JPH1098631A - Corner focus correction waveform generating circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct the focus of each corner of a screen independently M. SOLUTION: The circuit generates respectively a first half signal and a latter half signal of one period in a signal whose level is changed parabolically in this period synchronously with one period of a horizontal deflection synchronizing signal. Furthermore, the circuit generates respectively a first half signal and a latter half signal of one period in a signal whose level is changed parabolically in this period synchronously with one period of a vertical deflection synchronizing signal. The signals are multiplied by multiplier circuits 27-30 respectively and Each level of the multiplication output is adjusted respectively at level adjustment circuits 31-34 depending on an external signal. The signals from the adjustment circuits are added by an adder circuit 21 and the sum signal is used for focus correction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corner focus correction waveform generating circuit, and more particularly to a CRT (Cathode).
(Ray Tube) The present invention relates to a circuit for generating a corner focus correction waveform of a display device.

[0002]

2. Description of the Related Art In recent years, in a display device using a CRT, such as a television receiver, a focus device is used to correct a focus shift of an electron beam due to a difference in deflection distance between a central portion and a peripheral portion of a screen. ing.

The focus shift of the electron beam is such that the focus voltage increases from the center of the screen to the periphery. That is, to perform focus correction,
A voltage proportional to the square of the distance from the center of the raster is required.

Therefore, when attention is paid to the horizontal period, a higher voltage is required toward the horizontal edge of the screen. At this time, since the magnitude of the voltage is proportional to the square of the distance, the waveform has a parabolic shape with a horizontal period. In addition, when focusing on the vertical cycle, a higher voltage is required toward the vertical end of the screen. At this time, since the magnitude of the voltage is proportional to the square of the distance, the waveform has a parabolic shape with a vertical period.

When this focus voltage is viewed in a vertical section and a horizontal section of the screen, both the horizontal and vertical components have parabolic waveforms as shown in FIG. In this case, the horizontal component of the focus voltage is, as shown in FIG.
This is a parabolic waveform in which the signal level changes in a parabolic manner during one period of the horizontal deflection synchronization signal in synchronization with one period. Similarly, the vertical component is a parabolic waveform in which the signal level changes in a parabolic manner during one period of the vertical deflection synchronizing signal, as shown in FIG.

In a conventional focusing device, a parabolic waveform synchronized with the horizontal deflection cycle and a parabolic waveform synchronized with the vertical deflection cycle are divided into a first half waveform and a first half waveform, respectively. Adjusted to voltage level. Then, focus correction is performed using the adjusted waveform.

This conventional focus correction waveform generation circuit will be described with reference to FIG. In FIG. 1, a conventional circuit includes a waveform generation circuit 100 that generates focus correction waveforms 13 to 17 based on a horizontal deflection synchronization signal and a vertical deflection synchronization signal, an addition circuit 21 that adds the waveforms 13 and 14, An addition circuit 22 for adding the waveforms 15 to 17; an amplification circuit 23 for amplifying the addition output 18 of the addition circuit 21 to drive the winding coil of the focus magnet 25; And an amplifier circuit 24 for driving a magnet 26. In this circuit, it is assumed that the display employs the electromagnetic focus. However, in the case of the display employing the electrostatic focus, the focus electrode is driven.

Here, the waveform generating circuit 100 includes a parabolic waveform generating circuit 101 for synchronizing with one cycle of the horizontal deflection synchronizing signal and generating a signal whose signal level changes in a parabolic manner during one cycle, and a vertical deflection synchronizing signal. A parabolic waveform generation circuit 10 which generates a signal whose signal level changes in a parabolic manner during one period in synchronization with one period of the synchronization signal
2 and a switch (S) that performs an on / off operation with a horizontal deflection synchronization signal having a pulse duty ratio (DUTY) of 50% and outputs the first half waveform of the signal of the parabolic waveform generation circuit 101 (S
W) 103 and the parabolic waveform generation circuit 1 which is turned on / off by a horizontal deflection synchronization signal having a pulse duty ratio of 50%.
Switch 10 for outputting the second half waveform of the output signal 01
4, a switch 105 that is turned on / off by a vertical deflection synchronization signal having a pulse duty ratio of 50% and outputs the first half waveform of the output signal of the parabolic waveform generation circuit 102, and is turned on / off by a vertical deflection synchronization signal having a pulse duty ratio of 50%. And a switch 106 for outputting the second half waveform of the output signal of the parabolic waveform generation circuit 102.

