High-precision pixel calibration apparatus and method

Abstract

To provide a calibration device..SOLUTION: A calibration device is provided, comprising: an acquisition unit for acquiring a captured image from an image capturing device configured to capture an image of a specified region with a plurality of markers indicated therein; and an analysis unit configured to determine the physical size of each pixel in the captured image through analysis of physical movement data of at least either of the specified region and the image capturing device, and the captured image.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an apparatus and method for calibrating the physical size of image pixels. [Background technology]

[0002] Pixel calibration measures the physical distance of one pixel (size, width, height, diagonal, diameter, etc.), and when measuring overlay, the value measured in pixels can be converted to a unit of length such as meters.

[0003] Conventionally, a method has been adopted in which a target whose physical distance can be measured is photographed with a camera, and the physical size of each pixel is determined by measuring how many pixels exist within the target.

[0004] However, the conventional method has problems such as low measurement accuracy and poor repeatability. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides a calibration apparatus and method for accurately analyzing and calibrating the size per pixel of an image of an object. [Means for solving the problem]

[0006] The calibration device of the present invention may include an acquisition unit that acquires a captured image from a camera that captures a set area in which a plurality of markers are displayed; and an analysis unit that analyzes the physical size per pixel of the captured image by analyzing the set area, physical movement data of at least one of the camera, and the captured image.

[0007] The calibration method of the present invention may include an acquisition step of acquiring a captured image from a camera that captures an image of a set area where a plurality of markers are displayed; a pixel step of determining a pixel distance corresponding to the number of pixels existing between a first marker and a second marker; a coordinate step of determining a coordinate distance corresponding to the physical distance between the first marker and the second marker using physical movement data from the first marker to the second marker; and an analysis step of determining a physical size per pixel using the pixel distance and the coordinate distance. [Effects of the Invention]

[0008] The calibration device of the present invention can operate in a manner distinct from a method that uses preset values ​​such as the actual size of the markers marked on the test board and the actual distance between the markers.

[0009] That is, by determining how many pixels are contained in a marker of a set size and dividing the size of the marker by the number of pixels, the size per pixel can be easily calculated.

[0010] When photographing a minute object such as a wafer, an additional optical magnifying glass is required, and the addition of such an additional means may cause distortion in the measurement image. As a result, although the size of the marker included in the photographed image remains unchanged physically, it may be distorted on the image.

[0011] Since the size per pixel is processed on the image, it is difficult to apply the pre-defined physical size of the markers, the distance between markers, etc. for the above reasons, because the measurement accuracy and repeatability (reproducibility) decrease when targeting minute objects.

[0012] The calibration apparatus and method of the present invention can provide another alternative that can accurately analyze, set, and calibrate the size per pixel.

[0013] According to the present invention, a plurality of markers are provided, and the distance between the markers can be physically measured. For example, the calibration device of the present invention can move the camera so that a specific point of the marker, for example, the center of the marker, is located at the center of the captured image, or can move a set area to be captured by the camera. The set area may include a chuck or test bed on which a wafer is placed, or a test board placed on the chuck or test bed. Moving the set area can mean moving the chuck or test bed on which the wafer or test board is placed.

[0014] At this time, the calibration device can define the distance the moving object has moved as the position coordinates of the corresponding marker. The calibration device defines and sets the position coordinates for each marker, and uses the position coordinates to calculate the distance between two markers.

[0015] According to the present invention, the position coordinates set for each marker may be values ​​actually measured at the current time, and the number of pixels between each marker may also be values ​​actually measured by analyzing the captured image.

[0016] As a result, according to the present invention, even if the distance between the markers changes due to damage or warping of the test board, the physical distance between the markers and the number of pixels can be accurately measured regardless of the environment, thereby making it possible to very accurately grasp the physical size per pixel.

[0017] According to the present invention, a plurality of markers are formed in a set area, and a plurality of physical sizes per pixel are obtained using the plurality of markers. The calibration device of the present invention can analyze, set, and calibrate the average value of the plurality of obtained physical sizes per pixel as the physical size per pixel of the currently captured image. This allows the physical size per pixel to be obtained robustly and accurately even in a noisy environment such as a captured image. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic diagram illustrating a calibration device of the present invention. [Figure 2] FIG. 1 is a schematic diagram showing an analysis system of a comparative example. [Figure 3] FIG. 2 is a schematic diagram showing an image captured by a camera. [Figure 4] FIG. 1 is a schematic diagram showing an encoder. [Figure 5] FIG. 2 is a schematic diagram illustrating the operation of a pixel unit. [Figure 6] FIG. 1 is a schematic diagram showing a test board. [Figure 7] 10 is a table showing the pixel coordinates and position coordinates of each marker. [Figure 8] 1 is a schematic diagram illustrating a distortion phenomenon of a photographed image; [Figure 9] 1 is a flowchart illustrating a calibration method of the present invention. [Figure 10] FIG. 1 illustrates a computing device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will now be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. In the drawings, parts that are not relevant to the description will be omitted in order to clearly explain the present invention, and similar parts will be designated by similar reference numerals throughout the specification.

