Particle measuring device and particle measuring method

Abstract

Lenses 152, 154 and a beam splitter 156 are disposed so that an intersection point of the optical axis and the exit pupil of the lens 154 through which scattered light LS from particles passes and a light-condensing point of reference light LR exiting from the lens 152 are in a conjugate relationship to each other. In addition, the lens 152 adjusts the spread of the reference light LR so that the reference light covers a wide range of a light-receiving surface. In such a particle measuring device, the wave surfaces of the scattered light LS and the reference light LR do not match at the time of multiplexing in the beam splitter 156, but the optical axes thereof enter a detector 160 in parallel to each other. On light-receiving elements 162, the wave surface of the scattered light LS in the range of the beam diameter thereof is always substantially parallel to the wave surface of the reference light LR. Therefore, it is possible to effectively obtain a change in interference intensity between the scattered light LS and the reference light LR and to efficiently detecting the particles. In addition, at the time of multiplexing the scattered light LS and the reference light LR, matching the wave surface shapes thereof is not necessary. Therefore, a high degree of freedom in design is achieved.

Description

Particle measuring device and particle measuring method

[0001] The present invention relates to an apparatus and method for measuring the number, particle size, refractive index, etc. of particles contained in a fluid.

[0002] One method for measuring particles contained in a fluid involves irradiating the fluid with light and receiving scattered light (hereinafter referred to as "scattered light from particles") that is generated when the irradiated light strikes particles. In this type of measurement, the following method is known for detecting particles with smaller particle sizes (see, for example, Patent Documents 1 and 2). In this method, light from a light source is separated into irradiated light and reference light, the scattered light from the particles is made to interfere with the reference light, and the particles are counted by particle size based on the interference light that enters a detector.

[0003] Japanese Patent No. 5859154 Japanese Patent No. 6030740

[0004] In order to efficiently obtain the intensity change due to the interference between the scattered light from the particle and the reference light, it is desirable that the optical axes of the scattered light and the reference light beam are parallel to each other and that they are incident on the detector in an overlapping manner. If the optical axes of the scattered light and the reference light are deviated from the parallel state, the detection sensitivity will decrease.

[0005] In addition, in order to increase detection sensitivity, the wavefront of the scattered light and the wavefront of the reference light are generally made to roughly coincide. In this case, the total power of the light beam resulting from the combination of the scattered light and the reference light is constant at any position along the optical axis. Furthermore, reducing the spot size of the scattered light allows the size of the light-receiving surface to be reduced, thereby reducing noise. For this reason, the detector (light-receiving element) is often placed near the beam waist of the scattered light (see Figure 3).

[0006] In the two prior arts described above, as shown in (A) in Figure 8, both the scattered light and the reference light are adjusted to become plane waves when combined, and the light-receiving element is positioned near the beam waist. However, because the scattered light and the reference light are focused at the same position on the light-receiving element in the detector, the interference between the scattered light and the reference light forms a small spot. Therefore, as shown in (B-1) in Figure 8, only a portion of the entire light-receiving surface of the light-receiving element is used, and it can be seen that the light-receiving element cannot be used efficiently.

[0007] Furthermore, in the two prior arts described above, the optical axes of the scattered light and reference light may deviate from parallel depending on the position of the particle being observed. Therefore, as shown in (B-2) in FIG. 8, when the scattered light is no longer parallel to the reference light and the wavefront of the scattered light is tilted, the overlap with the reference light decreases, the interference between the scattered light and the reference light weakens, and the detection sensitivity decreases. Furthermore, in a configuration in which multiple light-receiving elements are aligned in a row or two-dimensionally on the same surface, there are slight gaps between the light-receiving elements. Therefore, as shown in (B-3) in FIG. 8, when the reference light is incident at a position offset from the center of each light-receiving element and the reference light spot extends into the gap, it becomes difficult to form an interference spot with the scattered light on the light-receiving surface, leading to a decrease in detection sensitivity.

[0008] The present invention has been made in view of these problems, and has an object to provide a technique for efficiently detecting particles.

