Abstract: An auto-focus system for a DVD reader or other optical access unit which reads and/or writes information from/to at least two information layers on an optical storage medium such as a DVD or DVR. The auto-focus system includes an astigmatic lens. A confocal aperture is placed at the first focal line image generated by the astigmatic lens from light rays reflected from the addressed information layer. The placement of the confocal aperture allows extraneous out-of-focus light rays reflected from non-addressed information layers to be blocked from reaching the photo detector array which then creates a focus error signal (FES). The FES drives a servo assembly connected to an access head of the optical access unit, bringing the access head into focus. In some embodiments, the confocal aperture is “bow-tie” shaped, allowing for simplified assembly and easing in-plane rotational alignment.

Abstract: An auto-focus system for a DVD reader or other optical access unit which reads and/or writes information from/to at least two information layers on an optical storage medium such as a DVD or DVR. The auto-focus system includes an astigmatic lens. A confocal aperture is placed at the first focal line image generated by the astigmatic lens from light rays reflected from the addressed information layer. The placement of the confocal aperture allows extraneous out-of-focus light rays reflected from non-addressed information layers to be blocked from reaching the photo detector array which then creates a focus error signal (FES). The FES drives a servo assembly connected to an access head of the optical access unit, bringing the access head into focus. In some embodiments, the confocal aperture is “bow-tie” shaped, allowing for simplified assembly and easing in-plane rotational alignment.

Abstract: A magnetooptical disk recording device has a far-field detector for detecting radial position of a laser beam with respect to tracks on the disk. The far-field detector has a reference line dividing first and second photo detectors. The reference line is centered radially with respect to center lines of the tracks. The reference line is also center lengthwise to be tangentially center with respect to a tangential point on the track. The detector is adjustable both radially and tangentially. The tangential adjustment is based upon sensing two low reflective calibration marks on the disk that indicate centering the laser beam, hence the track tangent point, on the reference line. The calibration is based upon obtaining minimum noise in the detector output signal that signifies that the laser beam is centered on the length of the detector reference line. The calibration marks are in a mirror area disposed at one radial extremity of the disk.

Abstract: A magnetooptical disk recording device has a far-field detector for detecting radial position of a laser beam with respect to tracks on the disk. The far-field detector has a reference line dividing first and second photo detectors. The reference line is centered radially with respect to center lines of the tracks. The reference line is also center lengthwise to be tangentially center with respect to a tangential point on the track. The detector is adjustable both radially and tangentially. The tangential adjustment is based upon sensing two low reflective calibration marks on the disk that indicate centering the laser beam, hence the track tangent point, on the reference line. The calibration is based upon obtaining minimum noise in the detector output signal that signifies that the laser beam is centered on the length of the detector reference line. The calibration marks are in a mirror area disposed at one radial extremity of the disk.