Method and system for detecting at least one hazardous substance

Abstract

Method for detecting at least one hazardous substance, in particular an explosive, in a sample (26), in particular in a spatial detection area (18), wherein a first optical spectrum of the sample (26) is recorded using a first optical spectroscopy method during a first spectrum acquisition time window (106) and a second optical spectroscopy method is used to record a second optical spectrum of the sample (26) during a second spectrum acquisition time window (108), wherein the first and the second optical spectroscopy methods differ, wherein the first optical spectrum and the second optical spectrum are compared with provided reference spectra of the at least one hazardous substance to determine whether the at least one hazardous substance is present in the sample (26) or not, wherein the first optical spectroscopy method is infrared spectroscopy, in particular MIR reflection spectroscopy.and that an infrared spectrum is recorded as the first spectrum of the sample (26), that the second optical spectroscopy method is Raman spectroscopy, in particular UV Raman spectroscopy, and that a Raman spectrum is recorded as the second spectrum of the sample (26), characterized in that the first spectrum recording time window (106) and the second spectrum recording time window (108) overlap at least partially in time, in particular completely, that to record the first optical spectrum the sample (26) is exposed to first pulsed electromagnetic radiation (50) and that an intensity of first scattered radiation (60) backscattered from the sample (26) is detected, that to record the second optical spectrum the sample is exposed to second pulsed electromagnetic radiation (76) and that an intensity of second scattered radiation (86) backscattered from the sample (26) is detected with spectral resolution.

Description

[0001] The present invention relates to a method for detecting at least one hazardous substance, in particular an explosive, in a sample, particularly in a spatial detection area, in which a first optical spectrum of the sample is recorded during a first spectrum acquisition time window using a first optical spectroscopy method, and a second optical spectrum of the sample is recorded during a second spectrum acquisition time window using a second optical spectroscopy method, wherein the first and the second optical spectroscopy methods differ, wherein the first optical spectrum and the second optical spectrum are compared with provided reference spectra of the at least one hazardous substance to determine whether the at least one hazardous substance is present in the sample or not, wherein the first optical spectroscopy method is infrared spectroscopy, in particular MIR reflection spectroscopy.and that the first spectrum recorded from the sample is an infrared spectrum, that the second optical spectroscopy method is Raman spectroscopy, in particular UV Raman spectroscopy, and that the second spectrum recorded from the sample is a Raman spectrum.

[0002] Furthermore, the invention relates to a system for detecting at least one hazardous substance, in particular an explosive, in a sample, particularly in a spatial detection area, which system comprises a first optical spectroscopy device for recording a first optical spectrum of the sample during a first spectrum recording time window and a second optical spectroscopy device for recording a second optical spectrum of the sample during a second spectrum recording time window, wherein the first and the second optical spectroscopy device are different, wherein the system comprises an evaluation device for comparing the first optical spectrum and the second optical spectrum with provided reference spectra of the at least one hazardous substance and for determining whether the at least one hazardous substance is present in the sample or not.wherein the first optical spectroscopy device is or comprises an infrared spectrometer, in particular a MIR reflection spectrometer, wherein the second optical spectroscopy device is or comprises a Raman spectrometer, in particular a UV Raman spectrometer.

[0003] Various devices are used, particularly security scanners, X-ray machines, and metal detectors, to detect dangerous objects, especially during security checks at border crossings or airports. However, these devices cannot directly detect or identify hazardous materials, such as explosives. To date, direct detection of such hazardous materials has only been demonstrated under laboratory conditions using large quantities of pure substances. Therefore, security checks still only involve randomly taking samples from suspicious surfaces to test individuals and their luggage for contamination and contact with hazardous materials. The analysis of these samples is currently performed as an additional control step.

[0004] It is well known to characterize chemical substances using optical spectroscopy. Raman spectroscopy and infrared spectroscopy are particularly common techniques. In infrared spectroscopy, the wavelength of the light exciting the sample is tuned, and the sample's absorption is determined as a function of the excitation wavelength. Absorption bands are observed especially at wavelengths corresponding to molecular vibrations or rotations. Raman spectroscopy investigates the inelastic scattering of light by molecules. The sample is exposed to light of very short wavelengths. Due to interactions with molecules in the sample, the wavelength of the backscattered light is shifted towards longer wavelengths. The intensity of the backscattered light is measured as a function of wavelength using a detector. A shift in wavelength corresponds to a specific vibration of the molecule.

[0005] One problem with detecting hazardous substances is that the known methods are very time-consuming, making real-time detection practically impossible. Therefore, using systems of the type described above for security checks is not feasible in practice, as the required measurement times are too long, especially to check every person and every piece of luggage for hazardous substances.

[0006] US Patent 2016 / 0041101A1 describes methods and devices for detecting and identifying non-volatile substances in a gas phase using surface-enhanced vibrational spectroscopy. In "HAMM, P. [et al.]: The two-dimensional IR nonlinear spectroscopy of a cyclic penta-peptide in relation to its three-dimensional structure. Proceedings of the National Academy of Sciences USA, Vol. 96, 1999, pp. 2036-2041," the two-dimensional nonlinear IR spectroscopy of a cyclic penta-peptide in relation to its three-dimensional structure is disclosed. US Patent 7,675,611B2 discloses a handheld device for performing infrared and Raman measurements. Femtosecond Raman spectroscopy is described in “KUKU-RA, P. [et.al.]: Femtosecond stimulated Raman spectroscopy. Annual review of Physical Chemistry, Vol. 58, 2007, pp. 461-488”.

[0007] It is therefore an object of the present invention to improve a method and a system of the type described above in such a way that it can be used in particular for security checks for all persons and objects to be checked.

[0008] This problem is solved according to the invention in a method of the type described above by ensuring that the first spectrum acquisition time window and the second spectrum acquisition time window overlap at least partially in time. In particular, the two spectrum acquisition time windows overlap completely such that, for the acquisition of the first optical spectrum, the sample is exposed to first pulsed electromagnetic radiation and an intensity of first scattered radiation backscattered from the sample is detected; and for the acquisition of the second optical spectrum, the sample is exposed to second pulsed electromagnetic radiation and an intensity of second scattered radiation backscattered from the sample is detected with spectral resolution.

[0009] The solution proposed according to the invention makes it possible, in particular, to apply two spectroscopic methods simultaneously or at least partially simultaneously to test a sample, for example, a piece of clothing or a person's luggage, for hazardous substances. By applying two different spectroscopic methods, more comprehensive measurement data can be acquired, with which the sample, and especially any hazardous substances present on it, can be reliably and quickly characterized. For example, two different optical spectra can be recorded simultaneously, which can then be compared with corresponding reference spectra of different hazardous substances. If a match is found, it provides highly reliable proof that one or more hazardous substances are adhering to the sample.During evaluation, it is not strictly necessary, but possible, to record the two spectra separately and compare them with separate spectra from different spectroscopy methods. Alternatively, it is also possible to process the acquired measurement data from both spectroscopy methods together in a single dataset and compare it with a corresponding reference dataset of one or more hazardous substances. This approach enables efficient and rapid data processing, particularly a quick comparison of the acquired measurement data with known reference data. Specifically, the first spectrum acquisition time window can be identical to the second. Furthermore, one spectrum acquisition time window can be completely encompassed by the other.Furthermore, it is advantageous if the spectroscopic methods differ in such a way that no interactions can occur during the measurements. This is particularly possible if the measurements take place in different spectral ranges, for example, in the infrared spectral range on the one hand and in the ultraviolet spectral range on the other. It is advantageous if the first optical spectroscopic method is infrared spectroscopy and if an infrared spectrum is recorded as the first spectrum of the sample. In particular, the spectroscopic method can be MIR reflection spectroscopy. In this method, the wavelength of a MIR laser is continuously tuned, specifically after a certain number of pulses emitted by the laser.The absorption of MIR laser radiation by the sample is measured in backscatter geometry, so that after a complete measurement cycle, an absorption spectrum of a surface of the sample is obtained. It is advantageous that, to record the first optical spectrum, the sample is first exposed to pulsed electromagnetic radiation, and the intensity of the first scattered radiation backscattered by the sample is detected. In this way, a large number of individual measurements can be performed. For example, each pulse of electromagnetic radiation can be used to interact with the sample, and the first scattered radiation backscattered by the sample can be detected. In this way, an absorption spectrum of the sample can be recorded in a particularly simple manner. According to the invention, the second optical spectroscopy method is Raman spectroscopy, and a Raman spectrum is recorded from the sample as the second spectrum.In particular, Raman spectroscopy can refer to UV Raman spectroscopy. In this spectroscopic method, the sample is exposed to ultraviolet radiation. An advantage is that, to record the second optical spectrum, the sample is exposed to second pulsed electromagnetic radiation, and that the intensity of the second scattered radiation backscattered from the sample is detected with high spectral resolution. Through the interaction of the second pulsed electromagnetic radiation with the sample, second scattered radiation is backscattered, which, in Raman spectroscopy, exhibits characteristic Stokes lines and anti-Stokes lines adjacent to the frequency of the pulsed electromagnetic radiation when detected on a wavelength-dependent basis. The distances between the respective detected lines, and between them and the wavelength of the second pulsed electromagnetic radiation, correspond to the vibrational frequencies of the backscattering molecules.A shift towards longer wavelengths occurs when a molecule absorbs energy from the radiation field. The energy difference corresponds to the energy of a vibrational state of the molecule. Both IR spectroscopy and Raman spectroscopy detect vibrational bands of molecules that are characteristic of those molecules. In particular, the position and intensity of the respective signals in the spectra allow conclusions to be drawn about the characteristic vibrations of specific molecules.

