Disclosure of Invention
Accordingly, what is needed is a method and apparatus for assessing ambient light conditions of an OLED display while eliminating the need for and disadvantages associated with conventional ambient light sensors.
(1) A dual function Organic Light Emitting Diode (OLED) display comprising: a column of pixels, each pixel comprising an OLED coupled in series with a channel of a drive transistor, wherein the series-coupled OLED and the drive transistor of each pixel in the column of pixels are coupled together in a parallel combination; a current sensor configured to convert a current flowing through the parallel combination into an output voltage; a switch configured to decouple the parallel combination from the current sensor in a first switching state and couple the parallel combination to the current sensor in a second switching state; and a controller configured to control the switch to be in the first switch state and to control the drive transistor of each of the pixels in the column to be in a saturation region of operation if the column of pixels is to function in a display mode, and to control the switch to be in the second switch state and to control the drive transistor of each of the pixels in the column to be in a linear region of operation if the column of pixels is to function in a sensing mode.
(2) The dual function OLED display of (1), wherein the switch is further configured to couple a first terminal of the parallel combination to a first bias voltage in the first switch state, wherein the first bias voltage is positive with respect to a second bias voltage coupled to a second terminal of the parallel combination.
(3) The dual function OLED display of (2), wherein the switch is further configured to couple the first end of the parallel combination to a third bias voltage in the second switch state, wherein the third bias voltage is negative with respect to the second bias voltage coupled to the second end of the parallel combination.
(4) The dual function OLED display of (2), wherein the switch is further configured to couple the first end of the parallel combination to a third bias voltage in the second switch state, wherein the third bias voltage is equal to the second bias voltage coupled to the second end of the parallel combination.
(5) The dual function OLED display of (1), wherein the current sensor includes:
an impedance configured to convert a current flowing through the parallel combination into a sense voltage; and
an amplifier configured to amplify the sense voltage to provide the output voltage.
(6) The dual function OLED display of (1), further comprising:
a current reporting circuit configured to communicate the output voltage to the controller.
(7) The dual function OLED display of (6), wherein the current reporting circuit comprises a multiplexer.
(8) The dual function OLED display of (1), wherein the controller is further configured to determine an ambient light level in an environment of the dual function OLED display from the low pass filtered samples of the output voltage.
(9) The dual function OLED display of (8), wherein the controller is further configured to adjust the brightness of the column of pixels when functioning in a display mode based on the ambient light level.
(10) The dual function OLED display of (8), wherein the controller is further configured to determine over a period of time that the column of pixels has been touched based on a difference between an illumination level associated with one or more samples of the output voltage taken over the period of time and the ambient illumination level.
(11) The dual function OLED display of (8), wherein the controller is further configured to determine a proximity of an object to the column of pixels over a period of time based on a difference between an illumination level associated with one or more samples of the output voltage taken over the period of time and the ambient illumination level.
According to an aspect of the present invention, a method of operating a dual function Organic Light Emitting Diode (OLED) display is provided.
(12) A method of operating a dual function Organic Light Emitting Diode (OLED) display, the display comprising a column of pixels, each pixel including an OLED coupled in series with a channel of a drive transistor, the series coupled OLED and drive transistor of each pixel in the column of pixels being coupled together in a parallel combination, the method comprising:
converting the current flowing through the parallel combination into an output voltage with a current sensor;
decoupling the parallel combination from the current sensor with a switch in a first switch state;
coupling the parallel combination to the current sensor with the switch in a second switch state;
controlling the switch to be in the first switch state and the drive transistor of each pixel in the column of pixels to be in a saturated region of operation if the column of pixels is to function in a display mode; and
controlling the switch to be in the second switch state and controlling the drive transistor of each pixel in the column of pixels to be in a linear region of operation if the column of pixels is to function in a sensing mode.
(13) The method of (12), further comprising:
coupling a first terminal of the parallel combination with a first bias voltage in the first switch state, wherein the first bias voltage is positive with respect to a second bias voltage coupled to a second terminal of the parallel combination.
