Browse Prior Art Database

High Density Tracking With Low Density Grooves

IP.com Disclosure Number: IPCOM000121690D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 73K

Publishing Venue

IBM

Related People

Sincerbox, GT: AUTHOR

Abstract

Disclosed is a method for increasing the recording track density in an optical data storage system without requiring the fabrication of a more closely spaced groove or sector servo marks. Alternatively, this method can be used to relax groove spacing requirements at current track densities.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

High Density Tracking With Low Density Grooves

      Disclosed is a method for increasing the recording track
density in an optical data storage system without requiring the
fabrication of a more  closely spaced groove or sector servo marks.
Alternatively, this method can be used to relax groove spacing
requirements at current track densities.

      An increase in track density is achieved by using a laser array
consisting of a central read/write laser and adjacent tracking lasers
on each side in conjunction with grooves or sector servo marks that
are spaced so as to permit multiple data tracks between them.  In the
most simple case, a single read/write laser spot is flanked by low
power tracking laser spots on each side.  The laser spots on each
side are spaced from the read/write laser spot by a distance equal to
a fraction of the groove spacing.  In this example, the first data
track is accessed by activating the left-hand tracking laser and
causing it to follow the left-hand groove.  The second data track is
accessed by activating the right-hand tracking laser and following
the right-hand groove.  The exact spacing selected will depend on the
relative groove-to-land width and the desired data track spacing.
For example, a laser spacing equal to l/3 the groove spacing will
produce two data tracks equally spaced between the grooves.  A
spacing of l/4 will produce equally spaced data tracks independent of
the grooves.  With smaller spot sizes and no change in groove pitch,
two data tracks can occupy the same space as previously occupied by
one data track.  Alternatively, a data track spacing of l.5 mm
(today's density) can be obtained with grooves 3.0 mm apart, thus
easing manufacturing.

      This concept is easily extended to more...