From Event: SPIE Optical Engineering + Applications, 2016
Laser speckle imaging is an optical metrology technique for examining various forms of object motion in fields from material engineering to bio-medical. As highly coherent illumination encounters the rough surface or scattering medium, due to the multiple interference, the randomly distributed black and white spots formed and are known as speckles. By analyzing speckle images, surface information or scattering medium motion could be recovered. In this study, an optical system for acquiring speckle images from rabbit retina is built for characterizing the blood vessel properties with speckle correlation time constant. As laser illuminates onto the rabbit retina, speckles are formed due to the moving red blood cells inside the retinal blood vessel. The intensity of speckles fluctuate along time and are recorded with high speed CMOS at frame rate 150 frames per second. Speckle correlation time constant describe the relation between frames as the decay rate. Two approaches are used for the processing of image sequences for correlation time constant, one is utilizing asymptotic equation from speckle contrast result, and another is correlation based approach. To determine the performance of our system and algorithms, we compare two regions on the retina with different properties, one region contains faster blood flow while another with slower blood flow. Both approaches shows distinct differences in the value of correlation time constant of two regions.
Meng-Chieh Lin, Wan-Huseh Lai, and Chung-Hao Tien, "Characterization of retinal blood vessel by laser speckle correlation time constant
(Conference Presentation)," Proc. SPIE 9970, Optics and Photonics for Information Processing X, 997005 (Presented at SPIE Optical Engineering + Applications: August 29, 2016; Published: 2 November 2016); https://doi.org/10.1117/12.2236429.5186291898001.
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