A single-shot line-scanning spatially dispersed short coherence interferometer using Fourier transform profilometry

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Hassan, Mothana A. ; Martin, Haydn ; Jiang, Xiang (2015)
  • Publisher: EUSPEN
  • Subject: Q1 | QC

Single-shot inspection at nanoscale resolution is a problematic challenge for providing on-line inspection of manufacturing techniques such as roll-to-roll processes where the measurand is constantly moving. An example of such a measurement challenge is defect detection on vapor barrier films formed by depositing an aluminum oxide layer several tens of nanometres thick on a flexible polymer substrate. Effective detection and characterisation of defects in this layer requires a single-shot approach with nanometre scale vertical resolution.\ud This paper describes a line-scanning interferometer where a short coherence light source having a 25 nm linewidth source is spatially dispersed across the measurand thus encoding spatial position along a profile by wavelength. Phase shift interferometry (PSI) can be used to decode phase and thus height information, but requires multiple image captures. In order to realise single-shot measurement which is more suitable for online applications, a Fourier transform profilometry (FTP) approach is necessary. This paper explores the implementation of the FTP approach and presents a comparison of the measurement capability of FTP with the previously reported PSI method.
  • References (6)

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    [3] Hassan, M. A., Martin, H., & Jiang, X. (2014). “Surface profile measurement using spatially dispersed short coherence interferometry.” Surface Topography: Metrology and Properties, 2(2), 024001

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    [5] Xangqian Jiang, K. W., Feng Gao, and Hussam Muhamedsalih. (2010) “Fast surface measurement using wavelength scanning interferometry with compensation of environmental noise.” Optical Society of America

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