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Center Independent Research & Development: GSFC IRAD

On laser sensor image fringe detection and mitigation in real-time processing based on firmware supported Hilbert-Huang Transform for 2-Dimensions

Completed Technology Project

Project Introduction

In physics, interference is a phenomenon in which two waves superimpose to form a new complex wave and fringes are observed wherever the two or more waves overlap. Fringe analysis has a wide range of applications in physical and engineering measurements interpretation and its state-of-the-art static processing is using linearity-assumed Fourier Transform that is inadequate due to fringe non-linear and non-stationary nature. This breakthrough technology for optical testbed verification experiments and fringe analysis, as well as phase unwrapping of spaceflight grade optical components and systems, is based on firmware supported dynamic near real-time Hilbert-Huang Transform for 2-dimensions (HHT2-Fringe).

The image of a laser source through quartz substrate of the filter wheel or enclosure on the CCD detector is prone to unwanted interference fringes due to the impurities of quartz material. Applying antireflection coatings on both sides of the substrate could substantially reduce these fringes but does not remove them completely. Alternatively, the interference fringes analogous to Moire pattern could be removed statically using image processing after the in-situ measurement or dynamically while an experiment is in process. It’s highly beneficial to eliminate these patterns dynamically using a near-real time processing. The benefit is due itself to the dynamic and nonlinear nature of these fringes where the beam source location could change at any angle. However, the static fringe analysis is using linearity-based Fourier Transforms and the dynamic fringe analysis techniques are in embryonic state.

One innovative approach to detect and remove the unwanted fringes dynamically is by applying the combination of the Empirical Mode Decomposition (EMD2) and the Hilbert Spectral Analysis (HSA2) for 2-dimensions and specifically researching and developing the HHT2 into fringe detection and mitigation engineering tool HHT2-Fringe. The EMD2 and HSA2 comprise the Hilbert-Huang Transforms for 2-dimensions or HHT2 that was recently accomplished within the Goddard internal research and development program (IRAD). The HHT2 is designed specifically for analyzing data from nonlinear and non-stationary processes in 2-dimensions.

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