BitLight: Turning DLP Projections into an Interactive Surface through Bit-level Light Encoding

AbstractThis paper presents BitLight, a novel paradigm that uses the rapid flashing of a digital light processing (DLP) projector to encode an imperceptible mask temporally that, when sensed by a photodiode, uniquely specifies where the photodiode is located on the projected image. BitLight is inspired by the psychophysical phenomenon that the human visual system (HVS) cannot resolve rapid temporal changes in optical signals, so redundant optical signals could be inserted for tracking with some or little compromise on the original human perceived visual content. BitLight is the first to devise a bit-level temporal encoding to display RGB colors while also embedding tracking signals in a digital fashion. Compared to traditional visible-light-communication (VLC) systems that use frame-level encoding techniques such as luminance changes [10, 25, 26, 32] and alpha channel [16], the bit-level encoding of BitLight makes better use of the ultra-fine temporal division capabilities of DLP projectors to embed a much higher tracking data throughput and thus achieve faster localization speed. With our current prototype hardwares of a low-end microcontroller, cheap photodiodes, and a commercial off-the-shelfDLP projector, evaluation results have demonstrated an average of only 9.5ms to localize the sensor, versus 200ms by a comparison testbed that uses simple frame-level encodings.