INHERENT BIAS IN CORRELATION AVERAGED IMAGES

The correlation averaging algorithm frequently used to enhance microgr aphs of repeating structures contains an inherent bias that favours im ages with larger pixel values or positive noise levels, This bias not only skews the composite image toward higher pixel values, but also di storts the image by increasing the value of high-valued pixels more th an that of low-valued pixels, These errors are especially important in scanning probe microscopy images where the pixel value reflects a dis tinct height, A similar algorithm that uses a structure function in pl ace of the correlation function eliminates this bias.