Current measurement technique and current measurement apparatus

1. A current measurement method for measuring a current that flows in an electric current transmission line of an electric circuit, comprising the steps of:

installing a magnetooptical device in a magnetic field which is generated based upon an electric current that flows in the electric current transmission line;

making a polarized light incident on the magnetooptical device; and

acquiring a current based upon the variation of the polarization of reflected light from the magnetooptical device on which the polarized light is incident.

2. A current measurement method according to claim 1 , wherein the polarized light is made incident on the magnetooptical device in a state in which a magnetic field generated by a magnetic field generator is further applied to the magnetooptical device.

3. A current measurement method according to claim 1 , wherein the direction of magnetization in the incident position of the polarized light and the direction in which the polarized light travels are parallel.

4. A current measurement method according to claim 1 , wherein the electric circuit is a circuit which is a load of small impedance and the current is high frequency current.

5. A current measurement method for measuring a current that flows in a transmission line of an electric circuit provided with a first transmission line which is on an approach route of the flow of current and a second transmission line which is on a return route of the flow of the current, comprising the steps of:

arranging a magnetooptical device in a magnetic field which is generated based upon current that flows in the first transmission line and in a magnetic field which is generated based upon current that flows in the second transmission line;

making a polarized light incident on the magnetooptical device and between the first transmission line and the second transmission line; and

acquiring a current based upon the variation of the polarization of reflected light from the magnetooptical device on which the polarized light is incident.

6. A current measurement method according to claim 5 , wherein the polarized light is made incident on the magnetooptical device in a state in which a magnetic field generated by a magnetic field generator is further applied to the magnetooptical device.

7. A current measurement method according to claim 5 , wherein the direction of magnetization in the incident position of the polarized light and the direction in which the polarized light travels are parallel.

8. A current measurement method according to claim 5 , wherein the electric circuit is a circuit which is a load of small impedance and the current is high frequency current.

9. A current measurement method for measuring a current that flows in an electric current transmission line of an electric circuit, comprising the steps of:

installing a magnetooptical device in a magnetic field which is generated based upon a low impedance current that flows in the electric current transmission line;

making a polarized light incident on the magnetooptical device; and

acquiring a current based upon the variation of the polarization of reflected light from the magnetooptical device on which the polarized light is incident.

10. A current measurement method according to claim 9 , wherein the polarized light is made incident on the magnetooptical device in a state in which a magnetic field parallel to the polarized incident plane of the magnetooptical device is generated by an external magnetic field generator and further applied to the magnetooptical device.

11. A current measurement method according to claim 9 , wherein the current flowing through the electric current transmission line is a high frequency current.