A low-cost Raspberry Pi based imaging system for analysis of fiber specklegram sensors.

In this paper, a low-cost, Raspberry Pi based imaging system is proposed as compact standalone interrogation unit for analysis of fiber specklegram sensors. Standard methods for specklegram analysis are based on image correlation. Proposed imaging system is used for both capturing specklegram images at the output of the standard telecommunication optical fiber and for correlation analysis. Experimental setup for controlled mechanical deformation of the optical fiber is designed and zero-normalized cross-correlation, structural similarity and normalized mutual information score correlation methods are implemented and compared in order to verify proposed Raspberry Pi based imaging system functionally. A statistical method for detection of region of interest is used for dynamic output range extension. Additionally, to further extend dynamic range and increase linearity, correlation output is provided as difference of correlation coefficient for two reference samples located at the ends of measurement range. [ABSTRACT FROM AUTHOR]