Interferometer apparatus incorporating a spherical element of index of

Abstract

An interferometer arrangement of either the transmission or reflection type incorporating at least a pair of partially spherical or spherical elements having an index of refraction of approximately two is disclosed. In a preferred embodiment, the spherical or radiation directing elements are glass spheres having an index of refraction of approximately two at the wavelength of a light source being utilized. In a transmission type interferometer, both the spherical or radiation directing elements are utilized as beam splitters and collimators while, in the reflection type interferometer, one of these spheres is used as a beam splitter and collimator while the other is utilized as a retroreflector. The complete spherical symmetry of such radiation directing elements permits them to function with any orientation relative to the optical path between them. Mechanisms in which desired motions are controlled with high precision by applying mechanical feedback to position a movable body relative to a fixed reference body, using the above described interferometer arrangement are also disclosed. The same mechanisms are capable of being controlled from a programmed computer causing the movable body to exhibit a desired motion using interference fringe detection schemes to both monitor and accurately position the movable body relative to a reference body. Also disclosed is an actuator based on a hollow hydraulic cylinder having a given longitudinal axis which includes an interferometer arrangement incorporating at least a pair of spherical elements which have an optical axis substantially coincident with the longitudinal axis of the actuator. Also disclosed are transducer arrangements disposed in series with the actuator which are utilized to meet high frequency stability requirements.