Lidar system with distributed laser and multiple sensor heads
In one embodiment, a lidar system includes a light source configured to emit pulses of light. The lidar system also includes multiple optical links and multiple sensor heads. Each optical link couples the light source to a corresponding sensor head, and each optical link is configured to convey at least a portion of the emitted pulses of light from the light source to the corresponding sensor head. Each sensor head includes a scanner configured to scan pulses of light across a field of regard of the sensor head, where the scanned pulses of light include the portion of the emitted pulses of light conveyed from the light source to the sensor head by the corresponding optical link. Each sensor head also includes a receiver configured to detect at least a portion of the scanned pulses of light scattered or reflected by a target located downrange from the sensor head.
1. A lidar system comprising:
a light source configured to emit pulses of light;
a plurality of optical links, wherein each optical link couples the light source to a corresponding sensor head of a plurality of sensor heads, wherein the optical link is configured to convey at least a portion of the emitted pulses of light from the light source to the corresponding sensor head; and
the plurality of sensor heads, wherein each sensor head comprises:
a scanner configured to scan pulses of light across a field of regard of the sensor head, wherein the scanned pulses of light comprise the portion of the emitted pulses of light conveyed from the light source to the sensor head by the corresponding optical link; and
a receiver configured to detect at least a portion of the scanned pulses of light scattered or reflected by a target located downrange from the sensor head, wherein the receiver comprises:
an avalanche photodiode (APD) configured to receive a pulse of light of the portion of the scanned pulses of light scattered or reflected by the target and generate an electrical-current signal corresponding to the received pulse of light;
a transimpedance amplifier configured to produce a voltage signal that corresponds to the electrical-current signal;
a voltage-gain circuit configured to amplify the voltage signal to produce an amplified voltage signal;
a plurality of comparators, each comparator configured to produce an electrical-edge signal when the amplified voltage signal rises above or falls below a predetermined threshold voltage; and
a time-to-digital converter (TDC) configured to:
receive two or more electrical-edge signals from one or more of the comparators;
determine two or more intervals of time between emission of the pulse of light by the light source and receipt of each of the electrical-edge signals; and
determine, based at least in part on the two or more intervals of time, a duration of the received pulse of light.
2. The lidar system of claim 1 , wherein:
the target is at least partially contained within the field of regard of the sensor head and is located a distance from the sensor head that is less than or equal to a maximum range of the lidar system; and
the sensor head further comprises a processor configured to determine the distance from the sensor head to the target based at least in part on one or more of the intervals of time between emission of the pulse of light and receipt of the electrical-edge signals.
3. The lidar system of claim 1 , wherein the lidar system is incorporated into a vehicle wherein the sensor heads are positioned to provide a 360-degree view of an environment around the vehicle.
4. The lidar system of claim 1 , wherein each optical link comprises a fiber-optic cable having a length greater than or equal to 1 meter.
5. The lidar system of claim 1 , further comprising a plurality of electrical links corresponding to the plurality of optical links, wherein each electrical link couples the light source to a respective sensor head of the plurality of sensor heads, wherein the electrical link is configured to convey electrical power or one or more electrical signals between the light source and the respective sensor head.
6. The lidar system of claim 1 , wherein the light source comprises:
a seed laser configured to produce low-power optical pulses; and
one or more optical amplifiers configured to amplify the low-power optical pulses to produce the pulses of light emitted by the light source.
7. The lidar system of claim 6 , wherein the light source further comprises one or more optical filters, wherein each optical filter is configured to reduce an amount of amplified spontaneous emission light produced by one or more of the optical amplifiers.
8. The lidar system of claim 6 , wherein the light source further comprises a supplemental light source combined with the seed laser, wherein light from the supplemental light source is configured to prevent at least one of the optical amplifiers from spontaneously emitting an optical pulse during a time after amplification of a first low-power optical pulse and prior to receipt of a second low-power optical pulse.
9. The lidar system of claim 1 , wherein the light source comprises:
a plurality of laser diodes, wherein each laser diode is configured to produce light at a different operating wavelength; and
an optical multiplexer configured to combine the light produced by each laser diode into a single optical fiber.
10. The lidar system of claim 1 , wherein the light source comprises a wavelength-tunable laser configured to produce optical pulses at a plurality of wavelengths of light corresponding to the plurality of sensor heads, wherein each wavelength produced by the wavelength-tunable laser is conveyed to a corresponding sensor head.
11. The lidar system of claim 1 , wherein the light source comprises an optical amplifier comprising one or more optical filters, wherein each optical filter is configured to reduce an amount of amplified spontaneous emission light produced by the optical amplifier.
12. The lidar system of claim 1 , wherein:
the lidar system comprises N optical links coupled to N respective sensor heads; and
the light source comprises a 1×N optical demultiplexer configured to distribute the emitted pulses of light between the N optical links.
13. The lidar system of claim 12 , wherein the optical demultiplexer comprises an optical-power splitter, an optical switch, or a wavelength demultiplexer.
14. The lidar system of claim 12 , wherein distributing the emitted pulses of light between the N optical links comprises:
splitting each emitted pulse of light into N pulses of light; and
sending each pulse of the N pulses to a corresponding optical link for transmission to a corresponding sensor head.
15. The lidar system of claim 12 , wherein:
the pulses of light emitted by the light source comprise pulses having N different wavelengths; and
distributing the emitted pulses of light between the N optical links comprises sending each pulse having a particular wavelength to a corresponding optical link for transmission to a corresponding sensor head.
16. The lidar system of claim 1 , wherein each optical link comprises a gain fiber of a fiber-optic amplifier, wherein the gain fiber is configured to amplify the portion of the emitted pulses of light while propagating from the light source to the corresponding sensor head.
17. The lidar system of claim 1 , wherein each optical link comprises a gain fiber of an optical amplifier, wherein the gain fiber is distributed along a length of the optical link and is configured to amplify the portion of the emitted pulses of light while the portion of the emitted pulses of light is conveyed from the light source to the corresponding sensor head.
18. The lidar system of claim 1 , wherein each sensor head further comprises an optical amplifier configured to:
amplify the pulses of light conveyed to the sensor head by the optical link; and
send the amplified pulses of light to the scanner for scanning across the field of regard of the sensor head.
19. The lidar system of claim 18 , wherein the optical amplifier is a free-space amplifier or a fiber-optic amplifier.
20. The lidar system of claim 1 , wherein:
the TDC is further configured to receive an electrical trigger signal that corresponds to a time when the pulse of light is emitted by the light source; and
the TDC is configured to determine the two or more intervals of time between emission of the pulse of light and receipt of the electrical-edge signals based at least in part on the received electrical trigger signal.