A method for imaging a moving target based on an optical waveguide phased array

Abstract

The application discloses a kind of motion target scattering imaging methods based on optical waveguide phased array, comprising: when there is no scattering medium, the output light beam of optical waveguide phased array is calibrated, so that it generates the scanning light beam of different scanning angles under preset spatial resolution, then join scattering medium and record corresponding light field distribution, then when there is scattering medium, the calibration of flat-top light beam of optical waveguide phased array is carried out, so that it generates the flat-top light beam of different scanning angles in each spatial resolution in different spatial resolution;Then, the scanning light beam of preset spatial resolution is output by optical waveguide phased array to cover imaging field of view, when target moves in field of view, whether target is detected by comparing the consistency of the light field distribution of echo signal of each scanning light beam and the light field distribution recorded previously is judged, and the motion information and profile of target are determined, and spatial field of view is divided according to profile;According to the division result and motion information, the flat-top light beam of specific resolution under specific scanning angle is output, and imaging is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical imaging, and particularly relates to a moving target scattering imaging method based on a light waveguide phased array. BACKGROUND

[0002] Scattering is a common optical phenomenon in nature, and the research on imaging a target through a scattering medium has important significance and application value in production and life. Researchers at home and abroad have carried out in-depth research and proposed a variety of solutions. Related technologies play an important role in the fields of medicine, autonomous driving, national security, etc. With the development of research, the current scattering imaging methods mainly include the following:

[0003] 1) Optical phase conjugation technology. This technology uses the reversibility of light propagation to obtain the light field distribution after transmitting through the medium, and compensates for the disturbance of the scattering medium to the light field by inputting the conjugate waveform of the transmitted light field. However, this technology has advantages in complex medium scattering imaging, but the modulation efficiency of the algorithm is poor and is not suitable for dynamic scenes.

[0004] 2) Scattering medium imaging technology based on feedback optimization wavefront shaping. This technology calibrates the point spread function of the scattering medium to a pulse function form, so as to "approximate" the scattering light field to a lens imaging system, and realize the imaging of the target. However, the imaging field of view and imaging timeliness under this technology are limited by the feedback optimization process.

[0005] 3) Discrete transmission matrix method. This method discretizes the input and output complex amplitude light fields into the scattering medium, and calibrates the complex mapping coefficients between the input and output fields in advance, and then combines the phase conjugation technology to complete the focusing of the light field at any position. Although the transmission matrix obtained by this method can well reflect the characteristics of the scattering medium, due to the long calibration time, this method is currently only suitable for static target scattering imaging and is not suitable for dynamic scattering scenes.

[0006] 4) Imaging method using speckle autocorrelation. By recovering the amplitude spectrum signal of the target in the scattering medium and the inverse phase, the image of the target to be measured can be reconstructed. Through frame-by-frame speckle difference analysis of moving target objects, this method realizes the imaging of dynamic scattering target objects. However, speckle autocorrelation is not a strict impulse function, so high-frequency information will be lost during imaging, causing image distortion, and the position and direction information of the target cannot be obtained, making it difficult to apply to complex moving target scattering imaging.

[0007] That is, the existing target scattering imaging methods have certain limitations and cannot realize higher quality moving target scattering imaging. SUMMARY

[0008] In order to solve the above problems existing in the related art, the present application provides a moving target scattering imaging method based on an optical waveguide phased array.

[0009] The present application provides a moving target scattering imaging method based on an optical waveguide phased array, comprising:

[0010] In the case of no scattering medium and with scattering medium, the optical waveguide phased array is calibrated respectively to obtain the calibrated scanning beam control voltage and the flat-top beam control voltage of the optical waveguide phased array; the optical waveguide phased array is used to output a scanning beam of a full field of view at a preset spatial resolution under the calibrated scanning beam control voltage, and output a flat-top beam of the full field of view at a plurality of different spatial resolutions under the calibrated flat-top beam control voltage;

[0011] At the same time of outputting the scanning beam by the optical waveguide phased array, the light field distribution of the echo signal of the scanning beam received by the detector is detected;

[0012] When it is judged that there is a moving target according to the detected light field distribution and the prior light field distribution, the movement information and the contour information of the moving target are determined through the scanning beam output by the optical waveguide phased array;

[0013] The full field of view is divided according to the contour information of the moving target, the flat-top beam is emitted according to the movement information of the moving target and the divided field of view, and the scattering imaging of the moving target is completed.

[0014] The present application has the following beneficial technical effects:

[0015] 1. By using the optical waveguide phased array as a wavefront coding device for scattering imaging, the ability of fast wavefront modulation is utilized to realize high frame frequency imaging; in addition, the optical waveguide phased array is calibrated and scanned, and combined with the prior light field distribution, the field of view range of scattering imaging can be expanded (compared with the existing moving target scattering imaging method); by outputting the flat-top beam, the imaging distortion problem of the scattering medium can be solved, and the imaging quality can be improved; thereby the quality and frame frequency of the moving target scattering imaging can be effectively improved.

