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Browse Prior Art Database

Laser Power Temperature Compensating Method

IP.com Disclosure Number: IPCOM000114211D
Original Publication Date: 1994-Nov-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Demura, M: AUTHOR [+4]

Abstract

A method for maintaining constant optical power at the surface of optical media is disclosed. The method compensates for temperature effects.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 57% of the total text.

Laser Power Temperature Compensating Method

      A method for maintaining constant optical power at the surface
of optical media is disclosed.  The method compensates for
temperature effects.

      In an optical storage drive means for maintaining a known laser
power level at the optical media is required.  Uncertainty in
knowledge of the power levels at the optical media can result in
degradation of customer data, suboptimal writing of customer data,
and a shorter laser life.  This is especially important in Write-Once
style drives where it is quite difficult to do any write power
calibration without eating into the available space for customer
data.  Fig. 1 shows the typical method employed in current art to
control the laser power.  Light from a laser diode is first
collimated and then diverted into a beamsplitter which transmits most
of the light out toward the media.  Light not transmitted at the
beamsplitter is reflected toward a power servo photodetector.
Current from this photodetector is fed into a power servo circuit
which supplies the necessary laser driver current to maintain a
constant photodetector current.  By maintaining a constant
photocurrent, the power at the detector is held constant, implying
the power at the media is held constant as well.  At time of
manufacture, a power meter is placed in lieu of the optical media.
The gain of the power servo loop is adjusted until the desired power
is achieved.

      This method works well as...