Multi-Wavelength Polarized Light Topography Measurement
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Solution Overview
Problem
Current methods for deriving the topography of large, polished object surfaces are time-consuming and inaccurate, often requiring manual inspection and limited to small areas due to the need for precise surface measurements in industrial processes like automotive, medical, and optical manufacturing.
Innovation Solution
A method and apparatus using linearly polarized light waves directed towards an object surface and a reference surface, capturing images for multiple wavelengths and polarizations to derive topography, allowing for accurate and rapid measurement of large surface areas with improved accuracy and reduced ambiguity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional single-wavelength interferometry is used to measure surface topography, then measurement precision is achieved, but measurement time increases and productivity decreases
Solution Approach 1:
The patent uses multiple wavelengths (405nm, 532nm, 635nm) to perform sequential measurements, where each wavelength provides periodic interference patterns that are combined to achieve both high precision and fast measurement. The multi-wavelength approach allows the system to capture surface topography data more efficiently than single-wavelength methods.
2Productivity
If multi-wavelength interferometry is used to improve measurement speed, then productivity increases, but measurement precision deteriorates due to wavelength calibration complexity
Solution Approach 1:
The patent introduces a reference surface with known topography features as an intermediary element. This reference surface provides stable reference points that enable accurate wavelength calibration and phase unwrapping across multiple wavelengths, thereby maintaining measurement precision while achieving fast multi-wavelength measurement.
3Ease of operation
If white light interferometry is used to increase working distance, then ease of operation improves, but measurement precision deteriorates due to ambiguity
Solution Approach 1:
The patent segments the white light spectrum into multiple discrete wavelength components (405nm, 532nm, 635nm). Each wavelength segment is measured separately and then combined through phase unwrapping algorithms, which resolves the ambiguity problem of white light interferometry while maintaining the advantage of long working distance.
4Measurement precision
If manual inspection is used to ensure surface quality, then measurement precision is maintained, but productivity decreases and time consumption increases
Solution Approach 1:
The patent replaces manual visual inspection with an automated optical measurement system that captures surface topography data and automatically analyzes it against quality specifications. The system provides quantitative measurements of surface parameters (Ra, Rq, Rz) and generates pass/fail decisions, eliminating the need for manual inspection while maintaining or improving precision.
5Measurement precision
If small area measurements are used to achieve high precision, then measurement precision is maintained, but the area of measurement decreases
Solution Approach 1:
The patent extends the measurement capability from small areas to large areas by utilizing the temporal dimension through multi-wavelength sequential measurement. The system captures interference patterns at multiple wavelengths and combines them to achieve high precision over extended measurement areas, effectively adding a dimensional approach to overcome the area limitation.
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 fast and accurate determination of surface geometrical topography over large areas, providing quantitative feedback for polishing processes with increased robustness and reduced sensitivity to vibrations, suitable for industrial applications.
Implementation Method 1
a linearly polarized light wave is directed towards the object surface and a reference surface. Images of reflected linearly polarized light wave for a plurality of wavelengths are obtained.
Implementation Method 2
The topography of the object surface is derived based on the obtained images... the accuracy of a single wavelength interferometer and the ambiguity of a wide-bandwidth white light interferometer
Implementation Method 3
The images are obtained for at least four polarizations for each of the plurality of wavelengths. The reflected linearly polarized light wave is a reflection of the linearly polarized light wave directed towards the object surface
Data Source
AI summary
The embodiments herein relate to a method for deriving topography of an object surface. A linearly polarized light wave is directed towards the object surface and a reference surface. Images of reflected linearly polarized light wave for a plurality of wavelengths are obtained. The images are obtained for at least four polarizations for each of the plurality of wavelengths. The reflected linearly polarized light wave is a reflection of the linearly polarized light wave directed towards the object surface and the reference surface. The topography of the object surface based on the obtained images is obtained.