Automatic hue control for a television receiver

Claim 2

In a color television receiver for a composite signal comprising brightness signal components, a subcarrier signal modulated by color difference signals representing hue and saturation at different phases of the subcarrier and a burst component for phase locking the signal of an oscillator of the receiver to control color signal demodulators for the subcarrier at different phases of the oscillator signal, the subcarrier signal having an energy peak which tends to be fixed over a period of time at a particular phase with respect to the oscillator signal but the phase of which is subject to change with undesirable received signal variations causing hue changes in the reproduced television image, an automatic hue control circuit including in combination: phase responsive circuit means; a circuit applying the oscillator signal to said phase responsive circuit means as a reference signal phase locked to the burst signal; a circuit applying the subcarrier signal to the phase responsive circuit means, said phase responsive circuit means including an output circuit to provide a control signal representing the phase difference between the energy peak of the subcarrier signal and the reference signal; and means responsive to the control signal for adjusting the relative phases of the subcarrier signal and the oscillator signal to maintain constant the particular phase of the energy peak.

Claim 3

The combination according to claim 1 wherein the means responsive to the control signal shifts the phase of the oscillator output signal.

Claim 4

The combination according to claim 1 wherein the phase responsive circuit means includes first and second hue control demodulators and wherein the oscillator signal is supplied to each of the hue control demodulators at different phases displaced by equal amounts from said particular phase.

Claim 5

The combination according to claim 3 wherein the circuit for providing a control signal responds to the outputs of each of the demodulators and provides a control signal of a predetermined magnitude when the outputs of the hue control demodulators are of equal magnitudes, said control signal being above said predetermined magnitude when the output of the first hue control demodulator exceeds the output of the second hue control demodulator and said control signal being less than said predetermined magnitude when the output of the first demodulator is less than the output of the second demodulator.

Claim 6

In a color television receiver for a composite signal comprising brightness signal components of a television image, a subcarrier signal modulated by color difference signals representing hue and saturation of the image at different phases of the subcarrier And a burst component for phase locking the signal of an oscillator of the receiver to control color signal demodulators for the subcarrier at different phases of the oscillator signal, the subcarrier signal exhibiting a characteristic of a predominance of color information which tends to be balanced over a period of time about a particular phase of the subcarrier, an automatic hue control circuit including in combination: first and second hue control demodulators; means for supplying the modulated subcarrier signal to the first and second demodulators; means for supplying the oscillator output signal to the first demodulator at a first phase which is a predetermined amount greater than said particular phase; means for supplying the oscillator output signal to the second demodulator at a second phase which is said same predetermined amount less than said particular phase; means for combining the outputs of the demodulators to produce a control voltage, the value of which is dependent upon the relative amplitudes of the outputs of the demodulators; and means responsive to the control voltage for controlling the relative phases of the modulated subcarrier signal and the oscillator output signal to adjust the hue of the image reproduced by the color television receiver to maintain the predominance of color information balanced about said particular phase.

Claim 7

In a color television receiver for a composite signal comprising brightness signal components of a television image, a subcarrier signal modulated by color difference signals representing hue and saturation of the image at different phases of the subcarrier And a burst component for phase locking the signal of an oscillator of the receiver to control color signal demodulators for the subcarrier at different phases of the oscillator signal, the subcarrier signal exhibiting a characteristic of a predominance of color information which tends to be balanced over a period of time about a particular phase of the subcarrier, an automatic hue control circuit including in combination: first and second hue control demodulators; means for supplying the modulated subcarrier signal to the first and second demodulators; means for supplying the oscillator output signal to the first demodulator at a first phase which is a predetermined amount greater than said particular phase; means for supplying the oscillator output signal to the second demodulator at a second phase which is said same predetermined amount less than said particular phase; means for combining the outputs of the demodulators to produce a control voltage, the value of which is dependent upon the relative amplitudes of the outputs of the demodulators; and means responsive to the control voltage for controlling the relative phases of the modulated subcarrier signal and the oscillator output signal to adjust the hue of the image reproduced by the color television receiver to maintain the predominance of color information balanced about said particular phase.

Claim 8

The combination according to claim 5 wherein said receiver further includes means for rendering the first and second hue control demodulators non-responsive to the composite signal received during the interval of the burst component.

Claim 9

The combination according to claim 5 wherein the outputs of the demodulators are inverted with respect to one another.

Claim 10

The combination according to claim 7 further including a time delay circuit for delaying the changes in the control voltage applied to the control voltage responsive means.

Claim 11

The combination according to claim 8 wherein the time delay circuit is an integrating circuit.

Claim 12

The combination according to claim 7 further including a pair of half-wave rectifiers oppositely poled with respect to one another with one of the rectifiers connected between the output of the first demodulator and the combining means and the other of the rectifiers connected between the output of the second demodulator and the combining means.

Claim 13

The combination according to claim 10 wherein the combining means includes means for supplying outputs of each of the half-wave rectifiers to opposite ends of a potentiometer, having an intermediate tap from which is obtained the control voltage.

