JP2012189493A - Particle detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve sensitivity and detection accuracy of a particle detector and miniaturize the same.SOLUTION: A particle detector 10 comprises: a light source 11 for applying light to a sample fluid F; and a light receiving element 12 for detecting the scattered light which is formed by scattering the light L emitted from the light source 11 by particles in a sample fluid F. A flow passage 13 for passing the sample fluid F connects between a pair of plate-like light receiving elements 12 and 12 arranged in parallel with light-receiving surfaces 12A and 12A opposed to each other with a predetermined interval and the pair of light receiving elements and is formed in a square columnar shape by a pair of plate-like reflecting mirrors arranged in parallel with light-receiving surfaces 16A and 16A opposed to each other. The pair of light receiving elements 12 and 12 are arranged in parallel with a light path along a light path of the light L emitted from the light source 11 and disposed so as to sandwich the light path from both sides in a direction orthogonal to the light path by the light-receiving surfaces 12A and 12A.

Description

  The present invention relates to a particle detector.

  Conventionally, for example, a light source and a photodetector are arranged so as to be sandwiched from both sides in a direction crossing a gas flow containing particles to be detected, and laser light is emitted from the light source so as to cross the gas flow. There is known a particle measuring device that detects particles contained in a gas flow by detecting scattered light obtained by being scattered by particles using an optical sensor. (For example, refer to Patent Document 1).

JP 2009-539084 A

By the way, in the particle measuring instrument according to the above prior art, it is desired to improve the measurement accuracy by obtaining sufficient scattered light.
On the other hand, for example, in order to increase the incident light intensity to the gas flow particles by condensing the laser beam, configuring an optical system including a lens increases the cost required for the configuration and increases the size of the lens. In addition, there is a problem that the particle measuring instrument becomes large due to securing a predetermined focal length.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a particle detector that can improve sensitivity and detection accuracy and can be miniaturized.

  In order to solve the above problems and achieve the object, a particle detector according to claim 1 of the present invention includes a light source that irradiates light toward a sample fluid (for example, light source 11 in the embodiment), A light receiving element (for example, the light receiving element 12 in the embodiment) for detecting scattered light generated by the light emitted from the light source being scattered by particles in the sample fluid. The light receiving surface (for example, the light receiving surface 12A in the embodiment) is parallel to the optical path along the optical path of the light emitted from the light source.

  Furthermore, the particle detector according to claim 2 of the present invention includes at least one pair of the light receiving elements, and the light receiving surfaces of the at least one pair of the light receiving elements are from the both sides in a direction orthogonal to the optical path. Is inserted.

  Furthermore, the particle detector according to claim 3 of the present invention includes a flow path (for example, the flow path 13 in the embodiment) through which the sample fluid passes, and the light receiving element is an inlet portion of the flow path. (For example, the inlet portion 13a in the embodiment) to the outlet portion (for example, the outlet portion 13b in the embodiment), and the light is reflected back and forth between the inlet portion and the outlet portion. At least one pair of reflecting mirrors (for example, the reflecting mirror 16 in the embodiment).

  Furthermore, a particle detector according to a fourth aspect of the present invention includes a second light receiving element (for example, the second light receiving element 17 in the embodiment) that detects the scattered light, and a light receiving surface of the second light receiving element. Is orthogonal to the plane containing the optical path.

  Furthermore, in the particle detector according to claim 5 of the present invention, the light receiving surface of the light receiving element has a microstructure that bulges in an arc shape toward the inside of the light receiving element.

According to the particle detector according to claim 1 of the present invention, the light receiving surface of the light receiving element is parallel to the optical path along the optical path of the light emitted from the light source. Sensitivity to scattered light having strong directivity in the forward direction of the light path of emitted light, for example, Mie scattered light can be improved.
In addition, Mie scattered scattered light has higher scattering intensity than other scattered light under predetermined conditions with respect to the wavelength of light and the particle size of the particles, etc., while preventing the particle detector from increasing in size. The sensitivity to scattered light can be improved, and sufficient scattered light can be obtained to improve particle detection accuracy.

  Furthermore, according to the particle detector of claim 2 of the present invention, the sensitivity to scattered light is further improved and detection accuracy is improved by sandwiching the optical path between the light receiving surfaces of at least one pair of light receiving elements. Can do.

  Furthermore, according to the particle detector according to claim 3 of the present invention, it is possible to increase the scattered light by providing at least one pair of reflecting mirrors that reciprocally reflect the light emitted from the light source. Accuracy can be improved.

