JP2609823B2 - Target mark center position detection method by image processing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the center position of a target mark by image processing.

[0002]

2. Description of the Related Art In a work such as a printed circuit board, target marks are provided at four corners in order to form a reference hole, and the printed circuit board is transported by a fixed amount feeding device such that each target mark is located immediately below an image pickup section. At the same time, the center of the target mark is detected by predetermined means, and the drill is corrected and moved by an amount of error from the detected center via the X- and Y-axis feed mechanisms so that the center of the drill and the center of the target mark are shifted. And the drill is raised in the Z direction from that position to drill a reference hole at the center of the target mark. The above-mentioned predetermined means means that the target mark is received by the image pickup unit, the image signal is binarized by the image processing unit, the binarized image is enlarged and displayed on a monitor, and the center of gravity is measured by a dynamic window method. A method of detecting the center of a target mark (hereinafter, referred to as the former), a binarized image is enlarged and displayed on a monitor screen, and the target mark is searched in the X and Y directions from the center of the cursor to have different gradations. Find the intersection of the perpendicular bisector between each of the X and Y points,
This method uses the intersection as the center of the target mark (hereinafter referred to as the latter).

[0003]

By the way, the target mark is concentric with the center of the disk.
The ring-shaped outer peripheral part and the center of the gradation different from the central part
In general, a plan view shape in which a plurality of portions and a ring-shaped outer peripheral portion having the same gradation are alternately provided. However, in the former, the pattern other than the target mark is converted to black and white by binarization (negative /
When the transformation is performed, the transformation coordinate system is greatly affected, and a problem arises in that the center of the target mark cannot be accurately detected. In the latter case, the center of the target mark cannot be detected unless the center of the cursor on the monitor screen is positioned at the target mark, and only the diameter in the X and Y directions is searched to find the intersection of the bisector between each two points. Since the detection is performed as the center of the target mark, when a pattern having the same condition as the target mark is generated on the monitor screen, there is a problem that the center of the pattern is erroneously recognized as the center of the target mark and detected.

The present invention has been made in view of the conventional circumstances, and has as its object the object that the center of the cursor on the monitor screen (displaying a binarized image) is the center of the disk of the target mark.
The part is located in the outer part of the outside of the center part where the gradation is different
An object of the present invention is to provide a method capable of accurately detecting the center of a target mark when a workpiece is sent with a feeding error. Another object of the present invention is to provide a method capable of accurately detecting the center position of a target mark regardless of whether a workpiece feeding error is large or small.

[0005]

Means for Solving the Problems] technical means taken to achieve the above object, according to claim 1, set at the four corners of the work
Around the center of the disk.
Outer ring with concentricity with the center and different gradation from the center
Alternate the peripheral part and the ring-shaped peripheral part with the same gradation as the central part
The target marker is provided immediately below the imaging unit.
Every time the workpiece is transported by the fixed amount feeder so that the workpiece is positioned
The target mark is received by the imaging unit at
The image signal is binarized by the image processing unit and displayed on the monitor screen.
Image processing to detect the center of the target mark
A method for detecting a center position of a target mark, wherein when a cursor center of a monitor screen is not located within a center portion of a binarized target mark, a binarized image is radially searched from the cursor center at predetermined angles. to explore the starting point W having the same tone as the central portion, the starting point X1, X2 gradation different from the central portion to further explore the gradation in the partial in the X or Y direction from the open starting point W And then search in the other axis direction on the midpoint coordinate position between the start points X1 and X2 of the gradation to search for start points Y1 and Y2 of a gradation different from the center .
Then, a search is made on the midpoint coordinate position between the start points Y1 and Y2 in a direction parallel to the directions of the start points X1 and X2 to search for start points X1 'and X2' having different gradations from the center. , The diameter reference values in the X and Y directions and the starting point Y1,
The distance between Y2 and the distance between start points X1 'and X2' are compared, and the start points Y1, Y2,
The gist of the present invention is to identify the cross point of the cross point between the two start points X1 'and X2' as the center of the target mark. The second aspect is concentric with the center of the disk.
Ring-shaped outer peripheral part with a different gradation from the central part and its central part
An image pickup unit receives an image of a target mark provided with a plurality of ring-shaped outer peripheral portions having the same gradation alternately, binarizes the image signal with an image processing unit, and converts the binarized image into an image processing unit. Is displayed on the monitor screen associated with, and on the monitor screen, the image processing unit sets a number of search reference points at vertical and horizontal intervals and sets the order of the search reference points at which the search is started, and the search reference points are
When located at the same gradation as the central part, the reference point position
Is the starting point W, and the search reference point has a different gradation from the central part.
At a predetermined angle from the search reference point
And search for a point that has the same gradation as the center
A start point W is set, and the inside of the gradation portion is further searched in the X or Y direction from the start point W to search for start points X1 and X2 of different gradations from the central portion. X1,
Search the middle point coordinate position between X2 in the other axis direction and center
Parts and explore the starting point Y1, Y2 of different gradations and
The start point X is located on the middle point coordinate position between the start points Y1 and Y2.
1. Search in the direction parallel to the X2 direction to search for start points X1 ′, X2 ′ of different gradations from the central part, and store the diameter reference values in the X, Y directions stored in the storage unit and the start points Y1, The distance between Y2 and the distance between the start points X1 'and X2' are compared, and the start points Y1, Y2, and the start point X are matched with the diameter reference value.
1 ', X2' of the cross-shaped intersection of the two points recognized as the center of the target mark, exploration of the next turn if you can not certified
Perform the same search from the reference point in the same way, and
The gist of the present invention is to perform an error process when the above-mentioned exploration from the point cannot be recognized . After the claims 3 detected the center of the central portion of the target mark of claim 1 or 2 wherein the central
The inside part, and exploration X-shaped or radially with a desired inclination angle intersecting the detection center to explore the starting point Z1, Z2 made of different tone from the central portion, the distance between the open start Z1, Z2 The gist is that the detection center is recognized as the center of the target mark in conformity with the diameter reference values in the X and Y directions of the center portion taught in the storage unit.

