JPH10215463A - Display device using color picture tube having automatic white balance adjustment circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain broad band and low loss processing for a video circuit by excluding a cut-off adjustment margin from a signal dynamic range of circuits of stages before a video output circuit in the display device provided with the automatic white balance adjustment circuit. SOLUTION: An input terminal of a level correction circuit 31B that controls a DC level of each red, green, blue primary color signal based on a reference signal for white balance adjustment inserted in a vertical blanking period of a video signal is connected to an output terminal of a video output circuit that drives a color picture tube 6 and includes a control voltage source 351B that adds a separate DC voltage whose level is controlled by a control signal from an automatic white balance adjustment circuit 33 to the primary color signal including a DC voltage outputted from the video output circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display using a color picture tube having an automatic white balance adjusting circuit.

A display using a color picture tube (character graphic display, television receiver,
Or a monitor television, etc.), a relatively dark white signal is input as a reference signal for white balance adjustment, and the ratio of the respective cathode currents of red, green, and blue at that time becomes a predetermined ratio. A cut-off adjustment for adjusting the DC level of the input signal, and a relatively bright white signal as a reference signal for white balance adjustment, and the ratio of the respective cathode currents of red, green, and blue at that time. Is adjusted so that the gain of the amplifier circuit for the input signal is adjusted so that the ratio becomes a predetermined ratio, and when a black and white image is reproduced with a color picture tube, the brightness of the screen is varied. The automatic white balance adjustment circuit makes an achromatic color at this point. The present invention relates to an improvement of the automatic white balance adjustment circuit provided in the display.

[0003]

2. Description of the Related Art Conventionally, there has been a problem that the white balance of a color receiver adjusted at the time of shipment from a factory is likely to change over a long period of use. This was due to the aging of the color picture tube such as a decrease in the emission of the cathode and the drift of the circuit. An automatic white balance adjustment circuit for restoring such a change in white balance is disclosed in, for example,
No. 8087, “Color Television Receiver”.

FIG. 11 is a block diagram showing such a conventional automatic white balance adjustment circuit. In FIG. 11, R (red), input to the input terminals 1R, 1G, and 1B, respectively,
The G (green) and B (blue) primary color signals are amplified by drive variable gain amplifier circuits 10R, 10G, and 10B through signal synthesizing circuits 8R, 8G, and 8B, respectively, and level correction for cutoff adjustment is performed. The level is shifted by the circuits 11R, 11G, 11B, and the video output circuits 12R, 12G, 12
At B, the signal is amplified to a picture tube driveable amplitude and supplied to the picture tube 6 for image display via the cathode current detection circuits 9R, 9G, and 9B.

The automatic white balance adjustment operation performed at this time will be described below with reference to signal waveforms of respective parts shown in FIG.

The vertical blanking pulse input terminal 3V and the horizontal blanking pulse input terminal 3H of the signal generating circuit 2 for automatic white balance adjustment have signals (b) and (c) shown in FIG. (A signal extracted from a composite video signal to be output) and two kinds of signals 4B (for cutoff adjustment) and 4W (for drive adjustment) shown in FIG. The signal is input to the above-described signal synthesizing circuits 8R, 8G, and 8B via the signal line 4 as a reference signal for adjustment.

If one of the three input primary color signals R, G and B (composite video signal) is shown in FIG. 12A, a corresponding signal synthesizing circuit (for example, 8R for 8R)
Output has a signal waveform as shown in FIG. Assuming that the signal in FIG. 9E corresponds to the primary color signal of B, the transistor 2 in the cathode current detection circuit 9B
The detection voltage proportional to the cathode current from the cathode 7B flowing into the emitter of the cathode 8 is applied to the cathode current detection signal line 30.
The signal is input to the sampling circuit 13 via B. Since 9R and 9G have the same circuit configuration as 9B, 9R and 9G are simply shown as blocks to simplify the drawing. The same applies to 12R, 12G, and 12B.

[0008] Sampling circuits 13R, 13G, 13B
, Via the gate signal line 5, the above-mentioned reference signals 4B,
A gate pulse synchronized with 4 W is supplied, and a cut-off adjustment comparator (or operational amplifier) 16B and a drive adjustment comparator (or operational amplifier) 17B perform a negative feedback operation, so that the cut-off adjustment is performed. Optimal adjustment level and gain variable amplification circuit 1 in level correction circuit 11B
If the control voltage in the sampling circuit 13B at that time corresponds to the optimum adjustment level of the level correction circuit 11B for cutoff adjustment, the hold capacitor 15B for cutoff adjustment is used.
Further, the one corresponding to the optimum adjustment gain of the variable gain amplifier circuit 10B is held in the drive adjustment hold capacitor 14B, and is supplied to the comparators 17B and 16B as a control voltage until the next sampling time.

Here, the reference voltage sources 17 and 18 are used to control the cathode currents at the time of cutoff adjustment and drive adjustment, respectively, to specified values. Further, the above operation is the same for the R and G primary color signal circuits.

Here, the reference voltage source 17 is commonly used for the comparators 16R, 16G and 16B corresponding to the three primary color signals, and the reference voltage source 18 is also used for the comparators 17R and 17R corresponding to the three primary color signals. 17G and 17B are commonly used, but the detected voltage value of the cathode current input to the inverting terminal (−) of each of these comparators via the sampling circuit 13 is used for three primary color signals. By setting the required predetermined ratio, it is possible to control the cathode current of each primary color to a predetermined ratio necessary for maintaining the white balance. In other words, the white balance can be stabilized by controlling the cathode current of each primary color of the picture tube at the time of inserting the reference signal to a constant value at a predetermined ratio.

[0011]

In the case where the same color display is used as a television receiver or a monitor television, an overscan system is employed. In other words, of the retrace period and the image display period which constitute one scanning cycle, the image display period is set to be slightly longer than the screen width of the display, and as a result, a part of the image information extends outside the screen and becomes invisible. (Lost), a system in which the retrace period is never displayed on the screen is employed as an overscan system.

On the other hand, in the case of, for example, a character graphic display used as a computer terminal, an underscan system is employed. That is, of the retrace period and the image display period, which constitute one scanning cycle, the image display period is set at the very end of the screen width of the display so that the image information to be displayed is not lost at all, and instead, the retrace operation is performed. A system is adopted in which a part of the period may be leaked and displayed on the screen.

A display provided with the above-described automatic white balance adjustment circuit described as the prior art is a display (for example, a character graphic graphic) employing the underscan system among the overscan system and the underscan system described above. Display), the following problem occurs.

(1) As described above, when the white balance adjustment circuit according to the prior art is used in a display employing an overscan system, the above-described reference signal for white balance adjustment is displayed on a screen. Never. However, in a display employing an underscan system, the above-described reference signal is displayed as a bright line when white balance is adjusted, giving a user discomfort.

(2) A display employing an underscan system is often used for an interface of a specific computer or the like, and the display contents are always limited in a similar manner. The luminous efficiency degradation of the phosphor becomes large, and luminance unevenness becomes remarkable.

