JPS63133041A - Light scattering type fine particle meter - Google Patents

Abstract

PURPOSE:To achieve a higher detection sensitivity, by arranging the lens optical axis of a focusing system on a surface orthogonal to an electric field vibrating surface of irradiation laser light including the irradiation laser light to pass through a measuring area while a slit is provided to remove stray light. CONSTITUTION:A sample air current 12 flows out from a nozzle 13 and into a nozzle 14 maintaining a laminar flow state running through an irradiation laser beam 1. On the other hand, the irradiation laser beam 1 has an electric field vibrating surface 9 determined depending on the direction of a slant section of a polarization window 17 of a laser oscillation tube 16. The lens optical axis 11 of a focusing system is so arranged on a plane 10 orthogonal to the electric field vibrating surface 9 of the irradiation laser light including the laser beam 1 to pass through a measuring area. An image in the measuring area is separated from stray light with a slit 7 placed near an imaging position of scattering light by a focusing lens system 6. Scattered beams from fine particles in the sample are focused by the focusing lens system 6 in the direction of maximizing intensity and received with a light receiving element 3 cleared of the stray light with the slit 7 to be converted into an electrical signal, which is amplified and processed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a light scattering particle meter, and more particularly to a light scattering particle meter using a laser as a light source.

[Conventional technology]

Conventionally, a light scattering particle meter uses a laser as a light source,
In particular, the scattered light condensing system used an elliptical mirror as shown in FIG. 3, or a parabolic mirror as shown in FIG. That is, the measurement region (S) of a sample flowing in a direction perpendicular to the plane of the paper is irradiated with laser light (1) in a direction perpendicular to the flow direction, and the scattered light by fine particles in the sample is detected as shown in Fig. 3. In the case of Fig. 4, the light is focused on the light receiving element (3) by an elliptical mirror (2a), and in the case of Fig. 4, a parabolic mirror (2b),
Light receiving element (3) using a plane mirror (4), lens (5), etc.
The light was focused on.

All of the configurations described above have the advantage of being able to obtain a large amount of light because they have a large solid angle of light convergence, but on the other hand, optical noise due to so-called stray light, including light scattered by molecules such as sample air, is generated. The disadvantage was that the components were also large.

Further, in the case of using these aspherical mirrors, it is difficult to accurately form an image of scattered light, and therefore a slit cannot be used for removing stray light.

On the other hand, the lens shown in FIG.
), the scattered light can be focused accurately, so the stray light can be removed using one or more slits (force), and the scattered light can be collected with a high S/N ratio. .

[Problem that the invention seeks to solve]

As described above, the conventional light-scattering particle meter equipped with a lens-based condensing system, as explained in Figure 5, has low detection sensitivity because it cannot obtain a large solid angle of convergence like an aspherical mirror. There was a problem.

This invention was made in order to solve this problem, and Kokichi provides a light scattering particle meter using a laser as a light source, which can obtain sufficient sensitivity by using a lens in the condensing system. This is the purpose.

[Means for solving problems]

The light scattering type particle meter according to the present invention has the following features:
The optical axis of the lens of the condensing system is arranged so as to pass through the measurement area, and a slit is provided to remove stray light.

[Effect]

In this invention, the optical axis of the scattered light condensing system is located in the plane where the intensity of the scattered light is strongest, and stray light is removed, so detection sensitivity is significantly improved.

〔Example〕

First, the principle of this invention will be explained with reference to FIG.

As a feature of laser light, the electric field vibration plane and magnetic field vibration plane of the light are determined by the direction of the Brewster window of the laser oscillation tube in the case of a Cass laser, and by the direction of the junction surface in the case of a semiconductor laser.

As shown in Figure 2, the intensity of the scattered light generated when fine particles in the measurement area (S) are irradiated with the laser beam (1) is 1, as shown by the electric field of the laser beam (1). Vibration surface (9)
It is the thickest on the plane that is perpendicular to the plane and includes the laser beam (1). (10) shows the magnetic field vibration plane.

This invention makes use of the above-mentioned properties, and as shown in FIG. on the surface,
The lens optical axis (11) of the condensing system is arranged so as to pass through the measurement area (S). Then, stray light is removed by at least one slit (7) placed near the imaging position of the scattered light, and the scattered light is efficiently focused.

FIG. 1 shows an embodiment of the present invention when an external mirror type laser of a Kass laser is used as a light source, in which a sample air stream (12) containing fine particles flows out from an outflow nozzle (13) and is irradiated. After passing through the laser beam, it flows into the exhaust nozzle (14) opposite the outflow nozzle (13) while maintaining a laminar flow state. (15) is an external mirror.

The region where the sample air flow (12) passes through the irradiated laser beam (1) is the measurement region (S). It is important that the sample air flow (12) be in a laminar flow state when passing through this measurement area (S), so the outer periphery of the sample air flow (12) is wrapped with clean source air and the sample air flow (12) is laminar. Two nozzles (13) (
14) Allow for flow between spaces.

On the other hand, the electric field vibration plane (9) of the irradiated laser beam (1) is determined by the orientation of the oblique section of the Brewster window (17) of the laser oscillation tube (work 6). Generally, the plane determined by the perpendicular line placed at the center of this oblique section and the irradiated laser beam (1) becomes the electric field vibration plane. On a plane that is orthogonal to this electric field vibration plane (9) and that includes the irradiated laser beam (1), the lens optical axis (11) of the condensing system is arranged so as to pass through the measurement region (S).

A slit (7) placed near the imaging position of the scattered light by the condenser lens system (6) separates the image of the measurement area (S) from the stray light.

With the above configuration, the light scattered by the fine particles in the sample is focused by the condensing lens system (6) in the direction where its intensity is maximum,
In addition, stray light is removed by the slit (7) and the light receiving element (
3), the light is received and converted into an electrical signal, which is then amplified and processed.

〔Effect of the invention〕

As is clear from the above description, the present invention has a method in which the lens optical axis of the condenser lens system is positioned through the measurement region on a plane that is perpendicular to the electric field vibration plane of the irradiated laser beam and that includes the irradiated laser beam. This allows us to efficiently collect scattered light and eliminate stray light using slits.
This has the effect of significantly improving detection sensitivity.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the arrangement of essential parts of an embodiment of the present invention;
Figure 2 is a schematic diagram for explaining the invention in detail;
5 to 5 are plan cross-sectional views showing the arrangement of main parts of a conventional light scattering type particle meter. (1)...Irradiated laser beam, (3)...Photodetector, (6
)... Condensing lens system, (7)... Surin l-, (9)...
Electric field vibration plane + (11)...Optical axis of condensing lens system,
(12)...Sample air flow, (S)...Measurement area.

Claims (1)

[Scope of Claims] A light scattering particle meter that uses a laser beam as a light source and condenses light scattered by fine particles onto a light-receiving element using a condensing lens system, wherein the optical axis is orthogonal to the electric field vibration plane of the irradiated laser beam. A light source comprising: the condensing lens system located on a plane containing the irradiated laser beam through the measurement area of the fine particles; and a slit disposed near the imaging position of the scattered light. Scattering particle meter.