Patent Publication Number: US-9851289-B2

Title: Particle detecting and differentiating device and method

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2013-261305, filed on Dec. 18, 2013, the entire content of which being hereby incorporated herein by reference. 
     FIELD OF TECHNOLOGY 
     The present disclosure relates to an environment evaluating technology, and, in particular, relates to a particle detecting device and particle detecting method. 
     BACKGROUND 
     In clean rooms, such as bio clean rooms, airborne microorganism particles and non-microorganism particles are detected and recorded using particle detecting devices. See, for example, Japanese Unexamined Patent Application Publication No. 2011-83214, Published Japanese Translation of a PCT Application Originally filed in English 2008-530583, and N. Hasegawa, et al.,  Instantaneous Bioaerosol Detection Technology and Its Application , azbil Technical Review, 2-7, Yamatake Corporation, December 2009. The state of wear of the air-conditioning equipment of the clean room can be ascertained from the result of the particle detection. Moreover, a record of particle detection within the clean room may be added as reference documentation to the products manufactured within the clean room. Optical particle detecting devices draw in air from a clean room, for example, and illuminate the drawn-in air with light. If a particle is included in the gas, then the particle that is illuminated by the light will produce scattered light. Moreover, if the particle is a microorganism particle board a non-microorganism fluorescent particle, then the particle that is illuminated with light will emit fluorescence. The particle detecting device is thus able to detect particles in the air through measuring the scattered light and the fluorescent light. For example, if scattered light and florescent light are measured simultaneously, then the particle detecting device evaluates that there is a fluorescent particle. Moreover, if scattered light is measured but no florescent light is measured, the particle detecting device evaluates that there is a non-fluorescent particle. Moreover, there is the need for technologies for accurately detecting particles in a fluid outside of clean rooms as well. See, for example, Japanese Unexamined Patent Application Publication No. 2013-117466. 
     Given this, an aspect of the present disclosure is to provide a particle detecting device and particle detecting method wherein particles can be detected accurately. 
     SUMMARY 
     In an example of the present invention, a particle detecting device is summarized to include: (a) a light source that illuminates, with an excitation beam, a fluid that contains a plurality of particles; (b) a fluorescence measuring instrument that measures fluorescence that is produced in a region that is illuminated by the excitation beam; (c) a scattered light measuring instrument that measures scattered light that is produced in a region that is illuminated by the excitation beam; (d) an interference status evaluating portion that evaluates whether the scattered light that is measured is producing constructive interference or producing destructive interference; and (e) a particle counting portion that counts a plurality of particles depending on the measured interference of the measured light. Note that a “fluid” includes “gases” and “liquids.” “Fluorescent light” includes autofluorescent light. 
     If, for example, the scattered light that is measured produces constructive interference and the lengths of the times over which the scattered light and the fluorescent light are measured are essentially equal, then the particle counting portion will evaluate that all of a plurality of particles is fluorescent particles. Moreover, if, for example, constructive interference is produced by the scattered light that is measured and the lengths of the times over which the scattered light and the fluorescent light are measured are different, then the particle counting portion will evaluate that some of the plurality of particles is fluorescent particles. Furthermore, if the scattered light that is measured produces constructive interference and no florescent light is measured, then the particle counting portion will evaluate that all of the plurality of particles is non-fluorescent particles. 
     If, for example, peaks of scattered light are measured multiple times due to destructive interference, the time at which florescent light began to be measured and the first time at which scattered light began to be measured are essentially equal, and the time at which the measurement of the fluorescent light ended and the last time at which the measurement of scattered light ended are essentially equal, then the particle counting portion evaluates that all of the plurality of particles is fluorescent particles. Moreover, if, for example, peaks of scattered light are measured multiple times due to destructive interference, the time at which florescent light began to be measured and the first time at which scattered light began to be measured are different, or the time at which the measurement of the fluorescent light ended and the last time at which the measurement of scattered light ended are different, then the particle counting portion evaluates that some of the plurality of particles is fluorescent particles. Furthermore, if peaks of scattered light are measured multiple times due to destructive interference and no florescent light is measured, then the particle counting portion evaluates that all of the plurality of particles is non-fluorescent particles. 
     If, for example, scattered light is measured over a prescribed time and temporal variation of the intensity of the scattered light is below that which is prescribed, then the interference status evaluating portion evaluates that the measured scattered light is not producing interference. Moreover, if scattered light is measured over a prescribed time and the temporal variation of the intensity of the scattered light is equal to or greater than that which is prescribed, then the interference status evaluating portion evaluates that the measured scattered light is producing constructive interference. Furthermore, if scattered light peaks are measured multiple times within a prescribed time interval, the interference status evaluating portion evaluates that the measured scattered light is producing destructive interference. 
     Moreover, another aspect of the present invention is a particle detecting method including: (a) directing an excitation beam into a fluid that includes a plurality of particles; (b) measuring fluorescence that is produced in a region illuminated by the excitation beam; (c) measuring scattered light that is produced in a region illuminated by the excitation beam; (d) evaluating whether the measured scattered light is producing constructive interference and whether it is producing destructive interference; and (e) counting a plurality of particles in response to an interference status of the measured scattered light. 
     For example, if the measured scattered light is producing constructive interference and the lengths of times over which the scattered light and the fluorescent light are measured are essentially equal, then there is an evaluation that all of the plurality of particles is fluorescent particles. Moreover, if, for example, the measured light is producing constructive interference and the length of times over which the scattered light and the fluorescent light are measured are different, there is an evaluation that some of the plurality of particles is fluorescent particles. Moreover, if, for example, the measured scattered light is producing constructive interference and no florescent light is measured, then there is an evaluation that all of the plurality of particles is non-fluorescent particles. 
     If, for example, peaks for scattered light are measured multiple times due to destructive interference, the time of the beginning of measurement of the fluorescent light and the time of the beginning of measurement of the first scattered light are essentially equal, and the time of the end of measurement of fluorescent light and the time of the end of measurement of the last scattered light are essentially equal, then there is an evaluation that essentially all of the plurality of particles is fluorescent particles. Furthermore, if, for example, peaks for scattered light are measured multiple times due to destructive interference, and the time of the beginning of measurement of the fluorescent light and the time of the beginning of measurement of the first scattered light are different or the time of the end of measurement of the fluorescent light and the time of the end of measurement of the last scattered light are different, then there is an evaluation that some of the plurality of particles is fluorescent particles. Furthermore, if, for example, peaks for scattered light are measured multiple times due to destructive interference but no florescent light is measured, then there is an evaluation that all of the plurality of particles is non-fluorescent particles. 
