JP3597519B2 - Electric field detection optical device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention detects an electric field induced and transmitted by an electric field transmission medium, which is a living body, based on transmission information in a transceiver used for data communication between, for example, a wearable computer (computer attached to the body). The present invention relates to an electric field detection optical device that converts an electric signal into an electric signal.
[0002]
[Prior art]
Wearable computers have been attracting attention due to miniaturization and high performance of mobile terminals. FIG. 3 shows an example of a case where such a wearable computer is worn on a human and used. As shown in FIG. 1, the wearable computer 1 is attached to a human arm, shoulder, torso, etc. via a transceiver 3 to transmit and receive data to and from each other, and further includes transceivers 3a, 3b attached to the tips of limbs. It communicates with a personal computer (PC) 5 provided outside via a cable.
[0003]
As described above, the wearable computer 1 is attached to a human being as a living body via the transceiver 3 to perform data communication. In this transceiver 3, transmission data from the wearable computer 1 is induced as an electric field in the living body as an electric field transmission medium, As shown by a broken line in FIG. 3, the electric field is transmitted to other parts of the living body as an electric field, and the electric field induced and transmitted by the living body is received by the transceiver 3 as reception data and sent to the wearable computer 1.
[0004]
Transceiver 3 is configured as shown in FIG. 4, and receives transmission data from wearable computer 1 via input / output (I / O) circuit 101, and transmits the transmission data to transmission electrode 105 via transmission section 103. Then, an electric field is induced from the transmission electrode 105 through the insulating film 107 to the living body 100 as an electric field transmission medium, and the electric field is transmitted to another part of the living body 100 via the living body 100.
[0005]
Further, the transceiver 3 receives the electric field induced and transmitted to the living body 100 from another transceiver attached to another part of the living body 100 at the receiving electrode 111 via the insulating film 109, and receives the received electric field. Is coupled to the electric field detection optical unit 110 and converted into an electric signal. The electric signal is subjected to signal processing such as amplification, noise elimination, and waveform shaping by the signal processing circuit 115, and then supplied to the wearable computer 1 via the input / output circuit 101.
[0006]
The electric field detection optical unit 110 of the transceiver 3 detects an electric field induced and transmitted to the living body 100 and coupled through the insulating film 109 and the receiving electrode 111, converts the electric field into an electric signal, and outputs the electric signal to the signal processing circuit 115. Although it functions as described above, it is configured in detail as shown in FIG.
[0007]
The electric field detection optical unit 110 shown in FIG. 5 detects an electric field by an electro-optical method using a laser beam and an electro-optical crystal, and includes a laser diode 121 constituting a laser light source and an electro-optical element including the electro-optical crystal. 123. The electro-optical element 123 has sensitivity only to an electric field that is coupled in a direction perpendicular to the traveling direction of the laser light from the laser diode 121, and the optical characteristics, that is, the birefringence, change according to the intensity of the electric field. The change in the birefringence changes the polarization of the laser light.
[0008]
First and second electrodes 125 and 127 are provided on both side surfaces of the electro-optical element 123 that face each other in the vertical direction in the drawing. The first and second electrodes 125 and 127 sandwich the traveling direction of the laser light from the laser diode 121 in the electro-optical element 123 from both sides, and couple the electric field to the laser light at right angles. ing.
[0009]
The electric field detecting optical device 110 has a signal electrode 129 constituting the receiving electrode 111 shown in FIG. 4, and this signal electrode 129 is connected to the first electrode 125. Further, the second electrode 127 facing the first electrode 125 is connected to the ground electrode 131, and is configured to function as a ground electrode for the first electrode 125. When detecting the electric field induced and transmitted to the living body 100, the signal electrode 129 transmits the electric field to the first electrode 125 and couples to the electro-optical element 123 via the first electrode 125. ing.
[0010]
The laser light output from the laser diode 121 is converted into parallel light through the collimating lens 133, and the parallel light is adjusted in the polarization state by the first wavelength plate 135 and enters the electro-optical element 123. . The laser light incident on the electro-optical element 123 propagates between the first and second electrodes 125 and 127 in the electro-optical element 123, and during the propagation of the laser light, the signal electrode 129 is applied to the living body as described above. When an electric field induced and transmitted by the sensor 100 is detected and the electric field is coupled to the electro-optical element 123 via the first electrode 125, the electric field is connected from the first electrode 125 to the ground electrode 131. The birefringence, which is an optical characteristic of the electro-optical element 123, changes toward the second electrode 127 and is perpendicular to the direction of travel of the laser light incident on the electro-optical element 123 from the laser diode 121. This changes the polarization of the laser light.
