Minimizing scanning electron microscope artefacts by filter design.

A new type of non-linear filter for digital images has been developed. By using distance transforms we estimate the average point spread function for a set of fibre cross-sectional images. Then a fast filter technique, based on lookup tables for distance layers, attenuates the uneven background response from the scanning electron microscope. Compared to the convolution-based techniques that we tried, this approach caused less blurring effects on our fibre images and also made the background pixels more homogeneous. The only assumption we make is that we can roughly segment the background pixels by using a pixel-wise classifier. Although the assumption that the uneven background response can be described by a circular point spread function is only approximately true in the case discussed here, this method greatly attenuates the effect and provides a fast and general filtering method that can also be of use for other applications.