JPH0693032B2 - Visibility meter calibration device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a visibility meter calibrating device that calibrates a visibility meter for measuring visibility on a road or the like based on the contrast of an index detected from a predetermined distance. It is a thing.

[Conventional technology]

FIG. 3 is an explanatory view showing a conventional visibility meter calibration device. In the figure, 1 is an environmental test room for reproducing the test environment of the visibility meter. Reference numeral 2 is a visibility condition reproducing apparatus for creating visibility conditions such as rainfall and snowfall in the environmental test room 1, and 3 is installed in the environmental test room 1 and has a bright area painted in white and a dark area painted in black. It is an index having and. Reference numeral 4 is a visibility meter to be calibrated, reference numeral 4a is the visibility meter 4, a brightness detection device such as a television camera for detecting the brightness of the index 3, and 4b is a visibility meter 4 together with the brightness detection device 4a. The image processing device calculates the visibility based on the light-dark contrast of the index 3 obtained from the light-dark information detected by the light-dark detection device 4a.

Next, the operation will be described. When calibrating the visibility meter 4,
First, a visibility test environment having a predetermined visibility value is created in the environment test chamber 1 by rainfall, snowfall, or the like by the visibility situation reproduction device 2.

Then, under such visibility condition, the predetermined distance D
The index 3 is photographed with the brightness detection device 4a from a position distant from
The image information is sent to the image processing device 4b. FIG. 4 is an explanatory diagram showing an example of the image information of the index 3 photographed by the brightness detection device 4a. From the received image information, the image processing device 4b cuts out a portion surrounded by a square from each of the dark area 3a painted black and the bright area 3b painted white of the index 3 to obtain the data Bt of each brightness.
Bb is read, and the brightness contrast Cd of the index 3 from the position separated by the distance D is obtained from the brightness data Bt and Bb by the following equation.

Cd = | Bt−Bb | / Bb Next, the light-dark contrast Cd at this distance D and the index 3
The image processing device 4b calculates the visibility V under the visibility situation based on the light-dark contrast Co when the measurement is performed at the minimum measurable distance by the following equation.

V = D × [ln (E) / ln (Cd / Co)] Here, E is a discrimination threshold in the above equation.

The calculated visibility V is output to the outside as a visibility output, and is compared with a predetermined visibility value according to the visibility situation created in the environmental test room 1 to calibrate the visibility meter 4.

[Problems to be Solved by the Invention]

Since the conventional visibility meter calibration device is configured as described above, when calibrating the visibility meter 4, it is necessary to reproduce a predetermined visibility condition in the environmental test room 1 by rainfall, snowfall, or the like. The environmental test room 1 needs a full-scale and large-scale one, and the visibility meter 4 cannot be easily calibrated in a factory or the like, and there is a problem that the cost is large. .

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a visibility meter calibrating device that can easily and inexpensively calibrate a visibility meter in a factory or the like.

[Means for Solving the Problems]

The visibility meter calibration apparatus according to the present invention prepares a calibration index in which a plurality of visibility adjusting means are detachably arranged on the front surface of an index body having a bright area and a dark area, and is reproduced by the visibility adjusting means. Under a predetermined visibility condition, the brightness detection means detects the brightness of the bright area and the dark area of the index main body from a predetermined distance, and the brightness detection is performed at the minimum distance at which the index main body without the visibility adjustment means can be measured. The calibration visibility is obtained by the processing means based on the light-dark contrast obtained from the luminance information detected from the predetermined distance and the light-dark contrast obtained at the minimum distance.

[Operation] The calibration index in the present invention reproduces a predetermined visibility state by attaching and detaching a plurality of visibility adjusting means arranged on the front surface of the index body, and the index body of the index body is reproduced under the reproduced visibility state. By detecting the brightness of the bright area and the dark area from a predetermined distance, and obtaining the calibration visibility from the brightness contrast obtained from the brightness information and the brightness contrast measured at the minimum distance that can measure the index main body without the visibility adjusting means. A large-scale environmental test room is not required for calibrating the visibility meter, which enables inexpensive and easy calibration of the visibility meter.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, 4 is a perimeter to be calibrated, 4a is its brightness / darkness detection device, and 4b is its image processing device, which are the same as or equivalent to those of the conventional devices denoted by the same reference numerals in FIG. The description is omitted.

Further, 5 is a calibration index forming the visibility meter calibration device of this embodiment, and FIG. 2 is a plan view, front view and side view showing the details of the structure. In FIG. 2, reference numeral 6 is an index body having a dark area 6a painted in black and a bright area 6b painted in white. Reference numeral 7 denotes a plurality of visibility adjusting means detachably arranged on the front surface of the index main body 6, and in this embodiment, a fine mesh which is arranged on the front surface of the index main body 6 so as to be detachable is used.

