Abstract:
The invention relates to a device for controlling a material, said device comprising at least means for transmitting an electromagnetic signal at a carrier frequency Fp to illuminate the material and means for receiving the electromagnetic signal, characterized in that said device further comprises first means for modulating the electromagnetic signal at a frequency Fm1, said modulation means being arranged, on the signal path, between the transmission means and the material in order to spatially sample the emitted electromagnetic signal; second means for modulating the electromagnetic signal at a frequency Fm2, said modulation means being arranged, on the signal path, between the material and the electromagnetic signal reception means in order to spatially sample the electromagnetic signal passed through the material.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a device for controlling a material. The present invention also relates to a method using said device. 
       TECHNOLOGICAL BACKGROUND  
       [0002]    The device according to the invention can be used for different applications. 
         [0003]    In particular, the device according to the invention enables controls of materials that are not entirely composed of metal, such as wood, paper, rock or glass wool, glass, plastics, agri-food compatible material, or radiating elements, etc. 
         [0004]    For such types of materials, the device can especially enable measurement of material physical properties (density, moisture) or even detection of defects of the controlled material (cavities, inclusions, etc.). 
         [0005]    Controlling materials on industrial production lines requires use of devices that are rapid and most frequently non-invasive. Such non-invasive devices are known, such as X-ray, gamma, and infrared or ultrasound devices, for example, each of these devices having its own specific applications. 
         [0006]    To improve the performance of these devices, it has been suggested to combine them so as to at least be able to obtain the advantages of each device taken independently. 
         [0007]    However, for applications to non-metallic materials, even though use of devices based specifically on electromagnetic waves provides definite advantages (in particular substantial penetration of electromagnetic waves into the interior of non-metallic materials), current technology remains limited with regard to industrial applications. 
         [0008]    Indeed, such industrial applications require real-time measurements considering speed rate at which the material to be inspected progresses along the production line and considering the necessity to control large sections of the materials. 
         [0009]    The purpose of the invention is to remedy the limitations mentioned above. 
         [0010]    More precisely, a first purpose of the present invention is providing a device capable of controlling a material that is not entirely composed of metal. 
         [0011]    Another purpose of the invention is providing a device that can conduct a real-time control of material. 
         [0012]    Yet another purpose of the invention is enabling control over large portions of the materials. 
         [0013]    Still another purpose of the invention is providing a modular device that is easily adaptable to all types of production lines and easily installed. 
       PRESENTATION OF THE INVENTION  
       [0014]    To this end, the object of the invention is to provide a device for controlling a material, said device comprising at least means for transmitting an electromagnetic signal at a carrier frequency Fp to illuminate the material and means for receiving the electromagnetic signal, characterized in that said device further comprises first means for modulating the electromagnetic signal at a frequency Fm1, said modulation means being arranged, on the signal path, between the transmission means and the material in order to spatially sample the emitted electromagnetic signal; second means for modulating the electromagnetic signal at a frequency Fm 2 , said modulation means being arranged, on the signal path, between the material and the electromagnetic signal reception means in order to spatially sample the electromagnetic signal passed through the material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0015]    The invention will be easier to understand, and other objectives, aims, and advantages will become clear on reading the following description, provided for non-limiting purposes, with reference to the appended drawings, in which: 
           [0016]      FIG. 1  shows a schematic view of a device for controlling a material in transmission mode; 
           [0017]      FIG. 2  shows a block diagram of a device for controlling a material according to the invention; 
           [0018]      FIG. 3  shows a schematic view of a device for controlling a material according to the invention in reflective mode; 
           [0019]      FIG. 4  shows a schematic view of a sensor having a modulation element; 
           [0020]      FIG. 5  shows a diagram of an array of sensors having the modulation elements according to  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     1. Device for Controlling a Material in Transmission Mode 
       [0021]      FIGS. 1 and 2  feature a device  100  for controlling a material  150  in a transmission configuration. 
