JPH0783434B2 - Dynamic focus circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A Field of Industrial Application The present invention relates to a dynamic focus circuit, and is particularly suitable for application to a display device having a structure using a cathode ray tube for displaying a raster image.

B. Summary of the Invention The present invention effectively eliminates the defocusing of the beam spot generated on the screen of the cathode ray tube by providing a fine adjustment circuit in series with the step-up transformer in the dynamic focus circuit of the display device having the cathode ray tube. It can be corrected.

C Conventional technology For example, a monitor for air traffic control or CAD / CAM (computer aide)
In d design / computer aided manufacturing), use a large-screen cathode ray tube with a high resolution (for example, having a resolution of 2000 dots x 200 dots and a screen of about 20 inches x 20 inches) for the purpose of graphic processing. Is being considered.

D. Problems to be Solved by the Invention When attempting to realize such a large-sized and ultra-high-definition display device, the first problem is, as shown in FIG. 5, a screen of a cathode ray tube (CRT). Since the shape of the beam spot SPT on the surface DIP causes defocusing in different directions depending on the landing position, it is necessary to correct this by a simple method.

That is, in order to realize it with a cathode ray tube (CRT) of such a large-sized and ultra-high-definition display device, in order to make it as easy as possible to see, as shown in FIG. It is required to be flat. In order to realize a CRT 1 satisfying this requirement, when the electron beam 3 formed in the main lens system 2 passes through the deflection center P ₀ and goes straight to the central portion of the screen surface DIP, the beam spot SPT
Even if it can be made into a perfect circle, it is inevitable that the defocus of the beam spot SPT becomes considerably large because the screen surface DIP is largely deviated from the virtual spherical surface CIR in the peripheral portion of the screen surface DIP.

In fact, in a CRT1 with such a high resolution, the shape of the beam spot SPT is corrected in the main lens system 2 using a correction device such as an electromagnetic quadrupole or a pair of electromagnetic octupoles. However, it is unavoidable that the size of the spot SPT on the screen surface DIP will change when these correction devices are adjusted, so that the dynamic focus of the entire screen surface DIP in the horizontal direction. It is necessary to be able to fine-tune the circuit voltage.

As a means for realizing this, it is generally considered to use a transistor circuit. However, in the high definition display device as described above, the horizontal frequency is 130 [kHz].
It is necessary to select a very high frequency,
When fine-tuning the dynamic focus voltage, 1
It is necessary to process a high voltage signal of about [kV]. If signal processing is attempted using a transistor circuit under such conditions, there is an unavoidable problem as a dynamic focus correction circuit that the loss is large and the circuit configuration becomes complicated.

The present invention has been made in consideration of the above points, and an object of the present invention is to propose a dynamic focus focus circuit capable of easily performing fine adjustment of the dynamic focus focus voltage with a relatively simple configuration. Is.

E Means for Solving the Problems In order to solve the above problems, in the present invention, the input pulse P _IN generated in the secondary winding of the horizontal output transformer 21 is boosted by the boosting transformer 33 and the vertical parabolic voltage V is applied. _{In the} dynamic focus circuit 11, which is added to _PARA and supplies the added output V _DIN to the main lens system 15 of the cathode ray tube as the focus output FV, is connected in series between the secondary winding of the horizontal output transformer 21 and the step-up transformer 33. A controllable impedance element 32, and first and second variable resistance elements 55 and 62,
The impedance of the controllable impedance element 32 is controlled by inputting the vertical parabolic voltage S _PARA and applying the control current I _C generated according to each resistance value to the control winding of the controllable impedance element 32, The variable resistance element 55 adjusts the modulation degree of the horizontal parabolic voltage e ₂ and the second variable resistance element 62 adjusts the amplitude value of the horizontal parabolic voltage e ₂ and a variable resistance element 47 is provided. Then, the vertical parabolic voltage S _PARA is input, the amplitude value of the vertical parabolic voltage V _PARA is adjusted according to the resistance value, and the adjusted vertical parabolic voltage V _PARA is applied to the secondary side of the step-up transformer 33. 34, and the first and second variable resistance elements 55 and 6 of the horizontal parabolic voltage adjusting circuit 31.
2, and the variable resistance element 4 of the vertical parabola voltage adjustment circuit 34
The focus output FV is adjusted by adjusting the resistance value of 7.

F-action Since the fine adjustment circuit 31 having the controllable impedance element 32 is inserted in series with the step-up transformer 33,
Beam spot S in the center on the screen surface DIP of the cathode ray tube
With respect to the PT, the shape or size of the beam spot SPT in the peripheral portion can be effectively variably controlled as necessary.

G Embodiment One embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, reference numeral 11 denotes a dynamic focus circuit, which controls the high voltage HV obtained from the flyback transformer 12 to CR.
The focus voltage FV obtained from the focus volume 14 is supplied to the main lens system 15 while being supplied to the high voltage electrode of T13.

The dynamic focus circuit 11 has a horizontal output transformer.
An input pulse P _IN is supplied from the horizontal deflection circuit 22 via 21.

