System for controlling light in dependence of time-of-flight signal

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.

2. The lighting system of claim 1 , wherein said processing system is arranged to analyse a dynamic behaviour of said time-of-flight signals and to send control signals to said light control system in dependence of said dynamic behaviour.

3. The lighting system of claim 1 , wherein said processing system is arranged to stop sending said control signals if said time-of-flight signal changed from a dynamic behaviour to a value that has been substantially constant for a first predetermined period of time, said first predetermined period of time preferably being in a range of 0.5-2 s.

4. The lighting system of any of claim 1 , wherein said ultrasonic transmitter comprises a horn for reducing the beam cone angle of the light beam.

5. The lighting system of claim 4 , wherein said beam cone angle of the light beam is smaller than 15°.

6. The lighting system of claim 1 , wherein said ultrasonic transmitter and receiver are arranged to transmit and receive ultrasonic signals in a direction extending within the light beam of the lamp.

7. The lighting system of any of claim 1 , wherein said lamp is a plurality of LEDs.

8. The lighting system of claim 7 , wherein said ultrasonic transmitter and receiver extend substantially between said plurality of LEDs.

9. An electronic system comprising:

an electronic device;

a control system arranged to drive said electronic device;

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 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.

10. The electronic system of claim 9 , wherein said processing system is arranged to analyse a dynamic behaviour of said time-of-flight signal and to send control signals to said control system in dependence of said dynamic behaviour.

11. The electronic system of claim 9 , wherein said processing system is arranged to stop sending said control signals if said time-of-flight signal changed from a dynamic behaviour to a value that has been substantially constant for a first predetermined period of time, said first predetermined period of time preferably being in a range of 0.5-2 s.

12. The electronic system of claim 9 , wherein said electronic device is a lamp arranged to transform electricity into a light beam having properties including intensity, colour, colour temperature, direction and beam cone angle, and said control system is arranged to adjust said light beam properties.