emitting element of the laser light irradiator. EFFECTS OF THE INVENTION
[0010]
Thus, according to the present invention, it is possible to accurately identify a type of a floating particle while simplification of a configuration of the device is achieved.
BRIEF DESCRIPTION OF THE DRAWINGS [0011]
FIG. 1 is a diagram schematically showing a configuration of a floating particle detection device according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing an internal configuration of a back-monitor-value holder.
FIG. 3 is a flowchart showing internal processing of the back-monitor-value holder.
FIG. 4 is a diagram schematically showing maj or scattered light generated when a floating particle is irradiated with a .1 aser beam.
FIG. 5 is a diagram in which parts A and B show polarization directions of an irradiation laser beam with which irregular-shaped and spherical-shaped floating particles are irradiated in the floating particle detection device according to the first embodiment with double-headed arrows on a plane perpendicular to an optic-.l axis; parts C and D show polarization directions of scattered light generated when the irregular-shaped and spherical-shaped floating particles are irradiated with the irradiation laser beam with double-headed arrows on the plane perpendicular to the optical axis; parts E and F show polarization components of the scattered light in the direction which is orthogonal to the polarization direction of the irradiation laser beam; and parts G and H show polarization components of the scattered light in the

same direction as the polarization direction of the irradiation laser beam.
FIG. 6 fa) is a diagram schematically showing an example of a detection waveform when a scattered light receiving element in a scattered light receiver of the floating particle detection device according to the first embodiment detects scattered light from an irregular-shaped particle; FIG. 6(b) is a diagram schematically showing an example of a detection waveform when the scattered light receiving element in the scattered light receiver of the floating particle detection device according to the first embodiment detects scattered light from a spherical-shaped particle.
FIG. 7 is a diagram schematically showing a configuration of the floating particle detection device according to the first embodiment.
FIG. 8 is a block diagram showing internal processing of a second identification unit in a case where a normalized peak value is appli ed.
FIG. 9 is a flowchart showing a flow of the internal processing of the second identification unit.
FIG. 10(a) is a diagram schematically showing an example of a detection waveform which is detected by a back-monitor-use light receiving element and is input Lo a waveform adjuster in the floating particle detection device according to the first embodiment; FIG. 10(b) is a diagram schematically showing an example of the detection waveform adjusted by the waveform adjuster in the floating particle detection device according to the first embodiment; FIG. 10(c) and FIG. 10(d) are diagrams schematically showing a waveform of an alternating-current component and a waveform of a direct-current component generated by a direct-current/alternating-current separator in the floating particle detection device

direction of the irradiation laser beam LI. For this reason, the scattered light detection element 21 outputs a detection value corresponding to the degree of shape irregularity of the floating particle 50. The ^degree of shape irregularity' means the degree of how much it deviates from a spherical shape. The degree of shape irregularity (shape irregularity degree) can be indicated, when a particle is approximated to an ellipsoidal sphere, as a ratio between the length of a long axis and the length of a short axis of the ellipsoidal sphere. The degree of shape irregularity can also be indicated, when a particle is approximated to an ellipsoidal sphere, as a difference value between the length of a long axis and the length of a short axis of the ellipsoidal sphere, and so on. [0035]
FIG. 5 is a diagram showing polarization directions or polarization components on a plane perpendicular to an optical axis. In FIG. 5, parts A and B show the polarization directions of the irradiation laser beam with which irregular-shaped and spherical-shaped floating particles are irradiated in the floating particle detection device according to the first embodiment, with double-headed arrows on the plane perpendicular to the optical axis; parts C and D show polarization directions of scattered light generated when the irregular-shaped and spherical-shaped floating particles are irradiated with the irradiation laser beam, with double-headed arrows on the plane perpendicular to the optical axis; parts E and F show polarization components of the scattered light in the direction which is orthogonal to the polarization direction of the irradiation laser beam; and parts G and H show polarization components of the scattered light in the same direction as the polarization direction of the

