Alignment of large aperture optical systems using a bi-directional telescope and a variable offset periscope
Two instruments have been developed, the Bi-Directional Telescope (BDT) and the Variable Offset Periscope, that will aid the alignment of large aperture, long pathlength optical systems. The BDT has been designed to view two ends of a complex long pathlength optical system along a common optical axis. The BDT provides a beam whose maximum offset between beams approaches .001: and maximum angular misalignment approaches 6.0 microradians. The other instrument, the Variable Offset Periscope, has been developed to align multiple mirror or annular optical systems to a common axis, where the optical axis is obscured. The periscope is capable of offsetting a beam over most of a 23.0: diameter aperture with an angular error of less than 2.0 microradians between input and output beams.