JP3759124B2 - Electric field sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electric field sensor that uses an electro-optic (EO) crystal to detect an electric field transmitted through an electric field transmission medium.
[0002]
[Prior art]
The sensitivity of the electric field sensor using the electro-optic crystal is proportional to the voltage applied between a pair of electrodes provided on the side surface of the electro-optic crystal so as to sandwich the electro-optic crystal.
[0003]
FIG. 3 is a diagram showing a configuration of a receiving terminal 100 in which such an electric field sensor is applied to detect a data signal transmitted as an electric field from a transmitter to a human body. In the figure, the data signal output from the signal electrode 33 of the data signal generator 31 constituting the transmitter 3 is induced as an electric field in the human body 5 which is an electric field transmission medium via the transmission electrode 41 and propagates in the human body 5. Then, the signal is received by the receiving electrode 43.
[0004]
The electric field received by the receiving electrode 43 is coupled to the electro-optic crystal 11 via the first electrode 12 provided on one side surface of the electro-optic crystal 11 and provided on the other side surface of the electro-optic crystal 11. The second electrode 14 is drawn. When the electro-optic crystal 11 is coupled with an electric field via the first electrode 12, the birefringence, which is an optical characteristic, changes depending on the electric field strength.
[0005]
On the other hand, the electro-optic crystal 11 is output from the laser light source 13, converted into parallel light by the first optical system 15, and laser light whose polarization state has been adjusted is incident between the first and second electrodes 12 and 14. However, the polarization of the incident laser light is changed according to the intensity of the electric field coupled through the first electrode 12 as described above. Thus, the laser beam that has undergone polarization change according to the electric field intensity is emitted from the electro-optic crystal 11 and is incident on the second optical system 17. The second optical system 17 converts the polarization change of the laser light incident from the electro-optic crystal 11 into a light intensity change and supplies it to the photodetector 19. The photodetector 19 converts the light output from the second optical system 17 into an electric signal and outputs it as an electric field detection signal. The laser light source 13 and the photodetector 19 are operated by being supplied with a voltage from the first power supply circuit 21, and the ground of the first power supply circuit 21 is connected to the circuit ground 23 of the receiving terminal 100.
[0006]
[Patent Document 1]
Japanese Patent Application No. 2001-295139 [0007]
[Patent Document 2]
Japanese Patent Application No. 2001-295121 [0008]
[Problems to be solved by the invention]
Since the sensitivity of the electric field sensor is proportional to the voltage applied between the electrodes, it is desirable that the voltage between the electrodes is sufficiently high. However, as described above, the first electrode 12 of the electro-optic crystal 11 is the receiving electrode 43. The second electrode 14 of the electro-optic crystal 11 is not connected to the ground electrode 35 of the transmitter 3, whereas the human body 5 is connected to the signal electrode 33 of the transmitter 3 via the transmission electrode 41. Since the absolute potential of the circuit ground 23 of the receiving terminal 100 varies greatly in reality and becomes noise, the second electrode 14 of the electro-optic crystal 11 is also insulated from the circuit ground 23 of the receiving terminal 100. In addition, the voltage applied between the electrodes of the electro-optic crystal 11 is generally minute, and there is a problem that the sensitivity of the electric field sensor is insufficient.
[0009]
The present invention has been made in view of the above, and the object thereof is to amplify the voltage applied between the electrodes of the electro-optic crystal and apply a sufficient voltage between the electrodes of the electro-optic crystal, The object is to provide an electric field sensor with increased sensitivity.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention according to claim 1 is an electric field sensor that detects an electric field transmitted through an electric field transmission medium using an electro-optic crystal, and the electric field transmitted through the electric field transmission medium. Receiving electrode, a pair of electrodes provided on the side surfaces of the electro-optic crystal so as to sandwich the electro-optic crystal, a light source that generates light of a single wavelength, and the light from the light source is made parallel light A first optical system that is incident between the electrodes of the electro-optic crystal, and a second optical system that converts parallel light incident from the first optical system and passing through the electro-optic crystal into a change in light intensity, Photoelectric conversion means for converting the optical output from the second optical system into an electrical signal; an amplifier for amplifying an electric field received by the receiving electrode; and applying between the electrodes of the electro-optic crystal; the light source and the light Supply operating power to electrical conversion means 1 and a power supply circuit, wherein they are insulated with respect to the circuit ground of the first power supply circuit, and summarized in that with a second power supply circuit for supplying operating power to the amplifier.
