Optical instrument for measuring the divergence of two approximately colinear optical axes.

摘要

An optical instrument for measuring the divergence of two approximately colinear optical axes comprises an afocal telescope (4) having a comparator (9) disposed transversely to its longitudinal axis, the comparator comprising a beam splitter (10), an eyepiece (11) and a graticule (12). The instrument is used in conjunction with a mirror (15) disposed orthogonally with respect to one of the optical axes, the telescope being approximately aligned with the other optical axis and disposed so that light rays passing through it are reflected back by the mirror to the beam splitter and hence to the eye piece. The instrument is insensitive to small inaccuracies in telescope alignment and is particularly applicable to testing the accuracy of a gun sight, in which application it may be hand held.