A long-wave infrared remote sensing imaging spectrometer objective

Abstract

The application relates to a long-wave infrared remote sensing imaging spectrometer objective, which is composed of a meniscus positive lens A, a meniscus negative lens B and a meniscus positive lens C arranged in sequence along the same optical axis; the convex surface of the meniscus positive lens A and the meniscus negative lens B faces the object side; the convex surface of the meniscus positive lens C faces the image side; an aperture diaphragm is located on the front surface or the rear surface of the meniscus positive lens A, and the chief ray of each field of view is parallel to the optical axis when exiting the lens; and infrared radiation emitted by an object is imaged on the focal plane of the objective. The application effectively corrects the aberration of the lens and realizes the output of a telecentric light path; when the temperature changes, the focal plane displacement of the objective matches the expansion and contraction of the aluminum alloy lens barrel, and the imaging position is relatively stable.

Description

Technical Field

[0001] This invention belongs to the field of lens technology and relates to a remote sensing imaging spectrometer objective lens that operates in the long-wave infrared band and can adapt to a wide temperature range. Background Technology

[0002] Long-wave infrared imaging spectrometers have significant applications in remote sensing. They can classify the landforms of remotely sensed areas, identify mineral types and vegetation types, and determine vegetation growth. Based on the characteristic absorption lines of certain gases in the long-wave infrared band, long-wave infrared imaging spectrometers can also identify gas composition and detect corresponding gas concentrations.

[0003] The optical system of a long-wave infrared remote sensing imaging spectrometer typically consists of four parts: an objective lens, a collimating lens, a beam splitter, and a condenser lens. The objective lens, as the front-end optical module, directly images the infrared radiation emitted by the object onto the slit of its focal plane, determining the spatial resolution of the imaging spectrometer. The optical performance of the objective lens directly affects the quality of the imaging spectrometer.

[0004] In traditional long-wave infrared objective lens design, germanium has always been the preferred lens material due to its high refractive index and low dispersion. However, germanium's refractive index is extremely sensitive to temperature, and high-performance germanium lenses operating at room temperature often experience a significant drop in image quality when operating at high or low temperatures. Although mechanical focusing compensation or thermal optical-mechanical design can maintain high image quality at both high and low temperatures, this undoubtedly increases the complexity of the system. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an objective lens for a long-wave infrared remote sensing imaging spectrometer. The objective lens has a compact structure and can acquire hyperspectral images of objects over a wide temperature range without the need for focusing or complex optomechanical compensation.

[0006] To solve the above-mentioned technical problems, the objective lens of the long-wave infrared remote sensing imaging spectrometer of the present invention is composed of a meniscus positive lens A, a meniscus negative lens B, and a meniscus positive lens C arranged sequentially along the same optical axis; the convex surfaces of the meniscus positive lens A and the meniscus negative lens B face the object side; the convex surface of the meniscus positive lens C faces the image side; the aperture stop is located on the front or rear surface of the meniscus positive lens A, and the principal rays of each field of view are parallel to the optical axis when they exit the lens; the infrared radiation emitted by the object is imaged onto the focal plane I of the objective lens.

[0007] The ratio of the focal lengths of the positive meniscus lens A, negative meniscus lens B, and positive meniscus lens C is (1-1.07):-1:(1.23-1.3).

[0008] Each lens surface is spherical.

[0009] The positive meniscus lens A and positive meniscus lens C are made of chalcogenide glass, while the negative meniscus lens B is made of ZnSe.

[0010] Preferably, the meniscus lens A and meniscus lens C are made of Se. 60 As 40 Material.

[0011] Preferably, the focal lengths of the meniscus positive lens A, meniscus negative lens B, and meniscus positive lens C are 21.8 mm, -20.4 mm, and 26.3 mm, respectively.

[0012] Furthermore, the radius of curvature of the optical surface of each lens, the thickness of the lens, and the spacing between adjacent lenses are shown in the table below, where R... i Let t represent the radius of curvature of the i-th optical surface, i = 1, 2, 3, ..., 6; j d represents the thickness of the j-th lens, where j = 1, 2, 3; n D1 represents the air gap between the rear surface of the nth lens and the front surface of the next lens, where n = 1, 2; D2 represents the distance from the rear surface of the third lens 3 to the focal plane of the objective lens.

