Ultrashort pulses in LiDAR systems
LiDAR system and methods discussed herein use ultrafast light pulses. Use of ultrafast light pulses can result in reduced power consumption compared to longer length or conventional light pulses.
1. A light detection and ranging (LiDAR) system comprising:
a light source configured to output a plurality of light pulses;
a controller configured to:
control pulse duration of each of the light pulses,
control a plurality of time delays including variable time delays such that at least two of the plurality of time delays are different among successive light pulses, and
select, in a pseudo-random manner, the plurality of time delays between the successive light pulses, wherein the pulse duration of each of the light pulses is substantially the same and is characterized as an ultrashort light pulse, and wherein at least one ultrashort light pulse of the light pulses is emitted during a span of one non-ultrashort light pulse having a pulse duration on the order of nanosecond;
a steering system configured to control a scanning direction of each ultrashort light pulse to a particular location within a LiDAR field-of-view (FOV); and
a detection system configured to monitor for returned ultrashort pulses and determine one or more time durations between successive outputs of a detector of the detection system,
wherein the controller is further configured to correlate the determined one or more time durations with the variable time delays to distinguish between noise and the returned ultrashort pulses.
2. The LiDAR system of claim 1 , wherein the detection system comprises:
at least one receiving lens;
the detector comprising a single photon avalanche diode (SPAD) detector; and
a time-to-digital converter (TDC).
3. The LiDAR system of claim 2 , wherein the SPAD detector is configured to generate one or more output signals in response to light energy received through the at least one receiving lens, and wherein the TDC is configured to determine one or more time durations between successive outputs of the SPAD detector.
4. The LiDAR system of claim 1 , wherein the pulse duration of an ultrashort light pulse is on the order of picoseconds.
5. The LiDAR system of claim 1 , wherein the pulse duration of an ultrashort light pulse ranges between 10 picoseconds and 900 picoseconds.
6. The LiDAR system of claim 1 , wherein the pulse duration of an ultrashort light pulse ranges between 100 picoseconds and 200 picoseconds.
7. The LiDAR system of claim 1 , wherein the detection system comprises:
at least one receiving lens;
the detector comprising an avalanche photo diode (APD) detector; and
an analog-to-digital converter (ADC).
8. The LiDAR system of claim 7 , wherein the APD detector is configured to generate an output signal proportional to light energy received through the at least one receiving lens, and wherein the ADC is configured to convert the output signal to a digital signal.
9. The LiDAR system of claim 8 , wherein the controller is configured to compare the digital signal to a threshold to determine whether a returned ultrashort pulse has been received.
10. The LiDAR system of claim 1 , wherein the detection system comprises:
at least one receiving lens;
the detector comprising an avalanche photo diode (APD) detector, wherein the APD detector produces a current signal in response to a returned ultrashort pulse;
a limiting transimpedance amplifier (LTA) configured to generate a square wave signal based on the current signal; and
a time-to-digital converter (TDC).
11. The LiDAR system of claim 10 , wherein at least one of the plurality of time delays between the successive light pulses is provided with a reference clock to the TDC, and wherein the TDC determines a time delay between the reference clock and the square wave signal that is used to determine a distance to an object that returned the returned ultrashort pulse.
12. A method for using a light detection and ranging (LiDAR) system, comprising:
transmitting a plurality of ultrashort light pulses to a steering system that redirects the ultrashort light pulses to a field of view of the LiDAR system,
wherein pulse duration of each of the ultrashort light pulses is substantially the same and is controlled by a controller of the LIDAR system,
wherein a plurality of time delays between successive ultrashort light pulses are variable time delays controlled by the controller of the LiDAR system such that at least two of the time delays are different among the successive ultrashort light pulses,
wherein the plurality of time delays between the successive ultrashort light pulses are selected by the controller of the LiDAR system in a pseudo-random manner,
and wherein at least one ultrashort light pulse of the plurality of ultrashort light pulses is emitted during a span of one non-ultrashort light pulse having a pulse duration on the order of nanosecond;
receiving, via a detection system, light energy signals comprising at least one of noise and returned ultrashort pulses;
determining one or more time intervals between successively received light energy signals; and
correlating the determined one or more time intervals with the plurality of variable time delays to distinguish between noise and returned ultrashort pulses.
13. The method of claim 12 , wherein the ultrashort light pulses range between 10 picoseconds and 900 picoseconds.
14. The method of claim 12 , wherein the ultrashort light pulses range between 100 picoseconds and 200 picoseconds.
15. A method for using a light detection and ranging (LiDAR) system, comprising:
transmitting a plurality of ultrashort light pulses to a steering system that redirects the ultrashort light pulses to a field of view of the LiDAR system,
wherein pulse duration of each of the ultrashort light pulses is substantially the same and is controlled by a controller of the LIDAR system,
wherein a plurality of time delays between successive ultrashort light pulses are variable time delays controlled by the controller of the LiDAR system such that at least two of the time delays are different among the successive ultrashort light pulses,
wherein the plurality of time delays between the successive ultrashort light pulses are selected by the controller of the LiDAR system in a pseudo-random manner,
and wherein at least one ultrashort light pulse of the plurality of ultrashort light pulses is emitted during a span of one non-ultrashort light pulse having a pulse duration on the order of nanosecond;
receiving, via a detection system, light energy signals comprising noise and returned ultrashort pulses, wherein each of the received light energy signal produces an analog intensity level;
converting the analog intensity level to a digital intensity level; and
distinguishing between noise and returned ultrashort pulses based on the digital intensity level and the variable time delays.
16. The method of claim 15 , wherein the ultrashort light pulses range between 10 picoseconds and 900 picoseconds.
17. The method of claim 15 , wherein the ultrashort light pulses range between 100 picoseconds and 200 picoseconds.
18. A method for using a light detection and ranging (LiDAR) system, comprising:
transmitting a plurality of ultrashort light pulses to a steering system that redirects the light pulses to a field of view of the LiDAR system,
wherein pulse duration of each of the ultrashort light pulses is substantially the same and is controlled by a controller of the LIDAR system,
wherein each of the transmitted ultrashort light pulse corresponds to a reference clock, wherein a plurality of time delays between successive ultrashort light pulses are variable time delays controlled by a controller of the LiDAR system such that at least two of the time delays are different among the successive ultrashort light pulses,
wherein the plurality of time delays between the successive ultrashort light pulses are selected by the controller of the LiDAR system in a pseudo-random manner,
and wherein at least one ultrashort light pulse of the plurality of ultrashort light pulses is emitted during a span of one non-ultrashort light pulse having a pulse duration on the order of nanosecond;
receiving, via a detection system, light energy signals, and wherein each of the received light energy signals produces a current level;
converting the current level to a square wave signal; and
obtaining, based on the square wave signal and the variable time delays, a time delay between transmission of an ultrashort light pulse and a corresponding return light pulse.
19. The method of claim 18 , wherein the ultrashort light pulses range between 10 picoseconds and 900 picoseconds.
20. The method of claim 18 , wherein the ultrashort light pulses range between 100 picoseconds and 200 picoseconds.
21. The LiDAR system of claim 1 , wherein the controller is further configured to control the pulse duration of each of the light pulses to be ultrashort such that a size of a receiving aperture of the steering system is reduced compared to if the light pulses are non-ultrashort pulse.
22. The LiDAR system of claim 1 , wherein the controller is further configured to control the pulse duration of each of the light pulses to be ultrashort such that average power consumption by the light source is reduced compared to if the light pulses are non-ultrashort pulse.