Relative Position Calibration Method and Related Device for Alignment Camera and Measurement Camera

Abstract

The present application discloses a method for calibrating the relative positions of an alignment camera and a measurement camera and related devices, which relates to the technical field of chip manufacturing. A calibration plate image including two right-angled sides is selected, and the corner points of the two right-angled sides are used as the target points for calibration. First, the first corner point coordinates of the corner points in the first calibration plate image under the alignment camera are obtained, then the second corner point coordinates of the corner points in the second calibration plate image under the measurement camera are obtained, and finally the relative position relationship between the alignment camera and the measurement camera is obtained through coordinate conversion. Since the calibration plate image includes two right-angled sides, has positioning features in the horizontal and vertical directions, has a unique direction, and can be imaged under both the alignment camera and the measurement camera at the same time, it can accurately calibrate the relative positions of the alignment camera and the measurement camera.

Description

Technical Field

[0001] The present application relates to the technical field of chip manufacturing, and in particular, to a method for calibrating the relative positions of an alignment camera and a measurement camera and related devices. Background Art

[0002] A chip is the core and foundation of high-end manufacturing, determining the development of the high-tech industry. Lithography is a crucial step in the chip manufacturing process, and the process level of lithography directly determines the process and performance of the chip. A chip is composed of multiple layers of circuits stacked on top of each other, and the manufacturing of a single chip often requires dozens of lithography operations to be completed. The alignment deviation between adjacent circuit layers in a chip is also known as overlay error. The rapid measurement and accurate evaluation of overlay error are the keys to optimizing the operating parameters of a lithography machine and managing process yield.

[0003] After lithography is performed by a lithography machine, there will always be a certain overlay deviation. If accurate measurement of the overlay deviation is to be carried out, first, the wafer needs to be centered and flattened under the alignment camera, and then a wafer coordinate system under the alignment camera is established. Then, according to the positional relationship between the alignment camera and the measurement camera, the wafer coordinate system under the alignment camera is mapped to the measurement camera, so as to accurately find the target point to be measured for measurement. It can be seen that the calibration accuracy of the relative positional relationship between the alignment camera and the measurement camera affects the accuracy of finding the target mark under the measurement camera, and thus affects the measurement accuracy of the overlay deviation. Summary of the Invention

[0004] In view of the above problems, the present application provides a method for calibrating the relative positions of an alignment camera and a measurement camera and related devices, which accurately realizes the calibration of the relative positions of the alignment camera and the measurement camera. The specific solutions are as follows:

[0005] The first aspect of the present application provides a method for calibrating the relative positions of an alignment camera and a measurement camera, including:

[0006] Moving the alignment camera to a first preset position to obtain a first calibration plate image, where the first preset position corresponds to the position coordinates of the alignment camera in the workbench coordinate system, and the first calibration plate image includes corner points formed by two right-angled sides;

[0007] Moving the measurement camera to a second preset position to obtain a second calibration plate image, where the second preset position corresponds to the position coordinates of the measurement camera in the workbench coordinate system, and the second calibration plate image includes the corner points;

[0008] Determining the first corner point coordinates of the corner points in the first calibration plate image, and determining the second corner point coordinates of the corner points in the second calibration plate image;

[0009] Determine the position calibration information between the alignment camera and the measurement camera by using the matching relationship between the first corner point coordinates and the second corner point coordinates.

[0010] In a possible implementation, the determining the position calibration information between the alignment camera and the measurement camera by using the matching relationship between the first corner point coordinates and the second corner point coordinates includes:

[0011] Determine the first calculation relationship between the first corner point coordinates and the center pixel coordinates of the first calibration plate image, the pixel equivalent under the pre-calibrated alignment camera, the position coordinates of the alignment camera in the workbench coordinate system, and the physical coordinates of the corner point under the alignment camera;

[0012] Determine the second calculation relationship between the second corner point coordinates and the center pixel coordinates of the second calibration plate image, the pixel equivalent under the pre-calibrated measurement camera, the position coordinates of the measurement camera in the workbench coordinate system, and the physical coordinates of the corner point under the measurement camera;

[0013] Make the physical coordinates of the corner point under the alignment camera equal to the physical coordinates of the corner point under the measurement camera, and determine the relative position between the alignment camera and the measurement camera according to the first calculation relationship and the second calculation relationship.

[0014] In a possible implementation, determining the first corner point coordinates of the corner point in the first calibration plate image and determining the second corner point coordinates of the corner point in the second calibration plate image includes:

[0015] Perform the following operations on the calibration plate images obtained by the alignment camera and the measurement camera respectively:

[0016] Perform edge detection on the calibration plate image, and determine the position of the corner point area in the calibration plate image according to the edge detection result;

[0017] Perform skew correction on the calibration plate image to obtain a target calibration plate image, and the two right-angle sides of the corner point in the target calibration plate image are respectively in the horizontal direction and the vertical direction;

[0018] Determine the corner point pixel coordinates in the target calibration plate image;

[0019] Determine the corner point pixel coordinates in the calibration plate image according to the tilt angle of the right-angle side in the calibration plate image and the corner point pixel coordinates in the target calibration plate image;

[0020]

[0021] ​Among them, the corner pixel coordinates in the first calibration plate image are the first corner coordinates, and the corner pixel coordinates in the second calibration plate image are the second corner coordinates.

[0022] In a possible implementation, the edge detection of the calibration plate image and determining the position of the corner region in the calibration plate image according to the edge detection result include:

[0023] Performing edge detection on the calibration plate image to obtain an edge region;

[0024] Performing an opening operation on the edge region in the horizontal direction to remove the noise region in the vertical direction and obtain a horizontal region;

[0025] Performing an opening operation on the edge region in the vertical direction to remove the noise region in the horizontal direction and obtain a vertical region;

[0026] Determining the intersection of the horizontal region and the vertical region as the corner region.

