Variable axis electron beam projection system
US4376249A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 6, 1980 |
| Grant date | Mar 8, 1983 |
| Priority date | — |
| Expiry date | Nov 6, 2000 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01J37/1474
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
An electron beam projection system having a projection lens arranged so that upon pre-deflection of the electron beam the electron optical axis of the lens shifts to be coincident with the deflected beam. The projection system includes means for producing an electron beam, means for deflecting the beam, a magnetic projection lens having rotational symmetry for focusing the deflected beam and a pair of magnetic compensation yokes positioned within the bore of the projection lens means. The pair of correction yokes has coil dimensions such that, in combination, they produce a magnetic compensation field proportional to the first derivative of the axial magnetic field strength distribution curve of the projection lens. Upon application of current to the pair of compensation yokes the electron optical axis of the projection lens shifts to the position of the deflected beam so that the electron beam remains coincident with the shifted electron optical axis and lands perpendicular to a target.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.