Abstract:
Disclosed herein is a biosignal detecting electrode which includes a rotary part which is rotatably attached on a brace mountable on a living body and has a first side that joins to the brace and a second side opposite to the first side, and a plurality of electrode terminals attached to the rotary part in such a way that they obliquely project from the second side of the rotary part.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to Japanese Priority Patent Application JP 2010-262978 filed in the Japan Patent Office on Nov. 25, 2010, the entire content of which is hereby incorporated by reference. 
       BACKGROUND 
       [0002]    The present application relates to a biosignal detecting electrode and a biosignal detecting device equipped therewith, the biosignal detecting electrode is designed to detect biosignals when brought into contact with the site of a human or animal body where there exists hair. 
         [0003]    It is common practice to analyze electrical signals (or biosignals), such as electroencepharogram and electromyogram, in order to grasp a human&#39;s or animal&#39;s health state. Measurement of such biosignals is usually accomplished by means of a measuring electrode brought into contact with the site of a human body for measurement. If the site for measurement is a hair-growing one, there will be an instance in which the hair existing between the skin and the measuring electrode prevents electrical contact between them. 
         [0004]    Under these circumstances, there has been developed a device for measuring biosignals which is equipped with an electrode to acquire biosignals at the site where there exists hair. For example, Japanese Patent Laid-open No. Sho 62-231621 (The upper right portion of the third page, and FIG. 7) (hereinafter referred to as Patent Document 1) discloses “Head set for measurement of electroencepharogram” which is equipped with an electrode of bundled silver wires. The bundled silver wires are impregnated with an electrolytic solution, and the electrode of bundled silver wires is brought into contact with the patient&#39;s head. 
       SUMMARY 
       [0005]    The electrode of bundled silver wires disclosed in Patent Document 1 suffers the disadvantage of causing pain to the patient when it is brought into contact with the patient&#39;s head. Moreover, the tightly bundled silver wires prevent the electrode from complete contact with the scalp in the presence of hair. 
         [0006]    The foregoing motivated the present application, which is intended to provide a biosignal detecting electrode that can be brought into contact with the skin without being hindered by hair. 
         [0007]    According to one embodiment, the biosignal detecting electrode is composed of a rotary part and a plurality of electrode terminals. 
         [0008]    The rotary part is rotatably attached to a brace that can be mounted on a living body. It has a first side attached to the brace and a second side opposite to the first side. 
         [0009]    The electrode terminals project obliquely from the second side of the rotary part. 
         [0010]    The foregoing structure permits the electrode terminals, which project obliquely with respect to the second side, to move hair aside and come into good contact with the skin as the rotary part rotates. 
         [0011]    The rotary part is capable of rotation on the axis which is a straight line passing though the centers of the first and second sides. The electrode terminals are arranged rotationally symmetrical with respect to the axis. In addition, the electrode terminals are exactly or approximately uniform in length from the first side to their tips. 
         [0012]    The electrode terminals constructed as mentioned above come into complete contact with the skin because they have their tips evenly positioned and have their contact pressure evenly distributed. 
         [0013]    The electrode terminals may be formed from a liquid holding material impregnated with an electrolytic solution. 
         [0014]    With the foregoing structure, the electrode terminals achieve good electrical contact with the skin because they permit the electrolytic solution to ooze out of them when they come into mechanical contact with the skin. 
         [0015]    The electrode terminals may be formed from any elastic material. 
         [0016]    The resulting electrode terminals deform in conformity with the shape of the skin, thereby coming into close contact with the skin. 
         [0017]    According to one embodiment, the biosignal detecting device is composed of an attaching brace, a rotary part, and electrode terminals. 
         [0018]    The attaching brace is intended to attach the biosignal detecting device to the patient&#39;s body. 
         [0019]    The rotary part is rotatably mounted on the attaching brace. It has a first side fixed to the attaching brace and a second side opposite to the first side. 
         [0020]    The electrode terminals project obliquely from the second side of the rotary part 
         [0021]    The electrode terminals projecting obliquely from the second side move hair aside for their complete contact with the skin. 
         [0022]    The biosignal detecting device mentioned above may additionally have a driving mechanism to turn the rotary part and a control unit to control the driving mechanism in response to the contact resistance of the electrode terminals. 
