JPH06118907A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display device which make sufficient contour corrections for picture quality improvement without causing a decrease in S/N due to the generation of ringing and an emphasized noise component. CONSTITUTION:The liquid crystal display device is equipped with a contour correction signal generating circuit 60 which generates a contour correction signal on the basis of a video signal inputted through a terminal 61 and a PLL circuit 63 which generates a clock signal synchronized with a horizontal synchronizing signal, inputted through a terminal 63, on the basis of it. The contour correction signal from a correction quantity adjusting circuit 604 and the clock signal from the PLL circuit 63 are both supplied to a phase modulating circuit 68. The phase modulating circuit 68 imposes phase modulation on the output signal from a VCO 66 according to the contour correction signal to generate the phase-modulated signal as a sample clock signal. This sample clock signal is outputted to the X driver of a liquid crystal panel through a terminal 69.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device in which a plurality of switching elements such as thin film transistors arranged in a matrix form corresponding pixels.

[0002]

2. Description of the Related Art In recent years, many video display devices using a liquid crystal panel have been marketed, and video display devices using this liquid crystal panel include pocket liquid crystal televisions, laptop computers,
Used in many products such as word processors.

As this image display device, there is one using an active matrix type liquid crystal panel having a plurality of switching elements such as a plurality of thin film transistors forming respective corresponding pixels, and this liquid crystal panel has a halftone. It is suitable for displaying the images that it has, and the image quality is improved. Further, this active matrix type liquid crystal panel has a plurality of switching elements such as thin film transistors that form corresponding pixels.

As shown in FIG. 6, the active matrix type liquid crystal panel 1 sends video signals corresponding to the respective switching elements of the display section 4 to signal lines X1, X2, X3 ,.
.., and a Y driver 3 that supplies a scanning signal for sequentially driving each of the switching elements of the display unit 4 via the scanning signal lines Y1, Y2, Y3 ,. With.

As shown in FIG. 7A, the display section 4 has color filters arranged in stripes.
Instead of the color filters arranged in a stripe pattern, color filters arranged in a mosaic pattern may be used as shown in FIG. 7B. Also,
Some liquid crystal projectors use three monochrome liquid crystals without color filters.

The X driver 2 has a plurality of terminals 5, 6, 7 and 8 as shown in FIG. The terminal 5 is supplied with R, G, B video signals whose polarities are inverted in a predetermined cycle. A horizontal scanning start signal is supplied to the terminal 6, a sample clock signal is supplied to the terminal 7, and an OE signal (output enable signal) is supplied to the terminal 8.

The horizontal start signal and the sample clock signal are applied to the shift register 32. With the input of the horizontal start signal and the sample clock signal, the shift register 32 outputs an ON pulse to each sampling switch 34.
, And each sampling switch 34 is closed based on the ON pulse. Each sampling switch 3
The signals of R, G, B supplied to the terminal 5 are sequentially sampled by the closing operation of 4 sequentially, and the sampled signals of R, G, B are held in the corresponding sampling capacitors 33. It One of the sampling capacitors 33 is connected to the common electrode 31 of all horizontal lines.

The data held in the sampling capacitor 33 is output to the video signal lines X1, X2, X3, ... For each scanning line through the corresponding driver 35 at a predetermined timing based on the OE signal. Each video signal line X1, X
2, X3 ... Are connected to corresponding switching elements (not shown).

The Y driver 3 has a plurality of terminals 9 and 10, as shown in FIG. A vertical scanning clock signal is supplied to the terminal 9, and a vertical scanning start signal is supplied to the terminal 10. The Y driver 3 receives each scanning signal line Y1, based on the vertical scanning clock signal and the vertical scanning start signal.
High-level data is sequentially supplied to Y2, Y3, .... The switching elements corresponding to the scanning signal lines Y1, Y2, Y3, ... Are turned on based on the high-level data, and the sampling data supplied from the corresponding video signal lines X1, X2, X3 ,. .

