JP3521592B2 - Error diffusion processing device for display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an error diffusion processing device of a display device using a display panel having a gradation number outside the factorial display of 2. For example, the number of gradations deviating from the factorial display of 2 is 12 (2 3
4) and 28 (not 2 4 or 2 5), and the display panel includes, for example, a PDP (plasma display panel) or an LCD (liquid crystal display panel).

[0002]

2. Description of the Related Art Recently, PDPs (plasma display panels) and LCDs have been used as thin and lightweight display devices.
The one using (liquid crystal display panel) is drawing attention. This PDP drive system is completely different from the conventional CRT drive system, and is a direct drive system using a digitized input video signal. Therefore, the brightness gradation emitted from the panel surface is determined by the number of bits of the signal to be handled.

PDPs are AC type and D type which have different basic characteristics.
It is divided into two types, C type. AC-type PDPs have sufficient characteristics in terms of brightness and life, but regarding gray-scale display, only a maximum of 64 gray-scale displays at the prototype level was reported, but the address / display separation type driving method (ADS) was used. A future 256-gradation method based on the subfield method) has been proposed.

In the ADS subfield method, for example, in the case of 8-bit, 256 gradation display, one frame is
The relative ratio of brightness is 1, 2, 4, 8, 16, 32, 64, 1
It is composed of 8 sub-fields of 28, and 256 gradations are displayed by combining the brightness of 8 screens. Each subfield is composed of an address period for writing refreshed data for one screen and a sustain period for determining the luminance level of the subfield.

In the AC driving method as described above, as the number of gradations is increased, the number of bits in the address period as a preparation period for lighting and emitting the panel within one frame period is increased. The period is relatively short and the maximum brightness is low. In this way, since the brightness gradation emitted from the panel surface is determined by the number of bits of the signal to be handled, 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, and conversely If the number of bits is reduced, the light emission luminance is increased, but gradation display is reduced and the image quality is deteriorated.

The error diffusion process for minimizing the contrast error between the input signal and the emission luminance while reducing the bit number of the output diffusion output signal than the bit number of the input signal is a process for expressing a pseudo halftone. Yes, it is used when expressing light and shade with few gradations.

A conventional display device using a general sub-field method and error diffusion processing is constructed as shown in FIG. That is, if the error diffusion circuit 10 is previously ROM
By performing the error diffusion process using the emission luminance level set to 12, the m
A spread output signal of (≦ n−1) bits is obtained. Then, the data conversion circuit 14 time-divisions one m-bit spread output signal into a plurality of subfields and displays a halftone image on the PDP 16 having the number of display gradations p (p = 2 to the mth power). To drive signals for.

As a result, as shown in FIG. 6, although the light emission luminance level like the step of the solid line is momentarily output, the light emission luminance levels above and below the step of the solid line are actually output. Are alternately output at a predetermined ratio, so that they are recognized in an averaged state and become a corrected luminance line of y = x like a dotted line.

[0009]

However, the light emission luminance characteristic of the PDP 16 may change depending on the data to be displayed and may be different from the light emission luminance characteristic shown in FIG. 5. In such a case, as shown in FIG. However, in the method of adjusting to the typical emission luminance characteristic, there is a problem that it cannot fully adapt to the gradation characteristic, and a pseudo contour appears due to the gradation non-adaptation. In order to solve such a problem, the present applicant has already proposed a display device using a gradation adaptive error diffusion process as shown in FIG.

Further, in a case where one frame is composed of a plurality of sub-fields SF1 to SFm having different luminance relative ratios, and a combination of luminances of m screens is used to display 2 m gray scales, the luminance level of the drive signal is Is from "2 to the m-1" to "2
M-th power ”(eg, from“ 7 ”to“ 8 ”or“ 15 ”)
There is a problem that granular noise is seen on the screen corresponding to the changed portion when changing from "16" to "16". In order to solve such a problem, the present applicant has already proposed that the weighting of at least two subfields among a plurality of subfields forming one frame is equalized as shown in FIG. did.

That is, the display device using the gradation adaptive type error diffusion processing as shown in FIG.
The error diffusion circuit 10 obtains the emission luminance characteristic of the PDP 16 for each one or a plurality of frames based on the drive signal output from the error diffusion circuit 10.
a light emission luminance characteristic acquisition circuit 18 for outputting to a, and instead of the light emission luminance level given from the ROM 12 of FIG. 5, the light emission luminance level is updated every one frame or every plural frames to perform error diffusion. Prevent the appearance of false contours.