[0009] To solve the above problems, the present invention employs the following particle measurement device and method implemented by this particle measurement device. Note that the following words in parentheses are merely examples, and the present invention is not limited thereto.

[0010] That is, the particle measuring device of the present invention includes a light source that emits light, a first beam splitter that splits the light from the light source into two, directing one light, the illumination light, toward a flow path into which a fluid is flowing and the other light, the reference light, in a direction different from the flow path, an optical system that adjusts the cross-sectional shape and spread angle of the reference light so that it covers a wide range or the entire light receiving portion of the detector, a second beam splitter that combines scattered light from particles contained in the fluid generated in a detection region formed within the flow path by irradiating the illumination light onto the flow path and the reference light that has passed through the optical system, with the wavefronts not coinciding, and a detector that has one or more light receiving elements that receive interference light between the scattered light and the reference light combined by the second beam splitter and output a signal corresponding to the intensity of the interference light. Note that if the light emitted by the light source has a spread in its cross section (i.e., the cross section is not a tiny dot but has a spread shape such as a line, a band, a square, a circle, etc.), an optical system that adjusts the spread of the reference light or the light from the light source may not be provided.

[0011] In this particle measuring device, the reference light can cover a wide range of the light receiving element. Therefore, even if the incident position of the scattered light on the detector changes depending on the position of the particle in the detection area, the scattered light and the reference light can be interfered with effectively, making it possible to efficiently detect particles. Furthermore, in this particle measuring device, when the scattered light and the reference light are combined by the second beam splitter, it is not necessary to match the wavefronts of the two (match the wavefront shapes). Therefore, compared to particle measuring devices that match the wavefront shapes and combine the lights, the degree of freedom in installing components can be increased.

[0012] Preferably, in the particle measuring device of the above aspect, the second beam splitter is positioned so that the direction of the chief ray of the scattered light generated at an arbitrary position in the detection region substantially coincides with the direction of the ray of the reference light passing through the same location as the chief ray of the scattered light.

[0013] In this particle measuring device, the scattered light and the reference light are superimposed and incident on the detector, so that the intensity change due to the interference between the scattered light and the reference light can be effectively obtained on the light receiving element, thereby enabling the particle measuring device to detect particles more efficiently.

[0014] More preferably, the particle measuring device of the above aspect further comprises a telecentric optical system that receives scattered light generated in the detection region and emits its chief ray parallel to the optical axis in image space, and the second beam splitter combines the reference light and the scattered light emitted from the telecentric optical system so that their optical axes are parallel.

[0015] In this particle measuring device, regardless of the position of the particle in the detection region, the scattered light heading toward the detector is parallel to the optical axis of the telecentric optical system. This makes it easier to make the wavefronts of the scattered light and the reference light coincide with each other on the light receiving element, thereby enabling the scattered light and the reference light to interfere more effectively on the light receiving element. Therefore, this particle measuring device allows for more efficient particle detection.

[0016] More preferably, in the particle measuring device of the above aspect, the detector is disposed in the vicinity of the beam waist of the scattered light.

[0017] In this particle measuring device, the wavefront of the scattered light from the particles is generally flat on the light receiving element of the detector. Therefore, the wavefront of the scattered light and the wavefront of the reference light are generally parallel, so that the intensity change of the interference between the scattered light and the reference light can be obtained effectively. As a result, the particle measuring device of this embodiment can detect particles more efficiently.

[0018] As described above, the particle measuring device of the present invention can efficiently detect particles contained in a fluid.

[0019] FIG. 1 is a block diagram showing the configuration of a particle measuring device 100 according to a first embodiment. FIG. 2 is a diagram showing the detailed positional relationship between components in a combining / collecting optical system 150. FIG. 3 is a diagram explaining a beam waist. FIG. 4 is a diagram showing an example of the manner in which scattered light and reference light are incident on a light receiving element 162. FIG. 5 is a block diagram showing the configuration of a particle measuring device 200 according to a second embodiment. FIG. 6 is a diagram showing the manner in which scattered light and reference light travel in a combining / collecting optical system 250. FIG. 7 is a diagram showing a modified example of the combining / collecting optical system. FIG. 8 is a diagram explaining the prior art.

