Short-mid wave infrared catadioptric athermalized imaging spectral optical system

Abstract

This invention relates to the field of optical technology and provides a short-to-mid-wave infrared hybrid refractive-diffraction athermalized imaging spectral optical system. Along the optical path, it sequentially includes an entrance pupil, a first lens, a second lens, a third lens, a first beam splitter, a first compensation plate, a stepped micromirror, a second beam splitter, a second compensation plate, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a filter, a detector window, a cold stop, and a detector back focal plane. By employing hybrid refractive-diffraction lenses, cylindrical mirrors, and a telecentric optical path design, a short-to-mid-wave imaging spectral optical system is achieved, including a telescope head and a detector-matched lens, achromatic and athermalized design. Simultaneously, the number of lenses required for the optical system design is minimized, achieving a miniaturized design of the spectral imager optical system.

Description

Technical Field

[0001] This invention relates to the field of optical technology, specifically providing a short-to-mid-wave infrared refraction-diffraction hybrid thermodynamic imaging spectral optical system. Background Technology

[0002] The design criteria for imaging spectral optical systems include the application band of the imaging spectrum, the working environment, imaging resolution, and instrument size and weight. With the continuous expansion of the application fields of imaging spectrometers and the increasing complexity of application environments, the design requirements for optical imaging systems are constantly increasing. Static interferometric imaging spectral systems based on stepped micromirrors have advantages such as high stability, high spectral scanning speed, and imaging resolution, making them suitable for imaging spectral detection under complex environmental conditions in multiple fields. Infrared static interferometric imaging spectrometers based on stepped micromirrors cover the short and mid-wave infrared bands, making them suitable for real-time monitoring of pollutant emissions. This places high demands on the optical imaging system: ① Achieving achromatic and thermal design across a wide band; ② Achieving a matching design between the telescope head and the detector lens; ③ Achieving a compact and lightweight optical system design; ④ Balancing the large orders of magnitude astigmatism introduced by the beam splitter and compensation plate. Currently, the design bands for infrared optical systems are generally mid-wave and long-wave infrared. There are few design examples of short and mid-wave infrared optical systems, and design examples of infrared optical systems that meet the above design requirements are almost impossible to find. Summary of the Invention

[0003] This invention addresses the technical problems existing in the prior art by providing a short-to-mid-wave infrared refraction-diffraction hybrid thermodynamic imaging spectral optical system.

[0004] This invention provides a short-to-mid-wave infrared refraction-diffraction hybrid athermalized imaging spectral optical system. The short-to-mid-wave infrared refraction-diffraction hybrid athermalized imaging spectral optical system includes, along the optical path direction, an entrance pupil, a first lens, a second lens, a third lens, a first beam splitter, a first compensation plate, a stepped micromirror, a second beam splitter, a second compensation plate, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a filter, a detector window, a cold aperture, and a detector back focal plane.

[0005] The first lens is a negative power negative meniscus aspherical lens; the second lens is a negative power negative meniscus lens; the third lens is a positive power cylindrical lens; the fourth lens is a zero power cylindrical lens; the fifth lens is a positive power positive meniscus lens; the sixth lens is a positive power positive meniscus refractive-diffraction hybrid lens; the seventh lens is a negative power negative meniscus lens; the eighth lens is a negative power negative meniscus aspherical lens; and the ninth lens is a positive power positive meniscus aspherical lens.

[0006] The incident light beam, after passing through the entrance pupil, sequentially passes through the first lens, the second lens, the third lens, the first beam splitter, the first compensation plate, the stepped micromirror, the second beam splitter, the second compensation plate, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the filter, the detector window, and the cold aperture before being imaged onto the back focal plane of the detector.

[0007] The optical path direction is the direction of the incident beam from the object side to the image side.

[0008] Preferably, the entrance pupil has an aperture of 50 mm, the cold aperture has an aperture of 5.275 mm, and the back focal plane of the detector has dimensions of 9.6 mm × 7.68 mm.

[0009] Preferably, the stepped micromirror is square.

[0010] Preferably, the stepped micromirror has 320 steps, the width of a single step is 0.15 mm, and the total width of the stepped micromirror is 48 mm.

[0011] Preferably, both the filter and the detector window are zero-optical-power flat plates, and the filter and the detector window are arranged parallel to each other.

[0012] Preferably, the first beam splitter, the second beam splitter, the first compensation plate, and the second compensation plate are all flat plates inclined at 45°. The first beam splitter and the first compensation plate are arranged parallel to each other, and the second beam splitter and the second compensation plate are arranged parallel to each other.

[0013] Preferably, the surfaces of 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 coated with an infrared anti-reflection film, and the average transmittance of the nine lenses is greater than or equal to 98%.

[0014] Preferably, the first front surface of the first lens is aspherical, and the first rear surface of the first lens is spherical; the second front surface and the second rear surface of the second lens are both spherical; the third front surface of the third lens is spherical, and the third rear surface of the third lens is cylindrical; the fourth front surface of the fourth lens is cylindrical, and the fourth rear surface of the fourth lens is planar; the fifth front surface and the fifth rear surface of the fifth lens are both spherical; the sixth front surface of the sixth lens is spherical, and the sixth rear surface of the sixth lens is an aspherical binary diffraction surface; the seventh front surface and the seventh rear surface of the seventh lens are both spherical; the eighth front surface of the eighth lens is aspherical, and the eighth rear surface of the eighth lens is spherical; the ninth front surface of the ninth lens is spherical, and the ninth rear surface of the ninth lens is aspherical.

