JP2007333409A - Suspended particle measurement device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent suspended particle measurement device capable of suitably obtaining size of suspended particles in a predetermined spatial cross section in a fluid, the number of the suspended particles, and the distribution of the suspended particles without requiring a complicated calculation process, and of specifically acquiring motion of the suspended particles in the spatial cross section in the fluid. <P>SOLUTION: This suspended particle measurement device includes: a low-coherent light source 1 irradiating the fluid T containing the suspended particles R with low-coherent light B1; a beam splitter 4 separating the low-coherent light B1; an imaging part 6 arranged on a path of interference light B6 where reference light B3 interferes with scattering light B5, detecting spectrum intensity of the interference light B6 generated by the reference light B3 and the scattering light B5, and obtaining its interference image; and a calculation part 7d obtaining at least one of the quantity, the distribution and the size of the suspended particles R based on the interference image provided by the imaging part 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a suspended particle measuring apparatus that measures the number, distribution, or size of suspended particles contained in a fluid by irradiating the fluid with low-coherent light.

  2. Description of the Related Art Conventionally, a fluid inspection apparatus that detects particles contained in a fluid used when manufacturing a semiconductor element or the like and can check the characteristics and size of the particles is known.

  Specifically, this type of fluid inspection apparatus includes, for example, a laser light source that emits laser light, a beam splitter that divides the laser light emitted by the laser light source into sample light and reference light, and a sample that is divided by the beam splitter. An objective lens having a function of condensing and irradiating light onto the particle and a function of condensing the scattered light scattered by the particle toward the beam splitter, and the reference light, the objective lens, and the beam splitter. It is possible to distinguish between the size of the particles and whether the particles are metal or dielectric by analyzing the detection signal obtained by the detector. (For example, refer patent document 1).

  Further, a remote particle counter device that remotely measures the number of fine particles floating in the atmosphere, the particle size distribution, and the like is known.

Specifically, this type of remote particle counter device is a high-sensitivity two-dimensional light detection device such as a pulse laser, laser emission optical system, scattered light condensing optical system, CCD camera having a high-speed gate function as a scattered light detector A fine particle floating in the atmosphere by detecting backscattered light from each particle generated as a result of laser irradiation from airborne fine particles in the atmosphere far from the laser emission point. The number of particles, the particle size distribution, etc. can be measured remotely (see, for example, Patent Document 2).
Japanese Unexamined Patent Publication No. 01-292235 JP 2004-233078 A

  However, in the conventional configuration, particularly in the configuration of Patent Document 1, the reference light and the scattered light that has returned through the objective lens and the beam splitter are detected, and the size of the particle, and whether the particle is a metal or a dielectric However, it is difficult to know in which spatial section the particle being measured exists. This is because a coherent laser beam is used for the measurement, and therefore, for a plurality of particles having a positional relationship shifted in the traveling direction of the laser beam and around an integral multiple of the wavelength, the context is accurately known. This is because, as a result, the number and distribution of particles in the spatial section cannot be accurately known.

  Further, in the configuration of Patent Document 2, since the laser beam is irradiated to the space where the particle group exists and the scattered light from the particle in the space is measured, the spread angle of the emitted laser, There is a problem in that the concentration of fine particles must be calculated from the magnification of the camera and the delay time of the shutter, which complicates the arithmetic processing. Further, similarly to the above problem in Patent Document 1, there is a problem that the number and distribution of particles in a certain spatial section cannot be accurately known.

  Furthermore, in any of the configurations of Patent Document 1 and Patent Document 2, the movement of particles in a certain space section cannot be specifically grasped.

  The present invention has been made paying attention to such a problem, the main purpose is not to require a complicated calculation process, the size of the suspended particles in a predetermined space section in the fluid, the number of suspended particles, Providing an excellent suspended particle measuring device that can suitably determine the distribution of suspended particles, and specific movement of suspended particles in a predetermined space section in a fluid without requiring complicated calculation processing It is to provide an excellent suspended particle measuring apparatus that can be easily grasped.

