Browse Prior Art Database

Single Lens Remote Focus Actuator

IP.com Disclosure Number: IPCOM000107958D
Original Publication Date: 1992-Apr-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Stahl, R: AUTHOR

Abstract

In an optical drive, access time is limited by the mass of the coarse actuator. In traditional layouts, the bulk of the optics is placed in a fixed head known as the FOE (Fixed Optical Elements). The moving mass in the drive consists of a beam bender, an objective lens, a fine actuator for following media runout, and a coarse carriage for seeking (Fig. 1).

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Single Lens Remote Focus Actuator

       In an optical drive, access time is limited by the mass
of the coarse actuator.  In traditional layouts, the bulk of the
optics is placed in a fixed head known as the FOE (Fixed Optical
Elements).  The moving mass in the drive consists of a beam bender,
an objective lens, a fine actuator for following media runout, and a
coarse carriage for seeking (Fig. 1).

      By removing function from the coarse actuator and placing it
back in the FOE, the mass that must be moved for a seek is reduced.
This article describes a technique for moving the focus function of
the fine actuator to the FOE.

      The objective lens is designed for use as an infinite conjugate
lens, focussing a collimated beam emitted by the FOE to a focused
spot at the media active layer.  By changing the collimation of the
beam exiting the FOE (i.e., making it a converging or diverging
beam), the axial distance from the objective to the focused spot can
be controlled.  This collimation can be changed by passing the
collimated beam through a nominally afocal lens system, and varying
the power of the system.  Shown in Fig. 2 is a compact, single lens
system for performing this function.  The beam is passed through an
additional beam splitter and a single infinite conjugate lens.  The
light is focused on a mirror and returns back through the same lens.
The beam splitter then sends the beam out to the coarse actuator and
beam bender.  By varying the s...