Backlight detection system and pixel-level light field modulation method thereof

Abstract

The present invention relates to the field of optical technology, and in particular to a backlight detection system and a pixel-level light field modulation method thereof, wherein the system comprises a main optical system, a polarization beam splitter, a relay lens group, a visible light detector, a pixel-level polarization light field modulator, a polarization detector and a high-dynamic fusion component, wherein the radiation energy collected by the main optical system is incident on the polarization detector and the pixel-level polarization light field modulator respectively through the polarization beam splitter, the polarization detector acquires a polarization image, the radiation energy output by the pixel-level polarization light field modulator is imaged to the visible light detector in turn through the polarization beam splitter and the relay lens group to obtain a visible light image, the polarized visible light image is sent to the high-dynamic fusion component for detection target recognition and motion trajectory prediction, the pixel-level polarization light field modulator is modulated according to the detection target recognition and motion trajectory prediction results, so that the background radiation energy is reflected out of the backlight detection system along the original path. The present invention realizes high-precision target recognition of the detection target.

Description

Technical Field

[0001] The invention belongs to the field of optical technology, and in particular relates to a backlight detection system and a pixel-level light field modulation method thereof. Background Art

[0002] High-sensitivity detection is the premise for high-precision identification of dim and stealth targets. Under backlight conditions, the background brightness is extremely high, which makes the brightness distribution of the detected space target uneven or completely submerged by stray light. Therefore, the key to solving the problem of visible light detection of dim and stealth targets lies in how to suppress the strong light background.

[0003] When a strong light source such as the sun is close to the imaging field of view, in addition to the scattered stray light that enters the optical system after scattering, a certain amount of scattered stray light will be generated inside the system. The physical model of stray light suppression based on surface absorption and scattering of the traditional optical system is no longer applicable to the suppression of background stray light. When a strong light source directly enters the imaging field of view, the background stray light generated by reflection, scattering and diffraction of the internal structure of the system will be superimposed on the imaging light of the strong background, resulting in a more complex illumination distribution on the visible light image plane, which greatly affects the detection and recognition of targets within a limited dynamic range.

[0004] In order to solve the problem of backlight detection, optical detectors currently mainly use the following technical means to solve it: 1. Turn off the optical detector within the backlight angle range to avoid strong light interference; 2. Adjust the aperture of the optical detector to reduce the amount of light passing through and weaken the interference of strong light; 3. Use spectral filters to reduce the imaging spectrum to a narrowband spectrum to reduce the amount of light passing through; 4. Intensity attenuation imaging technology: use the Baader film to attenuate the imaging light; 5. Improve the dynamic range of the optical detector and reduce the probability of saturation of the optical detector; 6. Use event cameras to improve the imaging dynamic range.

[0005] The above method circumvents the technical barriers of spatial backlighting detection to a certain extent, but does not fundamentally solve the problem of spatial backlighting detection.

[0006] Turning off optical detectors at backlight angles to avoid strong light interference will create detection blind spots, which is particularly disadvantageous in the field of space game confrontation and has low detection efficiency.

[0007] Adjusting the optical detector aperture to reduce the amount of light will seriously weaken the irradiation intensity of the detected target, which may cause the loss of the target or its detailed features.

[0008] The use of spectral filters to reduce strong stray light interference has a certain effect on the specific spectral optical characteristics of specific targets, but is limited by the single reflection characteristics of the target and has great limitations.

[0009] The use of intensity attenuation imaging technology will reduce the contrast of the object, resulting in the optical detector being unable to observe the detailed information of the target and only being able to observe bright targets but not dark targets.

[0010] Improving the dynamic range of optical detectors can reduce the saturation probability of optical detectors, which is an important direction for the development of backlight detection technology. However, in the near-Earth space, the intensity of sunlight reaches 1360W / m 2 , and the target in the backlight area, both the infrared radiation characteristics and the visible light radiation characteristics are much smaller than the solar radiation. In some scenarios of long-distance detection, the dynamic range of the optical detector needs to exceed 200dB, but the dynamic range of the current optical detector is far from reaching the above indicators. From the current research status at home and abroad, there is no space backlight detection technology with strong adaptability that has been successfully applied.

[0011] Although the use of event cameras can record the results of large dynamic range imaging, when recording events, if the brightness is too low, the exposure time is too long, which may cause the camera's internal capacitor to be forced to reset, resulting in information loss and failure to meet the requirements of real-time shooting. In addition, when the event camera shoots the target under backlight conditions, although the target's contour information is retained, most of the target's effective detail information has been lost, which brings great difficulties to the subsequent identification and confirmation of key parts of the target.

