Blurring

Blurring usually occurs as a result of defects in the lenses used to capture the image, but may also occur as a result of second order effects between adjacent photoreceptors. This produces an unwanted smoothing effect as described above.

In order to reverse this effect, it is necessary to sharpen the image rather than smooth it. Blurring reduces an edge in the original image to a gentle gradient in the observed signal. In order to restore a sharp edge, the image can be analysed to find all the locations in which a fairly large spatial differential exists. In areas in which the pixels consistently show this gradient, the band can be reduced to a single thin line, using such methods as morphological processing [15].