Komag Corporation

Wd Media, LLC

Daryl M Shiraki

David Treves

Shoji Suzuki

Thomas Anthony O'Dell

Balvinder Singh

Dan Frusescu

Jayadev P Patel

Tuan H Hua

An apparatus is disclosed comprising a thermal sensor operable to detect at least one protrusion defect and at least one recess defect on a disk, the thermal sensor operable to generate a sensor signal. An attack time of the sensor signal is measured when the thermal sensor passes over one of the protrusion defect and the recess defect, and the protrusion defect is discriminated from the recess defect based on the attack time.

Discriminating between protrusion defects and recess defects on a disk recording medium

A calibration disk for calibrating the fly height of a head, includes spaced circumferencial bands on the disk extending in a concentric fashion from adjacent an outer diameter of the disk to near an inner diameter of the disk. Each of the bands include radial and circumferencial spaced asperity emulating bumps having a population sufficient to produce a constant and continuous output signal from a glide head when the glide head flies lower than a maximum height of the bumps. The height of the bumps within individual bands are substantially uniform, and the average heights of the bumps in each band differ from each other. The configuration of the bumps on the calibration disk advantageously avoids errors caused by disk waviness, runout, and contamination. Further, using the differing heights of the bumps on the calibration disk, a glide head can be calibrated on the glide tester without using an independent fly height measurements for the glide head. Thus, errors in the fly height measurement and the delay in mounting each glide head to a fly height tester are avoided.

Calibration disk having discrete bands of calibration bumps

A memory media tester uses a dynamic threshold margin between the sensor signal produced by a sensor and a threshold level. The dynamic threshold margin is generated as a function of a DC signal generated by converting the sensor signal to a DC voltage, where the sensor signal is composed of a noise level and signal spikes. The rate of change of the DC converted signal is controlled in order to prevent the DC converted signal from being significantly affected by the signal spikes. The dynamic threshold margin may be produced as a dynamic threshold level, a dynamically amplified output signal, or both. The sensitivity of the dynamic threshold margin may be electronically adjusted. The dynamic threshold margin automatically adjusts to changes in the DC converted signal, such as when there is a change in the surface roughness of the media, or when the sensor loses sensitivity. The sensor signal may then be compared to the threshold level, where the difference between the threshold level and the noise level is the dynamic threshold margin. A defect is found when the sensor signal exceeds the threshold signal.

Dynamic threshold margin to test memory storage media

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Daryl M Shiraki