An underwater polarization ghost imaging method and device based on linear circular polarization composite modulation

Abstract

The application discloses an underwater polarization ghost imaging method and device based on linear and circular polarization composite modulation, relates to the technical field of optical imaging and ocean detection, and collects the multi-polarization state intensity distribution of a reflected laser signal of a target area and a bucket detection light intensity value, calculates a Stokes vector based on the intensity distribution, calculates a polarization ghost image based on the bucket detection light intensity value, calculates a stabilization correction parameter based on the polarization ghost image, calculates linear polarization background scattering parameters and water body transmission functions based on the Stokes vector and the stabilization correction parameter, calculates a linear polarization despeckling recovered image based on the polarization ghost image, the linear polarization background scattering parameters and the water body transmission functions, calculates circular polarization background scattering parameters and circular polarization water body transmission functions based on the linear polarization despeckling recovered image and the stabilization correction parameter, and calculates a circular polarization despeckling recovered image based on the linear polarization despeckling recovered image and the circular polarization water body transmission functions. The imaging quality is significantly improved.

Description

Technical Field

[0001] This invention relates to the fields of optical imaging and marine exploration technology, and in particular to an underwater polarization ghost imaging method and apparatus based on linear and circular polarization composite modulation. Background Technology

[0002] Underwater optical imaging has significant applications in marine resource exploration, underwater archaeology, and target detection. However, the scattering of light by suspended particles and water molecules in water produces strong backscattered light, which is superimposed on the reflected light from the target, resulting in a severe decrease in image contrast and limiting the effective detection range of underwater optical imaging.

[0003] To overcome the aforementioned problems, researchers have proposed various technical solutions, including range-gated imaging, polarization imaging, ghost imaging, and image post-processing enhancement. Among these, polarization imaging technology has attracted considerable attention due to its simple system and strong scattering suppression capabilities. This technology analyzes the changes in polarization characteristics after light wave scattering, acquires images of different polarization states, and uses the polarization difference between the target light and the scattered light to separate them, thereby recovering a clear image. Ghost imaging technology utilizes the correlation characteristics of light field intensity fluctuations, collecting the total light intensity through a bucket detector and correlating it with a reference light field to reconstruct the image, providing a new approach for underwater imaging.

[0004] However, existing underwater polarization imaging techniques have significant shortcomings. On the one hand, in highly turbid waters, intense multiple scattering disrupts the polarization state of light, causing traditional polarization descattering methods to fail and resulting in a sharp decline in image quality. On the other hand, many existing polarization imaging models oversimplify the physical processes, often setting the target's own polarization degree to a constant value or ignoring it entirely, considering only the polarization characteristics of scattered light. This simplification fails to adequately separate target information from background scattering when dealing with complex targets or highly turbid environments, limiting the effectiveness of backscattering suppression and ultimately leading to poor image reconstruction quality.

[0005] Therefore, there is an urgent need to develop an underwater polarization imaging method with better imaging quality and stronger backscattering suppression capability. Summary of the Invention

[0006] This invention provides an underwater polarization ghost imaging method and apparatus based on linear and circular polarization composite modulation to solve the above-mentioned problems existing in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] An underwater polarization ghost imaging method based on linear and circular polarization composite modulation includes:

[0009] S01: Collect the multi-polarization state intensity distribution of the reflected laser signal in the target area and the intensity value of the barrel probe light, and calculate the Stokes vector based on the intensity distribution;

[0010] S02: Calculate the polarization ghost image based on the barrel probe light intensity value, and calculate the stabilization correction parameters based on the polarization ghost image;

[0011] S03: Calculate the linearly polarized background scattering parameters and water transmission function based on Stokes vector and stabilization correction parameters; calculate the linearly polarized descattering restored image based on polarization ghost image, linearly polarized background scattering parameters, and water transmission function.

[0012] S04: Calculate the circularly polarized background scattering parameters and the circularly polarized water body transmission function based on the linearly polarized descattering restored image and the stabilization correction parameters. Calculate the circularly polarized descattering restored image based on the linearly polarized descattering restored image and the circularly polarized water body transmission function.

[0013] Further, step S01 includes:

[0014] S11: Acquire multiple sets of polarization state intensity distributions of the reflected laser signal after being modulated by a combination of a quarter-wave plate and a linear polarizer;

[0015] S12: Based on the intensity distribution of each polarization state, calculate the total intensity component, horizontal-vertical polarization difference component, diagonal polarization difference component, and circular polarization difference component of the Stokes vector;

[0016] S13: Collect the barrel probe light intensity value sequence in the horizontal and vertical polarization directions.

[0017] Further, step S02 includes:

[0018] S21: Perform correlation operations between the bucket probe light intensity value sequence and the spatially modulated speckle intensity distribution sequence to generate horizontally polarized ghost images and vertically polarized ghost images;

[0019] S22: Calculate the mean polarization degree of the target region based on the horizontal and vertical polarization ghost images;

[0020] S23: Calculate the stabilization correction parameters based on the difference between the polarization ghost image and the difference between the background scattered light intensity.