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For ease of explanation, the components constituting the particle measurement device and the shape of the wavefront of light are shown in simplified form in the drawings. Furthermore, to facilitate understanding of the invention, in the block diagrams (FIGS. 1 and 5), the direction of light traveling between components is indicated by dashed arrows, and the direction of signals is indicated by solid arrows.

[0021] First Embodiment FIG. 1 is a block diagram showing the configuration of a particle measuring device 100 according to a first embodiment.

[0022] The particle measuring device 100 mainly includes a light source 110 and a reference light LR and an irradiation light L, which are light beams emitted from the light source 110 and are described later. Ａ and a beam splitter 120 that splits the reference light L Ｒ A mirror 130 that changes the direction of the irradiated light L Ａ and a flow cell 140 through which light passes, and a particle P contained in the fluid is irradiated with light L. Ａ Scattered light L Ｓ While collecting scattered light L Ｓ and reference light L Ｒ and a beam combining / condensing optical system 150 that combines the beams and guides them to a detector 160.

[0023] More specifically, the particle measuring device 100 includes, for example, a light source 110, various optical elements 120, 122, 124, 130, 152, 154, 156, a flow cell 140, and a detector 160 as components for detecting particles, and includes a counting unit 170 as a component for counting the detected particles.

[0024] The light source 110 emits light of a predetermined wavelength (e.g., laser light). The beam splitter 120 splits the light from the light source 110 into transmitted light and reflected light at a predetermined ratio. Hereinafter, the light transmitted through the beam splitter 120 will be referred to as "irradiation light," and the reflected light will be referred to as "reference light."

[0025] Illumination light L emitted from the beam splitter 120 Ａ The irradiated light L passes through the lens 122 and travels to the flow cell 140. Ａ is focused toward the flow cell 140, and the irradiated light LＡ The light collection area (irradiation light L Ａ The degree of light collection onto the flow cell 140 is adjusted.

[0026] The flow cell 140 is made of a glass material such as synthetic quartz or optical glass, or a crystalline material such as synthetic corundum, and has a flow path formed therein through which a fluid flows. A detection area is set within the flow path, and irradiation light L is directed toward the detection area. Ａ From another perspective, the irradiated light L Ａ is incident on the flow cell 140, the irradiation light L Ａ When a particle P is present in the detection area, the irradiated light L Ａ hits the particle P and scatters light L Ｓ occurs.

[0027] The lens 154 reflects the scattered light L from the particle P. Ｓ The detector 160 is configured to focus the scattered light L Ｓ The scattered light L Ｓ The scattered light L that has passed through the lens 154 is arranged near the beam waist of the lens 154. Ｓ The irradiated light L transmitted through the beam splitter 156 is directed to the detector 160. Ａ is absorbed by the beam damper 142.

[0028] On the other hand, the reference light L emitted from the beam splitter 120 Ｒ The light travels through lens 124 , mirror 130 , lens 152 and beam splitter 156 to detector 160 .

[0029] The mirror 130 reflects the reference light L Ｒ The lens 124 arranged upstream of the mirror 130 and the lens 152 arranged downstream of the mirror 130 reflect the reference light L Ｒ The reference light L is incident on the detector 160 so as to cover a wide range of the light receiving surface formed inside the detector 160. Ｒ The beam splitter 156 adjusts the spreading of the reference light L Ｒis reflected in the direction of the detector 160, and the reference light L Ｒ The scattered light LS and the transmitted scattered light LS are spatially superimposed (hereinafter referred to as "combined light") and emitted.

[0030] Thus, the combining / condensing optical system 150 includes the lenses 152 and 154 and the beam splitter 156 described above.

[0031] FIG. 2 shows the detailed positional relationships between components in the beam combining / collecting optical system 150.

[0032] In the combining and focusing optical system 150, the scattered light L Ｓ The intersection of the exit pupil of the lens 154 through which the reference light L passes and the optical axis, and the ... reference light L Ｒ The lenses 152 and 154 and the beam splitter 156 are arranged so that the focal points (beam waists) of the first and second beams are conjugate with each other.

