JP5002564B2 - Particle property measuring device - Google Patents

Description

  The present invention relates to a particle property measuring apparatus capable of measuring physical properties related to particle shape or particle size distribution such as aspect ratio and aggregation degree of particles (or particle groups) dispersed in a cell.

  Recently, the demand of the industry for fine particles having various shapes is increasing, and the market needs to measure the physical properties such as the particle size and shape of the fine particles in detail.

  For example, Patent Document 1 proposes a technique for measuring specific physical properties of fine particles by measuring scattered light using polarized light.

  The apparatus described in Patent Document 1 measures the shape of a particle by irradiating polarized light onto particles dispersed in a cell and detecting the polarization of the scattered light on the light receiving side. . According to this apparatus, on the optical path from the light source to the cell, the optical elements are arranged in the order of the convex lens 13, the polarizer 32, the 1/2 wavelength plate 33, and the 1/4 wavelength plate 34 as shown in FIG. The optical elements are arranged in the order of the half-wave plate 35, the polarizer 36, and the convex lens 17 in front of the light receiving element.

By the way, in the scattered light measurement, a plurality of light receiving elements are provided to detect the intensities of a plurality of scattered lights scattered at different angles. In Patent Document 1, a configuration in which the light receiving optical system mechanism can rotate around a cell is provided. The scattered light intensity at different angles can be detected with a single light receiving element.
US 6,721,051

  However, in this kind of particle physical property measuring apparatus, scattered light having a very wide intensity range can be generated from very strong scattered light to very weak scattered light depending on the angle and polarization direction of the scattered light. Such a single light receiving element configuration may not cover the intensity range. In addition, since the device described in Patent Document 1 uses many optical elements related to polarized light and the like, it causes an increase in cost, and in addition, it is unpredictable such as a decrease in transmittance, generation of stray light, or an increase in adjustment points. Many problems can occur.

  Therefore, the present invention can guarantee the measurement accuracy even though the light receiving element (light detection means) has a single configuration, and further reduces the number of optical elements as much as possible to suppress cost increase, stray light, and adjustment points. The present invention is intended to provide a particle physical property measuring apparatus capable of reducing or the like.

That is, the particle property measuring apparatus according to the present invention includes a transparent cell that contains a sample in which fine particles are dispersed in a dispersion medium, a light source, and an optical path from the primary light emitted from the light source to the cell. , An irradiation optical system mechanism having an incident side polarizer and an incident side quarter wave plate provided in order, a light detection means for detecting the intensity of received light, and secondary light scattered by particles in the cell A light-receiving optical system mechanism having an emission-side quarter-wave plate and an emission-side polarizer provided in order on an optical path leading to the light intensity detection means, and supported rotatably around the cell; and dimming means for light attenuation can be changed the extinction ratio and without changing the polarization state of the primary light or the secondary light, and controls the light receiving optical system mechanism to a plurality of rotational angular positions, each angular position The polarization angle of the exit-side polarizer in Control the dimming rate by the dimming means so that the detected light intensity at each polarization angle at each rotation angle position is within the measurement range of the photodetecting means, and an angle control unit that controls to a plurality of angles A light extinction rate control unit, a physical property calculation unit that calculates the physical properties of the particles based on the light extinction rate at each polarization angle at each rotation angle position and the detected light intensity after dimming, and the light detection means A particle size distribution calculating unit that calculates a particle size distribution based on the fluctuation of the light intensity detected in step, and the angle control unit measures the particle concentration in the sample during the particle size distribution measurement by the particle size distribution calculating unit. The rotational angle position of the light receiving optical system mechanism is changed according to the above .

  If it is such, it is suitable for the light detection means for strong light while using a high-sensitivity light detection means that can detect low light intensity so that it can be measured even at low concentrations and fine particles. Therefore, it is possible to perform appropriate dimming by the dimming means so that the light intensity becomes high, and therefore, it is possible to perform highly accurate physical property measurement over a wide range using a single photodetecting means. In addition, there are only two optical elements for controlling the polarization on the incident side and the output side, the quarter λ plate and the polarizer. Moreover, the polarizers on the output side, the incident side, and the output side rotate for measurement. Since there are only ¼λ plates, adjustment points can be reduced as much as possible to improve operability and measurement accuracy. Furthermore, it is possible to prevent a decrease in transmittance and stray light generation.

