Liquid Light Guide for Non-Destructive Surface Inspection
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Solution Overview
Problem
Existing nondestructive inspection methods for surface structures, such as tool inserts for producing optical surfaces, fail to accurately replicate the optical functioning of the structures, leading to erroneous rejection of high-quality surface structures, and are limited by sample size and localized measurement capabilities.
Innovation Solution
A method involving the formation of a liquid light guide on the surface structure, where light is coupled into the liquid using LEDs or other light sources, allowing for total internal reflection and imaging of the surface structure's inverse shape, enabling evaluation of optically relevant defects without damaging the structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional inspection methods (SEM, laser scanning microscopy) are used, then measurement capability is provided, but the optical functioning of the surface structure cannot be replicated leading to erroneous rejection of high-quality surfaces
Solution Approach 1:
The patent creates an optical copy of the surface structure by forming a liquid light guide that replicates the optical functioning of the original surface structure. The liquid light guide acts as an optical replica that can be inspected without damaging the original, allowing accurate evaluation of optical properties without false rejections.
Solution Approach 2:
The liquid light guide serves as an intermediary between the surface structure to be inspected and the inspection system. It couples the optical fields from the surface structure to the detection system, enabling indirect inspection that preserves the optical functioning while providing measurement capability.
2Measurement precision
If scanning electron microscopy is used, then excellent resolution is achieved, but sample size is limited and only localized measurement of microstructures is possible
Solution Approach 1:
The liquid light guide system provides universal inspection capability that can accommodate various sample sizes and configurations. Unlike SEM which requires specific sample preparation and has limited field of view, the liquid light guide can be formed over different areas and maintains optical functionality throughout the entire sample surface.
3Productivity
If laser scanning microscopy with reflected light detection is used, then inspection capability is provided, but optical functioning cannot be replicated causing high-quality surfaces to be erroneously rejected
Solution Approach 1:
The patent changes the fundamental parameter of light interaction by using a liquid light guide that transmits light through the surface structure rather than relying on reflected light. This parameter change enables the system to detect optical properties directly without the false positives that occur with reflected light detection methods.
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 method allows for nondestructive inspection of surface structures, accurately identifying only optically relevant defects, enabling the use of high-quality surface structures for producing optical components, while being economically viable and capable of inspecting fine structures in the micrometer and nanometer range.
Implementation Method 1
at least a portion of the in-coupled light propagates in the light guide formed from the liquid through total internal reflection (light conductor effect) within the light guide
Data Source
AI summary
A method for the nondestructive inspection of a surface structure, including: preparing the surface structure; wetting a portion of the surface structure with a liquid, the variation in the thickness of the liquid above the portion of the surface structure being at most 50% of the maximum thickness of the liquid above the surface structure, so that the liquid forms a light guide which has, and is bounded by, the inverse shape of the surface structure at a first large surface and is bounded by air at a second large surface; coupling light into the light guide so that the inverse shape of the surface structure at the first large surface is impinged by light such that light coupled into the light guide is coupled out of the light guide via the second large surface; capturing an image of the light coupled out and; evaluating the captured image.