That is, the parabolic front waveform of the horizontal deflection cycle is obtained by the on / off operation of the switch 103. In short, the parabolic waveform of the horizontal deflection cycle and a pulse having a duty ratio of 50% of the horizontal deflection cycle are input to the switch 103. The switch 103 is connected only when this pulse is at the front of the horizontal deflection cycle, and a parabolic front waveform of the horizontal deflection cycle is obtained.

Similarly, the switch 104 is connected only when the pulse having a pulse duty ratio of 50% in the horizontal deflection cycle is at the rear of the horizontal deflection cycle, and the parabola rear waveform of the horizontal deflection cycle is obtained. is there. Similarly, when the parabolic front and rear waveforms of the vertical deflection period are generated, the switches 105 and 106 switch the vertical deflection period parabolic waveform to the vertical deflection period pulse duty ratio of 50%.
Is obtained by inputting the following pulse.

The waveform generating circuit 100 adjusts the voltage level of the output of the switch 103 in response to an external signal (not shown) and outputs a waveform 13 and a level adjusting circuit 107 (not shown). A level adjustment circuit 108 that adjusts the voltage level of the output of the switch 104 in accordance with the signal and outputs the waveform 14 and a waveform that adjusts the voltage level of the output of the switch 105 in accordance with an external signal (not shown). 15 and a voltage adjustment circuit 109 for adjusting the voltage level of the output of the switch 106 in response to a signal (not shown) from the outside.
6 and a level adjustment circuit 111 that adjusts the voltage level of the DC voltage according to an external signal (not shown) and outputs a waveform 17.

According to such a configuration, as shown in FIG. 11, the first half of the one cycle of a signal in which the signal level is changed in a parabolic manner during one cycle in synchronization with one cycle of the horizontal deflection pulse. Waveform 1, which is the signal of the second half of the signal, and the first half of the signal of which the signal level is changed in a parabolic manner during one period in synchronization with one period of the vertical deflection pulse. A waveform 3 which is a partial signal and a waveform 4 which is a signal of the same second half are obtained.

Waveforms 13 to 16 are obtained by adjusting the levels of these waveforms 1 to 4. By adding these waveforms for each of the horizontal and vertical components, the correction of the upper half, lower half, left half, and right half of the screen shown in FIGS. 9A and 9B is independent of each other. You can do it.

The correction can be made in the same manner in the circuits described in JP-A-5-268492 and JP-A-57-180272.

[0015]

According to the above-mentioned conventional focus device, the upper half, the lower half, the left half, and the right half of the screen can be corrected independently of each other. However, such a device has a drawback that, for example, even when it is desired to change the correction voltage level only in the upper left portion while keeping the upper right portion of the screen unchanged, this cannot be changed. In other words, there is a drawback that when the front waveform of the parabolic waveform synchronized with the vertical deflection period is changed to correct the upper left portion, the waveform changes to the upper right portion. The circuits described in the above publications have similar disadvantages.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and has as its object the upper left, upper right, lower left and lower right portions of the screen, that is, the focus of each corner can be adjusted independently of each other. An object of the present invention is to provide a corner focus correction waveform generation circuit that can perform correction.

[0017]

A corner focus correction waveform generating circuit according to the present invention is characterized in that one cycle of a signal whose signal level changes in a parabolic manner during one cycle in synchronization with one cycle of a horizontal deflection synchronizing signal. A first signal generating means for respectively generating a first signal which is a first half and a second signal which is a second half of the vertical synchronizing signal; A second signal generating means for respectively generating a third signal which is a first half of the one cycle of the signal changing in a parabolic manner and a fourth signal which is a second half of the one cycle, the first and second signals and Multiplying means for multiplying the third and fourth signals respectively, level adjusting means for adjusting the levels of these multiplied outputs in accordance with external signals,
An adder for adding each of the adjusted signals and the first and second signals is included, and focus correction is performed using the added output.

In the present invention, each of the above-mentioned waveforms is adjusted to an appropriate voltage, and each is added to the waveform output from the conventional waveform generating circuit. By doing so, in addition to the correction by the conventional circuit, the upper left, upper right, lower left and lower right portions of the screen can be corrected independently of each other, and a highly accurate focus can be obtained over the entire screen.

