KR20170077386A - Image processing circuit and organic emitting diode display device having the same - Google Patents

Abstract

The present invention relates to an image processing circuit and an organic light emitting diode display device having the same, which can improve lifetime without deterioration in image quality. An image processing circuit according to the present invention analyzes input data to determine a time of luminance change, And gradually restores the blue data at the time when the luminance is changed.

Description

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

The present invention relates to an image processing circuit capable of improving the lifetime without deterioration of image quality and an organic light emitting diode display device having the image processing circuit.

The image display device that realizes various information on the screen is a core technology of the information communication age and it is becoming thinner, lighter, more portable and higher performance. Accordingly, a flat panel display device capable of reducing weight and volume, which is a disadvantage of a cathode ray tube (CRT), has attracted attention. Examples of such flat panel display devices include a liquid crystal display (LCD) using liquid crystal, an OLED display using an organic light emitting diode (OLED), an electrophoretic display using an electrophoretic particle ; EPD).

Among them, the OLED display uses an OLED element, which is self-emitting by the organic light emitting layer between the anode and the cathode, as each subpixel, and shows excellent image quality such as excellent contrast ratio characteristics. .

However, due to the self-emission characteristics of the OLED device, the OLED display device is deteriorated as the driving time elapses, so that a difference in brightness is caused by a deterioration difference between adjacent unit pixels, and a color difference occurs due to a deterioration difference between sub- do. Such a difference in brightness and color is perceived by the user and is perceived as a permanent afterimage, and the lifetime is also deteriorated.

An object of the present invention is to provide an image processing circuit and an organic light emitting diode display device having the image processing circuit, which can improve the lifetime without lowering the image quality.

In order to achieve the above object, an image processing circuit and an organic light emitting diode display device having the image processing circuit according to the present invention are characterized by analyzing input data to determine a luminance change time point, And restores the blue data at the time of the change in luminance.

According to the present invention, the blue data is reduced to a level that is not perceived by a human, thereby improving the lifetime of the blue sub-pixel without lowering the image quality and improving the lifetime of the blue sub-pixel having the shortest life time among the red, The lifetime and power consumption of the light emitting diode display device can be improved.

1 is a block diagram showing an organic light emitting diode display device according to the present invention.
2 is a view showing each sub-pixel of the display panel shown in Fig.
3 is a block diagram specifically showing a first embodiment of the image processing circuit shown in FIG.
4 is a flowchart illustrating an image processing method using the image processing circuit shown in FIG.
5 is a view for explaining a weight applied to blue data in the image processing circuit shown in Fig.
6 is a block diagram specifically showing a second embodiment of the image processing circuit shown in FIG.
7 is a flowchart for explaining an image processing method using the image processing circuit shown in FIG.
8 is a diagram for explaining a weight applied to blue data in the image processing circuit shown in Fig.
9 is a diagram illustrating an image simulation result according to a weight of blue data according to the present invention.

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

1 is a block diagram illustrating an OLED display having an image processing circuit 130 according to the present invention.

1 includes a display panel 100, a panel driver including a data driver 108 and a scan driver 106 for driving the display panel 100, a timing controller (not shown) for controlling the panel driver, 120).

The scan driver 106 sequentially drives the scan lines SL of the display panel 100 in response to a scan control signal from the timing controller 120. The scan driver 106 supplies a scan pulse in a high state for each scan period of each scan line SL and a scan pulse in a low state during a remaining period in which the scan scan line SL is driven.

The data driver 108 converts the digital data from the timing controller 120 into an analog data voltage in response to the data control signal DCS from the timing controller 120 so that data Line DL.

The timing controller 120 is connected to the data driver 108 (not shown) using a plurality of synchronizing signals input from a host computer (not shown), that is, a vertical synchronizing signal Vsync, a horizontal synchronizing signal Hsync, A data control signal DCS for controlling the driving timing of the scan driver 106 and a scan control signal SCS for controlling the driving timing of the scan driver 106 are generated. The timing controller 120 outputs the generated data control signal DCS and the scan control signal SCS to the data driver 108 and the scan driver 106, respectively. The data control signal DCS includes a source start pulse and a source sampling clock for controlling the latch of the data signal, a polarity control signal for controlling the polarity of the data signal, a source output enable signal for controlling the output period of the data signal, . The scan control signal SCS includes a scan start pulse and a scan shift clock for controlling scanning of a scan signal, and a scan output enable signal for controlling an output period of the scan signal.