  That is, the suspended particle measuring apparatus according to the present invention includes a low-coherent light source that irradiates a fluid containing suspended particles with low-coherent light, and the low-coherent light irradiated from the low-coherent light source. And a beam splitter that separates toward the reference mirror, a reference light that is separated by the beam splitter and then reflected by the reference mirror, and a scattered light that is separated and scattered by the suspended particles, Based on the interference image obtained by the imaging unit that is arranged on the interference light path that interferes and obtains an interference image of the interference light by detecting the spectral intensity of the interference light generated by the reference light and the scattered light And an arithmetic unit that obtains at least one of the quantity, distribution, and size of the suspended particles.

  Here, “low coherent light” refers to light that does not interfere with each other, such as white light and LED light, or light that does not interfere with each other, and is highly coherent like laser light. It does not include light having sex.

  In this case, of the scattered light scattered by the suspended particles, the backscattered light from suspended particles equidistant from the beam splitter to the reference mirror is coherent in time and space with respect to the reference light. It becomes a relationship. On the other hand, scattered light from suspended particles that are not equidistant from the beam splitter from the beam splitter does not have a coherent relationship with the reference light. Therefore, only such backscattered light appears as a bright spot in the interference image due to interference with the reference light.

  Here, for comparison, let us consider the light irradiated to the fluid as laser light. For example, when one of the two suspended particles is one that is equidistant from the beam splitter to the reference mirror, and the other is in a position shifted in the laser beam irradiation direction and an integral multiple of its wavelength. The backscattered light from both suspended particles interferes with the reference light and appears in the interference image due to the coherent nature of the laser light.

  In this way, if the light applied to the fluid is laser light, it becomes impossible to reliably know the front and rear positions of the suspended particles, and as a result, in the spatial section equidistant from the beam splitter to the reference mirror, Whether or not airborne particles are present cannot be determined accurately.

  On the other hand, if the light applied to the fluid is low coherent light as in the present invention, it can be accurately determined whether or not suspended particles are present in the spatial section.

  Therefore, according to the suspended particle measuring apparatus of the present invention, it is possible to know whether or not suspended particles are present in the spatial section equidistant from the beam splitter to the reference mirror by the presence or absence of the bright spot. By counting the number of particles, the number of suspended particles existing in the spatial section can be known. Further, the size of suspended particles can be grasped by the area of the bright spot. It is also possible to know the distribution of suspended particles in the spatial section.

  That is, no complicated calculation processing is required, and the size of suspended particles, the number of suspended particles, and the distribution of suspended particles in a spatial section of a fluid equidistant from the beam splitter can be suitably obtained. A suspended particle measuring apparatus can be provided.

  As another desirable mode of the suspended particle measuring apparatus according to the present invention, the suspended particle measuring apparatus is irradiated with a low coherent light source that irradiates a fluid containing suspended particles with low coherent light and the low coherent light source. A beam splitter that transmits and reflects low-coherent light toward the fluid and a reference mirror; and a reference beam that is separated by the beam splitter and then reflected by the reference mirror; An imaging unit that obtains an interference image of the interference light by detecting the spectral intensity of the interference light generated by the reference light and the scattered light, which is arranged on the interference optical path where the scattered light scattered by the suspended particles interferes. And an image output unit that outputs a plurality of interference images obtained by the imaging unit in order of imaging time. It is below.

  In such a case, since the light applied to the fluid is low-coherent light, as described above, whether or not suspended particles exist in the spatial section equidistant from the beam splitter to the reference mirror. And the like can be accurately obtained from the bright spots appearing in the interference image.

  Thus, according to the suspended particle measuring apparatus of the present invention, the image output unit continuously outputs a plurality of interference images obtained by the imaging unit in the order of the imaging time. The movement can be observed dynamically, and the movement of the suspended particles in the space section can be grasped specifically.

