JPH0425662B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a flat cathode ray tube used in color television receivers, computer terminal displays, and the like.

Conventional Structure and Problems There is a prior art flat cathode ray tube created by the present applicant with a structure shown in FIG. In reality, each electrode is housed in a vacuum envelope (glass container), but the vacuum envelope is omitted in the figure to make the internal electrodes clear. Further, in order to clarify the horizontal and vertical directions of the screen on which images, characters, etc. are displayed, a horizontal direction H and a vertical direction V are illustrated on the face plate portion.

First, a plurality of vertically long linear cathodes 10 each having an oxide cathode formed on the surface of a tungsten wire are independently arranged at equal intervals in the horizontal direction. The number of linear cathodes 10 and the spacing between them are design matters. For example, if the display screen size is 10 inches, the horizontal spacing between them is approximately 10 mm.
20 linear cathodes are arranged vertically with a length of approximately 160 mm. On the opposite side of the face plate portion 9 across the linear cathode 10, there are strips arranged vertically at equal pitches on the insulating support 11 in close proximity to the linear cathode 10, and electrically divided and elongated in the horizontal direction. Vertical scanning electrodes 12 are arranged. These vertical scanning electrodes 12 are formed as independent electrodes in the vertical direction equivalent to the number of horizontal scanning lines (approximately 480 in the NTSC system) if a normal television image is to be displayed. Next, between the linear cathode 10 and the face plate 9, a planar first grid electrode 13 having an opening formed in a portion corresponding to the linear cathode 10 is arranged sequentially from the linear cathode 10 side. Next, a second grid electrode 14 for beam modulation is arranged corresponding to each linear cathode 10 and is electrically insulated from each other and has an electron beam passage hole. A third grid electrode 15 having a similar shape is arranged. Next, a horizontal deflection electrode 16 is arranged to apply a horizontal deflection to the electron beam passing through the aperture provided in each electrode. A light emitting layer 17 consisting of a phosphor and a metal back electrode is arranged on the inner surface of the face plate 9. When displaying a monochrome image, the phosphor may be one layer, but when displaying a color image, it is formed as stripes or dots of red R, green G, and blue B sequentially in the horizontal direction.

Next, we will discuss the operation of the above flat plate cathode ray tube in the second section.
This will be explained using FIG. FIG. 2 shows a horizontal cross-sectional structure of the flat cathode ray tube shown in FIG. The electrons generated by heating the linear cathode 10 are applied to the vertical scanning electrode 12 at a voltage that is approximately the same potential as the linear cathode 10, and to the first grid electrode 13 at a voltage that is lower than the potential of the linear cathode 10. As a result of the application of a high voltage, the particles also advance toward the openings of the first grid electrode 13. In FIG. 2, the electron beam trajectory is indicated by 18. First grid electrode 1
The electron beam passing through the aperture 3 is modulated by the second grid electrode 14. In the case of color image display, the image is modulated by a point-sequential video signal specified as R→G→B→R→G→B→.... Second
The electron beam passing through the grid electrode 14 is focused by the third grid electrode 15 so as to form a small beam spot on the phosphor emitting layer 17. Next, wires 16i, 1 are connected to the horizontal deflection electrode 16.
A sawtooth wave or step-like horizontal deflection voltage is applied through the electron beam 6, and the electron beam 18 is deflected horizontally by a predetermined width, stimulating the light emitting layer 17 on the face plate 9 to obtain a light emitting image. In order to display a color image, when each electron beam horizontally scans the light emitting layer 17 as described above, a second modulation signal is generated for the color corresponding to the color phosphor on which the electron beam is incident.
applied to grid electrode 14.

Next, vertical scanning will be explained using FIG. 3. Close to the back of the linear cathode 10, there is a vertical line that is long in the horizontal direction and divided vertically into the number of horizontal scanning lines necessary to form an effective screen, for example, in the case of the NTSC system, about 480 lines. Scanning electrode 1
2 are arranged, and a vertical scanning signal is applied to each of these electrodes. As described above, the electric potential of the space surrounding the linear cathode 10 is
Generation of electrons from the linear cathode 10 is controlled by controlling the voltage of the vertical scanning electrode 12 so that the potential is more positive or negative than the potential of the linear cathode 10. At this time, if the distance between the linear cathode 10 and the vertical scanning electrode 12 is small, the control voltage may be small; for example, if the distance is about 0.3 mm, the control voltage will be 5V _pp
The generation of electrons can be controlled with a voltage of about In the case of a TV image that uses an interlaced method, the vertical scanning electrode 12 has a
There is a signal (hereinafter ON) that causes the beam to be generated only during the horizontal scanning period (hereinafter referred to as 1H), a signal that causes the beam to be ON only for the next 1H at 12C, and a signal that causes the beam to be ON only for the next 1H in order from every other vertical scanning electrode. When the ON signal is applied and the 12X at the bottom of the screen is completed, the vertical scanning of the first field is completed. next second
Similarly, to the field 12B, a signal is applied that turns on the beam only for 1H, and finally 1H is applied.
One frame of vertical scanning is completed by scanning up to 2Y.

