Patent Publication Number: US-11663966-B2

Title: Degradation compensation device and display device including the same

Description:
This application claims priority to Korean Patent Application No. 10-2019-0019840, filed on Feb. 20, 2019, and all the benefits accruing therefrom under 35 U.S.C. § 119, the content of which in its entirety is herein incorporated by reference. 
     BACKGROUND 
     1. Field 
     Embodiments of the invention relate to a degradation compensation device and a display device including the degradation compensation device. 
     2. Description of the Related Art 
     An organic light emitting diode display includes an organic light emitting diode for controlling a luminance by a current or a voltage and a thin film transistor driving the organic light emitting diode. 
     In such an organic light emitting diode display, a pixel may be degraded by a degradation of the organic light emitting diode and the thin film transistor. Even if a same voltage is applied to the pixel, the current flowing through the pixel decreases due to the degradation of the organic light emitting diode and the thin film transistor, thereby deteriorating the luminance of the pixel. 
     The display device may update the accumulated usage time of the pixel and compensates for the degradation of the pixel by compensating for the grayscale value corresponding to the pixel based on the accumulated usage time. 
     SUMMARY 
     Recently, a display device includes an optical sensor to sense a light penetrated through a display panel, and the display panel may have a partially different resolution to improve the sensitivity of the optical sensor. 
     In such a display device, a relatively high current may be provided to a pixel in a relatively low resolution region to compensate for the difference in the luminance due to the difference in the resolution. However, the degradation of the pixel in a relatively low resolution region may be accelerated, and the degradation compensation may not be properly performed. 
     An exemplary embodiment of the invention provides a degradation compensation device and a display device including the degradation compensation device that effectively compensates for a degradation of pixels in the display panel having partially different resolutions. 
     An exemplary embodiment of a display device according to the invention includes a display unit including a first pixel disposed in a first region and a second pixel disposed in a second region different from the first region; a degradation compensator which generates a first compensated grayscale value by compensating for a first grayscale value for the first pixel based on a first degradation curve, and generates a second compensated grayscale value by compensating for a second grayscale value for the second pixel based on a second degradation curve, wherein the first degradation curve defines a luminance reduction rate according to a first accumulated usage time of the first pixel, and the second degradation curve defines a luminance reduction rate according to a second accumulated usage time of the second pixel; and a data driver which generates a first data signal based on the first compensated grayscale value to supply the first data signal to the first pixel, and generates a second data signal based on the second compensated grayscale value to supply the second data signal to the second pixel, where a light transmittance of the second region is greater than a light transmittance of the first region. 
     According to an exemplary embodiment of the invention, the display unit may include a transmissive region between the second pixel and an adjacent pixel in the second region, the transmissive region may transmit at least a portion of incident light, the adjacent pixel may be disposed adjacent to the second pixel in the second region, and a resolution of the second region may be lower than a resolution of the first region. 
     According to an exemplary embodiment of the invention, the display device may further include an optical sensor disposed to overlap the second region of the display unit, where the optical sensor senses light transmitted to the second region. 
     According to an exemplary embodiment of the invention, a voltage level of the first data signal may be different from a voltage level of the second data signal when the first grayscale value and the second grayscale value are the same, and a difference between a voltage level of the first data signal and a voltage level of the second data signal increases as the first accumulated usage time or the second accumulated usage time increases when the first accumulated usage time and the second accumulated usage time are equal to each other. 
     According to an exemplary embodiment of the invention, each of the first pixel and the second pixel may include a transistor and a light emitting element connected to the transistor to receive a driving current through the transistor, and a second driving current flowing in the second pixel corresponding to the second data signal may be greater than a first driving current flowing in the first pixel corresponding to the first data signal when the first grayscale value and the second grayscale value are equal to each other. 
     According to an exemplary embodiment of the invention, the degradation compensator may compensate for a first grayscale value using a first lookup table and compensate for a second grayscale value using a second lookup table, the first lookup table may include a first grayscale compensation value corresponding to the first accumulated usage time based on the first degradation curve, and the second lookup table may include a second grayscale compensation value corresponding to the second accumulated usage time based on the second degradation curve. 
     According to an exemplary embodiment of the invention, a second degradation acceleration factor, which refers to a slope of a tangent with respect to the second degradation curve, may be greater than a first degradation acceleration factor, which refers to a slope of a tangent with respect to the first degradation curve. 
     According to an exemplary embodiment of the invention, the degradation compensator may include an accumulator which calculates the first accumulated usage time by accumulating the first compensated grayscale value and calculates the second accumulated usage time by accumulating the second compensated grayscale value; a memory which stores the first and second accumulated usage times and the first and second lookup tables; and a compensator which obtains the first grayscale compensation value based on the first accumulated usage time and the first lookup table to compensate for the first grayscale value and obtains the second grayscale compensation value based on the second accumulated usage time and the second lookup table to compensate for the second grayscale value. 
     According to an exemplary embodiment of the invention, when the first grayscale value and the second grayscale value are equal to each other during a reference time, a change in the second accumulated usage time may be greater than a change in the first accumulated usage time during the reference time. 
     According to an exemplary embodiment of the invention, the first grayscale value and the second grayscale value may be included in an image data, and the compensator may include a selector which selects the first lookup table based on position information of the first grayscale value in the image data and selects the second lookup table based on position information of the second grayscale value in the image data; and a calculator which calculates the first compensated grayscale value by adding the first grayscale compensation value obtained from the first lookup table to the first grayscale value and calculates the second compensated grayscale value by adding the second grayscale compensation value obtained from the second lookup table to the second grayscale value. 
     According to an exemplary embodiment of the invention, the second pixel may include a plurality of sub-pixels which emit light of different colors from each other, and the second lookup table includes sub-lookup tables corresponding to degradation curves of the plurality of sub-pixels, respectively. 
     According to an exemplary embodiment of the invention, the second lookup table may be set for a representative grayscale value, the representative grayscale value is a grayscale value within a grayscale range of the second grayscale value, the degradation compensator may compensate for the second grayscale value based on a grayscale factor, and the grayscale factor may be a degradation compensation ratio set based on the representative grayscale value. 
     According to an exemplary embodiment of the invention, the degradation compensator may further include a first factor lookup table including the grayscale factor set for each grayscale value. 
     According to an exemplary embodiment of the invention, the second lookup table may include a plurality of sub-lookup tables for a plurality of representative grayscale values, and the degradation compensator may select first and second sub-lookup tables from the sub-lookup tables corresponding to a first and second representative grayscale values adjacent to the second grayscale value of the representative grayscale values from the sub-lookup tables, obtain a grayscale compensation value from each of the first and second sub-lookup tables based on the second accumulated usage time, and calculate the second grayscale compensation value by interpolating a grayscale compensation value obtained from the first sub-lookup table and a grayscale compensation value obtained from the second sub-lookup table. 
     According to an exemplary embodiment of the invention, the degradation compensator may determine a temperature factor based on temperature information received from an outside and compensate for the second grayscale value based on the temperature factor. 
     According to an exemplary embodiment of the invention, the degradation compensator may further include a second factor lookup table including the temperature factor set by temperature. 
     According to an exemplary embodiment of the invention, the second lookup table may include a plurality of sub-lookup tables set by temperature, and the degradation compensator may select one of the sub-lookup tables based on temperature information received from an outside and obtain the second grayscale compensation value from the selected one of the sub-lookup tables based on the second accumulated usage time. 
     According to an exemplary embodiment of the invention, the first pixel and the second pixel may have a same pixel structure as each other, and the second region may have a same luminance as a luminance of the first region. 
     An exemplary embodiment of a degradation compensation device according to the invention includes an accumulator which calculates a first accumulated grayscale value by accumulating a first grayscale value of an image data for a pixel in a first region and calculates a second accumulated grayscale value by accumulating a second grayscale values of the image data for a pixel in a second region; a storage unit which stores a first lookup table including a first grayscale compensation value corresponding to the first accumulated grayscale value and a second lookup table including a second grayscale compensation value corresponding to the second accumulated grayscale value; and a compensator that compensates for the first grayscale value based on the first lookup table and compensates for the second grayscale value based on the second lookup table, where the first grayscale value and the second grayscale value correspond to a same color as each other. 
     According to an exemplary embodiment of the invention, when the first grayscale value and the second grayscale value are equal to each other during a reference time, a change in the second accumulated grayscale value may be greater than a change in the first accumulated grayscale value during the reference time. 
     In exemplary embodiment, a degradation compensation device and a display device including the degradation compensation device may compensate for a degradation of a pixel more accurately by performing degradation compensation for pixels disposed in regions having relatively different resolutions by using independent degradation curves of which degradation acceleration factors are different from each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features of exemplary embodiments of the invention will become readily apparent by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which: 
         FIG.  1    is a perspective view of a display device according to an exemplary embodiment of the invention; 
         FIG.  2    is a cross-sectional view taken along line I-I′ of  FIG.  1    illustrating an exemplary embodiment of a display device; 
         FIG.  3    is a block diagram for illustrating an exemplary embodiment of a display panel included in a display device of  FIG.  2   ; 
         FIG.  4    is a drawing for illustrating an exemplary embodiment of pixels disposed in a sensing region of  FIG.  3   ; 
         FIG.  5    is a waveform diagram for illustrating an exemplary embodiment of a data signal applied to pixels of  FIG.  4   ; 
         FIG.  6    is a graph illustrating a degradation characteristic of pixels of  FIG.  4   ; 
         FIG.  7    is a circuit diagram for illustrating an exemplary embodiment of a pixel of  FIG.  4   ; 
         FIG.  8    is a block diagram for illustrating an exemplary embodiment of a degradation compensator included in a display panel of  FIG.  3   ; 
         FIGS.  9 A and  9 B  are graphs illustrating a degradation characteristic of each pixel of  FIG.  4   ; 
         FIGS.  10 A and  10 B  are block diagrams for illustrating an alternative exemplary embodiment of a degradation compensator included in a display panel of  FIG.  3   ; 
         FIG.  11    is a graph illustrating an exemplary embodiment of a grayscale factor used in a degradation compensator of  FIG.  10 A ; 
         FIGS.  12 A and  12 B  are is a block diagram for illustrating another alternative exemplary embodiment of a degradation compensator included in a display panel of  FIG.  3   ; and 
         FIG.  13    is a graph illustrating an exemplary embodiment of a temperature factor used in a degradation compensator of  FIG.  12 A . 
     
