Optics: measuring and testing – By polarized light examination – With birefringent element
Patent
1996-02-07
1997-02-11
Epps, Georgia
Optics: measuring and testing
By polarized light examination
With birefringent element
356351, G01B 902
Patent
active
056026439
ABSTRACT:
An improvement to phase-shifting interferometry that consists of the addition of a pupil mask with two parallel slits and a polarizer in the optical path of a conventional phase-shifting interferometer. The pupil-mask/polarizer combination is adapted to produce a linearly polarized wavefront of light reaching the sample surface at a predetermined angle of incidence, thereby producing a corresponding phase shift on reflection. The relative orientation of the mask and polarizer can be changed to take measurements with the polarizer parallel or perpendicular to the mask slits, in each case producing a phase shift on reflection related to the test sample's refractive index and extinction coefficient. Four phase-shifting measurements conducted at .pi./2 intervals for each polarization axis yield sufficient interferometric information to map n, k and the height profile of the sample surface. The preferred mask consists of an opaque disk structure having two opposite annular slits approximately 90-degrees wide and with an outer annular radius approximately twice the size of the inner annular radius.
REFERENCES:
patent: 5387975 (1995-02-01), Ishida et al.
patent: 5548403 (1996-08-01), Sommargren
Max Born & Emil Wolf, "Principles of Optics," Fourth Edition, pp. 614-617.
Durando Antonio R.
Epps Georgia
Kim Robert
Wyko Corporation
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