In a horizontal cathode ray tube that forms the entire screen through vertical scanning, beam modulation, and horizontal deflection as described above, the amount of electron beams that pass through the apertures of each electrode and enter the phosphor surface is determined by the amount of electrons emitted from the cathode. It is not constant due to variations in characteristics, variations in the size of each electrode opening, etc. For this reason, when a completely white screen is displayed, some dark or bright areas occur, making it impossible to obtain an image with uniform brightness, resulting in an extremely poor image quality.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a flat cathode ray tube having a large number of electron beam sources, such as the above flat cathode ray tube, with uniform characteristics of each electron beam source.

Structure of the Invention In the flat cathode ray tube of the present invention, one electrode having the same structure as the second grid electrode is inserted between the second grid electrode and the third grid electrode, and the horizontal retrace period (which means the horizontal scanning start part) By keeping the operating conditions of the electron beam emission source constant to form an image of one horizontal scanning line during a horizontal blanking period (hereinafter referred to as the H-BL period), the amount of electron beam flowing into the insertion grid electrode is equal to the amount of electron beam flowing into the insertion grid electrode during one horizontal scanning period. This is a flat plate cathode ray tube in which the amount of electron beam emission is controlled to be constant.

DESCRIPTION OF EMBODIMENTS FIG. 4 is a perspective view of a flat cathode ray tube according to a first embodiment of the present invention, and FIG. 5 is a horizontal sectional view thereof. Since the parts other than the electrode 45 are the same as those in FIGS. 1 and 2, they will be given the same reference numerals and a detailed explanation will be omitted. It has a hole of
It is divided horizontally.

A method of controlling the amount of electron beams from each electron beam emission source 10 of the flat cathode ray tube having the above electrode configuration will be described with reference to FIGS. 6 and 7.
The operation of the vertical scanning electrode 12 is the same as that of the flat cathode ray tube shown in FIG. 1, and the vertical scanning power supply 62 supplies signals 12A, 12C, 12E, . . . as shown in FIG.
A voltage that turns on the beam only during and 1H is sequentially applied. Then, during the H-BL period at the beginning of the 1H scan, a predetermined voltage (FIG. 7, 44) is applied to the second grid electrode 14 so that a constant beam passes through the aperture of the second grid electrode 14. For this purpose, the video signal 61 and the H-BL signal 63 are mixed in a mixing circuit 68, amplified in an amplifier 64, and the signal voltage shown in FIG. 7 is applied to the second grid electrode 14. When this H-BL signal 63 is received, the electron beam passes through the aperture of the second grid electrode 14 and enters the fluorescent surface 17, so it is necessary to prevent the electron beam from reaching the fluorescent surface 17 during this period. Must be. Therefore, the H-BL signal 63 is amplified by the amplifier 66 and supplied to the third grid electrode 15 (FIG. 7, 46), thereby blocking the electron beam during the H-BL period. At this time, by detecting the current flowing into each insertion electrode 45 with the current detector 65, variations in the amount of electron beam from the cathode 10 to the insertion electrode 45 passing through the opening of the second grid electrode 14 are eliminated. This detected current is shown in Fig. 745.
The control signal is sent from the control circuit 67 to the cathode drive amplifier 6 so that it becomes a constant value within the H-BL period as shown in FIG.
0 to control the cathode potential of the electron beam emitting section. The controlled cathode potential is maintained for 1H.

As described above, H-
By making the amount of electron beams from each electron beam emission source 10 constant during the BL period and maintaining this for 1 hour, image noise in brightness and darkness due to variations in the amount of electron beams incident on the fluorescent surface can be removed. I can do it.

In the above embodiment, the cathode potential is controlled so that the current flowing into the insertion electrode 45 is constant, but a control signal from the control circuit 67 is input to the amplifier 64 to change the amplification factor of the video signal. It is also possible.

Next, a second embodiment will be described in which the electron beam is modulated by applying a video signal to the cathode or the first grid electrode. FIG. 8 shows an example of applying a video signal to the cathode 10. When applying the video signal to the first grid 13, it is divided horizontally into two grid electrodes 14 corresponding to each cathode 10. It is only necessary to use the electrode as the first grid electrode, so the explanation will be omitted.

