Calibration method and device of motion platform

Abstract

The invention provides a calibration method and device for a motion table, and belongs to the technical field of semiconductor manufacturing, and the method comprises the steps: placing a calibration marking plate with line segment marks and feature marks on the motion table, collecting the images of the marking plate before and after the rotation of the motion table, and extracting the position coordinates of each line segment mark and feature mark before and after the rotation; constructing a direction vector according to the position coordinates to calculate a cosine value and a sine value of a rotation angle so as to determine the rotation angle of the motion platform; and calculating each connecting line vector according to the position coordinates, determining a vertical bisector unit vector, calculating the distance of the rotation center along the unit vector by combining the rotation angle, and determining the position coordinates of the rotation center of the motion platform by combining the rotation direction. According to the method, transmission and accumulation of mechanical and assembly errors are avoided, systematic deviation of fitting processing is avoided, the calibration process is visual and easy to operate, and the motion control precision and stability of the motion table are powerfully guaranteed.

Description

Technical Field

[0001] The present application relates to the field of semiconductor manufacturing technology, and in particular to a motion stage calibration method and device thereof. Background Art

[0002] In the semiconductor manufacturing field, motion stages are used to carry and move processing objects such as wafers to meet the positioning requirements of various manufacturing links. Their control is of great significance to product quality and production efficiency. In particular, for motion stages with an Rz rotation axis (referring to the axis that rotates around the z-axis), the calibration and alignment of their rotation angle and rotation center are key to ensuring the accuracy of the motion stage. However, current methods for calibrating the rotation angle and rotation center of motion stages often rely on the collaborative operation of multiple modules such as cameras, motion stage mobile devices, and alignment stage mobile devices. This approach has obvious drawbacks: First, each module introduces multiple error sources during the mechanical contact, motion control, and data acquisition stages, such as measurement tool accuracy limitations and repeated positioning errors of the motion stage and alignment stage. Furthermore, errors accumulate during multiple measurements and data fitting, seriously reducing the accuracy of the calibration results. Second, the multi-module collaborative operation process is complex and easily interfered with by human factors, which in turn affects the accuracy and reliability of the calibration. Summary of the Invention

[0003] The present application provides a motion stage calibration method and apparatus thereof, aiming to solve the problem of how to calibrate the rotation angle and rotation center of the motion stage.

[0004] In a first aspect, the present application provides a method for calibrating a motion platform, the method comprising:

[0005] A calibration marker plate with line segment markers and feature markers is placed on a motion stage, images of the marker plate are collected before and after the motion stage is rotated, and the position coordinates of each line segment marker and each feature marker before and after the rotation are extracted from the collected images;

[0006] constructing a direction vector according to the position coordinates before and after the rotation, and calculating the cosine and sine of the rotation angle based on the constructed direction vector to determine the rotation angle of the motion stage;

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

[0008] In a second aspect, the present application further provides a calibration device for a sports platform, the device comprising:

[0009] An image acquisition module is used to place a calibration marker plate with line segment markers and feature markers on the motion stage, capture images of the marker plate before and after the motion stage is rotated, and extract the position coordinates of each line segment marker and each feature marker before and after the rotation from the captured images;

[0010] A rotation angle calculation module is used to construct a direction vector based on the position coordinates before and after the 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 platform;

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

[0012] This application provides a motion stage calibration method and apparatus. First, a calibration marker plate with specific markings is placed on the motion stage. Images of the marker plate before and after the motion stage's rotation are captured, and the position coordinates of each line segment marker and feature marker are extracted from these images. Next, a direction vector is constructed using the position coordinates, and the cosine and sine 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 the rotation to determine the perpendicular bisector unit vector. Based on this unit vector and the rotation angle, the distance of the rotation center along this unit vector is calculated. Finally, the position coordinates of the rotation center are finally determined based on the rotation direction, thereby calibrating the rotation angle and rotation center of the motion stage.

[0013] Therefore, this application avoids the error transmission and accumulation caused by mechanical errors and assembly deviations by placing a calibration marker plate with specific markings on the motion stage, collecting images before and after rotation, and extracting the position coordinates of each line segment marker and feature marker. In terms of algorithm, 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 between the marking pattern before and after rotation, effectively avoiding the systematic deviations caused by fitting processing. The entire calibration process is intuitive and easy to operate, convenient for practical application, and effectively guarantees the motion control accuracy and stability of the motion stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the present application or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0015] Figure 1This is a flow chart of a method for calibrating the rotation angle and rotation center position coordinates of a motion stage provided by the present application;

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

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

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

[0019] Figure 5 This is a structural block diagram of the device for calibrating the rotation angle and rotation center position coordinates of the motion platform provided in this application. DETAILED DESCRIPTION

[0020] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0021] In semiconductor manufacturing, motion stages play a critical role. Their primary function is to carry and move processing objects, such as wafers, to meet the precise positioning requirements of processing objects throughout the semiconductor manufacturing process. Precise control of motion stages is crucial for product quality and production efficiency.

