JP3996272B2 - Aerosol detection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aerosol detection method for detecting aerosols such as dust floating in the air. For example, a laser beam is repeatedly moved or reciprocated at a high speed so that a part or all of the passing area coincides with a detection target area. The present invention relates to an aerosol detection method for detecting an aerosol by detecting scattered light generated when the aerosol exists in the detection target region.
[0002]
[Prior art]
As such an aerosol detection technique, a technique described in Japanese Patent Laid-Open No. 7-35764 (hereinafter simply referred to as a prior example) is known. As shown in FIG. 5, the preceding example reflects a laser oscillation device 101 and a laser beam L10 from the laser oscillation device 101 and a direction in which the reflected laser beam L11 rotates around itself within a predetermined angular range. The laser beam L11 reciprocating around the vibrating mirror 102 is irradiated to the detection target space, and the scattered light generated when the aerosol exists in the passing region of the irradiated laser beam L11. Is captured by the image pickup tube camera 103, and the photographing result is recorded by the video deck 104 as necessary and displayed on the monitor 105.
[0003]
In the preceding example, a filter 103F having a high transmittance only in the wavelength range of the irradiation laser light is attached to the lens 103A of the image pickup tube camera 103, so that unnecessary light from the background or illumination is not detected. .
[0004]
[Problems to be solved by the invention]
However, the aerosol detection technique of this prior example has not been able to accurately detect the aerosol.
That is, when the laser beam reciprocating in the direction of turning around the vibrating mirror is irradiated as in the preceding example so that the passing region is aligned with the detection target region, first, the laser beam is directed toward the detection target portion on the end side of the laser beam. The staying time is shortened and the detection ability is also lowered. Secondly, the laser beam reciprocating in the direction around the vibrating mirror has a particularly long stay time at both ends of movement (indicated by L11a and L11b in FIG. 5) compared to other parts, and the detection capability at both ends of the movement Becomes relatively high. Thus, if the detection capability in the detection target region is non-uniform, accurate aerosol detection is impossible.
[0005]
In addition, the aerosol detection technology according to the preceding example attaches a filter having a relatively high transmittance only to the wavelength range of the irradiated laser beam to the lens of the image pickup tube camera, thereby removing unnecessary light from the background or illumination. Although the detection is not performed, the effect is exhibited when the three conditions of the wavelength range of the laser beam to be used, the wavelength characteristics of the background and illumination, and the transmittance characteristics of the filter are met. Therefore, unnecessary light from the background, illumination, etc. is detected depending on the equipment used and the environment in use, and the aerosol cannot be detected accurately.
[0006]
Furthermore, the aerosol detection technique of the prior example requires that an operator continuously observe the laser beam passage area or the monitor display. Even if a video deck is used, the worker still displays all of the recorded results on a monitor and visually observes them. And when detecting aerosol by the visual observation by this worker, an oversight and a misidentification cannot be avoided. Therefore, it is impossible to accurately detect the aerosol with the aerosol detection technique of the prior example. In addition, the labor of workers is great.
[0007]
Then, the main subject of this invention is providing the aerosol detection method which can detect an aerosol correctly.
[0008]
[Means for Solving the Problems]
The aerosol detection method of the present invention that has solved the above-described problems is a method in which a laser beam from a laser oscillation device is reciprocated or repeatedly moved in a direction around the laser beam by deflecting the laser beam with an optical scanning element at a frequency of 60 Hz or more,
Receiving a laser beam that reciprocates or reciprocates in the direction of turning around this optical scanning element, and emits it as a laser beam that reciprocates in parallel and reciprocally moves by an optical element,
A non-reflective background that is non-reflective with respect to light of the oscillation wavelength of the laser oscillation device is set in a region that is a background of the detection target region,
The detection target area is captured by an imaging tube camera using an avalanche imaging tube, with a lens hood attached to the lens, so as not to capture an area other than the detection target area,
Analog captured image signal from the tube camera, analog differential processing by an analog differential processing device to obtain an analog differential processing image,
Irradiating a laser beam that reciprocates parallel or reciprocally moves from the optical element so that a part or all of the passage area thereof coincides with the detection target area, and performs imaging with the imaging tube camera,
An analog differential processing image obtained by analog differential processing of the analog photographed image signal by the analog differential processing device is created by accumulating a plurality of frames by the image cumulative processing device, and a cumulative image is created based on the cumulative image. It is characterized by detecting an aerosol.
