Title:
APPARATUS AND METHOD FOR MEASURING THE REFRACTIVE INDEX AND OPTICAL PATH LENGTH EFFECTS OF AIR USING MULTIPLE-PASS INTERFEROMETRY
Document Type and Number:
WIPO Patent Application WO1999042785
Kind Code:
A3
Abstract:
The invention employs multiple pass interferometry (69, 70, 90) to provide measurements of dispersion of the refractive index(n), the dispersion being substantially proportional to the density of the gas, and/or measurements of dispersion of the optical path length(L), the dispersion of the optical path length being related to the dispersion of the refractive index and the physical length of the measurement path. The refractive index of the gas and/or the optical path length effects of the gas are subsequently computed from the measured dispersion of the refractive index and/or the measured dispersion of the optical path length, respectively. In preferred embodiments, differential plane mirror interferometer architecture (69, 70) are utilized, the operating wavelengths (kQ, 2) are approximately harmonically related and may be monitored and/or controlled to meet precision requirements, heterodyne and superheterodyne processing are beneficially used, and phase redundancy is resolved.
Inventors:
HILL HENRY ALLEN
DE GROOT PETER
DEMAREST FRANK C
DE GROOT PETER
DEMAREST FRANK C
Application Number:
PCT/US1999/003499
Publication Date:
February 17, 2000
Filing Date:
February 18, 1999
Export Citation:
Assignee:
ZYGO CORP (US)
International Classes:
G01B9/02; G01J9/02; G01N21/45; (IPC1-7): G01B9/02
Foreign References:
| US5404222A | 1995-04-04 |
Other References:
See also references of EP 1066495A4
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