JPH11153535A - Visualization system for fine particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a visualization system, for a fine particle, by which the fine particle can be visualized with uniform sensitivity and surely by powerful laser sheet light. SOLUTION: A visualization system for a fine particle is constituted in such a way that a light source 10, a beam expander 12, a guide mirror 14, a multiple reflection mirror 20, a beam trap 22, an analog differentiating camera 30 and a display device 40 are contained. Laser light which is output from the light source 10 is made incident on the multiple reflection mirror 20 via the beam expander 12 and the guide mirror 14 so as to be reflected in a multiple manner, and sheet light is formed. The analog differentiating camera 30 photographs scattered light generated when the sheet light hits the fine particle, its output is differentiated, and a high-frequency component corresponding to the scattered light of the fine particle is emphasized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine particle visualization system for visualizing various floating fine particles.

[0002]

2. Description of the Related Art In the field of the semiconductor industry, fine particles present in air in a clean room cause various troubles. Also, in daily life, an enormous amount of fine particles of various substances are discharged into the atmosphere daily from automobiles and factories, and these fine particles accumulated in the human body are harmful to human health.

[0003] In view of the above, in particular, recently, it is necessary to manage fine particles floating in the air, and various techniques for visualizing the fine particles in the air have been proposed in order to manage fine particles in the air. . For example, JP-A-61-02972
No. 9 discloses a conventional technique of converting a laser beam into a fan-shaped sheet light by passing through a cylindrical lens, and irradiating the fan-shaped sheet light to fine particles in the air to visualize the fine particles. I have. In addition, Japanese Unexamined Patent Application Publication No.
Japanese Patent Publication No. 307346 discloses a technique for irradiating a polygon mirror with laser light and rotating the polygon mirror to form a light film, thereby visualizing smoke or mist.

[0004]

In the method disclosed in Japanese Patent Application Laid-Open No. 61-029729, since one laser beam is spread into a fan-shaped sheet light, it is inversely proportional to the projection distance. Therefore, even if fine particles of the same size are floating, the appearance of the visualized fine particles, that is, the detection sensitivity is different depending on the floating position, which is not preferable. Further, in the method disclosed in Japanese Patent Application Laid-Open No. 4-307346 described above, since one laser beam is optically scanned (or rotated) to form a fan-shaped sheet beam, each sheet beam is individually scanned. Since the time synchronization is lost at the position, the fine particle image is formed by the scattered light at the moment when the laser light crosses the fine particles,
As the distance from the polygon mirror increases, the scattering time decreases and the apparent sensitivity decreases. When the movement of the fine particles to be observed is perpendicular to the sheet light, the fine particles that cannot be detected by the phase of the laser light (laser However, there is an inconvenience that fine particles that pass through the laser beam without being scattered without being exposed to light exist.

[0005] As described above, when visualization of fine particles is performed using various conventional techniques, there are cases where the detection sensitivity is not uniform or the fine particles cannot be detected depending on the observation position. Visualization could not be performed.

The present invention has been made in view of the above points, and an object of the present invention is to provide a fine particle visualization system capable of surely visualizing fine particles with uniform sensitivity. .

[0007]

In order to solve the above-mentioned problems, a system for visualizing fine particles according to the present invention is provided. The fine particles existing between the pair of reflecting members are visualized by photographing the multi-reflected space by the photographing means. In particular, since the energy density of the laser light is high, the intensity of the scattered light when the laser light hits the fine particles is large, which is suitable for photographing. Also,
By using a reflective member having a high reflectivity (less loss due to reflection), the intensity of the laser beam can be kept substantially uniform over the entire range of multiple reflections, and fine particles can be visualized with uniform sensitivity. In addition, the multiple-reflected laser light is stationary and has synchronism, and the fine particles crossing the laser light can be reliably visualized.

Further, by further providing a differentiation processing means for differentiating a signal output from the photographing means, a video signal having a high frequency component scattered by the fine particles is differentially emphasized, so that the sensitivity of visualization can be further increased. it can.

It is preferable that the above-mentioned photographing means is an avalanche multiplication operation type image pickup tube. The avalanche multiplying operation type imaging tube has a high gain and a wide dynamic range due to the avalanche effect, so is suitable for photographing a subject which is fine and has little change in luminance, and can visualize fine particles with high sensitivity. In particular, by combining with the above-mentioned differential processing means, the saturation of the output amplitude is eliminated, and the dynamic range of the image pickup tube can be used 100%, so that an S / N characteristic advantageous for visualizing fine particles can be obtained.

