Calibration method and device for motion stage

Abstract

The application provides a kind of motion platform calibration method and its device, belong to the technical field of semiconductor manufacturing, this method is with line segment mark and characteristic mark calibration mark plate is placed on motion platform, collect motion platform before and after rotating mark plate image and extract each line segment mark and the position coordinates of characteristic mark before and after rotating;According to the position coordinates, the cosine value and the sine value of the rotation angle are calculated by constructing the direction vector, to determine the rotation angle of motion platform;Again according to the position coordinates, the perpendicular bisector unit vector is determined by calculating each connecting line vector, combined with the rotation angle, the distance of the rotation center along the unit vector is calculated, and then combined with the rotation direction to determine the position coordinates of the rotation center of motion platform.The application avoids the transmission and accumulation of mechanical and assembly errors, avoids the systematic deviation of fitting processing, and the calibration process is intuitive and easy to operate, which effectively guarantees the motion control precision and stability of motion platform.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and specifically to a calibration method and apparatus for a motion stage. Background Technology

[0002] In the semiconductor manufacturing field, motion stages are used to support and move wafers and other processing objects to meet the positioning requirements of various manufacturing stages. Their control is of great significance to product quality and production efficiency. Especially for motion stages with an Rz rotation axis (referring to the axis of rotation around the z-axis), the calibration and alignment of their rotation angle and rotation center are the core points to ensure the accuracy of the motion stage. However, current methods for calibrating the rotation angle and rotation center of motion stages mostly rely on the coordinated operation of multiple modules such as cameras, motion stage moving devices, and alignment stage moving devices. This approach has obvious drawbacks: First, the mechanical contact, motion control, and data acquisition stages of each module introduce various error sources, such as the accuracy limitations of measuring tools and the repeatability errors of the motion stage and alignment stage. Moreover, errors accumulate continuously in multiple measurements and data fitting, seriously reducing the accuracy of the calibration results. Second, the multi-module coordinated operation process is complex and susceptible to human interference, which in turn affects the accuracy and reliability of the calibration. Summary of the Invention

[0003] This application provides a calibration method and apparatus for a motion table, aiming to solve the problem of how to calibrate the rotation angle and rotation center of the motion table.

[0004] In a first aspect, this application provides a calibration method for a motion table, the method comprising:

[0005] Place the calibration marker plate with line segment marks and feature marks on the motion table, acquire images of the marker plate before and after the motion table rotates, and extract the position coordinates of each line segment mark and each feature mark from the acquired images before and after rotation.

[0006] Construct a direction vector based on the position coordinates before and after rotation, and calculate the cosine and sine values ​​of the rotation angle based on the constructed direction vector to determine the rotation angle of the motion table;

[0007] Calculate the vectors of each connecting line based on the position coordinates before and after rotation, determine the unit vector of the perpendicular bisector based on the connecting line vectors, calculate the distance of the rotation center along the unit vector in combination with the rotation angle, and then determine the position coordinates of the rotation center of the motion table in combination with the rotation direction.

[0008] Secondly, this application also provides a calibration device for a motion table, the device comprising:

[0009] The image acquisition module is used to place a calibration mark plate with line segment marks and feature marks on a motion table, acquire images of the mark plate before and after the motion table rotates, and extract the position coordinates of each line segment mark and each feature mark before and after rotation from the acquired images;

[0010] The rotation angle calculation module is used to construct a direction vector based on the position coordinates before and after rotation, and to calculate the cosine and sine values ​​of the rotation angle based on the constructed direction vector in order to determine the rotation angle of the motion table.

[0011] The rotation center determination module is used to calculate the vectors of each connecting line based on the position coordinates before and after rotation, determine the unit vector of the perpendicular bisector based on the connecting line vectors, calculate the distance of the rotation center along the unit vector in combination with the rotation angle, and then determine the position coordinates of the rotation center of the motion table in combination with the rotation direction.

[0012] This application provides a calibration method and apparatus for a motion table. First, a calibration marker plate with specific markings is placed on the motion table. Images of the marker plate before and after rotation are acquired, and the position coordinates of each line segment mark and feature mark are extracted from the images. Then, a direction vector is constructed using the position coordinates, and the cosine and sine values ​​of the rotation angle are calculated to determine the rotation angle. Finally, a connecting vector is calculated based on the position coordinates before and after rotation to determine the perpendicular bisector unit vector. Based on this unit vector and the rotation angle, the distance of the rotation center along the unit vector is calculated. Finally, combined with the rotation direction, the position coordinates of the rotation center are determined, thereby calibrating the rotation angle and rotation center of the motion table.

[0013] Therefore, this application avoids the error propagation and accumulation caused by mechanical errors and assembly deviations by placing a calibration mark plate with specific markings on the motion stage, acquiring images before and after rotation, and extracting the position coordinates of each line segment mark and feature mark. Algorithmically, the rotation angle is calculated by constructing a direction vector using the position coordinates, and the rotation center position coordinates are determined by calculating the connecting vector based on the coordinates. This calculation is based on the geometric relationship of the mark pattern before and after rotation, effectively avoiding systematic deviations caused by fitting processing. The entire calibration process is intuitive and easy to operate, facilitating practical application and effectively ensuring the motion control accuracy and stability of the motion stage. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1This is a flowchart of the calibration method for the rotation angle and rotation center position coordinates of the motion table provided in this application;

[0016] Figure 2 This is a schematic diagram of the marking pattern provided in this application;

[0017] Figure 3 This is a schematic diagram illustrating the principle of rotation angle calculation provided in this application;

[0018] Figure 4 This is a schematic diagram illustrating the calculation principle of the rotation center provided in this application;

[0019] Figure 5 This is a structural block diagram of the calibration device for the rotation angle and rotation center position coordinates of the motion table provided in this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] In the semiconductor manufacturing industry, motion stages play a crucial role. Their main function is to support and move workpieces such as wafers, aiming to meet the precise positioning requirements of each stage of semiconductor manufacturing. Precise control of motion stages is of paramount importance to product quality and production efficiency.

