Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
Biennial Report 2005-2007 - Saha Institute of Nuclear Physics
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High Energy <strong>Physics</strong> and Microelectronics 93These filters are used for digital processing <strong>of</strong> images for the tasks <strong>of</strong> Edge Detection and Enhancement.Sandip Sarkar, Kuntal Ghosh, Kamales BhaumikMED3.2.1.2 Low-level brightness contrast illusions and non-classical receptive field <strong>of</strong>mammalian retinaOur proposed model <strong>of</strong> retinal ganglion cells functionality is built around Gaussians and takes intoaccount the contributions <strong>of</strong> extended surround <strong>of</strong> the visual receptive field. Success <strong>of</strong> this modelto reproduce several low-level processing tasks gave us impetus to find a possible applicability <strong>of</strong>this model for reproducing several illusive effects we perceive everyday. Studies revealed that thismodel not only reproduces the illusions believed to be the contribution <strong>of</strong> low-level processing butalso could reproduce several illusions believed to be the contribution <strong>of</strong> higher level <strong>of</strong> perception.Our model, for the first time, suggests that these illusions might be the result <strong>of</strong> lower-level <strong>of</strong>computation in the retinal ganglion cells which is contrary to the popular belief. We, therefore,feel that our proposed model could be useful for the study <strong>of</strong> Artificial Vision Systems.Kuntal Ghosh, Sandip Sarkar, Kamales BhaumikMED3.2.1.3 Development <strong>of</strong> a Prototype Delta-Sigma ADCWe have developed a Delta-Sigma ADC setup for doing studies in signal processing. The postprocessing filtration <strong>of</strong> the ADC output is performed with a Digital FIR Filter. This filter isimplemented on Xilinx FPGA and programmed through Labview.Sandip Sarkar, Subhajit Karmakar, Swapan SenMED3.2.1.4 Stochastic Resonance, Zero Crossing Maps and the Center SurroundNoise is a part and parcel <strong>of</strong> neural systems <strong>of</strong> every living being. Studies on the usefulness <strong>of</strong> noiseby several authors reveal that many living creatures including human use the noise in a constructiveway. One such phenomenon is the enhancement <strong>of</strong> information content in the presence <strong>of</strong> noisethrough the process <strong>of</strong> Stochastic Resonance. There are also evidences <strong>of</strong> enhancement <strong>of</strong> visualinformation by humans through Stochastic Resonance. Taking impetus from the success <strong>of</strong> ourproposed model to explain various low-level tasks and illusions we ventured to find the usefulness<strong>of</strong> this model for performing enhancement <strong>of</strong> visual information through Stochastic Resonance.Studies through simulation reveal that our model is capable <strong>of</strong> enhancing visual information throughstochastic resonance in the presence <strong>of</strong> additive zero-mean Gaussian noise. It has also been foundthat the enhancement <strong>of</strong> visual information is the best for an optimal image contrast in the presence<strong>of</strong> optimal noise strength. This behaviour is similar to the result obtained in a psychophysicalexperiment with humans.Sandip Sarkar, Kuntal Ghosh, Kamales BhaumikMED
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