DE1138815B - Circuit for setting the background brightness together in a television display device - Google Patents

Description

The invention relates to a circuit arrangement for setting the basic brightness in at least one television display apparatus containing two electron beam sources.

Such playback devices are used, inter alia, in color television. In general there are three electron beam sources. These can each be separately in an electron beam display tube be built in, but it is of course also possible that all three sources in only xo a tube are housed.

It is now known to be desirable in the reproduction of a color television picture that a change in the The basic brightness in a color image is such that no color change occurs. With regard to the The fact that the relationships between the changes in brightness brought about by the various sources and the changes in brightness relate to a particular one Basic color of the scene to be reproduced, voltage changes on the control electrodes of the The sources concerned are generally different, it is not possible to change the basic brightness without causing color changes by the bias voltages of the electrode systems of the three Sources are increased or decreased by the same amount.

In general, the luminous flux brought about by a display system Φ almost through

where V _{g is} the voltage between the cathode and the control grid of the associated electron beam source, V _go that value of this voltage at which Φ is just zero, and C and γ are constants which depend on the type of tube and the type of phosphor used are dependent.

Circuit for common setting

the background brightness in a television display device

Applicant:

N.V. Philips' Gloeilampenfabrieken, Eindhoven (Netherlands)

Representative: Dipl.-Ing. EE Walther, patent attorney, Hamburg I ₅ Mönckebergstr. 7,

Claimed priority: The Netherlands of 7 March 1958 (No. 225 645)

Teunis Poorter and Josue Jean Philippe Valeton,

Eindhoven (Netherlands) have been named as inventors

For the reproduction of white with the help of three systems, one of which is the basic red color, the the second contains the green and the third contains the blue, must apply:

Φ _τ : Φ _Β : Φϋ = a: b: c.

a, b, c are constants, the values of which depend on the color points of the selected phosphors and the type of white to be reproduced. The indices indicate the color of the assigned luminous flux.

From this it follows for the tensions:

- V ₁ ^ r : (V _g - V _g ) _g : (V _g - V ₃₀ ), = Cr

where Cr, C _g and Cb are the values of C in the reproduction This relationship must be for all brightness output devices which apply the red, the blue values of the white to be reproduced, or which supplies the green luminous flux; According to a known solution to this problem, the values of γ so are generally almost the same for the different colors in the cathode circles of three electron beams. systems voltage divider resistors arranged, and

2OJ 679/146

In addition, control resistors are used in the grid circles. Here and in the following, a "current source" is switched on, whereby the color image signals are also understood to be those that are directed from the load through these resistor arrangements and are not absorbed by the voltages in the outer circle. This results in a relatively pending current, which may be set, complicated circuit, which can also be a disruptive effect. A “voltage source” is to be understood as a flow of the actual image display triggering those whose internal resistance can be neglected. In particular, there are difficulties that are negligibly small such that their terminal voltage of color image signals together with the DC component is independent of the external load circuit which component to supply, as can be adjustable for a perfect terminal voltage. Reproduction in itself is desirable. io The set value of the variable resistors 1 be-There are also known circuit arrangements in which the voltage drop at the relevant those with HiKe of a resistance measuring device both resistance and superposition on the voltage supplied by the individual setting of the basic brightness corresponding voltage source values for each Color as well as a common electrode is effective. alteration is to adjust the basic brightness of the possible overall 15 By controlling the voltage sources V _n V ₉ and entire image. For a complete counter-Vb, the individual brightnesses of the verseitige dependence of the settings different electron beam sources of light, but produced is not achieved thereby, so that regulated the streams with a change and can therefore the differences in overall background brightness, a change of the Abkneifspannungen Vg ₀ (Blocking voltages) occurs from color components, which can be matched in particular in a 20. Expresses the color falsification of gray areas by setting the value. Resistors 1 can compensate for the differences between the three electron beam source systems for the setting of the basic brightness in a television-operational basic brightness control Voltage drops with the same currents of the power sources, these disadvantages can be avoided, and with I _n I _g and / &, only one of the control electrodes required for each ratio can be selected, i.e. the ratio beam system is without, just like the desired adjustment of the bias voltage between
Color change an operational setting of the

