JPH07101192B2 - Gas leak monitor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a tank in a factory,
The present invention relates to a gas leak monitoring device for detecting a gas leak of a gas to be detected which leaks from an outdoor or indoor pipe in a home such as a pipe or an embedded conduit on a road or the like.

[0002]

2. Description of the Related Art Conventionally, in gas leak detection in a factory, a plurality of detection devices are arranged in a monitoring target area to grasp the situation of gas leak. However, in this method, detection is limited to single point detection. Furthermore, there was a device that detects the gas concentration using laser light.

[0003]

However, all of the above are limited to those in which a point or one dimension is a monitoring region or a detection target. Therefore, in order to monitor the monitored area two-dimensionally, an irradiation device that irradiates the monitored area two-dimensionally with a laser beam having a wavelength absorbed by the gas to be detected and the transmission through the monitored area are monitored. The detection means for detecting the laser light reflected by the background of the target area and the detection information obtained by the detection means are also included in the background image of the monitoring target area.
Including being configured and display means for two-dimensionally image display, the operator by viewing the image information displayed on the display means, has been proposed for monitoring gas leakage. However, in such a monitoring device,
The detection signal is weak and the display is not properly displayed. (The screen is excessively bright or dark depending on the day or the season due to the influence of sunlight etc., and the resolution of the brightness for the gas concentration of the monitoring target is poor. However, even if it is displayed, there is a drawback that the presence of gas cannot be clearly confirmed. In addition, publicly available
Since the output of a strong laser is weak,
Human beings who are good at being unaffected by sunlight etc.
Is difficult to obtain, and this process
It becomes a problem. Therefore, an object of the present invention is to provide a monitoring device in which the display on the display means is appropriately performed in such a monitoring device.

[0004]

[Means for Solving the Problems] To achieve this object
Characteristic feature of the monitoring device of the present gun invention is the irradiation unit, the irradiation
Focus the laser light and change the area of the irradiation target area
An irradiation area changing means is provided, and a laser is used as a detecting means (R).
The wavelength (λ) of the light (L) is set at the approximate center position, and
Limiting the band of the luminous flux entering the output means (R)
And a transmission bandwidth changing means (R
4) is provided . The action and effect are as follows.

[0005]

In the monitoring device as described above, it is necessary to properly adjust the signal and deliver it to the display means side. The application of the monitoring device to this, the transmission band width changing means and the irradiation area changing means are provided together.

That is , as shown in FIG. 2 and FIG. 4, the area of the laser light irradiated by the irradiation area changing means is variable (in FIG. 2 , the monitoring area in the normal state is irradiated with a chain double-dashed line). The monitoring area in a state where the area is reduced is indicated by a dashed line). Then, in a normal monitoring state, laser light is emitted with a large viewing angle so as to cover a relatively wide area. In this state, a relatively high concentration gas region is displayed on the display device. On the other hand, when it becomes necessary to perform centralized monitoring in the monitored area, the irradiation area changing means
Laser light is irradiated in a concentrated manner in a certain area. And
In this state, even a relatively low concentration gas region is displayed with good contrast. Explain this state in more detail
Then, in the device of the present application, the transmission bandwidth changing means is used.
Therefore, the transmission bandwidth passed to the detecting means is limited.
Within this transmission bandwidth, the information on the laser beam is mainly
Is a signal related to gas, and signals near that wavelength are mainly
It becomes a background signal. Here, change the irradiation area to
Increase or decrease the amount of irradiation laser light for a gas within a certain range
If you try, the ratio of the gas signal amount to the background signal amount changes,
Contrast the gas image on the display with the background image
It is possible to achieve a state in which it can be displayed well.

Furthermore, the transmission band width of the signal passed to the detection means by the transmission bandwidth varying means is varied. Naturally , since the wavelength of the laser light is included in this band, the information (referred to as S) due to the laser light becomes a signal mainly relating to gas, and a signal in the vicinity of that wavelength (referred to as N). ) Is mainly the background signal. Here, in the display means, a normalization process is generally performed. In this processing, the integrated value of the signal within the detection band is taken, the maximum value of the output signal is determined according to this integrated value, and the signal is normalized according to this value. And this is dominated by the transmission bandwidth described above. Therefore, by changing this bandwidth to an appropriate value, the S / N ratio is changed, and this ratio can be freely selected in an appropriate display state on the image side. Therefore,
By adjusting this ratio appropriately , the background image and the gas image
It is possible to make the balance of the display of the image good so that it can be identified .

[0008]

Therefore, in such a monitoring device,
It is possible to obtain a monitoring device that is appropriately displayed so that the display on the display device matches the gas monitoring.

