JP2811235B2 - Particle size distribution measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of irradiating a laser beam to a particle group such as a fuel spray of an automobile, receives a laser beam diffracted by the particle group, and based on the diffraction pattern, the diameter of the particle group. The present invention relates to a particle size distribution measuring device for measuring the distribution of particles.

[0002]

2. Description of the Related Art When a group of particles having a predetermined diameter is irradiated with laser light and a Fraunhofer diffraction image of the group of particles is observed, attention is paid to the fact that the diffraction pattern and the diameter of the group of particles correspond one to one. There is known a method of analyzing a composite diffraction pattern of laser light diffracted from a group of fine particles having various diameters based on a predetermined algorithm to know the distribution of the particle size of the group of fine particles (for example, “surface”). Vol.22 No.2 (1984) 87 (27)
Pp. 94-34). In this method, since the diffraction pattern is a concentric pattern centered on the spot of the 0th-order light, the diffraction pattern is received using, for example, 15 concentric ring-shaped optical sensors. The particle size distribution is obtained by analyzing the received diffraction pattern.

In the above-described method using a large number of annular optical sensors, it is necessary to precisely adjust the position so that the center of a photodetector composed of the multiple annular optical sensors exactly coincides with the optical axis. There was a problem that preparation before measurement was difficult. Therefore, in order to simplify this preparation, a solid-state imaging device such as a CCD is used in place of the detector composed of a large number of annular optical sensors, the position is roughly adjusted, and the diffracted light is received. A method of calculating the center of the optical axis by calculation utilizing the fact that the pattern of the diffracted light is rotationally symmetric is also conceivable.

[0004]

By the way, when measuring the particle size distribution of the fine particles such as the fuel spray of an automobile, for example, the particle size distribution of the fine particles near the outlet of the fine particles or the distance from the outlet of the fine particles are measured. In some cases, it is necessary to separately measure the particle size distribution of the fine particle group at the position where the laser beam is emitted. In some cases, it is difficult to see with the eyes, and it is difficult to accurately adjust the position.

The present invention has been made in view of the above circumstances, and has as its object to provide a particle size distribution measuring apparatus capable of easily visually recognizing a relative arrangement between a group of fine particles and a laser beam irradiation position in the group of fine particles. And

[0006]

In order to achieve the above object, a particle size distribution measuring apparatus according to the present invention comprises: an irradiation optical system for irradiating a laser beam to a particle group; and a solid-state imaging device for receiving a diffraction image by the particle group. A particle size distribution measuring device comprising: a device; and arithmetic means for calculating a particle size distribution by the particle group based on a diffraction image pattern received by the solid-state imaging device. An illumination optical system that illuminates over an area wider than the area including the area illuminated by light, an image of the fine particle group, a monitor unit that clearly displays the area illuminated by the laser light, A separation optical system that guides only the laser light out of the illumination light and the laser light to the solid-state image pickup device is provided.

[0007]

The particle size distribution measuring apparatus of the present invention illuminates a fine particle group over a wide area, and displays an image of the fine particle group by clearly illuminating an area irradiated with a laser beam. Even when it is difficult to visually recognize the position, the position can be adjusted while viewing the displayed image.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a particle size distribution measuring apparatus according to one embodiment of the present invention. The laser light 2 of wavelength λ ₁ emitted from the laser light source 1 is narrowed down by the lens 3, passes through a pinhole formed in the pinhole plate 4, is reflected by the half mirror 5, and then becomes parallel light by the lens 6. Then, the particles are emitted to a particle group 8, such as fuel spray of an automobile, which is blown out from the outlet 7.

The wavelength λ ₂ emitted from the laser light source 9
Laser light 10 passes through the lens 11, the half mirror 5, and the lens 6, and illuminates the fine particle group 8 over a wide range.
The laser beams 2 and 10 transmitted through the fine particle group 8 are split into two by the half mirror 12. The laser beams 2 and 10 reflected by the half mirror 12 enter a CCD camera 14 via a lens 13, and pass through a lens 15 provided in the CCD camera 14 onto a light receiving surface of the CCD 16 to form a fine particle group 8.
Is imaged.

The CCD camera 14 is a monitor television 17
Are connected, and the particle group is displayed on the display screen 17a. In this display, the area irradiated by the laser light 2 is displayed with higher brightness than the surrounding area or in a color different from the surrounding area, whereby any part of the particle group 8 is irradiated with the laser light 2. It will be specified whether or not it is done.

Here, this apparatus is provided with moving means (not shown) for moving the laser light source 1 together with the lens 3 and the pinhole plate 4 in the direction of the arrow AB shown in the drawing or in the direction perpendicular to the plane of the drawing. Thereby, the irradiation position of the particle group 8 by the laser beam 2 is changed. The change of the irradiation position is performed while visually recognizing the irradiation position of the laser beam 2 displayed on the monitor television 17.

On the other hand, the laser beams 2 and 10 transmitted through the half mirror 12 transmit the laser beam 2 having the wavelength λ ₁ and cut the laser beam 10 having the wavelength λ _2.
The laser beam 2 irradiating the interference filter 8 and passing through the interference filter 18 is incident on the CCD camera 19. The laser light 2 incident on the CCD camera 19 irradiates the light receiving surface of the CCD 21 after passing through the lens 20. With this, CCD2
At 1, a diffraction image of the laser beam 2 by the fine particle group 8 is received.