Further, when the white balance adjusting circuit according to the above-mentioned prior art is used for a display employing an overscan system, there are the following problems.

(3) Even if the ratio of the cathode current for each primary color is controlled to a predetermined ratio, it is not possible to compensate for the shift in white balance due to the aging of the phosphors for each primary color.

(4) Further, in the conventional example shown in FIG. 11, since the level correction circuits 11R, 11G, and 11B are located before the video output circuits 12R, 12G, and 12B, respectively, the signals after these video output circuits are provided. The dynamic range must be set wide in consideration of the level shift amount. For example, it is necessary to increase the power supply voltage applied to the terminal 27 in the video output circuit. Also, in order to ensure the resolution required for the receiver, a decrease in the cutoff frequency of the output circuit, which is determined by the output capacitance including the collector resistor 26 in the video output circuit and the floating capacitance of the wiring, must be suppressed. , The collector resistance 26 cannot be set to a high value.

For these reasons, an increase in the power consumption of the video output circuit is inevitable, and it has been difficult to realize automatic white balance adjustment particularly for a high-definition display or the like that requires wideband characteristics.

An object of the present invention is to solve the above-mentioned problems.
In particular, it is an object of the present invention to provide a display having an automatic white balance adjustment circuit capable of solving the above-mentioned problem (4).

[0021]

In order to achieve the above object, according to the present invention, the primary colors of red, green and blue are determined based on a reference signal for white balance adjustment inserted during a vertical blanking period of a video signal. A level correction circuit for controlling the DC level of the signal,
And a display using a color picture tube having an automatic white balance adjustment circuit for outputting a control signal to a gain variable control amplification circuit for controlling the amplification gain of the primary color signal and performing white balance adjustment,

The level correction circuit has an input terminal connected to an output terminal of a video output circuit for driving the color picture tube, and applies the automatic white balance to a primary color signal including a DC voltage output from the video output circuit. A control voltage source for adding another DC voltage whose level is controlled by a control signal from the adjustment circuit is included.

[0023]

By arranging the control voltage source after the video output circuit as described above, it is possible to eliminate a margin for cutoff adjustment from the signal dynamic range of the circuit before the video output circuit, and to reduce the wide band of the video circuit. Loss becomes possible.

[0024]

FIG. 1 is a block diagram showing a display having an automatic white balance adjusting circuit according to an embodiment of the present invention.

In FIG. 1, reference numeral 22 denotes a deflection control circuit;
1R, 31G, 31B are level correction and cathode current detection circuits, 12R, 12G, 12B are video output circuits,
10R, 10G and 10B denote variable gain amplifier circuits for drive adjustment, 32R, 32G and 32B denote adder circuits for inserting reference signals, and 33 denotes a white balance control circuit.

Each of the primary color signals input to the input terminals 1R, 1G, 1B is supplied to a drive adjustment variable gain amplifier 10R, 10G, 10B and a video output circuit 12R, 1B.
Amplified by 2G, 12B, 31R, 31G, 31B
Is applied to the cathodes 7R, 7G, 7B of the picture tube 6 via the level correction and cathode current detection circuit.

Also in FIG. 1, the automatic white balance adjustment
The reference signals transmitted from the white balance control circuit 33 via the reference signal line 4 and exemplified by 4B and 4W shown in FIG. 12D are added in the retrace period of each primary color signal.
At this time, the white balance is adjusted by controlling the cathode current ratio between the primary colors or the cathode current value to be constant.

As described above, when the reference signal is added during the retrace period of the primary color signal (or the primary color signal is separated and the reference signal alone is inserted), if the receiver is an image receiver employing an overscan system, As described above, the screen display of the reference signal can be easily avoided. However, if the receiver employs an underscan system, such as a character graphic display,
In order to maintain the image quality such as focus characteristics and convergence characteristics, when the peripheral area is used for that purpose and cannot be used for screen display within the effective screen where the picture of the picture tube can be displayed, other than the video display period May appear in the effective screen, and the above-mentioned white balance adjustment reference signal may be displayed on the screen.

Therefore, the deflection control circuit 22 creates an additional deflection signal and supplies it to the deflection coil of the deflection yoke 21 so that the raster during periods other than the image display period is removed from the effective screen, thereby achieving the white balance. The reference signal for adjustment is not displayed on the screen.

FIG. 2 shows a waveform example of the deflection signal to which the additional deflection signal is added. In FIG. 2, a solid line 43 is a conventional original deflection signal waveform, which is deformed (modulated) by an additional deflection signal as indicated by a broken line 44 at the beginning of the display period, so that a raster is formed at the beginning of the display period. It can deviate from the effective screen. In the case of a multi-scan type receiver in which various types of signals having different deflection frequencies are input, the rear part of the dashed line 44 of the deflection signal waveform is changed to a dashed line 45 to limit the range of raster deviation. It is better to do.

This is because, when the electron beam is excessively deflected, it collides with the inner surface of the glass bulb of the picture tube, the conductive film applied thereto, and other metal parts in the bulb, causing reflection and scattering.
The emission of secondary electrons causes a phenomenon (halation) that causes the phosphor to emit light, and this is to suppress this phenomenon. As a result of this phenomenon, image quality deterioration such as what appears to be a dark image shining appears.

When modulation is applied to the original deflection signal waveform as shown by broken lines 44 and 45, the deflection signal waveform is broken due to negative feedback used for control of the deflection circuit and higher-order resonance factors existing in the circuit. Ringing occurs immediately after the bent portion, and the image tends to be geometrically distorted. In such a case, FIG.
By changing the modulation period of the deflection signal waveform to the end of the scanning period as shown by broken lines 46 and 47, ringing during the display period can be eliminated.

Although FIG. 1 shows an electromagnetic deflection system using a deflection yoke 21 as a deflection device of the picture tube 6, even if this is an electrostatic deflection system using a deflection plate, it is shown in FIG. This can be handled by considering the deflection signal waveform as a deflection voltage instead of a deflection current.

Further, the above description holds for both horizontal deflection and vertical deflection. The deflection signal waveform shown in FIG. 2 can be distributed to a plurality of deflection devices (electromagnetic / electrostatic type can also be used) in consideration of the performance of the deflection device such as loss and signal dynamic range. . Therefore, the conventional deflection signal can be inputted to the conventional deflection device, and the deflection signal waveform to be added can be added to the separately added deflection device.

FIG. 3 shows an example of a circuit for obtaining the deflection signal waveform described with reference to FIG. That is, FIG. 3 is a circuit diagram showing a part including the deflection control circuit 22, the deflection yoke 21, and the deflection circuit in the picture tube 6 in FIG. Is shown as an example.

In FIG. 3, from the conclusion, the waveform of the vertical synchronizing signal input to the terminal 22V and the waveform of the deflection signal to be added input from the signal line 42 from the white balance control circuit 33 (FIG. 1) Alternatively, a deflection signal having a waveform as shown in FIG. 2 flows through the 21D vertical deflection yoke in response to a control signal such as an additional timing (these signals will be referred to as deflection control signals).

