Dynamic Sideband Locking for Variable Synthetic Wavelength Ranging
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Solution Overview
Problem
Current multi-wavelength interferometry methods face challenges in achieving high frequency tuning accuracy and constructing a continuous multi-level synthetic wavelength for large-scale absolute distance measurement, due to limitations in laser wavelength tuning resolution, stability, and efficiency.
Innovation Solution
A variable synthetic wavelength absolute distance measuring device locked to a high-frequency electro-optic phase modulator (EOM) dynamic sideband, which generates laser sidebands with equal frequency intervals, allowing for dynamic frequency adjustments and continuous construction of synthetic wavelengths from kilometers to millimeters, using a reference laser, tunable laser, and sinusoidal phase modulation interferometer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional fixed-wavelength lasers are used to construct synthetic wavelengths, then measurement accuracy is maintained, but device complexity increases and adaptability decreases due to requiring multiple lasers
Solution Approach 1:
The patent employs a single tunable laser that can operate at multiple wavelengths, replacing the need for multiple fixed-wavelength lasers. This universal laser source can be tuned to different wavelengths to construct various synthetic wavelengths, thereby reducing device complexity while maintaining measurement accuracy through precise wavelength control
2Adaptability or versatility
If tunable laser current modulation is used to achieve multiple wavelengths, then adaptability improves, but frequency tuning accuracy deteriorates due to low resolution and environmental interference
Solution Approach 1:
The patent implements a feedback control system using an optical frequency comb as a reference. The tunable laser frequency is continuously monitored and adjusted based on the comb reference, ensuring high frequency tuning accuracy while maintaining the ability to switch between multiple wavelengths. This closed-loop feedback mechanism compensates for environmental interference and achieves both adaptability and precision
Solution Approach 2:
The optical frequency comb serves as an intermediary reference that mediates between the tunable laser and the desired wavelength targets. By using the comb's precisely known frequency lines as stepping stones, the system achieves accurate wavelength tuning without direct current modulation, thereby improving frequency accuracy while maintaining adaptability
3Measurement precision
If femtosecond optical frequency comb locking is used to improve frequency tuning accuracy, then measurement precision improves, but productivity decreases due to frequent locking and unlocking requirements
Solution Approach 1:
The patent performs preliminary frequency locking of the tunable laser to the optical frequency comb before measurement begins. Once locked, the laser maintains its frequency relationship with the comb throughout the measurement process, allowing multiple wavelength constructions without repeated locking and unlocking. This preliminary action establishes a stable frequency reference that enables both high precision and improved productivity
4Measurement precision
If optical frequency comb repetition frequency limits are applied, then frequency tuning accuracy is maintained, but adaptability deteriorates due to inability to construct large synthetic wavelengths
Solution Approach 1:
The patent dynamically adjusts the tunable laser wavelength across a broad range by exploiting the full tuning capability of the laser while maintaining locking to the optical frequency comb. The system can adaptively select different wavelength combinations to construct synthetic wavelengths spanning from millimeter to kilometer scales, thereby achieving both frequency accuracy and wide adaptability through dynamic wavelength selection
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 enhances measurement accuracy and efficiency by enabling precise control of laser frequency, maintaining the tunable laser locked state, and achieving large-scale absolute distance measurements with micron-level accuracy within a kilometer-level range.
Implementation Method 1
a high-frequency electro-optic phase modulator (EOM), which generates laser sidebands with equal frequency intervals
Implementation Method 2
Multi-wavelength interferometry based on synthetic wavelength is widely used in the field of absolute distance interferometry
Data Source
AI summary
A variable synthetic wavelength absolute distance measuring device locked to a dynamic sideband and a method thereof are disclosed. A high-frequency electro-optic phase modulator driven by an adjustable clock source to modulate a single-frequency reference laser to generate laser sidebands with equal frequency intervals. The tunable laser is locked to the fifth-order sideband through an offset frequency locking technology. After locking, the interval frequency of the sideband is determined by the adjustable clock source, namely dynamic sideband. The frequency of the adjustable clock source is dynamically adjusted, the interval frequency of the sideband and the frequency difference between the two lasers will change accordingly. Combined with the multi-wavelength interferometry, the constructed synthetic wavelength is also determined by the adjustable clock source, that is, the variable synthetic wavelength. The variable synthetic wavelength is dynamically adjusted, and the multi-level second-level synthetic wavelength is continuously constructed from large level to small level.