KR20030087692A - Method For Enlarging Dynamic Range Of Plasma Display Panel And Apparatus Of Driving Using Thereof - Google Patents

Abstract

PURPOSE: A method for enlarging the dynamic range of a plasma display panel and a driving device by using the same are provided to display a clear motion picture by improving the contrast of the motion picture input image with enlarging the dynamic range of the motion picture input image. CONSTITUTION: A method for enlarging the dynamic range of a plasma display panel includes the steps of: detecting each gray level for a motion picture input image; detecting a histogram distribution ratio as to the distribution number of the detected gray level; determining lower and upper gray levels of a minimum distribution by using the histogram distribution ratio; and enlarging the dynamic range of the input image by applying the minimum distribution lower and upper gray levels.

Description

Method for Enlarging Dynamic Range of Plasma Display Panel and Driving Device Using Method {Method For Enlarging Dynamic Range Of Plasma Display Panel And Apparatus Of Driving Using Thereof}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma display panel, and more particularly, to a method for expanding a dynamic range of a plasma display panel and a driving apparatus using the same, which can obtain a clear image by enlarging a dynamic range when displaying a moving image to improve contrast of a display screen. .

Plasma Display Panel (hereinafter referred to as "PDP") is a display device using visible light generated from a phosphor when ultraviolet light generated by gas discharge excites the phosphor. PDP is thinner and lighter than Cathode Ray Tube (CRT), which has been the mainstay of display means, and has the advantage of realizing high definition / large screen.

The PDP has an upper substrate and a lower substrate which are installed to face each other with partition walls therebetween. The upper substrate includes a scan electrode and a sustain electrode formed in a direction crossing the partition wall. The lower substrate includes an address electrode formed in a direction parallel to the partition wall, and a dielectric layer formed to cover the address electrode. The discharge cell is positioned at the intersection of the scan electrode, the sustain electrode and the address electrode.

The PDP is driven by dividing one frame into several subfields having different emission counts in order to realize gray levels of an image. Each subfield is divided into a reset period for uniformly causing discharge, an address period for selecting a discharge cell, and a sustain period for implementing gray scale according to the number of discharges.

In the address period, scan pulses are supplied to the scan electrodes, and data pulses synchronized with the scan pulses are supplied to the address electrodes. At this time, an address discharge occurs in the discharge cell supplied with the scan pulse and the data pulse. After the scan pulses are supplied to all the scan electrodes, the sustain pulses are alternately supplied to the scan electrodes and the sustain electrodes. When a sustain pulse is supplied to the scan electrode and the sustain electrode, sustain discharge occurs in the discharge cells in which the address discharge has occurred.

When the image is to be displayed in 256 gray levels, the frame period (16.67 ms) corresponding to 1/60 second is divided into eight subfields. Here, the reset period and the address period of each subfield are the same for each subfield, while the sustain period and the number of discharges thereof are 2 ⁿ (n = 0,1,2,3,4,5,6,7) in each subfield. , 8). As described above, since the sustain period is changed in each subfield, gray levels of an image can be realized.

1 is a block diagram showing a driving apparatus of a PDP according to the prior art.

Referring to FIG. 1, a driving apparatus of a PDP according to the related art includes a frame memory 4 and a PDP driving unit 6.

The frame memory 4 stores data from the input line 2 in units of frames and supplies the data to the PDP driver 6.

The PDP driver 6 corrects the digital signal input from the frame memory 4 and supplies it to the panel. To this end, the PDP driver 6 includes a first inverse gamma correction unit 12A, a gain control unit 14, an error diffusion unit 16, a subfield mapping unit 18, and a data alignment unit 20 as shown in FIG. And a second inverse gamma correction unit 12B, an average picture level (APL) unit 24, a waveform generator 26, and a panel 28.

The first and second inverse gamma correction units 12A and 12B inversely gamma correct the gamma corrected video signal (digital signal) to linearly convert luminance values according to grayscale values of the image signal.