[0016] 2. By optimizing and calibrating the scanning beam and the flat-top beam, and through a special calculation method to calculate the evaluation value during specific calibration, and by adjusting the step length in the calibration process in moderation, the calibration process can quickly converge and avoid iterative local optimal solution, thereby the quality and efficiency of the calibration can be improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1A flow chart of the motion target scattering imaging method based on the optical waveguide phased array provided by the embodiment of the present application is shown in FIG. 1.

[0018] Figure 2 A principle diagram of the flat-top beam illuminating the target to be measured to improve the imaging quality is shown in FIG. 2.

[0019] Figure 3 A principle diagram of the motion target scattering imaging method based on the optical waveguide phased array provided by the embodiment of the present application is shown in FIG. 1. DETAILED DESCRIPTION

[0020] The present application will be further described below in conjunction with specific embodiments, but the embodiments of the present application are not limited thereto.

[0021] In the description of the present application, the terms "first", "second", etc. are used only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0022] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the description of the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in the specification.

[0023] Although the present application is described herein in conjunction with various embodiments, other variations of the disclosed embodiments can be understood and implemented by those skilled in the art with reference to the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "one" does not exclude a plurality. A single processor or other unit can implement several functions listed in the claims. Some measures described in mutually different dependent claims can be combined and produce good results.

[0024] Figure 1is a flowchart of a motion target scattering imaging method based on an optical waveguide phased array provided by an embodiment of the present application. The method provided by the present application can be executed by a host computer, as shown in Figure 1 The method comprises the following steps:

[0025] S101, calibrate the optical waveguide phased array in the case of no scattering medium and in the case of having scattering medium, to obtain the calibrated scanning beam control voltage and the flat-top beam control voltage of the optical waveguide phased array; the optical waveguide phased array is used to output a scanning beam of a full field of view at a preset spatial resolution under the calibrated scanning beam control voltage, and output a flat-top beam of the full field of view at a plurality of different spatial resolutions under the calibrated flat-top beam control voltage.

[0026] Here, the scanning beam control voltage of the optical waveguide phased array at each first scanning position can be calibrated in the case of no scattering medium, to obtain the calibrated scanning beam control voltage at each first scanning position; each first scanning position constitutes a full field of view. The flat-top beam control voltage of the optical waveguide phased array at each second scanning position under each spatial resolution can be calibrated in the case of having scattering medium, to obtain the calibrated flat-top beam control voltage at each second scanning position under each spatial resolution of the plurality of different spatial resolutions; each second scanning position constitutes a full field of view. The first scanning position is a position for outputting a scanning beam, and the second position is a position for outputting a flat-top beam.

[0027] For example, the preset spatial resolution can be the smallest spatial resolution of the optical waveguide phased array. The plurality of different spatial resolutions are spatial resolutions that the optical waveguide phased array itself has.

[0028] Specifically, in the case of no scattering medium, the step of calibrating the scanning beam control voltage of the optical waveguide phased array at each first scanning position comprises:

[0029] S1011, for each first scanning position, determine the target light field distribution of the first scanning position, the mth random disturbance voltage, the mth scanning beam control voltage and the mth step size; when m is 1, the mth scanning beam control voltage is a preset scanning beam control voltage, and the mth step size is a preset step size; m is an integer greater than or equal to 1.

[0030] Here, each first scanning position corresponds to a target light field distribution, which can be set according to actual needs. When m = 1, the mth scanning beam control voltage is a preset scanning beam control voltage (which can be arbitrarily set), and the mth step size is a preset step size (which can be set according to an empirical value).

[0031] S1012. Based on the target light field distribution, the control voltage of the m-th scanning beam, and the random disturbance voltage of the m-th time, determine the m-th basic evaluation value, the m-th first disturbance evaluation value, and the m-th second disturbance evaluation value.

[0032] Specifically, the voltage u of the beam is controlled by the optical waveguide phased array during the m-th scan. (m) The m-th scanning beam is generated, and the optical field distribution of the echo signal of the m-th scanning beam is detected by an area array detector. Based on the target optical field distribution and the optical field distribution of the echo signal of the m-th scanning beam, the m-th basic evaluation value J is calculated. EF (m) The control voltage u of the m-th scan beam (m) and the m-th random disturbance voltage δu (m) By performing summation and subtraction respectively, the accumulated voltage u can be obtained. (m) +δu (m) With voltage difference u (m) -δu (m) ; through optical waveguide phased arrays, respectively at the accumulated voltage u (m) +δu (m) With voltage difference u (m) -δu (m) The m-th first perturbation scan beam and the m-th second perturbation scan beam are generated accordingly, and the first optical field distribution of the m-th first perturbation scan beam and the second optical field distribution of the m-th second perturbation scan beam are detected accordingly. Based on the target optical field distribution and the first optical field distribution, the m-th first perturbation evaluation value J is calculated. EF+ (m) Furthermore, based on the target light field distribution and the second light field distribution, the m-th second disturbance evaluation value J is calculated. EF- (m) .