[0019]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a corner focus correction waveform generating circuit according to the present invention, and the same parts as those in FIG. 10 are denoted by the same reference numerals. This circuit differs from the conventional circuit shown in FIG. 10 in that a multiplication circuit 27 for multiplying waveform 1 and waveform 3, a multiplication circuit 28 for multiplying waveform 2 and waveform 3, a waveform 1 and waveform 4 , A multiplication circuit 30 that multiplies the waveform 2 and the waveform 4, a level adjustment circuit 31 that adjusts the voltage level of the waveform 5 that is a multiplication result of the multiplication circuit, and a multiplication result of the multiplication circuit. A level adjustment circuit 32 that adjusts the voltage level of a certain waveform 6, a level adjustment circuit 33 that adjusts the voltage level of a waveform 7 that is a multiplication result of the multiplication circuit, and adjusts a voltage level of a waveform 8 that is a multiplication result of the multiplication circuit And a level adjustment circuit 34 that performs the adjustment. Then, the adjusted waveforms 9 to 12 are added by the adding circuit 21 to the waveforms 13 and 14 output from the waveform generating circuit 100.

The generation of the parabolic front waveform of the horizontal deflection period is constituted by a switch. A parabolic waveform having a horizontal deflection period and a pulse having a duty ratio of 50% are input to this switch. The switch is connected only when this pulse is at the front of the horizontal deflection cycle, and a parabolic front waveform of the horizontal deflection cycle is obtained. Similarly, the pulse duty ratio of the horizontal deflection cycle of 50%
The switch is connected only when this pulse is at the rear of the horizontal deflection period, and a parabolic front waveform of the horizontal deflection period is obtained. Generation of the parabolic front and rear waveforms of the vertical deflection period can be similarly obtained by inputting a parabolic waveform of the vertical deflection period and a pulse having a pulse duty ratio of 50% of the vertical deflection period.

The operation of each section of the circuit having the above configuration will be described with reference to FIG. In FIG.
Are denoted by the same reference numerals.

First, the upper left of the screen is corrected by the multiplication circuit 27.
And the level adjustment circuit 31. In this case, a waveform 1 which is a front waveform of the parabolic waveform synchronized with the horizontal deflection cycle and a waveform 3 which is a front waveform of the parabolic waveform synchronized with the vertical deflection cycle are input to the multiplication circuit 27. The waveform output from the multiplying circuit 27 is a multiplied waveform of the waveform 1 and the waveform 3 like the waveform 5. This waveform is input to the level adjustment circuit 31 to adjust the level, and a waveform 9 is obtained.

The upper right portion of the screen is corrected by a multiplication circuit 28.
And the level adjustment circuit 32. In this case, a waveform 2 which is a rear waveform of the parabolic waveform synchronized with the horizontal deflection cycle and a waveform 3 which is a front waveform of the parabolic waveform synchronized with the vertical deflection cycle are input to the multiplication circuit 28. The waveform output from the multiplication circuit 28 is a multiplication waveform of the waveform 2 and the waveform 3 like the waveform 6. This waveform is input to the level adjustment circuit 32 to adjust the level, and the waveform 10 is obtained.

On the other hand, the lower left portion of the screen is corrected by a multiplication circuit 29.
And the level adjustment circuit 33. In this case, the waveform 1 which is the front waveform of the parabolic waveform synchronized with the horizontal deflection cycle and the waveform 4 which is the rear waveform of the parabolic waveform synchronized with the vertical deflection cycle are input to the multiplication circuit 29. The waveform output from the multiplying circuit 29 is a multiplied waveform of the waveform 1 and the waveform 4 like the waveform 7. This waveform is input to the level adjustment circuit 33 to adjust the level, and the waveform 11 is obtained.

The correction at the lower right of the screen is performed by the multiplication circuit 30.
And the level adjustment circuit 34. In this case, a waveform 2 which is a trailing waveform of the parabolic waveform synchronized with the horizontal deflection cycle and a waveform 4 which is a trailing waveform of the parabolic waveform synchronized with the vertical deflection cycle are input to the multiplication circuit 30. The waveform output from the multiplication circuit 30 is a multiplication waveform of the waveform 2 and the waveform 4 as shown in a waveform 8. This waveform is input to the level adjustment circuit 34 to adjust the level, and the waveform 12 is obtained.

Referring now to FIG. 3, in the conventional circuit,
The upper half, lower half, left half, and right half of the screen are corrected using the horizontal parabolic waveform shown in FIG. 11A and the vertical parabolic waveform shown in FIG. . In this circuit, the waveform 9 shown in FIG.
１２12 is added to perform corner focus.

