Signal processing method, signal processor, and display device including signal processor

A method of signal-processing input image data of a display device including a plurality of pixels, each pixel including a green subpixel and one of a red subpixel and a blue subpixel, the method includes: performing a gamma-conversion on input image data corresponding to the one of the red subpixel and the blue subpixel in each pixel; distributing the gamma-converted input image data corresponding to a center pixel to image data of a pixel in a vertical direction based on the center pixel by a first ratio; and distributing the gamma-converted input image data corresponding to the center pixel to image data of a pixel in a horizontal direction based on the center pixel by a second ratio, where the green subpixel and the one of the red subpixel and the blue subpixel are diagonally disposed in each pixel.

This application claims priority to Korean Patent Application No. 10-2013-0083015, filed on Jul. 15, 2013, and all the benefits accruing therefrom under 35 U.S.C. §119, the content of which in its entirety is herein incorporated by reference.

BACKGROUND

Exemplary embodiments of the invention relate to a signal processing method, a signal processor, and a display device including the signal processor. More particularly, the exemplary embodiments relate to a display device having a pentile structure, and a signal processing method and a signal processor of the display device having the pentile structure.

(b) Description of the Related Art

A pixel of a conventional display device typically includes red, green and blue subpixels. In general, the pixel of the conventional display device has a stripe structure where red, green and blue subpixels are vertically arranged in a unit pixel area.

Alternatively, the pixel may have a pentile structure, where only some of red, green and blue subpixels are provided in the unit pixel area, or some of red, green and blue subpixels are provided only in a predetermined region of the unit pixel area.

Since the number of subpixels per unit pixel or an area of the subpixels per unit pixel is small in the pentile structure, pixel performance per unit area of the pentile structure may be lower than pixel performance per unit area of the stripe structure.

SUMMARY

Exemplary embodiments provide a signal processing method, a signal processor for processing a signal, and a display device having a pentile structure and including the signal processor.

An exemplary embodiment provides a method of processing input image data of a display device including a plurality of pixels, each including a green subpixel and one of a red subpixel and a blue subpixel, the method including: performing a gamma-conversion on input image data corresponding to the one of the red subpixel and the blue subpixel in each pixel; distributing the gamma-converted input image data corresponding to a center pixel to image data of a pixel in a vertical direction based on the center pixel by a first ratio; and distributing the gamma-converted input image data corresponding to the center pixel to image data of a pixel in a horizontal direction based on the center pixel by a second ratio, where the green subpixel and the one of the red subpixel and the blue subpixel are diagonally disposed in each pixel.

In an exemplary embodiment, the method may further include distributing the gamma-converted input image data corresponding to the center pixel to image data of the center pixel by a third ratio.

In an exemplary embodiment, the method may further include: distributing the gamma-converted input image data corresponding to another pixel in the vertical direction based on the center pixel to the image data of the center pixel by the first ratio; and distributing the gamma-converted input image data corresponding to another pixel in the horizontal direction based on the center pixel to the image data of the center pixel by the second ratio.

In an exemplary embodiment, the method may further include performing an inverse-gamma conversion on the image data of the center pixel.

In an exemplary embodiment, the signal processing method may further include summing input image data of the green subpixel of the center pixel and the inverse-gamma-converted image data of the center pixel to output an output image data of the center pixel.

Another exemplary embodiment provides a signal processor for processing input image data of a display device including a plurality of pixels, each including a green subpixel and one of a red subpixel and a blue subpixel, the signal processor including: an input gamma unit which performs a gamma-conversion on input image data corresponding to the one of the red subpixel and the blue subpixel in each pixel; a subpixel rendering unit which distributes the gamma-converted input image data corresponding to a center pixel to image data corresponding to a pixel in the vertical direction based on the center pixel by a first ratio, and distributes the gamma-converted input image data corresponding to the center pixel to image data of a pixel in the horizontal direction based on the center pixel by a second ratio, where the green subpixel and the one of the red subpixel and the blue subpixel are diagonally disposed in each pixel.

In an exemplary embodiment, the subpixel rendering unit may distribute the gamma-converted input image data corresponding to the center pixel to image data of the center pixel by a third ratio.

In an exemplary embodiment, the subpixel rendering unit may distribute the gamma-converted input image data corresponding to another pixel in the vertical direction in image data based on the center pixel to the image data of the center pixel by the first ratio, and distributes the gamma-converted input image data corresponding to another pixel in the horizontal direction based on the center pixel to the image data of the center pixel by the second ratio to generate the image data of the center pixel.

In an exemplary embodiment, the signal processor may further include an output gamma unit which performs an inverse gamma-conversion on the image data of the center pixel.

