FMCW LIDAR Phase Correction for Speckle-Resilient Heterodyne Detection
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Solution Overview
Problem
LIDAR imaging systems with FMCW heterodyne detection suffer from reduced performance due to speckle patterns in the backscattered object signal, affecting the quality of the heterodyne signal in terms of intensity, alternating component intensity, and signal-to-noise ratio.
Innovation Solution
A LIDAR imaging system with a phase correction device that includes a spatial phase modulator to apply a corrected spatial phase distribution to the reference signal, optimized based on the spatial intensity distribution of the backscattered object signal, to improve the spatial distribution of parameters such as heterodyne signal intensity, alternating component intensity, or signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If heterodyne detection is used to obtain distance map of illuminated scene, then distance measurement capability is achieved, but speckle pattern degrades the quality of heterodyne signal
Solution Approach 1:
The patent applies spatial phase modulation to the reference signal, changing its spatial phase distribution parameter to match the speckle pattern of the backscattered object signal. This parameter change enables the reference signal to compensate for the speckle-induced degradation, thereby maintaining high-quality heterodyne detection and accurate distance measurement despite the presence of speckle patterns.
2Reliability
If spatial phase modulation is applied to reference signal, then heterodyne signal quality is improved, but device complexity increases
Solution Approach 1:
The patent introduces a spatial light modulator as an intermediary device to apply spatial phase modulation to the reference signal. This intermediary component enables precise control of the reference signal's spatial phase distribution without requiring fundamental changes to the overall heterodyne detection system architecture, thus improving signal quality while managing device complexity through a dedicated modular component.
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
Enhances the quality of the heterodyne signal by optimizing its spatial distribution, leading to improved intensity and signal-to-noise ratio, even in the presence of speckle patterns.
Implementation Method 1
a spatial phase modulator, arranged on the path of the reference signal upstream of the optical imaging device, adapted to apply a spatial phase distribution, called corrected spatial phase distribution, to the reference signal
Implementation Method 2
the matrix photodetector, adapted to receive the backscattered object signal and the reference signal, which interfere in order to form a heterodyne signal
Implementation Method 3
the backscattered object signal and the reference signal, which interfere in order to form a heterodyne signal
Implementation Method 4
the optical imaging device, adapted to receive part of the object signal then backscattered by the illuminated scene and to transmit it in order to thus form the image of the illuminated scene on the matrix photodetector
Data Source
AI summary
The invention relates to a LIDAR imaging system of the FMCW type, comprising a light source (10), an optical projection device (20), an optical transmission device (30), an optical imaging device (40), and a matrix photodetector (50). It further comprises a phase correction device (60) comprising a spatial phase modulator (61) for applying a corrected spatial phase distribution to the reference signal, and a computation unit (62) for determining the corrected spatial phase distribution, by taking into account a spatial distribution representing a spatial intensity distribution of the backscattered object signal, so that the reference signal has a corrected spatial intensity distribution in the reception plane optimizing a spatial distribution of a parameter of interest representing the heterodyne signal.