CN110749986A - Infrared continuous zooming area array scanning optical system and image motion compensation method - Google Patents

Abstract

The invention discloses an infrared continuous zoom area array scanning optical system and an image movement compensation method. From the object plane to the image plane, it includes: a front fixed group, a compensation group, a variable magnification group, a rear fixed group, a scanning galvanometer, and a secondary convergence. group, catadioptric mirror, triple imaging group, optical window, aperture diaphragm. When the scanning galvanometer is in the locked state, the optical system can work in the gaze tracking mode, the zoom ratio can reach 6 times, and the distortion of each focal length is less than 0.5%. When the scanning galvanometer scans back and forth within a certain angle range, the optical system can work in the area scan search mode, the system can zoom between multiple focal lengths, the scanning process does not produce defocus, and the image is clear. The zoom and scanning form of the system is simple, and the scanning mirror is introduced through the movement of two sets of optical elements and the intermediate parallel optical path, so that the system has small scanning mirror size, no defocusing during scanning, multi-level area scan, ultra-low optical distortion, and continuous staring. The feature of zoom can be applied to the infrared system integrating search and tracking.

Description

A kind of infrared continuous zoom area scan optical system and image movement compensation method

technical field

The invention relates to an infrared detection optical system, in particular to an infrared optical system and an image movement compensation method for continuous zoom area scan.

Background technique

Infrared search and tracking uses the infrared characteristics of the target to detect and track the target, can provide panoramic surveillance capabilities, can search for targets at night or in poor visibility conditions, and improve the system's ability to sense threats to targets in the air, ground and sea. It has become an important modern technology. One of the weapons. The infrared search and tracking system has two functions: target search and target tracking. First of all, the infrared system platform scans and images in 360° azimuth or within the angle range of key areas at a certain rotational speed. After finding the target, the system switches to tracking mode. Infrared search and tracking system has many advantages such as good concealment, wide detection range, high positioning accuracy, strong recognition and camouflage ability, and anti-electromagnetic interference, and has been widely concerned and applied.

The infrared warning system using infrared array detectors can scan through the platform to perform imaging in the 360° range of azimuth. After the target is discovered, the target cannot be tracked. With the application requirements of the integration of search and tracking, the continuous scanning area array detector imaging system was developed. The scanning of the continuous scanning area array imaging system during the integration time will cause relative motion between the focal plane and the scene, resulting in smearing and blurring of the image. Through the swing-back compensation technology, an area-array scanning infrared system with infrared scanning search and gaze tracking functions at the same time can be realized.

The related application research of scanning infrared search and tracking system based on area array detector has been carried out abroad. In 2014, the French company HGH Infrared Systems developed the high-resolution wide-area surveillance system Spynel-X8000. The system can scan 360° in azimuth and 5° in elevation with a search rate of 2 seconds/circle. The system adopts the reverse scan compensation type image movement compensation scheme, and adopts the cooling type medium wave infrared area array detector.

In 2012, Xi'an University of Technology carried out research on the photoelectric early warning detection system, using an area array detector with a medium wave of 3.7-4.8um and a resolution of 320×256. The output image frame rate is 50Hz, the system focal length is 90mm, and the F number of the optical system is 2. The reverse scan compensation method uses a DC torque motor with a limited rotation angle to drive the mirror to realize the gaze compensation function of the system focusing plane thermal imager, eliminating the phenomenon of image smearing during the scanning process of the surface array device. (Bai Bo. Research on key technology of infrared search and tracking system using focal plane detector, research on key technology of infrared search and tracking system using focal plane detector [D]. Xi'an University of Technology).

In 2014, CN 104539829 A disclosed an optical-mechanical structure based on scanning and imaging of an infrared area array detector. The structure realizes a 360-degree omnidirectional scanning and imaging of a single infrared area array detector, ensuring that the infrared image acquisition is not The blurring effect caused by the rotation of the platform can give full play to the long integration time and high sensitivity of the area array infrared focal plane detector.

