KR100536248B1 - A plasma display panel, a luminance control device and method thereof - Google Patents

Abstract

The present invention relates to a plasma display panel, a brightness control apparatus and a control method thereof. In the present invention, the number of used tones is calculated by calculating a histogram for each line of the input image data, and when the number of used tones is equal to or less than a certain number, it is determined whether there is a flat portion in which lines having similar gray levels are continuous. Then, if the flat portion is present, the luminance step correction is performed by multiplying the video signal by the correction rate. In this way, the luminance step can be eliminated.

Description

A plasma display panel, a luminance control device and method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma display panel, and more particularly, to a plasma display panel for preventing a luminance step of a plasma panel, a luminance control device thereof, and a control method thereof.

Recently, flat display devices such as liquid crystal displays (LCDs), field emission displays (FEDs), and PDPs have been actively developed. Among these flat panel display devices, PDPs have advantages of higher luminance and luminous efficiency and wider viewing angles than other flat panel display devices. Therefore, the PDP is in the spotlight as a display device to replace the conventional cathode ray tube (CRT) in a large display device of 40 inches or more.

PDPs are flat display devices that display characters or images using plasma generated by gas discharge, and dozens to millions or more of pixels are arranged in a matrix according to their size. Such PDPs are classified into a direct current type (DC type) and an alternating current type (AC type) according to the shape of the driving voltage waveform applied and the structure of the discharge cell.

In the DC-type PDP, since the electrode is exposed to the discharge space as it is, the current flows in the discharge space while voltage is applied, and there is a disadvantage in that a resistance for current limitation must be made for this purpose. On the other hand, in the AC type PDP, the electrode covers the dielectric layer, so the current is limited by the formation of a natural capacitance component, and the electrode is protected from the impact of ions during discharge.

1 is a partial perspective view of an AC plasma display panel.

As shown in FIG. 1, the scan electrode 4 and the sustain electrode 5 covered with the dielectric layer 2 and the protective film 3 are arranged in parallel on the first substrate 1. A plurality of address electrodes 8 covered with the insulator layer 7 are provided on the second substrate 6. A partition 9 is formed on the insulator layer 7 between the address electrodes 8 in parallel with the address electrode 8. In addition, the phosphor 10 is formed on the surface of the insulator layer 7 and on both side surfaces of the partition wall 9. The first substrate 1 and the second substrate 6 may be arranged with the discharge space 11 therebetween so that the scan electrode 4 and the address electrode 8 and the sustain electrode 5 and the address electrode 8 are orthogonal to each other. It is arranged toward. The discharge space at the intersection of the address electrode 8 and the pair of the scanning electrode 4 and the sustain electrode 5 forms a discharge cell 12.

2 shows a three-electrode surface discharge structure of the plasma display panel.

Referring to FIG. 2, an address electrode is disposed to face the scan electrode and the sustain electrode which are formed in parallel in the discharge space formed by the partition wall. In this structure, a discharge is generated to generate wall charges to select a pixel between the address electrode and the scan electrode, and then a discharge for displaying an image between the scan electrode and the sustain electrode is repeated for a predetermined time.

In addition to forming a discharge space, the partition wall blocks light generated during discharge to prevent cross talk of neighboring pixels. A plurality of such unit structures are formed on a single substrate in a matrix form, and a fluorescent material is applied to each unit structure to form one pixel, and the pixels are gathered to form a plasma display panel. Plasma display panels, which are currently commercialized, generate a discharge in each pixel, and excite a fluorescent material coated on the inner wall of the pixel with ultraviolet rays generated by the discharge to realize a desired color.

In such a plasma display panel, the brightness varies depending on the load per line.

This characteristic causes luminance steps. The luminance step means a difference in brightness generated by a difference in load per line. An example of such luminance step is shown in FIG.

Referring to FIG. 3, when the background is white, that is, gradation 255, and there is a black rectangle in the middle, the luminance is brighter than the line where only white exists because the load is less on the line where the rectangle exists. Therefore, there is a problem that the white in the A area and the white in the B area appear to be different gray levels due to the luminance step phenomenon.

The technical problem to be solved by the present invention is to solve such a conventional problem, by analyzing the characteristics of the image to detect the luminance stepped line, and correcting the image data with a predetermined weight according to the load difference for each line to reduce the luminance step A plasma display panel and a control method thereof are provided.

The brightness control method of the plasma display panel according to an aspect of the present invention for achieving the above object,

A brightness control method of a plasma display panel including a plurality of address electrodes and a plurality of scan electrodes and sustain electrodes arranged in pairs with each other,

Calculating a number of gray levels used by calculating a histogram for each line of the input image data;

If the number of used gradations is less than or equal to a certain number, determining whether there is a flat portion where lines having similar gradations are continuously present;

If the flat portion is present, performing the luminance step correction.