[0015] Preferably, the first lens is made of silicon; the second lens is made of calcium fluoride; the third lens is made of zinc selenide; the fourth lens is made of zinc selenide; the fifth lens is made of zinc selenide; the sixth lens is made of zinc selenide; the seventh lens is made of silicon; the eighth lens is made of silicon; and the ninth lens is made of zinc sulfide.

[0016] Preferably, the thickness of the first lens is 11 mm, the radius of curvature of the first front surface is 241.8, the radius of curvature of the first rear surface is 156.8, and the distance between the first rear surface and the second front surface is 6 mm.

[0017] The second lens has a thickness of 11 mm, the radius of curvature of the second front surface is 220.902, the radius of curvature of the second rear surface is 180.223, and the distance between the second rear surface and the third front surface is 6 mm.

[0018] The thickness of the third lens is 14mm, the radius of curvature of the third front surface is 204.9, the radius of curvature of the third rear surface is -1.264E+05, and the distance between the third rear surface and the front surface of the first beam splitter is 466.24mm.

[0019] The thickness of the first beam splitter is 8mm, and the distance between the rear surface of the first beam splitter and the front surface of the first compensation plate is 8mm.

[0020] The thickness of the first compensation plate is 8 mm, and the distance between the rear surface of the first compensation plate and the stepped micromirror is 48 mm; the distance between the stepped micromirror and the front surface of the second beam splitter is 40 mm.

[0021] The thickness of the second beam splitter is 8mm, and the distance between the rear surface of the second beam splitter and the front surface of the second compensation plate is 8mm.

[0022] The thickness of the second compensation plate is 8 mm, and the distance between the rear surface of the second compensation plate and the fourth front surface is 548.14 mm.

[0023] The thickness of the fourth lens is 12.9 mm, the radius of curvature of the fourth front surface is 1.66E+05, the curvature of the fourth rear surface is 0, and the distance between the fourth rear surface and the fifth front surface is 28 mm.

[0024] The fifth lens has a thickness of 14.07 mm, a radius of curvature of 90.1 mm on the fifth front surface, a radius of curvature of 135.15 mm on the fifth rear surface, and a distance of 7.023 mm between the fifth rear surface and the sixth front surface.

[0025] The sixth lens has a thickness of 17.29 mm, a radius of curvature of 61.47 mm on the sixth front surface, a radius of curvature of 108.53 mm on the sixth rear surface, and a distance of 4.965 mm between the sixth rear surface and the seventh front surface.

[0026] The seventh lens has a thickness of 10.71 mm, a radius of curvature of 108.5 mm on the seventh front surface, a radius of curvature of 46.95 mm on the seventh rear surface, and a distance of 24 mm between the seventh rear surface and the eighth front surface.

[0027] The thickness of the eighth lens is 10.54 mm, the radius of curvature of the eighth front surface is 70.08 mm, the radius of curvature of the eighth rear surface is 53.9 mm, and the distance between the eighth rear surface and the ninth front surface is 2.69 mm.

[0028] The thickness of the ninth lens is 12.26 mm, the radius of curvature of the ninth front surface is 52.38 mm, the radius of curvature of the ninth rear surface is 215.44 mm, and the distance between the ninth rear surface and the front surface of the filter is 19.05 mm.

[0029] The filter has a thickness of 1 mm, both the front and rear surfaces of the filter are planar, both the front and rear surfaces of the filter have a curvature of 0, and the distance between the rear surface of the filter and the front surface of the detector window is 4 mm.

[0030] The detector window has a thickness of 1 mm, and both the front and rear surfaces of the detector window are flat. The curvature of both the front and rear surfaces of the detector window is 0. The distance between the rear surface of the detector window and the cold aperture is 2.95 mm.

[0031] The distance between the cold aperture and the back focal plane of the detector is 19.8 mm.

[0032] Preferably, the short- and mid-wave infrared refractive-diffraction hybrid athermal imaging spectral optical system has a focal length of 100 mm, a field of view of ±2.75°×±2.25°, and an F-number of 2, where the F-number is the ratio of the focal length to the aperture of the optical system.

[0033] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0034] The short-to-mid-wave infrared refracto-diffraction hybrid thermochromic imaging spectral optical system provided by this invention achieves a short-to-mid-wave imaging spectral optical system by adopting a refracto-diffraction hybrid lens, cylindrical mirror, and telecentric optical path design. It includes a telescope head and detector matching lens, achromatic and thermochromic design; at the same time, it minimizes the number of lenses required for the optical system design, realizing the miniaturization design of the spectral imager optical system.

