A galvanometer offset considering linear laser self-scanning system calibration method and system

Abstract

The application belongs to the technical field of line laser vision three-dimensional measurement, and discloses a line laser self-scanning system calibration method and system considering mirror deflection, which comprises the following steps: fixing the mirror rotation angle, moving the calibration board back and forth, calculating the three-dimensional coordinates of each point on the laser stripe center line, fitting a single line laser plane, changing the mirror rotation angle to obtain multiple sets of line laser plane parameters; fitting the mirror rotation shaft direction with the multiple sets of line laser planes, and projecting multiple two-dimensional laser lines along the direction; presetting the initial angle of the mirror surface, and using the two-dimensional laser lines to calibrate the related parameters of the mirror; traversing the initial angle of the mirror with a certain step, and repeating the above steps, taking the area of the triangle formed by the incident laser, the reflected laser and the intersection of the mirror surface as the cost function, finding the initial angle with the minimum cost function, and simultaneously optimizing all parameters. The application considers the mirror deflection, and realizes the accurate calibration of various parameters of the line laser self-scanning system.

Description

Technical Field

[0001] This invention belongs to the technical field of line laser vision three-dimensional measurement, and more specifically, relates to a calibration method and system for a line laser self-scanning system that takes into account galvanometer offset. Background Technology

[0002] Line laser vision 3D measurement uses a laser line to construct features for the object being measured. A camera and a line laser form a triangulation system to complete the 3D measurement of a scene. It is an active, non-contact measurement method widely used in industry. There are generally three scanning methods: one where the object being measured moves, one where the measurement system moves, and the last where the measurement system itself can scan. Due to the need for lightweight design, a galvanometer is typically used as the self-scanning mechanism. It reflects the incident laser plane and changes its rotation angle according to the input voltage to achieve self-scanning. The thickness of the galvanometer itself and the offset of the incident laser plane directly affect the position of the output laser plane. Errors caused by galvanometer offset are difficult to eliminate through manufacturing and assembly. The pose error of the laser plane will cause the final 3D reconstruction error, making it difficult to adapt to high-precision industrial 3D measurement.

[0003] Therefore, many scholars have conducted in-depth theoretical and methodological research and innovative structural design for line laser self-scanning systems. Some scholars have adopted an eccentric self-scanning mechanism in their structural design to achieve the coincidence of the reflecting surface and the rotation axis, but this results in huge cost. Most scholars have ignored the two influencing factors mentioned above caused by galvanometer offset. Therefore, it is urgent to design a precise calibration method for line laser self-scanning systems that takes into account galvanometer offset, in order to reduce the measurement errors caused by the offset of the galvanometer surface relative to the rotation axis and the offset of the galvanometer rotation axis relative to the incident laser plane. Summary of the Invention

[0004] To address the above-mentioned deficiencies or improvement needs of existing technologies, this invention provides a calibration method and system for a line laser self-scanning system that considers galvanometer offset. It can accurately calibrate the galvanometer rotation method, the relationship between galvanometer rotation angle and input voltage, the translation from the three-dimensional camera system to the two-dimensional galvanometer system, the galvanometer offset parameters, and the initial angle between the incident laser plane and the galvanometer surface, taking into full account the offset of the galvanometer surface relative to the rotation axis and the offset of the galvanometer rotation axis relative to the incident laser plane.

[0005] To achieve the above objectives, according to one aspect of the present invention, a calibration method for a line laser self-scanning system considering galvanometer offset is provided, comprising: S1: fixing the galvanometer rotation angle, moving a calibration plate back and forth, and obtaining points on the center line of the laser stripe based on the pose of the calibration plate and the principle of constant cross ratio, and constructing a line laser plane based on the points on the center line of the laser stripe; S2: changing the galvanometer rotation angle multiple times using the method in step S1 to obtain multiple sets of line laser planes; S3: obtaining the galvanometer rotation axis direction by fitting multiple sets of line laser planes, and projecting the multiple sets of line laser planes onto the galvanometer rotation axis direction to obtain multiple two-dimensional laser lines; S4: presetting an initial angle between the galvanometer surface and the incident laser, constructing a corrected incident laser line including the offset of the galvanometer rotation axis relative to the incident laser using the initial angle, and constructing a corrected galvanometer surface including the offset of the galvanometer surface relative to the rotation axis using the initial angle; S5: obtaining the corrected intersection point of the corrected incident laser line and the corrected galvanometer surface, and using the corrected intersection point and multiple two-dimensional laser lines... S6: Construct a set of constraint equations for the emitted laser line; S7: Solve the set of constraint equations for the emitted laser line using least squares to obtain the parameters to be determined under the initial angle. The parameters to be determined include: the offset of the galvanometer surface relative to the rotation axis, the offset of the galvanometer rotation axis relative to the incident laser, and the translation parameters from the 3D camera system to the 2D galvanometer system; S8: Construct an error triangle using the corrected incident laser line, the corrected galvanometer surface, and the emitted laser line, and construct a cost function with the minimum area of ​​the error triangle; S9: Update the initial angle with a preset step size, and execute steps S4 to S6 on the updated initial angle to obtain multiple sets of initial angles and their corresponding parameters to be determined. Obtain the initial angle and parameters to be determined that minimize the cost function. Use the initial angle and parameters to be determined that minimize the cost function as the initial values ​​and perform iterative optimization using the LM method to obtain the target initial angle, the offset of the target galvanometer surface relative to the rotation axis, the offset of the target galvanometer rotation axis relative to the incident laser, and the translation parameters from the target 3D camera system to the 2D galvanometer system.

