Abstract: In order to correctly detect the width of wiring pattern on a printed board, a multiple train operator applied to image data. The multiple train operator consists of arms each having three unit arms. The binary data obtained by applying the multiple train operator to the image data is converted into a single horizontal arm and a single vertical arm. The combination of the horizontal and vertical arms corresponds to a single cross operator. The conversion into the single cross operator form is conducted through a logical operation on the binary data obtained by the multiple train operator, so that quantization errors are compensated and fine pattern defects can be detected. As a result, the width of the wiring pattern etc. are correctly obtained.

Abstract: A cross operator is applied to the image of a wiring pattern provided on a printed board, to obtain respective sizes of the image in first and second directions. When the condition that the size of the wiring pattern in one of first and second directions is larger than a threshold value but the size in the other direction is smaller than the threshold value is satisfied, it is decided that the wiring pattern is a wiring line., The width of the wiring line is measured with the operator and is compared with a predetermined allowable range of the width. A land and a pin hole which may be present on the printed board do not satisfy the condition for detecting the wiring line and accurate inspection of the wiring line is attained.