In addition, by adding a beam expander for widening the beam width of the laser beam to the above-described configuration, the number of times of multiple reflection by a pair of reflecting members to form a uniform sheet light can be reduced, or an adjacent beam can be reduced. The gap between light can be reduced.

Further, it is preferable to use an argon laser as a light source for outputting the laser light. The laser light output from the argon laser has a wavelength in a wavelength region (about 450 to 520 nm) in which the light receiving sensitivity of the avalanche multiplying operation type imaging tube is good and the energy density is high, so that the laser light is scattered. Suitable for visualizing fine particles for capturing light.

In addition, since the laser beam is multiply reflected as described above, it is preferable that the reflection loss by the reflection member is small and the reflection is close to total reflection. However, by using a dielectric multilayer mirror as the reflection member, the argon laser can be used. A wide range of light including the wavelength of the laser light output from the light source can be reflected in a state almost close to total reflection, and sheet light with uniform intensity can be obtained.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A fine particle visualization system according to an embodiment of the present invention generates a sheet light having a uniform intensity by irradiating a laser beam to a multiple reflection mirror.
It is characterized in that the scattered light of the fine particles irradiated with the sheet light is photographed by a camera, thereby visualizing the fine particles floating in the air. Hereinafter, a fine particle visualization system according to one embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a system for visualizing fine particles according to the present embodiment. The visualization system shown in FIG. 1 includes a light source 10, a beam expander 12, a guide mirror 14, a multiple reflection mirror 20, a beam trap 22, an analog differential camera 30, and a display device 40.

The light source 10 is, for example, an argon laser, and the output laser beam has a plurality of wavelength components near 500 nm. Specifically, 488 nm and 514 n
m has a large peak of the wavelength component, and is otherwise 457.9 nm, 465.8 nm, 476 / 472.7.
nm, 496.5 nm, and 501 nm.

The beam expander 12 converts a thin parallel light beam output from the light source 10 into a thick parallel light beam, and is composed of, for example, two sets of lenses whose focal positions are matched. By passing through the beam expander 12, a laser beam having a predetermined width is obtained. The guide mirror 14 is a beam expander 1
2 to reflect the laser light passing through the
In the opposite region.

The multiple reflection mirror 20 includes a pair of dielectric multilayer mirrors 20A and 20B which are arranged in parallel at a predetermined distance so that the reflection surfaces face each other. Each of the dielectric multilayer mirrors 20A and 20B is also called a multilayer dielectric reflector, and has a reflective film in which several to several tens of dielectric thin films having a high refractive index and a low refractive index are alternately stacked. Since a dielectric material is used, light absorption is small. Since interference is used, a spectral reflectance can be freely selected, and a light having a specific wavelength can have a reflectance close to 100%. It has the feature. The number of reflections of the laser light by the multiple reflection mirror 20 is determined by the angle of incidence of the laser light, the distance between the dielectric multilayer mirrors 20A and 20B, the length, and the like. The multiple reflection mirror 20
The installation angle and height can be adjusted, and the incident position and incident angle of the laser beam can be adjusted within a certain range.

FIG. 2 is a diagram showing the reflection characteristics of the dielectric multilayer mirrors 20A and 20B used in the present embodiment. In the figure, the horizontal axis represents the wavelength of the reflected light, and the vertical axis represents the return loss. As shown in the figure, the dielectric multilayer mirrors 20A and 20B have almost no reflection loss with respect to light in the wavelength region of about 450 nm to 540 nm, and can reflect incident light in a state close to total reflection. As described above, the wavelength of the laser beam output from the argon laser as the light source 10 is included in the range of about 450 nm to 520 nm, and the dielectric multilayer mirrors 20A and 20B.
Can be almost totally reflected. Therefore,
Even when multiple reflections occur between the dielectric multilayer mirrors 20A and 20B, the degree of laser light attenuation can be minimized.

In this manner, sheet light using laser light is formed by multiple reflection by the multiple reflection mirror 20, and this planar sheet light is used as a photographing space of the analog differential camera 30, that is, an observation space for fine particles. .

The beam trap 22 includes the multiple reflection mirror 2
This is for absorbing the laser light passing through zero. The provision of the beam trap 22 can suppress generation of unnecessary scattered light.

The analog differential camera 30 is arranged in a direction perpendicular to the sheet light forming surface formed by the multiple reflection mirror 20, and is for photographing the whole or a part of the sheet light and converting it into a video signal. For example, an avalanche multiplication operation type imaging tube is used for the light receiving unit. The back side of the multiple reflection mirror 20 (analog differential camera 3
It is preferable that an area that becomes the background when the photographing is performed using 0 is a non-reflective background.

