JP5086958B2 - Particle property measuring device - Google Patents

Description

  The present invention relates to a particle physical property measuring apparatus capable of measuring physical properties related to the shape of particles such as the aspect ratio and the degree of aggregation 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 irradiates particles dispersed in a cell with polarized primary light such as laser light, and detects the polarization of the scattered light on the light receiving side, thereby changing the shape of the particles. Measure.

  In particular, in Patent Document 1, the light receiving optical system mechanism is configured to be rotatable around a cell, so that scattered light intensities having different angles can be detected by a single light receiving element. With such a configuration, there is an advantage that reduction of the number of parts can be promoted and an instrumental difference in the light receiving element does not occur in the first place.

  By the way, the intersection of the light beam irradiated by the primary light at the center of the cell and the light beam at the detection angle on the light receiving side is called the scattering volume, and a pinhole with a diameter corresponding to this scattering volume is placed in front of the detector. In this type of particle physical property apparatus, only scattered light is received. This is to enable measurement with a high S / N ratio.

  Taking the above-mentioned Patent Document 1 as an example, optical elements are arranged in the order of a pinhole 19, a half-wave plate 35, a polarizer 36, a convex lens 17, and a pinhole 31 before the light receiving element.

By the way, in ordinary scattered light measurement, a plurality of light receiving elements are provided to detect the intensity of a plurality of scattered lights scattered at different angles. In Patent Document 1, the light receiving optical system mechanism can be rotated around a cell. Thus, the scattered light intensity at different angles can be detected by a single light receiving element. With such a configuration, there is an advantage that reduction of the number of parts can be promoted and an instrumental difference in the light receiving element does not occur in the first place.
US 6,721,051

  However, in order to be able to rotate the light receiving optical system mechanism, a mechanical mechanism supporting part such as a rail or a rotating plate is actually required, and the light receiving optical system mechanism itself has a mechanical error. I have to be affected.

  Therefore, when the light receiving system optical system mechanism is rotated and measured, the position of the secondary light beam with respect to the pinhole differs at each measurement angle position, and the detected light quantity at each measurement angle position varies. There is a problem.

  Therefore, although the present invention is configured to measure by rotating a single light receiving element (light detection means), it is possible to suppress variation in the amount of light at each measurement angle position, and keep the S / N ratio high. The present invention is intended to provide a particle property measuring apparatus that can ensure accuracy.

  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; The light receiving optical system mechanism is rotated around the cell and controlled to a plurality of measurement angle positions, and at each measurement angle position, an angle control unit that controls the polarization angle of the exit side polarizer to a plurality of angles, and each measurement Of detected light intensity at angular position A correction parameter storage unit that stores positive parameters, a sample detection light intensity that is a detection light intensity at each polarization angle at each measurement angle position, and a physical property related to the shape of the particle based on the correction parameter. And a physical property calculation unit for calculating.

  In such a case, since the correction parameter is determined for each measurement angle position, it is possible to correct the variation in the amount of light due to the mechanical error at each measurement angle position by using each correction parameter. Therefore, the physical properties related to the shape of the particles can be accurately measured. In addition, it is possible to realize a simple configuration without requiring a particularly complicated mechanism.

  As the correction parameter, the detection light intensity obtained by irradiating the primary light to the cell in the particle-free state and acquired at each measurement angle position may be used. In such a case, the correction parameter is updated every time the sample is measured, so that it is possible to easily cope with a change with time.

  On the other hand, in order to reduce the positional deviation of the light beam of the secondary light with respect to the pinhole as much as possible and to suppress the variation in the detected light quantity at each measurement angle position, in the light receiving optical system mechanism, it is perpendicular to the rotation plane. A slit extending in the direction may be provided in front of the light detection means. Since the actual mechanical deviation at each measurement angle position described above appears in a direction perpendicular to the rotation surface of the light receiving optical system mechanism, the above-described slit can reliably pass scattered light even by mechanical deviation. It is because it can be made.

  In order to be able to accurately measure the physical properties of particles over a wide range while using a single light detection means, the amount of light can be changed without changing the polarization state of the primary light or secondary light. Dimming means for dimming, and dimming for controlling the dimming rate by the dimming means so that the detected light intensity at each polarization angle at each measurement angle position is within the measurement range of the photodetecting means. It is desirable to further include a rate control unit.

  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.

  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.

  According to the present invention having such a configuration, since the correction parameter is determined for each measurement angle position, the variation in the amount of light due to a mechanical error at each measurement angle position is corrected using each correction parameter. Therefore, the physical properties related to the shape of the particles can be measured with high accuracy. In addition, it is possible to realize a simple configuration without requiring a particularly complicated mechanism.

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 has, for example, a hollow cylindrical shape that can accommodate therein a sample in which the microparticles S are dispersed in a dispersion medium. 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 receives light detection means 31 that detects the intensity of received light and scattered light L <b> 2 that is secondary light scattered by the microparticles S. And a plurality of optical elements led to the light detecting means 31 and having a structure rotatable 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.

  The optical element in this embodiment includes a convex lens 32, a quarter-wave plate 33 (hereinafter also referred to as an output-side quarter-wave plate 33), and a polarizer 34 (hereinafter referred to as the cell 4). , Also referred to as an output side polarizer 34), a convex lens 35, and a slit 37.

  The light detection means 31 is of a type that outputs the number of photons of received light, and for example, a photomultiplier tube is used here.

  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-wave plate 33 can be extracted. is there.

  The slit 37 has a belt-like shape extending perpendicularly to the rotation surface of the light receiving optical system mechanism 3, and the width of the slit 37 is set to a dimension corresponding to the scattering volume described above. Further, the length is larger than the width dimension, and is set to a minimum dimension that allows the scattered light to almost pass through the slit 37 by absorbing the positional deviation of the scattered light caused by a mechanical error or the like.