[0020] In this specification, duplicated explanations of the same components will be omitted.

[0021] Furthermore, when a component is referred to as being "coupled" or "connected" to another component, it should be understood that the component may be directly coupled or connected to the other component, but that there may be other components in between. In contrast, when a component is referred to as being "directly coupled" or "directly connected" to another component, it should be understood that there are no other components in between.

[0022] Furthermore, the terms used in this specification are merely used to describe particular embodiments and are not intended to limit the present invention.

[0023] Furthermore, in this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0024] Furthermore, in this specification, the terms "comprise" or "have" and the like are intended to specify only the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and should be understood not to preclude the presence or possible addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0025] Also, as used herein, the term "and / or" includes a combination of multiple listed items or any of multiple listed items. As used herein, "A or B" may include "A," "B," or "both A and B."

[0026] In addition, in this specification, detailed descriptions of known functions and configurations that may obscure the gist of the present invention will be omitted.

[0027] Fig. 1 is a schematic diagram showing a calibration device 100 of the present invention. Fig. 7 is a table showing pixel coordinates and position coordinates of each marker. Fig. 8 is a schematic diagram showing distortion of a captured image.

[0028] The calibration device 100 shown in FIG. 1 includes an acquisition unit 110, a pixel unit 130, a coordinate unit 150, and an analysis unit 170.

[0029] The acquisition unit 110 acquires a captured image from the camera 10 that captures an image of a set area where a plurality of markers are displayed. To this end, the acquisition unit 110 includes a communication module that can communicate with the camera 10 via wired or wireless communication.

[0030] The analysis unit 170 analyzes the physical size per pixel of the captured image by analyzing the physical movement data of at least one of the set area and the camera 10 and the captured image.

[0031] For example, the number of pixels between a specific marker and another marker can be determined by analyzing the captured image. A specific marker placed at an aim point on the captured image can be used as a starting point, and the camera 10 or the set area can be moved so that the other marker is at the aim point. In this case, the linear distance traveled by the camera 10 or the set area can correspond to the actual physical distance between the specific marker and the other marker. Once the number of pixels between the specific marker and the other marker and the actual physical distance between the two markers are determined, the physical size per pixel can be determined by dividing the actual physical distance by the number of pixels.

[0032] Alternatively, each marker may be formed in the shape of a closed curve, for example, a square, having a size larger than a pixel and including a plurality of subpixels.

[0033] Unlike existing methods that use the size of the markers, the analysis unit 170 uses the measured value of the distance between the markers.

[0034] FIG. 2 is a schematic diagram showing an analytical system of a comparative example.

[0035] According to the analysis system of the comparative example, a figure or line n having a set line width can be photographed, and the image k of the photographed line n is as shown in FIG.

[0036] The line width has already been determined, and the number of pixels contained within the line width can be easily determined by analyzing the image k. The line width is then divided by the number of pixels to derive the physical size per pixel.

[0037] To improve the accuracy of the comparative example, the line edges must be accurately detected. However, unlike the real world, it is difficult to clearly determine the location of the line edges in an image k. To solve this problem, an edge detection method using gray levels is used, as shown in Figure 2(b).

[0038] This edge detection method finds the minimum and maximum values ​​of the gray level (circled number 1), and uses the hysteresis (circled number 3) with the rising edge location (circled number 4) and falling edge location (circled number 5) as the upper and lower limits to recognize the relative threshold position (circled number 2) as an edge.

[0039] However, the comparative example has a problem in that the exact value of the line width cannot be determined in reality. Furthermore, the comparative example has a limit of repeatability of about 1 / 20 (one pixel divided into 20 parts) to 1 / 10 (one pixel divided into 10 parts) subpixels. Therefore, the comparative example is difficult to apply to fields such as wafer inspection, which requires consideration of units down to 1 / 10,000 subpixels.

[0040] In addition, a solution is required that can take into account issues such as distortion of the captured image, the FOV (Field of View) position, and deformation of the test board corresponding to the object that provides the display area where multiple markers are displayed.