[0035] The short- and mid-wave infrared refracto-diffraction hybrid athermalized imaging spectral optical system provided by this invention solves the problems of high difficulty in designing achromatic and athermalized imaging in the short- and mid-wave wide infrared band, high difficulty in matching lenses between the static interferometric imaging telescope head and detector based on stepped micromirrors, and high difficulty in introducing large-scale astigmatism and aberrations into the interferometric imaging optical system through the balanced beam splitter and compensation plate. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of a short- and mid-wave infrared refractive-diffraction hybrid thermodynamic imaging spectral optical system according to a specific embodiment of the present invention;

[0037] Figure 2 This is a partially enlarged schematic diagram of the structure of a short- and mid-wave infrared refractive-diffraction hybrid athermalized imaging spectral optical system according to a specific embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of the structure of the stepped micromirror according to a specific embodiment of the present invention;

[0039] Figure 4 This is an MTF curve of the imaging spectral optical system at 20°C according to a specific embodiment of the present invention;

[0040] Figure 5 This is a graph showing the variation of distortion of the imaging spectral optical system with the field of view according to a specific embodiment of the present invention;

[0041] Figure 6 This is a graph showing the average MTF curve of the imaging spectral optical system according to a specific embodiment of the present invention under an ambient temperature range of -20℃ to 60℃.

[0042] Figure label:

[0043] 0 - Entrance pupil, 1 - First lens, 2 - Second lens, 3 - Third lens, 4 - First beam splitter, 5 - First compensation plate, 6 - Stepped micromirror, 7 - Second beam splitter, 8 - Second compensation plate, 9 - Fourth lens, 10 - Fifth lens, 11 - Sixth lens, 12 - Seventh lens, 13 - Eighth lens, 14 - Ninth lens, 15 - Filter, 16 - Detector window, 17 - Cold stop, 18 - Detector back focal plane. Detailed Implementation

[0044] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0046] In a specific embodiment of the present invention, a short-to-mid-wave infrared refraction-diffraction hybrid athermalized imaging spectral optical system is provided. The short-to-mid-wave infrared refraction-diffraction hybrid athermalized imaging spectral optical system includes, in sequence along the optical path, an entrance pupil, a first lens, a second lens, a third lens, a first beam splitter, a first compensation plate, a stepped micromirror, a second beam splitter, a second compensation plate, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a filter, a detector window, a cold aperture, and a detector back focal plane.

[0047] The first lens is a negative power negative meniscus aspherical lens; the second lens is a negative power negative meniscus lens; the third lens is a positive power cylindrical lens; the fourth lens is a zero power cylindrical lens; the fifth lens is a positive power positive meniscus lens; the sixth lens is a positive power positive meniscus refractive-diffraction hybrid lens; the seventh lens is a negative power negative meniscus lens; the eighth lens is a negative power negative meniscus aspherical lens; and the ninth lens is a positive power positive meniscus aspherical lens.

[0048] The incident light beam, after passing through the entrance pupil, sequentially passes through the first lens, the second lens, the third lens, the first beam splitter, the first compensation plate, the stepped micromirror, the second beam splitter, the second compensation plate, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the filter, the detector window, and the cold aperture before being imaged onto the back focal plane of the detector.

[0049] The optical path direction is the direction of the incident beam from the object side to the image side.

[0050] In a specific implementation, the aperture of the entrance pupil is 50mm, the aperture of the cold aperture is 5.275mm, and the size of the back focal plane of the detector is 9.6mm × 7.68mm.

[0051] In a specific embodiment, the stepped micromirror is square; the stepped micromirror has 320 steps, each step has a width of 0.15 mm, and the total width of the stepped micromirror is 48 mm. The filter and the detector window are both zero-optical-power flat plates, and they are arranged parallel to each other. The first beam splitter, the second beam splitter, the first compensation plate, and the second compensation plate are all flat plates tilted at 45°, with the first beam splitter and the first compensation plate arranged parallel to each other, and the second beam splitter and the second compensation plate also arranged parallel to each other.

[0052] In a specific embodiment, the surfaces of 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 coated with an infrared anti-reflection film, and the average transmittance of the nine lenses is greater than or equal to 98%.

[0053] In a specific embodiment, the first front surface of the first lens is aspherical, and the first rear surface of the first lens is spherical; the second front surface and the second rear surface of the second lens are both spherical; the third front surface of the third lens is spherical, and the third rear surface of the third lens is cylindrical; the fourth front surface of the fourth lens is cylindrical, and the fourth rear surface of the fourth lens is planar; the fifth front surface and the fifth rear surface of the fifth lens are both spherical; the sixth front surface of the sixth lens is spherical, and the sixth rear surface of the sixth lens is an aspherical binary diffraction surface; the seventh front surface and the seventh rear surface of the seventh lens are both spherical; the eighth front surface of the eighth lens is aspherical, and the eighth rear surface of the eighth lens is spherical; the ninth front surface of the ninth lens is spherical, and the ninth rear surface of the ninth lens is aspherical. The first lens is made of silicon; the second lens is made of calcium fluoride; the third lens is made of zinc selenide; the fourth lens is made of zinc selenide; the fifth lens is made of zinc selenide; the sixth lens is made of zinc selenide; the seventh lens is made of silicon; the eighth lens is made of silicon; and the ninth lens is made of zinc sulfide.