    
    
     DETAILED DESCRIPTION 
     The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. This invention may, however, be embodied in many different forms, and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout. 
     It will be understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present. 
     It will be understood that, although the terms “first,” “second,” “third” etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, “a first element,” “component,” “region,” “layer” or “section” discussed below could be termed a second element, component, region, layer or section without departing from the teachings herein. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms, including “at least one,” unless the content clearly indicates otherwise. “Or” means “and/or.” As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. 
     Furthermore, relative terms, such as “lower” or “bottom” and “upper” or “top,” may be used herein to describe one element&#39;s relationship to another element as illustrated in the Figures. It will be understood that relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. For example, if the device in one of the figures is turned over, elements described as being on the “lower” side of other elements would then be oriented on “upper” sides of the other elements. The exemplary term “lower,” can therefore, encompasses both an orientation of “lower” and “upper,” depending on the particular orientation of the figure. Similarly, if the device in one of the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. The exemplary terms “below” or “beneath” can, therefore, encompass both an orientation of above and below. 
     “About” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system). For example, “about” can mean within one or more standard deviations, or within ±30%, 20%, 10%, 5% of the stated value. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Exemplary embodiments are described herein with reference to cross section illustrations that are schematic illustrations of idealized to embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments described herein should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region illustrated or described as flat may, typically, have rough and/or nonlinear features. Moreover, sharp angles that are illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the present claims. 
     Hereinafter, exemplary embodiments of the invention will be described in detail with reference to the accompanying drawings. 
       FIG.  1    is a perspective view of a display device according to an exemplary embodiment of the invention. 
     Referring to  FIG.  1   , an exemplary embodiment of a display device DD includes a display region DA and a non-display region NDA. The display region DA and the non-display region NDA may be defined on a surface (or a display surface) of the display device DD. The display region DA may be a region where an image is displayed, and the non-display region NDA may be disposed along a boundary of the display region DA, but not being limited thereto. In one exemplary embodiment, for example, the non-display region NDA may be disposed at one side of the display region DA. 
     In an exemplary embodiment, the display region DA may include a sensing region SA and a non-sensing region NSA. The display device DD may not only display an image but also detect light incident from outside (e.g., a front) through the sensing region SA. The non-sensing region NSA may surround the sensing region SA, but not being limited thereto. The sensing region SA has a circular planar shape and is disposed close to one side in the display region DA in  FIG.  1   , but not being limited thereto. The shape, size and disposition of the sensing region SA may be variously modified according to a sensor described later. 
       FIG.  2    is a cross-sectional view taken along a line I-I′ of  FIG.  1    for illustrating an exemplary embodiment of a display device. 
     Hereinafter, a direction perpendicular to a display surface, on which an image is displayed, is defined as an upper direction, and a direction opposite to the upper direction is defined as a lower direction in the display device DD. An exemplary embodiment of the display device DD will hereinafter be described in greater detail. 
     Referring to  FIGS.  1  and  2   , an exemplary embodiment of the display device DD may include a display panel DP, a polarizer POL, a black matrix BM, a window WD and an optical sensor OS. 
     The display panel DP may display an image based on image data supplied from the outside. In one exemplary embodiment, for example, the display panel DP may be an organic light emitting diode display panel including an organic light emitting diode, but not being limited thereto. 
     The polarizer POL may be disposed on the display panel DP and may restrain light incident thereto from an outside from being reflected to the outside by polarizing light incident from the outside. In such an embodiment, the polarizer POL may perform antireflection function and effectively prevent the visibility of the display panel DP from being degraded by the light incident from the outside. 
     The window WD may be disposed above the polarizer POL and may protect a structure therebelow (e.g., the display panel DP) from external impacts. The window WD may be attached to the polarizer POL by an optical clear adhesive OCA. 
     The black matrix BM may be disposed between the window WD and the display panel DP in the non-display region NDA. The black matrix BM may absorb light incident from the outside and prevent a structure therebelow (e.g., display panel DP) disposed in the non-display region NDA from being viewed from the outside. 
     The optical sensor OS may be disposed under the display panel DP in the sensing region SA. The optical sensor OS may sense the light RAY transmitted through the sensing region SA of the display panel DP. In one exemplary embodiment, for example, the optical sensor OS may be implemented as an infrared sensor and sense infrared light (i.e., light in the infrared wavelength band) transmitted through the sensing region SA of the display panel DP. The light sensed by the optical sensor OS may be used to authenticate the user&#39;s biometric information (e.g., iris, fingerprint, etc.). 
     In an exemplary embodiment of the invention, a transmittance (i.e., light transmittance or transmittance of light) in the sensing region SA of the display panel DP may be greater than a transmittance in the non-sensing region NSA. In one exemplary embodiment, for example, the sensing region SA of the display panel DP may include a transmissive region (or a transparent region) for transmitting light and thus a resolution (or pixel density) in the sensing region of the display panel DP may be lower than a resolution in the non-sensing region NSA. The resolution of the sensing region SA will be described later in greater detail with reference to  FIG.  4   . 
     In such an embodiment, where the resolution of the sensing region SA is lower than the resolution of the non-sensing region NSA, a current flowing through a pixel in the sensing region SA may be greater than a current flowing through a pixel in the non-sensing region NSA to display an image with a uniform luminance, such that the pixel in the sensing region SA may be degraded faster than the pixel in the non-sensing region NSA, and a degradation characteristic of the pixel in the sensing region SA may be different from a degradation characteristic of the pixel in the non-sensing region NSA. 
     Accordingly, an exemplary embodiment of the display device DD (or display panel DP) according to the invention may respectively perform a degradation compensation for pixels in the sensing region SA and pixels the non-sensing region NSA based on different degradation curves (or degradation compensation curves). 
       FIG.  3    is a block diagram for illustrating an exemplary embodiment of a display panel included in a display device of  FIG.  2   . 
     Referring to  FIG.  3   , the display panel DP may include a display unit  100 , a scan driver  200 , a light emission driver  300 , a data driver  400 , a timing controller  500 , and a degradation compensator  600 . 
     The display unit  100  may include scan lines SL 1  to SLn (here, n is a positive integer greater than 2), light emission lines EL 1  to ELn, data lines DL 1  to DLm (here, m is a positive integer greater than 2), and a pixel PX. In one exemplary embodiment, for example, the pixel PX may be disposed in a region (e.g., pixel region) partitioned by the scan lines SL 1  to SLn, the light emission lines EL 1  to ELn, and the data lines DL 1  to DLm. 
