Ultra-short light medium-wave infrared continuous zooming optical system

Abstract

The utility model relates to an ultra-short light medium-wave infrared continuous zooming optical system, which sequentially consists of a front fixing group, a zooming group, a compensation group, a focusing group, a relay group and a medium-wave HOT infrared detector along the transmission direction of incident infrared radiation. According to the utility model, only two common infrared materials of Si and Ge are used, the six lenses are totally used, and through the relative movement of the zoom lens group and the compensation lens group, clear imaging within the focal length range of 36.5-220mm is realized. The total length from the front surface of the first lens to the image plane is 66.2 mm, the telephoto ratio is 0.3, the total optical length is very short, the axial size of the system is shortened, the weight and the cost are reduced, 100% cold shield efficiency is achieved, the imaging quality is improved, good imaging quality is kept within the range of-40 DEG C to 60 DEG C, athermalization, low cost, light and small size and high performance are achieved, and the lens is suitable for large-scale popularization and application. The optical system is suitable for all light and small photoelectric systems with strict requirements on the size and the weight of the optical system, in particular to handheld portable photoelectric products.

Description

Technical Field

[0001] The utility model relates to the field of infrared complete machine, optoelectronic system technology system - optical design technology, specifically to an ultra-short and lightweight medium-wave infrared continuous zoom optical system, which is mainly used in the fields of handheld infrared thermal imagers, small unmanned vehicles and drones. Background Art

[0002] As thermal imagers are increasingly used in security patrols, target identification, and rescue operations, they are increasingly required to achieve continuous zoom, high performance, and a lightweight and compact design. In the future, thermal imagers will be used in applications such as lightweight handheld thermal imagers, thermal imagers for miniature unmanned vehicles, and thermal imagers for small drones.

[0003] Therefore, an ultra-short, lightweight, medium-wave infrared continuous zoom optical system can enable handheld thermal imagers to acquire high-resolution infrared images in real time, thereby improving the accuracy and efficiency of exploration and identification. Furthermore, this optical system can be integrated into the thermal imagers of micro-unmanned vehicles and small drones, improving all-round surveillance and intelligence gathering capabilities and effectively enhancing target recognition capabilities.

[0004] The ultra-short and lightweight medium-wave infrared continuous zoom optical system can keep the target image clear at all times during the zoom process and can realize the transformation of any field of view within the zoom range. Users can more accurately lock the target and obtain key information, thereby improving the reconnaissance effect.

[0005] Due to the size and weight limitations of handheld thermal imagers, micro-unmanned vehicles, and micro-UAVs, continuous zoom optical systems have the problems of being bulky, heavy, expensive, and inconvenient to carry. Therefore, the miniaturization and lightweight design of infrared optoelectronic equipment with continuous zoom function is crucial.

[0006] "Design of Miniaturized Medium-Wave Infrared Continuous Zoom Optical System" (Laser & Infrared [J], Issue 5, 2023: pp. 772-776) discloses a three-component linkage mechanical compensation miniaturized medium-wave infrared continuous zoom optical system; the system has an F number of 5.5, can achieve 20-275mm continuous zoom, and the system length is 90.6mm; its lens uses a three-group linkage method to achieve zoom, which requires high servo control accuracy of the optical system.

[0007] CN114460730A discloses an ultra-miniaturized airborne medium-wave refrigerated infrared continuous zoom optical system. The system uses 8 lenses, has a zoom range of 20 to 200 mm, and a total length of 100 mm. The compensation group of the system consists of 2 lenses, which is difficult to drive.

[0008] CN113625438A discloses a small, lightweight, medium-wave continuous zoom refrigerated infrared optical system. The system adopts a refractive-diffractive hybrid design, has 8 lenses, a zoom range of 19mm to 200mm, and the ratio of the total length of the optical system to the maximum focal length of the optical system satisfies ≤0.5.

[0009] Therefore, it is very necessary to develop an ultra-short and lightweight medium-wave infrared continuous zoom optical system to meet the needs of continuous zoom optical systems in application fields such as handheld thermal imagers, micro unmanned vehicles and micro drone infrared thermal imagers, and to achieve the requirements of portability, lightweight and high observation capability. Utility Model Content

[0010] To overcome the shortcomings of the prior art, the present invention provides an ultra-short, lightweight, medium-wave infrared continuous zoom optical system. This optical system utilizes only six optical lenses to achieve continuous zoom using a medium-wave HOT device-based medium-wave infrared optical system. The total optical system length is 66.20 mm, reducing system cost and weight. By employing secondary imaging technology to constrain the large objective lens diameter and achieve 100% cold screen efficiency, the system achieves clear imaging in both high and low temperature conditions through the rational combination of infrared materials and active compensation athermalization technology, meeting the performance requirements of harsh environmental suitability.

