Speckle contrast calculation based on pixels correlation: spatial analysis

B. Coyotl-Ocelotl; J. C. Juarez Ramirez; R. Ramos-Garcia; R. Chiu; Teresita Spezzia-Mazzocco; J. C. Ramirez-San-Juan

doi:10.1117/12.2321271

18 August 2018 Speckle contrast calculation based on pixels correlation: spatial analysis

B. Coyotl-Ocelotl, J. C. Juarez Ramirez, R. Ramos-Garcia, R. Chiu, Teresita Spezzia-Mazzocco, J. C. Ramirez-San-Juan

Proceedings Volume 10749, Interferometry XIX; 1074903 (2018) https://doi.org/10.1117/12.2321271
Event: SPIE Optical Engineering + Applications, 2018, San Diego, California, United States

Abstract

A trustworthy speckle contrast calculation is fundamental in many applications, such as “laser speckle contrast Imaging” (LSCI), which is a non-invasive technique commonly employed to estimate relative blood speed. In LSCI, the local contrast of a speckle image is calculated using spatial, temporal analysis or a combination of both. In this work, we focus on the spatial analysis. To calculate the local spatial contrast, typically, a sliding window of 5x5 pixels is used to calculate the standard deviation (σ_s) and the mean intensity (<I>_s) of those 5x5 pixels and the calculated contrast K_S=σ_s/(<I>_s) is assigned to the central pixel of the sliding window. In this work, we show that this experimental procedure to calculate the local speckle contrast does not match the corresponding spatial theoretical model and we propose an alternative method that considers correlations of the central pixel with the other ones. We have found a better agreement of the contrast measurement with our numerical calculation.

Citation Download Citation

B. Coyotl-Ocelotl, J. C. Juarez Ramirez, R. Ramos-Garcia, R. Chiu, Teresita Spezzia-Mazzocco, and J. C. Ramirez-San-Juan "Speckle contrast calculation based on pixels correlation: spatial analysis", Proc. SPIE 10749, Interferometry XIX, 1074903 (18 August 2018); https://doi.org/10.1117/12.2321271

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