Optical device for aligning an object located at an arbitrary distance from the device

Claim 1

An optical device for aligning a radiation emanating object located at an arbitrary distance from the device with an optical axis of the device comprising two substantially identical concave mirrors having opposing reflective concave surfaces forming an optical cavity, the centers of curvatures of each of the mirrors lying on the surface of the opposing mirror and forming therewith said axis of the optical device, whereby a first portion of radiation from said object passes directly through and a second portion of said radiation is multiply reflected by the opposing mirrors of the optical cavity before passing out of said cavity, optical encoding means within the optical cavity for imparting a different optically distinguishable quality to each of said portions of said radiation, whereby said first portion of radiation passing through the cavity and said second portion reflected within the cavity are formed into two optically distinguishable beams, a beam chopper in the path of the two optically distinguishable beams, a beam splitter in the path of the radiation passing through the beam chopper for spatially separating the two beams and photodetector means for receiving said spatially separated beams and converting same into electrical signals, whereby the phase relationship between said signals can be used to determine alignment of said object.