     The pixel PX may be connected to a corresponding one of the scan lines SL 1  to SLn, a corresponding one of the light emission lines EL 1  to ELn, and a corresponding one of the data lines DL 1  to DLm. In one exemplary embodiment, for example, the pixel PX may be connected to an i-th scan line SLi, an i-th light emission line ELi, and a j-th data line DLj (here, i and j are positive integers). 
     The pixel PX may emit light corresponding to a data signal supplied through the j-th data line DLj in response to a scan signal supplied through the i-th scan line SLi and a light emission signal supplied through the i-th light emission line ELi. The configuration and operation of the pixel PX, will be described later in greater detail with reference to  FIG.  7   . 
     In an exemplary embodiment, as described above with reference to  FIGS.  1  and  2   , the resolution in the sensing region SA may be lower than the resolution in the non-sensing region NSA. 
     The scan driver  200  may generate a scan signal based on a scan control signal SCS and sequentially supply the scan signal to the scan lines SL 1  to SLn. Here, the scan control signal SCS may include a start signal (or a scan start signal), clock signals (or scan clock signals) or the like, and may be supplied from the timing controller  500 . In one exemplary embodiment, for example, the scan driver  200  may include a shift register that sequentially generates and outputs a scan signal in response to the start signal based on the clock signals. The scan driver  200  may be disposed or formed in the display unit  100  or may be implemented as an integrated circuit (“IC”) and connected to the display unit  100  in a form of a tape carrier package. 
     The light emission driver  300  may generate a light emission signal based on a light emission control signal ECS and supply the light emission signal to the light emission lines EL 1  to ELn. In an exemplary embodiment, the light emission control signal ECS may include a light emission start signal, a light emission clock signals or the like. In one exemplary embodiment, for example, the light emission driver  300  may sequentially generate and output a light emission signal in response to the light emission start signal based on the light emission clock signals. The light emission driver  300  may be disposed or formed in the display unit  100  or may be implemented as an IC and connected to the display unit  100  in a form of a tape carrier package. In one exemplary embodiment, for example, the light emission driver  300  and the scan driver  200  may be implemented as a single IC. 
     The data driver  400  may generate data signals based on a compensated data DATA 3  supplied from the degradation compensator  600  and supply the data signals to the display unit  100  or the pixel PX. The data driver  400  may be connected to the display unit  100  in a form of a tape carrier package. In one exemplary embodiment, for example, the data driver  400  and the scan driver  200  may be implemented as a single IC. 
     The timing controller  500  may receive input image data DATA 1  and a control signal CS from outside or an external device (e.g., a graphic processor or a graphics processing unit), generate scan control signal SCS and light emission control signal ECS, and generate the image data DATA 2  by converting the input image data DATA 1 . In one exemplary embodiment, for example, the timing controller  500  may convert input image data DATA 1  in RGB format to image data DATA 2  in RGBG format that conforms to a pixel array in display unit  100 . 
     The degradation compensator  600  may calculate a degree of degradation of the pixel PX based on the image data DATA 2  and generate the compensated data DATA 3  (or degraded compensated data) to compensate for the image data DATA 2  based on the degree of degradation of the pixel PX. 
     In one exemplary embodiment, for example, the degradation compensator  600  may calculate the degree of degradation (or accumulated usage time, stress) of the pixel PX by accumulating a grayscale value (i.e., the grayscale value corresponding to the pixel PX) included in the image data DATA 2 , and may calculate the compensated grayscale value by compensating the grayscale value based on a predetermined degradation curve and the degree of degradation of the pixel PX. Here, the degradation curve may represent luminance reduction rate according to the degree of degradation and the compensated grayscale value may be included in the compensated data DATA 3 . 
     In an exemplary embodiment of the invention, the degradation compensator  600  may compensate for a first grayscale value corresponding to the pixel PX in the non-sensing region NSA and a second grayscale value corresponding to the pixel PX in the sensing region SA by using degradation curves different from each other. 
     In one exemplary embodiment, for example, the degradation compensator  600  may compensate for the first grayscale value corresponding to the pixel PX in the non-sensing region NSA based on a first degradation curve (or using a degradation compensation equation corresponding to the first degradation curve or a lookup table), and may compensate for the second grayscale value corresponding to the pixel PX in the sensing region SA based on a second degradation curve (or using degradation compensation equation corresponding to the second degradation curve or a lookup table). 
     The configuration and operation of the degradation compensator  600  will be described later in greater detail with reference to  FIG.  8   . 
     In an exemplary embodiment, first and second power source voltages VDD and VSS may be supplied to the display unit  100 . The power source voltages VDD and VSS are voltages used for the operation of the pixel PX. A voltage level of the first power source voltage VDD may be higher than a voltage level of the second power source voltage VSS. In an exemplary embodiment, although not shown in  FIG.  1   , an initialization voltage may be applied to the display unit  100 , and the initialization voltage may be used to initialize a previous data signal stored in the pixel PX. 
     In an exemplary embodiment, the timing controller  500  and the degradation compensator  600  may be separated from each other as shown in  FIG.  3   . Alternatively, the timing controller  500  and the degradation compensator  600  may be implemented as a single IC since the timing controller  500  and the degradation compensator  600  are conceptually separated according to functions. Alternatively, the timing controller  500  may include a data driver  400  or the like. 
       FIG.  4    is a drawing for illustrating an exemplary embodiment of pixels disposed in a sensing region of  FIG.  3   .  FIG.  4    shows arrangements of pixels PX 1 , PX 2 , and PX 3  (or sub-pixels) in the display unit  100  with reference to the sensing region SA shown in  FIG.  3   . 
     Referring to  FIG.  4   , the display unit  100  may include first to third pixels PX 1 , PX 2 , and PX 3 . 
     The first to third pixels PX 1 , PX 2  and PX 3  may be arranged in a matrix form in the display unit  100  and emit lights of different colors. 
     In one exemplary embodiment, for example, the first pixel PX 1  may emit light of a first color (e.g., a red color), the second pixel PX 2  may emit light of a second color (e.g., a green color), and the third pixel PX 3  may emit light of a third color (e.g., a blue color). 
     In an exemplary embodiment, the first to third pixels PX 1 , PX 2 , and PX 3  may be arranged in a form of a pentile. In such an embodiment, as shown in  FIG.  4   , the first pixel PX 1 , the second pixel PX 2 , the third pixel PX 3 , and the second pixel PX 2  may be disposed sequentially and repeatedly in one direction. But, the embodiments are not limited thereto. In one exemplary embodiment, for example, the first to third pixels PX 1 , PX 2 , and PX 3  may be disposed in the form of an RGB stripe. 
     In an exemplary embodiment, the sensing region SA of the display unit  100  may include a transmissive region TPA (or a transparent region). Here, the transmissive region TPA is a region for transmitting light and may include a transparent material instead of the pixels PX 1 , PX 2 , and PX 3 . In one exemplary embodiment, for example, the transparent material may be a resin such as polyethylene terephthalate (“PET”), polyacrylate, polyimide (“PI”), polycarbonate (“PC”) or the like. 