[0009]

Embodiments of the present application will be described with reference to the drawings. FIG. 1 shows a state in which the gas leakage monitoring device 1 of the present application is used to monitor gas leakage in the vicinity of the spherical holder 2 (a flange connection portion 2a of a pipe connected to the spherical holder 2) in a gas manufacturing factory. It is shown. That is, the presence or absence of leakage of the combustible gas g as the gas to be detected is monitored in the leakage monitoring area A with the spherical holder 2 as a background of the monitoring target area in the background. Explaining the schematic configuration of the monitoring operation, a laser beam L having a specific wavelength λ is emitted from an irradiation device E as an irradiation unit provided in the gas leakage monitoring device 1 through the leakage monitoring area A to a spherical holder. It is irradiated toward the area with 2 as the background. Then, the laser light L reflected from this background is detected by a detection device R as a detection means, and is displayed on a TV device S (having a storage device 5) as a display means connected to the detection device R. To be done. First, the gas leak monitoring device 1 of the present application
The detailed configuration of the above will be described with reference to FIGS. 2 and 3 .
The gas leak monitoring device 1 is a device for irradiating a leak monitoring area A with a laser beam L absorbed by a combustible gas g such as methane, ethane, propane, butane, which is a gas to be monitored, and a leak monitoring device. The detection device R is configured to detect the laser light L transmitted through the area A and reflected from the background. Further, the detection signal is sent from the detection device R to the TV device S, which is a display means, and an image is displayed. The irradiation device E includes a laser generation device E1 and a light beam diffusion device E2 (including a beam expander and a zoom mechanism) as irradiation area changing means for changing the irradiation area of the laser irradiation light arranged on this optical path.
And are provided. Naturally, this luminous flux diffusion device E2
Almost all of the light emitted from the laser generator E1 is transmitted to the irradiation side while changing the area of the irradiation target area (actually the viewing angle) without energy attenuation. On the other hand, the detection device R is configured to include a zoom device R2, a bandpass filter R3, and an infrared image sensor R1 from the light incident side. Here, a plurality of bandpass filters R3 are prepared, and the switching device R4 can change the bandwidth of transmitted light. The specifications of each element in the above-described device will be listed. Infrared source as laser generator E1 Laser type Helium-neon laser Nominal output 8mW Center wavelength λ 3.39μm, Transmission spectrum width 0.09μm Viewing angle Normal use Max 14 ° Focusing use 1 ° Distance to background Several meters to several meters 100m Image sensor R1 Detection wavelength range 3 μm to 5 μm Maximum detection temperature difference 0.15 ° C. or less (NETD) Bandpass filter width α + β 0.1 to 2 μm where α and β are set arbitrarily.

The operation of the gas leak monitoring device 1 of the present application will be described below. First, the principle will be described. The laser light L is emitted from the irradiation device E of the gas leakage monitoring device 1 toward the area with the spherical holder 2 as the background through the leakage monitoring area A, and the laser light L is also emitted from this background. L is reflected and is incident on the detection device R of the device 1, and this signal is detected and displayed on the TV device S connected to this detection device R. Here, if there is a flammable gas g to be monitored in the leakage monitoring area A, the laser beam L is absorbed in the forward path and backward path to the combustible gas g, spatial (secondary source to the laser beam L Intensity differences (at different positions when imaged ). Therefore, this information is detected by the image sensor R1, if displayed, as shown in FIG. 3, the background
As a two-dimensional image including, the image is displayed as a grayscale image or a different color image (when such a process is performed) according to the presence or absence of gas and the concentration.

The operating principle of the monitoring device 1 is as described above. However, when the monitoring device 1 is simply provided with a device system that operates as described above, the screen of the TV device S is reflected by sunlight or the like. For example, it becomes excessively bright or dark depending on the background light intensity. Further, there is a problem that the difference in brightness on the display screen with respect to the concentration of the gas to be monitored is low, and even if it is displayed, the presence of gas cannot be clearly confirmed.
Therefore, in order to solve these problems, in the monitoring device 1 of the present application, a plurality of light beam diffusion devices E2 for changing the irradiation area of the laser irradiation light and a plurality of band pass filters R3 are prepared, and a switching device R4 is used to provide the same. It is configured so that the transmission bandwidth can be changed.

