相关申请的交叉参考Cross References to Related Applications
本申请要求于2015年5月21日提交的美国专利申请14/286,711的优先权，在这里将该在先申请的全部内容以引用的方式并入本文。This application claims priority to US Patent Application 14/286,711 filed May 21, 2015, the entire content of which is hereby incorporated by reference.
技术领域technical field
本发明大体上涉及使用诸如OLED之类的发光器件的显示器，且更具体地涉及为了补偿发光器件的老化而在此类显示器中提取不同应力条件下的特性关联曲线。The present invention relates generally to displays using light emitting devices such as OLEDs, and more particularly to extracting characteristic correlation curves under different stress conditions in such displays in order to compensate for aging of the light emitting devices.
背景技术Background technique
相对于常规液晶显示器，有源矩阵有机发光器件(AMOLED)显示器提供了更低的功耗、制造灵活性和更快的刷新速率的优点。与常规液晶显示器相比，AMOLED显示器中不存在背光，这是因为每个像素由独立发光的不同颜色的OLED构成。OLED基于由驱动晶体管提供的电流发光。驱动晶体管通常是薄膜晶体管(TFT)。每个像素的功耗与该像素中产生的光的大小具有直接的关系。Active matrix organic light emitting device (AMOLED) displays offer the advantages of lower power consumption, manufacturing flexibility, and faster refresh rates relative to conventional liquid crystal displays. In contrast to conventional LCD displays, there is no backlight in AMOLED displays because each pixel is made of OLEDs of different colors that emit light independently. OLEDs emit light based on current supplied by a drive transistor. The drive transistor is usually a thin film transistor (TFT). The power consumption of each pixel has a direct relationship to the amount of light generated in that pixel.
在有机发光二极管器件的运行期间，其遭受劣化，这导致恒定电流下的光输出随着时间减小。OLED器件还遭受电学劣化，这导致恒定偏置电压下的电流随着时间降低。这些劣化基本上是由与OLED上的施加电压的大小和持续时间以及由此在该器件中产生的电流相关的应力引起的。这类劣化由于诸如温度、湿度或氧化剂的存在之类的环境因素的随时间的贡献而混合在一起。薄膜晶体管器件的老化速率也取决于环境和应力(偏置)。针对先前数次存储的像素历史数据来校准像素，以确定像素上的老化效应，从而可适当地确定像素晶体管和OLED的老化。因此，在显示装置的整个寿命期间需要精确的老化数据。During operation of an organic light emitting diode device, it suffers from degradation, which leads to a decrease in light output at constant current over time. OLED devices also suffer from electrical degradation, which causes the current at a constant bias voltage to decrease over time. These degradations are essentially caused by stresses related to the magnitude and duration of the applied voltage across the OLED and the resulting current flow in the device. Such degradation is compounded over time by the contribution of environmental factors such as temperature, humidity or the presence of oxidizing agents. The aging rate of thin film transistor devices also depends on the environment and stress (bias). The pixel is calibrated against previous stored pixel history data to determine aging effects on the pixel so that aging of the pixel transistor and OLED can be properly determined. Therefore, accurate aging data is required over the lifetime of the display device.
在一种OLED显示器补偿技术中，提取像素面板的老化(和/或均匀性)并将其作为原始的或经处理的数据存储在查找表中。接着，补偿模块使用所存储的数据来补偿OLED的电学参数和光学参数的任何偏移(例如，OLED运行电压和光学效率的偏移)以及背板的电学和光学参数的任何偏移(例如，TFT的阈值电压偏移)，因而根据所存储的数据和视频内容来修改每个像素的编程电压。补偿模块按照使足够的电流经过OLED以针对每个灰度水平保持相同的亮度水平的方式修改驱动TFT的偏置。换句话说，合适的编程电压适当地抵消了OLED的电学老化和光学老化以及TFT的电学劣化。In one OLED display compensation technique, the aging (and/or uniformity) of the pixel panel is extracted and stored as raw or processed data in a lookup table. The compensation module then uses the stored data to compensate for any shifts in the electrical and optical parameters of the OLED (e.g., shifts in the OLED operating voltage and optical efficiency) and any shifts in the electrical and optical parameters of the backplane (e.g., The threshold voltage of the TFT is shifted), thus modifying the programming voltage of each pixel according to the stored data and video content. The compensation module modifies the bias of the drive TFT in such a way that enough current is passed through the OLED to maintain the same brightness level for each gray level. In other words, a suitable programming voltage properly offsets the electrical and optical aging of the OLED and the electrical degradation of the TFT.
在显示器的寿命期间，通过基于电学反馈的测量电路持续地监测并提取背板TFT和OLED器件的电学参数。进一步，根据OLED的电学劣化数据来估计OLED器件的光学老化参数。然而，OLED的光学老化效应也取决于单独像素上的应力条件，且由于应力在像素间变化，所以不能确保精确的补偿，除非确定出适合于具体应力水平的补偿。During the lifetime of the display, the electrical parameters of the backplane TFT and OLED devices are continuously monitored and extracted by an electrical feedback based measurement circuit. Further, the optical aging parameters of OLED devices are estimated according to the electrical degradation data of OLEDs. However, the optical aging effects of OLEDs also depend on the stress conditions on individual pixels, and since the stress varies from pixel to pixel, precise compensation cannot be ensured unless a compensation tailored to a specific stress level is determined.
因此，对于有源像素上的应力条件，需要有效地提取精确的光学参数和电学参数的特性关联曲线以用于补偿老化效应和其它效应。对于有源像素在显示器的运行期间可能经受的各种应力条件，需要具有各种特性关联曲线。Therefore, for the stress conditions on the active pixels, it is necessary to efficiently extract accurate characteristic correlation curves of optical parameters and electrical parameters for compensating aging effects and other effects. It is desirable to have various characteristic correlation curves for the various stress conditions that the active pixels may experience during operation of the display.
发明内容Contents of the invention
根据一个实施例，提供了一种用于确定基于阵列的半导体器件中的有机发光器件(OLED)的效率劣化的系统，所述半导体器件具有像素的阵列，且所述像素包括OLED。在所述系统中，针对至少一个应力条件，确定所述OLED的电学运行参数的变化与所述OLED的所述效率劣化之间的关系；测量所述OLED的所述电学运行参数的变化；确定所述半导体器件中的至少一个像素或像素组的应力条件；以及通过使用所确定的关系和所确定的应力条件，确定所述OLED的与所述OLED的所述电学运行参数的所测量的变化相对应的所述效率劣化。According to one embodiment, a system for determining efficiency degradation of an organic light emitting device (OLED) in an array-based semiconductor device having an array of pixels, the pixels comprising OLEDs is provided. In said system, for at least one stress condition, determining a relationship between a change in an electrical operating parameter of said OLED and said efficiency degradation of said OLED; measuring a change in said electrical operating parameter of said OLED; determining a stress condition of at least one pixel or group of pixels in the semiconductor device; and determining a measured change of the OLED from the electrical operating parameter of the OLED by using the determined relationship and the determined stress condition Correspondingly, the efficiency deteriorates.
在一种实施例中，使用所确定的应力条件来选择所确定的关系，以用于确定所述OLED的与所述OLED的所述电学运行参数(例如，OLED电压)的所测量的变化相对应的所述效率劣化。所述OLED的应力条件可以是根据所述OLED的应力历史(例如，所述OLED经受的应力条件的移动平均)确定的，或者是根据所述OLED的所述电学运行参数的随时间的变化速率确定的，所述OLED的所述电学运行参数的随时间的变化速率是所述OLED经受的应力的函数。In one embodiment, the determined stress conditions are used to select the determined relationship for determining the phase of said OLED with respect to a measured change in said electrical operating parameter of said OLED (e.g. OLED voltage). Correspondingly, the efficiency deteriorates. The stress condition of the OLED may be determined from a stress history of the OLED (e.g., a moving average of stress conditions to which the OLED is subjected) or from a rate of change of the electrical operating parameter of the OLED over time It is determined that the rate of change over time of the electrical operating parameter of the OLED is a function of the stress to which the OLED is subjected.
鉴于参考附图进行的各种实施例的详细描述，本领域技术人员将明白本发明的各方面，其中将在下面给出这些附图的简要。Aspects of the invention will become apparent to those skilled in the art in view of the detailed description of various embodiments, taken with reference to the accompanying drawings, a brief summary of which is given below.
附图说明Description of drawings
通过参考下面的结合附图进行的说明可以最好地理解本发明。The present invention is best understood by reference to the following description taken in conjunction with the accompanying drawings.
图1是具有补偿控制的AMOLED显示器系统的框图。Figure 1 is a block diagram of an AMOLED display system with compensation control.
图2是用于基于测量数据来修改特性关联曲线的图1中的参考像素中的一者的电路图。FIG. 2 is a circuit diagram of one of the reference pixels in FIG. 1 for modifying a characteristic correlation curve based on measurement data.
图3是从有源像素发出的亮度的曲线图，该曲线图反映出可需要不同补偿的随时间的不同水平的应力条件。3 is a graph of luminance emanating from an active pixel reflecting different levels of stress conditions over time that may require different compensation.
