JPS5934961B2 - Pattern inspection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pattern inspection method and apparatus.

Conventionally, pattern inspection and identification devices have a method of preparing several standard patterns and inspecting and identifying the input pattern by pattern matching with the input pattern, and a method of inspecting and identifying the input pattern by matching some geometric features of the target pattern with the input pattern. There was a method for determining, comparing with that of the standard pattern, and inspecting and identifying the pattern.

However, the former method has drawbacks such as the need to prepare a large number of standard patterns and the need for alignment, while the latter method may lead to misunderstandings if many judgment criteria are not provided. There are drawbacks. An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art, and to determine whether or not a missing rank exists in a two-dimensional pattern with 90 degree rotational symmetry or point symmetry (180 degree rotational symmetry) with a simple structure, efficiently, and with high accuracy. It is an object of the present invention to provide a pattern inspection method and apparatus that enable accurate inspection.

That is, in the present invention, a pattern that normally has 90 degree rotational symmetry or point symmetry is imaged using one imaging device, and a video signal obtained from this one imaging device is converted into two by a binarization circuit.
This binary pixel-formed signal is sequentially stored in two-dimensionally arranged storage elements of a storage device large enough to cut out the above pattern at once based on a synchronization signal using a group of shift registers. The pattern is cut out by moving in the row direction and the column direction, and the center line of the length of the pattern read out from this cut out storage device and projected in the row direction and the center line of the length of the pattern projected in the column direction are calculated. Detecting that the intersection point is located in a predetermined storage element of the storage device, and two memories that are symmetrical when rotated by 90 degrees or 180 degrees with respect to the position of the intersection determined by this detection. The two binary pixelated signals stored in the elements are read across the storage elements in the area covered by the binary pattern cut out in the storage device, compared to see if they are the same, and rotated by 90 degrees. It is a pattern inspection method characterized by inspecting whether or not there is a defect in a pattern that is symmetrical or point symmetrical. One imaging device that captures an image, a binarization circuit that binarizes a video signal obtained by the one imaging device at a predetermined threshold value, samples it, and converts it into picture elements, and the binarization circuit. A storage device that sequentially transfers and extracts a binary pixelated signal outputted from a group of shift registers to two-dimensionally arranged storage elements in the row and column directions based on a synchronization signal such as a sampling signal. and the center line of the length of the pattern projected in the row direction by an exclusive OR circuit etc. and the center line of the length of the pattern projected in the column direction for a predetermined storage element of the storage device. a detection means for detecting that the intersection point is located; and when the detection means detects that the intersection point is located in the predetermined storage element, the detection means is in a symmetrical relationship rotated by 90 degrees or 180 degrees with respect to the intersection point. The two binary pixelized signals stored in the two storage elements are
and a comparing means for reading out the storage elements in the area included in the cut out binary pattern in the storage device and comparing whether or not they are the same, and depending on the output of the comparing means, the storage elements are read out across the storage elements in the area included in the cut out binary pattern. A pattern inspection device is characterized in that it is configured to inspect whether or not a defect exists in a point-symmetric pattern.

The present invention will be explained below based on embodiments shown in the drawings.

FIG. 1 is a diagram showing the configuration of a pattern inspection apparatus according to the present invention. As shown in the figure, 1 is the target image (two-dimensional pattern) 9
It is an object with a drawn on it. This target image 9 is formed from a rectangular or circular image that has the same shape even when rotated by 90 degrees or 180 degrees. In other words, target image 9 is 90
It is formed in a two-dimensional pattern with rotational symmetry or point symmetry. Reference numeral 2 denotes an imaging device, which is composed of a TV camera, a photodiode array, or the like, and captures an image while scanning the two-dimensional pattern of the object 1, and converts the image into a video signal.

3 is a binarization circuit, which binarizes the above video signal with a predetermined threshold value, samples it and converts it into picture elements, and converts it into "0-"
The signal is converted into a binary pixelated signal consisting of 1.

4 is a shift register group, and each shift register 4
1-4.

, is composed of a large number of storage elements for storing the binary video signal of each row (scanning line) of the two-dimensional pattern, and is configured to shift the binary picture element video signal stored in each storage element. There is. 5 is a two-dimensional memory formed from Nxn storage elements Aij (j-1 to N, j=1 to n),
The output signals from the binarization circuit 3 and shift registers 41 to 40-1 are stored in storage elements Aij (1=1 to N, j=1 to n).
are connected to input into each line.

6 is a two-dimensional memory and storage element Bij(1-
1 to N, j=1 to n), and the binarization circuit 3 and shift registers 41 to 4.