[0033] Specifically, the Fraunhofer diffraction formula can be used to calculate the optical field distribution characteristics of both the target and detected optical field distributions, and the peak signal-to-noise ratio (PSNR) between the target and actual optical field distributions can be used as the evaluation function. For example, the m-th basic evaluation value J can be calculated using... EF (m) Taking this as an example, after detecting the light field distribution of the m-th scan beam, the characteristics of the light field distribution of the m-th scan beam can be calculated using the Fraunhofer diffraction formula, and the characteristics of the light field distribution of the target light field distribution can also be calculated using the Fraunhofer diffraction formula. Then, based on the characteristics of the light field distribution of the m-th scan beam and the target light field distribution, the peak signal-to-noise ratio (SNR) between the target light field distribution and the light field distribution of the m-th scan beam is calculated, and this SNR is used as the m-th basic evaluation (function) value J. EF (m)The mth first perturbation evaluation value J EF+ (m) The mth second perturbation evaluation value J EF- (m) The calculation principle is the same as the principle. Specifically, the Fraunhofer diffraction formula is as follows: Wherein, x is the distance coordinate on the observation screen, x1 is the distance coordinate on the plane of the transmitting antenna of the optical waveguide phased array, d represents the interval of adjacent antennas, f represents the focal length of the lens, i is the imaginary symbol, k is the wave vector symbol, alpha = pi asin theta / lambda f, The phase difference of adjacent light fields is P. The light intensity of point P can be represented as: Theta is the scanning angle, N is the number of antenna elements, and different phases are selected to generate scanning beams at different scanning positions and flat-top beams at different scanning positions.

[0034] S1013, according to the mth random perturbation voltage, the mth scanning beam control voltage, the mth step, the mth first perturbation evaluation value and the mth second perturbation evaluation value, determine the mth calibration control voltage.

[0035] Specifically, the mth calibration control voltage u' can be calculated by the following formula: (m) : u' (m) = u (m) + gamma (m) delta u (m) Delta J EF (m) ; wherein, gamma (m) is the mth step, delta u (m) is the mth random perturbation voltage, Delta J EF (m) = J EF+ (m) -J EF- (m) .

[0036] S1014, when the mth calibration control voltage satisfies the stop iteration condition, the mth calibration control voltage is taken as the calibrated scanning beam control voltage at the first scanning position; when the stop iteration condition is not satisfied, the mth + 1 scanning beam control voltage and the mth + 1 step of the first scanning position are determined according to the basis evaluation value and the calibration control voltage from the m-xth to the mth, and the mth + 1 random perturbation voltage is determined; x is a preset integer.

[0037] Specifically, the optical waveguide phased array is controlled by the mth calibration control voltage u' (m)output the scanning light beam and detect the light field distribution of the scanning light beam by the area array detector; calculate an evaluation value according to the detected light field distribution and the target light field distribution; when the evaluation value is less than or equal to a preset cut-off threshold, it is indicated that the mth calibration control voltage u (m) meets the stop iteration condition; when the evaluation value is greater than the preset evaluation threshold, it is indicated that the mth calibration control voltage u (m) does not meet the stop iteration condition. When the mth calibration control voltage u (m) does not meet the stop iteration condition, a first change trend value L1 and a second change trend value L2 are calculated according to the basis evaluation values from the m-xth to the mth; when the first change trend value L1 is less than or equal to a first preset value ε (a positive number) and the second change trend value L2 is greater than or equal to a second preset value μ (a positive number), the mth step size γ (m) is reduced by a preset coefficient value κ (a decimal number between 0 and 1) to obtain an m+1th step size γ (m+1) , and the mth calibration control voltage u (m) is taken as the m+1th scanning light beam control voltage u (m+1) of the first scanning position; when the first change trend value L1 is greater than the first preset value ε or the second change trend value L2 is less than the second preset value μ, a third change trend value is calculated according to the mth calibration control voltage u (m) , the m-1th calibration control voltage u (m-1) and the target light field distribution; when the third change trend value is greater than or equal to a third preset value threshold (which can be set arbitrarily according to actual conditions), the mth step size γ (m) is reduced by the preset coefficient value κ to obtain an m+1th step size γ (m+1) , and the maximum calibration control voltage among the calibration control voltages obtained in the previous m times is taken as the m+1th scanning light beam control voltage u (m+1) of the first scanning position.

