JP2001165850A - Oil film detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oil film detector to detect an oil film thinner than that of a conventional one by solving problems that a very thin oil film in the initial stage flowing into an intake must be detected, and the sensitivity of the conventional oil film detector is insufficient when mixture of a small amount of oil causes a problem in monitoring the water intake though the conventional oil film detector by the polarization analytical method is less easily affected by the wave on the water surface and capable of detecting the oil film with the equivalent sensitivity as the visual detection. SOLUTION: The sensitivity is improved by providing a light beam flooding means to diagonally irradiate the beam onto the water surface with an oil film floating thereon, a reflective mirror to reflect the reflected light from the water surface again, a light receiving means to measure the light quantity of the P polarized wave component and the S polarized wave component by receiving the re-reflected light from the water surface, and a signal processing means to detect the oil film on the water surface based on the polarization ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for detecting an oil film on a water surface. More specifically, the present invention relates to an oil film detecting device that automatically detects an oil component flowing into a water purification plant, a farm, or the like, or an oil component flowing out of a factory drainage facility or the like as an oil film on the water surface.

[0002]

2. Description of the Related Art In a water purification plant, most of the water quality accidents in raw water are caused by oil pollution, which is a serious accident that requires the suspension of water intake and cleaning of the water purification plant. Because of the danger of contamination or death,
There is a need for a method and apparatus for constantly monitoring the flow of oil into these water intake facilities. On the other hand, in industrial wastewater, discharging wastewater mixed with oil into public waters is a social problem as water pollution, and it is necessary to meet wastewater standards, so oil remains in the treated wastewater. There is a need for a method and apparatus for continuously monitoring for presence.

As methods for automatically detecting the inflow of oil into water at a water purification plant in a non-contact manner, a reflectance measuring method and an image monitoring method using a TV camera have been conventionally known. However, these oil detection devices have a problem that it is difficult to detect a trace amount of oil, and in order to solve them, an oil film detection device based on ellipsometry has been developed by the present inventors. It is filed as Kaihei 10-281980.

FIG. 5 shows an example of the configuration of this conventional oil film detecting device based on ellipsometry, and an outline of the measuring method will be described below. In this figure, a laser light source 1
The light beam 2 from the laser light source 1 is applied obliquely to the wavy water surface 4 on which the oil film 3 floats. The polarization state of the reflected light 5 reflected from the water surface 4 is measured by the light receiving means 6, the details of which are as follows. That is, of the reflected light 5 scattered in various directions due to the waving of the water surface 4, the reflected light reflected at a certain angle is received through the pinhole 7. This received light is converted by the polarizing beam splitter 8 into P
The light is separated into a polarized light component 9 and an S-polarized light component 10, and the separated P-polarized light component 9 and S-polarized light component 10 are photoelectrically converted by a photodiode 11 and a photodiode 12, respectively, and each light amount is converted into an electric signal. Each of the photoelectrically converted electric signals is
The signal is input to the signal processing means 13, and the signal processing means 13 calculates the light quantity ratio of the P-polarized component and the S-polarized component (hereinafter referred to as polarization ratio). The presence / absence of an oil film is determined by comparing with the reference value. The P-polarized light component and the S-polarized light component in the above description are defined as a plane including the normal line of the water surface and the incident optical axis set at the point where the incident optical axis of the light beam 2 intersects the flat water surface without waves.
A parallel polarization component is defined as a P polarization component, and a vertical polarization component is defined as an S polarization component.

When an oil film is present on the water surface, the reflected light intensity changes due to the difference in the refractive index between oil and water. When this change is divided into reflected light of the P-polarized component and the S-polarized component, the change is reflected. Each is different. Therefore, when the polarization ratio is calculated from the measurement of the amount of the polarized light component, the oil film can be detected because the value of the polarization ratio changes due to the presence of the oil film.

