IT202100007148A1 - TECHNIQUE AND SYSTEM OF TESTING A MATERIAL SAMPLE USING RADIOMETRY OR INFRARED THERMOGRAPHY - Google Patents

Description

Description of the invention entitled:

?TECHNIQUE AND SYSTEM OF TESTING A MATERIAL SAMPLE THROUGH THE USE OF INFRARED RADIOMETRY OR THERMOGRAPHY?

Description

Technical sector

The present invention relates in general to the analysis of materials and samples of materials by means of electromagnetic radiation, in particular by examining the temperature increase produced on the surface of the material by the radiation.

Known technique

The traditional Doppler effect ? known already? for a long time to researchers and technicians. The change in frequency of an electromagnetic wave when a source and receiver are in relative motion with respect to each other? was first described by Christian Doppler in 1842 [1]. He applied erroneously the effect to explain the different colors of the stars. Subsequently Buys Ballot [2] made experiments with sound waves and Fizeau [3] in 1848 proposed that lines in optical spectra could show frequency variations depending on the speed? relative of the source and of the observer, forecast then confirmed by Sir William Huggins [4], which showed? the red frequency shift of the hydrogen lines recorded by Sirius, indicating a recessive movement.

The Doppler effect, in its traditional conception, then gave rise to innumerable applications for electromagnetic waves and ultrasounds. In fact, since its discovery the Doppler effect ? become fundamental in the description of our world and in the development of a multitude of applications mainly for the determination of the speed? of moving objects.

? been applied in radar astronomy and other forms of radar to measure speed? of the detected objects: speed cameras, speed? of cloud fronts in meteorology, etc. In biomedical applications, Eco-Doppler flowmeters and Acoustic Doppler Velocimeter (ADC) have been developed, in which a source of sound waves, generally ultrasound, is suitably oriented. These acoustic waves are then reflected with a new frequency (depending on the vector velocity of the blood particles), which is detected and reprocessed in order to obtain this velocity measurement. Further application ? the laser Doppler imager, used in particular for studies on angiogenesis, endothelial dysfunction, skin ulcers, for the evaluation of pharmaceutical or cosmetic products for local application, for the study of burns. The Doppler ultrasound or more? simply echoDoppler? a non-invasive technique used for over thirty years in medicine for the study of the anatomical and functional situation of blood vessels, arteries and veins, and of the heart in real time and simultaneously (Duplex-Scanner).

The Doppler effect has also affected photoacoustics. Indeed, the Doppler effect of acoustic waves emitted by moving amplitude-modulated optical sources? was explored several decades ago by Soviet researchers including Bozhkov, [5?8] Bunkin, [5-7,9] and Kolomenskii [7,8] so? as per researchers in the United States [10]. Unfortunately, due to the proposed application for undersea communication, most of the published work by Soviet researchers centered on the problem of a moving laser beam directed at the interface between a transparent gas and an absorbent liquid where it? been modulated? intensity? of the radius, making it more? difficult to understand the shape of sound patterns in space and resulting in complex mathematical expressions. In addition, the case is not modulated not ? been analyzed [5-9, 11-14].

Pi? recently the complete theory on the displacement of photoacoustic sources in one, two and three dimensions ? been extensively discussed by W. Bai and G.J.Diebold [15, 16], applying the detection of trace gases with dynamic photoacoustic spectroscopy (DPAS) [17-19].

The study of materials can also take place with the thermographic technique.

As known, each body emits a quantity? of electromagnetic radiation proportional to the fourth power of its absolute temperature (Kelvin scale) according to the Stefan-Boltzmann Law [20]. Thermographic sensors can detect a portion of the radiation emitted by the body in the infrared range of the electromagnetic spectrum, making it possible to view absolute values and body temperature variations.

Thermography? therefore a non-destructive analysis technique which is based on the acquisition of images in the infrared providing a map of temperature and emissivity? of the objects framed by an infrared camera.

The thermographic analysis can? be conducted in active and passive conditions. In the first case, the element to be investigated is heated to increase the thermographic response and, at the same time, activate the heat flows which allow for different responses to be obtained from the elements with different capacities. thermal. In the passive conditions, instead, the surface is analyzed so? as it presents itself at the time of the investigation.

The thermographic method finds application in numerous sectors, including: iron and steel, construction, medicine and veterinary medicine, chemical industry, cultural heritage, aeronautics, automotive, environmental protection, etc.

In the building industry, for example, thermographic analyzes allow for the verification of insulation, the verification of waterproofing, the analysis of degradation due to humidity, the search for causes of water infiltration and the search for hidden construction elements.

In the case more general science of materials thermographic analyzes allow to measure defects, sub-surface cracks, residual stresses, fatigue limits, being widely applied in mechanical engineering for non-destructive testing of welds, suspension arms and bolt connections. Infrared thermography also allows the quantitative evaluation of the properties thermal properties of materials (for example the measurement of thermal diffusivity). Recently ? a thermographic method has been introduced which can be applied to moving samples which are heated by a continuous focused laser beam (c.w.), without any temporal modulation [21, 22]. Will you understand? how this application is technologically different from the one presented in the present patent application, since? it does not use temporal modulation of the laser beam, with a consequent reduction of the signal-to-noise ratio which limits its capacity? diagnostics and the estimation of the diffusivity? thermal, which instead can? be largely improved in time-modulated heating regimes.

The inventor of the present patent application adopts a thermographic technique in which the Doppler effect plays an important role.

Description of the invention

The present invention is based in part on the Doppler effect in the field of thermal waves. Thermal waves in media have been known for a long time. The Doppler effect on oscillating thermal fields is presented by the inventor of the present invention who demonstrates its validity experimental and theoretical and indicates its various applications, for example in the biomedical sector.

The inventor highlights the link between the observable frequency shift, the speed? relative between source and detector, and the speed? of the thermal wave linked in turn to the diffusivity? medium temperature.

The discovery of precise functional relationships between the thermophysical and kinematic parameters involved provides a key to be able to develop innovative applications that exploit this new effect to measure the speed? of particles in motion and/or the diffusivity? temperature of materials along a production line, in ranges of frequencies, speeds? and observability? of the different and complementary phenomenon compared to the standard applications of the Doppler effect in acoustics or electromagnetism.

The object of the present invention is generally to provide a technique for testing a material sample by using infrared radiometry or thermography, according to claim 1, and a system for testing a material sample by using use of infrared radiometry or thermography, according to claim 18.

The dependent claims concern aspects more? particulars of the invention that offer certain advantages.

Basically, the basic concept of the present invention consists in irradiating with a high density light source of energy (by heating up by a few degrees), in particular a laser, a surface of the material or of the medium to be examined. According to the present invention, the laser light is modulated with suitable modulation means (chopper, electro-optical system, laser diode activated by a square wave, etc.) at a fixed and predetermined modulation angular frequency ?. The wavelength of the laser is chosen so that the sample of material irradiated by it can be adequately examined. The laser could also be of variable wavelength, selectable for the specific application. Could the modulator also be made with angular frequency modulation? variable, selectively chosen for each specific application. Does the length of thermal diffusion depend on the diffusivity? thermal in the sample and from the frequency of modulation, for which choosing opportunely this? last one will be able? penetrate the material up to the right depth.