[0021] Furthermore, the formula for calculating the polarization ghost image is:

[0022]

[0023]

[0024] in, A ghost image representing the horizontal polarization direction; A ghost image representing the vertical polarization direction; The intensity value of the barrel probe light, indicating horizontal polarization; The intensity value of the barrel probe light, indicating vertical polarization; Indicates the first Intensity distribution of secondary projection speckle; Indicates the total number of projected speckle patterns; This indicates calculating the system average.

[0025] The formula for calculating the stabilization correction parameter is:

[0026]

[0027] in, These represent the stabilization correction parameters for the reflected signal from the target area. This represents the light intensity of a horizontally polarized scattering medium at infinity. This represents the light intensity of a vertically polarized scattering medium at infinity. As a stabilization parameter, its value can be set according to the average noise level of the system; Represents a symbolic function.

[0028] Furthermore, step S03 includes:

[0029] S31: Calculate the background scattered light intensity and degree of linear polarization based on the linear polarization component of the Stokes vector;

[0030] S32: Calculate the transmission function of linearly polarized water based on the degree of linear polarization and the stabilization correction parameters;

[0031] S33: Calculate the intensity of the reflected laser signal based on the polarization ghost image, linear polarization degree, and mean polarization degree of the target region;

[0032] S34: Calculate the linearly polarized descattering restored image based on the intensity of the reflected laser signal, the intensity of the background scattered light, and the water transmission function.

[0033] Furthermore, the formula for calculating the transmission function of linearly polarized water is:

[0034]

[0035] in, This represents the error correction coefficient, used to improve the background noise caused by the absence of a target area. Slight changes in selection led to The effectiveness of error estimation for value changes; The degree of linear polarization of the background scattered light, representing the linearly polarized portion of the light; and These represent the horizontal and vertical polarization difference components and the diagonal polarization difference components, respectively. Indicates adjustment coefficient Used for adjustment Transmission function of water body The impact;

[0036] The formula for calculating the linearly polarized descattered image is:

[0037]

[0038]

[0039] in, This is represented as the descattered image of the target region under test, recovered from the linear polarization portion.

[0040] Furthermore, step S04 includes:

[0041] S41: Calculate the intensity value and degree of circular polarization of the background scattered light based on the circular polarization difference component of the linearly polarized descattered image and the Stokes vector;

[0042] S42: Calculate the transmission function of circularly polarized water based on the degree of circular polarization and the stabilization correction parameters;

[0043] S43: Calculate the circularly polarized descattering restored image based on the linearly polarized descattering restored image, the intensity of the circularly polarized background scattered light, and the circularly polarized water body transmission function.

[0044] Furthermore, the formula for calculating the transmission function of circularly polarized water is:

[0045]

[0046] in, Indicates adjustment coefficient Used for adjustment Transmission function of water body The impact, Represents the circular polarization difference component; Indicates something slightly larger than The parameters are used to improve the performance due to the lack of background in the target area. Slight changes in selection led to The effectiveness of error estimation for value changes; The degree of polarization of the scattered light in the background region representing the circularly polarized light portion; This represents the intensity of backscattered light at infinity in the circularly polarized portion of the light.

[0047] The formula for calculating the circularly polarized descattered image is:

[0048]

[0049]

[0050] in, This represents the descattered, restored image of an underwater target.

[0051] Furthermore, an apparatus for underwater polarization ghost imaging based on linear and circular polarization composite modulation includes:

[0052] Laser source used to generate linearly polarized laser light;

[0053] The polarization conversion module includes a quarter-wave plate whose fast axis is at a predetermined angle to the polarization direction of the incident laser, used to convert linearly polarized laser into circularly polarized light;

[0054] Spatial light modulator, employing digital micromirror devices, is used to spatially speckle modulate circularly polarized light and project it onto a target area;

[0055] The ghost imaging receiving unit includes a polarization beam splitter, a first barrel detector, and a second barrel detector. The polarization beam splitter decomposes the laser signal sampled by the upstream beam splitter into two orthogonal linearly polarized beams, and the first barrel detector and the second barrel detector respectively receive the light intensity values ​​of the horizontal polarization component and the vertical polarization component.

[0056] The polarization image receiving unit includes an adjustable quarter-wave plate with a fast axis direction, a rotatable linear polarizer, and a camera, which acquires intensity distribution images of multiple polarization directions through combined adjustment;

[0057] The data processing unit includes a modulation control module for generating random speckle patterns and driving a spatial light modulator, and a polarization information analysis module for calculating Stokes parameters.

[0058] Compared with the prior art, the present invention has the following advantages:

[0059] This application discloses an underwater polarization ghost imaging method and device based on linear and circular polarization composite modulation. By combining linear and circular polarization light composite modulation with a ghost imaging algorithm, a target descattering restoration image is finally generated, which can significantly suppress backscattered light and improve image contrast and clarity. By introducing stabilization correction parameters, the true polarization characteristics of the target can be restored and numerical stability can be improved while accurately eliminating the influence of scattered light, thus significantly improving the imaging quality.

