JPH0654288B2 - Particle detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention irradiates a fluid beam containing dilute concentration of fine particles with focused beam light and detects scattered light of the beam light by individual fine particles. The present invention relates to a particle detection device for measuring the number of particles, the particle size, and the like.

[Conventional technology]

In the manufacturing process of semiconductors and pharmaceuticals, to check the cleanliness of ambient air, ultrapure water, the quality of chemicals, etc., and in the field of research such as medicine and biology, to check the state of cells, dust and cells etc. There is a need for a fine particle detection device for detecting the above fine particles, but recently, there has been a demand for the fine particle detection device to have the capability of detecting particles having a particularly fine particle size.

FIG. 8 is a block diagram of a conventional particle detection device for fluid, in which 1 is a flow cell having a transparent side wall having a rectangular cross section and allowing a measurement fluid 2 containing particles to flow in a direction perpendicular to the paper surface. , 3 is a beam irradiation mechanism consisting of a focusing lens 7 for the beam 6 to focus the light emitter 5 and the light beam 4 which emits a parallel light beam 4. Beam light irradiation mechanism 3
Is the beam of light 6 through the transparent side wall of the measuring fluid 2 in the flow cell 1, the optical axis of which is the axis B ₁ -B shown in the figure.
Irradiation is performed so as to coincide with ₂ . Axis B ₁ -B ₂ is an axis assumed in the plane of the drawing that constitutes three spatial axes orthogonal to the axis C ₁ -C ₂ and the axis perpendicular to the plane of the drawing, and O is set in the flow cell 1. It is the intersection of the three axes. 8, the measurement fluid 2 is a condenser lens 9 focusing light scattered light emitted from the particles in the fluid 2 in the intersection O vicinity by being irradiated by the beam light 6, condensed by the lens 9 Light The electric signal 10 according to the amount of light
A circular through hole 11a is provided so as to be interposed between the photoelectric converter 10 for converting to a and outputting the light and the lens 9 and the converter 10 and to limit the incident angle of light incident on the converter 9. A light receiving mechanism including the opening member 11 and the light receiving mechanism 8
Are arranged so that their optical axes coincide with the axes C ₁ -C ₂ . A beam block 12 is provided so that the beam light 6 that has passed through the flow cell 1 does not enter the light receiving mechanism 8 as stray light, and the block 12 is configured to absorb the beam light 6. Reference numeral 14 denotes a signal processing unit which performs predetermined signal processing on the electric signal 10a and displays the state of fine particles such as the number of fine particles and particle size distribution.

Next, the operation of the light receiving mechanism 8 in the detection device shown in FIG. 8 will be described with reference to FIG. That is, FIG. 9 is an enlarged perspective view of a main part in FIG. 8, and in the drawing, A ₁ -A ₂ is an axis that forms an orthogonal triaxial axis with an axis B ₁ -B ₂ and an axis C ₁ -C _{2 at an} intersection O. Then, the axes A ₁ -A ₂ also coincide with the longitudinal axis of the flow cell 1. P is the axis A ₁
-A ₂ in parallel, a arrow indicating the direction of flow of the measurement fluid 2. 13 is a stereoscopic viewing area of the light-receiving mechanism 8 formed in the vicinity of the intersection O, the viewing area 13, since the light receiving mechanism 8 is configured as described above, the axis C ₁ -C around the intersection point O
_It has a spindle shape with ₂ as the axis. Area 13 is a light receiving mechanism
Since the field of view is 8 , only the light captured by the light receiving mechanism 8 out of the light emitted from the region 13 is photoelectrically converted by the mechanism 8 . In FIG. 9, the main part is configured so that the entire visual field region 13 exists within the light beam 6, and therefore, when fine particles carried by the measurement fluid 2 pass through the region 13, scattered light is generated in a pulse shape. Then
Therefore, the scattered light is incident on the photoelectric converter 10 and the signal 10a photoelectrically converted is also pulse-shaped. Therefore signal 10
Field of view 1 depending on the number and magnitude of the pulses forming a
It is possible to detect the number and the particle size of the fine particles passing through 3. The signal processing unit 14 in FIG. 8 is configured to perform such signal processing.

