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Calibrating Optical-Disk Tracking Circuits Disclosure Number: IPCOM000064897D
Original Publication Date: 1985-Sep-01
Included in the Prior Art Database: 2005-Feb-19

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Cohen, DK Underwood, KL [+details]


Quad, or quadrant, detectors are commonly employed for controlling track following in optical-disk recorders. A critical aspect is the geometric orientation of the quad detectors to the track being followed. A comparison circuit is added to the recorder for determining which set of two possible sets of connections provides a largest- amplitude signal response. In this manner, variations in manufacture from recorder to recorder can be accommodated. A quad detector having four photocells A, B, C and D is suitably mounted in a recorder (not shown). The astigmatic axis of the optical system conveying light reflected from the track being followed to the quad detector is shown as the dashed line.