DE3319989A1 - COLOR CATHODE RAY TUBES AND COLOR SCREEN SYSTEM WITH SUCH A COLOR CATHODE RAY TUBE - Google Patents

Description

Marconi Avionics Limited, Rochester, Kent, England

Color
^ §EäE £ ig_en_Color cathode ray tube

The invention relates to a color cathode ray tube with a screen which has a number of nested Has sets of strips of material, each set of which upon electron impact light of a certain color emitted, with an electron gun that emits an electron beam to scan the lines of the Screen generated, which extend in the direction of the stripes and with sensor devices for generating a Control signal that directs the electron beam with great accuracy along each stripe in turn as well as a color display system using such a color cathode ray tube.

Color display systems have been in use for many years used by shadow mask color cathode ray tubes and work satisfactorily for general use.

Such systems are suitable for use in aircraft however, the disadvantages that the power required for their operation is too great, that heat loss or overheating problems occur on a large scale and become unreliable in such a highly vibrating environment work.

One embodiment of a display system utilizing a color cathode ray tube with beam indexing or with a switching beam is better suited for use in an environment such as, for example is present on an airplane.

in a conventional beam indexing color cathode ray tube A single electron beam scans horizontally across the vertical strips of emitting different colors Phosphors.

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As detailed in UK Patent Application 2,057,187A various interrelated difficulties arise with such an arrangement. In order to reduce these difficulties, a new embodiment is disclosed in the aforementioned GB patent application 2,057,187A a color cathode ray tube proposed, in which the electron beam has a linear arrangement of during operation Light of different colors emitting strips in the longitudinal direction of the strips are scanned and sensor devices are provided to generate a control signal which the electron beam with great accuracy along each stripe steers in turn.

In the aforementioned patent application, the beam directing devices include Rows of ultraviolet light emitting segments in the spaces between adjacent ones Pairs of visible light emitting strips are arranged and are further deflectors provided on the ultraviolet light emitted by the segments respond to generate a control signal for the precise tracking of the electron beam longitudinally each strip is used in series.

The object of the invention is to improve a color cathode ray tube 5 and a color display system of the type described above so that the scanning of the light-emitting strips in their longitudinal direction by the electron beam leads to a different beam steering with increased accuracy.
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According to the invention, this object is achieved by a color cathode ray tube solved according to the features of the preamble of claim 1 in that the sensor devices comprise an electrode array associated with the strips and arranged so that along their length each of at least a selection of strips a corresponding gap between a pair of electrodes of the electrode arrangement overstretched.

Everyone spans a corresponding gap Strips arranged centrally to the gap spanned by it.

In an embodiment of the invention, the electrode arrangement comprises two electrodes, each of which has a number of fingers, occupy a nested reference position to the fingers of the other electrode, so that each strip that spanning a gap, a corresponding gap between a finger of one electrode and an adjacent finger the other electrode spanned.

In a further development of the invention, the electrode arrangement has electrically conductive coatings on the side of the Strips are attached, which is closer to the electrode gun and which is made of a partial for the electron beam made of transparent material and reflect the light emitted by the strips.

Using the color display system of the invention a color cathode ray tube is characterized in that line and field deflection devices for deflection of the beam generated by the electron gun of the cathode ray tube over the cathode ray tube hood in a grid are available in which each grid line is in register with another strip is that beam modulator means the electron beam with a video signal modulate to match the color of the light emanating from the strip nominally scanned at the time is emitted that beam deflectors respond to the control signal to set the field deflectors in a way to control that the deviations of the electron beam from the desired position on the screen during the scanning can be reduced.

In an embodiment of the color screen system, the electrode arrangement has two electrodes, each containing a number of fingers nested in one

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Are related to the fingers of the other electrode, so that each strip spanning a gap has a corresponding one Spans a gap between a finger on one electrode and an adjacent finger on the other electrode, It is considered that the beam deflectors contain means for generating a signal which is the difference between reproduces the currents that arise at the two electrodes as a result of the impingement of the electron beam that over a variable amplifier stage sends the signal to the field deflectors is supplied and that a circuit increases the gain of the variable amplifier stage as a function of controls the electron beam current so that the fluctuations in the signal applied to the field deflectors in Can be reduced depending on the electron beam current. 15th

The following describes a color cathode ray tube and a color display system using such a color cathode ray tube is used, described in more detail with reference to the drawings. Show it: 20th

Figure 1 - a schematic sectional view of part of the

Color cathode ray tube screen; Figure 2 - a schematic rear view of part of the Color cathode ray tube screen; and FIG. 3 is a schematic block diagram of part of the

Color screen system.

