JPS62293143A - Measuring instrument for corpuscle - Google Patents

Abstract

PURPOSE:To give sufficient linearity to response characteristics to particle size although a laser beam source is used and to eliminate mismeasurement by irradiating the same corpuscle detection area with light beams from >=2 homonochromaticous light sources such as laser beam sources which differ in wavelengths. CONSTITUTION:The two laser beam sources 5A and 5B which differ in wavelength are arranged and the laser beams 6A and 6B emitted by the light sources 5A and 5B are projected on the same corpuscle detection area 4 at the same time. The corpuscles to be measured are spouted out of a nozzle 2 along with gaseous sample 1, and protected and guided by sheath air 3 to reach the area 4 as one flow. The corpuscles to be measured in case of passing through the area 4 are projected with the rays of light 6A and 6B at the same time to generate scattered light. This scattered light is converged by a lens 7 and converted into an impulsive electric output by a photoelectric converter 8.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a particle measuring device, and more specifically, to an improvement of a light source that irradiates a particle detection area with a light beam.

[Prior art]

Currently, an incandescent light bulb or a laser light source is usually used as a light source for a light scattering type particle measuring device.

Compared to particle measuring devices that use incandescent light bulbs as light sources, particle measuring devices that use a laser light source can narrow the luminous flux at the focal point, increasing the energy density and detecting particles with smaller diameters. It is detectable up to 0.
It is often used to detect extremely small particle sizes such as 1 μm.

Furthermore, since the laser light source has a long life, it also has the advantage of not requiring replacement of the light source for a long period of time.

FIG. 3 is a diagram showing the main part of a particulate detection section in a conventional light scattering type particulate measuring device using a laser light source.

Reference numeral 1 denotes a gas sample (air) containing fine particles to be measured, and sheath air 3 is drawn from the tip of the nozzle 2 by the action of an air pressurization system (not shown) or an air suction system (not shown).
At the same time, the particles are ejected, protected and guided by the sheath air 3, and pass through the particle detection area 4 as a single stream.

A laser beam 6 is emitted from a laser light source 5 so as to intersect the gas sample 1 in the particle detection region 4 . Therefore, every time the particles contained in the gas sample 1 pass through the particle detection area 4, scattered light is generated. Reference numeral 7 denotes a lens for condensing this scattered light, and the scattered light condensed by this lens 7 is guided to a photoelectric converter 8 and converted into a pulsed electric signal. This electrical signal is guided to a suitable electrical circuit (not shown) and subjected to electrical processing to finally obtain measurement results such as particle size distribution and number.

[Problem that the invention seeks to solve]

In the conventional light scattering type particle measurement device using a monochromatic laser light source as described above, the relationship between the size of the particles that generate scattered light and the relative intensity of the light beam scattered in a specific direction is generally as follows. It's proportional. In other words, the response characteristics have linearity and increase monotonically. Therefore, the larger the particle size of the fine particles, the stronger the intensity of the scattered light in a specific direction generated by the fine particles.

However, there is always a lack of linearity in the relationship between the scattered light intensity and particle size of fine particles within a specific particle size range depending on the wavelength of the laser beam to be irradiated, which cannot be ignored in practice.

Here, in such a device, where the diameter of the spherical particle that generates the scattered light is DP, and the wavelength of the irradiated monochromatic laser beam is λ, consider a size parameter α of α=π・Dp/λ, and this size parameter The relationship between the relative intensity I of the scattered light in the 70° direction with respect to α is calculated and shown in FIG. The relationship between the size parameter α and the relative intensity I shown in FIG. 4 holds regardless of the wavelength of the laser beam used.

A detailed explanation of this can be found, for example, in "Air Cleaning", Vol. 22, No. 4, pages 1 to 5, published on February 1, 1985.

As is clear from FIG. 4, there is a significant lack of linearity in the region where α is 1 to 1.5. Regarding fine particles having a particle size within this range, a disadvantage arises in that fine particles of different particle sizes emit scattered light of the same intensity, and fine particles with a small particle size emit stronger scattered light. This means that particle measuring devices, which normally classify and count the particle size of detected particles based on the intensity of scattered light, misidentify the particle size or are unable to identify the particle size, and the device This is a serious problem in terms of performance.

This phenomenon depends on the wavelength of the irradiated light.For fine particles with a particle size within a certain range, the light source of the scattered light cannot be considered to be a single point, but rather has multiple sources that cannot be ignored with respect to the wavelength. This is a physical phenomenon caused by the fact that the light sources at these multiple locations interfere with each other.

Therefore, this phenomenon does not occur when a so-called white light source, which includes miscellaneous wavelengths approximately evenly, such as an incandescent light bulb, is used as the irradiation light source.