In FIG. 8, fine particle detection is performed as described above, but if the light receiving amount of the light receiving mechanism 8 is small, accurate fine particle detection becomes impossible. Therefore, in order to increase the amount of scattered light, it is usual to narrow the beam light 6 to increase the light intensity. Therefore, in general, the intersection point O of the beam light 6 is increased.
The diameter in the vicinity is several hundreds to several tens of μm. 8th
The focusing lens 7 in the figure is provided for this reason.

[Problems to be Solved by the Invention]

In FIG. 8, the number and the particle size of the fine particles passing through the visual field region 13 are detected as described above, but as will be described below, the intensity distribution of the light beam 6 in the region 13 is non-uniform. A detection error will occur. That is, FIG. 10 is an explanatory diagram for explaining the reason why such a detection error occurs.
FIG. 0 (A) shows the vicinity of the region 13 in FIG. 9 as the axis A ₁ -A ₂
It is a figure corresponding to the figure cut by the plane formed by and the axes C ₁ -C ₂ . Reference numerals 15 and 16 in FIG. 10 (A) denote the area 13 and the field of view corresponding to the light beam 6 and the light beam in FIG. 9, and in this case, the light beam 16 penetrates the area 15.

17a and 17b are conveyed by the measurement fluid 2 and move in the P direction across the area 15 on the paper surface of the drawing,
Two spherical fine particles having the same particle size. Fig. 10
When the particles 17a and 17b move as described above in (A), the intensity distribution on the paper surface of the beam light 16 as shown in FIG. 10 (B) shows the maximum value of the light intensity at the point O. If it has a hanging bell shape, the fine particles 17a,
Depending on the path 17b traverses the region 15, the beam of light 16
In some cases, the scattered light may not be generated, or in some cases, scattered light having different intensities may be generated for the fine particles 17a and 17b having the same size. Therefore, in the former case, a detection error with respect to the number of fine particles occurs, and in the latter case, a detection error with respect to the particle size of fine particles occurs. In the above-mentioned particle detection device, a laser beam is usually used as the beam light in order to increase the intensity of the beam light for irradiating the measurement fluid so as to detect particles having a particle size as small as possible. Since the light intensity distribution of such a laser beam is as shown in FIG. 10 (B), the above-described detection error occurs.

For this reason, conventionally, the measurement fluid is only in the vicinity of the axis A ₁ -A ₂ shown in FIG. 10 (A), where the light intensity is almost uniform on the light intensity distribution curve shown in FIG. 10 (B). A method of narrowing the fluid so as to flow or a method of arranging the visual field region 13 in a portion where the light intensity distribution of the beam light 6 is substantially uniform in FIG. 9 are adopted. In the particle detection device adopting the method, if the beam intensity is narrowed to increase the light intensity in order to reduce the particle size of the detectable particles, the nonuniformity of the light intensity distribution in the measurement fluid part increases, so the particle size Detection error becomes large, in other words, the resolution of the detection device with respect to the particle size of fine particles becomes poor, and in order to prevent such deterioration of particle size resolution, the measurement fluid is further narrowed down so that the fluid has one of the beam light intensity distributions. To exist only in the part , There is a problem that the measured amount of fluid that can be inspected in a predetermined time is less. Further, in the particle detection device adopting the latter method, when the beam light 6 is narrowed down in order to reduce the detectable particle size of the particle, the visual field region 13 of the light receiving mechanism 8 is arranged over almost the entire area of the beam light 6. Has a problem that the particle size resolution is lowered due to the non-uniformity of the light intensity distribution as described above, and the through hole 11a of the opening member is used to narrow the visual field region 13 in order to prevent such a resolution reduction. When is smaller, the amount of light that can pass through the through-hole is reduced, so that the amount of scattered light that enters the photoelectric converter 10 does not increase even if the light intensity of the beam light 6 is increased. Can not.

An object of the present invention is to solve the problems in the conventional particle detection device as described above, and to detect the detectable particle size without reducing the volume of the particle-containing fluid that can be inspected within a certain period of time and the particle size resolution. It is an object of the present invention to provide a particle detection device that can be reduced in size.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present invention includes a beam light deflection unit for linearly repeatedly scanning a focused beam light across a flow of a measurement fluid containing fine particles to a predetermined width of the measurement fluid. A beam light irradiation mechanism, a light receiving mechanism for receiving scattered light emitted from the fine particles by irradiation of the beam light and outputting a signal pulse train corresponding to the scattered light converted into an electric signal by a photoelectric converter, and the pulse train And a signal processing unit for processing the peak value of the maximum pulse and the group number information of the pulse train group and outputting the particle size and the number of particles.

