JPH05328163A - Display device - Google Patents

Abstract

PURPOSE:To obtain the display device in which a digital trapezoidal distortion correction circuit is adopted to improve the accuracy, the circuit is integrated through the adoption of gate arrays and the control by key operation is attained. CONSTITUTION:The display device is made up of a period discrimination circuit 21 counting 0 to M-1 of a vertical synchronizing signal based on a reference clock to discriminate the period, a period/N generating circuit 22 generating a 2nd clock being 1/N division of the period of the period discrimination circuit 21, a fixed counter circuit 23 counting 0 to N-1 by the 2nd clock, D/A converter circuits 25, 26 converting an output of the fixed counter circuit 23 into an analog signal to correct trapezoidal distortion with high accuracy by digital control. As a result, the accuracy is improved by digital processing and the key operation control is implemented and the circuit is integrated by adoption of gate arrays and then the cost is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device capable of performing trapezoidal distortion correction effective for monitor receivers such as televisions and displays.

[0002]

2. Description of the Related Art In a display device such as a display, in order to scan an electric image in an image pickup tube or a fluorescent surface of a picture tube to form a raster, an electron beam of the picture tube is deflected in horizontal and vertical directions. A coil for
A sawtooth wave current as shown in (a) is passed to perform electromagnetic deflection.

As shown in FIG. 4B, the horizontal deflection current has a constant horizontal amplitude in the horizontal direction while the vertical deflection current scans the screen vertically. As described above, the parabolic wave-like amplitude modulation is performed in the vertical deflection cycle, and a screen as shown in FIG. 4C is obtained.
However, if the magnetic field distribution of the vertical deflection coil is unbalanced or the mechanical center point of the electron beam is deviated,
The screen becomes as shown in FIG. 4D, and trapezoidal distortion occurs.

Conventionally, in order to correct this trapezoidal distortion, FIG.
The circuit shown in was used. In FIG. 5, reference numeral 51 is a horizontal deflection power supply circuit, 52 is a horizontal deflection output circuit, 53 is a horizontal deflection coil, 54 is an adder circuit for adding both waveforms of vertical sawtooth wave voltages having different polarities, and 55 is the polarity of the vertical sawtooth wave voltage. , 56 is a vertical deflection output circuit, 57 is a vertical deflection coil, 58 is a coupling capacitor, and 59 is a resistor for extracting a vertical sawtooth wave voltage waveform.

The operation of the analog trapezoidal distortion correction control circuit of the display device configured as described above will be described. First, when the vertical deflection output circuit 56 operates, a vertical sawtooth wave current flows through the vertical deflection coil 57, and a vertical deflection sawtooth wave voltage is obtained at the resistor 59. The vertical deflection sawtooth wave voltage is added by the adder circuit 54 with different polarities,
In addition, the output is added to the sawtooth wave output of the variable gain inverting circuit 55 whose output amplitude is variable. At this time, the variable gain inverting circuit 55
The output amplitude of is controlled in amplitude and phase as shown in FIG. 6 (a). Then, the power supply voltage of the horizontal deflection power supply circuit 51 is modulated by the output waveform of the adder circuit 54 as shown in FIG. 6B, and the horizontal deflection current is modulated as shown in FIG. 6C. As a result, the trapezoidal distortion of the screen as shown in FIG. 4D caused by the imbalance of the magnetic field distribution of the vertical deflection coil 57 and the deviation of the geometric center of the electron beam is corrected, and FIG. A distortion-free screen as shown in is obtained.

However, in such a conventional correction method, since the sawtooth wave current of vertical deflection operates so as to ensure the linearity of the image on the fluorescent screen of the picture tube, the voltage waveform across the resistor 59 is actually Has impaired linearity as shown in FIG. Therefore, the horizontal deflection current and the screen are in a state as shown in FIG. 7C, and complete trapezoidal distortion correction is not performed.

The reason why the linearity of the waveform is impaired as shown in FIG. 7B is that, as shown in FIG. 7A, the same deflection angle .theta. On the other hand, the amount of electron beam movement in the peripheral portion is larger than that in the central portion of the tube surface, and in order to correct this distortion and ensure the linearity of the image, as shown in FIG. This is because the vertical deflection current for S-shaped correction that reduces

[0008]

However, in the above-mentioned conventional trapezoidal distortion correction of the display device, the waveform of the vertical deflection output circuit is extracted to obtain a triangular wave for horizontal deflection. This triangular wave is ideal. It was not possible to completely correct the trapezoidal distortion instead of the triangular wave, and it was difficult to support the digital control method in which the user controls were key operations. The present invention solves the above-mentioned conventional problems,
It is an object of the present invention to provide a display device that enables ideal trapezoidal distortion correction, is compatible with digital control, and can be integrated into a custom Ic such as a gate array.