[0022] Especially for motion stages with an Rz axis (rotating around the z-axis), accurately calibrating and calibrating its rotation angle and center of rotation is a key task in ensuring high-precision operation. Only by accurately determining the rotation angle and center of rotation can the motion stage ensure that processing objects such as wafers are precisely positioned when rotating around the z-axis, thereby ensuring the accuracy and stability of the semiconductor manufacturing process, ultimately affecting product quality and production efficiency.

[0023] However, most current methods for calibrating the rotation angle and center of rotation of a motion stage require the coordinated work of multiple modules, including a camera, a motion stage moving device, and an 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 measurement tools themselves have precision limitations, which directly affect the accuracy of the measurement data. The motion stage and alignment stage also generate errors during repeated positioning. These errors do not cancel each other out during multiple measurements and subsequent data fitting, but instead accumulate. This accumulated error can severely reduce the accuracy of the final calibration results, causing the actual rotation angle and center of rotation of the motion stage to deviate significantly from the calibrated values. This in turn affects the motion stage's positioning accuracy, ultimately negatively impacting semiconductor product quality and production efficiency.

[0025] Secondly, the coordinated operation of multiple modules involves multiple links and steps, and the process is very complicated. In actual operation, it is easily interfered with by human factors, such as the operator's proficiency, operating habits, and working status, which may lead to operational differences and errors. These human factors affect the accuracy of data collection and the operating status of the equipment, thereby adversely affecting the accuracy and reliability of the entire calibration. The calibration results may not truly reflect the actual rotation characteristics of the motion stage, reducing the control accuracy and stability of the motion stage.

[0026] Based on the above problems, the present application provides a calibration method and device for a motion stage. In the field of semiconductor manufacturing, a motion stage is used to carry and move processing objects such as wafers to meet the positioning requirements of various manufacturing links. The purpose of calibrating the motion stage is mainly to ensure its accuracy. Accurately calibrating the rotation angle and rotation center of the motion stage can enable the motion stage to accurately position the processing object to the required position during operation, prevent processing errors due to positioning deviations, and thus improve product quality and yield rate. At the same time, accurate calibration can reduce production interruptions and rework caused by inaccurate positioning of the motion stage, making the production process more efficient and smooth, and improving overall production efficiency. Moreover, by calibrating and calibrating the rotation characteristics of the motion stage, it helps to maintain the stability of the motion stage performance, extend the service life of the equipment, and reduce maintenance costs and downtime caused by equipment accuracy issues.

[0027] The motion stage calibration method described in this application first places a calibration marker plate with line segment markers and feature markers on the motion stage, captures images of the marker plate before and after the motion stage is rotated, and extracts the position coordinates of each line segment marker and each feature marker from the captured images before and after the rotation. Next, a direction vector is constructed based on the position coordinates. By operating 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 stage. Finally, the connecting line vectors are calculated based on the position coordinates before and after the rotation, and the perpendicular bisector unit vector is determined based on geometric properties. The distance of the rotation center along the unit vector is calculated based on the unit vector and the rotation angle. Finally, the position coordinates of the rotation center of the motion stage are finally determined based on the rotation direction. This is described in detail below with reference to the accompanying drawings.

[0028] Please refer to Figure 1 , Figure 1 The present invention provides a flow chart of a method for calibrating the rotation angle and the rotation center position coordinates of a motion stage. A motion stage calibration method includes:

[0029] S110, placing a calibration marker plate with line segment markers and feature markers on a motion stage, collecting images of the marker plate before and after the motion stage is rotated, and extracting the position coordinates of each line segment marker and each feature marker before and after the rotation from the collected images.

[0030] For example, please refer to Figure 2 , Figure 2 It is a schematic diagram of the marking pattern provided in the present application. A marking plate for calibration is placed on a moving table with an Rz rotation axis. A marking pattern is set on the surface of the marking plate, and the marking pattern includes line segment marks and feature marks. The line segment marks are straight line segments with clear edges, and each line segment mark is distributed in different areas of the marking plate and has different line widths. Feature marks are patterns with geometric features, such as squares, triangles, quadrilaterals, pentagons, and hexagons; each feature mark is located in a different area of ​​the marking plate and has different geometric features; wherein the number of line segment marks and feature marks are two or more groups, and there is a difference in brightness or grayscale value between the pattern of the line segment marks and feature marks and the background. The marking pattern adopts a redundant design, and the arithmetic mean of the calibration results can be measured multiple times, which greatly reduces random errors and improves the accuracy and reliability of the calibration results.

