Method and apparatus for sensing different levels

摘要

An invisible electromagnetic beam which is produced by a radiating element -2- is focussed by means of a lens -3- to form a convergent beam -4- and is directed directly at the surface to be sensed. The beam -4- is partially reflected back from the surface -5- through the measurement aperture -6- and through the interference filters -7, 8- to two highly-sensitive measuring devices for electromagnetic beams -9, 10-. The analog values measured in this way are fed directly and after amplification to a microprocessor -11- which is programmed to produce a digital signal in the case of different levels. <IMAGE>