  Furthermore, according to the particle detector according to claim 4 of the present invention, by providing the second light receiving element, it is possible to further improve the sensitivity to scattered light and improve the detection accuracy.

  Furthermore, according to the particle detector according to claim 5 of the present invention, the scattered light having a large incident angle with respect to the light receiving surface of the light receiving element is efficiently reflected by multiple reflections in a micro structure that bulges in an arc shape toward the inside of the light receiving element. Can be detected well.

  That is, this microstructure includes a plurality of recesses formed on the surface of the light receiving element, and each recess crosses the internal space as it goes from the opening end on the surface of the light receiving element to an appropriate depth. An arc-shaped bulge with a curved inner wall whose area tends to increase, and a curved inner where the cross-sectional area of the internal space changes toward a decreasing trend from the appropriate depth toward the bottom of the recess It has the shape which consists of an arcuate reduction part which has a wall surface.

For this reason, even if it is scattered light with a large incident angle with respect to the light-receiving surface of a light receiving element, an incident angle becomes small with respect to the arc-shaped enormous part of each recessed part, and reflection is suppressed.
Moreover, even if this scattered light is reflected by the arc-shaped enormous portion, the reflected light from this reflection is likely to be reflected toward the inside of the recess so that the incident angle becomes small with respect to the inner wall surface of the recess. Further reflections are suppressed.
In addition, even if the scattered light incident on the recess is repeatedly reflected inside, it is suppressed that the reflected light escapes outside the recess and can be detected through multiple reflections inside the recess. The nature is getting higher.
As a result, the sensitivity to scattered light can be further improved and the detection accuracy can be improved.

It is a lineblock diagram showing some particle detectors concerning an embodiment of the invention. It is a lineblock diagram of the particle detector concerning an embodiment of the invention. It is a lineblock diagram showing some particle detectors concerning an embodiment of the invention. It is a lineblock diagram showing some particle detectors concerning an embodiment of the invention. It is a figure which shows an example of angle distribution of the output intensity of the scattered light of Mie scattering by the particle | grains of the predetermined particle diameter with respect to the light of the predetermined wavelength which concerns on embodiment of this invention. It is a figure which shows an example of the output intensity | strength of Mie scattering when the light of the several predetermined wavelength which concerns on embodiment of this invention injects into particle | grains. It is a perspective view which shows the micro structure formed in the light-receiving surface of the light receiving element of the particle | grain detector which concerns on embodiment of this invention. It is sectional drawing which shows the microstructure formed in the light-receiving surface of the light receiving element of the particle | grain detector which concerns on embodiment of this invention. FIG. 9A is a diagram showing an example of light reflection and absorption in the microstructure of the light receiving element in the example according to the embodiment of the present invention, and FIGS. 9B and 9C are diagrams of the present invention. It is a figure which shows the example of reflection and absorption of the light in the light receiving element in the 1st comparative example and 2nd comparative example which concern on embodiment. It is a figure which shows the example of the change according to the incident angle of the received light intensity of the scattered light in the light-receiving surface of the light receiving element in the Example which concerns on embodiment of this invention, and a 1st comparative example. It is a figure which shows each process of the method of manufacturing the microstructure provided in the light-receiving surface of the light receiving element of the particle | grain detector which concerns on embodiment of this invention.

  Hereinafter, a particle detector according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  The particle detector 10 according to the present embodiment is installed in, for example, a clean room and is used as a system for managing the cleanliness of air in the clean room. For example, particulate dust or It detects particles such as airborne microorganisms such as bacteria and viruses.

  A particle detector 10 according to the present embodiment is emitted from a light source 11 that irradiates light L toward a sample fluid F such as air and the light source 11 as shown in FIGS. 1A and 1B, for example. The light receiving element 12 detects the scattered light SL generated by the scattered light L being scattered by the particles P in the sample fluid F.

The light source 11 is, for example, a laser light source that emits laser light having a predetermined wavelength with a predetermined output.
The light receiving element 12 is, for example, a photodiode, and the light receiving surface 12A of the light receiving element 12 is disposed along the optical path of the light L emitted from the light source 11 in parallel with the optical path.
The particle detector 10 detects the particle size and the number of particles P in the sample fluid F from the optical output waveform output from the light receiving element 12 (that is, the output waveform of the scattered light SL).

