JP4602266B2 - Electric field detection optical system and transceiver - Google Patents

Description

  The present invention relates to a potential adjustment technique for adjusting a potential of an electric signal, and more particularly, to a technique for adjusting a potential of an electric signal converted from an electric field induced and transmitted by an electric field transmission medium.

  Although wearable computers are attracting attention due to the miniaturization and high performance of portable terminals, FIG. 5 shows an example in which such wearable computers are worn and used by humans. As shown in the figure, the wearable computer 7 is mounted on a person's arm, shoulder, torso, etc. via a transceiver 9 to transmit / receive data to / from each other, and is provided on the wall or floor so that it can be touched by the tip of a limb. Communication is performed with a personal computer (PC) 8 provided outside through the transceivers 9a and 9b and the cables.

  Here, the transceiver 9 used for data communication between the wearable computer 7 and between the wearable computer 7 and the PC 8 has, for example, a configuration as shown in FIG. It uses signal detection technology based on electro-optic techniques that use a signal, induces an electric field based on information to be transmitted in a living body that is an electric field transmission medium, and transmits and receives information using the induced electric field. .

  More specifically, when the transceiver 9 receives transmission data from the computer 6 via the input / output (I / O) circuit 901, the transceiver 9 supplies the transmission data to the transmission / reception electrode 903 via the transmission unit 902. An electric field is induced in the electric field transmission medium via 903 and the insulating film 904, and this electric field is transmitted to other parts of the electric field transmission medium. In addition, the electric field induced and transmitted by the electric field transmission medium is detected by the transmission / reception electrode 903 via the insulating film 904, and this electric field is coupled to the electric field detection optical unit 905 and converted into an electric signal. . This electric signal is subjected to signal processing such as amplification and noise removal by the signal processing circuit 906, and further subjected to waveform shaping by the waveform shaping circuit 907, and then via the input / output (I / O) circuit 901. Is output.

As prior art document information related to this application, for example, there is the following.
JP 2001-352298 A

  In the transceiver shown in FIG. 6, the optical module of the electric field detection optical unit 905 has variations due to individual differences in the electric field transmission medium. Therefore, there is a potential difference between the two signals input from the electric field detection optical unit 905 to the signal processing circuit 906. appear. In order to absorb the potential difference and maintain the performance of the electric field detection optical unit 905, the signal processing circuit 906 includes, for example, a differential balance adjustment circuit as shown in FIG.

  The differential balance adjustment circuit diagram is a circuit for adjusting the balance of voltages (potentials) of two signals input from the electric field detection optical unit 905. The illustrated differential balance adjustment circuit includes a first input terminal P1 to which a first signal is input, a first resistor 101, a first capacitor 102, and a second signal to which a second signal is input. An input terminal P2, a second resistor 201, a second capacitor 202, a differential amplifier 300, and an output terminal 400 are provided. The second resistor 201 is a variable resistor that can be manually adjusted.

  In the case of the differential balance adjustment circuit diagram shown in the drawing, the second resistor 201 is manually manually prepared in advance at the time of manufacturing (shipment) of the transceiver 9 in order to eliminate manufacturing variations of components (optical modules and the like) of the electric field detection optical unit 905. Need to be adjusted. Accordingly, there is a problem that work load and work cost are generated.

  The present invention has been made to solve the above-described object, and aims to automatically adjust the balance of two signal voltages input from the electric field detection optical unit 905 to further reduce the work load and work cost. To do.

In order to achieve the above object, a first aspect of the present invention is an electric field detection optical system having an electric field detection optical device and a differential balance adjustment circuit, wherein the electric field detection optical device is induced in an electric field transmission medium. The transmitted electric field is detected and converted into a plurality of electric signals, and the differential balance adjustment device includes a plurality of potential adjustment circuits and a differential amplifier, and each of the potential adjustment circuits includes the electric field detection An electrical signal converted by the optical device is input, an impedance converter that converts the current of the input signal into a voltage, and whether the input signal converted by the impedance converter includes a DC voltage is detected. If a voltage is included, a potential detector that generates a negative potential equal to or exceeding a predetermined voltage, and a negative potential generated by the potential detector is applied to the input signal to generate a negative feedback. Anda adjustment potential application device for performing the differential amplifier, the inputs of the output signal after the potential adjustment each potential adjusting circuit is outputted, and outputs the difference of the output signal.

