KR101964457B1 - Organic light emitting diode display device and method for driving the same - Google Patents

Abstract

The present invention relates to an organic light emitting diode display and a driving method thereof. The organic light emitting diode display according to an embodiment of the present invention includes a first conversion unit for converting first digital image data into first luminance data and color difference data, a second conversion unit for converting the first luminance data and the color difference data, A second conversion unit for converting the first luminance data into the second luminance data so that the first luminance data is smaller than the difference between the maximum value and the minimum value of the data and a second conversion unit for converting the second luminance data and the color difference data into second digital image data 3 conversion section; A data driving circuit for converting the second digital image data into analog data voltages and supplying the analog data voltages to the data lines of the display panel; And a gate driving circuit for sequentially supplying gate pulses to the gate lines of the display panel.

Description

Technical Field [0001] The present invention relates to an organic light emitting diode (OLED) display device,

The present invention relates to an organic light emitting diode display and a driving method thereof.

As the information society develops, the demand for display devices for displaying images is increasing in various forms. In recent years, various flat panel display devices such as a liquid crystal display (LCD), a plasma display panel (PDP), and an organic light emitting diode (OLED) have been used . Among these flat panel display devices, organic light emitting diode display devices are capable of low voltage driving, are thin, have excellent viewing angles, and have a high response speed. An active matrix type organic light emitting diode display device in which a plurality of pixels are arranged in a matrix form to display an image is widely used in organic light emitting diode display devices.

An active matrix type organic light emitting diode display device includes a plurality of pixels arranged in a matrix form. Each of the pixels is supplied with a scan TFT (Thin Film Transistor) for supplying a data voltage of a data line in response to a gate signal of a gate line and an organic light emitting diode (OLED) according to a data voltage supplied to the gate electrode And a driving TFT for adjusting the amount of current to be supplied. As the gray level to be expressed by the pixel is higher, the current flowing through the organic light emitting diode of the pixel becomes larger.

On the other hand, the organic light emitting diode has a problem that it deteriorates when it is driven for a long time. In particular, an organic light emitting diode of a pixel whose relatively high gray level is expressed relatively frequently such as a white gray level is degraded more rapidly than an organic light emitting diode of a pixel whose relatively low gray level is expressed relatively frequently like a black gray level. The difference in the deterioration of the organic light emitting diode may cause a residual image. Specifically, due to the difference in brightness between the organic light emitting diode in which the deterioration is relatively advanced and the organic light emitting diode in which the deterioration is relatively slow, a static or amorphous permanent afterimage may be induced. In the industry, it is said that the after-image life is over when permanent or permanent afterimages occur. The fixed or indefinite persistent afterimage is caused by a difference in brightness occurring between pixels or a difference in color sensation occurring between sub pixels in a pixel.

The present invention provides an organic light emitting diode display device and a driving method thereof that can improve the afterglow life.

The organic light emitting diode display according to an embodiment of the present invention includes a first conversion unit for converting first digital image data into first luminance data and color difference data, a second conversion unit for converting the first luminance data and the color difference data, A second conversion unit for converting the first luminance data into the second luminance data so that the first luminance data is smaller than the difference between the maximum value and the minimum value of the data and a second conversion unit for converting the second luminance data and the color difference data into second digital image data 3 conversion section; A data driving circuit for converting the second digital image data into analog data voltages and supplying the analog data voltages to the data lines of the display panel; And a gate driving circuit for sequentially supplying gate pulses to the gate lines of the display panel.

A method of driving an OLED display according to an exemplary embodiment of the present invention includes a first step of converting first digital image data into first luminance data and color difference data; A second step of converting the first luminance data into the second luminance data so that the difference between the maximum value and the minimum value of the second luminance data becomes smaller than the difference between the maximum value and the minimum value of the first luminance data; And a third step of converting the second luminance data and the color difference data into second digital image data.

The present invention analyzes input digital image data and converts digital image data so that the difference between the maximum gradation value (maximum luminance value) and the minimum gradation value (minimum luminance value) is reduced. Accordingly, the present invention is applicable to an organic light emitting diode (OLED) of a pixel relatively high in gray level (luminance) such as white tones and an organic light emitting diode (OLED) of a pixel relatively low in gray level ) Can be reduced. Therefore, the present invention can improve afterglow life.

Further, the present invention calculates the perceived level reduction ratio according to the peak luminance, and reduces the difference between the maximum gradation value (maximum luminance value) and the minimum gradation value (minimum luminance value). That is, the present invention reduces the difference between the maximum gradation value (maximum luminance value) and the minimum gradation value (minimum luminance value) by reflecting the difference in cognitive ability, It is possible to prevent the deterioration of the perceived image quality that may occur according to the change in peak luminance due to the decrease in the difference in the peak luminance.

