Multimode Lidar Receiver for Coherent Range and Velocity Detection
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Solution Overview
Problem
Conventional lidar devices face challenges in maintaining coherence and signal-to-noise ratio due to environmental uncertainties, leading to inaccurate velocity and distance detection, as they typically collect a single mode while eliminating other reflected modes.
Innovation Solution
The system employs a multimode processing approach that spatially separates multiple modes of the reflected signal, using local oscillator copies and photodetectors to enhance coherence and SNR by combining electronic signals, compensating for atmospheric and optical distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional lidars collect only a single mode while eliminating other reflected modes, then device complexity is reduced, but measurement precision and reliability deteriorate due to environmental uncertainties affecting coherence and signal-to-noise ratio
Solution Approach 1:
The patent segments the reflected signal into multiple spatial modes using mode-separating optics (such as lens arrays or spatial light modulators). Each mode is directed to a separate photodetector, allowing independent processing of each spatial channel. This segmentation enables the system to preserve multiple modes rather than eliminating them, thereby maintaining measurement precision under varying environmental conditions while managing complexity through structured signal distribution.
Solution Approach 2:
The patent combines electronic signals from multiple photodetectors that have independently processed different spatial modes. By coherently combining these signals, the system achieves improved signal-to-noise ratio and maintains coherence despite environmental uncertainties. This merging of multiple mode signals resolves the contradiction by preserving measurement precision through signal integration while managing complexity through systematic combination procedures.
2Device complexity
If conventional lidars eliminate reflected modes other than the collected single mode, then signal processing is simplified, but reliability deteriorates due to loss of information from discarded modes
Solution Approach 1:
The patent segments the reflected signal into multiple spatial modes using mode-separating optics (such as lens arrays or spatial light modulators). Each mode is directed to a separate photodetector, allowing independent processing of each spatial channel. This segmentation enables the system to preserve multiple modes rather than eliminating them, thereby maintaining measurement precision under varying environmental conditions while managing complexity through structured signal distribution.
Solution Approach 2:
The patent changes the spatial distribution parameter of the reflected signal by using mode-separating optics to distribute different spatial modes to different photodetectors. This parameter change allows the system to capture and process multiple spatial modes simultaneously, preserving information that would otherwise be lost and improving reliability under environmental variations without significantly increasing processing complexity.
3Device complexity
If conventional lidars use a single mode collection approach, then device complexity is reduced, but measurement precision deteriorates due to atmospheric and optical distortions
Solution Approach 1:
The patent segments the reflected signal into multiple spatial modes using mode-separating optics (such as lens arrays or spatial light modulators). Each mode is directed to a separate photodetector, allowing independent processing of each spatial channel. This segmentation enables the system to preserve multiple modes rather than eliminating them, thereby maintaining measurement precision under varying environmental conditions while managing complexity through structured signal distribution.
Solution Approach 2:
The patent combines electronic signals from multiple photodetectors that have independently processed different spatial modes. By coherently combining these signals, the system achieves improved signal-to-noise ratio and maintains coherence despite environmental uncertainties. This merging of multiple mode signals resolves the contradiction by preserving measurement precision through signal integration while managing complexity through systematic combination procedures.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method improves the accuracy, reliability, and consistency of lidar devices by harnessing information from multiple modes, optimizing performance under varying environmental conditions.
Implementation Method 1
an optical subsystem configured to receive a beam reflected from an object, the beam having a plurality of modes
Implementation Method 2
a plurality of light detectors, each of the plurality of light detectors configured to receive, from the optical subsystem: a respective mode of the plurality of modes, and a local oscillator (LO) copy of a beam transmitted towards the object, and to output: one or more electronic signals representative of a difference between the respective mode of the plurality of modes and the LO copy
Implementation Method 3
a combiner, operatively coupled with the plurality of light detectors, to produce a combined electronic signal based on the one or more electronic signals output by each of the plurality of light detectors
Implementation Method 4
one or more circuits, operatively coupled with the combiner, to determine, based on the combined electronic signal, at least one of a velocity of the object or a distance to the object
Implementation Method 5
Coherent rangefinders, which utilize the Doppler effect, can determine a longitudinal (radial) component of the object's velocity by detecting a change in the frequency of the arrived wave from the frequency of the emitted signal
Data Source
AI summary
The subject matter of this specification can be implemented in, among other things, systems and methods that enable lidar devices capable of detecting and processing multiple optical modes present in a beam reflected from a target object. Different received optical modes can be spatially separated and electronic signals can be generated that are representative of a coherence information contained in various optical modes. Multiple generated electronic signals can be amplified, phase-shifted, mixed, etc., to identify signals, individually or in a combination, that can be used for identification of a range and velocity of the target object with the highest accuracy.