Three-dimensional sensing based on a dynamically focused laser optical feedback imaging technique

A new method analogous to three-dimensional confocally based sensing is pro posed. This method uses the technique of laser optical feedback imaging, wh ich takes advantage of the resonant sensitivity of a short-cavity laser to frequency-shifted optical feedback for highly sensitive detection, making i t ideal for surface and volume measurements of noncooperative targets. Rapi d depth scanning is made possible by use of an electrically controlled vari able-focus lens. The system is able to detect height discontinuities, and b ecause detection occurs along the axis of projection the system does not ha ve problems of shadow. Preliminary results for a depth range of 15 mm and a resolution of 100 mum are presented. (C) 2001 Optical Society of America.