JPH03291089A - Method for generating digital convergence correction data - Google Patents

Abstract

PURPOSE:To generate an efficient correction data by using a grating point on a pattern as a convergence adjustment point and implementing the correction to a convergence correction data according to a linear function having a prescribed parameter. CONSTITUTION:A grating point on a pattern of a TV or the like is used as a convergence adjustment point and the convergence is adjusted by a prescribed quantity to the picture toward the optimum state via a CPU while observing the pattern. After a 1st adjustment, When the convergence correction data at a pattern position between the convergence adjustment point and the adjustment point is subject to interpolation calculation, the data is calculated according to the Lagrange's interpolation formula being a (n-1)th order function having adjustment of n-set of adjustment points on a horizontal or vertical line on the pattern as parameters, then the density modulation is suppressed and the accuracy of correction is enhanced to reduce the adjustment point number and the correction data is generated efficiently in a short time.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to convergence correction on a cathode ray tube screen of a color television receiver, etc., and more specifically, the screen is divided into a plurality of sections and each Obtaining convergence correction data at the adjustment point for each section,
Furthermore, it relates to a digital convergence correction data creation method that makes it possible to increase the precision of the convergence correction data obtained and shorten the adjustment time required to obtain the convergence correction data when obtaining convergence correction data other than adjustment points by interpolation calculation. It is.

[Conventional technology]

Generally, color television receivers have red and green.

An image is created by combining three blue light beams on a phosphor screen or a projected screen, but accurate alignment of these three color light beams, that is, convergence adjustment, determines the image quality. This is a contributing factor.

Conventionally, this has been done by creating a correction waveform synchronized with the horizontal and vertical scanning periods and adjusting this waveform. However, this method tends to have large convergence defects at the periphery of the screen, and requires skill to adjust. Therefore, in order to perform convergence adjustment with higher precision, a method of digitally creating a convergence correction waveform has been proposed.

First, digital convergence correction will be explained using FIGS. 2 and 3.

FIG. 3 is a pro-rough diagram showing an outline of a correction device that creates required digital convergence correction data and performs digital convergence correction using this data.

In the figure, 34 is a memory for storing the created convergence correction data, 31 is a central processing unit (CPU) for creating the convergence correction data to be stored in the memory, and 32 is a CPU for creating the convergence correction data. An instruction device 33 is a memory 34 for instructing the CPU 31 when an operator looks at the image of the adjustment point on the screen and performs image adjustment to obtain more accurate adjustment data. 35 is a D/A converter (D/A) that converts the adjustment data read from the memory 34 into digital/analog; 36 is a D/A converter; 35 is a low-pass filter (LPF) to smooth the output, 37 is a voltage-to-current conversion amplifier (AMP), and 3B is a convergence yoke (CY) for convergence correction attached to the cathode ray tube neck.

FIG. 2 is an explanatory diagram showing the selected matrix on the cathode ray tube screen. In the figure, the lattice points on the matrix are used as convergence adjustment points, and 1: the iron has 7 points in the horizontal direction and 9 points in the vertical direction.

The operation of the circuit shown in FIG. 3 will be explained.

The worker operates the CPU 31 using the instruction device 32 while looking at the images at the adjustment points in FIG. Obtain correction data. The obtained convergence correction data is then stored in the memory 34 as digital data. The convergence correction data stored in the memory 34 is read out by the address counter 33 synchronized with the scanning of the screen, this digital data is converted into an analog waveform by the D/A converter 35, and after being smoothed by the LPF 36, the AMP 37
is used to drive the convergence yoke CY3B to perform convergence correction.

By the way, regarding the horizontal direction, as mentioned above, by reading out the correction data stored in the memory 34 with the address counter 33 and passing it through the D/A converter 35 and LPF 36,
A waveform based on discrete correction data was used as a continuous convergence correction waveform.

However, while it was possible to interpolate in the horizontal direction using the LPF36, the vertical direction of the screen is a collection of horizontal scanning lines, that is, a collection of discrete data, so interpolation using the analog circuit described above is not possible. .

Therefore, for any position between adjustment points along the vertical direction, convergence correction data is calculated by digital interpolation using the given convergence correction data at each adjustment point, and the convergence correction data is used as is. ing.

