CN115393441B - Light spot high-precision extraction and positioning method based on liquid crystal light closed-loop system - Google Patents
Light spot high-precision extraction and positioning method based on liquid crystal light closed-loop system Download PDFInfo
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Abstract
The invention relates to a light spot high-precision extraction and positioning method based on a liquid crystal light closed-loop system, which comprises the following steps of: s1, filtering the collected original diffraction spot image; s2, performing threshold segmentation on the processed light spot image and outputting the image; s3, performing open operation on the image output in the S2; s4, performing transverse scanning and longitudinal scanning on the image subjected to the opening operation to find an area where a target light spot is located; and S5, extracting the edge contour line of the target light spot saturated plane area in the image processed in the S2 according to the area where the target light spot is located obtained in the S4, performing Gaussian section fitting on the extracted edge contour line to obtain a distribution expression of edge pixel points, performing least square fitting by using the expression as a target function, and calculating the central coordinate of the light spot.
Description
Technical Field
The invention relates to the technical field of space laser communication, in particular to a light spot high-precision extraction and positioning method based on a liquid crystal light closed-loop system.
Background
A typical wireless laser communication system mainly includes a terminal transmitting and receiving system and an APT beam control system. At the transmitting end, a signal to be transmitted is coded by a coder and then transmitted to a modulator, a modulation circuit converts the coded data into a corresponding voltage signal, the modulation signal is loaded on a semiconductor laser after passing through an automatic power control system, and finally a modulated light beam emitted by the laser is transmitted out at a very small beam divergence angle through an optical transmitting antenna. At a receiving end, the optical receiving antenna collects signal light in a free space, after the light beam passes through the beam splitting system, one part of the light beam is transmitted to the APT system, and the other part of the light beam is transmitted to the signal receiving detector. The APT system takes the position error of the light beam as feedback to realize the functions of capturing, aligning and tracking the light beam; and on the other hand, the optical signal is converted into an electric signal through a photoelectric detection system, a baseband signal is restored through a demodulation circuit, and finally, an original signal is output through a decoder. In a conventional APT system, beam position is adjusted by using a Fast Steering Mirror (FSM) driven by piezoelectric ceramics. In a traditional piezoelectric ceramic driving mode, the bandwidth of a control mode of mechanical servo can only reach dozens of to hundreds of hertz. In order to solve the problem, scientific researchers provide a non-mechanical servo control mode, and the method is suitable for larger bandwidth magnitude, larger vibration amplitude and a higher frequency range.
A closed loop system of liquid crystal spatial light modulator is a typical non-mechanical servo control system. The liquid crystal spatial light modulator has an electrically controlled birefringence effect, and the light beam can be deflected by changing the voltage. A simplified model of a system constructed from liquid crystal spatial light modulators is shown in fig. 1. After laser passes through a laser, a polarizer and a spectroscope and is spread for a certain distance in space, light beams strike the liquid crystal spatial light modulator, the light beams can generate a Bragg diffraction effect after passing through the liquid crystal spatial light modulator, and a plurality of diffraction light spots are horizontally arranged in an image in a straight line after being received by the CCD camera. Extracting and positioning the +1 st-order diffraction light spots with the maximum energy to obtain the spatial position of the light spots; and then feeding back the spatial position to a servo system, so that the voltage applied to the liquid crystal spatial light modulator is changed, and further the position of the light spot is changed to be aligned to a receiving end of the wireless laser communication system. The diffraction spot image collected by the CCD camera is shown in fig. 2. A series of light spots are horizontally arranged in the image, and the light spots around the +1 st order diffraction light spots become smaller gradually with the increasing distance.
