A number of sensors exist which measure 3D range information using both active (projected light patterns or laser scanning) or passive (shape from shading or stereo camera) methods. For many applications, use of active systems is impractical, and the range of depth achievable with a stereoscopic camera system is limited to the baseline separation of the cameras. Presented here is a passive 3D range sensor based on a pupil-division and signal correlation scheme. The method for the extraction of range information compares signals from the upper and lower entrance pupil halves of the objective. The phase of the signals obtained from the correlation of light from both pupil halves with an oscillating optical grating are compared, and the result provides the range information. Using a microlens and sensor array, this system has been expanded to analyze 49 channels in parallel in the field of view. Preliminary studies indicate that the system is capable of measuring ranges from 2 to 10 meters with a precision of less than one percent. The measurement speed is limited by the mechanical oscillation frequency of the grating and is currently in the range of 1 - 3 frames/second. A single channel experimental system has been completed and a 49 channel prototype will be completed during the summer of 1997. Presented here are details regarding the development of this sensor. Suitable theoretical background to understand the system is provided. Results of the prototype system and applications of sensors that extract range data from a 2D field of view and a 1D strip will also be presented. Planned future developments to miniaturize and improve speed performance will also be outlined.
Roland H. Schaefer,
"Multiple channel passive 3D range sensor", Proc. SPIE 3100, Sensors, Sensor Systems, and Sensor Data Processing, (25 September 1997); doi: 10.1117/12.287748; https://doi.org/10.1117/12.287748