Constant volume gas cell optical phase-shifter
- Dublin, CA
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.
- Research Organization:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
- DOE Contract Number:
- W-7405-ENG-48
- Assignee:
- The Regents of the University of California (Oakland, CA)
- Patent Number(s):
- US 6421130
- OSTI ID:
- 874593
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
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
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