图4是不同特性关联曲线的曲线图以及使用预定应力条件来确定补偿的技术的结果的曲线图。Figure 4 is a graph of different characteristic correlation curves and the results of a technique using predetermined stress conditions to determine compensation.
图5是基于预定应力条件下的参考像素组来确定和更新特性关联曲线的过程的流程图。FIG. 5 is a flowchart of a process of determining and updating a characteristic correlation curve based on a reference pixel set under a predetermined stress condition.
图6是使用预定的特性关联曲线来补偿显示器上的有源像素的编程电压的过程的流程图。6 is a flowchart of a process for compensating programming voltages of active pixels on a display using a predetermined characteristic correlation curve.
图7是OLED效率劣化与OLED电压的变化的相关性曲线。Fig. 7 is a correlation curve of OLED efficiency degradation and OLED voltage variation.
图8是OLED应力历史与应力强度的曲线图。Figure 8 is a graph of OLED stress history versus stress intensity.
图9A是不同的应力条件下的OLED电压变化与时间的曲线图。FIG. 9A is a graph of OLED voltage change versus time under different stress conditions.
图9B是不同的应力条件下的OLED电压变化速率与时间的曲线图。Figure 9B is a graph of OLED voltage change rate versus time under different stress conditions.
图10是不同的应力条件下的OLED电压变化速率与OLED电压变化的曲线图。Fig. 10 is a graph of OLED voltage change rate and OLED voltage change under different stress conditions.
图11是根据诸如OLED电压之类的OLED参数的变化来提取OLED效率劣化的过程的流程图。11 is a flowchart of a process of extracting OLED efficiency degradation from changes in OLED parameters such as OLED voltage.
虽然本发明易受到各种修改和替代形式，但是在附图中已经通过实例的方式示出了特定实施例并在本文中详细说明。然而，应当理解，本发明并不意图限于所公开的特定形式。相反，本发明覆盖落入由所附权利要求限定的本发明的精神和范围内的所有修改、等同物和替代方案。While the invention is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and described in detail herein. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed. On the contrary, the invention covers all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
具体实施方式Detailed ways
图1是具有有源矩阵区域或像素阵列102的电子显示器系统100，在该有源矩阵区域或像素阵列102中，以行和列的配置布置有有源像素104的阵列。为方便图示，仅示出了两行和两列。在有源矩阵区域(像素阵列102)的外部是外围区域106，在外围区域106中布置有用于驱动和控制像素阵列102的区域的外围电路。外围电路包括栅极或地址驱动器电路108、源极或数据驱动器电路110、控制器112和可选的电压源(例如，EL_Vdd)驱动器114。控制器112控制栅极驱动器108、源极驱动器110和电压源驱动器114。在控制器112的控制下，栅极驱动器108对地址或选择线SEL[i]、SEL[i+1]等进行操作，其中在像素阵列102中的像素104的每一行中存在一条地址或选择线。在下述像素共用配置中，栅极或地址驱动器电路108还可以可选地对全局选择线GSEL[j]且可选地对/GSEL[j]进行操作，全局选择线GSEL[j]或/GSEL[j]对像素阵列102中的像素104中的多个行(例如，像素104的每两行)进行操作。在控制器112的控制下，源极驱动器电路110对电压数据线Vdata[k]、Vdata[k+1]等进行操作，其中在像素阵列102中的像素104的每一列中存在一条电压数据线。电压数据线向每个像素104运送用于表示像素104中的每个发光器件的亮度的电压编程信息。每个像素104中的存储元件(例如，电容器)存储电压编程信息，直到发光或驱动周期开启发光器件。在控制器112的控制下，可选的电压源驱动器114控制电压源(EL_Vdd)线，其中在像素阵列102中的像素104的每一行中存在一条电压源线。控制器112还连接到存储器118，存储器118用于存储下面将说明的像素104的各种特性关联曲线以及老化参数。存储器118可以是闪速存储器、SRAM、DRAM、它们的组合和/或其它存储器中的一者或更多者。1 is an electronic display system 100 having an active matrix area or pixel array 102 in which an array of active pixels 104 are arranged in a row and column configuration. For ease of illustration, only two rows and two columns are shown. Outside the active matrix area (pixel array 102 ) is a peripheral area 106 in which peripheral circuits for driving and controlling the area of the pixel array 102 are arranged. Peripheral circuitry includes a gate or address driver circuit 108 , a source or data driver circuit 110 , a controller 112 and an optional voltage source (eg, EL_Vdd) driver 114 . Controller 112 controls gate driver 108 , source driver 110 and voltage source driver 114 . Under the control of controller 112, gate driver 108 operates on address or select lines SEL[i], SEL[i+1], etc., where there is one address or select line in each row of pixels 104 in pixel array 102 Wire. In the pixel sharing configuration described below, the gate or address driver circuit 108 may also optionally operate on global select line GSEL[j] and optionally on /GSEL[j], global select line GSEL[j] or /GSEL [j] Operates on multiple rows of pixels 104 in pixel array 102 (eg, every two rows of pixels 104). Under the control of the controller 112, the source driver circuit 110 operates on voltage data lines Vdata[k], Vdata[k+1], etc., where there is one voltage data line in each column of pixels 104 in the pixel array 102 . The voltage data lines carry voltage programming information to each pixel 104 representing the brightness of each light emitting device in the pixel 104 . A storage element (eg, a capacitor) in each pixel 104 stores voltage programming information until a light emission or drive cycle turns on the light emitting device. Under the control of controller 112 , optional voltage source driver 114 controls voltage source (EL_Vdd) lines, where there is one voltage source line in each row of pixels 104 in pixel array 102 . The controller 112 is also connected to a memory 118 for storing various characteristic correlation curves and aging parameters of the pixel 104 which will be described below. Memory 118 may be one or more of Flash memory, SRAM, DRAM, combinations thereof, and/or other memory.
显示器系统100还可以包括电流源电路，该电流源电路在电流偏置线上提供固定电流。在一些配置中，能够向电流源电路提供参考电流。在这类配置中，电流源控制部控制在电流偏置线上施加偏置电流的时序。在不向电流源电路提供参考电流的配置中，电流源地址驱动器控制在电流偏置线上施加偏置电流的时序。Display system 100 may also include a current source circuit that provides a fixed current on the current bias line. In some configurations, a reference current can be provided to the current source circuit. In such configurations, the current source control controls the timing of applying the bias current on the current bias line. In configurations where no reference current is supplied to the current source circuit, the current source address driver controls the timing of applying the bias current on the current bias line.
已知的是，对于显示器系统100中的每个像素104，需要使用用于表示该像素104中的发光器件的亮度的信息来对其编程。帧定义了包括编程周期或阶段以及驱动或发光周期或阶段的时间段，其中在编程周期或阶段期间，使用用于表示亮度的编程电压来编程显示器系统100中的每个像素，并且在驱动或发光周期或阶段期间，每个像素中的每个发光器件被开启以按照与存储在存储元件中的编程电压相对应的亮度发光。因此，帧是组成显示器系统100上所显示的完整的运动图片的许多静态图像中的一个。存在至少两种用于编程和驱动像素的方案：逐行或者逐帧。在逐行编程时，对一行像素进行编程，并接着在对下一行像素进行编程和驱动之前驱动该行像素。在逐帧编程时，首先对显示器系统100中的所有行的像素进行编程，并且逐行地驱动所有帧。任一种方案都可以在每个时段的开始或结束处采用短暂的未对像素进行编程或驱动的垂直消隐时间。It is known that for each pixel 104 in the display system 100 it needs to be programmed with information representing the brightness of the light emitting device in that pixel 104 . A frame defines a period of time that includes programming cycles or phases during which each pixel in the display system 100 is programmed with a programming voltage representing brightness and driving or emitting cycles or phases During an emission cycle or phase, each light emitting device in each pixel is turned on to emit light at a brightness corresponding to the programming voltage stored in the memory element. Thus, a frame is one of many still images that make up a complete motion picture displayed on display system 100 . There are at least two schemes for programming and driving pixels: row by row or frame by frame. In row-by-row programming, a row of pixels is programmed and then driven before the next row of pixels is programmed and driven. In frame-by-frame programming, all rows of pixels in the display system 100 are programmed first, and all frames are driven row by row. Either scheme can employ a brief vertical blanking time at the beginning or end of each period when no pixels are programmed or driven.
位于像素阵列102外部的组件可以布置像素阵列102周围的外围区域106中，外围区域106与像素阵列102布置在相同的物理基板上。这些组件包括栅极驱动器108、源极驱动器110和可选的电压源控制部114。可替代地，外围区域中的一些组件可以与像素阵列102布置在相同的基板上，而其它组件布置在不同的基板上，或者外围区域中的所有组件可以与像素阵列102布置在不同的基板上。栅极驱动器108、源极驱动器110和电压源控制部114一起构成显示驱动器电路。某些配置中的显示驱动器电路可以包括栅极驱动器108和源极驱动器110但不包括电压源控制部114。Components located outside of the pixel array 102 may be arranged in a peripheral region 106 around the pixel array 102 that is arranged on the same physical substrate as the pixel array 102 . These components include a gate driver 108 , a source driver 110 and an optional voltage source control 114 . Alternatively, some components in the peripheral area may be arranged on the same substrate as the pixel array 102 while other components are arranged on a different substrate, or all components in the peripheral area may be arranged on a different substrate from the pixel array 102 . The gate driver 108, the source driver 110, and the voltage source control section 114 together constitute a display driver circuit. Display driver circuitry in some configurations may include gate driver 108 and source driver 110 but not voltage source control 114 .
