JPS6439569A - Optical magnetic field sensor - Google Patents

Abstract

PURPOSE:To improve temperature characteristics by interposing 1/4-wavelength plates between a polarizer and a Farady effect element, or the Faraday effect element and an analyzer at 45 deg. to each other. CONSTITUTION:The polarizing element 5 and analyzer 7a are arranged in the same polarizing direction on an optical axis and the Faraday effect element 6 is arranged between them. Further, the 1/4-wavelength plates 9 and 10 are arranged between the polarizer 5 and element 6 while having their axial direction at an angle theta=45 deg. to each other. Then light which is incident from the polarizer 5 becomes single polarized light, which passes through the wavelength plate 9 to generate a 90 deg. phase difference between two optical main axes, thereby generating circular polarized light. The wavelength plate 10 generates a 90 deg. phase difference between two main axial directions while shifting in axial direction by 45 deg. from the wavelength plate 9, so polarized light exiting from the polarizer 5 becomes linear polarized light whose plane of polarization rotates by 45 deg. eventually. When this linear polarized light passes through the element 6, the plane of polarization is rotated by a magnetic field to extract the same polarized component as that of the polarizer 5, and then light which is intensity- modulated almost in proportion to the magnetic field is guided out.