         [0022]    The control device  100  appears in the form of:
       transmission means  100  of an electromagnetic signal at a carrier frequency Fp for illuminating the material  150  to be controlled;   modulation means  140  at a frequency Fm2 of the electromagnetic signal received from the material  150 ;   reception means  130  of the electromagnetic signals created by the modulation.       
 
         [0026]    Modulation means  140  are arranged, on the signal path, between the material  150  and reception means  130  of the electromagnetic signals created by the modulation. 
         [0027]    Transmission means  110 , on one hand, and modulation  140  and reception means, on the other hand, are arranged on either side of the material  150  under examination such that the modulation means  140  receive the transmitted signal after it has passed through the material  150 . 
         [0000]    a. Transmission Means 
         [0028]    Transmission means  100  comprise an array of adjacent transmission antennas intended to transmit the electromagnetic signal at the carrier frequency Fp. The signal, more precisely, is an electromagnetic plane wave. The frequency Fp falls within the field of microwave frequencies. 
         [0029]    The antennas are preferably patch antennas. 
         [0000]    b. Modulation Means 
         [0030]    Modulation means  140  include an array of sensors  200  arranged facing the material  150  and aligned in a common plane perpendicular to propagation direction of the signal transmitted by transmission means  110 . 
         [0031]    The role of modulation means is to locally disturb the electromagnetic field at the modulation frequency F2 in order to spatially sample the electromagnetic signals passed through the material  150  into as many independent signals as there are sensors  200 . 
         [0032]    The sensors  200  integrating the modulation elements for the spatial separation will be described in greater detail in association with  FIGS. 4 and 5 . 
         [0033]    Furthermore, an alternative embodiment of the present invention suggests modulation means that produce the following modulation frequencies: Fm2, Fm2-1, Fm2-2 . . . Fm2-i, with “i” corresponding to the nth sensor. 
         [0000]    c. Reception Means 
         [0034]    Reception means  130  moreover include an array of aligned reception antennas preferably of the same type or even identical to the antennas of the transmission array. 
         [0035]    The array of reception antennas is positioned behind the array of spatial modulation sensors  200 . 
         [0036]    Said array of reception antennas is intended to collect the signals at the carrier frequency and the signals at the modulated frequencies Fp±Fm resulting from the modulation. 
         [0037]    In one variation of the embodiment of reception means  130 , the array of reception antennas and the array of spatial modulation sensors  200  can be found as an array of independent elements each including an integrated reception antenna and an integrated spatial modulation sensor. 
         [0000]    d. Other Elements of the Control Device 
         [0038]    As can be seen in  FIG. 2 , the device also includes means  180  for demultiplexing the signal modulated at the frequency Fm2. Said demultiplexing means  180  serve to address the different sensors  200 , that is to say they enable reception means  130  to distinguish the origin of the different signals resulting from the sensors  200 . 
         [0039]    Said demultiplexing means can be either temporal or spatial demultiplexing means. 
         [0040]    In the case of temporal demultiplexing, the distinction is achieved by distributing sequentially the modulating signal toward the different sensors  200 . 
         [0041]    In the case of spatial demultiplexing, the distinction is achieved by attributing a different modulation frequency Fm or a set of orthogonal modulations to each sensor  200  of the array simultaneously. 
         [0042]    The device further includes filtering means  190  and amplification means  191  of the signals at the carrier frequency Fp and at modulated frequencies Fp±Fm received by reception means  130 . 
         [0043]    More precisely, filtering means  190  include a band pass filter in which the cut off frequency and the bandwidth are adapted to eliminate the carrier frequency Fp prior to amplification of the modulated signals. 
         [0044]    The effective dynamic range of the functioning of a sensor  163  collecting the rays having passed through the material  150  is thus updated based on the signals modulated at frequencies Fp±Fm whose levels customarily range from 60-80 dB below that of the selected carrier frequency Fp. 