显示器系统100还包括电流源和读取电路120，电流源和读取电路120从数据输出线VD[k]、VD[k+1]等读取输出数据，其中在像素阵列102中的有源像素104的每一列中存在一条数据输出线。成组的可选的参考器件(例如，参考像素)130被制造在外围区域106中并布置在像素阵列102的位于有源像素104外部的边缘上。参考像素130还可以从控制器112接收输入信号，并且可以将数据信号输出到电流源和读取电路120。参考像素130包括驱动晶体管和OLED，但是不是用于显示图像的像素阵列102的一部分。如将在下面所说明，不同组的参考像素130经由来自电流供应电路120的不同电流水平而处于不同的应力条件。由于参考像素130不是像素阵列102的一部分并且因此不显示图像，因此参考像素130可以提供用于表示不同应力条件下的老化效应的数据。虽然图1中仅仅示出了一行和一列的参考像素130，但是应当理解，可以存在任意数目的参考像素。图1所示出的示例中的每个参考像素130被制造成相邻于对应的光传感器132。光传感器132用于确定由对应的参考像素130发出的亮度水平。应当理解，参考器件(例如，参考像素130)可以是独立的器件而不是被制造在具有有源像素104的显示器上。The display system 100 also includes a current source and readout circuit 120. The current source and readout circuit 120 reads output data from the data output lines VD[k], VD[k+1], etc., wherein the active elements in the pixel array 102 There is one data output line in each column of pixels 104 . Groups of optional reference devices (eg, reference pixels) 130 are fabricated in peripheral region 106 and arranged on edges of pixel array 102 outside active pixels 104 . Reference pixel 130 may also receive input signals from controller 112 and may output data signals to current source and readout circuitry 120 . Reference pixel 130 includes a drive transistor and an OLED, but is not part of pixel array 102 for displaying an image. As will be explained below, different sets of reference pixels 130 are subjected to different stress conditions via different current levels from the current supply circuit 120 . Since the reference pixel 130 is not part of the pixel array 102 and thus does not display an image, the reference pixel 130 may provide data representative of the effects of aging under different stress conditions. Although only one row and one column of reference pixels 130 are shown in FIG. 1, it should be understood that any number of reference pixels may exist. Each reference pixel 130 in the example shown in FIG. 1 is fabricated adjacent to a corresponding light sensor 132 . The light sensor 132 is used to determine the brightness level emitted by the corresponding reference pixel 130 . It should be understood that a reference device (eg, reference pixel 130 ) may be a stand-alone device rather than being fabricated on a display with active pixels 104 .
图2示出了用于图1中的一个示例参考像素130的驱动器电路200的一个示例。参考像素130的驱动器电路200包括驱动晶体管202、有机发光器件(OLED)204、存储电容器206、选择晶体管208和监测晶体管210。电压源212连接到驱动晶体管202。如图2所示，在该示例中，驱动晶体管202是由非晶硅制造的薄膜晶体管。选择线214连接到选择晶体管208以激活驱动器电路200。电压编程输入线216将编程电压施加到驱动晶体管202。监测线218监测OLED204和/或驱动晶体管202的输出。选择线214连接到选择晶体管208和监测晶体管210。在读取时间期间，选择线214被拉高。可以经由编程电压输入线216来施加编程电压。可以从与监测晶体管210连接的监测线218读取监测电压。可以与像素编程周期并行地发送至选择线214的信号。FIG. 2 shows an example of a driver circuit 200 for one example reference pixel 130 in FIG. 1 . The driver circuit 200 of the reference pixel 130 includes a drive transistor 202 , an organic light emitting device (OLED) 204 , a storage capacitor 206 , a select transistor 208 and a monitor transistor 210 . A voltage source 212 is connected to the drive transistor 202 . As shown in FIG. 2 , in this example, the drive transistor 202 is a thin film transistor fabricated from amorphous silicon. Select line 214 is connected to select transistor 208 to activate driver circuit 200 . A voltage programming input line 216 applies a programming voltage to the drive transistor 202 . Monitor line 218 monitors the output of OLED 204 and/or drive transistor 202 . Select line 214 is connected to select transistor 208 and monitor transistor 210 . During the read time, select line 214 is pulled high. The programming voltage may be applied via the programming voltage input line 216 . The monitor voltage can be read from monitor line 218 connected to monitor transistor 210 . The signal to select line 214 may be sent in parallel with the pixel programming cycle.
可以通过向编程电压输入线216施加恒定电压来以一定的电流水平向参考像素130加应力。如将在下面说明，基于被施加到编程电压输入线216的参考电压从监测线218测量的电压输出允许在参考像素130的运行时间内针对所施加的应力条件确定电学特性数据。可替代地，监测线218和编程电压输入线216可以合并成一条线(即，Data/Mon)，以通过该单条线执行编程和监测这两种功能。光传感器132的输出允许在参考像素130的运行时间内针对应力条件确定光学特性数据。Reference pixel 130 may be stressed at a certain current level by applying a constant voltage to programming voltage input line 216 . As will be explained below, the measured voltage output from monitor line 218 based on the reference voltage applied to programming voltage input line 216 allows electrical characteristic data to be determined for the applied stress condition during the operational time of reference pixel 130 . Alternatively, monitor line 218 and programming voltage input line 216 may be combined into one line (ie, Data/Mon) to perform both programming and monitoring functions through this single line. The output of the light sensor 132 allows determination of optical property data for stress conditions within the runtime of the reference pixel 130 .
根据一个示例性实施例，在图1中的显示器系统100中，基于至少一个像素的老化来调节每个像素(或者子像素)的亮度，以在系统的工作寿命(例如，75000小时)期间保持基本均匀的显示。包含显示器系统100的显示器件的非限制性示例包括移动电话、数字相机、个人数字助理(PDA)、计算机、电视机、便携式视频播放器、全球定位系统(GPS)等。According to an exemplary embodiment, in the display system 100 in FIG. 1 , the brightness of each pixel (or sub-pixel) is adjusted based on the aging of at least one pixel to maintain A substantially uniform display. Non-limiting examples of display devices incorporating display system 100 include mobile phones, digital cameras, personal digital assistants (PDAs), computers, televisions, portable video players, global positioning systems (GPS), and the like.
随着有源像素104的OLED材料老化，用于保持OLED中的给定水平的恒定电流所需的电压增大。为了补偿OLED的电学老化，存储器118存储每个有源像素的用于保持恒定电流所需的补偿电压。它还针对不同应力条件存储具有特性关联曲线形式的数据，控制器112使用该数据来确定补偿电压，以修改用于驱动有源像素104的每个OLED的编程电压，从而通过增大OLED的电流并由此补偿OLED的光学老化来合适地显示期望输出水平的亮度。特别地，存储器118存储多个预定义的特性关联曲线或函数，这些预定义的特性关联曲线或函数表示在不同的预定应力条件下运行的OLED的亮度效率的劣化。不同的预定应力条件一般表示有源像素104在像素寿命期间可能遭受的不同类型的应力或运行条件。不同的应力条件可以包括从低到高的不同水平的恒定电流需求、从低到高的恒定亮度需求或者两个以上的应力水平的混合。例如，应力水平在时间的某个百分比中可以是某个电流下的应力水平以及在时间的另一百分比中可以是另一电流下的应力水平。其它应力水平可以是专门的(specialized)应力水平，例如，用于表示显示器系统100上所显示的平均流视频(averagestreamingvideo)的水平。最初，诸如参考像素130之类的参考器件在不同应力条件下的基准电学特性和基准光学特性被存储在存储器118中。在该示例中，在制造参考器件之后，立即从该参考器件测量该参考器件的基准电学特性和基准光学特性。As the OLED material of active pixels 104 ages, the voltage required to maintain a given level of constant current in the OLED increases. In order to compensate for the electrical aging of the OLED, the memory 118 stores the compensation voltage required for maintaining a constant current for each active pixel. It also stores data in the form of characteristic correlation curves for different stress conditions, which the controller 112 uses to determine compensation voltages to modify the programming voltages used to drive each OLED of the active pixels 104, thereby increasing the OLED current And thereby compensate for the optical aging of the OLED to properly display the desired output level of brightness. In particular, the memory 118 stores a plurality of predefined characteristic correlation curves or functions representing the degradation of the luminance efficiency of OLEDs operating under different predetermined stress conditions. Different predetermined stress conditions generally represent different types of stress or operating conditions that active pixel 104 may be subjected to during the lifetime of the pixel. Different stress conditions may include varying levels of constant current demand from low to high, constant brightness demand from low to high, or a mix of more than two stress levels. For example, a stress level may be a stress level at a certain current for a certain percentage of time and a stress level at another current for another percentage of time. Other stress levels may be specialized stress levels, eg, for representing levels of average streaming video displayed on display system 100 . Initially, reference electrical and optical characteristics of a reference device, such as reference pixel 130 , under different stress conditions are stored in memory 118 . In this example, reference electrical and reference optical properties of the reference device were measured from the reference device immediately after fabrication of the reference device.
