Short-middle wave infrared wide-band relay imaging system

Abstract

This invention relates to the field of optical technology and provides a short-to-mid-wave infrared broadband relay imaging system. Along the optical path, it sequentially includes a stepped micromirror, a beam splitter, a compensation plate, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a filter, a detector window, a cold stop, and a detector back focal plane. The six lenses are, respectively, a zero-power wedge plate, a positive-power cylindrical lens, a positive-power binary diffraction positive meniscus lens, a negative-power negative meniscus lens, a negative-power negative meniscus lens, and a positive-power positive meniscus lens. By combining the wedge plate and the cylindrical mirror, it eliminates large-scale astigmatism in the broadband infrared band, achieving broadband infrared chromatic aberration correction and thermal-free design. It solves the significant difference in imaging transfer functions between the meridional and sagittal directions of the lens, addresses the problem of reduced transfer function, and can meet the imaging requirements of the short-to-mid-wave infrared band under complex environmental conditions.

Description

Technical Field

[0001] This invention relates to the field of optical technology, specifically providing a short-mid-wave infrared broadband relay imaging system. Background Technology

[0002] The Fourier transform imaging spectrometer based on stepped micromirrors replaces the moving mirror system in the traditional Michelson interferometer system with stepped micromirrors, achieving static spectral sampling. The compact and stable interferometric system gives the instrument a wider range of applications.

[0003] In a stepped-micromirror Fourier transform imaging spectrometer, a relay lens is used to re-image the interferometric image modulated by the stepped-micromirror onto the back focal plane of the infrared detector. The imaging quality of the relay lens directly determines the accuracy of the imaging spectral information measurement. The most similar existing technical solution to this invention is the optical lens protected in (ZL.201911390942.4), which is applicable to the mid-infrared spectral band, has a maximum field of view of 32mm×32mm, uses a combination of infrared optical materials such as silicon, germanium, and chalcogenide glass for achromatic design, and uses cylindrical mirrors to balance the large order of magnitude astigmatism introduced by the beam splitter and compensation plate in the interferometric imaging optical path.

[0004] Existing relay imaging lens technologies generally only meet the requirements of mid-wave or long-wave infrared applications, with few addressing design methods for the short- to mid-wave wide infrared spectral band. Imaging spectrometers based on stepped-micromirrors place even greater demands on relay imaging lenses, requiring astigmatism correction, thermal ablation, a large field of view, and a telecentric optical path design. The same infrared optical material exhibits significant differences in dispersion characteristics between short-wave and mid-wave, making it difficult with current technology to achieve achromatic and astigmatism correction designs for relay imaging lenses in stepped-micromirror imaging spectrometers across the short and mid-wave infrared range. In other words, existing relay imaging lens technologies cannot achieve achromatic, astigmatism correction, and thermal ablation designs for the short- to mid-wave wide infrared band and a larger field of view of 48mm × 48mm. Summary of the Invention

[0005] This invention addresses the technical problems existing in the prior art by providing a short-to-mid-wave infrared broadband large field-of-view astigmatism-free and thermal relay imaging system, specifically a short-to-mid-wave infrared broadband large field-of-view astigmatism-free and thermal relay imaging lens.

[0006] This invention provides a short-mid-wave infrared broadband relay imaging system, which includes, along the optical path direction, a stepped micromirror, a beam splitter, a compensation plate, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a filter, a detector window, a cold aperture, and a detector back focal plane.

[0007] The first lens is a zero-power wedge-shaped plate; the second lens is a positive-power cylindrical lens; the third lens is a positive-power binary diffraction positive meniscus lens; the fourth lens is a negative-power negative meniscus lens; the fifth lens is a negative-power negative meniscus lens; and the sixth lens is a positive-power positive meniscus lens.

[0008] The light beam reflected by the stepped micromirror passes sequentially through the beam splitter, the compensation plate, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the filter, the detector window, and the cold aperture before being imaged onto the back focal plane of the detector.

