A large-telephoto-ratio wide-band athermalized optical imaging system

Abstract

The application relates to a large-telephoto-ratio wide-waveband athermalized optical imaging system, which is composed of a plano-concave lens G1, a double-convex lens G2, a double-concave lens G3, a negative-power meniscus lens G4, a double-convex lens G5, a diaphragm, a negative-power meniscus lens G6, a double-convex lens G7, a negative-power meniscus lens G8 and a double-convex lens G9 arranged in sequence along an optical axis from an object side to an image side; the negative-power meniscus lens G6 and the double-convex lens G7 form a cemented lens; all the lens surfaces are spherical surfaces except that the front surface of the plano-concave lens G1 is a plane; the convex surfaces of the negative-power meniscus lens G4 and the negative-power meniscus lens G6 face the object side, and the concave surface of the negative-power meniscus lens G8 faces the object side; the application has a wide working waveband range, high resolution, can clearly image a micro target in a wide temperature range, has a large telephoto ratio, and is beneficial to placing other optical components such as light splitting elements or mechanical components.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of imaging optical system design, and particularly relates to a wide-band athermalized optical imaging system with a large telephoto ratio. BACKGROUND

[0002] The spectral response range of a common camera is the visible light range. According to the imaging characteristics of different wave bands, it is necessary to develop imaging systems suitable for various environments and covering multiple wave bands, which will greatly improve the ability to detect and identify targets and the identification rate. According to different needs, a wide-band imaging system often adds a light splitting element or other mechanical components in front of the detector, which requires a long back working distance, i.e., a large telephoto ratio, for the optical imaging system.

[0003] When an optical imaging system works in an environment with large temperature variation, it is necessary to use athermalization technology to compensate for the thermal defocus caused by the optical system in order to have good performance in the entire temperature range. In the past, athermalization design was mostly used for infrared optical systems or aviation lenses, while optical imaging systems working in the visible light or near-infrared range mostly used ordinary optical glass, which has a very small temperature refractive index coefficient, so the thermal defocus caused by temperature is often ignored. However, when the back working distance of an optical system is long, the mechanical structure or mechanical connection is also long, and the thermal defocus cannot be ignored. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a wide-band athermalized optical imaging system with a large telephoto ratio.

[0005] In order to solve the above technical problem, the wide-band athermalized optical imaging system with a large telephoto ratio comprises, in order along the optical axis from the object side to the image side, a plano-concave lens G1, a double convex lens G2, a double concave lens G3, a negative power meniscus lens G4, a double convex lens G5, a diaphragm, a negative power meniscus lens G6, a double convex lens G7, a negative power meniscus lens G8, and a double convex lens G9; the negative power meniscus lens G6 and the double convex lens G7 form a cemented lens; except that the front surface of the plano-concave lens G1 is a plane, the other lens surfaces are spherical surfaces; the convex surfaces of the negative power meniscus lens G4 and the negative power meniscus lens G6 face the object side, and the concave surface of the negative power meniscus lens G8 faces the object side.

[0006] Further, the flat-concave lens G1 has a front surface curvature radius of ∞ and a back surface curvature radius of 20.56-24.99 mm; the biconvex lens G2 has a front surface curvature radius of 31.05-34.14 mm and a back surface curvature radius of -44.04--41.23 mm; the biconcave lens G3 has a front surface curvature radius of -26.49--22.84 mm and a back surface curvature radius of 11.93-13.56 mm; the negative-power meniscus lens G4 has a front surface curvature radius of 119.52-143.58 mm and a back surface curvature radius of 10.14-10.96 mm; the biconvex lens G5 has a front surface curvature radius of 10.85-11.63 mm and a back surface curvature radius of -33.23--27.51 mm; the negative-power meniscus lens G6 has a front surface curvature radius of 59.65-68.10 mm and a back surface curvature radius of 9.06-9.17 mm; the biconvex lens G7 has a front surface curvature radius of 9.06-9.17 mm and a back surface curvature radius of -9.21--8.62 mm; the negative-power meniscus lens G8 has a front surface curvature radius of -8.75--8.54 mm and a back surface curvature radius of -32.34--30.85 mm; and the biconvex lens G9 has a front surface curvature radius of 37.87-41.13 mm and a back surface curvature radius of -13.09--12.94 mm.

