Polarization Enhanced Laser Speckle Contrast Imaging For Vascular Dynamic Study

The contrast in laser speckle imaging with controlled polarization conditions for illumination and imaging was studied in a blood vessel mimic flow phantom. Either linear or circular polarization was used to illuminate samples. The polarization in imaging was controlled, to be either orthogonal (cross) or parallel to the polarization of the illumination beam. Temporal contrast imaging, was obtained by calculating the pixelwise contrast among a series of successfully recorded snapshot images. Then, temporal-spatial contrast imaging was calculated from temporal contrast imaging by calculating the spatial contrast among the pixels in a temporal contrast image. The results have shown that the parallel polarization setting had a near doubled contrast dynamic range compared to the cross polarization setting. Linear polarization and circular polarization did not show significant differences in contrast dynamic range. The results obtained here can be generally applied to all laser speckle based imaging, because they are all interference based imaging, and it is suggested that parallel polarization imaging setting can be considered for a better imaging contrast between flow and solid tissue background. In addition, in a preliminary flow speed test, the temporal-spatial contrast values did not show a statistical difference among different flow speeds due to the current experiment settings.