JPH0815145A - Transmissiometer - Google Patents

Abstract

PURPOSE:To obtain a highly reliable transmissiometer requiring no correction of measurement. CONSTITUTION:The transmissiometer comprises a target 1 having a pattern representative of contrast, a unit 2 for picking up the image of the target 1 or measuring the illuminance thereof, an image processing section 3 for processing the output signal therefrom to operate a transmittance, and means 11 for irradiating the target 1 and the space between the target 1 and the unit 2 with light during the night time and the intermediate time band between day time and night time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a visibility measuring device which can measure a visibility value with high reliability without requiring correction.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing the configuration of a conventional visibility measuring device disclosed in Japanese Patent Laid-Open No. 63-188741. In the figure, 1 is a diamond-shaped dedicated target having a "black" portion and a "white" portion backlit by a light emitting diode, and 1a is a backlight mechanism by a light emitting diode. Reference numeral 2 denotes an image pickup device for picking up an image of the dedicated target 1, and for example, a black and white industrial TV camera or the like is used. The dedicated target 1 is, for example, installed around a road, and is imaged by the imaging device 2 arranged at intervals of several tens of meters. An image processing unit 3 processes a video signal output when the imaging device 2 images the dedicated target 1 and calculates a visibility value.

Next, the operation will be described. The dedicated target 1 installed around the road is photographed by the imaging device 2 which is several tens of meters away. The image processing unit 3 processes the video signal output from the imaging device 2 and cuts out a part of the image of the “black” portion and the “white” portion of the dedicated target 1. Next, the lightness ratio of the cut out "black" portion and "white" portion is calculated, and the visibility distance is calculated by the following equation (1).

[0004]

[Equation 1]

Here, V is the visibility distance, D is the distance between the dedicated target 1 and the image pickup device 2, and Cd is the brightness of the "black" portion and the "white" portion when the dedicated target 1 is viewed from a position separated by the distance D. The ratio, Co, is the lightness ratio between the “black” part and the “white” part when the dedicated target 1 is viewed from the closest position, E is the visual identification threshold value, and is 0.05 in road weather.

During the daytime, when snowstorm blows, the brightness of the "black" part of the dedicated target 1 increases, the brightness ratio between the "black" part and the "white" part decreases, and the visibility becomes short. On the other hand, when the snowstorm blows at night, the brightness of the "white" portion of the dedicated target 1 decreases, the brightness ratio decreases, and the visibility decreases. However, even if the snowstorm is of the same level, the change in brightness differs between daytime and nighttime, so it is necessary to correct the visibility value measured at night. Therefore, in the measurement of the visibility value in the time zone midway between day and night, it is necessary to properly use the equation (1) including the correction term and the equation not including the correction term.

The correction term in this case includes, as an element, information such as the diaphragm adjustment amount extracted from the automatic diaphragm adjusting mechanism of the image pickup apparatus 2.

[0008]

Since the conventional visibility measuring device is constructed as described above, it is necessary to correct it because different visibility values can be obtained during the daytime and at night even with the same amount of snowstorm. However, in order to obtain an accurate visibility value, it is not easy to determine at what time the corrected visibility value should be adopted in the middle of the day and night.
There is a problem that it is difficult to measure an accurate visibility value.

The invention of claim 1 has been made in order to solve the above-mentioned problems, and a visibility measuring device capable of measuring a highly reliable visibility value without requiring correction of the measured visibility value. Aim to get.

It is an object of the present invention to provide a visibility measuring device capable of suppressing manufacturing costs.

It is an object of the present invention to provide a visibility measuring device capable of improving the accuracy of measuring the visibility value.

It is an object of the present invention to provide a visibility measuring device capable of improving the accuracy of measuring the visibility value.

[0013]

The visibility measuring apparatus according to the invention of claim 1 irradiates the target and the space between the target and the imaging device with light at night and in the time zone between day and night. It is equipped with.

A visibility measuring device according to a second aspect of the present invention has a structure in which the target is backlit by a fluorescent tube.

A visibility measuring device according to a third aspect of the present invention comprises a plurality of luminance meters for measuring the luminance in each pattern of "bright" and "dark" indicating the contrast of light and dark.

According to a fourth aspect of the present invention, in the visibility measuring device, the brightness of the irradiation means for irradiating the target and the space between the target and the image pickup device with light at night and in the time zone between day and night is adjusted. It is provided with adjusting means.

[0017]

The irradiation means of the visibility measuring device according to the invention of claim 1 irradiates the target and the space between the target and the image pickup device with light at night and in the time zone between day and night, and the night or day and night. To obtain a reliable visibility value by making the brightness ratio when shooting the target in the middle of the time of day close to the brightness ratio when shooting the target in the daytime, eliminating the need to correct the measured visibility value. To enable.

