Abstract:
The present invention provides a method and apparatus for receiving data in a human body communication system. The receiving apparatus, which comprises plural receiving electrodes, selects the optimum pair of receiving electrodes when receiving data, so that it can improve quality of received information and obtain position information of a sensor in the human body.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a 35 U.S.C. § 371 national phase conversion of PCT/KR2003/002938 filed 31 Dec. 2003, which claims priority of Korean Patent Application No. 10-2003-0005058 filed 25 Jan. 2003. 
     TECHNICAL FIELD 
     The present invention relates to a method and apparatus for receiving data in a human body communication system that can improve the quality of received information and grasp the position information of a sensor in the human body by using plural receiving electrodes. 
     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 a general data transmitting method, there is a communication cable method applied to an endoscope 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 a patient. The communication cable method has high reliability and high data quality, however, a patient may suffer from severe pain during an endoscope operation. 
     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, image data in the human body photographed by a camera of the endoscope is transmitted to a receiving unit located outside the human body, and then displayed in a monitor. 
     However, because the M2A employs a radio wave method as a signal transmitting method, power consumption is increased, an operational time is reduced, and receiving sensitivity is deteriorated due to interference of various electric waves from the outside of the human body. In addition, because the M2A requires a radio transmitter such as a converter circuit for converting an image signal into a high frequency and an antenna for signal transmission, a volume is increased and production cost is high, and also the high frequency may be harmful to the human body. Accordingly, the present applicant has developed a human body communication system capable of transmitting data about the inside of the human body to the outside of the human body with a low frequency current by using the human body as a conductor. 
     In the human body communication system, an electric potential difference between transmitting electrodes that are formed on the surface of the capsule type endoscope put in the human body generates a current. As the current flows through the human body, it induces the voltage between two receiving electrodes installed on the surface of the human body, and accordingly a receiving apparatus can receive data regarding the inside of the human body. 
       FIG. 1  shows a human body communication system including a capsule type endoscope and two receiving electrodes. As depicted in  FIG. 1 , a capsule type endoscope  10  is located inside the human body  1 , and a receiving apparatus  20  is located outside the human body. A transmitting electrode  11  is formed on the surface of both ends of the capsule type endoscope  10 , and the receiving apparatus  20  is connected with two receiving electrodes  30  contacted to the surface of the human body. After medical information collected by the capsule type endoscope  10  is signal-processed, when electric potential difference occurs between the two transmitting electrodes  11 , a current flows through the human body  2  since the two transmitting electrodes  11  are contacted with each other through body fluids and form a closed-loop. The current flowing on the surface of the human body induces a voltage between the two receiving electrodes  30  installed on the surface of the human body. The induced voltage is in proportion to the current and distance between the two receiving electrodes  30 . The receiving apparatus  20  located outside the human body senses a signal transmitted from the capsule type endoscope  10  in the human body by the induced voltage. 
     However, when only the two receiving electrodes are used, if a direction of the current is vertical to an aligning direction of the receiving electrodes, voltage is not induced or a small amount of voltage is induced in the receiving electrodes. Accordingly, the receiving apparatus outside the human body may not receive accurately a signal transmitted from the capsule type endoscope in the human body. 
     In more detail, as illustrated in  FIG. 1 , when the capsule type endoscope  10  is located in an (A) direction, the aligning direction of the two receiving electrodes  30  is coincided with the direction of the transmitting electrode  11 . In this case, a maximum current flows between the two receiving electrodes  30 , so that the receiving apparatus  20  obtains good receiving sensitivity. However, when the capsule type endoscope  10  is located in a (B) direction, the aligning direction of the two receiving electrodes  30  is vertical to the direction of the transmitting electrode  11 . In this case, a current does not flow between the two receiving electrodes  30 , so that the receiving apparatus  20  can not receive a signal transmitted from the capsule type endoscope  10 . Briefly, because the receiving electrode  30  is fixed and aligning direction of the transmitting electrode  11  is varied at any time, receiving sensitivity is varied as time elapses, a transmitted signal may be lost, and accordingly quality of receiving information is lowered. 
     In addition, when only the two receiving electrodes are used, position of the capsule type endoscope in the human body can not be detected, and accordingly the capsule type endoscope can not be used efficiently. For example, if we know a current position of the capsule type endoscope when the capsule type endoscope catches an abnormal symptom in the digestive organs, an accurate operation and remedy can be performed. 