According to a second aspect of the present invention, there is provided a transceiver for inducing an electric field based on information to be transmitted in an electric field transmission medium and transmitting and receiving information by detecting the induced electric field. An electric field detection optical device that detects an electric field generated and converts the electric field into a plurality of electric signals, a plurality of electric potential adjustment circuits that input the electric signals and adjust the electric potential of the input signals, and the electric potential adjustment circuits A differential amplifier that inputs a plurality of output signals and outputs a difference between the plurality of output signals, and each of the potential adjustment circuits includes an impedance converter that converts a current of the input signal into a voltage; Detects whether or not a DC voltage is included in the input signal converted by the impedance converter, and if a DC voltage is included, a negative potential equal to a predetermined voltage or exceeds a predetermined voltage Has a potential detector for generating an electric potential, and a adjustment voltage application section that performs negative feedback by applying a negative potential to the potential detector is generated on the input signal.

  According to the present invention, the work load and the work cost can be further reduced by automatically adjusting the balance between two input signal voltages. Further, according to the present invention, the performance of the electric field detection optical unit can be ensured, and the optical path noise can be further reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a transceiver 1 according to an embodiment of the present invention. The transceiver 1 shown in FIG. 1 uses a signal detection technique based on an electro-optic technique using a laser beam and an electro-optic crystal, and induces an electric field based on information to be transmitted in a living body that is an electric field transmission medium. A transceiver that transmits and receives information using an induced electric field.

  More specifically, when the transceiver 1 receives transmission data from the computer 6 via the input / output (I / O) circuit 901, the transceiver 1 supplies the transmission data to the transmission / reception electrode 903 via the transmission unit 902. An electric field is induced in the electric field transmission medium via 903 and the insulating film 904, and this electric field is transmitted to other parts of the electric field transmission medium. In addition, the electric field induced and transmitted by the electric field transmission medium is detected by the transmission / reception electrode 903 via the insulating film 904, and this electric field is coupled to the electric field detection optical unit 905 and converted into an electric signal. This electric signal is subjected to signal processing such as amplification and noise removal by the signal processing circuit 906 and further subjected to waveform shaping by the waveform shaping circuit 907.

  The transceiver 1 of this embodiment includes a differential balance automatic adjustment circuit 110 between the electric field detection optical unit 905 and the signal processing circuit 906. The differential balance automatic adjustment circuit 110 automatically adjusts the voltages (potentials) of the two electric signals output from the electric field detection optical unit 905, differentially amplifies the electric signals having the opposite phases after adjustment, and performs a signal processing circuit 906. Output to. Thereby, optical path noise can be further reduced.

  The differential balance automatic adjustment circuit 110 will be described below.

  FIG. 2 is a diagram illustrating a potential adjustment circuit included in the differential balance automatic adjustment circuit 110 as a basic configuration. The potential adjustment circuit controls the voltage (potential) of the electrical signal to be constant without being affected by the current of the electrical signal input to the potential adjustment circuit. The potential adjustment circuit shown in the figure includes an input terminal P, a transimpedance amplifier (impedance converter) 202, a feedback amplifier (FB) 204, a transistor (Tr) 205, and an output terminal 209.

  A transimpedance amplifier (hereinafter “TIA”) 202 amplifies a signal (a minute current signal) input from the electric field detection optical unit 905 via the input terminal P. That is, the output current of the electric field detection optical unit 905 is input to the inverting input terminal of the TIA 202, and the output current is converted into a voltage (potential). In this case, the absolute value of the transimpedance gain is equal to the value of the resistor R.

  The feedback amplifier 204 receives the signal output from the TIA 202, uses the set voltage set by the constant voltage source 203 as a reference voltage for DC voltage detection, and whether or not the input signal includes a DC voltage. To detect. When no DC voltage is included, the feedback amplifier 204 outputs the input signal as it is to the output terminal 209.

On the other hand, when a DC voltage is included, the feedback amplifier 204 negatively feeds back the input signal to the TIA 202. That is, the feedback amplifier 204 compares the input signal voltage with the set voltage of the constant voltage source, and generates a negative voltage (negative potential) according to the DC voltage so that the input signal voltage is equal to a constant voltage. The transistor 205 is controlled to perform negative feedback. Note that the feedback amplifier 204 may generate a negative voltage (negative potential) according to the direct-current voltage so that the input signal voltage exceeds a certain voltage, and perform negative feedback by controlling the transistor 205.
The transistor 205 applies a negative voltage (negative potential) to the signal output from the feedback amplifier 204 based on the control of the feedback amplifier 204. That is, the transistor 205 adjusts only the DC component of the input signal, and negatively feeds back the AC component (signal component) to the TIA 202. Note that the transistor 205 removes a DC component from an input signal by flowing the DC component to a connected ground.