[0011] Specifically, the technical solution of the present utility model is:

[0012] An ultra-short, lightweight, medium-wave infrared continuous zoom optical system comprises a front fixing group, a zoom group, a compensation group, a focusing group, a relay group, and a medium-wave HOT infrared detector, which are arranged in sequence on the same optical axis from the object side to the image side.

[0013] The negative optical focal length biconcave lens of the zoom group and the positive optical focal length biconvex lens of the compensation group both move along the optical axis to achieve continuous zooming. The zoom group lens moves along the optical axis to achieve focal length change. During the change from short focus 36.5mm to long focus 220mm, the zoom group lens moves away from the front fixed group lens from left to right. The movement of the compensation group lens along the optical axis compensates for the image plane defocus caused by the movement of the zoom group lens, thereby achieving clear imaging during the zooming process. During the change from short focus 36.5mm to long focus 220mm, the zoom group lens approaches the front fixed group lens from right to left; the front fixed group lens, the focusing group lens, and the relay group lens are fixed lenses and remain in place during the zooming process.

[0014] An aperture stop is provided at the exit pupil of the optical system, and the aperture stop coincides with the cold stop of the infrared detector.

[0015] The primary image plane of the optical system is located between the zoom group and the relay group.

[0016] The optical material of the front fixing group is silicon material, the optical material of the zoom group is single crystal germanium material, the optical material of the compensation group is silicon material, the optical materials of the focusing group are single crystal germanium material and silicon material respectively, and the optical material of the relay group is silicon material.

[0017] The optical system has an operating wavelength range of 3.7 μm to 4.8 μm, an F# of 5.5, and a zoom range of 36.5 mm to 220 mm.

[0018] The utility model is suitable for the 640×512@15μm medium wave HOT detector.

[0019] Due to the adoption of the above-mentioned technical solution, the utility model has the following beneficial effects:

[0020] The utility model discloses an ultra-short, lightweight, medium-wave, cooled, infrared continuous zoom optical system. The zoom group adopts a germanium lens with a high refractive index and negative optical focal length, and the compensation group adopts a silicon lens with positive optical focal length. Only six lenses are used to achieve continuous zoom of 36.5mm to 220mm. The zoom stroke is short. The zoom curve of the optical system of the utility model is smooth and continuous without inflection points, which can effectively avoid the system from getting stuck during the zoom process. The total optical length of the continuous zoom optical system is 66.2mm, and the total length / maximum focal length ratio is 0.3. The total optical length of the system is short, which reduces weight and volume. It achieves 100% cold screen efficiency and improves imaging quality. It uses reasonable optical material matching and active focusing and heat dissipation to maintain good imaging quality in the range of -40℃ to 60℃. It is suitable for lightweight and small optoelectronic systems with strict requirements on the volume and weight of the optical system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the zoom optical system of the present invention; in the figure: 1, front fixed group, 2, zoom group, 3, compensation group, 4, focusing group (401, positive focal length meniscus lens, 402, negative focal length meniscus lens), 5, relay group, 6, medium-wave HOT infrared detector;

[0022] Figure 2 This is the optical system diagram of the utility model when the focal length is 220mm;

[0023] Figure 3 This is the optical system diagram of the utility model when the focal length is 120mm;

[0024] Figure 4 This is the optical system diagram of the utility model when the focal length is 65mm;

[0025] Figure 5 This is the optical system diagram of the utility model when the focal length is 36.5mm;

[0026] Figure 6This is a transfer function diagram of the optical system of the utility model when the focal length is 220mm;

[0027] Figure 7 This is a transfer function diagram of the optical system of the utility model when the focal length is 120mm;

[0028] Figure 8 This is a transfer function diagram of the optical system of the utility model when the focal length is 65mm;

[0029] Figure 9 This is a transfer function diagram of the optical system of the utility model when the focal length is 36.5mm;

[0030] Figure 10 This is the modulation transfer function diagram of the utility model at a small field of view of 220mm focal length at -40℃;

[0031] Figure 11 This is the modulation transfer function diagram of the utility model at +60°C with a small field of view and a focal length of 220mm;

[0032] Figure 12 This is a zoom curve diagram of the optical system of the utility model. DETAILED DESCRIPTION

[0033] In order to make the purpose, content and technical advantages of the present invention clearer, the specific implementation methods of the present invention are further described below in conjunction with the accompanying drawings and examples.

