METHOD FOR DETECTING FLAW OF PLANAR BODY

摘要

PURPOSE:To enhance detection sensitivity by selecting only beam necessary for detecting the presence of the flaw of a planar body, by guiding the reflected or transmitted beam from the planar body guided by an optical fiber to a light receiving element through an interference filter and a condenser. CONSTITUTION:A planar body 5 having a flaw to be detected runs in the direction shown by an arrow and laser beam formed by converging parallel beam emitted from the laser beam source 2 of a beam irradiating system is allowed to irradiate the surface of the planar body 5 from above by a lens 3 to be scanned in the lateral direction of the planar body 5 by a beam scanning means 4 such as a rotary mirror. Next, the transmitted beam from the planar body 5 is incident to the optical fibers 7 arranged to the lower part of the planar body 5 from one ends thereof over a scanning width to be guided through the optical fibers 7 and emitted from the other ends of the optical fibers 7 bundled into one. Next, disturbance beam is inhibited by an interference filter 8 and a condenser lens 9 and detection sensitivity is enhanced. The transmitted beam is incident to a beam receiving element and the change in quantity of beam is detected.