[0027] In a possible implementation, the tilt correction of the calibration plate image to obtain a target calibration plate image includes:

[0028] Generating a rectangular frame with a preset size in the corner region and calculating the average gray value in the rectangular frame;

[0029] Taking the average gray value as a threshold, performing binarization on the image in the rectangular frame to obtain a foreground region and a background region;

[0030] Calculating the average gray values of the foreground region and the background region respectively;

[0031] Generating a corner standard template image according to the average gray values of the foreground region and the background region;

[0032] Performing template matching of the corner standard template image on the calibration plate image and calculating the tilt angle of the right-angle side in the calibration plate image;

[0033] Performing tilt correction on the calibration plate image according to the tilt angle to obtain the target calibration plate image.

[0034] In a possible implementation, the determination of the corner pixel coordinates in the target calibration plate image includes:

[0035] Performing gray-scale projection on the image in the horizontal and vertical directions respectively within the region of interest of the corner in the target calibration plate image to obtain gray-scale curves in the horizontal and vertical directions;

[0036] Calculate the gradient curves corresponding to the grayscale curves in the horizontal and vertical directions respectively, and determine the edge position as the position with the maximum gradient;

[0037] Determine the corner pixel coordinates in the target calibration plate image according to the edge positions in the horizontal and vertical directions.

[0038] The second aspect of the present application provides a relative position calibration device for an alignment camera and a measurement camera, including:

[0039] A first image acquisition unit, configured to move the alignment camera to a first preset position to acquire a first calibration plate image, where the first preset position corresponds to the position coordinates of the alignment camera in the workbench coordinate system, and the first calibration plate image includes corners formed by two right-angled sides;

[0040] A second image acquisition unit, configured to move the measurement camera to a second preset position to acquire a second calibration plate image, where the second preset position corresponds to the position coordinates of the measurement camera in the workbench coordinate system, and the second calibration plate image includes the corners;

[0041] A coordinate determination unit, configured to determine the first corner coordinates of the corners in the first calibration plate image, and determine the second corner coordinates of the corners in the second calibration plate image;

[0042] A calibration unit, configured to determine the position calibration information between the alignment camera and the measurement camera by using the matching relationship between the first corner coordinates and the second corner coordinates.

[0043] The third aspect of the present application provides an electronic device, including at least one processor and a memory connected to the processor, where:

[0044] The memory is used to store a computer program;

[0045] The processor is configured to execute the computer program so that the electronic device can implement the relative position calibration method for the alignment camera and the measurement camera in the first aspect or any implementation manner of the first aspect.

[0046] The fourth aspect of the present application provides a computer program product, including computer-readable instructions, which, when running on an electronic device, enable the electronic device to implement the relative position calibration method for the alignment camera and the measurement camera in the first aspect or any implementation manner of the first aspect.

[0047] A fifth aspect of the present application provides a computer storage medium carrying one or more computer programs, which, when executed by an electronic device, can enable the electronic device to perform the method for calibrating the relative positions of the alignment camera and the measurement camera in the first aspect or any implementation manner of the first aspect.

[0048] With the above technical solution, the present application provides a method and related device for calibrating the relative positions of an alignment camera and a measurement camera. A calibration plate image including two right-angled sides is selected, and the corner points of the two right-angled sides are used as the target points for calibration. First, the first corner point coordinates of the corner points in the first calibration plate image under the alignment camera are obtained, then the second corner point coordinates of the corner points in the second calibration plate image under the measurement camera are obtained, and finally the relative position relationship between the alignment camera and the measurement camera is obtained through coordinate conversion. Since the calibration plate image includes two right-angled sides, has positioning features in the horizontal and vertical directions, has a unique direction, and can be imaged under both the alignment camera and the measurement camera at the same time, it can accurately calibrate the relative positions of the alignment camera and the measurement camera. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In combination with the accompanying drawings and with reference to the following specific embodiments, the above and other features, advantages and aspects of the various embodiments of the present disclosure will become more apparent. Throughout the drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and the original elements and elements are not necessarily drawn to scale.

[0050] Figure 1 It is a schematic diagram of a calibration pattern provided by the present application;

[0051] Figure 2 It is another schematic diagram of a calibration pattern provided by the present application;

[0052] Figure 3 It is a flowchart of a method for calibrating the relative positions of an alignment camera and a measurement camera provided by an embodiment of the present application;

[0053] Figure 4 It is a schematic diagram of a calibration pattern provided by an embodiment of the present application;

[0054] Figure 5 It is an example diagram of a first calibration plate image obtained by the alignment camera provided by an embodiment of the present application;

[0055] Figure 6 It is an example diagram of a second calibration plate image obtained by the alignment camera provided by an embodiment of the present application;

[0056] Figure 7 It is a schematic diagram of an edge intensity image provided by an embodiment of the present application;

[0057] Figure 8Schematic diagram of the binarized edge region provided by the embodiment of the present application;

[0058] Figure 9 Schematic diagram of the horizontal region provided by the embodiment of the present application;

[0059] Figure 10 Schematic diagram of the vertical region provided by the embodiment of the present application;

[0060] Figure 11 Schematic diagram of the corner region provided by the embodiment of the present application;

[0061] Figure 12 Schematic diagram of the position of the corner region in the calibration board image provided by the embodiment of the present application;

[0062] Figure 13 Schematic diagram of the corner standard template image corresponding to the corner region provided by the embodiment of the present application;