[0009] The optical path direction is the direction of the light beam from the object side to the image side.

[0010] Preferably, the stepped micromirror is square.

[0011] 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.

[0012] Preferably, both the beam splitter and the compensation plate are flat plates inclined at 45°, and the beam splitter and the 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, and the sixth lens are all coated with an infrared anti-reflection film, and the average transmittance of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens is greater than or equal to 98%.

[0014] Preferably, the first front surface of the first lens is an inclined surface, and the first rear surface of the first lens is a plane; the second front surface of the second lens is a cylindrical surface, and the second rear surface of the second lens is a spherical surface; the third front surface of the third lens is a spherical surface, and the third rear surface of the third lens is a binary diffraction surface; the fourth front surface and the fourth rear surface of the fourth lens are both spherical surfaces; the fifth front surface of the fifth lens is an aspherical surface, and the fifth rear surface of the fifth lens is a spherical surface; the sixth front surface of the sixth lens is a spherical surface, and the sixth rear surface of the sixth lens is an aspherical surface.

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

[0016] Preferably, the height of the stepped micromirror is 48 mm, the distance between the stepped micromirror and the front surface of the beam splitter is 75 mm, the thickness of the beam splitter is 8 mm, the distance between the rear surface of the beam splitter and the front surface of the compensation plate is 8 mm, the thickness of the compensation plate is 8 mm, and the distance between the rear surface of the compensation plate and the first front surface of the first lens is in the range of 420 mm to 425 mm.

[0017] The thickness of the first lens is 10mm, and the distance between the first rear surface and the second front surface ranges from 11mm to 12mm;

[0018] The thickness of the second lens is 7-8 mm, and the distance between the second rear surface and the third front surface is 45 mm-50 mm.

[0019] The thickness of the third lens is 16mm, and the distance between the third rear surface and the fourth front surface ranges from 3.5mm to 4mm.

[0020] The thickness of the fourth lens is 10.8 mm, and the distance between the fourth rear surface and the fifth front surface ranges from 2 mm to 2.5 mm.

[0021] The thickness of the fifth lens is 11 mm, and the distance between the fifth rear surface and the sixth front surface is 18.3 mm;

[0022] The thickness of the sixth lens is 11mm, and the distance between the sixth rear surface and the front surface of the filter is 15mm.

[0023] The filter has a thickness of 1 mm, and the distance between the rear surface of the filter and the detector window is 4 mm.

[0024] The detector window has a thickness of 1 mm, and the distance between the rear surface of the detector window and the cold aperture is 2.95 mm.

[0025] The aperture of the cold stop is 10.55 mm, and the distance between the cold stop and the back focal plane of the detector is 19.8 mm.

[0026] Preferably, the first front surface is a wedge-shaped flat inclined surface with an inclination angle of 0.068°, and the first rear surface is a plane perpendicular to the optical axis.

[0027] The second front surface is a cylindrical surface in the sagittal direction, and the curvature range of the second front surface is 1.0E+05mm to 1.3E+05mm; the radius of curvature of the second rear surface ranges from -840mm to -830mm.

[0028] The radius of curvature of the third front surface ranges from 55 mm to 60 mm; the radius of curvature of the third rear surface is 222.8 mm.

[0029] The curvature range of the fourth front surface is 330mm to 335mm, and the curvature range of the fourth rear surface is 200mm to 205mm.

[0030] The radius of curvature of the fifth front surface is 204.75 mm, and the radius of curvature of the fifth rear surface is 62.87 mm.

[0031] The radius of curvature of the sixth front surface is 33.3 mm, and the radius of curvature of the sixth rear surface is 41.88 mm.

[0032] Preferably, the field of view height of the short-mid-wave infrared broadband relay imaging system is 48 mm, the number of pixels on the back focal plane of the detector is 640×512, the pixel size on the back focal plane of the detector is 15 μm, and the cutoff frequency of the short-mid-wave infrared broadband relay imaging system is 34 lp / mm.

