JPH04142547A - Register mark position detection device - Google Patents

Abstract

PURPOSE:To accurately detect the positioning points of various register marks with simple constitution by picking up an image of a sheet where a register mark(RM) is recorded as a binary image, performing arithmetic operation based upon data obtained by scanning the binary image, and recognizing the directions and positions of one straight line and another straight line which constitute the register mark. CONSTITUTION:The image of the sheet SH where the register mark RM is recorded is picked up as the binary image. On each scanning line in one direction, singular points such as the center position and end position of an area where picture elements indicating one of the two values of the binary data continue are extracted and their frequencies of appearance are calculated. This arithmetic operation is repeated while the direction of the scanning line is rotated until the appearance frequency distribution meets specific requirements. The direction and position of the scanning line when the appearance distribution meets the specific requirements are recognized as the direction and position of one straight line L1. The angle of the scanning direction is switched to recognize the direction and position of the other straight line L2 which differ in angle.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a register mark position detection device used in the printing field and other fields. The present invention relates to a device that recognizes a register mark (so-called register mark) and detects the position of an alignment point formed from the shape of a straight line portion of the register mark.

[Prior Art] Register marks have traditionally been used to align original films and originals, and various devices for detecting the positions of register marks have been proposed in order to automate the alignment of originals, etc. ing. For example, the applicant of the present application has previously proposed a device (Japanese Patent Application Laid-Open No. 62-206403) that images a register mark using a photoelectric conversion element and identifies the position of the register mark based on changes in the amount of light. Another idea is to use an imaging means such as a television camera instead of a simple photoelectric conversion element, and perform processing such as image recognition on the obtained image to detect the position of the register mark. There is.

(Problems to be Solved by the Invention) However, the shapes of register marks that are actually used are various, and for example, in a type of device that detects by photoelectric conversion, it is difficult to automatically detect register marks in shapes other than a simple cross shape. In addition, even in the case of a simple cross shape, it was sometimes difficult to detect it simply because the thickness of the straight line was different.

On the other hand, when trying to adopt an image recognition method, it is necessary to extract the straight lines that make up the register mark, and the straight line extraction process requires complex calculations, which reduces processing speed and increases the complexity of the equipment. We must solve the problem of increasing size.

The register mark position detection device of the present invention has been made to solve the above-mentioned problems and to accurately detect alignment points of various types of register marks with a simple configuration. The configuration of the present invention that achieves this objective will be described below.

[Means for Solving the Problems] As illustrated in FIG. 1, the register mark position detection device of the present invention includes at least two straight line portions Ll having different angles.

In the register mark position detection device that recognizes the register mark RM having the register mark L2 and detects the position of the alignment point formed from the shape of the straight line part of the register mark RM, the sheet SH on which the register mark RM is recorded is An imaging means M1 for capturing an image as a value image, and a register mark RM
coarse position setting means M2 for positioning the image within the field of view of the imaging means M1, and a pixel indicating one of the binary values in each scanning line that scans in one direction the binary image taken by the imaging means M1; Singular point extracting means M3 extracts singular points such as the central position and end position of a continuous region; Appearance frequency calculation means M4 calculates the frequency of occurrence of the extracted singular points at each position on the scanning line; Seat SH
rotating the direction of the scanning line by a predetermined amount relative to
a control means M5 for extracting a singular point based on the captured binary image and calculating the frequency of appearance, and repeating this until the distribution of the calculated frequency of appearance satisfies a predetermined condition; and a distribution of the frequency of appearance; A first straight line recognition in which a predetermined direction with respect to the scanning line when satisfies a predetermined condition is the direction of one straight line L1 constituting the register mark RM, and a predetermined position determined from the condition is recognized as the position of the straight line L1. means M6; and a second straight line recognition means that switches the scanning direction for the binary image by a predetermined angle, executes each of the above processes, and recognizes the direction and position of another straight line L2 different from the first straight line L1. M7, and alignment point detection means M8 for detecting the position of the alignment point of the register mark RM based on the direction and position of the recognized at least two straight lines Ll and L2. do.