In an exemplary embodiment, the signal processor may further include an output interface which sums input image data of the green subpixel and the inverse-gamma-converted image data of the center pixel to output an output image data of the center pixel.

Another exemplary embodiment provides a display device including: a plurality of pixels, each pixel including a green subpixel and one of a red subpixel and a blue subpixel, where the green subpixel and the one of the red subpixel and the blue subpixel are diagonally disposed in each pixel; and a signal processor which performs a gamma-conversion on input image data corresponding to the one of the red subpixel and the blue subpixel in each pixel, distributes the gamma-converted input image data corresponding to a center pixel to image data corresponding to a pixel in a vertical direction based on the center pixel by a first ratio, and distributes the gamma-converted input image data corresponding to the center pixel to image data of a pixel in a horizontal direction based on the center pixel by a second ratio.

In an exemplary embodiment, the signal processor may distribute the gamma-converted input image data corresponding to the center pixel to image data of the center pixel by a third ratio.

In an exemplary embodiment, the signal processor may distribute the gamma-converted input image data corresponding to another pixel in the vertical direction in image data based on the center pixel to the image data of the center pixel by the first ratio, and distributes the gamma-converted input image data corresponding to another pixel in the horizontal direction based on the center pixel to the image data of the center pixel by the second ratio to generate the image data of the center pixel.

In an exemplary embodiment, the signal processor may include an output gamma unit which performs an inverse gamma-conversion on the image data of the center pixel.

In an exemplary embodiment, the signal processor may further include an output interface which sums input image data of the green subpixel and the inverse-gamma-converted image data of the center pixel to output an output image data of the center pixel.

In an exemplary embodiment, a sum of the first ratio, the second ratio, and the third ratio may be one.

Exemplary embodiments of the invention provide the signal processor of a display device having a pentile structure, the method of processing input image data of the display device, and the display device including the signal processor.

DETAILED DESCRIPTION

Embodiments of the invention are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the invention should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the claims set forth herein.

Hereinafter, exemplary embodiments of the invention will be described in further detail with reference to accompanying drawings.

FIG. 1is a diagram illustrating pixels including a plurality of subpixels having a pentile structure, which are disposed in a vertical-horizontal direction.

FIG. 2is a diagram illustrating pixels in an S-pentile structure.

FIG. 1andFIG. 2illustrate some of a plurality of pixels of an exemplary embodiment of a display device.

In the drawings, a red subpixel is expressed as an oblique line “/”, a green subpixel is expressed as a horizontal line “—”, and a blue subpixel is expressed as an oblique line “\”.

In the pixels including red, green and blue subpixels arranged the S-pentile structure, the red subpixel and the green subpixel are disposed in a diagonal direction in a pixel area, and the blue subpixel and the green subpixel are disposed in the diagonal direction in the pixel area.

As shown inFIG. 1, in the pixels having a pentile structure in vertical-horizontal directions, one of a first pixel11including a red subpixel and a green subpixel and a second pixel12including a blue subpixel and a green subpixel is disposed in a pixel area.

In an exemplary embodiment, as shown inFIG. 1, a plurality of first pixels and a plurality of second pixels12are alternately arranged in vertical-horizontal directions in a region which 4×4 pixels PX are arranged.

In an alternative exemplary embodiment, the pixels may have the S-pentile structure as shown inFIG. 2. In such an embodiment, a first pixel13including a red subpixel and a green subpixel disposed in a diagonal direction and a second pixel14including a blue subpixel and a green subpixel disposed in the diagonal direction are alternately arranged in the horizontal-vertical directions.

Since pixels in the pentile structure shown inFIG. 1andFIG. 2has a lesser number of sub-pixels in a pixel area than pixels in the stripe structure, a subpixel rendering (“SPR”) scheme may be applied to an exemplary embodiment of the display device having the pentile structure for a data processing thereof. In such an embodiment, pixel expression is reduced according to the reduced number of pixels. In such an embodiment, a rendering scheme for sharing image data between adjacent pixels is applied to a display device having the pentile structure as the SPR scheme to compensate the reduced pixel expression.

In such an embodiment, the SPR scheme may use various types of filters. In one exemplary embodiment, for example, the filters include a D filter, a DS filter and an HB filter.

The D filter uses a basic scheme which applies the greatest center weight value to image data of a center pixel in a 3×3 mask, and distributes image data of the center pixel in upper/lower/left/right directions.

The DS filter has a characteristic of relatively emphasizing sharpness by increasing a weight value of a center to be greater than a weight value of a center of the D filter, and slightly reducing a value of an edge.

The HB filter shares insufficient image data of the red or blue subpixel in an input direction. The HB filter is simpler than other filters such that a processing rate is high and the HB filter may be implemented by only using a 2×1 mask rather than a 3×3 mask. Accordingly, the number of line buffers of the HB filter used for filtering is less than other filters. For example, other filters having the 3×3 mask may use additional two line buffers as compared to the HB filter using the 2×1 mask.

