JP2003316332A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device which has a liquid crystal panel to be driven by a dot line inversion driving system and can prevent the occurrence of luminance unevenness by insufficient writing. <P>SOLUTION: The liquid crystal display device having the liquid crystal panel to be driven by the dot line inversion driving system is provided with first means for detecting the pixel in which the insufficient writing is predicted to arise in consequence of the writing system specific to the dot line inversion driving system in accordance with an input video signal and second means for correcting the video signal of the pixel in which the insufficient writing is predicted to arise so as to compensate the insufficient writing. <P>COPYRIGHT: (C)2004,JPO

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, and more particularly to a liquid crystal display device including a liquid crystal panel driven by a dot line inversion driving method.

[0002]

2. Description of the Related Art FIG. 1 shows the configuration of a signal processing circuit of a conventional liquid crystal display device.

A signal processing circuit of a conventional liquid crystal display device comprises a scan conversion circuit 1, a gamma correction / color unevenness correction / timing control circuit 2, a sample & hold circuit 3 and a liquid crystal panel 4. The signal processing circuit of the conventional liquid crystal display device has a problem that uneven brightness occurs due to the following reasons.

FIG. 2 shows a state in which a black window 7 is written on a gray background 8 on the liquid crystal panel.

The quadrangle shown in FIG. 5 represents one pixel, "G" inside the quadrangle indicates that the pixel is gray (intermediate luminance), and "B" indicates that the luminance of the pixel is a black level. It means that.

Further, the upper and left arrows in the figure indicate the scanning direction of the liquid crystal panel, and in the case of FIG. 2, writing is performed in order from the upper left to the lower right. This liquid crystal panel is driven by a dot line inversion driving method. Dotted lines connecting pixels in the figure show the same write line. In the dot line inversion driving method, odd-numbered columns and even-numbered columns on the same write line are temporally different (an even-numbered column is an image one line before an odd-numbered column) video signal.

That is, the dot line inversion driving method is characterized in that pixels which are before and after one line are sequentially written. However, the unique writing method may cause uneven brightness due to insufficient writing.

For example, as shown in FIG. 2, one write line group (a series of lateral chains connected by dotted lines) is
When classified into A to D, since gray (intermediate luminance) is written in all the dots of the line A and the line D, writing is performed up to the original luminance, and insufficient writing does not occur.

On the other hand, in the line B, from the first column to the tenth column, and in the line C, from the first column to the eleventh column,
The black level and gray level video signals are written alternately. In this case, when a video signal is written to a pixel colored in gray 10 in FIG. 2, a black level is written to a pixel in the previous row, and a writing shortage that does not reach the original brightness occurs. As a result, uneven brightness occurs every other dot in the outer frame of the window.

[0010]

SUMMARY OF THE INVENTION The present invention provides a liquid crystal display device having a liquid crystal panel driven by a dot line inversion drive system, which can prevent uneven brightness from occurring due to insufficient writing. The purpose is to

[0011]

According to a first aspect of the present invention, in a liquid crystal display device having a liquid crystal panel driven by a dot line inversion driving method, writing is performed due to a writing method peculiar to the dot line inversion method. A first means for detecting a pixel expected to run short based on an input video signal, and a second means for correcting a video signal of a pixel in which a write shortage occurs so as to compensate for the write shortage. Is characterized by.

According to a second aspect of the present invention, in the liquid crystal display device according to the first aspect, the first means includes a video signal of a pixel of interest and a video signal of a pixel written immediately before the pixel of interest. It is characterized in that it is provided with means for judging whether or not insufficient writing occurs in the pixel of interest based on the video signal written one pixel after the pixel of interest.

According to a third aspect of the present invention, in the liquid crystal display device according to the second aspect, the second means provides the video signal of the pixel of interest, which is determined to cause insufficient writing, and one pixel before the pixel of interest. It is characterized in that a means for correcting the video signal of the pixel of interest is provided based on the video signal of the pixel to be written and the video signal written one after the pixel of interest.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS.

FIG. 3 shows the configuration of the signal processing circuit of the liquid crystal display device according to the embodiment of the present invention.

