Apparatus and method for reading at least partially unmetallized optical

Abstract

An optical disc player adapted to read an optical disc having a plurality of pits and lands representative of information stored on the optical disc; the optical disc being at least in part unmetallized. The player includes a semiconductor laser for generating a variable power laser beam, the power of the beam being controlled by a control signal applied to a control terminal of a semiconductor laser driver. A focusing servo is provided for focusing the beam on the optical disc such that a portion of the beam is reflected back from the optical disc indicative of the pits or lands. The portion of the beam reflected back from the optical disc being substantially less from unmetallized portions of the disc than from metallized portions of the disc. The focusing servo has a focal point constrained to lock on a pit plane of the optical disc. An automatic power control component is also provided for generating the control signal in response to a comparison of an average power level of the reflected portion of the beam and a reference level so as to maintain a substantially constant average power level of the reflected portion of the beam. As such, the player is capable of playing completely unmetallized optical discs or optical discs wherein a portion of the optical disc is metallized and a portion of the optical disc is unmetallized.