Focus and tracking error detector apparatus for optical and magneto-optical information storage systems

摘要: Focus and tracking error optical servo detector apparatus is shown employing a single four element array. detection based on spot size sensing described in which focus offset caused by beam transition between track non-track areas substantially reduced shaping the so as to derive signals from only overlap lobes zeroth order diffraction plus minus first beams readout recording element. The incident anamorphically shaped retain high signal gain while reducing sensitivity direction movement of factors such thermally induced misalignment, vibration like. optionally provided with polarizer sheet positioned front its transmission axis parallel polarization for purpose blocking birefringence effects adversely affecting performance.