Fabry-Perot Interferometer Miniaturization for Position Detection
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Solution Overview
Problem
Existing position finding technologies, such as dual Michelson interferometers, face challenges in miniaturization and accuracy, particularly in determining displacement direction and achieving consistent accuracy across extreme values, and are limited by the need for multiple channels and large physical units, making them unsuitable for compact or extreme environments.
Innovation Solution
The use of a Fabry-Perot interferometer with a single detector and demodulation at two different frequencies allows for accurate position finding using the quadrature detection method, enabling miniaturization and precise determination of displacement direction without the need for multiple channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dual Michelson interferometer is used for position finding, then the accuracy of determining displacement direction and position is improved, but the device size and complexity increase, making it unsuitable for miniaturization
Solution Approach 1:
The patent combines the functions of two separate Michelson interferometers into a single Fabry-Perot interferometer. The Fabry-Perot interferometer uses two mirrors (one fixed, one movable) to create multiple beam interference, which can simultaneously provide both quadrature signals needed for accurate position and direction detection, eliminating the need for two separate interferometer channels
Solution Approach 2:
The Fabry-Perot interferometer is designed to perform multiple functions: it simultaneously measures displacement magnitude, determines displacement direction, and provides quadrature detection signals. This multi-functional capability replaces what previously required two separate Michelson interferometers, each dedicated to specific measurement tasks
2Measurement precision
If a dual Michelson interferometer with two detectors is used, then quadrature detection for determining displacement direction is achieved, but the quantity of components and device size increase
Solution Approach 1:
The patent merges the detection functions of two separate detectors into a single detector. The Fabry-Perot interferometer produces interference patterns that contain information from both 'channels' simultaneously, allowing one detector to capture all necessary quadrature signals through the multiple beam interference pattern
Solution Approach 2:
The movable mirror in the Fabry-Perot interferometer acts as an intermediary that modulates the interference pattern in a way that encodes both magnitude and direction information. By analyzing the phase and amplitude variations of the single detector signal, the system extracts quadrature information without requiring physical separation into two detection channels
3Measurement precision
If reference mirrors are arranged with intervals of λ/8+N λ/2 for quadrature detection, then displacement direction can be determined, but the manufacturing precision requirements increase
Solution Approach 1:
The patent employs dynamic modulation of the interference pattern through the movable mirror's oscillation or scanning motion. By dynamically varying the optical path difference and analyzing the time-dependent interference signal, the system determines displacement direction without requiring static mirror intervals to be manufactured with extreme precision
Solution Approach 2:
The system changes the operating parameters of the interferometer by modulating the optical path length dynamically. This allows the determination of displacement direction based on the phase relationship of the modulated signal rather than relying on fixed geometric relationships that would require high manufacturing precision
4Volume of moving object
If a compact position finding device is needed for extreme environments, then miniaturization is required, but existing interferometer designs cannot be reduced in size
Solution Approach 1:
The patent integrates all necessary interferometric components into a single compact Fabry-Perot interferometer unit. The alignment-free design and integrated structure enable miniaturization while maintaining reliability in extreme environments, as there are no multiple separate channels or complex alignment requirements that would be difficult to maintain in compact or harsh conditions
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 high-accuracy position finding with a compact, miniaturized system capable of determining displacement direction and maintaining consistent accuracy, suitable for applications in small or extreme environments, such as sub-millimetre or sub-micron range positioning.
Implementation Method 1
an interferometer, which produces an interference pattern for the wave field which is dependent on the length of the measurement section
Implementation Method 2
wave field variation device for varying a wavelength of the wave field over time
Data Source
AI summary
An apparatus for position finding, including a light source to produce a wave field in a measurement section, a wave field variation device to generate a variation of a wavelength of the wave field over time, an interferometer to produce an interference pattern for the wave field which is dependent on the length of the measurement section, a detector to produce a measurement signal on the basis of the detected interference pattern, and an evaluation circuit to evaluate the measurement signal on the basis of the variation over time.