The Human-Computer Interaction Institute at Carnegie Mellon University in the U.S. has developed a smartwatch which features projection onto the arm of the wearer and turns the arm into a touch surface. A slide-to-unlock mechanism rejects inadvertent touches and provides projection calibration before apps can be used.
The LumiWatch prototype features a tiny laser projector and depth sensor array, which allows the projected interface to be tapped and swiped on just like a normal touchscreen.
The prototype measures 50×41×17mm, nominally larger than the production 42mm Apple Watch Series 3 (43×36×11 mm).
The team designed and manufactured a custom 15-lumen pico-projector module for the LumiWatch. The projector uses three lasers (red, green and blue) with a pair of MEMS mirrors operating in a raster-scan mode (i.e. a scanned laser design. This emits a 1024×600 image at 60 Hz across a 39º×22.5º field of view. The projector module measures 25.8x16.6x5.2mm, and consumes up to 2.7W of power displaying a maximum brightness, full-white image. With scanned-laser designs, power usage varies by content, e.g., black imagery requires almost no power. The projector module is paired with custom drive electronics that controls the lasers and mirrors, while exposing a standardised display interface to the Android firmware.
The touch interface it provides can be as large as 40 sq cm in size.
LumiWatch features a Qualcomm 1.2 Ghz quad-core CPU with Android 5.1 OS, 768MB of RAM, 4GB of memory, and a 740 mAh lithium-ion battery, good enough to power the watch for over an hour continuously, or a full day with occasional use.
LumiWatch also features also Bluetooth and Wi-Fi support, and a battery and logic board.