JP4456301B2 - Particle size distribution measuring device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a particle size distribution measuring device such as a laser beam diffraction / scattering particle size distribution measuring device.
[0002]
[Prior art]
Particle measurement technology is indispensable for determining and evaluating the performance of powders in a wide range of fields such as medicine, food, ceramics, cosmetics, paints, and pigments, and its importance is increasing day by day. Yes. One of the devices for measuring the particle size distribution of such a granular material is a laser beam diffraction / scattering particle size distribution measuring device.
[0003]
Then, as the laser beam diffraction / scattering particle size distribution measuring apparatus, a paste type cell composed of two plate-like bodies having light permeability held with a sample sandwiched therebetween, and light is applied to this cell. Some include an irradiating unit for irradiating and a detecting unit for detecting secondary light generated by irradiating the sample with light from the light source.
[0004]
In the particle size distribution measuring apparatus having the above-described configuration, the paste type cell is irradiated with laser light, and the laser light diffracted and / or scattered by the sample particles in the paste type cell is detected by a detection means, and thereby obtained. The intensity distribution of the diffracted and / or scattered light is processed on the basis of Franhofer diffraction and Mie scattering theory to determine the particle size distribution of the sample particles.
[0005]
[Problems to be solved by the invention]
However, the conventional particle size distribution measuring apparatus has the following problems. That is, in the paste-type cell, large particles and small particles are not mixed completely at random, so that different particle size distributions are measured depending on the area exposed to light. Since the paste type cell could not be moved during the measurement of the particle size distribution, the light from the light source could only be applied to a specific position of the paste type cell, and the sample particles in that region Only the particle size distribution could be measured. Therefore, reproducibility was poor and accurate measurement could not be performed.
[0006]
The present invention has been made in consideration of the problems as described above, and its purpose is to measure a larger area in the paste-type cell, and to measure particles with an accurate particle size distribution. It is to provide a diameter distribution measuring device.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the particle size distribution measuring apparatus of the present invention includes a paste type cell composed of two plate-like bodies having optical transparency held with a sample sandwiched therebetween, and the paste type cell. A particle size distribution measuring apparatus comprising: an irradiating unit that irradiates light to the sample; and a detecting unit that detects secondary light generated by irradiating the sample with light from the irradiating unit. A moving mechanism is provided for moving the cell on a plane whose normal is the optical axis of the light emitted from the irradiation unit ,
The paste type cell is intermittently moved by the moving mechanism so that light from the irradiation unit is irradiated over different areas of the paste type cell,
Measurement is performed while the paste-type cell is stopped, and before starting the measurement, it is automatically determined whether or not there is a deviation of the optical axis of the laser beam irradiated from the irradiation unit (Claim 1).
[0008]
According to the present invention having the above-described configuration, it is possible to provide a particle size distribution measuring apparatus capable of measuring a larger area in the paste type cell and measuring an accurate particle size distribution.
[0009]
In addition, when the measurer performs a measurement start operation to start the measurement of the particle diameter, before starting the measurement, it automatically determines whether there is a deviation of the optical axis of the laser light emitted from the irradiation unit, without the optical axis deviation to start the measurement, the optical axis misalignment has an optical axis adjusting function to start the measurement after the optical axis adjustment if any, if it is confirmed that the optical axis is correct Since no optical axis adjustment work is performed, unnecessary time spent on the optical axis adjustment work can be eliminated, and when a measurement start operation is performed, the presence or absence of optical axis deviation is automatically determined. Therefore, it is possible to reliably prevent the measurer from forgetting to adjust the optical axis and obtaining inaccurate measurement data.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an explanatory diagram schematically showing the configuration of a laser beam diffraction / scattering particle size distribution measuring apparatus D according to an embodiment of the present invention.
The particle size distribution measuring device D includes a paste-type cell 2 (hereinafter referred to as a cell) made up of two plate-like bodies 1 and 1 having light transmittance, which is held with a sample S interposed therebetween, and An irradiation unit 3 that irradiates light to the sample S and a detection unit 4 that detects secondary light (diffracted light and / or scattered light) generated when the sample S is irradiated with light from the irradiation unit 3 are provided. ing.
[0011]
The particle size distribution measuring apparatus D irradiates the sample S in the cell 2 with laser light, detects the laser light diffracted and / or scattered by the sample S by the detection means 4, and obtains the diffraction obtained thereby. And / or a laser diffraction / scattering particle size distribution measuring apparatus for processing the intensity distribution of scattered light based on the Franhofer diffraction or Mie scattering theory to obtain the particle size distribution of the sample S.
