JP2006049755A - Rotation center calculation method and work positioning device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the accuracy of a work positioning by accurately finding the coordinate of a rotation center in a stage by a simple method. <P>SOLUTION: The work of model is brought in on the stage provided with a rolling mechanism, and the position of the work is adjusted so as to allow positioning marks diagonal to each work to remain within fields R1, R2 of two cameras. After a first picture is taken under the condition, the stage is rotated in a scope that each mark never goes out of the fields R1, R2 and a second picture is taken. Next, the coordinates of a1, a2, b1, b2 showing the positions of each mark from each image obtained by taking the pictures twice, the rotation angle dT of the stage is calculated using the quantities of movement of each mark found from these coordinates and the distances L between marks beforehand inputted. Further, the coordinates (cx, cy) of the rotation center C in the stage are calculated using the rotation angle dT and the coordinates of the points, a1, a2, b1, b2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for aligning a workpiece by supporting a workpiece such as a glass substrate on a stage having a rotation mechanism and controlling the operation of the stage using a positioning mark provided on the workpiece as an index. . In particular, the present invention relates to a method for obtaining coordinates of a rotation center of a stage necessary for correcting a rotational deviation of a workpiece in the workpiece alignment process, and a workpiece positioning apparatus to which this method is applied.

  The stage used in this type of workpiece positioning apparatus generally includes a moving mechanism and a rotating mechanism in the horizontal direction (X-axis direction) and the vertical direction (Y-axis direction). The workpiece placed on the stage is transferred to a predetermined position by each moving mechanism and then adjusted so as to have an appropriate posture by the rotating mechanism.

  Further, a substrate that is a typical workpiece is provided with a positioning mark (hereinafter sometimes simply referred to as a “mark”) at a corner or the like for the above-described alignment. In the conventional positioning device, after moving the workpiece so that each mark is positioned in the vicinity of a predetermined reference position, the workpiece is imaged by the camera, and the position of each mark and the reference position are obtained using the obtained image. The shift mechanism and the rotation mechanism are controlled so that the shift is eliminated.

  Further, when manufacturing a structure in which a plurality of substrates having a fine structure such as a liquid crystal substrate or a plasma display are overlaid, it is necessary to accurately align the substrates constituting each layer. In such a case, the cameras were individually installed toward the reference positions of two or more marks in a diagonal relationship, and the workpiece was moved until the corresponding marks were in the field of view of these cameras. Thereafter, a minute shift amount of each mark is extracted using an image obtained by each camera.

  Patent Document 1 below describes adjusting the amount of rotational deviation of a workpiece by simultaneously observing two alignment marks formed on a substrate with two cameras (paragraph [0005]. ]reference.).

JP 7-199139 A

  In the conventional method in which the rotational deviation of the workpiece is adjusted using two cameras, a deviation amount (deviation amount in the x direction and the y direction) with respect to the reference position is extracted for each mark, and these deviation amounts are used. To calculate the rotation angle of the workpiece. Then, the stage is rotated according to this rotation angle.

  In order to obtain the rotation angle of the workpiece, the coordinates of the rotation center of the stage are required. In the conventional method, the coordinates of a position regarded as the center, such as the rotation axis of the stage, are measured in advance and used as the coordinates of the rotation center.

  Also, the coordinates of the center of rotation may be obtained by calculation using a model work. In this method, after the mark is imaged by each camera, the stage is rotated by a predetermined angle, and the mark is imaged again. Then, the coordinates of the center of rotation are calculated using the coordinates of the mark measured from each image before rotation, the coordinates of the mark measured from each image after rotation, and the rotation angle of the stage.

In the method of measuring the coordinates of the rotation center in advance, the calculated coordinates of the workpiece are not accurate because the measured coordinates do not necessarily correspond to the actual rotation center. Even in the method of calculating the rotation center by calculation, an error occurs in the actual stage rotation angle, so the calculation result of the rotation center becomes inaccurate, and the rotation angle of the workpiece can be obtained by using the incorrect rotation center. Will also be inaccurate.
As described above, it is difficult to obtain the rotation angle of the workpiece with high accuracy regardless of which method is used.

