A mid-wave infrared polarization detection optical system for long-distance target detection

Abstract

A mid-wave infrared polarization detection optical system for long-distance target detection, which relates to the field of target detection. In the present invention, the target beam collected by the front imaging optical system is reflected by the main beam splitter and then incident on the first beam splitter. The beam transmitted by the first beam splitter is incident on the first point source detector through the first polarization analyzer with a certain angle of the transmission axis. The beam reflected by the first beam splitter is incident on the second point source detector through the second polarization analyzer with a certain angle of the transmission axis. The target beam collected by the front imaging optical system is transmitted by the main beam splitter and then incident on the second beam splitter. The beam transmitted by the second beam splitter is incident on the third point source detector through the third polarization analyzer with a certain angle of the transmission axis. The beam reflected by the second beam splitter is incident on the fourth point source detector through the fourth polarization analyzer with a certain angle of the transmission axis. The present invention can realize real-time imaging detection for simultaneously obtaining the spatial information and polarization information of the target, and has the advantages of high resolution and the ability to detect moving targets, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of space target detection, and particularly relates to a mid-wave infrared polarization detection optical system for long-distance target detection. Background Art

[0002] Polarization imaging technology can obtain the spatial information, spectral information, and polarization information of each spectral band of a target object, and fuse the spatial, spectral, and polarization information of the target object. It can not only increase the amount of information obtained about the target object, but also enhance the detection and recognition capabilities of the target object. When the polarization imaging technology is used to detect and identify a target object compared with the traditional detection technology, its advantages are mainly reflected in the following aspects: First, when the radiation of the target object is weak while the background radiation is strong, it becomes more difficult for the traditional detection technology to clearly distinguish the characteristics of the target object from the background, while using the polarization imaging technology, it is easier to highlight the target; Second, in the atmospheric environment, the polarization imaging technology can increase the detection distance under the conditions of smoke and fog, and the polarization information has better retention than the intensity scattering information. At the same time, compared with other infrared bands, the mid-wave infrared band is the key band for infrared polarization detection, and many toxic and harmful gases have strong absorption bands in the mid-wave infrared band. Existing experiments have shown that the polarization characteristics of an object are determined by factors such as its own temperature, material, surface roughness, and texture. Generally, the polarization degree of artificial targets is significantly stronger than that of natural backgrounds. By using the surface characteristics of objects, including smoothness, texture, and material, etc., artificial targets can be separated from complex natural backgrounds.

[0003] Currently, the existing time-sharing infrared polarization imaging technology mainly uses a rotating polarizer structure to obtain polarization state images of the same target scene at different times. This time-sharing infrared polarization imaging technology is mainly applicable to the infrared polarization imaging detection of stationary targets. Since long-distance targets are non-stationary targets with characteristics such as a large detection range and a fast moving speed, the existing time-sharing infrared polarization imaging technology is not applicable to the detection of long-distance targets. Therefore, how to achieve high-resolution mid-wave infrared polarization real-time imaging detection for simultaneous acquisition of spatial information and polarization information of long-distance targets is of great significance for the research of long-distance target detection. Summary of the Invention

[0004] The purpose of the present invention is to provide a mid-wave infrared polarization detection optical system for long-distance target detection to solve the problems existing in the prior art.

[0005] The technical solution adopted by the present invention to solve the technical problems is as follows:

[0006] A mid-wave infrared polarization detection optical system for long-distance target detection according to the present invention includes: a front imaging optical system, a main beam splitter, a first beam splitter, a first polarization analyzer with a specific transmission axis angle, a first point source detector, a second polarization analyzer with a specific transmission axis angle, a second point source detector, a second beam splitter, a third polarization analyzer with a specific transmission axis angle, a third point source detector, a fourth polarization analyzer with a specific transmission axis angle, and a fourth point source detector; the target beam collected by the front imaging optical system is reflected by the main beam splitter and then incident on the first beam splitter. The beam transmitted through the first beam splitter is incident on the first point source detector through the first polarization analyzer with a specific transmission axis angle, and the beam reflected by the first beam splitter is incident on the second point source detector through the second polarization analyzer with a specific transmission axis angle; the target beam collected by the front imaging optical system is transmitted through the main beam splitter and then incident on the second beam splitter. The beam transmitted through the second beam splitter is incident on the third point source detector through the third polarization analyzer with a specific transmission axis angle, and the beam reflected by the second beam splitter is incident on the fourth point source detector through the fourth polarization analyzer with a specific transmission axis angle; the polarization intensities of polarized light in four different polarization directions are obtained on the first point source detector, the second point source detector, the third point source detector, and the fourth point source detector respectively, realizing real-time imaging detection for simultaneous acquisition of target spatial information and polarization information.