[0041] To solve this problem, the calibration device 100 employs a method of actually measuring various necessary data when calculating the physical size per pixel.

[0042] The pixel portion 130 and coordinate portion 150 may be used to provide various measurements to the analysis portion 170 .

[0043] The number of pixels between the markers is defined as the pixel distance, and the physical distance between the markers is defined as the coordinate distance.

[0044] The pixel unit 130 determines a pixel distance corresponding to the number of pixels existing between a first marker and a second marker selected from the plurality of markers. The pixel unit 130 can determine the pixel distance up to 1 / 10000 sub-pixel units.

[0045] The pixel unit 130, which divides a single pixel into a plurality of sub-pixels, can express decimal values ​​of pixel coordinates using the number of sub-pixels as shown in Fig. 7. For example, in Fig. 7, "Target" indicates the identification number of a marker. It can be seen that the marker corresponding to target 1 is 320 pixels away from the reference position along the x-axis, and the marker corresponding to target 2 is 120.1235 pixels away from the reference position along the x-axis.

[0046] The coordinate unit 150 obtains a coordinate distance corresponding to the physical distance between the first marker and the second marker using physical movement data from the first marker to the second marker, for example, an x-axis movement distance and a y-axis movement distance. The coordinate unit 150 may obtain the coordinate distance using a 1 / 10000 sub-pixel unit.

[0047] The analysis unit 170 uses the pixel distance and the coordinate distance to determine, analyze, set, and calibrate the physical size per pixel. As described above, the analysis unit 170 can determine the physical size per pixel by dividing the coordinate distance between the first marker and the second marker by the pixel distance.

[0048] FIG. 3 is a schematic diagram showing an image captured by the image capturing device 10. As shown in FIG.

[0049] The photographed image i may be a photograph of a set area t in which a plurality of markers m1, m2, m3, . . . are displayed.

[0050] The pixel unit 130 counts the number of pixels (including sub-pixels) that exist from the reference position o of the photographed image i to a specific marker included in the photographed image i through image analysis, and the pixel unit 130 can express the position of the specific marker relative to the reference position o as pixel coordinates corresponding to the number of pixels that exist between the two.

[0051] The pixel unit 130 can grasp the pixel distance corresponding to the number of pixels existing between the first marker and the second marker using the pixel coordinates of each marker.

[0052] For example, if the pixel coordinates of the first marker are (230.6351, 250.8354) and the pixel coordinates of the second marker are (120.1235, 136.3154), the difference between the two coordinates (110.5116, 114.5200) corresponds to the pixel distance between the first marker and the second marker.

[0053] The analysis unit 170 uses the pixel distance to analyze the physical size per pixel.

[0054] The coordinate unit 150 grasps the position coordinates of each marker relative to the image capturing device 10 .

[0055] The coordinate unit 150 obtains a coordinate distance corresponding to the physical distance between the first marker and the second marker using the position coordinates of each marker.

[0056] The analyzer 170 uses the coordinate distance to analyze the physical size per pixel.

[0057] Length measuring equipment such as an encoder may be used to assign position coordinates to the markers included in the captured image i.

[0058] FIG. 4 is a schematic diagram showing an encoder.

[0059] For example, the coordinate unit 150 can move at least one moving body 90 in the camera 10 and the set area t. In this case, the set area t may include a chuck or test bed 20 whose movement can be controlled by the coordinate unit 150. When the captured image i is formed parallel to a virtual xy plane, the moving body can be moved in the x-axis direction or y-axis direction by an xy robot.

[0060] The encoder can measure the length or distance traveled by the moving object in the x-axis direction and the length or distance traveled by the moving object in the y-axis direction by an xy robot. For example, the encoder may include a scale 23 formed along the x-axis or y-axis direction as shown in FIG. 4, and a scanner 21 for reading the scale. One of the scale and the scanner is fixed, and the other is connected to the moving object. When the scale or scanner connected to the moving object moves, the distance traveled by the moving object in the x-axis or y-axis direction can be determined.

[0061] As another example, an encoder can measure the number of rotations of a motor that moves a moving object. If you know the distance the moving object moves per rotation of the motor, you can use the number of rotations of the motor to determine the distance the moving object moves.

[0062] The coordinate unit 150 can obtain the image captured by the camera 10 in real time.

[0063] The coordinate unit 150 can identify a target corresponding to an image of a specific marker by analyzing a photographed image obtained in real time at the current position of the moving object.

