JP3258889B2 - Optical axis adjustment method in scattering particle size distribution analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of irradiating a sample with light from a light source, and then causing scattered light to be incident on a photodetector via a condenser lens. The present invention relates to an optical axis adjusting method in a scattering type particle size distribution measuring device for measuring a particle size distribution in a sample based on a pattern.

[0002]

2. Description of the Related Art FIG. 4 shows a main part of a general scattering type particle size distribution measuring apparatus. In this figure, reference numeral 1 denotes a laser tube for emitting a laser beam 2, and 3 denotes a beam for appropriately expanding the laser beam 2. Magnifier 4, a cell for housing sample 5, 6 a condenser lens provided behind cell 4, 7 a photodetector comprising a photodiode for detecting scattered light from condenser lens 6,
8 is a multiplexer for taking in the signal from the photodetector 7;
9 receives a signal from the multiplexer 8 and performs a calculation based on the scattered light intensity pattern to obtain a particle size distribution.
PU.

In the scattering type particle size distribution measuring device,
When the sample 5 is accommodated in the cell 4 and the laser light 2 is irradiated on the sample cell 4, a part of the laser light 2 irradiates the particles in the sample 5 in the cell 4 to become scattered light 10, and the remaining The light passes between the particles and becomes transmitted light 11. And
Both the scattered light 10 and the transmitted light 11 reach the photodetector 7 via the condenser lens 6.

In the scattering type particle size distribution measuring apparatus, the optical axis of the laser tube 1 as a light source and the optical axis of the photodetector 7 must be strictly coincident with each other. The bench (not shown) provided with the cell 4, the lens 6, the photodetector 7, etc. is distorted by heat, and when the cell 4 is replaced, the mounting position is changed. The optical axis sometimes shifted.

Therefore, in a conventional scattering type particle size distribution measuring apparatus, as shown in FIG. And the position of the photodetector 7 is adjusted so that the intensity signals output from the four light receiving elements 12a to 12d constituting the optical axis adjusting light receiving unit 12 are equal to each other. Axis alignment was performed.

In FIG. 5, reference numeral 13 denotes a scattered light detecting measuring unit comprising a plurality of scattered light receiving elements 13a, 13b, 13c,... 13n provided concentrically around the optical axis adjusting light receiving unit 12. 14 is each scattered light receiving element 13a-1
3n is an isolation gap 14 provided between 3n.

In order to perform the optical axis adjustment as described above, the optical axis adjusting light receiving section 12 has a radius equal to or larger than the variation of the laser light emitted from the laser tube 1. When the laser beam fluctuates, for example, by a maximum of 100 μm, the optical axis adjusting light receiving unit 12 having a radius of 100 μm is required to measure the fluctuation.

[0008]

By the way, in the scattering type particle size distribution measuring device, the larger the particle diameter,
Since the angle of the scattered light with the optical axis becomes small, it is necessary to form the scattered light detection measurement unit 13 at a position close to the optical axis center part 7A. In the case where the light receiving unit 12 for adjusting the axis is provided, the scattered light receiving element 13a or the like cannot be provided in the vicinity of the center 7A of the optical axis, and therefore, there is a certain limit in the measurement of particles having a large diameter. Was.

[0009] The present invention has been made in mind the above-mentioned matters, and its object is also sufficiently close to the optical axis center of the photodetector provided scattered light receiving element to ensure optical axis alignment An object of the present invention is to provide an optical axis adjustment method (hereinafter simply referred to as an optical axis adjustment method) in a scattering type particle size distribution measuring device that can perform the method.

[0010]

According to the present invention, a diffracted light generating means is provided on an optical axis connecting a light source and a photodetector, and diffracted light generated by the diffracted light generating means is provided. To adjust the optical axis.

[0011]

According to the present invention, a sample is irradiated with light from a light source , and scattered light at that time is made incident on a photodetector via a condenser lens, and a scattered light intensity pattern obtained at this time is obtained. In a scattering particle size distribution measuring device that measures the particle size distribution in the sample based on the above, while providing a diffracted light generating means in the optical path between the light source and the condensing lens, the optical axis center of the photodetector Around three or more diffracted light detectors,
Equivalently arranged so as not to overlap with the scattered light measurement detection unit provided in the photodetector, diffracted light generated when light from the light source passes through the diffracted light generation means enters the diffracted light detector. The optical axis is adjusted by changing the position of the photodetector or the light source so that the respective outputs at the same time become equal.

