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Laser-Power Monitor Method for a Two-Laser Array Using Front and Back Detectors

IP.com Disclosure Number: IPCOM000103060D
Original Publication Date: 1990-May-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 44K

Publishing Venue

IBM

Related People

Dickson, L: AUTHOR [+2]

Abstract

Disclosed is a means for monitoring the power in each of the two lasers used in a dual laser DRAW (Direct Read After Write) Optical Storage Head. In the method described, power monitoring of the two beams is obtained without requiring physical separation of the two collimated beams. The normal method for doing this is to separate the two beams by using a lens to focus the overlapping collimated beams and placing a split detector at the focal plane of the lens.

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Laser-Power Monitor Method for a Two-Laser Array Using Front and Back Detectors

      Disclosed is a means for monitoring the power in each of the
two lasers used in a dual laser DRAW (Direct Read After Write)
Optical Storage Head.  In the method described, power monitoring of
the two beams is obtained without requiring physical separation of
the two collimated beams.  The normal method for doing this is to
separate the two beams by using a lens to focus the overlapping
collimated beams and placing a split detector at the focal plane of
the lens.

      In the disclosed method, two detectors are used to provide the
necessary power monitoring - a front, or fore, detector, which is
placed in the overlapping collimated beams, and a rear, or aft,
detector, which is placed near the back facets of the laser array.
The back facet outputs are masked so that only the verify beam
strikes the aft-detector.  The back facet R/W beam is blocked with an
opaque mask.  The fore-detector is illuminated by the overlapping
collimated beams from both lasers.

      During the non-verify read mode, only the R/W laser is on and
its output is monitored by the fore-detector.  During the verify
mode, the aft-detector monitors the Verify laser. Both front beams
illuminate the fore-detector when the R/W beam is writing in the
verify mode and the resultant fore-detector signal is the sum of the
two laser powers. During this mode of operation, the R/W laser power
can be monitored and co...