The following is a description. The sawtooth wave generated by the vertical oscillation circuit 22OS passes through an addition circuit 22A1, is amplified by a drive circuit 22DR and an output circuit 220 in the vertical amplification circuit 22AMP, and is applied to a vertical deflection yoke 21D. Drive circuit 2DR by a negative feedback system using a feedback circuit 22R and a feedback circuit 22FB.
Is controlled by adjusting the gain of

That is, the deflection current flowing through the vertical deflection yoke 21D is detected as a voltage value by the deflection current detection resistor 22R. When the voltage value is large, the deflection current is fed back to the drive circuit 22DR via the feedback circuit 22FB to reduce the amplification gain. When the voltage value is small, the voltage is fed back to the drive circuit 22DR via the feedback circuit 22FB to increase the amplification gain so that a constant deflection current always flows through the vertical deflection yoke 21D. Negative feedback control is being performed.

A feature of the circuit shown in FIG. 3 is that the deflection signal to be added, generated by the additional deflection signal generation circuit 22I, is
The addition circuit 22A1 is connected to the sawtooth wave input line in the deflection circuit.
Is added to the original deflection signal, or is substantially added to the original deflection signal by being inserted into the feedback line by the addition circuit 22A2.

The deflection signal to be added is, for example, a signal corresponding to the difference between the solid lines 43 and the broken lines 44 and 45 and another pair of broken lines 46 and 47 shown in FIG. It can be easily generated by inputting a blanking pulse as a trigger to the circuit. The obtained deflection signal to be added is added to the addition circuit 22A1.
When using the adder circuit 22A2, it is sufficient to invert and add.

Further, in order to suppress an increase in the loss of the vertical amplifier circuit 22AMP due to the implementation of the above technique, the power supply voltage source 2
Both or one of 22V1 and 22V3 is added to 2V2, and each is switched by switch circuits 22S1 and 22S2.

In this method, power consumption is suppressed by increasing the magnitude of the power supply voltage to be applied and reducing the average value of the power supply voltage as much as possible only during the period in which the rate of change of the deflection current is large. The switch circuit 22S1 is turned ON only during the flyback period and the additional deflection period when the deflection current sharply increases.
2S2 is O only during the additional deflection period when the deflection current is sharply reduced.
N is controlled by the additional deflection signal generation circuit 22I or automatically. Diodes 22D1 and 22D
2 indicates that the switch circuits 22S1 and 22S2 are OF
It works as an automatic switch that turns ON only at F.

As a method for reducing the loss based on the same principle as the above-described power supply switching method, the power supply voltage source 22V1 shown in FIG.
And 22V3 may be replaced by large-capacity capacitors charged to the same voltage as 22V2, respectively, and switching may be performed at the same timing as in the above method (which may be referred to as a pumping up & down method).

Next, even in the case of the overscan system as well as in the case of the underscan system, the reference signal for white balance adjustment is prevented from being displayed on the screen as a bright line for some reason. FIG. 4 shows an example of a circuit for a color picture tube which is effective for the reference.

FIG. 4 is a partial sectional view of a color picture tube.
In the figure, 6G is a panel glass, 6K is a fluorescent film applied to the panel glass, 6S is a shadow mask, 6S
1 is a shadow mask frame, 6ES is an electron shield, and 6P is a panel pin used only at the upper and lower parts of the picture tube. The structure described above is conventionally used.

However, due to the manufacturing accuracy of the panel glass 6G and the electron shield 6ES, since the electron shield 6ES is made of a thin aluminum plate and easily deformed, a gap is generated between the two. This gap is likely to occur at a corner portion having a complicated shape, and the same can be said to some extent even at the upper and lower portions where the panel pin 6P is located.

Here, considering the electron beam 6B1 deflected to a position just deviating from the display period, the electron beam 6B1 is blocked by the electron shield 6ES, and is incident on the fluorescent film 6K as an effective screen. No halation, which is phosphor emission due to a scattered beam, does not occur. However, the electron beam 6B2 entering the corner of the color picture tube is scattered by hitting the inner surface of the panel glass 6G, and the electron shield 6ES and the panel glass 6G are scattered.
The light passes through the gap of G or the panel pin 6P, enters the fluorescent screen 6K of the effective screen, and causes halation.

However, in this circuit example, by providing the electron shield frame 6EF shown in FIG. 4 as shown, the incidence of the electron beam 6B2 is blocked.
Halation by the electron beam 6B2 does not occur.
Even if there is a gap between the electron shield frame 6EF and the panel glass 6G, the electron beam is extinguished during the multiple reflection.

[0049] Further, the electron beam collides with each part.
In order to suppress the secondary electron emission, the emission suppression part is 6SG in FIG.
It is also conceivable to cover with a suppressor grid as shown in 1 and 6SG2.

Secondary electron emission, which is likely to occur when an electron beam collides with the inside of a color picture tube, particularly a metal part such as the electron shield 6ES or a metallic electron shield frame 6EF, is near the surface with respect to the collision surface potential. Can be suppressed by lowering the space voltage. A voltage lower than the anode voltage must be applied to the suppressor grids 6SG1 and 6SG2 used for this purpose. The following two methods can be considered as examples of a method for obtaining this voltage.

(1) Each electrode voltage such as a focus voltage applied to the electron gun or a voltage exclusively for the suppressor grid is
It is applied to the suppressor grids 6SG1 and 6SG2 via a pattern formed by the internal conductive film of the picture tube.

(2) Suppressor grid 6 SG1 or 6
SG2 is fixed via a material having low conductivity (preferably, secondary electron emission is unlikely to occur), and a necessary voltage is obtained by self-charging due to electron beam collision with the grid.

However, if an extremely low conductivity material such as glass is used as the fixing material, internal discharge may occur, so a heat-resistant resin containing fine carbon particles is suitable. By developing this idea, apply the above-mentioned heat-resistant resin in the form of a lattice-shaped pattern to the area where suppression of secondary electron emission is necessary, and re-apply a conductive film such as carbon on the pattern. It is also possible to do this.

Next, the white balance control circuit 3 shown in FIG.
FIG. 5 shows an example of the configuration 3. 5, the same components as those in FIG. 11 showing the conventional example are denoted by the same reference numerals.

The configuration example shown in FIG. 5 differs greatly from the conventional example in that the drive adjustment hold capacitor 14
R, 14G, 14B and cut-off adjustment hold capacitors 15R, 15G, 15B are directly connected to control lines 19R, 19G, 19B of the variable gain amplifier circuit and control lines 20R, 20G, 20B of the level correction circuit, respectively. Is to be stabilized with high precision.

That is, in the conventional example shown in FIG.
Each of the above hold capacitors 14R, 14G, 14B,
15R, 15G, 15B are comparators (or operational amplifiers) 16R, 16G, 16B, 17R, 17G, 17B
Since the sag due to the discharge of the hold capacitor is amplified due to the connection to the inverting input of the above, this effect is significantly increased and becomes unstable, or the open loop gain of the feedback system must be suppressed to avoid this. As a result, the control accuracy of the white balance is deteriorated.

