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Browse Prior Art Database

Write Recalibration in Single and Dual Headed Optical Disk Drives

IP.com Disclosure Number: IPCOM000107281D
Original Publication Date: 1992-Feb-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 92K

Publishing Venue

IBM

Related People

Fennema, AA: AUTHOR [+4]

Abstract

An optical jukebox can be exposed to sizeable thermal variations, such as 10 degrees Celsius/hour. The temperature of the media will affect the quality of the written data. If the laser is writing on warm media while actually calibrated to cold media, the written marks on the media may be oversized. Conversely, if the laser is writing on cold media while actually calibrated to warm media, the spot size may be insufficient for subsequent reading. Humidity can have an effect, too, because water vapor absorbs infrared radiation and the beam splitter ratios can be affected. Thus, the integrity of the written data may be compromised by inaccurate calibration of the optical laser to the optical media.

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This is the abbreviated version, containing approximately 52% of the total text.

Write Recalibration in Single and Dual Headed Optical Disk Drives

       An optical jukebox can be exposed to sizeable thermal
variations, such as 10 degrees Celsius/hour.  The temperature of the
media will affect the quality of the written data.  If the laser is
writing on warm media while actually calibrated to cold media, the
written marks on the media may be oversized.  Conversely, if the
laser is writing on cold media while actually calibrated to warm
media, the spot size may be insufficient for subsequent reading.
Humidity can have an effect, too, because water vapor absorbs
infrared radiation and the beam splitter ratios can be affected.
Thus, the integrity of the written data may be compromised by
inaccurate calibration of the optical laser to the optical media.

      It is the intent of this article to have the laser properly
tuned to the immediate environment.  It is known to the art that the
following write calibrate steps will be done once the optical disk is
loaded into an optical drive if there is either a pending or
anticipated write operation: (a) focus runout calibrate, (b) focus
offset calibrate, (c) write-operation calibrate, and (d) tracking
offset and amplitude calibrate.

      What is new with this article is that specific steps are now
proposed to invoke recalibration of the write function.  Such write
recalibration would consist of the same four steps involved with the
original write calibration.

      In addition to doing a write recalibration when a write-verify
check was encountered, a write recalibration during periods where the
drive is otherwise inactive is superior to waiting for a write-verify
failure to trigger this action.

      The periodic write calibrate could be controlled a number of
different ways.  For drives with one optical head, the preferred way
would be to embed it in the clean-up routines in the control unit of
the optical jukebox.  To avoid code complexity, the clean-up routines
could be issued at a fixed time interval such as hourly.  In a stand-
alone drive, IBM PS/2* or optical drive microcode could issue the
same command.

      Such periodic write recalibration may be hard-coded or, via a
menu, the user could be offered a simple yes/no question as to
whether or not periodic write-calibrate is desired.  The write
calibration takes abou...