Patent Publication Number: US-2023161066-A1

Title: Metal detection system using search coil-type sensor

Description:
TECHNICAL FIELD 
     The present invention relates to a metal detecting system using a search-coil type sensor, and more specifically, to a technology of detecting a specific object such as firearms and tracking the object. 
     BACKGROUND ART 
     Various technologies of SQUID, Fiber-Optic, Flux-Gate, Magnetic Impedance, or the like are applied to magnetic sensors, and the magnetic sensors are highly improved to be applied to respective industrial fields which demand such technologies. In particular, as the Fourth Industrial Revolution era arrives, various IoT products are launched, and thus an application range of the magnetic sensor technology is expanded to an area of everyday life. 
     Accordingly, Samsung Electro-Mechanics in Korea, Honeywell International Inc. as a multinational conglomerate corporation, and the like have each developed a magnetic sensor in a more compact chip shape and have invested in a variety of research and development for improving a sensing sensitivity or range and reducing a sensing error. 
     Recently, firearm accidents increase in the U.S.A or the like, and thus there is a growing interest and demand for a system for improving detection performance with respect to a specific object such as an firearm. 
     Korean Patent Registration No. 10-0867375 (Title of the Invention: Apparatus and Method for Measuring Information of Location and Direction of Moving Object Using Three Magnetic Field Sensors) discloses a method including an installation step of installing two magnetic field sensors corresponding to a surface formed by x and y axes, respectively, to a moving object and installing a magnetic field sensor corresponding to a z axis to the moving object, a storing step of measuring the earth&#39;s magnetic field corresponding to x, y, and z axes and storing information values of a reference magnetic field in an internal memory in the moving object, a determining step of causing the moving object to measure magnitudes of a magnetic field on x, y, and z axes while the moving object moves and then determining whether or not an absolute value of a difference between a measured Z-axis magnetic field value and a Z-axis reference magnetic field value is smaller than an error range set in a magnetic field sensor, and an updating step of updating a direction information value of the moving object by using measured x- and y-axes magnetic field values, when determination in the determining step is that the absolute value of the difference between the measured Z-axis magnetic field value and the reference value is smaller than the error range of the sensor. 
     [Citation List] [Patent Literature] Korean Patent Registration No. 10-0867375 
     SUMMARY OF INVENTION 
     Technical Problem 
     An object of the present invention to solve such a problem described above is to enable a location, displacement, or the like of an object to be detected using a fine magnetic field of the object containing iron without causing any change to a core and a coil which do not have any magnetic component. 
     In addition, another object of the present invention is to inhibit a detection delay due to a range (non-polarity range) in which a magnetic field subsides temporarily during a change in pole with respect to a sensor due to displacement of an object containing iron. 
     In addition, still another object of the present invention is to enable measurement or the like of locations of a plurality of objects to be performed and respective movement paths or the like of the plurality of objects to be determined. 
     Further, still another object of the present invention is to detect a specific object such as firearms and track the object. 
     Technical objects to be achieved by the present invention are not limited to the technical objects mentioned above, and the following description enables other unmentioned technical objects to be clearly understood by a person of ordinary skill in the art to which the present invention pertains. 
     Solution to Problem 
     The present invention to achieve the above-described objects has a configuration including: sensor modules that detect respective objects that move around the corresponding sensor modules, each sensor module having one or more sensors that include respective housings having respective inner spaces, respective cores formed to be inserted into the inner spaces of the housings, and respective coils which are each wound around a portion of an outer circumferential surface of each of the housings, the portion corresponding to a position of each of the cores; imaging units that image the respective objects which move around the corresponding sensor modules or persons possessing the respective objects; impedance matching units that are connected to a plurality of the sensor modules, respectively, and perform impedance matching; and amplifiers that are connected to the impedance matching units, respectively, and amplify a fine current and voltage generated during approach of the objects to the sensor modules. The sensor modules have respective induced magnetic fields formed due to a change in distance from the objects containing iron (Fe). The objects are analyzed using information acquired by the sensor modules and captured images acquired by the imaging units. 
     In an embodiment of the present invention, the metal detecting system using a search-coil type sensor may further include a first control unit that is connected to the amplifiers and analyzes a waveform of the amplified current and voltage; and a second control unit that is connected to the first control unit to generate object analysis information by analyzing movement and magnetic flux density of the objects and is connected to the imaging units to collect the captured images. 
     In the embodiment of the present invention, the second control unit may categorize the objects using the object analysis information and the captured images. 
     In the embodiment of the present invention, the second control unit may determine whether the magnetic flux density of the objects is within a predetermined magnetic flux density range and then determine types of objects by analyzing the captured images. 
     In the embodiment of the present invention, the second control unit may generate an alarm signal when determining that the objects are firearms. 
     In the embodiment of the present invention, the metal detecting system using a search-coil type sensor may further include an output unit that is connected to the second control unit, visually outputs locational changes of the objects, and outputs the alarm signal. 
     In the embodiment of the present invention, the plurality of sensor modules may be formed, and the impedance matching units and the amplifiers may be connected to the each of the plurality of sensor modules, respectively. 
     In the embodiment of the present invention, a plurality of the sensors may be arranged in parallel or radially with each other. 
     In the embodiment of the present invention, the plurality of coils provided in the sensors may be arranged in series with each other. 
     Advantageous Effects of Invention 
     According to the above-described configuration, the present invention is effective in that a fine change in magnetic field and flux quantity of an object containing iron can be detected such that a location, displacement, or the like of the object containing iron can be detected with ultra-low electric power. 
     In addition, the present invention is effective in that, even when a range (non-polarity range) in which a magnetic field subsides temporarily is formed during a change in pole with respect to a sensor due to displacement of an object containing iron, a magnetic field of the object containing iron can be detected by another adjacent sensor or coil such that the system can be normally and continuously operated. 
     In addition, the present invention is effective in that detection and measurement can be performed regardless of arrangement or the like of sensors or sensor modules. 
     In addition, the present invention is effective in that measurement or the like of locations of a plurality of objects can be performed using a plurality of sensor modules, and thereby respective movement paths or the like of the plurality of objects can be determined. 
     In addition, the present invention is effective in that, since measurement of the object can be performed using a combination of object analysis information acquired by the sensor module and a captured image acquired by an imaging unit, a measurement speed and measurement accuracy of the objects can be improved. 
