| 摘要 |
PURPOSE:To attain precise measurement by eliminating an influence of noises by converting an analog signal, outputted by a charge beam detecting method, into a digital signal and then by differentiating the contents of cumulative storage of a cumulative storage method. CONSTITUTION:Electron beam 2 is shaped by passing through rectangular slit 3 and made to scan on shielding member 5 through deflector 4. A beam reflected by shielding member 5 is detected by detector 6, amplified and then differentiated by digital differentiator 13 after passing through analog-digital converter 11 and cumulative memory unit 12, thereby measuring waveform width Wp. As a result, a waveform with superposed noises is digitally converted and stored in comulative memory unit 12, and those operations are repeated several times to cancel noises generated at random. Consequently, an analogically-converted signal has few noises and waveform width Wp can be measured accurately.
|
