Use of frequency offsets in generation of LIDAR data
A LIDAR system includes a light source that outputs an outgoing LIDAR signal that includes multiple different channels. The LIDAR system also generate multiple composite light signals that each carries a signal couple and are each associated with a different one of the channels. A signal couple includes a reference signal and an associated comparative signal. The comparative signals each include light from the outgoing LIDAR signal that has been reflected by one or more objects located outside of the LIDAR system. The reference signals also include light from the outgoing LIDAR signal but also exclude light that has been reflected by any object located outside of the LIDAR system. There is a frequency differential between a frequency of the reference signal and a frequency of the associated comparative signal. The frequency differential includes a contribution from a frequency offset that is induced by electronics. The electronics induce the frequency offset such that the frequency offset is different for each signal couple.
1. A method of operating a LIDAR system, comprising:
a step for outputting from a light source an outgoing LIDAR signal,
a step for generating multiple composite light signals that each carries at least a signal couple, a signal couple including a reference signal and an associated comparative signal, each signal couple being associated with a different channel,
the comparative signals each including light from the outgoing LIDAR signal that has been reflected by one or more objects located outside of the LIDAR system and the reference signals each including light from the outgoing LIDAR signal but excluding light that has been reflected by any object located outside of the LIDAR system; and
a step for outputting from the LIDAR system LIDAR output signals,
the LIDAR output signals having a frequency versus time pattern that is repeated over sequential cycles,
the comparative signals each including light from a different one of the LIDAR output signals,
each cycle includes multiple data periods and the frequency versus time pattern is the same for corresponding data periods in different cycles,
one or more of the data periods includes an output period and a feedback period, a rate of a frequency change in the LIDAR output signals being the same during the output period and the feedback period of the same data period, and
an offset period being present between the output period and the feedback period in each data period that is included in the one or more data periods, the frequency of the LIDAR output signal changing by a frequency offset during the offset period.
2. The method of claim 1 , wherein light included in each reference signal and in the associated comparative signal was generated by the same laser.
3. The method of claim 1 , wherein each signal couple has a non-zero frequency differential.
4. The method of claim 3 , wherein the frequency offset of each LIDAR output signal is a portion of the frequency differential for the signal couple having the comparative signal that includes light from the LIDAR output signal.
5. The method of claim 4 , wherein a portion of the frequency differential is induced by a distance between the LIDAR system and the one or more objects located outside of the LIDAR system.
6. The method of claim 1 , wherein for at least a portion of the LIDAR output signals, each cycle includes multiple data periods and each data period includes an offset period between the output period and the feedback period.
7. The method of claim 1 , further comprising: generating LIDAR data from composite signals that occur during the feedback periods but not during the output periods, the LIDAR data indicating a distance and/or radial velocity between the LIDAR system and the one or more objects.
8. The method of claim 1 , wherein the composite light signals are each generated by a light-combining component configured to combine one of the reference signals with the associated comparative signal.