Basic brightness possible if, according to the invention 30 l_a _ \ - (JL \ ~ _unc j ( ^c \ - the bias voltage of each electron beam source is taken from \ C _r / VQ / I C & / 'from a point of a resistor
and if the potential at one end of this resistor can be adjusted independently and if the nominal brightness of the voltage drop to be reproduced at each resistor between the image can be changed without the color change point and the mentioned end of the image appearing, the ratio of the basic brightness may be operationally the same between the different voltage drops at the electrodes that are at the same time increased by an equal fraction or sources effective voltage drops are reduced and if the range of these understandings 1 do not change.

increase or decrease for each resistor 40. In the circuit arrangement of FIG

is adjustable. achieved by the fact that the

In a circuit according to the invention, the currents supplied are always kept equal to one another

It is surprisingly easy to achieve that the pros. By simultaneously and in the same way the

voltage of the different electron beam sources three current sources are changed, thus the

is changed at the same time in such a way that the basic brightness of the picture to be displayed is changed,

tensions always the condition according to the above without changing the color of this picture. In

meet the mentioned formulas. the figure is this relationship between the three

The invention is illustrated by the dashed line on the basis of the power sources in the drawing,

illustrated figures explains in more detail which characteristics A pleasant property of the circuit arrangement

management examples of circuit arrangements according to 50 tion is that when the power sources supplied

represent the invention. ferten currents are zero, the voltage across the

In Fig. 1 I _n l _g and 1 »designate variable resistors, electrodes equal to the voltages of the voltage

which is always in series with the voltage sources V _r , V ₀ , regardless of the size of the resistors 1,

or Vd and the current sources I _n I _g and h switched so that the voltage sources are readily available on the

are. The terminals 2 _r , 2 _g and 2 _{b of} these resistors 55 correct value can be set. Through this,

are each with an electrode of electron beam that one lets the current sources deliver current, can

sources connected that each have a luminous flux in one of the values of the resistors 1 likewise without further ado

create a certain basic color. The power sources can be adjusted.

and the voltage sources are all changeable. It should be noted that it is also possible to adjust the voltage drop across the resistors I _n l _g and 60 position of the current sources to compensate for the differences in the Is is only dependent on the slope of the current source in question and is dependent on the current supplied by a suitable change, since this current from which the resistors set the basic brightness, voltage source lying in the relevant branch un- If the resistors 1 are equal to one another, it can be dependent. The voltage at the terminals 3 _r , 3 _g this is done in that the three resistors on and 3b of the resistors but can only be changed by the same way of the 65. The voltage source supplied by the current-related voltage source is set desired ratio between, since this voltage is independent of the current flowing through the voltage drops across these resistors. not changed by this change.

It is also noted that the variable resistors in FIG. 1 are harmless by fixed resistors can be replaced in which the bias voltages variable taps, z. B. sliding contacts, be taken, as Fig. 1 a shows. The voltage drop between a terminal 3 and the electrode an electron beam source is then not by the set value of a resistor, but due to the location of a tap.

preferably provided with separate variable voltage sources. The resistors 9 can then be solid resistances.

In Fig. 3, finally, an embodiment of a circuit arrangement according to the invention is shown, where no voltage stabilizers are required.

In Fig. 3, 11, -, U _g and 11 & denote the resistors whose sliding contacts 12 with the electrodes of the

In Fig. 2, a circuit arrangement i ° electron beam sources are also connected, each one shown according to the invention. Deliver luminous flux with a certain basic color.

In this circuit arrangement, the resistors are These resistors are via sliding contacts 18 _r , 18 ^ stands 4, ·, 4 _g and 4 & those in which the voltage and 18 »with an adjustable part of the resistance would be at a certain point and the voltage drop would be 13 _r , 13 _S and 13 & connected in series. The resistances of these resistances, understood independently of one another, are again large compared to the resistors. These resistances, with sliding stands 13, are assumed. These resistors, which contacts 5 _r , 5 _g and 5 & are provided with which are the same as the parts connected to each other, as well as their adjustable electrodes of the electron beam sources, are across the resistors 14, ·, 14 _ff and 14 & are, respectively, are across the sliding contacts 6, ·, 6 _g and 6 & with 15 »·, 15 _ff or 15», with which they are coupled by the sliding con resistors Ir, Ig and 7b, each of which has a 20 cycle 16, -, 16 _? and 16 & and 17, ·, VJ ₀ and 17s respectively, stabilizing devices S _r , S ₀ and 8 & are bridged to the terminals of a (for all networks. It is assumed that the resistors 4
are large compared to the resistors 7. In row
with these stabilizers there are resistances 9 _r , 9 _g