An apparatus for controlling brightness of a plasma display panel according to another aspect of the present invention for achieving the above object,

In the brightness control apparatus of a plasma display panel comprising a plurality of address electrodes, a plurality of scan electrodes and a sustain electrode arranged in pairs with each other,

An inverse gamma correction unit configured to output an inverse gamma correction signal output from the outside;

A power control unit calculating a load ratio of the image signal output by the reverse gamma correction and outputting maintenance discharge information corresponding to the load ratio;

A luminance step detection unit for detecting a luminance step of the image signal output by inverse gamma correction;

A gray level correction unit for multiplying and outputting an image signal by a correction rate corresponding to a load difference when a luminance step is detected;

And a subfield data generator for generating and outputting image data output from the gray scale value corrector as subfield data.

According to another aspect of the present invention for achieving the above object,

A plasma display panel including a plurality of address electrodes, a plurality of scan electrodes, and a sustain electrode;

Detects the luminance step of the video signal, multiplies and corrects it by the correction rate corresponding to the load difference, generates and outputs the corrected video data as subfield data, measures the load ratio of the video signal, and corresponds to the measured load ratio. A controller for outputting sustain discharge pulse information;

An address electrode driver for applying a voltage corresponding to the subfield data output from the controller to the address electrode of the plasma panel;

And a sustain scan electrode driver for generating sustain pulses and scan pulses corresponding to the sustain discharge information from the controller, and applying the sustain pulses and scan pulses to the sustain electrodes and the scan electrodes, respectively.

Next, the present invention will be described with reference to the accompanying drawings so that the present invention may be easily implemented by those skilled in the art as follows.

4 is a configuration diagram of a plasma display panel according to an exemplary embodiment of the present invention.

Referring to FIG. 4, a plasma display panel according to an exemplary embodiment of the present invention includes a plasma display panel 100, a controller 300, an address electrode driver 200, and a sustain scan electrode driver 400.

The plasma display panel 100 includes a plurality of address electrodes and a plurality of scan electrodes and sustain electrodes arranged in pairs with each other. The controller 300 detects the luminance step of the image signal, multiplies the correction rate corresponding to the load difference, corrects the result, generates and outputs the corrected image data as subfield data, and measures and measures the load ratio of the image signal. The sustain discharge pulse information corresponding to the loaded load rate is output. The address electrode driver 200 applies a voltage corresponding to the subfield data output from the controller 300 to the address electrode of the plasma panel. The sustain scan electrode driver 400 generates sustain pulses and scan pulses corresponding to the sustain discharge information from the controller 300, and applies them to the sustain electrodes and the scan electrodes.

5 illustrates an internal configuration of the controller 300 of FIG. 4.

Referring to FIG. 5, the controller 300 includes a gray value corrector 310, an inverse gamma corrector 320, a subfield data generator 340, a power controller 330, and a luminance step detector 350. do. The inverse gamma correction unit 320 inversely gamma corrects and outputs an image signal input from the outside. The power control unit 330 calculates the load ratio of the image signal output by the reverse gamma correction and outputs the sustain discharge information corresponding to the load ratio. The luminance step detector 350 detects the luminance step of the image signal output by inverse gamma correction. When the luminance difference is detected, the inverse gamma correction unit 320 multiplies the image signal by a correction rate corresponding to the load difference, and outputs the multiplication rate. The subfield data generator 340 generates and outputs image data output from the gray scale value corrector as subfield data.

Next, the operation of the plasma display panel, the luminance control method thereof, and the apparatus according to the exemplary embodiment of the present invention having the above configuration will be described in detail.

First, an image signal including data components (R, G, B) and synchronization signals (Hsync, Vsync) is input from the outside.

Then, the inverse gamma correction unit 320 of the controller 300 outputs the inverse gamma correction.

Then, the power controller 330 measures the average signal level of the data components R, G, and B, and outputs sustain discharge information corresponding to the measured load factor to the sustain scan electrode driver 400.

Then, the sustain scan electrode driver 400 receives sustain discharge information and applies the sustain pulse and the scan pulse corresponding to the load ratio to the sustain electrode and the scan electrode.

Meanwhile, the luminance step detector 350 detects whether a luminance step occurs for each line. This will be described in detail with reference to FIG. 6.

Referring to FIG. 6, in the luminance step correction method of the present invention, the luminance step detection unit 350 calculates the histogram line by line in order to detect the luminance step by line as a line-by-line processing method (S601). Then, the luminance step detection unit 350 calculates the number of gray levels used for each line through the histogram calculation (S602).

Then, the luminance step detection unit 350 determines whether the number of gradations is equal to or less than the predetermined reference value Nth. At this time, the predetermined reference value is obtained by experiment as the number of gradations in which the luminance step appears.