可以通过如下方式向成组的参考像素(例如，参考像素130)施加每个这类应力条件：在一个时间段内保持参考像素130中的恒定电流；在一个时间段内保持参考像素130的恒定亮度；和/或在一个时间段内以不同的预定水平和预定间隔改变参考像素中的电流或参考像素的亮度。在参考像素130中产生的电流或亮度水平可以是显示器系统100的特定应用所预期的例如高值、低值、和/或平均值。例如，诸如计算机监视器之类的应用要求高值。类似地，在参考像素中产生电流或亮度水平的时间段可取决于显示器系统100的特定应用。Each of these stress conditions can be applied to groups of reference pixels (e.g., reference pixels 130) by: maintaining a constant current in reference pixels 130 for a period of time; maintaining a constant current in reference pixels 130 for a period of time. brightness; and/or changing the current in the reference pixel or the brightness of the reference pixel at different predetermined levels and predetermined intervals within a period of time. The current or brightness level generated in reference pixel 130 may be, for example, a high value, a low value, and/or an average value as expected for a particular application of display system 100 . For example, applications such as computer monitors require high values. Similarly, the period of time for which a current or brightness level is generated in a reference pixel may depend on the particular application of display system 100 .
预期的是，为了在每个预定应力条件下获得相同的老化效应，在显示器系统100的运行期间向不同的参考像素130施加不同的预定应力条件。换句话说，将第一预定应力条件施加到第一组参考像素，将第二预定应力条件施加到第二组参考像素，等等。在该示例中，显示器系统100具有多组参考像素130，这些参考像素在处于像素的低电流值到高电流值的范围内的16个不同的应力条件下被加应力。因此，在该示例中存在16个不同组的参考像素130。当然，可以采用更大或更小数量的应力条件，这取决于诸如补偿的期望精确度、外围区域106中的物理空间、可用的处理能力的量以及用于存储特性关联曲线数据的存储器的量之类的因素。It is contemplated that different predetermined stress conditions are applied to different reference pixels 130 during operation of display system 100 in order to obtain the same aging effect under each predetermined stress condition. In other words, a first predetermined stress condition is applied to the first set of reference pixels, a second predetermined stress condition is applied to the second set of reference pixels, and so on. In this example, the display system 100 has sets of reference pixels 130 that are stressed under 16 different stress conditions ranging from low current values to high current values of the pixels. Thus, there are 16 different sets of reference pixels 130 in this example. Of course, a greater or lesser number of stress conditions may be employed, depending on factors such as the desired accuracy of compensation, the physical space in the peripheral region 106, the amount of processing power available, and the amount of memory used to store the characteristic correlation curve data. and other factors.
通过使参考像素或参考像素组连续地经受应力条件，参考像素的组件根据应力条件的运行条件而老化。当在系统100的运行期间将应力条件施加到参考像素时，测量和评估参考像素的电学特性和光学特性，以获得用于确定校正曲线的数据，其中这些校正曲线用于补偿阵列102中的有源像素104的老化。在该示例中，对于每组参考像素130，每小时一次地测量光学特性和电学特性。因此，针对参考像素130的测量特性，更新对应的特性关联曲线。当然，可以在更短的时间段或者更长的时间段内进行这些测量，这取决于老化补偿所期望的精确度。By continuously subjecting a reference pixel or group of reference pixels to a stress condition, the components of the reference pixel age according to the operating conditions of the stress condition. When stress conditions are applied to the reference pixels during operation of the system 100, the electrical and optical properties of the reference pixels are measured and evaluated to obtain data used to determine calibration curves used to compensate for the active elements in the array 102. Aging of source pixels 104 . In this example, for each set of reference pixels 130, the optical and electrical properties are measured hourly. Therefore, for the measured characteristic of the reference pixel 130, the corresponding characteristic correlation curve is updated. Of course, these measurements could be made for shorter or longer periods of time, depending on the desired accuracy of the aging compensation.
一般地，OLED204的亮度与被施加到OLED204的电流具有直接的线性关系。OLED的光学特性可以被表示为：Generally, the brightness of OLED 204 has a direct linear relationship with the current applied to OLED 204 . The optical properties of OLEDs can be expressed as:
L＝O*IL=O*I
在该公式中，亮度L是基于OLED的特性的系数O乘以电流I的结果。随着OLED204老化，系数O减小，并且因此在恒定电流值下，亮度减小。因此，在给定电流下测量的亮度可用于针对预定应力条件下在特定时间处确定特定OLED204的系数O的由老化引起的特性变化。In this formula, the luminance L is the result of multiplying the current I by the coefficient O based on the characteristics of the OLED. As the OLED 204 ages, the coefficient O decreases, and thus at a constant current value, the brightness decreases. Accordingly, the measured luminance at a given current can be used to determine the aging-induced characteristic change of coefficient O for a particular OLED 204 at a particular time under predetermined stress conditions.
测量的电学特性表示被提供到驱动晶体管202的电压与由此在OLED204中产生的电流之间的关系。例如，可以利用电压传感器或诸如图2中的监测晶体管210之类的薄膜晶体管来测量用于实现参考像素的OLED中的恒定电流水平所需的电压的变化。所需的电压一般随着OLED204和驱动晶体管202老化而增大。所需的电压与输出电流具有幂次律关系，如以下公式所示。The measured electrical characteristic represents the relationship between the voltage supplied to the drive transistor 202 and the current generated in the OLED 204 thereby. For example, a voltage sensor or a thin film transistor such as monitor transistor 210 in FIG. 2 can be used to measure the change in voltage required to achieve a constant current level in the OLED of the reference pixel. The required voltage generally increases as OLED 204 and drive transistor 202 age. The required voltage has a power law relationship with the output current, as shown in the following equation.
I＝k*(V-e)aI=k*(Ve)a
在该公式中，电流I由与输入电压V减去系数e的结果相乘的常数k确定，其中系数e表示驱动晶体管202的电学特性。因此，电压与电流I具有变量a的幂次律关系。随着晶体管202老化，系数e增大，由此，需要更大的电压来产生相同的电流。因此，从参考像素测量的电流可以用于针对被施加到参考像素的应力条件在特定时间处确定特定参考像素的系数e的值。In this formula, the current I is determined by a constant k multiplied by the input voltage V minus a coefficient e, where the coefficient e represents the electrical characteristics of the driving transistor 202 . Therefore, the voltage and the current I have a power law relationship of the variable a. As the transistor 202 ages, the coefficient e increases, whereby a greater voltage is required to generate the same current. Thus, the current measured from a reference pixel can be used to determine the value of the coefficient e for a particular reference pixel at a particular time for a stress condition applied to the reference pixel.
如上所述，光学特性O表示由光传感器132测量的图2中的参考像素130的OLED204的亮度与OLED204中的电流之间的关系。所测量的电学特性e表示所施加的电压与由此产生的电流之间的关系。在将应力条件施加到参考像素时，可通过诸如图1中的光传感器132之类的光传感器来测量参考像素130在恒定电流水平下的亮度相对于基准光学特性的变化。可以从监测线测量电学特性相对于基准电学特性的变化，以确定电流输出。在显示器系统100的运行期间，将应力条件电流水平连续地施加到参考像素130。当期望测量时，移除该应力条件电流，并且激活选择线214。施加参考电压，并从光传感器132的输出获得由此产生的亮度水平，并且从监测线218测量输出电压。将由此获得的数据与先前的光学数据和电学数据进行比较，以针对特定应力条件确定由老化引起的电流输出和亮度输出的变化，并更新该应力条件下的参考像素的特性。使用经更新的特性数据来更新特性关联曲线。As described above, the optical characteristic O represents the relationship between the brightness of the OLED 204 of the reference pixel 130 in FIG. 2 measured by the light sensor 132 and the current in the OLED 204 . The measured electrical characteristic e represents the relationship between the applied voltage and the resulting current. The change in brightness of reference pixel 130 at a constant current level relative to a reference optical characteristic may be measured by a light sensor, such as light sensor 132 in FIG. 1 , when a stress condition is applied to the reference pixel. A change in the electrical characteristic relative to a reference electrical characteristic can be measured from the monitoring line to determine the current output. During operation of the display system 100 , stress-conditioned current levels are continuously applied to the reference pixels 130 . When a measurement is desired, the stress condition current is removed and select line 214 is activated. A reference voltage is applied and the resulting brightness level is obtained from the output of light sensor 132 and the output voltage is measured from monitor line 218 . The data thus obtained is compared with previous optical and electrical data to determine aging-induced changes in current output and luminance output for a particular stress condition and to update the characteristics of the reference pixel under that stress condition. The property correlation curve is updated using the updated property data.