[0063] Figure 14 Schematic diagram of the target calibration board image provided by the embodiment of the present application;

[0064] Figure 15 Schematic diagram of the region of interest of the corner provided by the embodiment of the present application;

[0065] Figure 16 Schematic diagram of the gradient curve in the horizontal direction provided by the embodiment of the present application;

[0066] Figure 17 Schematic diagram of the gradient curve in the vertical direction provided by the embodiment of the present application;

[0067] Figure 18 Schematic diagram of the workbench coordinate system provided by the embodiment of the present application;

[0068] Figure 19 Schematic diagram of the structure of the relative position calibration device for the alignment camera and the measurement camera provided by the embodiment of the present application;

[0069] Figure 20 Schematic diagram of the structure of an electronic device provided by the embodiment of the present application. Detailed implementation manners

[0070] In the following elaboration, in order to ensure the accuracy of citation and the fluency of reading, the key technical terms, abbreviations or acronyms involved in the text are summarized and explained as follows:

[0071] The embodiments of the present application will be described below with reference to the accompanying drawings in the embodiments of the present application. The terms used in the implementation part of the present application are only used to explain the specific embodiments of the present application, and are not intended to limit the present application.

[0072] The embodiments of the present application will be described below with reference to the accompanying drawings. Those of ordinary skill in the art will understand that with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of the present application are equally applicable to similar technical problems.

[0073] The terms "first", "second", etc. in the description and claims of the present application and the above-mentioned accompanying drawings are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances, which is only a way of distinguishing objects with the same attributes when describing the embodiments of the present application. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion, so that a process, method, system, product or device including a series of units does not have to be limited to those units, but may include other units that are not clearly listed or are inherent to these processes, methods, products or devices.

[0074] Currently, a circular pattern as shown in Figure 1 is used to calibrate the relative positions of two cameras. However, since the alignment camera's field of view is 25 times that of the measurement camera, it is impossible to use a circle of the same size that can be clearly seen under the alignment camera and the entire circle can be completely seen under the measurement camera, that is, Figure 1 the circular image shown cannot meet the relative position calibration requirements of the alignment camera and the measurement camera.

[0075] Instead, two circles of different sizes as shown in Figure 2 are used as the calibration plate image, with the centers of the large circle and the small circle coinciding. The large circle is used to calibrate the position of the alignment camera, and the small circle is used to calibrate the position of the measurement camera. However, the processing accuracy of the calibration plate image will affect the center coincidence accuracy of the two circles, thereby affecting the relative position calibration accuracy of the alignment camera and the measurement camera. That is, if there is a deviation in the positions of the centers of the large circle and the small circle, this deviation will be introduced into the relative position calibration error of the alignment camera and the measurement camera.

[0076] To solve the above technical problems, the embodiments of the present application provide a method for calibrating the relative positions of an alignment camera and a measurement camera. The method for calibrating the relative positions of the alignment camera and the measurement camera in the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0077] Referring to Figure 3 , Figure 3 which is a schematic flow chart of a method for calibrating the relative positions of an alignment camera and a measurement camera provided by the embodiments of the present application. As shown in Figure 3 , the method for calibrating the relative positions of an alignment camera and a measurement camera provided by the embodiments of the present application may include steps 301 to 304, which will be described in detail below.

[0078] 301: Move the alignment camera to the first preset position to obtain the first calibration board image. The first preset position corresponds to the position coordinates of the alignment camera in the workbench coordinate system. The first calibration board image includes corner points formed by two right-angled sides.

[0079] As Figure 4 shown in the calibration pattern, in this embodiment, a calibration pattern with right-angled side features is used. The corner points of the right-angled sides themselves have positioning features in the X and Y directions, with unique directions, and can be imaged under both the alignment camera and the measurement camera at the same time, enabling stable and reliable position calibration between the alignment camera and the measurement camera.

[0080] 302: Move the measurement camera to the second preset position to obtain the second calibration board image. The second preset position corresponds to the position coordinates of the measurement camera in the workbench coordinate system. The second calibration board image includes the above-mentioned corner points.

[0081] When the alignment camera and the measurement camera perform imaging, it is necessary to ensure that there is only one corner point in the entire field of view as much as possible. Exemplarily, the first calibration board image obtained by the alignment camera is as Figure 5 shown, and the second calibration board image obtained by the measurement camera is as Figure 6 shown.

[0082] 303: Determine the first corner point coordinates of the corner point in the first calibration board image, and determine the second corner point coordinates of the corner point in the second calibration board image.

[0083] After obtaining the first calibration board image and the second calibration board image, perform corner point detection to obtain the first corner point coordinates of the corner point in the first calibration board image, and determine the second corner point coordinates of the corner point in the second calibration board image.

[0084] It should be noted that the first corner point coordinates are the corner point pixel coordinates under the alignment camera, and the second corner point is the corner point pixel coordinates under the measurement camera.

[0085] 304: Use the matching relationship between the first corner point coordinates and the second corner point coordinates to determine the position calibration information between the alignment camera and the measurement camera.

[0086] Use the matching relationship between the first corner point coordinates and the second corner point coordinates to calculate the relative positions of the alignment camera and the measurement camera through a series of coordinate conversions.

[0087] A method for calibrating the relative position of an alignment camera and a measurement camera disclosed in this embodiment selects a calibration plate image including two right-angled sides, and uses the corner points of the two right-angled sides as the target points for calibration. First, obtain the first corner point coordinates of the corner points in the first calibration plate image under the alignment camera, then obtain the second corner point coordinates of the corner points in the second calibration plate image under the measurement camera, and finally obtain the relative position relationship between the alignment camera and the measurement camera through coordinate conversion. Since the calibration plate image includes two right-angled sides, has positioning features in the horizontal and vertical directions, has a unique direction, and can be imaged under the alignment camera and the measurement camera at the same time, it can accurately calibrate the relative position of the alignment camera and the measurement camera.

