Method and device for detecting circle center position in laser spot image

Abstract

The invention discloses a method and device for detecting the center position in a laser spot image, and the method comprises the steps: obtaining a laser spot image which is a fuzzy circle / circular ring light spot, and solving the center-of-gravity coordinate of the fuzzy circle / circular ring light spot as an initial center position; calculating radial distances from the initial circle center position along a plurality of different directions of the fuzzy circle / circular ring light spot, and calculating an average value of the radial distances in the different directions as an average radius; based on the average radius, utilizing a least square method to fit a new circle center position; and taking the new circle center position as an initial circle center position, repeating iterative calculation until the difference between the current fitting new circle center position and the previous fitting new circle center position is smaller than a preset threshold value, and determining the current fitting new circle center position as a final circle center position. The method is more accurate in circle center position detection and higher in calculation speed.

Description

Technical Field

[0001] The present invention relates to the field of laser communication technology, and in particular to a method and device for detecting a center position of a circle in a laser spot image. Background Art

[0002] In the application of laser communication, the transmitter uses laser as a carrier to transmit information, and the receiver converts the received laser signal into an electrical signal through a photodetector, and carries information by decoding the beam to achieve the purpose of laser communication. However, laser communication requires very high alignment accuracy between the transmitter and the receiver. However, during the communication process, the laser will be disturbed by the atmosphere, causing the center position of the beam to drift, resulting in signal unlocking, inability to effectively align the optical center position, and information loss. At the same time, the waveform is distorted and diffused, and the center position of the beam is difficult to determine, resulting in uneven signal strength received by the receiver, information transmission errors, increased bit error rate, and reduced channel capacity.

[0003] Therefore, in order to monitor and correct the offset or blur of the light beam, monitoring measures will be added to the system design, such as using a CCD camera or CMOS sensor to capture the image of the light spot, and it is necessary to study the position acquisition algorithm of the blurred circle center and the ring center to reduce information errors caused by signal loss of lock and improve communication quality.

[0004] The existing methods for determining the center of a circle are mainly divided into methods for obtaining the center of a distorted circle and methods for obtaining an obscured circle. For the center of a partially obscured circle, the center position can be determined by the intersection of multiple perpendicular bisectors of chords based on the theory that the perpendicular bisector of the chord passes through the center of the circle; or the unique circle theory can be determined based on three points on the circle to find the center position. However, these methods will calculate multiple centers when used to process diffuse and blurred circles, and the original unique center cannot be determined. The center position is relatively random and time-consuming. At present, the more commonly used method is to obtain the center position by solving the center of gravity of the circle. It obtains the horizontal and vertical coordinates of the center of the circle by solving the center of gravity in the horizontal and vertical directions, but this method does not fully utilize the symmetry of the circle, and there will be large errors when calculating the center of the unevenly distorted circle.

[0005] Therefore, how to provide a method and device for detecting the center position of a circle in a laser spot image with higher accuracy is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0006] In view of the above research status and existing problems, the present invention provides a method and device for detecting the center position of a circle in a laser spot image. Compared with the center of gravity method, the method is more accurate in detecting the center position of a circle and the calculation speed is also faster.

[0007] The present invention provides a method for detecting the center position of a circle in a laser spot image, comprising the following steps:

[0008] S1: Acquire a laser spot image, wherein the spot image contains a blurred circle / ring spot, and obtain the centroid coordinates of the blurred circle / ring spot as the initial circle center position;

[0009] S2: Calculate radial distances in multiple different directions along the blur circle / ring light spot starting from the initial circle center position, and calculate the average value of the radial distances in different directions as the average radius;

[0010] S3: Based on the average radius, fitting a new circle center position using the least squares method;

[0011] S4: taking the new circle center position as the initial circle center position, repeating S2-S3 until the difference between the current fitted new circle center position and the previous fitted new circle center position is less than a predetermined threshold, and then the current fitted new circle center position is determined as the final circle center position.