[0064] The coordinate unit 150 may move the moving object from a specific position as a starting point so that a specific point of the target is located at the center of the captured image during analysis of the captured image. The specific point of the target may be set in various ways, such as the center point of the target or a vertex on one side of the target. It may be advantageous to set the specific point to a size of a subpixel. In this case, the position coordinates may be determined in units of at least the size of a subpixel.

[0065] The state in which a specific point on the target comes to the center o of the photographed image i due to the movement of the moving object starting from a specific position is defined as a "matching state." Generally, the center o of the photographed image i coincides with the position of the camera 10.

[0066] The coordinate unit 150 can grasp the straight line distance and the shortest distance that the moving object has traveled from a specific position until a matching state is reached in the analysis of the photographed image i.

[0067] The coordinate unit 150 can set the position coordinates of a specific marker using the linear distance of the moving object from a specific position. For example, if a matching state occurs when the moving object at a specific position moves about 10 mm on the x-axis and 5 mm on the y-axis, the position coordinates of the specific marker are set to (10 mm, 5 mm).

[0068] In this manner, the coordinate unit 150 can move the moving object so that the first marker m1 is located at the center o of the captured image i.

[0069] The coordinate unit 150 can set the coordinates of the moving object measured in a state where the first marker m1 is placed at the center o of the photographed image i as the first position coordinates of the first marker m1.

[0070] The coordinate unit 150 can move the moving body so that the second marker m2 is placed at the center o of the photographed image i.

[0071] The coordinate unit 150 can set the coordinates of the moving object measured in a state where the second marker m2 is placed at the center o of the photographed image i as the second position coordinates of the second marker m2.

[0072] The coordinate unit 150 may interpret the difference between the first position coordinate and the second position coordinate as a coordinate distance corresponding to the physical distance between the first marker and the second marker. The coordinate unit 150 provides the interpreted coordinate distance to the analysis unit 170. The analysis unit 170 analyzes the physical size per pixel using the coordinate distance.

[0073] The coordinate unit 150 can set position coordinates for a plurality of markers in the following manner.

[0074] As described above, when the photographed image i is formed parallel to the xy plane formed by the x-axis and y-axis, the coordinate unit 150 can move the moving object at the initial position so that a specific marker is located at the center of the photographed image i. The coordinate unit 150 can set the x-axis distance value and the y-axis distance value of the moving object moved from the initial position to the specific marker as the position coordinates of the specific marker.

[0075] Thereafter, to set the position coordinates of another marker, the coordinate unit 150 may return the moving object located at the specific marker to its initial position and set the position coordinates of another marker by applying the above-described method again. However, for speed, it may be advantageous to immediately move the moving object located at the specific marker to another marker.

[0076] That is, when the setting of the position coordinates of a specific marker is completed, the coordinate unit 150 can move the moving object located at the specific marker so that another marker is located at the center of the captured image.

[0077] The coordinate unit 150 can set the position coordinates of other markers by adding the x-axis distance value and the y-axis distance value of the moving object from a specific marker to the position coordinates of the specific marker.

[0078] In this manner, the coordinate unit 150 can set position information for each of the multiple markers.

[0079] The coordinate unit 150 can grasp a coordinate distance corresponding to the difference between the position coordinates of a first marker m1 and a second marker m2 selected from the plurality of markers.

[0080] The analysis unit 170 can determine the physical size per pixel between the first marker m1 and the second marker m2 using the coordinate distance between the first marker m1 and the second marker m2.

[0081] The pixel unit 130 can grasp the pixel distance for each of the plurality of markers included in the set region t. Accordingly, there can be a plurality of pixel distances.

[0082] The coordinate unit 150 can grasp the coordinate distance for each of the plurality of markers included in the set area t. Therefore, there can be a plurality of coordinate distances.

[0083] The analysis unit 170 may primarily calculate a plurality of first sizes corresponding to physical sizes per pixel between each marker using the plurality of pixel distances and the plurality of coordinate distances.

[0084] The analysis unit 170 can secondarily calculate the average value of the first sizes calculated multiple times.

[0085] The analyzer 170 finally determines the average value of the first sizes as a second size corresponding to the physical size per pixel of the entire captured image i. The analyzer 170 can calibrate the physical size per pixel to the second size.

[0086] For example, the analysis unit 170 can form multiple groups, each paired with two markers.

[0087] In this case, an additional rule may be applied that each marker is included in only two groups, according to which the chain structure is grouped.