[Operation] The register mark position detection device of the present invention having the above configuration detects the sheet SH on which the register mark RM is recorded by the imaging means M1 in which the register mark RM is aligned within the field of view by the rough position setting means M2. Capture as a binary image. In each scanning line that scans the binary image taken by the imaging means Ml in one direction, a singular point extraction means M
3 extracts singular points such as the center position and end positions of a region where pixels indicating one of the binary values are continuous, and the appearance frequency calculation means M4 calculates the frequency of appearance of this singular point at each position on the scanning line. demand. Here, if the register mark uses the intersection of straight lines as the alignment point, the center position of the area is used as the singular point, and in the case of a register mark for cutting, which uses the outer edge of the line, the singular point is , the end position of the region can be used.

The control means M5 performs the extraction of the singular point and the calculation of the frequency of appearance.
is repeated while rotating the direction of the scanning line by a predetermined amount relative to the sheet SH until the obtained distribution of appearance frequencies satisfies a predetermined condition. The first straight line recognition means M6 sets a predetermined direction with respect to the scanning line when the width of the frequency distribution satisfies the condition as the direction of one straight line Ll constituting the register mark, and sets a predetermined position determined from the condition as a straight line. It is recognized as the L1 position. On the other hand, the second straight line recognition means M7
The scanning direction for the binary image is switched by a predetermined angle, the above-mentioned processes are executed, and the direction and position of another straight line L2 having a different angle is recognized.

The alignment point detection means M8 detects at least two straight lines L having different angles of the thus recognized register mark RM.
1 and L2, the position of the alignment point of the register mark RM is detected.

Note that the control means M5 rotates the direction of the scanning line relative to the sheet SH by a predetermined amount in reality.
Alternatively, it may be realized by rotating the sheet SH, or by storing image data or binarized image data captured by the imaging means M1, and adjusting the reading order from this image data relative to the scanning line direction. It may be realized by changing it in accordance with the amount of rotation.

Also, 1st. Second straight line recognition means M6. The conditions for M7 to recognize the direction and position of the straight line L1 constituting the register mark RM include the condition that the peak value of the frequency of appearance is the maximum, and the condition that the distribution of the frequency of appearance near the peak value of the frequency of appearance is constant. You can consider conditions such as being less than or equal to the width. At this time, the straight line L1. The direction of L2 is a direction perpendicular to the scanning line, and the direction of straight line L1. The position L2 is the position with the maximum frequency of appearance.

Note that the straight lines forming the register mark RM do not necessarily need to intersect at right angles, and may intersect at 60 degrees or 45 degrees, for example. It may be a type of register mark in which three or more straight lines intersect.

In addition, since the position and direction of the straight line are determined from the condition of the frequency of appearance, even a type of register mark with a missing straight line at the intersection can be detected in the same way as a type of register mark where straight lines actually intersect. I can do it.

(Embodiments) In order to further clarify the structure and operation of the present invention described above, preferred embodiments of the register mark position detection device of the present invention will be described below. FIG. 2 is a schematic configuration diagram of the register mark position detection device 1 as an embodiment, and FIG. 3 is a control system diagram thereof. Note that this register mark position detection device 1 has a function that even performs alignment of the document.

As shown in the figure, this register mark position detection device 1 includes a transparent glass table 7 on which a transparent base sheet 3 is positioned and placed using a bin 5, and a gate-shaped moving table 10 arranged to straddle the table 7. ．． A document holding mechanism 15 provided on the gate-shaped moving table 10 and holding down the document 12 placed on the base sheet 3;
It is comprised of a shaft drive device 17, an X-axis drive device 19 for moving the gate-shaped moving table 1o in the front-rear direction (direction of arrow X in FIG. 2), a control panel 22 equipped with a CRT monitor 20, etc. Note that three television cameras 24 and 25° 26 are installed under the transparent glass table 7 and are movable by motors, respectively, and can take images of the original 12 placed on the base sheet 3.

The original pressing mechanism 15 includes two pressing feet 30 . which press the original 12 against the base sheet 3 . It is comprised of a rotating shaft 32 that rotatably supports this presser foot 30, a motor 37 that rotates the rotating shaft 32 by driving a pulley 34 provided at the end of the rotating shaft 32 with a belt 35, and the like.

