The applicability of multiple exposure time based LASCA was demonstrated on skin blood perfusion monitoring. The method was compared to ?-corrected and non-corrected single exposure time measurements while the data simultaneously recorded by a laser Doppler system were used as reference. The skin of the forearm was illuminated with the light of an 808 nm laser diode. Speckle images were recorded in the exposure time range of 1-100 ms and relative perfusion changes caused by ischemia were determined. The results showed an obvious nonlinear relationship between the data of the non-corrected single exposure time LASCA method and the laser Doppler system, while a good linearity was observed for the multiple exposure time method with a correlation factor of 0.83.
Computer Simulation of Fresnel Diffraction from Triple Apertures by Iterative Fresnel Integrals MethodThe Iterative Fresnel Integrals Method (IFIM) has been applied for the simulation and generation of the complete near-field Fresnel diffraction images created by triple apertures for the first time. The simulation can be performed in any PC using an included MATLAB program. Necessary formalism has been derived and simulation algorithm has been developed for this application. An interesting combination of interference effects with Fresnel diffraction has been observed in the simulation images. Transition to the expected Fraunhofer diffraction pattern from Fresnel diffraction for triple apertures is also observed by the simulations. The program can serve as a useful tool to study the complex phenomenon of Fresnel diffraction from triple apertures.
Photothermal deflection is described in this article to detect the change in the thermal and optical properties of the track nuclear detector CR-39 when irradiated to alpha particles. The probe laser beam deflection was found to decrease with the increase of time of exposure to alpha particles. A novel technique, in-situ image analysis of the photothermal deflection spot is presented to assess the detection of the CR-39 to any nuclear particle or radiation instantaneously. This technique offers the ability to acquire data very rapidly and can be used for monitoring any source of nuclear radiations immediately.
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