WO2012085401A1

WO2012085401A1 - Device for measuring a degree of misalignment, and method for using said device

Info

Publication number: WO2012085401A1
Application number: PCT/FR2011/053013
Authority: WO
Inventors: Pascale Launois; Denis Petermann; Michaël HUARD; Julien CAMBEDOUZOU; Gilles GUILLIER; Philippe Joly
Original assignee: Centre National De La Recherche Scientifique
Priority date: 2010-12-22
Filing date: 2011-12-15
Publication date: 2012-06-28
Also published as: FR2969749A1

Abstract

The present invention relates to a device (100) for measuring a degree of misalignment of objects that are contained in a diaphragm (2) and aligned mainly in a predetermined direction or in a predetermined plane, the measuring device (100) including: a means (11) for emitting an X-ray beam (6) propagating along a propagation axis (350); a means (7) for detecting the X-ray beam so as to measure a scattered beam (8) after the former has passed through the diaphragm (2); and a holder for receiving the diaphragm (2), located between the emission means (1) and the detection means (7). The holder is arranged so as to receive the diaphragm (2) such that the propagation axis (350) is not contained within a diaphragm plane. The diaphragm plane forms a nonzero angle α with the propagation axis (350). The invention also relates to a method for using the device (100) according to the invention and to a computer program product arranged to execute the steps of the method according to the invention.

Description

'Device for measuring a degree of misalignment and method

of use of said device

Technical area

The present invention relates to a device for measuring a degree of misalignment of objects contained in a membrane (for example a polymer membrane) and aligned mainly in a predetermined direction or in a predetermined plane.

It also relates to a method of using said measuring device.

The field of the invention is more particularly but in a nonlimiting manner that of measurements of degree of misalignment of objects contained in a large membrane, in particular membranes having one or two lateral dimensions greater than 2 mm.

State of the art

Various embodiments of a device for measuring a degree of misalignment of objects contained in a membrane and aligned mainly in a predetermined direction or in a predetermined plane are known.

A preferred embodiment according to the prior art comprises:

means for transmitting an X-ray beam propagating along an axis of propagation,

means for receiving a membrane plane in which the plane membrane is contained, so that the axis of propagation is contained in the membrane plane and

detection means, for measuring a scattered beam corresponding to the diffusion, under the influence of the objects contained in the membrane, of the X-ray beam incident on the membrane. We can then, from the diffusion figure, find the degree of misalignment of the objects contained in the membrane.

This embodiment does not, however, make it possible to measure a degree of misalignment of objects contained in a membrane, when the membrane dimensions exceed a certain limit, for example a length of 1cm, 4mm, or even 1mm.

Several difficulties make the measurement impossible:

the membrane length traversed by the X-ray beam is such that the absorption of X-rays by the membrane becomes problematic: the light intensity at the level of the detection means may become too low compared to the sensitivity of the detection means, or only a portion of the membrane is actually measured, that which receives X-rays first;

the analysis of the diffusion figure does not make it possible to easily find the degree of misalignment of the objects contained in the membrane, different scattering patterns corresponding to different locations along the membrane being mixed at the level of the detection means,

the membrane may be too large and involve too much backward movement of the detector, thus preventing the beams being measured at sufficiently large angles (the width of the detector being fixed),

the scattered beam may be too wide in the radial direction on the detector

These difficulties can be overcome by cutting a large membrane into thin slices, then analyzing each slice. The disadvantage is of course that the studied membrane is destroyed.

The object of the present invention is to provide a device for non-destructive measurement of a degree of misalignment of objects contained in a membrane and aligned mainly in a predetermined direction or in a predetermined plane, which does not have the limitations of the prior art.

In particular, an object of the present invention is to propose a device for measuring a degree of misalignment of objects contained in a membrane, making it possible to obtain good results even for large membranes (for example having a superior lateral dimension at 1mm, 1cm, 50cm, or even lm) without having to destroy these membranes. Another object of the present invention is to propose a method of using the measuring device according to the invention, as well as a computer program product arranged to execute the steps of the method according to the invention when it is executed in a computer.

Presentation of the invention

This object is achieved with a device for measuring a degree of misalignment of objects contained in a membrane and aligned mainly in a predetermined direction or in a predetermined plane, the measuring device comprising:

means for transmitting an X-ray beam propagating along an axis of propagation,

means for detecting the X-ray beam for measuring a scattered beam after passing through the membrane,

a support for receiving the membrane, located between the transmission means and the detection means.

The support is arranged to receive the membrane so that the axis of propagation is not contained in a membrane plane, the membrane plane forming an angle not zero with the axis of propagation.

The invention therefore relates in particular to a use of said measuring device according to the invention. It is to use said measuring device to measure a degree of misalignment of objects contained in a membrane, each of said objects being aligned, with a misalignment, with a predetermined common direction or with a common predetermined plane.

The angle α, between 0 and 90 °, can be defined as the complement of the angle between the axis of propagation and the normal to the membrane at the intersection between the membrane and the axis of propagation. The normal to the membrane is advantageously normal to the membrane plane.

The membrane is preferably plane: in this case the membrane plane corresponds to the plane in which the membrane is entirely located (the plane of the membrane).

The membrane may not be flat: in this case the plane of the membrane corresponds to the plane tangential to the membrane, at the level of the intersection between the X-ray beam emitted by the emission means, and the membrane.

Objects are said to be aligned mainly in a predetermined direction or in a predetermined plane.

They may for example be aligned mainly in the predetermined direction which is perpendicular to the surface of the membrane: they are perpendicular to the surface of the membrane at an angle Θ, where Θ is an angle expressed for example in degrees.

They may for example be aligned mainly along a predetermined plane which is the plane parallel to the surface of the membrane: they are parallel to the surface of the membrane at an angle Θ, where Θ is an angle expressed for example in degrees.

In general, the objects are therefore aligned at a certain angle in a given frame, at an angle Θ, where Θ is an angle expressed for example in degrees.

The degree of misalignment κ of the objects contained in the membrane is given by the width of a function of distribution of the orientations Θ taken on all the objects (of the portion of membrane traversed by the X-ray beam). κ is between 0 ° and 90 °, preferably between 0 ° and 30 ° for example.

The objects in a membrane may be formed by aligned leaflets substantially parallel to the surface of the membrane, by elongate recesses aligned substantially perpendicular to the surface of the membrane, by tubes aligned substantially perpendicular to the surface of the membrane, etc.

When the objects are cylinders of small diameter relative to their length (for example a ratio 1000), one can speak of one-dimensional objects.

