WO2005085907A1

WO2005085907A1 - Method and device for detecting foreign objects

Info

Publication number: WO2005085907A1
Application number: PCT/NL2005/000154
Authority: WO
Inventors: Petrus Joannes Wilhelmus Van Herp; Johannes Hermanus Petrus Maria Oonk
Original assignee: Van Herp Petrus Joannes Wilhel; Oonk Johannes Hermanus Petrus
Priority date: 2004-03-03
Filing date: 2005-03-02
Publication date: 2005-09-15

Abstract

A method is described for detecting the presence of at least one foreign object (41,42) in or on a human or animal body (30), by analysing ultrasonic reflection signals (R1, R2, R3, Rx). The method comprises the steps of: sending an ultrasonic emission signal (S) through the air to the body (30) to be examined; receiving reflection signals (R; R1, R2, R3, Rx); analysing the received reflection signals. If the reflection signal ® contains suspicious reflection components (Rx) which are indicative for foreign objects, an alarm signal is issued.

Description

Title: Method and device for detecting foreign objects

The present invention relates in general to a method, for detecting whether a person (or animal) carries foreign objects with him. There are various examples of situations where one wants to be able to detect whether a person carries objects with him. For example, it may be that one wants to counteract smuggling of, for example, drugs, gems, and the like. Also for security reasons it can be desired to detect whether a person carries explosives, weapons, and the like. In particular such problems play a role on airports and the like, where it s desired to check persons before they go on board of a plane. In principle, it would be possible to examine each individual person extensively, but such an approach has various disadvantages. Firstly, passengers find it unpleasant if they are examined extensively. Secondly, such an approach takes much time, and this again means that, particularly on air-ports which have to handle large numbers of passengers, many specially trained personnel are needed to perform such ch.ecks, and this again leads to large costs. In principle, it is also possible that one makes an x-ray photo of each passenger. Such a method provides good certainty, but, apart from the fact that this method is expensive, this method is socially unacceptable because of the use of x-rays and the health risks associated with it. The present invention aims at providing a method with which, in a relatively simple and fast way, yet with good reliability, it is possible to make a pre-selection, namely determining whether it is probable that a person carries undesired objects with him. More particularly, the invention aims at providing such a method that lacks the aforementioned disadvantages . More particularly, the present invention aims at providing a method for detecting the presence of foreign and potentially dangerous objects in or on a human or animal body. When such objects are not detected, and that will be the case with the largest part of the passengers, one can let those passengers pass the check post without reckoning that a more extensive check is needed. When the detection result indicates that foreign objects have been found, or at least that there is a certain chance that the person carries foreign objects with him, then the person concerned may be subjected to a more extensive check. Thus, performing a check which is labour- intensive and experienced as unpleasant is limited to persons of which, based on the results of the method proposed by the present invention, one has reason to assume that they carry foreign objects with them, while the vast majority of the passenger flow can pass without the time-consuming more extensive check.

The detection method proposed by the present invention is based on the use of ultrasonic signals. A body to be examined is subjected to an ultrasonic sound pulse. This pulse may be transmitted with a contact transmitter, i.e. a transmitter which makes contact with the body to be examined, but in a preferred embodiment the transmitter remains at a distance from the body to be examined, and the transmitted sound pulse travels through the air from the transmitter to the body to be examined. With respect to ultrasonic sound, the human (and animal) body has certain transmission properties and reflection properties, which are expressed in the form of the reflection signal. This reflection signal is measured with the aid of at least one receiver, and the received signal is analysed in a signal processing device. This signal processing device may be an appropriately programmed computer, or the like . The results of the analysis can be made known to an operator in various ways. In a preferred embodiment, an examination apparatus has a visual indication, preferably in the form of two lamps with different colours, for example red and green. When the signal processing device finds in the received reflection signal no reflection components which originate from foreign objects, then the signal processing device issues a pass signal, for example by switching on the green lamp, as a sign that the person concerned is allowed to pass unhindered. If the signal processing device finds a suspicious signal component in the received reflection signals, the signal processing device issues an alarm signal, for example by switching on the red lamp, as a sign that possibly there are suspicious objects with the person concerned. As a reaction to this signal, guarding personnel can ask the person concerned to go along to another examination location for a more extensive examination.

