JPS63260365A - Dynamic focus circuit - Google Patents

Abstract

PURPOSE:To improve the accuracy of focus correction by applying time setting till the end point of a display area based on the start point of a display area by a pulse width adjusting circuit of horizontal and vertical deflection sides and generating a correction wave corresponding to the set display area from the output of the pulse width adjusting circuit. CONSTITUTION:A horizontal synchronizing signal is fed to a pulse width adjusting circuit 1 and the time adjustment of a one-shot multivibrator is applied while being activated at the trailing edge of the synchronizing signal so as to obtain a pulse wave having a pulse width T1 in one horizontal period, and the pulse width T1 corresponds to the time from the synchronizing signal till the display area start point of the picture. Then the time adjustment of a one- shot multivibrator operated at the leading edge of the pulse wave is applied to obtain a pulse wave having a pulse width T2 at one horizontal period and the pulse width T2 corresponds to the display area period of the picture. The output is fed to an integration circuit 2 and the obtained sawtooth wave is fed to an integration circuit 3 to obtain a parabolic voltage. It is fed to a CRT 12. This is applied similarly to the correction in the vertical direction.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dynamic focus circuit that improves the effect of correcting focus shift in the periphery of the CRT display area in a CRT (cathode ray tube) display device. be.

[Conventional technology]

FIG. 3 is a block diagram showing a focus correction circuit in a conventional CRT display VT device.

In FIG. 3, the horizontal synchronizing signal is amplified by an amplifier circuit 21, passed through integration circuits 2 and 3, and then applied to an output circuit 4. I am trying to add it to 13. Thus, a horizontal focus correction circuit is configured.

Similarly, the vertical synchronization signal is generated by the rectangular wave pulse generation circuit 22.
The output of this rectangular wave pulse generation circuit 22 is applied to an output circuit 9 via an integrating circuit 7.8, and the output of this output circuit 9 is applied to the focus grid 13 via a coupling capacitor 10. Thus, a vertical focus correction circuit is constructed.

A flybank transformer 11 supplies a DC focus voltage to the CRT 12, and a focus grid 13 synthesizes all focus correction voltages.

Next, the operation of the focus correction circuit in the conventional CRT display device shown in FIG. 3 will be explained.

First, the horizontal synchronizing signal (H, 5YNC) shown in FIG.
) is waveform shaped and amplified by the amplifier circuit 21, and then the integrator circuit 2
A sawtooth wave signal (IH) with a horizontal period shown in FIG.
A parabolic signal with a horizontal period (T) shown in C1 is obtained. This parabolic signal is amplified to a predetermined level by the output circuit 4 to obtain a focus correction voltage.

Separately, using a vertical synchronizing signal (V, 5YNC), a rectangular wave pulse generating circuit 22 generates a rectangular wave pulse whose phase matches the timing of vertical scanning, and from this rectangular wave pulse, an integrator circuit 7 generates a sawtooth wave with a vertical period. Obtain a wave signal.

This sawtooth wave signal is applied to an integrating circuit 8 to obtain a parabolic signal with a vertical period. This parabolic signal is amplified to a predetermined level by an output circuit 9 to obtain a focus correction voltage.

Each focus correction voltage obtained as described above is supplied from the output circuit 4.9 to the focus grid 13 of the CRT 12 via the coupling capacitor 5.10, and the DC focus voltage is supplied from the flyback transformer 11 to the CRT 12. When supplied to the focus grid 13, the three types of focus correction voltages described above are combined in this focus grid 13.

[Problem that the invention seeks to solve]

Since the conventional focus correction circuit is configured as described above, the correction voltage at the end of the display area shown in Fig. 4 is a correction voltage lower than the peak value, so if a higher correction signal is required, the correction voltage is lower than the peak value. The power supply voltage for the circuit must be increased, and the components used must also have high withstand voltages.

Further, there is a problem that the center of the correction waveform and the center of the display area are different, making the correction asymmetrical with respect to the display area.

This invention was made to solve such problems, and it is possible to match the edges of the display area with the left and right edges, which are the peaks of the correction wave, and also make it possible to match the center of the correction waveform with the center of the display area. The purpose is to obtain a dynamic focus circuit that can match the

Means for Solving Problem c] The dynamic focus circuit according to the present invention sets the time to the start point of the display area based on the horizontal periodic signal and the vertical synchronization signal, respectively, and displays the display area using the start point of the display area as the reference. The first step is to set the time to the end of the area. The second noise level adjustment circuit and the first and second
The first one generates a correction wave corresponding to each set display area in response to the output of the pulse width adjustment circuit of the first one. A second circuit is provided.

[For production]

In this invention, 1. The correction waves obtained by the second pulse width adjustment circuit are respectively applied to the first and second pulse width adjustment circuits. In addition to the second circuit, this correction wave is corrected by a parabolic voltage corresponding to each display area, so that the peak value of the correction wave coincides with the edge of the display area on the CRT, and the center of the display area and the center of the correction wave. matches.

(Example) Hereinafter, an example of the dynamic focus circuit of the present invention will be described based on the drawings. FIG. 1 is a block diagram showing the configuration of one embodiment.

In FIG. 1, the same parts as in FIG. 3 will be described with the same reference numerals.

In FIG. 1, a pulse width adjustment circuit 1.6 is used in place of the amplifier circuit 21 and rectangular pulse generation circuit 22 in FIG. 3, respectively.