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

[0034] The short-to-mid-wave infrared broadband relay imaging system provided by this invention eliminates large-scale astigmatism in the broadband infrared spectrum by combining a wedge-shaped plate and a cylindrical mirror. Through innovative combinations of optical materials and a binary optical diffraction surface design, it achieves broadband infrared chromatic aberration correction and calorimetric design. It solves the problem of astigmatism introduced by beam splitters and compensation plates leading to huge differences in the imaging transfer functions of the lens in the meridional and sagittal directions. At the same time, it also solves the problem of reduced transfer function due to the temperature sensitivity of infrared imaging lenses. It meets the imaging requirements of the short-to-mid-wave infrared spectrum under complex environmental conditions. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of a short- and mid-wave infrared broadband relay imaging system according to a specific embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the structure of the stepped micromirror according to a specific embodiment of the present invention;

[0037] Figure 3 This is a relative illumination curve of the image plane of a short-to-medium wave infrared broadband relay imaging system according to a specific embodiment of the present invention;

[0038] Figure 4 This is a graph showing the distortion of a short-to-medium wave infrared broadband relay imaging system as a function of the field of view, according to a specific embodiment of the present invention.

[0039] Figure 5This is an MTF curve of a short-to-medium wave infrared broadband relay imaging system at -20℃ according to a specific embodiment of the present invention.

[0040] Figure 6 This is an MTF curve of a short-to-medium wave infrared broadband relay imaging system at 0°C according to a specific embodiment of the present invention.

[0041] Figure 7 This is an MTF curve of a short-to-medium wave infrared broadband relay imaging system at 20°C according to a specific embodiment of the present invention.

[0042] Figure 8 This is an MTF curve of a short-to-medium wave infrared broadband relay imaging system at 40°C according to a specific embodiment of the present invention.

[0043] Figure 9 This is an MTF curve of a short-to-medium wave infrared broadband relay imaging system at 60°C according to a specific embodiment of the present invention.

[0044] Figure label:

[0045] 1-Stepped micromirror, 2-Beam splitter, 3-Compensation plate, 4-First lens, 5-Second lens, 6-Third lens, 7-Fourth lens, 8-Fifth lens, 9-Sixth lens, 10-Filter, 11-Detector window, 12-Cold aperture, 13-Detector back focal plane. Detailed Implementation

[0046] 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.

[0047] 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.

[0048] In a specific embodiment of the present invention, a short-mid-wave infrared broadband relay imaging system is provided. The system, along the optical path, sequentially includes a stepped micromirror, a beam splitter, a compensating plate, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a filter, a detector window, a cold aperture, and a detector back focal plane. The detector window, cold aperture, and detector back focal plane together constitute an infrared detector. The first lens is a zero-power wedge-shaped plate; the second lens is a positive-power cylindrical lens; and the third lens is a positive-power binary lens. The system includes a diffractive positive meniscus lens; a fourth lens is a negative optical power negative meniscus lens; a fifth lens is a negative optical power negative meniscus lens; and a sixth lens is a positive optical power positive meniscus lens. The light beam reflected by the stepped micromirror passes sequentially through the beam splitter, the compensation plate, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth 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 from the object side to the image side of the light beam.

[0049] In a specific embodiment, the stepped micromirror is square; 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.

[0050] In a specific implementation, both the beam splitter and the compensation plate are flat plates tilted at 45°, and the beam splitter and the compensation plate are arranged parallel to each other.

[0051] In a specific embodiment, the surfaces of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all coated with an infrared anti-reflection film, and the average transmittance of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens is greater than or equal to 98%.

