane and the optical lens is greater than 25 mm.

[0038] An embodiment of the present invention further provides a low-distortion athermalized correctable short-wave infrared lens, which includes the low-distortion athermalized correctable short-wave infrared optical system as described above.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects:

[0040] In an embodiment of the present invention, a low-distortion athermal correctable short-wave infrared optical system is provided, which is composed of a full-sphere and has good imaging performance in a wide temperature range and vacuum environment. At the same time, the system has the characteristics of low distortion.

[0041] In the embodiments of the present invention, a low-distortion, athermal, correctable short-wave infrared optical system is provided. An adjustable optical element is introduced at the back end to solve the problem of non-uniform correction of images during field applications. Compared with other short-wave infrared optical systems, it has an image correction function for field applications.

[0042] In an embodiment of the present invention, a low-distortion athermal correctable short-wave infrared optical system is provided, which uses a specific arrangement of five spherical lenses in a "positive-negative-positive-negative-negative" pattern to optimize imaging performance through optical power distribution.

[0043] In an embodiment of the present invention, a low-distortion athermalized correctable short-wave infrared optical system is provided, which has an athermalization mechanism that utilizes the matching of material thermal properties with optical power to achieve passive athermalization in a wide temperature environment without the need for active temperature control.

[0044] In an embodiment of the present invention, a low-distortion athermal correctable short-wave infrared optical system is provided, which adopts a full-spherical surface structure, avoids the complex processing of aspherical / diffractive surfaces, and reduces production costs and assembly difficulty.

[0045] The low-distortion athermalized, correctable short-wave infrared lens of the present invention includes the aforementioned low-distortion athermalized, correctable short-wave infrared optical system and thus possesses at least all the features and advantages of the aforementioned low-distortion athermalized, correctable short-wave infrared optical system, which are not further elaborated herein. Additional aspects and advantages of the present invention will be set forth in part in the following description and will become apparent from the description or learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A diagram of a low-distortion athermalized short-wave infrared optical system disclosed in one embodiment of the present invention;

[0047] Figure 2 Modulation transfer functions of optical systems under different environments disclosed in one embodiment of the present invention;

[0048] Figure 3 An embodiment of the present invention is disclosed in Figure 1 Diagram of a low-distortion athermalized short-wave infrared optical system with a correction mirror introduced on this basis;

[0049] Figure 4 This is a distortion curve diagram of an optical system disclosed in one embodiment of the present invention.

[0050] Description of reference numerals:

[0051] 1-first lens; 2-second lens; 3-third lens; 4-fourth lens; 5-fifth lens; 6-focal plane; 7-correction lens. DETAILED DESCRIPTION

[0052] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0053] The embodiments of the present invention are described in detail below through specific embodiments and application scenarios with reference to the accompanying drawings.

[0054] In some embodiments of the present invention, a low-distortion athermal correctable short-wave infrared optical system is provided, comprising a biconvex first lens 1, a concave-convex second lens 2, a biconvex third lens 3, a biconcave fourth lens 4, and a concave-convex fifth lens 5, arranged in sequence along the optical axis from the object side to the image side.

[0055] The optical system comprises a first lens 1 with positive optical power, a second lens 2 with negative optical power, a third lens 3 with positive optical power, a fourth lens 4 with negative optical power, and a fifth lens 5 with negative optical power, which are arranged in sequence from the object side to the image side along the optical axis.

[0056] The first lens 1 is a biconvex lens with positive optical power;

[0057] The second lens 2 is a concave-convex lens, with the concave surface facing the object side;

[0058] The third lens 3 is a biconvex lens with positive optical power;

[0059] The fourth lens 4 is a biconcave lens with negative optical power;

[0060] The fifth lens 5 is a meniscus lens with the concave surface facing the object side;

[0061] The front surface of the first lens 1 is provided with an aperture;

[0062] The optical centers of the first lens 1 , the second lens 2 , the third lens 3 , the fourth lens 4 , and the fifth lens 5 are located on the same straight line.

[0063] The low distortion athermalization can correct the short-wave infrared optical system, and the entire optical system introduces optical elements at the back end, such as Figure 3 As shown, a correction lens 7 is introduced behind the fifth lens (i.e., between the fifth lens 5 and the focal plane 6) to achieve image correction in field applications. Correction lens 7 is fixed to the rear end of the optical path via a switching mechanism. Different correction lens parameters can be switched based on the specific conditions of the current system to achieve varying degrees of light divergence. When correction is not required, the correction lens is removed for normal imaging. The introduced optical element can be a lens with a certain curvature or frosted glass.

[0064] The low-distortion athermalized correctable short-wave infrared optical system utilizes reasonable optical power distribution and material matching to achieve an optical passive athermalization design over a wide temperature range, enabling the system to meet the requirements of use under high and low temperature and vacuum conditions.

[0065] The low-distortion athermal correctable short-wave infrared optical system has all lenses that are spherical, which reduces processing cost and difficulty.

[0066] The low-distortion athermal correctable short-wave infrared optical system has a system focal length of 107.1 mm, an operating band of 1-2.5 μm, and a distortion of less than 0.3%.