[0011]
The laser light whose polarization has been changed by the electric field from the first electrode 125 in the electro-optical element 123 in this way is incident on the polarization beam splitter 139 after its polarization state is adjusted by the second wave plate 137. The polarization beam splitter 139 separates the laser light incident from the second wavelength plate 137 into a P wave and an S wave, and converts the laser light into a change in light intensity. The laser beam split into a P-wave component and an S-wave component by the polarization beam splitter 139 is condensed by first and second condenser lenses 141a and 141b, respectively, and then the first component constituting the photoelectric conversion means is formed. Are received by the second photodiodes 143a and 143b, and the first and second photodiodes 143a and 143b convert the P-wave optical signal and the S-wave optical signal into respective electric signals and output the electric signals.
[0012]
As described above, the electric signals output from the first and second photodiodes 143a and 143b are subjected to signal processing such as amplification, noise removal, and waveform shaping by the signal processing circuit 115 shown in FIG. The data is supplied to the wearable computer 1 via the output circuit 101.
[0013]
As shown in FIG. 6, a photodiode 143 for converting a P-wave or S-wave optical signal into an electric signal is connected between a bias voltage source 153 and the ground via a load resistor 151 connected in series. Then, a reverse bias voltage of the bias voltage source 153 is applied to operate.
[0014]
When the photodiode 143 receives the laser light separated into the P-wave component and the S-wave component by the polarization beam splitter 139, the photodiode 143 generates a photocurrent according to the intensity of the laser light. This photocurrent is output as a voltage drop of the load resistor 151.
[0015]
[Problems to be solved by the invention]
In the conventional electric field detecting optical device configured as described above, there is a method of increasing the light amount of the laser diode 121 as a method for improving the electric field detection sensitivity. The DC photocurrent flowing through 143 increases, and the voltage drop across the load resistor 151 increases. As a result, the reverse bias voltage applied to the photodiode 143 decreases. When the reverse bias voltage is reduced, the photodiode 143 does not operate normally, and the sensitivity is degraded and the communication error increases despite the increase in the amount of laser light.
[0016]
If the load resistance 151 is reduced to avoid such a problem, there is a problem that the signal component is reduced.
[0017]
Further, even if an attempt is made to increase the bias voltage in order to apply a sufficiently large reverse bias voltage, there is a problem that the bias voltage cannot be sufficiently increased due to the rating of the photodiode 143.
[0018]
Even if the rating of the photodiode is high, a circuit for boosting the battery voltage is required to increase the bias voltage. However, a booster circuit is generally inefficient and therefore consumes a large amount of power as heat, causing a problem in terms of heat generation and battery consumption. In addition, switching noise from the booster circuit is mixed and measurement accuracy deteriorates. The problem described above is likely to occur.
[0019]
The present invention has been made in view of the above, and aims at increasing the amount of parallel light to improve S / N, secure a sufficient reverse bias, and suppress heat generation and battery consumption. An object of the present invention is to provide an electric field detection optical device that can achieve high sensitivity.
[0020]
[Means for Solving the Problems]
In order to achieve the above object, the present invention according to claim 1 is an electric field detection optical device for detecting an electric field induced and transmitted by an electric field transmission medium and converting the electric field into an electric signal. A polarization changing unit that changes the polarization of parallel light in response to an electric field that is incident and combined, separates the light into a P-wave and an S-wave that are orthogonal to each other, and outputs a P-wave emitted from the polarization-changing unit. First and second beam splitters for further dividing each of the wave and the S wave into two parallel light beams having the same light amount, and converting the four parallel light beams separated by the first and second beam splitters into electric signals The first to fourth opto-electrical converting means and two signals of opposite phases among the four output signals output from the first to fourth opto-electrical converting means are input, and the difference between the two signals is calculated. First and second differences to amplify And summarized in that a an amplifier, a third differential amplifier for amplifying a difference between the two signals respectively output signals of the first and second differential amplifiers as input.
[0021]
According to the first aspect of the present invention, the polarization of the parallel light is changed by the electric field combined by the polarization changing means into which the parallel light is incident, and each of the P wave and the S wave emitted from the polarization changing means is changed. Further, the light is separated into two parallel light beams having the same light amount, the separated four parallel light beams are converted into electric signals, and signals having opposite phases are differentially amplified to generate an output signal. Even if the amount of light is increased, the light is separated into a plurality of laser beams of the same amount, dispersing the amount of light to each photodiode as in the past, and the photodiode will not operate normally due to the reverse bias problem, and the sensitivity will be reduced. A high-sensitivity electric-field detection optical device is achieved by eliminating the problem of worsening communication errors and eliminating problems such as photodiode rating problems, bias voltage boost problems, heat generation and battery consumption problems. It can, also the noise component is removed by phase components cancel each other by the differential amplifier, it is possible to significantly improve the S / N.
