JP5498308B2 - Light scattering intensity measurement method - Google Patents

Description

The present invention relates to a method for measuring light scattering intensity.

  The dynamic light scattering method is now an established technology, and particle size measuring devices for fine particles using this method are widely used (see, for example, Non-Patent Document 1). Advantages include fewer required parameters, non-destructive measurement, and easy handling. This dynamic light scattering method realizes high-accuracy measurement in an environment where a single scattering theory, that is, a theory that once scattered light can be detected without being scattered again by other fine particles can be applied. For example, in a dilute particle-containing solution having fine particles of 0.01% by mass or less, a measurement value relating to the particle diameter can be obtained with high accuracy. However, on the other hand, depending on the particle size and refractive index, if the effect of the phenomenon that the concentration of fine particles is high and multiple scattering, that is, once scattered light hits other fine particles and is scattered again, is not negligible, The dynamic characteristics of fine particles required by a measuring instrument on the premise of single scattering theory are different from actual ones.

FIG. 6 is an explanatory diagram modeling and showing the difference in the light scattering phenomenon as described above depending on the particle concentration. In general, in a dilute system, it can be assumed that the particle S ₁ can freely perform Brownian motion and the light L is scattered only once (see FIG. 6A). On the other hand, in the dense system, since one or more scatterings are mixed (see FIG. 6B), in the measurement based on the single scattering, the phenomenon does not match the theory and the actual measurement, and the measurement cannot be performed.

BERNE, B.J., `` DYNAMIC LIGHT SCATTERING WITH APPLICATION TO CHEMISTRY, BIOLOGY, AND PHYSICS '' JOHNWILEY, 1976

  In contrast, the present inventors have previously developed a dynamic light scattering measurement apparatus and a light scattering intensity measurement method that enable measurement of particle diameter with high accuracy in a dispersion containing fine particles at a high concentration (special characteristics). Application 2009-159307). This is a dynamic light scattering measurement apparatus having a low coherence light source and incorporating a Mach-Zehnder interferometer. This enables accurate particle size measurement in a dispersion containing fine particles at a high concentration. Furthermore, the present inventors have extracted a specific problem in the measurement technique using such a low-coherence light source, solved this, and made a dynamic light scattering measurement that enables a more accurate and simple measurement operation. Research and development on the device and light scattering intensity measurement method were advanced. In addition, we considered that the technology can be applied to an apparatus incorporating a Michelson interferometer using a low-coherence light source, and considered providing it as a highly versatile technology.

Therefore, the present invention provides a light scattering intensity using a low-coherence light source that enables measurement of the average particle size and distribution of fine particles with high accuracy and simple operation even in a dispersion containing fine particles at a high concentration. It is an object to provide a measurement method .

The above problem has been solved by the following means.
(1) An irradiation condensing unit that uses a Mach-Zehnder type interferometer having a low coherence light source, irradiates light to the fine particles in the dispersion in which the fine particles are dispersed , and collects backscattered light . 1 is a light scattering intensity measurement method in which the end of one optical fiber is inserted into a dispersion to measure the dynamic characteristics of fine particles. A Mach- Zehnder interferometer uses light from a low- coherence light source as a first light. branches at the coupler, one of the light branching and reference light, the other light is a scattered light obtained by being light collector is irradiated to the fine particle dispersion through the irradiation condensing unit, the the reference light scattering Light is coupled by a second optical coupler, the light from the low coherence light source is branched by the first optical coupler, and the second to fourth light is coupled to the second optical coupler via the phase converter. The first optical coupler is guided by a fiber and used as a reference light. The irradiating light branched off at-is guided to the circulator by the fifth optical fiber, the irradiating light from the circulator is guided to the dispersion liquid by the first optical fiber, and the scattered light from the dispersion liquid is guided to the circulator by the first optical fiber. The scattered light from the circulator is guided by Iva that guides the scattered light to the second optical coupler through the sixth optical fiber, and the scattered light is guided from the circulator to the second optical coupler by the sixth optical fiber. Method.
( 2 ) The method for measuring light scattering intensity according to (1) , wherein the coherence length of the low- coherence light source is 0.1 to 100 μm.
( 3 ) The method for measuring light scattering intensity according to (1) or (2) , wherein optical path length decomposition of scattered light is possible and particle size and / or particle size distribution can be measured by Brownian motion.