[0006] Preferably, the step S5, which involves constructing a set of emission laser line constraint equations using the correction intersection point and multiple two-dimensional laser lines, specifically includes: S51: obtaining any point on a two-dimensional laser line and connecting the correction intersection point and the arbitrary point to obtain a connecting line; S52: constructing a parallel constraint with the connecting line and the direction vector of the two-dimensional laser to obtain the emission laser line constraint equations; S53: sequentially obtaining multiple emission laser line constraint equations corresponding to multiple two-dimensional laser lines using the methods in steps S51 and S52, thereby obtaining the set of emission laser line constraint equations.

[0007] Preferably, step S1 specifically includes: obtaining the three-dimensional coordinates of each point on the center line of the laser stripe in three-dimensional space, and using the least squares method to fit the three-dimensional coordinates on the center line of the laser stripe to obtain the line laser plane.

[0008] Preferably, the step S3 of obtaining the galvanometer rotation axis direction by fitting multiple sets of line laser planes specifically involves: the direction of the galvanometer rotation axis being perpendicular to the normal of the line laser plane, constructing a vertical constraint, and using the least squares method to traverse all line laser planes based on the vertical constraint, taking the direction corresponding to the least squares solution as the direction of the galvanometer rotation axis.

[0009] Preferably, the correction of the incident light in step S4 G l in for:

[0010] G l in =[a in b in d] T

[0011] Among them, a in = -cos(2θ0-π / 2), b in =sin(2θ0-π / 2), where θ0 is the initial included angle. G l in Let be the corrected incident ray in the galvanometer coordinate system {G}, and d be the offset of the galvanometer axis relative to the incident laser.

[0012] Preferably, the surface of the calibration galvanometer in step S4 is:

[0013] G l j =[a j b j r] T

[0014] in, G l j Let a be the corrected galvanometer surface equation corresponding to the j-th rotation angle in the galvanometer coordinate system {G}, where j = 0, 1, ..., J-1. j = -cos(θ0-jΔθ / 2), b j = sin(θ0 - jΔθ / 2), where θ0 is the initial angle and Δθ is the angle between the laser plane at the j-th turn and the laser plane at the (j+1)-th turn. r is the offset of the galvanometer surface relative to the axis of rotation.

[0015] Preferably, the set of equations for constraining the emitted laser line in step S5 is as follows:

[0016]

[0017] Among them, A j =b in / (a in b j -a j bin ), B j =-b j / (a in b j -a j b in ), C j =a in / (a j b in -a in b j ),

[0018] D j =-a j / (a j b in -a in b j ), v jx Let v be the x-component of the two-dimensional emitted laser line direction at the j-th rotation angle of the galvanometer system. jy Let q be the y-component of the two-dimensional emitted laser line direction at the j-th rotation angle of the galvanometer system. jx Let q be the x-component of a point on the two-dimensional emitted laser line at the j-th rotation angle of the galvanometer system. jy Let y be the y-component of a point on the two-dimensional emitted laser line at the j-th rotation angle of the galvanometer system.

[0019] Preferably, the cost function Cost is:

[0020]

[0021] Where j is the j-th rotation angle of the galvanometer, S Δej The area of ​​the error triangle constructed for correcting the incident laser line, the galvanometer surface, and the outgoing laser line at the j-th rotation angle.

[0022] Preferably, in step S1, the gray-scale centroid method is used to obtain the points on the center line of the laser stripe.

