Length or angle optical measurement system - has astigmatic or anamorphotic optics for limiting illumination of scanning region by concentrating LED rays crossing incremental scale and expanding rays in scale direction

摘要

A scale in the form of a grating is read by a sensor movable in the measurement direction relative to the scale. An optical system (3) in the sensor limits the illumination of the sensing region on the scale (4) by focussing the illumination beam transversely w.r.t. the measurement direction but allowing it to extend in the measurement direction. An optical astigmatism component can be used with a cylindrical lens (3b) whose focal line is parallel to the measurement direction and a condenser (3a) which collimates the beam in the measurement direction. USE/ADVANTAGE - For length or angle measurement. Insensitive to Moire tilting around axis perpendicular to scale.