These and other aspects, features and advantages of the present invention will be further explained by the following description with reference to the drawings, in which same reference numbers indicate same or similar parts, and in which: figure 1 schematically shows a test arrangement; figure 2 is a graph which schematically illustrates emission and reflection signals; figures 3A to C show examples of oscilloscope images of reflection signals obtained with the test arrangement of fig.

1; figure 4 schematically shows a test arrangement; figure 5 is a graph which schematically illustrates emission and reflection signals for the test arrangement of figure 4; figure 6 shows an example of an oscilloscope image of a reflection signal obtained with the test arrangement of figure

4; figure 7A is a schematic front view of a human; figure 7B is a schematic horizontal cross section according to the line B-B in figure 7A; figure 7C is a graph which schematically illustrates obtained emission and reflection signals; figure 8A is a schematic front view of a human; figure 8B is a schematic horizontal cross section according to the line B-B in figure 8A; figure 8C is a graph which schematically illustrates obtained emission and reflection signals; figure 9A is a schematic front view of a human; figure 9B is a schematic horizontal cross section according to the line B-B in figure 9A; figure 9C is a graph which schematically illustrates obtained emission and reflection signals;

Figure 1 schematically shows a test arrangement with an ultrasonic transducer 10 and a test object 20. The ultrasonic transducer 10 has a transmission part 11 and a reception part 12, which two components in figure 1 are sketched next to each other and apart from each other for the sake of clarity, but usually a transducer 10 has a single combined transmission/reception part. Since ultrasonic transducers are known per se, while the present invention can be implemented with commercially available ultrasonic transducers known per se, while further the present invention does not relate to providing an ultrasonic transducer, it is not necessary here to further explain the design and functioning of an ultrasonic transducer. In a test experiment, an ultrasonic sound pulse S is transmitted to the test object 20, and the reflection signal R reflected by the test object 20 is detected by the transducer 10. Figure 2 is a graph which schematically illustrates the transmission and reflection signals S and R. The horizontal axis in figure 2 corresponds to the time, the vertical axis in figure 2 corresponds to signal strength, in arbitrary units. The time distance Δt between the pulses S and R corresponds to the time the transmission signal S needs to travel from the transducer 10 to the test object 20, plus the time the reflection pulse R needs to travel from the test object 20 back to the transducer 10. As will be clear to a person skilled in the art, the following relation applies to this time difference: Δt = 2d/V wherein d is the distance between the transducer 10 and the object 20, and wherein V is the speed of sound of the ultrasonic signal in air. When, for example, the distance between the transducer 10 and the object 20 is set to 75 cm, and assuming that the speed of sound of ultrasonic sound in air is approximately 300 m/sec, Δt approximately equals 5 s, which is very well measurable. The experiment described above was performed with different test objects 20, wherein the test objects differed from each other by different materials, while the other circumstances were kept the same as good as possible. The frequency of the ultrasonic signal was always approximately 50 kHz. The transducer used was able to generate ultrasonic sound up to about 100 kHz. Preferably, the frequency is higher than 25 kHz; in general it applies that a higher frequency yields a higher resolution, but also a higher absorption. The figures 3A to C show examples of oscilloscope images of actually obtained reflection signals R. Figure 3A is a representative example of a reflection signal which is obtained when a chicken fillet is used as test object. The soft meat of the chicken fillet can be considered to have reflection properties corresponding to those of the soft parts (flesh, organs) of the human body. Figure 3B is a representative example of a reflection signal which is obtained with an aluminium test object. Figure 3C is a representative example of a reflection signal which is obtained with a leather test object. The examples discussed above relate to reflection signals of a single object. An important aspect of the present invention is that ultrasonic signals partly pass objects (transmission properties of objects concerned), and may then reflect from an object located farther on. Figure 4 is a figure similar to figure 1, illustrating a test arrangement wherein a second test object 21 was positioned in front of the first test object 20, in front of its side facing the transducer 10. Figure 5 is a graph similar to figure 2, illustrating the signals obtained with this test arrangement. A first reflection signal Rl originates from the second test object 21 which is situated closest to the transducer 10. A second reflection signal R2, which is measured later in time than the first reflection signal, originates from the first test object 20 located farther on. This second reflection signal originates from sound which has passed the second test object 21, has reflected from the first test object 20, and has subsequently passed the second test object 21 again. Figure 5 also shows that further reflection signals R3 may be measured, originating from sound which has passed the second test object 21, reflects back and forth from the first test object 20 to the second test object 21 and then back to the first test object 20 and again to the second test object 21, in order to pass the second test object 21 only now. Such reflection signals originating from multiple reflections will be much weaker than the primary reflection signals Rl and R2. Figure 6 is an oscilloscope image similar to the figures 3A to C, illustrating the actually measured reflection signals in a situation that the first test object 20 was an aluminium plate while the second test object 21 was a fabric stretched in front of the first test object 20 at a distance of 5 mm. This fabric was common T-shirt fabric, i.e. a cotton tissue. Figure 6 illustrates that it is possible with ultrasonic signals to measure through objects, wherein thus a reflection signal is obtained based on a combination of transmission and reflection properties of materials. An important aspect of the present invention is based on the fact that different materials have different reflection and transmission properties, which is expressed in the characteristic shape of the detected reflection signals. The exact shape, in particular the envelope, of a reflection signal will also depend on the shape of the emission signal, but with different materials and otherwise constant circumstances there are characteristic differences in the reflection signals, as illustrated by the figures 3A to C. The exact shape of a reflection signal will still depend on the exact shape of the emission signal, but, if the emission signal is known and the other circumstances are known, characteristic differences in detected reflection signals are caused only by differences in materials. Within the context of the present invention it is of particular importance that there is a very clear and well detectable difference between signals originating from relatively soft, "solid" materials such as flesh, fat, organs, etc. on the one hand, and hard materials such as bone, metal, synthetic material, wood, etc. on the other hand. Also reflection signals originating from clothing have their own characteristic features which are well recognizable. The method proposed by the present invention is based on the aforementioned differences .

