Method of and apparatus for inspecting conductive pattern on pri

Details Method of and apparatus for inspecting conductive pattern on pri Method of and apparatus for inspecting conductive pattern on pri

1990-03-27

1991-06-25

Boudreau, Leo H.

Image analysis

Histogram processing

For setting a threshold

382 9, 382 16, 382 25, 358106, 356237, 364559, 364556, G06K 900, G01B 1126, H04N 718

Patent

active

050274171

ABSTRACT:
A printed circuit board (11) is provided with a conductive pattern (P, R) and a through hole (H) thereon. Respective images of the conductive pattern and a through hole are photoelectrically read with an image reader (20). The conductive pattern image is magnified in size to obtain a magnified pattern image (PI.sub.m), while the hole image is magnified at different magnification factors to obtain magnified hole images (HI.sub.n, HI.sub.n-i). A ring image (RP) is defined by the difference of the magnified hole images. The overlapped region (WR) on which the ring image and the magnified pattern image overlap each other is then calculated, and a defect or an opening of the conductive pattern is detected by calculating the aperture angle (.theta.) of the overlapped image.

REFERENCES:
patent: 4295198 (1981-10-01), Copeland et al.
patent: 4635289 (1987-01-01), Doyle et al.
patent: 4797939 (1989-01-01), Hoki et al.
patent: 4799175 (1989-01-01), Sano et al.
patent: 4953100 (1990-08-01), Yotsuya

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