JPH0558726B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Technical Field] The present invention provides a system for detecting biological signals between a plurality of biological signal detection units and a biological signal processing unit that processes the biological signals detected by the biological signal detection units. This invention relates to a biological signal processing device which is connected by an optical transmission means.

[Prior Art] In a conventional biological signal processing device, such as an electrocardiograph, the electrodes and the electrocardiograph body are connected by a metal inductive cord with a length of about 2 m to 3 m, and there is no connection between the two components. connected in direct current.

Then, the detected voltage sent through this induction cord was amplified by the main unit's amplifier circuit, and this amplified signal was actually processed.

[Problems to be solved by the invention] However, the level of the voltage induced by the human body and detected by the electrodes is about several mV, and the part along the human body has a shielding effect, etc., so it does not have much of an effect. The reliability of the detection signal is low due to the effects of various induction noises between the distance from the human body and the electrocardiograph itself, and complicated configurations and controls are required to remove the induction noise. For example, two
In the case of a 40W fluorescent lamp, induced noise of about 4 to 7mV is generated. In addition, various electrostatic and electromagnetic noises come from coolers, induction devices in pumps, etc., and it has been difficult to countermeasures against them.

In addition, since the electrodes and the electrocardiograph body are connected in a direct current manner, if a situation such as deterioration of the insulation performance of the electrocardiograph body occurs, there is a concern that the leakage current may affect the human body. This was a point to consider.

[Means for Solving the Problems] The present invention has been made for the purpose of solving the above-mentioned problems, and as a means for achieving this purpose, the present embodiment has the following configuration.

A biosignal processing device comprising at least two biosignal detection sections that detect an analog biosignal, and a biosignal processing section that processes the analog biosignal detected by the biosignal detection section, the biosignal processing device comprising: a first light transmitting means for directly transmitting the emitted light from the light emitting means to a plurality of biological signal detecting sections; a modulation means for optically modulating the input light from the biosignal processing unit light emitting means, which is incident through the optical transmission means of 1, according to the analog biosignal detected by the biosignal detection unit; a second optical transmission means for returning the light to the processing section; and a second optical transmission means provided in the biological signal processing section.
The apparatus includes a light receiving means for receiving the modulated light from the light transmitting means, and a biological signal processing means for converting the modulated light signal received by the light receiving means into a corresponding electric signal and processing it.

[Function] In the above configuration, the biological signal detection section and the biological signal processing section are connected by an optical transmission means, electrically insulated, and a highly reliable device that is not affected by induced noise etc. is provided. Can be provided.

[Embodiment] An embodiment of the present invention will be described in detail below with reference to the drawings.

[First Embodiment] FIG. 1 is a block diagram of an embodiment according to the present invention, and the following description will explain an example in which the present invention is applied to an electrocardiograph.

In the figure, 1 is the electrocardiograph main body, and the electrocardiograph main body 1 is an electrocardiograph processing unit 2 that processes detection signals from the electrode group using a known method, and emits light of a constant intensity when emitting light.
Each modulated signal from the light source 3 composed of an LED or a semiconductor laser (LD), etc., and the light receiving cables 15, 25, 35, etc. is demodulated and output to the electrocardiogram processing unit 2.
It is composed of an optical demodulator 4 including a light receiving element such as a PIN-PD or APD.

The optical cable (optical fiber) used here is made of a completely electrically insulating material such as well-known fused silica glass, and has a core of 9 μm to 60 μm.
The cladding can be constructed with a thickness of approximately 125μm, making it lightweight, meticulous,
It has advantages such as complete insulation and low dielectric constant. Note that even if this optical cable is made of plastic, the core can be made of 200 μm to 1 mm.

Reference numerals 10, 20, 30, and 40 are electrode units, and since the electrode units all have the same configuration, the configuration will be explained using the electrode unit 10 as an example. That is, the electrode unit 10 includes an electrode section 11, a light modulation section 12,
It is composed of a suction section 13. Also, 14,2
4 and 34 are light output cables, and 15, 25, and 35 are light receiving cables.

