An optical system, capable to admit a light beam (200), the optical system comprising: a plurality of reflectors (210a, 210b) configured to reflect the light beam, wherein each of the reflectors is configured to reflect an incident light beam such that the path of the incident light beam and the path of the reflected light beam are parallel to each other. Each of the reflectors has a reflection center axis (250a； 250b) positioned centrally between the path of the incident light beam and the path of the reflected light beam. At least two of the reflectors are arranged relative to each other such that their respective reflection center axes do not overlap, thereby enabling the path of the light beam to pass at least one of the at least two of the reflectors multiple times.
