KR102437168B1 - Image processing circuit and organic emitting diode display device having the same - Google Patents

Abstract

The present invention relates to an image processing circuit capable of improving lifespan without degrading image quality and an organic light emitting diode display having the same. The image processing circuit according to the present invention analyzes input data to determine when a luminance change is recognized, and The blue data included in the signal is gradually reduced until the luminance change is recognized, and the blue data is restored at the luminance change recognition time.

Description

An image processing circuit and an organic light emitting diode display having the same

The present invention relates to an image processing circuit capable of improving lifespan without degrading image quality and an organic light emitting diode display having the same.

A video display device that implements various information on a screen is a key technology in the information and communication era, and is developing in the direction of thinner, lighter, more portable and high-performance. Accordingly, flat panel display devices capable of reducing weight and volume, which are disadvantages of cathode ray tubes (CRTs), are in the spotlight. As such a flat panel display, a liquid crystal display (LCD) using liquid crystal, an OLED display using an organic light emitting diode (hereinafter referred to as OLED), and an electrophoretic display using electrophoretic particles (ElecToPhoretic Display) ; EPD) and the like.

Among them, the OLED display uses an OLED element in which the organic light emitting layer between the anode and the cathode emits light as each sub-pixel, and shows excellent image quality such as excellent contrast ratio characteristics. is gaining popularity as

However, the OLED display device deteriorates with the lapse of driving time due to the self-luminous nature of the OLED element, so that a difference in brightness occurs due to a difference in deterioration between adjacent unit pixels, and a difference in color occurs due to a difference in deterioration between sub-pixels in each unit pixel. do. This difference in brightness and color is perceived by the user as a permanent afterimage, and there is a problem in that the lifespan is also reduced.

SUMMARY OF THE INVENTION The present invention is to solve the above problems, and the present invention is to provide an image processing circuit capable of improving lifespan without degrading image quality and an organic light emitting diode display having the same.

In order to achieve the above object, an image processing circuit and an organic light emitting diode display having the same according to the present invention determine a luminance change recognition time point by analyzing input data, and gradually convert blue data included in the input data to a luminance change recognition time point. , and the blue data is restored when the luminance change is recognized.

In the present invention, the lifespan of the blue sub-pixel can be improved without deterioration in image quality by reducing the blue data to a level that humans cannot perceive, and the lifespan of the blue sub-pixel with the lowest lifespan among the red, green, and blue sub-pixels is improved. Lifespan and power consumption of the LED display device may be improved.

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

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the accompanying drawings.

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

The OLED display shown in FIG. 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, and a timing controller ( 120) is provided.

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 high-state scan pulse for each corresponding scan period of each scan line SL, and supplies a low-state scan pulse for the remaining period in which the scan scan line SL is driven.

The data driver 108 converts digital data from the timing controller 120 into an analog data voltage in response to a data control signal DCS from the timing controller 120 to convert data whenever each scan line SL is driven. It is supplied to the line (DL).

The timing controller 120 uses a plurality of synchronization signals input from a host computer (not shown), that is, a vertical synchronization signal (Vsync), a horizontal synchronization signal (Hsync), a data enable signal, and a dot clock to the data driver 108 . ), a data control signal DCS for controlling the driving timing 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, and a source output enable signal for controlling the output period of the data signal. include The scan control signal SCS includes a scan start pulse and a scan shift clock for controlling scanning of the 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 image data input from the host system and supplies it to the data driver 108 . The image processing circuit 130 changes at least one of red, green, and blue data in consideration of the lifespan of the red, green, and blue pixels and outputs the variable to the data driver 108 .

Meanwhile, although the image processing circuit 130 has been described as being embedded in the timing controller 120 as an example, the image processing circuit 130 may be located between the timing controller 120 and the data driver 108 or located at the input terminal of the timing controller 120 . may be A detailed description of the 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 is composed of red (R), green (G), blue (B), and white (W) sub-pixels. As shown in FIG. 2 , each sub-pixel includes a pixel driving circuit and an organic light emitting diode (OLED).

The pixel driving circuit supplies a data current corresponding to the data signal supplied to the data line DL to the OLED in response to the scan signal supplied to the scan line SL. To this end, the pixel driving circuit includes a switching transistor Tr_S, a driving transistor Tr_D, and a capacitor C. FIG. The switching transistor Tr_S is switched according to the scan signal supplied to the scan line SL and supplies the data signal supplied to the data line DL to the driving transistor Tr_D. The driving transistor Tr_D is switched according to a data signal supplied from the switching transistor Tr_S to control a current flowing from the high potential power VDD to the organic light emitting diode OLED. The capacitor C is connected between the scan terminal of the driving transistor Tr_D and the low potential power VSS to store a voltage corresponding to the data signal supplied to the scan terminal of the driving transistor Tr_S, and use the stored voltage to the driving transistor The turn-on state of (Tr_D) is maintained constant for one frame.