[0034] Combined with attachment Figures 1 to 5 The ultra-short, lightweight, medium-wave, cooled infrared continuous zoom optical system provided by the utility model has the direction close to the object space as the object side, the direction close to the image space as the image side, and the two sides of the lens from the object side to the image side are the incident surface and the exit surface respectively, including a positive focal length meniscus lens 1 as a front fixed group, a negative focal length biconcave lens 2 as a zoom group, a positive focal length biconvex lens 3 as a compensation group, a positive focal length meniscus lens 401 and a negative focal length meniscus lens 402 as a focusing group, a positive focal length biconvex lens 5 as a relay group, and an infrared detector 6, which are arranged on the same optical axis from the object side to the image side.

[0035] like Figure 1As shown in the figure, it is a schematic diagram of the continuous zoom optical system of the present invention. The biconcave lens as the zoom group 2 is the zoom lens. The focal length is changed by the biconcave lens independently moving along the optical axis according to a predetermined stroke. In the process of changing from short focus 36.5mm to long focus 220mm, the biconcave negative lens moves away from the positive focal length meniscus lens as the front fixed group 1 from left to right. The biconvex lens as the compensation group 3 is the compensation lens. The movement of the biconvex positive lens along the optical axis compensates for the image plane defocus caused by the movement of the zoom lens. During the zoom process from short focal length 36.5mm to long focal length 220mm, the biconvex lens of compensation group 3 approaches the meniscus lens 1 of the front fixed group from right to left, thereby achieving clear imaging during the zoom process. The travel of the biconcave lens of zoom group 2 is 6.1mm, and the travel of the biconvex lens of compensation group 3 is 11.2mm. The meniscus lens of front fixed group 1, the positive focal length meniscus lens 401 and the negative focal length meniscus lens 402 of focusing group 4, and the biconvex lens of relay group 5 are fixed lenses and remain in place during the zoom process. Figure 12 It can be seen that the zoom curve of the optical system of the present invention is smooth and continuous without inflection points, which can effectively avoid the occurrence of stuck phenomena during the zoom process;

[0036] The primary image plane is located between the focusing group and the relay group. Setting a field stop at the primary image plane can effectively reduce the influence of stray light on the system imaging and improve the signal-to-noise ratio of the system. An aperture stop is provided at the exit pupil. The aperture stop coincides with the cold stop of the infrared detector, achieving 100% cold stop efficiency, reducing beam energy loss and improving system sensitivity.

[0037] The optical material of the front fixed group is silicon, the optical material of the zoom group is single crystal germanium, the optical material of the compensation group is silicon, the optical materials of the focusing group are single crystal germanium and silicon respectively, and the optical material of the relay group is silicon.

[0038] The rear surface of the positive power meniscus lens of the front fixed group 1, the rear surface of the negative power biconcave lens of the zoom group 2, the front surface of the positive power biconvex lens of the compensation group 3, the front surface of the positive power meniscus lens 401 of the focusing group 4, and the front surface of the negative power meniscus lens 402 are all even-order aspherical surfaces, and the surface equation is:

[0039]

[0040] Wherein, z is the distance vector height from the vertex of the aspheric surface at a height of r along the optical axis, c is the curvature, c = 1 / R, R represents the radius of curvature of the lens surface, r is the radial coordinate of the lens surface perpendicular to the optical axis, k is the quadratic curve constant of the lens surface, A is the fourth-order aspheric coefficient of the lens surface, B is the sixth-order aspheric coefficient of the lens surface, and C is the eighth-order aspheric coefficient of the lens surface;

[0041] The front surface of the positive power biconvex lens of relay group 5 adopts a diffractive aspheric surface. The aspheric surface and the diffractive surface act on the same lens surface. The surface equation is:

[0042]

[0043] in, is the phase of the diffraction surface, Y is the semi-aperture of the lens perpendicular to the optical axis; H1, H2, H3 are the phase coefficients of the diffraction surface.