(14) The method of (13), further comprising:
coupling a third bias voltage to the first end of the parallel combination in the second switching state, wherein the third bias voltage is negative with respect to the second bias voltage coupled to the second end of the parallel combination.
(15) The method of (13), further comprising:
coupling, with the switch in the second switch state, the first end of the parallel combination to a third bias voltage, wherein the third bias voltage is equal to the second bias voltage coupled to the second end of the parallel combination.
(16) The method of (12), further comprising:
determining an ambient light level in an environment of the dual function OLED display from the low pass filtered samples of the output voltage.
(17) The method of (16), further comprising:
the brightness of the column of pixels is adjusted when functioning in a display mode based on the ambient light level.
(18) The method of (16), further comprising:
determining, over a period of time, that the column of pixels has been touched based on a difference between a light level associated with one or more samples of the output voltage taken over the period of time and the ambient light level.
(19) The method of (16), further comprising:
determining proximity of an object to the column of pixels over a period of time based on a difference between an illumination level associated with one or more samples of the output voltage taken over the period of time and the ambient illumination level.
Detailed Description
In the following description, numerous specific details are set forth in order to provide a thorough understanding of embodiments of the invention. It will be apparent, however, to one skilled in the art that the embodiments (including structures, systems, and methods) may be practiced without these specific details. The descriptions and representations herein are the ones by which those of ordinary skill in the art effectively convey the substance of their work to others of ordinary skill in the art. In other instances, well-known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention.
References in the specification to "one embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an exemplary embodiment, it is submitted that it is within the knowledge of one skilled in the relevant art to affect such feature, structure, or characteristic in connection with other exemplary embodiments whether or not explicitly described.
I. Overview
The present invention is directed to a method and apparatus for evaluating ambient lighting conditions for an OLED display while eliminating the need for and disadvantages associated with conventional ambient light sensors. Embodiments of the method and apparatus use one or more rows of OLEDs in a display to perform two functions: a typical function of emitting light in the display mode, and an additional function of sensing light in the sensing mode. To perform additional sense mode functions, one or more columns of OLEDs in the display are temporarily placed in a photovoltaic and/or photoconductive mode. In the photovoltaic mode, the OLED is not biased, while in the photoconductive mode, an external reverse bias is applied across the OLED. When the OLED is unbiased in the photovoltaic mode or reverse biased in the photoconductive mode, the OLED operates as a photodiode capable of converting light into electrical current.
The method and apparatus of the present invention uses a sensing circuit (when operating in a sensing mode) to measure the current produced by one or more columns of OLEDs and report the current to a controller. The magnitude of the current is represented by the intensity of light striking one or more columns of OLEDs and can be used by the controller to assess the ambient lighting conditions of the environment in which the OLED display is currently operating. The ambient light may come from several light sources, including the OLED of the display itself (e.g., by reflection from an object in the environment in which the OLED is currently operating). In fact, in a dark room, the reflected light from the OLED becomes the main ambient light source inside. Once evaluated, the controller can use the evaluated ambient light to adjust the brightness or illumination of the OLEDs in the display to meet (but not far exceed) the brightness or illumination required by the ambient lighting conditions, thereby reducing the power consumed by the display. Additionally, the methods and apparatus of the present invention may also perform touch and/or proximity sensing functions using the evaluated ambient lighting conditions. Thus, conventional ambient light sensors, as well as conventional passive or capacitive touch panels and touch controllers, which optionally perform a proximity sensing function, can be eliminated as their functionality can be replaced by the methods and apparatus of the present invention. In addition, a conventional stylus designed for a passive or capacitive touch panel may be replaced with a stylus in the form of a light pen or an LED pen (e.g., a pen that outputs light at its tip), or similar stylus designed to affect an OLED light sensing circuit. These and other features of the method and apparatus of the present invention will be further described with reference to fig. 2-7.
