US-12625262-B2 - Lidar system with enhanced performance

US12625262B2US 12625262 B2US12625262 B2US 12625262B2US-12625262-B2

Abstract

A LIDAR system includes a transmitter, a receiver, and a processor. The transmitter directs a sequence of illumination pulses toward a scene. The receiver including an array of photodetectors, which receive optical radiation reflected from the scene and output respective signals in response to the received optical radiation, a shutter which modulates the signals output by the photodetectors by applying a chirp shutter function, having a selected chirp period, to the signals, and a readout circuit, which samples and digitizes the modulated signals in each of a plurality of sampling windows, which span the chirp period, thereby generating a corresponding plurality of digitized output signals. The processor selects respective sampling windows for the photodetectors, and processes the digitized output signals in the selected respective sampling windows to generate a depth map of the scene.

Inventors

Vladimir Koifman
Tiberiu Galambos

Assignees

APPLE INC.

Dates

Publication Date: 20260512
Application Date: 20230116

Claims (9)

1 . A LIDAR system, comprising: a transmitter, which is configured to direct a sequence of illumination pulses toward a scene; a receiver, comprising: an array of photodetectors, which are configured to receive optical radiation reflected from the scene and to output respective signals in response to the received optical radiation; a shutter, which is configured to modulate the signals output by the photodetectors by applying a chirp shutter function, having a selected chirp period, to the signals; and a readout circuit, which is configured to sample and digitize the modulated signals in each of a plurality of sampling windows, which span the chirp period, thereby generating a corresponding plurality of digitized output signals; and a processor, which is configured to select respective sampling windows for the photodetectors, and to process the digitized output signals in the selected respective sampling windows to generate a depth map of the scene.
2 . The LIDAR system according to claim 1 , wherein the readout circuit is configured to integrate the sampled signals over each of the sampling windows.
3 . The LIDAR system according to claim 1 , wherein the processor is configured to calculate a time-frequency transform for the sampling windows in a given chirp period, and to select a sampling window in the given chirp period based on partial subsets of frequency-domain bins, corresponding respectively to the sampling windows.
4 . The LIDAR system according to claim 3 , wherein the processor is configured to calculate the time-frequency transform by calculating only the partial subsets of the frequency-domain bins.
5 . A LIDAR system, comprising: a transmitter, which is configured to direct a sequence of illumination pulses toward a scene; a receiver, comprising: an array of photodetectors, which are configured to receive optical radiation reflected from the scene and to output respective signals in response to the received optical radiation; a shutter, which is configured to modulate the signals by applying an ascending chirp shutter function, having a selected chirp period, to the signals output by at least a first group of the photodetectors and simultaneously applying a descending chirp shutter function, having the same chirp period as the ascending chirp shutter function, to a load; and a readout circuit, which is configured to sample and digitize the modulated signals to generate digitized output signals; and a processor, which is configured to process the digitized output signals to generate a depth map of the scene.
6 . The system according to claim 5 , wherein the load comprises a second group of the photodetectors, different from the first group of the photodetectors.
7 . A LIDAR system, comprising: a transmitter, which is configured to direct a sequence of illumination pulses toward a scene; a receiver, comprising: an array of photodetectors, which are configured to receive optical radiation reflected from the scene and to output respective signals in response to the received optical radiation; a shutter, which is configured to modulate the signals output by the photodetectors by applying a chirp shutter function, having a selected chirp period, to the signals, wherein the shutter comprises a switched circuit comprising a differential track-and-hold or a differential sample-and-hold circuit, which is controlled to apply the chirp shutter function; and a readout circuit, which is configured to sample and digitize the modulated signals to generate digitized output signals; and a processor, which is configured to process the digitized output signals to generate a depth map of the scene.
8 . The LIDAR system according to claim 7 , wherein the switched circuit is configured to reduce flicker noise using a chopping technique.
9 . The LIDAR system according to claim 7 , wherein the switched circuit comprises an integrating sampler comprising a transconductor stage followed by a sampler.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application 63/345,921, filed May 26, 2022, whose disclosure is incorporated herein by reference. TECHNICAL FIELD Embodiments described herein relate generally to LIDAR systems, and particularly to methods and systems for enhancing performance of LIDAR systems. BACKGROUND Light Detection and Ranging (LIDAR) techniques are typically used for determining ranges to objects in a scene and for creating a Three-Dimensional (3D) model of the scene. LIDAR systems are known in the art. For example, U.S. patent application Ser. No. 16/949,835, whose disclosure is incorporated herein by reference, describes a chirp-based illumination LIDAR system having a transmitter that may include a pulsed radiation illuminator that is followed by a beam forming optics. The transmitter may be configured to output, during each illumination period of a sub-group of illumination periods, a first plurality of radiation pulses that form a decimated chirp sequence of radiation pulses; the decimated chirp sequence is a sparse representation of a chirp signal. A receiver of the system may be configured to receive, during each reception period of a sub-group of reception periods, one or more received light pulses from one or more objects that were illuminated by the one or more radiation pulses transmitted during each illumination period. The receiver may include multiple radiations sensing elements, multiple shutter circuits, and multiple processing circuits for converting the one or more received light pulses to output information; wherein the multiple shutter circuits may be configured to apply a shutter function on intermediate signals, the intermediate signals represent radiation sensed by the multiple radiations sensing elements, wherein the shutter function represents the chirp signal. SUMMARY An embodiment that is described herein provides a LIDAR system, including a transmitter, a receiver and a processor. The transmitter is configured to direct a sequence of illumination pulses toward a scene. The receiver including an array of photodetectors, a shutter, and a readout circuit. The photodetectors are configured to receive optical radiation reflected from the scene and to output respective signals in response to the received optical radiation. The shutter is configured to modulate the signals output by the photodetectors by applying a chirp shutter function, having a selected chirp period, to the signals. The readout circuit is configured to sample and digitize the modulated signals in each of a plurality of sampling windows, which span the chirp period, thereby generating a corresponding plurality of digitized output signals. The processor is configured to select respective sampling windows for the photodetectors, and to process the digitized output signals in the selected respective sampling windows to generate a depth map of the scene. In some embodiments, the readout circuit is configured to integrate the sampled signals over each of the sampling windows. In other embodiments, the processor is configured to calculate a time-frequency transform for the sampling windows in a given chirp period, and to select a sampling window in the given chirp period based on partial subsets of the frequency-domain bins, corresponding respectively to the sampling windows. In yet other embodiments, the processor is configured to calculate the time-frequency transform by calculating only the partial subsets of the frequency-domain bins. There is additionally provided, in accordance with an embodiment that is described herein, a LIDAR system, including a transmitter, a receiver, and a processor. The transmitter is configured to direct a sequence of illumination pulses toward a scene. The receiver including an array of photodetectors, a shutter, and a readout circuit. The photodetectors are configured to receive optical radiation reflected from the scene and to output respective signals in response to the received optical radiation. The shutter is configured to modulate the signals by applying an ascending chirp shutter function, having a selected chirp period, to the signals output by at least a first group of the photodetectors and simultaneously applying a descending chirp shutter function, having the same chirp period as the ascending chirp shutter function, to a load. The readout circuit is configured to sample and digitize the modulated signals to generate digitized output signals. The processor is configured to process the digitized output signals to generate a depth map of the scene. In some embodiments the load includes a second group of the photodetectors, different from the first group of the photodetectors. There is additionally provided, in accordance with an embodiment that is described herein, a LIDAR system, including a transmitter, a receiver, and a processor. The transmitter is configured to direct a sequence of illumination pulses