JP3312529B2 - Display device driving method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of driving a display device in which one frame is composed of a plurality of sub-frames or sub-fields having different relative ratios of luminance and a multi-gradation video signal is projected. Things.

[0002]

2. Description of the Related Art Recently, as a thin and lightweight display device, P
DP (plasma display panel) has attracted 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 or subfield method) has been proposed. FIGS. 4A and 4B show a driving sequence and a driving waveform of the PDP used in this method.

In FIG. 4 (a), for example, in the case of 256 gradations, one frame has a relative luminance ratio of 1, 2, 4,.
The display is composed of eight subframes of 8, 16, 32, 64, and 128, and displays 256 gradations by combining the luminances of eight screens. In FIG. 4B, 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 the AC driving method described above, as the number of gradations is increased, the number of bits in an address period as a preparation period for lighting and emitting a panel within one frame period is increased. The period becomes relatively short, and the maximum luminance decreases. As described above, the luminance gradation emitted from the panel surface is determined by the number of bits of a signal to be handled. Therefore, if the number of bits of the signal to be handled is increased, the image quality is improved, but the light emission luminance is reduced. Conversely, if the number of bits of the signal to be handled is reduced, the light emission luminance is increased, but the gradation display is reduced and the image quality is reduced. Causes a decline.

The error diffusion process for minimizing the shading error between the input signal and the emission luminance while reducing the number of bits of the output drive signal from the number of bits of the input signal is a process for expressing a pseudo halftone. , Which is used when expressing gradation with a small number of gradations. That is, in a conventional general error diffusion processing circuit, a video signal of an original pixel Ai, j of n (for example, 8) bits is input to a video signal input terminal, and is passed through a vertical direction addition circuit and a horizontal direction addition circuit. Further, the bit conversion circuit performs a process of reducing the number of bits to m (for example, 4) bits, and emits light from the PDP via the PDP driving circuit.

The error diffusion signal from the horizontal addition circuit is compared with data stored in advance by an error detection circuit, and the difference is taken. The difference is multiplied by a predetermined coefficient by an error load circuit and weighted. , The error detection output to the original pixel Ai, j
A pixel before the h line, for example, a reproduction error Ej-1 generated one line in the past is added to the vertical addition circuit via an h line delay circuit that outputs a reproducibility error Ej-1, and d dots before the original pixel Ai, j. , For example, one dot, a reproduction error Ei-1 generated in the past by a d-dot delay circuit that outputs a reproduction error Ei-1 is added to the horizontal direction addition circuit. In addition,
The coefficients in the error load circuit are generally set so that the sum of all becomes 1.

As a result, although the light emission luminance level represented by four bits, such as a staircase, is instantaneously output to the output terminal of the bit conversion circuit, in practice, the light emission luminance of the upper and lower steps is actually increased. Since the levels are alternately output at a predetermined ratio, the levels are recognized in an averaged state, and a corrected luminance line of substantially y = x is obtained.

[0009]

However, in the sub-frame lighting method, there is a problem that when a certain change occurs in the input level of the original signal, the image quality is deteriorated in a part of the screen. For example, as shown in FIG. 3A, in a case where four bits for scanning from SF4 to SF1 in order of luminance are used as an image signal, the input of the first frame of the original signal is at level 7, and When the input of the frame changes to level 8, level 7 is quantized by 0111 and level 8 is quantized by 1000. Therefore, at the transition point from level 7 to 8, as shown in FIG.
At 11000, the lighting of levels 7 and 8 continues, and the luminance at that time reaches about twice that of levels 7 and 8.

As described above, in the method of displaying and reproducing the image signal by dividing the image signal into subframes, when displaying a moving image that changes in the time axis direction, the level change point does not always coincide with the change of the original signal at the level change point. Exists. For this reason, there is a problem that image quality is reduced. In particular, when performing pseudo halftone display by error diffusion or the like between one grayscale level, there is a problem because it blinks in the time axis direction.

SUMMARY OF THE INVENTION It is an object of the present invention to compensate for a decrease in the image quality of a moving image due to a sub-frame halftone display.

[0012]

According to the present invention, there is provided a display apparatus comprising a plurality of sub-frames having different relative ratios of luminance so as to project a multi-gradation video signal. Medium minimum luminance subframe
In addition, the minimum luminance
Sub-frames are added adjacent to each other , and the added minimum brightness sub-frame and maximum
Combination with other subframes except luminance subframe
Lights up to obtain the same brightness as the maximum brightness subframe.
A driving method of a display device is characterized in that as that.