[0054] In a specific embodiment, the thickness of the first lens is 11mm, the radius of curvature of the first front surface is 241.8, the radius of curvature of the first rear surface is 156.8, and the distance between the first rear surface and the second front surface is 6mm.

[0055] The second lens has a thickness of 11 mm, the radius of curvature of the second front surface is 220.902, the radius of curvature of the second rear surface is 180.223, and the distance between the second rear surface and the third front surface is 6 mm.

[0056] The thickness of the third lens is 14mm, the radius of curvature of the third front surface is 204.9, the radius of curvature of the third rear surface is -1.264E+05, and the distance between the third rear surface and the front surface of the first beam splitter is 466.24mm.

[0057] The thickness of the first beam splitter is 8mm, and the distance between the rear surface of the first beam splitter and the front surface of the first compensation plate is 8mm.

[0058] The thickness of the first compensation plate is 8 mm, and the distance between the rear surface of the first compensation plate and the stepped micromirror is 48 mm; the distance between the stepped micromirror and the front surface of the second beam splitter is 40 mm.

[0059] The thickness of the second beam splitter is 8mm, and the distance between the rear surface of the second beam splitter and the front surface of the second compensation plate is 8mm.

[0060] The thickness of the second compensation plate is 8 mm, and the distance between the rear surface of the second compensation plate and the fourth front surface is 548.14 mm.

[0061] The thickness of the fourth lens is 12.9 mm, the radius of curvature of the fourth front surface is 1.66E+05, the curvature of the fourth rear surface is 0, and the distance between the fourth rear surface and the fifth front surface is 28 mm.

[0062] The fifth lens has a thickness of 14.07 mm, a radius of curvature of 90.1 mm on the fifth front surface, a radius of curvature of 135.15 mm on the fifth rear surface, and a distance of 7.023 mm between the fifth rear surface and the sixth front surface.

[0063] The sixth lens has a thickness of 17.29 mm, a radius of curvature of 61.47 mm on the sixth front surface, a radius of curvature of 108.53 mm on the sixth rear surface, and a distance of 4.965 mm between the sixth rear surface and the seventh front surface.

[0064] The seventh lens has a thickness of 10.71 mm, a radius of curvature of 108.5 mm on the seventh front surface, a radius of curvature of 46.95 mm on the seventh rear surface, and a distance of 24 mm between the seventh rear surface and the eighth front surface.

[0065] The thickness of the eighth lens is 10.54 mm, the radius of curvature of the eighth front surface is 70.08 mm, the radius of curvature of the eighth rear surface is 53.9 mm, and the distance between the eighth rear surface and the ninth front surface is 2.69 mm.

[0066] The thickness of the ninth lens is 12.26 mm, the radius of curvature of the ninth front surface is 52.38 mm, the radius of curvature of the ninth rear surface is 215.44 mm, and the distance between the ninth rear surface and the front surface of the filter is 19.05 mm.

[0067] The filter has a thickness of 1 mm, both the front and rear surfaces of the filter are planar, both the front and rear surfaces of the filter have a curvature of 0, and the distance between the rear surface of the filter and the front surface of the detector window is 4 mm.

[0068] The detector window has a thickness of 1 mm, and both the front and rear surfaces of the detector window are flat. The curvature of both the front and rear surfaces of the detector window is 0. The distance between the rear surface of the detector window and the cold aperture is 2.95 mm.

[0069] The distance between the cold aperture and the back focal plane of the detector is 19.8 mm.

[0070] In a specific implementation, the short-to-mid-wave infrared refraction-diffraction hybrid athermal imaging spectral optical system of the present invention operates in the short-to-mid-wave infrared band. Specifically, the focal length is 100mm, the field of view is ±2.75°×±2.25°, and the F-number is 2, where the F-number is the ratio of the focal length to the aperture of the optical system.

[0071] The short-to-mid-wave infrared refracto-diffraction hybrid thermochromic imaging spectral optical system provided in this invention eliminates the large-scale astigmatism generated by the beam splitter and compensation plate in the short-to-mid-wave wide infrared band by combining refracto-diffraction hybrid lenses, cylindrical mirrors, and telecentric optical path design, thus achieving achromatic design in the short-to-mid-wave wide spectral band of the imaging spectral optical system. By adopting the refracto-diffraction hybrid design, the number of lenses required by the system is reduced to the greatest extent, realizing a lightweight and miniaturized optical system design, reducing the system size and weight, and improving the compactness of the imaging spectrometer.

[0072] The short- and mid-wave infrared refracto-diffraction hybrid athermal imaging spectral optical system provided in the specific embodiments of the present invention achieves athermal design of the imaging spectral optical system by adopting a refracto-diffraction hybrid design, which meets the working requirements under wide temperature difference environment conditions; at the same time, by designing the cylindrical surface on the rear surface of the third lens, the assembly and adjustment difficulty of the optical system is reduced.

[0073] The short- and mid-wave infrared refraction-diffraction hybrid thermal imaging spectral optical system provided in the specific embodiments of the present invention achieves image-side telecentricity and object-side telecentricity by reasonably setting the aperture stop and cold stop of the telescope head and detector matching lens, thereby realizing distortion-free interferometric imaging, suppressing crosstalk between interferometric channels, and ensuring the accuracy of image spectral information measurement.

