WO2001050114A2

WO2001050114A2 - Device for detecting munitions, drugs, explosives etc. using molecular spectroscopy in the radio frequency range

Info

Publication number: WO2001050114A2
Application number: PCT/EP2000/013197
Authority: WO
Inventors: Jörn Fischer
Original assignee: Sebacur Ag
Priority date: 1999-12-29
Filing date: 2000-12-22
Publication date: 2001-07-12
Also published as: WO2001050114A3; AU3016501A; DE19963669A1

Abstract

The invention relates to a device for detecting munitions, drugs, explosives, hand grenades, mines and atomic substances using at least a high-frequency transmitter and receiver, a memory and a processor, or programmable module. According to the invention, a. The sample is exposed to radiation which is as monochromatic as possible and which changes its frequency over time, thus covering a frequency range b. During this exposure, the radiation which is absorbed by the sample and the surrounding material is measured progressively, whereby the effects of absorption resonance provide the characteristic spectra of a sample, c. Using a correlation or a distance determination the measured spectrum is compared with a previously determined molecular specific table which must have been stored previously in the memory for each material to be detected (drugs, munitions etc.), d. If the correlation value exceeds a predetermined threshold value, or if the distance lies below a previously defined threshold value, the sample is confirmed as one of the materials whose data is stored in the table.

Description

description

control system

The invention relates to a device for the detection of substances, mixtures in various physical states.

Devices for the detection of various atomic substances or molecules are already known (WO 98 36 265). For example, there is a device that can recognize, on the basis of polymers, the molecules with which the polymers have come into contact. Different polymers, which are provided with a conductive substance, change their volume and thus their resistance when the molecule is taken up. This in turn can be measured and allows conclusions to be drawn about the molecule.

There are devices for laser spectroscopy that can examine gas mixtures for their composition even at a distance. However, no material that is opaque to this light should stand in the way of this.

The invention has for its object to detect non-contact substances such as drugs, explosives and / or atomic substances at a distance. According to the invention, the object is achieved by the following features: a. by means of at least one high-frequency transmitter b. a radio frequency receiver c. a processor or programmable device d. and a memory, wherein the rays emanating from the radio-frequency transmitter strike the substance or the mixture and excite at least one molecule and then measure the returning radiation and summarize the resulting information in a vector.

It is particularly important here that the RF excitation field (HF = high frequency) is not, as is usual in many test arrangements, homogeneous, but is radiated radially, since no conclusions have to be drawn about the structure of the material and no scatter data are determined, but instead the material should only be "recognized" based on its energy level.

An important step is achieved in that the difficulty in separating spectral components of the absorption from the sample and the environment is largely solved by the correlation with the values specified in the table. If the correlation exceeds a defined threshold value or the distance falls below a previously defined threshold, the sample is the material whose data have been stored in the table.

Likewise, the method of distance determination (e.g. Euclidean) between a measured absorption vector offers and the tabularly stored pattern absorption vectors which belong to the material to be detected, a possibility of distinguishing the spectra of other materials from the material to be detected.

A contact-free measuring method is thus advantageously used here, the molecules being excited to oscillations and vibrations by means of HF rays. The returning rays are processed and evaluated. In this way the molecule can be determined.

This also gives the possibility that a relatively small energy in the range of 10 mW can be used for the spectroscopy, so that no significant disturbances of the environment take place during the measurement, e.g. B. generally no damage or no interference signals for electronic or other devices take place.

Also advantageous is a processor integrated directly in the receiving or transmitting apparatus, which takes over part of the preprocessing of the data, since this relieves the processor of the main computer and the data transmission to the main computer can be carried out with a low transmission rate.

It is of particular importance that the device uses high-frequency radio waves for detection, since the substances can also be “recognized” through walls, glass and other opaque materials. It is particularly advantageous that several HF measuring devices can be connected to a main computer, since this enables central monitoring of several stations

As a result, it is advantageous that the sample is exposed to radiation emanating from the high-frequency transmitter, which is approximately monochromatic, changing its frequency over time and thus sweeping over a frequency range, and the radiation emitted by the sample and is absorbed by the surrounding materials, absorption resonance effects providing characteristic spectra of a sample, the measured spectrum being compared by means of a correlation or a distance determination with a previously determined molecular-specific table, and the correlation or the distance being compared to a previously defined threshold value ,

It is also advantageous that the RF transmitter station sends an RF signal between 3 10 ⁴ Hz and 3 10 ⁹ Hz to the sample and changes the frequency with time in order to scan a frequency range. In this area, the molecules are easily excited to oscillate and vibrate. In order to hit the specific excitation frequencies, the frequency range is scanned.

