Patent ID: 6691074
Filing Date: 2004-02-10
Classification: G06K,G06T

Abstract:
A system for indicating a disturbance in an electromagnetic field, the system comprising:a plurality of transmitters operative to transmit a corresponding plurality of alternating electromagnetic fields within a three-dimensional space; and at least one sensor arranged to be fixed to at least one corresponding portion of a moving object whose position it is sought to monitor, each of said at least one sensors comprising: an electromagnetic field receiver having at least one active axis and operative to receive at least one component, lying along the at least one active axis respectively, of each of the plurality of alternating electromagnetic fields; an accelerometer operative to independently measure at least one component of the acceleration of the moving object; and a digital signal processor for storing at least one characteristic of each of the plurality of electromagnetic fields as received by the electromagnetic field receiver, and at least one characteristic of the acceleration as measured by the accelerometer, wherein said digital signal processor is adapted to transmit the at least one stored characteristic of each of the plurality of electromagnetic fields to a Kalman filter and calculate therefrom a first estimate of at least one component of the position and orientation of the moving object; transmit the at least one stored characteristics of each of the plurality of electromagnetic fields and the at least one characteristic of the acceleration as measured by the accelerometer to the Kalman filter, and calculate therefrom a second estimate of at least one component of the position and orientation of the moving object; and compare said first and second estimates for a discrepancy indicating a disturbance in the electromagnetic field, wherein a discrepancy indicating a disturbance in the electromagnetic field comprises a discrepancy of greater than the expected absolute accuracy of the measurement of the position and orientation of the moving object.