然后，通过使用从参考像素测量的电学特性和光学特性，针对预定应力条件确定随时间的特性关联曲线(或函数)。针对在该应力条件下运行的给定像素，特性关联曲线提供了预期的电学老化和光学劣化之间的可量化关系。更特别地，特性关联曲线上的每个点确定了在对参考像素130进行测量的给定时间处该应力条件下的给定像素的OLED的光学特性和电学特性之间的相关性。然后，对于在与被施加到参考像素130的应力条件相同的应力条件下已经老化的有源像素104，控制器112可以使用该特性来确定适当的补偿电压。在另一个示例中，可以在测量参考像素的OLED的光学特性的同时周期性地从基础OLED器件测量基准光学特性。基础OLED器件不被加应力或者以已知和受控的速率被加应力。这将消除对参考OLED特性的任何环境影响。Then, by using the electrical and optical properties measured from the reference pixels, a characteristic correlation curve (or function) over time is determined for predetermined stress conditions. The characteristic correlation curve provides a quantifiable relationship between the expected electrical aging and optical degradation for a given pixel operating under this stress condition. More particularly, each point on the characteristic correlation curve determines the correlation between the optical and electrical properties of the OLED of a given pixel under that stress condition at a given time at which the reference pixel 130 is measured. Controller 112 may then use this characteristic to determine an appropriate compensation voltage for active pixels 104 that have aged under the same stress conditions as were applied to reference pixel 130 . In another example, a reference optical characteristic can be periodically measured from the base OLED device at the same time as the optical characteristic of the OLED of the reference pixel is measured. The base OLED device was either unstressed or stressed at a known and controlled rate. This will remove any environmental influence on the characteristics of the reference OLED.
由于本领域技术人员已知的制造工艺和其它因素，显示器系统100的每个参考像素130可能不具有均匀的特性，这导致不同的发光性能。在一种技术中，对通过在预定应力条件下由成组的参考像素获得的电学特性的值和亮度特性的值求平均。应力条件对平均像素的影响的更好表达是通过如下方式获得的：向成组的参考像素130加应力条件，并且应用轮询平均(pollingaveraging)技术以避免在向参考像素加应力条件期间可能出现的缺陷、测量噪声和其它问题。例如，可以通过平均化来去除错误值(例如，由于噪声或失效的参考像素而确定的错误值)。这种技术可以具有必须在那些值被包含在平均化中之前被满足的预定的亮度水平和电学特性。对于给定应力条件下的参考像素，还可以使用额外的统计回归技术向与其它测量值显著不同的电学和光学特性值提供较小权重。Due to manufacturing processes and other factors known to those skilled in the art, each reference pixel 130 of the display system 100 may not have uniform characteristics, resulting in different light emitting properties. In one technique, values of electrical characteristics and values of luminance characteristics obtained by groups of reference pixels under predetermined stress conditions are averaged. A better representation of the effect of a stress condition on an averaged pixel is obtained by applying a stress condition to groups of reference pixels 130, and applying a polling averaging technique to avoid possible occurrences during stressing of the reference pixels. imperfections, measurement noise, and other issues. For example, erroneous values (eg, erroneous values determined due to noise or failed reference pixels) may be removed by averaging. Such techniques may have predetermined brightness levels and electrical characteristics that must be met before those values are included in the averaging. Additional statistical regression techniques can also be used to give less weight to electrical and optical property values that differ significantly from other measurements for a reference pixel at a given stress condition.
在该示例中，将每个应力条件施加到不同组的参考像素。测量参考像素的光学特性和电学特性，并且采用轮询平均技术和/或统计回归技术来确定与每个应力条件对应的不同特性关联曲线。将不同的特性关联曲线存储在存储器118中。虽然该示例使用参考器件来确定关联曲线，但可以按照诸如根据历史数据或者由制造商预定的方式之类的其它方式来确定关联曲线。In this example, each stress condition is applied to a different set of reference pixels. The optical and electrical properties of the reference pixels are measured, and round-robin averaging techniques and/or statistical regression techniques are used to determine different property correlation curves corresponding to each stress condition. The various characteristic correlation curves are stored in the memory 118 . Although this example uses a reference device to determine the correlation curve, the correlation curve may be determined in other ways, such as from historical data or predetermined by the manufacturer.
在显示器系统100的运行期间，每组的参考像素130可以经受各自的应力条件，并且可通过控制器112来更新最初被存储在存储器118中的特性关联曲线以反映出从与有源像素104经受相同的外部条件的参考像素130获得的数据。因而，可以基于在显示器系统100的运行期间对参考像素130的电学特性和亮度特性的测量来调整每个有源像素104的特性关联曲线。因此，将每个应力条件下的电学特性和亮度特性存储在存储器118中并在显示器系统100的运行期间对其更新。数据的存储可以是分段线性模型。在该示例中，这种分段线性模型具有16个系数，这16个系数在测量参考像素130的电压和亮度特性时被更新。可替代地，可以通过使用线性回归或者通过将数据存储在存储器118中的查找表中来确定和更新曲线。During operation of the display system 100, each set of reference pixels 130 may be subjected to individual stress conditions, and the characteristic correlation curves originally stored in the memory 118 may be updated by the controller 112 to reflect the stresses experienced from the active pixels 104. Data obtained from the reference pixel 130 under the same external conditions. Thus, the characteristic correlation curve for each active pixel 104 may be adjusted based on measurements of the electrical and luminance characteristics of the reference pixel 130 during operation of the display system 100 . Accordingly, the electrical and luminance characteristics for each stress condition are stored in memory 118 and updated during operation of display system 100 . The storage of data can be a piecewise linear model. In this example, such a piecewise linear model has 16 coefficients that are updated when measuring the voltage and luminance characteristics of the reference pixel 130 . Alternatively, the curve may be determined and updated by using linear regression or by storing the data in a lookup table in memory 118 .
产生和存储每个可能应力条件下的特性关联曲线是不切实际的，这是因为将会需要大量的资源(例如，存储器存储、处理能力等)。所公开的显示器系统100通过如下操作克服了这种限制：确定和存储预定的应力条件下的特性关联曲线的离散数，并且随后通过使用线性或非线性算法来组合那些预定义的特性关联曲线以根据每个像素的特定的运行条件合成显示器系统100的每个像素104的补偿因子。如上所述，在该示例中，存在16个不同的预定应力条件的范围，并且因此在存储器118中存储有16个不同的特性关联曲线。It is impractical to generate and store characteristic correlation curves for every possible stress condition, since significant resources (eg, memory storage, processing power, etc.) would be required. The disclosed display system 100 overcomes this limitation by determining and storing a discrete number of characteristic correlation curves under predetermined stress conditions, and then combining those predefined characteristic correlation curves by using linear or non-linear algorithms to The compensation factor for each pixel 104 of the display system 100 is synthesized according to the particular operating conditions of each pixel. As mentioned above, in this example there are 16 different ranges of predetermined stress conditions, and thus 16 different characteristic correlation curves stored in the memory 118 .
对于每个像素104，显示器系统100分析正被施加到该像素104的应力条件，并且通过使用算法并基于面板像素的预定义的特性关联曲线和所测量的电学老化来确定补偿因子。然后，显示器系统100基于补偿因子向像素提供电压。因此，控制器112确定特定像素104的应力，并且针对特定像素104的应力条件确定最接近的两个预定应力条件以及从在这些预定的应力条件下的参考像素130获得的伴随的特性数据。因此，有源像素104的应力条件落在低的预定应力条件与高的预定应力条件之间。For each pixel 104, the display system 100 analyzes the stress conditions being applied to that pixel 104 and determines a compensation factor by using an algorithm based on the panel pixel's predefined characteristic correlation curve and the measured electrical aging. The display system 100 then provides voltages to the pixels based on the compensation factor. Accordingly, the controller 112 determines the stress of a particular pixel 104 and determines the closest two predetermined stress conditions for the particular pixel 104 stress condition and the accompanying characteristic data obtained from the reference pixel 130 under these predetermined stress conditions. Accordingly, the stress condition of the active pixel 104 falls between a low predetermined stress condition and a high predetermined stress condition.
为了便于公开，通过两个这种预定义的特性关联曲线来描述以下用于对特性关联曲线进行组合的线性和非线性公式的示例；然而，应当理解，在用于组合特性关联曲线的示例性技术中可以利用任何其它数量的预定义特性关联曲线。这两个示例性特性关联曲线包括针对高应力条件确定的第一特性关联曲线和针对低应力条件确定的第二特性关联曲线。For ease of disclosure, the following examples of linear and non-linear formulations for combining property-correlation curves are described in terms of two such predefined property-correlation curves; however, it should be understood that in the exemplary Any other number of predefined characteristic correlation curves may be utilized in the technique. The two exemplary characteristic correlation curves include a first characteristic correlation curve determined for high stress conditions and a second characteristic correlation curve determined for low stress conditions.
