Main electron lens for e.g. in-line type electron gun, has two electron-optical plates, each with two outer holes of elliptic shape whose inner and outer horizontal dimension ratio is determined using formula relating to delta focus

摘要

The lens has a focus electrode (G8) and an accelerating electrode (G9) with two optic plates (1, 2), each equipped with a central hole and two outer holes of elliptic shape. A ratio of internal horizontal dimension (delta Hint) and external horizontal dimension (delta Hout) of outer holes is determined by a formula delta Hint/delta Hout = A1x(delta Delta focus) + A0, where A1 and A0 are constants and delta Delta focus is a variation of a delta focus function desired for the system.