JPH11133906A - Crt display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a CRT display which reduces moire phenomena generated by interference between a picture signal pattern and a shadow mask pitch without degrading the picture quality. SOLUTION: Picture signals 1 are converted into digital signals by an A/D converter 2 to be stored in a line memory 3 and read out by a line memory 3 by a read-out clock R whose frequency is modulated at a horizontal period so that the picture signals 1 are modulated in the time-axis direction and converted again into the analog signals A by a D/A converter 4. A voltage control oscillator circuit 9 is varied by changing the frequency deviation at a prescribed modulation level so that the relation of the interval between respective dots of the picture signals 1 to the mask pitch is deviated so as to prevent the degradation of the picture quality and reduce the moire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CRT display device, and more particularly to a CRT display device in which horizontal moire phenomenon is reduced.

[0002]

2. Description of the Related Art In a conventional CRT display device, when an image display pattern having a luminance difference for each dot is displayed with an increase in size and resolution, interference occurs between the display pattern and the mask pitch of the CRT. The moiré phenomenon degrades the quality of the screen, and an increase in the number of devices equipped with a moiré canceling circuit for reducing the quality of the screen increases. As shown in FIG. The deflecting circuit 112 delicately changes the phase of the deflection current or the phase of the video signal 1 every horizontal period.
, The moire generated on the screen of the CRT 6 is reduced.

Further, by inputting a moiré cancel signal to a focus circuit of the CRT 6, the focus of the screen is degraded, and the size of one dot of the display pattern is increased to make the moiré phenomenon less noticeable.

[0004]

However, in the conventional CRT display device, by adding a moiré cancel signal to a phase shift circuit, the phase of the input video signal or the phase of the deflection current is delicately changed every one horizontal period. In order to change it, the characters on the screen become jagged and the image quality deteriorates. By inputting a moiré cancel signal to the focus circuit, the focus of the screen is deteriorated and the size of one dot of the display pattern is increased. In the method of making the moiré phenomenon inconspicuous, the quality of a screen in a high-resolution signal is deteriorated.

Accordingly, an object of the present invention is to provide a method for reducing moiré without impairing display quality.

[0006]

In order to solve the above-mentioned problems, a CRT display device according to the present invention provides an A / D converter for converting a video signal output based on a horizontal synchronization signal and a vertical synchronization signal into a digital signal. A converter, a line memory for storing the digital signal converted by the A / D converter for each horizontal period, a D / A converter for converting the digital signal stored in the line memory to an analog signal,
An output circuit that processes and outputs the analog signal converted by the D / A converter, a CRT that displays the analog signal processed by the output circuit, and a synchronization circuit that processes the horizontal synchronization signal and the vertical synchronization signal. A modulation circuit that modulates the horizontal synchronization signal processed by the synchronization circuit and outputs a modulation signal; a voltage control oscillation circuit that voltage-controls the modulation signal from the modulation circuit; And a write clock circuit for sending a sampling clock and a write clock to the A / D converter and the line memory based on the output signal from the write clock circuit and the voltage-controlled modulation signal. And a read clock circuit for generating a read clock to be read.
The moire interference is reduced by shifting the relationship between the RT and the shadow mask pitch.

[0007]

Next, a CRT display device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a CR according to an embodiment of the present invention.
It is a block diagram of a T display device.

FIG. 2 shows a CR according to an embodiment of the present invention.
It is a video signal waveform diagram in one horizontal period of a T display device.

A CRT display device according to an embodiment of the present invention includes an A / D converter 2 for converting a video signal 1 output based on a horizontal synchronizing signal H and a vertical synchronizing signal V into a digital signal, and an A / D converter 2. A line memory 3 for storing the digital signal converted by the D converter 2 for each horizontal period
A D / A converter 4 for converting a digital signal stored in the line memory 3 into an analog signal A;
An output circuit 5 that processes and outputs the analog signal A converted by the / A converter, a CRT 6 that displays the analog signal A processed by the output circuit 5, and processes the horizontal synchronization signal H and the vertical synchronization signal V. A synchronizing circuit 11, a modulating circuit 10 that modulates the horizontal synchronizing signal H processed by the synchronizing circuit 11 and outputs a modulating signal M, a voltage control oscillator 9 that voltage-controls the modulating signal from the modulating circuit 10, , A write clock circuit 7 for sending a sampling clock and a write clock W to the A / D converter 2 and the line memory 3 based on the horizontal synchronizing signal H and the vertical synchronizing signal V, and an output signal from the write clock circuit 7. And a read clock circuit 8 that generates a read clock R to be sent to the line memory 3 based on the voltage-controlled modulation signal M.

