Optics: measuring and testing – By polarized light examination – Of surface reflection
Patent
1997-04-11
1998-11-03
Pham, Hoa Q.
Optics: measuring and testing
By polarized light examination
Of surface reflection
356351, 356357, 369110, G01B 902, G01J 400
Patent
active
058317333
ABSTRACT:
An apparatus and methods for measuring and compensating for birefringence in a rotating ground glass disk (20) such as are employed in polarization based optical flying height testers. The polarized light (1, 3) impinges on the top surface (24) of the disk (20) and is refracted through the disk to a measurement point (90) on the opposite surface (25) from which it is reflected back through the disk (20) and refracted before it exits the disk (20) in a beam (9) containing both s .alpha.and p polarizations which are detected by a phase detector (13) which measures any difference in phase between the s and p polarizations. Any variation of the phase .theta..sub.G with respect to the position defined by the measurement point provides the birefringence parameters b.sub..parallel.,b.sub..perp. for the positions on the disk (20). The phase detector (13) measures the phase .theta..sub.G at a skew angle .zeta. defined between the plane of incidence (101), defined by the existing beam (9) and the incident beam (3), drawn through the measurement point (90) perpendicular to a radius line (102) for the disk (20).
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Caufield Francis J.
Pham Hoa Q.
Zygo Corporation
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