In this example, six electrode units are provided for the chest and four units are provided for the extremities.
One of the units (electrode unit 40 in FIG. 1) is a common electrode, and the detected potential from the common electrode becomes the common potential of each of the other electrodes.

In the above configuration, the light sent from the light source 3 of the electrocardiograph main body 1 to the light modulation section 12 etc. via the light output cable 14 etc. is subjected to optical modulation in the light modulation section 12 corresponding to the detected potential from the electrode section 11. , this modulated light is sent to the optical demodulator 4 via a light receiving cable 15 or the like.
This modulated optical signal is then demodulated by the optical demodulator 4, where it is converted into an electrical signal and sent to the electrocardiogram processor 2, where it is processed.

Details of this electrode unit 10 are shown in FIG.

As shown in FIG. 2, the electrode unit consists of an electrode section 101, a light modulation section 102, and an attraction section 103.
A common signal line 45 from a common electrode unit 40 is supplied to the other electrode of the optical modulator 107.

To attach this electrode unit, for example, to a measurement site on a human body, the suction section 103 is pressed to remove the air inside, and the electrode section 101 is pressed against the measurement site, and then the suction section 103 is released. , the air pressure in the space formed between the electrode section 101 and the surface of the measurement site of the human body becomes a low pressure state, the surface skin is drawn into the electrode section 101, and the electrode section 101 is fixed to the measurement site. And Idemitsu cable 10
The light guided into the optical modulator 107 from 4 is optically modulated by the action of the electric field generated between the two electrodes of the optical modulator 107, and is optically demodulated in the electrocardiograph main body 1 via the optical receiving cable 105. It will be sent to Department 4.

In the electrode of this embodiment, at least the inner surface of the electrode 101 is conductive, and by housing the light modulating section 102 inside the electrode section 101, the shielding effect of the electrode section 101 prevents electrically induced noise from the outside. can eliminate the influence of Furthermore,
By surrounding the modulation element, which will be described later, with electrodes, it can be expected that fluctuations in modulated light intensity with respect to temperature due to the pyroelectric effect of the modulation element can be suppressed.

The detailed configuration of the optical modulator 107 is shown in FIG.

In this embodiment, an optical waveguide type modulator (branching interference type optical intensity modulation element which is a single crystal electro-optic crystal) is used. The details of this optical waveguide type modulator are described in, for example, Corona Publishing's ``Light Wave Electronics'' (co-authored by Koyama and Nishihara).

In FIG. 3, a diffused optical waveguide 111 is formed on a Y-cut lithium niobate (LiNbO ₃ ) substrate 110 by patterning by Ti vapor deposition, and positive electrodes 112a, 112 are placed on both sides of the diffused optical waveguide 111.
b and the common electrode 113 are patterned. The incident light from the light output cable is branched to 111.
The first optical path 111b and the second optical path 111b having different optical path lengths due to a
The optical path 111c is split almost equally into two, and each receives opposite phase modulation due to the action of an electric field generated by a difference in the voltages applied to both electrodes 111 and 112. Thereafter, the asymmetrical light waves are combined in the combining section 111d, modulated into intensity light according to the phase difference by the interference effect after the combination, and output to the light receiving cable 105. The optical demodulator 4 demodulates this modulated light. In this optical waveguide type modulator, in order to suppress fluctuations in modulated light intensity due to temperature fluctuations due to the pyroelectric effect, a method is used in which electrodes are provided around the positive electrode and the common electrode to surround them.

Although the above explanation has been given as an example of optical modulation using an optical branching waveguide type modulator, the modulator of the present invention is not limited to this. (effect) may be used. The authors believe that BSO, BGO,
There are crystals such as LiTaO ₃ , LiNbO ₃ , quartz, etc. Especially as Pockels elements for low voltage, BSO, BGO,
LiTaO ₃ , LiNbO ₃ etc. are suitable.

Next, various Pockels γmR matrices necessary for designing these general Pockels elements are shown below.