The output signal from the storage element Bij (1=1~N, j-1
~n) are connected to input each column. 7 is a comparison logic circuit that compares the two-dimensional pattern stored in the two-dimensional memory 5 and the two-dimensional pattern stored in the two-dimensional memory 6, and is a combination of an exclusive OR circuit, an AND circuit, or an OR circuit, etc. It is formed in

10 is a detection circuit that detects when the center of the target image (two-dimensional pattern) 9 cut out and stored in the two-dimensional memory 5 is located at the center of the two-dimensional memory 5; specifically, as shown in FIG. As shown, the storage element Aij(
1-1 to N, j=1 to n) across each row Bij-Bnjl and each column Bil-Bin OR circuit 11a or logic of a row that takes the logical product (in the case of a pixelated signal) or logical product (in the case of a binary pixelated signal where the target image is 1 "" and the background is a binary pixelated signal where the background is "1") The product circuit and the logical sum circuit 11b or logical product circuit of the column and the n-1n+3n-3 row (? OR circuit 11a or AND of the above lines (row and ? line, -? line and 222n +5n-(n-2) n+n - line, ...? line and ? line) Row exclusive OR circuit 12 that takes exclusive OR of circuit outputs
a and the -1111011U column (?) symmetrical about the center n+1 (?) (where n is an odd number) of the two-dimensional memory 5.
With a column of? A row of ? Exclusive OR of the outputs of the OR circuit 11b or the AND circuit of the columns 000n + 5n- (n-2 no n+n ? column, ...? 1 column and ? column). Exclusive OR circuit 12 for columns that take
b, and the outputs of the exclusive OR circuit in this row and the exclusive OR circuit in the column no longer contain 11゛, so that all 60
'', the output signals of each of the OR/NOT circuits 13a and 13b become 61'', the logical product of the AND circuit 14 is taken, and the target image (2 It is detected that the center of dimensional pattern) 9 is located.

Further, the output of the detection circuit 10 is connected to the comparison logic circuit 7. With the above configuration, the target image (two-dimensional pattern) 9 of the object 1 is converted into a video signal by the imaging device 2,
The signal is converted into a binary video signal by the digitization circuit 3 and inputted to the two-dimensional memories 5 and 6 and the shift register group 4. The shift register group 4 is constructed by connecting shift registers in series to store one scanning line imaged by the imaging device 2, and each shift register outputs a binary pixelated signal shifted by a sampling signal. The pattern is input in parallel to the two-dimensional memories 5 and 6, and two-dimensional patterns 6 are sequentially cut out and transferred to the two-dimensional memories 5 and 6 according to the sampling signal. As a result, a two-dimensional pattern rotated by 90 degrees with respect to the two-dimensional memory 5 is recorded in the two-dimensional memory 6.
The contents of the target images (two-dimensional patterns) 9 stored in the two-dimensional memory 5 and two-dimensional memory 6 are stored in the image capturing device 2.
The transition is performed while being shifted based on a synchronization signal synchronized with the scanning signal. During this time, when the center of the target image 9 is located at the center of the target image (two-dimensional pattern) stored in the two-dimensional memory 5, a signal of 61'' is output from all the exclusive OR circuits 12a and 12b of the detection circuit 10. A gate provided in the comparison logic circuit 7 is opened so that the output and detected binary video signals from the two-dimensional memory 5 and the two-dimensional memory 6 can be applied to the comparison logic circuit 7.This opens the gate provided in the comparison logic circuit 7. 7 compares the target image (two-dimensional pattern) stored in the two-dimensional memory 5 with the target image (two-dimensional pattern) stored in the two-dimensional memory 6, and inspects the quality of the target image 9 existing on the object. , outputs a determination signal 8.
Next, a case where the target image 9 is formed in a square shape and there are defects 11 at the corners as shown in FIG. 2a will be specifically explained.

First, the detection circuit 10 detects that the center P of the target image 9 is located at the center Q of the two-dimensional memory 5 (1Σ11Σ1Aij), i21j=1, as shown in FIG. 2b.

At this time, a square target image 9a is cut out as a binary video signal and stored in the two-dimensional memory 5, as shown in FIG. 2b. On the other hand, in the two-dimensional memory 6, a target image 9b obtained by rotating the square target image 9a by 90 degrees is cut out and stored as a binary video signal as shown in FIG. 2c.
When these two target images 9a and 9b are exclusive ORed by an exclusive OR circuit built in the comparison logic circuit 7, storage elements A4, 8, storage elements B4, 8, storage elements A5, 8, and storage element B5,8, storage element A8,7 and storage element B8,7, storage element A8,8 and storage element B8,8
Since the memory contents of each image are different, a signal of "1" is output, and it is determined that the target image 9 has a defect 11 and is determined to be a defective product. However, if the target image 9 does not have a defect 11, is the storage element Ai of the two-dimensional memory 5
10 from the exclusive logic circuit of the comparison logic circuit 7 because the contents of Bij match the contents of storage element Bij of the two-dimensional memory 6.
A signal ``'' is output, and the target image 9 is determined to have no defects and is determined to be a good product. However, since a quantization error actually occurs, it is necessary to take this quantization error into consideration in the above determination. By the way, in the above embodiment, the target image 9 is stored in the two-dimensional memory 6 as 9 in the two-dimensional memory 5.
The two-dimensional memory 6 is also stored in the same manner as the two-dimensional memory 5 without being rotated, and the comparison logic circuit 7 compares the memory elements at the same corresponding positions by rotating them by 0 degrees and storing them in the comparison logic circuit 7. When comparing, it is clear that the same effect will be obtained even if a predetermined storage element of the two-dimensional memory 5 is compared with a storage element of the two-dimensional memory 6 at a position rotated 90 degrees with respect to this storage element. However, in the present invention, it is clear that any two-dimensional pattern that originally has 90 degree rotational symmetry or point symmetry is sufficient.