[0044] In the specific optical path transmission, the light emitted by the infrared radiation of the external scene is converged by the meniscus lens of the front fixed group 1 and reaches the double concave lens of the magnification group 2, diverged by the double concave lens of the magnification group 2 and reaches the double convex lens of the compensation group 3, converged by the double convex lens of the compensation group 3 and reaches the positive focal length meniscus lens 401 of the focusing group 4, converged by the positive focal length meniscus lens 401 and reaches the negative focal length meniscus lens 402, diverged by the negative focal length meniscus lens 402 and reaches the double convex positive lens of the relay group 5, and after converging, the double convex positive lens of the relay group 5 forms an image on the focal plane 6 of the infrared detector.

[0045] Example 1

[0046] The specific technical indicators of the optical system of this utility model are:

[0047] Compatible detectors: 640×512@15μm and 1024×768@10μm medium-wave HOT infrared detectors;

[0048] Working band: 3.7μm~4.8μm;

[0049] F number: 5.5;

[0050] Focal length: 36.5mm~220mm;

[0051] Total optical length: ≤66.2mm;

[0052] Total optical length / longest focal length: ≤0.3;

[0053] As shown in Table 1, the detailed data of each lens of the optical system in this embodiment when the focal length is 36.5 mm to 220 mm (including the surface shape, curvature radius, thickness, aperture, material, and aspheric / diffractive surface parameters of each lens, where the unit of the curvature radius, thickness, and aperture of the lens is mm, and the curvature radius of the spherical and aspheric surfaces refers to the curvature radius at the intersection of the lens surface and the optical axis).

[0054] Table 1 Detailed data of each lens

[0055]

[0056]

[0057] As shown in Table 1, in this embodiment, the aspheric coefficients of the rear surface of the positive power meniscus lens of the front fixed group 1, the rear surface of the negative power biconcave lens of the zoom group 2, the front surface of the positive power biconvex lens of the compensation group 3, the front surface of the positive power meniscus lens 401 of the focusing group 4, and the front surface of the negative power meniscus lens 402 are shown (the figure uses scientific notation, for example, -3.284985e-7 represents -3.284985×10 -7 );

[0058] As shown in Table 1 (expressed in scientific notation), the diffraction aspheric coefficients of the front surface of the positive power biconvex lens of relay group 5 in this embodiment are:

[0059] After optical design software simulation:

[0060] like Figure 6 、 Figure 7 、 Figure 8 、 Figure 9 As shown, when the characteristic frequency of the infrared detector is 33lp / mm, the transfer function of the optical system of the utility model is close to 0.2 when the focal length is 220mm, 120mm, 65mm, and 36.5mm;

[0061] The biconcave lens of the zoom group 2 and the biconvex lens of the compensation group 3 are in a close position to each other. At this time, the system forms a 220mm focal length small field optical path. The distance between the meniscus lens of the front fixed group 1 and the biconcave lens of the zoom group 2 is 14.5mm, the distance between the biconcave lens of the zoom group 2 and the biconvex lens of the compensation group 3 is 1.0mm, and the distance between the biconvex lens of the compensation group 3 and the focusing group 4 is 7.7mm. The optical path is as follows Figure 2 As shown;

[0062] When the system is at a low temperature of -40°C, focus compensation is performed by moving the focus group 4 along the optical axis toward the object by 0.02 mm. The optical modulation transfer function of the system after focus compensation is as follows: Figure 10 As shown, it shows that the system has clear imaging.

[0063] When the system is at a high temperature of +60°C, focus compensation is performed by moving the focus group 4 along the optical axis toward the image side by 0.04 mm. The optical modulation transfer function of the system after focus compensation is as follows: Figure 11 As shown, it shows that the system has clear imaging.

[0064] The parts of the present invention that are not described in detail are prior art. It is obvious to those skilled in the art that the present invention is not limited to the details of the above-mentioned exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the appended claims rather than the above description. Therefore, it is intended that all changes that fall within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any figure marks in the claims should not be regarded as limiting the claims involved.