[0052] In a specific embodiment, the first front surface of the first lens is an inclined surface, and the first rear surface of the first lens is a plane; the second front surface of the second lens is a cylindrical surface, and the second rear surface of the second lens is a spherical surface; the third front surface of the third lens is a spherical surface, and the third rear surface of the third lens is a binary diffraction surface; the fourth front surface and the fourth rear surface of the fourth lens are both spherical surfaces; the fifth front surface of the fifth lens is aspherical, and the fifth rear surface of the fifth lens is spherical; the sixth front surface of the sixth lens is spherical, and the sixth rear surface of the sixth lens is aspherical; the material of the first lens is silicon; the material of the second lens is zinc selenide; the material of the third lens is zinc selenide; the material of the fourth lens is silicon; the material of the fifth lens is silicon; and the material of the sixth lens is zinc sulfide. By combining a wedge-shaped plate and a cylindrical mirror to eliminate large-scale astigmatism across a wide infrared spectrum, and through an innovative combination of optical materials for six different lenses and a binary optical diffraction surface design, wide-band chromatic aberration correction and calorimetric design were achieved. This solved the problem of astigmatism introduced by the beam splitter and compensation plate leading to a huge difference in the imaging transfer function of the lens in the meridional and sagittal directions. At the same time, it also solved the problem of the transfer function reduction caused by the temperature sensitivity of the infrared imaging lens. This meets the imaging requirements of the short-to-mid-wave infrared spectrum under complex environmental conditions.

[0053] In a specific embodiment, the step-micromirror has a field of view height of 48mm, the distance between the step-micromirror and the front surface of the beam splitter is 75mm, the beam splitter has a thickness of 8mm, the distance between the rear surface of the beam splitter and the front surface of the compensation plate is 8mm, the compensation plate has a thickness of 8mm, and the distance between the rear surface of the compensation plate and the first front surface of the first lens ranges from 420mm to 425mm; the first lens has a thickness of 10mm, and the distance between the first rear surface and the second front surface ranges from 11mm to 12mm; the second lens has a thickness range of 7 to 8mm, and the distance between the second rear surface and the third front surface ranges from 45mm to 50mm; the third lens has a thickness of 16mm, and the distance between the third rear surface and the fourth front surface... The distance between the fourth lens and the fifth front lens ranges from 3.5mm to 4mm; the thickness of the fourth lens is 10.8mm, and the distance between the fourth rear surface and the fifth front surface ranges from 2mm to 2.5mm; the thickness of the fifth lens is 11mm, and the distance between the fifth rear surface and the sixth front surface is 18.3mm; the thickness of the sixth lens is 11mm, and the distance between the sixth rear surface and the front surface of the filter is 15mm; the thickness of the filter is 1mm, and the distance between the rear surface of the filter and the detector window is 4mm; the thickness of the detector window is 1mm, and the distance between the rear surface of the detector window and the cold stop is 2.95mm; the aperture of the cold stop is 10.55mm, and the distance between the cold stop and the back focal plane of the detector is 19.8mm.

[0054] In a specific embodiment, the first front surface is a wedge-shaped inclined plate with an inclination angle of 0.068°; the first rear surface is a plane perpendicular to the optical axis; the second front surface is a sagittal cylindrical surface with a curvature range of 1.0E+05mm to 1.3E+05mm; the second rear surface has a curvature radius range of -840mm to -830mm; the third front surface has a curvature radius range of 55mm to 60mm; the third rear surface has a curvature radius of 222.8mm; the fourth front surface has a curvature range of 330mm to 335mm; and the fourth rear surface has a curvature range of 200mm to 205mm.

[0055] The radius of curvature of the fifth front surface is 204.75 mm, and the radius of curvature of the sixth rear surface is 62.87 mm; the radius of curvature of the sixth front surface is 33.3 mm, and the radius of curvature of the sixth rear surface is 41.88 mm.

[0056] In a specific implementation, the field of view height of the short-mid-wave infrared broadband relay imaging system is 48mm, the number of detector pixels is 640×512, the pixel size of the detector is 15μm, and the cutoff frequency of the short-mid-wave infrared broadband relay imaging system is 34lp / mm.