In the liquid crystal display device using the liquid crystal panel 1 described above, as in the CRT type display device, a secondary differential signal is generated from the contour portion of the video signal, and the contour correction is performed by superimposing this signal on the sharpened signal to obtain a sharp edge. Image quality adjustment (outline correction) is performed to improve the image quality.

Next, the configuration of the image quality adjustment circuit for performing the above image quality adjustment will be described with reference to the drawings. FIG. 9 is a block diagram showing the configuration of an image quality adjustment circuit used in a conventional liquid crystal display device, and FIG. 10 is a waveform diagram for explaining the operation of each part of the image quality adjustment circuit in the figure.

As shown in FIG. 9, the image quality adjusting circuit outputs the input video signal 140 supplied through the terminal 40 to a predetermined T.
It has a delay element 41 that delays by an amount of time and generates a delayed video signal 141 delayed by T time with respect to the input video signal. The delayed video signal 141 delayed by T time from the input video signal is given to the delay element 42. The delay element 42 further delays the delayed video signal 141 input thereto by T time to generate a delayed video signal 142 delayed by 2T time from the input video signal.

Delayed video signal 142 delayed by 2T time
Is given to the adder 43 together with the input video signal 140,
The adder 43 outputs the delayed video signal 142 delayed by 2T time.
And the input video signal 140 are added, and an addition signal 143 generated by this addition is output.

The addition signal 143 is given to the inverting amplifier 44, and the inverting amplifier 44 multiplies the addition signal 143 by -0.5,
The signal 144 multiplied by -0.5 is output.

This signal 144 is given to the adder 45. The adder 45 delays the delayed video signal 14 by T time.
1 and the signal 144 from the inverting amplifier 44 are added, and this addition generates the secondary differential signal 145.

This secondary differential signal 145 is given to the variable gain amplifier 46, and the variable gain amplifier 46 receives the secondary differential signal 1
45 is amplified and output. The secondary differential signal 146 amplified by the variable gain amplifier 4 is given to the adder 47, and the adder 47 adds the secondary differential signal 146 and the delay signal 141 delayed by T time, and corrects by this addition processing. The generated video signal 147 is generated. Corrected video signal 147
Is output via terminal 48.

The amount of addition of the secondary differential signal 146 to the delay signal 141 is adjusted by the variable gain amplifier 46, and by this adjustment, the contour-corrected video signal 147 is obtained.

In the image quality adjusting circuit used in the above-mentioned liquid crystal display panel, the frequency characteristic is f as shown in FIG.
Since it is set to have a peak at 0 = 1 / 2T, the high frequency is boosted and the noise component is emphasized with respect to the signal having a poor S / N ratio. In addition, when ringing occurs in the signal, this ringing is emphasized, and ringing easily occurs by superimposing the secondary differential waveform.

Further, since the display dynamic range of the liquid crystal display panel is narrower than the display dynamic range of the CRT, when the correction amount is the same, the visual effect obtained in the liquid crystal display panel is smaller than the visual effect in the CRT, and the liquid crystal In the image quality adjustment for the display panel, the correction amount tends to increase.

[0020]

As described above, in the image quality adjusting circuit used in the conventional liquid crystal display panel,
When the sharpness is improved by increasing the correction amount, ringing is likely to occur and the noise component is emphasized. As a result, the S / N ratio is lowered due to the occurrence of ringing and the emphasis of noise components, and the outline correction for improving the image quality cannot be sufficiently performed.

The present invention provides a liquid crystal display device capable of sufficiently performing contour correction for improving image quality without causing a reduction in S / N ratio due to occurrence of ringing and enhancement of noise components. To aim.

