JP3966851B2 - Light scattering particle counter - Google Patents

Description

  The present invention relates to a light scattering particle counter that measures the number of particles in a gas using light scattering characteristics. More specifically, the present invention relates to an improvement in the beam shape of laser light applied to a sample fluid.

  As shown in FIG. 6, this type of light scattering particle counter 100 includes a light source 102 that emits laser light 101, a light projecting lens 103 that focuses the laser light 101 onto a sample fluid 104, and a sample fluid 104. An apparatus including a flow channel means 105, a light receiving lens 107 that collects scattered light 106 generated by particles (dust) in the sample fluid 104, and a light receiving element 108 that photoelectrically converts the collected scattered light 106. Are known. Since the magnitude of the electric output pulse obtained from the light receiving element 108 and the suspended particle diameter have a correlation, the particle diameter can be obtained from the magnitude of the electric output pulse. Further, since a pulse is generated when particles pass, the number of particles can be obtained from the number of pulses.

  In order to detect the scattered light 106 with high accuracy, it is advantageous that the energy density of the laser light 101 is high. Therefore, the light projecting lens 103 is provided so as to condense the laser light 101 into small dots. Then, the sample fluid 104 passes through the dotted detection area 109. The sample fluid 104 is circulated from the downstream side using a suction pump.

  On the other hand, when the apparatus 100 is used as an apparatus for generating an alarm when the pollution degree of a clean room is monitored and contamination is expected, a large degree of accuracy can be predicted by monitoring many sample fluids 104 in a short time. It is desirable to issue an alarm early in the process.

JP-A-9-178645

  However, in the above-described light scattering particle counter 100, the laser light 101 is collected in a dot shape, so the sample fluid 104 must pass through a very narrow detection area 109. For this reason, in order to monitor many sample fluids 104 in a short time, it is necessary to distribute gas at high speed. Therefore, a large-capacity suction pump must be used, leading to an increase in size and cost of the apparatus 100. In addition, since it is necessary to increase the speed of the detection circuit, the circuit becomes complicated.

  Accordingly, an object of the present invention is to provide a light scattering type particle counter capable of detecting particles without circulating a sample fluid at high speed.

In order to achieve such an object, the invention according to claim 1 is a light scattering type particle counting device that irradiates a measurement region with laser light and counts particles based on scattered light generated by particles existing in the measurement region. And a flow path means for flowing the sample fluid containing the particles in a certain direction with a certain thickness, and the laser beam is formed in a belt-like laser beam and in a wide direction of the belt-like laser beam. The entire width of the sample fluid is traversed, and the flow of the sample fluid is 45 degrees with respect to the wide surface of the laser beam .

Therefore, since the laser beam is strip-shaped, the detection area can be widened as compared with the laser beam condensed like a dot as in the prior art. For this reason, since more sample fluid can be passed per unit time, the suction pump can be downsized and the detection circuit can be simplified. In addition, it has flow path means for flowing the sample fluid containing particles in a certain direction so as to traverse the entire width of the sample fluid in the wide direction of the belt-like laser beam, and further the flow of the sample fluid An angle of 45 degrees is formed with respect to the wide surface of the laser beam. Accordingly, since the laser beam covers the entire width of the sample fluid and is incident on the sample fluid at an angle of 45 degrees, the measurement region that is a portion where the laser beam and the sample fluid intersect can be enlarged. The particles can be counted reliably.

According to a second aspect of the present invention, in the light scattering type particle counter according to the first aspect, particles existing in the measurement region are generated in a direction perpendicular to the optical axis of the laser beam irradiated on the measurement region. A light receiving element for receiving scattered light is disposed. Therefore, since the direction orthogonal to the beam plane formed by the belt-shaped laser beam does not coincide with the direction in which the sample fluid flows, the arrangement of the light receiving elements that receive the scattered light is arranged to flow the sample fluid in a certain direction. The arrangement of the means can be prevented from overlapping, and the particles can be counted reliably.

As described above, according to the light scattering type particle counting apparatus of the first aspect, since the laser beam is in a band shape, the detection area is widened as compared with the conventional laser beam focused in a dot shape. be able to. For this reason, since more sample fluid can be passed per unit time, the suction pump can be downsized and the detection circuit can be simplified. Further, it is possible to predict the pollution degree with higher accuracy and to issue an alarm at an earlier time without increasing the size of the suction pump and the complexity of the detection circuit. Therefore, a warning can be given before the clean room is polluted. In addition, since the laser beam covers the entire width of the sample fluid and is incident on the sample fluid at an angle of 45 degrees, the measurement region that is the portion where the laser beam and the sample fluid intersect can be enlarged. The particles can be counted reliably.