The X-ray beam advantageously designates a beam of light rays whose wavelength is between 5 μm and 10 nm.

The detection means are advantageously placed transversely with respect to the reference plane.

The X-ray beam incident on the membrane can be divided into three components after passing through at least a portion of the membrane: a transmitted beam: it is the portion of the incident beam that is not deviated from its rectilinear trajectory after passing through at least a portion of the membrane, in particular the portion of the membrane lying in the path of the X-ray beam emitted by the transmitting means;

a scattered beam: it is a portion of the incident beam which is deviated from its rectilinear trajectory after passing through at least a portion of the membrane. X-ray scattering is a phenomenon well known to those skilled in the art. If the objects are full, the scattering centers are for example atoms of the objects contained in the membrane, atoms arranged periodically or not in space.

If the objects are recessed, the scattering centers can be formed by these empty zones of atoms, arranged periodically or not in space.

The scattered waves from each diffuser center can interfere with each other. We can then speak of diffraction, which is a special case of diffusion;

an absorbed beam: it is the portion of the incident beam that is absorbed by the medium traversed between the transmission means and the detection means. In some cases, part of the absorbed beam is restored as a fluorescence signal. The study of the fluorescence signal can give information on the particular chemical composition of the medium passed through.

The support is located between the transmission means and the detection means: the study is done in transmission.

The studied membrane may have a surface greater than for example 2cm by 2cm, 4cm by 10cm, 15cm by 15cm, 20cm by 30cm, lm by 2m, etc.

Thus, a device for measuring a degree of misalignment of objects contained in a membrane is used to implement a measurement based on the analysis of a diffusion figure. The measurement is nondestructive, regardless of the dimensions of the membrane. This scattering pattern can be measured directly with a two-dimensional detector or reconstructed by moving a point or linear detector.

Only a portion of the membrane, which is the intersection between the X-ray beam and the membrane, is studied.

The membrane length traversed by the X-ray beam is limited to this portion of membrane: the dimensions of the entire membrane are therefore no longer problematic, particularly with regard to the light intensity of the scattered X-ray beam arriving at the level of the membrane. detection means.

Only this portion of membrane is traversed by the X-ray beam: the scattered beam measured by the detection means corresponds to this single portion. An analysis of said scattered beam is therefore particularly fast and easy to implement even for large diaphragms.

Only a membrane portion is located between the transmitting means and the detection means: it is therefore not necessary to move the detector backwards, and the scattered beam is not widened in the radial direction of the detector.

The present invention thus solves all the technical problems of the prior art.

Preferably, the measuring device according to the invention is such that the plane of the membrane can be defined by two axes, at least one of which is perpendicular to the axis of propagation.

The orientation in the space of the membrane plane with respect to the axis of propagation is generally defined by two angles. If one of these angles is fixed at 90 °, said orientation can then be defined entirely by the angle a.

Advantageously, only one of the axes defining the membrane plane is perpendicular to the axis of propagation.

The angle α can be between 20 ° and 80 ° or between 10 ° and 80 °. More particularly, the angle α may be between 50 ° and 70 °.

Advantageously, the measuring device according to the invention comprises means for measuring the intensity of a beam transmitted by the membrane. We can thus estimate a density of objects in the membrane. The membrane may be flat and contained in the membrane plane. The means for measuring the intensity of the beam transmitted by the membrane may comprise a photodiode placed on the optical path of the beam transmitted by the membrane (that is to say behind the portion of the membrane situated on the optical path of the beam of X-rays emitted by the transmitting means, and in front of the detection means). It is thus possible both to measure the intensity of the beam transmitted by the membrane, and to stop the beam transmitted by the membrane before it reaches the detection means. Indeed, the beam transmitted by the membrane may have a much higher intensity than the scattered beam, and thus blind the detection means (that is to say that the intensity of the beam transmitted may be such that in comparison the intensity of the scattered beam is too small to be accurately detected or the detection means are deteriorated).

The measuring device may comprise means for measuring a fluorescence signal emitted by the membrane in response to the beam emitted by the transmitting means. The beam emitted by the emitting means is partially absorbed by the medium through, in particular the portion of membrane lying in the path of said beam. This membrane portion may emit back a fluorescence signal characteristic of at least one chemical compound present in the membrane. It is thus possible to perform a chemical analysis of the composition of the membrane. The signal may be representative of the concentration of a given component, for example iron.

Preferably, the means for measuring a fluorescence signal are arranged to work in reflection, that is to say on the side of the emission means with respect to the membrane portion traversed by the incident beam.

The support according to the invention may comprise means for moving the membrane.

Advantageously, the support according to the invention may comprise means for moving the membrane in at least one translation in the membrane plane. Thus, the orientation of the membrane plane relative to the axis of propagation remains constant. For example, the angle a remains constant. The membrane can thus be studied in a whole series of points. The membrane is preferably fixed during a measurement and then moved for the next measurement.

It is not necessary, for each point, to record the value of the orientation of the membrane plane with respect to the axis of propagation (for example the value of the angle a), as a parameter for calculating a degree of misalignment of objects contained in a membrane, since this orientation remains constant for all measurements. The treatment time is therefore decreased.

The invention also relates to a method for using the measuring device according to the invention.

The method according to the invention comprises the following steps:

a signal of intensity corresponding to a diffusion pattern formed by the scattered beam is measured;

for the orientation of the chosen membrane such that the axis of propagation is not contained in the membrane plane (in particular for the value of the non-zero angle α chosen), the degree of misalignment of the objects contained in the membrane by connecting a measurement on the diffusion figure with the degree of misalignment of the objects contained in the membrane.

Whereas in the prior art the axis of propagation was contained in the membrane plane (and the angle α chosen was zero), the method according to the invention takes into account an additional parameter since the orientation of the membrane plane relative to the axis of propagation, in particular the value of the non-zero angle a chosen, can take an infinity of values.

The measurement of a degree of misalignment obtained relates to the portion of membrane traversed by the X-ray beam.

The diffusion pattern may designate the different intensities recorded by the measuring means and corresponding to the scattered beam. It may be in particular a diffraction pattern.

To connect a measurement on the diffusion pattern with a degree of misalignment of the objects contained in the membrane, a calculation can be made taking into account in particular the value of a determined non-zero. This calculation is based on the theory of diffusion and diffraction. It is also possible to make a database of couples {measure in the diffusion figure; degree of misalignment of the objects contained in the membrane}. The degrees of misalignment can then be experimental values and / or obtained by theoretical calculations. The values of this database are then used to quickly connect a measurement on the scatter pattern with a degree of misalignment of the objects contained in the membrane. The values in this database can be discrete values. We can also extrapolate a mathematical model from the discrete values to obtain a continuum of values.

