Dg. Fischer et B. Ovryn, Interfacial shape and contact-angle measurement of transparent samples with confocal interference microscopy, OPTICS LETT, 25(7), 2000, pp. 478-480
A model has been developed that predicts the effective optical path through
a thick, refractive specimen on a reflective substrate, as measured with a
scanning confocal interference microscope equipped with a high-numerical-a
perture objective. Assuming that the effective pinhole of the confocal micr
oscope has an infinitesimal diameter, only one ray in the illumination bund
le (the magic ray) contributes to the differential optical path length (OPL
). A pinhole with finite diameter, however, allows rays within a small angu
lar cone centered on the magic ray to contribute to the OPL. The model was
incorporated into an iterative algorithm that allows the measured phase to
be corrected for refractive errors by use of an a priori estimate of the sa
mple profile. The algorithm was validated with a reflected-light microscope
equipped with a phase-shifting laser-feedback interferometer to measure th
e interface shape and the 68 degrees contact angle of a silicone-oil drop o
n a coated silicon wafer. (C) 2000 Optical Society of America. OCIS codes:
120.3180, 170.1790, 180.3170, 120.3940, 120.2830.