JP2002005813A - Grain diameter distribution measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grain diameter distribution measuring device, capable of easily adjusting light intensity without generating an optical noise which adversely affects measurements. SOLUTION: In the grain diameter distribution measuring device for converting scattering light 4, generated by irradiating a sample to be measured 2 with laser light 3 into an electrical detection signal to compute the grain diameter distribution of particles contained in the sample to be measured 2 on the basis of the detection signal, with the center of a diaphragm 30 for reducing the quantity of scattered light 4 is made to coincide with an optical axis L of an optical system 1, the diaphragm 30 is set at a location, so that the scattered light 4 and/or laser light 3 is a light 3f which is parallel with respect to the optical axis L. The diaphragm 30 in a minimum open state is formed larger than the incident beam diameter of the laser light 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel particle size distribution measuring apparatus in which a sample to be measured is irradiated with laser light and an optical system for guiding generated scattered light to a detector is provided with a stop.

[0002]

2. Description of the Related Art In a particle size distribution measuring apparatus utilizing dynamic light scattering by a laser beam, particles dispersed in a liquid are irradiated with a laser beam, and the particle size distribution is calculated from the light scattered by the particles. By inserting a neutral density filter (referred to simply as a filter) in the optical path, the light intensity of the laser incident light may be reduced to irradiate the sample with a high concentration of measurement, or the light scattered to the detector may be too strong. It has been conventionally performed to reduce the light intensity when the light intensity is high. For example, when the concentration of the sample to be measured is high, or when the particle size of the particles contained in the sample to be measured is large, the light intensity of the scattered light condensed on the detector increases, so the filter is used to reduce the light intensity. Is inserted in the optical path.

[0003]

On the other hand, when the concentration of the sample to be measured is low, or when the particle diameter of the particles is small, for example, even if the power of the laser incident light is increased, as in the case of a polymer, etc. For a sample to be measured having low light intensity, it is necessary to remove the filter from the optical path. For this reason, optical noise may be generated due to filter dirt or scratches caused by the filter removing operation.

[0004] Further, since the optical path length changes due to the light refraction of the filter material depending on whether the filter is in the optical path or not, the focal position may be shifted.

Furthermore, laser oscillation may be unstable due to laser return light from the filter surface, or optical noise may increase due to scattered light.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned circumstances, and has as its object to provide a particle size distribution measuring apparatus capable of easily adjusting light intensity without generating optical noise or the like which adversely affects measurement. It is to be.

[0007]

In order to achieve the above object, the present invention irradiates a sample to be measured with laser light,
In a particle size distribution measuring device that converts generated scattered light into an electrical detection signal and calculates a particle size distribution of particles contained in the measurement target sample based on the detected signal, a diaphragm that reduces the amount of the scattered light With the center thereof coincident with the optical axis of the optical system, and the scattered light and / or
Alternatively, the laser light is installed at a position where the laser light is parallel light, and the aperture is formed to be larger than the incident light beam diameter of the laser light in a minimum aperture state.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show a first embodiment of the present invention in which an iris diaphragm for reducing the amount of scattered light is installed at a position where scattered light from a sample to be measured is parallel light in the cell unit. The form is shown.

In FIG. 1 and FIG. 2, reference numeral 1 denotes an optical system which irradiates a laser beam 3 of a constant frequency to a measurement target sample 2 and guides scattered light 4 from the measurement target sample 2 to a detector 5. The optical system includes an incident light optical system 8 that guides a laser beam 3 emitted from, for example, a semiconductor laser 6 as a laser light source to a cell 7, and an outgoing light that guides backscattered light 4 from a sample 2 to be measured to a detector 5. It comprises an optical system 9.

Reference numeral 10 denotes a cell unit portion from which the cell 7 is installed so as to be taken out. The cell 7 is held by a cell holder 11. Examples of the sample 2 to be measured include various samples such as a stock solution having a high concentration, a dispersion in an acid / alkali solvent, and a dispersion in an organic solvent.
Therefore, the cell 7 is made of glass. Since the Brownian velocity of the fine particles dispersed in the liquid in the cell 7 may be sensitively changed depending on the temperature, it is important to control the temperature of the sample 2 to be measured. It is configured to provide stable and highly accurate measurement with functions.

Reference numeral 12 denotes signal conversion means comprising a preamplifier and an AD converter, 13 denotes a CPU, and 14 denotes a CPU 1
This is a personal computer provided with a display unit 14a for displaying the particle size distribution calculated in Step 3.