The organic light emitting diode OLED is electrically connected between the source terminal of the driving transistor Tr_D and the low potential power VSS, and emits light according to a current corresponding to a data signal supplied from the driving transistor Tr_D. To this end, the organic light emitting diode 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/hole transport layer/light emitting layer/electron transport layer/electron injection layer and the like.

Accordingly, each of the red (R), green (G), and blue (B) sub-pixels flows from the high potential power VDD to the organic light emitting diode OLED using the switching of the driving transistor Tr_D according to the data signal. A predetermined color is expressed by emitting light from the light emitting layer of the organic light emitting diode (OLED) by controlling the magnitude of the current.

Among these red (R), green (G), and blue (B) sub-pixels, the blue (B) sub-pixel has the lowest luminous efficiency. Accordingly, since the blue (B) sub-pixel needs to be driven more than the other color sub-pixels to achieve the same luminance, the lifespan of the blue (B) sub-pixel is shortened. In this case, when a white image is implemented using the red (R), green (G), and blue (B) sub-pixels, an afterimage of yellow color instead of white is generated. As such, the blue (B) sub-pixel has the shortest lifespan and has the greatest influence on the afterimage. To solve this problem, in the present invention, the lifespan of the blue (B) sub-pixel can be improved by varying the blue (B) data supplied to the short-lived blue sub-pixel to a level that a human cannot perceive.

Accordingly, in the present invention, blue (B) data is varied through the image processing method illustrated in FIG. 4 using the image processing circuit 130 illustrated in FIG. 3 . 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) is provided.

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

The APL storage unit 134 stores the APL of each frame calculated by the APL calculation unit 132 in units of frames.

The luminance 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 there is a luminance change (scene change). That is, when the difference between the APL of the previous frame and the APL of the current frame exceeds the threshold, the luminance change determining unit 136 recognizes the luminance change by performing a scene change (scene A → scene B; scene B scene A → scene C). It is determined that there is a high state recognition signal RecS is generated (step S12). Then, when the difference is within the threshold, the luminance change determining unit 136 determines that the luminance change is not recognized because the scene change is not performed and generates a low-state recognition signal RecS (step S12 ). For example, when the APL of the current frame decreases by exceeding a threshold of 10% compared to the APL of the previous frame, the luminance change determining unit 136 determines that the luminance change has been recognized, and the APL of the current frame is the APL of the previous frame. If it is reduced to less than 10% compared to the APL, it is determined that the luminance change is not recognized. Meanwhile, since the threshold value may vary depending on the characteristics of the display device and the driving environment of the display device, the threshold of 10% is only an example and is not limited thereto.

The data converter 138 changes the luminance of blue data in response to the high and low recognition signals RecS. That is, the data converter 138 reduces the blue data by reflecting the blue weight (gain) to the blue data until the recognition signal RecS in the high state is input in response to the recognition signal RecS in the low state ( step S13). In this case, the data converter 136 gradually or gradually reduces the luminance of the blue data within a level that a human cannot recognize, that is, within a blue data variable limit value. For example, the data conversion unit 136 applies a blue weight applied to the blue data to be less than 1 to reduce the blue data and output (RGB') (step S15), and the blue weight is shown in FIG. 5 as time elapses. As shown in Fig.

Then, the data converter 138 restores the reduced luminance of the blue data to the original luminance (ie, the normal luminance) in response to the high state recognition signal RecS (step S14). Accordingly, the data conversion unit 138 restores and outputs the blue data RGB in response to the high state recognition signal RecS (step S15).

As described above, the present invention detects a scene change and gradually decreases the luminance of blue data when a scene is not changed within a range that a person does not recognize, restores the luminance of blue data during a scene change, and reduces and restores blue data By repeating , the lifespan of the blue sub-pixel, which has a shorter lifespan than the red and green sub-pixels, can be improved without degrading the image quality.

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

The image processing circuit 130 shown in FIG. 6 varies the luminance of blue data by detecting a change in weight. To this end, the image processing circuit 130 shown in FIG. 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 calculator 232 calculates a weight (gain) of blue data corresponding to a driving time (driving amount) of the organic light emitting diode display at regular intervals based on the input data RGB (step S21 ). In particular, the weight calculator 232 calculates a falling weight that gradually decreases as shown in FIG. 8 as time elapses in response to the low state recognition signal RecS. In addition, the weight calculator 232 calculates a rising weight that gradually or gradually increases as time elapses in response to the high state recognition signal RecS.

The memory 234 stores the lowest weight. On the other hand, since the human eye does not recognize a color difference (Δu'v') of 0.02 or less, the lowest weight is set based on 0.02, which is the perceptual limit color difference (Δu'v'). For example, the lowest weight is set to less than 0.85. Meanwhile, 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 less than 0.85 is only an example and 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 there is a luminance change (step S22 ). That is, when the falling weight calculated by the weight calculation unit 232 and the lowest weight stored in the memory 234 are the same, the luminance change determining unit 236 determines that the luminance decrease change is recognized, and thus a high state recognition signal RecS ) is generated (step S12). Then, when the falling weight calculated by the weight calculator 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 a low state recognition signal RecS. do.