According to a first advantageous embodiment, the method according to the invention can comprise the following steps:

for measuring the intensity signal corresponding to a diffusion pattern formed by the scattered beam, measuring an intensity signal corresponding to a scattering pattern at the small angles of the beam after passing through the membrane,

to connect the measurement on the diffusion figure with the degree of misalignment of the objects contained in the membrane:

• the shape of the diffusion pattern is measured,

· For the orientation of the chosen membrane such that the axis of propagation is not contained in the membrane plane (in particular for the value of the non-zero angle α chosen), the degree of misalignment of the objects contained is determined in the membrane by connecting this form with the degree of misalignment of the objects contained in the membrane.

During a preliminary step, the remote detection means of the membrane are placed to measure a small-angle diffusion pattern.

This first embodiment is particularly advantageous in the case of poorly organized structures or having fairly large characteristic lengths, that is to say between 5 nm and 100 nm, which are considered homogeneous.

The small angle scattering figure here designates the intensity distribution corresponding to the small angle X-ray scattering. X-ray scattering at small angles is also referred to as the SAXS for small angle X-ray scattering. This technique, well known to those skilled in the art, makes it possible to study the structural properties of materials on a scale typically ranging from 5 nm to 100 nm.

According to a second advantageous embodiment, the method according to the invention can comprise the following steps:

for measuring the intensity signal corresponding to a scattering pattern formed by the scattered beam, measuring an intensity signal corresponding to a scattering pattern at the large angles of the beam after passing through the membrane,

A characteristic dimension of a peak of the curve representing the intensity variation of a line of the diffusion pattern is measured as a function of the direction of the scattered beam for a constant diffusion angle,

For the orientation of the chosen membrane such that the axis of propagation is not contained in the membrane plane (in particular for the value of the non-zero angle α chosen), the degree of misalignment of the objects contained in the membrane by connecting this characteristic dimension with the degree of misalignment of the objects contained in the membrane.

During a preliminary step, the detection means are placed close to the membrane, to measure a large-angle diffusion figure.

This second embodiment is particularly advantageous in the case of crystalline structures.

The wide-angle scattering figure here refers to the intensity distribution corresponding to X-ray scattering at large angles.

One can use a technique known to those skilled in the art, also called X-ray diffractometry.

It is possible to measure an intensity signal corresponding to a scattering pattern at the large angles of the beam after passing through the membrane, in in particular, a signal of intensity corresponding to a diffraction line sensitive to the inclination of the membrane according to the non-zero angle α.

A peak may designate a portion of the curve of the intensity variation, comprising a maximum of intensity.

A characteristic dimension of a peak of the curve representing the intensity variation of a line of the scattering pattern is preferably the half-height width of this peak.

We can consider as a maximum of intensity the absolute maximum and any local maximum of the curve greater than or equal to 50%, for example of the absolute maximum.

For example, the absolute minimum of the intensity signal can be defined:

The mid-height of an intensity peak then corresponds to H = (M- m _a bs) / 2 + rriabs, with M the value of the maximum of said intensity peak.

The width at half height of the intensity peak corresponds to the difference between the two abscissa values having the mid-height of the peak, and surrounding the abscissa corresponding to said ordinate maximum M.

According to this second embodiment, it is possible to choose as membrane multiwall nanotubes impregnated in a polymer and to measure an intensity signal corresponding to the diffraction line 002. (The intensity signal advantageously corresponds to said curve representing the variation the intensity of a line of the scatter pattern as a function of the direction of the scattered beam at a constant scattering angle.)

The diffraction line 002 denotes the first harmonic among the different diffraction lines, corresponding to the inter-wall distance of the multiwall carbon nanotubes, when the inter-wall distance is approximately constant. The designation of a three-digit diffraction line refers to families of lattice planes (hkl) in crystallography, where h, k and I are whole numbers.

Advantageously, the membrane is chosen from at least one of:

a membrane formed by alumino-silicate nanotubes impregnated in a polymer or a ceramic or non-impregnated; a membrane formed by metal nanowires impregnated in a polymer or a ceramic or non-impregnated;

a membrane formed by nanotubes of titanium oxide impregnated in a polymer or a ceramic or non-impregnated; a membrane formed by mono- or multiwall carbon nanotubes impregnated in a polymer or a ceramic or non-impregnated;

a membrane formed of empty through tubes;

a membrane formed of leaflets,

a membrane formed of clay sheets parallel to the plane of the membrane.

It can be seen that the invention applies to tubular geometries (tubes) as to planar geometries (leaflets).

Preferably, the orientation of the membrane, and in particular the angle α, is determined as a function of the desired accuracy on the measurement of the degree of misalignment of the objects contained in the membrane.

To have a good precision, it is necessary that a peak of intensity is the finest possible. Now, the smaller the angle, the higher the intensity peak.

Advantageously, the orientation of the membrane, and in particular the angle α, is determined as a function of a first approximation of the degree of misalignment of the objects contained in the membrane. This first approximation may for example be provided by a manufacturer of the membrane containing the objects.

On the other hand, the smaller the degree of misalignment, the finer the peak of intensity.

The orientation of the membrane, and in particular the angle α, can be determined as a function of a space constraint.

Advantageously, the orientation of the membrane, and in particular the angle α, is determined as a function of the bulk of the membrane. The higher the angle α, the less the device according to the invention is bulky for fixed membrane dimensions.

In practice, a compromise can be achieved in order to obtain the desired precision, while minimizing the angle while respecting the space requirements of the device according to the invention (an angle of close to 90 ° limits the overall dimensions of the device according to the invention). According to a first approximation of the degree of misalignment and the desired accuracy on the measurement of degree of misalignment, it is possible to choose a suitable value for the angle a.

The method according to the invention may comprise the following steps: the following steps are carried out at least once:

the degree of misalignment of the objects contained in the membrane at a point in the membrane is determined,

the membrane is displaced according to at least one translation in the membrane plane,

the degree of misalignment of the objects contained in the membrane is determined at another point of the membrane, then

a mapping is made of the degrees of misalignment of the objects contained in the membrane for each studied point of the membrane.

It is also possible to map the intensity of the beam transmitted by the membrane for each studied point of the membrane. In this case, the mapping may correspond to a mapping of a density of objects in the membrane.

