DEVICE FOR INSPECTING SURFACE DEFECT OF SCREW

PURPOSE:To inspect a surface defect of a screw, by irradiating light at a prescribed angle to a normal irradiated to the surface of the screw, also scanning it in parallel with the axial direction, and detecting a variation of an electric signal, which is caused by its reflected light. CONSTITUTION:Light is projected to a screw 1 by making it greatly shift from a normal passing through the center of the screw 1 along the axial direction, is scanned and becomes scanned incident light 2. In this case, reflected light 3 from the screw crest part is generated to a screw crest outside circumferential circle 9, reflected light 5 from the root part is generated to a root outside circumferential circle 10, and between them, reflected light 4 from the edge line part is generated. These reflected rays are made incident to photoelectric elements 6, 8 and 7 having a shape elongated slenderly in the axial direction of the screw 1, are photoelectrically converted, and a reflecting signal to each part of the screw 1 is obtained. In this case, the reflected rays 3-5 which are made incident to the elements 6-8 are greatly separated spatially, therefore, an output signal is obtained without being influenced by each other. By detecting disorder of a waveform of this output signal, a defective part of the screw can be extracted.