Referring to the following figures, it will be explained how those characteristic differences can be used to detect whether there are foreign objects in or on a human body. Figure 7A is a schematic front view of a human 30, and figure 7B is a schematic horizontal cross section according to the line B-B in figure 7A. In figure 7A, a measuring arrangement with the ultrasonic transducer 10 is sketched in a way similar to figure 1. Figure 7C is a graph similar to figure 2 which schematically illustrates obtained emission and reflection signals. In the arrangement of figure 7B, the ultrasonic transducer 10 is arranged opposite the front side of the body, i.e. opposite the belly. In a reflection signal, three signal components Rl, R2 and R3 will be recognizable. The first reflection signal component Rl originates from the front side 31 of the body 30, where the transmission signal S encounters the body 30. Thus, in this test arrangement this corresponds to the belly. In figure 7C it is to be seen that the first reflection signal Rl is observed first in time, because the belly 31 is located closest to the transducer 10. A second reflection component R2 originates from the spine 32. Since the spine 32 is relatively hard relative to the abdominal wall 31, there are characteristic differences between the second reflection signal R2 and the first reflection signal Rl . A third reflection signal R3 originates from the rear side of the body 30, i.e. the back side 33, in this example being directed away from the transducer 10. This reflection component R3 originates from a transition from body 30 to air, and has a characteristic which clearly differs from the characteristic of the second reflection signal R2 originating from the spine. It is noted that in general the third reflection signal R3 may be less clear than the first reflection signal Rl . Viewed from the transducer placed in front of the person 30, one first sees the abdominal wall 31, then the spine 32, and then the back side 33. In figure 7C this is expressed in that the first reflection component Rl originating from the belly 31 is observed first, some time later followed by the second reflection component R2 originating from the spine 32, which, in turn, is again some time later followed by the third reflection component R3 originating from the back side 33. The signal sketched in figure 7C is representative for a person 30 carrying no foreign objects with him. The figures 8A to 8C are figures similar to the figures 7A to 7C, respectively, but now the person 30 has foreign objects 41 in his stomach. By way of example, these foreign objects may be swallowed diamonds or swallowed balls with drugs . In figure 8B it is shown that these foreign objects 41 in the stomach of the person 30 will also reflect the emission signal S, which is indicated by an additional reflection component Rx. In figure 8C this additional reflection component Rx is sketched in its time relation to the other reflection components Rl, R2 and R3. The location of the additional reflection component Rx between the first reflection component Rl and the second reflection component R2 indicates that this additional reflection component Rx originates from objects located in between the abdominal wall 31 and the spine 32, i.e. inside the body of the person 30. The shape of this additional reflection signal Rx will be indicative for the material of the foreign objects 41 concerned; in general, these will be fairly hard objects, and the additional reflection signal Rx will have the typical features of a reflection signal originating from hard material . In a similar way as the figures 8A to 8C, the figures 9A to 9C illustrate a situation wherein the person 30 carries a foreign object 42 with him, this time outside his body, more particularly stuck in front of his belly, as is to be seen in the schematic section of figure 9B. Also in this case, the object 42 may be smuggling goods such as drugs, gems, and the like, but the object may also be a weapon. Also in this case, the foreign object 42 will cause an additional reflection signal Rx, which now arrives earlier than the first reflection component Rl, as sketched in figure 9C, because the object 42 is closer to the transducer 10 than the abdominal wall 31. Also in this case, the additional reflection signal Rx will have the typical features of a reflection signal originating from a hard material. The figures 7 to 9 illustrate that with ultrasonic measurements as proposed according to the invention it is possible to detect whether a person carries hard objects with him. When that is not the case, the measured reflection signal has in general the pattern illustrated in figure 7C. When the person has hard objects in his stomach, the detected reflection signal has the pattern illustrated in figure 8C. When a person carries a hard object on his body, the detected reflection signal has the pattern illustrated in figure 9C. It is noted that similar reflection signal components will be measured when the hard object is mounted at another place, for example at the back side 33. Such an object will be susceptible of being detected with an ultrasonic transducer located at the front side of the body, opposite the belly 31, as illustrated in figure 9B, but can be detected better with a transducer located at the rear side of the body 30, opposite the back side 33, but that is not shown in the figures. It is possible to conclude that there are foreign objects present solely on the basis of the characteristic features of a reflection signal component, in a situation that no relatively hard objects whatsoever are expected. It is also possible to conclude that there are foreign objects present inside the body on the basis of the characteristic features of a reflection signal component in combination with a position determination, i.e. the time relation of that reflection signal component relative to other reflection signal components of which one knows the source. For example, the presence of a suspicious reflection signal component Rx between the first and second signal components indicates the presence of an object inside the body. However, it is possible that the first reflection signal component is not very clear; in that case it is possible to deduce the spatial distance between a reflecting object and the spine 32 from the time distance between the suspicious reflection signal component Rx and the second reflection signal component R2, and to determine on the basis of that distance whether the reflecting object is situated inside or outside the body.