Relevant literature information is lacked at home and abroad about extracting a specific light spot from a plurality of light spots. According to the energy characteristic of the light spot required to be extracted by the liquid crystal spatial light modulator closed-loop system, the target light spot required to be extracted has the maximum energy. The light spot with the maximum energy occupies the most gray sum and the largest area in the CCD acquired image, so the common methods are a method of extracting a connected domain and then selecting the largest connected domain and a method of extracting a target edge contour and then selecting the longest contour. However, extracting the largest connected domain requires traversing and marking each connected domain in the image for 2 times, and then selecting the connected domain, and meanwhile, certain difficulty is also brought to hardware implementation. The longest edge profile is extracted, and the maximum light spots are obtained by extracting the light spot profiles one by one and comparing the light spot profiles.
Light beams in a wireless laser communication system belong to lasers, and a plurality of methods for extracting laser spots are proposed by predecessors for reference. One is a gray value-based method, wherein the gray centroid method and the Gaussian surface fitting method are representative, and the other is an edge-based method, which is commonly a circle fitting method, an ellipse fitting method, a Hough transform method and an improvement method thereof. When burrs and irregular edges exist in the laser spot profile, and the center is calculated by using an edge-based method, error points are inevitably introduced in a residual error item; meanwhile, the energy distribution of the laser spots conforms to Gaussian distribution, so that the method based on the gray value can well conform to the energy distribution characteristic. The method most suitable for Gaussian distribution characteristics is a Gaussian surface fitting method. However, due to the fact that laser energy is too high, gray value saturation of light spots shot by a CCD camera exists in a central area, errors are introduced when a simple Gaussian surface fitting cannot collect enough sample points, and larger delay time is introduced when the calculation amount of the method is too large.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to overcome the defects that in the prior art, the error is introduced when a simple Gaussian curve fitting cannot collect enough sample points, and the larger delay time is introduced when the calculated amount of the method is too large, so that the light spot high-precision extraction and positioning method based on the liquid crystal light closed-loop system is provided.
A light spot high-precision extraction and positioning method based on a liquid crystal light closed-loop system comprises the following steps:
s1, performing median filtering processing on an original diffraction spot image acquired by a CCD (charge coupled device);
s2, performing threshold segmentation on the light spot image subjected to median filtering by an iteration method and outputting the image;
s3, performing open operation on the image output in the S2;
s4, performing transverse scanning and longitudinal scanning on the image subjected to the opening operation, and searching a communication area with the largest transverse and longitudinal span, namely an area where a target light spot is located;
s5, according to the area where the target light spot obtained in the S4 is located, extracting an edge contour line of a target light spot saturated plane area in the image subjected to median filtering in the S2, and performing Gaussian section line fitting on the extracted edge contour line, wherein the distribution expression of edge pixel points is as follows:
wherein: x and y are the horizontal and vertical coordinates of the pixel points in the image, x 0 And y 0 Is the spatial position of the vertex of the sigmoid, delta x And delta y Is the variance of the Gaussian surface function, and A is the amplitude;
using the expression as a target function to carry out least square fitting to obtain x 0 And y 0 ，（x 0 ，y 0 ) Namely the coordinate of the center of the light spot.
Further, the step S2 of segmenting the threshold value by the iterative method specifically includes:
s2.1, selecting an initial threshold value T 0 ；
S2.2, dividing the image into two parts by using a threshold value T0, wherein the gray levels of the two parts are R1 and R2 respectively;
s2.3 calculating the mean value of R1 and R2, respectively denoted as mu 1 And mu 2 ；
S2.4, selecting a new threshold value T, and
；
s2.5, if the absolute value of the difference value between T and T0 is less than the preset value, T is the final threshold value, otherwise, T is enabled to be equal to the preset value 0 And = T and repeats step S2.2-S2.5。
Further, the step S4 of transversely scanning the image includes the specific steps of:
s4.1.1: scanning a first line of the image, recording the number of points with pixel values of 1 in the line, and pressing the points into a stack;
s4.1.2: traversing all the rows, and repeating the step of scanning the first row in the step S4.1.1 for other rows;
s4.1.3: reading out elements in the stack one by one, and recording the reading sequence;
s4.1.4: the sequence with the longest non-zero values that can be read out continuously is found, and the reading order of the sequence corresponds to the row position of the main spot.