     In one exemplary embodiment, for example, the pixels PX 1 , PX 2 , and PX 3  may be disposed in each of a first to fifth rows of the non-sensing region NSA, the pixels PX 1 , PX 2 , and PX 3  may be disposed in the first, third, and fifth rows (e.g., odd numbered rows) of the sensing region SA, and the transmissive region TPA may be disposed instead of the pixels PX 1 , PX 2  and PX 3  in the second and fourth rows (e.g., even numbered rows) of the sensing region SA, as shown in  FIG.  4   . The position of the transmissive region TPA shown in  FIG.  4    is merely exemplary, and not being limited thereto. In one exemplary embodiment, for example, the transmissive region TPA may correspond to the k-th and (k+2)-th data lines DLk and DLk+2 (here, k is an integer greater than 4) or may be arranged in a lattice form in the sensing region SA. In such an embodiment, the arrangement of the transmissive region TPA may be modified in various ways. 
     In an exemplary embodiment, the transmissive region TPA may include a color filter material that transmits or blocks only light of a specific wavelength. In one exemplary embodiment, for example, the transmissive region TPA may include a filter material that blocks visible light (i.e., light in visible wavelength band) and transmits only infrared light (i.e., light in an infrared wavelength band). 
     Since the sensing region SA includes the transmissive region TPA, the transmittance of the sensing region SA may be higher than the transmittance of the non-sensing region NSA and the resolution of the sensing region SA may be lower than the resolution of the non-sensing region NSA. 
     If the pixels PX 1 , PX 2 , and PX 3  emit light with a same luminance as each other, the luminance of the sensing region SA may be lower than the luminance of the non-sensing region NSA depending on the resolution. In this case, the sensing region SA that has a relatively low-luminance may be viewed by the user. 
     In an exemplary embodiment, the data driver  400 , as described with reference to  FIG.  3   , may apply a relatively high or low data voltage to the pixels PX 1 , PX 2 , and PX 3  of the sensing region SA to improve luminance uniformity. Accordingly, a driving current (or a second driving current) greater than a driving current (or a first driving current) flowing in the pixels PX 1 , PX 2 , and PX 3  of the non-sensing region NSA may flow in the pixels PX 1 , PX 2 , and PX 3  of the sensing region SA, and the luminance of the sensing region SA may be the same as the luminance of the non-sensing region NSA. 
       FIG.  5    is a waveform diagram for illustrating an exemplary embodiment of a data signal applied to pixels of  FIG.  4   .  FIG.  5    shows an exemplarily embodiment of the data signal VDATA applied to one data line (e.g., the k-th data line DLk) connected to the pixels PX 1 , PX 2 , and PX 3  in the sensing region SA shown in  FIG.  4    during one frame  1  FRAME. It is assumed that the pixels PX 1 , PX 2 , and PX 3  include P-type transistors and the grayscale values corresponding to the pixels PX 1 , PX 2 , and PX 3  are the same each other. 
     Referring to  FIGS.  3  to  5   , the data signal VDATA (or the first data signal) may have a first voltage level V 1  in a period between a reference time when the data signal VDATA is applied (or written) to the non-sensing region NSA and a first time point t 1  and in a period between a second time point t 2  and a third time point t 3 . The data signal VDATA (or second data signal) may have a second voltage level V 2  in a period between the first time point t 1  and the second time point t 2  when the data signal VDATA is applied to the sensing region SA. The second voltage level V 2  may be different from the first voltage level V 1 , and may be lower than the first voltage level V 1  by a certain level (A V), for example. Accordingly, each of the pixels PX 1 , PX 2 , and PX 3  in the sensing region SA may emit light at a luminance higher than each of the pixels PX 1 , PX 2 , and PX 3  in the non-sensing region NSA. 
     In such an embodiment, as the relatively high driving current is continuously applied, the degradation of the pixels PX 1 , PX 2 , and PX 3  (see  FIG.  4   ) in the sensing region SA may be accelerated, and the luminance in the sensing region SA may be reduced faster than the luminance in the non-sensing region NSA with time. 
       FIG.  6    is a graph illustrating a degradation characteristic of pixels of  FIG.  4   .  FIG.  6    shows a first degradation curve CURVE 1  for the pixel PX in a non-sensing region NSA and a second degradation curve CURVE 2  for the pixel PX in a sensing region SA shown in  FIG.  4   . Each of the first and second degradation curves CURVE 1  and CURVE 2  represents a luminance change (or luminance reduction rate) according to the accumulated usage time (or stress) of the pixel PX. 
     Referring to  FIG.  6   , at the first accumulated usage time ST 1 , the luminance of the pixel PX in the sensing region SA may be lower than the luminance of the pixel PX in the non-sensing region NSA. 
     In an exemplary embodiment, at a first accumulated usage time ST 1 , a second slope GRAD 2  of a second tangent of the second degradation curve CURVE 2  may be greater than a first slope GRAD 1  of a first tangent of the first degradation curve CURVE 1 . The second slope GRAD 2  may be defined as a second degradation acceleration factor representing the degree of the degradation acceleration of the pixel PX in the sensing region SA at corresponding time. Similarly, the first slope GRAD 1  may be defined as a first degradation acceleration factor representing the degree of degradation acceleration of the pixel PX in the non-sensing region NSA at corresponding time. 
     That is, even if the luminance of the entire display device DD (or the display unit  100 ) becomes uniform by providing a relatively high driving current to the pixels PX 1 , PX 2 , and PX 3  of the sensing region SA, image sticking may occur in the sensing region SA as the pixels PX 1 , PX 2 , and PX 3  of the sensing region SA are degraded faster. 
     As shown in  FIG.  6   , the luminance of the pixel PX in the non-sensing region NSA at a second accumulated usage time ST 2  may be higher than the luminance of the pixel PX in the sensing region SA at the first accumulated usage time ST 1 . Here, the second accumulated usage time ST 2  may be about twice the first accumulated usage time ST 1 . 
     That is, as the degradation of the pixel PX in the sensing region SA is accelerated, the degradation characteristic of the pixel PX in the sensing region SA may be worse than the degradation characteristic of the pixel PX in the non-sensing region NSA. Therefore, the degradation characteristic of the pixel PX in the sensing region SA and the degradation characteristic of the pixel PX in the non-sensing region NSA may not be effectively defined by a single degradation curve (e.g., the first degradation curve CURVE 1 ). 
     Accordingly, an exemplary embodiment of a display device DD (or display panel DP) according to the invention may perform degradation compensation by storing the first and second degradation curves CURVE 1  and CURVE 2  (or lookup tables for corresponding degradation compensation), respectively, applying the first degradation curve CURVE 1  to the pixel PX in the non-sensing region NSA, and applying the second degradation curve CURVE 2  to the pixel PX in the sensing region SA. 
       FIG.  7    is a circuit diagram for illustrating an exemplary embodiment of a pixel of  FIG.  4   .  FIG.  7    shows a pixel circuit for one of the pixels PX 1 , PX 2 , and PX 3  shown in  FIG.  4   . Since the pixels PX 1 , PX 2 , and PX 3  shown in  FIG.  4    are substantially the same as each other, the pixels PX 1 , PX 2 , and PX 3  will be described with reference to the pixel PX. 
     Referring to  FIG.  7   , an exemplary embodiment of the pixel PX may include first to seventh transistors T 1  to T 7 , a storage capacitor CST, and a light emitting diode LD. 
     The first to seventh transistors T 1  to T 7  may be a P-type transistor, e.g., a P-type metal-oxide-semiconductor (“PMOS”) transistor, but not being limited thereto. In one exemplary embodiment, for example, at least one of the first to seventh transistors T 1  to T 7  may be implemented as an N-type transistor, e.g., N-type metal-oxide-semiconductor (“NMOS”) transistor. 