[0012] To address the backlight problem, a Chinese invention patent entitled "A backlight imaging device based on polarized light" (publication number CN114002699A, publication date February 1, 2022) uses polarization technology to image the sun, and its polarization degree and polarization angle images will appear completely black. However, this method and detection device have certain limitations. First, the device relies on active laser irradiation, and the laser output spot needs to cover the target. Under backlight conditions, it is difficult to make an initial prediction of the target's direction in advance; secondly, when the target is far away or the target size is small, the stability of the optical axis pointing is extremely high; in addition, the system has a narrow operating band, and its detection capability for weak targets is also extremely limited.

[0013] The Chinese invention patent entitled "A spatial light modulated polarization imaging device and imaging method that is resistant to strong light interference" (publication number CN116907647B, publication date December 8, 2023) uses a secondary imaging optical system, a transmissive spatial light modulator, and an adaptive aperture automatic adjustment system to achieve spatial target detection in strong light scenes. This method mainly relies on a transmissive spatial light modulator with editable transmittance to absorb sunlight, and then the adaptive aperture automatic adjustment system controls the light flux. The limitations of this method include two aspects: First, in The image acquisition unit to be detected uses an adjustable aperture, which can only achieve low dynamic range imaging. A larger aperture cannot attenuate ambient light and has a lower contrast. A smaller aperture results in a greater loss of target energy and less information collected by the detector. Ultimately, the effect brightness level is limited, the details are not rich, and dynamic adjustment is impossible. Secondly, a transmissive spatial light modulator is used to modulate the transmittance, which requires reducing the transmittance at the position of the sun spot so that the energy is absorbed by the spatial light modulator. Due to the strong solar energy, the stability of the modulator material at high temperatures is required to be high, and the device heat dissipation pressure is relatively high.

[0014] The Chinese invention patent named "A system and method for space target detection under strong light background" (publication number CN117590480A, publication date February 23, 2024) adopts a secondary imaging optical system and a switchable adaptive strong light filter component to realize space target detection in strong light scenes. This method mainly relies on a filter with two-dimensional movement to attenuate strong light. The limitations of this method include three aspects: First, the position of the filter needs to be aligned with the position of the sunlight spot. The alignment accuracy and speed are limited by the two-dimensional platform. In addition, during the dynamic detection process, the position information of the sunlight spot changes at any time, and the filter needs to correspond to it in real time; secondly, the size of the filter must match the spot size. Due to the diffuse distribution of the edge of the sunlight spot, the size requirements of the filter are relatively strict and demanding. Too large a size will affect the overall detection energy, and too small a size will affect the backlight suppression effect; finally, the efficiency of the filter is a fixed value and cannot be dynamically adjusted according to the target and background response. Summary of the invention

[0015] During the detection process, the precise positioning of dim stealth targets with extremely high background brightness under backlight conditions mainly relies on avoiding strong background light and improving the dynamic range of imaging.

[0016] In view of this, the present invention aims to provide a backlight detection system and a pixel-level light field modulation method thereof to solve the problems of high-sensitivity optical detection of space targets under backlight conditions in terms of dynamic range, imaging time and imaging quality. The present invention adopts pixel-level light field continuous modulation technology and polarization detection technology to achieve high-precision target recognition of the detection target.

[0017] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0018] A backlight detection system comprises a main optical system, a polarization beam splitter, a relay lens group, a visible light detector, a pixel-level polarization light field modulator, a polarization detector and a high-dynamic fusion component, wherein the main optical system collects radiation energy containing a detection target and a background, the radiation energy is incident on the polarization detector and the pixel-level polarization light field modulator respectively through the polarization beam splitter, the polarization detector obtains a polarization image containing the detection target and the background, the radiation energy output by the pixel-level polarization light field modulator is imaged onto the visible light detector in turn through the polarization beam splitter and the relay lens group, and a visible light image containing the detection target and the background is obtained, the polarization image and the visible light image are sent to the high-dynamic fusion component for recognition of the detection target and motion trajectory prediction, the high-dynamic fusion component also inputs the recognition result and motion trajectory prediction result of the detection target into the pixel-level polarization light field modulator, the pixel-level polarization light field modulator performs modulation according to the recognition result and motion trajectory prediction result of the detection target, so that the radiation energy of the background incident on the polarization beam splitter is reflected out of the backlight detection system through the original path of the main optical system.

[0019] Furthermore, the backlight detection system also includes a field of view diaphragm, which is arranged between the polarization beam splitter and the pixel-level polarization light field modulator, and the field of view diaphragm suppresses stray light incident on the pixel-level polarization light field modulator.

