WO2013139691A2

WO2013139691A2 - Method and device for determining the size of an opaque translucent particle

Info

Publication number: WO2013139691A2
Application number: PCT/EP2013/055348
Authority: WO
Inventors: Cameron Tropea; Walter Schäfer
Original assignee: Technische Universität Darmstadt
Priority date: 2012-03-20
Filing date: 2013-03-15
Publication date: 2013-09-26
Also published as: DE102012102364A1; WO2013139691A3

Abstract

Method for determining the size of an opaque translucent particle (3), wherein the particle (3) is illuminated with light from a light source (1), wherein a time-resolved intensity curve (10) of light from the light source (1) scattered at the particle (3) is measured at a predeterminable scattering angle θ_s by a radiation detector (8), wherein characteristic scattered light peaks are determined in the intensity curve and wherein the size of the particle (3) is determined on the basis of a time difference between two scattered light peaks, characterised in that two time-resolved intensity curves (10, 11) of light scattered by the particle (3) are measured, in that the two intensity curves (10, 11) are associated with one another by a comparison of an intensity peak (12) that was generated by scattering inside the particle, in that a reflection peak (13, 14) produced by reflection from an interface surface of the particle is determined in each intensity curve (10, 11), and in that a time difference between the two reflection peaks (13, 14) is determined as a measure for the size d of the particle (3).

Description

Method and apparatus for determining the size of an opaque translucent particle

The invention relates to a method for determining the size of an opaque translucent particle, wherein the particle is illuminated with light from a light source, wherein with a radiation detector at a predetermined scattering angle 9 _S a time-resolved intensity profile of light scattered on the particle light of the light source is measured in the intensity curve characteristic scattered light peaks are determined and wherein based on a

Time difference between two scattered light peaks a size of the particle is determined.

Determination of various characteristic

Properties of individual particles whose size is in the range of millimeters and smaller are of great importance for research as well as for the industrial and commercial use of products or processes. Often, the characteristics of interest relate to size, shape, speed, and

Refractive index of individual particles. The simultaneous

Determination of both the size and the velocity of individual particles is of particular interest, since with this information a flux density such as a mass flow or a volume flow can be determined. In addition, individual particles can be identified in a large number of particles and individually be characterized, such as individual

Droplets in an aerosol or spray.

The determination of characteristic properties

For example, individual droplets are used to optimize fuel injection operations

Combustion chamber or for the characterization of a

Spray of a paint or varnish during Aufsprühvorgangs needed. The particles whose

Properties to be determined, are not only liquid droplets in a gas such as air, but depending on the application

Solid particles, gas bubbles in a liquid or else a droplet emulsion of a first liquid which is distributed in a second liquid.

From practice, various measuring methods are known. In many cases, optical measuring methods are advantageous because they do not or not significantly affect the individual particles whose properties are to be determined.

The optical measuring methods known from practice and from research include, for example, high-resolution imaging techniques, intensity measurements, interferometry or the evaluation of reflected and refracted or refracted light beams which are scattered by a particle to be measured.

The method of the type mentioned can for transparent and almost transparent particles one

Size determination is possible and is described for example in N. Damaschke, H. Nobach, N. Semidetnov, C. Tropea (2002) Optical Particle Sizing in Backscatter, Applied Optics 41, 5713-5727 or A. Kretschmer, N. Damaschke, N. Semidetnov, C. Tropea (2006) Application of the Time-Shift Technique for Spray Measurement, 13th Int. Symp. On Appl. laser

Techniques to Fluid Mechanics, Lisbon, Portugal, June 26-29, 2006.

While this method of measurement gives good results in theory, its practical use is often limited. Different intensity maxima can also be generated, for example, by illuminating two different particles one after the other from the light source and scattering scattered light in the direction of a radiation detector. Especially with dense particle accumulations, individual peaks can no longer be assigned reliably to individual particles. In addition, the shape of the measured particles can deviate from a spherical shape, so that the assumed for the determination of the size

geometric assumptions do not apply and the values determined can deviate significantly from actual size values. To the reliability of the measurement results

To be able to check a very considerable expenditure on equipment is required, which in many cases means that this measurement method does not make economic sense

can be used.