     Further, the present invention is effective in that, since a fine change in magnetic field and flux quantity of an object containing iron can be detected, the system can exhibit the same performance regardless of an effect of air, soil, water, or the like. 
     The effects of the present invention are construed not to be limited to the above-described effects but to include every effect that can be derived from the configurations of the present invention described in detailed description or claims of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS.  1  and  2    are schematic diagrams illustrating a metal detecting system according to an embodiment of the present invention. 
         FIG.  3    is a schematic diagram illustrating a sensor according to a first embodiment of the present invention. 
         FIG.  4    is a schematic diagram illustrating a sensor module according to the first embodiment of the present invention. 
         FIG.  5    is a schematic diagram illustrating a sensor according to a second embodiment of the present invention. 
         FIG.  6    is a schematic diagram illustrating a sensor module according to the second embodiment of the present invention. 
         FIG.  7    is a schematic diagram illustrating magnetic field regions of the sensors according to the embodiments of the present invention. 
         FIG.  8    is a schematic diagram illustrating a sensor according to a third embodiment of the present invention. 
         FIG.  9    is a schematic diagram illustrating a sensor module according to the third embodiment of the present invention. 
         FIG.  10    is a schematic diagram illustrating a sensor module according to a fourth embodiment of the present invention. 
         FIGS.  11  and  12    illustrate signal pattern graphs obtained in a state where an object passes by the sensor according to the first embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The preferred embodiment according to the present invention includes: sensor modules that detect respective objects that move around the corresponding sensor modules, each sensor module having one or more sensors that include respective housings having respective inner spaces, respective cores formed to be inserted into the inner spaces of the housings, and respective coils which are each wound around a portion of an outer circumferential surface of each of the housings, the portion corresponding to a position of each of the cores; imaging units that image the respective objects which move around the corresponding sensor modules and image respective persons possessing the respective objects; impedance matching units that are connected to a plurality of the sensor modules, respectively, and perform impedance matching; and amplifiers that are connected to the impedance matching units, respectively, and amplify a fine current and voltage generated during approach of the objects to the sensor modules. The sensor modules have respective induced magnetic fields formed due to a change in distance from the objects containing iron (Fe). The objects are analyzed using information acquired by the sensor modules and captured images acquired by the imaging units. 
     EMBODIMENTS 
     Hereinafter, the present invention will be described with reference to the accompanying drawings. However, the present invention can be realized as various different examples and, thus, is not limited to embodiments described here. Further, a part irrelevant to the description is omitted from the drawings in order to clearly describe the present invention, and similar reference signs are assigned to similar parts through the entire specification. 
     In the entire specification, a case where a certain part “is connected to (accesses, is in contact with, or is coupled to)” another part means not only a case where the parts are “directly connected” to each other, but also a case where the parts are “indirectly connected” to each other with another member interposed therebetween. In addition, when a certain part “comprises” a certain configurational element, this means that another configurational element is not excluded, but the certain configurational element can be further included unless specifically described otherwise. 
     Terms used in this specification are only used to describe a specific embodiment and are not intentionally used to limit the present invention. A word having a singular form also includes a meaning of its plural form, unless obviously implied otherwise in context. In this specification, a term such as “to comprise” or “to have” is construed to specify that a feature, a number, a step, an operation, a configurational element, a part, or an assembly thereof described in the specification is present and not to exclude presence or a possibility of addition of one or more other features, numbers, steps, operations, configurational elements, parts, or assemblies thereof in advance. 
     Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 
       FIGS.  1  and  2    are schematic diagrams illustrating a metal detecting system according to an embodiment of the present invention. In addition,  FIG.  3    is a schematic diagram illustrating a sensor  100  according to a first embodiment of the present invention, and  FIG.  4    is a schematic diagram illustrating a sensor module  10  according to the first embodiment of the present invention. In addition,  FIG.  5    is a schematic diagram illustrating a sensor  100  according to a second embodiment of the present invention, and  FIG.  6    is a schematic diagram illustrating a sensor module  10  according to the second embodiment of the present invention. Further,  FIG.  7    is a schematic diagram illustrating magnetic field regions of the sensors  100  according to the embodiments of the present invention. Here, (a) of  FIG.  7    is a diagram illustrating a state where an object  70  containing iron (Fe) moves with respect to the sensor module  10  according to the first embodiment of the present invention, and (b) of  FIG.  7    is a diagram illustrating a state where the object  70  containing iron (Fe) moves with respect to the sensor module  10  according to the second embodiment of the present invention. Directions can be set based on right, left, top, and bottom of the drawings. Hereinafter, the same is true of the following. In the drawings of the present invention, the object  70  containing iron (Fe) has marks of the N pole and the S pole; however, the marks are only provided for the convenience of understanding, and the marks do not indicate that the object  70  is a magnet or an electromagnet. In  FIGS.  4 ,  6 , and  9   , a first control unit  41  and a second control unit  42  are connected by an arrow; however, the arrow only means signal transmission and does not mean that the first control unit  41  and the second control unit  42  are formed separately from each other for each sensor module  10 . 
     As illustrated in  FIGS.  1  and  2   , the metal detecting system of the present invention includes sensor modules  10  that detect respective objects  70  that move around the corresponding sensor modules, each sensor module having one or more sensors  100  that include respective housings  130  having respective inner spaces, respective cores  110  formed to be inserted into the inner spaces of the housings  130 , and respective coils  120  which are each wound around a portion of an outer circumferential surface of each of the housings  130 , the portion corresponding to a position of each of the cores  110 ; imaging units  60  that image the respective objects  70  that move around the corresponding sensor modules  10  and image respective persons possessing the respective objects  70 ; impedance matching units  20  that are connected to a plurality of the sensor modules  10 , respectively, and perform impedance matching; and amplifiers  30  that are connected to the impedance matching units  20 , respectively, and amplify a fine current and voltage generated during approach of the objects  70  to the sensor modules  10 . 
     The sensor modules  10  can have respective induced magnetic fields formed due to a change in distance from the objects  70  containing iron (Fe). That is, the sensors  100  can have respective induced magnetic fields formed due to a change in distance from the objects  70  containing iron (Fe). This is because the object  70  containing iron (Fe) can have a fine magnetic field due to a property of the iron (Fe) having magnetism, and a movement or direction change of the object  70  containing iron (Fe) can cause the induced magnetic field to be formed in the sensor  100 . 
