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High Speed Magneto–Optical Sensor for Magnetic Stripe Readout

Authors:
Johannes Egger
Bernhard Zagar

Keywords: Faraday effect; magnetic field sensor; magnetic field imaging; magnetic tape; quality control

Abstract:
We report on a Faraday–sensor to read out optically test pattern recorded to magnetic stripes on smart cards in a non– contacting way at scanning speeds of several meters per second. The pattern densities of several bits per millimeter can be resolved properly. The sensor employs a magneto–optical crystal of iron doped Yttrium–Aluminum–Garnet known to exhibit one of the highest known Verdet–constants ( 130 rad/Tm). It is epitaxially grown to a rather small thickness of approximately 50m, a small thickness that on the one hand reduces the overall sensitivity dramatically but on the other hand allows for a very fine pitched spatial resolution to image the normal component of the magnetic flux density. The to be tested specimen in the production line is moving at a rather high speed so the optical system and the readout electronics is geared toward rapid scan and to maintain a rather high sustained data streaming rate onto a solid state disk for archival purposes. Scan rates exceeding 50.000 scans per second (@ 128 pixels per scan) were attained and the camera still is sufficiently exposed to attain a fair signal to noise ratio.

Pages: 68 to 71

Copyright: Copyright (c) IARIA, 2016

Publication date: July 24, 2016

Published in: conference

ISSN: 2308-3514

ISBN: 978-1-61208-494-7

Location: Nice, France

Dates: from July 24, 2016 to July 28, 2016