Particle detection device

Abstract

To provide a particle detector that can correct a measurement error, while continuing continuous monitoring in a production site and the like.SOLUTION: A particle detector (1) comprises: a light emitting unit (31) that emits irradiation light toward a detection area (36); a light receiving unit (32) that detects passage light passing through the detection area (36) or scattered light being the irradiation light scattered by particles present in the detection area (36); and a signal processing unit (43) that detects the particles based on the intensity of the received light detected by the light receiving unit (32). In a light passage area (37) between the detection area (36) and the light receiving unit (32), the signal processing unit (43) performs light amount switching processing of switching between an extinction state in which the amount of light passage is reduced and a normal state in which the amount is not reduced, and corrects the criterion for detecting the particles based on the intensity of received light in the extinction state.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a particle detection device.

Background Art

[0002] In recent years, various techniques for detecting fine particles and the like have been proposed. For example, in the particle detection sensor described in Patent Document 1 below, the signal processing circuit acquires the amount of change over time in the received light intensity of stray light received by the light receiving unit when a plurality of particles have not passed through the detection region. Then, the signal processing circuit corrects the received light intensity of the scattered light based on the acquired amount of change over time. The signal processing circuit is configured to classify the target particles into any one of a plurality of particle sizes and specify the number of detected target particles based on the corrected received light intensity of the scattered light.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the conventional technology as described above, when a plurality of particles have not passed through the detection region, the received light intensity of the scattered light is corrected based on the amount of change over time in the received light intensity of the stray light received by the light receiving unit. In this case, since only the received light intensity of the stray light is considered, changes over time due to other factors are not considered. Therefore, there is a problem that the correction for changes over time becomes insufficient.

[0005] On the other hand, one method for correcting measurement errors in particle detection devices is to introduce only reference particles into the detection area and perform actual measurements. In this case, in order to accurately introduce only the reference particles into the detection area, the reference particles must be moved from the inspection position and the correction work must be performed in a different location. Therefore, during this time, monitoring of particles at the production site will be interrupted, and there is a risk of missing important changes in environmental conditions.

[0006] In one aspect, this invention has been made in consideration of the above problems, and aims to provide a particle detection device that can correct measurement errors while continuously monitoring production sites and the like. [Means for solving the problem]

[0007] To solve the above-mentioned problems, the present invention employs the following configuration.

[0008] In other words, a particle detection device according to one aspect of the present invention includes: a light-emitting unit that emits irradiation light toward a detection area; a light-receiving unit that detects transmitted light that has passed through the detection area, or scattered light that has been scattered by particles present in the detection area; a signal processing unit that detects particles based on the light-receiving intensity detected by the light-receiving unit; a light-intensity switching unit that performs a light-intensity switching process in the light-passing area between the detection area and the light-receiving unit, switching between a light-intensity changing state that reduces the amount of transmitted light passing through or increases the amount of scattered light, and a normal state in which the light-intensity is not changed; and a reference correction unit that corrects the particle detection determination criterion in the signal processing unit based on the light-receiving intensity in the light-intensity changing state.

[0009] According to the above configuration, the light intensity switching unit can be used to switch to a light intensity change state in the light-passing region between the detection region and the light-receiving unit, either by reducing the amount of transmitted light or increasing the amount of scattered light, making it possible to set the system so that only reference particles are introduced into the detection region. Furthermore, in this light intensity change state, the reference correction unit can correct the particle detection judgment criterion in the signal processing unit based on the light intensity detected by the light-receiving unit, enabling accurate correction of measurement errors. In addition, the particle detection judgment criterion in the signal processing unit can be corrected without moving the particle detection device from the inspection position. Therefore, it is possible to correct measurement errors while continuing continuous monitoring in production sites and the like.

[0010] In the particle detection device described above, the light intensity switching unit may perform the light intensity switching process by moving a light-shielding member of a predetermined shape within the light-passing region. According to the above configuration, by moving a light-shielding member of a predetermined shape within the light-passing region, it is possible to achieve a light-shielding amount equivalent to that of a reference particle.

[0011] In the particle detection device described above, the light intensity switching unit may perform the light intensity switching process by switching between a normal flow channel member through which the particles pass and which is not provided with a light-reducing section that reduces the amount of light passing through, and a correction flow channel member that has the same structure as the normal flow channel member but is provided with the light-reducing section. With the above configuration, by setting the amount of light shielding of the light-reducing section provided in the correction flow channel member to the same amount of light shielding as the reference particles in advance, the reference correction unit can accurately correct the measurement error. Furthermore, by switching the flow channel member through which the particles pass to the normal flow channel member, particle detection can be performed with high accuracy.

[0012] In the particle detection device described above, the light intensity switching unit may perform the light intensity switching process by controlling the voltage applied to an electrically controlled light control unit, which changes the amount of light transmitted by controlling the voltage applied to the medium. With this configuration, the amount of light transmitted can be changed by controlling the voltage applied to the electrically controlled light control unit, and the amount of light shielding of the electrically controlled light control unit can be easily set to the same amount of light shielding as that of a reference particle with a simple configuration.

[0013] In the particle detection device described above, the light intensity switching unit may perform the light intensity switching process by moving a light scattering member of a predetermined shape within the light-passing region. According to the above configuration, by moving a light scattering member of a predetermined shape within the light-passing region, it is possible to achieve diffuse light equivalent to that of a reference particle.

[0014] In the particle detection device described above, a particle entry prevention unit may be further provided to prevent particles from entering the detection area from the outside during the period when the light intensity switching unit is in a light intensity change state. With this configuration, during the period when the light intensity is change state, the particle entry prevention unit can prevent particles from entering the detection area from the outside, thereby reducing measurement noise and improving correction accuracy.

[0015] In the particle detection device described above, the particle entry prevention unit has a structure that allows manual switching between a sealed state, where the entrance to the flow channel member through which the particles pass is sealed, and an open state, and the light intensity switching unit may perform the light intensity switching process in conjunction with the switching between the open state and the sealed state. With the above configuration, since the particle entry prevention unit has a structure that can be switched manually, it can be made into a simple configuration and manufacturing costs can be reduced. In addition, it is possible to set the light intensity to a change state in conjunction with the sealed state of the particle entry prevention unit and to a normal state in conjunction with the open state, thereby reducing measurement noise and improving correction accuracy. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a particle detection device capable of correcting measurement errors while continuously monitoring a production site or the like at all times.

Brief Description of Drawings

[0017] [Figure 1] It is an external perspective view schematically showing an example of a particle detection device according to the first embodiment. [Figure 2] It is a perspective view schematically showing an example of a configuration for switching to a light attenuation state of a particle detection device according to the first embodiment. [Figure 3] It is a cross-sectional view schematically showing an example of a configuration for switching to a light attenuation state of a particle detection device according to the first embodiment. [Figure 4] It is a block diagram showing an example of an electrical configuration of a particle detection device according to the first embodiment. [Figure 5] It is a diagram schematically showing an example of an output signal of a light receiving circuit when a particle passes through a detection region. [Figure 6] It is a main flowchart showing an example of a first correction process executed by a signal processing unit. [Figure 7] It is a sub flowchart showing an example of a sub process of a detection reference correction process in FIG. 6. [Figure 8] It is a diagram schematically showing an example of an output signal of a light receiving circuit when in a light attenuation state, in normal times and when correction is required for the peak threshold value. [Figure 9] It is a perspective view schematically showing an example of a configuration for moving a light shielding member of a particle detection device according to the second embodiment. [Figure 10] It is a perspective view schematically showing an example of a configuration for switching to a light attenuation state of a particle detection device according to the third embodiment. [Figure 11] It is a block diagram showing an example of an electrical configuration of a particle detection device according to the third embodiment. [Figure 12] It is a flowchart showing an example of a second correction process executed by a signal processing unit. [Figure 13] It is a perspective view schematically showing an example of a configuration for manually switching to a light attenuation state of a particle detection device according to the fourth embodiment. [Figure 14] It is a flowchart showing an example of the third correction process executed by the signal processing unit. [Figure 15] It is a perspective view schematically showing an example of a configuration for manually switching to a dimming state of the particle detection device according to the fifth embodiment. [Figure 16] It is a flowchart showing an example of the fourth correction process executed by the signal processing unit. [Figure 17] It is a perspective view schematically showing an example of a configuration for switching to a dimming state of the particle detection device according to the sixth embodiment. [Figure 18] It is a flowchart showing an example of the fifth correction process executed by the signal processing unit. [Figure 19] It is a perspective view schematically showing an example of a configuration for switching to a dimming state of the particle detection device according to the seventh embodiment. [Figure 20] It is a perspective view schematically showing an example of a configuration for switching to a dimming state of the particle detection device according to the eighth embodiment.

Mode for Carrying Out the Invention

[0018] Hereinafter, the first to eighth embodiments embodying the present invention will be described in detail with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and redundant explanations will be omitted as appropriate.

[0019] [First Embodiment] The particle detection device 1 according to the first embodiment will be described in detail based on FIGS. 1 to 8. First, the schematic configuration of the particle detection device 1 will be described based on FIGS. 1 to 3. FIG. 1 is an external perspective view schematically showing an example of the particle detection device 1 according to the first embodiment. FIG. 2 is a perspective view schematically showing an example of a configuration for switching to a dimming state (light quantity change state) of the particle detection device 1 according to the first embodiment. FIG. 3 is a cross-sectional view schematically showing an example of a configuration for switching to a dimming state of the particle detection device according to the first embodiment.