Further, the step S4 of longitudinally scanning the image includes the specific steps of:
s4.2.1: scanning a first column of the image, recording the number of points with pixel values of 1 in the column, and pressing the points into a stack;
s4.2.2: traversing all columns, repeating the step of scanning the first column in step S4.2.1 for other rows;
s4.2.3: reading elements in the stack one by one, and recording the reading sequence;
s4.2.4: the longest sequence of non-zero values that can be read out continuously is found, the read-out order of the sequence corresponding to the column position of the main spot.
Further, the initial threshold T 0 Is the average of the maximum and minimum gray values in the image.
Further, the preset value is 0.1.
An electronic device comprising a memory storing a computer program and a processor implementing the steps of any of the above methods when the processor executes the computer program.
A computer readable storage medium storing computer instructions which, when executed by a processor, perform the steps of any of the above methods.
The technical scheme of the invention is suitable for light spot extraction in a liquid crystal space light closed-loop system, has higher operation speed on the premise of ensuring high precision compared with other extraction and positioning methods, and is more suitable for realizing a hardware environment logically.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a simplified block diagram of a system of liquid crystal spatial light modulators;
FIG. 2 is a diffraction spot image;
FIG. 3 is a schematic diagram of the light spot extraction result;
FIG. 4 is a three-dimensional diagram of the energy distribution of +1 order diffraction spots;
fig. 5 is a peripheral outline of the peak of the + 1-order spot.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplification of description, but do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
A light spot high-precision extraction and positioning method based on a liquid crystal light closed-loop system comprises the following steps:
s1, carrying out median filtering processing on an original diffraction spot image acquired by a CCD (charge coupled device), eliminating the influence of single-pixel noise and achieving the filtering effect;
s2, performing threshold segmentation on the light spot image subjected to median filtering by an iteration method and outputting the image;
s3, performing open operation on the image output in the S2; in the light spot image obtained by the iteration method, a series of burrs still exist around the light spot, which is not beneficial to the accurate extraction of the subsequent light spot, so that the method adds the operation of opening operation after the threshold segmentation, and eliminates the burr edge around the light spot without obviously changing the area of the light spot;
s4, the basic idea of light spot extraction in the invention is to utilize the characteristics that light spots are horizontally distributed and target light spots have the highest energy and the largest area, so that the image after the operation is transversely scanned and longitudinally scanned, a connected region with the largest transverse and longitudinal spans is searched, two coordinate ranges with the largest direction spans, namely the positions of the target light spots, are searched through two scans, and the result of light spot extraction is shown in FIG 3;
the light spots required to be extracted are laser light spots, the ideal energy distribution of the laser light spots presents Gaussian distribution, but after the diffraction light spots in the system are collected by a CCD camera, due to the fact that photosensitive elements of the CCD camera are saturated, pixel values of one area in the center of each light spot are displayed as the maximum pixel value. As shown in fig. 4, it can be seen that the energy of the diffracted spot is clipped to form a plane at the peak due to saturation.
In fig. 3, the light spot can be located by using a gaussian surface fitting method, and the function formula of the energy distribution of the light spot is as follows:
in the above formula, ƒ (x, y) represents the energy of the light spot, the energy of the light spot is the gray value of the pixel point in the image, x and y are the horizontal and vertical coordinates of the pixel point in the image, and x 0 And y 0 The space position of the vertex of the Gaussian surface is, the delta x and the delta y are variances of the Gaussian surface function, and A is an amplitude;
however, the accuracy of the reduction of the sample points is lower than the extraction effect of the complete light spot, and a large number of sample points are required to be brought in by the Gaussian curve fitting method. To this end, the present invention proposes a method of fitting gaussian section lines, where the pixel values at the top plane of fig. 4 are all 255, and we use a round of closed curve at the periphery of the top plane, where the spatial positions of the points on the closed curve are different, but the gray values are all 255. The method has higher precision, greatly reduces the number of sample points to be fitted, and considers the two aspects of precision and efficiency at the same time, specifically as step S5;
s5, according to the area where the target light spot is located obtained in the S4, extracting the edge contour line of the target light spot saturated plane area in the image after median filtering in the S2, specifically: traversing the space region where the target light spot is located, finding out the pixel point with the pixel value of 255 adjacent to the pixel point smaller than 255, and extracting the outline as shown in fig. 5;
and performing Gaussian section fitting on the extracted edge contour line, wherein the distribution expression of the edge pixel points is as follows:
A、δx、δy、x 0 and y 0 The undetermined parameter is obtained by performing least square fitting by taking the formula (2) as an objective function to obtain x 0 And y 0 ，（x 0 ，y 0 ) Namely the coordinate of the center of the light spot.