对不同的水平使用不同特性关联曲线的能力能够向经受与被施加到参考像素130的预定应力条件不同的应力条件的有源像素104提供了精确的补偿。图3是示出了有源像素104的随时间的不同应力条件的曲线图，其示出了随时间发出的亮度水平。在第一时间段期间，有源像素的亮度由迹线302表示，迹线302示出了亮度在300与500尼特(cd/cm2)之间。因此，在迹线302期间被施加到有源像素的应力条件相对较高。在第二时间段中，有源像素的亮度由迹线304表示，迹线304示出了亮度在300与100尼特之间。因此，在迹线304期间的应力条件低于第一时间段的应力条件，并且在此期间的像素的老化效应不同于高应力条件下的老化效应。在第三时间段中，有源像素的亮度由迹线306表示，迹线306示出了亮度在100与0尼特之间。在该时段期间的应力条件低于第二时间段的应力条件。在第四时间段中，有源像素的亮度由迹线308表示，迹线308示出了向基于400与500尼特之间的较高亮度的较高应力条件的返回。The ability to use different characteristic correlation curves for different levels can provide accurate compensation for active pixels 104 subjected to different stress conditions than the predetermined stress conditions applied to the reference pixel 130 . FIG. 3 is a graph illustrating different stress conditions for active pixels 104 over time, showing emitted brightness levels over time. During the first time period, the luminance of the active pixels is represented by trace 302, which shows a luminance between 300 and 500 nits (cd/cm2 ). Therefore, the stress conditions applied to the active pixels during trace 302 are relatively high. During the second time period, the brightness of the active pixels is represented by trace 304, which shows that the brightness is between 300 and 100 nits. Thus, the stress conditions during trace 304 are lower than the stress conditions of the first time period, and the aging effects of the pixels during this period are different from the aging effects of the high stress conditions. During the third time period, the brightness of the active pixels is represented by trace 306, which shows that the brightness is between 100 and 0 nits. The stress conditions during the time period are lower than the stress conditions of the second time period. In the fourth time period, the brightness of the active pixels is represented by trace 308, which shows a return to higher stress conditions based on higher brightness between 400 and 500 nits.
对于每个有源像素104的具体应力条件，有限数量的参考像素130以及对应的有限数量的应力条件可要求使用平均或连续(移动)平均。对于每个像素，具体应力条件可以被映射为来自多个参考像素130的特性关联曲线的线性组合。预定应力条件下的两个特性曲线的组合能够对出现在这些应力条件之间的所有应力条件进行精确的补偿。例如，高和低应力条件下的两个参考特性关联曲线能够为具有处于这两个参考曲线之间的应力条件的有源像素确定接近的特性关联曲线。控制器112使用加权移动平均算法(weightedmovingaveragealgorithm)来组合被存储在存储器118中的第一和第二参考特性关联曲线。有源像素在某个时间处的应力条件St(ti)可以被表示为：For a particular stress condition for each active pixel 104, a limited number of reference pixels 130 and a corresponding limited number of stress conditions may require the use of an average or a running (moving) average. For each pixel, a specific stress condition may be mapped as a linear combination of characteristic correlation curves from multiple reference pixels 130 . The combination of the two characteristic curves at predetermined stress conditions enables an accurate compensation of all stress conditions occurring between these stress conditions. For example, two reference characteristic correlation curves at high and low stress conditions can determine a close characteristic correlation curve for active pixels with stress conditions between these two reference curves. The controller 112 combines the first and second reference characteristic correlation curves stored in the memory 118 using a weighted moving average algorithm. The stress condition St(ti ) of an active pixel at a certain time can be expressed as:
St(ti)＝(St(ti-1)*kavg+L(ti))/(kavg+1)St(ti )＝(St(ti-1 )*kavg +L(ti ))/(kavg +1)
在该公式中，St(ti-1)是在先前时间处的应力条件，kavg是移动平均常数。L(ti)是有源像素在该某个时间处的测量亮度，其可以通过如下公式确定：In this formula, St(ti-1 ) is the stress condition at the previous time and kavg is the moving average constant. L(ti ) is the measured brightness of the active pixel at that certain time, which can be determined by the following formula:
在该公式中，Lpeak是显示器系统100的设计容许的最高亮度。变量g(ti)是在测量时的灰度，gpeak是使用的最高灰度值(例如，255)，且γ是伽马常数。使用预定的高和低应力条件的特性关联曲线的加权移动平均算法可以经由以下公式来确定补偿因子Kcomp：In this formula, Lpeak is the highest brightness allowed by the design of the display system 100 . The variable g(ti ) is the grayscale at the time of measurement,gpeak is the highest grayscale value used (eg, 255), and γ is the gamma constant. A weighted moving average algorithm using characteristic correlation curves for predetermined high and low stress conditions can determine the compensation factorKcomp via the following formula:
Kcomp＝Khighfhigh(ΔI)+Klowflow(ΔI)Kcomp ＝Khigh fhigh (ΔI)+Klow flow (ΔI)
在该公式中，fhigh是与高预定应力条件的特性关联曲线相对应的第一函数，并且flow是与低预定应力条件的特性关联曲线相对应的第二函数。ΔI是在固定电压输入下OLED中的电流的变化，其示出了在特定时间处测量的由老化效应引起的变化(电学劣化)。应当理解，电流的变化可以被替换为固定电流下的电压的变化ΔV。Khigh是被分配给高应力条件的特性关联曲线的加权变量，并且Klow是被分配给低应力条件的特性关联曲线的权重。可以根据以下公式来确定加权变量Khigh和Klow：In this formula, fhigh is a first function corresponding to a characteristic correlation curve for a high predetermined stress condition, and flow is a second function corresponding to a characteristic correlation curve for a low predetermined stress condition. ΔI is the change in current in the OLED at a fixed voltage input, which shows the change caused by aging effects (electrical degradation) measured at a specific time. It should be understood that a change in current may be replaced by a change ΔV in voltage at a fixed current. Khigh is a weighting variable assigned to the property correlation curve for high stress conditions, and Klow is a weight assigned to the property correlation curve for low stress conditions. The weighting variables Khigh and Klow can be determined according to the following formula:
Khigh＝St(ti)/LhighKhigh ＝St(ti )/Lhigh
Klow＝1-KhighKlow ＝1-Khigh
这里，Lhigh是与高应力条件相关的亮度。Here, Lhigh is the brightness associated with high stress conditions.
在运行期间的任何时间处的有源像素中的电压或者电流的变化表示电学特性，而作为高或低应力条件的函数的一部分的电流变化表示光学特性。在该示例中，将高应力条件下的亮度、峰值亮度和平均补偿因子(两个特性关联曲线之间的差的函数)Kavg存储在存储器118中，以用于确定每个有源像素的补偿因子。将附加变量存储在存储器118中，附加变量包括但不限于显示器系统100容许的最大亮度的灰度值(例如，灰度值255)。另外，可以根据将应力条件施加到参考像素期间获得的数据来凭经验地确定平均补偿因子Kavg。A change in voltage or current in an active pixel at any time during operation represents an electrical characteristic, while a change in current as a fraction of a function of high or low stress conditions represents an optical characteristic. In this example, the luminance under high stress conditions, the peak luminance, and the average compensation factor (a function of the difference between the two characteristic correlation curves) Kavg are stored in memory 118 for use in determining the luminance of each active pixel. compensation factor. Additional variables are stored in memory 118 including, but not limited to, the grayscale value of the maximum brightness allowed by display system 100 (eg, grayscale value 255). Additionally, the average compensation factor Kavg can be empirically determined from data obtained during application of stress conditions to the reference pixels.
因而，可以调整显示器系统100中的任何像素104的光学劣化和电学老化之间的关系，以避免与由不同的应力条件引起的特性关联曲线的差别(divergence)相关的误差。所存储的特性关联曲线的数量还可以被最小化到如下数量，该数量确保平均技术对于所要求的补偿水平来说是足够精确的。Thus, the relationship between optical degradation and electrical aging for any pixel 104 in the display system 100 can be adjusted to avoid errors associated with divergence of characteristic correlation curves caused by different stress conditions. The number of stored characteristic correlation curves can also be minimized to a number which ensures that the averaging technique is sufficiently accurate for the required level of compensation.
补偿因子Kcomp可以用于通过调节有源像素的编程电压来补偿OLED光效率老化。另一个用于针对有源像素上的应力条件确定适当的补偿因子的技术可以被称为动态移动平均(dynamicmovingaveraging)。动态移动平均技术包括：在显示器系统100的寿命期间改变移动平均系数Kavg，以对不同的预定应力条件下的两个特性关联曲线之间的差别进行补偿，从而防止显示器输出的畸变。随着有源像素的OLED老化，不同应力条件下的两个特性关联曲线之间的差别增大。因此，在显示器系统100的寿命期间可以增大Kavg，以避免具有落在两个预定应力条件之间的应力条件的有源像素的两个曲线之间的急剧过渡。可以使用所测量的电流变化ΔI来调节Kavg值，以提高用于确定补偿因子的算法的性能。The compensation factor Kcomp can be used to compensate OLED light efficiency aging by adjusting the programming voltage of active pixels. Another technique for determining an appropriate compensation factor for stress conditions on active pixels may be referred to as dynamic moving averaging. The dynamic moving average technique includes: changing the moving average coefficient Kavg during the lifetime of the display system 100 to compensate for the difference between the two characteristic correlation curves under different predetermined stress conditions, thereby preventing distortion of the display output. As the OLED of the active pixel ages, the difference between the two characteristic correlation curves under different stress conditions increases. Accordingly, Kavg may be increased during the lifetime of the display system 100 to avoid sharp transitions between the two curves for active pixels having stress conditions that fall between two predetermined stress conditions. The measured current change ΔI can be used to adjust the Kavg value to improve the performance of the algorithm used to determine the compensation factor.