The document holding mechanism 15 includes a vertical mechanism (not shown) that moves the presser foot 3o up and down to press or release the document 12, and a vertical mechanism (not shown) that moves the presser foot 3o up and down to press or release the document 12, and a vertical mechanism (not shown) that applies negative pressure to the surface of the presser foot 3o that contacts the document 12 to press the document 12. A suction mechanism (not shown) for suctioning 12 is also provided.

As shown in FIG. 2, the X-axis drive device 17 includes a drive motor 41, a pole screw 43, etc. that converts the rotation of this motor into linear motion. Similarly, the X-axis drive device 19 also includes a drive motor 51 and a ball screw 53.
It is composed of etc.

Next, the configuration of a control device that controls these moving mechanisms, television cameras, etc. will be explained. As shown in FIG. 3, the electronic control device 60 of the register mark position detecting device 1 includes a well-known CPU 61. R○M62. It is configured as an arithmetic and logic operation circuit from a RAM 64, etc., and its common bus 65 is connected to a serial communication board (SIO) 67 for exchanging data with the host computer, and input terminals to which motors 37, 41, and 51 of each mechanism are connected. An output interface 68, an input/output interface 77 to which motors 74 to 76 for controlling the positions of the television cameras 24 to 26 are connected, and the like are connected.

Furthermore, the electronic control device 60 is equipped with a circuit that inputs and processes image signals from the three television cameras 24 to 26 that image the original 12. This circuit is
A switch 81 switches the image signals from the three television cameras 24 to 26, and the output signal of this switch 81 (NT
a synchronization separation filter 82 that inputs a signal (SC) and separates image data from horizontal and vertical synchronization signals; an A/D converter 84 that converts the output image data into a digital signal;
A comparator 85 that compares the image data converted into a digital signal with a reference value specified by the CPU 61 and binarizes it.
, a binarized data memory 87 that stores binarized image data, and a counting processing section 90 that counts the median value based on the binarized image data. A timing signal generation circuit 91 is provided.Furthermore, the electronic control device 60 has a function of outputting a signal (NTSC) output from the switching device 81 to the CRT monitor 20 and displaying images captured by the television cameras 24 to 26. However, for this purpose, 24 or 2 television cameras were used.
6, a CRT controller 92 that controls the CRT
Also provided are a frame memory 94 for storing image signals generated by the controller 92, a CRT monitor interface 95 for converting the output into an image signal, and a superimpose circuit 96 for inserting the image in the frame memory 94 into the image signal from the switch 81. It is being

A counting processing unit 90 that performs processing based on the binarized image data includes an X-direction run length median counting counter 97 that counts the median value in the It consists of a median value counting counter 98 and a control circuit 99 that controls these counters 97 and 98. Fig. 4 shows how the counters 97 and 98 count the median value. For example, the transparent part of the background There is an area BI formed as an opaque black part against the scanning line SL in the X direction.
Considering I to SL5, area B on scanning line SLI
The center position of the run length RL of I is a point CP, and the value of the counter at the Y-direction address y1 corresponding to this point is counted by 1. As shown in FIG. 4, the next scanning line SL2.
The median value on 3 belongs to the Y direction address y2 and is on the scanning line SL.
The median value on 4 belongs to Y-direction address y3 and is located on scanning line SL.
There is no area BT on S. Therefore, in the example shown in FIG. 4, the address [yl, y2 . y3, y4]
The count value stored in is [1,2°11 ○].

Next, a process for recognizing register marks (so-called registration marks) using the count values stored in the count processing section 90 will be described. The CPU 61 reads the program stored in the R○M 62, and according to the procedure, recognizes the register mark on the original 12 from the image taken by the television cameras 24 to 26, determines the position of the original 12, and drives each motor. Then, a series of operations are performed to correct the position of the document 12 to a predetermined position. This series of operations is shown in the flowchart of FIG. When the automatic document alignment processing routine shown in FIG. 5 is started, processing for switching the television cameras 24 to 26 is first performed (step 100).

