JPH03183274A - Color television camera - Google Patents

Abstract

PURPOSE:To suppress the variance of a focusing voltage by taking out only the focusing voltage component from a deflected saw tooth wave voltage and applying it to a focusing voltage control circuit so that it is negatively fed back. CONSTITUTION:When the potential of the large-amplitude deflected saw tooth wave voltage is varied, it is detected by focusing voltage detecting circuits 19, 20, 21, and 22 and is compared with an external reference voltage, which is applied to a terminal 23, by a focusing voltage comparing amplifier 18, and the voltage of this error is amplified. The amplified error voltage is equally supplied to bases of transistors 5 and 6 in the same direction through focusing voltage coupling resistances 15, 16, and 17 so that a focusing voltage control circuit loop forms a negative feedback path. Thus, the focusing error voltage is suppressed in this focusing voltage control circuit 11 and the focusing voltage always coincides with the external reference voltage, and the stable focusing voltage is applied to an image pickup tube.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to suppression of fluctuations in focused voltage in a deflection sawtooth voltage generation circuit in a multi-tube television camera using an electrostatic deflection type image pickup tube. It is.

[Conventional technology]

A block diagram of a deflection circuit for an electrostatic deflection tube is shown in FIG. Second
In the figure, 248 is a positive polarity large amplitude sawtooth voltage generator;
24b is a large-amplitude sawtooth voltage generator with negative polarity, 25a is a mixing amplifier that adds the deflection correction voltage for the red channel to the deflection voltage of positive polarity, and 25b adds the deflection sleeve positive voltage for the red channel to the deflection voltage of negative polarity. It is a mixing amplifier. 25 are green channel and blue channel mixing amplifiers each having the same power loss.

31a, 31b, 32a, 32b, 33a,
33b are deflection correction input terminals for the red channel, green channel, and blue channel, respectively, and these terminals are supplied with correction waveforms and focusing adjustment voltages for improving deterioration in image overlay accuracy caused by variations in image pickup tubes. , centering adjustment voltage, etc. are applied.

In the circuit block configuration of FIG. 2, most of the deflection sawtooth voltage and focusing voltage are supplied from positive and negative polarity large-amplitude sawtooth voltage generators 24B, 24b, and deflection correction voltage mixing amplifiers 25a, 25b.

The correction voltages added at 26a, 26b, 27a, and 27b are low-level voltages that only need to correct variations in the image pickup tubes for red, green, and blue channels. Therefore, fluctuations in the large amplitude sawtooth voltage generator due to various causes directly result in fluctuations in the red, green, and blue deflection voltages. However, the fluctuations are almost the same for all three channels.

For this purpose 9, for example, a sawtooth voltage generator 24a.

When the amplitude changes at 24b, red and green appear accordingly.

The amplitude of the blue image changes. However, since the change is the same for all three channels, the superimposition accuracy of the nine images does not change, and no image quality deterioration occurs in this regard. This is the reason why the circuit block configuration shown in FIG. This deteriorates the focusing degree of the electron beam and greatly deteriorates the sharpness of the nine images.

[Problem to be solved by the invention]

As mentioned above, fluctuations in the focusing voltage deteriorate the sharpness of the image, but since the amplitude of the deflection sawtooth voltage is large, it is difficult to efficiently separate and detect small fluctuations in the focusing voltage. It is not possible to control only the focused voltage with a generator without affecting the centering voltage, and conventional methods have been developed passively, such as by minimizing fluctuations in the circuit configuration and selecting circuit components with little fluctuation. Only countermeasures were taken.

An object of the present invention is to solve these drawbacks and suppress fluctuations in the focusing voltage to always obtain highly sharp images.

[Means and operations for solving the problem] In order to achieve the above object, the present invention extracts only a focused voltage component from a deflection sawtooth voltage, compares the focused voltage with a reference voltage, detects an error voltage, and detects the error voltage. is applied to the focusing voltage control circuit according to the present invention in a negative feedback manner to suppress fluctuations in the focusing voltage.