[0007] Further, the flat-concave lens G1 has a center thickness of 1.86-1.94 mm; the biconvex lens G2 has a center thickness of 4.98-5.02 mm; the biconcave lens G3 has a center thickness of 1.88-1.92 mm; the negative-power meniscus lens G4 has a center thickness of 4.96-5.04 mm; the biconvex lens G5 has a center thickness of 4.98-5.02 mm; the negative-power meniscus lens G6 has a center thickness of 1.88-1.92 mm; the biconvex lens G7 has a center thickness of 6.17-6.23 mm; the negative-power meniscus lens G8 has a center thickness of 1.18-1.22 mm; and the biconvex lens G9 has a center thickness of 3.98-4.03 mm.

[0008] Further, the center air gap of the plano-concave lens G1 and the biconvex lens G2 is 1.18-1.22 mm; the center air gap of the biconvex lens G2 and the biconcave lens G3 is 7.48-7.60 mm; the center air gap of the biconcave lens G3 and the negative-power meniscus lens G4 is 20.44-20.68 mm; the center air gap of the negative-power meniscus lens G4 and the biconvex lens G5 is 0.38-0.42 mm; the center air gap of the biconvex lens G5 and the diaphragm is 1.95-2.03 mm; the center air gap of the diaphragm and the negative-power meniscus lens G6 is 0.48-0.52 mm; the center air gap of the biconvex lens G7 and the negative-power meniscus lens G8 is 0.71-0.75 mm; the center air gap of the negative-power meniscus lens G8 and the biconvex lens G9 is 0.10-0.12 mm; and the center air gap of the biconvex lens G9 to the image plane is 28.01-28.24 mm.

[0009] Further, in the present application, all the lenses are made of glass, the refractive index Nd1 and the dispersion coefficient Vd1 of the plano-concave lens G1 satisfy the conditions: 1.6

[0010] The working waveband of the application covers the visible light and near-infrared spectrum region of 400-1000nm, the back working distance is 28.01-28.24mm, the telephoto ratio is 2.24-2.26, the total optical length (the distance between the center vertex of the front surface of the flat-concave lens G1 and the image surface) is 92.6-93.92mm; the imaging resolution can reach 2600x2160, when imaging in the working environment of-40℃-60℃, all the lenses, diaphragms and image surfaces remain unchanged, without any adjustment, the image quality is excellent.

[0011] The application has the advantages that: the optical system has a wide working waveband range, can simultaneously image the visible light spectrum region and the near-infrared spectrum region of the target, improves the observation ability of the optical system to the target and expands the application field; the optical system has high resolution, can clearly image the tiny target in a wide temperature range, the optical system adopts athermalization design, without adding a mechanical focusing mechanism, in different temperature working environments, the optical elements and the image surface can realize non-defocus without any adjustment, the structure is simple; the long back working distance is beneficial to placing other optical components such as light splitting elements or mechanical components. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a structure diagram of the wide waveband athermalization optical imaging system with a large telephoto ratio of the application;

[0013] Figure 2 is a modulation transfer function curve diagram of the wide waveband athermalization optical imaging system with a large telephoto ratio of the application at 20℃;

[0014] Figure 3 is a modulation transfer function curve diagram of the wide waveband athermalization optical imaging system with a large telephoto ratio of the application at-40℃;

[0015] Figure 4 is a modulation transfer function curve diagram of the wide waveband athermalization optical imaging system with a large telephoto ratio of the application at 60℃;

[0016] Figure 5 is a defocus curve diagram of the wide waveband athermalization optical imaging system with a large telephoto ratio of the application at 20℃;

[0017] Figure 6 is a defocus curve diagram of the wide waveband athermalization optical imaging system with a large telephoto ratio of the application at-40℃;