     If, for example, scattered light is measured over a prescribed time and temporal variation of the intensity of the scattered light is below that which is prescribed, then there is an evaluation that the measured scattered light is not producing interference. Moreover, if scattered light is measured over a prescribed time and the temporal variation of the intensity of the scattered light is equal to or greater than that which is prescribed, then there is an evaluation that the measured scattered light is producing constructive interference. Furthermore, if, for example, scattered light peaks are measured multiple times within a prescribed time interval, then there is an evaluation that the measured scattered light is producing destructive interference. 
     The present disclosure enables the provision of a particle detecting device and particle detecting method wherein particles can be detected accurately. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a clean room set forth in Example according to the present invention. 
         FIG. 2  is a schematic diagram of a particle detecting device as set forth in the Example according to the present invention. 
         FIG. 3  is a schematic diagram of an optics system for a particle detecting device as set forth in the Example according to the present invention. 
         FIG. 4  is a schematic diagram illustrating the positional relationship between the beam cross-section of the excitation light and a particle in relation to the Example according to the present disclosure. 
         FIG. 5  is a schematic diagram illustrating the positional relationship between the beam cross-section of the excitation light and a particle in relation to the Example according to the present disclosure. 
         FIG. 6  is a schematic diagram illustrating the positional relationship between the beam cross-section of the excitation light and a particle in relation to the Example according to the present disclosure. 
         FIG. 7  is a graph illustrating schematically changes in time of the received light intensities for scattered light in relation to the Example according to the present disclosure. 
         FIG. 8  is a graph illustrating schematically changes in time of the received light intensities for fluorescent light in relation to the Example according to the present disclosure. 
         FIG. 9  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when a single fluorescent particle passes through the beam cross section of the excitation light in relation to the Example according to the present disclosure. 
         FIG. 10  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when a single non-fluorescent particle passes through the beam cross section of the excitation light in relation to the Example according to the present disclosure. 
         FIG. 11  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when two fluorescent particles pass through the beam cross section of the excitation light, producing destructive interference, in relation to the Example according to the present disclosure. 
         FIG. 12  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when, following a single fluorescent particle, a single non-fluorescent particle passes through the beam cross section of the excitation light, producing destructive interference, in relation to the Example according to the present disclosure. 
         FIG. 13  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when, following a single non-fluorescent particle, a single fluorescent particle passes through the beam cross section of the excitation light, producing destructive interference, in relation to the Example according to the present disclosure. 
         FIG. 14  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when two non-fluorescent particles pass through the beam cross section of the excitation light, producing destructive interference, in relation to the Example according to the present disclosure. 
         FIG. 15  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when two fluorescent particles pass through the beam cross section of the excitation light, producing constructive interference, in relation to the Example according to the present disclosure. 
         FIG. 16  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when, following a single fluorescent particle, a single non-fluorescent particle passes through the beam cross section of the excitation light, producing constructive interference, in relation to the Example according to the present disclosure. 
         FIG. 17  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when, following a non-single fluorescent particle, a single fluorescent particle passes through the beam cross section of the excitation light, producing constructive interference, in relation to the Example according to the present disclosure. 
         FIG. 18  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when two non-fluorescent particles pass through the beam cross section of the excitation light, producing constructive interference, in relation to the Example according to the present disclosure. 
         FIG. 19  is a graph illustrating schematically changes in time of the received light intensities for scattered light in relation to Another Example according to the present disclosure. 
         FIG. 20  is a graph illustrating schematically changes in time of the received light intensities for fluorescent light in relation to the Another Example according to the present disclosure. 
         FIG. 21  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when a single fluorescent particle passes through the beam cross section of the excitation light in relation to the Another Example according to the present disclosure. 
         FIG. 22  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when a single non-fluorescent particle passes through the beam cross section of the excitation light in relation to the Another Example according to the present disclosure. 
         FIG. 23  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when two fluorescent particles pass through the beam cross section of the excitation light, producing destructive interference, in relation to the Another Example according to the present disclosure. 
         FIG. 24  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when, following a single fluorescent particle, a single non-fluorescent particle passes through the beam cross section of the excitation light, producing destructive interference, in relation to the Another Example according to the present disclosure. 
         FIG. 25  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when, following a single non-fluorescent particle, a single fluorescent particle passes through the beam cross section of the excitation light, producing destructive interference, in relation to the Another Example according to the present disclosure. 
         FIG. 26  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when two non-fluorescent particles pass through the beam cross section of the excitation light, producing destructive interference, in relation to the Another Example according to the present disclosure. 
         FIG. 27  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when two fluorescent particles pass through the beam cross section of the excitation light, producing constructive interference, in relation to the Another Example according to the present disclosure. 
         FIG. 28  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when, following a single fluorescent particle, a single non-fluorescent particle passes through the beam cross section of the excitation light, producing constructive interference, in relation to the Another Example according to the present disclosure. 
         FIG. 29  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when, following a non-single fluorescent particle, a single fluorescent particle passes through the beam cross section of the excitation light, producing constructive interference, in relation to the Another Example according to the present disclosure. 
         FIG. 30  is a graph illustrating schematically changes in time of the received light intensities for scattered light and fluorescent light when two non-fluorescent particles pass through the beam cross section of the excitation light, producing constructive interference, in relation to the Another Example according to the present disclosure. 
         FIG. 31  is a schematic diagram of an optics system of a particle detecting device according to an alternate example according to the present disclosure. 
         FIG. 32  is a schematic diagram of an optics system of a particle detecting device according to another alternate example according to the present disclosure. 
         FIG. 33  is a schematic diagram of an optics system of a particle detecting device according to yet another alternate example according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Examples of the present disclosure will be described below. In the descriptions of the drawings below, identical or similar components are indicated by identical or similar codes. Note that the diagrams are schematic. Consequently, specific measurements should be evaluated in light of the descriptions below. Furthermore, even within these drawings there may, of course, be portions having differing dimensional relationships and proportions. 
     Example 
     As illustrated in  FIG. 1 , a particle detecting device  1  according to the present example is disposed in, for example, a clean room  70 . In the clean room  70 , clean air is blown in through a duct  71  and through a blowing opening  72  having an ultrahigh performance air filter such as a HEPA filter (High Efficiency Particulate Air Filter) or ULPA filter (Ultra Low Penetration Air Filter), or the like. 
     Manufacturing lines  81  and  82  are arranged inside of the clean room  70 . The manufacturing lines  81  and  82  are manufacturing lines, for, for example, precision instruments, electronic components, or semiconductor devices. Conversely, the manufacturing lines  81  and  82  may be manufacturing lines for foodstuffs, beverages, or pharmaceuticals. For example, in the manufacturing lines  81  and  82 , an infusion liquid may be filled into an intravenous infusion device or a hypodermic. Conversely, the manufacturing lines  81  and  82  may manufacture oral medications or Chinese herb medications. On the other hand, the manufacturing lines  81  and  82  may fill containers with a vitamin drink or beer. 
