A kind of active and passive integrated spectral polarization imaging device under extreme light environment

Abstract

The application discloses an active and passive integrated spectral polarization imaging device in an extreme light environment, and belongs to the field of target detection in an extreme light environment. The device comprises a main and passive common optical axis imaging module, a laser active illumination module, an imaging detection module and a mode control and signal processing module. The main and passive common optical axis imaging module establishes a common optical axis transmission channel in which an active emission light path and a target reflection receiving light path are spatially overlapped. The laser active illumination module provides 532nm and 808nm switchable coaxial illumination. The imaging detection module comprises a receiving imaging sub-module, a polarization modulation sub-module and a detection output sub-module, and is used for collecting intensity images and polarization images. The mode control and signal processing module realizes adaptive switching and cooperative control of an active illumination imaging mode and a passive polarization imaging mode. The device can realize natural correspondence of active intensity information and passive polarization information in space, and avoids parallax and registration errors caused by separate arrangement of multiple systems.

Description

Technical Field

[0001] This invention belongs to the field of target detection in extreme lighting environments, and particularly relates to an active and passive integrated spectral polarization imaging device for extreme lighting environments. Background Technology

[0002] In the field of photoelectric imaging detection, for complex lighting environments such as weak light, backlight, strong background light, low contrast and scattering blockage, two technical approaches are usually adopted in engineering: active illumination imaging and passive polarization imaging.

[0003] Active illumination imaging uses lasers or other artificial light sources to illuminate the target scene and utilizes the received reflected light signals to improve target detectability and imaging signal-to-noise ratio under low-light conditions. Related laser illumination / active imaging systems have been extensively researched and implemented in target detection, identification, and imaging under low-visibility conditions.

[0004] Passive polarization imaging utilizes the differences in polarization characteristics (such as Stokes parameters, degree of linear polarization (DoLP), and angle of polarization (AoP)) between the target and the background under natural lighting conditions to enhance contrast or extract material / surface information. In recent years, focal plane polarization cameras (DoFP) have been widely used for polarization measurement in dynamic scenes due to their advantage of simultaneous imaging in multiple polarization directions. However, they also bring problems such as resolution loss and inconsistent response between pixels, which usually require calibration and correction for pixel-level polarization response differences.

[0005] To further enhance adaptability to complex scenarios, this invention attempts to use "active (laser)" and "passive (polarization)" information for complementary acquisition in the same task or on the same platform, for target differentiation or identification and evaluation. However, from a system implementation perspective, existing active and passive imaging devices and integration solutions still generally suffer from the following objective shortcomings:

[0006] 1) Active imaging and polarization imaging systems are usually designed independently and lack a unified integrated structure.

[0007] Existing active laser imaging technologies primarily focus on acquiring target distance and intensity information. These systems typically consist of a laser emitting module, a receiving optical system, a detection array, and a signal processing unit, with optimizations focused on the imaging mechanism and echo detection mechanism. Polarization imaging technology, on the other hand, focuses on acquiring the polarization characteristics of the reflected light from the target, extracting Stokes parameters and the degree of polarization through polarization modulation or a focal plane structure. These two types of systems have relatively independent technological development paths, with their optical structures, modulation methods, and signal processing flows each optimized separately. Existing literature often constructs and operates active and polarization imaging systems separately, failing to establish a structurally integrated imaging system that achieves coordinated acquisition of active illumination and passive polarization information under a unified incident light window and optical axis. This often necessitates separate equipment deployment or post-processing data registration in practical applications.

[0008] 2) Active imaging systems lack stability in recognizing complex geometric postures.

[0009] Existing active imaging systems primarily rely on distance and intensity images for target recognition. Related research indicates that the stability of recognition algorithms is affected by changes in target pose, scale, or affine transformations. Experimental results show a significant decrease in recognition rate under geometric transformations, indicating that the distance or intensity features acquired by existing systems are highly sensitive to changes in target pose. Furthermore, active imaging signals are influenced by the target surface reflection characteristics, incident angle, and spatial structure variations, resulting in fluctuations in feature representation under complex geometric conditions. Therefore, the robustness of single active imaging information still has room for improvement under conditions of variable target pose or complex scene structures.

[0010] 3) Polarization imaging is limited by ambient light, and its detection capability is insufficient at night or under extreme lighting conditions.

[0011] Polarization imaging technology primarily utilizes the difference in polarization characteristics between the target and the background to enhance contrast, and its imaging effect depends on the illumination conditions of natural light or ambient light. Related research indicates that in low-light or nighttime environments, the polarization signal intensity weakens due to reduced incident light energy, leading to a decrease in image quality. Furthermore, in environments with strong background light or complex scattering, stable extraction of polarization information requires high precision in optical modulation and system calibration. Existing polarization imaging systems are mostly based on passive optical structures and lack active illumination mechanisms, thus limiting their detection capabilities in extreme lighting or low-light environments.

[0012] 4) The existing system lacks a mechanism for collaborative acquisition of active and passive information.