[0018] Figure 7 is a defocus curve diagram of the wide waveband athermalization optical imaging system with a large telephoto ratio of the application at 60℃;

[0019] Figure 1 in which 0 is a diaphragm and 1 is an image surface. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0021] like Figure 1 As shown, the high telephoto ratio, wide-band athermal optical imaging system of the present invention comprises, along the optical axis from object to image, a plano-concave lens G1, a biconvex lens G2, a biconcave lens G3, a negative power meniscus lens G4, a biconvex lens G5, an aperture stop, a negative power meniscus lens G6, a biconvex lens G7, a negative power meniscus lens G8, and a biconvex lens G9. The negative power meniscus lens G6 and the biconvex lens G7 are cemented together to form a cemented lens. Except for the plano-concave lens G1, which has a planar front surface, all other lens surfaces are spherical. The convex surfaces of the negative power meniscus lenses G4 and G6 face the object, and the concave surface of the negative power meniscus lens G8 faces the object. Commonly known plano-concave lenses and biconcave lenses are all negative power lenses, while biconvex lenses are all positive power lenses.

[0022] When the wide-band calorimetric, high-telephoto-ratio, calorimetric optical imaging system of the present invention is used in an operating environment of -40℃ to 60℃, all lenses, apertures and image planes remain fixed.

[0023] Example 1:

[0024] The specific parameters of each lens in this embodiment are shown in Table 1.

[0025] Table 1

[0026]

[0027] In this embodiment, the high-resolution wideband optical imaging system operates in the 400–1000 nm band, has an effective focal length of 12.5 mm, an F-number of 2.8, a maximum diagonal half-field of view of 18.6°, a compatible detector array of 2600×2160 pixels with a pixel size of 2.5 μm × 2.5 μm, an operating temperature of -40°C to 60°C, a rear working distance of 28.15 mm, a total optical length (distance from the center vertex of the front surface of the first lens G1 to the image plane) of 93.3 mm, and a telephoto ratio of 2.25.

[0028] Figure 2 The modulation transfer function curve of the optical imaging system in this embodiment at 20°C shows that the modulation transfer function value of the central field of view at the cutoff frequency of 200 lp / mm is better than 0.41; the modulation transfer function value of the maximum field of view at the cutoff frequency of 200 lp / mm is better than 0.21, indicating that the optical imaging system can clearly image small targets.

[0029] Figure 3The modulation transfer function curve of the optical imaging system in this embodiment at -40°C shows that the modulation transfer function value of the central field of view at the cutoff frequency of 200 lp / mm is better than 0.38; the modulation transfer function value of the maximum field of view at the cutoff frequency of 200 lp / mm is better than 0.20. The optical imaging system can clearly image small targets at low temperatures.

[0030] Figure 4 The modulation transfer function curve of the optical imaging system in this embodiment at 60°C shows that the modulation transfer function value of the central field of view at the cutoff frequency of 200 lp / mm is better than 0.38; the modulation transfer function value of the maximum field of view at the cutoff frequency of 200 lp / mm is better than 0.24. The optical imaging system can clearly image small targets at high temperatures.

[0031] Figure 5 , Figure 6 , Figure 7 The defocus curves of the optical imaging system in this embodiment at different temperatures show that, except for the maximum field of view, the curves of each field of view are relatively concentrated, and the maximum field of view curve deviates very little from the other fields of view, which can meet the requirement of not defocusing.

[0032] Example 2

[0033] The specific parameters of each lens in this embodiment are shown in Table 2.

[0034] Table 2

[0035]

[0036]

[0037] In this embodiment, the high-resolution wideband optical imaging system operates in the 400–1000 nm band, has an effective focal length of 12.5 mm, an F-number of 2.8, a maximum diagonal half-field of view of 18.6°, a compatible detector array of 2600×2160 pixels with a pixel size of 2.5 μm × 2.5 μm, an operating temperature of -40°C to 60°C, a rear working distance of 28.24 mm, a total optical length (distance from the center vertex of the front surface of the first lens G1 to the image plane) of 93.92 mm, and a telephoto ratio of 2.26.