[0074] The following detailed description, in conjunction with specific embodiments, provides further details.

[0075] Example

[0076] like Figure 1 The diagram shown is a schematic representation of the short-to-mid-wave infrared refraction-diffraction hybrid thermal imaging spectral optical system provided in this specific embodiment of the present invention. Figures 1-2 As can be seen, following the optical path direction from the object side to the image side, the short-to-mid-wave infrared refraction-diffraction hybrid athermalized imaging spectral optical system sequentially includes an entrance pupil 0, a first lens 1, a second lens 2, a third lens 3, a first beam splitter 4, a first compensation plate 5, a stepped micromirror 6, a second beam splitter 7, a second compensation plate 8, a fourth lens 9, a fifth lens 10, a sixth lens 11, a seventh lens 12, an eighth lens 13, a ninth lens 14, a filter 15, a detector window 16, a cold aperture 17, and a detector back focal plane 18. Specifically, the aperture stop is used as the entrance pupil 0 of the entire optical system.

[0077] In this embodiment, the entrance pupil 0 has a diameter of 50mm. The first lens 1 is a negative power negative meniscus aspherical lens made of silicon; the second lens 2 is a negative power negative meniscus lens made of calcium fluoride; the third lens 3 is a positive power cylindrical lens made of zinc selenide; the first beam splitter 4 is a parallel plate made of zinc selenide; the first compensation plate 5 is a parallel plate made of zinc selenide; the first beam splitter 4 and the first compensation plate 5 are arranged parallel to each other; the stepped micromirror 6 is coated with an anti-reflection film; the second beam splitter 7 is a parallel plate made of zinc selenide; the second compensation plate 8 is a parallel plate made of zinc selenide; the second beam splitter 7 and the second compensation plate 8 are arranged parallel to each other; the fourth lens 9 is a zero power cylindrical lens. The detector comprises the following lenses: a fifth lens 10, a positive power positive meniscus lens, and a sixth lens 11, a positive power positive meniscus refractive-diffraction hybrid lens, and a seventh lens 12, a negative power negative meniscus lens, and a silicon lens; an eighth lens 13, a negative power negative meniscus aspherical lens, and a silicon lens; a ninth lens 14, a positive power positive meniscus aspherical lens, and a zinc sulfide lens; a parallel plate filter 15, made of sapphire and coated with an anti-reflection coating; a parallel plate detector window 16, made of silicon; a cold stop 17, which restricts infrared stray light from entering the detector, with an aperture of 5.275 mm; and a detector back focal plane 18 with dimensions of 9.6 mm × 7.68 mm.

[0078] like Figure 3 The diagram shows a schematic of the stepped micromirror structure in the short-to-mid-wave infrared refraction-diffraction hybrid thermodynamic imaging spectral optical system of this embodiment. As can be seen from the diagram, in this embodiment, the stepped micromirror 6 has 320 steps, each step has a width of 0.15 mm, and the total width of the stepped micromirror 6 is 48 mm, meaning the field of view height of the entire relay imaging system is 48 mm. In this embodiment, the incident light passes through the beam splitter and the compensation plate twice, that is, the incident light passes through the first beam splitter 4, the first compensation plate 5, the second compensation plate 8, and the second beam splitter 7 sequentially.

[0079] In this embodiment, the thickness of the first lens 1 is 11 mm, the first front surface is aspherical with a radius of curvature of 241.8, and the aspherical coefficient is shown in Table 1. The first rear surface is spherical with a radius of curvature of 156.8, and the distance between the first rear surface and the second front surface is 6 mm.

[0080] The second lens 2 has a thickness of 11 mm, a second front surface that is spherical with a radius of curvature of 220.902, a second rear surface that is spherical with a radius of curvature of 180.223, and a distance of 6 mm between the second rear surface and the third front surface.

[0081] The thickness of the third lens 3 is 14mm, the third front surface is spherical with a radius of curvature of 204.9, the third rear surface is cylindrical with a radius of curvature of -1.264E+05, and the distance between the third rear surface and the front surface of the first beam splitter 4 is 466.24mm.

[0082] The thickness of the first beam splitter 4 is 8mm, and the distance between the rear surface of the first beam splitter 4 and the front surface of the first compensation plate 5 is 8mm.

[0083] The thickness of the first compensation plate 5 is 8mm, and the distance between the rear surface of the first compensation plate 5 and the stepped micro-reflector 6 is 48mm; the distance between the stepped micro-reflector 6 and the front surface of the second beam splitter is 40mm.

[0084] The thickness of the second beam splitter 7 is 8mm, and the distance between the rear surface of the second beam splitter 7 and the front surface of the second compensation plate 8 is 8mm.

[0085] The thickness of the second compensation plate 8 is 8mm, and the distance between the rear surface of the second compensation plate 8 and the fourth front surface is 548.14mm.

[0086] The fourth lens 9 has a thickness of 12.9 mm, a cylindrical fourth front surface with a radius of curvature of 1.66E+05, a planar fourth rear surface with a curvature of 0, and a distance of 28 mm between the fourth rear surface and the fifth front surface.