  This invention pays attention to said problem, and it aims at enabling positioning of a workpiece | work with high precision by calculating | requiring accurately the coordinate of the rotation center of a stage with a simple method.

  In this invention, a work having a plurality of positioning marks on its surface is set on a stage having a rotation mechanism, and at least imaging means are set toward the reference positions of two positioning marks having a diagonal relationship. Then, the present invention is applied to a workpiece positioning process for controlling the operation of the stage so that each positioning mark matches the reference position by using an image obtained by each imaging means. The “diagonal marks” referred to in this specification are in a relationship of facing each other across the center point of the workpiece in addition to a pair of marks provided at the corners connected by the diagonal lines of the workpiece. It shall include a pair of marks.

  In the workpiece positioning process described above, it is desirable that each imaging unit is fixedly installed toward the reference position of the corresponding positioning mark. However, when a plurality of types of workpieces are to be processed, it is desirable that the position of the imaging means can be changed in accordance with the workpiece. For these cameras, it is desirable that calibration is performed in advance so that real coordinates on the stage (coordinates set on a virtual plane including the upper surface of the stage) can be obtained from the coordinates on the image.

  It is desirable that the field of view of each imaging means is set in a minimal region centered on the reference position. In this case, the coordinates of the center position of the mark extracted from the image from each imaging means are converted into the coordinates of the real coordinate system using the parameters obtained by the calibration, and the shift amount of the converted coordinates with respect to the reference position Can be requested. Further, the amount of rotation deviation (rotation angle of the workpiece) can be obtained using the coordinates of the mark, the coordinates of the reference position, and the coordinates of the rotation center.

  In this invention, the step A for inputting data for specifying the distance between the positioning marks on the workpiece, and the step B for setting the model workpiece on the stage and imaging the corresponding positioning marks by the respective imaging means. Obtained by the steps B and C, after the stage is rotated in a range where the positioning marks do not come out of the field of view of the corresponding imaging means, and the imaging marks are imaged again by the imaging means. The coordinates of the rotation center of the stage are calculated using the image and the distance between the positioning marks.

FIG. 1 shows the principle of the method for calculating the coordinates of the center of rotation of the present invention.
In this example, it is assumed that the imaging unit is installed toward the reference position of two marks (hereinafter referred to as “marks M1 and M2”) in a diagonal relationship. In the figure, R1 is the field of view of the imaging means corresponding to the mark M1, and R2 is the field of view of the imaging means corresponding to the mark M2. Further, by rotating the stage counterclockwise, the mark M1 moves from the point a1 in the visual field R1 to the point b1, and the mark M2 moves from the point a2 in the visual field R2 to the point b2. In this case, an intersection C between a vector from the point a1 to the point a2 (hereinafter referred to as “vector A”) and a vector from the point b1 to the point b2 (hereinafter referred to as “vector B”) is the rotation center. It can be considered that the angle dT formed by the vectors A and B corresponds to the rotation angle of the stage.

  In the present invention, the rotation angle dT of the stage is set to an arbitrary angle. Therefore, when calculating the coordinates of the rotation center, it is necessary to first obtain the rotation angle dT. Here, if the distance between the marks M1 and M2 is L, the rotation angle dT can be obtained by the following equation (1) using the vectors A and B and the distance L.

Next, with respect to the marks M1 and M2, the amounts of movement in the respective axial directions of x and y are (dx1, dy1) and (dx2, dy2), and the vector A = (x _A , y _A ) and the vector B = ( x _A + (dx2−dx1), y _A + (dy2−dy1)), the inner product A · B is expressed by equation (2).
A · B = x _A ² + y _A ² + x _A (dx2-dy1) + y _A (dy2-dy1) (2)

From | A | = | B | = L ² ,
Since x _A ² + y _A ² = (x _A + dx2−dy1) ² + (y _A + dy2−dy1) ² = L ² , the above equation (2) can be transformed into equation (3). .