[0060] This application's device achieves integrated synchronous acquisition of polarization images and polarization ghost images through a linear-circular polarization composite modulation and dual-channel parallel reception design. This device not only avoids timing errors in time-division systems, improving data accuracy and acquisition efficiency, but also enhances system stability and reliability through an integrated architecture, ultimately achieving a comprehensive improvement in imaging quality and information dimensions.

[0061] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention.

[0062] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0063] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0064] Figure 1 This is a schematic diagram of the underwater polarization ghost imaging method based on linear and circular polarization composite modulation in an embodiment of the present invention.

[0065] Figure 2 This is a schematic diagram of the underwater polarization ghost imaging device based on linear and circular polarization composite modulation in an embodiment of the present invention.

[0066] The components include: optical emission and guidance unit 1, laser 6, collimating lens 7, quarter-wave plate 8, digital micromirror device (DMD) 9; signal receiving unit 2, polarization image receiving unit 5, beam splitter 10, quarter-wave plate (QWP) 11, linear polarizer 12, monochrome CCD camera 13, ghost imaging receiving unit 4, polarization beam splitter 14, first barrel detector 15, second barrel detector 16, signal processing unit 3, oscilloscope 17, data acquisition card 18, and data processing unit 19. Detailed Implementation

[0067] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0068] This invention provides an underwater polarization ghost imaging method based on linear and circular polarization composite modulation, comprising:

[0069] S01: Collect multiple sets of polarization state intensity distributions and barrel probe light intensity values ​​of the reflected laser signal in the target area, and calculate the Stokes vector based on the intensity distribution;

[0070] S02: Calculate the polarization ghost image based on the barrel probe light intensity value, and calculate the stabilization correction parameters based on the polarization ghost image;

[0071] S03: Calculate the linearly polarized background scattering parameters and water transmission function based on Stokes vector and stabilization correction parameters; calculate the linearly polarized descattering restored image based on polarization ghost image, linearly polarized background scattering parameters, and water transmission function.

[0072] S04: Calculate the circularly polarized background scattering parameters and the circularly polarized water body transmission function based on the linearly polarized descattering restored image and the stabilization correction parameters. Calculate the circularly polarized descattering restored image based on the linearly polarized descattering restored image and the circularly polarized water body transmission function.

[0073] The following is a detailed description with reference to specific embodiments.

[0074] Example 1:

[0075] This embodiment provides an underwater polarization ghost imaging method based on linear and circular polarization composite modulation, such as... Figure 1 As shown:

[0076] S1: Based on the Stokes vector of the reflected laser signal in the target detection area, calculate the background scattered light intensity value at infinity of the linearly polarized light part, the degree of linear polarization of the background scattered light, and the background scattered light intensity of the linearly polarized part.

[0077] S2: Calculate the horizontal and vertical polarization ghost images based on the barrel probe intensity values ​​in the horizontal polarization direction and the probe intensity values ​​in the vertical polarization direction of the reflected laser signal.

[0078] S3: Based on the horizontally polarized ghost image and the vertically polarized ghost image, calculate the mean polarization degree of the target region;

[0079] S4: Based on horizontally polarized ghost imaging, vertically polarized ghost image, mean polarization degree of the target region, linear polarization degree of the background scattered light of linearly polarized light, calculate the light intensity value of the laser signal reflected from the target region.

[0080] S5: Based on the horizontally polarized ghost image and the vertically polarized ghost image, adjust the coefficients and calculate the stabilization correction parameters of the reflected signal in the target area.

[0081] S6: Based on the stabilization correction parameters of the reflected signal in the target area, the intensity value of the background scattered light at infinity, and the degree of polarization of the background scattered light of the linearly polarized light, determine the expression of the water body transmission function.

[0082] S7: Based on the light intensity value of the laser signal reflected from the target area, the background scattered light intensity of the linearly polarized part, and the water body transmission function, determine the descattering restoration image of the target area to be tested recovered by the linearly polarized light part.

[0083] S8: Descattering restoration image of the target area based on linear polarization, Stokes vector of circular polarization, calculation of backscattered light intensity at infinity of circular polarized light, degree of polarization of background scattered light, and light intensity of background scattered area of ​​circular polarized light.

[0084] S9: Based on the light intensity distribution of the background scattering region of circularly polarized light, the backscattered light intensity value at infinity of the circularly polarized part, the stabilization correction parameters of the reflection signal of the target area, and the expression for calculating the water body transmission function.

[0085] S10: Based on the descattering restoration image of the target area to be tested recovered from the linearly polarized part, the light intensity distribution of the background scattering region of the circularly polarized light part, and the water transmission function, determine the restored image of the circularly polarized part, and use the restored image of the circularly polarized part as the restored image of the underwater detection target.

[0086] Specifically, the following steps are included:

[0087] Step S1: 1) Emit a circularly polarized beam modulated by DMD towards the target area, rotate and adjust the quarter-wave plate and linear polarizer, collect multiple sets of polarization state intensities and barrel detection intensities of the reflected laser signal, and calculate the Stokes vector of the reflected laser signal. , , , The intensity of the collected laser signal is as follows:

[0088]

[0089] in, An image showing the intensity distribution of light along the horizontal polarization direction; An image showing the intensity distribution of light along the vertical polarization direction; Indicates direct and reflected laser signals Related light intensity distribution images; Indicates the use of measurement and Image of the intensity distribution of the direction-dependent linearly polarized components.

