1. An optical tracking system, comprising: at least one optical detector unit having a scanning mirror and one or more fixed photodetectors located near the scanning mirror, wherein the scanning mirror is configured to rotate about one or more axes in order to deflect a light beam from a source towards a target and the photodetectors are configured to collect a portion of the light beam that is reflected from the target, wherein the one or more fixed photodetectors are configured such that the optical path from the source to the optical detector unit does not intersect the scanning mirror along a return portion of the optical path from the target to the one or more photodetectors.