The APL unit 24 receives the video data corrected by the second inverse gamma correction unit 12B and generates an N-stage signal for adjusting the number of sustain pulses. The gain control unit 14 amplifies the video signal corrected by the first inverse gamma correction unit 12A by the effective gain.

The error diffusion unit 16 finely adjusts the luminance value by diffusing an error component of a cell into adjacent cells. The subfield mapping unit 18 reallocates the video data corrected by the error diffusion unit 16 for each subfield.

The data aligner 20 aligns the video signal to be supplied to the panel 28 and supplies the video signal to an address driving integrated circuit (IC) not shown.

The waveform generator 26 generates a timing control signal based on the N-stage signal input from the APL unit 24, and converts the generated timing control signal into an address driving IC, a scan driving IC, and a sustain driving IC of the panel 28. Supply.

In detail, the second inverse gamma correction unit 12B first performs inverse gamma correction on the gamma gamma corrected video signal and supplies the inverse gamma correction unit to the APL unit 24. The APL unit 24 that receives the inverse gamma corrected video signal generates an N-stage signal for adjusting the number of sustain pulses and supplies it to the waveform generator 26. The waveform generator 26 generates a timing control signal using the N-stage signal input from the APL unit 24, and supplies the generated control signal to the address driving IC, the scan driving IC, and the sustain driving IC.

The first inverse gamma correction unit 12A performs inverse gamma correction on the gamma corrected video signal and supplies it to the gain control unit 14. The gain control unit 14 receiving the inverse gamma corrected video signal amplifies the corrected video signal by an effective gain and supplies it to the error diffusion unit 16. The error diffusion unit 16 finely adjusts the luminance value by error diffusion of the video signal input from the gain control unit 14. The video signal output from the error diffusion unit 16 is input to the subfield mapping unit 18. The subfield mapping unit 18 recycles the error-diffused video data for each subfield and supplies it to the data alignment unit 20. The data aligning unit 20 aligns the video signal and supplies it to the address driver IC.

Thereafter, the image corresponding to the video signal is displayed on the panel 28 by the control of the address driving IC, the scan driving IC, the sustain driving IC, and the like. As described above, the conventional PDP driving apparatus shown in FIGS. 1 and 2 displays a predetermined image corresponding to an analog signal input from the outside. In a conventional PDP driving apparatus, a distribution of gray levels of a data signal input from the outside is obtained. However, in the PDP driving apparatus of the related art, when the lower gray level value MIN having a small distribution and the upper gray level value MAX having a small distribution for each gray distribution are obtained, MIN = 0 and MAX = 255.

In this case, the dynamic range cannot be expanded in response to data changes input from the outside. Here, the dynamic range refers to a range of the minimum gray level value and the maximum gray level value for the input data, that is, the range in which the gray level of the input data is converted. If the dynamic range cannot be expanded, the input data proceeds to the output signal as it is, so that a complete display image cannot be displayed.

Accordingly, an object of the present invention is to expand the dynamic range of input data using a histogram, which is the number of distributions for gray levels, to improve the contrast of a display image, and a driving apparatus using the same. To provide.

1 is a block diagram illustrating a driving apparatus of a plasma display panel according to the related art.

FIG. 2 is a block diagram illustrating in detail the PDP driver shown in FIG. 1.

3 is a block diagram showing an apparatus for driving a PDP according to an embodiment of the present invention.

4 is a block diagram illustrating in detail the PDP driver illustrated in FIG. 3.

FIG. 5 is a flowchart for explaining the dynamic range expansion method described with reference to FIG. 3.

6 is a diagram showing a histogram distribution change with respect to a gray level according to the present invention.

7A and 7B are diagrams illustrating changes of a display image according to the conventional and exemplary embodiments of the present invention.

FIG. 8 is a diagram for comparing only a part of the display image illustrated in FIG. 7B.

9A and 9B illustrate changes in histogram distribution after dynamic range expansion according to an embodiment of the present invention.

10A to 11B are views illustrating a change of a display image of a portion of FIG. 8.

