JPH05275013A - Method of measuring luminescent line width in color cathode-ray tube - Google Patents

Abstract

PURPOSE:To obtain the line width at a sufficient accuracy by applying the magnetic field in parallel with a tube axis of a color cathode-ray tube from the outside to pick up image of an inclined luminescent line, and dividing the obtained luminescent line image into plural areas, and computing a luminescent line width on the basis of the luminance distribution obtained in each area. CONSTITUTION:A driving device 12 scans a phosphor screen 19 of a color cathode-ray tube 10 to output, for example, a horizontal luminescent line on the phosphor screen 19 on the basis of the image signal generated by a signal generator 13, and a TV camera 16 picks up this horizontal luminescent line for enlargement. The obtained image is stored in an image memory of an image processing device 17. This electrode is displayed on the screen 19 to compute, for example, a vertical luminescent line, and the processing area is set to detect the distribution of luminance in the direction orthogonally crossing the luminescent line. In this distribution of luminance, the center coordinate is obtained on the basis of a mean value of each coordinate value of both sides of the luminescent line as a predetermined threshold value S, and each luminance is overlapped thereon, and the distribution of luminance is estimated by means of the interpolation to obtain the corresponding luminescent line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring the line width of a color cathode ray tube by measuring the line width on a phosphor screen of a color cathode ray tube having a large number of phosphor dots in a predetermined array to evaluate the resolution. ..

[0002]

2. Description of the Related Art As a method for evaluating the resolution of a so-called dot matrix type color cathode ray tube having a phosphor screen in which a large number of phosphor dots are arranged in a predetermined array, Japanese Patent Application Laid-Open No. 62-245226 discloses. , A beam spot is made to appear on the phosphor screen, the deflection current is changed while measuring the brightness of the beam spot on the phosphor screen, and the brightness is predetermined for the deflection current and its brightness at the maximum brightness. A method is shown in which the size of the beam spot, that is, the bright line width, is set to a value proportional to the difference from the deflection current when the ratio becomes proportional.

Further, in Japanese Patent Laid-Open No. 3-108235, the brightness value of the phosphor dots emitted from the screen is displayed by displaying a lattice pattern or dot pattern on the phosphor screen and capturing the image with a TV camera. From this, the method of approximating the luminance distribution including the non-luminous portion outside the phosphor dot by the interpolation method or curve fitting, and calculating the bright line width and dot size from the shape of this estimated distribution is available. It is shown.

However, by changing the deflection current of the former, a value proportional to the difference between the deflection current when the brightness of the beam spot is maximum and the deflection current when the brightness has a predetermined ratio to the brightness is obtained. Since the method of determining the size of the beam spot is not a measurement in a normal raster scanning state, it is necessary to use a special device for the deflection circuit or the like. Therefore, it is difficult to apply it to the inspection in the manufacturing line of the color cathode ray tube and the inspection in the state in which the color cathode ray tube is driven in the set actually used.

In the latter method, the brightness distribution including the non-luminous portion outside the phosphor dots is approximately estimated from the brightness values of the phosphor dots, and the bright line width and the dot size are calculated from the shape of the distribution. , There is no problem like the former because a special device is not required to drive the color cathode ray tube, but if the number of phosphor dots emitting light is small due to the emission line width or phosphor dots, interpolation or curve There is a problem that the accuracy of the approximate estimation of the luminance distribution by fitting is poor, and sufficient measurement accuracy cannot be obtained.

Particularly in the peripheral portion of the display screen of the color cathode ray tube, the aberration of the deflection yoke makes the luminance distribution of the beam spot asymmetrical, so that the measurement accuracy is remarkably lowered.

That is, this latter method is shown in FIG.
As shown in (a), a vertical bright line is formed on a phosphor screen 2 having a large number of phosphor dots 1 having an array axis in the vertical direction.
When 3 is displayed, cross the vertical bright line 3 at a right angle A
By detecting the brightness values on the 1-A2 line and the B1-B2 line, the brightness distributions 4a and 4b shown in FIGS. 7B and 7C are obtained, respectively, and these brightness distributions 4a and 4b are superposed, It is assumed that the brightness distribution 5 shown in FIG. 8 is obtained. The brightness value at the center of the phosphor dot that is emitting light is extracted from this brightness distribution 5, and the bright line including the non-emission part outside the phosphor dot is extracted by the sampling function (sinx / x) or spline interpolation. Estimate the luminance distribution 6 and
Calculate the line width from 6.