II. Dual function OLED device
As described above, the brightness or luminance of an OLED, when forward biased, can be controlled by adjusting the current through it. Thus, pixel circuits are used in OLED displays to control the current flowing through the OLEDs making up the display so that the image can be formatted. For example, in an active matrix OLED (amoled) display, the pixel circuit includes at least two Thin Film Transistors (TFTs) and a storage capacitor that controls current through the OLED. FIG. 2 shows one example of a pixel circuit 200 of an AMOLED display, which includes an OLED 202, a drive TFT 204, a storage capacitor 206, and an access TFT 208.
In operation, a controller (not shown) selects a pixel circuit 200 in the pixel circuit array using the select line 210 and programs (programs) the brightness or illumination of the OLED 202 using the data line 212. More specifically, the controller applies the appropriate voltage on the select line 210 to turn on the access TFT 208, and once the access TFT 208 is turned on, the controller applies the appropriate voltage on the data line 212 to program the voltage on the gate of the drive TFT 204 so that the OLED 202 provides the desired brightness or illumination.
The storage capacitor 206 is used to prevent the voltage programmed on the gate of the drive TFT 204 from discharging (due to leakage at the access TFT 208). By preventing the voltage programmed on the gate of the drive TFT 204 from discharging, the storage capacitor 206 allows the OLED 202 to be continuously driven by the drive TFT 204 at a desired brightness or luminance while other pixels in the display are selected and programmed. The driving TFT 204 drives the OLED 202 with power provided by a positive voltage source coupled to a first biasing voltage line 214 and a second biasing voltage line 216. The positive voltage source also forward biases the OLED 202.
The drive TFT 204 is saturation biased (i.e., | V) during normal operation of the pixel circuit 200d|>|Vgs-Vt|) so as to appear as a constant current source controlled by the voltage programmed on its gate. Thus, changing the voltage programmed on the gate of the drive TFT 204 changes the current through the OLED 202, thereby controlling its brightness or illumination in a predictable manner. The configuration of pixel circuit 200 may be used to individually program the brightness or illumination of each OLED in the pixel array to format the image for display.
The present invention relates to a method and apparatus for controlling a pixel 200 to perform the function of sensing light in a sensing mode (in addition to emitting light in a display mode as described above). To perform additional sense mode functions, the OLEDs 202 in the pixel circuit 200 are temporarily placed in a photovoltaic and/or photoconductive mode. In the photovoltaic mode, the OLED 202 is not biased, while in the photoconductive mode, an external reverse bias is applied across the OLED 202. When the OLED 202 is unbiased (in photovoltaic mode) or reverse biased (in photoconductive mode), the OLED 202 operates as a photodiode capable of converting light impinging on its surface into electrical current.
A controller (not shown) is configured to place the OLED 202 in the photovoltaic mode and/or the photoconductive mode by controlling the voltages applied on the first bias voltage line 214 and the second bias voltage line 216. More specifically, the controller can alternately switch the voltage applied on the first bias voltage line 214 and the second bias voltage line 216 from a positive voltage (sufficient to forward bias the OLED 202) operating in the display mode to a zero voltage or a negative voltage (sufficient to reverse bias the OLED 202) operating in the sensing mode.
When the pixel 200 is to operate in the sensing mode, the controller is further configured to bias the drive TFT 204 in the linear region (i.e., | V)d|<|Vgs-Vt|) as opposed to its saturation region when the pixel circuit 200 is functioning in the display mode. The controller can do this by programming the appropriate voltage on the gate of the drive TFT 204.
It should be noted that the pixel circuit 200 provides only one example of a pixel circuit of an AMOLED display. Other pixel circuits may also be used in embodiments of the present invention. For example, other pixel circuits with additional circuitry (e.g., to compensate for non-uniformity and stability issues associated with TFTs), different TFT types (e.g., n-type instead of p-type), and/or different programming methods (e.g., current programming instead of voltage programming) may be used. However, each pixel circuit implementation typically includes a drive TFT with its channel in series with the OLED, similar to drive TFT 204 and OLED 202 in fig. 2.