In the D filter and the DS filter, image data of the center pixel is widely scattered (as compared with the HB filter) such that an image blur may be viewed. The HB filter may share image data only between adjacent pixels in a horizontal direction to provide better image quality.

However, in an exemplary embodiment, where subpixels are disposed in a diagonal direction in the S-pentile structure, the pixel structure is asymmetrical. Accordingly, the HB filter where image data are shared in a horizontal direction may not be effectively applied to the S-pentile structure. When the HB filter is applied to the S-pentile structure, the pixels are divided into an red/blue (“R/B”) group including upper red and blue subpixels and a green (“G”) group including lower green subpixels such that a divided image may be viewed.

FIG. 3is a diagram illustrating a portion of a pixel row of pixels in the S-pentile structure.

As shown inFIG. 3, the R/B group and the G group are distinguished from each other. Particularly, only the G group is disposed at a lower side, and if a conventional filter is used, a color shift may be viewed when a white letter is displayed. That is, the white letter of the upper R/B group is pinkishly viewed, and the white letter of the lower G group is greenishly viewed. Accordingly, the G group may be easily distinguished due to high luminance of the G group than the R/B group such that a color separation occurs, and a color shift (e.g., the white letter is colored) thereby occurs. This may deteriorate image quality.

A plurality of red image data and a plurality of blue image data corresponding to a plurality of pixels included in a unit mask may be distributed in red image data or blue image data corresponding to other adjacent pixels by an exemplary embodiment of a filter according to the invention. In such an embodiment, the red image data and the blue image data are rendered by an exemplary embodiment of a filter. Since the green subpixel is included in all pixels, separate signal processing for green image data corresponding to a green subpixel may not be performed.

Hereinafter, red image data or blue image data not passed through the filter will be referred to as an input image data, e.g., a first input image data or a second input image data, and rendered red image data or blue image data passed through the filter will be referred to as an image data, e.g., a first image data or a second image data.

FIG. 4is a block diagram illustrating an exemplary embodiment of a signal processor including a rendering device according to the invention.

Referring toFIG. 4, in an exemplary embodiment, the rendering device of the signal processor7may be a subpixel rendering unit3.

An exemplary embodiment of the signal processor7includes an input interface1, an input gamma unit2, the subpixel rendering unit3, a line buffer4, an output gamma unit5and an output interface6. The signal processor7receives an input video signal RGB, and generates an output image data, e.g., red-green image data RG and blue-green image data BG.

The input video signal RGB is input through the input interface1. The input video signal RGB includes red image data, green image data and blue image data. The input interface1transfers the first input image data and the second input image data to the input gamma unit2.

The input gamma unit2converts the first input image data and the second input image data based on gamma characteristics to output converted data.

In an exemplary embodiment, the subpixel rendering unit3renders the first input image data and the second input image data passed through the input gamma unit2using an HBV filter.

FIG. 5is a diagram illustrating pixels corresponding to a mask of an exemplary embodiment of a filter. In an exemplary embodiment, the pixels may be 3×3 pixels corresponding to a 3×3 mask. In such an embodiment, as shown inFIG. 5, the pixels may include a center pixel CPX including a red subpixel, an upper pixel HPX including a blue subpixel, and a left pixel LPX including a blue subpixel.

In an exemplary embodiment, the mask may be an HVB filter. In such an embodiment, the HVB filter divides the first input image data of the center pixel CPX into second input image data corresponding to another pixel of a horizontal direction in a mask, e.g., the left pixel LPX, and the second input image data corresponding to another pixel in the vertical direction, e.g., the upper pixel HPX.

In such an embodiment, another pixel in the horizontal direction may be a pixel located at a left side based on the center pixel, and another pixel in the vertical direction may be a pixel located at an upper side based on the center pixel, but not being limited thereto.

In an exemplary embodiment, the HVB filter may be expressed by the following Equation 1.

Equation 1 shows an exemplary embodiment of the HVB filter where the size of the mask is 3×3. The size of the mask may be changed based on a design, and is not limited thereto.

In Equation 1, R/B denotes input image data of the center pixel. That is, input image data of a red subpixel or a blue subpixel of the center pixel is referred to as R/B.

In such an embodiment, a half of the first input image data of the center pixel CPX is divided as the first image data of the center pixel CPX, a quarter of the first input image data of the center pixel CPX is divided as the second image data corresponding to an upper pixel HPX, and a quarter of the first input image data of the center pixel CPX is divided as the second image data of the left pixel LPX.