The screen of the color cathode ray tube partially shown in FIGS. 1 and 2 comprises red, blue and green Light emitting sets of fluorescent strips R, B and G placed on the inside of a glass plate 1 of the cathode ray tube envelope are arranged. The sentences are regularly nested, so that red, blue and green emitting Stripes appear in a repeating order across the screen. Any adjoining couple of strips R, B and G is separated by a so-called security strip 3, which has a width that is im is substantially equal to the width of the R, B and G strips

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and made of a non-light emitting material such as carbon black. The stripes will be on the side remote from the faceplate 1 covered by an electrode arrangement, the two electrodes 5 and 7, each of which is formed by a thin coating of aluminum.

Each of the electrodes 5 and 7 comprises a number of parallel, spatially separated fingers 5A and 7A, which extend from a part 5B and 7B, respectively, which serves to connect the fingers to one another. The number of Finger 5A, 7A in each electrode 5, 7 is equal to half the total number of strips R, B and G, and the electrodes are arranged with their fingers in a spaced interleaved relationship such that each Strip R, G or B centrally a corresponding gap between a finger of one electrode and an adjacent one Partially overstretched fingers of the other electrode. At one end of the strip, in Figure 2 at the right end, the electrode fingers extend beyond the strips.

The electrodes 5 and 7 serve to improve the brightness of the light by reflection of the fluorescent strips emitted light. In addition, the electrodes 5 and 7 / which are sufficiently thin / µm for the electron beam become to be semi-transparent / used in a manner which will be described in more detail below to a control signal for directing the electron beam of the color cathode ray tube with great accuracy along the fluorescent strips to deliver.

As can be seen in particular from Figure 3, the color cathode ray tube is in a color screen system with line and field deflection devices consisting of line and field deflection coils 9, and a generator circuit 11 for the line deflection voltage and a generator circuit 13 available for the field deflection voltage, from

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which the latter has a stepped output signal instead a linear sawtooth waveform. The deflectors serve to control the electron beam generated by a single electron gun 15 of the color cathode ray tube will deflect across the cathode ray tube screen in a rectangular grid, with the grid lines are nominally aligned with the fluorescent strips.

The electron beam current of the cathode ray tube is through modulates a signal applied to a control grid 17 of the electron gun from a video driver circuit 19. Red, blue and green video signals are in reverse order of the driver circuit 19 via a switch circuit 21 supplied from a screen generator not shown. 15th

The operation of the switch circuit 21 and deflection circuits 9 and 13 is synchronized by line and field sync pulses generated by the screen generator are fed in, ensuring that during each line scan the corresponding red, blue and green Video signal of the video drive circuit 19 is supplied.

The line and field sync pulses are conventional Way fed to the generator circuits 9 and 13 for the field deflection voltage. In addition, the synchronization pulses a line counting circuit 23, the output of which controls the operation of the switch circuit 21 and also the timing of the steps in the field deflection voltage.

The output voltage of the circuit 13 for the field deflection voltage is also controlled to ensure that during each line scan the electron beam with great accuracy along the center line of the respective fluorescent strip, which is being scanned is guided.

The electrodes 5 and 7 of the color cathode ray tube are at the same potential via corresponding equivalent ones

Resistors 25 and 27 like the not shown end anode of the electron gun 15 and are connected to the inputs of a differential amplifier 29 connected via corresponding capacitors 31 and 33, with the same size resistors 35 and are connected between the amplifier inputs and ground.

The output of amplifier 29 becomes a variable amplifier stage 39 is supplied, the output of which is via a reversing switch circuit 41 which is controlled by the line counter 23 is fed to the field deflection circuit 13. The gain of stage 39 is controlled by a signal which comes from the video driver circuit 19 via a shaping circuit 43.

In operation, the currents in the resistors 25 and depend on the impact positions of the electron beam on the Screen of the color cathode ray tube, or more precisely, on the electrode assembly. When the electron beam is guided centrally along a fluorescent strip R, B or G, so that equal areas of the beam on the Touch the fingers of the electrodes that define the gap, which the strip spans, the input signals of the amplifier 29 with respect to ground are the same, and the The amplifier output is then zero. On the other hand generated the amplifier 29 has an output of one polarity or the other, depending on whether the beam hits the strip scanned offset to one side or the other from the centerline of the strip.

