Use of the Gabor Filter for Edge Detection in the Analysis of Zinc Oxide Nanowire Images

Semi-automated processing of microscopy images can significantly enhance the capacity for objective nanostructure characterization. However, background complexity, intricate object features and overlapping of objects can make this a difficult task. Here we describe use of the Gabor filter [1, 2] to facilitate the identification and outlines of the top surfaces of nanowires of zinc oxide (ZnO), imaged with scanning electron microscopy (SEM). The Gabor filter is a sinusoidal function multiplied by a Gaussian envelope. The sinusoidal shape makes the filter sensitive to spatial frequencies and the Gaussian envelope limits the frequency sensitivity to localized areas of the image. In particular, the Gabor filter enhances lines and edges in a direction perpendicular to the direction of the sinusoid. This sensitivity to linear parts of an image make it particularly well suited to analysis of the top surfaces of the ZnO nanowires which have a regular hexagonal shape and bright edges in the SEM images.