[Action]

By configuring as described above, the intensity distribution uniform region of the beam light in the measurement fluid portion irradiated by the beam light is substantially expanded in the scanning direction of the beam light,
Moreover, the shape of the intensity distribution of the beam light does not affect the particle size resolution of the particle detection device. Therefore, it becomes possible to obtain a fine particle detection device capable of reducing the detectable particle size without causing a decrease in the volume of the fine particle-containing measurement fluid that can be inspected within a fixed time and a decrease in the particle size resolution.

〔Example〕

FIG. 1 is a block diagram of the first embodiment of the present invention. The main difference from FIG. 8 in FIG. 1 is that a beam light deflector 18 for linearly and repeatedly scanning the measuring fluid 2 with the beam light 6 is provided between the focusing lens 7 and the flow cell 1. And the signal processing unit 31 for performing signal processing different from that of the signal processing unit 14 in FIG. 8 is provided. In this case, the light emitter 5 emits the laser beam as the parallel light beam 4 He. -Ne laser generator. Reference numeral 19 denotes a beam light irradiation mechanism including a light emitter 5, a focusing lens 7 and a beam light deflector 18, and the beam light deflector 18 is configured as shown in FIG. That is, FIG. 2 is a configuration diagram of the main part in FIG. It is a reflecting mirror that can be repeatedly changed in an oscillating manner within a range of 2θ. Since the beam light deflecting section 18 is composed of the reflecting mirror 20 and the electromagnet 21 configured as described above, the beam light 6 emitted from the deflecting section 18 also vibrates within the range of the angle 2θ as shown in the figure. Direction changes. Therefore, in FIG. 1, the measuring fluid 2 is linearly scanned by the light beam 6 whose direction is changed as described above. In this case, the rotation of the light beam 6 about the point Q is performed. The main part is constructed so that the formed scanning surface coincides with the paper surface of FIG. As is apparent from FIG. 2, the light beam 6 is designed to be touched on both sides of the axis B ₁ -B _{2 by} an angle θ.

FIG. 3 is an explanatory view of the operation of the particle detection device shown in FIGS. 1 and 2. FIG. 3A is a plan view of the measurement fluid portion corresponding to the paper surface of FIG. 1, and FIG. FIG. 11 is a side sectional view of FIG. 1 corresponding to FIG. 10 (A). In FIG. 3, E, F
Is the intersection of the optical axis of the light beam 6 and the axis C ₁ -C ₂ when the light beam 6 touches the outermost side, L is the distance between points Q and O, l is the distance between points E and F, d Means that the optical axis of the light beam 6 is a point E or F.
The diameter of the circular spot 22 or 23 due to the beam light 6 formed on the surface formed by the axis A ₁ -A ₂ and the axis C ₁ -C ₂ respectively when passing through. As mentioned above,
In this case, since the light beam 6 vibrates in the range of the angle 2θ, _one having a length of l and a width of d on the surface formed by the axes A ₁ -A ₂ and C ₁ -C _2. Shaped band portion 24a
The region 24 composed of the semicircular portion 24b connected to each end of the strip portion 24a is periodically and repeatedly irradiated by the light beam 6. In other words, the area 24 is an irradiation area by the light beam 6, and in this case, the visual field area 13 is an irradiation area.
It is arranged so as to include 24 . Since in the third diagram irradiation region 24 and field area 13 is arranged as described above, the scattered light based on the particles passing through the irradiated region 24, FIG. 4 from the photoelectric converter 10 of FIG. 1 The electric signal 10a as shown in is output.

