Abstract:
An arrangement and method recognizes and classifies preferably hidden objects in object and/or human traffic. Objects relevant to security are recognized, located and tracked through the surroundings thereof in moving object and human traffic isolated in real time. Use is made of a combination of a field generator, the field of which is modified by at least one corresponding object within the scanned space, first sensors which repeatedly record the changes in the field and provide corresponding signals, second sensors which record defined surroundings of the object in real-time with relation to the first sensors and provide corresponding signals and analytical means which correlate and collate the signals from the sensors with each other and which give from the same the shape, spatial position and/or spatial orientation of the object.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an arrangement and method for recognizing and classifying preferably hidden objects in object and/or human traffic within a detection area. Said recognition and classification depend on the material of the objects, and are carried out without contacting them. The invention can be applied both in safety engineering and for the registration of the movement of structures. 
     To ensure safety at public places, in buildings, at airports and railway stations and at other security-relevant traffic, transport and industrial plants, different monitoring systems are used for persons, pieces of luggage, packages, freights, containers, means of transport and other objects. For this purpose, the persons or objects are normally monitored in real spatio-temporal course individually and in security gate areas. Mostly, the technical means used for this purpose help to detect potential danger situations and to automatically classify the risk levels, thus supporting the security personnel by drawing their attention to such persons and objects. In particular, individual sensor-based methods only allow a sensor-specific pre-selection. 
     A task that has not been solved, so far, is the detection of specific weapon- or bomb-like objects carried by individual persons on their bodies or in pieces of luggage in human traffic that cannot be isolated. Here, the security personnel can only implement random controls. The selection of the random sampling is based on visual observation, directly by persons on site or indirectly by technical means (closed circuit TV) that possibly allow experience-based conclusions to be drawn about a danger potential from specific person characteristics or the odd behavior of the persons. 
     The object of this invention is to develop an arrangement and a method that allow to security-relevant objects to be recognized, located and tracked in moving object and human traffic that generally cannot be isolated. 
     SUMMARY OF THE INVENTION 
     According to the present invention, this object is solved by a method and apparatus by which magnetic fields are changed by at least one corresponding object in a scanned space, field changes are repeatedly recorded and corresponding signals outputted, a defined surrounding of the object in real-time with relation to the first sensors are recorder and corresponding signals delivered with relation to the field changes, and the signals are correlated and collated with each other so as to show the shape, spatial position and/or spatial orientation of the object. The generation of magnetic or radiation fields, which are spatially and temporally changed by security-relevant objects, and the use of sensors measuring or indicating these changes, as well as the visual recording of the whole object and/or human traffic within the detection area by suitable sensors, preferably video sensors, and at least the appropriate linkage and assignment of the signals provided by the sensors, allow the arrangement according to the invention to recognize and record the shape and size of security-relevant objects and persons in object and/or human traffic. If at least one security-relevant object is in the detection area, not only the shape, size, spatial position and orientation of the object can be recognized on the basis of the measured signals provided by the magnetic or radiation sensors in the analytical unit, but it is also possible to repeatedly mark, save and image the specific position in a video photo and thus a quasi virtual isolation can be achieved. Almost in real-time, security-relevant measures can then be implemented. 
     The field generators used in connection with the invention can be magnetic, electro-magnetic, electrical, mechanical, electro-mechanical, optical, acoustic and/or thermal ones. The sensors of the invention are magnetic, electro-magnetic, capacitive, inductive, mechanical, optical, acoustic, thermal, atomic, biological and/or chemical sensors. The second sensors of the invention are mainly magnetic or optical sensors. The sensors mentioned can also be used together in any combination. In an advantageous embodiment of the invention, a magnetic field is generated as a continuous or an alternating field by permanent and/or electro-magnets in the detection area, and this field is scanned or recorded by means of magnetic sensors (first sensors) that deliver their measured signals to the analytical means or analytical unit where they are correlated and collated with each other. In the detection area, the first sensors can be arranged under or/and above the object and/or human traffic (traffic) in at least one line positioned at a right angle with respect to the traffic in such a way that the complete width of the traffic is registered. Advantageously, the first sensors are arranged in several lines orientated rectangular with respect to the traffic. This also ensures that the traffic is recorded in a sufficient depth. 
     To detect magnetic objects, it is possible to use distortions of the terrestrial magnetic field that are measured by a three-dimensional magnetic-field sensor. 
