Methodical errors caused by superposition of electrical and optical signals in a heterodyne laser interferometer

Distortions of the displacements measured by the heterodyne interferometer due to penetration of the electric excitation signal of the acousto-optic modulator into the path of registration and processing of optical signals are considered. The level of this type of noise is estimated and the ways of its elimination from data obtained using a three-coordinate heterodyne interferometer are proposed. (paper)