Noise from the sensors
Ultra High Speed Digital Imaging

For image sensors in general, noise refers to any signal that does not contribute to the formation of the desired image (Figure 13 ). Its origin can vary widely, ranging from the collection of photons as charge to the conversion of charge into voltage, including all transfer processes between rows, columns, frames, and blocks. This noise is also related to thermal effects (primarily Johnson noise), light irradiation during transfer, the filling and overflow of wells into neighboring ones, as well as quantization noise at the output of the chain.