  Therefore, the inner product A · B is obtained by applying the movement amounts (dx1, dy1), (dx2, dy2) of the marks M1, M2 and the distance L between the marks to the equation (3), and further calculating the inner product A · B. By applying B and the distance L to the equation (1), the rotation angle dT can be obtained. Here, the distance L can be measured from the workpiece of the model, and the amount of each movement is the position of each mark before the stage is rotated (the coordinates of points a1 and a2) and the position of each mark after the rotation (point b2). , B2 coordinates). Therefore, by rotating the stage by an arbitrary angle within a range where the marks M1 and M2 do not come out of the visual fields R1 and R2, the marks M1 and M2 are imaged before and after the rotation and the positions thereof are measured. And the rotation angle dT can be obtained from the position L measured in advance.

After obtaining the rotation angle dT in this way, the coordinates (cx, cy) of the rotation center C can be obtained using the positions before and after the rotation of the marks M1, M2 and the rotation angle dT. .
That is, if the position of the mark M _i (i = 1, 2) before rotation is (sx _i , sy _i ), the position after rotation is (x _i , y _i ), and θ = −dT,
x _i = cos θ (sx _i −cx) −sin θ (sy _i −cy) + cx
y _i = sin θ (sx _i −cx) + cos θ (sy _i −cy) + cy
From these two formulas, formulas (4) and (5) can be derived as formulas for calculating cx and cy, respectively.

  The above equations (4) and (5) can be executed for each of the marks M1 and M2, but may be executed for at least one mark. More preferably, equations (4) and (5) are executed for each of the marks M1 and M2, and the average value of cx and cy obtained for each mark is used as the rotation center coordinate.

  Thus, in the present invention, the rotation center of the stage can be calculated using the images obtained before and after the rotation of the stage and the distance between the marks. In addition, the rotation angle of the stage can be set arbitrarily within the range where each mark does not come out of the field of view of the corresponding camera, so the accuracy based on the actual rotation angle of the stage is not affected by the accuracy of the rotation mechanism. It is possible to perform a good calculation process. Therefore, in the workpiece positioning process, the rotation angle of the workpiece is accurately obtained by using the position of each mark obtained from the image obtained by the imaging means, the reference position of each mark, and the coordinates of the rotation center. Thereafter, the posture of the workpiece can be adjusted by driving the rotation mechanism.

  The data input as the data for specifying the distance L between the marks is preferably the value of L itself, but is not limited to this, and the distance L such as data indicating the position of each mark on the workpiece is not limited. Data that can be calculated may be input.

  In a preferred aspect of the rotation center calculation method according to the present invention, in the process of calculating the coordinates of the rotation center of the stage, the images obtained in the steps B and C are used for the two positioning marks having a diagonal relationship, respectively. A first step for obtaining the coordinates before the stage rotation and the coordinates after the stage rotation, a second step for obtaining a movement amount of each positioning mark due to the rotation of the stage from the coordinates calculated in the first step, and the positioning Using the distance between the marks and the amount of movement of each positioning mark obtained in the second step, a third step for obtaining the rotation angle of the stage, and the rotation angle obtained in the third step and at least one positioning mark The fourth step of calculating the coordinates of the rotation center using the coordinates before and after the stage rotation is executed. In the third step in this case, it can be considered that the process of calculating the rotation angle using the inner product of the vector connecting the positioning marks before the stage rotation and the vector after the stage rotation is executed.

  Note that the number of marks used for calculating the center of rotation is not limited to two, and three or more marks may be used. In this case, the rotation angle dT and the rotation center C are obtained by the above-described procedure for each set while sequentially selecting a pair of workpieces in a diagonal relationship, and a value obtained by averaging the calculation results of each set is set as the rotation center. can do.

