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Browse Prior Art Database

Reduction of Optical Disk Noise by Collection of Scattered Light

IP.com Disclosure Number: IPCOM000119453D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 1 page(s) / 44K

Publishing Venue

IBM

Related People

Chen, M: AUTHOR [+2]

Abstract

Higher signal-to-noise ratio is desired since this allows larger data densities to be recorded on an optical disk. The maximum signal-to-noise achievable by present day optical storage media is often limited by media noise. One significant component of the media noise arises from light which is scattered from the disk and not collected by the objective lens. This invention is a device which collects much of the scattered light, hence reducing the noise.

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This is the abbreviated version, containing approximately 98% of the total text.

Reduction of Optical Disk Noise by Collection of Scattered Light

      Higher signal-to-noise ratio is desired since this allows
larger data densities to be recorded on an optical disk. The maximum
signal-to-noise achievable by present day optical storage media is
often limited by media noise.  One significant component of the media
noise arises from light which is scattered from the disk and not
collected by the objective lens.  This invention is a device which
collects much of the scattered light, hence reducing the noise.

      This invention is a light collector which surrounds the
standard objective lens.  It collects light scattered at an angle
larger than the maximum incident light angle and focuses it onto the
read detector.  It can be a lens or wide area, fast response
detector.  If it is a lens, it can be molded plastic or a Fresnel
lens to cut down weight.  It can be stationary and surround the
diffraction limited objective lens.  If a detector is used, the
output signal would be added to the read detector signal.  The
invention provides the advantage of very high numerical aperture for
collecting the scattered light, without sacrificing the mechanical
response time or depth of field achieved with the high NA diffraction
limited lenses used for writing.  The invention is applicable to any
optical storage system (magneto-optic, phase change, reversible,
write-once or ROM) in which some of the media noise is due to
scattered light.

      Disc...