     The first transistor T 1  (or driving transistor) may include a first electrode that is electrically connected to a first node N 1 , a second electrode that is electrically connected to a second node N 2 , and a gate electrode that is electrically connected to a third node N 3 . 
     The second transistor T 2  may include a first electrode connected to the data line (i.e., line transmitting a data signal VDATA), a second electrode connected to the first node N 1 , and a gate electrode connected to a first scan line (i.e., line transmitting a first scan signal GW). The second transistor T 2  may be turned on in response to the first scan signal GW supplied through the first scan line and transmit the data signal VDATA supplied through the data line to the first node N 1 . In one exemplary embodiment, for example, the scan signal may be a pulse signal with a turn-on voltage level (or logic low level) that turns on the transistor. 
     The third transistor T 3  may include a first electrode connected to the second node N 2 , a second electrode connected to the third node N 3 , and a gate electrode connected to the first scan line. The third transistor T 3  may be turned on in response to the first scan signal GW and may transmit the data signal VDATA transmitted through the first transistor T 1  from the first node N 1  to the third node N 3 . 
     The storage capacitor CST may be connected between the first power line and the third node N 3 . Here, a first power source voltage VDD may be applied to the first power line. The storage capacitor CST may store the data signal VDATA transmitted to the third node N 3 . 
     The fourth transistor T 4  may include a first electrode connected to the third node N 3 , a second electrode connected to the initialization voltage line, and a gate electrode connected to a second scan line (i.e., line transmitting a second scan signal GI). Here, the second scan line is a scan line adjacent to the first scan line, and the second scan signal GI may be a previous scan signal supplied before the first scan signal GW. The fourth transistor T 4  may be turned on in response to the previous scan signal supplied through the second scan line or the second scan signal GI and may initialize the third node N 3  by using an initialization voltage VINT supplied through the initialization voltage line. That is, a node voltage (or the data signal VDATA stored in the storage capacitor CST in a previous frame) of the third node N 3  may be initialized to the initialization voltage VINT. 
     The fifth transistor T 5  may include a first electrode connected to the first power line (or the first power line to which the first power source voltage VDD is applied), a second electrode connected to the first node N 1 , and a gate electrode connected to the light emission line (i.e., line transmitting the light emission signal EM). In such an embodiment, the sixth transistor T 6  may include a first electrode connected to the second node N 2 , a second electrode connected to the fourth node N 4 , and a gate electrode connected to the light emission line. 
     The fifth transistor T 5  and the sixth transistor T 6  may be turned on in response to the light emission signal EM supplied through the light emission line, and a path of a driving current Ids may be formed between the first power line and the fourth node N 4  (or second power line to which the second power source voltage VSS is applied). 
     The light emitting diode LD may include an anode connected to the fourth node N 4  and a cathode connected to the second power line. In one exemplary embodiment, for example, the light emitting diode LD may be an organic light emitting diode or an inorganic light emitting diode. The light emitting diode LD may emit light with a luminance corresponding to the driving current Ids (or the current amount of the driving current Ids). 
     The seventh transistor T 7  may include a first electrode connected to the fourth node N 4 , a second electrode connected to the initialization voltage line, and a gate electrode connected to a third scan line (i.e., line transmitting a third scan signal GB). The seventh transistor T 7  may initialize the fourth node N 4  (or parasitic capacitor of the light emitting diode LD) in response to the third scan signal GB. Here, the third scan signal GB may be the same as the second scan signal GI or may be supplied after the first scan signal GW. 
     In  FIG.  7   , the pixel PX is shown as including the first to seventh transistors T 1  to T 7 , but this is merely exemplary and the pixel PX is not limited thereto. In one exemplary embodiment, for example, the pixel PX may include a driving transistor connected between the first power line and the second power line, and a switching transistor connected between the data line and the gate electrode of the driving transistor. That is, various known pixel circuits may be applied to the pixel PX. 
       FIG.  8    is a block diagram for illustrating an exemplary embodiment of a degradation compensator included in a display panel of  FIG.  3   . 
     Referring to  FIGS.  3  and  8   , an exemplary embodiment of the degradation compensator  600  may include an accumulator  810 , a storage unit  820 , and a compensator  830 . 
     The accumulator  810  (or stress calculator, usage time calculator) may calculate an accumulated usage time (or stress) of each pixel based on the compensated data DATA 3 . 
     In one exemplary embodiment, for example, the accumulator  810  may accumulate a first compensated grayscale value GRAY 1 ′ (or first conversion grayscale value) included in the compensated data DATA 3  to calculate a first accumulated usage time of a pixel (hereinafter referred to as “first pixel”) in the non-sensing region NSA, and may accumulate a second compensated grayscale value GRAY 2 ′ (or second conversion grayscale value) included in the compensated data DATA 3  to calculate a second accumulated usage time of a pixel (hereinafter referred to as “second pixel”) in the sensing region SA. Here, the first compensated grayscale value GRAY 1 ′ may be a grayscale value obtained by converting the first grayscale value GRAY 1  corresponding to the first pixel by the degradation compensation, and the second compensated grayscale value GRAY 2 ′ may be a grayscale value obtained by converting the second grayscale value GRAY 2  corresponding to the second pixel by the degradation compensation. 
     In one exemplary embodiment, for example, the accumulator  810  may accumulate the first compensated grayscale value GRAY 1 ′ for each frame or may average and downscale the first compensated grayscale value GRAY 1 ′ output for a specific period to calculate a first accumulated usage time for the first pixel. The accumulator  810  may add the first accumulated usage time to the first accumulated grayscale value GRAY_AC 1  or update the first accumulated grayscale value GRAY_AC 1  based on the first accumulated usage time. Here, the first accumulated grayscale value GRAY_AC 1  may be included in the accumulated data DATA_AC (or usage time data), and the accumulated data DATA_AC may be stored and updated in the storage unit  820  described later. 
     In such an embodiment, the accumulator  810  may calculate the second accumulated usage time for the second pixel to update the second accumulated grayscale value GRAY_AC 2 , and the second accumulated grayscale value GRAY_AC 2  may be included in the accumulated data DATA_AC and stored and updated in the storage unit  820 . 
     The storage unit  820  (or memory device) may store the accumulated data DATA_AC, supply the accumulated data DATA_AC to the accumulator  810  in response to a request from the accumulator  810  (i.e., request for supplying the accumulated data DATA_AC), and update the accumulated data DATA_AC in real time or periodically. 
     In an exemplary embodiment, the storage unit  820  may store lookup tables LUT 1  and LUT 2  (or degradation compensation lookup tables). A first lookup table LUT 1  may include the compensated grayscale values or the degradation compensation ratio of the first pixel for each accumulated usage time according to the degradation characteristic (e.g., the first degradation curve CURVE 1  described with reference to  FIG.  6   ) of the first pixel as shown in Table 1 below. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Division 
                 0 
                 T1 
                 T2 
               