[0022]

According to the present invention, a plurality of switching elements such as thin film transistors arranged in a matrix form a corresponding pixel, and an X driver extracts an input video signal based on a sample clock signal. A liquid crystal display device which supplies a predetermined number of sample data to a corresponding switching element, and supplies a write operation instruction signal of sample data to a corresponding switching element by a Y driver, wherein the switching elements cooperate with each other. Contour correction signal generating means for generating a contour correction signal for correcting the contour of an image to be formed, and phase modulation for a clock signal having a predetermined frequency based on the contour correction signal generated by the contour correction signal generating means. Either one of the frequency modulation processes is applied, and the clock signal subjected to this modulation process is applied. The and a modulating means for outputting a sample clock signal of the X driver.

[0023]

In the liquid crystal display device of the present invention, a contour correction signal generating means for generating a contour correction signal for correcting a contour of an image formed by the switching elements in cooperation with each other, and the contour correction signal generating means. The clock signal having a predetermined frequency is subjected to modulation processing of either phase modulation or frequency modulation on the basis of the contour correction signal generated in step (1), and the clock signal subjected to the modulation processing is subjected to the X
A modulation means for outputting as a sample clock signal of the driver is provided.

Since the sample clock signal of the X driver is a signal obtained by subjecting the clock signal to the modulation processing with the contour correction signal, the timing for extracting the sample data from the video signal is the contour of the video signal. The sample data changes nonlinearly and the sample data is extracted nonlinearly. Therefore, the sharpness of the contour portion of the display image is improved with the extraction of the non-linear sample data, and the S / N ratio is not reduced due to the occurrence of ringing and the enhancement of the noise component.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the main part of one embodiment of the liquid crystal display device of the present invention.

As shown in FIG. 1, the liquid crystal display device includes a contour correction signal generation circuit 60 for generating a contour correction signal based on a video signal input via a terminal 61, and a horizontal input signal via a terminal 63. A PLL circuit (phase-locked loop circuit) 63 that generates a clock signal synchronized with the synchronization signal based on the synchronization signal.

The contour correction signal generating circuit 60 has a differentiating circuit 601 for generating a primary differential signal from the contour portion of the video signal input via the terminal 61. The primary differential signal for the rising portion of the video signal of the primary differential signal and the primary differential signal for the falling portion of the video signal have polarities different from each other.

The primary differential signal from the differentiating circuit 601 is given to the absolute value circuit 602. The absolute value circuit 602 aligns the primary differential signal from the differentiating circuit 601 with one polarity, and outputs the signal with this polarity aligned.

The signal from the absolute value circuit 602 is the differential circuit 6
03, the differential circuit 603 generates a secondary differential signal by differentiating the signal from the absolute value circuit 602.

The secondary differential signal from the differentiating circuit 603 is given to the correction amount adjusting circuit 604, and the correction amount adjusting circuit 604 adjusts the level of the secondary differential signal from the differentiating circuit 603 to an optimum level and adjusts the level. To generate a contour correction signal.

The PLL circuit 63 includes a phase detection circuit 64 and
It is composed of an LPF (low pass filter) 65, a VCO (voltage controlled oscillator) 66, and a frequency divider 67. VCO
The oscillation frequency of 66 is set to f _VCO (= n × f _HD ),
The frequency division ratio of the frequency divider 67 is set to 1 / n.

The output signal from the VCO 66 is a phase modulation circuit 68 together with the contour correction signal from the correction amount adjustment circuit 604.
Given to. The phase modulation circuit 68 performs phase modulation processing on the output signal from the VCO 66 based on the contour correction signal, and generates this phase-modulated signal as a sample clock signal. This sample clock signal is output to the X driver of the liquid crystal panel via the terminal 69.

Next, the operation of the contour correction signal generating circuit in the liquid crystal display device will be described with reference to the drawings. FIG. 2 is a waveform diagram for explaining the operation of the contour correction signal generating circuit of the liquid crystal display device of FIG.

First, as shown in FIG. 2, a video signal 160 is input to the contour correction signal generation circuit 60 via a terminal 61.