The visibility measuring device according to the invention of claim 2 is
Backlighting the target with a fluorescent tube suppresses an increase in the manufacturing cost of the visibility measuring device.

The visibility measuring device according to the invention of claim 3 is
The luminance of each pattern of “bright” and “dark” indicating the contrast of light and dark is measured by each luminance meter, and the accuracy of measuring the visibility value is improved.

The visibility measuring device according to the invention of claim 4 is
Adjusting the brightness of the target and the space between the target and the image pickup device at night and at the time between day and night, the brightness of the irradiating means is adjusted, and the night for the visibility value measured under the same conditions during the day Further, the error in the visibility value measured in the time zone between daytime and night is reduced to improve the accuracy of the visibility value measurement.

[0021]

【Example】

Example 1. Hereinafter, an embodiment of the inventions of claims 1 and 4 will be described with reference to the drawings. FIG. 1 is an overall configuration diagram showing the configuration of the visibility measuring device of this embodiment. In FIG.
The same parts as the above are given the same reference numerals and the description thereof will be omitted. In the figure, reference numeral 11 denotes a light projector (irradiation means) for irradiating the dedicated target 1 and the snowstorm state between the dedicated target 1 and the imaging device 2 at night and in the time zone between daytime and nighttime. Reference numeral 12 is a power source of the projector 11, and 13 is an adjusting means for adjusting the brightness of the projector 11. A variable resistor of a slidac or tap switching type, a variable voltage regulator of a phase control type, or the like can be used as the adjusting means. The "white" portion of the dedicated target 1 is backlit by the backlight mechanism 1a using a light emitting diode, and is configured to have a high contrast pattern with respect to the "black" portion.

Next, the operation will be described. In this embodiment, the projector 11 illuminates the snowstorm between the dedicated target 1 and the imaging device 2. In this case, the brightness of the projector 11 is set in advance so that substantially the same visibility value can be measured with respect to the snowstorm at night, which is similar to the snowstorm during the day.
This brightness adjustment of the floodlight 11 performed in advance is performed in an artificial environment in which, for example, the conditions of snowstorm on the site, daytime and nighttime, and the time zone between daytime and nighttime are reproduced experimentally before being installed on the site. When measuring the visibility value, day and night,
Further, the brightness is adjusted to the optimum brightness so that the error of the visibility value in the time zone between the daytime and the nighttime becomes as small as possible. In addition, adjustment data and the like regarding the relationship between the shooting direction of the image pickup device 2 and the irradiation direction and irradiation angle of the projector 11 should be obtained in advance.

Since the floodlight 11 whose brightness is adjusted in this way illuminates the snowstorm between the dedicated target 1 and the image pickup device 3 at night and in the time zone between night and day, it is the same as the daytime. Also in the middle of the day and night, the brightness of the "black" part of the dedicated target 1 increases, the brightness ratio of the "black" part and the "white" part becomes small, and the visibility becomes short. Since the brightness of the projector 11 is adjusted as described above, the difference between the visibility value measured at night or during the snowstorm in the time zone between day and night and the visibility value measured at the same snowstorm during the day is A small visibility value can be measured with high reliability without requiring correction of the visibility value measured at night and in the snowstorm in the time zone between daytime and nighttime. The calculation formula used to obtain the visibility value in the present embodiment is the above formula (1) that does not include a correction term.
Will be used.

Further, when the visibility measuring device is installed on the site, the visibility value measured in the daytime under the condition of snowstorm of the same degree is different from the visibility value measured in the nighttime, and in the time zone between the daytime and the nighttime. If so, the adjusting means 13
Therefore, it is possible to adjust the brightness of the projector 11 at night and in the time zone between daytime and nighttime so that the error can be minimized.

Example 2. In the first embodiment described above, it is described that the dedicated target 1 is provided with the backlight mechanism 1a using the light emitting diode, but the dedicated target 1 is irradiated by the projector 11 without providing the backlight mechanism 1a. It is also possible to simplify the structure of the dedicated target 1 and suppress an increase in the manufacturing cost of the dedicated target 1.

Example 3. In addition, in the first and second embodiments described above, the case where the dedicated target 1 is formed in a rhombus as shown in FIG. 2C is explained, but as shown in FIG. The target 14 may be used. With such a configuration, when the “white” portion and the “black” portion are cut out from the image of the dedicated target 14 in the image processing unit 3, the cutout is performed as shown in FIG. Since the areas of the “white” portion 14b and the “black” portion 14a can be made larger than in the case of FIG. 7C, the visibility value measurement accuracy can be improved.

Example 4. An embodiment of the invention of claim 2 will be described below with reference to the drawings. FIG. 3 is an overall configuration diagram showing the configuration of the visibility measuring device of this embodiment. In FIG. 3, the same parts as those in FIG. In the figure, 1b is a backlight mechanism for backlighting the "white" portion of the dedicated target by a fluorescent tube.