1 is a block diagram schematically illustrating an organic light emitting diode display device according to an embodiment of the present invention.
2 is a block diagram showing the image processing circuit of FIG. 1 in detail;
3A is an exemplary illustration showing an RGB to YCbCr conversion formula;
FIG. 3B is an exemplary view showing a YCbCr to RGB conversion formula; FIG.
4 is a block diagram illustrating a second conversion unit according to the first embodiment of the present invention in detail.
5 is a detailed flowchart showing a data conversion method of a second conversion unit according to the first embodiment of the present invention;
6 is an exemplary view showing a histogram of the first luminance data and the second luminance data;
FIG. 7 is an exemplary view showing a minimum value parameter and a maximum value parameter calculation graph according to the first embodiment of the present invention; FIG.
FIG. 8 is an exemplary view showing a minimum value parameter and a maximum value parameter calculation graph according to the second embodiment of the present invention; FIG.
FIGS. 9A and 9B are exemplary diagrams showing examples of first and second look-up tables. FIG.
10 is a block diagram showing a second conversion unit according to the second embodiment of the present invention in detail.
11 is a detailed flowchart showing a data conversion method of the second conversion unit according to the second embodiment of the present invention.
FIG. 12 is an exemplary view showing an example of a peak luminance calculation graph of the peak luminance calculation unit of FIG. 10; FIG.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The component name used in the following description may be selected in consideration of easiness of specification, and may be different from the actual product name.

1 is a block diagram schematically showing an organic light emitting diode display device according to an embodiment of the present invention. 1, an OLED display according to an exemplary embodiment of the present invention includes a display panel 10, a gate driving circuit 110, a data driving circuit 120, a timing controller 130, 140, and a host system 150, and the like.

The display panel 10 is formed so that the data lines D and the gate lines G intersect with each other. In the display panel 10, a pixel array in which pixels P are arranged in the form of a matrix is formed in a crossing region of the data lines D and the gate lines G. [ Each of the pixels P of the display panel 10 includes at least one thin film transistor, a driving TFT, an organic light emitting diode element, and at least one capacitor. Each of the pixels P controls an electric current flowing through the organic light emitting diode element using a switching TFT and a driving TFT to display an image. The display panel 10 may display an image in the form of bottom emission and top emission depending on the pixel structure.

The data driving circuit 120 includes a plurality of source drive ICs. The source drive ICs receive the second digital image data RGB 'from the timing controller 130. The source drive ICs convert the second digital image data RGB 'into an analog data voltage in response to the source timing control signal DCS from the timing controller 130, and synchronize the analog data voltage with the gate pulse To the data lines (D) of the display panel (10). The data driving circuit 120 may be mounted on a tape carrier package (TCP), bonded to a lower substrate of the display panel 10 by a TAB (tape automated bonding) process, Lt; / RTI > The data driving circuit 120 may be bonded on the lower substrate of the display panel 10 by a COG (chip on glass) process.

The gate driving circuit 110 supplies gate lines with at least one gate pulse for controlling at least one switching TFT. The gate drive circuit 110 may be mounted on the TCP and bonded to the lower substrate of the display panel 10 by a TAB process. In addition, the gate drive circuit 110 may be formed directly on the lower substrate simultaneously with the pixel array by a GIP (Gate In Panel) process.

The timing controller 130 receives the second digital image data RGB 'from the image processing circuit 140. The timing controller 130 receives a vertical synchronization signal, a horizontal synchronization signal, a data enable signal, a dot clock, and the like from the image processing circuit 140 As shown in FIG. The timing controller 130 generates timing control signals for controlling the operation timings of the gate driving circuit 110 and the data driving circuit 120 based on the second digital image data RGB 'and the timing signal. The timing control signals include a gate timing control signal GCS for controlling the operation timing of the gate driving circuit 110 and a data timing control signal DCS for controlling the operation timing of the data driving circuit 120. The timing controller 130 outputs the gate timing control signal GCS to the gate driving circuit 110 and the data timing control signal DCS to the data driving circuit 120. In addition, the timing controller 130 outputs the second digital image data RGB 'to the data driving circuit 120.

The image processing circuit 140 receives the first digital image data RGB and the timing signals from the host system 150. The image processing circuit 140 analyzes the inputted first digital image data and converts the first digital image data so that the difference between the maximum gradation value and the minimum gradation value is reduced. Due to the image processing circuit 140, the present invention is applicable to an organic light emitting diode (OLED) of a pixel in which a high gray level (luminance) is relatively frequently expressed such as a white gray level and a pixel The difference in the degradation progress of the organic light emitting diode OLED of FIG. Therefore, the present invention has an effect of improving the after-image lifetime. The image processing circuit 140 converts the first digital image data RGB to second digital image data RGB and then outputs the second digital image data RGB and the timing signals to the timing controller 130 do. The image processing circuit 140 may be designed to be embedded in the timing controller 130 or the host system 150. [ A detailed description of the image processing circuit 140 will be given later with reference to FIG.

The host system 150 includes a system-on-chip (DVS) chip having a built-in scaler for converting first digital image data (RGB) input from an external video source device into a data format of a resolution suitable for display on the display panel 10 (System on Chip). The host system 150 supplies the first digital image data RGB and the timing signals to the image processing circuit 140 through an interface such as a Low Voltage Differential Signaling (LVDS) interface and a Transition Minimized Differential Signaling (TMDS) interface.

