A nanosecond gated and actively illuminated spatial back-lighting imaging system and method

Abstract

The application discloses a kind of nanosecond gate and active illumination's space backlight imaging system and method, belong to optical imaging and computer vision technical field.The application includes: nanosecond gate and active pulse illumination synchronous control, reduce sunlight background interference;Multi-frame local block superposition, according to regional brightness adaptive distribution superposition frame number, dark area multi-frame improves signal-to-noise ratio, less frame prevents overexposure;With pixel half-saturation as closed-loop criterion, real-time adjustment gate width and local superposition frame number;High sensitivity qCMOS imaging module is used to carry out low-noise, high frame frequency acquisition.The application can realize high contrast, large dynamic range imaging in strong backlight environment, and is suitable for space non-cooperative target identification, outdoor monitoring, industrial detection and the like.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging and computer vision technology, specifically relating to a nanosecond gated and active illumination spatial backlighting imaging system and method. It is suitable for high-contrast, large dynamic range clear imaging in strong sunlight and strong backlighting outdoor scenes. It can be used for non-cooperative target recognition, pose estimation, navigation docking and other applications, and can also be widely applied in security monitoring, outdoor monitoring, industrial inspection, autonomous driving assisted imaging and other fields. Background Technology

[0002] In complex lighting conditions such as strong backlight, direct sunlight, and haze scattering, the strong background light formed by direct or scattered sunlight can severely overwhelm the reflected signals of the target object, resulting in problems such as extremely low contrast, insufficient dynamic range, and excessive background noise in the image. This typically manifests as overexposure in highlight areas, underexposure in shadow areas, and loss of target details, making it difficult to meet the image clarity requirements of applications such as non-cooperative target recognition in space, pose estimation, navigation docking, outdoor monitoring, and autonomous driving assistance.

[0003] Existing backlight imaging technologies have several limitations in addressing the aforementioned issues. Traditional high dynamic range (HMR) imaging techniques typically employ multi-frame synthesis with different exposure parameters, but this is prone to motion artifacts, highlight clipping, and amplified noise in dark areas during dynamic scenes, and it cannot effectively suppress continuous strong sunlight backgrounds. Optical filter methods can only attenuate specific wavelengths and cannot prevent overexposure under strong backlight conditions at all times. While multi-segment exposure fusion methods can extend the dynamic range, they are prone to edge artifacts and loss of detail, especially in areas with low signal-to-noise ratios.

[0004] Time-gated imaging technology, through nanosecond-level time gating, can separate target signals from background light in the time domain, possessing the potential to suppress continuous background light. However, existing gated imaging systems mostly employ fixed gating widths and fixed stacking frame numbers, lacking adaptive adjustment mechanisms and relying on manually set parameters, making them difficult to adapt to rapidly changing outdoor environments with varying lighting conditions. Furthermore, gated imaging typically requires coordination with active pulsed illumination; existing systems lack closed-loop linkage between synchronization accuracy, illumination control, and imaging feedback, resulting in unstable image quality.

[0005] In terms of imaging devices, traditional scientific-grade complementary metal-oxide-semiconductor (CMOS) cameras, while possessing low readout noise, suffer from insufficient full-well capacity in strong backlight scenes, making them prone to high-light saturation. Electron-multiplying charge-coupled devices (CCDs), on the other hand, offer high gain in low light but have limited dynamic range in strong light, making it difficult to balance weak signal extraction with high-light suppression. Quantum-efficiency scientific-grade CMOS technology, which has emerged in recent years, boasts advantages such as high quantum efficiency, low readout noise, and large full-well capacity, potentially resolving these contradictions. However, a systematic adaptive gating and image fusion solution has yet to be developed in the field of backlight imaging.

[0006] In conclusion, achieving high-contrast, wide-dynamic-range backlighting imaging under strong sunlight, with adaptive adjustment capabilities, remains a pressing technical challenge in the field of optical imaging. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a spatial backlight imaging system and method with nanosecond gating and active illumination. By using nanosecond-level time gating to synchronize active pulse illumination, the system enhances the target brightness within the instant of shooting. Furthermore, based on the pixel half-saturation state, the system adaptively adjusts the gating parameters and the number of frames superimposed on multiple frames in local areas in a closed loop, thereby achieving high-contrast, wide-dynamic-range, and clear imaging under strong backlight conditions.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A nanosecond-gated and actively illuminated spatial backlighting imaging system includes:

[0010] A nanosecond-level pulse active illumination module is used to emit nanosecond-level narrow-pulse illumination light to illuminate the target under the control of a trigger signal;

[0011] The high-sensitivity qCMOS imaging module consists of an image intensifier coupled with a qCMOS detector. It is used to receive the target reflected light signal and perform image acquisition during the opening of the gated window, and output raw image data.