[0022] Especially for motion stages with an Rz rotation axis (an axis that rotates around the z-axis), precise calibration and alignment of its rotation angle and rotation center are core tasks to ensure the high-precision operation of the motion stage. Only by accurately determining the rotation angle and rotation center can the motion stage accurately position the wafer and other processing objects to the required position when rotating around the z-axis, thereby ensuring the accuracy and stability of the semiconductor manufacturing process, and ultimately affecting product quality and production efficiency.

[0023] However, current methods for calibrating the rotation angle and center of rotation of the motion table mostly require the coordinated operation of multiple modules, including the camera, the motion table moving device, and the alignment stage moving device. This multi-module collaborative approach has significant drawbacks:

[0024] First, throughout the entire operation, various modules introduce multiple sources of error at different stages. For example, the measuring tools themselves have inherent precision limitations, which directly affect the accuracy of the measurement data. Errors arise during repeated positioning of the motion stage and alignment stage; these errors do not cancel each other out during multiple measurements and subsequent data fitting, but rather accumulate. This accumulation of errors severely reduces the accuracy of the final calibration results, causing significant deviations between the actual rotation angle and rotation center of the motion stage and the calibrated values. This, in turn, affects the positioning accuracy of the motion stage, ultimately negatively impacting semiconductor product quality and production efficiency.

[0025] Secondly, multi-module collaborative operation involves multiple stages and steps, making the process quite complex. In actual operation, it is easily affected by human factors, such as the operator's skill level, operating habits, and work status, all of which can lead to differences and errors. These human factors can affect the accuracy of data acquisition and the operating status of the equipment, thus adversely impacting the accuracy and reliability of the overall calibration. This results in calibration results that do not accurately reflect the actual rotational characteristics of the motion table, reducing the control precision and stability of the motion table.

[0026] To address the aforementioned issues, this application provides a calibration method and apparatus for a motion stage. In the semiconductor manufacturing field, motion stages are used to support and move processing objects such as wafers to meet the positioning requirements of various manufacturing stages. The primary purpose of calibrating the motion stage is to ensure its accuracy. Precise calibration of the motion stage's rotation angle and rotation center enables it to accurately position the processing object to the required location during operation, preventing processing errors caused by positioning deviations, thereby improving product quality and yield. Simultaneously, accurate calibration reduces production interruptions and rework caused by inaccurate motion stage positioning, making the production process more efficient and smoother, and improving overall production efficiency. Furthermore, calibrating the rotational characteristics of the motion stage helps maintain stable performance, extends equipment lifespan, and reduces maintenance costs and downtime caused by equipment accuracy issues.

[0027] The calibration method for the motion table described in this application first places a calibration marker board with line segment marks and feature marks on the motion table, and acquires images of the marker board before and after rotation of the motion table. The position coordinates of each line segment mark and each feature mark before and after rotation are extracted from the acquired images. Then, a direction vector is constructed based on the position coordinates. By performing calculations on the direction vector and using trigonometric functions, the cosine and sine values ​​of the rotation angle are calculated to determine the rotation angle of the motion table. Finally, the vectors of each connecting line are calculated based on the position coordinates before and after rotation. The perpendicular bisector unit vector is determined based on geometric properties, and the distance of the rotation center along this unit vector is calculated based on this unit vector and the rotation angle. Combined with the rotation direction, the final position coordinates of the rotation center of the motion table are determined. The following is a detailed description with reference to the accompanying drawings.

[0028] Please refer to Figure 1 , Figure 1 This is a flowchart illustrating the calibration method for the rotation angle and rotation center position coordinates of the motion table provided in this application. A calibration method for a motion table, the method comprising:

[0029] S110, Place the calibration mark plate with line segment marks and feature marks on the motion table, acquire images of the mark plate before and after the motion table rotates, and extract the position coordinates of each line segment mark and each feature mark before and after rotation from the acquired images.

[0030] For example, please refer to Figure 2 , Figure 2 This is a schematic diagram of the marking pattern provided in this application. A calibration marking plate is placed on a motion stage with an Rz rotation axis. The marking pattern is set on the surface of the marking plate, which includes line segment markings and feature markings. The line segment markings are straight line segments with clear edges, distributed in different areas of the marking plate, and have different line widths. The feature markings are patterns with geometric features, such as squares, triangles, quadrilaterals, pentagons, and hexagons; each feature marking is located in different areas of the marking plate and has different geometric features; wherein, the number of line segment markings and feature markings is two or more sets, and there is a difference in brightness or grayscale value between the patterns of the line segment markings and feature markings and the background. The marking pattern adopts a redundant design, which allows for multiple measurements of the calibration results to be taken and the arithmetic mean obtained, significantly reducing random errors and improving the accuracy and reliability of the calibration results.

[0031] For example, a vision system can be used to acquire images of the marker board and obtain the position coordinates of each line segment marker and each feature marker before and after the motion table rotates, as follows:

[0032] The position coordinates of the two endpoints of the i-th group of line segments before rotation are denoted as x-coordinates. i 1. The vertical axis is y i 1, and the x-coordinate is x i 2. The vertical axis is y i 2, that is (x i 1, y i 1) and (x) i 2, y i 2) The position coordinates of the j-th group of feature markers before rotation are denoted as x-coordinate p. j The vertical axis is q j That is (p j q j ).