or 9b and 10, ·, 10 ^ or 10 & between the terminals 25 a decrease or increase in the resistance
a (common) voltage source V. In FIG. 2, resistors 9 are presupposed to be controllable for an equal increase or decrease in the resistance; through this
Regulation is the voltage at the connection point
between a resistor 9 and a stabilizer 8

works common) voltage source V.

The sliding contacts 16, - and 17 _r can use the

Resistors 14 _r and \ 5 _{r are moved in} such a way that

Standes 15 _r leads. In the figure, the coupling used for this purpose between the sliding contacts 16, - and 17 _r is shown schematically by a double dashed line

changed. The setting of the sliding contacts 6 is conditional, 30 shown. This means that the voltage drop

what part of the voltage drop across the resistors 7, which is kept constant by the stabilizers is effective via the resistors 4, and the setting of the sliding contacts 5 determines which part of this variable Voltage drop at the electrodes of the electron beam sources is effective.

The setting of the resistors 9 determines the individual brightnesses of the light fluxes brought about by the various electron beam sources; By regulating the resistors 9, the differences in the pinch-off voltages V _g " can thus be compensated for again. By adjusting the position of the sliding contacts 5, the differences in the steepnesses of the three electron beam source systems are compensated for for the general brightness control.

If the basic brightness is to be set operationally without changing the color of the displayed image, so the set fractions of the voltage drops across the resistors 4 must continuously have desired mutual relationship. Are the voltages set by the stabilizers equal to one another, the sliding contacts 6 must always have corresponding positions on the resistors 7.

at the resistor 13, - and also at the adjustable part of the resistor 13, - and thus also at the resistor 11 _{r is} independent of the position of the sliding contacts 16, - and VJ _r .

The movement of sliding contacts 16 ^ and 17 _ff or 16 »and VJb is similar in such a way that the voltage drop across resistors 13 # and 13 & is also independent of the position of these sliding contacts.

The sliding contacts 18 _r , 18 _ff and 18 & are coupled to one another (shown schematically in the figure by the single dashed line) that the adjustable parts of the resistors 13, -, 13 _ff and 13 & are always the same as possible.

By means of the sliding contacts 12, ·, 12 _? and 12 »you can set which part of the voltage drop across the resistors ll _r , \\ _g and lls is fed to the electrodes of the associated electron beam sources.

If the sliding contacts 12 _r , Vl ₀ and 12 & are set correctly, as well as the position of the sliding contacts 16 and 17, the basic brightness can be changed operationally by changing the position of the sliding contacts 18 at the same time, without the color of the

In the figure, the coupling used for this purpose is between

the sliding contacts 6 by a simple dashed 55 reproduced image changes.

Line shown schematically. In practice, the circuit arrangements according to FIGS. 2 and 3

for this purpose z. B. use three equal potentiometers, their sliding contacts by means of a common shaft are moved.

In Fig. 2, the resistors 9 are presumed controllable for the purpose of regulating the voltage at the connection point between a resistor 9 and a stabilizer 8. This voltage can also be changed by changing the voltage on the series connection naturally have the same properties with regard to the setting as the circuit arrangement according to Fig. 1.

It should be noted that in Fig. 2 the resistors 7 with the sliding contacts 6 and from the Resistors 4 with the sliding contacts 5 formed potentiometer circuits and in Fig. 3 by the Resistors 13 with the sliding contacts 10 and of

a resistor 9, a stabilizer 8 (with pulling resistors 11 with the sliding contacts 12 orderly parallel connection of resistors 4 and 7) formed potentiometer circuits mutually
and a resistor 7 can be changed. In this are changeable. By setting the Gleitkon trap, the various series connections are clocked 16 and 18 then the slope compensation

brought about, and the sliding contacts 5 and 12, the basic brightness is set.