On the other hand, in the configuration example shown in FIG. 5, the increase in the amplification from each amplifier circuit at the subsequent stage of each hold capacitor to the cathode current detection circuit is suppressed, and the sensitivity of each comparator (or operational amplifier) is suppressed. , The detection signal lines 30R, 30G, 30
The detected voltage of B can be accurately adjusted to the respective voltages of the reference voltage sources 17 and 18.

The reference signal generating circuit 4P only receives a timing pulse from the automatic white balance adjusting signal generating circuit 2, and the waveform of the reference signal is set independently according to the necessity of each embodiment described later. Or it can be controlled.

Further, in FIG. 5, dashed frames 163 and 1
Each comparator (or operational amplifier) in 73 can be shared by the following method.

(1) Switch circuits 13CR, 13CG,
The comparator output terminals of 13CB and 13DR, 13DG, and 13DB are short-circuited between the same primary color circuits, respectively, so that a one-primary-color one-comparator configuration in which one comparator is used at the time of drive adjustment and cutoff adjustment is used. At this time, the reference voltage sources 17 and 18 are switched or the comparator (or operational amplifier) is used as the same voltage.
To the non-inverting input of

(2) When the sequence of the automatic white balance adjustment is a method of sequentially adjusting each primary color signal circuit, the terminal of the switch circuit is connected to one comparator (or 1) between the primary colors in the same manner as (1). By connecting to the output of an operational amplifier, a three-primary-color one-comparator configuration using only one comparator (or operational amplifier) is obtained. At this time, the reference voltage sources 17 and 18
Is also the same as (1) above.

Since the output of each comparator (or operational amplifier) is short-circuited to each hold capacitor when the switch circuit is ON, the comparator (or operational amplifier) is set to a current output type, and the output current when the switch is OFF is output. By setting it to zero, the switch circuit can be omitted.

However, when the comparator (or operational amplifier) is shared as described above, a current output circuit is required instead of the switch circuit. Since the input / output characteristics of the operational amplifier can be regarded as the same as those of the comparator, both are referred to as a comparator in the following description.

FIG. 6 is a block diagram showing another example of the configuration of the white balance control circuit 33 in FIG. That is, the control lines 19R, 19G,
19B and control lines 20R, 20G of the level correction circuit,
This is a configuration example of a white balance control circuit in which a control signal of 20B is stabilized by storing the control signal using a storage circuit instead of the hold capacitor.

The digital signal processing circuit 48 shown in FIG.
Are a microcomputer circuit 51, a storage circuit 52, an interface circuit 50, and a data bus connecting them.
It comprises an address bus and a control bus (only the data bus 53, the address bus 54 and the control bus 55, which are representative signal flows, are shown in the figure).

In FIG. 6, 4DA is D for generating a reference signal.
A conversion circuit (digital / analog conversion circuit)
The control block of the primary color signal circuit of R is shown in a broken line frame 49R, and the control blocks of the primary color signal circuits of G and B, which are similar blocks, are collectively shown at 49.

In the control block in the broken line frame 49R,
The comparator 16R and the AD conversion circuit (analog / digital conversion circuit) 15AD are used in both the drive adjustment and the cutoff adjustment. Switch circuit 1 for drive adjustment
Only the 3DR is inverted, the output of the comparator 16R is taken into the digital signal processing circuit 48 via the AD conversion circuit 15AD, stored in the storage circuit 52 as necessary, and held at the output of the DA conversion circuit 14DA. The signal is output to the control line 19R by the re-inversion of the switch circuit 13DR after the adjustment is completed.

At the time of cutoff adjustment, the switch circuit 13C
Only R is inverted, the output of the comparator 16R is taken into the digital signal processing circuit 48 via the AD conversion circuit 15AD, stored in the storage circuit 52 as necessary, and held at the output of the DA conversion circuit 15DA. The signal is output to the control line 20R by the re-inversion of the switch circuit 13CR after the adjustment is completed.

By using the circuit configuration shown in FIG. 6, there is no need to perform automatic white balance adjustment in the deflection cycle. Further, if the output of the DA conversion circuit 17DA is updated with the integrated cathode current value, the change with time of the picture tube 6 can be corrected.
The manual switch 3SW in the figure will be described in a circuit example described later.

In the circuit configuration shown in FIG. 6, negative feedback at the time of white balance adjustment is performed by a high-speed analog circuit (for example, the comparator 1).
6R), and only the capture and holding of each control signal is performed by a digital signal system, so that the white balance adjustment can be speeded up. On the other hand, AD as shown by 15AD
Due to the converter, the switch circuits 13DR and 13CR, etc., there is a possibility that an increase in the number of partial points and an increase in the price may become a problem.

FIG. 7 is a block diagram showing still another example of the configuration of the white balance control circuit 33 shown in FIG. 1, and shows an example of the configuration of the white balance control circuit which can solve the above-mentioned problem.

The difference between the circuit configuration of FIG. 7 and that of FIG. 6 is that the above-described AD conversion circuit 15AD and switch circuit 13D
R and 13CR are eliminated, and instead, the output of the comparator 16R is detected by the interface circuit 15I and is taken in as each control data. Since the output of the comparator 16 is an analog quantity, it cannot be handled by the digital signal processing circuit 48 unless it is converted into a digital quantity. This analog-digital conversion operation is to be executed without using a dedicated converter such as 15AD in FIG.

Considering a case where the control data output from the comparator 16 has a digital value of 8 bits, in principle, the control data obtained from the DA conversion circuit 14DA or 15DA can be used.
Check the output of comparator 16R against 6 all the control signals of step (= 2 ⁸ steps), by it taking a control signal from the DA converter 14DA or 15DA when becomes zero) that, suitability Control data can be captured.

However, this method requires a maximum of 256 trial times, and there is a risk that the adjustment time will increase.
By using the adjustment method as described below with reference to FIG. 8, appropriate control data can be acquired with the number of trials of (the number of bits forming the control data minus one). In this method, the range including the target value is rapidly narrowed while dividing the data dynamic range by half. A specific example of the method will be described with reference to FIG.

Since the target value of the control data to be fetched is actually an analog amount, the number of significant digits is increased to 01010010.1 in consideration of a quantization error.
A register and a B register are prepared in the storage area.

First, the intermediate value 10000000 of the data dynamic range is input to the A register serving as the input data of the DA conversion circuits 14DA and 15DA, and the half value 0
10000000000 is input to the B register which is an internal operation register. And the DA conversion circuit 14DA or 15
Comparator 16R when updating DA output with A register value
The magnitude relationship between the target value and the A register value is determined according to whether the output of the register is-or +. If the value is +, it is determined that the value is large, the B register value is added to the A register value, and the result is set as the next A register value. At this time, the B register value is also updated to a half value (actually, the counter value may be shifted once to the lower bit side).

By repeating this process as shown in FIG. 8 (the number of bits constituting control data minus one), in this example, seven times, control data is taken into the A register.
When the white balance adjustment is performed again, the above-mentioned fetching method may be repeated by using the current value of the A register value and the value of the B register value obtained from the maximum drift amount.