  Specific physical properties that can be measured include physical property values related to particle shape such as particle aspect ratio and aggregation degree.

  The dimming means may be capable of continuously changing the dimming rate in a stepless manner, but actually only needs to be able to change the dimming rate in a plurality of steps. For this purpose, the dimming means includes a plurality of ND filters having different dimming rates, and a filter changing mechanism for selectively inserting one of these ND filters on the optical path of the primary light or the secondary light. It is preferable that it is equipped.

  As a specific filter changing mechanism, a rotation holding plate having a plurality of ND filters arranged in the periphery is provided, and by rotating the rotation holding plate, any one of the ND filters can transmit the primary light or the secondary light. The thing comprised so that it may be located on an optical path can be mentioned.

  In order to be able to measure the transmitted light intensity with the light receiving optical system mechanism and to simplify the optical system mechanism, the light receiving optical system mechanism can be arranged on the extension line of the primary light transmitted through the cell, It is desirable that the intensity of the transmitted light transmitted through the cell can be measured by the light detection means.

  According to the present invention, the particle size distribution can also be measured using the irradiation optical system mechanism and the light receiving optical system mechanism used for measuring the particle shape as they are. In that case, applying the static particle size distribution measurement method to calculate the particle size distribution by changing the angular position of the light receiving optical system mechanism and measuring the intensity distribution of scattered light (secondary light) at multiple angles Alternatively, a dynamic particle size distribution measuring method for calculating the particle size distribution based on the fluctuation of the light intensity detected by the light detection means can be applied. With the dynamic particle size distribution measurement method, it is basically unnecessary to change the angular position of the light-receiving optical system mechanism, and the photon correlation method is used to obtain autocorrelation from the time-series change of the number of photons of the detected secondary light. If the particle size distribution is measured by using the reference optical system, the reference optical system becomes unnecessary, and the particle size distribution can be measured without difficulty.

  When applying the dynamic particle size distribution measurement method, in order to ensure measurement accuracy even when the concentration changes, the rotational angle position of the light receiving optical system mechanism is changed according to the particle concentration in the sample. It is even better if it is configured.

  According to the present invention having such a configuration, by performing appropriate dimming by the dimming means at the time of detecting the light intensity, it is possible to perform highly accurate physical property measurement over a wide range even though it is a single photodetecting means. be able to. In addition, since fewer optical elements are required, it is possible to prevent a decrease in transmittance and stray light generation, and the optical elements that are rotationally driven for measurement need only be a polarizer on the output side. As a result, the operability and measurement accuracy can be improved.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

The particle physical property measuring apparatus according to the present embodiment irradiates the microscopic particles dispersed in the dispersion medium with polarized light, and measures the angular distribution of the intensity and the degree of conservation of polarization in the scattered light, thereby The physical properties related to the shape such as the aspect ratio and the degree of aggregation are measured.
In FIG. 1, the whole outline | summary of this particle | grain physical property measuring apparatus 1 is shown with a schematic diagram. In the figure, reference numeral 2 denotes an irradiation optical system mechanism that irradiates a transparent cell 4 containing a sample with laser light L1 as primary light, and reference numeral 3 denotes secondary light from the microparticles S, that is, scattered light L2. Is a light receiving optical system mechanism for receiving light.

  As shown in FIG. 2, the cell 4 can accommodate a sample in which fine particles S are dispersed in a dispersion medium, for example, has a hollow cylindrical shape. In this embodiment, a temperature adjusting mechanism (not shown) that can maintain the cell 4 at a constant temperature is provided.

  The irradiation optical system mechanism 2 includes a semiconductor laser 21 that is a light source and a plurality of optical elements that guide the laser beam L1 emitted from the semiconductor laser 21 to the cell 4. In this embodiment, however, as the optical element, the convex lens 22, the dimming means 23, the polarizer 24 (hereinafter also referred to as the incident-side polarizer 24), the quarter wavelength plate 25 (hereinafter referred to as the incident-side quarter wavelength). The convex lens 26 is also arranged in this order as viewed from the semiconductor laser 21.