[0038] Specifically, the calculation formula of the first change trend value is: The calculation formula of the second change trend value is: wherein k=m-x, and x may be 29, for example, is the average value of J i , and is the average value of J j .

[0039] Specifically, the principle of calculating the third change trend value according to the mth calibration control voltage u (m) , the m-1th calibration control voltage u (m-1) and the target light field distribution is as follows: the light waveguide phased array is controlled by the mth calibration control voltage u (m)The scanning light beam is outputted and the light field distribution of the scanning light beam is detected by the area array detector to obtain u' (m) corresponding light field distribution; and the light field distribution characteristics of the corresponding light field distribution u' (m-1) The scanning light beam is outputted and the light field distribution of the scanning light beam is detected by the area array detector to obtain u' (m-1) corresponding light field distribution; then, the Fraunhofer diffraction formula is used to calculate u' (m-1) corresponding light field distribution; then, the Fraunhofer diffraction formula is used to calculate u' (m) corresponding light field distribution; then, the Fraunhofer diffraction formula is used to calculate u' (m) corresponding light field distribution and the light field distribution characteristics of the target light field distribution, to obtain the evaluation value J' EF (m) corresponding light field distribution and the light field distribution characteristics of the target light field distribution, to obtain the evaluation value J' (m-1) corresponding light field distribution and the light field distribution characteristics of the target light field distribution, to obtain the evaluation value J' EF (m-1) Finally, u' is taken as the third change trend value calculated.

[0040] S1015, according to the target light field distribution, the m+1th scanning light beam control voltage, the m+1th step and the m+1th random disturbance voltage, the m+1th calibration control voltage is determined, whether the m+1th calibration control voltage meets the stop iteration condition is determined, the calibrated scanning light beam control voltage at the first scanning position is determined, or the m+2th scanning light beam control voltage, the m+2th step and the m+2th random disturbance voltage are determined, and the cycle iteration is repeated until the calibrated scanning light beam control voltage at the first scanning position is obtained.

[0041] Specifically, the principle of determining the m+1th calibration control voltage u' (m+1) is the same as that of determining the mth calibration control voltage u' (m) , which will not be repeated here. When calibrating the light beam control voltage at each first scanning position, the cycle iteration principle described in S1011-S1015 is used.

[0042] The S1011-S1015 above can be referred to as a target weight adaptive random parallel gradient descent method. A most commonly used calibration algorithm in the prior art does not need wavefront measurement, only takes the control signal applied to the wavefront corrector as an optimization parameter, selects a proper performance evaluation function and a gain coefficient, and thus can realize wavefront correction. However, in actual application, the algorithm has problems of slow convergence speed and easy falling into a local optimal solution, and the algorithm belongs to a model-free optimization algorithm and is difficult to be applied to wavefront calibration of a flat-top beam. Compared with a traditional algorithm, the target weight adaptive random parallel gradient descent method provided by the application adds a function value that can be calculated according to a target light field distribution, and can adaptively modulate a search step length according to a change trend of the function value, so that the number of iterations can be reduced, the algorithm can be prevented from falling into a local optimal solution, and the calibration quality and efficiency are improved. In addition, the target weight adaptive random parallel gradient descent method provided by the application can also be applied to application scenarios such as vortex light calibration.

[0043] Specifically, in the case of a scattering medium, the principle of calibrating the flat-top beam control voltage of the optical waveguide phased array at each second scanning position is the same as that of the steps S1011-S1015, except that the target light field distribution at each second scanning position is used when calibrating the flat-top beam control voltage of the optical waveguide phased array at each second scanning position, and the target light field distribution at each second scanning position is different from the target light field distribution at each first scanning position (for example, the target light field distribution at each second scanning position can be set according to experimental results), the preset step length at the first iteration when calibrating the flat-top beam control voltage of the optical waveguide phased array at each second scanning position is different from the preset step length at the first iteration when calibrating the scanning beam control voltage of the optical waveguide phased array at each first scanning position, and the random disturbance voltage at each iteration when calibrating the flat-top beam control voltage of the optical waveguide phased array at each second scanning position is different from the random disturbance voltage at each iteration when calibrating the scanning beam control voltage of the optical waveguide phased array at each first scanning position. The first preset value ε, the second preset value μ and the third preset value threshold used when calibrating the flat-top beam control voltage of the optical waveguide phased array at each second scanning position can be the same as or different from the first preset value ε, the second preset value μ and the third preset value threshold used when calibrating the scanning beam control voltage of the optical waveguide phased array at each first scanning position.

[0044] S102, while outputting the scanning beam by the optical waveguide phased array, detecting the light field distribution of the echo signal of the scanning beam received by the detector.