[0031] For example, a visual system may be used to capture an image of the marker plate to obtain the position coordinates of each line segment marker and each feature marker before and after the motion stage rotates, as follows:

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

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

[0034] The position coordinates of the two endpoints of the i-th group of line segments after rotation are recorded as x i 1′, vertical coordinate is y i 1′, and the horizontal coordinate is x i 2′, vertical coordinate is y i 2′, that is (x i 1′, y i 1′) and (x i 2′, y i 2′); the position coordinates of the jth group of feature marks after rotation are recorded as the horizontal coordinate p j ′, vertical coordinate q j ′, that is (p j ′,q j ′).

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

[0036] S120 , constructing a direction vector according to the position coordinates before and after the rotation, and calculating the cosine value and sine value of the rotation angle based on the constructed direction vector to determine the rotation angle of the motion stage.

[0037] For example, two position coordinates can be randomly selected from all position coordinates before rotation to construct a direction vector, which is recorded as Its horizontal component is V xn , the vertical component 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 of position coordinate combinations n 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 position coordinates of two groups of line segment markers (such as the first group is k1 and the second group is k2) are selected, the direction vector is: the horizontal coordinate of an endpoint in the first group of line segment markers minus the horizontal coordinate of an endpoint in the second group of line segment markers, and the vertical coordinate of the endpoint in the first group of line segment markers minus the vertical coordinate of the endpoint in the second group of line segment markers, that is, There are two possible endpoint positions for each set of line segment markers, namely, m, h∈{1, 2}.

[0041] If the position coordinates of a certain group (such as k1) of line segment markers and the position coordinates of a certain group (such as k2) of feature markers are selected, the direction vector is: the horizontal coordinate of an endpoint in the group of line segment markers minus the horizontal coordinate of the group of feature markers, and the vertical coordinate of the endpoint in the group of line segment markers minus the vertical coordinate of the group of feature markers, that is, There are two possible endpoint positions for each set of line segment markers, namely m∈{1, 2}.

[0042] If the position coordinates of two groups of feature markers (such as the first group is k1 and the second group is k2) are selected, the direction vector is: the horizontal coordinate of the first group of feature markers minus the horizontal coordinate of the second group of feature markers, and the vertical coordinate of the first group of feature markers minus the vertical coordinate of the second group of feature markers, that is,

[0043] For example, see Figure 3 , Figure 3 This is a schematic diagram of the rotation angle calculation principle provided by this application. By obtaining the position coordinates 1 (x11, y11) and position coordinates 2 (x12, y12) of the first set of line segment marks, the direction vector is constructed.

[0044] For example, the direction vector is constructed using the position coordinates after rotation in the same way as the direction vector before rotation. The direction vector is recorded as Its horizontal component is V x ' n , the vertical component is V y ' n ,Right now

[0045] For example, Figure 3 As shown, by obtaining the position coordinates 1′(x11′, y11′) and position coordinates 2′(x12′, y12′) of the first group of line segment marks after rotation, the direction vector is constructed.

[0046] Specifically, construct the direction vector The way is as follows:

[0047] Get the position coordinates of the two sets of line segment markers k1 and k2 after rotation, and construct the direction vector 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 endpoints of the k2th group of line segment markers after rotation.

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

[0049]

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

[0051] Exemplarily, calculating the cosine and sine of the rotation angle based on the constructed direction vector to determine the rotation angle of the motion stage includes:

[0052] Calculate the modulus of the forward and backward direction vectors respectively, calculate the dot product and cross product of the forward and backward direction vectors, and then 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 modulus of the forward and backward direction vectors, and determine the rotation angle of the motion platform based on the sine and cosine values.

[0053] Specifically, calculate the modulus of the direction vector before and after rotation: The absolute value of Its length is the horizontal component V of the direction vector xn The square of the vertical component V yn Add the squares of , and then take the square root of the sum, that is For the rotated direction vector The absolute value of Its length is the horizontal component V of the direction vector x ' n The square of the vertical component V t ' nAdd the squares of , and then take the square root of the sum, that is

[0054] Calculate the dot product of the vectors before and after the rotation n :The horizontal component V of the direction vector before rotation xn The horizontal component V of the direction vector after rotation x ' n Multiply, and add the vertical component V of the direction vector before rotation yn The component V perpendicular to the direction vector after rotation y ' n The result of multiplication, that is, dot n =V xn ×V x ' n +V yn ×V y ' n .

[0055] Calculate the cross product of the rotation vector before and after n :Use the horizontal component V of the direction vector before rotation xn The horizontal component V of the direction vector after rotation x ' n The result of the multiplication is subtracted from the vertical component V of the direction vector before rotation. yn The component V perpendicular to the direction vector after rotation y ' n The result of multiplication, that is, cross n =V xn ×V x ' n -V yn ×V y ' n .