[0022]
According to a second aspect of the present invention, there is provided an electric field detection optical device for detecting an electric field induced and transmitted by an electric field transmission medium and converting the electric field into an electric signal, each of which receives a parallel light having a single wavelength. And a plurality of polarization changing means for changing the polarization of the parallel light in response to the combined electric field and separating and outputting the P and S waves orthogonal to each other, And a plurality of opto-electrical converting means for converting each of the P-wave and the S-wave into an electric signal, and differentially amplifying a pair of signals having opposite phases among output signals of the plurality of opto-electrical converting means for all combinations Differential amplification means for sequentially and repeatedly performing the differential amplification processing to generate the differentially amplified output signal by performing the differential amplification processing in the same manner also on the differential amplification signal generated by the differential amplification processing. That is the gist.
[0023]
According to the second aspect of the present invention, the polarization of the parallel light is changed by the electric field coupled to each of the plurality of polarization changing means into which the parallel light is incident, and the P wave and the S wave emitted from the polarization changing means are changed. Each of the waves is further separated into two parallel light beams having the same light amount, the separated parallel light beams are converted into electric signals, and the signals having opposite phases among the plurality of electric signals are differentially amplified to output signals. Therefore, even if the amount of parallel light is increased to improve the sensitivity, it is separated into a plurality of laser beams of the same amount, dispersing the amount of light to each photodiode as in the past, and the Diode does not operate properly, sensitivity is deteriorated, communication errors are increased, and problems such as photodiode rating, bias voltage boost, heat generation and battery consumption are eliminated. It is possible to achieve a sensitivity field detecting optical system, also the noise component is removed by phase components cancel each other by the differential amplifier, it is possible to significantly improve the S / N.
[0024]
Further, according to a third aspect of the present invention, in the first or second aspect of the present invention, the polarization changing means changes the optical characteristics in response to an electric field into which the parallel light is incident and coupled. The gist of the present invention is to include an element and an analyzer that separates parallel light that has passed through the electro-optical element into a P-wave and an S-wave and converts the light into a change in light intensity.
[0025]
The present invention according to claim 4 is an electric field detection optical device that detects an electric field induced and transmitted by an electric field transmission medium and converts the electric field into an electric signal, wherein the light source generates light of a single wavelength; A collimating lens that converts light from the light source into parallel light, an electro-optical element that receives parallel light from the collimating lens, and changes optical characteristics in response to an electric field to be coupled, and an electro-optical element that is induced in the electric field transmission medium. A first electrode for coupling the applied electric field to the electro-optical element, an analyzer for separating parallel light passing through the electro-optical element into a P wave and an S wave, and converting the light into a change in light intensity; and the analyzer. First and second beam splitters for separating the P wave and the S wave separated by the above into two parallel lights of the same light amount, respectively, and the four parallel lights separated by the first and the second beam splitters. The first to convert to electric signal A fourth opto-electrical converter, and a first amplifying unit that receives two signals of opposite phases among the four output signals output from the first to fourth opto-electrical converters and amplifies a difference between the two signals. And a second differential amplifier, and a third differential amplifier that receives respective output signals of the first and second differential amplifiers and amplifies a difference between the two signals.
[0026]
According to the present invention, an electric field induced and transmitted by the electric field transmission medium is coupled to the electro-optical element via the first electrode, and parallel light is incident on the electro-optical element. The parallel light emitted from the electro-optical element is separated into a P-wave and an S-wave by an analyzer, and the P-wave and the S-wave are separated into two parallel light beams having the same light amount and converted into an electric signal. In order to generate an output signal by differentially amplifying the signal of the opposite phase among the electric signals of the above, even if the light amount of the parallel light is increased to improve the sensitivity, it is separated into a plurality of laser lights of the same light amount, Disperses the amount of light to each photodiode as before, eliminates the problem that the photodiode does not operate normally due to the reverse bias problem, lowers the sensitivity, and increases the communication error. Voltage boost A high-sensitivity electric field detection optical device can be achieved without the problem of heat generation, battery consumption, and the like. In addition, the noise component is removed by canceling the common-mode components mutually by differential amplification, and the S / N ratio is reduced. Can be significantly improved.
[0027]
According to a fifth aspect of the present invention, there is provided an electric field detection optical device for detecting an electric field induced and transmitted by an electric field transmission medium and converting the electric field into an electric signal, comprising a light source for generating light of a single wavelength. A collimating lens that converts light from the light source into parallel light, a beam splitter unit that divides the parallel light from the collimating lens into a plurality of parallel light beams having the same amount of light, and a plurality of parallel light beams that are separated by the beam splitter unit. A plurality of electro-optical elements, each of which receives light and changes optical characteristics in response to the coupled electric field; and each couples the electric field induced in the electric field transmission medium to each of the plurality of electro-optical elements. A plurality of first electrodes; a plurality of analyzers each of which separates parallel light, which has passed through each of the plurality of electro-optical elements, into a P wave and an S wave, and converts the light into a change in light intensity; Each of the analyzers A plurality of photoelectric conversion means for respectively converting the separated P-wave and S-wave into electric signals; and differential amplification of a pair of signals having opposite phases among output signals of the plurality of photoelectric conversion means for all combinations. Differential amplification means for performing differential amplification processing to perform differential amplification processing to be performed on the differential amplification signal generated in the differential amplification processing in order to generate differentially amplified output signals. It is the gist to have.
