KR20060134369A - Apparatus and method of converting image signal for four color organic light emitting diode display - Google Patents

Abstract

A method and an apparatus for converting an image signal of a four-color organic light emitting display are provided to represent the same brightness at a low current by using only white pixels for representing a white color. An apparatus for converting an image signal of a four-color organic light emitting display converts a three-color image signal to a four-color image signal including a white signal. A maximum/minimum extractor(651) extracts the maximum and minimum values of the 3-color image signal. A region determining unit(652) determines a conversion region, to which the 3-color image signal belongs, from the maximum and minimum values. A 4-color signal converter converts the 3-color image signal to the 4-color image signal according to the conversion region. A 4-color signal extractor(655) extracts a 4-color signal value based on the converted result from the 4-color signal converter. The 4-color signal extractor differentiates a white image signal from other 3-color image signals.

Description

Image signal conversion device and conversion method of a four-color organic light emitting display {APPARATUS AND METHOD OF CONVERTING IMAGE SIGNAL FOR FOUR COLOR ORGANIC LIGHT EMITTING DIODE DISPLAY}

With reference to the accompanying drawings will be described in detail the embodiments of the present invention to make the present invention clear.

1 is a block diagram of an organic light emitting diode display according to an exemplary embodiment of the present invention.

2 is an equivalent circuit diagram of one pixel of an organic light emitting diode display according to an exemplary embodiment of the present invention.

3 to 8 are graphs for explaining a method of converting a three-color video signal into a four-color video signal according to an embodiment of the present invention.

9 is a schematic block diagram of a data processor shown in FIG. 1.

10 is an example of a flowchart showing the operation of the video signal conversion apparatus shown in FIG. 9 in order.

<Description of Drawing>

300: display panel 400: scan driver

500: data driver

600: signal controller 650: data processor

651: maximum value, minimum value extraction unit 652: region determination unit

653: fixed scaling unit 654: variable scaling unit

655: 4-color signal extractor

R, G, B: Input video signal R ', G', B ', W: Output video signal

DE: data enable signal Hsync: horizontal sync signal

Vsync: Vertical Sync Signal MCLK: Main Clock

CONT1: scan control signal CONT2: data control signal

PX: Pixel Von, Voff: Scanning Signal

G1-Gn: scan signal line D1-Dm: data line

Qs: switching transistor Qd: driving transistor

LD: organic light emitting diode Cst: capacitor

The present invention relates to an image signal conversion device and method of a four-color organic light emitting display device.

Recently, organic light emitting diode (PDP), plasma display panel (PDP), and liquid crystal display (LCD) are substituted for heavy and large cathode ray tube (CRT). Flat panel display devices such as are being actively developed.

Such flat panel displays typically display colors using three primary colors of red, green, and blue.

Meanwhile, in the organic light emitting diode display, many polymer materials, which are relatively easy to manufacture, are used. However, in the case of using a polymer material, there are many difficulties in large area due to problems such as nonuniformity due to deterioration. In order to solve this problem, methods using low molecular weight materials have been proposed. While low molecular weight materials are difficult to pattern, the large area formation process is easy. Taking advantage of these advantages, a method of applying a low molecular weight and white OLED material to the front of a panel and using a color filter to implement color display has been attempted. In this case, the reduction in overall luminance due to the use of color filters may be a problem.

As a method of compensating for such a decrease in luminance, a method of adding white in addition to three primary colors has been attempted, and adding a white pixel in addition to these three colors is called a four-color flat panel display. The four-color flat panel display converts an input three-color video signal into a four-color video signal for display.

The present invention provides a method for converting a three-color image signal into a four-color image signal and an organic light emitting display device including the same.

According to an embodiment of the present invention for achieving the technical problem, the apparatus for converting a three-color image signal to a four-color image signal including a white signal, the maximum value for extracting the maximum value and the minimum value of the three color image signal And a minimum value extractor, a region determiner configured to determine a converted region to which the three-color image signal belongs, from the maximum value and the minimum value, and convert the three-color image signal into the four-color image signal according to the converted region to which the three-color image signal belongs. And a four-color signal extractor for extracting a four-color signal value based on the converted value from the four-color signal converter, wherein the four-color signal extractor It is extracted by dividing into a case of maximizing and a case of maximizing a value of the three-color video signal.

The converted value includes a maximum value, a median value, and a minimum value, and the four-color signal extracting unit subtracts the value of the white image signal from the minimum value of the converted values when maximizing the value of the white image signal. If greater than 0, the maximum value that can be assigned to the white image signal is the value of the white image signal, and the value obtained by subtracting the value of the white image signal from the maximum value, the median value, and the minimum value is obtained from the three color image signal. Can be extracted by value.