[0020] Furthermore, the high dynamic fusion component includes a high dynamic image reconstruction module, an image preprocessing module, a target detection module, a target tracking module, a threshold segmentation module and a trajectory prediction module which are connected in sequence. The high dynamic image reconstruction module performs high dynamic image reconstruction on the visible light image and the polarization image; the image preprocessing module performs image preprocessing operations on the high dynamic image; the target detection module detects the detection target on the preprocessed high dynamic image; the target tracking module tracks the detection target according to the detection result of the detection target; the threshold segmentation module segments the detection target according to the target tracking result of the detection target to realize the recognition of the detection target, and inputs the recognition result of the detection target to the pixel-level polarization light field modulator; the trajectory prediction module predicts the motion trajectory of the detection target according to the recognition result of the detection target, and inputs the motion trajectory prediction result of the detection target to the pixel-level polarization light field modulator.

[0021] Furthermore, the main optical system is a multi-stage imaging main optical system. When the main optical system is a secondary imaging optical system, the field diaphragm and the pixel-level polarization light field modulator are placed at the primary image plane of the secondary imaging optical system; when the main optical system is a tertiary imaging optical system, the field diaphragm and the pixel-level polarization light field modulator are placed at the secondary image plane of the tertiary imaging optical system.

[0022] Furthermore, the main optical system is a transmissive optical system, a catadioptric optical system or a total reflection optical system.

[0023] Furthermore, the visible light detector is CMOS or CCD, and the polarization detector is CMOS or CCD.

[0024] Furthermore, the pixel-level polarization light field modulator includes a polarization light field modulator, and the minimum adjustable unit of the polarization light field modulator is 3 ~10 , the polarization light field modulator has continuous dimming capability.

[0025] Furthermore, the relay mirror group images the radiation energy output by the pixel-level polarization light field modulator onto the visible light detector, and the absolute distortion of the relay mirror group is less than 1 , the telecentricity is less than 2mrad; the relay lens group includes a convex lens, a first double convex lens, a second double convex lens, a first double concave lens, an aperture, a second double concave lens, a third double convex lens, a fourth double convex lens and a concave lens arranged in sequence from the object plane to the image plane; the convex surface of the convex lens faces the image plane, and the concave surface of the concave lens faces the image plane;

[0026] The radius of curvature of the lens close to the object plane in the convex lens is -278.131mm, and the radius of curvature of the lens close to the image plane in the convex lens is -88.887mm;

[0027] The curvature radius of the lens close to the object plane in the first biconvex lens is 144.736 mm, and the curvature radius of the lens close to the image plane in the first biconvex lens is -94.393 mm;

[0028] The curvature radius of the lens close to the object plane in the second biconvex lens is 42.211 mm, and the curvature radius of the lens close to the image plane in the second biconvex lens is -259.266 mm;

[0029] The curvature radius of the lens close to the object plane in the first biconcave lens is -245.531 mm, and the curvature radius of the lens close to the image plane in the first biconcave lens is 24.238 mm;

[0030] The curvature radius of the lens close to the object plane in the second biconcave lens is -24.238 mm, and the curvature radius of the lens close to the image plane in the second biconcave lens is 245.531 mm;

[0031] The curvature radius of the lens close to the object plane in the third biconvex lens is 259.266 mm, and the curvature radius of the lens close to the image plane in the third biconvex lens is -44.211 mm;

[0032] The curvature radius of the lens close to the object plane in the fourth biconvex lens is 94.393 mm, and the curvature radius of the lens close to the image plane in the fourth biconvex lens is -144.736 mm;

[0033] The radius of curvature of the lens close to the object plane in the concave lens is 88.887 mm, and the radius of curvature of the lens close to the image plane in the concave lens is 278.131 mm.

[0034] Further, the air gap between the object plane and the convex lens is 60 mm, the air gap between the convex lens and the first biconvex lens is 41.645 mm, the air gap between the first biconvex lens and the second biconvex lens is 0.1 mm, the air gap between the second biconvex lens and the first biconcave lens is 0.103 mm, the air gap between the first biconcave lens and the aperture is 8.763 mm, the air gap between the aperture and the second biconcave lens is 8.763 mm, the air gap between the second biconcave lens and the third biconvex lens is 0.103 mm, the air gap between the third biconvex lens and the fourth biconvex lens is 0.1 mm, the air gap between the fourth biconvex lens and the concave lens is 41.645 mm, and the air gap between the concave lens and the image plane is 59.252 mm;

[0035] The thickness of the convex lens is 12.099 mm, the thickness of the first biconvex lens is 15.992 mm, the thickness of the second biconvex lens is 16.078 mm, the thickness of the first biconcave lens is 20.277 mm, the thickness of the second biconcave lens is 20.277 mm, the thickness of the third biconvex lens is 16.078 mm, the thickness of the fourth biconvex lens is 15.992 mm, and the thickness of the concave lens is 12.099 mm;

[0036] The glass material of the convex lens, the first biconcave lens, the second biconcave lens and the concave lens is HZF6-CDGM; the glass material of the first biconvex lens and the fourth biconvex lens is HZF9B-CDGM; the glass material of the second biconvex lens and the third biconvex lens is HZF11-CDGM.

