SYNCHRONOUSLY AND LOCALLY TURNING-OFF SUB-PIXELS IN UNDER-DISPLAY SENSOR AREA OF AMOLED PANEL

Abstract

An apparatus is described that includes a display panel and a sensor. The display panel includes an array of pixels configured to direct light through a front side of the display panel. Each pixel includes sub-pixels, each of which includes an organic light emitting diode (OLED) and an integrated circuit (IC) for controlling an electrical current to the OLED. The sensor is arranged at a back side of the display panel. The sensor includes an emitter configured to emit electromagnetic radiation transmitted through a first area of the display panel. The IC of sub-pixels of the array of pixels outside the first area includes a first IC arrangement. The IC of sub-pixels of the array of pixels within the first area includes a transistor in addition to the first IC arrangement. The transistor is configured to operate as a control switch controlling emission of light from the sub-pixel.

Claims

1. An apparatus, comprising: a display panel comprising an array of pixels configured to direct light through a front side of the display panel, each pixel comprising one or more sub-pixels, each sub-pixel comprising an organic light emitting diode (OLED) and an integrated circuit for controlling an electrical current to the OLED; and a sensor arranged at a back side of the display panel, the back side being opposite the front side, the sensor comprising an emitter configured to emit electromagnetic (EM) radiation transmitted through a first area of the display panel, wherein the integrated circuit of one or more sub-pixels of the array of pixels outside the first area of the display panel comprises a first integrated circuit arrangement, the integrated circuit of one or more sub-pixels of the array of pixels within the first area of the display panel comprising a transistor in addition to the first integrated circuit arrangement, the transistor being configured to operate as a control switch controlling emission of light from the sub-pixel, wherein the transistor is connected between a power source that supplies current to the sub-pixel circuit of the one or more sub-pixels of the array of pixels within the first area and the OLED of the corresponding sub-pixel.

2. (canceled)

3. The apparatus of claim 1, wherein a gate of the control switch is connected to a control device configured to synchronize emission of light from a sub-pixel with emission of EM radiation from the sensor to reduce undesirable light emission from the sub-pixel due to absorption of EM radiation by the integrated circuit of the sub-pixel.

4. The apparatus of claim 3, wherein the synchronized emission prevents abnormal brightening of at least one sub-pixel of the array of pixels within the particular area.

5. The apparatus of claim 3, wherein the control device is configured to synchronize emission of light from multiple sub-pixels in the first area of the display panel with emission of EM radiation from the sensor to reduce undesirable light emission from the sub-pixel due to absorption of EM radiation by the integrated circuits of the multiple sub-pixels.

6. The apparatus of claim 1, wherein the first integrated circuit arrangement is a seven transistor, one capacitor arrangement.

7-15. (canceled)

16. The apparatus of claim 1, further comprising a control switch connected to the integrated circuit of the one or more sub-pixels of the array of pixels within the first area of the display panel, the control switch being configured to provide the integrated circuit of the one or more sub-pixels of the array of pixels within the first area of the display panel with a selection between a first initialization voltage and a second initialization voltage higher than the first initialization voltage.

17. The apparatus of claim 16, wherein the control switch is controlled to select the second initialization voltage as the other voltage when the emitter emits the electromagnetic radiation.

18. The apparatus of claim 17, wherein the control switch is controlled by signals generated from one of a display driver IC, a timing controller IC, or a sensor system.

19. The apparatus of claim 16, wherein the selection of the second initialization voltage renders a transistor of the integrated circuit of the one or more sub-pixels of the array of pixels within the first area in an off state, the off state of the transistor preventing the sub-pixel from emitting light.

20. The apparatus of claim 1, wherein each pixel comprises a red sub-pixel, a green sub-pixel, and a blue sub-pixel.

21. A mobile device comprising the apparatus of claim 1.

Description

DESCRIPTION OF DRAWINGS

[0016] FIG. 1A and FIG. 1B are a plan view and a cross-sectional view, respectively, of an apparatus including a display panel and sensors electrically connected to and located below specific locations (also referred to as areas) of the screen of a computing device.

[0017] FIG. 2 is a cross-sectional view of an apparatus, showing various parts of a signal emitted from the sensor emitter, and a portion of such signal (e.g., the off-state signal) being leaked back into the sensor receiver.

[0018] FIGS. 3A-3C are circuit diagrams illustrating a process of undesirable brightening of a sub-pixel in an apparatus in response to electromagnetic absorption in circuit layers.

[0019] FIG. 4 is a circuit diagram of a sub-pixel circuit including a first modification to the sub-pixel circuit of FIGS. 3A-3C for areas above the locations of the sensors (i.e., for “local” areas).