In contrast, when the maximum value of the white image signal is maximized, the four-color signal extracting unit subtracts the value of the white image signal from the minimum value of the converted values when the value of the white image signal is less than zero. A value obtained by subtracting the white image signal from the maximum value, the median value and the minimum value may be extracted as the value of the remaining three color image signals.

On the other hand, the converted value includes a maximum value, a median value and a minimum value, and the four-color signal extracting unit, when the value of the converted value is greater than 1 when maximizing the value of the three-color image signal, the maximum value at the A value obtained by subtracting 1 may be a value of the white image signal, and a value obtained by subtracting the value of the white image signal from the maximum value, the median value, and the minimum value may be extracted as the value of the three color image signal. When the value of the three-color video signal is maximized and the converted value is less than 1, the value of the white video signal may be set to 0, and the converted value may be extracted as the value of the three-color video signal as it is.

In this case, 1 may be a maximum value of normalized grayscales or luminances of the three-color image signal.

The transform region includes a fixed transform region and a variable transform region,

The four-color signal converter performs a fixed signal conversion based on a fixed scaling factor for the three-color image signal belonging to the fixed conversion region, and the three-color image signal for the three-color image signal belonging to the variable conversion region. The four-color video signal obtained by applying the variable signal conversion to an arbitrary three-color video signal may be smaller than the four-color video signal obtained by applying the fixed signal conversion. Can be.

According to an exemplary embodiment of the present invention, a video signal conversion method of an organic light emitting display device for converting a three-color image signal including red, green, and blue into a four-color image signal including a white signal may include converting the three-color image signal. Classifying the signal into a signal having a maximum value, a minimum value, and a median value, determining whether the three-color image signal belongs to a first conversion area or a second conversion area based on a ratio of the maximum value and the minimum value, Obtaining a first transformed value by multiplying the video signal by a predetermined multiple when belonging to the first transform region, and expanding the video signal by a predetermined multiple to the video signal when belonging to the second transform region. Converting the signal to a value smaller than the multiplication value to obtain a second transform value, and extracting the four-color image signal value based on the first transform value or the second transform value. It comprises the step and the step of extracting the four-color image signal values are extracted by dividing the case that the value of a and the three-color image signal if the value of said white image signal with a maximum at the maximum.

The first and second converted values include a maximum value, a median value, and a minimum value,

When the value of the white image signal is maximized when the value obtained by subtracting the value of the white image signal from the minimum value of the converted values is greater than zero, the maximum value that can be assigned to the white image signal is determined by the value of the white image signal. The value obtained by subtracting the value of the white image signal from the maximum value, the median value and the minimum value may be extracted as the value of the three-color image signal. Alternatively, when the value of the white image signal is maximized, If the value obtained by subtracting the value of the white image signal from the minimum value among the converted values is less than 0, the minimum value is the value of the white image signal, and the maximum value, the median value, and the minimum value are subtracted from the white image signal. The value can be extracted as the value of the remaining three-color video signal.

On the other hand, the converted value includes a maximum value, a median value and a minimum value. When the value of the converted value is greater than 1 when the value of the three-color video signal is maximized, the value obtained by subtracting 1 from the maximum value is white. A value obtained by subtracting the white image signal from the maximum value, the median value and the minimum value may be extracted as the value of the three-color image signal. Alternatively, the value of the three-color image signal may be extracted. When the conversion value is less than 1, the value of the white image signal may be set to 0, and the converted value may be extracted as the value of the three-color image signal as it is.

In this case, 1 may be a maximum value of normalized grayscales or luminances of the three-color image signal.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

Now, a four-color liquid crystal display and an image signal conversion method thereof according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of an organic light emitting diode display according to an exemplary embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of one pixel of the organic light emitting diode display according to an exemplary embodiment of the present invention.

As shown in FIG. 1, an organic light emitting diode display according to an exemplary embodiment includes a display panel 300, a scan driver 400 and a data driver 500 connected thereto, and a signal controller for controlling the display panel 300. And 600.

The display panel 300 is connected to a plurality of display signal lines G ₁ -G _n , D ₁ -D _m , a plurality of driving voltage lines (not shown), and are arranged in a substantially matrix form in an equivalent circuit. A plurality of pixels PX is included.

The display signal lines G ₁ -G _n and D ₁ -D _m may include a plurality of scan signal lines G ₁ -G _n transmitting the scan signals and a plurality of data lines D ₁ -D _m transferring the data voltages. Include. The scan signal lines G ₁ -G _n extend substantially in the row direction and are separated from each other and are substantially parallel. The data lines D ₁ -D _m extend approximately in the column direction and are separated from each other and are substantially parallel.

The driving voltage line transfers the driving voltage Vdd to each pixel PX.

2, the pixels (PX), for example, scanning signal lines (G _i) and the data lines (D _j) in the pixel includes an organic light emitting diode (LD), a driving transistor (Qd), a capacitor which is connected (Cst), and the switching transistor (Qs).