     TECHNICAL GIST OF THE PRESENT INVENTION 
     In order to solve the above-mentioned problems, it is an object of the present invention to provide a method and apparatus for receiving data in a human body communication system, which are capable of receiving data with optimum sensitivity and extracting position information of a capsule type endoscope in the human body to use the position information as medical information. 
     In order to achieve the above-mentioned object, a method for receiving data in a human body communication system in accordance with the present invention comprise the steps of: selecting a pair of receiving electrodes sequentially among plural receiving electrodes; processing a voltage value of the selected pair of receiving electrodes and storing it in a memory; performing a predetermined operations for values stored in the memory to select an optimum pair of receiving electrodes; and performing image processing for a value corresponding to the optimum pair of receiving electrodes among the values stored in the memory. 
     In addition, an apparatus for receiving data in a human body communication system in accordance with the present invention comprises plural receiving electrodes installed on the surface of the human body; a switching means for selecting a pair of receiving electrodes sequentially among the plural receiving electrodes; a processing means for processing a voltage value of a pair of receiving electrode selected by the switching means; a memory for storing the processed value; a comparing-operating means for calculating a maximum value among values stored in the memory; an image processing means for performing image processing for the maximum value; and a control means for controlling the switching means and the comparing-operating means to provide the maximum value to the image processing means. 
    
    
     
       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 a diagram for showing problems occurred in data receiving in the conventional human body communication system; 
         FIG. 2  is an exemplary view illustrating plural receiving electrodes installed on the surface of the human body in accordance with the present invention; and 
         FIG. 3  is a block diagram illustrating a receiving apparatus in accordance with the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, the preferred embodiment of the present invention will be described with reference to accompanying drawings. 
       FIG. 2  is a plane view illustrating plural receiving electrodes installed on the surface of the human body. As depicted in  FIG. 2 , eight receiving electrodes are respectively installed on the surface of the human body, for example, the chest, the navel, an upper portion of the back, a lower portion of the back, the axillae and the sides. When current generated by electric potential difference between transmitting electrodes  11  of a capsule type endoscope  10  reaches plural receiving electrodes through the human body, a voltage is induced between the two receiving electrodes in proportion to the current and distance between the two receiving electrodes. 
     With reference to  FIG. 2 , considering receiving electrodes  1  and  2  as a pair of receiving electrodes, the greatest voltage is detected between receiving electrodes  1  and  2 . That is because an aligning direction of the transmitting electrode  11  is coincided with that of the receiving electrodes  1  and  2  and also distance between the capsule type endoscope  10  and the receiving electrodes is the shortest. On the other hand, considering receiving electrodes  3  and  4  or receiving electrodes  7  and  8  as a pair of receiving electrodes, a voltage is not detected between the receiving electrodes. That is because an aligning direction of the transmitting electrode  11  of the capsule type endoscope  10  is vertical to an aligning direction of the receiving electrodes. In addition, considering receiving electrodes  5  and  6  as a pair of receiving electrodes, voltage between the receiving electrodes  5  and  6  is less than that between the receiving electrodes  1  and  2 . That is because an aligning direction of the transmitting electrode  11  of the capsule type endoscope  10  is coincided with an aligning direction of the receiving electrodes, but distance between the capsule type endoscope  10  and the receiving electrodes  5  and  6  is farther than that between the capsule type endoscope  10  and the receiving electrodes  1  and  2 . 
     As described-above, by measuring and comparing voltages between each pair of receiving electrodes, we select the receiving electrodes  1  and  2  to obtain better receiving sensitivity from the fact that the voltage between the receiving electrodes  1  and  2  is the greatest. In addition, we know the capsule type endoscope is located closer to the receiving electrodes  1  and  2  from the fact that a voltage of the receiving electrodes  1  and  2  is greater than that of the receiving electrodes  5  and  6 . 
     An accurate position of the capsule type endoscope  10  in the human body can be extracted by comparing and operating voltages sensed in each pair of receiving electrodes at predetermined time-intervals. Also, a moving path, speed and direction, etc. of the capsule type endoscope in the human body can be known by processing an extracted position of the capsule type endoscope  10  sequentially. 
