Unshielded Optical Magnetometer for Ambient Magnetic Field Measurement

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Solution Overview

Problem

Conventional optical magnetometers are large, expensive, and sensitive to external magnetic interferences, limiting their ability to accurately measure magnetic field changes in uncontrolled environments due to the need for magnetic shielding.

Innovation Solution

An optical magnetometer design featuring a pulsed-mode pump laser and a probe laser with a vapor cell, capable of computing magnetic field changes based on differences in temporally-distinct response frequency values, which can operate either magnetically shielded or unshielded, using alkaline atoms like Cesium, Rubidium, or Potassium, and employing a diffraction grating and polarizers to tune and filter the laser beams.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If magnetic shielding is used to protect against external magnetic interferences, then measurement precision is improved, but device complexity and cost increase

Engineering Contradiction:

Improvemeasurement precisionVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts and removes the magnetic shielding component from the magnetometer system. By operating without magnetic shielding, the device eliminates the complexity and cost associated with shielding structures while maintaining measurement capability through a different operational approach (measuring changes rather than absolute values).

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of protecting the measurement system from external magnetic fields through shielding, the patent inverts the approach by directly measuring the ambient magnetic field changes without shielding. The system accepts the ambient field as the measurement target rather than treating it as interference to be blocked.

Inventive Principle:

Principle #13The other way round (Inversion)

2Measurement precision

If magnetic shielding is used to protect against external magnetic interferences, then measurement precision is improved, but manufacturing cost increases

Engineering Contradiction:

Improvemeasurement precisionVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent removes the magnetic shielding component from the system, eliminating the manufacturing cost and complexity associated with acquiring, installing, and maintaining magnetic shielding materials and structures.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent adopts a simpler, more economical approach by using unshielded components and accepting ambient magnetic field conditions, thereby reducing manufacturing costs while maintaining functional capability through alternative measurement strategies.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Measurement precision

If conventional optical magnetometers are used in controlled environments with magnetic shielding, then measurement precision is improved, but adaptability to uncontrolled environments decreases

Engineering Contradiction:

Improvemeasurement precisionVSAvoidadaptability

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent inverts the conventional approach by designing the magnetometer to operate directly in uncontrolled environments without magnetic shielding. Instead of creating a controlled environment through shielding, the system adapts to and measures the ambient magnetic field conditions directly.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent creates a universal magnetometer design that can operate in both controlled and uncontrolled environments. By removing the requirement for magnetic shielding and designing the system to measure magnetic field changes in ambient conditions, the device gains versatility across different operational environments.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 design allows for accurate measurement of small magnetic field changes, including those from ambient sources, with high sensitivity (up to pT levels) without the need for shielding, using a compact and cost-effective setup.

Implementation Method 1

The atoms are optically pumped by a pump laser beam

Methodology Applied

Scientific EffectOptical pumping:

Implementation Method 2

Larmor precession, in which metal atom spins have a precession at a frequency proportional to the ambient magnetic field

Methodology Applied

Scientific EffectLarmor precession:

Implementation Method 3

their spin rotation frequency is measured by a probe laser beam

Methodology Applied

Scientific EffectProbe beam detection:

Implementation Method 4

said pump laser further comprises a diffraction grating configured to tune the pulsating laser beam

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 5

said circular polarizer is a λ/4 quarter wave plate

Methodology Applied

Scientific EffectPolarization: Polarisation

Data Source

PatentUS10712407B2Device and methodology for measuring minute changes in ambient magnetic field

Publication Date: 2020.07.14 BEN GURION UNIVERSITY OF THE NEGEV

AI summary

An optical magnetometer comprising: a response frequency measurement unit comprising a vapor cell, a pulsed-mode pump laser and a probe laser; and a computing unit configured to compute a magnetic field change based on a difference between at least two temporally-distinct response frequency values received from the frequency measurement unit. Optionally, the response frequency measurement unit is magnetically non-shielded.