[0056] Calculate the rotation angle θ corresponding to each set of direction vectors n 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 of the rotated direction vector The product of the absolute values ​​of

[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 of the rotated direction vector The product of the absolute values ​​of

[0059]

[0060] Determine the rotation angle θ of the motion stage: First, calculate the arc tangent of the result of dividing the sine value of the rotation angle corresponding to each set of direction vectors by the cosine value, add all the arc tangent results, and then divide the sum by the number of direction vector groups, that is:

[0061]

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

[0063] S130, calculate each connecting vector according to the position coordinates before and after the rotation, determine the perpendicular bisector unit vector based on the connecting vector, calculate the distance of the rotation center along the unit vector in combination with the rotation angle, and then determine the rotation center position coordinates of the motion platform in combination with the rotation direction.

[0064] Exemplarily, calculating each line vector based on the position coordinates before and after the rotation includes:

[0065] Calculate the connecting vector of the position coordinates before and after rotation, and record the connecting vector as The connection vector The component in the horizontal direction is denoted as lig xo , the component in the vertical direction is recorded as lig yo ,Right now Among them, the position coordinates are the position coordinates of the line segment marker or the position coordinates of the feature marker; the total number o of position coordinates 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 the coordinates of the first endpoint of a group of line segment markers (such as k1) before rotation and the coordinates of the second endpoint of another group of line segment markers (such as k2) after rotation are selected, the connecting vector is: the abscissa of the second endpoint of the group of line segment markers after rotation minus the abscissa of the first endpoint of the group of line segment markers before rotation, and the ordinate of the second endpoint of the group of line segment markers after rotation minus the ordinate of the first endpoint of the group of line segment markers before rotation, that is:

[0067]

[0068] If we select the first endpoint position coordinates of a certain group of line segment markers (such as k1) before rotation and the feature position coordinates of a certain feature marker (such as k2) after rotation, the connecting vector is: the abscissa of the feature marker after rotation minus the abscissa of the first endpoint of the group of line segment markers before rotation, and the ordinate of the feature marker after rotation minus the ordinate of the first endpoint of the group of line segment markers before rotation, that is:

[0069]

[0070] If the feature position coordinates of a feature marker before rotation (such as k1) and the feature position coordinates of another feature marker after rotation (such as k2) are selected, the connecting vector is: the horizontal coordinate of the feature marker after rotation minus the horizontal coordinate of the feature marker before rotation, and the vertical coordinate of the feature marker after rotation minus the vertical coordinate of the feature marker before rotation, that is:

[0071]

[0072] For example, see Figure 4 , Figure 4 This is a schematic diagram of the rotation center calculation principle provided by this application. The connection vector 1 and the connection vector 2 are obtained by calculating the position coordinates.

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

[0074] Calculate the modulus L of each line vector o :It is calculated by adding the horizontal component lig of the connecting vector xo The square of the vertical component lig yo Add the squares of , and then take the square root of the sum, that is:

[0075]

[0076] Calculate the midpoint coordinates M of the connecting vector o =(M xo , M yo ), there are three situations:

[0077] If the coordinates of the first endpoint of a group of line segment markers before rotation (such as k1) and the coordinates of the second endpoint of another group of line segment markers after rotation (such as k2) are selected, the midpoint coordinates are half the sum of the horizontal coordinates of the two endpoints and half the sum of the vertical coordinates, that is:

[0078]

[0079] If the coordinates of the first endpoint of a certain group of line segment markers (such as k1) before rotation and the coordinates of the feature position of a certain feature marker (such as k2) after rotation are selected, the midpoint coordinates are half of the sum of the horizontal coordinates of the feature marker and the horizontal coordinates of the endpoints of the line segment marker, and half of the sum of the vertical coordinates of the feature marker and the vertical coordinates of the endpoints of the line segment marker, that is:

[0080]

[0081] If the feature position coordinates of a feature marker before rotation (such as k1) and the feature position coordinates of another feature marker after rotation (such as k2) are selected, the midpoint position coordinates are half of the sum of the horizontal coordinates of the two feature markers and half of the sum of the vertical coordinates, that is:

[0082]

[0083] like Figure 4 As shown, by calculating the module length and midpoint position of the connecting vector, the module length L1 and midpoint position coordinate M1 of the connecting vector 1, and the module length L2 and midpoint position coordinate M2 of the connecting vector 2 can be obtained.