     In an advantageous embodiment, a single-signal and series-signal processing unit is arranged downstream of the magnetic-field sensors to allow a spatial and time correlation processing of the signals and their collation. Permanent magnets can be used as magnetic field generators, and are positioned so that stray fields caused by magnetic objects that are carried by, or positioned near to, persons, are amplified when the traffic passes the detection area. Said permanent magnets generate a continuous magnetic field. If several permanent magnets are installed in a line in rectangular position with respect to the traffic, they can be arranged either with the same polarization or with always alternating polarization one next to the other or one behind the other for amplifying the stray field. An amplification of the stray fields can also be achieved if the permanent magnets are provided with ferromagnetic short-circuit units at their side opposite to the detection area and outside the object and/or human traffic. Advantageously, the permanent magnets are oblong rectangular parallelepipeds that are orientated towards the traffic direction and the ferromagnetic short-circuit units. In this arrangement, the height of the permanent magnets on the polarization level and the height or thickness of the ferromagnetic short-circuit units have a defined ratio to each other. The primary field of at least two permanent magnets, which are arranged in an alternating orientation, can be varied in its shape and range in dependence of the magnetic moment of the permanent magnets used and of their distance to each other. With respect to the traffic, the magnetic field sensors (first sensors) can be arranged either on the same side of or opposite to the magnetic field generators. If the magnetic field sensors are positioned on the side of the magnetic field generators, advantageously one magnetic field sensor and one magnetic field generator are always arranged next to the other, and the distances between the magnetic field sensors and the magnetic field generators are identical. To eliminate the direct influence of the primary field on the magnetic field sensors, one magnetic compensation unit is arranged for each magnetic field sensor and at the place of the sensor said unit generates a field that is opposite to the primary field and has the same strength. If the magnetic field sensors are arranged in line, disturbance and surrounding fields can be suppressed by frequency, high- and low-pass filters and by differential procedures so that the stray fields generated by the objects in the detection area can be discriminated. 
     Advantageously, the object-induced stray fields can be repeatedly measured at intervals so that the magnetic field changes can be spatially ascribed to different magnetic field sensor areas. The measurements are preferably repeated at a frequency ranging from 4 to 16 Hz. The repeated time- and spatial-relevant measurement of the stray field caused by magnetic objects allows to recognize characteristics of the field, such as for example poles, minima and maxima hardly or strongly separated with respect to space and time as well as the absolute and relative zero crossings of the stray field components. 
     To determine the shape of magnetic objects that cause the measured stray fields, they are compared or correlated with stored magnetic signatures (pattern signatures). It is also possible to verify or correlate the spatial and time assignment of the objects recognized by the magnetic field sensors by the parallel use of additional other sensors. The recognized objects in the detection area can be reliably tracked by their corresponding marking (time stamp). 
     The results gained from the signals of the first and second sensors in the analytical unit can be sent to stationary or mobile information or communication devices, or they can be saved in a cache or final memory. In each embodiment, the mobile visualization of the security-relevant persons and pieces of luggage is possible in real-time, so that security measures can be taken immediately in case of a potential danger. On the basis of the video sensors used, an image processing system is coupled to the person and object tracking, and provides the tracks of the persons and objects after they have passed a measuring bench in the detection area. In this way, identified persons and objects can be rapidly found, recognized, tracked and observed by technical means or visually on the basis of their movement direction in adjacent or other video-monitored areas. 
     To generate alternating magnetic fields, the permanent magnets positioned at right angles to the traffic direction can rotate around axes that are oriented parallel to the traffic flow. In the same way, the magnetic compensation units can rotate around parallel axes. 
     In the following, the invention is explained in detail in schematic drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic depiction of a detection area with the basic arrangement possibilities of the field generators and sensors according to an embodiment of the invention in a perspective view; 
         FIG. 2  is a schematic depiction of the first and second sensors used according to the invention and their connection to the analytical unit, image processing system included, 
         FIG. 3  is a schematic depiction of an arrangement of field generators and first sensors with means for field amplification, 
         FIG. 4  is a cross-section of a detection area with a first arrangement of the field generators and sensors belonging to them, 
         FIG. 5  is a cross-section of a detection area with a second arrangement of the field generators and sensors belonging to them, and 
         FIG. 6  is a schematic depiction of an arrangement of rotating permanent magnets and a compensation unit belonging to the sensor according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  schematically depicts a detection area or scanned space  10 , for example an entry and/or exit area of a department store in which persons  11  and objects  12  move towards different directions. In the detection area  10 , all persons  11  and objects  12  are visually registered by means of second sensors  13  and  14  several times. This registration is performed at a frequency of for example 8 Hz. But it can also be performed at a lower or higher frequency, depending on the object and human traffic  11 ,  12  and the depth of the detection area (spherical area). 