FIG. 3 shows the relationship between positive polarity and negative polarity sawtooth voltages, focusing voltages, and centering voltages, where the horizontal axis is time and the vertical axis is voltage. In the figure, 348 takes a as the starting point and b
34b is a sawtooth voltage of positive polarity ending at C'& starting point, and 34b is a sawtooth voltage of negative polarity ending at d. The electron beam of the image pickup tube is deflected by an electric field created by the potential difference between the positive and negative sawtooth voltages 34a and 34b at each WI# of scanning. Deflection scanning starts at time TO.

It ends at time T. The voltage VFA corresponding to the intersection 36a of the sawtooth voltages 34a and 34b (this voltage is equal to the average voltage of the sawtooth voltages 34a and 34b) is a focusing voltage, and at this time the deflection electric field is zero. For,
At this moment, the electron beam is scanning the center of the image pickup tube surface. Therefore, when the crossing point voltage VFA changes, the focusing voltage changes, and when the time TI of the crossing point 36a changes, the image position changes. For example, For some reason, the positive polarity sawtooth voltage 34a is 358 K, and the negative polarity sawtooth voltage 34b is
When moves to 35b, the intersection point 36a moves to 36b.

The focusing voltage changes from VFA to VFR. Further, the crossing point time moves from TI to T2. Therefore, the position of the image also moves. As is clear from Figure 3.

If the sawtooth voltages 34a and 34b fluctuate by the same amount in the same direction (either in the direction of high voltages or in the direction of low voltages), the crossing point time Tl does not change, and only the crossing point voltage VFA changes. do. That is, the centering does not change, only the focusing voltage changes. Furthermore, if the sawtooth voltages 34a and 34b change by equal amounts in opposite directions, the crossing point voltage (focusing voltage) VFA does not change, but only the centering changes.

FIG. 4 shows an example of a circuit for extracting a focused voltage from positive and negative polarization sawtooth voltages, with terminals 37a and 37b having
Sawtooth output voltages of positive polarity and negative polarity are applied, respectively. 38a and 38b are voltage adder circuits, and the output terminal of the resistor 39 is the sum of the voltages applied to the terminals 37a and 37b.

That is, a focused DC voltage VFA appears.

Note that the capacitor 4o is used to bypass alternating current components generated due to minute differences between positive and negative sawtooth waves.

FIG. 5 is a diagram schematically showing the operation of a conventionally used positive and negative polarity sawtooth voltage generator.

1 and 2 are constant current sources with a current flow of 0, which charge and discharge integral capacitors 3 and 4 to create a sawtooth voltage of positive polarity between the terminals of integrating capacitor 3 and a sawtooth voltage of negative polarity between the terminals of integrating capacitor 4. Generate wave voltage. switch 9
and lO are periodically turned on/on, capacitors 3, 4
Charge and discharge electric charge. 12 and 14 are fixed resistors with a resistance value of R3.

13 is a variable resistor with a resistance value R4, and the starting points a and C of the sawtooth wave voltages 34a and 34b in FIG.
Determine the potential of If we ignore the base-emitter voltage of transistors 5 and 60.

Therefore, when the resistance value R4 is changed, the potentials ■Sl and Vs
z changes by the same amount in the same direction.

That is, referring to FIG. 3, the sawtooth voltage 34
Starting point potential V B of a and 34b! and Vcc-
VS2 changes by an equal amount in the opposite direction. That is, only the centering of the image changes, and the focusing voltage does not change. FIG. 6 shows a circuit that enables independent adjustment of the focusing voltage in addition to the centering adjustment function of FIG. 5. In Figure 6,
12, 13, and 14 are resistors having the same function as those in FIG. In FIG. 6, resistors 12 and 13. And the DC power supply 4 is connected to the connection point between 13 and 14 through resistors 15, 16 and 17.
1 (voltage: fixed at T Vcc) and 42 (voltage: variable in the positive and negative directions at ΔV) are applied.

Assuming that the resistance values of resistors 12, 13, 14, 15, and 16.17 are R3, R4, R3, R5, R5, and R6, respectively, the value is V! and ■2, the following formula is obtained.

As is clear from the above equation, in the circuit of FIG.

When the resistance value R4 of the resistor 13 is changed, the potentials vl and v
2 cause equal voltage changes in mutually opposite directions, and when the voltage ΔV of the power supply 42 is changed, the potentials v1 and 2 cause equal voltage changes in the same direction. In other words.

According to the circuit shown in FIG. 6, the centering of the image can be achieved by changing the resistance value of the resistor 13, and the focusing voltage can be adjusted by changing the voltage of the power supply 42.

