JPS6216075B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam control device used in a picture tube, etc., which supplies a beam current up to near the saturation region of a phosphor. change the spot shape of
The purpose is to automatically obtain images with well-balanced white color from low-brightness areas to high-brightness areas.

Generally, when reproducing colors on color television, the color temperature of white changes depending on the brightness level of the image (depending on the beam current), and white with a higher color temperature tends to be preferred as the brightness level increases. It is in. That is, it is desirable to set the color temperature to a relatively low color temperature at low luminance, and to control the white color so that the color temperature becomes higher as the luminance level increases.

Therefore, a white color control method in a conventional direct viewing tube will be explained. A typical example of this is that in the past, the cathode resistor, which is the front stage of the cathode input signal of a color picture tube, automatically outputs red and
There was a device equipped with a gamma switching circuit that combined a resistor and a Zener diode to control the green and blue beam currents.

In the above device, if the brightness signal level is low and the beam current flowing through each electron gun is small, the Zener diode provided for control does not conduct, so each electron gun operates with the same characteristics as shown by the broken line 4 in Figure 1. do. Therefore, a reference color of constant chromaticity is obtained. Next, when the brightness signal level increases and the beam current increases, the Zener diode becomes conductive, and the cathode resistance at this time of conduction is blue resistance <
Since the settings are set so that the relationship of green resistance < red resistance is obtained, the solid lines 1 (blue), 2 (green), and 3 in Figure 1
The characteristics of each color shown in (red) are obtained. At this time, the smaller the resistance, the larger the correction, and the higher the luminance level, the higher the color temperature of the reference white moves. Since the control method used in the above-mentioned device detects the beam current that directly controls the amount of light emitted from the phosphor, highly accurate and stable control is achieved. However, although the above control method is a good method for low current density regions such as direct viewing tubes, it is not suitable for projecting picture tubes that flow much higher current density than direct viewing tubes, as described below. It was not effective.

When reproducing images using a projection type, three projection type picture tubes each having red, green, and blue phosphors are used to maintain a constant white balance in the low to high brightness area. It is desirable that the brightness increase characteristics of each color of green and blue be proportional to the beam current. However, the brightness characteristics with respect to the increase in the amount of beam current differ depending on the red, green, and blue fluorescent materials used in the projection picture tube for each color. In particular, projection picture tubes are driven in a high current density region, 10 to 20 times that of a direct viewing tube, so in areas where the beam current is large, the saturation characteristic region of each phosphor is used, and the beam Because the saturation ranges of the three types of phosphors differ with respect to an increase in current, the white balance at high brightness is disrupted, resulting in chromatic colors instead of white.

Furthermore, by applying the gamma switching circuit,
In other words, even if the gamma characteristics are emphasized for each color, the beam current will certainly increase partially, but since the phosphor has already entered the saturation region, the brightness characteristics will not follow sufficiently, and the color temperature will increase. Another disadvantage was that it was not possible to control the increase in temperature sufficiently.

The present invention provides a control magnetic field generator that changes the beam shape in response to the imbalance of the white balance of images due to differences in the characteristics of each color phosphor when used in an area of high current density. For example, by controlling the shape of the spot on the phosphor surface of the beam image reproducing device into a vertically elongated shape and increasing the spot area in the phosphor saturation region, the brightness can be increased with respect to the increase in beam current. realized,
This improves the white characteristics in areas where the amount of electron beam is large so that a correct white balance can be obtained. Furthermore, even in areas where the beam current is large, the effect of the gamma correction circuit for increasing the white color temperature can be fully demonstrated.

An embodiment of the present invention will be described in detail below.

FIG. 2 shows a projection television receiver equipped with a magnetic field generating device for controlling three picture tubes. 5
is a screen, 6, 7, 8 are projection type picture tubes for red, green, and blue, 9, 10, 11 are deflection yokes and convergence yokes, 12, 13, 14
15, 16, 17 are control magnetic field generators, 18 is a deflection drive circuit, 19 is an electromagnetic focusing device drive circuit, and 20 is a beam current detection circuit.
Note that the block shown at 21 is an electron beam control device.

FIG. 3 shows an example including an electron beam detection means, which detects the electron beam from the cathode portion of the picture tube. In other cases, the ABL point of a flyback transformer may be used. The one in Figure 3 is the picture tube 2.
A cathode resistor 24 connected to the cathode 23 of No. 2
A detection circuit 25 is provided to detect and amplify the amount of beam fluctuation from the cathode resistor 24, and by applying the output of the detection circuit 25 to the control magnetic field generator 26, the spot of the electron beam can be adjusted as described above. It is configured to change shape.

4 and 5 show control magnetic field generators 15 and 1.
Examples 6 and 17 are shown below.

As shown in FIG. 4, in one control magnetic field generator 27, the horizontal direction is defined as the x-axis, and the direction perpendicular thereto is defined as the y-axis. 45 each for x-axis and y-axis
゜A total of 4 cores are formed on a set of rotated shafts,
Windings 28 and 28a are applied to the two opposing poles. This 2
No winding is applied to the cores of the two poles in the direction perpendicular to the poles. When an electron beam from the front on the z-axis passes through the control magnetic field generator 27 with a circular distribution and a certain diameter, the beam flux A narrows in the x-axis direction and narrows in the y-axis direction. receives a force of each magnitude in the direction of stretching it, and the shape of the beam bundle is controlled. There is no magnetic field at the center of the beam flux A, and the magnitude only needs to increase as it moves away from the axis, so the direction of the current flowing through the windings 28 and 28a is such that when the current flows, it moves toward the center and a magnetic field is generated. Just let it flow like this. That is, the windings 28, 28
The directions of a must be the same polarity.