The driving transistor Qd is a three-terminal element whose control terminal is connected to the switching transistor Qs and the capacitor Cst, the input terminal is connected to the driving voltage Vdd, and the output terminal is the organic light emitting diode LD. )

A switching transistor and also a three-terminal device (Qs) The control terminal and the input terminal of each of the scanning signal lines (G _i) and the data lines (D _j) is connected to the output terminal is a capacitor (Cst) and the driving transistor (Qd) It is connected.

The capacitor Cst is connected between the switching transistor Qs and the driving voltage Vdd, and charges the data voltage from the switching transistor Qs and maintains it for a predetermined time.

An anode and a cathode of the organic light emitting diode LD are connected to the driving transistor Qd and the common voltage Vss, respectively. The organic light emitting diode LD displays an image by emitting light at different intensities according to the magnitude of the current I _LD supplied from the driving transistor Qd. The magnitude of the current I _LD depends on the magnitude of the voltage Vgs between the control terminal and the output terminal of the driving transistor Qd.

The switching and driving transistors Qs and Qd are composed of n-channel field effect transistors (FETs) made of amorphous silicon or polycrystalline silicon. However, these transistors Qs and Qd may also be p-channel field effect transistors (FETs), in which case the p-channel field effect transistors (FETs) and n-channel field effect transistors (FETs) are complementary to each other. ), The operation and voltage and current of the p-channel field effect transistor (FET) are opposite to that of the n-channel field effect transistor (FET).

Referring back to FIG. 1, the scan driver 400 is connected to the scan signal lines G ₁ -G _n to allow a high voltage Von to turn on the switching transistor Qs and a low voltage Voff to turn off. A scan signal consisting of a combination of the signals is applied to the scan signal lines G ₁ -G _n .

The data driver 500 is connected to the data lines (D ₁ -D _m) and applies the data voltages to the data lines (D ₁ -D _m).

The scan driver 400 or the data driver 500 may be mounted directly on the display panel 300 in the form of at least one driver integrated circuit chip, or mounted on a flexible printed circuit film (not shown). The display panel 300 may be attached to the display panel 300 in the form of a tape carrier package (TCP). Alternatively, the scan driver 400 or the data driver 500 may be integrated in the display panel 300.

The signal controller 600 controls operations of the scan driver 400, the data driver 500, and the like.

The signal controller 600 is configured to control the input image signals R, G, and B and their display from an external graphic controller (not shown), for example, a vertical synchronization signal Vsync and a horizontal synchronization signal ( Hsync, main clock MCLK, and data enable signal DE are provided. The signal controller 600 converts the image signals R, G, and B into four color image signals R ', based on the input image signals R, G, and B and the input control signal, according to the operating conditions of the display panel 300. G ', B', W) and the four color image signals R ', G', B ', and W are properly converted and processed, and then the scan control signal CONT1 is sent to the scan driver 400. The data control signal CONT2 and the processed image signals R ', G', B ', and W are sent to the data driver 500. Here, the data processor 650 included in the signal controller 600 converts the three-color image signals R, G, and B into four-color image signals R ', G', B ', and W. This will be described later in detail.

The scan control signal CONT1 includes a vertical synchronization start signal STV for instructing the start of scanning of the high voltage Von and at least one clock signal for controlling the output of the high voltage Von.

The data control signal CONT2 is a load signal LOAD and a data clock signal HCLK for applying a corresponding data voltage to the horizontal synchronization start signal STH and the data lines D ₁ -D _m indicating data transmission of one pixel row. ), And the like.

According to the data control signal CONT2 from the signal controller 600, the data driver 500 receives the image signals R ′, G ′, B ′, and W for one row of pixels PX, and respectively. The digital image signals R ', G', B ', and W are converted into analog data signals and then applied to the corresponding data lines D ₁ -D _m .

The scan driver 400 applies a scan signal to the scan signal lines G ₁ -G _n in response to the scan control signal CONT1 from the signal controller 600, and is connected to the scan signal lines G ₁ -G _n . (Qs) is turned on, so that the data voltage applied to the data lines (D ₁ -D _m ) is applied to the control terminal of the driving transistor (Qd) through the corresponding switching transistor (Qs) turned on.

The data voltage applied to the driving transistor Qd is charged to the capacitor Cst, and the charged voltage is maintained even when the switching transistor Qs is turned off. The driving transistor Qd to which the data voltage is applied is turned on and outputs a current depending on the voltage. As the current flows through the organic light emitting diode LD, the pixel PX displays an image.

After one horizontal period 1H, the data driver 500 and the scan driver 400 repeat the same operation with respect to the pixels PX in the next row.

Next, an image signal conversion method of the four-color organic light emitting diode display according to an exemplary embodiment of the present invention will be described in detail with reference to FIGS. 3 to 8.

