Apple's Patent Reveals Micro-LED based 'Smart-Pixel' Technology for Possible Future iMacs, iPhone & TV
A new report posted yesterday by DigiTimes quoted the chairman for Taiwan-based LED epitaxial wafer and chip maker Epistar stating that Micro LED technology could be commercially applied in smart wearables, VR or AR in 1-2 years at the earliest, with larger displays coming 3-5 years after. As shown by a survey by the Taiwan Electronic Equipment Industry Association, 57% of surveyed experts think that Micro LED technology will be initially used in smartwatches in three years.
In May Patently Apple posted a report titled "Interest in Micro-LED Displays is Exploding as Test Runs are Reportedly Scheduled by Apple in 2017 and others in 2018," followed by a report in June titled "Industry Insiders Claim Apple working on their Augmented Reality Headset that will Indeed use a Micro-LED Display."
Yesterday's DigiTimes report added that Apple is likely to introduce micro-LED displays in small to medium sized displays which points to the Apple Watch and perhaps smartglasses of one kind or another.
Today the US Patent & Trademark Office published a patent application from Apple that relates to micro-LED displays covering all sizes from small through to smartphones, computer displays, high definition televisions and beyond using smart pixel technology.
Flat panel displays utilizing LED devices are gaining popularity in a wide range of electronic devices, from small, handheld electronic devices to large outdoor displays. High-resolution LED displays, such as those used in modern computer displays, smart phones and televisions, typically use an active matrix display structure. In an active matrix display, active driving circuitry is attached to each pixel or sub-pixel, allowing precise voltage switching for the individual pixels that passive matrix displays lack. The precise voltage switching allows for improved image quality and response time in comparison to passive matrix displays. In conventional active matrix displays, the switching circuitry at each pixel is implemented using a thin-film transistor (TFT) backplane driving the emissive elements. A typical TFT switching circuit used in emissive active matrix displays is the 2T1C circuit, which contains two transistors and one capacitor, although more advanced TFT circuits is possible.
The use of the TFT backplane allows improved precision in relation to passive matrix displays, however the use of the thin-film transistor backplane is not without drawbacks. High quality TFT fabrication is costly. The highest quality TFTs require fabrication on a quartz substrate due to the high temperatures involved in the fabrication process. Lower temperature processes can be used with a glass substrate, however the resulting transistors may suffer from low carrier mobility, reducing the conductivity of the transistors. Current leakage and power consumption can also become a problem, and uniformity issues can arise at various points during the fabrication process.
The Smart-Pixel Microcontroller
A smart-pixel microcontroller for controlling light emitting diodes is described. The smart-pixel microcontroller can be used to replace the TFT backplane used in LED and LCD display technology, and can add new functionality not previously possible using thin film transistors as switching and driving element in a display. In an embodiment a light emitting assembly includes one or more light emitting diode (LED) devices and one or more microcontroller to switch and drive the one or more LED devices. The one or more LED devices and the one or more microcontrollers are bonded to the same side of a substrate. In an embodiment, an LED device and microcontroller are bonded to the substrate with a material such as indium, gold, silver, copper, or alloys thereof.
In one embodiment, the smart-pixel integrated circuit is configured for analog input, and has an input block and an output block containing electronics. In such embodiment, the smart-pixel microcontroller is controlled with a voltage applied to scan lines and a data lines, similar to an active matrix display. In analog form, the smart-pixel microcontroller can accept at least one analog data input to control at least one LED device, although multiple LED devices can be controlled with a single microcontroller. In one embodiment, the smart-pixel microcontroller supplements analog circuitry with digital storage to facilitate adaptive refresh rates and display self-refresh. In one embodiment, capacitive storage is used to storage analog input.
In one embodiment, the smart-pixel microcontroller is configured for digital input, and has an input block and output block containing digital logic, and a storage module with embedded memory. Digital input can come by way of a digital bus or point-to-point data link. Multiple LED devices or sensor devices can be controlled with a single microcontroller. In one embodiment, adaptive display updates are facilitated by data storage in each integrated circuit.
In one embodiment, a plurality of LED devices are bonded to the same side of the substrate as the microcontroller, and are in electrical connection with the microcontroller. The LED devices can be used as sub-pixels in a display, and can be configured in a red, green, blue (RGB) sub-pixel arrangement. Other sub-pixel arrangements and schemes are also possible. In an embodiment, the light emitting assembly includes an array of LED devices and an array of microcontrollers bonded to the same side of the substrate. The number of microcontrollers in the array of microcontrollers is less than the number of LED devices in the array of LED devices. In an embodiment, each microcontroller is in electrical connection with a plurality of pixels to drive a plurality of LED devices in each pixel.
In addition to the controlling the emissive elements of the display, the microcontroller can couple with one or more optical, electrical or thermal sensors. Alternatively the microcontroller may include one or more sensors. In one embodiment, the smart-pixel microcontroller couples with one or more pressure sensors, which can be used to give visual display feedback on a display when the display is touched, or to transmit user input in a touch display. In one embodiment, sensors can be used to detect a drift in the white point of the display over time, and the display can be re-calibrated from time to time to maintain a consistent white point.
In one embodiment, the smart-pixel micro-matrix is constructed on a receiving substrate suitable for use in lighting devices. The smart-pixel microcontrollers can be used to maintain precise brightness, uniformity, and color control over the emitted light. In one embodiment, the smart-pixel micro-matrix is used as an LED backlight, for liquid crystal display (LCD) devices. Blue or UV LEDs in combination with a yellow, blue-yellow or white phosphor can be used to provide a white backlight for LCD displays. White light can also be generated by various combinations of single color LED devices with or without the use of phosphors. In addition to white lighting, additional single color LED devices (e.g., red, amber, green, blue, etc.) devices can also be used to provide a wider color gamut and color rendering index than otherwise possible with white backlights.
One or more smart-pixel microcontrollers may also couple to form a microcontroller network. A hierarchy of microcontrollers can be used, where a tiered arrangement exists between microcontrollers. Multiple types of microcontrollers can be used for various applications, and the microcontrollers can each be tied to a common data bus, coupled in a daisy chain, or may communicate wirelessly. The microcontroller network can enable fault tolerance, and can be used to determine the state of the smart-pixel micro-matrix.
It was interesting to learn from Apple's patent filing that micro LED devices are highly efficient at light emission and may consume very little power (e.g., 250 milliwatts for a 10 inch display) compared to 5-10 watts for LCD or OLED emission. Such a display for an iPad would extend battery life considerably.
Apple's Patent FIG. 16 above is an illustration processing micro-device substrates of micro devices into a receiving substrate; FIG. 17 noted below is an illustration of a smart-pixel display assembly created from an array of smart-pixels assembled on a display or lighting substrate.
It's interesting to note that in Apple's patent FIG. 9 that note that "The smart-pixel micro-matrix #920 can correspond to a single display, or a portion of a display, such as a high definition television, or large outdoor display." TV's were also mentioned in the DigiTimes report pointing to Sony working on that size of micro-LED device.
Apple's patent application 20170206845 was filed back in Q2 2017. The original patent was granted to LuxVue in 2015. Considering that this is a patent application, the timing of such a product to market is unknown at this time.
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