[0012] A picosecond-level synchronous timing gating module is used to generate synchronous trigger signals, which are output to the nanosecond-level pulse active illumination module and the high-sensitivity qCMOS imaging module, respectively.

[0013] The local frame overlay and large dynamic range imaging module is connected to the high-sensitivity qCMOS imaging module. It is used to divide the original image data into several local regions, independently set the number of overlay frames for each local region, perform multi-frame overlay fusion, and output the half-saturation detection result.

[0014] A pixel-level closed-loop control unit is used to receive the half-saturation detection result output by the local frame overlay and large dynamic range imaging module, generate control commands based on the pixel half-saturation threshold, output to the picosecond-level synchronous timing gating module to adjust the gating window width, and output to the local frame overlay and large dynamic range imaging module to adjust the number of multi-frame overlay frames in each local area.

[0015] Furthermore, the nanosecond-level pulse active illumination module uses a semiconductor pulsed laser with an emission wavelength of 850nm, a pulse width adjustment range of 1ns~100ns, and a pulse frequency of 1kHz~10kHz.

[0016] Furthermore, the picosecond-level synchronization timing gating module uses a field-programmable gate array chip with a clock frequency of 100MHz to generate a synchronization trigger signal with an accuracy of 10ps and a trigger jitter of less than 35ps.

[0017] Furthermore, the qCMOS detector in the high-sensitivity qCMOS imaging module is a global shutter detector with readout noise as low as 2.6e. - It has a quantum efficiency of over 70% and a pixel size of 1.6μm × 1.6μm.

[0018] Furthermore, the local frame overlay and large dynamic range imaging module includes:

[0019] The image segmentation module is used to divide the original image data into several local regions;

[0020] The half-saturation detection module is used to detect the average pixel grayscale value of each local area in real time, determine whether the half-saturation threshold has been reached, and generate the half-saturation detection result.

[0021] The parameter adjustment module is used to adjust the width of the gate window and the number of multi-frame overlay frames in each local area according to the half-saturation detection result.

[0022] The image fusion module is used to overlay multiple frames of each local region according to the adjusted number of frames, and to use a weighted fusion algorithm to eliminate regional boundary traces.

[0023] Furthermore, the pixel half-saturation threshold is defined as the pixel grayscale value reaching 40% to 60% of the full-well capacity of the qCMOS detector photosensitive chip.

[0024] Furthermore, the control logic of the pixel-level closed-loop control unit is as follows: when the average gray value of pixels in a local area is lower than the half-saturation threshold, the number of superimposed frames in that area is increased, and the width of the gate window is increased; when the average gray value of pixels in a local area exceeds the half-saturation threshold, the number of superimposed frames in that area is reduced, and the width of the gate window is decreased.

[0025] When the state of half saturation is reached, keep the current parameters unchanged.

[0026] On the other hand, the present invention provides a nanosecond-gated and active-illuminated spatial backlighting imaging method, applied to the aforementioned system, comprising:

[0027] Step S1: The picosecond-level synchronous timing gating module generates a synchronous trigger signal to control the nanosecond-level pulse active illumination module to emit narrow pulse illumination light to illuminate the target. At the same time, it triggers the high-sensitivity qCMOS imaging module to open the gating window. The synchronization delay between the gating window and the illumination light is determined according to the target distance. The raw image data is acquired and output.

[0028] Step S2: Divide the original image data into several local regions, and set the number of frames for overlay independently according to the brightness of each local region. Increase the number of frames for dark areas and decrease the number of frames for bright areas. Then, blend them after overlay.

[0029] Step S3: Detect the average grayscale value of pixels in each local area. Use the half-saturation threshold as the criterion. If the value is lower than the half-saturation threshold, increase the number of stacked frames and the gate width. If the value is higher than the half-saturation threshold, decrease the number of stacked frames and the gate width.