[0057] The short-to-mid-wave infrared broadband relay imaging system provided in the specific embodiments of the present invention adopts a binary diffraction surface design, which reduces the size and weight of the system and achieves achromatic and thermal design; specifically, through the geometry of wedge-shaped plates and cylindrical mirrors, the large-scale astigmatism introduced by beam splitters and compensation plates in short-to-mid-wave infrared interferometric imaging is eliminated.

[0058] The short-to-mid-wave infrared broadband relay imaging system provided in the specific embodiments of the present invention adopts an object-side telecentric optical path design, which makes the relative illumination at the edge of the image plane close to 1, thereby improving the accuracy of imaging spectral measurement; it achieves a calorimetric design by combining a refractive-diffractive hybrid lens and infrared materials with different thermal expansion coefficients, thus meeting the working requirements under wide temperature difference environments; and it achieves a short-to-mid-wave infrared broadband achromatic design by combining a refractive-diffractive hybrid lens and infrared materials with different dispersion characteristics.

[0059] The following detailed description is provided in conjunction with specific embodiments.

[0060] Example

[0061] like Figure 1 The figure shows a schematic diagram of the short-mid-wave infrared broadband relay imaging system provided in this specific embodiment of the present invention. As can be seen from the figure, according to the incident direction of the light, that is, the light beam from the object side to the image side, the short-mid-wave infrared broadband relay imaging system includes, in sequence, a stepped micromirror 1, a beam splitter 2, a compensation plate 3, a first lens 4, a second lens 5, a third lens 6, a fourth lens 7, a fifth lens 8, a sixth lens 9, a filter 10, a detector window 11, a cold aperture 12, and a detector back focal plane 13.

[0062] In this embodiment, both the beam splitter 2 and the compensation plate 3 are parallel flat plates made of zinc selenide; the first lens 4 is a zero-power wedge-shaped plate made of silicon; the second lens 5 is a positive-power cylindrical lens made of zinc selenide; the third lens 6 is a positive-power binary diffraction lens made of zinc selenide; the fourth lens 7 is a negative-power negative meniscus lens made of silicon; the fifth lens 8 is a negative-power negative meniscus aspherical lens made of silicon; and the sixth lens 9 is a positive-power aspherical lens made of zinc sulfide. Creative material combination and power allocation designs are implemented based on the dispersion characteristics (Abbe number) and thermal characteristics (coefficient of thermal expansion) of different materials in different infrared spectral bands, ensuring that the short-to-mid-wave infrared broadband relay imaging system as a whole satisfies the achromatic and pyrochemical equations. All six lenses are coated with infrared anti-reflection films, achieving an average transmittance of over 98% in the applied spectral band, guaranteeing high light throughput for the system.

[0063] like Figure 2 The figure shows a schematic diagram of the stepped micromirror structure in the short-to-mid-wave infrared broadband relay imaging system in this embodiment. As can be seen from the figure, in this embodiment, the stepped micromirror 1 has 320 steps, the width of a single step is 0.15 mm, and the total width of the stepped micromirror 1 is 48 mm. That is, the field of view height of the entire relay imaging system is 48 mm, the detector has 640×512 pixels, the pixel size is 15 μm, and the system cutoff frequency is 34 lp / mm.