  More specifically, as shown in FIG. 2, for example, the particle detector 10 includes a flow path 13 that allows the sample fluid F to pass therethrough, a pump 14 that introduces the sample fluid F into the flow path 13, and a flow path 13. The light absorption part 15 connected is comprised.

  The flow path 13 includes, for example, a pair of plate-shaped light receiving elements 12 and 12 arranged in parallel with each other with the light receiving surfaces 12A and 12A facing each other at a predetermined interval, and a pair of light receiving elements 12 and 12. A pair of plate-like reflecting mirrors 16 and 16 arranged in parallel with the reflecting surfaces 16A and 16A facing each other are formed in a rectangular tube shape.

  Of the inlet portion 13a and the outlet portion 13b that open at both ends of the flow path 13, the outlet portion 13b is connected to, for example, a pump 14 for suction, and the inlet portion 13a that opens so that the sample fluid F communicates with the outside. The sample fluid F introduced into the flow path 13 and circulated in the flow path 13 is sucked into the pump 14 from the outlet portion 13b.

The light source 11 is disposed at a position shifted to one side of the pair of reflecting mirrors 16 and 16 in the inlet portion 13a of the flow path 13, and the flow path 13 is formed at a predetermined angle with respect to the direction from the one side to the other side. It is arrange | positioned so that the light L may be radiate | emitted toward the direction inclined to the exit part 13b side.
The pair of light receiving elements 12 and 12 are arranged in parallel to the optical path along the optical path of the light L emitted from the light source 11, and the light receiving surfaces 12A and 12A pass the optical path from both sides in the direction orthogonal to the optical path. It is arranged so as to be sandwiched.

Further, on the reflecting surface 16A of each reflecting mirror 16, for example, as shown in FIGS. 3 and 4, the center portion in the direction orthogonal to the optical path is shifted to both sides, that is, the pair of light receiving elements 12 and 12 side. A pair of second light receiving elements 17, 17 are provided.
The second light receiving element 17 is, for example, a photodiode, and the light receiving surface of the second light receiving element 17 is disposed so as to be orthogonal to a plane including the optical path of the light L, for example.
The light L emitted from the light source 11 is reflected back and forth between the reflecting surfaces 16A and 16A of the pair of reflecting mirrors 16 and 16, and is guided from the inlet portion 13a of the flow path 13 to the outlet portion 13b.

  The light absorbing portion 15 communicates with the outlet portion 13 b of the flow path 13, and the light L that has been guided to the outlet portion 13 b while being reciprocally reflected in the flow path 13 is transmitted from the flow path 13 to the light absorbing portion. 15 is formed by a light absorber having a shape leading to the inside.

  As described above, the light receiving element 12 arranged in parallel to the optical path along the optical path of the light L emitted from the light source 11 causes the light L emitted from the light source 11 to be scattered by the particles P in the sample fluid F. Among the various scattered light SL generated in Step 1, the sensitivity to the scattered light SL having strong directivity in the forward direction of the optical path of the light L emitted from the light source 11, for example, the Mie scattered scattered light SL can be improved.

For example, as shown in FIG. 5, the output intensity of the scattered light SL of Mie scattering by the particle P having a predetermined particle diameter (for example, diameter d = 1.0 μm, 0.5 μm) with respect to the light L having a predetermined wavelength (for example, 660 nm). According to the angular distribution, the Mie scattered scattered light SL has directivity in the forward direction of the optical path of the light L with respect to the particle P having a diameter d = 1.0 μm, which is the average size of the particles P in the clean room. It is recognized that it is strong.
In addition, Mie scattering is dominant in scattering by particles P having a predetermined particle diameter (for example, diameter d = 1.0 μm) with respect to light L having a predetermined wavelength (for example, 660 nm). By improving the sensitivity, sufficient scattered light SL can be obtained and the detection accuracy of the particles P can be improved.

  Therefore, the distance between the light receiving surface 12A of each light receiving element 12 and the optical path of the light L emitted from the light source 11 is preferably small.

Note that the output intensity of Mie scattering varies depending on the relationship between the wavelength λ of the light L and the size of the particle P (for example, the diameter d).
For example, as shown in FIG. 6, all the predetermined wavelengths (for example, 300 nm, 600 nm) are obtained from the output intensity of Mie scattering when light L having a plurality of predetermined wavelengths (for example, 300 nm, 600 nm, 900 nm) is incident on the particle P. , 900 nm), it is recognized that when d / λ is less than a predetermined value (for example, 0.5), the decrease in output intensity increases.
Accordingly, it is preferable to set d / λ = 0.5 as the lower limit value for d / λ.
In FIG. 6, the horizontal axis is the diameter d / wavelength λ, and the vertical axis is the value obtained by normalizing the output intensity of Mie scattering by the value of d / λ = 20.

