JPH08242389A - Deflection distortion correcting method, distortion correction circuit and cathode-ray tube display device - Google Patents

Abstract

PURPOSE: To provide a distortion correcting method(circuit) to adjust image distortion in the display device of a cathode-ray tube, etc. CONSTITUTION: This method is equipped with a function generation circuit 20 which generates a function x setting screen size, a screen position and a repeat period as parameters synchronizing with a timing signal P, a distortion correction function circuit 21 which multiplies the function x outputted from the circuit by an appropriate coefficient and outputs a distortion correction function g(x), an amplitude variable circuit 22 which varies the amplitude of the distortion correction function circuit, and an addition circuit 23 which superimposes an arbitrary DC component on the output of the amplitude variable circuit. When correction coefficients VLIN, VLIN.BAL are adjusted by the distortion correction function g(x) of the distortion correction function circuit 21, they are always set at a fixed value x at two reference points ±a on a display screen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting image distortion in a display device, such as a cathode ray tube (CRT), which deflects an electron beam to display an image, a circuit therefor, and a display device.

[0002]

2. Description of the Related Art A cathode line for displaying an image by emitting an electron beam from an electron gun provided in a vacuum container and deflecting the track of the electron beam by an externally applied magnetic field or electric field for deflection. Tube display devices are widely used in television receivers, computer monitor devices, and the like. FIG. 6 (a) is a view for explaining a display screen of a display device using such a cathode ray tube and a deflection angle of an electron beam. An electron beam emitted from an electron gun (not shown) is a well-known deflection device ( It is deflected in the vertical and horizontal directions by a deflection coil) and forms a raster on the display surface S, that is, the tube surface of a cathode ray tube (CRT). When the deflection center point of this electron beam is O, the maximum deflection angle in the vertical direction is ± θv, and when the length from the deflection center point O to the display surface S is r, the image size of the display surface is Lv = r · Tan. ±
It can be represented by θv.

Therefore, when the electron beam is deflected vertically and horizontally by the sawtooth deflection magnetic field, the display surface S
A raster as shown in FIG. 6B is displayed on the screen, and an image can be displayed by modulating the electron beam with a video signal. However, since the flight distance of the electron beam reaching the display surface is the longest at the four corners of the screen,
The raster displayed on this tube surface appears distorted as seen in FIG. 6 (b). This distortion also shifts symmetrically between left and right and up and down in terms of focus and convergence.

Such a distortion is a parabolic pincushion distortion (Pincu
shion strain) and linearity strain where the lattice spacing is not constant can be divided. The pincushion distortion is corrected by modulating the amplitude of the deflection waveform with a correction waveform, but the linearity distortion needs to be corrected by modulating the deflection waveform itself with the correction waveform. Become. The vertical linearity distortion and the horizontal pincushion distortion to be corrected by the correction waveform of the vertical cycle will be described below.

FIG. 7 shows the correction of vertical linearity. In this figure, vS is an input signal (television signal),
IS is a sawtooth waveform that serves as a reference in the vertical direction. This saw-tooth wave waveform IS is when the retort race time for returning the electron beam is ideally 0, and it is assumed that the distortion in the horizontal direction is zero. Let θS be the vertical angle of the voltage input to the deflection circuit and the electron beam emitted from the cathode of the CRT, that is, the vertical deflection sensitivity.
The relationship between this angle θS and the vertical position on the screen of the electron beam that strikes the display surface is uniquely determined by the characteristics of the display device. Center point O of angle θS showing the vertical deflection sensitivity
Corresponds to the center point on the screen, the flight distance of the electron beam becomes longer as it goes away from the center point as described above, so that the deflection characteristic of the CRT is considered to have the deflection sensitivity characteristic θV close to that of the TAN. To be

Then, an input signal v of 1 V (1 vertical period)
For example, horizontal positions S1, S2, S3 included in S,
..... S9 will appear on the display screen M1 as shown by the dotted line, and the grid-like raster will be dense in the central part of the screen and the grid spacing will be wide in the vertical direction of the screen. Distortion occurs. Therefore, in the case of a display device using a CRT, the deflection waveform is corrected in advance as shown in the sawtooth wave waveform IC in FIG. 7 as the deflection waveform in the vertical direction, and the electron beam is deflected for one vertical period. Horizontal positions S1 and S included in the (1V) input signal vS
, S3, ..., S9 form a grid at equal intervals as shown on the display screen M2.

