Method and system for encoding and decoding LiDAR
The present disclosure describes a system and method for encoding pulses of light for LiDAR scanning. The system includes a sequence generator, a light source, a modulator, a light detector, a correlator, and a microprocessor. The sequence generator generates a sequence code that the modulator encodes into a pulse of light from the light source. The encoded pulse of light illuminates a surface of an object, in which scattered light from the encoded light pulse is detected. The correlator correlates the scattered light with the sequence code that outputs a peak value associated with a time that the pulse of light is received. The microprocessor is configured to determine a time difference between transmission and reception of the pulse of light based on whether the amplitude of the peak exceeds the threshold value. The microprocessor calculates a distance to the surface of the object based on the time difference.
1. A light detection and ranging (LiDAR) scanning system, comprising:
a light source, wherein the light source is configured to transmit a pulse of light to illuminate a surface of an object;
a modulator operable to encode the pulse of light with a sequence code in response to a signal from a sequence generator;
a light detector configured to detect a pulse of scattered light from the surface of the object originating from the light pulse;
a correlator electrically coupled to the light detector, wherein the correlator is configured to correlate the pulse of scattered light with the sequence code and output a peak value associated with a time that the pulse of scattered light is received, and
a microprocessor electrically coupled to the light source and the correlator, wherein the microprocessor is configured to:
determine whether an amplitude of the peak value exceeds a threshold value;
in accordance with a determination that the amplitude of the peak exceeds the threshold value:
determine a time difference between a time that pulse of light was transmitted and the time that the pulse of light is received;
calculate a distance to the surface of the object based on the time difference; and
determine a reflectivity of the surface of the object based on the amplitude of the peak value.
2. The LiDAR scanning system of claim 1 , wherein the light source is a laser diode light source.
3. The LiDAR scanning system of claim 2 , wherein the modulator is configured to modulate an injection current to the laser diode in accordance with on-off keying.
4. The LiDAR scanning system of claim 1 , wherein modulator is an opto-electrical modulator situated in the optical path of the pulse of light.
5. The LiDAR scanning system of claim 1 , wherein modulator is a Mach-Zehnder modulator situated in the optical path of the pulse of light.
6. The LiDAR scanning system of claim 1 , wherein the detector is a photodiode.
7. The LiDAR scanning system of claim 1 , wherein the detector is a photomultiplier tube.
8. The LiDAR scanning system of claim 1 , wherein the detector further comprises an analog to digital converter configured to convert the detected pulse of scattered light to an electrical digital signal.
9. The LiDAR scanning system of claim 1 , wherein the correlator is a module embedded within the microprocessor.
10. The LiDAR scanning system of claim 1 , wherein the correlator is an optical modulator configured to implement four-wave-mixing.
11. The LiDAR scanning system of claim 1 , wherein the sequence generator is a module embedded within the microprocessor.
12. The LiDAR scanning system of claim 1 , wherein the sequence code is a pseudorandom bit sequence code.
13. The LiDAR scanning system of claim 12 , wherein the pseudorandom bit sequence code is PRBS-5.
14. The LiDAR scanning system of claim 1 , wherein the threshold value is at least one standard deviation above an average of the output from the correlator.
15. A method for light detection and ranging (LiDAR) scanning detection, the method comprising:
encoding a pulse of light from a light source with a sequence code;
transmitting the pulse of light to illuminate a surface of an object;
detecting, at a detector, a pulse of scattered light from the illuminated surface of the object;
correlating the detected pulse of scattered light with the sequence code that outputs a peak value associated with a time that the pulse of scattered light is received;
determining whether an amplitude of the peak value exceeds a threshold value;
in accordance with a determination that the amplitude of the peak exceeds the threshold value:
determining a time difference between a time that pulse of light was transmitted and the time the pulse of scattered light is received;
calculating a distance to the surface of the object based on the time difference; and
determining a reflectivity of the surface of the object based on the amplitude of the peak value.
16. The method of claim 15 , wherein the sequence code is a pseudorandom bit sequence code.
17. The method of claim 15 , wherein the threshold value is at least one standard deviation above an average of the output from the correlator.