| 摘要 |
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 G with respect to the position defined by the measurement point provides the birefringence parameters b PARALLEL ,b ORTHOGONAL for the positions on the disk (20). The phase detector (13) measures the phase theta 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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