This disclosure relates organic light emitting diode (OLED) displays having under-display sensors, and more particularly, to synchronously and locally turning-off light emission from sub-pixels in under-display sensor area of an active matrix organic light emitting diode (AMOLED) panel to avoid undesirable image variations caused by electromagnetic radiation (e.g., IR light) emitted from sensor emitters under the AMOLED panel.
Display panels of mobile devices can include a sensor embedded underneath the cover glass of the screen, such as a front facing camera or facial recognition sensor. When such sensor performs the sensing of an associated parameter—such as 3D detection, proximity, or the like—an emitter of the sensor emits electromagnetic radiation such as infrared waves through the display. Interaction between the electromagnetic radiation from the sensor and a pixel circuit for driving an AMOLED display pixel can cause undesirable effects in the display, such as an unintentional luminance increase of the pixels due to an interaction between the EM radiation and the pixel circuits. For example, conventional circuits of sub-pixels of the pixels arranged in such display panel can cause an unintentional luminance increase due to an increase of the off-leakage current of transistor switches in the pixel circuit due to absorption of the electromagnetic radiation in the transistor structure. Such a luminance increase can undesirably cause image distortion due to the increased luminance. The sensor's performance can also be affected by the illumination of the display sub-pixels when they capture signals (such as visible light, and infrared) through the display panel since a small portion of light from a sub-pixel can be reflected backward by the display panel internal structures, and becomes a noise to the sensors.
This disclosure relates to synchronously and locally turning-off sub-pixels in under-display sensor area of an organic light emitting diode (OLED) panel in coordination with the operation of the sensor. Such synchronous and local turning-off of the sub-pixels can reduce (e.g., avoid) undesirable brightness change resulting from electromagnetic radiation emitted by sensor emitters of the OLED panel.
In one aspect, 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 one or more sub-pixels. Each sub-pixel includes an organic light emitting diode (OLED) and an integrated circuit for controlling an electrical current to the OLED. The sensor is arranged at a back side of the display panel. The back side is opposite the front side. The sensor includes an emitter configured to emit electromagnetic (EM) radiation transmitted through a first area of the display panel. The integrated circuit of one or more sub-pixels of the array of pixels outside the first area of the display panel includes 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 includes a transistor in addition to the first integrated circuit arrangement. The transistor is configured to operate as a control switch controlling emission of light from the sub-pixel.
In some variations, one or more of the following can additionally be implemented either individually or in any feasible combination. 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. 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. The synchronized emission prevents abnormal brightening of at least one sub-pixel of the array of pixels within the particular area. 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.
The first integrated circuit arrangement is a seven transistor, one capacitor arrangement.
In another aspect, a mobile device is described that includes the apparatus referred to above.
In yet another aspect, an apparatus is described that includes at least one sensor and a display panel. The at least one sensor includes an emitter configured to emit electromagnetic radiation. The display panel includes an array of pixels located in a first area away from at least one sensor and a second area above the at least one sensor. Each pixel of the array of pixels includes two or more sub-pixels. One or more sub-pixels of the array of pixels within the first area includes a first sub-pixel circuit electrically initialized by a first initialization voltage during operation. One or more sub-pixels of the array of pixels in the second area includes a second sub-pixel circuit coupled to a control switch used to select a second initialization voltage during operation. The second initialization voltage is selected from options including the first initialization voltage and another voltage that is higher than the first initialization voltage. The control switch is controlled to select the second initialization voltage as the other voltage when the emitter emits the electromagnetic radiation.
In some variations, one or more of the following can additionally be implemented either individually or in any feasible combination. The control switch is controlled by signals generated from one of a display driver IC, a timing controller IC, or a sensor system. The second area includes a plurality of sub-pixel circuits including the second sub-pixel circuit. During operation, an initialization voltage of each sub-pixel circuit of the plurality of sub-pixel circuits is synchronized with other sub-pixel circuits of the plurality of sub-pixel circuits. The selection of the second initialization voltage is configured to render a transistor of the second sub-pixel circuit in an off state. The off state of the transistor prevents the second sub-pixel from emitting light.
The apparatus may further comprise an additional transistor configured to operate as a control switch controlling emission of light from the sub-pixel, as described further above.
In another aspect, a mobile device is described that includes the apparatus referred to above.
In some aspects, a method is described that modifies a sub-pixel circuit of an active matrix organic light emitting diode (AMOLED) display. A sub-pixel circuit is obtained. The sub-pixel circuit includes seven transistors and one capacitor. The sub-pixel circuit includes an input electrical node configured to be initialized with a first initialization voltage. The sub-pixel circuit is coupled to an organic light emitting diode (OLED) of a plurality of OLEDs of the AMOLED display. The sub-pixel circuit is configured to control a drive current to be passed through the OLED to control light emission from the OLED. An additional transistor is wired into the sub-pixel circuit. The additional transistor is configured to operate as a switch controlling a drive current in addition to already existing emission control switches in the sub-pixel circuit. A control switch is electrically connected to the input electrical node. The control switch provides the sub-pixel circuit with a selection between the first initialization voltage and a second initialization voltage to initialize the sub-pixel circuit. The second initialization voltage is higher than the first initialization voltage. The control switch is electrically connected to a control integrated circuit that causes the control switch to select the second initialization voltage when a sensor associated with the AMOLED display emits electromagnetic waves.
In some variations, one or more of the following can additionally be implemented either individually or in any feasible combination. The control integrated circuit is at least one of a display driver IC, a timing controller block, and a sensor system. The selection of the second initialization voltage renders a transistor of the sub-pixel circuit in an off-state that prevents light emission from the OLED. The above-referred method further includes assembling a mobile device that includes the AMOLED display and a sensor arranged behind the display and arranged to emit electromagnetic radiation through the display. It will be understood that features described above in combination with an apparatus may also be implemented in combination with the above described method.
Some implementations can have the following advantages. The synchronous and local turning-off of the sub-pixels in an under-display sensor area of an OLED panel can advantageously avoid undesirable brightness increase associated with electromagnetic radiation emitted by a sensor emitter underneath the OLED panel, thereby providing a more pleasing visual experience to a user.
The details of one or more implementations are set forth below. Other features and advantages of the subject matter will be apparent from the detailed description, the accompanying drawings, and the claims.
Like reference symbols in the various drawings indicate like elements.
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
Some disadvantages associated with traditional sub-pixel circuits that are overcome using the modified sub-pixel circuits are explained below with respect to
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.
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.
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.
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
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.
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
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 IOLED, which is the signal or current in the OLED of the traditional sub-pixel circuit 206. The increase in IOLED 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.
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 VDD and the color OLED. For example, the transistor T8 can be connected between the voltage point VDD 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.
In some implementations, a single emission control signal EMS can control all the local areas 108a and 108b, as described below with reference to
This arrangement is also shown in
Although the second portion of the sub-pixel circuit 414 is shown in this drawing as being independent of the first portion shown in
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
The pixel circuit is fabricated and a control switch (e.g., VA control switch, as shown in
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 VINIT_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.
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.
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.
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.
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.
Filing Document | Filing Date | Country | Kind |
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PCT/US2020/049253 | 9/3/2020 | WO | 00 |
Number | Date | Country | |
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Parent | 16559491 | Sep 2019 | US |
Child | 17291987 | US |