Next, the details of the level correction and cathode current detection circuits 31R, 31G, 31B in FIG. 1 will be described.

As already described in the section of the problem to be solved by the present invention, in the conventional example shown in FIG. 11, the level correction circuits 11R, 11G and 11B are respectively provided with the video output circuits 12R, 12G and 12B. Since it is in the former stage, the signal dynamic range after these video output circuits must be set wide considering the level shift amount. For example, it is necessary to increase the power supply voltage applied to the terminal 27 in the video output circuit. Also, in order to ensure the resolution required for the receiver, a decrease in the cutoff frequency of the output circuit, which is determined by the output capacitance including the collector resistor 26 in the video output circuit and the floating capacitance of the wiring, must be suppressed. , The collector resistance 26 cannot be set to a high value.

For these reasons, an increase in the power consumption of the video output circuit is inevitable, and it has been particularly difficult to realize automatic white balance adjustment for a high-definition display or the like that requires wideband characteristics.

In order to solve this problem, FIG.
The level correction circuit is arranged at the subsequent stage of the video output circuit, and is shown as a level correction and cathode current detection circuit regardless of the order of the cathode current detection circuit.

Next, a configuration example (a configuration example of the level correction and cathode current detection circuits 31R, 31G, and 31B in FIG. 1).
Is shown in FIG. 9A as a main part of the embodiment of the present invention. In FIG. 9A, after the video output circuit is broadened by cascode connection together with the emitter peaking of the resistor 41P and the capacitor 41C and the parallel peaking by the coil 37L, the electronic control voltage source 3 is used as a level correction circuit.
51B is connected, and the cathode 7B is driven via the cathode current detection / SEPP circuit and the protection resistor 7BR.

By disposing the electronic control voltage source 351B at the subsequent stage, a margin for cutoff adjustment can be eliminated from the signal dynamic range of the circuit before the video output circuit, and a wide band and low loss of the video circuit can be realized.

An example of the configuration of the electronic control voltage source 351B is shown in FIG. 9B as a further main part of the embodiment of the present invention. Here, the voltage level of a constant voltage circuit using the transistor 352T is controlled using the photocoupler 352F. The bypass capacitor 352C compensates for an increase in impedance of the electronic control voltage source 351B at a high frequency. Further, in order to reduce the impedance of the electronic control voltage source 351B, it is necessary to sufficiently supply a bias current using the current source 283.

However, if the cathode current detection circuit is arranged at the subsequent stage of the level correction circuit as shown in FIG. 9, the transistors 28 and 281 have a high withstand voltage characteristic between the collector and the emitter, and the frequency characteristics cannot be said to be sufficient. Elements must be selected. Further, as shown in FIG.
SEP without applying bias voltage between bases 8 and 281
When the P circuit is used for detecting the cathode current, the cathode current can be automatically detected, but the frequency characteristic is deteriorated due to a transmission dead zone at the time of rapid rise of the output voltage.

FIG. 10 shows a level correction and cathode current detection circuit which solves this problem. In other words, FIG. 10 is a circuit diagram showing another specific example of the level correction and cathode current detection circuit in FIG.

In the circuit shown in FIG. 10, the cathode current is detected by the SEPP circuit including the transistors 28 and 281 at the subsequent stage of the video output circuit, and the coupling capacitor 352 is detected.
Level correction is performed by a clamp circuit including B and a switch circuit 353B, and the cathode 7B of the picture tube 6 is driven via the series peaking coil 7BL.

To explain a little more specifically, the switching circuit 3
When 53B is turned on and closed, the voltage supplied from the white balance control circuit 33 causes the coupling capacitor 35B to turn on.
The output side of 2B is clamped, thereby performing level correction. When the switch circuit 353B is turned off and opened,
While it is open, the coupling capacitor 352B
The cathode current of the picture tube 6 flows into the picture tube 6 little by little to cause a level fluctuation, but every period (for example, a horizontal scanning period) in which the level fluctuation is small enough to be regarded as a constant level.
The switch circuit 353B is turned on at least once.

As a practical example, the switch circuit 353B
Are turned on by utilizing the rise of the cathode voltage of the picture tube 6 for blanking in the flyback period, and are turned off in the video display period by utilizing the fall of the cathode voltage. To do. As another example, a switch circuit 353B composed of active elements such as transistors is connected to the input 40 of the video output circuit.
There is a method of closing and turning on during a period when the cutoff investigation signal level is input to B. However, in this case, blanking is performed by applying a blanking signal to an electrode (for example, the first grid) of the picture tube 6 other than the cathode.

Although not shown, the clamp voltage applied from the white balance control circuit 33 to the switch circuit 353B is generated by a negative feedback circuit so that the cathode current in the picture tube 6 is detected and becomes a certain constant value. It is a matter of course that the voltage is the same. It will also be apparent that the coupling capacitor 352 is inserted in the signal path leading to the cathode of the picture tube 6 to couple the signal to the cathode side.

Since the above-mentioned SEPP circuit is located before the level correction circuit, the transistors 28 and
For 81, an element having a good frequency characteristic without a high withstand voltage can be selected. Further, by inserting the switch circuit 281S controlled to be turned off only when the cathode current is detected,
The above-described transmission dead zone of the EPP circuit can be eliminated, and frequency characteristic deterioration and compensation can be performed.

FIG. 13 shows a main part of a display having an automatic white balance adjusting circuit as a reference example of the present invention.

When automatic white balance adjustment is performed on a receiver using a wideband video signal such as a high-definition display, high-frequency crosstalk particularly increases due to an increase in signal leakage paths between primary color signal circuits. In the case of the embodiment of the present invention shown in FIG. 1, three reference signal generating circuits 4P shown in FIG. 5 are used in order to avoid crosstalk via the reference signal line 4 shared between the primary color signal circuits. A method of using these outputs exclusively for each primary color signal circuit is conceivable. However, this involves an increase in circuit scale. In the reference example shown in FIG. 13, the crosstalk is suppressed by suppressing an increase in circuit scale.

In FIG. 13, a reference signal is inserted from the reference signal line 4 by using signal switching circuits 32RS, 32GS, and 32BS instead of the reference signal insertion adders (32R, 32G, and 32B in FIG. 1). ing. The ON / OFF control of these switch circuits may be performed simultaneously or sequentially in each primary color signal circuit.

By using the switch circuit, a signal leakage path between the primary color signal circuits is formed by the parasitic capacitances 1R4C and 1G representing the parasitic capacitance between the switch circuit terminals and the capacitance between the signal lines.
4C and 1B4C can be regarded as only (the switch circuit control line 32S is for transmitting a logic signal, so that signal leakage can be easily suppressed). Needless to say, the present invention can be applied to the conventional overscan method that does not require the additional deflection.

However, also in the reference example shown in FIG. 13, crosstalk between primary color signal circuits generated through parasitic capacitances represented by 1R4C, 1G4C, and 1B4C in the figure cannot be suppressed. FIG. 14 shows a method of inserting a reference signal without providing any additional circuit between signal paths of the primary color signal circuits.