[0023] This application, in another aspect, provides a system for implementing the above-mentioned calibration method for a line laser self-scanning system considering galvanometer offset. The system includes: a first acquisition module: used to fix the galvanometer rotation angle, move a calibration plate back and forth, and obtain points on the center line of the laser stripes based on the pose of the calibration plate and the principle of constant cross-ratio, constructing a line laser plane based on the points on the center line of the laser stripes; a second acquisition module: used to repeatedly change the galvanometer rotation angle using the method in the first acquisition module to obtain multiple sets of line laser planes; a third acquisition module: used to obtain the galvanometer rotation axis direction by fitting multiple sets of line laser planes, projecting the multiple sets of line laser planes onto the galvanometer rotation axis direction to obtain multiple two-dimensional laser lines; a first construction module: used to preset the initial angle between the galvanometer surface and the incident laser, constructing a corrected incident laser line including the offset of the galvanometer rotation axis relative to the incident laser using the initial angle, and constructing a corrected galvanometer surface including the offset of the galvanometer surface relative to the rotation axis using the initial angle; a second construction module: used to obtain the corrected intersection point of the corrected incident laser line and the corrected galvanometer surface, and using the corrected intersection point and multiple two-dimensional laser lines... The system constructs a set of constraint equations for the emitted laser line. A solution module performs least-squares calculations on these equations to obtain the parameters to be determined at the initial angle. These parameters include the offset of the galvanometer surface relative to the rotation axis, the offset of the galvanometer rotation axis relative to the incident laser, and the translation parameters from the 3D camera system to the 2D galvanometer system. A third construction module constructs an error triangle using the corrected incident laser line, the corrected galvanometer surface, and the emitted laser line, and constructs a cost function with the area of ​​the error triangle being minimized. An iterative optimization module updates the initial angle with a preset step size, executes the steps of the first and second construction modules, and the solution module on the updated initial angle, obtains multiple sets of initial angles and their corresponding parameters to be determined, acquires the initial angle and parameters that minimize the cost function, and uses the initial angle and parameters with the minimum cost function as initial values ​​for iterative optimization using the LM method to obtain the target initial angle, the offset of the target galvanometer surface relative to the rotation axis, the offset of the target galvanometer rotation axis relative to the incident laser, and the translation parameters from the target 3D camera system to the 2D galvanometer system.

[0024] In summary, compared with the prior art, the calibration method and system for a line laser self-scanning system considering galvanometer offset provided by the present invention have the following advantages:

[0025] 1. This application obtains multiple sets of linear laser planes by changing the galvanometer rotation angle multiple times, obtains the galvanometer rotation axis direction by fitting multiple sets of linear laser planes, and constructs a corrected incident laser line offset relative to the incident laser and a corrected galvanometer surface offset relative to the rotation axis. By considering the two factors of galvanometer offset, compared with the existing calibration methods, more parameters can be calibrated effectively based on the same calibration data.

[0026] 2. The initial angle between the galvanometer surface and the incident laser plane was determined by a search method, which cleverly separated the linear and nonlinear parts of the system solution. The length and angle parameters were solved step by step, and a method was proposed to solve the initial angle by means of the outgoing laser plane.

[0027] 3. A cost function was constructed based on the area of ​​the error triangle, providing a search basis for the initial angle search and an objective function for iterative optimization. Simultaneous optimization was performed on the analytical solutions of each parameter to improve the calibration accuracy of each parameter and the final 3D measurement accuracy. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the calibration method for a line laser self-scanning system that takes into account galvanometer offset, as described in this application.

[0029] Figure 2 This is a schematic diagram of the line laser self-scanning system considering galvanometer offset in this application;

[0030] Figure 3 This is a schematic diagram of the reference frame of the line laser self-scanning system considering galvanometer offset in this application;

[0031] Figure 4 This is a schematic diagram of the calibration principle of the line laser self-scanning method considering galvanometer offset in this application;

[0032] Figure 5 This is a schematic diagram of data acquisition for the line laser self-scanning method considering galvanometer offset in this application;

[0033] Figure 6 This is a schematic diagram of the cost function of the line laser self-scanning method considering galvanometer offset in this application. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0035] The present invention provides a calibration method for a line laser self-scanning system that takes into account galvanometer offset. The method mainly includes the following steps S1 to S8.

[0036] S1: Fix the rotation angle of the galvanometer, move the calibration plate back and forth, and obtain the points on the center line of the laser stripe according to the pose of the calibration plate and the principle of constant cross ratio. Construct the line laser plane based on the points on the center line of the laser stripe.

[0037] The three-dimensional coordinates of each point on the center line of the laser stripe in three-dimensional space are obtained, and the line laser plane is obtained by fitting the three-dimensional coordinates of the laser stripe center line using the least squares method.

[0038] In a further preferred embodiment, the gray-scale centroid method is preferred to obtain the point on the center of the laser stripe.

