Transparent Sample Defect Detection via Brewster Angle Polarization
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Solution Overview
Problem
Current techniques face challenges in accurately detecting defects in thin transparent materials like glass due to low reflectivity and the difficulty in separating signals from the top and bottom surfaces, especially for fragile, asymmetric, or large samples, which are essential for high-tech product manufacturing.
Innovation Solution
An optical scanning system that irradiates the transparent sample at or near the Brewster's angle, using a phase retardance detector to differentiate signals from the top and bottom surfaces, and a spatial filter to isolate specific surface signals, allowing for sensitive defect detection and scanning of various sample shapes and sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional inspection techniques are used on transparent samples, then defects can be detected, but the sensitivity and accuracy are reduced due to low reflectivity and difficulty in separating signals from top and bottom surfaces
Solution Approach 1:
The patent segments the reflected light signals into two distinct components: light reflected from the top surface and light reflected from the bottom surface. This is achieved by analyzing different polarization states of the reflected light, allowing the system to separately detect defects on each surface of the transparent sample, thereby resolving the signal separation difficulty.
Solution Approach 2:
The patent utilizes changes in polarization parameters of light upon reflection from different surfaces. By measuring the polarization state of reflected light and comparing it with reference values, the system can distinguish between top surface and bottom surface reflections, significantly improving defect detection accuracy on transparent samples with low reflectivity.
2Productivity
If glass samples are spun for inspection, then defects can be detected across the sample, but fragile, asymmetric, or large samples cannot be tested
Solution Approach 1:
The patent replaces the mechanical spinning system with a stationary optical inspection system. The sample remains fixed while optical beams scan across the sample surface in controlled patterns, eliminating the need for mechanical rotation. This substitution enables inspection of fragile, asymmetric, and large samples that cannot be mechanically spun, while maintaining comprehensive defect detection coverage.
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 enhances sensitivity and accuracy in detecting film thickness and defects on transparent samples, enabling effective inspection of glass and other materials before and after film deposition, regardless of sample shape or size, by minimizing polarization change and reflectivity variations.
Implementation Method 1
a first time varying beam reflector that is configured to reflect the light beam through a scan lens towards a transparent sample at an incident angle that is not more than one degree greater or less than Brewster's angle of the transparent sample
Implementation Method 2
measuring phase change in light reflected from the thin transparent material
Data Source
AI summary
An optical scanning system including a radiating source that outputs a light beam, a time varying beam reflector that reflects the light beam through a scan lens towards a transparent sample, a focusing lens configured to be irradiated by light scattered from the transparent sample, and a detector that is irradiated by the light scattered from the transparent sample. The detector outputs a signal that indicates an intensity of light measured by the detector. None of the light scattered from the transparent sample is blocked. The light scattered from the transparent sample is scattered from the top surface of the transparent sample, the bottom surface of the transparent sample, or any location in between the top surface of the transparent sample and the bottom surface of the transparent sample.