LiTaO ₃ , LiNbO ₃ (3m group) 0 0 0 0 r ₄₂ −r ₂₂ −r ₂₂ r ₂₂ 0 r ₄₂ 0 0 r ₁₃ r ₁₃ r ₃₃ 0 0 0 ZnS, GaAs, BSO, BGO (24, 43m group) 0 0 0 r ₄₁ 0 0 0 0 0 0 r ₄₁ 0 0 0 0 0 0 r Figure 4a shows the basic configuration when using a vertical modulation element that utilizes the longitudinal effect of an electro-optic crystal of ₄₁ or more. An example of the characteristics of the output voltage obtained with respect to the applied voltage is shown in FIG. 4b.

As shown in the figure, in the vertical modulation element, the incident light is linearly polarized by the polarizer 412, enters the modulation element 400 through the transparent electrode 401, and the incident light is linearly polarized by the polarizer 412.
After being modulated by the action of the electric field generated between 1 and 402, the wavelength plate 413 and polarizer 41
The signal is output through an analyzer 414 having an axis perpendicular to 2. Its output characteristics are linear, but as it is, an applied voltage of several tens of volts is required. In order to improve the sensitivity, it is sufficient to lengthen the optical path, and FIG. 5 shows an example of an optical modulator using the principle of a vertical modulation element configured by extending this optical path.

This electro-optic effect element has dielectric multilayer films 215 and 216 formed on both opposing surfaces of an electro-optic crystal layer 210 made of lithium niobate (LiNbO ₃ ), and uses the dielectric multilayer films 215 and 216 as electrodes. At the same time, it also functions as a reflective film for the electro-optic crystal layer 210. Idemitsu cable 104
The light incident through the polarizer 212 is linearly polarized and enters the electro-optic crystal layer 210. This linearly polarized light is reflected by each of the dielectric multilayer films 215 and 216 in the electro-optic crystal layer 210, thereby extending the optical path and improving its sensitivity.
Then, at the exit of the optical path, there is a light filter 2 which is a λ/4 wavelength plate.
13 is disposed, and further an analyzer 214 having an axis orthogonal to the polarizer 212 is disposed. In this example, in order to lengthen the optical path, the electro-optic crystal layer 2
10 is set at approximately 5 degrees.

Here, the common signal line 4 is connected to the dielectric multilayer film 216.
5, a common potential is applied to the dielectric multilayer film 21.
When the detection potential from the electrode is applied to the electrode 5 through the signal line 108, the passing light becomes elliptically polarized light due to the electric field generated between the two electrodes, and since the degree of polarization is proportional to the electric field intensity, it is determined by the analyzer that it is proportional to the applied voltage. A light intensity modulated output is obtained. This modulated light is received by the light receiving cable 1.
05 to the optical demodulator 4.

Note that the present invention is not limited to this example of a configuration using a vertical modulation element, and the modulator can also be configured with a horizontal modulation element instead of a vertical modulation element. The basic configuration when using this horizontal modulation element is shown in Figure 6a.
FIG. 6b shows an example of the characteristics of the output voltage obtained with respect to the applied voltage.

In FIG. 6a, the light linearly polarized by the polarizer 412 and incident on the modulation element 420 is modulated by the action of the electric field generated between the electrodes 421 and 422, and then It is outputted via an analyzer 414 having a .

Also in this horizontal modulation element, the sensitivity is determined by the optical path length. That is, the sensitivity is determined by the length l in the longitudinal direction, and the sensitivity improves as l becomes longer. for example
For a crystal of 0.5 mm x 0.5 mm x 3 cm, an applied voltage of 2 to 3 V
A phase change of 0.1π is obtained.

That is, the phase change is δ=π/λ ₀ n ³ _e r ₃₃ y/dV.

Although it is possible to design a horizontal modulation element in this way, this modulation element has the disadvantage that the phase change easily changes depending on the temperature. To compensate for this drawback, as shown in FIG. 7a, crystals 450 and 460 of equal length cut out from the same crystal may be connected in series with their crystal axes at right angles.

FIG. 7b shows the temperature characteristics before and after compensation of the modulator subjected to temperature compensation as shown in FIG. 7a. In this way, constant output can be obtained over a wide temperature range. An example of the characteristics of the output voltage with respect to the temperature-compensated applied voltage is shown in FIG. 7c.