[0033] For example, such as Figure 2As shown, the endpoint coordinates 1 (x11, y11) and 2 (x12, y12) of the first set of line segment markers are obtained through the vision system.

[0034] The position coordinates of the two endpoints of the i-th group of line segments after rotation are denoted as x-coordinates. i 1′, with the ordinate as y i 1′, and the x-coordinate is x i 2′, with the ordinate as y i 2′, i.e. (x i 1′, y i 1′) and (x i 2′, y i 2′); The position coordinates of the j-th group of feature marks after rotation are denoted as the abscissa p. j ′、ordinate q j ′, that is (p j ′,q j ′).

[0035] For example, such as Figure 2 As shown, the endpoint coordinates 1 (x11′, y11′) and 2 (x12′, y12′) of the first set of line segment markers after rotation are obtained through the vision system.

[0036] S120: Construct a direction vector based on the position coordinates before and after rotation, and calculate the cosine and sine values ​​of the rotation angle based on the constructed direction vector to determine the rotation angle of the motion table.

[0037] For example, two position coordinates can be arbitrarily selected from all position coordinates before rotation to construct a direction vector, which is denoted as . Its horizontal component is V xn The component in the vertical direction is V. yn ,Right now Wherein, the position coordinates are the position coordinates of the line segment markers or the position coordinates of the feature markers; the total number n of position coordinate combinations is calculated by adding twice the number of line segment markers to the number of feature markers, multiplying the sum by the sum minus one, and then dividing the product by two, that is:

[0038]

[0039] Where L is the number of line segment markers and F is the number of feature markers.

[0040] For example, if the selected coordinates are the position coordinates of two sets of line segment markers (e.g., the first set is k1 and the second set is k2), then the direction vector is: the x-coordinate of an endpoint in the first set of line segment markers minus the x-coordinate of an endpoint in the second set of line segment markers, and the y-coordinate of that endpoint in the first set of line segment markers minus the y-coordinate of that endpoint in the second set of line segment markers, i.e. There are two possible endpoint positions for each group of line segment markers, namely m, h∈{1,2}.

[0041] If the selected coordinates are the position coordinates of a set of line segment markers (e.g., k1) and the position coordinates of a set of feature markers (e.g., k2), then the direction vector is: the x-coordinate of an endpoint in the set of line segment markers minus the x-coordinate of the feature marker in the set, and the y-coordinate of the endpoint in the set of line segment markers minus the y-coordinate of the feature marker in the set, i.e. Each group of line segment markers can have two possible endpoint positions, namely m∈{1,2}.

[0042] If the selected coordinates are the position coordinates of two sets of feature markers (e.g., the first set is k1 and the second set is k2), then the direction vector is: the x-coordinate of the first set of feature markers minus the x-coordinate of the second set of feature markers, and the y-coordinate of the first set of feature markers minus the y-coordinate of the second set of feature markers, i.e.

[0043] For example, please refer to Figure 3 , Figure 3 This is a schematic diagram illustrating the principle of rotation angle calculation provided in this application. A direction vector is constructed using the obtained position coordinates 1 (x11, y11) and 2 (x12, y12) of the first set of line segment markers.

[0044] For example, following the same method as constructing the direction vector before rotation, a direction vector is constructed using the rotated position coordinates, denoted as . Its horizontal component is V x ′ n The component in the vertical direction is V. y ′ n ,Right now

[0045] For example, such as Figure 3 As shown, by obtaining the position coordinates 1′(x11′, y11′) and 2′(x12′, y12′) of the first set of rotated line segment markers, a direction vector is constructed.

[0046] Specifically, constructing direction vectors The method is as follows:

[0047] Obtain the position coordinates of the endpoints of the two sets of line segment markers k1 and k2 after rotation, and construct the direction vectors according to the same rules. Here x k1 m′、y k1 m is the coordinate of the endpoint of the k1th group of line segment markers after rotation; x k2 h′、y k2 h′ is the coordinate of the endpoint of the k2th group of line segment markers after rotation.

[0048] Get the position coordinates x of the endpoints of the k1th line segment after rotation. k1 m′、y k1 m′ and the feature position coordinates p after rotation of the k2th group of feature markers k2 ′、q k2 Then construct the direction vector.

[0049]

[0050] Obtain the feature position coordinates of the two sets of feature labels k1 and k2 after rotation, and construct the direction vector. Here p k1 ′、q k1 ′ is the feature position coordinate after rotation of the k1th feature marker, p k2 ′、q k2 ′ is the feature position coordinate after the rotation of the k2th feature marker.

[0051] For example, calculating the cosine and sine values ​​of the rotation angle based on the constructed direction vector to determine the rotation angle of the motion table includes:

[0052] Calculate the magnitude of the direction vectors before and after rotation, calculate the dot product and cross product of the direction vectors before and after rotation, and then calculate the cosine and sine values ​​of the rotation angles corresponding to each group of direction vectors based on the dot product, cross product, and magnitude of the direction vectors before and after rotation. Finally, determine the rotation angle of the motion table based on the sine and cosine values.

[0053] Specifically, calculate the magnitude of the direction vector before and after the rotation: for the direction vector before the rotation... The absolute value, that is Its length is the horizontal component V of the direction vector. xn The square of the component V in the vertical direction yn Add the squares of the two numbers together, and then take the square root of the sum. For the rotated direction vector The absolute value, that is Its length is the horizontal component V of the direction vector. x ′ n The square of the component V in the vertical direction t ′ nAdd the squares of the two numbers together, and then take the square root of the sum.