3 to 8 are graphs for explaining a method of converting a three-color video signal into a four-color video signal according to an embodiment of the present invention.

First, the basic principle when converting a three-color video signal into a four-color video signal according to an embodiment of the present invention will be described in detail with reference to FIG. 3.

In FIG. 3, the horizontal and vertical axes represent normalized luminance and have the lowest gray level among three input image signals R, G, and B for displaying one color, that is, the red, green, and blue input image signals. Luminance (Min (R, G, B)) of the following (hereinafter referred to as 'minimum image signal') and luminance [Max (R, G, B) of the image signal having the highest gray level (hereinafter referred to as 'maximum image signal') ] And their converted values, respectively. When the input image signals R, G, and B are 8-bit signals, the gray level and the luminance represented by the image signals R, G, and B are all 256 steps from the 0th step to the 255th step. 1/255, 2/255, ..., 254/255, 1. For example, if the luminance of the red signal R is 255, the luminance of the green signal G is 100, and the luminance of the blue signal B is 60, the luminance of the blue signal B is the lowest and the red signal R is the same. ), The x coordinate is 60/255 and the y coordinate is 255/255 (= 1). In the following, the luminance of an image signal having a middle gray value (hereinafter, referred to as 'middle image signal') is denoted as Mid (R, G, B), and for convenience of description, the minimum, middle, and maximum image signals have the same meaning. (R, G, B) in parentheses may be omitted.

Extended conversion

Any three-color input video signal is located in a square region (hereinafter referred to as three color space) surrounded by (0, 0), (1, 0), (1, 1), (0, 1). When the ratio of the total luminance when the luminance of the three-color pixels is maximized to the maximum luminance of the white pixel is w, the maximum luminance when the three-color pixel and the white pixel are both increased by (1 + w). The present embodiment converts a three-color video signal to a four-color video signal based on this fact. For example, in FIG. 3, the point C1 indicated by the three-color input video signal is the point C1 and the origin (0). The distance between this point C1 and the origin point (0,0) is converted to the point C2 away from the origin point (0,0) by (1 + w) times along the straight line connecting .0). That is, points (Min (R, G, B), Max (R, G, B)) are points ((1 + w) Min (R, G, B), (1 + w) Max (R, G, B)), where (1 + w) is called a scaling factor.

However, the pure colors such as red, green, and blue no longer increase the luminance even if white pixels are added, and the closer to the pure color, the smaller the increase in luminance. For example, in FIG. 3, the point E1 indicated by the three-color input image signal should be converted into a four-color image signal that can be represented by the point E2, but the point E2 indicates a color that the display device cannot display.

To sum up, 6 defined by (0, 0), (1, 0), (1 + w, w), (1 + w, 1 + w), (w, 1 + w), (0, 1) Only the color in the rectangular area (hereinafter referred to as the 'expressable area') can be displayed as four-color pixels, and the shaded areas, that is, (1,0), (1 + w, 0), (1 + w, w) The color in the triangle area defined by and the triangle area defined by (0,1), (0, 1 + w) and (w, w + 1) (hereinafter referred to as 'non-expressable area') are represented by four-color pixels. Can not.

Therefore, it is necessary to draw to the points in the expressible region through the appropriate transformation for the points transformed into the non-expressable region.

Fixed and Variable Conversion Zones

First, it should be noted that in FIG. 3, since the horizontal axis is the minimum image signal and the vertical axis is the maximum image signal, the input image signal and its extended conversion value are always located in the region above the straight line y = x.

In FIG. 3, any point located in the area below the straight line 31 passing through the origin (0,0) and (w, 1 + w) always enters the expressible area when the expansion conversion of (1 + w) is performed. Points belonging to the region are extended by a scaling factor of (1 + w), and this region is called a fixed transformation region. Since the equation of the straight line 31 is y = (1 + w) x / w, the points belonging to the fixed transformation region satisfy y <(1 + w) x / w. therefore,

(1 + w) / w> Max / Min

On the contrary, points belonging to an area where (1 + w) / w <Max / Min may enter into an expressible area or an unexpressable area by performing an extended conversion of (1 + w). Specifically, when the extended transformation of (1 + w) belongs to the area below the straight line y = x + 1, that is,

(1 + w) [Max (R, G, B)-Min (R, G, B)] <1

If it is satisfied, it enters the expressible area, otherwise it enters the non-expressable area.

In this way, the scaling factor is smaller than (1 + w) for the points belonging to the region where (1 + w) / w <Max / Min, but changes according to the input image signal. Therefore, this area is called a variable conversion area.

Narrowing transform

A method of converting an image signal in the variable conversion region will be described in detail with reference to FIG. 4.

In FIG. 4, the horizontal and vertical axes represent normalized luminance, and represent the minimum and maximum image signals, which are expanded and reduced, respectively.