[0013] Laser active imaging emphasizes acquiring distance and intensity information of a target under artificial illumination, while polarization imaging emphasizes the polarization characteristics of the reflected light from the target. These two technologies are complementary in terms of information dimensions. However, existing research mainly focuses on optimizing their respective imaging systems or data-level fusion algorithms, and has not yet established a collaborative mechanism for simultaneously acquiring active illumination and passive polarization information at the structural level. In current technologies, active and passive information are often acquired through independent devices and then fused later, lacking a unified optical path, a unified field of view, and a real-time collaborative control structure. This results in room for improvement in system integration and information consistency.

[0014] The following problems exist with existing technologies:

[0015] Existing laser active imaging systems and polarization imaging systems are usually designed independently. Active imaging focuses on acquiring distance and intensity information, while polarization imaging focuses on extracting polarization features. The two types of systems are relatively separate in terms of optical structure and imaging mechanism, and have not yet formed an integrated structure under the conditions of unified optical window and unified optical axis, which leads to the need for separate deployment or post-registration in practical applications.

[0016] Existing active imaging systems have limited stability under complex geometric attitude changes. Target recognition based on distance or intensity features is sensitive to changes in target attitude, incident angle and structure, and lacks robustness in complex environments.

[0017] Existing polarization imaging systems rely on natural light or ambient light conditions, and their imaging capabilities are limited in low light, nighttime, or extreme lighting environments. Furthermore, the polarization modulation structure places high demands on the system's optical stability and calibration accuracy.

[0018] Meanwhile, existing publicly available technologies mostly focus on optimizing single active or passive imaging systems, lacking imaging systems that can achieve real-time collaborative acquisition of active illumination and passive polarization information under a unified structure. Information fusion largely relies on post-processing, and the system integration and information consistency need to be improved. Summary of the Invention

[0019] To achieve the above objectives, the present invention needs to solve the following technical problems:

[0020] (1) How to achieve coaxial integration of active laser illumination and passive polarization imaging in the same optical system, and avoid structural redundancy and inconsistent field of view caused by independent deployment of multiple systems;

[0021] (2) How to achieve stable switching or collaborative operation between active and passive modes under a unified optical path structure, and ensure the consistency and real-time performance of the two types of information acquisition;

[0022] (3) How to combine the advantages of active imaging and polarization imaging in complex lighting or low light environments to improve the stability of target detection and recognition;

[0023] (4) How to improve the ability to acquire multidimensional information (intensity, polarization) collaboratively at the system structure level and reduce the registration and fusion errors in the later stage.

[0024] This invention provides an integrated active and passive imaging device and method. By constructing a unified optical window and a coaxial structure, it achieves the coordinated acquisition of active laser illumination imaging and passive polarization imaging, thereby improving the comprehensive detection capability and system integration in complex lighting environments.

[0025] The present invention further aims to achieve stable switching or coordinated operation of active and passive imaging modes through structural optimization and mode control design, thereby reducing system errors and improving imaging consistency and recognition stability.

[0026] The technical solution of the present invention includes:

[0027] An integrated active and passive spectral polarization imaging device for extreme lighting conditions includes:

[0028] The active and passive coaxial imaging module includes a unified light inlet, a quarter-wave plate, a polarization beam splitter, and a displacement adjustment component, which are used to establish a coaxial transmission channel in which the active emission optical path and the target reflection and reception optical path are spatially coincident.

[0029] The laser active illumination module includes a laser emitting unit, a collimating lens, a polarizer, and an emission displacement switching component, used to provide controllable artificial illumination to a target area;

[0030] The imaging detection module, located at the end of the receiving optical path, includes a receiving imaging submodule, a polarization modulation submodule, and a detection output submodule, which are used to receive the target radiation signal converged by the main optical system and complete image acquisition.

[0031] The mode control and signal processing module is electrically connected to the active and passive coaxial imaging module, the laser active illumination module and the imaging detection module, respectively, and is used to complete the working mode switching, device collaborative control, image acquisition and polarization parameter calculation.

[0032] The laser active illumination module and the active-passive coaxial imaging module share the same main optical axis. The laser output by the laser active illumination module is emitted to the target area along the same main optical axis by the active-passive coaxial imaging module. The target reflected echo returns along the same main optical axis and enters the imaging detection module.

[0033] The active-passive coaxial imaging module is the fundamental optical module of the entire system, including a unified entrance port, a quarter-wave plate, a polarization beam splitter, and a displacement adjustment assembly. This module is used to establish a coaxial transmission channel where the active emission optical path and the target reflection and reception optical path spatially coincide. This allows the active laser illumination path and the passive polarization reception path to share the same principal optical axis and a unified field of view, thereby ensuring that the intensity information acquired actively and the polarization information acquired passively naturally correspond in space, reducing parallax errors and post-registration errors caused by the independent deployment of multiple systems.

[0034] The laser active illumination module provides controllable artificial illumination to a target area under conditions of low light, nighttime, or strong background interference. The module includes a 532nm laser emitting unit, an 808nm laser emitting unit, a collimating lens, and a polarizer. An electric displacement mechanism controls the entry and exit of different wavelength-emitting components into the main optical path. After collimation, polarization, and polarization modulation, the laser is coaxially emitted along the main optical axis to the target area. The reflected echo from the target returns to the receiver via the same main optical path, achieving active illumination imaging. By employing a multi-band switchable coaxial output structure, this invention can switch between different wavelength-band active illumination modes without changing the direction of the main optical axis, improving the system's adaptability to different scenes and target characteristics.