It is also possible to map the fluorescence signal measurements emitted by the membrane, for each studied point of the membrane. In this case, the mapping may correspond to a mapping of a concentration in the membrane of a given chemical element, for example iron, or of several given chemical elements.

The membrane can be moved in the plane of the membrane for a plane membrane.

The membrane can be moved in the plane tangential to the membrane at the intersection between the axis of propagation and the membrane, for a non-planar membrane.

The invention also relates to a computer program product arranged to execute the steps of the method according to the invention when it is executed in a computer, in particular the steps of measuring an intensity signal corresponding to a diffusion figure. and determining the degree of misalignment of the objects contained in the membrane.

Description of the Figures and Embodiments Other advantages and particularities of the invention will appear on reading the detailed description of implementations and non-limiting embodiments, and the following appended drawings:

- Figure 1A illustrates a schematic side view of a device according to the prior art for measuring a degree of misalignment of objects contained in a small membrane;

- Figure 1B illustrates a schematic top view of a device according to the prior art for measuring a degree of misalignment of objects contained in a small membrane;

- Figure 1C illustrates a schematic top view of a device according to the prior art for measuring a degree of misalignment of objects contained in a large membrane;

FIG. 2A illustrates a schematic side view of a device according to the invention for measuring a degree of misalignment of objects contained in a membrane;

FIG. 2B illustrates a schematic view from above of a device according to the invention for measuring a degree of misalignment of objects contained in a membrane,

FIG. 3 illustrates a perspective view of a membrane that can be studied thanks to the device according to the invention,

FIG. 4 illustrates a perspective view of the walls of a multiwall carbon nanotube,

FIG. 5 illustrates a large-angle diffraction pattern obtained in a device according to the prior art,

FIG. 6 illustrates a large-angle diffraction pattern obtained in a device according to the invention,

FIG. 7 illustrates a first device embodiment according to the invention,

FIG. 8 illustrates a second device embodiment according to the invention and its computing environment,

FIG. 9 illustrates a curve of a degree of misalignment of objects contained in a membrane as a function of a measurement on a corresponding diffraction pattern, for two values different from the angle a, FIG. 10 illustrates a circular section of the diffraction line 002 of multiwall carbon nanotubes, obtained in a device according to the prior art,

FIG. 11 illustrates a circular section of the diffraction line 002 of multiwall carbon nanotubes, obtained in a device according to the invention,

FIG. 12 illustrates an experimental measurement of the influence of the inclination of the membrane on a circular section of the diffraction line 002 of multiwall carbon nanotubes, obtained in a device according to the invention, for a first degree of misalignment ,

FIG. 13 illustrates a simulation of the influence of the inclination of the membrane on a circular section of the diffraction line 002 of multiwall carbon nanotubes, obtained in a device according to the invention, for a second degree of misalignment;

FIG. 14 illustrates a simulation of the influence of the inclination of the membrane on a circular section of the diffraction line 002 of multiwall carbon nanotubes, obtained in a device according to the invention, for a third degree of misalignment;

FIG. 15 illustrates a perspective view of the reference plane, of a membrane portion and of the plane tangential to the membrane at the intersection between the reference plane and the membrane, and

FIG. 16 illustrates a small angle scattering figure.

FIG. 3 shows a membrane 2 containing objects 3 which are aligned mainly perpendicular to the surface 4 of the membrane 2. The surface 4 of the membrane 2 designates one of the two larger surface faces of the membrane 2. The width and the length of the surface 4 form the two lateral dimensions of the membrane 2.

It can be seen in FIG. 3 that the objects 3 are not all perfectly aligned perpendicular to the surface 4 of the membrane, some forming an angle Θ with the perpendicular to the surface 4 of the membrane 2.

The degree of misalignment of the objects contained in the membrane 2 is given by the width of the distribution function of the orientations Θ taken on all objects. It is even smaller (close to zero) that the objects are aligned with a reference axis or plane.

The distribution function can be a Gaussian, a Lorentzian, etc. We can determine this distribution function from the theory of diffusion, knowing the nature of the objects contained in the membrane 2. We can also find this distribution function from the experimental measurements on beam scattering figures. X-rays through the membrane.

Firstly, with reference to FIGS. 1A and 1B, a device 1 according to the prior art for measuring such a degree of misalignment of objects contained in a membrane 2 will be described.

Figure 1A illustrates a schematic side view of the device 1 according to the prior art.

Figure 1B illustrates a schematic top view of the device 1 according to the prior art.

The device 1 according to the prior art comprises means (not shown) for transmitting an X-ray beam 6 propagating along a propagation axis 350, and detection means 7 for measuring, in transmission, a scattered beam 8 after crossing the membrane 2.

The axis of propagation 350 is entirely contained in the membrane plane.

The propagation axis 350 designates the direction of propagation of the X-ray beam 6 emitted by the transmitting means.

The membrane has a length 10 which is in the device 1 according to the prior art the length traversed by the beam 6 of X-rays.

FIG. 1C illustrates a schematic view from above of a device 1 according to the prior art, and shows the limitations of said device 1 according to the prior art in the case of a large membrane 2, for example a membrane 2 exhibiting a length greater than 2cm. The limit length beyond which the geometry shown in FIG. 1C is no longer usable depends on the material forming the membrane 2 and in particular on its diffusion and absorption capacities. Depending on the case, it may be limited to membranes 2 of length less than 1 mm and even 0.5 mm.

FIG. 1C shows that for each portion of the membrane 2, there are scattered beams 8 ', 8 ", 8"', leading to a radial enlargement of the measured signal. If the alignment varies for each portion of the membrane, the analysis of a diffusion figure obtained at the level of the measuring means 7 is therefore more complicated, and the processing time is therefore even longer. In addition, the intensity transmitted after crossing a certain length of membrane 2 is even lower than this length is large. Indeed, the intensity transmitted after crossing the membrane decreases exponentially as a function of the membrane length traversed by the beam 6 of X-rays. It is therefore possible that the intensity of 8 "'is no longer measurable because In addition, it can be seen in FIG. 1C that a large length of the membrane 2 can pose difficulties with regard to the size of the sensors: the detection means 7 have a given size and Therefore, since the diffused beam 8 is diverging, the more the detection means 7 are moved away from the membrane 2, the more the detection means must be able to detect over a large area in order to collect the entire image. 8. When the length of the membrane is large (for example greater than 5 cm), the scattered beam 8 'corresponding to the membrane portion furthest from the detection means 7 may have a diameter greater than the sensor size of the detection means 7, at the level of the detection means 7.

