Multi-Wavelength Optical Coating Thickness Measurement
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Solution Overview
Problem
Current optical thickness measurement methods face challenges in accurately measuring thin coating thicknesses (less than about 20 nm) and identifying small changes in coating thickness, especially at the 'hot end' of the glass container forming process, leading to potential inventory losses due to coating deficiencies.
Innovation Solution
An apparatus and method utilizing a light source and detector to capture images with multiple wavelength channels, determining a relative shift between these channels based on histograms, allowing for precise measurement of coating thickness and acceptability, even at high temperatures during in-line production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current optical thickness measurement methods are used, then measurement can be performed, but measurement precision deteriorates for thin coating thicknesses (less than 20 nm)
Solution Approach 1:
The patent applies parameter changes by utilizing multiple wavelength channels (e.g., blue, green, red wavelengths) to measure coating thickness. By measuring the relative shift in peak wavelengths across different channels and using this shift to determine thickness, the method achieves superior precision for thin coatings (less than 20 nm) compared to conventional single-wavelength optical methods.
2Measurement precision
If offline inspection procedures are used, then coating thickness can be measured, but productivity deteriorates due to periodic sampling every 4 to 8 hours
Solution Approach 1:
The patent replaces the mechanical offline sampling and measurement system with an in-line optical measurement system that operates during production. The system uses light sources and detectors positioned to measure coating thickness on containers as they pass through the forming process, eliminating the need to stop production for periodic offline inspection.
Solution Approach 2:
The measurement system performs coating thickness verification at the 'hot end' of the glass container forming process, before the containers are fully cooled and transported away. This preliminary measurement allows for real-time quality control and immediate process adjustment, preventing the production of large quantities of defective containers.
3Productivity
If in-line measurement at hot end is implemented, then productivity is improved through continuous monitoring, but measurement precision deteriorates due to high temperatures (excess of 400 degrees Centigrade)
Solution Approach 1:
The patent measures coating thickness at the hot end during the forming process when containers are at high temperatures (excess of 400 degrees Centigrade). By implementing temperature compensation algorithms and using optical wavelengths that are minimally affected by thermal conditions, the system maintains measurement precision while enabling continuous in-line monitoring that improves productivity.
4Quantity of substance
If conventional optical methods are used, then measurement can be performed, but detection capability deteriorates for small changes in coating thickness
Solution Approach 1:
The patent measures the relative shift in peak wavelengths across multiple wavelength channels to detect small changes in coating thickness. This differential measurement approach, where the shift in spectral peaks is analyzed, provides enhanced sensitivity for detecting minor variations in coating material amount compared to conventional optical methods that rely on absolute intensity measurements.
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
Enables accurate and efficient measurement of coating thickness, reducing inventory losses by providing real-time monitoring and control of coating thickness within tolerance ranges, even for thin coatings and small changes, at the 'hot end' of the glass container forming process.
Implementation Method 1
at least one light source configured to direct light toward an object at a predetermined location on the object such that a portion of the light interacts with the object
Implementation Method 2
a detector configured to capture an image having at least two wavelength channels produced by the portion of the light that interacts with the object
Implementation Method 3
determine a relative shift between each of the at least two wavelength channels based on a histogram of each wavelength channel of the at least two wavelength channels
Data Source
Figure 1~3
Figure 2A~2B
Figure 2C~2D
AI summary
Methods and apparatus for measuring a thickness of a coating on an object are provided. Light is directed toward the object at a predetermined location on the object such that a portion of the light interacts with the object. An image having at least two wavelength channels (e.g., color channels) is captured that is produced by the portion of the light interacting with the object. A relative shift is determined between each of the at least two wavelength channels, based on a histogram of each wavelength channel of the at least two wavelength channels. At least one of the thickness or an acceptability of the coating on the object is determined based on the determined relative shift.