[0090] 2) For the linearly polarized light portion, calculate the intensity of the background scattered light at infinity. linear polarization degree of background scattered light The calculation formula is as follows:

[0091]

[0092]

[0093] in, This represents the number of pixels in the background scattered light region where there is no target area. This represents the intensity difference between the horizontal and vertical polarization directions. express polarization components and The intensity difference of the polarization components; The total intensity distribution represents the Stokes vector of the reflected light.

[0094] 3) Based on the calculated Stokes vector of the reflected laser signal and the degree of linear polarization of the background scattered light in the linearly polarized light, the formula for the intensity of the background scattered light in the linearly polarized part can be obtained as follows:

[0095]

[0096] in, Indicates something slightly larger than The parameters are used to improve the performance due to the lack of background in the target area. Slight changes in selection led to The effect of error estimation on value changes.

[0097] Step S2: Calculate the horizontal and vertical polarization ghost images based on the barrel probe intensity values ​​in the horizontal and vertical polarization directions of the reflected laser signal, respectively. The calculation formula is as follows:

[0098]

[0099]

[0100] in, A ghost image representing the horizontal polarization direction; A ghost image representing the vertical polarization direction; The intensity value of the barrel probe light, indicating horizontal polarization; The intensity value of the barrel probe light, indicating vertical polarization; Indicates the first Intensity distribution of secondary projection speckle; Indicates the total number of projected speckle patterns; This indicates the calculation of the system average.

[0101] Step S3: Given that the outlines of the target region and the background region can be distinguished, select the target region within the field of view and calculate the average value of the target region. The calculated average value is considered the degree of polarization of the target region under circularly polarized light source illumination. Specifically, take any pixel of the horizontally polarized ghost image of the target region as the current pixel. For the current pixel, select the corresponding pixel of the vertically polarized ghost image of the target region and perform point-to-point pixel calculations to obtain the average degree of polarization of the target region, as detailed below.

[0102] Based on the horizontally polarized ghost image and the vertically polarized ghost image, the mean polarization degree of the target region can be calculated by the following formula:

[0103]

[0104] in, This indicates the number of pixels in the target area being detected.

[0105] Step S4: Based on the horizontally polarized ghost image, the vertically polarized ghost image, the mean polarization degree of the target area, and the linear polarization degree of the background scattered light, calculate the light intensity value of the reflected laser signal in the target area.

[0106]

[0107] in, This represents the intensity value of the reflected laser signal from the target area. A ghost image representing horizontal polarization; A polarization ghost image representing vertical polarization; This indicates the degree of linear polarization of the background scattered light in linearly polarized light. The polarization degree represents the mean value of the target region.

[0108] Step S5: Traditional underwater polarization imaging techniques often treat the target polarization degree as a constant or even ignore it. However, in some cases, the polarization degree of the reflected laser signal can significantly affect the estimated target image, severely impacting imaging quality. Therefore, a stabilization correction parameter is introduced into the difference term of the transmission function to adjust the effect of target polarization on the intrinsic background scattered light polarization and improve numerical stability, thereby enhancing image quality.

[0109] Optionally, the formula for calculating the stabilization correction parameter of the reflected signal in the target area is:

[0110]

[0111] in, These represent the stabilization correction parameters for the reflected signal from the target area. It is a small positive number, used as a stabilization parameter, and its value can be set according to the average noise level of the system; Represents a symbolic function; This represents the light intensity of a horizontally polarized scattering medium at infinity. This represents the light intensity of a vertically polarized scattering medium at infinity.

[0112] Step S6: Based on the stabilization correction parameters of the reflected signal from the target region, the intensity value of the background scattered light at infinity of the linearly polarized light portion, and the degree of polarization of the background scattered light, determine the expression for the water body transmission function:

[0113]

[0114] in, Indicates adjustment coefficient It can be used to adjust Transmission function of water body The impact.

[0115] Step S7: Based on the light intensity value of the laser signal reflected from the target area, the background scattered light intensity of the linearly polarized part, and the water transmission function of the linearly polarized light part, determine the descattering restoration image of the target area to be tested recovered by the linearly polarized light part.

[0116]

[0117]

[0118] in, Descattered reconstruction image of the linearly polarized light component in the reflected laser signal from the target region. Transmission function of water body The intensity of light reaching the detector after scattering and absorption; This is represented as the descattered restored image of the target region under test, which is partially recovered from linear polarization.

[0119] Step S8: Based on the descattering restoration image of the target area to be tested recovered from the linearly polarized part, determine the background scattered light intensity of the circularly polarized part and the backscattered light intensity at infinity, as well as the light intensity value of the background scattered area of ​​the circularly polarized light part.