  That is, the present invention provides an excellent suspended particle measuring apparatus that can specifically grasp the movement of suspended particles in a spatial section of a fluid equidistant from a beam splitter to a reference mirror without requiring complicated calculation processing. be able to.

  As described above, according to the suspended particle measuring apparatus of the present invention, since the light irradiated to the fluid is low coherent light, the suspended particles exist in the spatial section equidistant from the beam splitter to the reference mirror. Whether or not, etc., can be accurately obtained from the bright spots appearing in the interference image.

  Then, if the number of bright spots is counted in the calculation unit, the number of suspended particles existing in the cross section of the space can be known, and the size of the suspended particles can be grasped according to the area of the bright spot. The distribution of suspended particles in the cross section can also be known.

  In addition, since the image output unit continuously outputs a plurality of interference images obtained by the imaging unit in the order of the imaging time, it is possible to dynamically observe the movement of the bright spots appearing in the interference image. The movement of suspended particles in the cross section can be grasped specifically.

  That is, it provides an excellent suspended particle measuring device that can suitably calculate the size of suspended particles, the number of suspended particles, and the distribution of suspended particles in a predetermined space section in a fluid without requiring complicated calculation processing. It is possible to provide an excellent suspended particle measuring apparatus capable of specifically grasping the movement of suspended particles in a predetermined space section in a fluid without requiring complicated calculation processing. it can.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  The suspended particle measuring apparatus A according to the present embodiment is for measuring suspended particles R contained in a fluid T confined in a cell S as shown in FIG. A low-coherent light source 1 that emits coherent light B1, a collimator 2 that collimates the low-coherent light B1 emitted by the low-coherent light source 1, and a reflection that is incident after being separated and reflected by a beam splitter 4 described later. A reference mirror 3 that reflects the light B2 as the reference light B3, and a beam splitter 4 that transmits and reflects the parallel light that has been collimated by the collimator 2 and separates it toward the fluid T of the cell S and the reference mirror 3. An optical attenuator 5 disposed between the beam splitter 4 and the reference mirror 3, a CCD camera 6 (corresponding to the “imaging unit” of the present invention) disposed on the side opposite to the reference mirror of the beam splitter 4, and C Based on the interference image obtained by the D camera 6, formed by including an information processing unit 7 for processing to determine the size, etc. of suspended particles R. In addition, although the cell S is made into the cylindrical thing which was enclosed by the transparent wall S1 and this transparent wall S1, and had internal space S2 which accommodates the fluid T inside, the shape may be arbitrary. For example, it does not prevent the depth direction from being increased or decreased. Hereinafter, each part is demonstrated concretely.

  The low-coherent light source 1 emits white light, that is, low-coherent light B1 having a continuous spectrum at least in the visible band. In the present embodiment, the low coherent light source 1 uses a xenon flash lamp capable of repeatedly emitting short white light having a flash time of about tens of thousands of seconds for one second. .

  The collimating unit 2 includes two convex lenses 21 and 22 facing each other, and uses the refractive action of the convex lenses 21 and 22 to collate white light that is low-coherent light B1 incident from the low-coherent light source 1 in parallel. The light is emitted toward the beam splitter 4. Needless to say, this parallel light is light having low coherency.

  The reference mirror 3 is supported by an actuator (not shown) that moves the reference mirror 3 toward and away from the beam splitter 4. The information processing unit 7 outputs the contact / separation operation command to the actuator so that the distance between the reference mirror 3 and the beam splitter 4 can be changed while being managed by the information processing unit 7.

  The beam splitter 4 separates the reflected light B2 and the transmitted light B4 at a constant ratio regardless of the wavelength of the light incident on the beam splitter 4 at least in the visible region. The shape is used.