[0039] In this embodiment, as Figure 2 As shown, the self-scanning system includes a galvanometer, a line laser emitter, a camera, and an adjustment stage. Figure 3 As shown, the reference system includes a three-dimensional world reference system {W}, a three-dimensional camera reference system {C}, a two-dimensional pixel reference system {U}, a two-dimensional galvanometer reference system {G}, and a two-dimensional intermediate reference system {M}.

[0040] like Figure 5 As shown, the calibration plate moves to a total of I positions, and at each position the galvanometer rotates by the same J angles. The galvanometer angle is controlled by the input voltage, and K points are obtained by extracting the center line of the laser stripe under the corresponding conditions.

[0041] The incident laser plane and the galvanometer surface are pre-calibrated to be parallel, and the camera's extrinsic parameters are given by the calibration plate at the i-th position. A point on the center line of a laser stripe is represented in a two-dimensional pixel reference frame as: U p ijk The camera pose was obtained using the PnP method, and the points on the center line of the laser stripes were obtained using the gray-scale centroid method.

[0042] The transformation method for the calibration plate plane equation from the three-dimensional world reference frame {W} to the three-dimensional camera reference frame {C} is as follows:

[0043]

[0044] in,(·) -T This represents the transpose of the inverse of matrix ·. W π = [0 0 1 0] T It is the representation of the calibration plate plane in the three-dimensional world reference frame {W}. C π i It is the representation of the calibration plate plane in the camera reference frame.

[0045] The projective transformation between a 2D pixel reference frame {U} and a 3D camera reference frame {C} maintains the principle of invariant cross-ratio, meaning that the positional ratios between several collinear points remain fixed and independent of the reference frame. Four collinear points A1, B1, C1, D1 become A2, B2, C2, D2 after projective transformation. The cross-ratio is defined as:

[0046]

[0047] The principle of cross-ratio invariance ensures that CR(A1,B1;C1,D1)=CR(A2,B2;C2,D2), using a number of pixels. U p ijk A line can be fitted to represent the pixel line, which intersects with the reference line formed by the corner points of the calibration plate in the image. Based on the principle of constant cross-ratio, the three-dimensional coordinates of any point on the pixel line in the three-dimensional camera reference frame {C} can be obtained. C P ijk .

[0048] Furthermore, the line laser plane corresponding to the j-th rotation angle of the galvanometer C π .j. Available C P ijk The fitting yielded:

[0049] [ C P ijk 1] T C π ·j· =0

[0050] With the galvanometer rotation angle unchanged, the laser plane under the input voltage of the galvanometer can be obtained by using K points at all I positions based on the least squares method. By traversing all rotation angles, the equations of all laser planes can be obtained.

[0051] S2: Repeat the process in step S1 to change the galvanometer angle multiple times to obtain multiple sets of line laser planes.

[0052] S3: The direction of the galvanometer rotation axis is obtained by fitting multiple sets of line laser planes, and the multiple sets of line laser planes are projected onto the direction of the galvanometer rotation axis to obtain multiple two-dimensional laser lines.

[0053] In a further preferred embodiment, the step of obtaining the galvanometer rotation axis direction using multiple sets of line laser plane fitting specifically involves:

[0054] The direction of the galvanometer rotation axis is perpendicular to the normal of the line laser plane, thus constructing a vertical constraint. Based on the vertical constraint, the least squares method is used to traverse all line laser planes, and the direction corresponding to the least squares solution is taken as the direction of the galvanometer rotation axis.

[0055] The direction of the galvanometer rotation axis is perpendicular to the normal of all laser planes, thus a vertical constraint can be constructed:

[0056] C n j T C m=0

[0057] in, C n j The line laser plane corresponding to the j-th turning angle C π·j· The corresponding normal direction, C m is the direction of the galvanometer rotation axis in the 3D camera reference frame {C}. The least-squares solution of the galvanometer rotation axis direction can be obtained by using all laser planes.

[0058] S4: Set an initial angle between the galvanometer surface and the incident laser, use the initial angle to construct a corrected incident laser line that includes the offset of the galvanometer rotation axis relative to the incident laser, and use the initial angle to construct a corrected galvanometer surface that includes the offset of the galvanometer surface relative to the rotation axis.

[0059] All laser planes are aligned along the direction of the galvanometer rotation axis in the 3D camera reference frame {C}. C Projecting m, we obtain the emitted laser lines in a two-dimensional plane. The first emitted laser line is the x-axis, and the downward direction of the galvanometer rotation axis is the z-axis, where y = z × x. The x-axis and y-axis form a two-dimensional intermediate reference frame {M}. Therefore, the two-dimensional galvanometer reference frame {G} and the intermediate reference frame {M} differ only by a two-dimensional translation vector [x0 y0]. T There is no rotational transformation.