[0020] As shown in Figure 1, the particle detection device 1 has a box-shaped main body case 11 and four legs 12 that protrude downwards from the four corners of the bottom surface 13 of the main body case 11, each of the same length, for example, about 10 mm in length. As a result, when the particle detection device 1 is placed on the floor, a gap of a predetermined height, for example, about 10 mm in height, is formed between the bottom surface 13 of the main body case 11 and the floor surface (not shown).

[0021] In Figure 1, the particle detection device 1 has a display 16, a power switch 17, an output terminal 18, and an operating unit 19 arranged on the front wall 15. The display 16 is composed of a liquid crystal display, an organic EL display, etc., and displays detection results such as the number of small particles that have passed through. The power switch 17 is a switch that turns the power of the particle detection device 1 on and off.

[0022] The output terminal 18 is a terminal that outputs the measurement results from the particle detection device 1 to an electrically connected external device. The operation unit 19 consists of multiple button switches, and pressing the surrounding button switches moves the cursor displayed on the display 16. Pressing the central button switch of the operation unit 19 determines the input of the various instruction buttons where the cursor is located. The particle diameter detected by the particle detection device 1 is preset to, for example, 5 [μm], 10 [μm], 20 [μm], etc.

[0023] The particle detection device 1 has a roughly rectangular, flat top surface 22 through which a transparent, cylindrical suction channel section 21 with a roughly circular cross-section, into which small particles falling through the air can enter, extends vertically from the top surface 22 to the pump 25 housed in the main body case 11. The lower end of the suction channel section 21 is connected to an air intake port (not shown) located on the vertically upper side of the pump 25. In addition, a cylindrical exhaust channel section 26 with a roughly circular cross-section extends vertically from an exhaust port (not shown) located on the vertically lower side of the pump 25 to the bottom surface 13.

[0024] Pump 25 receives power, causing a fan (not shown) to rotate, drawing in air from an intake port (not shown) and exhausting it from an exhaust port (not shown). Therefore, by driving pump 25, outside air flows into the suction passage section 21 formed on the top surface 22 through the intake port 21A of the suction passage section 21, and outside air is exhausted from the exhaust port 26A of the exhaust passage section 26 formed on the bottom surface 13.

[0025] As shown in Figure 2, the suction channel section 21 has an internal space 23 with a roughly circular cross-section that penetrates vertically, formed by a roughly cylindrical wall surface 21B. Therefore, when small particles contained in the outside air flow into the intake port 21A, they pass through the internal space 23 and are discharged from the exhaust port 26A of the exhaust channel section 26. The wall surface 21B of the suction channel section 21 is formed of a transparent resin or the like, and is made to transmit light. Note that the suction channel section 21 is not limited to the configuration shown in Figure 2, and a detection unit 27, which will be described later, may be provided in the internal space of the suction channel section 21. In this case, the wall surface 21B of the suction channel section 21 may be made of a material that does not transmit light.

[0026] Furthermore, as shown in Figure 2, a detection unit 27 is arranged inside the main case 11 to detect small particles that enter the suction channel section 21 and pass through the internal space 23. This detection unit 27 will be explained based on Figures 2 and 3. As shown in Figures 2 and 3, the detection unit 27 consists of a light source 31 and a light receiving element 32, which are arranged facing each other with the suction channel section 21 in between. A light-emitting lens 33 is positioned between the light source 31 and the wall surface 21B. A light-receiving lens 35 is positioned between the light receiving element 32 and the wall surface 21B.

[0027] The light-emitting lens 33 is an optical component that collimates the light emitted from the light source 31 and irradiates the suction channel section 21 with approximately parallel light perpendicular to the vertical direction across the entire radial width of the wall surface 21B. The light-receiving lens 35 is an optical component that focuses the approximately parallel light that has passed through the suction channel section 21 across the entire radial width of the wall surface 21B and directs it into the light-receiving element 32. The optical axis of the irradiated light emitted from the light source 31 via the light-emitting lens 33 and the optical axis of the incident light received by the light-receiving element 32 via the light-receiving lens 35 are positioned on the same optical axis L1 perpendicular to the vertical direction.

[0028] As a result, as shown in Figure 3, the region of collimated light irradiated into the suction channel section 21 via the light-emitting lens 33 that can reach the light-receiving element 32 via the light-receiving lens 35 becomes the detection region 36 in which particles W passing through the suction channel section 21 can be detected. Therefore, the entire cross-sectional region in the internal space 23 of the suction channel section 21 that corresponds to the detection region 36 is a region that can detect particles W.

[0029] The light source 31 is a light source that emits light of a predetermined wavelength when power is supplied, and examples include LED (Light Emitting Diode) elements and semiconductor lasers. The wavelength emitted by the light source 31 is within the light-receiving bandwidth range of the light-receiving element 32, and examples include green light, blue light, and near-ultraviolet light. If a green LED is used as the light source 31, the wavelength of the irradiated light is shorter than that of infrared light or red light, making it possible to detect smaller particles W. The light-receiving element 32 receives light of a predetermined wavelength and converts the optical signal into an electrical signal, and examples include photodiodes and phototransistors whose spectral sensitivity peak wavelength is infrared or red.

[0030] Furthermore, as shown in Figures 1 to 3, a thin, axial light-shielding member 39 is positioned near the light-receiving element 32 side of the suction channel 21, protruding vertically from the top surface 22 to a predetermined height, for example, approximately 3 mm to 5 mm. The light-shielding member 39 is provided so as to be movable downward along the vertical direction until its upper end surface is flush with the top surface 22, and under normal circumstances, it protrudes from the top surface 22 to a predetermined height by a biasing member such as a compression coil spring (not shown). A thin pin gauge, for example, a pin gauge with a diameter of approximately 0.5 mm, can be used for the light-shielding member 39.

[0031] As shown in Figure 3, the light-shielding member 39 is positioned to face the light-passing region 37 between the detection region 36, which can detect particles W from the collimated light irradiated into the suction channel section 21 via the light-emitting lens 33, and the light-receiving lens 35. Preferably, the light-shielding member 39 is positioned on a vertical line perpendicular to the optical axis L1 within the light-passing region 37. The length of the light-shielding member 39 is normally set such that the lower end of the light-shielding member 39 is located vertically above the light-passing region 37. On the other hand, when the upper end surface of the light-shielding member 39 is flush with the top surface 22, the length of the light-shielding member 39 is set such that the lower end protrudes vertically downward from the light-passing region 37.

[0032] Furthermore, as shown in Figures 1 and 2, a substantially disc-shaped cover 41 is provided near the rear side of the intake port 21A of the suction channel section 21, in a direction perpendicular to the optical axis L1 of the illumination light emitted from the light source 31 through the light-emitting lens 33, so as to be able to open and close the intake port 21A. The cover 41 is provided so as to be able to rotate one side edge relative to the top surface 22, and under normal circumstances, it is tilted slightly in the rear direction relative to the suction channel section 21 by a biasing member such as a compression coil spring (not shown), thereby opening the intake port 21A.

[0033] On the other hand, by supplying power to the opening / closing actuator 42 (see Figure 4), the lid 41 is rotated toward the suction channel section 21 and comes into contact with the top surface 22 over its entire surface, closing the intake port 21A and pushing in so that the upper end surface of the light-shielding member 39 is flush with the top surface 22. As a result, the lower end of the light-shielding member 39 protrudes vertically downward from the light-passing region 37, blocking the collimated light and switching to a dimmed state in which the amount of light passing through the light-passing region 37 is reduced. Alternatively, the opening / closing actuator 42 may be omitted, and the lid 41 may be opened and closed manually by the user.

[0034] Here, the lower end of the light-shielding member 39 protrudes vertically downward from the light-passing region 37, and the amount of light shielding that blocks the collimated light is set to be equivalent to the amount of light shielding when only reference particles are introduced into the detection region 36 for detecting particles W, when correcting the measurement error of the particle detection device 1.

[0035] Furthermore, as shown in Figure 1, a signal processing unit 43 is located inside the main case 11 to calculate the number of small particles that have passed through based on the particle detection signal input from the detection unit 27. The signal processing unit 43 also drives and controls the light source 31, the pump 25, and the opening / closing actuator 42 (see Figure 4).

[0036] Next, an example of the electrical configuration of the particle detection device 1 will be described based on Figure 4. Figure 4 is a block diagram showing an example of the electrical configuration of the particle detection device 1 according to the first embodiment. As shown in Figure 4, the particle detection device 1 includes a detection unit 27, a signal processing unit 43, a display 16, an output terminal 18, an operation unit 19, a pump 25, and an opening / closing actuator 42.

[0037] The detection unit 27 includes a light source 31, a light source drive circuit 45 electrically connected to the light source 31, and a light receiving element 32. When the power switch 17 is turned on, the light source drive circuit 45 receives power from the power source and supplies power to the light source 31 according to the power instruction signal from the signal processing unit 43. As a result, the light source 31 emits light of a predetermined wavelength with the power supplied from the light source drive circuit 45.

[0038] The signal processing unit 43 is a so-called well-known computer equipped with a CPU, EEPROM (registered trademark), RAM, timer, etc. The signal processing unit 43 also includes a light receiving circuit 46. The CPU performs various calculations based on various programs and parameters stored in the EEPROM. The RAM temporarily stores the calculation results from the CPU and data input from the detection unit 27.

