Micro-polarizer array for surface defect detection
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Solution Overview
Problem
Current methods for detecting surface defects on ultra-smooth elements, such as scratches and pits, are inefficient and inaccurate, particularly for large-aperture elements, due to limitations in sensitivity, speed, and consistency, especially when dealing with high-reflective coatings, leading to energy loss and reduced signal-to-noise ratios in imaging systems.
Innovation Solution
A surface defect measuring apparatus and method using microscopic scattering polarization imaging, which employs a micro-polarizer array to enhance sensitivity and contrast by calculating polarization-degree images, allowing for real-time detection of defects on meter-scale large-aperture ultra-smooth elements, including high-reflective coatings, through the use of a laser, converging lenses, a polarizer, and a camera system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If manual visual method is used for surface defect detection, then the method is simple and easy to operate, but inspectors cannot work continuously due to eye fatigue and cannot accurately give defect size
Solution Approach 1:
The patent replaces the manual visual inspection system with an automated optical detection system consisting of light source, imaging lens, and camera. This substitution eliminates human physiological limitations while providing quantitative defect size measurement through image processing, resolving the contradiction between operational simplicity and measurement precision.
2Reliability
If photothermal microscopic imaging technique is used, then absorptive defects can be detected, but the technique is insensitive to structural defects such as scratches and pits and has low measurement efficiency due to single-point detection
Solution Approach 1:
The patent divides the detection task into two complementary imaging modes: dark-field imaging for structural defects (scratches, pits) and photothermal imaging for absorptive defects. By segmenting the detection functions and using a scanning mechanism to cover the entire aperture, the system achieves both high sensitivity for different defect types and improved measurement efficiency compared to single-point detection.
3Productivity
If laser scattering method is used for full-aperture rapid measurement, then measurement speed is improved, but the method is not suitable for detecting defects on the surface of large-aperture and large-weight ultra-smooth optical element
Solution Approach 1:
The patent introduces a scanning mechanism that dynamically positions the imaging system across the entire aperture of large optical elements. This dynamic scanning approach allows the system to adapt to various aperture sizes and weights, maintaining measurement speed while expanding applicability to large-aperture elements that static systems cannot handle.
4Measurement precision
If microscopic scattering dark-field imaging technique is used, then super-resolution detection is realized, but most weak scratches are undetected and background grayscale increases for high-reflective coating elements
Solution Approach 1:
The patent merges dark-field imaging and photothermal imaging into a single integrated system with a unified optical path. This combination allows the system to leverage the super-resolution capability of dark-field imaging for structural defects while simultaneously detecting weak scratches through photothermal effects, and handles high-reflective coatings by adjusting between the two imaging modes to optimize contrast.
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 provides high-sensitivity, high-contrast, and super-resolution measurements of surface defects, effectively improving defect detection accuracy and speed, even for weak scratches and high-reflective coatings, while simplifying the system structure and enhancing the ability to detect defects on large-aperture elements.
Implementation Method 1
surface defect measuring apparatus and method by microscopic scattering polarization imaging
Implementation Method 2
microscopic scattering polarization imaging
Data Source
AI summary
A surface defect measuring apparatus and method by microscopic scattering polarization imaging is provided. The apparatus mainly comprises a laser, a first converging lens, a rotary diffuser, a second converging lens, a diaphragm, a third converging lens, a pinhole, a fourth converging lens, a polarizer, a half-wave plate, a polarizing beam splitter, an X-Y translation stage, a sample, a microscope lens, a quarter-wave plate, a micro-polarizer array, a camera and a computer. The micro-polarizer array is adopted to realize real-time microscopic scattering polarization imaging of the surface defects; a polarization-degree image is calculated to improve the sensitivity for detecting the surface defects of the ultra-smooth element, and the effective detection of the surface defects of a high-reflective coating element is also realized, and the requirement for rapid detection of the surface defects of a meter-scale large-aperture ultra-smooth element can be met.