In such a manner, where the first input image data are divided by the HVB filter, the second input image data of each of a lower pixel DPX and a right pixel RPX are divided in the first image data of the center pixel CPX. In such an embodiment, the first image data of the center pixel CPX is calculated as a half of the first input image data of the center pixel CPX, a quarter of the second input image data of the lower pixel DPX, and a quarter of the second input image data of the right pixel RPX.

The line buffer4stores input image data, to which a filter is applied in the subpixel rendering unit3. In such an embodiment, image data are divided in the upper pixel based on the center pixel, the filter may include a line buffer to store only a single line.

If the subpixel rendering unit3renders image data using a D filter or a DS filter, where image data are divided in the upper pixel and the lower pixel based on the center pixel, the line buffer4may include a line buffer to store at least two lines. In an exemplary embodiment, as described above, the subpixel rendering unit3including the HVB filter may reduce the size of the line buffer4.

The output gamma unit5performs an inverse-gamma conversion on the image data output from the subpixel rendering unit3, and outputs the inverse-gamma-converted image data to the output interface6.

The output interface6sums the inverse-gamma-converted image data and input image data of the green subpixel, that is, green image data input from the output gamma unit5, to output the output image data, e.g., red-green image data or blue-green image data.

As described above, in an exemplary embodiment, the color shift in a horizontal direction may be effectively removed by adding a filter to a vertical direction component.

FIG. 6is a block diagram illustrating an exemplary embodiment of a display device including a signal processing circuit according to the invention.

In an exemplary embodiment, as shown inFIG. 6, the display device10includes a controller100, a scan driving circuit200, a data driving circuit300and a display unit400.

The controller100receives input video signals R, G, B and an input control signal to control display of the input video signals R, G, B. The input video signals R, G, B include luminance information of each pixel PX, and the luminance information includes a predetermined number of grayscales, for example, 1024=210, 256=28, or 64=26of grayscales. The input control signal includes a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync and a main clock signal MCLK.

The controller100processes the input video signals R, G, B suited to operation conditions of the display unit400and the data driving circuit300to generate image data signals DR, DG, DB. When the controller100processes the input video signals R, G, B to generate the image data signals DR, DG, DB, the above-mentioned signal processor may be used.

In one exemplary embodiment, for example, as shown inFIG. 6, the controller100includes the signal processor7, converts red-green image data RG and blue-green image data BG from the signal processor7into gamma voltage data based on gamma characteristics of the display device1, converts data to limit a current flowing through the display device10, or generates image data signals DR, DG, DB by performing a compensation operation such as degradation compensation, IR-drop compensation and threshold voltage deviation compensation, for example.

An operation of generating image data signals DR, DG, DB according to red-green image data RG and blue-green image data BG generated from the controller100is not limited to the operations described above.

Image data and input image data in the signal processor and the signal processing method described with reference toFIGS. 4 and 5are data corresponding to an input video signal indicating a grayscale value of one subpixel. Accordingly, the signal processor7generates a plurality of the first input image data and a plurality of the second input image data by an exemplary embodiment of the signal processing method according to the invention.

The signal processor7may sequentially perform a rendering operation for a plurality of input image data in one line unit, or may simultaneously perform a rendering operation for at least two input image data.

The controller100generates a data control signal CONT1and a scan control signal CONT2based on the input control signal.

The controller100may divide the input video signals R, G, B in synchronization with the vertical synchronization signal Vsync for each frame, and may identify the input video signals R, G, B in synchronization with the horizontal synchronization signal Hsync to arrange the image data signals DR, DG, DB. The controller100transfers the scan control signal CONT2to the scan driving circuit200, and transfers the data control signal CONT1and the image data signals DR, DG, DB to the data driving circuit300.

The scan driving circuit200transfers a plurality of scan signals S1-Sn to a plurality of scan lines S1-Sn based on the scan control signal CONT2. The data driving circuit300generates a plurality of data signals corresponding to the image data signals DR, DG, DB, and transfers the data signals to a plurality of data lines D1-Dm based on the data control signal CONT1.

The display unit400includes the data lines D1-Dm extending substantially in a first direction, the scan lines S1-Sn extending substantially in a second direction, and a plurality of subpixels SPX arranged substantially in a matrix form. In an exemplary embodiment, the first direction may be a pixel column direction, and the second direction may be a pixel row direction.

The data lines D1-Dm and the scan lines S1-Sn are connected to the subpixels SPX.

The subpixels SPX may display one of red, green and blue colors. A plurality of data voltages corresponding to the image data signals DR, DG, DB are transferred to the subpixels SPX through the data lines D1-Dm. The scan signals to select the subpixels SPX of a row unit are transferred to the subpixels SPX through the scan lines S1-Sn.

The subpixels SPX may include an organic light emitting diode (“OLED”) or a liquid crystal display (“LCD”) circuit.