JP3903473B2 - Particle size distribution measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for calculating a particle size distribution of a particle group based on measurement information of scattered light generated by irradiating the dispersed particle group with basic light.
[0002]
[Prior art]
Conventionally, as one of methods for measuring the particle size distribution of small particle groups, a so-called dynamic scattering type particle size distribution measuring method is known. This method utilizes the fact that the intensity of scattered light fluctuates over time due to the Brownian motion of these particles when the dispersed particles are irradiated with basic light, as shown in Patent Document 1, The particle size distribution is calculated by analyzing the fluctuation signal.
[0003]
[Patent Document 1]
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2002-221479
[Problems to be solved by the invention]
However, when a small amount of particle groups of different diameters are mixed in the predetermined particle group, the light fluctuation signal from the minute amount of different diameter particle groups is the light fluctuation signal scattered from the majority of the predetermined particle groups. It is buried inside and ignored. Also, in order to eliminate the ghost distribution that appears from noise etc. at the stage of calculating the particle size distribution, a certain threshold level is set at the time of distribution calculation. If the distribution of particle groups of different diameter is below the threshold level, there is no distribution May be converted. Furthermore, since the particle size distribution is replaced with the ratio distribution of 100% as a whole, the distribution shape is displayed as a distribution shape close to 0% in distribution and may not be recognized by the operator.
[0005]
Therefore, this problem is not only the dynamic scattering type particle size distribution measuring method, but also other particle size distributions such as the so-called scattering / diffraction type particle size distribution measuring method for measuring the particle diameter distribution by the angular distribution of scattered light intensity. The same applies to the measurement method.
[0006]
In view of this, the present invention provides a method for measuring the particle size distribution of this type, even when a small number of different-sized particle groups are mixed in a large number of predetermined particle groups. The main problem is to make it possible to calculate the value.
[0007]
[Means for Solving the Problems]
That is, the particle size distribution measuring method according to the present invention is a method for calculating the particle size distribution of the particle group included in the sample based on the scattered light information obtained from the scattered light generated by irradiating the sample with basic light. Te, along with obtaining a reference scattered light information from the reference scattered light generated by irradiating the fundamental light to a reference sample containing only a predetermined particles, the comprises the majority of the predetermined particle group, another diameter in addition to traces of its Scattered light information acquisition step for obtaining measurement sample scattered light information from measurement sample scattered light generated by irradiating basic light to a measurement sample comprising a measurement target particle group, and each obtained in the scattered light information acquisition step Based on the difference information generation step of taking the difference of the scattered light information and generating difference information, and the difference information generated in the difference information generation step, the difference is included in the measurement sample. It is characterized by having a particle size distribution calculation step of calculating a particle size distribution of the measured particles.
[0008]
If it is such, it will become possible to measure the particle size distribution of the small-diameter particles having different diameters contained in a large number of particle groups. For example, in quality control of products, it is possible to make a pass / fail judgment for products by measuring differences using this method using a genuine product as a reference sample and a manufactured product as a measurement sample, contributing to more precise quality control. it can. Specifically, when a defective product is mixed, the particle size distribution of the defective product can be known.
[0009]
Specific scattered light information in the so-called dynamic scattering type particle size distribution measuring method includes fluctuation information indicating fluctuation of scattered light intensity and power spectrum information calculated from fluctuation information indicating fluctuation of scattered light intensity. Can do. In addition, various calculation result information obtained from the fluctuation information may be used as scattered light information.
[0010]
On the other hand, specific scattered light information in the scattering / diffraction particle size distribution measuring method can include information on the angular distribution of scattered light intensity. Here, the “information about X” means not only information indicating X itself but also related information calculated based on X.
The particle size distribution measuring apparatus according to the present invention measures the particle size distribution of the particle group included in the sample based on the scattered light information obtained from the scattered light generated by irradiating the sample with basic light. A reference cell that contains a reference sample containing only the majority of predetermined particle groups and a measurement sample that contains a measurement sample comprising a measurement target particle group having a very small diameter in addition to the majority of predetermined particle groups. A basic light guide mechanism that divides basic light emitted from a cell and a single light source and directs the light to the reference sample and the measurement sample, and scattered light generated by irradiating the basic light to each sample, Based on the difference between the scattered light information detected by the light intensity detection unit and the scattered light guide mechanism that leads to the light intensity detection unit that detects the intensity of the measurement target particle group included in the measurement sample Characterized in that it comprises an information processing unit for calculating the size distribution, the.
