A scanning mirror system (310, 1100) comprising a MEMS scanning mirror assembly (310), the scanning mirror assembly comprising a reflective surface (334), wherein the scanning mirror assembly is configured to reflect a primary light beam in a first optical plane, the reflected primary light beam (312) forming a scanning beam (312), reflect a secondary light beam (400) in a second optical plane, the reflected secondary light beam forming a mirror position reference beam (402); and a position sensitive detector (160), wherein after reflection by the reflective surface (334), the mirror position reference beam (402) is incident on the PSD (160), and the PSD (160) is configured to detect the position of incidence of the mirror position reference beam (402), and wherein any stray light returned from the PSD (160) towards the reflective surface (334) is reflected by the reflective surface (334) in a third optical plane different from the first and second optical planes.