[0037] A pixel-level light field modulation method for a backlight detection system is implemented using the backlight detection system and specifically includes the following steps:

[0038] S1: The main optical system collects the radiation energy including the detection target and the background. The radiation energy is incident on the polarization detector and the pixel-level polarization light field modulator respectively through the polarization beam splitter;

[0039] S2: The polarization detector obtains a polarization image containing the detection target and the background. The radiation energy output by the pixel-level polarization light field modulator is imaged onto the visible light detector through the polarization beam splitter and the relay lens in turn, thereby obtaining a visible light image containing the detection target and the background.

[0040] S3: sending the polarization image and the visible light image to the high dynamic fusion component for target recognition and motion trajectory prediction. The high dynamic fusion component also inputs the target recognition result and motion trajectory prediction result into the pixel-level polarization light field modulator.

[0041] S4: The pixel-level polarization light field modulator performs modulation according to the recognition result of the detection target and the motion trajectory prediction result, so that the radiation energy of the background incident to the polarization beam splitter is reflected out of the backlight detection system through the original path of the main optical system.

[0042] Compared with the prior art, the invention can achieve the following beneficial effects:

[0043] (1) The pixel-level light field modulation method of the backlight detection system created by the present invention has the ability of pixel-level light field modulation, which can maximize the suppression of background light while retaining the details of weak targets.

[0044] (2) The pixel-level polarization light field modulator created by the present invention has the ability to be continuously adjustable, and the intensity modulation of the incident light or reflected light reaches 1 to 3000 times or more, which can achieve the optimal image contrast and target signal-to-noise ratio.

[0045] (3) The pixel-level polarization light field modulator created by the present invention can generate specific polarized light, realize polarization detection of weak targets and scenes through a polarization beam splitter, further suppress sunlight entering the field of view, realize solar background suppression and target intensity enhancement under backlight conditions, and improve the imaging contrast of space detection targets under strong backlight background.

[0046] (4) The pixel-level light field modulation method of the backlight detection system created by the present invention, combined with a high-dynamic fusion component, can effectively improve the dynamic range of the image, so that the dynamic range of a single image reaches more than 120dB. At the same time, the present invention can eliminate and suppress images with strong background light under backlight conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0048] Figure 1 A schematic diagram of the structure of the backlight detection system according to an embodiment of the present invention;

[0049] Figure 2 A schematic diagram of the structure of the relay mirror assembly described in an embodiment of the present invention;

[0050] Figure 3A schematic diagram of the structure of a high dynamic fusion component according to an embodiment of the present invention;

[0051] Figure 4 A schematic diagram of the modulation principle described in the embodiment of the present invention;

[0052] Figure 5 A flowchart of a pixel-level light field modulation method for a backlight detection system according to an embodiment of the present invention is provided.

[0053] Description of reference numerals:

[0054] 1. Main optical system; 2. Polarization beam splitter; 3. Pixel-level polarization light field modulator; 4. Relay lens group; 5. Visible light detector; 6. Polarization detector; 7. High dynamic fusion component; 8. Field of view aperture; 9. Detection target; 10. Strong light background; 4-1. Convex lens; 4-2. First biconvex lens; 4-3. Second biconvex lens; 4-4. First biconcave lens; 4-5. Aperture; 4-6. Second biconcave lens; 4-7. Third biconvex lens; 4-8. Fourth biconvex lens; 4-9. Concave lens; 7-1. High dynamic image reconstruction module; 7-2. Image preprocessing module; 7-3. Target detection module; 7-4. Target tracking module; 7-5. Threshold segmentation module; 7-6. Trajectory prediction module. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solution and advantages of the invention more clear, the invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the invention and do not constitute a limitation of the invention.

[0056] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0057] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0058] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0059] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0060] like Figure 1 As shown, the backlight detection system proposed in the present invention comprises a main optical system 1, a polarization beam splitter 2, a relay lens group 4, a visible light detector 5, a pixel-level polarization light field modulator 3, a polarization detector 6 and a high dynamic fusion component 7, wherein the main optical system 1 collects radiation energy containing the detection target and the background, and the radiation energy is incident on the polarization detector 6 and the pixel-level polarization light field modulator 3 respectively through the polarization beam splitter 2, and the polarization detector 6 obtains the polarization image containing the detection target and the background, and the radiation energy output by the pixel-level polarization light field modulator 3 is sequentially incident on the polarization detector 6 and the pixel-level polarization light field modulator 3. The lens group 4 is imaged onto the visible light detector 5 to obtain a visible light image containing the detection target and the background, and the polarization image and the visible light image are sent to the high dynamic fusion component 7 for detection target recognition and motion trajectory prediction. The high dynamic fusion component 7 also inputs the detection target recognition result and the motion trajectory prediction result into the pixel-level polarization light field modulator 3. The pixel-level polarization light field modulator 3 modulates according to the detection target recognition result and the motion trajectory prediction result, so that the background radiation energy incident on the polarization beam splitter 2 is reflected out of the backlight detection system through the main optical system 1 along the original path.

