Phase shift correction for displacement measuring systems using quadrature

摘要

Method and apparatus are disclosed for increasing accuracy of optical phase shift in quadrature systems by varying the angle at which light is directed through pairs of diffraction gratings. A more precise adjustment of the phase angle between two adjacent index gratings is achieved after manufacturing and assembly by using a light source and diverging or converging its rays of light. The accuracy of the phase shift of resultant signals is greatly improved over methods of mechanical alignment heretofore used. The improved accuracy allows for the manufacture of a broad tolerance system, with the inherent reduction of costs.