[0038] When the optical imaging system of this embodiment operates in a temperature range of -40℃ to 60℃, the modulation transfer function (MJF) values ​​at the cutoff frequency of 200 lp / mm for the central field of view are all better than 0.35, and the MJF values ​​at the cutoff frequency of 200 lp / mm for the maximum field of view are all better than 0.18. The optical imaging system can clearly image small targets. The defocus curves for different fields of view are relatively concentrated, which meets the optical system's requirement for non-defocusing.

[0039] Example 3

[0040] The specific parameters of each lens in this embodiment are shown in Table 3.

[0041] Table 3

[0042]

[0043]

[0044] In this embodiment, the high-resolution wideband optical imaging system operates in the 400–1000 nm band, has an effective focal length of 12.5 mm, an F-number of 2.8, a maximum diagonal half-field of view of 18.6°, a compatible detector array of 2600×2160 pixels with a pixel size of 2.5 μm × 2.5 μm, an operating temperature of -40°C to 60°C, a rear working distance of 28.01 mm, a total optical length (distance from the center vertex of the front surface of the first lens G1 to the image plane) of 92.6 mm, and a telephoto ratio of 2.24.

[0045] When the optical imaging system of this embodiment operates in a temperature range of -40℃ to 60℃, the modulation transfer function (MJF) values ​​at the cutoff frequency of 200 lp / mm for the central field of view are all better than 0.33, and the MJF values ​​at the cutoff frequency of 200 lp / mm for the maximum field of view are all better than 0.16. The optical imaging system can clearly image small targets. The defocus curves for different fields of view are relatively concentrated, which meets the optical system's requirement for non-defocusing.

Claims

1. A wide-band, calorimetric, high-telephoto-ratio, calorimetric optical imaging system, characterized in that... It consists of a plano-concave lens G1, a biconvex lens G2, a biconvex lens G3, a negative power meniscus lens G4, a biconvex lens G5, an aperture stop, a negative power meniscus lens G6, a biconvex lens G7, a negative power meniscus lens G8, and a biconvex lens G9 arranged sequentially along the optical axis from the object side to the image side; the negative power meniscus lens G6 and the biconvex lens G7 form a cemented lens; except for the front surface of the plano-concave lens G1, which is flat, the other lens surfaces are spherical; the convex surfaces of the negative power meniscus lenses G4 and G6 face the object side, and the concave surface of the negative power meniscus lens G8 faces the object side.

2. The wide-band, calorimetric, high telephoto ratio calorimetric optical imaging system according to claim 1, characterized in that... The plano-concave lens G1 has an infinity radius of curvature on its front surface and a radius of curvature of 20.56–24.99 mm on its rear surface; the biconvex lens G2 has infinity radii of curvature of 31.05–34.14 mm and -44.04–-41.23 mm on its front and rear surfaces, respectively; the biconcave lens G3 has infinity radii of curvature of -26.49–-22.84 mm and 11.93–13.56 mm on its front and rear surfaces, respectively; the negative power meniscus lens G4 has infinity radii of curvature of 119.52–143.58 mm and 10.14–10.96 mm on its front and rear surfaces, respectively; and the biconvex lens G5 has infinity radii of curvature of 10.85–11 mm on its front and rear surfaces, respectively. The negative power meniscus lens G6 has front and rear surface radii of curvature of 59.65–68.10 mm and 9.06–9.17 mm, respectively; the biconvex lens G7 has front and rear surface radii of curvature of 9.06–9.17 mm and -9.21–8.62 mm, respectively; the negative power meniscus lens G8 has front and rear surface radii of curvature of -8.75–8.54 mm and -32.34–30.85 mm, respectively; and the biconvex lens G9 has front and rear surface radii of curvature of 37.87–41.13 mm and -13.09–12.94 mm, respectively.

