JP2626009B2 - Particle size distribution analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a particle size distribution measurement based on a light diffraction / scattering method utilizing a diffraction phenomenon or a scattering phenomenon caused by irradiating light to particles in a dispersed and flying state. Related to the device.

<Prior art> A particle size distribution measuring apparatus utilizing the diffraction or scattering phenomenon of light by particles measures the intensity distribution of diffracted light or scattered light (the relationship between the diffraction angle or the scattering angle and the light intensity) and calculates the Fraunhofer diffraction. Alternatively, the particle size distribution of the sample is calculated by performing arithmetic processing based on the theory of Mie scattering.

By the way, in this type of apparatus, laser light is generally used as irradiation light because of measurement of diffracted light. Normally, the laser light is collimated to irradiate the sample particles, the diffracted / scattered laser light is condensed by a Fourier transform lens, and a ring-shaped photosensor array called a ring detector is formed on the focal plane. And the intensity distribution is measured.

<Problem to be Solved by the Invention> According to such a configuration, the particle size of the lower limit of measurement is restricted by the wavelength of the laser beam to be used, and in order to make the lower limit of measurement as small as possible under the restriction. Needs to measure even light with a large scattering angle. Here, the size of the ring detector is limited by this dimension because the semiconductor wafer is about 4 inches, so that it is necessary to shorten the focal length of the Fourier transform lens in order to receive light with a large scattering angle. is there. When the focal length is reduced, it becomes difficult to measure light having a small scattering angle (diffraction angle), and the upper limit of the measured particle diameter is restricted.

Conventionally, an optical system referred to as an inverse Fourier optical system may be used in order to escape the restrictions associated with the Fourier transform lens. In the inverse Fourier optical system, laser light is condensed by a condenser lens, a ring detector is arranged on the focal plane of the condenser lens, and particles to be measured are placed between the detector and the condenser lens. By using such an optical system, the lower limit of measurement is shifted to the smaller diameter side, but due to the restriction of the wavelength of the laser beam, the particle size of about 0.1 μm is the lower limit, and the upper limit in this case is about 80 μm. .

For the purpose of expanding the measurement range, multiple Fourier transform lenses with different focal lengths are selectably provided, and the ring detector is moved along the optical axis with it. However, since it is necessary to provide a movable portion, it is difficult to adjust the optical axis, and the lower limit of measurement based on the wavelength restriction still remains.

An object of the present invention is to use a complicated optical system without using
Moreover, the measurement range in one range is expanded without providing any movable part, and the measurement lower limit is set to the above particle size of 0.1 μm.
To lower than.

<Means for Solving the Problems> A configuration for achieving the above-described object will be described with reference to the drawings corresponding to the embodiments. In the present invention, one piece through which sample particles dispersed in a medium are flowed is described. In the flow cell 1 of
Parallel laser light L from laser optical system 2 and interference filter
Irradiation with a single wavelength M from the single wavelength optical system 3 including 35 is performed.

The laser light diffracted or scattered by the particles in the flow cell 1 is received by a ring-shaped photosensor array (ring detector) 5 via a Fourier transform lens 4 and its intensity distribution is measured as in the related art. Flow cell 1
The single-wavelength light scattered by the particles inside is received by a plurality of photosensors 6a, 6b,... Disposed at different scattering angle positions with respect to the flow cell 1, and the respective intensities are measured. The measurement data obtained by the plurality of photosensors 6a, 6b,... Is used together with the measurement data obtained by the ring-shaped photosensor array 5 as particle size distribution calculation data.

<Operation> Although the measurement lower limit of the particle size is restricted by the wavelength of the light used as described above, by making the wavelength of the single-wavelength light M shorter than the wavelength of the laser light L, the conventional laser light can be reduced. The measurement of the particle diameter smaller than the used lower limit of measurement becomes possible.

On the other hand, the measurement range of the diffraction / scattered light using the laser light L is determined by the size limitation of the ring-shaped photosensor array 5. Since measurement on the small diameter side can be performed by measuring at a plurality of scattering angles by 6a, 6b, etc., the focal length of the Fourier transform lens 4 can be expanded by selecting the upper limit of the measurement based on the main objective. it can.

<Embodiment> The drawings are perspective views showing the configuration of a measuring optical system according to an embodiment of the present invention.

In the flow cell 1, sample particles dispersed in a medium flow. The upper part of the flow cell 1 is used for measurement by a measurement optical system based on a normal laser light diffraction / scattering method,
The lower part is used for measurement by a measurement optical system using a single wavelength.

That is, the upper part of the flow cell 1 is irradiated with the parallel laser light L from the laser optical system 2 composed of the laser diode 21 and the collimator lens 22, and the diffraction / scattered light of the laser light L by the sample particles is reflected behind the flow cell 1. Is focused on the ring detector 5 by the Fourier transform lens 4 placed at the point, and forms a diffraction / scattered image here.