[0035] The imaging detection module is located at the end of the receiving optical path and is used to receive the target radiation signal converged by the main optical system and complete image acquisition. The imaging detection module may include an SCMOS camera and a polarization camera, where the SCMOS camera is used for echo intensity imaging in active laser illumination mode, and the polarization camera is used for polarization image acquisition in passive polarization imaging mode. Depending on the different operating modes, the direction of the receiving optical path is changed by a mirror assembly, a filter device, and a displacement adjustment mechanism, so that the returned light enters the corresponding detector to complete imaging, thereby realizing the separate reception and directional acquisition of active intensity information and passive polarization information.

[0036] The mode control and signal processing module is used to realize device linkage control, parameter configuration, image acquisition, data storage, and polarization parameter calculation in different operating modes. After receiving external task commands, this module analyzes the target operating mode and corresponding parameters, controls the electric displacement mechanism to adjust the positional relationship of the PBS component, reflector component, and laser emission component in the main optical path, and simultaneously controls the laser start / stop, camera exposure, and polarization modulation device operation. When the system operates in 532nm active illumination imaging mode, it controls the 532nm laser emission component, corresponding PBS component, and reflector component to enter the main optical path, and controls the SCMOS camera to acquire the target reflection image; when the system operates in 808nm active illumination imaging mode, it controls the 808nm laser emission component and corresponding optical components to enter the main optical path, and completes 808nm active illumination imaging; when the system operates in passive polarization imaging mode, it moves the active emission channel out of the main optical path, controls the polarization camera to work, and acquires and calculates the target polarization information. When necessary, it can also switch and operate in active mode, passive mode, or a combination of both, according to ambient lighting conditions and task requirements.

[0037] The present invention has the following beneficial effects:

[0038] (1) A common-aperture, common-optical-axis active-passive integrated imaging structure is proposed to realize the unified design of active laser illumination and passive polarization imaging under the same main optical system; a polarization modulation and analysis structure is embedded in the unified optical axis and optical path to realize the synchronous acquisition of intensity information and polarization information; a collaborative working mechanism between active mode and passive mode is constructed to realize the adaptive switching or collaborative operation of multiple imaging systems in the same system; and a scalable integrated optical architecture is formed to provide a unified platform for the integration of multimodal imaging systems.

[0039] (2) The co-optical axis integrated design of active laser illumination and passive polarization imaging is realized under the co-aperture structure of transmitting and receiving, and a multi-dimensional information collaborative acquisition mechanism at the physical level is constructed. The present invention realizes the co-aperture co-optical axis design of active laser illumination and passive polarization imaging under the same main optical system, so that the paths of active emission light and received light coincide in space, ensuring that intensity information and polarization information naturally correspond within the field of view, avoiding parallax error and subsequent geometric registration problems caused by the separate deployment of multiple systems, and improving the system structure integration and optical consistency.

[0040] (3) Breaking through the dependence of a single imaging system on environmental conditions, constructing an adaptive active and passive imaging mode; active imaging has advantages in low-light environments, but is limited by echo attenuation and system gain; polarization imaging has advantages in complex background recognition, but depends on ambient light. This invention achieves adaptive switching between active mode and passive polarization mode through a mode control mechanism, enabling the system to dynamically select or fuse information dimensions according to lighting and scene conditions, breaking through the environmental dependence of a single imaging system, and improving the continuous detection capability in complex lighting environments.

[0041] (4) Forming a scalable active-passive integrated imaging architecture foundation; The coaxial integrated structure constructed by this invention is not only applicable to single-band laser and polarization imaging, but also provides a unified optical platform for subsequent multi-band and multi-modal imaging expansion. This architecture can be further extended to multispectral or infrared bands to realize multi-dimensional detection system integration, and has strong potential for engineering promotion and system upgrades. Attached Figure Description

[0042] Figure 1 Schematic diagram of the active and passive coaxial imaging module;

[0043] Figure 2 This is a schematic diagram of a laser active illumination module;

[0044] Figure 3 This is a schematic diagram of the imaging detection module;

[0045] Figure 4 A schematic diagram of the receiving imaging submodule;

[0046] Figure 5 This is a schematic diagram of the polarization modulation submodule;

[0047] Figure 6 A schematic diagram of the detection output submodule;

[0048] Figure 7 This is a schematic diagram of the 532nm active illumination imaging mode;

[0049] Figure 8 This is a schematic diagram of the 808nm active illumination imaging mode;

[0050] Figure 9 This is a schematic diagram of the polarization passive imaging mode;

[0051] Figure 10 A flowchart illustrating the workflow of key components for visible light imaging;

[0052] Figure 11 This is a schematic diagram of laser illumination imaging.

[0053] Figure 12 Example image of the results from a polarization camera. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of the invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, the invention adopts the following technical solution. This invention provides an integrated active and passive spectral polarization imaging device for extreme lighting environments, comprising four parts: an active and passive coaxial imaging module, a laser active illumination module, an imaging detection module, and a mode control and signal processing module.