To facilitate the operation, we express equation (2) in a logarithmic form to obtain equation (3), which is as follows:
the formula (3) can be expressed in the form of a quadratic polynomial after further transformation, as shown in formula (4). The function is converted into the expression form of the polynomial, so that the function is convenient to convert, particularly, the result obtained after the derivative and the partial derivative of the function are still in the form of the polynomial, the combination of terms is facilitated, and the operation process is simplified;
wherein a, b, c, d and e are expressed as shown in the following formula (5):
a. b, c, d and e are unknowns to be solved, and after the unknowns are solved, the central coordinate (x) of the light spot can be solved according to the formula (5) 0 ，y 0 ）。
And (3) solving by using least squares so as to minimize the sum of squares of the residuals, wherein the sum of squares of the residuals is expressed by the formula (6):
the summation range in the above equation is a circle of pixel points at the periphery of the saturated portion of the light spot, i.e., the profile obtained in fig. 5, and x and y are the spatial positions of the peripheral pixel points, which are taken as known data.
According to the minimum condition, calculating the partial derivative of each variable and making the partial derivative be 0, and then performing item shifting to obtain an equation set (7), wherein the equation set is as follows:
equation set (7) can be further written in the form of a matrix, as shown in equation (8):
the matrix expression forms of B, K and C are respectively shown in formulas (9), (10) and (11), and are specifically as follows:
the spatial coordinates of the intercepted edge pixel points and an expression (9) are utilized to solve a series of parameter values of a, b, c, d and e, and finally, the central coordinate (x) of the light spot can be solved according to a formula (5) 0 ，y 0 ）。
The iterative threshold segmentation in the step S2 specifically comprises the following steps:
s2.1 selecting an initial threshold T 0 ；
S2.2 Using threshold T 0 Dividing an image into two parts, wherein the gray scales of the two parts are R1 and R2 respectively;
s2.3 calculating the mean value of R1 and R2, respectively denoted as mu 1 And mu 2 ；
S2.4, selecting a new threshold value T, and
；
s2.5 if T and T 0 If the absolute value of the difference is smaller than the preset value, T is the final threshold value, otherwise T is enabled 0 T and repeats steps S2.2-S2.5.
The step S4 of transversely scanning the image includes the specific steps of:
s4.1.1: scanning a first line of the image, recording the number of points with pixel values of 1 in the line, and pressing the points into a stack;
s4.1.2: traversing all the rows, and repeating the step of scanning the first row in the step S4.1.1 for other rows;
s4.1.3: reading elements in the stack one by one, and recording the reading sequence;
s4.1.4: the sequence with the longest non-zero values that can be read out continuously is found, and the reading order of the sequence corresponds to the row position of the main spot.
The specific steps of longitudinally scanning the image in the step S4 are as follows:
s4.2.1: scanning a first column of the image, recording the number of points with pixel values of 1 in the column, and pressing the points into a stack;
s4.2.2: traversing all columns, repeating the step of scanning the first column in step S4.2.1 for other rows;
s4.2.3: reading elements in the stack one by one, and recording the reading sequence;
s4.2.4: the longest sequence of non-zero values that can be read out continuously is found, the read-out order of the sequence corresponding to the column position of the main spot.
The initial threshold value T 0 Is the average of the maximum and minimum gray values in the image.
