Defect Inspection Device Using Spatial Light Phase Modulator

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Solution Overview

Problem

Existing defect inspection methods using the magneto optical effect face challenges in accurately detecting defects on non-plane surfaces due to mixed signals from surface shape and magnetic field changes, leading to deteriorated measurement accuracy.

Innovation Solution

A defect inspection device employing a spatial light phase modulator to measure surface shape and magnetic field distribution, with a data separation unit that distinguishes between surface shape and magnetic field specific data, improving defect detection accuracy by isolating defect-induced changes from surface shape effects.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a magnetic thin film is used as a magnetic transfer film on a non-plane inspection surface, then the inspection can be performed on complex surfaces, but measurement accuracy deteriorates due to gaps between the film and surface

Engineering Contradiction:

Improveapplicability to non-plane surfacesVSAvoidmagnetic field distribution measurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical contact-based magnetic thin film transfer method with an optical measurement system using a spatial light phase modulator. This optical system measures magnetic field distribution without requiring physical contact or film adhesion to the surface, thereby eliminating the gap problem while maintaining applicability to non-plane surfaces.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a spatial light phase modulator as an intermediary between the light source and the inspection surface. This modulator enables indirect measurement of magnetic field distribution through optical phase modulation, avoiding the need for direct film-to-surface contact and the associated accuracy losses.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Difficulty of detecting and measuring

If magneto optical effect is used to detect magnetic field changes, then defect detection capability is provided, but measurement accuracy deteriorates due to mixed signals from surface shape and magnetic field changes

Engineering Contradiction:

Improvedefect detection capabilityVSAvoidmagnetic field distribution measurement accuracy

Core Design Contradiction:

Difficulty of detecting and measuringVSMeasurement precision

Solution Approach 1:

The patent segments the measurement process into two independent components: surface shape measurement and magnetic field distribution measurement. By using the spatial light phase modulator to separately acquire and process these two types of information, the system can isolate defect-related magnetic field changes from surface shape effects, thereby improving measurement precision while maintaining defect detection capability.

Inventive Principle:

Principle #1Segmentation

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 solution effectively suppresses measurement accuracy deterioration caused by surface shape and enhances defect detection precision, while also canceling phase noise through shared light paths, resulting in improved defect inspection accuracy.

Implementation Method 1

using light applied to the inspection target via a spatial light phase modulator based on an interference state of reflected light from the inspection target

Methodology Applied

Scientific EffectInterference: Interference

Implementation Method 2

a magnetic field distribution measurement unit which measures magnetization distribution of a surface of the inspection target magnetized by an excitation device for magnetizing the inspection target using light applied to the inspection target via the spatial light phase modulator

Methodology Applied

Scientific EffectMagneto optical effect: Magneto-Optic Effects

Implementation Method 3

an excitation device for magnetizing the inspection target

Methodology Applied

Scientific EffectMagnetization: Magnetism

Data Source

PatentUS10317368B2Defect inspection device and defect inspection method

Publication Date: 2019.06.11 HITACHI LTD

AI summary

A defect inspection device configured to measure a surface shape of an inspection target using light applied to the inspection target via a spatial light phase modulator based on an interference state of reflected light from the inspection target obtained via the spatial light phase modulator, to measure magnetic field distribution of a surface of the inspection target magnetized by an excitation device for magnetizing the inspection target using light applied to the inspection target via the spatial light phase modulator based on an interference state of reflected light from the inspection target obtained via the spatial light phase modulator, and to separate data of a magnetic field specific portion which exists on the surface of the inspection target from magnetic field distribution data which is a measurement result of magnetic field distribution of the inspection target based on surface shape data which is a measurement result of the surface shape of the inspection target, to suppress deterioration of measurement accuracy of magnetic field distribution generated by the surface shape of the inspection target and to improve defect detection accuracy.