[0067] The low-distortion athermal correctable short-wave infrared optical system has a distance between the fifth lens and the image plane greater than 25 mm.

[0068] Example 1:

[0069] See also Figure 1 As shown in FIG, the system consists of a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, and a focal plane 6. The light path is from left to right, passing through the first lens 1, the second lens 2, the third lens 3, the fourth lens 4, the fifth lens 5, and finally reaching the focal plane 6.

[0070] The lens uses 5 lenses, all of which are spherical structures.

[0071] The entire lens adopts a spherical surface structure, achieving an athermal optical lens design with a focal length of 107.1mm and a distortion of 0.3%. All fields of view achieve a transfer function index of more than 0.6 at a spatial frequency of 35lp / mm.

[0072] The first lens 1 is made of zinc sulfide, and has a focal power of 0.009 < absolute value of focal power < 0.012.

[0073] The second lens 2 is made of a chalcogenide material, and has a focal power of 0.004 < absolute value of focal power < 0.006.

[0074] The third lens 3 is made of single crystal barium fluoride, and has a focal power of 0.01 < absolute value of focal power < 0.03.

[0075] The fourth lens 4 is made of single crystal calcium fluoride, and has a focal power of 0.01 < absolute value of focal power < 0.02.

[0076] The fifth lens 5 is made of a chalcogenide material, and has a focal power of 0.003 < absolute value of focal power < 0.006.

[0077] Focal plane 6 is 6.2 mm diagonal.

[0078] Table 1 shows the parameters of the optical mirrors of the optical system of one embodiment of the present invention.

[0079] Table 1 System coefficients

[0080] Surface number Y radius thickness Material 1 386.7906 3.1369 ZNS 2 -219.2746 1.8993 3 -81.4826 5.9953 Chalcogenide glass 4 -101.3462 0.3 5 34.8741 7.1974 474488.8156 6 -100.3052 1.0711 7 -90.4874 2 433837.9516 8 51.6584 55.1045 9 -14.6467 2.742 Chalcogenide glass 10 -17.0630 25.55

[0081] Parts of the present invention that are not described in detail may refer to the prior art or are well-known technologies to those skilled in the art, and this embodiment does not limit this and will not be described in detail here.

[0082] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. A low-distortion athermal correctable short-wave infrared optical system, characterized in that: The system: Through the distribution of optical power and the matching of materials of each optical lens, passive athermalization is achieved under wide temperature and vacuum conditions; By setting all lenses to spherical, the impact of aspheric surface processing errors on system accuracy, processing costs, and system assembly and adjustment is avoided; Image correction in an outdoor environment is achieved by introducing a detachable and switchable optical lens as a correction lens at the rear end.

2. The low-distortion athermalized correctable short-wave infrared optical system according to claim 1, characterized in that: The system uses a five-lens optical power configuration of positive-negative-positive-negative-negative; Among them, the four lenses of positive-negative-positive-negative are located at the front end, and the last negative lens is located at the back end.

3. The low-distortion athermalized correctable short-wave infrared optical system according to claim 2, characterized in that: The four lenses at the front are: The first lens is a biconvex lens with positive optical power; The second lens is a meniscus lens with negative optical power and the concave surface facing forward; The third lens is a biconvex lens with positive optical power; The fourth lens is a biconcave lens with negative optical power; The lens at the rear is: The fifth lens is a meniscus lens with negative optical power, and its concave surface faces forward.

4. The low-distortion athermalized correctable short-wave infrared optical system according to claim 3, characterized in that: The first lens is made of zinc sulfide, and the optical power is: 0.009<absolute value of optical power<0.012; The second lens is made of chalcogenide material, and the optical power is: 0.004<absolute value of optical power<0.006; The third lens is made of single crystal barium fluoride material, and the optical power is: 0.01<absolute value of optical power<0.03; The fourth lens is made of single crystal calcium fluoride, and the optical power is: 0.01<absolute value of optical power<0.

02.

5. The low-distortion athermalized correctable short-wave infrared optical system according to claim 3, characterized in that: The fifth lens is made of chalcogenide material, and its optical power is: 0.003<absolute value of optical power<0.

006.

6. The low-distortion athermalized correctable short-wave infrared optical system according to claim 2, wherein: There is an aperture at the front end of the five lenses.

7. The low-distortion athermalized correctable short-wave infrared optical system according to claim 2, wherein: The optical lens added at the rear end is located behind the rear negative lens.

8. The low-distortion athermalized correctable short-wave infrared optical system according to claim 1, wherein: The overall focal length of the optical system is 107.1 mm, the distortion is better than 0.3%, and the operating band is 1-2.5 μm.

9. The low-distortion athermalized correctable short-wave infrared optical system according to claim 1, wherein: The optical system further comprises a focal plane; The focal plane is arranged behind the optical lens added at the rear end, and the distance between the focal plane and the optical lens is greater than 25 mm.

10. A low-distortion athermal correctable short-wave infrared lens, characterized in that: A low-distortion athermalized correctable short-wave infrared optical system comprising the method of any one of claims 1 to 9.

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