According to the present invention ? it is also essential that the medium, i.e. the sample to be examined, is in relative motion with respect to the excitation light source, for example a laser, or that the particles inside the sample are in relative motion with respect to the excitation light source (for example a laser ). In the latter case the particles can move orthogonally to the surface of the sample or parallel to it, approaching or moving away from the surface of the sample, or always moving parallel to it. In general, the particles could also have a speed? in either direction, although this is not the preferred solution/application. In the following detailed description various practical applications of the invention are presented in which the particles move orthogonally to the surface of the sample (so-called ?out of plane motion?) or parallel to the surface of the sample (so-called ?in plane motion?). The laser light, in the case of the excitation of a particle with speed? V orthogonal to the surface of the sample (hereinafter for brevity? also ?vertical motion? i.e. V ? S), is concentrated on a minimal surface of the sample (for example 1 mm2), until it reaches the region of the particle to excite or heat it . Obviously, the wavelength of the laser will be? appropriately chosen so that? the laser beam can penetrate the material with low attenuation, finally being strongly and selectively absorbed by the moving particles which heat up.

By absorbing the time-modulated beam at the angular frequency ?, the particles themselves become moving sources of thermal waves at this angular frequency ? = 2?f. Thanks to the thermal conduction mechanism, the heat is transmitted to the entire volume of the material which undergoes a slight rise in temperature. The temperature induced on the surface of the sample ? also oscillating, but at a different angular frequency ?? = 2?f? from that of the modulated beam. Specifically, there is a Doppler effect of thermal waves, where if the particle approaches the surface of the sample and therefore an infrared detector integral with (ie fixed with respect to the reference system of) the excitation laser, then ?? > ? and vice versa ?? < ? if it moves away from the infrared detector. From the angular frequency shift ?? you derive the speed? V of the particle, while the momentary (initial) position Zo of a particle is derived from the phase ? and from the shift ?? of the signal.

In the case of a particle moving in the sample with uniform motion parallel to the surface, ? obviously necessary to irradiate a surface pi? extended sample. Once again we have a formula where the (maximum) frequency shift ? given by a formula analogous to the case of the vertical motion of the particle. The positions and speeds? of particles moving in the medium under investigation (sample) parallel to its surface are given by specific formulas given in the detailed description.

An example of parallel motion? that of the cytometric study in capillaries or capillaroscopy. The system of the invention can? allow the determination of position and speed? of red blood cells, platelets, platelet aggregates, micro emboli, aggregates with tumor cells, in blood vessels and fine capillaries (see detailed description below). Obviously the wavelength of the laser must be calibrated in order to distinguish the contribution of the various species of particles in motion, based on the different properties? absorbents of the various families of particles. ? for this it is necessary to choose, for example, a laser operating at N possible wavelengths if there are N dissimilar particles.

In the case of particles with horizontal motion (V ? S), from the following formula (7) of the detailed description it can be seen that ?Ts, i.e. the increase in temperature on the surface of the sample, depends on t, x, y, for constant z .

So the temperature rise generally represents a complicated spatio-temporal response to the excitation of the laser, ie a function ?Ts of the variables x and y, as well as? t, which d? information on the statistics of the particles present and mobile in the medium and which are excited by the laser. The IR detector actually measures a signal that derives directly from the ?Ts. Even in the case of parallel motion (V ? S) that is horizontal there is a frequency shift (Doppler effect), but this? last ? variable with the momentary position of the particle according to the law sin (?), being ? the angle of inclination with respect to the vertical of the segment that connects the particle to the center of the local coordinate system (0, 0), with the position of the detector on the plane (x, y) ? S. In this regard, see the corresponding formula of the detailed description.

The invention also includes the case in which the medium is (as a whole) in relative motion with respect to the infrared detector and the light source. Even in this situation there? a relative motion between the material to be analyzed and the light source (pump laser). However, the velocimetric parameters of the particles are not then detected, which by hypothesis in this case all move at the same speed? uniform V (known or unknown), bens? the diffusivity? temperature of the medium or of the material under examination (if V is an unknown then V is also measured). Differently from the prior art, in which the sample is fixed with respect to the? measuring apparatus, to measure the diffusivity? temperature (or another thermophysical parameter) a moving sample is used in the present invention. The applications are many and are dealt with in the detailed description (quality control of industrial processes, safety of railway lines (railway tracks, etc.).

Even if the mobile sample ? a material whose particles all move at the same speed? uniform V, the light source ? modulated with a modulator but it is not necessary then more? any spectrum analyzer as the detected signal has a frequency equal to ?, cio? to the frequency of the modulator (chopper, laser diode, electro-optical system, etc.) and will come? then used a ?lock-in? demodulation system. The so-called ?contour plots? of the phase (displacement with respect to the harmonic signal of the modulator) and of the logarithm of the amplitude of the signal (i.e. of the temperature induced on the surface), show the level lines i.e. of constant value, which for V = 0 are circles around the center of the detection zone, in the case in which the laser gives rise to a Gaussian spot on the surface S. While these level lines are circles also for V?0 in the case of the phase, for the logarithm of the signal amplitude the lines of level are ellipses. From the absolute value of the gradient of ? (r) (being ? the phase and r the distance from the center of the pump beam), we obtain experimentally the value of the thermal diffusion length ?, and finally the diffusivity? thermal D of the sample (moving medium/material being tested). (In this regard, compare the respective equations of the detailed description of the invention).

If the speed? V of the sample not ? known, the inventor proposes an optical system (for example with a cylindrical lens) to focus the beam on a strip along the y axis (axis perpendicular to V and parallel to S). In this case the space-time trend of ?Ts, how can one? show, ? the one reported in the formula (17) of the detailed description. Also in this case, being the time part equal to exp(j?t) it is not written in the equation (17). Basically, the logarithm of the signal amplitude has two measurable slopes, sA+ and sA-, which, together with the slopes of the phase shift (equal and of opposite sign) ? sph, measured in front of and behind the plane x = 0, i.e. upstream and downstream of the central line of the incidence strip of the pump light beam on the surface S of the sample, allow to determine both V and D (thermal diffusivity). (cf. detailed description equations).

In general it can be noted that in the invention, the spatio-temporal trend of the temperature increase induced on the sample in response to the excitation of the laser makes it possible to measure velocimetric parameters (in the case of mobile particles inside the sample as a whole ) and thermophysics (D) in the case of a speed? constant for all the particles that make up the tested sample.

In the invention ? essential that the sample, or its parts (mobile internal particles), are in relative motion with respect to the light source which is? always integral (same fixed reference system) to the IR detector.

The modulator? connected to the spectrum analyzer or to a unit? control and data processing, depending on the case (first implementation or second implementation of the invention). The IR detector? connected to the analyzer or to the unit? of control and processing, according to the cases (first realization or second realization of the invention).

In the Figures, the optical systems are represented for purely illustrative purposes by lenses; in reality, these lenses can be very complex optical systems of any type, wherever there is? what does it matter? their function. For example, the Ge (germanium) lens in Figure 5 must be able to form an image of the IR light (emitted by the surface portion S) on the sensitive surface of the IR detector, in all or part of the latter, without forming distortions. Note that if the speed? of the sample V not ? note (Fig. 10a), then the unit? control can? exchanging a feedback signal with the sensors and actuators (or drive means) of the moving sample, in order to be able to measure and adjust the speed in real time? of the same sample (Fig. 10(a)). There? can? be important in industrial production lines that use product or work piece conveyors.