2 is a detailed block diagram of the image processing circuit of FIG. Referring to FIG. 2, the image processing circuit 140 includes a first conversion unit 141, a second conversion unit 142, and a third conversion unit 143. The first conversion unit 141 converts the first digital image data RGB into the first luminance data Y and the color difference data Cb and Cr. Specifically, the first conversion unit 141 can convert the first luminance data Y and the color difference data Cb and Cr using the RGB to YCbCr conversion formula shown in FIG. 3A. However, it should be noted that the conversion formula of the first conversion unit 141 is not limited to the RGB to YCbCr conversion formula shown in FIG. 3A. The first conversion section 141 outputs the first luminance data Y to the second conversion section 142 and the color difference data Cb and Cr to the third conversion section 143.

The second conversion unit 142 converts the first luminance data Y into second luminance data Y '. In particular, the second conversion unit 142 converts the first luminance data Y so that the difference between the maximum value and the minimum value of the second luminance data Y 'becomes smaller than the difference between the maximum value and the minimum value of the first luminance data Y, Into second luminance data (Y '). The data conversion method of the second conversion unit 142 may be implemented as the first embodiment and the second embodiment. The data conversion method of the second conversion unit 142 according to the first embodiment of the present invention will be described later with reference to FIGS. 4 and 5, and the data of the second conversion unit 142 according to the second embodiment of the present invention The conversion method will be described later in conjunction with FIG. 11 and FIG. The second conversion unit 142 outputs the second luminance data Y 'to the third conversion unit 143.

The third conversion unit 143 converts the second luminance data Y 'and the color difference data Cb and Cr into the second digital image data RGB'. Specifically, the third conversion unit 143 converts the second luminance data Y 'and the color difference data Cb and Cr into the second digital image data RGB' using the YCbCr to RGB conversion formula shown in FIG. 3B. . ≪ / RTI > However, it should be noted that the conversion formula of the third conversion unit 143 is not limited to the YCbCr to RGB conversion formula shown in FIG. 3B. The third conversion unit 143 outputs the second digital image data RGB 'to the timing controller 130.

4 is a block diagram illustrating a second conversion unit according to the first embodiment of the present invention. 5 is a detailed flowchart illustrating a data conversion method of the second conversion unit according to the first embodiment of the present invention. Referring to FIG. 4, the second conversion unit 142 according to the first embodiment of the present invention includes a histogram analysis unit 201, a first average image level calculation unit 202, a minimum value parameter calculation unit 203, A second average image level calculating unit 205, a maximum value parameter calculating unit 206, a maximum value converting unit 207, and a data converting unit 208. The converting unit 204, the second average image level calculating unit 205, Hereinafter, the data conversion method of the second conversion unit 142 will be described in detail with reference to FIG. 4 and FIG.

First, the histogram analyzing unit 201 receives the luminance data Y from the first converting unit 141. [ The histogram analyzing unit 201 analyzes the first luminance data Y in the N frame period (where N is a natural number) as shown in FIG. 6 to generate a histogram of the first luminance data Y. FIG. One frame period is a period in which data is newly written in all the pixels of the display panel 10. [ For example, when the display panel 10 includes p x q (where p and q are natural numbers) pixels, the histogram analyzer 201 calculates p × q first luminance data Y for one frame period And generates a histogram of the first luminance data (Y).

6 is an exemplary view showing a histogram of the first luminance data and the second luminance data. In the upper graph of FIG. 6, the range of the first luminance data (Y) is shown on the x-axis and the frequency is shown on the y-axis. In FIG. 6, the first luminance data (Y) is 8 bits (bits). Since the first luminance data (Y) of 8 bits has a range of values from 0 to 255, values of 0 to 255 are shown on the x-axis. The histogram of the first luminance data (Y) is a graph showing the frequency of the first luminance data (Y). (S101)

Second, the first average image level calculating section 202 analyzes the histogram generated by the histogram analyzing section 201 to calculate a dark average pirate ratio (APLd). The first average image level calculating unit 202 calculates the dark average image level APLd using the frequency function H (Y) and the dark function D (Y) as shown in Equation (1).

In Equation 1, APLd is a dark average picture level, Y is first luminance data (Y), T is a maximum value that the first luminance data (Y) can have, and H (Y) (Y), and D (Y) denotes a dark function. For example, T is 255 when the first luminance data (Y) is 8 bits, and T is 1023 when the first luminance data (Y) is 10 bits. The dark function D (Y) can be defined as Equation (2).

 In Equation 2, D (Y) is a dark function, Y is first luminance data (Y), and T is a maximum value that the first luminance data (Y) can have. For example, T is 255 when the first luminance data (Y) is 8 bits, and T is 1023 when the first luminance data (Y) is 10 bits. The dark function D (Y) may be implemented so as to be in inverse proportion to the first luminance data Y as shown in FIG.