     Specifically, the core  110  does not contain any magnetic component, and the induced magnetic field can be formed in the sensor  100  due to an approach or separation of the magnetic field of the object  70  containing iron. Further, the generation of the induced magnetic field can cause a fine current and voltage to be generated in the coil  120 . That is, the configuration described above enables a magnetic flux quantity having an effect on the core  110  to be detected whenever a location or a direction of the object  70  containing iron (Fe) is changed, even when the core  110  is affected by a nano scale of flux quantity from the object  70  containing iron (Fe) or a magnetic field formed by the object  70  containing iron (Fe) has a magnetic flux density of equal to or smaller than several milligauss. 
     In order to fulfil a function described above, the core  110  can have good hysteresis characteristics and relatively high permeability. Specifically, in order to form the core  110 , metal powder is mixed in proportion of 4.6 to 5.2 wt. % of iron (Fe), 74.3 to 75.6 wt. % of nickel (Ni), 12.5 to 13 wt. % of silicon (Si), 1.5 to 1.6 wt. % of chromium (Cr), and 5.8 to 5.9 wt. % of cobalt (Co) and is molded through the injection molding at a temperature of 1,300° C. or higher into a ribbon (or tape) shape having a thickness of 0.025 mm or smaller considering the permeability and impact having an effect on remote sensing, and a thin and lightweight core can be obtained. In addition, a plurality of thin cores  110  formed as described above can be configured to be overlapped and integrated with each other. 
     Here, since a nickel content accounts for a significant percent by weight in the core  110 , it is important for nickel to be inhibited from dissolving at a low temperature. In addition, since a magnetic characteristic (hysteresis) of cobalt is degraded at a temperature of 1,200 to 1,300° C., it is important not to perform the injection molding at a temperature of 1,300° C. or higher. In addition, since the injection molding is vulnerable to impact, the injection molding has to be performed at a low injection speed and quenched at 106° C./sec such that the core  110  can have durability. 
     When a plurality of types of metal powder are mixed as described above, the mixed powder is heterogeneous, and thus particles can be arranged by providing a strong magnetic field while a heat treatment of heating the particles at a certain temperature is performed until the particles dissolve, so as for the particles of the mixed powder to maintain an arranged state in a certain direction. In addition, in order for the particles to maintain the arranged state, the core  110  formed in a process described above can be gradually cooled while being located in a magnetic field to be subjected to a magnetic field process. Accordingly, the hysteresis and the permeability of the core  110  can be increased. 
     As the characteristics of the core  110  becomes better when the thickness is thinner and the core  110  has to be lightweight so as to withstand impact, the core  110  made of an amorphous type of or permalloy metal is preferable; however, the permalloy metal has a higher degree of change due to impact than the amorphous metal does, and thus the amorphous core  100  can be used in the metal detecting system of the present invention. 
     The housing  130  can be formed into a cylindrical shape having an inner space, and the housing  130  can be made of an insulation material. In addition, the core  110  which is a passage of magnetic flux induced by the coil  120  can be formed in the inner space of the housing  130  corresponding to a position of the coil  120 . Further, the coil  120  can be made of a metal wire such as an iron wire, a nichrome wire, or a copper wire. 
     The metal detecting system of the present invention can measure movement of one or more objects  70 . Further, the metal detecting system can measure the number and a magnetic flux density of the objects  70 , as well as a location, a direction, a speed, or the like related to the movement of the objects  70 . In this respect, the plurality of sensor modules  10  can be formed, and the impedance matching units  20  and the amplifiers  30  can be connected to the plurality of sensor modules  10 , respectively. 
     In addition, the metal detecting system of the present invention can further include: a first control unit  41  that is connected to the amplifiers  30  and analyzes a waveform of the amplified current and voltage; and a second control unit  42  that is connected to the first control unit  41  to generate analysis information of objects  70  by analyzing movement and magnetic flux density of the objects  70  and is connected to the imaging units  60  to collect the captured images. 
     In the embodiment of the present invention, the sensor modules  10  (first to third sensor modules) are described to be arranged side by side at regular intervals; however, arrangement thereof is not limited thereto, and the arrangement of the sensor modules  10  can be modified depending on a use of the metal detecting system of the present invention. 
     As illustrated in  FIGS.  1  and  2   , the metal detecting system of the present invention can analyze movement paths, movement speeds, or the like using locations, directions, and speeds of the plurality of objects  70 , respectively, and can analyze relative movement between one object  70  and another object  70 . 
     As a specific embodiment, as illustrated in  FIG.  1   , a first object  71  possessed by a first person can move from left to right on the drawing toward a space between a first sensor module  11  and a second sensor module  12 , a second object  72  possessed by a second person can move toward a space above the second sensor module  12  based on the drawing, and a third object  73  possessed by a third person can move toward a space between the first sensor module  11  and a third sensor module  13 . 
     In the description of the embodiment of the present invention, the persons possess the respective objects  70  and move, and the imaging units  60  image the respective persons; however, only the objects  70  are illustrated in  FIGS.  1  and  2    for the convenience of understanding. The objects  70  can be possessed inside or outside clothes of the persons. 
     Hereinafter, generation of analysis information of the objects  70  through measurement of the movement, the number, the magnetic flux density, or the like of the objects  70  will be described, the measurement being performed by the sensor modules  10 . 
     The first object  71  can have a magnetic flux density of 5×10 −17  T (Tesla) and a speed of 4 km/h (normal walking speed of a person), the second object  72  can have a magnetic flux density of 3×10 −17  T (Tesla) and a speed of 4 km/h, and the third object  73  can have a magnetic flux density of 5×10 −17  T (Tesla) and a speed of 6 km/h. 
     Further, as illustrated in  FIG.  2   , a fourth object  74  possessed by a fourth person can move in a direction from the second sensor module  12  toward the first sensor module  11 , and a fifth object  75  possessed by a fifth person can move toward the first sensor module  11  and the third sensor module  13 . Here, the fourth object  74  can have a magnetic flux density of 5×10 −17  T (Tesla) and a speed of 4 km/h, and the fifth object  75  can have a magnetic flux density of 5×10 −17  T (Tesla) and a speed of 6 km/h. 