[0011]
In the first aspect of the present invention, the electric field received by the receiving electrode is amplified by the amplifier and applied between the electrodes of the electro-optic crystal. A voltage is applied, and the sensitivity as an electric field sensor can be significantly improved.
[0013]
In addition , since the second power supply circuit that supplies the operating power to the amplifier is insulated from the circuit ground of the first power supply circuit, the amplifier does not affect the electric field from the receiving electrode without being affected by the fluctuation of the circuit ground. Can be amplified.
[0014]
Further, the present invention according to claim 2 is the invention according to claim 1 , wherein the side surfaces of the electro-optic crystal are a pair of opposing side surfaces, and the electrodes are provided on each of the pair of side surfaces. The gist of this is the electrode.
[0015]
According to a third aspect of the present invention, in the first or second aspect of the present invention, a predetermined low frequency component is removed from the electric field received between the receiving electrode and the amplifier and received by the receiving electrode. The high-pass filter which passes only the high frequency of this and supplies it to the said amplifier is made into a summary.
[0016]
According to the third aspect of the present invention, since a predetermined low frequency component is removed by the high-pass filter and only the predetermined high frequency is input to the amplifier, noise due to potential fluctuations of the human body is mixed in the input of the amplifier. The amplifier outputs only a normal effective signal.
[0017]
The present invention according to claim 4 is characterized in that, in the invention according to claim 3 , the high-pass filter is constituted by a capacitor.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a receiving terminal to which an electric field sensor according to an embodiment of the present invention is applied, together with a transmitter. In the embodiment shown in FIG. 3, an amplifier 25 is connected to the first and second electrodes 12 and 14 provided on the side surfaces of the electro-optic crystal 11 in the conventional circuit configuration shown in FIG. The only difference is that a second power supply circuit 27 for supplying power is added. Other configurations and operations are the same as those in FIG. 3, and the same components are denoted by the same reference numerals. A configuration including the electro-optic crystal 11, the amplifier 25, and the second power supply circuit 27 is referred to as an electric field processing unit 20.
[0019]
The amplifier 25 is composed of an operational amplifier. A non-inverting input terminal indicated by a “+” symbol is connected to the reception electrode 43, and a voltage corresponding to the electric field received from the human body 5 is supplied to the reception electrode 43. ing. The output terminal of the amplifier 25 is connected to the first electrode 12, and the inverting input terminal indicated by the “−” symbol is connected to the second electrode 14.
[0020]
The second power supply circuit 27 that supplies operating power to the amplifier 25 is insulated from the first power supply circuit 21 and the circuit ground 23 of the receiving terminal 1.
[0021]
In the present embodiment configured as described above, the data signal transmitted from the transmitter 3 via the signal electrode 33 is received by the reception electrode 43 via the transmission electrode 41 and the human body 5, and from the reception electrode 43. It is supplied to the amplifier 25 to be amplified and applied to the electro-optic crystal 11 as a sufficiently large voltage via the first and second electrodes 12 and 14, so that the sensitivity as an electric field sensor can be remarkably improved. More specifically, the laser light incident on the electro-optic crystal 11 from the laser light source 13 via the first optical system 15 is sufficiently large to be applied to the electro-optic crystal 11 via the first and second electrodes 12 and 14. It receives a large change in polarization due to the voltage, is converted into a change in light intensity by the second optical system 17, is converted into a large electric signal by the photodetector 19, and is output as a sufficient electric field detection signal.
[0022]
The first optical system 15 includes a collimating lens that collimates the laser light and a wave plate that adjusts the polarization state of the laser light from the collimating lens, and the second optical system 17 includes an electro-optic crystal. 11 is composed of a polarization beam splitter that separates the laser light incident from 11 into P-wave and S-wave and converts it into a change in the intensity of light, and the photodetector 19 is composed of a photodiode.
[0023]
FIG. 2 is a diagram showing an electric field processing unit 20a used in a receiving terminal 1 similar to FIG. 1 to which an electric field sensor according to another embodiment of the present invention is applied.
[0024]
The electric field processing unit 20a of the embodiment shown in FIG. 2 corresponds to the electric field processing unit 20 of FIG. 1 and is provided in the receiving terminal 1 instead of the electric field processing unit 20 in FIG. 1 is different from the electric field processing unit 20 of FIG. 1 in that a capacitor 29 constituting a new high-pass filter is connected to a non-inverting input terminal indicated by a “+” symbol of the amplifier 25. The operation is the same as in FIG.