[0028]
According to the fifth aspect of the present invention, the electric field induced and transmitted by the electric field transmission medium is coupled to the plurality of electro-optical elements via the first electrode. Each of the plurality of parallel lights is made incident, and each of the plurality of parallel lights emitted from the plurality of electro-optical elements is separated into a P wave and an S wave by each analyzer, and the P wave and the S wave from each of the plurality of analyzers are separated. Is converted into an electric signal to generate a plurality of electric signals, and an output signal is generated by differentially amplifying a signal of the opposite phase among the plurality of electric signals, so that the amount of parallel light is increased to improve sensitivity. However, by separating the laser beam into a plurality of laser beams of the same light amount, the light amount for each photodiode is dispersed as in the past, the photodiode does not operate normally due to the reverse bias problem, the sensitivity deteriorates, and communication errors occur. Eliminate the problem of growth It is possible to achieve a high-sensitivity electric field detection optical device without causing problems such as photodiode rating problems, bias voltage boost problems, heat generation and battery consumption problems. Are mutually canceled and removed, so that the S / N can be significantly improved.
[0029]
Further, the present invention according to claim 6, in the invention according to claim 4 or 5, is provided near the incident end face of the electro-optical element to which the parallel light is incident, and adjusts the polarization state of the parallel light. A first wave plate incident on the electro-optical element, a second electrode provided opposite to the first electrode and functioning as a ground electrode with respect to the first electrode, and the electro-optical element and the detection electrode. The gist of the present invention is that it further includes at least one or more of the second wave plates that are provided between the photons and adjust the polarization state of the parallel light that has passed through the electro-optical element and are incident on the analyzer.
[0030]
According to a seventh aspect of the present invention, in the invention according to any one of the fourth to sixth aspects, the light source is a light emitting diode that generates a single wavelength light or a laser light source that generates a laser light. Make a summary.
[0031]
Further, the present invention described in claim 8 is characterized in that, in the invention described in any one of claims 4 to 7, the analyzer is a polarization beam splitter.
[0032]
BEST MODE FOR CARRYING OUT 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 an electric field detection optical device according to one embodiment of the present invention.
[0033]
The electric field detection optical device shown in FIG. 9 increases the light amount of the laser diode 121 in the conventional electric field detection optical device described with reference to FIG. 5 and also uses the laser beam passing through the polarization beam splitter 139 as a configuration after the polarization beam splitter 139. It is divided into a plurality of laser beams, and the increased amount of light of the laser diode is received by a plurality of photodiodes, which is different in that the conventional problem is solved. The same components are given the same two-digit numbers excluding the hundreds of numbers in FIG.
[0034]
In FIG. 1, the configuration after the polarization beam splitter 39 will be described in detail. The laser beams separated into a P-wave component and an S-wave component by the polarization beam splitter 39 are incident on first and second beam splitters 51 and 61, respectively. The light is split into two laser beams having the same light amount. As a result, four laser beams are generated.
[0035]
One of the laser beams split by the first beam splitter 51 is condensed by the first condensing lens 53a and is incident on the first photodiode 55a, and the other is condensed by the second condensing lens 53b. The light is condensed and enters the second photodiode 55b.
[0036]
One of the laser beams split by the second beam splitter 61 is condensed by the third condenser lens 63a and is incident on the third photodiode 65a, and the other is the fourth condenser lens. The light is condensed at 63b and enters the fourth photodiode 65b.
[0037]
The first to fourth photodiodes 55a, 55b, 65a, 65b receiving the separated laser beams are respectively connected to bias voltage sources 59a, 59b via load resistors 57a, 57b, 67a, 67b connected in series. , 69a, 69b and the ground, generate a photocurrent corresponding to the amount of each laser beam, and this photocurrent is applied to load resistors 57a, 57b, 67a, 67b connected in series to each photodiode. A voltage drop occurs, and this voltage drop is output as an output voltage. For example, when a positive-polarity rectangular wave is applied to the signal electrode 29, a rectangular wave as shown in FIG. 1 is output to the output side of each photodiode.
[0038]
As shown, these rectangular wave output signals are output from the first and second photodiodes 55a and 55b with a positive polarity and output from the third and fourth photodiodes 65a and 65b with a negative polarity. Thus, a pair of signals having opposite phases among these output signals, that is, the output of the second photodiode 55b is input to the negative input side of the first differential amplifier 71, The output of the third photodiode 65a is input to the positive input side of the first differential amplifier 71, and differential amplification is performed to amplify the difference between the two signals to generate an output signal. The signal, that is, the output of the first photodiode 55a is input to the positive input side of the second differential amplifier 73, and the output of the fourth photodiode 65b is input to the negative input side of the second differential amplifier 73. , Increase the difference between the two signals Performing differential amplification to generate an output signal.
