The technique of retroreflective grating analysis is presented to meas
ure surface contour. This noncontacting optical method can detect a de
nt with maximum depth less than 10 mu m. A comparison with some physic
al measuring systems indicates that it has advantage over such contact
ing measurements, especially for specular surfaces. (C) 1998 Society o
f Photo-Optical instrumentation Engineers. [S0091-3286(95)03105-5].