In 2016, the Shanghai Institute of Technical Physics, Chinese Academy of Sciences designed a continuous scanning imaging optical system for an area array detector, with a focal length of 73mm, F/2, and a 320×256 detector. (Yu Yang, Wang Shiyong et al. Continuous Scanning Imaging Optical System of Area Array Detector, Infrared and Laser Engineering, 2016, 45(1): 0118002-1～0118002-5).

In 2019, in the invention CN110119022A, a two-speed zoom area array scanning optical system was disclosed. The system can switch between large and small fields of view, and perform area array swing imaging in two states.

It can be seen that the currently reported infrared area scan optical systems are all fixed focal length or two-speed zoom designs, and do not yet have the multi-speed area scan and gaze tracking continuous zoom functions. During its 360° scan search and gaze tracking, the resolution of the target cannot be changed continuously, and it cannot take into account the functions of large field of view search and small field of view continuous tracking.

SUMMARY OF THE INVENTION

Based on the existence of the above problems, the present invention proposes an infrared continuous zoom area scan optical system. The purpose of the present invention is to provide an infrared continuous zoom area scan optical system, which can realize multi-step zoom area scan, continuous zoom gaze tracking, and a maximum optical zoom magnification of 6 times through the movement of the zoom group and the compensation group. Distortion during zooming is less than 0.5%, -30℃～+60℃ working temperature compensation, focusing for imaging at different distances.

The technical problems to be solved by the present invention are as follows: firstly, in the state of multiple focal lengths, the off-axis aberration caused by the swinging back of the scanning galvanometer is corrected to ensure that the scanning galvanometer can image clearly in the whole process of scanning; In the state of focal length, reduce the distortion caused by the galvanometer swing back, ensure the registration of the image in the full field of view during the swing back process, and keep the image stable. The third is to provide a solution that simultaneously realizes ultra-low distortion multi-speed zoom area scan, gaze tracking with a maximum magnification of 6 times continuous zoom, -30°C to +60°C operating temperature compensation, and focusing for imaging at different distances. The fourth is to use the middle optical path to introduce the galvanometer to perform the back-scanning compensation platform movement to solve the optical path design problem of the small-sized galvanometer scanning in the middle optical path.

The system uses a cooled infrared detector to achieve better detection performance. To suppress background radiation, the optical system aperture diaphragm is 100% matched to the detector cold diaphragm. At the same time, in order to reduce the volume of the optical system and the aperture of the first lens, the entrance pupil is designed on the front surface of the first lens. In order to further reduce the size of the galvanometer, the exit pupil of the telephoto system is designed to the position of the galvanometer.

The technical solution for solving the problem is shown in Figure 1. The present invention is realized by the following technical solutions: the optical system for infrared imaging consists of a front fixed group 1, a compensation group 2, and a variable magnification group 3 in order from the object side to the image side. , the rear fixed group 4, the scanning galvanometer 5, the secondary convergence group 6, the turning mirror 7, the tertiary imaging group 8, the optical window 9, the aperture diaphragm 10, and the image plane 11. The imaging beam from the object side passes through the front fixed group 1, the compensation group 2, the variable magnification group 3, and the rear fixed group 4 in sequence, and then becomes a parallel beam. After the mirror 7, the tertiary imaging group 8, the optical window 9, and the aperture stop 10, the image is formed on the image plane.

The working band of the system is 3-5μm; the short focal length is f ₁ , the long focal length is f ₂ , and the zoom ratio of the system is: Γ=f ₂ /f ₁ ; the zoom ratio range of the system is 1<Γ≤6 ; The F number range of the infrared system is: 4.0≤F/#≤5.5;

The zoom group 3 moves toward the object side, and the focal length becomes shorter; the zoom group 3 moves toward the image side, and the focal length becomes longer. During the movement of the zoom group 3, the compensation group 2 moves correspondingly to compensate for the movement of the image plane during the zooming process and realize continuous zooming.