[0039]
The output signal from the first differential amplifier 71 is negative as shown, the output signal from the second differential amplifier 73 is positive as shown, and both output signals are The signal is input to the differential amplifier 75, and the difference between them is amplified to generate an output signal as shown in the figure.
[0040]
In the present embodiment, although the light amount of the laser diode 21 is increased, the laser beam that has passed through the electro-optical element 23 and changed in polarization is separated into a P-wave component and an S-wave component by the polarization beam splitter 39, and this separation is performed. Since the laser light of each component is further separated into two laser light beams having the same light amount by the first and second beam splitters 51 and 61, even if the laser light amount is increased, the laser light for each photodiode is different from the conventional one. The amount of light is dispersed and does not increase, so that the voltage drop in the load resistance increases as in the past, the reverse bias voltage applied to the photodiode decreases, the photodiode does not operate normally, and the sensitivity decreases, Problems such as an increase in communication errors, problems with the rating of the photodiode, problems with boosting the bias voltage, and problems with heat generation and battery consumption may also occur. Ku, it is possible to achieve high sensitivity electric field detecting optical system.
[0041]
In particular, although the signal component increases due to the increase in the laser light amount, the noise component is removed by the differential amplification in the first to third differential amplifiers 71 to 75 so that the in-phase components cancel each other. Therefore, the S / N can be remarkably improved, and the reverse bias voltage applied to the photodiode can be secured with a sufficient operating voltage without being particularly boosted.
[0042]
Next, an electric field detecting optical device according to another embodiment of the present invention will be described with reference to FIG.
[0043]
The electric field detecting optical device shown in FIG. 9 is different from the conventional electric field detecting optical device shown in FIG. 5 in that the light amount of the laser diode 121 is increased and two electro-optical elements 123 are provided. The difference is that two sets are similarly provided corresponding to the optical elements, and the other structures and operations are the same. The same components have the same reference numerals as those in FIG. The same number of digits is given.
[0044]
That is, the electric field detecting optical device shown in FIG. 2 has first and second two electro-optical elements 23a and 23b, and the laser light from the laser diode 21 is applied to the two electro-optical elements 23a and 23b. For incidence, a beam splitter 77 for splitting the laser light into two is provided on the output side of the collimator lens 33 that converts the laser light from the laser diode 21 into parallel light. One of the two laser beams split by the beam splitter 77 is incident on the first electro-optical element 23a via the first wave plate 35a, and the other is further reflected by the prism 79, The light is incident on the second electro-optical element 23b via the third wave plate 35b.
[0045]
As in the case of FIG. 5, a first electrode 25a and a second electrode 27a are attached to the side surface of the first electro-optical element 23a, and a signal is applied to the first and second electrodes 25a and 27a, respectively. The electrode 29a and the ground electrode 31a are connected. Further, a second wave plate 37a for adjusting the polarization state of the laser light passing through the first electro-optical element 23a is provided on the emission end side, which is the other end of the first electro-optical element 23a. The laser beam that has passed through the wavelength plate 37a enters the first polarization beam splitter 39a and is converted into a change in the intensity of light separated into P waves and S waves.
[0046]
The two laser beams separated into a P-wave component and an S-wave component by the first polarization beam splitter 39a are condensed by first and second condenser lenses 53a and 53b, respectively, and then the first and second laser beams are condensed. Are received by the photodiodes 55a and 55b.
[0047]
The first and second photodiodes 55a and 55b are connected between the first and second bias voltage sources 59a and 59b and the ground via first and second load resistors 57a and 57b connected in series, respectively. , And operates by receiving a reverse bias voltage of a bias voltage source.
[0048]
When the first and second photodiodes 55a and 55b receive the laser light separated into the P-wave component and the S-wave component by the first polarization beam splitter 39a, respectively, the first and second photodiodes 55a and 55b change according to the intensity of the laser light. Each generates a photocurrent. This photocurrent causes a voltage drop in the first and second load resistors 57a and 57b, respectively, and this voltage drop is output as an output voltage. For example, when a positive-polarity rectangular wave is applied to the signal electrode 29a, a rectangular wave as shown in FIG. 2 is output to the output sides of the first and second photodiodes.
[0049]
The output signals of these rectangular waves are output in opposite phases, such as being output from the first photodiode 55a with a negative polarity and output from the second photodiode 55b with a positive polarity, as shown in the figure. The signal is input to one differential amplifier 71. The first differential amplifier 71 amplifies the difference between the two output signals, and outputs a signal of negative polarity as shown.
