JPH09160524A - Error diffusion processing device of display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the scale of the group of display area ratio monitoring circuits without reducing the accuracy. SOLUTION: This device includes an on sub-field control circuit 16, by which the turning on of each sub-field SF1 to SF6 constituting one field is controlled by setting at least two of the sub-field SF1 to SF6 (e.g. SF3 and SF4) to be weighted equally and by which a plurality of dots for turning on one of the equally weighted SF3 and SF4 are controlled so that the number of dots for turning on SF3 becomes equal to that of dots for turning on SF4; display area ratio monitoring circuits 201 to 206 for monitoring the display area ratio of a PDP; and a brightness characteristic computing circuit 22a which calculates an emission brightness characteristic based on the display area ratio calculated and outputs data to an error diffusion circuit 10. One monitoring circuit 204 serves as both monitoring circuits (203 ), 204 for a reduction in circuit scale. Moreover, the display area ratio for SF4 calculated by the common monitoring circuit 204 , becomes equal to that for SF3, so substitution is made possible to prevent the accuracy from decreasing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention performs error diffusion processing of an input video signal in an error diffusion circuit, and makes one field (or one frame) a plurality of subfields (subframes).
The present invention relates to an error diffusion processing device in a display device which displays a pseudo-halftone image on a display panel which is divided into and lit.

[0002]

2. Description of the Related Art Recently, as a thin and lightweight display device, P
Attention has been paid to DP (plasma display panel). 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.

PDPs are AC type and DC type which have different basic characteristics.
Type. The AC type PDP has obtained sufficient characteristics with respect to brightness and life, but with regard to gradation display, only a maximum of 64 gradations has been reported at the prototype level. However, the address / display separation type driving method (A
A future 256-gradation method based on the DS subfield method or the ADS subframe method has been proposed.

In the ADS subfield method, one field is composed of eight subfields having relative luminance ratios (that is, luminance weightings) of 1, 2, 4, 8, 16, 32, 64 and 128. 256 gradations are displayed by combining the brightness of 8 screens. Each subfield is composed of an address period in which data for one refreshed screen is written and a sustain period for determining a 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 field 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,
Although the image quality is improved, the emission brightness is reduced, and conversely, if the number of bits of a signal to be handled is reduced, the emission brightness is increased, but the gradation display is reduced and the image quality is deteriorated.

The error diffusion process for reducing the grayscale error between the input signal and the emission luminance while reducing the bit number of the output drive signal more than the bit number of the input signal is a process for expressing a pseudo halftone. , Used when expressing light and shade with few gradations.

In this error diffusion processing, the emission luminance characteristic of the PDP is measured from typical input data and stored in ROM, and the data corresponding to this emission luminance characteristic is sent to the error diffusion circuit side to input video signal. Pseudo-halftone display was performed by adding to and diffusing. As a result, as shown in FIG. 2, although the emission luminance level is momentarily stepwise like a solid line, it is actually recognized in an averaged state, and y = x like a dotted line is recognized. It becomes the corrected luminance line.

[0008]

However, the light emission luminance characteristic of the PDP may change depending on the data to be displayed and may be different from the light emission luminance characteristic shown in FIG. 2. In such a case, the representative shown in FIG. However, the method of adjusting to the specific emission luminance characteristic has a problem that it cannot fully adapt to the gradation characteristic and a pseudo contour appears due to the gradation inadequacy.

The present applicant has already constructed one field as shown in FIG. 3 in order to solve such a problem.
A tone adaptive type error diffusion processing device is proposed, which is configured as shown in FIG. In FIG. 4, the error diffusion circuit 10
However, the reproduction error data from the error detection circuit 12 is added to the n (eg, 8) -bit video signal input to the input terminal 14 to perform error diffusion processing, and an m (eg, 6) -bit diffused output signal is obtained. The lighting subfield control circuit 16 outputs a drive signal to the PDP via the output terminal 18.