[0010] It is advantageous to record the first and second optical spectra of the sample when the sample is positioned within a spatially defined detection area. This ensures that the sample is only analyzed when it is actually within this area. For example, at airport security checkpoints, the detection area could be a spatially delimited zone defined by a security gate. This could be the area defined by a metal detector when passing through or standing in a metal detector, or by a body scanner.

[0011] It is advantageous to tune the wavelength of the first pulsed electromagnetic radiation during the first spectrum acquisition window and to detect the intensity of the first scattered radiation as a function of the wavelength of the first pulsed electromagnetic radiation. For example, the wavelength of the first pulsed electromagnetic radiation can be changed after a certain number of pulses. The more individual measurements are performed at the same wavelength, the better the signal-to-noise ratio of the measurement.

[0012] Preferably, the first pulsed electromagnetic radiation is generated by a first radiation source. In particular, the first radiation source can be a first laser, and more specifically, an IR laser. A laser can provide the required intensity of the first pulsed electromagnetic radiation needed to record meaningful optical spectra.

[0013] Furthermore, it is advantageous if the initial pulsed electromagnetic radiation is scanned across the sample. In particular, it can be scanned one-dimensionally or two-dimensionally. This has the particular advantage that the sample can be examined over a large area, whereby, depending on the total available measurement time and taking into account a deflection or scan speed, a large number of individual measurements can be carried out not only in identical but also in different spatial regions of the sample.

[0014] Particularly for Raman spectroscopy, it is advantageous to keep the wavelength of the second pulsed electromagnetic radiation constant during the second spectrum acquisition window. This allows a number of individual measurements corresponding to the number of radiation pulses to be performed during the second spectrum acquisition window, and the signals from these measurements can be summed to form a complete spectrum.

[0015] Advantageously, the second pulsed electromagnetic radiation is generated by a second radiation source. This can be a second laser, such as a UV laser. Lasers have the particular advantage of being able to provide high intensities of electromagnetic radiation. This is especially beneficial in Raman spectroscopy, as it is the only way to obtain a detectable measurement signal.

[0016] To be able to examine and characterize the sample over a large area, it is advantageous to scan the sample with a second pulsed electromagnetic radiation beam. Specifically, this can be done in one or two dimensions.

[0017] Furthermore, it is advantageous if the first pulsed electromagnetic radiation is generated with a first repetition rate and the second pulsed electromagnetic radiation with a second repetition rate, and if the first and second repetition rates are identical or different. With identical repetition rates, synchronous measurements can be performed. This means that pulses of the first and second electromagnetic radiation are simultaneously directed at the sample, where they then interact. Scattered radiation backscattered from the sample is then detected. If the repetition rates are different, so-called crosstalk effects can be easily minimized. Furthermore, this allows for the best possible signal-to-noise ratio for the measured spectra to be achieved in the shortest possible time.Asynchronous means, in particular, that pulses of the first and second electromagnetic radiation do not arrive at the sample simultaneously, but rather at different times or only partially overlapping in time.

[0018] Furthermore, it is advantageous if the sample is synchronously exposed to the first and second pulsed electromagnetic radiation and if the first and second scattered radiation backscattered by the sample are detected synchronously. This allows for rapid characterization of the sample using two different optical spectroscopy methods. This yields additional, redundant, or complementary information about the sample, thus reducing the overall measurement time.

[0019] Alternatively, it can be advantageous to asynchronously expose the sample to the first and second pulsed electromagnetic radiation and to asynchronously detect the first and second scattered radiation backscattered by the sample. This method allows crosstalk effects to be eliminated and, moreover, enables the acquisition of two different optical spectra of the sample in the shortest possible time with the best possible signal-to-noise ratio.

[0020] It is advantageous to determine the distance of the sample from the first and / or second radiation source by measuring the transit time of the pulses of the first and / or second pulsed electromagnetic radiation. This allows verification, in particular, of whether the signals actually correlate with the preset distance between the radiation sources and the sample. Furthermore, this additional information can be used to further increase the sensitivity and thus the reliability of the method. Specifically, measurement time windows can be automatically defined based on the determined transit time, with their temporal width corresponding to the pulse width of the electromagnetic radiation. Signals can then be measured within these time windows, allowing a DC value to be output as a signal for each window.Furthermore, a background measurement time window can be automatically defined for each of the two spectroscopic methods, during which only a background signal is expected. The difference between the signals in the measurement time windows on the one hand and the background measurement time windows on the other then yields a background-free measurement signal. In this way, interference influences, such as those from sunlight or room lighting, can be effectively suppressed.

[0021] It is advantageous to divide the initial spectrum acquisition window into multiple initial measurement intervals, to generate a pulse of the initial electromagnetic radiation with a defined pulse width in each initial measurement interval, and to detect the initial scattered radiation within the initial measurement window of the first measurement interval. This approach offers the particular advantage of enabling a large number of individual measurements to be performed in each spectrum acquisition window for each of the two optical spectroscopy methods. This significantly improves the signal-to-noise ratio. Furthermore, by precisely defining a time delay between the initial measurement window and each pulse of electromagnetic radiation, it can be ensured that only backscattered radiation from the sample is detected, and not the pulsed electromagnetic radiation generated by the initial radiation source.

[0022] To avoid interference, it is advantageous for the first measurement window to have a duration corresponding to the first pulse width. This makes it possible, in particular, to average measurement signals over time within the first measurement window, for example using a Field Programmable Gate Array (FPGA).

[0023] The sensitivity of spectroscopic analysis can be increased, in particular, by limiting the pulse width to a maximum of 10% of the first measurement interval. This corresponds to a low duty cycle of no more than 10%. In this way, the distance to the sample can be determined, especially based on the transit time of each electromagnetic pulse. Furthermore, as described, measurement time windows and background measurement time windows can be precisely defined.

[0024] It is advantageous if, in each initial measurement interval, background radiation is detected in a first background measurement window after each initial measurement window. By calculating the difference between the signals in each initial measurement window and in each initial background measurement window, a background-free measurement signal can be obtained, effectively suppressing interference.

[0025] It is advantageous if the first background window has a duration corresponding to the first pulse width. In particular, if the first measurement window also has a duration corresponding to the first pulse width, any background radiation can be easily eliminated by differential measurement.

[0026] To determine a background-free measurement signal, it is advantageous to calculate a difference between the detected first scattered radiation and the detected first background radiation in order to determine the first optical spectrum.

[0027] According to a further preferred embodiment of the method according to the invention, the second spectrum acquisition time window can be divided into a plurality of second measurement intervals, a pulse of the second electromagnetic radiation with a second pulse width is generated in every second measurement interval, and the second scattered radiation is detected in a second measurement time window of the second measurement interval. In this way, the second scattered radiation can be detected independently of the pulse of the second electromagnetic radiation, thus avoiding interference from the pulse on the measurement signal.

[0028] Preferably, the second measurement window has a duration corresponding to the second pulse width. This ensures, in particular, that the second scattered radiation, which results from the interaction of the second electromagnetic radiation pulse with the sample, can be completely detected.

[0029] Ideally, the second pulse width corresponds to a maximum of 10% of the second measurement interval. As described above, the sensitivity of the method can be increased by a duty cycle of no more than 10%.

[0030] Furthermore, it is advantageous if, in every second measurement interval, a second background radiation is detected after every second measurement window. Here too, as described, a difference can be calculated between the measurement signal in the second measurement window and the measurement signal in the second background measurement window in order to eliminate the background radiation and thus any potential interference.

[0031] It is advantageous if the second background measurement window has a duration corresponding to the first pulse width. This allows measurement signals to be time-averaged over both the second measurement window and the second background window, particularly if the second measurement window also has a duration corresponding to the second pulse width. Furthermore, a background-free measurement signal can be easily obtained by calculating the difference between the two windows.

[0032] It is advantageous to calculate the difference between the detected second scattered radiation and the detected second background radiation to determine the second optical spectrum. This allows for the reliable elimination of interfering influences, such as those caused by sunlight or room lighting.

[0033] The procedure can be carried out in a particularly simple way if the first pulse width and the second pulse width are specified identically. Especially in synchronous measurements with synchronously generated pulses of the first and second electromagnetic radiation, a sample can thus be characterized with high accuracy in a very short time.

[0034] The problem stated at the outset is further solved according to the invention in a system of the type described above by the fact that the first spectrum acquisition time window and the second spectrum acquisition time window overlap at least partially in time. In particular, the spectrum acquisition time windows can overlap completely, provided that the first spectroscopic device comprises a first radiation source for generating first pulsed electromagnetic radiation and a first detector for measuring the intensity of first scattered radiation backscattered from the sample, and that the second spectroscopic device comprises a second radiation source for generating second pulsed electromagnetic radiation and a second detector for measuring the wavelength-dependent intensity of second scattered radiation backscattered from the sample.