3. The wide-band, calorimetric, high telephoto ratio calorimetric optical imaging system according to claim 2, characterized in that... The center thickness of the plano-concave lens G1 is 1.86–1.94 mm; the center thickness of the biconvex lens G2 is 4.98–5.02 mm; the center thickness of the biconcave lens G3 is 1.88–1.92 mm; the center thickness of the negative power meniscus lens G4 is 4.96–5.04 mm; the center thickness of the biconvex lens G5 is 4.98–5.02 mm; the center thickness of the negative power meniscus lens G6 is 1.88–1.92 mm; the center thickness of the biconvex lens G7 is 6.17–6.23 mm; the center thickness of the negative power meniscus lens G8 is 1.18–1.22 mm; and the center thickness of the biconvex lens G9 is 3.98–4.03 mm.

4. The wide-band, calorimetric, high telephoto ratio athermal optical imaging system according to claim 1, characterized in that... The air gap between the centers of the plano-concave lens G1 and the biconvex lens G2 is 1.18–1.22 mm; the air gap between the centers of the biconvex lens G2 and the biconcave lens G3 is 7.48–7.60 mm; the air gap between the centers of the biconcave lens G3 and the negative power meniscus lens G4 is 20.44–20.68 mm; the air gap between the centers of the negative power meniscus lens G4 and the biconvex lens G5 is 0.38–0.42 mm; the air gap between the center of the biconvex lens G5 and the aperture stop is... The air gap is 1.95–2.03 mm; the center air gap between the aperture stop and the negative power meniscus lens G6 is 0.48–0.52 mm; the center air gap between the biconvex lens G7 and the negative power meniscus lens G8 is 0.71–0.75 mm; the center air gap between the negative power meniscus lens G8 and the biconvex lens G9 is 0.10–0.12 mm; the center air gap from the biconvex lens G9 to the image plane is 28.01–28.24 mm.

5. The wide-band, calorimetric, high telephoto ratio calorimetric optical imaging system according to claim 1, characterized in that... All lenses are made of glass. The refractive index Nd1 and dispersion coefficient Vd1 of the plano-concave lens G1 satisfy the following conditions: 1.6 < Nd1 < 1.7, 45 < Vd1 < 50; the refractive index Nd2 and dispersion coefficient Vd2 of the biconvex lens G2 satisfy the following conditions: 1.7 < Nd2 < 1.8, 50 < Vd2 < 55; the refractive index Nd3 and dispersion coefficient Vd3 of the biconcave lens G3 satisfy the following conditions: 1.5 < Nd3 < 1.6, 70 < Vd3 < 75; the refractive index Nd4 and dispersion coefficient Vd4 of the negative optical power meniscus lens G4 satisfy the following conditions: 1.5 < Nd4 < 1.6, 70 < Vd4 < 75; the refractive index Nd5 and dispersion coefficient Vd5 of the biconvex lens G5 satisfy the following conditions: The following conditions must be met: 1.7 < Nd5 < 1.8, 40 < Vd5 < 45; The refractive index Nd6 and dispersion coefficient Vd6 of the negative optical power meniscus lens G6 must meet the following conditions: 1.7 < Nd6 < 1.8, 30 < Vd6 < 35; The refractive index Nd7 and dispersion coefficient Vd7 of the biconvex lens G7 must meet the following conditions: 1.4 < Nd7 < 1.5, 90 < Vd7 < 95; The refractive index Nd8 and dispersion coefficient Vd8 of the negative optical power meniscus lens G8 must meet the following conditions: 1.6 < Nd8 < 1.7, 50 < Vd8 < 60; The refractive index Nd9 and dispersion coefficient Vd9 of the biconvex lens G9 must meet the following conditions: 1.4 < Nd9 < 1.5, 90 < Vd9 < 95.

6. The wide-band, calorimetric, high telephoto ratio calorimetric optical imaging system according to claim 1, characterized in that... The system has a working distance of 28.01–28.24 mm, a telephoto ratio of 2.24–2.26, and a total optical length of 92.6–93.92 mm.

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