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

A new method analogous to three-dimensional confocally based sensing is proposed. This method uses the technique of laser optical feedback imaging, which takes advantage of the resonant sensitivity of a short-cavity laser to frequency-shifted optical feedback for highly sensitive detection, making it ideal for surface and volume measurements of noncooperative targets. Rapid depth scanning is made possible by use of an electrically controlled variable-focus lens. The system is able to detect height discontinuities, and because detection occurs along the axis of projection the system does not have problems of shadow. Preliminary results for a depth range of 15 mm and a resolution of 100 mum are presented.