[0009]
That is, the point of the detection method of the present invention is that a laser beam reciprocating or reciprocating in the direction of rotating around the optical scanning element is a laser beam reciprocating in parallel reciprocating or reciprocating in parallel. The moving laser beam is used as a laser beam for aerosol detection. Therefore, in the method of the present invention, as shown in FIGS. 1 and 2, the staying time of the laser beams L3 and L3 ′ that reciprocate in parallel or move repeatedly is constant in the direction in which the laser beams L3 and L3 ′ pass in the detection target region. It becomes. Therefore, in the device of the present invention, the detection capability in the detection target region can be made uniform in the direction of passage of the laser beams L3 and L3 ′.
[0010]
In particular, when a laser beam that repeatedly moves in parallel is used as a laser beam for aerosol detection, as can be seen from FIG. 2, the stay time at both ends of the laser beam L3 ′ that moves repeatedly in parallel is the stay time at other sites. Is the same. Therefore, in this case, the stay time of the laser beam that repeatedly moves in parallel is constant in the parallel movement direction, and thus more uniform detection capability is exhibited in the detection target region.
[0011]
As described above, since the aerosol detection method of the present invention has a uniform detection capability in the detection target region, accurate detection is possible, and whether or not aerosol is present, such as a cleanliness survey in a clean room. It is particularly suitable for aerosol detection when it is unknown.
[0012]
In a preferred embodiment of the method of the present invention, the optical scanning element is a galvanometer mirror or a polygon mirror. When these optical scanning elements are employed, the laser beam from the laser oscillation device is reflected by the respective mirrors, and the reflected laser beam is reciprocated or repeatedly moved in the direction of turning around each device. Since these optical scanning elements can reciprocate or repeatedly move the reflected laser beam in the direction around itself at a high speed, it is possible to detect by irradiating the aerosol passing through the detection target region without exception.
[0013]
In a preferred embodiment of the method of the present invention, the optical element is a convex lens, a combination lens, or a concave mirror from the viewpoint of being inexpensive.
[0014]
Furthermore, in a preferred embodiment of the method of the present invention, a non-reflective background is set in a background region when detecting scattered light generated when aerosol is present in the detection target region. As a result, the background in the detection target region becomes uniform, so that the detection capability is further uniformed, and the contrast between the scattered light scattered by the aerosol and the background increases, so that accurate detection is possible.
[0015]
For example, it is preferable that at least an aerosol having a particle size of 0.3 μm or more can be detected in order to be used for detecting a naturally occurring minute and minute amount of aerosol.
[0016]
In a preferred embodiment of the apparatus of the present invention, it is preferable that an imaging tube camera that captures the detection target region is provided, and that aerosol is detected based on the imaging result of the imaging tube camera. Although the scattered light can be detected by another camera or the like, it is preferable to employ an imaging tube camera capable of obtaining an analog image signal in order to detect minute scattered light.
[0017]
In this case, the tube camera is preferably a tube camera using an avalanche tube. Furthermore, it is preferable that a lens hood for blocking an area other than the detection target area is attached to the lens of the imaging tube camera. With these configurations, the detection capability can be improved.
[0018]
When an image accumulation processing device that accumulates a plurality of frames of the analog differential processing image to create a cumulative image, and configured to detect aerosol based on the accumulated image by the image accumulation processing device, all of the detected aerosol is, for example, Since it can be displayed on one screen (one frame), even if visual observation is performed, oversight and misidentification can be reduced, and the labor of an operator can be reduced. Further, for example, the trajectory of aerosol can be easily observed.
[0019]
When an automatic counting device that automatically counts the number of aerosol particles by automatically counting the number of scattered light from the detection target area based on the analog differential processing image is provided, the aerosol is automatically detected regardless of visual observation by an operator. Since the number of particles can be counted, the aerosol can be detected accurately, and the labor of the worker can be reduced or the labor can be saved.