The output of amplifier 29 controls the output the generator circuit for the field deflection voltage in the Way that the output of the amplifier 29 tends towards zero so that the arrangement operates as a position feedback servo system works for the electron beam.

The reverse switch circuit 41 is required because the Polarity of the output signal of the amplifier 29 with respect to the direction of displacement of the electron beam itself

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changes from strip to strip. So if everyone Strips are scanned in sequence during a raster that switch circuit 41 at the end of each line is operated. On the other hand, when interlacing is carried out, the switch circuit 41 is actuated with the field frequency, since only alternating strips are scanned in each field.

The variable amplifier stage 39 is operated to keep the control signal supplied to the circuit 13 independent of the video signal level. On the other hand, the position feedback system would become unstable or inadequate if the level of the video signal rises and falls.
15th

Typically, is an operation speed of the position feedback system required, which is approximately a third or a quarter of the line scan period, since geometrical errors in the beam position usually do not have components that are greater than three or four times Line scanning frequency are.

The values of the capacitors 31 and 33 and the resistors 25, 27, 35 and 37 must be chosen in a suitable way, to ensure a satisfactory operation at the lowest possible frequencies. Since the If the lowest frequencies are comparable to the line frequency, the selection of these values is not critical.

It goes without saying that the exact sampling of the Stripes R, B and G are achieved regardless of changes, for example in the deflection sensitivity, caused by changing the accelerating voltage of the electron gun of the color cathode ray tube. Likewise be Distraction disorders due to dislocations or a pincushion distortion in the field scanning direction is reduced by the feedback factor.

It is first assumed that relatively large deflection errors occur at the beginning of every line and every field. To correct such large errors without visual effect and without too great demands on the design of the deflectors To make it possible, the electrodes 5 and 7 extend over the strips R, B and G on the Side of the screen where the scan begins. The space required for this is usually not greater than 10 mm. In order to reduce the loss of image area, the electrodes 5 and 7 can be extended over the fluorescent strips R, B and G are continued out into the curved part of the envelope of the color cathode ray tube.

It is evident that a beam steering control signal is too is required at all times so that the electron beam of the cathode ray tube is never completely switched off can be, that is, the beam current must be prevented from falling below a predetermined minimum value. This is achieved by a bias level control circuit 45 connected between the cathode 47 and the usual Brightness control 49 of the color cathode ray tube is switched and through an associated resistor 51, the Measures beam current.

Instead of controlling the gain of amplifier 39 with the output of video driver circuit 19, can alternately the gain of the amplifier 39 directly depending on the beam current of the color cathode ray tube being controlled. Any non-linear effect due to the gamma correction of the color cathode ray tube can then be prevented from influencing the beam guidance,

A signal used to control the gain of the amplifier in a direct manner depending on the beam current of the color cathode ray tube is appropriately over the resistor 51 for measuring the beam current is obtained, as indicated by the dashed line in FIG is, the connection between the shaping circuit 43 and

the video driver circuit 19 is then not required in a characteristic embodiment of that in the figures 1 and 2 partially shown color cathode ray tube, the fluorescent strips R, B and G have a length of 134 mm, and the fingers of electrodes 5 and 7 have one Length of 140 mm so that the fingers extend about "6 mm beyond the strips at one end. In one In such an arrangement, the gaps between adjacent fingers are approximately 0.08 mm, and the spacing of the gaps between the fingers is about 0.23 mm so that the width of the electrodes is about 0.15 mm and the diameter of the electron beam on the screen is controlled within a range of 0.1 to 0.13 mm, the Strips are approximately 0.15 mm wide, i.e. approximately the same width as the electrodes.

In a modified embodiment, not shown, of the system shown in FIG. 3, the potential or the Voltage between electrodes 5 and 7 to the input of amplifier 29 via an inductive coupling instead of a capacitive one Coupling fed. In such an arrangement, the transformer windings form the inductive coupling the required high DC voltage isolation. In order to avoid the use of a large transformer, to make an adequate To achieve coupling at lower frequencies, the electron beam of the color cathode ray tube can with a sufficiently high frequency to be chopped to prevent visual effects on the screen, i.e. above the highest video frequency used and the resulting AC signal on the secondary winding of the transformer be demodulated before it is fed to the amplifier 29.

It goes without saying that it is also possible differently than is the case, for example, in the arrangements described above, where each fluorescent strip has a corresponding one Gap between sensor electrodes 5 and 7

spanned, in other arrangements in accordance with
of the invention only selected strips of this type
Can span the gap. The beam guidance is then of course only influenced for these selected strips, but this can be sufficient to ensure a satisfactorily precise beam guidance along the intermediate strips for all of them
practical use cases.