irradiation laser beam. In parts A to H of FIG. 5, horizontal axes are x axes. In parts A to H of FIG. 5, vertical axes are y axes. Z axes which are perpendicular to x-y planes are respective travel directions of the irradiation laser beam LI and the scattered light. The polarization direction of the irradiation laser beam LI is a y-axis direction. The x axis is a direction which is orthogonal to the polarization direction (y~axis direction). Part A of FIG. 5 is a diagram showing the polarization direction of the irradiation laser beam Ll with which the irregular-shaped floating particle is irradiated, with the double-headed arrow on the plane perpendicular to the optical axis, in the floating particle detection device 1 according to the first embodiment. Part B of FIG. 5 is a diagram showing the polarization direction of the irradiation laser beam Ll with which the spherical-shaped floating particle is irradiated, with the double-headed arrow on the plane perpendicular to the optical axis, in the floating particle detection device 1 according to the first embodiment. Part C of FIG. 5 is a diagram showing the polarization direction of the scattered light Ls generated when the irregular-shaped floating particle is irradiated with the irradiation laser beam Ll, with the double-headed arrow on the plane perpendicular to the optical axis. Part D of tIG. 5 is a diagram showing the polarization direction of the scattered light Ls generated when the spherical-shaped floating particle is irradiated with the irradiation laser beam Ll, with the double-headed arrow on the plane perpendicular to the optical axis. Part E of FIG. 5 is a diagram showing the polarization component of the scattered light Ls from the irregular-shaped floating particle in a direction which is orthogonal to the

material of the particle. These factors cause a change in the light amount of the scattered light itself to be included in the value P of the signal Sp. [0046]
By carrying out this normalization, it is possible to cancel a change in the peak value P of the value Sp (signal level) of the signal S2 4 due to a change in the light amount of the scattered light itself. It is also possible to reduce an error in identification of the degree of shape irregularity by the size determination of the peak value P of the value Sp (signal level) of the signal S24 with reference to the threshold value THp. FIG. 7 is a diagram schematically showing a configuration of the floating particle detection device 1 according to the first embodiment when the normalized peak value P/Ak is used. The configuration for inputting the AC component Sac of the signal S31 output from the DC/AC separator 32 to the second identification unit 35 is additionally added, in comparison to the configuration of the floating particle detection device 1 shown in FIG. 1. [0047]
FIG. 8 is a block diagram showing internal processing of the second identification unit 35 in a case where the normalized peak value is applied. FIG. 9 is a flowchart showing a flow of the internal processing of the second identification unit 35. A peak detector 350 detects the peak value P of the value Sp of the signal S24. Then, a peak detector 351 detects the level value Ak which is a peak of the AC-component signal Sac of the detection signal S31 (step ST11). Then, a normalized-peak-value calculator 352 normalizes the peak value P by using the level value Ak. Then, the normalized-peak-value calculator 352 outputs a normalized signal S35 (step ST12). [0048j

value Sa and the value Sp. For this reason, it is possible to keep with high accuracy a ratio of the value Sp of the polarization component which is in orthogonal relationship to the ideal polarization component of the irradiation laser beam Ll to the value Sa of the polarization component which is in the same relationship to the polarization component of the irradiation laser beam Ll. [0080]
In the conventional floating particle detection device (patent document 1), for identifying a shape of a floating particle, a plurality of detection optical systems was necessary on its light receiver side. These detection optical systems individually detect two polarization components of scattered light. On the other hand, the floating particle detection device 1 according to the first embodiment described above includes only the detection optical system for detecting one polarization component, and thus can achieve the simple configuration. The floating particle detection device 1 detects the presence of the floating particle or the size of the floating particle by using the return light on the light source side. The floating particle detection device 1 is capable of identifying the type of the floating particle by using results of these detections. [0081]
In the invention of the first embodiment, detection of the scattered light generated when the floating particle is irradiated with the laser beam is performed by the single scattered light receiver, and detection of the backscattered light generated when the floating particle is irradiated with the laser beam is performed by the back-monitor-use light receiving element which is a part of the laser light irradiator. Therefore, it is possible to suppress an increase in components of the device and

What is claimed is:
1. A floating particle detection device comprising:
a laser light irradiator that includes a laser light emitting element including a front-side edge surface that emits an irradiation laser beam with which a detection-target region where floating particles are present is irradiated and a back-side edge surface that emits a back-monitor-use laser beam which travels in a direction opposite to a travel direction of the irradiation laser beam, and a back-monitor-use light receiving element disposed in a position where the back-monitor-use laser beam is incident, the back-monitor-use light receiving element generating a first detection signal according to an amount of incident light;
a scattered light receiver that selectively receives light of a predetermined polarization component among scattered light of the irradiation laser beam, the scattered light being generated when a floating particle is irradiated, thereby generating a second detection signal; and
an identification processor that identifies a type of the floating particle on a basis of the first detection signal and the second detection signal;
wherein the incident light entering the back-monitor-use light receiving element includes the back-monitor-use laser beam and backseattered light travelling toward the laser light irradiator among the scattered light of the irradiation laser beam with which the floating particle is irradiated.
2. The floating particle detection device according to claim 1, wherein a fluctuation of the back-monitor-use laser beam is used for the identification of the type of the floating particle, the fluctuation being caused by entering of the

