Abstract: Methods and apparatus are provided for reducing cross-talk and jitter caused by track offsets in multi-beam optical disks. The method and apparatus involve using split detectors and cross-talk cancellation algorithms in the multi-element photodetector of the multi-beam optical disks. The cross-talk cancellation algorithms are applied according to the value of the track offset as a function of the track pitch.

Abstract: Apparatus and methods are provided for using a single multi-element detector and multi-channel signal conditioning circuitry to simultaneously read multiple tracks from either a CD disk or a DVD disk. The multi-element detector has a staggered arrangement and includes elongated detector elements, so that multiple reading beams reflected from multiple tracks of a CD disk are projected onto the detector, as are multiple reading beams reflected from multiple tracks of a DVD disk. The multi-channel signal conditioning circuitry conditions the signals produced by the multi-element detector, and produces signals for each of the tracks that is simultaneously read, as well as a tracking error signal, a focus error signal, a magnification error signal, and signals useful for reading DVD-RAM disks and for rapidly accessing tracks on an optical disk.

Abstract: Methods and apparatus are provided for reducing cross-talk and jitter caused by track offsets in multi-beam optical disks. The method and apparatus involve using split detectors and cross-talk cancellation algorithms in the multi-element photodetector of the multi-beam optical disks. The cross-talk cancellation algorithms are applied according to the value of the track offset as a function of the track pitch.

Abstract: A switchable liquid crystal diffractive element for use in an optical drive capable of reading multiple tracks of an optical disk simultaneously, and writing or erasing at least one track of the optical disk is disclosed. When the liquid crystal diffractive element is in an “on” state, it splits an incident beam into multiple beams suitable for simultaneously reading multiple tracks of an optical disk. When the liquid crystal diffractive element is in an “off” state, it permits an incident beam to pass through without being split, for writing to an optical disk. Embodiments are disclosed that use multiple electrodes to create switching and non-switching regions of a liquid crystal element to form a switchable phase grating, and that use a single switching liquid crystal element and a non-switching grating, or a birefringent non-switching grating, to form a switchable diffractive element.