JP3849935B2 - Particle size distribution measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a particle size distribution measuring apparatus for measuring a particle size distribution based on an angular distribution of scattered light intensity that is scattered by irradiating light to a measurement target particle in a sample.
[0002]
[Prior art]
This type of device measures the angular distribution (scattering pattern) of the intensity of the scattered laser light by irradiating the measurement target particles dispersed in the cell with laser light, and measures the scattering pattern based on the MIE scattering theory. The particle size distribution of the target particles is obtained. For the measurement of the scattered light pattern, a plurality of photodetectors (eg, photodiodes) arranged around the cell are used, and the intensity for each angle of the scattered light is detected by these photodetectors (Patent Document 1). ).
[0003]
Specifically, pre-amplifiers that are first-order lag elements are connected to each photodiode, and impedance conversion is performed by these pre-amplifiers, and the signal waveform is slightly dulled and averaged, so that subsequent signal amplification processing and Smoothness in AD conversion processing or the like is ensured or noise removal is performed.
[0004]
[Patent Document 1]
[Patent Document 1] Japanese Patent Laid-open No. 2000-21468
[Problems to be solved by the invention]
By the way, the particles to be measured dispersed in the cell may be mixed in various sizes, and the ratio of the numbers may be greatly different. For example, in actuality, the number of large-diameter particles is often smaller than that of small-diameter particles. In such a case, scattered light from small-diameter particles is generated without interruption, whereas scattered light from large-diameter particles is intermittent. Will occur.
[0006]
Conventionally, however, the response time (time constant) of each preamplifier is set to be constant and large to some extent, so that the scattered light intensity signal from small-diameter particles, which is a continuous signal, is further averaged to remove noise and the like. However, the scattered light intensity signal from large-diameter particles that have a peaky chevron waveform and need to capture high frequency components is distorted by the filter effect of the preamplifier. It's hard to say.
[0007]
On the other hand, if the response time (time constant) of the preamplifier is all made small in order to reliably measure the scattered light intensity signal from the large particle, the averaging of the scattered light intensity signal from the small particle is hindered, such as noise. Is also not removed, which may adversely affect measurement accuracy. Furthermore, if the sampling interval for AD conversion is made small accordingly, the total amount of data acquisition becomes enormous, which may prolong the processing time and impose a burden on the processing circuit and the arithmetic program.
[0008]
The present invention has been made in view of such problems, and even in the case where various measurement target particles having different diameters are mixed in a sample and the ratio of the number is greatly different, the particle size distribution thereof is also provided. The main object is to provide a particle size distribution measuring apparatus that can reliably measure the particle size without burden on hardware or the like.
[0009]
[Means for Solving the Problems]
That is, the particle size distribution measuring apparatus according to the present invention should detect a light irradiation unit that irradiates light to the measurement target particles dispersed in the cell, and an angular distribution of scattered light intensity that scatters on the measurement target particles. A plurality of detectors arranged around the cell, receiving the scattered light and outputting a scattered light intensity signal having a value corresponding to the intensity, and receiving each scattered light intensity signal output from the detectors. A particle size distribution measuring apparatus comprising: a signal processing unit that performs the above-described processing; and a calculation unit that calculates a particle size distribution based on the value of the scattered light intensity signal processed by the signal processing unit, wherein the signal processing The unit is equipped with a plurality of transmission elements that transmit the scattered light intensity signal output from each detector with a predetermined response time, and transmission corresponding to a detector whose main detection target is a particle having a diameter that seems to be large Increase element response time Characterized in that it shortens the response time of the transfer element corresponding to the detector for the particle diameter you think that the fewer the main detection target.
Further, the particle size distribution measuring apparatus according to the present invention detects a light irradiation unit that irradiates light to the measurement target particles dispersed in the cell, and an angular distribution of scattered light intensity that the light scatters on the measurement target particles. Therefore, a plurality of detectors are arranged around the cell, receive the scattered light and output a scattered light intensity signal having a value corresponding to the intensity, and receive each scattered light intensity signal output from the detector. A particle size distribution measuring apparatus comprising: a signal processing unit that performs a predetermined process; and a calculation unit that calculates a particle size distribution based on a value of a scattered light intensity signal processed by the signal processing unit. The processing unit includes a plurality of transmission elements that transmit the scattered light intensity signals output from the respective detectors with a predetermined response time, and the transmission elements corresponding to detectors having a large main target diameter for detection have the response time as described above. That it ’s set short. And butterflies.