[0035] As explained in detail above, this allows two different optical spectra to be acquired simultaneously or much faster compared to serial measurements. This makes such a system particularly suitable for personnel screening, for example, passenger checks at airports. Sample characterization can be performed completely contactlessly and from a predetermined distance using the described method. In particular, the proposed system improves the reliability of characterizing a sample to determine whether it contains hazardous substances. Specifically, the intensity of the electromagnetic radiation emitted by the spectroscopic equipment can be kept below a predefined limit to avoid any health risks.In particular, such a system can be used simultaneously when, for example, a passenger is being screened for dangerous objects with a security scanner. The system allows for a parallel, non-contact scan of the lower leg area. The sample would then be, for example, the passenger's shoes or trousers. Furthermore, the system can be designed so that the measurement is imperceptible to the person being screened, which is particularly possible when spectroscopy is performed in optical spectral ranges outside the visible spectrum, such as the infrared and ultraviolet ranges. The first optical spectroscopy device includes, or is itself an, an infrared spectrometer. Specifically, it can be designed as a MIR reflection spectrometer.An infrared spectrometer can directly record absorption spectra in the infrared spectral range, for example, in the mid-infrared. It measures the attenuation of the excitation radiation by the sample, which is wave-dependent. Infrared radiation is absorbed particularly when molecules are excited to vibrations or rotations. It is advantageous that the first spectroscopic device comprises a first radiation source for generating pulsed electromagnetic radiation and a first detector for measuring the intensity of the first scattered radiation backscattered from the sample. In particular, this allows for the measurement of correlated first scattered radiation that is backscattered from the sample due to the interaction with the first pulsed electromagnetic radiation. It is advantageous that the second optical spectroscopic device is or includes a Raman spectrometer.In particular, this could be a UV Raman spectrometer. A Raman spectrometer can determine the interaction of monochromatic radiation with a molecule whose polarizability changes upon rotation or vibration. In the spectrum of the light scattered by the sample, in addition to the incident frequency caused by Rayleigh scattering, other signals are observed. Frequency differences from the incident light correspond to the energies characteristic of rotational, vibrational, phonon, or spin-flip processes for the respective substance. Similar to an infrared spectrum, conclusions about the substance under investigation can be drawn from the resulting spectrum. The lines appearing in a Raman spectrum are also called Stokes lines and anti-Stokes lines.It is advantageous that the second spectroscopic apparatus includes a second radiation source for generating second pulsed electromagnetic radiation and a second detector for measuring the wavelength-dependent intensity of the second scattered radiation backscattered from the sample. With appropriately suitable detectors, different wavelengths can be detected simultaneously. For example, a suitable photodiode array can be used. By pulsedly irradiating the sample with electromagnetic radiation, a multitude of individual measurements can then be performed as described above. The signals from these individual measurements can be summed to obtain the corresponding lines in the Raman spectrum of sufficient quality and intensity to unambiguously determine the presence of specific molecules, particularly the hazardous substances to be detected.

[0036] It is advantageous if the system includes a spatially defined detection area in which the sample is positioned to record the first and second optical spectra. For example, the detection area for a person can be defined by a marking on the floor. The detection area can also be defined by a three-dimensionally limited space, as is the case, for example, with a body scanner.

[0037] Preferably, the first radiation source is configured to tune a wavelength of the first pulsed electromagnetic radiation during the first spectrum acquisition time window. This allows the first optical spectroscopy device to record the sample's absorption as a function of wavelength. Absorption maxima for the sample always occur at those wavelengths at which vibrations or rotations of the molecules are excited. Such vibrations and rotations are characteristic of each molecule due to its structure. Thus, an infrared spectrum of a molecule represents a "fingerprint" of that molecule.

[0038] To provide sufficient radiation intensity for recording infrared spectra, it is advantageous for the first radiation source to be in the form of a first laser. In particular, it can be an IR laser. For example, the laser can be a tunable, pulsed quantum cascade laser with a tuning range of 6 µm to 11.5 µm. Using such a laser, tuning speeds of up to 5000 cm⁻¹ can be achieved, especially in a wavelength-scan mode. -1 / s or even higher.

[0039] To ensure that not only a small area of ​​the sample can be examined, it is advantageous for the system to include a primary scanning unit for scanning the initial pulsed electromagnetic radiation across the sample. Specifically, the scanning unit can be configured for one-dimensional or two-dimensional scanning. This allows for line scans or area scans across the sample. In this way, the probability of detecting hazardous substances, if they are actually present in the sample, can be significantly improved.

[0040] Especially for Raman spectroscopy, it is advantageous if the second radiation source is designed to generate the second pulsed electromagnetic radiation with a constant wavelength.

[0041] To ensure sufficient intensity for conducting Raman spectroscopic investigations, it is advantageous for the second radiation source to be in the form of a second laser. This could be a UV laser. Ultraviolet radiation is invisible to the human eye, allowing the system to be used without the person being monitored being aware of the investigation.

[0042] Preferably, the system comprises a second scanning device for scanning the second pulsed electromagnetic radiation across the sample. In particular, the sample can be scanned in one or two dimensions. If the system comprises two scanning devices, these can be configured to deflect the first and second pulsed electromagnetic radiation across the sample in such a way that they always scan different areas of the sample. This helps to avoid unwanted interactions.

[0043] According to a further preferred embodiment of the invention, the first radiation source can be configured to generate the first pulsed electromagnetic radiation with a first repetition rate, and the second radiation source can be configured to generate the second pulsed electromagnetic radiation with a second repetition rate. The first and second repetition rates can be identical or different. Particularly with identical repetition rates, the optical spectra can be recorded completely synchronously with the two spectroscopy devices. Specifically, the pulses of electromagnetic radiation can be applied to the sample simultaneously and with the same pulse duration or pulse width. Different repetition rates enable, in particular, asynchronous measurements.Pulses of electromagnetic radiation thus strike the sample at different times for the various spectroscopy devices. In particular, the pulse lengths or pulse widths of the electromagnetic radiation can also be selected differently. This makes it easy to eliminate crosstalk effects.

[0044] Preferably, the system comprises a distance determination device for determining the distance of the sample from the first radiation source and / or from the second radiation source. The distance determination device can be configured, in particular, to perform a time-of-flight measurement for the laser pulses. Especially by considering such distance information, which can be calculated from the time of flight of a laser pulse, a first and / or second measurement time window can be automatically predefined at a time interval corresponding to the sample's distance from the pulse of electromagnetic radiation. In this way, a measurement time window can also be predefined in which scattered radiation, also known as back radiation, from the sample can be measured; this back radiation is always caused by the pulsed electromagnetic radiation.

[0045] For the system to function effectively, it is advantageous if it has a user interface for data input. This allows, for example, a user to enter the necessary data and settings for the system's operation.

[0046] Advantageously, the system includes a control unit for controlling the first and / or second optical spectroscopy unit. Such a control unit allows for the optimization of the interaction between the two spectroscopy units. In particular, it ensures that the spectrum acquisition time windows overlap sufficiently, and ideally completely, to minimize the overall time required for analysis of the sample.

[0047] Preferably, the system includes a storage device for storing reference spectra of hazardous substances and for storing the measured first and second optical spectra. Reference spectra also include, in particular, reference data provided by combining different optical spectra. This eliminates the need to compare two measured spectra with two reference spectra; instead, only a single comparison is required if the measured data from both spectroscopic devices are combined through suitable processing. This significantly reduces evaluation time.

[0048] Preferably, the system includes an output device for providing information on whether or not at least one hazardous substance is present in the sample. The output device can, in particular, provide visual and / or audible signals or information. Contaminated samples can thus be easily selected and, in the case of a positive result, further investigated.

[0049] Furthermore, the use of one of the systems described above to carry out one of the procedures described above is proposed. Hazardous substances can then be detected simply, quickly, and reliably in the manner described.

