Browse Prior Art Database

Sectored Servo Headers for Optical Storage Devices

IP.com Disclosure Number: IPCOM000034579D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 2 page(s) / 160K

Publishing Venue

IBM

Related People

Korth, HE: AUTHOR

Abstract

An improved format for sectored servo headers defining the location, number and synchronization of data tracks in storage disks uses alternating and conjugate sectors with a Gray-coded header pattern inverting between even and odd sector numbers. The headers are hard-coded on the disks. Fig. 1B shows the improved format compared with that of the art, which is illustrated in Fig. 1A. The advantages obtained are listed below. - There is no separate synchronization bit, as the leading edge of the Gray code field is used for this purpose. If this field starts with the high-order bit of the code and subsequent sector code patterns are inverted, a synchronization mark will be detected in one of two sectors. (Image Omitted) - At high search speed, a Gray code with the low-order bits (Fig.

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Sectored Servo Headers for Optical Storage Devices

An improved format for sectored servo headers defining the location, number and synchronization of data tracks in storage disks uses alternating and conjugate sectors with a Gray-coded header pattern inverting between even and odd sector numbers. The headers are hard-coded on the disks. Fig. 1B shows the improved format compared with that of the art, which is illustrated in Fig. 1A. The advantages obtained are listed below. - There is no separate synchronization bit, as the leading edge of the Gray code field is used for this

purpose. If this field starts with the high-order bit

of the code and subsequent sector code patterns are

inverted, a synchronization mark will be detected in

one of two sectors.

(Image Omitted)

- At high search speed, a Gray code with the

low-order bits (Fig. 1B) positioned close to the

center of the code pattern is used. When scanning is

effected across a bit change region, decoding errors

are avoided by using the Gray code. This code has the

property that subsequent numeric values differ by a 1

bit setting. - The width of the Gray code bits is reduced by 20 to

30%, since the signal-to-noise ratio of the hard-coded

sector pattern is much higher than for optical data. - For generating the tracking signal, a single quadrature field is sufficient. This field is a grid structure

with a period of two tracks. The length of the grid

lines is determined by the signal averaging time

required, the l...