Scanning Fabry-Pérot Interferometer for Lidar Wavelength Drift
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Solution Overview
Problem
LIDAR systems face challenges in maintaining an ideal signal-to-noise ratio due to ambient light interference and laser wavelength drift, particularly in outdoor environments, where static band-pass filters are insufficient in filtering out unwanted wavelengths.
Innovation Solution
A scanning Fabry-Pérot interferometer is used on the light path, dynamically adjusting its pass band to match the changing wavelength of the emitted laser light, combined with an order-sorting filter to reduce ambient light interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a static band-pass filter is used with a broad pass band to accommodate laser wavelength drift, then the filter can maintain laser light transmission over time and temperature variations, but the signal-to-noise ratio deteriorates because more ambient light wavelengths pass through to the detector
Solution Approach 1:
The patent applies a scanning Fabry-Pérot interferometer that dynamically adjusts its pass band to track the laser wavelength in real-time. The interferometer scans through a wavelength range and identifies the laser peak position, then centers the narrow pass band on this detected wavelength, maintaining optimal filtering performance despite laser drift
Solution Approach 2:
The system implements feedback by using a wavelength meter or spectrometer to continuously monitor the actual laser wavelength and feeding this information back to adjust the Fabry-Pérot interferometer's tuning. This closed-loop control ensures the narrow pass band remains precisely aligned with the laser wavelength
2Object-affected harmful factors
If the laser intensity is reduced to ensure eye safety in ambient environments, then human safety is improved, but the signal-to-noise ratio worsens because the reflected laser signal becomes weaker relative to ambient light
Solution Approach 1:
The patent changes the spectral parameter of the filtering system by using a narrow pass band Fabry-Pérot interferometer instead of a broad pass band filter. This spectral selectivity allows the system to maintain high signal-to-noise ratio even with reduced laser intensity, as the narrow bandwidth rejects most ambient light wavelengths while transmitting the laser wavelength
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 configuration significantly improves the signal-to-noise ratio by maintaining a narrow pass band aligned with the laser wavelength, reducing ambient light impact and enhancing measurement accuracy.
Implementation Method 1
a scanning Fabry-Pérot interferometer configured to transmit laser light only in a cavity resonance wavelength range
Implementation Method 2
The measurement arrangement comprises, on the light path from the object in the surrounding environment to the one or more light detectors, an order-sorting filter configured to transmit laser light only in a first wavelength range, and a scanning Fabry-Pérot interferometer configured to transmit laser light only in a cavity resonance wavelength range
Implementation Method 3
a laser device configured to emit laser light with a laser wavelength toward the surrounding environment
Implementation Method 4
one or more light detectors configured to absorb inbound laser light after it has been reflected back towards the measurement arrangement from an object in the surrounding environment
Data Source
AI summary
A measurement arrangement for measuring the travel time of a laser beam, comprising a laser device configured to emit laser light with a laser wavelength toward the surrounding environment and one or more light detectors configured to absorb inbound laser light after it has been reflected back towards the measurement arrangement. The measurement arrangement also comprises an order-sorting filter configured to transmit laser light only in a first wavelength range, and a scanning Fabry-Pérot interferometer configured to transmit laser light only in a cavity resonance wavelength range. The first wavelength range is broader than the cavity resonance wavelength range, and a control unit is configured to shift the center of the cavity resonance wavelength range when the temperature of the laser device changes.