[0010]
In such a case, even if the particles to be measured having different diameters are mixed in the sample and the ratio of the numbers is greatly different, there is even a small estimate that the number of particles of each diameter is large. If possible, increase the response time of the transfer element corresponding to the detector whose main detection target is a particle with a large number of particles, and detect the particle with a small particle size as the main detection target. By shortening the response time of the transfer element corresponding to the vessel, each scattered light intensity signal can be measured with high accuracy.
[0011]
In practice, the number of large particles is often smaller than that of small particles, so the transfer element corresponding to a detector with a large particle size as the main target of detection is set so that its response time is shorter. It is desirable to keep it.
[0012]
In addition, if the signal processing unit further includes an AD converter connected to the transmission element, the AD conversion interval by the AD converter is made different according to the response time of each transmission element. Since the transmission element with a longer response time can set the interval of AD conversion for the output signal longer, the waste of the entire data acquisition amount can be suppressed, so that the processing time is prolonged and the processing circuit and calculation program are burdened. It is possible to avoid problems such as that.
[0013]
As a specific embodiment, there can be mentioned one in which the transfer element is composed of a first-order lag integration circuit using an operational amplifier.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1, 2, and 3.
[0015]
The particle size distribution measuring apparatus 1 according to the present embodiment utilizes the fact that the scattering pattern of scattered light (angle distribution of scattered light intensity) generated when light is irradiated on the particles is determined by the particle diameter from the MIE scattering theory, The particle size distribution is measured by detecting the scattering pattern. Specifically, as schematically shown in FIG. 1, a cell 2 that contains a sample in which particles S to be measured are dispersed in a solvent, and a laser beam L that is a coherent fundamental light are supplied to the cell 2. An irradiation unit 5 that is disposed around the cell 2 and receives scattered light and / or diffracted light (hereinafter referred to as scattered light) LS generated by irradiation with the laser light L, and an analog corresponding to the intensity thereof A plurality of detectors 3 that output scattered light intensity signals that are electrical signals, a signal processing unit 4 that receives each scattered light intensity signal output from the detectors 3 and performs processing such as conversion, and the signal processing unit And a calculation unit 7 that calculates the particle size distribution based on the value of each scattered light intensity signal processed in step 4. Reference numeral 6 denotes a convex lens for condensing scattered light on the light receiving surface of the detector 3.
[0016]
Specifically, as shown in FIG. 1, the cell 2 is a transparent container made of glass or the like, and is arranged on a sample circulation path for circulating the sample by a pump (not shown), for example. Then, by flowing the sample from the inflow port 21 and discharging the sample from the discharge port 22, the internal sample always flows and the measurement target particles S are dispersed.
[0017]
The light irradiation unit 5 includes a light source 51 such as a semiconductor laser and a light guide mechanism 52 that guides the laser light L emitted from the light source 51 to the cell 2. Reference numeral 521 in FIG. 1 is a beam expander that constitutes the light guiding mechanism 52 and expands the diameter of the laser light L emitted from the light source 51. The light source 51 may of course be a gas laser or the like, and a light source that emits light having a wavelength suitable for the particle size range to be measured may be selected. In this specification, “light” includes not only visible light but also electromagnetic waves including ultraviolet light and infrared light.
[0018]
The detector 3 is, for example, a photodiode. In the present embodiment, the detector 3 has a fan-shaped light receiving surface centering on the optical axis of the laser light L transmitted through the cell 2 in order to measure forward scattered light. As shown in FIG. 2, the detector array 3R is configured by concentrically arranging the light receiving surfaces of the detectors 3.