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

[0085] Calculate the slope of each connecting vector o :It is calculated as the horizontal component lig of the connecting vector xo Divide by the vertical component lig yo ,Right now:

[0086]

[0087] Calculate the slope perpslope of the perpendicular bisector of each connecting vector o : It is calculated as the negative reciprocal of the slope of the connecting vector, that is:

[0088]

[0089] Among them, the modulus of the perpendicular bisector unit vector |m| is calculated. o is the slope of the perpendicular bisector divided by 1 o Add the squares of , and then take the square root of the sum, that is:

[0090]

[0091] Calculate the unit vectors of the perpendicular bisectors of each connecting vector The horizontal component of the unit vector is the inverse of the modulus of the perpendicular bisector unit vector, and the vertical component is the slope of the perpendicular bisector divided by the modulus of the perpendicular bisector unit vector, that is:

[0092]

[0093] Calculate the distance d between the center of rotation and the unit vector along the perpendicular bisector of each connecting vector o : The distance is the modulus of the connecting vector divided by twice the tangent of the rotation angle of the motion stage, that is:

[0094]

[0095] like Figure 4 As shown in , d1 is calculated based on the rotation angle θ of the motion platform 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 connecting vector module. Similarly, d2, the distance of the rotation center along the perpendicular bisector of the connecting vector 2, can also be calculated.

[0096] Exemplarily, determining the rotation center position coordinates of the motion stage in combination with the rotation direction includes:

[0097] The rotation direction is determined based on the sine value of the rotation angle and the relationship between the visual system and the horizontal direction of the motion stage coordinate system; the rotation center position coordinates obtained by each connecting vector are calculated based on the rotation direction; and the rotation center position coordinates of the motion stage are obtained based on the rotation center position coordinates.

[0098] Specifically, the rotation direction is determined based on the sine value of the rotation angle and the relationship between the visual system and the horizontal direction of the motion stage coordinate system.

[0099] When the pixel coordinate system of the visual system is in the same or opposite horizontal direction as the motion stage 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 visual system and the horizontal direction of the motion stage coordinate system are unidirectionally opposite, 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 obtained by calculating each connecting vector according to the rotation direction include:

[0102] If the rotation direction is counterclockwise, the rotation center position coordinate C is calculated by each connecting vector o =(C xo , C yo ), its horizontal coordinate C xo M is the horizontal 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 with the perpendicular bisector unit ox The product of, 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 is the perpendicular component of the unit vector to the perpendicular bisector o / |m| o The product of , that is:

[0103]

[0104] If the rotation direction is clockwise, the rotation center position coordinate C is calculated by each connecting vector o =(C xo , C yo ), its horizontal coordinate C xo M is the horizontal 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 with the perpendicular bisector unit ox The product of, 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 is the perpendicular component of the unit vector to the perpendicular bisector o / |m| o The product of , that is:

[0105]

[0106] Specifically, the coordinates of the rotation center position of the motion platform are obtained according to the coordinates of the rotation center position of each connecting line vector, including:

[0107] Add the horizontal coordinates of all the rotation center position coordinates calculated by each connecting vector ∑C xo Then divide by the number of connecting vectors o, and add ∑C to the vertical coordinates yo Then divide it by the number of connecting vectors o to obtain the rotation center position coordinate C of the motion platform, that is:

[0108]

[0109] In summary, compared with the existing technology, the present application has many beneficial technical effects: in terms of mechanical structure implementation, it only relies on the measurement accuracy of a single camera, effectively avoiding the error transmission and accumulation caused by mechanical errors and assembly deviations; the algorithm uses geometric calculations, and there is no need to fit points, curves or trajectories, avoiding the systematic deviations that may be introduced by the fitting algorithm; the marking pattern is composed of line segment marks of straight line segments and feature marks of patterns with geometric features. It adopts a redundant design, and the calibration results can be measured multiple times and the arithmetic average can be taken, which effectively reduces random errors and improves the robustness of the calibration of rotation angles and rotation centers; the operation does not require complicated processes, and the calibration process is intuitive and easy to operate.

[0110] The following describes the calibration device of the motion stage provided in the present application. The calibration device of the motion stage described below and the calibration method of the motion stage described above can be referenced to each other.

[0111] Please refer to Figure 5 , Figure 5 The present invention provides a block diagram of a device for calibrating the rotation angle and rotation center coordinates of a motion stage. The device 500 for calibrating a motion stage includes an image acquisition module 510 , a rotation angle calculation module 520 , and a rotation center determination module 530 .

[0112] Exemplarily, the image acquisition module 510 is used to place a calibration marker plate with line segment marks and feature marks on a motion stage, capture images of the marker plate before and after the motion stage rotates, and extract the position coordinates of each line segment mark and each feature mark before and after rotation from the captured images.

[0113] Exemplarily, the rotation angle calculation module 520 is used to construct a direction vector according to the position coordinates before and after the 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 platform.

[0114] Exemplarily, the rotation center determination module 530 is used to calculate each connecting vector based on the position coordinates before and after the rotation, determine the perpendicular bisector unit vector based on the connecting vector, 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 platform in combination with the rotation direction.