         [0023]    The control unit determines the degree of contact between the electrode terminals and the skin and controls the rotation of the rotary part according to the result of determination. This automatically ensures good contact between the electrode terminals and the skin. 
         [0024]    As mentioned above, the present disclosure provides a biosignal detecting electrode which can be brought into contact with the skin, with hair moved aside. 
         [0025]    Additional features and advantages are described herein, and will be apparent from the following Detailed Description and the figures. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0026]      FIG. 1  is a perspective view showing the biosignal detecting device according to the first embodiment; 
           [0027]      FIG. 2  is a perspective view showing the parietal electrode of the same biosignal detecting device as above; 
           [0028]      FIG. 3  is a perspective view showing the parietal electrode of the same biosignal detecting device as above, with the attaching brace removed; 
           [0029]      FIGS. 4A and 4B  are a plan view and a side view, respectively, showing the structure of the electrode terminals of the parietal electrode of the same biosignal detecting device as above; 
           [0030]      FIG. 5  is a sectional view showing the structure of one of the electrode terminals of the parietal electrode of the same biosignal detecting device as above; 
           [0031]      FIG. 6  is a block diagram illustrating the functional structure of the same biosignal detecting device as above; 
           [0032]      FIG. 7  is a block diagram illustrating the circuit structure of the signal processing unit of the biosignal detecting device; 
           [0033]      FIG. 8  is a block diagram illustrating the functional structure of the biosignal detecting device according to the second embodiment; and 
           [0034]      FIG. 9  is a flow chart showing the action of the same biosignal detecting device as above. 
       
    
    
     DETAILED DESCRIPTION 
     The First Embodiment 
       [0035]    The following is a description of the first embodiment. 
       [Structure of the Biosignal Detecting Device] 
       [0036]      FIG. 1  is a perspective view showing the biosignal detecting device  1  according to the first embodiment. 
         [0037]    The biosignal detecting device  1  has the head band  21  to be supported on the patient&#39;s head. To the head band  21  are connected the parietal electrode  22 , the occipital electrode  23 , the right electro-ocular electrode  24 , the left electro-ocular electrode  25 , the right reference electrode  26 , the left reference electrode  27 , and the enclosure  29 . 
         [0038]    The head band  21  is a member extending from the forehead to the parietal and occipital of the patient. It takes on an arched shape that fits to the patient&#39;s head. Moreover, the head band  21  holds the patient&#39;s head with its elastic force. The head band  21  has four arms  21   a  each supporting the right electro-ocular electrode  24 , the left electro-ocular electrode  25 , the right reference electrode  26 , and the left reference electrode  27 . The shape of the head band  21  may be properly varied 
         [0039]    The parietal electrode  22  comes into contact with the patient&#39;s parietal, and the occipital electrode  23  comes into contact with the patient&#39;s occipital. The parietal electrode  22  and the occipital electrode  23  are intended to measure the patient&#39;s electroencephalogram (EEG). Since they are placed on the patient&#39;s sites where there exist hair, it is necessary that they come into contact with the scalp directly (with hair moved aside) so that they effectively acquire the EEG. Their structure to achieve this object will be detailed later. 
         [0040]    The right electro-ocular electrode  24  comes into contact with the patient&#39;s right temple, and it is a flat electrode made of conductive material. It is attached to the arm  21   a  extending from the head band  21  to the patient&#39;s right temple when the patient wears the biosignal detecting device  1 . Similarly, the left electro-ocular electrode  25  comes into contact with the patient&#39;s left temple, and it is a flat electrode made of conductive material. It is attached to the arm  21   a  extending from the head band  21  to the patient&#39;s left temple when the patient wears the biosignal detecting device  1 . The right electro-ocular electrode  24  and the left electro-ocular electrode  25  are intended to measure the patient&#39;s eye movement. 
         [0041]    The right reference electrode  26  comes into contact with the back of the patient&#39;s earlobe, and it is a flat electrode made of conductive material. It is attached to the arm  21   a  extending from the head band  21  to the patient&#39;s right ear when the patient wears the biosignal detecting device  1 . It has the earlobe holder  26   a  which holds the earlobe in conjunction with it as it is positioned on the front of the earlobe. Similarly, the left reference electrode  27  comes into contact with the back of the patient&#39;s earlobe, and it is a flat electrode made of conductive material. It is attached to the arm  21   a  extending from the head band  21  to the patient&#39;s left ear when the patient wears the biosignal detecting device  1 . It has the earlobe holder  27   a  which holds the earlobe in conjunction with it as it is positioned on the front of the earlobe. 