FIG. 3 is a diagram showing the structure of an avalanche multiplication operation type imaging tube. The avalanche multiplying operation type imaging tube 32 shown in FIG. 1 generates an electron beam and has an electron gun 33 having a deflection electrode for scanning the generated electron beam, and a high voltage applied to the amorphous semiconductor film. HARP (High-gain Avalanche Rushing amorphous Ph) which multiplies the charge by the avalanche effect in the thickness direction of the semiconductor film.
otoconductor) target 34. For example, as the avalanche multiplication type imaging tube 32, a high-sensitivity imaging tube called a super harpicon has been commercialized.

This avalanche multiplication operation type imaging tube 32
Is based on the principle of operation of a photoconductive target that performs avalanche multiplication of charges in an amorphous semiconductor, as described above, and has high sensitivity and high resolution, and particularly has good light reception for the wavelength of ultraviolet light. Has sensitivity. For example, 6
A gain of about 4 to 100 times can be easily obtained, and it is also possible to obtain a gain of 1000 times on a test basis.

The above-mentioned avalanche multiplication type image pickup tube 3
2 is compared with the conventional SIT (Silicon Intensifier Target) and II (Image Intensifier) CCD.
It is possible to obtain a captured image with a small fluctuation of amplification and a high SN ratio.

FIG. 4 shows an avalanche multiplication operation type imaging tube 3.
FIG. 4 is a diagram illustrating spectral sensitivity characteristics of FIG. In the figure, the horizontal axis represents the light wavelength, and the vertical axis represents the normalized spectral sensitivity. As shown in the figure, the avalanche multiplication operation type imaging tube of the present embodiment has a spectral sensitivity peak at 400 to 500 nm, and has a sensitivity of 50% or more of the peak sensitivity even at 300 nm, which is a shorter wavelength. doing.
As described above, the wavelength of the laser light output from the argon laser is included in the wavelength range of 450 to 520 nm, and there is a peak in spectral sensitivity for light in this wavelength range. By using 32, it is possible to most efficiently capture the scattered light due to the laser light output from the argon laser.

FIG. 5 shows an avalanche multiplication operation type imaging tube 3.
FIG. 2 is a diagram illustrating an overall configuration of an analog differential camera 30 including the second embodiment; As shown in FIG.
In addition to the avalanche multiplication type imaging tube 32, an amplifier 35, a differentiation circuit 36, a luminance information compression circuit 37, an addition circuit 38, and an amplifier 39 are provided.

The signal extracted from the avalanche multiplying operation type imaging tube 32 is amplified by a low noise amplifier 35 and then divided into an analog differentiation circuit 36 having no information loss and a luminance information compression circuit 37. The differentiating circuit 36 is for amplifying and extracting information having a high frequency component such as fine particles, and the luminance information compressing circuit 37 adjusts the amplitude of the video signal so as to be within a predetermined voltage (for example, 1 V _PP ). Do.
The signals processed by these two circuits are combined by an adder circuit 38, and after gain adjustment and format processing are performed by an amplifier 39, are output as video signals from the analog differential camera 30. The output video signal is input to the display device 40 and is displayed on the screen.

The above-mentioned multiple reflection mirror 20 corresponds to a reflection member, and the analog differential camera 30 corresponds to a photographing means and a differentiation processing means.

As described above, the fine particle visualization device of the present embodiment forms the sheet light by irradiating the laser beam to the multiple reflection mirror 20, and forms the dielectric multilayer mirror 20 A, The scattered light can be generated by irradiating the sheet light to the fine particles existing in the predetermined region sandwiched by the sheets 20B. Therefore, by photographing the scattered light with the analog differential camera 30, only the scattered light can be photographed, and the fine particles can be visualized.

In particular, since the laser light output from the argon laser transmitter has a high energy density, the intensity of the scattered light generated by the fine particles is large, and the sensitivity of photographing can be increased. Also, the dielectric multilayer mirrors 20A, 20A
By configuring the multiple reflection mirror 20 using B,
Since the laser light can be substantially totally reflected, the overall intensity of the sheet light can be kept substantially uniform, and the detection sensitivity (photographing sensitivity) of the fine particles does not vary depending on the photographing position. Further, since the laser beam is not formed into a sheet shape by vibration or the like, the simultaneousness of visible light can always be ensured. Further, since the analog differentiation processing is performed on the output of the image pickup tube 32 using the analog differentiation camera 30, only the high frequency components such as the scattered light of the fine particles can be emphasized and photographed. Visualization can be performed reliably. Further, by using the beam expander 12, the beam width of the laser light incident on the multiple reflection mirror 20 can be increased, so that the gap between adjacent multiple reflection laser lights can be reduced, or the multiple reflection mirror 20 can be used. Can reduce the number of reflections.

