Abstract: In a volume determination process, a slit pattern is projected obliquely downwardly, or slit patterns are projected obliquely downwardly and upwardly, onto an article which is at rest or in motion. The slit pattern or patterns are in the form of a parallel stripe pattern or a grid pattern. The surface or surface onto which the slit pattern or patterns are projected are imaged by a television camera, and the heights of slit positions on the article are computed on the basis of the image or images picked up by the television camera. The volume of the article is computed on the basis of the computed heights of the slit positions. The weight of the article can be derived by multiplying the volume by the specific gravity of the article. It is determined whether there is a surface flaw or not by determining whether differentials of the slit pattern or patterns are discrete or not.