[0007] Further, the front imaging optical system includes: a scanning mirror, a first reflecting mirror, a second reflecting mirror, a third reflecting mirror, and a scanning mirror driving motor; the scanning mirror driving motor is connected to the scanning mirror, and the scanning mirror is driven by the scanning mirror driving motor to scan the target beam in the entire field of view. The collected target beam is successively reflected by the scanning mirror, the first reflecting mirror, the second reflecting mirror, and the third reflecting mirror to the main beam splitter.

[0008] Further, the scanning mirror adopts a planar scanning mirror, whose shape is an ellipse, with a major axis of 164 mm, a minor axis of 88 mm, a thickness of 15 mm, and both sides are coated with a high-reflection film.

[0009] Further, the first reflecting mirror is an ellipsoidal reflecting mirror, with a radius of curvature of 172.442 mm, a conic coefficient conic = -0.821, the material is selected as K9, and the surface is coated with a high-reflection film.

[0010] Further, the second reflecting mirror is a spherical reflecting mirror, with a radius of curvature of 33.10 mm, the material is selected as K9, and the surface is coated with a high-reflection film.

[0011] Further, the third reflecting mirror is a planar reflecting mirror, the material is selected as K9, and the surface is coated with a high-reflection film.

[0012] Further, the materials of the main beam splitter, the first beam splitter, and the second beam splitter are all selected as silicon, and the surfaces are all coated with a semi-transparent and semi-reflective film.

[0013] Furthermore, the first light-transmitting axis angle analyzer, the second light-transmitting axis angle analyzer, the third light-transmitting axis angle analyzer, and the fourth light-transmitting axis angle analyzer all adopt a structural form combining a phase retarder and a polarizer.

[0014] Furthermore, the first point source detector, the second point source detector, the third point source detector, and the fourth point source detector all adopt mercury cadmium telluride point source detectors.

[0015] Furthermore, the parameters of this mid-wave infrared polarization detection optical system are as follows:

[0016] (1) Focal length: 1000 mm;

[0017] (2) Entrance pupil diameter: 80 mm;

[0018] (2) Field of view: ±0.2°;

[0019] (4) Imaging circle diameter: <1 mm;

[0020] (5) Total system length: 320 mm.

[0021] The beneficial effects of the present invention are:

[0022] Based on polarization imaging technology, the present invention designs a mid-wave infrared polarization detection optical system for long-distance target detection. By introducing target polarization information using polarization imaging technology, it is more conducive to mid-wave infrared polarization detection of long-distance targets. A mid-wave infrared polarization detection optical system for long-distance target detection according to the present invention uses four polarization analysis channels, namely, a 0° polarization analysis channel, a 90° polarization analysis channel, a 45° polarization analysis channel, and a 135° polarization analysis channel, to divide the target beam collected by the front imaging optical system into four beams with different polarization directions, and obtain the polarization light intensities corresponding to four different polarization directions on four point source detectors. Based on the theoretical basis of the Stokes vector polarization measurement method, the Stokes vector is calculated using the polarization light intensity values at different polarization angles, so as to realize real-time imaging detection for simultaneous acquisition of target spatial information and polarization information. Compared with the existing polarization methods, the time-sharing and amplitude-division real-time detection method adopted by the present invention has the advantages of high resolution, simultaneous acquisition of target spatial information and polarization information, and the ability to detect moving targets.