The light scattering intensity measurement method using the low coherence light source of the present invention enables measurement of the average particle size and distribution of fine particles with high accuracy and simple operation even in a dispersion containing fine particles at a high concentration. Become.

It is an apparatus block diagram which shows roughly one Embodiment of the dynamic light-scattering measuring apparatus of this invention provided with the Mach-Zehnder type interferometer. It is a principal part expanded sectional view which showed typically the periphery of the irradiation condensing part of the apparatus shown in FIG. It is a block diagram which shows roughly one Embodiment of the dynamic light-scattering measuring apparatus of this invention provided with the Michelson type interferometer. It is sectional drawing which shows an example of the cell structure applicable to the apparatus of this invention. It is sectional drawing which shows another example of the cell structure applicable to the apparatus of this invention. It is a graph of the particle size distribution which shows the analysis result of Example 2, and the analysis result measured using the collimator lens. FIG. 4 is an explanatory diagram modeling light scattering phenomena in a dilute dispersion having a low concentration of fine particles and a concentrated dispersion having a high concentration of fine particles, respectively. It is sectional drawing which shows the method (conventional example) which irradiates light to a sample cell through a lens, and condenses scattered light.

Hereinafter, preferred embodiments of the light scattering intensity measurement method of the present invention will be described in detail with reference to the drawings. As such an embodiment, a dynamic light scattering measurement apparatus using a Mach-Zehnder interferometer (first embodiment) and a dynamic light scattering measurement apparatus using a Michelson interferometer will be described separately. Both form a single inventive concept with the same or corresponding technical features. Note that this description is not construed as being limited by the description of this embodiment.

[First Embodiment]
FIG. 1a is a configuration diagram schematically showing an embodiment of a dynamic light scattering measurement apparatus of the present invention equipped with a Mach-Zehnder interferometer. FIG. 1 b is an enlarged cross-sectional view of a main part schematically showing the periphery of the irradiation condensing part. In the present embodiment, a low coherence light source 1 made of SLD (Super Luminescent Diode) is used as the light source. The optical system constituting the Mach-Zehnder interferometer in this embodiment includes a first optical coupler 2 that is an optical branching mechanism, optical fibers F _{2 to} F ₇ , and a collimator that is a coupler between the optical fiber and the air. lens 8a, 8b, the phase modulator 10 directs the light from the optical fiber F ₅ on the optical fiber F _1, circulator 3 is an optical path converter for guiding light from the optical fiber F ₁ to the optical fiber F _6, and the light It is comprised by the 2nd optical coupler 4 which is a coupling mechanism. Furthermore, an optical fiber F ₇ is connected to the optical coupler 4, a detector 5 is connected to the optical fiber F ₇ , and an A / D board 6 that is an electric signal reading unit is connected via a BNC cable 6 a. And connected to the PC 7 for data processing and analysis. The dispersion liquid (measurement sample) S is obtained by dispersing the fine particles S ₁ in the medium S ₂ .

As shown the enlarged sectional view in FIG. 1 (b), the irradiation condensing section for condensing the scattered light is irradiated to the microparticles S ₁ dispersed in the dispersion liquid S is irradiated condensing the optical fiber F ₁ Part (optical fiber end) F _1a is preferred. Face end F _1a of the optical fiber F _1, for example a core 23, cladding 22, so that each of the irradiated condensing section end surface (end surface optical fiber) F _1b is substantially coplanar, where the optical fiber F ₁ and example cut May be the end face. Furthermore, the aim of flights measurement, may comprise a housing to be able to fix the optical fiber F _1.

The end F _1a of the optical fiber F ₁ is inserted at a necessary distance from the bottom and wall surface of the cell 11 so as not to take in the bottom and wall surface of the cell and the specific convection and the adsorption effect on the wall surface. is necessary. Further, the end face F _1b of the optical fiber F ₁ is separated from the bottom and wall surface of the cell by 50 μm or more, preferably by 200 μm or more, and more preferably by 1000 μm or more.

