JPH10161588A - Method and circuit for driving display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving method and a driving circuit in which the display luminance is undeviated and quality deterioration is prevented in a display device which displays the half-tone picture images of inputted video data by constituting one frame with plural subframes including at least two equally weighted subframes by uniforming the probability of lighting of equally weighted subframes. SOLUTION: The device is provided with an input signal discriminating section 12, lighting bit designating section 14, and a lighting bit switching section 16. The input signal discriminating section 12 judges in the unit of dot whether input video data is a signal which lights one of the equally weighted subframes or not and, based on this discriminating signal, the lighting bit designating section 14 outputs a lighting bit switching signal. Based on this switching signal, the lighting bit switching section 16 switches lighting of equally weighted subframes to uniform the lighting probability of equally weighted subframes and eliminates the deviation of display luminance and prevents quality deterioration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises one frame (or one field) composed of a plurality of subframes (or subfields), weights the luminance of each subframe, and weights at least two subframes. And a driving method and a driving circuit of a display device for displaying a halftone image (for example, 256 gradation image) of an input video signal (for example, 8-bit video data).

[0002]

2. Description of the Related Art Recently, as a thin and lightweight display device, P
DP (plasma display panel) has been attracting attention. The driving method of this PDP is completely different from the conventional CRT driving method, and is a direct driving method using digitized video input signals. Therefore, the luminance gradation emitted from the panel surface is determined by the number of bits of the signal to be handled.

[0003] PDPs are AC type and D type having different basic characteristics.
It is divided into two types of C type. In the AC type PDP, sufficient characteristics have been obtained with respect to luminance and life, but there has been only a report of a gradation level of up to 64 gradation display at the prototype level. However, the address / display separated driving method (A
DS subframe method) has been proposed. The driving sequence and driving waveform of the PDP used in this method are shown in FIG.
(A) and (b).

In FIG. 3A, for example, in the case of 256 gradations, one frame has a relative luminance ratio of 1, 2, 4,
8, 16, 32, 64 and 128 subframes S
F1 to SF8, and display of 256 gradations is performed by combining the luminances of eight screens. In FIG. 3B, each sub-frame includes an address period in which data for one refreshed screen is written and a sustain period for determining a luminance level of the sub-frame. In the address period, first, wall charges are initially formed on each pixel at the same time for the entire screen, and then a sustain pulse is applied to the entire screen to perform display. The brightness of the sub-frame is proportional to the number of sustain pulses and is set to a predetermined brightness. In this way, 256 gradation display is realized.

In order to prevent a decrease in the image quality of a moving image (for example, false contour) due to the halftone display of the sub-frame method, at least two of a plurality of sub-frames constituting one frame as shown in FIG. One in which the weights of two subframes are equal has been proposed. That is, 1
The frame is composed of five subframes SF1 to SF5, the luminance levels of SF1 and SF5 are set to the same 1, and the luminance levels of SF2, SF3, and SF4 are 2, 4, and 8.
It becomes as.

[0006]

However, when one of the subframes SF1 and SF5 of the same weight is turned on to display an image in the subframe configuration shown in FIG. Since the lighting is biased to one side, there is a problem that a difference in display luminance occurs and image quality deteriorates. For example, luminance level 5
Is displayed, one of the sub-frames SF1 and SF5 of the luminance level 1 and the sub-frame SF3 of the luminance level 4 may be lit, but the lighting is biased toward one of the sub-frames SF1 and SF5. Therefore, a burden is applied only to one subframe, and the SF of the subframe
There is a problem that a difference occurs in the display luminance when 1 and SF5 are turned on, and the image quality deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. One frame is composed of a plurality of subframes, and the luminance of each subframe is weighted, and the weighting of at least two subframes is made equal. In a display device for displaying a halftone image of an input video signal by using the same method, a driving method and a driving circuit of a display device capable of eliminating a difference in display luminance by equalizing lighting opportunities of subframes having equal weights and preventing image quality deterioration. The purpose is to:

[0008]

According to the method of the present invention, one frame is composed of a plurality of sub-frames, the luminance of each sub-frame is weighted, and the weight of at least two sub-frames is made equal to each other. In the method of driving a display device for displaying a halftone image, it is determined whether or not the input video signal is a signal for lighting one of the sub-frames having the same weight, in dot units. Is turned on and off, and a halftone image is displayed.

It is determined on a dot-by-dot basis whether or not the input video signal is a signal for turning on one of the sub-frames with the same weight and turning off the other, and this discrimination signal turns on and off the sub-frame with the same weight. , The halftone image is displayed, so that the lighting opportunities of the sub-frames with the same weight are equalized, and the unevenness of the display luminance is eliminated to prevent the image quality from deteriorating.