The image processing circuit 130 of the timing controller 120 processes the image data input from the host system and supplies the image data to the data driver 108. The image processing circuit 130 varies at least one of the red, green, and blue data in consideration of the lifetime of the red, green, and blue pixels, and outputs the resulting data to the data driver 108.

The image processing circuit 130 is included in the timing controller 120. The image processing circuit 130 may be disposed between the timing controller 120 and the data driver 108 or may be located at the input end of the timing controller 120. [ It is possible. A detailed description of this image processing circuit 130 will be described later.

The display panel 100 displays an image through unit pixels arranged in a matrix form. The unit pixel is composed of red (R), green (G) and blue (B) sub pixels or red (R), green (G), blue (B) and white (W) sub pixels. Each sub-pixel has a pixel driving circuit and an organic light emitting element OLED, as shown in Fig.

The pixel driving circuit supplies a data current corresponding to a data signal supplied to the data line DL to the organic light emitting diode OLED in response to a scan signal supplied to the scan line SL. To this end, the pixel driver circuit includes a switching transistor Tr_S, a driving transistor Tr_D, and a capacitor C. The switching transistor Tr_S is switched according to a scan signal supplied to the scan line SL to supply a data signal to the data line DL to the drive transistor Tr_D. The driving transistor Tr_D is switched in accordance with the data signal supplied from the switching transistor Tr_S to control the current flowing from the high potential power supply VDD to the organic light emitting element OLED. The capacitor C is connected between the scan terminal of the drive transistor Tr_D and the low potential power supply VSS and stores a voltage corresponding to the data signal supplied to the scan terminal of the drive transistor Tr_S, (Tr_D) is kept constant for one frame.

The organic light emitting element OLED is electrically connected between the source terminal of the driving transistor Tr_D and the low potential power supply VSS and emits light by a current corresponding to the data signal supplied from the driving transistor Tr_D. To this end, the organic light emitting device OLED includes an anode electrode connected to the source terminal of the driving transistor Tr_D, an organic layer formed on the anode electrode, and a cathode electrode formed on the organic layer. Here, the organic layer may include a hole injection layer / a hole transporting layer / a light emitting layer / an electron transporting layer / an electron injection layer.

Thus, each of the red (R), green (G) and blue (B) sub-pixels is driven by the switching of the driving transistor Tr_D in accordance with the data signal to flow from the high potential power source VDD to the organic light emitting element OLED A predetermined color is expressed by controlling the magnitude of the current to cause the light emitting layer of the organic light emitting element OLED to emit light.

Among these red (R), green (G) and blue (B) sub-pixels, the luminous efficiency of the blue (B) sub-pixel is the lowest. Thus, the blue (B) sub-pixel has to be driven further than the other sub-pixels in order to achieve the same luminance, so that the lifetime of the blue (B) sub-pixel is shortened. In this case, when a white image is implemented using red (R), green (G), and blue (B) sub-pixels, a residual image with a yellow color rather than white is generated. As described above, the blue (B) sub-pixel has the shortest lifetime and the greatest influence on the afterimage. In order to solve this problem, in the present invention, the lifetime of the blue (B) sub-pixel can be improved by changing the blue (B) data supplied to the blue sub-pixel having a short life span to a level not recognized by a human.

Accordingly, in the present invention, blue (B) data is varied through the image processing method shown in FIG. 4 using the image processing circuit 130 shown in FIG. 3 includes an average picture level (APL) calculation unit 132, an APL storage unit 134, a luminance change determination unit 136, and a data conversion unit 138).

The APL calculation unit 132 calculates the APL every frame of the input image (step S11). The APL is an average brightness value for pixel data of one frame. The higher the APL, the brighter the image. The lower the APL, the darker the image.

The APL storage unit 134 stores the APL of each frame calculated from the APL calculation unit 132 on a frame-by-frame basis.