The signal processing circuit of this liquid crystal display device includes a scan conversion circuit 1, a writing unevenness correction circuit 11 in dot line inversion driving, a gamma correction / color unevenness correction / timing control circuit 2, a sample & hold circuit 3 and a liquid crystal panel 4. It consists of That is, in the signal processing circuit of this liquid crystal display device, the writing unevenness correction circuit 11 in the dot line inversion drive is inserted between the scan conversion circuit 1 and the gamma correction / color unevenness correction / timing control circuit 2.

FIG. 4 shows the internal structure of the uneven write correction circuit 11 in the dot line inversion drive.

Here, it is assumed that pixel data is represented by 8 bits, black has a value of 0, and white has a value of 255.

Of the video signal data divided into the first odd-numbered column data A and the first even-numbered column data B, the signal on the even-numbered column side is delayed by one line by the one-line delay circuit 12 to obtain the second even number. Create column data B ′. Further, the second even-numbered column data B ′ is further delayed by one dot by the 1-dot delay circuit 16 to create third even-numbered column data B ″. In addition, the first odd column data A is transferred to the 1-dot delay circuit 1
The second odd-numbered column data A'is created by delaying 1 dot by 6.

If n is an integer (0, 1, 2, ...),
Column numbers X (A), X (A ') of A, A', B ', B'',
X (B ′) and X (B ″) can be expressed by the following equation (1).

[0021] X (A) = 2n + 3 X (A ') = 2n + 1 X (B ') = 2n + 4 X (B ″) = 2n + 2 (1)

For example, when n = 1, X
(A) = 5, X (A ′) = 3, X (B ′) = 6, X
(B ″) = 4.

The first odd column data A, the second odd column data A ′, the second even column data B ′ and the third even column data B ″ are sent to the comparison circuit 13. The first odd column data A is also sent to the odd column correction circuit 14. The third even column data B ″ is also sent to the even column correction circuit 15.

That is, the correction processing is performed on the first odd-numbered column data A and the third even-numbered column data B ″. First, the correction process for the third even column data B ″ will be described.

In the comparison circuit 13, the brightness difference ΔLa (B ″) between the first odd-numbered column data A and the third even-numbered column data B ″.
-A = [Delta] La) and the brightness difference [Delta] Lb (B "-A '= [Delta] Lb) between the second odd-numbered column data A'and the third even-numbered column data B''.
To calculate.

For example, when n = 1, ΔLa
Is a value obtained by subtracting the pixel data of the fifth column from the pixel data of the fourth column, and ΔLb is a value obtained by subtracting the pixel data of the third column from the pixel data of the fourth column.

Here, when ΔLa> 0 and ΔLb> 0, the average value of the luminance differences La and Lb {(ΔLa + ΔLb) /
2} is calculated and output as ΔLB. In other cases, ΔLB = 0 is output. That is, when the third even-numbered column data B ″ is larger than the odd-numbered column data A and A ′ on both sides thereof, the average value {(ΔLa + ΔL) of the luminance differences La and Lb.
b) / 2} is output as ΔLB.

The reason for this is that 1 of the third even column data B ″ is used.
When the odd-numbered column data A ′ written immediately before is smaller than the third even-numbered column data B ″, insufficient writing occurs for the third even-numbered column data B ″ and the third even-numbered column data B ″. This is because, when the odd-numbered column data A written next to ″ is smaller than the third even-numbered column data B ″, uneven brightness occurs due to insufficient writing to the third even-numbered column data B ″.

ΔLB calculated by the comparison circuit 13
Are sent to the even column correction circuit 15. Even column correction circuit 1
A correction coefficient K is given to 5. The correction coefficient K is
For example, it takes a value within the range of 1/2 to 1/255, and is set to, for example, 1/64.

The even-numbered column correction circuit 15 corrects the even-numbered column data B ″ ′ based on the brightness difference ΔLB and the correction coefficient K for the third even-numbered column data B ″ by the following equation (2). To calculate. That is, if ΔLB = 0 is not satisfied, the third even-numbered column data B ″ is corrected so that its luminance value becomes high.

[0031]   Corrected even column data B ′ ″ = 1 line delay even column data B ″ + (ΔLB × K)                                                               … (2)

Next, the correction process for the first odd column data A will be described.

In the comparison circuit 13, the brightness difference ΔLc (A- between the first odd column data A and the second even column data B '.
B ′ = ΔLc), and the brightness difference ΔLd (AB − == Ld) between the first odd column data A and the third even column data B ″ is calculated.