[0039] The EEPROM stores, for example, a program for the first correction process (see Figure 6) which corrects the pulse height threshold, which is the particle detection criterion in the signal processing unit 43. The light receiving circuit 46 is electrically connected to the light receiving element 32, and receives a current signal based on the received light intensity from the light receiving element 32. The light receiving circuit 46 converts the current signal input from the light receiving element 32 into a voltage value, amplifies it, and then converts the analog voltage value into a digital signal and outputs it to the signal processing unit 43.

[0040] The signal processing unit 43 is electrically connected to the light source drive circuit 45 and outputs a power instruction signal to the light source drive circuit 45 to instruct it on the amount of power to supply to the light source 31. The signal processing unit 43 is electrically connected to multiple button switches of the operation unit 19 and receives operation signals from each button switch. The signal processing unit 43 is electrically connected to the display 16 and the output terminal 18 and displays, for example, the result of detecting the number of particles that have flowed into the suction channel 21 on the display 16. If another device is electrically connected to the output terminal 18, the signal processing unit 43 outputs the measurement result from the output terminal 18 to the other device.

[0041] Next, the signal waveform output from the light receiving circuit 46 to the signal processing unit 43 will be explained based on Figure 5. Figure 5 is a schematic diagram showing an example of the output signal of the light receiving circuit 46 when a particle passes through the detection area 36 of the detection unit 27. As shown in Figure 5, when a particle of a predetermined particle size, for example, a particle size of 10 [μm], passes through the detection area 36 of the detection unit 27, the signal waveform of the light receiving circuit 46 decreases, and this decrease, the peak value P, exceeds the peak threshold PTH. Therefore, the signal processing unit 43 determines that a particle of a predetermined particle size, for example, a particle size of 10 [μm], has passed through at the light receiving timing when the peak value P of the signal waveform of the light receiving circuit 46 exceeds the peak threshold PTH, and counts the number of particles that have passed.

[0042] Next, an example of a first correction process performed by the signal processing unit 43 of the particle detection device 1 configured as described above, which corrects the pulse height threshold PTH, which is the detection criterion for particles that have passed through the detection area 36 of the detection unit 27, will be explained based on Figures 6 to 8. Figure 6 is a main flowchart showing an example of the first correction process performed by the signal processing unit 43.

[0043] Furthermore, when activated, the signal processing unit 43 repeatedly executes the processing procedure shown in the flowchart of Figure 6 at predetermined time intervals (for example, at intervals of approximately 5 to 10 minutes). The programs shown in the flowcharts of Figures 6 and 7 are pre-stored in the EEPROM. The signal processing unit 43 also outputs a power instruction signal corresponding to the set power to the light source drive circuit 45.

[0044] As shown in Figure 6, first, in step S11, the signal processing unit 43 determines, based on the time information input from the timer, whether the current time is a correction timing for correcting the pulse height threshold PTH, which is the particle detection criterion. For example, the signal processing unit 43 determines whether it is the time when the factory production line has stopped. If the signal processing unit 43 determines that the current time is not a correction timing for correcting the pulse height threshold PTH, which is the particle detection criterion (S11: NO), it terminates the first correction process. Note that the determination of whether or not it is a correction timing may also be determined by the timing at which a correction instruction input is received from the user.

[0045] On the other hand, if the signal processing unit 43 determines that the current time is the correction timing to correct the pulse height threshold PTH, which is the particle detection criterion (S11: YES), it proceeds to step S12. In step S12, the signal processing unit 43 stops driving the pump 25 and stops the suction of outside air into the suction channel 21, and then proceeds to step S13.

[0046] In step S13, the signal processing unit 43 supplies power to the opening / closing actuator 42. Specifically, the signal processing unit 43 rotates the lid 41 toward the suction channel section 21, bringing it into contact with the top surface 22 over its entire surface, closing the intake port 21A, and pushing the light-shielding member 39 so that its upper end surface is flush with the top surface 22. As a result, the lower end of the light-shielding member 39 protrudes vertically downward from the light-passing region 37, blocking the collimated light and switching to a dimmed state in which the amount of light passing through the light-passing region 37 is reduced. In addition, since the intake port 21A is closed by the lid 41, it is possible to prevent particles from entering the suction channel section 21. After that, the signal processing unit 43 proceeds to step S14.

[0047] Furthermore, if the lid 41 is configured to be closed manually by the user, the closing of the lid 41 may trigger the stopping of the pump 25's operation and the following detection criterion correction process.

[0048] In step S14, the signal processing unit 43 performs a sub-process of the detection criterion correction process (see Figure 7), which will be described later, and then proceeds to step S15. By performing the sub-process of the detection criterion correction process, the signal processing unit 43 corrects the pulse height threshold PTH, which is the particle detection criterion, in response to changes in the light source 31 over time.

[0049] In step S15, the signal processing unit 43 stops supplying power to the opening / closing actuator 42. In other words, the signal processing unit 43 returns the lid 41 to its normal position, tilted slightly inward relative to the suction flow path 21. As a result, the air intake port 21A becomes open, returning to its normal state where outside air can flow in. The light-shielding member 39 is also set to its normal state, protruding a predetermined height from the top surface 22, with its lower end positioned vertically above the light-passing region 37. After that, the signal processing unit 43 proceeds to step S16.

[0050] In step S16, the signal processing unit 43 restarts the pump 25 and then finishes the first correction process. Once the pump 25 is restarted, outside air flows into the suction channel 21 from the intake port 21A, and particles contained in the outside air pass through the detection area 36 of the detection unit 27. As a result, the signal processing unit 43 detects the particles again and counts the number of particles.

[0051] Next, the details of the subprocessing of the detection reference correction process performed by the signal processing unit 43 in step S14 will be explained with reference to Figure 7. Figure 7 is a subflowchart showing an example of the subprocessing of the detection reference correction process. As shown in Figure 7, first, the signal processing unit 43 outputs a power instruction signal to the light source drive circuit 45 to irradiate light of a predetermined wavelength from the light source 31. Then, the signal processing unit 43 measures the pulse height value P of the signal input from the light receiving circuit 46, stores it in RAM as the pulse height value P of the attenuated state in which the amount of light passing through the light passing region 37 has decreased, and then proceeds to step S22. In step S22, the signal processing unit 43 reads the pulse height value P of the attenuated state from RAM and determines whether this pulse height value P has exceeded the reference pulse height threshold GTH.

[0052] Here, as shown on the left side of Figure 8, when the output of the light source 31 is normal, closing the lid 41 reduces the amount of light passing through the light-passing region 37, and the pulse height value P in the dimmed state matches the reference pulse height threshold GTH. On the other hand, as the light source 31 deteriorates over time, the amount of light emitted decreases, and the amount of light received also changes due to other factors. As a result, as shown on the right side of Figure 8, closing the lid 41 reduces the pulse height value P in the dimmed state, and the amount of light passing through the light-passing region 37 changes, and the pulse height value P is different from the reference pulse height threshold GTH (in the example shown in Figure 8, the pulse height value P is greater than the reference pulse height threshold GTH).

[0053] Therefore, for example, it becomes necessary to correct the detection criteria for particles by subtracting the difference ΔP1 between the pulse height threshold PTH and the reference pulse height threshold GTH. The reference pulse height threshold GTH is the pulse height value P in the dimmed state, which corresponds to the amount of light shielding when only reference particles are introduced into the detection area 36 for detecting particles W. This value is measured in advance through experiments or other means and stored in the EEPROM.

[0054] Then, in step S22, the signal processing unit 43 reads the peak value P of the dimmed state from RAM and determines that this peak value P is approximately equal to the reference peak threshold GTH (S22: NO), and determines that it is normal. The signal processing unit 43 then outputs a power stop signal to the light source drive circuit 45, instructing it to stop supplying power to the light source 31. After that, the signal processing unit 43 finishes the sub-processing of the detection reference correction process, returns to the main flowchart, and proceeds to step S15 above.

[0055] On the other hand, in step S22, the signal processing unit 43 reads the peak value P of the dimmed state from RAM and determines that this peak value P is different from the reference peak threshold GTH (S22: YES), then proceeds to step S23. In step S23, the signal processing unit 43 calculates the difference ΔP1 of the peak value P of the dimmed state exceeding the reference peak threshold GTH, stores it in RAM as a correction amount for the peak threshold PTH, and then proceeds to step S24.

[0056] In step 24, the signal processing unit 43 reads the difference ΔP1 stored in RAM as the correction amount for the pulse height threshold PTH from RAM. Then, the signal processing unit 43 reads the current pulse height threshold PTH from EEPROM, subtracts the difference ΔP1 from this pulse height threshold PTH, and stores it again in EEPROM as the pulse height threshold PTH. Then, the signal processing unit 43 outputs a power stop signal to the light source drive circuit 45, instructing it to stop supplying power to the light source 31. After that, the signal processing unit 43 finishes the sub-processing of the detection reference correction process, returns to the main flowchart, and proceeds to step S15 above.

[0057] As described in detail above, in the particle detection device 1 according to the first embodiment, when the signal processing unit 43 reaches the correction timing for correcting the pulse height threshold PTH, it supplies power to the opening / closing actuator 42 to rotate the lid 41 toward the suction channel section 21 and bring it into contact with the top surface 22 over its entire surface. As a result, the lid 41 closes the intake port 21A of the suction channel section 21 and is pushed in so that the upper end surface of the light-shielding member 39 is flush with the top surface 22. As a result, the lower end of the light-shielding member 39 protrudes vertically downward from the light-passing region 37, blocking the collimating light and switching to a dimmed state in which the amount of light passing through is reduced, making it possible to set the device to a state in which only reference particles are introduced into the detection region 36.