[0006]

According to the above technical means, the following effects are obtained. (Claim 1) An image signal of a target mark received by an imaging unit is binarized by an image processing unit, and the binarized image is displayed on a monitor. When the center of the cursor is not located in the center of the binarized image of the target mark, the binarized image is radially searched for every predetermined angle from the center of the cursor, and the start point W of the same gradation as the center is determined. Quest. Next, from the start point W, the inside of the gradation portion is searched, for example, in the X direction, and the start points X1 and X2 of the gradation different from the central portion are searched for, and the middle point coordinate position is calculated. Then, the center point coordinate position is used as a reference point to search in the Y direction to obtain start points Y1 and Y2 of different gradations from the central part . The distance between the start points Y1 and Y2 is
It is the diameter in the Y-axis direction of a certain location that was searched assuming the center . Then, the midpoint coordinate position is searched in the X-axis direction this time, and the starting points X1 'and X2' having different gradations from the central part are obtained. The distance between the start points X1 'and X2' is the diameter in the X-axis direction of a certain location searched assuming the center . Finally, the reference value of the diameter of the target mark in the X-axis and Y-axis directions stored in the storage unit is compared with the distance between the start points Y1 and Y2 and the distance between the start points X1 'and X2', and conforms to the diameter reference value. Then, it is determined that the target mark is the center of the target mark having the regular area, and the start points Y1, Y2, X
The cross-shaped intersection of two points 1 ′ and X2 ′ is determined as the actual center. Therefore, one outside of the center of the target mark
Feed error such that the center of the cursor on the monitor screen is positioned within the outer periphery of the ring (feed error of a work such as a printed circuit board)
The center of the target mark can be detected even when there is a mark.
When the center of the cursor is located in the center of the binarized image of the target mark, the gray scale portion is searched using the center of the cursor as the start point W without searching radially for one pixel pitch at every predetermined angle. , And reliably detect the center of the target mark. (Claim 2) Inside the target mark
When there is a feed error (feed error of a work such as a printed circuit board) larger than the center of the cursor on the monitor screen is located in the outer peripheral portion of one central portion outside the central portion having a different gradation from the central portion. In the first aspect, the center of the center cannot be detected. For this purpose, a large number of search reference points are set on the monitor screen at vertical and horizontal intervals including the center of the cursor, and search is performed from the search reference points in a predetermined order. This makes it possible to detect the center of the central portion by probing from any of the search reference point by. Exploration is carried out in a predetermined search criterion point order that is determined to the center of the target mark the central portion is detected, it does not perform exploration from the remaining search reference point when the center is detected by ends there. (Claim 3) Even if a portion other than the center portion has a condition that temporarily matches the reference diameter in the X and Y directions as taught in claims 1 and 2, it is recognized as a center portion except for a perfect circular disk. Not
The center of the center can be reliably detected.