[0050] The foregoing description therefore includes in particular the embodiments of methods and systems for detecting at least one hazardous substance, defined below in the form of numbered sentences: 1. A method for detecting at least one hazardous substance, in particular an explosive, in a sample (26), in particular in a spatial detection area (18), in which a first optical spectroscopy method is used to record a first optical spectrum of the sample (26) during a first spectrum acquisition time window (106) and a second optical spectroscopy method is used to record a second optical spectrum of the sample (26) during a second spectrum acquisition time window (108), wherein the first and the second optical spectroscopy methods differ, wherein the first optical spectrum and the second optical spectrum are compared with provided reference spectra of the at least one hazardous substance to determine whether the at least one hazardous substance is present in the sample (26) or not, characterized in thatthat the first spectrum acquisition time window (106) and the second spectrum acquisition time window (108) overlap at least partially in time, in particular completely. 2. Method according to sentence 1, characterized in that the first and second optical spectra of the sample (26) are recorded when the sample (26) is arranged in a spatially predetermined detection area (18). 3. Method according to one of the preceding sentences, characterized in that the first optical spectroscopy method is infrared spectroscopy, in particular MIR reflection spectroscopy, and that an infrared spectrum is recorded as the first spectrum of the sample (26). 4. Method according to one of the preceding sentences, characterized in that, to record the first optical spectrum, the sample (26) is exposed to first pulsed electromagnetic radiation (50) and that an intensity of first scattered radiation (58) backscattered from the sample (26) is detected. 5. Method according to sentence 4, characterized in that a wavelength of the first pulsed electromagnetic radiation (50) is tuned during the first spectrum recording time window (106) and that the intensity of the first scattered radiation (58) is detected as a function of the wavelength of the first pulsed electromagnetic radiation (50). 6. Method according to sentence 4 or 5, characterized in that the first pulsed electromagnetic radiation (50) is generated with a first radiation source (48), in particular in the form of a first laser (52), further in particular in the form of an IR laser (54). 7. Method according to one of sentences 4 to 6, characterized in that the first pulsed electromagnetic radiation (50) is scanned over the sample (26), in particular one- or two-dimensionally. 8. Method according to one of the preceding sentences, characterized in that the second optical spectroscopy method is Raman spectroscopy, in particular UV Raman spectroscopy, and that a Raman spectrum is recorded as the second spectrum of the sample (26). 9. Method according to one of the preceding sentences, characterized in that, in order to record the second optical spectrum, the sample is exposed to second pulsed electromagnetic radiation (76) and that an intensity of second scattered radiation (86) backscattered from the sample (26) is detected with spectral resolution. 10. Method according to sentence 9, characterized in that a wavelength of the second pulsed electromagnetic radiation (76) is kept constant during the second spectrum recording time window (108). 11. Method according to sentence 9 or 10, characterized in that the second pulsed electromagnetic radiation (76) is generated with a second radiation source (74), in particular in the form of a second laser (78), further in particular in the form of a UV laser (80). 12. Method according to one of sentences 9 to 11, characterized in that the second pulsed electromagnetic radiation (76) is scanned over the sample (26), in particular one- or two-dimensionally. 13. Method according to one of sentences 9 to 12, characterized in that the first pulsed electromagnetic radiation (50) is generated with a first repetition rate and that the second pulsed electromagnetic radiation (76) is generated with a second repetition rate, and that the first repetition rate and the second repetition rate are identical or different. 14. Method according to one of sentences 9 to 13, characterized in that the sample (26) is synchronously exposed to the first pulsed electromagnetic radiation (50) and the second pulsed electromagnetic radiation (76) and that the first scattered radiation (60) and second scattered radiation (86) backscattered by the sample (26) is synchronously detected. 15. Method according to one of sentences 9 to 14, characterized in that the sample (26) is asynchronously exposed to the first pulsed electromagnetic radiation (50) and the second pulsed electromagnetic radiation (76) and that the first scattered radiation (60) and second scattered radiation (86) backscattered by the sample (26) is asynchronously detected. 16. Method according to one of sentences 9 to 15, characterized in that a distance (58, 84) of the sample (26) from the first radiation source (48) and / or from the second radiation source (74) is determined by a time-of-flight measurement of the pulses (110, 112) of the first pulsed electromagnetic radiation (50) and / or the second pulsed electromagnetic radiation (76). 17. Method according to one of sentences 7 to 16, characterized in that the first spectrum acquisition time window (106) is divided into a plurality of first measurement intervals (M n) is subdivided and that in each first measurement interval (M n ) a pulse (110) of the first electromagnetic radiation (50) with a first pulse width is generated, such that the first scattered radiation (60) is detected in a first measurement time window (116) of the first measurement interval (M n ) is detected. 18. Method according to sentence 17, characterized in that the first measurement time window (116) has a length which corresponds to the first pulse width. 19. Method according to sentence 17 or 18, characterized in that the first pulse width is a maximum of 10% of the first measurement interval (M n ) corresponds. 20. Method according to one of sentences 17 to 19, characterized in that in each first measurement interval (M n ) after each first measurement time window (116) in a first background measurement time window (120) first background radiation is detected. 21. Method according to sentence 20, characterized in that the first background measurement time window (120) has a length which corresponds to the first pulse width. 22. Method according to sentence 20 or 21, characterized in that a difference is formed between the detected first scattered radiation (60) and the detected first background radiation to determine the first optical spectrum. 23. Method according to one of sentences 9 to 22, characterized in that the second spectrum acquisition time window (108) is divided into a plurality of second measurement intervals (R m ) is subdivided and that in every second measurement interval (R m ) a pulse (112) of the second electromagnetic radiation (76) with a second pulse width is generated, such that the second scattered radiation (86) is detected in a second measurement time window (118) of the second measurement interval (R) m ) is detected. 24. Method according to sentence 23, characterized in that the second measurement time window (118) has a length which corresponds to the second pulse width. 25. Method according to sentence 23 or 24, characterized in that the second pulse width is a maximum of 10% of the second measurement interval (R m ) corresponds. 26. Method according to one of sentences 23 to 25, characterized in that in every second measurement interval (R m ) after every second measurement window (118) in a second background measurement window (122) second background radiation is detected. 27. Method according to sentence 26, characterized in that the second background measurement time window (122) has a duration which corresponds to the first pulse width. 28. Method according to sentence 26 or 27, characterized in that a difference is formed between the detected second scattered radiation and (86) the detected second background radiation to determine the second optical spectrum. 29. Method according to one of sentences 23 to 28, characterized in that the first pulse width and the second pulse width are specified identically. 30. System (10) for detecting at least one hazardous substance, in particular an explosive, in a sample, in particular in a spatial detection area (18), which system (10) comprises a first optical spectroscopy device (28) for recording a first optical spectrum of the sample (18) during a first spectrum recording time window (106) and a second optical spectroscopy device (30) for recording a second optical spectrum of the sample (18) during a second spectrum recording time window (108), wherein the first and the second optical spectroscopy devices (28, 30) are different, wherein the system (10) comprises an evaluation device (42) for comparing the first optical spectrum and the second optical spectrum with provided reference spectra of the at least one hazardous substance and for determining whether the at least one hazardous substance is present in the sample (26) or not, characterized in thatthat the first spectrum acquisition time window (106) and the second spectrum acquisition time window (108) overlap at least partially in time, in particular completely. 31. System according to sentence 30, characterized in that the system comprises a spatially defined detection area (18) in which the sample (26) is arranged to record the first and second optical spectra. 32. System according to sentence 30 or 31, characterized in that the first optical spectroscopy device (28) is or comprises an infrared spectrometer (44), in particular an MIR reflection spectrometer (46). 33. System according to one of sentences 30 to 32, characterized in that the first spectroscopy device (28) comprises a first radiation source (48) for generating first pulsed electromagnetic radiation (50) and a first detector (64) for measuring an intensity of first scattered radiation (60) backscattered from the sample (26). 34. System according to sentence 33, characterized in that the first radiation source (48) is designed to tune through a wavelength of the first pulsed electromagnetic radiation (50) during the first spectrum recording time window (106). 35. System according to sentence 33 or 34, characterized in that the first radiation source (48) is designed in the form of a first laser (52), in particular in the form of an IR laser (54). 36. System according to one of sentences 33 to 35, characterized in that the system (10) comprises a first scanning device (38) for scanning the first pulsed electromagnetic radiation (50) over the sample (26), in particular one- or two-dimensionally. 37. System according to one of sentences 30 to 36, characterized in that the second optical spectroscopy device (30) is or comprises a Raman spectrometer (70), in particular a UV Raman spectrometer (72). 38. System according to one of sentences 30 to 37, characterized in that the second spectroscopy device (30) comprises a second radiation source (74) for generating second pulsed electromagnetic radiation (76) and a second detector (90) for measuring wavelength-dependent intensity of second scattered radiation (86) backscattered from the sample (26). 39. System according to sentence 38, characterized in that the second radiation source (74) is designed to generate the second pulsed electromagnetic radiation (76) with constant wavelength. 40. System according to sentence 38 or 39, characterized in that the second radiation source (74) is designed in the form of a second laser (78), in particular in the form of a UV laser (80). 41. System according to one of sentences 38 to 40, characterized in that the system (10) comprises a second scanning device (40) for scanning the second pulsed electromagnetic radiation (76) over the sample (26), in particular one- or two-dimensionally. 42. System according to one of sentences 38 to 41, characterized in that the first radiation source (48) is configured to generate the first pulsed electromagnetic radiation (50) with a first repetition rate and that the second radiation source (74) is configured to generate the second pulsed electromagnetic radiation (76) with a second repetition rate and that the first repetition rate and the second repetition rate are identical or different. 43. System according to one of sentences 38 to 42, characterized in that the system (10) comprises a distance determination device (58, 84) for determining a distance of the sample (26) from the first radiation source (48) and / or from the second radiation source (74). 44. System according to sentences 30 to 43, characterized in that the system (10) comprises an operating device (22) for entering data. 45. System according to one of sentences 30 to 44, characterized in that system (10) comprises a control device (32) for controlling the first and / or second optical spectroscopy device (28, 30). 46. ​​Device according to one of sentences 30 to 45, characterized in that the system (10) comprises a storage device (26) for storing reference spectra of hazardous substances and for storing the measured first and second optical spectra. 47. System according to one of sentences 30 to 46, characterized in that the system (10) comprises an output device (34) for outputting information as to whether the at least one hazardous substance is present on the sample (26) or not. 48. Use of a system (10) according to one of sentences 30 to 47 to carry out a procedure according to one of sentences 1 to 29.