[0009]

In order to achieve this object, the display device of the present invention is a first counting means for counting the interval of the synchronizing signal input to a monitor receiver such as a television or a display with a reference clock. A frequency dividing means for generating a clock having a period obtained by dividing the output value of the first counting means by N; a second counting means for counting the output from the frequency dividing means from 0 to N-1; And a conversion means for converting the output value of the counting means into an analog value.

[0010]

With this structure, a highly accurate triangular wave can be obtained, the linearity of the trapezoidal distortion correcting waveform is significantly improved, and the circuit can be integrated by the gate array.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an entire display device according to an embodiment of the present invention. In FIG. 1, 1 is a signal processing circuit that changes the brightness and color of the screen by changing the amplitude and brightness of the R, G, and B video signals, and 2 is a horizontal sync signal (H) and a vertical sync signal (V). The synchronous signal processing circuit that determines and processes the input state of the synchronous signal and sends it out to each block. 3 is a vertical deflection circuit that generates a vertical sawtooth current for deflecting the electron beam in the vertical direction. , A horizontal deflection circuit for generating a horizontal sawtooth wave current for deflecting the laser beam, a digital triangular wave generation circuit 5 for generating a triangular wave that is a correction waveform for correcting trapezoidal distortion, and an electron gun 6 for emitting an electron beam, Reference numeral 7 is a deflection coil for deflecting the electron beam in the horizontal and vertical directions, and 8 is a cathode ray tube for converting an electric signal into a change in light and displaying it on a fluorescent screen.

FIG. 2 is a detailed block diagram of the trapezoidal distortion digital control circuit of the display device according to the embodiment of the present invention. In FIG. 2, reference numeral 21 denotes a cycle discriminating circuit that discriminates the length of the cycle by counting the cycle of a vertical synchronizing signal input to a vertical circuit of a display device such as a television or a display from 0 to M−1 with a reference clock, and 22. Is the cycle of generating the second clock having a cycle obtained by dividing the cycle of the cycle determination circuit 21 by N / N
A generation circuit, 23 is a fixed counter circuit that counts the second clock output from the cycle / N generation circuit 22 from 0 to N−1, 24 is an inverter circuit that inverts the output of the fixed counter circuit 23, and 25 and 26 are Fixed counter circuit 23
And D for converting the output of the inverter circuit 24 into analog
A / A conversion circuits 27 and 28 are D / A conversion circuits 25 and 2
An inverting amplifier circuit for amplifying the output of 6, an output level control circuit 29 for varying the amplification degree of the inverting amplifier circuit 27,
Reference numeral 30 is an adder circuit for adding the output waveforms of the inverting amplifier circuits 27 and 28, 31 is a horizontal deflection power supply circuit, 22 is a horizontal deflection output circuit, and 33 is a horizontal deflection coil.

The operation of the trapezoidal distortion digital control circuit of the display device constructed as described above will be described. First, the cycle determining circuit 21 is reset at the falling edge of the vertical synchronizing signal output from the synchronizing signal processing circuit 2 of the display device as shown in FIG. 0 to M-1 as shown in (b)
By counting up to M and latching the count value M, the period length of the vertical synchronizing signal is determined. Next cycle /
In the N generation circuit 22, the reference clock is divided by M / N to generate a second clock as shown in FIG. The fixed counter circuit 23 is reset at the falling edge of the vertical synchronization signal, and the cycle / N generation circuit 2
The second clock generated in 2 is counted from 0 to N-1 as shown in FIG. The counted output waveform is converted into an analog signal by the D / A conversion circuit 25 and filtered to obtain a linear triangular wave waveform as shown in FIG. Similarly, the inverter circuit 2
4, the D / A conversion circuit 26 obtains an inverted triangular waveform.

The respective waveforms output from the D / A conversion circuit 25 and the D / A conversion circuit 26 are inverted and amplified by the inverting amplifier circuit 27 and the inverting amplifier circuit 28, respectively. The amplification factors of the inverting amplification circuit 27 and the inverting amplification circuit 28 are DC-controlled by the output level control circuit 29 when the inverting amplification circuit 28 is multiplied by A times, and 0 to 0
It can be changed up to 2A. The outputs of the inverting amplifier circuit 27 and the inverting amplifier circuit 28 are added by the adder circuit 30, and the output waveform from the adder circuit 30 has an amplification factor A output from the inverting amplification circuit 28 according to the amplification factor of the inverting amplification circuit 27. A triangular wave that can be varied in the range from the double output waveform to the amplification factor −A times output from the inverting amplifier circuit 27 is obtained. Then, as in the conventional case, the power supply voltage of the horizontal deflection power supply circuit 31 is modulated by the output waveform of the adding circuit 30 as shown in FIG. 6B, and the horizontal deflection current is modulated as shown in FIG. 6C. As a result, the screen state of FIG.
The trapezoidal distortion can be controlled.