[0020] FIG. 5 is a circuit diagram showing sub-pixel circuits within each “local” area of the display panel being controlled by additional pixel emission control signal, EMS, such that light emission from local sub-pixel circuits can be turned on/off together being synchronized with the operation of a sensor underneath the display, while other sub-pixel circuits are controlled only by a conventional emission control signal.

[0021] FIG. 6 illustrates an additional pixel emission control signal (EMS) controlling all sub-pixel circuits within two local areas of a display panel.

[0022] FIG. 7 is a circuit diagram of a sub-pixel circuit including a second modification to the sub-pixel circuit of FIGS. 3A-3C.

[0023] FIG. 8 is a circuit diagram showing a local pixel emission control for the voltage V.sub.A across node A in each sub-pixel circuit within a local area.

[0024] FIG. 9 illustrates a configuration of a switching block at a display panel border region, as described using circuits in FIGS. 7 and 8.

[0025] FIG. 10 is a flow chart showing a method of modifying a conventional 7T1C sub-pixel circuit to attain the modifications of FIGS. 4, 5, 7 and 8 so as to eliminate leakage current.

[0026] Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

[0027] FIG. 1A and FIG. 1B are a plan view and a cross-sectional view, respectively, of an example apparatus 102 (e.g., a smartphone) including a display panel 104 and sensors 106 located below the display panel. Apparatus 102 is part of a computing device 112 (e.g., a smartphone) for which display panel 104 forms a screen 110. Screen 110 includes discrete areas 108a and 108b under which sensors 106 are located. As discussed below, the operation of display 104 and sensors 106 can be electrically synchronized at specific areas 108a and 108b. Each of the locations 108a and 108b can also be referred to as “local” areas.

[0028] The display panel 104 includes pixels, each of which can include two or more sub-pixels—e.g., red sub-pixels, green sub-pixels, and blue sub-pixels. Each sub-pixel has a corresponding sub-pixel circuit 114, which controls emission from a respective organic light emitting diode (OLED) of the sub-pixel. The OLED for the sub-pixel circuit 114 for the red sub-pixel is shown as R, the OLED for the sub-pixel circuit 114 for the green sub-pixel is shown as G, and the OLED for the sub-pixel circuit 114 for the blue sub-pixel is shown as B. The OLED R is configured to emit red light, the OLED G is configured to emit green light, and the OLED B is configured to emit blue light. The OLEDs R, G and B are part of the corresponding sub-pixel circuits 114 (as clarified in FIGS. 3A-3C, 4, 5, 7 and 8), but are shown separate in FIG. 1B only for simplicity. The sub-pixel circuits 114 are a part of the display panel 104. The display panel 104 can further includes a cover glass 116 and/or other components (e.g., a polarizer and/or other optical or protective layers).

[0029] Some disadvantages associated with traditional sub-pixel circuits that are overcome using the modified sub-pixel circuits are explained below with respect to FIGS. 2 and 3A-3C, and aspects of the modified sub-pixel circuits are described in greater detail below by FIGS. 4-9.

[0030] Sensor 106 includes a receiver 118 and an emitter 120. During operation, emitter emits electromagnetic (EM) radiation 126 (e.g., infrared radiation) which travels through display panel 104 and into the ambient environment. Some of the emitted EM radiation is reflected back to the sensor, and is received by receiver 118 as a signal 122. Generally, the type of EM radiation emitted by sensor 106 depends on the type of sensor.

[0031] The display panel 104 can be driven with an active matrix addressing scheme, and can be referred to as an active matrix organic light emitting diode (AMOLED) panel. The active matrix display scheme can be advantageous over a passive matrix display scheme in a passive matrix organic light emitting diode (PMOLED) panel, as AMOLED panels can provide higher refresh rates than PMOLED panels, and consume significantly less power than PMOLED panels. A sub-pixel can also be denoted using the term subpixel.

[0032] Sensor 106 can include one or more of: at least one facial detection sensor, at least one proximity sensor, an image sensor such as a front facing camera or at least one sensor configured to sense machine readable representation of data such as barcode and/or quick response (QR) code, any other one or more sensors that have an emitter, and/or any combination thereof. In some implementations, the apparatus 102 can, in addition or as an alternate to the sensor 106, include other sensors such as the at least one global positioning system (GPS), at least one ambient light sensor, at least one fingerprint sensor, at least one heart rate sensor, at least one thermometer, at least one air humidity sensor, at least one radiation level sensor, and any other appropriate sensor.