[0051] The following description of preferred embodiments of the invention, in conjunction with the drawings, serves for further explanation. The drawings show: Fig. 1: a schematic representation of a first embodiment of a system for detecting hazardous substances; Fig. 2: a schematic representation of another embodiment of a system for the detection of hazardous substances; Fig. 3: another perspective view of the arrangement from Fig. 2; Fig. 4: a schematic diagram of a further embodiment of a system for detecting hazardous substances; Fig. 5: a schematic representation of another embodiment of a system for detecting hazardous substances; Fig. 6: a schematic representation of overlapping spectrum acquisition time windows for two different spectroscopy methods; Fig. 7: a schematic representation similar Fig. 6 with an explanation of the division of the spectrum recording time windows into a plurality of measurement intervals; Fig. 8: a schematic representation of two partially overlapping spectrum acquisition time windows; Fig. 9: a schematic representation of two completely overlapping spectrum acquisition time windows; Fig. 10: a schematic representation of two spectrum recording time windows, one of which fully encompasses the other in time; Fig. 11: a schematic representation of a wavelength-dependent excitation of a sample for measuring a spectral signature of the same using MIR reflection spectroscopy; Fig. 12: a schematic representation of the excitation of a sample in UV Raman spectroscopy with a constant wavelength of the excitation laser; Fig. 13: a schematic representation of three measurement intervals in a synchronous measurement of two optical spectra; Fig. 14: a schematic representation of an asynchronous temporal sampling of a sample for measuring two optical spectra; Fig. 15: a schematic representation of the procedure for measuring a Raman spectrum; Fig. 16: a schematic representation of the procedure for measuring an infrared spectrum; Fig. 17: a schematic representation of a further embodiment of a system for detecting hazardous substances when scanning the sample in the detection area; Fig. 18: a schematic representation of optical components of a system for detecting hazardous substances; Fig. 19: a schematic representation of another embodiment of a system for detecting hazardous substances; Fig. 20: a schematic representation of the process of examining a sample; Fig. 21: a schematic representation of the data acquisition process using preprocessed measurement data to identify conspicuous substances; Fig. 22: a photographic reproduction of a material sample on which ammonium nitrate was applied within a marked area; and Fig. 23: An exemplary representation of a difference spectrum, which was determined from Raman measurements inside and outside the marked area.

[0052] In Fig. Figure 1 schematically illustrates a first embodiment of a system 10 for detecting one or more hazardous substances. It comprises a housing 12 in which two spectroscopy devices are arranged, which emit a first pulsed laser radiation field 14 and a second pulsed laser radiation field 16 into a detection area 18. A person 20, for example, can position themselves in the detection area 18 so that the radiation fields 14 and 16 strike their feet and lower legs.

[0053] An operating device 22, comprising the system 10 and in the form of a touch panel which constitutes a user interface, enables an operator of the system 10 (not shown) to enter data and read measurement results. For this purpose, the operating device 22 may, in particular, include a display device.

[0054] The two laser radiation fields 14 and 16 are emitted simultaneously or overlapping in time onto the detection area 18. For example, if a passenger 20 is being screened for dangerous objects with a security scanner at an airport or similar location, their lower legs can be checked simultaneously and without contact using system 10. In particular, integration of system 10 into a security scanner is possible.

[0055] In the Fig. 2 and Fig. Figure 3 schematically illustrates another application example for a system 10 for detecting one or more hazardous substances. The person 20 is positioned inside a security scanner 24, which is used to screen them for hazardous objects. The security scanner 24 can be either a metal detector or a body scanner. Simultaneously with the screening for hazardous objects, the system can also perform a non-contact and eye-safe scan of the lower legs and shoes of the person 20 for hazardous substance residues, particularly explosive residues.

[0056] System 10 enables individual examination of persons 20. This allows for a clear assignment of an examination result to the respective person 20 examined.

[0057] System 10, in combination with the Security Scanner 24, enables various checks to be performed in a single screening step: specifically, whether a person is carrying dangerous items and is contaminated with hazardous substances. This significantly reduces the time required for screening individuals. This is a major advantage, particularly in passenger processing at airports, as the additional check of person 20 to determine whether they are contaminated with hazardous substances does not require an extra screening step.

[0058] The area of ​​the shoes and the lower leg area of ​​person 20 define a sample 26, which is examined with system 10.

[0059] A simplified block diagram of an exemplary embodiment of a system 10 for detecting one or more hazardous substances is shown in [reference to be added]. Fig. 4 shown.

[0060] System 10 comprises a first spectroscopy device 28 and a second spectroscopy device 30. These are connected to a control device 32.

[0061] The control device 32 is also connected to the operating device 22 in a control-effective manner, as well as to an output device 34, which can output information on whether one or more hazardous substances are present on the sample 26, and to a storage device 36, which is designed to store reference data or reference spectra of hazardous substances and to store measured optical spectra.

[0062] System 10 further comprises a first scanning device 38 and a second scanning device 40, each assigned to one of the spectroscopy devices 28 and 30. They serve to scan the laser radiation fields 14 and 16 in a predefined manner, for example one-dimensionally or two-dimensionally, over the detection area 18.

[0063] The two spectroscopy devices 28 and 30 are designed differently.

[0064] The control device 32 may in particular include an evaluation device 42 for comparing measured types with reference data in order to determine, based on the comparison, whether one or more hazardous substances are present in the sample or not.

[0065] Fig. Figure 5 shows an example block diagram of another embodiment of a system 10 in somewhat more detail.

[0066] The first spectroscopic device 28 is designed in the form of an infrared spectrometer 44, specifically in the form of a MIR reflection spectrometer 46. It comprises a first radiation source 48 for generating first pulsed electromagnetic radiation 50. The first radiation source 48 is designed in the form of a first laser 52, namely an IR laser 54. The first radiation source 48 is also designed to tune a wavelength of the radiation 50 within a predetermined time window.

[0067] The radiation 50 generated by the first radiation source 48 is deflected onto the first scanning device 38 by a beam-adapting device 56, which comprises one or more optical elements. This then deflects the radiation 50 onto the sample 26.

[0068] A wavelength of radiation 50 lies in a range from 3 µm to about 50 µm in the so-called mid-infrared spectral range.

[0069] The first spectroscopy device 28 is positioned at a defined distance 58 relative to the detection area 18.

[0070] The first scattered radiation 60 reflected from sample 26 is focused onto a first detector 64 via a receiving optic 62. The detector 64 measures the time-dependent intensity of the first scattered radiation 60. Since the excitation of sample 26 with the radiation 50 is wavelength-dependent, the temporal resolution of a detection signal at the first detector 64 yields a wavelength-dependent MIR reflection spectrum.

[0071] The first detector 64 is connected to a first data acquisition device 68 via a data connection 66.

[0072] The second spectroscopy device 30 is designed in the form of a Raman spectrometer 70, namely a UV Raman spectrometer 72.

[0073] The second spectroscopy device 30 comprises a second radiation source 74 for generating second pulsed electromagnetic radiation 76. The second radiation source 74 is configured to generate the second pulsed electromagnetic radiation 76 with a constant wavelength. For this purpose, the second radiation source 74 is configured as a second laser 78, namely as a UV laser 80. This is configured to generate the second radiation 76 in the deep ultraviolet spectral range, specifically with a wavelength in the range of approximately 200 nm to approximately 400 nm.

[0074] The second radiation 76 generated by the second radiation source 74 strikes a second beam-adapting device 82 and is directed by it to the second scanning device 40. From there, the second pulsed electromagnetic radiation 76 also strikes the detection area 18 and is scanned across the sample 26.

[0075] The second spectroscopy device 30 is arranged at a distance from the detection area 18. Distance 84, like distance 58, lies within a range of approximately 1 m to approximately 5 m. Preferably, distances 58 and 84 are approximately 2 m.

[0076] The second scattered radiation 86, backscattered from sample 26 due to exposure to the second pulsed electromagnetic radiation 76, is focused onto a second detector 90 by a second receiving optic 88. The second detector 90 is designed for high-resolution, wavelength-dependent measurement of the intensity of the second scattered radiation 86.

[0077] The second detector 90 is connected to a second data acquisition device 94 via a data connection 92.

[0078] The control unit 32 is effectively connected to both the radiation sources 48 and 74 as well as to the data acquisition units 68 and 94. An operator can control the entire system 10 via the operating unit 22, which is effectively connected to the control unit 32. For example, an operator can start and, if necessary, also stop a measurement to examine sample 26 using the operating unit 22.

[0079] The data signals from detectors 64 and 90, acquired by data acquisition units 68 and 94, are transmitted via data connections 96 and 98 to a transformation unit 100. There, the measurement data from the first spectroscopic unit 28 and the second spectroscopic unit 30—that is, the MIR measurement on the one hand and the Raman measurement on the other—are combined for further data analysis. Thus, instead of recording two separate spectra and comparing them with corresponding reference MIR and Raman spectra, which would also be possible, the data are combined into a single data set. In this way, the complementary properties of both spectroscopic units 28 and 30 can be utilized.

[0080] These transformed data are forwarded via a further data connection 102 to the evaluation unit 42. This unit further processes the measurement data combined with the transformation unit 100 using suitable algorithms and compares the resulting data set with data sets in a database containing corresponding data sets, i.e., spectral information determined by MIR and Raman measurements, with the transformed data. The evaluation unit 42 transmits the result of the evaluation to the output unit 34. This output unit can be integrated with the operating unit 22 or configured separately.