As the diffracted light generating means, for example, a pinhole may be formed in a plate that blocks light, and conversely, a small-diameter light-shielding portion may be formed in a light-transmitting plate. .
In any case, desired diffracted light can be obtained.

In performing the adjustment based on the light intensity of the diffracted light, if the optical axis is finely adjusted so that the light condensed by the condenser lens is maximized, the optical axis position accuracy can be further improved. .

[0014]

Embodiments will be described with reference to the drawings. In the following drawings, the same components as those shown in FIGS. 4 and 5 are the same components, and the description thereof will be omitted.

FIG. 1 shows the configuration of a scattering type particle size distribution measuring apparatus to which the present invention is applied. This scattering type particle size distribution measuring device is basically the same as the scattering type particle size distribution measuring device shown in FIG. 4, and is used for adjusting the optical axis in the optical path between the laser tube 1 and the condenser lens 6. The difference is that the diffracted light generating means 15 used for the above is provided and the diffracted light generated by the diffracted light generating means 15 is detected by the photodetector 16. Hereinafter, these details will be described.

FIG. 2 shows an example of the diffracted light generating means 15. In FIG. 2, reference numeral 17 denotes a plate made of a light-blocking material, and a pinhole 18 is opened substantially at the center thereof.

FIG. 3 shows an example of a planar configuration of the photodetector 16. In FIG. 3, reference numeral 19 denotes an output monitoring detector provided at the center O of the optical axis of the photodetector 16. It has a light receiving section equivalent to the beam diameter of the laser light 2. 20 is the optical axis center O (output monitor detector 19)
And a plurality of scattered light receiving elements 20a to 20n provided concentrically in a fan shape with a spread angle of 90 °
A scattered light detecting measurement unit 21 includes an isolation gap 21 provided between the scattered light receiving elements 20a to 20n. 22 is an output monitoring detector 19
And a diffracted light detector provided at a position that does not overlap with the scattered light receiving elements 20a to 20n.
It is provided so that the circumference may be evenly distributed.

In the scattering type particle size distribution measuring apparatus having the above configuration, when measuring the particle size distribution of the sample 5, the laser beam 2 is irradiated by the laser tube 1 in a state where the sample 5 is accommodated in the cell 4. At this time, the diffracted light generating means 15 moves in the direction of arrow U in FIG. 1 and is retracted from the optical path so as not to disturb the measurement. Part of the laser light 2 irradiates the particles in the sample 5 in the cell 4 to become scattered light 10, and the remaining light passes between the particles and transmits light 11.
Becomes Then, both the scattered light 10 and the transmitted light 11 reach the photodetector 16 via the condenser lens 6. Then, the output of the photodetector 16 obtained at this time is input to the CPU 9 via the multiplexer 8, and the CPU 9 performs an arithmetic operation based on the scattered light intensity pattern to obtain the particle size distribution.

When adjusting the optical axis, the diffracted light generating means 15 is moved in the direction of arrow V in FIG. 1 and is interposed between the beam expander 3 and the cell 4. When the laser light 2 is emitted toward the cell in this state, a diffracted light approximated by Fraunhofer diffraction I is generated.

I = I ₀ (J ₁ (x) / x) ² x = 2πrs / λf where λf; wavelength r; pinhole radius s; detector position J ₁ ; first-order Bessel function I ₀ ; Light intensity

In this case, the diffracted light generated by the diffracted light generating means 15
The diameter of the pinhole 18 provided in the plate member 17 is appropriately set so as to be incident on the plate 2. Then, the position of the photodetector 16 is finely moved so that the outputs from the four diffracted light detectors 22 become equal. Then, a point where the outputs of the respective diffracted light detectors 22 become equal to each other is obtained, and the light detector 16 is fixed at that position. For example, the diameter of the pinhole 18 only needs to be 320 μm so that the light intensity of １ ／ of the maximum diffracted light intensity comes to the position of 50 μm. The diffracted light at that time spreads to a radius of 820 μm. Therefore, it is possible to adjust the optical axis fluctuation of the laser beam 2 within this range.

As can be understood from FIG. 3, the light receiving elements 22a to 22d constituting the diffracted light detector 22 are the scattered light receiving elements 20a to 20n of the scattered light detecting measurement unit 20.
And the element (in this case, 20 a) inside the scattered light detection measurement unit 20 is arranged in a state very close to the optical axis center O of the photodetector 16. Therefore, since the light receiving element of the scattered light detection measurement unit 20 can be arranged very close to the optical axis center O, it is possible to sufficiently measure particles having a large diameter, which has been conventionally difficult.

