How to obtain knowledge about the degradation
There are three knowledge about the degradation
Estimation by Image observation
Estimation by Experimentation
Estimation by Modeling
Given a degraded image without knowledge about H, one way to estimate H is to gather information from the image itself
the effect of noise is negligible because of our choice of a strong-signal area
Restoration process estimation
This case used when we kknow only g(x,y) and cannot repeat experiment