JP4382139B2 - Fine particle detection apparatus and fine particle detection method - Google Patents

Description

  The present invention relates to a fine particle detection apparatus and a fine particle detection method for detecting fine particles in a light-transmitting medium.

  Detecting fine particles in a light-transmitting medium is important in managing the quality of a system that uses the medium and the products produced by the system. For example, in water purification quality control at water purification plants, sea and river pollution surveys, and measurement of lubricating oil contamination, particulates in liquid media such as water purification plant water, seawater and river water, and lubricating oil from various machines and plants are detected. There is a need to. In addition, for example, in the air cleanliness of an atmosphere in a specific space such as a clean room or dust detection of atmospheres in various environments, it is necessary to detect fine particles in the gas medium. In addition, there is a need for the detection of impure particles in a transparent solid medium such as glass.

  In the detection of fine particles, there is a method of observing changes in the amount of light due to light scattering or shielding of the fine particles and detecting the presence of the fine particles from the amount of change. As a method for detecting fine particles using light, for example, there is a “fine particle detection device in fluid” described in Patent Document 1 below. This is done by focusing the coherent light from the laser with the lens optical system in the test liquid, detecting the light diffracted by the fine particles passing through the light collection area with an array-shaped photodetector, and analyzing the diffracted light. It detects fine particles. The “fine particle measuring device” described in the following Patent Document 2 is a technique for irradiating parallel light produced using a lens optical system to a cell through which fine particles pass and detecting it with a light receiving element. A shielding plate with an opening is provided so that scattered light from the fine particles is not detected, and changes in the detected light due to the light shielding of the fine particles are observed.

JP 2003-130784 A JP 2002-228574 A

  However, a lens optical system is indispensable for the fine particle detection techniques disclosed in Patent Documents 1 and 2 above. Therefore, it is necessary to converge and expand the laser beam by the lens optical system, and there is a problem that adjustment such as axial alignment of the lens optical system is difficult. In addition, it is necessary to adjust the light receiving sensor and the laser light source. In addition, expensive scanning components such as a laser light source and a lens optical system are used to detect fine particles to be detected, and optical scanning such as narrowing of inspection light or parallel light is necessary. For this reason, it is also difficult to provide the device to the user at a low cost.

  The present invention has been made in view of the above, and an object of the present invention is to provide a fine particle detection apparatus and a fine particle detection method capable of reducing the apparatus cost while ensuring the detection sensitivity of the fine particles in the inspection object.

(1) In order to achieve the above-described object, the present invention detects fine particles in the object to be inspected by detecting fluctuations in the detection light intensity caused by the interference effect of the detection light caused by the fine particles crossing the irradiation region of the inspection light. A fine particle detection apparatus, wherein the emitted inspection light is incident on the inspection object in the pipe without being narrowed, and the laser light emission means attached to the outside of the pipe, and the laser emission means that is incident through the inspection object A light receiving means attached outside the pipe for receiving the inspection light from the pipe, and a light transmission provided between the outer peripheral surface of the pipe and the light receiving means for limiting a detection area of the inspection light incident on the light receiving means. Based on a signal from the light-shielding means having a hole and the light-receiving means, a change in detection light intensity caused by an interference effect of the inspection light caused by the fine particles moving in the detection region is detected to detect the fine particles in the inspection object. Signal processing And a device, the diameter of the light transmission hole, the can observe the laser emitting means from the receiving means in the area to be observed through the light transmitting hole, and, when crossing the observation area is fine, the laser light emitting means The signal processing device has a waveform memory that records fluctuations in the detection light detected by the light receiving means, and is capable of detecting interference between the direct light directly incident from the light and the reflected light reflected by the fine particles. And an arithmetic unit for judging whether or not the detected fine particles are spherical depending on whether or not the detected waveform recorded in the waveform memory is temporally symmetrical about the optical axis.

( 2 ) In the above (1), preferably, a means for suppressing the reflection of the inspection light or a means for scattering the inspection light is provided in a portion other than the optical path of the inspection light in the inner surface of the passage of the inspection object, and the laser emission The amount of light returning to the means is suppressed.

( 3 ) In the above (1), it is preferable that a high-frequency superimposing circuit for extending the emission spectrum of the inspection light is incorporated in a current source for supplying a driving current for the laser emission means.

( 4 ) In the above ( 3 ), preferably, a polarization plane changing means for changing the polarization plane of the inspection light is provided.

( 5 ) In order to achieve the above object, the present invention also detects fine particles in the object to be inspected by detecting fluctuations in the detection light intensity caused by the interference effect of the detection light caused by the fine particles crossing the inspection light irradiation region. A method for detecting fine particles, wherein the inspection light emitted from laser light emitting means attached to the outside of the pipe is incident on the inspection object flowing through the piping without being narrowed, and the laser light emission means is incident through the inspection object Is received by a light receiving means attached to the outside of the pipe, and a light transmitting hole provided in the light shielding means is provided between the outer peripheral surface of the pipe and the light receiving means, thereby receiving the light from the laser light emitting means. The detection area of the inspection light incident on the means is limited , and the direct light that passes through the object to be inspected and directly enters from the laser light emitting means, and the reflected light that is reflected by the fine particles flowing in the object to be inspected and incident on the light. Transparency Through the holes is received by said light receiving means, wherein based on a signal from the light receiving means, wherein the detection region to detect a variation in detected light intensity generated by the interference effect of the inspection light by fine particles to move with the object to be inspected in And detecting whether or not the detected fine particles are spherical depending on whether or not the detected waveform is temporally symmetrical about the optical axis. It is characterized by that.

  According to the present invention, the device cost can be reduced while ensuring the detection sensitivity of the fine particles in the object to be inspected.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the particle detection technique according to the present embodiment, the inspection light is irradiated from the light emitting means to the light receiving means with the object to be inspected, and the particles in the inspection object cross the detection area in the irradiation area of the inspection light. At this time, the presence of the fine particles is detected by observing that the inspection light is blocked by the fine particles and the light intensity decreases. Only the inspection light that has passed through a plurality of light transmission holes provided in the light shielding unit is incident on the light receiving unit. In this way, the inspection light is incident on the light receiving element through the plurality of light transmission holes, so that the region that actually contributes to the detection of the fine particles in the irradiation region of the inspection light on the inspection object (the region incident on the light receiving element) The detection area is limited. Only the inspection light that has passed through the light transmission hole is incident on the light receiving means. In this way, by making the inspection light incident on the light receiving element through the light transmission hole, a detection region that is an area that actually contributes to the detection of fine particles (an area incident on the light receiving element) in the irradiation region of the inspection light on the inspection object. Is limited.

  In addition, the inspection light is irradiated from the light emitting means to the light receiving means with the object to be inspected, and the light intensity decreases when the fine particles cross the detection region, and the light from the light emitting means and the reflected light of the fine particles The presence of fine particles can also be detected by simultaneously observing the phenomenon in which the intensity of the detection light fluctuates due to interference with each other. In this case, the waveform of the detection light composed of light shielding, diffracted light, and interference light is analyzed in detail, and it is determined whether the detected fine particle is spherical, so that the fine particle is, for example, a minute void or other detection should be performed. It can be estimated whether it is an impurity particle.