               
                   
               
             
            
               
                 . . . 
                 . . . 
                 . . . 
                 . . . 
               
               
                 GRAY1_L1 
                 GRAY1_L1 
                 GRAY1_L1′ 
                 GRAY1_L1″ 
               
               
                   
                   
                 (GRAY1_L1 + 
                 (GRAY1_L1 + 
               
               
                   
                   
                 GRAY1_D1) 
                 GRAY1_D2) 
               
               
                 . . . 
                 . . . 
                 . . . 
                 . . . 
               
               
                   
               
            
           
         
       
     
     Table 1 shows an exemplary embodiment of the first lookup table LUT 1 . 
     According to an exemplary embodiment, the first lookup table LUT 1  may correspond to the first input grayscale value GRAY 1 _L 1  and may include compensated grayscale values GRAY 1 _L 1 ′ and GRAY 1 _L 1 ″ corresponding to each accumulated usage time T 1  and T 2 . 
     According to an exemplary embodiment, the first lookup table LUT 1  may include grayscale compensation values GRAY 1 _D 1  and GRAY 1 _D 2  (or compensation grayscale values) instead of compensated grayscale values GRAY 1 _L 1 ′ and GRAY 1 _L 1 ″. Here, the grayscale compensation values GRAY 1 _D 1  and GRAY 1 _D 2  may be a difference between the compensated grayscale values GRAY 1 _L 1 ′ and GRAY 1 _L 1 ″ according to the accumulated usage times T 1  and T 2  and the first input grayscale value GRAY 1 _L 1 . 
     In such an embodiment, a second lookup table LUT 2  may include the compensated grayscale values or the degradation compensation ratio corresponding to the accumulated usage time of the second pixel in response to the degradation characteristic (e.g., the second degradation curve CURVE 2  described with reference to  FIG.  6   ) of the second pixel. According to the degradation characteristic (i.e., second degradation curve CURVE 2 ) of the second pixel, the compensated grayscale values of the second pixel may be greater than the compensated grayscale values of the first pixel for the same accumulated usage time respectively. 
     The storage unit  820  may supply the lookup tables LUT 1  and LUT 2  to the compensator  830  in response to a request from the compensator  830 . In an exemplary embodiment, the storage unit  820  may supply the accumulated data DATA_AC to the compensator  830  in response to the request from the compensator  830 . 
     The compensator  830  may generate the compensated data DATA 3  by compensating the image data DATA 2  based on the accumulated data DATA_AC and the lookup tables LUT 1  and LUT 2 . 
     In one exemplary embodiment, for example, the compensator  830  may calculate the first compensated grayscale value GRAY 1 ′ from the first grayscale value GRAY 1  (i.e., the grayscale value corresponding to the first pixel) based on the first accumulated grayscale value GRAY_AC 1  and the first lookup table LUT 1 . In such an embodiment, the compensator  830  calculate the second compensated grayscale value GRAY 2 ′ from the second grayscale value GRAY 2  (i.e., the grayscale value corresponding to the second pixel) based on the second accumulated grayscale value GRAY_AC 2  and the second lookup table LUT 2 . 
     In an exemplary embodiment, the compensator  830  may include a selector  831  and a calculator  832 . 
     The selector  831  may generate a compensation data DATA_C corresponding to the image data DATA 2  based on the accumulated data DATA_AC and the lookup tables LUT 1  and LUT 2 . 
     In one exemplary embodiment, for example, the selector  831  may select the first lookup table LUT 1  based on position information (i.e., coordinate in the image data DATA 2 , which is a coordinate of the corresponding pixel in the display unit  100 ) of the first grayscale value GRAY 1 , and may obtain a first grayscale compensation value from the first lookup table LUT 1  based on the first accumulated usage time (or the first accumulated grayscale value GRAY_AC 1 ) of the first grayscale value GRAY 1 . In such an embodiment, the selector  831  may select the second lookup table LUT 2  based on position information of the second grayscale value GRAY 2 , and may obtain a second grayscale compensation value from the second lookup table LUT 2  based on the second accumulated usage time (or the second accumulated grayscale value GRAY_AC 2 ) of the second grayscale value GRAY 2 . That is, the selector  831  may determine whether the position information of the grayscale values corresponds to the predetermined sensing region SA and select one of the lookup tables LUT 1  and LUT 2  based on the determination result. 
     The selector  831  may generate compensation data DATA_C including the first grayscale compensation value and the second grayscale compensation value. 
     The calculator  832  may generate compensated data DATA 3  by adding the compensation data DATA_C to the image data DATA 2 . In one exemplary embodiment, for example, the calculator  832  may calculate a first compensated grayscale value GRAY 1 ′ by adding the first grayscale compensation value to the first grayscale value GRAY 1 , and calculate a second compensated grayscale value GRAY 2 ′ by adding the second grayscale compensation value to the second grayscale value GRAY 2 . 
     As described with reference to  FIG.  8   , the degradation compensator  600  may compensate for the first grayscale value GRAY 1  corresponding to the first pixel in the non-sensing region NSA by using the first lookup table LUT 1 , and may compensate for the second grayscale value GRAY 2  corresponding to the second pixel in the sensing region SA by using the second lookup table LUT 2 . 
     In an exemplary embodiment, when the display panel DP (or display unit  100 ) of  FIG.  3    includes pixels (e.g., the first to third pixels PX 1 , PX 2  and PX 3  described with reference to  FIG.  4   ) emit different colors from each other, the degradation compensator  600  may compensate for the pixels by using different degradation curves (or degradation compensation equations, lookup tables). 
       FIGS.  9 A and  9 B  are graphs illustrating a degradation characteristic of each pixel of  FIG.  4   .  FIG.  9 A  shows sub-degradation curves CURVE_S 1 , CURVE_S 2 , and CURVE_S 3  for the pixels PX 1 , PX 2 , and PX 3  in the non-sensing region NSA shown in  FIG.  4   , and  FIG.  9 B  shows sub-degradation curves CURVE_S 4 , CURVE_S 5 , and CURVE_S 6  for the pixels PX 1 , PX 2 , and PX 3  in the sensing region SA. As described with reference to  FIG.  4   , the pixels PX 1 , PX 2 , and PX 3  may emit different colors from each other. 
     Each of the sub-degradation curves CURVE_S 1  to CURVE_S 6  represents a luminance change (or luminance reduction rate) according to the accumulated usage time (or stress) of the pixels PX 1 , PX 2 , and PX 3 . 
     First, referring to  FIGS.  8  and  9 A , the first sub-degradation curve CURVE_S 1  represents a degradation characteristic of the first pixel PX 1  in the non-sensing region NSA, and the second sub-degradation curve CURVE_S 2  represents a degradation characteristic of the second pixel PX 2  in the non-sensing region NSA, and the third sub-degradation curve CURVE_S 3  represents a degradation characteristic of the third pixel PX 3  in the non-sensing region NSA. 
     According to the first to third sub-degradation curves CURVE_S 1  to CURVE_S 3 , the second pixel PX 2  may represent a larger degradation acceleration (i.e., has a relatively large degradation acceleration factor) than the first pixel PX 1  based on the accumulated usage time, and the third pixel PX 3  may represent a larger degradation acceleration than the second pixel PX 2  based on the accumulated usage time. 
     Therefore, the storage unit  820 , which is described with reference to  FIG.  8   , may store the lookup tables corresponding to the first to third sub-degradation curves CURVE_S 1  to CURVE_S 3  respectively, and the compensator  830  (or selector  831 ) may select one of the lookup tables based on color or arrangement position of the pixel corresponding to the grayscale value included in the image data DATA 2  and compensate for the grayscale value based on the selected one lookup table. 
     Referring to  FIGS.  8  and  9 B , the fourth sub-degradation curve CURVE_S 4  represents the degradation characteristic of the first pixel PX 1  in the sensing region SA, the fifth sub-degradation curve CURVE_S 5  represents the degradation characteristic of the second pixel PX 2  in the sensing region SA, and the sixth sub-degradation curve CURVE_S 6  represents the degradation characteristic of the third pixel PX 3  in the sensing region SA. 
