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Two Pass Remote Reference Interferometer

IP.com Disclosure Number: IPCOM000050752D
Original Publication Date: 1982-Dec-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Wilson, AD: AUTHOR

Abstract

An optical interferometer is described which has the ease of alignment of a four-pass interferometer, but has the added convenience of having a remote reference surface.

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Two Pass Remote Reference Interferometer

An optical interferometer is described which has the ease of alignment of a four-pass interferometer, but has the added convenience of having a remote reference surface.

A four-pass interferometer normally compares a four-pass measurement path to a two-pass reference path. Because of the difference in path sensitivity, the reference in a four-pass interferometer normally cannot be made remote. If two positions are to be compared using a four-pass interferometer, the interferometer position itself normally must represent one of the compared positions. With a two-pass interferometer, both the reference and measurement paths have two passes, so that the reference can be remote. However, a two-pass interferometer is much more sensitive to alignment than a four-pass interferometer, and since a two-pass interferometer has only one optical axis rather than two, it adversely affects laser performance due to optical feedback much more than a four-pass interferometer.

The illustrated interferometer combines the advantages of both by fixing the path length of two passes in the four-pass path of a four-pass interferometer. Since the measurement path and the reference path now both have the same sensitivity (effectively two-pass sensitivity), the reference can be remote.

The illustrated system works as follows: Light from source 1 (a Zeeman laser, for example) is reflected by interferometer light splitter 3 through quarter- wave plate...