Referring now to FIG. 3, a dual function AMOLED display 300 having an array of pixel circuits 200-1 through 200-9 (each having the same orientation and configuration as the pixel circuit 200 of FIG. 2) that can be used to emit light in a display mode and to sense light in a sensing mode is shown in accordance with an embodiment of the present invention. The AMOLED display 300 includes a select line driver 302, a data line driver 304, and a sensing circuit 306 in addition to the array of pixel circuits 200-1 to 200-9.
In operating one or more of the pixel circuits 200-1 to 200-9 in the display mode, the select line driver 302 and the data line driver 304 work together under the control of a controller (not shown) to select and program each pixel circuit to provide a particular brightness or illumination. More specifically, the select line driver 302 is configured to select a row of pixel circuits for programming by applying an appropriate voltage on one of the select lines 210. For example, select line driver 302 may select pixel circuits 200-2, 200-5, and 200-8 for programming by applying appropriate voltages on select lines of select lines 212 coupled to those pixels. In embodiments where the pixel circuits 200-2, 200-5, and 200-8 have the same orientation and configuration as the pixel circuit 200 of fig. 2, the select line driver 302 selects the row of pixel circuits by turning on the respective access TFTs.
Upon selection, or upon turning on the access TFT using the select line driver 302, the data line driver 304 may program a particular one of the selected pixel circuits by applying an appropriate voltage on a data line of the data lines 212 coupled to the particular pixel circuit. For example, assuming that pixel circuits 200-2, 200-5, and 200-8 are selected by select line driver 302, data line driver 304 may program pixel circuit 200-5 by applying an appropriate programming voltage on one of data lines 212 coupled to pixel circuit 200-5. The programming voltage is programmed onto the gate of the drive TFT of a particular pixel circuit, since the drive TFT is biased in its saturation region in the display mode, as described in fig. 2, the programming voltage on its gate determines the current through the OLED of the pixel circuit, and thus its brightness or illumination.
Each OLED in the array of pixel circuits 200-1 through 200-9 operating in the display mode can be independently selected and programmed by the select line driver 302 and the data line driver 304 in the manner described above to format or create an image for display by the AMOLED display 300. The OLED of each pixel circuit 200-1 to 200-9 operating in the display mode is forward biased by a positive voltage (sufficient to forward bias the OLED) applied on the first bias voltage line 214 and the second bias voltage line 216 coupled to those pixel circuits (i.e., positive with respect to the voltage on the first bias voltage line 214 of the second bias voltage line 216).
In operating one or more of the pixel circuits 200-1 to 200-9 in the sensing mode, the select line driver 302 and the data line driver 304 work together under the control of a controller (not shown) to select and program one or more columns of pixel circuits (or a portion of one or more columns of pixel circuits) for sensing light over a period of time without emitting light. For example, the column of pixel circuits 200-1, 200-2, and 200-3 may be selected by the select line driver 302 and programmed by the data line driver 304 such that their respective drive TFTs operate in their linear operating region, as opposed to their saturated operating region. More specifically, in one embodiment, the data line driver 304 may program the gate of each driving TFT corresponding to the pixel circuits 200-1, 200-2, and 200-3 having the same or similar voltages so that the driving TFTs operate in a linear operation region having the same or similar resistance.
In addition, to operate in the sensing mode, one or more columns of pixel circuits for sensing light are placed in the photovoltaic and/or photoconductive mode under the control of a controller (not shown) by sensing circuitry 306. More specifically, the sensing circuit 306 includes a series of switches S1, S2, and S3, each coupled to a respective column of the array of pixel circuits 200-1 through 200-9. Each switch couples a first one of the first bias voltage lines 214 of the respective column of pixel circuits to one of two different bias voltages Vb1 and Vb3, depending on the mode in which the column of pixel circuits is to operate.
For example, if the column of pixel circuits 200-1, 200-2, and 200-3 is operating in the display mode, the controller may control the switch S1 to couple the first bias voltage line (corresponding to the first bias voltage line in the first bias voltage lines 214 of the column of pixel circuits 200-1, 200-2, and 200-3) to the bias voltage Vb 1. The bias voltage Vb1 is positive with respect to the bias voltage Vb2, and the bias voltage Vb2 is coupled to the second bias voltage line (corresponding to the second bias voltage line in the second bias voltage lines 216 of the column of pixel circuits 200-1, 200-2, and 200-3). Accordingly, the pixel circuits 200-1, 200-2, and 200-3 are forward biased and capable of emitting light in the display mode.
