Method and apparatus for maintaining the beam current of an image-display device within controlled limits

Claim 3

The method of claim 1, in which said modifying comprises automatically adjusting the DC component of said original brightness control signal.

Claim 4

The method of claim 1, in which said modifying comprises clipping said original brightness control signal at a controlledly variable level thereof.

Claim 5

The method of claim 3, in which said modifying comprises providing DC restoration of said clipped brightness control signal prior to its application to said image display device.

Claim 6

Apparatus for preventing quality-degrading decreases in the anode voltage of a cathode-ray tube due to excessive average cathode-ray beam current, comprising: means for sensing imminence of said quality-degrading decreases in anode voltage and for producing an electrical control signal indicative thereof; means for scanning said beam over an area of said tube; and means for maintaining above a lower threshold the minimum average value of current of said beam as averaged over at least a portion of said area, despite the action of said control signal to reduce said average current.

Claim 7

Apparatus for preventing quality-degrading decreases in the anode voltage of a cathode-ray tube due to excessive average cathode-ray beam current, comprising: means for sensing imminence of said quality-degrading decreases in anode voltage and for producing an electrical control signal indicative thereof; means for scanning said beam over an area of said tube; and means for maintaining above a lower threshold the minimum average value of current of said beam as averaged over at least a portion of said area, despite the action of said control signal to reduce said average current.

Claim 8

Apparatus in accordance with claim 5, comprising threshold means operative to prevent said control signal from reducing the average current of said beam except when tendencies for said quality-degrading decreases in final anode voltage are sensed.

Claim 9

Apparatus for preventing quality-degrading decreases in the anode voltage of a color television image-display cathode-ray tube due to excessive average cathode-ray beam current, comprising: means for sensing imminence of said quality-degrading decreases in anode voltage and for producing an electrical control signal indicative thereof; and means tending to maintain said beam current at or above a predetermined minimum value as averaged over at least a portion of the scanning of said viewing area by said beam.

Claim 10

Apparatus for preventing quality-degrading decreases in the anode voltage of a color television image-display cathode-ray tube due to excessive average cathode-ray beam current, comprising: means for sensing imminence of said quality-degrading decreases in anode voltage and for producing an electrical control signal indicative thereof; and means tending to maintain said beam current at or above a predetermined minimum value as averaged over at least a portion of the scanning of said viewing area by said beam.

Claim 11

Apparatus in accordance with claim 7, comprising threshold means for preventing said reduction in average current of said beam except when said quality-degrading decreases in final anode voltage are sensed.

Claim 12

Apparatus in accordance with claim 7, in which said means for producing a control signal comprises means for sensing the cathode current of said tube.

Claim 13

In a color television receiver system comprising An indexing cathode-ray image-presentation tube having indexing elements scanned by the cathode-ray beam of the tube to produce index signals, having beam intensity control means for controlling the intensity of said beam, and having a high-voltage anode; brightness-channel means for receiving color television signals to produce a brightness signal representative of changes in brightness of the image to be reproduced for application to said beam-intensity controlling means; means for producing chroma signals representative of the coloration of the image to be reproduced; means for combining said chroma signals and said index signals to produce a color-controlling signal for application to said beam-intensity controlling means to control the coloration of the reproduced image; and high-voltage supply means for supplying high voltage to said anode of said tube, said supply means producing a voltage which varies with the average current of said cathode-ray beam, the improvement comprising: means for producing a control signal indicative of a change of said voltage, and means responsive to said control signal for controlling said average value of said beam current; said brightness-channel means comprising signal-clipping means to clip said brightness signal at different levels depending upon the value of said control signal, and DC restorer means responsive to said clipped brightness signal to clamp it at a substantially fixed level with respect to its clipping level and to supply it to said beam-intensity controlling means, said control signal being of the sense to clip said brightness signal farther toward the peak-brightness extreme thereof when said high-voltage tends to decrease.

Claim 14

In a color television receiver system comprising An indexing cathode-ray image-presentation tube having indexing elements scanned by the cathode-ray beam of the tube to produce index signals, having beam intensity control means for controlling the intensity of said beam, and having a high-voltage anode; brightness-channel means for receiving color television signals to produce a brightness signal representative of changes in brightness of the image to be reproduced for application to said beam-intensity controlling means; means for producing chroma signals representative of the coloration of the image to be reproduced; means for combining said chroma signals and said index signals to produce a color-controlling signal for application to said beam-intensity controlling means to control the coloration of the reproduced image; and high-voltage supply means for supplying high voltage to said anode of said tube, said supply means producing a voltage which varies with the average current of said cathode-ray beam, the improvement comprising: means for producing a control signal indicative of a change of said voltage, and means responsive to said control signal for controlling said average value of said beam current; said brightness-channel means comprising signal-clipping means to clip said brightness signal at different levels depending upon the value of said control signal, and DC restorer means responsive to said clipped brightness signal to clamp it at a substantially fixed level with respect to its clipping level and to supply it to said beam-intensity controlling means, said control signal being of the sense to clip said brightness signal farther toward the peak-brightness extreme thereof when said high-voltage tends to decrease.