     First, in analysis of the number of objects  70 , when the first object  71 , the second object  72 , and the third object  73  move as described above, sensors  100  of the first sensor module  11 , the second sensor module  12 , and the third sensor module  13  can generate signals depending on movements of the objects  70 , respectively, and all of the signals of the sensors  100  can be transmitted to the first control unit  41  through the impedance matching units  20  and the amplifiers  30  connected to the respective sensor modules  10 . The first control unit  41  can analyze a plurality of such signal patterns, thereby, determining the number of objects  70  which pass adjacent to the respective sensor modules  10 . The first control unit  41  stores data of respective signal patterns based on magnetic flux densities and speeds of the objects  70  and data of a compound pattern obtained when two or more signal patterns are superimposed, and the first control unit  41  can calculate the number of unique signal patterns of the objects  70  by analyzing the respective signal patterns, thereby analyzing the number of objects  70  which pass by the metal detecting system of the present invention. Here, data of the signal patterns or the compound patterns can be stored through experiments. However, another technology in the related art can be used as a signal separating technology for identifying the objects  70 . 
     This can be also applied to a case where the fourth object  74  and the fifth object  75  move. As a result, through analysis performed by the first control unit  41 , the objects  70  can be individually identified, and signal patterns of the objects  70  can be separated from each other. 
     In the description of the embodiment of the present invention, one person possesses one object  70 ; however, one person can possess two or more objects  70 , or two or more persons can carry one object  70 . That is, a possession relationship between persons and objects  70  is not limited. Accordingly, the number of objects  70  possessed by persons needs to be determined, and thus combined analysis performed by a linkage of the sensor modules  10  and the imaging units  60  can be performed using the imaging units  60  to be described below. This is to be described below in detail. 
     In the analysis of the movement paths, the movement speeds, and the magnetic flux densities of the objects  70 , the objects  70  are individually identified by the signal pattern analysis performed by the first control unit  41 , and respective signal patterns of the objects  70  can be transmitted to the second control unit  42 . Further, the second control unit  42  can analyze the movement paths and the movement speeds of the objects  70  by analyzing the respective signal patterns. 
     Specifically, as illustrated in  FIG.  1   , when the first object  71 , the second object  72 , and the third object  73  move rectilinearly in one direction (reference direction), the objects  70  can be individually identified as described above, and thereby the signal patterns of the objects  70  can be separated from each other by the first control unit  41  and be transmitted to the second control unit  42 . Here, the second control unit  42  can analyze that the objects  70  form respective signal patterns, each of which has certain strength, with respect to the respective sensor modules  10 , thus determining that the first object  71 , the second object  72 , and the third object  73  move in the same direction and determining the magnetic flux densities and the movement speeds of the objects  70  based on the respective signal patterns of the objects  70 . Here, similarly to the first control unit  41 , the second control unit  42  can store data of respective signal patterns depending on the magnetic flux densities and the speeds of the objects  70 , and the second control unit  42  can use the stored data. 
     Further, as illustrated in  FIG.  2   , when the fourth object  74  and the fifth object  75  move in respective directions different from each other, the objects  70  can be individually identified as described above, and thereby the signal patterns of the objects  70  can be separated from each other by the first control unit  41  and be transmitted to the second control unit  42 . Here, the second control unit  42  can analyze a phenomenon in which the strength of a signal pattern of the fourth object  74  gradually increases in the first sensor module  11  and gradually decreases in the second sensor module  12 , a pattern of a strength change thereof, or the like, thereby determining that the fourth object  74  moves to form a certain angle with respect to a reference direction (direction in which the fifth object  75  moves) and determining the magnetic flux density and the movement speed based on the signal pattern of the fourth object  74 . The analysis of the movement of the fifth object  75  can be similar to the analysis of the first object  71  and the like described above. 
     Hereinafter, analysis of the objects  70  by using the information of the sensor modules  10  and the captured images will be described. 
     As illustrated in  FIGS.  1  and  2   , one or more of the imaging units  60  can be formed to acquire the captured images of the entirety of measurable regions of the sensor modules  10 . The imaging units  60  can be variously arranged corresponding to the arrangement of the sensor modules  10 . Further, any device such as a camera or an image sensor which can acquire an image can be used as the imaging unit  60 . 
     The objects  70  can be analyzed using the information acquired by the sensor modules  10  and the captured images as images acquired by the imaging units  60 . In this respect, the second control unit  42  can categorize the objects  70  using the analysis information of the objects  70  and the captured images. Here, the second control unit  42  can determine whether or not the magnetic flux density of the objects  70  is within a predetermined magnetic flux density range and then determine types of objects  70  by analyzing the captured images. The analysis information of the objects  70  can include information of the number of objects  70 , the movement paths and movement speeds of the objects  70 , the magnetic flux density of the objects  70 , or the like. 
     The second control unit  42  can discriminate between the objects  70  having respective magnetic flux densities within the predetermined magnetic flux density range. That is, the second control unit  42  can determine whether or not a specific object  70  passes by the metal detecting system of the present invention. Specifically, as described above, the first control unit  41  can identify the individual objects  70 , separate the signal patterns of the individual objects  70 , and transmit the separated signal patterns to the second control unit  42 , and the second control unit  42  can analyze the transmitted signal patterns of the objects  70  to determine whether a magnetic flux density of a corresponding object  70  is within a predetermined magnetic flux density range. That is, since the objects  70  passing by the metal detecting system can have respective different amounts of iron component so as to have respective different magnetic flux densities and the magnetic flux density of a category of a specific object  70  can be within the predetermined magnetic flux density range, the second control unit  42  can determine whether an object  70  belongs to the category of the specific object  70  using the magnetic flux density of the object  70 . 
     Specifically, firearms can contain a relatively high density of iron component due to a forging process, thus having a relatively high magnetic flux density. Accordingly, the magnetic flux density of the firearms can form a predetermined magnetic flux density, and the second control unit  42  can discriminate an object  70  as a firearm when a magnetic flux density of the corresponding object  70  is within a magnetic flux density of the firearms. 
     However, when discrimination between the objects  70  is performed only using the magnetic flux density, an object  70  which is not a firearm but has a magnetic flux density within the magnetic flux density range of the firearms can be determined as the firearm. Hence, after primary analysis of a type of object  70  as described above, secondary analysis using captured images can be performed. Hereinafter, an object  70  which is categorized primarily as a firearm using the magnetic flux density can be referred as a suspected firearm object. 
