Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1996-03-11
1998-02-03
Font, Frank G.
Optics: measuring and testing
By polarized light examination
With light attenuation
G01B 1114
Patent
active
057150605
ABSTRACT:
An apparatus and method is disclosed for measuring the distance between a first body having a first surface separated by a medium from a second body through the use of transmitted evanescent radiation. The first body is substantially radiation transparent and has a critical angle of total internal reflection with respect to the medium and the second body has an optically disseminative opposing surface, that is, the opposing surface inherently disseminates radiation nonspecularly, and is capable of frustrating total internal reflection when brought into close proximity with the first surface. The apparatus and method provides for directing incident radiation into the first body toward the first surface at an angle exceeding the critical angle for total internal reflection in the first body so as to transmit radiation to the optically disseminative opposing surface, measuring the intensity of the transmitted radiation disseminated by the optically disseminative opposing surface, and calculating the distance between the first surface and the optically disseminative opposing surface based on the measured intensity of the disseminated transmitted radiation. Preferably, the optically disseminative opposing surface is composed of a material having a heterogeneous or otherwise spatially varying refractive index or a material that is capable of absorbing and reemitting the transmitted radiation. The method and apparatus may be used in a preferred embodiment for testing the distance between a magnetic recording head and a recording disk.
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Carnegie Mellon University
Font Frank G.
Smith Zandra V.
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