01-01-2011, 11:31 AM
SUBMITTED BY:
CHINMAYA BISWAL
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ABSTRACT
The world might have been reaching new heights in technology, man might have made artificial residential environment in outer space. But all this will end up to one primary objective. The aim of every human research is how to make life more comfortable and decrease the mortality of human beings.
For this reason a crucial visual study of animal tissue and environment is highly critical. The number of CMOS technology used as light sensors in different imaging system has been on rise in recent decade. The use of appropriate CMOS photo-detector structures and imagers can bring a revolution in field of medicine, agriculture and bio-defence. Some of the pronounced fields where photo-detectors are regularly used are protein detection, gene expression, cell migration and evaluation of animal models of human cancer.
Therefore, to develop we need to make the available technology cheap and miniaturise it, so that it can be made available through hand held devices, and can be brought to masses as a low cost technology implementation.
INTRODUCTION
Imaging has been very attractive sphere of interest for many individuals. Some refer it to be hobby, some refer it to quest, some refer it to research, and some refer it to be revelation. The desire of man to represent and record the 3-D world around him and to be capable of retrieving the data at any desired moment has led to development of many new technologies which wouldn’t have existed 2-3 decades ago.
Medicine industry has seen many transitions in technology, because it needs state of art artefacts to detect diseases and different infections. The technology currently used is Fluorescence. Next to it is Photo Multiplier Tubes. These devices are capable of rendering high gain to currents, and require high operating voltages.
The technology which is creeping into use is CMOS based technology. These include pixels with photo current integration, high dynamic range imaging, and avalanche photodiode system. These systems are briefly discussed in this paper and their results have been compared.
Fluorescence
Cells contain molecules, which become fluorescent when excited by UV/Vis radiation of suitable wavelength. This fluorescence emission, arising from endogenous fluoro-phores, is an intrinsic property of cells and is called auto-fluorescence to be distinguished from fluorescent signals obtained by adding exogenous markers. The majority of cell auto-fluorescence originates from mitochondria and lysosomes. Together with aromatic amino acids and lipo-pigments, the most important endogenous fluorophores are pyridinic (NADPH) and flavin coenzymes. In tissues, the extracellular matrix often contributes to the auto-fluorescence emission more than the cellular component, because collagen and elastin have, among the endogenous fluorophores, a relatively high quantum yield. Changes occurring in the cell and tissue state during physiological and/or pathological processes result in modifications of the amount and distribution of endogenous fluoro-phores and chemical-physical properties of their microenvironment. Therefore, analytical techniques based on auto-fluorescence monitoring can be utilized in order to obtain information about morphological and physiological state of cells and tissues. Moreover, auto-fluorescence analysis can be performed in real time because it does not require any treatment of fixing or staining of the specimens. In the past few years spectroscopic and imaging techniques have been developed for many different applications both in basic research and diagnostics.