Further, according to the light scattering type particle counter according to claim 2, light reception for receiving scattered light generated by particles existing in the measurement region in a direction perpendicular to the optical axis of the laser light irradiated on the measurement region. Since the elements are arranged, the arrangement of the light receiving elements that receive the scattered light can be prevented from overlapping with the arrangement of the channel means for flowing the sample fluid in a fixed direction. The arrangement of the light receiving elements and the channel means Is easy and particle counting can be performed reliably.

  Hereinafter, the configuration of the present invention will be described in detail based on the best mode shown in the drawings.

1 and 2 show an example of an embodiment of the light scattering particle counter 1 of the present invention. This light scattering type particle counter 1 irradiates a measurement region 3 with laser light 2 and counts particles 4 based on scattered light 5 generated by particles (dust) 4 existing in the measurement region 3. . The laser beam 2 is formed into a belt-like laser beam. Moreover, it has the flow path means 7 which flows the sample fluid 6 containing the particle | grains 4 in a fixed direction. The laser light 2 is wider than the thickness of the sample fluid 6 circulated by the flow path means 7 , and is at an angle of 45 degrees with respect to the traveling direction of the laser light 2 and in the wide direction of the laser light 2. It crosses over the entire width.

  The light scattering type particle counter 1 includes a light source 8 that emits laser light 2, a light projecting lens 9 that focuses the laser light 2 on a sample fluid 6, a flow path means 7, and particles 4 in the sample fluid 6. The light receiving lens 10 which condenses the scattered light 5 which generate | occur | produces, and the light receiving element 11 which photoelectrically converts the condensed scattered light 5 are provided.

  The light source 8 is a laser diode. The light projecting lens 9 includes a collimator lens 12 and a cylindrical lens 13. The collimator lens 12 changes the laser light 2 into parallel light. The cylindrical lens 13 is a set of two lenses, and the elliptical laser beam 2 is further converted into a flat strip-shaped light beam. For example, the laser beam 2 has a width (width in the direction perpendicular to the paper surface of FIG. 2A) of 4 mm and a thickness (thickness in the vertical direction in FIG. 2A) of about 50 μm. The energy density of the laser beam 2 is increased by the cylindrical lens 13.

  A beam pocket 14 is disposed on the downstream side of the light projecting lens 9. The beam pocket 14 traps the projected laser beam 2. Thereby, stray light due to reflection of the laser beam 2 inside the device 1 can be reduced, and background noise incident on the light receiving element 11 can be reduced. Therefore, it is possible to increase the signal-to-noise ratio and increase the signal amplification.

  The flow path means 7 includes an airtight portion 15 disposed on the downstream side of the light projecting lens 9, a supply pipe 16 that supplies the material fluid 6 to the airtight portion 15, a suction pump 17 that makes the airtight portion 15 a negative pressure, It has. Further, a portion where the laser beam 2 and the sample fluid 6 intersect becomes a measurement region 3.

The light receiving lens 10 faces the measurement region 3 and has its optical axis orthogonal to the optical axis of the laser light 2. As already described, since the light receiving lens 10 condenses the scattered light 5 on the light receiving element 11, the light receiving element 11 is also in a state orthogonal to the optical axis of the laser light 2. As the light receiving element 11, a SiPIN photodiode with a preamplifier is used. Thereby, a sensitivity and an S / N ratio can be improved.

  The operation of the above-described light scattering particle counter 1 will be described below.

  The laser light 2 emitted from the light source 8 passes through the light projection lens 9 and is formed into a belt shape. This belt-shaped laser beam 2 is projected to the airtight portion 15. On the other hand, the sample fluid 6 is circulated in the airtight portion 15 by the operation of the suction pump 17. Then, the laser beam 2 passes through the sample fluid 6. Here, the projected laser beam 2 is wider than the thickness of the sample fluid 6 circulated by the flow path means 7, and is full width of the sample fluid 6 in the direction perpendicular to the traveling direction and in the wider direction of the laser beam 2. Across. That is, the laser beam 2 is formed so that its width in the direction perpendicular to the paper surface of FIG. 2A is wider than the flow of the outermost layer of the sample fluid 6, and the laser beam 2 is the outermost layer of the sample fluid 6 in the direction perpendicular to the paper surface. Crosses the flow part of the outer layer.

