Description and Operation
Typically 3 or more mirrors are used, so that counter-propagating light beams follow a closed path such as a triangle or square.(Fig. 1) Alternatively fiber optics can be employed to guide the light through a closed path.(Fig. 2) If the platform on which the ring interferometer is mounted is rotating, the interference fringes are displaced compared to their position when the platform is not rotating. The amount of displacement is proportional to the angular velocity of the rotating platform. The axis of rotation does not have to be inside the enclosed area.
The Sagnac effect in a circular loop can be understood as follows. When the loop is rotating, the point of entry/exit moves during the transit time of the light. The backwards-propagating beam covers less distance than the forwards-propagating beam and arrives earlier.(Fig. 3) This creates a shift in the interference pattern. The shift of the interference fringes is thereby proportional to the platform's angular velocity.
The rotation thus measured is an absolute rotation, that is, the platform's rotation with respect to an inertial reference frame.
Read more about this topic: Sagnac Effect
Famous quotes containing the words description and/or operation:
“Why does philosophy use concepts and why does faith use symbols if both try to express the same ultimate? The answer, of course, is that the relation to the ultimate is not the same in each case. The philosophical relation is in principle a detached description of the basic structure in which the ultimate manifests itself. The relation of faith is in principle an involved expression of concern about the meaning of the ultimate for the faithful.”
—Paul Tillich (1886–1965)
“Human knowledge and human power meet in one; for where the cause is not known the effect cannot be produced. Nature to be commanded must be obeyed; and that which in contemplation is as the cause is in operation as the rule.”
—Francis Bacon (1560–1626)