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Optical Storage Multitrack Reading

IP.com Disclosure Number: IPCOM000039973D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Arter, NK: AUTHOR [+2]

Abstract

In an optical storage device wherein binary data is stored in the parallel tracks of removable, multitrack storage media, for example, an optical disk or card, the device's reading head is dithered in a direction transverse to the track direction, and the data content of each track of a band of tracks is sequentially read by the head, as the head passes over each track. A tracking servo monitors the head's signal, and operates to maintain the head centered over this band of tracks. The identifier data (ID) block of one of these tracks is read in order to initialize the tracking servo to follow that track. A focusing servo (not shown) maintains the head in a focused position on an axis which extends perpendicular to the media. (Image Omitted) In Fig. 1, laser 10 provides a beam of energy which impinges upon mirror 11.

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Optical Storage Multitrack Reading

In an optical storage device wherein binary data is stored in the parallel tracks of removable, multitrack storage media, for example, an optical disk or card, the device's reading head is dithered in a direction transverse to the track direction, and the data content of each track of a band of tracks is sequentially read by the head, as the head passes over each track. A tracking servo monitors the head's signal, and operates to maintain the head centered over this band of tracks. The identifier data (ID) block of one of these tracks is read in order to initialize the tracking servo to follow that track. A focusing servo (not shown) maintains the head in a focused position on an axis which extends perpendicular to the media.

(Image Omitted)

In Fig. 1, laser 10 provides a beam of energy which impinges upon mirror 11. The beam is thereby reflected upward to flat optical card 12. Card 12 moves in the linear direction indicated by arrow 13, as the band of parallel data tracks 14, including center track 15, is scanned by the laser beam. The scanning beam now reflects vertically down from card 12, and a portion of the reflected beam impinges upon focus detector 21. This detector controls the position of an objective lens (not shown) in order to maintain the beam in focus on the card's data plane. Mirror 11 is mounted on a crystal element 16. Energization of this crystal element causes the beam to move transverse the band of tracks, as indicated by arrow 17. This movement is at a known high frequency, the frequency being so high, relative the speed of movement of the card, that each data bit cell (see Fig. 2) of each track is scanned a number of times by the beam before the card's bit cell moves on past the scanning beam. Fig. 2 shows a band of card data tracks comprising tracks N-3 through N+3, track N being the center track of this band. In the indicated bit cell, the presence of a binary "1" is indicated by the presence of a pit 22 which is formed into the surface of the card. The presence of a binary "0" is indicated b...