Notation and Model

The notation that will be used in this paper can be summarized as follows:

We shall work with the following model: an object emits light with intensity given by a spatial distribution . The light is focused by the optical system over a detector array consisting of individual discrete and independent detectors. Each detector has a different quantum efficiency characterized by a gain correction distribution . A certain background radiation , coming mainly from the sky but also from sources internal to the detector, is detected along with the spatial distribution . We assume that the detection process is Poisson distributed. Finally, the detector is read by an electronic process which adds a Gaussian read-out noise with zero mean and known standard deviation . The imaging equation corresponding to this model is:

Equation (1) in discrete form becomes:

Most of the imaging systems used in astronomy, such as charge coupled device (CCD) cameras and image pulse counting systems (IPCS), are described by Eq. (1).