[0088] In a possible implementation, determining the first corner point coordinates of the corner points in the first calibration plate image and determining the second corner point coordinates of the corner points in the second calibration plate image includes:

[0089] Perform the following operations on the calibration plate images obtained by the alignment camera and the measurement camera respectively:

[0090] 3031: Perform edge detection on the calibration plate image, and determine the position of the corner point area in the calibration plate image according to the edge detection result;

[0091] Perform edge detection on the calibration plate image, and identify the right-angled sides in the horizontal direction and the vertical direction. Since the corner points are the intersections of the right-angled sides in the horizontal direction and the vertical direction, the corner point area can be obtained after identifying the right-angled sides in the horizontal direction and the vertical direction.

[0092] 3032: Perform skew correction on the calibration plate image to obtain a target calibration plate image;

[0093] Noise or errors in the image capture, edge detection, or other processes may cause the two right-angled sides of the corner points in the calibration plate image not to be in the horizontal and vertical directions. To improve the calculation accuracy, it is necessary to perform skew correction on the calibration plate image so that the two right-angled sides of the corner points in the obtained target calibration plate image are respectively in the horizontal and vertical directions.

[0094] 3033: Determine the corner point pixel coordinates in the target calibration plate image;

[0095] The principle of determining the corner point pixel coordinates is still to determine the corner point pixel coordinates according to the intersection of the two right-angled sides of the corner points.

[0096] 3034: Determine the corner point pixel coordinates in the calibration plate image according to the tilt angle of the right-angled sides in the calibration plate image and the corner point pixel coordinates in the target calibration plate image.

[0097] Restore the corner pixel coordinates in the target calibration plate image to the corner pixel coordinates in the calibration plate image before skew correction.

[0098] In a possible implementation, step 3031 in the above embodiment includes the following steps A1 - A4:

[0099] A1: Perform edge detection on the calibration plate image to obtain an edge region;

[0100] There are various methods to perform edge detection on the calibration plate image, such as using the sobel algorithm for edge detection, using the Prewitt operator for edge detection, using the Canny operator for edge detection, etc.

[0101] Exemplarily, use the sobel algorithm for edge detection.

[0102] The Sobel calculation formula is as follows:

[0103]

[0104]

[0105]

[0106] Where A is the grayscale value of the current pixel point, Gx is the grayscale value of the pixel point after filtering in the X direction, Gy is the grayscale value of the pixel point after filtering in the y direction. G is the finally obtained grayscale value after Sobel filtering at this pixel point.

[0107] After processing by the sobel algorithm, an edge intensity image as shown in Figure 7 is obtained, and then the edge intensity image is binarized to obtain a binarized edge region as shown in Figure 8 .

[0108] A2: Perform an opening operation on the edge region in the horizontal direction to remove the noise region in the vertical direction and obtain a horizontal region;

[0109] Performing an opening operation on the edge region in the horizontal direction, that is, performing an opening operation on the edge region in the X direction, and then removing the edge region in the vertical direction, that is, removing the noise region in the vertical direction, to obtain the horizontal region as described in Figure 9 .

[0110] A3: Perform an opening operation on the edge region in the vertical direction to remove the noise region in the horizontal direction and obtain a vertical region;

[0111] Perform an opening operation on the edge region in the vertical direction, that is, perform an opening operation on the edge region in the Y direction, and then remove the edge region in the horizontal direction, that is, remove the noise region in the horizontal direction, to obtain as Figure 10 the vertical region described above.

[0112] A4: Determine the intersection of the horizontal region and the vertical region as the original corner point region.

[0113] It can be understood that the corner point is the intersection of the right-angled side in the horizontal direction and the right-angled side in the vertical direction. Therefore, the intersection of the horizontal region and the vertical region is the corner point region as Figure 11 shown, and the position of the corner point region in the calibration plate image is as Figure 12 shown.

[0114] In a possible implementation, step 3032 in the above embodiment includes the following steps B1 - B6:

[0115] B1: Generate a rectangular frame with a preset size in the corner point region, and calculate the average gray value in the rectangular frame;

[0116] Exemplarily, generate a 64×64 rectangular frame (64×64 is only an example, and rectangular frames of other sizes can also be generated) centered on the corner point region.

[0117] B2: Use the average gray value as a threshold to binarize the image in the rectangular frame to obtain a foreground region and a background region;

[0118] Set the gray value of the points with gray values greater than the threshold to the first pixel value, and set the gray value of the points with gray values less than the threshold to the second pixel value. Then, the corner point region can be clearly divided into two parts, namely the foreground region and the background region.

[0119] B3: Calculate the average gray values of the foreground region and the background region respectively;

[0120] B4: Generate a corner point standard template image according to the average gray values of the foreground region and the background region;

[0121] It can be understood that a 64×64 rectangular frame is generated centered on the corner point region. In the case where the right-angled sides of the corner point are not inclined, the lower right 1 / 4 region in the rectangular frame should be the foreground region, and the remaining 3 / 4 region should be the background region. Therefore, as Figure 13 shown, the lower right 1 / 4 region in the rectangular frame is used as the target foreground region in the corner point standard template image, and the remaining 3 / 4 region is used as the target background region in the corner point standard template image, and the angle of the horizontal boundary of the target foreground region is 0, that is, the angle of the horizontal right-angled side of the corner point is 0.