[0013] Table 1

[0014]

[0015] The surfaces of each lens can also be aspherical.

[0016] When this invention is in operation, the lens images a distant line-field target, and the size of the imaged surface is 7mm × 0.2mm.

[0017] Beneficial effects

[0018] This invention employs a combination of two chalcogenide glass positive meniscus lenses and one ZnSe negative meniscus lens, matched with an aluminum alloy thermal expansion system to achieve calorific value. Lens aberrations are effectively corrected by controlling the lens curvature direction. Simultaneously, the lens aperture is located on the front or rear surface of the first lens, enabling telecentric optical path output. This invention achieves a calorific lens design through the combination of positive and negative lens materials and an aluminum alloy lens barrel. When the temperature changes, the focal plane displacement of the objective lens matches the expansion and contraction of the aluminum alloy lens barrel, maintaining a relatively stable imaging position. Attached Figure Description

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 This is a schematic diagram of the structure of the present invention.

[0021] Figure 2 This is the modulation transfer function curve of the present invention at 20°C.

[0022] Figure 3 This is the modulation transfer function curve of the present invention at -40℃.

[0023] Figure 4 This is the modulation transfer function curve of the present invention at 80°C. Detailed Implementation

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] like Figure 1 As shown, the objective lens of the long-wave infrared remote sensing imaging spectrometer of the present invention consists of a meniscus positive lens A, a meniscus negative lens B, and a meniscus positive lens C arranged sequentially along the same optical axis; the convex surfaces of the meniscus positive lens A and the meniscus negative lens B face the object side; the convex surface of the meniscus positive lens C faces the image side; the aperture stop is located on the front or rear surface of the meniscus positive lens A, and the principal rays of each field of view are parallel to the optical axis when they exit the lens; the infrared radiation emitted by the object is imaged onto the focal plane I of the objective lens.

[0026] The following is the most preferred embodiment of the present invention.

[0027] The focal lengths of the meniscus positive lens A, meniscus negative lens B, and meniscus positive lens C are 21.8 mm, -20.4 mm, and 26.3 mm, respectively; the surface of each lens is spherical.

[0028] The meniscus lens A and meniscus lens C mentioned above use Se. 60 As 40 The meniscus negative lens B is made of ZnSe material. The positive lens Se in the lens... 60 As 40 The combination of this material and the negative lens ZnSe material enables a heat-free lens design. When the temperature changes, the focal plane shift of the objective lens matches the expansion and contraction of the aluminum alloy lens barrel, keeping the imaging position relatively constant.

[0029] The radii of curvature of the optical surfaces of the three lenses, the thickness of the lenses, and the spacing between adjacent lenses are shown in the table below. In the table, R... i Let t represent the radius of curvature of the i-th optical surface, i = 1, 2, 3, ..., 6; j d represents the thickness of the j-th lens, where j = 1, 2, 3; nD1 represents the air gap between the rear surface of the nth lens and the front surface of the next lens, where n = 1, 2; D2 represents the distance from the rear surface of the third lens 3 to the image plane of the detector.

[0030] Table 1

[0031]

[0032] The modulation transfer function curves for field angles of 0°, 2.5°, 5°, 7.5°, and 10° at a temperature of 20°C are shown in the example below. Figure 2 As shown in the figure, the modulation transfer function values ​​for each field of view at 20 lp / mm are close to the diffraction limit, indicating that the lens has good imaging quality across the entire field of view within its operating wavelength range.

[0033] The modulation transfer function curves for field of view angles of 0°, 2.5°, 5°, 7.5°, and 10° at a temperature of -40°C are shown below. Figure 3 As shown in the figure. The modulation transfer function values ​​for each field of view are... Figure 2 The result is comparable, indicating that the image quality of the lens at -40℃ is almost unchanged compared to that at 20℃.

[0034] The modulation transfer function curves for field angles of 0°, 2.5°, 5°, 7.5°, and 10° at a temperature of 80°C are shown below. Figure 4 As shown in the figure. The modulation transfer function values ​​for each field of view are... Figure 2 The result is comparable, indicating that the image quality remains almost unchanged when the lens operates at 80°C compared to 20°C.