The advantage of setting the ratio between the P-polarized light component and the S-polarized light component is that the ratio is hardly affected by ripples on the water surface or floating foreign matter. For example, if the water surface is wavy, irregularly reflected light will be generated, so simply monitoring the intensity of the reflected light will change the intensity, making stable measurement impossible and lowering the sensitivity. As long as light is received at a fixed reflection angle, the ratio of the polarization components is hard to change, so that stable and highly sensitive measurement can be performed.

[0007]

The oil film detecting device based on the above-mentioned ellipsometry is hardly affected by the ripples on the water surface.
Oil film can be detected with the same sensitivity as visual inspection. However, especially when used for monitoring water intake at a water purification plant, contamination of a small amount of oil becomes a problem, and therefore higher sensitivity is desirable. In addition, in order to detect oil slicks early, it is necessary to detect a small amount of oil slicks in the initial stage where oil diffused in rivers flows into the intake.
In this case, the sensitivity of the conventional oil film detection device is insufficient.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a more sensitive oil film detecting device capable of detecting an oil film thinner than the conventional one.

[0009]

Means for Solving the Problems To solve the above problems, the first apparatus of the present invention employs a method in which an oil film floats on the water surface.
A light projecting means for irradiating a light beam containing both a P-polarized component and an S-polarized component, a reflecting mirror for reflecting the reflected light from the water surface to the water surface again, and receiving the light re-reflected from the water surface The light receiving means for measuring the light quantity of the P-polarized component and the light quantity of the S-polarized component and the signal processing means for detecting the oil film on the water surface based on the light quantity ratio of the P-polarized component and the S-polarized component are employed as technical means. .

[0010] In the first device, the light reflected from the water surface due to the light beam irradiation is reflected again on the water surface by the reflection mirror, and the light reflected twice from the water surface is received.
If there is an oil slick on the water surface, it will be affected twice,
The sensitivity of oil film detection is improved. For example, when the incident angle of the irradiation light and the incident angle of the re-irradiation light from the reflection mirror are the same,
The light amount of the P-polarized light component and the light amount of the S-polarized light component that are reflected twice on the water surface and reach the light receiving means are respectively the light amounts obtained by squaring the reflectance at the time of the single reflection. Therefore, the polarization ratio of light reflected twice on the water surface is the square of the polarization ratio in the case of single reflection, the difference due to the presence or absence of an oil film is further amplified, and the film thickness sensitivity of oil film detection is improved. Thus, the oil film detecting device invented can detect the oil film with higher sensitivity than the conventional device.

According to a second apparatus of the present invention, a specular reflection mirror is employed as the reflection mirror in the first apparatus of the invention, and the light returns along the same optical path as the irradiation light in the direction opposite to the traveling direction of the irradiation light. A non-polarizing beam splitter which reflects a part of the reflected light in the horizontal direction by 90 ° and guides the reflected light to the light receiving means is employed as a technical means. Since the second device uses a regular reflection mirror as the reflection mirror, the irradiation light and the re-irradiation light from the regular reflection mirror can irradiate the same place on the water surface, and even when the oil film has uneven position, the irradiation position When an oil film is present in the oil film, the oil film can always be irradiated twice, and a stable sensitivity improving effect can be obtained. The re-reflected light (return light) from the water surface of the irradiation light and the re-irradiation light passes through the same optical path. Therefore, in order to guide the return light returning in the direction opposite to the traveling direction of the irradiation light to the light receiving unit, the return light is required. It is necessary to reflect a part of the light beam in the 90 ° lateral direction by a non-polarizing beam splitter and guide it to the light receiving means. The other configuration is the same as the first means, and the oil film is formed with higher sensitivity than the conventional device. Can be detected.

According to a third aspect of the present invention, in the first or the second aspect of the invention, the light beam scanning means for linearly scanning the light projecting means with a light beam and irradiating the water surface is used as technical means. adopt. This third apparatus uses a light beam scanning unit that linearly scans a light beam with a light projecting unit and irradiates the water surface with the light beam, so that a wide range of oil film on the water surface can be detected. At this time, the scanning light turned back by the reflection mirror passes through the scanning optical system again in the direction opposite to the traveling direction of the irradiation light and returns to one light beam. Therefore, the configuration other than the light projecting means is the same as the first means. Therefore, it is possible to detect an oil film in a wide measurement area with higher sensitivity than a conventional apparatus.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on two embodiments. Embodiment 1 FIG. 1 shows an oil film detecting device as a first embodiment of the present invention. In this figure, the same components as those shown in FIG. 5 indicate the same components.

