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Browse Prior Art Database

Analog Error Detection for Magneto Optic Systems

IP.com Disclosure Number: IPCOM000091529D
Original Publication Date: 1968-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Banks, WK: AUTHOR

Abstract

In a conventional magneto-optical data recording system, readout of the data is achieved by passing polarized light beam 1 from source 2 through memory element 3. By detecting beam rotation, the recorded data can be read. However, holes or dust particles on element 3 can cause an erroneous data reading by also modulating beam 1.

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Analog Error Detection for Magneto Optic Systems

In a conventional magneto-optical data recording system, readout of the data is achieved by passing polarized light beam 1 from source 2 through memory element 3. By detecting beam rotation, the recorded data can be read. However, holes or dust particles on element 3 can cause an erroneous data reading by also modulating beam 1.

To read the data, the readout beam is split into components 5 and 6 by splitter 4 with one component being analyzed at 90 degrees relative to the other. By directing the beams onto photodiodes D1 and D2 biased and balanced by the parallel circuit of C1, C2, R4, R5, and R6, a voltage signal is generated across R1 and R2 indicative of the intensity of each beam component. This signal, detected at A and B, can be differentially added to cancel the common mode signal and leave the signal responsive to the rotation of beam 1 caused by element 3.

To detect the possibility of erroneous signal data, the voltage across R3 is detected at C. Holes or dust at element 3 increases or decreases radically the common mode signal at both A and B by changing the beam transmission, and thus the intensity, of beam 1 after passage through element 3. By limit detecting a signal A + B, a signal is generated indicating the possibility of an error in the data when the common mode signal exceeds predetermined limits.

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