Claims (1)

Marconi Avionics Limited, Rochester, Kent, England Θ- '1/. Color cathode ray tube with a screen, the one Number of nested sets of strips of material (R, G, B), each set upon electron impact Light of a certain color is emitted with an electron gun (15) which sends an electron beam to the Generated raster-shaped scanning of the lines of the screen, which extend in the direction of the strips and with sensor devices (5, 7) for generating a control signal that the electron beam with great accuracy along each Strips one after the other, characterized in that the sensor devices have an electrode arrangement (5, 7) include, which is associated with the strips (R, G, B) and arranged such that along their length each of at least a selection of strips spanning a corresponding gap between a pair of electrodes of the electrode arrangement. 2- color cathode ray tube according to claim 1, characterized in that each strip spans a respective gap is arranged centrally to the gap spanned by it. 3. color cathode ray tube according to claim 1 or 2, characterized in that that the electrode arrangement comprises two electrodes (5, 7), each of which has a number of fingers (5A, 7A), occupy a nested reference position to the fingers of the other electrode, so that each strip of the one Gap spanned, a corresponding gap between one Spanned fingers of one electrode and an adjacent finger of the other electrode. 4. Color cathode ray tube after each of the foregoing Expectations, characterized / that the electrode arrangement has electrically conductive coatings which are attached to the side of the strips, which is closer to the electron gun (15) and which is off consist of a material partially permeable to the electron beam and the light emitted by the strips reflect. 5. Color cathode ray tube according to any of the preceding claims, characterized in that at one end of the strip the electrodes (5, 7) of the arrangement extend beyond the strips. 6. color cathode ray tube according to any of the preceding claims, characterized in that the width of the strips is twice the gap width. 7. color cathode ray tube according to any of the preceding claims, characterized in that the width of the electrodes is equal to the width of the strips is. 8. A color display system with a color cathode ray tube , which has a display screen which contains a number of nested sets of strips of material (R, G, 5 B), each set of which emits light of a certain color upon electron impact, with an electron gun (15), which generates an electron beam to scan the lines of the screen that are razor-shaped extend in the direction of the strips, with sensor means (5, 7) for generating a control signal which directs the electron beam with great accuracy along each strip in turn,
characterized in that line and field deflection devices (11, 13) for deflecting the beam generated by the electron gun (15) of the cathode ray tube are provided over the cathode ray tube screen in a grid in which each grid line is in register with another strip, that beam modulation devices (19 , 21) modulate the electron beam with a video signal corresponding to the color of the light emitted from the strip nominally scanned at the time, so that beam deflectors (25 to 43) are responsive to the control signal to control the field deflectors in a manner that the deviations of the electron beam from the desired position on the screen during the scan are reduced, that the sensor devices comprise an electrode arrangement (5, 7) which is associated with the strips (R, G, B) and is arranged in such a way that along their length each of at least a selection of strips has a corresponding one Gap spanned between a pair of electrodes of the arrangement and that the beam deflectors are responsive to currents which arise as a result of the impingement of the electron beam on the electrodes of the electrode arrangement. 9. color display system according to claim 8, characterized in that the electrode arrangement comprises two electrodes (5, 7), each of which contains a number of fingers (5A, 7A) which are in a nested relationship with the fingers of the other electrode, so that each strip which spans a gap spans a corresponding gap between a finger of one electrode and an adjacent finger of the other electrode, that the beam deflection devices (25, 27, 29, ι * 4 - ** 31, 33, 35, 37) for generating a signal that represents the difference between the currents applied to the two electrodes as a result of the impact of the electron beam arise that via a variable amplifier stage (39) the signal is fed to the field deflection devices and that a circuit (43) amplifies the variable Amplifier stage as a function of the electron beam current controls so that the fluctuations of the signal applied to the field deflectors as a function of the electron beam current can be reduced. 10. Color screen system according to claim 9, characterized in that that the circuit (43) for controlling the gain of the variable amplifier stage on the output of the beam modulation devices appeals to. 11. color screen system according to claim 9, characterized in that the circuit for controlling the gain of the variable Amplifier stage responds directly to the current of the beam from the cathode ray tube. 12. Color screen system according to any one of claims 8 to 11, characterized in that a circuit (47) reduces the current of the Prevents the beam of the cathode ray tube from falling below a predetermined minimum level.