[0045] Specifically, the light waveguide phased array can output a scanning beam to each different first scanning position at a preset spatial resolution, and simultaneously detect the light field distribution of the echo signal of the received scanning beam by the area array detector; then, the detected light field distribution at each first scanning position is compared with the prior light field distribution corresponding to each first scanning position, and when the detected light field distribution at a first scanning position is different from the corresponding prior light field, it is judged that there is a moving target; wherein the prior light field distribution is obtained by detecting the light field distribution of the scanning beam output by the light waveguide phased array at a preset spatial resolution and at each different first scanning position in the full field of view.

[0046] It should be noted that the "light field distribution of the scanning beam" in the present application is the "light field distribution of the echo signal of the scanning beam".

[0047] For example, when there are 16 different first scanning positions in the full field of view, the 16 different first scanning positions correspond to 16 prior light field distributions one by one.

[0048] S103, when it is judged that there is a moving target according to the detected light field distribution and the prior light field distribution, the scanning beam output by the light waveguide phased array is used to determine the motion information and the contour information of the moving target.

[0049] Here, the initial minimum external rectangle and the initial centroid of the moving target can be obtained according to the scanning beam output by the light waveguide phased array to different scanning positions and by using the existing contour retrieval algorithm; the minimum external rectangle and the centroid of the moving target at multiple time points are obtained by using the target tracking algorithm according to the initial minimum external rectangle and the initial centroid; the minimum external rectangle is used as the contour information of the moving target; the motion speed of the moving target in the x direction and the y direction is determined according to the initial centroid and the centroid at multiple time points, which is used as the motion information of the moving target.

[0050] Specifically, when the light waveguide phased array outputs a light beam to scan the target, the first scanning position point at which the target is detected can be used as a starting point, and the profile point (i.e. scanning position point) of the uppermost edge of the target can be quickly retrieved by using the method of large steps forward and small steps backward, and other edge profile points (e.g. rightmost edge profile point, leftmost edge profile point, lowermost edge profile point) of the target can be obtained according to the same principle. The minimum external rectangle (MER) and the centroid of the target are determined according to the four edge profile points of the target.

[0051] Specifically, the principle of the contour retrieval algorithm is: obtaining a first detected target scanning position point (x0, y0), recording the effective echo signal as (x, y), scanning along the y direction with (x0, y0) as the starting coordinate point and R as the scanning interval until the uppermost contour point of the target is found, and saving the coordinate of the point, scanning along the x direction with (x0, y0) as the starting coordinate point and R as the scanning interval until the uppermost contour point of the target is found, and saving the coordinate of the point, continuing to scan (x, y) until the rightmost contour point is found, and then taking the coordinate of the rightmost contour point as the starting coordinate point and S (S is smaller than R) as the scanning interval to scan along the x direction in the reverse direction until the leftmost contour point of the target is found; then, similar to the above process, the left and right contour edge points of the bottom of the target are retrieved from top to bottom, and finally the four edge contour points of the target to be measured are obtained; the four edge contour points constitute the MER of the target, and the centroid can be calculated according to the coordinates of the four edge contour points.

[0052] Specifically, the calculation formula of the centroid is as follows: Where (x0, y0) represents the calculated coordinate of the centroid, and M in the formula can be represented as: n represents the total number of edge contour points, and (x1, y1) is the coordinate of the first detected edge contour point.

[0053] Here, the target tracking algorithm can be an existing spiral detection algorithm, which controls the light waveguide phased array output to follow an Archimedes spiral scanning beam to retrieve the target. The Archimedes spiral is an equidistant spiral, and its parametric equation can be represented as: Where x c and y c are the horizontal and vertical coordinates of the starting point; a s represents the distance between the starting point of the spiral and the origin, for example, 0; θ s represents the total angle of the spiral rotation, which is an increasing variable; b s represents the spiral spacing, and the spacing between adjacent spirals is 2πb. To avoid missing detection, the spiral spacing needs to be adaptively set during the algorithm running process, and its value cannot exceed the horizontal or vertical length of the target, for example, b s satisfies

[0054] Here, there can be many ways to determine the movement speed of the moving target in the x direction and the y direction according to the coordinates of multiple centroids, which are not limited by the present application.

[0055] S104, dividing the full field of view according to the contour information of the moving target, and emitting a flat-top light beam according to the movement information of the moving target and the divided field of view to complete the scattering imaging of the moving target.

[0056] Here, the size of the profile information of the moving target is taken as the size of the minimum field of view unit to divide the whole field of view; the position of the moving target is estimated according to the motion information of the moving target; and a flat-top light beam is output at the estimated position at a specific spatial resolution by the light waveguide phased array according to the divided field of view, so as to complete the scattering imaging of the moving target.

[0057] Here, the specific spatial resolution is a resolution corresponding to the divided field of view.

