SU805126A1 - Method of particle dimensions determination - Google Patents

Description

The invention relates to optical measurements and can be used to control the size and concentration of particles, in particular in the chemical-photographic industry ³ for controlling the physical maturation of the emulsion.

Known methods for determining particle sizes by light scattering β].

However, in the practical implementation of these methods, a large error in the measurement results is made by contamination of the cell windows.

The closest in technical essence to the proposed one is the 15th method of determining particle sizes, which consists in passing two beams of light through a cuvette at equal angles to the plane of the input window and comparing the intensities of the first 20 beams directly passing through the cuvette and emerging at a certain angle to the plane the exit window and the beam formed during the scattering of the second beam in a given volume of the cell and leaving the cell at the same angle to the plane of the output window as the first beam [2].

The disadvantage of this method is that in order to determine the particles т 30 particles from the turbidity data obtained by this method, it is necessary to know either the concentration of particles or to make measurements at an unknown but identical for particles of all sizes of concentrations.

The purpose of the invention is the exclusion of the dependence of the measurement result on the concentration of particles.

The goal is achieved by passing a third ray of light through the entrance window of the cuvette at the same angle to the plane of the entrance window as the first two rays and comparing the intensities of the beam generated by the scattering of the second ray and the beam formed by the scattering of the third ray in a given volume cell, in which it is scattered at the same angle as the beam scattered by the second beam, and leaves the cell at the same angle to the plane of the window as the directly transmitted beam, and the optical paths of all beams in the cell are different. ''

The drawing shows a diagram of a device for implementing the proposed method.

The device consists of a laser 1, pyramid 2 with mirrored grades 805126, mirrors 3-5, input and output windows 6 and 7, beams 8-10, given volumes 11 and 12 _{f of} light traps 13 and 14, lenses 15-17, photodetectors 18-20, blocks 21 and 22 measuring relations, recording devices 23 and 24.

The device operates as follows.

The laser beam 1 is split into three beams by a pyramid 2 with mirror faces. These rays mirrors 3-5 are sent to the input window 6 of the cell. The entrance window of the cuvette is oriented so that all three rays intersect the plane of the window at the same angle. The first beam 8 exits through the exit window 7 of the cuvette and is focused by the lens 17 onto the photodetector 20. A beam of light generated by the scattering of the second beam 9 in a given volume 12, leaving the window 7 is focused by the lens 16 on the photodetector 19. A beam of light generated by the scattering of the third beam 10 in a given volume 11, which emerges through the window 7, is focused by the lens 15 on the photodetector 18. The light traps 13 and 14 are used to absorb the first and second beam whose. The signals from the photodetectors 19 and 20 are fed to the signal ratio measuring unit 22, the Of value of which is counted by the device 30 ’24. The signals from the photodetectors 18 and 19 are fed to the signal ratio measuring unit 21, the 8g value of which is measured by the device 23.

The intensities of the beams emerging from the cell are determined by the expressions ναν '^ τ, τ ,.

(ί) to ^r «e 1 ^

V- is the volume from which * light scattered by the third ray is removed;

Slj is the solid angle at which light scattered by the second ray is received;

- the solid angle at which light is received is scattered. third ray;

L is the path traveled by the first ¹ beam in the cell;

L> “the path traveled by the second beam in the cell from the input window to the scattering point;

Lg is the path traveled by a beam of light scattered by a second ray to exit the cell;

Lj is the path traversed by the third ray in the cuvette from the entrance window to the scattering point:

L is the path 'traveled by a beam of light scattered by a third ray to exit the cell;

a, b, c - constants that determine the distribution of the source intensity over the rays and the loss of light in optics;

. - transmission of the input window of the cell;

T - transmission output window ² cells.

Using equalities (I), (2), (3), we can write expressions for the measured intensity ratios. ^I 2 * ' ^bI o ^e ' · * XpfrH (»·, Θ1

V ₂ pl

- the intensity of the first beam that directly passed the cell;

is the intensity of the beam, which is obvious by the second beam, coming from the cell through the new window;

- the intensity of the beam yannoy third beam, coming from the cell through the exit window;

- attenuation coefficient of the measured medium;

η is the concentration of particles (the number of particles per unit volume) is the cross section for attenuation of a particle of size g;

scattering cross section of a particle of size g;

particle scattering indicatrix of dimension r at an angle 4>, the volume from which the light scattered by the second beam is removed;

(2) through

Z3 (r)

Ep (r) i (g, Q) ^V 2 * total higher output 45

SO

1 _e s * - de ^p . (5)

Here the dimensionless constant J is the dimensionless constant / dimensionless constant (6),

I * ⁵

- the constant is not equal to zero, due to the choice of the paths of the second and third rays (7) 'depend on

Relations and U _{2 are} not contamination of the cell windows, since the transmission of the cell windows is equal for all three beams and they are reduced when measuring the ratio.

