Precision beam pointer for optical radiation - uses dioptre to separate beam into transmitted and reflected fractions

摘要

A precision beam pointer for optical radiation detects very small angular deviations of an electromagnetic beam, e.g. a light beam from a reference direction, measures these deviations and enables a beam which is stable indirection to be produced. It comprises a dioptre (P) which receives the beam on its face having the higher index and at an angle of incidence which is near to the limiting angle, and means of comparing the intensities of the transmitted and reflected fractions of the beam, using a mirror arrangement (M, M1, M2) a photodiode (R) and a sliding shutter (A) and a mechanical or electrical modulator (M).