The compensation group 2 moves along the direction of the optical axis, taking into account the zoom image plane drift, the image plane drift under different working temperatures, and the imaging image plane drift compensation function at different object distances. It can realize continuous zoom, working temperature in the range of -30℃～+60℃, and the imaging object distance range from 10 meters to infinity, etc., the image quality is good, and the focal plane position remains unchanged.

The telephoto system is composed of the front fixed group 1, the compensation group 2, the zoom group 3, and the rear fixed group 4. The light from infinity, after passing through the first four groups, becomes parallel light, and its exit pupil is located at the scanning galvanometer 5 Location. In the longest focus state, the position of the entrance pupil of the optical system is located on the front surface of the front fixed first lens 1-1. The aperture diaphragm 10 coincides with the position of the cold diaphragm in the infrared detector matched with the system, and has the same diameter. The angle between the turning mirror 7 and the light path is 45°, and the light path is turned by 90°.

The scanning galvanometer 5 is located in a parallel optical path; it has two working states: a locked state and a scanning state; when the scanning galvanometer 5 is in a locked state, it is placed at 45° with the optical axis of the telescope, and the optical path is turned 90°. When the scanning galvanometer 5 is in the reciprocating scanning state, the image is clear. The optical system can be used in scanning mode under the state of multiple focal lengths. α is the effective swing-back scanning half angle of the scanning galvanometer 5; The rotational speed is ω, and the integration time of the area array detector is τ; when the infrared optical system performs image movement compensation of the area array circular scan, the galvanometer compensation angle α should satisfy:

The front fixed group 1 is composed of a front fixed first lens 1-1 and a front fixed second lens 1-2. The front fixed first lens 1-1 is a meniscus-type silicon lens with positive refractive power bent toward the image side. The front fixed second lenses 1-2 are all meniscus aspheric germanium lenses with negative refractive power bent toward the image side.

The compensation group 2 is a meniscus aspheric germanium lens with negative refractive power bent toward the image side.

The variable magnification group 3 is an aspherical zinc selenide lens with a biconvex positive refractive power.

The rear fixing group 4 is composed of a rear fixing first lens 4-1 and a rear fixing second lens 4-2; the rear fixing first lens 4-1 is a meniscus spherical surface with negative refractive power bent to the object side. The germanium lens and the second rear fixed lens 4-2 are meniscus aspherical diffractive germanium lenses with positive refractive power bent to the object side.

The secondary convergence group 6 is composed of a secondary convergence first lens 6-1 and a secondary convergence second lens 6-2; Calcium lens; the second converging second lens 6-2 is a positive refractive power aspheric AMTIR1 lens bent to the turning mirror 7;

The triple imaging group 8 is composed of a first lens 8-1 for triple imaging and a second lens 8-2 for triple imaging. The first lens 8 - 1 for tertiary imaging is a meniscus spherical silicon lens with a positive refractive power that is bent to the catadioptric mirror 7 . The third imaging second lens 8-2 is a meniscus aspherical silicon lens with positive refractive power bent toward the image side.

The biggest feature of the infrared continuous zoom area scan optical system of the present invention is: through the movement of the zoom group and the compensation group and the reciprocating scanning of the scanning galvanometer, the area scan with multiple focal lengths and the continuous zoom gaze tracking are realized; During the scanning process of multiple focal lengths, the images in the entire field of view are accurately registered to ensure the clarity and stability of the imaging. The distance of the compensation group is fine-tuned before and after, and at the same time, it can realize the compensation of -30℃～+60℃ working temperature and the focusing of imaging at different distances. The optical system features search, tracking, continuous zoom, wide operating temperature range, and distance range for clear imaging. Mainly used in infrared search and tracking integrated system.

