Patent ID: 8242718
Filing Date: 2012-08-14
Classification: G06F,H03K,H05B,Y02B

Abstract:
1. A lighting system comprising: a lamp arranged to transform electricity into a light beam having properties including intensity, colour, colour temperature, direction and beam cone angle; a light control system arranged to adjust said light beam properties; an ultrasonic transmitter arranged to transmit ultrasonic signals; an ultrasonic receiver arranged to receive reflected ultrasonic signals; and a processing system arranged to derive a time-of-flight signal representing the time differences between said transmitted and received ultrasonic signals and to send control signals to said light control system in dependence of said time-of-flight signal wherein said processing system is arranged to determine and store a reference value, which reference value is determined as the value that has been present during most of a second predetermined period of time of several minutes, and that said processing system is further arranged to start sending said control signals if said time-of-flight signal changed from said reference value to a lower value that has been substantially constant for at least a shorter third predetermined period of time, said third predetermined period of time preferably being in a range of 0.5-2 seconds.