SEM resolution is tested in terms of a combination of criteria, namely resolved gaps and the number of gray levels in the image. This is to ensure that the resolution has not been distorted by using the contrast to maximize visibility of edges. High resolution images ideally should show fine detail together with a lack of noise evidenced by a good range of gray levels.
For resolution test of SE and BSE imaging and also for chemical mapping in high-resolution systems such as an Auger scanning instrument. Each test specimen has a square grid pattern with large crystals in the center of each square, and very fine crystals at the edges of each grid. Thus medium and high resolution gap tests are performed on the same specimen. Meantime, the larger crystals show facets which allow an assessment of the gray level reproduction available at high resolution. Gold particle range from 5nm to 150 nm approximately.