  The object to be inspected including the fine particles to be detected may be a substance having optical transparency, and the state is not particularly limited. In addition to fluids such as liquid and gas, solids such as glass are also included. Further, when the detection area and the fine particles are relatively moved, the detection area may be stationary and the inspection object may be moved, the inspection object may be stationary and the detection area may be moved, May be moved. When both are moved, they may be moved in different directions so that the detection region scans the object to be inspected two-dimensionally.

  Hereinafter, representative examples of the present invention will be described sequentially.

  FIG. 1 is a schematic configuration diagram of a first embodiment of a particle detection apparatus according to the present invention, and a detection unit 1 is shown in cross section.

  The particle detection apparatus shown in FIG. 1 includes a detection unit 1 that detects particles in a test object (fluid in this example), a current source 2 that is an energy source of inspection light, a current-voltage converter 3, and a detection unit. 1 is provided. The signal processing circuit 4 processes one output signal.

  The detection unit 1 includes a light emitting element 1-1 that irradiates the inspection object with inspection light, a light receiving element 1-2 that receives inspection light from the light emitting element 1-1 that passes through the inspection object, and the light emitting element 1. -1 holding plate 1-3, holding plate 1-4 holding the light receiving element 1-2, cell 1-5 for circulating the object to be inspected, and plural (in this example) provided on the holding plate 1-4. 2) light transmission holes 1-6 and 1-7 (see FIG. 2).

  A light source that emits coherent light such as a laser can be used for the light emitting element 1-1, but a light source that emits incoherent light such as an LED (Light Emitting Diode) is sufficient. The light emitting element 1-1 emits light by the driving current from the current source 2. For the light receiving element 1-2, for example, a light receiving sensor such as a PD (Photo Diode) can be used. The photocurrent received by the light receiving element 1-2 is converted into a voltage signal by the current-voltage converter 3 and subjected to signal processing by the signal processing circuit 4.

  The transparent tube-shaped cell 1-5 is passed between the holding plates 1-3 and 1-4. By passing the object to be inspected through the cell 1-5, the object to be inspected is detected by the detection unit 1. Move relative to. At this time, the light emitting element 1-1 held by the holding plate 1-3 emits inspection light toward the light receiving element 1-2 held by the holding plate 1-4. A portion between the light emitting element 1-1 and the light receiving element 1-2 of the holding plate 1-4 that holds the element 1-2 serves as a light shielding unit that blocks the inspection light.

  FIG. 2 is a sectional view showing the holding plates 1-3 and 1-4 extracted.

  As shown in FIG. 2, in this embodiment, a cavity 1-8 is provided in the holding plate 1-4 of the light receiving element 1-2 between the light emitting element 1-1 and the light receiving element 1-2. The light transmission holes 1-6 and 1-7 are formed in the inner wall of the cavity 1-8 along the traveling direction of the inspection light from the light emitting element 1-1 toward the light receiving element 1-2. Accordingly, only the light beam passing through the light transmitting holes 1-6 and 1-7 among the inspection light passing through the cell 1-5 between the holding plates 1-3 and 1-4 reaches the light receiving element 1-2. Detected. That is, the detection region 1-9 that enters the light receiving element 1-2 out of the inspection light irradiated on the object to be inspected passes through both the light transmitting holes 1-6 and 1-7 from the light emitting element 1-1. It is limited (restricted) only to the light beam (hatched portion in FIG. 2) incident on the light receiving element 1-2. If fine particles cross the detection region 1-9, a part of the inspection light is blocked and the light intensity detected by the light receiving element 1-2 decreases. Thereby, only the detection region 1-9 in the irradiation region of the inspection light can be observed by the light receiving element 1-2.

  The width, length, and cross-sectional shape of the detection region 1-9 are the size and shape of the light transmission holes 1-6 and 1-7, the distance between the light transmission holes 1-6 and 1-7, and the light emitting element 1-1. The detection region can be adjusted according to the interval between the plates 1-4 (the interval between the holding plates 1-3 and 1-4), depending on the light transmittance of the object to be inspected and the size, properties, concentration, etc. of the particles to be detected. 1-9 can be arbitrarily changed. For example, when the light transmission holes 1-6 and 1-7 have the same diameter, the diameter of the detection region 1-9 decreases as the apertures of the light transmission holes 1-6 and 1-7 decrease and the interval increases. Further, when the interval between the holding plates 1-4 and 1-5 is increased, the diameter of the detection region 1-9 is increased and the length is increased.

  In this embodiment, a fluid such as a gas or a liquid is used as the object to be inspected. Therefore, in FIG. 2, the object to be inspected is circulated in the tube-shaped cell 1-5. It is also possible to use a solid having a test object. For example, if the object to be inspected is rod-like or plate-like glass, glass (object to be inspected) is passed between the holding plates 1-3 and 1-4 instead of the cell 1-5, and at least the detection unit 1 or the glass A configuration may be adopted in which one is moved.

  FIG. 3 is a schematic configuration diagram of the signal processing circuit 4.

  The signal processing circuit 4 shown in FIG. 3 includes a bandpass filter 4-1, an inverting amplifier 4-2, a detector 4-3, a summing amplifier 4-4, a voltage source 4-5, a comparator 4-6, a pulse rate. A detection circuit 4-7 is provided.

  The band pass filter 4-1 removes a direct current component from the output signal of the light receiving element 1-2 of the detection unit 1 and reduces a noise component. The inverting amplifier 4-2 amplifies the polarity of the signal from the bandpass filter 4-1 by reversing the polarity. The detector 4-3 detects from the inverted and amplified output signal. The voltage source 4-5 outputs a signal having a preset constant voltage. The adding amplifier 4-4 adds a constant voltage from the voltage source 4-5 to the detection signal from the detector 4-3. The comparator 4-6 compares the output of the summing amplifier 4-4 with the inverting amplifier 4-2, and outputs a constant voltage signal when the output of the inverting amplifier 4-2 is larger than the output of the summing amplifier 4-4. The pulse rate detection circuit 4-7 obtains the output generation rate of the comparator 4-6 and outputs it to an external display (not shown) or the like.

  FIG. 4 is a diagram showing the output waveform of each part of the signal processing circuit 4.

  The output signal of the light receiving element 1-2 has a waveform obtained by superimposing a dimming signal generated when a fine particle crosses the detection region 1-9 on the substantially constant inspection light in the light intensity detection region 1-9 (FIG. 4). (See (a)). An electric noise signal is also superimposed on the output signal from the light receiving element 1-2.

  The waveform obtained by processing the output signal from the light receiving element 1-2 by the band-pass filter 4-1 is a waveform in which the direct current component is removed by the wide band filtering and the noise is reduced by the low band filtering (see FIG. 4B). . The cut-off frequency (electric filter frequency) used in each filtering process is set as follows, for example. First, the passage speed of the object to be inspected through the cell 1-5 is known (in this example, it can be calculated from the pipe diameter of the cell 1-5 and the flow rate of the object to be inspected flowing through the cell 1-5). Can be estimated by the velocity of the fine particles crossing the detection region 1-9. Next, from the width (diameter) of the detection region 1-9 and the passage speed of the fine particles, the width of the dimming pulse by the fine particles, that is, the frequency component of the dimming signal by the fine particles can be calculated. The cut-off frequency is set based on this frequency component, and a dimming signal due to fine particles is extracted by comparison with the cut-off frequency.