[0012] Preferably, S1 comprises the following steps:

[0013] S11: Calculate the grayscale value I(x,y) corresponding to the coordinates (x,y) of all pixel points in the laser spot image;

[0014] S12: Calculate the centroid coordinates (x0, y0) of the blur circle / ring light spot in the laser light spot image based on the grayscale value, and use the centroid coordinates as the initial center coordinates of the blur circle / ring light spot:

[0015]

[0016] Preferably, S2 comprises the following steps:

[0017]

[0018] In the formula, R i is the average radius calculated based on i different directions of the blur circle / ring light spot starting from the initial circle center position, (x ij ,y ij ) is the pixel coordinate of the blurred circle / ring light spot, that is, the coordinate of pixel point j in direction i, (x0, y0) is the center coordinate of the blurred circle / ring light spot.

[0019] Preferably, S3 comprises the following steps:

[0020] (x Ri -x k ) 2 +(y Ri -y k ) 2 =R i 2 ;

[0021] In the formula, (x Ri ,y Ri ) is the average radius R of the blur circle / ring spot i The corresponding pixel coordinates, (x k ,y k ) is the new center position of the fitting circle, R i is the average radius calculated based on i different directions of the blur circle / ring light spot starting from the initial center position.

[0022] Preferably, S4 comprises the following steps:

[0023] (x k -x k-1 ) 2 +(y k -y k-1 ) 2 <ε;

[0024] In the formula, (x k ,y k ) is the new center position of the current fitting, (x k-1 ,y k-1 ) is the new center position of the previous fitting, and ε is the predetermined threshold.

[0025] The present invention also provides a device for detecting the center position of a circle in a laser spot image according to the method for detecting the center position of a circle in a laser spot image, comprising:

[0026] An initial circle center position calculation module is used to obtain a laser spot image, wherein the spot image contains a blurred circle / ring spot, and obtain the centroid coordinates of the blurred circle / ring spot as the initial circle center position;

[0027] An average radius calculation module, used to calculate radial distances in multiple different directions along the blur circle / ring light spot starting from the initial circle center position, and calculate the average value of the radial distances in different directions as the average radius;

[0028] The new circle center position fitting module is used to fit the new circle center position based on the average radius using the least squares method, and the new circle center position is fitted by repeatedly calling the average radius calculation module until the difference between the current fitted new circle center position and the previous fitted new circle center position is less than a predetermined threshold, and the current fitted new circle center position is determined as the final circle center position.

[0029] Preferably, the detection device is located at a laser receiving end, and the laser receiving end is used to receive a laser beam carrying information.

[0030] Compared with the prior art, it has the following beneficial effects:

[0031] The present invention can accurately solve the center positions of the blurred distortion circle and the ring in the laser spot image, and the calculation speed is relatively fast.

[0032] By accurately obtaining the center position of the circle, information errors caused by signal loss can be effectively reduced, thereby improving the stability of the laser communication system.

[0033] Compared with traditional methods for determining the center of a circle, such as the center of gravity method, the present invention uses an iterative algorithm to quickly solve the center of a circle position, which not only improves the calculation speed, but also reduces the impact of distortion on the calculation of the center of a circle position, thereby making the calculation more efficient.

[0034] Using the least squares fitting method to obtain the center position of the circle can overcome the error accumulation problem in the calculation of the center position of the irregular or unevenly distorted circle to a certain extent, improve the robustness of the algorithm, and enable it to work stably in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on the provided drawings without creative work.

[0036] Figure 1 A flow chart of a method for detecting the center position of a circle in a laser spot image provided by an embodiment of the present invention;

[0037] Figure 2 The original blurred distorted circular image provided by the embodiment of the present invention;

[0038] Figure 3 A schematic diagram of a comparison circle detection result of an original blurred and distorted circular image provided by an embodiment of the present invention;

[0039] Figure 4 The original blurred distorted ring image provided by the embodiment of the present invention;

