Google’s long-term goal for its hardware is to have technology always available in the background to help you. Google’s latest work towards Ambient Computing is for “hidden interfaces” where the display is invisible unless used. This is similar to the Nest 2020 Thermostat with its mirror-finish screen.
Sleek device integration requires adapting to existing user aesthetics and styles rather than simply adding screens, which can easily disrupt a visual space, especially when they become monolithic surfaces or black screens when they are turned off or not actively used.
Regarding the technology landscape, the company believes that AMOLED is too expensive and complex (in terms of manufacturing) for ambient computing, while LCD and e-ink “do not have a brightness enough to penetrate materials.
Google has turned to passive-matrix OLEDs (PMOLEDs) which benefit from a “simple design that dramatically reduces cost and complexity”. However, it first reduced flicker and increased brightness by switching to parallel rendering instead of scanline rendering. the the differences are detailed in the full blog.
To implement proof-of-concept hidden interfaces, we use a PMOLED display with 128×96 resolution that has all row and column drivers routed to a connector for direct access. We use a custom printed circuit board (PCB) with fourteen 16-channel digital-to-analog converters (DACs) to directly interface these 224 lines from a Raspberry Pi 3 A+. Touch interaction is enabled by a ring-shaped PCB surrounding the screen with 12 electrodes arranged in arc segments.
The end result, which involved creating an effective font for the new display technology, consisted of demonstrations of a rolling clock, caller ID display, countdown with zoom and a music visualizer.
Per-frame control of font properties combined with the high frame rate of the display enables very smooth animations – this capability greatly extends the expressiveness of rectilinear graphics far beyond what is possible on fixed LED displays 7 segments.
Parallel PMOLED was found to be brighter than AMOLED on most materials tested, including mirror, textile, wood veneer, and acrylic.
Going forward, the team wants to aim for “complex vector images and graphics”, as well as more efficient material designs.
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