US 12,117,475 B2
Electric field sensor
Yoshinori Matsumoto, Musashino (JP); Mitsuru Shinagawa, Tokyo (JP); and Jun Katsuyama, Musashino (JP)
Assigned to YOKOGAWA ELECTRIC CORPORATION, Tokyo (JP); and Hosei University, Tokyo (JP)
Appl. No. 17/424,194
Filed by Yokogawa Electric Corporation, Tokyo (JP); and Hosei University, Tokyo (JP)
PCT Filed Jan. 21, 2020, PCT No. PCT/JP2020/001833
§ 371(c)(1), (2) Date Jul. 20, 2021,
PCT Pub. No. WO2020/153322, PCT Pub. Date Jul. 30, 2020.
Claims priority of application No. 2019-008252 (JP), filed on Jan. 22, 2019.
Prior Publication US 2022/0107349 A1, Apr. 7, 2022
Int. Cl. G01R 29/14 (2006.01); G01R 15/24 (2006.01); G01R 29/08 (2006.01)
CPC G01R 29/14 (2013.01) [G01R 15/241 (2013.01); G01R 29/0885 (2013.01)] 18 Claims
OG exemplary drawing
 
1. An electric field sensor comprising:
a light source;
an electro-optical crystal on which light in a predetermined polarization state based on light emitted by the light source is incident and which receives an electric field generated by an object;
a first separator that separates light emitted from the electro-optical crystal into a P wave and an S wave;
a first wavelength plate that changes a phase of light at a pre-stage of the first separator;
a first light receiver that receives the P wave light and converts the received light into a first electrical signal;
a second light receiver that receives the S wave light and converts the received light into a second electrical signal;
a differential amplifier that generates a differential signal between the first electrical signal converted by the first light receiver and the second electrical signal converted by the second light receiver;
a controller that adjusts a wavelength of the light source such that an output value of a direct-current component of the differential amplifier is within a predetermined value range in a state in which light is emitted from the light source and the electric field is applied to the electro-optical crystal;
a first variable gainer that changes a first gain of the first electrical signal of the first light receiver; and
a second variable gainer that changes a second gain of the second electrical signal of the second light receiver,
wherein the controller adjusts the first gain of the first variable gainer and the second gain of the second variable gainer such that the output value of the direct-current component of the differential amplifier is within the predetermined value range in a state in which light is emitted from the light source and the electric field is not applied to the electro-optical crystal.