| 摘要 |
<P>PROBLEM TO BE SOLVED: To stabilize the operation of detecting a foreign matter from a photographed image by a background difference method. <P>SOLUTION: A difference image is binarized by threshold processing (S103), foreign matters and others (noise) other than the foreign matters are discriminated, and then a threshold is adjusted for each pixel (S104). The threshold is switchable between a threshold TH1 predetermined corresponding to the magnification of the noise generated in a photographing environment and a threshold TH2 a prescribed value lower than the threshold TH1. The prescribed value is determined on the basis of the variation of the actually measured noise. In the threshold adjustment (S104), the threshold adjustment of performing adjustment to the value of the threshold TH2 when a foreign matter is discriminated at the initial threshold TH1 and returning it to the threshold TH1 thereafter when the foreign matter is not discriminated anymore in consecutively executed binarization processing by the threshold TH2 is executed for each pixel. By the adjustment, a foreign matter detecting operation is prevented from becoming instable without being affected by almost all generated noise. <P>COPYRIGHT: (C)2012,JPO&INPIT |