<Description of Symbols for Main Parts of Drawings>

4,34: frame memory 6,38: gamma correction

8,40: PDP driver 12,52: reverse gamma correction unit

14,54: gain control unit 16,56: error diffusion unit

18,58: subfield mapping unit 20,60: data alignment unit

24, 64 APL section 26, 66 waveform generation section

28, 68: Panel 36: Dynamic range adjustment unit

42: histogram distribution detection unit of gray level

44: minimum distribution gray level value determination unit

In order to achieve the above object, the dynamic range expansion method of the PDP according to the present invention comprises the steps of detecting each gray level of the moving image input image, detecting the histogram distribution ratio which is the number of distribution of the detected gray level, Determining a minimum distribution lower and upper gray level using the histogram distribution ratio, and expanding the dynamic range of the input image by applying the minimum distribution lower and upper gray level values.

The detecting of the histogram distribution ratio in the present invention may include determining the histogram number of each gray level, and dividing the histogram number by the resolution of the input image as a percentage.

Determining the minimum and lower gray level of the minimum distribution in the present invention includes setting a threshold for the histogram distribution ratio, and setting the first gray level that is higher than or equal to the threshold to be the minimum and lower gray level. It is characterized by including.

The step of enlarging the dynamic range of the input image according to the present invention may include determining a gray level of the image data input from the outside, and correcting the image using the gray level, minimum distribution lower and upper gray levels of the input image data. Determining a gray level of the data.

In the present invention, the gray level of the corrected image data is obtained by subtracting the gray level of the pre-corrected image data by subtracting the minimum distributed lower gray level by the difference between the minimum distributed upper gray level and the minimum distributed lower gray level, and multiplying the maximum gray level. Characterized in that it is determined.

An apparatus for driving a plasma display panel using a dynamic range expansion method according to an embodiment of the present invention includes a frame memory for storing moving image data input from the outside in units of frames, and a frame memory connected in parallel with the frame memory. A histogram detector of a lower gray level for detecting a histogram distribution ratio that is a number of distribution of lower gray levels after detecting each gray level of the video data during a frame; After detecting each gray level, the histogram detector of the upper gray level detects the histogram distribution ratio which is the number of distribution of the upper gray levels, and the histogram detector of the lower gray level in series to determine the lowest distributed lower gray level. A distributed lower gray level determination unit, a minimum distributed upper gray level determination unit connected in series with the histogram detection unit of the upper gray level to determine a minimum distributed upper gray level, and the frame memory, the minimum distributed lower and upper gray level determination units A dynamic range adjusting unit connected to the dynamic range adjusting unit to generate correction data in which a dynamic range is enlarged using data input from the frame memory and the minimum distribution lower and upper gray level values, and the dynamic range adjusting unit connected to the dynamic range adjusting unit. And a plasma display panel driver which controls the enlarged corrected image data signal and supplies the same to the panel.

In the present invention, the plasma display panel driver includes an inverse gamma correction unit that inversely gamma corrects a video signal via the dynamic range adjustment unit and linearly converts luminance values according to grayscale values of an image signal, and the inverse gamma correction unit. A gain control unit for amplifying the corrected video signal by effective gain, an error diffusion unit for finely adjusting the luminance value by diffusing an error component of the cell into adjacent cells, and the video data corrected from the error diffusion unit for each subfield. And a data alignment unit for aligning the video signal to be supplied to the display panel.

Other objects and features of the present invention in addition to the above object will become apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 3 to 11B.

3 is a block diagram showing an apparatus for driving a PDP according to an embodiment of the present invention.

Referring to FIG. 3, the driving apparatus of the PDP according to the embodiment of the present invention includes a frame memory 34, lower and upper gray level histogram detectors 42A and 42B, minimum distribution lower and upper gray level value determiners 44A, and 44B), the dynamic range adjusting unit 36 and the PDP driving unit 38 are provided.

The frame memory 34 stores data from the input line 32 in one frame unit and supplies the data to the dynamic range adjusting unit 36.