[0060] Furthermore, the transformation from the 3D camera reference frame {C} to the intermediate reference frame {M} is obtained through two rotations. The first rotation aligns the z-axis of the 3D camera reference frame {C} with... C m-alignment, the rotation matrix is ​​obtained from the Rodrigues formula. Then the laser plane is also rotated accordingly, along the axis. C m is projected, and the second rotation is around... C The m-axis is used to align the corresponding remaining two axes; the rotation matrix is... Therefore, only a rotational transformation is needed to move from the 3D camera reference frame {C} to the intermediate reference frame {M}.

[0061] After the above transformations, the three-dimensional output laser plane Cπ can be obtained. ·j· The corresponding emitted laser line in the two-dimensional intermediate reference frame {M} is: M t j Using the point method, it can be expressed as [ M q j M v j ] T , M q j For point, M v j For direction.

[0062] The equation of the emitted laser line, after translation and transformation, and then transformed to the galvanometer reference frame {G}, is as follows:

[0063] G q j= M q j -[x0 y0] T =[q jx -x0 q jy -y0] T

[0064] G v j = M v j =[v jx v jy ] T

[0065] in, G t j =[ G q j G v j ] T Let q be the output laser line in the galvanometer reference frame {G}, where the two reference frames {G} and {M} are only transformed by translation. jx Let q be the x-component of a point on the two-dimensional emitted laser line at the j-th rotation angle of the galvanometer system. jy Let y be the y-component of a point on the two-dimensional emitted laser line at the j-th rotation angle of the galvanometer system.

[0066] like Figure 4 As shown, the unknown quantities to be calibrated are clearly defined and discussed in {G}. If the initial angle θ0 between the galvanometer surface and the incident laser is known, the following four parameters can be calculated simultaneously, including the offset r of the galvanometer surface relative to the rotation axis, the offset d of the galvanometer rotation axis relative to the incident laser, and the two translation components x0 and y0.

[0067] The corrected incident light G l in for:

[0068] G l in =[a in b in d] T

[0069] Among them, a in = -cos(2θ0-π / 2), b in =sin(2θ0-π / 2), where θ0 is the initial included angle. G l in Let be the corrected incident ray in the galvanometer coordinate system {G}, and d be the offset of the galvanometer axis relative to the incident laser.

[0070] The surface of the correction galvanometer is:

[0071] G lj =[a j b j r] T

[0072] in, G l j Let a be the corrected galvanometer surface equation corresponding to the j-th rotation angle in the galvanometer coordinate system {G}, where j = 0, 1, ..., J-1. j = -cos(θ0-jΔθ / 2), b j = sin(θ0 - jΔθ / 2), where θ0 is the initial angle and Δθ is the angle between the laser plane at the j-th turn and the laser plane at the (j+1)-th turn. · represents the inner product, Δθ represents the acute angle, and r represents the offset of the galvanometer surface relative to the rotation axis.

[0073] S5: Obtain the correction intersection point of the correction incident laser line and the correction galvanometer surface, and construct the output laser line constraint equation set using the correction intersection point and multiple two-dimensional laser lines.

[0074] Step S5 specifically includes steps S51 to S52.

[0075] S51: Obtain any point on a two-dimensional laser line, and connect the corrected intersection point and the arbitrary point to obtain a connecting line.

[0076] Correcting the intersection of the incident laser line and the galvanometer surface G p j It can be represented by r and d:

[0077] G p j =[p jx p jy ] T =[A j r+B j d C j r+D j d] T

[0078] Among them, A j =b in / (a in b j -a j b in ), B j =-b j / (a in b j -a j b in ), C j =a in / (a j bin -a in b j ), D j =-a j / (a j b in -a in b j ).

[0079] S52: Construct parallel constraints using the connecting line and the direction vector of the two-dimensional laser to obtain the emission laser line constraint equation.

[0080] G q j and G p j The line connecting two points must intersect with the line connecting the two points. G v j Parallelism exists, therefore parallelism constraints exist:

[0081] G p j - G q j )× G v j =0 (1)

[0082] Where × represents the cross product, A j B j C j D j Substituting into equation (1), we get:

[0083]

[0084] Separating the unknowns yields:

[0085]

[0086] S53: Using the methods in steps S51 and S52, multiple emission laser line constraint equations corresponding to multiple two-dimensional laser lines are obtained sequentially, thereby obtaining the emission laser line constraint equation set.