     The manufacturing lines  81  and  82  normally are controlled so that microorganism particles and non-microorganism particles, and the like, are not dispersed into the air within the clean room  70 . However, manufacturing lines  81  and  82 , for some reason, are sources that produce microorganism particles and non-microorganism particles that become airborne in the clean room  70 . Moreover, factors other than the manufacturing lines  81  and  82  also disperse microorganism particles and non-microorganism particles into the air of the clean room  70 . 
     Examples of microorganism particles that may become airborne in the clean room  70  include microbes. Examples of such microbes include Gram-negative bacteria, Gram-positive bacteria, and fungi such as mold spores.  Escherichia coli , for example, can be listed as an example of a Gram-negative bacterium.  Staphylococcus epidermidis, Bacillus atrophaeus, Micrococcus lylae , and  Corynebacterium afermentans  can be listed as examples of Gram-positive bacteria.  Aspergillus niger  can be listed as an example of a fungus such as a mold spore. However, the microorganism particles that may become airborne in the clean room  70  are not limited to these specific examples. Examples of non-microorganism particles that may become airborne in the clean room  70  include splashed chemical substances, pharmaceuticals, or foodstuffs, along with dust, dirt, grime, and the like. 
     When a particle is illuminated with light, Mie scattered light, for example, is produced at the particle. Moreover, if a microorganism particle is illuminated with light, the nicotinamide adenine dinucleotide (NADH) and the flavins, and the like, that are included in microorganism particle produce fluorescent light. The wavelength of the fluorescence that derives from NADH is in the neighborhood of 480 nm. Moreover, the wavelength of the fluorescence that derives from flavins is in the neighborhood of 530 nm. Moreover, non-microorganism fluorescent particles that fall off of a gown, made from polyester, for example, that has been cleaned will emit fluorescence when illuminated with light. Moreover, polystyrene particles also emit fluorescence, and then fade. Note that “fluorescent light” includes autofluorescent light. In the below, both microorganism particles and non-microorganism fluorescent particles will be referred to as “fluorescent particles.” 
     Here, as illustrated in  FIG. 2  and  FIG. 3 , a particle detecting device  1  includes a light source  10  for directing an excitation beam into a fluid that contains a plurality of particles, a fluorescence measuring instrument  2  for measuring fluorescent light that is produced in the region that is illuminated by the excitation beam, and a scattered light measuring instrument  5  for measuring the scattered light that is produced in the region that is illuminated by the excitation beam. The fluorescence measuring instrument  2  and the scattered light measuring instrument  5  are connected electrically to a central calculating processing device (CPU)  300 . The CPU  300  includes an interference status evaluating portion  301 , for evaluating whether the measured scattered light is producing constructive interference and whether it is producing destructive interference, and a particle counting portion  302  for counting a plurality of particles in accordance with the interference status of the measured scattered light. 
     While, in the Example, the explanation will be for an example wherein the fluid that is subject to inspection is air, examples of the present invention are not limited thereto, but rather the fluid that is subject to inspection may be a liquid. 
     The light source  10 , the fluorescence measuring instrument  2 , and the scattered light measuring instrument  5  are provided in a frame  30 . A light source driving power supply  11 , for supplying electric power to the light source  10 , is connected to the light source  10 . A power supply controlling device  12 , for controlling the electric power that is supplied to the light source  10 , is connected to the light source driving power supply  11 . The particle detecting device  1  further includes a first suction device for drawing the air, into the frame  30  that is illustrated in  FIG. 2 , from within the clean room  70 , illustrated in  FIG. 1 . The air that is drawn in by the first suction device is expelled from the tip end of a nozzle  40 A of the flow path, shown in  FIG. 3  within the frame  30 . The air that is emitted from the tip end of the nozzle  40 A is drawn in, through a nozzle  40 B, by a second section device that is disposed within the frame  30 , facing the tip end of the nozzle  40 A. 
     Through a light source  10  emits through, converting lenses  61  and  62 , for example, an excitation beam of a wide wavelength band towards the gas flow of the air that is expelled from the tip end of the nozzle  40 A and drawn into the second suction device from the nozzle  40 B. A laser, a light-emitting diode (LED), a halogen lamp, a xenon lamp, or the like, may be used for the light source  10 . The wavelength of the excitation beam is, for example, between 250 and 550 nm. The excitation beam may be of visible light, or of ultraviolet light. If the excitation beam is of visible light, then the wavelength of the excitation beam is within a range of, for example, 400 to 550 nm, for example, 405 nm. If the excitation beam is ultraviolet radiation, then the wavelength of the excitation beam is in a range of, for example, between 300 and 380 nm, for example, 340 nm. However, the wavelength of the excitation beam is not limited to these. 
     If a particle is included in the gas flow that is expelled from the nozzle  40 A, Mie scattered light is produced at the particle that is illuminated by the excitation beam. The Mie scattered light that is produced by the particles is measured by the scattered light measuring instrument  5  illustrated in  FIG. 2 . The scattered light measuring instrument  5  is provided with a scattered light photodetecting element  50  for detecting scattered light. A photodiode, or the like, may be used for the scattered light photodetecting element  50 , where, when light is received, the optical energy is converted into electrical energy. An amplifier  51 , for amplifying the electric current that is produced by the scattered light photodetecting element  50  is connected to the scattered light photodetecting element  50 . An amplifier power supply  52 , for supplying electric power to the amplifier  51 , is connected to the amplifier  51 . Furthermore, a scattered light intensity calculating device  53 , for receiving the electric current that has been amplified by the amplifier  51 , to calculate the intensity of the scattered light that has been received by the scattered light photodetecting element  50 , is connected to the amplifier  51 . A scattered light intensity storing device  54 , for storing the intensity of the scattered light, calculated by the scattered light intensity calculating device  53 , is connected to the scattered light intensity calculating device  53 . 
     As illustrated in  FIG. 4 , when a first and a second particle are carried in a gas flow and the first particle enters into the cross-section of the excitation beam, scattered light is produced by the first particle, and is detected by a photosensitive surface of the scattered light photodetecting element  50 . Additionally, if, as illustrated in  FIG. 5 , the first and second particles both enter into the cross-section of the excitation beam, scattered light will be produced by both the first and the second particles, to be detected by the photosensitive surface of the scattered light photodetecting element  50 . If here both the first and the second particles exist within an interference area of the excitation beam, then the scattered light produced by the first particle and the scattered light produced by the second particle will interfere depending on the difference in the optical paths between the optical path length L 1  from the first particle to the photosensitive surface of the scattered light photodetecting element  50  and the optical path length L 2  from the second particle to the photosensitive surface of the scattered light photodetecting element  50 . Thereafter, when the first particle exits the beam cross-section of the excitation beam, as illustrated in  FIG. 6 , scattered light will be produced by the second particle alone, to be detected by the scattered light photodetecting element  50 . 