[0054] Calculate the dot product of the direction vectors before and after rotation. n : The horizontal component V of the direction vector before rotation xn The horizontal component V of the rotated direction vector x ′ n Multiply, and add the vertical component V of the direction vector before rotation. yn The component V of the rotational direction vector in the vertical direction y ′ n The result of multiplication, i.e., dot n =V xn ×V x ′ n +V yn ×V y ′ n .

[0055] Calculate the cross product of the direction vectors before and after the rotation. n : The horizontal component V of the direction vector before rotation xn The horizontal component V of the rotated direction vector x ′ n The result of the multiplication is minus the vertical component V of the original direction vector. yn The component V of the rotational direction vector in the vertical direction y ′ n The result of multiplication, i.e., cross n =V xn ×V x ′ n -V yn ×V y ′ n .

[0056] Calculate the rotation angle θ corresponding to each group of direction vectors. n The cosine and sine values: The cosine value is the dot product of the direction vectors before and after the rotation, divided by the direction vector before the rotation. The absolute value and the rotated direction vector The product of the absolute values, that is:

[0057]

[0058] The sine value is the cross product of the direction vectors before and after the rotation, divided by the direction vector before the rotation. The absolute value and the rotated direction vector The product of the absolute values, that is:

[0059]

[0060] To determine the rotation angle θ of the motion table: First, calculate the arctangent of the result of dividing the sine of the rotation angle corresponding to each group of direction vectors by the cosine. Then, sum all the obtained arctangent results and divide the sum by the number of groups of direction vectors.

[0061]

[0062] For example, such as Figure 3 As shown, using the constructed direction vector and direction vector Calculate the rotation angle θ1 of the motion table. Finally, use the arithmetic mean of the rotation angles calculated from all position coordinates to obtain the actual rotation angle θ of the motion table.

[0063] S130: Calculate the vectors of each line based on the position coordinates before and after rotation, determine the unit vector of the perpendicular bisector based on the line vectors, calculate the distance of the rotation center along the unit vector in combination with the rotation angle, and then determine the position coordinates of the rotation center of the motion table in combination with the rotation direction.

[0064] For example, calculating the vectors of each connecting line based on the position coordinates before and after rotation includes:

[0065] Calculate the vector connecting the position coordinates before and after rotation; this vector is denoted as... The connecting vector The component in the horizontal direction is denoted as lig. xo The component in the vertical direction is denoted as lig. yo ,Right now Wherein, the position coordinates are the position coordinates of the line segment markers or the position coordinates of the feature markers; the total number of position coordinates o is the sum of twice the number of line segment markers L and the number of feature markers F, that is, o = 2L + F.

[0066] Specifically, if we select the coordinates of the first endpoint of a group of line segments before rotation (e.g., k1) and the coordinates of the second endpoint of another group of line segments after rotation (e.g., k2), then the connection vector is: the x-coordinate of the second endpoint of the group of line segments after rotation minus the x-coordinate of the first endpoint of the group of line segments before rotation; and the y-coordinate of the second endpoint of the group of line segments after rotation minus the y-coordinate of the first endpoint of the group of line segments before rotation, that is:

[0067]

[0068] If we select the coordinates of the first endpoint of a group of line segments (e.g., k1) before rotation and the coordinates of a feature marker (e.g., k2) after rotation, then the connection vector is: the x-coordinate of the feature marker after rotation minus the x-coordinate of the first endpoint of the group of line segments before rotation, and the y-coordinate of the feature marker after rotation minus the y-coordinate of the first endpoint of the group of line segments before rotation, that is:

[0069]

[0070] If we select the feature position coordinates of one feature marker before rotation (e.g., k1) and the feature position coordinates of another feature marker after rotation (e.g., k2), then the connecting vector is: the x-coordinate of the feature marker after rotation minus the x-coordinate of the feature marker before rotation, and the y-coordinate of the feature marker after rotation minus the y-coordinate of the feature marker before rotation, that is:

[0071]

[0072] For example, please refer to Figure 4 , Figure 4 This is a schematic diagram illustrating the principle of rotation center calculation provided in this application. Connecting vector 1 and connecting vector 2 are obtained through the calculation of position coordinates.

[0073] For example, determining the unit vector of the perpendicular bisector and the distance of the rotation center along that unit vector based on the connecting vector includes:

[0074] Calculate the magnitude L of each connecting vector. o Its calculation method is to convert the horizontal component lig of the connecting vector into a linear component. xo The square of lig and its component in the vertical direction yo Add the squares of the two numbers together, and then take the square root of the sum, which is:

[0075]

[0076] Calculate the coordinates M of the midpoint of the connecting vector. o =(M xo M yo There are three possibilities:

[0077] If the selected coordinates are the coordinates of the first endpoint of a line segment marker before rotation (e.g., k1) and the coordinates of the second endpoint of a line segment marker after rotation (e.g., k2), the coordinates of the midpoint are half the sum of the x-coordinates and half the sum of the y-coordinates of these two endpoints, that is:

[0078]

[0079] If the selected coordinates are the coordinates of the first endpoint of a line segment marker before rotation (e.g., k1) and the coordinates of a feature marker after rotation (e.g., k2), the midpoint coordinates are half the sum of the x-coordinate of the feature marker and the x-coordinate of the line segment marker endpoint, and half the sum of the y-coordinate of the feature marker and the y-coordinate of the line segment marker endpoint, that is:

[0080]

[0081] If the selected feature position coordinates are those of a feature marker before rotation (e.g., k1) and another feature marker after rotation (e.g., k2), the midpoint coordinates are half the sum of the x-coordinates and half the sum of the y-coordinates of these two feature markers, that is:

[0082]

[0083] like Figure 4 As shown, by calculating the magnitude and midpoint position of the connecting vectors, we can obtain the magnitude L1 and midpoint coordinates M1 of connecting vector 1, and the magnitude L2 and midpoint coordinates M2 of connecting vector 2.