[0030] Step S4: The target reflected light signal is acquired in real time using a high-sensitivity qCMOS imaging module, and multiple frames are superimposed according to the adjusted superposition frame number. A weighted fusion algorithm is used to output a high-contrast imaging image.

[0031] Step S5: Repeat steps S2 to S4, continuously detect the average grayscale value of pixels in each local area, dynamically adjust the gating parameters and the number of superimposed frames, and stabilize at the optimal working point of half saturation.

[0032] Furthermore, in step S2, 32 to 64 frames are superimposed in the dark area, 8 to 16 frames are superimposed in the mid-gray area, 1 to 4 frames are superimposed in the bright area, and the number of superimposed frames in the local area is adjusted from 1 to 64 frames.

[0033] Furthermore, in step S3, when the average grayscale value of pixels in a local area is lower than the half-saturation threshold, the number of superimposed frames is increased by 8 frames each time, with a maximum of 64 frames, and the gate window width is increased by 10ns each time, with a maximum of 500ns; when the average grayscale value of pixels in a local area exceeds the half-saturation threshold, the number of superimposed frames is decreased by 4 frames each time, with a minimum of 1 frame, and the gate window width is decreased by 10ns each time, with a minimum of 10ns.

[0034] Thirdly, the present invention provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned nanosecond-gated and active-illuminated spatial backlighting imaging method.

[0035] Fourthly, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enable the processor to implement the aforementioned nanosecond-gated and active-illuminated spatial backlighting imaging method.

[0036] The beneficial effects of this invention are as follows:

[0037] Strong background light suppression capability: It adopts nanosecond-level gating and active pulse illumination synchronous control, and the gating window width can be finely adjusted to accurately capture the target reflected light, effectively improve the target brightness in the instant of shooting, thereby reducing continuous background light interference and significantly improving the imaging contrast in backlight environments.

[0038] High dynamic range and high signal-to-noise ratio: By adaptive multi-frame stacking in local areas, high frame rate stacking is used in dark areas to improve the signal-to-noise ratio, while low frame rate stacking is used in bright areas to prevent overexposure. After fusion, a high dynamic range and high contrast image is obtained, which is far superior to traditional high dynamic range imaging methods.

[0039] Adaptive closed-loop control: Based on pixel half-saturation as the feedback benchmark, the gate delay, window width and local overlay frame number are adjusted in real time in a closed loop. No manual parameter tuning is required. It can adaptively adapt to changes in light intensity and the system has strong robustness.

[0040] High-sensitivity, low-noise acquisition: It adopts a high-performance imaging module with high quantum efficiency, low readout noise, and large full-well capacity, which takes into account both weak light signal extraction and strong light suppression to ensure imaging quality.

[0041] Wide applicability: It is suitable for non-cooperative target recognition in space, pose estimation, navigation docking, as well as backlight imaging scenarios such as outdoor monitoring, industrial inspection, and autonomous driving assistance, and has good engineering application value. Attached Figure Description

[0042] Figure 1 This is a structural block diagram of a nanosecond-gated and active-illuminated spatial backlight imaging system according to the present invention;

[0043] Figure 2 This is a flowchart of a spatial backlight imaging method with nanosecond gating and active illumination according to the present invention. Detailed Implementation

[0044] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0045] like Figure 1 As shown, the method described in this invention is implemented based on a nanosecond-gated and actively illuminated spatial backlighting imaging system. The specific parameter settings for each module of the system are as follows:

[0046] (1) Nanosecond-level pulse active illumination module: This module emits nanosecond-level narrow pulse width illumination light to provide active illumination for the target object. It uses a semiconductor pulsed laser with an emission wavelength of 850nm, a pulse width adjustment range of 1ns~100ns (set to 10ns~50ns in this embodiment), a pulse frequency of 1kHz~10kHz, and the output power can be adjusted according to the distance to the target to ensure that the light signal reflected by the target can be returned to the camera and effectively acquired. This module is controlled by the trigger signal of the picosecond-level synchronization timing gating module and emits pulse light for illumination only when the synchronization command arrives.