[0088] The analysis unit 170 primarily calculates a first size corresponding to the physical size per pixel between two markers forming each group using the pixel distance and the coordinate distance. The analysis unit 170 secondarily calculates an average value of the first sizes primarily calculated. The analysis unit 170 may output the second average value of the first sizes as a second size corresponding to the physical size per pixel of the entire captured image.

[0089] The value of the second size changes depending on how the markers are paired. Therefore, it is better to provide a method for pairing or grouping markers in a way that improves the accuracy of the second size.

[0090] FIG. 5 is a schematic diagram illustrating the operation of the pixel unit 130.

[0091] For example, the further a moving object moves mechanically, the more length errors or tolerances tend to accumulate, and it may be advantageous to group markers that are as close together as possible to minimize the resulting errors.

[0092] The grouping can be performed by the pixel unit 130 that identifies the markers through analysis of the captured image.

[0093] The pixel unit 130 may pair a second marker m2, which is closest to the first marker m1 among the plurality of markers, with the first marker m1 by analyzing the captured image.

[0094] The pixel unit 130 can determine a first pixel distance corresponding to the number of pixels present between a pair of first and second markers.

[0095] The coordinate unit 150 can grasp a first coordinate distance corresponding to the physical distance between the first marker and the second marker.

[0096] The analysis unit 170 can determine the physical size per pixel between the first marker and the second marker using the first pixel distance and the first coordinate distance.

[0097] According to the above embodiment, the closest markers can be grouped together, and since it is advantageous to know as many first sizes as possible to improve the accuracy of the second sizes, it is preferable to perform chain-like grouping.

[0098] To form a chain-like group, the pixel unit 130 can pair a third marker that is closest to the second marker, excluding the first marker, among the plurality of markers on the captured image, with the second marker.

[0099] The pixel unit 130 can grasp a second pixel distance corresponding to the number of pixels existing between the paired second and third markers.

[0100] The coordinate unit 150 can grasp a second coordinate distance corresponding to the physical distance between the second marker and the third marker.

[0101] The analysis unit 170 can determine the physical size per pixel between the second marker and the third marker using the second pixel distance and the second coordinate distance.

[0102] In this case, due to distortion, etc., the physical size per pixel covering the first range between the first marker and the second marker and the physical size per pixel covering the second range between the second marker and the third marker may be different.

[0103] The analysis unit 170 can calculate the average value of the physical size per pixel between the first marker and the second marker and the average value of the physical size per pixel between the second marker and the third marker, and can analyze and calibrate the physical size per pixel of the captured image i using the average value.

[0104] If the same method is applied to the remaining markers, such as the third marker, fourth marker, fifth marker, etc., the physical size per pixel is calculated for all of the multiple markers included in the set area, and the average value is derived as the physical size per pixel of the captured image i.

[0105] However, during the grouping process, a situation may occur in which a marker closest to a particular marker is already included in two other groups. In this case, a situation occurs in which the particular marker has no choice but to be grouped with markers located farther away. A method can be provided to prevent the phenomenon of markers located farther away than the allowable distance being grouped together and to calculate the physical size per pixel uniformly across the entire captured image.

[0106] For example, the pixel unit 130 can divide the captured image i into a plurality of detailed regions each having the same area.

[0107] The pixel unit 130 can grasp the pixel distance between only the markers included in the same detailed region.

[0108] The coordinate unit 150 can grasp the coordinate distances only between markers included in the same detailed region.

[0109] The analysis unit 170 calculates the physical size per pixel in detail region units using the pixel distance and the coordinate distance.

[0110] The analysis unit 170 may calculate an average value by summarizing all the physical sizes per pixel calculated for each detailed region.

[0111] The analyzer 170 can output the average value as the physical size per pixel of the entire captured image.

[0112] For example, a specific detailed region may include three markers. In this case, the analysis unit 170 may calculate the size per pixel (first average value) of the entire specific detailed region by first averaging the sizes per pixel between the three markers included in the specific detailed region. The analysis unit 170 may then collect the first average values ​​for each detailed region and calculate a second average. The analysis unit 170 may output the second average value (second average value) as the physical size per pixel of the entire captured image.

[0113] Meanwhile, the pixel unit 130 may form four or more detailed regions for the captured image i. In this case, the analysis unit 170 may compare the physical size per pixel (first average value) for each detailed region with each other, eliminate the detailed regions with the largest and smallest values, and calculate a second average value using the first average values ​​for the remaining detailed regions.

[0114] When dividing the photographed image i into four detailed regions, the pixel unit 130 can divide the photographed image i into four detailed regions using two virtual line segments that are perpendicular to each other and cross the center o of the photographed image i.

