MULTIBEAM CATHODE RAY TUBE APPARATUS INCORPORATING CONTROL CIRCUIT MEANS FOR MAINTAINING THE RELATIVE INTENSITY OF THE BEAMS OVER A RANGE OF SETTINGS OF THE BRIGHTNESS CONTROL

• Main Author: AINSCOW, FRANK
• Format: Patent
• Language: English
• Published: 21.12.1983
• Subjects: ELECTRIC COMMUNICATION TECHNIQUE; ELECTRICITY; PICTORIAL COMMUNICATION, e.g. TELEVISION

Multibeam cathode ray tube apparatus incorporates control circuits for maintaining the relative intensity of the beams over a range of settings of the brightness control. As applied to a three beam colour tube, at least two, and preferably all three, of the electron guns have each a control circuit located between the control grid (Vg1) and a variable voltage source (V) which constitutes the brightness control of the display. A potentiometer (R,) allows the voltage (V) to be variably attenuated and a second potentiometer (R2) acting in conjunction with a current source (1) allows the attenuated voltage to have a variable voltage added thereto. The potentiometers (R, and R2) for each electron gun are adjusted to bring the brightness versus control voltage characteristic for each gun into coincidence. The current source (I) may be constituted by a fixed resistor and a fixed voltage. The invention is also applicable to multibeam monochrome tubes.