The wavelength of the SLD of the low coherence light source 1 employed in the present embodiment is not particularly limited, but is preferably 0.125 to 2 μm, and more preferably 0.250 to 1.5 μm, for example. Speaking of the coherence length, for example, 0.1 to 100 μm is preferable, and 1 to 50 μm is more preferable. For the optical coupler 2, it is preferable that the branching ratio can be changed according to the object to be measured.
In the middle of the optical path through which one of the divided lights is guided, a phase modulation unit including collimator lenses 8a and 8b and a modulator 10 is configured. As shown in the figure, the phase modulator may emit light into space to perform modulation, or may modulate in an optical fiber. Alternatively, such a phase modulation unit is configured in the same manner as the circulator 3 and the optical fiber F ₁ provided in the middle of the optical path through which the other light is guided, and includes a mirror that can vibrate instead of the dispersion liquid S. It is also possible to modulate the light so as to give an arbitrary phase. Furthermore, it is possible to adjust the amount of light by interposing an attenuator between the optical fiber F ₃ and the optical fiber F ₄ if necessary. The A / D board 6 and the PC 7 can be replaced with a spectrum analyzer or the like. As the circulator 3, a 1: 1 optical coupler can be used. For each of the above components, the optical coupler 4 and the detector 5, it is possible to adopt commercially available products having necessary specifications.

Below, the optical path of the reference light and scattered light (measurement light) in this embodiment is demonstrated.
(Reference light)
The light of the low coherence light source 1 propagates through the optical fiber F ₂ , enters the optical coupler 2, and is split into two lights by the first optical coupler 2. One light split by the optical coupler 2 passes through the optical fiber F ₃ , is collimated by the collimator lens 8 a, passes through the phase modulator 10, enters the optical fiber F ₄ by the collimator lens 8 b, and enters the optical coupler. 4 is reached. This light is the reference light in this embodiment. From the first optical coupler 2 to the second optical coupler 4, the reference light has an optical path length d _ref that is fixed to a predetermined value.

(Scattered light)
In contrast, the other of the lights divided by the first optical coupler 2 is passed through the optical fiber F ₅ through the optical fiber F ₁ by the circulator 3, from the end portion F _1a of the optical fiber F ₁ to the dispersion S Incident light L ₁ is incident. Resulting in backscattered light is incident again end F _1a of the optical fiber F ₁ as shown scattered light L _2, through the optical fiber F _1, it passes through the optical fiber F ₆ by circulator 3, Reach the optical coupler 4. This light is the scattered light in this embodiment. The optical path length d ₁ from the first optical coupler 2 to the location where scattering occurs in the dispersion S and the optical path length d ₂ from the location where scattering occurs in the dispersion S to the second optical coupler 4 From the first optical coupler 2 to the second optical coupler 4, the scattered light has an optical path length d _sca = d ₁ + d ₂ . Therefore, the optical path length d _sca includes a reciprocating distance from the interface P ₁ to the scattering position P ₂ . Further, due to the behavior of the fine particles S ₁ that freely move in Brownian motion, the intensity of the scattered light has temporal fluctuation fluctuations.

Therefore, in consideration of the phase modulation adjusted by the phase modulator 10, the backscattered light from the fine particle S _{1 at the} position having the specific optical path length d _sca corresponding to the optical path length d _ref of the reference light is detected by the detector 5. It can be measured as the light intensity. Since the measured light intensity has fluctuations with time as described above, the diffusion coefficient indicating the Brownian motion speed and the particle size distribution of the fine particles can be obtained by obtaining the autocorrelation function. Therefore, once the distance between the collimator lenses 8a and 8b is moved to adjust the optical path length of the reference light, the end of the optical fiber F ₁ can be replaced even if the cell 11 containing the dispersion liquid S to be measured is replaced. Since F _1a comes into contact with the dispersion S, it is possible to measure the fine particles S _{1 at} the same position having the same optical path length d _sca with high accuracy.

Hereinafter, an embodiment of a dynamic light scattering measurement apparatus as a reference example provided with a Michelson interferometer will be described in detail with reference to the drawings. FIG. 2 shows a schematic configuration diagram.

The optical system constituting the Michelson interferometer includes an optical coupler 12 that is an optical branching mechanism, optical fibers F ₁ , F ₈ , F ₉ , F ₁₀ , a reference light processing unit 13 (a reference light mirror 13 b, a piezoelectric drive). It comprises a device 13a) and a detector 14. In the data processing, data processing and analysis are performed using the A / D board 6 and the PC 7 as in the Mach-Zehnder type described above. About each of the above each component, it is possible to employ | adopt the commercial item provided with required specification.