As shown in FIG. 2, the television cameras 24 to 26 are provided corresponding to the register marks RM on the document, and the television cameras 24 to 26 are set to correspond to the register marks RM on the document, and are switched to the television by sending a switching signal to the switch 81 (see FIG. 3). The cameras 24 to 26 are sequentially switched to perform the following processing.

First, select the television camera 24 (step lO○),
Next, rough position adjustment processing is executed (step 110). This rough position adjustment process adjusts the positions of the television cameras 24 to 26 provided corresponding to each register mark RM so that the register mark RM enters approximately the center of the corresponding television camera. It is processing. The motors 74 to 76, which are provided so that the positions of the television cameras 24 to 26 in the X direction or the Y direction can be adjusted, are driven and operated via the input/output interface 77.
control and make rough position adjustments.

Note that the rough position adjustment is performed by the X-axis drive device 17. when the document 12 is placed on the base sheet 3. Y-axis drive device 19.
There is no problem even if all three register marks RM are completed by driving the motors 74 to 76. Further, the motors 74 to 76, etc. may be driven manually by the operator while looking at the CRT monitor 20.

After adjusting the rough position, processing is performed to capture the image as a binary image based on the signal from the television camera 24 (25, 26) (step 120). This processing converts the NTSC format signal from the television camera 24 (25, 26) into
Switch 81. Synchronous separation filter 82. A/Di converter 8
4 as a digital signal and convert it to CP.
This is performed by comparing the comparison value specified in advance by U61 with the comparison value by the comparator 85, converting it into a value, and loading it into the memory 87 for binary data.

Next, based on the captured binary image, counting processing in the X direction (step 13o) and counting processing in the Y direction (step 1
40). In the counting process in each direction, the data stored in the binarized data memory 87 is read out in the order corresponding to the X direction and Y direction of the image, and as already described with reference to FIG. This is done by incrementing the contents of a counter corresponding to the coordinates of the median run length of the corresponding black area by a value of 1. This process will be explained in detail.

FIG. 6 is an explanatory diagram illustrating the counting process. As shown in FIG. 6(A), the horizontal direction is the X direction and the vertical direction is the Y direction, and as shown in FIG. 6(B), the run length on the scanning line in the Y direction with respect to the register mark RM is The process of finding the median value, sequentially incrementing the contents of the corresponding address by a value of 1, and counting the median value is repeated for each scanning line. Similarly, in the X direction, data at the corresponding address of the X direction run length median counter 97 is updated, as shown in FIG. 6(C). When looking at each scanning line in the Y direction (as shown in FIG. 6(E), if the register mark RM is at a position rotated by a slight angle with respect to the This results in a state in which the values match in several adjacent scanning lines.

In this case, each direction run length median count counter 97
, 98, the frequency of occurrence of the median value is counted with a certain width, as shown in FIG. 6(D).

After counting the frequency of occurrence of the median value in the X direction and the Y direction, it is determined whether the widths dx and dy of the distribution of the frequency of occurrence are less than a predetermined value ε (step 15).
0). If the straight line forming the register mark RM is inclined with respect to the direction of the scanning line, the widths dx, d of this distribution
Since y has a considerable range, the judgment at step 150 is "
No.” In this case, steps 160 to 1
By executing the process in step 75 and then returning to the process in step 130, the width dx is adjusted while rotating and correcting the direction of the scanning line for the binary image little by little.

A process of repeating counting is executed until dy becomes less than a predetermined value ε. This repeated process is performed as follows.

First, by rotationally correcting the direction of the scanning line, the width dx, dy
It is determined whether or not there is a tendency for contraction/11 (step 160). This is the width dx, d obtained from the previous counting.
This can be determined by determining whether the widths dx and dy obtained by the current count are smaller than y. If it is determined that there is a tendency to reduce, the scanning direction is further rotated and corrected in that direction (step 170); if there is not a tendency to reduce, rotation is corrected in the opposite direction (step 175). After correcting the rotation in the scanning direction, steps 130 to 150 are executed again, and the widths dx and dy are set to the predetermined value ε.
These processes are repeated until the value is less than 1, that is, until the scanning direction matches the direction of the straight line forming the register mark RM.

