Abstract:
The present invention provides method and system for data communication in the human body and a sensor therefor. The method and system transmit information through the human body to a receiver located outside the human body using low current and voltage polarity, so that they cause no damage to the human body and achieve low power consumption and better receiving sensitivity. In addition, the sensor contains a CMOS image sensor on which all circuits are integrated without radio transmitter and antenna, so that it achieves a low-priced and small-sized capsule type endoscope.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a 35 U.S.C. §371 national phase conversion of PCT/KR2003/002937 filed 31 Dec. 2003, which claims priority of Korean Patent Application No. 10-2003-0005059 filed 25 Jan. 2003. 
     TECHNICAL FIELD 
     The present invention relates to a method and system for transmitting data from a sensor put in the human body to the outside of the human body to collect various medical information, and particularly to a method and system for data communication in human body, wherein a current generated from the sensor flows through the human body as a conductor to transmit data to the outside of the human body. 
     BACKGROUND ART 
     Various sensors for collecting medical information in the human body have been developed and used, herein, not only a technique for collecting information in the human body but also a technique for transmitting collected information to the outside of the human body are very important. 
     In general data transmitting methods, there is a communication cable method applied to an endoscope which is developed for observing the stomach and intestines. In the communication cable method, a cable made of a conducting wire or an optic fiber is inserted into the human body through throat of the patient. The communication cable method has high reliability and high data quality, however, it may cause severe pain to the patient. 
     In order to solve the above-mentioned problem, Given Imaging LTD. in Israel has developed a capsule type endoscope called M2A. When a patient swallows the capsule type endoscope like a tablet, video data in the human body photographed by a camera of the endoscope are transmitted to an external-receiving unit, and displayed in a monitor. 
     However, in the capsule type endoscope, since radio wave is used to transmit a signal, power consumption is large, so that operation time is short, and receiving sensitivity is deteriorated due to interference of various electric waves from the outside of the human body. In addition, radio-transmitting apparatus such as a converter circuit for converting a video signal into a high frequency signal and an antenna for signal transmission, etc. are required, so that volume is increased and production cost is increased. Also, high frequency may be harmful to the human body. 
     SUMMARY OF THE INVENTION 
     In order to solve the above-described problems, it is an object of the present invention to provide a method and system for data communication in the human for flowing a current generated from the sensor through the human body to transmit data to the outside of the human body. 
     In addition, it is another object of the present invention to provide a sensor having a transmitting electrode capable of generating a current in the human body to flow a current through the human body to transmit data to the outside of the human body. 
     In order to achieve the above-mentioned objects, in a method for transmitting a signal from a sensor put in the human body to the outside of the human body, a method for data communication in the human body in accordance with the present invention includes the steps of generating electric potential difference between transmitting electrodes installed on the surface of the sensor; supplying a current from the transmitting electrode having higher electric potential to the inside of the human body to flow the current through the surface of the human body back into the inside of the human body and sinking the current to the transmitting electrode having lower electric potential; and inducing a voltage between receiving electrodes installed on the surface of the human body by the current flowing through the surface of the human body. 
     In addition, a system for data communication in the human body in accordance with the present invention includes a sensor, which is put in the human body, having transmitting electrodes for generating electric potential difference; and a receiver installed on the surface of the human body for receiving a current generated by the electric potential difference through the human body. 
     In addition, a sensor in accordance with the present invention includes a lighting device for irradiating the inside of the human body; a lens for focusing light incident from the inside of the human body; a CMOS image sensor for generating an electric signal from the light focused by the lens; a housing for containing the lighting device, the lens and the CMOS image sensor; and a transmitting electrode installed on the surface of the housing to receive the electric signal. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
       In the drawings: 
         FIG. 1  is an exemplary view illustrating a method for data communication in the human body in accordance with the present invention; 
         FIG. 2  are perspective views illustrating several embodiments of a transmitting electrode installed to the surface of a sensor used in a system for data communication in the human body in accordance with the present invention; 
         FIG. 3  is a sectional view illustrating the sensor of the system for data communication in the human body in accordance with the present invention; and 
         FIG. 4  is a circuit diagram illustrating an internal construction of a CMOS image sensor of the sensor. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, the preferred embodiment of the present invention will be described with reference to accompanying drawings. 
       FIG. 1  is an exemplary view illustrating a method and a system for data communication in the human body in accordance with the present invention. As depicted in  FIG. 1 , a sensor  10  placed inside the human body  1 , for example, in the digestive organs transmits information of the inside of the human body  1  to a receiver  20  installed on the surface of the human body through the human body  2 . 
