Browse Prior Art Database

Original Publication Date: 1979-Jun-13
Included in the Prior Art Database: 2007-Mar-30

Publishing Venue

Software Patent Institute

Related People

Hoagland, A.S.: AUTHOR [+4]


RJ2561(33161) 6/13/79 Engineering Technology

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RJ2561(33161) 6/13/79

Engineering Technology

A. S. Hoagland
W. F. Oehme
F. E. Talke

IBM Research Laboratory
San Jose, California 95193

ABSTRACT: The defect behavior of thick particulate media is investigated by introducing artificial defects of known depth, measuring their signal loss characteristics as a function of frequency, and then relate actual measured drop-out lengths to the experimentally determined artificial defect depth data. The results indicate that the number of drop-outs per track is exponentially related to a "critical depth" parameter. The data can be used to extrapolate density capabilities of a given medium using
a set of experimental artificial defect data taken a t a lower performance level.

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   In a recent paper by Hoagland, Oehme, and ~alke,' the defect behavior
of flexible media was studied at high linear and track densities. Using
a Bernoulli-type flexible disk arrangement, the authors measured the total
dropout length per track as a function of track width, threshold, and
linear density, and observed that with a reasonable sample size the total
dropout length per track varies only slightly with track width but
increases substantially with both linear density and threshold. Auxiliary
optical and SEM investigations into the physical shape of the defects
indicated furthermore, that most of the medium defects are pressed into
the surface, and, therefore, the authors suggested that defects on thick
media could be analytically approximated by platelettes extending a certain
depth A into the medium. Unlike the model of Ogawa et a1.2 which treated
thin coatings, here we were concerned with a thick medium where the defects
penetrate up to a certain depth A into the medium rather than going
straight through to the substrate. Consequently, the signal loss caused
by such a defect is a function of the recording frequency, i.e., at high
frequencies where the signal mainly arises from the upper layer of the
medium, the effect of missing signal is progessively more detrimental and
a defect of even small depth becomes of increasing importance on the signal

   This paper is a continuation of this previous study,
with the objective to:

(a) further improve our understanding of the defect characteristics
of thick particulate media,

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(b) present a simple procedure that allows an estimate of the total defect length per track a t higher recording densities based on defect data obtained at lower frequencies, and

(c) show that a defect distribution having an exponential decrease with depth is consistent with our experimental results.


  In Table 1...