The idea underlying the invention is therefore to modify the device 1 according to the prior art so as to overcome the limitations of the prior art.

FIGS. 2A and 2B schematically show a device 100 according to the invention.

FIG. 2A illustrates a schematic side view of the device 100 according to the invention.

FIG. 2B illustrates a schematic view from above of the device 100 according to the invention.

Figures 2A and 2B will be described only for their respective differences with respectively Figures 1A and 1B or 1C.

FIG. 2B shows that the axis of propagation 350 is not contained in the plane of membrane 20 which is here coincident with the plane of the membrane 2 since the membrane shown is plane. It is the same in Figures 7 and 8. FIG. 2B shows that the propagation axis 350 forms an angle β with the normal 600 to the membrane at the intersection between the membrane 2 and the propagation axis 350. The angle a is complementary to this angle β. The angle a is non-zero.

Figure 15 illustrates the case of a non-planar membrane 2. In this case, the membrane plane 20 is defined as the plane tangent to the membrane portion 2 at the intersection between the x-ray beam 6 and the membrane 2.

Only a portion of membrane 2 is traversed by the beam 6 of X-rays.

This eliminates the difficulties concerning the intensity transmitted after passing through the membrane by the X-ray beam 6.

The thickness of membrane 2 crossing is of the order of the thickness of the membrane divided by sin (a) is for example a few hundred micrometers for values of a between 10 ° and 80 ° and for a membrane of 100 micrometers thick.

It is not necessary to align the entire length of the membrane 2 with the membrane plane 20.

The diffused beam 8 obtained in the device according to the invention corresponds to the only portion of membrane 2 crossed by the beam 6 of X-rays.

It is possible to place said membrane portion 2 at the desired distance from the detection means 7, to ensure that the set of a diffusion pattern to be studied is detected by the detection means 7.

In addition, there is no dispersion of scattered beams corresponding to parts distant from each other (at least 2 mm for example) of the same membrane 2. The diffusion pattern obtained can then be more simply and quickly analyzed, without ambiguities.

A first embodiment of device 100 according to the invention will now be described more precisely and with reference to FIG.

The device 100 according to the invention comprises:

means 11 for transmitting an X-ray beam, constituted here by a rotating anode (not shown in FIG. 7) generating X-rays and a monochromation and X-ray collimation system (it is possible to also provide that the transmission means 11 are constituted by another type of anode or synchrotron radiation);

detection means 7 of the X-ray beam diffused by the membrane 2, here consisting of a CCD sensor,

a support 12 for receiving a plane membrane 2 (shown here transparent for a better readability of the figure), the support 12 here consisting of two windows transparent to X-rays between which the membrane 2 is placed, the windows being mounted in a frame 15cm on 15cm for example.

The support 12 is mounted on adjustment means 380 for varying the orientation of the support 12 (rotation 195). Two translation tables 190 make it possible to move it and thus to probe different points of the membrane with the beam 6.

In the example shown in FIG. 7, the plane of the membrane (that is to say the plane in which the membrane 2 is located) is defined by two axes W1, W2, one of which W2 is perpendicular to the propagation axis 350.

The membrane plane forms a non-zero angle α with the axis of propagation 350.

More particularly, in Figure 7 the axis of propagation 350 is in a horizontal plane, while the membrane plane is vertical.

While in the general case it takes two angles to define the orientation in the space of the membrane plane, we are here in a particular case where we define the orientation of the membrane by the single angle a.

The objects contained in the membrane form for example a carpet. In this case, the objects, one-dimensional, are aligned mainly perpendicularly to the surface of this carpet. There may be an inclination of the carpet with respect to the polymer membrane. Rotating means (not shown) may be provided to correct a possible inclination of the carpet, with respect to the polymer membrane, so as to obtain a measurement of a degree of inclination of the objects with respect to the plane of the carpet and not relative to the surface 4 of the membrane.

In the example shown in FIG. 7, the device 100 according to the invention also comprises means 14 for measuring a fluorescence signal, working in reflection. The means 14 for measuring a fluorescence signal are located on the same side of the membrane 2 as the transmission means 11. They make it possible to measure a fluorescence signal, characteristic of the chemical composition of the membrane portion 2 traversed by the x-ray beam 6.

In the example shown in FIG. 7, the device 100 according to the invention also comprises means for measuring the intensity 15, for measuring the intensity of the beam transmitted by the membrane 2. These means for measuring the intensity 15 measure the intensity of the portion of the incident beam on the membrane 2 which has not undergone any deviation or absorption. They are located in front of the detection means 7. The intensity of the X-ray beam portion which does not undergo a deflection is generally greater than the intensity of the portion of the scattered beam. The intensity measuring means 15 are located in a cache (commonly called "well" or "beamstop" by those skilled in the art). Thus, the transmitted beam does not reach the detection means 7 and does not disturb the measurement of the scattered beam 8.

Note that the device 100 can be rotated in its entirety at any angle around the axis of propagation 350, for example 90 °, which would make the horizontal membrane for an angle equal to 0 °.

FIG. 8 illustrates the operation of a second device embodiment 100 according to the invention.

The device 100 according to the invention illustrated in FIG. 8 comprises:

means 11 for transmitting an X-ray beam 6,

detection means 7 for measuring a scattered beam 8, which may consist of a flat CCD sensor,

a support not shown for receiving a plane membrane 2.

In the example shown in FIG. 8, the orientation of the membrane plane (that is to say the plane in which the membrane 2 is located) corresponds to an angle a, which is the angle complementary to the angle β between the axis of propagation 350 and the normal 600 at the membrane 2 at the intersection between the membrane and the axis of propagation 350.

The axis of propagation 350 propagates in a horizontal plane, while the membrane is inclined both with respect to the vertical and relative to the horizontal.

The plane of the CCD sensor 7 may be vertical, that is to say defined by two axes, at least one of which is perpendicular to the axis of propagation. Note that the device 100 can be rotated in its entirety at any angle around the direction 6 of the incident beam.

It can be seen that the beam 6 of X-rays emitted by the emission means 11 is decomposed under the influence of the membrane portion 2 situated in the path of said x-ray beam 6 by:

a scattered beam 8, corresponding to a portion of the X-ray beam 6 deflected under the influence of the membrane 2,

a transmitted beam 16 corresponding to a portion of the X-ray beam 6 neither deflected nor absorbed under the influence of the membrane 2,

a fluorescence signal 17 emitted by the membrane 2 as a result of a partial absorption of the x-ray beam 6 by the membrane 2.