The data converter 238 changes the luminance of blue data in response to the recognition signal RecS in the high and low states.

That is, the data converter 238 reduces the blue data by applying a falling weight to the blue data in response to the low state recognition signal RecS. Accordingly, the data converter 238 gradually reduces the luminance of the blue data from the original luminance (ie, normal luminance) to a level that is not recognized by humans in response to the high state recognition signal RecS (step S23). output (RGB') (step S25).

In addition, the data converter 238 restores the lowered blue data by applying a rising weight to the blue data in response to the high state recognition signal Recs. Accordingly, the data converter 138 gradually restores the luminance of the blue data until the luminance of the blue data becomes the original luminance (ie, the normal luminance) in response to the low-state recognition signal RecS (step S24) and outputs (RGB) (RGB). ") (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 FIG. 8. For example, n The data down-conversion period T1 and the data up-conversion period T2 may be repeated for every (n, 2n, 3n...)-th frame (where n is a natural number greater than 2).

As described above, the present invention detects a change in weight and repeatedly reduces and restores the luminance of blue data to a level that a human cannot recognize, so that the lifespan and power consumption of the blue sub-pixel can be improved.

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

As shown in FIG. 9 , it can be seen that even if the luminance of the blue data is lowered to a level that a human cannot perceive by applying a weight to the blue data, the image quality is not deteriorated. In this way, when the image is realized without deterioration of image quality by reducing the blue data, it can be seen that the ratio of current consumption occupied by the blue sub-pixel among all the sub-pixels including the red, green, and blue sub-pixels is lowered as shown in Table 1.

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

Accordingly, in the present invention, the lifespan of the blue sub-pixel is improved, and the lifespan of the blue sub-pixel, which has a shorter lifespan compared to the red and green sub-pixels, is improved, thereby improving the lifespan and power consumption of the organic light emitting diode display.

Meanwhile, in the present invention, only the blue data supplied to the blue sub-pixel, which has a lower lifespan compared to the red and green sub-pixels, is changed as an example. A different weight may be applied to data supplied to the blue sub-pixel. For example, when the lifespan characteristics are 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-pixel at a level not recognized by humans Set the weight (gain; less than 1) higher in the order of blue data.

The above description is merely illustrative of the present invention, and various modifications may be made by those of ordinary skill in the art to which the present invention pertains without departing from the technical spirit of the present invention. Therefore, the embodiments disclosed in the specification of the present invention do not limit the present invention. The scope of the present invention should be interpreted by the following claims, and all technologies within the scope equivalent thereto should be construed as being included in the scope of the present invention.

130: image processing circuit 131: APL calculator
232: weight calculation unit 136,236: luminance change determination unit
138,238: data conversion unit

Claims (8)

a luminance change determination unit that analyzes the input data to determine when a luminance change according to a scene change is recognized;
Image processing comprising a data converter configured to gradually reduce the luminance of blue data within a range that a person cannot recognize when a scene is not changed according to the input data, and to restore the blue data at a point in time when the luminance change is recognized when a scene is changed Circuit. The method of claim 1,
and an average image level calculation unit for calculating an average image level of the input data,
The luminance change determining unit is an image processing circuit for determining whether to change a scene by comparing an average image level of a previous frame with an average image level of a current frame. 3. The method of claim 2,
When the difference between the average image level of the previous frame and the average image level of the current frame is within a threshold, the data converter applies a weight less than 1 to the blue data to gradually reduce the blue data,
The data conversion unit restores the blue data when a difference between the average image level of the previous frame and the average image level of the current frame exceeds a threshold. 4. The method of claim 3,
The data conversion unit gradually reduces the blue data when the average image level of the current frame is reduced within 10% compared to the average image level of the previous frame,
The data converter restores the blue data when the average image level of the current frame is reduced by more than 10% compared to the average image level of the previous frame. a weight calculator for calculating a weight of blue data corresponding to a driving time of the device at regular intervals based on the input data;
a luminance change determining unit that compares the weight calculated by the weight calculating unit with a preset minimum weight to determine whether there is a luminance change;
and a data converter configured to gradually decrease the luminance of the blue data within a range that a human cannot perceive or to restore the blue data according to a comparison result between the calculated weight and the preset minimum weight. 6. The method of claim 5,
The data conversion unit gradually decreases the blue data when the calculated weight and the lowest weight are different,
The data converter is an image processing circuit that gradually restores the blue data when the calculated weight and the lowest weight are the same. 7. The method of claim 6,
wherein the lowest weight is less than 0.85. The image processing circuit according to any one of claims 1 to 7;
a display panel for displaying the image supplied from the image processing circuit;
and a panel driver driving the display panel so that the image supplied from the image processing circuit is displayed on the display panel.

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