However, according to this method, when the luminance distribution 6 is asymmetric as shown in FIG. 8, it is difficult to estimate with the sampling function. In the case of spline interpolation, A1-A2 line,
If the number of phosphor dots 1 emitting light on the B1-B2 line is small, the interpolation accuracy becomes insufficient, and the accuracy of the bright line width decreases significantly.

[0009]

As described above, as a conventional method for evaluating the resolution of a color cathode ray tube, a beam spot is made to appear on a phosphor screen, and the brightness of the beam spot on this phosphor screen is measured. While changing the deflection current, the beam spot size is determined by a value proportional to the difference between the deflection current when the luminance is maximum and the deflection current when the luminance is a predetermined ratio with respect to the luminance. It has been known.

Further, a lattice pattern or a dot pattern is projected on the phosphor screen, imaged by a TV camera, and the brightness value of the phosphor dots emitted from the screen is interpolated or fitted with a curve. There is known a method in which a luminance distribution including a non-luminous portion outside a phosphor dot is approximately estimated, and a bright line width and a dot size are calculated from a shape of the estimated distribution.

However, these methods have problems that a special device is required for driving the color cathode ray tube and that the measurement accuracy is insufficient because the approximation accuracy is poor.

The present invention has been made in order to solve the above-mentioned problems, and obtains a bright line width measuring method with sufficient accuracy necessary for evaluation of resolution by using an ordinary driving device for a color cathode ray tube. The purpose is to

[0013]

In a method of measuring a line width of a color cathode ray tube, a horizontal or vertical line is drawn on a phosphor screen of the color cathode ray tube having a large number of phosphor dots in a predetermined array, and the color cathode line is formed. A magnetic field parallel to the tube axis is applied from the outside of the tube to incline the emission lines with respect to the array direction of the phosphor dots, and the emission lines are imaged by a TV camera placed at a position facing the phosphor screen. The image of the obtained bright line is divided into a plurality of regions, the luminance distribution in each of the plurality of regions is detected, and the central coordinates of the bright line are obtained from two coordinate values that are predetermined luminance threshold values for these luminance distributions. The brightness distributions of the bright lines are estimated by superimposing the brightness distributions in each of the plurality of areas with reference to the center coordinates and interpolating the overall brightness distributions thus superposed. And to calculate the linewidth from the luminance distribution of the emission line.

[0014]

As described above, by applying a magnetic field parallel to the tube axis from the outside of the color cathode ray tube, the horizontal or vertical bright line inclined with respect to the array direction of the phosphor dots is imaged by the TV camera, and the image is taken. The image of the obtained bright line is divided into a plurality of regions, the brightness distribution in each region is detected, the center coordinates of the bright line are obtained, and the brightness distributions of the respective regions are superposed on the basis of this center coordinate, By estimating the luminance distribution of the bright line by interpolating the luminance distribution and calculating the bright line width from the luminance distribution of the bright line, the number of luminance values when interpolating the luminance distribution and estimating the luminance distribution of the bright line is calculated. You can increase. As a result, the interpolation accuracy of the luminance distribution is improved, and the bright line width can be calculated with sufficient accuracy.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings.

FIG. 1 shows the arrangement of a bright line width measuring apparatus according to the embodiment. This measuring apparatus includes a cathode ray tube drive circuit for driving the color cathode ray tube 10, a drive apparatus 12 having a deflection yoke drive circuit for driving a deflection yoke 11 mounted on the color cathode ray tube 10, and a phosphor of the color cathode ray tube 10. A signal generator 13 for displaying horizontal or vertical bright lines on the screen, a rotation coil 14 installed outside the color cathode ray tube 10, a rotation coil power supply 15 for driving the rotation coil 14, and a color cathode ray tube 10.
TV camera 16 facing the phosphor screen of
And an image processing device 17 for processing the image signal sent from the TV camera 16.

Next, a method of measuring the bright line width by this measuring device will be described.