[0120] Specifically, 1) the descattered image of the target region to be measured, recovered from the linearly polarized portion, is used as the basis for image recovery of the circularly polarized portion. That is, based on the descattered image of the target region to be measured recovered from the linearly polarized portion, the backscattered light intensity value at infinity of the circularly polarized light portion is determined. polarization degree of scattered light from the background region .

[0121]

[0122]

[0123] in, The number of pixels representing the background scattered light region without a target area; The Stokes vector, representing the circularly polarized portion, can be considered as the difference between the left and right circular polarizations.

[0124] 2) Based on the degree of polarization of the scattered light in the background region of the circularly polarized part and the Stokes vector of the circularly polarized part, the light intensity distribution of the background scattering region of the circularly polarized light part is obtained.

[0125]

[0126] in, Indicates something slightly larger than The parameters are used to improve the performance due to the lack of background in the target area. Slight changes in selection The effect of error estimation on value changes.

[0127] Step S9: Based on the light intensity distribution of the background scattering region of circularly polarized light, the backscattered light intensity value at infinity of the circularly polarized part, and the stabilization correction parameters of the reflection signal of the target area, the expression of the water body transmission function is obtained.

[0128]

[0129] in, These represent the stabilization correction parameters for the reflected signal from the target area. Indicates adjustment coefficient It can be used to adjust Transmission function of water body The impact; The Stokes vector, represented as the circularly polarized portion, can be seen as the difference between the left and right circular polarizations. Indicates something slightly larger than The parameters are used to improve the performance due to the lack of background in the target area. Slight changes in selection led to The effectiveness of error estimation for value changes; It is expressed as the intensity of backscattered light at infinity in the circularly polarized region.

[0130] Step S10: Based on the descattering restored image of the target area to be tested recovered from the linearly polarized part, the light intensity distribution of the background scattering area of ​​the circularly polarized light part, and the water transmission function, determine the restored image of the circularly polarized part, and use the restored image of the circularly polarized part as the restored image of the underwater detection target imaging.

[0131] Specifically, based on the combination of the computational ghost imaging model and the traditional underwater polarization imaging model, the parameters of the linearly polarized light component obtained from the combination of the computational ghost imaging model and the traditional underwater polarization imaging model are introduced into the traditional underwater polarization imaging model. Combined with the parameters of the circularly polarized component, a restored image of the underwater detection target is achieved, as shown in the following formula. and Based on the traditional underwater polarization imaging model, this is a descattered reconstruction image of the circularly polarized light portion of the laser signal actually reflected by the target object. Transmission function of water body The intensity of the light reaching the detector after scattering and absorption is , The background light intensity at infinity underwater for the circularly polarized light portion and water body transmission function The function; the image restored by descattering the linearly polarized light portion. As the radiance for image recovery under circularly polarized light, and combined with the water body transmission function The parameters of the circular polarization component ultimately enable the reconstruction of the underwater target image.

[0132]

[0133]

[0134] in, This represents the descattered, restored image of an underwater target.

[0135] This embodiment utilizes a combination of linearly and circularly polarized light modulation, along with a polarization ghost imaging algorithm, and optimizes the transmission function by introducing stabilization correction parameters, effectively suppressing underwater backscattered light. This method can effectively preserve and restore the true polarization characteristics of the target while removing scattered light interference. Compared to traditional polarization imaging methods, it significantly improves imaging contrast and clarity.

[0136] Example 2:

[0137] This embodiment provides an apparatus for use with the underwater polarization ghost imaging method based on linear circular polarization composite modulation described in Embodiment 1, such as... Figure 2 As shown, the device includes an optical transmitting and guiding unit 1, a signal receiving unit 2, and a signal processing unit 3.

[0138] The optical emission and guidance unit 1 includes: a laser 6, a collimating lens 7, a quarter-wave plate 8, and a digital micromirror device (DMD) 9.

[0139] Specifically, the linearly polarized laser emitted by laser 6 is collimated into a parallel beam by collimating lens 7, then becomes a circularly polarized beam by quarter-wave plate 8, and finally illuminates the target detection area after passing through the DMD modulator. Laser 6 is a 532nm laser, emitting continuous laser light with a wavelength of 532nm, providing a high-quality light source for effectively penetrating water over a certain distance and illuminating the target detection area, thus providing the entire system with an initial light field of known polarization state and stable intensity. Collimating lens 7 is used to collimate the laser beam emitted from laser 6, keeping the laser beam parallel and ensuring high spatial consistency during underwater transmission and modulation; this lays the necessary foundation for the DMD to achieve uniform, high-contrast speckle modulation. The fast axis direction of quarter-wave plate 8 is perpendicular to the polarization direction of the linearly polarized beam emitted by laser 6. The DMD modulator receives a sequence of random binary speckle patterns generated in real time from the back-end data processing unit 19, and modulates the incident circularly polarized light field with binary amplitude through the micromirror unit. The coded illumination method of the DMD modulator ultimately completes the dynamic and precise scanning of the target detection area.

[0140] The signal receiving unit 2 is divided into a ghost imaging receiving unit 4 and a polarization image receiving unit 5.