[0081] Output device 34 informs an operator of system 10 whether one or more hazardous substances have been detected in sample 26. The output can be visual, for example, via differently colored signal areas, or audible. Furthermore, output device 34 can optionally also output the full text of the test results for the detected hazardous substances.

[0082] Scanning devices 38 and 40 scan sample 26 simultaneously or at least with a temporal overlap, as explained in more detail below. Scanning devices 38 and 40 make it possible, in particular, to examine sample 26 over a large area.

[0083] The procedure for examining sample 26 is schematically described in Fig. Figure 6 shows that an operator starts the process by entering data at the control unit 22 at time t. Sthe investigation. The control unit 32 activates the first spectroscopy unit 28 at time t. S and at time t1 the second spectroscopy device 30. The control device 32 terminates the operation of the first spectroscopy device 28 at time t2 and the operation of the second spectroscopy device 30 at time t E .

[0084] With the first spectroscopy device 28, a MIR reflection spectrum is thus recorded in a first spectrum acquisition time window 106. The first spectrum acquisition time window 106 extends between the time points t S and t2.

[0085] A Raman spectrum is recorded using the second spectrometry device 30 in a second spectrum acquisition time window 108. The second spectrum acquisition time window 108 extends between time points t1 and t2. E .

[0086] The spectrum acquisition time windows 106 and 108 overlap as schematically shown in Fig. 6 is shown partially in time, namely between times t1 and t2 for the duration Δt, which corresponds to the difference between times t2 and t1, i.e. Δt = t2 - t1.

[0087] Due to the overlap of the spectrum acquisition time windows 106 and 108 for the duration Δt, the total measurement time or the total examination time of the sample 26 is reduced compared to serially, i.e., successively, performed measurements with the first spectroscopic device 28 and the second spectroscopic device 30. With the described procedure, Raman and infrared spectra can thus be recorded and evaluated simultaneously, enabling a more specific and reliable detection of any hazardous substances adhering to the sample 26.

[0088] Fig. Figure 7 schematically shows the division of the two measurements performed with the spectroscopic devices 28 and 30. The first spectroscopic device 28 is used to record the first spectrum acquisition time window 106 in n first measurement intervals M. n Accordingly, the second spectrum acquisition time window is divided into 108 m with identical measurement intervals R. m subdivided. As described in more detail below, M is measured in each measurement interval. n and R m a pulse of the respective radiation or 76 was radiated onto the sample 26 and in each of the mentioned measurement intervals M n and R m A measurement signal associated with the first and second scatter radiation 60 and 86 was recorded.

[0089] As in Fig. As shown schematically in 7 below, M is measured in each measurement interval. n The wavelength λ of the first radiation source 48 was continuously tuned.

[0090] The values ​​in the respective measurement intervals M nand R m The collected data are added up and, as described, recorded using data acquisition devices 24 and 68 and forwarded to transformation device 100.

[0091] The Fig. Figures 8 to 10 schematically show possible overlaps between the spectrum acquisition time windows 106 and 108.

[0092] In Fig. Figure 8 is a simplified schematic representation of the situation. Fig. Figure 6 shows that the spectrum acquisition time windows 106 and 108 overlap for the time period Δt between time points t1 and t2.

[0093] Fig. Figure 9 shows the case in which there is a complete temporal overlap of the spectrum acquisition time windows 106 and 108. Both spectrum acquisition time windows 106 and 108 begin at time t. S and end at time t E In other words, the times t coincide. S and t1 on the one hand and t E and t2 together.

[0094] Fig. Figure 10 shows an example case where the spectrum acquisition time windows 106 and 108 are of different lengths. In the example shown, the spectrum acquisition time window 108 is shorter than the spectrum acquisition time window 106. In this case, as in the example in Fig. In the case shown in point 9, the times t S and t E defined by the spectrum acquisition time window 106. The spectrum acquisition time window 108 lies entirely within the spectrum acquisition time window 106. A temporal overlap in the period Δt thus corresponds to the time difference between the times t2 and t1, which define the end and beginning of the spectrum acquisition time window 108, respectively. Of course, the case that occurs in Fig. As shown schematically in Figure 10, it can also be the other way around, i.e. the spectrum acquisition time window 106 can be shorter than the spectrum acquisition time window 108 and lie entirely within the latter.

[0095] Fig. Figure 11 schematically illustrates the procedure for MIR reflection spectroscopy. As mentioned previously, the wavelength of the first radiation source 48 is tuned. This wavelength tuning can be performed, in particular, between successive pulses generated by the first radiation source 48. In principle, tuning the wavelength during a single pulse would also be conceivable. The backscattered first scattered radiation 60 is detected by the spectrally broadband detector 90.

[0096] The procedure is different for UV Raman spectroscopy. As in Fig. As schematically represented in Figure 12, the wavelength of the second radiation source 74 remains constant over the entire second spectrum recording time window 108. The second scattered radiation 86 is detected with spectral resolution by the detector 64.

[0097] The described embodiments of systems 10 allow, in particular, the implementation of two different measurement techniques.

[0098] Fig. Figure 13 schematically illustrates the procedure for a synchronous measurement. At the beginning of each of the two measurement intervals R1 and M1, which completely overlap in time, a first pulse 110 or 112 of the first radiation 50 or the second radiation 76, respectively, is generated. At a time interval 114, which corresponds to twice the light travel time for intervals 58 and 84, both the first scattered radiation 60 and the second scattered radiation 86 are detected in measurement time windows 116 and 118, respectively. The measurement time windows 116 and 118 correspond to the pulse durations of pulses 110 and 112.

[0099] Slightly time-distant from measurement window 118, a background signal from sample 26 is measured in a background measurement window 120. The signal measured in measurement window 116 can then be corrected, in particular, for the measurement signal in the background measurement window 120, in order to effectively suppress interference, for example from sunlight or room lighting.

[0100] In the described manner, during a synchronous measurement, M is measured in all measurement intervals. n and R m This approach allows for averaging of the specific Raman data to improve the signal-to-noise ratio.

[0101] The procedure for an asynchronous measurement is schematically shown in Fig. Figure 14 shows that pulses 110 and 112 are not triggered synchronously, but asynchronously. Furthermore, the measurement intervals M n and R mThe measurements are of different lengths. Therefore, they are taken at different repetition rates. The first radiation source 48 is measured at a repetition rate f. MIR and the second radiation source 74 is emitted with a repetition rate f R operated. Fig. Figure 14 schematically shows the case where the repetition rate f MIR is greater than the repetition rate f R .

[0102] The asynchronous triggering of pulses 110 and 112 eliminates crosstalk effects. Furthermore, the different repetition rates allow for the rapid achievement of the best possible signal-to-noise ratio for spectral measurement. Additionally, the widths of pulses 110 and 112 can be optimally matched to the gate times of detectors 64 and 90 to achieve maximum sensitivity while simultaneously enabling rapid tuning of the wavelength of the first radiation source 48.

[0103] The Fig. 15 and Fig. Figure 16 shows the procedure for asynchronous measurement in a slightly modified representation. Fig. Figure 15 shows a section of the spectrum acquisition time window 108 and a measurement interval R1. Fig. Figure 16 schematically shows a section of the spectrum acquisition time window 116 and a section of the measurement interval M2. In the measurement interval M2, the wavelength of the first radiation source 48 is changed after each pulse 110, for example, continuously tuned to longer wavelengths. This tuning of the wavelength of the first radiation source 48 takes place in each measurement interval M2. n .

[0104] Fig. Figure 17 shows an example of a possible procedure for scanning the detection area 18. A first scan path 124 of the first radiation 50 over the detection area 18 is shown schematically, as is a second scan path 126 of the second radiation 76 over the detection area 18. In this way, very reliable data acquisition can be achieved, since within the entire measurement time, i.e., between the time points t S and t E , the entire detection area was scanned with one of the two radiations 50 or 76 respectively.

[0105] The scanning devices 38 and 40 preferably operate in opposite directions to ensure rapid signal acquisition and high reliability even when the sample 26, and in particular a person 20, is moving, since the entire detection area 18 has already been scanned with one of the two different spectroscopic methods within half the total measurement time. The described scanning also allows for improved subtraction of background effects and increased sensitivity by comparing areas with and without contamination from hazardous substances. Furthermore, scanning the sample 76 reliably localizes potential local contamination points.

[0106] In Fig. Figure 18 schematically shows another embodiment of a system 10. In particular, the two spectroscopy devices 38 and 40 can be housed in a casing 12 which has a length 128 of about 80 cm, a width 130 of about 40 cm and a height 132 of about 50 cm.

[0107] In Fig. 18 elements of system 10 are designated with the same reference numerals as in the embodiments, in particular the Fig. 4 and Fig. 5.

[0108] In Fig. Figure 19 schematically illustrates another embodiment of system 10. Identical components and assemblies are designated with the same reference numerals as in the embodiments of Figure 19. Fig. 4 and Fig. 5.

[0109] A touchscreen display serves as an example of the function of the operating unit 22 and the output unit 34, allowing an operator to input data and display measurement results. Alternatively, a keyboard and a separate display can be used. The display of measurement results is customized according to the operator's specifications. For example, test results can be displayed qualitatively, such as with the message "hazardous substance present," or quantitatively, through a corresponding classification.