On the other hand, if the column of pixel circuits 200-1, 200-2, and 200-3 is operating in the sensing mode, the controller may control the switch S1 to couple the first bias voltage line (corresponding to the first bias voltage line in the first bias voltage lines 214 of the column of pixel circuits 200-1, 200-2, and 200-3) to the bias voltage Vb 3. The bias voltage Vb3 is negative relative to the bias voltage Vb2 or equal to the bias voltage Vb2, where the bias voltage Vb2 is coupled to the second bias voltage line (corresponding to the second bias voltage line in the second bias voltage lines 216 of the column of pixel circuits 200-1, 200-2, and 200-3). Thus, the pixel circuits 200-1, 200-2, and 200-3 are reverse biased and in their photoconductive mode, or unbiased and in photovoltaic mode, and thus capable of sensing light in the sensing mode.
As described above, the columns of pixel circuits 200-1, 200-2, and 200-3 each include an OLED coupled in series with the channel of the drive TFT as shown in FIG. 2. The serially coupled OLEDs and the drive TFTs of each of the pixel circuits 200-1, 200-2 and 200-3 in the column are further coupled together in a parallel combination. The current sensor included in sensing circuit 306 is configured to measure the resulting current flowing through the parallel combination due to light striking the surface of the OLEDs of pixel circuits 200-1, 200-2, and 200-3 when operating in the sensing mode.
The current sensor in sensing circuit 306, specifically configured to measure the current generated by light striking the OLEDs of pixel circuits 200-1, 200-2, and 200-3, includes an impedance Z1 having a resistive component and a sense amplifier SA 1. The resistive component of impedance Z1 converts the current generated by light striking the OLEDs of pixel circuits 200-1, 200-2 and 200-3 into a sense voltage that is then amplified by sense amplifier SA 1. Sense amplifier SA1 outputs a voltage representative of the magnitude of the measured current and provides the voltage to current reporting circuit 308 for reporting to a controller (not shown).
Other columns of pixel circuits in the array of pixel circuits 200-1 through 200-9 have similar current sensor configurations. For example, the second column of pixel circuits 200-4, 200-5 and 200-6 is coupled to a current sensor having an impedance Z2 and a sense amplifier SA2, and the third column of pixel circuits 200-7, 200-8 and 200-9 is coupled to a current sensor having an impedance Z3 and a sense amplifier SA 3. In addition, each of these current sensors also provides a respective output voltage to the current reporting circuit 308 for reporting to a controller (not shown). It should be noted, however, that the current sensor shown in fig. 3 for each column of pixel circuits represents only one possible current sensor configuration, and that other current sensor configurations may be used. For example, fig. 5 shows another current sensor 500 that may be used. The current sensor 500 includes an amplifier 502 and an optional feedback impedance 504.
The current reporting circuit 308 may communicate the output voltage of each current sensor to a controller (not shown) using any of a number of suitable means. In at least one embodiment, the current reporting circuitry 308 includes at least one multiplexer configured to select one of the output voltages of the current sensors of the sensing circuitry 306 to report to the controller at a time. In other embodiments of sensing circuit 306, current reporting circuit 308 is not used and the output voltage is sent directly to the controller without any intermediate processing (e.g., except for converting the current sensor output voltage from an analog value to a digital value).
Once the output voltage of the current sensor is reported to a controller (not shown), the controller may use the output voltage representing the intensity of light striking the column of OLEDs corresponding to the current sensor to assess the ambient lighting conditions of the environment in which the AMOLED display 300 is currently operating. For example, in one embodiment, the controller may low pass filter a plurality of samples of the output voltage taken over a period of time and reported to it from one or more current sensors in order to assess the ambient lighting conditions of the environment in which the AMOLED display 300 is currently operating. In bright environments, the light generated by the AMOLED display 300 and reflected on the AMOLED display 300 is typically a non-dominant source of the ambient light being evaluated. However, in dark environments, the light generated by and reflected on the AMOLED display 300 typically becomes the dominant source of the evaluated ambient light.
