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Disk Runout Free Calibration Method for Optical Disk Drive

IP.com Disclosure Number: IPCOM000106895D
Original Publication Date: 1992-Jan-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Kagami, N: AUTHOR [+3]

Abstract

Disclosed is a method for an optical disk drive to enable the tracking/focus servo calibration without depending on the number of track crossing signals (runout). The typical runout waveform is shown in the figure. This method is applicable to a spiral track optical disk.

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Disk Runout Free Calibration Method for Optical Disk Drive

       Disclosed is a method for an optical disk drive to enable
the tracking/focus servo calibration without depending on the number
of track crossing signals (runout).  The typical runout waveform is
shown in the figure.  This method is applicable to a spiral track
optical disk.

      This tracking/focus servo calibration is to normalize or
maximize the track crossing signal amplitude by adjusting the
gain/offset amplifier under the control of a microprocessor.  Basic
conception of the method is to determine the capture time while the
track crossing signal peak appears.  In the spiral track media, the
minimum number of track crossing is one per revolution.  In the worst
case, the optical drive system gets one track crossing peak signal in
one disk revolution time.  But, in the normal case, the runout is
more than one per disk one revolution, and one track crossing peak is
enough to recognize the peak value. To minimize the measuring time,
the system estimates the lowest runout frequency (time period).

      The calibration flow is as follows:
   Step 1:  Measuring the number of the track crossings (runout) in
one disk revolution using a track counter.
   Step 2:  Based on the measured number, estimate the longest time
period. This estimation means solving the equation, and equation
parameter given by experimental value.
             Example:  Time = ( -25 / (X * X) + 54 / X...