[0058] Furthermore, in this dimmed state, the signal processing unit 43 calculates the difference ΔP1 between the pulse height value P input from the light receiving circuit 46 and the reference pulse height threshold GTH, and can correct the pulse height threshold PTH by the difference ΔP1, thereby enabling accurate correction of measurement errors. In addition, the pulse height threshold PTH, which is the particle detection judgment criterion in the signal processing unit 43, can be corrected without moving the particle detection device 1 from the inspection position. This makes it possible to correct the measurement errors of the particle detection device 1 while continuing continuous monitoring in production sites, etc.

[0059] Furthermore, during periods when the amount of light passing through the light-transmitting region 37 is reduced, the cover 41 prevents particles from entering the detection region 36 from the outside, thereby reducing measurement noise.

[0060] Here, the light source 31 functions as an example of a light-emitting unit. The light-receiving element 32 functions as an example of a light-receiving unit. The light-shielding member 39, the lid 41, the opening / closing actuator 42, and the signal processing unit 43 constitute an example of a light intensity switching unit. The signal processing unit 43 functions as an example of a reference correction unit. The lid 41, the opening / closing actuator 42, and the signal processing unit 43 constitute an example of a particle entry prevention unit.

[0061] [Second Embodiment] Next, the particle detection device 51 according to the second embodiment will be described with reference to Figure 9. The particle detection device 51 according to the second embodiment has substantially the same structure as the particle detection device 1 according to the first embodiment. Furthermore, the electrical configuration of the particle detection device 51 according to the second embodiment is substantially the same as the electrical configuration of the particle detection device 1 according to the first embodiment. However, as shown in Figure 9, the particle detection device 51 according to the second embodiment differs in that a cover 53 is provided instead of a cover 41. The configuration of the cover 53 will be described with reference to Figure 9.

[0062] As shown in Figure 9, the plate-shaped lid 53, which is roughly fan-shaped in plan view, has a through hole 53A formed on the base end where the width narrows. The lid 53 is positioned so that it can rotate horizontally around the shaft 55, which protrudes vertically from the top surface 22 of the main body case 11, and is inserted into the through hole 53A, allowing it to slide on the top surface 22. In the normal state, the lid 53 is located to the left of the intake port 21A of the suction flow path section 21 and the light-shielding member 39 protruding from the top surface 22 when viewed from the front. The radius dimension from the through hole 53A to the tip of the lid 53 and the circumferential width are formed so that the lid 53 can cover the intake port 21A and the light-shielding member 39 when the lid 43 rotates horizontally around the shaft 55.

[0063] Furthermore, the lid 53 has a groove 57 formed along a circle 56 that passes through the axis of the light-shielding member 39, centered on the axis of the shaft 55. The groove 57 has a U-shaped cross-section and protrudes inward from the side edge of the lid 53 on the intake port 21A side, on the opposite side (upward) from the top surface 22. The width of the groove 57 is greater than the diameter of the light-shielding member 39, for example, 2 to 4 times the diameter of the light-shielding member 39. The height of the side edge of the groove 57 is slightly greater than the normal protrusion height of the light-shielding member 39 from the top surface 22. The height of the inner ceiling surface of the groove 57 gradually decreases as you move inward along the circle 56 from the side edge until you reach the bottom surface.

[0064] Furthermore, the width from the inner end of the groove 57 to the side edge of the lid 53 opposite to the air intake 21A is formed to be wide enough to cover the air intake 21A and the light-shielding member 39. In addition, under normal circumstances, the lid 53 is positioned to the left of the air intake 21A and the light-shielding member 39 in a front view by a biasing member such as a compression coil spring (not shown), thereby opening the air intake 21A.

[0065] Meanwhile, the lid 53 is rotated horizontally toward the air intake 21A and the light-shielding member 39 by supplying power to the opening / closing actuator 42 (see Figure 4). The upper end of the light-shielding member 39 then enters the groove 57 and is pushed vertically downward, so that the upper end surface of the light-shielding member 39 becomes flush with the top surface, and the air intake 21A is closed by the lid 53. As a result, the lower end of the light-shielding member 39 protrudes vertically downward from the light-passing region 37, blocking the collimated light and switching to a dimmed state in which the amount of light passing through the light-passing region 37 is reduced. The opening / closing actuator 42 can be implemented as a solenoid or a stepping motor. Alternatively, as in Embodiment 1, the lid 41 may be opened and closed manually by the user without an opening / closing actuator 42.

[0066] Here, the lower end of the light-shielding member 39 protrudes vertically downward from the light-passing region 37, and the amount of light shielding that blocks the collimating light is set to be equivalent to the amount of light shielding when only reference particles are introduced into the detection region 36 for detecting particles W, when correcting the measurement error of the particle detection device 51.

[0067] Accordingly, in the particle detection device 51 according to the second embodiment, the signal processing unit 43 supplies power to the opening / closing actuator 42 in step S13 when executing the first correction process (see Figure 6). In other words, the signal processing unit 43 rotates the lid 53 horizontally toward the intake port 21A and the light-shielding member 39, closing the intake port 21A and pushing the light-shielding member 39 so that its upper end surface is flush with the top surface 22. After that, the signal processing unit 43 proceeds to step S14.

[0068] As a result, the lower end of the light-shielding member 39 protrudes vertically downward from the light-passing region 37, blocking the collimated light, thereby reducing the amount of light passing through the light-passing region 37 and switching to a dimmed state. In addition, since the intake port 21A is closed by the lid 53, it is possible to prevent particles from entering the suction channel section 21.

[0069] Furthermore, when the signal processing unit 43 performs the first correction process (see Figure 6), in step S15, it stops supplying power to the opening / closing actuator 42. In other words, the signal processing unit 43 returns the lid 53 to its normal position, which is located to the left of the air intake 21A and the light-shielding member 39 when viewed from the front. After that, the signal processing unit 43 proceeds to step S16.

[0070] As a result, the air intake 21A is left open, returning to a normal state where outside air can flow in. The light-shielding member 39 is also set to a normal state where it protrudes a predetermined height from the top surface 22, and the lower end of the light-shielding member 39 is positioned vertically above the light-transmitting region 37.

[0071] As described in detail above, the particle detection device 51 according to the second embodiment can achieve the same effects as the particle detection device 1 according to the first embodiment. Here, the light-shielding member 39, the lid 53, the opening / closing actuator 42, and the signal processing unit 43 constitute an example of a light intensity switching unit. The lid 53, the opening / closing actuator 42, and the signal processing unit 43 constitute an example of a particle entry prevention unit.

[0072] [Third Embodiment] Next, the particle detection device 61 according to the third embodiment will be described with reference to Figures 10 to 12. The particle detection device 61 according to the third embodiment has substantially the same configuration as the particle detection device 1 according to the first embodiment. However, as shown in Figure 10, it differs in that an electric dimming unit 63 is provided instead of the light-shielding member 39. The schematic configuration of the particle detection device 61 according to the third embodiment will be described with reference to Figure 10.

[0073] As shown in Figure 10, on the wall surface 21B of the suction channel section 21 of the particle detection device 61, instead of the light-shielding member 39, an elongated rectangular electro-dimming unit 63 is positioned opposite the light-receiving lens 35, with the light-passing region 37 protruding vertically on both the upper and lower sides. The electro-dimming unit 63 is a component that can switch between transparency and opacity by turning the voltage application on and off, or by adjusting the applied voltage value. For example, the electro-dimming unit 63 is composed of a dimming film that can switch between transparency and opacity by turning the voltage application on and off, or a liquid crystal or organic EL that can switch between transparency and opacity by adjusting the applied voltage value.

[0074] The electrical dimming unit 63 transmits collimating light when it is made transparent, and blocks collimating light when it is made opaque. Here, the amount of light blocking when the electrical dimming unit 63 is made opaque and blocks collimating light is set to be the same amount of light blocking as when only reference particles are placed in the detection area 36 for detecting particles W during correction of the measurement error of the particle detection device 61.

[0075] Furthermore, it is preferable that the electric dimming unit 63 is positioned on a vertical line perpendicular to the optical axis L1 within the light-passing region 37, and that the optical axis L1 passes perpendicularly through the electric dimming unit 63 at approximately the center in the width direction. In addition, the electric dimming unit 63 may be positioned in the light-passing region 37 in contact with the wall surface 21B, or it may be positioned in the light-passing region 37 near the wall surface 21B.

[0076] Furthermore, a lid detection switch 65 is positioned near the intake port 21A of the suction channel section 21 to detect the lid 41 in contact with the top surface 22. The lid detection switch 65 is composed of a mechanical switch or a Hall element. For example, the lid detection switch 65 outputs an ON signal when it detects the lid 41, and an OFF signal when it does not detect the lid 41.

[0077] Next, an example of the electrical configuration of the particle detection device 61 will be described with reference to Figure 11. As shown in Figure 11, the electrical configuration of the particle detection device 61 is substantially the same as that of the particle detection device 1 according to the first embodiment. However, an electric dimming unit 63 is electrically connected to the signal processing unit 43 in place of the light-shielding member 39. In addition, a lid detection switch 65 is electrically connected to the signal processing unit 43.

