OptiBasePen: Mobile Base+Pen Input on Passive Surfaces by Sensing Relative Base Motion Plus Close-Range Pen Position

Digital pen input devices based on absolute pen position sensing, such as Wacom Pens, support high-fidelity pen input. However, they require specialized sensing surfaces like drawing tablets, which can have a large desk footprint, constrain the possible input area, and limit mobility. In contrast, digital pens with integrated relative sensing enable mobile use on passive surfaces, but suffer from motion artifacts or require surface contact at all times, deviating from natural pen affordances. We present OptiBasePen, a device for mobile pen input on ordinary surfaces. Our prototype consists of two parts: the "base" on which the hand rests and the pen for fine-grained input. The base features a high-precision mouse sensor to sense its own relative motion, and two infrared image sensors to track the absolute pen tip position within the base’s frame of reference. This enables pen input on ordinary surfaces without external cameras while also avoiding drift from pen micro-movements. In this work, we present our prototype as well as the general base+pen concept, which combines relative and absolute sensing.