  As shown in FIG. 2, the dimming means 23 is composed of a plurality of ND filters 231 having different dimming rates and a filter changing mechanism 232 that holds the ND filters 231. The ND filter 231 has a plate shape that attenuates light without changing the polarization state. The filter changing mechanism 232 includes a rotation holding plate 232a that holds the plurality of ND filters 231 at the peripheral edge, and a motor (not shown) that rotationally drives the rotation holding plate 232a. Then, by rotating the rotation holding plate 232a around its center, one of the ND filters 231 is set to be positioned on the optical path of the laser light L1.

  The irradiation optical system mechanism 2 is provided with a plurality of reflecting mirrors 27 for bending the optical path closer to the semiconductor laser 21 than the polarizer. This is because the reflection mirror 27 changes the polarization direction of the light. After the polarization direction is determined, that is, on the optical path of the laser light L1 from the incident side polarizer 24 to the cell 4, the reflection mirror A member such as 27 that can change the polarization direction is not provided.

  On the other hand, as shown in FIGS. 1 and 2, the light receiving optical system mechanism 3 converts the light detection means 31 for detecting the intensity of the received light and the scattered light L2 that is the secondary light scattered by the microparticles S into the cell. 4 and a plurality of optical elements led to the light detection means 31. In this embodiment, the optical elements are a convex lens 32, a quarter wavelength plate 33 (hereinafter referred to as an emission side quarter wavelength plate 33). A polarizer 34 (hereinafter also referred to as an output-side polarizer 34) and a convex lens 35 are arranged in this order as viewed from the cell 4. The light detecting means 31 is of a type that outputs the number of photons of received light (or a photon number related value such as a voltage value proportional to the number of photons). The exit-side polarizer 34 is configured to be rotatable by a motor or the like (not shown) around the optical axis so that a plurality of different polarization direction components of the scattered light L2 that has passed through the quarter wavelength plate can be extracted. .

  The light receiving optical system mechanism 3 has a structure that can rotate around the cell 4. Specifically, the light detection means 31 and each optical element are integrally supported by a substrate 36, and the substrate 36 is rotated around the cell 4 by a rotation support mechanism including a support shaft and an arcuate rail (not shown). I support it as possible.

  Reference numeral 5 in FIG. 1 controls the rotation angle position of the light receiving optical system mechanism 3 and the rotation angle around the optical axis of the output side polarizer 34, that is, the polarization angle, and is based on the detected light intensity by the light detection means 31. It is an information processing apparatus that performs shape analysis and the like. The information processing apparatus 5 includes a CPU, a memory, an A / D converter, and the like. By causing the CPU and its peripheral devices to cooperate in accordance with a program stored in the memory, an angle control unit 51, which will be described later, The light attenuation rate control unit 52, the physical property calculation unit 53, the particle size distribution calculation unit 54, and the like are configured to exhibit functions.

  Next, the operation of the particle property measuring apparatus 1 will be described in detail with reference to the flowchart of FIG.

  First, dark measurement is performed by the information processing apparatus 5 (step S1). Dark measurement refers to obtaining a light intensity detection value by a photodetector in a non-light state. Here, the rotation holding plate 232a is driven to position the region without the ND filter 231 on the optical path of the laser light L1, so that the rotation holding plate 232a functions as a light shielding plate. In this state, a signal from the light detection means 31 is received, and a light intensity detection value in a non-light state is acquired. In this embodiment, the light intensity is detected by measuring the number of photons counted within a certain gate time.