[0033] With this arrangement, the scattered light L Ｓ and reference light L Ｒ The optical axes of the scattered light L are parallel to each other and enter the detector 160. Ｓ and reference light L Ｒ At the surface where the scattered light L and the scattered light L are combined, that is, at the reflecting surface (half mirror) 156a of the beam splitter 156, Ｓ and reference light L Ｒ The wavefronts do not match.

[0034] Furthermore, the mirror 130 (not shown in FIG. 2) and the beam splitter 156 split the reference light L incident on the detector 160. Ｒ is scattered light L passing through lens 154 and heading to detector 160. Ｓ is arranged so as to be parallel to

[0035] For example, scattered light L Ｓ The distance between the exit pupil of the lens 154 through which the reference light L passes and the center of the beam splitter 156 is Ｒ and the center of the beam splitter 156 (both are distances D), and the scattered light L Ｓ The optical axis of the reference light L ＲWhen the optical axis of the beam splitter 156 intersects with the optical axis of the beam splitter 156 at a right angle, the reflecting surface 156a of the beam splitter 156 reflects the scattered light L Ｓ The scattered light L is arranged so as to have an inclination of 45 degrees with respect to the optical axis (θ=45 degrees). Ｓ The optical axis of the reference light L Ｒ When the optical axis of the reference light L does not intersect at a right angle, Ｒ The optical axis of the scattered light L Ｓ The reflecting surface 156a of the beam splitter 156 may be adjusted so that the light beam enters the detector 160 parallel to the optical axis of the beam splitter 156.

[0036] When the components of the beam combining / condensing optical system 150 are arranged in the above-described relationship, the scattered light L Ｓ The chief ray of a certain reference light L Ｒ The light incident on the detector 160 is received by the light receiving element 162.

[0037] The lenses 152 and 154 may each be configured as a single lens, or may be configured as a plurality of optical elements (lenses, mirrors, diffractive optical elements, etc.), or one or both of the lenses 152 and 154 may be omitted. Ｓ The intersection of the exit pupil and the optical axis and the reference light L Ｒ It is also possible to design the beam waist of the scattered light L at another position. Ｓ The intersection of the exit pupil and the optical axis and the reference light L Ｒ The beam waists of the scattered light L may be aligned on the reflecting surface 156a of the beam splitter 156. Ｓ The exit pupil and the reference light L Ｒ The beam waists of the reference light L may be made to coincide with each other, or may be made to coincide virtually downstream of the detector 160. Furthermore, for example, the lenses 124 and 152 may be configured to include lenses with different curvatures in the vertical and horizontal directions, such as cylindrical lenses, toroidal lenses, or ellipsoidal lenses, to obtain the reference light L. Ｒ is given astigmatism, and the reference light L seen from a certain direction is Ｒ The beam waist and scattered light L ＳThe intersection of the exit pupil and the optical axis is in a conjugate relationship, and the reference light L seen from a direction perpendicular to this Ｒ The beam waist and scattered light L Ｓ It is also possible to design the beam waists of the two beams to match.

[0038] Returning to FIG. 1, the configuration of the particle measuring device 100, particularly the configuration downstream of the combining / collecting optical system 150, will be further described.

[0039] The detector 160 outputs a signal whose magnitude corresponds to the intensity of light received by the light-receiving element. The light-receiving element of the detector 160 can be a photodiode, a phototransistor, an image sensor, a photomultiplier tube, or the like. The detector 160 may have a single light-receiving element forming a continuous light-receiving surface, or may have a light-receiving surface divided into a grid pattern by arranging multiple light-receiving elements in a row or two-dimensionally, such as a segmented photodiode. Alternatively, multiple detectors 160 can be used in an array.

[0040] The counting unit 170 calculates the particle size from the magnitude of the signal output from the detector 160, and counts the number of particles from the number of signals.

