Patent ID: 6495978
Filing Date: 2002-12-17
Classification: H01J

Abstract:
A CRT display device comprising:a CRT including an electron gun having: a cathode for each of red, green and blue which emits a quantity of electrons in accordance with an applied voltage in a direction of a phosphor screen in which phosphors of red, green and blue are disposed; a G1 electrode, a G2 electrode and a G3 electrode each of which is provided in said direction of the phosphor screen from said cathode and forms an electric field by being applied with a specified voltage; and a modulation electrode which is disposed between said G2 electrode and said G3 electrode and which changes the electric field formed by each of said G1 electrode, said G2 electrode and said G3 electrode in accordance with an applied voltage; a modulation electrode voltage source which applies voltage having a predetermined, specified voltage value to said modulation electrode; and a cathode voltage source which sets a voltage value such that it becomes the same as a modulation electrode voltage value to be applied to said modulation electrode by said modulation electrode voltage source and, further, applies a black level bias voltage value that is determined by a cutoff adjustment which finely adjusts said voltage value for the cathode for each of red, green and blue such that a black color of a displayed video when a video signal is in a black level agrees with a specified black color to said cathode when the video signal is in the black level.