AUTOMATED 3-DIMENSIONAL SURFACE PROFILOMETRY USING DUAL-FREQUENCY OPTIC FIBER PHASE-SHIFTING METHOD

A novel automatic profilometry technique using the dual frequency of a n optical fiber projection grating is introduced, 3-D shape can be mea sured automatically with this technique even with the problems of true discontinuities and phase noise. This method combines a single-mode o ptical fiber phase-shifting interferometer as the illumination part of the configuration. The design of the optical fiber interferometer has the following features: (1) easily adjustable fringe space and rotati on and (2) automatic phase shifting. In addition, it has a number of i mportant advantages over the more conventional methods for producing p rojection fringes, such as extremely small size and weight, high visib le fringes with little noise and absolute sinusoidal intensity distrib ution, etc, These are very important and necessary to dual-frequency a utomatic measurement of 3-D shapes. Fringes generated by the interfero meter are analyzed, and the relationship between the fringe phase and height distribution of an illuminated diffused surface is derived. The dual-frequency automatic phase unwrapping method is described. An exa mple of the profilometry in operation is given. (C) 1997 Society of Ph oto-Optical Instrumentation Engineers.