[0064] In this embodiment, the height of the stepped micromirror 1 is 48mm, its distance from the front surface of the beam splitter 2 is 75mm, the thickness of the beam splitter 2 is 8mm, and the distance from the rear surface of the beam splitter 2 to the front surface of the compensation plate 3 is 8mm. The thickness of the compensation plate 3 is 8mm, and the distance from the rear surface of the compensation plate 3 to the first front surface of the first lens 4 ranges from 420mm to 425mm. The thickness of the first lens 4 is 10mm, and the first front surface of the first lens 4 is a wedge-shaped inclined plate with a radius of curvature of ∞ and a tilt angle of -0.001185° in the Y direction (i.e., the tilt angle of the wedge-shaped inclined plate is 0.068°). The first rear surface of the first lens 4 is perpendicular to the light... The distance from the first rear surface of the first lens 4 to the second front surface of the second lens 5 in the plane of the axis ranges from 11mm to 12mm; the thickness of the second lens 5 ranges from 7mm to 8mm; the first front surface of the second lens 5 is a cylindrical surface in the sagittal direction with a curvature range of 1.0E+05mm to 1.3E+05mm; the second rear surface is a spherical surface with a radius of curvature range of -840mm to -830mm; and the distance from the second rear surface of the second lens 5 to the third front surface of the third lens 6 ranges from 45mm to 50mm; the thickness of the third lens 6 is 16mm; the third front surface is a spherical surface with a radius of curvature range of 55mm to 60mm; and the third rear surface is a binary diffraction surface with a radius of curvature of 222. The thickness of the fourth lens 7 is 8mm. The aspherical coefficient and diffraction coefficient are shown in Table 1. The distance from the third rear surface to the fourth front surface of the fourth lens 7 ranges from 3.5mm to 4mm. The thickness of the fourth lens 7 is 10.8mm. The curvature of the fourth front surface ranges from 330mm to 335mm, and the curvature of the fourth rear surface ranges from 200mm to 205mm. The distance from the fourth rear surface to the fifth lens 8 ranges from 2mm to 2.5mm. The thickness of the fifth lens 8 is 11mm. The fifth front surface is aspherical with a radius of curvature of 204.75mm. The aspherical coefficient is shown in Table 1. The fifth rear surface is spherical with a radius of curvature of 62.87mm. The distance from the fifth rear surface to the sixth lens 9... The distance between the sixth front surface and the sixth lens 9 is 18.3 mm; the thickness of the sixth lens 9 is 11 mm, the radius of curvature of the sixth front surface is 33.3 mm, the sixth rear surface is aspherical with a radius of curvature of 41.88 mm, and the aspherical coefficient is shown in Table 1. The distance between the sixth rear surface and the front surface of the filter 10 is 15 mm; the thickness of the filter 10 is 1 mm, and the distance between the rear surface of the filter 10 and the detector window 11 is 4 mm; the thickness of the detector window 11 is 1 mm, and the distance between the rear surface of the detector window 11 and the detector cold stop 12 is 2.95 mm; the aperture of the cold stop 12 is 10.55 mm, and the distance between it and the detector back focal plane 13 is 19.8 mm.

[0065] Table 1. Aspherical coefficients and diffraction phase coefficients of each aspherical surface and binary diffraction surface in the system.

[0066]

[0067] In the short-mid-wave infrared broadband relay imaging system provided by this specific embodiment of the present invention, the aspherical surface satisfies the following formula:

[0068]

[0069] In the formula, Z For aspherical sag, c For the curvature of the aspherical vertex, k The 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...

[0070] The short- and mid-wave infrared broadband relay imaging system provided in this embodiment reduces the system size and weight by employing a binary diffraction lens.

[0071] Specifically, the phase function of the binary diffraction lens is:

[0072]

[0073] In the formula, For normalized radial aperture coordinates, A i for 2 i power coefficient i= 1, 2, 3, 4...

[0074] 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:

[0075]

[0076] In the formula, The center wavelength, For the shortest wavelength, It is the longest wavelength.

[0077] In the short-to-mid-wave infrared broadband relay imaging system provided in this embodiment, through reasonable material combination and optical power allocation, each lens element simultaneously satisfies the optical power allocation equation, chromatic aberration equation, and thermal aberration equation:

[0078]

[0079]

[0080]

[0081] In the formula, For the optical power of the relay imaging lens, The incident height of paraxial aperture rays 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 due to 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.