The preset value is 0.1.
The invention also comprises an electronic device comprising a memory storing a computer program and a processor implementing the steps of any of the above methods when the processor executes the computer program.
The invention also includes a computer readable storage medium for storing computer instructions which, when executed by a processor, perform the steps of any of the methods described above.
The memory in the embodiments of the present application may be either volatile memory or nonvolatile memory, or may include both volatile and nonvolatile memory. The non-volatile memory may be a Read Only Memory (ROM), a Programmable ROM (PROM), an Erasable PROM (EPROM), an electrically Erasable EPROM (EEPROM), or a flash memory. Volatile memory can be Random Access Memory (RAM), which acts as external cache memory. By way of example, but not limitation, many forms of RAM are available, such as Static Random Access Memory (SRAM), dynamic Random Access Memory (DRAM), synchronous Dynamic Random Access Memory (SDRAM), double data rate SDRAM, enhanced SDRAM, SLDRAM, synchronous Link DRAM (SLDRAM), and direct rambus RAM (DR RAM). It should be noted that the memories of the methods described herein are intended to comprise, without being limited to, these and any other suitable types of memories.
In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, cause the processes or functions described in accordance with the embodiments of the application to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored on a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, from one website, computer, server, or data center to another website, computer, server, or data center via wire (e.g., coaxial cable, fiber optic, digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device, such as a server, a data center, etc., that incorporates one or more of the available media. The usable medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a magnetic tape), an optical medium (e.g., a Digital Video Disk (DVD)), or a semiconductor medium (e.g., a Solid State Disk (SSD)), among others.
In implementation, the steps of the above method may be performed by integrated logic circuits of hardware in a processor or instructions in the form of software. The steps of a method disclosed in connection with the embodiments of the present application may be directly implemented by a hardware processor, or may be implemented by a combination of hardware and software modules in a processor. The software modules may be located in ram, flash, rom, prom, or eprom, registers, etc. as is well known in the art. The storage medium is located in a memory, and a processor reads information in the memory and completes the steps of the method in combination with hardware of the processor. To avoid repetition, it is not described in detail here.
It should be noted that the processor in the embodiments of the present application may be an integrated circuit chip having signal processing capability. In implementation, the steps of the above method embodiments may be performed by integrated logic circuits of hardware in a processor or instructions in the form of software. The processor described above may be a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components. The various methods, steps, and logic blocks disclosed in the embodiments of the present application may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in connection with the embodiments of the present application may be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor. The software module may be located in ram, flash memory, rom, prom, or eprom, registers, etc. storage media as is well known in the art. The storage medium is located in a memory, and a processor reads information in the memory and completes the steps of the method in combination with hardware of the processor.
The method is suitable for light spot extraction based on a liquid crystal space light closed-loop system, and has higher operation speed on the premise of ensuring high precision compared with other extraction and positioning methods.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (8)
1. A light spot high-precision extraction positioning method based on a liquid crystal light closed-loop system is characterized by comprising the following steps:
s1, performing median filtering processing on an original diffraction spot image acquired by a CCD (charge coupled device);
s2, performing threshold segmentation on the light spot image subjected to median filtering by an iteration method and outputting the image;
s3, performing open operation on the image output in the S2;
s4, performing transverse scanning and longitudinal scanning on the image subjected to the opening operation, and searching a connected region with the largest transverse and longitudinal spans, namely a region where the target light spot is located;