As for the point of the variable conversion region, as shown in Fig. 4, the points Min (R, G, B) and Max (R, G, B) are once expanded by (1 + w) times and the points (( After moving to 1 + w) Min (R, G, B), (1 + w) Max (R, G, B)), the point on the area that can be expressed through appropriate transformation (MinP (R, G, B) ), And move it down to MaxP (R, G, B)).

1. Reduced conversion principle

Point (MinP, MaxP) should be located on the straight line 41 connecting the origin and the point (Min, Max), that is, y = [Max / Min] x should be located in terms of color retention, the minimum point of (x, y) And maximum points are preferable in terms of maintaining the order of gradations to be converted into the minimum and maximum points of the representable area, respectively. In the expressible area, the minimum point on the straight line 41 is also the origin point (0,0), and the maximum point is the intersection point of the straight line 41 and the straight line 43.

(xw, yw) = (Min / (Max-Min), Max / (Max-Min))

2. Setting the Conversion Subarea

The extended value of the video signal belonging to the variable conversion region is divided into two or more subregions, and a different conversion equation is applied to each subregion. When dividing into three sub-areas, there are many possibilities, but considering the symmetry, two straight lines 42, 44 connecting the coordinates (w, 1 + w) and the points on the y-axis (1-V1, 1 + w * V2) ) And a straight line y = x + 1, which is a boundary of the non-expressable area, in the subregion between the two straight lines 42 and 44. Here, V1 and V2 are parameters introduced for convenience of calculation and may be determined according to characteristics of the display device.

The point to be transformed with respect to the coordinates Min and Max to be converted is located on the straight line 41 y = [Max / Min] x.

Among the points on the straight line 41, the points located in the subregion between the two straight lines 42 and 44 are the intersection points x1 and y1 of the straight line 41 and the straight line 42 and the straight line 41 and the straight line ( These points are located between the intersections (x2, y2) of 44).

Since the equation of the straight line 42 is y = [(w + v1) / w] x + (1-V1), the coordinates (x1, y1) of the intersection point of the straight line 41 and the straight line 42 are:

x1 = (1-V1) / [(Max-Min) / Min-V1 / w]

y1 = x1 * Max / Min

Since the equation of the straight line 44 is y = (1-V2) x + (1 + w * V2), the coordinates (x2, y2) of the intersection point of the straight line 41 and the straight line 44 are:

x2 = (1 + w * V2) / [(Min Max) / Min + V2]

y2 = x2 * Max / Min

However, the number of subareas may be four or more.

3. Double line way

Next, the conversion equation according to an embodiment of the present invention will be described in detail with reference to FIGS. 4 and 5.

In FIG. 5, the horizontal axis x represents the expansion-converted maximum image signal [(1 + w) Max], and the vertical axis y represents the reduction-converted maximum image signal MaxP (R, G, B).

Referring to FIGS. 4 and 5, the points located in the lower subregion of the straight line 42 are left as they are (straight line 1), and the points located in the subregion between the two straight lines 42 and 44 are (y1 => y1), (y2 => yw) is converted by linear mapping (straight line 2), and the points located in the upper subregion on the straight line 44 are all converted to yw (straight line 3).

Therefore, the transformation in each region is a linear transformation and the graph of FIG. 5 is expressed as follows.

MaxP = Max (0 = Max≤y1)

MaxP = (yw-y1) (Max-y1) / (y2-y1) + y1 (y1 = Max≤y2)

MaxP = yw (y2 = Max≤1 + w)

From this, the converted value [MaxP (R, G, B)] of the maximum video signal [Max (R, G, B)] can be obtained, and the converted value [of the minimum video signal [Min (R, G, B)] [ MinP (R, G, B)] can be obtained from the equation y = [Max (R, G, B) / Min (R, G, B)] x of the straight line 41, and the intermediate image signal [Mid (R , G, B)] is determined using the ratio of the three input video signals. That is, MinP: MidP: MaxP = Min: Mid: Max or MidP / MaxP = Mid / Max, MinP / MidP = Min / Mid. Of course, MinP / MaxP = Min / Max also holds from the equation of the straight line 41. For example, when the maximum red signal (R) is 100 after conversion, the blue signal (B) is minimum 60, and the ratio of the three color signals before conversion is R: G: B = 5: 4: 3. At this time, the green signal G having a medium size is determined as 80.

Here, it is preferable that V1, V2> 0, because otherwise there are only two conversion expressions, which narrows the expression range. For example, when V2 = 0, the values of the sections yw to y2 are all converted to the maximum value yw, so the image may not be distinguished because there is no gradation difference between the sections yw to y2. As another example, when V1 = 0 and V2 = 1, gray levels may be distinguished over the entire range (0 to 1 + w), but may be dark overall.