[0122] B5: Perform template matching of the corner standard template image on the calibration board image, and calculate the inclination angle of the right-angle side in the calibration board image;

[0123] Specifically, perform template matching of the corner standard template image on the calibration board image according to the position of the corner region, so that the corner region in the corner standard template image coincides with the corner region in the calibration board image. Then, the angle between the horizontal right-angle side in the corner standard template image and the horizontal right-angle side in the calibration board image is the inclination θ of the right-angle side in the calibration board image.

[0124] B6: Perform tilt correction on the calibration board image according to the inclination angle to obtain the target calibration board image.

[0125] As Figure 14 shown, through tilt correction, the two right-angle sides in the target calibration board image coincide with the two right-angle sides of the corner standard template image respectively, that is, the two right-angle sides of the corner in the target calibration board image are respectively in the horizontal direction and the vertical direction.

[0126] In a possible implementation, step 3033 in the above embodiment includes the following steps C1 - C3:

[0127] C1: Perform gray-scale projection on the image in the horizontal and vertical directions respectively within the region of interest of the corner in the target calibration board image to obtain gray-scale curves in the horizontal and vertical directions;

[0128] As Figure 15 shown, generate a 64×64 rectangular region of interest (other sizes of regions of interest can also be generated) centered on the corner region in the target calibration board image, and perform gray-scale projection on the image in the horizontal direction (i.e., the X direction) and the vertical direction (i.e., the Y direction) within the region of interest.

[0129] C2: Calculate the gradient curves corresponding to the gray-scale curves in the horizontal and vertical directions respectively, and determine the edge positions as the positions with the maximum gradient;

[0130] Take the first derivative of the gray-scale curves in the horizontal and vertical directions to obtain the gradient curves in the horizontal and vertical directions. As Figure 16 shown by the gradient curve in the horizontal direction, the position with the maximum gradient is the edge position in the horizontal direction. As Figure 17 shown by the gradient curve in the vertical direction, the position with the maximum gradient is the edge position in the vertical direction.

[0131] C3: Determine the corner pixel coordinates in the target calibration board image according to the edge positions in the horizontal and vertical directions.

[0132] The edge position in the horizontal direction determines the abscissa Px1' of the corner point, and the edge position in the vertical direction determines the ordinate Py1' of the corner point, thereby obtaining the pixel coordinates (Px1', Py1') of the corner point in the target calibration plate image.

[0133] Furthermore, after obtaining the pixel coordinates of the corner points in the target calibration plate image (Px1', Py1'), it is necessary to restore the coordinate position of the pixel coordinates of the corner points to the position coordinates before the tilt correction, that is, rotate θ degrees around the image center to obtain the original pixel coordinates of the corner points (Px1, Py1). The calculation formula is as follows:

[0134] .

[0135] The pixel coordinates of the corner points in the first calibration plate image are the first corner point coordinates, and the pixel coordinates of the corner points in the second calibration plate image are the second corner point coordinates.

[0136] After obtaining the coordinates of the first corner point and the coordinates of the second corner point, the position calibration information between the alignment camera and the measurement camera can be determined by using the matching relationship between the coordinates of the first corner point and the coordinates of the second corner point. In a possible implementation, the following steps D1-D3 are specifically included:

[0137] D1: Determine a first calculation relationship between the coordinates of the first corner point and the central pixel coordinates of the first calibration plate image, the pre-calibrated pixel equivalent under the alignment camera, the position coordinates of the alignment camera in the workbench coordinate system, and the physical coordinates of the corner point under the alignment camera;

[0138] D2: Determine a second calculation relationship between the coordinates of the second corner point and the central pixel coordinates of the second calibration plate image, the pixel equivalent under the pre-calibrated measurement camera, the position coordinates of the measurement camera in the workbench coordinate system, and the physical coordinates of the corner point under the measurement camera;

[0139] D3: Make the physical coordinates of the corner point under the alignment camera equal to the physical coordinates of the corner point under the measurement camera, and determine the relative position of the alignment camera and the measurement camera according to the first calculation relationship and the second calculation relationship.

[0140] like Figure 18 As shown, when the alignment camera moves to the first preset position, the position coordinates (xa, ya) of the alignment camera in the workbench coordinate system are obtained, and the coordinates of the first corner point (Px1, Py1) are calculated. When the measurement camera moves to the second preset position, the position coordinates (xm, ym) of the measurement camera in the workbench coordinate system are obtained, and the coordinates of the second corner point (Px2, Py2) are calculated.

[0141] In this embodiment, the pixel equivalents PixelSizeX1 and PixelSizeY1 under the alignment camera, and the pixel equivalents PixelSizeX2 and PixelSizeY2 under the measurement camera are pre-calibrated. Additionally, the central pixel coordinates (Pxa, Pya) of the first calibration plate image and the central pixel coordinates (Pxm, Pym) of the first calibration plate image are known.

[0142] Let the physical coordinates of the corner point under the alignment camera be (x1, y1). Then, the first calculation relationship among the first corner point coordinates, the central pixel coordinates of the first calibration plate image, the pre-calibrated pixel equivalent under the alignment camera, the position coordinates of the alignment camera in the workbench coordinate system, and the physical coordinates of the corner point under the alignment camera is as follows:

[0143] x1 = xa + (Px1 - Pxa) × PixelSizeX1 (1),

[0144] y1 = ya - (Py1 - Pya) × PixelSizeY1 (2).

[0145] Let the physical coordinates of the corner point under the measurement camera be (x2, y2). Then, the second calculation relationship among the second corner point coordinates, the central pixel coordinates of the second calibration plate image, the pre-calibrated pixel equivalent under the measurement camera, the position coordinates of the measurement camera in the workbench coordinate system, and the physical coordinates of the corner point under the measurement camera is as follows:

[0146] x2 = xm + (Px2 - Pxm) × PixelSizeX2 (3),

[0147] y2 = ym - (Py2 - Pym) × PixelSizeY2 (4).