在另一个用于提高补偿处理的性能的技术(被称为基于事件的移动平均)中，在每个老化阶段之后使系统复位。该技术进一步提高了对每个有源像素104的OLED的特性关联曲线的提取。在每个老化阶段之后(或者在用户开启或者关闭显示器系统100之后)复位显示器系统100。在该示例中，通过如下公式来确定补偿因子Kcomp：In another technique for improving the performance of the compensation process, known as event-based moving average, the system is reset after each aging period. This technique further improves the extraction of the characteristic correlation curve of the OLED of each active pixel 104 . The display system 100 is reset after each burn-in period (or after the user turns the display system 100 on or off). In this example, the compensation factor Kcomp is determined by the following formula:
Kcomp＝Kcomp_evt+Khigh(fhigh(ΔI)-fhigh(ΔIevt))+Klow(flow(ΔI)-flow(ΔIevt))Kcomp ＝Kcomp_evt +Khigh (fhigh (ΔI)-fhigh (ΔIevt ))+Klow (flow (ΔI)-flow (ΔIevt ))
在该公式中，Kcomp_evt是在先前时间处计算的补偿因子，并且ΔIevt是在固定电压下在先前时间期间的OLED电流的变化。如同其它补偿确定技术一样，电流的变化可以被替换为固定电流下的OLED电压的变化。In this formula, Kcomp_evt is a compensation factor calculated at a previous time, and ΔIevt is a change in OLED current at a fixed voltage during a previous time. As with other compensation determination techniques, changes in current can be replaced by changes in OLED voltage at a fixed current.
图4是示出了基于不同技术的不同特性关联曲线的曲线图400。曲线图400比较了光学补偿百分比的变化和用于产生给定电流所需的有源像素的OLED的电压的变化。如曲线图400所示，在用于反映有源像素老化的电压的更大的变化处，高应力预定特性关联曲线402从低应力预定特性关联曲线404偏离。成组的点406表示通过移动平均(movingaveraging)技术并根据预定特性关联曲线402和404在不同的电压变化处确定的用于有源像素的电流补偿的校正曲线。随着用于反映老化的电压的变化增大，校正曲线406的过渡在低应力特性关联曲线404和高应力特性关联曲线402之间具有急剧过渡。成组的点408表示通过动态移动平均(dynamicmovingaveraging)技术确定的特性关联曲线。成组的点410表示通过基于事件的移动平均(event-basedmovingaveraging)技术确定的补偿因子。基于OLED特性，可以使用上述技术中的一种技术来提高对OLED效率劣化的补偿。FIG. 4 is a graph 400 showing different characteristic correlation curves based on different technologies. Graph 400 compares the change in percent optical compensation to the change in voltage used to produce the OLED of an active pixel required for a given current. As shown in graph 400 , high stress predetermined characteristic correlation curve 402 deviates from low stress predetermined characteristic correlation curve 404 at greater changes in voltage used to reflect active pixel aging. Groups of points 406 represent correction curves for current compensation of active pixels determined by a moving averaging technique and according to predetermined characteristic correlation curves 402 and 404 at different voltage variations. The transition of the calibration curve 406 has a sharp transition between the low stress characteristic correlation curve 404 and the high stress characteristic correlation curve 402 as the change in voltage to reflect aging increases. Groups of points 408 represent characteristic correlation curves determined by dynamic moving averaging techniques. Groups of points 410 represent compensation factors determined by an event-based moving averaging technique. Based on OLED characteristics, one of the techniques described above can be used to improve compensation for OLED efficiency degradation.
如上所述，测量第一组样本像素的电学特性。例如，可以通过与每个像素连接的薄膜晶体管(TFT)来测量第一组样本像素中的每个像素的电学特性。可替代地，例如，可以通过为第一组的样本像素中的每个像素设置的光传感器来测量光学特性(例如，亮度)。可以根据一个以上的像素的电压的漂移来提取每个像素的亮度所要求的变化量。这可以通过用于确定被提供到像素的电压或者电流的漂移和/或该像素中的发光材料的亮度之间的相关性的一系列计算来实现。As described above, the electrical characteristics of the first set of sample pixels are measured. For example, the electrical characteristics of each pixel in the first set of sample pixels can be measured through a thin film transistor (TFT) connected to each pixel. Alternatively, for example, an optical characteristic (eg, luminance) may be measured by a photosensor provided for each of the sample pixels of the first group. The required amount of change in brightness of each pixel can be extracted from the shift in voltage of more than one pixel. This may be achieved by a series of calculations for determining the correlation between the drift of the voltage or current supplied to the pixel and/or the brightness of the luminescent material in the pixel.
可以通过诸如图1中的控制器112的处理器件或者其它此类器件之类的处理器件来执行上述用于提取特性关联曲线以补偿阵列中的像素的老化的方法，对于计算机、软件和网络领域的技术人员来说能够理解的是，可以据如本文中描述和示出的教导而经过编程的一个以上的通用计算机系统、微处理器、数字信号处理器、微控制器、专用集成电路(ASIC)、可编程逻辑器件(PLD)、现场可编程逻辑器件(FPLD)、现场可编程门阵列(FPGA)等方便地实现上述处理器件。The above-mentioned method for extracting a characteristic correlation curve to compensate for aging of pixels in an array may be performed by a processing device such as the processing device of the controller 112 in FIG. 1 or other such devices, for computer, software and network fields It will be understood by those skilled in the art that one or more general purpose computer systems, microprocessors, digital signal processors, microcontrollers, application specific integrated circuits (ASIC ), Programmable Logic Devices (PLD), Field Programmable Logic Devices (FPLD), Field Programmable Gate Arrays (FPGA), etc. to conveniently implement the above processing devices.
另外，两个以上的计算系统或器件可以代替本文中描述的控制器中的任何一个。因此，如需要，还能够实现诸如冗余、复制等之类的分布式处理的原理和优点，以增加本文中描述的控制器的稳健性和性能。Additionally, two or more computing systems or devices may replace any one of the controllers described herein. Thus, the principles and advantages of distributed processing such as redundancy, replication, etc. can also be implemented, if desired, to increase the robustness and performance of the controllers described herein.
可以通过机器可读指令来执行用于补偿老化方法的示例特性关联曲线的操作。在这些示例中，机器可读指令包括由如下装置执行的算法：(a)处理器、(b)控制器、和/或(c)一个以上的其它合适的处理器件。算法可以被实施为诸如闪存存储器、CD-ROM、软盘、硬盘驱动、数字视频(多用途)盘(DVD)之类的有形介质或者其它存储器件上存储的软件，但是本领域技术人员将容易理解，整个算法和/或其部分能够可替代地由除处理器以外的器件执行和/或以公知的方式被实施为固件或专用硬件(例如，它可以由专用集成电路(ASIC)、可编程逻辑器件(PLD)、现场可编程逻辑器件(FPLD)、现场可编程门阵列(FPGA)、离散的逻辑等来实施)。例如，用于补偿老化方法的特性关联曲线的组成部分的任一者或全部能够由软件、硬件和/或固件来实施。此外，可以手动地实施所描绘的机器可读指令的一些或全部。Operations of example characteristic correlation curves for compensating aging methods may be performed by machine readable instructions. In these examples, machine-readable instructions include algorithms executed by (a) a processor, (b) a controller, and/or (c) one or more other suitable processing devices. The algorithm may be implemented as software stored on a tangible medium such as flash memory, CD-ROM, floppy disk, hard drive, digital video (versatile) disk (DVD), or other storage device, but will be readily understood by those skilled in the art. , the entire algorithm and/or portions thereof can alternatively be executed by a device other than a processor and/or be implemented as firmware or dedicated hardware in a known manner (e.g., it can be implemented by an application-specific integrated circuit (ASIC), programmable logic device (PLD), field programmable logic device (FPLD), field programmable gate array (FPGA), discrete logic, etc.). For example, any or all of the components of the characteristic correlation curve for the compensation aging method can be implemented by software, hardware and/or firmware. Additionally, some or all of the depicted machine-readable instructions may be implemented manually.
图5是用于确定和更新显示器系统(例如，图1中的显示器系统100)的特性关联曲线的过程的流程图。选择应力条件，以提供用于对有源像素的应力条件的范围进行关联的充分的基准(500)。然后，为每个应力条件选择一组参考像素(502)。然后，在每个应力条件处对与该应力条件相对应的每个组的参考像素加应力，并且存储基准的光学特性和电学特性(504)。以周期性间隔测量并记录每个组中的每个像素的亮度水平(506)。然后，通过对每个应力条件下的像素组中的每个像素的所测量的亮度求平均来确定亮度特性(508)。确定每组中的每个像素的电学特性(510)。确定组中的每个像素的平均值，以确定平均电学特性(512)。然后，使用每组的平均亮度特性和平均电学特性来更新对应的预定应力条件下的特性关联曲线(514)。一旦确定和更新关联曲线，控制器可以使用经更新的特性关联曲线来补偿经受不同应力条件的有源像素的老化效应。FIG. 5 is a flowchart of a process for determining and updating a characteristic correlation curve for a display system (eg, display system 100 in FIG. 1 ). The stress conditions are selected to provide a sufficient basis for correlating a range of stress conditions for active pixels (500). Then, a set of reference pixels is selected for each stress condition (502). Each set of reference pixels corresponding to the stress condition is then stressed at each stress condition and the optical and electrical properties of the reference are stored (504). The brightness level of each pixel in each group is measured and recorded at periodic intervals (506). A brightness characteristic is then determined by averaging the measured brightness for each pixel in the pixel group under each stress condition (508). Electrical characteristics of each pixel in each group are determined (510). An average value is determined for each pixel in the group to determine an average electrical characteristic (512). The average luminance characteristic and the average electrical characteristic of each group are then used to update the characteristic correlation curve under the corresponding predetermined stress condition (514). Once the correlation curve is determined and updated, the controller can use the updated characteristic correlation curve to compensate for aging effects of active pixels subjected to different stress conditions.
