Patent ID: 7798648
Filing Date: 2010-09-21
Classification: G02B,H04N

Abstract:
1. An optical path length adjuster for varying an optical path length between an input optical path and an output optical path, comprising: a first polarisation switch for selecting a polarisation state for an input beam on the input optical path; and first and second beam splitters having at least two possible optical paths of different lengths therebetween, for passing the input beam along a selected one of said at least two possible optical paths according to the selected polarisation state of the input beam and for providing an output beam of light, on said optical output path, that has travelled along the selected optical path; the first beam splitter has a first optical input coupled to the optical output of the first polarisation switch, for diverting light at the optical input of the first splitter to first and second optical outputs respectively according to a polarisation state of the light at the optical input of the first splitter; the second beam splitter has first and second optical inputs respectively optically coupled to the first and second outputs of the first beam splitter, via respective said first and second optical paths, the second beam splitter diverting light at the first and second inputs to first and second outputs of the second beam splitter according to a polarisation state of light at the first and second inputs thereof; the first output of the second beam splitter defines the optical output path, and the second output of the second beam splitter is optically coupled to a second input of the first beam splitter via a third optical path; each of the first, second and third optical paths respectively includes one of a second, a third and a fourth polarisation switch, the first, second, third and fourth polarisation switches adapted to thereby select cumulative combinations of one or more of said first, second, and third optical paths between the input optical path and the output optical path.