[0020]
[0021]
[0022]
[0023]
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows an example of an aerosol detection device 1 according to the present invention, which is a laser oscillation device 2 and a direction in which the laser beam L1 from the laser oscillation device 2 is deflected and turns around itself. An optical scanning element 3 that reciprocates and an optical element 4 that receives a laser beam L2 that reciprocates in the direction of revolving around the optical scanning element 3 and emits it as a laser beam L3 that reciprocates in parallel are provided.
[0025]
First, various laser oscillation devices 2 can be used, but it is preferable to use an argon laser oscillation device because continuous oscillation can be obtained and high output can be easily obtained. Of course, other laser oscillation devices such as an Nd-YAG laser oscillation device can also be used.
[0026]
The used wavelength of the laser light may be in the ultraviolet (wavelength 390 nm or less) or infrared (800 nm or more) region, but is preferably in the visible region. That is, a laser beam having a wavelength in the ultraviolet region generates ozone in the air, may cause visual impairment, or has a reaction wavelength of a photoresist used in semiconductor manufacturing in the ultraviolet region (365 nm). Therefore, the place of use etc. will be limited. In addition, infrared rays may heat surrounding objects, and it is difficult to detect scattered light because they are actively emitted from high-temperature objects and illumination lamp surfaces. Not suitable for use in
[0027]
Next, the optical scanning element 3 shown in FIG. 1 has a mirror 3A that vibrates at a predetermined speed, reflects the laser beam L1 from the laser oscillation device 2, and reflects the reflected laser beam L2 around itself. It is reciprocated at a predetermined speed in a predetermined angle range in the direction of rotation. That is, the reflected laser beam L2 from the mirror 3A oscillates so as to reciprocate between one radial edge and the other radial edge in a fan-shaped reflected laser beam passage region centered on the rotation axis of the mirror 3A. . The speed of vibration of the mirror 3A is not particularly limited, but is preferably 60 Hz or more in terms of frequency in order to detect an aerosol having a particle size of 0.3 μm. A specific example of the optical scanning element that can vibrate the mirror at such a frequency is a galvanometer mirror.
[0028]
As the optical scanning element 3 of the present invention, as shown in FIG. 2, a so-called rotating mirror type optical deflector 3 ′ (polygon mirror) having a polygonal column mirror 3A ′ that is rotationally driven at a predetermined speed is used. You can also. In this case, as shown in the figure, the laser beam L1 from the laser oscillation device 2 is reflected by the rotating polygonal columnar mirror 3A ', and the reflected laser beam L2' is reflected by the rotating mirror type optical deflector 3 '. It is repeatedly moved in a predetermined angle range and at a predetermined speed in the direction of turning around (that is, in the fan-shaped reflection laser beam passage region centered on the rotation axis of the polygonal columnar mirror 3A ′, The one-way movement to the edge in the radial direction is repeated), and the laser beam L2 ′ that repeatedly moves is converted into a laser beam L3 ′ that repeatedly moves in parallel by the optical element 4. 1 'has shown the aerosol detection apparatus.
[0029]
The optical element 4 receives laser beams L2 and L2 ′ that reciprocate or reciprocate in the direction of rotation around the optical scanning elements 3 and 3 ′, and receive laser beams L3 and L3 ′ that reciprocate and reciprocate in parallel. Although it will not specifically limit if it can radiate | emit, For example, various convex lenses, such as a cylindrical surface plano-convex lens shown in FIG. 1, can be used. Various combination lenses such as the f (θ) lens 4 ′ shown in FIG. 3 and various concave mirrors such as a total reflection cylindrical concave mirror 40 as shown in FIG. 4 can also be used. 3 and 4 do not show the optical scanning elements 3 and 3 ′.
[0030]
On the other hand, upon detection, a laser beam L3 that reciprocates in parallel from the optical element 4 (a laser beam L3 ′ that reciprocally moves in parallel when the rotating mirror type optical deflector 3 ′ is used) is partly transmitted. Alternatively, the detection target space is irradiated so that the whole matches the detection target region. When the aerosol exists in the detection target region, the laser beam L3 (or L3 ′) passing through the part is scattered by the aerosol. Therefore, the aerosol can be detected by detecting the scattered light SL.