[0082] In this embodiment, the lens barrel material of the short-to-mid-wave infrared broadband relay imaging 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 relay imaging system, i.e., the relay imaging lens, is carried out.

[0083] In this embodiment, the combination of a wedge-shaped plate and a cylindrical lens eliminates the large-scale astigmatism introduced by the beam splitter and compensation plate in the short-to-mid-wave wide infrared band during interferometric imaging. This solves the problem of the huge difference in the imaging transfer function of the lens in the meridional and sagittal directions caused by the astigmatism introduced by the beam splitter and compensation plate. The design of the short-to-mid-wave wide infrared relay imaging system meets 100% cold aperture matching, suppressing the influence of stray light on infrared imaging.

[0084] In this embodiment, the relay imaging lens adopts an object-side telecentric design, with a relative illumination of close to 1 at the edge of the image plane and an image plane distortion of less than 0.5%, which improves the accuracy of imaging spectrum detection when the lens is used for imaging spectrum detection.

[0085] like Figure 3 The figure shows the relative illumination curve of the image plane of the short-to-mid-wave infrared broadband relay imaging system in this embodiment. As can be seen from the figure, the relative illumination uniformity of the edge field of view of the short-to-mid-wave infrared broadband relay imaging system in this embodiment is good, and the edge field of view illumination is close to 1.

[0086] like Figure 4 The figure shows the distortion curve of the short-to-medium wave infrared broadband relay imaging system in this embodiment as a function of the field of view. As can be seen from the figure, the edge field of view distortion of the relay imaging lens system in this embodiment is less than 0.5%.

[0087] like Figures 5-9The figures shown are the MTF curves of the short-to-mid-wave infrared broadband relay imaging system in this embodiment at temperatures of -20℃, 0℃, 20℃, 40℃, and 60℃. As can be seen from the figures, the athermal design of the relay imaging lens in this embodiment can meet the application requirements of complex environments, achieving high MTF imaging over a wide temperature range through passive athermal design. Figure 7 The MTF curve at 20℃ shows that the transfer function of each field of view in the system is greater than 0.55 at 34lp / mm, which fully demonstrates that the relay imaging lens in this embodiment has high imaging quality.

[0088] The short-to-mid-wave infrared broadband relay imaging system provided by this invention adopts an object-side telecentric optical path design, which makes the relative illumination at the edge of the image plane close to 1, thus improving the accuracy of imaging spectral measurement. It achieves a calorimetric design by combining a refractive-diffractive hybrid lens and infrared materials with different thermal expansion coefficients, meeting the requirements for operation in a wide temperature range environment. It also achieves a short-to-mid-wave infrared broadband achromatic design by combining a refractive-diffractive hybrid lens and infrared materials with different dispersion characteristics.

[0089] 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.

[0090] 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-medium wave infrared wide-spectrum relay imaging system, characterized in that, The short-to-mid-wave infrared broadband relay imaging system includes, in sequence along the optical path, a stepped micromirror, a beam splitter, a compensation plate, a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a filter, a detector window, a cold aperture, and a detector back focal plane. The first lens is a zero-power wedge-shaped plate; the second lens is a positive-power cylindrical lens; the third lens is a positive-power binary diffraction positive meniscus lens; the fourth lens is a negative-power negative meniscus lens; the fifth lens is a negative-power negative meniscus lens; and the sixth lens is a positive-power positive meniscus lens. The first lens has a first front surface that is inclined and a first rear surface that is planar; the second lens has a second front surface that is cylindrical and a second rear surface that is spherical; the third lens has a third front surface that is spherical and a third rear surface that is a binary diffraction surface; the fourth lens has a fourth front surface and a fourth rear surface that are both spherical; the fifth lens has a fifth front surface that is aspherical and a fifth rear surface that is spherical; the sixth lens has a sixth front surface that is spherical and a sixth rear surface that is aspherical; the first front surface is a wedge-shaped inclined plate with an inclination angle of 0.068°, and the first rear surface is a plane perpendicular to the optical axis; The second front surface is a cylindrical surface in the sagittal direction, and the curvature range of the second front surface is 1.0E+05mm to 1.3E+05mm; the radius of curvature of the second rear surface ranges from -840mm to -830mm. The radius of curvature of the third front surface ranges from 55 mm to 60 mm; the radius of curvature of the third rear surface is 222.8 mm. The curvature range of the fourth front surface is 330mm to 335mm, and the curvature range of the fourth rear surface is 200mm to 205mm. The radius of curvature of the fifth front surface is 204.75 mm, and the radius of curvature of the fifth rear surface is 62.87 mm. The radius of curvature of the sixth front surface is 33.3 mm, and the radius of curvature of the sixth rear surface is 41.88 mm. The light beam reflected by the stepped micromirror passes sequentially through the beam splitter, the compensation plate, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth 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 light beam from the object side to the image side.