If it is such, it will become possible to measure the particle size distribution of the small-diameter particles having different diameters contained in a large number of particle groups. For example, in quality control of products, it is possible to make a pass / fail judgment for products by measuring differences using this method using a genuine product as a reference sample and a manufactured product as a measurement sample, contributing to more precise quality control. it can. Specifically, when a defective product is mixed, the particle size distribution of the defective product can be known.
[0011]
FIG. 1 is a schematic diagram showing an embodiment of a particle size distribution measuring apparatus 1 that embodies the measuring method according to the present invention. The particle size distribution measuring apparatus 1 is of a dynamic scattering type, and includes a transparent measurement cell 2a for storing a measurement sample OS, a transparent reference cell 2b for storing a reference sample RS, and holding and storing these cells 2a and 2b. A cell unit 3 to be split, a single light source (semiconductor laser) 4, and a laser beam L, which is a basic light emitted from the semiconductor laser 4, are divided into two, and the reference sample RS and the measurement sample OS are divided into cells 2 a and 2 b. The basic light guide mechanism 5 for guiding light from outside the light, the light intensity detector (photo detector) 6 for detecting the light intensity, and the scattered light for guiding the scattered lights LNa and LNb from the respective samples OS and RS to the photodetectors 6a and 6b. Based on the difference in intensity fluctuation between the scattered light LNa and LNb detected by the guide mechanism 7 and the photodetectors 6a and 6b. And a processing unit 8 which calculates the particle size distribution of measured particle group C contained in the measurement sample OS.
[0012]
Explaining each part, the measurement cell 2a and the reference cell 2b are made of the same hollow hollow glass and are accommodated in the cell unit 3. The reference sample RS accommodated in the reference cell 2b is obtained by dispersing a predetermined particle group in a solvent. In the present embodiment, the reference sample RS is a monodisperse sample composed of a single particle group. Of course, the reference sample RS is composed of a plurality of particle groups. It may be a thing. On the other hand, the measurement sample OS accommodated in the measurement cell 2a is obtained by further mixing a minute amount of different diameter particles into the reference sample RS. In addition, in the present embodiment, a temperature control mechanism (not shown) that controls the temperature in the cell unit unit 3 may be used because the Brownian motion of the particles changes sensitively due to changes in temperature and may affect the measurement. Is provided to stabilize the temperature of the sample during measurement so that highly accurate measurement can be performed.
[0013]
The basic light guiding mechanism 5 includes a collimator lens 51 that converts the diffused laser light L emitted from the semiconductor laser 4 into a parallel laser light L having a predetermined diameter, and a light beam Lb that transmits and reflects the parallel laser light L. A half mirror 52 that is a light splitting element that is spatially divided into two and a condensing lens 53a for a measurement sample that condenses the first laser light La that has passed through the half mirror 52 on the inner wall surface of the measurement cell 2a. And a reference cell condensing lens 53b that condenses the second laser light Lb reflected by the half mirror 52 on the inner wall surface or slightly inside of the reference cell 2b.
[0014]
As is well known, the photodetectors 6a and 6b receive light in a predetermined wavelength band and output an optical intensity signal that is an electric signal having an intensity corresponding to the intensity of the light. In this embodiment, the photodetectors 6a and 6b are used for measurement samples. Two are provided, one for the sample 6a and one for the reference sample 6b.
