Browse Prior Art Database

Electronically Controlled Halfwave Plate for MO Recording

IP.com Disclosure Number: IPCOM000037906D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-30
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Finkelstein, BI: AUTHOR [+2]

Abstract

This invention dynamically balances the light incident on differential detectors in MO recording. This improves the SNR of the system.

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

Page 1 of 1

Electronically Controlled Halfwave Plate for MO Recording

This invention dynamically balances the light incident on differential detectors in MO recording. This improves the SNR of the system.

In order for differential detection to be optimally effective in optical recording, the light incident must be balanced between the two detectors. In current systems, this is done manually with a halfwave plate. Changing lasers or discs requires either sub-optimal performance or readjustment of halfwave plate.

The proposed electronic controlled light balance consists of a transmission LCD and a feedback network to control the polarization of the light. The polarization vector of light can be altered in transmission through the LCD by changing the bias voltage.

In an optical system with differential detection, the difference signal is bandlimited and used to control the bias voltage through an electronic feedback network.

The low pass filter that bandlimits the signal should have a very low (5 - 10 hz) cutoff frequency to minimize any possibility of effecting data detection.

The LCD acts as a halfwave plate, rotating the polarization vector at the polarizing beam splitter to maintain DC balance and a high common mode rejection ration. Any induced birefringence can be compensated for with a quarterwave plate, and any possible signal decrease is made up for by lowering the noise.

(Image Omitted)

Disclosed anonymously.

1