Patent ID: 7505149

Claim:
A method of inspecting surface condition of a target object having a slope on surface, said method comprising the steps of: setting a plurality of light sources emitting light of different colors each arranged so as to have a different elevation angle with respect to said target object at an inspection position; projecting light from said light sources on said target object at said inspection position; obtaining an image of said target object by a camera unit positioned above said inspection position; setting an inspection area including said target object on said image; converting three-dimensional image data comprising gradation data of color components corresponding to said plurality of light sources for each of pixels in said inspection area into one-dimensional color phase data; observing sequentially a plurality of pixels in said inspection area, based on said color phase data, and calculating differences in color phase data between said observed pixels and neighboring pixels as changes in the color phase data; defining as standard direction the direction in which specified one of the color components corresponding to said light sources changes to another specified one of the color components corresponding to said light sources along the direction in which the slope on said surface changes when surface conditions of the target object in said inspection area are suitable and preliminarily setting said standard direction; extracting by using said calculated changes in color phase data a direction along which said color phase data change to larger values indicating higher intensities or smaller values indicating lower intensities, and specifying a direction in which color phase of light corresponding to arrangement of each of said light sources changes on said image along sloped surface of said target object; making a comparison between said specified direction and the preliminarily set standard direction; and judging appropriateness of said sloped surface of said target object from the result of said comparison and thereby determining appropriateness of the surface condition of said target object.