JP2000002658A - Measuring method for permeability of air - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring method for the permeability of air, in which the permeability can be measured with a high resolution and immediately on a two-dimensional plane, regarding a method in which a change in the permeability of air due to smoke and fog, dust or the lie, floating in the air is measured on a road, in a tunnel, in an airport or the like. SOLUTION: In the measuring method for the permeability of air, every pixel of an image is changed into a numerical value, the inclination of a luminance value in the vertical direction and that in the horizontal direction are found respectively in every pixel, the square mean to the absolute sum of the inclinations of the luminance values is defined as the clearness of a screen in every pixel, the clearness of the screen is found with respect to various permeabilities of the air, a relationship to the permeabilities of the air is approximated by a polynominal expression, the clearness of the screen found by the same procedure as before regarding every pixel of the image in a place to be measured is substituted into the polynominal expression, and the permeability is found.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a road, a tunnel,
The present invention relates to a method for measuring a change in air permeability due to fumes, dust and the like floating in the air at an airport or the like.

[0002]

2. Description of the Related Art Conventionally, a light projecting unit and a light receiving unit are arranged to face each other at a fixed interval, and light emitted from the light projecting unit is received by a light receiving unit.
A method of measuring the transmittance from the received light amount is known. Note that a laser diode is often used as a light emitting element, and a photodiode is often used as a light receiving element.

[0003]

The conventional method for measuring air permeability has the following problems.

[0004] Measurement accuracy may be degraded due to vibrations when passing through the vehicle or misalignment due to improper installation. At the time of measurement, the optical axes must first be aligned. Therefore, measurement could not be performed immediately.

[0005] The measurement of the transmittance is limited to the space between the light emitting unit and the light receiving unit that are arranged to face each other, and is a local measurement. Therefore, when it is desired to measure the transmittance of a certain space, it is necessary to prepare a plurality of light-emitting units and light-receiving units that are arranged to face each other. This not only makes the whole device large, but also makes it difficult to analyze the measurement data. Had become.

[0006] Further, in the measurement by the light emitting part and the light receiving part which are arranged opposite to each other, the spatial resolution is very low and several cm or more.
Therefore, even if the air transmittance was uneven within the range, the unevenness could not be measured, and only the average air transmittance could be measured.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned disadvantages of the prior art, and to provide an air transmittance measuring method which has a high resolution and can immediately measure a transmittance on a two-dimensional plane.

[0008]

In order to achieve the above object, the present invention quantifies each pixel of an image into a luminance value, and obtains a vertical and horizontal gradient of the luminance value for each pixel. The root mean square or absolute sum of the slope of the luminance value is defined as the clarity of the screen at each pixel, and the clarity of the screen is obtained for various air transmittances, and the relationship with the air transmittance is approximated by a polynomial. Then, an air transmittance measurement method is adopted in which the clarity of the screen obtained in the same procedure as described above for each pixel of the image of the measured portion is substituted into the polynomial to determine the transmittance.

Alternatively, each pixel of the image is quantified into a luminance value, and the inclination of the luminance value in each of the vertical direction, the horizontal direction, and the direction rotated by ± 45 degrees from the horizontal direction is determined for each pixel, and the maximum value of the luminance value is obtained. The value is defined as the clarity of the screen at each pixel, the clarity of the screen is determined for various air transmittances, the relationship with the air transmittance is approximated by a polynomial, and each pixel of the image of the measured location is The air transmittance measurement method may be employed in which the clarity of the screen obtained by the same procedure as described above is substituted into the polynomial to obtain the transmittance.

[0010]

FIG. 1 is a flowchart showing a first embodiment of the air permeability measuring method of the present invention. The measured portion is photographed using a CCD (Charge Coupled Device) camera, and the image is transmitted to an image processing circuit. The image transmitted to the image processing circuit is digitized into a luminance value for each pixel. Since one image is usually composed of tens of thousands of pixels, the spatial resolution per pixel is generally high and depends on the magnification at which the image is taken. At this time, the air permeability in that state is measured at the same time.

Next, for each pixel of the image, the inclination of the luminance value in the vertical direction and the inclination of the luminance value in the horizontal direction around the pixel are determined. Then, a root mean square or an absolute sum of the obtained luminance values is calculated to define the clarity of the screen at this pixel. This work is also performed at different air transmittances, and the relationship between the clarity of the screen at each pixel and the air transmittance is approximated by a polynomial, and this approximation formula is used as a transmittance estimation formula.

[0012] Then, a portion where the transmittance is to be obtained is photographed using a camera, and the photographed image is transmitted to an image processing circuit. The image transmitted to the image processing circuit is digitized into a luminance value for each pixel. Then, for each pixel, the inclination of the luminance value is calculated in the vertical direction and the horizontal direction around the pixel, and the root mean square or the absolute sum of the calculated luminance values is calculated, and the clarity of the screen at that pixel is calculated. Ask for.
The air transmittance can be determined by substituting the clarity of the screen into the previously determined polynomial, that is, the transmittance estimation formula.

