| 摘要 |
PURPOSE:To reduce the spherical aberration factor by applying the individual potentials phio, phic, phii on three electrodes having same diameter and located coaxially with such relation as phic<=(phio.phii)<1/2> while making the length of the intermediate electrode and the gap between the electrodes equal to the diameter of the electrode. CONSTITUTION:Three electrodes 6, 7, 8 having same diameter are arranged coaxially then individual potentials phio, phic, phii are applied on each electrode to constitute a tri-potential lens. Assuming the intermediate electrode phic<=(phio.phii)<1/2> and the gap between the electrodes S*=0.36R (R is the diameter of the electrode.), the aberration factor K*sr will become the minimum when S*/l*=1. Consequently a tri-potential electronic lens having low spherical aberration factor can be obtained. |