[0058] The imaging method of the present application needs two types of light fields to work together, in which the scanning light beam is a common Gaussian field distribution, and the imaging light field is a flat-top light beam. Based on the Fraunhofer diffraction principle, the formula for deriving the far-field light beam distribution of the light waveguide phased array is: U(θ x ,θ y )=S(θ x ,θ y )·M(θ x ,θ y ), where θ x ,θ y are corresponding scanning angles, P and Q respectively correspond to the number of elements of the light waveguide phased array in the horizontal and vertical directions, is the phase difference between adjacent antennas in the x direction, is the phase difference between adjacent antennas in the y direction. dx is the distance between adjacent antennas in the x direction, and dy is the distance between adjacent antennas in the y direction. φ0 is the initial phase distribution of the antenna array. When the above formula is determined, it can be known that the far-field distribution of the light beam output by the diffraction antenna array of the light waveguide phased array is determined by two factors: the envelope S(θ x ,θ y ) of a single antenna and the array factor M(θ x ,θ y ) determined by the antenna arrangement. When the amplitude distribution of the target is as shown in Figure 2 (a), the envelope shown in Figure 2 (b) can be obtained by using MATLAB to calculate the relevant parameters. When the envelope acts on the light field of the target, the image edge obtained by the detector will appear distortion phenomenon due to the influence of the illumination light field. Therefore, the flat-top light beam is used as the imaging light beam, and the imaging result is as shown in Figure 2 (c). As can be seen from Figure 2 (a) to (c), the method of using the flat-top light beam for imaging effectively solves the problem of imaging contrast distortion, so as to improve the quality of imaging the target.

[0059] Here, since the target and its outline can be detected by comparing the consistency between the received light field and the prior light field, only the low-frequency information of the target can be obtained and it cannot be used for imaging. Therefore, this application can achieve imaging of the moving target in the scattering medium based on the detection of the target through steps S103 to S104.

[0060] Figure 3 This is a schematic diagram illustrating the principle of the moving target scattering imaging method based on an optical waveguide phased array provided by the present invention. Figure 3 As shown, the method includes: Step 1: 1) Using as... Figure 3 The system shown demonstrates the application of optical waveguide phased arrays (including...) without a scattering medium. Figure 3 The output light field of the laser, on-chip devices, modulator array, and transmitting antenna array in the optical waveguide phased array is directionally calibrated (pre-calibrated). During calibration, the scanning beam control voltage of scanning beams at different scanning positions and sizes needs to be recorded so that the optical waveguide phased array can output a scanning beam covering the entire field of view with minimal spatial resolution, and the corresponding scanning beam control voltage is recorded; 2) such as Figure 3 The system shown incorporates a scattering medium, and uses a planar array detector to detect and record the light field distribution at different scanning angles across the entire field of view as the prior light field distribution (prior result); 3) In the presence of a scattering medium, the flat-top beam of the optical waveguide phased array is oriented and calibrated (pre-calibrated). During calibration, the control voltage of the flat-top beam at different scanning positions and sizes needs to be recorded. Second step: 1) The optical waveguide phased array randomly outputs oriented scanning beams according to its minimum resolvable point. When the detector detects that the current field distribution differs from the prior light field distribution (mismatch), it is considered to have detected a moving target; 2) The host computer ( Figure 3 (Not shown in the image) Based on the scanning beam output by the optical waveguide phased array, and existing contour retrieval and target tracking algorithms, the contour information (number of pixels occupied by the target) and motion information of the moving target are determined. The spatial field of view is then divided based on the number of pixels occupied by the target, and the position of the moving target at the next moment is predicted based on the target's motion information. Third step: Based on the divided field of view and the predicted position, the optical waveguide phased array outputs a flat-top beam (imaging beam) with a specific spatial resolution at the corresponding position to illuminate the moving target, thus completing the imaging of the moving target in the scattering medium and obtaining the imaging result.

[0061] The present invention has the following beneficial technical effects:

[0062] a.A new type of moving target scattering imaging method is proposed. The traditional method has low precision and slow speed in complex moving target imaging. The present application uses optical waveguide phased array as wavefront coding device for scattering imaging, which can realize high frame frequency imaging by using the ability of fast wavefront modulation. In addition, the optical waveguide phased array can realize beam calibration scanning, combined with prior results, which can expand the field of view of scattering imaging. Through the output of flat-top beam, the problem of imaging distortion of scattering medium can be solved, and the imaging quality is improved. This method can effectively improve the quality and frame frequency of moving target scattering imaging.

[0063] b.A new type of moving target wavefront correction method is proposed. The existing optical waveguide phased array output beam calibration method has slow iteration speed, poor calibration quality, long running time, and is not suitable for moving target scattering imaging scene. The present application proposes a target weight adaptive random parallel gradient descent algorithm, which can optimize and calibrate a variety of light fields, and has good application value and innovation. The algorithm adds a target weight calculation module (i.e. the content corresponding to the above calculation evaluation value), sets a special algorithm evaluation function, which can realize the optimization and calibration of a variety of light fields, and improves the calibration efficiency. In addition, the adaptive search step modulation module can adjust the search step in moderation, so that the algorithm can quickly converge and avoid iterative local optimal solution. Finally, the calibration quality and efficiency of the output beam of the optical waveguide phased array are improved.

