Patent ID: 7706598

Claim:
A visual inspection method of comparing a plurality of photographed images of areas of an article with each other, and inspecting an appearance of said article from a difference between said plurality of images, said visual inspection method comprising: a first step, at an image input unit, of acquiring a plurality of pieces of image data based on said photographed images, the plurality of photographed images having been captured by an image photographing device, a second step, at an image comparison unit, of two or more comparisons among at least three different pieces of image data respectively for each of three different respective photographed areas of said article, to acquire at least two pieces of signed difference-image data, wherein: said at least two pieces of said signed difference-image data are arranged to be generated from a first common image data of said at least three different pieces of image data, one of said signed difference-image data is generated from a second image data of said at least three different pieces of image data which is processed with said first common image data, another one of said signed difference-image data is generated from a third image data of said at least three different pieces of image data which is processed with said first common image data, and said first common image data is for an area of the article positioned between the respective areas of said second image data and said third image data; a third step, at a difference-image comparison unit, of subtracting one of said at least two pieces of signed difference-image data from another of said at least two pieces of signed difference-image data for acquiring a difference data, and a fourth step, at a judgment unit, of subjecting said difference data having been acquired from said signed difference-image data to a threshold-value processing.