Optical disc reader having diffraction minima at non- interrogated tracks

Abstract From the Canadian patent

Abstract of the Disclosure, The invention relates to a method and a device for the optical reading of information recorded on a support along a track in the form of diffracting elements. A diffraction pattern comprising a luminous central spot centered on the section of the track to be read and alternately dark and bright adjacent fringes is projected onto the support the, dark fringes adjacent to the central spot coinciding with the track sections in the neighborhood of the track section to be read. To that effect a pupil limited by two edges which are parallel to the direction of travel of the track is utilised, this pupil being placed against the reading objective.