Group Delay Filter for OPM Noise Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing magnetic field measurement systems, particularly those using optically pumped magnetometers (OPMs), face challenges in maintaining stable input light intensity and are prone to optical noise, which affects sensitivity and operational range, especially in mobile or wearable devices.
Innovation Solution
A magnetic field measurement system that includes a light source, optical fiber, variable optical attenuator, beam splitter, monitor detector, OPM detector, and a group delay filter to stabilize light intensity and reduce optical noise by accounting for phase differences between monitor and OPM signals, using a filtering algorithm to combine these signals and generate a reduced noise OPM signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a variable optical attenuator is used to stabilize input light intensity, then light intensity stability is improved, but optical noise is introduced
Solution Approach 1:
The patent implements a feedback mechanism where a monitor detector continuously monitors the light intensity after the variable optical attenuator, and a controller adjusts the attenuator's settings based on this monitoring to maintain stable intensity while compensating for noise introduced by the attenuator
Solution Approach 2:
The patent introduces an intermediary signal processing system including a monitor detector, controller, and group delay filter that mediates between the noisy variable optical attenuator and the OPM detector, filtering out optical noise while preserving the stabilized light intensity signal
2Measurement precision
If SQUIDs are used for MEG measurement, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces expensive, complex SQUID systems with more affordable OPM systems that use standard optical components and electronics, making the technology accessible for mobile and wearable applications without sacrificing measurement capability
Solution Approach 2:
The patent substitutes the mechanical cryogenic cooling system required for SQUIDs with an optically-based measurement system that operates at room temperature, eliminating the need for complex cryogenic infrastructure while maintaining magnetic field detection capability
3Ease of operation
If OPMs are used for portable MEG, then device portability is improved, but optical noise compromises sensitivity
Solution Approach 1:
The patent introduces an intermediary signal processing chain with a monitor detector and group delay filter that stands between the light source and the OPM detector, filtering out optical noise while preserving the magnetic field signal, thereby enabling portable OPM systems to achieve sensitivity comparable to fixed installations
Solution Approach 2:
The patent dynamically adjusts operational parameters including the variable optical attenuator settings and group delay filter characteristics in real-time to optimize the balance between light intensity stability and optical noise suppression, maintaining high sensitivity across varying operating 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
The system achieves photon shot noise-limited sensitivity even with noisy input light, reducing noise significantly and enabling the use of low-cost, noisy variable optical attenuators without compromising sensitivity, allowing for wearable MEG systems to operate outside magnetically shielded rooms.
Implementation Method 1
an optical fiber configured to transmit the light beam from the light source
Implementation Method 2
a vapor cell with alkali metal atoms disposed therein and configured for transmission of the OPM light beam through the vapor cell
Data Source
AI summary
A magnetic field measurement system includes a light source that emits a light beam; an optical fiber to transmit the light beam; a variable optical attenuator to increase stability of an intensity of the light beam; a beam splitter to divide the light beam into an OPM light beam and a monitor light beam; a monitor detector to detect the monitor light beam and generate a monitor signal; a vapor cell with alkali metal atoms disposed therein and configured for transmission of the OPM light beam through the vapor cell; an OPM detector to detect the OPM light beam after transmission through the vapor cell and generate an OPM signal; and a group delay filter to combine the monitor signal and the OPM signal to generate a reduced noise OPM signal, where the group delay filter accounts for a phase difference between the monitor signal and the OPM signal.