[0015]
The scattered light guide mechanism 7 is for measuring backscattered light, for example. The scattered light LNa and LNb generated by irradiating the sample OS and RS with laser light La and Lb, respectively, are used as the respective photodetectors 6a. , 6b, each of which leads to a pair of components. Constituent elements include collimating lenses 71a, 71b, and parallel light that make scattered light LNa and LNb scattered in the direction opposite to the traveling direction of incident laser light La and Lb into parallel light having a diameter larger than that of the parallel laser light La and Lb. Noise light cut portions 72a and 72b for cutting light that causes noise such as multiple scattered light from the scattered light LNa and LNb, and scattered light LNa and LNb emitted from the noise light cut portions 72a and 72b Mirrors 74a and 74b for condensing and irradiating the light-receiving surfaces of the photodetectors 6a and 6b with the reflection mirrors 73a and 73b for reflecting the light and changing the optical path. The collimating lenses 71a and 71b also serve as the condensing lenses 53a and 53b in the basic light guiding mechanism 5 so that the optical paths of the scattered light LNa and LNb coincide with the optical paths of the incident laser lights La and Lb halfway. It is. The noise light cut portions 72a and 72b are formed by arranging a pair of convex lenses R1 and R2 before and after a shielding plate B having a pinhole PH. Since the reflection mirrors 73a and 73b are installed on the optical paths of the parallel laser beams La and Lb, the laser beams having substantially the same diameter are passed through the central portion so that the parallel laser beams La and Lb can pass through without changing the light amounts. A hole LH is provided. In this embodiment, the semiconductor laser 4, the cells 2a and 2b, the cell unit 3, the basic light guiding mechanism 5, the scattered light guiding mechanism 7, the photodetectors 6a and 6b, and the like are accommodated in the same casing.
[0016]
The information processing unit 8 exhibits its function by the operation of the CPU and peripheral hardware based on the program stored in the storage device and the operation of the dedicated discrete circuit. The scattered light output from each of the photodetectors 6a and 6b Data relating to the refractive index, temperature, viscosity, etc. of the solvent and particles, in addition to the difference information 81 that accepts each time fluctuation of the intensity signal as fluctuation information and takes the difference between them, and the difference information generated by the difference part As a parameter, the calculation unit 82 calculates the particle size distribution, and the output unit 83 outputs the result to a display or printer in a predetermined manner. In the present embodiment, the homodyne detection method is used, and the inventor has clarified the detailed contents of the algorithm and the like relating to the particle size distribution calculation based on each parameter in Japanese Patent Application Laid-Open No. 2000-171383. The description in is omitted. Of course, it can be applied to the heterodyne detection method. Further, in the present embodiment, as shown in FIG. 3, in the difference unit 81, each scattered light intensity signal is differentiated by using a discrete difference circuit as an analog signal, and the result is digitally converted to the calculation unit 82. However, the difference may be calculated after each scattered light intensity signal is converted into a digital signal.
[0017]
Next, an operation example of the apparatus 1 configured as described above will be described with reference to FIG.
[0018]
When the laser beam L is irradiated from the semiconductor laser 4, the laser beam is divided into two laser beams La and Lb having the same intensity by the half mirror 52, and each of the measurement sample OS in the measurement cell 2a and the reference sample RS in the reference cell 2b. Irradiated. Next, the scattered lights LNa and LNb generated in the cells 2a and 2b are guided to the scattered light guide mechanism 7, received by the photodetectors 6a and 6b, and output as analog scattered light intensity signals, respectively.
[0019]
The information processing unit 8 receives the analog scattered light intensity signals, and obtains reference scattered light fluctuation information and measurement sample scattered light fluctuation information, which are temporal fluctuations (scattered light information acquisition step S1).
[0020]
Next, the information processing section 8 takes the difference between the scattered light fluctuation information obtained in the scattered light information acquisition step and generates difference information (difference information generation step S2).
[0021]
Then, after performing the arithmetic processing such as converting the difference information generated in the difference information generation step into power spectrum information by performing Fourier transform processing, the particle size distribution of the measurement target particle group included in the measurement sample is calculated. (Particle size distribution calculating step S3), and the result is output to a display, a printer or the like in a predetermined manner (step S4).
[0022]
Accordingly, in such a case, the scattered light information from a large amount of the particle group is canceled due to the difference, so that it is possible to measure the particle size distribution of the different-diameter trace particles contained in the measurement sample OS. For example, in quality control of products, it is possible to make a pass / fail judgment for products by measuring differences using this method using a genuine product as a reference sample and a manufactured product as a measurement sample, contributing to more precise quality control. it can. Specifically, when a defective product is mixed, the particle size distribution of the defective product can be known.
[0023]
Furthermore, in the present embodiment, the cells 2a and 2b are held in the same cell unit 3 so that the surrounding environment is kept substantially equal, and the scattered light LNa and LNb from the cells 2a and 2b are completely simultaneously measured. As a result, noise caused by disturbances such as local vibration effects and scattering effects due to differences in refractive index at the interface are equally superimposed on each fluctuation information. Since the difference of the fluctuation information is taken, the noise is effectively canceled, and even if the measurement target particle is a very small amount, the distribution can be accurately obtained without being disturbed by the noise.