参考图6，示出了使用如在图5中的过程中获得的用于显示器系统100的适当的预定特性关联曲线来确定给定时刻处的有源像素的补偿因子的过程的流程图。基于最高亮度和编程电压来确定有源像素发出的亮度(600)。基于先前的应力条件、所确定的亮度以及平均补偿因子测量特定有源像素的应力条件(602)。从存储器读取适当的预定应力特性关联曲线(604)。在该示例中，两个特性关联曲线对应于预定应力条件，其中，有源像素的所测量的应力条件落在这些预定应力条件之间。然后，控制器112通过使用从有源像素测量的电流或电压变化并根据每个预定应力条件来确定系数(606)。然后，控制器确定修改后的系数，以计算补偿电压并将其添加到有源像素的编程电压(608)。将所确定的应力条件存储在存储器中(610)。然后，控制器112存储新的补偿因子，然后可以在测量参考像素130之后的每个帧时段期间采用该新的补偿因子来修改有源像素的编程电压(612)。Referring to FIG. 6 , there is shown a flowchart of a process for determining a compensation factor for an active pixel at a given instant using an appropriate predetermined characteristic correlation curve for the display system 100 as obtained in the process in FIG. 5 . The brightness emitted by the active pixel is determined based on the highest brightness and the programming voltage (600). The stress condition for a particular active pixel is measured based on the previous stress condition, the determined brightness, and the average compensation factor (602). The appropriate predetermined stress profile is read from memory (604). In this example, the two characteristic correlation curves correspond to predetermined stress conditions between which the measured stress conditions of the active pixels fall. The controller 112 then determines a coefficient according to each predetermined stress condition by using the current or voltage change measured from the active pixel (606). The controller then determines the modified coefficients to calculate and add the compensation voltage to the active pixel's programming voltage (608). The determined stress conditions are stored in memory (610). The controller 112 then stores the new compensation factor, which can then be employed to modify the programming voltage of the active pixels during each frame period after measuring the reference pixel 130 (612).
能够基于OLED电学变化与效率劣化之间的相关性曲线(例如，图7中的相关性曲线)来计算OLED效率劣化。这里，检测OLED电学参数的变化，并使用这个值来从曲线提取效率劣化。接着，可相应地调节像素电流，以补偿劣化。主要挑战在于，相关性曲线是应力条件的函数。因此，为了实现更精确的补偿，一种需要就是考虑不同应力条件的影响。在一种方法中，使用每个像素(像素组)的应力条件在不同的相关性曲线之中进行选择，以针对每个具体情形提取适当的效率损失。现在，将描述多个用于确定应力条件的方法。OLED efficiency degradation can be calculated based on a correlation curve (eg, the correlation curve in FIG. 7 ) between OLED electrical changes and efficiency degradation. Here, the variation of the OLED electrical parameter is detected and this value is used to extract the efficiency degradation from the curve. Then, the pixel current can be adjusted accordingly to compensate for the degradation. The main challenge is that the correlation curve is a function of stress conditions. Therefore, in order to achieve more accurate compensation, one need is to take into account the effect of different stress conditions. In one approach, the stress condition for each pixel (pixel group) is used to choose among different correlation curves to extract the appropriate efficiency loss for each specific case. Now, a number of methods for determining stress conditions will be described.
首先，可以创建每个像素(像素组)的应力历史。简单地，应力历史可以是应力条件的移动平均。为了提高计算精确度，可以使用加权的应力历史。这里，如在图8中描述的示例中，每个应力的影响可具有基于应力强度或周期的不同权重。例如，在OLED相关性曲线的选择方面，低强度应力的影响小。因此，可以使用在小强度下具有小权重的曲线，例如图8中的曲线。还可以使用子采样(sub-sampling)来计算应力历史，以降低存储器传递活动(memorytransferactivity)。在一种情况下，可以假定应力历史在时间上是低频的。在这种情况下，不需要对每帧的像素条件进行采样。可以基于内容帧速率(contentframerate)修改不同应用的采样速率。这里，在每个帧期间，仅选择少量的像素来获得更新的应力历史。First, a stress history for each pixel (pixel group) can be created. Simply, the stress history can be a moving average of stress conditions. To increase calculation accuracy, weighted stress histories can be used. Here, as in the example depicted in FIG. 8 , the influence of each stress may have a different weight based on stress intensity or period. For example, low-intensity stress has little effect on the selection of OLED correlation curves. Therefore, a curve with small weights at small intensities can be used, such as the curve in Fig. 8 . The stress history can also be calculated using sub-sampling to reduce memory transfer activity. In one case, the stress history can be assumed to be low frequency in time. In this case, there is no need to sample pixel conditions every frame. The sampling rate can be modified for different applications based on the content framerate. Here, during each frame, only a small number of pixels are selected to obtain an updated stress history.
在另一种情况下，可以假定应力历史在空间上是低频的。在这种情况下，不需要对所有像素进行采样。这里，使用像素子集来计算应力历史，并接着可以使用插值技术来计算所有像素的应力历史。In another case, the stress history can be assumed to be spatially low-frequency. In this case, not all pixels need to be sampled. Here, a subset of pixels is used to calculate the stress history, and then an interpolation technique can be used to calculate the stress history for all pixels.
在另一种情况下，可以组合时间上的低采样速率和空间上的低采样速率。In another case, a low sampling rate in time and a low sampling rate in space may be combined.
在一些情况下，可能不能包含应力历史所需的存储器和计算模块。这里，如图9A和9B所示，可以使用OLED电学参数的变化速率来提取应力条件。图9A示出在低、中和高应力条件下的ΔVOLED随时间的变化，且9B示出了相同应力条件下的变化速率与时间的相关性。In some cases, it may not be possible to incorporate the memory and computational modules required for the stress history. Here, as shown in FIGS. 9A and 9B , the stress condition can be extracted using the rate of change of the electrical parameters of the OLED. Figure 9A shows the time-dependent variation of ΔVOLED under low, medium and high stress conditions, and 9B shows the time dependence of the change rate under the same stress conditions.
如图10所示，可以将电学参数的变化速率用作应力条件的指示器。例如，如图10所示，针对不同应力条件，可以对基于电学参数变化的电学参数变化速率进行建模，或者通过实验来提取。还可使用变化速率来基于所测量的变化与电学参数变化速率的比较提取应力条件。这里，使用为电学参数的变化和变化速率建立的函数。可替代地，可以使用应力条件、相关性曲线和所测量的变化参数。As shown in Figure 10, the rate of change of the electrical parameter can be used as an indicator of the stress condition. For example, as shown in FIG. 10 , for different stress conditions, the change rate of the electrical parameter based on the change of the electrical parameter can be modeled or extracted through experiments. The rate of change can also be used to extract stress conditions based on a comparison of the measured change to the rate of change of the electrical parameter. Here, functions established for the change and rate of change of the electrical parameters are used. Alternatively, stress conditions, correlation curves and measured variation parameters may be used.
图11是用于基于OLED电学参数的变化和变化速率的测量来补偿OLED效率劣化的过程的流程图。在这个过程中，在步骤1101中提取OLED参数(例如，OLED电压)的变化，并接着在步骤1102中基于先前提取的值来计算OLED参数的变化速率。接着，步骤1103使用参数的变化和变化速率来识别应力条件。最后，步骤1104根据应力条件、所测量的参数和相关性曲线来计算效率劣化。11 is a flowchart of a process for compensating for OLED efficiency degradation based on measurements of changes and rates of change in OLED electrical parameters. In this process, the variation of an OLED parameter (eg OLED voltage) is extracted in step 1101, and then the rate of change of the OLED parameter is calculated in step 1102 based on the previously extracted values. Next, step 1103 uses the change and rate of change of the parameter to identify stress conditions. Finally, step 1104 calculates efficiency degradation based on the stress conditions, measured parameters and correlation curves.
虽然已经示出和描述了本发明的特定实施例、方面和应用，但是应当理解，本发明不限于在本申请中公开的精确的配置和布局，并且在不脱离如所附权利要求所限定的本发明的精神和范围的情况下各种修改、改变和变化可以根据上述说明而变得明显。While particular embodiments, aspects and applications of the present invention have been shown and described, it is to be understood that the invention is not limited to the precise configurations and arrangements disclosed herein, and without departing from the invention as defined in the appended claims. Various modifications, changes and variations within the spirit and scope of the invention may become apparent from the foregoing description.
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