Patent ID: 7428086

Claim:
A method of applying a substantially linearly varying optical path length delay to an optical beam, the method comprising: rotating an optical path element about an axis so that the optical path element intersects an incidence line during a first fraction of each cycle of rotation; inserting an input beam along the incidence line so that during the first fraction of each cycle the beam enters the optical path element at a predefined range of angles over which an optical path length of the optical path element varies substantially linearly with rotation; reflecting the beam from the incidence line to a reinsertion line outside of the first fraction of each cycle when the optical path element does not intersect the Incidence line; and reinserting the beam into the optical path element along the reinsertion line that is separated from the axis of rotation a same distance as the incidence line defining a second fraction of each cycle of rotation during which the optical path length varies.