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Optical Media With Magnetically Transduced Reflectivity

IP.com Disclosure Number: IPCOM000101809D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 98K

Publishing Venue

IBM

Related People

Jan, DK: AUTHOR [+3]

Abstract

Described is a new type of optical media which can be read by WORM (Write Once Read Mostly) devices, and yet can be rewritten a large number of times by a modified WORM device. This media uses flat, optically reflective magnetic particles of very small dimension distributed in a transparent medium. The particles are oriented so that the media is a second class mirror when unused; the reflecting surface is finely fragmented, being composed of reflecting particles oriented parallel to the flat surfaces of the media; very small portions of the mirror surface can be modified by deflecting the particles in such areas. This is done by liquefying the transparent medium in which the particles are dispersed, while applying a magnetic field that causes the particles to be deflected.

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Optical Media With Magnetically Transduced Reflectivity

       Described is a new type of optical media which can be
read by WORM (Write Once Read Mostly) devices, and yet can be
rewritten a large number of times by a modified WORM device. This
media uses flat, optically reflective magnetic particles of very
small dimension distributed in a transparent medium.  The particles
are oriented so that the media is a second class mirror when unused;
the reflecting surface is finely fragmented, being composed of
reflecting particles oriented parallel to the flat surfaces of the
media; very small portions of the mirror surface can be modified by
deflecting the particles in such areas.  This is done by liquefying
the transparent medium in which the particles are dispersed, while
applying a magnetic field that causes the particles to be deflected.
After information is written on the media by deflecting the particles
as described above, such information can be read in the same fashion
as WORM media.  The deflection of the particles is reversible, thus
allowing a large number of rewrite operations on this media.

      The figure illustrates the principle of operation of this new
media.  It is assumed that the reflecting particles are permanent
magnets with the polarity aligned with their largest dimension.
Shown is a portion of the media under the ERASE/WRITE/READ head.  The
substrate of the media is a polycarbonate blank with pregrooved
tracks (C), identical to WORM media blanks already in use.  The
reflecting particles are dispersed in a transparent medium to form a
phase-change ink, which is deposited within the grooves of the
substrate (D).  The transparent medium can rapidly change phase from
solid to liquid when heated by laser light during the ERASE and WRITE
operations.  A laser provides a power source to generate four
separate beams which are used for tracking, erasing, and writing (and
reading).

      The tracking is performed in a similar manner as the current
triple beam tracking system used in some current WORM designs, using
the tracking beams T-T'....