[0019]
As shown in FIGS. 1 and 3, the signal processing unit 4 performs processing such as impedance conversion, averaging, and AD conversion on each scattered light intensity signal output from the detector 3. A preamplifier 41, one or a plurality of AD converters 42, and a multiplexer (analog switch) 43 that selectively connects each preamplifier 41 to the AD converter 42, a buffer memory 44, and the like. The preamplifier 41 is an integration circuit using an operational amplifier 411, a resistor 412, and a capacitor 413, and plays a role as a first-order lag element. The analog switch 43 is configured to selectively connect one of the preamplifiers 41 to the AD converter 42 by switching contacts according to a control signal from the outside. The AD converter 42 is a well-known one, and samples an analog signal at a predetermined interval based on a conversion start signal or the like given from the outside and converts it into a digital signal. Then, the scattered light intensity signal converted into the digital signal is configured to be transmitted to the calculation unit 7 described later via the buffer memory 44.
[0020]
The calculation unit 7 is configured by physically separating a general-purpose computer such as a personal computer and a dedicated processing computer from the viewpoints of, for example, processing speed, usability, and maintenance (of course, they may be integrated), and as a whole As shown in FIG. 4, the basic device configuration includes an input / output interface 102, a storage device 104 (an internal memory 1042 and an external memory 1041), etc. in addition to the CPU 101, and includes a display 73, input means 74, and printer 75. Etc. are connected. Then, the scattered light intensity signal value for each detector 3 output as a digital signal from the AD converter 42 is fetched from the input / output interface 102 and calculated according to a predetermined program based on the MIE scattering theory stored in the storage device 104. By doing so, the particle size distribution or the like is output to the display 73, the printer 75, or the like.
[0021]
Thus, in the present embodiment, the preamplifier 41 corresponding to the detector 3 having a large particle size as the main target of detection has a shorter response time, and the signal from the preamplifier 41 with a shorter response time is the AD converter. 42 is set to shorten the conversion interval (sampling interval).
[0022]
Specifically, the preamplifier 41 corresponding to the center, that is, the detector closer to the basic optical axis, has a smaller response time (time constant) with the resistance value × capacitor capacity as a parameter, and the preamplifier corresponding to the outer detector 3. The response time is set as large as 41. As a method for setting the response time, for example, the response time of each detector 3 may be determined so as to be inversely proportional to the distance from the center. Further, when AD converting a signal from the preamplifier 41 having a short response time, the sampling interval is correspondingly reduced, and when AD converting a signal from the preamplifier 41 having a long response time, the sampling interval is appropriately increased.
[0023]
On the other hand, generally, the number of large-sized particles contained in a sample is small, and the number of small-sized particles tends to be large. Therefore, the frequency with which large-diameter particles pass through the cell is low, and the scattered light intensity signal waveform due to the scattered light LS from the large-diameter particles is not of a uniform size, but is a sharp mountain with a narrow width that occurs intermittently It will be a thing. In this embodiment, the preamplifier 41 corresponding to the large-diameter particles has a shorter response time. Therefore, the chevron-shaped waveform including high frequency components is reliably transmitted to the AD converter 42 without being cut or enlarged. can do. Moreover, since the sampling interval of the AD converter 42 is set sufficiently small, the value of the peaky analog scattered light intensity signal can be converted into a digital value with high accuracy.
[0024]
On the contrary, since the small-diameter particles have a large number of particles and pass through the cells uniformly, the scattered light intensity signal waveform due to the scattered light LS from the small-diameter particles becomes substantially constant. Since the response time of the preamplifier 41 corresponding to the small-diameter particles is set to be long, the waveform is further averaged to improve the accuracy in AD conversion. In addition, since the sampling interval of the AD converter 42 is set to be large, the amount of data captured in a certain time does not increase unnecessarily.
[0025]
As described above, according to the present embodiment, accurate particle size distribution data can be obtained from a large number of small particles to a large number of small particles without burdening the hardware and software with as little data as possible. can get.
[0026]
The present invention is not limited to the above embodiment. For example, the response time of the preamplifier need not be different for each individual, but may be varied step by step for a plurality of preamplifiers. The length of the response time may be set according to the measurement mode.
