Coherence Scanning Interferometry Phase Gap Map Correction
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Solution Overview
Problem
Conventional coherence scanning interferometry techniques face challenges in accurately determining surface height profiles due to sensitivity to vibrations, noise, and fringe order ambiguity, which can lead to errors and limitations in measuring rough surfaces.
Innovation Solution
The method involves obtaining scanning interferometry data, calculating coherence and phase profiles, generating a phase gap map to correct distortions in the coherence profile, and determining the surface height based on the corrected coherence profile, thereby reducing errors and improving accuracy across various surface textures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional coherence scanning interferometry is used to measure surface profiles, then height information can be obtained from interference fringes, but measurement precision deteriorates due to sensitivity to vibrations and noise
Solution Approach 1:
The patent introduces a phase gap map as an intermediary element that mediates between the coherence profile and phase profile. This phase gap map captures the discrepancies caused by vibrations and noise, allowing these harmful factors to be identified and corrected separately, thereby protecting the final height measurement from their adverse effects
Solution Approach 2:
The patent implements a feedback mechanism where the phase gap map is used to correct the coherence profile. By continuously comparing the coherence profile with the phase profile and using the phase gap information to adjust and correct measurements, the system compensates for vibrations and noise in real-time, improving measurement precision
2Manufacturing precision
If coherence profiling is used to determine surface height, then height information can be extracted from fringe localization, but manufacturing precision deteriorates due to fringe order ambiguity
Solution Approach 1:
The patent merges coherence profiling and phase profiling into a unified measurement approach. By combining the fringe localization information from coherence profiling with the phase information from phase profiling, and using the phase gap map to reconcile differences, the method eliminates fringe order ambiguity and achieves higher surface profile accuracy
Solution Approach 2:
The phase gap map serves as an intermediary that resolves the fringe order ambiguity problem. It captures the phase differences that arise from fringe order uncertainties and provides a mechanism to correct these errors, enabling accurate determination of absolute surface height
3Measurement precision
If phase profiling is used to extract height information, then phase information can be obtained from interference fringes, but device complexity increases due to the need for complex fringe order correction processes
Solution Approach 1:
The patent merges coherence and phase profiling methods into a single integrated process. By simultaneously acquiring both coherence and phase information and processing them together through the phase gap map, the system achieves accurate height measurements without requiring separate, complex fringe order correction procedures
Solution Approach 2:
The phase gap map enables the system to self-correct measurement errors automatically. By using the phase information to identify and correct discrepancies in the coherence profile, the system performs its own calibration and error correction without external intervention or complex additional processing
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 the precision of surface profiling by reducing sensitivity to vibrations and noise, allowing for accurate height measurements on both smooth and rough surfaces with reduced complexity in correcting fringe order errors.
Implementation Method 1
interfering a measurement wavefront reflected from the test object surface with a reference wavefront to obtain an interference intensity signal
Data Source
AI summary
Determining a height profile of a test object surface includes obtaining, from a scanning interferometry device, scanning interferometry data for the test object surface, calculating a coherence profile of the test object surface and a phase profile of the test object surface based on the scanning interferometry data, calculating an phase gap map based on the coherence profile and the phase profile, modifying the coherence profile based on the phase gap map to obtain a corrected coherence profile, and determining a height of the test object surface based on the corrected coherence profile.