FIG. 8 showing a frame structure for preventing granular noise from appearing on the screen is shown in FIG. 8 in which a plurality of sub-frames constituting one frame have a relative luminance ratio of 1, 2,
Six subfields SF1, SF of 4, 4, 8 and 8
2, SF3, SF4, SF5, and SF6 are provided to prevent a large change in brightness when the brightness level changes, thereby preventing deterioration of image quality. At this time, the six subfields SF1, SF2, SF3, SF4, SF
28 with a combination of 5 and 6 screen brightness corresponding to SF6
Gradation display is performed.

A factorial of 2 as described above (eg 2 of 6)
PDP1 with a gradation number less than the power of 64 (eg 28)
Considering the case of performing error diffusion processing using 6,
In order to bring the gradation steps closer to a straight line, the ROM 12 of FIG.
A method is conceivable in which the light emission luminance level stored in advance is configured as shown in FIG. In other words, it is a method of compensating for a gradation that is insufficient in the factorial of 2 by using one gradation twice in the middle of the gradation. However, when the tone-adaptive error diffusion processing as shown in FIG. 7 is performed corresponding to the emission luminance characteristic as shown in FIG. 9, the following problems occur.

That is, the characteristics of the emission luminance level with respect to the drive signal of the PDP 16 are stepwise such that the same gray level in the middle is used twice as shown in FIG. 9 every constant period (for example, every one or a plurality of frames). Then, the emission brightness characteristic of the PDP 16 is obtained and the emission brightness level is updated. For this reason, at consecutive points of the same brightness level (for example, in FIG. 9, the brightness level 32 where the drive signal level exceeds 32 and less than 64, or the brightness level 96 where the drive signal level exceeds 112 and less than 144), the pseudo gradation However, there is a problem in that the result of the smooth error diffusion processing cannot be obtained.

In order to solve such a problem, the present applicant has already proposed an error diffusion processing device for a display device as shown in FIGS. 10 (a) and 10 (b). That is, the emission brightness characteristic obtained by the emission brightness characteristic acquisition circuit 18a every fixed period (for example, one or a plurality of frames) and output to the error diffusion circuit 20 is set in advance as shown in FIG. The correction luminance line Q stored in the memory 22 in advance corresponding to P is set as shown in FIG. 10B, and the error diffusion circuit 20 sets the correction luminance line Q set and stored and the emission luminance line. By performing an error diffusion process using the light emission luminance characteristic (light emission luminance line) for gradation adaptation obtained by the light emission luminance characteristic acquisition circuit 18a corresponding to P, a pattern generated at a dark level is made inconspicuous and
Made possible to create smooth and continuous gradation.

However, in the proposed device shown in FIGS. 10A and 10B, the drive signal level Dk (= 176)
However, since the brightness level is saturated at the upper level beyond the drive signal level Dk, the PDP 16a with the number of gradations k does not reach the nth power of 2. Only pseudo-halftone images with gradations (for example, 176 gradations) can be displayed, and 2 nth gradations (for example, 256 gradations)
However, there is a problem that the pseudo halftone image cannot be displayed. Further, although the gamma correction circuit 24 for correcting the upper saturation part is provided, there is a problem that continuous 2 n-th gradation (for example, 256 gradations) cannot be displayed.

The present invention has been made in view of the above-mentioned problems, and a gray scale (for example, 176 gray scales) which does not reach the n-th power gray scale in the conventional example with respect to an input video signal of n (for example, 8) bits. ), Using the display panel that was only capable of displaying pseudo halftone images, 2 consecutive nth gradations (for example, 256 gradations)
It is an object of the present invention to provide an error diffusion processing device of a display device capable of displaying the pseudo-halftone image.

[0018]

According to a first aspect of the present invention, an error is obtained by performing an error diffusion process using error data to obtain an m (≤n-1) -bit diffused output signal from an n-bit input video signal. A diffusion circuit and an m-bit diffusion output signal obtained by this error diffusion circuit are time-divided into a plurality of sub-fields, and a halftone is displayed on a display panel with a display gradation number k (<2 to the m-th power). A data conversion circuit for converting into a drive signal for displaying an image, and a brightness correction memory for outputting preset error data to the error diffusion circuit using the m-bit diffusion output signal obtained by the error diffusion circuit as an address. The error data preset in the luminance correction memory includes the light emission luminance line preset for the display panel and the luminance level 0 at the drive signal 0 level of the light emission luminance line.
Point Zp and point M of the maximum brightness level in the maximum drive signal
It is characterized in that it is error data at each drive signal level of m bits between the correction luminance line connecting p.