Brief description of the drawings

This invention will come now described in detail for illustrative and non-limiting purposes based on the two embodiments discussed and with reference to the annexed drawings, which show these new methodologies based on the Doppler effect (Doppler thermography) of thermal waves, applied for the non-destructive measurement of diffusivity? thermal of the materials and of the speed? of moving particles. The drawings show in detail:

FIGURE 1 the configuration of the test setup/complex in the case of the first embodiment of the present invention (first variant), for measuring the velocimetric statistics (position and velocity) concerning the particles in vertical movement in the test sample;

FIGURE 2 a purely schematic representation of the application of the embodiment of Fig. 1 of the present invention to the study of skin hydration;

FIGURE 3a a diagram of the IR signal as a function of time, in the case of the setup of Figs.1 and 2, for certain realistic values of the parameters f, ?, Zo, V, D relating to the application shown in Fig. 2, and for a particle approaching and respectively for a particle moving away from the surface of the sample;

FIGURE 3b the trend of the exponential gain of the module signal in a given period of time (5s);

FIGURE 3c the curves of the values of the speeds? V recalculated on the basis of the ?? derived from Fig. 3a, for that given speed? V (constant) over the same period of time (5s), with a blind test;

FIGURE 3d the trend of the depth? Zo over the same time period recalculated based on Fig. 3a, over the same time period (5s), with a blind test;

FIGURE 4 a schematic representation of a further possible practical application of the invention, once again relating to the first variant of the first embodiment, to the case of the non-destructive measurement of glucose migration in the interstitial fluid of the epidermis, with the use of a wavelength source selectively absorbable by glucose particles (EC-QCL laser); FIGURE 5 the configuration of the setup/test complex in the case of the first embodiment of the present invention (second variant), for measuring the velocimetric statistics (position and velocity) concerning the particles in horizontal movement in the test sample;

FIGURE 6 the temporal dynamics (with time normalized to the modulator period) of the IR signal for two different values of the ratio between the speed? V of the particle and the speed? of? thermal wave (speed? normalized), respectively for three depths? normalized to the thermal diffusion length, and compared to the reference signal of the pump beam of angular frequency ?; still in Fig. 6 the frequency shift is shown below (normalized to ?) as a function of the normalized time, for the three values of the depth? normalized, always in the same period of time as the other diagrams of Fig. 6;

FIGURE 7 above, contour plots of normalized frequency shift, drawn in the (x,z) plane for normalized values of x and z, for given predetermined values of ? and Zo, where the curves correspond to various constant values of the normalized shift; below, the diagrams of the trend of the frequency shift as a function of the normalized distance x, again for the ?in plane motion? of Fig. 5;

FIGURE 8 a diagram of the depth? normalized reconstructed (ie obtained from? equation (13)) as a function of the depth? normalized (assigned as a fixed parameter to the particle);

FIGURE 9 a possible application of the first variant of the first embodiment of the invention to cytometric study in capillaries or capillaroscopy, where the various species of particles move in the capillary substantially parallel to the skin surface;

FIGURE 10a the configuration of the test setup (assembly of components), in the case of the first variant of the second embodiment of the present invention, for measuring the diffusivity? thermal in the test sample mobile with speed? Note V with respect to the light source and IR sensor;

FIGURE 10b the configuration of the test setup (assembly of components), in the case of the second variant of the second embodiment of the present invention, for measuring the diffusivity? thermal D in the test sample and the speed? V of the latter with respect to the light source and the IR sensor;

FIGURE 11 the contour plots (x/?, y/?) of the logarithm of the amplitude and phase of the sensor IR signal with respect to the modulation signal, referred to the normalized coordinates of the (x, y) plane of the sample surface, where the origin of the coordinates (x, y) coincides with the central point of incidence of the spot of the Gaussian beam, for three different values of ? = V/?(2?D) (normalized speed), according to the setup of Fig. 10a;

FIGURE 12 the diagrams of the logarithm of the IR signal module amplitude and respectively of its phase shift (with respect to the source modulation signal) as a function of the normalized distance (x/?) from the center of the incident laser light strip (axis y);

FIGURE 13 a railroad non-destructive testing locomotive according to an application of the second embodiment of the present invention.

Description of some preferred embodiments of the invention

All the details useful for a person skilled in the art for the purpose of understanding some preferred embodiments of the invention and their variants are described below. All those details not strictly necessary will be omitted since? known to those who have a solid technical background in the sector.

A) First preferred embodiment of the invention

A1) ?out of plane motion? configuration (Fig. 1), variant 1

Inside a material 1 are there some particles 2 at a certain depth? Zo from the surface S. Are they moving with a velocity? V directed along the local normal z to the surface S. The convention ? chosen so that V>0 for particles 2 approaching the surface, and V<0 in the opposite case of moving away.

A pump laser beam 3 is used as a light source for excitation of the particles 2 in motion. The wavelength? is selected so that the material 1 is (partially) transparent so that? the beam 3 can penetrate it with weak attenuation, finally being strongly and selectively absorbed by the particles 2 in motion which heat up by a few degrees centigrade.

The laser beam 3 is temporally modulated at an angular frequency ?=2?f by means of a mechanical obturator (chopper) 4 or with an electroptic system (not shown), or finally by a switch controlled by a square wave generator, in the case of laser diodes (not shown).

The modulated beam 5 is finally collimated with a system of lenses 6 on a suitable area of interest 7 of the material (typically 1mm<2>), thus managing to illuminate even in depth moving particles 2.

By absorbing the modulated beam 5, the particles 2 become moving sources of thermal waves at the angular frequency ?=2?f. Thanks to the thermal conduction mechanism, the heat is transmitted to the entire volume of the material which undergoes a slight rise in temperature. The temperature induced on the surface of the material sample 1, as shown in the appendix, is also oscillating but at an angular frequency ?? =2?f? different from that of the modulated beam? due to a Doppler effect on thermal waves recently discovered by the inventor of the present invention. The surface temperature rise ?Ts ? shown to have a temporal dynamic (note 1 in the appendix):

Where ? the following nomenclature was used:

t: time;

I: intensity? absorbed by the particle;

?: modulation angular frequency;

Q: diffusivity? thermal in the sample;

k: conductivity? thermal in the sample;

?= 2 D ? : thermal diffusion length;

eff =k D : effusiveness? sample thermal;

Zo: depth? to which ? initially positioned the particle;

V: speed? of the particle;

of the thermal wave

The temperature increase induced on the surface is detected by a fixed radiometric apparatus operating in remote sensing at a distance of about 20 cm from the surface S of the material sample 1.

The measuring apparatus can? alternatively be:

- a microbolometric IR camera, indicated with 8 in Fig. 1, operating in the LWIR range 8-14 micron complete with optics for focusing;

- an infrared system more? economic formed by a Germanium lens (not shown in Fig. 1), for the collection of the infrared radiation emitted by the surface, connected to a Peltier cooled HgCdZnTe IR sensor operating in the infrared range SWIR 3-5 micron.

The choice of the apparatus? also dictated by the infrared range suitable for the specific application, so as to receive infrared radiation 9 only from the surface S of sample 1.

The output of the infrared sensor or camera? connected to the input of a spectrum analyzer 10 which also receives the modulation signal of the excitation beam 3 on a line 11, as in the usual "lock-in" techniques. The analyzer 10 measures the difference between the modulation frequency ? and the new frequency detected by the infrared sensor ?? (reference 8), providing a signal proportional to the increase in surface temperature ?Ts reported in Eq. (1), decomposing the signal into module and phase. The analysis of the data is then managed by an ad hoc software program.

The output from the spectrum analyzer 10 is connected via a line 12 to a computer 13 which processes the data with dedicated software for calculating the kinematic parameters of an ensemble of moving particles 2. The operating principle is shown below schematically for a single moving particle 2. The signal detected by the sensor 8, proportional to the surface temperature increase ?Ts, ? broken down into module and phase by the spectrum analyzer 10 which also supplies the angular frequency shift according to the following formulas (note 1 in the appendix):

where A ? an amplitude factor that summarizes all the constants of the measuring instruments.

