Multi-line, high-definition LiDAR device and method with integrated direct spatial reference
The present disclosure relates to a FMCW Light Detection and Ranging system, a wave train of carrier frequency is modulated in narrow-band sequence, an delay interferometer with in-phase and quadrature outputs extracts the phase of this frequency modulation, and a coherent receiver with in-phase and quadrature outputs detects the phase of reflected light from a remote object, the ratio between two phases determines the distance of the remote object.
1. A Light Detection and Ranging (LiDAR) system comprising,
a light source configured to emit light with a frequency modulated in narrow-band time sequence;
an optical transmitter waveguide configured to guide the emitted light toward a remote object;
an optical receiver waveguide configured to receive reflection light from the remote object;
a reference delay interferometer configured to interfere reference light with a delay of the reference light and produce a first in-phase output and a first quadrature output;
a coherent receiver configured to mix the emitted light with the reflection light and produce [an]a second in-phase output and a second quadrature output; and
a processor configured to calculate a first phase variance related to the modulated frequency based on the first in-phase output, the first quadrature output, and a second phase variance related to the modulated frequency based on second in-phase output and the second quadrature output,
wherein the reference light is derived from the emitted light.
2. The LiDAR system according to claim 1 , wherein the optical transmitter waveguide and the optical receiver waveguide are integrated in a duplex waveguide.
3. The LiDAR system according to claim 1 , further comprising optical lens arranged after the optical transmitter waveguide and the optical receiver waveguide.
4. The LiDAR system according to claim 1 , wherein the processor is further configured to derive a ratio between the first phase variance and the second phase variance and calculate the absolute distance of the remote object.
5. The LiDAR system according to claim 1 , wherein the second in-phase output and second quadrature output comprise a low frequency component representing the trending of phase change, the processor is configured to extract [a]the low frequency component of the second in-phase output and second quadrature output, and calculate a relative radial velocity of the remote object based on the low frequency component.
6. The LiDAR system according to claim 1 , further comprising a multiple line generation circuit configured to duplicate the output of the transmitter waveguide and/or the input of the receiver waveguide into multiple lines.
7. The LiDAR system according to claim 6 , further comprising multiple optical switches each corresponding to each of the multiple lines.
8. The LiDAR system according to claim 6 , further comprising a mechanical system configured to rotate and delivers the emitted light towards different orientations.
9. The LiDAR system according to claim 6 , further comprising an echo cancelling electrical circuit configured to mitigate unintended reflection from components within the system.
10. The LiDAR system according to claim 9 wherein the echo cancelling electrical circuit comprising, an echo detector coupled to the coherent receiver; and
a loopback control path configured to calculate an add-on current and apply the add-on current to a current received from the second in-phase output and the second quadrature output of the coherent receiver.
11. The LiDAR system according to claim 6 , further comprising an echo cancelling optical circuit, configured to mitigate unintended reflection from components within the system.
12. The LiDAR system according to claim 11 , wherein the echo cancelling optical circuit comprising:
an echo detector coupled to the coherent receiver;
a variable optical attenuator coupled to the optical transmitter waveguide and the optical receiver waveguide;
a phase adjustor coupled to the optical attenuator; and
a loopback control path configured to calculate an attenuation of the variable optical attenuator and a phase value of the phase adjustor so as to match the unintended reflection applied to the coherent receiver.
13. A light detection and ranging method comprising:
emiting light with a frequency modulated in narrow-band time sequence;
guiding the emitted light toward a remote object;
receiving reflection light from the remote object;
interfering reference light with a delay of the reference light and produce a first in-phase output and a first quadrature output;
mixing the emitted light with the reflection light and produce [an]a second in-phase output and a second quadrature output; and
calculating a first phase variance related to the modulated frequency based on the first in-phase output and the first quadrature output, and a second phase variance related to the modulated frequency based on second in-phase output and the second quadrature output;
wherein the reference light is derived from the emitted light.
14. The method according to claim 13 , further comprising deriving a ratio between the first phase variance and the second phase variance and calculate the distance of the remote object.
15. The method according to claim 14 , wherein the second in-phase output and second quadrature output comprise a low frequency component representing the trending of phase change, and the method further comprising extracting a low frequency component of the second in-phase output and second quadrature output, and calculating a relative radial velocity of the remote object based on the low frequency component.