     According to the fourth to sixth sub-degradation curves CURVE_S 4  to CURVE_S 6 , the second pixel PX 2  may represent a larger degradation acceleration (i.e., has a relatively large degradation acceleration factor) than the first pixel PX 1  based on the accumulated usage time, and the third pixel PX 3  may represent a larger degradation acceleration than the second pixel PX 2  based on the accumulated usage time. In addition, the fourth to sixth sub-degradation curves CURVE_S 4  to CURVE_S 6  may be different from the first to third sub-degradation curves CURVE_S 1  to CURVE_S 3  shown in  FIG.  9 A . 
     Therefore, the storage unit  820 , which is described above with reference  FIG.  8   , may further store lookup tables corresponding to the fourth to sixth sub-degradation curves CURVE_S 4  to CURVE_S 6 , and the compensator  830  (or selector  831 ) may select one of the lookup tables based on color or arrangement position of the pixel corresponding to the grayscale value included in the image data DATA 2  and compensate for the grayscale value based on the selected one of the lookup tables. 
       FIGS.  10 A and  10 B  are block diagrams for illustrating an alternative exemplary embodiment of a degradation compensator included in a display panel of  FIG.  3   .  FIG.  11    is a graph illustrating an exemplary embodiment of a grayscale factor used in a degradation compensator of  FIG.  10 A . 
     First, referring to  FIGS.  8  and  10 A , the degradation compensator  600  shown in  FIG.  10 A  is substantially the same as or similar to the degradation compensator  600  shown in the  FIG.  8    except for a factor determinator  1040  (or first factor determinator). Thus, for convenience of description, any repetitive detailed description of the same or like elements will be omitted. 
     Each of the first lookup table LUT 1  and the second lookup table LUT 2  may include only compensated grayscale values or grayscale compensation values for the first representative grayscale value. In one exemplary embodiment, for example, the first representative grayscale value may be a grayscale value of 255 of a 255 grayscale values, and the first lookup table LUT 1  may include only compensated grayscale values or grayscale compensation values for a grayscale value of 255. In such an embodiment, a size of the lookup table may be smaller than a size of the lookup table for entire grayscale values. 
     In such an embodiment, the compensated grayscale values or grayscale compensation values of the first representative grayscale value (e.g., a grayscale value of 255) may be different from the compensated grayscale values or grayscale compensation values of other grayscale values (e.g., a grayscale value of 100). 
     Therefore, the degradation compensator  600  of  FIG.  10 A  may compensate for other compensated grayscale value by using a grayscale factor (or degradation acceleration factor for each grayscale) representing the degradation compensation ratio (or weight value) of other compensated grayscale value with reference to the first representative grayscale value. 
     In an exemplary embodiment, the storage unit  820  may further include a first factor lookup table. Here, the first factor lookup table may be set based on grayscale factor curves CURVE_AF 1  and CURVE_AF 2  shown in  FIG.  11    and may include a grayscale factor set for each grayscale. 
     Referring to  FIG.  11   , a first grayscale factor curve CURVE_AF 1  represents a degradation acceleration factor set for each grayscale at the first accumulated usage time (e.g., time when accumulated usage time is 0), and a second grayscale factor curve CURVE_AF 2  represents a degradation acceleration factor set for each grayscale at the second accumulated usage time. Here, the second accumulated usage time may be greater than the first accumulated usage time. 
     According to the first and second grayscale factor curves CURVE_AF 1  and CURVE_AF 2 , the first grayscale factor increases as the grayscale value increases in the low grayscale region having a low grayscale value, and the first grayscale factor decreases as the grayscale value increases in the high grayscale region having a high grayscale value. In addition, as the accumulated usage time increases, the first grayscale factor may decrease overall. 
     Referring back to  FIG.  10 A , the factor determinator  1040  may generate degradation acceleration data DATA_F based on the compensated data DATA 3  and the first factor lookup table. The degradation acceleration data DATA_F may include the first grayscale factor AF 1  for the first pixel (i.e., the pixel in the non-sensing region NSA) and the second grayscale factor AF 2  for the second pixel (i.e., the pixel in the sensing region SA). 
     In one exemplary embodiment, for example, the factor determinator  1040  may calculate the first grayscale factor AF 1  for the first compensated grayscale value GRAY 1 ′ based on the first factor lookup table (e.g., the first grayscale factor curve CURVE_AF 1 ). In such an embodiment, the factor determinator  1040  may obtain the first accumulated usage time for the first pixel from the accumulator  810  (or storage unit  820 ) and may select one of a plurality of factor lookup tables (e.g., one of the lookup tables corresponding to the first and second grayscale factor curves CURVE_AF 1  and CURVE_AF 2 ) based on the first accumulated usage time to calculate the first grayscale factor AF 1 . In such an embodiment, the factor determinator  1040  may calculate the second grayscale factor AF 2  for the second compensated grayscale value GRAY 2 ′ based on the first factor lookup table. 
     According to an exemplary embodiment, the compensator  830  may generate compensated data DATA 3  by compensating image data DATA 2  based on the first and second lookup tables LUT 1  and LUT 2 , accumulated data DATA_AC and degradation acceleration data DATA_F. 
     In one exemplary embodiment, for example, the selector  831  may compensate for the first grayscale compensation value GRAY 1 _D 1  by multiplying the first grayscale factor AF 1  with the first grayscale compensation value GRAY 1 _D 1  (see Table 1) obtained based on the first lookup table LUT 1  and the first accumulated grayscale value GRAY_AC 1 . In such an embodiment, the selector  831  may compensate for the second grayscale compensation value by multiplying the second grayscale factor AF 2  with the second grayscale compensation value obtained based on the second lookup table LUT 2  and the second accumulated grayscale value GRAY_AC 2 . 
     As described above with reference to  FIGS.  10 A and  11   , the degradation compensator  600  may perform the degradation compensation for the first and second pixels by using the first and second lookup tables LUT 1  and LUT 2  and the first factor lookup table (or the grayscale factor curves CURVE_AF 1  and CURVE_AF 2 ) for the representative grayscale values. Thus, a storage capacity (or cost) of the degradation compensator  600  may be reduced. 
     In an exemplary embodiment, the factor determinator  1040  may be independent of the compensator  830  as shown in  FIG.  10 A , but not being limited thereto. In one alternative exemplary embodiment, for example, the factor determinator  1040  may be included in the compensator  830  or the selector  831 . 
     Referring to  FIGS.  8  and  10 B , the degradation compensator  600  shown in  FIG.  10 B  is substantially the same as or similar to the degradation compensator  600  shown in the  FIG.  8    except that the degradation compensator  600  shown in  FIG.  10 B  receives the compensated data DATA 3  from the selector  831  (or compensator  830 ). Thus, for convenience of description, any repetitive detailed description of the same or like elements will be omitted. 
     Each of a first lookup table set LUT_SET 1  and a second lookup table set LUT_SET 2  may include sub-lookup tables (or lookup tables) including compensated grayscale values or grayscale compensation values for each of the representative grayscale values. Each of the sub-lookup tables may be substantially the same as or similar to the first lookup table LUT 1  or the second lookup table LUT 2  described above with reference to  FIG.  8   . 
     In one exemplary embodiment, for example, the representative grayscale values may include a grayscale value of 1, a grayscale value of 81, and a grayscale value of 255 of total 255 grayscale values, the first sub-lookup table included in the first lookup table set LUT_SET 1  may include only compensated grayscale values or grayscale compensation values for the first representative grayscale value (e.g., the grayscale value of 255), and the second sub-lookup table may include only compensated grayscale values or grayscale compensation values for the grayscale value of 81. In an alternative exemplary embodiment, each of the first lookup table set LUT_SET 1  and the second lookup table set LUT_SET 2  may include compensated grayscale values or grayscale compensation values for each representative grayscale value as one lookup table. 
