Parallel line lidar with frequency domain filtering

Simple, low-cost, rangefinders using parallel beams and a single camera are often used for underwater ranging, but they have limited performance in turbid operating environments such as those associated with coastlines and harbors. A new approach to parallel beam ranging is described which incorporates a combination of simple receiver optics and image processing to significantly reduce the effects of scatter, thereby extending and improving performance. The technique is demonstrated using commercial-off-the-shelf (COTS) cameras and experimental results are presented comparing the new approach to the traditional parallel beam rangefinder. Improvements of multiple attenuation lengths are reported.