The horizontal deflection circuit 22 includes a horizontal output transistor 23 and a damper diode that perform a switching operation according to the horizontal drive signal S _H.
A switch output pulse P _SW (FIG. 2 (A)) is generated by 24 and is applied to a sawtooth wave generation circuit composed of a horizontal deflection coil 25, an S-shaped capacitor 26, and a resonance capacitor 27. Applied to the next side, thus input pulse P _IN
(FIG. 2 (B)) is supplied to the dynamic focus circuit 11.

This input pulse P _IN passes through the impedance control saturable reactor 32 of the fine adjustment circuit 31 to the step-up transformer 33 1
It is given to the next winding.

Thus, on the secondary side of the step-up transformer 33, It is possible to obtain a voltage output e ₂ represented by Here, n is the winding ratio of the step-up transformer 33, and is selected as primary winding: secondary winding = 1: n (2). L ₁ is the impedance of the saturable reactor 32 for impedance control, and L ₂ is the step-up transformer 33.
Impedance of the primary winding, e ₁ is the horizontal output transformer
It is the voltage across the secondary winding of 21.

One end of the secondary winding of the step-up transformer 33 is grounded through the output capacitor 35 of the vertical parabolic voltage forming circuit 34, and the other end is connected through the coupling capacitor 36 to the focus volume.
Connected to 14 outputs.

The vertical parabolic voltage forming circuit 34 rectifies the switch output pulse P _SW of the horizontal deflection circuit 22 in a peak rectifying circuit including a resistor 41, a diode 42, and a capacitor 43, and then a resistor 44
Is supplied to the collector of the amplifying transistor 45 via.

The vertical parabolic signal S _PARA input from the fine adjustment terminal 46 is input to the base of the amplification transistor 45 through the vertical parabolic voltage adjustment variable resistor 47 and the coupling capacitor 48.

Thus, as shown in FIG. 3 (B), the collector of the amplifying transistor 45 can obtain a vertical parabolic voltage V _PARA that changes its voltage value so as to draw a parabolic waveform during the vertical period V. The voltage across the output capacitor 35 is applied to one end of the secondary winding of the step-up transformer 33.

In addition to the above configuration, the fine adjustment circuit 31 receives the vertical parabola signal S _PARA input from the fine adjustment terminal 46 through the modulation degree adjusting variable resistor 55 and the coupling capacitor 56 at the base of the amplifying transistor 57 to control it. By controlling the control transistor 60, the control current I _C flowing through the control winding of the impedance control saturable reactor 32 connected to the control transistor 60 is controlled.

Thus, the impedance L ₁ of the saturable reactor 32 is _adjusted by the vertical parabolic signal S _PARA (FIG. 3 (A)) when the voltage level of the saturable reactor 32 changes with the vertical synchronizing section V as a cycle. Impedance L
₁ is controlled as shown by the curve K shown in FIG.

As a result, in the equation (1), if the impedance L ₁ of the saturable reactor 32 is controlled, the voltage division ratio between it and the impedance L ₂ of the step-up transformer 33 is controlled accordingly, so that the step-up transformer 33 is controlled. The secondary winding voltage e ₂ changes into a parabolic wave shape at every horizontal period H according to the input pulse P _IN , and the amplitude is amplitude-modulated by the vertical parabolic voltage V _PARA (Fig. 3 (B)). Then, a horizontal parabolic waveform voltage e ₂ (FIG. 3 (C)) is generated.

A bias circuit composed of an amplitude adjusting variable resistor 62 and a resistor 63 is connected to the base of the amplifying transistor 57 of the fine adjusting circuit 31, and by adjusting the amplitude adjusting variable resistor 62,
The amplitude V ₂ of the horizontal parabolic waveform voltage e ₂ can be controlled.

The output voltage e ₂ of the step-up transformer 33 (FIG. 3 (C)) is the vertical parabolic voltage V charged in the output capacitor 35.
_It is added to _PARA to obtain the dynamic focus correction voltage V _DIN as shown in FIG. It is supplied to the lens system 15 as a drive output.

As a result, the main lens system 15, as shown in FIG.
The focus voltage FV is corrected by the dynamic focus correction voltage V _DIN which changes along the parabolic waveform in the horizontal direction and whose amplitude changes in the vertical direction along the vertical parabola voltage V _PARA .

In the above configuration, the CRT 13 is a vertical parabolic voltage forming circuit for the beam spots on the periphery of the screen surface DIP.
Based on the vertical parabolic voltage V _PARA (FIG. 3 (B)) generated by the 34 and the input pulse P _IN obtained via the horizontal output transformer 21, it is obtained on the secondary winding side of the step-up transformer 33. With the horizontal parabola voltage e ₂ (FIG. 3 (C)), it is possible to form a beam spot having a shape similar to that of the beam spot SPT in the central portion after the dynamic focus correction.