Claim 15

The system of claim 10, in which said DC restorer means clamps said brightness signal at a value such as to maintain a predetermined minimum intensity of said beam as it scans the viewing area of said tube.

Claim 16

In a system according to claim 10, means for effectively adding said chroma signals to said brightness signal.

Claim 17

Apparatus in accordance with claim 10, comprising means for periodically blanking said beam when it scans beyond the area of said tube on which the viewed image is formed.

Claim 18

Apparatus in accordance with claim 10, comprising means for periodically interrupting application of said chroma and brightness signals to said beam-intensity controlling means and for applying other signals to said beam-intensity controlling means during said interrupting.

Claim 19

Apparatus for preventing substantial defocusing of a scanning cathode-ray beam in the color-image reproducing cathode-ray tube of a color television receiver, due to increases of the average cathode-ray beam current above a predetermined level, comprising: means responsive to changes in the average value of said beam current for producing a control signal; means responsive to said control signal for modifying the signal applied to the beam-intensity controlling electrode of said tube in such a direction as to tend to prevent said average beam current from exceeding said predetermined level; and means to maintain at no less than a minimum value the current in said beam during at least a portion of its scanning.

Claim 20

Apparatus for preventing substantial defocusing of a scanning cathode-ray beam in the color-image reproducing cathode-ray tube of a color television receiver, due to increases of the average cathode-ray beam current above a predetermined level, comprising: means responsive to changes in the average value of said beam current for producing a control signal; means responsive to said control signal for modifying the signal applied to the beam-intensity controlling electrode of said tube in such a direction as to tend to prevent said average beam current from exceeding said predetermined level; and means to maintain at no less than a minimum value the current in said beam during at least a portion of its scanning.

Claim 21

Apparatus in accordance with claim 15, comprising a high-voltage supply for the final anode of said tube including a horizontal deflection transformer, and in which said means for producing a control signal comprises means connected to said transformer for sensing decreases in the amplitude of the horizontal flyback pulse produced in said transformer.

Claim 22

Apparatus in accordance with claim 15, in which said means responsive to said control signal comprises variable-gain means in the signal channel through which a brightness-representing component of the received television signal is supplied to the intensity-controlling electrode of said tube and supplied with said control signal.

Claim 23

Apparatus for preventing substantial defocusing of the cathode-ray beam in the coloR-image reproducing cathode-ray tube of a color television receiver, due to increases of the average cathode-ray beam current above a predetermined level, comprising: means responsive to changes in the average value of said beam current for producing a control signal; means responsive to said control signal for modifying the signal applied to the beam-intensity controlling electrode of said tube in such a direction as to tend to prevent said average beam current from exceeding said predetermined level; and a high-voltage supply for the final anode of said tube including a high-voltage regulating device; said means for producing a control signal comprising means for sensing when said regulator is near one end of its regulation range.

Claim 24

Apparatus for preventing substantial defocusing of the cathode-ray beam in the coloR-image reproducing cathode-ray tube of a color television receiver, due to increases of the average cathode-ray beam current above a predetermined level, comprising: means responsive to changes in the average value of said beam current for producing a control signal; means responsive to said control signal for modifying the signal applied to the beam-intensity controlling electrode of said tube in such a direction as to tend to prevent said average beam current from exceeding said predetermined level; and a high-voltage supply for the final anode of said tube including a high-voltage regulating device; said means for producing a control signal comprising means for sensing when said regulator is near one end of its regulation range.

Claim 25

Apparatus in accordance with claim 18, in which said high-voltage supply comprises voltage regulating means and said sensing means comprises means for sensing the current through said voltage regulating means.

Claim 26

Apparatus in accordance with claim 19, in which said voltage regulating means is a shunt regulator.

Claim 27

Apparatus for preventing substantial defocusing of the cathode-ray beam in the color-image reproducing cathode-ray tube of a color television receiver, due to increases of the average cathode-ray beam current above a predetermined level, comprising: means responsive to changes in the average value of said beam current for producing a control signal; and means responsive to said control signal for modifying the signal applied to the beam-intensity controlling electrode of said tube in such a direction as to tend to prevent said average beam current from exceeding said predetermined level; said means for producing a control signal comprising means for sensing the cathode current of said tube.