[0115] It can be understood that the calibration device of the motion stage solves the problem of calibrating the rotation angle and rotation center of the motion stage through the collaborative work of three modules. The image acquisition module first places a calibration marker plate with specific line segment marks and feature marks on the motion stage, collects images of the marker plate before and after the rotation of the motion stage, and then extracts the position coordinates of each line segment mark and each feature mark before and after the rotation from the image. The rotation angle calculation module uses the position coordinates before and after the rotation obtained by the image acquisition module to construct a direction vector, and calculates the cosine and sine values ​​of the rotation angle through the direction vector to determine the rotation angle of the motion stage. The rotation center determination module also calculates each connecting vector based on the position coordinates provided by the image acquisition module, determines the perpendicular bisector unit vector based on the connecting vector, calculates the distance of the rotation center along the unit vector in combination with the rotation angle, and finally determines the position coordinates of the rotation center of the motion stage in combination with the rotation direction, thereby completing the calibration of the rotation angle and rotation center of the motion stage.

[0116] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for calibrating a motion platform, characterized in that: The method comprises: A calibration marker plate with line segment markers and feature markers is placed on a motion stage, images of the marker plate are collected before and after the motion stage is rotated, and the position coordinates of each line segment marker and each feature marker before and after the rotation are extracted from the collected images; constructing a direction vector according to the position coordinates before and after the rotation, and calculating the cosine and sine of the rotation angle based on the constructed direction vector to determine the rotation angle of the motion stage; Calculate each connecting vector according to the position coordinates before and after the rotation, determine the perpendicular bisector unit vector based on the connecting vector, calculate the distance of the rotation center along the unit vector in combination with the rotation angle, and then determine the rotation center position coordinates of the motion platform in combination with the rotation direction.

2. The method for calibrating a sports table according to claim 1, wherein: The line segment marks are straight line segments, and each line segment mark is distributed in different areas of the marking plate and has different line widths; The characteristic marks are patterns with geometric features, and each characteristic mark is located in a different area of ​​the marking plate and has different geometric features; The number of the line segment marks and the number of the characteristic marks are both two or more, and there is a difference in brightness or grayscale value between the patterns of the line segment marks and the characteristic marks and the background.

3. The method for calibrating a sports table according to claim 1, wherein: The step of collecting the marking plate images before and after the motion stage is rotated, and extracting the position coordinates of each line segment mark and each feature mark before and after the rotation from the collected images comprises: The position coordinates of the two endpoints of the i-th group of line segments before rotation are recorded as x i 1. The vertical coordinate is y i 1, and the horizontal axis is x i 2. The vertical coordinate is y i 2. The position coordinates of the jth group of feature marks before rotation are recorded as the horizontal coordinate p j , the vertical axis is q j ; The position coordinates of the two endpoints of the i-th group of line segments after rotation are recorded as x i 1′, vertical coordinate is y i 1′, and the horizontal coordinate is x i 2′, vertical coordinate is y i 2′; the position coordinates of the jth group of feature marks after rotation are recorded as the horizontal coordinate p j ′, vertical coordinate q j ′.

4. The method for calibrating a sports table according to claim 1, wherein: The constructing of the direction vector according to the position coordinates before and after the rotation includes: From all the position coordinates before rotation, arbitrarily select two position coordinates to construct a direction vector, which is recorded as Its horizontal component is V xn , the vertical component is V yn ; wherein the position coordinates are the position coordinates of line segment marks or the position coordinates of 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 result of subtracting one from the sum, and then dividing the product by two.

5. The method for calibrating a sports table according to claim 4, wherein: The constructing of the direction vector according to the position coordinates before and after the rotation includes: If the position coordinates of two sets of line segment markers are selected, the direction vector is: the abscissa of an endpoint in the first set of line segment markers minus the abscissa of an endpoint in the second set of line segment markers, and the ordinate of the endpoint in the first set of line segment markers minus the ordinate of the endpoint in the second set of line segment markers; where each set of line segment markers can have two possible endpoint positions. If the position coordinates of a certain set of line segment markers and a certain set of feature markers are selected, the direction vector is: the abscissa of an endpoint in the set of line segment markers minus the abscissa of the feature markers, and the ordinate of the endpoint in the set of line segment markers minus the ordinate of the feature markers. There are two possible endpoint positions for each set of line segment markers. If the position coordinates of two groups of feature markers are selected, the direction vector is: the horizontal coordinate of the first group of feature markers minus the horizontal coordinate of the second group of feature markers, and the vertical coordinate of the first group of feature markers minus the vertical coordinate of the second group of feature markers.

6. The method for calibrating a sports table according to claim 4, wherein: The constructing of the direction vector according to the position coordinates before and after the rotation includes: The direction vector is constructed using the same method as before rotation using the position coordinates after rotation. The direction vector is recorded as Its horizontal component is V x ′ n , the vertical component is V y ′ n .