Description of drawings

Figure 1 is the optical layout of the infrared continuous zoom area scan short focus 60mm; 1 is the front fixed group, 2 is the compensation group, 3 is the zoom group, 4 is the rear fixed group, 5 is the scanning galvanometer, and 6 is the secondary convergence Group, 7 is a turning mirror, 8 is a three-time imaging group, 9 is an optical window, 10 is an aperture diaphragm, and 11 is an image plane;

Figure 2 is the optical layout of the infrared continuous zoom area scan mid-focus 180mm;

Figure 3 is the optical layout of the infrared continuous zoom area scan telephoto 360mm;

Figure 4 is a short-focus 60mm optical modulation transfer function diagram;

Figure 5 is a diagram of the optical modulation transfer function of the short-focus 60mm galvanometer with an included angle of 44.35°;

Fig. 6 is the optical modulation transfer function diagram of the short-focus 60mm galvanometer with an included angle of 45.65°;

Figure 7 is a short-focus 60mm optical distortion diagram;

Fig. 8 is the optical modulation transfer function diagram of the mid-focus 180mm;

Fig. 9 is the optical modulation transfer function diagram of the middle focus 180mm galvanometer with an angle of 44.35°;

Figure 10 is a diagram of the optical modulation transfer function of the mid-focus 180mm galvanometer with an angle of 45.65°;

Figure 11 is the optical distortion diagram of the mid-focus 180mm;

Figure 12 is a diagram of a telephoto 360mm optical modulation transfer function;

Figure 13 is an optical modulation transfer function diagram of a telephoto 360mm galvanometer with an angle of 44.35°;

Figure 14 is a diagram of the optical modulation transfer function of a telephoto 360mm galvanometer with an angle of 45.65°;

Figure 15 is a diagram of optical distortion at a telephoto 360mm.

Detailed ways

The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

As shown in Fig. 1, Fig. 2, Fig. 3, the infrared continuous zoom area scanning optical system of the present invention includes a front fixed group 1, a compensation group 2, a variable magnification group 3, and a rear fixed group in order from the object side to the image side. 4. Scanning galvanometer 5 , secondary convergence group 6 , turning mirror 7 , tertiary imaging group 8 , optical window 9 , aperture stop 10 .

In the following, an infrared continuous zoom area scan optical system with a focal length variation range of 60 mm to 360 mm is taken as an embodiment for description. The optical system of the invention is a six-fold continuous zoom area array scanning optical system, the working band is 3.0-5.0 μm; the F number of the infrared system is F/4; the infrared two-speed zoom area array scanning optical system is matched with a cooling type infrared detector , the detector array is 640×512; the pixel size is 15μm;

The short focal length of the focal length system is f ₁ =60mm, and the long focal length is f ₂ =360mm. The zoom ratio of the system is: Γ=f ₂ /f ₁ =6; the corresponding optical field coverage is 1.53°×1.22° To 9.15° × 7.33°, the F-number is constant at 4 throughout the zoom range. The optical system adopts the structure of refracting-diffraction-mixed transmissive tertiary imaging, with 100% cold aperture efficiency. Fig. 1, Fig. 2, Fig. 3 are the schematic diagrams at the positions of the large field of view 60mm, the middle field of view 180mm, and the small field of view 360mm respectively.

At the short focal position of 60 mm, the distance between the center of the rear surface of the compensation group 2 relative to the front fixed second lens 1-2 is 5.14 mm; the distance between the center of the front surface of the zoom group 3 relative to the rear fixed first lens 4-1 is 58.58 mm; the compensation group 2. The distance between the rear surface and the center of the front surface of the zoom group is 57.25mm;

At the mid-focus position of 180 mm, the distance between the center of the rear surface of the compensation group 2 relative to the front fixed second lens 1-2 is 23.67 mm; the distance between the center of the front surface of the zoom group 3 relative to the rear fixed first lens 4-1 is 36.75 mm; the compensation group 2. The distance between the rear surface and the center of the front surface of the zoom group is 60.55mm;