That is, the dark average picture level APLd is an average picture level calculated with a relatively high weight on the first luminance data Y located in the dark area which is the low luminance area. Therefore, the smaller the dark average picture level APLd, the higher the ratio of the first luminance data Y located in the low luminance area, and the larger the dark average picture level APLd, (Y) is low. (S102)

Thirdly, the minimum value parameter calculating section 203 calculates a minimum value parameter Pmin for converting the minimum value Ymin of the first luminance data according to the dark average picture level APLd. The minimum value conversion unit 204 converts the minimum value Ymin of the first luminance data using the minimum value parameter Pmin.

The minimum value parameter calculating section 203 can calculate the minimum value parameter Pmin in proportion to the dark average picture level APLd as shown in FIG. 8, the minimum value parameter calculating section 203 calculates the minimum value parameter Pmin in proportion to the dark average picture level APLd in the first range (0 to 127), and calculates the minimum value parameter Pmin in the second range 127 to 255, The minimum value parameter Pmin can be calculated as the first value V1 irrespective of the dark average image level APLd. 7 and 8, the x axis indicates the dark average picture level APLd and the y axis indicates the value of the minimum value parameter Pmin.

Alternatively, the minimum value parameter calculator 203 may include a first look-up table 203a that receives the dark average picture level APLd as an input address and outputs a minimum value parameter Pmin corresponding to the input address as shown in FIG. 9A, The minimum value parameter Pmin can be calculated. In this case, the first look-up table 203a outputs the minimum value parameter Pmin as 0 when the dark average picture level APLd has a value between 0 and 31 as shown in FIG. 9A, Value, the minimum value parameter (Pmin) can be output as 5. It should be noted that the first look-up table 203a shown in FIG. 9A is merely an example created for convenience of explanation. 9A, the minimum value parameter Pmin is output according to the range to the dark average image level APLd for convenience of explanation. However, when the dark average image level APLd and the minimum value parameter Pmin are 1: 1 . ≪ / RTI >

The minimum value converter 204 calculates the minimum value (Y'min) of the second luminance data by adding the minimum value parameter (Pmin) to the minimum value (Ymin) of the first luminance data. In particular, the minimum value (Y'min) of the second luminance data may be set to be greater than or equal to the minimum value (Ymin) of the first luminance data. For example, when the minimum value parameter Pmin is calculated as 0, the minimum value conversion unit 204 calculates the minimum value Y'min of the second luminance data equal to the minimum value Ymin of the first luminance data. When the minimum value parameter Pmin is calculated as 5, the minimum value conversion unit 204 calculates the minimum value (Y'min) of the second luminance data by adding 5 to the minimum value (Ymin) of the first luminance data. The minimum value converter 204 outputs the minimum value (Y'min) of the second luminance data to the data converter 208. (S103)

Fourth, the second average image level calculating section 205 analyzes the histogram generated by the histogram analyzing section 201 to calculate a bright average pirate ratio (APLb). The second average image level calculating unit 205 calculates the bright average image level APLb using the frequency function H (Y) and the brightness function B (Y) as shown in Equation (3).

In Equation 3, APLb is a bright average image level, Y is first luminance data (Y), T is a maximum value that the first luminance data (Y) can have, and H (Y) (Y), and B (Y) is a bright function. T is 255 when the first luminance data (Y) is 8 bits, and T is 1023 when the first luminance data (Y) is 10 bits. The brightness function B (Y) can be defined as Equation (4).

 In Equation (4), B (Y) is the brightness function, Y is the first luminance data, and T is the maximum value that the first luminance data (Y) can have. T is 255 when the first luminance data (Y) is 8 bits, and T is 1023 when the first luminance data (Y) is 10 bits. The brightness function B (Y) may be implemented so as to be proportional to the first luminance data Y as shown in FIG. As a result, the bright average image level APLb means an average image level calculated with a relatively high weight to the first luminance data Y located in the bright region which is the high luminance region. Therefore, the smaller the average brightness level APLb is, the lower the ratio of the first brightness data Y located in the high brightness region, and the larger the brightness average image level APLb, the higher the brightness data Y ) Is high. (S104)

Fifth, the maximum value parameter calculating section 206 calculates a maximum value parameter Pmax for converting the maximum value (Ymax) of the first luminance data according to the bright average picture level APLb. The maximum value converter 207 converts the maximum value Ymax of the first luminance data using the maximum value parameter Pmax.

The maximum value parameter calculating section 206 can calculate the maximum value parameter Pmax in inverse proportion to the bright average picture level APLb as shown in FIG. 8, the maximum value parameter calculating section 206 calculates the maximum value parameter Pmax as the first value V1 irrespective of the bright average image level APLb in the first range (0 to 127) , And in the second range (127 to 255), the maximum value parameter Pmax can be calculated in proportion to the bright average image level APLb. In Figs. 7 and 8, the x-axis indicates the bright average image level APLb, and the y-axis indicates the value of the maximum value parameter Pmax.