The histogram detectors 42A and 42B of the lower and upper gray levels detect the histograms of the lower and upper gray levels for each gray level on the basis of the data from the input line 32 by one frame. This first obtains the overall distribution of each gray level for the input screen of one frame. The histogram H (I), which is a gray level distribution value of the input data, is detected based on the overall distribution. At this time, histograms are mainly detected at gray levels, such as about 0 to 20 gray and 220 to 255, to determine minimum and maximum gray levels (MIN and MAX).

The minimum distribution lower and upper gray level value determination units 44A and 44B determine a reference ratio arbitrarily set and determine lower and upper gray levels (MIN, MAX) having less gray level distribution through histograms of the detected lower and upper gray levels. do.

The dynamic range adjusting unit 36 enlarges the dynamic range of the input data by using the data input from the frame memory 34, the minimum distribution lower and upper gray level values. The dynamic range adjuster 36 supplies input data having an enlarged dynamic range to the PDP driver 38.

The PDP driver 38 corrects the digital signal input from the dynamic range adjuster 36 and supplies it to the panel. To this end, the PDP driver 38 includes a first inverse gamma correction unit 52A, a gain control unit 54, an error diffusion unit 56, a subfield mapping unit 58, and a data alignment unit 60 as shown in FIG. And a second inverse gamma correction unit 52B, an average picture value (APL) unit 64, a waveform generator 66, and a panel 68.

The first and second inverse gamma correction units 52A and 52B linearly convert the luminance value according to the gray value of the image signal by performing inverse gamma correction on the video data having an extended dynamic range.

The APL unit 64 receives the video data corrected by the second inverse gamma correction unit 52B and generates an N-stage signal for adjusting the number of sustain pulses. The gain controller 54 amplifies the video signal corrected by the first inverse gamma correction unit 52A by the effective gain.

The error diffusion unit 56 finely adjusts the luminance value by diffusing an error component of a cell into adjacent cells. The subfield mapping unit 58 reallocates the video data corrected by the error diffusion unit 56 for each subfield.

The data aligning unit 60 aligns the video signal to be supplied to the panel 68 and supplies the video signal to an address driver integrated circuit (IC) not shown.

The waveform generator 66 generates a timing control signal based on the N-stage signal input from the APL unit 64, and converts the generated timing control signal into an address driving IC, a scan driving IC, and a sustain driving IC of the panel 68. Supply.

In detail, the second inverse gamma correction unit 52B first performs inverse gamma correction on the video signal input from the dynamic range adjustment unit 36 and supplies the inverse gamma correction unit to the APL unit 64. The APL unit 64 receiving the inverse gamma corrected video signal generates an N-stage signal for adjusting the number of sustain pulses, and supplies it to the waveform generator 66. The waveform generator 66 generates a timing control signal using the N-stage signal input from the APL unit 64, and supplies the generated control signal to the address driving IC, the scan driving IC, and the sustain driving IC.

The first inverse gamma correction unit 52A performs inverse gamma correction on the video signal input from the dynamic range adjustment unit 36 and supplies it to the gain control unit 54. The gain control unit 54 receiving the inverse gamma corrected video signal amplifies the corrected video signal by the effective gain and supplies it to the error diffusion unit 56. The error diffusion unit 56 finely adjusts the luminance value by error diffusion of the video signal input from the gain control unit 54. The video signal output from the error diffusion unit 56 is input to the subfield mapping unit 58. The subfield mapping unit 58 reallocates the error-diffused video data for each subfield and supplies the data to the data alignment unit 60. The data alignment unit 60 aligns the video signal and supplies it to the address driver IC.

Thereafter, the image corresponding to the video signal is displayed on the panel 68 by the control of the address driving IC, the scan driving IC, the sustain driving IC, and the like. In the driving apparatus of the PDP according to the embodiment of the present invention according to the above configuration, a clear image can be obtained by improving contrast through an enlarged dynamic range.

FIG. 5 is a flowchart illustrating the dynamic range expansion method described with reference to FIG. 3.