Figure 10 schematically shows the important elements of a detection device 1 according to the present invention. A signal processing device 100, for example a suitably programmed computer, microprocessor, or the like, has a signal input 103 to which an ultrasonic transducer 10 is connected. Further, the signal processing device 100 has a control output 104, connected to a control input of the transducer 10, for controlling the functioning and in particular the timing of the transducer 10. Alternatively, the transducer 10 could be a free-running transducer, emitting a sound pulse S at regular points in time, for example once per second. When the transducer is adapted to emit a sound pulse at the reception of a control command of the signal processing device 100, this has the advantage that the signal processing device 100 knows the emission times of the emission pulses S. At its signal input 103, the signal processing device 100 receives a measurement signal M given by the transducer 10, which is representative for the reflection signals R received by the transducer 10. The signal processing device 100 is adapted to analyse the measurement signals M of the transducer 10. Under normal circumstances, i.e. when the measurement signal M is representative for reflection signals as sketched in figure 7C, the signal processing device 100 concludes that the person concerned most probably does not carry foreign objects with him, and issues a pass signal as a sign that the person concerned can pass unhindered. In the preferred embodiment shown, the signal processing device 100 therefore has a first signal output 101, with which a first signal lamp 111 is controlled, for example a green lamp. When the signal processing device 100 finds suspicious signal components in the measurement signal M received from the transducer 10, which are indicative for foreign objects, for example because the measurement signal M is representative for a reflection signal as illustrated in figure 8C or in figure 9C, the signal processing device issues an alarm signal, which is a sign for guarding personnel that the person concerned has to be examined closer. In the preferred example shown, the signal processing device 100 therefore has a second signal output 102 with which a second lamp 112 is controlled, for example a red lamp. In a preferred embodiment, the signal processing device 100 is adapted to distinguish between reflection signals as illustrated in figure 8C, indicative for the presence of one or more foreign objects inside the body, and the reflection signals as illustrated in figure 9C, indicative for the presence of foreign objects outside the body, and to express this distinction by controlling two different signal lamps, so that guarding personnel knows where to look.