The speed estimate? of particle V is obtained after simple algebraic steps (reported in note 2 in the appendix) by inverting Eq. (2) which leads to the simple expression as a function of the frequency shift

A second expression for speed? V is also obtained alternatively from? exponential amplification that undergoes the module over time when the particle approaches, experimentally measurable by the time constant g (s<-1>) of the exponential gain of the module from which one can? obtain V as (see note 3 in the appendix)

The position of particle 2 starting from the depth? Zo is finally calculated from the phase measurement ? (see note 4 in the appendix) as follows

Examples of applications of the ?out of plane motion? configuration

As an example, some applications of this methodology are reported.

1) The first in the biomedical field concerns the study of skin hydration. One of the still open issues? that of the determination of the content and migration of water in the skin tissues. While in the dermis, what? vascularized, the water content ? homogeneous and similar to that of the body, about 70%, in the epidermis, where the water penetrates by diffusion from the underlying dermis, the water content varies from about 70% in the basal layer to about 20% in the stratum corneum (see figure 2). The speed? diffusion depends on the concentration gradient and pu? vary in a wide range from 10<-7 >m/s to 10<-5 >m/s also in virtue? the application of moisturizers.

In this case an Er:YAG is used as an excitation laser which emits radiation at the infrared wavelength of 2.94 ?m, in correspondence with the water absorption peak, with good penetration into the skin layer and negligible absorption effects on hemoglobin (see figure 2). There? it allows only the excitation of the water particles that diffuse towards the surface. Sensor 8 in the LWIR range (IR camera) instead allows the measurement of skin temperature only.

The diffusivity? temperature in the epidermis and stratum corneum is D=1x10<-7 >m<2>/s The thickness of the stratum corneum ? of about 20?m. The modulation frequency pu? be chosen in the interval [1Hz ? 100Hz] in order to have a thermal diffusion length ? [10?m ? 100?m] cos? to be able to study the phenomenon of migration up to the right depth.

In the example the following parameters are chosen: f=3Hz, ?=100?m, Zo=20?m, V=4?10<-6 >m/s. The graphs in Fig. 3a refer to a numerical simulation of the signal detected for a particle moving towards the surface (red curve) compared with that of the same particle traveling in the opposite direction (blue curve). Figure 3b) shows the simulations of the modules which, as expected, have an increasing exponential trend (exp(g?t) with g>0) for the approaching particle and decreasing in the opposite case (with g<0).

For the analysis of the signal yes ? proceeded to a data processing in ?blind? in which the data simulated in figure 3a) have been processed by a spectrum analyzer together with the reference data of the modulator, without any information on the speed? and particle position set in the simulation. In practice, the spectrum analyzer calculates the angular frequency ?? from the time interval ?to that elapses between two consecutive passages for the 0 of the IR signal, using the formula ??=?/?to. Compare the perceived angular frequency ?? with the original one of the modulation ?, calculating the frequency shift ??=??- ?.

? In the example in figure 3a) the perceived angular frequency for the red curve ? evaluated 14 times during an observation period of 5 seconds providing the average value ??=18.888 rad/s against the original angular frequency ?=18.850 rad/s, with a frequency shift ??=??- ?=0.039 rad/ s.

From the measurement of the shift ??, and assuming the known length of thermal diffusion in the skin <? = 2 D ? >=103?m, the speed? of the particle? was calculated using Eq. 3 during the 5 second observation period. Fig. 3c shows the estimates obtained with this procedure for the two speeds? ?4?10<-6>m/s (with positive sign for the red curve and negative for the blue one). The speeds? what? reconstructed from data processing in ?blind? are in excellent agreement with the speed? set at the beginning of the simulation, with a deviation of ?1% of a random, non-systematic nature, attributable to the resolution of the spectrum analyzer and therefore to the sampling time of the IR signal, therefore subject to improvements by increasing the precision of the instrumentation used.

The spectrum analyzer also measures a phase shift value ?= -0.98 rad, from which, by applying Eq. 5, the estimate on the initial position Zo=20?m (shown in Fig. 3d) is calculated in excellent agreement with the value set initially in the simulations.

The speed? of the particle is also calculated with a second method which exploits the formula in Eq. (4). In fact, from the amplitude of the IR signal simulated and shown in figure 3b), the time constant of the exponential law of value g=0.0039 s<-1> is first calculated, and subsequently, by applying Eq. (4) with D=1x10<-7 >m<2>/s, does one arrive at an estimate of the speed? of the particle 4?10<-6>m/s (red curve) very close to the effective value. Also in this case the same observations made previously regarding the measurement error linked to the precision of the instruments and in particular to the overall signal/noise ratio in the measurement chain are valid. It is also emphasized that in the case of an ensemble of particles in motion with different speeds, given the linearity of the system, the IR signal ? the result of the superimposition of the effects caused by the motion of each single particle. The overall signal processed by the spectrum analyzer therefore shows a frequency band corresponding to the distribution of the various speeds. From the deconvolution of the signal, for each frequency ?? is calculated the module M(??) which is proportional to the concentration of the particles traveling at the corresponding speed? V(??). Then from the spectrum of the module M(??) is also reconstructed the statistics of the speed? of the particle ensemble.

2) Another example still in the biomedical field? the nondestructive measurement of glucose migration into the interstitial fluid of the epidermis (Fig. 4).

In this case an EC-QCL laser that can be selectively absorbed by glucose should be used. In this case the frequency regime ? [0.05Hz ? 1Hz] in order to have a thermal diffusion length ? [100?m ? 1mm] what? to be able to study the phenomenon of migration in the dermis and epidermis with the same methodology described previously.

3) Other applications in the field of non-destructive testing concern the kinematics of micro-bubbles of air, oils and other aggregates in the production of mixed liquid products, and the determination of the concentration and kinematic parameters of impurities, of aggregated and/or thickened products in production processes of oils, wines, juices and fluid products in general.

A2) Configuration ?in plane motion? (Fig. 5), variant 2

Is this setup applied to measure particles 2? in motion along the (x, y) plane or surface of sample 1. Is it hypothesized that particles 2 are found inside a material 1? at a certain depth? Zo from surface S, moving with velocity? V directed along any direction in the xy plane. Without loss of generality? in the diagram in Fig. 5 the x axis? been chosen as the axis of motion: the convention on the sign of the speed? ? chosen so that V>0 for a particle that approaches the area where the temperature is measured, while V<0 is valid in the opposite case of moving away.

The excitation system and the experimental measurement apparatus are the same described in the ?out of plane motion? configuration, with the only differences in the focus of the instruments.

In particular in the ?in plane motion? (Fig. 5) is the pump beam 3 not focused but collimated so as to illuminate an area 7? of about 1cm<2 >being able so? follow particle dynamics 2? along the x axis. Furthermore, the 8a infrared detector is calibrated with a diaphragm in order to limit its sensitive area (0.5mm x 0.5mm). This allows to receive the signal only from a limited area on the surface of the sample (0.5mm x 0.5mm), thanks to a Germanium 8b lens which reproduces the image of the sensitive area of the detector 1:1. The single particle 2? absorbs the modulated beam 5 and becomes a moving source of thermal waves at the angular frequency ?=2?f. the heat is transmitted by conduction to the entire volume of the material 1 which undergoes a slight rise in temperature. The numerical simulations of the induced temperature are performed here by first calculating the response function of a point particle positioned at the point rS?(xS,yS,zS) and impulsively heated with the energy of 1J. The study of this function capable of satisfying the boundary conditions at the interface between material and air leads to the expression

This expression is then also used in the case of absorbed power with harmonic law P?exp(j?t). In this case the temperature rise ?T is obtained from the convolution integral of the impulsive response in Eq. (6) with the expression of the absorbed power with harmonic law as follows

Where ? the following nomenclature was used:

t: current time, ?: time at the moment the particle is heated;