The device 100 according to the invention illustrated in FIG. 8 also comprises:

measuring means 14 for a fluorescence signal;

adjustment means 380 making it possible to vary the orientation of the support 12 (not shown) so as to be able to modify, for example, the value of the angle of inclination α of the membrane 2 with respect to the axis of propagation 350 ;

means 190 for moving the membrane in a direction contained in the plane of the support 12, for example in the direction represented by the arrows 19. It is thus possible to scroll a membrane 2 of large size to carry out successively measurements in different locations of the membrane 2. It can be provided two translation directions to move the membrane 2, which allows to study a membrane 2 regardless of its dimensions. For example, a line-by-line study can be provided directly at the output of the membrane production, which makes it possible to control a production stoppage in the case where the measurements made exceed a predetermined threshold. During a measurement, the membrane 2 is fixed.

a processor 21.

If the membrane is not flat, one can have a variable angle during the scrolling of the membrane. This difference can be taken into account by modifying the orientation of the support, for example to find a constant angle a during the scrolling of the membrane. It can also be taken into account when processing data during which connects a measurement on the diffusion figure with the degree of misalignment of the objects contained in the membrane.

The processor 21 receives information on the detected signals:

by the measuring means 14 of a fluorescence signal (see arrow 123);

by the detection means 7 (see arrow 22);

by the means for measuring the intensity 15 (see arrow 122) working in transmission.

The processor 21 can therefore analyze the detected signals and calculate in return, for the membrane portion 2 crossed by the beam 6 of X-rays respectively:

an indicator of chemical composition, for example to ensure the absence of catalytic particles, which may be iron-based, in a carbon nanotube membrane, in particular by detecting the presence or absence of iron. This indicator quantifies a concentration of one or more chemical elements in the membrane;

a degree of misalignment of the objects contained in the membrane 2. This degree of misalignment constitutes a quantitative analysis of the alignment of the objects in the membrane;

a density of objects in the membrane 2. It is also possible to quantify an average number of carbon nanotubes forming the objects contained in the membrane.

The device 100 according to the invention then constitutes a computerized measurement bench directly providing an interpretation of the results thanks to the processor 21.

This information can each be presented in the form of maps where each point corresponds to a measurement on the membrane 2.

The processor 21 is included in a computer capable of executing software (computer program product), said software enabling the processor 21 to analyze the detected signals and to perform the calculations mentioned above.

It can further be provided that, thanks to the computer program product according to the invention, the processor 21 controls:

the scrolling of the membrane (see arrow 23), the detection means 7, the means 14 for measuring a fluorescence signal and the means for measuring the intensity 15, and / or

certain parameters of the transmission means 11, for example the power of the x-ray beam 6 (see arrow 24).

The processor 21 equipped with the software according to the invention can also exchange information with the adjustment means 380 (see arrow 25). The processor 21 can detect the position of the adjustment means 380 in order to deduce the orientation of the membrane, in particular the angle a, to be taken into account in a calculation of degree of misalignment. It can also be provided that a human operator sets the device 100 according to the invention by specifying in the processor 21 an angle a to be taken into account, the processor 21 then controlling the positioning of the adjustment means 380 to position the membrane 2 according to the invention. chosen orientation.

It can also be provided that the processor 21 equipped with the software according to the invention makes it possible to determine how to orient the membrane, then automatically directs the membrane support to the desired angles. The processor can determine an adequate angle a, depending on:

a desired accuracy in measuring a degree of misalignment,

a first approximation of the degree of misalignment,

- A congestion allowed for the device according to the invention and the bulk of the membrane.

The device 100 according to the invention can make it possible to study any membrane 2 containing objects aligned mainly in a predetermined direction or in a plane, for example:

unidimensional objects aligned mainly perpendicular to the plane of the surface of the membrane;

- lamellae aligned mainly parallel to the surface of the membrane.

The membrane must be diffusing, the diffusion signal being isotropic for a certain orientation of the membrane (a = 90 °), and anisotropic for any other orientation.

The membrane 2 may have an amorphous structure. In this case, the detecting means 7 are placed at a distance from the membrane 2, for example at more than one meter, for a small-angle analysis. We can study mesoporous materials, and so on. The objects contained in the membrane can be hollow structures. Wide-angle analysis can also be done for some amorphous structures.

The objects of the membrane 2 whose alignment is studied may have a crystallized structure. In this case, the detection means 7 are placed near the membrane 2, for example less than 10 cm, for a wide-angle analysis.

In a particular example, a membrane 2 obtained from a carpet of carbon nanotubes impregnated in a polymer such as polystyrene is studied, the assembly then being polished.

Some uses of the carbon nanotube membranes require that they remain intact, of large size, hence the interest of a possible non-destructive analysis with the device 100 according to the invention. The performance of these membranes is related to their structural quality, including the density and good alignment of the nanotubes in the membrane.

FIG. 4 illustrates a carbon nanotube having a plurality of walls

26.

For example, transmission means 11 emitting an X-ray beam 6 at the wavelength of copper Ka: 1.54 angstrom are used. The objects contained in the membrane have dimensions (for example an inter-wall distance in nanotubes) of the order of magnitude of the wavelength of the X-ray beam 6. For example, the membrane has a thickness of 100 μm.

We will now focus on the method implemented in a device 100 according to the invention.

According to a first variant of the method according to the invention, the detection means 7 are placed at a distance from the membrane 2, for example 3 m, to measure a small-angle diffusion pattern.

FIG. 16 illustrates a small angle scattering pattern 27 that can be measured by the detecting means 7. The scattering pattern

27, shown schematically, does not have a disk shape: the diffusion figure 27 is therefore called anisotropic. From the measurement of the shape of the scattered signal, in particular a degree of deformation of this shape with respect to a disc of the same surface, and knowing the orientation of the membrane, one can determine the degree of misalignment of the objects in the membrane 2.

According to another variant of the method according to the invention, the detection means 7 are placed near the membrane 7, for example 10 cm, to measure a diffusion figure 40 at large angles.

FIG. 6 illustrates a large-angle diffusion pattern 40 that can be measured by the detection means 7, in particular in the configuration shown in FIG. 7. In this particular case, it is a diffraction pattern. The ring 31 corresponds to the diffraction line 002 of the multiwall carbon nanotubes. This diffusion line is chosen in particular because it is the most intense, and because it is sensitive to the orientation of the carbon nanotubes.

