JP3075335B2 - Halftone display method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plasma display panel (hereinafter referred to as a PDP (Plasma Display panel)) or a DMD (Digital Micromirror Device).
The present invention relates to a halftone display method for a display device using a so-called subfield method, which has a memory of values and displays a plurality of binary images each weighted with a moving image having a halftone. .

[0002]

2. Description of the Related Art A conventional so-called subfield method is used for displaying an image having a halftone on a display device having a binary memory effect as shown in Japanese Patent Application Laid-Open No. 4-195087. It is. FIG. 6 shows an example of this display method. This is an example of displaying an 8-bit, 256-gradation television image.

In this conventional example, one image (one field) is composed of eight binary images (subfields). In each subfield, in the period during which the black portion in FIG. 6A emits light, weighting is performed in each subfield according to the time length of this portion or the number of light emitting pulses in this portion (ie, Brightness). In the example of FIG. 6, each subfield is "1",
"2", "4", "8", "16", "32", "6"
4 "and" 128 ". PDP
Each pixel displays a halftone by a combination of which subfield emits light as shown in FIG. 6B. For example, the luminance corresponding to “173” is
Subfield number 8 with weight "128", subfield number 6 with weight "32", subfield number 4 with weight "8", subfield number 3 with weight "4" and weight "1" It is obtained by causing each subfield of subfield number 1 to emit light.

In a still image, since the line of sight is almost fixed, the addition of subfields is normally performed in each pixel, so that there is no deterioration in image quality. By employing such a driving method, the light emitting operation of each pixel can be continued for one field until the next field starts, so that the light emitting time ratio per pixel can be increased.

[0005]

However, in the above display method using the conventional subfield method, the literature (“Pseudo-contour noise seen in pulse-width modulation moving image display”): Television Society Technical Report, Vol. No.2, IDY95-21, pp.61-6
As shown in 6), there is a problem that a unique pseudo-contour-like noise is seen in a moving image and image quality is deteriorated. This is because the eye follows the moving image, and the temporal integration region of the eye changes spatially. That is, if the line of sight moves at a speed of moving a plurality of pixels within one field display period, the addition of subfields is performed not over a single pixel but over a plurality of pixels, and a normal image cannot be obtained. Deteriorates.

FIG. 7 shows a computer simulation of an image seen when a moving ramp waveform is displayed by a conventional subfield method in order to quantitatively measure this amount. In this simulation method, the temporal integration amount of the eye when moving in the left direction at the speed of 5 pixels during each field display period is calculated.

[0007] The ramp waveform is originally a straight oblique line. However, in the conventional method, when the line of sight changes from “127” to “128” or from “63” to “64”, that is, where a new bit is set in binary display, it is remarkable. Noise is seen. In an actual image, this results in a pseudo-contour-like image quality deterioration.

[0008] As described above, the gradation display by the subfield method is unnatural when there is a considerable luminance difference between pixels having almost no original luminance difference when the screen is observed following the movement of the image. There is a problem that the user may be perceived.

An object of the present invention is to solve the above-mentioned problems, and to prevent the image quality of a moving image from being deteriorated when the subfield method is used.

[0010]

SUMMARY OF THE INVENTION A halftone display method according to the present invention.
Can be used to scan one field of a moving image
Represents a plurality of binary images weighted by the number of pulses.
Intermediate display of image subfields superimposed temporally
In the tonal display method, the upper half of the halftone displayed in binary
The part corresponding to the multiple bits of
Number of subfields and the remaining lower bits
Is displayed as a binary image weighted according to the binary system
Halftone display method, with multiple higher-order subfields
Are arranged continuously in one field period.
In addition, as the number of gradations increases,
If there is a lit subfield in the field
Is the upper rank adjacent to the lit subfield
One of the subfields of
It is characterized by being newly lit.

With this configuration, it is possible to prevent the occurrence of an abnormal image due to the addition of subfields due to the movement of the line of sight, and to improve the image quality of a moving image.

[0012]

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

(First Embodiment) FIG. 1 is a diagram for explaining a first embodiment, in which 8 bits, that is, 25 bits, are used.
This is an example in the case of displaying an image of six gradations. FIG. 1A is a table showing the configuration of a subfield, and FIG. 1B is a table showing which subfield emits light with respect to gradation. FIG.
In (a), as in the case of FIG. 6 described in the conventional example, in the period in which the black portion emits light, weighting is performed according to the time length of this portion or the number of light emitting pulses in this portion.

In the first embodiment, one field is displayed by using 12 subfields, and the upper 3 bits out of 8 bits are subjected to continuous time width modulation by 7 subfields having a weight of "32". Display is performed, and the lower 5 bits are displayed in five binary fields with five subfields having weights of "16", "8", "4", "2", and "1", respectively. In FIG. 1A, the subfields of subfield numbers 6 to 12 represent the upper three bits, and the subfields of subfield numbers 1 to 5 represent the lower 5 bits .
That is, as shown in FIG. 1B, the subfield for displaying the upper 3 bits is changed from the subfield number 6 to the subfield number 12 every time the gradation increases by 32, that is, each time the upper 3 bits are increased by one. The sub-fields that emit light one by one in order up to the sub-fields are continuously increased.

FIG. 2 is a computer simulation of an image seen when a moving ramp waveform is displayed in the first embodiment. The simulation method is the same as the method described in the conventional example, in which the temporal integration amount of the eye when moving in the left direction at the speed of 5 pixels during each field display period is calculated. The waveform of FIG. 2 is different from the waveform of FIG. 7 when the line of sight changes from “127” to “128” or from “63” to “64”, that is, a new image is displayed in binary notation. It can be seen that the noise at the place where the bit stands is greatly reduced. As a result, the image quality deterioration of the pseudo contour shape in the moving image is greatly improved.