     In a subarea  101 , which has normally a considerably lower depth expansion than the detection area  10 , field generators  15 , preferentially magnetic field generators, and first sensors  16  are arranged in the floor and/or in the ceiling under or above the object and human traffic  11 ,  12 . They react to the generated fields (magnetic or radiation fields), and their changes cover the total width of the detection area  10 , and as a whole, they form a measuring bench  18 . The field generators can be for example at least one line of permanent magnets  15 , and first sensors  16  are arranged opposite to them in corresponding lines. If the magnetic field of the permanent magnets  15  is disturbed by an object  121  in a specific area, it will be timely and spatially registered, the first sensors  16  deliver corresponding signals to an analytical unit  24  (see  FIG. 2 ), said signals will be collated with the corresponding signals of the second sensors  13 ,  14 , and the object with its surrounding  102  is shown on a display  17  (PDA). The figure represents a person  111  that carries a suitcase  121  containing a security-relevant, hidden object. The sensor  13  is required for the exact assignment of the objects and persons to the magnetic field signals, whereas the sensor  14  is necessary for visually recording the persons. Moreover, the signals of the sensors  15 , which are arranged in at least one line, can be correlated with each other in such a way that a shape image of the object contained and hidden in the suitcase  121  is generated in the area, and can be compared in a preferably automatic manner with the pattern image of the object. Principally, the object can also be carried by a person more or less visibly on his or her body. 
     In detail for example the following happens in  FIG. 1 : 
     Within the subarea  101  the first sensors  16  record the spatial/time course of persons  11  who pass the detection area  10  with or without objects  12  to be detected at a defined measuring frequency that is at least as high as the frequency of sensor  13 . Due to the spatially adjacent, cluster-type repeated arrangement of the first sensors  16 , a spatial/time correlation of all signals of the sensors, sensor  14  included, is possible. The measurement is carried out by microcontrollers (not shown in the figure), and the data obtained are analyzed by a common, not shown, industrial PC, depending on the number of modules that can be combined in the analytical unit  24  ( FIG. 2 ). 
     If the sensor lines of first sensors  16  detect a suspicious object or several such specific objects, each of these events will be assigned to one segment of the sensor lines  15  in a spatially and timely separated manner. Then, each of the position- and time-related events will be correlated to optically (visually) isolated persons in the space-time object track coordinates and the shape extensions of the sensor  13 . Other thermal profiles and height profiles spatially and timely generated in the area of the measuring bench  18  can be included into this correlation, too. As a result of this procedure, the following information is provided at this point of time:
         at least one special object is in the subarea  101 ,   the point of time and the extension of the special object on the measuring bench  18  in the width direction due to the number of the stimulated sensors, and   the object is located directly on a person&#39;s body or possibly in a piece of luggage belonging to the person.       

     If such a special object is detected on or with a person, a critical situation has been reached from the point of view of safety, has caused a reasonable initial suspicion, and requires a verified action of the safety staff. 
     If the detection area  10  is recorded by a closed-circuit TV camera  14 , at the height of the measuring bench  18  below the sensor  13 , this technical means can be integrated in a time- and spatial-limited manner as a measuring range into the cluster of the first sensors  16  in order to avert a danger. In the case of a reasonable initial suspicion, the multisensor system accesses single images  102  in a spatial—and time-limited manner in the subarea  101 . Via the spatially limited segmentation determined by the first sensors  16  and the sensor  13  in the range of the measuring bench  18 , it is possible to create a contour frame as a partial area of the subarea  101  via the contour width of the top view of the detected anonymous person with or without a piece of baggage, and the contents of said partial area will be saved alone and/or presented in a PDA. 
