Browse Prior Art Database

Minimizing Use of Automated Laser Power Control Fields on WORM Media

IP.com Disclosure Number: IPCOM000114438D
Original Publication Date: 1994-Dec-01
Included in the Prior Art Database: 2005-Mar-28
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Jaquette, GA: AUTHOR [+2]

Abstract

A method which allows Automatic Laser Power Control (ALPC) or Qualification (ALPQ), without using the ALPC region of every sector written, is disclosed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 70% of the total text.

Minimizing Use of Automated Laser Power Control Fields on WORM Media

      A method which allows Automatic Laser Power Control (ALPC) or
Qualification (ALPQ), without using the ALPC region of every sector
written, is disclosed.

      A number of deleterious effects can result from the calibration
on the ALPC field of every sector written on a WORM disk, such as
glitches on the Tracking Error Signal when the ALPC field is
traversed at high speeds.

      The solution lies in minimizing the number of ALPQ fields
written.  Servo mis-counting due to TES spikes caused by ALPQ fields
will be minimized if the number of ALPQ fields used is minimized.
The ALPQ field is primarily to test whether the laser efficiency
shift estimation is accurate, and to check for any gross hardware
failure.  Both of these can be determined on the very first sector of
a multiple sector write.  If the ALPQ write is inhibited after the
power qualification is performed on the first sector of a multiple
sector operation, all following sectors are written without this
glitch-causing field.  On the sectors without ALPQ fields, this two
bytes can be left blank or written with something else, such as 3T -
giving a 14 byte VFO3 field.

      This can be carried out to various extents.  One could always
write the first sector of any multiple sector write operation, but an
application which writes one sector at a time will write just as many
ALPQ fields as before.  One could write only the...