Optical Magnetic Stray Field Imaging for Parallel Pixel Detection

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Solution Overview

Problem

Existing systems for detecting magnetic stray fields on the surface of test objects are inefficient and costly, as they require sequential scanning, lacking the ability to simultaneously detect multiple pixels with the required sensitivity.

Innovation Solution

A system comprising a radiation source, magnetic field-sensitive medium, magnetic shield, illumination optics, reflective element, digital image sensor, and control and evaluation unit, which uses pump and probe radiation to optically detect free spin precession in the magnetic field-sensitive medium, allowing simultaneous detection of multiple pixels with high sensitivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If sequential scanning is used to detect magnetic stray field, then system complexity is reduced, but detection time and productivity deteriorate

Engineering Contradiction:
Improvesystem complexityVSAvoiddetection speed
Core Design Contradiction:
Device complexityVSProductivity

Solution Approach 1:

The detection system is segmented into multiple independent pixel elements, each capable of detecting magnetic field at its specific location. This segmentation allows parallel detection across the entire surface simultaneously, eliminating sequential scanning while maintaining manageable complexity through modular pixel design

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The system transitions from temporal dimension (sequential scanning over time) to spatial dimension (simultaneous detection across multiple pixels). By distributing detection capabilities across multiple spatial locations, the system achieves parallel measurement without requiring complex scanning mechanisms

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Productivity

If multiple pixels are detected simultaneously, then productivity is improved, but device complexity and cost increase

Engineering Contradiction:
Improvedetection speedVSAvoidsystem complexity
Core Design Contradiction:
ProductivityVSDevice complexity

Solution Approach 1:

Multiple pixel elements are merged into a single integrated detection system that shares common components such as the magnetic field-sensitive medium, illumination source, and signal processing unit. This merging approach enables simultaneous multi-pixel detection while avoiding the need for separate detection systems at each location, thereby controlling overall complexity

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The system employs universal components that serve multiple pixels simultaneously, including a single magnetic field-sensitive medium that responds to fields across the entire surface and a common illumination system that excites all pixels. This multi-functionality reduces the number of required components while maintaining simultaneous detection capability

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Measurement precision

If high sensitivity detection is achieved, then measurement precision is improved, but device complexity increases

Engineering Contradiction:
Improvemagnetic field sensitivityVSAvoidsystem complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

A magnetic field-sensitive medium acts as an intermediary between the magnetic field and the detection pixels. This medium converts magnetic field information into detectable signals that can be read by the pixel elements, enabling high sensitivity detection without requiring each pixel to directly measure the magnetic field, thus reducing individual pixel complexity

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The system replaces direct mechanical or electronic magnetic field sensing with an optical detection mechanism using magnetic field-sensitive medium that modulates optical properties. This substitution allows pixels to detect magnetic fields indirectly through optical signal changes, reducing the complexity of direct magnetic sensing components while achieving high sensitivity

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

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 enables cost-effective, efficient, and sensitive detection of magnetic stray fields with spatial resolution, capable of resolving local stress concentrations and defects in components before failure, with a sensitivity of less than one nanotesla.

Implementation Method 1

the pump radiation is first injected into the magnetic field-sensitive medium to optically pump it

Methodology Applied
Scientific EffectOptical pumping:

Implementation Method 2

the probe radiation is subsequently injected into the magnetic field-sensitive medium to probe the absorption modulated by the Larmor frequency due to the stray field

Methodology Applied
Scientific EffectLarmor frequency:

Implementation Method 3

it enables spin precession with a Larmor frequency dependent on the stray field

Methodology Applied
Scientific EffectSpin precession: Precession

Implementation Method 4

the probe radiation is subsequently injected into the magnetic field-sensitive medium to probe the absorption modulated by the Larmor frequency due to the stray field

Methodology Applied
Scientific EffectLarmor frequency:

Implementation Method 5

a digital image sensor, an imaging optic, and a control and evaluation unit... the probe radiation is subsequently injected into the magnetic field-sensitive medium to probe the absorption modulated by the Larmor frequency

Methodology Applied
Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentEP4644889A1System for spatially resolved recording of a measure for the magnetic flux density of a magnetic stray field at the surface of a test object
Publication Date: 2025.11.05 FRAUNHOFER GESELLSCHAFT ZUR FORDERUNG DER ANGEWANDTEN FORSCHUNG EV
  • EP4644889A1 patent drawingFigure 1~2
  • EP4644889A1 patent drawingFigure 3
  • EP4644889A1 patent drawingFigure 4

AI summary

The present invention relates to a system for spatially resolved detection of a measure of the magnetic flux density of a magnetic stray field at the surface of a test object. The system according to the invention comprises a radiation source, a magnetic field-sensitive medium, a magnetic shield with a shielded volume, an illumination optic, a reflective element, a digital image sensor, an imaging optic, and a control and evaluation unit.