     Note that if the light source  10  is a unitary coherent light source, such as a laser, then the susceptibility to interference of the excitation beam will be high, and the interference area will be large. If the light source  10  is an incoherent light source, such as an LED, a halogen lamp, a xenon lamp, or the like, then the susceptibility to interference in the excitation beam will be low, and the interference area will be small. However, regardless of whether the light source  10  is a coherent light source or an incoherent light source, in either case there will be interference between the scattered light produced by the first particle and the scattered light produced by the second particle when both the first and second particles are within the interference area of the excitation beam. 
       FIG. 7( a )  illustrates the temporal variation in the scattered light intensity detected by the scattered light photodetecting element  50  when only a single particle passes through the cross-section of an excitation beam in a case wherein the optical intensity of the excitation beam is uniform across the cross-section thereof.  FIG. 7( b )  illustrates the temporal variation of the intensity of the scattered light that is detected by the scattered light photodetecting element  50  when two particles pass through the cross-section of the excitation beam wherein the difference in the optical path lengths between and optical path length L 1  between the first particle and the photosensitive surface of the scattered light photodetecting element  50  and the optical path length L 2  between the second particle and the photosensitive surface of the scattered light photodetecting element  50  corresponds to, for example, an odd multiple of the half wavelengths of the scattered light so that the scattered lights interfere destructively with each other.  FIG. 7( c )  illustrates the temporal variation in the intensity of the scattered light that is detected by the scattered light photodetecting element  50  when two particles pass through the cross-section of the excitation beam and the difference in the optical path lengths corresponds, for example, to an integer multiple of the wavelength of the scattered light so that the scattered lights interfere constructively with each other. 
     In  FIG. 7( b )  and  FIG. 7( c ) , during the interval from time t 1  to t 2 , only the first particle is passing through the cross-section of the excitation beam. In the interval from time t 2  to t 3 , the first and second particles are passing through the cross-section of the excitation beam. At time t 3 , the first particle exits the cross-section of the excitation beam, and during the interval from time t 3  to t 4 , only the second particle is passing through the cross-section of the excitation beam. 
     In  FIG. 7( b ) , destructive interference is produced between the scattered lights that are produced by the first and second particles, during the interval from time t 2  through t 3 , and thus the intensity of the scattered light detected by the scattered light photodetecting element  50  is essentially zero. Because of this, in intervals within a prescribed time, within the interval from time t 1  to time t 4 , peaks for the scattered light will be measured twice. Note that although there may be cases wherein the intensity of the scattered light that is detected will not be perfectly zero, even when destructive interference occurs, because of false signals due to stray random electric noise or stray random electromagnetic emission lines, still it is possible to suppress the effects of false signals through, for example, canceling any calculated optical intensity that is less than a standard value. 
     In  FIG. 7( c ) , the intensity of the scattered light that is detected by the scattered light photodetecting element  50  increases due to the occurrence of constructive interference between the scattered lights produced by the first and second particles, during the interval from time t 2  through t 3 . Because of this, the temporal variation of the intensity of the scattered light, which is continuously measured without interruption across the prescribed time during the interval from time t 1  through time t 4 , will be above a prescribed standard for the scattered light. Note that this prescribed standard for the scattered light is, for example, a threshold value that is able to discriminate between the temporal variation of the intensity of scattered light produced by a single particle and the temporal variation in the intensity when produced through constructive interference of the scattered light that is produced by a plurality of particles, acquired by checking both in advance. 
     If a microorganism particle, such as a bacterium, or the like, is included in the gas flow that is expelled from the nozzle  40 A, illustrated in  FIG. 3 , scattered light is produced at the microorganism particle, and, additionally, the microorganism particle that is illuminated by the excitation beam will emit fluorescence. Moreover, even in a case wherein a non-microorganism fluorescent particle, such as a polyester particle, is included in the gas flow that is expelled from the nozzle  40 A, scattered light will be produced at the non-microorganism fluorescent particle, and also the non-microorganism fluorescent particle that is illuminated by the excitation beam will emit fluorescence. Note that with fluorescent light, there is no interference between the fluorescent lights because of the phase of the excitation beam being random. 
     The fluorescence measuring instrument  2 , illustrated in  FIG. 2 , measures the fluorescence that is produced by the microorganism particles and the non-microorganism fluorescent particles. The fluorescence measuring instrument  2  is provided with a fluorescence detecting element  20  for detecting fluorescent light. A photodiode or a photoelectron multiplier tube, or the like, may used for the fluorescence detecting element  20 , where, when fluorescent light is received, the optical energy is converted into electrical energy. An amplifier  21 , for amplifying the electric current that is produced by the fluorescence detecting element  20  is connected to the fluorescence detecting element  20 . An amplifier power supply  22 , for supplying electric power to the amplifier  21 , is connected to the amplifier  21 . Furthermore, a fluorescent light intensity calculating device  23 , for receiving the electric current that has been amplified by the amplifier  21 , to calculate the intensity of the fluorescence that has been received by the fluorescence detecting element  20 , is connected to the amplifier  21 . A fluorescent light intensity storing device  24 , for storing the intensity of the fluorescence, calculated by the fluorescent light intensity calculating device  23 , is connected to the fluorescent light intensity calculating device  23 . 
       FIG. 8( a )  illustrates the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when only a single fluorescent particle passes through the cross-section of an excitation beam in a case wherein the optical intensity of the excitation beam is uniform across the cross-section thereof.  FIG. 8( b )  illustrates the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when two single fluorescent particles pass through the cross-section of the excitation beam. In  FIG. 8( b ) , first, at time t 1 , the first fluorescent particle enters into the cross-section of the excitation beam alone, and during the interval from time t 1  to t 2 , only the first fluorescent particle is passing through the cross-section of the excitation beam. At time t 2 , the second fluorescent particle also enters into the cross-section of the excitation beam, and during the interval from time t 2  to t 3 , both the first and second fluorescent particles are passing through the cross-section of the excitation beam. At time t 3 , the first fluorescent particle exits the cross-section of the excitation beam, and during the interval from time t 3  to t 4 , only the second fluorescent particle is passing through the cross-section of the excitation beam. At time t 4 , the second fluorescent particle exits the cross-section of the excitation beam. 
     In the interval from time t 2  through t 3 , there is no interference between the fluorescence emitted from the first and second fluorescent particles, and thus the respective fluorescent intensities add together. Because of this, the temporal variation of the intensity of the fluorescent light, which is continuously measured without interruption across the prescribed time during the interval from time t 1  through time t 4 , will be above a prescribed standard for the fluorescent light. Note that this prescribed standard for the fluorescent light is, for example, a threshold value that is able to discriminate between the temporal variation of the intensity of fluorescent light produced by a single fluorescent particle and the temporal variation in the intensity of the fluorescent light that is produced by a plurality of fluorescent particles, acquired by checking both in advance. 