  A workpiece positioning apparatus according to the present invention includes a stage having a rotation mechanism, a plurality of imaging means for imaging a positioning mark of the workpiece on the stage, and each positioning mark using an image obtained by each imaging means. And a control device that controls the operation of the stage so as to match each of the reference positions, and the plurality of imaging units are respectively arranged toward the reference positions of at least two diagonal positioning marks. Is done. The control device includes input means for inputting data for specifying a distance between the positioning marks in the diagonal relationship, and corresponds to each imaging means when a model workpiece is placed on the stage. After imaging the positioning mark, the stage is rotated by a predetermined amount so that each imaging means images each positioning mark again, and each image obtained before and after the rotation of the stage and the positioning mark input from the input means The coordinates of the rotation center of the stage are calculated using the distance between them.

  The control device is preferably a computer as a control subject. The input means can be configured by an input device such as a keyboard or a mouse, but is not limited to this. For example, a communication circuit that accepts transmission of data specifying the distance between marks from an external device can be made to function as the input means.

A program for executing the above-described rotation center calculation method can be incorporated in the control device. In the process of rotating the stage after the first imaging, it is desirable to set the operation amount of the rotation mechanism in advance so that each mark does not go out of the field of view of the corresponding imaging means. However, the rotation of the stage is not limited to automatic control, but can be controlled in accordance with a user operation.
Further, it is desirable to store the coordinates of the rotation center calculated by the control device in an internal memory in order to calculate the rotation angle of the workpiece to be processed thereafter.

  In the workpiece positioning apparatus according to a preferred aspect, the control device uses, for each of the two positioning marks in the diagonal relationship, the coordinates before the stage rotation and the coordinates after the stage rotation using the images obtained from the imaging means. Coordinate calculation means to be obtained; Movement amount calculation means for obtaining a movement amount of each positioning mark by rotation of the stage from each coordinate calculated by the coordinate calculation means; Distance between the positioning marks and each positioning value calculated by the movement amount calculation means And a rotation angle calculation means for obtaining the rotation angle of the stage using the movement amount of the mark, and the rotation angle calculated by the rotation angle calculation means and the stage rotation before and after the stage applied to at least one positioning mark The coordinates of the rotation center are calculated using the later coordinates.

  According to the present invention, the coordinates of the rotation center of the stage can be calculated using the images obtained before and after the rotation of the stage and the distance between the marks. In addition, the rotation angle of the stage can be arbitrarily set within a range where each mark does not come out of the field of view of the corresponding camera, so that accurate calculation processing can be performed without being influenced by the accuracy of the rotation mechanism. it can. Therefore, since the rotation center of the stage can be calculated easily and accurately, the accuracy of workpiece positioning can be significantly improved by using the calculation result.

  FIG. 2 shows a configuration example of a workpiece positioning apparatus to which the present invention is applied. This work positioning apparatus is used for alignment of the substrates constituting each layer in the manufacturing process of a multilayer substrate such as a liquid crystal substrate. , Simply referred to as “cameras 21 and 22”), the controller 3 and the like.

  The stage 1 includes a table unit 10 that supports the workpiece 4 as a main body. Although not shown here, the stage 1 includes a moving mechanism for moving the table unit 10 in the x and y axis directions, a rotating mechanism for rotating the table unit 10, and the like. . Each camera 21, 22 is supported by a movable arm portion (not shown) in a state where the optical axis is directed in a vertical direction at a predetermined position above the table portion 10.

  On the upper surface of the workpiece 4 (substrate) to be positioned in this embodiment, positioning marks M1 and M2 are provided on the two corner portions 41 and 42 in a diagonal relationship, respectively. Each camera 21 and 22 is disposed at a position corresponding to the reference position of the marks M1 and M2.

  As shown in FIG. 3, the controller 3 is composed of a personal computer. As shown in FIG. 3, the CPU 34 controls the memory 35, the image memory 33, the image input units 31, 32 corresponding to the cameras 21, 22, and the stage. A control unit 36, an input unit 37, an output unit 38, and the like are provided.

