Image filtering
	• Increase the contrast of sources with respect to the background noise. • Linear or non-linear § Linear filtering: for an isolated profile f (x) superimposed to a (wide-sense stationary) background noise with spectral power P (u), the optimum filter is the convolution with the matched filter § In most cases (CCD images with local background subtracted), the noise spectrum can be considered as “white” on source scales: P (u) = cste