       FIGS. 9( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when only a single fluorescent particle passes through the cross-section of an excitation beam in a case wherein the optical intensity of the excitation beam is uniform across the cross-section thereof. In this case there is no interference, and thus, the temporal variation of the intensity of the scattered light, which is continuously measured without interruption across the prescribed time during the interval from time t 1  through time t 3 , will be less than the prescribed standard for the scattered light. Additionally, the temporal variation of the intensity of the fluorescent light, which is continuously measured without interruption across the prescribed time during the interval from time t 1  through time t 3 , will be less than the prescribed standard for the fluorescent light. 
     Additionally, the time t 1  at which the measurement begins with the scattered light photodetecting element  50  detecting the scattered light is essentially the same as time the t 1  at which the fluorescent light photodetecting element  20  begins measuring through detecting the fluorescent light. Furthermore, the time t 3  that is the end of the measurement, when the scattered light photodetecting element  50  ceases detecting scattered light, is essentially equal to the time t 3  at which the fluorescent light photodetecting element  20  ends the measurement because fluorescent light ceases to be detected. Because of this, the length of time over which the scattered light is measured and the length of time over which the fluorescent light is measured are essentially equal. Note that the clock monitoring the time over which the scattered light is measured and the clock monitoring the time over which the fluorescent light is measured will not be perfectly synchronized, due to drift in the liquid crystal oscillators of the internal clocks in the fluorescence measuring instrument  2  and the scattered light measuring instrument  5 , and the like, producing error between the time over which the scattered light is measured and the time over which the fluorescent light is measured. However, discrepancies in times within a tolerance range are ignored. 
       FIGS. 10( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when only a single non-fluorescent particle passes through the cross-section of the excitation beam. In this case as well there is no interference, and thus, the temporal variation of the intensity of the scattered light, which is continuously measured without interruption across the prescribed time during the interval from time t 1  through time t 3 , will be less than the prescribed standard for the scattered light. Note that the non-fluorescent particles do not emit fluorescent light, so during the interval that the photodetecting element  50  is detecting scattered light, the intensity of the light detected by the fluorescent light photodetecting element  20  remains at essentially zero. 
       FIGS. 11( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when two fluorescent particles pass through the cross-section of the excitation beam and destructive interference is produced between the scattered lights that are produced by the two fluorescent particles. In this case, peaks for the scattered light will be measured twice in intervals within a prescribed time, within the interval from time t 1  to time t 4 , due to the destructive interference. Additionally, because in the interval from time t 2  to time t 3 , the fluorescent lights that are produced from the two fluorescent particles add together, so that the temporal variation of the intensity of the fluorescent light, which is continuously measured without interruption across the prescribed time during the interval from time t 1  through time t 4 , will be equal to or greater than the prescribed standard for the fluorescent light. Additionally, the time t 1  at which the measurement begins with the scattered light photodetecting element  50  detecting the scattered light is essentially the same as time the t 1  at which the fluorescent light photodetecting element  20  begins measuring through detecting the fluorescent light. Furthermore, the time t 4  that is the end of the measurement, when the scattered light photodetecting element  50  ceases detecting scattered light, is essentially equal to the time t 4  at which the fluorescent light photodetecting element  20  ends the measurement because fluorescent light ceases to be detected. 
       FIGS. 12( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when one non-fluorescent particle following one fluorescent particle pass through the cross-section of the excitation beam and destructive interference is produced between the scattered light that is produced by the fluorescent particle and the scattered light that is produced by the non-fluorescent particle. In this case, peaks for the scattered light will be measured twice in intervals within a prescribed time, within the interval from time t 1  to time t 4 , due to the destructive interference. Additionally, the time t 1  at which the measurement begins with the scattered light photodetecting element  50  detecting the scattered light is essentially the same as time the t 1  at which the fluorescent light photodetecting element  20  begins measuring through detecting the fluorescent light. However, because the non-fluorescent particle that exits the cross-section of the excitation beam after the fluorescent particle does not emit fluorescent light, the time t 4  that is the end of the measurement, when the scattered light photodetecting element  50  ceases detecting scattered light, is different from the time t 3  at which the fluorescent light photodetecting element  20  ends the measurement because fluorescent light ceases to be detected. 
       FIGS. 13( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when one fluorescent particle following one non-fluorescent particle pass through the cross-section of the excitation beam and destructive interference is produced between the scattered light that is produced by the non-fluorescent particle and the scattered light that is produced by the fluorescent particle. In this case, peaks for the scattered light will be measured twice in intervals within a prescribed time, within the interval from time t 1  to time t 4 , due to the destructive interference. Additionally, the time t 1  at which the measurement begins with the scattered light photodetecting element  50  detecting the scattered light is different from as time the t 2  at which the fluorescent light photodetecting element  20  begins measuring through detecting the fluorescent light. However, because the fluorescent particle that exits the cross-section of the excitation beam after the non-fluorescent particle emits fluorescent light until time t 4 , the time t 4  that is the end of the measurement, when the scattered light photodetecting element  50  ceases detecting scattered light, is essentially the same as the time t 4  at which the fluorescent light photodetecting element  20  ends the measurement because fluorescent light ceases to be detected. 
       FIGS. 14( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when two non-fluorescent particles pass through the cross-section of the excitation beam and destructive interference is produced between the scattered lights that are produced by the two non-fluorescent particles. In this case, peaks for the scattered light will be measured twice in intervals within a prescribed time, within the interval from time t 1  to time t 4 , due to the destructive interference. Moreover, because the two non-fluorescent particles do not emit fluorescent light, during the interval that the photodetecting element  50  is detecting scattered light fluorescent light is also not measured, so the intensity of the light detected by the fluorescent light photodetecting element  20  remains at essentially zero. 
       FIGS. 15( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when two fluorescent particles pass through the cross-section of the excitation beam and constructive interference is produced between the scattered lights that are produced by the two fluorescent particles. Because of the constructive interference in this case, the temporal variation of the intensity of the scattered light, which is continuously measured without interruption across the prescribed time during the interval from time t 1  through time t 4 , will be above a prescribed standard for the scattered light. Additionally, because in the interval from time t 2  to time t 3 , the fluorescent lights that are produced from the two fluorescent particles add together, so that the temporal variation of the intensity of the fluorescent light, which is continuously measured without interruption across the prescribed time during the interval from time t 1  through time t 4 , will be equal to or greater than the prescribed standard for the fluorescent light. Additionally, the time t 1  at which the measurement begins with the scattered light photodetecting element  50  detecting the scattered light is essentially the same as time the t 1  at which the fluorescent light photodetecting element  20  begins measuring through detecting the fluorescent light. Furthermore, the time t 4  that is the end of the measurement, when the scattered light photodetecting element  50  ceases detecting scattered light, is essentially equal to the time t 4  at which the fluorescent light photodetecting element  20  ends the measurement because fluorescent light ceases to be detected. Because of this, the times over which the scattered light in the fluorescent light are measured will be essentially equal. 