[0064] The above is a further detailed description of the present application in combination with a specific preferred embodiment, which cannot be regarded as limiting the specific implementation of the present application to these descriptions. For ordinary skilled persons in the technical field to which the present application belongs, some simple deductions or substitutions can be made without departing from the concept of the present application, which should be regarded as falling within the protection scope of the present application.

Claims

1. A method for imaging moving targets by scattering light based on an optical waveguide phased array, characterized in that, include: The optical waveguide phased array is calibrated under both scattering and non-scattering media conditions to obtain the calibrated scanning beam control voltage and flat-top beam control voltage. The optical waveguide phased array is used to output a full-field scanning beam with a preset spatial resolution under the calibrated scanning beam control voltage, and to output a full-field flat-top beam with various different spatial resolutions under the calibrated flat-top beam control voltage. While the optical waveguide phased array outputs a scanning beam, the optical field distribution of the echo signal of the scanning beam received by the detector is detected. When a moving target is determined to exist based on the detected light field distribution and the prior light field distribution, the motion information and contour information of the moving target are determined by the scanning beam output by the optical waveguide phased array. The full field of view is divided according to the contour information of the moving target, and a flat-top beam is emitted according to the motion information of the moving target and the divided field of view to complete the scattering imaging of the moving target. The calibration of the optical waveguide phased array under conditions of no scattering medium and with scattering medium, respectively, to obtain the calibrated scanning beam control voltage and flat-top beam control voltage of the optical waveguide phased array, includes: In the absence of a scattering medium, the scanning beam control voltage of the optical waveguide phased array is calibrated at each first scanning position to obtain the calibrated scanning beam control voltage at each first scanning position; each first scanning position constitutes the full field of view. In the presence of a scattering medium, the flat-top beam control voltage of the optical waveguide phased array at each second scan position under each spatial resolution is calibrated to obtain the calibrated flat-top beam control voltage at each second scan position under each spatial resolution in multiple different spatial resolutions; each second scan position constitutes the full field of view. The step of calibrating the scanning beam control voltage of the optical waveguide phased array at each first scanning position to obtain the calibrated scanning beam control voltage at each first scanning position includes: For each first scan position, determine the target light field distribution, the m-th random disturbance voltage, the m-th scan beam control voltage, and the m-th step size for that first scan position; when m is 1, the m-th scan beam control voltage is a preset scan beam control voltage, and the m-th step size is a preset step size; m is an integer greater than or equal to 1. Based on the target light field distribution, the control voltage of the beam in the mth scan, and the random disturbance voltage in the mth scan, determine the basic evaluation value, the first disturbance evaluation value, and the second disturbance evaluation value in the mth scan. The m-th calibration control voltage is determined based on the m-th random disturbance voltage, the m-th scanning beam control voltage, the m-th step size, the m-th first disturbance evaluation value, and the m-th second disturbance evaluation value. When the m-th calibration control voltage meets the stop iteration condition, the m-th calibration control voltage is used as the calibrated scan beam control voltage at the first scan position; when the stop iteration condition is not met, the (m+1)-th scan beam control voltage and the (m+1)-th step size at the first scan position are determined based on the basic evaluation values ​​from the mx-th to the m-th calibration control voltage, and the (m+1)-th random disturbance voltage is also determined; x is a preset integer; Based on the target light field distribution, the (m+1)th scan beam control voltage, the (m+1)th step size, and the (m+1)th random perturbation voltage, determine the (m+1)th calibration control voltage. Based on whether the (m+1)th calibration control voltage meets the stopping iteration condition, determine the calibrated scan beam control voltage at the first scan position, or determine the (m+2)th scan beam control voltage, the (m+2)th step size, and the (m+2)th random perturbation voltage. Repeat this iterative process until the calibrated scan beam control voltage at the first scan position is obtained.

2. The moving target scattering imaging method based on optical waveguide phased array according to claim 1, characterized in that, The process of determining the m-th basic evaluation value, the m-th first perturbation evaluation value, and the m-th second perturbation evaluation value based on the target light field distribution, the m-th scanning beam control voltage, and the m-th random perturbation voltage includes: The optical waveguide phased array generates the m-th scanning beam under the control voltage of the m-th scanning beam, and the optical field distribution of the m-th scanning beam is detected. Based on the target light field distribution and the light field distribution of the m-th scan beam, the m-th basic evaluation value is calculated. The control voltage of the m-th scanning beam and the random disturbance voltage of the m-th scan are accumulated and subtracted respectively to obtain the accumulated voltage and voltage difference. The optical waveguide phased array generates the m-th first perturbation scanning beam and the m-th second perturbation scanning beam respectively under the accumulated voltage and the voltage difference, and detects the first optical field distribution of the m-th first perturbation scanning beam and the second optical field distribution of the m-th second perturbation scanning beam. Based on the target light field distribution and the first light field distribution, the m-th first disturbance evaluation value is calculated, and based on the target light field distribution and the second light field distribution, the m-th second disturbance evaluation value is calculated.

