Browse Prior Art Database

Simple Optical Recording Head

IP.com Disclosure Number: IPCOM000038307D
Original Publication Date: 1989-Dec-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Chen, M: AUTHOR

Abstract

A simple optical recording head is described in which array lasers are used to write/read as well as generate focus and tracking signals. Optical feedback induced modulation of the laser operating condition is used to detect data and servo error signals. This greatly simplifies the design of the head.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 1

Simple Optical Recording Head

A simple optical recording head is described in which array lasers are used to write/read as well as generate focus and tracking signals. Optical feedback induced modulation of the laser operating condition is used to detect data and servo error signals. This greatly simplifies the design of the head.

Figure 1 illustrates a possible implementation. Data detection using feedback signal has been described in the open literature. Tracking error may be generated using any one of three well known methods: (1) sample servo, (2) beam wobbling and (3) three-spot method (requiring two lasers in addition to read laser, aligned carefully with respect to the tracking grooves). Focus signal may be generated with two lasers, in addition to the read laser, such that one laser (a) is confocal with the disk while the other one (b) is slightly off confocal. The confocal laser detects focus error while the other laser detects the sign of the error as illustrated in Figure 2. These two lasers may be produced by using etched facets and offsetting the facet surfaces as shown in Figure 1. Alternatively, gain-guided lasers with large astigmatism may be used. Operating these laser at different power levels will produce a relative focal point shift at the disk.

Disclosed anonymously.

1