[0033] The local areas 108a and 108b are shown at certain locations (e.g., areas) on the screen 110. In alternate implementations, the sensors 106 and corresponding local areas 108a and 108b can be located at any other one or more places on the screen 110 where sensor 106 is located. In some implementations, the local areas 108a and 108b can occupy any less amount or any more amount of screen space than that shown in FIG. 1A. The local areas 108a and/or 108b may be referred to as a first area. Areas away from the sensors 106 may be referred to as a second area.

[0034] In general, the computing device 112 can be a mobile device, such as a phone, a tablet computer, a phablet computer, a laptop computer, a wearable device such as a smartwatch, a digital camera, any other one or more mobile device, and/or the like. In alternate implementations, the computing device 112 can be any other computing device such as a desktop computer, a kiosk computer, a television, and/or any other one or more computing devices.

[0035] FIG. 2 illustrates operation of sensor 106 and display panel 104 in a manner lacking synchronization between them. Specifically, sub-pixels proximate to receiver 118 emit light 202 which contributes to an image being presented by the display. Some of this light 204 is leaked backward by the pixels towards receiver 118. Such light 204 can be noise to the sensor 106. Simultaneously, the sensor emitter 120 emits EM radiation 126 which is to return to the sensor receiver 118 through the display panel depicted by signal 122. The EM radiation from the sensor emitter 120 can cause the unintended pixel operation by increasing the transistor off-leakage current in the pixel circuit when the EM radiation 126 passes through the display panel from the backside of the panel, and could affect the image quality on the screen.

[0036] However, such effects can be mitigated by modifying the sub-pixel circuits for those pixels affected. For example, the sub-pixel circuits 114 in the apparatus 102 can include modifications to conventional sub-pixel circuits 206, as described by FIGS. 4-9, and such modifications minimize and/or eliminate undesirable impact on image quality as caused by the off-state leakage current of transistor switches in the sub-pixel circuit 114. Such modifications in the sub-pixel circuits 114 can minimize or eliminate adverse effects on image quality by (1) locally turning off light emission from the sub-pixels for as short a time as possible in the area where the sensors 106 are located underneath, while (2) synchronizing the light emission from the sub-pixels with operation of the sensor 106.

[0037] FIGS. 3A-3B illustrate the process of undesirable brightening of a sub-pixel in during conventional operation in response to EM radiation absorption in pixel circuit layers. A conventional apparatus has traditional sub-pixel circuits 206, such that each traditional sub-pixel circuit 206 can have a sub-pixel circuit structure that specifically has seven transistors and one capacitor (i.e., the seven transistors and one capacitor sub-pixel circuit structure, which can also be simply referred to as the 7T1C sub-pixel circuit structure).

[0038] The traditional sub-pixel circuit 206 can receive, at 304, EM radiation 126 from an emitter of the sensor under the conventional display screen. In response to the EM radiation 126, the sub-pixel circuit 206 can generate an off-state signal (e.g., leakage signal, which can be leakage current) 302. The leakage signal/current can, at 306, cause the electrical charge transfer through the transistors T3 and T4, which are both configured to be switches within the traditional sub-pixel circuit 206. Because of the leakage current through the transistors T3 and T4, the voltage at the gate electrode G decreases at 308, which in turn causes an increase, also at 308, in I.sub.OLED, which is the signal or current in the OLED of the traditional sub-pixel circuit 206. The increase in I.sub.OLED causes the sub-pixel associated with the traditional sub-pixel circuit 206 to become abnormally brighter than usual. This abnormally brighter sub-pixels can cause undesirable glowing of the sub-pixels while the local area is supposed to display black images, which is the case when the sensors under the local area are in operation.

[0039] FIG. 4 illustrates a first portion of the sub-pixel circuit 414 showing a first modification to the conventional sub-pixel circuit 206 of FIGS. 3A-3C for areas above the locations of the sensors 106 (i.e., for “local” areas 108a and 108b). This first modification is addition of an emission control switch, which allows emission for the corresponding sub-pixel to be switched off synchronously with the operation of the sensor. In this case, the emission control switch is an additional transistor, T8 to the conventional circuit to provide an emission control signal, EMS, for the areas of the display panel 104 below which the sensor 106 is located.

[0040] Although the transistor T8 is shown as being implemented between transistor T6 and the color OLED, in alternate implementations the transistor T8 can be connected anywhere between the voltage point V.sub.DD and the color OLED. For example, the transistor T8 can be connected between the voltage point V.sub.DD and the transistor T5, the transistor T5 and the transistor T1, the transistor T1 and the transistor T6, and the transistor T6 and the anode of the color OLED.