These methods, which are based on the evaluation of refracted light beams, are scarcely or not at all for non-transparent or opaque translucent particles

suitable. The intensity of refracted rays is usually so low in opaque particles that no meaningful evaluation of the measurement results is possible. For Emulsions such as, for example, milk (dissolved fat droplets in water) or suspensions such as, for example, paints (dissolved color pigments in solvents) are not known for easily determinable sizing methods. As opaque translucent particles, all particles are considered that are neither completely transparent (for example, water) nor nearly completely reflective

Have boundary surface (for example, metal). It is therefore considered to be an object of the present invention to provide a method of the aforementioned type for determining the size of a particle in such a way that a reliable determination of the particle size is also made possible for opaque translucent particles.

This object is achieved according to the invention by measuring two time-resolved intensity profiles of the scattered light scattered by a particle, that the two intensity profiles are obtained by comparing an intensity peak which is scattered within the

Particle was generated, are assigned to each other, that in each intensity curve each generated by reflection at an interface of the particle reflection peak is determined and that a time difference between the two reflection peaks is determined as a measure of the size of the particle.

It is exploited that the scattered light, which is scattered or generated by a particle, essentially composed of two different components. At the interface or on the outside of the particle reflection takes place. For a given by the measuring apparatus scattering angle of a through the

Measuring volume passing particles

Intensity maximum generated by stray light. The time at which the reflection peak occurs is essentially dependent on the geometric conditions and in particular on the scattering angle at which the scattered light is measured.

A large portion of the light impinging on the particle penetrates into the particle and generates there

scattering centers also reflection. The measurable under a given scattering angle intensity of this reflection from the interior of the particle is out

significantly dependent on the shape of the particle, or of the area of the interior of the particle detected by the incident light. If the particle is larger than the light beam incident on the particle, successively larger and then decreasing areas of the particle are successively illuminated and excited to reflections. The temporally resolved

The intensity profile of the reflections generated in the interior of the particle is therefore significantly dominated by the shape of the particle in question and represents a property of the particle characteristic of the particle in question. This proportion of the measurable scattered light is referred to below as the "particle peak" the intensity peak that passes through

Dispersion has been generated within the particle, has an individual shape for each particle and allows a distinction between different particles and therefore also an assignment of two different temporally resolved intensity gradients to the same particle. When spaced with two in the particle flight direction

arranged radiation detectors under magnitude of the same scattering angle is detected scattered light scattered by a particle, the respective proportions of the particle peak, which were generated by scattering within the particle, identical match with respect to the intensity profile within the measurement accuracy.

However, due to the geometrical arrangement of the radiation detectors, the reflection peak generated at the particle's interface, which is superimposed on the particle peak in each case, is detected by the two radiation detectors at a different point in time.

The time interval of these two reflection peaks depends on the size of the particle and its velocity. If the velocity of the measured particle is known, can from the distance of the two

Reflection peaks are determined the size of the particle.

The width of the particle peak also depends on the size and velocity of the particle. This information can also be evaluated and used either to control or to improve the results obtained from the reflection peaks. According to an advantageous embodiment of

The idea of the invention is that either two spaced in the particle flight direction and on both sides the light source arranged symmetrically

Radiation detectors each a first and a second temporally resolved intensity profile of scattered on the particle light of the light source is measured, or that the particle with two particle flight direction spaced and illuminated on both sides of the radiation detector symmetrically arranged light sources and the measured with the radiation detector time-resolved

Intensity profile in a first intensity profile caused by the first light source and in a second intensity profile caused by the second light source is decomposed.