As mentioned above, when a conventional monochromatic laser light source is used alone as a light source for a particulate detection unit, the linearity of the response characteristic to the particle size of the device to which it is applied is limited to a specific particle size range corresponding to the wavelength of the laser beam. There was a serious problem in that the particle size was misidentified and highly accurate measurement of particle size distribution was impossible.

[Purpose of the invention]

The present invention uses a laser light source, which has many advantages in particle measurement as described above, and also takes into account the special advantages of an incandescent light bulb.Therefore, even though it uses a laser light source, its response characteristics to particle size have sufficient linearity. The object of the present invention is to provide a particulate measuring device that is free from the risk of erroneous measurements.

Means for Solving Problem C] In order to achieve the above object, the particle measuring device according to the present invention includes two or more monochromatic light sources such as laser light sources with different wavelengths, and The light beams are made to irradiate the same particulate detection area at the same time.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a main part of a particulate detection section in a light scattering type particulate measuring device to which the present invention is applied.

In FIG. 3, the same parts are given the same reference numerals.

In this embodiment, two laser light sources 5A and 5B with different wavelengths are arranged, and the light source 5A.

Laser beams 6A and 6B respectively emitted from 5B are irradiated onto the same particulate detection area 4 at the same time.

The particles to be measured are ejected from the tip of the nozzle 2 together with the sample gas 1 (air in this embodiment), protected and guided by the sheath air 3, and reach the particle detection area 4 in a single stream. When the particles to be measured pass through the particle detection area 4, they are simultaneously irradiated with the laser beams 6A and 6B to generate scattered light. This scattered light is collected by a lens 7 as in FIG. 3, and converted into a pulsed electrical output by a photoelectric converter 8 and processed.

Next, the effects of this embodiment will be explained based on FIG. 2, which shows the relationship between the relative intensity and the particle size of light rays scattered in the 70° direction. This FIG. 2 corresponds to FIG. 4 shown as a conventional example.

In Fig. 2, since it is necessary to simultaneously illustrate the relative intensities of two laser beams with different wavelengths, the horizontal axis is plotted with the particle diameter D instead of the size parameter α as in Fig. 4 to avoid complication.
Use p.

First, Ia is the response characteristic of the relative intensity of the scattered light with respect to the particle size when it is assumed that only the laser beam 6A (wavelength is λa) is irradiated to the gas sample, and then Ib is the response characteristic of the relative intensity of the scattered light with respect to the particle size. , λa<λb) is assumed to be irradiated onto a gas sample. However, in reality, the gas sample is irradiated with the laser beams 6A and 6B at the same time, so the relative intensity of the scattered light with respect to the particle size in this example is a smooth one expressed by rt, which is the combination of Ia and Ib mentioned above. The linearity of the response characteristic of the relative intensity of the scattered light is significantly improved compared to when the laser beam 6A or the laser beam 6B is irradiated individually. The linearity of the response characteristic of scattered light is close to that in the case of .

In this example, an example was shown in which two laser light sources were arranged and two laser beams were irradiated, but the number is not limited to two, and in short, it is possible to irradiate two or more laser beams to the same particulate detection area. Batariru. Of course, if more laser light sources with different wavelengths are used to simultaneously irradiate the particle detection area with their light beams, the scattered light will approach the scattered light generated by a white light source, and the relative intensity of the scattered light will depend on the particle size. This is more preferable because linearity increases.

Also, although we only explained gas (air) as a sample,
It goes without saying that the present invention can be applied to liquids as well.

(Effects of the Invention) As explained above, according to the present invention, it is possible to simultaneously irradiate a fluid sample flow with two or more monochromatic light beams with different wavelengths in the same particle detection area, so that Although the response characteristic of the relative intensity of the scattered light to the particle size of the particle has the same level of linearity as when the particle detection area is irradiated with light from a white light source such as an incandescent light bulb, at the same time it is We provide a particulate measuring device that has features that are difficult to discard, such as high sensitivity, the ability to detect even smaller particles, and a light source that is long-lasting and easy to maintain. It has become possible to do so, and the effect is extremely large.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a main part of a particulate detection section showing an embodiment of the present invention, and FIG. 2 is a response characteristic diagram thereof. FIG. 3 shows a configuration diagram of the main part of a particulate detection section in a conventional light scattering type particulate measuring device, and FIG. 4 similarly shows a response characteristic diagram thereof.

Claims (2)

[Claims] (1) In a light scattering type particle measuring device that detects and processes the particles by irradiating light beams onto particles floating in a fluid sample in a particle detection area and measuring the resulting scattered light, the particles A particulate measuring device characterized in that two or more monochromatic light sources with different wavelengths are used as light sources for irradiating, and the light rays from each of the monochromatic light sources are simultaneously irradiated onto the same particulate detection area through which the fluid sample passes. (2) The particle measuring device according to claim (1), wherein a laser light source is used as the monochromatic light source.