Sub-surface Defect Detection via Thermal Fluctuation Analysis
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Solution Overview
Problem
Existing imaging methods struggle to detect sub-surface defects in samples due to limited contrast and resolution, as normal imaging techniques are hindered by the opaqueness of the sample, making it difficult to visualize and identify sub-surface defects effectively.
Innovation Solution
The method employs an imaging system that includes a sample holder, an excitation source, and an optical sensor. The excitation source induces temporal fluctuations on the sample surface, and the optical sensor captures multiple images of the sample surface at different times. By analyzing the pixel value distributions and comparing cumulants, a cumulant map is generated to enhance contrast and detect sub-surface defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If normal imaging methods are used to image sub-surface defects, then the imaging process is simple and direct, but the contrast between defect regions and background regions is insufficient due to sample opaqueness
Solution Approach 1:
The patent changes the parameter being measured from static optical properties to dynamic thermal response. By heating the sample and measuring temperature changes over time at each pixel location, the method extracts temporal information that reveals sub-surface defects. Defect regions exhibit different thermal response characteristics compared to healthy regions, enabling detection despite sample opaqueness.
Solution Approach 2:
The patent applies a preliminary heating action to the sample before measurement. By uniformly heating the entire sample surface first, then allowing different regions to cool or respond thermally, the method creates distinguishable thermal signatures. This preliminary thermal excitation enables subsequent detection of sub-surface defects through temporal temperature analysis.
2Device complexity
If regular imaging methods are used, then the equipment and procedure are straightforward, but the resolution of sub-surface defect images is reduced due to diffraction limit
Solution Approach 1:
The patent replaces direct optical imaging (mechanical/optical system limited by diffraction) with thermal field measurement and temporal analysis. Instead of relying on optical resolution to directly image sub-surface defects, the method uses thermal response measurements combined with cumulant analysis to infer defect characteristics, effectively bypassing the diffraction limit constraint.
3Measurement precision
If excitation patterns are applied to enhance defect contrast, then sub-surface defects become more detectable, but the imaging process and data analysis become more complex
Solution Approach 1:
The patent applies periodic or controlled thermal excitation to the sample and measures the temporal response. By analyzing how different regions respond over time to the applied excitation, the method enhances defect contrast. The temporal dimension provides additional information that distinguishes defect regions from background, justifying the increased process complexity.
Solution Approach 2:
The patent introduces thermal response as an intermediary between the sample and the detection system. Instead of directly imaging optical properties of sub-surface defects, the method uses thermal field as a mediator that translates sub-surface structural information into measurable surface temperature variations, enabling indirect but effective defect detection.
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 improves the detection of sub-surface defects by increasing contrast and resolution, allowing for more accurate identification and characterization of defects beneath the sample surface.
Implementation Method 1
exciting the sample by inducing temporal fluctuations in the sample by providing an excitation pattern to the sample surface
Implementation Method 2
obtaining multiple surface images of the sample surface with an optical sensor comprising multiple pixels, wherein each surface image is separated from a subsequent surface image by a time dt
Data Source
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AI summary
The invention relates to a method for sub-surface defect detection of a sample having a sample surface wherein use is made of an imaging system. The invention further relates to an imaging system for sub-surface defect detection for use in the method of the invention. The imaging system comprises: - a sample holder for holding the sample therein; - an excitation source for exciting the sample in the sample holder; - an optical sensor for obtaining an image of the sample surface of the sample in the sample holder, wherein the optical sensor comprises multiple pixels; and - a processor operatively connected to the excitation source and the optical sensor.