In this case, since the luminance step is mainly noticeable in the area having a monotonous gray level, that is, the area having a small number of gray levels can be expected as an area in which the luminance step may occur, so that the luminance level detecting unit 350 calculates the gray level. Calculate the histogram separately. For example, if a histogram is created for the luminance step generation pattern in Fig. 3, the same result as in Fig. 7 can be obtained for the generation line. 7 is a result obtained by assuming that the number of horizontal pixels in the panel is 1024, and the sum of the number of pixels for all gray levels is 1024, which is the number of horizontal pixels.

When the histogram result of FIG. 7 is represented graphically, it is shown as FIG.

As a result of the histogram of Fig. 7, the number of gray levels of the line where the luminance step occurs in Fig. 3 becomes two. That is, since it has a small number of gray scales, it can be detected as the luminance step region in the example of FIG.

In the gray level determination part of FIG. 6, when the gray number is 1, it is determined as no correction (S604). Since all of the lines have the same gray level, the luminance step is not generated.

In the luminance step detection unit 350 according to the embodiment of the present invention, not only the histogram is used, but also the luminance step detection unit 350 determines whether there is a flat portion for each line (S605). If the flat portion exists (S606), the luminance step detection unit 350 performs luminance step correction. Here, the line-level flat portion refers to an area having a gray level that is partially similar to the previous line and the current line. If there is no flat portion of the continuous line, there is no problem because there is no area for recognizing the luminance step.

The calculation for determining the presence or absence of the flat part is calculated by the signal flow chart of FIG.

In FIG. 9, x denotes a position of a pixel in one line, PL (x) denotes a gray level of a pixel at an L line and an x position, and Td denotes a threshold value even for a reference that is a reference of a flat portion.

First, after initialization (S901), the position of the pixel is increased by one (S902), and even the system between lines is obtained (S903).

Then, even if the system at the same position for each line is less than or equal to Td, it is regarded as a flat pixel.

Then, the m value is increased by one (S905), and it is determined whether this m value is larger than the threshold value Mth (S906). If the m value representing the continuity of the flat pixel is larger than the reference threshold Mth, the corresponding line is determined to include the flat part (S907).

 If the m value is not greater than the reference threshold Mth, it is determined whether the position x value of the pixel is N (S909), and if it is not N, the process is repeated from step S902.

On the other hand, even if the system is more than Td, since it is not a flat pixel, m is set to 0 and then the next process (S909) is performed.

In other words, when a plurality of flat pixels are gathered for a predetermined number, the luminance step is likely.

When it is determined that the luminance stepped region is determined by the luminance step detecting process of FIG. 6, the grayscale value correcting unit 310 performs the correction. Since the luminance step is caused by the difference in load for each line, the gray value correcting unit 310 corrects the gray level according to the load difference. The load per line is calculated by the following equation.

That is, the average value of the gray level for each line was used as a load value. Finally, the difference in load value from the previous line is used as the input value for the gray value correction. The difference in load value is calculated by Equation 2.

When the load value difference is calculated by Equation 2, the gray level of the corresponding line is corrected according to the predetermined load differential correction rate. When the correction rate is determined, an output gray scale in which the luminance step is corrected is calculated by Equation 3 below. In the equation, r [] corresponds to the correction factor.

At this time, the load differential correction ratio r [] may be determined as shown in FIG. 10, for example.

10 is an example of determining a correction rate according to a load difference.

In FIG. 10, when the load difference is 0, since there is no luminance step, the correction rate is 1, and as the load difference increases, the luminance step increases, so that the correction rate for compensating for this also decreases.

The correction ratio according to the load difference can be corrected not only by the method as shown in FIG. 10, but also by using the LUT by separately determining each load difference value. It is also possible to use different values for the load differential correction ratio relationship by another factor. For example, it may have a different correction rate for each APC determined by the load of one frame.

The corrected image signal is input to the subfield data generation unit 340, and the subfield data generation unit 340 generates the image data output from the gray value correction unit 310 as subfield data to generate the address electrode driver. Output to (200).

Then, the address electrode driver 200 applies a voltage corresponding to the subfield data to the address electrode of the plasma panel.

By such a process, data having no luminance step is displayed on the plasma panel 100.

The present invention is not limited to the above embodiments, but may be modified and improved by those skilled in the art within the spirit and scope of the invention as defined in the claims.

As described above, in the embodiment of the present invention, in order to improve the luminance step caused by the difference in the load for each line, the characteristics of the image are analyzed for each line to detect the luminance step region, and the luminance step generation area for each line The luminance step can be compensated by compensating the gradation value by the correction rate according to the load difference, and the side effect caused by changing the image data is minimized in the area where the luminance step is not generated by detecting the luminance step by line. A plasma display panel, a luminance controller, and a control method thereof having an effect of correcting a luminance step with respect to a specific pattern in which the luminance step occurs can be provided.