[0047] (2) Picosecond-level synchronous timing gating module: This is the core of the entire system's timing control. It uses an FPGA chip (Xilinx Artix-7 series in this embodiment), with a clock frequency of 100MHz. It can generate synchronous trigger signals with an accuracy of 10ps and a trigger jitter of less than 35ps. It supports multi-channel synchronous output and various trigger modes (internal trigger, external trigger, fast trigger, etc.) to achieve synchronous control of the nanosecond-level pulse active illumination module, the high-sensitivity qCMOS imaging module, and the image intensifier gating. Specifically: The synchronous trigger signal generated by this module is divided into two paths:

[0048] First channel (trigger output → nanosecond-level pulse active illumination module): triggers the laser to emit nanosecond-level narrow pulse illumination light.

[0049] The second channel (trigger output → high-sensitivity qCMOS imaging module): triggers the image intensifier to open the nanosecond-level optical gating window, and simultaneously triggers the qCMOS camera to start signal acquisition in global shutter mode.

[0050] The delay between the two trigger signals can be adaptively adjusted according to the target distance (0.1m~100m) (in this embodiment, the target distance is 10m, and the delay is set to 66.7ns) to ensure that when the reflected light from the illumination pulse reaches the target and reaches the camera, the gating window of the image intensifier is just open. The gating window width can be adjusted from 1ns to 1000ns (in this embodiment, it is set to 10ns~500ns).

[0051] (3) High-sensitivity qCMOS imaging module: Composed of an image intensifier coupled with a qCMOS detector, it is used to receive the target reflected light signal and perform low-noise, high-sensitivity acquisition. The target reflected light signal first enters the image intensifier. Under the trigger control of the picosecond-level synchronous timing gating module, the image intensifier only opens the optical shutter within the nanosecond-level gating window, allowing the reflected light to pass through; the shutter is closed during the time period outside the window, effectively reducing interference from continuous background light such as sunlight. The image intensifier supports an adjustable optical gate width of 500ps~3ns, a shutter repetition frequency of up to 500kHz, and photocathodes such as Hi-QE, HotS20, and GaAs, covering the ultraviolet to near-infrared bands. It supports a zero-noise mode to eliminate inherent sensor noise and has ultra-high linearity, ultra-large dynamic range, and strong light saturation resistance.

[0052] The light signal passing through the gating window is amplified by the image intensifier and then coupled to the qCMOS detector. A global shutter qCMOS detector is used, with selectable sizes of 1600×1088@9μm or 3200×2200@4.5μm. This embodiment uses a Qbit4610 camera equipped with the same image sensor as Hamamatsu's qCMOS sensor. The image sensor has a back-illuminated structure and a readout noise as low as 2.6e. -With a quantum efficiency >70% at 525nm, a pixel size of 1.6μm × 1.6μm, 9.4 million pixels, and a frame rate of 60fps, this qCMOS detector boasts high linearity, high full-well performance, and resistance to strong light saturation. Combined with a zero-noise mode, it is suitable for scenarios involving both backlighting, high-brightness lighting, and gated low-light conditions. It enables low-noise, high-sensitivity, and high-frame-rate image acquisition, providing high-quality raw data for subsequent image processing.

[0053] After the qCMOS detector completes the photoelectric conversion, it outputs the raw image data to the next-level local frame overlay and large dynamic range imaging module.

[0054] (4) Local Frame Overlay and Large Dynamic Range Imaging Module: Receives raw image data from the qCMOS imaging module and runs image processing algorithms on an embedded processor (ARM Cortex-A9, operating frequency 1GHz in this embodiment), including an image segmentation module, a half-saturation detection module, a parameter adjustment module, and an image fusion module, with a processing delay ≤10ms; where,

[0055] The image segmentation module is used to divide the original image into several local regions, and the number of overlay frames for each region is calculated independently.

[0056] The half-saturation detection module is used to detect the average pixel grayscale value of each local area in real time and compare it with the half-saturation threshold set by the pixel-level closed-loop control unit to determine whether the half-saturation state has been reached.

[0057] The parameter adjustment module is used to adaptively adjust the width of the gate window and the number of frames superimposed on each local area based on the half-saturation detection results. In the highlight area, fewer frames or no superposition are used to prevent overexposure and improve contrast.

[0058] The image fusion module is used to overlay multiple frames of each local region according to the adjusted frame number. After the overlay is completed, a weighted fusion algorithm is used to eliminate regional boundary traces and output a fused image with high contrast and large dynamic range.