backseattered light travelling toward the laser light irradiator, among the scattered light of the irradiation laser beam with which the floating particle is irradiated, through the front-side edge surface of the laser light emitting element of the laser light irradiator.
3. The floating particle detection device according to claim 1 or 2, wherein the incident light entering the back-monitor-use light receiving element includes at least one of a component entering the back-monitor-use light receiving element among the backscattered light and another component entering through the front-side edge surface of the laser light emitting element among the backscattered light.
4. The floating particle detection device according to any one of claims 1 to 3, wherein the scattered light receiver includes:
a polarizing filter that transmits only light of the predetermined polarization component among the scattered light of the irradiation laser beam; and
a scattered light detection element that receives the light of the polarization component transmitted through the polarizing filter, thereby generating the second detection signal.
5. The floating particle detection device according to any one of claims 1 to 4, wherein the light of the predetermined polarization component among the scattered light of the irradiation laser beam is light of linear polarization having a polarization direction which is orthogonal to a polarization direction of the irradiation laser beam emitted from the laser light emitting element.
6. The floating particle detection device according to any

one of claims 1 to 5, wherein the identification processor includes a first identification unit that detects at least one of size of the floating particle and density of the floating particles, on a basis of the first detection signal generated by the back-monitor-use light receiving element.
7. The floating particle detection device according to claim
6, wherein the identification processor further includes a
direct-current/alternating-current separator that separates
the first detection signal generated by the back-monitor-use
light receiving element into a first direct-current
component which corresponds to the back-monitor-use laser
beam and an alternating-current component which corresponds
to the backseattered light travelling toward the laser light
irradiator;
the detection of at least one of the size of the floating particle and the density of the floating particles by the first identification unit is performed on a basis of the first direct-current component and the alternating-current component separated by the direct-cur rent /alternating-cur rent separator.
8. The floating particle detection device according to claim
6, wherein the identification processor further includes:
a waveform adjuster that adjusts a waveform of the first detection signal generated by the back-monitor-use light receiving element so that an alternating-current component corresponding to the backscattered light is emphasized more than a first direct-current component corresponding to the back-monitor-use laser light; and
a direct-current/alternating-current separator t hat-separates the first detection signal adjusted by the waveform adjuster into the first direct-current component and the alternating-cur.rent component;

the detection of at least one of the size of the floating particle and the density of the floating particles by the first identification unit is performed on a basis of the first direct-current component and the alternating-current component separated by the direct-cur rent /alternating- cur rent separator.
9. The floating particle detection device according to claim
7 or 8, wherein the identification processor further
includes a back-monitor-value holder that holds the first
direct-current component as a second direct-current
component at a predetermined time point.
10. The floating particle detection device according to claim 9, further comprising a light emitting element controller that controls driving of the laser light emitting element on a basis of the second direct-current component held in the back-monitor-value holder.
11. The floating particle detection device according to claim 9 or 10, wherein the first identification unit performs an identification of the floating particle on a basis of a result of comparison of the second direct-current component held in the back-monitor-value holder and the first direct-current component which is a direct current component presently separated by the direct-cur rent /alternating-current separator.
12. The floating particle detection device according to any one of claims 1 to 11, wherein the identification processor includes a second identification unit that identifies a shape of the floating particle, on a basis of the second detection signal generated by the scattered light receiver.

13. The floating particle detection device according to any
one of claims 6 to 11, wherein the identification processor
includes:
a second identification unit that identifies a shape of the floating particle, on a basis of the second detection signal generated by the scattered light receiver; and
a third identification unit that identifies the type of the floating particle, on a basis of at least one of the size of the floating particle and the density of the floating particles obtained from the first identification unit, and the shape of the floating particle obtained from the second identification unit.
14. The floating particle detection device according to any one of claims 1 to 13, further comprising a light reflection member that changes a travel direction of a laser beam which is part of the irradiation laser beam has passed through the detection-target region, to a direction toward the laser light emitting element.
15. The floating particle detection device according to any one of claims 1 to 14, wherein the detection-target region where the floating particles are present is a region in a gas .
16. The floating particle detection device according to any one of claims 1 to 14, further comprising a container that accommodates a liquid and is transparent or translucent,
wherein the detection-target region where the floating particles are present is a region in the liquid accommodated in the container.
17. The floating particle detection device according to
claim 16, wherein the container includes an aberration

corrector for correcting aberration of the irradiation laser beam, the aberration corrector being provided in a position through which the irradiation laser beam passes.