Abstract:
A mobile terminal capable of measuring a biological signal is provided. The terminal comprises a terminal body; an electrode for human body earth or system reference, placed on an outer surface of the terminal body so as to be contactable with the skin of a user of the mobile terminal; and differential electrodes. The measured biological signals include an electromyography signal and an electroencephalogram signal. The differential electrodes can be external to the terminal body and be connected via lead lines to the terminal body.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention generally relates to mobile terminals capable of measuring biological signals, and specifically relates to such a mobile terminal having an electrode for human body earth or system reference, placed on an outer surface of a terminal body.  
           [0003]    2. Description of the Related Art  
           [0004]    For example, when a handicapped person such as a person having no laryngopharynx or the oral part of pharynx after undergoing a laryngectomy tries to speak in vain, what the person is trying to speak can be determined by detecting perioral muscle activities. Then a speech synthesizer is driven to produce synthetic speech in place of the person&#39;s voice.  
           [0005]    One good example of such research works is published in Noboru Sugie et. al., A Speech Prosthesis Employing a Speech Synthesizer—Vowel Discrimination from Perioral Muscle Activities and Vowel Production, IEEE transactions on Biomedical Engineering, Vol. 32, No. 7, pp 485-490, the entire contents of which are hereby incorporated by reference.  
           [0006]    According to the research work, the movements of the mouth are picked up via three channels of electromyography with Ag—AgCl surface electrodes. After band-pass filtering of the electromyography, a thresholding operation is performed to reduce the noise component. Then the number of crossings of the threshold level is counted for each channel. Depending on the number of the count at each time interval, each muscle is assigned a 1 or 0 to designate an active or inactive state, respectively. Then a sequence of 3-bit numbers is fed to a finite automaton for vowel discrimination out of all the five basic Japanese vowels: /a/, /e/, /i/, /o/, and /u/. The output of the automaton is used to drive a speech synthesizer for vowel production.  
           [0007]    One example of detecting electromyography signals to discriminate between Japanese vowels is shown in Japanese Patent Laid-open publication No. 7-181888, the entire contents of which are hereby incorporated by reference.  
           [0008]    In this example, as shown in FIG. 5, a speech synthesizer  50  includes an electromyography (EMG) signal detecting unit  15  for detecting EMG signals caused by muscle movements due to speech activities, a syllable identifying unit  11  for generating identifying signals corresponding to desired syllables, a learning unit  13  for learning based on detected signals fed from the EMG signal detecting unit  15  and the identifying signals fed from the syllable identifying unit  11 , a discrimination unit  17  for receiving input patterns fed from the EMG signal detecting unit  15  and discriminating and outputting sound syllable signals corresponding to the input patterns, a sound synthesizing unit  18  for synthesizing sound signals corresponding to the sound syllable signals fed from the discrimination unit  17  and converting the sound signals to sounds, a sound outputting unit  19  for outputting the sounds converted by the sound synthesizing unit  18 .  
           [0009]    The EMG signal detecting unit  15  has a plurality of skin surface electrodes  14  for detecting EMG signals corresponding to muscle movements, amplifiers  16  for amplifying the EMG signals detected by the skin surface electrodes  14 , filters (not shown) for filtering out low and high frequency components from the amplified signals, and converters (not shown) for converting the filtered signals to power spectrums. Further, after the conversion to the frequency spectrums, the components separated by band can be processed in parallel, and therefore consonant discrimination becomes possible.  
           [0010]    In addition to such medical use, there has recently been an increasing demand for human interfacing purposes to easily obtain and process human biological signals such as electromyography signals and electroencephalogram (brain wave) signals.  
           [0011]    When obtaining biological signals such as EMG signals or electroencephalogram signals, operational amplifiers are normally used for reducing the external noise component. A plurality of electrodes are required to be attached to a human body in order to obtain EMG signals using the operational amplifiers. For example, in order to obtain one kind of EMG signal, at least three electrodes should be attached to a human body. That is, two electrodes for the operational amplifier and one electrode for body earth or system reference are needed. Some measurement devices require one electrode dedicated to the body earth and another electrode dedicated to the system reference. In this case, four electrodes are necessary for getting one kind of EMG signal.  