Below, the optical path of the reference light and measurement light (scattered light) in this embodiment is demonstrated.
(Reference light)
The light from the low-coherence light source 1 propagates through the optical fiber F ₈ , enters the optical coupler 12, and is split into two lights by the optical coupler 12. One light split by the optical coupler 12 passes through the optical fiber F ₉ and is reflected by the optical path length arbitrarily changed by the reference light mirror 13b. At this time, modulation is applied by vibrating the reference light mirror 13b by the piezo drive device 13a. The reflected light from the reference light mirror 13b again enter the optical fiber F _9, reach the detector 14 via the optical coupler 12 and the optical fiber F _10. This light is the reference light in this embodiment.

(Scattered light)
In contrast, the other of the lights divided by the optical coupler 12 through the optical fiber F _1, is incident from the end F _1a of the optical fiber F ₁ to the dispersion S. As a result the backscattered light generated by the incident again on the end portion F _1a of the optical fiber F _1, passes through the optical fiber F _1, passes through the optical fiber F ₁₀ via the optical coupler 12, reaching the detector 14. This light is the scattered light in this embodiment. The processing of the reference light and scattered light incident on the detector 14 is the same as in the case of the Mach-Zehnder interferometer described above. Therefore, the backscattered light from the fine particles S _{1 at the} position having the specific optical path length d s _′ corresponding to the optical path length d _{ref ′ of} the reference light adjusted by the reference light mirror 13 is detected by the detector 14. Can be measured as Therefore, once the optical path length is adjusted by the reference light mirror 13, the end F _1a of the optical fiber F ₁ is in contact with the dispersion S even if the cell 11 containing the dispersion S to be measured is replaced. Therefore, it is possible to measure with high accuracy similarly for the fine particles S _{1 at} positions having the same optical path length d _{sca ′} . Other preferred forms are the same as those in the first embodiment.

Use one of the above-described dynamic light scattering measuring apparatus, the light scattering intensity measuring method of the present invention for measuring the dynamic characteristics of the dispersion particles S ₁ dispersed in S is in particulate S ₁ light The irradiation condensing part which irradiates and condenses backscattered light is inserted in the dispersion liquid S, and it can measure, and it can measure more simply and with high precision. The dynamic characteristics of the fine particles are characteristics specified by the Brownian motion in the fine particle dispersion, and include the particle size, distribution thereof, and the like. The optical path length decomposition of light scattered light is a function of detecting light scattered by a specific optical path length from scattered light generated by a sample. More specifically, single scattered light is a function for distinguishing between a region having a short main optical path length and multiple scattered light being a region having a long main optical path length. In addition, it is a function capable of distinguishing between scattered light generated in the vicinity of the cell / dispersion liquid or fiber end face / dispersion interface and scattered light generated in a deep part away from the interface.

3 and 4 show examples of various cells suitable for the present invention in cross-sectional views.
As shown in the sectional view of FIG. 3, the cell 11 having a structure in which the irradiation condensing part F _1a of the optical fiber F ₁ is inserted into the dispersion S together with the viscometer and the thermometer 20 is suitable. is there. In order to make it possible to measure the particle size and the particle size distribution by the Brownian motion, since the Brownian motion changes depending on the temperature, it is essential to measure the exact temperature at the same time. Therefore, by inserting the irradiation condensing part (end part) F _1a of the optical fiber F ₁ into the dispersion liquid S together with the thermometer 20, the behavior and temperature of the fine particles can be measured simultaneously, which is high. It becomes possible to measure with accuracy. Further, such a structure is preferably applied even in the case of cells having other shapes.

Further, as shown in the cross-sectional view of FIG. 4, the irradiation condensing part (end part) F _1a is the dispersion liquid S in the state where the optical fiber F ₁ vertically penetrates the lid 21a using the vial bottle 21 or the like. as inserted placed within the optical fiber F ₁ may be fixed integrally to the lid 21a. Thereby, it becomes possible to measure more simply.