As described in Japanese Patent Publication No. 5,616,9985, the conventional method of obtaining digital convergence correction data by interpolation is to connect the adjustment points with a straight line and extract the convergence correction data along the straight line. A linear interpolation operation was used.

Linear interpolation is the simplest of the interpolation methods.

In other words, it can be said that this is a calculation method that linearly approximates adjacent adjustment points.

Furthermore, the linear interpolation calculation will be explained in detail with reference to FIGS. 2 and 4.

In FIG. 2, the horizontal coordinate position is X, and the vertical coordinate position is Y. Now, in the vertical direction, it is assumed that the adjustment points are equally spaced every two horizontal scanning lines, and in particular, the coordinates of the adjustment points are assumed to be X for the horizontal direction and Y for the vertical coordinate.

Here, Y, l = n*z...
・ (1) However, * indicates multiplication, n=o, 1, 2
It is ゜3,...

Convergence correction data f(X, Y) at arbitrary position coordinates (X, Y) by linear interpolation is calculated using the following formula (%) ) (2) However, YIl< Y < Y-1 Figure 4 (a), (b ) and (c) are graphs showing the relationship between the screen vertical position and the vertical convergence correction data, respectively. The horizontal axis in the graph corresponds to the vertical position of the screen, and the vertical axis represents vertical convergence correction data at each vertical position.

It is assumed that the line (waveform) shown in FIG. 4(a) is the originally desired convergence correction waveform. The line shown in FIG. 4(b) is the convergence correction waveform obtained by linear interpolation calculation. Figure 4 (C) shows the lines (a) and (b) being the same.
This is shown in the figure.

The waveform shown in FIG. 4(b) takes the form of a line graph with no continuity, and so-called density modulation of the scanning lines occurs on the cathode ray tube screen. That is, the spacing between scanning lines becomes coarser and finer, and bright horizontal stripes appear on the screen where the spacing is denser, and dark horizontal stripes appear on the screen where the spacing is coarser, degrading the image quality.

In other words, although linear interpolation calculations are easy to perform, as the amount of correction increases, the range surrounded by the two lines shown in FIG. 4(C), that is, the correction error increases.

In order to solve this problem, conventional methods have been used in conjunction with analog convergence to reduce the amount of correction in digital processing and increase quantization accuracy.

[Problem to be solved by the invention]

However, the above method has problems such as increased cost due to increased circuit scale, increased adjustment time required to obtain convergence correction data and perform correction, and difficulty in automatic adjustment.

An object of the present invention is to solve the above-mentioned problems, and to suppress density modulation caused by conventional interpolation calculations, reduce the number of adjustment points, and make it possible to perform adjustment efficiently in a digital convergence correction device. An object of the present invention is to provide a method for creating digital convergence correction data.

[Means to solve the problem]

In order to achieve the above object, the present invention uses the following means.

Instead of using the conventional linear interpolation formula as the interpolation calculation formula, we use a curve that passes through all adjustment points and closely matches the original correction curve shown in Figure 4(a), that is, Y=aX' Interpolate by +bX"+cX"-" + --.-.

However, if the above formula is used as is, first the coefficients a, b, c-0, and then Xn, Xn-IX''-
”... must be found, which makes the calculations complicated.

Therefore, we use Lagranche's interpolation formula, which allows the above equation to be easily obtained.

Lagrange's interpolation formula (Lagrange's 1
(interpolation formula) will be explained.

Now, if Y=f(X), then X is Xo.

When taking Xly...

f (X) = a o (X) ・f (Xo) + a
+(X) −f (XI)+ −・・−・・+ a ,
t(X) ・f (X, l) However, ao(X) = (X-XI) (X-Xri ・ ・(X-
X, )/(xo-x,)/(Xo-xz)/・・/(
Xn-Xn)at(X)=(XXo)(X-Xz)
...(X X1l)/(x, -Xn)/(X l
-xz)/.../(XI-X, 1)a, I(X)"(X
-Xo)(X-XI) --(X-X,,-0)/(
X−Xo)/(Xrl XI)/ ・ ・/(X, l
(3) The suitability of Lagranche interpolation as a digital convergence correction data interpolation calculation method can be explained as follows.