In FIG. 14, the primary color signals input from terminals 1R, 1G, 1B are subjected to contrast control by 57R, 57G, 57B, and are added to adders 56R, 56G,
After being subjected to bright control by 56B or 58R, 58G, 58B, the variable gain amplifier circuits 10R, 10G, 1
0B receives automatic control of drive adjustment. Volumes 61V and 62V are for brightness adjustment and contrast adjustment, respectively.

Here, the DC level added to each primary color signal by the above-described bright control is compared with the sample-and-hold circuit (configured using a hold capacitor or using a digital storage circuit) 60R, 60G, and 60B. Since the signals are transmitted through the devices 59R, 59G, and 59B, the occurrence of the crosstalk is sufficiently suppressed.

In the above-described bright control, each of the primary color signals is subjected to DC reproduction by the comparators 59R, 59G, and 59B at the timing of the clamp pulse generated from the synchronization pulse, and the DC addition level at that time is subjected to the sample-and-hold circuit. This is performed while maintaining the display period.

Therefore, if the matching between the primary color signal circuits is made sufficiently high by using an integrated circuit or the like, the comparator 59 is used.
R, 59G, 59B are deleted, and the DC voltage of the bright control terminal 61 (or the DC voltage corresponding to this voltage) is simply obtained.
Can be controlled through the sample and hold circuits 60R, 60G, and 60B. Alternatively, a comparator can be connected to only one primary color signal circuit, and a bright control signal can be applied to the comparison input terminal.

The above description regarding FIG. 14 is for an example of a conventional brightness control method. In this circuit, a reference signal for automatic white balance adjustment is inserted into each primary color signal using the brightness control circuit. .

For this reason, as shown in FIG. 14, the above-mentioned reference signal is used as a bright control voltage by the switch circuit 63 during automatic white balance adjustment. Bright adjustment in a direct-coupled video circuit such as an IC is stabilized by NFB for its output. Therefore, this circuit is suitable for performing automatic white balance adjustment using a general-purpose video processing IC. Further, it goes without saying that this circuit can be applied to an overscan type receiver that does not require the additional deflection.

Subsequently, without using the additional deflecting means,
FIG. 15 shows an example of a circuit that enables automatic white balance adjustment of a receiver of an underscan system. The circuit example of FIG. 15 has a configuration in which the deflection control circuit 22 is removed from that of FIG. 1, and the automatic white balance adjustment reference signal is displayed on the picture tube but is inconspicuous or gives a user discomfort. It is controlled not to be.

The following are some examples of this control method. (1) The automatic white balance adjustment is not performed in the vertical deflection cycle (or horizontal deflection cycle) as seen in the reference signals 4B and 4W of the waveform (d) in FIG. 12, so that the user does not feel uncomfortable. Perform in a long cycle. And this automatic adjustment,
If the white balance control circuit 33 using a hold capacitor shown in FIG. 5 needs to be performed in a long cycle so that it cannot be performed stably, the white balance control circuit 33 using the storage circuit shown in FIG. 6 or FIG. Use

(2) By dispersing the display position of the reference signal for automatic white balance adjustment (particularly, the reference signal of the white level for drive adjustment) in the picture tube effective screen, the user is not discomforted. . For example, the period of the white level of the reference signal is reduced to only a very short period of the horizontal scanning line, or the scanning line used for displaying the reference signal is periodically changed.

(3) The above (1) and (2) are used in combination.
As a method of inserting the reference signal, in addition to using the adder circuits 32R, 32G, and 32B shown in FIG. 15, a method using a signal switching switch circuit and a bright control circuit as shown in FIGS. Needless to say, there is.

Further, when the user turns on the switch for automatic white balance adjustment as necessary, the automatic white balance adjustment is performed. At this time, even if the adjustment reference signal is displayed on the picture tube effective screen. FIG. 16 shows a circuit example in a case where it is unavoidable.

In FIG. 16, the white balance control circuit 3
3, an automatic white balance adjustment switch 3SW is added. For example, the automatic white balance adjustment is performed only when the switch 3SW is turned on by a user. And the control signals on 20R, 20G and 20B are maintained.

Therefore, as the white balance control circuit 33, a system using the storage circuits shown in FIGS. 6 and 7 is advantageous. Also, if the adjustment pattern for the deflection circuit system and the convergence circuit system is displayed by using the white balance control circuit 33 that outputs the reference signal by the switch 3SW, various adjustments can be performed efficiently, and the adjustment signal This is a built-in receiver.

Further, as in FIG. 15, it goes without saying that an adder circuit or a bright control circuit may be used for the method of inserting the reference signal.

Next, FIG. 17 shows a circuit example of an automatic white balance adjustment circuit that can be used in both systems without the need to generate a reference signal for automatic white balance adjustment and therefore regardless of underscan and overscan. Show.

In FIG. 17, the ratio of the input signal levels (including the brightness level) between the primary color signals is controlled so that the ratio between the primary color signals of the cathode current detection level is uniform.

For example, the average value, peak value, minimum value, or instantaneous value of the primary color signal input to the input terminal 1R is detected by the input signal level detection circuit 64R. Also,
Similarly, the cathode current level detection circuit 66R detects an average value or a peak value, or a minimum value or an instantaneous value of the cathode current.

Here, 64R, 64G, 64B and 66
A gate circuit that turns on only a part of the front or back porch of the synchronization pulse may be connected in series to the input terminals of the R, 66G, and 66B detection circuits, and cutoff (low luminance level white balance). The output for adjustment and the output for drive adjustment are transmitted to the white balance control circuit 33 through a time-division output line or two output lines synchronized with the adjustment.

For example, the cutoff (low luminance level white balance) adjustment is performed using the instantaneous value of a part of the front and back porch of the synchronization pulse in the input primary color signal and the cathode current detection signal or the minimum value of the display period. The cut-off (low brightness level white balance) adjustment of the receiver with the brightness adjustment function is performed by changing the above-described cathode current detection level according to the brightness control or by setting a part of the blanking period (when the primary color signal is blanked). A reference signal irrelevant to the brightness control must be inserted immediately before / after the blanking pulse that has not been applied. And
The drive adjustment is performed using the peak value or the average value of the input primary color signal and the cathode current detection signal (the peak value or the average value only during the display period is possible).

However, when detecting these peak values or average values, a limiter function for maximum value control and minimum value compensation in consideration of the signal dynamic range or a noise limiter function in consideration of malfunction due to noise is added. Is also good.

Next, FIG. 18 shows a reference example as a reference example of a circuit capable of correcting the unevenness in luminance and chromaticity of a color picture tube and its aging.

Generally, a color picture tube has luminance unevenness which is difficult to remove in the manufacturing process due to a difference in thickness of a front glass or a coating state of a phosphor. FIG. 19 shows a distribution example of the luminance unevenness as a solid line. Further, in the image receiver using the deflection high voltage integrated circuit, the polarization unevenness applied to the horizontal deflection current for correcting the pincushion distortion cannot be removed from the horizontal flyback pulse, and the above-mentioned luminance unevenness may be promoted.