P: power absorbed by the particle;

?: modulation angular frequency;

Q: diffusivity? sample thermal;

C: specific heat of the sample;

?: density? of the sample;

: relationship between the speed? of the V particle and that of the thermal wave

: thermal diffusion length;

where also the source point travels at the speed? V as indicated in the figure from which:

zS =Zo: depth? constant at which the particle travels;

xS=xo-V?: position of the particle at the time it is heated

yS=0; why? the motion occurs only on the x axis;

From a series of simulations carried out by varying all the parameters of Eq. (7) it is shown that, also in the ?motion in plane? configuration, a particle 2? illuminated with light 3 modulated at the angular frequency ?, traveling at a depth? Zo along x with speed? V, generates a thermal wave which is detected on the surface by an IR sensor 8a at an increased angular frequency ??> ? during the phase in which particle 2? approaches the detection zone, which then decreases ??< ? during the withdrawal phase with a certain analogy with the Doppler effect in acoustics. Fig. 6 shows two examples of temporal dynamics of the IR signal for speed? normalized ?=0.03, and ?=0.1 as a function of time normalized to the period t/T. Do the curves refer to different depths? normalized to the thermal diffusion length Zo/? from 0.25 to 1, and compared with the pump beam reference signal at angular frequency ?. In all the curves we find a maximum of the signal during the transit of the particle along the vertical line below the detector reception area (for t/T?3), an instant which divides the initial phase of approach with ??> ?, with that departure ending ??<?.

As further proof, Fig. 6 shows the percentage variation in frequency ??/? calculated from the IR signal during the motion of particle 2? for ?=0.03 at different depths?. This figure clarifies how ??/? changes from positive (approaching) to negative (moving away). The maximum frequency shift coincides with that described in Eq. (2)

where again the signs /- are for the approach and departure phase. By inverting Eq. (8) it is shown that the estimate of the speed? V of the particle from the data of ?? ? obtainable by analogous expression to Eq. (3) used for the first configuration

The depth estimate? Zo to which the particle travels? obtainable from the study of

frequency shift dynamics The proof is provided in Figure 7 where

are reported the theoretical results of the observable at each point of the xz plane for a particle in motion at the speed? normalized ?=0.03, to the depth? normalized Zo/?=1.5. The contour plot reveals that the frequency shift observed at a point on the surface ? tied also to? the corner ? of inclination between the particle, which is in the position (0, Zo), and the observation point on the surface, which is in the position (x, 0), according to the law

The validity? of Eq. (10) ? proven in figure 7 (below) where they are reported

the results of the simulations of (with Eq.7) as a function of x/? and for different values of Zo/?, together with the expected values using formula (10) (black curves). The curves

show the maximum variation for x=0 (when the particle passes under the detector and ?=0). From Eq. (10) the value of the derivative of the frequency shift over time is calculated

which reaches the maximum value at x=0

Eq. (12) is used to derive the depth? Zo which the particle travels

By applying Eq. (13) ? It is therefore possible to provide an estimate of Zo. Also in this case ? was a virtual experiment done in ?blind? doing numerical simulations to calculate the IR signal of a particle traveling with speed? V at depth Zo. The signal ? was then processed by a spectrum analyzer which measured the relative frequency shift ??/? as a function of time (Fig. 6) without any information on the speed? and particle position set in the simulation. By processing this data as required by Eq. (13) ? been reconstructed the depth? Particle zrec. At the conclusion of the virtual experiment in ?blind? the Zrec value? been compared with the real value of the depth? Zo set in the simulation. Fig. 8 shows the estimate of the depth? Zrec as a function of depth? real Zo. The graph? universal and normalized with respect to the thermal diffusion length ?.

The black bisector represents the ideal case of perfect depth reconstruction. Deviations from the ideal case are <5%. deviations more relevant when Zo>1.5? when what? particle 2? is too deep for the thermal diffusion length.

Examples of applications of the configuration ?in plane motion?

1) As an example, an application of this methodology in the biomedical field is reported on the cytometric study in capillaries or capillaroscopy. Such a system can allow the determination of position and speed? of red blood cells, platelets, platelet aggregates, aggregates with tumor cells and micro emboli in fine vessels and capillaries.

The wavelength of the excitation beam 3 is chosen so as to be able to penetrate the epidermis barrier and be selectively absorbed by red blood cells or microemboli. In this regard, the use of a laser operating at 4 possible different wavelengths (532, 671, 820, and 1064 nm) allows us to distinguish the contribution of the various species in motion on the basis of the different properties? absorbents from the various families of particles 2? By motorbike.

The sensor in the LWIR range instead allows the measurement of skin temperature only.

The diffusivity? thermal in the dermis is D=1x10<-7 >m<2>/s

The area under investigation? in the dermis and subcutaneous tissue 0.5 to 2 mm below the surface. The modulation frequency? can? be chosen in the interval [0.05 Hz ? 0.5 Hz] in order to have a thermal diffusion length ? [0.2mm ? 1mm] what? to be able to study the phenomenon up to the right depth.

The speed? V of the blood cells in the capillaries pi? thin pu? be very slow in the range [0.1 mm/s ? 1mm/s], for which the speed? normalized ? falls in the range [0.1 - 3]. In this range of values? You can use the formulas from Eq. (9) to Eq. (13) for the estimation of the positional and velocity parameters of the particles moving in the capillaries.

B) Second preferred embodiment of the invention

This second embodiment of the invention describes a technique for measuring the diffusivity? thermal of materials in remote sensing with infrared radiometric or thermographic techniques.

One of the main applications in the field of thermal engineering concerns the accurate measurement of the diffusivity? thermal solids. In recent years, many experimental setups have been proposed to measure the thermal parameters of different types of materials and shapes: bulk, thin films, etc. In all these experimental apparatuses the sample under examination is fixed on a sample holder and heated by frequency modulated or pulsed laser sources.

In the present invention an original methodology is proposed for measuring the diffusivity? heat of materials moving at speed? constant. This new approach envisages the use of a stationary measuring apparatus (or in relative motion with respect to the sample) which inspects a moving material/sample (relative with respect to the measuring apparatus) which flows for example on a production line. Does the measurement methodology therefore meet the requirements of industrial production, inspection and quality control processes? online, where local thermal parameters must be measured in real time, without interrupting the production chain.

Figure 10 shows a representative diagram of a measuring apparatus. Champion 1? ? subject to a translation at speed? constant V along the horizontal x axis as it occurs along a production line. Material 1? is heated by a ?fixed? pump laser beam 3, modulated at the angular frequency ?, focused on the sample 1? by a cylindrical lens 6 (Fig. 10b) so as to generate a plane thermal wave along the plane yz. Alternatively, in a second configuration (Fig. 10a) a lens 6 is chosen which is capable of focusing the beam on a Gaussian spot of small dimensions [10 - 50?m]. A ?fixed? infrared camera is used for inspection and non-destructive control in remote sensing? 8, ie integral with the excitation system, which uses the lock-in technique to detect the infrared signal emitted by the surface S of the sample in terms of amplitude and phase. In this case, the angular frequency detected ? does it coincide with that imposed by the modulation of the beam? because? the light/heat source 3 and the detector 8 are not in relative motion to each other.

? important to underline that the methodology described here ? original and differs from other recent methods where sample 1? in movement it is heated by a laser beam focused in continuous (c.w.), without any temporal modulation [21]. About this previous methodology? to specify that the application of the thermographic technique with continuous heating on the one hand has the advantage of a simplification of the experimental setup which does without the modulator 4 and the demodulation lock-in system 15, but on the other it presents a series of disadvantages compared to the modulated techniques: a) excessive sensitivity? to noise for example due to thermal sources external to the system; b) the difficulty? in filtering unwanted signals due to beams reflected or scattered by the sample which mistakenly enter the sensitive area of the IR camera; c) the need? to use high powers to improve the signal-to-noise ratio, which heat the material by several tens of degrees with the risk of degradation in biological materials, as well as non-linear thermal effects due to the excessive variability? of thermal parameters with temperature.