3. Nonlinear Method

Next, a conversion equation according to another embodiment of the present invention will be described in detail with reference to FIG. 6.

6 is a view for explaining a conversion method according to another embodiment of the present invention.

In FIG. 6, the horizontal axis x represents the maximum image signal [(1 + w) Max (R, G, B)] in the extended conversion state, and the vertical axis y represents the maximum image signal [MaxP after the reduction conversion. (R, G, B)].

In the method shown in FIG. 6, instead of dividing into three sub-regions as shown in FIG. 4, it is divided into only two sub-regions, that is, two regions separated by a straight line 42. As shown in FIG. In addition, the subregion located below the straight line 42 is not converted as in the case of FIG. 5, but the second functional nonlinear mapping is performed for the subregion located above the straight line 42. In other words,

MaxP = Max (0 = Max≤y1)

MaxP = a * Max2 + b * Max + c (y1 = Max≤1 + w)

If MaxP = y and Max = x, the quadratic function y = ax2 + bx + c preferably satisfies the following conditions.

First, y = y1, x = y1,

Second, the slope of the tangent line at y = y1 is 1,

Third, y = yw at x = (1 + w)

Here, the first and third conditions are for continuity in the transformation, and the second condition is for smooth transformation of the transformations at the boundary points between the subregions.

From these conditions we find c, d and e

a =-(1 + w-yw) / (1 + w-y1) 2

b = 1-2 * a * y1

c = yw-(1 + w) * b2-(1 + w) 2 * a

Then, the converted value [MaxP (R, G, B)] of the maximum image signal [Max (R, G, B)] is obtained from the function determined as described above, and the minimum image signal [Min (R) is obtained using the equation (41) of the straight line. , G, B)] to obtain the converted value [MinP (R, G, B)]. In addition, the conversion value MidP (R, G, B) of the intermediate video signal Mid (R, G, B) is determined according to the ratio of the input video signal as described above.

4-color video signal extraction

Next, a method of extracting a four-color signal including a white signal will be described in detail with reference to FIGS. 7 and 8.

7 and 8 illustrate a four-color video signal MinF (R, using the above-described conversion values MinP (R, G, B), MidP (R, G, B), and MaxP (R, G, B). It is a figure which shows the method of obtaining G, B), MidF (R, G, B), MaxF (R, G, B), and WF). Here, MinF, MidF, MaxF, and WF represent the final transform value of the minimum video signal, the final transform value of the intermediate video signal, the final transform value of the maximum video signal, and the white video signal, respectively.

In the embodiment of the present invention, a method of obtaining four color image signal values, for example, a method of allocating a white image signal value to the maximum and a method of allocating the remaining three color image signal values to the maximum, will be described.

1. Maximum allocation of white video signal values

First, a method of maximally allocating a white image signal value will be described with reference to FIG. 7.

이라 할 때, Referring to FIG. 7, two points P1 and P2 are displayed in the fixed conversion area, and these points P1 and P2 are converted through expansion or reduction conversion as described above. At this time, the vector from the origin (0, 0) to the point P1 is

When I say

는 3색 신호의 휘도 벡터이고,

는 백색 신호의 휘도 벡터 중 최대값을 나타낸 것으로서, 변환된 점(P1)은 3색 신호 성분(

)과 백색 신호 성분(

)으로 분해할 수 있다. here,

Is the luminance vector of the three-color signal,

Denotes the maximum value of the luminance vectors of the white signal, and the converted point P1 represents the three-color signal component (

) And the white signal component (

Can be decomposed into

If we rewrite these vector components into a matrix,

Given by

Therefore, the luminance value assigned to each of the four color image signals, that is, the final converted value is

Is given by In other words, when the maximum luminance value (w) of the white image signal is subtracted from the minimum value of the minimum image signal (MinP), this means that the maximum value can be assigned to the white image signal. The luminance value is one.

Similarly, in the case of the point P2, it can decompose into a three-color signal component and a white signal component.

), 3색 신호의 휘도 벡터(

)는 유기 발광 표시 장치가 표시할 수 있는 범위를 벗어나므로 색을 표현할 수 없다. 즉, 그래프의 1사분면 안에 존재하여야 하고, 앞서 설명한 것처럼 최소 영상 신호의 중간값(MinP)에서 백색 영상 신호의 최대 휘도값(w)을 뺀 것이 0보다 작은 경우에 해당한다. 따라서, 이 경우에는 백색 신호의 휘도를 적절히 조절하여 3색 신호의 값이 표시 가능 영역에 위치하도록 해야 한다. However, if the luminance of the white signal is maximized as shown by the point P1 as indicated by the dotted line (

), The luminance vector of the three-color signal (

) Is outside the range that the organic light emitting display can display, and thus color cannot be expressed. That is, it must exist in the first quadrant of the graph, and as described above, the subtraction of the maximum luminance value w of the white image signal from the median value MinP of the minimum image signal is less than zero. Therefore, in this case, the luminance of the white signal should be appropriately adjusted so that the value of the three-color signal is located in the displayable area.

