Optimum filters for an image restoration are formed by a degradation operat
or, a covariance operator of original images, and one of noise. However, in
a practical image restoration problem, the degradation operator and the co
variance operators are estimated on the basis of empirical knowledge. Thus,
it appears that they differ from the true ones. When we restore a degraded
image by an optimum filter belonging to the family of Projection Filters a
nd Parametric Projection Filters, it is shown that small deviations in the
degradation operator and the covariance matrix can cause a large deviation
in a restored image. In this paper, we propose new optimum filters based on
the regularization method called the family of Regularized Projection Filt
ers, and show that they are stable to deviations in operators. Moreover, so
me numerical examples follow to confirm that our description is valid.