Abstract

This invention concerns inspection of surface conditions to detect locations, sizes and nature of flaws, defects or stains not only on a flat surface but also on an undulating or stepped surface, and includes the steps of: scanning an inspecting surface of a specimen with a spot-like laser beam projected obliquely from a light source; detecting the height of the inspecting surface from a reflected image of the scanning light picked up by a TV camera located above the inspecting surface, to maintain the inspecting surface at a constant height; converging reflected and diffracted light from the inspecting surface toward a photo-detector having measuring points at the point of convergence and at a number of positions along a concentric circle around the point of convergence; measuring the energy of the reflected and diffracted light by photoelectric transducers connected to the respective measuring points; and displaying locations, sizes and nature of surface flaws, defects and stains of the specimen on a monitor, with combined use of information provided by the picture image of the TV camera as to variations in surface level and cracks on the inspecting surface.