     When the suspected firearm object is detected as described above, a captured image of the suspected firearm object or a person possessing the suspected firearm object can be transmitted to the second control unit  42  in real time. The second control unit  42  can store images of the objects  70  corresponding to various types of firearms, and thus the second control unit  42  can perform analysis by comparing the suspected firearm object and the stored image and definitively determine whether or not the suspected firearm object is a firearm. 
     However, a case of determination of the suspected firearm object using an instant captured image as described above can be a case where the suspected firearm object is exposed outside from a person possessing the corresponding object  70 . On the other hand, in a state where the suspected firearm object is located inside the person possessing the corresponding object  70 , that is, in a state where the suspected firearm object is hidden under clothes of the person, it is not possible to easily analyze by comparing an instant captured image and the image stored in the second control unit  42  as described above. 
     In such cases, the imaging unit  60  can have a heat detecting function. When the second control unit  42  does not detect a firearm on the captured image even though a suspected firearm object is detected, the second control unit  42  can transmit a control signal to the imaging unit  60 , and the imaging unit  60  which received the control signal can start to operate the heat detecting function and collect a thermal image as a captured image of a person who is tracked due to a possibility of possession of a suspected firearm object. The thermal image can be transmitted to the second control unit  42 , and the second control unit  42  can determine whether a firearm is hidden under clothes of the corresponding person. Here, even when a firearm is hidden under the clothes of the person, the shape of the firearm is shown due to a temperature difference during performing the thermal function of the imaging unit  60 , and thereby the determination can be performed. 
     The second control unit  42  can generate an alarm signal when determining that the object  70  is a firearm. Further, the metal detecting system of the present invention can further include an output unit  50  that is connected to the second control unit  42 , visually outputs locational changes of the objects  70 , and outputs the alarm signal. 
     The alarm signal can be transmitted to the output unit  50 , and the alarm signal can be visually or audibly realized. Further, when the second control unit  42  definitively determines that the suspected firearm object is a firearm, the second control unit can transmit a captured image of a person possessing the corresponding object  70  to a security guard&#39;s communication device. 
     Further, the output unit  50  can receive information from the second control unit  42 , display a three-dimensional coordinate change of the movement path of the object  70  on a graph, an image, or the like, and display numerical value information of the movement speed, the magnetic flux density, or the like of the object  70  on a screen. 
     As described above, a suspected firearm object is discriminated from a plurality of objects  70  primarily using the magnetic flux density, the location of the discriminated suspected firearm object (or person possessing the corresponding object  70 ) is tracked, and, secondarily, analysis of the suspected firearm object is performed using the analysis information of the object  70  and the captured image of the suspected firearm object. In this manner, a detection speed of a firearm object  70  can be remarkably improved. 
     Further, since measurement of the object  70  can be performed using a combination of the analysis information of the object  70  acquired by the sensor modules  10  and the captured images acquired by the imaging unit  60 , the measurement accuracy of the object  70  can be improved. 
     In the embodiment of the present invention, discrimination between the firearm objects  70  is specifically described; however, the types of discriminated objects  70  are not limited to the firearms, and the same principle of discrimination can be used for another object  70 . 
     Hereinafter, installation of the sensors  100  included in the sensor module  10  will be described.  FIG.  8    is a schematic diagram illustrating a sensor  100  according to a third embodiment of the present invention, and  FIG.  9    is a schematic diagram illustrating a sensor module  10  according to the third embodiment of the present invention. Further,  FIG.  10    is a schematic diagram illustrating a sensor module  10  according to a fourth embodiment of the present invention. 
     As illustrated in  FIGS.  3 ,  4 , and  7  to  10   , a plurality of sensors  100  can be arranged in parallel or radially with each other. First, a case where the plurality of sensors  100  are arranged in parallel with each other is to be described. 
     As illustrated in  FIGS.  3  and  4   , the plurality of sensors  100  can be arranged in parallel with each other, and a position of a core  110  and a coil  120  with respect to one housing  130  can differ from a position of a core  110  and a coil  120  with respect to another housing  130 . Specifically, of the plurality of sensors  100 , a 1-1st sensor  101  and a 1-2nd sensor  102  can be formed in parallel to be positioned side by side, a 1-1st core  111   a  and a 1-1st coil  121   a  can be formed at a right portion of the first sensor  100 , and a 1-2nd core  111   b  and a 1-2nd coil  121   b  can be formed at a left portion of the second sensor  10 . 
     As illustrated in  FIGS.  3 ,  4 , and  7   , when the object  70  containing iron (Fe) moves to approach the sensor  100  from the left side to the right side of the drawings, a change in magnetic field momentarily occurs in the core  110 , and thus a fine voltage and current can be induced to be generated in the coil  120 . In this case, when a non-polarity part (represented by Reference sign A in  FIG.  7   ) as a part in which N pole and S pole of the object  70  containing iron (Fe) is switched passes by the 1-1st core  111   a , the generation of the voltage and the current induced by the 1-1st core  111   a  and the 1-1st coil  121   a  provided in the 1-1st sensor  101  can be stopped. Here, not only when a magnetic line of force does not affect the 1-1st core  111   a  and the 1-1st coil  121   a  at all due to the non-polarity part, but also when the magnetic line of force partially affects the 1-1st core  111   a  and the 1-1st coil  121   a  as illustrated in  FIG.  7   , the magnetic flux density can be remarkably reduced in the vicinity of the non-polarity part such that generation of an induced voltage and current can be stopped. 
     On the other hand, at the same time, since the 1-2nd core  111   b  and the 1-2nd coil  121   b  provided in the 1-2nd sensor  102  are affected by distortion of a magnetic field through the N or S pole which is generated by the object  70  containing iron (Fe), that is, affected by magnetic field movement of the object  70  containing iron (Fe), a fine voltage and current can be induced in the 1-2nd coil  121   b.    
     Further, one end of a coil  120  provided in one sensor  100  can be connected to one end of a coil  120  provided in another sensor  100 , and the other end of the coil  120  provided in the one sensor  100  can be connected to the other end of the coil  120  provided in the other sensor  100 . Accordingly, a lead wire of the one sensor  100  and a lead wire of the other sensor  100  can be connected to have the same signal. 
