Transparent Article Inspection via Edge Illumination
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Solution Overview
Problem
Existing methods for inspecting transparent articles, such as glass substrates for hard disk drives, often fail to detect surface and subsurface defects due to the majority of light penetrating and refracting through the article, leaving some defects undetected.
Innovation Solution
An apparatus that uses a photon emitter to direct photons into the article from its circumferential edge at an angle greater than or equal to the critical angle, causing total internal reflection, and a photon detector array to detect scattered photons from surface features, allowing for improved visibility and detection of defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light is projected onto a transparent article from above, then the article can be illuminated for imaging, but most light penetrates and refracts through the article causing defects to go undetected
Solution Approach 1:
Instead of illuminating the transparent article from above (conventional approach), the patent inverts the illumination approach by directing light from the circumferential edge at a grazing angle. This inversion causes total internal reflection within the article, making defects visible through scattered light patterns while the majority of light reflects rather than penetrates through to the other side.
2Measurement precision
If a camera records images of a transparent article with conventional illumination, then the imaging apparatus can operate simply, but defects remain undetected due to light refraction
Solution Approach 1:
The patent changes the illumination parameters by adjusting the angle of incident light to be at or above the critical angle for total internal reflection. This parameter change transforms the optical behavior from refraction (conventional) to total internal reflection, enabling defect detection without requiring complex additional imaging systems.
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 enables more accurate and efficient detection of surface and subsurface defects, enhancing the quality of the inspection process by ensuring that all defects are identified, even those hidden by the transparency of the article.
Implementation Method 1
direct photons into the article from its circumferential edge at an angle greater than or equal to the critical angle, causing total internal reflection
Implementation Method 2
detect photons scattered from features of the article
Data Source
AI summary
Provided herein is an apparatus, comprising a first photon emitter configured to emit photons into an article from a circumferential edge of the article, and a photon detector array configured to detect photons scattered from features of the article.