JPH0378563B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] A plurality of sets of article direction detection devices are provided, and from the directions detected by each set of direction detection devices, the same number of directions indicating both outer sides are excluded and the remaining directions are detected. The direction of the article is detected, thereby eliminating errors in direction detection due to defects on the edge of the article.

[Industrial application field]

In a device that automatically performs visual inspection by capturing images of printed wiring boards or photomask patterns, resist patterns, etc. for manufacturing printed wiring boards using a video camera or optical scanning device, the direction of the object to be inspected is set in a predetermined direction. or keep it in
Alternatively, it is necessary to rotate the imaged pattern so that it is substantially in a predetermined orientation, and in any case the orientation of the article must be detected.

The present invention relates to a method for detecting the orientation of these articles with reference to their edges.

[Conventional technology]

Some conventional devices of this type detect the direction of the edge of an article based on information from pixels located on a predetermined circumference of an image of the article.

As shown in Figure 2, this means that the information of eight pixels A to H located on the circumference, separated by 45 degrees, is A, b, c, d, e, f, g, h A.・B・c・d・e・f・g・H A・B・C・d・e・f・G・H A・B・C・D・e・F・G・H , the edges of this article are pixels A-E
It is almost perpendicular to the line connecting A.
b, c, d, e, f, g, H A, B, c, d, e, f, G, H A, B, C, d, e, F, G, H, The edge of this article is pixel A-
It can be seen that it is almost parallel to the lines connecting H, BG, CF, etc.

Here, uppercase letters are information indicating that the article exists, and lowercase letters are information indicating that the article does not exist.

Note that it is clear that the accuracy of the detection direction improves as the angular interval at which pixels are selected becomes narrower.

[Problem that the invention seeks to solve]

In the above-mentioned conventional technology, if there is an abnormality such as a protrusion or a deletion on the edge of the article, the direction of the edge will be detected incorrectly.

In other words, if a protrusion like the one shown by the dotted line in FIG.
Although it is parallel to the line connecting pixel CG, it is detected as being parallel to the line connecting pixel CG.

[Means for solving problems]

The present invention provides a memory element that selects and holds information on pixels located in the same direction on the circumference of a plurality of concentric circles from image information of an article to be inspected, and stores information on pixels located on the same circumference. A direction detector is provided for each circumference to detect the direction of the article from information stored in the memory element, and a direction selector is provided to which direction information from these direction detectors is supplied.

Then, this direction selector detects the direction of the article by excluding the outermost direction information from among the direction information from each direction detector or by averaging the direction information from each direction detector. I did it like that.

[Effect]

As shown in FIG. 3, _eight pixels A 1 - are arranged at intervals of 45 degrees on three concentric circles in the first to third columns.
When H ₁ , A ₂ −H ₂ , A ₃ −H ₃ are selected for direction detection, the image of the article with the lower edge indicated by the line X-Y causes the first column of pixels A ₁ , B ₁ , H ₁ , second column pixels A ₂ , B ₂ , H ₂ and third column pixels A ₃ , B ₃ ,
Since all _H3 sense the presence of an article, the direction perpendicular to the edge of the article (for convenience of explanation, the direction perpendicular to the edge will be used as the direction of the article hereinafter) is detected in each row as in the prior art described above. Both are detected as being in the direction of I.

However, if the article has a protrusion as shown by A in the same figure, the pixels in the first row will be A ₁ , B ₁ , G ₁ ,
H ₁ senses the presence of the article and detects the direction of the article assuming that the direction of the article is between I and H 1 .

In the present invention, even in such a case, the pixels in the second column are only A ₂ , B ₂ , and H ₂ , and the pixels in the third column are also A ₃ , B 2 , and H 2 .
Since only B ₃ and H ₃ sense the presence of the object, the second
Since the column and the third column both detect the direction of the article as the I direction, in one embodiment,
By excluding the direction intermediate to I detected by the first column, which is the outermost among the three detected directions, and one of the directions of I detected by the second column and the third column, The direction of the remaining I is detected as the direction of the article.