(Second Embodiment) FIG. 3 shows a second embodiment. This is the same as the first embodiment except that the columns of the subfields are reversed. Even in this case, a similar effect can be obtained.

(Third Embodiment) FIG. 4 shows a third embodiment. This means that the subfields 6 to 12 for displaying the upper three bits are sequentially increased one by one in the left and right direction each time the gradation increases by 32. In this way, in addition to the first and second embodiments, even if the number of gradations increases, the change in the center of gravity of the luminance in the time axis direction can be reduced. Deterioration can be greatly improved.

(Fourth Embodiment) FIG. 5 shows a fourth embodiment. In the fourth embodiment, one field is displayed using 14 subfields, and the upper 3 bits of the 8 bits are 8 subfields having a weight of "25" and 1 subfield having a weight of "24". The display is performed by continuous time width modulation, and the lower 5 bits are each set to “1”.
6 "," 8 "," 4 "," 2 ", and five subfields having a weight of" 1 "are displayed in binary notation. FIG.
In (a), subfield numbers 6 to 14
The subfields of the subfield No. 1 represent the upper 3 bits, and the subfields of subfield numbers 1 to 5 display the lower 3 bits. That is, as shown in FIG. 5B, in the subfields for displaying the upper 3 bits, the number of subfields that emit light one by one sequentially increases every time the gradation increases by 25. However, subfield “24” of subfield number 14
With weight.

As described above, it is necessary to set the weight of the subfield indicating the upper bits to the same (32) weight as the gradation indicated by the lowest bit (third bit in this embodiment) of the upper bits. Absent. That is, the number of sub-fields may be increased so that the weight may be smaller than the gradation indicated by the lowest bit in the upper bits. Further, the weights of the subfields for displaying the upper bits need not be exactly the same, and may be substantially the same. In this way, it is possible to freely select the weight of the subfield for displaying the higher-order bits according to the total number of subfields that can be driven, so that extremely effective subfield division can be performed, and furthermore, the It is possible to greatly improve the image quality deterioration of the pseudo contour.

Also, as shown in the second and third embodiments, if the subfields for displaying the upper bits continuously increase without leaving, the right (back)
The direction, the left (front) direction, or the left and right (front and back) may be combined.

The subfield for displaying the lower bits may be positioned right (back), left (front), or left and right (front and back) of the subfield for displaying the upper bits.

In the above embodiment, the subfields for displaying the lower bits are arranged in ascending or descending order, but the arrangement is not limited to this.

Further, the above-described embodiment uses 8 bits, 256 bits,
Although an image having a gradation is displayed, the number of bits, that is, the number of gradations is not limited to this.

In the above embodiment, the upper 3 bits of the 8 bits are displayed by continuous time width modulation, and the lower 5 bits are displayed in a binary system. However, the upper and lower division points are not limited to this. is not.

[0025]

As described above, according to the halftone display method of the present invention, it is possible to prevent the occurrence of an abnormal image due to the addition of erroneous subfields due to the movement of the line of sight and to improve the image quality of a moving image.

[Brief description of the drawings]

FIG. 1A is a diagram illustrating a subfield configuration according to a first embodiment. FIG. 1B is a diagram illustrating a subfield selection table according to the first embodiment.

FIG. 2 is a diagram showing a simulation of an image seen when a ramp waveform is moved by the display method according to the present invention.

FIG. 3A is a diagram illustrating a subfield configuration according to a second embodiment; FIG. 3B is a diagram illustrating a subfield selection table according to the second embodiment;

FIG. 4A is a diagram illustrating a subfield configuration according to a third embodiment; FIG. 4B is a diagram illustrating a subfield selection table according to the third embodiment;

5A is a diagram showing a subfield configuration according to a fourth embodiment; FIG. 5B is a diagram showing a subfield selection table according to a fourth embodiment;

FIG. 6A is a diagram showing a subfield configuration example showing a conventional subfield method. FIG. 6B is a diagram showing a subfield selection table in the conventional example.

FIG. 7 is a diagram showing a simulation of an image seen when a ramp waveform is moved by the conventional subfield method.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Kokubu 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Japan Broadcasting Corporation Research Institute of Broadcasting (72) Inventor Juzo Koura 1-10-11 Kinuta, Setagaya-ku, Tokyo No. Japan Broadcasting Corporation Broadcasting Research Institute (72) Inventor Toshihiro Yamamoto 1-10-11 Kinuta, Setagaya-ku, Tokyo Japan Broadcasting Corporation Broadcasting Research Institute (72) Inventor Mitsuhiro Kasahara 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric (72) Inventor Toshiro Nozoe 1006 Kazuma Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Akio Niwa 1-1, Sachimachi, Takatsuki-shi, Osaka Matsushita Electronics Co., Ltd. (72) Inventor Naoki Kosugi 1-1, Sachimachi, Takatsuki City, Osaka Prefecture Inside Matsushita Electronics Corporation (56) References JP-A-8-254965 (JP, ) Patent flat 7-175439 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) G09G 3/28 G09G 3/32 G09G 5/36 H04N 5/66

Claims (1)

(57) [Claims] 1. A halftone display method for displaying a plurality of subfields, which are a plurality of binary images, each of which is weighted by a time width or the number of pulses in one field of a moving image having a halftone. The sub-fields with approximately equal weight are assigned to the parts corresponding to the high-order bits of the halftone displayed by
A halftone display method for displaying a portion corresponding to the remaining lower bits as a binary image weighted according to a binary system.
The upper sub-fields in one field period
They are arranged continuously, and increase as the gradation increases.
The lit sub of multiple subfields
If a field exists, the above lit subfield
Of the upper sub-fields adjacent to the field
Wherein one of the subfields is newly lit.