Absolute Distance Measurement Using Optical Frequency Sweeping
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Solution Overview
Problem
Existing absolute distance measurement methods using interference principles face limitations in measurement uncertainty and require the measurement target to be moved, leading to accumulated error components, and are restricted by the stability and accuracy of wavelengths, making it challenging to achieve high precision across a wide range.
Innovation Solution
An absolute distance measurement method utilizing an optical frequency generator that generates multiple stabilized wavelengths, combines the principles of multi-wavelength and frequency sweeping interferometers to expand measurement range and accuracy, by generating a plurality of wavelengths with high frequency stability and accuracy, and compensates for refractive index variations in air.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-wavelength interferometer is used to achieve high measurement uncertainty, then measurement precision is improved, but measurement range is limited to predetermined range
Solution Approach 1:
The patent employs dynamic wavelength tuning by sweeping the optical frequency across a continuous range rather than using fixed discrete wavelengths. The optical frequency generator dynamically adjusts the wavelength during measurement, enabling the system to adapt to different measurement ranges while maintaining high precision through the use of multiple wavelengths at different stages of the sweep.
Solution Approach 2:
The patent changes the optical frequency parameter continuously during measurement. By sweeping the frequency from an initial value to a final value, the system transitions between different wavelength regimes, allowing it to overcome the fixed range limitation of conventional multi-wavelength interferometers while maintaining the precision benefits of using multiple wavelengths.
2Adaptability or versatility
If frequency sweeping interferometer is used to expand measurement range, then measurement range is improved, but measurement uncertainty increases
Solution Approach 1:
The patent segments the frequency sweep into multiple stages or intervals, each optimized for different measurement ranges. By dividing the continuous frequency sweep into manageable segments and applying appropriate processing to each, the system maintains high measurement uncertainty performance across the entire expanded range rather than degrading uniformly.
Solution Approach 2:
The patent implements feedback mechanisms that use information from the frequency sweep to adjust and refine measurements. By continuously monitoring the interference patterns during the sweep and applying real-time corrections, the system compensates for the inherent uncertainties in frequency sweeping, thereby maintaining high measurement precision across extended ranges.
3Measurement precision
If conventional interferometer is used to achieve high measurement uncertainty, then measurement precision is improved, but measurement can only be performed on moved target
Solution Approach 1:
The patent performs preliminary frequency sweeping to establish the absolute distance before any measurement operation. This preliminary action provides the initial condition needed for subsequent high-precision measurements without requiring the target to be moved, thereby eliminating the operational complexity of target motion while maintaining measurement uncertainty performance.
Solution Approach 2:
The patent introduces an optical frequency generator as an intermediary that bridges the gap between absolute distance measurement and high-precision interferometry. This intermediary device enables the system to first establish the absolute position through frequency sweeping, then perform precise measurements on stationary targets, avoiding the need for target motion.
4Measurement precision
If relative displacement measurement is performed by continuously integrating phase variation, then measurement precision is improved, but error components are accumulated
Solution Approach 1:
The patent performs a preliminary frequency sweep to establish the absolute distance before integrating phase variations. This preliminary action provides a reliable initial condition that resets any accumulated errors, allowing subsequent phase integration to proceed without carrying forward previous measurement errors, thereby improving reliability while maintaining precision.
Solution Approach 2:
The patent uses rapid frequency sweeping to quickly establish the absolute distance baseline before detailed phase integration begins. By rushing through the initial absolute measurement phase, the system minimizes the time during which errors could accumulate, then transitions to the high-precision phase integration mode with a fresh error baseline.
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 approach enables precise absolute distance measurement with reduced uncertainty, allowing for applications in various fields such as spectroscopy, biotechnology, and large-scale precision apparatus positioning, while maintaining the advantages of relative displacement interferometry.
Implementation Method 1
generating a plurality of different stabilized wavelengths by using an optical frequency generator
Implementation Method 2
analyzing an uncertainty range of the obtained initial estimation value; measuring excess fraction parts of the different wavelengths by analyzing interference signals for each of the wavelengths
Data Source
AI summary
The present invention relates to absolute distance measurement method and system using an optical frequency generator. The absolute distance measurement method using the optical frequency generator includes (a) generating a plurality of different stabilized wavelengths by using the optical frequency generator; (b) obtaining an initial estimation value of a distance to be measured by using a frequency sweeping interferometer; (c) analyzing an uncertainty range of the obtained initial estimation value; (d) measuring excess fraction parts of the different wavelengths by analyzing interference signals for each of the wavelengths; (e) determining integer parts for each of the different wavelengths within the uncertainty range of the initial estimation value; and (f) measuring an absolute distance to be measured by using the excess fraction part and the integer parts for each of the different wavelengths.