The brightness change determination unit 136 compares the APL of the previous frame stored in the APL storage unit 134 with the APL of the current frame calculated by the APL calculation unit 132 to determine whether the brightness is changed (scene change). That is, when the difference between the APL of the previous frame and the APL of the current frame exceeds the threshold value, the luminance change determining unit 136 determines that the scene change (scene A → scene B → scene B scene A → scene C) And generates a high acknowledge signal RecS (step S12). When the difference is within the threshold value, the luminance change determining unit 136 determines that the scene change is not performed and the luminance change is not recognized, and generates a low acknowledge signal RecS in step S12. For example, when the APL of the current frame is decreased by more than a threshold value of 10% compared to the APL of the previous frame, the luminance change determining unit 136 determines that the luminance change is recognized, It is judged that the change in luminance is not recognized when it is reduced to 10% or less with respect to APL. On the other hand, since the threshold value may vary depending on the characteristics of the display device and the driving environment of the display device, the threshold value of 10% is only an example and is not limited thereto.

The data converter 138 varies the brightness of the blue data in response to the acknowledge signal RecS in the high and low states. That is, in response to the acknowledge signal RecS in the low state, the data converter 138 reduces the blue data by reflecting the blue weight (gain) in the blue data until the acknowledge signal RecS in the high state is input S13). At this time, the data conversion unit 136 gradually or gradually reduces the luminance of the blue data within a level that the human can not recognize, that is, within the blue data variable limit. For example, the data conversion unit 136 reduces the blue data by applying a blue weight value applied to the blue data to be smaller than 1 (step S15), and the blue weight value is output as shown in FIG. 5 As shown in Fig.

Then, the data converter 138 restores the luminance of the reduced blue data to the original luminance (i.e., the normal luminance) in response to the acknowledge signal RecS in the high state (S14). Accordingly, the data converter 138 restores and outputs (RGB) the blue data in response to the acknowledge signal RecS in the high state (S15).

As described above, according to the present invention, the scene change is detected, the luminance of the blue data is gradually reduced within a range in which the luminance of the blue data can not be perceived by the person when the scene is not switched, the luminance of the blue data is restored at the time of scene change, It is possible to improve the lifetime of the blue sub-pixel whose lifespan is shorter than that of the red and green sub-pixels without lowering the image quality.

FIG. 6 is a block diagram showing an image processing circuit according to a second embodiment of the present invention, and FIG. 7 is a flowchart for explaining an image processing method using the image processing circuit shown in FIG.

The image processing circuit 130 shown in FIG. 6 changes the brightness of the blue data by sensing a weight change. 6 includes a weight calculation unit 232, a memory unit 234, a luminance change determination unit 236, and a data conversion unit 238. The weight calculation unit 232,

The weight calculation unit 232 calculates the weight (gain) of the blue data corresponding to the driving time (driving amount) of the organic light emitting display device every predetermined period based on the input data RGB (step S21). In particular, the weight calculation unit 232 calculates a falling weight that gradually decreases as time elapses in response to the acknowledge signal RecS in the low state. Then, the weight calculation unit 232 calculates a rising weight that increases stepwise or gradually with the lapse of time in response to the acknowledge signal RecS in the high state.

The memory 234 stores the lowest weight. On the other hand, since the human eye can not recognize the color difference (u u 'v') of 0.02 or less, the lowest weight is set based on 0.02, which is the perceived limit color difference (u u 'v'). For example, the lowest weight is set to less than 0.85. On the other hand, since the lowest weight may vary depending on the characteristics of the display device and the driving environment of the display device, the lowest weight value of less than 0.85 is only an example, but is not limited thereto.

The luminance change determining unit 136 compares the falling weight calculated by the weight calculating unit 232 with the lowest weight stored in the memory 234 to determine whether the luminance is changed or not (S22). That is, when the falling weight calculated by the weight calculating unit 232 is equal to the lowest weight stored in the memory 234, the luminance change determining unit 236 determines that the luminance decrease change is recognized, (Step S12). When the falling weight calculated by the weight calculating unit 232 is higher than the lowest weight stored in the memory 234, the luminance change determining unit determines that the luminance decrease change is not recognized and generates the low state acknowledge signal RecS do.

The data converter 238 varies the brightness of the blue data in response to the acknowledge signal RecS in the high and low states.

That is, the data converter 238 reduces the blue data by applying the falling weight to the blue data in response to the acknowledge signal RecS in the low state. Accordingly, the data converter 238 gradually decreases the luminance of the blue data from the original luminance (i.e., normal luminance) to a level that the human can not perceive in response to the acknowledge signal RecS in the high state (step S23) (RGB ') (S25).