[0035] The theoretical focal length ratio of the meniscus positive lens A, meniscus negative lens B, and meniscus positive lens C is 1:-1:1.3; during actual debugging, the imaging effect of each field of view in the temperature range of -40℃ to 80℃ is slightly worse than that of the above-mentioned optimal embodiment.

[0036] The meniscus positive lens A, meniscus negative lens B, and meniscus positive lens C are respectively made of Se 60 As 40 , ZnSe and Ge 20 Se 65 Sb 15 After optimization, the lens produces good image quality within a temperature range of -15℃ to 55℃, but the image quality deteriorates beyond this temperature range.

[0037] The meniscus positive lens A, meniscus negative lens B, and meniscus positive lens C are respectively made of Ge, ZnSe, and Ge. 28 Se 60 Sb 12 After optimization, the lens produces good image quality within a temperature range of 10℃ to 30℃, but poor image quality at low and high temperatures.

[0038] The meniscus positive lens A, meniscus negative lens B, and meniscus positive lens C are respectively made of Ge 10 Se 50 As 40 , ZnSe and Ge 28 Se 60 Sb 12 After optimization, the lens image quality is only good within the temperature range of -10℃ to 50℃.

[0039] The meniscus positive lens A, meniscus negative lens B, and meniscus positive lens C are respectively made of Se 63 As 30 Sb4Sn3, ZnSe and Se 63 As 30 When using Sb4Sn3, after optimization, the lens image quality is better when operating only within the temperature range of -20℃ to 60℃.

[0040] There are many types of chalcogenide glass. For the three lens materials, the image quality obtained by each combination is unknown in advance. The inventors of this invention have also used many other material combinations, but the lenses could not achieve good imaging effects in the temperature range of -40℃ to 80℃.

[0041] The difficulty of this invention lies in the selection and matching of lens materials, and the optimal combination of materials that can achieve good imaging effect in a temperature range of -40℃ to 80℃.

[0042] Aspherical surfaces can also be used on the surfaces of the lenses. While aspherical surfaces are more expensive, they can produce better image quality.

Claims

1. An objective lens for a long-wave infrared remote sensing imaging spectrometer, characterized in that... It consists of a meniscus positive lens A, a meniscus negative lens B, and a meniscus positive lens C arranged sequentially along the same optical axis; the convex surfaces of meniscus positive lens A and meniscus negative lens B face the object side; the convex surface of meniscus positive lens C faces the image side; the aperture stop is located on the front or rear surface of meniscus positive lens A, and the principal rays of each field of view are parallel to the optical axis when they exit the lens. The infrared radiation emitted by the object is imaged onto the focal plane I of the objective lens; the radius of curvature of each lens's optical surface, the lens thickness, and the spacing between adjacent lenses are shown in the table below, where R... i Let represent the radius of curvature of the i-th optical surface, i = 1, 2, 3, ..., 6; t j d represents the thickness of the j-th lens, where j = 1, 2, 3; n D1 represents the air gap between the rear surface of the nth lens and the front surface of the next lens, where n = 1, 2; D2 represents the distance from the rear surface of the third lens 3 to the focal plane of the objective lens.

2. The objective lens of the long-wave infrared remote sensing imaging spectrometer according to claim 1, characterized in that... The ratio of the focal lengths of the positive meniscus lens A, negative meniscus lens B, and positive meniscus lens C is (1~1.07):-1:(1.23~1.3).

3. The objective lens of the long-wave infrared remote sensing imaging spectrometer according to claim 1, characterized in that... Each lens surface is spherical.

4. The objective lens of the long-wave infrared remote sensing imaging spectrometer according to claim 1, characterized in that... The positive meniscus lens A and positive meniscus lens C are made of chalcogenide glass, while the negative meniscus lens B is made of ZnSe.

5. The objective lens of the long-wave infrared remote sensing imaging spectrometer according to claim 4, characterized in that... The meniscus lens A and meniscus lens C mentioned above use Se. 60 As 40 Material.

6. The objective lens of the long-wave infrared remote sensing imaging spectrometer according to claim 1, characterized in that... The focal lengths of the meniscus positive lens A, meniscus negative lens B, and meniscus positive lens C are 21.8 mm, -20.4 mm, and 26.3 mm, respectively.

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