Abstract

A system for phase-matching arrayed telescopes by means of a corner-cube-bridge metering rod comprises a plurality of arrayed telescopes 10, a source 30 of laser light reflecting means 32,40,42,44,46 for directing the laser beam through the telescopes 10, one of the reflecting means being a beam splitter 42 for directing a different portion of the laser beam through each telescope 10, an absolute distance interferometer (ADI) 38, boresighting means including a hole plate 32, a focusing lens 34 and an alignment sensor 36, and a metering rod 16 carrying four corner-reflector cubes, two near each end. The ADI beam is aligned with the laser source beam by using the boresighting means. The metering rod 16 is mounted between two adjacent telescopes 10 so that two adjacent corner cubes reflect the beam coming through one telescope and the other two adjacent cubes reflect the beam coming through the other telescope. The ADI 38 is then used to measure the optical path length (OPL) of the beam reflected from each corner cube 22,24,26 and 28. The deviation of each OPL from the others is adjusted by an optical trombone 44,48 in each optical path to change the path lengths so as to bring them all into equality, or identical phase.