In the error diffusion processing, error diffusion processing is performed by taking in corresponding error data from the brightness correction memory using the output m-bit diffusion output signal as an address. At this time, the error data preset in the brightness correction memory includes the emission luminance line preset for the display panel, the point Zp of the luminance level 0 at the drive signal 0 level of this emission luminance line, and the maximum drive signal. Point Mp of maximum brightness level
Error data at each drive signal level of m bits between the correction luminance line that connects the points B and the correction luminance line that connects the points. Therefore, error diffusion along the correction luminance line that connects the point Zp of the luminance level 0 and the point Mp of the maximum luminance level. Processing is performed, and in the conventional example, continuous 2 pixels are displayed by using the display panel with the display gradation number k, which was only capable of displaying the pseudo halftone image of the gradation (for example, 176 gradations) that does not reach the nth power gradation of 2. It is possible to display a pseudo halftone image of nth gradation (for example, 256 gradations).

According to a second aspect of the present invention, an error diffusion circuit for obtaining an m (≤n-1) -bit diffused output signal from an n-bit input video signal by performing an error diffusion process using a light emission luminance characteristic, and In order to display a halftone image on a display panel having a display gradation number k (<2 to the m-th power) by time-dividing an m-bit diffused output signal obtained by the error diffusion circuit into a plurality of subfields. a data conversion circuit for converting the driving signal, based on a drive signal obtained by the data conversion circuit, light emission luminance characteristic acquisition for obtaining the preset emission luminance lines of the display panel corresponding to the corrected luminance line at regular intervals circuit and the; and a memory storing a preset corrected luminance line, the set emission luminance lines, from level 0 of the drive signal to a level Dk corresponding to the display gradation number k emission luminance level But : Stepwise increased at the rate of 1, for driving signal exceeds the level Dk is set so that the light emission luminance level is repeated up to the luminance level, setting the stored corrected luminance line in the memory, the set Emission brightness
The error diffusion circuit is set on the line connecting the point Zp of the brightness level 0 at the drive signal 0 level of the line and the point Mp of the maximum brightness level at the maximum drive signal. An error diffusion process is performed using the corrected luminance line set and stored in the memory.

In order to perform gradation adaptive error diffusion processing,
The light emission luminance characteristic obtained and updated by the light emission luminance characteristic acquisition circuit at regular intervals is the light emission luminance level from level 0 of the drive signal to level Dk (for example, 176) corresponding to the number of display gradations k (for example, 12). Corresponding to a light emission luminance line preset such that the light emission luminance level repeats the maximum luminance level (for example, 176) for the drive signal exceeding the level Dk in a stepwise manner at a ratio of 1: 1. Therefore, the same brightness level is not used twice in the staircase before being saturated. Moreover, the correction luminance line used with the emission luminance characteristic in the error diffusion circuit is set to a line connecting the point Zp of the luminance level 0 of the set emission luminance line and the point Mp of the maximum luminance level in the maximum drive signal. Therefore, when a pseudo-halftone image is displayed by gradation adaptive error diffusion, smooth and continuous gradation can be produced, and continuous 256 gradations can be displayed.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the data conversion circuit is an error diffusion circuit in order to prevent granular noise from being seen on the screen corresponding to the brightness level changing portion. The obtained m-bit spread output signal is time-divided from one frame into a plurality of subfields including at least two subfields of equal weighting, and an intermediate is displayed on a display panel having a number of display gradations k (<2 to the m-th power). The signal is converted into a signal for displaying a toned image.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of an error diffusion processing device for a display device according to the invention of claim 1. FIG. 1A shows a block diagram of the device. In this figure, 26 is an error diffusion circuit, and the error diffusion circuit 26 is a brightness correction memory 28 composed of a ROM (Read Only Memory) or the like. By performing an error diffusion process in which error data stored in advance is taken and added to the original video signal, 4 (from m = n−1, m = 4) from an input video signal of 8 (n = 8) bits. In the case of), it is configured to obtain a spread output signal of bits.