The display area ratio monitoring circuits 20 _{1 to} 20 ₆ provided for each subfield obtain the display area ratio of each subfield based on the signal output from the lighting subfield control circuit 16 to the PDP. Luminance characteristic calculation circuit 22
Calculates the light emission luminance characteristics based on the display area ratios obtained by the display area ratio monitoring circuits 20 _{1 to} 20 ₆ and outputs corresponding data (for example, brightness deviation data) to the error detection circuit 12. The error detection circuit 12 detects an error based on the diffusion output signal of the error diffusion circuit 10 and the output data of the luminance characteristic calculation circuit 22, and outputs the reproduction error data to the error diffusion circuit 10.

As described above, instead of the typical light emission luminance characteristic given from the conventional ROM, the light emission luminance characteristic calculated for each field or every plural fields is updated to perform the error diffusion processing. It was possible to prevent the appearance of false contours due to grayscale non-adaptation.

Further, the lighting sub-field control circuit 16 of FIG. 4 controls the brightness of the six sub-fields SF1 to SF6 forming one field in order to prevent the false contour from appearing on the screen when the moving image is displayed. As shown in FIG. 3, the weighting is set to 1, 2, 4, 4, 8, and 8, and when there is a dot for which only one of the two subfields having the same weighting (for example, SF3 and SF4) is illuminated and displayed, The control is performed so that the subfields to be turned on are switched for each dot and each field, each line and each field, or each dot, each line, and each field.

For example, when displaying a screen composed of dots having a brightness level of 4, each dot may light one of SF3 and SF4. In such a case, the lighting subfield control circuit 16 causes the lighting subfield control circuit 16 to emit SF3. By controlling the switching on and off of SF4 for each dot, each line and each field, it is possible to prevent a false contour from appearing on the screen when a moving image is displayed.

[0014] However, in the error diffusion processing device already proposed as shown in FIG. 4, 1 six display area ratio monitoring circuit corresponding to the number of subfields SF1~SF6 constituting the field 20 ₁ to 20 ₆ is required to Therefore, there is a problem that the circuit scale becomes large. Further, in order to reduce the circuit scale, six display area ratio monitoring circuits 20 _{1 to} 20 ₆
Of subfields SF3 to
Four display area ratio monitoring circuits 20 ₃ to 20 2 corresponding to SF6
0 ₆ but also conceivable to configure only, it means that does not monitor the display area ratio of the sub-fields SF1, SF2 corresponding to the two display area rate monitoring circuit 20 _1, 20 ₂ is omitted, fall accuracy There was a problem.

The present invention has been made in view of the above-mentioned problems, and it is possible to reduce the circuit scale of the display area ratio monitoring circuit group in the gradation adaptive error diffusion processing device without lowering the accuracy. The purpose is to

[0016]

According to a first aspect of the present invention, there is provided an error diffusion processing device in which an error diffusion circuit performs an error diffusion process on an input video signal, and one field is divided into a plurality of subfields and turned on. In a display device for displaying a pseudo-halftone image, the weighting of at least two subfields among the plurality of subfields is set to be equal, and lighting of each subfield is controlled based on the output signal of the error diffusion circuit. For a plurality of dots that illuminate either one of the two subfields having the same weighting, make the number of dots illuminating one subfield having the same weighting equal to the number of dots illuminating the other subfield. Lighting subfield control circuit for controlling the lighting of the subfield and this lighting subfield Display area ratio monitoring circuit group that monitors the display area ratio of each sub-field on the display panel based on the output signal of the control circuit, and the emission luminance characteristic is calculated based on the display area ratio calculated by this display area ratio monitoring circuit group. A plurality of display area ratio monitoring circuits for monitoring the display area ratios of subfields of the display area ratio monitoring circuit group, which have the luminance characteristic calculation circuit for outputting corresponding data to the error diffusion circuit side, One of the plurality of display area ratio monitoring circuits is also used as a display area ratio monitoring circuit.