The differentiating circuit 601 receives the input video signal 1
A primary differential signal 161 is generated from the contour portion of 60. The part of the primary differential signal 161 for the rising part of the video signal and the part for the falling part of the video signal are shown in FIG.
As shown in (b), they have different polarities.

First-order differential signal 161 from the differentiating circuit 601
Is given to the absolute value circuit 602. Absolute value circuit 602
Aligns the first-order differential signal 161 from the differentiating circuit 601 with one polarity, and outputs the signal 162 with this polarity aligned.

The signal 162 from the absolute value circuit 602 is given to the differentiating circuit 603, and the differentiating circuit 603 receives the absolute value circuit 6.
A second derivative signal 163 is generated by differentiating the signal 162 from 02.

The secondary differential signal 163 from the differential circuit 603
Is supplied to the correction amount adjustment circuit 604, and the correction amount adjustment circuit 6
Reference numeral 04 adjusts the level of the secondary differential signal 163 from the differentiating circuit 603 to an optimum level, and the contour correction signal is generated by this level adjustment.

Next, the outline correction principle by phase-modulating the sample clock signal of the X driver in the liquid crystal display device with the outline correction signal will be described with reference to the drawings. FIG. 3 is a diagram for explaining the principle of contour correction in the liquid crystal display device of FIG. A video signal is shown in the first quadrant in the figure, and the vertical axis thereof is amplitude and the horizontal axis is time. In the second quadrant in the figure, a video signal written in each pixel of the liquid crystal panel is shown, the vertical axis thereof represents the display luminance, and the horizontal axis thereof represents the pixel position. The sampling timing of the X driver is shown in the fourth quadrant in the figure.

Referring to FIG. 3, since the sample clock signal generated by the phase modulation circuit 68 is a signal obtained by subjecting the output signal from the VOC 66 to phase modulation processing with the contour correction signal, this sample clock signal is used. The timing for indicating the sampling operation by the signal becomes non-linear, and as is clear from the video signal shown in the second quadrant,
The rising edge of the video signal written in each pixel becomes steep.
Therefore, the sharpness is improved, and the S / N ratio is not lowered due to the occurrence of ringing and the emphasis of the noise component,
It is possible to sufficiently perform contour correction for improving image quality. The fall of the video signal written in each pixel becomes steep like the rise, and the sharpness is improved.

Next, another liquid crystal display device using an adder instead of the phase modulation circuit will be described with reference to the drawings. FIG. 4 is a block diagram showing the main part of another embodiment of the liquid crystal display device of the present invention.

As shown in FIG. 4, the liquid crystal display device includes a contour correction signal generation circuit 60 for generating a contour correction signal based on a video signal input via a terminal 61, and a horizontal input signal via a terminal 63. And a PLL circuit 63 for generating a clock signal synchronized with the synchronizing signal.

The PLL circuit 63 includes a phase detection circuit 64 and
It is composed of an LPF 65, an adder 80, a VCO (voltage controlled oscillator) 66, and a frequency divider 67.

The adder 80 adds the output signal from the LPF 65 and the contour correction signal from the correction adjustment circuit 604,
The signal generated by this addition processing is given to the VCO 66. The VCO 66 generates a sample clock signal having a predetermined frequency based on the signal from the adder 80.

As described above, the phase-modulated sample clock signal can be obtained from the VCO 66 by superimposing the contour correction signal on the output from the LPF 65 by the adder 80 which replaces the phase modulation circuit, and it is necessary to provide the phase modulation circuit. Absent.

Next, another liquid crystal display device using a frequency modulation circuit instead of the phase modulation circuit will be described with reference to the drawings. FIG. 5 is a block diagram showing the main part of still another embodiment of the liquid crystal display device of the present invention.

As shown in FIG. 5, the liquid crystal display device includes a contour correction signal generation circuit 60 for generating a contour correction signal based on a video signal input through a terminal 61, and a horizontal input signal through a terminal 63. And a PLL circuit 63 for generating a clock signal synchronized with the synchronizing signal.