[0148] Since the physical coordinates of the corner point calculated under the alignment camera and the physical coordinates calculated under the measurement camera are theoretically coincident, there is:

[0149] x1 = x2 (5)

[0150] y1 = y2 (6)

[0151] From formulas (1) - (6), the position relationship between the alignment camera and the measurement camera is calculated as follows:

[0152] Δx = xm - xa = -(Px2 - Pxm) × PixelSizeX2 + (Px1 - Pxa) × PixelSizeX1,

[0153] Δy = ym - ya = (Py2 - Pym) × PixelSizeY2 - (Py1 - Pya) × PixelSizeY1。

[0154] The above has introduced a method for calibrating the relative positions of an alignment camera and a measurement camera provided by an embodiment of the present application. The following will introduce an apparatus for performing the above method for calibrating the relative positions of the alignment camera and the measurement camera.

[0155] Please refer to Figure 19 , Figure 19 which is a schematic structural diagram of a wafer center positioning apparatus provided by an embodiment of the present application. As Figure 19 shown, the apparatus for calibrating the relative positions of the alignment camera and the measurement camera includes:

[0156] A first image acquisition unit 1901, configured to move the alignment camera to a first preset position to acquire a first calibration plate image, where the first preset position corresponds to the position coordinates of the alignment camera in the workbench coordinate system, and the first calibration plate image includes corner points formed by two right-angled sides;

[0157] A second image acquisition unit 1902, configured to move the measurement camera to a second preset position to acquire a second calibration plate image, where the second preset position corresponds to the position coordinates of the measurement camera in the workbench coordinate system, and the second calibration plate image includes the corner points;

[0158] A coordinate determination unit 1903, configured to determine first corner point coordinates of the corner points in the first calibration plate image, and determine second corner point coordinates of the corner points in the second calibration plate image;

[0159] A calibration unit 1904, configured to determine position calibration information between the alignment camera and the measurement camera by using a matching relationship between the first corner point coordinates and the second corner point coordinates.

[0160] In a possible implementation, the calibration unit 1904 is specifically configured to determine a first calculation relationship among the first corner coordinates, the central pixel coordinates of the first calibration plate image, the pixel equivalent under the alignment camera that has been pre-calibrated, the position coordinates of the alignment camera in the workbench coordinate system, and the physical coordinates of the corner under the alignment camera; determine a second calculation relationship among the second corner coordinates, the central pixel coordinates of the second calibration plate image, the pixel equivalent under the measurement camera that has been pre-calibrated, the position coordinates of the measurement camera in the workbench coordinate system, and the physical coordinates of the corner under the measurement camera; make the physical coordinates of the corner under the alignment camera equal to the physical coordinates of the corner under the measurement camera, and determine the relative position between the alignment camera and the measurement camera according to the first calculation relationship and the second calculation relationship.

[0161] In a possible implementation, the coordinate determination unit 1903 includes:

[0162] An edge detection sub-unit, configured to perform edge detection on the calibration plate image, and determine the position of the corner region in the calibration plate image according to the edge detection result;

[0163] An inclination correction sub-unit, configured to perform inclination correction on the calibration plate image to obtain a target calibration plate image, where the two right-angle sides of the corner in the target calibration plate image are respectively in the horizontal direction and the vertical direction;

[0164] A first coordinate determination sub-unit, configured to determine the corner pixel coordinates in the target calibration plate image;

[0165] A second coordinate determination sub-unit, configured to determine the corner pixel coordinates in the calibration plate image according to the inclination angle of the right-angle side in the calibration plate image and the corner pixel coordinates in the target calibration plate image;

[0166] Wherein, the corner pixel coordinates in the first calibration plate image are the first corner coordinates, and the corner pixel coordinates in the second calibration plate image are the second corner coordinates.

[0167] In a possible implementation, the edge detection sub-unit is specifically configured to perform edge detection on the calibration plate image to obtain an edge region; perform an opening operation on the edge region in the horizontal direction to remove the noise region in the vertical direction and obtain a horizontal region; perform an opening operation on the edge region in the vertical direction to remove the noise region in the horizontal direction and obtain a vertical region; and determine the intersection of the horizontal region and the vertical region as the corner region.

[0168] In a possible implementation, the tilt correction subunit is specifically configured to generate a rectangular frame with a preset size in the corner region, and calculate the average gray value in the rectangular frame; use the average gray value as a threshold to binarize the image in the rectangular frame to obtain a foreground region and a background region; calculate the average gray values of the foreground region and the background region respectively; generate a corner standard template image according to the average gray values of the foreground region and the background region; perform template matching of the corner standard template image on the calibration plate image, and calculate the tilt angle of the right-angle side in the calibration plate image; perform tilt correction on the calibration plate image according to the tilt angle to obtain the target calibration plate image.

[0169] In a possible implementation, the first coordinate determination subunit is specifically configured to perform gray-scale projection on the image in the horizontal and vertical directions respectively within the region of interest of the corner in the target calibration plate image to obtain gray-scale curves in the horizontal and vertical directions; calculate the gradient curves corresponding to the gray-scale curves in the horizontal and vertical directions respectively, and determine the edge position as the position with the maximum gradient; determine the corner pixel coordinates in the target calibration plate image according to the edge positions in the horizontal and vertical directions.