  The output of the bandpass filter 4-1 is inverted and amplified by the inverting amplifier 4-2. Further, using the fact that the change in the envelope of the noise component is sufficiently smaller than the change in the dimming pulse, detection is performed by the detector 4-3 having a long time constant, and the output of the detector 4-3 is output by the addition amplifier 4-4. Add the output of voltage source 4-5. The output waveforms of the inverting amplifier 4-2, the detector 4-3 and the summing amplifier 4-4 are illustrated in FIG.

  The comparator 4-6 compares the output of the summing amplifier 4-4 with the output of the inverting amplifier 4-2, and detects the dimming pulse when the output signal of the inverting amplifier 4-2 is larger than the output of the summing amplifier 4-4. The particle detection pulse (voltage) at a certain level is output (see FIG. 4D). The generation rate of the fine particle detection pulse is measured by the pulse rate detection circuit 4-7. For example, when the generation rate of the fine particle detection pulse increases, it can be determined that there are a large number of dimming pulses (that is, the number of fine particles has increased). it can.

  As described above, in the present embodiment, the detection region 1-9 can be narrowed by the plurality of light transmission holes 1-6 and 1-7, and therefore the detection region 1-9 when the fine particles enter the detection region 1-9. The ratio of the size of the fine particles to the diameter of the fine particles can be increased, and the ratio of light reduction due to the light shielding of the fine particles can be increased to increase the sensitivity. In addition, by increasing the length of the detection region 1-9, the volume of the detection region 1-9 can be increased, and the detection efficiency of the fine particles is improved.

  In addition, when increasing the detection sensitivity and detection efficiency of fine particles, it is a great advantage that the detection region 1-9 can be formed thin and long without using a laser beam or a lens optical system. For the light emitting element 1-1 and the light receiving element 1-2, LEDs and PDs that are extremely inexpensive compared to a laser light source or the like can be used. In addition, when the lens optical system is adopted by selecting an inexpensive material that is light-shielding and easy to process for the holding plates 1-3 and 1-4 as the light-shielding means for providing the light transmitting holes 1-6 and 1-7. The required cost is extremely low.

  Furthermore, troublesome operations such as axial alignment of the lens optical system and adjustment of the laser light source are not required as in the fine particle detection technique in which coherent light such as laser is adjusted by the lens optical system. Further, the light transmission holes 1-6 and 1-7 are not provided with the cell 1-5 interposed therebetween, but the light transmission holes 1-6 and 1-7 are provided on the light emitting element 1-1 or the light receiving element 1-2 side. By providing both, the accuracy required for the alignment of the light transmitting holes 1-6 and 1-7 can be further lowered.

  According to the present embodiment, as described above, the fine particles contained in the object to be inspected can be easily detected at low cost with high sensitivity. Further, the fine particles can be detected simply by passing the inspection object through the detection region, and the fine particles can be monitored online. For this reason, ensure the quality of industrial products and the cleanliness of the environment, such as water purification quality control at water purification plants, detection of contamination of seawater and rivers, detection of contamination of lubricating oil, dust monitors in clean rooms, and monitors for foreign objects in glass products. Above all, it is very effective.

  The holding plates 1-3 and 1-4 are made of a light-shielding material, and the case where the light transmission holes 1-6 and 1-7 are provided in the holding plate 1-4 has been described as an example. The holding plates 1-3 and 1-4 holding the light emitting element 1-1 and the light receiving element 1-2 are not used as light shielding means, but a dedicated light shielding means is provided separately from the holding plates 1-3 and 1-4. The light-transmitting holes 1-6 and 1-7 may be provided in the light shielding means. In this example, the detection area 1-9 is defined by the two light transmission holes 1-6 and 1-7. However, when the detection area 1-9 is further narrowed, the detection area 1-9 is aligned along the traveling direction of the inspection light. Three or more light transmission holes may be provided, and inspection light passing through the three or more light transmission holes may be incident on the light receiving element 1-2. What is described in this paragraph is the same for the following examples.

  FIG. 5 is a cross-sectional view showing extracted holding plates 1-3 and 1-4 provided in the second embodiment of the particle detecting apparatus according to the present invention.

  As shown in FIG. 5, the present embodiment is different from the first embodiment in the configuration of the detection unit 1. The fine particle detection apparatus of this embodiment has a plurality (three in this example) of light receiving elements 1-2. In this embodiment, the light receiving side holding plate 1-4 is configured to hold a plurality (three in this example) of light receiving elements 1-2 facing the cell 1-5. A plurality of light transmission holes are provided between the light emitting element 1 and the light emitting element 1-1 so as to follow the traveling direction of the inspection light, respectively, as in the first embodiment. In the holding plate 1-4 of the present example, light transmitting holes 1-6 and 1-7 are provided between the light emitting element 1-1 and the light receiving element 1-2 in the center in the figure, and the left side in the figure. Light-transmitting holes 1-6 'and 1-7' are provided between the light-receiving elements 1-2, and light-transmitting holes 1-6 "are provided between the light-emitting element 1-1 and the right-side light-receiving element 1-2 in the figure. , 1-7 ″ are provided. Each light receiving element 1-2 is connected to a signal processing circuit 4 via a current-voltage converter 3. Other configurations are the same as those of the first embodiment.

  By providing a plurality of light receiving elements 1-2 in this manner, detection areas 1-9 corresponding to the respective light receiving elements 1-2 are formed. Therefore, the accuracy and reliability of particle detection by the plurality of detection areas 1-9, The detection efficiency can be further improved.

  In the present embodiment, the plurality of light receiving elements 1-2 may be arranged one-dimensionally or two-dimensionally. When the light receiving elements 1-2 are arranged one-dimensionally, they may be arranged along the moving direction of the object to be inspected, or may be arranged along the direction intersecting with the moving direction of the object to be inspected. When arranging two-dimensionally, they may be arranged in a grid pattern like intersections of lattice lines, or may be arranged in a staggered pattern or randomly. Moreover, although the several light receiving element 1-2 was provided with respect to one light emitting element 1-1, the light emitting element 1-1 (namely, several light emitting element 1-1 corresponding to each of the some light receiving element 1-2). ) May be provided.

  In addition, a one-dimensional or two-dimensional array photodetector such as a CCD (Charge Coupled Device) element may be used as the light receiving element 1-2. In this case, if one array-shaped photodetector can cover the inspection light that has passed through the light transmission holes 1-7, 1-7 ′, 1-7 ″ closest to the light receiving element, one array-shaped detector. However, in this case, each light receiving element on which the inspection light from the light transmission holes 1-7, 1-7 ′, 1-7 ″ of the array detector is incident is described above. It corresponds to a plurality of light receiving elements 1-2.

  When the light receiving area of each light receiving element of the arrayed photodetector is equal to the size of the light transmitting holes 1-7, 1-7 ′, 1-7 ″ closest to the light receiving element, the detection region 1− Since the light receiving elements of the arrayed photodetector function in the same manner as the light transmission holes 1-7, 1-7 ′, 1-7 ″ when narrowing down 9, the light transmission holes 1-7, 1-7 ′, 1-7 ″ may be omitted. That is, the inspection light that has passed through the light transmitting holes 1-6, 1-6 ′, 1-6 ″ on the light emitting side is equivalent to the light transmitting holes of the arrayed photodetector. When detecting with the light receiving element having the light receiving area, the light incident on each light receiving element through the light transmitting holes 1-6, 1-6 ′, 1-6 ″ is equivalent to the detection area 1-9 in FIG. Therefore, the detection sensitivity equivalent to that of the first or second embodiment can be obtained by monitoring the output of a specific light receiving element on which the inspection light in the inspection region is incident. It can be current.

