Abstract: A laser light emitting diode (1, 2) situated at a focal point of a specially shaped lens (3, 4) produces a very thin intense fan-shaped beam. One or two such laser light transmitters are used to radiate a fan-shaped beam which is intercepted by a person or object thereby scattering laser light, by diffuse reflection. A cylindrical lens (5) receives a reflected component and this is detected by sensors (6) which are connected to circuitry including a synchronous detector (12) and comparator network (13, 14). The synchronous detector (12) is driven by a square wave oscillator (8) which modulates the laser light.

Abstract: Apparatus for controlling a lift door in which a detection zone (10) is illuminated with an infrared light source (15) and reflected light is received by image sensing device (18). A data processing device (17) is programmed to analyse video information stored in a video memory (22) and a reference field memory (23) so as to distinguish an object approaching the lift doors (1, 2) from an object passing by the lift, and also distinguishes stationary objects in the path of the lift doors (1, 2) from background objects. In a preferred embodiment, a low resolution image sensing device (18) is used and video information is binned and stored in the video memory (22).

Abstract: Proximity sensor apparatus has at least first and second antenna strips arranged along the edge of a structure. The antenna strips receive signals reflected by an object whose proximity is to be detected. Signal processing circuitry is coupled to the antenna strips for receiving and processing the signals picked up by the antenna strips. Proximity detection may occur when the difference in signal strength received by the two antenna strips exceeds a threshold level. In one embodiment, the difference between the maximum and minimum signals is determined and increases the threshold as the difference between signals decreases. In another embodiment, the difference in signal strength is used to determine the position of the object on one side or another of the antenna strips. In yet another embodiment, a bootstrap electrode is positioned behind a single antenna strip and is electrically connected to follow the voltage induced on the antenna strip by the received signal.