[0084] For example, determining the unit vector of the perpendicular bisector and the distance of the rotation center along that unit vector based on the connecting vector includes:

[0085] Calculate the slope of each connecting vector. o Its calculation method is the horizontal component lig of the connecting vector. xo Divide by the vertical component lig yo ,Right now:

[0086]

[0087] Calculate the slope of the perpendicular bisector of each connecting vector. o The calculation method is the negative reciprocal of the slope of the connecting vector, that is:

[0088]

[0089] Among them, the magnitude |m| of the unit vector of the perpendicular bisector is calculated. o It is the slope of the perpendicular bisector, which is 1. o Add the squares of the two numbers together, and then take the square root of the sum, which is:

[0090]

[0091] Calculate the unit vector of the perpendicular bisector of each connecting vector. The horizontal component of this unit vector is the reciprocal of the magnitude of the unit vector along the perpendicular bisector, and the vertical component is the slope of the perpendicular bisector divided by the magnitude of the unit vector along the perpendicular bisector. That is:

[0092]

[0093] Calculate the distance d between the center of rotation and the unit vector of the perpendicular bisector of each connecting vector. o The distance is the magnitude of the connecting vector divided by the tangent of twice the rotation angle of the motion platform, i.e.:

[0094]

[0095] like Figure 4 As shown, d1 is calculated based on the rotation angle θ of the motion table and the geometric relationship between the distance of the rotation center along the perpendicular bisector of each connecting vector 1 and the length of the magnitude of the connecting vector. Similarly, the distance d2 of the rotation center along the perpendicular bisector of the connecting vector 2 can also be obtained.

[0096] For example, determining the coordinates of the rotation center of the motion table in conjunction with the rotation direction includes:

[0097] The rotation direction is determined by the sine of the rotation angle and the relationship between the vision system and the horizontal direction of the motion table coordinate system; the rotation center position coordinates are calculated from the vectors of each line based on the rotation direction; and the rotation center position coordinates of the motion table are obtained based on the rotation center position coordinates.

[0098] Specifically, determining the direction of rotation based on the sine of the rotation angle and the relationship between the vision system and the horizontal direction of the motion table coordinate system includes:

[0099] When the pixel coordinate system of the vision system is in the same or opposite direction to the horizontal direction of the motion table coordinate system, if the sine value is greater than 0, the rotation direction is clockwise; if the sine value is less than 0, the rotation direction is counterclockwise.

[0100] When the pixel coordinate system of the vision system and the motion table coordinate system are unidirectionally opposite in the horizontal direction, if the sine value is greater than 0, the rotation direction is counterclockwise; if the sine value is less than 0, the rotation direction is clockwise.

[0101] Specifically, the coordinates of the rotation center position derived from the connecting vectors based on the rotation direction include:

[0102] If the rotation direction is counterclockwise, then the coordinates C of the rotation center position are calculated using the vectors connecting the lines. o =(C xo C yo ), its x-coordinate C xo M is the x-coordinate of the midpoint of the connecting vector. xoSubtract the distance d in the direction of the perpendicular bisector of the connecting vector. o The horizontal component of the unit vector of the perpendicular bisector ox The product of, with the ordinate C yo M is the ordinate of the midpoint of the connecting vector. yo Subtract the distance d in the direction of the perpendicular bisector of the connecting vector. o perpslope, the perpendicular component of the unit vector of the perpendicular bisector o / |m| o The product of, i.e.:

[0103]

[0104] If the rotation direction is clockwise, then the coordinates C of the rotation center position are calculated using the vectors connecting the lines. o =(C xo C yo ), its x-coordinate C xo M is the x-coordinate of the midpoint of the connecting vector. xo Add the distance d in the direction of the perpendicular bisector of the connecting vector o The horizontal component of the unit vector of the perpendicular bisector ox The product of, with the ordinate C yo M is the ordinate of the midpoint of the connecting vector. yo Add the distance d in the direction of the perpendicular bisector of the connecting vector o perpslope, the perpendicular component of the unit vector of the perpendicular bisector o / |m| o The product of, i.e.:

[0105]

[0106] Specifically, obtaining the rotation center coordinates of the motion table based on the rotation center coordinates of each connecting vector includes:

[0107] Sum the x-coordinates of all the rotation center position coordinates calculated from each connecting vector, ∑C xo Then divide by the number of connecting vectors o, and sum the ordinates ∑C yo Then, divide by the number of connecting vectors o to obtain the coordinates C of the rotation center of the motion table, that is:

[0108]

[0109] In summary, compared with the prior art, this application has many beneficial technical effects: In terms of mechanical structure implementation, relying solely on the measurement accuracy of a single camera effectively avoids the transmission and accumulation of errors caused by mechanical errors and assembly deviations; in terms of algorithm, geometric calculation is used, eliminating the need for fitting points, curves, or trajectories, thus avoiding systematic biases that may be introduced by fitting algorithms; the marking pattern consists of line segment markings of straight line segments and feature markings of geometrically characteristic patterns, employing a redundant design that allows for multiple measurements of the calibration results and taking the arithmetic mean, effectively reducing random errors and improving the robustness of rotation angle and rotation center calibration; in terms of operation, no complex procedures are required, and the calibration process is intuitive and easy to operate.