[0061] The backlight detection system also includes a field of view aperture 8, which is disposed between the polarization beam splitter 2 and the pixel-level polarization light field modulator 3, and the field of view aperture 8 suppresses stray light incident on the pixel-level polarization light field modulator 3.

[0062] The main optical system 1 is a multi-stage imaging main optical system 1. When the main optical system 1 is a secondary imaging optical system, the field stop 8 and the pixel-level polarization light field modulator 3 are placed at the primary image plane of the secondary imaging optical system; when the main optical system 1 is a tertiary imaging optical system, the field stop 8 and the pixel-level polarization light field modulator 3 are placed at the secondary image plane of the tertiary imaging optical system, and there is no physical interference between the field stop and the pixel-level polarization light field modulator 3. The main optical system 1 is a transmission optical system, a catadioptric optical system or a total reflection optical system.

[0063] The visible light detector 5 is a CMOS or a CCD, and the polarization detector 6 is a CMOS or a CCD.

[0064] The pixel-level polarization light field modulator 3 includes a polarization light field modulator, and the minimum adjustable unit of the polarization light field modulator is 3 ~10 , the polarization light field modulator has continuous dimming capability.

[0065] The polarization beam splitter 2 has the polarization splitting and gating capabilities with a high signal-to-noise ratio.

[0066] The optical design software may be CODEV, ZEMAX or other software, and the optical design software is used to design a part of the optical path of the backlight detection system.

[0067] like Figure 2 As shown, the relay mirror group 4 images the radiation energy output by the pixel-level polarization light field modulator 3 onto the visible light detector 5, and the absolute distortion of the relay mirror group 4 is less than 1 , the telecentricity is less than 2mrad; the relay lens group 4 includes a convex lens 4-1, a first biconvex lens 4-2, a second biconvex lens 4-3, a first biconcave lens 4-4, an aperture 4-5, a second biconcave lens 4-6, a third biconvex lens 4-7, a fourth biconvex lens 4-8 and a concave lens 4-9, which are arranged in sequence from the object plane to the image plane;

[0068] The convex surface of the convex lens 4-1 faces the image plane, and the concave surface of the concave lens 4-9 faces the image plane;

[0069] The curvature radius of the lens close to the object plane in the convex lens 4-1 is -278.131 mm, and the curvature radius of the lens close to the image plane in the convex lens 4-1 is -88.887 mm;

[0070] The curvature radius of the lens close to the object plane in the first biconvex lens 4-2 is 144.736 mm, and the curvature radius of the lens close to the image plane in the first biconvex lens 4-2 is -94.393 mm;

[0071] The curvature radius of the lens close to the object plane in the second biconvex lens 4-3 is 42.211 mm, and the curvature radius of the lens close to the image plane in the second biconvex lens 4-3 is -259.266 mm;

[0072] The curvature radius of the lens close to the object plane in the first biconcave lens 4-4 is -245.531 mm, and the curvature radius of the lens close to the image plane in the first biconcave lens 4-4 is 24.238 mm;

[0073] The curvature radius of the lens close to the object plane in the second biconcave lens 4-6 is -24.238 mm, and the curvature radius of the lens close to the image plane in the second biconcave lens 4-6 is 245.531 mm;

[0074] The curvature radius of the lens close to the object plane in the third biconvex lens 4-7 is 259.266 mm, and the curvature radius of the lens close to the image plane in the third biconvex lens 4-7 is -44.211 mm;

[0075] The curvature radius of the lens close to the object plane in the fourth biconvex lens 4-8 is 94.393 mm, and the curvature radius of the lens close to the image plane in the fourth biconvex lens 4-8 is -144.736 mm;

[0076] The radius of curvature of the lens close to the object plane in concave lens 4-9 is 88.887 mm, and the radius of curvature of the lens close to the image plane in concave lens 4-9 is 278.131 mm.

[0077] The air interval between the object plane and the convex lens 4-1 is 60 mm, the air interval between the convex lens 4-1 and the first biconvex lens 4-2 is 41.645 mm, the air interval between the first biconvex lens 4-2 and the second biconvex lens 4-3 is 0.1 mm, the air interval between the second biconvex lens 4-3 and the first biconcave lens 4-4 is 0.103 mm, the air interval between the first biconcave lens 4-4 and the diaphragm 4-5 is 8.763 mm, the air interval between the diaphragm 4-5 and the second biconcave lens 4-6 is 8.763 mm, the air interval between the second biconcave lens 4-6 and the third biconvex lens 4-7 is 0.103 mm, the air interval between the third biconvex lens 4-7 and the fourth biconvex lens 4-8 is 0.1 mm, the air interval between the fourth biconvex lens 4-8 and the concave lens 4-9 is 41.645 mm, and the air interval between the concave lens 4-9 and the image plane is 59.252 mm;