These disadvantages are instead overcome by using the technique with time modulation described in the present patent application.

From a series of simulations carried out on the basis of Eqs. (6) and (7) as all the parameters vary, it is shown that the infrared images of the surface (xy plane) show distortions and asymmetries due to the motion of sample 1?, as shown by the numerical simulations shown in Figure 11 relating to the configuration in Figure 10a.

The contour plots in figures 11 show the logarithm of the signal amplitude (figures 11 a, c, e) and the phase shift with respect to the harmonic signal of the modulator (figures 11 b, d, f). Contour lines are shown as a function of position on the sample surface, with both abscissas x/? and order y/? normalized to the length of thermal diffusion to give greater universality? to the graphs. The figures refer to three values of the speed? normalized

=0, 0.5, 1 (note that the figures are perfectly symmetric for ?=0

when the sample ? stopped).

However in figures 11 (b, d, f) it is also seen that the phase of the signal retains its radial symmetry in the xy plane regardless of the value of the speed? ?. The phase of the signal can you? express how

Where ? the distance from the center of the pump beam, while

as it is known. Eq. (14) shows a trend

of the phase which decreases linearly with the distance r. From?linear trend you can? calculate the absolute value of the sph slope

(15)

That ? related to the thermal diffusion length ? and consequently to the diffusivity? thermal. After a few algebraic passages summarized in note 5 in the appendix ? is it possible to reach the expression of the estimate of the diffusivity? thermal according to the formula

? it is also easy to verify that in the particular case of a stationary sample (V=0) Eq.

(16) converges towards the known expression used for the

determination of the diffusivity? of materials with traditional static measurements with stationary sample. In this sense Eq. (16) reflects a new approach and represents a new original formula that allows to extend the measures of diffusivity? samples in motion, which for example translate at speed? subsidiary V along a production line.

Eq. (16) can? For? be used only when ? note the speed? Translation V of sample 1?. If, on the other hand, both the diffusivity? thermal D that the speed? V ? instead it is indicated to use the second configuration in Fig. 10b which uses a cylindrical optical lens 6 to focus the beam on a strip along the y axis. This configuration? particularly robust for the simplicity? of the collection of the infrared signal which is measured and analyzed only along the x axis, with evident savings in the measurement times of the infrared sensor 8.

In this case ? a simple analytical expression was found for the complex signal (module and phase) to the left (x<0) and to the right (x>0) of the strip illuminating the sample at x=0. IR signal? proportional to the temperature increase ?Ts which is valid in this case

(17)

where A=?Ts(0) ? the temperature value at x=0, irrelevant for the purposes of data analysis. The results of the numerical simulations are shown in Fig. 12 where both the logarithm of the amplitude (Fig. 12a) and the phase (Fig. 12b) are reported as a function of the normalized horizontal offset (x/?) for different speeds? sample entrainment. Both the phase and the logarithmic amplitude behave linearly with the offset. Looking at Eq. (17) there are 3 relevant slopes:

the two slopes sA+ and sA-, calculated from the linear behavior of the logarithm of amplitude for x> 0 and x<0 (the amplitude is not symmetrical with x), and the slope sPh calculated from the phase (the phase is symmetrical with x) .

From Eq. (17) the expression of the three slopes is obtained:

(18)

where for greater simplicity? we repeat the definition of the symbols involved in (18)

After simple algebraic passages we obtain that ?/?=(sA--sA+)/2=?sA/2 and also a/?=(sA-+sA+)/2. Combining the equations and using the property? a?b=1 you can? make explicit the expression of the thermal diffusion length ? and the speed? normalized ? as a function of the three experimentally measurable slopes

(19)

from Eq. (19) are finally obtained the quantities? unknowns: the diffusivity? thermal D and the speed? of translation of the sample V

(20)

It is worth noting that Eq. (20) ? fundamental for an accurate measurement of the diffusivity? local thermal in case of quality control? in line of industrial products moving on a conveyor belt, and inspected by lock-in thermography according to the scheme in Fig. 10b, but can? also detect the speed? V of translation that could have variations due to unforeseen events or a simple change of modality? of translation. A unit of control 14 connected to the modulator 4 through a line 15 (in the present case a spectrum analyzer is obviously not needed), would it allow to control the speed? V for deviations from a nominal value (cf. Figs. 10a and b).

For speed? of translation very high ?>>1, the slope sA- becomes very high and not easily measurable. In the absence of the data sA- the Eq. (20) not ? applicable, but in note 6 in the appendix ? shown as there is another alternative method to measure the diffusivity? thermal from only the measurements to the right of sph and sA+ according to the approximate expression

<(21)>

That ? applicable when ? note the speed? of translation V.

Examples of applications of the second embodiment of the invention

As an example, an application scheme in the automotive sector is shown. One of the topics in strong development? that of non-destructive tests on the railway network using equipped locomotives. Ultrasonic techniques are usually used for the control of the railway line which, however, are unable to precisely investigate the properties thermomechanical in some areas at the end of the track. A thermographic Doppler system instead pu? measure in a non-destructive way the diffusivity? surface along the track during the motion of a suitably equipped locomotive. From the measurement of the diffusivity? thermal can you? finally calculate the surface hardness along the track and check any points at risk of the line (this is possible after calibrating the material of the railway line and note the correlation table between the hardness values and those of thermal diffusivity). This thermographic analysis also makes it possible to verify the homogeneity? of the surface of the railway line and the presence of superficial and sub-superficial cracks.

Fig. 13 shows the system discussed in Fig. 10b mounted on board a locomotive 17. The system provides a laser 20 to heat the track 18 and the use of more? infrared sensors 19 to follow the temperature induced when the locomotive 17 moves at speed? high V [5 ? 20 km/h].

For this application, the diffusivity? thermal D of track 18 ? usually in the range [5?10<-6 >? 2?10<-5 >m<2>/s]. The range of useful frequencies? [1?100 Hz] in order to have a speed? normalized ? in the range [5?50] that can? greatly lengthen the length of thermal diffusion perceived by the ?ph sensors up to 50 times allowing a good measurement of the phase.

By way of example, with reference to Fig. 13, the results of a numerical simulation made with a laser diode of 10 W power, operating at 808 nm, voltage modulated at a frequency of 5 Hz on board a locomotive traveling at speed 5 are reported. of 5 km/h inspecting a railway line of diffusivity? unknown thermal (in the simulations we set D=1?10<-5 >m<2>/s)

To study a concrete and feasible case? It is necessary to distance the two IR sensors in Fig. 13 by 1.5 meters such that x2-x1=1.5 m (this can be done in the locomotive carriage).

Once these parameters are set, the two IR sensors measure:

a) a mutual phase difference ??=?1??2=33.93 rad

b) and a ratio between their modules M2/M1=0.9945

From these experimental data the phase slope sph=22.62 rad/m and the slope of the right amplitude logarithm sA+=0.00368 m<-1> are calculated

both to the right of the pump laser. The data to the left in Fig. 13 , i.e. to the left of the laser 20 , are in this case not measurable.

Under these conditions, assuming note V=5km/h and applying Eq. (16) is there an excellent estimate of the diffusivity? thermal D=1?10<-5 >m<2>/s with a calculation error of 0.07%, due to rounding, while applying Eq. (21) we arrive at the same estimate but with a systematic error of about 0.13% due to the approximation of the formula.