Using equations (4) and (5), we can express the concentration-independent quantity x ”in terms of the experimentally determined quantities U ₄ and U ₂ and the constants y - * *? - (v LI

The constants I and L are uniquely determined by the dimensions of the cell and are calculated by equations (6) and (7), where C, L ₂ , Lj, L · ', are measured directly. The constant d is determined * in a known way * from equation (5) when measuring the quantity U ^, for suspension of particles with a reference attenuation coefficient p. After this, the constant q is determined from equation (4) while measuring quantities and § ^ 2 | (g.f). For example, it may be a suspension of Rayleigh, non-absorbing particles, for which ξΡ) = 1, and the indicatrix, scattering is known.

Indeed, from equations (4) and (5) we find

Since on the right-hand side of this equality the quantity 5 ^ K | (r, Q) is known, the constants d and a are determined, and U and U _{2 are} measured, it uniquely determines the constant q.

Thus, determined by equality (8) through experimentally measured values of 0 ^ and II, the value of X can serve as a measure of the particle size, independent of their concentration. In this case, the independence of the measurement result from contamination, the windows of the cell.

The proposed method significantly increases the accuracy of measuring the size of dispersed particles and reduces the cost of cleaning the windows of the cell from contamination and thereby increases the economic efficiency of using particle size measuring devices in a production environment.

Claims (2)