[0055] 1. Active and passive coaxial imaging module

[0056] The active-passive coaxial imaging module is the fundamental optical module of the entire device. Its main function is to construct an optical channel with a unified entrance port, a unified principal optical axis, and a shared aperture for transmission and reception, ensuring that the active laser emission path and the target reflection and reception path coincide spatially. Simultaneously, it provides a receiving optical path for passive polarization imaging. This module ensures that the intensity information acquired actively and the polarization information acquired passively remain consistent within the field of view, reducing parallax errors and post-registration errors caused by independent deployment of multiple systems. Positioned in the central optical path of the entire system, between the front and middle sections of the device, the front end connects to the external target scene, while the rear end connects to both the active laser illumination module and the imaging detection module. The active laser illumination module is arranged around the principal optical axis defined by this module, and the imaging detection module is located at its rear imaging output position.

[0057] 2. Laser active illumination module

[0058] The primary function of the laser active illumination module is to provide artificial illumination under low light, nighttime, or complex background conditions to enhance the target echo signal and improve the target imaging signal-to-noise ratio and detectability. This module includes a laser emitting unit, collimating lens, polarizer, and emission shift switching assembly. It can output 532nm and / or 808nm laser light, which, after collimation and polarization modulation, is coaxially emitted along the principal optical axis to the target area. Positioned on one side of the emission optical path of the active-passive coaxial imaging module, it shares the same principal optical axis with the active-passive coaxial imaging module. The emitting end is located in the upper layer of the system's light source emission area. The emitted light is coupled through the active-passive coaxial imaging module and then directed towards the target. The target's reflected echo returns via the same coaxial optical path and enters the subsequent imaging and detection module.

[0059] 3. Imaging Detection Module

[0060] The main function of the imaging detection module is to receive the transmitted target light signal and convert it into image data for output, used to complete data acquisition for active illumination imaging and passive polarization imaging. This module can correspond to detection units such as SCMOS cameras and polarization cameras: in active illumination mode, it receives laser echoes to form intensity images; in passive polarization mode, it receives polarization-modulated target reflected light to form polarization images. Positioned at the end of the entire receiving optical path, after the polarization modulation module, and connected to the rear optical path of the active-passive coaxial imaging module, it represents the final imaging output position of the entire system.

[0061] 4. Mode Control and Signal Processing Module

[0062] The main function of the mode control and signal processing module is to control, switch, and process data for each operating mode of the system. Based on system commands, ambient light intensity, or task requirements, this module uniformly schedules the laser emission state, PBS and mirror positions, polarization modulation state, and imaging detector operating state, enabling switching between 532nm active illumination imaging mode, 808nm active illumination imaging mode, passive polarization imaging mode, and active-passive combined mode. Simultaneously, it uniformly processes, stores, and outputs the intensity and polarization data acquired by the detector to ensure the consistency of multidimensional information in time and space. Positioned in the lower layer of the system or in a non-main optical path area, it is not directly located in the imaging optical path but is electrically connected to the laser active illumination module, polarization modulation module, and imaging detection module to control the coordinated operation of each module.

[0063] The specific structure of the above modules is as follows:

[0064] 1. Active and passive coaxial imaging module

[0065] like Figure 1As shown, the active and passive coaxial imaging module includes a unified light inlet, a visible light quarter-wave plate, a near-infrared quarter-wave plate, a visible light polarization beam splitter (PBS), a near-infrared polarization beam splitter (PBS), and a displacement adjustment component. The unified light inlet serves simultaneously as the receiving port for light from the target scene and the exit port for active illumination light, structurally forming a common-aperture basis for transmission and reception. The quarter-wave plate provides phase delay for both the transmitted and received light paths. The PBS splits or couples light rays with different polarization states, enabling separation and conversion of actively emitted light and received echoes within the same optical path. The displacement adjustment component allows the PBS to enter or exit the main optical path in different operating modes. The unified light inlet is located at the front of the system, with two quarter-wave plates positioned behind it along the unified main optical axis. The PBS is located at the center of the main optical path, and the displacement adjustment component is connected to the PBS to switch its position. The front of this module corresponds to the external target scene, while the rear connects to the laser active illumination module and the imaging detection module, forming the unified optical foundation of the entire system.

[0066] 2. Laser active illumination module

[0067] like Figure 2 As shown, the active laser illumination module includes a 532nm laser emitting unit, an 808nm laser emitting unit, a 532nm laser collimating lens, an 808nm laser collimating lens, a visible-near-infrared polarizer, and an emission shift switching component. The 532nm and 808nm laser emitting units output active illumination lasers of different wavelengths to adapt to different scene conditions and detection requirements. The two collimating lenses collimate the diverging laser beam to meet the requirements of long-distance coaxial emission. The visible-near-infrared polarizer unifies the laser polarization state, providing stable input for subsequent polarization beam splitting and waveplate modulation. The emission shift switching component drives devices in different wavelength laser emission paths to enter or exit the main optical path, thereby achieving switching between the 532nm and 808nm modes. The two laser emitting units are located on the emitting side, the two collimating lenses are positioned in front of their respective laser emitting units, the visible-near-infrared polarizer is located behind the two collimating lenses, and the emission shift switching component is connected to the laser emitting units of different wavelengths and their corresponding collimating lenses. This module is optically connected to the active-passive coaxial imaging module, and its control terminal is electrically connected to the mode control and signal processing module. The output laser is emitted to the target area along the same main optical axis through the active-passive coaxial imaging module.