For example, using the intermediate transform value MinP of the minimum image signal as the white signal value WF, it is substituted into Equation 11 to obtain the remaining final transform values MinF, MidF, and MaxF.

In other words,

MinF = MinP-MinP = 0

MidF = MidP-MinP

MaxF = MaxP-MinP

WF = MinP

2. Maximum allocation of three-color video signal

Referring to FIG. 8, two points P3 and P4 are shown, and a square region consisting of (0, 0), (1, 0), (1, 1), and (0, 1), that is, a three-color color space. It can be divided into a point P4 located inside and a point P3 located outside thereof.

라 할 때, At this time, the vector from the origin (0, 0) to the point P3 is

When we say

는 3색 영상 신호의 최대 휘도 벡터이고,

는 백색 영상 신호의 휘도 벡터이다.It can be represented as. here,

Is the maximum luminance vector of the three-color video signal,

Is the luminance vector of the white image signal.

At this time, if the final conversion value MaxF of the maximum video signal is 1, the maximum value, the y component of the white video signal is' MaxP-1 ', and the final conversion value MinF of the minimum video signal is' MinP-(MaxP-1) '

This is summarized as follows.

MinF = MinP-(MaxP-1)

MidF = MidP-(MaxP-1)

MaxF = 1

WF = MaxP -1

At this time, looking at the sign of the final value (MinF) of the minimum video signal, as shown in equation (2), divided into a region that can be expressed and a region that can not be expressed around a straight line y = x + 1, It is an area that can be expressed below. Therefore, if MaxP < MinP +1, it is an expressible area, and the final transformed value MinF of the minimum video signal is always positive as long as it is in the expressible area.

In addition, in the case of the point P4 which belongs to a square area | region, it is good to use it as it is without needing to allocate white brightness separately.

MinF = MinP

MidF = MidP

MaxF = MaxP

WF = 0

In summary, if the intermediate values (MinP, MidP, MaxP) are located outside the square area, that is, if the median value (MaxP) of the maximum image signal is greater than 1, the final converted value (MaxF) of the maximum image signal is 1, and the intermediate If the values MinP, MidP, and MaxP are located in the square region, that is, if the median value MaxP of the maximum image signal is less than 1, the final converted value WF of the white image signal is zero.

Next, an image signal conversion apparatus and a method thereof according to an embodiment of the present invention will be described with reference to FIGS. 9 and 10.

9 is a block diagram of an apparatus for converting video signals according to an embodiment of the present invention, which corresponds to the data processor 650 shown in FIG. 10 is an example of a flowchart showing the operation of the video signal conversion apparatus shown in FIG. 9 in order.

As shown in FIG. 9, the data processor 650 includes a maximum and minimum value extractor 651, an area determiner 652, fixed and variable converters 653 and 654 connected thereto, and fixed and variable values. And a four-color signal extractor 655 connected to the converters 653 and 654.

The maximum value and the minimum value extractor 651 compares the magnitude (or gradation) of the three-color video signal of red, green, and blue (S901), and compares the minimum value (Min) and the maximum value (Max) with each other. Obtained (S902). The median value Mid is naturally determined when the maximum and minimum values are determined.

Next, the area determining unit 652 determines whether the video signal belongs to the fixed conversion area or the variable conversion area (S903). At this time, based on Equation 1, if (1 + w) / w> Max / Min is satisfied, it is determined that it belongs to the fixed transformation region, and if not, it belongs to the variable transformation region.

When the input image signal belongs to the fixed conversion region, the fixed conversion unit 653 outputs the minimum value Min, the maximum value Max, and the intermediate value Mid by multiplying the scaling factors of (1 + w) (S904). ). In contrast, if the input image signal belongs to the variable conversion region, the variable conversion unit 654 performs the maximum value conversion given by Equation 6 or Equation 7 to obtain MaxP, MinP, and MidP and output the same (S905).

The four-color signal extractor 655 extracts the value of the white signal and the remaining three-color signal from the values from the converters 653 and 654 based on Equations 9 to 15 (S906).

In this way, it prevents to some extent the deterioration over time, which is one of the weak points of the OLED. In the case of a conventional three-color display device, all three primary colors have to flow current to emit white color, which affects a lifetime. However, in the case of the four-color organic light emitting diode display, since the primary color is used to represent an image and the white color is used only to the white pixel, the lower current is lower than that of the white color using the three primary pixel. The same brightness can also be expressed.