As a light source can be any suitable

Light source can be used, the light is scattered by the particles to be measured with sufficient intensity and whose focused diameter is sufficiently small in relation to the particle size. In order for the particle peak to be used for the evaluation described above, the particle or the interior of the transilluminated particle may not be almost identical

Scatter point scattering center in a much larger light beam. The light beam must be smaller than the particle and successively separate areas of the

Illuminate the interior of the particle. The temporal

Intensity distribution of the particle peak then substantially corresponds to the shape of the particle, while the temporal intensity distribution of the reflection peak of the spatial intensity distribution of the light source

equivalent. An approximately Gaussian spatial

Intensity distribution of the light source leads to Gaussian time intensity distributions of the same Reflection peaks, while the intensity distribution of the particle peak also and largely depends on the shape of the particle. An advantageous embodiment of the inventive concept is provided that a spatial

Intensity distribution of the light source along an optical axis determined and with a temporal

Intensity distribution of the reflection peak in the

Intensity course is compared. In order to improve the reliability and validity of the determinations carried out in each case on a particle size, it is provided that a size determination is carried out only for those particles in which the reflection peak correlates with the spatial intensity distribution of the light source

have temporal intensity distribution. A divergent and non-correlating intensity distribution is a reliable indication that the measured temporal intensity distribution can not be assigned to a single particle, but by a

Overlaying the scattering of several particles was caused. It is also conceivable that the measured

Although intensity distribution of a single particle

can be assigned, however, this particle

for example, has no spherical shape. In both cases, the meaningfulness would be one with these

Measured values determined particle size extremely low. For this reason, for such uncorrelated

Intensity distributions no determination of particle size performed. According to a particularly advantageous embodiment of the inventive concept, it is provided that the velocity of the particle is determined from a width of the temporal intensity distribution of the reflection peak.

In particular for those intensity distributions in which the above-discussed plausibility checks have been successfully passed, starting from a characteristic width of the temporal

Intensity distribution of a reflection peak the

Particle velocity can be determined if the correlating spatial beam width of the light source is known or can be determined in advance by measurements. The width of each reflection peak depends only on the velocity and not on the size of the particle. On the assumption of a known spatial

Intensity distribution of the light source can be determined by suitable evaluation methods from the measured time interval of these reflection peaks and from the measured width of the reflection peaks, which were generated at the interface of the particle, the size of the particle and its

Speed can be determined.

Additional measuring methods and a concomitant additional expenditure on equipment are not required in order to be able to determine both the particle velocity and, to the knowledge of this, the particle size. As for the determination of the particle size only the temporal

Intensity profile of the particle scattered light of the light source must be measured, can be determined with the method described above, the particle size quickly, reliably and extremely cost. There are various possibilities, from the time-resolved intensity course of the particle

scattered light to determine more information and to use for the determination of particle properties.

According to an advantageous embodiment of

Erfindungsgedankenens is provided that each one

Width of the particle peaks in the two temporally resolved intensity gradients is determined and only for those particles, a sizing is performed, in which the width of the two particle peaks coincide. Provided that either two light sources or two detectors with matching optical

Properties must be used, the width of the two particle peaks must agree, since this width depends only on the size and velocity of the particle according to the foregoing. If the width of the particle peaks does not match, it is no longer necessary to make a detailed comparison of the shaping of the two particle peaks in order to discard the respective measured values in case of deviations and none

Size determination to perform.

It is possible for this comparison, in principle, to use any definition or any method for determining the width of the particle peaks, if for the determination of the width of both

Particle peaks the same definition, or the same method is applied. However, it is useful to determine the width of the particle peaks as the time period in which the particle peak differs from the signal noise of the detector used. It is preferably provided that in each case a beginning and / or an end of the particle peaks is determined and a ratio of a time difference between a maximum of a reflection peak and the beginning or the end of the

Particle peaks to the width of the particle peak is determined, and that the determined ratio of the time difference is compared with a theoretically determined value for the ratio. The time difference between a maximum of a reflection peak and the beginning or end of the

Particle peaks depend in addition to the particle size and the particle velocity exclusively on the scattering angle 9 _S from. The scattering angle 9 _S is given by the arrangement of the light source and the detector, which for the

Measurement of the time-resolved intensity curve can be used. The arrangement of the light source and the detector can be specified with great precision or

be determined. The theoretical value for the ratio of

Time differences can be calculated with knowledge of the particle size, the particle velocity and the scattering angle 9 _S. Should those from the temporally resolved

Intensity curves determined values for the ratio of the time differences deviate significantly from the theoretical value for the ratio in question, probably a basic assumption for the determination of the particle size is not met, so that the values determined with these temporally resolved intensity gradients for the

Particle size and particle velocity are not

but should be discarded. The ratio of the time difference between a maximum of a reflection peak and the beginning or end of the particle peak on the one hand to the width of the particle peak on the other hand, or a quotient of these time differences depends solely on the scattering angle 9 _S , since the values for the particle size and the particle velocity cancel each other out at the ratio.

