JPH0468388A - Crt display device - Google Patents

Abstract

PURPOSE:To prevent the focus from deteriorating as a result of brightness adjustment and contrast adjustment by decreasing or increasing a focus voltage according to a rise or fall in 1st grid voltage. CONSTITUTION:This device is equipped with a brightness adjusting circuit 31 which adjusts the brightness by varying the 1st grid voltage, a contrast adjusting circuit 32 which adjusts the contrast by varying a cathode voltage, and a focus adjusting circuit 33 which adjusts the focus by varying a focus voltage. Then the focus voltage is decreased or increased as the 1st grid voltage rises or falls. Therefore, even when the brightness is adjusted by varying the 1st grid voltage, the focus voltage which provides the best focus of an image is obtained at all times. Consequently, the resolution can be prevented from deteriorating owing to the brightness adjustment, and the display device of high quality is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a CRT display device used in document filing systems and the like.

[Prior Art] FIG. 3 shows a circuit diagram of a conventional CRT display device. 8 in Figure 3, 67.9. ] 0 is a resistor, 5, 8.21 is a variable resistor, 31 is a brightness adjustment circuit that adjusts the chanting by changing the first grid voltage, 32 is a contrast adjustment circuit that adjusts the contrast by changing the cathode voltage, 33 is a focus adjustment circuit that adjusts the focus by changing the focus voltage, and 34 is a video preamplifier. Further, the cathode ray tube 11 uses a BPF (high potential focus) electron gun, and G1 to G4 are the first to fourth grids.

In this case, the third grid G3 becomes the focus electrode.

In addition, +81. 183 is a positive voltage application point, and B2 is a negative voltage application point.

The focus voltage of the third grind G3, which is a focus electrode, is adjusted by the focus adjustment variable resistor 5 so that the focus of the image is optimal.

The video signal A is amplified by the video amplification circuit 12, and the cathode K
is applied to

In order to increase the brightness, it is sufficient to increase the voltage of the first grid G1, and the voltage of the first grid G1 is adjusted by the brightness adjustment variable resistor 8.

The focus voltage of the third grid G3 is constant regardless of the voltage to the cathode or the voltage of the first grid Gl.

The solid line (■) shown in FIG. 4 shows the relationship between the brightness and focus voltage of the CRT display device shown in FIG. As shown by the solid line ■, the focus voltage is unrelated to the brightness and is constant.

[Problems to be Solved by the Invention] If we define the voltage of the focus electrode that optimizes the focus of the image as the optimal focus voltage, then the optimal focus voltage can vary depending on the brightness as shown by the broken line ■ in Figure 4. Are known. The change in brightness means that
The voltage on the cathode and the voltage on the first grid G1 change, that is, the optimal focus voltage changes depending on the voltage on the cathode and the voltage on the first grid G1.

The resolution of CRT display devices used in personal computers, CAD, etc. is generally 4 dots/depression or less, and in this case, there is no practical problem in resolution deterioration due to changes in the optimal focus voltage, so the voltage of the focus electrode is adjusted to increase the brightness. There was no need to change due to changes in

However, CR used for document filing systems, etc.
The resolution required for a T-display is 8 dots/-, and in this case, changes in the optimum focus voltage due to changes in brightness cannot be ignored.

An object of the present invention is to provide a CRT display device that can prevent deterioration of focus caused by brightness adjustment and contrast adjustment and can realize high quality and ultra-high resolution.

[Means for Solving the Problem] The CRT display device according to claim (1) is characterized in that the focus voltage is decreased or increased according to the increase or decrease in the first grid voltage. A CRT display device is characterized in that a focus voltage is increased or decreased in response to an increase or decrease in cathode voltage.

(Function) According to the configuration described in claim (1), since the focus voltage is decreased or increased in accordance with the increase or decrease in the first glyph voltage, the brightness can be adjusted by changing the first grid voltage. The focus voltage can always be set to the voltage that optimizes the focus of the image.

According to the configuration described in claim (2), the focus voltage is increased/decreased according to the increase/decrease of the cathode voltage, so that even if the contrast is adjusted by changing the cathode voltage, the focus voltage can always be adjusted to optimally focus the image. The voltage can be set to

〔Example〕

Figure 1 shows a circuit diagram of a CRT display device according to a first embodiment of the present invention. In Figure 1,
1, 2.4 is a resistor, and 3 is a transistor. The other configurations are the same as those shown in FIG. 3 as a conventional example, and corresponding parts are given the same reference numerals.

FIG. 1 shows a configuration in which the voltage of the first grid G1 is directly detected and the focus voltage of the third grid G3 is corrected to the optimum focus voltage.

As shown in FIG. 1, the focus voltage of the third grid G3 is determined by the combined resistance of the resistor 1.2 and the transistor 3. Since the base of the transistor 3 is connected to the first grid G1 through the resistor 4, the brightness can be changed.
In other words, the first grid G is controlled by the brightness adjustment variable resistor 8.
By changing the voltage of the transistor 3, the resistance value of the transistor 3 can be changed, and the change in the resistance value of the transistor 3 also changes the focus voltage of the third grid G3.