A data conversion circuit 14a is coupled to the output side of the error diffusion circuit 26. This data conversion circuit 1
Reference numeral 4a denotes a diffusion output signal output from the error diffusion circuit 26, and four subfields SF1, SF2, in which one frame is weighted as 4, 2, 1, 4 as shown in FIG.
The number of display gradations is 12 (k = 12) by time division into SF3 and SF4.
In case of), 256 gradations (2 8 gradations) with PDP 16a
The pseudo halftone image is converted into a drive signal for display and output to the PDP 16a.

The error data stored in advance in the brightness correction memory 28 is the PDP 16 as shown in FIG.
Between the emission luminance line P preset for a and the correction luminance line q connecting the point Zp of the luminance level 0 at the drive signal 0 level of the emission luminance line P and the point Mp of the maximum luminance level at the maximum drive signal. Error data d ₀ (= 0), d ₁ , d ₂ , ..., D ₁₅ at each m-bit drive signal level.

Next, the operation of FIG. 1A will be described with reference to FIG.
(B) will be described together. The error diffusion circuit 26 performs error diffusion processing of taking in corresponding error data (for example, d ₉ ) from the brightness correction memory 28 by using the output m-bit diffusion output signal as an address, and performing addition / subtraction (for example, subtraction) on the original video signal. . At this time, the brightness correction memory 2
The error data preset to 8 is set to error data d ₀ , d ₁ , d ₂ , ..., D ₁₅ between the emission luminance line P and the correction luminance line q at each m-bit drive signal level. Therefore, the point Zp at the brightness level 0 and the point M at the maximum brightness level
Error diffusion processing is performed along the corrected luminance line q connecting p,
4 from the input 8-bit (when n = 8) video signal
Obtain a spread output signal of bits (when m = 4).

The data conversion circuit 14a includes an error diffusion circuit 2
The diffused output signal of No. 6 is converted into a drive signal corresponding to the subfield display method and output to the PDP 16a. That is,
As shown in FIG. 3, one frame includes four subfields S.
The signals are time-divided into F1, SF2, SF3, and SF4, and a signal for displaying the screen of one frame with the combination of the brightness of four screens is output to the PDP 16a.

Therefore, the PDP 16a having the display gradation number of 12 is used.
Then, by the error diffusion processing accompanied by the brightness correction by the error diffusion circuit 26 and the subfield method by the data conversion circuit 14a, 256 gradations continuous along the corrected brightness line q (2 = nth power gradation n = 8 The pseudo halftone image of (in case) is displayed.

In the above embodiment, the brightness correction memory 2 is used.
In order to obtain the error data preset to 8, PDP1
As shown in FIG. 1B, the emission luminance line P set for 6a has an emission luminance level of 1: from the level 0 of the drive signal to the level Dk (= 176) corresponding to the number k of display gradations.
The driving signal (192, 268, 2) that exceeds the level Dk in a stepwise manner at 0, 16, 32, ...
24, ...), the maximum luminance level 176 is repeated as the emission luminance level. However, the present invention is not limited to this, and as shown in FIG. It may be an emission luminance line that is used frequently. in this case,
Error data d ₀ preset in the brightness correction memory 28,
The values of d ₁ , d ₂ , ..., D ₁₅ are different from those of the above embodiment.

FIG. 2 shows an embodiment of an error diffusion processing device for a display device according to the present invention. In the figure, reference numeral 30 denotes an error diffusion circuit, and the error diffusion circuit 30 uses the emission luminance level obtained and updated for each one or a plurality of frames and the luminance using the corrected luminance line Q set and stored in the memory 32 in advance. By performing error diffusion processing with correction, a diffusion output signal of 4 bits (when m ≦ n−1 and m = 4) is obtained from an input video signal of 8 bits (when n = 8). Has been done.

A data conversion circuit 14a is coupled to the output side of the error diffusion circuit 30. This data conversion circuit 1
Reference numeral 4a denotes a diffusion output signal output from the error diffusion circuit 30, and four subfields SF1, SF2, in which one frame is weighted as 4, 2, 1, 4 as shown in FIG.
The number of display gradations is 12 (k = 12) by time division into SF3 and SF4.
In case of), 256 gradations (2 8 gradations) with PDP 16a
The pseudo halftone image is converted into a drive signal for display and output to the PDP 16a.