Since a plurality of display area ratio monitoring circuits for monitoring the display area ratios of subfields having the same weight in one field are also used by one of the display area ratio monitoring circuits, the display area ratio monitoring circuit. The circuit scale of the group can be reduced. In addition, the lighting subfield control circuit sets the number of dots for lighting one of the two subfields having the same weight and the number of dots for lighting the other subfield of the plurality of dots having the same weighting. Since the lighting of the corresponding sub-fields is controlled so that the numbers of are substantially equal to each other, the display area ratio obtained by the dual-use display area ratio monitor circuit is
The display area ratio for other subfields is almost the same, and it can be substituted for other subfields, and the accuracy does not deteriorate.

According to a second aspect of the present invention, in the first aspect of the present invention, in order to omit a large-scale display area ratio monitoring circuit, a plurality of subfields having the same weighting in one field are subfields having a large weighting. Set.

According to a third aspect of the invention, in the second aspect of the invention, one field is weighted by 1, 2, 4, 4, 8, 8
6 sub-fields.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. In FIG. 1, the same parts as those in FIG. In FIG. 1, reference numeral 10 is an error diffusion circuit for performing an error diffusion process for minimizing a grayscale error between the input video signal and the emission brightness of the PDP. The error diffusion circuit 10 is
Error diffusion processing is performed by adding reproduction error data from the error detection circuit 12 to an n (for example, 8) -bit video signal input to the input terminal 14, and m (m≤n-1, for example, 6) bits. Is configured to output the spread output signal of.

A PDP (not shown) as a display panel is coupled to the output side of the error diffusion circuit 10 via a lighting subfield control circuit 16 and an output terminal 18. This PDP has six subfields SF1, SF2, SF3, SF4, SF5, S in which one field is weighted as 1, 2, 4, 4, 8, 8 as shown in FIG.
By dividing the light into F6 and turning on the light, it is possible to display 28 gradations.

The lighting subfield control circuit 16 is
A plurality of subfields SF1 to SF6 are controlled to be lit based on the diffusion output signal obtained by the error diffusion circuit 10, and a plurality of subfields of equal weighting (for example, SF3 and SF4) are lit. Regarding dots, the subfields (for example, SF3 and S3) are equalized so that the number of dots for lighting one subfield (for example, SF3) having the same weight is approximately equal to the number of dots for lighting the other subfield (for example, SF4).
The lighting of F4) is controlled.

20 ₁ , 20 ₂ , 20 ₄ , and 20 ₆ are subfields SF1, SF2, and S having different weights, respectively.
A display area ratio monitor circuit for monitoring the display area ratios of F4 and SF6. These display area ratio monitor circuits 20 ₁ , 20 ₂ , 20
Reference numerals ₄ and 20 ₆ determine the display area ratios of the subfields SF1, SF2, SF4, and SF6 based on the drive signals output from the lighting subfield control circuit 16 to the PDP. Reference numeral 22 denotes a brightness characteristic calculation circuit, and this brightness characteristic calculation circuit 22a is the display area ratio monitoring circuit 2
The light emission luminance characteristics are calculated based on the display area ratios obtained in 0 ₁ , 20 ₂ , 20 ₄ , and 20 ₆ , and corresponding data (for example, luminance deviation data) is output to the error detection circuit 12.

The error detection circuit 12 detects an error based on the diffusion output signal of the error diffusion circuit 10 and the output data of the luminance characteristic calculation circuit 22a, and reproduces the reproduction error data. Output to 10.

