Optics: measuring and testing – By polarized light examination – With birefringent element
Patent
1999-01-16
2000-09-26
Kim, Robert H.
Optics: measuring and testing
By polarized light examination
With birefringent element
356349, 356358, 356351, G01B 982
Patent
active
061249319
ABSTRACT:
Interferometric apparatus and method for measuring and monitoring intrinsic optical properties of a gas, especially the reciprocal dispersive power of the gas, so that information about the gas properties can be used in downstream applications, such as interferometric distance measuring instruments, to increase accuracy by correcting for refractive index of the gas and especially environmental and air turbulence effects in the measurement path. The apparatus comprises a concentric measurement cell having an inner chamber containing a vacuum surrounded by an outer occupied by the gas. Wavelength selective mirrors are arranged at each end of the measurement cell and operate in conjunction with plane mirror interferometers to change the phase of orthogonally polarized components of light beams of different wavelength introduced in the measurement cell from opposite ends of the cell. Preferably, the polarized components are frequency-shifted to facilitate the generation of heterodyne and superheterodyne signals which contain information about the intrinsic optical properties of the gas. The heterodyne and superheterodyne signals are electronically analyzed by a general purpose computer programmed for that purpose or from a specially programmed microprocessor.
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Caufield Francis J.
Kim Robert H.
Lee Andrew H.
Zygo Corporation
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