Therefore, the case of a circular pattern will be explained. Figure 5A
, b, and c show the state in which each normal circular pattern, a circular pattern with a defect on the upper right, and a circular pattern with a defect on the right are cut out in the two-dimensional memory 5. On the other hand, the detection circuit 10 detects the centers P, , P2, and P2 of each circular pattern.
It is detected that P3 has come to the center of the two-dimensional memory 5.
Therefore, the comparison logic circuit 7 compares the results, and the non-coincidence states are shown in FIGS. 6A and 6 corresponding to the patterns shown in FIGS. 5A, b, and c.
This is the shaded area shown in b and c.

As described above, according to the method of the present invention, even if the square target image 9 is input to the two-dimensional memory 5 in an inclined state as shown in FIG. It is no longer necessary to rotate the pattern to return it to its normal state or to prepare a standard pattern in an inclined state. In addition, compared to the method of determining the contour length of the target image 9 and using this as the determination criterion, the method of the present invention uses the area of the mismatched part between the target image rotated by 90 degrees and the original target image as the determination criterion. is effective in determining the quality of the target image. As explained above, according to the present invention, there is no need to compare with a standard pattern (dictionary pattern), so even if a symmetrical two-dimensional pattern is tilted with respect to the imaging device, it can be rotated by 90 degrees. Even if the size or inclination (direction) of a two-dimensional pattern having symmetry or point symmetry changes, the presence or absence of defects can be efficiently and precisely inspected.

Further, according to the present invention, by providing a single imaging device and having a simple configuration, it is possible to efficiently inspect whether or not a defect exists in a two-dimensional pattern having symmetry in real time when the imaging device takes an image. It is also effective. Further, when the present invention is applied to automatic visual inspection of semiconductors or automatic assembly of parts that requires simple pattern recognition, its effects are significant.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the pattern inspection device of the present invention, and FIGS. 2A, b, and c show the state in which a target image formed from a square is comparatively inspected using the device shown in FIG. 1. The figure shown in Fig. 3 is a diagram showing the state when a tilted square target image is input into the two-dimensional memory shown in Fig. 1.
Fig. 4 is a diagram specifically showing the detection circuit shown in Fig. 1, and Fig. 5 A, b, and c are the states in which the circular patterns of normal, upper right defective, and right defective are cut out into the two-dimensional memory. FIGS. 6A, b, and c are diagrams illustrating states in which the comparison logic circuit compares and determines, corresponding to FIGS. 5A, b, and c, respectively. 4...Shift register group, 41 to 4n-1...
...Shift register, 5,6...Two-dimensional memory, 7...Comparison logic circuit, 9...
Target image, 10...Detection circuit, Aij, Bij
...Memory element.

Claims (1)

[Claims] 1. A pattern that normally has 90 degree rotational symmetry or point symmetry is imaged using one imaging device, and a video signal obtained from this one imaging device is converted into a binary picture by a binarization circuit. This binary pixelized signal is stored in two storage devices large enough to cut out the above pattern at once using a group of shift registers.
Based on the synchronization signal, the dimensionally arranged storage elements are sequentially moved in the row direction and column direction and cut out, and the center line of the length of the pattern read out from the cut out storage device and projected in the row direction. It is detected that the intersection of the length of the pattern projected in the column direction with the center line is located in a predetermined storage element of the storage device, and the angle is 90 degrees to the position of the intersection determined by this detection. , or two binary pixelated signals stored in two storage elements that are symmetrical when rotated by 180 degrees, over the storage elements in the area covered by the cut out binary pattern in the storage device. A pattern inspection method characterized by reading out and comparing whether or not they are the same, and inspecting whether or not there is a defect in a pattern that is rotationally symmetrical or point symmetrical by 90 degrees. 2. One imaging device that scans and images a pattern that normally has 90 degree rotational symmetry or point symmetry, and binarizes the video signal obtained by the one imaging device using a predetermined threshold value. A binarization circuit that samples and converts it into pixels, and a binary pixelization signal output from the binarization circuit that is synchronized with the sampling signal, etc. to storage elements arranged two-dimensionally via a group of shift registers. A storage device that sequentially moves and cuts in the row direction and column direction based on a signal, and a pattern length that is projected in the row direction by an exclusive OR circuit etc. to a predetermined storage element of the storage device. a detection means for detecting that an intersection point between a center line and a center line of a length of a pattern projected in a column direction is located; and when the detection means detects that the intersection point is located in the predetermined storage element. , the two binary pixelized signals stored in two storage elements that are symmetrically rotated by 90 degrees or 180 degrees with respect to this intersection are shown in the binary pattern cut out in the storage device. a comparison means for reading across storage elements in an area and comparing whether or not they are the same, and depending on the output of the comparison means, it is determined whether a defect exists in a pattern that is 90 degrees rotationally symmetric or point symmetric. A pattern inspection device characterized in that it is configured to inspect.