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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).