[0041] In some implementations, a single emission control signal EMS can control all the local areas 108a and 108b, as described below with reference to FIG. 6. In alternate implementations, a separate emission control signal EMS can be used for each corresponding local area 108a/108b such that sub-pixels for each local area 108a/108b can be controlled independently of other local areas 108b/108a.

[0042] FIG. 5 illustrates portions of sub-pixel circuits 414 within each local area 108a/108b of the display panel 104. Outside of local areas 108a/108b are traditional sub-pixel circuits 206. Every circuit 414 can be controlled by a single emission control signal EMS such that each such sub-pixel circuit 414 can be turned on/off together (which is to turn-off all sub-pixels in the local area 108a/108b at the same time being synchronized with the operation of the sensors underneath. For example, the EMS can stop emission from the corresponding sub-pixels for short time periods (e.g., 10 milliseconds or less, 5 milliseconds or less, 2 milliseconds or less) while the sensor is emitting and/or detecting EM radiation.

[0043] This arrangement is also shown in FIG. 6, which is described below. Turning off the sub-pixels using the EMS eliminates the creation of increased I.sub.OLED (which was the problem with traditional sub-pixel circuits 206, as shown in FIGS. 3A-3C), which in turn obviates the problem in conventional sub-pixel circuits 206 regarding abnormal brightness of the sub-pixels. Note that the non-local areas (i.e., areas of the display panel that do not have sensors 106 below them) have sub-pixel circuits 206 rather than sub-pixel circuits 414.

[0044] FIG. 6 illustrates a single electromagnetic control signal (EMS) (labeled local black control signals) controlling all sub-pixel circuits 414 within the two local areas of a display panel 104, as described using circuits in FIG. 5. Here, a single emission control signal EMS can control sub-pixels in all the local areas, as described below by FIG. 6. In alternate implementations, a separate emission control signal EMS can be used for each corresponding local area such that sub-pixels for each local area can be controlled independent of other local areas. The single emission control signal EMS can be generated and supplied from the display driver IC or a timing controller circuit in the display driving system, and the trace line/lines for the EMS signal can be placed on the panel edge areas reaching the local areas 108a 108b.

[0045] FIG. 7 illustrates a second portion of the sub-pixel circuit 414 showing another modification to the traditional sub-pixel circuit 206 of FIGS. 3A-3C. This modification is to place locally independent voltage supplies for the initialization voltage V.sub.INIT_LOCAL for sub-pixels in the local areas 108a and 108b (which may be referred to as a second area) and another initiation voltage V.sub.INIT for all other sub-pixels (i.e., sub-pixels in the non-local areas of the display panel 104, which may be referred to as a first area). During the pixel circuit 414 operation, the node A voltage, V.sub.A, can be two or more different levels, such as V.sub.INIT_LOCAL and V.sub.INIT, depending on the operation of sensors underneath. That is, this voltage level change can be synchronized to the sensor operation. When the sensors (receivers or emitters) are in operation, V.sub.A is configured to be V.sub.INIT_LOCAL, which is preferably higher voltage than V.sub.INIT, such that the pixel circuits 414 do not generate I.sub.OLED to the corresponding OLED device in the pixel, and the pixel area becomes black. A switch block 710 that selects one of multiple voltage levels for V.sub.A, such as V.sub.INIT_LOCAL and V.sub.INIT, can be located in the display driver IC, a separate discrete power management IC, or a panel border region. The application of a higher voltage V.sub.INIT_LOCAL to the sub-pixel circuit 414 results in the transistor switch T1 to be rendered in an off state, which can prevent current from going to the color OLED, which in turn darkens the sub-pixels in the local areas 108a and 108b. It will be appreciated that the terms “first area” and “second area” are used as labels, and do not imply any technical limitations to the areas referred to, and that these terms can be reversed as required.

[0046] Although the second portion of the sub-pixel circuit 414 is shown in this drawing as being independent of the first portion shown in FIGS. 4-6, in an alternate circuit both the first portion and the second portion of the sub-pixel circuit 414 can co-exist.

[0047] FIG. 8 illustrates a single control for the voltage V.sub.A across node A in each sub-pixel circuit 414 within a local area 108a and/or 108b. This can synchronize the impact of the functioning of the control switch. That is, rather than providing a separate switch block 710 for each sub-pixel circuit 414 within the local areas 108a and/or 108b, each of which would need to be provided with a control signal, it is possible to provide a switch block which is operable to provide an appropriate voltage V.sub.A (e.g. either V.sub.INIT_LOCAL and V.sub.INIT) to several sub-pixel circuits 414 within the local areas 108a and/or 108b simultaneously.

