Wiener-filter enhancement of noisy HREM images

The use of Wiener filters to restore noisy HREM images is discussed, exploiting the fact that the noise spectrum can be rather simply estimated. Conventional Wiener, Cannon, parametric versions of these and a random-phase form are found to be very effective. Quantitative analysis indicates that the signal-to-noise ratio is improved by a factor of 3–7, with better results for larger pictures. Such filtering techniques should have rather wide applicability in electron microscopy, and could be applied on-line with TV systems.