A light emission luminance characteristic acquisition circuit 18a is coupled to the output side of the data conversion circuit 14a. The light emission luminance characteristic acquisition circuit 18a includes the data conversion circuit 14a.
Based on the drive signal obtained in step 1, the light emission luminance of the PDP 16a corresponding to a preset light emission luminance line P (a line representing the light emission luminance characteristic) as shown in FIG. The characteristic is obtained and output to the error diffusion circuit 30.

The set emission brightness line P is shown in FIG.
As shown in (b), from the level 0 of the drive signal to the level Dk (= 176) corresponding to the number k of display gradations, the emission brightness level is 0, 16, 32, ... 176 at a ratio of 1: 1. Drive signal (192,
268, 224, ...) The emission brightness level is set to repeat the maximum brightness level 176.

As shown in FIG. 2B, the correction luminance line Q preset and stored in the memory 32 has a point Zp at the luminance level 0 at the driving signal 0 level of the light emission luminance line P and a maximum driving signal at the maximum driving signal. It is set to a line connecting the points Mp of the maximum brightness level.

Next, the operation of FIG. 2A will be described with reference to FIG.
(B) will be described together. The error diffusion circuit 30 corrects the brightness difference between the emission brightness characteristic obtained and updated by the emission brightness characteristic acquisition circuit 18a for each one or a plurality of frames and the corrected brightness line Q preset and stored in the memory 32 (luminance). By performing error diffusion processing (with correction)
4 from the input 8-bit (when n = 8) video signal
Obtain a spread output signal of bits (when m = 4).

The data conversion circuit 14a includes an error diffusion circuit 3
The diffused output signal of 0 is converted into a drive signal corresponding to the subfield display method and output to the PDP 16a. That is,
As shown in FIG. 2, one frame includes four subfields S.
The signals are time-divided into F1, SF2, SF3, and SF4, and a signal for displaying the screen of one frame with the combination of the brightness of four screens is output to the PDP 16a.

Therefore, the PDP 16a having the display gradation number of 12 is used.
Then, a pseudo halftone image of 256 gradations is displayed by the error diffusion process involving the brightness correction by the error diffusion circuit 30 and the subfield method by the data conversion circuit 14a.

The light emission luminance characteristic acquisition circuit 18a is based on the drive signal obtained by the data conversion circuit 14a.
Corresponding to the preset emission luminance line P as shown in (b), the emission luminance characteristic of the PDP 16a for each one or a plurality of frames is obtained and output to the error diffusion circuit 30. For this reason,
The error diffusion circuit 30 performs error diffusion processing involving gradation adaptive luminance correction using the emission luminance characteristic obtained and updated for each one or a plurality of frames and the corrected luminance line Q set and stored in the memory 32. Done.

As described above, the emission brightness characteristics obtained and updated by the emission brightness characteristic acquisition circuit 18a for performing the gradation adaptive type error diffusion processing are the display gradation number 12 from the level 0 of the drive signal. Level 1 corresponding to (k = 12)
Up to 76 (Dk = 176), the emission luminance level increases stepwise at a ratio of 1: 1, and the emission luminance level repeats the maximum luminance level 176 for a drive signal exceeding the level 176. Since it corresponds to the characteristic, the same brightness level is not used twice in the staircase before saturation. Moreover, the correction luminance line Q used together with the emission luminance characteristic in the error diffusion circuit 30 is set to a line connecting the point Zp of the luminance level 0 of the set emission luminance line P and the point Mp of the maximum luminance level in the maximum drive signal. ing. Therefore, when a pseudo-halftone image is displayed by gradation adaptive error diffusion, smooth and continuous gradation can be created, and continuous 256 gradations can be displayed.

In the above-described embodiment, one frame is divided into two sub-fields SF1 having the same weighting, as shown in FIG. 3, in order to prevent granular noise from being seen on the screen corresponding to the changing portion of the brightness level. The case of time division into four subfields SF1 to SF4 including SF4 has been described, but the present invention is not limited to this, and one frame can be used for time division into a plurality of subfields.

For example, as shown in FIG. 4, one frame is divided into two sets of subfields (SF1 and SF6; It is also possible to use a time-divided subfield including six subfields SF1 to SF6 including SF2 and SF5). Alternatively, it is also possible to use one frame time-divided into a plurality of subfields having different weightings.

