JP2000293149A - Intermediate gradation controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of video flicker and fixed patterns and to obtain a high quality picture by improving the generating method of dither patterns. SOLUTION: In the controller, plural pixels are combined to form pixel blocks, the number of driving pixels in a block is determined to provide gradation to the block and a function is provided to selectively switch the driving pixels. In order to realize the function, dither processing circuits 111, 112 and 113 are provided to generate different dither patterns for plural constituting elements (R, G and B signals) that constitute color video signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gradation control device, and is useful as a drive circuit for driving a matrix display panel such as a plasma display, an EL display device, a fluorescent display tube, and a liquid crystal display device. is there.

[0002]

2. Description of the Related Art When an image signal is supplied to a liquid crystal panel to display an image, gradation control is required.

An input video signal is passed through a gradation control circuit having a dither pattern generation circuit for gradation control. This technique is disclosed in, for example, JP-A-11-38944.

[0004]

In order to generate a dither pattern, a table is selected using the lower two bits of an input signal, and pixel data is varied. The driving pixel can be selected from the block of pixels, and the gray scale can be varied as 0, 1, 2, and 3.

[0005] However, when the same gradation continues for a long time, a fixed pattern may be generated in the image or a change in luminance (flicker) may occur, and the image quality may be degraded due to the influence of the dither pattern.

An object of the present invention is to provide a gradation control device which can contribute to obtaining a higher quality image by devising a method of generating a dither pattern.

[0007]

In order to achieve the above object, the present invention combines a plurality of pixels into a pixel block, and applies a driving pixel in the pixel block to give a gradation to the pixel block. In a halftone control device having a function of determining the number and selectively switching the driving pixels, the function of selectively switching the driving pixels is provided for each of a plurality of components constituting the color video signal. A different dither pattern is generated.

As a result, since the pixel selection pattern for each pixel block of each component of the video signal is different, the dither pattern is less likely to interfere with a displayed pattern or a change in luminance (flicker). It contributes to improvement.

[0009]

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

Reference numeral 100 denotes a signal processing unit. The processed video signal is output as, for example, R, G, and B signals.
Analog to digital converters 101, 102, 10 respectively
3 and digitized. The digitized R, G, and B signals are respectively applied to dither processing circuits 111, 1
12 and 113 are input. Each dither processing circuit 111,
Reference numerals 112 and 113 have the same configuration. Therefore, the R signal dither processing circuit 111 will be described. Input terminal 121R
Is supplied with an 8-bit R signal.
The bits are input to adder 124R, and the lower two bits are applied to dither pattern generation circuit 123R.

The dither pattern generating circuit 123R can generate binarized information of the pattern shown in the column of R in FIG. 2 based on the input 2 bits by using a dither pattern table. This binarized information is added to the upper 6 bits in the adder 124R. As a result, a 6-bit signal subjected to dither processing is obtained from the adder 124R. This signal is supplied to the R drive circuit of the liquid crystal panel 130 via the output terminal 125R.

Since the internal components of the other dither processing circuits 112 and 113 have the same configuration, the same reference numerals as those of the internal components of the R signal dither processing circuit 111 denote the same components, and a description thereof will be omitted.

Here, the dither pattern generation circuit 123
The difference between R, 123G and 123B is as shown in FIG. That is, a plurality of pixels are combined to form a pixel block, the number of driving pixels in the pixel block is determined in order to give a gradation to the pixel block, and a function of selectively switching the driving pixels is provided. Is controlled, the function of selectively switching the driving pixels generates different dither patterns for a plurality of components constituting the color video signal. That is, in the above embodiment, the dither patterns of the R, G, and B signals are set to be different. The pixel block in FIG.
1 shows an example composed of one pixel. Of the four pixels, the hatched pixels are the selected drive pixels, and the number of selections is set by a dither pattern according to the gradation. However, even in the case of the same gradation, R, G, and B have different patterns in this embodiment.

When different dither patterns are used as described above, it is possible to suppress the occurrence of flickers, fixed patterns, and the like in an image due to a shuffling effect.

In the above embodiment, the dither patterns of the R, G, and B signals are set to be different. However, the present invention is not limited to this, and various embodiments are possible.

FIG. 3 shows another embodiment of the present invention.
Parts corresponding to those in the apparatus of FIG. 1 are denoted by the same reference numerals.
In this embodiment, the dither pattern generation circuit 123
Pattern table selection circuits 126R, 126G, and 126B are provided before R, 123G, and 123B, respectively.

