Atomic Magnetometer Gradient Measurement via Polarization Rotation

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Solution Overview

Problem

Existing atomic magnetometers face challenges in measuring magnetic field gradients with high sensitivity due to non-uniform amplification factors and noise between individual photo-detectors, leading to mixed noise in magnetic field gradient information.

Innovation Solution

The solution involves measuring the difference in magnetic field intensity between two positions as a difference in polarization rotation angle of a laser beam, using a probe beam that changes polarization rotation angle based on magnetic field intensity, and employing a magnetic sensing method with a pump beam to uniformize atomic spin directions and a linearly polarized probe beam for precise measurement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If differential information on electric signals from individual photo-detectors is used to obtain magnetic field gradient information, then measurement capability is provided, but noise is mixed in due to non-uniform amplification factors and noise characteristics between individual photo-detectors

Engineering Contradiction:

Improvemagnetic field gradient measurement precisionVSAvoidnoise mixing from photo-detector characteristic differences

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent uses a single photo-detector to detect the same probe beam at multiple measurement positions, creating copies of the detection path rather than using multiple independent photo-detectors. This eliminates the noise mixing problem while maintaining the ability to measure magnetic field gradients through sequential measurements at different positions.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent segments the measurement process into sequential steps at different measurement positions along the probe beam propagation path. By measuring at position 1, then position 2, and calculating the difference, the system obtains gradient information without requiring simultaneous multi-position detection that would introduce photo-detector variability.

Inventive Principle:

Principle #1Segmentation

2Adaptability or versatility

If multiple photo-detectors are used to measure magnetic field gradient at different positions, then spatial measurement coverage is improved, but device complexity and noise from non-uniform characteristics increase

Engineering Contradiction:

Improvespatial measurement coverageVSAvoidnumber of photo-detectors and their calibration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

A single photo-detector performs multiple functions by detecting the probe beam at different measurement positions sequentially. The same photo-detector measures the magnetic field gradient at position 1, then at position 2, eliminating the need for multiple specialized detectors while maintaining spatial measurement capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The system performs preliminary measurements at different positions before final gradient calculation. By sequentially measuring the probe beam characteristics at position 1 and position 2, the system prepares the data needed to calculate the magnetic field gradient without requiring complex simultaneous multi-position detection hardware.

Inventive Principle:

Principle #10Preliminary action

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 approach allows for high-sensitivity measurement of magnetic field gradients by directly measuring the difference in polarization rotation angles, reducing noise interference and enhancing sensitivity, thereby providing accurate magnetic field gradient information.

Implementation Method 1

a medium which changes a polarization rotation angle of the probe beam depending on a magnetic field intensity at a first measurement position and a magnetic field intensity at a second measurement position

Methodology Applied

Scientific EffectFaraday effect: Faraday Effect

Implementation Method 2

irradiating the atomic group contained in a hollow portion of a cell with a pump beam to uniformize directions of spin of atoms constituting the atomic group

Methodology Applied

Scientific EffectOptical pumping:

Implementation Method 3

a detector for detecting information on a polarization rotation angle of the linearly polarized light

Methodology Applied

Scientific EffectPolarization rotation measurement:

Data Source

PatentUS8405389B2Atomic magnetometer and magnetic sensing method

Publication Date: 2013.03.26 CANON KK

AI summary

An atomic magnetometer includes a light source for a probe beam and a medium in which the probe beam is to be propagated. The medium is a substance which changes a polarization rotation angle of the probe beam depending on a magnetic field intensity at a first measurement position and a magnetic field intensity at a second measurement position different from the first measurement position. The atomic magnetometer directly measures a difference between the magnetic field intensity at the first measurement position and the magnetic field intensity at the second measurement position as a difference in polarization rotation angle, along a propagation path of the probe beam.