| 摘要 |
PURPOSE:To obtain a measuring function with high precision by providing two- stage deflection units between an objective lens and an image formation lens system and displaying the peak value of a scanning signal as it is or by converting it into a distance on a sample. CONSTITUTION:A scanning signal, e.g., rectangular wave, periodically changing at a constant amplitude is fed from a scanning signal generator 14 to two-stage deflection units 11, 12 with an interlock ratio via a deflection width changer 13. Electron rays (e) transmitted through a sample 4 and image-formed by an objective lens 5 are deflected in opposite directions in turn across the optical axis Z as shown by dotted lines e1 and two-dot chain lines e2 and form images 4a, 4b at the objective positions of an intermediate lens 6. These images are magnified by the intermediate lens 6 and further by a projection lens and are doubly projected on a fluorescent screen as shown by images 16, 16'. The deflection width changer 13 is controlled so that the B point of the image 16 and the A' point of the image 16' coincide at the center O of the fluorescent screen 8, and a distance l is displayed on a display unit 15 based on the previously calibrated relationship between the peak value of the scanning signal and the distance on the sample. |