  The image input units 31 and 32 are configured by a camera interface circuit, an A / D conversion circuit, and the like. The image memory 33 is for storing the image data digitally converted by the image input units 31 and 32, and has a capacity sufficient to store a plurality of images for each camera. The memory 35 stores a program and setting data necessary for the operation of the CPU 34 and a work data storage area.

  The stage control unit 36 outputs a control signal corresponding to the operation amount calculated by the CPU 34 to each moving mechanism and rotating mechanism of the stage 1. Accordingly, each moving mechanism moves the table unit 10 by a distance corresponding to the operation amount, and the rotation mechanism rotates the table unit 10 by an angle corresponding to the operation amount.

  The input unit 37 is used to input setting data such as the distance L between the marks M1 and M2, and includes the keyboard 371 and the mouse 372 shown in FIG. The output unit 38 is used to output information indicating that the alignment process has been completed and measurement results (such as rotation angles and coordinates of the center position) in the setting process described later, and includes the monitor 30 in FIG.

  In the above configuration, the controller 3 uses the images of the marks M1 and M2 obtained by the cameras 21 and 22, and the amount of deviation dx of the workpiece 4 in the x-axis direction, the amount of deviation dy in the y-axis direction, and the rotation of the workpiece 4 The angle dθ is calculated (hereinafter, dx, dy, dθ are collectively referred to as “deviation amount”). Then, the marks M1 and M2 of the workpiece 4 are aligned with the reference position by operating the moving mechanism and the rotating mechanism of the stage 1 based on these deviation amounts.

Further, prior to performing the above alignment processing, the controller 3 performs calibration for each of the cameras 21 and 22, and sets parameters necessary for replacing each point included in the image from the camera with real coordinates. calculate. Further, in the controller 3 of this embodiment, a process for obtaining the coordinates of the rotation center of the stage 1 is performed in order to calculate the rotation angle dθ of the deviation amount of the workpiece.
The real coordinates described above represent a position on a virtual plane including the upper surface of the table unit 10. For example, the origin is set at the upper left corner of the movable area of the table unit 10.

FIG. 4 shows a procedure at the time of setting processing by the controller 3.
First, in the first ST1 (ST is an abbreviation of a step. The same applies to the following), the calibration of the cameras 21 and 22 is executed. Each conversion parameter obtained by this calibration is stored in the memory 35.

  Next, in ST2, the reference positions of the marks M1 and M2 and the distance L between the marks M1 and M2 are received and registered. The user obtains the positions of the marks M1 and M2 viewed from a predetermined position (for example, the upper left end point) of the work 4 from the measurement using the actual work 4 or the design data of the work 4, and based on these position data. The real coordinates where the marks M1 and M2 should be located can be specified. The real coordinates specified here are input as a reference position. Similarly, the distance L between the marks can be obtained from the position data of the marks M1 and M2 and input.

In ST3, the model work is placed on the stage 1, and the stage 1 is moved until the marks M1 and M2 are included in the fields of view of the corresponding cameras 21 and 22, respectively. In the next ST4, the cameras 21 and 22 are driven to generate images of the marks M1 and M2.
Note that the movement of the stage 1 in ST3 and ST4 can be automatically performed based on a preset operation amount, but is not limited thereto, and may be moved according to a user operation. The same applies to ST21 in FIG.

  In subsequent ST5, the positions of the marks M1 and M2 are measured using images obtained by the cameras 21 and 22. In this measurement process, first, the center point of the mark on the image is extracted, and the coordinates of the center point are converted into real coordinates using the parameters set in ST1. The actual coordinates of the marks M1 and M2 obtained in ST5 correspond to the points a1 and a2 in FIG.

  In the next ST6, the stage 1 is rotated in a range where the marks M1 and M2 do not come out of the field of view of the corresponding cameras 21 and 22. In ST7, the cameras 21 and 22 are re-driven to execute the second imaging process. In ST8, the positions of the marks M1 and M2 are measured again using the image obtained in the second imaging process. The actual coordinates of the marks M1 and M2 obtained in ST8 correspond to the points b1 and b2 in FIG.

