Guzik Technical Enterprises

Boris Slutsky

Nahum E Guzik

Ufuk Karaaslan

Michael Mager

A magnetic head and disk tester which has linear encoders (40 and 42) installed on lateral sides of a carriage (30) which carries a magnetic head (34), movable in a radial direction along a hard disk. Positions of the magnetic head with respect to the hard disk are measured by means of the linear encoders which are arranged on both lateral sides of the carriage. Outputs of the encoders are supplied to an arithmetic unit (45) which calculates the arithmetic mean of the encoder's outputs and transmits the resulting signal via a feedback line (47) to a piezoelectric translator (37). The translator is the final drive element in the carriage-drive system and is used for fine positioning of the carriage. Thus, if during positioning of the magnetic head the latter is installed in an erroneous position, e.g., because of yawing which may result from asymmetrical friction on both sides of the carriage, the feedback-positioning system composed of the encoders, the arithmetic unit, and the piezoelectric translator calculates the error and shifts the carriage in a direction opposite to the error to the correct position.

Method and apparatus for compensating positioning error in magnetic-head

An apparatus employs the phenomenon of frustrated total internal reflection for measuring nanometric distances. It includes a two-piece glass reference disk (200) consisting of an inner disk (202) and a coupling lens (212). The inner disk (202) contains a convex spherical surface (204) and a flat bottom surface (206). The coupling lens has a planar top surface (214) and a concave spherical surface (216). It is fixed over the inner disk which is rotated by a spindle (208). Aligned prisms (218 and 220) have polished planes (222 and 224) and polished surfaces (230 and 232). These surfaces provide optical contact of the prisms with the planar top surface of the coupling lens. A magnetic head (238) is suspended over the flat bottom surface of the inner disk. Other configurations of the reference disk and optical prisms are possible. One of the variations of the optical system contains a colored-light source (248), aimed at the polished prism surface at essentially normal incidence, a beam expander ( 250), placed between the light source and the polished prism surface, and a TV camera (252), which is positioned opposite the polished prism surface (222). As the spindle rotates the inner disk, the magnetic head floats on an air cushion created by the surface of the glass disk. A light beam (242), generated by the light-source, is converted into a wide parallel beam (244), which is directed at the surface of the magnetic head. A reflected beam (246) is received by the TV camera. The spacing between the magnetic head and the disk surface can be calculated from the drop in intensity of reflected light.

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Palo Alto, CA, United States of America

Boris Slutsky