[0110] The control unit 32 is implemented by a computer. It forms an interface between the operator and hardware of the system 10. Special software controls a Field Programmable Gate Array (FPGA), drivers of the lasers 52 and 78, an external water cooling system for the UV laser 80, and the detector 90, in order to switch these components on and off.

[0111] The FPGA 134 is used to synchronize the spectroscopy devices 28 and 30. Parallel processing of the FPGA 134 is used to trigger lasers 52 and 78 via an electronic pulse and to emit corresponding pulses 110 and 112.

[0112] For the first spectroscopy device 28, the FPGA 134 is simultaneously used to acquire voltages from the detector 64 with a large bandwidth / sample rate and high bit resolution via an analog-to-digital converter 136. This signal is further processed in parallel in the FPGA 134 by an implemented boxcar averaging algorithm 138 and sent back to the control device 32.

[0113] Furthermore, additional, slow digital outputs of the FPGA 134 are used to digitally control peripheral components of the system 10, for example a water cooling system 142 for the first radiation source 48 and the first detector 64, or a status LED to indicate the status of the peripheral components.

[0114] The second laser 78 is designed in the form of a pulsed nanosecond laser that emits in the deep UV spectral range.

[0115] The second beam-adapting device 82 may optionally include a telescope for beam expansion in order to adjust the laser intensity of the radiation 76 in accordance with the optical radiation protection regulations so that it lies in the eye-safe range outside the system 10.

[0116] The second scanning device 40 is designed in the form of a high-speed galvo mirror for rapid beam guidance, so that, for example, the sample 26, in particular a shoe area of ​​person 20, can be scanned with a one-dimensional line scan.

[0117] The receiving optics 88 comprise a mirror and lens arrangement for collecting the backscattered second scattered radiation 86. This consists in particular of the Stokes-shifted photons. The second receiving optics 88 is equipped with specially designed anti-reflective coatings for UV wavelengths.

[0118] To suppress the wavelength of the second laser 78 and other possible sources of interference, an optical filter 146 is arranged between the second receiving optics 88 and the second detector 90. This filter is formed by a combination of notch and longpass filters, optionally also a bandpass filter, so that only the backscattered Raman signal of the second scattered radiation 86 is detected.

[0119] The first laser, 52, is designed as a tunable, pulsed quantum cascade laser with a tuning range of 6 µm to 11.5 µm. In wavelength scan mode, tuning speeds of up to 5000 cm⁻¹ are possible. -1 / s can be reached.

[0120] Pulsed operation of the first laser 52, triggered by the FPGA 134, with a duty cycle of 10%, enables the application of a boxcar averaging measurement scheme, thus effectively suppressing background signals from interference sources. The water cooling system 142 serves to thermally stabilize the first laser 52.

[0121] The first beam-adapting device 56 also includes a telescope arrangement with a combination of germanium lenses with special anti-reflective coating or a combination of gold mirrors.

[0122] The first scanning device 38 also includes high-speed galvo mirrors for rapid beam guidance, so that the thrust area of ​​the person 20 to be monitored can be scanned with a one-dimensional line scan. Gold mirrors are used for beam guidance here.

[0123] The first receiving optics component comprises a 3" off-axis parabolic mirror with a gold coating. Alternatively, a 3" germanium lens with an anti-reflective coating can be used. The size of the receiving optics can be adjusted, if necessary, to optimize signal strength.

[0124] In this embodiment of the system 10, an optical filter 148 in the form of a MIR bandpass filter is arranged between the first receiving optics 62 and the first detector 64 to suppress interference sources in the sensitivity range of the first detector 64. The optical filter 148 blocks the wavelengths outside the tuning range of the first laser 48.

[0125] In this embodiment of the system 10, the first detector 64 is designed as a MIR point detector with an integrated four-stage TEC and preamplifier. For heat dissipation and to achieve maximum detectability, the first detector 64 is cooled by the water cooling system 142. Electrical voltages from the first detector 64 are acquired by the analog-to-digital converter 136 and further processed by the FPGA 134.

[0126] Fig. Figure 20 schematically shows a block diagram illustrating the process of examining a sample 26 or a person 20. After user input, the sample examination is started. The detection area 18, also known as the region of interest (ROI), is defined. The scan units 38 and 40 are reset to their respective starting positions. The FPGA 134 sends trigger pulses to the individual devices to start the measurements. In this way, the measurements of the two spectroscopy units 28 and 30 are electronically synchronized. Here, either a synchronous or an asynchronous measurement can be performed, as described above.

[0127] The Raman spectrum and the MIR reflection absorption spectrum are recorded at different positions on sample 26 over time. To obtain a two-dimensional image, the radiation fields 14 and 16 are scanned across the detection area 18.

[0128] In Fig. Figure 21 is an example of a detailed recording of the measurement data.

[0129] For data acquisition, an MCT detector 64 is used as the first detector. Its signal is digitized via an analog-to-digital converter (ADC) for further processing. In parallel, a second MCT detector measures the time of occurrence of the positive edge of pulse 110 directly at the laser output. This measurement is used for the described time-of-flight determination to calculate the distance 58 and for further synchronization. Additionally, the power of each pulse is determined using a look-up table to eliminate laser fluctuations caused by the balance detection scheme. Based on the time of flight of the laser pulses, the measurement window 116 is defined, from which measurement data is extracted and averaged. The data is then adjusted for further data processing.

[0130] In Raman spectroscopy, multiple channels are recorded simultaneously, for example, 1064 channels, so that the complete Raman spectrum is captured in each measurement. Additionally, a dark spectrum is recorded in the background measurement time windows 120 and 122 to minimize the influence of external environmental factors such as temperature and humidity on the spectra.

[0131] Due to the high spectral tuning rate of the IR laser 54 used, a corresponding repetition rate f MIR The entire detection range 18 can be captured with sufficient accuracy within a period of approximately one second.

[0132] In Fig. Figure 22 shows a photograph of a material sample on which minute amounts of ammonium nitrate (NH4O3) have been applied within the marked area. This is a substance used particularly in the manufacture of explosives.

[0133] Although no residues are visible to the naked eye on the surface of sample 26, contamination of the sample can be detected within a few seconds using the described method. Fig. Figure 23 shows the measurement of a Raman spectrum as a difference measurement between areas inside and outside the marked area. The spectrum reveals a characteristic vibration band of ammonium nitrate at 1040 cm⁻¹. -1 .

[0134] The described embodiments of systems 10 for detecting one or more hazardous substances are particularly suitable for use in security checks at airports. Furthermore, such systems 10 can also be used in other areas, for example, in security checks at large events such as festivals and sporting events.

[0135] The described systems enable, in particular, the fully automated identification of persons 20 who have had contact with explosive hazardous materials. The investigations can be documented in a traceable and automated manner. Detection of the detection area 18 can be performed automatically using a camera, and a corresponding scan with the radiations 50 and 76 can be automatically specified. Furthermore, the systems 10 also make it possible to search for anomalies in the detected signals in order to discover unknown, novel substances.

[0136] Furthermore, the privacy of the persons examined is guaranteed, as no photos are taken, but only physical information is evaluated.

[0137] The described systems 10 are easy to operate. They require an unobstructed field of view and allow for an open and transparent testing environment. Furthermore, the combined use of two different optical spectroscopy methods enables extremely short overall measurement times. System 10 can be configured as a compact, lightweight device for flexible use, particularly in mobile applications.

[0138] Technically, the systems offer high resolution, bandwidth, and dynamic range, resulting in a high detection rate for potential hazardous substances. This minimizes the risk of false alarms. Furthermore, reliable and quiet continuous operation is possible.

[0139] The systems 10 enable the search for conspicuous substances in the detection area 18. This is independent of the specific properties of the sample 26 in the detection area, i.e., independent of the material on which the hazardous substances to be detected are located.

[0140] The proposed method is also insensitive to temperature fluctuations. Furthermore, the systems 10 can also be integrated into local networks.

[0141] The fire load of systems 10 is low. Furthermore, their use is safe, as they can be operated in an eye-safe manner. Future adjustments are possible via software updates. Reference sign 10 System 12 cases 14 first laser radiation field 16 second laser radiation field 18 Detection range 20 people 22 Control unit 24 security scanners 26 Sample 28 first spectroscopy device 30 second spectroscopy unit 32 Control unit 34 Output device 36 Storage device 38 first scanning setup 40 second scanning unit 42 Evaluation unit 44 Infrared spectrometers 46 MIR reflection spectrometers 48 first radiation source 50 first radiation 52 first laser 54 IR lasers 56 first beam-adapting device 58 distance 60 first scattered radiation 62 first receiving optics 64 first detector 66 Data connection 68 first data collection facility 70 Raman spectrometers 72 UV Raman spectrometers 74 second radiation source 76 second radiation 78 second laser 80 UV lasers 82 second beam adjusting device 84 distance 86 second scattered radiation 88 second receiving optics 90 second detector 92 Data connection 94 second data collection device 96 Data connection 98 Data connection 100 transformation facility 102 Data connection 104 Data connection 106 first spectrum acquisition time window 108 second spectrum acquisition time window 110 pulse 112 pulse 114 distance 116 measurement time windows 118 measurement time windows 120 background measurement time windows 122 background measurement time windows 124 first scan section 126 second scan path 128 length 130 width 132 Height 134 FPGA 136 AD converters 138 Boxcar Averaging Algorithm 140 digital output 142 Water cooling 144 status LEDs 146 optical filters 148 optical filters