The first embodiment (embodiment using a Mach-Zehnder type interferometer) is preferably applied to the measurement in the dispersion liquid containing fine particles of high concentration and nanometer order. According to the first embodiment, it is possible to easily perform particle size measurement with extremely high accuracy in a dispersion containing fine particles having a particle size of less than 100 nm (actually 10 nm or more) and having a high concentration of fine particles. In addition, it is possible to measure a wide particle size, or to measure and calculate their scattering coefficient, and to calculate a diffusion coefficient in a dispersion liquid containing a fine particle having a particle size of less than 100 nm and a particle having a particle size of 100 nm or more. Is possible. The polydispersed state typically refers to a state in which fine particles having different particle diameters are present in the dispersion and show two or more peaks in the particle size distribution. However, a broad particle size distribution may exist in a wide particle size range, and this may be included in polydispersion.
Furthermore, in order to adjust the reference light intensity and the scattered light intensity to an appropriate intensity ratio, the branching ratio of the first optical coupler 2 in the Mach-Zehnder interferometer shown in FIG. 1 (FIGS. 1a and 1b) is adjusted. Thus, it is possible to achieve a sensitivity improvement of about 10 to 100 times or more compared to the case where such adjustment is not performed. Such sensitivity improvement can also be realized by adjusting an optical coupler in the Michelson interferometer of the second embodiment.

  According to the first and second embodiments, in a dispersion containing pigments such as a color filter and an ink jet ink, under conditions containing fine particles at a high concentration (the concentration is not particularly limited, for example, 0.0001 to 50% by mass) , Preferably 0.001 to 50% by mass, more preferably 0.01 to 30% by mass), and the aggregation state can be quantified, and further, quality control and process management using the same can be performed. In addition, the measurement target is not limited to inorganic and organic particles, and in a wide range of fields such as magnetic particles used in recording media and various particles used in the medical and bio fields, etc. It can be applied to light scattering analysis that can be developed for behavioral evaluation. Furthermore, the present invention is not limited to fine particles, and can be applied to analysis of gel structures and polymer structures in solutions that cause multiple scattering and differences between places.

The present invention is not limited to the embodiment shown above . It is possible to apply the other various changes.

  In the following, including the points already mentioned above, the specific advantages obtained by the preferred embodiments of the present invention will be described.

A. Efficient measurement operation (no need for focusing and optical path adjustment)
First, for the purpose of contributing to an understanding of the characteristics of the dynamic light scattering measurement device and the light scattering intensity measurement method of the present invention, an irradiation condensing unit using a collimator lens 8 and an objective lens 9 which are different from those in the main part. An apparatus having the above will be described (see FIG. 7). In such measurement by the irradiation condensing unit, focusing and scattered light are usually performed so that the position (scattering position) P ₂ where the fine particle scattering is effectively generated in the sample cell 11 has an optical path length suitable for the measurement. And the optical path of the reference beam must be adjusted. Depending on the nature of the measurement sample and the required measurement accuracy, a highly skilled operation may be required, and this focusing may be a burden on the measurement process. On the other hand, according to the preferred embodiment of the present invention, as described with reference to FIG. 1b, the tip of the optical fiber to be the irradiation condensing part may be inserted almost arbitrarily into the sample dispersion. Thereby, the distance from the end face F _1b of the irradiation condensing section to the scattering position P ₂ is for naturally determined in the sample, complicated focusing, and preferably without the need for optical path adjustment of the scattered light and the reference light. In addition, in the measurement in a high concentration dispersion, the above focusing may be particularly difficult, and such a situation can be particularly preferably improved by the above embodiment of the present invention. Moreover, according to the present invention, it is only necessary to immerse the end of the fiber in a measurement target, which is preferable in that a small amount of a measurement sample can be handled appropriately.

B. Diversification of measurement forms (easy combination with other measuring devices)
According to a preferred embodiment of the present invention, as described above, the irradiation condensing unit can be used by being inserted into a dispersion together with a detection unit such as a commercially available vibration type viscosity measuring device or a temperature control system. it can. Therefore, for example, viscosity, temperature, and the like and information on the size of the fine particles can be measured and collected at the same time, and simultaneous measurement / simultaneous evaluation of many items, which has been difficult in the past, becomes possible. As a result, it is possible to deal with a small amount of sample and in a field where high-precision measurement without deviation of the sample state is required.

C. Elimination of the influence of the outer surface of the sample cell (exclusion of frost adhesion)
In the apparatus configuration shown in FIG. 7, depending on the temperature of the measurement sample and the material of the wall of the cell, frost forms on the surface of the cell 11, or the outer surface of the cell becomes cloudy or scratched due to another factor. Sometimes. According to the preferred embodiment of the present invention, these influences can be completely eliminated, restrictions on the measurement environment, cell material, sample temperature and the like are eliminated, and extremely accurate measurement is possible.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not construed as being limited thereto.