[0012]
The said plate-shaped body 1 consists of a glass plate made into the substantially rectangular shape, for example.
[0013]
The irradiation unit 3 includes a laser light source 5 that emits laser light in a horizontal direction, a condensing lens 6 that converges divergent laser light emitted from the laser light source 5, and a laser light that is converged through the condensing lens. It has a mirror 7 that irradiates the cell 2 with 90 degrees of bending (hereinafter referred to as a condensed laser beam), and a laser optical axis adjustment mechanism 8 that holds the mirror 7 and is automatically controlled.
[0014]
The detection means 4 includes a photodetector 9 (ring detector) and a wide-angle scattered light detection group 10.
[0015]
The photodetector 9 is provided at a position where the condensed laser light that has passed through the cell 2 is focused, and as shown in FIG. 2, rings having different radii around the optical axis of the condensed lens light. A plurality of photosensors 11 having a light receiving surface in the shape of a ring or a semi-ring are arranged concentrically, and are diffracted at a relatively small angle out of the condensed laser light diffracted and / or scattered by the sample S in the cell 2. / The scattered light is received at each scattering angle and the light intensity is measured.
[0016]
A preamplifier 12 for amplifying the output is connected to each photosensor 11 constituting the photodetector 9.
[0017]
The wide-angle scattered light detection group 10 is provided in the vicinity of the cell 2, and is diffracted and / or scattered at a relatively large angle out of the condensed laser light diffracted and / or scattered by the sample S in the cell 2. The detected light is individually detected for each scattering angle.
[0018]
The wide-angle scattered light detection group 10 includes a plurality of photosensors 13 to 18 provided at different angles with respect to the photodetector 9, and has a predetermined angle according to the sample S in the cell 2 according to each arrangement angle. Detects scattered light. That is, the photosensors 13 to 16 detect forward scattered light, the photosensor 17 detects side scattered light, and the photosensor 18 detects backscattered light.
[0019]
A preamplifier 19 for amplifying the output of each photosensor 13 to 18 is connected to each of the photosensors 13 to 18.
[0020]
In addition, two light shielding plates 20 and 21 that are parallel to each other are erected on the front side (light incident side) of the wide-angle scattered light detection group 10 (photosensors 13 to 18). In the shielding plates 20 and 21, a plurality of openings, for example, slits 22 and 23 for allowing only the scattered light having a specific scattering angle to pass through the photosensors 13 to 18 are opened by a technique such as etching. .
[0021]
Note that, for example, the slits 22 and 23 corresponding to one photosensor 13 that detects forward scattered light are not necessarily the same shape and size, and among the forward scattered light from the cell 2, scattered light having a predetermined scattering angle. The mutual positions are set so that only the light enters the photosensor 13. The same applies to the slits 22 and 23 corresponding to the other photosensors 14 to 18.
[0022]
The preamplifiers 12 and 19 are connected to a multiplexer 24 that sequentially captures the outputs from the preamplifiers 12 and 19 and sequentially sends them to the AD converter 25. The AD converter 25 receives the output of the AD converter 25. A computer 26 as an arithmetic processing unit to be input is connected.
[0023]
The computer 26 processes the outputs of the photodetector 9 and the photosensors 13 to 18 (digital data relating to the light intensity) converted into digital signals based on Fraunhofer diffraction theory and Mie scattering theory, and the particle diameter in the particle group Stores a program for obtaining the distribution. The computer 26 is connected to a color display 27 for displaying calculation results and the like.
[0024]
In the particle size distribution measuring apparatus D configured as described above, the condensed laser light applied to the sample S in the cell 2 is diffracted and / or scattered by the sample S in the cell 2, and the diffracted light and / or Alternatively, light having a relatively small scattering angle among the scattered light is imaged on the photodetector 9.
[0025]
At this time, in the photodetector 9, the photosensor 11 on the outer peripheral side receives light with a large scattering angle, and the photosensor 11 on the inner peripheral side receives light with a small scattering angle. Therefore, the light intensity detected by the outer photosensor 11 reflects the amount of sample particles having a smaller particle diameter, and the light intensity detected by the inner photosensor 11 is larger than that of the sample particles having a larger particle diameter. It reflects the amount. The light intensity detected by each of the photosensors 11 is converted into an analog electric signal, and further input to the multiplexer 24 via the preamplifier 12.