If the linearity correction as described above is performed in a form that includes parameters relating to the screen size, screen position, and vertical period that are input to the function circuit that generates the correction waveform, once adjusted, the screen size is adjusted. It is known that the distortion of the display surface does not change even when the screen position and the screen cycle are changed. FIG. 8 shows an example of a circuit for generating a deflection waveform of a display device in such a system.

In this figure, 10 is a timing pulse P of a vertical cycle which is a time reference, a screen size V _SIZE , and a screen position V.
_This is a sawtooth wave generation circuit in which _CENT and vertical period f _V are input as parameters, and its output is a function of time x (t)
And 11 is a function x output from the sawtooth wave generation circuit
(t) (hereinafter, also simply referred to as function x) A screen correction function generation circuit for generating a correction function g (x) for screen distortion correction, and 12 is an output g (x of the screen correction function generation circuit 11 ) Variable amplitude circuit (variable amplifier) to control the amplitude of 1)
Reference numeral 3 designates an adder circuit for superimposing a DC voltage 14 (Vdc) for shifting the screen on the output of the variable amplitude circuit 12, and 15 a deflection circuit for deflecting the electron beam of the CRT, the output (deflection current) of which is the CRT. Will be supplied to the deflection coil. Depending on the system, the variable amplitude circuit 1
In some cases, the adder circuit 13 is omitted.

In such a display device deflection system,
First, based on the parameters (V _SIZE , V _CENT , f _V ) input to or set in the sawtooth wave generation circuit 10, the equation (1) is obtained.
A function x that changes linearly with time t is generated as shown in FIG.

[Equation 1] That is, as shown in FIG. 9, every time a timing pulse P having a vertical cycle is input, a sawtooth wave increasing with time t is output as a function x (t). However, at time t = 0, the function x
(0) is "a _{V CENT -V SIZE], t =} 1 / t V clogging 1V x at the end of (tv) is [V _CENT + V _SIZE].
Also, at time t = t _V / 2, the function x (t) indicates V _CENT, that is, the center position of the screen.

Next, the distortion correction function circuit 11 outputs a function output x
On the other hand, the distortion is corrected by the correction function g (x) as shown in the following equation (2), and the S-shaped sawtooth waveform is generated.

[Equation 2] In the equation (2), the coefficient a3 performs the third-order correction, and the coefficient a2 performs the second-order correction. The coefficient a2 corrects the imbalance in the vertical direction from the screen center as shown by the curve IC2 in FIG. 9, and the coefficient a3 is the same in the vertical direction about the screen center as seen in the curve IC3. Make such a correction. Generally, linearity is almost completely corrected by the third-order correction.

The output corrected by the correction function g (x) is controlled by the next variable amplitude circuit 13 so that only the amplitude is multiplied by V _GAIN , and further, the DC voltage V _{dc is} added by the adder circuit 13.
Are superimposed. Therefore, the output Y of the adder circuit 13 is expressed by the equation (3).

(Equation 3)

When the deflection device is driven by the thus corrected deflection waveform, the deflection characteristic of the CRT has a TAN characteristic. Therefore, when the electron beam lands on the tube surface of the CRT, the actual deflection sensitivity shown in FIG. A linear deflection sensitivity can be obtained as shown by the straight line θC. Then, the sensitivity gradient is changed by θC1 by the amplitude varying circuit 13 described above, and the voltage V superimposed on the adding circuit is changed.
_{Due to dc} , this sensitivity gradient shifts up and down like θC2 to change the size of the screen and the center of the screen. As a result, the horizontal positions S1, S2, S3 of the input signal vS,
The position of S9 can be a grid at equal intervals as shown in the screen M1 of FIG. Also, the DC voltage V _dc
By adjusting, the position of the grid raster can be vertically shifted as shown in the screen M2 of FIG.