Referring to FIG. 5, first, input data RGB from the outside is input to the lower and upper gray level histogram detectors 42A and 42B.

The histogram H (I) of each gray level is detected (S12). This first obtains an overall distribution of gray levels for an input screen of one frame. Based on the overall gray level distribution, the ratio of the histogram, which is the number of distributions of 0 to 255 gray levels, can be known. For example, in a PDP with WVGA (853 * 480) resolution mode, if the number of histograms with 2 grays is 245, the distribution ratio is Becomes When the distribution ratio of each gray level is obtained, the histogram ratio with respect to the input data appears as shown in Tables 1 and 2.

Histogram % Of distribution Hist [0] 0.02 Hist [1] 0.04 Hist [2] 0.06 Hist [3] 0.0 … … Hist [17] 0.03 Hist [18] 0.09 Hist [19] 0.1 Hist [20] One

Histogram % Of distribution Hist [220] 1.0 Hist [221] 0.1 Hist [222] 0.06 Hist [223] 0.001 … … Hist [252] 0.03 Hist [253] 0.02 Hist [254] 0.09 Hist [255] 0.05

Here, the histogram distribution ratio (%) for each gray level may vary depending on the input data for one frame.

Based on the histogram distribution ratio (%), the minimum distribution lower and upper gray levels (MIN, MAX) are determined. (S14) First, before determining the minimum distribution lower and upper gray level values, the threshold value of the histogram distribution ratio (%) is determined. Decide In Figure 5, 0.1% was set as the threshold. This sets the first gray level with 0.1% or more as the minimum distributed lower gray level (MIN) and the minimum distributed upper gray level (MAX). (S18) When the distribution ratio is 0.1% or less, the next histogram distribution ratio is continuously searched. (S16)

Thus, in the case of Table 1 and Table 2, the gray level is determined as the minimum distributed lower gray level MIN is 19 and the minimum distributed upper gray level MAX is 221.

The values of the minimum distribution lower and upper gray levels (MIN, MAX) determined as described above are input to the dynamic range determination unit 36. The dynamic range determiner 36 rearranges the input image by using Equation 1 with the input minimum distribution lower and upper gray levels MIN and MAX.

Where X is the gray level of the input data before correction and Y is the gray level of the input data after correction. In addition, MAX is the value of the minimum distributed upper gray level, and MIN is the value of the minimum distributed lower gray level.

When X is 40, the minimum distribution lower and upper gray level values determined through Table 1 and Table 2 are applied to Equation 1. By Y, the minimum gray level value after correction for X becomes 26.5. This changes the input data of 40 to a lower value of 26.5. That is, in the present invention, as shown in FIG. 6, the histogram distribution I according to the gray level in the dotted line form may be obtained as the histogram distribution II according to the gray level in the solid line form in which the dynamic range is expanded. As a result, as the dynamic range is enlarged, the contrast of the screen is improved to obtain a clear screen. In other words, the bright part is displayed brighter and the dark part is displayed darker so that the contrast between the bright part and the dark part of the screen can be clearly displayed.

7A and 7B illustrate changes in the display image according to the conventional and exemplary embodiments of the present invention. As the contrast between the bright and the dark of the screen becomes clear, the display image of which the dynamic range is enlarged by the present invention shown in FIG. 7B is enlarged. It can be seen that this is clearer than FIG. 7A.

FIG. 8 is a view for designating a predetermined area for comparing only a part of the display image shown in FIG. 7B, and FIGS. 9A and 9B are views showing a change in histogram distribution after a dynamic range enlargement process according to an embodiment of the present invention. 10A through 11B are diagrams illustrating a change of a display image with respect to a portion of FIG. 8.

9A and 9B, the distribution of the histogram according to the embodiment of the present invention of FIG. 9B is lower than the distribution of the histogram according to the prior art of FIG. 9A by expanding the dynamic range according to the minimum distribution lower and upper gray level values. You can see that it has moved towards the gray level. As a result, as described above, the darker portions become darker and the brighter portions appear brighter.

