Abstract

Jet Propulsion Laboratory is developing a rangefinder camera system for the study of ocean waves. The system can be used as a real-time, three-dimensional television camera for general application. We have conducted an analytical study of the system to establish a theoretical framework and to determine the optimum parameters for recording ocean wave information. We are building an operating prototype based on theoretical work. Techniques have been developed to measure the arbitrary shape of a surface using "time of flight" and modulated laser systems. Our system uses a modulated laser, but no scanning is required. Instead, a charge-coupled device (CCD) camera performs the spatial sorting of picture elements, thus simplifying the system considerably. The imaged scene is illuminated with pulses of light generated with a Nd:YAG laser or simply with a flash lamp. The camera is electronically shuttered at the pulse rate. This way, a simple synchronous, or homodyne, detection of phase is accomplished. The phase of the modulated light reflected from each object picture element is proportional to its distance and to the number of collected electrons in that pixel. Our images of the ocean surface locate specular reflections three-dimensionally. We find that it is possible to recover a three-dimensional surface from specularities.

© 1990 Optical Society of America