7. The method for calibrating a sports table according to claim 1, wherein: Calculating the cosine and sine of the rotation angle based on the constructed direction vector to determine the rotation angle of the motion platform includes: Calculate the modulus of the forward and backward direction vectors respectively, calculate the dot product and cross product of the forward and backward direction vectors, and then 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 modulus of the forward and backward direction vectors, and determine the rotation angle of the motion platform based on the sine and cosine values.

8. The method for calibrating a sports table according to claim 7, wherein: Calculating the cosine and sine of the rotation angle based on the constructed direction vector to determine the rotation angle of the motion platform includes: Calculate the modulus of the direction vector before and after rotation: For the direction vector before rotation The absolute value of the direction vector is V in the horizontal direction. xn The square of the vertical component V yn Add the squares of the vectors and take the square root of the sum; for the direction vector after rotation The absolute value of the direction vector is V in the horizontal direction. x ′ n The square of the vertical component V y ′ n Add the squares of , and then take the square root of the sum; Calculate the dot product of the direction vectors before and after the rotation: the horizontal component V of the direction vector before rotation xn The horizontal component V of the direction vector after rotation x ′ n Multiply, and add the vertical component V of the direction vector before rotation yn The component V perpendicular to the direction vector after rotation y ′ n The result of multiplication; Calculate the cross product of the direction vector before and after rotation: use the horizontal component V of the direction vector before rotation xn The horizontal component V of the direction vector after rotation x ′ n The result of the multiplication is subtracted from the vertical component V of the direction vector before rotation. yn The component V perpendicular to the direction vector after rotation y ′ n The result of multiplication; Calculate the cosine and sine of the rotation angle corresponding to each set of direction vectors: 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 of the rotated direction vector 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 of the rotated direction vector The product of the absolute values ​​of Determine the rotation angle of the motion stage: first calculate the arc tangent of the result of dividing the sine value of the rotation angle corresponding to each set of direction vectors by the cosine value, add all the arc tangent results, and then divide the sum by the number of direction vector sets.

9. The method for calibrating a sports table according to claim 1, wherein: Calculating each line vector according to the position coordinates before and after the rotation includes: Calculate the connecting vector of the position coordinates before and after rotation, and record the connecting vector as The connection vector The component in the horizontal direction is denoted as lig xo , the component in the vertical direction is recorded as lig yo ; wherein the position coordinates are the position coordinates of the line segment mark or the position coordinates of the feature mark; the total number of position coordinates is the sum of twice the number of line segment marks and the number of feature marks.

10. The method for calibrating a sports table according to claim 9, wherein: Calculating each line vector according to the position coordinates before and after the rotation includes: If you 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 connecting vector is: the abscissa of the second endpoint of the group of line segment markers after rotation minus the abscissa of the first endpoint of the group of line segment markers before rotation, and the ordinate of the second endpoint of the group of line segment markers after rotation minus the ordinate of the first endpoint of the group of line segment markers before rotation; If the coordinates of the first endpoint of a certain group of line segment markers before rotation and the coordinates of the characteristic position of a certain feature marker after rotation are selected, the connecting vector is: the horizontal coordinate of the feature marker after rotation minus the horizontal coordinate of the first endpoint of the group of line segment markers before rotation, and the vertical coordinate of the feature marker after rotation minus the vertical coordinate of the first endpoint of the group of line segment markers before rotation; If the feature position coordinates of a feature marker before rotation and the feature position coordinates of another feature marker after rotation are selected, the connecting vector is: the abscissa of the feature marker after rotation minus the abscissa of the feature marker before rotation, and the ordinate of the feature marker after rotation minus the ordinate of the feature marker before rotation.

11. The method for calibrating a sports table according to claim 1, wherein: Determining a perpendicular bisector unit vector based on the connecting line vector, and calculating a distance of the rotation center along the unit vector in combination with the rotation angle includes: First, calculate the modulus of each connecting vector, and then calculate the coordinates of the midpoint position of the connecting vector; then calculate the slope of each connecting vector to obtain the slope of its perpendicular bisector, and then calculate the modulus of the perpendicular bisector unit vector, and then calculate the unit vector of the perpendicular bisector of each connecting vector, and finally calculate the distance of the rotation center along the perpendicular bisector unit vector of each connecting vector.