FIG. 4 is an explanatory diagram corresponding to FIG. 3 (B), and the visual field region 13 in FIG. 3 (B) is omitted in the figure for convenience of explanation. In FIG. 4, reference numeral 17 denotes fine particles that move at a constant velocity in the P direction parallel to the axis A ₁ -A ₂ and cross the region 24,
25 is a light intensity distribution characteristic line of the beam spot 22 along the axis C ₁ -C ₂ , and 26 is a light intensity distribution characteristic line of the beam spot 23 corresponding to the characteristic line 25. Characteristic lines 25 and 26
Is a bell-shaped curve having the same shape, and as a result, in the irradiation region 24, the light intensity distribution in the portion between the points E and F on the axis C ₁ -C ₂ becomes maximum. In this case, the main part is configured such that 1> d. In FIG. 4, when the deflection speed of the beam light 6 in FIG. 3 is set to be considerably faster than the moving speed of the fine particles 17, the scattered light emitted from the fine particles 17 when the fine particles 17 cross the irradiation region 24 is generated. Accordingly, an electric signal 10a including a series of pulse trains as illustrated
Occurs, and an envelope 27 connecting the top of the signal 10a with a broken line in the figure becomes a bell shape corresponding to the characteristic line 25 or 26. Therefore, the number of the fine particles 17 passing through the region 24 can be detected by counting the number of pulse train groups having such an envelope shape, and the peak of the maximum pulse in the pulse train 10a corresponding to each fine particle can be detected. Value 10
Since the particle size of the fine particles 17 can be detected by measuring m, the signal processing unit 31 in FIG.
0a is configured to perform such signal processing. In the embodiment of FIG. 1, for example, d = 0.1 [mm] is set, and the oscillation frequency of the beam light 6 is 20 [KH].
z], the moving speed of the fine particles 17 is set to 5
The time required for the fine particles 17 to pass through the region 24 is 0.1 / 50 = 2 × 10 ⁻³ [s], which is 0 [mm / s].
The number of pulses forming 7 is about 80. As is clear from the above description, the larger the number of pulses forming the envelope 27, the more the envelope 27 approximates the shape of the characteristic line 25 or 26. improves. When the number of the pulses is small, the characteristic line 2
Since the probability of irradiating the particles in the 5 or 26 beak portion is lowered, the particle size resolution is lowered.

Since the particle detection apparatus of FIG. 1 performs particle detection as described above, the shape of the intensity distribution characteristic line 25 or 26 shown in FIG. 4 in the beam light 6 affects the particle size resolution of the particle detection apparatus. In addition, in the particle detection device of FIG. 1, as can be seen from FIG.
The intensity distribution uniform region of the beam light in the portion of the measurement fluid 2 irradiated by is expanded and expanded in the scanning direction of the beam light 6 as compared with the case of FIG. Therefore, in the particle detection device having such a configuration,
Even if the beam light 6 is narrowed down to narrow the intensity distribution uniform region of the beam light in order to reduce the detectable particle size of the particle, the particle size resolution does not decrease, and the particle detection device having such a configuration is used. In the above, since the deflection width 1 of the beam light 6 can be set independently of the intensity of the beam light, detection is performed in the case of a fine particle detection device in which the flow path of the measurement fluid 2 is set so as to cross the irradiation region 24 in FIG. Even if the beam light 6 is narrowed down in order to reduce the possible particle size, it is not necessary to narrow the flow path of the measurement fluid 2. That is, the particle detection device of FIG. 1 can reduce the detectable particle size without causing a decrease in the volume of the measurement fluid 2 that can be inspected within a certain period of time and a decrease in particle size resolution.

FIG. 5 is a block diagram of the second embodiment of the present invention, which is different from FIG. 1 in that the converging lens 7 and the beam light polarization section 18 are arranged in reverse order. Lens 7 and polarization unit 18
It is clear that the particles can be detected in the same manner as in the case of FIG. 1 by arranging and in such a manner, but particularly in the case of FIG. 5, since the lens 7 is arranged in the vicinity of the flow cell 1, A lens having a short focal length can be used for the lens 7, and therefore, the numerical aperture of the lens 7 can be increased, so that the beam light 6 can be focused finely.
As a result, the particle detection device of FIG. 5 has an advantage that the detectable particle size can be reduced.

FIG. 6 is a block diagram of a third embodiment of the present invention. The difference from FIG. 1 of the present drawing is that the light receiving mechanism 8 is arranged to receive the forward scattered light of the beam light 6 in the flow cell 1. is there. It is apparent that the apparatus shown in FIG. 6 can detect fine particles in the same manner as the apparatus shown in FIG.
In the case of the figure, since the intensity of the forward scattered light is higher than the intensity of the side scattered light as in each of the above-mentioned embodiments, there is an advantage that the fine particles can be easily detected.

