Optical Filter Defect Detection via Dual-Spectrum Photodetector Array
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical filter inspection processes are inadequate for detecting small defects, particularly pinholes and point defects, which can significantly degrade filter performance in applications like imaging, where visual inspection is difficult and time-consuming.
Innovation Solution
A test device and method using a two-dimensional array of photodetectors to distinguish between pinholes and point defects by illuminating the optical filter with passband and stopband light, where pinholes allow stopband light to pass and defects block passband light, enabling efficient detection without the need for spectral characterization equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visual inspection is used to detect defects, then the inspection process is simple, but small defects like pinholes and point defects cannot be detected reliably
Solution Approach 1:
The patent replaces visual inspection (mechanical/optical system) with an automated photodetector array system that uses electrical signals and image processing to detect defects. The photodetector array captures light transmission patterns, and computer algorithms analyze the data to identify pinholes and point defects, substituting human visual inspection with an automated electronic system.
Solution Approach 2:
The patent introduces an intermediary photodetector array between the light source and the defect detection process. The photodetectors convert light signals into electrical signals, which are then processed by computer algorithms to identify defects. This intermediary system enables automated, precise defect detection without requiring direct visual inspection.
2Reliability
If spectral measurement equipment is used to characterize filters, then filter specifications can be confirmed, but the inspection process becomes time-consuming and expensive
Solution Approach 1:
The patent extracts the specific function of defect detection from the comprehensive spectral measurement process. Instead of using full spectral measurement equipment to detect defects, the system uses a simplified photodetector array that specifically targets defect detection by measuring light transmission at defect locations, separating this function from the broader spectral characterization process.
Solution Approach 2:
The patent employs a relatively simple and cost-effective photodetector array system instead of expensive spectral measurement equipment. The system uses standard photodetectors and computer processing to achieve rapid defect detection, providing an economical alternative to high-cost spectral characterization for the specific purpose of identifying pinholes and point defects.
3Manufacturing precision
If comprehensive spectral characterization is performed at multiple areas, then thickness non-uniformity can be detected, but the inspection process becomes complex and time-consuming
Solution Approach 1:
The patent replaces comprehensive spectral measurement (mechanical/optical system) with a photodetector array system that rapidly captures spatial information about the filter. The array simultaneously measures light transmission across multiple areas, and computer algorithms analyze the data to detect thickness variations and defects, significantly reducing inspection time while maintaining precision.
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 allows for rapid and cost-effective detection of pinholes and point defects across the entire filter area, improving filter quality and performance by identifying defects that would otherwise go undetected in conventional inspections.
Implementation Method 1
a passband illumination source configured to illuminate the optical filter under test with passband illumination whose spectral range at least overlaps a passband of the optical filter under test
Implementation Method 2
a stopband illumination source configured to illuminate the optical filter under test with stopband illumination whose spectral range lies entirely outside of the passband of the optical filter under test
Implementation Method 3
a two-dimensional array of photodetectors arranged to detect the passband illumination after passing through the optical filter under test and to detect the stopband illumination after passing through the optical filter under test
Data Source
AI summary
Devices and methods are disclosed for characterizing point flaws (including pinholes and point defects) of an optical filter. A passband test is performed, including: illuminating the optical filter with passband illumination whose spectral range at least overlaps a passband of the optical filter; acquiring a passband map of the optical filter using a two-dimensional array of photodetectors while illuminating the optical filter with the passband illumination; and identifying point defects of the optical filter as low intensity locations of the passband map. A stopband test is performed, including: illuminating the optical filter with stopband illumination whose spectral range lies entirely outside of the passband of the optical filter; acquiring a stopband map of the optical filter using the two-dimensional array of photodetectors while illuminating the optical filter with the stopband illumination; and identifying pinholes of the optical filter as high intensity locations of the stopband map.