Electromagnetic FPCB micromirror based scanning laser rangefinder
This thesis presents an electromagnetic FPCB (Flexible Printed Circuit Board) micromirror based scanning triangulation laser rangefinder (LRF). Two configuration designs of the electromagnetic FPCB micromirror have been developed and tested. The FPCB micromirror has a large aperture (8 mm x 5.5 mm) and high flatness (ROC, radius of curvature, ~ 15m), that overcomes conventional MEMS micromirrors’ limitation of small aperture (less than 5 mm). Subsequently high power lasers with large beam sizes and good collimation can be used in micromirror based scanning LRF for better performance. As a result, the LRF in this thesis achieved a larger scanning angle and longer detecting distance than those in literature. Both modelling and prototyping are presented. Three lasers (Laser 1: 2 mW; Laser 2: 20 mW; and Laser 3: 100 mW) are used to characterise the LRF. Eye-safety calculation is presented for the three lasers. Achieved performance (measurement distance and FOV, field of view) is: with Laser 1, distance of 15 – 70 cm and FOV of -15° to 10°, error ≤ 4% ; with Laser 2, distance of 15 – 130 cm and FOV of 15° to 15°, error ≤ 5%; with Laser 3, distance 15 – 200 cm and FOV of -15° to (5~9°), error ≤ 5%. Fatigue test indicates 1.2 billion scanning cycles have been reached.