[0024]
The present invention is not limited to the above embodiment.
[0025]
For example, the difference unit may take a difference of midway calculation information calculated from each fluctuation information. As an example of such midway calculation information, there can be mentioned frequency intensity distribution information of fluctuation information, that is, power spectrum information. Specifically, as shown in FIG. 4, the difference unit 81 is provided with an AD conversion unit, an FFT processing unit, a difference processing unit, etc., and each fluctuation information is digitized and subjected to Fourier transform processing to obtain power spectrum information and After that, the difference may be taken.
[0026]
In this way, if the difference is taken after the conversion to midway calculation information that does not use time as a parameter, complete simultaneous measurement of the fluctuation of scattered light from each sample and simultaneous difference are not required as in the above embodiment. Therefore, many variations can be given to the instrument configuration and the scattered light measurement method. For example, the scattered light from each sample can be selectively measured, or the samples can be exchanged and measured separately.
[0027]
Further, the present invention is applied not only to the above-described dynamic scattering type particle size distribution measuring apparatus but also to a so-called scattering / diffraction type particle size distribution measuring apparatus that measures the particle size distribution from the angular distribution of scattered light intensity. The same effect as the embodiment can be obtained.
[0028]
In addition, the reference sample may be only a solvent such as water (including dust and impurity particles). Even if impurities and the like are mixed instead of a pure solvent as in the prior art, the true sample particle size distribution can be obtained by subtracting them.
[0029]
Of course, a noise cut part is not necessarily required, and forward scattering and side scattering may be used.
[0030]
In addition, the present invention is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.
[0031]
【The invention's effect】
As described in detail above, according to the present invention, the scattered light information from a large number of particle groups is canceled due to the difference, so that it is possible to measure the particle size distribution of the different diameter trace particles contained therein. It becomes. For example, in quality control of products, it is possible to make a pass / fail judgment for products by measuring differences using this method using a genuine product as a reference sample and a manufactured product as a measurement sample, contributing to more precise quality control. it can. Specifically, when a defective product is mixed, the particle size distribution of the defective product can be known.
[Brief description of the drawings]
FIG. 1 is a schematic overall view of a particle size distribution measuring apparatus according to an embodiment of the present invention.
FIG. 2 is a flowchart showing the operation steps of the dynamic scattering type particle size distribution measuring apparatus according to the embodiment.
FIG. 3 is a functional block diagram showing a detailed function of a difference unit in the embodiment.
FIG. 4 is a functional block diagram showing detailed functions of a difference unit according to another embodiment of the present invention.
[Explanation of symbols]
RS: Reference sample L, La, Lb: Basic light (laser light)
LNb ... reference scattered light OS ... measurement sample LNa ... measurement sample scattered light S1 ... scattered light information acquisition step S2 ... difference information generation step S3 ... particle size distribution calculation step

Claims (4)

Based on scattered light information obtained from scattered light generated by irradiating a sample with basic light, the particle size distribution of a particle group included in the sample is measured,
A reference cell containing a reference sample containing only a predetermined particle group;
A measurement cell that contains a large number of the predetermined particle groups, and that contains a measurement sample that includes a measurement target particle group that has a small amount of another diameter,
A basic light guide mechanism that divides basic light emitted from a single light source and guides it to the reference sample and the measurement sample, respectively;
A scattered light guide mechanism for guiding scattered light generated by irradiating each sample with basic light to a light intensity detector that detects the intensity of the light;
A particle size distribution measuring apparatus comprising: an information processing unit that calculates a particle size distribution of a measurement target particle group included in the measurement sample based on a difference between pieces of scattered light information detected by the light intensity detection unit. . The scattered light information, a particle size distribution measuring apparatus according to claim 1, wherein the fluctuation information indicating the fluctuation of the scattered light intensity. The scattered light information is a power spectrum information calculated from the fluctuation information indicating the fluctuation of the scattered light intensity claim 1 particle size distribution measuring apparatus according. The scattered light information is information about the angular distribution of scattered light intensity claim 1 particle size distribution measuring apparatus according.

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