In the example shown, we study carbon nanotubes having a distance interparoi 33 (see Figure 4) approximately constant, for example within 5%. The first ring 31 thus corresponds to the diffraction due to the walls of the carbon nanotubes, for an approximately constant inter-wall distance 33.

The diffusion figure 40 of FIG. 6 has two intensity maxima 34. For the study of the diffusion pattern 40, a circular section 35 (shown in dotted lines) of the 002 diffraction line is made. Figure 11. In Figure 11, the abscissa is graduated in degrees (circular section). The ordinate axis is representative of the intensity measured in the diffraction pattern. FIG. 11 therefore shows a curve representing the intensity variation of a line (the diffraction line 002) of the diffusion figure 40, as a function of the direction of the scattered beam and for a constant diffusion angle ( circular cut and centered on the axis of propagation). We will speak more quickly of circular section of the diffraction line 002.

The circles in Figure 11 represent these experimental measurements. There are two maxima spaced in this example of about 150 ° (value less than 180 °).

For comparison, FIG. 5 represents the diffusion pattern obtained in a device 1 according to the prior art, and FIG. 10 represents the circular section of the diffraction line 002 of multiwall carbon nanotubes, corresponding to the diffusion figure of Figure 5. The maxima are spaced 180 °.

The degree of misalignment of the carbon nanotubes in the membrane is determined by adjusting the experimental curve with an adjusted curve 370 (by an interpolation calculation).

This adjusted curve 370 makes it possible to quantitatively determine the degree of misalignment, via a calculation based on the theory of diffraction (or via a suitable tabulation), which integrates the degree of orientation of the nanotubes in the membrane and the orientation of the membrane, in particular the value of the angle a, chosen to carry out the measurement.

Whether the degree of misalignment is measured from a large angle or small angle scatter pattern, a measurement on the scatter pattern can be related to a degree of misalignment of the objects in the membrane 2:

using a database storing pairs {measure on the diffusion figure; degree of misalignment} for a given membrane orientation, so as to quickly associate a measurement on the scatter pattern to a degree of misalignment. This database can be made from experimental data (measurements are made on a scattering pattern, for a known membrane and a known membrane orientation) or theoretical (from the known theory of diffusion). In this case, the analysis time is, for example, 3 seconds per measurement point, for a diameter of the x-ray beam 6 equal to 1 mm; or

by calculating on a case-by-case basis, from the scattering theory, and knowing the orientation of the predetermined membrane, the degree of misalignment corresponding to the measurement made on a diffraction pattern. In this case, the analysis time is for example 30 seconds per measurement point, for a diameter of the beam 6 of X-rays equal to 1 mm.

Figure 9 illustrates the correspondence between:

the widths at mid-height of a peak of the adjusted curve representing the variation of intensity of the diffraction line 002 (obtained thanks to a device 100 according to the invention) as a function of the direction of the scattered beam and for a constant diffusion angle, and degrees of misalignment of objects contained in a membrane. The x-axis is graduated in degrees: it corresponds to degrees of misalignment of the objects. The ordinate axis corresponds to the width at mid-height of the peaks 37 on the left (or on the right). For peak 37 of the adjusted curve shown on the left in FIG. 11, the width at half height is determined as follows.

the absolute minimum U is determined;

the maximum V is determined;

the value W of the mid-height of this peak, that is to say the value U plus half of the difference between the values V and U, is determined;

the abscissa S of the point of the peak having the ordinate V is located;

the two abscissas R and T of the points of the peak having the ordinate W are identified;

the difference (T-R) between these two abscissae corresponds to the width at half height of the peak.

The circles in Fig. 9 show the correspondence for a predetermined non-zero angle α. For comparison, the squares in Figure 9 represent the correspondence for another angle to zero. We see that it is possible to extrapolate between the discrete values presented here. The extrapolation curves being monotonic, one can unambiguously find the degree of misalignment from a measurement on a diffusion figure.

We can therefore, from a few discrete values, determine a mathematical model to obtain a continuum of pairs {measure on the diffusion figure; degree of misalignment} for a given membrane orientation. It is therefore possible to make a database as defined above quite complete.

The optimal orientation of the membrane 2 depends on several parameters.

FIG. 12, which corresponds to experimental measurements, illustrates the effect of the inclination of the membrane on a circular section of the diffraction line 002 of multiwall carbon nanotubes, obtained in a device 100 according to the invention, for a degree of misalignment given. The x-axis is graduated in degrees (cf circular section of the 002 diffraction line). The y-axis corresponds to the measured intensities, which are translated vertically for greater clarity. For each curve, the value of the corresponding angle α was noted on the left (one of the axes of the membrane being here perpendicular to the axis of propagation of the incident X-rays). It can thus be seen that for an angle α between 0 and 60 °, two well-defined peaks 37 are obtained allowing an accurate calculation of a degree of misalignment. Beyond that, it is no longer feasible so easily. For a = 90 °, the curve should be a horizontal line (the deviation to the right is related to different experimental aspects that will not be discussed here): the degree of misalignment can not be measured in this geometry.

The calculation of the degree of misalignment is all the more precise as the peaks are well defined.

For example, for a degree of misalignment of 20 °:

FIGS. 13 and 14 respectively illustrate simulations showing the influence of the angle of inclination of the nanotube membrane on the circular section of the diffraction line 002 of multiwall carbon nanotubes, obtained in a device 100 according to FIG. invention, for a greater degree of misalignment in FIG. 14 than in FIG. 13.

In the two figures, which are obtained from calculations based on diffraction theory, the x-axis is graduated in degrees, and we see several circular sections of the diffraction line 002, for an angle of inclination. of the membrane ranging from 55 ° to 65 ° (from top to bottom in the figures). Here again it is seen that the lower the inclination angle of the membrane, the better the peaks are defined. It is also seen, by comparing Figures 13 and 14, that the greater the degree of misalignment, the less well defined are the peaks, which further degrades the precision on the calculation of the degree of misalignment. The higher the peaks, the better the accuracy of the calculation of the degree of misalignment.

By way of example, for an angle of inclination of the membrane of 60 ° we have: Degree of misalignment Accuracy on the measurement of a

degree of misalignment

4 ° +/- 0.3 °

10 ° +/- 0.8 °

20 ° +/- 2 °

We will now study the case of an unknown membrane.

In this case, we begin by studying the membrane and its diffusion pattern.

This study is carried out for different orientations of the membrane.

A theoretical model of diffusion by the membrane is then established.