Alternatively, the maximum value parameter calculator 206 may calculate the maximum value parameter Pmax by inputting the bright average picture level APLb as the input address and outputting the maximum value parameter Pmax corresponding to the input address as shown in FIG. 9B 206a can be used to calculate the maximum value parameter Pmax. In this case, the second look-up table 206a outputs a maximum value parameter Pmax as 0 when the bright average picture level APLb has a value between 243 and 255 as shown in FIG. 9b, and outputs a maximum value parameter Pmax between 191 and 243 The maximum value parameter Pmax can be output as 5. It should be noted that the second look-up table 206a shown in FIG. 9B is merely an example created for convenience of explanation. 9B, the maximum value parameter Pmax is output to the bright average image level APLb according to the range. However, when the bright average image level APLb and the maximum value parameter Pmax are 1 : 1 < / RTI >

The maximum value converter 207 calculates the maximum value Y'max of the second luminance data by subtracting the maximum value parameter Pmax from the maximum value Ymax of the first luminance data. In particular, the maximum value (Y'max) of the second luminance data may be set to be less than or equal to the maximum value (Ymax) of the first luminance data. For example, when the maximum value parameter Pmax is calculated as 0, the maximum value converter 207 calculates the maximum value (Y'max) of the second luminance data equal to the maximum value (Ymax) of the first luminance data as . When the maximum value parameter Pmax is calculated as 5, the maximum value conversion unit 207 calculates the maximum value Y'max of the second luminance data by subtracting 5 from the maximum value Ymax of the first luminance data do. The maximum value conversion unit 207 outputs the maximum value (Y'max) of the second luminance data to the data conversion unit 208. (S105)

Sixth, the data converter 208 converts the first luminance data Y using the minimum value (Y'min) of the second luminance data and the maximum value (Y'max) of the second luminance data, as shown in Equation (5) Into second luminance data (Y ').

In Equation (5), Y 'is the second luminance data, T is the maximum value that the first luminance data (Y) can have, Y'max is the maximum value of the second luminance data (Y' 2 is the minimum value of the luminance data (Y '), and Y is the first luminance data. T is 255 when the first luminance data (Y) is 8 bits, and T is 1023 when the first luminance data (Y) is 10 bits.

As a result of the data conversion by the data conversion unit 208, the luminance range of the second luminance data (Y ') becomes narrower than the luminance range of the first luminance data (Y) as shown in FIG. The data conversion unit 208 outputs the second luminance data Y 'to the third conversion unit 143. (S106)

As described above, the first embodiment of the present invention analyzes the input digital image data and converts the digital image data so that the difference between the maximum gradation value (maximum luminance value) and the minimum gradation value (minimum luminance value) decreases. The present invention can reduce the difference in the degradation progress of the organic light emitting diode of a pixel relatively high in gray scale (brightness) such as white tones and the organic light emitting diode of a pixel relatively low in gray tones (brightness) have. Therefore, the present invention can improve afterglow life.

FIG. 10 is a block diagram showing a second conversion unit according to the second embodiment of the present invention. 11 is a detailed flowchart illustrating a data conversion method of the second conversion unit according to the second embodiment of the present invention. 10, the second conversion unit 142 according to the second embodiment of the present invention includes a peak luminance calculation unit 301, a perception level reduction ratio calculation unit 302, a histogram analysis unit 401, A minimum value parameter calculating unit 403, a minimum value converting unit 404, a second average image level calculating unit 405, a maximum value parameter calculating unit 406, a maximum value converting unit 407 ), And a data conversion unit 408. Hereinafter, the data conversion method of the second conversion unit 142 will be described in detail with reference to FIGS. 10 and 11. FIG.

First, the peak luminance calculating section 301 receives the first luminance data Y from the first converting section 141. [ The peak luminance calculating section 301 calculates an average picture ratio (APL) of the first luminance data Y in the N frame period (N is a natural number). The average picture level APL of the first luminance data Y can be calculated as an average value of the first luminance data Y in the N frame period. (S201)

Secondly, the peak luminance calculating section 301 calculates the peak luminance according to the average picture level APL. Fig. 12 is an exemplary diagram showing an example of a peak luminance calculation graph of the peak luminance calculation unit of Fig. 10; Fig. In Fig. 12, the x-axis indicates the average image level (APL), and the y-axis indicates the peak luminance (unit candela). Referring to FIG. 12, the peak luminance calculating section 301 can calculate the peak luminance lower as the average picture level APL is higher than the predetermined threshold value TH, as the average picture level APL is higher. This is because the degradation rate of the organic light emitting diode device may increase as the average image level APL is higher. The peak luminance calculating section 301 calculates the peak luminance as the maximum peak luminance (MPL) irrespective of the average picture level APL when the average picture level APL is equal to or less than the predetermined threshold value TH . (S202)

Thirdly, the perceptual level reduction ratio calculation section 302 calculates the perception level reduction ratio based on the peak luminance. First, the perceptual level decreasing ratio calculating unit 302 calculates the perceptual level decreasing rate using the NMI (National Electrical Manufacture Association) DICOM (Just Noticeable Difference) of the peak luminance calculated from the peak luminance calculating unit 301 The perceived level reduction ratio? Is calculated. NEMA DICOM JND stands for the difference in cognitive ability (difference in brightness discrimination ability) between medical digital imaging and communication specified as an international standard. The awareness level reduction ratio calculating unit 302 may calculate the awareness level decrease ratio? As shown in Equation (6).

