Gradiometer System with Actuation Module for Noise Reduction
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Solution Overview
Problem
Conventional magnetic survey techniques lack the sensitivity and resolution to detect small magnetic anomalies buried at various depths beneath the Earth's surface, particularly for unexploded ordnances and border protection, due to limitations in sensor sensitivity and internal noise, especially 1/f noise, which degrades signal-to-noise ratio and accuracy.
Innovation Solution
A novel magnetic field gradiometer system that varies the sensing positions of scalar magnetic sensors according to a known displacement function, allowing for differential measurements that distinguish between gradiometer signals and noise, thereby reducing the impact of 1/f noise and enhancing sensitivity and accuracy, using either a single sensor or multiple sensors with orientation stabilization to maintain accurate orientation and reduce cumulative noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetic sensors are used for surveying, then the survey can be conducted, but the sensitivity and resolution are insufficient to detect small magnetic anomalies buried at various depths
Solution Approach 1:
The patent divides the measurement into multiple discrete sensing positions along a scanning path. By segmenting the continuous magnetic field measurement into discrete points and comparing differences between adjacent positions, the system enhances detection sensitivity while suppressing internal noise through differential measurement techniques.
Solution Approach 2:
The patent replaces traditional mechanical scanning systems with an optical implementation using a Sagnac interferometer. This substitution eliminates mechanical noise and instability, providing a more stable reference signal for differential measurements and improving overall measurement precision.
2Measurement precision
If the sensing position is varied to improve measurement accuracy, then the signal-to-noise ratio improves, but the device complexity increases due to actuation modules and orientation stabilization
Solution Approach 1:
The patent implements a multi-functional actuation module that simultaneously performs positioning, orientation stabilization, and displacement function control. This universal module reduces overall system complexity by consolidating multiple functions into a single integrated unit rather than requiring separate systems for each function.
Solution Approach 2:
The patent introduces an intermediary orientation stabilization mechanism that decouples the complex coupling between position variation and orientation control. This intermediary system maintains accurate orientation during sensing position variation, enabling improved signal-to-noise ratio without proportionally increasing system complexity.
3Measurement precision
If multiple sensors are used to reduce noise, then the measurement accuracy improves, but the cumulative noise and device complexity increase
Solution Approach 1:
The patent uses a Sagnac interferometer to create an optical copy of the reference signal that traverses the same path as the measurement signal. This copied reference signal experiences identical environmental conditions and internal noise, allowing for perfect correlation and cancellation when subtracted from the measurement signal, thereby reducing cumulative noise while maintaining high accuracy.
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 and sensitive mapping of magnetic fields with high signal-to-noise ratio, capable of detecting minute variations in the magnetic field, improving the detection of small magnetic anomalies and reducing noise components, thus enhancing the reliability of magnetic surveys for threat detection and location.
Implementation Method 1
The Larmor precession causes an ac rotation of the polarization of a separate probe beam; the polarization rotation frequency provides a measure of the magnetic field.
Implementation Method 2
an actuation module that is connectable to at least one of the scalar magnetic sensors and is configured and operable to repeatedly vary the sensing position(s) at which the sensor(s) connected thereto sense the magnetic field according to a certain displacement function
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 2C~2E
AI summary
A gradiometer system including one or more magnetic sensor(s) is disclosed. The gradiometer includes an actuation module connectable to the magnetic sensor(s) to vary one or more sensing positions at which a magnetic field is sensed thereby. The one or more sensing positions are varied according to a certain displacement function indicating a predetermined displacement between the sensing positions as a function of time. A controller of the gradiometer system is adapted to determine at least one vector component of a gradient of the magnetic field sensed by the sensor(s) by carrying out the following: (i) obtaining readout data from the sensor(s) indicative of the magnetic field sensed at the varied sensing positions during a certain measurement time duration; (ii) processing the readout data to determine a differential magnetic field time profile indicating a difference between the magnetic fields sensed at at least two of the sensing positions during the measurement time duration; and (iii) demodulating the differential magnetic field time profile in accordance with the displacement function to thereby determine a demodulated time profile indicative of the at least one vector component of the gradient of the measured magnetic field.