| 摘要 |
PURPOSE:To facilitate an analysis of a sample surface at particle drifting by branking scanned beams during a retrace period for every scanning of a proper number of scanning lines in the X direction, and correcting a background while sampling an output from a measuring system during a blanking period. CONSTITUTION:A detector D detects radiation emitted from a sample S excited by electron beams E, and a detected output is inputted as a brightness signal to a CRT via a buffer amplifier A1, an amplifier A2, and a differential amplifier A3. A blanking signal is inputted from a scanning circuit C to a buffer circuit B, and to a beam deflecting coil K via a driver circuit Dr. When the blanking signal is inputted to the coil K, beams E do not enter the sample S, and an output from the detector D shows a background level. The blanking signal from the circuit B allows via a waveform forming circuit F a sampling switch Sw to operate, and the background signal is held in a sample and hold circuit H. An output from the circuit h is applied to an inverted terminal of the amplifier A3, enabling a net signal from the detector D to be detected.
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