JPS59107201A - Measuring device of foreign matter in fluid - Google Patents

Abstract

PURPOSE:To improve the reliability of measured data by providing two optical foreign matter detectors in directions different from each other. CONSTITUTION:A light-transmissive part 3 is formed on the way of a tube 2 where a liquid 1, where mixed foreign matters 9 should be measured, is flowed. Two optical foreign matter detectors 4 and 11 are provided to cross each other in the transverse section of the liquid 1 in the light-transmissive part 3. Detectors 4 and 11 consist of light sources 5 and 12, slits 6 and 13, and photodetectors 7 and 14. If the light source 5 projects light momently when the foreign matter 9 passes a measuring region 15, the quantity of received light of the photodetector 7 is reduced, and the area of a section of the foreign matter 9 orthogonal to the measuring axis is attained. Similarly, the area of a section different from said section by 90 deg. is attained with the light source 12 and the photodetector 14. Since the section is measured in two directions orthogonal to each other, the size of the foreign matter 9 is measured accurately.

Description

[Detailed description of the invention] The present invention relates to a device for measuring foreign matter in a fluid.

Generally, in the manufacturing process of semiconductor devices, ultrafine processing is performed, so it is important to avoid foreign substances such as dust and microorganisms being mixed into liquids such as purified water for cleaning and etching liquid. . Therefore.

Measurement of the number of foreign substances mixed in such a liquid and the thickness of the liquid has been carried out.

As a conventional foreign matter inspection device of this type in liquid.

For example, there is one shown in FIG.

In FIG. 1, this device is equipped with a tube 2 through which a liquid to be measured 1 flows at a constant speed, and in the middle of this tube 2 there is a transparent section 3 with a part of the tube wall cut out or It is formed by fitting a transparent material such as quartz or glass into it. An optical foreign object detector 4 is installed outside the light-transmitting part 3.
This detector 4 is provided with a light source 5, a light-transmitting slit 6, and a light receiver 7, and the light transmitted through the slit 6 crosses the light-transmitting part 3 and reaches the light receiver 7. It is configured to receive light.

When a foreign object 9 in the liquid passes through the measurement region 8 formed by the intersection area of the light and the liquid 1, the foreign object 9 blocks light, so that the amount of light received by the light receiver 7 decreases. therefore,
The number of foreign particles mixed in is measured based on the number of decreases, and the size of the foreign particles is estimated based on the rate of decrease in the amount of light.

If the size of the foreign object is on the same order as the wavelength of the emitted light, it is difficult to measure the shading, so in that case the scattered light is measured.

However, in such conventional foreign object measurement devices in liquid, the measured value of the size of the foreign object varies depending on the orientation of the light receiver with respect to the measurement axis when passing through the measurement area, so the m constant value and the actual value may differ. However, the reliability of the measured data is extremely low.

SUMMARY OF THE INVENTION An object of the present invention is to provide a foreign matter measuring device in a fluid that can overcome the drawbacks of the prior art and achieve high reliability. - Hereinafter, the present invention will be explained according to embodiments shown in the drawings.

FIG. 1 is a perspective view showing an embodiment of a foreign matter measuring device in a fluid according to the present invention, and FIG. 2 is a diagram showing measurement timing.

In this embodiment, a tube 2 through which a liquid l as a fluid to be measured for mixed foreign matter 9 flows at a constant speed and in a laminar flow state.
A light-transmitting part 3 is formed in the middle of the light-transmitting part 3, and two sets of optical foreign object detectors 4 and 11 are arranged on the outside of the light-transmitting part 3 so as to be mutually arranged in the cross section of the liquid l in the light-transmitting part 3. It is set up so that it intersects with the

The rain detector 4.11 includes light sources 5, 12 and a slit 6.1.
3, and light receiving parts i%7 and 14, respectively, so that the light transmitted through the second slit 6 crosses the light transmitting part 3 to the first light receiving part 'm7, and the light transmitted through the second slit 13 is transmitted. Light part 3
It is configured such that the light beams are received by the second light receiver 14 across the two directions.

When the fluid 1 flowing through the tube 2 becomes a laminar flow state at a constant speed in the transparent part 3, each light source 5 in the first detector 4 and the second detector 11 is turned off with a time sure as shown in FIG. and 12 are flashed alternately at high speed.

