Browse Prior Art Database

Optical Disk Read Channel

IP.com Disclosure Number: IPCOM000038792D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Arter, NK: AUTHOR [+2]

Abstract

The electronic read channel for an optical disk drive, which is usable either with factory-recorded read-only disks or write-once (or erasable) disks, is a dual channel, switchable, read channel. One half (phase channel) processes the signal from factory-recorded disks, and the other half (magnitude channel) processes the signal from write-once disks. A sensor identifies which type disk is in use, and enables the appropriate read channel. The read channel is a switchable dual channel. One-half of the channel is referred to as the phase channel. This channel processes the signal read from factory-recorded read-only disks and from the read-only portion of write-once disks (for example, the track identifiers). The other half of the channel is the magnitude channel.

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Optical Disk Read Channel

The electronic read channel for an optical disk drive, which is usable either with factory-recorded read-only disks or write-once (or erasable) disks, is a dual channel, switchable, read channel. One half (phase channel) processes the signal from factory-recorded disks, and the other half (magnitude channel) processes the signal from write-once disks. A sensor identifies which type disk is in use, and enables the appropriate read channel. The read channel is a switchable dual channel. One-half of the channel is referred to as the phase channel. This channel processes the signal read from factory-recorded read-only disks and from the read-only portion of write-once disks (for example, the track identifiers). The other half of the channel is the magnitude channel. This channel processes the signal read from write-once (or erasable) disks. In the figure, output signals from focus detector 10 and tracking detector 12 are amplified and collected by sum and difference circuitry 14. The magnitude channel, consisting of filter 16, derivative circuit 18 and comparator 20, receives summed signal (F + T). The phase channel, consisting of filter 22 and comparator 24, receives the difference signal (F - T). A derivative circuit is not necessary in the phase channel as the difference signal is already a doublet-type signal (resembles the derivative of a pulse) rather than a pulse. Comparators 20 and 24 search for the zero-crossing in the center of the doublet signal which each comparator receives as input. In function, these comparators are equivalent to comparing a doublet to a zero reference. This results in the generation of a trans...