[0041] In such a particle measuring device 100, scattered light L propagating toward the detector 160 depends on the position of the particle P in the detection region. Ｓ The angle of the reference light L Ｒ The scattered light L is incident on the detector 160 so as to cover a wide range of the light receiving surface. As shown in FIG. Ｓ The detector 160 is disposed near the beam waist of the particle P, and the wavefront of the light is substantially flat at the beam waist. Ｓ The wavefront of the light beam L is approximately flat, and the minute scattered light L Ｓ Within the beam diameter range of Ｒ Therefore, the scattered light L Ｓ The change in intensity of the scattered light L Ｓ and reference light L Ｒ Therefore, it is possible to effectively obtain the intensity change of the interference light with the particle P, and it is possible to efficiently receive the interference light and thereby detect the particle P.

[0042] In addition, in the particle measuring device 100, the scattered light L Ｓ and reference light L Ｒ Since there is no need to align the wavefront shapes when combining the two beams, there is a high degree of freedom in installing the components. Note that the above-mentioned "degree of freedom in installing the components" refers to both the degree of freedom in "designing" the optical system in the particle measuring device 100 and the degree of freedom "when installing" the various optical components provided in the particle measuring device 100.

[0043] As shown in FIG. 4, in the particle measuring device 100, the reference light L Ｒ The reference light L covers a wide range of the light receiving surface. Ｒ Therefore, the spread of the scattered light L varies depending on the position of the particle P. Ｓ Even if the incident position of the scattered light L Ｓ Reference light L Ｒ Furthermore, the reference light L Ｒ The horizontal extent of the reference light L is greater than the horizontal width of the aligned light receiving elements 162 (in the illustrated example, four light receiving elements 162 are aligned in a row). Ｒ Even if the incident position of the light receiving element is slightly shifted in the horizontal direction, the scattered light L incident on the light receiving surface can be sufficiently covered. Ｓ and can be effectively interfered with.

[0044] The number and arrangement of the light receiving elements 162 shown in FIG. Ｒ For example, the reference light L may be spread so as to cover almost the entire or a part (for example, 50 out of 100 light receiving elements) of a light receiving surface formed by arranging a plurality of light receiving elements in a row or two-dimensionally. Ｒ The spreading (cross-sectional shape) of the reference light L Ｒ However, instead of or in addition to this, the vertical extension may be provided with a margin sufficient to cover the light receiving element, which makes it possible to deal with cases where the incident position of the reference light LR is shifted in the vertical direction.

[0045] On the other hand, in FIG. 4, the reference light L is projected so as to cover only a part of the vertical direction of the light receiving element. Ｒ In this case, the spread of the reference light L Ｒ and scattered light L Ｓ Although the ability to deal with vertical deviations in the incident position of the reference light L is limited, the particle detection sensitivity can be increased instead. Ｒ If the vertical direction is shortened without changing the total light amount of the reference light L Ｒ The particle detection sensitivity is improved because the energy density of the reference light L Ｒ Without changing the energy density of the reference light L Ｒ By shortening the vertical direction of the light receiving element 162, the amount of light incident on the light receiving element 162 is reduced, the output noise of the light receiving element 162 is reduced, and the particle detection sensitivity can be improved. Ｒ In consideration of the amount of vertical shift of the incident position of the reference light L Ｒ It is desirable to keep the vertical length of the sheet to the minimum necessary.

[0046] When the light emitted by the light source 110 has a linear, stripe, square, circular, or other spread in a cross section perpendicular to the direction of travel, the reference light L Ｒ can cover a wide range of the light receiving surface of the detector 160. For example, this is the case when the light source 110 emits light at a spread angle within a range that can be considered parallel, and the cross section of the light immediately after being emitted from the light source 110 has a certain area, or when the cross section has a shape exceeding a predetermined size. Therefore, the range in which particles can be detected in the detection region formed in the flow cell 140 is wide, and particles P contained in the fluid can be detected more efficiently.

[0047] Alternatively, the reference light L Ｒ The reference light L Ｒ For example, if the lenses 124 and 152 are configured to include lenses with different curvatures in the vertical and horizontal directions, such as cylindrical lenses, toroidal lenses, or ellipsoidal lenses, the reference light L Ｒ The cross section of the can be expanded and shaped into a flattened shape as shown in FIG.