Next, a CRT according to an embodiment of the present invention will be described.
The operation of the display device will be described with reference to the drawings.

As shown in FIGS. 1 and 2, the operation of a CRT display device according to an embodiment of the present invention is as follows. An input video signal 1 is converted into a digital signal by an A / D converter 2 and a line memory 3 is used. The read digital signal is read by a read clock R that has been frequency-modulated in a horizontal cycle, and the read digital signal is converted into a signal that has been modulated in the time axis direction.
Is converted into an analog signal A, and the write clock circuit 7
Receives a horizontal synchronizing signal H and a vertical synchronizing signal V, generates a write clock W for the A / D converter 2 and the line memory 3, and converts an analog signal into a digital signal at the timing of the write clock W. Is written to the line memory 3.

On the other hand, the read clock R has an oscillation frequency modulated by a modulation signal M generated by the horizontal period modulation circuit 10, and is synchronized with the write clock W by a signal output from the voltage controlled oscillation circuit 9. It becomes a clock for reading the line memory 3 and the level to be modulated is the modulation circuit 10
, And the line memory 3 performs reading with the read clock R modulated in the horizontal cycle.

The video signal 1 and the analog signal A 1
In the operation during the horizontal period, as shown in FIG. 2, the frequency increases as the control voltage of the voltage-controlled oscillation circuit 9 increases,
Conversely, the frequency is set so as to decrease as the control voltage decreases. In the case of mode 1, the voltage near t2 is reduced by the modulation circuit 10, so that the output of the voltage controlled oscillation circuit 9 is t
When the frequency near 2 decreases and the line memory 3 is read by using this signal as a clock, the dot interval of the video signal 1 near t2 increases, and the dot interval slightly increases near the center of the screen. Will be.

Further, when the modulating signal M in mode 2 is changed, the modulating signal M has a higher voltage near t1 than near t3.
When the signal is read from the line memory 3 using the signal as a clock, the dot interval of the video signal 1 near t3 is wider than the dot interval near t1, and the frequency becomes shorter from the left to the right of the screen. , The dot interval of the video signal 1 gradually increases.

[0016]

As described above, the CRT according to the present invention is
According to the display device, the relationship between the interval between each dot of the video signal and the shadow mask pitch is shifted by slightly modulating the video signal input to the CRT in the time axis direction within the horizontal period. Since moiré as stripes can be reduced and the phase of the video signal and the deflection current and the focus circuit are not controlled, there is an effect of preventing the display screen from being jagged or from deteriorating image quality such as focus deterioration. .

[Brief description of the drawings]

FIG. 1 is a block diagram of a CRT display device according to an embodiment of the present invention.

FIG. 2 is a video signal waveform diagram in one horizontal period of the CRT display device according to one embodiment of the present invention.

FIG. 3 is a block diagram of a conventional CRT display device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 video signal 2 A / D converter 3 line memory 4 D / A converter 5 output circuit 6 CRT 7 write clock circuit 8 read clock circuit 9 voltage controlled oscillation circuit 10 modulation circuit 11 synchronization circuit 12 deflection circuit

Claims (1)

[Claims] An A / D for converting a video signal output based on a horizontal synchronization signal and a vertical synchronization signal into a digital signal.
A converter, a line memory for storing the digital signal converted by the A / D converter every horizontal period, a D / A converter for converting the digital signal stored in the line memory into an analog signal, and a D / A converter An output circuit that processes and outputs the analog signal converted by the A converter, a CRT that displays the analog signal processed by the output circuit, a synchronization circuit that processes the horizontal synchronization signal and the vertical synchronization signal, A modulation circuit that modulates the horizontal synchronization signal processed by the circuit and outputs a modulation signal; a voltage-controlled oscillation circuit that voltage-controls the modulation signal from the modulation circuit; and sampling based on the horizontal synchronization signal and the vertical synchronization signal. A write clock circuit for sending a clock and a write clock to the A / D converter and the line memory;
A read clock circuit that generates a read clock to be sent to the line memory based on the output signal from the write clock circuit and the voltage-controlled modulation signal;
A CRT display device wherein the relationship between the dot pitch of the video signal and the shadow mask pitch of the CRT is shifted to reduce moire interference.