           [0012]    Out of these electrodes, two electrodes for the operational amplifiers should be attached or patched on human skin in the gliding direction of muscle and at a place to be measured. On the other hand, the place where the electrode for the body earth or the system reference is attached is not specially limited, because the electrode is attached for the purpose of getting a reference potential for the operational amplifier or equalizing the operational amplifier ground potential with the human body.  
           [0013]    In order to attach such electrodes, an operator should apply paste to the electrodes and then attach the electrodes to human skin, and fix them on the human body using tape. These processes need a lot of time and are troublesome. With regard to the body earth electrode or the system reference electrode, a band electrode can be wrapped around an upper extremity or an arm, or a lower extremity or a leg, or a clip electrode can be used by clipping it onto a lobule of auricle or an earlobe. Even if these simple electrodes are utilized, the electrode attaching operation is still necessary and troublesome.  
           [0014]    Conventionally, the measurement of EMG signals and electroencephalogram signals has been mainly aimed at medical clinical examination or therapy, and therefore the prior art electrodes were assumed to be used only in examination rooms or operating rooms. Therefore, where the biological signals such as EMG signal or electroencephalogram are utilized as human interfacing means, it is necessary to make the electrode attaching operation easier and simpler as much as possible to reduce user&#39;s workload. And even when the biological signals such as the EMG signals or electroencephalogram signals are used for the purposed of examination or therapy, it is much better to make the electrode attaching operation easier or simpler.  
           [0015]    As mentioned above, in order to obtain biological signals such as EMG signals or electroencephalogram signals, it is necessary to attach two kinds of electrodes: differential electrodes, and a body earth or system reference electrode. The place where the differential electrodes should be attached is limited to areas to be measured. The place where the body earth or system reference electrode should be attached is not specially limited. Therefore, the differential electrodes have limited places to be attached, and therefore should be attached to the most appropriate portion using the best attaching method. The differential electrode is therefore usually not necessarily attached in a simple manner.  
           [0016]    On the other hand, the body earth or the system reference electrode without limitation to the attaching places can be attached anywhere in a predetermined certain area. Therefore, if there would exist one way to attach the body earth or the system reference electrode to a certain area of a human body in a simple manner, then it would be possible to avoid trouble when attaching the electrode. Specific examples for simply attaching are the above mentioned band electrode or clip electrode.  
           [0017]    When the biological signals such as EMG signals or electroencephalogram signals are measured for the purpose of human interface use, the utility value of the biological signal measurement would be significantly increased if such measurement could be performed without any limitation in its measuring place, and the measured results could be identified and transmitted to a remote area through wired or wireless communication.  
           [0018]    In order to realize the above mentioned improvement, it is desired to utilize a mobile terminal such as a mobile phone or a personal digital assistant (PDA) for obtaining biological signals such as EMG signals or electroencephalogram signals. When using a mobile terminal such as a mobile phone or a PDA to measure biological signals such as EMG signals or electroencephalogram signals, it is especially important to be able to simply and easily attach an electrode for body earth or system reference to a human body.  
         SUMMARY OF THE INVENTION  
         [0019]    Accordingly, it is one object of the present invention to provide a mobile terminal such as a mobile phone or a PDA that is capable of measuring a biological signal, with an electrode for human body earth or system reference having no limitation in place to be attached.  
           [0020]    Another and more specific object of the present invention is to provide a mobile terminal capable of measuring a biological signal, comprising: a terminal body; an electrode for human body earth or system reference, placed on an outer surface of the terminal body so as to be contactable by the skin of a user of the mobile terminal; and differential electrodes.  
