Image inspection apparatus, image inspection method, image inspection program, computer-readable recording medium and recording device

An image inspection apparatus for performing visual inspection of a workpiece, the apparatus comprising:

• three or more illumination sections which are arranged in an annular shape for illuminating the workpiece from mutually different illumination directions;
• an illumination controlling section for turning on the three or more illumination sections one by one in a turning-on order;
• an imaging section for capturing an image of the workpiece from a certain direction at illumination timing for turning on each of the illumination sections by the illumination controlling section, to capture a plurality of partial illumination images with different illumination directions,
• a normal vector calculating section for calculating a normal vector with respect to a surface of the workpiece at each of pixels by a photometric stereo method by use of a pixel value of each of pixels having a corresponding relation among the plurality of partial illumination images captured by the imaging section;
• a texture extraction image generating section for calculating, from a normal vector at each of the pixels which exists in number corresponding to the number of times of illumination performed by the illumination sections and is calculated by the normal vector calculating section, albedos of each of the pixels in the same number, to generate from the albedos a texture extraction image that shows a design obtained by removing an inclined state of the surface of the workpiece.