JPH0364274A - Dynamic focus correcting device - Google Patents

Abstract

PURPOSE:To reduce the distortion of a parabolic waveform by providing a means for generating a timing pulse by using a synchronizing signal as a trigger, a saw tooth wave generating part, and a means for generating a parabolic wave signal by squaring by a computing element. CONSTITUTION:Saw tooth wave generating parts 4, 5 generate positive/negative symmetrical saw tooth output waveforms by charging a capacitor with a constant-current at the time when a timing pulse is ON, and generating a saw tooth pulse and disconnecting a DC portion by capacitors 6, 7 by a method for executing quick discharge at the time of OFF, and they are brought to square operation by squaring devices 8, 9 and a parabolic output waveform A and a parabolic output waveform B are generated within one period, amplified by an output amplifier 12 and superposed on an output of a focus power source 15 through a capacitor 13. In this case, the maximum value VFO of the parabolic output waveform can lower the amplitude of a parabolic output portion generated in a blanking period, therefore, a load resistance value of an amplifying circuit can be made smaller. In such a way, the distortion of a waveform can be reduced and a satisfactory focus image is obtained in the whole area of a screen.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dynamic focus correction device used in a testing device for a high-definition monitor receiver or a high-definition picture tube.

[Conventional technology]

Conventionally, the correction signal of this type of dynamic focus correction device is generated by generating a voltage having a parabolic waveform based on a synchronization signal or a signal synchronized with a deflection pulse, amplifying the voltage, and then applying the voltage to a focusing electrode of a picture tube. Improvements to focus images were made. The period during which images are displayed on the picture tube is the signal display period, and is not displayed during the blanking period. Therefore, the blanking period does not have to produce a parabolic waveform. In the conventional system, as shown in FIG. 3, since a parabolic waveform is generated during the blanking period, the output amplitude ■Fl of the parabolic waveform becomes large.

[Problem to be solved by the invention]

In recent years, the radius of curvature of picture tubes has tended to be larger than before, mainly to improve visibility, and the amplitude of the dynamic focus correction signal required for such picture tubes has reached 500V to 100OV. The dynamic focus correction signal of conventional high-definition monitor receivers has a horizontal deflection frequency that is 3 to 5 times higher than that of television monitor receivers, resulting in waveform distortion near the peak of the waveform and insufficient output amplitude. There was a drawback that the waveform was not optimal.

[Means to solve the problem]

The present invention has a means for generating a timing pulse using a synchronization signal as a trigger, a sawtooth wave generating section, and a means for generating a parabolic wave signal by squaring it with an arithmetic unit. Furthermore, this is a dynamic focus correction device in which a boosted parabolic wave signal is applied to a focusing electrode of a picture tube.

[Effect]

According to this device, it is possible to reduce the distortion of the parabolic waveform in a high-definition monitor receiver or picture tube testing device, so that a good focused image can be obtained over the entire screen.

〔Example〕

Hereinafter, the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of the present invention. The horizontal and vertical synchronizing signals are supplied to a timing generator 1, each adjusted to an appropriate pulse width by a variable resistor 2.3, and input to sawtooth wave generators 4 and 5, respectively. Here, when the timing pulse is ON, the capacitor is charged with a constant current, and when the timing pulse is OFF, a sawtooth pulse is generated by rapidly discharging the charged charge.
．． By cutting off the DC component at 7, a sawtooth output waveform with positive and negative polarity as shown in FIG. 2 is generated. This sawtooth waveform is squared by 8
．． 9 is squared and parabolic output waveform A is calculated within one cycle.
and a parabolic output waveform B is generated, and the output amplifier 12
A signal of approximately 10 Vp-p is amplified approximately 100 times, passes through a capacitor 13, is superimposed on the output of the focus power supply 15, and is applied to the focusing power of the picture tube 16. The adjustment method is
While viewing the image, the variable resistor 10 for adjusting the output voltage in the horizontal direction and the variable resistor 11 for adjusting the output voltage in the vertical direction are adjusted so that the best focused image is obtained on the screen of the picture tube 16.

FIG. 4 is a block diagram of a second embodiment of the present invention. The picture tube 16 had an electron gun with a focusing electrode divided into two poles, one pole applied a fixed voltage, and the other pole applied a voltage obtained by superimposing a parabolic wave on the fixed voltage to improve the focused image. This is an example. Each of the horizontal and vertical synchronization signals enters a phase shift circuit 100, and the timing of parabolic generation relative to the image signal can be adjusted using variable resistors 101 and 102, so the phase of the parabolic waveform can be matched to the timing of the signal. Therefore, a highly accurate dynamic focus correction device can be achieved.

〔Effect of the invention〕

According to the present invention, the maximum value ■I-o of the parabolic output waveform is the maximum value V of the parabolic output waveform of the conventional method shown in FIG.
Since the amplitude of the disparate outputs generated during the blanking period can be lowered compared to Pl, the load resistance value of the amplifier circuit can be made smaller, and the frequency band becomes wider. This allows waveform distortion to be reduced and a well-focused image to be obtained across the entire screen.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
The figure shows the timing of the signal display period, the sawtooth output waveform, and the parabolic output waveform in the present invention. FIG. 3 shows the parabolic output waveform in the conventional method. FIG. It is a block diagram. 1... Timing generation section, 2, 3.10.11...
Variable resistor, 4, 5... Sawtooth wave generator, 6,7°13
...-capacitor, 8.9... squarer, 12... output amplifier, 14... high voltage resistor, 15... direct current power supply for focus, 16... picture tube, 100... phase Shift circuit, 101, 102... variable resistor.

Claims (1)

[Claims] It has means for generating a sawtooth waveform of positive and negative polarity synchronized with a synchronization signal or a deflection pulse, and means for squaring the waveform, and generates a parabolic waveform during a blanking period and a signal display period, respectively. A dynamic focus correction device characterized in that the dynamic focus correction device is configured to correct a focused image on a screen of a picture tube by applying the following to a focusing electrode of a picture tube.