Next, the operation of the above embodiment will be described.
For convenience of explanation, the video signal input to the input terminal 14 is subjected to error diffusion processing by the error diffusion circuit 10, passes through the lighting subfield control circuit 16, and then passes through the output terminal 18 to the PDP.
A case where the luminance level of the drive signal output to is 4 will be described. In this case, the subfield SF1 shown in FIG.
One of the subfields SF3 and SF4 having a luminance weighting of 4 of SF6 to SF6 may be turned on, but the lighting subfield control circuit 16 sets the subfields to be turned on for each dot, each line and each field to SF3 and SF4. This is replaced to prevent false contours from appearing on the screen when a moving image is displayed.

In this case, the lighting subfield control circuit 1
When 6 controls the lighting of the subfield SF3 of the PDP, the brightness characteristic calculation circuit 22a monitors the display area ratio of the subfield SF4.
0 ₄ is used to calculate the subfield SF3
The light emission luminance characteristic of is calculated instead. That is, the display area ratio monitoring circuit 20 ₄ replaces the already proposed display area ratio monitoring circuit 20 ₃ shown in FIG. At this time, SF3 and SF
Since the lighting of No. 4 is switched for each dot, for each line, and for each field, the number of dots illuminated by SF3 and the number of dots illuminated by SF4 in the display screen are substantially equal, and the accuracy of the obtained display area ratio is It never falls.

Further, when the lighting subfield control circuit 16 controls the lighting of the subfield SF4 of the PDP, the luminance characteristic calculation circuit 22a causes the display area of the subfield SF4 to be displayed as in the already proposed method shown in FIG. The emission luminance characteristic of the subfield SF4 is calculated using the display area rate obtained by the display area rate monitoring circuit 20 ₄ for monitoring the rate.

In the above embodiment, in order to prevent a false contour from appearing on the screen when displaying a moving image, the lighting subfield control circuit illuminates two subfields (SF3 and SF4) having the same weight for each dot. , Every line and every field, so that one subfield (for example, SF3) in the display screen has substantially the same number of dots as the other subfield (for example, SF4) has the same number of dots. However, the present invention is not limited to this.

For example, in order to prevent a false contour from appearing on the screen when a moving image is displayed, the lighting subfield control circuit illuminates two subfields having the same weight for each dot and each field, or for each line. Alternatively, the number of dots illuminated in one subfield in the display screen may be made substantially equal to the number of dots illuminated in the other subfield in the display screen.

Alternatively, m lines × n dots (m and n are mx
A unit screen is a positive integer that satisfies n ≧ 3, and one of the two subfields (eg, SF3) having the same weight in the unit screen is lit and the other dot (eg, SF4) is lit. The number of dots is made substantially equal, and a plurality of types of unit screen patterns in which the arrays of these two types of dots are different from each other are created, and the plurality of types of unit screen patterns are switched and displayed for each field. This prevents false contours from appearing on the screen when a moving image is displayed, and thus the number of dots in one subfield (for example, SF3) of the display screen in the display screen and the other subfield (for example, SF3) are turned on. The number of dots for which SF4) lights up may be made substantially equal.

Alternatively, a screen of dots in which either one of two subfields (eg, SF3 and SF4) having the same weight is turned on is displayed for each dot and each field.
By displaying each line and each field, or each dot, each line and each field by switching them at random, it is possible to prevent false contours from appearing on the screen when a moving image is displayed. The number of dots that one subfield (for example, SF3) lights up,
The number of dots illuminated in the other subfield (eg, SF4) may be made substantially equal.

In the above-described embodiment, one of the two subfields having the drive signal having the luminance level of 4 and having the same weight is lit, and the other subfield is not lit.
3 and SF4 have been described, the present invention is not limited to this. For example, if the brightness level of the drive signal is 8
, One of the two subfields having the same weight is lit and the other subfield is unlit is SF5 and S5.
It can also be used in the case of F6.

In the embodiment described above, one frame is composed of six subframes SF1 to SF6, and one of them is
Although the weights of 3 and SF4 and SF5 and SF6 are set to be equal to each other, the present invention is not limited to this, and one frame includes a plurality of subframes SF1 to SFn.
(For example, n is 8), and can be used for at least two subframes (for example, SF1 and SF8) in which the luminance weighting is set equal.