  The center of the beam splitter 4 is disposed on the shortest line connecting the cell S and the light source, and the beam splitter 4 is disposed at an angle of about 45 degrees with respect to the line. As a result, the light B1 incident from the collimating unit 2 is reflected in a direction that forms 90 degrees with respect to the transmission line B4 that passes through the beam splitter 4 and travels directly toward the cell S with respect to the line. The light is separated into reflected light B2 toward the reference mirror 3.

  The optical attenuator 5 appropriately attenuates the transmitted light amount of light passing through the optical attenuator 5 (light B3 directed from the reference mirror 3 to the beam splitter 4 and light B4 directed from the beam splitter 4 to the reference mirror 3), The light amount of the reference light B3 can be adjusted.

  The CCD camera 6 separates the reference light B3 reflected by the reference mirror 3 after being separated by the beam splitter 4 and the interference light B6 on which the scattered light B5 scattered by the floating particles R after the separation interferes. The spectral intensity of the interference light B6 generated by the reference light B3 and the scattered light B5 is detected, the interference image of the interference light B6 obtained by detection is converted into an electrical signal, and information This is output to the processing unit 7.

  As shown in FIG. 2, the information processing unit 7 communicates with a CPU 101, an internal memory 102, an external storage device 103 such as an HDD, an input device 104 such as a mouse or a keyboard, a display device 105 such as a liquid crystal display, and a CCD camera 6. In this embodiment, a personal computer having a general information processing function is used.

  In the present embodiment, the information processing unit 7 operates the CPU 101 and its peripheral devices in cooperation with each other in accordance with a program stored in the internal memory 102, for example. As shown, the reference mirror position designation command reception unit 7a, the reference mirror position designation command output unit 7b, the interference image reception unit 7c, the calculation unit 7d, the calculation result storage unit 7e, and the image output unit 7f are at least exhibited. It is configured.

  The reference mirror position designation command accepting unit 7a accepts a command for designating the reference mirror 3 position, and is configured using the input device 104 or the like. Here, a specific example of the “reference mirror 3 position” includes, for example, the position of the reference mirror 3 with respect to the beam splitter 4. The position of the reference mirror 3 relative to the CCD camera 6 is not limited to this. Furthermore, it does not prevent receiving a command specifying the movement distance of the reference mirror 3 itself, instead of receiving a command specifying the distance to the other of the reference mirror 3 in this way.

  The reference mirror position designation command output unit 7b outputs the reference mirror position designation command received by the reference mirror position designation command reception unit 7a to an actuator that supports the reference mirror 3, and includes a communication interface 106 and the like. It is configured using.

  The interference image receiving unit 7c receives an interference image from the CCD camera 6 and is configured using the communication interface 106 or the like.

  The computing unit 7d obtains the quantity, size, and distribution of the suspended particles R based on the interference image stored in the interference image receiving unit 7c. Specifically, for the quantity of suspended particles R, for example, by counting the number of bright spots having an area larger than a predetermined area, the quantity of suspended particles R existing in the space section T1 described later can be known. ing. As for the size of the suspended particles R, the size of each suspended particle R can be known by obtaining the area of each bright spot. As for the distribution of the suspended particles R, the distribution of the suspended particles R can be known by generating a distribution image obtained by cutting out all or part of the spatial section T1. That is, the calculation unit 7d can calculate the distribution of suspended particles in the space section.

  The calculation result storage unit 7e temporarily stores the calculation result output from the calculation unit 7d and the reference mirror position information indicated by the reference mirror position designation command in association with each other. It is formed in a predetermined area.

  The image output unit 7f continuously outputs a plurality of interference images obtained by the imaging unit and stored in the calculation result storage unit 7e in the order of the imaging time, and is configured using the display device 105 or the like. is doing.

  The image output unit 7f not only outputs a planar image on the spatial section T1, but also outputs a stereoscopic image based on the reference mirror position information stored in the calculation result storage unit 7e. Can do.

  Hereinafter, the operation of the suspended particle measuring apparatus A of the present embodiment will be described.