In this embodiment, since the "white" part of the dedicated target is backlit by the fluorescent tube, compared with the backlight mechanism of the light emitting diode shown in the first embodiment,
Manufacturing cost and structure can be simplified.

Embodiment 5 FIG. An embodiment of the invention of claim 3 will be described below with reference to the drawings. FIG. 4 is an overall configuration diagram showing the configuration of the visibility measuring device of this embodiment. 4, the same parts as those in FIGS. 1 and 3 are designated by the same reference numerals and the description thereof will be omitted. In the figure, 21 is a first luminance meter for measuring the luminance of the "white" portion of the dedicated target 1, and 22 is a second luminance meter (luminance meter) for measuring the luminance of the "black" portion of the dedicated target 1. The luminance information of the “white” portion measured by the first luminance meter 21 and the luminance information of the “black” portion measured by the second luminance meter (luminance meter) 22 are supplied to the image processing unit 3, and the image processing unit 3 Dedicated target 1 for 3
The brightness ratio between the "black" part and the "white" part of is calculated.

Also in the present embodiment, the difference between the visibility value measured in the daytime and the visibility value measured in the night for the same degree of snowstorm, the visibility value measured in the daytime and the visibility measured in the time zone between the daytime and the nighttime. The visibility value is measured by using the above equation (1) having no correction term using a projector whose brightness is adjusted so that the error from the value is as small as possible.

In the first to fourth embodiments, an industrial TV camera is used as the image pickup device. This industrial TV camera is usually provided with an automatic aperture adjustment mechanism, and when an industrial TV camera is used as an image pickup device, the brightness of the shooting location is changed between daytime and nighttime and between daytime and nighttime. Even if the light is emitted by the projector, the amount of aperture adjustment obtained from this automatic aperture adjustment mechanism will be different between daytime and nighttime, and between midday and nighttime. Could be. For this reason, in this embodiment, a luminance meter not provided with an automatic diaphragm mechanism is used instead of the industrial TV camera, and the luminances of the "black" portion and the "white" portion of the dedicated target 1 are measured, and the brightness ratio is used. It is possible to obtain the visibility value with high accuracy.

[0032]

As described above, according to the first aspect of the invention, the target and the space between the target and the image pickup device are provided with the irradiation means for irradiating light at night and in the time zone between day and night. Since it is configured as described above, there is an effect that a visibility measuring device capable of measuring a visibility value with high reliability can be obtained without requiring correction of the measured visibility value.

According to the second aspect of the invention, since the target is configured to be backlit by the fluorescent tube, there is an effect that a visibility measuring device capable of suppressing the manufacturing cost can be obtained.

According to the third aspect of the invention, since the luminance in each pattern showing the contrast of light and dark is measured by the luminance meter, the visibility measuring device capable of improving the measurement accuracy of the visibility value is provided. There is an effect to be obtained.

According to the fourth aspect of the present invention, the target and the space between the target and the image pickup device are provided with adjusting means for adjusting the brightness of the irradiating means for irradiating light at night and in the time zone between day and night. With this configuration, it is possible to obtain a visibility measuring device that can improve the measurement accuracy of the visibility value.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a configuration of a visibility measuring device according to an embodiment of the inventions of claims 1 and 4. FIG.

FIG. 2 is an explanatory view showing a dedicated target of a visibility measuring device according to another embodiment of the inventions of claims 1 and 4. FIG.

FIG. 3 is an overall configuration diagram showing a configuration of a visibility measuring device according to an embodiment of the invention of claim 2;

FIG. 4 is an overall configuration diagram showing a configuration of a visibility measuring device according to an embodiment of the invention of claim 3;

FIG. 5 is an overall configuration diagram showing a configuration of a conventional visibility measuring device.

[Explanation of symbols]

1 dedicated target, 2 imaging device, 3
Image processing unit, 11 Projector (irradiation means), 13
Adjusting means, 21 first luminance meter (luminance meter), 22 second
Luminance meter (luminance meter).

Claims (4)

[Claims] 1. A target having a pattern showing a contrast of brightness and darkness, an imaging device for imaging the target or a luminance meter for measuring the luminance of the target, and a visibility by processing an output signal from the imaging device or the luminance meter. A visibility measuring apparatus comprising: an image processing unit that calculates a value; and an irradiation unit that irradiates light to the target and a space between the target and the imaging device at night and in a time zone between daytime and nighttime. 2. The visibility measuring device according to claim 1, wherein the target is backlit by a fluorescent tube. 3. The luminance meter for measuring the luminance of the target is a plurality of luminance meters for respectively measuring the luminance in each pattern of “bright” and “dark” indicating the contrast of light and dark. Item 1. The visibility measuring device according to item 1. 4. The visibility measuring device according to claim 1, further comprising an adjusting unit that adjusts a brightness when the light is emitted by the emitting unit.