JPS63116339A - Convergence measuring method for color cathode-ray tube - Google Patents

Abstract

PURPOSE:To make an accurate convergence compensated variable findable without changing size of a measuring pattern image on a camera element even if imaging the measuring pattern at any position on a color cathode-ray tube, by using a telecentric optical system as an image pickup optical system. CONSTITUTION:A telecentric pickup optical system 9 forms the measuring pattern image reflected on a phosphor screen on a color camera element 10. A signal amplifier circuit 11 amplifies an output signal of the color camera element 10, outputting it to an image memory circuit. A probe 2 has a focus adjusting ring 12 at its tip, and it is constitued so as to go forward or backward in an optical axis direction from a body of the probe 2 by a helicoid being installed in an interspace with the body side of the probe 2, whereby a distance between a face-plate surface 1c and the pickup optical system 9 is adjustable. With this constitution, since the pattern image to be measured is able to form it on the camera element at constant magnification without entailing any its lateral magnification, an accurate convergence compensated variable is measurable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for measuring the state of concentration, ie, convergence, of three electron beams in a color cathode ray tube.

[Conventional technology]

Color cathode ray tubes have phosphors that emit red, green, and blue colors printed on the display surface, and electron beams corresponding to red, green, and back are projected onto the display surface, and the electron beams are controlled according to video signals to display images. However, in order to obtain images with normal colors, it is necessary to adjust the three electron beams corresponding to red, green, and blue so that they pass through the predetermined positions of the shadow mask and hit the predetermined phosphors. This adjustment is called convergence adjustment.

In the conventional convergence GIU, measurement buttons for convergence adjustment are displayed on the display surface of a color cathode ray tube, and these measurement buttons are separated into red, green, and blue colors by color separation filters and used in industrial television cameras. There is a method in which an image is taken with a camera, the center of gravity of the luminance of each color is determined from the output signal, and the deviation of the relative position is obtained as a convergence correction amount (see Japanese Patent Application Laid-Open No. 74780/1983).

[Problem that the invention seeks to solve]

However, the thickness of the face plate of a color cathode ray tube differs between the central portion and the peripheral portion, with the peripheral portion being thicker. For this reason, when an industrial television camera images the measurement surface on the display surface of a color cathode ray tube, there are two different ways to capture the measurement surface on the display surface of a color cathode ray tube. The distance to the imaging lens changes, and the lateral magnification of the imaged fluorescent surface changes. Unfortunately, even if we calculate the center of gravity of the luminance of each of the red, green, and blue phosphors that emit light, it includes changes in the center of gravity caused by changes in the magnification of the photographic optical system.
It was not possible to obtain an accurate convergence correction amount.

To explain this with reference to FIG. 4(a), the optical system shown here is a non-telecentric optical system and represents a magnification imaging system. In the figure, numeral 30 indicates a lens system having a focal length f, and numeral 31 indicates an aperture. An object 34 located at a distance of 3f from the front principal point 32 of the lens is '
:? An image 36 of the same magnification is formed on the image sensor surface 35 located at a distance of 2f behind. The chief ray passing through the vertex of the object at this time is indicated by t.

In this optical system, when the object moves away by Δd along the optical axis and comes to the position 34b in the figure, the chief ray passing through the apex of the object becomes as shown at m, and the image 36b appears on the image sensor surface 35.
imaged as.

At this time, the image on the imaging surface is out of focus, but considering that its brightness center almost coincides with the principal ray, the change in lateral magnification Δβ can be approximately expressed as f 2 . This is specifically f = 40 rrt
m.

When Δd=3++a++, the horizontal magnification will change by 2.5%, which is 25% for each misconvergence question.
This means that an error of μm occurs.

