JP3326555B2 - Transmittance measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmittance measuring method, and more particularly to a transmittance measuring method for measuring the transmittance of a gas existing in a space.

[0002]

2. Description of the Related Art Generally, in a tunnel, the inside air is easily polluted by exhaust gas from a vehicle, and since it is almost a closed space, the degree of contamination is greater than that in the field. It is easy to cause harm to the human body. To remedy this situation, we measured the transmittance of the atmosphere in the tunnel and, depending on the degree,
A system for driving a ventilator that ventilates the inside of the tunnel is installed.

Conventionally, as a method for measuring the transmittance of gas (atmosphere) in such a space, a transmittance measurement method as shown in the figure has been used. FIG. 7 is an explanatory view showing a conventional transmittance measuring method. In the space, here in a tunnel, a light emitter 71 for emitting a light beam at a predetermined level, and this light emitter 7
A photodetector 72 that receives the light beam from No. 1 is disposed facing the same optical axis.

[0004] In particular, the light emitting device 71 and the light receiving device 72 are arranged at a distance of about 100 m, for example, along a straight section of a road. Then, based on the output of the light receiver 72, the attenuation measuring device 73 measures the attenuation of the light beam attenuated in the atmosphere in the tunnel, and calculates the transmittance according to the measurement result.

[0005]

However, such a conventional transmittance measuring method requires a light emitting device that emits a light beam at a predetermined level accurately and a light receiving device that accurately measures the light receiving level of the light beam. Therefore, there is a problem that the whole system becomes large and expensive. An object of the present invention is to solve such a problem, and an object of the present invention is to provide a transmittance measurement method that can be relatively reduced in size and can be realized at low cost.

[0006]

In order to achieve the above object, a first aspect of the present invention relates to a transmittance measuring method for measuring the transmittance of a gas existing in a space. Is a luminance indicating the brightness of the predetermined visual field area, and the steady luminance indicating the brightness by the illumination light illuminating the space is calculated, and the brightness of the predetermined visual field area of the image photographed in the space is calculated. Brightness that indicates the brightness due to the scattered light scattered by the fine particles floating in the space, and calculates the brightness in the space based on the brightness ratio between the steady brightness and the brightness of the light curtain. This is to determine the transmittance of a gas to be generated.

According to a second aspect of the present invention, in the transmittance measuring method according to the first aspect, the steady-state luminance is calculated by statistically processing the luminance of each pixel in a predetermined visual field region of an image photographed in a space. It is something that you get. According to a third aspect of the present invention, in the transmittance measuring method according to the first aspect, a luminance of each pixel in a predetermined visual field region of an image photographed in a space is statistically processed to obtain a light curtain luminance. It was made. According to a fourth aspect of the present invention, in the transmittance measurement method according to the first aspect, in the same image photographed in the space, the stationary luminance and the light curtain luminance are obtained from the corresponding viewing areas. .

According to a fifth aspect of the present invention, in the transmittance measuring method according to the first aspect, a representative transmittance is calculated for each period by statistically processing a plurality of transmittances calculated within a predetermined period. It is obtained and output. According to a sixth aspect of the present invention, in the transmittance measuring method of the first aspect, the presence or absence of a foreign substance that does not always exist in each visual field region is detected, and the transmittance is calculated only when the foreign substance does not exist. Things. According to a seventh aspect of the present invention, in the transmittance measuring method according to the first aspect, a viewing area is provided on a substantially black target existing in the space, and luminance obtained from the viewing area is used as light curtain luminance. It is like that.

According to the invention of claim 8, in the transmittance measuring method according to claim 7, when the transmittance in the tunnel is measured, a peripheral portion of a road surface, an inspection road or a sidewalk is used as a target. Things. According to a ninth aspect of the present invention, in the transmittance measuring method according to the eighth aspect, a peripheral portion of a road surface, an inspection road, or an upper surface of a sidewalk, which is a target, is black. Further, the invention of claim 10 is the invention of claim 7
In the transmittance measurement method described above, when the transmittance in the tunnel is measured, a convex portion having a semicircular cross-section extending in the vertical direction of the side wall is provided along the side wall in the tunnel at intervals along the vehicle traveling direction. Is used as a target.

