PIXEL CIRCUITS FOR AMOLED DISPLAYS
A method and system determine the characteristics of drive devices and load devices in selected pixels in an array of pixels in a display in which each pixel includes a drive device for supplying current to a load device. The method and system supply current to the load device via the drive device in a selected pixel, the current being a function of a current effective characteristic of at least one of the drive device and the load device; measure the current via a measurement line that is shared by adjacent pixels, and extract the value of a selected effective characteristic of one of the drive and load devices from the effect of the current on another of the drive and load devices. Current may be measured via a read transistor in each pixel.
1 - 10 . (canceled)
11 . A method of determining at least one characteristic of a first organic light emitting device (OLED) in a first pixel in pair of pixels in an array of pixels in a display in which each pixel includes, a drive transistor coupling a supply voltage source to an OLED for controlling the supply of current to the OLED from said supply voltage source, a voltage or current of the first OLED affecting measurements of a second OLED of a second pixel of the pair of pixels and a voltage or current of the second OLED affecting measurements of the first OLED, said display system including a monitor line controllably coupled to said pair of pixels, said method comprising:
measuring a voltage or current over the monitor line generating one or more measurements; and
determining the at least one characteristic of the first OLED with use of said one or more measurements taking into account the effect of the voltage or current of the first OLED on measurements of the second OLED and the effect of the voltage or current of the second OLED on measurements of the first OLED.
12 . The method of claim 11 wherein measuring the voltage or current over the monitor line comprises measuring the at least one characteristic of the second OLED, and wherein determining the at least one characteristic of the first OLED comprises extracting from the one or more measurements, the effect of the voltage or current of the first OLED on the measurements of the at least one characteristic of the second OLED.
13 . The method of claim 11 further comprising:
prior to measuring the voltage or current over the monitor line, forcing the second pixel into a known state,
wherein measuring the voltage or current over the monitor line comprises:
forcing the first OLED into different states and for each state, measuring the at least one characteristic of the first OLED, generating said one or more measurements, and
wherein determining the at least one characteristic of the first OLED comprises extracting from the one or more measurements, the effect of the voltage or current of the second OLED on the one or more measurements of the at least one characteristic of the first OLED.
14 . The method of claim 13 wherein forcing the second pixel into the known state comprises programming the drive transistor of the second pixel to a full ON state.
15 . The method of claim 14 wherein forcing the second pixel into a known state comprises adjusting the voltage of the supply voltage source coupled to the second pixel.
16 . The method of claim 13 wherein the state of the first OLED is controlled with use of the monitor line.
17 . The method of claim 11 further comprising:
prior to measuring the voltage or current over the monitor line, forcing the first pixel and the second pixel into a known state;
wherein measuring the voltage or current over the monitor line comprises:
measuring the voltage or current while the first and second pixels are in the known state, generating a first measurement of the one or more measurements, and
measuring the voltage or current after the first OLED has been controlled by the monitor line into a different state, generating a second measurement of the one or more measurements;
wherein determining the at least one characteristic of the first OLED comprises extracting the at least one characteristic of the first OLED from the second measurement by subtracting out the effect of the voltage or current of the second OLED on the second measurement of the at least one characteristic of the first OLED with use of the first measurement.
18 . The method of claim 11 further comprising adjusting the voltage of the supply voltage source coupled to the second pixel to match a voltage of the monitor line.
19 . A system for determining at least one characteristic of a first organic light emitting device (OLED) in a first pixel of a pair of pixels in an array of pixels in a display in which each pixel includes a drive transistor coupling a supply voltage source to an OLED for controlling the supply of current to the OLED from said supply voltage source, a voltage or current of the first OLED affecting measurements of a second OLED of a second pixel of the pair of pixels and a voltage or current of the second OLED affecting measurements of the first OLED, said display system including a monitor line controllably coupled to said pair of pixels, said system comprising a controller adapted to:
measure a voltage or current over the monitor line generating one or more measurements; and
determine the at least one characteristic of the first OLED with use of said one or more measurements taking into account the effect of the voltage or current of the first OLED on measurements of the second OLED and the effect of the voltage or current of the second OLED on measurements of the first OLED.
20 . The system of claim 19 in which said controller is adapted to measure the voltage or current over the monitor line by measuring the at least one characteristic of the second OLED, and adapted to determine the at least one characteristic of the first OLED by extracting from the one or more measurements, the effect of the voltage or current of the first OLED on the measurements of the at least one characteristic of the second OLED.
21 . The system of claim 19 wherein the controller is further adapted to:
prior to measuring the voltage or current over the monitor line, force the second pixel into a known state,
wherein the controller is adapted to measure the voltage or current over the monitor line by:
forcing the first OLED into different states and for each state, measuring the at least one characteristic of the first OLED, generating said one or more measurements, and
wherein the controller is adapted to determine the at least one characteristic of the first OLED by extracting from the one or more measurements, the effect of the voltage or current of the second OLED on the one or more measurements of the at least one characteristic of the first OLED.
22 . The system of claim 21 wherein the controller is adapted to force the second pixel into the known state by programming the drive transistor of the second pixel to a full ON state.
23 . The system of claim 22 wherein the controller is adapted to force the second pixel into the known state by adjusting the voltage of the supply voltage source coupled to the second pixel.
24 . The system of claim 21 wherein the controller is further adapted to control the state of the first OLED with use of the monitor line.
25 . The system of claim 19 wherein the controller is further adapted to:
prior to measuring the voltage or current over the monitor line, force the first pixel and the second pixel into a known state;
wherein the controller is adapted to measure the voltage or current over the monitor line by:
measuring the voltage or current while the first and second pixels are in the known state, generating a first measurement of the one or more measurements, and
measuring the voltage or current after the first OLED has been controlled by the monitor line into a different state, generating a second measurement of the one or more measurements;
wherein the controller is adapted to determine the at least one characteristic of the first OLED by extracting the at least one characteristic of the first OLED from the second measurement by subtracting out the effect of the voltage or current of the second OLED on the second measurement of the at least one characteristic of the first OLED with use of the first measurement.
26 . The system of claim 19 wherein the controller is further adapted to:
adjust the voltage of the supply voltage source coupled to the second pixel to match a voltage of the monitor line.