[0059] (5) Pixel-level closed-loop control unit: This unit constitutes the system's feedback control loop, working in conjunction with the local frame overlay and large dynamic range imaging module to form a complete closed-loop control. The half-saturation detection result in the local frame overlay and large dynamic range imaging module is input as a feedback signal to the pixel-level closed-loop control unit. The pixel-level closed-loop control unit generates control commands based on the pixel half-saturation state (defined as the pixel grayscale value reaching 40%~60% of the full-well capacity of the camera's image sensor; in this embodiment, 50% is used as the benchmark):

[0060] When the average grayscale value of pixels in a local area is detected to be lower than the half-saturation threshold, the control unit outputs the following instructions: ① Increase the number of superimposed frames in that area (increase by 8 frames each time, up to a maximum of 64 frames); ② Simultaneously send instructions to the picosecond-level synchronous timing gating module to increase the gating window width (increase by 10ns each time, up to a maximum of 500ns).

[0061] When the average grayscale value of pixels in a local area exceeds the half-saturation threshold, the control unit outputs the following instructions: ① Reduce the number of superimposed frames in the area (reducing by 4 frames each time, with a minimum of 1 frame); ② Simultaneously send instructions to the picosecond-level synchronous timing gating module to reduce the gating window width (reducing by 10ns each time, with a minimum of 10ns).

[0062] When the state of half saturation is reached, keep the current parameters unchanged.

[0063] In summary, this invention utilizes a closed-loop circuit—pixel-level closed-loop control unit → picosecond-level synchronous timing gating module (adjusting gating parameters) → nanosecond-level pulse active illumination module (optionally adjusting illumination power) → high-sensitivity image-enhanced qCMOS imaging module (acquiring images) → local frame overlay and large dynamic range imaging module (detecting half-saturation state) → feedback to the pixel-level closed-loop control unit—to achieve real-time iterative adjustment. This ensures the system remains consistently stable at the optimal half-saturation operating point without requiring manual parameter tuning.

[0064] like Figure 2 As shown, this embodiment, based on the above system, performs the following steps:

[0065] Step S1: Nanosecond-level gating and active pulse lighting synchronization control

[0066] During system initialization, the initial width of the gating window (50ns in this embodiment), the pulse illumination width (20ns in this embodiment), and the pulse frequency (5kHz in this embodiment) are set. The FPGA chip generates a synchronization trigger signal to control the nanosecond-level pulse active illumination module to emit narrow pulse illumination light, simultaneously triggering the qCMOS camera to open the nanosecond-level gating window. The synchronization delay between the gating window and the pulse illumination light is calculated based on the target distance (10m in this embodiment, with a delay of 66.7ns), ensuring that the gating window is open when the target reflected light reaches the camera, accurately capturing the target reflected light signal, reducing interference from continuous background light such as sunlight, and achieving sunlight background suppression in the time domain. During this process, the qCMOS acquires the gating signal using a global shutter method, effectively avoiding backlight saturation by utilizing its high full-well characteristics.

[0067] The gating window width is adjustable from 1ns to 1000ns, the pulse illumination beam width is adjustable from 1ns to 100ns, and the synchronization delay is adaptively matched according to the target distance.

[0068] Step S2: Multi-frame local block overlay

[0069] The original single-frame image captured by the camera is divided into several local regions (in this embodiment, it is divided into 16×16 local regions, each region being 64×64 pixels in size). Based on the brightness characteristics of each local region, the number of frames for multi-frame overlay is independently set for different local regions: 32-64 frames are overlaid in dark areas (initially set to 32 frames in this embodiment, later adjusted to 40 frames), 8-16 frames are overlaid in mid-gray areas (12 frames are maintained in this embodiment), and 1-4 frames are overlaid in bright areas (initially set to 2 frames in this embodiment, later adjusted to 1 frame). More frames are used in dark areas to improve the signal-to-noise ratio, while fewer frames are used or no frames are used in bright areas to prevent pixel oversaturation. The images after overlaying the local regions are then fused to obtain a high-contrast, wide dynamic range image. The range of the number of frames for local region overlay is 1 to 64 frames.

[0070] Step S3: Pixel half-saturation closed-loop control

[0071] The pixel grayscale values ​​of each local region are detected in real time, and the half-saturation state of the image pixels is used as the closed-loop criterion to construct a dual closed-loop adaptive control mechanism of gating parameters and local overlay frame number. The pixel half-saturation state is defined as the pixel grayscale value reaching 40% to 60% of the full-well capacity of the camera's image sensor (50% is used as the feedback benchmark in this embodiment).