The TIA 202 converts the negative feedback signal (AC component) from the transistor 205 into a voltage as described above, and outputs the voltage to the feedback amplifier 204. As described above, the feedback amplifier 204 detects whether the signal input from the TIA 202 includes a DC voltage. If the DC voltage is not included, the feedback amplifier 204 outputs the input signal to the output terminal 209.
By using such a potential adjustment circuit, the voltage (potential) of the signal input from the electric field detection optical unit 905 can be kept constant at all times.

  FIG. 3 is a diagram illustrating the differential balance automatic adjustment circuit 110.

  The automatic differential balance adjustment circuit 110 shown in the figure includes a first potential adjustment circuit 210, a second potential adjustment circuit 220, a first capacitor 230, a second capacitor 240, and a differential amplifier (differential amplifier). 250). The potential adjustment circuits 210 and 220 are the same as the potential adjustment circuit of FIG. As described with reference to FIG. 2, each of the potential adjustment circuits 210 and 220 outputs a signal whose potential is adjusted to a constant value to the differential amplifier 250 via the capacitors 230 and 240.

  The differential amplifier 250 receives the signal output from the first potential adjustment circuit 210 and the signal output from the second potential adjustment circuit 220, differentially amplifies these two signals, and outputs them to the output terminal. . For example, when the signal input from the first potential adjustment circuit 210 is a positive signal and the signal input from the second potential adjustment circuit 220 is a negative signal, the signal doubled by the differential amplifier 250 Is output to the output terminal 260.

  Each potential adjustment circuit adjusts the voltage (potential) of the input signal to be constant, so that a signal having an equal potential maintained at a constant voltage is input to the differential amplifier 250 from each potential adjustment circuit. .

  FIG. 4 is a diagram showing an electric field detection optical system having an electric field detection optical unit 905 and a differential balance automatic adjustment circuit 110.

  The illustrated automatic differential balance adjustment circuit 110 is the same as the potential adjustment circuit described with reference to FIG. The electric field detection optical unit 905 functions to detect an electric field that is induced and transmitted by the electric field transmission medium and is coupled via the transmission / reception electrode 903, converts the electric field into an electric signal, and outputs the electric signal to the differential balance automatic adjustment circuit 110. To do. The electric field detection optical unit 905 is described in, for example, Japanese Patent Application Laid-Open No. 2004-012202.

  The electric field detection optical unit 905 detects an electric field by an electro-optic technique using laser light and an electro-optic crystal, and has an electro-optic element composed of a laser diode and an electro-optic crystal that constitute a laser light source. The electro-optical element has sensitivity only to an electric field coupled in a direction perpendicular to the traveling direction of the laser light from the laser diode, and the optical characteristics, that is, the birefringence changes depending on the electric field strength. The polarization of the laser light is changed by the change of the refractive index.

  First and second electrodes are provided on opposite side surfaces of the electro-optic element. The first and second electrodes sandwich the traveling direction of the laser light from the laser diode in the electro-optic element from both sides, and couple the electric field to the laser light at a right angle. The electric field detection optical unit 905 has a signal electrode constituting the transmission / reception electrode 903, and the signal electrode is connected to the first electrode. The second electrode facing the first electrode is connected to the ground electrode and is configured to function as a ground electrode with respect to the first electrode. When the signal electrode detects an electric field that is induced and transmitted by the electric field transmission medium, the signal electrode transmits the electric field to the first electrode and is coupled to the electro-optic element via the first electrode.

  Laser light output from the laser diode is converted into parallel light through a collimator lens, and the laser light that has become parallel light is adjusted in polarization state by the first wavelength plate and enters the electro-optic element. The laser light incident on the electro-optic element propagates between the first and second electrodes in the electro-optic element, and the signal electrode is induced and transmitted by the electric field transmission medium during the propagation of the laser light. When an electric field is detected and coupled to the electro-optic element via the first electrode, the electric field is formed from the first electrode toward the second electrode connected to the ground electrode, and the laser diode Therefore, the birefringence, which is the optical characteristic of the electro-optical element, changes, and the polarization of the laser light changes accordingly.