Further, since a picture tube such as a character display uses the upper left area of the effective screen frequently, the luminance unevenness distribution changes as shown by a broken line in FIG. 19 due to aging. In many cases, the degree of aging differs between the primary color phosphors, and the chromaticity also becomes uneven. The unevenness of luminance and chromaticity and their aging can be removed by the present circuit.

In FIG. 18, it is possible to exclude the cathode current detection signal lines 30R, 30G, and 30B so that the cathode current is not detected. Instead, an optical sensor for directly detecting the light emission luminance of the phosphor is used. It is necessary to connect 68 or the video camera 69 to the white balance control circuit 33.

The automatic white balance adjustment method is, for example, to display a test pattern which also serves to adjust a deflection system such as a small window cross hatch disposed at the center and the periphery of the effective screen area, and to use the optical sensor 68 (projection type image reception). In the case of a machine, it can be installed behind the screen so that the user does not notice it) or the video camera 69 detects the luminance and chromaticity of each part and performs automatic white balance adjustment to eliminate unevenness.

More specifically, light detection is performed by the optical sensor 68 and the video camera 69 on a screen having uneven luminance and chromaticity depending on the screen position, and the amount of light detected regardless of the screen position is determined. If the gain adjustment of the variable gain amplifier circuits 10R, 10G, and 10B and the level correction of the level correction circuits 31R, 31G, and 31B are performed by the white balance control circuit 33 so as to be constant, unevenness in luminance and chromaticity of the screen is eliminated. You can do it.

On the other hand, during normal image display, white balance control data is sequentially transmitted to the white balance control circuit 3 in accordance with scanning.
Read from 3. At this time, when the above-described screen incorporates the optical sensor 68 or when the white balance can be always detected by using the video camera 69, the cathode current need not be detected.

When an optical sensor, a video camera, or the like cannot be used for white balance detection at all times, the cathode current after detecting and adjusting the luminance and chromaticity is detected, and control is usually performed with reference to the cathode current.

In the case of the video camera 69 or the like, since the display position can be detected by photographing the entire screen of the picture tube, fully automatic adjustment is possible. Further, the number of signal lines may be reduced to two, that is, a luminance signal and a color difference signal, and the primary color signal may be reproduced later. The white balance control circuit 33 includes a storage circuit 52 as shown in FIGS. 6 and 7, in which a control map storing display positions and white balance control data is formed. Then, the white balance control data is sequentially read out in accordance with the timing of the blanking pulse or the magnitude of the deflection current to remove the above-mentioned unevenness in luminance and chromaticity.

It is needless to say that the white balance can be detected by the optical sensor 68 or the video camera 69 at all times. By storing the chromaticity unevenness compensation data and the aging compensation data in the white balance control circuit 33, it is possible to remove the luminance and chromaticity unevenness of the color picture tube and the aging of the image receiver. The clock and the vertical synchronization pulse in the control circuit 33 are counted, and the detection is performed using the integrated value of the cathode current of the picture tube).

In other words, compensation data indicating how much the cathode current can eliminate unevenness in luminance and chromaticity of the screen and compensation data for aging (how much luminance unevenness and chromaticity unevenness occur after many years) Therefore, compensation data such as how much the cathode current should be changed to compensate for it and eliminate unevenness) can be obtained in advance by various tests and experiments on the manufacturer side. If stored in the storage circuit, unevenness in luminance and chromaticity of the screen can be eliminated without using a photodetector such as the optical sensor 68 or the video camera 69.

Further, as in FIG. 15, it is needless to say that an adder circuit or a bright control circuit may be used for the method of inserting the reference signal. Subsequently, a circuit example considered to prevent the deterioration of the frequency band of the primary color signal circuit will be described.

In the automatic white balance adjusting circuit described above, the cathode current detecting circuit is added as shown in FIGS. 9 and 10, so that the output capacity increases and the frequency band of the video output circuit is narrowed. Was.

In order to solve this problem, in this circuit example, the cathode current detection circuit is deleted, and the beam current of each primary color is detected from the anode current of the picture tube. Conventionally, the detection of the anode current of a picture tube has been performed as a part of an automatic brightness limiting (ABL) circuit as shown in FIG.

In FIG. 20, 74 is a flyback transformer, 76 is a high voltage detection terminal, and 70 is an ABL terminal.
However, the detected current 79 includes the current 80 flowing through the bleeder resistors 77 and 78 for detecting a high voltage in addition to the anode current 81. Further, in order to stabilize the operation of the automatic brightness limiting circuit, the anode current detecting resistor 72 and the stabilizing capacitor 7
The time constant of 1 is extremely large, and the peak value of the current 79 cannot be detected.

Therefore, in the circuit example, as shown in FIG. 21, a peak of the current 79 is detected by inserting a stabilizing resistor 83 which can be regarded as a sufficiently high resistance value with respect to the anode current detecting resistor 72. I have. Also, the current 80
Can be regarded as substantially constant, the anode current 81 is detected from the amount of change in the current 79 generated when a signal voltage is applied to the cathode of the picture tube 6.

In practice, a reference signal is inserted for each single color of each primary color signal circuit, and the anode current 81 is detected. However,
In addition to the beam current, the anode current 81 also has a current component flowing to other electrodes such as the second grid, and a higher-order distortion current having a deflection cycle flowing to a parasitic capacitance between the ground of each winding of the flyback transformer or the ABL terminal wiring. Although the distortion current component is included, the amplitude other than the beam current can be regarded as substantially constant amplitude. Therefore, the beam current of each primary color can be detected by detecting the peak value and average value of the current 79 and the amount of change in the instantaneous value at the time of sampling. This circuit can be applied not only when the receiver is an underscan system but also when it is an overscan system.

Finally, FIG. 24 shows a main part of a circuit example in which the user can easily adjust the color temperature of the reference white by adjusting the white balance, and this will be described.

Before that, a schematic CIE chromaticity diagram of white in FIG. 22 is shown. In FIG. 22, 87R, 87G, and 87B indicate emission chromaticity coordinates of each primary color phosphor of the picture tube, and points 84 and 85 are respectively used as reference white (9300K + 27).
The chromaticity coordinates of (MPCD) and (6550K + 7MPCD) are shown. The chromaticity locus when the color temperature of the reference white is changed passes through the points 84 and 85 and changes along the black body radiation locus 86, so that it can be regarded as a substantially straight line.

For example, FIG. 2 shows a relationship between a reference white temperature having a constant luminance and a cathode current for each primary color in a certain picture tube.
As shown in FIG. The illustrated color temperatures 91 and 92 indicate 6550K and 9300K, respectively.

Since the primary current cathode current characteristics 88, 89, and 90 in FIG. 23A can be regarded as substantially straight lines in the range of use, an automatic white balance adjustment circuit using the volume configuration shown in FIG. 24 for the cathode current detection circuit. By doing so, the color temperature of the reference white can be adjusted by the user.