[0048] In FIG. 2, the reference light L Ｒ However, instead of this, the reference light L Ｒ By adjusting the optical elements arranged on the optical path of the reference light L Ｒ Alternatively, the light may be incident as a convergent beam that covers a wide area of ​​the light receiving surface.

[0049] In the above example, the light receiving surface of the detector 160 receives the scattered light L Ｓ However, the light receiving surface is arranged in the vicinity of the beam waist in a state where it is almost perpendicular to the optical axis direction of the scattered light L Ｓ The direction of the optical axis of the scattered light L Ｓ The detector may be placed at a position other than the beam waist position. Even with such a placement, it is possible to ensure a certain degree of particle detection accuracy.

[0050] The split ratio of the transmitted light (illumination light) to the reflected light (reference light) in the beam splitter 120 can be set according to the expected intensity of the scattered light, i.e., the size of the particles generally expected to be detected. For example, the illumination light may be 95% and the reference light may be 5%, or the illumination light may be 99% and the reference light may be 1%, or both may be 50% and 50%.

[0051] Similarly to the above-described lenses 152 and 154, the lenses 122 and 124 may each be configured as a single lens, or may each be configured as a plurality of optical elements (lenses, mirrors, diffractive optical elements, etc.). Alternatively, one or both of the lenses 122 and 124 may be eliminated.

[0052] Second Embodiment FIG. 5 is a block diagram showing the configuration of a particle measuring device 200 according to a second embodiment.

[0053] The particle measuring device 200 measures scattered light L from particles P. Ｓ The particle measuring device 200 uses a telecentric optical system 254 (for example, an image-side telecentric lens) as an optical element that condenses the reference light L Ｒand the scattered light L emitted from the telecentric optical system 254 Ｓ and are combined by a beam splitter 156, in other words, the combining / focusing optical system 250 has a telecentric optical system 254 and the above-mentioned lens 152 and beam splitter 156, which is particularly different from the particle measuring device 100 of the first embodiment (FIG. 1).

[0054] In the particle measuring device 200, similarly to the particle measuring device 100, the scattered light L Ｓ and reference light L Ｒ When the scattered light L Ｓ and reference light L Ｒ The wavefronts of the scattered light L Ｓ The intersection of the exit pupil and the optical axis and the reference light L Ｒ The components of the combining / condensing optical system 250 are arranged so that the beam waists of the reference light L incident on the beam splitter 156 and the detector 160 are in a conjugate relationship. Ｒ becomes parallel light. Hereinafter, a description of the points common to the particle measuring device 100 will be omitted.

[0055] FIG. 6 shows the scattered light L in the combining / collecting optical system 250. Ｓ and reference light L Ｒ This shows the progression of the above.

[0056] The telecentric optical system 254 scatters the scattered light L from the incident particle P. Ｓ The telecentric optical system 254 emits the chief ray parallel to the optical axis of the telecentric optical system 254. Generally, a telecentric optical system refers to a configuration in which the chief ray is parallel to the optical axis of the lens in both object space and image space, and a configuration in which the chief ray is parallel to the optical axis only in object space is called object-side telecentric, and a configuration in which the chief ray is parallel to the optical axis only in image space is called image-side telecentric. Here, in this embodiment, the telecentric optical system 254 is configured so that the chief ray is parallel to the optical axis at least in image space. In other words, in the telecentric optical system 254, the chief ray may or may not be parallel to the optical axis in object space.

[0057] The telecentric optical system 254 is disposed so that its optical axis coincides with the direction of maximum sensitivity of the light receiving element 162. For example, the optical axis of the telecentric optical system 254 may be disposed so as to be approximately perpendicular to the light receiving surface of the light receiving element 162, prioritizing the density of incident light, or may be disposed in a manner other than approximately perpendicular, taking into account various factors that affect the wavelength dependency of the sensitivity of the light receiving element 162. Note that in the illustrated example, the telecentric optical system 254 is composed of two lenses, but the telecentric optical system 254 may be composed of a single lens or multiple optical elements.