  For example, it is preferable to set, for example, d = 5 μm as the upper limit value for the diameter d of the particles P, for example, according to the desired air cleanliness in the clean room.

  For example, as shown in FIGS. 7A and 7B, the light receiving surface 12 </ b> A of the light receiving element 12 has a micro structure 20 that bulges in an arc toward the inside of the light receiving element 12.

For example, as shown in FIG. 8, the microstructure 20 includes a plurality of recesses 21 formed on the light receiving surface 12 </ b> A of the light receiving element 12.
Each concave portion 21 has a curved light-receiving inner wall surface 31A in which the cross-sectional area of the internal space changes in an increasing trend as it goes from the opening end 21a on the light-receiving surface 12A of the light-receiving element 12 to an appropriate depth. An arc-shaped enlarging portion 31 having a curved light-receiving inner wall surface 32A in which the cross-sectional area of the internal space changes in a decreasing tendency from the appropriate depth toward the bottom of the concave portion 21. It has the shape which consists of.

  With this microstructure 20, for example, as in the embodiment shown in FIG. 9A, even with the scattered light SL having a large incident angle with respect to the light receiving surface 12A of the light receiving element 12, the arc-shaped enormous portion 31 of each concave portion 21 is prevented. As a result, the incident angle is reduced and reflection is suppressed.

  Even if the scattered light SL is reflected by the arc-shaped enormous portion 31, the reflected light SLa due to this reflection goes to the inside of the concave portion 21, and the inner wall surface of the concave portion 21 (for example, the light receiving inner wall surface 32A of the arc-shaped reducing portion 32). ) Is more likely to be reflected such that the incident angle becomes smaller, and further reflection is suppressed.

  Further, even when the scattered light SL incident on the recess 21 is repeatedly reflected inside, it is suppressed that the reflected light SLa, SLb,... Escapes to the outside of the recess 21. The possibility of being detected through multiple reflections is high.

  With this microstructure 20, as shown in the embodiment shown in FIG. 10, for example, as the incident angle of the scattered light SL with respect to the light receiving surface 12A of the light receiving element 12 increases, the sensitivity to the scattered light SL changes in an increasing trend. It is recognized that

  On the other hand, when the light receiving surface 12A of the light receiving element 12 is flat (that is, when it does not have a micro structure) as in the first comparative example shown in FIG. 9B, for example, as shown in FIG. As in the first comparative example, as the incident angle of the scattered light SL with respect to the light receiving surface 12A of the light receiving element 12 increases to a predetermined angle (for example, 70 °) or more, the scattered light SL is reflected by the light receiving surface 12A. It becomes easier to see that the sensitivity to the scattered light SL changes in a decreasing trend.

  Further, as in the second comparative example shown in FIG. 9C, for example, the taper in which the cross-sectional area of the internal space changes in a decreasing trend as it goes from the opening end 21a on the light receiving surface 12A of the light receiving element 12 to the inside. Compared to the embodiment, the scattered light SL incident on the concave portion 21 is reflected outside to the outside of the concave portion 21 only by having a micro structure composed of a concave portion or a concave portion having a constant cross-sectional area of the internal space. It can be seen that it is difficult to improve the sensitivity to the scattered light SL that is easily pulled out and has a large incident angle with respect to the light receiving surface 12A of the light receiving element 12.

  Below, the manufacturing method of the microstructure 20 and the manufacturing method of the microstructure (for example, the light receiving element 12 which is a photodiode) which has the microstructure 20 are demonstrated.

First, as shown in FIG. 11A, for example, a p-type silicon substrate 50 is prepared.
Next, an oxide film having a predetermined thickness (for example, 100 nm) is formed by thermal oxidation at a predetermined temperature (for example, 1100 ° C.) for a predetermined time (for example, 60 minutes), for example, as shown in FIG. 51 is formed.

Next, a liquid photoresist is applied on the surface of the oxide film 51 by spin coating or the like to form a resist layer 52 as shown in FIG. 11C, for example.
Next, the resist layer 52 is exposed using an exposure mask and developed with a developer, thereby forming a resist mask 52b having a predetermined pattern of openings 52a as shown in FIG. 11D, for example.