[0068] 3. Imaging Detection Module

[0069] like Figure 3As shown, the imaging detection module is used to receive, polarize, detect, and calculate parameters of the target's reflected light. It is the core receiving module for both active and passive polarization imaging. This module includes a receiving imaging submodule, a polarization modulation submodule, and a detection output submodule.

[0070] like Figure 4 As shown, the receiving imaging submodule includes an SCMOS imaging lens, a polarization camera imaging lens, a mirror assembly, and an optical path switching assembly. These components are used to transmit and focus the target light signal returned from the active-passive coaxial imaging module along a predetermined path. The front end of the receiving imaging submodule is connected to the active-passive coaxial imaging module, and the rear end is connected to the polarization modulation submodule and the detection output submodule.

[0071] like Figure 5 As shown, the polarization modulation submodule includes a filter assembly, a rotatable quarter-wave plate, a polarizer, a motor drive unit, a mounting base, and a control interface unit. It is used to modulate the polarization state and select the polarization direction of the target reflected light entering the receiving optical path to obtain light intensity information under different polarization directions. The rotatable quarter-wave plate rotates at a preset angle under motor drive, the polarizer filters the polarization components of the modulated light, and the control interface unit receives control commands from the mode control and signal processing module. This submodule is positioned after the receiving imaging submodule and before the detection output submodule, coaxially arranged along the receiving optical axis, ensuring that the target return light undergoes polarization modulation and analysis before entering the detector.

[0072] like Figure 6 As shown, the detection output submodule includes an SCMOS camera, a polarization camera, and a data output interface, used to convert the received target light signal into image data for output. In active illumination imaging mode, the SCMOS camera is used to receive laser echoes to form an intensity image; in passive polarization imaging mode, the polarization camera is used to receive polarization-modulated target reflected light to form a polarization image. The detection output submodule is located at the end of the imaging detection module and is connected to the receiving imaging submodule and the polarization modulation submodule, respectively. Its output is connected to the mode control and signal processing module.

[0073] 4. Mode Control and Signal Processing Module

[0074] The main body of the mode control and signal processing module is an industrial computer, such as... Figure 7As shown, this module is used to control and switch between various operating modes, link components, acquire images, calculate polarization parameters, and store data. It includes a mode control unit, a displacement drive control unit, a laser control unit, a camera control unit, a data acquisition unit, an image processing unit, a polarization parameter calculation unit, a data storage unit, and a power management unit. Specifically, the mode control unit selects between 532nm active illumination imaging mode, 808nm active illumination imaging mode, and passive polarization imaging mode; the displacement drive control unit controls the movement of each displacement component; the laser control unit controls laser emission parameters; the camera control unit controls the operation of the SCMOS camera and polarization camera; the data acquisition and image processing units receive and process images; the polarization parameter calculation unit calculates Stokes parameters, DoLP, and AoP based on data acquired at different polarization angles; the data storage unit stores raw data and processing results; and the power management unit supplies power to all parts of the system. This module is located in the lower-level non-main optical path area of ​​the system and is electrically or data-connected to the active / passive coaxial imaging module, the laser active illumination module, and the imaging detection module.

[0075] The coaxial design of active and passive light sources in this invention forms the fundamental optical structure of the entire imaging system. Its core lies in achieving spatial overlap between the active laser emission path and the target reflection and reception path by unifying the principal optical axis and the transmit / receive optical system, and integrating a polarization analysis structure within the same optical channel. By mechanically adjusting or switching the positions of the polarization beam splitter (PBS), the laser emitting unit, and the reflector, the system can switch between active and passive polarization imaging modes at different wavelengths. Different operating modes only change the light source state and the spatial positions of the optical elements, while the principal optical axis direction and the main lens system remain unchanged, thus ensuring the consistency of the information acquired in each mode in spatial coordinates. Based on the aforementioned coaxial structure, this invention forms three typical operating modes, corresponding to 532nm active illumination imaging, 808nm active illumination imaging, and passive polarization imaging, respectively.

[0076] Operating Mode 1: 532nm Active Illumination Imaging Mode

[0077] Unified light inlet, visible light quarter-wave plate, near-infrared quarter-wave plate, visible light polarization beam splitter PBS and displacement adjustment assembly.

[0078] like Figure 7As shown, in this mode, a 532nm laser is used as the active illumination source. The laser is output from the 532nm laser emitting unit, collimated by a collimating lens, and propagates along the principal optical axis. It then passes through a visible-near-infrared polarizer and enters a visible light polarization beam splitter (operating wavelength range of 420nm~680nm). After being polarized and split by a PBS, the laser's polarization state is adjusted by a visible-near-infrared achromatic quarter-wave plate to achieve coaxial emission with the principal optical axis. The target reflected light returns along the same optical axis, is split again by the visible light polarization beam splitter, and enters the receiving optical path. It is then guided by the first and second reflecting mirrors to the SCMOS camera lens and the SCMOS camera for imaging.

[0079] In this mode, the vertical position of the PBS is adjusted using a displacement stage, and the horizontal movement of the second reflector is also achieved using the displacement stage, thus ensuring that the transmitting and receiving optical axes are strictly coincident in space, realizing a co-aperture and co-axial structure for transmission and reception. Because the active transmission path and the receiving path are coaxially arranged, the intensity information remains consistent in space, providing a unified optical reference for subsequent polarization coordination.

