JP3029439B2 - Digital convergence correction data creation method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to convergence correction in a cathode ray tube screen of a color television receiver or the like. More specifically, the present invention relates to a screen divided into a plurality of sections, When obtaining the convergence correction data at the adjustment points for each section and obtaining the convergence correction data other than the adjustment points by interpolation, the accuracy of the obtained convergence correction data and the adjustment time required to obtain the convergence correction data are reduced. The present invention relates to a digital convergence correction data generation method capable of shortening.

[Conventional technology]

Generally, in a color television receiver, an image is created by synthesizing light beams of three colors of red, green and blue on a phosphor screen or on a projected screen. That is, the convergence adjustment is a factor that affects the image quality.

Conventionally, a correction waveform synchronized with the horizontal and vertical scanning periods has been created and adjusted. However, in this method, the convergence defect in the peripheral portion of the screen tends to increase, and the adjustment requires skill. In order to perform convergence adjustment with higher accuracy, a method of digitally creating a convergence correction waveform has been proposed.

First, digital convergence correction will be described with reference to FIG. 2 and FIG.

FIG. 3 is a block diagram showing an outline of a correction device for creating required digital convergence correction data and performing digital convergence correction using the 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, 32 is a memory for creating the convergence correction data. When an operator looks at the image of the adjustment point on the screen and adjusts the image in order to obtain higher-precision adjustment data, a pointing device such as a keyboard for instructing the CPU 31 to that effect, and 33 is a memory 34 An address counter for generating an address for writing or reading adjustment data to the memory; 35, a D / A converter (D / A) for digital / analog conversion of the adjustment data read from the memory 34; 36, D / A
A low-pass filter (LPF) for smoothing the output of the converter 35, a voltage-current conversion amplifier (AMP) 37, and a convergence yoke (CY) 38 for convergence correction attached to a cathode ray tube neck or the like. .

FIG. 2 is an explanatory diagram showing a matrix selected on a cathode ray tube screen. In the figure, lattice points on the matrix are convergence adjustment points, where seven points are taken in the horizontal direction and nine points are taken in the vertical direction.

 The circuit operation of FIG. 3 will be described.

The worker looks at the image at the adjustment point in FIG.
The CPU 31 is operated by the pointing device 32 so as to obtain an optimal state of convergence, and this is repeated by trial and error to obtain convergence correction data at each adjustment point. The obtained convergence correction data is stored in the memory 34 as digital data. The convergence correction data stored in the memory 34 is read by an address counter 33 synchronized with the scanning of the screen, and this digital data is converted into an analog waveform by a D / A converter 35, and the LPF 36
Then, the convergence correction is performed by driving the convergence yoke CY38 using the AMP37.

In the horizontal direction, the correction data stored in the memory 34 is read out by the address counter 33 as described above, and is passed through the D / A converter 35 and the LPF 36, whereby the waveform of the discrete correction data is continuously output. Convergence correction waveform.

However, while the horizontal direction can be interpolated by the LPF 36, the vertical direction of the screen is a set of horizontal scanning lines, that is, a set of discrete data, so the interpolation by the analog circuit as described above cannot be performed. .

Therefore, at an arbitrary position between the adjustment points along the vertical direction, convergence correction data is obtained by digital interpolation using given convergence correction data at each adjustment point, and is used as it is. ing.

As a conventional method of obtaining digital convergence correction data by interpolation, as described in Japanese Patent Publication No. 56-16985, an adjustment point is connected by one straight line, and convergence correction is performed along the straight line. A linear interpolation operation to find the data was used.

The linear interpolation calculation is the simplest interpolation method. That is, it can be said that this is a calculation method of linearly approximating between adjacent adjustment points.

2 and FIG.
This will be described with reference to the drawings.

In FIG. 2, the horizontal coordinate position is X, and the vertical coordinate position is Y. In the vertical direction, it is assumed that the adjustment points are at equal intervals for every z horizontal scanning lines, and in particular, the coordinates of the adjustment points are X in the horizontal direction and Y in the vertical direction.

