| 摘要 |
PURPOSE:To improve picture quality by subtracting a signal obtained from each hoirzontal scanning and that obtained from its previous horizontal scanning, obtaining noise components, and removing the noise components from a picture signal. CONSTITUTION:The electron beam from an electron gun 1 is focussed by a focussing lens 2 and an objective lens 3 and is projected on a sample 4. The secondary electron from the sample 4 is detected by a detector 8. The output of the detector 8 is sent to the grid of a cathode-ray tube 7 through switching devices 14a and 14b and an amplifier 15. The output of the detector 8 is subtratcted by a subtractor 11 together with a signal which is delayed for a single horizontal scanning period by a delay circuit 10. The output of the subtractor 11 becomes noise components. After these noise components are compared with the output of reference power supplies 13a and 13b, they become the signals which control the switching devices 14a and 14b. |
