A comparative study of information capacity for biophysical and silicon photoreceptors

We employ communication theory to analyze information processing in a silicon photoreceptor and in a biophysical model of the blowfly photoreceptor. We take channel capacity to be a quantitative measure of performance which is independent of any particular task. The physical instantiation of any channel determines the noise, the signal constraints and the channel capacity. The channel model for each of the two systems is a cascade of linear bandlimiting sections followed by additive noise. Filters and noise are modelled from first principles when possible. Parameters for the blowfly model are determined from biophysical data available in the literature. Such a comparative study is a first step towards understanding the performance, and the tradeoffs between system performance and associated costs such as size, reliability and energy requirements for natural and engineered sensory systems.