(b) It is easy to calculate and can be calculated in a short time.

aO+al+...Jan is a constant and can be determined in advance. Therefore, the interpolation calculation formula is only n
By multiplying times and adding (n-1) times, f at any point
(X) can be found.

Although it is possible to perform interpolation calculations with higher-order functions using formulas other than Lagranche interpolation, in general, increasing the order requires more time to calculate, so this method is superior in terms of ease of calculation as described above.

(b) Xo l XI 1... in the above formula can be set freely.

This means that the adjustment point interval can be freely set. The advantage of this is that, in general, the convergence shift is thicker (and the distortion is also larger) at the periphery of the screen than at the center of the screen. Therefore, the distribution density of adjustment points is set to be denser in areas with large distortion, and denser in areas with large distortion. This is because if the parts are made sparse, it becomes possible to perform interpolation with higher precision.

Lagranche interpolation has a relatively simple formula, but compared to linear interpolation, the calculation speed inevitably increases. Therefore, in order to reduce the increase in calculation speed during adjustment when creating and finding convergence correction data, workers look at the image of the adjustment point on the screen and perform image adjustment to find more accurate adjustment data. indicator 32 to
Therefore, when instructing the CPU 31, linear interpolation calculation (interpolation calculation with high calculation speed) is used for interpolation calculation of the screen position between adjustment points, and this is the last adjustment at the time of final adjustment. Lagranche interpolation calculation (interpolation calculation with slow calculation speed) is used to interpolate the screen position between the point and the adjustment point.
The method of applying

Furthermore, not only the vertical direction but also the horizontal direction interpolation, which was previously only interpolated by the LPF 36, is combined with interpolation using a higher-order function to reduce the number of adjustment points.

[Operation] Lagranche's interpolation formula interpolates using a high-order function, so it produces a waveform that is smooth and close to the original convergence correction waveform shown in Figure 4 (a), that is, with less interpolation error. can get.

Accordingly, even if the number of adjustment points is reduced, the density modulation that has conventionally been observed can be suppressed.

Furthermore, by using linear interpolation and Lagranche interpolation in combination, the same result can be obtained while suppressing the increase in calculation time that would occur when using only Lagranche interpolation.

〔Example〕

A first embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3.

FIG. 1 is a flowchart showing an embodiment of the convergence correction data creation method according to the present invention.

First, how to use Lagranche's interpolation formula for interpolation calculations for digital convergence will be explained using FIG. 2.

We now focus on vertical interpolation. Assuming that the adjustment points are equally spaced between every two scanning lines, the value of convergence correction data at the adjustment point coordinates (X, Y) is f(X, Y), and when applied to the above equation (3), the following is obtained. It becomes like this.

f(X,Y)""a, (Y) ・f(X,Yo)+a
+ (Y) ・f (X, Yg) + a z (Y)
-f (X, Yi) + as (Y)・f (X, Ya) + a 4 (Y) ・f (X, Ys) However, a o (Y)” (Y-YZ) (Y-Yi) ( Y-Yi)
(Y-Ys)/(y,-Yz)/(Yo-Y,)/(Y
o-Yi)/(Yo-Yg)a +(Y)=(Y-Y,
)(Y-Y,)(Y-Yi)(Y-Yl)/(yz-Y
O)/(YZ-Yi)/(YZ-Yri/(Y, -ys)
a x(Y)=(Y-YO)(Y-Yri(Y-Yi)(
Y-Yll)/(Yi-Y,))/(Y,-yz)/(
y4-Yi)/(Y,-ys)a z(Y)=(Y-Y
o) (Y-YZ) (Y-Yi) (Y-Yl)/(Yi-
YO)/(Y, -Yi)/(Y, -Yi)/(Y, -Yl
)a 4(Y)”(Y-YO)(Y-Yz)(Y-Yi
)(Y-Yi)/(Yl-Y,)/(Yl-Yri/(Y
l-Yi)/(Yl-Y Ridashi Yo"'0.Yz=
2 z, Y4=4 z.