         [0042]    The enclosure  29  is attached to the head band  21  in such a way that it permits the patient to easily wear the biosignal detecting device  1 . It contains electronic components such as processor, memory, and communication interface. The head band  21  and the arms  21   a  are provided with wiring (not shown) for connection with the electrodes and the electronic components. 
       [Structure of the Parietal Electrode and the Occipital Electrode] 
       [0043]    The following is a detailed description of the parietal electrode  22  and the occipital electrode  23 . Since these constituents are of the same structure, the description is limited to the former. 
         [0044]      FIG. 2  is a perspective view showing the structure of the parietal electrode  22 . 
         [0045]    The parietal electrode  22  is composed of the base  30 , the four electrode terminals  31 , and the support  32 . The base  30  is connected to the head band  21 . The electrode terminals  31  are mounted on the base  30 . In addition, the support  32  on the base  30  partly covers the electrode terminals  31 .  FIG. 3  is a perspective view showing the parietal electrode  22 , with the support  32  removed. 
         [0046]    The base  30  is a flat member made of conductive material. It is rotatably supported on the head band  21 , so that the parietal electrode  22  can be turned by the patient. Alternatively, the base  30  may be so designed as to be turned by a rotary drive (such as motor) or a mechanical power source, as mentioned later. As the base  30  turns relative to the head band  21 , the parietal electrode  22  entirely turns relative to the head band  21 . The base  30  has wiring (not shown) for connection with electronic components contained in the enclosure  29 . 
         [0047]    The support  32 , which is fixed to the base  30 , covers the electrode terminals  31  in such a way that at least the top of each electrode terminals  31  is exposed. It is formed from a flexible material such as polyurethane. It may take on any shape, such as cylinder and truncated cone. 
         [0048]    The rotary part  35  is composed of the base  30  and the support  32 . It turns, relative to the head band  21 , together with the electrode terminals  31 . It has the first side  35   a  (which is away from the head band  21 ) and the second side  35   b  (which is in contact with the head band  21 ). It turns around the axis which is the straight line connecting the center of the first side  35   a  and the center of the second side  35   b . This line is represented by L in  FIG. 2 . 
         [0049]    The electrode terminals  31  are rod-like members formed on the base  30 .  FIGS. 4A and 4B  are a top view and a side view both showing the structure of the electrode terminals  31 . There are four electrode terminals  31  in this embodiment; however, their number may be changed to three or five or more. The electrode terminals  31  are arranged (on the second side  35   b ) rotationally symmetrical with respect to the axis (or the line L) 
         [0050]    To be more specific, the electrode terminals  31  are inclined at a certain angle toward the plane on which their tips are positioned. The direction of inclination may be the direction in which the parietal electrode  22  turns. Incidentally, the parietal electrode  22  may rotate in either clockwise and counterclockwise directions but the electrode terminals  31  should be inclined in only one direction. 
         [0051]    The electrode terminals  31  are constructed such that they have exactly or approximately equal distances from the first side  35   a  to their tips. Owing to this structure, the electrode terminals  31  have their tips positioned uniformly on a plane and they receive stress evenly when the biosignal detecting device  1  is brought into contact with the patient&#39;s head. The fact that the electrode terminals  31  are inclined at the same angle keeps them in contact with the skin at approximately equal angles, which ensures their effective contact with the skin. 
         [0052]    The electrode terminal  31  is constructed as shown in  FIG. 5  which is a sectional view. It is composed of the core  33  and the liquid holding part  34  covering the core  33 . The core is made of stiff material such as metal and plastics. The liquid holding part  34  is made of any material capable of holding a liquid, such as felt, hard felt, felt pen refill, compressed fibrous plastics, and porous plastics. The liquid holding part  34  is impregnated with an electrolytic solution, such as a 30:70 mixture of physiological saline (containing 1% sodium chloride) and glycerin. 
         [0053]    The electrode terminal  31  will have elasticity when the core  33  and the liquid holding part  34  are formed from adequate materials, so that it deforms in conformity with the object for its close contact. 