It is also advantageous that the HF receiving station decomposes the radiation coming back from the sample into its spectral components. This makes it possible to determine the spectrum that is characteristic of the molecule. It is also advantageous that the spectrum is filtered. The quality of the detection can hereby be increased.

It is also advantageous that the spectral components are normalized and combined in a vector. This ensures that the information required for further processing is, because of the standardization, independent of the overall intensity of the radiation, that is to say independent of the distance from the transmitter and receiver to the sample, and can be further processed vectorially.

It is also advantageous that each material to be detected is also assigned to a standardized comparison vector, which is stored in a table. The materials to be detected are also each assigned to a vector, which are stored in a molecular-specific table, and can then be used for comparison in the measurement.

In a further embodiment of the invention, it is advantageous that the correlation of each vector of the table with the vector of the sample is calculated. By forming the correlation, a value is determined which is a measure of the similarity of the sample to the molecule from the molecular-specific table. The largest of all determined correlation values is searched for. This allows you to find the material whose spectrum is most similar to the sample. It is also advantageous that the largest previously calculated correlation value is determined in order to compare it with a threshold value and, if the threshold value is exceeded, to assign the sample the property of the material which belongs to the associated table entry. The comparison of the largest correlation value with a predetermined threshold decides whether the sample is the material stored in the table.

It is also advantageous that the distance between each vector in the table to the sample vector is calculated. The distance determined is a measure of the similarity of the sample to the molecule from the molecular-specific table.

It is also advantageous according to another exemplary embodiment that the table entry with the shortest distance is determined in order to compare it with another threshold value and to confirm the detection of the material belonging to the table entry when the threshold value is undershot. The comparison of the smallest distance value with another predetermined threshold decides whether the sample is the material stored in the table.

In addition, it is advantageous that radiation is emitted by the HF transmitting station, which emits all frequency components at the same time. By transmitting many frequencies at the same time, it is no longer necessary to run through the frequencies one after the other. It is also advantageous that the RF receiving station detects the returning radiation at a very high time and breaks it down into its spectral components by means of a Fourier transformation. With alternative measurements by means of the Fourier transformation, spectral decomposition can again be achieved in accordance with the features of claim 4.

With the device according to the invention, a complex pulse can thus be emitted and then the withdrawn radiation can be detected in a very short time resolution. The spectrum of the withdrawn pulse can then be determined with the aid of a Fourier transformation.

Further advantages and details of the invention are Chen in the claims and explained in the description and m shown in the figures. It shows:

FIG. 1 device and the associated measuring arrangement,

FIG. 2 typical absorption spectrum of a sample (vector),

3a, b implementation of the absorption energy n molecule-specific vibrations and rotations of a molecule,

FIG. 4 forces which act on a dipole in an electrical field,

Figure 5 shows the schematic arrangement of the measuring arrangement. 1 and 5 show a device for the detection of substances and mixtures in various physical states, hereinafter referred to as samples. FIG. 5 shows a computer 3 connected via a radio link 13 to a radio modem 12 m. The computer 3 is configured or set via a handheld device 14, e.g. B. on continuous measurement. This is supposed to check everything. Furthermore, the computer 3 can be set so that only very specific substances can be detected. Furthermore, on the computer 3, as shown in FIG. 1, there is an HF transmission station 1. The computer 3 causes the HF transmission station to transmit signal 9 and to direct this to the sample 8. As explained below, the features (FIGS. 3a, b) are excited in the sample.

At certain frequencies, the molecules shown in FIGS. 3a, b are rotated about the axis 15, that is to say set in rotation and vibration, so that the energy is absorbed by the sample at a certain frequency. The input radiation energy is converted into rotational energy, vibration energy, that is to say the sample 8 transmits certain frequencies, and this has the consequence that the return radiation 10 is input to the RF receiving station 2 and measured. In this way, one determines for certain frequencies that are transmitted - e.g. B. in 15 KHz steps -.

