Method and apparatus for processing a video signal from a scanning electron microscope

A scanning electron microscope incorporating a means for irradiating a specimen with an electron beam, a deflecting means for scanning the electron beam over the surface of said specimen, a detecting means for detecting the secondary electrons or the like emitted from the specimen as a result of electron beam impingement and producing a pulsed video signal indicative thereof, and a display means for displaying a scanning image of said specimen by using the pulsed output signal from said detecting means which is synchronized with said deflecting means, the improvement comprising a signal processing circuit located between said detecting means and display means for extracting noise pulses from the pulsed video signal comprising means for detecting the absolute value of the pulse height difference between successive pulses of said pulsed video signal and means for rejecting video pulse signals when the absolute value of the pulse height difference exceeds a selected value twice in succession.