Data input devices and methods for detecting movement of a tracking surface by detecting laser doppler self-mixing effects of a frequency modulated laser light beam

摘要: A data input device for use with a tracking surface having light-scattering properties respect to the device. The comprising single laser modulated light beam. beam splitter splits into two beams projected along separate paths toward surface. portion of striking reflects back cavity self-mixing light, thereby altering first and second characteristics according directions associated detector detects altered by laser, controller responsive determines relative movement one another as function detected detector.