US-20260126534-A1 - MONITORING SIGNAL CHIRP IN LIDAR OUTPUT SIGNALS

US20260126534A1US 20260126534 A1US20260126534 A1US 20260126534A1US-20260126534-A1

Abstract

A LIDAR system is configured to output a system output signal that travels away from the LIDAR system and can be reflected by an object located outside of the LIDAR system. The system output signal includes light from an outgoing LIDAR signal. The LIDAR system has a feedback loop configured to control a frequency versus time pattern of the system output signal. The feedback loop includes an interferometer with a recirculation pathway configured such that a circulated signal travels through the recirculation pathway multiple times before being included in the output of the interferometer. The circulated signal includes light from the outgoing LIDAR signal.

Inventors

Amir Ali Tavallaee
PATRICK NERCESSIAN
Farzin Beygi Azar Aghbolagh
Bradley Jonathan Luff

Assignees

SILC TECHNOLOGIES, INC.

Dates

Publication Date: 20260507
Application Date: 20241105

Claims (11)

1 . A system, comprising: a LIDAR system configured to output a system output signal that travels away from the LIDAR system and can be reflected by an object located outside of the LIDAR system, the system output signal including light from an outgoing LIDAR signal; and the LIDAR system including a feedback loop configured to control a frequency versus time pattern of the system output signal, the feedback loop including an interferometer with a recirculation pathway, and the interferometer being configured such that a circulated signal travels through the recirculation pathway multiple times before being included in an output of the interferometer, the circulated signal including light from the outgoing LIDAR signal.
2 . The system of claim 1 , wherein the interferometer includes a light signal combiner configured to combine light from the circulated signal with light from an expedited signal so as to generate an optical beating signal, the expedited signal including light from the outgoing LIDAR signal.
3 . The system of claim 1 , wherein the LIDAR system includes a frequency identifier configured to identify a frequency of the outgoing LIDAR signal.
4 . The system of claim 1 , wherein an active portion of the circulated signal travels through the recirculation pathway an active number of times and an inactive portion of the circulated signal travels through the recirculation pathway an inactive number of times, the active number of times being greater than or equal to 2 , and the feedback loop being configured to use the active portion of the circulated signal to control the frequency versus time pattern of the system output signal without using the inactive portion of the signal to control the frequency versus time pattern of the system output signal.
5 . The system of claim 4 , wherein the feedback loop includes a filter configured to filter out a contribution of the inactive portion of the circulated signal from a circulation resultant signal, the circulation resultant signal including a contribution from the circulated signal, and the feedback loop being configured to use the circulation resultant signal to control the frequency versus time pattern of the system output signal.
6 . The system of claim 5 , wherein the circulation resultant signal is an optical signal.
7 . The system of claim 6 , wherein the circulation resultant signal is an electrical signal.
8 . The system of claim 1 , wherein the interferometer includes a light signal combiner configured to combine light from the circulated signal with light from an expedited signal so as to generate an optical beating signal that serves as an output of the interferometer, the expedited signal including light from the outgoing LIDAR signal, and the LIDAR system includes a frequency identifier configured to identify a frequency of the outgoing LIDAR signal.
9 . The system of claim 1 , wherein the recirculation pathway has a length selected such that a circulation time for the circulated signal to make a single pass through the recirculation pathway is less than 30 ns.
10 . The system of claim 9 , wherein the recirculation pathway has a length selected such that the circulation time is greater than 1 ns.
11 . The system of claim 4 , wherein the interferometer includes a light signal combiner configured to combine light from the circulated signal with light from an expedited signal so as to generate an optical beating signal that serves as an output of the interferometer, the expedited signal including light from the outgoing LIDAR signal, and the interferometer having a delay pathway from an input of the interferometer to the light signal combiner, the delay pathway including the recirculation pathway, the interferometer having an expedited pathway from an input of the interferometer to the light signal combiner, the length of the expedited pathway and the delay pathway being selected such that a difference between a time that the light from the expedited signal travels the expedited pathway and a time that light from the active portion of the circulated signal travels the delay pathway is more than 1 ns and less than 30 ns.

