Automatic contrast and dark level control for scanning electron microscopes

摘要

A scanning electron microscope in which the contrast and the dark level of the video signal is automatically controlled. Specifically, the peak-to-peak video signal level or contrast is detected and compared with a reference signal. The difference signal therebetween is employed to control the gain imparted to the video signal and to thereby automatically control the video signal contrast. Similarly, the dark level is detected and compared with a reference signal. The difference signal therebetween is employed to bias the video signal and thereby automatically control the dark level of the video signal.