  Reference numeral 5 in FIG. 1 controls the measurement 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). In the blank measurement, a sample in which the sample and the dispersion medium are the same but no particles are contained in the cell 4, and in this state, the light intensity detection value by the photodetector is acquired. 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. Each detected light intensity in the blank measurement is a correction parameter for correcting the detected light intensity in the sample measurement described later. The detected light intensity by the blank measurement is stored in the correction parameter storage unit 55 set in the memory.

  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 (or a value related to the number of photons such as a voltage value proportional to the number of photons) is measured. Is determined to be saturated beyond the measurement range of the light detection means 31, the rotation holding plate 232 a is rotated so that the number of photons is within the measurement range of the light detection means 31. The ND filter 231 having a high attenuation rate is positioned on the optical path of the laser light L1.

Next, sample 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. As with the blank measurement, the light intensity of the polarization component is measured while appropriately adjusting the light attenuation rate so as to be within the measurement range of the light detection means (as the angle control unit 51 and the light attenuation rate control unit 52). Function, 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 blank measurement measured at each measurement angle position of the light receiving optical system mechanism 3 and each polarization angle of the output side polarizer 34, respectively. Based on the detected light intensity, the detected light intensity at the time of sample measurement, the light attenuation rate, etc., the distribution relating to the shape of the particles, particularly the aspect ratio (aspect ratio or aggregation degree) is calculated (function as the physical property calculating unit 53, Step S24).

  Here, an example of calculation for correcting the detected light intensity at the time of sample measurement based on the detected light intensity in the blank measurement will be described. In the case where there is a variation in the detected light intensity in the blank measurement where all the same values should be expected, the cause is caused by the shift of the slit 37 and the scattered light due to the rotation of the light receiving optical system mechanism 3 at each measurement angle position. I think that. Therefore, the maximum value is extracted from each detected light intensity in the blank measurement, and the ratio of each detected light intensity in the blank measurement to the maximum value is multiplied by the corresponding detected light intensity in the sample measurement. To correct it.

  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. However, other methods such as measuring scattered light with a DC value may be used.

  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 °.

  Thus, according to the particle property measuring apparatus 1 configured as described above, a blank measurement for correction is performed for each polarization angle at each measurement angle position, and a mechanical error at each measurement angle position is determined from the measurement result. Therefore, even with the single light detection means 31, the physical properties related to the shape of the particles can be measured with high accuracy.

  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, the ND filter can reduce the light and ensure a wide measurement range. Can contribute to measurement.

  In addition, since it can be measured by a single light detection means 31, it contributes to cost reduction and, while sharing the shape measurement and optical hardware, the angular distribution of scattered light such as particles of 100 nm or less, for example, Even for particles that are difficult to measure, the particle size can be measured by the dynamic light scattering method.

  Furthermore, since the temperature of the cell 4 can be adjusted, particles that change in size and shape depending on temperature, such as biological materials and polymers, can be stably measured.

The present invention is not limited to the above embodiment.
For example, in the embodiment, blank measurement for correction is performed for each polarization angle at each measurement angle position, but blank measurement is performed only for each measurement angle position without performing blank measurement for each polarization angle. Also good.
In addition, it is not necessary to perform blank measurement every time the sample is measured. If the sample or dispersion medium is the same type, the blank measurement data is registered in advance in the correction parameter storage unit, and the value registered in the correction parameter storage unit. May be used to correct each detected light intensity at the time of sample measurement.

Furthermore, it is needless to say that other correction calculation methods can be considered.
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 ... Secondary light (scattered light)
2 ... Irradiation optical system mechanism 21 ... Light source (semiconductor laser)
23... Dimming means 231... ND filter 232... Filter changing mechanism 24... Incident side polarizer 25... Incident side quarter wave plate 3.・ Light detection means 33... Exit side quarter wavelength plate 34... Exit side polarizer 4... Cell 51... Angle control unit 52 .. dimming rate control unit 53. Unit 54... Particle diameter distribution calculation unit 55... Correction parameter storage unit

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;
An angle control unit that rotates the light receiving optical system mechanism around a cell to control a plurality of measurement angle positions, and controls a polarization angle of the output-side polarizer to a plurality of angles at each measurement angle position;
At each measurement angle position , a correction parameter storage unit that stores correction parameters for detected light intensity when the polarization angle of the output-side polarizer is a plurality of angles, and
A physical property calculation unit that calculates a physical property related to the shape of the particle based on the sample detection light intensity, which is the detection light intensity at each polarization angle at each measurement angle position, and the correction parameter. A particle physical property measuring apparatus. By irradiating the primary light in the cell in which the particle-free state, in each of the measurement angular position, the detection light intensity when the polarization angle of the exit side polarizer to a plurality of angles acquires each detection light intensity The particle physical property measuring apparatus according to claim 1, wherein: is used as the correction parameter.   The light receiving optical system mechanism further comprises a slit disposed in front of the light detection means, and is configured to receive secondary light that has passed through the slit by the light detection means, wherein the slit is 3. The particle physical property measuring apparatus according to claim 1, wherein the particle physical property measuring apparatus extends in a direction perpendicular to a rotation surface of the light receiving optical system mechanism. A dimming means for dimming the primary light or the secondary light so as to change the light amount without changing the polarization state;
A dimming rate control unit for controlling the dimming rate by the dimming means so that the detected light intensity at each polarization angle at each measurement angle position is within the measurement range of the photodetecting means. The particle physical property measuring apparatus according to any one of claims 1 to 3.   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.