Next, the oxide film 51 is wet-etched according to a predetermined pattern of the resist mask 52b to form an oxide film mask 51b having an opening 51a of a predetermined pattern, for example, as shown in FIG.
Next, for example, as illustrated in FIG. 11F, the resist mask 52b is removed.

  Next, an anisotropic etching process is performed on the silicon substrate 50 by DRIE (deep reactive ion etching) using the region of the silicon substrate 50 exposed through the opening 51a as an etched portion according to a predetermined pattern of the oxide film mask 51b. A first etching step is performed to form a recess 50a on the surface of the silicon substrate 50, for example, as shown in FIG.

  In the first etching process, a step of performing isotropic plasma etching on the portion to be etched and a step of forming a protective film on at least the side surface of the portion to be etched are alternately specified at predetermined intervals (for example, 18 seconds). Execute the number of times (for example, twice).

This first etching process is a so-called Bosch process, and is a step of performing isotropic plasma etching mainly using sulfur hexafluoride gas, and using a fluororesin-based gas (C ₄ F ₈ gas or the like). The step of forming a protective film on at least the side surface of the etched portion is alternately performed.
Thereby, when etching is performed in the depth direction of the etched portion (thickness direction of the silicon substrate 50), the side surface of the etched portion is protected and lateral etching is suppressed.

  Therefore, the concave portion 50a formed by the first etching step is formed on the side surface as it goes from the opening end 50b on the surface of the silicon substrate 50 to the inside in the depth direction (that is, the thickness direction of the silicon substrate 50). It has an uneven shape called a scallop.

Next, after the execution of the first etching step, a second etching step in which isotropic plasma etching is mainly performed using a sulfur hexafluoride gas over a predetermined period (for example, 23 seconds) on the portion to be etched. Execute.
As a result, for example, as shown in FIG. 11 (H), the arc expands as it goes from the opening end 50b on the surface of the silicon substrate 50 to the inside in the depth direction (that is, the thickness direction of the silicon substrate 50). A recessed portion 50c is formed.

The concave portion 50c has a curved inner wall portion 61A having a curved inner wall surface 61A in which the cross-sectional area of the inner space changes in an increasing tendency as it goes from the opening end 50b on the surface of the silicon substrate 50 to an appropriate depth. And an arcuate reduced portion 62 having a curved inner wall surface 62A in which the cross-sectional area of the internal space changes in a decreasing tendency from the appropriate depth toward the bottom of the recess 50c. Yes.
In this embodiment, the opening end 50b protrudes most on the inner wall surface.

  Next, as shown in FIG. 11I, for example, the oxide film mask 51b is removed by etching.

  Next, phosphorus is thermally diffused by thermal diffusion treatment for a predetermined time (for example, 40 seconds) at a predetermined temperature (for example, 935 ° C.) on the surface of the silicon substrate 50 in which the plurality of recesses 50c are formed. For example, as shown in FIG. 11J, an impurity layer 71 is formed.

  Next, as shown in FIG. 11K, for example, an aluminum (Al) film 72 is formed on the back surface of the silicon substrate 50 in which the plurality of recesses 50c are formed, and predetermined patterning is performed, and a predetermined temperature ( For example, annealing is performed for a predetermined time (for example, 10 minutes) at 450 ° C. or the like, and the aluminum (Al) film 72 is bonded.

Next, as shown in FIG. 11L, for example, an aluminum (Al) film 73 is formed at a predetermined position (for example, an end portion) of the surface of the silicon substrate 50 on which the plurality of concave portions 50c are formed. And the aluminum (Al) film 73 is bonded.
At this time, it is not always necessary to perform annealing. When n-type silicon is used, ohmic contact can be realized without annealing.

  As described above, according to the particle detector 10 according to the present embodiment, the light receiving surface 12A of the light receiving element 12 is parallel to the optical path along the optical path of the light L emitted from the light source 11, so Of the scattered light SL, the sensitivity to the scattered light SL having strong directivity in the forward direction of the optical path of the light L emitted from the light source 11, for example, the scattered light SL of Mie scattering can be improved.

  In addition, Mie-scattered scattered light has a higher scattering intensity than other scattered light under predetermined conditions for the wavelength of the light L and the particle size of the particles P, so that the size of the particle detector 10 is increased. While preventing, the sensitivity with respect to scattered light SL can be improved, sufficient scattered light SL can be obtained, and the detection accuracy of particle | grains P can be improved.

