The triangulation principle is basic for this measurement method (exception LLD). The laser beam in the form of a small spot arrives on the surface of the target, while the detector of the system captures its position. The distance itself is calculated by means of the change of the angle. Achievable resolution and accuracy are therefore influenced mainly by the distance d: In proximity of the sensor, a large angular change a1 can be obtained, whereas larger values result in a smaller angle a2, thus in reduced accuracy (see drawing).
A photo diode array integrated in the sensor represents the receiver, high speed versions use a PSD element. The receiver is directly coupled to a micro-controller, being part of the system. This micro-controller analyses the light distribution on the element, calculates the exact angle and out of it the distance to the object. The calculated distance is either transferred to a serial port or alternatively is converted to a proportional output current. The micro-controller guarantees a very high linearity and accuracy. The combination of photo diode array and micro-controller allows a suppression of interfering reflections and ensures a reliable results even on most critical surfaces. The sensor automatically adapts to the surface colour by a change of its internal sensitivity. This way influences due to the target colour are nearly excluded. An integrated digital output is activated whenever the sensor does not receive enough light (pollution signal), or if no object within the measuring range can be detected at all.