           [0021]    The biological signal includes an electromyography (EMG) signal and an electroencephalogram signal or brain wave in a non-limiting sense. The mobile terminal includes a mobile phone, a personal digital assistance (PDA), a head mount display (HMD), and a wrist watch type terminal, and any other small mobile terminal that can measure the biological signal. The mobile terminal may include a function for analyzing or transmitting the biological signal. While holding a mobile terminal with a hand, or wearing it on ears, biological signals such as an EMG signal and a brain wave signal can be measured, and stored or transmitted via wired or wireless communication. It is important here that the mobile terminal necessarily contacts the human skin; a mobile phone and a PDA contact the hand, and an HMD contacts the forehead or temples.  
           [0022]    In this manner, when measuring an EMG signal or an electroencephalogram signal using a mobile terminal according to the present invention, in which an electrode for human body earth or system reference is placed on an outer surface of the terminal body, it is possible to easily obtain body earth or system reference potential without specially attaching an electrode to the human body.  
           [0023]    [0023]FIG. 1 shows a basic concept of the present invention. A mobile terminal having electrodes includes a mobile phone, a PDA, an HMD, a wrist watch terminal and other varieties of terminals as mentioned above, and a rectangular  10  in FIG. 1 represents all of such terminals. The mobile terminal  10  is provided with an electrode  12  as shown in FIG. 1. The electrode  12  is placed on an outer surface of the mobile terminal  10 , at a portion that may contact human skin. The mobile terminal  10  is further provided with a plurality of electrodes  14  for operational amplifiers.  
           [0024]    The electrode  12  placed at a portion that may contact human skin may function as a body earth electrode or a system reference electrode. Accordingly, a user only has to hold or wear the mobile terminal  10  to measure a body earth or system reference potential, without need to specially attach another body earth or system reference electrode. By attaching remaining differential electrodes at desired portions, it becomes possible to easily and quickly measure biological signals or biometrics signals such as an EMG signal or an electroencephalogram signal. In this manner, troublesome operations for attaching an electrode for body earth or system reference can be eliminated.  
           [0025]    Features and advantages of the present invention will be set forth in the description that follows, and in part will become apparent from the description and the accompanying drawings, or may be learned by practice of the invention according to the teachings provided in the description. Objects as well as other features and advantages of the present invention will be realized and attained by an apparatus particularly pointed out in the specification in such full, clear, concise, and exact terms as to enable a person having ordinary skill in the art to practice the invention.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    [0026]FIG. 1 shows a basic concept of the present invention;  
         [0027]    [0027]FIG. 2 is a schematic view of a mobile phone according to a first embodiment of the present invention;  
         [0028]    [0028]FIG. 3 is a schematic view of a PDA according a second embodiment of the present invention;  
         [0029]    [0029]FIG. 4 is a schematic view of an HMD or glasses according to a third embodiment of the present invention; and  
         [0030]    [0030]FIG. 5 is a schematic block diagram of a speech synthesizer. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    In the following, embodiments of the present invention will be described with reference to the accompanying drawings.  
         [0032]    [0032]FIG. 2 schematically shows a mobile phone  20  as a mobile terminal and its electrode configuration according to one embodiment of the present invention. The mobile phone  20  has an electrode  22  for body earth or system reference on a side surface thereof. A plurality of electrodes  24  for operational amplifiers are placed on a front surface of the mobile phone  20 . While a user holds the mobile phone  20  to make a phone call, the mobile phone  20  maintains contact with a the skin on a hand and the face of a user. For example, a side surface of the mobile phone  20  contacts fingers, the back surface of the mobile phone  20  contacts a palm, or the front surface of the mobile phone  20  contacts an ear or a cheek. The contacting potions vary and are dependent on the shape of the mobile phone  20 . A candy bar type mobile phone and clam shell type mobile phone have different contacting portions. Whatever shape mobile phones have, the mobile phones make contact with human skin. Therefore, an electrode for body earth or system reference can be placed at an appropriated portion of the mobile phone.  