In the above embodiment, the display panel is the PDP.
However, the present invention is not limited to this, and can be applied to the case of a digital display panel (for example, LCD).

[0043]

According to the invention of claim 1, in an apparatus for displaying a pseudo halftone image on a display panel by the subfield method and the error diffusion processing, the error diffusion processing fetches the error from the brightness correction memory and performs the error diffusion processing. The data is the emission luminance line preset for the display panel and the point Zp of the luminance level 0 at the drive signal 0 level of this emission luminance line.
And the correction luminance line connecting the point Mp of the maximum luminance level in the maximum driving signal are set in the error data at each driving signal level of m bits, so that the point Zp of the luminance level 0 and the point of the maximum luminance level are set. The number of display gray scales, in which the error diffusion processing is performed along the corrected luminance line connecting Mp, and only the pseudo halftone image display of gray scales (for example, 176 gray scales) that does not reach the nth power gray scale of 2 is performed in the conventional example. Using the k display panel, it is possible to display continuous pseudo-halftone images of 2 n-th gradation (for example, 256 gradations).

According to a second aspect of the present invention, in a device for displaying a pseudo-halftone image on a display panel by the subfield method and the gradation adaptive error diffusion processing, a fixed period is required for performing the gradation adaptive error diffusion processing. The emission luminance characteristic obtained and updated every time (for example, every one or a plurality of frames) is the emission luminance level from the level 0 of the drive signal to the level Dk (for example 176) corresponding to the number of display gradations k (for example, 12). Corresponding to a preset emission luminance characteristic such that the emission luminance level repeats the maximum luminance level (for example, 176) for a drive signal exceeding the level Dk in a stepwise manner at a ratio of 1: 1. Therefore, the same brightness level is not used twice in the staircase before being saturated. Moreover, the correction luminance line used with the emission luminance characteristic in the error diffusion circuit is set to the line connecting the point Zp of the luminance level 0 of the set emission luminance characteristic and the point Mp of the maximum luminance level in the maximum drive signal. Therefore, the gradation adaptive error diffusion makes it possible to display a smooth and continuous pseudo-halftone image of 2 n-th gradation (for example, 256 gradations when n = 8).

According to a third aspect of the present invention, in the first or second aspect of the invention, the data conversion circuit uses the m-bit spread output signal obtained by the error diffusion circuit for two subfields in which at least one frame has an equal weight. In the case where the display panel having the number of display gradations k (<2 to the m-th power) is time-divided into a plurality of sub-fields including It is possible to make granular noise invisible on the screen corresponding to the changed portion.

[Brief description of drawings]

1A and 1B show a first embodiment of an error diffusion processing device for a display device according to the present invention, wherein FIG. 1A is a block diagram of the device, and FIG. 1B is a gradation adaptive type device by the device of FIG. FIG. 9 is a light emission luminance characteristic chart set in advance corresponding to the light emission luminance characteristic updated by the error diffusion processing.

2A and 2B show a second embodiment of an error diffusion processing device of a display device according to the present invention, wherein FIG. 2A is a block diagram of the device, and FIG. 2B is a gradation adaptive type device by the device of FIG. FIG. 9 is a light emission luminance characteristic chart set in advance corresponding to the light emission luminance characteristic updated by the error diffusion processing.

FIG. 3 illustrates the structure of one frame time-divided by a data conversion circuit when the number of display gradations k of the PDP of FIGS.
It is explanatory drawing of the drive sequence in 2-gradation display.

FIG. 4 is an explanatory diagram of a drive sequence in 28-gradation display by the subfield method when the number of display gradations k of the PDP of FIGS. 1 and 2 is 28.

FIG. 5 is a block diagram of an error diffusion processing device of a display device using a general subfield method and an error diffusion process.

FIG. 6 is a characteristic diagram showing a typical example of emission luminance characteristics.

FIG. 7 is a block diagram of an error diffusion processing device of a display device which performs gradation adaptive error diffusion processing.

FIG. 8 is an explanatory diagram of a drive sequence in 28 gradation display.

FIG. 9 shows the number of display gradations that is less than the factorial of 2 (for example, 1
FIG. 9 is a characteristic diagram of a light emission luminance level stored in advance in a ROM, which is conceived to bring a gradation step closer to a straight line when a pseudo halftone image is displayed by an error diffusion process on a PDP having 2).