The present invention is not limited to the above embodiment, but can be implemented in various modifications. For example, as the means 15 for generating the diffracted light, a device in which a small-diameter light-shielding portion is formed on a translucent member may be used. That is, the plate 17 shown in FIG.
Instead of 8, spherical particles made of a light-shielding material may be formed in this portion.

The insertion and retreat of the diffracted light generating means 15 into and out of the optical path may be automatically performed by an appropriate mechanism. Further, the installation position of the diffracted light generating means 15 may be any position as long as it is an optical path between the laser tube 1 and the condenser lens 6.

In the above-described optical axis adjustment method, since the diffracted light generating means 15 is inserted with the cell 4 provided in the optical path, it is suitable for a scattering type particle size distribution measuring apparatus in which the cell 4 cannot be removed. However, instead of this method, cell 4
May be removed from the optical path, and the diffracted light generating means 15 may be set at that position.

The number of light receiving elements constituting the diffracted light detector 22 provided in the light detector 16 may not be four, and the laser light 2 may be directed in the directions indicated by arrows X and Y in FIG. In other words, it is only necessary to detect a shift in the two-dimensional direction and correct the shift. Therefore, at least three light receiving elements are required, and more preferably, they are arranged concentrically around the optical axis center O.

Further, in the various optical axis adjustment methods described above, if the optical axis is finely adjusted so that the laser beam condensed by the condenser lens 6 is maximized, the optical axis position accuracy can be further improved. it can.

It is needless to say that this optical axis adjusting method can be applied not only to the laser 2 but also to a scattering type particle size distribution measuring apparatus using other light beams.

[0029]

The present invention is embodied in the above-described embodiment and has the following effects.

Since the light-receiving element of the measuring unit for detecting scattered light can be arranged closer to the center of the optical axis of the photodetector than in the prior art, it is possible to measure particles having a larger diameter than before. , A particle size distribution having a wider measurement range can be measured at a time.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an example of a scattering type particle size distribution measuring apparatus to which an optical axis adjusting method of the present invention is applied.

FIG. 2 is a perspective view showing an example of a diffracted light generating means used in the optical axis adjusting method.

FIG. 3 is a diagram schematically showing a planar configuration of a photodetector of the scattering type particle size distribution measuring device.

FIG. 4 is a diagram schematically showing a configuration of a general scattering type particle size distribution measuring device.

FIG. 5 is a diagram schematically showing a planar configuration of a photodetector of the scattering type particle size distribution measuring device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Light source, 6 ... Condensing lens, 10 ... Scattered light, 15 ... Diffracted light generation means, 16 ... Photodetector, 17 ... Light shielding member, 18
... pinhole, 19 ... monitor detector for output detection, 22
… Diffraction light detector, O… Center of optical axis.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-215662 (JP, A) JP-A-62-100637 (JP, A) JP-A-5-273114 (JP, A) 172730 (JP, A) Hikaru Hei 1-124550 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 15/02 G01N 21/47

Claims (5)

(57) [Claims] 1. A diffractive light generating means is provided on an optical axis connecting a light source and a photodetector, and an optical axis is adjusted using diffracted light generated by the diffracted light generating means. Optical axis adjustment method in scattering type particle size distribution measuring device. 2. A light from a light source is applied to a sample, and scattered light at that time is made incident on a photodetector via a condenser lens. In a scattering type particle size distribution measuring apparatus for measuring a particle size distribution, a diffracted light generating means is provided in an optical path between the light source and the condenser lens, and three or more diffraction lights are provided around an optical axis center of the photodetector. The photodetectors are equally arranged so as not to overlap with the scattered light measurement detection unit provided in the photodetector, and the diffracted light generated when light from the light source passes through the diffracted light generating means is diffracted by the diffracted light. The optical axis in a scattering type particle size distribution measuring device, characterized in that the optical axis is adjusted by changing the position of the optical detector or the light source so that each output when entering the optical detector becomes equal. Adjustment method. 3. The method for adjusting an optical axis in a scattering type particle size distribution measuring apparatus according to claim 1, wherein a means for forming a pinhole in a light-shielding member is used as the diffracted light generating means. 4. The optical axis adjusting method in a scattering type particle size distribution measuring apparatus according to claim 1, wherein a means for forming a small-diameter light-shielding portion on a translucent member is used as the diffracted light generating means. 5. An output detection monitor detector is provided at a center portion of an optical axis, and a monitor output when light transmitted through a condenser lens is incident on the monitor detector is maximized. 5. An optical axis adjustment method in the scattering type particle size distribution measuring device according to any one of 4.