Patent ID: 6066852
Filing Date: 2000-05-23
Classification: H01J

Abstract:
An electron energy filter for deflecting electrons in vacuum through the effect of magnetic fields, filtering only the electrons having a specific magnitude of energy, and forming an image of said electrons, comprising:a first pair of magnetic poles for generating a first deflecting magnetic field and a second pair of magnetic poles for generating a second deflecting magnetic field directed in the same direction as said first deflecting magnetic field; andwherein after an electron beam is incident to said first pair of magnetic poles, said electron beam is deflected a first deflecting angle WM1 with a first trace radius AM1 through the effect of said first deflecting magnetic field, passed through a free space having a distance DL2 causing no magnetic field and then is incident to said second deflecting magnetic field, after that, said electron beam is deflected a second deflecting angle WM2 with a second trace radius AM2, passed through said free space having the thickness DL2 causing no magnetic field and again is incident to said first deflecting magnetic field, after that, said electron beam is deflected said first deflecting angle WM1 with said first trace radius AM1 and then outgoes in the substantially same direction as the incident one of said electron beam to said first deflecting magnetic field, andsaid first trace radius AM1, said second trace radius AM2, said first deflecting angle WM1, said second deflecting angle WM2, and said free space distance DL2 meet the following relation of80.degree..ltoreq.WM1.ltoreq.100.degree.2 AM2.ltoreq.AM1.ltoreq.3 AM2160.degree..ltoreq.WM2.ltoreq.200.degree.0.5 AM1.ltoreq.DL2.