[0026]
On the other hand, among the condensed laser light diffracted and / or scattered by the sample particles, the light having a relatively large scattering angle is limited by the slits 22 and 23 formed in the light shielding plates 20 and 21 respectively, and the specific scattered light. Only angle scattered light is incident on the photosensors 13 to 18 respectively, and the light intensity distribution is measured.
[0027]
At this time, scattered light from sample particles having a large particle diameter is detected in the order of the forward scattered light photosensors 13 to 16, the side scattered light photosensor 17, and the backscattered light photosensor 18. The light intensity detected by each of the photosensors 13 to 18 is converted into an analog electric signal, and further input to the multiplexer 24 via the preamplifier 19.
[0028]
In the multiplexer 24, the measurement data from the photodetector 9 and the photosensors 13 to 18, that is, analog electric signals are sequentially taken in a predetermined order and converted into a serial signal, which is sequentially digitalized by the AD converter 24. The light intensity data for each scattering angle that is converted into a signal and further input to the computer 26 and obtained by the photodetector 9 and the photosensors 13 to 18 is processed based on Fraunhofer diffraction theory and Mie scattering theory. The processing result is displayed on the color display 27.
[0029]
As described above, in the particle size distribution measuring apparatus D, the light intensity distribution of the scattered light with respect to the large particle size range is measured by the photodetector 9, and the wide angle with respect to the small particle size range is measured. Since the light intensity distribution of the scattered light is measured by the photosensors 13 to 18 and the outputs of the photodetector 9 and the photosensors 13 to 18 are processed by the computer 26, the particle size distribution in the particle group is determined. It can be obtained all at once over a wide range from a relatively large particle size to a very small particle size.
[0030]
FIG. 3 is a perspective view schematically showing the configuration of the cell holder 30.
The particle size distribution measuring apparatus D includes a holding unit 28 that holds the cell 2 and a plane that uses the cell 2 together with the holding unit 28 and the optical axis of light emitted from the irradiation unit 3 as a normal line. A cell holder 30 having a moving mechanism 29 for moving is provided. The cell holder 30 is held upright on the upper surface of the optical bench base 31 (see FIG. 1).
[0031]
The holding portion 28 has a U-shaped cross section and an L shape in front view, and has a placement portion 32 on which the cell 2 is placed and three abutting on the cell 2 from one side. Abutting bodies 33, 33, 33 are provided.
[0032]
The mounting portion 32 is provided in parallel with each other, and each side wall portion 32a, 32a having a substantially L-shape in front view, and a gap formed between the two side wall portions 32a, 32a. Part 32b.
[0033]
The contact body 33 has a male screw portion (not shown) that is screwed into a female screw hole 32 c formed in one side wall portion 32 a of the mounting portion 32, and a handle portion 33 a of the contact body 33. , The contact body 33 can be moved in a direction approaching the other side wall portion 32a, and the handle portion 33a is rotated in the other direction to move the contact body 33 to the other side wall portion 32a. It can be moved in a direction away from the side wall 32a.
[0034]
The three contact bodies 33 are all provided for one side wall portion 32a, and are disposed, for example, at both ends and the center portion of the one side wall portion 32a.
[0035]
In order to fix the cell 2 to the holding portion 28 having the above-described configuration, first, the cell 2 is placed on the placement portion 32, and in this state, the three contact bodies 33, 33 with respect to the cell 2. , 33 may be moved so as to contact each other, whereby the cell 2 is sandwiched between the three contact bodies 33, 33, 33 and the other side wall 32a in the mounting portion 32. Will be held.
[0036]
The moving mechanism 29 moves the cell 2 in one direction (for example, the vertical direction or the vertical direction, hereinafter referred to as the X direction) on a plane whose normal is the optical axis of the light emitted from the irradiation unit 3. The first mechanism 34 for causing the cell 2 to move in the other direction perpendicular to the X direction (for example, left and right of the cell 2) And a second mechanism 35 for moving in the width direction or horizontal direction (hereinafter referred to as Y direction).
[0037]
The first mechanism 34 protrudes from the holding portion 28 and has a protruding portion 36 having a female screw hole 36a and a through hole 36b provided in the X direction, and a male screw body 37 screwed into the female screw hole 36a. A guide body 38 that is inserted through the through hole 36b, and a biasing means (for example, a spring) 39 that is held on the outer periphery of the guide body 38 and biases the protruding portion 36 in the length direction of the guide body 38; A driving means (for example, a stepping motor) 40 for rotating the male screw body 37 about its axis is connected to both ends of the guide body 38, and the male screw body 37 can be rotated about its axis. And a main body 41 to be held. The driving means 40 is also fixed to the main body 41.