Claims (12)

PATENT CLAIMS: 1. Circuit arrangement for jointly setting the basic brightness in a television playback device with at least two electron beam sources, in particular for color television, characterized in that the bias of each electron beam source is taken from a point (2, 5, 12) of a resistor (1, 4, 11) and that the potential at one end (3) of this resistor can be adjusted independently (V, 9, 15/17) and that the voltage drop at each resistor (1, 4, 11) between the pick-off point (2, 5, 12) and the mentioned end (3) for setting the basic brightness is operationally simultaneously increased or decreased by an equal fraction ao (/, 6, 18) and that the (absolute) range of this increase or decrease is adjustable for each resistor (1, 5, 12 ). 2. Circuit arrangement according to claim 1, characterized in that the resistors (l _r , l _g and la) each in the series connection of a variable voltage source (V _n V _g or Vb), the voltage of which is independent of the current flowing through the source , and a variable current source (I _r , I _g or / &), which supplies a current that is independent of the voltage source mentioned. 3. Circuit arrangement according to claim 2, characterized in that the resistors (I _n Ig and h) are variable and that the biases are removed at fixed points (2 _r , 2 _g and 2b) of these resistors. 4. Circuit arrangement according to claim 2, characterized in that the resistors are fixed resistances and the bias voltages at variable taps of these resistors be removed (Fig. 1 a). 5. Circuit arrangement according to claim 2, 3 or 4, characterized in that to control the basic brightness with constant setting of the control resistors or with constant setting of the variable taps, the current sources (Ir, Ig or, Ib) can be controlled such that when the supplied by these power sources currents of the voltage drop between the point _(r 2, 2g and 2b, respectively) of a resistor to which the bias voltage is decreased, and the mentioned specific point (3J, _3g, 3b) for the various resistors to a the same fraction is enlarged or reduced. 6. Circuit arrangement according to claim 2, 3 or 4, characterized in that to control the basic brightness with constant setting of the current sources, the variable resistors can be controlled or the variable taps on the resistors are adjustable such that the voltage drop between the point of a resistor, at which the bias is removed, the various resistances are increased or decreased by an equal fraction. 7. Circuit arrangement according to claim 1, characterized in that the first resistors (4 or 11) are constant and each parallel to an adjustable part of a second resistor (7 or 13) at which the voltage drop is constant, and that the Bias voltages from variable taps (5 or 12) of these resistors (4 or 11) can be removed. 8. Circuit arrangement according to claim 7, characterized in that parallel to this second resistor (7) is a voltage stabilizer (8) and that this parallel connection in a series connection of a voltage source (V) and two resistors (9, 10), of which at least one is variable, is switched on (Fig. 2). 9. Circuit arrangement according to claim 7, characterized in that the ends of the second resistor (13) are connected via two series resistors (14, 15) to the terminals of a voltage source (V) , the two series resistors (14, 15) being controlled in this way that a decrease in one resistor (14) brings about an equal increase in the other resistor (15) (Fig. 3). 10. Circuit arrangement according to claim 7, 8 or 9, characterized in that to control the basic brightness with constant setting of the variable taps (5 or 12) on the first-mentioned resistors (4 or 11), the adjustable parts of the second resistors (7 or 13) can be regulated in such a way that the voltage drop between the point (2) of a first resistor, at which the bias is removed, and the specific point (3) for the various first resistors is increased or decreased by an equal fraction. 11. Circuit arrangement according to claim 7, 8 or 9, characterized in that to control the basic brightness with constant setting of the adjustable parts of the second resistors (7 or 13), the variable taps (5 or 12) on the first resistors (4 or 11) can be regulated in such a way that the voltage drop between the point (2) of a first resistor (4 or 11), at which the bias voltage is removed, and the specific point (3) for the various first-mentioned resistors is the same Fraction is enlarged or reduced. 12. Circuit arrangement according to claim 1, in which the position of to regulate the basic brightness Taps is regulated on constant resistances, characterized in that this Resistors form parts of equal potentiometers, which position the taps conditional arms (grinder) are arranged on a common shaft. Documents considered: German Auslegeschrift No. 1 018 457; Swiss Patent No. 319 090; U.S. Patent No. 2,804,496; Television Engineering Handbook by Fink, Kawird, and the specific point mentioned for 6g pitel 16, pp. 227 and 228. For this purpose, 1 sheet of drawings © 209 679/146 10.62