[Means for solving problems]

In order to solve the above-mentioned problems, this invention uses a telecentric optical system as an optical system for imaging the measurement pattern of a color cathode ray tube onto an image sensor, and uses a telecentric optical system to form an image of a measurement pattern of a color cathode ray tube on an image sensor. This is a convergence measuring device in which the lateral magnification of the measurement target on the imaging element does not change even if the distance between the fluorescent surface and the imaging optical system changes due to changes in the distance between the fluorescent surface and the imaging optical system. First, the telecentric optical system will be explained. FIG. 4(b) shows an imaging system using a telecentric optical system. In the figure, reference numeral 40 denotes an imaging lens system, which has an aperture 41 on its focal plane on the image side. Object 44 at a distance of 3f from the front principal point 42 of the lens
is imaged 46 at a given magnification on an imaging surface 45 located %f behind the rear principal point 43 of the lens 40. At this time, the chief ray at the vertex of the image is indicated by n in the figure. In this imaging system, even when the object moves by Δd along the optical axis and is at position 44b, the principal ray at the apex of the image is indicated by n in the figure, and the image on the imaging surface 45 is out of focus. However, it can be considered that the center of brightness almost coincides with the chief ray, and the magnification does not change.

In fact, in the telecentric optical system shown at 9 in FIG. 2, when f = 40 mm and Δd = 3 mm, the change in magnification is suppressed to 0.3%.

Therefore, the convergence measurement device for a color cathode ray tube according to the present invention includes means for displaying a convergence measurement pattern on the display surface of the color cathode ray tube to be measured, an image pickup element for capturing an image of the convergence measurement pattern, and a device for displaying the convergence measurement pattern on the display surface of the color cathode ray tube to be measured. A telecentric optical system that does not cause a change in magnification due to the movement of an object to be imaged on an image sensor, and a convergence correction amount by determining the center of gravity of the luminance of each color emitting phosphor from the output of each color detected by the image sensor. The present invention is characterized by comprising a calculation means for outputting calculations.

[For production]

The convergence measurement pattern displayed on the display surface of a color cathode ray tube is imaged onto an image sensor using an imaging optical system.
The luminance center of gravity of each color light emitting body is determined from the output of each color of emitted light detected by the image sensor, and from this, the separation distance of other colors from the center of gravity of the light emitting body of a specific color is calculated and output as a convergence correction amount by a calculation means. .

The distance between the fluorescent surface and the imaging optical system changes because the thickness of the color cathode ray tube's face plate differs depending on the part, but since a telecentric optical system is used as the imaging optical system, Even if the position measurement button is imaged, the size of the measurement point image on the image sensor does not change, and an accurate convergence correction amount is required.

〔Example〕

Examples of the present invention will be described below.

FIG. 1 is a circuit block diagram schematically showing the configuration of a convergence measuring device according to an embodiment of the present invention. In the figure, l is a color cathode ray tube to be measured, and 2 is a measurement probe, which is movable to multiple locations on the display surface of the color cathode ray tube 1 and is not shown so as to be pressed against the display surface of the color cathode ray tube. It is done by a mechanism. The probe has a built-in industrial color television camera that captures images of the measurement screen projected on the display screen of a color cathode ray tube, and displays red (R), green (G), and blue (B).
It outputs a video signal separated into three primary colors. 3 is A/D
A video memory circuit consisting of a converter and a buffer memory, which temporarily stores the R, G, and B video signals output from the probe as digital video information.
It is equipped with a, 3b, and 3c. Reference numeral 4 denotes an arithmetic control circuit, which is composed of a microprocessor, and controls the operation of the measuring device according to a control program stored in the memory 5.

This operation control causes the arithmetic control circuit 4 to control the video memory circuit 3.
The convergence correction amount is calculated by calculating the video information stored in the , and is stored in the memory 5 and output to the data output device 6 . Note that 7 is a drive circuit for a color cathode ray tube, and 8 is a measurement nozzle generator.

FIG. 2 is a diagram schematically showing the configuration of the probe, and also shows a part of the color cathode ray tube to be measured as a cross section. In the figure, 1a shows the face plate of the color cathode ray tube 1, 1c shows the front surface of the face plate, and 1b shows the fluorescent surface provided on the back surface of the face plate.

Reference numeral 9 denotes a telecenter) IJ sock image optical system that forms the measuring nozzle image reflected on the fluorescent surface onto the color image pickup device 10. Reference numeral 11 denotes a signal processing circuit that amplifies the output signal of the color image sensor 10 and outputs it to the video memory circuit 3.

The probe 2 has a focus adjustment ring 12 at its tip, and is configured to move forward and backward from the main body of the probe 2 in the optical axis direction by means of a helicoid 13 provided between the probe 2 and the main body of the probe 2. The distance between the faceplate surface 1c and the imaging optical system 9 can be adjusted.

