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Ismael Kelly Pérez, Haroun Al-Mohamedi, Andreas Prinz, Theo Oltrup, Guido Mieskes, Thomas Bende; Dual scattering pattern to characterize the size of particles inside a heterogeneous medium. Invest. Ophthalmol. Vis. Sci. 2014;55(13):5194.
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The purpose of the project is to characterize the size of particles inside an optical heterogeneous medium, similar to that of the crystalline lens with cataract. In order to do that, the scattering effect is measured after the light of two different wavelengths pass across the medium. The correlation obtained on the point-spread functions (PSF’s∫) is related with the size and density of the particles inside the medium.
The technique is based on the analysis of the forward scattering on the two PSF’s. The experimental setup consists of two LED lights 400 and 700 nm, which are directed trough a heterogeneous medium. In this single pass experiment latex microparticles, of 1 and 3 microns, are randomly distributed in small silicon container, which simulate the human lens. Each size of particles is measured for 4 different densities (100,000 to 400,000 particles). A CCD camera captures data of scattered light. The relative difference of the radial profiles of PSF’s is analyzed. This is related to the size and density of the particles.
The obtained PSF’s are superimposed and a crossing point between both radial profiles is observed. The distance from the optical axis to the crossing point is related with the size of the particles. In the used set-up the distance of the crossing point is 3 times larger for 1 micro compare to the 3 microns particles. This means the size of the two sizes particles is clearly distinguishable. On the other hand, the density of the particles shows linear correlation in the amplitude of the signal.
Measuring in a heterogeneous medium, the scattering effect of two different light sources results in a good approach of the size and density of the particles. According to the experiments, the resolution becomes better by increasing the difference of the wavelengths within the visible light range.
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