gives rise to photon shot noise, (2) random electron generation due to thermal
vibrations, called thermal noise, (3) random fluctuations in the analog electric
signals in the imaging sensors before digitization, referred to as readout noise,
and (4) round-off error introduced by converting the analog signal into digital
form, known as quantization noise. Whereas thermal, readout, and quantization
noise can be controlled by careful electronic design and proper operating
conditions, photon shot noise is inherent to optical imaging and can only be
reduced by increasing exposure [14].
Although noise cannot be avoided during acquisition, it can be reduced
afterwards, to some degree, by image processing. A wide variety of ‘‘denoising’’
techniques are available ...