Frequency-Domain LiDAR for Remote Micro-Movement Detection
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Solution Overview
Problem
Conventional LiDAR systems lack sensitivity for detecting small-scale movements or vibrations with micrometer-level precision, especially in remote and hazardous environments, and existing high-precision sensing systems are costly and complex, limiting their deployment in critical applications.
Innovation Solution
An ultraprecision frequency-domain LiDAR system incorporating a laser diode, bandpass filter, Michelson interferometer, fiber-optic delay line, semiconductor optical amplifier, and photodetector, with a feedback loop and frequency-domain analyzer to detect micro-movements by analyzing frequency shifts in RF signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional LiDAR systems are used for long-range detection, then detection range is improved, but measurement precision for micro-movements deteriorates
Solution Approach 1:
The patent segments the detection function into two distinct optical paths: a reference path (first optical path) that provides a stable frequency reference, and a measurement path (second optical path) that interacts with the target. This segmentation allows the system to maintain long-range detection capability while achieving micro-movement precision by comparing the measurement path signal against the stable reference path signal, thereby resolving the contradiction between detection range and measurement precision.
Solution Approach 2:
The patent employs frequency-domain analysis to transform the detection approach from spatial/temporal domain to frequency domain. By modulating the laser signal at a specific frequency and analyzing the reflected signal's frequency characteristics, the system can detect micrometer-level movements even at long ranges. This parameter transformation (from direct distance measurement to frequency shift analysis) resolves the contradiction by enabling high precision measurements independent of detection range.
2Measurement precision
If high-precision sensing systems are deployed for micro-movement detection, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the laser signal serve multiple functions simultaneously: it acts as both the measurement probe (interacting with the target) and the frequency reference (providing the stable baseline for comparison). The single laser source generates the modulated signal that is split into reference and measurement paths, eliminating the need for separate reference sources and reducing overall system complexity while maintaining micro-movement detection precision.
Solution Approach 2:
The patent introduces an optoelectronic oscillator as an intermediary element that bridges the optical domain (laser) and electrical domain (frequency analysis). The oscillator converts optical phase information into electrical frequency signals that can be easily analyzed by standard electronic equipment. This intermediary approach enables high-precision micro-movement detection using conventional, low-cost electronic frequency analyzers rather than requiring complex optical measurement equipment.
3Adaptability or versatility
If conventional LiDAR systems are used in hazardous environments, then remote operation capability is improved, but sensitivity to micro-movements deteriorates
Solution Approach 1:
The patent transforms the detection parameter from direct optical distance measurement to frequency-domain analysis. By modulating the laser at a known frequency and detecting the frequency shift in the reflected signal, the system achieves micro-movement sensitivity that is independent of the remote detection distance. This parameter transformation enables the system to maintain high sensitivity to micrometer-level movements even when operating remotely in hazardous environments where direct physical access is impossible.
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
Enables accurate detection of minute displacements and vibrations with high precision, suitable for structural health monitoring, volcanic eruption detection, and seismic activity, while being cost-effective and resilient to environmental interference.
Implementation Method 1
a laser diode (102) configured to generate intensity modulated optical signals
Implementation Method 2
a Michelson interferometer (104) including a 50/50 directional coupler (106) configured to split the intensity modulated optical signals into a first optical path and a second optical path
Implementation Method 3
The first optical path includes a fiber-optic delay line (108) configured to generate phase shifted intensity modulated optical signals
Implementation Method 4
a silver coated end (110) connected to the fiber-optic delay line at a distance l1 from the laser diode. The silver coated end is configured to reflect the phase shifted intensity modulated optical signals back
Implementation Method 5
an optical collimator (114) connected between the SOA and a free-space propagation region... an amplifier, by a semiconductor optical amplifier (SOA) connected between the 50/50 directional coupler and the optical collimator, the reflected collimated second optical stream
Implementation Method 6
an optical collimator (114) connected between the SOA and a free-space propagation region
Implementation Method 7
a photodetector (120) connected to the 50/50 directional coupler. The photodetector is configured to receive the phase shifted intensity modulated optical signals and the amplified intensity modulated optical signals and convert the phase-shifted intensity modulated optical signals and the amplified intensity modulated optical signals into electrical signals
Implementation Method 8
a bandpass filter connected to the laser diode. The bandpass filter is configured to modulate a power provided by the power source by a Radio Frequency (RF) signal
Data Source
AI summary
An ultraprecision frequency-domain Light Detection and Ranging (LiDAR) system for remote micro-movement sensing includes a laser diode with a bandpass filter configured to modulate power using RF signals to generate intensity-modulated optical signals. The LiDAR system includes a Michelson interferometer to split generated optical signals via a 50/50 directional coupler into two optical paths. A first optical path includes a fiber-optic delay line with a silver-coated end reflecting phase-shifted optical signals towards a photodetector. A second optical path features a semiconductor optical amplifier amplifying the generated optical signals, with an optical collimator and a target beyond a free-space propagation region. A photodetector is connected to the 50/50 directional coupler that receives both the phase-shifted and amplified optical signals, converting them to electrical signals. A feedback loop, including a bandpass filter and a frequency-domain analyzer detects frequency shifts caused by micro-movements of the target.