  FIG. 6 is a cross-sectional view showing extracted holding plates 1-3 and 1-4 provided in the third embodiment of the particle detecting apparatus according to the present invention.

  As shown in FIG. 6, this embodiment is different from the first embodiment in the configuration of the detection unit 1, and the light transmission side light transmission hole 1-6 is provided in the light emission side holding plate 1-3. In the point. The light transmission hole 1-7 on the light receiving side is provided in the holding plate 1-4 on the light receiving side. Other configurations are the same as those of the first embodiment.

  The inspection light emitted from the light transmission hole 1-6 provided in the light-emission-side holding plate 1-3 spreads larger than the hole diameter of the light transmission hole 1-6 as the distance from the light transmission hole 1-6 increases. However, if the inspection light that has passed through the light transmitting hole 1-6 is collected by the light transmitting hole 1-7 provided on the light receiving side holding plate 1-4, the light transmitting hole 1-7 on the light receiving side is viewed from the light receiving side. The light emitted from the light transmitting hole 1-6 on the light emission side through is observed. Therefore, for example, when the light transmission holes 1-6 and 1-7 of the two holding plates 1-3 and 1-4 are circles having the same diameter, the detection region 1-9 between the holding plates 1-3 and 1-4 is detected. Is formed in a cylindrical shape having substantially the same diameter as the light transmitting holes 1-6 and 1-7. The presence of the fine particles is detected by detecting the decrease in the inspection light due to the shielding of the fine particles passing through the cylindrical detection region 1-9.

  In this embodiment, the same effect as that of the first embodiment can be obtained. Further, in this embodiment, the detection area 1-9 can be made to have substantially the same thickness (uniform diameter), and there is no difference in the amount of light reduction regardless of which part of the detection area 1-9 passes the fine particles. This is also an advantage in improving detection sensitivity.

  Of course, the light transmitting holes 1-6 and 1-7 may have other shapes such as a rectangle instead of a circle, but it is preferable to match the shapes of the two. In order to further narrow down the detection region 1-9, a plurality of light transmitting holes 1-6 or 1-7 on the holding plate 1-3 or 1-4 side may be provided along the traveling direction of the inspection light. good. A plurality of both light transmission holes 1-6 and 1-7 may be provided along the traveling direction of the inspection light. Further, a configuration in which a plurality of light transmission holes are provided along the traveling direction of the inspection light only on the light emission side holding plate 1-3 without providing the light transmission holes on the light receiving side holding plate 1-4 is also conceivable.

  FIG. 7 is a schematic configuration diagram showing a partial cross-section of the detection unit 1 of the fourth embodiment of the particle detection apparatus according to the present invention.

  As shown in FIG. 7, the particle detector of the present embodiment includes a light guide 1-10 provided between the light emitting element 1-1 and the light transmitting hole 1-6 on the light emitting side closest thereto, A light guide path 1-11 provided between the element 1-2 and the light transmission hole 1-7 on the light receiving side closest thereto is provided. Other configurations are substantially the same as those of the third embodiment.

  The light guide path 1-10 on the light emitting side functions as a light collecting means for condensing and guiding the inspection light from the light emitting element 1-1 to the light transmission hole 1-6 of the light holding plate 1-3 on the light emitting side. The outer wall is covered with an optical reflector so that the inspection light from the light emitting element 1-1 does not leak outside. The inspection light from the light emitting element 1-1 passes through the inside of the light guide 1-10 and is emitted from the cell 1-5 side tip of the light guide 1-10 inserted into the light transmission hole 1-6.

  The light guide path 1-11 on the light receiving side has a function of guiding the inspection light incident through the light transmitting hole 1-7 on the light receiving side to the light receiving element 1-2, and the light transmitting hole 1- on the light receiving side. The outer wall is covered with an optical reflector so that the inspection light incident from 7 does not leak outside. The inspection light incident from the light transmitting hole 1-7 on the light receiving side enters the light guide 1-11 from the tip of the cell 1-5 inserted into the light transmitting hole 1-7, and passes through the inside of the light guide 1-11. Incident on the light receiving element 1-2.

  In the case of the present embodiment, the detection region 1-9 is formed in the same manner as in the third embodiment, and the effects obtained in the third embodiment can be obtained. In addition, in each of the embodiments described above, the detection region 1-9 having a small cross section is formed by blocking a part of the inspection light with the light transmitting holes 1-6 and 1-7. In this case, since the inspection light from the light emitting element 1-1 is guided to the light transmission hole 1-6 without being blocked, the amount of light blocked by the light transmission hole 1-6 is small and the loss of inspection light is reduced. be able to. Moreover, since the inspection light incident on the light transmission hole 1-7 does not leak to the outside even on the light receiving side, the light receiving efficiency of the light receiving element 1-2 is improved. As a result, the detection sensitivity can be further improved. For example, in order to obtain a detection sensitivity equivalent to that in each of the previous embodiments, the light emission amount of the light receiving element 1-1 can be reduced.

  In this embodiment, the case where the light guide paths 1-10 and 1-11 are provided on both the light emitting side and the light receiving side has been described as an example. However, the light guide paths 1-10 and 1-11 are effective for each. Even if one of them is omitted, a corresponding effect can be obtained.

  FIG. 8 is a schematic configuration diagram of a fifth embodiment of the particle detection apparatus according to the present invention, and the detection portion is shown in cross section. Further, FIG. 9A shows an enlarged view of part A in FIG. 8, and FIG. 9B shows an enlarged view of part B in FIG.

  The fine particle detection apparatus according to the present embodiment detects fine particles in an object to be inspected by detecting fluctuations in detection light caused by light shielding, diffraction, or interference effects caused by fine particles moving in the detection region in the inspection light irradiation region. Is.

  The particle detection apparatus shown in FIG. 8 includes a pipe 11 through which an object to be inspected (fluid in this example) containing particles, a light emitting element 12 that irradiates the inspection object with inspection light, and a current source that is an energy source of the light emitting element 12. 13. A light receiving element 14 that receives inspection light from the light emitting element 12 that is incident through the object to be inspected, and a light transmission hole that is provided between the pipe 1 and the light receiving element 14 and narrows the detection area in the irradiation area of the inspection light. The aperture plate 17 serving as a light-shielding unit 17-1, the photocurrent-voltage converter 15 for converting the photocurrent of the light received by the light receiving element 14 into a voltage, and the output signal of the photocurrent-voltage converter 15 are processed. A signal processing device 16, a rate meter 18 for counting output pulses processed by the signal processing device 16, and a display device 19 for displaying a coefficient result by the rate meter 18 are provided.

  In the present embodiment, the pore plate 17 is interposed between the outer peripheral surface of the pipe 11 and the light receiving element 14, and is a light emitting element except for light transmitted through a light transmitting hole 17-1 having a minute diameter. The inspection light from 12 is blocked. The light transmission hole 17-1 is provided on a line connecting the light emitting element 12 and the light receiving element 14. A region observed from the light receiving element 14 side through the light transmitting hole 17-1 (a linear region observed from the light receiving element 12 through the light transmitting hole 17-1) is a detection region, but the light transmitting hole 17- When the light source (light emitting element 12) is observed from the light receiving element 14 through the light transmission hole 17-1, and the reflection source (fine particle) crosses the observation area, the aperture of 1 is two. The size is determined in advance so that interference generated by light can be detected.