FIG. 2 is a diagram showing an example of a diffraction image pattern on the front surface of the CCD 6. When the particle group 8 is composed of only particles having a predetermined diameter, CC
For example, a diffraction pattern 31 indicated by a broken line in FIG. 2 is generated on D6, and when the fine particle group 8 is composed of only a fine particle group having another predetermined diameter, a diffraction pattern 32 indicated by a chain line in FIG. 2 is generated. Here, since the fine particle group 8 is composed of fine particles having various diameters, the diffraction pattern 30 formed by the fine particle group 8 is superimposed with the diffraction patterns (diffraction patterns 31, 32, etc.) of the fine particles having various diameters. It will be.

The diffraction pattern received by the CCD 21 shown in FIG. 1 and converted into an electric signal is input to an arithmetic circuit 22. In the arithmetic circuit 22, an example is shown in FIG. 3 based on a signal representing the diffraction pattern. As shown, the particle size distribution N of the particles having each particle size d is obtained. FIG.
FIG. 2 is a front view showing an example of a CCD in which a glass plate provided with a mask for cutting zero-order light and a filter for attenuating diffracted light is attached to the surface.

In this embodiment, the CCD 21 is scheduled to roughly adjust its optical axis so that the zero-order light is irradiated to the upper left end of FIG. Is attached to the upper left corner of the surface of the CCD 21. On the other hand, as shown in FIG. 2, the amount of light in the diffraction pattern is larger in the area closer to the center of the optical axis (the irradiation position of the zero-order light) on average, and the amount of light decreases as the distance from the center of the optical axis increases. Therefore, in the present embodiment, adjacent to the mask 40,
An ND filter 41 having a uniform density is attached to an upper left area of FIG.

Here, since the left end of the CCD 21 is covered with the mask 40 and the zero-order light is not received, this embodiment utilizes the fact that the diffracted light pattern is to be rotated about the center of the optical axis. In the means 22 (see FIG. 1), C
By performing binarization processing on the diffraction pattern received by the CD 21 with a predetermined threshold value, for example, an arc 42 shown by a broken line in FIG. 4 is obtained, and a center point 0 of the arc 42 is obtained. The point is set to the optical axis center 0. After calculating the optical axis center 0 as described above, the calculating means 22 corrects the portion of the diffraction pattern attenuated by the ND filter 41, and based on the corrected diffraction pattern, the particle size distribution of the fine particle group 8 Is required.

The obtained particle size distribution is displayed on the display screen 23a of the monitor CRT display device 23 in the form of, for example, a graph shown in FIG.
In the above embodiment, the moving means described above is provided to change the irradiation position of the particle group 8 by the laser beam 2 without moving the entire image of the particle group displayed on the monitor television 17. Instead of having transportation means,
The irradiation position of the particle group 8 by the laser beam 2 may be changed while moving the entire apparatus.

In the above embodiment, the two laser beams 2, 10 are combined, divided, and separated by using the half mirror 5 and the interference filter 18, but the laser beam having the wavelength λ ₁ is used instead of the half mirror 5. For example, a dichroic mirror or the like that reflects the laser beam ₂ and transmits the laser beam 10 having the wavelength λ ₂ may be provided.
Instead of 8, a filter or the like is provided at the position of the half mirror 12 so as to divide the laser light 2 having the wavelength λ ₁ into transmitted light and reflected light and reflect the laser light 10 having the wavelength λ _2. You may.

Further, in the above embodiment, the image of the particle group is displayed on the monitor television 17 using the monitor CCD camera 14. However, instead of including the CCD camera 14 and the monitor television 17, the particle group 8 is displayed. May be configured to be optically projected on a screen without being converted into an electric signal. Since the laser beam 10 among the two laser beams 2, 10 is used for illumination, it need not be a laser beam, and may be incoherent light emitted from various light sources. It is preferable that the light has a wavelength that can be sufficiently separated from the laser light 2 having the wavelength λ ₁ .

[0020]

As described in detail above, the particle size distribution measuring apparatus according to the present invention provides an illumination optical system for illuminating a fine particle group over a wide area, and a method for obtaining an image of the fine particle group as a diffraction image pattern. Monitor means for clearly displaying the irradiation position of the laser light, and a separation optical system for separating the illumination light and the laser light and guiding only the laser light to a solid-state imaging device for detecting a diffraction image pattern. In addition, it is possible to easily confirm at which position of the particle group the particle size distribution measurement is being performed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a particle size distribution measuring device according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a diffraction image pattern on a front surface of a CCD.

FIG. 3 is a diagram illustrating an example of a measured particle size distribution.

FIG. 4 is a front view showing an example of a CCD in which a glass plate provided with a mask for cutting zero-order light and a filter for attenuating diffracted light is adhered to the surface.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser light source 4 pinhole plate 5 half mirror 7 outlet 8 particle group 9 laser light source 12 half mirror 14 monitor CCD camera 17 monitor TV 18 interference filter 19 measurement CCD camera 22 arithmetic means 23 monitor CRT display device 30 combined Diffraction pattern 40 mask 41 ND filter

Claims (1)

(57) [Claims] An irradiation optical system for irradiating a group of particles with a laser beam, a solid-state imaging device for receiving a diffraction image of the group of particles, and a solid-state imaging device for receiving the diffraction image of the group of particles based on a diffraction image pattern received by the solid-state imaging device. A particle size distribution measuring apparatus comprising: a calculating means for calculating a particle size distribution, wherein the illumination optical system illuminates the fine particle group with an illumination light over a wider area including an area irradiated by the laser light. System, monitor means for clearly displaying the image of the fine particle group in an area irradiated by the laser light, and separation optics for guiding only the laser light of the illumination light and the laser light to the solid-state imaging device And a particle size distribution measuring device.