[0087] Using the above method, a system of linear equations AX = b can be constructed using multiple two-dimensional laser lines:

[0088]

[0089] Among them, A j =b in / (a in b j -a j b in ), B j =-b j / (ain b j -a j b in ), C j =a in / (a j b in -a in b j ), D j =-a j / (a j b in -a in b j ), v jx Let v be the translation in the x-direction from the 3D camera system to the 2D galvanometer system at the j-th rotation angle of the galvanometer. jy Let q be the translation in the y-direction from the 3D camera system to the 2D galvanometer system at the j-th rotation angle of the galvanometer. jx Let q be the x-component of a point on the two-dimensional emitted laser line at the j-th rotation angle of the galvanometer system. jy Let y be the y-component of a point on the two-dimensional emitted laser line at the j-th rotation angle of the galvanometer system.

[0090] S6: Solve the line constraint equations of the emitted laser line by least squares to obtain the offset of the galvanometer surface relative to the rotation axis, the offset of the galvanometer rotation axis relative to the incident laser, and the translation parameters from the three-dimensional camera system to the two-dimensional galvanometer system under the initial angle.

[0091] S7: Construct an error triangle using the corrected incident laser line, the corrected galvanometer surface, and the emitted laser line, and construct a cost function with the minimum area of ​​the error triangle.

[0092] like Figure 6 As shown, if θ0 is accurate, then the galvanometer surface is calibrated. G l j Correcting the incident light G l in Emitting laser beam G t j The three points intersect at a single point; if θ0 is inaccurate, then the three points intersect at three points. Therefore, the triangle formed by the three points is defined as the error triangle, and the sum of the areas of all error triangles is the cost function Cost.

[0093]

[0094] Where j is the j-th rotation angle of the galvanometer, S Δej The area of ​​the error triangle constructed for correcting the incident laser line, the galvanometer surface, and the outgoing laser line at the j-th rotation angle.

[0095] S8: Update the initial included angle with a preset step size, and execute steps S4 to S6 on the updated initial included angle to obtain multiple sets of initial included angles and their corresponding parameters to be determined. Obtain the initial included angle and parameters to be determined that minimize the cost function. Use the initial included angle and parameters to be determined that minimize the cost function as initial values ​​and perform iterative optimization using the LM method to obtain the target initial angle, the offset of the target galvanometer surface relative to the rotation axis, the offset of the target galvanometer rotation axis relative to the incident laser, and the translation parameters from the target three-dimensional camera system to the two-dimensional galvanometer system.

[0096] Furthermore, given an θ0, a cost function value can be obtained. Usually, depending on the actual scenario, a one-dimensional search space W is given for θ0. The values ​​of θ0 are taken with a certain step size, and r, d, x0, y0 and the cost function are calculated. The θ0 that minimizes the cost function is the correct initial angle.

[0097] Using the obtained θ0, r, d, x0, y0 as initial values, and with Cost as the objective function, the LM method is used for iterative optimization, simultaneously optimizing the above five parameters to obtain the optimal solution. All calibration parameters have been obtained, including the galvanometer rotation axis direction. C m is a two-dimensional translation vector [x0 y0] perpendicular to the axis. T , r is the offset of the galvanometer surface relative to the rotation axis, and d is the offset of the galvanometer rotation axis relative to the incident laser.

[0098] Another aspect of this application provides a system for implementing the above-described calibration method for a line laser self-scanning system considering galvanometer offset, the system comprising:

[0099] The first acquisition module is used to fix the rotation angle of the galvanometer, move the calibration plate back and forth, and obtain the points on the center line of the laser stripe according to the pose of the calibration plate and the principle of constant cross ratio. Based on the points on the center line of the laser stripe, a line laser plane is constructed.

[0100] Second acquisition module: used to change the galvanometer angle multiple times using the method in the first acquisition module to obtain multiple sets of line laser planes;

[0101] The third acquisition module is used to obtain the galvanometer rotation axis direction by fitting multiple sets of line laser planes, and to project the multiple sets of line laser planes onto the galvanometer rotation axis direction to obtain multiple two-dimensional laser lines.

[0102] First construction module: used to preset the initial angle between the galvanometer surface and the incident laser, use the initial angle to construct a corrected incident laser line including the offset of the galvanometer rotation axis relative to the incident laser, and use the initial angle to construct a corrected galvanometer surface including the offset of the galvanometer surface relative to the rotation axis;

[0103] The second construction module is used to obtain the correction intersection point between the correction incident laser line and the correction galvanometer surface, and to construct the output laser line constraint equation set using the correction intersection point and multiple two-dimensional laser lines.