Reference numeral 15 denotes a perforated mirror provided with a hole 16 having a size through which the laser light 3 can pass, and the optical axis L of the incident light optical system 8 passes through the center of the hole 16 and is provided with a light source. It is installed at an acute angle θ with respect to the axis L. This perforated mirror 15 has a mirror surface 15a at least on the detector 5 side. Reference numeral 18 denotes a laser beam 3a which has been converted into parallel light by a collimating lens
It is a pinhole guided through. In this case, the light is focused on the pinhole 18 by the lens 20. Reference numeral 21 denotes a lens that converts the laser light 3b that has spread out of the pinhole 18 into parallel light 3c again. 22 is the cell unit section 10
The converging lens installed in the inside has a function of condensing the parallel light 3c on the sample 2 to be measured in the cell 7. The hole 16 of the perforated mirror 15 is formed to be slightly larger than the diameter of the parallel lights 3c and 3a, so that the total amount of the laser light 3 does not change before and after passing through the hole 16. . 3d is the condensed laser light. Further, the condensing lens is provided with scattered light 3e from particles dispersed in the liquid.
[See FIGS. 2A and 2B] are received by the entire lens (lens diameter D), and are scattered parallel light 3f as scattered light having a diameter G larger than the diameter F of the incident parallel light 3c. It also has functions. The scattered parallel light 3f returns to the perforated mirror 15 along the same optical path as that at the time of incidence. That is, the scattered parallel light 3
f is condensed on the pinhole 18 by the lens 21, and then the scattered light 3 g that has spread out from the pinhole 18 is converted again into the scattered parallel light 3 h by the lens 20, and this scattered parallel light 3
h is reflected by the mirror surface 15a of the perforated mirror 15 in the direction (R direction) of the detector 5, and the reflected scattered parallel light 3
i is focused on the detector 5 by the detector focusing lens 23.
Then, the scattered parallel light 3i detected by the detector 5 is converted as an electric signal by the signal conversion means 12, and the converted data is processed by the CPU 13.

Hereinafter, a characteristic configuration of the present invention will be described.

Reference numeral 30 denotes an iris diaphragm provided in the emission light optical system 9 for guiding the scattered light 4 from the sample 2 to be measured to the detector 5. The center of the diaphragm 30 and the optical axis L are set to be coincident with each other. The iris diaphragm 30 has a function of reducing the amount of the scattered parallel light 3f.

The iris diaphragm 30 has a variable aperture 31 at the center. The variable opening 31 is configured to open and close substantially concentrically. However, even in the state where the variable opening 31 is minimized, that is, in the minimum opening state as shown in FIG. The structure is such that the minimum opening 31a having a diameter of several mm can be maintained so as not to be fully closed. The size of the minimum opening 31a is as shown in FIG.
As shown in FIG.
The iris diaphragm 30 is set to be larger than the luminous flux diameter of the iris diaphragm 30 so that the total amount of the incident parallel light 3c can be maintained before and after the iris diaphragm 30.

In FIG. 2C, the variable opening 31 indicated by a two-dot chain line indicates the maximum opening state when the variable opening 31 is opened to the maximum. This maximum opening 31b is also shown in FIG. On the other hand, FIG.
This shows a state in which 1 is reduced, whereby it can be seen that the total amount of light is reduced by the amount by which the beam diameter of the scattered parallel light 3f is reduced.

Reference numeral 33 denotes a plurality of displacement members provided for forming the variable opening 31 having a predetermined size by manual operation of the lever 34. Each of the displacement members 33 can be interlocked by a hinge (not shown). Pivoted on the lever 3
By the manual operation of 4, the plurality of displacement members 33 are displaced so as to simultaneously open and close the variable openings 31. The iris diaphragm 30
Can be manually operated because the cell unit 10 in which the sample 2 to be measured can be replaced instead of the optical system 1
This is because the iris diaphragm 30 is installed in the inside.

FIG. 2B shows a case where the sample 2 to be measured is changed from a sample having a low concentration to a sample having a high concentration.
When the concentration of the sample 2 to be measured is too high as shown in
The scattered parallel light 3f, which is scattered light from the sample 2 to be measured
Has an excessively high light intensity, the variable aperture 31 in the fully opened state when the sample 2 to be measured as shown in FIG. 2 (A) has a low concentration is squeezed to make the state shown in FIG. 2 (B). .

On the other hand, as shown in FIG. 2A, when the concentration of the sample 2 to be measured is low, since the scattered parallel light 3f has a weak light intensity, it is not necessary to stop down the variable aperture 31 and the maximum aperture is not required. The measurement can be performed while maintaining the state of 31b.
In this case, the scattered light 3f can be reduced while the iris diaphragm 30 is left in the optical path, and the filter is not used as in the related art. It is possible to eliminate the positional shift and the influence of the return light. Moreover, the lever 3 of the iris diaphragm 30 installed in the cell unit section 10
The light beam diameter of the scattered parallel light 3f, that is, the light amount can be easily adjusted only by manually operating the light beam 4.

In the meantime, in the particle size distribution measuring apparatus shown in FIG. 1, a sample 2 to be measured having a too high concentration such that scattered parallel light 3f having an excessively high light intensity is generated without using the iris diaphragm 30 is measured. If it is desired to perform the measurement, the sample 2 cannot be measured unless the sample 2 is diluted.
There is an advantage that the labor of the dilution can be omitted.