  First, when the low-coherent light B1 irradiated by the low-coherent light source 1 is incident on the collimating unit 2, the collimating unit 2 converts the low-coherent light B1 into parallel light.

  Then, when the low-coherent light B1 that has become parallel light is incident on the beam splitter 4, the low-coherent light B1 of the parallel light is reflected by the beam splitter 4 and transmitted through the reflected light B2 toward the reference mirror 3. Then, it is separated into transmitted light B4 traveling toward the cell S.

  The reflected light B2 directed toward the reference mirror 3 is reflected by the reference mirror 3 and returns toward the beam splitter 4 as the reference light B3. On the other hand, the transmitted light B <b> 4 toward the cell S is scattered by the suspended particles R in the cell S, and a part thereof returns toward the beam splitter 4. (In FIG. 1, the scattered light etc. which do not return to the beam splitter 4 among the scattered light B5 are abbreviate | omitted suitably for convenience of drawing.)

  In this way, the reference light B3 and the scattered light B5 respectively returning to the beam splitter 4 are transmitted and reflected by the beam splitter 4 and travel toward the CCD camera 6.

  At this time, of the scattered light B5 scattered by the suspended particles R, the backscattered light B5a from the suspended particles R1 that are equidistant from the beam splitter 4 to the reference mirror 3 (spatial section T1) is timed relative to the reference light B3. It is a coherent relationship both above and in space. On the other hand, the scattered light B5b from the suspended particle R2 that is not equidistant from the beam splitter 4 and the reference mirror 3 (spatial section T1) does not have a coherent relationship with the reference light B3. Accordingly, only the backscattered light B5a interferes with the reference light B3, so that the CCD camera 6 appears as a bright spot of the interference image, and the CCD camera 6 outputs this as an electrical signal.

  In the present embodiment, an interference image is captured in synchronization with the irradiation timing of the low-coherent light source 1, thereby improving the accuracy of imaging sensitivity.

  Thus, the interference image converted into the electrical signal output from the CCD camera 6 is appropriately calculated by the information processing unit 7, and the quantity of the suspended particles R in the spatial section T1, the size of the suspended particles R, and The distribution of the suspended particles R can be visually confirmed.

  Therefore, according to the suspended particle measuring apparatus A according to the present embodiment configured as described above, the light irradiated to the fluid T is the low coherent light B1, so that the beam splitter 4 is equidistant from the reference mirror 3. Whether or not the suspended particles R are present in a certain space section T1 can be accurately determined from the bright spots appearing in the interference image.

  Then, since the number of bright spots is counted by the calculation unit 7d, the quantity of the suspended particles R existing in the spatial section T1 can be known, and the size of the suspended particles R can be grasped by the area of the bright spots. In addition, the distribution of the suspended particles R in the space section T1 can also be known.

  In addition, since the image output unit 7f continuously outputs a plurality of interference images obtained by the CCD camera 6 in the order of the imaging time, the movement of the bright spot appearing in the interference image can be dynamically observed, The movement of the suspended particles R in the spatial section T1 can be specifically grasped.

  That is, complicated calculation processing is not required, and the size of the floating particles R, the number of the floating particles R, and the distribution of the floating particles R in the predetermined space section T1 in the fluid T can be suitably obtained. It is possible to provide an excellent suspended particle measuring apparatus A that can specifically grasp the movement of suspended particles R in a predetermined space section T1 therein.

  Since an optical attenuator 5 capable of adjusting the amount of transmitted light is disposed between the beam splitter 4 and the reference mirror 3, the intensity of the reference light B3 is adjusted by adjusting the amount of transmitted light of the optical attenuator 5, and interference is caused. The contrast of the interference image can be adjusted by changing the degree of interference of the light B6. The number of the suspended particles R1, the distribution of the suspended particles R1, and the size of the suspended particles R1 can be accurately known from the interference image whose contrast is adjusted.

