Individually-addressable pixels for ultra-low power MicroOLED
When built into smart glasses to display real-time data (such as heart rate, GPS information, distances etc…) the new OLED only refreshes the pixels that need an update while retaining the overall state of whatever static background pixels. In some cases, that may be only the last digits of evolving data, hence refreshing only a fraction of the whole display. In another example, you could only refresh the pixels where the action takes place in a video, while static background would remain unchanged.
The research center says that for video applications, the new approach was able to reduce power consumption from 200mW (typical of microdisplays) to between 2 and 3mW, two orders of magnitude.
“While in traditional microdisplays, the whole image is refreshed line by line, we’ve redesigned the control circuitry in order to be able to address every single pixel individually, like in a memory with address lines and columns”, explained Philipp Wartenberg, IC Design Engineer and Project Manager in the Department of IC & System Design at Fraunhofer FEP, adding that the AMOLED is fabricated onto a CMOS electronic backplane. The display pixels are equipped with static memory and arranged in a freely addressable matrix, explains Fraunhofer FEP in its brochure.
“We’ve analyzed different applications, and we thought it would be nice to build a display onto which all the pixels could be addressed individually. We can achieve significant energy savings by doing that, even more so in the whole electronic system than just at the display level” Wartenberg told eeNews Europe.
In some applications, you know the region where the pixels are changing, where you’ll get status information, and you can optimize the electronics for that, but in the case of live video streams, the application could use a compression algorithm to modify and recalculate the video data so it would only refresh the pixels that need it. This could be done on a smartphone or even in the cloud upon the app’s request.
This would not only reduce display power consumption but also reduce the strain on the microprocessors, since less video data would require processing (fewer full frames). In wearables, this means longer lasting batteries and less heat.
In effect, the whole display is architected so as to allow for a flexible refresh rate for each pixel. While the whole display could be refreshed at about 30fps, smaller areas can be refreshed at significantly higher rates.
“For a fixed bandwidth, it follows a simple ratio. If you refresh half the pixels, then you can double the frame rate for the corresponding partial image”, noted Wartenberg.
By refreshing only a quadrant, you could quadruple the frequency, although you may prefer to keep a reasonably low refresh rate to minimize data transfers and limit power consumption.
The new display will be presented at the electronica trade fair in Munich from November 08-11, 2016.
Visit Fraunhofer FEP at www.fep.fraunhofer.de
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Flexible OLED in the starting blocks for automotive lighting
Grey-scale OLED patterns reach 12,700 dpi resolution
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