     According to an exemplary embodiment, the compensator  830  may generate compensation data DATA_C for image data DATA 2  based on the first and second lookup table sets LUT_SET 1  and LUT_SET 2 , the accumulated data DATA_AC, and the compensated data DATA 3 . 
     In one exemplary embodiment, for example, the selector  831  may select the first and second sub-lookup tables for the two representative grayscale values adjacent to the first compensated grayscale value GRAY 1 ′ from the first lookup table set LUT_SET 1 , obtain the grayscale compensation value from each of the first and second sub-lookup tables based on the first accumulated grayscale value GRAY_AC 1  (i.e., accumulated usage time of the first pixel), and calculate the first grayscale compensation value for the first grayscale value GRAY 1  by interpolating the grayscale compensation value of the first sub-lookup table and the grayscale compensation value of the second sub-lookup table based on the first accumulated grayscale value GRAY_AC 1 . 
     In such an embodiment, the selector  831  may select the third and fourth sub-lookup tables for the two representative grayscale values adjacent to the second compensated grayscale value GRAY 2 ′ from the second lookup table set LUT_SET 2 , obtain the grayscale compensation value from each of the third and fourth sub-lookup tables based on the second accumulated grayscale value GRAY_AC 2 , and calculate the second grayscale compensation value for the second grayscale value GRAY 2  by interpolating the grayscale compensation value of the third sub-lookup table and the grayscale compensation value of the fourth sub-lookup table based on the second accumulated grayscale value GRAY_AC 2 . 
     In an exemplary embodiment, as described with reference to  FIG.  10 B , the degradation compensator  600  may perform the degradation compensation for the first and second pixels by using the first and second lookup table sets LUT_SET 1  and LUT_SET 2  and interpolation techniques for representative grayscale values that are a portion of the entire grayscale values. Thus, a storage capacity (or cost) of the degradation compensator  600  may be reduced. 
       FIGS.  12 A and  12 B  are is a block diagram for illustrating another alternative exemplary embodiment of a degradation compensator included in a display panel of  FIG.  3   .  FIG.  13    is a graph illustrating an exemplary embodiment of a temperature factor used in a degradation compensator of  FIG.  12 A . 
     First, referring to  FIGS.  8  and  12 A , the degradation compensator  600  shown in  FIG.  12 A  is substantially the same as or similar to the degradation compensator  600  shown in the  FIG.  8    except for a factor determinator  1240  (or second factor determinator). Thus, for convenience of description, duplicate descriptions will be omitted. 
     The degradation compensator  600  of  FIG.  12 A  may receive temperature information TEMP from a temperature sensor TEMP SENSOR and perform degradation compensation for the first and second pixels based on the temperature information TEMP. In an exemplary embodiment, the temperature sensor TEMP SENSOR may be provided in the display device DD (or display panel DP) and generate the temperature information TEMP by measuring a temperature inside the display panel DP or the display device DD. 
     The factor determinator  1240  may calculate the temperature factor TF based on the temperature information TEMP. In one exemplary embodiment, for example, the factor determinator  1240  may obtain the temperature factor TF corresponding to the temperature information TEMP by using the second factor lookup table. The second factor lookup table may include the temperature factor TF representing the additional degradation ratio (or additional luminance reduction ratio) corresponding to a temperature and be stored in the storage unit  820 . Herein, a “lookup table set by temperature” means a lookup table includes values corresponding to predetermined temperatures as the second factor lookup table. 
     Referring to  FIG.  13   , the third temperature factor curve CURVE_AF 3  (or third degradation acceleration factor curve) represents a degradation acceleration factor according to temperature. According to the third temperature factor curve CURVE_AF, the temperature factor TF may increase as the temperature increases. 
     Referring back to  FIG.  12 A , the compensator  830  may generate compensated data DATA 3  by compensating image data DATA 2  based on the first and second lookup tables LUT 1  and LUT 2 , the accumulated data DATA_AC, and the temperature factor TF. 
     In one exemplary embodiment, for example, the selector  831  may compensate for the first grayscale compensation value GRAY 1 _D 1  by multiplying the temperature factor TF with the first grayscale compensation value GRAY 1 _D 1  (see Table 1) obtained based on the first lookup table LUT 1  and the first accumulated grayscale value GRAY_AC 1 . In such an embodiment, the selector  831  may compensate for the second grayscale compensation value by multiplying the temperature factor TF with the second grayscale compensation value obtained based on the second lookup table LUT 2  and the second accumulated grayscale value GRAY_AC 2 . 
     In an exemplary embodiment, the factor determinator  1240  may be independent of the compensator  830  as shown in  FIG.  12 A , but not being limited thereto. In one alternative exemplary embodiment, for example, the factor determinator  1240  may be included in a compensator  830  or the selector  831 . 
     Referring to  FIGS.  8  and  12 B , the degradation compensator  600  shown in  FIG.  12 B  is substantially the same as or similar to the degradation compensator  600  shown in the  FIG.  8    except that the degradation compensator  600  shown in  FIG.  12 B  receives the temperature information TEMP from the selector  831  (or compensator  830 ). Thus, for convenience of description, any repetitive detailed description of the same or like elements will be omitted. 
     Each of the first lookup table set LUT_SET 1  and the second lookup table set LUT_SET 2  may include sub-lookup tables (or lookup tables). Each of the sub-lookup tables may be substantially the same as or similar to the first lookup table LUT 1  or the second lookup table LUT 2  described above with reference to  FIG.  8   . 
     In one exemplary embodiment, for example, the first sub-lookup table included in the first lookup table set LUT_SET 1  may include compensated grayscale values or grayscale compensation values according to the accumulated usage time at a first temperature, and the second sub-lookup table may include compensated grayscale values or grayscale compensation values according to the accumulated usage time at a second temperature. 
     According to an exemplary embodiment, the compensator  830  may generate compensation data DATA_C for image data DATA 2  based on the first and second lookup table sets LUT_SET 1  and LUT_SET 2 , the accumulated data DATA_AC, and the temperature information TEMP. 
     In one exemplary embodiment, for example, the selector  831  may select the first sub-lookup table corresponding to the temperature information TEMP from the first lookup table set LUT_SET 1  and obtain the first grayscale compensation value corresponding to the first compensated grayscale value GRAY 1 ′ from the first sub-lookup table. In such an embodiment, the selector  831  may select the second sub-lookup table corresponding to the temperature information TEMP from the second lookup table set LUT_SET 2  and obtain the second grayscale compensation value corresponding to the second compensated grayscale value GRAY 2 ′ from the second sub-lookup table. 
     In an exemplary embodiment, as described above with reference to  FIGS.  12 A and  12 B , the degradation compensator  600  may perform the degradation compensation for the first and second pixels based on the temperature information TEMP of the display panel DP (or display device DD). Thus, the degradation of the first and second pixels may be accurately compensated. 
     According to exemplary embodiments of the invention as described herein, a degradation compensation device and a display device the degradation compensation device may compensate for a degradation of a pixel more accurately by performing degradation compensation for pixels disposed in regions having relatively different resolutions by using independent degradation curves of which degradation acceleration factors are different from each other. 
     The invention should not be construed as being limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the invention to those skilled in the art. 
     While the invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit or scope of the invention as defined by the following claims.