An optical system including multiple lenses to receive respective laser beams, and including a combiner (an optical device) to receive the laser beams from the multiple lenses and to combine the laser beams into a single beam. The optical assembly includes a micro-electro-mechanical system (MEMS) mirror to reflect the single beam from the combiner and provide a reflected beam as an exit beam through a window to an object. The optical assembly includes a single-pixel photodetector to collect light reflected from the object.