  The pipe 11 is made of a transparent material at least for the portion through which the inspection light passes in order to irradiate the inspection object flowing therethrough and inject the inspection light into the light receiving element 14. An antireflection portion formed by applying an antireflection paint that reflects light on the inner wall portion around the light transmission hole 17-1 on the light receiving element 14 side, except for a portion where the inspection light on the inner surface of the pipe 11 passes. 30 (see FIG. 9A) is provided to suppress the instability of the amount of the inspection light irradiated from the light emitting element 12 toward the light receiving element 14 by the reflected light reflected and returned from the inner surface of the pipe 11. It is preferable. Further, the configuration is not limited to the configuration in which the portion of the inner surface of the pipe 11 that is irradiated with light other than the inspection light in the inspection region is covered with the antireflection portion 30. It is done. The inspection light sorting means 31 and 32 shown in FIGS. 9A and 9B are an example.

  The inspection light sorting means 31 and 32 can be appropriately configured with a simple lens, prism, or the like, and an optical axis is provided at an inspection light incident portion (the vicinity including the optical axis) so as to pass inspection light in a detection region to be passed. A flat portion having a constant area orthogonal to the outer periphery of the flat portion, and the periphery thereof is inclined with respect to the flat portion. The inspection light sorting means 31 has a shape obtained by cutting the top of the cone, and the inspection light sorting means 32 has a spherical shape arranged so that the optical axis passes through the top of the surface on which the inspection light is incident or in the vicinity thereof. I am doing. In this example, the case where the inspection light sorting units 31 and 32 are arranged on the light receiving element 14 side and the light emitting element 12 side of the pipe 11 has been described as an example, but the reverse arrangement may be used, or the inspection light sorting unit 31 may be arranged. 32 may be disposed at both positions, or the inspection light sorting means 31 or 32 may be provided only on either the light receiving element 14 side or the light emitting element 12 side. By arranging the inspection light sorting means on the optical axis in this way, the inspection light that has passed through the inspection region or the vicinity thereof passes through the flat portion of the inspection light sorting means and proceeds toward the light receiving element 14 to be inspected. The inspection light deviated from the region is reflected (scattered) in a direction deviated from the direction returning to the light emitting element 12 at the inclined portion of the inspection light sorting means 31 and 32. By configuring as shown in FIGS. 9A and 9B, noise light caused by internal reflection of the pipe 11 is incident on the light receiving element 14 and is detected, and the emitting element is detected by internal reflection of the pipe. The return of reflected light to 12 is reduced.

  The light emitting element 12 uses a laser light source that generates coherent light having coherence and has a small light emitting region. The light emitting element 12 emits light by the driving current from the current source 13. As the laser light source, for example, a semiconductor laser having a wider oscillation spectrum than a single mode laser such as a self-excited oscillation type or a gain waveguide type is used. In the case of using a single mode laser, a known high frequency superposition circuit is incorporated in the current source 13 to emit light with a high frequency current to broaden the emission spectrum from the original spectrum. Further, if the laser light source is, for example, a semiconductor laser, a polarization plane changing means such as a known half-wave plate or quarter-wave plate is provided on the optical path of the laser beam, and the polarization plane of the laser beam is changed to a different polarization angle. It is also possible to reduce the influence of the return light.

  The light receiving element 14 may be a light receiving sensor such as a PD (Photo Diode). The light receiving element 14 is provided with the above-described pore plate 17, and the light that has passed through the light transmitting hole 17-1 of the pore plate 17 is detected by the light receiving element 14. The photocurrent received by the light receiving element 14 is converted into a voltage signal by the photocurrent-voltage converter 15 and signal processed by the signal processing device 16. The number of output pulses processed by the signal processing device 16, that is, the number of detected particles is counted by the rate meter 18, and the coefficient result is displayed on the display device 19.

  Here, FIG. 10 is a conceptual diagram for explaining the principle that the light intensity waveform of the detection light changes due to the fine particles in the inspected body, and FIGS. 11A and 11B show examples of the waveform of the detection light intensity. It is.

  As shown in FIG. 10, in the present embodiment in which the lens optical system for narrowing the inspection light irradiated from the light emitting element 12 is not used, the intensity of the inspection light L from the light emitting element 12 is expressed by its optical axis (light The higher the distance from the optical axis, the lower the distance from the optical axis. The waveform of the inspection light L detected by the light receiving element 14 after passing through the pore plate 17 passes through the light transmitting hole 17-1 and is detected by the light receiving element 14 when there is no particulate passing through the vicinity of the inspection region. The inspection light is constant without being affected by light shielding / diffraction / scattering (see FIG. 11A). On the other hand, when there are fine particles P moving in the detection region, in addition to the shielding of the inspection light by the fine particles P, the scattered light (reflected light) reflected by the fine particles P and the inspection light (direct light) directly incident from the light emitting element 12 Interference occurs. Since direct light and reflected light have different optical path lengths, coherent laser beams interfere with each other to cause light interference. Therefore, when the fine particles P move with time, the intensity fluctuation of the detection light due to interference increases in reflection intensity as the fine particles P approach the optical axis after entering the detection region as shown in FIG. Along with this, the particle P becomes smaller as it moves away from the optical axis. In this embodiment, such a change in intensity is detected to detect fine particles. The pore plate 17 in this embodiment is used to sharpen the interference effect between the reflected light and the direct light from the fine particles located at a position shifted from the optical axis of the inspection light by limiting the detection region. Therefore, high detection sensitivity is ensured.

  FIG. 12 is a block diagram of the signal processing device 16. The processing contents of the detection light of this embodiment by the signal processing device 16 will be described with reference to FIG.

  The signal processing device 16 includes a bandpass filter 16-1, an amplifier 16-2, a detector 16-3, and a comparator 16-4. The band-pass filter 16-1 includes a low-pass filter that removes a high-frequency noise component and a high-pass filter that removes only a component of intensity variation by removing a DC component of the detected light. Further, the cut-off frequency of each bandpass filter is determined in advance based on frequency characteristics corresponding to the speed of the object to be inspected. The amplifier 16-2 amplifies the intensity fluctuation processed by the band-pass filter 16-1 of the detection signal as necessary. The detector 16-3 performs full-wave rectification and detection of the waveform. The comparator 16-4 compares the detection signal of the detector 16-3 with a preset comparison level to make a pulse, and outputs the pulse to the rate meter 18. The rate meter 18 obtains a count rate per unit time of the pulse, and this is displayed on the display device 19. This count value is the number of times the fine particles are detected.

  As described above, according to the present embodiment, in addition to shielding the inspection light by the fine particles, the detection of the fine particles is detected by looking at the fluctuation range of the detected light intensity due to the phenomenon such as scattering and diffraction. As in the previous embodiments, in addition to improving the detection sensitivity by narrowing the detection region, there is an advantage that only one light transmission light 17-1 is sufficient. When a plurality of light transmission holes are provided to limit the detection area as in each of the above-described embodiments, the detection area is limited as compared with the case where the detection area is narrowed down by performing alignment or adjustment of the lens optical system or the like. Although the labor required is greatly reduced, in the case of the present embodiment, it is not necessary to align the light transmitting holes, and the labor required for the alignment can be further reduced.

