IMAGE DEFECT INSPECTION METHOD, IMAGE DEFECT INSPECTION APPARATUS AND APPEARANCE INSPECTION APPARATUS

A new image defect inspection method and a new image defect inspection apparatus capable of being used for automatic setting of a threshold value for an appearance inspection apparatus with a high throughput have been disclosed. According to the image defect inspection method and the image defect inspection apparatus, cumulative frequencies of gray level differences of the corresponding parts of two images are calculated, converted cumulative frequencies are calculated by converting the cumulative frequencies so as to be linear with the gray level differences in a predetermined distribution, a straight line approximation to the converted cumulative frequencies is calculated, and a threshold value is determined from a predetermined cumulative frequency based on the calculated straight line approximation according to a predetermined calculation method. Because there holds a linear relationship between the converted cumulative frequencies and the gray level differences, the following process for determining a threshold value is facilitated.