[0078] The thickness of the convex lens 4-1 is 12.099 mm, the thickness of the first biconvex lens 4-2 is 15.992 mm, the thickness of the second biconvex lens 4-3 is 16.078 mm, the thickness of the first biconcave lens 4-4 is 20.277 mm, the thickness of the second biconcave lens 4-6 is 20.277 mm, the thickness of the third biconvex lens 4-7 is 16.078 mm, the thickness of the fourth biconvex lens 4-8 is 15.992 mm, and the thickness of the concave lens 4-9 is 12.099 mm;

[0079] The glass material of the convex lens 4-1, the first biconcave lens 4-4, the second biconcave lens 4-6 and the concave lens 4-9 is HZF6-CDGM; the glass material of the first biconvex lens 4-2 and the fourth biconvex lens 4-8 is HZF9B-CDGM; the glass material of the second biconvex lens 4-3 and the third biconvex lens 4-7 is HZF11-CDGM.

[0080] like Figure 3As shown, the high dynamic fusion component 7 includes a high dynamic image reconstruction module 7-1, an image preprocessing module 7-2, a target detection module 7-3, a target tracking module 7-4, a threshold segmentation module 7-5 and a trajectory prediction module 7-6 connected in sequence. The high dynamic image reconstruction module 7-1 performs high dynamic image reconstruction on the visible light image and the polarization image (adopting the existing high dynamic image fusion algorithm based on machine learning, the compressed sensing image reconstruction algorithm based on neural network and other algorithms to achieve high dynamic image reconstruction); the image preprocessing module 7-2 performs image preprocessing operations on the high dynamic image, and the image preprocessing operations include image denoising (specifically, image denoising can be performed by using methods such as mean filtering, median filtering and Gaussian filtering), elimination of residual images (specifically, using histogram equalization, Gamma transformation, Laplace transformation and other algorithms to enhance the image, complete the elimination of residual images, and eliminate small block and strip-shaped background interference contained in the residual image) and image high resolution reconstruction operations (image The resolution is reconstructed so that the processed image meets the detection requirements of the target); the target detection module 7-3 detects the detection target on the pre-processed high-dynamic image (using algorithms such as histogram equalization, Gamma transformation, Laplace transformation, etc. to detect the detection target); the target tracking module 7-4 tracks the detection target according to the detection result of the detection target (using algorithms such as Kalman filter algorithm, particle filter algorithm and center of gravity tracking method to track the target); the threshold segmentation module 7-5 segments the detection target according to the target tracking result of the detection target (using two-bit maximum entropy threshold method to achieve threshold segmentation), realizes the recognition of the detection target, and inputs the recognition result of the detection target to the pixel-level polarization light field modulator 3; the trajectory prediction module 7-6 predicts the motion trajectory of the detection target according to the recognition result of the detection target (using the least squares method to predict the target trajectory), and inputs the motion trajectory prediction result of the detection target to the pixel-level polarization light field modulator 3.

[0081] The present invention adopts a multi-level imaging main optical system 1, and solves the problem of high dynamic imaging under backlight conditions and improves the recognition accuracy of targets through a pixel-level light field modulation method and a pixel-level polarization detection method, combined with stray light suppression technology inside and outside the field of view.

[0082] Firstly, a multi-stage imaging main optical system 1 with good stray light performance is designed to obtain the radiation energy of the detection target and its background within the imaging field of view. The radiation energy of the detection target and its background enters the polarization light field modulator through the polarization beam splitter 2. After reflection from the polarization light field modulator, the polarization state changes. Then, the polarized light formed by the polarization beam splitter 2 is finally imaged onto the visible light detector 5 through the relay lens group 4. The radiation energy of the detection target and its background also enters the polarization detector 6 through the polarization beam splitter 2 for imaging, thereby obtaining a polarization image including the detection target and the background.

[0083] The visible light detector 5 obtains a visible light image including the detection target and the background according to the image grayscale response, sends the polarization image and the visible light image to the high dynamic fusion component 7 to determine the position and area of ​​the strong light background, and feeds back to the polarization light field modulator. Through the pixel-level polarization gating modulation, the radiation energy of the strong light background will be reflected to the main optical system 1 and leave the imaging light path when it passes through the polarization beam splitter 2 again. The imaging area of ​​the detection target is not modulated, and the imaging position and imaging performance are unchanged, finally realizing the high-sensitivity detection of spatially dim targets under backlight conditions.

