FIGURE 6-22 Low pass filtering of the step on the left (A) results in the shape shown on the right (B). The amount of distortion depends on the amount of filtering applied to the image.

When images are viewed that have substantial low pass filtering, the dimensions in the image can appear distorted. Other artifacts can appear as a sharpness at the edge of steps in an image.

6.3.3 Matrix Filter / Smoothing

Matrix filtering is very effective at "smoothing" images and removing noise from the image. However, the filtering process often reduces the resolution of the image. As a rule of thumb, if the image has no noise in it, then the data has probably been compromised.

6.3.4 Fourier Filtering

Periodic structures can easily be introduced into images with Fourier filtering. This can be used for creating "atomic structure" in images. As an example, images of "white noise" can be filtered to give periodic structure that looks like atomic structure.

FIGURE 6-23 A: AFM image of nanospheres with no filtering. The image shows noise in the associated line profile. B: The image generated after matrix smoothing. The line profile shows no noticeable noise and the shape of the particle is altered.