     Specifically, when an induced magnetic field is generated to the core  110  and the coil  120  (the 1-1st core  111   a  and the 1-1st coil  121   a ) provided in the one sensor  100  and the core  110  and the coil  120  (the 1-2nd core  111   b  and the 1-2nd coil  121   b ) provided in the other sensor  100 , a fine current and voltage can be generated in the coil  120  provided in the one sensor  100  such that a + pole and a − pole can be formed therein, and similarly, a fine current and voltage can be formed in the coil  120  provided in the other sensor  100  such that a + pole and a − pole can be formed therein. In this case, the + pole of the coil  120  provided in the one sensor  100  can be connected to the + pole of the coil  120  provided in the other sensor  100 , and the − pole of the coil  120  provided in the one sensor  100  can be connected to the − pole of the coil  120  provided in the other sensor  100 . 
     Even when the non-polarity part of the object  70  containing iron (Fe) passes by the one sensor  100  as described above, and the generation of the current and the voltage is stopped in the coil  120  provided in the one sensor  100 , the connection of the same signal as described above enables the current and the voltage to be generated in the coil  120  provided in the other sensor  100  such that the sensor  100  can be continuously and normally operated. 
     The impedance matching units  20  can be connected to lead wires connected to the plurality of coils  120 , respectively, and perform impedance matching. The impedance matching unit  20  can maximize a signal transmission efficiency by reducing a loss of signal by reducing reflection due to an impedance difference between signals (fine current or voltage) transmitted from both ends of each of the sensors  100 . Further, the amplifier  30  can include an amplification circuit for amplifying a transmitted signal, amplify the signal transmitted from the impedance matching unit  20 , and transmit the amplified signal to the first control unit  41 . 
     The first control unit  41  can determine whether displacement occurred to the object  70  containing iron (Fe) or displacement occurred to the sensor modules  10  by analyzing a waveform of an amplified signal. 
     The first control unit  41  can be realized by a signal processing module such as a microcomputer or an FPGA, and a software algorithm (SW algorithm) can be applied thereto. The SW algorithm can determine whether the displacement occurred to the object  70  containing iron (Fe), the sensor  100  provided in the sensor module  10 , or both the object and the sensor based on a difference in information of a signal pattern obtained during the occurrence of displacement to the sensor  100  and a signal pattern obtained during movement of the object  70  containing iron (Fe). 
     Specifically, since the sensors  100  respond to a fine magnetic field, in a case where the displacement occurred to the sensor  100 , the signal pattern can be formed by being affected by a change in magnetic field of the Earth, magnetic field of another object  70  around the sensor, or the like, in addition to a magnetic field change due to the occurrence of relative displacement of the sensor  100  with respect to the object  70  containing iron (Fe), while in a case where the displacement occurred to the object  70  containing iron (Fe), the sensor  100  is affected only by a change in magnetic field due to the occurrence of the relative displacement with respect to the object  70  containing iron (Fe). Hence, different signal patterns can be formed depending on both the cases. Further, similarly, in a case where displacement occurred to the object  70  containing iron (Fe) and the sensors  100  simultaneously, another signal pattern can be formed. 
     As described above, different signal pattern can be formed depending on cases, and the signal patterns formed for each cases can be stored in the first control unit  41  and form reference data. Here, the signal pattern stored in the reference data of the first control unit  41  can be experimentally derived. The first control unit  41  can analyze similarity or the like by determining through comparison between a signal pattern transmitted from the amplifier  30  and the signal pattern in the reference data of the first control unit  41 , thereby performing determination of whether the displacement occurred to the object  70  containing iron (Fe) or the sensors  100 . 
     The second control unit  42  can receive, from the first control unit  41 , information of whether the displacement occurred to the object  70  containing iron (Fe) or the displacement occurred to the sensors  100  and data of a waveform of the signal pattern and analyze an actual displacement path of a displaced agent. The second control unit  42  can be realized by a signal processing module such as a microcomputer or an FPGA, and a software algorithm (SW algorithm) can be applied thereto. 
     Specifically, the signal pattern for the occurrence of displacement of the object  70  containing iron (Fe), the signal pattern of the occurrence of displacement of the sensor  100 , or the signal pattern of the simultaneous occurrence of displacement of the object  70  containing iron (Fe) and the sensor  100  can be all stored in the second control unit  42  and form reference data. Here, the signal patterns stored in the reference data of the second control unit  42  can be experimentally derived. 
     The second control unit  42  can first confirm a displaced agent based on the information transmitted from the first control unit  41 , select a data category related to a displaced agent from the reference data of the second control unit  42 , and then analyze similarity by determining through comparison between the waveform of the signal pattern transmitted from the first control unit  41  and the signal pattern in the reference data of the second control unit  42 , thereby, performing a coordinate change based on the occurrence of the displacement of the object  70  containing iron (Fe), a coordinate change based on the occurrence of the displacement of the sensors module  10 , or the like. 
     In the embodiment of the present invention, the first control unit  41  and the second control unit  42  are described to be sequentially connected to each other; however, connection thereof is not limited thereto, and the first control unit  41  and the second control unit  42  can be configured simultaneously or independently. 
     That is, as described above, the first control unit  41  can determine whether the displacement occurred to the object  70  or the sensor module  10  in addition to identifying the object  70  by separating the signal patterns, the second control unit  42  can analyze the movement path and the movement speed of an object  70  and simultaneously analyze a movement path of the sensor module  10 . 
     Next, a case where the plurality of sensors  100  are arranged radially with each other is to be described. In  FIGS.  8  and  10   , regions enclosed by two-dot chain lines may indicate measurable regions (ranges) of the sensors  100  corresponding to the respective regions. 
     In  FIGS.  8  and  10   , for the convenience of understanding, the measurable regions of the sensors  100  are illustrated to be rather small; however, the measurable region is not limited thereto, and the measurable regions of the sensors  100  can be formed to be larger. Further, in  FIG.  10   , for the convenience of understanding, connection or the like of lead wires is omitted, and only arrangement of the sensors  100  is illustrated. 
     As illustrated in  FIGS.  8  to  10   , the plurality of sensors  100  can be radially arranged. Specifically, of the plurality of sensors  100 , a 3-1st sensor  103  and a 3-2nd sensor  104  can be radially formed (other sensors  100  are also radially formed; however, for the convenience of understanding, only the 3-1st sensor  103  and the 3-2nd sensor  104 , to which Reference signs are assigned, are to be described). 