Yi-6z, Ys=8Z・
・・・・・・ (4) Any point (
Interpolation can be performed using a quartic function of X, Y).

Also, regarding the horizontal direction, f(X, Y)=b, (X)・f(X,,Y)+b,
(X) −f (X,, Y) 10bz(X)・f(X4
．． Y) + b 1(X)・f(Xi, Y) However, bo(X)=(X−Xri(X−X,)(χ−X,)/(
XO-Xri/(XO-X4)/(XO-Xi)b, (X
)=(XX,)(XX,)(XX,)(XX,
)/(Xt Xo)/(Xi X4)/(Xi-χ
,)b,(X)=(X-X,)(X-XZ)(X-X,
)/(X4-χ.)/(X4-X,)/(X,-Xi)
b3(X)=(X-XO)(X-X,)(X-X4)/
(X, -X,)/(X, -X,)/(Xi-X4) where χ. =O,XZ=2. X4=4. X1=6...
...The formula (5) holds true, and similarly to vertical interpolation, any point (
Interpolation can be performed using a cubic function of X, Y).

a o(y), a + (Y), a! (YL a 5
(Y), a4(y).

b o(X), b +(X), b z(X), b
5(X) is f(X.

Y) In other words, since it is unrelated to the convergence correction data value, it is determined in advance and stored in the memory.

Next, the flow of creating convergence correction data will be explained using FIG.

First, the adjuster (worker) determines which adjustment point to adjust on the screen, and selects the desired adjustment point.

From now on, the process shown in FIG. 1 begins. Initially, the CPU 31 in FIG. 3 is in a state of waiting for input from the instruction device (keyboard) 32.

(1-■) Next, the adjuster looks at the screen and determines what kind of adjustment should be made to the adjustment points, and uses the keyboard 32 to make the adjustment to the CPU 31.
Instruct the person to make adjustments.

The CPU 31 adjusts the convergence state of the adjustment points on the screen in accordance with instructions from the keyboard 32, and obtains adjustment point data at that stage. (1-■) The CPU 31 uses the convergence correction data of the adjustment point just obtained to create convergence correction data of the screen position other than the adjustment point by Lagranche interpolation. (knee ■) When the Lagranche interpolation is completed, the process returns to the state (1-■) waiting for input from the keyboard 32.

The adjuster looks at the convergence state of the adjustment points on the screen, and if the convergence state is still insufficient, he or she operates the keyboard 32 to repeat the above-described operation flow, and if the convergence state is determined to be sufficient, the adjustment ends.

According to this embodiment, (a) convergence correction data interpolation calculation using a high-order function becomes possible, so density modulation caused by interpolation errors can be reduced.

(b) Simple to calculate, only 5 for vertical interpolation
Convergence correction data at an arbitrary position can be created by four multiplications and four additions, and four multiplications and three additions during horizontal interpolation.

(C) The distribution arrangement of adjustment points on the screen can be freely set.

(d) The number of adjustment points can be reduced and the time required for adjustment can be shortened.

Next, a second embodiment will be explained using FIGS. 3 and 5.

The digital convergence correction data creation method in this embodiment uses Lagranche interpolation as in the first embodiment. However, we have devised ways to reduce the increased calculation time due to the adoption of Lagranche interpolation.
This point is different from the first embodiment shown in FIG.

FIG. 5 is a flowchart showing the flow of operations for creating convergence correction data in this embodiment.

The adjuster determines which adjustment point to correct on the screen,
Select the desired adjustment point.

From now on, the process shown in FIG. 5 begins.

Initially, the CPU 31 in FIG. 3 is in a state of waiting for input from the instruction device (keyboard) 32. (5-
■) Next, the adjuster looks at the screen and decides what kind of adjustment should be made to the adjustment points, and uses the keyboard 32 to make the adjustment to the CPU 31.
instruct adjustment.