Once evaluated, the controller may use the evaluated ambient lighting conditions to adjust the brightness or illumination of the OLEDs in the AMOLED display 300 to meet (but not far exceed) the brightness or illumination required by the ambient lighting conditions, thereby reducing the power consumed by the display. Thus, if the evaluated ambient lighting condition is bright, the controller may increase the brightness or illumination of the OLEDs in AMOLED display 300, and if the evaluated ambient lighting condition is less bright in comparison, the controller may decrease the brightness or illumination of the OLEDs in AMOLED display 300.
Additionally, the controller may also perform touch and/or proximity sensing functions using the evaluated ambient lighting conditions. For example, in one embodiment, the controller may determine that one or more pixel circuits of a column of pixel circuits in AMOLED display 300 are touched by a finger or some other object based on a difference between an illumination level associated with one or more samples of the output voltage of the current sensor associated with those pixel circuits employed over a period of time and a current estimate of the ambient illumination level. If the difference is greater than some threshold amount, the controller may determine that one or more of those pixels in the column are touched. In general, the evaluated ambient lighting conditions are used to "calibrate" the touch sensing function. The proximity of an object to one or more pixel circuits of a column of pixel circuits in AMOLED display 300 may be determined in a similar manner.
In another example, the controller may also perform a document scanning function commonly used for facsimile operations, or a fingerprint scanning function commonly used for physical user authentication security operations, using the evaluated ambient lighting conditions and one or more pixel circuits configured to operate in a sensing mode and a display mode.
It should be noted that the array of pixel circuits 200-1 to 200-9 includes only a small number of pixel circuits for the sake of clarity. However, in practical implementations of the AMOLED display 300, the array will typically include substantially more pixel circuits, although not all of the pixel circuits are necessary for emitting light in the display mode and sensing light in the sensing mode.
For example, the small group of pixel circuits may be configured to operate in a display mode and a sensing mode, while the other pixel circuits are configured to operate only in the display mode. The sets of pixel circuits configured to operate in the display mode and the sensing mode may be distributed across the entire array of pixel circuits making up the AMOLED display and may include any number of pixel circuits. For example, pixel circuits configured to operate in a display mode and a sensing mode and may be distributed in 10 × 10, 20 × 10, or non-rectangular groupings of an array of pixel circuits making up the AMOLED display, with pixel circuits configured only to operate in the display mode interposed between sets of dual function pixel circuits.
In addition, multiple sets of dual function pixel circuits may be placed in the sensing mode at the same time or at different times and placed in the sensing mode for the same duration or for different durations. However, in at least one embodiment, the multiple sets of dual function pixel circuits are placed in the sensing mode for only a limited period of time before being placed back in the display mode, so that a user of the AMOLED display cannot readily perceive when the multiple sets of dual function pixel circuits are not operating in the operating mode or are serving both purposes.
It should also be noted that the pixel circuit 200 provides only one example of a pixel circuit for implementing the pixel circuits 200-1 to 200-9 shown in fig. 3. Other pixel circuits may also be used in embodiments of the present invention. For example, other pixel circuits with additional circuitry (e.g., to compensate for non-uniformity and stability issues associated with TFTs), different TFT types (e.g., n-type instead of p-type), and/or different programming methods (e.g., current programming instead of voltage programming) may be used. However, each pixel circuit implementation typically includes a drive TFT with its channel in series with the OLED, similar to drive TFT 204 and OLED 202 in fig. 2.
Referring now to FIG. 4, a dual function AMOLED display 400 having an array of pixel circuits 200-1 through 200-9 (each having the same orientation and configuration as the pixel circuit 200 of FIG. 2) that can be used to emit light in a display mode and to sense light in a sensing mode is shown in accordance with an embodiment of the present invention. The AMOLED display 400 is configured to function in the same manner as the AMOLED display 300 described above and shown in fig. 3. However, the AMOLED display 400 includes different sensing circuits 402.