Here, Y _n = n * z (1) where * represents multiplication and n = 0, 1, 2, 3,....

Convergence correction data f (X, Y) at arbitrary position coordinates (X, Y) by linear interpolation is expressed by the following equation.

f (X, Y) = { f (X, Y n + 1) -f (X, Y n)} * (Y-Y n) / z + f (X, Y n) ...... (2) provided that Y _n < Y <Y _{n + 1} FIGS. 4 (a), (b) and (c) are graphs each showing the relationship between the screen vertical direction position and the vertical convergence correction data. The horizontal axis in the graph corresponds to the vertical position of the screen, and the vertical axis indicates the convergence correction data in the vertical direction at each vertical position.

It is assumed that the line (waveform) shown in FIG. 4A is an originally desired convergence correction waveform. The line shown in FIG. 4 (b) is the convergence correction waveform obtained by performing the linear interpolation operation. FIG. 4 (c) shows the lines (a) and (b) in the same figure.

The waveform shown in FIG. 4 (b) has a shape like a line graph without continuity, and so-called density modulation of scanning lines occurs on a cathode ray tube screen. In other words, the scanning line intervals become coarse and dense, and the dense portions appear on the screen as bright horizontal stripes, and the rough portions appear as dark horizontal stripes on the screen, deteriorating the image quality. That is, the linear interpolation calculation is easy to perform, but when the correction amount increases, the range surrounded by the two lines shown in FIG. 4C, that is, the correction error increases.

Conventionally, in order to solve this problem, a method has been adopted in which the amount of correction in digital processing is reduced to increase the quantization accuracy by using the analog convergence together.

[Problems to be solved by the invention]

However, the above-described method has problems such as an increase in cost due to an increase in circuit scale, an increase in adjustment time required to obtain and correct convergence correction data, and difficulty in automatic adjustment.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to enable a digital convergence correction apparatus to suppress density modulation caused by conventional interpolation operation, reduce the number of adjustment points, and to perform adjustment efficiently. An object of the present invention is to provide a digital convergence correction data creation method.

[Means for solving the problem]

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

Instead of using a conventional linear interpolation formula, a curve that passes through all adjustment points and closely fits the original correction curve shown in FIG. 4A, that is, Y = aX ⁿ + BX ^n-1 + cX ^n-2 +...

However, if the above equation is used as it is, the coefficients, a, b, c..., And then X ⁿ , X ⁿ⁻¹ , X ^N−2. become.

Therefore, Lagrange's interpolation formula that can easily obtain the above equation is used.

Lagrange's interpolation formula
formula) is explained.

Now, if Y = f (X), X is X ₀ , X ₁ ,... X _n
, The following equation holds, which gives an n-order polynomial that takes (n + 1) indicated function values.

f (X) = a ₀ (X) · f (X ₀ ) + a ₁ (X) · f (X ₁ ) +... + a _n (X) · f (X _n ) where a ₀ ( X) = (X−X ₁ ) (X−X ₂ ) · (X−X _n ) / (X ₀ −X ₁ ) / (X ₀ −X ₂ ) / · / (X ₀ −X _n ) a ₁ (X) = (X−X ₀ ) (X−X ₂ ) · (X−X _n ) / (X ₁ −X ₀ ) / (X ₁ −X ₂ ) / ·· / (X ₁ − _{X n): a n (X} ) = (X-X 0) (X-X 1) ·· (X-X n-1) / (X n -X 0) / (X n -X 1) / · · / (X _n -X _n-1 ) (3) Lagrange interpolation is suitable for the digital convergence correction data interpolation calculation method as follows.

(B) Calculation is easy and can be performed in a short time.

_{a 0, a 1, ···,} a n is a constant, it can be determined in advance. Therefore, the interpolation operation expression can obtain f (X) at an arbitrary point X by only n multiplications and (n-1) additions.