       FIG. 2  shows the analytical unit  24  that is connected both with different sensors  14 ,  19 ,  20 ,  21 ,  22 ,  23  individually or in various combinations, and with a display  17  that can be a part of a PDA of the security staff. Here, the sensor  14  is used for video-recording the complete structure of the detection area  10 , in particular the subarea  101 . It can be arranged laterally and in front of the object and/or human traffic. A sensor  19  allows the movements  191  (see  FIG. 1 ) of all persons and objects being in the detection area  10  to be tracked. Sensor  19  can be installed at the ceiling of the detection area  10 , and preferably designed as a video camera. A sensor  20  delivers a height profile of the object and/or human traffic in the range of the measuring bench  18  (see  FIG. 1 ), and like the sensor  19 , it can also be installed at the ceiling of the detection area  10 . The specific design of the sensor can be a laser. A sensor  20  for measuring the height profile is provided in the measuring bench  18 . Generally, radar laser sensors in line-type arrangement can be used. A thermal sensor  22  that is also installed in the measuring bench  18  several times (as a multisensor) can be used for recording a thermal profile. A radiation or magnetic field sensor  23  is also provided in the measuring bench  18  several times, and can be designed as a radiation sensor (for example as an ABC sensor) or as a magnetic field sensor. Like the sensor  22  it can also be installed in the floor or at the ceiling of the detection area  10 . Principally, at least magnetically or radiologically acting sensors can be arranged on the sides of the detection area  10 , too. 
       FIG. 3  demonstrates permanent magnets  15  with different, alternating polarizations N/S that are arranged in a line and are designed as rectangular parallelepipeds. The rectangular parallelepiped magnets  15  are provided at the same distances from each other and are connected by magnetic short-circuit units  25  on one and the same side. The rectangular parallelepiped magnets  15  generate a magnetic field with magnetic flux lines  31  that, due to the short-circuit units, propagate increasingly towards one side, i.e., the side of the traffic  11 ,  12 . Between the rectangular parallelepiped magnets, magnetic field sensors  16  are provided to measure disturbances in the magnetic field, that is a continuous field, in this case. The disturbances in the magnetic field are possibly caused by objects  12 ,  121 . 
     In the cross-section of the detection area  10  that is presented at the measuring bench  18  in  FIG. 4 , an object and human traffic  11 ,  111 ,  121  exists between the floor  29  and the ceiling  30  of the detection area  10 . In the floor  29  of the detection area  10 , permanent magnets  15  with different polarizations N/S, magnetic field sensors  16  and thermal sensors  22  are installed. The magnetic field sensors  16  are provided with compensation units  26  that eliminate the influence of the primary field of the permanent magnets  15  on these sensors so that the latter only record the disturbances in the primary magnetic field. In the ceiling, a sensor  19  for determining a motion track  191  ( FIG. 1 ), a line of sensors  20  for recording a distance or height profile and sensors  22  for determining a thermal profile are installed. The sensors  20  and  22  put out signals that determine the thermal profile and the height profile  27 . The magnetic field sensors  16  record a magnetic profile  28  that shows a clear maximum at the place of the object  121 . This maximum indicates that a security-relevant object could be in the suitcase  121 . 
       FIG. 5  shows again the floor  29  and the ceiling  30  of the detection area  10  in a cross-section at the measuring bench  18 . In the floor, rectangular parallelepiped magnets  15 , magnetic field sensors  16  with compensation units  26  and thermal sensors  26  are arranged. The same arrangement is also provided at the ceiling  30 . The thermal sensors  22  determine the thermal profiles  27  for each person or group of persons. The magnetic field sensors  16  determine magnetic field profiles  28  that show higher values at the places at which persons or groups of persons are, than at the places between the persons or groups of persons. This indicates that each of the persons carries objects of ferromagnetic material. However, the considerably deviating maximum  281  in the magnetic profile  28  shows that the person  111  carries lots of ferromagnetic material in the suitcase  121 . Therefore, this person would be pursued, as explained in the description relative to  FIG. 1 . 
       FIG. 6  represents magnetic field generators  15  with different polarizations N/S that can be rotated around their axes between two positions staggered by 180°, with said axes being orientated rectangular with respect to the plane of projection. In this way, for example, an alternating magnetic field can be generated that is defined by the flux lines  31 . Short-circuit units  25  are arranged between the magnetic field sensors  15 . Between the magnetic field generators  15 , magnetic field sensors  16  are installed and provided with compensation units  26  on either side. The polarizations N/S of these compensation units  26  are opposite to the polarizations of the magnetic field generators  15 . For the rest, the explanations given to the figures above are applicable. 
     The arrangements of the sensors and field generators to each other and to the object and/or human traffic can also vary from the combinations described so far. 
     All elements presented in the description and the subsequent claims can be decisive for the invention both as single elements and in any combination.