[0080] Operating Mode 2: 808nm Active Illumination Imaging Mode

[0081] like Figure 8 As shown, in this mode, the system switches to 808nm laser active illumination. The horizontal position of the 808nm laser emitting unit is switched via a transmitter displacement switching component, allowing the 808nm beam to enter the main optical axis path. The system is then replaced with a near-infrared polarization beam splitter (620nm~1000nm operating band) to match the polarization beam splitting requirements of the 808nm band. After being output through a collimating lens, the 808nm laser enters the near-infrared polarization beam splitter along the main optical axis, where it is polarized and modulated with a quarter-wave plate to achieve coaxial emission.

[0082] The target echo returns along the original optical axis, is split by a near-infrared polarization beam splitter, and then enters the imaging path through a reflector. Since different wavelengths use corresponding polarization beam splitters (PBS), the system ensures that the optical axes remain aligned after switching between different wavelengths through mechanical adjustments of the first and second optical path switching components, thus maintaining a unified coaxial structure under multi-band active illumination conditions. This design enables coaxial operation of lasers of different wavelengths within the same optical channel, avoiding the field-of-view shift problem caused by the discrete deployment of multi-band systems.

[0083] Operating Mode 3: Passive Polarization Imaging Mode

[0084] like Figure 9As shown, in this mode, the system shuts down the laser emitting unit and uses only ambient light for passive polarization imaging. Target reflected light and ambient light enter the system along the principal optical axis, are processed by an achromatic quarter-wave plate, and then enter the polarization analysis path. The active emission channel is moved off the principal optical axis by adjusting the displacement adjustment component, and the reflector structure is adjusted by the optical path switching component to allow the light path to directly enter the polarization lens and polarization camera.

[0085] A 532nm filter, a quarter-wave plate (driven by a self-rotating motor), and a polarizer are placed in front of the polarization camera to collect light intensity in different polarization directions, thereby obtaining Stokes parameters, degree of linear polarization, and polarization angle information. Since the passive mode still uses the same principal optical axis and principal lens system, the polarization information is consistent with the intensity information obtained in the active mode in spatial coordinates, achieving natural alignment of active and passive information.

[0086] The control flow of the entire system is as follows Figure 10 As shown, the system starts upon order placement. After task analysis, it first determines the working mode and automatically switches to three different imaging paths based on requirements: If the 532nm laser active illumination imaging mode is selected, the system sequentially completes the placement of the 532nm PBS+1 / 4 waveplate, the 532nm laser emitting unit and polarizer, and the reflector, followed by the emission of the 532nm laser and image capture via an SCMOS camera; if the 808nm laser active illumination imaging mode is selected, the system sequentially completes the placement of the 808nm laser PBS+1 / 4 waveplate, the 808nm laser emitting unit and polarizer, and the reflector, followed by the emission of the 808nm laser and image capture via an SCMOS camera; if the polarization camera imaging mode is selected, the PBS+1 / 4 waveplate and reflector are moved out of the main optical path, and the polarization camera directly captures the image, followed by the calculation of Stokes parameters and polarization parameters. The imaging data from all three modes are ultimately stored in a designated location. The process ends after the system returns an imaging completion signal, achieving integrated and automated operation of active illumination imaging and polarization imaging.

[0087] Figure 11 This is an example of using the system for active illumination imaging with a 532nm laser in a dark room environment; Figure 12 Examples of polarization camera imaging results using this system in strong light conditions are shown below. The example images are the I, Q, U, and V components of the Stokes matrix, as well as the circular polarization degree DoCP, linear polarization degree DoLP, polarization degree DoP, and polarization angle AoP.

[0088] The laser active illumination module of this invention adopts a multi-band switchable coaxial output structure. By arranging two sets of polarization beam splitters (PBS) at 532nm and 808nm and their corresponding quarter-wave plates on a unified optical platform, coaxial emission of lasers of different bands on the same principal optical axis is achieved. The module is mounted on an electrically driven displacement stage. The electric displacement mechanism controls the entry and exit of different band PBS components into or out of the principal optical axis position, thereby achieving band switching without changing the direction of the principal optical axis. After being output by the collimating optical system, the lasers of each band are uniformly polarized by a visible and near-infrared polarizer before entering the corresponding band PBS component for polarization beam splitting and polarization state modulation. Under the action of the quarter-wave plate, the polarization optimization of the emitted light and the matching of the echo separation conditions are achieved. Through this combination of multi-band PBS + wave plate and electric displacement switching structure, active illumination light of different bands can work stably in the same optical channel, while ensuring a strict coaxial relationship with the receiving optical path, thus achieving a unified optical axis design for multi-band active illumination at the structural level.

[0089] The imaging detection module of this invention is disposed in the receiving optical path for polarization state modulation and analysis of the reflected light from the target. This module employs an integrated design of optical components and a motor drive structure, with a rotatable quarter-wave plate assembly placed between the lens and the detector. The quarter-wave plate is mounted on a rotatable mounting base, and its angle is precisely controlled by a lower motor drive mechanism, allowing for controllable modulation of the incident light between different polarization states. By changing the rotation angle of the wave plate, the different polarization direction components of the reflected light from the target can be measured, thereby enabling the determination of the Stokes parameters.

