Development of algorithms and software for the LASCA techniques for monitoring flow and velocity

He, Xiao Wei (1999) Development of algorithms and software for the LASCA techniques for monitoring flow and velocity. (PhD thesis), Kingston University, .


Laser speckle is an interference effect, which can be observed either in free space or on the image plane of a diffuse object illuminated by coherent laser light. The possibility of using the spatial statistics of time-integrated laser speckle pattern for monitoring capillary blood flow in quasi real-time has been demonstrated recently. However, there are still several important unresolved issues. First, the validity of the fundamental laser speckle statistical techniques used still requires verification. Second, the existing algorithms and software need to be re-examined and improved for achieving a real-time solution and new algorithms and software need to be introduced with a higher statistical accuracy and higher spatial resolution. Finally, a comprehensive theory and model(s) are needed to guide any further development. This thesis begins by studying the laser and laser speckle concepts and principles. Then the original laser speckle contrast analysis (LASCA) model and algorithms have been evaluated and re-examined. A real-time solution has been presented by using improved computational algorithms. The study of LASCA theory starts by exploring the biomedical structure of skin and tissue optics. A more comprehensive LASCA theory has then been established, with which three new LASCA computational models have been developed, based on temporal speckle statistics, spatial speckle statistics and temporal-spatial speckle statistics, respectively. To obtain a real-time solution, a class of highly efficient algorithms has been designed and developed, based on the three new computational models. To implement these algorithms, the LASCA foundation classes library and its application software have been developed accordingly, with the characteristics of portability, reusability, and modularity. To build up an optimised LASCA system, the LASCA related experimental parameters have also been analysed and discussed in detail and solutions have been proposed. As a result, the enhanced LASCA theory, LASCA system design techniques, LASCA related algorithms and software should become valuable tools in' guiding and assisting a more extensive study on the LASCA techniques.

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