[0115] The pixel unit 130 pairs markers in pairs in a clockwise or counterclockwise direction for markers included in the same detailed region. For example, in FIG. 5, four markers m1, m2, m3, and m4 are provided in two quadrants, and in a counterclockwise direction, the first marker m1 is paired with the second marker m2. The second marker m2 is paired with the third marker m3, and the third marker m3 is paired with the fourth marker m4. The fourth marker m4 is paired with the first marker m1. In FIG. 5, the fifth marker m5, the sixth marker m6, the seventh marker m7, the eighth marker m8, and the ninth marker m9 are arranged in a counterclockwise direction in one quadrant and can be grouped in a similar manner to the first marker, etc.

[0116] The analysis unit 170 may calculate a physical size per pixel for each detailed region using the pixel distance and coordinate distance between each pair of markers. The analysis unit 170 may calculate an average value for all the physical sizes per pixel calculated for each detailed region.

[0117] The analyzer 170 may output the average value as the physical size per pixel of the entire captured image and perform calibration. After post-processing of the captured image through calibration, the size of the pixels included in the captured image becomes the output value of the analyzer 170.

[0118] The calibration device 100 may include a specially constructed test board to improve the accuracy of the average value calculated using multiple markers.

[0119] FIG. 6 is a schematic diagram showing the test board.

[0120] The test board may be mounted on a separate target device that is mechanically separable from calibration device 100 .

[0121] The test board may have a setting area t on which a number of markers are displayed.

[0122] The test board can divide the set area into four detailed areas using two virtual lines that cross the center point and are perpendicular to each other.

[0123] The same number of markers may be formed for each detail area of ​​the test board.

[0124] The multiple markers placed in each detailed area of ​​the test board may be arranged at positions that are point-symmetrical with respect to the center points e1, e2, e3, and e4 of the virtual line segments h1, h2, h3, and h4 that form the boundaries with other adjacent detailed areas.

[0125] Using the above test board, the pixel unit 130 can easily distinguish between the four detailed regions. Also, since the same number of markers are arranged in each detailed region with corresponding structures, the reliability and accuracy of the physical size per pixel of the entire captured image i can be improved.

[0126] The above calibration device may be applied to an overlay device.

[0127] The overlay apparatus can inspect whether or not alignment errors occur between the formed patterns when the circuit patterns are stacked on the wafer.

[0128] As an example, the calibration device of the present invention may be applied to calibrate an overlay device before overlay measurement.

[0129] FIG. 9 is a flowchart illustrating the calibration method of the present invention.

[0130] The calibration method of FIG. 9 is performed by the calibration device 100 shown in FIG.

[0131] The calibration method includes an acquisition step (S510), a pixel step (S520), a coordinate step (S530), and an analysis step (S540).

[0132] In the acquisition step (S510), a photographed image is acquired from the camera 10 that photographs the set area where the plurality of markers are displayed. The acquisition step (S510) may be performed by the acquisition unit 110.

[0133] The pixel step (S520) may be performed by the pixel unit 130 to determine a pixel distance corresponding to the number of pixels present between the first marker and the second marker.

[0134] The coordinate step (S530) may be performed by the coordinate unit 150. The coordinate step (S530) may be performed by using physical movement data from the first marker to the second marker to determine a coordinate distance corresponding to the physical distance between the first marker and the second marker.

[0135] The analysis step (S540) uses the pixel distance and the coordinate distance to determine the physical size per pixel. The analysis step (S540) may be performed by the analysis unit 170.

[0136] The calibration method of the present invention can determine the physical size per pixel using the coordinate distance and pixel distance measured at the time of calibrating the physical size per pixel, thereby significantly improving the accuracy of the physical size per pixel and providing accuracy up to 1 / 10000 sub-pixel units.

[0137] 10 is a diagram illustrating a computing device according to an embodiment of the present invention. The computing device TN100 of FIG. 10 may be a device described herein (such as the calibration device 100).

[0138] 10, computing device TN100 may include at least one processor TN110, a transceiver device TN120, and a memory TN130. Computing device TN100 may further include a storage device TN140, an input interface device TN150, an output interface device TN160, etc. The components included in computing device TN100 are connected by a bus TN170 to communicate with each other.

[0139] The processor TN110 can execute program commands stored in at least one of the memory TN130 and the storage device TN140. The processor TN110 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are executed. The processor TN110 may be configured to implement procedures, functions, methods, etc. described in connection with embodiments of the present invention. The processor TN110 can control each component of the computing device TN100.