Claim 28

Apparatus for preventing substantial defocusing of the cathode-ray beam in the color-image reproducing cathode-ray tube of a color television receiver, due to increases of the average cathode-ray beam current above a predetermined level, comprising: means responsive to changes in the average value of said beam current for producing a control signal; and means responsive to said control signal for modifying the signal applied to the beam-intensity controlling electrode of said tube in such a direction as to tend to prevent said average beam current from exceeding said predetermined level; said means for producing a control signal comprising means for sensing the cathode current of said tube.

Claim 29

Apparatus for preventing substantial defocusing of the cathode-ray beam in the color-image reproducing cathode-ray tube of a color television receiver, due to increases of the average cathode-ray beam current above a predetermined level, comprising: means responsive to changes in the average value of said beam current for producing a control signal; means responsive to said control signal for modifying the signal applied to beam-intensity controlling means of said tube in such a direction as to tend to prevent said average beam current from exceeding said predetermined level; signal-clipping means supplied with a brightness-representing component of the received television signal to produce clipped brightness-representing signals; and DC restorer means supplied with said clipped brightness-representing signals for clamping said clipped brightness-representing signals at a substantially fixed level with respect to their clipped level and for supplying said clamped signals to said beam-intensity-controlling means of said tube; said means responsive to said control signal comprising means for automatically varying the clipping level in said clipping means.

Claim 30

Apparatus for preventing substantial defocusing of the cathode-ray beam in the color-image reproducing cathode-ray tube of a color television receiver, due to increases of the average cathode-ray beam current above a predetermined level, comprising: means responsive to changes in the average value of said beam current for producing a control signal; means responsive to said control signal for modifying the signal applied to beam-intensity controlling means of said tube in such a direction as to tend to prevent said average beam current from exceeding said predetermined level; signal-clipping means supplied with a brightness-representing component of the received television signal to produce clipped brightness-representing signals; and DC restorer means supplied with said clipped brightness-representing signals for clamping said clipped brightness-representing signals at a substantially fixed level with respect to their clipped level and for supplying said clamped signals to said beam-intensity-controlling means of said tube; said means responsive to said control signal comprising means for automatically varying the clipping level in said clipping means.

Claim 31

In a cathode-ray tube system comprising a cathode-ray tube image-display device, circuit means for supplying a television signal to beam-intensity controlling means of said image-display device, and a high-voltage supply for said image-display device; DC restorer means for clamping the black-going extreme excursions of said television signal at a predetermined value; and control circuit means for clipping said black-going extreme excursions of said signal at controlledly different levels prior to application of said signal to said DC restorer, thereby to vary the average brightness of the image displayed by said device without changing substantially the minimum brightness thereof established by said DC restorer means; means for sensing a quantity related to said average brightness to produce a control signal; and means for controlling said control circuit means in response to said control signal to vary said clipping level only when said average brightness exceeds a predetermined maximuM value.

Claim 32

In a cathode-ray tube system comprising a cathode-ray tube image-display device, circuit means for supplying a television signal to beam-intensity controlling means of said image-display device, and a high-voltage supply for said image-display device; DC restorer means for clamping the black-going extreme excursions of said television signal at a predetermined value; and control circuit means for clipping said black-going extreme excursions of said signal at controlledly different levels prior to application of said signal to said DC restorer, thereby to vary the average brightness of the image displayed by said device without changing substantially the minimum brightness thereof established by said DC restorer means; means for sensing a quantity related to said average brightness to produce a control signal; and means for controlling said control circuit means in response to said control signal to vary said clipping level only when said average brightness exceeds a predetermined maximuM value.

Claim 33

In apparatus for preventing quality-degrading decreases in the anode voltage of a cathode-ray tube due to excessive cathode-ray beam current, comprising a source of high-voltage for said tube and voltage regulator means connected to said source: means for sensing when said regulator is near the end of its regulation range and for producing a control signal indicative thereof; and means responsive to said control signal for reducing said beam current.

Claim 34

In apparatus for preventing quality-degrading decreases in the anode voltage of a cathode-ray tube due to excessive cathode-ray beam current, comprising a source of high-voltage for said tube and voltage regulator means connected to said source: means for sensing when said regulator is near the end of its regulation range and for producing a control signal indicative thereof; and means responsive to said control signal for reducing said beam current.

Claim 35

Apparatus according to claim 24, in which said regulator is connected in shunt with said source, and said sensing means comprises means for sensing when the current through said regulator decreases to a predetermined value.