[0104] Solving module: used to perform least squares solution on the constrained equations of the outgoing laser line to obtain the parameters to be determined under the initial angle. The parameters to be determined include: the offset of the galvanometer surface relative to the rotation axis, the offset of the galvanometer rotation axis relative to the incident laser, and the translation parameters from the three-dimensional camera system to the two-dimensional galvanometer system.

[0105] The third construction module is used to construct an error triangle with the corrected incident laser line, the corrected galvanometer surface, and the outgoing laser line, and to construct a cost function with the minimum area of ​​the error triangle.

[0106] Iterative optimization module: Update the initial included angle with a preset step size, and execute the first construction module, the second construction module, and the solution module on the updated initial included angle to obtain multiple sets of initial included angles and their corresponding parameters to be determined. Obtain the initial included angle and parameters to be determined that minimize the cost function. Use the initial included angle and parameters to be determined that minimize the cost function as initial values ​​and perform iterative optimization using the LM method to obtain the target initial angle, the offset of the target galvanometer surface relative to the rotation axis, the offset of the target galvanometer rotation axis relative to the incident laser, and the translation parameters from the target 3D camera system to the 2D galvanometer system.

[0107] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A calibration method for a line laser self-scanning system considering galvanometer offset, characterized in that, include: S1: Fix the rotation angle of the galvanometer, move the calibration plate back and forth, and obtain the points on the center line of the laser stripe according to the pose of the calibration plate and the principle of constant cross ratio. Construct the line laser plane based on the points on the center line of the laser stripe. S2: Using the method in step S1, the galvanometer rotation angle is changed multiple times to obtain multiple sets of line laser planes; S3: The direction of the galvanometer rotation axis is obtained by fitting multiple sets of line laser planes, and the multiple sets of line laser planes are projected onto the direction of the galvanometer rotation axis to obtain multiple two-dimensional laser lines; S4: Set an initial angle between the galvanometer surface and the incident laser, use the initial angle to construct a corrected incident laser line that includes the offset of the galvanometer rotation axis relative to the incident laser, and use the initial angle to construct a corrected galvanometer surface that includes the offset of the galvanometer surface relative to the rotation axis. S5: Obtain the correction intersection point between the correction incident laser line and the correction galvanometer surface, and construct the output laser line constraint equation set using the correction intersection point and multiple two-dimensional laser lines; S6: Solve the equations for the constrained line of the emitted laser by least squares to obtain the parameters to be determined under the initial angle. The parameters to be determined include: the offset of the galvanometer surface relative to the rotation axis, the offset of the galvanometer rotation axis relative to the incident laser, and the translation parameters from the three-dimensional camera system to the two-dimensional galvanometer system. S7: Construct an error triangle using the corrected incident laser line, the corrected galvanometer surface, and the outgoing laser line; construct a cost function with the minimum area of ​​the error triangle. S8: Update the initial included angle with a preset step size, and execute steps S4~S6 on the updated initial included angle to obtain multiple sets of initial included angles and their corresponding parameters to be determined. Obtain the initial included angle and parameters to be determined that minimize the cost function. Use the initial included angle and parameters to be determined that minimize the cost function as initial values ​​and perform iterative optimization using the LM method to obtain the target initial angle, the offset of the target galvanometer surface relative to the rotation axis, the offset of the target galvanometer rotation axis relative to the incident laser, and the translation parameters from the target 3D camera system to the 2D galvanometer system.

2. The calibration method for a line laser self-scanning system considering galvanometer offset according to claim 1, characterized in that, Step S5, which involves constructing a set of constraint equations for the emitted laser line using the corrected intersection points and multiple two-dimensional laser lines, specifically includes: S51: Obtain any point on a two-dimensional laser line, and connect the correction intersection point and the arbitrary point to obtain a connecting line; S52: Construct parallel constraints using the connecting line and the direction vector of the two-dimensional laser to obtain the emission laser line constraint equation; S53: Using the methods in steps S51 and S52, multiple emission laser line constraint equations corresponding to multiple two-dimensional laser lines are obtained sequentially, thereby obtaining the emission laser line constraint equation set.

3. The calibration method for a line laser self-scanning system considering galvanometer offset according to claim 1, characterized in that, Step S1 specifically includes: The three-dimensional coordinates of each point on the center line of the laser stripe in three-dimensional space are obtained, and the line laser plane is obtained by fitting the three-dimensional coordinates of the laser stripe center line using the least squares method.

4. The calibration method for a line laser self-scanning system considering galvanometer offset according to claim 1 or 3, characterized in that, The step S3, which involves obtaining the galvanometer rotation axis direction using multiple sets of line laser plane fitting, specifically involves: The direction of the galvanometer rotation axis is perpendicular to the normal of the line laser plane, thus constructing a vertical constraint. Based on the vertical constraint, the least squares method is used to traverse all line laser planes, and the direction corresponding to the least squares solution is taken as the direction of the galvanometer rotation axis.