[0170] This embodiment discloses a relative position calibration device for an alignment camera and a measurement camera. A calibration plate image including two right-angle sides is selected, and the corners of the two right-angle sides are used as the target points for calibration. First, the first corner coordinates of the corners in the first calibration plate image under the alignment camera are obtained, then the second corner coordinates of the corners in the second calibration plate image under the measurement camera are obtained, and finally the relative position relationship between the alignment camera and the measurement camera is obtained through coordinate conversion. Since the calibration plate image includes two right-angle sides, has positioning features in the horizontal and vertical directions, has a unique direction, and can be imaged under the alignment camera and the measurement camera at the same time, it can accurately realize the relative position calibration of the alignment camera and the measurement camera.

[0171] This application embodiment also provides an electronic device. Refer to Figure 20 As shown, it shows a schematic structural diagram of an electronic device suitable for implementing the electronic device in the embodiments of the present application. The electronic device in the embodiments of the present application may include, but is not limited to, fixed terminals such as mobile phones, laptop computers, PDAs (Personal Digital Assistants), PADs (Tablet Computers), desktop computers, and the like. Figure 20 The electronic device shown is only an example and should not bring any limitations to the functions and usage scopes of the embodiments of the present application.

[0172] As Figure 20As shown, the electronic device may include a processing device (such as a central processing unit, a graphics processing unit, etc.) 701, which may perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 702 or a program loaded from a storage device 708 into a random access memory (RAM) 703. When the electronic device is powered on, various programs and data required for the operation of the electronic device are also stored in the RAM 703. The processing device 701, the ROM 702, and the RAM 703 are connected to each other through a bus 704. An input / output (I / O) interface 705 is also connected to the bus 704.

[0173] Generally, the following devices may be connected to the I / O interface 705: an input device 706 including, for example, a touch screen, a touch pad, a keyboard, a mouse, a camera, a microphone, an accelerometer, a gyroscope, etc.; an output device 707 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; a storage device 708 including, for example, a memory card, a hard disk, etc.; and a communication device 709. The communication device 709 may allow the electronic device to communicate with other devices wirelessly or wiredly to exchange data. Although Figure 20 an electronic device with various devices is shown, it should be understood that it is not required to implement or have all the shown devices. Instead, more or fewer devices may be implemented or had.

[0174] In an embodiment of the present application, there is also provided a computer program product including computer-readable instructions. When the computer-readable instructions run on an electronic device, the electronic device is enabled to implement any one of the relative position calibration methods for an alignment camera and a measurement camera provided in the embodiments of the present application.

[0175] In an embodiment of the present application, there is also provided a computer-readable storage medium. The storage medium carries one or more computer programs. When the one or more computer programs are executed by an electronic device, the electronic device is enabled to implement any one of the relative position calibration methods for an alignment camera and a measurement camera provided in the embodiments of the present application.

[0176] In addition, it should be noted that the device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. In addition, in the drawings of the device embodiments provided in the present application, the connection relationships between the modules indicate that they have communication connections, which may be specifically implemented as one or more communication buses or signal lines.

[0177] Through the description of the above embodiments, those skilled in the art can clearly understand that the present application can be implemented by means of software plus necessary general hardware. Of course, it can also be implemented by dedicated hardware including application-specific integrated circuits, dedicated CPUs, dedicated memories, dedicated components, etc. Generally, functions completed by computer programs can be easily implemented by corresponding hardware, and the specific hardware structures for implementing the same function can also be diverse, such as analog circuits, digital circuits, or dedicated circuits, etc. However, for the present application, software program implementation is a better embodiment in more cases. Based on such an understanding, the technical solution of the present application, in essence, or the part that makes a contribution to the prior art, can be embodied in the form of a software product. This computer software product is stored in a readable storage medium, such as a floppy disk, USB flash drive, mobile hard disk, ROM, RAM, magnetic disk, or optical disc of a computer, etc., and includes several instructions to enable a computer device (which can be a personal computer, training device, or network device, etc.) to execute the methods described in various embodiments of the present application.

[0178] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product.

[0179] The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the processes or functions described in the embodiments of the present application are generated in whole or in part. The computer can be a general-purpose computer, a dedicated computer, a computer network, or other programmable devices. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from a website, computer, training device, or data center to another website, computer, training device, or data center by wire (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that a computer can store, or a data storage device such as a training device or data center that includes one or more integrated available media. The available medium can be a magnetic medium (such as a floppy disk, hard disk, magnetic tape), an optical medium (such as a DVD), or a semiconductor medium (such as a solid-state drive (SSD)).

Claims

1. A relative position calibration method for an alignment camera and a measurement camera, characterized in that: The calibration plate image includes two right-angled edges, has positioning features in the horizontal direction and the vertical direction, has directional uniqueness, and is imaged under the alignment camera and the measurement camera at the same time. The relative position calibration method of the alignment camera and the measurement camera includes: Move the alignment camera to a first preset position to acquire a first calibration plate image, wherein the first preset position corresponds to the position coordinates of the alignment camera in the workbench coordinate system, and the first calibration plate image includes a corner point formed by two right-angled sides; Move the measurement camera to a second preset position to obtain a second calibration plate image, wherein the second preset position corresponds to the position coordinates of the measurement camera in the workbench coordinate system, and the second calibration plate image includes the corner point; Determine the first corner point coordinates of the corner point in the first calibration plate image, and determine the second corner point coordinates of the corner point in the second calibration plate image; Position calibration information between the alignment camera and the measurement camera is determined by using the matching relationship between the first corner point coordinates and the second corner point coordinates.