[0141] The ghost imaging receiver 4 is used to receive two beams with mutually perpendicular polarization directions to acquire polarization ghost imaging data of the underwater target detection area. The first barrel detector 15 or the second barrel detector 16 converts the received optical signal into an electrical signal for subsequent analysis and processing.

[0142] The polarization image receiving unit 5 is used to receive polarization images with four different polarization directions, and to obtain key parameters of the linearly polarized and circularly polarized light components in the reflected laser signal from the underwater target detection area. The monochrome CCD camera 13 converts the received optical signal into an electrical signal for subsequent analysis and processing.

[0143] Signal receiving unit 2, serving as the information sensing front-end of this device, adopts a beam-splitting parallel acquisition architecture and integrates ghost imaging receiving unit 4 and polarization image receiving unit 5. This design enables the simultaneous acquisition of optical information in different dimensions of the target echo signal, providing raw data for subsequent calculations of ghost imaging reconstruction and full polarization state analysis.

[0144] In this embodiment, such as Figure 2 As shown, the ghost imaging receiving unit 4 in the signal receiving unit 2 includes a first barrel detector 15, a second barrel detector 16, and a polarization beam splitter 14 (PBS14).

[0145] The ghost imaging receiving unit 4 is responsible for acquiring the polarization-resolved light intensity signal used to calculate ghost imaging. This unit consists of a polarization beam splitter 14 (PBS14) and two matched barrel detectors (first barrel detector 15 and second barrel detector 16). The specific process is as follows: The laser signal reflected from the target detection area is sampled by the upstream beam splitter and guided to the optical path of this unit. This beam is transmitted to the polarization beam splitter 14 (PBS), which, based on its inherent polarization selectivity, decomposes the incident light into two linearly polarized beams with mutually orthogonal vibration directions, and guides them to two independent exits. The horizontal polarization component (the 0° channel of the PBS) is received by the first barrel detector 15, while the vertical polarization component (the 90° channel of the PBS) is received by the second barrel detector 16. The two detectors simultaneously measure the total light intensity in their respective channels, denoted as _____. and This configuration enables simultaneous and independent measurement of the intensities of the two orthogonal polarization components in the target scattered light, providing crucial input for subsequent ghost imaging algorithms based on polarization differences.

[0146] In one implementation, such as Figure 2 As shown, the polarization image receiving unit 5 in the signal receiving unit 2 includes a quarter-wave plate (QWP11), a linear polarizer (12), and a monochrome CCD camera (13).

[0147] The polarization image receiving unit 5 is responsible for acquiring the spatial polarization distribution information of the target. This unit consists of a quarter-wave plate (QWP) 11, a rotatable linear polarizer 12, and a high-resolution monochrome CCD camera 13 arranged sequentially. This optical path receives another signal from the upstream beam splitter 10, performing sequential modulation and spatially resolved detection of the beam's polarization state. The beam first passes through the QWP, whose fast axis direction can be precisely adjusted according to measurement requirements (typically set to 0° or 45°) to change the circular polarization component of the beam. Subsequently, the beam passes through a linear polarizer 12 whose polarization direction can be precisely controlled; this component is used to selectively transmit linearly polarized light in a specific direction. Finally, the modulated light intensity distribution is recorded by the monochrome CCD camera 13, generating a two-dimensional intensity image. By systematically combining and adjusting the fast axis direction of the QWP and the transmission axis angle of the linear polarizer 12, this unit can acquire a set of intensity images for four key polarization states, specifically including:

[0148] When the fast axis of the QWP is 0° and the transmission axis of the linear polarizer is 0°, the image is acquired. ;

[0149] When the fast axis of the QWP is 0° and the transmission axis of the linear polarizer is 90°, the image is acquired. ;

[0150] When the fast axis of the QWP is 45° and the transmission axis of the linear polarizer is 45°, the image is acquired. ;

[0151] When the fast axis of the QWP is 0° and the transmission axis of the linear polarizer is 45°, the image is acquired. .

[0152] The series of images constitutes a complete measurement set. By performing mathematical processing on them based on Stokes vectors, key parameters such as the degree of linear polarization and circular polarization at each point in the target's reflected light field can be accurately calculated, thereby achieving in-depth perception of the target's material, surface characteristics, and other physical properties.

[0153] like Figure 2 As shown, the signal processing unit 3 includes an oscilloscope 17, a data acquisition card 18, and a data processing unit 19.

[0154] Specifically:

[0155] Oscilloscope 17 is connected to the first barrel detector 15 and the second barrel detector 16 in the ghost imaging receiver unit 4. Its function is to perform high-fidelity real-time monitoring of the light intensity signals output from the two barrel detectors, accurately capturing the waveform characteristics, transient fluctuations, and background noise characteristics of the signals, providing intuitive evidence for system status diagnosis and data quality assessment. An oscilloscope with a sampling rate of 2GS / s and a bandwidth of 150MHz can be selected, ensuring its distortion-free capture capability for high-frequency and rapidly changing signals.