         [0045]    Filtering means  190  allow for the receiver  163  not to be saturated by the signal at the carrier frequency Fp, thereby making it possible to obtain far better dynamics of the device. 
         [0046]    In the case of a device of multiple carrier frequencies, it is possible to use filters that are centered on each of the carrier frequencies and that move along the frequency bands such as, for example, Yttrium Iron Garnet YIG filters. 
         [0047]    Furthermore, amplification means  191  include a low noise amplifier intended to receive the filtered signals and to amplify them prior to their being collected by the receiver  163 . 
         [0048]    Finally, the device has a processor  170  that communicates with specific units  161 ,  162 , and  163  which are respectively intended to manage transmission of the signal at the level of transmission means  110 , demultiplexing means, and the receiver  163  connected to the reception means in order to measure the real and imaginary parts of the modulated electromagnetic signals. 
         [0049]    The processor  170  likewise includes means for treating the real and imaginary signals from the receiver  163  in order to improve disturbance detection of the electromagnetic signal transmitted by transmission means  110 . 
         [0050]    The processor  170  furthermore includes display means for the post-treatment display of an image of the controlled material  150 , said image being created on the basis of the signals resulting from the modulation. 
         [0000]    e. Operating Principle of the Control Device 
         [0051]    With such means, it is possible to use a process in which an electromagnetic signal is transmitted at a frequency Fp in order to illuminate the material  150  to be controlled. 
         [0052]    Furthermore, once the electromagnetic signal has been transmitted by transmission means  110 , it propagates across the material  150  to be controlled. 
         [0053]    The slightest inhomogeneity of the material  150  or a difference in density, moisture or temperature thereof can bring about a change in the behavior of the electromagnetic field propagated in the material  150 . 
         [0054]    Similarly, the presence of defects, due to their dielectric or magnetic properties, which are different from those of the material  150 , results in a disturbance of the electromagnetic signal propagated in the material  150  at the location of the defect. 
         [0055]    The signal thus modified is received by the sensors  200  of the array of modulation means  140 . 
         [0056]    Thereafter, in each of its sensors  200 , the electromagnetic signal issued from the material  150  is modulated at a modulation frequency Fm 2 . The modulated signals issued from each sensor  200  are subsequently received by the antennas of reception means  130 . 
         [0057]    In this manner, it is possible to recognize, subsequent to reception at the level of reception means  130  of the signals that have already been modulated, which sensor(s)  200  have detected a disturbed signal. This particular sensor  200  will correspond with a localized zone of the material  150 . 
         [0058]    These signals modulated and received by reception means  130  are then filtered, amplified, and treated in order to obtain an image of the material  150  to be controlled. 
         [0059]    The disturbance of an electromagnetic signal caused by the presence of defects in a zone of the material  150  will be visible on the image atone or more specific sensors  200 , thereby making it possible for the defect to be located. 
         [0060]    Similarly, the inhomogeneity or the difference in density, moisture or temperature in the material  150  will be detected by the device. 
         [0061]    In an alternative embodiment of  FIG. 1 , the radiating parts of the device being reciprocal, provisions have moreover been made for transmissions to be transmitted by the antennas of the reception means  130  and for receptions to be received by the antennas of the transmission means  110 . 
         [0000]    f. Double Modulation Inspection Device 
         [0062]    It has been allowed for to add to the device of  FIG. 1  means to modulate the signal transmitted by transmission means  100  at the modulation frequency Fm1. 
         [0063]    This modulation frequency Fm1 can be identical to or different from the modulation frequency of the electromagnetic signal received by the material  150 . 
         [0064]    These means are similar to modulation means  140  hereinbefore mentioned and described in relation to  FIGS. 4 and 5 . 
         [0065]    Moreover, a variant of the embodiment of the present invention proposes modulation means that present the following modulations: Fm1, Fm1-1, Fm1-2 . . . Fm1-i, with “i” corresponding to the n th  sensor. 
         [0066]    The modulation means are arranged on the signal path between transmission means  110  and the material to be analyzed  150 . 