[0090] The module employs a coaxial mechanical structure design to ensure that the optical center is aligned with the main optical axis. A motor drive unit is fixed beneath the module, driving the waveplate rotation via a precision coupling structure. An external control interface module is also included to enable programmed control of the polarization modulation angle. This design allows the polarization modulation process to be completed within the same optical channel, avoiding the field-of-view shift issues caused by discrete polarization devices, while improving the repeatability and stability of polarization measurements. Through the combination of a mechanically adjustable waveplate structure and fixed polarization analysis elements, this module can achieve high-precision acquisition of linear polarization degree, polarization angle, and Stokes parameters, providing a polarization characteristic foundation for the fusion of active and passive multi-dimensional information.

[0091] For the polarization parameter inversion section, the present invention uses four polarization angles—0°, 30°, 60°, and -45°—for data acquisition. The data acquired at these four polarization angles are then used to calculate the Stokes parameters I, Q, U, and V of the measured light.

[0092] Incident light [I, Q, U, V] is represented by intensity signals from four directions. T It can be solved as follows:

[0093] ;

[0094] in, , , , With the starting angle data of 0°, 30°, 60°, and -45°, the polarization parameters such as DoLP and AoP of the light can be further solved based on the analytical Stokes parameters.

[0095] ;

[0096] After receiving an order from the system, the mode control and signal processing module first parses the operating mode and parameter setting requirements according to the system instructions. Then, it selects the corresponding mode for imaging based on the order requirements. Finally, it stores the imaging result in the designated location and returns a completion signal.

[0097] When the 532nm laser active illumination imaging mode is selected, the PBS and quarter-wave plate covering the 532nm band at the light inlet are moved into the main optical path. The emitter displacement switching component moves the output fiber head of the 532nm fiber laser into the emitter main optical path, and the optical path switching component moves the reflector into the receiver main optical path. After these preparations are completed, a transmission command is transmitted to the laser, and the 532nm laser emits energy outward. After passing through the PBS and quarter-wave plate, the 532nm laser light exits as circularly polarized light. After reflection from the target, the light radiation energy enters the system's light inlet. After passing through the PBS, only P-rays enter the imaging optical path. The reflector reflects the light returning after being illuminated by the laser into the SCMOS imaging optical path, and then controls the SCMOS camera to image, completing one 532nm laser active illumination imaging task.

[0098] When the 808nm laser active illumination imaging mode is selected, the PBS and quarter-wave plate covering the 808nm band at the light inlet are moved into the main optical path. The emission displacement switching component moves the output fiber head of the 808nm laser emitting unit into the main emission optical path, and the optical path switching component moves the reflector into the main receiving optical path. After these preparations are completed, a transmission command is transmitted to the laser, and the 808nm laser emitting unit emits energy outward. After passing through the PBS and quarter-wave plate, the 808nm laser light exits as circularly polarized light. After reflection from the target, the light radiation energy enters the system's light inlet. After passing through the PBS, only P-rays enter the imaging optical path. The reflector reflects the light returning after being illuminated by the laser into the SCMOS imaging optical path, and then controls the SCMOS camera to image, completing one 808nm laser active illumination imaging task.

[0099] When selecting the polarization camera imaging mode, the PBS and quarter-wave plate are moved out of the main optical path at the light inlet, and the optical path switching component moves the reflector out of the receiving main optical path. After these preparations are completed, the polarization camera is controlled to perform imaging, and Stokes parameters and polarization parameters such as DOLP are calculated for the results of different polarization directions. The calculation results are then stored in a designated location, thus completing one polarization camera imaging task.

[0100] Based on the above-mentioned device, the present invention also provides an active-passive integrated spectral polarization imaging method under extreme lighting conditions, comprising the following steps:

[0101] 1) Based on mission requirements or ambient lighting conditions, the mode control and signal processing module selects the active illumination imaging mode, passive polarization imaging mode, or active-passive combined imaging mode.

[0102] 2) Control the corresponding laser emitting unit, polarization beam splitter, quarter-wave plate, mirror assembly and imaging detection module to enter the set working state and establish the corresponding transmission and reception optical paths;

[0103] 3) The transmission, reception and imaging of radiation information of the target scene are completed by unifying the main optical axis. The target intensity image is acquired in active mode and the image data of different polarization directions is acquired in passive mode.

[0104] 4) The collected data is stored, preprocessed, and polarization parameters are calculated to obtain target intensity information, Stokes parameters, linear polarization degree DoLP, and polarization angle AoP, thereby achieving stable detection and identification of targets under complex lighting conditions.