A diffusion line is determined which will be studied, in particular because it is sensitive to the orientation of the objects contained in the membrane and which it is desired to determine the degree of misalignment.

The opening cone of the portion of the scattering beam to be exploited is determined to the extent of a degree of misalignment. This cone determines the field of a camera constituting the detection means 7. It is also possible to operate on the wavelength of the x-ray beam 6 to vary the aperture of the diffusion cone, for example to adapt it to a given camera. The longer the wavelength, the larger the cone opening.

The anisotropy of the diffusion pattern is then simulated as a function of the orientation of the membrane to experimentally verify the validity of the model.

An orientation of the membrane is chosen, in particular as a function of the desired accuracy on the measurement of the degree of misalignment and the maximum permitted space requirement.

One can then parameterize a software executed by the processor 21: with this orientation of the membrane and

- with the theoretical model of the membrane.

This setting then causes the control of the support 12 by the software for the automatic adjustment of the support 12 to this desired orientation. Then we can note a signal of intensity corresponding to a figure of transmission diffusion, make a measurement on this intensity signal, and associate with this measurement a degree of misalignment.

Of course, the invention is not limited to the examples that have just been described and many adjustments can be made to these examples without departing from the scope of the invention.

Claims

A device (100) for measuring a degree of misalignment of objects contained in a membrane (2) and aligned mainly in a predetermined direction or in a predetermined plane, the measuring device (100) comprising:

means for transmitting (11) an X-ray beam (6) propagating along an axis of propagation (350),

detection means (7) of the X-ray beam for measuring a scattered beam (8) after passing through the membrane (2), a support (12) for receiving the membrane (2), located between the transmitting means (11) and the detection means (7),

characterized in that the support (12) is arranged to receive the membrane (2) so that the axis of propagation (350) is not contained in a membrane plane (20), the membrane plane (20) ) forming a non-zero angle with the axis of propagation (350).

2. Device (100) for measuring according to claim 1, characterized in that the membrane plane (20) can be defined by two axes (W1, W2) of which at least one (W2) is perpendicular to the axis propagation (350).

3. Device (100) for measuring according to claim 1 or 2, characterized in that the membrane (2) is flat.

4. Device (100) for measuring according to any one of claims 1 to 3, characterized in that the angle a is between 20 ° and 80 °.

5. Device (100) for measuring according to any one of claims 1 to 4, characterized in that it comprises means for measuring the intensity (15) of a transmitted beam (16) by the membrane (2). ).

6. Device (100) for measuring according to claim 5, characterized in that the means for measuring the intensity (15) of the transmitted beam (16) by the membrane (2) comprises a photodiode placed on the optical path of the beam transmitted (16) by the membrane (2).

7. Device (100) for measuring according to any one of claims 1 to 6, characterized in that it comprises means (14) for measuring a fluorescence signal emitted by the membrane (2) in response to the beam (6) emitted by the transmitting means (11).

8. Device (100) for measuring according to any one of claims 1 to 7, characterized in that the support (12) comprises means (190) for moving the membrane (2) in at least one translation in the plane of membrane.

9. A method of using the measuring device according to any one of claims 1 to 8, characterized in that it comprises the following steps:

an intensity signal corresponding to a diffusion pattern (27; 40) formed by the scattered beam (8) is measured;

for the orientation of the chosen membrane such that the axis of propagation (350) is not contained in the plane of membrane (20), the degree of misalignment of the objects contained in the membrane (2) is determined by connecting a measurement in the diffusion pattern (27; 40) with the degree of misalignment of the objects contained in the membrane (2).

10. Method according to claim 9, characterized in that it comprises the following steps:

for measuring the intensity signal corresponding to a scattering pattern (27; 40) formed by the scattered beam, measuring an intensity signal corresponding to a scattering pattern (27) at the small angles of the beam (6) after crossing the membrane (2),

to connect the measurement on the diffusion pattern (27) with the degree of misalignment of the objects contained in the membrane (2):

The shape of the diffusion pattern (27) is measured,

For the orientation of the chosen membrane such that the axis of propagation (350) is not contained in the membrane plane (20), the degree of misalignment of the objects contained in the membrane (2) by connecting this shape with the degree of misalignment of the objects contained in the membrane (2).

11. Method according to claim 9, characterized in that it comprises the following steps:

for measuring the intensity signal corresponding to a scattering pattern (27; 40) formed by the scattered beam, measuring an intensity signal corresponding to a scattering pattern (40) at the large beam angles after crossing the beam. membrane (2),

to connect the measurement on the diffusion figure (40) with the degree of misalignment of the objects contained in the membrane (2):

A characteristic dimension of a peak (37) of the curve representing the variation of intensity of a line of the diffusion pattern (40) is measured as a function of the direction of the scattered beam (8) for an angle of constant diffusion,

For the orientation of the chosen membrane such that the axis of propagation (350) is not contained in the plane of membrane (20), the degree of misalignment of the objects contained in the membrane (2) is determined by connecting this characteristic dimension with the degree of misalignment of the objects contained in the membrane

(2).

12. The method of claim 11, characterized in that one chooses as membrane (2) of multiwall carbon nanotubes impregnated in a polymer and measuring an intensity signal corresponding to the diffraction line 002.

13. Method according to one of claims 9 to 11, characterized in that the membrane (2) is chosen from at least one of:

a membrane formed of empty through tubes;

a membrane formed of leaflets;

a membrane formed of clay sheets parallel to the plane of the membrane.

14. Method according to any one of claims 9 to 13, characterized in that the orientation of the membrane (2) is determined according to the desired accuracy on the measurement of degree of misalignment of the objects contained in the membrane (2).

15. Method according to any one of claims 9 to 14, characterized in that the orientation of the membrane (2) is determined according to a first approximation of the degree of misalignment of the objects contained in the membrane (2). ).

16. Method according to any one of claims 9 to 15, characterized in that the orientation of the membrane (2) is determined as a function of the bulk of the membrane (2).

17. Method according to any one of claims 9 to 16, characterized in that the following steps are carried out at least once:

the degree of misalignment of the objects contained in the membrane (2) at a point in the membrane is determined,

the membrane (2) is moved in at least one translation in the plane of the membrane,

the degree of misalignment of the objects contained in the membrane (2) is determined at another point of the membrane, then

a mapping is made of the degrees of misalignment of the objects contained in the membrane (2) for each studied point of the membrane (2).

18. Computer program product, characterized in that it is arranged to perform the steps of the method according to any one of claims 9, 10, 11, 14, 15, 16 or 17 when executed in a computer .