  Next, after confirming the dispersion medium set by the operator (step S2), the information processing apparatus 5 performs blank measurement (steps S3 to S8). Blank measurement refers to obtaining a light intensity detection value by a photodetector in a state of only a dispersion medium in which particles are not present. Here, the light-receiving optical system mechanism 3 is set at a plurality of angular positions (for example, in increments of 4 ° from 10 ° to 162 °), and at each angular position, the output-side polarizer 34 is set at a plurality of angles (for example, in increments of 15 °). In addition, the predetermined reference angle is set to 0 °, which is substantially matched with the original polarization angle of the semiconductor laser 21), and blank measurement at each of these angles is performed. I do. That is, by stepwise rotation of the light receiving optical system mechanism 3 and the exit side polarizer 34, the light intensities of a plurality of polarization components in the scattered light at a plurality of angles are measured. Further, as shown in FIG. 1, the light receiving optical system mechanism 3 faces the irradiation optical system mechanism 2 and overlaps the optical axis of the laser light L1, that is, the laser light transmitted through the cell 4 by the light receiving optical system mechanism 3. It can be rotated to a position where L1 can be measured (this angular position is set to 0 °). In the blank measurement, the transmitted light intensity is also measured by setting the angular position of the light receiving optical system mechanism 3 to 0 °. . In the measurement of each light intensity, as described above, the number of photons counted within a certain gate time is measured. If the number of photons exceeds the measurement range of the light detection means 31, it is saturated. If it is determined, the rotation holding plate 232a is rotated so that the ND filter 231 having a higher light attenuation rate is placed on the optical path of the laser light L1 so that the number of photons is within the measurement range of the light detection means 31. Position it.

Next, this measurement is performed. That is, when an operator or the like places a sample in which particles are dispersed into the cell 4 and presses a start button (step S10), the information processing apparatus 5 turns on the laser (step S11) and the detected light intensity is light. The rotation holding plate 232a is rotated so that it falls within the measurement range of the detection means 31, and any one of the ND filters 231 is positioned on the optical path of the laser light L1 (step S12). Then, the polarizer is set to a reference angle, and the light receiving optical system mechanism 3 is set to an angular position of 0 ° (steps S13 and S14). And the transmittance | permeability at that time is calculated based on the following formula | equation (step S15).
Transmittance = (1 / light attenuation of ND filter 231) × detection light intensity at sample / detection light intensity at blank

  If it is determined from this transmittance that the concentration exceeds the measurable concentration (step S16), a message indicating that the concentration is too high is displayed and the operator is prompted to adjust the concentration.

  On the other hand, when it is determined that the concentration is measurable (step S16), similarly to the blank measurement, a plurality of angles of scattered light at a plurality of angles are obtained by the stepwise rotation of the light receiving optical system mechanism 3 and the output side polarizer 34. The light intensity of the polarization component is measured while appropriately adjusting the light attenuation rate (functions as the angle control unit 51 and the light attenuation rate control unit 52, steps S17 to S21).

  Then, each part is returned to the initial state such as turning off the laser 21 (steps S22 and S23), and at the same time, blank measurement is performed at each rotation angle position of the light receiving optical system mechanism 3 and each polarization angle of the output side polarizer 34. Based on the detected light intensity, the detected light intensity by the particles, the dimming rate in each measurement, and the like, the distribution relating to the shape of the particles, particularly the aspect ratio (aspect ratio or aggregation degree) is calculated (as the physical property calculating unit 53) Function, step S24).

  In addition, in this embodiment, the same optical system mechanism is used to measure the particle size distribution by the dynamic light scattering method. The calculation of the particle size distribution is performed by the information processing apparatus 5 (function as the particle size distribution calculating unit 54). Here, the photon correlation method, that is, the autocorrelation data is generated from the time-series data of the number of received photons, and the particle size distribution of the particle group is calculated by performing a predetermined calculation process based on the autocorrelation data. I have to.

  In addition, since the suitable position (angle) of the scattered light at the time of measuring a particle diameter (particle diameter distribution) changes with the density | concentration of a sample, the light of the sample calculated when measuring an aspect ratio and / or aggregation degree According to the transmittance, when the transmittance is high (the sample concentration is low), an optical path perpendicular to the laser beam L1, that is, 90 ° scattered light is received, and when the transmittance is low (the sample concentration is high), Further, the information processing device 5 controls the angular position of the light receiving optical system mechanism 3 so as to receive scattered light at an angle rearward, that is, at an angle exceeding 90 °.

  Therefore, according to the particle physical property measuring apparatus 1 configured as described above, cost reduction can be promoted by simplifying the optical system, and reduction in transmittance and generation of stray light can be suppressed.

