We report a new calibration system and algorithm design for micro scanning mirrors (MSMs) which are an important component in many active sensors used in robotic applications. In fact, our MSM is a 3 degree-of-freedom soft-hinged robot with a triaxial Hall sensor as feedback. Our calibration rig design employs a minimal 2-laser beam approach and the new algorithm builds on reflection principle to precisely measure MSM poses. To establish the mapping between Hall sensor readings and MSM poses, we propose a self-synchronizing periodicity-based model fitting calibration approach. We achieve an MSM poses estimation accuracy of 0.020{\deg} with a standard deviation of 0.011{\deg}.