Near field optical certifying head for disc asperity mapping
AssigneeSeagate Technology LLC
InventorsLing Wang, Li Li
Life of this patent
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Abstract
An optical certifying head flies above a disc surface within an evanescent decay length of the disc surface. A light beam is focused through an objective lens, and further focused through a SIL. The SIL-focused light is coupled to the disc surface through near-field coupling. The light is reflected from the disc surface depending on a surface condition of the disc such that the surface condition can be determined.
Claims14
An apparatus for optically mapping asperities on a rotating disc surface, of a disc to be screened, the apparatus comprising:
- a controller;
- an actuator coupled to the controller;
- a suspension assembly coupled to the actuator;
- an optical certifier head including a first SIL and an air bearing slider, the head coupled to the suspension assembly such that the head is disposed within an evanescent decay length from the rotating disc surface, and wherein the controller causes movement of the head over the surface of the rotating disc;
- a light source operably coupled to the certifier head such that light is focussed through the first SIL onto the disc surface by near field coupling;
- a sensor operably coupled to the head and to the controller, the sensor providing a signal based upon an intensity of light reflected from the disc, the signal having a normal characteristic output signal during normal operation, and an asperity characteristic output signal when an asperity disc surface is within the evanescent decay length of the head;
- and
- wherein the controller correlates the asperity characteristic output signal with a location on the disc surface.
A method of detecting asperities on a surface of a rotating disc, the method comprising the steps of:
- providing a first light beam;
- focussing the first light beam through a first SIL;
- optically coupling the focussed first light beam to the disc surface through near-field coupling;
- and
- measuring an intensity of first reflected light from the disc surface;
- and
- determining asperity presence based upon the measured intensity of first reflected light.
An apparatus for optically mapping asperities on a rotating disc surface, the apparatus comprising:
- optical head means for coupling an optical signal to the disc surface and providing a reflected signal output;
- and
- means for detecting an asperity on the disc surface as a function of the reflected signal output.
Dependencies are inferred from the claim text.