[0013]

In the case of such a sawtooth wave correction system, for example, when the setting of the third-order correction coefficient a _{3 in} the distortion correction function circuit 11 is changed, the curve IC3 in FIG. 9 is obtained. As can be seen, the screen size also changes at the same time, and when the distortion is corrected with the quadratic correction coefficient a ₂ , the vertical position of the screen moves as shown by the curve IC2, and the monitor image is entirely changed. It will go up and down.
Therefore, when the linearity distortion correction is actually performed in this system, the following procedure is unavoidable. First, parameters of frequency f _V , screen size V _SIZE , and screen position V _CENT are set. Next, V _GAIN , V _dc , coefficients a3, a
2. Set V _GAIN and V _dc to adjust the screen size and screen position. The coefficients a ₃ and a ₂ are adjusted so as to eliminate the screen distortion. When the screen distortion is reduced by this adjustment, the screen size and the screen position are changed this time. Therefore, V _GAIN and V _dc are adjusted again to adjust the screen position and the size. By this adjustment, the screen distortion deviates from the optimum state, and therefore the screen distortion is taken again by the coefficients a ₃ and a ₂ . Hereinafter, the adjustments of V _GAIN and V _{dc and} the adjustments of a ₃ and a ₂ are repeated several times until the distortion is within the allowable range.

That is, in order to adjust the surface distortion, V _GAIN , V _dc , a ₃ , a ₂ or V _{SI ZE} , V _CENT ,
The problem remains that the distortion cannot be adjusted within the allowable range unless the four parameters a ₃ and a ₂ are tracked. The function g (x) when the adjustment is completed
The range of the value of is different in each display device, and the deflection angle changes depending on the size and variation of the CRT. Therefore, it is difficult to set the dynamic range when designing a circuit, and it can be used effectively. There is a problem that you cannot do it.

[0015]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an appropriate position on the tube surface of a display device, particularly, a device which is vertically or horizontally separated from a center point.
A point is selected as a reference point, and the input and output values of the screen distortion correction function generating means are set corresponding to this reference point.

[0016]

[Function] Since two points separated by an appropriate distance on the screen are used as the reference points for the distortion correction, the amplitude and the screen position of the screen are corrected even when various kinds of correction coefficients and set values are given for the distortion correction. Is almost eliminated, and the distortion is adjusted in a very similar manner.

[0017]

1 is a block diagram for explaining a deflection distortion correction method and a distortion correction circuit thereof according to the present invention. 20 in this figure
As the timing pulses P of the vertical period is a measure of time, and screen size data V _SIZE corresponding to the reference point of the two points of the display screen to be described later, screen position data V _CENT is entered, repeating at the vertical period f _V It is a function generating circuit that generates a large sawtooth wave, and its output is a function x (t). 21
Is a distortion correction function generation circuit for screen correction that generates a function g (x) for screen distortion correction based on the output of the function x (t) output from the function generation circuit 20, and is set on the screen. At the two reference points + a and −a, the output x of the function x (t) is output so as to have a constant value regardless of the screen distortion correction coefficient V _LIN and V _{LIN · BAL} , and the other points are corrected. Coefficient V
A correction function g (x) for image distortion correction that eliminates distortion on the screen by _LIN and V _{LIN BAL} is set.

Reference numeral 22 is a function output of the distortion correction function generating circuit 21.
A variable amplitude circuit (variable amplifier) that controls the amplitude of g (x), 23 is an adder circuit that superimposes a DC voltage (V _dc ) that shifts the screen on the output of the variable amplitude circuit 22, and 24 is a CR
A deflection circuit for deflecting the electron beam of T, comprising:
This output (deflection current) is supplied to the deflection coil 25 of the CRT. In the case of a monitor system in which the display screen is always constant and its size and position are not deflected, the variable amplitude circuit 22 and the adder circuit 23 can be omitted.

Also in the case of the present invention, first, the parameters (V _SIZE , V _CENT ,
f _V ,) to generate a sawtooth wave function x (t) that changes linearly with time, and the parameters V _SIZE and V _CENT of this function x (t) are up and down from the center point of the display screen. This is performed by setting two reference points + a and -a which are separated in the direction. That is, as shown in FIG. 2, the function x (t) output for the video signal v _{S of} 1 V in one vertical period
For example, the first reference point + near the start point of the synchronization signal
a and set a second reference point near the end point of the sync signal −
Set a. Then, when the time t changes, x (t) =
The points to be ± a are the reference points + a, − of the formula (1) and FIG.
Equations (4) and (5) are formed from the time corresponding to a.

