FPCB Micromirror Scanning ToF LiDAR for Touchless Interface

This thesis paper demonstrates the design, fabrication, and integration of a flexible printed circuit board (FPCB) based rotational optical scanner with laser-based ranging for twodimensional finger input recognition applications. A two-dimensional (2D), position array of fingers was captured by utilizing light detection and ranging (lidar) and time-of-flight (ToF) sensors. The optical scanner and ranging sensors are implemented in two frequently touched scenarios, elevator call buttons, and automated teller machine (ATM) displays. While there are existing, vision based touchless interfaces requiring machine learning algorithms and/or advanced camera technologies, the thesis explores alternative methods to develop low-cost, easy-to-manufacture, and highly integrative sensing solutions [8]. The FPCB scanner consists of two main components; an optical reflector based on a silicon micro-mirror, and a FPCB polyamide fixture that oscillates within a magnetic field created by permanent magnets (PM) dipole. The optical scanner developed has a 15 x 15 mm aperture and can achieve 40.3° of optical angle, while being operated at a low voltage of ± 7.5 V. The measurable rotational angle of the optical scanner was determined to be 23.4° optical (combined positive and negative direction from the axis of rotation). The thesis also presents measurement limitations of the angular position of the scanner and inconsistent scan patterns at low operational frequencies due to material properties, assembly processes, and environmental conditions.