s5, according to the area where the target light spot is obtained in the S4, extracting an edge contour line of a target light spot saturated plane area in the image subjected to median filtering in the S2, specifically: traversing the spatial region where the target light spot is located, finding out the pixel point with the pixel value of 255 adjacent to the pixel point smaller than 255, and performing Gaussian sectional fitting on the extracted edge contour line, wherein the distribution expression of the edge pixel point is as follows:
wherein: x and y are the horizontal and vertical coordinates of the pixel points in the image, x 0 And y 0 Is the spatial position of the vertex of the sigmoid, delta x And delta y Is the variance of the Gaussian surface function, and A is the amplitude;
A、δx、δy、x 0 and y 0 For undetermined parameters, performing least square fitting by taking a distribution expression of edge pixel points as a target function to obtain x 0 And y 0 ，x 0 ，y 0 The coordinate of the light spot center is obtained;
expressing the distribution expression of the edge pixel points in a logarithmic mode, wherein the logarithmic expression is as follows:
expressing the logarithmic expression in the form of a quadratic polynomial, wherein the quadratic polynomial is specifically as follows:
ln 255 ＝ax 2 +by 2 +cx+by+e，
wherein the expressions of a, b, c, d and e are specifically as follows:
a. b, c, d and e are unknowns to be solved, and then the central coordinate x of the light spot is solved according to the expression of a, b, c, d and e 0 ，y 0 ；
And solving by using least squares to minimize the sum of squares of the residuals, wherein the expression of the sum of squares of the residuals is as follows:
Q＝∑(ax 2 +by 2 +cx+dy+e-ln 255 ) 2 ，
the summation range in the residual square sum expression is a circle of pixel points at the periphery of the saturated part of the light spot, and x and y are the spatial positions of the peripheral pixel points and are taken as known data to be brought in;
according to the minimum condition, calculating the partial derivative of each variable and making the partial derivative be 0, and then performing item shifting to obtain an equation set, wherein the equation set is as follows:
writing the equation set into an expression form of a matrix, wherein the matrix is specifically as follows:
BK＝C
BK＝C，
wherein the matrix expressions of B, K and C are respectively as follows:
the values of parameters a, B, c, d and e are solved by using the intercepted space coordinates of the edge pixel points and the matrix expression of B, and finally the central coordinate x of the light spot is solved according to the expressions of a, B, c, d and e 0 ，y 0 。
2. The method according to claim 1, wherein the iterative threshold segmentation in step S2 specifically comprises the steps of:
s2.1 selecting an initial threshold T 0 ；
S2.2 Using threshold T 0 Dividing an image into two parts, wherein the gray scales of the two parts are R1 and R2 respectively;
s2.3 calculating the mean value of R1 and R2, respectively denoted as mu 1 And mu 2 ；
S2.4, selecting a new threshold value T, and
s2.5 if T and T 0 If the absolute value of the difference is smaller than the preset value, T is the final threshold value, otherwise T is enabled 0 T and repeat steps S2.2-S2.5.
3. The method according to claim 1, wherein the step S4 of scanning the image laterally comprises the following specific steps:
s4.1.1: scanning a first line of the image, recording the number of points with pixel values of 1 in the line, and pressing the points into a stack;
s4.1.2: traversing all the rows, and repeating the step of scanning the first row in the step S4.1.1 for other rows;
s4.1.3: reading elements in the stack one by one, and recording the reading sequence;
s4.1.4: the sequence with the longest non-zero values that can be read out continuously is found, and the reading order of the sequence corresponds to the row position of the main spot.
4. The method according to claim 1, wherein the step S4 of longitudinally scanning the image comprises the following specific steps:
s4.2.1: scanning a first column of the image, recording the number of points with the pixel value of 1 in the column, and pressing the points into a stack;
s4.2.2: traversing all columns, repeating the step of scanning the first column in step S4.2.1 for other rows;
s4.2.3: reading elements in the stack one by one, and recording the reading sequence;
s4.2.4: the longest sequence of non-zero values that can be read out continuously is found, the read-out order of the sequence corresponding to the column position of the main spot.
5. Method according to claim 2, characterized in that said initial threshold T is 0 Is the average of the maximum and minimum gray values in the image.
6. The method according to claim 2, characterized in that said preset value is 0.1.
7. An electronic device comprising a memory and a processor, the memory storing a computer program, wherein the processor, when executing the computer program, performs the steps of the method according to any of claims 1-6.
8. A computer-readable storage medium storing computer instructions, which when executed by a processor implement the steps of the method of any one of claims 1 to 6.
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