[0010]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a functional block diagram showing a transmittance measuring method according to an embodiment of the present invention, and FIG. 5 is a flowchart showing an example of an actual processing procedure. According to the present invention, there are a steady luminance that shows a substantially constant value even when the gas (atmosphere) transmittance existing in the space changes, and a light curtain brightness whose value varies according to the change in the gas transmittance in the space. Is measured, and the transmittance of the gas in the space is measured based on the luminance ratio.

In FIG. 5, first, image data is taken in by the image pickup section 1 (step 50). The imaging unit 1 captures an image of an arbitrary field of view in a space such as a tunnel by using an imaging device such as a CCD, and outputs image data including luminance information of a large number of pixels constituting the image. This image data is output after the luminance characteristic of the image sensor is corrected by the luminance correction unit 2 (Step 5).
1).

Subsequently, the presence of a traveling vehicle or the like that is not always present, for example, in a tunnel, is detected in the visual field region of the imaging unit 1 by the foreign object detection unit 7 (step 5).
2). If a foreign object is detected (step 5
2: YES), it is determined that the image data is not suitable for transmittance calculation, and the subsequent transmittance calculation processing is interrupted, and the process returns to step 50.

On the other hand, if no foreign substance is detected (step 52: NO), it is determined that the image data is suitable for calculating the transmittance, and the following transmittance calculating process is executed. First, the steady-state luminance calculation unit 3 statistically processes the luminance information of the pixels in the predetermined visual field region in the image data after the luminance correction, so that the luminance indicating the brightness by the illumination light illuminating the space, that is, the steady-state luminance, The luminance (average luminance) is calculated (step 53).

The light curtain luminance calculating section 4 statistically processes the luminance information of the pixels in the predetermined visual field area of the image data after the luminance correction, so that fine particles floating in the gas in the space, for example, exhaust gas. The brightness indicating the brightness due to the scattered light scattered by the soot, that is, the light curtain brightness is calculated (step 53).

The steady luminance and the light curtain luminance measured by the stationary luminance calculator 3 and the light curtain luminance calculator 4 are input to a luminance ratio calculator 5, and the ratio between them, that is, the luminance ratio (= light curtain luminance / A steady luminance is calculated (step 54). Then, based on the brightness ratio calculated by the brightness ratio calculation unit 5, the transmittance in the space is calculated by the transmittance calculation unit 6 from the relationship between the brightness ratio and the transmittance (step 55).

FIG. 2 is an explanatory diagram showing the relationship between the transmittance, the steady luminance, and the light curtain luminance. Since the light curtain brightness 22 is a brightness indicating the brightness due to the scattered light scattered by the fine particles floating in the space, the value varies according to the amount of the fine particles, that is, the change in the transmittance of the gas in the space. . On the other hand, the steady luminance 21 is a luminance indicating the overall brightness due to the indirect light of the illumination light illuminating the space, that is, the light reflected from the illuminator on the inner peripheral surface in the space. If the amount (energy) of the illumination light at is constant, the value is always constant.

FIG. 3 is an explanatory view showing the relationship between the transmittance and the brightness ratio between the steady brightness and the light curtain brightness. According to the measurement by the inventors, the brightness ratio and the transmittance are almost proportional. It turned out to be. Thereby, the steady-state luminance and the light curtain luminance are measured in the space, and the luminance ratio is obtained, whereby the transmittance of the gas in the space is obtained from the relationship between the luminance ratio and the transmittance.