1 is a partial perspective view of an AC plasma display panel.

2 shows a three-electrode surface discharge structure of the plasma display panel.

3 is a diagram showing an example of occurrence of luminance steps.

4 is a configuration diagram of a plasma display panel according to an exemplary embodiment of the present invention.

5 is a detailed view of the controller of FIG. 4.

6 is an operation flowchart for detecting the luminance step.

7 is a diagram showing a histogram result.

8 is a graph of line-by-line histograms.

9 is an operation flow chart for determining the presence or absence of flat parts for each line.

10 is a diagram illustrating a correction rate according to a load difference.

Claims (16)

In the brightness control apparatus of a plasma display panel comprising a plurality of address electrodes, a plurality of scan electrodes and a sustain electrode arranged in pairs with each other, An inverse gamma correction unit configured to output an inverse gamma correction signal output from the outside; A power control unit calculating a load ratio of the image signal output by the reverse gamma correction and outputting maintenance discharge information corresponding to the load ratio; A luminance step detection unit for detecting a luminance step of the image signal output by inverse gamma correction; A gray level correction unit for multiplying and outputting an image signal by a correction rate corresponding to a load difference when a luminance step is detected; And a subfield data generation unit configured to generate and output image data output from the gray scale value correction unit as subfield data. The method of claim 1, And the luminance step detection unit calculates the number of usage grays by calculating a histogram for each line, and corrects the luminance step if the usage gray number is equal to or less than a reference value and the flat portion exists. The method of claim 2, And the luminance step detection unit does not correct the luminance step when the number of used gradations is one. The method of claim 2, The luminance step detection unit And the line-based system is equal to or less than the first reference value, and the case is determined as the flat part when the second reference value is continued. The method of claim 2, The gray value correction unit, And if the load difference for each line is 0, the correction rate is set to 1, and the correction rate decreases as the load difference increases. A plasma display panel including a plurality of address electrodes, a plurality of scan electrodes, and a sustain electrode; Detects the luminance step of the video signal, multiplies and corrects it by the correction rate corresponding to the load difference, generates and outputs the corrected video data as subfield data, measures the load ratio of the video signal, and corresponds to the measured load ratio. A controller for outputting sustain discharge pulse information; An address electrode driver for applying a voltage corresponding to the subfield data output from the controller to the address electrode of the plasma panel; And a sustain scan electrode driver for generating sustain pulses and scan pulses corresponding to sustain discharge information from the controller, and applying the sustain pulses and scan pulses to the sustain electrodes and the scan electrodes, respectively. The method of claim 6, The control unit, An inverse gamma correction unit configured to output the inverse gamma correction to the video signal; A power control unit calculating a load ratio of the image signal output by the reverse gamma correction and outputting maintenance discharge information corresponding to the load ratio; A luminance step detection unit for detecting a luminance step of the image signal output by inverse gamma correction; A gray level correction unit for multiplying and outputting an image signal by a correction rate corresponding to a load difference when a luminance step is detected; And a subfield data generation unit configured to generate and output image data output from the gray level correction unit as subfield data. The method of claim 7, wherein And the luminance step detection unit calculates the number of usage grays by calculating a histogram for each line, and corrects the luminance step if the usage gray number is equal to or less than a reference value and the flat portion exists. The method of claim 8, And the luminance step detection unit does not perform luminance step correction when the number of used gradations is one. The method of claim 8, The luminance step detection unit And the line-based system is determined as a flat part when even the line-based system is less than or equal to the first reference value, and such a case is continuous beyond the second reference value. The method of claim 7, wherein The gray value correction unit, And if the load difference per line is 0, the correction rate is set to 1, and as the load difference increases, the correction rate decreases. A brightness control method of a plasma display panel including a plurality of address electrodes and a plurality of scan electrodes and sustain electrodes arranged in pairs with each other, Calculating a number of gray levels used by calculating a histogram for each line of the input image data; A second step of determining whether there is a flat part in which lines having similar gray levels are continuous, when the number of used gray numbers is equal to or less than a predetermined number; And performing a luminance step correction by multiplying an image signal by a correction rate when the flat portion is present. The method of claim 12, And in the second step, the luminance level correction is performed when the number of used gradations is less than or equal to the reference value and the flat portion is present. The method of claim 13, In the second step, the luminance step correction is not performed when the number of used gradations is one. The method of claim 14, And the second step is determined as a flat part when even the line-based system is less than or equal to the first reference value, and such a case is continuous more than or equal to the second reference value. The method of claim 12, The third step, And if the load difference per line is 0, the correction rate is set to 1, and as the load difference increases, the correction rate decreases.