[0007] Since the present invention is configured as described above, it has the following advantages. (Claim 1) the cursor around the target between the monitor screen for displaying the binary image by the image processing unit
The center position of the target mark can be reliably detected even if the printed circuit board or the like is fed in error so as to be located on the outer periphery of the ring outside the central portion of the mark. (Claim 2)
A large number of search reference points are set on the monitor screen at vertical and horizontal intervals, and the set reference points are radially searched for each predetermined angle in a predetermined order to obtain a portion having the same gradation as the center portion , from there. Since the search method is used, if the center of the target mark is located on the monitor screen, the center position of the target mark can be determined by searching from any of the search reference points regardless of whether the workpiece feed error is large or small. It can be detected reliably. (Claim 3) The same condition as the diameter in the X and Y directions of the central portion detected by the first and second aspects is satisfied.
Since even if generated on the outer peripheral portion of the annular or the like surrounding the part to further explore portion thereof other than a true circular disc determines that not a central portion, erroneous than the center of the central portion of the target mark No worries about detecting.

[0008]

Next, an embodiment of the present invention will be described with reference to the drawings. FIGS. 1 to 5 show a first embodiment of a method for detecting the center position of a target mark by image processing according to the present invention, and FIGS. 6 to 8 show a second embodiment thereof. First, a first embodiment will be described.

[0009] The punching device A is a work B such as a printed circuit board.
Imaging unit 1 for receiving a transmission image obtained by illuminating the image from below or a reflection image obtained by illumination from above, and image processing for performing image processing to binarize an image signal received by the imaging unit 1 Unit 2, a monitor 3 for displaying the binarized image, a drill 4 for drilling provided opposite to the image pickup unit 1, an X, Y-axis feed mechanism 5, and a Z-axis feed mechanism for the drill 4. 6 and so on.

The image processing unit 2 includes an image processing device 12 for performing arithmetic processing such as binarization on an image signal received by the imaging unit 1, an image memory 22 for storing the binarized data, and a predetermined program. A central processing unit 32 to be executed; a RAM (storage unit) 42 for storing data necessary for the central processing unit 32;
(Storage unit) 52 and the like, and a fixed-quantity feeding device such that the center of the target mark b of a work B such as a printed circuit board having target marks b attached at four corners coincides with the center of the cursor 13 on the monitor 3 screen. Each time the target mark b is automatically transferred by a not-shown image, the target mark b is received by the imaging unit 1, the image signal is binarized by the image processing unit 12 by image processing, and the binarized data is stored in an image memory. Remember at 22,
The binarized image is displayed on the monitor 3, the binarized image is searched from the center of the cursor 13 of the monitor 3, the center of the target mark b is detected, and the center of the cursor 13 and the center of the detected target mark b are detected. Is detected.

The central processing unit 32 of the punching device A is arranged such that the center of the target mark b of the workpiece B is moved by the constant-rate feeding device (not shown) so that the center of the target mark b coincides with the center of the cursor 13. Is executed. In the image processing device 12, a threshold value is set for black and white determination, and a level higher than the threshold value is determined as white or black, and a level lower than the threshold value is determined as black or white. In addition, the control program includes a target mark ( around the center of the disk).
Ring-shape with a different gradation from the center
Alternately outer peripheral portion and the outer peripheral portion of the central portion and the same tone of annular
Relatively large, data feed error by quantitative feeder of the work B having a plurality planar view shape) b (not shown)
The disc-shaped central portion b1 of the target mark b is the gradation
The center outer part b1 of the outer peripheral part b2
The center of the cursor 13 on the monitor 3 screen is within the range of the large diameter.
This is for detecting the center of the target mark b when there is a positioning error, and is incorporated in the ROM 52.

