Lidar system using a pseudo-random pulse sequence

1. A light detection and ranging system, comprising:

a transmitter transmitting a transmitted tight pulse timing sequence, with pseudo-random timing and including a plurality of light pulses, toward a target;

an optical receiver receiving a reflected light pulse timing sequence including a plurality of light pulses from the target; and

an electronic control unit identifying a time delay between the transmitted light pulse timing sequence and the reflected light pulse timing sequence as a function of a correlation between the transmitted and reflected light pulse timing sequences, the correlation being a representation of a single-bit clipped square wave representation of the transmitted light pulse timing sequence overlaid by, and shifted from, the reflected light pulse timing sequence, which is unclipped.

2. The light detection and ranging system as set forth in claim 1 , wherein the light pulses of the transmitted light pulse timing sequence include peaks above a predetermined transmit-threshold at respective time intervals.

3. The light detection and ranging system as set forth in claim 2 , wherein the time intervals between the transmitted light pulse timing sequence peaks are chosen to reduce spurious self-correlations.

4. The light detection and ranging system as set forth in claim 3 , wherein the time intervals between the transmitted light pulse timing sequence peaks are related to prime numbers.

5. The light detection and ranging system as set forth in claim 2 , wherein:

the light pulses of the reflected light pulse timing sequence include peaks above a predetermined reflected threshold at the time intervals.

6. The light detection and ranging system as set forth in claim 1 , wherein:

the correlation is a representation of the transmitted light pulse timing sequence overlaid by, and shifted from, the reflected light pulse timing sequence.

7. The light detection and ranging system as set forth in claim 6 , wherein:

respective shifts represent a time between the transmitted and reflected light pulse timing sequences;

for each of the shifts, respective products are determined for values of the transmitted and the reflected light pulse timing sequences at a plurality of times;

for each of the shifts, a sum of the products is determined;

a sum having a correlation peak above a predetermined threshold is identified; and

the time delay between the transmitted and reflected light pulses is determined as a function of the shift between the transmitted and reflected light pulse timing sequences at the correlation peak.

8. The light detection and ranging system as set forth in claim 7 , wherein:

a range between the target and the receiver is determined as a function of the time delay.

9. The light detection and ranging system as set forth in claim 7 , wherein:

a second sum having a second correlation peak above the predetermined threshold is identified; and

a second time delay between the transmitted and reflected light pulses is determined as a function of the shift between the transmitted and reflected light pulse timing sequences at the second correlation peak.

10. The light detection and ranging system as set forth in claim 9 , wherein:

a second range between a second target and the receiver is determined as a function of the second time delay.

11. The light detection and ranging system as set forth in claim 1 , wherein:

respective shifts represent a time between the square wave representation and the reflected light pulse timing sequence;

for each of the shifts, a sum of values of the reflected light pulse timing sequence is determined for times at which the square wave representation is not zero;

a sum having a correlation peak above a predetermined threshold is identified; and

the time delay between the transmitted and reflected light pulse timing sequences is determined as a function of the shift between the square wave representation and the reflected light pulse timing sequence at the correlation peak.

12. A method of determining a range to a target, the method comprising:

transmitting a transmitted light pulse timing sequence, with pseudo-random timing and including a plurality of light pulses, toward the target;

receiving, at an optical receiver, a reflected light pulse timing sequence including a plurality of light pulses from the target; and

identifying a time delay between the transmitted light pulse timing sequence and the reflected light pulse timing sequence as a function of a correlation between the transmitted and reflected light pulse timing sequences, the correlation being a representation of a single-bit clipped square wave representation of the transmitted light pulse timing sequence overlaid by, and shifted from, the reflected light pulse timing sequence, which is unclipped.

13. The method of determining a range to a target as set forth in claim 12 , wherein the transmitting step includes:

transmitting peaks, in the light pulses, above a predetermined transmit-threshold at respective time intervals.

14. The method of determining a range to a target as set forth in claim 13 , further including:

relating the time intervals between the transmitted light pulse timing sequence peaks to prime numbers.

15. The method of determining a range to a target as set forth in claim 12 , further including:

creating the correlation between the transmitted and reflected light pulse timing sequences, including:

shifting a representation of the transmitted light pulse timing sequence from a representation of the reflected light pulse timing sequence; and

overlaying the representation of the transmitted light pulse timing sequence with the shifted reflected light pulse timing sequence.

16. The method of determining a range to a target as set forth in claim 15 , further including:

determining respective shifts representing a time between the transmitted and reflected light pulse timing sequences;

for each of the shifts, determining respective products for values of the transmitted and the reflected light pulse timing sequences at a plurality of times;

for each of the shifts, determining a sum of the products;

identifying a sum having a correlation peak above a predetermined threshold; and

determining the time delay between the transmitted and reflected light pulses as a function of the shift between the transmitted and reflected light pulse timing sequences at the correlation peak.

17. The method of determining a range to a target as set forth in claim 16 , further including:

determining a range between the target and the receiver as a function of the time delay.

18. A light detection and ranging system, comprising:

a pulse forming network generating an electrical pulse;

a converter that converts the electrical pulse into an optical pulse;

a splitter that divides the optical pulse into divided light pulses that form a transmitted light pulse timing sequence with pseudo-random timing and including a plurality of light pulses;

a transmitter transmitting the transmitted light pulse timing sequence toward a target;

an optical receiver receiving a reflected light pulse timing sequence including a plurality of light pulses from the target; and

an electronic control unit identifying a time delay between the transmitted light pulse timing sequence and the reflected light pulse timing sequence as a function of a correlation between the transmitted and reflected light pulse timing sequences, the correlation being a representation of a single-bit clipped square wave representation of the transmitted light pulse timing sequence overlaid by, and shifted from, the reflected light pulse timing sequence, which is unclipped.

19. The light detection and ranging system as set forth in claim 18 , further including:

a gain amplifier that amplifies the transmitted light pulse timing sequence to ensure all of the pulses have amplitudes greater than a predetermined transmit-threshold.

20. The light detection and ranging system as set forth in claim 18 , wherein the converter is a diode.