Laser interferometer system for straightness measurements

摘要

A laser interferometer system in particular for measuring the straightness of an object is described. This interferometer employs first prisms (15,16) to refract parallel laser beams by certain angles with respect to the principal axis of an incident beam, and prism reflectors (17,18,19) at least one of which (17,18) includes a refraction surface for introducing an optical path length difference upon transverse movement perpendicular to the principal axis. Three embodiments are described. A first is for long-range measurements and after leaving the first prisms the beams (23,43) are parallel when they reach the prism reflectors, one of which is a retroreflector and the other of which has a refraction surface. In the other embodiments the beams (23,36) after leaving the first prisms either converge or diverge respectively, and the prism reflectors (17,18) both include refraction surfaces arranged to refract the beams in opposite senses.