Pulsed interferometric remote gauge
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsJerry A. Blodgett, Raymond A. Patten
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Abstract
The invention comprises a method and means for measuring the separation been two optical surfaces. A short-coherence-length laser pulse is projected upon two optical surfaces separated by a distance, d. The reflected, coincident beams are directed into a Michelson interferometer in which one plane mirror is replaced by a stepped mirror. The beams reflected from the two mirrors are directed onto a film where they form interference images. A formula using the number of channels, n, between successive interference fringes and the step width of the stepped mirror is used to calculate d.
Claims4
Apparatus for measuring the separation distance between two light-reflecting surfaces comprising, in combination:
- means for irradiating a pair of spaced, light-reflecting surfaces with a laser pulse;
- interferometer means comprising an interferometer of the Michelson type having stepped mirror means in place of one of the two usual plane mirrors therein, said interferometer being positioned to receive the light reflected from said two light-reflecting surfaces;
- and
- means for deriving the interference pattern produced by said interferometer,
- each step of said stepped mirror having a step height .delta., and a step depth .DELTA., which are equal, the interference pattern containing a series of columns some of which have interference fringe regions therein, the number of columns between the corresponding edges of two successive interference regions being designated n, and the separation distance being obtained from the formula
- d=n.DELTA.
Dependencies are inferred from the claim text.