Methods and apparatus for LIDAR operation with pulse position modulation
Described examples include an integrated circuit that includes an encoder configured to modulate a driving signal for an optical transmitter with a plurality of encoded pulses corresponding to a code, in which the driving signal is transmitted to the optical transmitter periodically. The integrated circuit also includes a demodulator configured to receive a received 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 plurality of encoded pulses in the received signal and estimate a distance of the object.
1. An integrated circuit, comprising:
an encoder adapted to be coupled to an optical transmitter, the encoder configured to drive the optical transmitter to emit light having a sequence of encoded pulses according to a code, the encoded pulses including first and second pulses, in which a width or an amplitude of the first pulse varies from a width or an amplitude of the second pulse; and
a demodulator adapted to be coupled to an optical receiver, the demodulator configured to receive a signal from the optical receiver, in which the received signal includes pulses of a reflection of the emitted light, and the demodulator is configured to estimate a distance of the reflection by comparing the encoded pulses to the received signal's pulses.
2. The integrated circuit of claim 1 , wherein the code is encoded using pulse position modulation.
3. The integrated circuit of claim 1 , wherein the code is preassigned.
4. The integrated circuit of claim 1 , wherein the code is generated using a pseudo random generator.
5. The integrated circuit of claim 1 , wherein the demodulator includes an analog to digital converter configured to convert the received signal into a digital value.
6. The integrated circuit of claim 1 , wherein the demodulator includes a time to digital converter configured to convert the received signal into time signals.
7. The integrated circuit of claim 1 , wherein the optical transmitter is a laser diode.
8. The integrated circuit of claim 1 , wherein the optical receiver is a photodiode.
9. An apparatus, comprising:
an encoder having an encoder output and configured to provide a driving signal at the encoder output;
an optical transmitter having a transmitter input coupled to the encoder output, the optical transmitter configured to emit light responsive to the driving signal, the emitted light having a sequence of encoded pulses according to a code, the encoded pulses including first and second pulses, in which a width or an amplitude of the first pulse varies from a width or an amplitude of the second pulse;
an optical receiver having a receiver output, the optical receiver configured to receive a reflection of the emitted light and to provide a reflection signal at the receiver output that includes pulses of the reflection; and
a demodulator having a demodulator input coupled to the receiver output, the demodulator configured to estimate a distance of the reflection by comparing the encoded pulses to the reflection signal's pulses.
10. The apparatus of claim 9 , wherein the code is encoded using pulse position modulation.
11. The apparatus of claim 9 , wherein the demodulator includes an analog to digital converter configured to convert the reflection signal into a digital value.
12. The apparatus of claim 9 , wherein the code is preassigned.
13. The apparatus of claim 9 , wherein the code is generated using a pseudo random generator.
14. The apparatus of claim 9 , wherein the optical transmitter is a laser diode.
15. The apparatus of claim 9 , wherein the optical receiver is a photodiode.
16. A method, comprising:
at an optical transmitter, emitting light having a sequence of encoded pulses that include first and second pulses, in which a width or an amplitude of the first pulse varies from a width or an amplitude of the second pulse;
at an optical receiver, receiving a reflection of the emitted light, and providing a signal that includes pulses of the reflection;
determining a time of flight by comparing the encoded pulses to the provided signal's pulses; and
responsive to the time of flight, estimating a distance of the reflection.
17. The method of claim 16 , wherein the encoded pulses are encoded with an orthogonal code using pulse position modulation.
18. The method of claim 16 , wherein the encoded pulses are encoded with a preassigned code.
19. The method of claim 16 , wherein the encoded pulses are encoded with a code that is generated using a pseudo random generator.