FIG. 7 is a structural explanatory view of a beam light deflecting section 28 which replaces the beam light deflecting section 18 shown in FIG.
Is an ultrasonic transducer driven by a drive power source 30, 29
Reference numeral b denotes a photoacoustic medium having a function of propagating the ultrasonic wave emitted from the transducer 29a as a part of the function.
Also has a function of deflecting the traveling direction of the light beam incident thereon according to the state of ultrasonic waves propagating through the medium. 29c is a sound absorbing material that absorbs the ultrasonic waves that have propagated through the medium 29b. 29 is the above-mentioned vibrator 29a and medium 29
In the photoacoustic deflecting element composed of b and the sound absorbing material 29c, the beam light deflecting section 28 is composed of a deflecting element 29 and a power source 30. Also in the beam light deflector 28 , as shown in the figure,
Since the incident laser beam 4 can be made into the beam light 6 which oscillates at a high speed during the angle 2θ by the driving power source 30, such a deflecting unit 28 is used as a beam in the above-described embodiments of the particle detecting device. It can be used in place of the light deflector 18 .

In each of the above-described embodiments, the through hole 11a of the opening member 11 is used.
Although the through hole is circular, the through hole may be formed in a slit or another shape, and the optical axis of the light receiving mechanism 8 is the same as that of the beam light 6 in each of the above-described embodiments. The angle of intersection may be different from the angle of intersection. Further, in the present invention, the beam light 6 projected on the fine particle-containing measurement liquid 2 is not limited to the beam light having a circular cross section, but the cross sectional shape of the flow cell 1 and the triaxial A ₁ -A.
The spatial directions of ₂ , B ₁ -B ₂ and C ₁ -C ₂ are not limited to those in the above embodiment. The detection device according to the present invention can also measure the flow velocity of the particulate-containing measurement fluid by counting the number of pulses in the electric signal 10a shown in FIG.

〔The invention's effect〕

As described above, the particle detection device of the present invention includes the beam light deflector for linearly repeatedly scanning the focused beam light across the flow of the particle-containing measurement fluid to the predetermined width of the measurement fluid. Beam light irradiation mechanism, light receiving mechanism for receiving scattered light emitted from fine particles by irradiation of the beam light and outputting a signal pulse train corresponding to the scattered light, peak value of maximum pulse in the pulse train, and pulse train group And a signal processing unit for processing the group number information of (1) and outputting the particle size and the number of particles. With this configuration, the intensity distribution uniform region of the beam light in the measurement fluid portion irradiated with the beam light is substantially expanded in the scanning direction of the beam light, and the intensity distribution shape of the beam light is detected by the fine particles. As a result of not affecting the particle size resolution of the device, it is possible to reduce the detectable particle size without causing a decrease in the volume of fine particle-containing measurement fluid that can be inspected within a certain period of time and a decrease in particle size resolution. There is an effect that the detection device can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention, FIG. 2 is a configuration diagram of a main part in FIG. 1, and FIG. 3 is an operation explanatory diagram of the particle detection device shown in FIGS. 1 and 2. In the figure, (A) is a plan view and (B) is a side view. FIG. 4 is an explanatory view corresponding to FIG. 3 (B), FIGS. 5 and 6 are configuration diagrams of the second and third embodiments of the present invention, and FIG. 7 is shown in FIG. FIG. 8 is a structural explanatory view of a beam light deflecting unit different from the beam light deflecting unit, FIG. 8 is a structural diagram of a conventional fluid particle detection device, and FIG. 9 is an enlarged perspective view of an essential part in FIG. 8 and FIG. Is a diagram for explaining a detection error, FIG. 7A is a light beam arrangement diagram, and FIG. 7B is a light beam intensity distribution diagram. 2 ... Measuring fluid, 3 , 19 ... Beam light irradiation mechanism, 6,
16 ... Beam light, 8 ... Light receiving mechanism, 18 , 28 ... Beam light deflecting unit, 14 , 31 ... Signal processing unit.

Claims (1)

[Claims] 1. A beam light irradiation mechanism having a beam light deflector for linearly repeatedly scanning a focused beam light across a flow of a measurement fluid containing fine particles to a predetermined width of the measurement fluid; A light receiving mechanism that receives scattered light emitted from the fine particles by irradiation of beam light and outputs a signal pulse train corresponding to the scattered light, and a peak value of the maximum pulse in the pulse train and group number information of pulse train groups are processed. And a signal processing unit for outputting the particle size and the number of particles.