As in the case of displaying a normal image, the driving device 12 raster-scans the phosphor screen 19 of the color cathode ray tube 10, and the image signal generated by the signal generator 13 causes the phosphor screen 19 to be horizontally displayed on the phosphor screen 19. Or, the vertical luminescent line is displayed, and by the optical system attached to the TV camera 16,
Each phosphor dot is magnified and imaged at a magnification that allows the phosphor dots to be clearly separated. The image captured by the TV camera 16 is sent to the image processing device 17 and stored in the image memory provided in the image processing device 17 as image data. The image processing device 17 retrieves and processes the image data from the image memory, and calculates the horizontal or vertical bright line displayed on the phosphor screen 19.

That is, as shown in FIG. 2, first, an image is captured. Here, after controlling the image input to the image input unit of the image processing apparatus and controlling the transfer of the image from the image memory, the presence / absence of bright lines and the preprocessing such as setting of a plurality of processing areas are performed. Is performed. Next, the brightness distribution is detected for each set processing region, and then the center coordinates of the bright line in each processing region are calculated.

That is, as shown in FIG. 3A, the phosphor screen 19 is composed of a large number of phosphor dots 21 having an array axis 20 in the vertical (Y-axis) direction. Explaining the case where the vertical bright line 22 is drawn on the 19 above, in the vertical direction along the vertical bright line 22,
For example, three processing areas 23A, 23B, 23C including a plurality of phosphor dots 21 emitted by the bright line 22 are set. Then, for each of the processing areas 23A, 23B, and 23C, the luminance distribution in the direction (X direction) orthogonal to the direction (vertical direction) of the bright line 22 is detected. The brightness distributions of the processing areas 23A, 23B, and 23C are shown in FIG. 3B for the processing area 23A.
As shown in (c) for 23B and (d) for processed area 23C, the array axis of phosphor dots 21 is shown.
The luminance distributions 24A, 24B, and 24C have peak values on 20. Then, in this luminance distribution 24A, 24B, 24C,
The two coordinates 25b, 26b, 25c, 26c, 25d, 26d corresponding to both sides of the bright line having the predetermined threshold S are obtained, and the average value of these coordinates 25b, 26b, 25c, 26c, 25d, 26d is calculated as the bright line. The center coordinates are 27b, 27c, and 27d.

Next, as shown in FIG. 2, the brightness distribution of the phosphor dots is detected for each of the set processing regions, and the phosphor dots of each processing region are set with reference to the center coordinates of the bright line. The brightness distribution of is superimposed. Next, with respect to this brightness distribution, the brightness value at the center of the phosphor dot is extracted, and the brightness distribution including the non-luminous portion of the phosphor dot is estimated by interpolation.

That is, as shown in FIG. 4A, the phosphor dots 21 respectively set in the above-mentioned three processing regions.
Direction A1 -A2. B1-B2, C
The luminance distribution of the 1-C2 phosphor dots 21 is detected. The luminance distribution of the phosphor dots 21 is the same as that in the direction A1 -A2 in FIG. 4B and that in the direction B1 -B2 (c).
In the direction C1-C2, as shown in (d),
Luminance distribution 29 with a peak value on the array axis 20 of phosphor dots
It becomes A, 29B, 29C. These brightness distributions 29A, 29B, 29
With reference to the center coordinates 30b, 30c, 30d of the bright line, the position of C is corrected as shown in FIG.
Superimpose B and 29C. Next, with respect to the position-corrected luminance distributions 29A, 29B, and 29C, the luminance value at the center of the phosphor dot is extracted and interpolated by, for example, a spline curve, and the luminance distribution including the non-luminous portion of the phosphor dot is included. Estimate 31.

Next, as shown in FIG. 2, the bright line width is calculated from the interpolated luminance distribution.

That is, as shown in FIG.
The width w at which the luminance value H2 of a predetermined ratio is obtained with respect to the maximum value H1 of is calculated as the bright line width.

By the way, when the bright line width is obtained by the above method, the brightness value at the center of the phosphor dot is five as shown in FIG. 5, and the conventional method shown in FIG. 8 (JP-A-3-10).
The number of data can be increased with respect to the three luminance values of the method of Japanese Patent No. 8235). Therefore, when interpolating with a spline curve or the like, the accuracy of the interpolation can be greatly improved. Further, according to this method, the driving device 12 for driving the color cathode ray tube 10 and the deflection yoke 11 is used.
It is not necessary to use a special device for arranging the rotation coil 14 on the outside of the color cathode ray tube 10 and adding a rotation coil power supply 15 for driving the rotation coil 14, so that the production line of the color cathode ray tube 10 It is possible to obtain the effect that it can be applied to the inspection in the field and the inspection in the set actually used.