Thereafter, in step 56 of FIG. 5, after the transmittance thus obtained is temporarily stored in a memory (not shown), it is determined whether or not a predetermined time has elapsed since the first image capture (step 50). A decision is made (step 57). Here, if the predetermined time has not elapsed (step 57: NO),
Returning to step 50, the next transmittance is calculated.

On the other hand, if a predetermined time has elapsed from the first image capture (step 57: YES), the respective transmittances stored in the memory are statistically processed, so that a typical transmission within a predetermined period is performed. Calculate the rate (step 58)
This is output (step 59).

Then, returning to step 50, measurement of the first transmittance in a new period is started. Thereby, the representative transmittance is output for each period. It should be noted that the steady luminance calculating section 3 and the light curtain luminance calculating section 4
As specific statistical processing of the transmittance calculator 6, calculation processing of an average value, median value, or maximum frequency value of each value, data removal processing (noise removal) based on a standard deviation, or the like may be performed. .

As described above, according to the present invention, the image pickup section 1 is provided to pick up an image of a predetermined visual field in a space, calculate a steady luminance and a light curtain luminance from the obtained image data, and obtain a transmittance in the space. The change in transmittance is measured by detecting a change in brightness, that is, a light curtain brightness that varies according to a change in transmittance in a space, with reference to a brightness that is not influenced by a change in brightness, that is, a steady brightness. is there. In addition, the stationary luminance and the light curtain luminance are calculated by statistically processing the luminance of each pixel in the predetermined visual field area in the image data.

Therefore, as compared with the conventional case using a light-emitting device and a light-receiving device, a large-sized and expensive optical system is not required, and a general-purpose image pickup unit using a CCD or the like can constitute an image pickup section. Each calculation unit can be constituted by an arithmetic processing circuit, so that the whole system can be made relatively small and inexpensive. When the glass window of the imaging unit 1 is contaminated with soot such as exhaust gas, the absolute luminance decreases, but does not significantly affect the luminance ratio, so that the transmittance can be measured accurately and the maintenance cycle can be reduced. It can be extended and the work load can be reduced.

In addition, as in the prior art, strict adjustment (calibration) in which the light emitting device and the light receiving device face each other on the same optical axis.
Is not required, and the work load during installation and maintenance is reduced. Further, unlike the related art, it is not necessary to dispose the light emitting device and the light receiving device apart from each other, and if the respective visual field regions are adjusted, the two imaging units can be arranged in the same place.
The burden of installation work and power supply equipment work can be reduced.

It should be noted that separate imaging units may be provided for calculating the steady luminance and the light curtain luminance, and the steady luminance and the light curtain luminance may be calculated based on the image data captured by each imaging unit. Good. In FIG. 1 described above, the steady-state brightness and the light curtain brightness are calculated using the same image data captured by the imaging unit 1, so that the system configuration can be simplified and the steady-state brightness and light Curtain brightness can be calculated, and errors due to variations in equipment and capture timing can be suppressed.

Further, since a plurality of transmittances calculated within a predetermined period are statistically processed and a representative transmittance during the period is output, the transmittance of gas in the space temporarily fluctuates. In this case, for example, even when the transmittance temporarily decreases due to the exhaust gas of a large vehicle in a tunnel, a stable transmittance can be output, and the subsequent ventilation device and the like can be efficiently controlled.

Next, with reference to FIG. 4, a description will be given of the visual field region when measuring the steady luminance and the light curtain luminance. FIG. 4 is an explanatory diagram showing a visual field region used for measuring the steady luminance and the light curtain luminance. Here, a tunnel is shown as a space, (a) shows a cross section of the tunnel, and (b) shows an actual visual field in the tunnel.

As shown in FIG. 4 (a), a center line 32 is provided at the center of the road surface 31 of the road in the tunnel, and an inspection road (sidewalk) for tunnel management is provided on both sides of the road surface 31. 33 is provided at a position higher than the road surface 31 via the step portion 34. An illuminator 37 is provided at a corner between the tunnel side wall 35 and the ceiling 36 along the road to illuminate the inside of the tunnel.