Here, the luminance value and the clarity of the screen will be supplementarily described.

As described above, when an object to be measured is captured as an image using a camera or the like, the image is quantified into a degree of brightness called a luminance value for each pixel. If the air transmittance drops due to fumes or dust, the visibility becomes short, and the whole becomes haze, and the boundary between apparent objects becomes unclear.

FIG. 2 shows the relationship between the pixel position and the luminance value near the boundary between objects when the air transmittance is high. Similarly, FIG. 3 shows the relationship between the pixel position and the luminance value near the boundary between objects when the air transmittance is low.

When the transmittance is high, the boundary between the apparent object and the object is clear, so that the change in the luminance value at the boundary is sharp and the gradient of the luminance value is large. On the other hand, if the transmittance is low,
Since the boundary between the apparent object and the object is blurred, the change of the boundary is gradual, and the gradient of the luminance value is small. Therefore, the inclination of the luminance value with respect to a certain pixel can be obtained by the amount of change in luminance value / the amount of change in pixel position.

With one pixel as the center, inclinations of luminance values in various directions are obtained. For example, it is possible to calculate the inclination of the luminance value in a vertical direction and a horizontal direction with a certain pixel as a center. The root mean square or the absolute sum of the luminance values obtained in this way is calculated, and this can be defined as the clarity of the screen at the pixel. Alternatively, the maximum value of the gradient of the luminance value may be made clear, and definition according to the situation is possible.

FIG. 4 is a flowchart showing a second embodiment of the air permeability measuring method according to the present invention. The position to be measured is photographed using a CCD camera, and the image is transmitted to an image processing circuit. The image transmitted to the image processing circuit is digitized into a luminance value for each pixel as described above. At the same time, the air permeability in that state is measured.

Next, for each pixel of the image, the inclinations of the luminance values in a total of eight directions of the vertical direction, the horizontal direction, and the direction rotated ± 45 degrees from the horizontal direction are obtained with the pixel as a center. Then, the maximum value of the obtained luminance gradients in the eight directions is defined as the clarity of the screen at this pixel. This work is also performed at different air transmittances, and the relationship between the clarity of the screen at each pixel and the air transmittance is approximated by a polynomial, and this approximation formula is used as a transmittance estimation formula.

Then, a portion for which the transmittance is desired is photographed using a camera or the like, and the photographed image is transmitted to an image processing circuit. The image transmitted to the image processing circuit is digitized into a luminance value for each pixel. Then, for each pixel, luminance inclinations in a total of eight directions, that is, a direction rotated ± 45 degrees from the horizontal direction in the vertical direction, the horizontal direction, and the horizontal direction around the pixel, are obtained. Next, the maximum value of the eight luminance gradients is determined, and the clarity of the screen at the pixel is determined.
By substituting the clarity of this screen into the previously determined polynomial, that is, the transmittance estimation formula, the air transmittance can be determined.

[0021]

According to the air permeability measuring method of the present invention, the object to be measured is fetched as image data, the clarity of the screen of the boundary between objects is quantified, and this numerical value is substituted into a polynomial which has been obtained in advance. Since the transmittance is determined by the above method, an excellent effect that the resolution is high and the air transmittance can be immediately measured in a two-dimensional plane is exhibited.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a first embodiment of an air permeability measuring method according to the present invention.

FIG. 2 is an explanatory diagram showing a relationship between a pixel position and a luminance value when air permeability is high according to the first embodiment.

FIG. 3 is an explanatory diagram showing a relationship between a pixel position and a luminance value when the air transmittance is low according to the first embodiment.

FIG. 4 is a flowchart showing a second embodiment of the air permeability measuring method of the present invention.

Claims (2)

[Claims] 1. Each pixel of an image is quantified into a luminance value, the inclination of the luminance value in the vertical direction and the inclination of the luminance value in each of the pixels are determined for each pixel, and the root mean square or the absolute sum of the inclination of the luminance value is calculated for each pixel. In the definition of the clarity of the screen, the clarity of the screen is obtained for various air transmittances and the relationship with the air transmittance is approximated by a polynomial, and the same as described above for each pixel of the image of the measured position. An air permeability measurement method, wherein the air permeability is obtained by substituting the clarity of the screen obtained by the procedure into the polynomial. 2. Each pixel of the image is quantified into a luminance value, and the inclination of the luminance value in a direction rotated ± 45 degrees from the vertical direction, the horizontal direction, and the horizontal direction is obtained for each of the pixels.
The maximum value of the luminance value is defined as the clarity of the screen at each pixel, the clarity of the screen is obtained for various air transmittances, the relationship with the air transmittance is approximated by a polynomial, and The air permeability is determined by substituting the clarity of the screen obtained for each pixel of the image in the same procedure as above into the polynomial to obtain the air permeability.