The invention relates to optical measurements and can be used to control the size and concentration of particles, in particular in the chemical and photographic industry to control the physical maturation of the emulsion. Methods are known for determining particle sizes from light scattering p. However, in the practical implementation of these methods, the measurement results are heavily erroneous due to the contamination of the window windows. The closest in technical essence to the present invention is a method of determining particle sizes, which consists in passing two equal beams of light through a cuvette at equal angles to the plane of the entrance window and comparing the intensities of the first beam passing directly through the cuvette the plane of the exit window and the beam that forms when the second beam is scattered in a given volume of the cuvette and exits the cell at the same angle to the plane of the output window as the first beam .2. The disadvantage of this method is that to determine the frequency of the turbidity data obtained by this method, one needs to know either the concentration of particles or to make measurements with an unknown, but the same for particles of all sizes of concentrates. The purpose of the invention is to eliminate the dependence of the result of the measurements on the concentration of particles. The goal is achieved by passing the third beam of light at the entrance window of the cuvette at the same angle to the plane of the input window as the first two beams and comparing the intensity of the beam generated by scattering the second beam and the beam formed by scattering the third beam in a given volume The cell in which it is scattered at the same angle as the beam scattered by the second beam and exits the cell at the same angle to the window plane as the directly transmitted beam, and the optical paths of all the beams in the cell are different. The drawing shows a diagram of the device for implementing the proposed method. The device consists of laser 1, pyram ady 2 with mirror edges, mirrors 3-5, input and output windows 6 and 7, rays 8-10, given volumes 11 and 12, light traps 13 and 14, lenses 15-17, photodetectors 18 -20, blocks 21 and 2 of relationship measurement, recording devices 23 n 24. The device operates as follows. The laser beam 1 is split into three beams with pyramid 2 with specular edges. These rays by mirrors 3-5 are directed to the entrance window b of the cuvette, the input window of the cuvette is oriented so that all three beams intersect the window plane at the same angle. The first beam 8 emerges through the exit window 7 of the cuvette and is focused by the lens 17 on the photodetector 20. A beam of light, formed by scattering the second beam 9 in a given volume 12, coming through window 7, is focused by the lens 16 on the photodetector 19. A beam of light, which forms 1411 when scattering the third beam 1 in a given volume 11, emerged through the window 7, is focused by the lens 15 "and the photodetector 18 Light traps 13 and 14 serve to absorb the first and second rays. The signal from the photodetectors 19 and 20 pits to the unit 22 for measuring the ratio of signals, value and. which is measured by the device 24. The signals from the photoprinter IS and 19 are fed to the unit 21 of the measurement of the ratio of signals, the value of Uj which is measured by the device 2 The intensities of the beams coming out of the cell are defined by the expressions .Q. (v, {., 9). U la - bV i; Cioe 4p ((r, e) v, tte I where 1, the intensity of the first beam directly passing through the cuvette; the intensity of the beam scattered by the {% F beam emitted from the cuvette through the exit window ; 1 is the intensity of the beam, recovered by the third beam, coming out of the cuvette through the exit window, the attenuation coefficient of the measured medium, n is the concentration of particles (the number of particles per unit volume) (51 eC) is the section of attenuation of a particle of size g; p (r) is the cross section for the scattering of a particle 1 with the size r; Mr, Q) is the indicatrix of the scattering of particles of size g at an angle -fr, Vj is the volume from which the light scattered by the second beam is captured; the volume from which the light scattered by the third uchy is being shot; the solid angle in which the light scattered by the second beam is received; the solid angle in which the light scattered by the third ray is received; the path traversed by the first ray in the cell is the path traversed by the second linac. the beam in the cuvette from the entrance window to the scattering point; the path traversed by the beam scattered by the second ray of light to exit the cuvette, the path traversed by the third, in the cuvette from the entrance window to the scattering point: the path traversed by the beam scattered by the third ray of light to exit the cuvette; the constants determining the distribution of the source intensity by rays and the loss of light in optics; passing the cuvette entrance window; passing the cuvette exit window. Equality (1), (2), (3) contains expressions for intensity measurements) i (r, 9Wi e e4 |%, -t, V 5 ® 2 g 2-Ц-з 4 -., | g .- (r,).,. -, - - dimensionless {Ui Ua-U -L ML2) i а is constant b аЯа (уу2 is non-size by POST; Itbg b is non-size “V l4 4 3 by constant ( 6) ,;, .u; -constant is not equal to zero, due to the choice of the paths of the second and third rays (7N and and U do not depend on the windows of the cuvette, since the passages of the windows of the cuvette are equal for all three beams and when measuring the ratio they are reduced Using equations (k) and (5), one can express the value of X Saif) {ne), independent of the concentration, through the experiment The values of and and 2 and the constants X-5Shl (r t -.. U) are determined flaxally (Constant ° C and L are unambiguously determined by the dimensions of the cell and are calculated by equations (6) and (7), where L., -, 1-2, LL are measured directly. The constant d is determined in a known manner from Equation (5) when measuring the value of u2 for suspended particles with a reference attenuation coefficient - (i. After this, the constant I is determined from equations (4) while simultaneously measuring the magnitudes and and suspension of particles with the reference value of the magnitude (g.-b;) For example, this could be the suspension of the Rayluyevsky, aepogl -rotating particles, for which () 1, and the scattering indicatrix known. Indeed, from equations (k) and (5) we find also “O. y-tp (rV. 1 (g ШS. -} fr erf-fo -i4 2e (and 29 {v-) d l d. Since on the right-hand side of this equality the value 5 4 1 (g, Q) is known on, constant o1 and cf are defined and a and uj are measured, it uniquely determines the constant q. Thus, defined by equality (8) through the magnitude U and II measured experimentally, the value of X can serve as a measure of the size of a part independent of their concentration. This preserves the independence of the measurement result from contamination, the windows of the cuvette. The proposed method significantly improves the accuracy of measuring the sizes of dispersed particles and reduces costs of cleaning the windows of the cuvette from contamination, and thus the cost-effectiveness of using particle size measurement devices under production conditions. Invention The method for determining the size of particles, means that two beams pass through the cell under equal angles to the input oxide plane light and compare the intensity of the first beam, directly passing through the cuvette and the output of a beam under some 1: B4 angle to the plane of the output oxide, and the beam formed during the scattering of the second beam in The volume of the cell and the exit window leaving the cell under the same angle to the plane of the output window as the first beam, characterized in that, for the purpose of determining the law of dependence of the measurement result on particle concentration, the third Jty4 light passes under the same window The first two beams fit the plane of the entrance window and compare the intensity of the beam formed during the scattering of the second beam and the beam forming the state when the third beam is scattered in a given volume of the cell in which it is scattered. as a beam scattered w beam, and comes out of the cuvette at the same angle to the window plane as the direct beam, with the optical paths of all the beams in the cuvette being different. Sources of information taken into account in the examination 1.Coll rns E. A., Davidson A., Daniels S.А. Rewiew of Common Me-thods of Particle Size Heaterment I.of Paint Technology 47, 604, 1975, p, 33-41. 2.Patent of Great Britain No. 1414038 6 0) N 21/00, published. 1970 (prototype).