A last application of the present invention could relate to the assembly of a material sample analysis system, in accordance with the present invention, on a drone.

Appendices

Note 1: Diffusion equation for a moving source

The heat diffusion equation when a stationary source illuminates an absorbing material moving at speed? V ? given by the diffusion equation

where T ? the induced temperature increase,

D the diffusivity? thermal of the material,

k the conductivity? thermal of the material,

w is the heat induced in the material per unit? of time and per unit? in volume,

? the nabla operator known from basic physics courses.

In the case of a plane thermal source along the xy plane, as indicated in the experimental configurations in Fig. 1 and Fig.5, the temperature becomes a function of the spatial variable z only and the diffusion equation becomes

And finally in the case of modulation of the source at the angular frequency ? all quantities oscillate at the same angular frequency, and the equation in regime

harmonic becomes where yes ? hypothesized a

intensity absorption? luminous I by a layer of particles at the depth? Zo.

The equation of diffusion in harmonic regime described above ? a homogeneous second-order differential equation which has a general solution given by the superposition of two possible functions

where F and G are arbitrary constants to be determined with the boundary conditions, while the two factors present in the exponentials must satisfy the equation

Introducing the thermal diffusion length

become Finally introducing the speed? normalized we can rewrite the two

factors in the final form

where for simplicity? Yes ? placed in terms of the complex number

with

Assuming that the heat source is flat at the depth? ZS=Zo,-Vt the solution for the temperature in half-space z>0 is specified in the various zones: T1 in zone 0<z<ZS and T2 for z>ZS

The coefficients F, G, H are determined by imposing the following boundary conditions:

1) continuity? of the temperature at the interface z=ZS from which we obtain T1=T2 or F+G=H

2) thermal flux injected by the light source I divided into the two thermal fluxes (for z=ZS it must be I= k?dT1/dz - k?dT2/dz)

3) zero thermal flux to the surface z=0 with the air that ? insulator (condition k?dT1/dz=0)

By imposing the three conditions described above ? Is it possible to obtain the coefficients F, G, H in algebraic form and finally calculate the expression of the increase in temperature observable for z=0 on the surface which ? given by the expression

Where ? defined as effusivity? temperature of the sample.

because moreover, the particle, initially positioned at the depth? Zo, does it move towards the surface of uniform rectilinear motion with law ci? involves in the expression of the surface temperature a series of simplifying algebraic passages on the term

that they bring

to the final expression of the surface temperature increase

Note 2

Starting from the equation on the frequency variation

squaring both sides

thus isolating the radical

squaring and simplifying

isolating the term of speed? from which by extracting the quartic root from which

Note 3

Starting from the exponential time law of the magnitude of the signal in Eq. (2) exp (g?t )= exp[ (a+? ) ??t ] we obtain the time constant g in the exponential term

from which

is the speed explicit? of the particle:

Note 4

Starting from the expression of the phase of the signal in Eq. (2)

deep initial of

Then replacing V with

the final expression of note 2 is obtained

which after algebraic steps leads to

Note 5

By squaring Eq. (15) By isolating the radical we obtain

Quadranging

By simplifying the term and substituting we finally get

from which it is derived

Note 6

Starting from Eqs. (18), when ? Only slopes to the right of the can be measured

pump laser only the two data are accessible Multiplying i

data of the two slopes is obtained

On the other hand, when ?>>1 the factor b??, stopping the second order Taylor expansion tends to

By introducing this approximate result in the previous relation we arrive at

from which

explaining the diffusivity? heat, we arrive at the final formula

List of reference symbols

1 sample, with moving (inner) particles

1? sample

2 particle in vertical motion

2? particle in horizontal motion

3 light source (laser)

4 modulator of 3

5 modulated light beam

6 transmission optics

7 light incidence area

8 camera

8th sensor, detector

8b receiving optics, germanium lens

9 light re-emitted

10 spectrum analyzer

11 ?lock in? connecting lines

12 connecting line

13 computers, laptops

14 units? control

15 ?lock in? connecting line

16 connection line (for regulating the speed of the sample) 17 locomotive

18 track, rail

19 camera (on locomotive)

20 lasers (on locomotive)

S sample surface

Claims (26)