[0110] The calibration device for the motion table provided in this application will be described below. The calibration device for the motion table described below can be referred to in correspondence with the calibration method for the motion table described above.

[0111] Please refer to Figure 5 , Figure 5 This is a structural block diagram of the calibration device for the rotation angle and rotation center position coordinates of a motion table provided in this application. A calibration device 500 for a motion table includes an image acquisition module 510, a rotation angle calculation module 520, and a rotation center determination module 530.

[0112] For example, the image acquisition module 510 is used to place a calibration mark plate with line segment marks and feature marks on a motion table, acquire images of the mark plate before and after the motion table rotates, and extract the position coordinates of each line segment mark and the position coordinates of each feature mark before and after rotation from the acquired images.

[0113] For example, the rotation angle calculation module 520 is used to construct a direction vector based on the position coordinates before and after rotation, and calculate the cosine and sine values ​​of the rotation angle based on the constructed direction vector to determine the rotation angle of the motion table.

[0114] For example, the rotation center determination module 530 is used to calculate the connecting vectors based on the position coordinates before and after rotation, determine the perpendicular bisector unit vector based on the connecting vectors, calculate the distance of the rotation center along the unit vector in combination with the rotation angle, and determine the rotation center position coordinates of the motion table in combination with the rotation direction.

[0115] Understandably, the calibration device for this motion table uses three modules working collaboratively to address the calibration of its rotation angle and center of rotation. The image acquisition module first places a calibration marker plate with specific line segment and feature marks on the motion table, acquiring images of the marker plate before and after rotation. It then extracts the position coordinates of each line segment and feature mark from these images. The rotation angle calculation module uses the position coordinates obtained by the image acquisition module to construct a direction vector. It then calculates the cosine and sine values ​​of the rotation angle using this direction vector, thereby determining the rotation angle of the motion table. Similarly, the rotation center determination module calculates the connecting line vectors based on the position coordinates provided by the image acquisition module. Based on these connecting line vectors, it determines the perpendicular bisector unit vector, calculates the distance of the rotation center along this unit vector using the rotation angle, and finally determines the position coordinates of the rotation center of the motion table using the rotation direction, thus completing the calibration of the motion table's rotation angle and center of rotation.

[0116] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A calibration method for a motion table, characterized in that, The method includes: Place the calibration marker plate with line segment marks and feature marks on the motion table, acquire images of the marker plate before and after the motion table rotates, and extract the position coordinates of each line segment mark and each feature mark from the acquired images before and after rotation. Construct direction vectors based on the position coordinates before and after rotation, calculate the magnitude, dot product, and cross product of the direction vectors before and after rotation, and calculate the cosine and sine values ​​of the rotation angle corresponding to each group of direction vectors based on the dot product, cross product, and magnitude of the direction vectors before and after rotation. First, calculate the arctangent of the result of dividing the sine value of the rotation angle corresponding to each group of direction vectors by the cosine value, and add up all the obtained arctangent results. Then, divide the sum by the number of groups of direction vectors to determine the rotation angle of the motion table. Calculate the vectors of each connecting line based on the position coordinates before and after rotation, determine the unit vector of the perpendicular bisector based on the connecting line vectors, calculate the distance of the rotation center along the unit vector in combination with the rotation angle, and then determine the position coordinates of the rotation center of the motion table in combination with the rotation direction.

2. The calibration method for the motion table according to claim 1, characterized in that, The line segment markings are straight line segments, and each line segment marking is distributed in different areas of the marking board and has a different line width; The feature markers are patterns with geometric features, and each feature marker is located in a different area of ​​the marking plate and has different geometric features; The number of line segment markers and feature markers are two or more, and there is a difference in brightness or grayscale value between the patterns of the line segment markers and feature markers and the background.

3. The calibration method for the motion table according to claim 1, characterized in that, The process of acquiring images of the marker board before and after the motion table rotation, and extracting the position coordinates of each line segment marker and each feature marker from the acquired images before and after rotation, includes: The position coordinates of the two endpoints of the i-th group of line segments before rotation are denoted as x-coordinates. The vertical axis is and the x-axis is The vertical axis is The position coordinates of the j-th feature marker before rotation are denoted as the x-coordinate. The vertical axis is ; The position coordinates of the two endpoints of the i-th group of line segments after rotation are denoted as x-coordinates. The vertical axis is and the x-axis is The vertical axis is The position coordinates of the j-th group of feature markers after rotation are denoted as the x-coordinate. y-axis .

4. The calibration method for the motion table according to claim 1, characterized in that, The step of constructing the direction vector based on the position coordinates before and after rotation includes: From all the position coordinates before rotation, arbitrarily select two position coordinates to construct a direction vector, which is denoted as . Its horizontal component is The component in the vertical direction is Wherein, the position coordinates are the position coordinates of line segment marks or feature marks; the total number of position coordinate combinations is calculated by adding twice the number of line segment marks to the number of feature marks, multiplying the sum by the sum minus one, and then dividing the product by two.

