Scattered Radiation Optical Scanner for Transparent Sample Inspection
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Solution Overview
Problem
Current techniques for inspecting thin transparent materials like glass struggle with low reflectivity and high transparency, making it difficult to accurately detect defects, especially in fragile, asymmetric, or large samples, and fail to separate signals from the top and bottom surfaces effectively.
Innovation Solution
An optical scanning system that irradiates the sample at or near the Brewster's angle, using a combination of time-varying beam reflectors and phase retardance detectors to differentiate signals from the top and bottom surfaces, allowing for sensitive defect detection and scanning of various sample shapes and sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If glass samples are spun for inspection, then defect detection is enabled, but fragile, asymmetric, or large samples cannot be tested
Solution Approach 1:
The patent replaces the mechanical spinning system with a stationary sample holder and uses optical scanning instead. The laser beam is scanned across the sample surface using galvanometer mirrors, eliminating the need for mechanical rotation while still enabling comprehensive defect detection across the entire sample area.
Solution Approach 2:
The optical scanning system provides universal applicability to various sample types (fragile, asymmetric, large) by using non-contact optical measurement. The system can inspect any flat surface regardless of its mechanical properties, making it universally applicable to different glass sample configurations without requiring sample rotation.
2Measurement precision
If conventional reflection techniques are used, then defect detection is attempted, but low reflectivity and high transparency of glass make accurate detection difficult
Solution Approach 1:
The patent changes the optical parameters by using laser light with specific wavelength and polarization, and by controlling the incident angle precisely. These parameter changes enhance the interaction between light and the glass sample, improving the signal strength and detection accuracy despite the low reflectivity of glass.
Solution Approach 2:
The patent introduces phase modulation as an intermediary mechanism. By modulating the phase of the reflected light signal and using lock-in detection, the system enhances the detectability of weak signals from the glass surface, effectively acting as a signal amplifier for low-reflectivity materials.
3Measurement precision
If signals from top and bottom surfaces are not separated, then inspection is simpler, but accurate defect localization is impossible
Solution Approach 1:
The patent segments the reflected light signals into separate components corresponding to reflections from the top surface and bottom surface. By analyzing the temporal and phase characteristics of these segmented signals, the system can distinguish and localize defects on specific surfaces, enabling accurate defect localization.
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 to thin films on transparent samples, enabling accurate detection of defects and film thickness measurements while accommodating diverse sample geometries, improving the inspection process for high-tech products.
Implementation Method 1
a 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
Implementation Method 3
A spatial filter is configured to block the second portion of the light beam scattered from the second surface of the transparent sample
Data Source
AI summary
An optical scanning system includes a radiating source capable of outputting a light beam, a 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, and a focusing lens configured to be irradiated by light scattered from the transparent sample at an angle that is normal to the plane of incidence of the moving irradiated spot on the transparent sample. A first portion of the light beam is scattered from a first surface of the transparent sample and a second portion of the light beam is scattered from a second surface of the transparent sample. A spatial filter is configured to block the second portion of the light beam scattered from the second surface of the transparent sample.