The pattern table selection circuits 126R, 126
6G and 126B are circuits for switching the generation of the dither patterns of the corresponding dither pattern generation circuits 123R, 123G and 123B, for example, for each frame. FIG. 4 shows an example in which the dither pattern is periodically switched. As shown in FIG. 4, the selected pixel of the dither pattern of the R signal is different for each frame even when the gradation is the same. Although not shown in the figure, the dither pattern of the G signal and the B signal is similarly switched for each frame. Also in this example, in each frame,
The dither patterns of the R, G, and B signals are set to be different.

FIG. 5 shows still another embodiment of the present invention. Parts corresponding to those in the apparatus of FIG. 1 are denoted by the same reference numerals. In this embodiment, the dither pattern generation circuit 1
Pattern table selection circuits 127R, 127G, and 127B are provided in front of 23R, 123G, and 123B, respectively. This pattern table selection circuit 127R,
Each of the 127G and 127B randomly switches and selects the pattern generation table of the corresponding dither pattern generation circuit 123R, 123G or 123B. For example, in the example of FIG. 4, a fixed dither pattern is generated cyclically in the first, second, and third frames, but the purpose can be achieved by making this cycle random.

The above-described embodiment is also effective for still images, in which the occurrence of flickers and fixed patterns in images can be suppressed by the shuffling effect.

In the above description, the case where the lower two bits are binarized has been described. In the case where the lower m bits are binarized, a similar effect can be obtained by generating an m × m dither pattern. Obtainable.

In the above description, the example of the R, G, and B signals as a plurality of components constituting the color video signal has been described, but the present invention is not limited to this. For example, as the plurality of components, components based on luminance (Y), color difference (RY), (BY) may be used, or luminance (Y) and chroma (C) may be used.
It is needless to say that the components of the above may be targeted.

[0022]

As explained above, according to the present invention,
By devising a method of generating a dither pattern, it is possible to suppress the occurrence of flickers and fixed patterns in a video, and to contribute to obtaining a high-quality image.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a dither pattern shown for explaining the operation of the apparatus of FIG. 1;

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is an explanatory diagram of a dither pattern shown for explaining the operation of the apparatus of FIG. 3;

FIG. 5 is a diagram showing still another embodiment of the present invention.

FIG. 6 is an explanatory diagram showing an example of generation of a dither pattern.

[Explanation of symbols]

100: signal processing unit; 101, 102, 103: analog-to-digital converter; 111, 112, 113: dither processing circuit.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsukasa Sakamoto 1-9-1-2 Hara-cho, Fukaya-shi, Saitama F-term in Fukaya Plant, Toshiba Corporation (reference) 5C066 AA03 BA20 CA19 DD07 EC01 GA01 GA02 GA03 GA05 HA02 KE02 KE09 KE19 KM13 KM14 KM15 5C082 BA34 BA35 BA39 BD02 CA11 CA12 CA22 CB01 MM10

Claims (4)

[Claims] 1. A function of combining a plurality of pixels into a pixel block, determining the number of driving pixels in the pixel block to give a gradation to the pixel block, and selectively switching the driving pixels. In the intermediate gradation control device, the function of selectively switching the driving pixels includes a unit that generates a different dither pattern for each of a plurality of components constituting a color video signal. Gradation control device. 2. A function of combining a plurality of pixels into a pixel block, determining the number of driving pixels in the pixel block to give a gradation to the pixel block, and selectively switching the driving pixels. In the halftone control device, the function of selectively switching the driving pixels is to generate different dither patterns for a plurality of components constituting a color video signal, and to output each dither pattern for each frame. An intermediate gradation control device comprising means for rotating. 3. A function of combining a plurality of pixels into a pixel block, determining the number of driving pixels in the pixel block to give a gradation to the pixel block, and selectively switching the driving pixels. In the halftone control device, the function of selectively switching the driving pixels is to generate different dither patterns for a plurality of components constituting a color video signal, and to apply each dither pattern to each frame. An intermediate gradation control device comprising a means for generating random numbers. 4. A plurality of components constituting the color video signal include red (R), green (G), and blue (B) components, or luminance (Y), color difference (RY), (B The halftone control device according to any one of claims 1 to 3, wherein the halftone control device is a plurality of components of any one of -Y), luminance (Y), and chroma (C).