J (CPL) denotes the NEMA DICOM JND value of the peak luminance calculated from the peak luminance calculating section 301, and J (MPL) denotes the maximum peak luminance MPL) NEMA DICOM JND value. The perceptual level reduction ratio calculating unit 302 may calculate the NEMA DICOM JND value J (PL) as shown in Equation (7).

In Equation 7, J (PL) denotes the NEMA DICOM JND value of the peak luminance PL, A is a constant, and B, C, D, E, F, G, H and I are coefficients. In Equation 7, A may be implemented as 71.498068, B as 94.593053, C as 41.912053, D as 9.8247004, E as 0.28175407, F as -1.1878455, G as -0.18014349, H as 0.14710899, and I as -0.017046845. The perceptual level reduction ratio calculating section 302 can calculate J (CPL) by substituting the peak brightness calculated from the peak brightness calculating section 301 to "PL " in the equation (7) (MPL) can be calculated by substituting the maximum peak luminance (MPL) into the maximum peak luminance (MPL). The recognition level reduction ratio calculating unit 302 outputs the recognition level reduction ratio alpha to the minimum value conversion unit 404 and the maximum value conversion unit 407. [ (S203)

Fourth, the histogram analyzer 401 analyzes the first luminance data (Y) in the N frame period to generate a histogram of the first luminance data (Y). The histogram analyzing unit 401 generates the histogram of the first luminance data Y as described in step S101 of FIG. (S204)

Fifth, the first average image level calculating section 402 analyzes the histogram of the first luminance data Y to calculate the dark average image level APLd. The first average image level calculating section 402 calculates the dark average image level APLd as described in step S102 of FIG. (S205)

Sixth, the minimum value parameter calculator 403 calculates a minimum value parameter Pmin for converting the minimum value Ymin of the first luminance data according to the dark average picture level APLd. The minimum value parameter calculator 403 calculates the minimum value parameter Pmin as described in step S103 of FIG. (S206)

The minimum value converter 404 receives the minimum value parameter Pmin from the minimum value parameter calculator 403 and receives the recognition level decrease rate alpha from the recognition level decrease rate calculator 302. The minimum value parameter The minimum value conversion unit 404 calculates the minimum value conversion parameter P'min by multiplying the minimum value parameter Pmin by the perceived level reduction ratio [alpha]. The minimum value conversion unit 404 calculates the minimum value (Y'min) of the second luminance data by adding the minimum value conversion parameter (P'min) to the minimum value (Ymin) of the first luminance data. The minimum value conversion unit 404 outputs the minimum value (Y'min) of the second luminance data to the data conversion unit 408. (S207)

Eighth, the second average image level calculating section 405 analyzes the histogram of the first luminance data Y to calculate the bright average image level APLb. The second average image level calculating section 405 calculates the bright average image level APLb as described in step S104 of FIG. (S208)

For the ninth, the maximum value parameter calculating section 406 calculates a maximum value parameter Pmax for converting the maximum value (Ymax) of the first luminance data according to the bright average picture level APLb. The maximum value parameter calculator 406 calculates the maximum value parameter Pmax as described in step S105 of FIG. (S209)

The tenth maximum value conversion unit 407 receives the maximum value parameter Pmax from the maximum value parameter calculation unit 406 and inputs the recognition level reduction ratio? From the recognition level reduction ratio calculation unit 302 Receive. The maximum value conversion unit 407 calculates the maximum value conversion parameter P'max by multiplying the maximum value parameter Pmax by the perceived level reduction ratio [alpha]. The maximum value conversion unit 407 calculates the maximum value (Y'max) of the second luminance data by subtracting the maximum value conversion parameter (P'max) from the maximum value (Ymax) of the first luminance data. The maximum value conversion unit 407 outputs the maximum value (Y'max) of the second luminance data to the data conversion unit 408. (S210)

The data converting unit 408 converts the first luminance data Y into the second luminance data Y 'using the minimum value Y'min and the maximum value Y'max of the second luminance data, . The data conversion unit 408 converts the first luminance data Y into the second luminance data Y 'as described in step S106 of FIG. (S211)

As described above, the second embodiment of the present invention analyzes the input digital image data and converts the digital image data so that the difference between the maximum gradation value (maximum luminance value) and the minimum gradation value (minimum luminance value) decreases. As a result, the present invention has been made in view of the above-described problems, and it is an object of the present invention to provide an organic light emitting diode having a relatively high gradation (brightness), such as white tones, . Therefore, the present invention can improve afterglow life. In the second embodiment of the present invention, the perceived level reduction ratio is calculated according to the peak luminance, and the difference between the maximum gradation value (maximum luminance value) and the minimum gradation value (minimum luminance value) is reduced. That is, the present invention reduces the difference between the maximum gradation value (maximum luminance value) and the minimum gradation value (minimum luminance value) by reflecting the difference in cognitive ability, It is possible to prevent the deterioration of the perceived image quality that may occur according to the change in peak luminance due to the decrease in the difference in the peak luminance.

