In inspection processes at manufacturing sites, demand for the introduction of automated processes using nondestructive, high-speed imaging technologies has been increasing in recent years. However, as it is difficult to obtain clear images of microdefects using conventional optical imaging technologies, the inspection of microdefects still depends on visual inspection performed by skilled workers.
To rectify this situation, the Toshiba Group has developed an optical imaging technology focusing on the phenomenon that the bidirectional reflectance distribution function (BRDF) of light reflected from a surface with microdefects is different from that of light reflected from the normal surface. This novel approach, called one-shot BRDF technology, makes it possible to immediately obtain clear images of microdefects having a depth of as little as a few microns. The microdefects are visualized in colors that differ from those of the surroundings by converting the BRDF differences into color information. Experiments on a prototype one-shot BRDF optical system have verified that this technology has the potential to obtain clear images of microdefects on the surface of various samples, as well as to measure the inclination angle distributions of microconvex shape on the metallic surface with a high degree of accuracy.