10 shows an error diffusion processing device for a display device, which was separately filed by the applicant of the present application in order to solve the problem of the gradation adaptive type error diffusion processing device using the emission luminance characteristic of FIG. 8B is a block diagram of the device, and FIG. 8B is a light emission luminance characteristic diagram preset in correspondence with the light emission luminance characteristic updated by the gradation adaptive error diffusion processing by the device of FIG.

[Explanation of symbols]

10, 10a, 26, 30 ... Error diffusion circuit, 12 ... R
OM, 14, 14a ... Data conversion circuit, 16, 16a ...
PDP (one example of display panel), 18, 18a ... Emission luminance characteristic acquisition circuit, 22, 32 ... Memory (stores corrected luminance line Q), 24 ... Gamma correction circuit, 28 ... Luminance correction memory (for error data storage) , Dk ... Level of drive signal corresponding to display gradation number k, k ... Display gradation number of PDP, P ...
Preliminarily set emission luminance line (emission luminance characteristic), Q ... Corrected luminance line preset and stored, SF1 to SF4 ... Subfield.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Onodera 1116 Suenaga, Takatsu-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu General Co., Ltd. (72) Inventor Seiji Matsunaga 1116 Suenaga, Takatsu-ku, Kawasaki-shi, Kanagawa, Ltd.Fuji General Co., Ltd. (72) Inventor Toru Aida, 1116 Suenaga, Takatsu-ku, Kawasaki, Kanagawa, Ltd. (56) JP-A-9-81072 (JP, A) JP-A-9-146492 (JP, A) JP-A-9-179522 (JP, A) JP-A-7-140923 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G09G 3/00-3/38

Claims (3)

(57) [Claims] 1. An error diffusion process using error data is performed to obtain m (≤n-1) from an n-bit input video signal.
An error diffusion circuit for obtaining a bit diffusion output signal, and an m-bit diffusion output signal obtained by the error diffusion circuit are time-divided into a plurality of subfields for one frame, and the number of display gradations k
A data conversion circuit for converting into a drive signal for displaying a halftone image on a display panel (<2 m) and an m-bit diffusion output signal obtained by the error diffusion circuit are preset as addresses. A luminance correction memory for outputting error data to the error diffusion circuit is provided, and the error data preset in the luminance correction memory includes a light emission luminance line P preset for the display panel and this light emission. Error data at each drive signal level of m bits between the point Zp of the brightness level 0 at the drive signal 0 level of the brightness line P and the correction brightness line q connecting the point Mp at the maximum drive level of the maximum drive signal. An error diffusion processing device for a display device. 2. An error diffusion process using light emission luminance characteristics is performed to convert m (≦ n−) from an n-bit input video signal.
1) An error diffusion circuit for obtaining a bit diffusion output signal and an m-bit diffusion output signal obtained by the error diffusion circuit
A data conversion circuit that time-divides a frame into a plurality of subfields and converts into a drive signal for displaying a halftone image on a display panel with a display gradation number k (<2 to the m-th power), and this data conversion circuit Based on the obtained drive signal, the emission brightness of the display panel corresponding to the preset correction brightness line Q
And light emission luminance characteristic acquisition circuit for obtaining a line P at regular intervals, before
Note that the preset emission luminance line P has a memory for storing a preset correction luminance line Q , and the emission luminance level P set in this manner has an emission luminance level from level 0 of the drive signal to level Dk corresponding to the number k of display gradations. Level D gradually increasing at a ratio of 1: 1
For a drive signal exceeding k, the emission luminance level is set to repeat the maximum luminance level, and the corrected luminance line Q set and stored in the memory is the set emission luminance line.
The error diffusion circuit is set on the line connecting the point Zp of the brightness level 0 at the P drive signal 0 level and the point Mp of the maximum brightness level at the maximum drive signal, and the error diffusion circuit obtains the emission brightness characteristic obtained by the brightness characteristic acquisition circuit and the emission brightness characteristic. An error diffusion processing device for a display device, which performs an error diffusion process using a corrected luminance line Q set and stored in a memory. Wherein the data conversion circuit, the spread output signal of m bits obtained by the error diffusion circuit, display floor to time-divided into a plurality of subfields including two subfields equal at least weighting 1 frame Key k (<2 to the m-th power)
3. The error diffusion processing device for a display device according to claim 1, wherein the error diffusion processing device is converted into a signal for displaying a halftone image on the display panel.