         [0054]    The above-mentioned structure of the parietal electrode  22  is also applied to the occipital electrode  23 . Both the parietal electrode  22  and the occipital electrode  23  are rotatably supported on the head band  21 . They can be turned by the patient&#39;s hand or by a drive mechanism, such as motor (not shown), mounted on the head band  21 . The drive mechanism may be one which produces a rotary movement when they are pushed against the head band  21 . 
         [0055]    Although the biosignal detecting device  1  according to this embodiment is originally designed to be mounted on the patient&#39;s head, it may also be mounted on any other sites where hair grows. Moreover, it may also be applied to any haired animals. In such cases, the biosignal detecting device  1  will be properly modified in shape according to the object to which it is applied. Incidentally, the biosignal detecting device  1  according to this embodiment will be applied satisfactorily to any hairless site of humans and animals. 
       [Functional Structure of the Biosignal Detecting Device] 
       [0056]      FIG. 6  is a block diagram illustrating the functional structure of the biosignal detecting device  1 . 
         [0057]    As shown in  FIG. 6 , the biosignal detecting device  1  is composed of the parietal electrode  22 , the occipital electrode  23 , the right electro-ocular electrode  24 , the left electro-ocular electrode  25 , the right reference electrode  26 , the left reference electrode  27 , the signal processing unit  40 , and the communication interface (IF)  41 . The last two components are electronic components such as processor and memory, which are contained in the enclosure  29 . 
         [0058]    The parietal electrode  22 , the occipital electrode  23 , the right electro-ocular electrode  24 , the left electro-ocular electrode  25 , the right reference electrode  26 , and the left reference electrode  27  are connected to the signal processing unit  40  through wiring attached to the head band  21 . The signal processing unit  40  is connected to the communication IF  41 . 
         [0059]    The signal processing unit  40  is typically constructed as explained below.  FIG. 7  is a block diagram illustrating the circuit structure of the signal processing unit  40 . As shown in  FIG. 7 , the signal processing unit  40  is composed of the operational amplifier  42 , the filter  43 , the A/D converter  44 , the analyzer  45 , and the memory  46 . The operational amplifier  42  is connected to the parietal electrode  22 , the occipital electrode  23 , the right electro-ocular electrode  24 , the left electro-ocular electrode  25 , the right reference electrode  26 , and the left reference electrode  27 . The operational amplifier  42 , the filter  43 , the A/D converter  44 , the analyzer  45 , the memory  46 , and the communication IF  41  are sequentially connected one after another. 
         [0060]    The operational amplifier  42  amplifies the potential difference (as biosignals) between the parietal electrode  22  and the right reference electrode  26  and between the occipital electrode  23  and the left reference electrode  27 . The thus amplified biosignals are sent to the filter  43 , which removes signal components outside the frequency band set up therein and the remaining signal components are sent to the A/D converter  44 . 
         [0061]    The frequency band which is set up in the filter  43  includes δ-wave (1 to 3 Hz), θ-wave (4 to 7 Hz), α-wave (8 to 13 Hz), β-wave (14 to 30 Hz), γ-wave (31 to 64 Hz), ω-wave (65 to 128 Hz), ρ-wave (129 to 512 Hz), and σ-wave (513 to 1024 Hz). All or part of these frequency bands are set up in the filter  43  as the frequency bands for measurement. 
         [0062]    The A/D converter  44  converts biosignals into digital signals and sends the converted signals to the analyzer  45  which analyzes the biosignals. The analyzing process includes the determination of the sleep stage which denotes the degree of the patient&#39;s sleep. The analyzer  45  stores biosignals and analyzed results in the memory  46  and then sends them out through the communication IF  41 . 
         [0063]    The foregoing is a description of the structure of the biosignal detecting device  1 . Incidentally, the structure mentioned above may have an additional electrode for acquisition of biosignals from the patient&#39;s site other than mentioned above. 
       [Action of the Biosignal Detecting Device] 
       [0064]    The biosignal detecting device  1  is attached to the patient for its operation. It may be used not only for humans but also for animals (especially haired ones). During its operation, the parietal electrode  22  and the occipital electrode  23  rotate while being pressed against the patient&#39;s head. This rotation may be achieved by the patient or the drive mechanism attached to the biosignal detecting device. 