[0040] Figure 5 A schematic diagram of the comparison circle detection result of the original blurred and distorted circular ring image provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] like Figure 1 As shown, the first aspect of an embodiment of the present invention discloses a method for detecting the center position of a circle in a laser spot image, comprising the following steps: S1: acquiring a laser spot image, wherein the spot image contains a blurred circle / ring spot, and obtaining the centroid coordinates of the blurred circle / ring spot as the initial center position; S2: calculating the radial distances along multiple different directions of the blurred circle / ring spot starting from the initial center position, and calculating the average value of the radial distances in different directions as the average radius; S3: fitting a new center position based on the average radius using the least squares method; S4: taking the new center position as the initial center position, repeating S2-S3 until the difference between the current fitted new center position and the previous fitted new center position is less than a predetermined threshold, and the current fitted new center position is determined as the final center position.

[0043] It can be understood that the average radius is the average value of the distances from all pixels on the blur circle / ring spot to the center of the circle.

[0044] In one embodiment, S1 includes the following steps:

[0045] S11: Calculate the grayscale value I(x,y) corresponding to the coordinates (x,y) of all pixel points in the laser spot image;

[0046] S12: Calculate the centroid coordinates (x0, y0) of the blurred circle / ring light spot in the laser light spot image based on the gray value, and use the centroid coordinates as the initial center coordinates of the blurred circle / ring light spot:

[0047]

[0048] In one embodiment, S2 includes the following steps:

[0049]

[0050] In the formula, R i is the average radius calculated based on the i different directions of the blur circle / ring light spot starting from the initial center position, (x ij ,y ij ) is the pixel coordinate of the blurred circle / ring light spot, that is, the coordinate of pixel j in the i direction, (x0, y0) is the center coordinate of the blurred circle / ring light spot.

[0051] In one embodiment, S3 includes the following steps:

[0052] (x Ri -x k ) 2 +(y Ri -y k ) 2 =R i 2 ;

[0053] In the formula, (x Ri ,y Ri ) is the average radius R of the blur circle / ring spot i The corresponding pixel coordinates, (x k ,y k ) is the new center position of the fitting circle, R i is the average radius calculated based on i different directions of the blur circle / ring spot starting from the initial center position.

[0054] In one embodiment, S4 includes the following steps:

[0055] (x k -x k-1 ) 2 +(y k -y k-1 ) 2 <ε;

[0056] In the formula, (x k ,y k ) is the new center position of the current fitting, (x k-1 ,y k-1 ) is the new center position of the previous fitting, and ε is the predetermined threshold.

[0057] Taking blurred circles and rings as examples, the blurred laser spot obtained by simulation is usually a distorted circle or ring. The effectiveness of the embodiment method is tested by solving the center position of the circle. In order to make the result more intuitive, a circle with the obtained center position as the center and the average radius as the radius is drawn on the original image.

[0058] Example 1

[0059] like Figure 1 As shown, it is the original blurred distorted circular image. Figure 2 The corresponding detection result image includes a circle with the solved center coordinates as the center and the average radius as the radius, which can accurately reflect the center position and radius of the laser spot.

[0060] Example 2

[0061] like Figure 3 As shown, it is the original blurred distorted ring image. Figure 4 The corresponding detection result image includes a circle with the solved center coordinate as the center and the average radius as the radius, which can also accurately reflect the center position and radius of the laser spot.

[0062] The second aspect of the embodiment of the present invention provides a detection device for the center position of a circle in a laser spot image according to the first aspect of the embodiment, which is used to execute all the steps in the first aspect of the embodiment. It includes: an initial center position calculation module, which is used to obtain a laser spot image, in which the spot image is a blur circle / ring spot, and obtain the centroid coordinates of the blur circle / ring spot as the initial center position; an average radius calculation module, which is used to calculate the radial distances along multiple different directions of the blur circle / ring spot from the initial center position, and calculate the average value of the radial distances in different directions as the average radius; a new center position fitting module, which is used to fit a new center position based on the average radius using the least squares method, and fit the new center position by repeatedly calling the average radius calculation module until the difference between the current fitted new center position and the previous fitted new center position is less than a predetermined threshold, then the current fitted new center position is determined as the final center position.