[0013]

For example, when the level of the original signal changes from 7 to 8 (when the amount of change is the minimum value), the luminance of 5 bits and 5 screens is used. SF3, SF2, SF1, and SF1 are selected. In other cases, one frame is composed of four sub-frames SF4 and SF4 having a relative luminance ratio of 8, 4, 2, 1.
3, SF2 and SF1 are used. For example, level 8
Is selected as a sub-frame for.

When a display of 16 gradations is performed, for example, since the first frame in the original signal is at level 7, the four sub-frames SF4, SF3, SF3, SF out of SF2, SF1
2. Level 7 is quantized to “0111” by SF1. Only when the next frame changes from the level 7 to the level 8, the luminance arrangement of 8, 4, 2, 1, 1 and 5 bits and 5 screens is used. That is, when changing from level 7 to level 8, level 8 is SF4, SF3, SF2, SF2
Level 8 is quantized to “0111 1 ” by SF3, SF2, SF1, and SF1 out of SF1 and SF1. Therefore, at the transition point from level 7 to level 8, "0
111 ”and“ 01111 ”, which are level 7 and level 8
Since the lighting is not continuous, there is no large change in luminance at that time, and the image quality does not deteriorate.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. The first embodiment will be described with reference to FIG. In FIG. 1A, for example, when one frame is composed of four subframes, conventionally, four subframes SF4, SF3, with a relative luminance ratio of 8, 4, 2, 1 are defined as one frame.
However, in the present invention, as one frame, four sub-frames SF4, SF3, SF2, and SF1 having a relative luminance ratio of 8, 4, 2, and 1 further include a relative luminance minimum. The subframe SF1 having the ratio 1 is added adjacent to the original subframe SF1 having the relative ratio 1 of the minimum luminance, and the luminance of 5, 4, 2, 1, 1 and 5 bits and 5 screens are arranged.

Only when the level of the original signal changes from 7 to 8 (when the amount of change is the minimum value), 5-bit 5-screen luminance is used. 1 SF3, SF2, SF1, SF1
Is selected. In other cases, one frame is composed of four sub-frames SF4 and S4 having a relative luminance ratio of 8, 4, 2, 1.
F3, SF2, SF1 are used. For example, SF4 is selected as a subframe for level 8.

A description will be given of a case where a display of 16 gradations is performed using a combination of luminances of 5 bits and 5 screens. For example, as shown in FIG. Since the level is 7, the four subframes SF4, SF3,
By SF3, SF2 and SF1 among SF2 and SF1,
Level 7 is quantized with “0111”.

Only when the next frame changes from level 7 to level 8, the luminance arrangement of 8, 4, 2, 1, 1 and 5 bits and 5 screens is used. That is, from level 7 to level 8
, The level 8 is SF4, SF3, SF
2, SF1, SF1, SF2, SF1, and S1 of SF1
By F1, the level 8 is quantized to “0111 1 ”. Therefore, at the transition point from level 7 to level 8, as shown in FIG. 1B, "0111" and "01111"
Thus, since the lighting at the levels 7 and 8 is not continuous, there is no large change in the luminance at that time, and the image quality does not deteriorate.

A second embodiment will be described with reference to FIG. FIG.
In (a), for example, when one frame is composed of five subframes, the present invention similarly includes five subframes SF5, SF4, SF3, SF2, and SF1, as described above.
Further, a sub-frame SF1 having a relative ratio of minimum luminance of 1 is added adjacent to the original sub-frame SF1 having a relative ratio of minimum luminance of 1, and a luminance arrangement of 16, 8, 4, 2, 1, 1 and 6-bit 6-screen is performed. I do.

Only when the level of the original signal changes from 15 to 16 (when the amount of change is the minimum value), the luminance of the 6-bit 6-screen is used. 1, 1 SF4, SF3, SF
2, SF1 and SF1 are selected.

A case where a display of 32 gradations is performed by using such a combination of luminances of 6 bits and 6 screens will be described. For example, as shown in FIG. Since it is level 15, SF4, SF
3, level 15 is "0111" by SF2 and SF1.
1 ".

Only when the next frame changes from level 15 to level 16, level 16 becomes SF4, SF3, SF
2. Quantized by “011111” by SF1 and SF1. Therefore, at the transition point from the level 15 to the level 16, "01111""0" as shown in FIG.
11111 ", and the lighting at the level 15 and the level 16 is not continuous. Therefore, there is no large change in the luminance at that time, and the image quality does not deteriorate.

