| 摘要 |
PURPOSE:To accurately adjust a focal point by supplying the current which corresponds to the excitation current value of an auxiliary lens located near the magnetic field of an objective lens to an electron beam deflection means and moving the electron beam in an arbitray direction. CONSTITUTION:A voltage signal which is proportional to excitation current is supplied to an auxiliary lens 2 located near the magnetic field of an objective lens 1 and supplied to varible resistors 11 and 12 through a gain-1 inverted amplifier 10. The output is applied to horizontal and vertical amplifiers 6 and 7. Thus an electron beam can be moved in an arbitrary direction only for the quantity that is proportional to the excitation intensity of the auxiliary lens 2. As a result, the electron beam can completely be prevented from being moved on a sample by exciting the auxiliary lens 2 and a focal point accurately be adjusted. |
