发明授权
摘要:
In a cathode ray tube comprising beam producing means to direct a plurality of electron beams from spaced apart locations to impinge on an electron receiving screen, the beams are focused on the screen by a main focusing lens which is common to all of the beams and has an optical center, and an auxiliary lens disposed between the beam producing means and the main focusing lens and having all of the beams passing therethrough with at least two of the beams being at different distances from the optical axis of the auxiliary lens, such auxiliary lens is operative to cause the beams to intersect at the optical center of the main focusing lens and has pre-focusing effects on the beams which are different at least with respect to the said two beams, and an additional focusing lens means is disposed between the main focusing lens and the screen and acts on less than all of the beams to correct for the different pre-focusing effects and thereby cause all of the beams to be focused precisely at the screen.
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