[Equation 4]

(Equation 5) However, tSYNC is the vertical blanking period, tFP is the time corresponding to the position of point + a set at the top of the screen,
tBP is the time corresponding to point-a set at the bottom of the screen.

By solving this equation, V _SIZE and V such that the value of the point x corresponding to the top and bottom of the screen becomes ± a
The value of _CENT is _{calculated by} the following equations (6) and (7).

(Equation 6)

(Equation 7) Next, even if the function output g (x) of the distortion correction function generating circuit 21 that corrects the screen distortion adjusts the screen distortion, x (t) = g at the reference points ± a that are always set above and below the screen. In order to set (x), the correction function gC (x) that corrects the basic component x of the deflection that changes linearly with respect to the time t becomes a function that becomes zero at ± a points. If An example of such a function is shown by equation (8).

(Equation 8) In the equation (8), the function gC (x) is always zero when x = ± a.
Therefore, if g (x) is calculated by the sum of the function x (t) that changes linearly with time and such a function gC (x), the function output at x = ± a is always g (x) = ± a As the reference point is set to a point closer to the vertical edge of the display screen, the amplitude of the screen and the position of the screen center do not change due to the distortion correction.

The following expression (9) shows an example of a functional expression satisfying such a condition.

[Equation 9] In this equation, V _LIN is a vertical linearity correction coefficient, and V _{LIN · BAL} is a correction coefficient that balances distortion correction above and below the center point.

FIG. 3 (a) shows a basic sawtooth wave deflection output represented by a function x (t) that linearly changes with time t, and the above-mentioned reference point + a is shown at the top of the screen. Is set, and the reference point -a is set at the bottom of the screen.
The component gC (x) for correcting the distortion when deflected by the output x of such a function is shown by (b) in FIG.

The curve C _{LIN in} FIG. 3 (b) is x in the above equation (9).
· (X ± a) shows the tendency of (x ² -x ± a), the curve C
_{LIN / BAL} shows a tendency of (x + a) (x−a).
3 (c) shows the fundamental wave component X (t) of the sawtooth wave that changes linearly with time (t) and the distortion correction function gc (x) for correction.
The output of the correction function g (x) found in the above equation (9) formed by the sum of the above is shown, and the position is always constant regardless of the correction at the two reference points set at the top and bottom of the screen, Even if distortion correction is performed, the correction waveform IC3 in FIG.
As seen in IC2, the screen amplitude hardly changes.

When the sawtooth waveform corrected by the function output is changed according to the size of the CRT and the display mode of the CRT, the variable amplitude circuit 22 and the addition circuit 23 have predetermined amplitudes and screen positions. Can be adjusted, and this adjustment is done very much. That is, the function output for deflection corrected as shown in FIG. 4 is the gain V of the variable amplitude circuit 22.
_GAIN changes the overall amplitude level as shown by the dotted line and adjusts it so that it matches the monitor screen. Also,
When the direct current voltage V _dc is applied in the adder circuit 23, the function output is shifted in the upper limit direction as shown by the alternate long and short dash line depending on its polarity and magnitude, and the center of the screen can be adjusted to coincide with the center of the raster. The output of the adder circuit 23 is corrected by a deflection circuit (drive circuit) 24 such as pin distortion and supplied to a deflection coil 25. The deflection sensitivity on the tube surface of the CRT is as shown in FIG. Since the reverse S-shaped characteristic is shown in Fig. 4, the output Y of the adder circuit 23 and the position Lv of the beam on the tube surface linearly change as shown in Fig. 4C.

When the distortion correction function as described in the embodiment of the present invention is output, first, the position of the raster image (test image) desired to be input above and below the monitor screen is adjusted to V _GAIN , and Positioning is performed by adjusting V _dc , and then the state of distortion is observed or detected for the raster image that has been adjusted, and linearity correction and balance correction are performed on the V _LIN and V _{LIN · BAL.} Adjust by changing the coefficient of.

Even if the linearity is corrected in this way, the screen position at the reference point ± a does not change, so that it is not necessary to perform tracking as in the conventional case after the adjustment. Although the above embodiments have been described with respect to correction of vertical linearity, the distortion correction system of the present invention can also be applied when adjusting distortion correction related to focus and convergence.

