Lidar system with integrated frequency shifter for true doppler detection

Patent metadata

Field	Value
Publication number	US-2020088878-A1
Application number	US-201916554866-A
Country	US
Kind code	A1
Filing date	Aug 29, 2019
Priority date	Sep 14, 2018
Publication date	Mar 19, 2020
Grant date	—

Abstract

A vehicle, Lidar system and method of detecting an object is disclosed. The Lidar system includes a photonic chip having a laser, an on-chip frequency shifter, a combiner and a first set of photodetectors. The laser generates a transmitted light beam and an associated local oscillator beam within the photonic chip. The on-chip frequency shifter shifts a frequency of the local oscillator beam. The combiner combines a reflected light beam with the frequency-shifted local oscillator beam, wherein the reflected light beam is a reflection of the transmitted light beam from the object to generate a first electronic signal at the first set of photodetectors. A processor obtains a first measurement of a parameter of the object from the first electronic signal. The vehicle includes a navigation system for navigating the vehicle with respect to the object using at least the first measurement of the parameter.

First claim

What is claimed is:

1 . A method of detecting an object, comprising:
generating, at a laser of a photonic chip, a transmitted light beam and an associated local oscillator beam; shifting a frequency of the associated local oscillator beam via a frequency shifter of the photonic chip to obtain a frequency-shifted local oscillator beam; combining, at a combiner of the photonic chip, a reflected light beam with the frequency-shifted local oscillator beam, the reflected light beam being a reflection of the transmitted light beam from the object; and obtaining a first measurement of a parameter of the object from the combination of the reflected light beam and the frequency-shifted local oscillator beam at a first set of photodetectors.

2 . The method of claim 1 , further comprising generating the transmitted light beam and the associated local oscillator beam from a chirp signal.

3 . The method of claim 2 , further comprising shifting the frequency of the associated local oscillator beam by shifting a phase of the chirp signal in a local oscillator waveguide of the photonic chip by a selected amount.

4 . The method of claim 1 , further comprising transmitting the transmitted light beam from the photonic chip via a first aperture and receiving the reflected light beam at the photonic chip via a second aperture.

5 . The method of claim 1 , further comprising combining the reflected light beam with an unshifted local oscillator beam and obtaining a second measurement of the parameter of the object from the combination of the reflected light beam with the unshifted local oscillator beam at a second set of photodetectors.

6 . The method of claim 5 , further comprising removing a Doppler ambiguity for the object from a comparison of the first measurement of the parameter of the object and the second measurement of the parameter of the object.

7 . The method of claim 1 , further comprising navigating a vehicle with respect to the object using at least the first measurement of the parameter of the object.

8 . A Lidar system, comprising:
a photonic chip comprising:
a laser configured to generate a transmitted light beam and an associated local oscillator beam within the photonic chip;
an on-chip frequency shifter configured to shift a frequency of the associated local oscillator beam to obtain a frequency-shifted local oscillator beam;
a combiner configured to combine a reflected light beam with the frequency-shifted local oscillator beam, wherein the reflected light beam is a reflection of the transmitted light beam from an object; and
a first set of photodetectors configured to generate a first electronic signal related to the combination of the frequency-shifted local oscillator beam and the reflected light beam; and
a processor configured to obtain a first measurement of a parameter from the first electronic signal.

9 . The Lidar system of claim 8 , wherein the laser is controllable to generate a chirp signal for the transmitted light beam and the associated local oscillator beam.

10 . The Lidar system of claim 9 , wherein the on-chip frequency shifter is configured to shift the frequency of the associated local oscillator beam by shifting a phase of the chirp signal in a local oscillator waveguide by a selected amount.

11 . The Lidar system of claim 10 , further comprising a first aperture of the photonic chip by which the transmitted light beam exits the photonic chip and a second aperture of the photonic chip by which the reflected light beam enters the photonic chip.

12 . The Lidar system of claim 8 , wherein the photonic chip further comprises a second set of photodetectors configured to generate a second electronic signal related to a combination of the reflected light beam with an unshifted local oscillator beam.

13 . The Lidar system of claim 12 , wherein the processor is further configured to remove a Doppler ambiguity for the object from a comparison of the first electronic signal and the second electronic signal.

14 . The Lidar system of claim 8 , further comprising a navigation system configured to navigate a vehicle with respect to the object using at least the first measurement of the parameter of the object.

15 . A vehicle, comprising:
a photonic chip comprising:
a laser configured to generate a transmitted light beam and an associated local oscillator beam within the photonic chip;
an on-chip frequency shifter configured to shift a frequency of the associated local oscillator beam to obtain a frequency-shifted local oscillator beam;
a combiner configured to combine a reflected light beam with the frequency-shifted local oscillator beam, wherein the reflected light beam is a reflection of the transmitted light beam from an object; and
a first set of photodetectors configured to generate a first electronic signal related to the combination of the frequency-shifted local oscillator beam and the reflected light beam;
a processor configured to obtain a first measurement of a parameter from the first electronic signal; and a navigation system configured to navigate the vehicle with respect to the object using at least the first measurement of the parameter of the object.

16 . The vehicle of claim 15 , wherein the laser is controllable to generate a chirp signal for the transmitted light beam and the associated local oscillator beam.

17 . The vehicle of claim 16 , wherein the on-chip frequency shifter is configured to shift the frequency of the associated local oscillator beam by shifting a phase of the chirp signal in a local oscillator waveguide by a selected amount.

18 . The vehicle of claim 17 , further comprising a first aperture of the photonic chip by which the transmitted light beam exits the photonic chip and a second aperture of the photonic chip by which the reflected light beam enters the photonic chip.

19 . The vehicle of claim 15 , wherein the photonic chip further comprises a second set of photodetectors configured to generate a second electronic signal related to a combination of the reflected light beam with an unshifted local oscillator beam.

20 . The vehicle of claim 19 , wherein the processor is further configured to remove a Doppler ambiguity for the object from a comparison of the first electronic signal and the second electronic signal.

Assignees

• Gm Global Tech Operations Llc

Inventors

• Talty Timothy J
• Sayyah Keyvan
• Mulqueen Michael
• Kremer Richard

Classifications

• G01S17/931 Primary

  of land vehicles · CPC title

• G01S17/42 Primary

  Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S17/46) · CPC title

• G01S17/34

  using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal · CPC title

• G01S7/4913

  Circuits for detection, sampling, integration or read-out · CPC title

• G01S7/4817

  relating to scanning · CPC title