Further, reference numeral 8 is a light-and-darkness detecting means forming the visibility meter calibration device of this embodiment, and the index main body of the calibration index 5 in which a predetermined sighting condition is reproduced by the visibility adjusting means from a position separated by a predetermined distance D. 6 dark area 6a brightness or bright area
A pair of spot luminance meters that detect the luminance of 6b and output it as luminance information is used. Reference numeral 9 denotes an analog / digital converter (hereinafter referred to as an A / D converter) that converts the brightness information output from the brightness detection means 8 from an analog signal into a digital signal. Reference numeral 10 is a processing means for forming the visibility meter calibration device of this embodiment together with the calibration index 5 and the spot luminance meter 8, and obtains the light-dark contrast from the luminance information converted into a digital signal by the A / D converter 9. A calibration range is obtained based on the obtained contrast of light and darkness and the contrast of brightness when the index main body 6 without the visibility adjusting means 7 is measured at the minimum distance measurable by the brightness detecting means 8. A computer is used. A printer 11 prints the calibration visibility output from the processing means 10.

Next, the operation will be described. When calibrating the visibility meter 4,
First, the visibility adjusting means 7 arranged in front of the calibration index 5
By attaching and detaching and adjusting the number of sheets, a predetermined visibility situation is reproduced.

Then, under such a specified situation, the predetermined distance D
The dark area of the index main body 6 through the visibility adjusting means 7 by each spot luminance meter of the light and dark detecting means 8 from a position apart from
The brightness of 6a and the bright area 6b is detected and sent to the A / D converter 9 as brightness information. The A / D converter 9 converts the received brightness information from an analog signal into a digital signal and inputs it to the processing means 10. The processing means 10 calculates the brightness data Bt and Bb of the dark area 6a and the bright area 6b of the index body 6 based on the input brightness information.
Is read, and the light-dark contrast Cd of the calibration index 5 from the position separated by the distance D is obtained by the following equation.

Cd = | Bt−Bb | / Bb Next, based on the light-dark contrast Cd at this distance D and the light-dark contrast Co when the light-dark detecting means 8 can measure the index main body 6 without the visibility adjusting means 7, the processing is performed. The means 10 calculates the visibility V under the visibility condition by the following equation.

V = D × [ln (E) / ln (Cd / Co)] Here, E is a discrimination threshold in the above equation.

The calculated visibility V is output as the calibration visibility Vs and printed by the printer 11.

Then, the calibrated visibility meter 4 measures the visibility V from the position of the distance D using the calibration index 5. The measurement of the visibility V is similar to the description in the section "Prior Art".
When the calibration index 5 is photographed and the brightness data of the dark area 6a and the bright area 6b is obtained, and the brightness / darkness contrast based on the data and the index main body 6 without the visibility adjusting means 7 are measured at the minimum measurable distance. Calculated from light and dark contrast. The visibility V thus measured is referred to as the calibration visibility Vs.
The visibility meter 4 is calibrated by comparing with the value of.

In the above embodiment, the visibility adjusting means 7 uses a fine mesh, but frosted glass or the like may be used.

Further, in the above embodiment, the case of the visibility meter calibrating device has been described, but if the calibration index and the light / dark detecting means are provided with environment resistance as an outdoor device, it can be used as a visibility meter.

〔The invention's effect〕

As described above, according to the present invention, a predetermined visibility situation is reproduced by adjusting the number of visibility adjusting means arranged on the front surface of the index body, and under this visibility situation, the index body is moved from a predetermined distance. Of the brightness area and the dark area, and the calibration range is obtained from the brightness contrast obtained from the brightness information and the brightness contrast when the index main body without the visibility adjusting means is measured at the minimum measurable distance. Therefore, there is no need for a large-scale environmental test room for calibrating the visibility meter, and there is an effect that a visibility meter calibration device that can easily and easily calibrate the visibility meter is obtained in a factory or the like.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a visibility meter calibration device according to an embodiment of the present invention, FIG. 2 is a plan view showing the details of a calibration index, a front view and a side view, and FIG. 3 is a conventional visibility meter calibration. FIG. 4 is an explanatory diagram showing the device, and FIG. 4 is an explanatory diagram showing an example of image information of an index photographed by the brightness measuring device. Reference numeral 5 is a calibration index, 6 is an index main body, 6a is a dark area, 6b is a bright area, 7 is a visibility adjusting means, 8 is a brightness detection means, and 10 is a processing means. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A calibration index in which a plurality of visibility adjusting means is removably arranged on the front surface of an index body having a bright area and a dark area, and a predetermined viewing condition is reproduced by the visibility adjusting means. Brightness detection to detect the brightness of the bright and dark areas of the index body of the calibration index from a predetermined distance, and to measure the index body of the calibration index without the visibility adjusting means at the minimum measurable distance. A visibility meter calibrating apparatus comprising: means for calibrating the visibility based on the brightness contrast obtained from the brightness information detected from the predetermined distance by the brightness detecting means and the brightness contrast measured at the minimum distance.