A concept is described for phasing the outputs of a multiple telescope array used as a laser transmitter. The technique uses samples of the transmitted beams to control optical path lengths through the separate telescopes so that the beams add coherently at the receiver. The phasing concept is applicable both to systems which provide inputs to the multiple telescopes by dividing a single laser beam and to systems in which the inputs to the telescopes and multiple, phase-locked laser beams. The approach is also compatible with single line and multi-line lasers, and it does not entail stringent alignment requirements. The concept uses a three step procedure to find the zero optical path difference condition and to effect fine control of the optical path lengths through the different telescopes. Algorithms are described for estimating the phase mismatch from focal plane measurements. The technique is susceptible to errors induced by local aberrations within the individual telescopes. The errors and one possible solution, the use of redundant measurements, are discussed. Performance requirements for a phased array laser transmitter are described.

Date Published: 2 March 1984
PDF: 8 pages
Proc. SPIE 0440, Synthetic Aperture Systems I, (2 March 1984); doi: 10.1117/12.937580

Published in SPIE Proceedings Vol. 0440:
Synthetic Aperture Systems I
Janet S. Fender, Editor(s)