Noncontact distance sensor using spatial signal processing

To the best of our knowledge, proposed is the first distance-measurement sensor using direct spatial signal processing. The sensor is implemented using a laser beam engaged in target-dependent spatial beam processing using an electronically controlled variable focus lens (ECVFL). Specifically, the target-reflected beam is observed by an optical detector while electronically scanning the focal length of the ECVFL in the path of the laser beam. A received-beam minimum spatial size corresponds to a specific ECVFL focal length that in turn is used to compute the sensed target distance. Experiments have been conducted using a 633 nm He-Ne laser and a liquid ECVFL, giving target distance measurements from 6 to 109 cm with a < 1.7% sensor resolution. Various noncontact applications for the sensor include sensing of object measurement parameters of distance, motion displacement, three-dimensional structure, spatial profile, and levels.