[0063] In one embodiment, the detection device is located at a laser receiving end, and the laser receiving end is used to receive a laser beam carrying information.

[0064] The embodiment of the present invention obtains the initial value of the center position of the circle based on the centroid method, reduces the influence of distortion by solving the mean of the radial average radius in different directions, establishes a functional relationship between the radius and the center position of the circle, and obtains the center position through least squares fitting. Through multiple iterations, the solved average radius converges to the center position of the circle.

[0065] The above is a detailed introduction to a method and device for detecting the center position of a circle in a laser spot image provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

[0066] In this article, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

Claims

1. A method for detecting the center position of a circle in a laser spot image, characterized in that: The steps include: S1: Acquire a laser spot image, wherein the spot image contains a blurred circle / ring spot, and obtain the centroid coordinates of the blurred circle / ring spot as the initial circle center position; S2: Calculate radial distances in multiple different directions along the blur circle / ring light spot starting from the initial circle center position, and calculate the average value of the radial distances in different directions as the average radius; S3: Based on the average radius, fitting a new circle center position using the least squares method; S4: taking the new circle center position as the initial circle center position, repeating S2-S3 until the difference between the current fitted new circle center position and the previous fitted new circle center position is less than a predetermined threshold, and then the current fitted new circle center position is determined as the final circle center position.

2. The method for detecting the center position of a circle in a laser spot image according to claim 1, characterized in that: The S1 comprises the following steps: S11: Calculate the grayscale value I(x,y) corresponding to the coordinates (x,y) of all pixel points in the laser spot image; S12: Calculate the centroid coordinates (x0, y0) of the blur circle / ring light spot in the laser light spot image based on the grayscale value, and use the centroid coordinates as the initial center coordinates of the blur circle / ring light spot:

3. The method for detecting the center position of a circle in a laser spot image according to claim 1, characterized in that: The S2 comprises the following steps: In the formula, R i is the average radius calculated based on i different directions of the blur circle / ring light spot starting from the initial circle center position, (x ij ,y ij ) is the pixel coordinate of the blurred circle / ring light spot, that is, the coordinate of pixel point j in direction i, (x0, y0) is the center coordinate of the blurred circle / ring light spot.

4. The method for detecting the center position of a circle in a laser spot image according to claim 1, characterized in that: The S3 comprises the following steps: (x Ri -x k ) 2 +(y Ri -y k ) 2 =R i 2 ; In the formula, (x Ri ,y Ri ) is the average radius R of the blur circle / ring spot i The corresponding pixel coordinates, (x k ,y k ) is the new center position of the fitting circle, R i is the average radius calculated based on i different directions of the blur circle / ring light spot starting from the initial center position.

5. The method for detecting the center position of a circle in a laser spot image according to claim 1, characterized in that: The S4 comprises the following steps: (x k -x k-1 ) 2 +(and k -and k-1 ) 2 <e; In the formula, (x k ,y k ) is the new center position of the current fitting, (x k-1 ,y k-1 ) is the new center position of the previous fitting, and ε is the predetermined threshold.

6. A device for detecting the center position of a circle in a laser spot image according to a method for detecting the center position of a circle in a laser spot image according to any one of claims 1 to 5, characterized in that: include: An initial circle center position calculation module is used to obtain a laser spot image, wherein the spot image contains a blurred circle / ring spot, and obtain the centroid coordinates of the blurred circle / ring spot as the initial circle center position; An average radius calculation module, used to calculate radial distances in multiple different directions along the blur circle / ring light spot starting from the initial circle center position, and calculate the average value of the radial distances in different directions as the average radius; The new circle center position fitting module is used to fit the new circle center position based on the average radius using the least squares method, and the new circle center position is fitted by repeatedly calling the average radius calculation module until the difference between the current fitted new circle center position and the previous fitted new circle center position is less than a predetermined threshold, and the current fitted new circle center position is determined as the final circle center position.

7. The device for detecting the center position of a circle in a laser spot image according to claim 6, characterized in that: The detection device is located at a laser receiving end, and the laser receiving end is used to receive a laser beam carrying information.

Images