In addition to this, according to the above configuration, when the vertical parabolic voltage adjusting variable resistor 47 is adjusted in the vertical parabolic voltage forming circuit 34, the amplitude V ₁ of the vertical parabolic voltage V _PARA is
By changing (FIG. 3 (B)), the voltage level of the dynamic focus correction voltage V _DIN (FIG. 3 (D)) can be changed in the peripheral part with respect to the central part. Thus, it is possible to make a correction such that the size of the beam spot SPT is changed as it goes to the outer edge in the vertical direction with reference to the beam spot SPT at the center of the screen surface DIP.

In addition to this, in the fine adjustment circuit 31, the impedance L ₁ of the saturable reactor 32 for impedance control can be controlled by adjusting and operating the variable resistor 55 for adjusting the modulation degree, which allows the horizontal parabola voltage e ₂ ( By controlling the modulation degree shown in FIG. 3C, the ratio between the maximum amplitude value V ₂₁ and the minimum amplitude value V ₂₂ of the horizontal parabola voltage e ₂ can be variably controlled. As a result, for the horizontal parabolic waveform portion (FIG. 3 (D)) of the dynamic focus correction voltage V _DIN , the ratio of the amplitude V ₃₂ in the vertical direction to the amplitude V ₃₁ in the central portion is variably controlled. Thus, in each horizontal line of the screen surface DIP, the ratio of the size of the beam spots at both ends can be variably controlled with reference to the beam spot SPT at the center.

Further, in the fine adjustment circuit 31, the amplitude value V ₂₁ of the horizontal parabola voltage e ₂ (FIG. 3 (C)) can be variably controlled by adjusting the amplitude adjusting variable resistor 62.
Dynamic focus correction voltage V _DIN (Fig. 3 (D))
By controlling the amplitude of the parabolic waveform in each horizontal section, the size of the beam spot of each horizontal line on the screen surface DIP can be adjusted all at once.

For this reason, the dynamic focus correction voltage V _DIN
As a means for changing the impedance, the saturable reactor 32 is used to control the impedance, so that the loss can be further reduced as compared with the case where a transistor is used.

The voltage level E ₀ of the dynamic focus correction voltage V _DIN (FIG. 3 (D)) can be set by adjusting the focus volume 14.

Further, in the above-mentioned embodiment, the case where the horizontal parabolic waveform voltage is reduced in the peripheral portion of the screen surface DIP as in the case of using the electromagnetic quadrupole circuit has been described (Fig. 3 (C)). ), The present invention is not limited to this, and by changing the polarity according to the size of the beam spot and the focal length, it is possible to increase the horizontal parabolic voltage in the peripheral portion or to increase the horizontal parabolic voltage in the peripheral portion. The voltage may be arbitrarily selected from a low state to a high state as needed.

H Effect of the Invention As described above, according to the present invention, the impedance controllable saturable reactor 32 of the fine adjustment circuit 31 is provided in series with the step-up transformer 33 so that the impedance can be variably controlled as necessary. Therefore, regarding the size and shape of the beam spot on the screen surface of the CRT,
It is possible to obtain a dynamic focus circuit having a simple structure in which the peripheral beam spot with respect to the central beam spot can be easily adjusted and controlled with a small loss as required.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an embodiment of a dynamic focus circuit according to the present invention, FIGS. 2 and 3 are signal waveform diagrams showing signals of respective parts thereof, and FIG. 4 is for impedance control of FIG. A characteristic curve diagram showing the characteristic of the saturable reactor 32, FIGS. 5 and 6 are schematic diagrams for explaining the beam spot on the screen surface DIP of the conventional display device. 11 ... Dynamic focus circuit, 22 ... Horizontal deflection circuit, 21 ... Horizontal output transformer, 31 ... Fine adjustment circuit, 32 ...
… Saturable reactor for impedance control, 33 …… Boosting transformer, 34 …… Vertical parabolic voltage forming circuit.

Claims (1)

[Claims] 1. A dyna for supplying an input pulse generated in a secondary winding of a horizontal output transformer to a vertical parabolic voltage by boosting it by a boosting transformer and supplying the added output to a main lens system of a cathode ray tube as a focus output. In the microphone focus circuit, a controllable impedance element connected in series between the secondary winding of the horizontal output transformer and the step-up transformer, first and second variable resistance elements, and inputting the vertical parabolic voltage. Then, the impedance of the controllable impedance element is controlled by applying a control current generated in accordance with each resistance value to the control winding of the controllable impedance element, and the horizontal parabolic voltage of the horizontal parabolic voltage is controlled by the first variable resistance element. A horizontal parabola voltage adjusting circuit for adjusting the modulation degree and adjusting the amplitude value of the horizontal parabolic voltage by the second variable resistance element. When having a variable resistance element, and enter the vertical parabola voltage adjusts the amplitude value of the vertical parabola voltage in accordance with the resistance value, the adjusted vertical parabola voltage of the step-up transformer 2
A vertical parabola voltage adjusting circuit provided to the next side, and adjusting the resistance values of the first and second variable resistance elements of the horizontal parabolic voltage adjusting circuit and the variable resistance elements of the vertical parabolic voltage adjusting circuit. A dynamic focus circuit characterized by adjusting the focus output.