[0050]
On the other hand, a third electrode 25b and a fourth electrode 27b are similarly attached to the side surface of the second electro-optical element 23b, and the third and fourth electrodes 25b and 27b have a signal electrode 29b and a ground electrode, respectively. 31b is connected. Further, a fourth wavelength plate 37b for adjusting the polarization state of the laser light passing through the second electro-optical element 23b is provided on the emission end side, which is the other end of the second electro-optical element 23b. The laser beam that has passed through the wavelength plate 37b enters the second polarization beam splitter 39b, and is converted into a change in the intensity of light separated into P waves and S waves.
[0051]
The two laser beams separated into a P-wave component and an S-wave component by the second polarization beam splitter 39b are condensed by third and fourth condensing lenses 63a and 63b, respectively, and then the third and fourth laser beams are condensed. Are received by the photodiodes 65a and 65b.
[0052]
The third and fourth photodiodes 65a, 65b are connected between the third and fourth bias voltage sources 69a, 69b and ground via third and fourth load resistors 67a, 67b connected in series, respectively. , And operates by receiving a reverse bias voltage of a bias voltage source.
[0053]
When the third and fourth photodiodes 65a and 65b receive the laser light separated into the P-wave component and the S-wave component by the second polarization beam splitter 39b, respectively, the third and fourth photodiodes 65a and 65b respond to the intensity of the laser light. Each generates a photocurrent. This photocurrent causes a voltage drop in the third and fourth load resistors 67a and 67b, respectively, and this voltage drop is output as an output voltage. For example, when the positive-polarity rectangular wave applied to the signal electrode 29a is also applied to the signal electrode 29b, a rectangular wave as shown in FIG. 2 is output to the output side of the third and fourth photodiodes. Is output.
[0054]
Output signals of these rectangular waves are output in opposite phases to each other such that they are output from the third photodiode 65a as negative polarity and from the fourth photodiode 65b as positive polarity as shown in the figure. 2 differential amplifier 73. The second differential amplifier 73 amplifies the difference between the two output signals and outputs a positive signal as shown in the figure.
[0055]
As described above, the negative output signal from the first differential amplifier 71 and the positive output signal from the second differential amplifier 73 are input to the third differential amplifier 75, The difference is amplified and a positive polarity signal is output as shown.
[0056]
In the present embodiment, although the light amount of the laser diode 21 is increased, the laser light from the laser diode 21 through the collimating lens is split into two laser lights having the same light amount by the beam splitter 77, and the two laser lights are separated. The light is incident on the first and second electro-optical elements 23a and 23b to change the polarization, and then the respective laser lights are converted into P-wave components and S-wave components by the first and second polarization beam splitters 39a and 39b, respectively. Because of the separation, even if the laser light amount is increased, the light amount to each photodiode is not dispersed and increased as in the conventional case, so that the voltage drop in the load resistance is increased as in the conventional case and applied to the photodiode. If the reverse bias voltage decreases, the photodiode does not operate properly, sensitivity decreases, and communication errors increase. Cormorant problem, the rated problems photodiode, boosting problem of the bias voltage, without the occurrence of heat generation and battery depletion issues, it is possible to achieve high sensitivity electric field detecting optical system.
[0057]
In particular, although the signal component increases due to the increase in the laser light amount, the noise component is removed by the differential amplification in the first to third differential amplifiers 71 to 75 so that the in-phase components cancel each other. Therefore, the S / N can be remarkably improved, and the reverse bias voltage applied to the photodiode can be secured with a sufficient operating voltage without being particularly boosted.
[0058]
In the embodiment shown in FIG. 2, the laser beam that has passed through the collimator lens 33 is split into two laser beams by the beam splitter 77, and is incident on the first and second electro-optical elements 23a and 23b. As described above, the case where two electro-optical elements are used is described, but the present invention is not limited to this, and a plurality of electro-optical elements are provided, and a plurality of laser beams from a collimating lens are provided. It is also possible to adopt a configuration in which the light is divided and incident.
[0059]
In each of the above-described embodiments, the laser beam output from the laser diode 21 is used. However, the present invention is not limited to the laser beam, and may be any device that generates single-wavelength light. (LED). Also, each electro-optical element 23 has been described as detecting an electric field by an electro-optical method using an electro-optical crystal. However, the present invention is not limited to this, and for example, utilizing the magneto-optical phenomenon A magneto-optical element or the like may be used. In the case of an electro-optical element, the shape thereof is preferably, for example, a prism shape, but is not limited to a prism shape, and may be another shape, for example, a cylindrical shape.
[0060]
In each of the above embodiments, the ground electrode 31 is provided corresponding to the signal electrode 29. However, the ground electrode 31 may be connected to, for example, a battery of the apparatus or to a large metal. Function as a ground to improve the coupling of the electric field from the electrode 25 to the electro-optical element 23, but the ground electrode is not always required.