The basic structure of the electrodes is almost the same as that of the first embodiment, except that the insertion electrode 45 is not divided into parts but is integrated into one. A control method for making the amount of electron beams from each electron beam emission source uniform in a flat cathode ray tube having such an electrode configuration will be explained with reference to FIG. Since the operation of the vertical scanning electrode 12 is the same as that in the first embodiment, the same reference numerals are given and the explanation of the operation will be omitted. In this embodiment as well, during the H-BL period at the beginning of the 1H scan, the cathode 10 is
A predetermined voltage (80 in FIG. 10) is applied to. Therefore, since the beam current detection signal and the video signal are applied to the cathode 10, the video signal 91 and the H-BL signal 93 are mixed in the mixing circuit 98,
This is amplified by an amplifier 90 and applied to the cathode 10. Thus, even during the H-BL period, the electron beam passes through each electrode aperture and enters the phosphor surface, so it is necessary to prevent the beam from entering the phosphor surface during the H-BL period. Therefore, the insertion electrode 45
A signal from the H-BL signal amplifier 95 (85 in FIG. 10) is applied to the beam, and the beam is interrupted by the insertion electrode 45 during the H-BL period. In this way, the electron beam emitted from the cathode 10 will be incident on the corresponding second grid electrode 14. Therefore, this incident electron beam current is detected by the detector 97, and this detected current becomes H- as shown in FIG.
A control signal is sent from the control circuit 96 to the second grid drive circuit 94 to control the second grid voltage so that the current value is a predetermined value during the BL period. The controlled second grid voltage is maintained for 1H.

As described above, the present invention detects variations in the electron beam emission characteristics from an electron beam emission source caused by mechanical factors within the H-BL period at the beginning of the horizontal scanning period, and converts them into predetermined characteristics. It is possible to eliminate this by controlling it so that it is true and holding it for 1 hour, and it is possible to improve the image quality.

Effects of the Invention As described above, the present invention aims to eliminate variations in electron beam emission characteristics from each electron beam emission source of a flat cathode ray tube having a large number of electron beam emission sources. During the BL period,
This is done by detecting each electron beam emission characteristic and holding it for 1 hour so that it becomes a predetermined characteristic. Therefore, unlike conventional methods, brightness and darkness are fixed due to variations in each electron beam emission characteristic. Pattern noise can be removed from the displayed image,
Improves image quality.

[Brief explanation of drawings]

1 and 2 are respectively a perspective view and a sectional view showing the electrode structure of a flat cathode ray tube according to the prior art by the present applicant, and FIG. 3 is an explanatory diagram of the vertical scanning operation of the structure shown in FIG. 4 and 5 are perspective views and sectional views showing a first embodiment of the flat cathode ray tube of the present invention, FIG. 6 is a drive circuit diagram thereof, and FIG. 7 is a first embodiment of the present invention. FIG. 8 is a sectional view showing a second embodiment of the flat cathode ray tube of the present invention, FIG. 9 is a drive circuit system diagram thereof, and FIG. 10 is a diagram of the signal waveform applied to each electrode of the present invention. A signal waveform diagram applied to each electrode in the second example is shown. 12... Vertical scanning electrode, 10... Linear cathode, 13... First grid electrode, 14... Second grid electrode, 15... Third grid electrode, 45...
...insertion electrode, 16...horizontal deflection electrode, 17...fluorescent surface, 61,91...video signal, 63,93...
Horizontal blanking signal, 60, 90... Cathode drive amplifier, 64... Video signal amplifier, 65, 9
7... Current detector, 67, 96... Control signal generator.

Claims (1)

[Scope of Claims] 1. One or more filamentary cathodes, an elongated scanning electrode disposed behind the filamentous cathodes in a direction substantially perpendicular to the filamentous cathodes, and a fluorescent screen in front of the filamentous cathodes. An electrode that defines the amount of electron beam that reaches , and a plurality of electrodes arranged in front of the electrode, and a beam cutoff voltage is applied to one of the plurality of electrodes during a horizontal blanking period that is the start of horizontal scanning. , detecting a beam current flowing into an electrode disposed in front of the electrode to which the beam cutoff voltage is applied, and controlling the amount of the electron beam so that this current value becomes a predetermined current value for one horizontal scanning period. Characteristic flat cathode ray tube. 2. Claim 1, wherein the plurality of electrodes comprises a beam modulation electrode, a current detection electrode, and a beam focusing electrode, and a beam blocking voltage is applied to the beam focusing electrode.
The flat cathode ray tube described in Section 1. 3. The plurality of electrodes are composed of a beam modulating electrode, a beam focusing electrode, and an insertion electrode arranged between the two, and a beam cutting voltage is applied to the insertion electrode, and a beam current is detected by the beam modulation electrode. The flat cathode ray tube according to item 1.