Here, the focus voltage of the third grid G3 is ■r,
It is assumed that the amplification factor of the transistor 3 is sufficiently large, and that the amplification factor of the transistor 3 is sufficiently large.
If it is assumed that is sufficiently small to be ignored, then the focus voltage .

V, =VB CI-RZ/(R2+RS))RzR2V
c/R, (Rz+Rs) However, ■ is the voltage between ec, ■8 is the voltage between ed, ■,
is the voltage between ae, R1 is the resistance value of resistor 1, and R2 is the resistance value of resistor 2
R3 is the resistance value between bd and R2 is the resistance value between cd.

From the above equation, it can be seen that the focus voltage VF changes in proportion to the voltage V between ae and the slope is negative. In addition, the fourth
In the figure, since the slope of the dashed line (2) indicating the optimum focus voltage is negative, it can be seen that the focus voltage (2) can be corrected to the optimum focus voltage.

FIG. 2 shows a circuit diagram of a CRT display device according to a second embodiment of the present invention. In Figure 2,
21 is a variable resistor for contrast adjustment; 22 is an interlocking variable resistor linked to the variable resistor 21 for contrast adjustment;
23 is an interlocking variable resistor interlocked with the brightness adjustment variable resistor 8. The other configurations are the same as those shown in FIG. 3 as a conventional example, and corresponding parts are given the same reference numerals.

FIG. 2 shows a configuration in which the voltage at the cathode and the voltage of the first grid G1 are indirectly detected to correct the focus voltage of the third grid G3 to the optimum focus voltage.

As shown in FIG. 2, when the connection of the contrast BJjl adjustment variable resistor 21 is changed in the direction of the arrow 2, the connection of the interlocking variable resistor 22 is changed in the direction of the arrow 2. Further, when the connection of the brightness adjustment variable resistor 8 is changed in the direction of the arrow (2), the connection of the interlocking variable resistor 22 is changed in the direction of the arrow (2). In this way, by adjusting the contrast and brightness, the interlocking variable resistor 2
The resistance value of 2.23 changes, and the focus voltage of the third grid G3 changes. In other words, the voltage or first voltage applied to the cathode
The focus voltage of the third grid G3 can be controlled by changing the grid G1 voltage, and the focus voltage can be corrected to the optimum focus voltage. Note that the brightness and contrast increase by changing the connection of the variable resistor 8.21 in the directions of arrows (■) and (2).

〔Effect of the invention〕

In the CRT display device according to claim (1), the focus voltage is decreased or increased in response to an increase or decrease in the first grid voltage, so that even if the first grid voltage is changed and the brightness is adjusted, the focus voltage remains constant. The voltage can be set to optimally focus the image. As a result, deterioration of resolution due to brightness adjustment can be prevented, and a high-quality, ultra-high resolution CRT display device can be realized.

In the CRT display device according to claim (2), the focus voltage is increased or decreased in accordance with the increase or decrease in the cathode voltage, so that even if the contrast is adjusted by changing the cathode voltage, the focus voltage can always be adjusted to optimally focus the image. The voltage can be set to . As a result, deterioration of resolution due to contrast adjustment can be prevented, and a high quality CRT display device with ultra-low resolution can be realized.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a CRT display device according to a first embodiment of the present invention, FIG. 2 is a circuit diagram of a CRT display device according to a second embodiment of the present invention, and FIG. 3 is a circuit diagram of a CRT display device of a conventional example. FIG. 4, a circuit diagram of the display device, is a diagram showing the relationship between brightness and focus voltage. 1.2.4...Resistor, 3...Transistor, 222
3... Interlocking variable resistor, 3]... Brightness adjustment circuit, 3
2... Contrast adjustment circuit, 33... Focus adjustment circuit, K... Cathode, G1... First grid, do, G3... Third grid (focus electrode) 4...
Resistor 3...Transistor K...Cathode G1...I'! 1 grid G3・-$3 grid (focus electrode) /12

Claims (2)

[Claims] (1) A brightness adjustment circuit that adjusts the brightness by changing the first grid voltage, a contrast adjustment circuit that adjusts the contrast by changing the cathode voltage, and a focus adjustment circuit that adjusts the focus by changing the focus voltage. A CRT display device, characterized in that the focus voltage is increased or decreased in response to an increase or decrease in the first grid voltage. (2) A brightness adjustment circuit that adjusts the brightness by changing the first grid voltage, a contrast adjustment circuit that adjusts the contrast by changing the cathode voltage, and a focus adjustment circuit that adjusts the focus by changing the focus voltage. A CRT display device, characterized in that the focus voltage is increased or decreased in response to an increase or decrease in the cathode voltage.