As shown in FIG. 4, sensing circuit 402 includes an exemplary current sensor that includes an impedance Z1 and a sense amplifier SA1 coupled to one or more columns of pixel circuits 200-1 through 200-9. By coupling the current sensor to more than one column of pixel circuits 200-1 to 200-9, the number of components and the complexity of the sensing circuit 402 may be reduced. For example, rather than having separate circuit sensors sense the current flowing through each column of pixel circuits 200-1 to 200-9 operating in the sensing mode, a single current sensor may be used for multiple columns of pixel circuits. However, such grouping of columns may reduce sensing resolution, so a certain balance between the number of columns coupled with a single current sensor and the required sensing resolution may be beneficial.
Referring now to FIG. 6, a flow diagram 600 is shown of a method of operating a dual function AMOLED display, in accordance with an embodiment of the present invention. The method of flowchart 600 is described with continued reference to dual function AMOLED display 300 shown in fig. 3. It should be noted, however, that the method may be implemented by other AMOLED displays, such as AMOLED display 400 shown in fig. 4. It should also be noted that some of the steps of flowchart 600 do not necessarily have to occur in the order shown in fig. 6.
The method of flowchart 600 begins at step 602 and transitions to step 604. In step 604, it is determined by a controller (not shown) of the AMOLED display 300 whether a column of pixel circuits (or a portion of a column of pixel circuits) is operating in a sensing mode or a display mode. For exemplary purposes, the column of pixel circuits 200-1, 200-2, and 200-3 shown in FIG. 3 is discussed herein.
Assuming that the column of pixel circuits 200-1, 200-2, and 200-3 are to operate in the display mode rather than the sensing mode, the flow chart 600 proceeds from step 604 to step 606. In step 606, the controller of the AMOLED display 300 controls the switch S1 to couple the parallel combination of the series-coupled OLEDs and the driving transistors of the column of pixel circuits 200-1, 200-2 and 200-3 to the bias voltage Vb1, wherein the bias voltage Vb1 is substantially positive with respect to the bias voltage Vb 2. When coupled to the bias voltage Vb1, the pixel circuits 200-1, 200-2 and 200-3 are forward biased and can be used to emit light in the display mode as described above.
After step 606, the flowchart 600 transitions to step 608 where the controller of the AMOLED display 300 further controls the drive transistor of each pixel in the column of pixel circuits 200-1, 200-2, and 200-3 to be biased in the saturation region of operation.
Now assuming that the column of pixel circuits 200-1, 200-2, and 200-3 are to operate in a sensing mode rather than a display mode, the flow chart 600 proceeds from step 604 to step 610. In step 610, the controller of the AMOLED display 300 controls the switch S1 to couple the parallel combination of the series-coupled OLEDs and the driving transistors of the column of pixel circuits 200-1, 200-2 and 200-3 to the bias voltage Vb3, the bias voltage Vb3 being equal to or substantially negative with respect to the bias voltage Vb 2. When coupled to the bias voltage Vb3, the pixel circuits 200-1, 200-2, and 200-3 in this column are not biased or reverse biased and can be used to sense light in the sensing mode as described above.
After step 610, the flowchart 600 transitions to step 612 where the controller of the AMOLED display 300 further controls the drive transistors of each pixel in the column of pixel circuits 200-1, 200-2, and 200-3 to be biased in the linear region of operation.
After step 612, flowchart 600 transitions to step 614. In step 614, the current flowing through the parallel combination of the series-coupled OLED and the drive transistor in the column of pixel circuits 200-1, 200-2, and 200-3 operating in the sensing mode is sensed and reported to the controller of the AMOLED display 300. The controller may then use the reported value of current to evaluate an ambient lighting condition of the environment in which the AMOLED display 300 is currently operating.
