Browse Prior Art Database

Improved Read Head for Magneto-Optic Disk File

IP.com Disclosure Number: IPCOM000035709D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Block, TR: AUTHOR [+3]

Abstract

Described here is a compact and efficient layout for a magneto-optic disk read/write head. It uses a Wollaston prism 3 or similar element to split the beam returning from the disk into two (orthogonally polarized) beams with but a slight angular separation (e.g., 2 degrees). This allows a single detector 4, having two separate sensitive areas, to be used to differentially detect data from the disk.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 62% of the total text.

Page 1 of 2

Improved Read Head for Magneto-Optic Disk File

Described here is a compact and efficient layout for a magneto-optic disk read/write head. It uses a Wollaston prism 3 or similar element to split the beam returning from the disk into two (orthogonally polarized) beams with but a slight angular separation (e.g., 2 degrees). This allows a single detector 4, having two separate sensitive areas, to be used to differentially detect data from the disk.

Furthermore, one of the two detector areas is subdivided into four quadrants. This, in conjunction with the anamorphic lens 5, permits the same detector 4 to provide focus and tracking position error signals. Thus, all needed signals are derived from a single detector array.

(Image Omitted)

This technique allows making the head lighter, smaller, and less expensive than would otherwise be possible. Moreover, by allowing both sensitive areas of the detector to be fabricated with identical properties (i.e., in the same wafer processing batch, since the two areas can be on a single chip), the response of the two areas can be well matched, providing a better signal-to-noise ratio when using differential detection.

In application, the head shown (in the isometric view of Fig. 1 and the orthogonal view of Fig. 2) performs as follows:

The partially polarized laser source beam is collimated by the initial lens 6, then shaped and directed to the objective lens 7 by the polarizing beamsplitter prism 8 (amplitude beamsplitter would wo...