Browse Prior Art Database

Detection of Optical Disk Type

IP.com Disclosure Number: IPCOM000061439D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Arter, NK: AUTHOR [+2]

Abstract

An optical disk drive is usable with either read-only, write-once, and erasable optical disks. Certain functions of the drive must be tailored for the type disk then in use. A reflectance detector senses the type disk currently in use, and controls these functions of the disk drive accordingly. Media detection is accomplished by using signals received from the disk drive's focus detector while moving the lens toward the disk from a retracted position. As the focusing point of the beam moves toward the disk, the difference signal 11 (F1 - F2) between signals F1 and F2, which are received from each half F1 and F2 of the focus detector, is monitored. Signal 11 will peak just before the focusing point reaches the surfaces of the disk.

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Detection of Optical Disk Type

An optical disk drive is usable with either read-only, write-once, and erasable optical disks. Certain functions of the drive must be tailored for the type disk then in use. A reflectance detector senses the type disk currently in use, and controls these functions of the disk drive accordingly. Media detection is accomplished by using signals received from the disk drive's focus detector while moving the lens toward the disk from a retracted position. As the focusing point of the beam moves toward the disk, the difference signal 11 (F1 - F2) between signals F1 and F2, which are received from each half F1 and F2 of the focus detector, is monitored. Signal 11 will peak just before the focusing point reaches the surfaces of the disk. Read-only disks are more reflective than write-once disks, thus the peak amplitude 20 from a read-only disk is much higher than the peak amplitude 21 received from a write-once disk. Signal level detectors 12 and 14 monitor signal 11, and detect the type of disk currently in use as the lens moves toward the disk. Fig. 1 shows signal 11 (F1 - F2) as the lens moves toward the disk. The first low amplitude doublet pulse 22 occurs when the focusing point reaches the outside surface of the transparent disk cover, and the second low amplitude doublet pulse 23 occurs when the focusing point reaches the inside surface of the disk cover. When the focusing point reaches the surface of the disk, a large amplitude dou...