Beam mislanding correcting system for color cathode ray tube

In a color cathode ray tube including a color phosphor screen upon which electron beams impinge, a beam selecting structure disposed near the screen and through which said electron beams pass for landing on the screen during a scanning operation, and main deflection means for causing said beams to scan said screen, a system for correcting mislanding of said electron beams on said screen comprising a pair of magnetic cores disposed on opposite sides of said cathode ray tube and positioned between said main deflection means and said beam selecting structure, each of said magnetic cores including a central portion aligned substantially perpendicular to a beam scan line and respective end portions inclined inwardly toward said tube;

• coil means wound at least on each of said core end portions so as to produce, when energized, magnetic lines of flux which extend substantially perpendicular to the electron beam paths, the magnetic field produced by said coil means being relatively greater at said respective core end portions;
• and circuit means for supplying a variable energizing current to said coil means, said circuit means including first and second temperature detecting means which are spaced apart for detecting substantially the temperature of said beam selecting structure and substantially the ambient temperature about the tube, rspectively, and means for varying the magnitude of said current in accordance with changes in the difference between the temperatures respectively detected by said first and second temperature detecting means.

A system for correcting mislanding of electron beams on the color phosphor screen of a color cathode ray tube which contains a beam selecting structure disposed near the screen and through which the electron beams pass for landing on the screen during scanning of the latter by said beams;

• said system comprising electromagnetic means including coil means for producing magnetic fields in response to a current flowing in said coil means, said electromagnetic means being located adjacent said tube for the passage of said electron beams through said magnetic fields so as to change the paths of said beams through said beam selecting structure and thereby correct for mislanding of the beams on said screen;
• first temperature detecting means for detecting the temperature of said beam selecting structure;
• second temperature detecting means for detecting the ambient temperature about said tube;
• and circuit means for supplying said current to said coil means;
• said circuit means including a voltage source, a transistor having a collector-emitter path through which said coil means is connected with said voltage source, and a base-bias circuit for said transistor including said first and second temperature detecting means for varying said current in accordance with changes in the difference between the temperatures detected by said first and second temperature detecting means.