Optimum imaging position detecting method, optimum imaging position detecting device, photomask manufacturing method, and semiconductor device manufacturing method

An optimum imaging position detecting device comprising:

• an image acquisition section configured to acquire an image of a predetermined area of a substrate surface;
• a peak intensity calculation section configured to calculate, on the basis of the image of the predetermined area and for each of a plurality of intensity acquisition parts included in the predetermined area, peak intensity corresponding to a value obtained by subtracting average signal intensity of an area outside the intensity acquisition part from signal intensity of the intensity acquisition part;
• a variation calculation section configured to calculate variation of the peak intensity calculated for each of the plurality of intensity acquisition parts;
• an execution section configured to execute acquiring the image of the predetermined area, calculating the peak intensity, and calculating the variation of the peak intensity at each of a plurality of imaging positions;
• and
• an optimum imaging position determination section configured to determine, on the basis of the variation of the peak intensity obtained at each of the plurality of imaging positions, that a position of the maximum variation of the peak intensity is an optimum imaging position.