Cathode ray tube having auxiliary deflection plate to correct pincushion distortion

Claim 2

Cathode ray tube apparatus comprising: a cathode ray tube having a phosphor screen and containing two electron beam deflection systems each including vertical deflection means and horizontal deflection means, electron beam generating means adjacent said electron beam deflection systems for producing two electron beams, said vertical deflection means defining two pairs of vertical deflection plates with a pair thereof for each of said electron beam generating means auxiliary deflection plate means supported within said tube at a position between said two pairs of vertical deflection plates and having first section means disposed behind output ends of said two pairs of vertical deflection plates and second section means disposed forwardly of said output ends and extending longitudinally toward said phosphor screen, and means for applying an auxiliary deflection signal to said auxiliary deflection plate means.

Claim 3

Cathode ray tube apparatus comprising: A cathode ray tube containing two electron beam deflection systems each including a vertical deflection means and a horizontal deflection means, said vertical deflection means including two pairs of vertical deflection plates positioned on opposite sides of different ones of two electron beams produced in said tube; auxiliary deflection means including an auxiliary deflection plate supported within such tube by a support means extending between said two pairs of vertical deflection plates and insulated from the auxiliary plate so that said auxiliary plate is positioned between said two pairs of vertical deflection plates and extends forwardly of their output ends toward the phospher screen of such tube; and control means for deriving a correction signal from a ramp voltage corresponding to a horizontal ramp sweep signal applied to the horizontal deflection means and applying said correction signal to the auxiliary deflection plate so that it deflects the electron beams vertically within such tube in a manner which corrects for geometry distortion of their beam trace on the phosphor screen.

Claim 4

Cathode ray tube apparatus comprising: A cathode ray tube containing two electron beam deflection systems each including a vertical deflection means and a horizontal deflection means, said vertical deflection means including two pairs of vertical deflection plates positioned on opposite sides of different ones of two electron beams produced in said tube; auxiliary deflection means including an auxiliary deflection plate supported within such tube by a support means extending between said two pairs of vertical deflection plates and insulated from the auxiliary plate so that said auxiliary plate is positioned between said two pairs of vertical deflection plates and extends forwardly of their output ends toward the phospher screen of such tube; and control means for deriving a correction signal from a ramp voltage corresponding to a horizontal ramp sweep signal applied to the horizontal deflection means and applying said correction signal to the auxiliary deflection plate so that it deflects the electron beams vertically within such tube in a manner which corrects for geometry distortion of their beam trace on the phosphor screen.

Claim 5

Apparatus in accordance with claim 2 in which the tube also includes a wallband electrode coated on the inner surface of a tube envelope of insulative material, and means for applying a geometry correction voltage to said wallband electrode.

Claim 6

Apparatus in accordance with claim 2 in which the control means includes a pulse shaping circuit which produces said correction signal output of peak shape having positive and negative slope portions from a linear ramp input signal corresponding to the leading edge of the horizontal sweep signal.

Claim 7

Apparatus in accordance with claim 4 in which the control means produces a correction signal whose peak positive voltage occurs in the center of the horizontal sweep ramp and is approximately equal to the quiescent D.C. voltage of the vertical deflection plates so that the beam is not deflected thereby, while the positive slope portion and the negative slope portion on opposite sides of said peak voltage are of more negative voltage than said quiescent voltage and tend to deflect the beam away from the auxiliary deflection plate by an amount directly proportional to said more negative voltage and inversely proportional to the distance of the beam from said auxiliary plate.

Claim 8

Apparatus in accordance with claim 2 in which the tube contains two separate electron guns for forming said two electron beams.

Claim 9

Apparatus in accordance with claim 6 in which the horizontal deflection means is common to both electron beams and includes two horizontal deflection plates provided on opposite sides of both beams and positioned between the phosphor screen and the vertical deflection plates.

Claim 10

Apparatus in accordance with claim 2 in which the auxiliary deflection plate is mounted on a shield means positioned between the two pairs of vertical deflection plates.

Claim 11

Apparatus in accordance with claim 8 in which the tube includes a first shield electrode positioned between the two pairs of vertical deflection plates, and the auxiliary deflection plates is supported on said first shield electrode by insulative support means so that said auxiliary deflection plate extends substantially coplanar with said first shield electrode.

Claim 12

Apparatus in accordance with claim 9 in which the support means is a plate of ceramic material and the auxiliary deflection plate is provided by two interconnected conductive coatings on the opposite sides of such ceramic plate.

Claim 13

Apparatus in accordance with claim 10 in which the tube includes a second shield electrode positioned between the horizontal deflection means and the vertical deflection plates, and provided with beam aperture in alignment with the output ends of the two pairs of vertical deflection plates.

Claim 14

Apparatus in accordance with claim 11 in which the first shield electrode is attached to the second shield electrode at the center of the beam aperture to hold the ceraMic plate within a slot provided in the edge of the first shield electrode.