[0038]
The second mechanism 35 protrudes from the main body 41 of the first mechanism 34 and is screwed into the female screw hole 42a and a protruding portion 42 having a female screw hole 42a and a through hole 42b provided in the Y direction. A male screw body 43, a guide body 44 that is inserted through the through hole 42b, and a biasing means that is held on the outer periphery of the guide body 44 and biases the protruding portion 42 in the length direction of the guide body 44 (for example, A spring) 45, a driving means (for example, a stepping motor) 46 for rotating the male screw body 43 about its axis, and both ends of the guide body 44 are connected, and the male screw body 43 is connected to its axis. It consists of a main body 47 that holds the cell guide 30 in a rotatable manner and also serves as a gantry for the cell guide 30. The drive means 46 is also fixed to the main body 47.
[0039]
In the moving mechanism 29 having the above-described configuration, the male screw body 37 is rotated around its axis by the driving means 40, whereby the holding part 28 having the projecting portion 36 is moved in the axial direction of the male screw body 37, that is, in the X direction. Can be moved to. At this time, the projecting portion 36 is guided by the guide body 38 and is urged by the urging means 39 so that backlash does not occur. It will move smoothly in the X direction.
[0040]
Further, by rotating the male screw body 43 around its axis by the driving means 46, the first mechanism 34 having the projecting portion 42, the holding part 28, and the cell 2 are moved in the axial direction of the male screw body 43, that is, in the Y direction. Can be moved to. At this time, the projecting portion 42 is guided by the guide body 44 and is urged by the urging means 45 so that backlash does not occur. It will move smoothly in the Y direction.
[0041]
In the cell holder 30 having the above-described configuration, the cell 2 can be held without sandwiching either one of the left and right side portions and the upper side portion. Irradiation allows measurement.
[0042]
In the particle size distribution measuring apparatus D having the above-described configuration, the cell 2 starts to be moved simultaneously with the start of measurement, and the focused laser beam is not biased over the entire measurable region of the cell 2 until the end of the measurement. The cell 2 will continue to be moved so as to irradiate.
[0043]
Here, as a method of moving the cell 2, for example, as shown in FIG. 4A, the cell 2 may be moved so that the focused laser beam is irradiated in a zigzag shape. As shown to (B), you may move so that a condensing laser beam may be irradiated with respect to the cell 2 substantially spirally.
[0044]
Then, the data accumulated by irradiating the cell 2 with the focused laser beam as described above may be averaged lastly to obtain the value of the particle size distribution.
[0045]
In the particle size distribution measuring apparatus D having the above-described configuration, measurement can be performed by irradiating a wide area of the cell 2 with a focused laser beam, and the amount of measurement data to be obtained increases. The accuracy of the particle size distribution obtained by averaging increases, and the reproducibility of the measurement can be improved.
[0046]
Note that the cell 2 may be moved intermittently without continuing to move from the start of measurement to the end of measurement, and measurement may not be performed while the cell 2 is moving, but may be performed only while the cell 2 is stopped. .
[0047]
In the above embodiment, the cell 2 is moved in the X direction and the Y direction. However, the movement of the cell 2 is not limited to such a configuration. For example, the cell 2 is irradiated from the irradiation unit 3. You may make it rotate around the axis | shaft parallel to the optical axis of the light to be performed.
[0048]
In the particle size distribution measuring apparatus D having the above configuration, when the measurer presses a measurement start button (not shown) to start the measurement of the particle size, that is, when a measurement start operation is performed, before starting the measurement, It is automatically determined whether or not the position and direction of the optical axis of the laser light emitted from the irradiation unit 3 is correct. If the optical axis is correct, the measurement is started. If the optical axis is not correct, the adjustment is made. It has an optical axis adjustment function of starting measurement after performing.
[0049]
That is, the particle size distribution measuring apparatus D is a transmission light detector for adjusting an optical axis (for example, a check pattern by four light receiving elements, see FIG. 2) 48 arranged around the optical axis center of the photodetector 9. When the measurer presses the measurement start button, the optical axis deviation is determined based on the output from the transmitted light detector 48. If there is no optical axis deviation, the measurement is started, and there is an optical axis deviation. If so, software (not shown) for adjusting the optical axis and thereafter starting measurement, and an actuator for changing the orientation and position of the mirror 7 based on a control signal generated from the computer 26 (Not shown). The actuator is incorporated in the laser optical axis adjusting mechanism 8.