[0084] like Figure 4 As shown, before the pixel-level polarization light field modulator 3 modulates the radiation energy of the detection target 9 and the radiation energy of the strong light background 10 of the detection target 9, the P light of both the radiation energy of the detection target 9 and the radiation energy of the strong light background 10 of the detection target 9 passes through the polarization beam splitter 2 and is finally imaged on the visible light detector 5. After the light field calculation, the position and area of ​​the strong light background 10 are determined, and the pixel-level polarization light field modulator 3 modulates the radiation energy of the strong light background 10 to convert the P light of the radiation energy of the strong light background 10 into S light. Then, when the radiation energy of the strong light background 10 passes through the polarization beam splitter 2 again, it will be reflected to the main optical system 1 and leave the imaging light path.

[0085] like Figure 5 As shown, the pixel-level light field modulation method of the backlight detection system of the present invention is implemented by using the backlight detection system, and specifically includes the following steps:

[0086] S1: The main optical system 1 collects the radiation energy including the detection target and the background, and the radiation energy is incident on the polarization detector 6 and the pixel-level polarization light field modulator 3 respectively through the polarization beam splitter 2;

[0087] S2: The polarization detector 6 obtains a polarization image including the detection target and the background, and the radiation energy output by the pixel-level polarization light field modulator 3 is imaged onto the visible light detector 5 through the polarization beam splitter 2 and the relay lens group 4 in sequence, thereby obtaining a visible light image including the detection target and the background;

[0088] S3: sending the polarization image and the visible light image to the high dynamic fusion component 7 for detecting target recognition and motion trajectory prediction. The high dynamic fusion component 7 also inputs the detection target recognition result and motion trajectory prediction result to the pixel-level polarization light field modulator 3;

[0089] S4: The pixel-level polarized light field modulator 3 performs modulation according to the recognition result of the detection target and the motion trajectory prediction result, so that the background radiation energy incident on the polarization beam splitter 2 is reflected out of the backlight detection system through the main optical system 1 along the original path.

[0090] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the disclosure of the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and this document does not limit this.

[0091] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A backlight detection system, characterized in that: The invention comprises a main optical system, a polarization beam splitter, a relay lens group, a visible light detector, a pixel-level polarization light field modulator, a polarization detector and a high dynamic fusion component, wherein the main optical system collects radiation energy containing a detection target and a background, the radiation energy is incident on the polarization detector and the pixel-level polarization light field modulator respectively through the polarization beam splitter, the polarization detector obtains a polarization image containing the detection target and the background, the radiation energy output by the pixel-level polarization light field modulator is imaged onto the visible light detector through the polarization beam splitter and the relay lens group in turn, and a visible light image containing the detection target and the background is obtained, the polarization image and the visible light image are sent to the high dynamic fusion component for recognition of the detection target and motion trajectory prediction, the high dynamic fusion component also inputs the recognition result and motion trajectory prediction result of the detection target into the pixel-level polarization light field modulator, the pixel-level polarization light field modulator is modulated according to the recognition result and motion trajectory prediction result of the detection target, so that the radiation energy of the background incident on the polarization beam splitter is reflected out of the backlight detection system through the original path of the main optical system.

2. The backlight detection system according to claim 1, characterized in that: The backlight detection system also includes a field of view stop, which is arranged between the polarization beam splitter and the pixel-level polarization light field modulator, and the field of view stop suppresses stray light incident on the pixel-level polarization light field modulator.

3. The backlight detection system according to claim 1, characterized in that: The high dynamic fusion component includes a high dynamic image reconstruction module, an image preprocessing module, a target detection module, a target tracking module, a threshold segmentation module and a trajectory prediction module which are connected in sequence. The high dynamic image reconstruction module performs high dynamic image reconstruction on the visible light image and the polarization image; the image preprocessing module performs image preprocessing operations on the high dynamic image; the target detection module detects the detection target on the preprocessed high dynamic image; and the target tracking module tracks the detection target according to the detection result of the detection target. The threshold segmentation module segments the detection target according to the target tracking result of the detection target to realize the recognition of the detection target, and inputs the recognition result of the detection target into the pixel-level polarization light field modulator; the trajectory prediction module predicts the motion trajectory of the detection target according to the recognition result of the detection target, and inputs the motion trajectory prediction result of the detection target into the pixel-level polarization light field modulator.

4. The backlight detection system according to claim 2, characterized in that: The main optical system is a multi-stage imaging main optical system. When the main optical system is a secondary imaging optical system, the field of view diaphragm and the pixel-level polarization light field modulator are placed at the primary image plane of the secondary imaging optical system; when the main optical system is a tertiary imaging optical system, the field of view diaphragm and the pixel-level polarization light field modulator are placed at the secondary image plane of the tertiary imaging optical system.

5. The backlight detection system according to claim 1, characterized in that: The main optical system is a transmissive optical system, a catadioptric optical system or a total reflective optical system.

