Browse Prior Art Database

Simple Mo Head with Integrated Data and Servo Detection

IP.com Disclosure Number: IPCOM000122913D
Original Publication Date: 1998-Jan-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 4 page(s) / 91K

Publishing Venue

IBM

Related People

Dewey, A: AUTHOR [+2]

Abstract

There are 3 principal functions which must be achieved in an optical storage head: (1) MO signal detection (2)focus servo and (3) tracking servo. Those skilled in the art are familiar with the requirements imposed on these 3 functions. Most Magneto-optical head designs separate the servo functions from the data function.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Simple Mo Head with Integrated Data and Servo Detection

      There are 3 principal functions which must be achieved in an
optical storage head: (1) MO signal detection (2)focus servo and (3)
tracking servo.  Those skilled in the art are familiar with the
requirements imposed on these 3 functions.  Most Magneto-optical head
designs separate the servo functions from the data function.

      It is the purpose of this disclosure to describe a simple MO
head in which the track and focus servo and data functions are
combined.  A common optical path is used in which two optical system
is shown in Fig. 1.  In this figure (1) is a semiconductor laser; (2)
a collimating lens; (3) a partial polarizing beam splitter; (4) a
rotating MO disk; (5) a beam bender/objective lens combination (6) a
1/2 wave plate;  (7) a spherical focusing lens; (8) a beam splitting
plate having a polarizing beam splitter coating on the interface
surface and (9) a multi-element photodetector.

      A more detailed picture of the focus lens (7), beam splitting
plate (8) and detector place (9) is shown in Fig. 2.  This scale
drawing shows the relationship of the two focused beams as they
strike the detector plane.  The additional optical path of the
transmitted beam passing through the beam splitter coating results in
a longitudinal focus shift at the detector plane as well as a lateral
shift of the beam center.  The focus servo technique utilized in this
design is the  one-dimensional spot size measuring method of SSM.  By
placing the detector mid-way between the two focused beams a
differential SSM.  Signal or DSSM can be obtained.

      The MO data signal is obtained in a straightforward fashion
utilizing the 1/2 wave plate, polarizing the beam splitter coating and
differencing the signals from the two laterally separated beams.
Ligh...