         [0065]    The parietal electrode  22  and the occipital electrode  23 , both in rotary motion, cause their terminals  31  to move aside hair so that they come into direct contact with the scalp. The rotary motion may be one turn (or more) or half turn. The electrode terminals  31  may obliquely move hair aside for their easy contact with the skin. Moreover, they come into contact with the scalp without causing pain to it because they are made of elastic material, and they achieve good electrical contact with the scalp because they are impregnated with an electrolytic solution. 
         [0066]    Described above is the way in which the parietal electrode  22  and the occipital electrode  23  achieve their contact with the patient&#39;s scalp. The right electro-ocular electrode  24  and the left electro-ocular electrode  25  come into direct contact with the patient&#39;s hairless skin. Each electrode acquires biosignals and sends them to the signal processing unit  40 , which processes them and sends out the processed signals to external devices through the communication IF  41 . 
       The Second Embodiment 
       [0067]    The following is a description of the second embodiment. Incidentally, identical structures in the first and second embodiments are denoted by identical reference symbols without repeated explanation. 
       [Functional Structure of the Biosignal Detecting Device] 
       [0068]      FIG. 8  is a block diagram illustrating the functional structure of the biosignal detecting device according to the second embodiment. 
         [0069]    As shown in  FIG. 8 , the biosignal detecting device  101  is basically of the same structure but additionally has the drive mechanism  102  to rotate the parietal electrode  22 , the drive mechanism  103  to rotate the occipital electrode  23 , and the drive mechanism control unit  104  for their control, which is connected to the signal processing unit  40  and also to the drive mechanisms  102  and  103 . 
         [0070]    The drive mechanism  102 , which may be a motor, causes the parietal electrode  22  to rotate relative to the head band  21 . Likewise, the drive mechanism  103 , which may be a motor, causes the occipital electrode  23  to rotate relative to the head band  21 . The drive mechanism control unit  104  controls electric power to be applied to the drive mechanisms  102  and  103 , thereby controlling the rotation of the parietal electrode  22  and the occipital electrode  23 . It may rely for its function on the electronic components, such as processor, contained in the enclosure  29 . 
       [Action of the Biosignal Detecting Device] 
       [0071]      FIG. 9  is a flow chart showing the action of the biosignal detecting device  101 . In Step St 1 , the drive mechanism control unit  104  causes the drive mechanisms  102  and  103  to rotate through a prescribed angle, with the biosignal detecting device  101  mounted on the patient&#39;s head. 
         [0072]    In Step St 2 , the drive mechanism control unit  104  measures the contact resistance of the parietal electrode  22  and the occipital electrode  23 . The contact resistance may be measured by the fall-off-potential method, for example. In Step St 3 , comparison is made between the thus measured contact resistance and the previously established threshold value. If the result of comparison is “Yes” or the former is smaller than the latter, Step St 3  continues to Step St 4 . This result suggests that the terminals  31  of the parietal electrode  22  and the occipital electrode  23  are in good contact with the patient&#39;s scalp. In Step St 4 , the biosignal detecting device  101  measures biosignals in the same way as in the first embodiment. 
         [0073]    If the result of comparison in Step St 3  is “No” or the contact resistance is larger than the threshold value, the drive mechanism control unit  104  determines that the terminals  31  of the parietal electrode  22  and the occipital electrode  23  are not in good contact with the patient&#39;s scalp. In this case, the flow returns to Step St 1  so that the drive mechanism control unit  104  causes the drive mechanisms  102  and  103  to rotate again. And subsequent steps St 2  and St 3  are repeated so that the contact resistance of the parietal electrode  22  and the occipital electrode  23  is measured and the rotation of the parietal electrode  22  and the occipital electrode  23  is repeated until the contact resistance becomes smaller than the threshold value or the electrode terminals  31  come into good contact with the scalp. In this way, the biosignal detecting device  101  automatically brings the electrode terminals  31  into good contact with the scalp. 
         [0074]    The present disclosure is not restricted by the embodiments mentioned above but may be modified and changed variously within the scope thereof. 
         [0075]    It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present subject matter and without diminishing its intended advantages. It is therefore intended that such changes and modifications be covered by the appended claims.