The respective functions will be described below with reference to the drawings. As shown in FIGS. 2 and 4, by the light beam diffusing device E2 in the present application, in (Fig. 2 region of the laser light is varied to be irradiated, the surveillance area in a normal state by a two-dot chain line, the irradiation zone The monitoring area in the state where is made small is indicated by a dashed line). Then, in a normal monitoring state, laser light is emitted with a large viewing angle so as to cover a relatively wide area. In this state, the ratio of the noise intensity from the background to the signal intensity is large, so that the gas region G1 having a relatively high concentration is displayed on the display device. Now, when an abnormality is found in the monitored area, the laser light is focused on the area where the gas is present. In this irradiation, the target area is supposed to be considerably narrowed. Then, in this state, a high contrast is displayed even in the gas region G2 having a relatively low concentration. In Figure 4,
The relationship between the gas concentration and the spatial area to be detected is schematically drawn. The vertical axis of FIG. 4 is the gas concentration, and the horizontal axis is the monitoring control.
Is an arbitrary spatial area (position). like this
As a spatial area, the area (position) indicated by XX in FIG.
Can be mentioned. And as the gas shows in solid lines
As described above, it has a spatial distribution of various concentrations.
In the wide area irradiation state, a relatively high concentration is indicated by a double diagonal line.
Only the area G1 can be identified.
In the state, the area G2 indicated by a single diagonal line with a relatively low concentration is recognized.
You will be able to separate.

Next, the variable function of the transmission bandwidth will be described. The signal detected by the image sensor R1 is generally normalized. This process is a normalization process of the signal in the detection band, the maximum value of the output signal is determined according to the integrated value, and the signal is in accordance with this value. here,
For example, noise as in this application (this corresponds to the background)
To make the dark signal and the gas signal a bright signal,
The higher the gas signal amount, the brighter the image (in the opposite case, the darker)
Consisting of a but, if simply tolerate this condition, despite the gas signal <br/> No. is a strong signal, this signal is saturated,
In some cases, the entire screen may be displayed as a bright spot on a part of the TV apparatus S while it is dark. In this case, it cannot be said that the display device S accurately displays the state of gas leakage. Therefore, in the present application, the ratio of the gas signal to the noise is changed by changing the transmission bandwidth by replacing the bandpass filter R3 . In this way, the <br/> Display the definitive display device S, the identifiable state of the gas image to the background image
Therefore, it is possible to properly represent the situation of gas leakage. Here, the general TV apparatus S is equipped with a gain adjusting device (not shown), but it is possible to optimize the display state better by changing the transmission bandwidth than adjusting the gain adjusting device. Become. FIG. 5 shows the situation in which the transmission bandwidth changes.

[Other Embodiments] Other embodiments of the present application are listed below. (A) In the above-described embodiment, the laser light emitted by the irradiation device E is a single light, and the laser light having a wavelength absorbed by the combustible gas g is selected. With the laser light, the gas g
A detection system using a laser beam of a wavelength that is not absorbed is provided separately from the detection system of the above embodiment, the detection result of this system is used as the ground, and the result of the absorbed wavelength is used as gas information to detect the two wavelengths. The gas may be detected by the system. In this case, it is possible to determine the gas concentration.

(B) Further, as the background of the monitored area, in addition to the spherical holder 2, the ground, concrete wall,
It may be a painted steel structure or the like, and a screen may be provided for a specific area.

(C) Further, while the background is generally stationary, the leaked gas to be detected g flows. Therefore,
It is also possible to adopt a configuration in which the state of gas leakage can be grasped by comparing and analyzing the image information visualized by the gas leakage monitoring device 1 of the present application at different times.

(D) When the monitored area is wider, the irradiation area of the laser light may be moved relative to the monitored area for monitoring. It should be noted that reference numerals are added to the claims for convenience of comparison with the drawings, but the present invention is not limited to the configurations of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a gas leak monitoring device in use.

FIG. 2 is an explanatory diagram of a configuration of a gas leak monitoring device.

FIG. 3 is a diagram showing a display state by a display device.

FIG. 4 is an explanatory diagram showing a display limit when the condensed state of irradiation light is changed.

FIG. 5 is a diagram showing a change in transmission bandwidth by a bandpass filter.

[Explanation of symbols]

 A monitoring area E irradiation means E2 irradiation area changing means L laser light R detecting means R4 transmission bandwidth changing means S display means g detected gas

Claims (2)

[Claims] 1. An irradiation unit (E) for two-dimensionally irradiating a monitoring target area (A) with a laser beam (L) having a wavelength absorbed by a gas to be detected (g), and the monitoring target area. The area to be monitored (A) through (A)
The laser light that is reflected by the background and (L) detecting means for detecting the (R), the detection information obtained by the detection means (R), the audit
A gas leak monitoring device comprising: a display unit (S) that two-dimensionally displays the background image of the visual target area (A) , wherein the irradiation laser beam is focused on the irradiation unit (E). Then, the irradiation area changing means (E2) for changing the irradiation target area area
The detection means (R) has a wavelength (λ) of the laser light (L) at a substantially central position , and limits a band of a light beam entering the detection means (R). gas leak monitoring apparatus having a transmission band width changing means for changing the bandwidth (R4). 2. A zoom device (R) is attached to the detection means (R).
2) the gas leak monitoring apparatus according to claim 1, wherein are provided.