12. The method for calibrating a sports table according to claim 11, wherein: Determining a perpendicular bisector unit vector based on the connecting line vector, and calculating a distance of the rotation center along the unit vector in combination with the rotation angle includes: Calculate the modulus of each connecting vector: the calculation method is to add the connecting vector in the horizontal direction component lig xo The square of the vertical component lig yo Add the squares of , and then take the square root of the sum; Calculate the midpoint coordinates of the connecting vector, including the following three cases: If the selected coordinates are the first endpoint position coordinates of a group of line segment markers before rotation and the second endpoint position coordinates of another group of line segment markers after rotation, the midpoint position coordinates are half the sum of the horizontal coordinates of the two endpoints and half the sum of the vertical coordinates; If the selected coordinates are the first endpoint position coordinates of a group of line segment markers before rotation and the feature position coordinates of a feature marker after rotation, the midpoint position coordinates are half of the sum of the horizontal coordinate of the feature marker and the horizontal coordinate of the endpoint of the line segment marker, and half of the sum of the vertical coordinate of the feature marker and the vertical coordinate of the endpoint of the line segment marker; If the feature position coordinates of a feature mark before rotation and the feature position coordinates of another feature mark after rotation are selected, the midpoint position coordinates are half of the sum of the horizontal coordinates and half of the sum of the vertical coordinates of the two feature marks.

13. The method for calibrating a sports table according to claim 12, wherein: Determining a perpendicular bisector unit vector based on the connecting line vector, and calculating a distance of the rotation center along the unit vector in combination with the rotation angle includes: Calculate the slope of each connecting vector: the calculation method is the component lig of the connecting vector in the horizontal direction xo Divide by the vertical component lig yo ; Calculate the slope of the perpendicular bisector of each connecting vector: the calculation method is to take the negative reciprocal of the slope of the connecting vector; wherein, the modulus of the perpendicular bisector unit vector is calculated by adding 1 to the square of the slope of the perpendicular bisector and taking the square root of the sum; Calculate the unit vector of the perpendicular bisector of each connecting vector: the horizontal component of the unit vector is the inverse of the modulus of the perpendicular bisector unit vector, and the vertical component is the slope of the perpendicular bisector divided by the modulus of the perpendicular bisector unit vector; Calculate the distance of the rotation center along the unit vector of the perpendicular bisector of each connecting vector: the distance is the modulus of the connecting vector divided by twice the tangent of the rotation angle of the motion stage.

14. The method for calibrating a sports table according to claim 1, wherein: Determining the rotation center position coordinates of the motion stage in combination with the rotation direction includes: The rotation direction is determined based on the sine value of the rotation angle and the relationship between the visual system and the horizontal direction of the motion platform coordinate system; the rotation center position coordinates obtained by each connecting vector are calculated based on the rotation direction; and the rotation center position coordinates of the motion platform are obtained based on the rotation center position coordinates.

15. The method for calibrating a sports table according to claim 14, wherein: The method of determining the rotation direction based on the sine value of the rotation angle and the relationship between the visual system and the horizontal direction of the motion stage coordinate system includes: When the pixel coordinate system of the visual system is in the same or opposite horizontal direction as the motion stage 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 visual system and the horizontal direction of the motion stage coordinate system are unidirectionally opposite, 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.

16. The method for calibrating a sports table according to claim 14, wherein: The calculation of the rotation center position coordinates obtained by each connecting vector according to the rotation direction includes: If the direction of rotation is counterclockwise, the coordinates of the rotation center are calculated by the connecting vectors. The horizontal coordinate is the horizontal coordinate of the midpoint of the connecting vector minus the distance in the direction of the perpendicular bisector of the connecting vector and the horizontal component of the perpendicular bisector unit vector. The vertical coordinate is the vertical coordinate of the midpoint of the connecting vector minus the distance in the direction of the perpendicular bisector of the connecting vector and the vertical component of the perpendicular bisector unit vector. If the rotation direction is clockwise, the coordinates of the rotation center are calculated through each connecting vector. Its abscissa is the product of the abscissa 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 perpendicular bisector unit vector. The ordinate is the product of the ordinate of the midpoint of the connecting vector plus the distance in the direction of the perpendicular bisector of the connecting vector and the vertical component of the perpendicular bisector unit vector. The step of obtaining the rotation center position coordinates of the motion platform according to the rotation center position coordinates of each connecting line vector comprises: The horizontal coordinates of all the rotation center position coordinates calculated by each connecting vector are added up and divided by the number of connecting vectors, and the vertical coordinates are added up and divided by the number of connecting vectors to obtain the rotation center position coordinates of the motion platform.

17. A calibration device for a sports table, characterized in that: The device comprises: An image acquisition module is used to place a calibration marker plate with line segment markers and feature markers on the motion stage, capture images of the marker plate before and after the motion stage is rotated, and extract the position coordinates of each line segment marker and each feature marker before and after the rotation from the captured images; A rotation angle calculation module is used to construct a direction vector based on the position coordinates before and after the 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 platform; The rotation center determination module is used to calculate each connecting vector based on the position coordinates before and after the rotation, determine the perpendicular bisector unit vector based on the connecting vector, 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 platform in combination with the rotation direction.

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