[0023] In the present invention, the front imaging optical system only adopts a structural form combining a scanning mirror and a reflective optical system. The reflective optical system is a spherical surface form, which can converge all the light rays within a field of view of ±0.2° into the point source detector, greatly reducing the processing and detection costs of the system. At the same time, the materials of each lens in the system are all selected as silicon and germanium materials commonly used in mid-wave infrared, further reducing the cost and facilitating the engineering of the system. In addition, all four polarization axis angle analyzers adopt a structural form combining a phase retarder and a polarizer. This structure is relatively simple, reducing the number of hardware components and further reducing the system processing cost. Description of the Drawings

[0024] Figure 1 It is an optical path diagram of a mid-wave infrared polarization detection optical system for long-distance target detection according to the present invention.

[0025] Figure 2 It is an optical path diagram of the front imaging optical system.

[0026] In the figure, 1 is the front imaging optical system, 101 is the scanning mirror, 102 is the first reflecting mirror, 103 is the second reflecting mirror, 104 is the third reflecting mirror, 105 is the scanning mirror drive motor, 2 is the main beam splitter, 3 is the first beam splitter, 4 is the first polarization axis angle analyzer, 5 is the first point source detector, 6 is the second polarization axis angle analyzer, 7 is the second point source detector, 8 is the second beam splitter, 9 is the third polarization axis angle analyzer, 10 is the third point source detector, 11 is the fourth polarization axis angle analyzer, and 12 is the fourth point source detector. Detailed Embodiment

[0027] The present invention will be further described in detail below with reference to the accompanying drawings.

[0028] A mid-wave infrared polarization detection optical system for long-distance target detection according to the present invention can perform polarization measurement on a target, obtain the polarization light intensity at different polarization angles, and calculate the Stokes vector based on the theoretical basis of the Stokes vector polarization measurement method, so as to realize real-time imaging detection for simultaneous acquisition of target spatial information and polarization information.

[0029] A mid-wave infrared polarization detection optical system for long-distance target detection according to the present invention has the following parameters:

[0030] 1. Focal length: 1000 mm;

[0031] 2. Entrance pupil diameter: 80 mm;

[0032] 3. Field of view: ±0.2°;

[0033] 4. Imaging circle diameter: <1 mm (less than the photosensitive surface size of the point source detector);

[0034] 5. System total length: 320 mm.

[0035] The present invention realizes long - distance target detection by means of time - sharing and amplitude - division real - time detection, and has the advantages of high resolution and the ability to detect moving targets.

[0036] The specific structural composition of a mid - wave infrared polarization detection optical system for long - distance target detection according to the present invention is as Figure 1 shown. The system mainly includes: a front - end imaging optical system 1, a main beam splitter 2, a first beam splitter 3, a first transmission - axis angle analyzer 4, a first point - source detector 5, a second transmission - axis angle analyzer 6, a second point - source detector 7, a second beam splitter 8, a third transmission - axis angle analyzer 9, a third point - source detector 10, a fourth transmission - axis angle analyzer 11, and a fourth point - source detector 12.

[0037] As Figure 2 shown, the front - end imaging optical system 1 mainly includes: a scanning mirror 101, a first reflecting mirror 102, a second reflecting mirror 103, a third reflecting mirror 104, and a scanning mirror drive motor 105; the scanning mirror drive motor 105 is connected to the scanning mirror 101. The scanning mirror 101 is driven by the scanning mirror drive motor 105 to scan the target beam in the full field of view. The collected target beam is reflected by the scanning mirror 101 to the first reflecting mirror 102, then reflected by the first reflecting mirror 102 to the second reflecting mirror 103, then reflected by the second reflecting mirror 103 to the third reflecting mirror 104, and finally reflected by the third reflecting mirror 104 to the main beam splitter 2. The front - end imaging optical system 1 collects the target beam by combining the scanning mirror 101 with a globally spherical reflective optical system, and can converge all the light rays within a ±0.2° field of view into the subsequent point - source detectors, greatly reducing the processing cost and detection cost of the system.