[0058] The mirror 130 (not shown in FIG. 6) and the beam splitter 156 reflect the reference light L from the reflecting surface 156 a toward the detector 160 . Ｒ is arranged so as to be parallel to the optical axis of the telecentric optical system 254. Ｒ is emitted as parallel light.

[0059] In the particle measuring device 200 in which the beam combining / condensing optical system 250 is arranged in this manner, scattered light L from the particle P generated in the detection region Ｓ is incident on the telecentric optical system 254. The telecentric optical system 254 Ｓ The scattered light L is adjusted so that the chief ray is parallel to the optical axis of the telecentric optical system 254, regardless of the incident direction of the Ｓ The scattered light L emitted from the telecentric optical system 254 Ｓ is transmitted through the beam splitter 156. On the other hand, the reference light L Ｒ is reflected by the beam splitter 156 towards the detector 160 .

[0060] At this time, since the components of the combining / condensing optical system 250 are arranged in the above-described relationship, the scattered light L emitted from the beam splitter 156 Ｓ and reference light L Ｒ The principal rays of the two beams are parallel to each other and enter the detector 160 .

[0061] More specifically, scattered light L from a particle P generated at an arbitrary position within the detection region of the flow cell 140 Ｓand the scattered light L Ｓ Reference light L passing through the same place as the chief ray of Ｒ The light beam directions of the scattered light L and the scattered light L passing through the same place on the half mirror 156a are the same after the multiplexing. Ｓ The chief ray and the reference light L Ｒ The light beam is also incident on the detector 160 (light receiving element 162) at the same position.

[0062] Even in the configuration of the particle measuring device 200 of the second embodiment, the scattered light L Ｓ and reference light L Ｒ However, the wavefront of the reference light L Ｒ The wavefront of the scattered light L Ｓ The chief ray of the reference light L Ｒ In the particle measuring device 200, the scattered light L at the beam waist is perpendicular to the wavefront of the Ｓ The wavefront of the scattered light L on the light receiving element 162 is also flat, compared to the particle measuring device 100 of the first embodiment. Ｓ and reference light L Ｒ Therefore, the wavefront of the reference light L Ｒ and scattered light L Ｓ This allows for better interference between the particles P and the light, making it possible to detect the particles P more efficiently.

[0063] Advantages of the Present Invention As described above, the particle measuring device according to each of the above-described embodiments provides the following advantages.

[0064] (1) In the particle measuring device 100, scattered light L directed toward the detector 160 depending on the position of the particle P in the detection region. Ｓ However, the angle of the scattered light L Ｓ The wavefront of the reference light L is always Ｒ Since the wavefront of the scattered light L Ｓ This makes it possible to effectively obtain the intensity change of the particle, thereby enabling efficient particle detection.

[0065] (2) In the particle measuring device 200, the reference light L Ｒ The entire wavefront is flat, and the scattered light L heading toward the detector 160 regardless of the position of the particle P in the detection area. Ｓ The principal ray of the scattered light L on the light receiving element 162 is perpendicular to the wavefront of the reference light. Ｓ and reference light L Ｒ Since it is easy to make the wavefront of the reference light L coincide with that of the reference light L on the light receiving element 162, Ｒ and scattered light L Ｓ The interference between the two beams can be improved, and the intensity change can be obtained more effectively, making it possible to detect the particles P more efficiently.

[0066] (3) In the particle measuring devices 100 and 200, the reference light L Ｒ The reference light L is adjusted by adjusting the optical elements 124 and 152 provided on the optical path of the reference light L and the shape of the light emitted from the light source 110. Ｒ covers a wide range of the light receiving surface, the scattered light L varies depending on the position of the particle P in the detection area. Ｓ Even if the incident position of the reference light L Ｒ and can be effectively interfered with.

[0067] (4) In the particle measuring device 100, 200, the scattered light L Ｓ and reference light L Ｒ Since there is no need to match the wavefront shapes of the two when combining them, there is a high degree of freedom in installing the components.

[0068] The present invention is not limited to the above-described embodiment, and can be practiced in various modified forms.