In short, in the adder 21, all of the waveforms 9, 10, 11, and 12 are converted to the conventional waveform generator 10.
0 is added to the output waveforms 13 and 14, and the added output 18
Is amplified by the amplifier circuit 23. Then, the winding coil of the focus magnet 25 is driven by the amplified output.

Thus, in addition to the conventional correction, the upper left, upper right, lower left and lower right portions of the screen can be corrected independently of each other. Therefore, highly accurate focusing can be performed over the entire screen.

Here, an example of the internal configuration of each of the level adjustment circuits 31 to 34 will be described with reference to FIG. As shown in the figure, the level adjustment circuit includes a ladder resistance circuit R composed of ladder resistors connected in multiple stages and bipolar transistors provided in each stage, and a ladder resistance circuit R corresponding to each stage of the ladder resistance circuit R. A plurality of switches 303 provided for controlling a connection state of a ladder resistor of a corresponding stage, a switch controller 302 for turning on / off each switch 303 according to a digital signal D input from the outside, an operational amplifier 300 of an input stage, An output stage operational amplifier 301 is included.

In such a configuration, the LSB (least significant Bi) of the digital signal D
t) to MSB (Most Significant)
By changing the value up to Bit), the switch corresponding to each bit is turned on or off.

On the other hand, a current corresponding to the input voltage level to the inverting input terminal of the operational amplifier 300 flows through each transistor. Then, a current having a value corresponding to the on / off state of the switch 303 is input to the operational amplifier 301. As a result, the operational amplifier 301 derives a waveform in which the voltage level of the input waveform is adjusted. That is, this level adjustment circuit operates as an electronic attenuator that performs an attenuating operation of each multiplied output. It is assumed that the digital signal D is input by a manual operation of an adjuster.

Next, an example of the internal configuration of the adding circuit 21 will be described with reference to FIG. As shown in the figure,
The adder circuit 21 is a well-known inverting adder circuit that includes an operational amplifier 210 and includes a feedback resistor, an input resistor, and the like. An input resistor 211 is connected to the inverting input terminal of the operational amplifier 210.
Are connected, and the above-mentioned waveforms 9 to 14 are input through the input resistor, whereby an output waveform obtained by adding these is obtained.

That is, as shown in FIG. 6, the adder circuit 21 generates the waveforms 13 and 14 of the conventional circuit.
To the waveforms 9 to 12. Therefore, this addition circuit 2
1 provides an addition output 18 shown in FIG.
Then, the added output 18 is amplified by the amplifier circuit 23, and the winding coil of the focus magnet 25 is driven.

Here, the effect of the correction by the present circuit will be described with reference to FIGS. For the sake of simplicity, if the number of scanning lines in one screen is 10, the voltage distribution over the entire screen is as shown by a waveform H0 shown in FIG. That is, the vertical cycle V is the horizontal cycle H in FIG.
10 times of Also, odd numbers are assigned to the first half of the horizontal period H, and even numbers are assigned to the second half.

Here, the waveform H shown in FIG.
Each part of 0 corresponds to the same reference numeral of each part shown on the screen of FIG. Therefore, when it is desired to change the correction amount only for the upper left of the screen, the portions 1, 3, 5, 7
It is only necessary to change the waveforms of the portions corresponding to (9) and (9). When it is desired to change the correction amount only at the upper right of the screen, only the waveforms of the portions corresponding to portions 2, 4, 6, 8, and 10 need to be changed. When it is desired to change the correction amount only at the lower left of the screen, portions 11, 13, 15, 17, and 19
It is only necessary to change only the waveform of the portion corresponding to. To change the correction amount only for the lower right part of the screen,
Only the waveforms of the portions corresponding to 16, 18, and 20 need to be changed.

If it is desired to increase the correction amount for the upper left corner, the waveform H shown in FIG.
Just add 1. Conversely, when it is desired to reduce the correction amount, the waveform H2 shown in FIG.

Therefore, when it is desired to increase the correction amount for the upper left corner, a waveform H3 obtained by adding the waveform H1 to the original waveform H0 is applied as shown in FIG. You just have to do it. Conversely, if you want to reduce the amount of correction for the upper left corner,
As shown in FIG. 13C, a waveform H4 obtained by adding the waveform H2 to the original waveform H0 may be applied.

In addition, the correction amount can be similarly changed for each of the upper left corner, the lower right corner, and the upper right corner.

In the above embodiment, the case where the required multiplied waveforms are obtained using the parabolic waveform generating circuit, the parabolic front waveform generating circuit, the parabolic rear waveform generating circuit, and the multiplying circuit has been described. Alternatively, it may be generated using other means such as a digital arithmetic processing circuit.