Note that these crystals are not arranged in a single vertical row,
Two rows are arranged in parallel, and the incident light at the light exit of one crystal is 90
The length can be shortened by deflecting the incident light by 90 degrees at the input position of the other crystal arranged in parallel so that the incident light enters the other crystal.

Furthermore, a configuration may be adopted in which a reflecting plate is provided at one end of the crystal and the incident light is reflected by this reflecting plate. In the case of this configuration, the volume can be particularly reduced, and the modulator can be made small. Furthermore, when a polarization maintaining optical cable, which will be described later, is used, the mirror can be omitted as a result, resulting in a very simple configuration. That is, in the modulator using the above electro-optical element, the polarizer, analyzer, and light filter can be omitted.

In addition, in this example, if a large number of cables are connected to the electrocardiograph main body, and this poses a problem in terms of handling or cost, an optical distributor such as PLZT is inserted in the middle to connect the main body side. cables can be reduced.

Note that the above explanation has been given for an example in which the modulator is directly modulated by the detection output from the electrode 101, but if the detection potential from the electrode 101 is too small to directly modulate the light, the detection output from the electrode 101 can be amplified once using an amplifier.

FIG. 8 shows an example in which the electrode unit is equipped with an amplifier for amplifying the detection output from the electrode 101.

Components in the figure that are the same as those in FIG. 1 are designated by the same numbers, and explanations thereof will be omitted.

The electrocardiograph main body 1 is equipped with an energy light source 5 that emits light at a predetermined intensity or higher at all times, and the energy light source 5 supplies light energy to each electrode unit 10, 30, etc. via energy supply optical cables 16, 36, etc. Each electrode unit 10, 30, etc. converts this light energy into electric power with an optical-to-electrical converter 301 composed of a solar cell or the like, and transfers this electric power to the signal line 3.
03 to the amplifier 302. Note that the energy light source 5 has a wavelength of 0.78 μm and an output of approximately
It is composed of a 5 mW semiconductor laser, and the energy supply optical cable 16 and the like are composed of, for example, a step index type optical fiber with a diameter of about 200 μm.

Further, an electrode 101 is connected to one terminal of the amplifier 302.
The detection output from the terminal is supplied to the other terminal, and the common potential supplied via the common signal line 45 is supplied to the other terminal. Therefore, the detection signal from electrode 101 is amplified by amplifier 302, and this amplified signal is applied to the positive electrode of optical modulator 107 to perform optical modulation.

On the other hand, the reason why the electrocardiograph main body is equipped with the energy light source 5 is that if high-intensity light is irradiated from the electrocardiograph body, the light-to-electricity converter 301 on the electrode unit side can be downsized and is not affected by the usage environment. ,
This is to provide a highly reliable device. If used in an environment with sufficient ambient light intensity, energy light source 5
Regardless of the supplied light, the light is generated by incident light from the surroundings.
It can be configured to perform electrical conversion. In this case, in addition to the configuration shown in FIG. 1, it is sufficient to simply add an optical-to-electrical converter 301 and an amplifier 302 to the electrode unit.

Details of this optical-electrical converter 301 are shown in FIG.

The optical-electrical converter 301 includes a solar cell 311, a backflow prevention diode 312, a capacitor 313,
It is composed of a voltage regulator 314 and the like, and the capacitor 313 has a large capacity with little leakage current.The capacitor 313 stores the output from the solar cell 311 in the form of charge for a long time, and reduces the ambient light intensity. It is configured to be able to operate even in an unstable environment with insufficient security. capacitor 3
13, a secondary battery may be used. Further, the voltage regulator 314 is used to keep the output voltage from the photoelectric converter 301 constant regardless of the output voltage from the solar cell 311 which is influenced by the light intensity.

[Second Embodiment] The above explanation is based on transmitting light from the electrocardiograph main body 1 using the light output cable 14 and the like, and also using the light receiving cable 15.
An example in which modulated light from the electrode unit 10 is transmitted has been described in the above, but instead of transmitting light using these two cables, it is also possible to transmit the light using a single cable. In this case, a polarization maintaining cable may be used as the optical cable.