Assuming that the temporally resolved intensity gradients are each under one identical

Matching scattering angle 9 _S can be measured, each from the time resolved

Intensity curves determined ratios of

Time differences are compared with each other and should match. Otherwise, the values for particle size and particle velocity determined with these temporally resolved intensity curves should not be taken into account, but should also be discarded. For the comparison of the ratios of the time differences, it is not necessary to know or to the scattering angle 9 _S

determine as long as it is ensured that the

Scatter angle 9 _S for both time-resolved

Intensity gradients matches. The comparison of measured and from the temporally resolved

Intensity curves determined time differences can be performed numerically very quickly, without a comparison with a theoretical value and calculated as a function of the scattering angle 9 _S value is required. The invention also relates to a device for determining the size and the velocity of a particle with a light source, with two radiation detectors for detecting the scattered light scattered by the particle from the light source spaced in the particle flight direction on both sides of the light source symmetrical therewith to detect scattered light backscattered or backscattered in a magnitude matching scattering angle _S 9

are arranged, and with an evaluation device which is connectable to the radiation detectors to transmit data.

According to the invention, it is provided that the light source does not imitate coherent light. The light source may be, for example, a light-emitting diode (LED). The light source may also be formed of a plurality of LED's, which are arranged in a suitable manner. It is also possible that the light source emits coherent light, even if it has no greater importance for the implementation of the method according to the invention, whether the light source emits coherent or non-coherent light. To look for a large number of particles that are

If necessary, they can move in different directions, providing a rapid and reliable

To be able to carry out particle size is provided that the light source generates a light curtain.

Hereinafter, embodiments will be discussed in more detail, which are shown in the drawing. It shows:

Fig. 1 is a schematic representation of a measuring device and a particle illuminated by a light source as well as for a given scattering angle 9 _S

occurring courses of some excellent rays, FIG. 2 shows a schematic relationship between the spatial intensity distribution of a light beam of the light source falling on the particle and a temporal intensity distribution of the light source correlating therewith

measured scattered light,

3 shows a schematic representation of the two temporal intensity profiles as well as the information relevant for the evaluation of the light scattered by a particle in the scattering angle 9 _S , wherein the intensity profiles were measured with the two radiation detectors,

Fig. 4 is a schematic representation of the from

Intensity traces extracted information about two reflection peaks,

Fig. 5 shows an example of a measurement in which a proportion of the particle peaks caused by scattering within the

Particle was generated, does not match and the

Measurement results are discarded,

Fig. 6 shows an example of a measurement in which a proportion of the particle peaks caused by scattering within the

Particle was created, matches and the

Measurement results can be evaluated for a determination of the particle size

FIG. 7 shows the example shown in FIG. 6 for a measurement of two particle peaks, which are used for a further evaluation

were used, Fig. 8 is a schematic representation of individual ratios of time differences, starting from a first

Particle peak of the measurement shown in FIGS. 6 and 7 were determined, and

9 is a schematic representation according to FIG. 8 for the evaluation of a second particle peak of the measurement shown in FIGS. 6 and 7. In Fig. 1, a measuring device and the method according to the invention for determining the

Particle size relevant excellent rays in a scattering process in a scattering angle 9 _S shown. From a light source 1, a focused light beam 2 is incident on an opaque translucent particle 3, a milk droplet, which moves the light beam 2 across the light beam 2 through. The light beam 2 is outside at an interface 4 of the particle 3 to the surrounding medium

partially reflected. A portion of the light beam 2 penetrates into the opaque translucent particle 3. In the particle 3, minute dissolved fat droplets 5 each act as

point scattering centers that scatter the incident light beam 2 in all directions. Under a given scattering angle 9 _S are for the

Duration of passage of the particle 3 through the light beam 2 at the fat droplets 5 scattered shares 6 of

Stray light detected. The temporal intensity profile of this portion 6 of the scattered light scattered on the fat droplets 5 is decisive for the shape of the particle 3 or of the light beam 2 respectively illuminated Particle 3 dependent. This proportion 6 of

Scattered light is called a "particle peak".