Next, changes in the spot shape of the electron beam will be explained using FIG. The beam spot 30' at the crossover point 30 near the cathode is connected to the focusing lens 3.
1 to focus at position 32 on the z-axis. now,
Since the beam spot 27' that passes through the control magnetic field generator 27 has a certain size, the farther it is from the axis, the more force it receives, and after passing through the lens 31, the electrons in the y direction in particular end up at position 33 on the z axis. It will be focused. Since the fluorescent surface is actually located at position 32, the spot shape here is vertically elongated as shown at 32'. That is, the x-y magnetic field distribution of the control magnetic field generator 27 increases the spot area in the beam image reproducing device after passing through the beam focusing lens system, and the brightness can be increased.

FIG. 5 shows a control magnetic field generating device 27a in the case where current flows in opposite polarities, and the effect of its operation is the same as that of FIG. 4. Note 28,2
8a, 29, 29a are windings, and A is a beam bundle.

7 and 8 show various characteristics according to the above embodiment, and FIG. 7 shows the y of the beam spot with respect to the control current applied to the control magnetic field generator 27.
The curve 34 shows a positive correlation. Furthermore, FIG. 8 shows the luminance versus the length of the beam spot in the y-axis direction, and these FIGS.
It can be seen from FIG. 8 that the brightness can be improved by increasing the control current.

It is important that the brightness improvement described above does not depend on the beam current, that is, even if the beam current increases and the phosphor is in the saturated region, the brightness can be improved by controlling the current as described above. It is possible to increase

Next, it will be described that the above embodiment can maintain a sufficient white balance at high beam current.

FIG. 9 shows the general characteristics of a phosphor showing an increase in brightness as the beam current increases. Compared to the characteristics of the green phosphor (curve 36) and the characteristics of the red phosphor (curve 37), the characteristics of the blue phosphor (curve 38) enter the saturation region earlier as the beam current increases. . That is, when a high-brightness image is obtained using a high beam current in the conventional method, the white balance is disrupted due to insufficient blue brightness. On the other hand, FIG. 10 shows the brightness characteristics when the beam spot control according to this embodiment is performed only for the blue beam. The solid lines 36, 37, and 38 have the same green, red, and blue characteristics as in FIG. 9, respectively. A curve 39 shown by a broken line is a characteristic of the blue beam when an increase in the beam current is detected and the control current is increased to increase the brightness by changing the shape of the blue beam spot. That is, since the brightness of the blue phosphor is improved even when it is in a saturated state, it is possible to achieve white balance in a high-brightness image.

Furthermore, if a conventional gamma switching circuit is used, since the above embodiment achieves white color in a high brightness state, it becomes possible to correct the white color toward a higher color temperature, resulting in even higher quality. images can be obtained.

Although the beam control of the present invention is applied only to the blue beam in FIG. 10, it is sufficient to control each color in the most appropriate manner depending on the difference in the material of each phosphor with the configuration shown in FIG. Needless to say.

According to the above embodiment, it is possible to obtain an image with high brightness and good white balance, especially when reproducing a color image using a projection type picture tube, and further, by using a gamma characteristic correction circuit, the effect can be fully exhibited. Is possible.

Furthermore, since the control according to the present invention changes the shape of the beam spot vertically, it has the effect of realizing high brightness control without causing deterioration of the horizontal resolution of the television image.

As described above, the present invention provides an excellent electron beam control device that can control the electron beam to automatically balance the white color up to the high brightness region, including the phosphor saturation region due to high beam current. It is.

[Brief explanation of the drawing]

FIG. 1 is a white characteristic correction curve diagram for a conventional direct viewing tube, and FIG. 2 is a configuration diagram showing an embodiment of the present invention.
Fig. 3 is a configuration diagram of the main parts of this embodiment, Figs. 4 and 5 are front views of the control magnetic field generator which is the main part of this embodiment, Fig. 6 is an operation explanatory diagram, and Figs. 8 is an operating characteristic curve diagram, FIG. 9 is a general luminance characteristic curve diagram, and FIG. 10 is a luminance characteristic curve diagram of this embodiment. 6, 7, 8... Projection picture tube, 9, 10, 11
...deflection yoke and convergence yoke, 1
2, 13, 14... Electromagnetic focusing device, 15, 16,
17... Control magnetic field generator, 18... Deflection drive circuit, 19... Electromagnetic focusing device drive circuit, 20... Beam current detection circuit, 21... Electron beam control device.

Claims (1)

[Claims] 1. An electron gun device that forms an electron beam, a focusing lens device that focuses the electron beam, a deflection device for scanning the electron beam, and a phosphor that reproduces an image using the electron beam. and provided between the electron gun device and the focusing lens device,
A control magnetic field generating device that controls the cross-sectional shape perpendicular to the axis of the electron beam, and a control magnetic field that detects the amount of beam current where the luminance characteristics of the phosphor enters a saturation region and generates a control magnetic field by a detection output obtained when the beam current is higher than that. An electron beam control device comprising: a detection device that controls a generator to make the cross-sectional shape of the electron beam elongated in the vertical direction. 2. The control magnetic field generating device is characterized in that it has a control magnetic field section in which a plurality of opposing poles are provided inside an annular core, and each of the opposing poles is wound with a winding that generates the same polarity as each other. An electron beam control device according to claim 1.