Interpolation can be performed with a higher-order function by using a formula other than Lagrange interpolation, but generally it takes more time to increase the order, so that the above-described ease of calculation is excellent.

(B) X ₀ , X, ₁ ... in the above equation can be set freely.

This means that the adjustment point interval can be set freely. The advantage is that, in general, the convergence shift is larger in the peripheral portion of the screen than in the central portion of the screen, and the distortion is larger. Therefore, if the distribution density of the adjustment points is made dense in a portion having a large distortion and sparse in a portion having a small distortion, interpolation with higher accuracy can be performed.

Lagrange interpolation is relatively simple, but
As compared with linear interpolation, an increase in calculation speed is inevitable. Therefore, in order to suppress the increase in the calculation speed when making convergence correction data and making adjustments, the operator looks at the image of the adjustment points on the screen, seeks more accurate adjustment data, and performs image adjustment. To do, indicator 32
Therefore, when the CPU 31 is instructed, the interpolation calculation of the screen position between the adjustment points is performed by linear interpolation calculation (interpolation calculation with a high calculation speed), and this is the last adjustment performed at the final adjustment. For the interpolation calculation of the screen position between the point and the adjustment point,
A means of performing a Lagrange interpolation operation (an interpolation operation having a low operation speed) is used.

Further, not only in the vertical direction but also in the horizontal direction, which has only been interpolated by the LPF 36, interpolation using a higher-order function is used together to reduce the number of adjustment points.

[Action]

Since the Lagrange's interpolation formula uses a higher-order function to interpolate, a smooth and very close waveform to the original convergence correction waveform shown in FIG. 4A, that is, a waveform having a small interpolation error can be obtained. Accordingly, even if the number of adjustment points is reduced, density modulation that has conventionally occurred can be suppressed.

Further, by using both the linear interpolation and the Lagrangian interpolation, the same result can be obtained while suppressing an increase in the operation time caused by using only the Lagrange interpolation operation.

〔Example〕

Prior to the description of the embodiment of the present invention, a convergence correction data creating method useful for understanding the present invention will be described with reference to FIGS. 1, 2, and 3. FIG.

FIG. 1 is a flowchart showing an example of a convergence correction data creating method useful for understanding the present invention.

First, how the Lagrange's interpolation formula is used for an interpolation calculation for digital convergence will be described with reference to FIG.

Attention is now focused on vertical interpolation. The adjustment point is the scan line z
The value of the convergence correction data at the adjustment point coordinates (X, Y) is assumed to be f (X, Y), assuming that they are at equal intervals for each
When applied to the above equation (3), the following is obtained.

f (X, Y) = a 0 (Y) · f (X, Y 0) + a 1 (Y) · f (X, Y 2) + a 2 (Y) · f (X, Y 4) + a 3 (Y ) · F (X, Y ₆ ) + a ₄ (Y) · f (X, Y ₈ ) where a ₀ (Y) = (Y−Y ₂ ) (Y−Y ₄ ) (Y−Y ₆ ) (Y −Y ₈ ) / (Y ₀ −Y ₂ ) / (Y ₀ −Y ₄ ) / (Y ₀ −Y ₆ ) / (Y ₀ −Y ₈ ) a ₁ (Y) = (Y−Y ₀ ) (Y −Y ₄ ) (Y−Y ₆ ) (Y−Y ₈ ) / (Y ₂ −Y ₀ ) / (Y ₂ −Y ₄ ) / (Y ₂ −Y ₆ ) / (Y ₂ −Y ₈ ) a ₂ (Y) = (Y−Y ₀ ) (Y−Y ₂ ) (Y−Y ₆ ) (Y−Y ₈ ) / (Y ₄ −Y ₀ ) / (Y ₄ −Y ₂ ) / (Y ₄ −Y _{6) / (Y 4 -Y 8} ) a 3 (Y) = (Y-Y 0) (Y-Y 2) (Y-Y 4) (Y-Y 8) / (Y 6 -Y 0) / ( Y ₆ −Y ₂ ) / (Y ₆ −Y ₄ ) / (Y ₆ −Y ₈ ) a ₄ (Y) = (Y−Y ₀ ) (Y−Y ₂ ) (Y−Y ₄ ) (Y−Y _{6) / (Y 8 -Y 0} ) / (Y 8 -Y 2) / (Y 8 -Y 4) / (Y 8 -Y ₆ ) Here, Y ₀ = 0, Y ₂ = 2z, Y ₄ = 4z, Y ₆ = 6z, Y ₈ = 8z (4) In the above simple equation, the value of 4 at an arbitrary point (X, Y) is obtained. Interpolation by the following function can be performed.