[0087] The fifth lens 10 has a thickness of 14.07 mm, a fifth front surface that is spherical with a radius of curvature of 90.1 mm, a fifth rear surface that is spherical with a radius of curvature of 135.15 mm, and a distance of 7.023 mm between the fifth rear surface and the sixth front surface.

[0088] The sixth lens 11 has a thickness of 17.29 mm, a spherical front surface with a radius of curvature of 61.47 mm, a binary diffraction surface with a radius of curvature of 108.53 mm, aspherical coefficients and diffraction phase coefficients as shown in Table 1, and a distance of 4.965 mm between the sixth rear surface and the seventh front surface.

[0089] The seventh lens 12 has a thickness of 10.71 mm, a spherical front surface with a radius of curvature of 108.5 mm, a spherical rear surface with a radius of curvature of 46.95 mm, and a distance of 24 mm between the seventh rear surface and the eighth front surface.

[0090] The eighth lens 13 has a thickness of 10.54 mm, and its eighth front surface is aspherical with a radius of curvature of 70.08 mm. The aspherical coefficient is shown in Table 1. The eighth rear surface is spherical with a radius of curvature of 53.9 mm. The distance between the eighth rear surface and the ninth front surface is 2.69 mm.

[0091] The thickness of the ninth lens 14 is 12.26 mm. The ninth front surface is spherical with a radius of curvature of 52.38 mm. The ninth rear surface is aspherical with a radius of curvature of 215.44 mm. The aspherical coefficients are shown in Table 1. The distance between the ninth rear surface and the front surface of the filter 15 is 19.05 mm.

[0092] The filter 15 has a thickness of 1 mm. The front and rear surfaces of the filter 15 are both planar, and the curvature of the front and rear surfaces of the filter 15 is 0. The distance between the rear surface of the filter 15 and the front surface of the detector window 16 is 4 mm.

[0093] The detector window 16 has a thickness of 1 mm. The front and rear surfaces of the detector window 16 are both planar, and the curvature of the front and rear surfaces of the detector window 16 is 0. The distance between the rear surface of the detector window 16 and the cold stop is 2.95 mm. The distance between the cold stop 17 and the rear focal plane 18 of the detector is 19.8 mm.

[0094] Table 1. Aspherical coefficients and diffraction phase coefficients of each aspherical surface and binary diffraction surface in the system.

[0095]

[0096] A1 and A2 are diffraction phase coefficients.

[0097] In the short-to-mid-wave infrared refractive-diffraction hybrid thermodynamic imaging spectral optical system provided in this specific embodiment of the present invention, the aspherical surface satisfies the following formula:

[0098]

[0099] In the formula, Z For aspherical sag, c For the curvature of the aspherical vertex, kThe conic coefficient, r The radial distance from the optical axis of the aspherical surface. For the first i Sub-aspheric coefficient i= 1, 2, 3, 4...

[0100] The short- and mid-wave infrared refracting-diffraction hybrid thermodynamic imaging spectral optical system provided in this embodiment reduces the system size and weight by employing a binary diffraction lens.

[0101] Specifically, the phase function of the binary diffraction lens is:

[0102]

[0103] In the formula, For normalized radial aperture coordinates, A i for 2 i Power coefficient.

[0104] The dispersion characteristics of a binary diffractive optical element are independent of the material's refractive index, and its Abbe number satisfies the following equation:

[0105]

[0106] In the formula, The center wavelength, For the shortest wavelength, It is the longest wavelength.

[0107] In the short-to-mid-wave infrared refractive-diffraction hybrid thermodynamic imaging spectral optical system provided in this embodiment, through innovative combinations of optical materials and optical power allocation, each lens element simultaneously satisfies the optical power allocation equation, the chromatic aberration equation, and the thermal aberration equation:

[0108]

[0109]

[0110]

[0111] In the formula, For the optical power of the relay imaging lens, Here, represents the incident height of the paraxial aperture ray on each lens surface. The optical power of each lens, The chromatic aberration coefficients for each lens are... For the chromatic aberration coefficient of the relay imaging lens, The coefficient of thermal expansion of the lens barrel material is...L This refers to the total length of the relay imaging lens barrel. T This is to address thermal defocusing caused by temperature changes in the relay imaging lens. T i For the first i The thermal coefficient of each lens k This refers to the number of lens elements in the lens.

[0112] In this embodiment, the lens barrel material of the short- and mid-wave infrared refractive-diffraction hybrid athermal imaging spectral optical system is aluminum, with a coefficient of thermal expansion of 23.6 × 10⁻⁶. -6 By solving the above equations, the design optimization of the telescope lens and the detector matching lens is carried out.

[0113] In this embodiment, the zero-focal-power cylindrical lens effectively balances the large order-of-magnitude astigmatism introduced by the beam splitter and compensator in the wide infrared band during interferometric imaging.