At a certain point in time, the light beam 2 reflected at the interface 4 is deflected into the predetermined scattering angle _S 9. At this time, the at the

4 reflected reflection beam 7 scattered in addition to the particle peak in the direction of the scattering angle 9 _S , so that this reflected scattered light as

Reflection peak superimposed on the particle peak.

In the measuring device illustrated by way of example, two radiation detectors 8, 9 are spaced apart in the direction of flight from one another and opposite to the light source 1

arranged that both radiation detectors scatter the scattered light scattered by the particle 3 under a magnitude identical identical scattering angle 9 _S. Each of the two radiation detectors 8, 9

time-resolved intensity of the particle peak is identical for both radiation detectors 8, 9, since the

Evenly sprinkle grease droplets 5 in all directions as a point spray. The reflection beam 7 is, however, of the two radiation detectors 8, 9 to

recorded at different times, since initially in

Forward direction and then in the reverse direction relative to the direction of flight of the particle 3 the

geometric conditions for a reflection on the

Interface 4 of the particle 3 are met. In Fig. 2 is only schematically the relationship between a spatial intensity distribution of

incident light beam 2 and the temporal Intensity curve of the under the scattering angle 9 _S

demonstrated scattered light. An im

Essentially Gaussian intensity distribution of the incident light beam 2 leads to a likewise approximately Gaussian time profile of the

measured intensity of the scattered light. Such an intensity peak can be measured for all the above-described excellent beams. By the light beam 2 crossing particles 3 of the incident on the particle 3 light beam 2 is imaged in each radiation detector 8, 9, which by a

mathematical transformation can be described. The width b of the spatial intensity distribution of

incident light beam 2 corresponds to the width o of the time-resolved peak of the scattered light. The

Particle velocity v results from the

Quotients of the spatial width b and those

Time difference corresponding to the width o: v = b / o.

The width b and the width o can be determined, for example, by determining the half-width of the respective peaks. The spatial intensity distribution of the incident light beam 2 should therefore be determined in advance as precisely as possible.

In Fig. 3 are exemplary with the two

Radiation detectors 8, 9 measured temporally resolved intensity curves 10, 11 shown. It is

Representing the intensity of the Radiation detectors 8, 9 generated measured electrical signal S in mV over time t in ps. In both

Intensity curves 10, 11 is a coincident

Particle 12, ie, a proportion of the scattered light, which was generated by scattering within the particle 3. In addition, a reflection peak 13, 14 is superimposed on each individual intensity profile 10, 11. The width b _{R of} the reflection peaks 13, 14 correlates with the spatial intensity distribution of the light source 1 and the

Velocity v of the particle 3. The time interval At _{R of} the reflection peaks 13, 14 depends on the size d of the particle 3 and on its velocity v. The width b _{T of} the particle peak 12 also depends on the size d and the velocity v of the particle 3. From the

measured intensity curves 10, 11, both the speed v and the size d of the particle 3 can be determined.

In FIG. 4, the intensities of the two reflection peaks 13, 14 are shown isolated from the intensity profiles 10, 11 according to FIG. 3, in that the superimposed particle peaks 12 have been taken out. By a preceding

In comparison, it was found that the particle peaks 12 of the two intensity profiles 10, 11 in the context of

Accuracy of measurement match. By means of a numerical adaptation, the width b _{R of} the two reflection peaks 13, 14 and the time interval At _{R of} the reflection peaks 13, 14 can be determined. In order to determine the size d of the particle 3 from the two measured intensity profiles 10, 11, first the two particle peaks 12 of the intensity profiles 10, 11 are determined compared and with sufficient agreement of the

Particle peaks 12, the intensity curves 10, 11 used for the evaluation, but otherwise discarded. The two reflection peaks 13, 14 are filtered out and from the width b _{R of} the reflection peaks 13, 14 is the

Velocity v of the particle 3 is determined. From the time interval At _{R of} the reflection peaks 13, 14, which depends both on the velocity v and on the size d of the particle 3, the size d of the particle 3 can then be calculated with knowledge of the previously determined velocity v. Since also the width b _{R of} the particle peaks 12 of the quotient of the size d and the

Velocity v of the particle 3, this information from the particle peaks 12 can be used to control or to improve the accuracy of the determined size de.

