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Emerald Group Publishing Limited
Copyright © 2001, MCB UP Limited
Magneto-optic sensorKeywords: Sensors, Magnetic
Applicant: Mitsubisshi Gas Chemical Co. (JP)Patent number: US6128423Publication date: 3 October 2000Title: Reflection type magneto-optic sensor
An object of the present invention is to provide a reflection type magneto-optic sensor which is free from noise resulting from reflected light. A sensor of this type comprises a light path assembly, a lens, a polarizer, a bismuth-substituted rare earth iron garnet single crystal film (BIG film), a non-magnetic garnet substrate, and a mirror, all being aligned in this order along the optical axis. The lens has a focal point, an optical axis, and first and second surfaces normal to the optical axis. The light path assembly has a light-inputting path and a light-outputting path parallel to the optical axis, which paths are disposed in proximity to the focal point of the lens, so that light exiting the light inputting path enters the lens and is then reflected back by the mirror into the light-outputting path. The BIG film is grown on the non-magnetic garnet substrate by the liquid epitaxial method (LPE) and the polarizer is bonded on the BIG film, so that the BIG film is sandwiched between the polarizer and the non-magnetic garnet substrate. The polarizer and the non-magnetic garnet substrate are lapped to taper in opposite directions at an angle in the range from 3-20°, so that the BIG is at an angle when the sandwiched construction is positioned with the lapped surfaces at an angle with the optical axis of the lens.