Google Researchers Build "Hidden Interfaces" Using High-Brightness, Flicker-Free Parallel PMOLEDs

A research scientist and a hardware engineer, both working at Google, have put together a demonstration of what they describe as "hidden interfaces for ambient computing" — interactive light-up user interfaces hidden beneath the surface of seemingly-passive objects, using a flicker-free passive-matrix OLED display.

"We describe an interface technology that is designed to be embedded underneath materials and our vision of how such technology can co-exist with everyday materials and aesthetics," Alex Olwal and Artem Dementyev explain of their joint paper. "This technology makes it possible to have high-brightness, low-cost displays appear from underneath materials such as textile, wood veneer, acrylic or one-way mirrors, for on-demand touch-based interaction."

The team's work centres around the use of passive-matrix organic light-emitting diode (PMOLED) display panels, which are designed as simpler and lower-cost alternatives to more traditional active-matrix (AMOLED) panels. The biggest issue: Scanline rendering, which introduces flicker — something the pair were able to resolve by developing a means of rendering shapes in parallel.

The modified PMOLED displays proved capable of being perceived through a variety of materials, from acrylic and PETG to cloth, wood veneer, and a mirror — showing anything between a fivefold and 40x increase in brightness over an AMOLED panel, dropping to 3.6-9.3x in real-world rendering scenarios including text, numbers, and progress bars.

To prove the concept further, the pair developed prototype devices — powered by a custom board with fourteen 16-channel digital-to-analog converters (DACs), all linked to a 128×96 PMOLED display for parallel addressing, and a Raspberry Pi 3 Model A+ single-board computer — including a scalable clock, a caller ID display system, a countdown timer with zoom effect, and an audio visualizer.

"Our lab evaluation suggests unmet opportunities to introduce hidden displays with simple, yet expressive, dynamic and interactive UI elements and text in traditional materials, especially wood and mirror, to blend into people’s homes," the pair conclude. "Hidden interfaces demonstrate how control and feedback surfaces of smart devices and appliances could visually disappear when not in use and then appear when in the user's proximity or touch."

"We hope this direction will encourage the community to consider other approaches and scenarios where technology can fade into the background for a more harmonious coexistence with traditional materials and human environments."

More details are available on the Google AI Blog, while the paper is to be presented this May at the ACM CHI Conference on Human Factors in Computing Systems (ACM CHI '22).