[0050]
In the particle size distribution measuring apparatus D, when the measurer presses the measurement start button to start measuring the particle diameter, first, the optical axis deviation is determined based on the output from the transmitted light detector 48. Is done. The determination of the optical axis deviation may be performed based on, for example, whether the difference between the output values of the two light receiving elements facing each other among the four light receiving elements of the transmitted light detector 48 is within a certain value. it can. In order to facilitate the determination of the presence or absence of optical axis deviation, for example, when measuring the optical axis or adjusting the optical axis, a pinhole is inserted on the optical axis and the determination is made using the formed diffraction fringes. May be.
[0051]
As described above, it is determined whether or not there is an optical axis shift. If it is determined that there is no optical axis shift, measurement is started. If it is determined that there is an optical axis shift, a control signal is sent to the laser optical axis adjustment mechanism 8. The actuator is actuated based on this control signal, so that the condensed laser light reflected from the mirror 7 reaches the center of the photodetector 9, that is, the four transmitted light detectors 48 The angle of the mirror 7 and the like are adjusted so that the received light intensity by the light receiving element becomes substantially equal.
[0052]
Some conventional particle size distribution measuring devices have an automatic optical axis adjustment function that automatically adjusts the optical axis, but they have a function to confirm whether or not optical axis adjustment is actually required. Because it was not equipped, the measurer must always perform the optical axis adjustment work before the measurement, and even when the optical axis was in alignment, the measurer was performing unnecessary optical axis adjustment work. It was wasted time. For example, if the optical axis adjustment work is not performed or forgotten in order to shorten the measurement time, accurate measurement data cannot be obtained.
[0053]
However, as described above, when the measurer presses a measurement start button (not shown) to start the measurement of the particle diameter, the light of the laser beam emitted from the irradiation unit 3 before starting the measurement. Optical axis adjustment that automatically determines whether the position and direction of the axis are correct, starts measurement if the optical axis is correct, and starts measurement after adjusting if the optical axis is not correct In the particle size distribution measuring device D having a function, since it is not possible to perform the optical axis adjustment work if it can be confirmed that the optical axis is aligned, it is possible to eliminate wasted time for unnecessary optical axis adjustment work, When the measurement start button is pressed, it is configured to automatically determine whether there is an optical axis misalignment, so the measurer forgets to adjust the optical axis and obtains inaccurate measurement data. Can be surely prevented Than is.
[0054]
Note that it is particularly effective to add the above-described optical axis adjustment function to the particle size distribution measuring apparatus D adopting the configuration in which the cell 2 is moved during measurement as described above. Needless to say, the present invention can be applied to a particle size distribution measuring device other than the particle size distribution measuring device D.
[0055]
【The invention's effect】
According to the present invention having the above-described configuration, it is possible to provide a particle size distribution measuring apparatus capable of measuring a larger area in the paste type cell and measuring an accurate particle size distribution.
[Brief description of the drawings]
FIG. 1 is an explanatory view schematically showing the configuration of a particle size distribution measuring apparatus according to an embodiment of the present invention.
FIG. 2 is a perspective view schematically showing a configuration of a photodetector in the embodiment.
FIG. 3 is a perspective view schematically showing a configuration of a cell holder in the embodiment.
FIGS. 4A and 4B are explanatory views schematically showing an example of a locus of focused laser light irradiated on a cell in the embodiment and another example. FIGS.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Plate-shaped body, 2 ... Paste type cell, 3 ... Irradiation part, 4 ... Detection means, 29 ... Moving mechanism, D ... Particle size distribution measuring apparatus, S ... Sample.

Claims (1)

A paste-type cell composed of two plate-like bodies having light permeability held with a sample sandwiched therebetween, an irradiation unit for irradiating light to the paste-type cell, and light from the irradiation unit A particle size distribution measuring apparatus comprising a detecting means for detecting secondary light generated by irradiating the sample, wherein the paste-type cell is the normal axis of the optical axis of the light irradiated from the irradiating unit the moving mechanism for moving on the surface to be provided,
The paste type cell is intermittently moved by the moving mechanism so that light from the irradiation unit is irradiated over different areas of the paste type cell,
Particle size, characterized in that measurement is performed while the paste type cell is stopped, and whether or not there is a deviation of the optical axis of the laser beam irradiated from the irradiation unit before starting the measurement. Distribution measuring device.

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