OPTICAL INSPECTING APPARATUS FOR SUBSTRATE

PURPOSE:To enable optical inspection with a desired hole alone stopped even when through holes or the like with different diameters are mixed by taking reflected light and transmitted light from a substrate to be separated into a reflected light image and a transmitted light image. CONSTITUTION:Reflected light on a substrate 8 to be inspected by lighting 30 is taken with a camera 5. Light from one light source 2 appears on the surface of the substrate 8 from the rear thereof 8 passing through a bias hole and a through hole. Combined light of the transmitted light and the reflected light is taken with the device 5. As the lighting by the transmitted light is turned on or off repeatedly, an image taken has a transmitted light image contained in the reflected light at a fixed cycle. The transmitted light image alone is sampled from the images with an image separation circuit. Then, both of the reflected light and transmitted light images can be combined to accomplish an inspection of a desired image. Moreover, the transmitted light image alone with a hole diameter desired is taken out and combined by a degeneration/ expansion processing corresponding to the hole diameter thereby enabling an accurate pattern inspection of the image with the hole of the desired diameter alone stopped.