For example, when n = 1, ΔLc
Is a value obtained by subtracting the pixel data of the sixth column from the pixel data of the fifth column, and ΔLb is a value obtained by subtracting the pixel data of the fourth column from the pixel data of the fifth column.

Here, when ΔLc> 0 and ΔLd> 0, the average value of the luminance differences Lc and Ld {(ΔLc + ΔLd) /
2} is calculated and output as ΔLA. In other cases, ΔLA = 0 is output. That is, the first odd column data A
Is larger than the even-numbered column data B ′ and B ″ on both sides thereof, the average value of the luminance differences Lc and Ld {(ΔLc + ΔLd)
/ 2} is output as ΔLA.

The reason is that when the even-numbered column data B ″ written immediately before the first odd-numbered column data A is smaller than the first odd-numbered column data A, the first odd-numbered column data A is compared with the first odd-numbered column data A. When a write shortage occurs, the first odd column data A
This is because when the even-numbered column data B ′ written next to is smaller than the first odd-numbered column data A, the uneven brightness occurs due to insufficient writing to the first odd-numbered column data A.

ΔLA calculated by the comparison circuit 13
Is sent to the odd number column correction circuit 14. Odd column correction circuit 1
A correction coefficient K is given to 4.

The odd-numbered column correction circuit 14 calculates the corrected odd-numbered column data A ″ according to the following equation (3) for the first odd-numbered column data A based on the luminance difference ΔLA and the correction coefficient K. . That is, when ΔLA = 0 is not satisfied, the first odd-numbered column data A is corrected so that its luminance value becomes high.

[0039]   Odd-column data A ″ after correction = odd-column data A + (ΔLA × K) (3)

The corrected odd-numbered column data A ″ obtained by the odd-numbered-column correction circuit 14 is delayed by one line by the one-line delay circuit 12 to generate corrected odd-numbered column data A ″ ′. . Since the delay is performed line by line in both the odd-numbered column and the even-numbered column, the corrected even-numbered column data B ′ ″ and the corrected odd-numbered column data A ″ ′ are temporally matched. In this embodiment, the pixels in the first and last columns are not corrected.

[0041]

According to the present invention, it becomes possible to prevent uneven brightness from occurring due to insufficient writing.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a signal processing circuit of a conventional liquid crystal display device.

FIG. 2 is a schematic diagram for explaining a writing unevenness generation mechanism in a dot line inversion driving method.

FIG. 3 is a block diagram showing a configuration of a signal processing circuit of the liquid crystal display device according to the embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a write unevenness correction circuit of FIG.

[Explanation of symbols]

1 Scan conversion circuit 2 Gamma correction, color unevenness correction, timing control circuit 3 Sample and hold circuit 4 LCD panel 11 Writing unevenness correction circuit 12 1-line delay circuit 13 Comparison circuit 14 Odd column correction circuit 15 Even column correction circuit 16 1-dot delay circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/20 642 G09G 3/20 642A F term (reference) 2H093 NA32 NA36 NA43 NB07 NC11 NC16 NC23 NC25 NC59 NC62 ND09 ND36 5C006 AA01 AC26 AF43 AF45 AF46 BB11 BC16 BF07 BF14 BF28 FA25 5C080 AA10 BB05 DD05 EE28 FF09 JJ01 JJ02

Claims (3)

[Claims] 1. In a liquid crystal display device including a liquid crystal panel driven by a dot line inversion driving method, a pixel which is expected to cause insufficient writing due to a writing method peculiar to the dot line inversion method is used as an input video signal. The liquid crystal display device, further comprising: a first means for detecting based on the above, and a second means for correcting a video signal of a pixel in which insufficient writing occurs so as to compensate for insufficient writing. 2. The first means sets a pixel of interest based on a video signal of the pixel of interest, a video signal of a pixel written immediately before the pixel of interest, and a video signal written one after the pixel of interest. The liquid crystal display device according to claim 1, further comprising means for determining whether or not insufficient writing occurs. 3. The second means is a video signal of a pixel of interest, which is determined to be insufficiently written, a video signal of a pixel written immediately before the pixel of interest, and a video signal written after one of the pixel of interest. 3. A means for correcting the video signal of the pixel of interest based on
The liquid crystal display device according to item 1.