Patent ID: 6072174
Filing Date: 2000-06-06
Classification: G01D,G01P,G02F

Abstract:
A method of magneto-optically modulating light by way of an object capable of modulating a magnetic field, comprising the steps of:(a) producing a linearly-polarized light having a plane of polarization and a transmission path having said polarized light travel thereon;(b) preparing a magneto-optic effect element made of a magnetic substance having an internal magnetization with a predetermined spontaneous magnetization direction, said magneto-optic effect element being placed on said transmission path of said polarized light with the spontaneous magnetization direction of said magneto-optic effect element being substantially parallel with said transmission path of said polarized light, said internal magnetization of said magneto-optic effect element being oriented between two different magnetization directions consisting of a first magnetization direction in which said internal magnetization of said magneto-optic effect element is substantially parallel with said transmission path of said polarized light, and a second magnetization direction in which said internal magnetization of said magneto-optic effect element is substantially perpendicular to said transmission path of said polarized light, said internal magnetization of said magneto-optic effect element having said plane of polarization of said polarized light rotatable between two different states consisting of a first state in which said plane of polarization of said polarized light is rotated about said transmission path of said polarized light when said internal magnetization of said magneto-optic effect element is oriented to said first magnetization direction, and a second state in which said plane of polarization of said polarized light is maintained when said internal magnetization of said magneto-optic effect element is oriented to said second magnetization direction;(c) applying a magnetic field to said magneto-optic effect element to have said internal magnetization of said magneto-optic effect element oriented to said second magnetization direction to have said plane of polarization of said polarized light substantially maintained in said second state;(d) varying said magnetic field in accordance with a relative relationship between said object and said magneto-optic effect element to have said internal magnetization of said magneto-optic effect element varied between said first magnetization direction and said second magnetization direction to have said plane of polarization of said polarized light rotated about said transmission path between said first state and second state when said polarized light passes through said magneto-optic effect element.