[0140] Each of memory TN130 and storage device TN140 can store various information related to the operation of processor TN110. Each of memory TN130 and storage device TN140 may be configured with at least one of a volatile storage medium and a non-volatile storage medium. For example, memory TN130 may be configured with at least one of a read only memory (ROM) and a random access memory (RAM).

[0141] The transceiver TN120 can transmit or receive wired or wireless signals and can be connected to a network for communication.

[0142] On the other hand, the embodiments of the present invention may not be realized only by the above-mentioned devices and / or methods, but may also be realized by a program that realizes functions corresponding to the configuration of the embodiments of the present invention or a recording medium on which the program is recorded, and such realization can be easily achieved by a person of ordinary skill in the technical field to which the present invention belongs from the description of the above-mentioned embodiments.

[0143] Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited to these examples, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention. [Explanation of symbols]

[0144] 10 Camera 20 Testbed 100 calibration device 110 acquisition unit 130 pixel part 150 coordinate part 170 Analysis Department

Claims

1. an acquisition unit that acquires a captured image from a camera that captures an image of a set area on which a plurality of markers are displayed; an analysis unit that analyzes the physical size per pixel of the captured image by analyzing the physical movement data of at least one of the set area and the camera and the captured image; a pixel unit for determining a pixel distance corresponding to the number of pixels present between the first marker and the second marker; a coordinate unit that determines a coordinate distance corresponding to a physical distance between the first marker and the second marker using physical movement data from the first marker to the second marker; an encoder unit for measuring the length or distance of movement of at least one of the camera and the set area; the coordinate unit grasps, by an encoder unit, a coordinate distance corresponding to a physical distance from the first marker to the second marker due to movement of at least one of the camera and the set area; the analysis unit uses the pixel distance and the coordinate distance to determine the physical size per pixel; Calibration equipment.

2. The pixel unit counts the number of pixels existing from a reference position of the photographed image to a specific marker included in the photographed image, The pixel unit expresses the position of the specific marker relative to the reference position as a pixel coordinate corresponding to the number of pixels existing between the two, The calibration device of claim 1 , wherein the pixel unit determines a pixel distance corresponding to the number of pixels present between a first marker and a second marker using pixel coordinates of each marker.

3. The pixel unit divides a single pixel into a plurality of sub-pixels, The calibration device according to claim 2 , wherein the pixel unit expresses decimal values ​​of the pixel coordinates using the number of the sub-pixels.

4. the coordinate unit moves at least one moving body among the camera and the set area; The coordinate unit acquires the captured image of the camera in real time, The coordinate unit identifies a target corresponding to an image of a specific marker by analyzing a photographed image acquired in real time at the current position of the moving object, the coordinate unit moves the moving body from a specific position as a starting point so that a specific point of the target is located at the center of the photographed image upon analyzing the photographed image; When a state in which the specific point of the target comes to the center of the captured image due to the movement of the moving object starting from the specific position is defined as a matching state, The coordinate unit grasps the linear distance that the moving object has traveled from the specific position until the matching state is reached upon analysis of the captured image, The calibration device according to claim 1 , wherein the coordinate unit sets the position coordinates of the specific marker by using a linear distance that the moving object has moved from the specific position.

5. the coordinate unit moves at least one moving body among the camera and the set area; the coordinate unit moves the moving object so that the first marker is positioned at the center of the captured image; the coordinate unit sets the coordinates of the moving object measured in a state where the first marker is placed at the center of the captured image to first position coordinates of the first marker; the coordinate unit moves the moving object so that the second marker is positioned at the center of the captured image; the coordinate unit sets the coordinates of the moving object measured in a state where the second marker is placed at the center of the captured image to second position coordinates of the second marker; The calibration device according to claim 1 , wherein the coordinate unit grasps a difference between the first position coordinate and the second position coordinate as a coordinate distance corresponding to a physical distance between the first marker and the second marker.

6. the coordinate unit moves at least one moving body among the camera and the set area; When the photographed image is formed parallel to an xy plane formed by an x-axis and a y-axis, the coordinate unit moves the moving body from the initial position so that a specific marker is placed at the center of the photographed image; the coordinate unit sets the x-axis distance value and the y-axis distance value of the moving object moved from the initial position to the specific marker to the position coordinates of the specific marker; When the setting of the position coordinates of the specific marker is completed, the coordinate unit moves the moving object located at the specific marker so that another marker is placed at the center of the photographed image; the coordinate unit sets the position coordinates of the other marker by adding the x-axis distance value and the y-axis distance value of the moving object moved from the specific marker to the position coordinates of the specific marker; the coordinate unit sets position information for each of the plurality of markers; The calibration device according to claim 1 , wherein the coordinate unit determines a coordinate distance corresponding to a difference between position coordinates of a first marker and position coordinates of a second marker selected from the plurality of markers.

