Optical measuring system for cursor displacement - uses reflecting surfaces in prism to increase optical path length through gratings and light detectors for movement determination

摘要

The system includes main and counter optical gratings through which light is transmitted. Reflecting surfaces allow the gratings to be slightly mispaced and still provide a precise measuring waveform. A fixed transparent rule carries an optical grating on one face. A cursor slides along it carrying a light source and a transparent plate. The plate carries a counter grating and light intensity detectors to detect light from the source as it passes through the gratings to produce a periodic waveform for electronic processing to give direction and amplitude of movement. A prism receives the light from the source and directs it onto the gratings to increase path length and precision without increasing the size.