     As described above, when the plurality of sensors  100  are radially arranged, the measurable regions of the plurality of sensors  100  can be formed to be contiguous to each other or to intersect with each other such that the detection efficiency of the object detected by the metal detecting system of the present invention can be remarkably improved. In particular, as illustrated in  FIG.  10   , when the plurality of sensors  100  are arranged in a three-dimensionally radial shape, the measurable regions of the plurality of sensors  100  can be formed into spherical shapes. Hence, not only can the detection efficiency be increased as described above, but also an advantage of easy detection of the object can be obtained even when the object moves toward any of an x axis, a y axis, and a z axis. Further, when the sensors  100  are separately disposed from each other, arrangement with consideration for the measurable regions of the sensors  100  may not be easy. However, when the metal detecting system of the present invention which is formed as described above, in which the plurality of sensors  100  are radially arranged, is used, the measurable regions can be formed into a cylindrical shape, a spherical shape, or the like, and thereby the measurable regions can be easily calculated such that detection region design of the object can be easily performed. 
     As illustrated in  FIGS.  8  to  10   , when the object  70  containing iron (Fe) moves to approach the sensor  100  from the left side to the right side of the drawings, a change in magnetic field momentarily occurs in the core  110 , and thus a fine voltage and current can be induced and formed in the coil  120 . In this case, when the non-polarity part as a part in which N pole and S pole of the object  70  containing iron (Fe) is switched passes by a 3-1st core  113   a , the generation of the voltage and the current induced by the 3-1st core  113   a  and a 3-1st coil  123   a  provided in the 3-1st sensor  103  can be stopped. Here, not only when a magnetic line of force does not affect the 3-1st core  113   a  and the 3-1st coil  123   a  at all due to the non-polarity part, but also when the magnetic line of force partially affects the 3-1st core  113   a  and the 3-1st coil  123   a , the magnetic flux density can be remarkably reduced in the vicinity of the non-polarity part such that generation of an induced voltage and current can be stopped. 
     On the other hand, at the same time, since the 3-2nd core  113   b  and the 3-2nd coil  123   b  provided in the 3-2nd sensor  104  are affected by distortion of a magnetic field through the N or S pole which is generated by the object  70  containing iron (Fe), that is, affected by magnetic field movement of the object  70  containing iron (Fe), a fine voltage and current can be induced in the 3-2nd coil  123   b.    
     Further, one end of a coil  120  provided in one sensor  100  can be connected to one end of a coil  120  provided in another sensor  100 , and the other end of the coil  120  provided in the one sensor  100  can be connected to the other end of the coil  120  provided in the other sensor  100 . Accordingly, a lead wire of the one sensor  100  and a lead wire of the other sensor  100  can be connected to have the same signal. 
     Specifically, when an induced magnetic field is generated to the core  110  and the coil  120  (the 3-1st core  113   a  and the 3-1st coil  123   a ) provided in the one sensor  100  and the core  110  and the coil  120  (the 3-2nd core  113   b  and the 3-2nd coil  123   b ) provided in the other sensor  100 , a fine current and voltage can be generated in the coil  120  provided in the one sensor  100  such that a + pole and a − pole can be formed therein, and similarly, a fine current and voltage can be formed in the coil  120  provided in the other sensor  100  such that a + pole and a − pole can be formed therein. In this case, the + pole of the coil  120  provided in the one sensor  100  can be connected to the + pole of the coil  120  provided in the other sensor  100 , and the − pole of the coil  120  provided in the one sensor  100  can be connected to the − pole of the coil  120  provided in the other sensor  100 . 
     Even when the non-polarity part of the object  70  containing iron (Fe) passes by the one sensor  100  as described above and the generation of the current and the voltage is stopped in the coil  120  provided in the one sensor  100 , the connection of the same signal as described above enables the current and the voltage to be generated in the coil  120  provided in the other sensor  100  such that the sensor  100  can be continuously and normally operated. 
     The description of the rest of the impedance matching units  20 , the amplifiers  30 , the first control unit  41 , and the second control unit  42  is the same as the description of the impedance matching units  20 , the amplifiers  30 , the first control unit  41 , and the second control unit  42  when the plurality of sensors  100  are arranged in parallel with each other. 
     As illustrated in  FIGS.  5  to  6   , the plurality of coils  120  provided in the sensor  100  can be arranged in series with each other. That is, in the sensor  100  provided in the sensor module  10 , the plurality of coils  120  can be arranged in series with each other, and one core  110  can be formed to be separated from another core  110 . Specifically, a 2-1st coil  122   a  and a 2-2nd coil  122   b  can be formed in series at one housing  130 , and a 2-1st core  112   a  and a 2-2nd core  112   b  can be formed to correspond to the coils. Here, the sensor module  10  can include one or more sensors  100 . 
     As illustrated in  FIGS.  5 ,  6 , and  7   , when the object  70  containing iron (Fe) moves to approach the sensor  100  from the left side to the right side of the drawings, a change in magnetic field momentarily occurs in the core  110 , and thus a fine voltage and current can be induced to be formed in the coil  120 . In this case, when a non-polarity part (represented by Reference sign A in  FIG.  7   ) as a part in which N pole and S pole of the object  70  containing iron (Fe) is switched passes by the 2-1st core  112   a , the generation of the voltage and the current induced by the 2-1st core  112   a  and the 2-1st coil  122   a  can be stopped. Here, not only when a magnetic line of force does not affect the 2-1st core  112   a  and the 1-1st coil  122   a  at all due to the non-polarity part, but also when the magnetic line of force partially affects the 1-1st core  112   a  and the 2-1st coil  122   a  as illustrated in  FIG.  7   , the magnetic flux density can be remarkably reduced in the vicinity of the non-polarity part such that generation of an induced voltage and current can be stopped. 
     On the other hand, at the same time, since the 2-2nd core  112   b  and the 2-2nd coil  122   b  are affected by distortion of a magnetic field through the N or S pole which is generated by the object  70  containing iron (Fe), that is, affected by magnetic field movement of the object  70  containing iron (Fe), a fine voltage and current can be induced in the 2-2nd coil  122   b.    
     Further, of the plurality of coils  120 , one end of one coil  120  can be connected to one end of another coil  120 , and the other end of the one coil  120  can be connected to the other end of the other coil  120 . Accordingly, a lead wire of the one coil  120  and a lead wire of the other coil  120  can be connected to have the same signal. 
