H - Electricity – 01 – J
Patent
H - Electricity
01
J
355/13
H01J 29/54 (2006.01)
Patent
CA 1130929
ABSTRACT OF THE DISCLOSURE An electron beam tube electrostatic deflection system and method of operation is described. The electron beam tube includes an eight-fold deflec- tor and means are provided for applying two different quadrupole correction electric potentials to selected ones of the eight-fold deflector members and for applying an octupole correction electrical potential to all eight deflec- tor members. In the preferred embodiment, the quadrupole and octupole cor- rection potentials applied to one set of four deflector members are repre- sented by the respective values (V2c- ?), (-V2c- ?), (V2c- ?) and (-V2c- ?), and the quadrupole and octupole correction potentials applied to the second set of four deflector members are represented respectively by the values (V2s+ ?), (-V2s+ ?), (V2s+ ?) and (-V2s+ ?) where the quadrupole correction electric potential Image , (1) the quadrupole correction electric potential Image , (2) and the octupole correction potential ? applied to all eight of the eight-fold deflector members is given by the expression Image (3) where A2c, A2s and A4 are constants, Vx and Vy are the x and y deflection elec- tric potentials, and -Vc is the cathode voltage of the electron gun used in the electron beam tube apparatus. In preferred arrangements, the electrostatic deflection system further includes means for applying a dynamic focusing elec- tric potential to the objective lens assembly of the electron beam tube appar- atus in conjunction with both the correction and deflection electric potentials described above. The dynamic focusing electric potential is Image (4) where ADF is a constant and VOBJ(O) is the uncorrected value of the direct current objective lens supply voltage. Both deflection and correction electric potentials are developed by an eight-fold deflector voltage generator which includes as its heart a novel octupole-quadrupole generator. The corrected electrostatic deflection system can be used in a simple electron beam tube structure employing only a single eight-fold deflector assembly for deflecting with low aberration a finely focused electron beam onto any desired address point on a target plane. Alternatively, the corrected electrostatic deflec- tion system can be employed with a compound electron beam tube apparatus of the type employing a compound coarse and fine deflector system sometimes re- ferred to as a fly's-eye type electron beam tube. In the compound electron be m tube apparatus, the eight-fold deflector assembly is employed as the coarse deflector assembly and preferably is fabricated in two eight-fold sec- tions which are electrically interconnected.
385474
Control Data Corporation
Smart & Biggar
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