  FIG. 13 is a schematic configuration diagram of a sixth embodiment of the particle detection apparatus according to the present invention, in which the detection unit is shown in cross section. In FIG. 13, the same parts as those in the above-described drawings are denoted by the same reference numerals as those in the above-mentioned drawings, and description thereof is omitted.

  This embodiment is an example in which a function for determining whether or not a detected fine particle is spherical is added to the fifth embodiment. For example, when the object to be inspected is not a gas, the gas fine particles are often spherical, and if the detected fine particles are spherical, the fine particles can be estimated to be gas under certain conditions. In this example, using this fact, it is determined whether the detected fine particles are spherical or not, and if necessary, it is possible to reduce the false detection rate by excluding non-spherical fine particles, The reliability of the detection result can be improved. For example, when applying the particulate detection device of the present embodiment to the downstream portion of the filter of the water purification plant, when it is desired to prevent the detection of gas particles such as when solid or liquid particulates are to be detected, This embodiment is suitable.

  Note that the signal processing device 16A shown in FIG. 13 is partly different from the signal processing device 16 of the fifth embodiment, and can further control the drive current of the current source 13. This embodiment is substantially the same as the fifth embodiment except for the processing contents of the signal processing device 16A.

  FIG. 14 is a block diagram of a signal processing device 16A provided in the sixth embodiment of the particle detecting device according to the present invention. In FIG. 14, the same parts as those in the above-described drawings are denoted by the same reference numerals as those in the above-mentioned drawings, and description thereof is omitted.

  The signal processing device 16A of FIG. 14 includes a band pass filter 16-1, an amplifier 16-2, a waveform memory 16-5, and a calculator 16-6. The band-pass filter 16-1 is connected in series with a low-pass filter that removes high-frequency noise components and a high-pass filter that removes the detected DC component of light and extracts only the intensity variation. The amplifier 16-2 amplifies the intensity fluctuation processed by the band pass filter 16-1 as necessary. However, the output of the low pass filter of the band pass filter 16-1 is input to the waveform memory 16-5 without passing through the amplifier 16-2.

  The waveform memory 16-5 is composed of an analog-digital (A / D) converter and a ring-shaped memory, and the low-pass output of the band-pass filter 16-1 and the high-pass output of the amplifier 16-2 are set to a certain time width. When the intensity fluctuation signal (high-pass output) of the amplifier 16-2 exceeds the comparison level, a waveform having a certain time width before and after that point is recorded. The low pass output of the band pass filter 16-1 corresponds to the intensity of direct light from the light emitting element 12.

  The processing contents of the arithmetic unit 16-6 will be described later. In addition to the detection of fine particles and determination of whether or not the detected fine particles are spherical, the light emitting element so that the low pass output of the band pass filter 16-1 is constant. The drive current by the current source 13 is controlled so that the intensity of the inspection light irradiated from 12 is constant.

  Here, the light intensity waveform of the detection light by the fine particles in the inspected body will be described with reference to FIGS. 15A and 15B together with FIG.

  First, as shown in FIG. 10, the light intensity from the light emitting element 12 such as a semiconductor laser having a minute light emitting region is higher as it is closer to the optical axis and decreases as the distance from the optical axis is increased. As described above, when the fine particles P move in the irradiation region of the inspection light, the direct light from the light emitting element 12 interferes with the reflected light from the fine particles P, and the detection light intensity varies as the fine particles move.

  Here, in the model shown in FIG. 10, the line connecting the centers of the light emitting element 12 and the light transmitting hole 17-1 of the pore plate 17 coincides with the emission intensity central axis of the light emitting element 12, and Consider a case where the contour lines of the intensity distribution are circular in a cross section perpendicular to the optical axis. In this case, if the fine particle P is spherical and the light reflectance is constant regardless of the direction, the reflected light intensity obtained along with the movement of the fine particle P is symmetric with respect to the optical axis. The fluctuation waveform is symmetrical about the optical axis of the light (see the solid line in FIG. 15B). On the other hand, when the fine particles are non-spherical and the reflectance is non-uniform, the reflection intensity is not targeted around the optical axis. Therefore, as shown by a dotted line in FIG. 15B, an asymmetrical fluctuation waveform is obtained with the optical axis of the inspection light as the center. If the fine particles are on the optical axis, the inspection light is blocked and diffracted, which also changes the intensity of the detection light. Needless to say, the light intensity change by the spherical fine particles is symmetric with respect to the optical axis in both light shielding and diffraction.

  In this embodiment, first, the change in the intensity of the detection light is detected in the same manner as in the fifth embodiment to detect the fine particles, and it is further determined whether or not the detected fine particles are spherical. The pore plate 17 in the present embodiment is used to sharpen the interference effect between the reflected light of the fine particles in the part away from the optical axis and the direct light, and this can improve the detection sensitivity according to the fifth embodiment. It is the same.

  FIG. 16 is an explanatory diagram showing a procedure for collecting a waveform by the waveform memory 16-5.

  During operation, the waveform memory 16-5 always A / D-converts the intensity fluctuation signal of the amplifier 16-2 with its analog-digital (A / D) converter, and stores it in a ring-shaped memory of a certain length. I will do it. In the link memory, the old waveform data in time is sequentially rewritten with new data. When the signal intensity from the amplifier 16-2 exceeds the set comparison level (threshold value), the timing signal output from the computing unit 16-6 is input, and a record from a certain time before that point is left. By recording a certain period of time in the remaining storage area, it is possible to record waveforms before and after the output of the amplifier 16-2 exceeds the comparison level. This operation is a known technique executed by a commercially available waveform memory. Further, when the low pass output of the band pass filter 16-1 is recorded in the waveform memory 16-5, it can be recorded in the same manner. The low pass output of the band pass filter 16-1 is a non-variable component of the light receiving element 14 which is a direct current component, and this value is the output of the light emitting element 12 (for example, a laser diode) or clouding of the optical path (foreign matter on the inner surface of the pipe 11) Affected by fluctuations in the amount of light caused by the Therefore, the inspection light is observed by observing the low-pass output at a constant time interval and controlling the drive current of the current source 13 by, for example, the arithmetic unit 16-6 so as to make this (low-pass output other than when detecting fine particles) constant. The amount of light can be made constant.

  FIG. 17 is a flowchart showing the processing procedure of the arithmetic unit 16-6.

  When the processing unit 16-6 starts the processing of FIG. 17, first, in step S811, the processing parameter is set. The processing parameters set here are processing parameters such as the time for capturing the low-pass filter output of the received light signal and the detection level obtained by the light receiving element 14. These processing parameters are stored, for example, in a memory (not shown), and the computing unit 16-6 reads and sets the processing parameters from the memory in step S811. When the procedure moves to step S812, the arithmetic unit 16-6 determines whether or not the set time has elapsed. When the set time has elapsed, the computing unit 16-6 shifts to control of the drive current of the current source 13, and shifts to the particle detection procedure before the set time has elapsed.

