Patent ID: 11885841
Assignee: HOSEI UNIVERSITY
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 7:
8. An electric field sensor which measures an electric field generated by a target utilizing an electro-optic effect, the electric field sensor comprising:
a light source;
an electro-optic crystal on which light in a predetermined polarization state emitted from the light source is incident and which is subjected to the electric field generated by the target;
a reference electric field applicator configured to apply an electric field based on a reference signal with a known signal level to the electro-optic crystal;
a light receiver configured to receive light emitted from the electro-optic crystal and to convert the received light into an electric signal;
a separation corrector configured to separate the electric signal into a measurement signal based on the electric field generated by the target and the reference signal and to correct a signal level of the measurement signal on the basis of the signal level of the separated reference signal; and
a measurement electric field applicator configured to apply a referential signal with a known signal level to the target,
wherein the light receiver comprises:
a polarization beam splitter configured to separate circularly polarized light emitted from the electro-optic crystal into P-polarized light and S-polarized light; and
a differential amplifier configured to amplify a differential component of electric signals of the P-polarized light and the S-polarized light separated by the polarization beam splitter and to output the amplified electric signal to the separation corrector, and
wherein the separation corrector comprises:
a first amplifier configured to extract a signal component of an electric field based on the measurement signal in the electric signal output from the differential amplifier using the measurement signal;
a second amplifier configured to extract a signal component of an electric field based on the reference signal in the electric signal output from the differential amplifier using the reference signal;
a gain controller configured to generate a control signal that controls an amplification factor according to a signal component of the electric field based on the reference signal output from the second amplifier; and
a variable gain amplifier configured to vary an amplification factor of the electric signal of the signal component of the electric field based on the measurement signal output from the first amplifier according to the control signal output from the gain controller, and to output the electric signal.