III implementation of example computer System
It will be apparent to those skilled in the relevant art that various elements and features of the invention as described herein can be implemented in hardware using analog and/or digital circuitry, in software using one or more general or special purpose processors via execution of instructions, or as a combination of hardware and software.
For completeness, the following description of a general-purpose computer system is provided. Embodiments of the present invention may be implemented in hardware, or as a combination of software and hardware. As a result, embodiments of the present invention may be implemented in the context of a computer system or other processing system. Fig. 7 illustrates an example of such a computer system 700. Each of the steps of the flow diagrams depicted in fig. 6 and the controller (not shown) of AMOLED display 300 and AMOLED display 400 may be implemented on one or more distinct computer systems 700.
Computer system 700 includes one or more processors, such as a processor 704. The processor 704 may be a special purpose or general purpose digital signal processor. The processor 704 is connected to a communication infrastructure 702 (e.g., a bus or network). Various software implementations are described with respect to the exemplary computer system. After reading this description, it will become apparent to a person skilled in the relevant art how to implement the invention using other computer systems and/or computer architectures.
Computer system 700 also includes a main memory 706, preferably Random Access Memory (RAM), and may also include a secondary memory 708. For example, secondary memory 708 may include a hard disk drive 710 and/or a removable storage drive 712, representing a floppy diskette drive, a magnetic tape drive, a compact disk drive, etc. The removable storage drive 712 reads from and/or writes to a removable storage unit 716 in a known manner. Removable storage unit 716 represents a floppy disk, magnetic tape, optical disk, etc. which is read by and written to by removable storage drive 712. As will be appreciated by those skilled in the relevant art, the removable storage unit 716 includes a computer usable storage medium having stored therein computer software and/or data.
In alternative implementations, the secondary memory 708 may include other similar means for allowing computer programs or other instructions to be loaded into the computer system 700. Such means may include, for example, a removable storage unit 718 and an interface 714. Examples of such means may include a program cartridge and cartridge interface (such as that found in video game devices), a removable memory chip (such as an EPROM, or PROM) and associated socket, thumb drive and USB port, and other removable storage units 718 and interfaces 714 which allow software and data to be transferred from the removable storage unit 718 to computer system 700.
Computer system 700 may also include a communications interface 720. Communication interface 720 allows software and data to be transferred between computer system 700 and peripheral devices. Examples of communications interface 720 may include a modem, a network interface (e.g., an ethernet card), a communications port, a PCMCIA slot and card, and so forth. Software and data transferred via communications interface 720 are in the form of signals which may be electrical, electromagnetic, optical or other signals capable of being received by communications interface 720. These signals are provided to communications interface 720 through a communications path 722. Communications path 722 carries signals and may be implemented using wire or cable, fiber optics, a phone line, a cellular phone link, an RF link, and other communications channels.
The terms "computer program medium" and "computer-readable medium" as used herein are generally used to refer to tangible storage media such as removable storage units 716 and 718 or a hard disk installed in hard disk drive 710. These computer program products are means for providing software to computer system 700.
Computer programs (also called computer control logic) are stored in main memory 706 and/or secondary memory 708. Computer programs may also be received via communications interface 720. Such computer programs, when executed, enable computer system 700 to implement the present invention as discussed herein. In particular, the computer programs, when executed, enable the processor 704 to perform processes of the present invention, such as any of the methods described herein. Accordingly, such computer programs represent controllers of the computer system 700. Where the invention is implemented using software, the software may be stored in a computer program product and loaded into computer system 700 using removable storage drive 712, interface 714 or communications interface 720.
In another embodiment, the features of the present invention are implemented primarily in hardware using, for example, hardware components such as Application Specific Integrated Circuits (ASICs) and gate arrays. Implementation of a hardware state machine to perform the functions described herein will also be apparent to those skilled in the relevant art.
IV, conclusion
The present invention has been described above with the aid of functional building blocks illustrating specified functions and relationships thereof. The scope of the functional building blocks is arbitrarily defined herein for convenience of description. Alternate ranges may be defined so long as the specified functions and relationships thereof are appropriately performed.