     With reference to  FIG. 1 , in the system for data communication in the human body in accordance with the present invention, a method for data communication in the human body capable of transmitting a signal from the sensor  10  inside the human body  1  to the receiver  20  placed in the outside of the human body will be described in more detail. Various information (for example, pictures of the inside of the body, PH, temperature or electric impedance, etc.) collected by the sensor  10  is converted into an electric signal by a signal processing circuit of the sensor and is applied to a transmitting electrode  11  through an output line of the signal processing circuit, and accordingly electric potential difference occurs between the two transmitting electrodes  11 . Because the transmitting electrode  11  is contacted to the inside of the human body  1  (it is electrically connected with the human body through body fluids in the digestive organs), by electric potential difference between the two transmitting electrodes  11 , a current  3  flows through the human body  2 . The current  3  flows from the transmitting electrode having higher electric potential through the surface of the human body back into the inside of the human body  1  and is sunken to the transmitting electrode having lower electric potential. Herein, the current flowing through the surface of the human body induces a voltage between two receiving electrodes  21 , a signal transmitted from the sensor  10  put in the human body  1  can be sensed by the receiver  20  outside of the human body. The receiver  20  restores a video signal by processing the received signal, displays it on a monitor or stores it in a memory. 
       FIG. 2  illustrate several embodiments of the transmitting electrode  11  installed on the surface of the sensor  10  of the system for data communication in the human body in accordance with the present invention. On the surface of the sensor  10 , two metal plates, namely, two transmitting electrodes are formed, which are respectively connected to outlines of a signal processing circuit of the sensor. 
     If the two transmitting electrodes are electrically isolated and separated from each other sufficiently, the transmitting electrodes can be formed at any position of the surface of the sensor. Herein, it is preferable that the transmitting electrodes have a sensor-covering shape, namely, a three-dimensionally curved shape in order to be contacted with the inside of the human body easily. 
     In  FIG. 2 , (a) shows a structure of the transmitting electrode of sensor shown in  FIG. 1 . The transmitting electrode consists of a first electrode and a second electrode respectively surrounding the both ends of the sensor. A transmitting electrode shown in (b) consists of a first electrode surrounding an end of the sensor and a second electrode covering the other end of the sensor as a band shape. A transmitting electrode shown in (c) consists of a first electrode and a second electrode respectively covering both ends of the sensor as a band shape. In addition, a transmitting electrode shown in (d) consists of a first electrode and a second electrode symmetrically formed along a longer axis of the sensor. 
     Because the transmitting electrode is exposed to the inside of the human body, it has to be made of metal having good resistance against corrosion by a reactive material such as a digestive fluid, etc. and also harmless to the human body. In the embodiments of the present invention, as metal having good corrosion resistance and harmless to the human body, SUS316L or gold is used. In addition, in order to isolate the transmitting electrodes formed on the surface of the sensor electrically, the surface of the sensor has to be a nonconductor harmless to the human body. As a nonconductor harmless to the human body, peek, polyethylene or polypropylene in a plastic group may be used. In order to improve harmlessness to the human body, parylene may be coated onto the surface of the sensor made of peek, polyethylene or polypropylene. 
       FIG. 3  is a sectional view illustrating an internal structure of a capsule type endoscope as a sensor used for the system in accordance with the present invention. As depicted in  FIG. 3 , the capsule type endoscope has a diameter of 10 mm and a length of 20 mm. A light receiving window  17  of dome shape is formed in an end of a housing forming an external shape of the capsule type endoscope, and a rectangular container  18  is formed in the other end of the housing. Accordingly, the capsule type endoscope has a bullet shape. 
     In the capsule type endoscope, the light receiving window  17  which is a part for passing light is made of a nonconductor harmless to the human body and passing light. The container  18  that is a part for containing several devices also is made of a nonconductor harmless to the human body. The light receiving window  17  and the container  18  are sealed so that infiltration of a digestive fluid, etc. into the capsule type endoscope may be prevented and also leakage of substances in the capsule type endoscope into the human body may be avoided. 
     As depicted in  FIG. 3 , the capsule type endoscope has the external shape of the housing consisting of the light receiving window  17  and the container  18 . The container  18  includes a lighting device  12 , a lens  13 , a CMOS image sensor  14  and a battery  15  and a transmitting electrode  11  electrically isolated-formed on the surface of the container  18 . 