At the telephoto position of 360 mm, the distance between the center of the rear surface of the compensation group 2 relative to the front fixed second lens 1-2 is 5.88 mm; the distance between the center of the front surface of the zoom group 3 relative to the rear fixed first lens 4-1 is 15.19 mm; the compensation group 2. The distance between the rear surface and the center of the front surface of the zoom group is 99.9mm;

The optical system can perform area scan work in the state of three focal lengths. When the focal length is 360mm, the platform search speed is 60°/s; when the focal length is 180mm, the adaptive platform search speed is 120°/s; when the focal length is 60mm, the adaptive platform search speed is 360°/s.

Further, in order to correct chromatic aberration and large field of view aberration, the present invention adopts aspheric surface or aspheric surface plus diffractive surface on part of the lens surface, so as to improve image quality and reduce the number of lenses and lens volume.

Further, in order to correct the aberration of the system in multiple states, the system adds a diffractive surface to the rear fixed second lens 4-2, which can effectively eliminate chromatic aberration and offset the residual aberration of the front lens group.

Further, in order to improve the energy utilization efficiency, the present invention is coated with high-quality anti-reflection films on the front and rear surfaces of all lenses, so as to improve the system response sensitivity and detection distance.

The remarkable effect of the infrared continuous zoom area scan optical system of the present invention is shown in the accompanying drawings. In the accompanying drawings, FIG. 4 is a short-focus 60mm optical modulation transfer function diagram; Transfer function diagram; Figure 6 is a short focus 60mm galvanometer angle 45.65 ° optical modulation transfer function diagram; Figure 7 is a short focus 60mm optical distortion diagram; Figure 8 is a mid focus 180mm optical modulation transfer function diagram; Figure 10 is a mid focus 180mm The optical modulation transfer function diagram of the galvanometer angle of 45.65°; Figure 11 is the optical distortion diagram of the mid-focus 180mm; Figure 12 is the optical modulation transfer function diagram of the telephoto 360mm; Figure 13 is the telephoto 360mm galvanometer angle of 44.35°. Figure; Figure 14 is the optical modulation transfer function diagram of the telephoto 360mm galvanometer angle of 45.65°; Figure 15 is the optical distortion diagram of the telephoto 360mm;

The undescribed technical features of the present invention can be realized by the prior art, and are not repeated here. The above description is only an example of implementation of the present invention, not a limitation of the present invention, and the present invention is not limited to the above-mentioned examples. Adding or replacing, for example, replacing the lens material accordingly, or increasing or decreasing the number of lenses in the same lens group, should also belong to the protection scope of the present invention.

Claims (8)

1. The utility model provides an infrared continuous zoom area array scanning optical system, includes preceding fixed group (1), compensation group (2), zoom group (3), back fixed group (4), scanning galvanometer (5), secondary convergence group (6), turn speculum (7), cubic imaging group (8), optical window (9), aperture diaphragm (10), image plane (11), its characterized in that:

imaging light beams from an object space sequentially pass through a front fixing group (1), a compensation group (2), a zoom group (3) and a rear fixing group (4) and then are changed into parallel light beams, and after the parallel light beams are bent by a scanning galvanometer (5), the parallel light beams pass through a secondary convergence group (6), a bending reflector (7), a tertiary imaging group (8), an optical window (9) and an aperture diaphragm (10), and then are imaged on an image surface; magnification ratio Γ of optical system: 1< gamma is less than or equal to 6; f number of optical system: f is more than or equal to 4.0 and less than or equal to 5.5;

the zoom group (3) moves towards the object space, and the focal length is shortened; the zoom group (3) moves to the image side, and the focal length is lengthened. In the moving process of the zoom group (3), the compensation group (2) correspondingly moves to compensate the image surface movement in the zooming process, so that continuous zooming is realized;