         [0033]    In the first embodiment shown in FIG. 2, the electrodes  24  for operational amplifiers are also placed on the mobile phone  20 . These differential electrodes  24  need to be placed so as to make contact with a desired place of the human body to be measured. For example, when the mobile phone  20  is in contact with a cheek and the cheek is a place to be measured, the arrangement of the electrodes  24  as shown in FIG. 2 is appropriate.  
         [0034]    The electrodes  24  for operational amplifiers are not necessarily placed on the mobile phone itself; they can be external to the mobile phone  20  and remotely connected to the mobile phone  20  via lead lines (not shown).  
         [0035]    [0035]FIG. 3 schematically shows a personal digital assistant (PDA)  30  as a mobile terminal and its electrode configuration according a second embodiment of the present invention. The PDA  30  shown in FIG. 3 has an electrode  32  for body earth or system reference on a side surface thereof. A plurality of electrodes  34  for operational amplifiers are placed external to the mobile terminal  30  and remotely connected to the mobile terminal  30  via lead lines. These electrodes  34  may have Ag—AgCl surfaces.  
         [0036]    While a PDA user holds the PDA  30  with a hand, the PDA  30  maintains contact with the hand, fingers or an arm of the user, as similar to the mobile phone  20  shown in FIG. 2. The contacting portions vary and are dependent on the shape of the PDA  30 . Whatever shape PDAs have, the PDAs make contact with human skin without exception. Therefore, an electrode for body earth or system reference can be placed at an appropriated portion of the PDA  30 .  
         [0037]    The differential electrodes  34  can be attached to appropriate portions of the skin of a user to measure biological signals.  
         [0038]    Alternatively, the differential electrodes  34  may be placed on the PDA surface, if a human skin portion that makes contact with the PDA is to be measured.  
         [0039]    [0039]FIG. 4 schematically shows an HMD or glasses  40  as a mobile terminal and its/their electrode configuration according to a third embodiment of the present invention. In the HMD  40  shown in FIG. 4, electrodes  42  for body earth or system reference can be placed at temples of the HMD  40  and can be in contact with the temples of a user.  
         [0040]    Electrodes  44  for operational amplifiers can be remotely arranged and connected to the HMD  40  via lead lines. Alternatively, the electrodes  44  can be placed on the HMD  40  itself, if it is desired to measure a skin portion of the user that contacts the HMD  40 .  
         [0041]    In a case where a headset (not shown) is utilized as a mobile terminal, both a body earth or system reference electrode and differential electrodes can be placed on the headset to measure an electroencephalogram or a brain wave of a user.  
         [0042]    Although the above embodiments with reference to FIGS. 2, 3 and  4  are explained using a mobile phone, a PDA, an HMD and glasses as a mobile terminal, the present invention is not limited to these examples. “Mobile terminal” referred to in this Description and Claims includes a variety of terminals having various shapes or functions in addition to the above mentioned terminals. The present invention can be applied to, for example, a wrist watch terminal, a finger ring terminal, a necklace terminal and any other terminal that can contact human skin.  
         [0043]    In a mobile phone or a PDA according to the embodiments of the present invention, a body earth or system reference electrode can be easily placed without any trouble at an appropriate portion of a user&#39;s skin, and biological signals such as an EMG signal or a brain wave signal can be measured anywhere.  
         [0044]    The mobile phone according to the first embodiment of the present invention is useful for a handicapped person who has a speaking problem, and useful when used in a place where speaking audibly is inhibited, because perioral muscle activities can be identified to discriminate between the sounds the user wants to speak.  
         [0045]    In a case where a mobile terminal having communication function is utilized, it is possible to transmit measured biological signals to external devices, and realize broader applications in addition to medial use and human interfacing use.  
         [0046]    The present application is based on Japanese priority application No. 2002-178900 filed on Jun. 19, 2002 with the Japanese Patent Office, the entire contents of which are hereby incorporated by reference.