       FIGS. 16( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when one non-fluorescent particle following one fluorescent particle pass through the cross-section of the excitation beam and constructive interference is produced between the scattered light that is produced by the fluorescent particle and the scattered light that is produced by the non-fluorescent particle. Because of the constructive interference in this case, the temporal variation of the intensity of the scattered light, which is continuously measured without interruption across the prescribed time during the interval from time t 1  through time t 4 , will be above a prescribed standard for the scattered light. Additionally, the time t 1  at which the measurement begins with the scattered light photodetecting element  50  detecting the scattered light is essentially the same as time the t 1  at which the fluorescent light photodetecting element  20  begins measuring through detecting the fluorescent light. However, because the non-fluorescent particle that exits the cross-section of the excitation beam after the fluorescent particle does not emit fluorescent light, the time t 4  that is the end of the measurement, when the scattered light photodetecting element  50  ceases detecting scattered light, is different from the time t 3  at which the fluorescent light photodetecting element  20  ends the measurement because fluorescent light ceases to be detected. Because of this, the times over which the scattered light in the fluorescent light are measured will be different. 
       FIGS. 17( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when one fluorescent particle following one non-fluorescent particle pass through the cross-section of the excitation beam and constructive interference is produced between the scattered light that is produced by the non-fluorescent particle and the scattered light that is produced by the fluorescent particle. Because of the constructive interference in this case, the temporal variation of the intensity of the scattered light, which is continuously measured without interruption across the prescribed time during the interval from time t 1  through time t 4 , will be above a prescribed standard for the scattered light. Additionally, the time t 1  at which the measurement begins with the scattered light photodetecting element  50  detecting the scattered light is different from as time the t 2  at which the fluorescent light photodetecting element  20  begins measuring through detecting the fluorescent light. Because of this, the times over which the scattered light in the fluorescent light are measured will be different. However, because the fluorescent particle that exits the cross-section of the excitation beam after the non-fluorescent particle emits fluorescent light until time t 4 , the time t 4  that is the end of the measurement, when the scattered light photodetecting element  50  ceases detecting scattered light, is essentially the same as the time t 4  at which the fluorescent light photodetecting element  20  ends the measurement because fluorescent light ceases to be detected. 
       FIGS. 18( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when two non-fluorescent particles pass through the cross-section of the excitation beam and constructive interference is produced between the scattered lights that are produced by the two non-fluorescent particles. Because of the constructive interference in this case, the temporal variation of the intensity of the scattered light, which is continuously measured without interruption across the prescribed time during the interval from time t 1  through time t 4 , will be above a prescribed standard for the scattered light. Moreover, because the two non-fluorescent particles do not emit fluorescent light, during the interval that the photodetecting element  50  is detecting scattered light fluorescent light is also not measured, so the intensity of the light detected by the fluorescent light photodetecting element  20  remains at essentially zero. 
     The interference status evaluating portion  301  and the particle counting portion  302 , illustrated in  FIG. 2 , read out the temporal variation of the intensity of the scattered light from the scattered light intensity storing device  54 . Additionally, the interference status evaluating portion  301  and the particle counting portion  302  read out the temporal variation of the intensity of the fluorescent light from the fluorescent light intensity storing device  24 . A data storing device  351  is connected to the CPU  300 . The data storing device  351  stores a prescribed standard for the scattered light. The prescribed standard for the scattered light is adjusted as appropriate in response to the sizes, refractive indices, and reflectivities of the particles that are to be detected, and in accordance with the size of the scattered light photodetecting element  50 , and the like. The interference status evaluating portion  301  and the particle counting portion  302  read out the prescribed standard, for the scattered light, from the data storing device  351 . 
     The interference status evaluating portion  301  measures the scattered light continuously, without interruption, over the prescribed time interval, as illustrated in  FIG. 9  and  FIG. 10 , and if the temporal variation of the intensity of the scattered light is less than the prescribed standard for the scattered light, evaluates that a single particle has passed the cross-section of the excitation beam and that no interference was produced within the scattered light that was measured. If, as illustrated in any of the  FIG. 11  through  FIG. 14 , peaks in the scattered light are measured multiple times during the interval within the prescribed time, then the interference status evaluating portion  301  evaluates that at least two particles have passed through the cross-section of the excitation beam, and that destructive interference was produced in the scattered light that was measured. Furthermore, as illustrated in any of  FIG. 15  through  FIG. 18 , if scattered light is measured continuously without interruption across the prescribed time and the temporal variation of the intensity of the scattered light is equal to or greater than the prescribed standard for the scattered light, then the interference status evaluating portion  301  evaluates that at least two particles have passed through the cross-section of the excitation beam and that constructive interference was produced in the scattered light that was measured. 
     If, as illustrated in  FIG. 2 , the interference status evaluating portion  301  evaluates that a single particle has passed through the cross-section of the excitation beam, the particle counting portion  302  checks whether or not fluorescent light was measured. If, as illustrated in  FIG. 9 , fluorescent light was measured, then the particle counting portion  302 , illustrated in  FIG. 2 , evaluates that the single particle that has passed through the cross-section of the excitation beam was a fluorescent particle, and records, in the results storing device  352  that is connected to the CPU  300 , that a single fluorescent particle was detected. Moreover, if, as illustrated in  FIG. 10 , no fluorescent light was measured, then the particle counting portion  302 , illustrated in  FIG. 2 , evaluates that the single particle that passed through the cross-section of the excitation beam was a non-fluorescent particle, and records, in the results storing device  352 , that a single non-fluorescent particle was detected. 
     If, as illustrated in  FIG. 2 , the interference status evaluating portion  301  evaluates that, for example, two particles have passed through the cross-section of the excitation beam, and that the measured scattered light has produced destructive interference, the particle counting portion  302  checks whether or not fluorescent light was measured. Moreover, if, as illustrated in  FIG. 11  through  FIG. 13 , fluorescent light was measured, then the particle counting portion  302 , illustrated in  FIG. 2 , evaluates that at least one of the two particles that passed through the cross-section of the excitation beam was a fluorescent particle. 
     Moreover, if, as illustrated in  FIG. 11 , the time at which the measurement of the fluorescent light began is essentially equal to the time at which the measurement of the first scattered light began, and the time at which the measurement of the fluorescent light ended was essentially equal to the time at which the measurement of the last scattered light ended, then the particle counting portion  302 , illustrated in  FIG. 2 , evaluates that both of the two particles that passed through the beam cross-section of the excitation beam were fluorescent particles, and stores, in the results storing device  352 , that two fluorescent particles were detected. Moreover, if, as illustrated in  FIG. 13 , the time at which the measurement of the fluorescent light began is different from the time at which the measurement of the first scattered line began, or, as illustrated in  FIG. 12 , the time at which the measurement of the fluorescent light ended is different from the end of measurement of the scattered light, then the particle counting portion  302 , illustrated in  FIG. 2 , evaluates that one of the two particles that passed through the cross-section of the excitation beam was a fluorescent particle and the other particle was a non-fluorescent particle, and records, in the results storing device  352 , that there was a single fluorescent particle and a single non-fluorescent particle. 