[Preparation of dispersion]
Commercial polystyrene water dispersions 101a, 102a, and 103a were purchased and the particle size was evaluated with a transmission electron microscope. As a result, the center particle diameters of the polystyrene particles contained in the polystyrene aqueous dispersions 101b, 102b, and 103b were 252 nm, 99 nm, and 23 nm, respectively. Thereafter, using the aqueous polystyrene dispersions 101b, 102b, and 103b, dispersions 101, 102, and 103 having a fine particle concentration adjusted to 10% by mass were obtained and placed in vials, respectively.

Example 1
In this example, a dynamic light scattering measurement apparatus equipped with a Mach-Zehnder interferometer whose schematic configuration diagram and main part enlarged cross-sectional view are shown in FIG. 1 was used. The used low coherence light source 1 has a coherence length of 17 μm. For dispersion 101 described above, by using the dynamic light scattering measurement apparatus of the present embodiment, the end portion F _1a of the optical fiber F ₁ put inserted at a depth D of approximately 1mm in dispersion 101. Under the above setting conditions, measurement was performed regarding the particle size of the fine particles of each dispersion liquid sample. Thereafter, the cumulant average particle size was derived for the spectrum around the modulation frequency. Table 1 shows the evaluation of the analysis results.

FIG. 5A shows the analysis result of the sample 102 in a graph. FIG. 5B shows, as a reference example, a graph showing an analysis result measured using the collimator lens 8 and the objective lens 9 as shown in FIG. 7 before the optical fiber F ₁ . From this result, it can be seen that according to the measuring apparatus (Example) of the present invention, the particle size of the fine particles can be measured with the same accuracy as the measuring apparatus using the conventional lens.

( Reference Examples 1-3 )
In the reference example , a dynamic light scattering measurement apparatus equipped with a Michelson interferometer whose schematic configuration is shown in FIG. 2 was used. Other than that was measured and analyzed similarly to Examples 1-3, respectively. Table 1 shows the evaluation of the analysis results.

  As can be seen from the above results, according to the present invention, it can be seen that the average particle diameter and the distribution of the fine particles can be measured accurately and simply. In particular, it can be seen that by using a Mach-Zehnder type interferometer, even nanometer-sized fine particles can be accurately measured in a high-concentration dispersion.

1 Low coherence light source 2 Optical coupler (first coupler)
3 Circulator 4 Optical coupler (second coupler)
5 Detector 6 A / D board 6a BNC cable 7 PC
8 Collimator lens 9 Objective lens 10 Phase modulator 11 Cell 12 Optical coupler 13 Reference light mirror (reflector)
14 detector 15 spectrum analyzer 20 viscometer or thermometer 21 vial 21a cover _F 1 _{to F 10} optical fiber _{F 1a} irradiation condensing section (optical fiber ends)
F _1b irradiation condensing part end face (optical fiber end face)
L light L ₁ incident light L ₂ scattered light P ₁ interface P ₂ scattering position S dispersion S ₁ fine particle S ₂ medium

Claims (3)

First light, which is an irradiation condensing unit that uses a Mach-Zehnder type interferometer having a low-coherence light source, irradiates the fine particles in the dispersion in which the fine particles are dispersed , and collects the backscattered light. put insert the end of the fiber to the dispersion, a light scattering intensity measuring method for measuring the dynamic characteristics of the fine particles, the interferometer of the Mach-Zehnder type, the from the low coherence light source light to the first was divided by the optical coupler, one of the light branching and reference light, the other light is a scattered light obtained by being light collector is irradiated to the fine particle dispersion through the irradiation condensing section, the reference beam And the scattered light are coupled by a second optical coupler, the light from the low coherence light source is branched by the first optical coupler, and the second optical coupler is coupled to the second optical coupler via a phase converter. 2 to 4 optical fibers Guided as the reference light, the irradiation light branched by the first optical coupler is guided to a circulator by a fifth optical fiber, and the irradiation light is guided from the circulator to the dispersion liquid by the first optical fiber, Light scattering intensity measurement characterized in that the scattered light is guided from the dispersion liquid to the circulator by the first optical fiber, and the scattered light is guided from the circulator to the second optical coupler by the sixth optical fiber. Method.   2. The light scattering intensity measuring method according to claim 1, wherein a coherence length of the low-coherence light source is 0.1 to 100 [mu] m. The light scattering intensity measurement method according to claim 1 or 2 , wherein the optical path length of the scattered light can be resolved, and the particle size and / or particle size distribution can be measured by Brownian motion.

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