Abstract

This summary describes a system for remotely monitoring the position, transverse to the line of sight, of an object with retroreflector attached. This sensor system was designed to monitor the azimuthal twist of a 50-m high tower due to the wind. It consists of a corner-cube retroreflector aloft, and a laser transmitter and beam position sensor on the ground. A corner cube, unfilled by an incident collimated beam, produces a collimated reflected beam, collinear with but displaced from that incident beam. The displacement corresponds to the transverse location of the cornercube apex relative to the incident beam. This effect enables the relative displacement of the returned beam to reveal the transverse displacement of the corner cube. The returning collimated beam is partially focused on a quad-cell detector to transduce its transverse location into a pair of electrical signals. Details of this system are described and some of its practical capabilities and limitations are discussed. The tip/tilt effect of the atmosphere is the limiting noise of the system. Measurement results evaluating the sensor performance in the presence of this noise are presented.

© 1985 Optical Society of America