A light beam is directed at an angle to a glass surface for detection of cracks in it by a sensor positioned out of the direct beam path. A light controlling device positioned in this path prevents direct impingment of light on the sensor but proivides a passage for light reflectedat a predetermined angle by a crack to impinge on the sensor.
Origin
Unknown
Journal Title
U.S.P. 3478218, 11.11.69
Sector
Primary Papers
Class
PP 353