[0031]
In the illustrated example, the imaging tube camera 5 that captures the detection target region is used as the scattered light detection device, and the imaging result of the imaging tube camera 5 (particularly, a high-sensitivity imaging tube camera using an avalanche imaging tube is preferable) is monitored 8. And the scattered light is detected based on the display. In addition to being displayed on the monitor 8, the photographing results by the tube camera 5 are printed on a printer (not shown), recorded on a video (not shown), developed and printed, and the display is observed. Thus, the scattered light SL can be detected. When the scattered light SL is imaged by the imaging tube camera 5 or the like, the angle between the imaging direction and the passing region of the laser beam L3 reciprocally moving in parallel (or the laser beam L3 ′ moving in parallel repeatedly) is shown in the illustrated example. Although it is perpendicular, other angles can be used as required.
[0032]
In the aerosol detection apparatus 1 shown in FIG. 1, the staying time of the parallel reciprocating laser beam L3 is constant in the direction in which the laser beam L3 passes within the detection target region. Therefore, in the device according to the present invention, the detection capability in the detection target region can be made uniform in the direction in which the laser beam L3 passes.
[0033]
In particular, in the aerosol detection apparatus 1 ′ shown in FIG. 2, the staying time of the laser beam L3 ′ that repeatedly moves in parallel is constant in the direction in which the laser beam L3 ′ passes within the detection target region, and is also constant in the direction of translation ( Since the stay time at both ends of the movement is the same as the stay time at other parts), more uniform detection capability is exhibited in the detection target region.
[0034]
Thus, since the aerosol detection apparatuses 1 and 1 ′ according to the present invention have a uniform detection capability in the detection target region, accurate detection is possible, and in particular, a cleanliness survey in a clean room, etc. It is particularly suitable for aerosol detection when it is not known whether or not aerosol is present.
[0035]
In the present invention, the tube camera 5 is used, and an analog differential processing device 6 that performs analog differential processing of an analog photographed image signal is used as shown in the figure, and a differential processing image by the analog differential processing device 6 is displayed on the monitor 8. For example, aerosol is detected. By emphasizing only the high frequency components of the captured image signal by the differential processing, it becomes possible to detect scattered light from a finer aerosol. Therefore, the aerosol detection capability is improved. The analog differential processing may be real-time processing or batch processing. Further, the analog differential processing device may be built in the image pickup tube camera.
[0036]
Further, when aerosol is detected by using an image accumulation processing device 7 that accumulates a plurality of frames of images taken by the tube camera 5 to create a cumulative image and displaying the accumulated image by the image accumulation processing device 7 on a monitor 8. Since all the detected aerosols can be displayed on, for example, one screen (one frame), even if visual observation is performed, oversight and misidentification can be reduced, and the labor of the operator can be reduced. Further, for example, the trajectory of aerosol can be easily observed.
[0037]
Furthermore, when an automatic counting device (not shown) that automatically counts the number of aerosol particles by automatically counting the number of scattered light from the detection target region based on the image captured by the imaging tube camera 5 is used, the monitor 8 or the like. The number of aerosol particles can be automatically counted without observing the display means. Therefore, visual observation by the worker is substantially unnecessary, and the aerosol can be detected accurately and the labor of the worker can be reduced or the labor can be saved. However, display means such as the monitor 8 can also be used in this case.
[0038]
Preferably, a lens hood 5 </ b> B is attached to the lens 5 </ b> A of the imaging tube camera 5 so as not to capture an area other than the detection target area. As a result, only the detection target region can be imaged, and light from around the detection target region is not incident on the lens 5A, and the contrast of the captured image is increased, so that the detection capability is improved.
[0039]
More preferably, a non-reflective background 9 is provided in a region that becomes a background when detecting scattered light generated when aerosol exists in the detection target region. The non-reflective background 9 is substantially non-reflective with respect to light having the oscillation wavelength of the laser oscillation device 2. A specific example is a so-called black cloth. Thereby, the reflected light from the background is reduced, and the contrast of the captured image is increased. In addition, since the background becomes uniform, the uniformity of detection capability is also improved. Therefore, the aerosol can be accurately detected even by installing the non-reflective background 9. The non-reflective background 9 and the lens hood 5B described above can achieve accurate aerosol detection with little influence on the characteristics of the device used and the environment at the site of use.