As described above, the first half and the second half of the parabolic signal synchronized with the horizontal deflection synchronizing signal and the first half of the parabolic signal synchronized with the vertical deflection synchronizing signal are multiplied, and then the level is adjusted. Then, by adding each signal after this adjustment to the output of the conventional correction circuit, focus correction of the upper left, upper right, lower left and lower right portions of the screen can be performed independently of each other without affecting other portions. It is. As a result, optimal focus control can be performed over the entire screen, and highly accurate focus can be obtained over the entire screen.

The present invention can further take the following aspects in connection with the description of the claims.

(4) The level adjusting means according to any one of claims 1 to 3, wherein the level adjusting means is an electronic attenuator for performing an attenuating operation of the multiplied output according to a digital signal inputted from the outside. Corner focus correction waveform generation circuit.

(5) The corner focus correction waveform generating circuit according to any one of claims 1 to 4, wherein said adding circuit is an inverting adding circuit constituted by an operational amplifier.

[0045]

As described above, according to the present invention, the first half and the second half of the parabolic signal synchronized with the horizontal deflection synchronization signal and the first half of the parabolic signal synchronized with the vertical deflection synchronization signal are multiplied, respectively. After adjusting the level and adding each signal after this adjustment to the output of the conventional correction circuit, the focus correction at the upper left, upper right, lower left and lower right of the screen is not affected by other parts. There is an effect that they can be performed independently of each other. Thereby, it is possible to perform optimal focus control over the entire screen, and there is an effect that a highly accurate focus can be obtained over the entire screen.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a corner focus correction waveform generation circuit according to an embodiment of the present invention.

FIG. 2 is a waveform chart showing an operation of the corner focus correction waveform generation circuit of FIG.

3A and 3B are diagrams showing a focus voltage waveform, and FIG. 3C is a diagram showing a corner focus voltage waveform.

FIG. 4 is a diagram showing an example of the internal configuration of each level adjustment circuit in FIG. 1;

FIG. 5 is a diagram illustrating an example of an internal configuration of an adding circuit in FIG. 1;

FIG. 6 is a diagram illustrating the operation of the addition circuit.

7A is a diagram showing waveforms corresponding to each part of the screen, and FIG. 7B is a diagram showing positions on the screen corresponding to each waveform of FIG.

FIGS. 8A to 8C are diagrams illustrating the principle of corner focus correction.

FIGS. 9A and 9B are diagrams showing focus voltage waveforms.

FIG. 10 is a block diagram showing a configuration of a conventional corner focus correction waveform generation circuit.

11 is a waveform chart showing an operation of the corner focus correction waveform generation circuit of FIG.

[Explanation of symbols]

 21, 22 Addition circuit 23, 24 Amplification circuit 25, 26 Focus magnet 27-30 Multiplication circuit 31-34 Level adjustment circuit 100 Waveform generation circuit

Claims (3)

[Claims] 1. A first signal which is a first half of the one cycle of a signal whose signal level changes in a parabolic manner during one cycle in synchronization with one cycle of a horizontal deflection synchronization signal, and a first signal which is a latter half of the one cycle. A first signal generating means for respectively generating two signals, and one of the signals whose signal level changes in a parabolic manner during the one cycle of the vertical deflection synchronization signal during the one cycle.
A second signal generating means for respectively generating a third signal which is a first half of the cycle and a fourth signal which is a second half of the cycle, the first and second signals and the third and fourth signals being A multiplying means for multiplying each of the signals, a level adjusting means for adjusting the level of the multiplied output in accordance with an external signal, and an adding means for adding each of the adjusted signals and the first and second signals. And a focus correction using the added output. 2. The corner focus correction waveform generating circuit according to claim 1, wherein said adding means adjusts the levels of said first and second signals in accordance with an external signal and then adds them. 3. The apparatus according to claim 1, wherein the first and second signal generating means generate a parabolic signal whose signal level changes in a parabolic manner during one cycle of the horizontal deflection synchronizing signal in synchronization with the one cycle. A first switching means which receives the generated parabola signal as an input and turns on only during the first half of one cycle of the horizontal deflection synchronization signal; and a second half of the one cycle of the horizontal deflection synchronization signal which receives the parabola signal as input. 3. The corner focus correction waveform generating circuit according to claim 1, further comprising: a second switching unit that is turned on only at the second switching unit.