2. The relative position calibration method of the alignment camera and the measurement camera according to claim 1, characterized in that: The determining the position calibration information between the alignment camera and the measurement camera by using the matching relationship between the first corner point coordinates and the second corner point coordinates includes: Determine a first calculation relationship between the coordinates of the first corner point and the central pixel coordinates of the first calibration plate image, the pre-calibrated pixel equivalent under the alignment camera, the position coordinates of the alignment camera in the workbench coordinate system, and the physical coordinates of the corner point under the alignment camera; Determine a second calculation relationship between the coordinates of the second corner point and the central pixel coordinates of the second calibration plate image, the pre-calibrated pixel equivalent of the measurement camera, the position coordinates of the measurement camera in the workbench coordinate system, and the physical coordinates of the corner point in the measurement camera; The physical coordinates of the corner point under the alignment camera are made equal to the physical coordinates of the corner point under the measurement camera, and the relative positions of the alignment camera and the measurement camera are determined according to the first calculation relationship and the second calculation relationship.

3. The relative position calibration method of an alignment camera and a measurement camera according to claim 1, characterized in that: The determining of the first corner point coordinates of the corner point in the first calibration plate image, and determining the second corner point coordinates of the corner point in the second calibration plate image, comprises: The following operations are performed respectively for the calibration plate images acquired by the alignment camera and the measurement camera: Performing edge detection on the calibration plate image, and determining the position of the corner point area in the calibration plate image according to the edge detection result; Performing tilt correction on the calibration plate image to obtain a target calibration plate image, wherein two right-angled sides of the corner point in the target calibration plate image are respectively in the horizontal direction and the vertical direction; Determine the pixel coordinates of the corner points in the target calibration plate image; Determining the pixel coordinates of the corner points in the calibration plate image according to the inclination angle of the right-angled side in the calibration plate image and the pixel coordinates of the corner points in the target calibration plate image; The pixel coordinates of the corner points in the first calibration plate image are the first corner point coordinates, and the pixel coordinates of the corner points in the second calibration plate image are the second corner point coordinates.

4. The relative position calibration method of the alignment camera and the measurement camera according to claim 3, characterized in that: The performing edge detection on the calibration plate image and determining the position of the corner point area in the calibration plate image according to the edge detection result includes: Perform edge detection on the calibration plate image to obtain the edge area; Performing an opening operation on the edge region in the horizontal direction, removing the noise region in the vertical direction, and obtaining a horizontal region; Performing an opening operation on the edge region in the vertical direction, removing the noise region in the horizontal direction, and obtaining a vertical region; An intersection of the horizontal area and the vertical area is determined as the corner point area.

5. The relative position calibration method of an alignment camera and a measurement camera according to claim 3, characterized in that: The step of performing tilt correction on the calibration plate image to obtain a target calibration plate image comprises: Generate a rectangular frame of a preset size in the corner point area, and calculate the grayscale mean in the rectangular frame; Using the grayscale mean as a threshold, binarizing the image in the rectangular frame to obtain a foreground area and a background area; Calculating grayscale means of the foreground area and the background area respectively; Generate a corner point standard template image according to the grayscale mean of the foreground area and the background area; Perform template matching on the corner point standard template image and the calibration plate image to calculate the inclination angle of the right-angle side in the calibration plate image; The calibration plate image is tilt-corrected according to the tilt angle to obtain the target calibration plate image.

6. The relative position calibration method of an alignment camera and a measurement camera according to claim 3, characterized in that: The step of determining pixel coordinates of corner points in the target calibration plate image comprises: Performing grayscale projection on the image in the horizontal direction and the vertical direction in the region of interest of the corner point in the target calibration plate image, respectively, to obtain grayscale curves in the horizontal direction and the vertical direction; Calculate the gradient curves corresponding to the grayscale curves in the horizontal and vertical directions respectively, and determine the position with the largest gradient as the edge position; The pixel coordinates of the corner points in the target calibration plate image are determined according to the edge positions in the horizontal direction and the vertical direction.

7. A relative position calibration device for an alignment camera and a measurement camera, characterized in that: The calibration plate image includes two right-angled edges, has positioning features in the horizontal direction and the vertical direction, has directional uniqueness, and is imaged simultaneously under the alignment camera and the measurement camera. The relative position calibration device of the alignment camera and the measurement camera includes: A first image acquisition unit, used for moving the alignment camera to a first preset position to acquire a first calibration plate image, wherein the first preset position corresponds to the position coordinates of the alignment camera in the workbench coordinate system, and the first calibration plate image includes a corner point formed by two right-angled sides; A second image acquisition unit, used for moving the measurement camera to a second preset position to acquire a second calibration plate image, wherein the second preset position corresponds to the position coordinates of the measurement camera in the workbench coordinate system, and the second calibration plate image includes the corner point; a coordinate determination unit, configured to determine a first corner point coordinate of the corner point in the first calibration plate image, and determine a second corner point coordinate of the corner point in the second calibration plate image; A calibration unit is used to determine position calibration information between the alignment camera and the measurement camera by using the matching relationship between the first corner point coordinates and the second corner point coordinates.

8. An electronic device, characterized in that: The method comprises at least one processor and a memory connected to the processor, wherein: The memory is used to store computer programs; The processor is used to execute the computer program so that the electronic device can implement the relative position calibration method of the alignment camera and the measurement camera as described in any one of claims 1 to 6.

9. A computer program product, characterized in that Computer-readable instructions are stored, and when the computer-readable instructions are executed on an electronic device, the electronic device implements the relative position calibration method of an alignment camera and a measurement camera as described in any one of claims 1 to 6.

10. A computer storage medium, characterized in that: The storage medium carries one or more computer programs, and when the one or more computer programs are executed by an electronic device, the electronic device can implement the relative position calibration method of the alignment camera and the measurement camera as described in any one of claims 1 to 6.

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