JPH0378935A - Method for measuring of electron beam concentration in color cathode-ray tube - Google Patents

Abstract

PURPOSE:To allow the accurate measurement of the condition of electron beam concentration by obtaining the measuring values at two types of displaying of the distance from the brightness centeroid position of green to the brightness centeroid positoins of read and blue, calculating the arithmetic mean with the symbol inverted, assuming the result therefrom as misconvergence amount on fluorescent surface of the electron beams of different colors, and using it for judgement whether the electron beam concentrated condition is acceptable. CONSTITUTION:The distance between the brightness centeroid of G and R shall be r1 while the distance between those of G and B be b1, and when the sequence is inverted, the distance between the brightness centeroid positions of G and B shall be b2 while the distance between those of G and R be r2. The symbol for r2 is inverted and added to r1 and the mean is calculated, and alike the symbol for b2 is inverted and added to b1 and the mean is calculated. If misconvergence between the landing spots of the R, G, B electron beams thus obtained is below a certain allowable value, the concentrated condition of the color CRT concerned is judged as acceptable. Thus the concentrated condition of electron beams in a color CRT can be precisely measured using a monochro. video camera in comparatively simple structure and with good characteristics.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention provides a color cathode ray tube that enables accurate measurement of the concentration state (convergence) of a 3i color electron beam on a fluorescent surface of a shadow mask type color cathode ray tube. This invention relates to a method for measuring the state of electron beam concentration in a tube.

[Prior art] As is well known, a shadow mask type color cathode ray tube has three
A separate electron gun is provided for each of the primary colors, and the electron beam for each of the three primary colors emitted from these electron guns is configured to be concentrated at a - point at each point during scanning on the fluorescent surface. has been done. However, there are various factors that disturb convergence, and in actually manufactured color cathode ray tubes, the electron beams for each of the three colors, which should originally be concentrated at one point on the fluorescent surface to display the white point, are There is some deviation in the center and position of. If the deviation is slight, it does not appear as color blurring when viewed by humans and is acceptable.

However, if the deviation becomes large beyond a certain level, it becomes a color deviation that is recognized and cannot be tolerated. For this purpose, convergence measurements are performed on color cathode ray tubes, and quality is determined based on the magnitude of deviation between the electron beams of each color.

Conventionally, the above-mentioned convergence measurement was carried out by, for example, placing a black and white video camera with increased magnification close to the screen of the color cathode ray tube to be tested (such as displaying a dot pattern or a cross pattern on the screen of the test tube). The three primary color electron beams, which would normally display a white point at a specific position on the screen, are temporally separated for each color (at least one frame period), and red, green, and blue are each used as a single color. Let the display take place.

The image is photographed by the black and white video camera, and the display pattern for each single color is imported into the video camera's image memory.Then, the image is processed to calculate the position of the center of gravity of each color display pattern, and the position of the center of gravity of each color is calculated. Passage or failure was determined based on whether the difference (distance from the center of gravity of green to the center of gravity of red or blue) was within an acceptable range. Furthermore, a black and white video camera is used because there is no color separation filter, there is little loss of light, and it is easy to obtain a camera with good characteristics such as sensitivity and resolution. Note that a method for detecting image light of a cathode ray tube is disclosed in, for example, Japanese Patent Laid-Open No. 153921/1983.

[Problems to be Solved by the Invention] However, in the conventional method described above, the red, green, and blue patterns are photographed with a temporal shift for each single color, so the effects of vibrations in the display pattern and vibrations of the video camera are affected. The problem was that it appeared as an error.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for measuring concentrated S (convergence) of a color cathode ray tube, which does not have the problems of the conventional methods described above.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, if electrons are simultaneously applied to the electron guns for the respective colors, a single white spot or The 3M color signals that display crosshatches are applied to the electron gun for the corresponding color one after another at arbitrarily determined short fixed time intervals for each color signal, and the signals are displayed on the display surface of the color cathode ray tube to be tested. Displaying each color separately in the order of red, green, and blue, and then similarly displaying blue, green, and red separately in the order of the time difference,
The two types of display states are each photographed with a black and white video camera, and the luminance gravity center position of each color display is measured.
The measured values of the distance from the green luminance centroid position to the red and blue luminance centroid positions during the above two types of display are added and averaged with the signs reversed, and the results are calculated based on the deviation on the fluorescent surface of each color electron beam. It was used to determine the quality of the electron beam concentration of the color cathode ray tube under test.

[Function] In the present invention, in view of the fact that the interlayer points in the conventional measurement method are caused by the fact that a period of one frame or more has elapsed in the middle of photographing each color pattern display, They decided to simultaneously record the positions of the three primary color electron beams in one photograph. However, since a black-and-white video camera is used for photography, it is difficult to capture the state in which the color electron beams display a single white dot or crosshatch on the fluorescent surface. It is impossible to photograph. For this purpose, the system that is supposed to display a single white dot or crosshatch on the display surface of the color cathode ray tube under test is used.
'Separate the X color signal into each color signal, and set an arbitrary slight predetermined time difference (known to the measurer) between each color signal.
With a time difference that is much shorter than the frame period, the display position separated by color is placed close to the cathode ray tube screen within the field of view of a black and white video camera that is installed so that the display on the screen can be enlarged and photographed. (to a sufficiently large extent), and display the display position of each color separately in the order of red, green, and blue on the display surface of the color cathode ray tube to be tested, and then similarly, with the same time difference, blue, Green and red are displayed separately in that order, the two types of display states are photographed with a black and white video camera, and the luminance gravity center position of each color display position is measured, and the red, The distance between the center of gravity of the blue luminance is calculated by adding and averaging the two measurement values with opposite signs to each other. It was determined that this was a shift in the (center position) of the landing spot. Even in the method of the present invention, there is an extremely short time difference between the times when the display by the electron beam of each color appears on the screen of the color cathode ray tube, but this is not a problem as it is not as long as in the conventional case. Also, the reason why the color order is reversed and the measurements are taken twice is mainly to eliminate errors caused by the linearity of the deflection system (even if the time difference is the same, the distance between the electron beam landing spots tends to be wider closer to the periphery of the screen). be.