FIG. 2 shows that negative spades or indentations 2 to 18 are formed at certain frequencies, and sample 8 absorbs the frequencies particularly strongly (absorption energy with resonance absorption 4). So- with all substances that have a dipole moment can be detected with this device, ie the absorption values 2-18 are characteristic for the detection of the substance.

The spectra of the substances to be detected are stored in the computer and are used as a comparison spectrum and compared with the spectrum of the detected substance, as explained in more detail below

The molecules 11 of the sample to be detected are in the quantum mechanical states in HF spectroscopy. The in Figure 3a, 3b can by external excitation, for. B. by electromagnetic radiation according to Figure 1, or by collisions with other elementary particles in a state of higher energy. The difference to atomic spectroscopy is that the energy of the molecule can change not only through electronic transitions, but also through transitions between its rotational and its oscillation states.

A polyatomic molecule (see FIG. 3b) is not restricted to the energy transitions of its electrons like an individual atom, but can also be excited by rotation and vibration. A molecule 11a or 11b can be regarded as a rigid body, the shape of which is determined by the equilibrium position of the nuclei. 3 and 3a show that different molecules can have a different number of degrees of freedom. So molecule 11a only has two, but the molecule 11b three degrees of freedom of rotation.

In Fig. 3a, the axes of rotation 15 ', 15'^' , 15 ^'' for a 2-atom molecule are indicated, which rotate through the angles α and β. 3b shows a triatomic molecule which rotates about the axes 15 ^' , 15'^' , 15 ^' '^' .

The angular momentum L is quantized, that is to say discrete and not continuous and dependent on the degrees of freedom just described. Since the energy is proportional to the angular momentum, the energy is also quantized, so that the molecule can only be excited with certain energies that are equal to the energy difference between two angular momentum energy levels. The vibration energy levels as well as the energy levels of the electron states are quantized, so that here too only certain energies lead to excitation. An excited molecule in turn can spontaneously change the energy state from a higher level to a lower level and thereby emit a photon (or an electromagnetic wave), the frequency of which is proportional to this energy level difference. These energy level differences and thus the frequency of the emitted or absorbed rays are characteristic of the structure and composition of the molecule and can be represented in a spectrum.

2 shows an absorption spectrum of a diatomic molecule. The absorption edges 4 show at which frequencies, proportional to the reciprocal of the wavelengths 5, the energy is absorbed and converted into rotation and vibration. This energy level change is explained by a dipole moment of the molecule.

FIG. 4 shows such a dipole, the charges Q + and Q- being conceivable as charge shifts on the molecule 11a, 11b, to which a force acts and thus a moment within an electric field. If the sample 8, which contains the molecules 11a or 11b, is irradiated by the HF transmitter 1, a field is created in the sample 8. This inner field, the course of which depends on the sample properties and the geometry as well as the spatial structure of the outer field, excites the charge carriers and nuclei of the molecule via its electrical or magnetic HF component (radiation 9), which results in electrical or magnetic HF polarization or HF currents in the material of the sample 8 causes. These modify the outer field of the molecule 11a in a certain way, which is detected by the measuring device, namely the HF receiver 2 and the computer 3. The damping or the frequency shift of an RF resonance circuit by the sample 8 located in the RF field is used.

The measuring device must be calibrated first. For this purpose, the calibration data are anchored or stored in the program in the form of a molecular frequency table. First of all, the frequencies of the photons that the sample emits when excited can be measured using conventional measuring devices such as a proportional number tube, ionization chamber, semiconductor number, scintillation number and Cherenkov number. All of these measuring devices rest on the principle of ionization, whereby the resulting electrical impulse, which results from the charge separation during ionization, is suitably amplified and registered. The frequency f can then simply be determined from the measured energy W of the photons: W = hf (h = Planck's quantum of action = const.). This energy is equal to the difference energy between the excited and the relaxed state of the atoms or molecules of the sample.