5. The calibration method for the motion table according to claim 4, characterized in that, The step of constructing the direction vector based on the position coordinates before and after rotation includes: If the position coordinates of two sets of line segment markers are selected, the direction vector is: the x-coordinate of an endpoint in the first set of line segment markers minus the x-coordinate of an endpoint in the second set of line segment markers, and the y-coordinate of the endpoint in the first set of line segment markers minus the y-coordinate of the endpoint in the second set of line segment markers; where, there are two possible endpoint positions for each set of line segment markers. If the selected coordinates are the position coordinates of a set of line segment markers and the position coordinates of a set of feature markers, then the direction vector is: the x-coordinate of an endpoint in the set of line segment markers minus the x-coordinate of the set of feature markers, and the y-coordinate of the endpoint in the set of line segment markers minus the y-coordinate of the set of feature markers; where, there are two possible endpoint positions for each set of line segment markers. If the position coordinates of two sets of feature markers are selected, then the direction vector is: the x-coordinate of the first set of feature markers minus the x-coordinate of the second set of feature markers, and the y-coordinate of the first set of feature markers minus the y-coordinate of the second set of feature markers.

6. The calibration method for the motion table according to claim 4, characterized in that, The step of constructing the direction vector based on the position coordinates before and after rotation includes: Following the same method used to construct the direction vector before rotation, a direction vector is constructed using the rotated position coordinates. This direction vector is denoted as... Its horizontal component is The component in the vertical direction is .

7. The calibration method for the motion table according to claim 1, characterized in that, The calculation of the cosine and sine values ​​of the rotation angle based on the constructed direction vector to determine the rotation angle of the motion table includes: Calculate the magnitude of the direction vector before and after rotation: For the direction vector before rotation... The absolute value of the direction vector, whose length is the horizontal component of the direction vector. The square and the vertical component Add the squares together, then take the square root of the sum; for the rotated direction vector... The absolute value of the direction vector, whose length is the horizontal component of the direction vector. The square and the vertical component Add the squares of the two numbers together, and then take the square root of the sum. Calculate the dot product of the direction vectors before and after rotation: combine the horizontal components of the direction vector before rotation. The horizontal component of the rotational direction vector Multiply, and add the vertical component of the direction vector before rotation. The vertical component of the rotational direction vector The result of multiplication; Calculate the cross product of the direction vectors before and after rotation: use the horizontal component of the direction vector before rotation. The horizontal component of the rotational direction vector The result of the multiplication is the result of subtracting the vertical component of the original direction vector. The vertical component of the rotational direction vector The result of multiplication; Calculate the cosine and sine values ​​of the rotation angle corresponding to each group of direction vectors: the cosine value is calculated by dividing the dot product of the direction vectors before and after the rotation by the direction vector before the rotation. The absolute value and the rotated direction vector The product of the absolute values; the sine value is the cross product of the direction vectors before and after the rotation, divided by the direction vector before the rotation. The absolute value and the rotated direction vector The product of the absolute values ​​of .

8. The calibration method for the motion table according to claim 1, characterized in that, The calculation of each connecting vector based on the position coordinates before and after rotation includes: Calculate the vector connecting the position coordinates before and after rotation; this vector is denoted as... The connecting vector The component in the horizontal direction is denoted as The component in the vertical direction is denoted as Wherein, the position coordinates are the position coordinates of line segment marks or feature marks; the total number of position coordinates is the sum of twice the number of line segment marks and the number of feature marks.

9. The calibration method for the motion table according to claim 8, characterized in that, The calculation of each connecting vector based on the position coordinates before and after rotation includes: If we select the coordinates of the first endpoint of a group of line segment markers before rotation and the coordinates of the second endpoint of another group of line segment markers after rotation, then the connection vector is: the x-coordinate of the second endpoint of the group of line segment markers after rotation minus the x-coordinate of the first endpoint of the group of line segment markers before rotation, and the y-coordinate of the second endpoint of the group of line segment markers after rotation minus the y-coordinate of the first endpoint of the group of line segment markers before rotation. If we select the coordinates of the first endpoint of a certain group of line segment markers before rotation and the coordinates of the feature position of a certain feature marker after rotation, then the connecting vector is: the x-coordinate of the feature marker after rotation minus the x-coordinate of the first endpoint of the group of line segment markers before rotation, and the y-coordinate of the feature marker after rotation minus the y-coordinate of the first endpoint of the group of line segment markers before rotation. If we select the feature position coordinates of a feature mark before rotation and the feature position coordinates of another feature mark after rotation, then the connecting vector is: the x-coordinate of the feature mark after rotation minus the x-coordinate of the feature mark before rotation, and the y-coordinate of the feature mark after rotation minus the y-coordinate of the feature mark before rotation.

10. The calibration method for the motion table according to claim 1, characterized in that, Based on the connecting vector, the unit vector of the perpendicular bisector is determined, and the distance of the rotation center along this unit vector is calculated in conjunction with the rotation angle, including: First, calculate the magnitude of each connecting vector, then calculate the coordinates of the midpoint of each connecting vector; next, calculate the slope of each connecting vector to obtain the slope of its perpendicular bisector, then calculate the magnitude of the unit vector of the perpendicular bisector, then calculate the unit vector of the perpendicular bisector of each connecting vector, and finally calculate the distance of the rotation center along the unit vector of the perpendicular bisector of each connecting vector.

11. The calibration method for the motion table according to claim 10, characterized in that, Based on the connecting vector, the unit vector of the perpendicular bisector is determined, and the distance of the rotation center along this unit vector is calculated in conjunction with the rotation angle, including: Calculate the magnitude of each connecting vector: This is done by dividing the horizontal components of the connecting vectors. The square of the component in the vertical direction Add the squares of the two numbers together, and then take the square root of the sum. Calculate the coordinates of the midpoint of the connecting vector, including the following three cases: If the selected coordinates are the coordinates of the first endpoint of a set of line segment marks before rotation and the coordinates of the second endpoint of another set of line segment marks after rotation, the coordinates of the midpoint are half the sum of the x-coordinates and half the sum of the y-coordinates of these two endpoints. If the selected coordinates are the coordinates of the first endpoint of a certain group of line segment marks before rotation and the coordinates of a certain feature mark after rotation, the coordinates of the midpoint are half the sum of the x-coordinate of the feature mark and the x-coordinate of the endpoint of the line segment mark, and half the sum of the y-coordinate of the feature mark and the y-coordinate of the endpoint of the line segment mark. If the selected coordinates are the feature position coordinates of one feature mark before rotation and the feature position coordinates of another feature mark after rotation, the midpoint position coordinates are half the sum of the horizontal coordinates and half the sum of the vertical coordinates of the two feature marks.

