Valgusallikas, milleks peamiselt kasutatakse tahket laserit või kollimeeritud LED-i, kiirgab energiat elektromagnetlainena kandes mõõtesignaali, mis tavaliselt saadakse kiirguslaine moduleerimise teel.
The light source emits the energy as an electromagnetic wave. It carries the measuring signal which is normally obtained by modulation of the emitted wave. The light sources mainly used are the solid laser or collimated LED.