  In the next ST9, processing for obtaining the rotation angle dT of the stage 1 is executed. In this step, first, using the coordinates of the points a1 and a2 obtained in ST5 and the coordinates of the points b1 and b2 obtained in ST8, the movement amounts (dx1, dy1) (dx2, dy2) of the marks M1, M2 are used. ) Is calculated. Next, the inner product of the vectors A and B is obtained by applying these movement amounts and the distance L between the marks to the aforementioned equation (3). Then, the rotation angle dT is calculated by fitting the inner product and the distance L to the equation (1).

  When the rotation angle dT is obtained in this way, in ST10, the coordinates before the movement of the marks M1, M2 (the coordinates of the points a1, a2), the coordinates after the movement (the coordinates of the points b1, b2), and the rotation Using the angle dT, the equations (4) and (5) are executed to calculate the coordinates of the rotation center C for each mark. The average value of these coordinates is used as the rotation center coordinate. In ST11, the coordinates of the final center of rotation are registered in the memory 35, and then the process ends.

  In the above setting process, when it is desired to further improve the calculation accuracy of the rotation center, the processes of ST4 to ST10 are repeatedly executed for a plurality of cycles, and the average value of the rotation center coordinates obtained for each cycle is used as the final value. The center of rotation may be used. In this case, there is no problem even if the rotation angle of the stage 1 is different for each cycle.

FIG. 5 shows a procedure of alignment processing by the controller 3.
In ST21, which is the first step, the stage 1 on which the workpiece 4 to be processed is placed is moved to a position where the marks M1 and M2 are included in the fields of view of the cameras 21 and 22. In the next ST22, the cameras 21 and 22 are driven to generate images of the marks M1 and M2.

  In ST23, the positions of the marks M1 and M2 are measured using images from the cameras 21 and 22. In this step, similarly to ST5 and ST8 in FIG. 4, after the center position of the mark in the image is extracted, a process of converting the coordinates of the center position into real coordinates is executed.

  In ST24, using the measurement positions of the marks M1 and M2 obtained in ST23, workpiece displacement amounts dx, dy, and dθ are calculated. For dx and dy, after obtaining the difference in coordinates from the measurement position and the reference position for each mark, the average value of these differences is calculated. On the other hand, for dθ, the rotation angle is obtained for each mark using the measurement position and the reference position and the coordinates of the rotation center obtained in the setting process, and then the average value of each rotation angle is calculated.

  In ST25, based on the deviations dx, dy, dθ obtained in ST24, the operation amount of each moving mechanism and rotating mechanism is determined. Then, each mechanism is sequentially controlled by the determined operation amount, thereby correcting the positional deviation and rotational deviation of each of x and y in the respective axial directions, and thereafter the processing is terminated.

  By the way, even in the conventional method for obtaining the coordinates of the rotation center of the stage by calculation, after imaging two marks in a diagonal relationship, the stage is rotated, and after the rotation, each mark is imaged again. An operation using the obtained image is executed. That is, at first glance, the procedure related to the calculation method of the rotation center in this embodiment seems to be no different from the conventional method.

However, in this embodiment, the rotation angle of the stage is not particularly defined, whereas in the conventional method, the rotation angle is determined after the rotation angle of the stage is determined.
Since the actual rotation angle of the stage has an error due to the performance of the rotation mechanism, if the calculation is performed on the assumption that the stage is rotating accurately as in the past, an incorrect rotation center is derived. Will be. Due to this inaccurate rotation center, the rotation deviation correction cannot accurately determine the rotation angle of the workpiece, and an error also occurs when the stage is rotated for rotation correction. That is, in the conventional method, errors may be superimposed, and the accuracy of rotational deviation correction may be significantly deteriorated.