It will be clear to a person skilled in the art that the invention is not limited to the exemplary embodiments discussed above, but that several variations and modifications are possible within the protective scope of the invention as defined in the attached claims.

Claims

1. Method for detecting the presence of at least one foreign object (41, 42) in or on a human or animal body (30), by analysing ultrasonic reflection signals (Rl, R2, R3, Rx) .

2. Method according to claim 1, comprising the steps of: sending an ultrasonic emission signal (S) through the air to the body (30) to be examined; receiving reflection signals (R; Rl, R2, R3, Rx) ; analysing the received reflection signals.

3. Method according to claim 2 , wherein it is examined whether the reflection signal (R) contains suspicious reflection components (Rx) which are indicative for foreign objects, and wherein an alarm signal is issued if such suspicious reflection components are found.

4. Method according to any of the preceding claims, wherein it is determined whether a reflection component (Rx) is indicative for the presence of a foreign object on the basis of a characteristic shape of the reflection component (Rx) concerned.

5. Method according to any of the preceding claims, wherein it is determined whether a reflection component (Rx) is indicative for the presence of a foreign object on the basis of a time relation of that reflection component (Rx) relative to other reflection components (Rl, R2, R3) which originate from one or more known locations of the human body.

6. Method according to claim 5, comprising the steps of: detecting a first reflection component (Rl) originating from the surface of the body (30) facing a transmitter/receiver

(10); detecting a suspicious reflection component (Rx) having features which are indicative for a reflection by a relatively hard object; wherein the suspicious reflection component (Rx) is assessed as being indicative for the presence of a foreign object if the suspicious reflection component (Rx) is received earlier than the first reflection component (Rl) .

7. Method according to claim 5, comprising the steps of: detecting a second reflection component (R2) originating from the spine (32) of the body (30) ; detecting a suspicious reflection component (Rx) having features which are indicative for a reflection by a relatively hard object; wherein the suspicious reflection component (Rx) is assessed as being indicative for the presence of a foreign object if the suspicious reflection component (Rx) is received earlier than the second reflection component (R2), while the time distance between the suspicious reflection component (Rx) and the second reflection component (R2) corresponds to a spatial distance which is larger than the distance between the spine (32) and the surface of the body (30) facing a transmitter/receiver (10).

8. Method according to claim 5, comprising the steps of: detecting a first reflection component (Rl) originating from the surface of the body (30) facing a transmitter/receiver (10); detecting a second reflection component (R2) originating from the spine (32) of the body (30) ; detecting a suspicious reflection component (Rx) having features which are indicative for a reflection by a relatively hard object; wherein the suspicious reflection component (Rx) is assessed as being indicative for the presence of a foreign object if the suspicious reflection component (Rx) is received earlier than the second reflection component (R2), and later than the first reflection component (Rl) .

9. Detection apparatus (1), adapted for implementing the method according to any of the preceding claims.

10. Detection apparatus according to claim 9, comprising: an ultrasonic transducer (10) for sending an ultrasonic emission signal (S) and receiving ultrasonic reflection signals (R) , and providing a measurement signal (M) which is representative for the received reflection signals; a signal processing device (100), comprising an input (103) for receiving the measurement signals (M) provided by the transducer (10), and preferably provided with a control output (104) connected to the transducer (10) for controlling the transducer (10) ; wherein the signal processing device (100) is adapted for analysing the received measurement signals (M) .

11. Detection apparatus according to claim 10, wherein the signal processing device (1O0) has at least one first output

(101) for issuing a pass signal if the analysis of the received measurement signals (M) reveals that the reflection signals received by the transducer (10) originate from a body (30) without foreign objects; and wherein the signal processing device (100) has at least one second output (102) for issuing an alarm signal if the analysis of the received measurement signals (M) reveals that the reflection signals received by the transducer (10) comprise at least one suspicious signal component (Rx) originating from reflection from a foreign object (41, 42) .

12. The use of ultrasonic sound in detecting foreign objects.