Therefore, since the four-color organic light emitting display device may flow a low current as a whole, the OLED may have a low deterioration, thereby extending its lifespan.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (14)

A video signal conversion device of an organic light emitting display device for converting a three-color video signal into a four-color video signal including a white signal, A maximum and minimum value extracting unit for extracting a maximum value and a minimum value among the three color image signals; An area determination unit determining a conversion area to which the three-color video signal belongs from the maximum value and the minimum value; A four-color signal converter for converting the three-color video signal into the four-color video signal according to a conversion region to which the three-color video signal belongs; A four-color signal extractor for extracting a four-color signal value based on the converted value from the four-color signal converter Including; The four-color signal extracting unit extracts the image by dividing it into a case where the value of the white image signal is maximized and a case where the value of the three-color image signal is maximized. An image signal conversion device of an organic light emitting display device. In claim 1, The converted value comprises a maximum value, a median value and a minimum value, When the value of the white image signal is subtracted from the minimum value of the converted values when the value of the white image signal is maximized, the four-color signal extractor may be assigned to the white image signal. Is a value of the white image signal, and a value obtained by subtracting the white image signal from the maximum value, the median value and the minimum value is extracted as the value of the three color image signal. In claim 2, When the value of the white image signal is less than zero, the four-color signal extractor subtracts the minimum value to the value of the white image signal when the value of the white image signal is maximized. And extracting a value obtained by subtracting the white image signal from the maximum value, the median value, and the minimum value as values of the remaining three color image signals. In claim 1, The converted value comprises a maximum value, a median value and a minimum value, If the conversion value is greater than 1 when the value of the three-color video signal is maximized, the four-color signal extracting unit sets the value obtained by subtracting 1 from the maximum value as the value of the white video signal and the maximum value. And extracting a value obtained by subtracting the white image signal from the median value and the minimum value as the value of the three-color image signal. In claim 4, If the conversion value is less than 1 when the value of the three-color video signal is maximized, the four-color signal extracting unit sets the value of the white video signal to 0 and sets the converted value as it is. An image signal conversion device of an organic light emitting display that extracts a value of. In claim 5, 1 is a maximum value among normalized gray levels or luminances of the three-color image signal. In claim 3 or 6, The transform region includes a fixed transform region and a variable transform region, The four-color signal converter performs a fixed signal conversion based on a fixed scaling factor for the three-color image signal belonging to the fixed conversion region, and the three-color image signal for the three-color image signal belonging to the variable conversion region. To perform variable signal conversion dependent on Image signal conversion device of an organic light emitting display device. In claim 7, A four-color video signal obtained by applying the variable signal conversion to an arbitrary three-color video signal is smaller in size than the four-color video signal obtained by applying the fixed signal conversion. A video signal conversion method of an organic light emitting display device for converting a three-color video signal including red, green, and blue into a four-color video signal including a white signal. Classifying the three-color image signal into a signal having a maximum value, a minimum value, and a median value, Determining whether the three-color image signal belongs to a first conversion area or a second conversion area based on a ratio between the maximum value and the minimum value; Obtaining a first conversion value by multiplying the video signal by a predetermined multiple in the first conversion region; Obtaining a second converted value by converting the video signal into a value larger than the video signal and smaller than the product signal multiplied by the predetermined multiple in the second conversion region; and Extracting the four-color image signal value based on the first converted value or the second converted value Including, The extracting of the four-color video signal may be performed by dividing the four-color video signal into a case in which the value of the white image signal is maximized and a case in which the value of the three-color image signal is maximized. An image signal conversion method of an organic light emitting display device. In claim 9, The first and second converted values include a maximum value, a median value, and a minimum value, When the value of the white image signal is maximized when the value obtained by subtracting the value of the white image signal from the minimum value of the converted values is greater than zero, the maximum value that can be assigned to the white image signal is determined by the value of the white image signal. And extracting a value obtained by subtracting the white image signal from the maximum value, the median value, and the minimum value as the value of the three-color image signal. In claim 10, When the value of the white image signal is maximized and the value obtained by subtracting the value of the white image signal from the minimum value of the converted values is less than 0, the minimum value is set to the value of the white image signal, and the maximum value, the middle And a value obtained by subtracting a value of the white image signal from a value and a minimum value as values of the remaining three color image signals. In claim 9, The converted value comprises a maximum value, a median value and a minimum value, When the converted value is greater than 1 when the value of the three-color video signal is maximized, the value obtained by subtracting the 1 from the maximum value is the value of the white image signal, and the value is determined by the maximum value, the median value and the minimum value. A method of converting a video signal of an organic light emitting display device by extracting a value obtained by subtracting a value of a white image signal into a value of the three-color image signal. In claim 12, When the converted value is less than 1 when the value of the three-color image signal is maximized, the organic light emission of setting the value of the white image signal to zero and extracting the converted value as the value of the three-color image signal as it is Video signal conversion method of the display device. In claim 13, 1 is a maximum value among normalized gray levels or luminances of the three-color image signal.

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