In FIG. 24, the volumes 292R, 292
G and 292B use triple rotation angle control type elements.
FIG. 23B shows the relationship between the reference white color temperature and the normalized cathode current for each primary color, where one primary color of each primary color cathode current is a constant value.

In other words, at least two elements of the above-mentioned volume are sufficient. At this time, the reliability of the volume can be improved by selecting a primary color having a constant cathode current detection resistance. This is because if current is allowed to flow out of the volume slider for a long period of time, the carbon resistor around the slider contact is removed due to the electrolytic corrosion phenomenon, resulting in poor contact and discontinuous points in the variable resistance area. Will occur.

Therefore, by selecting a primary color having a constant cathode current detection resistance and changing the resistance values of the other two primary colors in the same direction, the occurrence of the above-described electrolytic corrosion phenomenon can be avoided.

Specifically, for a picture tube having the characteristics shown in FIG. 23, the cathode current detection resistor for the R or B primary color is set to a fixed value, and the cathode current detection resistors for the other two primary colors are set to the values shown in FIG. Is constructed using the connection between the regulators 292G and 292B shown in FIG.

Similarly, the color temperature can be varied by making one of the drive control and the cutoff control variable and following the other control by automatic white balance adjustment.

In the white balance control circuit 33 built in the storage circuit 52 shown in FIGS. 6 and 7, various types of data of the beam current ratio or the light emission luminance ratio of each primary color are prepared, and these are prepared by user operation. It is also possible to use it selectively.

At this time, an automatic white balance adjustment to a reference white at an arbitrary color temperature can be performed by an operation based on linear approximation or the like from a plurality of prepared data. It goes without saying that the above-described correspondence of the scanning position and the aging correction can be performed for the above color temperature setting.

As another application related to the present invention, the following can be considered. The cathode current detection resistors of the picture tubes of various color receivers are replaced with electronically controlled resistors, and the adjustment is performed by using the above-described optical sensor or the optical sensor and the automatic white balance adjusting device commonly for each of the receivers.

Alternatively, it is possible to externally control reference data for white balance adjustment built in various color receivers and systems, and to use the above-mentioned optical sensor or the optical sensor and the automatic white balance adjusting device in common for each receiver. To make adjustments. After the adjustment, use the cathode current detection resistance value corresponding to each picture tube, or use the reference data for white balance adjustment controlled externally, to compare the performance of the various picture receivers or simulate the color design Can be performed.

[0147]

According to the present invention, the DC level of each of the red, green, and blue primary color signals is controlled based on a white balance adjustment reference signal inserted during a vertical blanking period of a video signal. A level correction circuit, and a display using a color picture tube having an automatic white balance adjustment circuit for outputting a control signal to a gain variable control amplification circuit for controlling the amplification gain of the primary color signal to perform white balance adjustment,

The level correction circuit has an input terminal connected to an output terminal of a video output circuit for driving the color picture tube, and applies the automatic white balance to a primary color signal including a DC voltage output from the video output circuit. A control voltage source for adding another DC voltage whose level is controlled by a control signal from the adjustment circuit is included.

That is, by disposing the control voltage source after the video output circuit, it is possible to eliminate the cutoff adjustment margin from the signal dynamic range of the circuit before the video output circuit, and to reduce the wideband loss of the video circuit. There is an advantage of becoming.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a display using a color picture tube having an automatic white balance adjustment circuit as one embodiment of the present invention.

FIG. 2 is a waveform chart showing an example of a deflection signal used in the embodiment of FIG.

FIG. 3 is a circuit diagram showing details of a deflection circuit in FIG. 1;

FIG. 4 is a partial sectional view showing a main part of the color picture tube in FIG. 1;

FIG. 5 is a circuit diagram showing a specific configuration example of a white balance control circuit in FIG. 1;

FIG. 6 is a circuit diagram showing a specific configuration example of a white balance control circuit in FIG. 1;

FIG. 7 is a circuit diagram showing a specific configuration example of a white balance control circuit in FIG. 1;

FIG. 8 is an explanatory diagram showing a procedure for taking in control data in the white balance control circuit shown in FIG. 7;

9A is a circuit diagram showing a specific configuration example of a level correction circuit and a cathode current detection circuit in FIG. 1 as a main part of an embodiment of the present invention, and FIG. 9B is a circuit diagram of a main part of FIG. FIG. 3 is a circuit diagram showing details.

FIG. 10 is a circuit diagram showing another configuration example of the level correction circuit and the cathode current detection circuit.

FIG. 11 is a circuit diagram illustrating a display including a conventional automatic white balance adjustment circuit.

12 is a waveform chart showing signal waveforms at various parts in the conventional circuit shown in FIG. 11;

FIG. 13 is a circuit diagram showing a main part of a reference example related to the present invention.

FIG. 14 is a circuit diagram showing a main part of a reference example related to the present invention.

FIG. 15 is a circuit diagram showing a main part of a reference example related to the present invention.

FIG. 16 is a circuit diagram showing a main part of a reference example related to the present invention.

FIG. 17 is a circuit diagram showing still another reference example of the present invention.

FIG. 18 is a circuit diagram showing still another reference example of the present invention.

FIG. 19 is a distribution diagram showing an example of luminance unevenness distribution of a color picture tube.

FIG. 20 is a circuit diagram showing a conventional example of an anode current detection circuit.

FIG. 21 is a circuit diagram showing a main part (anode current detection circuit) of still another reference example of the present invention.

FIG. 22 is a schematic chromaticity diagram of reference white in a color receiver.

FIG. 23 is two characteristic diagrams showing a correlation example between the reference white color temperature and the cathode current.

FIG. 24 is a circuit diagram showing a main part of still another reference example of the present invention.

[Explanation of symbols]

10R, 10G, 10B: variable gain amplifier circuit for drive adjustment, 12R, 12G, 12B: video output circuit, 22
... Deflection control circuit, 31R, 31G, 31B... Level correction and cathode current detection circuit, 33.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Michitaka Osawa 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Home Appliance Research Laboratory, Hitachi, Ltd.

Claims (3)

[Claims] 1. A level correction circuit for controlling a DC level of each of red, green, and blue primary color signals based on a white balance adjustment reference signal inserted during a vertical blanking period of a video signal, and In a display using a color picture tube having an automatic white balance adjustment circuit that outputs a control signal to a gain variable control amplification circuit for controlling the amplification gain of the primary color signal and performs white balance adjustment, the level correction circuit includes: An input terminal thereof is connected to an output terminal of a video output circuit for driving the color picture tube, and a level control is performed on a primary color signal including a DC voltage output from the video output circuit by a control signal from the automatic white balance adjustment circuit. A display comprising a control voltage source for adding another DC voltage. 2. The display according to claim 1, wherein the level correction circuit includes a capacitor for compensating for an increase in impedance of the control voltage source. 3. The automatic white balance adjustment circuit according to claim 1, wherein the control voltage source includes a transistor for generating the another DC voltage, and a photocoupler connected between a base and an emitter of the transistor. 3. The display according to claim 1, wherein a control signal from the controller is supplied to control the level of the another DC voltage.