Detection of thin ferromagnetic layers based on Faraday effect

Abstract

Optical head with magnetized garnet layer is used to detect presence of thin ferromagnetic layers such as printed text. Mathematical model of the system presented further was created. By varying opaque material, layer thicknesses and air gap between optical head and scanned object optimal configuration of the system was calculated. Incident P-polarized light affected by garnet layer changes its polarization due to Faraday effect. We can detect presence or absence of ferromagnetic after studying changes in polarization of the reflected light. Comparing results with and without influence of the ferromagnetic layers recognition of printed pattern under opaque material is achieved.