Local oscillator tap using reflection for coherent lidar
A lidar device includes a laser source configured to emit a transmit beam, an optical scanner that has at least one lens and is configured to transmit a first portion of the transmit beam towards a target and receive a receive beam reflected by the target, and a transmission medium configured to provide a propagation path for the transmit beam and the receive beam. The lidar device also includes a target detection module that is configured to determine a range and/or a velocity of the target based on the receive beam and a second portion of the transmit beam reflected at a media-air interface defined at an end of the transmission medium where the first portion of the transmit beam is launched into air towards the at least one lens of the optical scanner.
1 . A lidar device, comprising:
a laser source configured to emit a transmit beam;
an optical scanner, comprising at least one lens, configured to transmit a first portion of the transmit beam towards a target and receive a receive beam reflected by the target;
a transmission medium configured to provide a propagation path for the transmit beam and the receive beam; and
a target detection module configured to determine a range and/or a velocity of the target based on the receive beam and a second portion of the transmit beam reflected at a media-air interface defined at an end of the transmission medium where the first portion of the transmit beam is launched into air towards the at least one lens of the optical scanner, wherein the media-air interface comprises an angled endface of a connector coupled to the transmission medium.
2 . The lidar device of claim 1 , wherein the second portion of the transmit beam is used as a local oscillator (LO) signal to determine the range and/or the velocity of the target.
3 . The lidar device of claim 1 , further comprising a mixer configured to mix the receive beam and the second portion of the transmit beam to generate a mixed signal having a beat frequency.
4 . The lidar device of claim 3 , wherein the range and/or the velocity of the target is determined from the beat frequency.
5 . The lidar device of claim 1 , wherein the target detection module is configured to determine a reflectivity of the target based on the receive beam and the second portion of the transmit beam.
6 . The lidar device of claim 1 , wherein a configuration of the media-air interface is adjustable to control at least one characteristic of the second portion of the transmit beam.
7 . The lidar device of claim 6 , wherein the at least one characteristic of the second portion of the transmit beam comprises an intensity of the second portion of the transmit beam.
8 . The lidar device of claim 6 , wherein the configuration of the media-air interface corresponds to a configuration of the transmission medium.
9 . A method of operating a lidar device, the method comprising:
emitting, via a laser source, a transmit beam;
transmitting, via an optical scanner comprising at least one lens, a first portion of the transmit beam towards a target;
receiving, via the optical scanner, a receive beam reflected by the target;
reflecting a second portion of the transmit beam at a media-air interface defined at an end of a transmission medium where the first portion of the transmit beam is launched into air towards the at least one lens of the optical scanner, the transmission medium being configured to provide a propagation path for the transmit beam and the receive beam; and
determining, via a target detection module, a range and/or a velocity of the target based on the receive beam and the second portion of the transmit beam, wherein the media-air interface comprises a grating integrated within the transmission medium.
10 . A method of manufacturing a lidar device, the method comprising:
optically coupling (i) a laser source configured to emit a transmit beam, (ii) an optical scanner, comprising at least one lens, configured to transmit a first portion of the transmit beam towards a target and receive a receive beam reflected by the target, and (iii) a transmission medium configured to provide a propagation path for the transmit beam and the receive beam;
adjusting a configuration of a media-air interface defined at an end of the transmission medium where the first portion of the transmit beam is launched into air towards the at least one lens of the optical scanner to control at least one characteristic of a second portion of the transmit beam reflected at the media-air interface, wherein the media-air interface comprises a grating integrated within the transmission medium; and
configuring a target detection module to determine a range and/or a velocity of the target based on the receive beam and the second portion of the transmit beam.
11 . The method of claim 10 , further comprising:
optically coupling a mixer to the transmission medium, the mixer configured to mix the receive beam and the second portion of the transmit beam to generate a mixed signal having a beat frequency.
12 . The method of claim 11 , wherein the range and/or the velocity of the target is determined from the beat frequency.
13 . The method of claim 10 , wherein adjusting the configuration of the media-air interface comprises adjusting a configuration of the transmission medium.
14 . The method of claim 10 , wherein the at least one characteristic of the second portion of the transmit beam comprises an intensity of the second portion of the transmit beam.
15 . A vehicle, comprising:
at least one lidar device of claim 1 , wherein each lidar device is configured to provide navigation and/or mapping for the vehicle and is disposed in an interior of the vehicle and/or on an exterior of the vehicle.
16 . The method of claim 9 wherein the grating integrated within the transmission medium is a fiber Bragg grating.
17 . The method of claim 10 wherein the grating integrated within the transmission medium is a fiber Bragg grating.