Claim 14

The combination according to claim 11 wherein the means responsive to the control voltage includes a field-effect transistor having at least a control electrode, with the control voltage being applied to the control electrode of the field-effect transistor to vary the conductivity thereof, and further including phase shift means controlled by the conductivity of the field-effect transistor for shifting the phase of the output signals from the oscillator.

Claim 15

The combination according to claim 12 further including an integrating circuit connected between the tap on the potentiometer and the control electrode of the field-effect transistor.

Claim 16

The combination according to claim 13 wherein the means connected to each end of the potentiometer each includes an emitter-follower transistor, having at least base and emitter electrodes, the emitters thereof being connected to the opposite ends of the potentiometer and the bases thereof being connected with the outputs of the respective half-wave rectifiers.

Claim 17

In color television receiver for a composite signal comprising brightness signal components, a subcarrier signal modulated by color difference signals representing hue and saturation at different phases of the subcarrier, and a burst component for phase-locking the signal of an oscillator of the receiver to control color signal demodulators for the subcArrier at different phases of the oscillator output signal, an automatic hue control circuit including in combination: first and second hue control demodulators; means for supplying the modulated subcarrier signal to the first and second demodulators; means for supplying the oscillator output signal to the first and second hue control demodulators, with the relative phases of the modulated subcarrier signal and the oscillator output signal applied to the first and second hue control demodulators being such as to cause the first demodulator to demodulate the subcarrier signal at a first phase which is a predetermined amount greater than a particular phase, and to cause the second demodulator to demodulate the subcarrier signal at a second phase which is substantially said same predetermined amount less than said particular phase; and means responsive to the outputs of the first and second demodulators for shifting the phases of the modulated subcarrier signals which are between the phases detected by the first and second demodulators toward said particular phase relative to the oscillator output signal.

Claim 18

In color television receiver for a composite signal comprising brightness signal components, a subcarrier signal modulated by color difference signals representing hue and saturation at different phases of the subcarrier, and a burst component for phase-locking the signal of an oscillator of the receiver to control color signal demodulators for the subcArrier at different phases of the oscillator output signal, an automatic hue control circuit including in combination: first and second hue control demodulators; means for supplying the modulated subcarrier signal to the first and second demodulators; means for supplying the oscillator output signal to the first and second hue control demodulators, with the relative phases of the modulated subcarrier signal and the oscillator output signal applied to the first and second hue control demodulators being such as to cause the first demodulator to demodulate the subcarrier signal at a first phase which is a predetermined amount greater than a particular phase, and to cause the second demodulator to demodulate the subcarrier signal at a second phase which is substantially said same predetermined amount less than said particular phase; and means responsive to the outputs of the first and second demodulators for shifting the phases of the modulated subcarrier signals which are between the phases detected by the first and second demodulators toward said particular phase relative to the oscillator output signal.

Claim 19

In a color television receiver for a composite signal comprising brightness signal components, a subcarrier signal modulated by color difference signals representing hue and saturation at different phases of the subcarrier, and a burst component for phase-locking the signal of an oscillator of the receiver to control color signal demodulators for the subcarrier at different phases of the oscillator output signal, an automatic hue control circuit including in combination: first and second hue control circuit means; means for supplying the modulated subcarrier signal to the first and second hue control circuit means; means for supplying the oscillator output signal to the first and second hue control circuit means, with the relative phases of the modulated subcarrier signal and the oscillator output signal applied to the first and second hue control circuit means being such as to cause the first hue control circuit means to develop a first control signal for a first phase which is a predetermined amount greater than a particular phase, and to cause the second hue control circuit means to develop a second control signal for a second phase which is substantially said same predetermined amount less than said particular phase; and means responsive to the outputs of the first and second hue control circuit means for effectively shifting the phases of the modulated subcarrier signals which are between the phases detected by the first and second hue control circuit means toward said particular phase relative to the oscillator output signal.

Claim 20

In a color television receiver for a composite signal comprising brightness signal components, a subcarrier signal modulated by color difference signals representing hue and saturation at different phases of the subcarrier, and a burst component for phase-locking the signal of an oscillator of the receiver to control color signal demodulators for the subcarrier at different phases of the oscillator output signal, an automatic hue control circuit including in combination: first and second hue control circuit means; means for supplying the modulated subcarrier signal to the first and second hue control circuit means; means for supplying the oscillator output signal to the first and second hue control circuit means, with the relative phases of the modulated subcarrier signal and the oscillator output signal applied to the first and second hue control circuit means being such as to cause the first hue control circuit means to develop a first control signal for a first phase which is a predetermined amount greater than a particular phase, and to cause the second hue control circuit means to develop a second control signal for a second phase which is substantially said same predetermined amount less than said particular phase; and means responsive to the outputs of the first and second hue control circuit means for effectively shifting the phases of the modulated subcarrier signals which are between the phases detected by the first and second hue control circuit means toward said particular phase relative to the oscillator output signal.