An example of an electrocardiograph using this polarization maintaining cable is shown in FIG. In FIG. 10, the same components as in FIG. 1 or FIG. 8 are given the same numbers, and their explanations are omitted.

In the electrocardiograph body 1, light from a light source 3 that is composed of an LED or a semiconductor laser (LD) and emits light of a constant intensity is linearly polarized by a polarizer 7, and then output to a polarizing beam splitter 6. be done. The polarizing beam splitter 6 converts the light from the polarizer 7 into a polarization-maintaining optical cable (polarization-maintaining optical fiber) 6.
1, 62, 63, ... and receives each modulation signal corresponding to the detection signal from the living body, which is sent from each electrode via polarization maintaining optical cables 61, 62, 63, .... The signals are separated and output to the demodulator 4.

The detailed configuration of the detection electrode unit and the electrocardiograph main body 1 of this embodiment will be explained with reference to FIG. 11.

In FIG. 11, the optical cable (fiber) between the electrocardiograph main body 1 and each electrode unit is composed of one cable 530, 510 is a polarization maintaining optical cable for signal transmission, and 520 is an energy supply optical cable. .

The detection output from the electrode 101 is supplied to one terminal of the amplifier 328, and the common potential supplied via the common signal line 45 is supplied to the other terminal. Therefore, the detection signal from the electrode 101 is amplified by the amplifier 328, and this amplified signal is sent to the modulator 32.
3 is applied. On the other hand, polarization maintaining optical cable 5
10 (61 in Fig. 10), the electrocardiograph main body 1
The polarized light sent from the polarized beam splitter 3
22 and enters the modulator 323. Therefore, the polarized light is optically modulated by the action of the electric field generated between both electrodes of the modulator 323 by the voltage applied by the amplifier 328 and corresponding to the detected biological signal. The mirrors 325 and 32 pass through an analyzer 324 disposed at the exit of the modulator 323.
6 and 327, the optical paths are changed by 90 degrees as shown in the figure, and the beams enter the polarizing beam splitter 322 again. and polarizing beam splitter 322
As a result, modulated light having a polarization orthogonal to the polarized light from the electrocardiograph main body 1 is output to the polarization-maintaining optical cable 510. This modulated light is transmitted to the electrocardiograph body 1
The light is sent to a polarization beam splitter 6, where it is separated and sent to an optical demodulator 4. Here, it is converted into an electrical signal proportional to the modulated light intensity, demodulated, and sent to the electrocardiogram processing section 2. Note that the optical demodulator 4 demodulates this modulated signal by performing division processing and the like.

The optical cable 520 in FIG. 11 is changed to a polarization-maintaining optical cable 510 for signal transmission as shown in FIG. 12.
By bundling the optical energy supplying cable 520 and the optical energy supplying fiber 520, and by bundling not one optical energy supplying fiber 520 but a plurality of optical energy supplying fibers 520, a large amount of optical energy can be sent. As a result, the solar cell 31
There are many advantages such as being able to increase the output power compared to 1 and improving the stability of the device.

With this configuration, it is possible to connect the electrocardiograph and the electrode unit with only one cable.

Furthermore, since the optical cable does not receive any electrical induction noise, there is no need for the electrocardiograph to have a complicated structure for removing induction noise, and it is possible to provide an electrocardiograph with high reliability and low cost.

Although the above description describes an example in which the present invention is applied to an electrocardiograph, the present invention is not limited to this and can be applied to any biological signal processing device. That is, in the case of an electroencephalograph that detects the brain waves of a living body, the electrodes for detecting brain waves and the main body of the electroencephalograph may be connected with an optical cable in the same way. It can also be applied to devices equipped with detection units for all kinds of biological signals, such as electromyographs, various devices for detecting heart sounds, and blood pressure monitors. In these cases as well, the same effects as in this embodiment can be provided.