The contour correction signal generation circuit 60 has a differential circuit 601 for generating a primary differential signal from the contour portion of the video signal input through the terminal 61 and a primary differential signal from the differential circuit 601 having one polarity. An absolute value circuit 602, a differential circuit 603 that generates a secondary differential signal by differentiating a signal from the absolute value circuit 602, and a differential circuit 603.
The differential circuit 605 that generates a third-order differential signal by differentiating the second-order differential signal from and the level of the third-order differential signal from the differentiating circuit 605 are adjusted to optimal levels, and the contour correction signal is adjusted by this level adjustment. And a correction amount adjusting circuit 604 to be generated.

Both the contour correction signal from the correction amount adjustment circuit 604 and the output signal from the VCO 66 are given to the frequency modulation circuit 90. The frequency modulation circuit 90 frequency-modulates the output signal from the VCO 66 based on the contour correction signal, and generates this frequency-modulated signal as a sample clock signal. This sample clock signal is output to the X driver of the liquid crystal panel via the terminal 69.

As described above, the difference between the frequency modulation and the phase modulation is the difference between the modulation signal and the differential signal. Therefore, the differential circuit for obtaining the third differential signal from the second differential signal. By providing 605, it is possible to obtain a sample clock signal for appropriately performing contour correction.

In this embodiment, the contour correction is performed by using the sample clock signal of the X driver determined by the contour correction signal. In addition to this contour correction, the image quality correction by the conventional second derivative method is performed. By doing so, the effect of further improving the image quality can be obtained, and the differentiating circuit of the contour correction signal generating circuit can be shared with the circuit used in the conventional system, and there is no fear that the circuit scale will become very large. .

[0053]

As described above, according to the liquid crystal display device of the present invention, the contour correction for improving the image quality can be performed without causing the S / N ratio to decrease due to the occurrence of ringing and the enhancement of the noise component. Can be enough.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of an embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a diagram showing waveforms for explaining the operation of a contour correction signal generation circuit used in the liquid crystal display device of FIG.

FIG. 3 is a diagram for explaining a contour correction principle in the liquid crystal display device of FIG.

FIG. 4 is a block diagram showing a main part of another embodiment of the liquid crystal display device of the present invention.

FIG. 5 is a block diagram showing a main part of still another embodiment of the liquid crystal display device of the present invention.

FIG. 6 is a diagram showing a configuration of a conventional active matrix type liquid crystal panel.

FIG. 7 is a diagram showing an arrangement example of color filters used in the liquid crystal panel of FIG.

8 is a block diagram showing an X driver used in the liquid crystal panel of FIG.

FIG. 9 is a block diagram showing an image quality adjustment circuit used in a conventional liquid crystal display device.

10 is a waveform diagram for explaining the operation of the image quality adjustment circuit in FIG.

11 is a diagram showing frequency characteristics of a contour correction signal of the image quality adjustment circuit of FIG.

[Explanation of symbols]

60 ... contour correction signal generating circuit (contour correction signal generating means), 63 ... PLL circuit, 68 ... phase modulating circuit, 80 ... adder, 90 ... frequency modulating circuit.

Claims (1)

[Claims] 1. A corresponding pixel is formed by a plurality of switching elements such as thin film transistors arranged in a matrix, and a predetermined number of sample data extracted from an input video signal based on a sample clock signal by an X driver is supported. A liquid crystal display device for supplying a write operation instruction signal of sample data to a corresponding switching element by a Y driver, which corrects an outline of an image formed by the switching element in cooperation with each other. A contour correction signal generating means for generating a contour correction signal for generating the contour correction signal, and one of phase modulation and frequency modulation for a clock signal having a predetermined frequency based on the contour correction signal generated by the contour correction signal generating means. And the clock signal subjected to this modulation processing is applied to the sample of the X driver. A liquid crystal display device comprising: a modulating means for outputting as Rukurokku signal.