Interferometer Absolute Position Measurement Without Stable Reference Axis
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Solution Overview
Problem
Existing interferometer systems are limited in determining the absolute position of movable objects due to the need for a stable reference axis and fast frequency modulating light sources, which complicates the measurement process and restricts their practical application.
Innovation Solution
A method and system using two light sources with different frequencies, one fixed and one tunable, to determine absolute position through a non-linear equation based on the relationship between wavelength and count offsets, eliminating the need for a stable reference axis and fast frequency modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stable reference axis is used in interferometer systems, then measurement reliability is improved, but device complexity increases due to the need for separate zeroing sensors and stable reference structures
Solution Approach 1:
The patent extracts the reference axis requirement by using only measurement axes that track movable objects. The interferometer system determines absolute positions by measuring displacements along measurement axes without requiring a separate stable reference axis, thereby removing the complexity of maintaining reference structures while preserving measurement reliability through the use of multiple measurement axes and mathematical reconstruction algorithms
Solution Approach 2:
The patent makes the measurement axes universal by having them serve dual purposes: both measuring relative displacements and determining absolute positions. The same measurement axes used for tracking movable objects also provide the basis for absolute position determination through mathematical reconstruction, eliminating the need for separate zeroing sensors and reference axis infrastructure
2Speed
If fast frequency modulation is implemented, then measurement speed is improved, but device complexity increases due to the need for fast frequency modulating light sources
Solution Approach 1:
The patent replaces the mechanical/optical approach of fast frequency modulation with a mathematical processing approach. Instead of modulating light frequency at high speeds to encode position information, the system uses continuous wavelength scanning combined with mathematical reconstruction algorithms to determine absolute positions, thereby achieving measurement speed without requiring fast frequency modulating light sources
Solution Approach 2:
The patent introduces dynamic wavelength scanning of the light source as a controlled variation to enable absolute position determination. By continuously changing the wavelength and recording interference patterns throughout the scan, the system captures sufficient information to reconstruct absolute positions mathematically, replacing the need for static frequency modulation schemes
3Adaptability or versatility
If the measurement range is extended beyond the zeroing sensor range, then adaptability is improved, but measurement precision deteriorates because the movable object must be repeatedly brought back into the small measurement range
Solution Approach 1:
The patent performs preliminary wavelength scanning to capture interference patterns that encode absolute position information before any displacement measurements are taken. By pre-establishing the relationship between wavelength, optical path length, and interference patterns through mathematical reconstruction, the system creates a reference framework that enables continuous absolute position determination without needing to repeatedly return the movable object to a zeroing sensor range
Solution Approach 2:
The patent introduces mathematical reconstruction algorithms as an intermediary between the raw interferometer measurements and the final position determination. These algorithms process the interference patterns from multiple measurement axes to reconstruct absolute positions, serving as a mediator that translates limited-range measurements into extended-range absolute position information without losing precision
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 determination of absolute position without requiring a stable reference axis or fast frequency modulation, allowing for broader application in interferometer systems.
Implementation Method 1
interferometer system...guiding the first beam and the further first beam along a first measurement axis to a first reflective surface...to obtain a first interferometer signal
Data Source
AI summary
A method to determine an absolute position of a first movable object using an interferometer system is described, said method comprising: providing first and second beams with a first light frequency from a first light source: providing further first and further second beams with a second (tunable) light frequency from a second light source: guiding the first and further first beams along a first axis to a reflective surface of the first object to obtain a first interferometer signal and guiding the second and further second beams along a second axis to a reflective surface of a second object to obtain a second interferometer signal, while changing the tunable frequency, detecting the first and further first interferometer signals detecting the second and further second interferometer signals, determining a first count offset and/or a further first count offset using a non-linear equation, and determining the absolute position of the first object.