Next, an enlarged view of a monitor screen showing a state in which the control program is searching for a binarized image image-processed by the image processing unit shown in FIGS. 2 to 4 is shown in FIG. A description will be given based on a flowchart of a program controlled by the processing device. The image of the target mark B is received by the image pickup unit 1, the image signal is subjected to image processing by the image processing device 12, and is binarized. First, the center of the cursor 13 is located at the center b1 of the target mark B.
Is determined (step 1). The center of the cursor 13 is located at the center b1 of the target mark B.
When located in the beginning point X1 gradation different from the central portion b1 to 1 addressed pixel pitch search in the X direction from the position as a starting point W the cursor 13 centered as shown in FIG. 3, X2
A point is searched for, the midpoint coordinate position (point) of the X1 point and the X2 point is calculated, and this point is temporarily stored in the RAM 42.
(Steps 2, 3, and 4). This time, a search is made on the above-mentioned middle point coordinate position (point) in the Y direction for one pixel pitch, and a start point Y1 of a gradation different from that of the central part b1 ,
The point Y2 is searched for, the coordinates of the middle point (point) of the points Y1 and Y2 are calculated, and the points are stored in the RAM 42 (steps 5, 6, and 7). Then, this intermediate coordinate position (point) is searched for one pixel pitch in the X direction, and the starting points X1 'and X2' of different gradations from the central part b1 are searched (steps 8 and 9). Further, the distance between the Y1 point and the Y2 point, the distance between the X1 ′ point and the X2 ′ point is stored in the ROM 52 at the center b of the target mark B which has been taught.
1 and is recognized as a diameter when they match, and a cross-shaped intersection O (virtual center) of each of two points Y1, Y2, X1 'and X2' is obtained and stored in the RAM 42 (steps 10 and 11). ). Even if the diameter in the X and Y directions matches the diameter reference value taught in the ROM 52, the probe is further searched in an X shape or a radial shape with a desired inclination angle crossing the intersection O (virtual center). Central part b
Search for starting points Z1, Z2 of gradations different from the gradation 1
When the distance between the search points conforms to the taught diameter reference value, it is recognized as a perfect circular disk for the first time, and the virtual center, which is the intersection O, is the center b1 of the target mark b for the first time.
(Steps 12 and 13).

Further, as shown in FIG. 2, the center of the cursor 13 is located at the center of the target mark one outside of the center b1.
When located in the outer peripheral portion b2 of the annular having different gradation is, the cursor 13 from the center 1 pixel pitch destined example 2m
The range of m is searched every 30 degrees to find a starting point W in the X direction having the same gradation as that of the center part b1 (steps 1, 14, 15,
16, 17), and from the start point W, the above steps 2 to 13 are executed respectively. As a result, if the center of the target mark and its center are not recognized even on the last search line, error processing is performed (step 18).

Therefore, the central part b1 of the target mark b
Central portion b1 gradation is different from the central portion b1 of the feed error and target mark b, such as the cursor 13 centers are located within
The center of the cursor 13 is located in the outer peripheral portion b2 on the outer side.
The center of the data <br/> over target mark central portion b1 when the workpiece B sent can be detected reliably and at high speed with a feed errors.

Reference numeral 7 denotes an I / O port, and its I / O port
The X / Y axis feed mechanism 5 is controlled by an X / Y axis driver circuit 8 connected to the / O port 7, and the Z axis feed mechanism 6 includes a solenoid 6a and an air cylinder 6b.

Next, a second embodiment will be described. In this embodiment, as long as the center of a target mark is located in a monitor screen, a feed error (a feed error of a printed circuit board or the like) is large or small. This is a method that can detect the center position of the target mark.

In this embodiment, the image processing device 12 sets a large number of search reference points C... At a vertical and horizontal interval including the center of the cursor 13 on the screen of the monitor 3 for displaying the binarized image. The configuration is the same as that of the above-described embodiment except that the central processing unit 32 executes a control program for searching in a predetermined order from the point C. By the way, when the computer control finds the same gradation point as that in the center part b1 of the target mark B during the search of the binarized image, the search does not proceed any further, and the search in that point does not proceed. Ending the exploration only by itself cannot detect the center. Central b cursor 13 center of the target mark B of the monitor 3 screen as (show binarized images)
One or in the case or if the cursor 13 center located in one of the feed error to the central portion b1 of the target mark B is located in the outer peripheral portion b2 of the central portion b1 immediately outer annular having different gradation The center can be detected by searching from the location (the center of the cursor 13), but if the feed error is larger than that, the first
The method of the embodiment cannot detect the center of the target mark. In order to prevent this, a large number of search reference points C are set on the screen of the monitor 3 at vertical and horizontal intervals including the center of the cursor 13. The number of the search reference points C is nine in the drawing in this embodiment. However, any number more than the search reference points C is, of course, arbitrary, and is effective when the shape of the target mark becomes more complicated as the number of the search reference points C increases.