[0048] FIG. 9 illustrates a display panel configuration when the V.sub.A control switch block is located on the top side of the display border. In this configuration, the switch control signals, SIC and SICb in FIG. 7 are routed in the display panel being generated from the display driver IC or a separate timing controller circuit, and are synchronized with the sensor 106 operation. The voltage level chosen by the switch block is supplied to the node A of each sub-pixel circuit in the local areas 108a and/or 108b, as described using circuits in FIGS. 7 and 8.

[0049] FIG. 10 illustrates a method of modifying a conventional 7T1C sub-pixel circuit 206 to attain the modifications of FIGS. 4, 5, 7 and 8 so as to eliminate leakage current. A design of a 7T1C sub-pixel circuit 206 can be obtained at 1002. The 7T1C sub-pixel circuit 206 can include seven transistors T1-T7 and one capacitor C.sub.ST. The 7T1C sub-pixel circuit 206 can include an input electrical node “A” configured to be powered with a first initialization voltage V.sub.INIT. The 7T1C sub-pixel circuit 206 can have an OLED of the number of OLEDs forming the pixels of the display. The 7T1C sub-pixel circuit 206 can be configured to control a drive current to be passed through the OLED to control light emission from the OLED. Collectively, the OLED pixels are addressed by an active matrix forming an active matrix organic light emitting diode (AMOLED) panel. The 7T1C sub-pixel circuit 206 can be above a sensor 106.

[0050] An eighth transistor T8 is added, at 1004, into the design of the 7T1C sub-pixel circuit 206. The eighth transistor T8 can be configured to operate as a switch controlling the drive current, for example as described above with reference to FIGS. 4 and 5.

[0051] The pixel circuit is fabricated and a control switch (e.g., V.sub.A control switch, as shown in FIG. 7) electrically connected, at 1006, to the input electrical node A. The control switch (e.g., the V.sub.A control switch) can provide the 7T1C circuit with a selection between the first initialization voltage V.sub.INIT and a second initialization voltage V.sub.INIT LOCAL to initialize electrodes in the 7T1C circuit 206. The second initialization voltage V.sub.INIT_LOCAL can be higher than the first initialization voltage V.sub.INIT. The control switch (e.g., V.sub.A control switch) can be electrically connected to a control integrated circuit (now shown) that can cause the control switch (e.g., the V.sub.A control switch) to select the second initialization voltage V.sub.INIT_LOCAL when the sensor 106 emits electromagnetic waves.

[0052] The control integrated circuit can be at least one of a display drive integrated circuit, a timing controller block, and a sensor system. The selection of the second initialization voltage V.sub.INIT_LOCAL can render a transistor T1 of the 7T1C circuit in an off-state that prevents flow of current from the transistor T1 to the OLED 110. The prevention of the flow of current to the OLED 110 can prevent undesired illumination of the pixels in the region where sensor emitters are located underneath areas 108a/108b.

[0053] Various implementations of the subject matter described herein can be implemented in digital electronic circuitry, integrated circuitry, specially designed application specific integrated circuits (ASICs), computer hardware, firmware, software, and/or combinations thereof. These various implementations can be implemented in one or more computer programs. These computer programs can be executable and/or interpreted on a programmable system. The programmable system can include at least one programmable processor, which can have a special purpose or a general purpose. The at least one programmable processor can be coupled to a storage system, at least one input device, and at least one output device. The at least one programmable processor can receive data and instructions from, and can transmit data and instructions to, the storage system, the at least one input device, and the at least one output device.

[0054] These computer programs (also known as programs, software, software applications or code) can include machine instructions for a programmable processor, and can be implemented in a high-level procedural and/or object-oriented programming language, and/or in assembly/machine language. As can be used herein, the term “machine-readable medium” can refer to any computer program product, apparatus and/or device (for example, magnetic discs, optical disks, memory, programmable logic devices (PLDs)) used to provide machine instructions and/or data to a programmable processor, including a machine-readable medium that can receive machine instructions as a machine-readable signal. The term “machine-readable signal” can refer to any signal used to provide machine instructions and/or data to a programmable processor.

[0055] To provide for interaction with a user, the screen 110 can display data to a user. The sensors 106 can receive data from the one or more users and/or the ambient environment. The computing device 112 can thus operate based on user or other feedback, which can include sensory feedback, such as visual feedback, auditory feedback, tactile feedback, and any other feedback. To provide for interaction with the user, other devices can also be provided, such as a keyboard, a mouse, a trackball, a joystick, and/or any other device. The input from the user can be received in any form, such as acoustic input, speech input, tactile input, or any other input.

[0056] Although various implementations have been described above in detail, other modifications can be possible. For example, the logic flows described herein may not require the particular sequential order described to achieve desirable results. Other implementations are within the scope of the following claims.