the compensation group (2) moves along the optical axis direction, and has the functions of zooming image plane drift, image plane drift at different working temperatures and imaging image plane drift compensation at different object distances;

a telescopic system is composed of a front fixed group (1), a compensation group (2), a zoom group (3) and a rear fixed group (4), rays from infinity pass through the front four groups and then become parallel rays to be emitted, and the exit pupil of the parallel rays is positioned at the position of a scanning galvanometer (5); the position of the entrance pupil of the optical system is positioned on the front surface of the front fixed first lens (1-1) in the longest focal state; the aperture diaphragm (10) is superposed with the cold diaphragm in the infrared detector matched with the system, and the apertures are the same; the angle between the turning reflector (7) and the light path is 45 degrees, and the light path is turned by 90 degrees.

2. The infrared continuous-zoom-area-array scanning optical system according to claim 1, characterized in that: the front fixed group (1) consists of a front fixed first lens (1-1) and a front fixed second lens (1-2); the front fixed first lens (1-1) is a meniscus silicon lens with positive focal power bent to the image side; the front fixed second lenses (1-2) are meniscus aspheric germanium lenses with negative focal power and bending towards the image.

3. The infrared continuous-zoom-area-array scanning optical system according to claim 1, characterized in that: the compensation group (2) is a meniscus type aspheric germanium lens with negative focal power and bent to the image side.

4. The infrared continuous-zoom-area-array scanning optical system according to claim 1, characterized in that: the zoom group (3) is an aspheric zinc selenide lens with double convex positive focal power.

5. The infrared continuous-zoom-area-array scanning optical system according to claim 1, characterized in that: the rear fixed group (4) consists of a rear fixed first lens (4-1) and a rear fixed second lens (4-2); the rear fixed first lens (4-1) is a meniscus spherical germanium lens with negative focal power and bent towards an object, and the rear fixed second lens (4-2) is a meniscus aspheric diffractive germanium lens with positive focal power and bent towards the object.

6. The infrared continuous-zoom-area-array scanning optical system according to claim 1, characterized in that: the secondary convergence group (6) consists of a secondary convergence first lens (6-1) and a secondary convergence second lens (6-2); the second-time convergence first lens (6-1) is a negative-focal-power spherical calcium fluoride lens which is bent to the scanning galvanometer (5); the second secondary converging lens (6-2) is a positive power aspheric AMTIR1 lens bent towards the turning reflector (7).

7. The infrared continuous-zoom-area-array scanning optical system according to claim 1, characterized in that: the cubic imaging group (8) consists of a cubic imaging first lens (8-1) and a cubic imaging second lens (8-2); the third imaging first lens (8-1) is a meniscus spherical silicon lens with positive focal power and bent towards the turning reflector (7); the third imaging second lens (8-2) is a meniscus type aspheric silicon lens with positive focal power and bent to the image side.

8. An image motion compensation method of an infrared continuous zooming area array scanning optical system based on claim 1 is characterized by comprising the following steps:

the optical system has two working modes, when the scanning galvanometer (5) is in a locking state, the scanning galvanometer is placed at an angle of 45 degrees with an optical axis of the telescope, a light path is turned by 90 degrees, the system works in a staring tracking mode, the maximum zooming magnification can reach 6 times, the distortion in the zooming process is less than 0.5%, when the scanning galvanometer (5) is in a back-and-forth retrace state, the optical system works in an area array circumferential scanning search mode, the system can zoom among multiple focal lengths, the defocusing is not generated in the scanning process, the imaging is clear, the optical system can be applied to the scanning mode under the state of the multiple focal lengths, α is an effective backswing scanning angle of the scanning galvanometer (5), β is an amplification magnification of the telescope system consisting of a front fixed group (1), a compensation group (2), a zoom group (3) and a rear fixed group (4) under the short-focus state, the circumferential scanning rotation speed of the optical system is omega, the area array detector integration time is tau, and when the infrared optical system performs image shift compensation:

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