| 摘要 |
PURPOSE: To monitor changes in the local shape and material of an object at high contrast and sensitivity by detecting the generation of a differential signal produced by deflection in an area where a change in the configuration of the object or in the material is present. CONSTITUTION: An electron beam 45 deflected by a superimpose signal is scanned over the surface of an object 24. This scan constitutes, e.g. a standard X-direction scan. The scan is effected in analog or digital form from the left to the right, and so-called local deflection of the beam is also effected. Since a beam position determined by a standard scan signal is apparently shown on a line 50, a relatively high frequency X-direction beam scan with a frequency fs occurs. With the line 50 as a center, a beam is moved at high speed between broken lines 52, 54 by a high frequency beam scan, while the beam position determined by the standard scan signal almost coincides with the stepped part 55 of the object 24. This serves as the base for gaining an output signal with a center frequency f5 . The output signal is proportional to the local shape scanned, e.g., the inclination of the stepped part 55. |