FIG. 3 shows a second embodiment of the present invention in which manual operation is difficult and the beam diameter of scattered light can be automatically varied. In FIG. 3, the same components as those shown in FIGS. 1 and 2 are the same or equivalent.

In FIG. 3, the iris diaphragm 30 is used to scatter parallel light 3 between the lens 20 and the perforated mirror 15.
The center of the iris diaphragm 30 and the optical axis L are set to coincide with the optical path of h.

In this case, since the iris diaphragm 30 is installed in the optical system 1, it is difficult to manually change the beam diameter of the scattered parallel light 3h as in the first embodiment. In this embodiment, the variable aperture 3 of the iris diaphragm 30
Automatic aperture control valve 40 that outputs a signal that makes variable 1 to an actuator (not shown) that drives a plurality of displacement members
Is provided, so that aperture adjustment can be performed automatically.

As a modification, an iris diaphragm 30 provided with the automatic diaphragm adjusting valve 40 is provided between the perforated mirror 15 and the condenser lens 23 for the detector as shown by a dashed line in FIG. In this case, reliable data can be obtained.

In each of the above embodiments, the case of backscattered light is shown, but the present invention can be applied to the case of sidescattered light.

FIG. 4 shows scattered parallel light 3j which is side scattered light.
A third embodiment of the present invention is shown in which the iris diaphragm 30 is installed such that the center of the iris diaphragm 30 and the optical axis L 'coincide with each other in the optical path. In FIG. 4, the same components as those shown in FIGS. 1 to 3 are the same or equivalent.

In this embodiment, the iris diaphragm 30 is installed not in the optical system 1 but in the cell unit 10. 23 ′ is a lens for condensing the side scattered light 3j ′ scattered by the particles dispersed in the liquid to form a parallel light 3j, and 23 ″ is a lens for detecting the side scattered parallel light 3j in the detector 5
This is a condenser lens for a detector for condensing light on a detector. The condenser lenses 23 ′ and 23 ″ are also provided in the cell unit 10.

In each of the above embodiments, the iris diaphragm 30 having the variable aperture 31 which can be concentrically squeezed is used as the diaphragm for reducing the amount of scattered light, but is shown in FIG. The aperture 53 formed so as to be able to adjust the size of the opening 52 formed between the vertical edges 51 of the pair of displacement members 50 and the concave edge 61 of the pair of displacement members 60 as shown in FIG. Opening 62 formed
Can be used.

In each of the above embodiments, the iris diaphragm 30 is used as the diaphragm for reducing the amount of scattered light. However, as shown in FIG. 5, between the vertical edges 51 of the pair of movable members 50 as shown in FIG. The aperture 53 formed between the V-shaped edges 61 of the pair of movable members 60 as shown in FIG.
An aperture 63 configured to be able to adjust the size of 2 can be used.

Further, in the present invention, the stop is installed at a position where the scattered light and / or the laser light is parallel light, so that the light flux of the parallel light is partially prevented from being diffracted and scattered by the stop. To do that.

[0032]

According to the present invention, an aperture is provided in the optical system for irradiating the sample to be measured with laser light and guiding the generated scattered light to the detector, so that the reliability of data can be improved without being affected by noise or the like. The light can be dimmed while maintaining the same, and the particle size distribution of the sample having a higher concentration can be measured.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an overall configuration showing a first embodiment of the present invention.

FIG. 2A is a configuration explanatory view showing a particle size distribution measurement state of a low-concentration sample to be measured in the embodiment.
(B) is a configuration explanatory diagram showing a state of measuring the particle size distribution of a high-concentration sample to be measured in the embodiment. (C)
FIG. 4 is a configuration explanatory view showing the operation of the diaphragm used in the embodiment.

FIG. 3 is an overall configuration explanatory view showing a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of the entire configuration showing a third embodiment of the present invention.

FIG. 5 is a view showing a modified example of the diaphragm used in the present invention.

FIG. 6 is a view showing another modified example of the diaphragm used in the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical system, 2 ... Sample to be measured, 3 ... Laser light, 3f ...
Parallel light, 4 ... scattered light, 5 ... detector, 6 ... semiconductor laser,
30 ... stop, L ... optical axis.

Claims (1)

[Claims] 1. A measuring object sample is irradiated with a laser beam to convert generated scattered light into an electrical detection signal, and a particle size distribution of particles contained in the measuring object sample is calculated based on the detection signal. In the particle size distribution measuring apparatus, the scattered light and / or the laser light are parallel to the optical axis in a state where the stop for reducing the amount of the scattered light is aligned with the optical axis of the optical system. It is installed in a position that is light,
The particle size distribution measuring apparatus, wherein the aperture is formed to be larger than the incident light beam diameter of the laser beam in a minimum aperture state.