Television receiver with picture level control

Claim 2

In a television receiver including a source of video signal, a picture tube and a coupling circuit for translating said video signal to said picture tube, an improved picture control system comprising: level setting means coupled to said coupling circuit for adjusting the electrical black level of said video signal to correspond to a desired minimum signal level to be applied to said picture tube, amplitude control means coupled to said coupling circuit for adjusting the maximum amplitude of said video signal to correspond to a desired level to be applied to said picture tube, said amplitude control means being arranged to modify said minimum signal level so that electrical black level is modified in proportion to maximum signal level adjustment, signal responsive means coupled to said coupling circuit and responsive to the average video signal level for adjusting the maximum amplitude of said video signal and rendering said electrical black level insensitive to the change in maximum amplitude caused by said signal responsive means.

Claim 3

The television receiver as defined in claim 1 wherein said receiver is a color television receiver and includes luminance and chrominance amplifiers, said amplifiers being connected to supply the luminance and chrominance components of said video signal to said picture tube and said amplitude control means and said signal responsive means being connected to control the maximum amplitude of said luminance and chrominance signals in preselected proportion.

Claim 4

The television receiver as defined in claim 1 wherein said amplitude control means includes means responsive to ambient lighting conditions for changing the maximum amplitude of said video signal.

Claim 5

The television receiver as defined in claim 1 wherein said signal responsive means comprises a overload protection circuit.

Claim 6

The television receiver as defined in claim 4 wherein said overload protection circuit is responsive to video drive current applied to said picture tube and prOvides a feedback signal to said coupling circuit to restrict said video signal to a predetermined level.

Claim 7

The television receiver as defined in claim 5 wherein said overload protection circuit includes means for establishing a threshold level below which level said overload circuit is inoperative to restrict said maximum video level.

Claim 8

The television receiver as defined in claim 1 wherein said amplitude control means is responsive to power supply variations to adjust said video signal to maintain electrical black level in correspondence with said desired minimum signal level.

Claim 9

The television receiver as defined in claim 1 wherein said level setting means includes a sync tip clamp DC restorer for adjusting said electrical black level to correspond to said desired minimum signal level.

Claim 10

The television receiver as defined in claim 1 wherein said signal responsive means comprises a video monitoring circuit responsive to the average level of said video signal.

Claim 11

The television receiver as defined in claim 1 wherein said signal responsive means comprises: an overload protection circuit responsive to drive current applied to said picture tube, said protection circuit including means for establishing an average drive current threshold level above which level feedback voltage is supplied to said coupling circuit to limit said video signal to a pre-determined level; and a video signal monitoring circuit responsive to the average video signal level to limit the maximum video signal level.

Claim 12

In a television receiver including a picture tube, a source of video signal and coupling means for coupling said video signal to said picture tube, an improved picture control comprising: level setting means coupled to said coupling means for setting the electrical black level of said video signal to correspond to optical black level; amplitude control means coupled to said coupling means for controlling the maximum video signal amplitude to be supplied to said picture tube and maintaining said electrical black level in correspondence with said optical black level in response to ambient light change.

Claim 13

In a television receiver including a picture tube, a source of video signal and coupling means for coupling said video signal to said picture tube, an improved picture control comprising: level setting means coupled to said coupling means for setting the electrical black level of said video signal to correspond to optical black level; amplitude control means coupled to said coupling means for controlling the maximum video signal amplitude to be supplied to said picture tube and maintaining said electrical black level in correspondence with said optical black level in response to ambient light change.

Claim 14

In a color television receiver including a source of luminance and chrominance signals, a picture tube and luminance and chrominance signal channels for coupling said luminance and chrominance signals to said picture tube, an improved picture control system comprising: amplitude control means for producing a first signal representative of a desired picture level on said picture tube; scene brightness control means connected to receive said luminance and chrominance signals and responsive thereto to produce a second signal proportional to the average value of said luminance signal; an overload protection circuit connected to monitor drive current applied to said picture tube, said protection circuit being responsive to the average value of said drive current exceeding a predetermined threshold level to produce a third signal; a first matrix connected to receive said first, second and third signals, said first matrix being adapted to combine said first, second and third signals in a predetermined ratio to produce a gain control signal for application to said luminance and chrominance signal channels for adjusting the amplitude of said luminance and chrominance signals; and a second matrix connected to receive said first, second and third signals, said second matrix being adapted to combine said first, second and third signals in a predetermined ratio to produce a reference voltage for application to said luminance channel to set the electrical black level of said luminance signal to correspond to a desired minimum luminance signal level.

Claim 15

In a color television receiver including a source of luminance and chrominance signals, a picture tube and luminance and chrominance signal channels for coupling said luminance and chrominance signals to said picture tube, an improved picture control system comprising: amplitude control means for producing a first signal representative of a desired picture level on said picture tube; scene brightness control means connected to receive said luminance and chrominance signals and responsive thereto to produce a second signal proportional to the average value of said luminance signal; an overload protection circuit connected to monitor drive current applied to said picture tube, said protection circuit being responsive to the average value of said drive current exceeding a predetermined threshold level to produce a third signal; a first matrix connected to receive said first, second and third signals, said first matrix being adapted to combine said first, second and third signals in a predetermined ratio to produce a gain control signal for application to said luminance and chrominance signal channels for adjusting the amplitude of said luminance and chrominance signals; and a second matrix connected to receive said first, second and third signals, said second matrix being adapted to combine said first, second and third signals in a predetermined ratio to produce a reference voltage for application to said luminance channel to set the electrical black level of said luminance signal to correspond to a desired minimum luminance signal level.

Claim 16

The color television receiver as defined in claim 12 including a level setting means connected to supply a voltage to said second matrix to establish an initial correspondence between said electrical black level and said minimum luminance signal level.

Claim 17

The color television receiver As defined in claim 13 including a preference control connected to modify said gain control signal being applied to said chrominance signal channel to establish a desired ratio of luminance to chrominance signal level.

Claim 18

The color television receiver as defined in claim 14 wherein said level setting means includes means to adjust black level to compensate for transmitted black level error.