JPS6053420B2 - Color - CRT color purity detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an in-line color cathode ray tube for a color television receiver, in which the electron beam emitted from an electron gun is applied to the front surface of the cathode ray tube.
A color used in the color purity adjustment process to adjust the Lande ink of the electron beam to accurately emit color phosphors, and to detect the Lande ink state of the electron beam on the cathode ray tube screen, which also takes into account the automation of color purity adjustment. This invention relates to a purity detection device.

Conventional color purity adjustment is performed using the following procedure.

First, a single-color full-screen raster signal is applied to an in-line color cathode ray tube (hereinafter abbreviated as CPT) by switching the cathode or the like so that the entire screen is an image of only one color among red, green, and blue. Then, as shown in Fig. 1, the deflection yoke 2 located at the neck of the CPTI is moved back and forth in the axial direction, and the deflection center of the deflection yoke is intentionally shifted from the exposure center of the C-circle 1. As shown, a color belt of the same monochromatic color as the video signal is created on the screen 7. Next, the center of the color belt is aligned with the center 6 of the screen by means of a magnet 3 for adjusting the image quality formed in the CPT neck. That is, the electron beam is made to accurately hit the phosphor at the center of the screen. This is called center color purity adjustment. Next, move the deflection yoke back and forth from the above position,
Adjust so that the entire surface of the cathode ray tube has the same monochromatic color as the center, and make sure that the electron beam accurately hits the phosphor even at the periphery of the CPT screen. This is called peripheral color purity adjustment. However, in the former center color purity adjustment,
The center color belt does not actually have a uniform width 4, but a belt 5 with uneven width, and the boundary line of the color belt is not clear, so it is not possible to visually adjust it by an adjuster. It was difficult to accurately align the center of the CPT screen with the center of the color belt.

As a result, variations in adjustment and a decrease in adjustment accuracy are unavoidable, and since there is no margin for color purity beams and land ink that were good at the time of adjustment, misland ink is likely to occur depending on the installation direction of the receiver, temperature, and aging. There was a drawback. The purpose of the present invention is to eliminate the above-mentioned drawbacks when adjusting center color purity, and to increase beam landing margin by allowing the center of the electron beam to accurately hit the center of the phosphor. An object of the present invention is to provide a color purity detection device for detecting a positional deviation between the position of a central color belt and the center of a CPT screen, with the aim of eliminating variations in adjustment. In the present invention, a color belt on the CPT screen is photographed over the entire surface of the CPT screen through an optical filter of the same color, using a black and white television camera installed in advance on an extension of the central axis of the CPT screen.

Then, with respect to the horizontal center line on the screen, two points on the left and right that are substantially symmetrical are set as monitoring positions, the amplitude level on the video signal corresponding to the position is extracted, and the difference in amplitude level between the two points is displayed. This set of monitoring positions is provided at several locations on the CPT screen, for example, at the top, middle, and bottom, and the amplitude level difference on the video signal corresponding to each location is displayed. Since the amplitude level of the video signal is proportional to the brightness at each position on the screen, the adjuster can adjust the color purity magnet so that each display shows zero without looking directly at the CPT screen. will now align exactly with the center of the screen. Further, by providing a drive device for the color purity magnet and operating the drive device according to each display level difference, it is possible to automate the adjustment of the color purity magnet. An example of the overall configuration of the present invention is shown in FIG. 3, and its contents will be explained below.

A video signal generator 13 supplies a single-color full-surface raster signal synchronized with a synchronizing signal generator 14 to a color cathode ray tube (CPT) 1 under test, and the deflection yoke 2 is moved back and forth.
A monochromatic color belt as shown in Figure 2 is displayed on the screen. Then, the black and white television camera 10 installed on the screen center axis extension of the CPTl screen is used to capture the image on the screen. Photographing is performed through an optical filter 11 of the same color as the monochromatic one. At this time, the scanning of the black and white television camera is also synchronized with the synchronization signal generator 14. 1
Reference numeral 2 denotes a video signal processing circuit which uses a synchronizing signal from a synchronizing signal generator 14 to set two points on the left and right sides of the screen that are substantially symmetrical with respect to a vertical center line 6 as a set of monitoring positions.