Next, the measurement of the convergence correction amount according to the above embodiment will be explained with reference to FIG. 3.

First, a white dot for convergence measurement, for example, a white dot like the one shown with reference numeral 20 in FIG. let

If you enlarge the area 21a that includes one of the white dots, you will see the area 22,
The probe 2 is pressed against the area including this one dot Z button, the focus is adjusted by turning the focus adjustment ring 12, and the dot is focused on the color image sensor 10 by the imaging optical system 9.
image on top.

The color image sensor 10 separates this into three colors, red, green, and blue, and the red color shown as 22R, 22G, and 22B in FIG.
It outputs an imaging signal representing green and blue dot images. These imaging signals are then stored in the image memories 3a13b and 3c. Note that the color image sensor 10 is a MOS type, C
There are various types such as the CD type, but all of them are well known and their configurations are not directly related to this invention, so a description thereof will be omitted.

Next, the brightness center, ie, the center of gravity, of the red, green, and blue dot images stored in the image memo IJ3a, 3b, and 3c is determined. That is, for example, the red dot image shown in FIG. 3 22R is composed of only a plurality of red phosphors out of a large number of red, green, and blue phosphors arranged in the area projected by the electron beam. Find the center of gravity of the brightness. This is achieved by processing the imaging signals stored in the image memo') 3a, s3b, 3c in the control calculation circuit 4.

Once the luminance centroids of the red, green, and blue light-emitting phosphors have been determined, for example, the separation distance RX, RY1BX% of the luminance centroids RO1BO of the red and blue phosphors with respect to the centroid Go of the green phosphor as a reference. BY is determined, and this calculation result is stored in the memory 5 as a convergence correction amount, and then outputted to the data output device 6 for recording and display.

The convergence correction amount for the measurement area containing one dot has been determined above, but the convergence correction amount can be measured at multiple points on the display surface of a color cathode ray tube.
That is, measurements are sequentially repeated at a large number of points such as points 21a to 21j shown in FIG.

〔Effect of the invention〕

As explained above, the present invention is useful for measuring the convergence correction amount of a color cathode ray tube using an industrial television camera. Even if fluctuations occur, by using a telecentric optical system in the imaging optical system for measuring the convergence on the display surface of a color cathode ray tube and imaging the S tan, it is possible to avoid changes in the lateral magnification of the S tan to be measured. Since the image can be formed on the image sensor at a constant magnification, it is possible to accurately measure the amount of convergence correction even if the thickness of the face plate of the color cathode ray tube changes.

Furthermore, if a color image sensor is used as the image sensor, it is possible to obtain three color imaging signals of red, green, and blue at the same time without using a color separation filter, so the power generated while detecting these image signals individually is reduced. It is unaffected by changes in measurement conditions such as fluctuations in brightness, noise generation, and changes in brightness due to synchronization errors.

In the above embodiments, a color TV camera is used as the camera for measurement and to take images of ζ tan, but this does not necessarily have to be a color TV camera; , blue color separation filters may be inserted alternately to obtain a button image in which the measurement button on the color cathode ray tube is separated into red, green, and blue.

[Brief explanation of the drawing]

Fig. 1 is a circuit block diagram of a convergence measuring device which is an embodiment of the present invention, Fig. 2 is a diagram showing an outline of the configuration of a zolobe, Fig. 3 is an explanatory diagram of a method for measuring a convergence correction amount, and Fig. 4 is an explanatory diagram of a non-telecentric optical system and a telecentric optical system. 1: Color cathode ray tube, 2 nib lobes, 3: Video memory circuit, 4. Arithmetic control circuit, 6: data output device, 8: measurement generator, 9 telecentric imaging optical system,
10゛ image sensor.

Claims (1)

[Claims] means for displaying a convergence measurement pattern on a display surface of a color cathode ray tube to be measured; an imaging device for capturing an image of the convergence measurement pattern; and an object movement that causes the convergence measurement pattern to be imaged on the imaging device. Telecentric optical system that does not cause magnification changes,
A convergence measurement device for a color cathode ray tube, characterized in that it is provided with a calculation means for calculating and outputting a convergence correction amount by determining the luminance center of gravity of each color light emitting phosphor from the output of each color of light emitted detected by the image sensor.