Claims

[1] Method for detecting at least one hazardous substance, in particular an explosive, in a sample (26), in particular in a spatial detection area (18), wherein a first optical spectroscopy method is used to record a first optical spectrum of the sample (26) during a first spectrum acquisition time window (106) and a second optical spectroscopy method is used to record a second optical spectrum of the sample (26) during a second spectrum acquisition time window (108), wherein the first and the second optical spectroscopy methods are different, wherein the first optical spectrum and the second optical spectrum are compared with provided reference spectra of the at least one hazardous substance to determine whether the at least one hazardous substance is present in the sample (26) or not, wherein the first optical spectroscopy method is infrared spectroscopy, in particular MIR reflection spectroscopy,and that an infrared spectrum is recorded as the first spectrum of the sample (26), that the second optical spectroscopy method is Raman spectroscopy, in particular UV Raman spectroscopy, and that a Raman spectrum is recorded as the second spectrum of the sample (26), , characterized by , that the first spectrum acquisition time window (106) and the second spectrum acquisition time window (108) overlap at least partially in time, in particular completely, that to acquire the first optical spectrum the sample (26) is exposed to first pulsed electromagnetic radiation (50) and that an intensity of first scattered radiation (60) backscattered from the sample (26) is detected, that to acquire the second optical spectrum the sample is exposed to second pulsed electromagnetic radiation (76) and that an intensity of second scattered radiation (86) backscattered from the sample (26) is detected with spectral resolution. [2] Method according to claim 1, characterized by , that the first optical spectrum and the second optical spectrum of the sample (26) are then recorded when the sample (26) is arranged in a spatially defined detection area (18). [3] Method according to any of the preceding claims, characterized by , that a) a wavelength of the first pulsed electromagnetic radiation (50) is tuned during the first spectrum acquisition time window (106) and that the intensity of the first scattered radiation (60) is detected as a function of the wavelength of the first pulsed electromagnetic radiation (50). and / or b) the first pulsed electromagnetic radiation (50) is generated with a first radiation source (48), in particular in the form of a first laser (52), further in particular in the form of an IR laser (54). and / or c) the first pulsed electromagnetic radiation (50) is scanned over the sample (26), in particular in one or two dimensions. [4] Method according to any of the preceding claims, characterized by , that a) a wavelength of the second pulsed electromagnetic radiation (76) is kept constant during the second spectrum recording time window (108) and / or b) the second pulsed electromagnetic radiation (76) is generated with a second radiation source (74), in particular in the form of a second laser (78), further in particular in the form of a UV laser (80). [5] Method according to any of the preceding claims, characterized by , that a) the second pulsed electromagnetic radiation (76) is scanned over the sample (26), in particular one- or two-dimensionally, and / or b) the first pulsed electromagnetic radiation (50) is generated with a first repetition rate and that the second pulsed electromagnetic radiation (76) is generated with a second repetition rate, and that the first repetition rate and the second repetition rate are identical or different. [6] Method according to any of the preceding claims, characterized by , that the sample (26) with the first pulsed electromagnetic radiation (50) and the second pulsed electromagnetic radiation (76) a) is synchronously actuated and that the first scattered radiation (60) and second scattered radiation (86) backscattered from the sample (26) are detected synchronously or b) is asynchronously actuated and that the first scattered radiation (60) and second scattered radiation (86) backscattered from the sample (26) is detected asynchronously. [7] Method according to any of the preceding claims, insofar as these are directly or indirectly related to alternative b) of claim 3 or to alternative b) of claim 4, characterized by , that a distance (58, 84) of the sample (26) from the first radiation source (48) and / or from the second radiation source (74) is determined by a time-of-flight measurement of the pulses (110, 112) of the first pulsed electromagnetic radiation (50) and / or the second pulsed electromagnetic radiation (76). [8] Method according to any one of claims 4 to 7, characterized by , that the first spectrum acquisition time window (106) is divided into a plurality of first measurement intervals (M n ) is subdivided and that in each first measurement interval (M n ) a pulse (110) of the first electromagnetic radiation (50) with a first pulse width is generated, such that the first scattered radiation (60) is detected in a first measurement time window (116) of the first measurement interval (M n) is detected, particularly a) the first measurement time window (116) has a length which corresponds to the first pulse width, and / or b) the first pulse width a maximum of 10% of the first measurement interval (M n ) corresponds and / or c) in each first measurement interval (M n ) after each first measurement time window (116) in a first background measurement time window (120) first background radiation is detected, particularly the first background measurement time window (120) has a length which corresponds to the first pulse width, and / or To determine the first optical spectrum, a difference is formed between the detected first scattered radiation (60) and the detected first background radiation. [9] Method according to any one of claims 6 to 8, characterized by, that the second spectrum acquisition time window (108) is divided into a plurality of second measurement intervals (R m ) is subdivided and that in every second measurement interval (R m ) a pulse (112) of the second electromagnetic radiation (76) with a second pulse width is generated, such that the second scattered radiation (86) is detected in a second measurement time window (118) of the second measurement interval (R) m ) is detected. [10] Method according to claim 9, characterized by , that a) the second measurement time window (118) has a length which corresponds to the second pulse width, and / or b) the second pulse width a maximum of 10% of the second measurement interval (R m ) corresponds and / or c) in every second measurement interval (R m ) after every second measurement window (118) in a second background measurement window (122) second background radiation is detected, particularly c1) the second background measurement time window (122) has a duration which corresponds to the first pulse width, and / or c2) to determine the second optical spectrum a difference is formed between the detected second scattered radiation and (86) the detected second background radiation, and / or d) the first pulse width and the second pulse width are specified identically. [11] System (10) for detecting at least one hazardous substance, in particular an explosive, in a sample, in particular in a spatial detection area (18), which system (10) comprises a first optical spectroscopy device (28) for recording a first optical spectrum of the sample (26) during a first spectrum recording time window (106) and a second optical spectroscopy device (30) for recording a second optical spectrum of the sample (26) during a second spectrum recording time window (108), wherein the first and the second optical spectroscopy device (28, 30) are different, wherein the system (10) comprises an evaluation device (42) for comparing the first optical spectrum and the second optical spectrum with provided reference spectra of the at least one hazardous substance and for determining whether the at least one hazardous substance is present in the sample (26) or not,wherein the first optical spectroscopy device (28) is or comprises an infrared spectrometer (44), in particular a MIR reflection spectrometer (46), wherein the second optical spectroscopy device (30) is or comprises a Raman spectrometer (70), in particular a UV Raman spectrometer (72), , characterized by, that the first spectrum acquisition time window (106) and the second spectrum acquisition time window (108) overlap at least partially in time, in particular completely, that the first spectroscopy device (28) comprises a first radiation source (48) for generating first pulsed electromagnetic radiation (50) and a first detector (64) for measuring an intensity of first scattered radiation (60) backscattered from the sample (26), that the second spectroscopy device (30) comprises a second radiation source (74) for generating second pulsed electromagnetic radiation (76) and a second detector (90) for wavelength-dependent measurement of an intensity of second scattered radiation (86) backscattered from the sample (26). [12] System according to claim 11, characterized by , that the system comprises a spatially defined detection area (18) in which the sample (26) is arranged to record the first optical spectrum and the second optical spectrum. [13] System according to claim 11 or 12, characterized by , that the first radiation source (48) is designed to tune through a wavelength of the first pulsed electromagnetic radiation (50) during the first spectrum recording time window (106). [14] System according to claim 13, characterized by , that the first radiation source (48) is in the form of a first laser (52), in particular in the form of an IR laser (54). [15] System according to claim 13 or 14, characterized by , that the system (10) comprises a first scanning device (38) for scanning the first pulsed electromagnetic radiation (50) over the sample (26), in particular one- or two-dimensionally. [16] System according to any one of claims 11 to 15, characterized by , that the second radiation source (74) is designed to generate the second pulsed electromagnetic radiation (76) with constant wavelength. [17] System according to any one of claims 11 to 15, characterized by , that the second radiation source (74) is in the form of a second laser (78), in particular in the form of a UV laser (80). [18] System according to claim 16 or 17, characterized by , that a) the system (10) comprises a second scanning device (40) for scanning the second pulsed electromagnetic radiation (76) over the sample (26), in particular one- or two-dimensionally and / or b) the first radiation source (48) is configured to generate the first pulsed electromagnetic radiation (50) with a first repetition rate and the second radiation source (74) is configured to generate the second pulsed electromagnetic radiation (76) with a second repetition rate and the first repetition rate and the second repetition rate are identical or different and / or c) the system (10) a distance measuring device includes determining the distance of the sample (26) from the first radiation source (48) and / or from the second radiation source (74). [19] System according to claims 11 to 18, characterized by , that the system (10) a) an operating device (22) comprises for entering data and / or b) a control device (32) comprises for controlling the first and / or second optical spectroscopy device (28, 30) and / or c) a storage device (36) comprises for storing reference spectra of hazardous substances and for storing the measured first optical spectrum and the measured second optical spectrum and / or d) an output device (34) includes for outputting information on whether the at least one hazardous substance is present in the sample (26) or not. [20] Use of a system (10) according to any one of claims 11 to 19 for carrying out a method according to any one of claims 1 to 10.

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