The accuracy of this trapezoidal distortion correction depends on the linearity of the triangular wave which is the correction waveform. Therefore, comparing the linearity of the triangular wave diagram 3 (e) of the digital control with the triangular wave diagram 7 (b) of the conventional analog control, the digital control is superior in linearity to the conventional analog control. Since a triangular wave can be obtained by an independent circuit instead of using a triangular wave generated in another circuit as in the conventional case, it is possible to obtain an image that is several steps superior.

[0017]

As described above, according to the present invention, the first counting means for counting the interval of the synchronizing signal with the reference clock, the frequency dividing means for dividing the output value of the first counting means into N, and this division. The second that counts the output from the peripheral means from 0 to N-1
By providing the counting means and the converting means for converting the output value of the second counting means to analog, a highly accurate triangular wave can be obtained, and the linearity of the trapezoidal distortion correction waveform is significantly improved. The image distortion can be eliminated, and the circuit can be integrated by the gate array.

[Brief description of drawings]

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

FIG. 2 is a block diagram of a trapezoidal distortion digital control circuit of a display device according to an embodiment of the present invention.

FIG. 3A is an output waveform diagram from a sync signal processing circuit of a display device according to an embodiment of the present invention. FIG. 3B is an output waveform diagram from a synchronization determination circuit of a display device according to an embodiment of the present invention. c) is the period / N of the display device in one embodiment of the present invention
Output waveform diagram from the generation circuit (d) is an output waveform diagram from the fixed counter circuit of the display device in one embodiment of the present invention. (E) is a D / A conversion circuit of the display device in one embodiment of the present invention. Output waveform diagram

FIG. 4A is a diagram showing the relationship between the screen of the display device and the deflection current. FIG. 4B is a diagram showing the relationship between the vertical deflection current and the horizontal deflection current of the display device. The figure showing the state of the screen without distortion of the device. (D) shows the state of the screen with the trapezoidal distortion of the display device.

FIG. 5 is an analog trapezoidal distortion correction control circuit diagram of a conventional display device.

6A is an output waveform diagram of a variable gain inverting circuit of a conventional display device, FIG. 6B is an output waveform diagram of an adding circuit of the conventional display device, and FIG. 6C is a waveform of a horizontal deflection current of the conventional display device. Figure

FIG. 7A is a relationship diagram between a deflection angle of a picture tube of a conventional display device and an electron beam moving amount. FIG. 7B is a voltage waveform diagram of both ends of a resistor for extracting a vertical sawtooth voltage waveform of the conventional display device. FIG. 3C is a diagram showing the relationship between the deflection current of the conventional display device and the screen.

[Description of symbols] 1 signal processing circuit 2 synchronization processing circuit 3 vertical deflection circuit 4 horizontal deflection circuit 5 digital triangular wave generation circuit 6 electron gun 7 deflection coil 8 cathode ray tube 21 cycle determination circuit 22 cycle / N generation circuit 23 fixed counter circuit 24 inverter Circuits 25, 26 D / A conversion circuits 27, 28 Inversion amplification circuits 29 Output level control circuits 30 Adder circuits 31 Horizontal deflection power supply circuits 32 Horizontal deflection output circuits 33 Horizontal deflection coils 51 Horizontal deflection power supply circuits 52 Horizontal deflection output circuits 53 Horizontal deflection Coil 54 Adder circuit 55 Variable gain inverting circuit 56 Vertical deflection output circuit 57 Vertical deflection coil 58 Capacitor 59 Resistance

Claims (2)

[Claims] 1. A first reference clock generating means for generating a reference clock, and a reference clock output from said reference clock generating means as a reference, counting the reference clock output until the next synchronizing signal is input. Counting means, a frequency dividing means for outputting a clock having a cycle obtained by dividing the output value of the first counting means by a predetermined number, and an output from the frequency dividing means based on the input synchronization signal. Second counting means for counting until a synchronization signal is input;
And a conversion means for converting the output value from the counting means of FIG. 2. The display device according to claim 1, wherein the synchronizing signal is a vertical synchronizing signal, and the signal output from the converting means is amplified to modulate the power supply voltage of the horizontal deflection circuit.