[0038] Preferably, the scanning mirror 101 is a planar scanning mirror, with an elliptical shape (major axis is 164 mm, minor axis is 88 mm), a thickness of 15 mm, and both sides are coated with a high - reflection film.

[0039] Preferably, the first reflecting mirror 102 is an ellipsoidal reflecting mirror, with a radius of curvature of 172.442 mm, a conic coefficient conic = - 0.821, the material is selected as K9, and the surface is coated with a high - reflection film (the wavelength band is the mid - wave infrared band, the central wavelength range is 3 - 5 μm, and the reflectivity R avg > 99%).

[0040] Preferably, the second reflecting mirror 103 is a spherical reflecting mirror, with a radius of curvature of 33.10 mm, the material is selected as K9, and the surface is coated with a high - reflection film (the wavelength band is the mid - wave infrared band, the central wavelength range is 3 - 5 μm, and the reflectivity R avg > 99%).

[0041] Preferably, the third mirror 104 is a plane mirror made of K9 with a highly reflective film deposited on its surface (the wavelength band is the mid-wave infrared band, the central wavelength range is 3 - 5 μm, and the reflectivity R avg > 99%).

[0042] Among them, the 0° polarization analysis channel is composed of the first beam splitter 3, the first polarization axis angle analyzer 4, and the first point source detector 5, and the 90° polarization analysis channel is composed of the first beam splitter 3, the second polarization axis angle analyzer 6, and the second point source detector 7. The first beam splitter 3 serves as a common component of the 0° and 90° polarization analysis channels and functions as a beam splitter.

[0043] Among them, the 45° polarization analysis channel is composed of the second beam splitter 8, the third polarization axis angle analyzer 9, and the third point source detector 10, and the 135° polarization analysis channel is composed of the second beam splitter 8, the fourth polarization axis angle analyzer 11, and the fourth point source detector 12. The second beam splitter 8 serves as a common component of the 45° and 135° polarization analysis channels and functions as a beam splitter.

[0044] The target beam collected by the front imaging optical system 1 is divided into four beams with different polarization directions by the main beam splitter 2 and the four polarization analysis channels, and the polarization light intensities of four different polarization directions are obtained on the four point source detectors respectively, so as to realize real-time imaging detection for simultaneous acquisition of target spatial information and polarization information. Specifically: the first target beam reflected by the main beam splitter 2 enters the 0° and 90° polarization analysis channels respectively through the beam splitting effect of the first beam splitter 3, that is, the beam transmitted through the first beam splitter 3 enters the first point source detector 5 through the action of the first polarization axis angle analyzer 4 and is received by the first point source detector 5, and the beam reflected by the first beam splitter 3 enters the second point source detector 7 through the action of the second polarization axis angle analyzer 6 and is received by the second point source detector 7; the second target beam transmitted through the main beam splitter 2 enters the 135° and 45° polarization analysis channels respectively through the beam splitting effect of the second beam splitter 8, that is, the beam transmitted through the second beam splitter 8 enters the third point source detector 10 through the action of the third polarization axis angle analyzer 9 and is received by the third point source detector 10, and the beam reflected by the second beam splitter 8 enters the fourth point source detector 12 through the action of the fourth polarization axis angle analyzer 11 and is received by the fourth point source detector 12.

[0045] Preferably, the main beam splitter 2 is made of silicon with a semi-transmissive and semi-reflective film deposited on its surface (the wavelength band is the mid-wave infrared band, the central wavelength range is 3 - 5 μm, and the reflectivity R avg ≈ 50%).

[0046] Preferably, the materials of the first beam splitter 3 and the second beam splitter 8 are both silicon, and semi-transmissive and semi-reflective films are coated on their surfaces (the wavelength band is the mid-wave infrared band, the center wavelength range is 3-5 μm, and the reflectivity R avg ≈50%).

[0047] Preferably, the first transmissive axis angle polarizer 4, the second transmissive axis angle polarizer 6, the third transmissive axis angle polarizer 9, and the fourth transmissive axis angle polarizer 11 specifically adopt a structural form combining a phase retarder and a polarizer. This structure is relatively simple, reduces the number of hardware components, and further reduces costs.