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

10: display panel 110: gate drive circuit
120: Data driving circuit 130: Timing controller
140: image processing circuit 141: first conversion section
142: second conversion section 143: third conversion section
150: Host system 201, 401: Histogram analysis unit
202, 402: first average image level calculating section 203, 403: minimum value parameter calculating section
203a, 403a: first look-up table 204, 404: minimum value conversion section
205, 405: second average image level calculating section 206, 406: maximum value parameter calculating section
206a, 406a: second look-up table 207, 407: maximum value conversion section
208, 408: Data conversion unit 301: Peak brightness calculation unit
302: A recognition level reduction ratio calculating unit

Claims (17)

A first conversion unit for converting the first digital image data into first luminance data and color difference data; a first conversion unit for converting the first digital image data into the first luminance data and the color difference data so that the difference between the maximum value and the minimum value of the second luminance data becomes smaller than the difference between the maximum value and the minimum value of the first luminance data; 1 luminance data into the second luminance data and converts a minimum value of the first luminance data into a minimum value of the second luminance data according to a dark average picture level of the first luminance data, A second conversion unit for converting the maximum value of the first luminance data into the maximum value of the second luminance data in accordance with the average brightness level of the bright image and a second conversion unit for converting the second luminance data and the color difference data into second digital image data An image processing circuit including a third conversion unit;
A data driving circuit for converting the second digital image data into analog data voltages and supplying the analog data voltages to the data lines of the display panel; And
And a gate driving circuit for sequentially supplying gate pulses to the gate lines of the display panel. The method according to claim 1,
Wherein the second conversion unit comprises:
A histogram analyzer for analyzing the first luminance data of N (N is a natural number) frame period to generate a histogram of the first luminance data;
A first average image level calculating unit for analyzing the histogram to calculate the dark average image level;
A minimum value parameter calculation unit for calculating a minimum value parameter for converting the minimum value of the first luminance data according to the dark average picture level;
A minimum value converter for converting the minimum value of the first luminance data into the minimum value of the second luminance data using the minimum value parameter;
A second average image level calculating unit for analyzing the histogram to calculate the bright average image level;
A maximum value parameter calculating unit for calculating a maximum value parameter for converting the maximum value of the first brightness data according to the brightness average image level;
A maximum value converter for converting a maximum value of the first luminance data to a maximum value of the second luminance data using the maximum value parameter;
And a data conversion unit converting the first luminance data into the second luminance data using a minimum value and a maximum value of the second luminance data. The method according to claim 1,
Wherein the second conversion unit comprises:
An average image level calculating unit for analyzing the first luminance data of N (N is a natural number) frame period and calculating an average picture level of the first luminance data;
A peak luminance calculating unit for calculating a peak luminance according to the average picture level;
A cognitive level reduction ratio calculation unit for calculating a cognitive level reduction ratio based on the peak luminance;
A histogram analyzer for analyzing the first luminance data of the N frame period to generate a histogram of the first luminance data;
A first average image level calculating unit for analyzing the histogram to calculate the dark average image level;
A minimum value parameter calculation unit for calculating a minimum value parameter for converting the minimum value of the first luminance data according to the dark average picture level;
A minimum value converter for converting a minimum value of the first luminance data into a minimum value of the second luminance data using the minimum value conversion parameter to which the perceptual level reduction ratio is applied to the minimum value parameter;
A second average image level calculating unit for analyzing the histogram to calculate the bright average image level;
A maximum value parameter calculating unit for calculating a maximum value parameter for converting the maximum value of the first brightness data according to the brightness average image level;
A maximum value conversion unit for converting a maximum value of the first luminance data into a maximum value of the second luminance data using a maximum value conversion parameter to which the perceptual level reduction ratio is applied to the maximum value parameter;
And a data conversion unit converting the first luminance data into the second luminance data using a minimum value and a maximum value of the second luminance data. The method according to claim 2 or 3,
Wherein the first average image level calculating section calculates,
The first luminance data is represented by Y, the dark function is represented by D (Y), the frequency function representing the frequency according to the first luminance data (Y) is represented by H (Y), the maximum value of the first luminance data is represented by T In other words,
The dark average picture level, APLd,

Lt; / RTI >
The dark function D (Y)

Lt; RTI ID = 0.0 > 1, < / RTI > The method according to claim 2 or 3,
Wherein the second average image level calculating section calculates,
(Y), a frequency function representing a frequency in accordance with the first luminance data (Y), a maximum value that the first luminance data can have, T (Y), a brightness function of B In other words,
The bright average image level APLb,

