| 摘要 |
PROBLEM TO BE SOLVED: To provide a detecting method and device allowing the detection of a desired material selected from a plurality of materials existing on an object depending on a difference in contrast. SOLUTION: A replacementΔD of a replaced image is varied so that a skew portion, where a gray level of an original image of a portion corresponding to the desired material to be detected is changed depending on a difference in degree of change between the gray levels of the original image of the portion corresponding to the desired material, is located on the positive side of an upper limit value or on the negative side of a lower limit value, whereby sensitivity of detecting the desired material is controlled and the desired material only selected from the plurality of materials on the object is detected.
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