         [0067]    They spatially sample the electromagnetic signal transmitted by transmission means  110  into as many signals as there are sensors in the array of modulation means. 
         [0068]    A double modulation of the electromagnetic signal at the carrier frequency Fp is thus obtained. 
         [0069]    For each transmission point of the electromagnetic signal, the signal having passed through the material is received by the collection of sensors  200  of the array of modulation means  140 . 
         [0070]    The signal collected on the sensor thus corresponds to different electromagnetic signal paths having passed through the material  150 . 
         [0071]    The collection of electromagnetic signal paths passing through the material  150  between all sensors of the two arrays is thus measured point-to-point. 
         [0072]    This makes it possible to achieve multistatic tomographic imagery in the analyzed material  150  and to obtain reconstructed images of high quality. 
       2. Device for Controlling a Material in Reflective Mode 
       [0073]      FIG. 3  shows a control device of material  150  in reflective mode. The means and theory of operation are the same as that of the control device in the transmission mode. 
         [0074]    The difference rests primarily in the arrangement of transmission means  110 , modulation means  140 , and reception means  130 . 
         [0075]    In the reflection mode, transmission means, on one hand, and modulation  140  and reception  130  means, on the other hand, are arranged on the same side of the material  150  to be controlled such that modulation means  140  receive the signal reflected by the material  150 . 
         [0076]    This device offers the advantage of operating in double transmission since in this mode, the electromagnetic signal at the carrier frequency passes twice through the material  150  being examined. This type of device is advantageous in cases where one side of the material  150  to be measured cannot be accessed or when the material  150  to be tested has a metal surface. 
         [0077]    One embodiment allows for the placement of a metal plate behind the material  150  under examination on the side opposite transmission means  110 , modulation means  140 , and reception means  130  in order to improve the reflection. 
       3. Array of Sensors 
       [0078]    The sensor  200  of the spatial modulation depicted in  FIG. 4  consists of four main elements, that is to say a collection of radiating wires  220 , a nonlinear electronic component  230 , feed wires  240 , and a substrate  210 . 
         [0079]    The principle of operation of a sensor  200  is described for the sensors  200  of modulation means  140  positioned on the signal path between the material  150  and reception means  130 . The description is as follows. 
         [0080]    The radiating wires  220  of the sensor  200  will pick up the electromagnetic signal at the carrier frequency Fp passed through the material  150 . 
         [0081]    The wires  220  are moreover charged by the nonlinear electronic component  230  that is itself polarized with the assistance of a signal at a modulation frequency Fm2. 
         [0082]    They thus generate a signal modulated at the frequency Fp+Fm2, a signal that will be received by reception means  130 . 
         [0083]    More precisely, each sensor  200  includes two radiating wires  220  each connected on either side of the nonlinear electronic component  230 . 
         [0084]    The nonlinear electronic component  230  is preferably an electric or photoelectric diode. 
         [0085]    It can also likewise be a nonlinear electronic component sensitive to temperatures such as a thermistor. 
         [0086]    The effectiveness of the modulation of the sensor  200  is directly linked to the contrast between the on state and the off state of the diode. 
         [0087]    The two radiating wires  220  are preferably in the shape of a rectangular segment. In one variant, other shapes are possible for the radiating wires  220 . 
         [0088]    The size of the wires  220  is preferably small compared to the wavelength. 
         [0089]    It should be noted that the more the surface of the wires  220  increases, the greater the amplitude of the electromagnetic signal modulated at the frequency Fp±Fm2. 
         [0090]    Furthermore, the wires  220  are positioned in an angular configuration determined with respect to the direction of the polarization of the array of antennas of transmission means  110 . The angle α formed between the longitudinal direction of the wires and the direction of polarization of the array of antennas can be between 0° and 180°. 
         [0091]    The wires  220  are preferably positioned at α=45° with respect to the direction of polarization of the array of antennas of transmission means  110 . 