Claims 1. Test technique of a material sample using infrared radiometry or thermography, characterized by the fact that it includes the following phases: a) make available a sample to be examined, which (a1) substantially forms a material whose particles are all at rest with respect to each other, at the level of macroscopic physics, or (a2) forms a material in which some particles are in motion with respect to the remaining and main part of the sample, at the level of macroscopic physics; b) making available a light source (3), preferably infrared, such as a pump laser beam (3), and a modulator (4) for temporally modulating at an angular frequency ? the light transmitted by said light source (3), c) provide a transmission optics (6) to collimate and/or focus and/or shape the transmitted light beam, and to project it onto an area of incidence (7) of the light on the surface (S) of the sample d) providing at least one detection system (8; 8a, 8b), formed by at least one receiving optics (8b) with detector (8a) or by at least one IR video camera (8), this detection system ( 8; 8a, 8b) receiving the re-emitted infrared light from said light incidence area (7) and from a surrounding heat diffusion area, and carrying the corresponding IR detection signal to a unit? control and data analysis system (10, 13,14), which is connected to said detection system (8; 8a, 8b); e) connecting (11; 15), said modulator (4) to said unit? control and data analysis (10, 13, 14), f) where, in case a1) the sample ? moving at a speed? V with respect to the detection system (8; 8a, 8b) and the light source (3), and in case a2) said moving particles, inside the sample, move with respect to the detection system (8; 8a, 8b) and to the light source (3), and by further comprising the following steps g) analyze the IR signal data collected through the unit? control and analysis, based on the spatio-temporal distribution of the temperature increase ?Ts in said area of incidence (7) of the light and in a surrounding area of heat diffusion, both located on the surface (S) of the sample, and in particular analyze the phase and the form of the IR signal, h) determine in case a1) the diffusivity? thermal D of the sample and/or the speed? V of the sample itself, or, in the case a2) to obtain a statistic of the parameters of position and speed? using frequency shift ?? due to the Doppler effect on the thermal waves produced by the single moving particles (2; 2?) heated by the light source. 2. Technique for testing a sample of material by using infrared radiometry or thermography, according to claim 1, characterized in that in case a2), said unit? of control and data analysis comprises a spectrum analyzer (10) connected to the modulator (4), and a computer (13). 3. Technique for testing a sample of material by using infrared radiometry or thermography, according to claim 1, characterized in that in case a1) said unit? of control and analysis includes a?unit? controller (14) and a computer (13), where the modulator (4) ? connected to the unit? controller (14) which uses a lock-in demodulator. 4. Technique for testing a material sample by using infrared radiometry or thermography, according to claim 3, characterized in that the unit? controller (14) is electrically or wirelessly connected to actuators or sample driving means (1?), to provide a feedback signal to said actuators or sample driving means, so as to adapt in real time the speed? V of the sample if this deviates from a substantially constant nominal value. 5. Test technique of a material sample by using infrared radiometry or thermography, according to claim 1, wherein the modulation performed by the modulator (4) can be obtained for example with a chopper of the light source, with a laser diode controlled by a square wave, or with an electro-optical system. 6. Test technique according to claim 1, characterized by the fact of choosing the modulation frequency ? of the modulator (4) in order to have a thermal diffusion length ? that overlaps at least in part with the values of the range of depth? of the positions of the moving particles with respect to the surface S of the sample. 7. Test technique according to claim 1, 2, 5 or 6, characterized in that the moving particles (2) move substantially in a vertical direction or perpendicular to the surface S of the sample, or the moving particles (2?) they move in a substantially horizontal direction, i.e. parallel to the surface S of the sample. 8. Test technique according to claim 7, characterized in that if the moving particles (2) move in a substantially vertical direction, then the transmitted light beam is collimated on a restricted area, for example of 1 mm<2 >, while if the particles (2?) move in a substantially horizontal direction, then the transmitted light beam of the light source is not focused but collimated so as to illuminate a wider area? extended, for example 1 cm<2>, to follow the motion of the particles moving along the direction defined by their speed. 9. Test technique according to claim 8, characterized in that the unit? control and analysis (10, 13) processes the IR signal data supplied by the IR sensor for substantially vertically moving particles (2) and uses the following formulas to calculate the speed? vertical and their position: being ?? the frequency shift, g the exponential gain of the IR signal, ? the phase of the latter, obtained from the spectrum analyzer (10). 10. Test technique according to claim 7 or 8, characterized in that the unit? of control and analysis (10,13) elaborates the data of signal IR supplied from the IR sensor for the particles in movement substantially horizontal (2?) and uses the following formulas for the calculation of the speed? horizontal and their position: 11. Test technique according to claim 1, characterized in that in the case of a Gaussian spot formed by the transmitted light source, and supposing the variable V is known, the unit? of control and analysis (13, 14) calculates the diffusivity? temperature D according to the following formula being sph obtainable from the unit? of control and analysis as the absolute value of the phase gradient of the IR signal with respect to the beam r equal to the distance from the center of the spot of the light source beam to the surface S of the sample. 12. Test technique according to claim 1, characterized in that by means of said transmission optics (6) the light beam transmitted on the surface S of the sample is focused along a strip perpendicular to the direction of motion V of the sample, and by using the? unit? of control and analysis (13, 14) to calculate the diffusivity? thermal D of the sample and the speed? V of the sample, which in this case is considered not known, using the following formulas: being the slopes sA+, sA- and sph quantity? obtainable from? unit? control and analysis by the IR signal measured downstream and respectively upstream of said strip, by the logarithmic amplitude and by the phase of said IR signal. 13. Test technique according to claim 1, characterized in that by means of said transmission optics (6) the light beam transmitted on the surface S of the sample is focused along a strip perpendicular to the direction of motion V of the sample, and by using the? unit? of control and analysis (13, 14) to calculate the diffusivity? temperature D of the sample using the following approximate formula, valid for large values of ?: being the slopes sA+ and sph quantity? obtainable from? unit? of control and analysis from the IR signal measured downstream of said strip, from the logarithmic amplitude and from the phase of said IR signal. 14. Test technique according to any one of the preceding claims, characterized in that the transmitting light source, for example a laser, is? tunable on, or has, N different wavelengths, ?1, ?2?. ?n, corresponding to the absorption wavelengths for N different species or families of particles in motion. The test technique according to any preceding claim, wherein the wavelength(s) of the laser are selected such that the sample material is at least partially transparent to the light beam of the transmitting light source so that the latter can penetrate it with weak attenuation, to finally be strongly and selectively absorbed by the moving particles. 16. Test technique according to any one of the preceding claims, characterized in that said detection system ? adapted to a specific application, i.e. to receive infrared radiation only from the surface S of the sample, blocking other disturbing light. 17. Test technique according to any one of the preceding claims, wherein in case a2) the sample to be examined can be a portion more? external S of the human body, and the moving particles can be, for example, glucose, water particles, corpuscles present in a blood vessel or a capillary, or the like, and in case a1) the sample can? be a railway line to be examined for possible defects or a series of products moving on a production line, for example on a conveyor belt, to carry out a quality control, or similar samples of an industrial production process. 18. Test system of a material sample using infrared radiometry or thermography, characterized in that it includes: a) a sample to be examined, which (a1) substantially forms a material whose particles are all at rest with respect to each other, at the level of macroscopic physics, or (a2) forms a material in which some particles are in motion with respect to to the remaining and main part of the sample, at the level of macroscopic physics; b) a light source (3), preferably infrared, such as a pump laser beam (3), and a modulator (4) for temporally modulating at an angular frequency ? the light transmitted by said light source, c) a transmission optics (6) for collimating and/or focusing and/or shaping the transmitted light beam, and for projecting it onto an area of incidence of the light on the surface (S ) of the sample, d) at least one detection system (8; 8a, 8b), formed by at least one receiving optics (8b) with sensor or detector (8a) or by at least one IR camera (8), this detection system (8; 8a, 8b) receiving the re-emitted infrared light from said light incidence area and a surrounding heat diffusion area, and carrying the corresponding IR detection signal to a unit? control and data analysis (10, 13, 14), which ? connected to said detection system (8; 8a, 8b); e) wherein said modulator (4) ? connected to this unit? control and data analysis (10, 13, 14), f) where, in case a1) the sample ? moving at a speed? V with respect to the detection system (8; 8a, 8b) and the light source (3), and in case a2) said moving particles, inside the sample, move with respect to the detection system (8; 8a, 8b) and to the light source (3), and by the fact that g) the unit? control and analysis analyzes the collected IR signal data, on the basis of the spatio-temporal distribution of the temperature increase ?Ts in said light incidence area (7) and in a surrounding heat diffusion area, both located on the surface (S) of the sample, and analyzes them regarding phase and IR signal modulus, h) the unit? of control and analysis determines in the case a1) the diffusivity? thermal D of the sample and/or the speed? V of the sample itself, or, in the case a2) obtains a statistic of the parameters of position and speed? using frequency shift ?? due to the Doppler effect on the thermal waves produced by the single moving particles (2; 2?) heated by the light source. 19. System for testing a sample of material by using infrared radiometry or thermography, according to claim 17, characterized in that in case a2), said unit? of control and data analysis (10, 13, 14) comprises a spectrum analyzer (10) connected to the modulator (4), and a computer (13). 20. System for testing a sample of material by using infrared radiometry or thermography, according to claim 18, characterized in that in case a1) said unit? of control and analysis (13, 14) comprises a unit? controller (14) and a computer (13), where the modulator (4) ? connected to the unit? controller (14) which uses a lock-in demodulator. 21. System for testing a sample of material by using infrared radiometry or thermography, according to claim 20, characterized in that the unit? control (14) ? connected electrically or wirelessly to actuators or sample driving means, to provide a feedback signal to such actuators or sample driving means, so as to adapt in real time the speed? V of the sample if this deviates from a substantially constant nominal value. 22. System for testing a sample of material by using infrared radiometry or thermography, according to claim 18, characterized in that the modulation performed by the modulator (4) is? obtained for example with a chopper of the light source, with a laser diode controlled by a square wave, or with an electro-optical system. 23. Test system according to claim 18, characterized in that the modulation frequency ? of the modulator (4) ? chosen in order to have a thermal diffusion length ? that overlaps at least in part with the values of the range of depth? of the positions of the moving particles with respect to the surface S of the sample. 24. Test system according to claim 18, 19, 22 or 23, characterized in that the moving particles (2) move substantially in a vertical direction i.e. perpendicular to the surface S of the sample, or the moving particles (2?) they move in a substantially horizontal direction, i.e. parallel to the surface S of the sample. 25. Test system according to claim 24, characterized in that if the moving particles move in a substantially vertical direction, then the transmitted light beam ? collimated on a narrow area, for example of 1 mm<2>, while if the particles move in a substantially horizontal direction, then the transmitted light beam of the light source is not? focused but collimated in order to illuminate a? area pi? extended, for example 1 cm<2>, to follow the motion of the particles moving along the direction defined by their speed. 26. Using a test system according to the preceding claims on or for a drone, for analyzing samples while the drone is moving.