In FIG. 1, a laser light source 1 is used as a light projecting means, and a light beam 2 containing a P-polarized component and an S-polarized component is used.
Is applied obliquely to the wavy water surface 4 on which the oil film 3 floats. Of the reflected light 5 scattered in various directions due to the waving of the water surface 4, the reflected light reflected at a fixed angle is specularly reflected by the reflection mirror 14 and irradiates the same position on the water surface again. The non-polarized beam splitter 15 receives the re-reflected light that reflects twice on the water surface and returns on the same optical path as the irradiated light in the direction opposite to the traveling direction of the irradiated light, and reflects 50% of the re-reflected light in the 90 ° lateral direction. Then, the light is guided to the light receiving means 6. The light receiving means 6 passes the received light through a polarization beam splitter 8 to separate it into a P-polarized component 9 and an S-polarized component 10. The separated P-polarized light component 9 and S-polarized light component 10 are separated into a photodiode 11 and a photodiode 12
, Respectively, and each light amount is converted into an electric signal.
Each of the photoelectrically converted electric signals is input to a signal processing unit 13, which calculates a polarization ratio between a P-polarized component and an S-polarized component, and uses the calculated polarization ratio as a standard when there is no oil film on the water surface. The presence or absence of the oil film is determined by comparing the value with the value.

Since the apparatus of the first embodiment receives light reflected twice from the water surface, the light quantity of the P-polarized light component and the light quantity of the S-polarized light component are each equal to the reflectivity at the time of single reflection. It becomes the light quantity of the power. Therefore, the polarization ratio of the re-reflected light is the square of the polarization ratio in the case of single reflection, the difference due to the presence or absence of the oil film is further amplified, and the oil film detection sensitivity is improved. The apparatus of the first embodiment of the present invention shown in FIG. 1 and the conventional apparatus shown in FIG.
FIGS. 2 and 3 show data obtained by measuring the polarization ratio of the water surface on which the oil film floats as a function of the film thickness. In both measurements, the wavelength of the laser beam is 633 nm, the incident angle is 70 °, and the type of oil is oil A heavy oil.

From the measurement data, the difference between the polarization ratio when there is no oil film (zero film thickness) and the polarization ratio when there is an oil film is that the apparatus of Example 1 is much larger than the conventional apparatus.
It is clear from FIGS. 2 and 3 that it can be seen that the device of Example 1 of the present invention can detect the oil film with higher sensitivity than the conventional device. [Embodiment 2] Fig. 4 shows an oil film detecting apparatus according to a second embodiment of the present invention. In this figure, the same components as those shown in FIGS. 5 and 1 indicate the same components.

In this embodiment, a light beam 4 is transmitted to a light beam scanning mechanism 18 comprising a polygon mirror 16 and a lens 17.
And irradiates the floating water surface of the oil film 3. The scanning direction 19 of the light beam intersects the direction 20 in which the oil film flows, and irradiates the oil film flowing within the scanning range one after another. The scanning light beam 21 specularly reflects the reflected light reflected at a certain angle among the reflected lights 5 scattered in various directions by the waves generated at the respective irradiation positions in the scanning range on the water surface by the elongated reflecting mirror 14. The same scanning position on the water surface is illuminated again. The scanning light that reflected the water surface twice,
The light again passes through the scanning optical system in the direction opposite to the traveling direction of the irradiation light, and
Return to the book light beam. The other configuration is the same as that of the first means, and it is possible to detect an oil film in a wide measurement area with higher sensitivity as compared with the conventional apparatus as in the first embodiment.