FIG. 4 (b) shows a field of view in the tunnel which is actually obliquely viewed from the front (or rearward) from almost the same height as the illuminator 37. Reference numeral 11 denotes a field of view for steady-state luminance measurement. , 12 indicate viewing field regions for light curtain luminance measurement. In particular, the brightness of the inspection road 33 on the opposite lane side, the ceiling 36, and the peripheral portion 31A of the road surface 31 on the inspection road 33 side of the road surface 31 are the lowest. The luminance of the illuminator 37 is extremely high, and the luminance of the road surface 31, the step 34, and the tunnel side wall 35 is relatively low.

Therefore, when measuring the steady luminance,
By using a relatively wide viewing area, for example, the viewing area 11, as the viewing area of the imaging unit, the brightness is averaged, and more stable steady brightness is obtained. In addition, by excluding extremely high luminance portions, such as the illuminator 37, from the visual field, stable steady luminance can be obtained without being affected by fluctuations in high luminance portions that are easily affected by transmittance.

On the other hand, when measuring the light curtain luminance, a light curtain luminance with a small error can be obtained by using a relatively narrow visual field area, for example, the visual field area 12 as the visual field area of the imaging unit. In addition, by selecting a field of view having relatively low luminance, a change in light curtain luminance can be detected efficiently. This is because, as shown in FIG. 2, if the amount of fine particles in the space decreases and the transmittance increases, the luminance of the light curtain decreases.

Here, if the luminance is originally relatively high,
Even if the transmittance increases, the luminance itself in the viewing area does not decrease, and a change in light curtain luminance cannot be detected efficiently. On the other hand, when the luminance is originally low and the transmittance increases, the luminance itself in the visual field region also decreases, so that a change in the light curtain luminance can be detected efficiently.

Therefore, by setting the viewing area 12 for measuring the light curtain luminance on a substantially black target existing in the space, a change in the light curtain luminance can be detected efficiently. As this target, a target existing in the space from the beginning may be used, or a new target may be installed for measuring the light curtain luminance.

When the transmittance is measured in the tunnel, as shown in FIG. 4 (b), a substantially black road surface peripheral portion 31A and an inspection road (or sidewalk) 33 are suitable as targets. . Further, the upper surfaces of the road surface peripheral portion 31A and the inspection road (or sidewalk) 33 serving as the target may be painted black or formed of a black material.

FIGS. 6A and 6B are explanatory diagrams showing an example of the configuration of a target for light curtain luminance measurement. FIG. 6A is a cross-sectional view when the tunnel is viewed from above, and FIG. 6B is a view when the tunnel is viewed from the side. It is a longitudinal cross-sectional view in the case. In the figure, 31 is a road surface, 33 is an inspection road, and 35 is a tunnel side wall, which are present in the visual field region of the imaging unit 1.

In this case, black projections 41 are provided on the tunnel side wall 35 at equal intervals along the vehicle traveling direction. The convex portion 41 is provided extending in the vertical direction of the side wall, and has a semicircular cross section. Here, the imaging unit 1
At a position distant to some extent from the projection 41, the tunnel sidewall 35 between the adjacent projections 41 becomes invisible due to the protrusion of the projection 41, and a black target is formed in the imaging unit 1 as a whole.

At this time, the tunnel side wall 35 does not become invisible in the vicinity of each projection 41, so that the illumination light from the illuminator 37 is reflected on the tunnel side wall 35, and a predetermined brightness is maintained. As described above, by providing the plurality of protrusions 41 on the tunnel side wall 35, a black target having a relatively large viewing angle can be obtained without installing a large area black target in the viewing area of the imaging unit 1 as a whole. Can form an object.

