Multi-etalon VISAR interferometer having an interferometer frame of high stiffness with a linear elongated slide bar

摘要

A multi-etalon VISAR interferometer with variable velocity-per- fringe constant, capable of measuring the velocity of a diffusely- reflecting surface, having design innovations which preserve the fringe alignment of the interferometer even when its velocity-per-fringe constant is changed or when it is exposed to environmental stress such as substantial temperature changes or being moved from one location to another. The interferometer stability is enhanced by using a very stiff interferometer frame, to which the alignment-sensitive components of the interferometer are attached. The movable interferometer components are attached to a relatively long slide bar which can be attached to the interferometer frame at various locations in a slide bar track in the interferometer frame. Delay leg spacers allow the slide bar, with its movable interferometer components, to be positioned easily and accurately when changing the velocity-per-fringe constant.