Tunable Lidar Phase Correction for Coherence and Vibration Accuracy
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Solution Overview
Problem
Conventional frequency modulated, continuous wave lidar systems face reduced coherence length and effective range due to phase wandering in tunable laser sources, which also fail to accurately measure sub-micron vibrations across a broad band of frequencies, as these vibrations appear as additive noise.
Innovation Solution
Implementing source phase correction near the laser source and target phase correction in the reflected signal to compensate for phase variance, using optical phase detectors and phase correction estimators to increase coherence length and effective range, and applying phase modulators to condition the laser output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase correction is applied across a wide band of frequencies, then measurement accuracy of vibrations is improved, but system complexity increases
Solution Approach 1:
The patent segments the phase correction process into two distinct components: source phase correction applied near the laser source, and target phase correction applied to the reflected signal. This segmentation allows each correction mechanism to be optimized independently for different frequency ranges, improving overall vibration measurement accuracy while managing system complexity through modular design
Solution Approach 2:
The patent introduces an intermediary processing stage where phase correction estimates are generated and applied between the laser source and the final measurement. This intermediary phase correction mechanism acts as a mediator that compensates for phase wandering effects across broad frequency bands without requiring complete system redesign
2Adaptability or versatility
If tunable laser sources are used to increase bandwidth, then effective bandwidth is improved, but coherence length is reduced
Solution Approach 1:
The patent applies preliminary phase correction near the laser source before the light interacts with the target. This preliminary action compensates for phase wandering that would otherwise limit coherence length, allowing the system to maintain long coherence lengths even while using tunable laser sources for broad bandwidth operation
Solution Approach 2:
The patent dynamically adjusts phase correction parameters based on the operating frequency and detected phase wandering characteristics. By changing the phase correction parameters in real-time, the system maintains optimal coherence length across the entire tunable bandwidth range, resolving the trade-off between bandwidth and coherence
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
Significantly reduces phase wandering, increases coherence length, and enhances the ability to measure vibrations by improving the sensitivity and effective bandwidth of the lidar system, allowing for accurate detection of sub-micron vibrations across a wide band of frequencies.
Implementation Method 1
an optical phase detector is configured to detect a phase variance of an output signal of the laser source
Implementation Method 2
a phase modulator is configured to modulate a phase of the output signal of the laser source
Data Source
AI summary
Various implementations of the invention compensate for “phase wandering” in tunable laser sources. Phase wandering may negatively impact a performance of a lidar system that employ such laser sources, typically by reducing a coherence length/range of the lidar system, an effective bandwidth of the lidar system, a sensitivity of the lidar system, etc. Some implementations of the invention compensate for phase wandering near the laser source and before the output of the laser is directed toward a target. Some implementations of the invention compensate for phase wandering in the target signal (i.e., the output of the laser that is incident on and reflected back from the target). Some implementations of the invention compensate for phase wandering at the laser source and in the target signal.