[0037]

As described above, the present invention captures a predetermined visual field region in a space, calculates the steady luminance and the light curtain luminance from the obtained image data, and controls the change in the transmissivity in the space. The change in transmittance is measured by detecting a change in brightness, that is, a change in light curtain brightness in accordance with a change in transmittance in the space, with reference to the brightness that is not performed, that is, the steady brightness. Therefore, as compared with the conventional case using a light emitting device and a light receiving device, a large and expensive optical system is not required, a general-purpose imaging unit using a CCD or the like can constitute an imaging unit, and each calculation can be performed. The unit can be composed of an arithmetic processing circuit, and the whole system can be relatively reduced in size and realized at low cost.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a transmittance measuring method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between transmittance, steady luminance, and light curtain luminance.

FIG. 3 is an explanatory diagram showing a relationship between a transmittance ratio and a brightness ratio between steady brightness and light curtain brightness.

FIG. 4 is an explanatory diagram showing a visual field region used for measuring a steady luminance and a light curtain luminance.

FIG. 5 is a flowchart illustrating an example of an actual processing procedure.

FIG. 6 is an explanatory diagram showing a configuration example of a target for light curtain luminance measurement.

FIG. 7 is an explanatory view showing a conventional transmittance measuring method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image pick-up part, 2 ... Brightness correction part, 3 ... Steady-state brightness calculation part, 4
... light curtain luminance calculation section, 5 ... luminance ratio calculation section, 6 ... transmittance calculation section, 7 ... foreign matter detection section, 21 ... stationary luminance, 22 ... light curtain luminance.

────────────────────────────────────────────────── ─── Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 21/00-21/01 G01N 21/17-21/958 JICST file (JOIS)

Claims (10)

(57) [Claims] 1. A transmittance measuring method for measuring the transmittance of a gas present in a space, wherein the brightness indicates a brightness of a predetermined visual field region in an image taken in the space and illuminates the space. Calculates the steady-state brightness that indicates the brightness due to the illumination light, and is the brightness that indicates the brightness of the predetermined viewing area of the image taken in the space, and is the scattered light that is scattered by the fine particles floating in the space. A transmittance measurement method comprising: calculating a light curtain luminance indicating brightness; and obtaining a transmittance of a gas existing in a space based on a luminance ratio between the steady luminance and the light curtain luminance. 2. The transmittance measurement method according to claim 1, wherein the steady-state brightness is obtained by statistically processing the brightness of each pixel in a predetermined visual field region of the image photographed in the space. Rate measurement method. 3. The transmissivity measuring method according to claim 1, wherein the luminance of the light curtain is obtained by statistically processing the luminance of each pixel in a predetermined visual field region of the image photographed in the space. Transmittance measurement method. 4. The transmittance measuring method according to claim 1, wherein a steady luminance and a light curtain luminance are obtained from respective corresponding visual field regions in the same image photographed in the space. 5. The transmittance measurement method according to claim 1, wherein a plurality of transmittances calculated within a predetermined period are statistically processed to obtain and output a representative transmittance for each period. Transmittance measurement method. 6. The transmittance measurement method according to claim 1, wherein the presence or absence of a foreign substance that does not always exist in each field of view is detected, and the transmittance is calculated only when the foreign substance does not exist. Measuring method. 7. The transmittance measuring method according to claim 1, wherein a visual field is provided on a substantially black target existing in the space, and the luminance obtained from the visual field is used as a light curtain luminance. Transmittance measurement method. 8. The transmittance measuring method according to claim 7, wherein when measuring the transmittance in the tunnel, a road shoulder, a sidewalk, or an inspection road is used as a target. 9. The transmittance measuring method according to claim 8, wherein a peripheral portion of a road surface, an inspection road, or an upper surface of a sidewalk as a target is black. 10. The transmittance measuring method according to claim 7, wherein when the transmittance in the tunnel is measured, the transmittance extends in a vertical direction of a side wall provided along the side wall in the tunnel at intervals along the vehicle traveling direction. A method for measuring transmittance, wherein an existing convex part having a semicircular cross section is used as a target.