5. The calibration method for a line laser self-scanning system considering galvanometer offset according to claim 1 or 2, characterized in that, The correction of the incident light in step S4 for: in, , , The initial included angle, For the galvanometer coordinate system The corrected incident light is given by d, where d is the offset of the galvanometer axis relative to the incident laser.

6. The calibration method for a line laser self-scanning system considering galvanometer offset according to claim 5, characterized in that, The surface of the calibration galvanometer mentioned in step S4 is: in, For the galvanometer coordinate system Next j The surface equation of the corrected galvanometer corresponding to each rotation angle. , , , The initial included angle, For the first j The laser plane at the first corner and the first j +1 angle between the laser plane and the lower corner. This represents the total number of galvanometer rotation angles. , For the first j The normal to the line laser plane corresponding to each corner For the first j The normal to the line laser plane corresponding to +1 turn. r This represents the offset of the galvanometer surface relative to the axis of rotation.

7. The calibration method for a line laser self-scanning system considering galvanometer offset according to claim 6, characterized in that, The line constraint equations for the emitted laser in step S5 are as follows: in, , , , , In the galvanometer system j The x-component of the two-dimensional emitted laser line direction at each corner. In the galvanometer system j The y-component of the two-dimensional emitted laser line direction at each corner. In the galvanometer system j The x-component of a point on a two-dimensional emitted laser line at a certain angle. In the galvanometer system j The y-component of a point on a two-dimensional emitted laser line at a certain angle. x 0 and y 0 represents the translation from the target 3D camera system to the 2D galvanometer system.

8. The calibration method for a line laser self-scanning system considering galvanometer offset according to claim 1, characterized in that, The cost function Cost is: in, j For the first galvanometer j At a corner, This represents the total number of galvanometer rotation angles. For the first j The area of ​​the error triangle formed by the incident laser line, the galvanometer surface, and the outgoing laser line at each rotation angle.

9. The calibration method for a line laser self-scanning system considering galvanometer offset according to claim 1, characterized in that, In step S1, the gray-scale centroid method is used to obtain the points on the center line of the laser stripe.

10. A system for implementing the calibration method for a line laser self-scanning system considering galvanometer offset as described in any one of claims 1 to 9, characterized in that, The system includes: The first acquisition module is used to fix the rotation angle of the galvanometer, move the calibration plate back and forth, and obtain the points on the center line of the laser stripe according to the pose of the calibration plate and the principle of constant cross ratio. Based on the points on the center line of the laser stripe, a line laser plane is constructed. Second acquisition module: used to change the galvanometer angle multiple times using the method in the first acquisition module to obtain multiple sets of line laser planes; The third acquisition module is used to obtain the galvanometer rotation axis direction by fitting multiple sets of line laser planes, and to project the multiple sets of line laser planes onto the galvanometer rotation axis direction to obtain multiple two-dimensional laser lines. First construction module: used to preset the initial angle between the galvanometer surface and the incident laser, use the initial angle to construct a corrected incident laser line including the offset of the galvanometer rotation axis relative to the incident laser, and use the initial angle to construct a corrected galvanometer surface including the offset of the galvanometer surface relative to the rotation axis; The second construction module is used to obtain the correction intersection point between the correction incident laser line and the correction galvanometer surface, and to construct the output laser line constraint equation set using the correction intersection point and multiple two-dimensional laser lines. Solving module: used to perform least squares solution on the constrained equations of the outgoing laser line to obtain the parameters to be determined under the initial angle. The parameters to be determined include: the offset of the galvanometer surface relative to the rotation axis, the offset of the galvanometer rotation axis relative to the incident laser, and the translation parameters from the three-dimensional camera system to the two-dimensional galvanometer system. The third construction module is used to construct an error triangle with the corrected incident laser line, the corrected galvanometer surface, and the outgoing laser line, and to construct a cost function with the minimum area of ​​the error triangle. Iterative optimization module: Update the initial included angle with a preset step size, and execute the first construction module, the second construction module, and the solution module on the updated initial included angle to obtain multiple sets of initial included angles and their corresponding parameters to be determined. Obtain the initial included angle and parameters to be determined that minimize the cost function. Use the initial included angle and parameters to be determined that minimize the cost function as initial values ​​and perform iterative optimization using the LM method to obtain the target initial angle, the offset of the target galvanometer surface relative to the rotation axis, the offset of the target galvanometer rotation axis relative to the incident laser, and the translation parameters from the target 3D camera system to the 2D galvanometer system.

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