[0040]
Here, when the present inventors examined the lower limit particle size of the aerosol that can be detected by the aerosol detection device according to the present invention, a high-sensitivity imaging tube camera using a galvanomirror (frequency 60 Hz), an avalanche imaging tube, The lower limit particle size of the aerosol that can be reliably detected in the case of using an analog differential processor, a lens hood, and a non-reflective background was 0.3 μm. In addition, this experiment was conducted by the present inventors in the 16th Air Cleaning and Contamination Control Research Conference (sponsored by the Japan Air Cleaning Association) on April 17, 1998. It was confirmed by the method announced with.
[0041]
<Others>
(A) Since the aerosol detection method of the present invention has a high detection capability without being affected by the characteristics of the device used or the environment at the site of use as described above, for example, a clean room cleanliness inspection (filter leak in a semiconductor manufacturing factory) It can be suitably used for detecting aerosols whose particle size and particle concentration are naturally unknown, such as inspection) and dust detection in food factories. In addition, the aerosol detection device of the present invention, as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 7-35764, also visualizes airflow using artificially generated aerosol (micro water droplet mist), Of course it can be used.
[0042]
(B) In the present invention, the laser beam L 1 from the laser oscillation device 2, the laser beams L 2 and L 2 ′ reciprocated or repeatedly moved in the direction around the laser scanning device 3, and the parallel from the optical element 4. At least one of the laser beams L3 and L3 ′ that reciprocate or repetitively move in parallel and the scattered light from the detection target region is used using an appropriate optical element such as a lens or a mirror according to the installation environment and installation mode of the apparatus. Can be deflected and condensed.
[0043]
[0044]
[0045]
[0046]
[0047]
【The invention's effect】
As described above, according to the present invention, the uniformity of the detection capability in the detection target region is improved, and the detection capability and the uniformity thereof are improved almost without being affected by the environment of the equipment used and the usage site, In addition, it is possible to accurately detect aerosols by eliminating the need for visual observation by workers.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of an aerosol detection device according to the present invention.
FIG. 2 is a perspective view showing an example of an aerosol detection device according to the present invention using another optical scanning element.
FIG. 3 is a front view showing another optical element.
FIG. 4 is a front view showing another optical element.
FIG. 5 is a perspective view showing a conventional aerosol detection device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Aerosol detection apparatus, 2 ... Laser oscillation apparatus, 3 ... Optical scanning element, 4 ... Optical element, 5 ... Imaging tube camera, 6 ... Analog differentiation processing apparatus, 7 ... Image accumulation processing apparatus, 8 ... Monitor, 9 ... None Reflective background.

Claims (2)

The laser beam from the laser oscillation device is deflected by an optical scanning element at a frequency of 60 Hz or more, and is reciprocated or repeatedly moved in a direction around itself,
Receiving a laser beam reciprocating or reciprocatingly moving in the direction of turning around the optical scanning element, and emitting it as a laser beam reciprocating in parallel reciprocating movement or parallel reciprocating movement, respectively,
A region to be a background of the detection subject region, established a nonreflective background nonreflective to light of the oscillation wavelength of the laser oscillating device,
The detection target area is captured by an imaging tube camera using an avalanche imaging tube, with a lens hood attached to the lens, so as not to capture an area other than the detection target area,
The analog captured image signal from the tube camera is subjected to analog differential processing by an analog differential processing device to obtain an analog differential processed image,
Irradiating a laser beam that reciprocates parallel or reciprocally moves from the optical element so that a part or all of the passage area coincides with the detection target area, and performs imaging with the imaging tube camera,
An analog differential processing image obtained by analog differential processing of the analog photographed image signal by the analog differential processing device is accumulated by an image cumulative processing device to create a cumulative image, and based on this cumulative image An aerosol detection method comprising detecting an aerosol.   The aerosol detection method according to claim 1, further comprising an automatic counting device that automatically counts the number of aerosol particles by automatically counting the number of scattered light from the detection target region based on the analog differential processing image.

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