Abstract: Respective images of a conductive pattern and through holes of a printed circuit board are obtained. The through holes are classified into normal through holes having a relatively large diameter and mini via holes having a comparatively small diameter. The mini via hole image is enlarged to become an enlarged mini via hole image (SHSm). The image of the conductive pattern has hole parts therein, which are filled with images generated from the normal through hole image and the mini via hole image to obtain a corrected pattern image (CPS). The edge of the corrected pattern image is detected and enlarged to obtain an enlarged edge image (SES). The enlarged edge image is classified into two areas, one of which overlaps with the enlarged mini via hole image (SHSm). These two areas are subjected to inspection in different inspection modes.

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.

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.

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.

Abstract: A binarized image data group of an inspected object for a plurality of pixels arrayed in the sub-scanning direction is sequentially created in order along the main scanning direction to determine whether or not the pattern of an inputted image corresponds to a standard through-hole pattern on the basis of the binarized image data group. When the determination is of yes, through-hole diameter masking data are sequentially created in order along the main scanning direction to sequentially perform masking processing on the binarized image data group of the inspected object arrayed in the sub-scanning direction. Thus, the through-hole pattern is automatically detected to be subjected to masking processing, whereby an inspected object having through-holes can be inspected by a pattern matching method.