  If the sample fluid 6 contains dust, scattered light 5 is emitted from the measurement region 3. The scattered light 5 enters the light receiving element 11 through the light receiving lens 10. Since the magnitude of the pulse of the electric output obtained from the light receiving element 11 and the particle diameter of the particle 4 have a correlation, the particle diameter can be obtained from the magnitude of the pulse of the electric output. Further, since a pulse is generated when the particle 4 passes, the number of particles can be obtained from the number of pulses.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in this embodiment, the laser light 2 exiting the light projecting lens 9 passes through the sample fluid 6 as it is. However, the present invention is not limited to this, and as shown in FIG. The laser beam 2 may be provided so as to pass through the sample fluid 6 after being reflected. According to this, since the optical path can be bent, the light scattering particle counter 1 can be miniaturized.

In the present embodiment, the flow of the sample fluid 6 is 45 degrees with respect to the wide surface of the laser beam 2. However, as a reference example different from the present invention , the flow is 90 degrees as shown in FIG. You may do it. In the light scattering type particle counter 1 shown in FIG. 4, the laser light 2 emitted from a light source (not shown) passes through two cylindrical lenses 13 and is compressed in a direction perpendicular to the paper surface so as to form a belt shape. I have to. A supply pipe 16 and a suction pump are provided so that the sample fluid 6 flows in a direction perpendicular to the paper surface.

  Further, in each of the above-described embodiments, the elliptical laser beam 2 is further flattened using the cylindrical lens 13, but the present invention is not limited to this, and the sample fluid 6 is directly irradiated with the elliptical laser beam 2. You may do it. Also in this case, since the laser beam 2 has a wide band shape, the sample fluid 6 can be irradiated widely.

  In each of the above-described embodiments, the sample fluid 6 flowing between the supply pipe 16 and the suction pump 17 is directly irradiated with the laser beam 2. However, the present invention is not limited to this, and is made of a transparent body that transmits the laser beam 2. The sample fluid 6 may be flowed through the pipe and the laser beam 2 may be irradiated from the outside.

  Further, in each of the above-described embodiments, the laser light 2 emitted from the light source 8 passes through the two cylindrical lenses 13 and is shown in the vertical direction (FIG. 2A, FIG. 3A) or on the paper surface. However, the present invention is not limited to this, and the light projecting lens 9 is made to be a collimator lens 12 as in the light scattering type particle measuring apparatus 1 shown in FIG. And only one cylindrical lens 13, and the laser beam 2 may pass through the sample fluid 6. According to this, the laser light 2 that has passed through the cylindrical lens 13 is not completely parallel light, but can be viewed as parallel light because the measurement region 3 is narrow, and the amount of particles is obtained in the same manner as in the above-described embodiments. be able to. Further, in the light scattering type particle measuring apparatus 1 shown in FIG. 5, a reflection mirror 20 is disposed on the side opposite to the light receiving element 11 and the light receiving lens 10. Thereby, the scattered light 5 scattered on the side opposite to the light receiving element 11 can be reflected by the reflection mirror 20 and condensed on the light receiving element 11, and the number of particles can be obtained more efficiently.

1 is a schematic perspective view showing the principle of a light scattering particle counter according to the present invention. (A), (B) is the schematic plan view and schematic side view which respectively show a light-scattering type particle counter. (A), (B) is the schematic plan view and schematic side view which show the other example of a light-scattering type particle counter, respectively. It is a top view which shows the reference example of a light-scattering type particle counter. (A), (B) is the schematic block diagram and schematic side view which show the other example of a light-scattering type particle counter, respectively. It is the schematic which shows the principal part of the conventional light-scattering type | mold particle counter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light-scattering type particle counter 2 Laser beam 3 Measurement area 4 Particle 5 Scattered light 6 Sample fluid 7 Channel means

Claims (2)

In a light scattering type particle counter that irradiates a laser beam to a measurement region and counts particles based on scattered light generated by particles present in the measurement region.
A flow path means for flowing the sample fluid containing the particles in a certain direction with a certain thickness, and the laser beam is formed in a belt-like laser beam, and in the wide direction of the belt-like laser beam, A light scattering type particle counting apparatus characterized in that the sample fluid traverses over the entire width of the sample fluid, and the flow of the sample fluid is 45 degrees with respect to the wide surface of the laser beam . The light scattering according to claim 1 , wherein a light receiving element that receives scattered light generated by particles existing in the measurement region is disposed in a direction orthogonal to an optical axis of laser light applied to the measurement region. Particle counter.

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