Device for operating a light source for the optical time-of-flight measurement
The invention relates to a device for operating a light source for the optical time-of-flight measurement. The light source operating device includes a light source, which is configured to emit light pulses according to a pulse signal sequence and a monitoring circuit for monitoring a light output emitted by the light source based on a current signal and/or voltage signal of the light source.
1. A device for operating a light source for an optical time-of-flight measurement, comprising:
a light source, which is configured to emit light pulses according to a pulse signal sequence; and
a monitoring circuit for monitoring a light output emitted by the light source based on a current signal and/or a voltage signal of the light source, wherein the monitoring circuit is configured to deactivate or not to activate the light source when the emitted light output exceeds a threshold value, wherein the monitoring circuit comprises first transducer for a first time-correlated scanning of the current signal from the light source, and a second transducer for a second time-correlated scanning of the voltage signal from the light source.
2. The device according to claim 1 , wherein the monitoring circuit comprises an on-time monitor, which is configured to monitor whether a continuous switch-on time of the light source is less than a specified switch-on time threshold value.
3. The device according to claim 1 , wherein the monitoring circuit comprises a duty factor monitor, which is configured to monitor whether a duty factor of the light pulses is smaller than a specified duty factor threshold value.
4. The device according to claim 1 , wherein the monitoring circuit comprises a window monitor, which is configured to monitor whether the light source is activated outside of the pulse signal sequence.
5. The device according to claim 1 , further comprising a pulse sequence generator, which is configured to generate the pulse signal sequence.
6. The device according to claim 5 , further comprising a pulse window generator, which generates a pulse window based on a pulse signal.
7. The device according to claim 1 , wherein the monitoring circuit comprises an energy calculator, which is configured to calculate an electrical energy value based on the current signal and/or the voltage signal of the light source.
8. The device according to claim 7 , further comprising a temperature compensator which is configured to correct the emitted light output based on the electrical energy value and an operating temperature value of the light source.
9. The device according to claim 8 , wherein the light source comprises a temperature sensor, which outputs the operating temperature value of the light source to the temperature compensator.
10. The device according to claim 1 , further comprising a measuring resistor, which outputs a voltage scanning signal based on the current signal of the light source.
11. The device according to claim 10 , further comprising a differential amplifier, which amplifies the voltage scanning signal for the measuring resistor.
12. The device according to claim 11 , further comprising a comparator, which compares the voltage scanning signal to a reference value and based thereon, outputs a status signal of the light source to the monitoring circuit.
13. The device according to claim 1 , wherein the monitoring circuit comprises an error logic, which is configured to deactivate the light source, based on the monitoring of the light output emitted by the light source.
14. A light detecting and ranging (LIDAR) device, comprising:
a light source to emit light pulses according to a pulse signal sequence;
a monitoring circuit for monitoring a light output emitted by the light source based on a current signal and a voltage signal of the light source;
an energy calculation circuit do determine an emitted light energy based on the current signal and the voltage signal; and
a pulse sequence generator to modify the pulse signal sequence responsive to the emitted light energy.
15. The LIDAR device of claim 14 , further comprising an on-time monitor to determine whether a continuous switch-on time of the light source exceeds a predefined switch-on time threshold value.
16. The LIDAR device of claim 14 , further comprising a duty factor monitor to integrate on-times of the light source to generate an error signal when a duty cycle of the light pulses exceeds a threshold value.
17. The LIDAR device of claim 14 , wherein the pulse sequence generator is configured to modify the pulse signal sequence when the emitted light energy exceeds an eye safety threshold.
18. A method comprising:
generating a pulse signal sequence, wherein the pulse signal sequence includes a first set of pulse periods in which a light source is to be activated and a second set of pulse periods in which the light source is not to be activated;
activating the light source according to the pulse signal sequence;
measuring a time-of-flight of pulses emitted by the light source to determine a distance to an object;
measuring a current signal of the light source;
measuring a voltage signal of the light source;
determining an emitted light energy from the current signal and the voltage signal;
determining that the emitted light energy exceeds a threshold; and
modifying the pulse signal sequence to reduce the emitted light energy.
19. The method of claim 18 , wherein the modifying the pulse signal sequence comprises decreasing a number of the first set of pulse periods.
20. The method of claim 18 , wherein the modifying the pulse signal sequence comprises increasing a number of the second set of pulse periods.