JPS5667739A - Defect inspecting apparatus - Google Patents

Abstract

PURPOSE:To improve a defect inspection reliably by employing a plurality of coherent light beams applied from different directions to each other. CONSTITUTION:Laser beams 101-103 from laser sources 51-53 at different positions from each other are applied to a point P on the surface of an object 1 being inspected, with incident angles of 1-3 deg., in other words, the beams 101-103 are applied nearly parallel to the surface of the object 1, and reflected from the point P to be reflected-lights 201-203. The light scattering at the point P is led to a photodetector 7 through a lens system 6 set vertically to the object 1. Therefore, the specular-reflection components of the laser beams are removed and only signals (scattered light) from a minute defect are received. Moreover, a rotating mechanism 3 and a moving mechanism 4 permit the beam irradiation point P to spirally scan the surface of the object 1. By this, the reliability of the defect inspection can be improved.