In another embodiment of the present invention, the direction of the article is determined by (45÷3) degrees from I, that is, by averaging the direction information detected by each column.
It will be detected as being 15 degrees counterclockwise from.

In this latter embodiment, in the case of an article having an edge as indicated by As the direction intermediate with I by column,
Since each is detected, the correct orientation of the article can be detected rather than in the first embodiment.

In the above explanation of the effect, the case where there is a protrusion on the edge of the article has been explained, but it is clear that the same effect can be obtained even when there is a deletion in a part of the edge.

〔Example〕

FIG. 1 shows an embodiment of the present invention, in which pixels in an image pattern of an object to be inspected obtained by a video camera or an optical scanning device correspond to pixels used for direction detection according to the present invention. registers A ₁ −H ₁ that hold information from these pixels at positions;
A ₂ −H ₂ and A ₃ −H ₃ are shown.

The first column of registers A ₁ -H ₁ arranged on the outermost concentric circle holds information from the pixels at the indicated positions on the image pattern of the object to be inspected, as described above. As in the prior art, the direction of the object to be inspected is detected by the first direction detector 1 based on the direction of the edge of the object. Registers A ₂ - H ₂ in the second column and registers A ₃ - H ₃ in the third column
Similarly to the first row of registers, the direction of the object to be inspected is detected by the second direction detector 2 and the third direction detector 3, respectively.

The directions of the object to be inspected detected by the first to third direction detectors 1, 2, and 3 are
In this embodiment, directions indicating both outer directions are removed in the direction selector 4, and the last remaining direction is detected as the direction of the object to be inspected.

In addition, as a second embodiment, the first to third
The direction of the article is detected by averaging the directions obtained by the direction detectors 1, 2, and 3 in the direction selector 4.

The output from the direction selector 4 can be used as a control signal for rotating the article itself to orient it in a predetermined direction, or as a control signal to rotate the image obtained by taking an image of the article to point the article substantially in a predetermined direction. It can be used as a control signal to obtain an image similar to that captured.

Note that the memory elements (A ₁ −H ₁ , A ₂ −H ₂ , A ₃ −H ₃ )
It is clear that there is no need to provide the memory at a position corresponding to the pixel, and a normal random access memory may be used. Furthermore, it goes without saying that the detection accuracy can be improved by increasing the number of pixels on the same circumference or the number of concentric circles.

〔Effect of the invention〕

Errors in the detected orientation of the article due to protrusions or defects on the edge of the article can be reduced, simplifying the pattern inspection apparatus and increasing the inspection speed.

[Brief explanation of drawings]

FIG. 1 is an embodiment of the present invention, FIG. 2 is a diagram for explaining the principle of direction detection, and FIG. 3 is a diagram for explaining the principle of the present invention. In the figure, A ₁ -H ₁ , A ₂ -H ₂ , A ₃ -H ₃ are memory elements that selectively store information on pixels arranged at corresponding positions, and 1 to 3 are first to third direction detection devices. 4 is a direction selector.

Claims (1)

[Claims] 1. A memory element (A ₁ -H ₁ , A ₂ -H ₂ , _A3 − _H3 )
and direction detectors 1, 2, which respectively detect the direction of the article from the information of pixels located on the same circumference (for example, _A1 - _H1 ) stored in these memory elements.
3; and a direction selector 5 to which direction information obtained from these direction detectors 1, 2, and 3 is supplied. 2. The method for detecting the direction of an article according to claim 1, wherein the direction selector 5 excludes direction information indicating both outer sides and detects the direction of the article based on the remaining directions. 3 The direction selector 5 selects the direction detectors 1, 2,
3. The method for detecting the direction of an article according to claim 1, wherein the direction of the article is detected by averaging the direction information obtained from the three directions.