[0078] The signal processing unit 43 switches between transparency and opacity of the electric dimming unit 63 by performing voltage application control, which involves turning the voltage application to the electric dimming unit 63 on or off, or adjusting the applied voltage value. The signal processing unit 43 also detects the open and closed states of the lid 41 from the ON / OFF signals input from the lid detection switch 65.

[0079] Next, an example of a second correction process performed by the signal processing unit 43 of the particle detection device 61 configured as described above, which corrects the pulse height threshold PTH, which is the detection criterion for particles that have passed through the detection area 36 of the detection unit 27, will be explained based on Figure 12. Figure 12 is a main flowchart showing an example of the second correction process performed by the signal processing unit 43.

[0080] Furthermore, when activated, the signal processing unit 43 repeatedly executes the processing procedure shown in the flowchart of Figure 12 at predetermined time intervals (for example, at intervals of approximately 5 to 10 minutes). The programs shown in the flowcharts of Figures 12 and 7 are pre-stored in the EEPROM. The signal processing unit 43 also outputs a power instruction signal to the light source drive circuit 45 according to the set power. The signal processing unit 43 supplies power to the pump 25 to drive it. In addition, the signal processing unit 43 controls the voltage application to the electric dimming unit 63 by turning it on and off, or by adjusting the applied voltage value, thereby making the electric dimming unit 63 transparent. In other words, under normal conditions, the electric dimming unit 63 is transparent.

[0081] As shown in Figure 12, the signal processing unit 43 executes steps S11 to S13 of the first correction process (see Figure 6) according to the first embodiment described above. In step S13, the signal processing unit 43 waits for an ON signal to be input from the lid detection switch 65 indicating that the closed lid 41 has been detected. When an ON signal is input from the lid detection switch 65, the signal processing unit 43 determines that the intake port 21A has been closed by the lid 41 and proceeds to step S31. This ensures that the intake port 21A is reliably closed, and that particles from the outside do not enter the detection area 36.

[0082] In step S31, the signal processing unit 43 controls the voltage application to the electric dimming unit 63 by turning it on or off, or by adjusting the applied voltage value, thereby opacifying the electric dimming unit 63. In other words, the signal processing unit 43 opacifies the electric dimming unit 63 and sets it to a light-shielding state that blocks the collimating light. As a result, the signal processing unit 43 switches to a dimmed state in which the amount of light passing through the light-passing region 37 is reduced via the electric dimming unit 63. After that, the signal processing unit 43 proceeds to step S14 of the first correction process (see Figure 6) according to the first embodiment described above.

[0083] In step S14, the signal processing unit 43 performs a sub-process of the detection criterion correction process (see Figure 7) and then proceeds to step S32. By performing the sub-process of the detection criterion correction process, the signal processing unit 43 corrects the pulse height threshold PTH, which is the particle detection criterion, in response to changes in the light source 31 over time.

[0084] In step S32, the signal processing unit 43 controls the voltage application to the electric dimming unit 63 by turning it on or off, or by adjusting the applied voltage value, thereby making the electric dimming unit 63 transparent again. In other words, the signal processing unit 43 makes the electric dimming unit 63 transparent and resets it to the normal state in which collimated light is transmitted. As a result, the signal processing unit 43 resets the amount of light transmitted in the light transmission region 37 to the normal state. After that, the signal processing unit 43 proceeds to step S15 of the first correction process (see Figure 6) according to the first embodiment described above.

[0085] In step S15, the signal processing unit 43 stops supplying power to the opening / closing actuator 42. The signal processing unit 43 then waits for an OFF signal to be input from the lid detection switch 65, which indicates that the lid 41 is not detected, meaning that the lid 41 has returned to its normal state and the air intake port 21A has been opened. When the signal processing unit 43 receives an OFF signal from the lid detection switch 65, it determines that the air intake port 21A has been opened and proceeds to step S16 of the first correction process (see Figure 6) according to the first embodiment described above.

[0086] In step S16, the signal processing unit 43 restarts the pump 25 and then finishes the second correction process. As a result, the intake port 21A is opened, returning to a normal state where outside air can flow in. The pump 25 is also restarted, and particles contained in the outside air pass through the intake port 21A into the detection area 36 of the detection unit 27. As a result, the signal processing unit 43 detects the particles again and counts the number of particles.

[0087] As described in detail above, in the particle detection device 61 according to the third embodiment, when the correction timing for pulse height threshold PTH correction is reached, the signal processing unit 43 supplies power to the opening / closing actuator 42 to rotate the lid 41 toward the suction channel section 21 and bring it into contact with the top surface 22 over its entire surface. As a result, the lid 41 closes the intake port 21A of the suction channel section 21. Furthermore, the signal processing unit 43 controls the voltage application of the electric dimming unit 63 to make it opaque and block the collimating light, thereby switching to a dimmed state in which the amount of light passing through the light-passing region 37 is reduced, making it possible to set the device so that only reference particles are introduced into the detection region 36.

[0088] Furthermore, in this dimmed state, the signal processing unit 43 calculates the difference ΔP1 between the pulse height value P input from the light receiving circuit 46 and the reference pulse height threshold GTH, and can correct the pulse height threshold PTH by the difference ΔP1, thereby enabling accurate correction of measurement errors. In addition, the pulse height threshold PTH, which is the particle detection judgment criterion in the signal processing unit 43, can be corrected without moving the particle detection device 61 from the inspection position. This makes it possible to correct the measurement errors of the particle detection device 61 while continuing continuous monitoring in production sites, etc.

[0089] Furthermore, during periods when the amount of light passing through the light-transmitting region 37 is reduced, the cover 41 prevents particles from entering the detection region 36 from the outside, thereby reducing measurement noise.

[0090] Furthermore, the amount of light transmitted can be changed by controlling the voltage applied to the electric dimming unit 63, and the amount of light shielding of the electric dimming unit 63 can be easily set to the same amount of light shielding as the reference particles with a simple configuration. Here, the electric dimming unit 63 and the signal processing unit 43 constitute an example of a light intensity switching unit.

[0091] [Fourth Embodiment] Next, the particle detection device 71 according to the fourth embodiment will be described with reference to Figures 13 and 14. The particle detection device 71 according to the fourth embodiment has substantially the same configuration as the particle detection device 1 according to the first embodiment. However, as shown in Figure 13, it differs in that, instead of the lid 41 and the opening / closing actuator 42, it is equipped with a manually detachable lid 73 on the intake port 21A of the suction flow path section 21. The lid 73 will be described with reference to Figure 13.

[0092] As shown in Figure 13, the lid 73 has a substantially cylindrical gripping portion 73A and a substantially cylindrical insertion portion 73B formed coaxially on one (lower) end face of the gripping portion 73A, and is made of an elastic material such as rubber. The insertion portion 73B is formed to have an outer diameter approximately equal to the inner diameter of the intake port 21A of the suction flow path portion 21, and is designed to be able to be pushed into the intake port 21A and removed from the intake port 21A. The gripping portion 73A is also formed to be cylindrical with a diameter that can be gripped with one hand. The outer diameter of the gripping portion 73A is formed to be approximately equal to the outer diameter of the lid 41 according to the first embodiment.

[0093] Therefore, when the insertion portion 73B of the lid 73 is pushed into the air intake port 21A and the lower end surface of the grip portion 73A is brought into contact with the top surface 22 of the main body case 11 over its entire surface, the upper end surface of the light-shielding member 39 is pushed in so that it is flush with the top surface 22. As a result, the lower end of the light-shielding member 39 protrudes vertically downward from the light-passing region 37, blocking the collimated light and switching to a dimmed state in which the amount of light passing through the light-passing region 37 is reduced.

[0094] Furthermore, when the insertion portion 73B of the lid 73 is pushed into the air intake port 21A, and the lower end surface of the gripping portion 73A is brought into contact with the top surface 22 of the main body case 11 over its entire length, the air intake port 21A is set to a sealed state, being blocked by the insertion portion 73B. On the other hand, when the gripping portion 73A of the lid 73 is grasped and the insertion portion 73B is removed from the air intake port 21A, the air intake port 21A becomes open, returning to a normal state where outside air can flow in.

[0095] Furthermore, a lid detection switch 75 is positioned near the light-shielding member 39 on the opposite side of the air intake port 21A to detect the gripping portion 73A of the lid 73 that is in contact with the top surface 22. The lid detection switch 75 is composed of a mechanical switch or a Hall element and is electrically connected to the signal processing unit 43. For example, when the lid detection switch 75 detects the gripping portion 73A of the lid 73, it outputs an ON signal to the signal processing unit 43, and when it does not detect the gripping portion 73A of the lid 73, it outputs an OFF signal to the signal processing unit 43.

[0096] Therefore, the electrical configuration of the particle detection device 71 is substantially the same as that of the particle detection device 1 according to the first embodiment. However, a lid detection switch 75 is electrically connected to the signal processing unit 43 in place of the opening / closing actuator 42.

[0097] Next, an example of a third correction process performed by the signal processing unit 43 of the particle detection device 71 configured as described above, which corrects the pulse height threshold PTH, which is the detection criterion for particles that have passed through the detection area 36 of the detection unit 27, will be explained based on Figure 14. Figure 14 is a main flowchart showing an example of the third correction process performed by the signal processing unit 43.

[0098] Furthermore, when activated, the signal processing unit 43 repeatedly executes the processing procedure shown in the flowchart of Figure 14 at predetermined time intervals (for example, at intervals of approximately 10 msec to 100 msec). The programs shown in the flowcharts of Figures 14 and 7 are pre-stored in the EEPROM. The signal processing unit 43 also outputs a power instruction signal corresponding to the set power to the light source drive circuit 45. The signal processing unit 43 supplies power to the pump 25 to drive it.