12. The calibration method for the motion table according to claim 11, characterized in that, Based on the connecting vector, the unit vector of the perpendicular bisector is determined, and the distance of the rotation center along this unit vector is calculated in conjunction with the rotation angle, including: Calculate the slope of each connecting vector: This is done by taking the horizontal component of the connecting vector. Divide by the component in the vertical direction ; Calculate the slope of the perpendicular bisector of each connecting vector: the calculation method is the negative reciprocal of the slope of the connecting vector; wherein, the magnitude of the unit vector of the perpendicular bisector is calculated by adding 1 to the square of the slope of the perpendicular bisector, and then taking the square root of the sum. Calculate the unit vector of the perpendicular bisector of each connecting vector: the horizontal component of this unit vector is the reciprocal of the magnitude of the unit vector of the perpendicular bisector, and the vertical component is the slope of the perpendicular bisector divided by the magnitude of the unit vector of the perpendicular bisector. Calculate the distance from the center of rotation along the perpendicular bisector of each connecting vector to the unit vector: this distance is the magnitude of the connecting vector divided by the tangent of twice the rotation angle of the motion table.

13. The calibration method for the motion table according to claim 1, characterized in that, The determination of the rotation center position coordinates of the motion table in conjunction with the rotation direction includes: The rotation direction is determined based on the sine of the rotation angle and the relationship between the vision system and the horizontal direction of the motion table coordinate system; the rotation center position coordinates are calculated based on the rotation direction and obtained from the connecting vectors; and the rotation center position coordinates of the motion table are obtained based on the rotation center position coordinates.

14. The calibration method for the motion table according to claim 13, characterized in that, Determining the rotation direction based on the sine of the rotation angle and the relationship between the vision system and the horizontal direction of the motion table coordinate system includes: When the pixel coordinate system of the vision system is in the same or opposite direction to the horizontal direction of the motion table coordinate system, if the sine value is greater than 0, the rotation direction is clockwise; if the sine value is less than 0, the rotation direction is counterclockwise. When the pixel coordinate system of the vision system and the motion table coordinate system are unidirectionally opposite in the horizontal direction, if the sine value is greater than 0, the rotation direction is counterclockwise; if the sine value is less than 0, the rotation direction is clockwise.

15. The calibration method for the motion table according to claim 13, characterized in that, The calculation of the rotation center position coordinates derived from each connecting vector based on the rotation direction includes: If the rotation direction is counterclockwise, the coordinates of the rotation center position are calculated through the connecting vectors. The x-coordinate is the x-coordinate of the midpoint of the connecting vector minus the product of the distance in the direction of the perpendicular bisector of the connecting vector and the horizontal component of the unit vector of the perpendicular bisector. The y-coordinate is the y-coordinate of the midpoint of the connecting vector minus the product of the distance in the direction of the perpendicular bisector of the connecting vector and the vertical component of the unit vector of the perpendicular bisector. If the rotation direction is clockwise, the coordinates of the rotation center position are calculated through each connecting vector. The horizontal coordinate is the product of the horizontal coordinate of the midpoint of the connecting vector plus the distance in the direction of the perpendicular bisector of the connecting vector and the horizontal component of the unit vector of the perpendicular bisector. The vertical coordinate is the product of the vertical coordinate of the midpoint of the connecting vector plus the product of the distance in the direction of the perpendicular bisector of the connecting vector and the vertical component of the unit vector of the perpendicular bisector. The process of obtaining the rotation center position coordinates of the motion table based on the rotation center position coordinates of each connecting vector includes: The coordinates of the rotation center position are obtained by summing the x-coordinates of all the rotation center position coordinates calculated from each connecting vector and dividing by the number of connecting vectors. The coordinates of the y-coordinates are also summed and divided by the number of connecting vectors.

16. A calibration device for a motion table, characterized in that, The device includes: The image acquisition module is used to place a calibration mark plate with line segment marks and feature marks on a motion table, acquire images of the mark plate before and after the motion table rotates, and extract the position coordinates of each line segment mark and each feature mark before and after rotation from the acquired images; The rotation angle calculation module is used to construct direction vectors based on the position coordinates before and after rotation, calculate the magnitude, dot product, and cross product of the direction vectors before and after rotation, and calculate the cosine and sine values ​​of the rotation angle corresponding to each group of direction vectors based on the dot product, cross product, and magnitude of the direction vectors before and after rotation. First, the arctangent of the result of dividing the sine value of the rotation angle corresponding to each group of direction vectors by the cosine value is calculated, and all the obtained arctangent results are added together. Then, the sum is divided by the number of groups of direction vectors to determine the rotation angle of the motion table. The rotation center determination module is used to calculate the vectors of each connecting line based on the position coordinates before and after rotation, determine the unit vector of the perpendicular bisector based on the connecting line vectors, calculate the distance of the rotation center along the unit vector in combination with the rotation angle, and determine the position coordinates of the rotation center of the motion table in combination with the rotation direction.

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