The foreign matter 9 mixed into the fluid 1 and flowing together with the liquid 1 passes through the measurement area 15, which is formed by the relationship between the flow velocity and the width in the same direction as the high return flow of the slit and photoreceiver. When the first light source 5 momentarily emits light while
blocks the light transmitted through the slit 6. This light-blocking state is a state in which the foreign object 9 passing through is directly projected onto the first light receiver 7. Therefore, the amount of light received by the first light receiver 7 decreases in accordance with the blocking of light, and based on the decrease 11, the area of the cross section of the foreign object 9 perpendicular to the measurement axis can be determined.

When the same foreign object 9 is passing through the same measurement area 15, the second light source 12 momentarily emits light.

The foreign object 9 blocks the light transmitted through the sleeve 13 and casts a shadow on the second light receiver 14. Due to this projection, the amount of light received by the second light receiver 14 decreases, and based on the amount of decrease, the area of the cross section of the foreign object 9 perpendicular to the measurement axis can be determined. However, since the first detector 4 and the second detector 11 are arranged in directions orthogonal to each other, the measurement of the cross-sectional area of the foreign object 9 by the second light receiver 14 this time is based on the previous first light reception. The measurement is performed in a direction perpendicular to the measurement of the cross-sectional area of the foreign object 9 by the instrument 7.

In this way, according to this embodiment, it is possible to measure the cross-sectional area of the same foreign object in two mutually perpendicular directions, making it possible to accurately measure the size of the foreign object. Improved reliability.

For example, when a plate-shaped foreign object flows in a direction parallel to the measurement axis of the first detector and passes through the detection area.

In the conventional measuring device shown in Fig. 1, the size of the foreign object is measured as minute, but in the measuring device shown in Fig. 2, the foreign object is oriented perpendicular to the measurement axis of the second detector. Therefore, the plate area is measured, and accurate measurement is achieved.

Note that in the embodiments described above, it is better to set the measurement area as small as possible. This is because if the direction of the foreign object changes while passing through the measurement area, measurements in two mutually orthogonal directions will not be performed, so it is necessary to reduce the risk of this change of direction as much as possible. . Additionally, it is desirable to separate the first and second detectors as much as possible to avoid mutual interference when performing measurements; however, if they are too far apart, the measurement area will become large. To avoid interference, the separation should be kept to the minimum possible.

In the above embodiment, a case has been described in which the distance between the measurement execution timings of the first detector and the second detector is obtained by the blinking timing of both light sources. etc. may be provided respectively, or the first
The detector and the second detector may be arranged offset in the flow direction to an extent that they do not interfere with each other.

In addition, although the case where two sets of detectors are arranged in two directions perpendicular to each other has been described, the present invention is not limited to this. For example, three sets of detectors may be arranged in three directions (so-called If a detector is installed, the three-dimensional size of a foreign object can be determined accurately, and if a large number of sets of detectors are arranged in multiple directions, mutual measurements can be compensated for.

Furthermore, the optical foreign object detector is not limited to one that detects a decrease in the amount of light due to light blocking by a foreign object as in the above embodiments, but may be a detection device that detects an increase in the amount of light due to diffuse reflection caused by a foreign object. In particular, for foreign particles on the μm order, the same effect can be obtained by using scattered light.

Furthermore, the present invention is not limited to measuring the size of foreign objects in liquid;
It can also be applied to a gaseous foreign matter inspection device that measures foreign matter in gas. In addition, the measurement of a number of foreign objects can be performed based on the number of changes in the measurement light intensity of the detector, as in the conventional example, and it is possible to correct and match the number of measurements using the measurement data of multiple sets of detectors. As described above, according to the present invention, it is possible to accurately measure foreign substances in a fluid.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a conventional example, FIG. 2 is a perspective view showing an embodiment of the present invention, and FIG. 3 is a perspective view showing the establishment timing. l...Liquid, 2...Pipe, 3...Transparent part, 4...
1st detector, 5.12...Light source, 6.13...Slit, 7°14...Aiji-candy, 9...Foreign object, 11.
...Second detector, 15...Measurement area.

Claims (1)

[Claims] 1. A device for measuring foreign matter in a fluid, characterized in that a plurality of optical foreign matter detectors are provided in different directions in a channel through which fluid flows at a constant speed.