Claims

1. An ultra-short, lightweight, medium-wave infrared continuous zoom optical system, characterized by: Along the transmission direction of the incident infrared radiation, the optical system is composed of a front fixed group (1), a zoom group (2), a compensation group (3), a focus adjustment group (4), a relay group (5) and a medium-wave HOT infrared detector (6); The front fixed group (1) is a positive focal meniscus lens, the zoom group (2) is a negative focal biconcave lens, the compensation group (3) is a positive focal biconvex lens, the focusing group (4) is composed of a positive focal meniscus lens (401) and a negative focal meniscus lens (402), and the relay group (5) is a positive focal biconvex lens.

2. The ultra-short, lightweight, medium-wave infrared continuous zoom optical system according to claim 1, characterized in that: The rear surface of the positive focal power meniscus lens of the front fixed group (1), the rear surface of the negative focal power biconcave lens of the zoom group (2), the front surface of the positive focal power biconvex lens of the compensation group (3), the front surface of the positive focal power meniscus lens (401) of the focusing group (4), and the front surface of the negative focal power meniscus lens (402) all adopt even-order aspheric surfaces.

3. The ultra-short, lightweight, medium-wave infrared continuous zoom optical system according to claim 1, characterized in that: The front surface of the positive power double convex lens of the relay group (5) adopts a diffraction aspheric surface, and the aspheric surface and the diffraction surface act on the same lens surface.

4. The ultra-short, lightweight, medium-wave infrared continuous zoom optical system according to claim 1, characterized in that: The meniscus positive lens (401) and the meniscus negative lens (402) are used to achieve clear imaging of a target at a distance of 5 m to ∞ within a temperature range of -40°C to +60°C when they move forward and backward along the optical axis.

5. The ultra-short, lightweight, medium-wave infrared continuous zoom optical system according to claim 1, characterized in that: An aperture stop is provided at the exit pupil of the optical system, and the aperture stop coincides with the cold stop of the medium-wave HOT infrared detector (6).

6. The ultra-short, lightweight, medium-wave infrared continuous zoom optical system according to claim 1, characterized in that: The positive power meniscus lens of the front fixed group (1) has a front surface curvature radius of 39.392 mm and a spacing of 5 mm, and a rear surface curvature radius of 94.708 mm and a spacing of 16.24 mm; The negative power biconcave lens of the zoom group (2) has a front surface curvature radius of -47.393 mm and a spacing of 1.6 mm, and a rear surface curvature radius of 22.889 mm and a spacing of 1 mm; The positive power biconvex lens of the compensation group (3) has a front surface curvature radius of 30.562 mm and a spacing of 3 mm, and a rear surface curvature radius of -41.3 mm and a spacing of 7.96 mm; The positive power meniscus lens (401) of the focusing group (4) has a front surface curvature radius of 7.568 mm and a spacing of 2 mm, and a rear surface curvature radius of 45.683 mm and a spacing of 0.5 mm; the negative power meniscus lens (402) has a front surface curvature radius of 7.232 mm and a spacing of 1.6 mm, and a rear surface curvature radius of 2.8 mm and a spacing of 6.5 mm; The positive power biconvex lens of the relay group (5) has a front surface curvature radius of 16.712 mm and a spacing of 2.3 mm, and a rear surface curvature radius of -14.704 mm and a spacing of 18.5 mm.

7. The ultra-short, lightweight, medium-wave infrared continuous zoom optical system according to claim 1, characterized in that: The optical material of the positive focal length meniscus lens of the front fixed group (1) is silicon material; The optical material of the negative focal power biconcave lens of the zoom group (2) is single crystal germanium; The optical material of the positive power biconvex lens of the compensation group (3) is silicon material; The optical materials of the positive focal power meniscus lens (401) and the negative focal power meniscus lens (402) of the focusing group (4) are single crystal germanium material and silicon material respectively; The optical material of the positive power biconvex lens of the relay group (5) is silicon material.

8. The ultra-short, lightweight, medium-wave infrared continuous zoom optical system according to any one of claims 1 to 7, characterized in that: The total length of the medium-wave infrared continuous zoom optical system is 66.2 mm, and the telephoto ratio of the optical system is 0.

3.

9. The ultra-short, lightweight, medium-wave infrared continuous zoom optical system according to any one of claims 1 to 7, characterized in that: The optical system has an operating wavelength range of 3.7 μm to 4.8 μm, an F# of 5.5, and a zoom range of 36.5 mm to 220 mm.

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