An enlarged view of a monitor screen showing a state in which the control program is searching for a binarized image image-processed by the image processing apparatus 12 of FIG. 6, and a central processing unit of the punching apparatus of FIGS. A description will be given based on a flowchart of the program controlled by. In this control program, the search is continued continuously in the order of the search reference points until the center of the center of the target mark is detected. Each step will be described with reference to the step NO of the first embodiment. First,
The image of the target mark B is received by the image pickup unit 1, the image signal is subjected to image processing by the image processing device 12, and is binarized. The search starts from the search reference point C1, and it is determined whether or not the search reference point C1 is located at the same gradation as the central part b1 of the target mark B (step 1). In FIG. 6, since the search reference point C1 is located at the same gradation as the central part b1 of the target mark B, the search reference point C1 is set as the start point W (not shown).
Steps 2 to 10 are executed from the start point W. However, X, for Y distance is not compatible with the diameter reference value of the central portion b1 of teaching the target mark B stored in the ROM 52, that is not a central portion and certification
Is determined . Then, the search from the search reference point C2 starts. Each of the search reference points C2 to C9 similarly has Steps 1 to 17 in FIG. This search reference point C2 is located at the center b1 of the target mark B.
Different order are located outermost in the peripheral portion b3 of the annular gradation, the same as the central portion b1 to search range from the search reference point C2 1 pixel pitch destined example 2mm every 30 degrees and Search for a gray scale start point W (not shown) (step 1)
4, 15, 16 and 17), and from the start point W (not shown), the steps 2 to 10 are executed. If the same gradation point as that of the center part b1 of the target mark B is found during the search, the search will not proceed any further. Therefore, between the outermost peripheral part b3 and the inner peripheral part b4 between the outermost peripheral part b3 and the inner peripheral part b4. becomes the outer periphery of the same tone as the central portion b1 (below referred to as concentric rings) b5 by executing the steps 2 through 10, be certified as non-central portion as a result. Then, the search from the search reference point C3 starts. Since the search reference point C3 is located within the concentric ring b5 having the same gradation as the center part b1 of the target mark B, the steps 2 to 10 are executed as it is, and the center is set similarly to the search from the search reference point C1. Department is not recognized . The search from the search reference point C4 has the same result as the search from the search reference point C1. In addition, the search from the search reference point C5 is different from the center b1 of the target mark B in gradation.
Since it is located in the outer peripheral portion b4 , a range of, for example, 2 mm addressed to one pixel pitch is set to 3 as in the search from the search reference point C2.
A search is made every 0 degrees to find a starting point W (not shown) having the same gradation as that of the central part b1 (steps 14, 15, 16, 1).
7) From the starting point W (not shown),
To perform each of steps 10 through 10, but not at the center
Be certified . Then, the search from the search reference point C6 starts. The search reference point C6 is located in an angular portion b2 of the annular differing one outer gradation of the central portion b1, the search reference point C6 from 1 pixel pitch destined example 2m
The range of m is searched every 30 degrees to find the starting point W of the same gradation as the central part b1 (steps 14, 15, 16, 1).
7), from its starting point is W, the steps 2 to 13 respectively perform, for detecting a center recognized for the first time as the central portion b1.
If the center of the central portion b1 is not detected in the search from the search reference point C6, the subsequent search reference points C7, C8,
The search from C9 is continued, and if not detected, the feed error (feed error of the printed circuit board or the like) is determined to be too large and error processing is finally performed (step 18). This is displayed on the monitor 3 or a warning is issued.

As described above, in the second embodiment, the search reference point C
1, C2, C3, C4, C5, C6, C7, C8, C9
Are set on the monitor 3 screen at a vertical and horizontal interval including the center of the cursor 13, and each of the search reference points C1, C2, C3,
Since the search is performed radially at predetermined angles in order from C4, C5, C6, C7, C8, and C9, any search criteria can be used as long as the center of the target mark B is located on the monitor screen 3. The center can be detected by searching from a point. In addition, the search reference points C1, C2, C
3, C4, C5, C6, C7, C8, and C9 are not limited to those having constant vertical and horizontal intervals as illustrated.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a punching apparatus for implementing a target mark center position detecting method according to a first embodiment.

FIG. 2 is different in gradation from a central part of a target mark.
The enlarged view of the monitor screen which shows the search state when the cursor center is located in the ring-shaped outer peripheral part one center part outside .

Figure 3 is an enlarged view of the monitor screen showing the search condition when the cursor around the center portion of the target mark is located.

FIG. 4 is an enlarged view of a monitor screen showing a state in which a central portion of a target mark is being searched for in a direction intersecting a virtual center (intersection point O).

FIG. 5 is a flowchart of a program controlled by a central processing unit of the punching device.