[0114] In this embodiment, the first lens 1, the second lens 2, and the third lens 3 are combined to form a telescope head, employing an image-side telecentric design; the fourth lens 9, the fifth lens 10, the sixth lens 11, the seventh lens 12, the eighth lens 13, and the ninth lens 14 are combined to form a detector matching lens, employing an object-side telecentric design. This telecentric optical path design solves the problem of perfectly aligning the telescope head and the detector matching lens. The imaging optical system design achieves 100% cold stop matching, suppressing the influence of stray light on infrared spectral interferometric imaging. By employing a hybrid refractive-diffractive optical design and introducing a binary diffractive lens, the optical system achieves achromatic and thermal design, enabling high-quality interferometric imaging within a temperature range of -20℃ to 60℃.

[0115] like Figure 4 The figure shows the MTF curve of the short-to-mid-wave infrared refracto-diffracto hybrid athermal imaging spectral optical system in this embodiment at 20℃. As can be seen from the figure, the field transfer function of the short-to-mid-wave infrared refracto-diffracto hybrid athermal imaging spectral optical system in this embodiment is better than 0.6 at 34lp / mm, which meets the imaging requirements of the short-to-mid-wave infrared band.

[0116] like Figure 5 The figure shows the distortion curve of the short- and mid-wave infrared refractive-diffraction hybrid athermal imaging spectral optical system in this embodiment as a function of the field of view. It can be seen from the figure that the distortion of the system's edge field of view is less than 0.2%.

[0117] like Figure 6The figure shows the transfer function curves of the short- and mid-wave infrared refracto-diffracto hybrid athermal imaging spectroscopic optical system in this embodiment at the cutoff frequency of 34 lp / mm under different temperature conditions. The temperature sampling range is -20℃ to 60℃, and the temperature sampling interval is 10℃. The scatter curves in the figure represent the average diffraction limits of the meridional and sagittal fields of view, and the solid curves in the figure represent the average MTF values ​​of the system in the meridional and sagittal directions of each field of view. It can be seen from the figure that within this temperature range, the MTF of the imaging spectrometer optical system is better than 0.5.

[0118] The short-to-mid-wave infrared refracto-diffraction hybrid athermalized imaging spectral optical system provided by this invention adopts a telecentric optical path design, making the relative illumination at the edge of the image plane close to 1, thus improving the accuracy of imaging spectral measurement; the athermalized design is achieved by combining a refracto-diffraction hybrid lens with infrared materials of different thermal expansion coefficients, meeting the working requirements in a wide temperature range environment; and the short-to-mid-wave infrared broadband achromatic design is achieved by combining a refracto-diffraction hybrid lens with infrared materials of different dispersion characteristics.

[0119] Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0120] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A short-to-mid-wave infrared refraction-diffraction hybrid thermal imaging spectral optical system, characterized in that, The short- and mid-wave infrared refraction-diffraction hybrid athermalized imaging spectral optical system includes, in sequence along the optical path, an entrance pupil, a first lens, a second lens, a third lens, a first beam splitter, a first compensation plate, a stepped micromirror, a second beam splitter, a second compensation plate, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a filter, a detector window, a cold aperture, and a detector back focal plane. The first lens is a negative power negative meniscus aspherical lens; the second lens is a negative power negative meniscus lens; the third lens is a positive power cylindrical lens; the fourth lens is a zero power cylindrical lens; the fifth lens is a positive power positive meniscus lens; the sixth lens is a positive power positive meniscus refractive-diffraction hybrid lens; the seventh lens is a negative power negative meniscus lens; the eighth lens is a negative power negative meniscus aspherical lens; and the ninth lens is a positive power positive meniscus aspherical lens. The incident light beam, after passing through the entrance pupil, sequentially passes through the first lens, the second lens, the third lens, the first beam splitter, the first compensation plate, the stepped micromirror, the second beam splitter, the second compensation plate, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the filter, the detector window, and the cold aperture before being imaged onto the back focal plane of the detector. The optical path direction is the direction of the incident beam from the object side to the image side.

2. The short-to-mid-wave infrared refraction-diffraction hybrid thermal imaging spectral optical system according to claim 1, characterized in that, The entrance pupil has an aperture of 50mm, the cold aperture has an aperture of 5.275mm, and the back focal plane of the detector has dimensions of 9.6mm × 7.68mm.

3. The short-to-mid-wave infrared refraction-diffraction hybrid thermal imaging spectral optical system according to claim 1, characterized in that, The stepped micromirror is square, has 320 steps, has a single step width of 0.15 mm, and a total width of 48 mm.

4. The short-to-mid-wave infrared refraction-diffraction hybrid thermal imaging spectral optical system according to claim 1, characterized in that, Both the filter and the detector window are zero-optical-power flat plates, and the filter and the detector window are arranged parallel to each other.

5. The short-to-mid-wave infrared refraction-diffraction hybrid thermal imaging spectral optical system according to claim 1, characterized in that, The first beam splitter, the second beam splitter, the first compensation plate, and the second compensation plate are all flat plates inclined at 45°. The first beam splitter and the first compensation plate are arranged parallel to each other, and the second beam splitter and the second compensation plate are arranged parallel to each other.

6. The short-to-mid-wave infrared refraction-diffraction hybrid thermal imaging spectral optical system according to claim 1, characterized in that, The surfaces of 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 coated with an infrared anti-reflection film, and the average transmittance of the nine lenses is greater than or equal to 98%.