[0069] In the above-described embodiment, the scattered light L transmitted through the beam splitter 156 Ｓ and the reflected reference light L Ｒ However, instead of this, or in addition to this, as in the modified example shown in FIG. Ｓ and the transmitted reference light L Ｒ The detector 160 may be arranged in the direction of travel of the beam.

[0070] The above-described embodiment has a configuration in which light emitted from light source 110 is incident directly on beam splitter 120. However, this configuration is not limited to this, and a configuration in which an optical element (lens, mirror, diffractive optical element, etc.) that adjusts the beam diameter or shape of the light emitted from light source 110 is disposed between light source 110 and beam splitter 120 may be used. Furthermore, the configuration is not limited to the configuration in which light emitted from beam splitter 156 is incident directly on detector 160, and a configuration in which an adjustment lens is disposed between beam splitter 156 and detector 160 may be used.

[0071] In the above-described embodiment, the mirror (mirror 130) that changes the traveling direction of the light is used to reflect the reference light L Ｒ However, the present invention is not limited to this configuration, and the reference light L Ｒ Not only on the optical path of the irradiated light L Ａ and scattered light L Ｓ Alternatively, a configuration may be adopted in which a mirror is disposed on each optical path, or a configuration in which mirrors are disposed at a plurality of locations on each optical path.

[0072] Furthermore, the configurations and numerical values ​​given in the course of the explanation of the particle measuring devices 100 and 200 are merely examples, and it goes without saying that they can be modified as appropriate when implementing the present invention.

[0073] REFERENCE SIGNS LIST 100 particle measuring device 110 light source 120 beam splitter 130 mirror 140 flow cell 150 beam combining / collecting optical system 160 detector 170 counting unit

Claims

1. A particle measuring device comprising: a light source that emits light; a first beam splitter that splits the light from said light source into two, directing one light, which is illumination light, toward a flow path into which a fluid is flowing, while directing the other light, which is reference light, in a direction different from the direction of said flow path; a second beam splitter that combines the reference light and scattered light from particles contained in the fluid, which is generated in a detection region formed within said flow path by illuminating said flow path with the illumination light, with the wavefronts not coinciding; and a detector having one or more light receiving elements that receive, with the light receiving element, interference light between the scattered light and the reference light combined by said second beam splitter, and outputs a signal according to the intensity of the interference light.

2. A particle measuring device according to claim 1, further comprising an optical system for adjusting the spread of the reference light or the light from the light source.

3. A particle measuring device according to claim 1 or 2, characterized in that the second beam splitter is arranged so that the direction of the chief ray of the scattered light generated at any position in the detection area is approximately the same as the direction of the ray of the reference light passing through the same location as the chief ray of the scattered light.

4. A particle measuring device according to claim 3, further comprising a telecentric optical system into which the scattered light generated in the detection region is incident and which emits its chief ray parallel to an optical axis in image space, and wherein the second beam splitter combines the reference light and the chief ray of the scattered light emitted from the telecentric optical system so that their optical axes are parallel.

5. A particle measuring device according to claim 1 or 2, characterized in that the detector is disposed in the vicinity of the beam waist of the scattered light.

6. A particle measuring device according to claim 2, wherein the optical system includes an asymmetric lens that generates astigmatism, the beam waist of the reference light as viewed from a predetermined direction is conjugate with the intersection of the exit pupil of the scattered light and the optical axis, and the detector is positioned at a position where the beam waist of the reference light and the beam waist of the scattered light approximately coincide with each other as viewed from a direction perpendicular to the predetermined direction.

7. A particle measurement method comprising: a splitting step of splitting light emitted from a light source into two, directing one light, which is illumination light, toward a flow path into which a fluid is flowing, while directing the other light, which is reference light, in a direction different from the direction of the flow path; a combining step of combining the reference light and scattered light from particles contained in the fluid, which is generated in a detection region formed within the flow path by irradiating the flow path with the illumination light, with the wavefronts not coinciding; and a detection step of receiving interference light between the scattered light and the reference light combined in the combining step, and outputting a signal corresponding to the intensity of the interference light.

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