Lt; / RTI >
The bright function B (Y)

Lt; RTI ID = 0.0 > 1, < / RTI > The method according to claim 2 or 3,
Wherein the data conversion unit comprises:
The first luminance data is Y ', the second luminance data is a minimum value Y'min, the maximum value of the second luminance data is Y'max, the first luminance data (Y) is Y' And the maximum value that can be obtained is T,
The second luminance data Y '

Lt; RTI ID = 0.0 > 1, < / RTI > The method of claim 3,
The peak luminance calculating section calculates,
Wherein when the average picture level is higher than a threshold value, the peak luminance is calculated to be lower as the average picture level is higher. 8. The method of claim 7,
The peak luminance calculating section calculates,
Wherein the peak luminance is calculated as the maximum peak luminance irrespective of the average picture level when the average picture level is lower than or equal to the threshold value. A first step of converting the first digital image data into first luminance data and color difference data;
A second step of converting the first luminance data into the second luminance data so that the difference between the maximum value and the minimum value of the second luminance data becomes smaller than the difference between the maximum value and the minimum value of the first luminance data; And
And a third step of converting the second luminance data and the color difference data into second digital image data,
Wherein the second step is a step of converting a minimum value of the first luminance data into a minimum value of the second luminance data according to a dark average picture level of the first luminance data, And converting a maximum value of the first luminance data to a maximum value of the second luminance data. 10. The method of claim 9,
The second step comprises:
Analyzing the first luminance data of N (N is a natural number) frame period to generate a histogram of the first luminance data;
Analyzing the histogram to calculate the dark average picture level;
Calculating a minimum value parameter for converting a minimum value of the first luminance data according to the dark average picture level and converting a minimum value of the first luminance data to a minimum value of the second luminance data using the minimum value parameter;
Analyzing the histogram to calculate the bright average image level;
Calculating a maximum value parameter for converting the maximum value of the first brightness data according to the brightness average image level and setting a maximum value of the first brightness data to a maximum value of the second brightness data using the maximum value parameter Converting; And
And converting the first luminance data into the second luminance data using a minimum value and a maximum value of the second luminance data. 10. The method of claim 9,
The second step comprises:
Analyzing the first luminance data of N (N is a natural number) frame period to calculate an average picture level of the first luminance data;
Calculating a peak luminance according to the average picture level;
Calculating an awareness level reduction ratio based on the peak luminance;
Analyzing the first luminance data of the N frame period to generate a histogram of the first luminance data;
Analyzing the histogram to calculate the dark average picture level;
Calculating a minimum value parameter for converting a minimum value of the first luminance data according to the dark average picture level;
Converting a minimum value of the first luminance data into a minimum value of the second luminance data using the minimum value conversion parameter to which the perceptual level reduction ratio is applied to the minimum value parameter;
Analyzing the histogram to calculate the bright average image level;
Calculating a maximum value parameter for converting the maximum value of the first luminance data according to the brightness average picture level;
Converting a maximum value of the first luminance data into a maximum value of the second luminance data using a maximum value conversion parameter to which the perceptual level reduction ratio is applied to the maximum value parameter;
And converting the first luminance data into the second luminance data using a minimum value and a maximum value of the second luminance data. The method according to claim 10 or 11,
Wherein the calculating the dark average picture level comprises:
The first luminance data is represented by Y, the dark function is represented by D (Y), the frequency function representing the frequency according to the first luminance data (Y) is represented by H (Y), the maximum value of the first luminance data is represented by T In other words,
The dark average picture level, APLd,

Lt; / RTI >
The dark function D (Y)

Of the organic light emitting diode display device. The method according to claim 10 or 11,
Wherein the step of calculating the bright average picture level comprises:
(Y), a frequency function representing a frequency in accordance with the first luminance data (Y), a maximum value that the first luminance data can have, T (Y), a brightness function of B In other words,
The bright average image level APLb,

Lt; / RTI >
The bright function B (Y)

Of the organic light emitting diode display device. The method according to claim 10 or 11,
Wherein the converting the first luminance data into the second luminance data comprises:
The first luminance data is Y ', the second luminance data is a minimum value Y'min, the maximum value of the second luminance data is Y'max, the first luminance data (Y) is Y' And the maximum value that can be obtained is T,
The second luminance data Y '

Of the organic light emitting diode display device. 12. The method of claim 11,
The step of calculating the peak luminance includes:
Wherein when the average picture level is higher than a threshold value, the peak luminance is calculated to be lower as the average picture level is higher. 16. The method of claim 15,
The step of calculating the peak luminance includes:
Wherein the peak luminance is calculated as the maximum peak luminance regardless of the average picture level when the average picture level is lower than or equal to the threshold value. 10. The method of claim 9,
A fourth step of converting the second digital image data into an analog data voltage and supplying the analog data voltage to the data lines of the display panel; And
And a fifth step of sequentially supplying gate pulses to the gate lines of the display panel.

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