According to the present invention, excitation frequencies or the radio signals 8 are emitted continuously. The HF transmitter 1 consists of a transmitter diode excited by a programmable oscillator, which can emit radio waves in the range between 3 10 ⁴ Hz to 3 10 ⁹ Hz.

The frequency of the incoming signals 10, which exceed a level of a certain signal intensity, is now measured in the RF receiving part 2 simultaneously with the excitation. For this purpose, the signals 10 are pre-amplified.

The measured values are then compared with the previously determined measured values of the comparison samples, substances such as morphs for the C17, H12, ONM. Morphine sulfate 5H20 or black powder KN03 or other substances, comparative samples correlated.

If the correlation exceeds a predetermined threshold, the material of the sample and its properties can be inferred from this. Instead of the correlation, a distance function (e.g. Euclidean distance) can optionally be defined and the distance between the measured state vector of the sample and the state vector of the comparison sample can be determined. If this distance is smaller than a previously defined threshold (different threshold than in the correlation), the measured sample can be assigned to the comparison sample.

LIST OF REFERENCE NUMBERS

1. High frequency transmitter

2. High frequency receiver

3. Computer

4. Absorption values 2 to 18, absorption energy with resonance absorption

5. Reciprocal wavelength axis (proportional to frequency)

6. Linear molecule rotatable about two axes 15

7. Nonlinear molecule rotatable about three axes

8. Rehearsal

9. Radiation, RF signals that hit the sample

10. Radiation, RF signals coming back from the sample

11a. A molecule with two degrees of rotational freedom

11b. A molecule with three degrees of rotational freedom

12. Radio modem

13. Radio link

14. Handheld device

15th axis 15 'axis

16. E field

Claims

claims

1. Device for the detection of substances, mixtures in various physical states with the following features: a. by means of at least one high-frequency transmitter (1) b. a radio frequency receiver (2) c. a processor or programmable chip (3) d. and a memory (3 '),

wherein the rays (9) emanating from the radio-frequency transmitter (1) strike the substance (sample 8) or the mixture and excite at least one molecule (11) and then measure the returning radiation (10) and summarize the resulting information in a vector ,

2. Device according to claim 1, characterized in that the sample is exposed to radiation emanating from the high-frequency transmitter, which radiation is approximately monochromatic, changing its frequency with time and thus sweeping over a frequency range, and the radiation is measured successively, which is absorbed by the sample and the surrounding materials, absorption resonance effects providing characteristic spectra of a sample, the measured spectrum being compared by means of a correlation or a distance determination with a previously determined molecular-specific table, and the correlation thereby exceeds one specified threshold value or the distance falls below a previously defined threshold.

3. Device according to claims 1 and 2, characterized in that the RF transmitter station (1) sends an RF signal (9) between 3 10 ⁴ Hz and 3 10 ⁹ Hz to the sample and changes the frequency with time, to sample a frequency range.

4. The device according to claim 1, characterized in that the RF receiving station (2) decomposes the radiation returning from the sample m its spectral components.

5. Apparatus according to claim 1, 2 or 4, characterized in that the spectrum is filtered.

6. The device according to claim 1, 2 or 3, characterized in that the spectral components are normalized and combined in a vector.

7. The device according to claim 1, characterized in that each material to be detected is also assigned a standardized comparison vector which is stored in a table.

8. The device according to claim 1, characterized in that the correlation of each vector of the table with the vector of the sample is calculated.

9. Device according to one of the preceding claims, characterized in that the largest previously calculated correlation value is determined in order to compare it with a threshold value and, when the threshold value is exceeded, to assign the sample the property of the material which belongs to the associated table entry.

10. Device according to one of the preceding claims, characterized in that the distance between each vector in the table to the sample vector is calculated.

11. Device according to one of the preceding claims, characterized in that the table entry with the shortest distance is determined in order to compare it with another threshold value and to confirm the detection of the material belonging to the table entry when the threshold value is undershot.

12. Device according to one of the preceding claims, characterized in that the RF transmitter station (1) emits radiation (9) which emits all frequency components at the same time.

13. Device according to one of the preceding claims, characterized in that the RF receiving station (2) detects the returning radiation at a very high time and decomposes its spectral components by a Fouπer transformation m.