A single-wavelength light M from a single-wavelength optical system 3 including an ultraviolet light source 31, such as a deuterium lamp, a spherical mirror 32, a slit 33, a lens 34, and an interference filter 35, is provided below the flow cell 1. Light is emitted from a direction orthogonal to the light L. In the single-wavelength optical system 3, the ultraviolet light from the ultraviolet light source 31 is focused on the slit 33 by the spherical mirror 32. The slit image is condensed by the lens 34, and only a single wavelength light having a wavelength of, for example, 350 nm is guided into the flow cell 1 by the interference filter 35 disposed between the flow cell 1 and the lens 34.

A photometric slit 7 is disposed orthogonally to the irradiation optical axis of the single-wavelength light M, and a plurality of photodiodes 6a, 6b,... It is arranged at a corner position. By the photodiodes 6a, 6b, among the scattered light of the single-wavelength light M by the sample particles, those having a relatively large scattering angle are measured at a plurality of scattering angles.

In the above configuration, each sensor output of the ring detector 5 is amplified by an amplifier and digitized by an A / D converter as in the related art, and is taken into a computer as particle size distribution calculation data. The outputs of the photodiodes 6a, 6b,... For measuring the scattered light of the wavelength light M are similarly taken into the computer as data for calculating the particle size distribution. At this time, the amount of light in the optical system using the interference filter 35 is considerably small, and therefore, the intensity of the scattered light is extremely small. Therefore, it is necessary to increase the amplification factor of the amplifier connected to the photodiodes 6a, 6b,..., But the S / N, drift and the like become problems. This problem can be solved by the following objects.

The S / N can be improved by taking measures such as guiding the outputs of the photosensors 6a, 6b,... To an integrator via a preamplifier, or interposing an appropriate filter. The drift can be reduced by stabilizing the drive circuit of the ultraviolet light source 31 or by compensating the temperature of the amplifiers of the photosensors 6a, 6b,.

In the above embodiment of the present invention, the Fourier transform lens 4
When the focal length is appropriately selected in consideration of the wavelength of the laser light to be used, in the measurement of diffraction / scattered light by the ring detector 5 using the laser optical system 2, the particle size measurement range is, for example, about 3 μm to 200 μm. Becomes

On the other hand, photodiodes 6a, 6
In the measurement of scattered light by b ..., if the wavelength is 350 nm, the particle size measurement range can be about 0.05 μm to 2 μm.

Therefore, measurement of one range using one flow cell 1 makes it possible to measure a particle size range of 0.05 μm to 200 μm as a whole.

Although five photodiodes 6a, 6b,... Are provided in the embodiment drawing, it is preferable to provide more photodiodes 6a, 6b, for example, more than ten, because the number of measurement points increases.

In addition, by preparing a plurality of types of interference filters 35 and making them selectable, if the wavelength of the single wavelength light M is changed, a large number of data can be obtained in the same manner, and the measurement accuracy is improved.

<Effects of the Invention> As described above, according to the present invention, one flow cell is irradiated with single-wavelength light together with parallel laser light, and the intensity distribution of scattered light (or diffracted light) of each light is measured. Since the particle size distribution is calculated using both data, the measurement is performed in one range using the same cell, for example, 0.05 μm, without providing a complicated optical system and a movable part.
A wide particle size measurement range of about m to 200 μm is obtained.

[Brief description of the drawings]

The drawing is a perspective view showing the configuration of the measuring optical system according to the embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Flow cell 2 ... Laser optical system 21 ... Laser diode 22 ... Collimator lens 3 ... Single wavelength optical system 31 ... Ultraviolet light source 32 ... Spherical mirror 33 ... Slit 34 ... Lens 35 ... Interference Filter 4 Fourier transform lens 5 Ring detector 6a, 6b 6e Photodiode 7 Photometric slit

Claims (1)

(57) [Claims] An apparatus for obtaining a particle size distribution of sample particles based on Fraunhofer diffraction or Mie scattering theory from an intensity distribution of diffracted light or scattered light generated by irradiating the sample particles in a dispersed and flying state with light. One flow cell through which the sample particles dispersed in
A laser optical system that irradiates the flow cell with parallel laser light, a single wavelength optical system that irradiates the flow cell with a single wavelength light created by an interference filter, and a laser that is diffracted or scattered by the sample particles in the flow cell. Light is received via a Fourier transform lens, and a ring-shaped photosensor array for measuring the intensity distribution is disposed at different scattering angle positions with respect to the flow cell, and each is scattered by sample particles in the flow cell. Particle size distribution measurement comprising a plurality of photosensors for receiving light of a single wavelength and measuring the intensity thereof, and using data measured by the ring-shaped photosensor array and the plurality of photosensors as data for calculating a particle size distribution. apparatus.