7. When the number of pixels between the markers is defined as the pixel distance and the physical distance between the markers is defined as the coordinate distance, The pixel unit grasps the pixel distance for each of the plurality of markers included in the set area, the coordinate unit grasps the coordinate distance for each of the plurality of markers included in the set area; The analysis unit primarily calculates a plurality of first sizes corresponding to physical sizes per pixel between the markers using the plurality of pixel distances and the plurality of coordinate distances; the analysis unit secondarily calculates an average value of the first sizes calculated multiple times, The calibration device of claim 1 , wherein the analysis unit determines the average value of the first sizes as a second size corresponding to a physical size per pixel of the entire captured image.

8. When the number of pixels between the markers is defined as the pixel distance and the physical distance between the markers is defined as the coordinate distance, The analysis unit forms a plurality of groups in which the markers are paired in pairs, The analysis unit primarily calculates a first size corresponding to a physical size per pixel between two markers forming each group using the pixel distance and the coordinate distance; the analysis unit secondarily calculates an average value of the first sizes calculated firstly, The calibration device of claim 1 , wherein the analysis unit outputs the second average value of the first sizes calculated as a second size corresponding to a physical size per pixel of the entire captured image.

9. The pixel unit pairs a second marker that is closest to the first marker among the plurality of markers with the first marker by analyzing the captured image; The pixel unit determines a first pixel distance corresponding to the number of pixels present between the paired first marker and the paired second marker, a coordinate unit configured to grasp a first coordinate distance corresponding to a physical distance between the first marker and the second marker; The calibration device of claim 1 , wherein the analysis unit uses the first pixel distance and the first coordinate distance to determine a physical size per pixel between the first marker and the second marker.

10. the pixel unit pairs a third marker, which is closest to the second marker but excludes the first marker, with the second marker on the captured image; The pixel unit determines a second pixel distance corresponding to the number of pixels present between the paired second marker and the paired third marker; the coordinate unit grasps a second coordinate distance corresponding to a physical distance between the second marker and the third marker; the analyzing unit uses the second pixel distance and the second coordinate distance to determine a physical size per pixel between the second marker and the third marker; The analysis unit calculates an average value of the physical size per pixel between the first marker and the second marker and the physical size per pixel between the second marker and the third marker; The calibration device of claim 9 , wherein the analysis unit analyzes the physical size per pixel of the captured image using the average value.

11. The pixel unit divides the captured image into a plurality of detailed regions each having the same area, The pixel unit grasps pixel distances between only markers included in the same detailed region, The coordinate unit grasps the coordinate distance between only the markers included in the same detailed region, the analyzing unit calculates a physical size per pixel in the detailed region unit using the pixel distance and the coordinate distance; The analysis unit calculates an average value of all the physical sizes per pixel calculated for each detailed region unit, The calibration device according to claim 1 , wherein the analysis unit outputs the average value as a physical size per pixel of the entire captured image.

12. The pixel unit divides the photographed image into four detailed regions using two virtual lines that cross the center of the photographed image and are perpendicular to each other, The pixel unit pairs two markers in a clockwise or counterclockwise direction for markers included in the same detailed region, The analysis unit calculates a physical size per pixel in the detailed region unit using pixel distances and coordinate distances between the paired markers, The analysis unit calculates an average value of all the physical sizes per pixel calculated for each detailed region unit, The calibration device according to claim 1 , wherein the analysis unit outputs the average value as a physical size per pixel of the entire captured image.

13. An overlay device to which the calibration device according to any one of claims 1 to 12 is applied.

14. A calibration method performed by a calibration device, comprising: an acquisition step of acquiring a photographed image from a camera that photographs a set area on which a plurality of markers are displayed; determining a pixel distance corresponding to the number of pixels present between a first marker and a second marker of the plurality of markers in the captured image; a coordinate step of determining a coordinate distance corresponding to a physical distance between the first marker and the second marker using physical movement data of a moving object from the first marker to the second marker; an analysis step of determining the physical size per pixel using the pixel distance and the coordinate distance; the analyzing step includes dividing the pixel distance by the coordinate distance to determine the physical size per pixel; The coordinate step includes determining the coordinate distance corresponding to a physical distance from the first marker to the second marker due to movement of at least one of the camera and the set area when an encoder measures a movement distance moved by the camera or the set area. Calibration method.

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