  Since the collimator 2 is disposed between the cell S and the beam splitter 4, the collimator 2 can collimate the low-coherent light B1 and irradiate the fluid T in a plane. Thus, the number of suspended particles R, the distribution of suspended particles R, and the size of suspended particles R in the space section T1 equidistant from the reference mirror 3 can be known at a time.

  Since the reference mirror 3 is configured to be capable of moving toward and away from the beam splitter 4 or the CCD camera 6, the distance between the beam splitter 4 and the reference mirror 3 is changed by moving the reference mirror 3 toward and away from the beam. The size of the suspended particles R can be known from the number of suspended particles R in the spatial section T1 that is equidistant from the changed distance and the distribution of the suspended particles R. That is, the quantity of the suspended particles R in the depth direction of the fluid T and the distribution of the suspended particles R can know the size of the suspended particles R, which contributes to a three-dimensional analysis.

  The present invention is not limited to the above embodiment.

  For example, the cell S may be a batch type in which the fluid is retained and measured, a flow type in which the fluid is kept flowing, or a combination type thereof.

  Further, the cell S needs to transmit light, but the entire cell S may be transparent, or a light transmission part (window) may be provided in a part or a wide range.

  Further, the light incident portion of the cell S can be configured so that the surface reflection does not return to the imaging unit. Specifically, for example, the incident light angle to the surface is other than 0 degrees (other than vertical), an antireflection coating is applied, or they are used in combination.

  Further, the suspended particles R contained in the fluid T in the cell S are measured, but the fluid T may not be confined in the cell S. For example, airborne particles contained in the atmosphere can be measured.

  Moreover, although the optical attenuator 5 that attenuates the amount of light is used as the transmitted light amount adjustment unit, it does not interfere with the use of the one that amplifies the amount of light. In addition, a configuration in which the transmitted light amount adjustment unit is not used may be employed.

  Moreover, the structure of the collimating part can be appropriately changed according to the embodiment.

  Further, the arrangement positions of the cell S and the reference mirror 3 may be interchanged.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

1 is an overall view schematically showing a suspended particle measuring apparatus according to an embodiment of the present invention. The equipment block diagram of the information processing part in the same embodiment. The function block diagram of the information processing part in the embodiment.

Explanation of symbols

A ... Airborne particle measuring device B1 ... Low coherent light B3 ... Reference light B5 ... Scattered light B6 ... Interference light R ... Airborne particle T ... Fluid 1 ... ··· Low coherent light source 2 ··· Collimator 3 ··· Reference mirror 4 ··· Beam splitter 5 ··· Transmitted light amount adjustment unit (optical attenuator)
6. Image pickup unit (CCD camera)
7d: arithmetic unit 7f: image output unit

Claims (2)

A low coherent light source that emits low coherent light to a fluid containing suspended particles;
A beam splitter that transmits and reflects low-coherent light emitted from the low-coherent light source toward the fluid and a reference mirror; and
The reference light reflected by the reference mirror after being separated by the beam splitter and the scattered light scattered by the suspended particles after being separated are arranged on an interference optical path that interferes with each other, and these reference lights And an imaging unit that obtains an interference image of the interference light by detecting the spectral intensity of the interference light caused by the scattered light,
An airborne particle measuring apparatus comprising: an arithmetic unit that obtains at least one of the number, distribution, and size of the airborne particles based on an interference image obtained by the imaging unit. A low coherent light source that emits low coherent light to a fluid containing suspended particles;
A beam splitter that transmits and reflects low-coherent light emitted from the low-coherent light source toward the fluid and a reference mirror; and
The reference light reflected by the reference mirror after being separated by the beam splitter and the scattered light scattered by the suspended particles after being separated are arranged on an interference optical path that interferes with each other, and these reference lights And an imaging unit that obtains an interference image of the interference light by detecting the spectral intensity of the interference light caused by the scattered light,
An airborne particle measuring apparatus comprising: an image output unit that continuously outputs a plurality of interference images obtained by the imaging unit in order of imaging time.