Optical Scanning System for Transparent Sample Inspection
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Solution Overview
Problem
Current techniques face challenges in inspecting glass samples due to their low reflectivity and high transparency, particularly in separating signals from the top and bottom surfaces, and in scanning various shapes and sizes of transparent samples for defects.
Innovation Solution
An optical scanning system that irradiates the transparent sample at or near the Brewster's angle, using a combination of time-varying beam reflectors, phase retardance detectors, and spatial filters to differentiate signals from the top and bottom surfaces, allowing for accurate defect detection and scanning of diverse sample shapes and sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If glass samples are spun for inspection, then defect detection coverage is improved, but fragile or large samples may be damaged or become difficult to handle
Solution Approach 1:
The patent replaces the mechanical spinning system with a stationary optical inspection system. The optical system uses a light source, scanner, and detector to inspect glass samples without mechanical contact, thereby eliminating the risk of damage to fragile or large samples while maintaining comprehensive defect detection coverage through optical scanning
2Productivity
If conventional optical inspection is used on transparent samples, then inspection speed is maintained, but signal separation from top and bottom surfaces becomes difficult
Solution Approach 1:
The patent changes the optical parameters by using specific wavelengths of light and controlling the incident angle. The system uses a light source that emits light at angles that create distinct reflection patterns from top and bottom surfaces, allowing the detector to separate and identify signals from each surface independently while maintaining high inspection speed
Solution Approach 2:
The patent introduces an intermediary optical system including scanners and beam splitters that mediate between the light source and the sample. This intermediary system directs light at controlled angles and separates reflected signals, enabling precise differentiation between top and bottom surface reflections without sacrificing inspection throughput
3Measurement precision
If Brewster's angle illumination is used, then surface sensitivity is improved, but polarization variations increase
Solution Approach 1:
The patent implements a feedback mechanism where the detector measures the polarization state of reflected light and the system adjusts illumination parameters accordingly. By monitoring polarization variations in real-time and adjusting the light source or scanner parameters, the system maintains optimal sensitivity for surface defect detection while compensating for polarization effects that would otherwise interfere with measurement accuracy
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 enhances sensitivity and accuracy in detecting defects on transparent samples by minimizing polarization change and reflectivity variations, enabling effective inspection of thin films on glass and other transparent materials.
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
The first time varying beam reflector causes a first phase retardance of the light beam and the second time varying beam reflector causes a second phase retardance of the reflected light beam in the opposite direction of the first phase retardance
Data Source
AI summary
An optical scanning system includes a radiating source capable of outputting a source light beam, a de-scan lens that is configured to output a de-scanned light beam, the de-scan lens is located approximately one focal length of the de-scan lens from an sample irradiation location, a focusing lens that is configured to output a focused light beam, a first non-polarizing beam splitter configured to be irradiated by at least a portion of the focused light beam, a second non-polarizing beam splitter configured to be irradiated by at least a portion of the focused light beam that is reflected by the first non-polarizing beam splitter, and a detector that is located at approximately one focal length of the focusing lens from the focusing lens, the detector is configured to be irradiated by at least a portion of the focused light beam that is not reflected by the second non-polarizing beam splitter.