Referring to the results of FIGS. 9A and 9B through FIGS. 10A through 11B, first, FIGS. 10A and 10B compare the area A of FIG. 8, and it can be seen that the dark part of the sky becomes darker. Next, FIGS. 11A and 11B compare the area B of FIG. 8 and show a display screen in which a bright part and a dark part coexist. In this case as well, the contrast between the bright and dark areas can be seen that the contrast is improved.

As described above, the dynamic range expansion method of the PDP according to the present invention and the driving apparatus using the same detect the minimum distribution lower and upper gray levels by the histogram distribution ratio with respect to the gray level of the moving image input image. Accordingly, the dynamic range enlargement method of the PDP and the driving apparatus using the same increase the dynamic range of the moving image input image, thereby improving the contrast of the moving image input image and displaying a clear moving image.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (8)

Detecting each gray level of a moving image input image; Detecting a histogram distribution ratio that is a distribution number of the detected gray levels; Determining a minimum distribution lower and upper gray level using the histogram distribution ratio; And enlarging the dynamic range of the input image by applying the minimum distribution lower and upper gray level values. The method of claim 1, The detecting of the histogram distribution ratio may include determining a histogram number of each gray level; And dividing the number of histograms by the resolution of the input image to express the percentage as a percentage. The method of claim 1, Determining the minimum and lower gray level distributions includes setting a threshold for the histogram distribution ratio; And setting the first gray level coming out above the threshold to a minimum distribution lower and upper gray level. The method of claim 1, The step of enlarging the dynamic range of the input image may include determining a gray level of image data input from the outside; And determining the gray level of the image data corrected using the gray level, the minimum distribution lower and upper gray level of the input image data. The method of claim 4, wherein The gray level of the corrected image data is determined by multiplying the maximum gray level after dividing a value obtained by subtracting the minimum distributed lower gray level from the gray level of the pre-corrected image data by the difference between the minimum distributed upper gray level and the minimum distributed lower gray level. A method of expanding the dynamic range of a plasma display panel. A frame memory for storing video data input from the outside in units of frames, A lower gray level histogram detector connected to the frame memory in parallel and detecting each gray level of video data during one frame input from the outside, and detecting a histogram distribution ratio that is a distribution number of lower gray levels; A histogram detection unit of a higher gray level connected in parallel with the frame memory to detect each gray level of video data during one frame input from the outside, and then detect a histogram distribution ratio that is a distribution number of a higher gray level; A minimum distributed lower gray level determination unit connected in series to the histogram detection unit of the lower gray level to determine a minimum distributed lower gray level; A minimum distributed upper gray level determination unit connected in series with the histogram detection unit of the upper gray level to determine a minimum distributed upper gray level; A dynamic range connected to the frame memory, the minimum distribution lower and upper gray level determination units, respectively, to generate correction data having an extended dynamic range using data input from the frame memory and the minimum distribution lower and upper gray level values. With the adjustment unit, And a plasma display panel driver connected to the dynamic range adjusting unit for controlling and supplying a corrected image data signal having an enlarged dynamic range to a panel. The method of claim 6, The plasma display panel driver includes an inverse gamma correction unit that linearly converts a luminance value according to a gray value of an image signal by performing an inverse gamma correction on the video signal via the dynamic range adjusting unit; A gain controller for amplifying the video signal corrected by the inverse gamma correction unit by an effective gain; An error diffusion unit for finely adjusting the luminance value by diffusing an error component of the cell into adjacent cells; A subfield mapping unit for reallocating the video data corrected by the error diffusion unit for each subfield; And a data alignment unit for aligning the video signal to be supplied to the display panel. The method of claim 7, wherein An average image value (APL) unit receiving the video data corrected by the inverse gamma correction unit and generating an N-stage signal for adjusting the number of sustain pulses; And a waveform generator for generating a timing control signal based on the N-stage signal input from the average image value unit and supplying the generated timing control signal to a driving integrated circuit of the display panel. An apparatus for driving a plasma display panel using the same.