3. The moving target scattering imaging method based on optical waveguide phased array according to claim 1, characterized in that, The method further includes: The optical waveguide phased array outputs a scanning beam under the m-th calibration control voltage, and the optical field distribution of the echo signal of the scanning beam is detected. The evaluation value is calculated based on the light field distribution and the target light field distribution; When the evaluation value is less than or equal to the preset evaluation threshold, it indicates that the m-th calibration control voltage meets the stop iteration condition; When the evaluation value is greater than the preset evaluation threshold, it indicates that the m-th calibration control voltage does not meet the stop iteration condition.

4. The moving target scattering imaging method based on optical waveguide phased array according to claim 1, characterized in that, When the stopping iteration condition is not met, the process of determining the (m+1)th scan beam control voltage and (m+1)th step size at the first scan position based on the basic evaluation values ​​from the mxth to the mth iteration and the calibration control voltage includes: When the stopping iteration condition is not met, the first trend value and the second trend value are calculated based on the basic evaluation values ​​from the mxth iteration to the mth iteration. When the first trend value is less than or equal to the first preset value and the second trend value is greater than or equal to the second preset value, the m-th step size is reduced by the preset coefficient value to obtain the (m+1)-th step size, and the m-th calibration control voltage is used as the (m+1)-th scanning beam control voltage at the first scanning position. When the first trend value is greater than the first preset value or the second trend value is less than the second preset value, the third trend value is calculated based on the m-th calibration control voltage, the (m-1)-th calibration control voltage, and the target light field distribution. When the third trend value is greater than or equal to the third preset value, the m-th step size is reduced by the preset coefficient value to obtain the (m+1)-th step size, and the largest calibration control voltage among the calibration control voltages obtained in the previous m times is used as the (m+1)-th scan beam control voltage for the first scan position.

5. The moving target scattering imaging method based on optical waveguide phased array according to claim 1, characterized in that, The scanning beam output through the optical waveguide phased array determines the motion information and contour information of the moving target, including: Based on the scanning beams output by the optical waveguide phased array to different scanning positions at the preset spatial resolution, the initial minimum circumscribed rectangle and the initial centroid of the moving target are obtained through a contour retrieval algorithm. Based on the initial minimum bounding rectangle and the initial centroid, the minimum bounding rectangle and centroid of the moving target at multiple time points are obtained through a target tracking algorithm. The minimum bounding rectangle is used as the contour information of the moving target; Based on the initial centroid and the centroids at the multiple moments, the motion velocities of the moving target in the x and y directions are determined as the motion information of the moving target.

6. The moving target scattering imaging method based on optical waveguide phased array according to claim 1 or 5, characterized in that, The step of dividing the full field of view based on the contour information of the moving target, and emitting a flat-top beam based on the motion information of the moving target and the divided field of view to complete the scattering imaging of the moving target includes: The size of the contour information of the moving target is used as the size of the smallest field of view unit to divide the entire field of view; Predict the position of the moving target based on its motion information; Based on the divided field of view, the optical waveguide phased array outputs a flat-top beam at a predetermined position with a specific spatial resolution, thereby completing the scattering imaging of the moving target.

7. The moving target scattering imaging method based on optical waveguide phased array according to claim 1, characterized in that, The process of simultaneously outputting a scanning beam through the optical waveguide phased array and detecting the optical field distribution of the echo signal of the scanning beam received by the detector includes: The optical waveguide phased array outputs scanning beams to different first scanning positions at the preset spatial resolution, and simultaneously detects the optical field distribution of the echo signal of the scanning beams received by the detector. The method further includes: The light field distribution detected at each first scanning position is compared with the prior light field distribution corresponding to each first scanning position. When the light field distribution detected at a first scanning position is different from the corresponding prior light field, it is determined that the moving target exists. The prior light field distribution is obtained by detecting the light field distribution of the echo signal of the scanning beam output by the optical waveguide phased array at each different first scanning position in the full field of view under the preset spatial resolution, in the presence of a scattering medium.

8. The moving target scattering imaging method based on optical waveguide phased array according to claim 4, characterized in that, When x is 29, the formula for calculating the first trend value is as follows: ； The formula for calculating the second trend value is as follows: ； in, The first trend value, This is the second trend value. =mx, for The average value, for The average value.

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