[0099] As shown in Figure 14, first, in step S41, the signal processing unit 43 determines whether the correction start button (not shown) has been selected from the various instruction buttons displayed on the display 16 via the operation unit 19. In other words, the signal processing unit 43 determines whether the user has pressed the button switches around the operation unit 19 to move the cursor over the correction start button, and then pressed the central button switch of the operation unit 19 to determine whether the correction start button has been selected. Then, if the signal processing unit 43 determines via the operation unit 19 that the correction start button displayed on the display 16 has not been selected (S41: NO), it terminates the third correction process.

[0100] On the other hand, if the signal processing unit 43 determines that the correction start button displayed on the display 16 has been selected via the operation unit 19 (S41: YES), it proceeds to step S12 of the first correction process according to the first embodiment (see Figure 6). In step S12, the signal processing unit 43 stops driving the pump 25 and stops the suction of outside air into the suction channel 21, and then proceeds to step S42.

[0101] In step S42, the signal processing unit 43 determines whether the insertion portion 73B of the lid 73 has been pushed into the air intake port 21A, thereby sealing the air intake port 21A, and whether the upper end surface of the light-shielding member 39 has been pushed in until it is flush with the top surface 22. In other words, the signal processing unit 43 determines whether an ON signal indicating that the gripping portion 73A of the lid 73 has been detected has been input from the lid detection switch 75.

[0102] Then, if the signal processing unit 43 receives an OFF signal from the lid detection switch 75 indicating that it has not detected the gripping portion 73A of the lid 73 (S42: NO), it waits for an ON signal to be received from the lid detection switch 75. On the other hand, if the signal processing unit 43 receives an ON signal from the lid detection switch 75 (S42: YES), it determines that the air intake port 21A is sealed by the lid 73 and proceeds to step S14 of the first correction process according to the first embodiment (see Figure 6).

[0103] In step S14, the signal processing unit 43 performs a sub-process of the detection criterion correction process (see Figure 7) and then proceeds to step S43. By performing the sub-process of the detection criterion correction process, the signal processing unit 43 corrects the pulse height threshold PTH, which is the particle detection criterion, in response to changes in the light source 31 over time.

[0104] In step S43, the signal processing unit 43 displays on the display 16 an indication that the correction of the pulse height threshold PTH, which is the particle detection criterion, has been completed, for example, "Correction completed.", and then proceeds to the process in step S44.

[0105] In step S44, the signal processing unit 43 determines whether the lid 73 has been removed from the air intake port 21A. That is, the signal processing unit 43 determines whether the air intake port 21A is open and the light-shielding member 39 is set to a normal state in which it protrudes from the top surface 22 to a predetermined height and the lower end of the light-shielding member 39 is positioned vertically above the light-passing region 37. Specifically, the signal processing unit 43 determines whether an OFF signal indicating that the gripping portion 73A of the lid 73 is not detected has been input from the lid detection switch 75.

[0106] Then, if the signal processing unit 43 receives an ON signal from the lid detection switch 75 indicating that it has detected the gripping portion 73A of the lid 73 (S44: NO), it waits for an OFF signal to be received from the lid detection switch 75. On the other hand, if the signal processing unit 43 receives an OFF signal from the lid detection switch 75 (S44: YES), it determines that the lid 73 has been removed and proceeds to step S16 of the first correction process according to the first embodiment (see Figure 6). In other words, the signal processing unit 43 determines that the air intake port 21A has been opened and the light-shielding member 39 has protruded from the top surface 22 to a predetermined height, and proceeds to step S16 of the first correction process according to the first embodiment (see Figure 6).

[0107] In step S16, the signal processing unit 43 restarts the pump 25 and then finishes the third correction process. As a result, the intake port 21A is opened, returning to a normal state where outside air can flow in. The pump 25 is also restarted, and particles contained in the outside air pass through the intake port 21A into the detection area 36 of the detection unit 27. As a result, the signal processing unit 43 detects the particles again and counts the number of particles.

[0108] As described in detail above, the particle detection device 71 according to the fourth embodiment can achieve the same effects as the particle detection device 1 according to the first embodiment. Furthermore, since the structure allows manual switching between a sealed state and an open state using the lid 73, the configuration can be simplified, and manufacturing costs can be reduced.

[0109] Furthermore, the amount of light passing through the light-passing region 37 can be set to a reduced state in conjunction with the sealing state of the air intake port 21A by the cover 73. Conversely, the amount of light passing through the light-passing region 37 can be set to a normal state in conjunction with the opening state of the air intake port 21A by the cover 73, thereby reducing measurement noise and improving correction accuracy. Here, the cover 73 functions as an example of a particle entry prevention unit.

[0110] [Fifth Embodiment] Next, the particle detection device 81 according to the fifth embodiment will be described with reference to Figures 15 and 16. The particle detection device 81 according to the fifth embodiment has substantially the same configuration as the particle detection device 71 according to the fourth embodiment. Furthermore, the electrical configuration of the particle detection device 81 according to the fifth embodiment is substantially the same as the electrical configuration of the particle detection device 71 according to the fourth embodiment. However, as shown in Figure 15, it differs in that the filter case 83 is fixed coaxially with the gripping portion 73A to the upper end surface of the gripping portion 73A of the lid 73. It also differs in that the lid 73 has a through hole 89 formed along its axis that penetrates from the upper end surface of the gripping portion 73A to the lower end surface of the insertion portion 73B.

[0111] The filter case 83 will be described with reference to Figure 15. As shown in Figure 15, the filter case 83 consists of a thin cylindrical suction tube portion 85, a filter tube portion 86, and a connecting tube portion 87, all coaxially connected and communicating with each other from the vertical upper side. The lower end surface of the connecting tube portion 87 communicates with a through hole 89 formed along the axis of the lid 73. The outer diameter of the filter tube portion 86 is slightly smaller than the outer diameter of the grip portion 73A of the lid 73. The outer diameter of the connecting tube portion 87 is also smaller than the outer diameter of the filter tube portion 86.

[0112] Furthermore, a zero-count filter 88 is housed in the filter cylinder portion 86. The zero-count filter 88 is formed in a cylindrical shape from ceramics or the like, and is configured to collect particles contained in the outside air that flows from the suction cylinder portion 85 into the filter cylinder portion 86, so that only particle-free outside air passes through to the connecting cylinder portion 87. Therefore, particles contained in the outside air that flows into the filter case 83 from the suction port 85A of the suction cylinder portion 85 are collected by the zero-count filter 88. As a result, only particle-free outside air flows out from the filter cylinder portion 86 through the connecting cylinder portion 87 and the through hole 89, and out from the lower end surface of the insertion portion 73B of the lid 73.

[0113] Next, an example of a fourth correction process performed by the signal processing unit 43 of the particle detection device 81 configured as described above, which corrects the pulse height threshold PTH, which is the detection criterion for particles that have passed through the detection area 36 of the detection unit 27, will be explained with reference to Figure 16. Figure 16 is a main flowchart showing an example of the fourth correction process performed by the signal processing unit 43.

[0114] Furthermore, when activated, the signal processing unit 43 repeatedly executes the processing procedure shown in the flowchart of Figure 16 at predetermined time intervals (for example, at intervals of approximately 10 msec to 100 msec). The programs shown in the flowcharts of Figures 16 and 7 are pre-stored in the EEPROM. The signal processing unit 43 also outputs a power instruction signal corresponding to the set power to the light source drive circuit 45. The signal processing unit 43 supplies power to the pump 25 to drive it.

[0115] As shown in Figure 16, the signal processing unit 43 executes the process of step S41 of the third correction process (see Figure 14) according to the fourth embodiment described above. If the signal processing unit 43 determines that the correction start button displayed on the display 16 has not been selected via the operation unit 19 (S41: NO), it terminates the fourth correction process.

[0116] On the other hand, if the signal processing unit 43 determines that the correction start button displayed on the display 16 has been selected via the operation unit 19 (S41: YES), it proceeds to step S42 of the third correction process according to the fourth embodiment (see Figure 14). In other words, the signal processing unit 43 proceeds to step S42 without stopping the pump 25. This is because, in the sub-process of the detection criterion correction process in step S14 described later (see Figure 7), during the period when the amount of light passing through the light-passing region 37 is reduced, the zero-count filter 88 housed in the filter case 83 prevents particles from entering the detection region 36 from the outside.

[0117] In step 42, the signal processing unit 43 waits for an ON signal to be input from the lid detection switch 75 (S42: NO). If an ON signal is input from the lid detection switch 75 (S42: YES), the signal processing unit 43 determines that the air intake port 21A is sealed by the lid 73 and proceeds to step S14 of the first correction process according to the first embodiment (see Figure 6).

[0118] In step S14, the signal processing unit 43 performs a sub-process of the detection criterion correction process (see Figure 7) and then proceeds to step S43 of the third correction process according to the fourth embodiment (see Figure 14). By performing the sub-process of the detection criterion correction process, the signal processing unit 43 corrects the pulse height threshold PTH, which is the particle detection criterion, in response to changes in the light source 31 over time.

[0119] In step S43, the signal processing unit 43 displays on the display 16 an indication that the correction of the pulse height threshold PTH, which is the particle detection criterion, has been completed, for example, "Correction completed.", and then proceeds to step S44 of the third correction process according to the fourth embodiment (see Figure 14).