The pulse width adjustment circuit 1 generates a pulse wave corresponding to the display area time in the horizontal direction, and the output of this pulse width adjustment circuit 1 is sent to an integration circuit 2. Converts a pulse wave to a sawtooth voltage.

The integrating circuit 3 converts the sawtooth voltage into a parabolic voltage and outputs it to the output circuit 4.

An output circuit 4 amplifies the correction voltage to a predetermined level and outputs it to the focus grid 1 of the CRT 12 via a coupling capacitor 5.
I'm trying to add it to 3.

Further, the pulse width adjustment circuit 6 generates a pulse wave corresponding to the display area time in the vertical direction and applies it to the integration circuit 7.

The integrating circuit 7 converts this pulse wave into a sawtooth wave voltage and applies it to the integrating circuit 8. This integrating circuit 8 converts the sawtooth voltage into a parabolic voltage and outputs it to an output circuit 9.

The output circuit 9 amplifies the correction voltage to a predetermined level and outputs it to the focus grid 1 of the CRT 12 via the coupling capacitor 10.
It is supposed to be added to 3. A DC focus voltage is applied to the focus grid 13 from the fly bank transformer 11.

Next, the operation of the dynamic focus correction circuit of the present invention will be explained. The pulse width adjustment circuit 1 shown in Fig. 2 Tal
By adding the horizontal synchronization signal shown in Figure 2(b) and adjusting the time of the one-shot multivibrator that operates at the falling edge of this synchronization signal, a pulse wave having one horizontal period and a pulse width TI as shown in Figure 2(b) is obtained. . This pulse width TI corresponds to the time from the synchronization signal to the start point of the image display area.

Next, by adjusting the time of the one-shot multivibrator that operates at the rising edge of the pulse wave shown in FIG. 2 obtained as described above, the pulse width T2 is This pulse width Tt corresponds to the display area period of the image.
The pulse wave shown in the figure (C1) becomes the cutting edge of the pulse width adjustment circuit 1.

Next, this output is applied to the integrating circuit 2 to obtain a sawtooth wave with one horizontal period shown in Fig. 2 +dl, and this sawtooth wave is applied to the integrating circuit 3 as shown in Fig. 2(e). Obtain parabolic voltage.

The parabolic voltage obtained by this integrating circuit 3 is output to an output circuit 4.
to amplify it to the level required for correction. This output is connected to the focus grid 1 of the CRT 12 via a coupling capacitor 5.
The above description has been made regarding correction in the horizontal direction when 0 or more is supplied to the output signal 3. However, regarding correction in the vertical direction, the operation is the same as above, although the pulse width setting time is different.

In addition, in the above embodiment, the case where the integration circuits 3 and 8 are used to obtain horizontal and vertical parabolic voltages has been described, but a multiplier may be used instead of the integration circuits 3 and 8, and the above embodiment The same effect as in the example can be obtained.

In addition, in the above embodiment, the center of the CRT 12 and the center of the display area are aligned, but if the center of the CRT 12 and the center of the display area are not aligned, the pulse width adjustment circuit 1.6 In Fig. 2 (
bl pulse width T, and FIG. 2 (C1 pulse width T8
By adjusting , the optimum correction voltage phase can be obtained.

〔Effect of the invention〕

As explained above, this invention sets the time to the start point of the display area based on the horizontal synchronization signal and the vertical synchronization signal, respectively, and also sets the time to the end point of the display area using the start point of the display area as the reference. This is done by the pulse width adjustment circuit on the vertical deflection side, and a correction wave corresponding to the set display area is generated from the output of this pulse width adjustment circuit, improving the accuracy of focus correction and making it possible to correct vertical and horizontal directions. It can be made symmetrical, and also has the effect of lowering the correction circuit power supply voltage and increasing the withstand voltage of the parts used.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the dynamic focus correction circuit of the present invention, FIG. 2 is a voltage waveform diagram of each part in the dynamic focus correction circuit of the present invention, and FIG.
FIG. 4 is a block diagram showing a focus correction circuit in a conventional CRT display device, and FIG. 4 is a voltage waveform diagram of various parts in the conventional focus correction circuit. 1.6... Pulse width adjustment circuit, 2, 3, 7.8...
Integrating circuit, 4, 9... Output circuit, 5, 10... Coupling capacitor, 11... Fly bank transformer, 12...
...CRT, 13... Focus grid. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (3)

[Claims] (1) First and second pulse widths that set the time to the start point of the display area based on the horizontal synchronization signal and vertical synchronization signal, respectively, and set the time to the end point of the display area based on the start point of the display area. an adjustment circuit, means for applying a DC focus voltage to the focus grid of the CRT, and first and second pulse width adjustment circuits that receive the outputs of the first and second pulse width adjustment circuits and apply correction waves corresponding to the display area to the focus grid. A dynamic focus circuit including a second circuit. (2) The first and second circuits each include first and second integrating circuits that receive the output pulses of the first and second pulse width adjustment circuits and convert them into sawtooth voltages, and 2
third and fourth integrator circuits that convert the sawtooth wave voltage output from the integrator circuit into a parabolic voltage correction voltage; 2. The dynamic focus circuit according to claim 1, further comprising first and second output circuits that amplify and apply the amplified signal to the focus grid. (3) The dynamic focus circuit according to claim 2, wherein the third and fourth integration circuits are replaced with first and second multipliers, respectively.