Methods and apparatus for LIDAR operation with narrowband intensity modulation

Patent metadata

Field	Value
Publication number	US-10908287-B2
Application number	US-201615396457-A
Country	US
Kind code	B2
Filing date	Dec 31, 2016
Priority date	May 10, 2016
Publication date	Feb 2, 2021
Grant date	Feb 2, 2021

Abstract

In described examples, an integrated circuit includes a modulator configured to modulate a driving signal for an optical transmitter with a narrow band modulation signal in which the driving signal with a fixed duration is transmitted to the optical transmitter periodically. The integrated circuit also includes a demodulator configured to receive a signal from an optical receiver that is configured to receive a reflection of light transmitted by the optical transmitter off an object, the demodulator configured to discriminate the narrow band modulation signal and estimate a distance of the object using the narrow band modulation signal.

First claim

What is claimed is:

1. An optical ranging apparatus comprising:
a modulator that generates a driving signal with a narrow band modulation signal and with a fixed duration, the modulator having an output;
an optical transmitter having an input coupled to the output of the modulator, and having an output configured to be coupled to a light source, wherein the light source emits a modulated light signal in response to a pulsed signal received from the output of the optical transmitter;
a first optical receiver having an input configured to receive the modulated light signal, and having an output;
a second optical receiver having an input configured to receive light from the modulated light signal reflecting off an object, and having an output; and
a demodulator having a first input coupled to the output of the first optical receiver, a second input coupled to the output of the second optical receiver, and a third input coupled to the output of the optical transmitter and receiving the pulsed signal from the output of the optical transmitter, wherein the demodulator is configured to discriminate the narrow band modulation signal, perform a correlation function on the narrow band modulated signal and the output of the first optical receiver, determine the peak in the correlation function corresponding to a time delay, and use the time delay to estimate a distance from the object.

2. The optical ranging apparatus of claim 1 in which the narrow band modulation signal is a single modulation tone.

3. The optical ranging apparatus of claim 1 in which the narrow band modulation signal is a pseudo-random sequence of tones.

4. The optical ranging apparatus of claim 1 in which the narrow band modulation signal is a monotonic sequence of tones.

5. The optical ranging apparatus of claim 1 in which the demodulator includes a narrow bandpass filter to discriminate the narrow band modulation signal.

6. The optical ranging apparatus of claim 1 in which the demodulator includes a plurality of bandpass filters to discriminate the narrow band modulation signal.

7. The optical ranging apparatus of claim 1 in which the narrow band modulation signal is a multiple tone signal and the demodulator includes a narrow bandpass filter to discriminate the narrow band modulation signals.

8. The optical ranging apparatus of claim 1 in which the optical transmitter is a laser emitting device and the optical receiver is a photodiode.

9. A method for operating an optical ranging apparatus comprising:
providing a narrow band modulation signal to a pulse generator to provide a pulsed modulated signal to a driver;
driving an optical transmitter using the pulsed modulated signal from the driver, the optical transmitter emitting a modulated light signal;
receiving the modulated light signal at a first optical receiver to provide a first received modulated signal;
receiving a modulated light signal reflected off an object at a second optical receiver to provide a second received modulated signal;
filtering the first and second received modulated signals with a narrow bandpass filter to provide a filtered received modulated signal;
receiving the pulsed modulated signal from the driver and the filtered first and second received modulated signals at a receive processor;
performing a correlation function on the filtered first and second received modulated signals, using the pulsed modulated signal as a time reference;
determining the peak in the correlation function, which corresponds to a time delay; and
estimating a distance of the object from the optical ranging apparatus using the time delay.

10. The method for operating an optical ranging apparatus of claim 9 in which the narrow band modulation signal includes a plurality of tones.

Assignees

• Texas Instruments Inc

Inventors

• Warke Nirmal C
• Magee David P
• Haroun Baher S

Classifications

• G01S17/10 Primary

  using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) · CPC title

• G01S7/487

  Extracting wanted echo signals {, e.g. pulse detection} · CPC title

• G01S7/484

  Transmitters · CPC title

• G01S17/42

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

• G01S17/32 Primary

  using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated · CPC title