[0120] In step S44, the signal processing unit 43 waits for an OFF signal to be input from the lid detection switch 75 (S44: NO). If an OFF signal is input from the lid detection switch 75 (S44: YES), the signal processing unit 43 determines that the lid 73 has been removed and terminates the fourth correction process. The pump 25 is driven continuously without being stopped.

[0121] As described in detail above, the particle detection device 81 according to the fifth embodiment can achieve the same effects as the particle detection device 1 according to the first embodiment. Furthermore, since the structure allows manual switching between a sealed state and an open state using the lid 73, the configuration can be simplified, and manufacturing costs can be reduced.

[0122] Furthermore, the amount of light passing through the light-passing region 37 can be set to a reduced state in conjunction with the sealing state of the air intake port 21A by the lid 73. Also, the amount of light passing through the light-passing region 37 can be set to a normal state in conjunction with the opening state of the air intake port 21A by the lid 73, thereby reducing measurement noise and improving correction accuracy. In addition, since the lid 73 is provided with a filter case 83, the amount of light passing through the light-passing region 37 can be set to a reduced state without stopping the pump 25, and measurement noise can be reduced and correction accuracy can be improved. Here, the lid 73 and the filter case 83 function as an example of a particle entry prevention unit.

[0123] [Sixth Embodiment] Next, the particle detection device 91 according to the sixth embodiment will be described with reference to Figures 17 and 18. The particle detection device 91 according to the sixth embodiment has substantially the same configuration as the particle detection device 1 according to the first embodiment. However, as shown in Figure 17, it differs in that, instead of the suction flow path section 21, a normal flow path member 92 and a correction flow path member 93 are provided.

[0124] As shown in Figure 17, the normal flow channel member 92 has almost the same structure as the suction flow channel section 21 and is formed as a transparent cylindrical shape with a substantially circular cross-section that allows small particles falling through the air to enter. The correction flow channel member 93 has the same shape as the normal flow channel member 92 and is formed as a transparent cylindrical shape with a substantially circular cross-section, and its upper end is closed by a thin disc-shaped lid 95. The normal flow channel member 92 and the correction flow channel member 93 are arranged side by side in a direction perpendicular to the optical axis L1 of the detection unit 27.

[0125] Furthermore, the normal flow channel member 92 and the correction flow channel member 93 are provided by a moving mechanism 96 so as to be able to reciprocate along a direction perpendicular to the optical axis L1 of the detection unit 27, passing through the detection area 36 of the detection unit 27. Under normal conditions, the normal flow channel member 92 is positioned in the detection area 36 of the detection unit 27 by the moving mechanism 96. When the signal processing unit 43 performs the sub-processing of the above-mentioned detection reference correction processing (see Figure 7), the correction flow channel member 93 is positioned in the detection area 36 of the detection unit 27 by the moving mechanism 96.

[0126] Furthermore, when the normal flow path member 92 is located in the detection area 36 of the detection unit 27, the opening at the upper end of the normal flow path member 92 is connected to the intake port 21A of the main body case 11. At the same time, the opening at the lower end of the normal flow path member 92 is connected to an intake port (not shown) located on the vertically upward side of the pump 25. On the other hand, when the correction flow path member 93 is located in the detection area 36 of the detection unit 27, the cover 95 of the correction flow path member 93 is connected to the intake port 21A of the main body case 11, closing the intake port 21A. At the same time, the opening at the lower end of the correction flow path member 93 is connected to an intake port (not shown) located on the vertically upward side of the pump 25.

[0127] Furthermore, as shown in Figure 17, on the wall surface 93B of the correction flow channel member 93, a light-reducing section 97, which is shaped like an elongated rectangle or an elongated axis when viewed from the front, is positioned opposite the light-receiving lens 35 so as to protrude on both the upper and lower sides along the vertical direction of the light-passing region 37. Here, the amount of light-reducing by the light-reducing section 97 is set to be equivalent to the amount of light-reducing when only reference particles are introduced into the detection region 36 for detecting particles W during correction of the measurement error of the particle detection device 91. Preferably, the light-reducing section 97 is positioned on a vertical line perpendicular to the optical axis L1 within the light-passing region 37, and the optical axis L1 is positioned perpendicular to the approximately center position in the width direction of the light-reducing section 97.

[0128] Furthermore, the electrical configuration of the particle detection device 91 is substantially the same as that of the particle detection device 1 according to the first embodiment. However, a moving mechanism 96 is electrically connected in place of the opening / closing actuator 42.

[0129] Next, an example of a fifth correction process, which is performed by the signal processing unit 43 of the particle detection device 91 configured as described above, to correct the pulse height threshold PTH, which is the detection criterion for particles that have passed through the detection area 36 of the detection unit 27, will be explained based on Figure 18. Figure 18 is a main flowchart showing an example of the fifth correction process performed by the signal processing unit 43.

[0130] Furthermore, when activated, the signal processing unit 43 repeatedly executes the processing procedure shown in the flowchart of Figure 18 at predetermined time intervals (for example, at intervals of approximately 5 to 10 minutes). The programs shown in the flowcharts of Figures 18 and 7 are pre-stored in the EEPROM. The signal processing unit 43 also outputs a power instruction signal corresponding to the set power to the light source drive circuit 45. The signal processing unit 43 supplies power to the pump 25 to drive it. In addition, under normal conditions, the normal flow path member 92 is positioned in the detection area 36 of the detection unit 27 by the moving mechanism 96.

[0131] As shown in Figure 18, the signal processing unit 43 executes steps S11 to S12 of the first correction process (see Figure 6) according to the first embodiment described above. Then, in step S12, the signal processing unit 43 stops driving the pump 25 and proceeds to step S51. In step S51, the signal processing unit 43 drives the moving mechanism 96 to move the normal flow channel member 92 and the correction flow channel member 93 along a direction perpendicular to the optical axis L1, for example, towards the back, that is, to the correction position. Then, when the correction flow channel member 93 is located in the detection area 36 of the detection unit 27, the signal processing unit 43 stops the moving mechanism 96.

[0132] As a result, the light-reducing section 97 positioned on the wall surface 93B of the correction flow channel member 93 protrudes both upward and downward along the vertical direction of the light-passing region 37, blocking the collimated light and switching to a light-reducing state in which the amount of light passing through the light-passing region 37 is reduced. In addition, since the intake port 21A is closed by the cover 95, it is possible to prevent particles from entering the correction flow channel member 93. After that, the signal processing unit 43 proceeds to step S14 of the first correction process (see Figure 6) according to the first embodiment described above.

[0133] In step S14, the signal processing unit 43 performs a sub-process of the detection criterion correction process (see Figure 7) and then proceeds to step S52. By performing the sub-process of the detection criterion correction process, the signal processing unit 43 corrects the pulse height threshold PTH, which is the particle detection criterion, in response to changes in the light source 31 over time.

[0134] In step S52, the signal processing unit 43 drives the moving mechanism 96 again to move the normal flow channel member 92 and the corrected flow channel member 93 along a direction perpendicular to the optical axis L1, for example, towards the front, that is, to their original positions in the normal state. Then, when the normal flow channel member 92 is located in the detection area 36 of the detection unit 27, the signal processing unit 43 stops the moving mechanism 96. After that, the signal processing unit 43 proceeds to step S16 of the first correction process (see Figure 6) according to the first embodiment described above. In step S16, the signal processing unit 43 drives the pump 25 again and then terminates the fifth correction process.

[0135] When the pump 25 is restarted, outside air flows into the normal flow path member 92 from the intake port 21A, and particles contained in the outside air pass through the detection area 36 of the detection unit 27. As a result, the signal processing unit 43 detects the particles again and counts the number of particles.

[0136] As described in detail above, in the particle detection device 91 according to the sixth embodiment, the signal processing unit 43 switches the normal flow channel member 92 to the detection region 36 under normal conditions, and to the correction flow channel member 93 to the detection region 36 when correcting the pulse height threshold PTH. This makes it possible to accurately correct measurement errors by setting the amount of light shielding of the light-reducing section 97 provided in the correction flow channel member 93 to the same amount of light shielding as the reference particle in advance. Furthermore, by switching the flow channel member through which the particles pass to the normal flow channel member 92, particle detection can be performed with high accuracy.

[0137] Therefore, the particle detection device 91 according to the sixth embodiment can achieve the same effects as the particle detection device 1 according to the first embodiment. In other words, the pulse height threshold PTH, which is the particle detection criterion in the signal processing unit 43, can be corrected without moving the particle detection device 91 from the inspection position. This makes it possible to correct the measurement error of the particle detection device 91 while continuing continuous monitoring at production sites, etc. Here, the lid 95 functions as an example of a particle entry prevention unit.

[0138] [Seventh Embodiment] Next, the particle detection device 101 according to the seventh embodiment will be described with reference to Figure 19. In the first embodiment, a particle detection device 1 of the pass-through light receiving type, which detects light that has passed through the detection area, was described. In the seventh embodiment, a particle detection device 101 of the scattered light receiving type, which detects scattered light scattered by particles present in the detection area, will be described.

[0139] The particle detection device 101 according to the seventh embodiment has substantially the same structure as the particle detection device 1 according to the first embodiment. However, as shown in Figure 19, a thin suction tube 103 is arranged along the axis of the suction channel section 21 to draw in air. The suction tube 103 is connected to an air intake port (not shown) of the pump 25 and is configured to draw in outside air that flows into the suction channel section 21.