In the above embodiment, the measurement of the bright line width of the vertical bright line has been described, but the present invention can be similarly applied to the case of measuring the bright line width of the horizontal bright line.

In addition, in the above embodiment, three processing areas are set when measuring the bright line width, but by setting a larger number of processing areas, it is possible to increase the number of data of luminance values and to improve the interpolation accuracy. It can be further improved.

[0028]

EFFECTS OF THE INVENTION A magnetic field parallel to the tube axis is applied from the outside of the color cathode ray tube, and a horizontal or vertical bright line inclined with respect to the arrangement direction of the phosphor dots is imaged by a TV camera. The image of the bright line is divided into a plurality of areas, the brightness distribution in each area is detected, the center coordinates of the bright line are obtained, the brightness distributions of the respective areas are overlapped on the basis of the center coordinates, and the entire brightness distribution is calculated. If the brightness distribution of the bright line is estimated by interpolation and the brightness line width is calculated from the brightness distribution of this bright line, the number of brightness values when interpolating the brightness distribution and estimating the brightness distribution of the bright line can be increased. .. As a result, the interpolation accuracy of the luminance distribution is improved, and the bright line width can be calculated with sufficient accuracy. Moreover, since a special driving device is not required to drive the color cathode ray tube and the deflection yoke, it can be applied to the inspection in the production line of the color cathode ray tube and the inspection in the set actually used. ..

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a bright line width measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining a method for measuring a bright line width by the above-mentioned bright line width measuring device.

FIG. 3A is a diagram for explaining a bright line displayed on a phosphor screen and setting of a processing region for this bright line; FIGS. 3B to 3D are luminances of the respective processing regions. It is a figure which shows distribution.

FIG. 4 (a) is a diagram for explaining a method for detecting the brightness distribution of phosphor dots in a processing region set for a bright line on a phosphor screen, and FIGS. 4 (b) to 4 (d). 3] is a diagram showing the luminance distribution of the phosphor dots in each of the processing regions.

FIG. 5 is a diagram showing a state in which the luminance distributions of the phosphor dots are position-corrected and superimposed.

FIG. 6 is a diagram for explaining a method of calculating a bright line width from a brightness distribution obtained by interpolating the brightness distribution of the superimposed phosphor dots.

FIG. 7 (a) is a diagram for explaining a luminance distribution measuring method in a conventional bright line width measuring method, and FIGS. 7 (b) and 7 (c) are diagrams showing the luminance distribution, respectively.

FIG. 8 is a diagram showing a luminance distribution obtained by superposing and interpolating the luminance distributions.

[Explanation of symbols]

 10 ... Color cathode ray tube 11 ... Deflection yoke 14 ... Rotation coil 16 ... TV camera 19 ... Phosphor screen 20 ... Phosphor dot array axis 21 ... Phosphor dots 22 ... Bright line 23A, 23B, 23C ... Processing area 24A, 24B, 24C ... Luminance distribution 27b, 27c, 27d ... Center coordinates 29A, 29B, 29C ... Luminance distribution 30b, 30c, 30d ... Center coordinate 31 ... Luminance distribution

Claims (1)

[Claims] 1. A horizontal or vertical bright line is drawn on a phosphor screen of a color cathode ray tube having a large number of phosphor dots in a predetermined array, and a magnetic field parallel to the tube axis is applied from the outside of the color cathode ray tube. A method of inclining a bright line with respect to the array axis of the phosphor dots, and a TV arranged at a position facing the phosphor screen.
A method of imaging the bright line with a camera, dividing the image of the bright line obtained by the imaging into a plurality of regions, and detecting the luminance distribution in each of the plurality of regions,
With respect to these luminance distributions, the center coordinates of the bright line are obtained from two coordinate values that are predetermined luminance thresholds, the luminance distributions in each of the plurality of regions are superposed on the basis of the center coordinates, and the whole superposed ones are superposed. A method for measuring the line width of a color cathode ray tube, which comprises: estimating the line luminance distribution by interpolating the line luminance distribution; and calculating the line width from the line luminance distribution.