Laser Interference Device Wavelength Drift Compensation
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Solution Overview
Problem
Traditional laser interference devices require complex calibration processes to maintain measurement accuracy due to changes in laser wavelength over time, which complicates the calibration work and affects measurement precision.
Innovation Solution
A laser interference device that divides the laser beam into a measurement laser beam and a frequency monitor laser beam, using the wavelength of the frequency monitor laser beam as a calibration value to calculate the displacement of a movable mirror, thereby eliminating the need for periodic calibration and reducing measurement errors caused by wavelength changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a typical wavelength stabilized helium neon laser is used, then measurement accuracy can be maintained by periodic calibration, but the calibration work becomes complicated and time-consuming
Solution Approach 1:
The laser beam is divided into two separate beams: a measurement laser beam for displacement measurement and a frequency monitor laser beam for wavelength monitoring. This segmentation allows independent monitoring of wavelength changes without affecting the measurement process, eliminating the need for complex periodic calibration while maintaining measurement accuracy.
Solution Approach 2:
A frequency monitor laser beam acts as an intermediary to monitor wavelength changes of the measurement laser beam. By measuring the beat frequency between the frequency monitor laser beam and a reference laser beam, the system indirectly tracks wavelength variations and compensates for them in real-time, avoiding complicated direct calibration procedures.
2Measurement precision
If periodic calibration is performed, then measurement accuracy is maintained, but measurement time is lost during calibration processes
Solution Approach 1:
The frequency monitor laser beam continuously monitors wavelength changes throughout the measurement process. This continuous monitoring enables real-time compensation for wavelength drift without interrupting the measurement, eliminating time loss associated with periodic calibration while maintaining measurement accuracy.
Solution Approach 2:
The wavelength of the frequency monitor laser beam is measured in advance by detecting the beat frequency with the reference laser beam. This preliminary wavelength information is stored and used for displacement calculations, allowing the system to proactively compensate for wavelength changes before they affect measurement accuracy, rather than requiring time-consuming periodic calibration.
3Device complexity
If laser wavelength changes are not monitored, then the device structure remains simple, but measurement error increases due to wavelength drift
Solution Approach 1:
The frequency monitor laser beam serves as an intermediary that monitors wavelength changes of the measurement laser beam. By measuring the beat frequency between these two beams, the system detects wavelength drift and compensates for it in displacement calculations, maintaining measurement accuracy without requiring complex additional monitoring equipment.
Solution Approach 2:
The system uses the beat frequency signal as feedback to determine wavelength changes of the measurement laser beam. This feedback mechanism allows the system to automatically adjust displacement calculations based on actual wavelength variations, maintaining measurement precision while keeping the device structure relatively simple through efficient use of existing laser beams.
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 solution allows for accurate displacement measurement of the movable mirror without the need for complex calibration, ensuring higher precision and reducing the workload of the measurer by using the wavelength measurement value periodically updated and stored for monitoring wavelength changes.
Implementation Method 1
a first beam splitter configured to divide the laser beam into a measurement laser beam and a frequency monitor laser beam
Implementation Method 2
a frequency detector configured to detect a beat frequency resulting from interference between the reference laser beam and the frequency monitor laser beam
Implementation Method 3
a second beam splitter configured to divide the measurement laser beam into a measurement light and a reference light
Implementation Method 4
a light detector configured to detect an interference light of the measurement light reflected on a measurement mirror and the reference light reflected on a reference mirror
Data Source
AI summary
A laser interference device includes a measurement laser that outputs a laser beam, a beam splitter that divides the laser beam into a measurement laser beam and a frequency monitor laser beam, a reference laser that outputs a reference laser beam, a frequency detector that detects a beat frequency resulting from interference between the reference laser beam and the frequency monitor laser beam, a wavelength calculator that calculates a wavelength of the frequency monitor laser beam (a wavelength measurement value) on the basis of the beat frequency, a light detector that detects an interference light of the measurement light and the reference light of the measurement laser beam and outputs a light detection signal, and a displacement calculator that calculates a displacement of the measurement mirror by performing an arithmetic process based on the wavelength measurement value and the light detection signal.