[0140] Furthermore, inside the main case 11, instead of the detection unit 27 (see Figure 2) according to the first embodiment, a second detection unit 105 is arranged to detect particles contained in the outside air that flows into the suction channel 21 and is drawn into the suction tube 103. The second detection unit 105 has a light source 31 and a light receiving element 32 arranged on either side of the suction channel 21. A light-emitting lens 106 is arranged between the light source 31 and the wall surface 21B. A light-receiving lens 107 is arranged between the light receiving element 32 and the wall surface 21B.

[0141] The light-emitting lens 106 is an optical component that focuses the light emitted from the light source 31 as illumination light onto the detection area 109 located directly above the suction tube 103. The light-receiving lens 107 is an optical component that focuses the light from the detection area 109 and directs it onto the light-receiving element 32. The optical axis L5 of the illumination light emitted from the light source 31 via the light-emitting lens 106 and the optical axis L6 of the incident light received by the light-receiving element 32 via the light-receiving lens 107 are arranged to intersect at a predetermined angle, for example, approximately 90 degrees, in the same plane perpendicular to the vertical direction. Therefore, the detection area 109 is set as the detection area for detecting particles W, where the plane region perpendicular to the vertical direction, where the respective optical axes L5 and L6 are located, is located directly above the suction tube 103.

[0142] Furthermore, a substantially cylindrical holding member 111 is positioned vertically above the detection area 109, coaxially holding a thin, axial light scattering member 39A at its lower end. The holding member 111 consists of a cylindrical main body 111A that tapers towards the bottom vertically, and a thin, axial shaft 111B that protrudes upward for a predetermined length from the center of the upper end surface of the main body 111A. Therefore, the light scattering member 39A protrudes downward coaxially from the lower end of the main body 111A.

[0143] Furthermore, the slender shaft portion 111B of the holding member 111 is positioned to protrude vertically from the top surface 22 to a predetermined height, for example, a height of approximately 3 mm to 5 mm. The main body portion 111A is provided so as to be movable downward along the vertical direction until the upper end surface of the slender shaft portion 111B becomes flush with the top surface 22. Normally, the slender shaft portion 111B protrudes from the top surface 22 to a predetermined height by a biasing member such as a compression coil spring (not shown). The light scattering member 39A can be a thin pin gauge, for example, a pin gauge with a diameter of approximately 0.5 mm.

[0144] Furthermore, when the lid 41 is rotated toward the top surface 22 and comes into contact with the top surface 22, the upper end surface of the slender shaft portion 111B protruding from the top surface 22 is pressed down by the lid 41 and pushed in so that it is flush with the top surface 22. As a result, the holding member 111 moves vertically downward, and the lower end of the light scattering member 39A protrudes vertically downward from the detection area 109, scattering the irradiated light, and a portion of it enters the light receiving lens 107. Therefore, in the light passing region 37 between the light receiving lens 107 and the light receiving element 32, the amount of scattered light is increased, switching to a light intensity change state.

[0145] Here, the amount of light received by the light-scattering member 39A into the light-receiving lens 107 is set to be equivalent to the amount of scattered light received when only reference particles are introduced into the detection area 109 for detecting particles W, during the correction of the measurement error of the particle detection device 101.

[0146] Furthermore, the electrical configuration of the particle detection device 101 according to the seventh embodiment is the same as the electrical configuration of the particle detection device 1 according to the first embodiment. Here, the light source 31 of the second detection unit 105 functions as an example of a light-emitting unit. The light-receiving element 32 of the second detection unit 105 functions as an example of a light-receiving unit.

[0147] In the particle detection device 101 configured as described above, the signal processing unit 43 can correct the pulse height threshold PTH, which is the detection criterion for particles that have passed through the detection area 109 of the second detection unit 105, by executing the first correction process according to the first embodiment (see Figure 6). In other words, the particle detection device 101 according to the seventh embodiment can achieve the same effect as the particle detection device 1 according to the first embodiment. Therefore, the pulse height threshold PTH, which is the detection criterion for particles in the signal processing unit 43, can be corrected without moving the particle detection device 101 from the inspection position. This makes it possible to correct the measurement error of the particle detection device 101 while continuing continuous monitoring at production sites, etc.

[0148] [Eighth Embodiment] Next, the particle detection device 121 according to the eighth embodiment will be described with reference to Figure 20. The particle detection device 121 according to the eighth embodiment has substantially the same configuration as the particle detection device 71 according to the fourth embodiment. Furthermore, the electrical configuration of the particle detection device 121 according to the eighth embodiment is substantially the same as the electrical configuration of the particle detection device 81 according to the fourth embodiment. However, as shown in Figure 20, the particle detection device 121 according to the eighth embodiment differs in that, instead of the light-shielding member 39, a thin, shaft-shaped light-shielding member 123 is provided on the lower end surface of the insertion portion 73B of the lid 73, protruding downward coaxially with the insertion portion 73B.

[0149] As shown in Figure 20, when the insertion portion 73B of the lid 73 is pushed into the air intake port 21A and the lower end surface of the gripping portion 73A is brought into contact with the top surface 22 of the main body case 11, the lower end of the light-shielding member 123 is configured to protrude vertically downward from the detection area 36 of the detection unit 27. As a result, the lower end of the light-shielding member 123 protrudes vertically downward from the detection area 36 and blocks the collimated light, thereby switching to a dimmed state in which the amount of light passing through the light-passing area 37 is reduced. The light-shielding member 123 can be a thin pin gauge, for example, a pin gauge with a diameter of approximately 0.5 mm.

[0150] Here, the lower end of the light-shielding member 123 protrudes vertically downward from the detection area 36, ​​and the amount of light shielding that blocks the collimating light is set to be equivalent to the amount of light shielding when only reference particles are introduced into the detection area 36 for detecting particles W, when correcting the measurement error of the particle detection device 121.

[0151] In the particle detection device 121 configured as described above, the signal processing unit 43 can correct the pulse height threshold PTH, which is the detection criterion for particles that have passed through the detection area 36 of the detection unit 27, by executing the third correction process according to the fourth embodiment (see Figure 14). In other words, the particle detection device 121 according to the eighth embodiment can achieve the same effect as the particle detection device 71 according to the fourth embodiment.

[0152] Furthermore, since the structure allows manual switching between a sealed state and an open state using the lid 73, a simple configuration can be achieved, thereby reducing manufacturing costs. In addition, by providing a thin, shaft-shaped light-shielding member 123 on the lower end surface of the insertion portion 73B of the lid 73, the amount of light passing through the light-passing region 37 can be set to a reduced state in conjunction with the sealed state of the air intake port 21A by the lid 73, further reducing manufacturing costs.

[0153] Furthermore, the pulse height threshold PTH, which is the particle detection criterion in the signal processing unit 43, can be corrected without moving the particle detection device 121 from its inspection position. This makes it possible to correct the measurement error of the particle detection device 121 while continuing continuous monitoring in production sites and the like.

[0154] The present invention is not limited to the first to eighth embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of Symbols]

[0155] 1, 51, 61, 71, 81, 91, 101, 121 Particle detection device, 21 Suction channel section, 31 Light source, 32 Light receiving element, 36 Detection area, 37 Light passing area, 39, 123 Light shielding member, 39A Light scattering member, 41, 73, 95 Cover, 43 Signal processing unit, 63 Electric dimming unit, 92 Normal channel member, 93 Correction channel member, 97 Light reduction unit

Claims

1. A light-emitting unit that emits light towards the detection area, A light receiving unit that detects transmitted light that has passed through the detection area, or scattered light that has been scattered by particles present within the detection area from the irradiated light, A signal processing unit that detects particles based on the light intensity detected by the light receiving unit, A light intensity switching unit performs a light intensity switching process in the light-passing region between the detection region and the light-receiving unit, which switches between a light intensity changing state in which the amount of transmitted light is reduced or the amount of scattered light is increased to a state equivalent to the light reception intensity when a reference particle is present in the detection region, and a normal state in which the amount of light is not changed. A reference correction unit corrects the particle detection criteria in the signal processing unit based on the light reception intensity in the light intensity change state, A particle detection device equipped with the following features.

2. The particle detection device according to claim 1, wherein the light intensity switching unit performs the light intensity switching process by moving a light-shielding member of a predetermined shape in the light-passing region.

3. The particle detection device according to claim 1, wherein the light intensity switching unit performs the light intensity switching process by switching between a normal flow channel member through which the particles pass and which is not provided with a light-reducing unit for reducing the amount of light that passes through, and a corrected flow channel member which has the same structure as the normal flow channel member but is provided with the light-reducing unit.

4. The particle detection device according to claim 1, wherein the light intensity switching unit performs the light intensity switching process by controlling the voltage applied to an electrical dimming unit, which changes the amount of light transmitted by controlling the voltage applied to the medium.

5. The particle detection device according to claim 1, wherein the light intensity switching unit performs the light intensity switching process by moving a light scattering member of a predetermined shape in the detection area.

6. The particle detection device according to any one of claims 1 to 5, further comprising a particle entry prevention unit that prevents particles from entering the detection area from the outside during the period when the light intensity switching unit is in a light intensity change state.

7. The particle entry prevention unit has a structure that allows manual switching between a sealed state, in which the entrance to the flow channel member through which the particles pass is sealed, and an open state, The particle detection device according to claim 6, wherein the light intensity switching unit performs the light intensity switching process in conjunction with the switching between the open state and the sealed state.

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