[Effects of the Invention] As explained above, according to the present invention, there is no need to provide the biosignal detection section with a light emitting means that consumes a large amount of power, and a large-capacity power supply for this purpose is no longer required. It is possible to make a compact calibration, and it is also possible to incorporate all the components into the detection electrode section attached to the living body.

Furthermore, the biological signal processing section and the biological signal detection section are connected by an optical transmission means such as an optical cable that can be completely electrically insulated, so that the insulation properties of the biological signal processing device are taken into consideration. Even if not, no leakage current will flow into the human body, and any adverse effects on the subject can be completely prevented.

In addition, by using an optical transmission means such as an optical cable, it is hardly affected by electrically induced noise, so there is no need to equip the biological signal processing device with a complicated configuration for removing induced noise, resulting in high reliability and cost. We can provide cheap products.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment according to the present invention, and FIG.
The figure is a detailed configuration diagram of the electrode unit of this example.
The figure shows a detailed configuration example of an optical waveguide modulator, FIG. 4a shows the basic configuration of a vertical modulation element,
Figure b shows the output characteristics of a vertical modulation element, Figure 5 shows the detailed configuration of a modulator using a vertical modulation element, and Figures 6a and 7a show the basic configuration of a horizontal modulation element. FIG. 6b and FIG. 7c are diagrams showing the output characteristics of the horizontal modulation element, and FIG. FIG. 8 is a configuration diagram of another embodiment according to the present invention,
FIG. 9 is a diagram showing the detailed configuration of the optical-electrical converter, and FIG. 10 is a configuration diagram of still another embodiment according to the present invention.
FIG. 11 is a detailed configuration diagram of the embodiment shown in FIG.
FIG. 12 is a diagram showing the detailed configuration of the optical cable. In the figure, 1... electrocardiograph main body, 2... electrocardiogram processing section,
3... Light source, 4... Optical demodulator, 5... Energy light source, 6,322... Polarizing beam splitter, 7,
212,412...Polarizer, 10,20,30,
40... Electrode unit, 11, 21, 31, 4
1,101...electrode, 12,102...light modulation section, 13,103...suction section, 14,24,3
4,104...Idemitsu cable, 15,25,3
5,105...Light receiving cable, 16,36...Energy supply optical cable, 45...Common signal line,
61-63...Polarization maintaining optical cable, 110,
210,400,420,450,460...electro-optic crystal, 111...diffusion optical waveguide, 112...
...Positive electrode, 113...Common electrode, 213...Photometer, 214,414...Analyzer, 215,21
6... Dielectric multilayer film, 301... Optical-electric converter, 302, 328... Amplifier, 323... Modulator, 324... Analyzer, 325-327... Mirror, 308... Amplifier, 311... ...Solar cell, 3
14... Voltage regulator, 530... Optical cable.

Claims (1)

[Claims] 1. A biosignal processing device comprising at least two biosignal detection units that detect analog biosignals and a biosignal processing unit that processes the analog biosignals detected by the biosignal detection units. a light emitting means for outputting light, which is included in the biological signal processing section; a first light transmission means for directly transmitting light emitted from the light emitting means to the plurality of biological signal detection sections; a modulation means for optically modulating input light from the biosignal processing unit light emitting unit, which is incident through the first light transmission unit included in the signal detection unit, according to an analog biosignal detected by the biosignal detection unit; , a second light transmission means for returning the modulated light of the modulation means to the biological signal processing section; and a light receiving means for receiving the modulated light from the second light transmission means provided in the biological signal processing section. A biosignal processing device comprising: a biosignal processing device that converts a modulated optical signal received by the light receiving device into a corresponding electrical signal and processes it. 2. The biological signal processing device according to claim 1, wherein the first and second optical transmission means are one polarization maintaining optical cable. 3. The biological signal processing device according to claim 1, wherein the first and second optical transmission means are each one optical cable. 4. The biological signal processing device according to any one of claims 1 to 3, wherein the modulation means performs modulation processing using an electro-optic effect element. 5. The biological signal processing device according to any one of claims 1 to 3, wherein the modulation means performs modulation processing by an optical waveguide modulator.