[0072] The half-saturation detection module calculates the average pixel grayscale value of each local area in real time and compares it with the half-saturation threshold to determine the brightness status of each area.

[0073] If the average grayscale value of pixels in a local area is lower than the half-saturation threshold (not reaching half-saturation), the parameter adjustment module increases the number of superimposed frames in that area (in this embodiment, it increases by 8 frames each time, with a maximum of 64 frames), and at the same time appropriately increases the width of the gate window (in this embodiment, it increases by 10ns each time, with a maximum of 500ns).

[0074] If the average grayscale value of pixels in a local area exceeds the half-saturation threshold, the parameter adjustment module reduces the number of superimposed frames in that area (in this embodiment, it reduces by 4 frames each time, with a minimum of 1 frame), and at the same time appropriately reduces the width of the gate window (in this embodiment, it reduces by 10ns each time, with a minimum of 10ns).

[0075] If the average grayscale value of pixels in a local area reaches a state of half saturation, then the number of superimposed frames and the width of the gate window in that area remain unchanged.

[0076] Through real-time iterative adjustments, it ensures that each local area is in the optimal imaging state, eliminating the need for manual parameter adjustment.

[0077] Step S4: Image acquisition and local multi-frame overlay and fusion output

[0078] A qCMOS imaging module is employed, leveraging the camera's low readout noise, high quantum efficiency, high frame rate, and large full-well capacity to achieve low-noise, high-sensitivity acquisition of target reflected light signals. The global shutter opening time is synchronized with the gating window to ensure that only target reflected light signals are acquired.

[0079] Based on the adjusted number of superimposed frames (40 frames for dark areas, 12 frames for mid-gray areas, and 1 frame for bright areas), multi-frame superposition processing is performed on each local area. The image fusion module uses a weighted fusion algorithm to fuse the superimposed images of each local area, eliminating regional boundary artifacts and obtaining a globally high-contrast, large dynamic range image, outputting a clear, high-contrast backlight imaging result.

[0080] Step S5: Iterate

[0081] The system repeats steps S2 to S4 in real time, continuously detects the half-saturation state of each local area, dynamically adjusts the gating parameters and the number of superimposed frames, and updates the gating, illumination, and superimposition parameters in real time to maintain a stable position at the optimal half-saturation working point, ensuring that clear and stable imaging results can still be output even when the backlight environment changes.

[0082] Thirdly, the present invention provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the aforementioned nanosecond-gated and active-illuminated spatial backlighting imaging method.

[0083] Fourthly, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enable the processor to implement the aforementioned nanosecond-gated and active-illuminated spatial backlighting imaging method.

[0084] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A nanosecond-gated and actively illuminated spatial backlighting imaging system, characterized in that, include: A nanosecond-level pulse active illumination module is used to emit nanosecond-level narrow-pulse illumination light to illuminate the target under the control of a trigger signal; The high-sensitivity qCMOS imaging module consists of an image intensifier coupled with a qCMOS detector. It is used to receive the target reflected light signal and perform image acquisition during the opening of the gated window, and output raw image data. A picosecond-level synchronous timing gating module is used to generate synchronous trigger signals, which are output to the nanosecond-level pulse active illumination module and the high-sensitivity qCMOS imaging module, respectively. The local frame overlay and large dynamic range imaging module is connected to the high-sensitivity qCMOS imaging module. It is used to divide the original image data into several local regions, independently set the number of overlay frames for each local region, perform multi-frame overlay fusion, and output the half-saturation detection result. A pixel-level closed-loop control unit is used to receive the half-saturation detection result output by the local frame overlay and large dynamic range imaging module, generate control commands based on the pixel half-saturation threshold, output to the picosecond-level synchronous timing gating module to adjust the gating window width, and output to the local frame overlay and large dynamic range imaging module to adjust the number of multi-frame overlay frames in each local area.

2. The spatial backlighting imaging system with nanosecond gating and active illumination according to claim 1, characterized in that, The nanosecond-level pulse active illumination module uses a semiconductor pulsed laser light source with an emission wavelength of 850nm, a pulse width adjustment range of 1ns~100ns, and a pulse frequency of 1kHz~10kHz.