  When the procedure shifts from step S812 to control of the current source 13, the calculator 16-6 first captures the low-pass filter output from the bandpass filter 16-1 into the memory of the waveform memory 16-5 in step S813. Then, the procedure proceeds to step S814, and the average value of the waveform data is calculated in order to read the waveform data taken into the waveform memory 16-5 and calculate the DC magnitude. In the subsequent step S815, the average value of the calculated waveform data is compared with the detection value (comparison value) of the light receiving element 14 calculated from the known relationship between the drive current of the light emitting element 12 and the detection value of the light receiving element 14. As a result, if there is a change in the detection value of the inspection light by the light receiving element 14, the procedure is shifted to step S816, and the current source 13 is controlled so that the deviation between the detection value by the light receiving element 14 and the comparison value is reduced. To do. If no change is found in the detection value of the inspection light, the procedure returns to step S812.

  On the other hand, when the set time has not elapsed in step S812 and the procedure proceeds to the particle detection procedure, the computing unit 16-6 first sends the fluctuation signal (FIG. 16) from the amplifier 16-2 to the waveform memory 16-5 in step S817. If there is a signal exceeding the comparison level shown in (1), the procedure returns to step S812. If there is a fluctuation signal in the waveform memory 16-5, the arithmetic unit 16-6 moves the procedure to step S818, reads the waveform (a waveform having a constant width before and after that point), and executes waveform processing (details will be described later). To do. When the waveform processing is completed, the computing unit 16-6 moves the procedure to step S819, confirms the presence or absence of the input signal for the termination instruction by the operator, and returns to the procedure in step S812 if there is no signal for commanding the termination. When the command signal is input, the procedure in FIG. 17 is terminated.

  FIG. 18 is a flowchart showing the processing procedure of the waveform processing executed by the computing unit 16-6 in step S818 of FIG.

  After shifting to the waveform processing procedure, the computing unit 16-6 first stores the waveform data of the waveform memory in its own memory in step S8181, and then proceeds to step S8182 to perform frequency component (frequency range) of the waveform by high-speed Fourier transform or the like. Is calculated.

  In the subsequent step S8183, the frequency component calculated in step S8182 is compared with a preset frequency component (setting range). If the calculated frequency component is different from the setting range, this waveform is determined to be noise and the procedure is performed. The process shifts to S8188 to display on the display device 19 that the detection result is noise. If the display of noise is unnecessary, the procedure of FIG. 18 may be terminated without going through step S8188, and the process may proceed from step S8183 to step 819 of FIG. If the waveform is significant rather than noise, the procedure moves to step S8184, and the autocorrelation function and convolution are calculated for the waveform data to determine each peak value. An example of the result of this waveform processing is shown in FIGS. FIG. 19 shows a case where the detected fine particles are spherical and the reflection is isotropic, and FIG. 20 shows a case where the detected fine particles are non-spherical and the reflection is anisotropic.

  In the following step S8185, it is determined as follows whether or not the detected fine particles are spherical based on the calculation result of step S8184, and information on the shape of the fine particles is obtained. When the detected fine particles are spherical, the reflection characteristics of the fine particles are symmetric with respect to the optical axis of the inspection light as described above with reference to FIG. 10. Therefore, in the example of FIG. The waveform has strong symmetry in the time direction. For this reason, the calculation results of the autocorrelation and the convolution of the detected waveform are approximate values, and the peak values are similar. On the other hand, when the detected fine particles are non-spherical as shown in FIG. 20, the detected waveform is less symmetrical with respect to the peak. As a result, the peak value of the convolution calculation result is relatively lower than the peak value of the autocorrelation. Therefore, the peak values of both the autocorrelation and convolution calculation results calculated for the detected waveform are compared. For example, the value of (peak value of the convolution calculation result) / (peak value of the autocorrelation calculation result) is preset. If the threshold value is less than the threshold value and close to 1, the detected fine particle can be determined to be spherical (transfer to step S8186-1), and if it is less than the threshold value, it can be determined to be non-spherical (transfer to step S8186-1). When the object to be inspected is other than gas, it is possible to estimate fine particles determined to be spherical as gas fine particles, and non-spherical fine particles as fine particles other than gas.

  When it is determined that the fine particle is spherical, the computing unit 16-6 moves the procedure to Step S8187-1, and calculates the coincidence between the detected waveform and the waveform model prepared in advance. The waveform model prepared in advance is data obtained in advance inspection, and was obtained by changing the speed of the object to be inspected, the intensity distribution of the light emitting element, the aperture of the light transmission hole, the particle size of the fine particles, the reflectance, etc. Is. In this case, the correlation calculation between the waveform model and the detected waveform is executed, and the particle size, reflectance, etc. of the detected fine particle can be calculated using the fine particle information of the waveform model having the highest coincidence with the detected waveform. When the information such as the particle diameter of the detected spherical fine particles is obtained, the calculator 16-6 moves to step S8188 to display the information on the display device 19, and ends the procedure of FIG. If gas particulates are not targeted for detection and information is not required, the procedure in FIG. 18 is terminated without going through step S8188, and when the particulates are determined to be spherical, step S8185 to step 819 in FIG. You may make it move to.

  On the other hand, when it is determined that the fine particle is non-spherical, the computing unit 16-6 moves the procedure to Step S8187-2 and calculates the coincidence between the detected waveform and the waveform model prepared in advance as in Step S8187-1. To do. The waveform model prepared in advance is data obtained in advance inspection, and is obtained by changing the speed of the object to be inspected, the intensity distribution of the light emitting element, the aperture of the light transmission hole, the particle size of the fine particles, the shape, the reflectance, etc. It has been done. When information such as the particle size of the non-spherical fine particles is obtained in this way, the process proceeds to step S8188 to display the information on the display device 19, and the procedure of FIG. If fine particles other than gas are not to be detected and information is not required, the procedure of FIG. 18 is terminated without going through step S8188, and when the fine particles are determined to be non-spherical, steps S8185 to FIG. 17 are performed. You may make it transfer to 819.

  According to the present embodiment, in addition to the same effects as in the fifth embodiment, information such as the shape of the detected fine particles can be acquired. In addition, for example, when information on gas particulates or particles other than gas is not required, acquisition of indispensable information can be omitted. Further, by excluding detection of fine particles out of the detected fine particles from the count, the false detection content rate can be reduced and the detection accuracy can be improved.

  FIG. 21 is a conceptual diagram for explaining the principle of change in the light intensity waveform of the detection light due to the fine particles in the subject in the seventh embodiment of the present invention, and FIGS. 22A and 22B are waveforms of the detection light intensity. It is a figure showing an example.

  The present embodiment is an example in which a light emitting element 12A using an LED (Light Emitting Diode) instead of a laser is used, and the other points are the same as in the fifth embodiment or the sixth embodiment. Since the emission spectrum of an LED is much wider than that of a laser diode, interference does not occur, but the point that the light intensity increases as the distance from the optical axis increases and decreases as the distance from the optical axis decreases. If there is no fine particle in the irradiation region of the detection light from the light emitting element 12A, direct light from the light emitting element 12A is detected, and the output of the light receiving element 14 becomes a constant output with little fluctuation as shown in FIG. On the other hand, when the fine particles cross the inspection light, the reflected light from the fine particles is added to the direct light, so that the intensity of the detection light increases as it approaches the optical axis and decreases as it moves away. However, it goes without saying that when the fine particles overlap with the optical axis, the detection light intensity decreases due to light shielding. Further, if the fine particle is spherical, the detected light intensity is symmetric about the optical axis (see the solid line in FIG. 22B), and if it is non-spherical, the symmetry is broken (see the dotted line in FIG. 22B). .