[0156] Data acquisition card 18 synchronously receives and acquires electrical signals from the two barrel detectors, converting the analog signals into a high-precision digital data stream for temporary storage. Data acquisition card 18 ensures a strict synchronous correspondence between the ghost imaging light intensity signal and the DMD modulated speckle field. All acquired data is ultimately packaged and transmitted to the back-end data processing unit 19, laying the data foundation for subsequent related calculations and image reconstruction.

[0157] Data processing unit 19 is the control and calculation center of the entire system, containing three core functions, specifically including:

[0158] 1) Modulation control: This unit is responsible for generating a series of random speckle patterns that meet specific statistical characteristics and driving the digital micromirror device DMD9 to perform dynamic spatial light modulation, thereby achieving coded illumination of the target area.

[0159] 2) Polarization Information Analysis: It simultaneously receives four sets of intensity images with different polarization configurations uploaded from the monochrome CCD camera 13 in the polarization image receiving unit 5. By processing these images, the unit can accurately calculate the linear polarization Stokes parameters and circular polarization components contained in the target reflected light.

[0160] 3) Information Fusion and Reconstruction: Finally, the data processing unit 19 correlates and fuses the barrel detector signal from the ghost imaging channel with the polarization parameters from the polarization imaging channel. By executing an advanced polarization ghost imaging reconstruction algorithm, it can effectively suppress underwater scattering interference, reconstruct a high-quality spatial structure image of the target object, and simultaneously acquire its complete polarization attribute information, thereby achieving a comprehensive improvement in detection performance.

[0161] (1) This application overcomes the limitations of traditional underwater polarization imaging models in dealing with the effects of scattered light in complex underwater environments by introducing a polarization ghost imaging model on the basis of the traditional underwater polarization imaging model based on linear and circular polarization composite modulation. Polarization ghost imaging utilizes the horizontal and vertical polarization information of the reflected laser signal, combined with the key parameters of the linearly polarized and circularly polarized light parts in the reflected laser signal, to significantly suppress underwater backscattering and improve the contrast and clarity of the image.

[0162] (2) This application introduces stabilization correction parameters This innovative method, by accurately eliminating backscattered light, can restore the true polarization characteristics of the target and improve numerical stability, thereby enhancing the overall performance of the device and improving the overall imaging quality. For complex underwater scenarios, this innovative method effectively overcomes the bottleneck of low backscattered light processing efficiency in traditional models. It can significantly improve numerical stability by more accurately correcting the polarization information of reflected laser light, thus recovering the target signal with high quality and significantly improving underwater imaging results.

[0163] (3) This application stabilizes the correction parameters This paper introduces a traditional polarization imaging model and adjusts the normalized target polarization intensity difference to improve the water transmission function. Combined with a variable adjustment coefficient, this method can flexibly adapt to different imaging conditions in complex underwater scenes, thus significantly improving the descattering effect. The proposed underwater polarization ghost imaging model based on linear and circular polarization composite modulation achieves a significant improvement in signal-to-noise ratio compared to traditional polarization imaging methods.

[0164] (4) The device of this application, through the design of linear circular polarization composite modulation and dual-path parallel reception, inherits the inherent anti-scattering advantage of ghost imaging while simultaneously acquiring the complete polarization information of the target, realizing the integrated synchronous acquisition of polarization image and polarization ghost image. This device not only fundamentally eliminates the timing error of the time-division system and significantly improves the data accuracy and acquisition efficiency, but also reduces moving parts and potential failure points through the integrated design of the system architecture, thereby comprehensively enhancing the stability, reliability and overall robustness of the device on the basis of improving imaging quality and information dimension.

[0165] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from the spirit and scope of this invention.

Claims

1. An underwater polarization ghost imaging method based on linear and circular polarization composite modulation, characterized in that, include: S01: Collect the multi-polarization state intensity distribution of the reflected laser signal in the target area and the intensity value of the barrel probe light, and calculate the Stokes vector based on the intensity distribution; S02: Calculate the polarization ghost image based on the barrel probe light intensity value, and calculate the stabilization correction parameters based on the polarization ghost image; S03: Calculate the linearly polarized background scattering parameters and water transmission function based on Stokes vector and stabilization correction parameters; calculate the linearly polarized descattering restored image based on polarization ghost image, linearly polarized background scattering parameters, and water transmission function. S04: Calculate the circularly polarized background scattered light intensity and circularly polarized water body transmission function based on the linearly polarized descattered image and stabilization correction parameters. Calculate the circularly polarized descattered image based on the linearly polarized descattered image, the circularly polarized background scattered light intensity, and the circularly polarized water body transmission function.

2. The underwater polarization ghost imaging method based on linear and circular polarization composite modulation according to claim 1, characterized in that, Step S01 includes: S11: Acquire multiple sets of polarization state intensity distributions of the reflected laser signal after being modulated by a combination of a quarter-wave plate and a linear polarizer; S12: Based on the intensity distribution of each polarization state, calculate the total intensity component, horizontal-vertical polarization difference component, diagonal polarization difference component, and circular polarization difference component of the Stokes vector; S13: Collect the barrel probe light intensity value sequence in the horizontal and vertical polarization directions.