     If, as illustrated in  FIG. 14 , no fluorescent light was measured, then the particle counting portion  302 , illustrated in  FIG. 2 , evaluates that both particles that passed through the cross-section of the excitation beam were non-fluorescent particles, and records, in the results storing device  352 , that two non-fluorescent particles were detected. 
     If, as illustrated in  FIG. 2 , the interference status evaluating portion  301  evaluates that, for example, two particles have passed through the cross-section of constructive excitation beam, and that the measured scattered light has produced destructive interference, the particle counting portion  302  checks whether or not fluorescent light was measured. Moreover, if, as illustrated in  FIG. 15  through  FIG. 17 , fluorescent light was measured, then the particle counting portion  302 , illustrated in  FIG. 2 , evaluates that at least one of the two particles that passed through the cross-section of the excitation beam was a fluorescent particle. 
     Moreover, if, as illustrated in  FIG. 15 , the lengths of time measured for the scattered light and for the fluorescent light were essentially equal, then the particle counting portion  302 , illustrated in  FIG. 2 , evaluates that both particles that passed through the cross-section of the excitation beam were fluorescent particles, and records, in the results storing device  352 , that two fluorescent particles were detected. Moreover, if, as illustrated in  FIG. 16  and  FIG. 17 , the lengths of time measured for the scattered light and for the fluorescent light were different, then the particle counting portion  302 , illustrated in  FIG. 2 , evaluates that one of the two particles that passed through the cross-section of the excitation beam was a fluorescent particle and the other particle was a non-fluorescent particle, and records, in the results storing device  352 , the detection of one fluorescent particle and of one non-fluorescent particle. 
     If, as illustrated in  FIG. 18 , no fluorescent light was measured, then the particle counting portion  302 , illustrated in  FIG. 2 , evaluates that both particles that passed through the cross-section of the excitation beam were non-fluorescent particles, and records, in the results storing device  352 , that two non-fluorescent particles were detected. Note that the results recorded in the results storing device  352 , described above, may also be outputted from an outputting device  401 , such as a printer, a display, or the like, connected to the CPU  300 . 
     With the conventional particle detecting device, no thought is given to interference between the scattered lights, so that each time a scattered light is detected, the detection of a single particle is recorded. However, if, as illustrated in  FIG. 15  through  FIG. 18 , there is constructive interference between the scattered light from a plurality of particles, scattered light is measured continuously, without interruption, over the prescribed time, and thus the number of times that scattered light has been measured will be only once. Because of this, in a conventional detecting device the record will be incorrect, with only a single particle being counted, despite, for example, two particles passing through the cross-section of the excitation beam. 
     In contrast, with the particle detecting device  1  according to the Example, illustrated in  FIG. 2 , an evaluation is performed as to whether there is constructive interference in the scattered light and whether there is destructive interference, to count a plurality of particles depending on the interference status of the scattered light. Because of this, even if there is constructive interference between the scattered lights, still the particle detecting device  1  counts a plurality of particles, enabling accurate recording. Furthermore, the particle detecting device  1  can count dividing the plurality of particles into fluorescent particles and non-fluorescent particles based on the measurement times of the scattered lights, the temporal variation within the intensities of the scattered lights, and the measurement times for the florescent lights, and the like. 
     Another Example 
     While in the Example the explanation was for a case wherein the optical intensity was uniform in the cross-section of the excitation beam, the excitation beam may be a Gaussian beam instead.  FIG. 19( a )  shows the temporal variation in the intensity of the scattered light detected by the scattered light photodetecting element  50 , illustrated in  FIG. 2 , when a single particle passes through the cross-section of the excitation beam when the excitation beam is a Gaussian beam.  FIG. 19( a )  shows the temporal variation in the intensity of the scattered light detected by the scattered light photodetecting element  50 , illustrated in  FIG. 2 , when two particles pass through the cross-section of the excitation beam and the scattered lights destructively interfere with each other.  FIG. 19( c )  shows the temporal variation in the intensity of the scattered light detected by the scattered light photodetecting element  50 , illustrated in  FIG. 2 , when two particles pass through the cross-section of the excitation beam and the scattered lights constructively interfere with each other. 
     In the case wherein there is no interference, in  FIG. 19( a ) , the temporal variation of the intensity of the scattered light, which is continuously measured without interruption across the prescribed time, will be less than the prescribed standard for the scattered light. In the case wherein there is destructive interference, in  FIG. 19( b ) , peaks for the scattered light will be measured twice within a prescribed time. In the case wherein there is constructive interference, in  FIG. 19( c ) , the temporal variation of the intensity of the scattered light, which is continuously measured without interruption across the prescribed time, will be equal to or greater than the prescribed standard for the scattered light. 
       FIG. 20( a )  illustrates the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when only a single fluorescent particle passes through the cross-section of an excitation beam in a case wherein the excitation beam is a Gaussian beam.  FIG. 20( b )  illustrates the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when two single fluorescent particles pass through the cross-section of the excitation beam. In  FIG. 20( b ) , there is no interference between the fluorescence emitted from the first and second fluorescent particles, and thus the respective fluorescent intensities add together. 
       FIGS. 21( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when only a single fluorescent particle passes through the cross-section of the excitation beam in a case wherein the excitation beam is a Gaussian beam. In this case the temporal variation of the intensity of the scattered light, which is continuously measured without interruption across the prescribed time, will be less than the prescribed standard for the scattered light. Additionally, the temporal variation of the intensity of the fluorescent light, which is continuously measured without interruption across the prescribed time, will be less than the prescribed standard for the fluorescent light. Additionally, the time t 1  at which the measurement begins with the scattered light photodetecting element  50  detecting the scattered light is essentially the same as time the t 1  at which the fluorescent light photodetecting element  20  begins measuring through detecting the fluorescent light. Furthermore, the time t 3  that is the end of the measurement, when the scattered light photodetecting element  50  ceases detecting scattered light, is essentially equal to the time t 3  at which the fluorescent light photodetecting element  20  ends the measurement because fluorescent light ceases to be detected. 
       FIGS. 22( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when only a single non-fluorescent particle passes through the cross-section of the excitation beam. In this case, the intensity of the light detected by the fluorescent light photodetecting element  20  remains at essentially zero during the interval that the photodetecting element  50  is detecting scattered light. 