3. The spatial backlighting imaging system with nanosecond gating and active illumination according to claim 1, characterized in that, The qCMOS detector in the high-sensitivity qCMOS imaging module is a global shutter detector with readout noise as low as 2.6e. - It has a quantum efficiency of over 70% and a pixel size of 1.6μm × 1.6μm.

4. The spatial backlighting imaging system with nanosecond gating and active illumination according to claim 1, characterized in that, The picosecond-level synchronous timing gating module uses a field-programmable gate array chip with a clock frequency of 100MHz to generate a synchronous trigger signal with an accuracy of 10ps and a trigger jitter of less than 35ps.

5. A spatial backlighting imaging system with nanosecond gating and active illumination according to claim 1, characterized in that, The local frame overlay and large dynamic range imaging module includes: The image segmentation module is used to divide the original image data into several local regions; The half-saturation detection module is used to detect the average pixel grayscale value of each local area in real time, determine whether the half-saturation threshold has been reached, and generate the half-saturation detection result. The parameter adjustment module is used to adjust the width of the gate window and the number of multi-frame overlay frames in each local area according to the half-saturation detection result. The image fusion module is used to perform multi-frame overlay on each local region according to the adjusted number of frames, and to use a weighted fusion algorithm to eliminate regional boundary traces.

6. A spatial backlighting imaging system with nanosecond gating and active illumination according to claim 1, characterized in that, The pixel half-saturation threshold is defined as the pixel grayscale value reaching 40% to 60% of the full-well capacity of the qCMOS detector photosensitive chip.

7. A nanosecond-gated and actively illuminated spatial backlighting imaging system according to claim 6, characterized in that, The control logic of the pixel-level closed-loop control unit is as follows: when the average gray value of pixels in a local area is lower than the half-saturation threshold, the number of superimposed frames in that area is increased, and the width of the gate window is increased; when the average gray value of pixels in a local area exceeds the half-saturation threshold, the number of superimposed frames in that area is decreased, and the width of the gate window is decreased; when the half-saturation state is reached, the current parameters are kept unchanged.

8. A nanosecond-gated and actively illuminated spatial backlighting imaging method, applied to the system described in any one of claims 1-7, characterized in that, include: Step S1: The picosecond-level synchronous timing gating module generates a synchronous trigger signal to control the nanosecond-level pulse active illumination module to emit narrow pulse illumination light to illuminate the target. At the same time, it triggers the high-sensitivity qCMOS imaging module to open the gating window. The synchronization delay between the gating window and the illumination light is determined according to the target distance. The raw image data is acquired and output. Step S2: Divide the original image data into several local regions, and set the number of frames for overlay independently according to the brightness of each local region. Increase the number of frames for dark areas and decrease the number of frames for bright areas. Then, blend them after overlay. Step S3: Detect the average grayscale value of pixels in each local area. Use the half-saturation threshold as the criterion. If the value is lower than the half-saturation threshold, increase the number of stacked frames and the gate width. If the value is higher than the half-saturation threshold, decrease the number of stacked frames and the gate width. Step S4: The target reflected light signal is acquired in real time using a high-sensitivity qCMOS imaging module, and multiple frames are superimposed according to the adjusted superposition frame number. A weighted fusion algorithm is used to output a high-contrast imaging image. Step S5: Repeat steps S2 to S4, continuously detect the average grayscale value of pixels in each local area, dynamically adjust the gating parameters and the number of superimposed frames, and stabilize at the optimal working point of half saturation.

9. A spatial backlighting imaging method with nanosecond gating and active illumination according to claim 8, characterized in that, In step S2, 32 to 64 frames are superimposed in the dark area, 8 to 16 frames are superimposed in the mid-gray area, 1 to 4 frames are superimposed in the bright area, and the number of superimposed frames in the local area is adjusted from 1 to 64 frames.

10. A spatial backlighting imaging method with nanosecond gating and active illumination according to claim 8, characterized in that, In step S3, when the average grayscale value of pixels in a local area is lower than the half-saturation threshold, the number of superimposed frames is increased by 8 frames each time, with a maximum of 64 frames, and the gate window width is increased by 10ns each time, with a maximum of 500ns; when the average grayscale value of pixels in a local area exceeds the half-saturation threshold, the number of superimposed frames is decreased by 4 frames each time, with a minimum of 1 frame, and the gate window width is decreased by 10ns each time, with a minimum of 10ns.

Images