Browse Prior Art Database

Method for Protecting Against Cluster Errors in Holographic Memory

IP.com Disclosure Number: IPCOM000118242D
Original Publication Date: 1996-Nov-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Blaum, MM: AUTHOR [+3]

Abstract

In holographic storage, two-dimensional data arrays (pages) are optically recorded via an interference process and subsequently retrieved by illumination of the hologram and forming an image on a matched two-dimensional array of photodetectors. One of the inherent advantages of this method of recording is its insensitivity to localized defects that normally inhibit the recording of individual bits. That is, the information is distributed throughout the recording volume and not localized as in conventional optical or magnetic data storage. However, localized defects within the medium (perhaps as thick as 1 mm), as well as surface imperfections such as scratches and pits, can cause light scattering into the direction of the reconstructed image.

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Method for Protecting Against Cluster Errors in Holographic Memory

      In holographic storage, two-dimensional data arrays (pages) are
optically recorded via an interference process and subsequently
retrieved by illumination of the hologram and forming an image on a
matched two-dimensional array of photodetectors.  One of the inherent
advantages of this method of recording is its insensitivity to
localized defects that normally inhibit the recording of individual
bits.  That is, the information is distributed throughout the
recording volume and not localized as in conventional optical or
magnetic data storage.  However, localized defects within the medium
(perhaps as thick as 1 mm), as well as surface imperfections such as
scratches and pits, can cause light scattering into the direction of
the reconstructed image.  This light will be detected by elements of
the array and may cause a 2-dimensional cluster error.  By this we
mean, an error affecting several contiguous bits in two dimensions.

A method and apparatus to overcome this problem is disclosed.

      Divide the data into symbols of size mxm, where (m*2)+1 is a
prime number.  The symbols are interleaved as follows:

                            (Image Omitted)

      The symbols with the same number correspond to the same
codeword, which belongs in one of the codes of length up to (m*2)+1
described in (1).  Those codes allow us to correct large symbols.
The interleaved sc...