Actually, the above-described visualization system was assembled and installed in a clean room, and the length of the multiple reflection mirror 20 was set to 100 m using an argon laser having an output of 500 mW.
m, the interval was set to 250 mm, and the number of reflections was set to 21 times.
The visualization of a micron particle image has been confirmed.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. For example, in the above-described embodiment, the light source 1
Although the case of using an argon laser as 0 has been described,
The shorter the wavelength of the laser light used, the higher the reflectance by the fine particles and the greater the intensity of the scattered light. Therefore, the light source 10 capable of outputting laser light with a shorter wavelength may be used. In this embodiment, the analog differential camera 30 is used to photograph the scattered light by the fine particles. However, a camera that does not include a differentiation function may be used depending on the size of the fine particles.

Although the system for visualizing fine particles according to the above-described embodiment visualizes fine particles existing in the space in which the multiple reflection mirror 20 is installed, various modifications are conceivable for using this visualization system. Can be For example, the multi-reflection mirror 20 is housed in a closed container with a window filled with clean air, and in this state, it is moved to a place where the fine particles are desired to be visualized, and the closed container is opened. Then, the fine particles to be visualized enter the closed container, so that the closed container is closed again after being left for a certain period of time. The sealed container containing the fine particles collected in this manner is brought back to the place where the light source 10 and the analog differential camera 30 are installed, and the laser beam is incident on the multi-reflection mirror 20 while maintaining the sealed state. The scattered light by the fine particles is photographed from the provided window. Alternatively, the multi-reflection mirror 20 is provided in a chamber replaced with clean air, and a gas separately collected by using a balloon or the like is introduced into the chamber, and fine particles contained in the collected gas are removed. Visualization may be performed.

[0034]

As described above, according to the present invention, a laser beam is made incident on one of the opposing surfaces of a pair of opposing reflecting members to cause multiple reflections, and this multiply reflected space is formed. By photographing with the photographing means, it becomes possible to visualize the fine particles existing between the pair of reflecting members. In particular, since the energy density of the laser light is high, the intensity of the scattered light when the laser light hits the fine particles is large, which is suitable for photographing. Also, by using a reflective member having a high reflectance,
The intensity of the laser beam can be kept substantially uniform over the entire range of the multiple reflection, and the fine particles can be visualized with uniform sensitivity. In addition, the multiple-reflected laser light is stationary and has synchronism, and the fine particles crossing the laser light can be reliably visualized. Further, by subjecting the signal output from the photographing means to analog differentiation processing, a signal having a high frequency scattered by the fine particles is emphasized, so that the sensitivity of visualization can be further increased.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a system for visualizing fine particles according to an embodiment.

FIG. 2 is a diagram showing reflection characteristics of a dielectric multilayer mirror used in the present embodiment.

FIG. 3 is a diagram illustrating a structure of an avalanche multiplication operation type imaging tube.

FIG. 4 is a diagram illustrating spectral sensitivity characteristics of an avalanche multiplication operation type imaging tube.

FIG. 5 is a diagram illustrating an overall configuration of an analog differential camera.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Light source 12 Beam expander 14 Guide mirror 20 Multiple reflection mirror 20A, 20B Dielectric multilayer mirror 22 Beam trap 30 Analog differentiation camera 32 Avalanche multiplication operation type imaging tube 33 Electron gun 34 Target 36 Differentiation circuit 40 Display device

Claims (6)

[Claims] A pair of reflecting members disposed opposite to each other; a light source that causes a laser beam to enter a facing surface of one of the pair of reflecting members to generate multiple reflections; And a photographing means for photographing a space where multiple reflections have occurred, and visualizing the fine particles present between the pair of reflecting members. 2. The system for visualizing fine particles according to claim 1, wherein the photographing means is an avalanche multiplication operation type imaging tube. 3. The system for visualizing fine particles according to claim 1, further comprising a differentiation processing unit that performs analog differentiation on a signal output from the imaging unit. 4. The fine particle visualization system according to claim 1, further comprising a beam expander for converting a thin laser beam emitted from the light source into a thick laser beam. 5. The system for visualizing fine particles according to claim 1, wherein an argon laser is used as the light source. 6. The system according to claim 1, wherein the reflection member is a dielectric multilayer mirror.