FIG. 6 is an enlarged view of a monitor screen showing a state in which a state in which the center of the target mark is detected in the second embodiment is being searched.

FIG. 7 is a flowchart of a program controlled by the central processing unit of the drilling device, showing a search starting from a search reference point C1.

FIG. 8 is a flowchart showing search reference points C2 to C9;
Indicates the time of exploration from.

[Explanation of symbols]

A: Punching device 2: Image processing unit 3: Monitor 13: Cursor 42, 52: Storage unit b: Target mark B: Work b1: Central part b2: One outer ring-shaped part whose gradation is different from that of the central part Perimeter
Parts C, C1, C2, C3, C4, C5, C6, C7, C
8, C9: Exploration reference point W: Start point

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location G01B 11/00 G01B 11/00 CH G06T 7/60 G06F 15/70 360

Claims (3)

(57) [Claims] 1. Target marks provided at four corners of a work
Around the center of the disk and concentric with the center
A ring-shaped outer peripheral part with a different gradation from the central part
And a plurality of ring-shaped outer peripheral portions having the same gradation are provided alternately,
Make sure that the target mark is located just below the imaging unit.
Each time a mark is transported by the fixed amount feeder,
The image signal is received by the imaging unit and the image signal is received by the image processing unit.
And display it on the monitor screen with the target mark
Of the target mark by image processing that detects the center of the image
A heart position detecting method, when the cursor center of the monitor screen in the central portion of the binarized target mark is not located, the central portion by probing a binary image from the cursor centered radially at predetermined angle same tone as the start point W explore made, the gradation in the portion from the the open start point W further explored in the X or Y direction starting point of a different tone with the central portion X1, X and
2 and then the other axis direction is searched on the middle point coordinate position between the start points X1 and X2 of the gray scale to search for the start points Y1 and Y2 of the gray scale different from the center part , and Its starting point Y
A search is made in the direction parallel to the start points X1 and X2 on the middle point coordinate position between the first and second points Y1 and Y2, and the start point X having a different gradation from the central part is detected.
1 ′ and X2 ′ are searched, and the diameter reference values in the X and Y directions stored in the storage unit are compared with the distance between the start points Y1 and Y2 and the distance between the start points X1 ′ and X2 ′. A method for detecting a center position of a target mark by image processing, wherein a cross-shaped intersection of each of the start points Y1, Y2 and the start points X1 ', X2' is determined as the center of the target mark. . 2. A disk-shaped central portion around a central portion.
The center of the ring is different from that of the center.
An image pickup unit receives an image of a target mark in which a plurality of center portions and a ring-shaped outer peripheral portion having the same gradation are alternately provided, binarizes the image signal with an image processing unit, and converts the binarized image into an image. Displayed on a monitor screen associated with the image processing unit, the image processing unit sets a large number of search reference points at vertical and horizontal intervals on the monitor screen, sets the order of search reference points at which the search is started, and performs the search.
When the reference point is located at the same gradation as the center,
The reference point position is the starting point W, and the search reference point is different from the central part.
Predetermined angle from the probe reference point when located Do that gradation
The point where the same gradation as the above-mentioned central part is obtained
The start point W is searched for, and the inside of the gradation portion is further searched in the X or Y direction from the start point W to search for start points X1 and X2 of a gradation different from the central portion. Is searched in the other axis direction on the midpoint coordinate position between the start points X1 and X2 of the image to find the start points Y1 and Y2 having different gradations from the center .
Then, a search is made on the midpoint coordinate position between the start points Y1 and Y2 in a direction parallel to the directions of the start points X1 and X2 to search for start points X1 'and X2' having different gradations from the center. , The diameter reference values in the X and Y directions and the starting point Y1,
The distance between Y2 and the distance between start points X1 'and X2' are compared, and the start points Y1, Y2,
The cross-shaped intersection of each of the two start points X1 'and X2' is recognized as the center of the target mark .
Repeat the above search from the search reference point No.
If the above search from the search reference point does not
-A method for detecting the center position of a target mark by image processing, characterized by performing processing. 3. After detecting the center of the central portion of the target mark, the inside central portion, and the gradation that is different from the desired tilt angle with and exploration X-shaped or radially the central portion intersecting said detection center Starting points Z1 and Z2 are found, and the distance between the starting points Z1 and Z2 is taught in the storage unit.
X of the central portion, the central position detection method of the target mark by image processing according to claim 1 or 2 wherein complies with Y diameter reference value, characterized in that certified the center of the target mark the detection center.