Digital optical tape read system

Abstract

Method and apparatus for reading digital data stored on an optical tape are achieved with a digital optical tape read system including an optical tape and an illumination arrangement. The optical tape has bit cells which are stored along a plurality of tracks of bit cells. Each track includes a line of bit cells, and each bit cell has either a first spot power reflectance representative of a first binary value, or a second spot power reflectance representative of a second binary value. The illumination arrangement functions to illuminate a predetermined area of the optical tape covering a plurality of bit cells with incident light that provides substantially a 180.degree. phase difference between adjacent bit cell locations on the optical tape to be concurrently read. The method of illuminating and reading data stored on an optical tape comprises a first step of generating a collimated coherent light beam which is directed at the optical tape, and a second step of imaging the coherent light beam into a predetermined area of the optical tape covering a plurality of bit cells with light that provides substantially a 180.degree. phase difference between adjacent bit cell locations on the optical tape to be concurrently read.