[0061]
【The invention's effect】
As described above, according to the present invention, the polarization of parallel light is changed by the electric field combined by the polarization changing means into which the parallel light is incident, and each parallel light of the opposite phase component emitted from the polarization changing means is changed. It is separated into two parallel light beams having the same light amount, the separated four parallel light beams are converted into an electric signal by photoelectric conversion means, and a signal having the opposite phase is differentially amplified to generate an output signal, thereby improving sensitivity. For this reason, even if the amount of parallel light is increased, the amount of light for each photodiode is dispersed as in the past by separating the laser light into a plurality of laser beams with the same amount of light, and the photodiode operates normally due to the reverse bias problem. Eliminates the problem of reduced sensitivity and increased communication errors, and eliminates problems such as photodiode rating problems, bias voltage boosting problems, and heat and battery consumption problems. Can achieve the optical detector, also the noise component is removed by phase components cancel each other by the differential amplifier, it is possible to significantly improve the S / N.
[0062]
Further, according to the present invention, the polarization of the parallel light is changed by the electric field combined in each of the plurality of polarization changing means into which the parallel light is incident, and the parallel light of the opposite phase component emitted from each polarization changing means is changed. Are respectively separated into two parallel light beams having the same light amount, the separated plurality of parallel light beams are converted into electric signals by photoelectric conversion means, and a signal having the opposite phase among the plurality of electric signals is differentially amplified and output. Since a signal is generated, even if the amount of parallel light is increased to improve sensitivity, it is separated into a plurality of laser beams with the same amount of light, dispersing the amount of light to each photodiode as in the past, and causing a reverse bias problem. The problem that the photodiode does not operate normally, the sensitivity deteriorates, and the communication error increases increases, the problem of the rating of the photodiode, the problem of the boost of the bias voltage, the problem of the heat generation and the consumption of the battery. What occurs without, can achieve high sensitivity electric field detecting optical system, also the noise component is removed by phase components cancel each other by the differential amplifier, it is possible to significantly improve the S / N.
[0063]
Furthermore, according to the present invention, the electric field induced and transmitted by the electric field transmission medium is coupled to the electro-optical element via the first electrode, and parallel light is incident on the electro-optical element. The parallel light emitted from the optical element is separated into a P-wave and an S-wave by an analyzer, and the P-wave and the S-wave are separated into two parallel light beams having the same light amount, and converted into an electric signal by photoelectric conversion means. Since the output signal is generated by differentially amplifying the signal of the opposite phase among the plurality of electric signals, even if the light amount of the parallel light is increased to improve the sensitivity, it is separated into a plurality of laser lights having the same light amount. By dispersing the amount of light to each photodiode as in the past, the problem that the photodiode does not operate normally due to the reverse bias problem, the sensitivity becomes worse, the communication error increases, and the problem of the rating of the photodiode, bias A high-sensitivity electric field detection optical device can be achieved without the problem of pressure boosting, heat generation, battery consumption, and the like, and the noise component is removed by canceling the common-mode components mutually by differential amplification. S / N can be significantly improved.
[0064]
According to the present invention, an electric field induced and transmitted by an electric field transmission medium is coupled to a plurality of electro-optical elements via a first electrode, and a plurality of parallel lights are respectively applied to the plurality of electro-optical elements. Each of the plurality of parallel lights emitted from the plurality of electro-optical elements is separated into a P wave and an S wave by each analyzer, and the P wave and the S wave from each of the plurality of analyzers are respectively converted into photoelectric conversion means. Is converted into a plurality of electric signals to generate an output signal by differentially amplifying a signal of the opposite phase among the plurality of electric signals, so that the amount of parallel light is increased to improve sensitivity. In addition, by separating the laser light into a plurality of laser beams of the same light amount, the light amount for each photodiode is dispersed as in the past, the photodiode does not operate normally due to the reverse bias problem, the sensitivity deteriorates, and the communication error increases. Solve the problem of It is possible to achieve a high-sensitivity electric field detection optical device without causing problems such as photodiode rating problems, bias voltage boost problems, heat generation and battery consumption problems. Are mutually canceled and removed, so that the S / N can be significantly improved.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an electric field detection optical device according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating a configuration of an electric field detection optical device according to another embodiment of the present invention.
FIG. 3 is an explanatory diagram illustrating an example of a case where a wearable computer is mounted on a human via a transceiver and used.
FIG. 4 is a block diagram showing a circuit configuration of a transceiver for attaching a wearable computer to a living body, to which the electric field detection optical device of the present invention is applied.
FIG. 5 is a diagram showing a configuration of a conventional electric field detection optical device.
FIG. 6 is a circuit diagram around a photodiode used in the electric field detection optical device shown in FIG.