In this embodiment, the scanning direction for the binary image read once is corrected by rotation, but the television camera 24 to 26 is rotated to read the image again, and the newly read image is corrected by the X and X directions again. It is also possible to adopt a configuration in which the median value of run lengths in the Y direction is counted. Further, in this embodiment, the median value is counted by software, but it may be counted by a hardware configuration.

The width dx, dy of the frequency distribution is a predetermined value ε (usually 1)
If it becomes less than
The contents of the run length median counters 97 and 98 in the Y direction are 0 except for the points corresponding to the intersections of the two straight lines of the register mark RM, and the values correspond to the lengths of the straight lines at the points corresponding to the intersections. The values will be y and X.

Then, from the address of the point with the values y and CPi position coordinates (Xi, Yi)
(step 180), and it is determined whether the above processing has been completed for all television cameras (step 190). If the processing has not been completed for all television cameras, the process returns to step 100 and repeats the above-mentioned processing (steps 100 to 19o) starting from switching the television cameras.

The above-mentioned processing is completed for all of the television cameras 24 to 26, and the alignment point C of each register mark RM is completed.
When the coordinates (Xi, Yi) of Pi (i=1.2.3) are calculated, the position of the original 12 is adjusted using these coordinates (Xi, Yi) (step 200). ). That is, the three register marks RM on the original 12
From the coordinates (Xi, Yi) of the alignment point cp, document 1
The document holding mechanism 15 . x-axis drive device 17. It drives the Y-axis drive device 19.

Note that the position of the original 12 may be adjusted by moving the original 12 by an amount that corrects the deviation of the original 12 at once, or by moving the original 12 by an amount that corrects the deviation of the original 12.
The positioning accuracy may be improved by moving the register mark RM and repeating the calculation of the coordinates of the alignment point CPi of the register mark RM as described above to gradually bring it closer to the normal position.

Through the above processing, the register mark position detection device of this embodiment calculates the median value of the run lengths on each scanning line in the X-axis and Y-axis directions, stores the frequency of its appearance in the counters 97 and 98, and calculates the frequency of its appearance. When the width of becomes less than the predetermined value ε,
The direction perpendicular to the direction of the scanning line is the register mark RM.
, and the peak point of the frequency of appearance is determined to be the position of that straight line. Therefore,
An advantage is obtained that no complicated calculation is required to detect the alignment position of the register mark RM, which is the intersection point CPi of two straight lines in this embodiment. As a result, the alignment points of the register marks RM can be calculated extremely quickly. In addition, since the frequency of appearance of the median run length is calculated, it is not affected by the line thickness of the register mark RM, and even if there is a part other than a straight line in the register mark RM, the recognition of the register mark RM is not affected. I never receive it.

For example, as shown in Figure 8, two
In the case of a register mark RN in which two rings are combined on a straight line of a book, the frequency of appearance in the X and Y directions is somewhat high in the area where the rings exist, but the frequency of appearance in the position where the straight part exists is extremely high. high and easy to distinguish.

Furthermore, even if there is a pattern or the like near the register mark RM and it is within the field of view of the television cameras 24 to 26, it is unlikely to be affected.

This is because by taking the median run length on the scanning line for the picture, the frequency of appearance will be a smaller value compared to a straight line orthogonal to the scanning line direction.

Therefore, according to the register mark position detecting device 1 of this embodiment, it is possible to correctly recognize the various shapes of register marks shown in FIG. 9 and easily determine their alignment positions. A register mark consisting of a straight line as shown in Fig. 9 (A) to F), a register mark consisting of a straight line and a ring as shown in Fig. 9 (G) to M), Fig. 9 (N),
The thick circular register mark shown in (0) was recognized without any problem, and the document 12 could be correctly positioned. In addition, the rectangles indicated by broken lines in FIGS. 9(H), (K), (L), and (N) indicate the field of view of the television camera,
Area P hatched in Figure 9 (F) (L) (M)
CT indicates an area where a pattern exists.

Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment (for example, one end point of the run length is extracted as a singular point, and the 10th
A configuration that detects register marks for cutting as shown in the figure, and a configuration that allows recognition of register marks that are not exactly orthogonal by setting the predetermined value ε for determining the width of the frequency distribution to a value greater than 1. It goes without saying that the invention can be implemented in various ways without departing from the spirit of the invention.

[Effects of the Invention] As detailed above, the register mark position detection device of the present invention has the excellent advantage of being able to easily and accurately detect register marks of various shapes that are actually used. be effective.

Moreover, since the process of extracting the straight lines that make up the register mark does not require complex calculations or analysis, the position of the register mark can be detected at high speed. There is no problem of upsizing.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the basic configuration of the present invention, FIG. 2 is a perspective view showing the appearance of a register mark tide position detection device 1 as an embodiment of the present invention, and FIG. 3 similarly illustrates the configuration. A block diagram, FIG. 4 is an explanatory diagram illustrating the function of the X and Y direction run length median counters 97 and 98,
FIG. 5 is a flowchart showing the processing in the electronic control unit 60, FIG. 6 is an explanatory diagram showing the scanning direction with respect to the register mark RM and counting of the appearance frequency of the run length median value, and FIG. 7 is a scanning line by rotation correction. An explanatory diagram showing the frequency of appearance when the direction and the direction of the straight line forming the register mark match. Figure 8 is an explanatory diagram showing the counted value of the frequency of appearance for a register mark having a double ring. Figure 9 (A) or 0
) are explanatory diagrams showing examples of register marks actually used, and FIG. 1 is an explanatory diagram showing an example of register marks for cutting. 1... Register mark position detection device 5... Bin 7... Table 2...
Original 15...Original holding mechanism 7...X
Axis drive device 19...Y-axis drive device 0...CRT
Monitors 4 to 26...TV camera O...Electronic control unit 61...CPU 8...I/O interfaces 4 to 76...Motor 7...I/O interface...Switcher 2... Synchronous separation filter 4...A/D converter 5...Comparator 7...Binarized data memory 0...Counting processing section 1...Timing signal generation circuit 92...CRT controller 94...Frame memory 95...CRT monitor interface 96...Superimpose circuit 97...X direction run length median value counter 98
...Y direction run length median count counter 99...
Control circuit Ml... Imaging means M2... Rough position setting means M3... Singular point extraction means M4... Appearance frequency calculation means M5... Control means M6... First straight line recognition means Ml. ...Second straight line recognition means M8...Positioning point detection means

Claims (1)

[Scope of Claims] 1. In a register mark position detection device that recognizes a register mark having at least two straight line portions with different angles and detects the position of an alignment point specified from the shape of the straight line portion of the register mark. , an imaging means for imaging a sheet on which register marks are recorded as a binary image; a coarse position setting means for positioning the register mark within a field of view of the imaging means; and a binary image taken by the imaging means. a singular point extracting means for extracting singular points such as the center position and end position of a region where pixels indicating one of the binary values are continuous in each scanning line scanned in one direction; an appearance frequency calculation means for calculating the appearance frequency at each position on the scanning line; extracting a singular point based on the captured binary image by rotating the direction of the scanning line relative to the sheet by a predetermined amount; a control means for executing the calculation and repeating the calculation until the distribution of the obtained frequency of occurrence satisfies a predetermined condition; and a control means for registering a predetermined direction with respect to the scanning line when the distribution of the frequency of occurrence satisfies a predetermined condition. a first straight line recognition means that recognizes a predetermined position determined from the condition as the direction of one straight line forming the mark as the position of the straight line; a second straight line recognition unit that recognizes the direction and position of another straight line different from the first straight line; and positioning of register marks based on the recognized at least first and second straight lines. 1. A register mark position detection device comprising: alignment point detection means for detecting the position of a point. 2. The register mark position detection device according to claim 1, wherein the predetermined condition in the control means is a condition in which the peak value of the frequency of appearance is the maximum, and the predetermined condition in the first straight line recognition means and the second straight line recognition means A register mark position detection device whose direction is perpendicular to a scanning line, and whose predetermined position is a position with a maximum frequency of appearance.