To illustrate, two intensity curves 10, 11 are shown superimposed over time in FIG. 5, which differ significantly from one another. These measured values are discarded because the respective particle peaks 12 clearly differ and the intensity profiles 10, 11

obviously can not come from the same particle 3.

In contrast, the particle peaks 12 of the two intensity profiles 10, 11 shown in FIG. 6 coincide almost identically, so that the two intensity profiles 10, 11 originate from the same particle 3 and the respective reflection peaks 13, 14 can be used for the evaluation. FIGS. 7, 8 and 9 schematically show individual variables which can be determined and taken into account for a further evaluation. The two intensity profiles 10 and 11 have a matching width, or time difference Δtb, between a start 15 and an end 16 of the particle peak 12 in a region which is significantly different from that of FIG

Signal noise of the time-resolved intensity curves 10 and 11 differs. The time difference At _b i corresponds to the quotient d / v of d here

Particle size and particle velocity v.

Since the time difference At _b i exclusively from the

Particle properties size d and speed v depends and both temporally resolved intensity gradients 10, 11 are assigned to the same particle 3, the two must each determined from an intensity curve 10 or 11 time differences At _b i within the measurement accuracy

to match. If this is not the case, a basic assumption would not apply or the two intensity profiles 10 and 11 can not originate from the same particle 3, so that these two intensity profiles 10 and 11 should not be used for further evaluation.

If the determined time differences At _b i agree, as is the case in the measurement illustrated in FIGS. 6 to 9, further evaluations or checks can be carried out. For this purpose, for example, based on the intensity curve 10, the time differences Ati and At2 between the reflection peak 13 and the beginning 15, or the end 16 of the particle peak 12 (FIG. 8).

be determined. In the same way, the time differences At ₃ and At ₄ between the reflection peak 14 and the beginning 15, or the end 16 of the particle peak 12 (FIG. 9) can be determined on the basis of the intensity profile 11.

For these time differences, the following relationships apply:

and

The time differences Ati to At ₄ depend exclusively on the particle size d, on the particle velocity v and on the scattering angle 9 _s . Using pre-determined values for the particle size d and the

Particle velocity v and in knowledge of the

Scattering angle 9 _S , the individual time differences Ati to At _{4 can} also be calculated theoretically without affecting the

To access measured values. The from the readings

determined time differences Ati to At ₄ can then with the theoretically calculated time differences Ati to At ₄

be compared. Should the determined time differences do not agree with the calculated time differences, the measurements should be discarded.

If the two radiation detectors 8 and 9 are arranged symmetrically and the two intensity profiles are measured with an identical coincident scattering angle 9 _S , ratios of the individual time differences can be determined, which are then exclusively determined by the

depend on predetermined or determined with high precision scattering angle 9 _S. For the symmetrical arrangement of the radiation detectors 8 and 9 and then identical identical scattering angle 9 _S apply the following

Relationships for the ratios of time differences:

In this case, η denotes a ratio of two time differences. The abbreviations "Detl" and "Det2" indicate the reference to the respective temporally resolved ones

Intensity curves 10 and 11, which with the

Radiation detectors 8 ("Detl") and 9 ("Det2") were measured. The individual ratios n ⁺ , η ^~ and n should agree for each measured intensity profile 10 and 11. Otherwise, the respective intensity profiles 10, 11 should be discarded and not used for the determination of the

Particle size d or particle velocity v

be used.

For a non-symmetrical arrangement of

Radiation detectors 8 and 9 and then not one

Matching scattering angle 9 _S , under which the two temporally resolved intensity curves 10, 11 are measured, also comparable time differences and ratios, or quotients of time differences can be determined. The formulas applicable to this case are different from the above relationships.