Description

FIELD The invention relates to optical devices. In particular, the invention relates to LIDAR systems. BACKGROUND There is an increasing commercial demand for LIDAR systems that can be deployed in applications such as ADAS (Advanced Driver Assistance Systems) and AR (Augmented Reality). LIDAR (Light Detection and Ranging) systems typically output a system output signal that is reflected by an object located outside of the LIDAR system. At least a portion of the reflected light signal returns to the LIDAR system. The LIDAR system directs the received light signal to a light sensor that converts the light signal to an electrical signal. Electronics can use the light sensor output to quantify LIDAR data that indicates the radial velocity and/or distance between the object and the LIDAR system. Many LIDAR systems tune the frequency of the system output signal linearly, or with other well-defined waveforms, over time to enable the accurate measurement of LIDAR data. In these instances, the LIDAR system can monitor the frequency of the system output signal and tune the frequency in response to the monitored frequency to achieve the desired waveform shape. The systems that monitor the frequency of the system output signal can require one or more waveguides that need to be undesirably long in order to achieve the desired results. As a result of this waveguide length, these systems often occupy a large percentage of the available space on a LIDAR chip. As a result, there is a need for an improved system for monitoring the frequency of LIDAR system output signals. SUMMARY A LIDAR system is configured to output a system output signal that travels away from the LIDAR system and can be reflected by an object located outside of the LIDAR system. The system output signal includes light from an outgoing LIDAR signal. The LIDAR system has a feedback loop configured to control a frequency versus time pattern of the system output signal. The feedback loop includes an interferometer with a recirculation pathway configured such that a circulated signal travels through the recirculation pathway multiple times before being included in the output of the interferometer. The circulated signal includes light from the outgoing LIDAR signal. In some instances, the interferometer includes a light signal combiner configured to combine light from the circulated signal with light from an expedited signal so as to generate a beating signal where the expedited signal includes light from the outgoing LIDAR signal. The LIDAR system can include a frequency identifier configured to identify a beat frequency of the outgoing LIDAR signal. In some instances, an active portion of the circulated signal travels through the recirculation pathway an active number of times and an inactive portion of the circulated signal travels through the recirculation pathway an inactive number of times. The active number is greater than 1. The feedback loop can be configured to use the active portion of the circulated signal to control the frequency versus time pattern of the system output signal without using the inactive portion of the signal to control the frequency versus time pattern of the system output signal. The feedback loop can include a filter configured to filter out a contribution of the inactive portion of the circulated signal from a circulation resultant signal that includes a contribution from the circulated signal. The feedback loop can be configured to use the circulation resultant signal to control the frequency versus time pattern of the system output signal. The interferometer can include a light signal combiner configured to combine light from the circulated signal with light from an expedited signal so as to generate an optical beating signal that serves as an output of the interferometer. The expedited signal can include light from the outgoing LIDAR signal. The LIDAR system can include a beat frequency identifier configured to identify a frequency of the outgoing LIDAR signal. BRIEF DESCRIPTION OF THE FIGURES FIG. 1A is a topview of a schematic of a LIDAR system that includes or consists of a LIDAR chip that outputs a LIDAR output signal and receives a LIDAR input signal on a common waveguide. FIG. 1B is a topview of a schematic of a LIDAR system that includes or consists of a LIDAR chip that outputs a LIDAR output signal and receives a LIDAR input signal on different waveguides. FIG. 1C is a topview of a schematic of another embodiment of a LIDAR system that that includes or consists of a LIDAR chip that outputs a LIDAR output signal and receives multiple LIDAR input signals on different waveguides. FIG. 2 is a topview of an example of a LIDAR adapter that is suitable for use with the LIDAR chip of FIG. 1B. FIG. 3 is a topview of an example of a LIDAR adapter that is suitable for use with the LIDAR chip of FIG. 1C. FIG. 4 is a topview of an example of a LIDAR system that includes the LIDAR chip of FIG. 1A and the LIDAR adapter of FIG. 2 on