6. The backlight detection system according to claim 1, characterized in that: The visible light detector is CMOS or CCD, and the polarization detector is CMOS or CCD.

7. The backlight detection system according to claim 1, characterized in that: The pixel-level polarization light field modulator includes a polarization light field modulator, and the minimum adjustable unit of the polarization light field modulator is 3 ~10 .

8. The backlight detection system according to claim 1, characterized in that: The relay mirror group images the radiation energy output by the pixel-level polarization light field modulator onto the visible light detector, and the absolute distortion of the relay mirror group is less than 1 , the telecentricity is less than 2mrad; the relay lens group comprises a convex lens, a first biconvex lens, a second biconvex lens, a first biconcave lens, an aperture, a second biconcave lens, a third biconvex lens, a fourth biconvex lens and a concave lens arranged in sequence from the object plane to the image plane; The convex surface of the convex lens faces the image plane, and the concave surface of the concave lens faces the image plane; The curvature radius of the lens close to the object plane in the convex lens is -278.131 mm, and the curvature radius of the lens close to the image plane in the convex lens is -88.887 mm; The curvature radius of the lens close to the object plane in the first biconvex lens is 144.736 mm, and the curvature radius of the lens close to the image plane in the first biconvex lens is -94.393 mm; The curvature radius of the lens close to the object plane in the second biconvex lens is 42.211 mm, and the curvature radius of the lens close to the image plane in the second biconvex lens is -259.266 mm; The curvature radius of the lens close to the object plane in the first biconcave lens is -245.531 mm, and the curvature radius of the lens close to the image plane in the first biconcave lens is 24.238 mm; The curvature radius of the lens close to the object plane in the second biconcave lens is -24.238 mm, and the curvature radius of the lens close to the image plane in the second biconcave lens is 245.531 mm; The curvature radius of the lens close to the object plane in the third biconvex lens is 259.266 mm, and the curvature radius of the lens close to the image plane in the third biconvex lens is -44.211 mm; The curvature radius of the lens close to the object plane in the fourth biconvex lens is 94.393 mm, and the curvature radius of the lens close to the image plane in the fourth biconvex lens is -144.736 mm; The curvature radius of the lens close to the object plane in the concave lens is 88.887 mm, and the curvature radius of the lens close to the image plane in the concave lens is 278.131 mm.

9. The backlight detection system according to claim 8, characterized in that: The air gap between the object plane and the convex lens is 60 mm, the air gap between the convex lens and the first biconvex lens is 41.645 mm, the air gap between the first biconvex lens and the second biconvex lens is 0.1 mm, the air gap between the second biconvex lens and the first biconcave lens is 0.103 mm, the air gap between the first biconcave lens and the diaphragm is 8.763 mm, the air gap between the diaphragm and the second biconcave lens is 8.763 mm, the air gap between the second biconcave lens and the third biconvex lens is 0.103 mm, the air gap between the third biconvex lens and the fourth biconvex lens is 0.1 mm, the air gap between the fourth biconvex lens and the concave lens is 41.645 mm, and the air gap between the concave lens and the image plane is 59.252 mm; The thickness of the convex lens is 12.099 mm, the thickness of the first biconvex lens is 15.992 mm, the thickness of the second biconvex lens is 16.078 mm, the thickness of the first biconcave lens is 20.277 mm, the thickness of the second biconcave lens is 20.277 mm, the thickness of the third biconvex lens is 16.078 mm, the thickness of the fourth biconvex lens is 15.992 mm, and the thickness of the concave lens is 12.099 mm; The glass material of the convex lens, the first biconcave lens, the second biconcave lens and the concave lens is HZF6-CDGM; the glass material of the first biconvex lens and the fourth biconvex lens is HZF9B-CDGM; the glass material of the second biconvex lens and the third biconvex lens is HZF11-CDGM.

10. A pixel-level light field modulation method for a backlight detection system, implemented by using the backlight detection system according to any one of claims 1 to 9, characterized in that: The specific steps include: S1: The main optical system collects radiation energy including detection targets and background, and the radiation energy is incident on the polarization detector and the pixel-level polarization light field modulator respectively through the polarization beam splitter; S2: the polarization detector acquires a polarization image including the detection target and the background, and the radiation energy output by the pixel-level polarization light field modulator is imaged onto the visible light detector through the polarization beam splitter and the relay lens in sequence to obtain a visible light image including the detection target and the background; S3: sending the polarization image and the visible light image to the high dynamic fusion component for detecting target recognition and motion trajectory prediction, and the high dynamic fusion component also inputs the detection target recognition result and motion trajectory prediction result into the pixel-level polarization light field modulator; S4: The pixel-level polarization light field modulator performs modulation according to the recognition result of the detection target and the motion trajectory prediction result, so that the background radiation energy incident on the polarization beam splitter is reflected out of the backlight detection system through the original path of the main optical system.

Images