2. The short-to-medium wave infrared wide spectral band relay imaging system according to claim 1, wherein, The stepped micromirror is square.

3. The short-to-medium wave infrared wide spectral band relay imaging system according to claim 1, wherein, 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.

4. The short-to-medium wave infrared wide spectral band relay imaging system according to claim 1, wherein, Both the beam splitter and the compensation plate are flat plates tilted at 45°, and the beam splitter and the compensation plate are arranged parallel to each other.

5. The short-to-medium wave infrared wide spectral band relay imaging system according to claim 1, wherein, The surfaces of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all coated with an infrared anti-reflection film, and the average transmittance of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens is greater than or equal to 98%.

6. The short-to-medium wave infrared wide spectral band relay imaging system according to claim 1, wherein, The first lens is made of silicon; the second lens is made of zinc selenide; the third lens is made of zinc selenide; and the fourth lens is made of silicon. The fifth lens is made of silicon; the sixth lens is made of zinc sulfide.

7. The short-to-medium wave infrared wide spectral band relay imaging system according to claim 1, wherein, The stepped micromirror has a field of view height of 48mm, the distance between the stepped micromirror and the front surface of the beam splitter is 75mm, the thickness of the beam splitter is 8mm, the distance between the rear surface of the beam splitter and the front surface of the compensation plate is 8mm, the thickness of the compensation plate is 8mm, and the distance between the rear surface of the compensation plate and the first front surface of the first lens ranges from 420mm to 425mm. The thickness of the first lens is 10mm, and the distance between the first rear surface and the second front surface ranges from 11mm to 12mm; The thickness of the second lens is 7-8 mm, and the distance between the second rear surface and the third front surface is 45 mm-50 mm. The thickness of the third lens is 16mm, and the distance between the third rear surface and the fourth front surface ranges from 3.5mm to 4mm. The thickness of the fourth lens is 10.8 mm, and the distance between the fourth rear surface and the fifth front surface ranges from 2 mm to 2.5 mm. The thickness of the fifth lens is 11 mm, and the distance between the fifth rear surface and the sixth front surface is 18.3 mm; The thickness of the sixth lens is 11mm, and the distance between the sixth rear surface and the front surface of the filter is 15mm. The filter has a thickness of 1 mm, and the distance between the rear surface of the filter and the detector window is 4 mm. The detector window has a thickness of 1 mm, and the distance between the rear surface of the detector window and the cold aperture is 2.95 mm. The aperture of the cold stop is 10.55 mm, and the distance between the cold stop and the back focal plane of the detector is 19.8 mm.

8. The short-to-medium wave infrared wide spectral band relay imaging system of claim 1, wherein, The field of view height of the short-mid-wave infrared broadband relay imaging system is 48 mm, the number of pixels on the back focal plane of the detector is 640×512, the pixel size on the back focal plane of the detector is 15 μm, and the cutoff frequency of the short-mid-wave infrared broadband relay imaging system is 34 lp / mm.

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