Further, with respect to the horizontal direction, f (X, Y) = b 0 (X) · f (X 0, Y) + b 1 (X) · f (X 2, Y) + b 2 (X) · f (X 4 _{, Y) + b 3 (X} ) · f (X 6, Y) where _{b 0 (X) = (X} -X 2) (X-X 4) (X-X 6) / (X 0 -X 2) / (X ₀ −X ₄ ) / (X ₀ −X ₆ ) b ₁ (X) = (X−X ₀ ) (X−X ₄ ) (X−X ₆ ) (X−X ₄ ) / (X ₂ −) X ₀ ) / (X ₂ −X ₄ ) / (X ₂ −X ₆ ) b ₂ (X) = (X−X ₀ ) (X−X ₂ ) (X−X ₆ ) / (X ₄ −X ₀₎ ) / (X ₄ −X ₂ ) / (X ₄ −X ₆ ) b ₃ (X) = (X−X ₀ ) (X−X ₂ ) (X−X ₄ ) / (X ₆ −X ₀ ) / (X ₆ −X ₂ ) / (X ₆ −X ₄ ) where X ₀ = 0, X ₂ = 2, X ₄ = 4, X ₆ = 6 (5), and the vertical interpolation is performed. In the same manner as in, interpolation of an arbitrary point (X, Y) by a cubic function can be performed.

_{a 0 (Y), a 1} (Y), a 2 (Y), a 3 (Y), a 4 (Y), b 0
Since (X), b ₁ (X), b ₂ (X), b ₃ (X) are not related to f (X, Y), that is, the convergence correction data value, they are obtained in advance and stored in the memory. .

Next, the flow of convergence correction data creation will be described with reference to FIG.

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

Now, the process shown in FIG. 1 is started. First, third
The CPU 31 in the figure is in a state of waiting for input from the pointing device (keyboard) 32. (1-) Next, the adjuster determines what kind of adjustment should be made to the adjustment point by looking at the screen, and the keyboard 32 gives the CPU 31
Instruct adjustment.

The CPU 31 adjusts the convergence state of the adjustment points on the screen according to the instruction from the keyboard 32, and obtains the adjustment point data at that stage. (1-) The CPU 31 uses the convergence correction data of the adjustment point just obtained, and creates convergence correction data of the screen position other than the adjustment point by Lagrangian interpolation. (1-) When the Lagrange interpolation is completed, The process returns to the input waiting state (1-).

The adjuster looks at the convergence state of the adjustment points on the screen, and if it is still inadequate, operates the keyboard 32 again to repeat the above operation flow.

According to the present example, (a) the convergence correction data interpolation calculation using a higher-order function can be performed, so that the density modulation caused by the interpolation error can be reduced.

(B) Calculation is simple, and only 5
The convergence correction data at an arbitrary position can be created by four multiplications and three additions in the case of horizontal interpolation by four multiplications and four additions.

(C) The distribution of the 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 reduced.

Next, an embodiment of the present invention will be described with reference to FIGS. 3 and 5 based on the above.

In the digital convergence correction data creation method according to the present embodiment, Lagrange interpolation is used as in the example described with reference to FIG. However, the use of Lagrange interpolation has been devised to reduce the operation time which has been increased, and this is a point different from the example shown in FIG.