The video signal levels at points corresponding to several sets of monitoring positions in several locations in the upper and lower directions of the screen are extracted, the signal level differences are amplified, and the display devices 15a, 15b, 15c, etc. are driven. Then, magnet 3 for color purity is set so that each display indicates zero.
Color purity can be adjusted by operating the . A specific example of the video signal processing circuit 12 is shown in FIG. As shown in this figure, the video signal is passed through an amplifier 21 and sampled by a high-speed sample/hold circuit 22 at each timing corresponding to the monitoring position on the screen.
Hold constant for a short period of time. At this time, the output signal waveform of the sample hold circuit J22 is shown in FIG. 6a. Furthermore, this hold voltage is applied to the next stage comparison circuits 23a, 23b, 23.
It seems like c. These comparison circuits are the same, and a concrete circuit of one of them 23a is shown in FIG. In FIG. 5, sampling is performed by low-speed sample-and-hold circuits 25a, 25b, etc. in correspondence with one sample-and-hold circuit at one monitoring point, and held during one screen scanning period. That is, the hold value of the video signal at the first monitoring point on the m-th horizontal scanning line of the n-th frame by the high-speed sample-and-hold circuit 22 is determined by the low-speed sample-and-hold circuit 25a.
Hold further. This hold value is the next (n
+1) After holding until the video signal at the first monitoring point on the m-th horizontal scanning line of the frame is obtained, the hold value of the high-speed sample and hold circuit 22 at this timing is held again. By constantly repeating this, the low-speed sample and hold circuit 25a always outputs a value obtained by converting the amplitude value of the video signal at the corresponding detection point into a DC level.
Similarly, the other low-speed sample and hold circuits convert the amplitude of the video signal at each corresponding detection point into a DC level and output the same. At this time, the output waveform obtained from the sample and hold circuits 25a and 25b is
Shown in Figures B and c. The differential output signals 30a, 30b, and 30c are used to drive display devices corresponding to the upper, middle, and lower monitoring positions on the screen via the differential amplifier 26 and the like. Here, the sampling timing generation of the high-speed sample and hold 22 and the low-speed sample and hold 25a, 25b, etc. is as follows.
This is performed by a video signal position designation circuit 24 which processes the horizontal synchronization signal 28 and vertical synchronization signal 29 and generates signals corresponding to the top, middle, and bottom monitoring positions on the screen. Here, as shown in FIG. 7, the vertical position on the video signal corresponding to the pair of left and right monitoring positions on the screen is as follows. It is said that

In this way, the high speed sample and hold 22 of FIG.
The monitoring position can be arbitrarily set in the horizontal direction regardless of the sampling time required for the low-speed sample holds 25a and 25b. Furthermore, by using a standard CPT that perfectly aligns the center of the color belt to set the horizontal position on the video signal, the left and right monitoring positions are set so that the display on the display device 15a shown in FIG. 3 is zero. I try to set it in advance. The positions of each set of monitoring points are set in advance as described above. In this way, it is possible to select the left and right positions for one set of screen monitoring as two points with characteristics that match the sensitivity to the brightness of the video signal, and the shading characteristics of a black and white television camera, that is, the video signal due to the deviation of the scanning position. The effect of variations in sensitivity to luminance is offset. According to the present invention, it becomes possible to objectively detect the color purity of a color cathode ray tube, thereby reducing variations in color purity adjustment and improving adjustment accuracy. Furthermore, the adjustment time can also be expected to be shortened. In addition, since contactless detection is possible, automation of color purity adjustment is easily possible by providing a color purity magnet drive device.

[Brief explanation of the drawing]

FIG. 1 shows an example of an in-line color cathode ray tube whose color purity is to be detected by the present invention. FIG. 2 shows an example of the shape of a monochromatic color belt appearing on a cathode ray tube screen. FIG. 3 shows an example of the overall configuration of the present invention. FIG. 4 shows a specific example of the video processing circuit shown in FIG. 3. FIG. 5 shows a specific example of the comparison circuit shown in FIG. Figure 6a shows the high speed sample and hold circuit 22 shown in Figure 4.
The output signal waveforms B and c show the output signal waveforms of each of the pair of low-speed sample and hold circuits 25a and 25b shown in FIG. FIG. 7 is a diagram showing the correspondence between monitoring point positions on a color cathode ray tube screen and positions on a video signal. 1
: In-line color cathode ray tube, 10: Black and white television camera, 11: Optical filter, 12: Video/image signal processing circuit, 13: Video signal generator, 14: Synchronous signal generator, 15
a, 15b, 15c: Display device.

Claims (1)

[Claims] 1. A raster generating means for generating an adjustment signal that, when supplied to a normally adjusted in-line color cathode ray tube, projects a monochromatic raster of only one of the three primary colors, and the adjustment signal is supplied. an imaging means for capturing an image of the in-line color cathode ray tube to be adjusted in synchronization with a synchronization signal in the adjustment signal, and a position approximately symmetrical to the vertical center line on the screen of the in-line color cathode ray tube to be adjusted A color purity detection device for a color cathode ray tube, comprising an extraction means for extracting the luminance level at a determined monitoring point from the output of the imaging means, and a comparison means for comparing the magnitude of the extracted luminance level.