Apparatus and method for cancellation of scattered light in lidar sensors
An apparatus for cancellation of scattered light in lidar sensors is provided. In some embodiments, the apparatus includes a lidar device with a transmitter configured to transmit optical signals and a receiver configured to receive return signals based on the optical signals. The receiver includes a first photodetector configured to receive a first return signal and a second return signal, and generate a first electrical current in response to the first return signal and the second return signal. The receiver further includes a second photodetector configured to receive the first return signal but not the second return signal, and generate a second electrical current in response to the first return signal. The receiver also includes an amplifier configured to receive a third electrical current equal to a difference between the first electrical current and the second electrical current.
1 . A lidar device comprising:
at least one far-field transmitter configured to emit optical signals as tightly focused beams, the at least one far-field transmitter being structured and arranged to scan a field of view (FOV) of the lidar system with the tightly focused beams;
a near-field transmitter structured and arranged to emit a diffuse flash beam optical signal separately and distinctly from the tightly focused beams emitted by the at least one far-field transmitter; and
a receiver configured to receive return signals based on the optical signals emitted by both the far-field and the near-field transmitters, the receiver comprising:
a first photodetector configured to (i) receive a dazzle signal arising from internal reflections and a valid return signal reflected from an object in the environment, and (ii) generate a first electrical current in response to the dazzle signal and the valid return signal;
a second photodetector configured to (i) receive the dazzle signal but not the valid return signal and (ii) generate a second electrical current in response to the dazzle signal; and
an amplifier configured to receive a third electrical current equal to a difference between the first electrical current and the second electrical current,
wherein the lidar device is configured to detect objects positioned from about 0.1 meters to about 0.6 meters from the device in response to the return signals generated by the near-field transmitter.
2 . The lidar device of claim 1 , wherein the first and second photodetectors are avalanche photodiodes or p-i-n junction (PIN) photodiodes.
3 . The lidar device of claim 1 , wherein the first and second photodetectors are disposed relative to one another such that (i) a footprint of the first return signal covers the first and second photodetectors and (ii) a footprint of the second return signal covers the first photodetector but not the second photodetector.
4 . The lidar device of claim 1 , wherein the first and second photodetectors are disposed on and electrically coupled to a circuit board.
5 . The lidar device of claim 1 , wherein the dazzle signal comprises a reflection or scattering of an optical signal off a component inside the lidar device.
6 . The lidar device of claim 1 , wherein the first photodetector comprises a first anode and a first cathode, wherein the second photodetector comprises a second anode and a second cathode, wherein the first cathode is electrically coupled to a positive voltage, wherein the second anode is electrically coupled to a negative voltage, and wherein the first anode is electrically coupled to the second cathode.
7 . The lidar device of claim 6 , wherein the amplifier is electrically coupled to the first anode.
8 . The lidar device of claim 1 , wherein the third electrical current corresponds to the second return signal.
9 . The lidar device of claim 1 , wherein the amplifier comprises a transimpedance amplifier configured to output a voltage corresponding to the second return signal.
10 . The lidar device of claim 1 , wherein the near-field transmitter is configured to emit the diffuse flash beam once each time the far-field transmitter scans the field of view.
11 . The lidar device of claim 1 , wherein the diffuse flash beam emitted by the near-field transmitter has a greater optical divergence and lower energy density than the beams emitted by the far-field transmitter and the near-field transmitter is structured and arranged such that the diffuse flash beam substantially fills both the horizontal and vertical field of view of the lidar device.
12 . The lidar device of claim 11 , wherein the at least one far-field transmitter comprises an array of far-field transmitters, each emitting a tightly focused optical beam, and wherein the array is configured to scan the entire field of view by emitting the tightly focused beams sequentially or in parallel to different portions of the field of view.
13 . A lidar method comprising:
providing a lidar device comprising:
a transmitter configured to transmit optical signals; and
a receiver configured to receive return signals based on the optical signals, the receiver comprising a first photodetector, a second photodetector, and an amplifier;
receiving, at the first photodetector, a first return signal and a second return signal;
generating, at the first photodetector, a first electrical current in response to the first return signal and the second return signal;
receiving, at the second photodetector, the first return signal but not the second return signal;
generating, at the second photodetector, a second electrical current in response to the first return signal; and
receiving, at the amplifier, a third electrical current equal to a difference between first electrical current and the second electrical current;
wherein the first return signal comprises a dazzle signal, and the second return signal comprises a reflection of an optical signal emitted into an environment outside the lidar device and received from an object positioned from about 0.1 m to about 0.6 m away from the lidar device.
14 . The method of claim 13 , wherein the first and second photodetectors are disposed relative to one another such that (i) a footprint of the first return signal covers the first and second photodetectors and (ii) a footprint of the second return signal covers the first photodetector but not the second photodetector.
15 . The method of claim 13 , wherein the first and second photodetectors are disposed on and electrically coupled to a circuit board.
16 . The method of claim 13 , wherein the dazzle signal comprises a reflection or scattering of an optical signal off a component inside the lidar device.
17 . The method of claim 13 , wherein the first photodetector comprises a first anode and a first cathode, wherein the second photodetector comprises a second anode and a second cathode, wherein the first cathode is electrically coupled to a positive voltage, wherein the second anode is electrically coupled to a negative voltage, and wherein the first anode is electrically coupled to the second cathode.
18 . The method of claim 17 , wherein the amplifier is electrically coupled to the first anode.
19 . The method of claim 13 , wherein the third electrical current corresponds to the second return signal.
20 . The method of claim 13 , wherein the amplifier comprises a transimpedance amplifier, and wherein the method further comprises outputting from the transimpedance amplifier a voltage corresponding to the second return signal.