Then, the data converter 238 applies a rising weight to the blue data in response to the acknowledge signal Recs in the high state to restore the lowered blue data. Accordingly, the data converter 138 gradually restores the luminance of the blue data until the luminance of the blue data becomes the original luminance (i.e., the normal luminance) in response to the acknowledge signal RecS in the low state (step S24) (Step S25). Meanwhile, the data down conversion period T1 to which the falling weight is applied and the data up conversion period T2 to which the rising weight is applied are the same as shown in Figure 8. For example, when n The data down conversion period T1 and the data up conversion period T2 can be repeated for every (n, 2n, 3n) th frame (where n is a natural number greater than 2).

As described above, according to the present invention, the brightness of the blue data is detected by detecting a change in weight, and the brightness of the blue data is reduced and restored to a level that the human can not perceive. Thus, the lifetime and the power consumption of the blue sub-pixel can be improved.

9 is an image simulation result according to the blue data weight according to the present invention.

As shown in FIG. 9, even if the brightness of the blue data is lowered to a level that the human being can not recognize by applying the weight to the blue data, the image quality is not deteriorated. As shown in Table 1, when the blue data is lowered to realize an image without degrading the image quality, the consumption current ratio occupied by the blue sub-pixels in all the sub-pixels including red, green, and blue sub-pixels is lowered.

Blue weight One 0.90 0.90 0.85 Current Consumption (Blue / Total) 7% 5% 4% 3%

Accordingly, the lifetime of the blue sub-pixel is improved, and the lifetime and the power consumption of the organic light emitting display device are improved by improving the lifetime of the blue sub-pixel having a lower life than the red and green sub-pixels.

Meanwhile, in the present invention, only the blue data to be supplied to the blue sub-pixels having a shorter lifetime than that of the red and green sub-pixels has been described as an example. However, the red, green, and blue sub- The weights may be applied to the data supplied to the blue sub-pixels differently. For example, when the lifetime characteristic is good in the order of green, red and blue sub-pixels, green data supplied to the green sub-pixel, red data supplied to the red sub-pixel, and blue data supplied to the blue sub- Set the weight (gain: less than 1) higher in blue data order.

The foregoing description is merely illustrative of the present invention, and various modifications may be made by those skilled in the art without departing from the spirit of the present invention. Accordingly, the embodiments disclosed in the specification of the present invention are not intended to limit the present invention. The scope of the present invention should be construed according to the following claims, and all the techniques within the scope of equivalents should be construed as being included in the scope of the present invention.

130: image processing circuit 131: APL calculation unit
232: Weight calculation unit 136, 236:
138, 238:

Claims (8)

A brightness change determination unit for determining input brightness data by analyzing input data;
And a data conversion unit for gradually reducing the blue data included in the input data until the luminance change is detected and restoring the blue data at the time of the change in luminance. The method according to claim 1,
And an average image level calculator for calculating an average image level of the input image,
Wherein the luminance change determination unit compares an average picture level of a previous frame with an average picture level of a current frame to determine whether or not a scene change occurs. 3. The method of claim 2,
Wherein the data conversion unit gradually reduces the blue data by applying a weight smaller than 1 to the blue data when the difference between the average picture level of the previous frame and the average picture level of the current frame is within a threshold value,
Wherein the data conversion unit restores the blue data when a difference between an average picture level of the previous frame and an average picture level of the current frame exceeds a threshold value. The method of claim 3,
Wherein the data conversion unit gradually decreases the blue data when the average picture level of the current frame is reduced to within 10% of the average picture level of the previous frame,
Wherein the data conversion unit restores the blue data when the average picture level of the current frame is decreased by more than 10% with respect to the average picture level of the previous frame. The method according to claim 1,
The image processing circuit
And a weight setting unit for calculating a weight of the input image,
Wherein the luminance change determination unit determines whether the lowest weight is equal to the calculated weight. 6. The method of claim 5,
Wherein the data conversion unit gradually decreases the blue data if the calculated weight and the lowest weight are different,
Wherein the data conversion unit gradually restores the blue data when the calculated weight is equal to the lowest weight. The method according to claim 6,
Wherein the lowest weight is less than 0.85. An image processing circuit according to any one of claims 1 to 7;
A display panel for displaying an image supplied from the image processing circuit;
And a panel driver for driving the display panel so that an image supplied from the image processing circuit is displayed on the display panel.

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