  Therefore, by detecting the fluctuation of the detected light intensity, the fine particles can be detected as in the fifth embodiment. Further, by determining the symmetry of the detected light intensity, information such as the particle diameter of the detected fine particles can be acquired in the same manner as in the sixth embodiment.

  Industrially, detecting fine particles in a light-transmitting medium is important in managing the quality of a system that uses the medium and the products produced by the system. In the present invention, by using a light shielding plate provided with a light transmission hole, it is possible to provide an inexpensive particle detection device that does not require a lens optical system for various adjustments of inspection light. Thereby, since it can test | inspect only by letting the microparticles | fine-particles contained in a liquid, gas, or a solid pass between a dispatch element and a light receiving element, on-line monitoring is possible. For this reason, it is extremely effective in ensuring the quality of industrial products, such as water pollution monitoring in water purification plants, clean room dust monitors, and the like.

It is a schematic block diagram of 1st Example of the microparticle detection apparatus which concerns on this invention. It is sectional drawing which extracted and represented the holding plate with which 1st Example of the microparticle detection apparatus which concerns on this invention was equipped. 1 is a schematic configuration diagram of a signal processing circuit provided in a first embodiment of a particle detection apparatus according to the present invention. It is a figure showing the output waveform of each part of the signal processing circuit with which 1st Example of the microparticle detection apparatus which concerns on this invention was equipped. It is sectional drawing which extracted and represented the holding plate with which 2nd Example of the microparticle detection apparatus concerning this invention was equipped. It is sectional drawing which extracted and represented the holding plate with which 3rd Example of the microparticle detection apparatus concerning this invention was equipped. It is a schematic block diagram which extracted the detection part of 4th Example of the microparticle detection apparatus based on this invention, and represents it with a partial cross section. It is a schematic block diagram of 5th Example of the microparticle detection apparatus which concerns on this invention. It is the A section enlarged view and B section enlarged view of FIG. It is a conceptual diagram explaining the principle that the light intensity waveform of a detection light changes with the microparticles | fine-particles in a to-be-inspected body in 5th Example of the microparticle detection apparatus which concerns on this invention. It is a figure showing an example of the waveform of the detection light intensity obtained in 5th Example of the microparticle detection apparatus which concerns on this invention. It is a block diagram of the signal processing apparatus with which 5th Example of the microparticle detection apparatus which concerns on this invention was equipped. It is a schematic block diagram of 6th Example of the microparticle detection apparatus which concerns on this invention. It is a block diagram of the signal processing apparatus with which 6th Example of the microparticle detection apparatus which concerns on this invention was equipped. It is a figure showing an example of the waveform of the detection light intensity obtained in 6th Example of the microparticle detection apparatus which concerns on this invention. It is explanatory drawing showing the collection procedure of the waveform by the waveform memory with which 6th Example of the microparticle detection apparatus which concerns on this invention was equipped. It is a flowchart showing the process sequence of the calculator provided in 6th Example of the microparticle detection apparatus which concerns on this invention. It is a flowchart showing the process sequence of the waveform process by the calculator provided in 6th Example of the microparticle detection apparatus which concerns on this invention. It is a figure which shows an example of the result of the waveform processing by the calculator provided in 6th Example of the microparticle detection apparatus which concerns on this invention. It is a figure which shows an example of the result of the waveform processing by the calculator provided in 6th Example of the microparticle detection apparatus which concerns on this invention. It is a conceptual diagram explaining the principle that the light intensity waveform of detection light changes with the microparticles | fine-particles in a to-be-inspected body in 7th Example of this invention. It is a figure showing an example of the waveform of the detection light intensity obtained in 7th Example of the microparticle detection apparatus which concerns on this invention.

Explanation of symbols

1-9 Detection area 1-1 Light-emitting element 1-2 Light-receiving element 1-3 Holding plate 1-4 Holding plate 1-6, 6 ', 6 "Light transmission hole 1-7, 7', 7" Light transmission hole 4 Signal processing circuit 4-1 Band pass filter 1-10 Light guide path 12 Light emitting element 14, 14 A Light receiving element 15-5 Waveform memory 16, 16 A Signal processing device 16-6 Calculator 17 Porous plate 17-1 Light transmission hole 30 Reflection Prevention part 31, 32 Inspection light sorting means L Inspection light P Fine particles

Claims (5)

A fine particle detection apparatus for detecting fine particles in an inspection object by detecting a change in detection light intensity caused by an interference effect of detection light caused by fine particles crossing an inspection light irradiation area,
Laser light emitting means attached outside the pipe for allowing the emitted inspection light to enter without being focused on the object to be inspected in the pipe;
A light receiving means attached to the outside of the pipe for receiving the inspection light from the laser light emitting means that is incident through the object to be inspected;
A light blocking means provided between an outer peripheral surface of the pipe and the light receiving means, and having a light transmission hole for limiting a detection region of inspection light incident on the light receiving means;
A signal processing device that detects a change in detected light intensity caused by an interference effect of the inspection light caused by the fine particles moving in the detection region based on a signal from the light receiving means and detects the fine particles in the inspection object. ,
The diameter of the light transmitting hole is such that the laser light emitting means can be observed in an area observed from the light receiving means through the light transmitting hole, and when the fine particles cross the observation area, the direct light incident directly from the laser light emitting means is directly received. It is a size that can detect interference between light and reflected light reflected by fine particles,
The signal processing device includes:
A waveform memory for recording fluctuations in the detected light detected by the light receiving means;
A particle detector comprising: an arithmetic unit for determining whether or not the detected particle recorded in the waveform memory is spherical with respect to whether the detected waveform is symmetrical about the optical axis in time. apparatus.   2. The fine particle detection apparatus according to claim 1, wherein means for suppressing the reflection of the inspection light or means for scattering the inspection light is provided in a portion other than the optical path of the inspection light in the inner surface of the passage of the inspection object, and the process returns to the laser emission means. A fine particle detector characterized in that the amount of light is suppressed.   2. The particle detecting apparatus according to claim 1, wherein a high-frequency superimposing circuit for extending the emission spectrum of the inspection light is incorporated in a current source for supplying a driving current for the laser emitting means. 4. The fine particle detection apparatus according to claim 3 , further comprising a polarization plane changing means for changing a polarization plane of the inspection light. A fine particle detection method for detecting fine particles in an inspection object by detecting fluctuations in detection light intensity caused by interference effect of detection light caused by fine particles crossing an inspection light irradiation area,
Inject the inspection light emitted from the laser emitting means attached to the outside of the pipe without being squeezed into the inspection object flowing through the pipe,
The inspection light from the laser emitting means that is incident through the object to be inspected is received by the light receiving means attached to the outside of the pipe,
By providing a light transmission hole provided in the light shielding means between the outer peripheral surface of the pipe and the light receiving means, the detection area of the inspection light incident on the light receiving means from the laser light emitting means is limited,
Direct light that is transmitted through the object to be inspected and directly incident from the laser light emitting means, and reflected light that is reflected by the fine particles flowing through the object to be inspected and received by the light receiving means through the light transmission hole, and Based on the signal from the light receiving means, the change in the detection light intensity caused by the interference effect of the inspection light due to the fine particles moving in the detection region is detected to detect the fine particles in the inspection object,
Fine particles characterized in that the detected fine particles detected by the light receiving means are recorded and it is determined whether or not the detected fine particles are spherical depending on whether or not the detected waveform is temporally symmetrical about the optical axis. Detection method.

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