  Moreover, since the measurement sensitivity is improved by counting photons, it is possible to improve the measurement accuracy of trace amounts and minute particles. On the other hand, as the measurement sensitivity is improved, high-intensity light cannot be detected and the measurement range tends to be small. However, a wide measurement range can be secured by dimming with the ND filter.

  Furthermore, since the temperature of the cell can be adjusted, particles that change in size and shape with temperature, such as biological materials and polymers, can be stably measured.

  In addition, even for particles that are difficult to measure with an angular distribution of scattered light, such as particles of 100 nm or less, the particle diameter can be measured by the dynamic light scattering method, and the same optical measurement as the shape measurement is used for the measurement. System mechanisms can be used.

The present invention is not limited to the above embodiment.
For example, the dimming means may be inserted in any part as long as it is on the optical path of the primary light and the secondary light.
In addition, it goes without saying that the present invention can be variously modified without departing from the spirit of the present invention.

1 is a schematic overall view showing an outline of a particle physical property measuring apparatus according to an embodiment of the present invention. The typical perspective view which shows especially the light reduction means in the same embodiment. The flowchart which shows operation | movement of the particle physical property measuring apparatus in the embodiment.

Explanation of symbols

1 ... Particle property measuring apparatus L1 ... Primary light (laser light)
L2 ... Scattered light (scattered light)
2 ... Irradiation optical system mechanism 21 ... Light source (semiconductor laser)
23... Dimming means 231... ND filter 232... Filter changing mechanism 232 a... Rotation holding plate 24... Incident side polarizer 25. Light-receiving optical system mechanism 31... Light detection means 33... Exit side quarter wave plate 34... Exit side polarizer 4. Part 53 ... Physical property calculation part 54 ... Particle size distribution calculation part

Claims (5)

A transparent cell containing a sample in which fine particles are dispersed in a dispersion medium;
An irradiation optical system mechanism having a light source, and an incident-side polarizer and an incident-side quarter-wave plate provided in order on an optical path from the light source to the cell where the primary light emitted from the light source reaches the cell;
Photodetection means for detecting the intensity of the received light, and an emission-side quarter-wave plate and an emission side sequentially provided on the optical path from the secondary light scattered by the particles in the cell to the light intensity detection means A light receiving optical system mechanism having a side polarizer and supported rotatably about the cell;
And dimming means for dimming the changeable and extinction ratio without changing the polarization state of the primary light or the secondary light,
An angle control unit that controls the light receiving optical system mechanism to a plurality of rotation angle positions, and controls the polarization angle of the exit-side polarizer to a plurality of angles at each rotation angle position;
A dimming rate controller for controlling the dimming rate by the dimming means so that the detected light intensity at each polarization angle at each rotation angle position is within the measurement range of the photodetecting means;
A physical property calculation unit that calculates the physical properties of the particles based on the light attenuation rate at each polarization angle at each rotation angle position and the detected light intensity after light attenuation ;
A particle size distribution calculator that calculates a particle size distribution based on fluctuations in light intensity detected by the light detection means ,
The particle property measuring apparatus , wherein the angle control unit changes a rotation angle position of the light receiving optical system mechanism in accordance with a particle concentration in the sample when the particle size distribution is measured by the particle size distribution calculating unit .   The particle physical property measuring apparatus according to claim 1, wherein the physical property calculating unit calculates a physical property value relating to a particle shape such as an aspect ratio and a degree of aggregation of particles.   The dimming means comprises a plurality of ND filters having different dimming rates, and a filter changing mechanism for selectively inserting one of these ND filters on the optical path of the primary light or secondary light. The particle physical property measuring apparatus according to claim 1.   The filter changing mechanism is provided with a rotation holding plate in which a plurality of ND filters are arranged in a peripheral portion, and by rotating the rotation holding plate, any one of the ND filters can transmit the primary light or the secondary light. 3. The particle physical property measuring apparatus according to claim 2, wherein the particle physical property measuring apparatus is configured to be positioned on an optical path.   5. The structure according to claim 1, wherein the light receiving optical system mechanism can be arranged on an extension line of primary light transmitted through the cell, and the intensity of the transmitted light transmitted through the cell can be measured by the light detection means. Or a particle physical property measuring apparatus.