Each can be adjusted independently.

As a result of the above, the detected focused voltage is compared with the reference voltage, the error voltage is amplified, and the voltage of the power supply 42 is set to provide negative feedback, thereby suppressing fluctuations in the focused voltage.

〔Example〕

FIG. 1 shows an embodiment of the present invention. 1 and 2 in Figure 1
is a constant current source with a current value of IO, 3 and 4 are capacitors that integrate the current IO and generate a sawtooth voltage, 5 and 6
is a transistor that sets the starting point potential of the sawtooth voltage; the voltage applied to the pace determines the emitter potential of the transistor, which becomes the starting point potential of the sawtooth voltage. 7 and 8 are buffer amplifiers for extracting sawtooth waves; 9 and 10 are switches for periodically discharging the charges accumulated in the capacitors 3 and 4;

11 is a focusing voltage control circuit and a centering voltage adjustment circuit according to the present invention.

The circuit 11 includes resistors for supplying the transistors 5 and 60 base voltage, 12.14. Variable resistor for centering voltage adjustment, 13. Resistors 15, 16, 17 . for coupling the focusing voltage. It is composed of a focusing voltage comparator amplifier 18, resistors 19, 20, 21, and a bypass capacitor 22 that constitute a focusing voltage detection circuit.

If the potential of the large-amplitude deflection sawtooth voltage varies for some reason, this variation will cause the focused voltage detection circuits 19 and 20 to
, 21, 22, and is compared with an external reference voltage applied to the terminal 23 in the focusing voltage comparison amplifier 18, and this error voltage is amplified. The amplified error voltage is applied to the focusing voltage coupling resistors 15, 16, 17.
The base potentials of transistors 5 and 60 are supplied by equal amounts in the same direction and in such a way that the focusing voltage control circuit loop is in negative feedback. Therefore, in the focusing voltage control circuit 11, the focusing error voltage is suppressed, the focusing voltage always matches the external reference voltage, and a stable focusing voltage can be applied to the image pickup tube.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to suppress the focusing voltage caused by fluctuations in the deflection sawtooth voltage generator,
High quality images can always be maintained.

[Brief explanation of drawings]

Fig. 1 shows the overall configuration 2 of the present invention and a block diagram showing one embodiment, and Fig. 2 shows a large-amplitude sawtooth voltage generator commonly used for each red, green, and blue channel, and a large-amplitude sawtooth voltage generator for each channel. FIG. 3 is a diagram showing the relationship between the deflection correction voltage mixing amplifier, which is applied individually; FIG. 3 is a diagram showing the relationship between the deflection sawtooth voltage and the centering and focusing voltage; FIG. 4 is the focusing voltage detection circuit;
FIG. 5 is a diagram showing the functions of a conventional large-amplitude deflection sawtooth wave generating circuit, and FIG. 6 is a diagram showing the functions of a centering voltage and focusing voltage generating circuit that can be independently controlled according to the present invention. 1: Constant current source for generating positive sawtooth voltage. 2: Constant current source for generating negative polarity sawtooth voltage, 3゜4:
Integrating capacitor, 5, 6. :) transistor, 7° 8: buffer amplifier, 9, 10: switch, 11: feedback circuit including focusing voltage control and centering adjustment circuit. 12, 13.14.15.16.17: Resistance, 18:
Focusing voltage comparison amplifier, 19.20.21: Resistor, 22: Shunt capacitor, 23: Focusing reference voltage input, 4
1: Power supply, 42: Variable voltage power supply. 2 items - f3rA ke 411 Y b items

Claims (1)

[Claims] 1. In a multi-tube color television camera that uses an electrostatic deflection type image pickup tube, the starting potential of the sawtooth wave of the positive and negative polarity large-amplitude sawtooth wave voltage generation circuits is changed by the same amount in the same direction. A focusing voltage control circuit, a detection circuit that detects a focusing voltage by adding positive polarity and negative polarity deflection sawtooth output voltages, and a circuit that compares the detected focusing voltage with a reference voltage to obtain and amplify an error voltage. A color television camera characterized in that the error voltage is applied to the focusing voltage control circuit in a negative feedback manner to suppress fluctuations in the focusing voltage.