7. The short-to-mid-wave infrared refraction-diffraction hybrid thermal imaging spectral optical system according to claim 1, characterized in that, The first front surface of the first lens is aspherical, and the first rear surface of the first lens is spherical; the second front surface and the second rear surface of the second lens are both spherical; the third front surface of the third lens is spherical, and the third rear surface of the third lens is cylindrical; the fourth front surface of the fourth lens is cylindrical, and the fourth rear surface of the fourth lens is planar; the fifth front surface and the fifth rear surface of the fifth lens are both spherical; the sixth front surface of the sixth lens is spherical, and the sixth rear surface of the sixth lens is an aspherical binary diffraction surface; the seventh front surface and the seventh rear surface of the seventh lens are both spherical; the eighth front surface of the eighth lens is aspherical, and the eighth rear surface of the eighth lens is spherical; the ninth front surface of the ninth lens is spherical, and the ninth rear surface of the ninth lens is aspherical.

8. The short-to-mid-wave infrared refraction-diffraction hybrid thermal imaging spectral optical system according to claim 7, characterized in that, The first lens is made of silicon; the second lens is made of calcium fluoride; the third lens is made of zinc selenide; the fourth lens is made of zinc selenide; the fifth lens is made of zinc selenide; the sixth lens is made of zinc selenide; the seventh lens is made of silicon; the eighth lens is made of silicon; and the ninth lens is made of zinc sulfide.

9. The short-to-mid-wave infrared refraction-diffraction hybrid thermal imaging spectral optical system according to claim 7, characterized in that, The thickness of the first lens is 11 mm, the radius of curvature of the first front surface is 241.8, the radius of curvature of the first rear surface is 156.8, and the distance between the first rear surface and the second front surface is 6 mm. The second lens has a thickness of 11 mm, the radius of curvature of the second front surface is 220.902, the radius of curvature of the second rear surface is 180.223, and the distance between the second rear surface and the third front surface is 6 mm. The thickness of the third lens is 14mm, the radius of curvature of the third front surface is 204.9, the radius of curvature of the third rear surface is -1.264E+05, and the distance between the third rear surface and the front surface of the first beam splitter is 466.24mm. The thickness of the first beam splitter is 8mm, and the distance between the rear surface of the first beam splitter and the front surface of the first compensation plate is 8mm. The thickness of the first compensation plate is 8 mm, and the distance between the rear surface of the first compensation plate and the stepped micromirror is 48 mm; the distance between the stepped micromirror and the front surface of the second beam splitter is 40 mm. The thickness of the second beam splitter is 8mm, and the distance between the rear surface of the second beam splitter and the front surface of the second compensation plate is 8mm. The thickness of the second compensation plate is 8 mm, and the distance between the rear surface of the second compensation plate and the fourth front surface is 548.14 mm. The thickness of the fourth lens is 12.9 mm, the radius of curvature of the fourth front surface is 1.66E+05, the curvature of the fourth rear surface is 0, and the distance between the fourth rear surface and the fifth front surface is 28 mm. The fifth lens has a thickness of 14.07 mm, a radius of curvature of 90.1 mm on the fifth front surface, a radius of curvature of 135.15 mm on the fifth rear surface, and a distance of 7.023 mm between the fifth rear surface and the sixth front surface. The sixth lens has a thickness of 17.29 mm, a radius of curvature of 61.47 mm on the sixth front surface, a radius of curvature of 108.53 mm on the sixth rear surface, and a distance of 4.965 mm between the sixth rear surface and the seventh front surface. The seventh lens has a thickness of 10.71 mm, a radius of curvature of 108.5 mm on the seventh front surface, a radius of curvature of 46.95 mm on the seventh rear surface, and a distance of 24 mm between the seventh rear surface and the eighth front surface. The thickness of the eighth lens is 10.54 mm, the radius of curvature of the eighth front surface is 70.08 mm, the radius of curvature of the eighth rear surface is 53.9 mm, and the distance between the eighth rear surface and the ninth front surface is 2.69 mm. The thickness of the ninth lens is 12.26 mm, the radius of curvature of the ninth front surface is 52.38 mm, the radius of curvature of the ninth rear surface is 215.44 mm, and the distance between the ninth rear surface and the front surface of the filter is 19.05 mm. The filter has a thickness of 1 mm, both the front and rear surfaces of the filter are planar, both the front and rear surfaces of the filter have a curvature of 0, and the distance between the rear surface of the filter and the front surface of the detector window is 4 mm. The detector window has a thickness of 1 mm, and both the front and rear surfaces of the detector window are flat. The curvature of both the front and rear surfaces of the detector window is 0. The distance between the rear surface of the detector window and the cold aperture is 2.95 mm. The distance between the cold aperture and the back focal plane of the detector is 19.8 mm.

10. The short-to-mid-wave infrared refraction-diffraction hybrid thermal imaging spectral optical system according to claim 1, characterized in that, The short- and mid-wave infrared refractive-diffraction hybrid athermal imaging spectral optical system has a focal length of 100 mm, a field of view of ±2.75°×±2.25°, and an F-number of 2.

Images