Variable black level bias image display

Claim 2

A video display in which a reference signal in the form of a pulse signal having a predetermined peak value is superimposed on an image signal during a fly-back time to set a black level bias voltage according to the reference signal peak value, comprising a reference signal level shift means for shifting the voltage level of the reference signal to be on the black level side more than the image signal pedestal level.

Claim 3

The image display according to claim 1, wherein the reference signal shift means includes stub pulse superimposing means for superimposing a pulse having a longer period than and the opposite polarity to the pulse-form reference signal.

Claim 4

The image display according to claim 1, which further comprises a negative reference signal generating means for changing the reference signal to a negative signal.

Claim 5

The image display according to claim 1, which further comprises time-division basis signal switching means for switching the reference signal and the image signal over to each other on a time-division basis.

Claim 6

An image display comprising: a stub pulse generator for generating a negative pulse having the pulse period equal to a vertical interval time code in the horizontal fly-back time to delete the vertical fly-back and provide for back luster float-up; a first adder for adding the stub pulse generated from the stub pulse generator to the image signal; a reference signal generator for generating a positive reference signal of the horizontal cycle during the stub pulse period; an image amplifier for amplifying the image signal with the superimposed stub pulse and reference signal; a beam current detector for detecting the beam current flowing through a cathode of a CRT 8 and converting the detected beam current into a corresponding voltage; a sample/hold circuit for sampling the converted voltage during the period of the reference signal inputted from the reference signal generator in correspondence to the timing of the reference signal, and holding the sampled voltage until the input of the next reference signal; a voltage comparator for comparing the output of sample/hold circuit and a reference voltage to generating a difference signal; and a bias amplifier for amplifying the difference signal to feed the amplified output to a grid of the CRT.

Claim 7

An image display comprising: a stub pulse generator for generating a negative pulse having the pulse period equal to a vertical interval time code in the horizontal fly-back time to delete the vertical fly-back and provide for back luster float-up; a first adder for adding the stub pulse generated from the stub pulse generator to the image signal; a reference signal generator for generating a positive reference signal of the horizontal cycle during the stub pulse period; an image amplifier for amplifying the image signal with the superimposed stub pulse and reference signal; a beam current detector for detecting the beam current flowing through a cathode of a CRT 8 and converting the detected beam current into a corresponding voltage; a sample/hold circuit for sampling the converted voltage during the period of the reference signal inputted from the reference signal generator in correspondence to the timing of the reference signal, and holding the sampled voltage until the input of the next reference signal; a voltage comparator for comparing the output of sample/hold circuit and a reference voltage to generating a difference signal; and a bias amplifier for amplifying the difference signal to feed the amplified output to a grid of the CRT.

Claim 8

The image display as set forth in claim 5, wherein the stub pulse is added by the first adder to shift the reference signal level to be on the black level side more than the pedestal level.

Claim 9

The image display as set forth in claim 5, wherein the image signal and the reference signal can be switched over to each other on a time-division basis.

Claim 10

The image display as set forth in claim 5, wherein the reference signal is generated right after the end of the vertical interval time code.

Claim 11

An image display in which a reference signal is superimposed on an image signal in a fly-back period for controlling a bias voltage on a cathode of a CRT or a reference signal or a bias voltage on a grid of the CRT such as to make the beam current in the CRT cathode to be constant by detecting the beam current in the reference signal period, while also obtaining brightness control, the image display comprising a stub pulse generator for providing a stub on the black level side more than the image signal pedestal level, and an adder for superimposing the stub pulse on the image signal.

Claim 12

An image display in which a reference signal is superimposed on an image signal in a fly-back period for controlling a bias voltage on a cathode of a CRT or a reference signal or a bias voltage on a grid of the CRT such as to make the beam current in the CRT cathode to be constant by detecting the beam current in the reference signal period, while also obtaining brightness control, the image display comprising a stub pulse generator for providing a stub on the black level side more than the image signal pedestal level, and an adder for superimposing the stub pulse on the image signal.