Optical Sensor Dual Detector Functions for Path Difference
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Solution Overview
Problem
Existing optical sensors using Fabry-Perot cavities face challenges in achieving reliable measurements across large temperature and pressure ranges while maintaining fine scale accuracy, particularly in startup conditions, and struggle to accurately determine optical path differences and physical parameters simultaneously.
Innovation Solution
An optical sensor system comprising one or more sensing interference elements, an optical source, a spectral engine, and multiple detector functions to generate coarse and refined optical path difference signals, enabling simultaneous measurement of multiple physical parameters and compensation for cross-sensitivities, such as temperature corrections in pressure measurements, using broad band or narrow band probe light and advanced spectral analysis techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If broad band probe light and white light interferometry techniques are used to measure large ranges of optical path difference, then the measurement range is improved, but the fine scale accuracy deteriorates
Solution Approach 1:
The measurement process is segmented into two distinct stages: a first detector function that generates coarse optical path difference signals to cover large measurement ranges, and a second detector function that generates refined optical path difference signals to achieve fine scale accuracy. This segmentation allows each detector function to be optimized for its specific purpose, resolving the contradiction between measurement range and fine scale accuracy.
2Device complexity
If single detector function is used to measure optical path difference, then the device complexity is reduced, but the ability to measure multiple physical parameters simultaneously deteriorates
Solution Approach 1:
The first detector function is designed to be universal by generating coarse optical path difference signals that can be applied to multiple different sensing interference elements measuring different physical parameters (temperature, pressure, acceleration). The second detector function then refines these measurements for each specific parameter. This multi-functionality allows simultaneous measurement of multiple physical parameters while maintaining manageable device complexity through shared detection architecture.
3Ease of operation
If conventional interference techniques are used for startup conditions, then the measurement process is simplified, but the accuracy of determining optical path differences deteriorates
Solution Approach 1:
The first detector function performs preliminary measurement to generate coarse optical path difference signals during startup conditions. This preliminary action establishes an initial measurement baseline that covers large ranges, and then the second detector function uses this as a foundation to perform refined measurements. This preliminary action ensures accurate optical path difference determination from the start-up phase while keeping the overall process straightforward.
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
The system achieves high resolution and accuracy over large dynamic ranges, allowing for precise measurement of temperature, pressure, and acceleration, with improved tracking of optical path differences and reduced errors due to temperature variations, enhancing the reliability and accuracy of sensor readings.
Implementation Method 1
one or more sensing interference elements each having an optical path difference; an optical source arranged to deliver probe light to the one or more sensing interference elements; a spectral engine arranged to detect an interference spectrum in probe light received from the one or more sensing interference elements
Implementation Method 2
pressure is measured by pressure-induced deflection of at least one reflective surface of a physical cavity in the sensor head
Implementation Method 3
Temperature is measured by thermal expansion and thermal response of refractive index giving rise to changes in optical path length of cavities formed of material of the sensor head
Data Source
AI summary
An optical sensor having one or more sensing interference elements is disclosed. A first detector function generates a coarse optical path difference signal for example using a discrete Fourier transform of a detected interference spectrum, and a second detector function generates a refined optical path difference signal using the coarse optical path difference signal and for example a cross correlation of the interference spectrum with one or more sets of periodic transfer functions.