[Example code] The present invention will be explained in more detail below with reference to one drawing.

The diagram on the left side of FIG. 1(a) shows a white dot pattern being displayed on the screen of a color cathode ray tube, and the circle on the right side shows an enlarged diagram of one dot. In this enlarged view, R, G, and B are each shown as one circle, but to be more precise, these are the layers of red and green that would have reached the fluorescent surface if there was no shadow mask. , should be understood to represent the blue electron beam landing spot. The thickness of the electron beam is generally considerably larger than the diameter of the dots of the phosphor on the phosphor surface, the diameter of the holes in the shadow mask, and the pitch of the holes. Therefore, the state of the phosphor surface that actually emits light due to the electron beam passing through the shadow mask becomes an aggregation of a plurality of small bright spots as shown in FIG. 1(b). These small bright spots are the phosphor dots of each color formed on the phosphor surface.

In the case of a color cathode ray tube that has been completed correctly as desired, the R2O and H circles should not be separated from each other, but should overlap one another, as shown in Figure 1(a). , that is, in a good convergence state, R and G shown in FIG. 1(a).

The circles in B should overlap into one, and there should be a uniform mixture of small bright spots inside, each emitting red, green, and blue light, as shown in Figure 1(b). It is.

However, in reality, the video camera used for measurement is black and white, so it cannot capture differences in color.

To do this, the three primary color signals that are supposed to display a single white dot or crosshatch on the display surface of the color cathode ray tube under test are separated into each color signal, and an arbitrarily short fixed time difference is set between each color signal. As shown in Figure 2, R (red), G (green), B (
The display positions are separated and displayed for each color in the order of (blue).

In reality, for example, each color signal, which should originally be applied all at once to each color electron gun of a color cathode ray tube under test, is separated and stored in the same memory at addresses a predetermined distance apart. It is sufficient to store the signals, call them sequentially using a clock, and apply them to the electron gun for the color corresponding to each signal of the color cathode ray tube to be tested.

In addition, when deflecting an electron beam, the distance between the beams from the electron gun and the fluorescent recirculator increases as the distance approaches the periphery of the screen. It tends to spread the closer you get. In order to eliminate this error, if the images are first separated in the order of red, green, and blue as shown in Figure 2, then the first image will be separated into blue, green, and red as shown in Figure 3. Reverse the order and separate and photograph. Although a display point of one color is actually a collection of a plurality of small bright spots as described above, the position of the center of gravity of the luminance of each color display point is determined by image processing of the photographed result. Since the order of signal application is known to the measurer, it is easy to determine which point corresponds to which color in images taken one minute apart. In the case shown in Fig. 2, the distance between the luminance centroid positions of G and R is denoted by r, and the distance between the luminance centroid positions of G and B is denoted by b.
If the order shown in Figure 3 is reversed, the distance between the luminance centroid positions of G and B is set as b2, the distance between the luminance centroid positions of G and R is set as r2, and the sign of r2 is reversed for r. Similarly, the sign of b2 is inverted and added to bl, and the average is taken. R, G, B obtained in this way
If the deviation of the landing spots between the ffi beams is less than a tolerance determined in advance through numerous experiments, the concentration state of the color cathode ray tube is determined to be acceptable.

Incidentally, the above-mentioned measurements can be easily carried out by using a combination of a black and white video camera and a device such as a so-called personal computer.

[Effects of the Invention] As explained above, according to the present invention, it is possible to accurately measure the concentration state of the electron beam of a color cathode ray tube using a relatively simple black and white video camera with good characteristics. I can do it.

[Brief explanation of drawings]

Figure 1 (a) is an explanatory diagram of a white dot pattern being displayed on the color cathode ray tube to be tested, Figure 1 (b) is an enlarged view of one display pattern, and Figures 2 and 3 are different. In order to identify the displayed colors on a black-and-white screen, the display time was shifted by a specified extremely short period of time, and the display positions were separated for each color, and a dot pattern was displayed on the screen of the color cathode ray tube under test. FIG.

Claims (1)

[Claims] 1. Arbitrarily determine three primary color signals that, if applied simultaneously to the electron guns for the respective colors, will display a single white dot or crosshatch on the display surface of the color cathode ray tube to be tested, separately for each color signal. The electron gun is applied to the electron gun for the corresponding color one after another with a short fixed time difference, and each color is displayed at a distance in the order of red, green, and blue on the display surface of the color cathode ray tube to be tested, and then the same is applied. Blue, green, and red are displayed separately at the time difference, and each of the two display states is photographed using a black and white video camera, and the position of the center of luminance of each color display is measured, and the center of luminance of green is determined. The measured values of the distance from the position to the center of gravity of red and blue brightness during the above two types of display are added and averaged with the signs reversed, and the result is regarded as the amount of deviation on the fluorescent surface of each color electron beam. A method for measuring an electron beam concentration state of a color cathode ray tube, characterized in that the method is used to determine whether the concentration state is good or bad.