In the above embodiment, the display panel is the PDP.
Although the case has been described, the present invention is not limited to this, and can also be used when the display panel is an LCDP (liquid crystal display panel).

[0035]

As described above, the invention of claim 1 provides a plurality of display area ratio monitoring circuits for monitoring the display area ratios of subfields having the same weighting in one field. Since the circuit is also used, the circuit scale of the display area ratio monitoring circuit group can be reduced. In addition, the lighting subfield control circuit determines, for a plurality of dots that light one of the two subfields having the same weight, the number of dots that one of the subfields having the same weight lights and the number of dots that the other of the subfields has the same weight. Since the subfield lighting is controlled so that the display area ratios are almost equal to each other, the display area ratio obtained by the dual-use display area ratio monitoring circuit is almost equal to the display area ratios of the other subfields. Can be used as a substitute, and the accuracy does not deteriorate.

According to the invention of claim 2, in the invention of claim 1, a plurality of subfields having the same weighting in one field are set by the subfields having a large weighting. The circuit can be omitted.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an error diffusion processing device of a display device according to the present invention.

FIG. 2 is a characteristic diagram showing a typical example of emission luminance characteristics.

FIG. 3 is an example of a driving sequence of a PDP capable of displaying 28 gradations in FIG.

FIG. 4 is a block diagram showing an error diffusion processing device of a display device proposed by the present applicant.

[Explanation of symbols]

10 ... Error diffusion circuit, 12 ... Error detection circuit, 14 ...
Video signal input terminal, 16 ... Lighting subfield control circuit, 18 ... Drive signal output terminal, 20 _{1 to} 20 ₆ ... Display area ratio monitoring circuit, 22, 22a ... Luminance characteristic calculation circuit,
SF1 to SF6 ... Subfields.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masayuki Kobayashi, 1116 Suenaga, Takatsu-ku, Kawasaki-shi, Kanagawa Prefecture, Fujitsu General Co., Ltd. (72) Seiji Matsunaga, 1116 Suenaga, Takatsu-ku, Kawasaki, Kanagawa Prefecture 72) Inventor Hayato Denda 1116 Suenaga, Takatsu-ku, Kawasaki-shi, Kanagawa Within Fujitsu General Co., Ltd. (72) Toru Aida 1116 Suenaga, Takatsu-ku, Kawasaki-shi, Kanagawa Within Fujitsu General Limited

Claims (3)

[Claims] 1. A display device for displaying a pseudo-halftone image on a display panel which performs error diffusion processing of an input video signal by an error diffusion circuit and divides one field into a plurality of subfields and turns on the display panel. At least two subfields in the field are weighted equally, the lighting of each subfield is controlled on the basis of the output signal of the error diffusion circuit, and the weights of the two subfields are equal.
For multiple dots that illuminate one of the two subfields, illuminate the subfield so that the number of dots that illuminate one subfield with the same weight is approximately equal to the number of dots that illuminate the other subfield. Lighting sub-field control circuit, a display area ratio monitoring circuit group for monitoring the display area ratio of each sub-field in the display panel based on the output signal of the lighting sub-field control circuit, and this display area ratio monitoring circuit group And a luminance characteristic calculation circuit that outputs corresponding data to the error diffusion circuit side based on the display area ratio obtained in step 1). A plurality of display area ratio monitoring circuits that monitor the display area ratio of the field are Error diffusion processing unit of a display device characterized by being combined with one display area rate monitoring circuit. 2. The error diffusion processing apparatus for a display device according to claim 1, wherein a plurality of subfields having the same weighting in one field are set by the subfields having a large weighting. 3. One field is weighted by 1, 2, 4,
3. The error diffusion processing device for a display device according to claim 2, wherein the error diffusion processing device comprises 6 subfields 4, 8, and 8.