| 摘要 |
<p>An electron-optical system comprising a plate (5) with openings (6) intended for measuring the electron beam aperture and fixed in relation to the optical axis of the system, and two deflection yokes (7 and 8) located on both sides of the plate (5), the first deflection yoke (7) causing the electron beam (15) to pass through one of the openings (6) of the plate (5) and the second deflection yoke (8) causing the electron beam (15) to return to the optical axis of the electron-optical system. </p> |
