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Title: Constant volume gas cell optical phase-shifter

Abstract

A constant volume gas cell optical phase-shifter, particularly applicable for phase-shifting interferometry, contains a sealed volume of atmospheric gas at a pressure somewhat different than atmospheric. An optical window is present at each end of the cell, and as the length of the cell is changed, the optical path length of a laser beam traversing the cell changes. The cell comprises movable coaxial tubes with seals and a volume equalizing opening. Because the cell is constant volume, the pressure, temperature, and density of the contained gas do not change as the cell changes length. This produces an exactly linear relationship between the change in the length of the gas cell and the change in optical phase of the laser beam traversing it. Because the refractive index difference between the gas inside and the atmosphere outside is very much the same, a large motion must be made to change the optical phase by the small fraction of a wavelength that is required by phase-shifting interferometry for its phase step. This motion can be made to great fractional accuracy.

Inventors:
 [1]
  1. (Dublin, CA)
Issue Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
OSTI Identifier:
874593
Patent Number(s):
6421130
Assignee:
The Regents of the University of California (Oakland, CA) LLNL
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Patent
Country of Publication:
United States
Language:
English
Subject:
constant; volume; gas; cell; optical; phase-shifter; applicable; phase-shifting; interferometry; contains; sealed; atmospheric; pressure; somewhat; window; length; changed; path; laser; beam; traversing; changes; movable; coaxial; tubes; seals; equalizing; temperature; density; contained; change; produces; exactly; linear; relationship; phase; refractive; index; difference; inside; atmosphere; outside; motion; fraction; wavelength; required; step; fractional; accuracy; laser beam; optical path; refractive index; particularly applicable; optical phase; gas cell; atmospheric gas; /356/

Citation Formats

Phillion, Donald W. Constant volume gas cell optical phase-shifter. United States: N. p., 2002. Web.
Phillion, Donald W. Constant volume gas cell optical phase-shifter. United States.
Phillion, Donald W. Tue . "Constant volume gas cell optical phase-shifter". United States. https://www.osti.gov/servlets/purl/874593.
@article{osti_874593,
title = {Constant volume gas cell optical phase-shifter},
author = {Phillion, Donald W.},
abstractNote = {A constant volume gas cell optical phase-shifter, particularly applicable for phase-shifting interferometry, contains a sealed volume of atmospheric gas at a pressure somewhat different than atmospheric. An optical window is present at each end of the cell, and as the length of the cell is changed, the optical path length of a laser beam traversing the cell changes. The cell comprises movable coaxial tubes with seals and a volume equalizing opening. Because the cell is constant volume, the pressure, temperature, and density of the contained gas do not change as the cell changes length. This produces an exactly linear relationship between the change in the length of the gas cell and the change in optical phase of the laser beam traversing it. Because the refractive index difference between the gas inside and the atmosphere outside is very much the same, a large motion must be made to change the optical phase by the small fraction of a wavelength that is required by phase-shifting interferometry for its phase step. This motion can be made to great fractional accuracy.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2002},
month = {1}
}

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