The distortion correction method described above is summarized in the steps shown in FIG.
That is, the vertical frequency period f _V and two reference points ± a on the screen are set, and V _SIZE corresponding to these reference points,
Enter V _CENT as a parameter. Next, since the function x (t) that changes with time is output by this setting, this function x (t) is always a distortion correction function g (x ).

Even if the coefficient of the distortion correction function is changed by this setting, the position of the reference point ± a point set on the screen becomes constant. Therefore, if necessary, depending on the scale and type of the display device. The deflection width and the display position may be set by V _GAIN and V _dc .

Although the above embodiment does not mention the correction of the pincushion distortion, the waveform operation for correcting the pincushion at the same time as the correction of the linearity is performed by, for example, a deflection circuit, or the correction is performed. It goes without saying that the correction of the pincushion distortion may be performed by applying a correction magnetic field to the deflection coil for use.

[0030]

As described above, in the deflection distortion correction method of the present invention, two reference points for correction are provided in the vertical direction of the display surface on which an image is displayed. At this reference point, linearity correction is performed. Since the correction function output that does not change the position of the beam spot is obtained, it is possible to prevent the screen size and the screen center from being displaced due to the linearity correction.

Further, since the size and the position of the display screen do not change due to the correction of the linearity, the distortion correction coefficient can be commonly used for CRTs of various sizes and CRTs having different sensitivity characteristics. That is, the dynamic range of the correction coefficient of the function generation circuit is made common, and the correction circuit can be constructed at low cost.

[Brief description of drawings]

FIG. 1 is a circuit diagram for explaining a distortion correction method of the present invention.

FIG. 2 is an explanatory diagram of a basic function output for deflection.

FIG. 3 is an explanatory diagram when performing distortion correction on a basic function output.

FIG. 4 is an explanatory diagram for adjusting the size and position of the screen of the distortion-corrected output.

FIG. 5 is a flowchart showing a flow of an adjusting method of the present invention.

FIG. 6 is an explanatory diagram showing a distorted image of a raster generated by linear deflection.

FIG. 7 is an explanatory diagram of a function for performing distortion correction and its screen.

FIG. 8 is a diagram showing a circuit configuration for obtaining a deflection-corrected deflection output.

FIG. 9 is an explanatory diagram showing states of graphs and rasters for distortion correction and image position adjustment.

[Explanation of symbols]

 20 Function Generating Circuit 21 Correction Distortion Function Generating Circuit 22 Variable Amplitude Circuit 23 Adder Circuit 24 Deflection Circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirotaka Takekoshi 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (7)

[Claims] 1. Setting two reference points for image distortion adjustment at a position apart from the center of the display screen, and performing distortion correction so that the value of the distortion correction function is always a constant value at the reference points. A deflection distortion correction method characterized by performing. 2. The deflection distortion correction method according to claim 1, wherein the two reference points are set at points equidistant in the vertical direction from the center of the display screen. 3. The distortion correction function is a function x proportional to time.
The deflection distortion correction method according to claim 2, wherein (t) and a higher-order correction function in which the function x (t) is always a constant value at the reference point. 4. A screen size in synchronization with a timing signal,
Function x with screen position and repetition period as parameters
(t) a function generating circuit for generating, and a distortion correcting function circuit for converting a function x (t) output from the function generating circuit with an appropriate correction coefficient and outputting a distortion correcting function g (x). In the distortion correction circuit provided with, the distortion correction function circuit is configured to always obtain a constant correction function g (x) = ± a at two reference points set on the screen. Correction circuit. 5. The distortion correction circuit according to claim 4, wherein the two reference points ± a are set based on vertical positions spaced apart in the vertical direction of the screen. 6. The distortion correction circuit according to claim 4 or 5, wherein the correction function g (x) is set by a functional expression of a third order or higher. 7. A screen size synchronized with a timing signal,
A function generating circuit for generating a function x having a screen position and a repetition period as parameters, and a function x output from the function generating circuit is multiplied by an appropriate correction coefficient to output a distortion correction function g (x). Distortion correction function circuit, amplitude variation circuit that varies the amplitude of the distortion correction function circuit, addition circuit that superimposes an arbitrary DC component on the output of the amplitude variation circuit, and the cathode ray tube is driven by the output of this addition circuit. A cathode ray tube display device, comprising: a deflection device, wherein the distortion correction function g (x) of the distortion correction function circuit is set to always have a constant value at two reference points on a display screen.