Patent ID: 8217595

Claim:
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 further arranged to perform a reference calibration step, wherein the time-of-flight (TOF) signal is repeatedly measured for a multitude of times, and wherein the processing system determines if a deviation of the majority of the measured time-of-flight values (TOFI) of said multitude of measurements is lower than a predetermined threshold (z), and wherein said processing system is arranged to calculate the average (TOFREF) of said measured time-of-flight values (TOFI) and store said average (TOFREF) in a memory device as a reference time-of-flight value if said deviation is lower than said threshold (z).