[0027]
Furthermore, the response time of the preamplifier may be changed. Specifically, a configuration in which the resistance can be switched or a variable one is used may be used. In that case, it is desirable that the conversion interval of the AD converter can be changed accordingly.
[0028]
The preamplifier as a transfer element may be a multi-order delay element as well as a first-order delay element.
[0029]
In addition, the response time of the preamplifier and the conversion interval of the AD converter may be shortened as the detector corresponding to the smaller number of particles, and the number of particles contained in the sample is smaller, for example, as the particle size is smaller. Needless to say, the setting is opposite to that in the above embodiment.
[0030]
In addition, the present invention is not limited to the above 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, even when the measurement target particles having different diameters are mixed in the sample and the ratio of the numbers is greatly different, If even a few estimations have been made to a certain extent, the response time of the transfer element corresponding to the detector whose main detection target is a particle with a large number of particles is lengthened, and particles with a small number of particles Each scattered light intensity signal can be measured with high accuracy by shortening the response time of the transfer element corresponding to the detector as the main detection target.
[0032]
In addition, if the signal processing unit further includes an AD converter connected to the transmission element, the AD conversion interval by the AD converter is made different according to the response time of each transmission element. The longer the response time, the longer the transmission time, the longer the AD conversion interval with respect to the output signal, the more the total data acquisition amount can be reduced as much as possible, and the waste can be suppressed. Or a burden on the processing circuit or the arithmetic program can be avoided.
[Brief description of the drawings]
FIG. 1 is an overall schematic diagram of a dynamic scattering particle size distribution measuring apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing a detector array in the same embodiment.
FIG. 3 is a schematic circuit diagram of a signal processing unit in the embodiment.
FIG. 4 is a device configuration diagram of a calculation unit in the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Particle size distribution measuring apparatus 2 ... Cell 3 ... Detector 4 ... Signal processing part 41 ... Transmission element (preamplifier)
411... Operational amplifier 42... AD converter 5... Light irradiation unit 7.

Claims (5)

A light irradiation unit for irradiating the measurement target particles dispersed in the cell with light, and a plurality of the light irradiation units disposed around the cell to detect the angular distribution of scattered light intensity scattered by the measurement target particles. And a signal processing unit that receives the scattered light intensity signals output from the detectors and performs predetermined processing, and this signal processing. A particle size distribution measuring apparatus comprising a calculation unit that calculates a particle size distribution based on the value of the scattered light intensity signal processed by the unit,
The signal processing unit includes a plurality of transmission elements that transmit a scattered light intensity signal output from each detector with a predetermined response time, and a detector that mainly detects particles having a diameter that seems to be large in number Particle size distribution measurement characterized in that the response time of the corresponding transfer element is lengthened and the response time of the transfer element corresponding to the detector whose main detection target is a particle with a small number of particles is shortened. apparatus. A light irradiation unit for irradiating the measurement target particles dispersed in the cell with light, and a plurality of the light irradiation units disposed around the cell to detect the angular distribution of scattered light intensity scattered by the measurement target particles. And a signal processing unit that receives the scattered light intensity signals output from the detectors and performs predetermined processing, and this signal processing. A particle size distribution measuring apparatus comprising a calculation unit that calculates a particle size distribution based on the value of the scattered light intensity signal processed by the unit,
The signal processing unit includes a plurality of transmission elements that transmit the scattered light intensity signals output from the detectors with a predetermined response time, and the transmission elements corresponding to the detectors having a large main target diameter of detection have the response. A particle size distribution measuring apparatus characterized in that the time is set short. It is one in which the signal processing unit further comprising a connected AD converter to said transfer element, the claim would be different in correspondence and to the response time of each transfer element conversion interval by the AD converter 1 or 2. The particle size distribution measuring apparatus according to 2. 4. The particle size distribution measuring apparatus according to claim 3, wherein the conversion interval by the AD converter is set longer for a signal from a transmission element having a longer response time.   The particle size distribution measuring apparatus according to claim 1, 2, 3, or 4, wherein the transmission element is constituted by a first-order lag integration circuit using an operational amplifier.

Images