[Explanation of symbols]
21 Laser Diode
23 Electro-optical element
25,27 electrodes
29 signal electrode
31 Ground electrode
33 Collimating lens
35, 37 Wave plate
39 Polarizing beam splitter
51,61,77 Beam splitter
53, 63 Condensing lens
55,65 photodiode
57, 67 Load resistance
59,69 bias voltage source
71-75 differential amplifier
79 Prism
100 living body (electric field transmission medium)

Claims (8)

An electric field detection optical device that detects an electric field induced and transmitted by an electric field transmission medium and converts the electric field into an electric signal,
Polarization changing means for receiving parallel light of a single wavelength and changing the polarization of the parallel light in response to an electric field to be combined, and separating and outputting P and S waves orthogonal to each other;
First and second beam splitters for dividing each of the P wave and the S wave emitted from the polarization changing unit into two parallel lights having the same light amount,
First to fourth photoelectric conversion means for converting the four parallel lights separated by the first and second beam splitters into electric signals;
First and second differential amplifiers that respectively input two signals of opposite phases among the four output signals output from the first to fourth photoelectric conversion units and amplify a difference between the two signals;
An electric field detection optical device, comprising: a third differential amplifier that receives output signals of the first and second differential amplifiers as inputs and amplifies a difference between the two signals. An electric field detection optical device that detects an electric field induced and transmitted by an electric field transmission medium and converts the electric field into an electric signal,
A plurality of polarization changing means, each of which receives parallel light of a single wavelength and changes the polarization of the parallel light in response to an electric field to be coupled, and separates and emits P and S waves orthogonal to each other; ,
A plurality of photoelectric conversion means for converting each of the P wave and the S wave respectively emitted from the plurality of polarization changing means into an electric signal;
The differential amplification process of performing differential amplification of a pair of signals of opposite phases among the output signals of the plurality of photoelectric conversion means for all combinations is similarly performed on the differential amplified signal generated by the differential amplification process. And a differential amplifying means for sequentially and repeatedly performing differential amplification processing to generate differentially amplified output signals. The polarization changing means,
An electro-optical element that receives the parallel light and changes optical characteristics in response to an electric field to be coupled,
3. The electric field detection optical device according to claim 1, further comprising an analyzer that separates the parallel light passing through the electro-optical element into a P wave and an S wave and converts the light into a change in light intensity. An electric field detection optical device that detects an electric field induced and transmitted by an electric field transmission medium and converts the electric field into an electric signal,
A light source that emits light of a single wavelength,
A collimating lens that converts light from the light source into parallel light,
An electro-optical element that receives parallel light from the collimating lens and changes optical characteristics in response to an electric field to be coupled;
A first electrode for coupling an electric field induced by the electric field transmission medium to the electro-optical element;
An analyzer that separates the parallel light passing through the electro-optical element into a P wave and an S wave, and converts the light into a change in light intensity;
First and second beam splitters for separating the P wave and the S wave separated by the analyzer into two parallel lights having the same light amount,
First to fourth photoelectric conversion means for converting the four parallel lights separated by the first and second beam splitters into electric signals;
First and second differential amplifiers that respectively input two signals of opposite phases among the four output signals output from the first to fourth photoelectric conversion units and amplify a difference between the two signals;
An electric field detection optical device, comprising: a third differential amplifier that receives output signals of the first and second differential amplifiers as inputs and amplifies a difference between the two signals. An electric field detection optical device that detects an electric field induced and transmitted by an electric field transmission medium and converts the electric field into an electric signal,
A light source that emits light of a single wavelength,
A collimating lens that converts light from the light source into parallel light,
Beam splitter means for dividing the parallel light from the collimating lens into a plurality of parallel lights having the same light amount,
A plurality of electro-optical elements each of which receives a plurality of parallel lights separated by the beam splitter means and changes optical characteristics in response to an electric field to be combined;
A plurality of first electrodes each coupling an electric field induced in the electric field transmission medium to each of a plurality of electro-optical elements;
A plurality of analyzers each of which separates parallel light that has passed through each of the plurality of electro-optical elements into a P wave and an S wave, and converts the light into a change in light intensity;
A plurality of photoelectric conversion means for respectively converting the P wave and the S wave separated by each of the plurality of analyzers into electric signals,
The differential amplification process of performing differential amplification of a pair of signals of opposite phases among the output signals of the plurality of photoelectric conversion means for all combinations is similarly performed on the differential amplified signal generated by the differential amplification process. And a differential amplifying means for sequentially and repeatedly performing differential amplification processing to generate differentially amplified output signals. A first wave plate that is provided close to an incident end face of the electro-optical element to which the parallel light is incident, adjusts a polarization state of the parallel light, and enters the electro-optical element;
A second electrode provided to face the first electrode and functioning as a ground electrode with respect to the first electrode; and a second electrode provided between the electro-optical element and the analyzer and passing through the electro-optical element. The electric field detection optical device according to claim 4, further comprising at least one of the second wave plates that adjusts the polarization state of the parallel light and enters the analyzer. The electric field detection optical device according to claim 4, wherein the light source is a light emitting diode that generates a single wavelength light or a laser light source that generates a laser beam. The electric field detection optical device according to claim 4, wherein the analyzer is a polarization beam splitter.

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