[0048] Preferably, the first point source detector 5, the second point source detector 7, the third point source detector 10, and the fourth point source detector 12 can specifically adopt mercury cadmium telluride point source detectors.

[0049] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A mid-wave infrared polarization detection optical system for long-distance target detection, characterized in that, Including: A front imaging optical system, a main beam splitter, a first beam splitter, a first transmission axis angle polarizer, a first point source detector, a second transmission axis angle polarizer, a second point source detector, a second beam splitter, a third transmission axis angle polarizer, a third point source detector, a fourth transmission axis angle polarizer, and a fourth point source detector; The target beam collected by the front imaging optical system is reflected by the main beam splitter and then incident on the first beam splitter. The beam transmitted through the first beam splitter is incident on the first point source detector through the first transmission axis angle polarizer, and the beam reflected by the first beam splitter is incident on the second point source detector through the second transmission axis angle polarizer; The target beam collected by the front imaging optical system is transmitted through the main beam splitter and then incident on the second beam splitter. The beam transmitted through the second beam splitter is incident on the third point source detector through the third transmission axis angle polarizer, and the beam reflected by the second beam splitter is incident on the fourth point source detector through the fourth transmission axis angle polarizer; The polarization light intensities of four different polarization directions are obtained on the first point source detector, the second point source detector, the third point source detector, and the fourth point source detector respectively, realizing real-time imaging detection for simultaneous acquisition of target spatial information and polarization information; The front imaging optical system includes: a scanning mirror, a first reflector, a second reflector, a third reflector, and a scanning mirror driving motor; The scanning mirror driving motor is connected to the scanning mirror, and the scanning mirror is driven by the scanning mirror driving motor to scan the target beam in the full field of view. The collected target beam is reflected by the scanning mirror, the first reflector, the second reflector, and the third reflector in sequence to the main beam splitter; The first transmission axis angle polarizer, the second transmission axis angle polarizer, the third transmission axis angle polarizer, and the fourth transmission axis angle polarizer all adopt a structural form combining a phase retarder and a polarizer.

2. The mid-wave infrared polarization detection optical system for long-distance target detection according to claim 1, characterized in that, The scanning mirror adopts a planar scanning mirror, with an elliptical shape, a major axis of 164 mm, a minor axis of 88 mm, a thickness of 15 mm, and both sides are coated with a high-reflection film.

3. The mid-wave infrared polarization detection optical system for long-distance target detection according to claim 1, characterized in that, The first reflector is an ellipsoidal reflector with a radius of curvature of 172.442 mm, a conic coefficient conic = -0.821, made of K9, and the surface is coated with a high-reflection film.

4. A mid-wave infrared polarization detection optical system for long-distance target detection according to claim 1, characterized in that, The second reflector is a spherical reflector with a radius of curvature of 33.10 mm, made of K9, and the surface is coated with a high-reflection film.

5. A mid-wave infrared polarization detection optical system for long-distance target detection according to claim 1, characterized in that, The third reflector is a planar reflector, made of K9, and the surface is coated with a high-reflection film.

6. The mid-wave infrared polarization detection optical system for long-distance target detection according to claim 1, characterized in that, The main beam splitter, the first beam splitter, and the second beam splitter are all made of silicon, and the surfaces are all coated with a semi-transparent and semi-reflective film.

7. The mid-wave infrared polarization detection optical system for long-distance target detection according to claim 1, characterized in that The first point source detector, the second point source detector, the third point source detector, and the fourth point source detector all adopt mercury cadmium telluride point source detectors.

8. The mid-wave infrared polarization detection optical system for long-distance target detection according to claim 1, characterized in that, The parameters of this mid-wave infrared polarization detection optical system are as follows: (1) Focal length: 1000 mm; (2) Entrance pupil diameter: 80 mm; (3) Field of view: ±0.2°; (4) Imaging circle diameter: <1 mm; (5) Total system length: 320 mm.

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