  Thus, the laser light whose polarization has been changed by the electric field from the first electrode in the electro-optic element is adjusted in the polarization state by the second wave plate and is incident on the polarization beam splitter. The polarization beam splitter separates the laser light incident from the second wave plate into P wave and S wave, and converts them into a change in light intensity. The laser beams separated into the P-wave component and the S-wave component by the polarization beam splitter are condensed by the first and second condenser lenses, respectively, and then supplied to the first and second photodiodes. In the first and second photodiodes, the P wave optical signal and the S wave optical signal are converted into respective electric signals and output.

  The electric signals output from the first and second photodiodes of the electric field detection optical unit 905 are input to the automatic differential balance adjustment circuit 110 through the input terminals P1 and P2.

  The differential balance automatic adjustment circuit 110 shown in FIG. 4 adjusts the voltage of the electric signal output from the photodiode to be constant, and differentially amplifies each electric signal. Thereby, the performance of the electric field detection optical unit 905 can be secured, and the optical path noise can be further reduced.

  In the present embodiment described above, the potential adjustment circuit automatically adjusts the voltage (potential) of the signal input from the electric field detection optical unit 905. Thereby, work load and work cost can be reduced more. In addition, it is possible to absorb manufacturing variations of components (such as an optical module) of the electric field detection optical unit 905, to secure the performance of the electric field detection optical unit 905, and to further reduce optical path noise.

  As mentioned above, although embodiment of this invention has been described, various deformation | transformation and change can be performed with respect to embodiment of this invention in the range which does not deviate from the summary of this invention.

It is a block diagram which shows schematic structure of the transceiver which concerns on embodiment of this invention. It is a figure which shows the structure of an automatic adjustment circuit. It is a figure which shows the structure of a differential balance automatic adjustment circuit. It is a figure which shows the structure of an electric field detection optical system. It is explanatory drawing which shows the example in the case of mounting | wearing and using a wearable computer for a person via a transceiver. It is a block diagram which shows the circuit structure of the conventional transceiver. It is a figure which shows the structure of the conventional differential balance adjustment circuit.

Explanation of symbols

1,9 Transceiver 6 Computer 7 Wearable computer 8 PC
110 differential balance automatic adjustment circuit 901 I / O circuit 902 transmission unit 903 transmission / reception electrode 904 insulating film 905 electric field detection optical unit 906 signal processing circuit 907 waveform shaping circuit 910 reception unit

Claims (4)

An electric field detection optical system having an electric field detection optical device and a differential balance adjustment circuit,
The electric field detection optical device detects an electric field transmitted by being induced in an electric field transmission medium and converts the electric field into a plurality of electric signals,
The differential balance adjustment device has a plurality of potential adjustment circuits and a differential amplifier,
Each of the potential adjustment circuits includes:
An impedance converter that inputs an electric signal converted by the electric field detection optical device and converts a current of the input signal into a voltage;
The input signal converted by the impedance converter detects whether or not a DC voltage is included. When the DC voltage is included, a negative potential equal to or exceeding a predetermined voltage is generated. A potential detector;
An adjustment potential applicator for applying a negative potential generated by the potential detector to the input signal to perform negative feedback, and
The electric field detection optical system, wherein the differential amplifier receives an output signal after potential adjustment output from each potential adjustment circuit and outputs a difference between the output signals. The electric field detection optical system according to claim 1 ,
The electric field detecting optical system, wherein the adjustment potential applicator is a transistor. A transceiver that induces an electric field based on information to be transmitted in an electric field transmission medium and detects the induced electric field to transmit and receive information,
An electric field detection optical device that detects an electric field transmitted by being induced in an electric field transmission medium and converts the electric field into a plurality of electric signals;
A plurality of potential adjustment circuits that input the electrical signals and adjust the potential of the input signals;
A plurality of output signals output by each of the potential adjustment circuits, and a differential amplifier that outputs a difference between the plurality of output signals.
Each of the potential adjustment circuits includes:
An impedance converter for converting the current of the input signal into a voltage;
The input signal converted by the impedance converter detects whether or not a DC voltage is included. When the DC voltage is included, a negative potential equal to or exceeding a predetermined voltage is generated. A potential detector;
And a regulated potential applicator for performing negative feedback by applying a negative potential generated by the potential detector to the input signal. The transceiver of claim 3 , wherein
The transceiver is characterized in that the adjustment potential applicator is a transistor.

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