  On the other hand, in this embodiment, the actual rotation angle of the stage 1 can be obtained with high accuracy by using the measurement position of each mark before and after the rotation of the stage 1 and the distance L between the marks. Therefore, the coordinates of the center of rotation can be obtained accurately. Therefore, the rotational angle of the workpiece 4 can be obtained with high accuracy even when the rotational deviation is corrected, and errors in the correction can be greatly reduced to increase the alignment accuracy.

It is a figure explaining the principle of the calculation process of the rotation center concerning this invention. It is explanatory drawing which shows the structural example of a workpiece | work positioning device. It is a block diagram which shows the electric constitution of a workpiece | work positioning device. It is a flowchart which shows the process sequence at the time of a setting process. It is a flowchart which shows the procedure at the time of the positioning process of a workpiece | work.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stage 3 Control apparatus 4 Work 10 Table part 21, 22 Camera 34 CPU
35 Memory 37 Input section M1, M2 mark

Claims (5)

A workpiece having a plurality of positioning marks on its surface is set on a stage having a rotation mechanism, and at least imaging means are set toward the reference positions of two positioning marks that are in a diagonal relationship. In the work positioning process for controlling the operation of the stage so that each positioning mark matches the reference position using the image obtained by the means, the coordinates of the rotation center of the stage necessary for correcting the rotational deviation of the work are obtained. A method,
Step A for inputting data for specifying a distance between positioning marks on the workpiece, Step B for placing a model workpiece on the stage, and causing each imaging means to image a corresponding positioning mark, The stage is rotated within a range where the positioning mark does not come out of the field of view of the corresponding imaging means, and after performing Step C in which each imaging means images the positioning mark again, the image obtained in Steps B and C and the positioning are obtained. A rotation center calculation method, wherein a coordinate of a rotation center of the stage is calculated using a distance between marks. The method of claim 1, wherein
In the process of calculating the coordinates of the rotation center of the stage, for the two positioning marks having the diagonal relationship, the coordinates before the stage rotation and the coordinates after the stage rotation are obtained using the images obtained in the steps B and C, respectively. The first step for obtaining the distance, the second step for obtaining the movement amount of each positioning mark by the rotation of the stage from the coordinates calculated in the first step, and the distance between the positioning marks and the second step. Using the movement amount of each positioning mark, the third step for obtaining the rotation angle of the stage, the rotation angle obtained in the third step, and the coordinates before and after rotation of at least one positioning mark. And a fourth step of calculating the coordinates of the rotation center of the stage. The method of claim 2, wherein
In the third step, a rotation center calculation method for calculating the rotation angle using an inner product of a vector connecting the positioning marks before the stage rotation and the vector after the stage rotation. A stage having a rotation mechanism, a plurality of imaging means for imaging the positioning marks of the workpiece on the stage, and the positioning marks using the images obtained by the imaging means so that each positioning mark matches the reference position, respectively. In a workpiece positioning device comprising a control device for controlling the operation of the stage,
The plurality of imaging means are respectively arranged toward the reference positions of at least two positioning marks in a diagonal relationship,
The control device includes input means for inputting data for specifying a distance between the positioning marks in the diagonal relationship, and corresponds to each imaging means when a model work is placed on the stage. After imaging the positioning mark, the stage is rotated by a predetermined amount so that each imaging means images each positioning mark again, and each image obtained before and after the rotation of the stage and the positioning mark input from the input means A workpiece positioning device that calculates the coordinates of the rotation center of the stage using the distance between them.   The control device includes coordinate calculation means for obtaining coordinates before and after rotation of the stage using the images obtained from the imaging means for the two positioning marks in the diagonal relationship, and the coordinate calculation Using the movement amount calculation means for obtaining the movement amount of each positioning mark by the rotation of the stage from each coordinate calculated by the means, the distance between the positioning marks and the movement amount of each positioning mark calculated by the movement amount calculation means Rotation angle calculation means for determining the rotation angle of the stage, using the rotation angle calculated by the rotation angle calculation means and the coordinates before and after the stage rotation related to at least one positioning mark, The work positioning apparatus according to claim 4, wherein coordinates of the rotation center of the stage are calculated.

Images