Differential photoelectric auto-collimator system - uses two auto-collimators sharing single mirror surface at half-focus position of objective lenses

摘要

The differential autocollimator system includes two photoelectric autocollimators. Each includes an objective lens (L), an emission micrometer consisting of an illuminated slit (7) in front of its respective light source (8), and a receiver-detector comprising arrays (13,13a) of photodiodes. The emission micrometer is placed at the focus of the objective lens and a mirror which lies at the half-focus position (3). This mirror is common to both autocollimators. Each of the autocollimators is associated with a target mirror (1) which is attached to the objects whose angular rotation is to be measured. The mirror at the half-focus position has a single reflecting surface common to both autocollimators, the surface being one face of a parallel sided block of glass.