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

The adjuster determines which adjustment point is to be corrected on the screen, and selects a desired adjustment point.

 Now, the process shown in FIG. 5 is started.

First, the CPU 31 in FIG. 3 is in a state of waiting for input from the pointing device (keyboard) 32. (5-) Next, the adjuster determines what kind of adjustment should be made to the adjustment point by looking at the screen, and instructs the CPU 31 to perform adjustment by the keyboard 32.

The CPU 31 adjusts the convergence state of the adjustment points on the screen according to the instruction from the keyboard 32, and obtains the adjustment point data at that stage. (5-) The CPU 31 first 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 linear interpolation. (1-) When the linear interpolation is completed, Lagrange interpolation
The convergence correction data at the screen position other than the adjustment point is interpolated again, but during this Lagrange interpolation calculation, the adjuster sees the convergence state of the adjustment point on the screen and determines that it is still insufficient. When there is an input from the keyboard 32 by further operating the keyboard 32, the Lagrange interpolation calculation is immediately interrupted, and the operation returns to the operation of step 5- instructed by the adjuster. (1-) The coordinator sees the convergence state of the adjustment points on the screen and judges that it is sufficient. If the instruction from the keyboard 32 is not sent, Lagrange interpolation is performed to the end and the adjustment points are adjusted. When high-precision convergence correction data of a screen position other than the above is obtained, the process returns to the state of waiting for input from the keyboard 32 (5-).

According to the present embodiment, Lagrange interpolation, which has a small interpolation error but takes a little time to calculate, can be used as if high-speed interpolation is performed in combination with linear interpolation.

〔The invention's effect〕

According to the present invention, realization of high-speed interpolation using a higher-order function suppresses density modulation caused by a convergence correction error, improves convergence correction accuracy, reduces the number of adjustment points involved, and improves convergence correction time due to improvement in usability. Can be reduced.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a method of creating convergence correction data useful for understanding the present invention, FIG. 2 is an explanatory diagram showing convergence correction adjustment points arranged on a cathode ray tube screen, and FIG.
4 is a block diagram showing the configuration of a digital convergence correction device. FIGS. 4 (a), 4 (b) and 4 (c) are graphs showing the relationship between the vertical position of the screen and the convergence correction data, respectively. 5 is a flowchart illustrating a method of creating convergence correction data as one embodiment. Description of reference numerals 31 ... CPU, 32 ... pointing device (keyboard), 33 ... address counter, 34 ... memory, 35 ... D / A converter, 36
…… LPF, 37 …… AMP, 38 …… Convergence York CY

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kunori Matsumi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside Hitachi Video Engineering Co., Ltd. (72) Inventor Makoto Shiomi 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. Inside the Home Appliances Research Laboratory (72) Inventor Michitaka Osawa 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Home Appliances Research Laboratory, Hitachi, Ltd. (56) References JP-A-63-43485 (JP, A) JP-A-62-60391 (JP, A) JP-A-55-163986 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 9/28

Claims (1)

(57) [Claims] 1. A convergence adjustment point, wherein a lattice point on a screen is set as a convergence adjustment point, and a convergence adjustment is performed by a fixed amount toward an optimum state while viewing an initial image at the adjustment point.
A second step of calculating convergence correction data at a screen position between the convergence adjustment points by interpolation from the fixed amount of adjustment data at the convergence adjustment point, and a second step of calculating the convergence correction data at the screen position between the convergence adjustment points. By repeating the second step, 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 screen 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 at the adjustment point at the position. A digital convergence correction data creating method comprising: Compensates the convergence correction data at the screen position. When calculating by the inter-operation, the calculation is performed by linear interpolation using the adjustment data of both adjustment points, and when obtaining the final convergence correction data at the screen position between the adjustment points in the third stage, Generating digital convergence correction data by performing an interpolation operation in accordance with 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. Method (where n is 3, or an integer greater than 3).