Gte Sylvania Incorporated

Other

Admiral Corporation

Gopal Krishna Srivastava

Dennis W Rhee

Robert C Wheeler

A single, combined contrast/brightness control is disclosed herein for a television receiver. A contrast control in the form of a variable potentiometer, is coupled to the output, driver transistor of the video amplifier, which serves to amplify and apply the video signal to the cathode ray tube (CRT) and including AC/DC coupling in the form of a resistor and a capacitor. The DC coupling resistor sets the DC bias level to the output transistor and in particular to its base at a level dependent upon the DC level established across the constrast/brightness control potentiometer. Further, the AC coupling capacitor is selectively charged to further adjust the DC bias of the output transistor to a level with the DC coupling resistor whereby the black level of the output signal applied to the cathode ray tube is maintained relatively constant with regard to a predetermined level. In a preferred embodiment of this invention, the predetermined level is the sync tip and back porch voltages and the charging of the AC coupling capacitor is carried out during the horizontal retrace cycle, at which time a charging circuit is formed through the capacitor whereby it is charged to a potential dependent upon the setting of the contrast control potentiometer, and thus, the bias level to the base of the output transistor is adjusted to set the black level to a predetermined level. In this manner, it is only necessary to use the single contrast/brightness control to set both the contrast and the brightness level of the displayed image upon the CRT.

Combination contrast/brightness control for a television receiver

An automatic hue control circuit is disclosed for a color television receiver, wherein the flesh-tone signals of the reproduced image are enhanced by spreading the phase angle between the R-Y and the B-Y reference signals before applying them to their respective demodulators. In one aspect of the invention, the flesh-tone enhancement by phase-shifting the R-Y and B-Y signals occurs only for positive values of the flesh-tone signals. In a further aspect of this invention, a simplified automatic hue control circuit is disclosed as comprising a matrix for receiving, respectively, the R-Y, the G-Y and the B-Y color signals to obtain a DC quiescent voltage with which the flesh-tone signal, as indicated by the sum of the R-Y and the G-Y signals, is compared to render conductive a switch, illustratively in the form of a diode, whereby the phase-shift is imparted to the R-Y and B-Y reference signals. In particular, the desired phase shift between the R-Y and B-Y signals is effected only when the flesh-tone signals are of a positive value, whereby a more accurate color reproduction is provided.

Automatic hue control circuit

A signal receiver having a source of video signals includes an aperture correction system wherein an electron device coupled to the video signal source provides first and second oppositely-phased output signals which are applied to a circuit means to be differentiated and delayed respectively and applied to a summing terminal with desired preshoot and overshoot characteristics. Moreover, these characteristics are selectable by an adjustable impedance coupled to the circuit means providing the differentiated and delayed signals.

Adjustable aperture correction system

In a television receiver having a chrominance signal channel coupled to a cathode ray tube, an automatic peak color control circuit includes an envelope detector means providing a combined chroma envelope and DC potential, a means for shifting the level of the combined chroma envelope and DC potential, a means for detecting the peak level of the chroma signal, and a means for comparing the detected peak chroma signal level and a reference potential level to provide a control signal for maintaining application of a substantially constant level of chroma signal to the cathode ray tube.

Automatic peak color control circuit

In a signal receiver utilizing a video signal having a blanking signal with a backporch portion whereat a color burst signal is disposed includes a ramp potential development means responsive to a pulse signal as well as a potential storage, clamping, and slope altering means for effecting alterations in the width of a burst gate potential. In another aspect, a potential storage, clamping, and slope altering means is responsive to the ramp potential development means for effecting clamping of the backporch portion of the blanking signal.

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Schaumburg, IL, United States of America

Gopal Krishna Srivastava