According to the circuit of the present invention, one frame is composed of a plurality of sub-frames, and the luminance of each sub-frame is weighted, and at least two sub-frames are weighted equally to display a halftone image of the input video signal. A drive circuit of a display device, comprising: an input signal discriminating unit for discriminating whether or not an input video signal is a signal for lighting one of sub-frames having the same weight in dot units; and a discrimination signal of the input signal discriminating unit. A lighting bit specifying unit that outputs a lighting bit switching signal based on a lighting bit switching unit that switches lighting bits corresponding to lighting subframes having the same weight based on the lighting bit switching signal of the lighting bit specifying unit. It is characterized by becoming.

The input signal discriminating unit discriminates, in dot units, whether or not the input video signal is a signal for lighting one of the sub-frames having the same weight, and the lighting bit designating unit determines whether the input video signal is a signal for lighting the input signal discriminating unit. Based on the lighting bit switching signal, the lighting bit switching unit switches the lighting bit based on the lighting bit switching signal. For this reason, each time a video signal that turns on one of the sub-frames with the same weight and turns off the other is input, the lighting of the sub-frame with the same weight is switched to equalize the lighting opportunity and eliminate the bias of the display luminance. To prevent image quality deterioration.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the circuit of the present invention for implementing the method of the present invention. In FIG. 1, 1
Reference numeral 0 denotes an input terminal for a video signal (for example, 5-bit video data), and reference numeral 12 denotes an input signal determination unit. The input signal determination unit 12 is configured to determine, in dot units, whether or not the video signal input to the input terminal 10 is a signal for lighting one of the sub-frames having the same weight.

Reference numeral 14 denotes a lighting bit designating unit. The lighting bit designating unit 14 is configured to output a lighting bit switching signal based on the discrimination signal of the input signal discrimination unit 12. Reference numeral 16 denotes a lighting bit switching unit. Based on the lighting bit switching signal of the lighting bit designating unit 14, the lighting bit switching unit 16 sets a lighting subframe having the same weight among the video signals input to the input terminal 10. A corresponding lighting bit is switched and output to a display device (for example, a PDP display device, not shown) via the output terminal 18.

Next, the operation of FIG. 1 will be described with reference to FIG. For convenience of explanation, one frame is composed of five sub-frames SF1 to SF5 as in the case of FIG. 4, and the luminance levels of SF1 and SF5 are set to 1, which is equal to the luminance of SF2, SF3, and SF4. Level 2, 4,
8 is assumed to be set. The input terminal 10 has a luminance level of each bit as a video signal of 1, 2,.
It is assumed that 5-bit video data of 4, 8, and 1 is input.

(1) When a video signal of a luminance level 5 (an example of an odd number level) is input to the input terminal 10, this signal is a signal for lighting one of the sub-frames SF1 and SF5 having the same weight. The unit 12 includes subframes SF1 and SF5 whose input video signals have the same weight.
And outputs a determination signal (for example, an H level signal).

(2) The lighting bit designating section 14 outputs a lighting bit switching signal based on the discrimination signal of the input signal discriminating section 12. For example, each time an H-level signal is input from the input signal discriminating unit 12, an H-level signal and an L-level signal are switched and output.

(3) Based on the lighting bit switching signals (H and L level signals) of the lighting bit designating section 14, the lighting bit switching section 16 turns on the lighting sub-elements having the same weight among the video signals input to the input terminal 10. The lighting bit corresponding to the frame is switched and output to a display device (for example, a PDP display device) via the output terminal 18. For example, of the 5-bit video data “10100” of luminance level 5 input to the input terminal 10, the first bit corresponding to the lighting subframes SF1 and SF5 having the same weight and the fifth bit
The data of the bit is alternately switched in dot units by the lighting bit switching signal of the H and L levels and output to the output terminal 18. Therefore, every time the video data “10100” of the luminance level 5 is input to the input terminal 10, the video data “00101” and “10100” that are switched between the first bit and the fifth bit in dot units are output alternately. Output to terminal 18.

(4) Therefore, in the display device coupled to the output terminal 18, when a video signal for lighting one of the sub-frames having the same weight is input to the input terminal 10, the sub-frame arrangement is changed to (a) in FIG. ) And (b) to display the image, so that the lighting opportunities of the sub-frames SF1 and SF5 having the same weight are equalized, the variation in the display luminance is eliminated, and the deterioration of the image quality can be prevented.

(5) When a video signal having an even-numbered luminance level is input to the input terminal 10, neither the sub-frames SF1 and SF5 having the same weight are turned on, or a signal for turning on both of them is input terminal 10. Therefore, the input signal determination unit 12 does not output the determination signal, and the lighting bit switching unit 16 does not switch the lighting bit.