Although the drawings of the first and second embodiments do not show a method of installing the oil film detecting device, the oil tank is fixed around a water tank in which the oil level does not change, and is floated in a river or ocean where the water level changes. And a method of floating on the water surface for installation. Also, when there is an influence of disturbance light such as sunlight, an interference filter that passes only the wavelength of the projected beam is provided in front of the photoelectric converter in the light receiving unit, or the projected beam is modulated and only the modulation frequency is signaled. The influence of disturbance light can be eliminated by sorting in the processing unit.

[0019]

The oil film detecting device according to the present invention relates to an oil film detecting device for automatically detecting an oil component flowing into a water purification plant, an aquaculture plant or the like, or an oil component flowing out of a factory drainage facility as an oil film on the water surface. In order to improve the film thickness measurement sensitivity, which is a problem of the conventional apparatus, the water surface was re-irradiated with the light reflected from the water surface by irradiating the light beam, and the water surface was again illuminated. Since the oil film is detected by analyzing the polarization ratio of the light reflected twice, the oil film can be detected with higher sensitivity as compared with a conventional device that analyzes the polarization ratio of the light reflected once on the water surface and detects the oil film.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an oil film detection device as a first embodiment of the present invention.

FIG. 2 is a diagram showing a change in a polarization ratio with respect to an oil film thickness when a water surface on which an oil film floats is measured by the apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a change in a polarization ratio with respect to an oil film thickness when a water surface on which an oil film floats is measured by a conventional apparatus.

FIG. 4 is a schematic view of an oil film detection device according to a second embodiment of the present invention.

FIG. 5 is a schematic view of a conventional oil film detection device.

[Explanation of symbols]

 1: Laser light source 2: Light beam containing P-polarized component and S-polarized component 3: Oil film 4: Water surface 5: Reflected light 6: Light receiving means 7: Pinhole 8: Polarized beam splitter 9: P-polarized component 10: S-polarized component 11, 12: Photodiode 13: Signal processing means 14: Reflecting mirror 15: Non-polarizing beam splitter 16: Polygon mirror 17: Lens 18: Light beam scanning mechanism 19: Scanning direction of light beam 20: Direction of oil film flow 21: Scanning Light beam

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naohiro Noda 1-1, Tanabe Nitta, Kawasaki-ku, Kawasaki, Kanagawa Prefecture Inside Fuji Electric Co., Ltd. (72) Inventor Hiroshi Tada No. 1, Tanabe Nitta, Kawasaki-ku, Kawasaki-ku, Kanagawa Prefecture No. 1 Fuji Electric Co., Ltd. (72) Inventor Yusuke Nakamura 1-1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture F-term in Fuji Electric Co., Ltd. (Reference)

Claims (3)

[Claims] 1. A polarization component parallel to a plane including the normal line of the water surface and the incident optical axis set at a point where the incident optical axis of light obliquely incident on the water surface on which the oil film floats intersects the water surface (hereinafter referred to as P-polarized light). Component) and a polarization component perpendicular to the plane (hereinafter, referred to as a component).
Light emitting means for irradiating a light beam containing both components, an S-polarized component, a reflecting mirror for reflecting the reflected light from the water surface to the water surface again, and receiving the light re-reflected from the water surface. Light receiving means for measuring the light amount of the P-polarized component and the light amount of the S-polarized component, and signal processing means for detecting an oil film on the water surface based on the light amount ratio (polarization ratio) of the P-polarized component and the S-polarized component. An oil film detection device characterized by the following. 2. The oil film detecting device according to claim 1, wherein the reflection mirror is a regular reflection mirror, and the re-reflected light returning in the same optical path as the irradiation light in the direction opposite to the traveling direction of the irradiation light. An oil film detecting device, comprising: a non-polarizing beam splitter that reflects a part of the light beam in a 90 ° lateral direction and guides the light beam to a light receiving unit. 3. The oil film detecting device according to claim 1, wherein said light projecting means comprises a light beam scanning means for linearly scanning a light beam and irradiating the water surface. Oil film detector.