Claims

1. A combined active and passive spectral polarization imaging device for extreme lighting conditions, characterized in that, include: The active and passive coaxial imaging module includes a unified light inlet, a quarter-wave plate, a polarization beam splitter, and a displacement adjustment component, which are used to establish a coaxial transmission channel in which the active emission optical path and the target reflection and reception optical path are spatially coincident. The laser active illumination module includes a laser emitting unit, a collimating lens, a polarizer, and an emission displacement switching component, used to provide controllable artificial illumination to a target area; The imaging detection module, located at the end of the receiving optical path, includes a receiving imaging submodule, a polarization modulation submodule, and a detection output submodule, which are used to receive the target radiation signal converged by the main optical system and complete image acquisition. The mode control and signal processing module is electrically connected to the active and passive coaxial imaging module, the laser active illumination module and the imaging detection module, respectively, and is used to complete the working mode switching, device collaborative control, image acquisition and polarization parameter calculation. The laser active illumination module and the active-passive coaxial imaging module share the same main optical axis. The laser output by the laser active illumination module is emitted to the target area along the same main optical axis by the active-passive coaxial imaging module. The target reflected echo returns along the same main optical axis and enters the imaging detection module. The unified light inlet of the active and passive coaxial imaging module serves as both the receiving port for light from the target scene entering the system and the exit port for active illumination light, forming a common aperture basis for transmission and reception. The quarter-wave plate includes a visible light quarter-wave plate and a near-infrared quarter-wave plate, which are arranged behind the unified light inlet along the same main optical axis. The polarization beam splitter includes a visible light polarization beam splitter and a near-infrared polarization beam splitter, located at the center of the main optical path. The displacement adjustment component is connected to the polarization beam splitter and is used to drive the polarization beam splitter to enter or move out of the main optical path in different operating modes. The active laser illumination module includes a 532nm laser emitting unit and an 808nm laser emitting unit, as well as corresponding 532nm and 808nm collimating lenses; the polarizer is a visible-near-infrared polarizer, located after the collimating lenses; the emission displacement switching component is connected to laser emitting units and corresponding collimating lenses of different wavelength bands, respectively, and is used to drive devices in different wavelength band laser emission paths to enter or move out of the main optical path, thereby realizing the switching between 532nm mode and 808nm mode; The receiving imaging submodule includes an SCMOS imaging lens, a polarizing camera imaging lens, a mirror assembly, and an optical path switching assembly, which are used to transmit and focus the target reflected echo returned by the active and passive coaxial imaging module along a predetermined path. The polarization modulation submodule includes a filter assembly, a rotatable quarter-wave plate, a polarizer, a motor drive unit, a mounting base, and a control interface unit, and is used to modulate the polarization state and select the polarization direction of the target reflected echo entering the receiving optical path. The detection output submodule includes an SCMOS camera, a polarization camera, and a data output interface. In active illumination imaging mode, the SCMOS camera receives the target reflected echo to form an intensity image, and in passive polarization imaging mode, the polarization camera receives the target reflected echo after polarization modulation to form a polarization image.

2. The active-passive integrated spectral polarization imaging device under extreme lighting conditions according to claim 1, characterized in that, In the polarization modulation submodule, the rotatable quarter-wave plate is mounted on the mounting base, the motor drive unit is fixed below the module and drives the rotatable quarter-wave plate to rotate through a precision coupling structure, and the control interface unit receives control commands from the mode control and signal processing module to realize programmed control of the polarization modulation angle.

3. The active-passive integrated spectral polarization imaging device under extreme lighting conditions according to claim 1, characterized in that, The mode control and signal processing module includes a mode control unit, a displacement drive control unit, a laser control unit, a camera control unit, a data acquisition unit, an image processing unit, a polarization parameter calculation unit, a data storage unit, and a power management unit; wherein, the polarization parameter calculation unit is used to calculate the Stokes parameter, linear polarization degree DoLP, and polarization angle AoP based on the data acquired under different polarization angles.

4. The active-passive integrated spectral polarization imaging device under extreme lighting conditions according to claim 1, characterized in that, The device has three operating modes: 532nm active illumination imaging mode, 808nm active illumination imaging mode, and passive polarization imaging mode. In the 532nm active illumination imaging mode, the visible light polarization beam splitter and the visible light quarter-wave plate enter the main optical path, the 532nm laser emitting unit operates, and the target reflected echo is guided to the SCMOS camera via the mirror assembly. In the 808nm active illumination imaging mode, the near-infrared polarization beam splitter and the near-infrared quarter-wave plate enter the main optical path, the 808nm laser emitting unit operates, and the target reflected echo is guided to the SCMOS camera via the mirror. In the passive polarization imaging mode, the polarization beam splitter and the quarter-wave plate move out of the main optical path, the mirror assembly moves out of the receiving main optical path, and the polarization camera directly acquires the image.

5. The active-passive integrated spectral polarization imaging device under extreme lighting conditions according to claim 4, characterized in that, In the passive polarization imaging mode, a filter, a quarter-wave plate driven by a self-rotating motor, and a polarizer are arranged in front of the polarization camera to collect light intensity in different polarization directions, and then calculate the Stokes parameters, degree of linear polarization, and polarization angle.

6. The active-passive integrated spectral polarization imaging device under extreme lighting conditions according to claim 1, characterized in that, In the active-passive coaxial imaging module, the vertical position adjustment of the polarization beam splitter is controlled by the displacement adjustment component, and the horizontal movement of the reflector component is controlled by the optical path switching component, thereby ensuring that the transmitting optical axis and the receiving optical axis are strictly coincident in space, realizing a coaxial structure with the same aperture for transmitting and receiving.

7. The active-passive integrated spectral polarization imaging device under extreme lighting conditions according to claim 1, characterized in that, The laser active illumination module is mounted on an electric displacement stage. The electric displacement mechanism controls the polarization beam splitter components and corresponding quarter-wave plates of different bands to enter or exit the main optical axis position, so as to achieve band switching without changing the direction of the main optical axis.

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