         [0092]    This provides the advantage of reducing the spacing between the different sensors  200  of an array, which results in increasing the density of the sensors  200  and thereby improving the spatial resolution of the device  100  as will be described hereinafter in relation to  FIG. 5 . 
         [0093]    Thus, a plurality of configurations can be adopted for the radiating wires  220  by adjusting the shape or by increasing or decreasing the length or width of the wires  220  and the positioning of the wires  220  according to the polarization of the array of antennas of transmission means  110 . 
         [0094]    Each sensor  200  furthermore includes two feed wires  240  that feed the nonlinear electronic component  230 , said feed wires  240  preferably being arranged perpendicular to the direction of polarization of the array of antennas of transmission means  110 . 
         [0095]    This provides the advantage of decreasing the influence of the feed wires  240  on the incident electromagnetic field. 
         [0096]    Moreover, the configuration in which the feed wires  240  and the wires  220  are respectively arranged perpendicularly and at α=45° with respect to the direction of polarization of the array of transmission antennas allows for free use of filtering means along the feed wires  240  and especially along the low pass filter that is intended to block the signals generated at the frequency Fp on the wires while ensuring the passage of the signals at the modulation frequency Fm2. 
         [0097]    Furthermore, the substrate  210 , on which the collection of the other elements is situated, can be flexible or rigid. It advantageously has dielectric properties as well as a minimal thickness which makes it possible to limit the reflections at the interface and to reduce the losses in amplitude of the incident electromagnetic signal. 
         [0098]    In the case of a substrate  210  that is flexible, conformed configurations of the arrays of sensors  200  are possible. For example, an array of sensors  200  of the circular type makes it possible to adapt the control to a material progressing along a tube, for example. 
         [0099]    The modulating elements  230  integrated in the sensors  200  are preferably nonlinear electrical components of electro-photonic components. 
         [0100]    The feed wires  240  can be printed electrical wiring or unprinted electrical wiring, while in the case of the electro-photonic sensors, the feed wires  240  are replaced by optical fibers or a laser beam. 
         [0101]      FIG. 5  depicts an array of sensors identical to the sensor  200  that will be described in relation to  FIG. 4 . 
         [0102]    The length of the array ought to be equal to or greater than the width of the material  150  to be controlled in order to make it possible to entirely control said material. 
         [0103]    The sensors  200  of the array are preferably regularly spaced. More specifically, they are spaced at a determined distance D, which make it possible to define the spatial resolution of the device. 
         [0104]    Indeed, the smaller the distance D, the smaller the width of the zone of the material  150  analyzed by a sensor  200 . 
         [0105]    Furthermore, the sensors  200  placed in the array can each have dimensions and angular positions that are different with regard to the polarization of the array of antennas of transmission means  110 . 
         [0106]    A variant of the embodiment enables arranging the sensors  200  successively with their wires  220  directed at α=+45° and α=−45° with respect to the direction of polarization of the array of antennas of transmission means  110 . 
         [0107]    This makes it possible to generate a bipolarization for the array of receivers  200  as well as to measure the two components of the incident electromagnetic field. 
         [0108]    Yet another variant of the embodiment provides for using an arrangement of a plurality of nonlinear electronic components  230  placed in series by, for example, charging the wires  220  of the sensor. 
         [0109]    Furthermore, another variant of the embodiment consists of fragmenting the wires  220  of the sensor that are charged by an arrangement of a plurality of nonlinear electronic components  230 . 
         [0110]    Moreover, yet another variant of the embodiment allows for stacking two sensors  200  having two angular positions that are different from the polarization of the array of antennas of transmission means  110 . This makes it possible to generate a bipolarization of the formed global sensor  200  as well as to measure the two components of the incident electromagnetic field in local coincidence. 
         [0111]    Finally, another variant of the embodiment provides for using the antennas of transmission means and/or the bipolarized reception in combinations with the bipolarized sensors in such a manner so as to make it possible to effect polarimetric measurements of the defects in the materials.