The CPU 31 adjusts the convergence state of the adjustment points on the screen in accordance with instructions from the keyboard 32, and obtains adjustment point data at that stage. (5-■) Using the convergence correction data of the adjustment point just obtained, the CPU 31 first creates convergence correction data of the screen position other than the adjustment point by linear interpolation. (l-■) When linear interpolation is completed, Lagranche interpolation is applied,
The convergence correction data for screen positions other than the adjustment points is re-interpolated, but during this Lagranche interpolation calculation, the adjuster looks at the convergence status of the adjustment points on the screen and determines that it is still insufficient. If an input is received from the keyboard 32 by further operating the keyboard 32, the Lagranche interpolation calculation is immediately interrupted and the process returns to step 5-2 instructed by the adjuster. (1-■) The adjuster looks at the convergence status of the adjustment points on the screen,
If the instruction is not sent from the keyboard 32 because it is judged as sufficient, execute Lagranche interpolation to the end and obtain highly accurate convergence correction data of screen value 1 other than the adjustment point, then the keyboard 32 Return to the input waiting state (5-■).

According to this embodiment, Lagranche interpolation, which has little interpolation error but takes some time to calculate, can be used in combination with linear interpolation as if it were high-speed interpolation.

〔Effect of the invention〕

According to the present invention, by realizing high-speed interpolation using a high-order function, density modulation caused by convergence correction errors is suppressed, and convergence correction accuracy is improved, the number of adjustment points is accordingly reduced, and convergence correction time is improved by improving usability. It is possible to measure the shortening of

[Brief explanation of drawings]

FIG. 1 is a flowchart showing a convergence correction data creation method as an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing convergence correction adjustment points arranged on a cathode ray tube screen.
Fig. 3 is a block diagram showing the configuration of the digital convergence correction device, Fig. 4 (a), (b), and (c) are graphs showing the relationship between the screen vertical position and convergence correction data, and Fig. 5 is a diagram showing the configuration of the digital convergence correction device. 7 is a flowchart showing a convergence correction data creation method as another embodiment of the invention. Explanation of symbols 31...CPU, 32...Instruction device (keyboard)
, 33...Address counter, 34...Memory, 3
5...D/A converter, 36...LPF, 37...
AMP, 38...Convergence yoke CY

Claims (1)

[Claims] 1. A first step in which a grid point on the screen is used as a convergence adjustment point, and while viewing the initial image at the adjustment point, the convergence is adjusted by a certain amount toward an optimal state; a second step of calculating convergence correction data at a screen position between the convergence adjustment points by interpolation calculation from the certain amount of adjustment data at the adjustment points; and repeating the first and second steps. By doing this, the adjustment amount required for the image at the convergence adjustment point to reach the optimum state from the initial state is obtained as the final adjustment data at the convergence adjustment point, and the adjustment amount at the screen position between the convergence adjustment point and the adjustment point is obtained. a third step of obtaining final convergence correction data corresponding to the final adjustment data; in the second step, convergence correction is performed at a screen position between the convergence adjustment points; When calculating data by interpolation calculation, the interpolation calculation is performed according to an (n-1) order function having adjustment data of n adjustment points on a horizontal or vertical straight line taken on the screen as parameters. A method for creating digital convergence correction data (where n is any integer). 2. A first step in which a grid point on the screen is set as a convergence adjustment point, and while looking at the initial image at the adjustment point, the convergence is adjusted by a certain amount toward the optimum state of the image, and the convergence is adjusted by a certain amount at the convergence adjustment point. a second step of calculating convergence correction data at a screen position between the convergence adjustment points by interpolation calculation from the adjustment data; and repeating the first and second steps to calculate the convergence adjustment point. The adjustment amount required for the image to reach the optimum state from the initial state is obtained as the final adjustment data at the convergence adjustment point, and the adjustment amount corresponding to the adjustment point final adjustment data at the screen position between the convergence adjustment point and the adjustment point is obtained. and a third step of obtaining final convergence correction data, wherein in the second step, convergence correction data at screen positions between convergence adjustment points is calculated by interpolation calculation. When obtaining the final convergence correction data at the screen position between the adjustment points in the third step, the convergence correction data is calculated by linear interpolation using the adjustment data of both adjustment points. A method for creating digital convergence correction data, characterized in that the data is obtained by performing an interpolation operation according to an (n-1) order function having adjustment data of n adjustment points on a horizontal or vertical straight line taken as parameters (however, n is any integer).