     First, the lens  13  is arranged behind the light receiving window  17 , and the CMOS image sensor  14  in which various circuits are integrated is arranged behind the lens  13 . A distance between the lens  13  and the CMOS image sensor  14  is adjusted so as to focus light incident through the light receiving window  17  on the surface of the CMOS image sensor  14 . Around the lens  13  and the CMOS image sensor  14 , plural lighting devices  12  are arranged as donut-shape. In the embodiment of the present invention, four LEDs are used for the lighting devices  12 . Non-reflection coating is performed on the inner and outer surfaces of the light receiving window  17  so that light irradiated from the lighting device  12  may pass through the light receiving window  17  smoothly and illuminate an object. A battery  15  as power supply is arranged behind the CMOS image sensor  14 . In the embodiment of the present invention, a silver oxide battery having an even discharge voltage and causing little harm to the human body is used as the battery  15 . 
     The operation of the capsule type endoscope will be described. While the lighting devices  12  irradiate a light, the CMOS image sensor  14  captures an image of the object through the lens  13 . The CMOS image sensor  14  processes the captured video signal through various internal circuits and applies the signal to the transmitting electrodes respectively connected to the two output lines  16 , and accordingly the receiving electrode placed in the outside of the human body can sense the signal, as described above. 
       FIG. 4  is a circuit diagram illustrating the CMOS image sensor  14  in order to describe the operation principles of the capsule type endoscope in more detail. 
     As depicted in  FIG. 4 , the CMOS image sensor  14  includes a pixel array  100  for capturing and storing a video signal; a read circuit  110  for fetching a signal of each pixel sequentially; a coding circuit  120  for coding an output signal of the read circuit  110 ; a switching circuit  130  for transmitting a signal coded in the coding circuit  120  through the two output lines; a current limiting circuit  140  for adjusting a current value so as to prevent flowing of a current causing damage to the human body; a control circuit  150  for controlling the signal processing and the operation of the lighting device  12 ; and an oscillating circuit  160  for determining an operational frequency. 
     In the embodiment of the present invention, the pixel array  100  (of 320×240 pixels) can capture and store video signals of high resolution. The read circuit  110  processes the stored video signals sequentially as a frame or more per 1 sec, and accordingly there is no need to have a memory disadvantageous in the cost and volume aspects. In addition, the control circuit  150  determines brightness inside the human body based on brightness of light incident to the pixel array  100  and controls the lighting device  12  to operate variably for 5˜200 msec. The video signals are captured by the pixel array  100  during that time. According to that, each video frame is instantly captured, and brightness thereof is better. And a PSK method that is simple and has strong tolerance against noise is used in encoding. 
     When the signal transmitted from the coding circuit  120  is “1”, the switching circuit  130  applies+voltage to the first output line  16   a  and grounds the second output line  16   b . When the signal transmitted from the coding circuit  120  is “0”, the switching circuit  130  grounds the first output line  16   a  and applies a+voltage to the second output line  16   b . As described-above, since the present invention transmits a signal using not the voltage size but the voltage polarity, it can be stronger to noise. 
     The current limiting circuit  140  serves to prevent a current more than 5 mA from flowing through the human body. In the embodiment of the present invention, the current limiting circuit  140  is implemented by serially connecting resistors to the two output lines  16  of the switching circuit  130  respectively. For example, assume that when a power voltage is 3 V the current limiting circuit  140  comprises resistors of 300 ohms serially connected to the two output lines respectively. In this case, although the transmitting electrode has a substantial short circuit because of very small resistance of the human body, current flowing through the human body does not exceed 5 mA. In addition, by connecting a capacitor to each resistance in parallel, it is possible to remove a high frequency component of the signal transmitted to the human body and perform electric matching with the human body, so that signal-transmitting performance can be improved. 
     The signal passing the current limiting circuit  140  is applied to the two transmitting electrodes  11  and is transmitted to the outside of the human body through the human body. In the conventional frequency communication method, a high frequency signal of several hundred MHz is required, however, in the present invention, a video signal captured by the capsule type endoscope can be transmitted to the outside of the human body with a low frequency signal of 10 MHz. 
     Industrial Applicability 
     Since the present invention uses a low frequency and current instead of a high frequency through antenna when communicating with sensor in the human body, it reduces power consumption and attenuation in human body, has no effect on external interference and cause no damage to the human body. In addition, since the invention transmits a signal using voltage polarity, it is strong to noise, and accordingly receiving sensitivity is superior. 
     In addition, the sensor in accordance with the present invention does not need a radio transmitter and antenna, and also does not need an additional memory because it processes video signals sequentially along the passage of time, so that a small-sized and low-priced capsule type endoscope can be provided.