Interference Photomagnetic Sensor DC Noise Reduction
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Solution Overview
Problem
The interference type optical magnetic field sensor device generates a large constant DC component in its detection signal, which lowers the signal-to-noise ratio (SNR) and sensitivity for magnetic field detection due to noise not contributing to the magnetic field measurement.
Innovation Solution
The device employs a configuration with a light emitter, optical elements, and a magnetic field sensor element using polarization-maintaining fibers, where linearly polarized light is split into S and P components, and their phases are adjusted to enhance signal separation, resulting in a detection signal with improved SNR by removing the DC component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photoelectric conversion is performed directly from light transmitted through the magnetic field sensor element, then the detection signal can be generated, but a large DC component is included which lowers the SN ratio
Solution Approach 1:
The incident light is segmented into two separate optical paths with orthogonal polarizations (S-polarization and P-polarization). Each path processes the light independently through the magnetic field sensor element, and the signals are subsequently combined. This segmentation allows the DC components from each path to cancel each other out when combined, while preserving the magnetic field signal information.
Solution Approach 2:
The harmful DC component is extracted and removed from the detection signal through differential processing. By measuring the light intensity in two orthogonal polarization states and calculating the difference between them, the common DC component present in both measurements is eliminated, leaving only the differential signal containing the magnetic field information.
2Productivity
If the detection signal contains large DC component, then photoelectric conversion can be performed, but the SN ratio of the detection signal is lowered
Solution Approach 1:
The detection process is segmented into two parallel measurement channels with orthogonal polarizations. Each channel generates a detection signal with DC component, but when the signals are combined through differential processing, the DC components cancel while the magnetic field signals add constructively, improving the SN ratio.
Solution Approach 2:
The harmful DC component present in both polarization channels is converted into a benefit through differential processing. By subtracting the two signals, the common DC component is eliminated and can even be used for normalization purposes, while the magnetic field-induced signal differences are preserved and enhanced.
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 configuration increases the SNR of the detection signal for magnetic fields by separating and differentially amplifying the S and P polarization components, effectively removing the DC noise and enhancing sensitivity.
Implementation Method 1
uses a probe type sensor provided with a Faraday rotator at the optical fiber tip as a magnetic field sensor element
Implementation Method 2
a first optical element emitting a first linearly polarized wave and a second linearly polarized wave orthogonal to the first linearly polarized wave
Data Source
AI summary
An interference type optical magnetic field sensor device 1 has a light emitter 10 emitting first linearly polarized light, a first optical element 30 emitting a first linearly polarized wave and a second linearly polarized wave orthogonal to the first linearly polarized wave with respect to incident the first linearly polarized light, and emitting a second linearly polarized light with respect to incident third linearly polarized wave and a forth linearly polarized wave orthogonal to the third linearly polarized wave, a magnetic field sensor element 50 disposed at least a portion thereof within a predetermined magnetic field an optical path unit 40 connected to the first optical element and the magnetic field sensor element, and having a first optical path propagating the first linearly polarized wave and the forth linearly polarized wave, and a second optical path propagating the second linearly polarized wave and the third linearly polarized wave, a detection signal generator 60 outputting a detection signal by separating the second linearly polarized light into an S polarization component and a P polarization component, converting the S polarization component and the P polarization component into an electric signal, and an optical branching element 20 transmitting the first linearly polarized light to the first optical element, and branching the second linearly polarized light to the detection signal generator, wherein the magnetic field sensor element emits the first linearly polarized wave and the second linearly polarized wave as incident light, and emits the third linearly polarized wave with respect to the first linearly polarized wave and the forth linearly polarized wave with respect to the second linearly polarized wave as return light.