[0025]
2 includes the electro-optic crystal 11, the first and second electrodes 12, 14, the amplifier 25, the capacitor 29, and the second power supply circuit 27. The electro-optic crystal 11 1 is connected to the laser light source 13, the first optical system 15, the second optical system 17, and the photodetector 19, and the non-inverting input terminal indicated by the “+” symbol of the amplifier 25 is a capacitor 29. Is connected to the reception electrode 43 via the receiver electrode 43, and further connected to the signal electrode 33 of the transmitter 3 via the human body 5 and the transmission electrode 41 from the reception electrode 43.
[0026]
As described above, the non-inverting input terminal of the amplifier 25 is connected to the human body 5 via the capacitor 29 and the receiving electrode 43. The human body 5 is generally said to have a potential that fluctuates slowly. Therefore, the capacitor 29 is connected to the input of the amplifier 25 as a high-pass filter in order to prevent noise caused by Therefore, noise due to the slowly varying potential of the human body 5 is removed by the capacitor 29 and is not input to the amplifier 25, and only a high-frequency effective data signal from the transmitter 3 passes through the capacitor 29 and passes through the amplifier 25. The amplifier 25 outputs only a normal signal with no noise.
[0027]
It should be noted that the frequency component of the potential fluctuation of the human body 5 is expected to be 1 kHz or less, and the data signal output from the transmitter 3 generally has a wide frequency component, but in practice, if a signal component of 100 kHz or more is detected, communication is performed. Assuming that the upper limit of the cutoff frequency fc by the capacitor 29 is about 100 kHz, the capacitor 29 only needs to have a capacitance of 1 μF or more.
[0028]
【The invention's effect】
As described above, according to the present invention, the electric field received by the receiving electrode is amplified by the amplifier and applied between the electrodes of the electro-optic crystal. A voltage is applied, and the sensitivity as an electric field sensor can be significantly improved.
[0029]
Further, according to the present invention, the second power supply circuit that supplies the operating power to the amplifier is insulated from the circuit ground of the first power supply circuit, so that the amplifier is not affected by fluctuations in the circuit ground. The electric field from the receiving electrode can be amplified.
[0030]
Furthermore, according to the present invention, a predetermined low frequency component is removed by the high-pass filter and only a predetermined high frequency is input to the amplifier, so that noise due to potential fluctuations of the human body is prevented from being mixed into the input of the amplifier, Only a normal valid signal is output from the amplifier.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a receiving terminal to which an electric field sensor according to an embodiment of the present invention is applied, together with a transmitter.
FIG. 2 is a diagram showing an electric field processing unit used in a receiving terminal similar to FIG. 1 to which an electric field sensor according to another embodiment of the present invention is applied.
FIG. 3 is a diagram showing a configuration of a receiving terminal to which a conventional electric field sensor is applied together with a transmitter.
[Explanation of symbols]
1 receiver terminal 3 transmitter 5 human body 11 electro-optic crystal 13 laser light source 15 first optical system 17 second optical system 19 photodetector 21 first power circuit 23 circuit ground 25 amplifier 27 second power circuit 29 capacitor 43 receiving electrode

Claims (4)

An electric field sensor that detects an electric field transmitted through an electric field transmission medium using an electro-optic crystal,
A receiving electrode for receiving an electric field transmitted through the electric field transmission medium;
A pair of electrodes provided on side surfaces of the electro-optic crystal so as to sandwich the electro-optic crystal;
A light source that generates light of a single wavelength;
A first optical system that collimates light from the light source and is incident between the electrodes of the electro-optic crystal;
A second optical system for converting the parallel light incident from the first optical system and passing through the electro-optic crystal into a change in light intensity;
Photoelectric conversion means for converting the light output from the second optical system into an electric signal;
An amplifier that amplifies the electric field received by the receiving electrode and applies between the electrodes of the electro-optic crystal ;
A first power supply circuit for supplying operating power to the light source and the photoelectric conversion means;
A second power supply circuit that is insulated from circuit ground of the first power supply circuit and supplies operating power to the amplifier;
An electric field sensor comprising: The side of the electro-optic crystal is a pair of opposing sides, said electrodes, an electric field sensor according to claim 1, wherein the a pair of electrodes provided on each of the pair of side surfaces. A high-pass filter that is connected between the receiving electrode and the input of the amplifier, removes a predetermined low frequency component in the electric field received by the receiving electrode, and passes only a predetermined high frequency to supply the amplifier to the amplifier; electric field sensor according to claim 1, wherein. The electric field sensor according to claim 3 , wherein the high pass filter includes a capacitor.

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