     In the embodiment of the present invention, flat-arranged plural receiving electrodes are described, however, the present invention is not limited by that. It is possible to extract three-dimensional position and direction of the capsule type endoscope  10  by distributing plural receiving electrodes onto the up/down, front/back and left/right of the human body. 
       FIG. 3  is a block diagram illustrating a receiving apparatus having plural receiving electrodes in accordance with the present invention. As depicted in  FIG. 3 , N receiving electrodes are respectively connected to a first switching circuit  21  and a second switching circuit  22  of a receiving apparatus  30 . An output line of the first switching circuit  21  is connected to a plus (+) terminal of a differential amplifier  23 , and an output line of the second switching circuit  22  is connected to a minus (−) terminal of the differential amplifier  23 . Under the control of a control circuit  28 , the switching circuits  22 ,  23  respectively select only one among inputs from the N receiving electrodes. 
     The operation of the receiving apparatus  30  will be described in detail. First, when the first switching circuit  21  selects the receiving electrode  1  and the second switching circuit  22  selects the receiving electrode  2 , a signal voltage between the receiving electrodes  1  and  2  is transmitted to the differential amplifier  23  to be amplified. The amplified signal passes a band pass filter  24  where noise is removed. The signal passing the band pass filter  24  is converted into a digital signal in an A/D converter  25  and is stored in a memory  27 . Next, as the first switching circuit  21  maintains the receiving electrode  1 , the second switching circuit  22  selects the receiving electrode  3 . And then a signal voltage between the receiving electrodes  1  and  3  is stored in a different address of the memory  27  through the above-mentioned process. Continuously, as the first switching circuit  21  maintains the receiving electrode  1 , the second switching circuit  22  selects the receiving electrode  4 ,  5 , . . . and N, and then signal voltages between the receiving electrode  1  and the other receiving electrodes are sequentially stored in the memory  27 . 
     Likewise, as the first switching circuit  21  maintains selection of the receiving electrode  2 , the second switching circuit  22  selects the other receiving electrodes  1 ,  3 , . . . and N sequentially, and then signal voltages between the receiving electrode  2  and the other receiving electrodes are sequentially stored in the memory  27 . As described above, if the first switching circuit  21  selects the receiving electrode  3 ,  4 , . . . and N sequentially and the second switching circuit  22  selects the other receiving electrodes sequentially, finally the (N-1) 2  number of signal voltages are stored in the memory  27 . Of course, signal voltages between the receiving electrodes may be sampled several times (more than two times) for an average value to be stored. Or, an average value of a voltage waveform for a certain time may be stored. In addition, in order to reduce memory capacity and processing time, once-selected pair of receiving electrodes is no longer selected and the only  n C 2  number of a pair of receiving electrodes may be selected. 
     A comparing-operating circuit  29  compares signal voltage values stored in the memory  27  and obtains the greatest value. From that result of the comparing-operating circuit  29 , it can be known a direction of the capsule type endoscope  10  is similar to an aligning direction of the pair of receiving electrodes in which the greatest value occurs. In addition, the comparing-operating circuit  29  may extract a three-dimensional position of the capsule type endoscope  10  by comparing and operating signal voltage values stored in the memory  27  and store it again in the memory  27 . 
     The control circuit  28  selects the pair of receiving electrodes in which the greatest voltage occurs as communication electrodes, and accordingly a signal transmitted from the capsule type endoscope  10  in the human body can be received with the best receiving sensitivity. In more detail, a signal of the pair of receiving electrodes in which the greatest receiving voltage occurs is processed in an image processing circuit  26 . 
     The above-described a pair of receiving electrodes combining procedure, signal voltage processing procedure, comparing-operating procedure and optimum pair of receiving electrodes selecting procedure, etc. are proceeded at a very quick speed (within 10 msec) and repeated at regular time-intervals (per 5 seconds). Accordingly, information transmitted from the capsule type endoscope  10  can be always received through an optimum pair of receiving electrodes. In addition, a moving path, a speed and a direction of the capsule type endoscope  10  in the human body can be measured by storing calculated position information in the memory  27  sequentially. 
     INDUSTRIAL APPLICABILITY 
     In the present invention, information transmitted from a capsule type endoscope using the human body as a communication conductor can be received with optimum receiving sensitivity to a receiving apparatus having plural receiving electrodes. Accordingly, it is possible to improve quality of received information, grasp a moving path, a speed and a direction of the capsule type endoscope in the human body and use them as medical information.