       FIGS. 23( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when two fluorescent particles pass through the cross-section of the excitation beam and destructive interference is produced between the scattered lights that are produced by the two fluorescent particles. In this case, the scattered light peaks will be measured twice within a prescribed time interval. Additionally, the temporal variation of the intensity of the fluorescent light, which is continuously measured without interruption across the prescribed time, will be equal to or greater than the prescribed standard for the fluorescent light. Additionally, the time t 1  at which the measurement begins with the scattered light photodetecting element  50  detecting the scattered light is essentially the same as time the t 1  at which the fluorescent light photodetecting element  20  begins measuring through detecting the fluorescent light. Furthermore, the time t 4  that is the end of the measurement, when the scattered light photodetecting element  50  ceases detecting scattered light, is essentially equal to the time t 4  at which the fluorescent light photodetecting element  20  ends the measurement because fluorescent light ceases to be detected. 
       FIGS. 24( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when one non-fluorescent particle following one fluorescent particle pass through the cross-section of the excitation beam and destructive interference is produced between the scattered light that is produced by the fluorescent particle and the scattered light that is produced by the non-fluorescent particle. In this case, the scattered light peaks will be measured twice within a prescribed time interval. Additionally, the time t 4  at which the measurement ends when the scattered light photodetecting element  50  ceases to detect scattered light is different from time the t 3  when the measurement by the fluorescent light photodetecting element  20  is completed because it ceases to detect fluorescent light. 
       FIGS. 25( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when one fluorescent particle following one non-fluorescent particle pass through the cross-section of the excitation beam and destructive interference is produced between the scattered light that is produced by the non-fluorescent particle and the scattered light that is produced by the fluorescent particle. In this case, the scattered light peaks will be measured twice within a prescribed time interval. Additionally, the time t 1  at which the measurement begins with the scattered light photodetecting element  50  detecting the scattered light is different from as time the t 2  at which the fluorescent light photodetecting element  20  begins measuring through detecting the fluorescent light. 
       FIGS. 26( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when two non-fluorescent particles pass through the cross-section of the excitation beam and destructive interference is produced between the scattered lights that are produced by the two non-fluorescent particles. In this case, the scattered light peaks will be measured twice within a prescribed time interval. Moreover, the intensity of the fluorescent light detected by the fluorescent light photodetecting element  20  remains at essentially zero. 
       FIGS. 27( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when two fluorescent particles pass through the cross-section of the excitation beam and constructive interference is produced between the scattered lights that are produced by the two fluorescent particles. In this case the temporal variation of the intensity of the scattered light, which is continuously measured without interruption across the prescribed time, will be equal to or greater than the prescribed standard for the scattered light. Additionally, the temporal variation of the intensity of the fluorescent light, which is continuously measured without interruption across the prescribed time, will be equal to or greater than the prescribed standard for the fluorescent light. Additionally, the time t 1  at which the measurement begins with the scattered light photodetecting element  50  detecting the scattered light is essentially the same as time the t 1  at which the fluorescent light photodetecting element  20  begins measuring through detecting the fluorescent light. Furthermore, the time t 4  that is the end of the measurement, when the scattered light photodetecting element  50  ceases detecting scattered light, is essentially equal to the time t 4  at which the fluorescent light photodetecting element  20  ends the measurement because fluorescent light ceases to be detected. Because of this, the times over which the scattered light in the fluorescent light are measured will be essentially equal. 
       FIGS. 28( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when one non-fluorescent particle following one fluorescent particle pass through the cross-section of the excitation beam and constructive interference is produced between the scattered light that is produced by the fluorescent particle and the scattered light that is produced by the non-fluorescent particle. In this case the temporal variation of the intensity of the scattered light, which is continuously measured without interruption across the prescribed time, will be equal to or greater than the prescribed standard for the scattered light. Additionally, the time t 4  at which the measurement ends when the scattered light photodetecting element  50  ceases to detect scattered light is different from time the t 3  when the measurement by the fluorescent light photodetecting element  20  is completed because it ceases to detect fluorescent light, and the lengths of the times over which the scattered light and the fluorescent light were measured are different. 
       FIGS. 29( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when one fluorescent particle following one non-fluorescent particle pass through the cross-section of the excitation beam and constructive interference is produced between the scattered light that is produced by the non-fluorescent particle and the scattered light that is produced by the fluorescent particle. In this case the temporal variation of the intensity of the scattered light, which is continuously measured without interruption across the prescribed time, will be equal to or greater than the prescribed standard for the scattered light. Additionally, the time t 1  at which the measurement begins with the scattered light photodetecting element  50  detecting the scattered light is different from as time the t 2  at which the fluorescent light photodetecting element  20  begins measuring through detecting the fluorescent light. Because of this, the times over which the scattered light in the fluorescent light are measured will be different. 
       FIGS. 30( a ) and ( b )  illustrate the temporal variation in the scattered light that is detected by the scattered light photodetecting element  50  and the temporal variation in the fluorescent light intensity detected by the fluorescent light photodetecting element  20  when two non-fluorescent particles pass through the cross-section of the excitation beam and constructive interference is produced between the scattered lights that are produced by the two non-fluorescent particles. In this case the temporal variation of the intensity of the scattered light, which is continuously measured without interruption across the prescribed time, will be equal to or greater than the prescribed standard for the scattered light. Moreover, the intensity of the fluorescent light detected by the fluorescent light photodetecting element  20  remains at essentially zero. 
     The other structural elements in the particle detecting device  1  according to the Another Example are identical to those in the Example. The particle detecting device  1  can count a plurality of particles, separated into fluorescent particles and non-fluorescent particles, even if the excitation beam is a Gaussian beam. 
     Other Examples 
     While there are descriptions of examples as set forth above, the descriptions and drawings that form a portion of the disclosure are not to be understood to limit the present disclosure. A variety of alternate examples and exemplary operating technologies should be obvious to those skilled in the art. For example, the location wherein the particle detecting device  1  according to the present example is not limited to being a clean room. Moreover, the optics system of the particle detecting device  1  is not limited to that which is illustrated in  FIG. 3 . For example, as illustrated in  FIG. 31 , a collimating lens  63  may be disposed in front of the fluorescent light photodetecting element  20  and a collimating lens  65  may be disposed in front of the scattered light photodetecting element  50 . Conversely, as illustrated in  FIG. 32 , a collimating lens  63  and a condensing lens  64  may be disposed in front of the fluorescent light photodetecting element  20  and a collimating lens  65  and a condensing lens  66  may be disposed in front of the scattered light photodetecting element  50 . For example, as illustrated in  FIG. 33 , a condensing lens  67  may be disposed in front of the fluorescent light photodetecting element  20  and a condensing lens  68  may be disposed in front of the scattered light photodetecting element  50 . In this way, the present disclosure should be understood to include a variety of examples, and the like, not set forth herein.