Claims

Patent claims

1. Method for determining the size of an opaque

Translucent particle (3), wherein the particle (3) is illuminated with light from a light source (1), wherein with a radiation detector (8) below a predetermined

Scattering angle 9 _{S is} a time-resolved intensity profile (10) of scattered on the particle (3) light of the light source (1) is measured, wherein in the intensity curve

Characteristic scattered light peaks are determined and wherein based on a time difference between two scattered light peaks, the size of the particle (3) is determined, thereby

characterized in that of a particle (3)

scattered scattered light two temporally resolved

Intensity curves (10, 11) are measured such that the two intensity profiles (10, 11) by a comparison of a particle peak (12), which was generated by scattering within the particle, are assigned to each other, that in each intensity profile (10, 11) respectively a reflection peak (13, 14) generated by reflection at an interface of the particle is determined and that a

Time difference between the two reflection peaks (13, 14) is determined as a measure of the size d of the particle (3).

2. The method according to claim 1, characterized in that spaced either with two in the particle flight direction and on both sides of the light source (1) symmetrically

arranged radiation detectors (8, 9) each have a first and a second temporally resolved intensity profile (10, 11) of the particle (3) scattered light of

Light source (1) is measured, or that the particle (3) with two particle flight direction spaced and on both sides of the radiation detector symmetrically arranged light sources (1) is illuminated and with a

Radiation detector (8) measured time resolved

Intensity profile in a first intensity profile (10) caused by the first light source (1) and in a second intensity profile (11) caused by the second light source is decomposed.

3. The method according to claim 1 or claim 2, characterized in that a spatial intensity distribution of the light source (1) along an optical axis determined and with a temporal intensity distribution of

Reflection peaks (13, 14) in the intensity profile (10, 11) is compared.

4. The method according to claim 3, characterized in that only for those particles (3) a size determination is performed, in which the reflection peak (13, 14) with the spatial intensity distribution of the

Light source (1) correlating temporal

Has intensity distribution.

5. The method according to claim 3 or claim 4, characterized in that from a width of the temporal Intensity distribution of the reflection peak (13, 14), the velocity v of the particle (3) is determined.

6. The method according to any one of the preceding claims, characterized in that in each case a width Atbi of a particle peak (12) from the temporally resolved

Intensitätsverläufen (10, 11) is determined and only for those particles (3) a sizing is performed, in which the width At _b i determined from the two temporally resolved intensity gradients (10, 11)

Particle peaks (12) matches.

7. The method according to any one of the preceding claims, characterized in that in each case a beginning (15) and / or an end (16) of the temporally resolved

Intensity curves (10, 11) certain particle peaks (12) is determined and a ratio n ⁺ , η ^~ one

Time difference between a maximum of a reflection peak (13, 14) and the beginning (15) or the end (16) of the

Particle peaks (12) to the width At _b i of the particle peak

(12) is determined, and that the determined ratio n ⁺ , η ^~ the time difference is compared with a theoretically determined value for the ratio n ⁺ , η ^~ .

8. The method according to claim 7, characterized in that the temporally resolved intensity profiles (10, 11) are each measured under an identical coincident scattering angle 9 _S and each of the temporally

resolved intensity curves (10, 11) determined

Ratios n ⁺ , η ^~ and n ^{* of} the time differences are compared with each other.

9. A device for determining the size of a particle (3) with a light source (1), comprising two radiation detectors (8, 9) for detecting the scattered light of the light source (1) scattered by the particle (3)

Particle flight direction spaced on both sides of the

Light source (1) symmetrical to this for detecting in a magnitude matching scattering angle 9 _S

forward scattered or backscattered scattered light

are arranged, and with an evaluation device which is connectable to transmit data to the radiation detector.

10. The device according to claim 9, characterized in that the light source (1) does not emit coherent light.

11. The device according to claim 10, characterized in that the light source (1) comprises an LED.

12. Device according to one of claims 9 to 11, characterized in that the light source (13) has a

Light curtain generated.