3. The underwater polarization ghost imaging method based on linear and circular polarization composite modulation according to claim 1, characterized in that, Step S02 includes: S21: Perform correlation operations between the bucket probe light intensity value sequence and the spatially modulated speckle intensity distribution sequence to generate horizontally polarized ghost images and vertically polarized ghost images; S22: Calculate the mean polarization degree of the target region based on the horizontal and vertical polarization ghost images; S23: Calculate the stabilization correction parameters based on the polarization ghost image difference and the background scattered light intensity difference; specifically: The formula for calculating the polarization ghost image is: ； ； in, A ghost image representing the horizontal polarization direction; A ghost image representing the vertical polarization direction; The intensity value of the barrel probe light, indicating horizontal polarization; The intensity value of the barrel probe light, indicating vertical polarization; Indicates the first Intensity distribution of secondary projection speckle; Indicates the total number of projected speckle patterns; This indicates calculating the system average. The formula for calculating the stabilization correction parameter is: ； in, These represent the stabilization correction parameters for the reflected signal from the target area. This represents the light intensity of a horizontally polarized scattering medium at infinity. This represents the light intensity of a vertically polarized scattering medium at infinity. As a stabilization parameter, its value can be set according to the average noise level of the system; Represents a symbolic function.

4. The underwater polarization ghost imaging method based on linear and circular polarization composite modulation according to claim 3, characterized in that, Step S03 includes: S31: Calculate the background scattered light intensity and degree of linear polarization based on the linear polarization component of the Stokes vector; S32: Calculate the transmission function of linearly polarized water based on the degree of linear polarization and the stabilization correction parameters; S33: Calculate the intensity of the reflected laser signal based on the polarization ghost image, linear polarization degree, and mean polarization degree of the target region; S34: Calculate the linearly polarized descattering restored image based on the intensity of the reflected laser signal, the intensity of the background scattered light, and the water transmission function.

5. The underwater polarization ghost imaging method based on linear and circular polarization composite modulation according to claim 4, characterized in that, The formula for calculating the transmission function of linearly polarized water is: ； in, The degree of linear polarization of the background scattered light, representing the linearly polarized portion of the light; and These represent the horizontal and vertical polarization difference components and the diagonal polarization difference components, respectively. This represents the error correction coefficient, used to improve the background noise caused by the absence of a target area. Slight changes in selection led to The effectiveness of error estimation for value changes; Indicates the adjustment factor: Used for adjustment Transmission function of water body The impact; The formula for calculating the linearly polarized descattered image is: ； ;in, This is represented as the descattered restored image of the target region under test, which is partially recovered from linear polarization.

6. The underwater polarization ghost imaging method based on linear and circular polarization composite modulation according to claim 1, characterized in that, Step S04 includes: S41: Calculate the intensity and degree of circular polarization of the background scattered light based on the circular polarization difference component of the linearly polarized descattered image and the Stokes vector; S42: Calculate the transmission function of circularly polarized water based on the degree of circular polarization and the stabilization correction parameters; S43: Calculate the circularly polarized descattering restored image based on the linearly polarized descattering restored image, the intensity of the circularly polarized background scattered light, and the circularly polarized water body transmission function.

7. The underwater polarization ghost imaging method based on linear and circular polarization composite modulation according to claim 6, characterized in that, The formula for calculating the transmission function of circularly polarized water is: ； in, Indicates the adjustment factor: Used for adjustment Transmission function of water body The impact; Represents the circular polarization difference component; Indicates something slightly larger than The parameters are used to improve the performance due to the lack of background in the target area. Slight changes in selection led to The effectiveness of error estimation for value changes; The degree of polarization of the scattered light in the background region representing the circularly polarized light portion. ; This represents the intensity of backscattered light at infinity in the circularly polarized portion of the light. The formula for calculating the circularly polarized descattered image is: ； ； in, The image represents the descattered, restored image of an underwater target; water transmission function. .

8. An apparatus for use in the underwater polarization ghost imaging method based on linear-circular polarization composite modulation according to any one of claims 1 to 7, characterized in that, include: Laser source used to generate linearly polarized laser light; The polarization conversion module includes a quarter-wave plate whose fast axis is at a predetermined angle to the polarization direction of the incident laser, used to convert linearly polarized laser into circularly polarized light; Spatial light modulator, employing digital micromirror devices, is used to spatially speckle modulate circularly polarized light and project it onto a target area; The ghost imaging receiving unit includes a polarization beam splitter, a first barrel detector, and a second barrel detector. The polarization beam splitter decomposes the reflected laser signal upstream of the beam splitter into two orthogonal linearly polarized beams, and the first barrel detector and the second barrel detector respectively receive the light intensity values ​​of the horizontal polarization component and the vertical polarization component. The polarization image receiving unit includes an adjustable quarter-wave plate with a fast axis direction, a rotatable linear polarizer, and a camera, which acquires intensity distribution images of multiple polarization directions through combined adjustment; The data processing unit includes a modulation control module for generating random speckle patterns and driving a spatial light modulator, and a polarization information analysis module for calculating Stokes parameters.

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