  Further, by sandwiching the optical path between the light receiving surfaces 12A and 12A of at least one pair of the light receiving elements 12, 12, the sensitivity to the scattered light SL can be further improved, and the detection accuracy can be improved.

  Furthermore, by providing at least one pair of reflecting mirrors 16 and 16 that reciprocally reflect the light L emitted from the light source 11, the scattered light SL can be increased, and detection accuracy can be further improved.

  Furthermore, by providing the second light receiving element 17, the sensitivity to the scattered light SL can be further improved, and the detection accuracy can be improved.

  Further, the scattered light SL having a large incident angle with respect to the light receiving surface 12 </ b> A of the light receiving element 12 can be efficiently detected by multiple reflection at the micro structure 20 that bulges toward the inside of the light receiving element 12.

That is, the microstructure 20 includes a plurality of recesses 21 formed on the surface of the light receiving element 12 (that is, the light receiving surface 12A), and each recess 21 is provided on the surface of the light receiving element 12 (that is, the light receiving surface 12A). An arc-shaped enormous portion 31 having a curved light-receiving inner wall surface 31A in which the cross-sectional area of the internal space changes in an increasing tendency as it goes from the opening end 21a to an appropriate depth, and a recess from the appropriate depth. 21 has an arcuate reduced portion 32 having a curved light-receiving inner wall surface 32A in which the cross-sectional area of the internal space changes in a decreasing tendency as it goes toward the bottom of 21.
Furthermore, in this embodiment, the opening end 21a is the most protruding structure on the inner wall surface.

For this reason, even if the scattered light SL has a large incident angle with respect to the light receiving surface 12 </ b> A of the light receiving element 12, the incident angle is small with respect to the arc-shaped enormous portion 31 of each recess 21, and reflection is suppressed.
Further, even if the scattered light SL is reflected by the arc-shaped enormous portion 31, the reflected light due to this reflection goes to the inside of the recess 21 and reaches the inner wall surface of the recess (for example, the light receiving inner wall surface 32A of the arc-shaped reduction portion 32). On the other hand, there is a high possibility that the light is reflected so as to reduce the incident angle, and further reflection is suppressed.

Further, even when the scattered light SL incident on the recess 21 is repeatedly reflected inside, it is suppressed that the reflected light escapes to the outside of the recess 21, and passes through multiple reflections inside the recess 21. The probability of being detected is high.
As a result, the sensitivity to the scattered light SL can be further improved, and the detection accuracy can be improved.

In the above-described embodiment, the particle detector 10 may include only one light receiving element 12.
In the above-described embodiment, the second light receiving element 17 may be omitted.
In the embodiment described above, the reflecting mirror 16 may be omitted.
In the embodiment described above, the pump 14 may be omitted.

  In the above-described embodiment, the particle detector 10 is installed in a clean room, and particles such as particulate dust and airborne microorganisms such as bacteria and viruses contained in the air that is the sample fluid are included. However, the present invention is not limited to this. For example, particles contained in a specific gas other than air may be detected. For example, particles that are impurities contained in a specific gas flowing into a film forming apparatus or the like may be detected.

DESCRIPTION OF SYMBOLS 10 Particle detector 11 Light source 12 Light receiving element 12A Light receiving surface 13 Flow path 13a Inlet part 13b Outlet part 16 Reflecting mirror 17 Second light receiving element

Claims (5)

A light source that irradiates light toward the sample fluid, and a light receiving element that detects scattered light generated by the light emitted from the light source being scattered by particles in the sample fluid,
The light receiving surface of the said light receiving element is parallel to the said optical path along the optical path of the said light emitted from the said light source, The particle detector characterized by the above-mentioned. Comprising at least one pair of the light receiving elements;
2. The particle detector according to claim 1, wherein the light receiving surfaces of the at least one pair of the light receiving elements sandwich the optical path from both sides in a direction orthogonal to the optical path. A flow path for passing the sample fluid;
The light receiving element is provided between an inlet portion and an outlet portion of the flow path,
The particle detector according to claim 1, further comprising at least one pair of reflecting mirrors that reciprocally reflect the light between the entrance and the exit. A second light receiving element for detecting the scattered light;
The particle detector according to any one of claims 1 to 3, wherein a light receiving surface of the second light receiving element is orthogonal to a plane including the optical path. The particle detector according to any one of claims 1 to 4, wherein a light receiving surface of the light receiving element has a microstructure that bulges in an arc shape toward the inside of the light receiving element.