A Statistical Model for Signal-Dependent Charge Sharing in Image Sensors

A Monte Carlo model based on the signal-dependent charge sharing mechanism during charge collection has been developed to explain the nonlinearity of the photon transfer curve (PTC) in image sensors. The model is based on tracing of individual electrons generated by Poisson-distributed photons and describes the PTC nonlinearity as a process with sub-Poisson variance, with an excellent qualitative agreement with the experimental data. A new PTC curve fitting formula is proposed, considering this nonlinearity. The new formula is an excellent fit to the data, does not require selection of linear section of data points and allows more robust calculation of the system conversion gain.