In the embodiment, the video signal input to the input terminal 10 is a sub-frame array SF for display.
1,..., SF6, the case where the luminance level of each bit is 5 bits of video data of 1, 2, 4, 8, 1 has been described. However, the present invention is not limited to this, and the present invention is not limited to this. Can be used also in the case of 5-bit video data in which the luminance levels are set to 8, 4, 2, 1, 1 in descending order. In this case, the subframe array S for display
F1,..., SF6 are performed on the display device side coupled to the output terminal 18.

In the above embodiment, one frame is composed of five subframes, and one type and two subframes S
Although the case where the luminance levels of F1 and SF5 are the same has been described, the present invention is not limited to this, and one frame is composed of a plurality of subframes, and n types (n ≧ 2) and m (m ≧ 2) ) Can also be used when the luminance levels of the sub-frames are the same.

In the above-described embodiment, the case where the display device is a PDP display device has been described. However, the present invention is not limited to this, and digital display such as an LCD (liquid crystal display panel) display device can be used. It can be used for general display devices.

[0023]

According to the method of the present invention, one frame is composed of a plurality of sub-frames, the luminance of each sub-frame is weighted, and the weights of at least two sub-frames are equalized to obtain a halftone image of the input video signal. In the method of driving a display device for displaying an image, it is determined whether or not the input video signal is a signal for lighting one of the sub-frames having the same weight, on a dot-by-dot basis. Since the halftone image is displayed by exchanging the lighting, the lighting opportunities of the sub-frames with the same weight are equalized, the display luminance is not shifted, and the image quality deterioration can be prevented.

The circuit of the present invention is a circuit for implementing the method of the present invention, and comprises an input signal discriminating section, a lighting bit designating section, and a lighting bit switching section. It is determined on a dot-by-dot basis whether or not it is a signal for lighting one of the sub-frames. Based on this determination signal, a lighting bit switching signal is output from the lighting bit designating section, and the lighting bit switching is performed based on the lighting bit switching signal. Since the unit is configured to switch the lighting bits corresponding to the lighting sub-frames having the same weight and the same weight, the lighting opportunities of the sub-frames having the same weight are equalized, and the unevenness of the display luminance can be eliminated, thereby preventing the deterioration of the image quality.

[Brief description of the drawings]

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

FIG. 2 shows one frame in FIG. 1 divided into five subframes SF1.
To SF5, and when a video signal of level 5 (an example of an odd number level) is input, the operation of switching the lighting of the sub-frames SF1 and SF5 having the same weight (SF)
(A) is an explanatory diagram in which the sub-frame SF1 is illuminated, and (b) is an explanatory diagram in which the sub-frame SF5 is illuminated.

FIG. 3 is a driving sequence (a) in 256 gradation display.
And a drive waveform diagram (b).

FIG. 4 is a diagram for explaining the biased sub-frame lighting in the conventional example, wherein one frame is divided into five sub-frames SF1 to SF.
5 is an explanatory diagram in which, when a video signal of level 5 is input, one of the sub-frames SF1 and SF5 having the same weight is lit.

[Explanation of symbols]

10 input terminal, 12 input signal discriminator, 14 lighting bit designator, 16 lighting bit switcher, 18
Output terminals, SF1 to SF5... Subframes forming one frame.

Claims (3)

[Claims] 1. One frame is composed of a plurality of subframes, and the luminance of each subframe is weighted.
In a driving method of a display device for displaying a halftone image of an input video signal by equalizing the weights of at least two sub-frames, it is determined whether the input video signal is a signal for lighting one of the sub-frames having the same weight. A method for driving a display device, characterized in that a halftone image is displayed by discriminating in dot units and exchanging lighting and non-lighting of subframes having the same weight with the discrimination signal. 2. One frame is composed of a plurality of subframes, and the luminance of each subframe is weighted.
A drive circuit of a display device for displaying a halftone image of an input video signal by equalizing weights of at least two sub-frames, wherein the input video signal is a signal for lighting one of the sub-frames having the same weight. An input signal discriminating unit for discriminating dot by dot, a lighting bit designating unit that outputs a lighting bit switching signal based on the discriminating signal of the input signal discriminating unit, and a lighting bit switching signal of the lighting bit designating unit. A driving circuit for a display device, comprising: a lighting bit switching unit that switches a lighting bit corresponding to a lighting subframe having the same weight. 3. One frame is composed of a plurality of sub-frames including two sub-frames having a luminance level of 1, and an input signal determining section determines whether or not the luminance level of the input video signal is an odd level. The driving circuit for a display device according to claim 2.