     Specifically, when an induced magnetic field is generated to one coil  120  (2-1st coil  122   a ) and another coil  120  (2-2nd coil  122   b ), a fine current and voltage can be formed in the one coil  120  such that a + pole and a − pole can be formed therein, and similarly, a fine current and voltage can be formed in the other coil  120  such that a + pole and a − pole can be formed therein. In this case, the + pole of the one coil  120  can be connected to the + pole of the other coil  120 , and the − pole of the one coil  120  can be connected to the − pole of the other coil  120 . 
     Even when the non-polarity part of the object  70  containing iron (Fe) passes by the one sensor  100  as described above and the generation of the current and the voltage is stopped in the coil  120  provided in the one sensor  100 , the connection of the same signal as described above enables the current and the voltage to be generated in the coil  120  provided in the other sensor  100  such that the sensor  100  can be continuously and normally operated. 
     The description of the rest of the impedance matching units  20 , the amplifiers  30 , the first control unit  41 , and the second control unit  42  is the same as the description of the impedance matching units  20 , the amplifiers  30 , the first control unit  41 , and the second control unit  42  when the plurality of sensors  100  are arranged in parallel with each other. 
     In the embodiments of the present invention, the parallel arrangement of the sensors  100  in the sensor module  10  and the serial arrangement of the coils  120  in the sensor  100  are described separately from each other. However, the sensor module  10  can be formed to include a plurality of sensors  100  in which the coils  120  are arranged in series in one sensor  100 , with the sensors  100  being arranged in parallel, and the coils  120  are provided at different respective positions with respect to each of the sensors  100  so as to inhibit an effect of the non-polarity part of the object  70  containing iron (Fe). Such a configuration and principle described above can also be applied to such a case described above in the same manner. 
       FIGS.  11  and  12    illustrate signal pattern graphs obtained in a state where the object  70  passes by the sensor  100  according to the first embodiment of the present invention. Specifically, (a) of  FIG.  11    illustrates a graph obtained in a state where a single sensor  100  according to the first embodiment of the present invention is formed and a lengthwise axis of the sensor  100  is perpendicular to the ground, and (b) of  FIG.  11    illustrates a graph obtained in a state where the sensors  100  according to the first embodiment of the present invention are arranged in parallel with each other and lengthwise axes of the sensors  100  are perpendicular to the ground. Further, (a) of  FIG.  12    illustrates a graph obtained in a state where a single sensor  100  according to the first embodiment of the present invention is formed and a lengthwise axis of the sensor  100  is horizontal to the ground, and (b) of  FIG.  12    illustrates a graph obtained in a state where the sensors  100  according to the first embodiment of the present invention are arranged in parallel with each other and lengthwise axes of the sensors  100  are horizontal to the ground. 
     As illustrated in  FIGS.  11  and  12   , when the metal detecting system of the present invention is used, it is possible to confirm easy performance of the detection of the object  70  by using the sensors  100  regardless of whether the lengthwise axis of the sensor  100  is perpendicular or horizontal to the ground. Further, as found in comparison between a case of using a single sensor  100  and a case of using the plurality of sensors  100  arranged in parallel with each other, the occurrence of displacement of the object  70  containing iron (Fe) can be normally and continuously measured regardless of the non-polarity part of the object  70  containing iron (Fe). 
     According to the above-described configuration, a fine change in magnetic field and flux quantity of the object  70  containing iron can be detected such that a position, displacement, or the like of the object  70  containing iron can be detected with ultra-low electric power. In addition, even when the non-polarity range as a range in which a magnetic field of the object  70  subsides is formed as described above, the magnetic field of the object  70  containing iron can be detected by another adjacent sensor  100  or coil  120  such that the sensor module  10  can be normally and continuously operated. 
     Further, as described above, an additional effect of an installation direction or the like of the sensor  100  with respect to the ground is minimized such that detection and measurement can be performed regardless of the arrangement of the sensor modules  10 . In addition, when the metal detecting system of the present invention is formed by arranging the plurality of sensor modules  10 , information of the movement path, the movement speed, the magnetic flux density, or the like of the object  70  containing iron can be determined to be used. 
     Further, since the metal detecting system of the present invention can detect a fine change in magnetic field and flux quantity of the object containing iron, the metal detecting system can exhibit the same performance regardless of an effect of air, soil, water, or the like. 
     The description of the present invention described above is provided as an example, and a person of ordinary skill in the art to which the present invention pertains can understand that it is possible to easily modify the present invention to another embodiment without changing the technical idea or an essential feature of the present invention. Therefore, the embodiments described above need to be understood as exemplified embodiments in every aspect and not as limiting embodiments. For example, the configurational elements described in singular forms can be realized in a distributed manner. Similarly, the configurational elements described in a distributed manner may be realized in a combined manner. 
     The scope of the present invention needs to be construed by the claims below, and the meaning and the scope of the claims and every modified or altered embodiment derived from an equivalent concept of the claims need to be construed to belong to the scope of the present invention. 
     REFERENCE SIGNS LIST 
     
         
         
           
               10 : Sensor Module 
               11 : First Sensor Module 
               12 : Second Sensor Module 
               13 : Third Sensor Module 
               20 : Impedance Matching Unit 
               30 : Amplifier 
               41 : First Control Unit 
               42 : Second Control Unit 
               50 : Output Unit 
               60 : Imaging Unit 
               70 : Object 
               71 : First Object 
               72 : Second Object 
               73 : Third Object 
               74 : Fourth Object 
               75 : Fifth Object 
               100 : Sensor 
               101 : 1-1st Sensor 
               102 : 1-2nd Sensor 
               103 : 3-1st Sensor 
               104 : 3-2nd Sensor 
               110 : Core 
               111   a:  1-1st Core 
               111   b:  1-2nd Core 
               112   a:  2-1st Core 
               112   b:  2-2nd Core 
               113   a:  3-1st Core 
               113   b:  3-2nd Core 
               120 : Coil 
               121   a:  1-1st Coil 
               121   b:  1-2nd Coil 
               122   a:  2-1st Coil 
               122   b:  2-2nd Coil 
               123   a:  3-1st Coil 
               123   b:  3-2nd Coil 
               130 : Housing