The above example is generally represented as follows. One frame is composed of n bits, and the relative ratio of luminance is 2 to the power of (n−1), 2 to the power of (n−2),.
n = 0) -th power of the nth subframe, and the 0th power of the subframe 2 having the relative ratio 1 of the minimum luminance adjacent to the 0th power of the subframe 2 having the relative ratio 1 of the minimum luminance. Deploy. As described above, the display of the 2 n -th power gradation is performed by using the combination of the (n + 1) bits and the luminance of the (n + 1) screen.

Then, the level of the original signal is "2 (n-
(1) power -1 "to" 2 to the power of (n-1) "(only when the amount of change is the minimum value), n + 1 bits, n + 1
The luminance of the screen is used, and SF “2 (n−2)” as a subframe for level “2 (n−1)”,
SF “2 to the (n−3) th power”,..., SF “2 to (n−n =
0) power "and SF" 2 to the power of (nn-0) "are selected. SF “2 to the (n−1) power” is selected as a subframe for the other levels “2 to the (n−1) power”.

[0025]

According to the present invention, there is provided a display apparatus comprising a plurality of sub-frames having different relative ratios of luminance to constitute one frame and projecting a multi-gradation video signal.
The minimum luminance subframe in the subframe
Next to the minimum luminance subframe with the same luminance as the
Touch and add , according to the change of the image brightness in the time axis direction ,
The added minimum luminance subframe and maximum luminance subframe
Lighting in combination with other subframes except
Since the same luminance as that of the maximum luminance subframe is obtained , for example, when displaying 16 gradations, the input of the original signal is performed.
Even when the level changes from level 7 to level 8,
There is no significant change in luminance due to the continuous lighting, and the image quality does not deteriorate. The present invention is particularly effective when performing pseudo halftone display by error diffusion or the like between one gradation level.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a driving sequence showing a first embodiment of a driving method of a display device according to the present invention.

FIG. 2 is an explanatory diagram of a driving sequence showing a second embodiment of the driving method of the display device according to the present invention.

FIG. 3 is an explanatory diagram of a driving sequence according to a conventional method.

FIG. 4 is a drive sequence and a drive waveform diagram in a 256 gradation method.

[Explanation of symbols]

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Junichi Onodera 1116 Suenaga, Takatsu-ku, Kawasaki, Kanagawa Prefecture Inside Fujitsu General Limited (72) Inventor Masayuki Kobayashi 1116, Suenaga, Takatsu-ku, Kawasaki, Kanagawa Fujitsu General Limited (72) Inventor Seiji Matsunaga 1116 Suenaga, Takatsu-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu General Limited (58) Field surveyed (Int.Cl. ⁷ , DB name) G09G 3/28 G09G 3/20 641

Claims (3)

(57) [Claims] 1. A display apparatus comprising a plurality of sub-frames having different luminance relative ratios to constitute one frame to project a multi-gradation video signal.
This minimum luminance subframe
Add the minimum luminance subframe with the same luminance as the adjacent frame
In addition , according to the change in the image brightness in the time axis direction,
Other than the small luminance subframe and the maximum luminance subframe
Lighting in combination with sub-frames of
A method for driving a display device, wherein the same luminance as that of a display frame is obtained . 2. One frame has a relative ratio of luminance of 2 (n
−1) power, 2 (n−2) power,..., 2 (n−n = 0)
N bits of n subframes (SF) to be raised to the power
The method of driving a display device according to claim 1, comprising : 3. In a display device in which one frame is composed of a plurality of sub-frames having different relative ratios of luminance and a multi-gradation video signal is projected, one frame is
The relative ratio of the luminance from the maximum luminance to the minimum luminance is 2 (n-
1) power, 2 (n−2) power,..., 2 (n−n = 0) power sub-frames (SF) having an n-bit configuration
To further minimize said minimum bright Dosa subframe same brightness
A luminance sub-frame is added adjacently and composed of n + 1 bits.
Form, sub-level of the original signal for "2 (n-1) power minus" from "a 2 (n-1) th power" to when the change level "2 (n-1) th power" 2 (n-
2) All powers of 2 to the power of (n-3),..., 2 to the power of (n−n = 0) , and all added subframes of the power of 2 to the power of (n−n = 0)
Beam is turned is selected, the level of the original signal is "2 (n
-1) to "2 (n-1)".
2 (n-1) power subframes are selected as subframes for levels other than "2 (n-1) power".
The driving method of a display device is characterized in that the so that the lighting Te.