JPH0718804B2 - Luminance measurement method in tunnel by image processing - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for measuring the brightness of a tunnel, and in particular, it is possible to comprehensively observe and evaluate the brightness difference between a road surface and a wall surface for enabling safe running of vehicles in the tunnel. The present invention relates to a method of measuring brightness in a tunnel by image processing.

[0002]

2. Description of the Related Art The visibility of the road surface and wall surfaces in a tunnel has a great influence on the safe running of vehicles. Therefore, the wall surfaces should be cleaned regularly to improve the lighting effect and ensure the initial visibility. There is. The greater the contrast between the road surface and the wall surface in the tunnel, the easier it will be to catch obstacles accurately. For this reason, measurement of the brightness distribution in the tunnel is an important factor.Therefore, in order to evaluate whether or not the visual environment as designed is obtained, the brightness of the road surface or wall surface is measured. There is.

Conventionally, in the case of measuring the brightness of the road and the wall surface in the tunnel, it is generally performed by a brightness meter using human hands, and the brightness meter is moved to a measured point to make many measurements. The luminance distribution of the entire tunnel was measured by analyzing the data obtained by directly measuring the luminance of the measured point.
That is, in the case of a tunnel, since the measurement points cannot be taken over the entire surface, the road surface and the wall surface are divided into a large number of cells, and each one point is measured by a luminance meter as a representative point.

[0004]

Therefore, in measuring the luminance distribution of a road surface or a wall surface in a tunnel by the above-mentioned luminance measuring method, since the representative points of the divided squares (range areas) are measured, the structure is not uniform. There is a measurement error in this part. For this reason, in order to accurately measure whether or not there is a brightness difference as designed, it is necessary to increase the number of measurement points infinitely. It requires personnel and time.

For this reason, attempts have been made to analyze the images taken by film photography and measure the luminance for the purpose of improving the work efficiency, but the work has not been significantly reduced.

The present invention was devised in view of the above problems, and the luminance distribution on the road surface and wall surface in a tunnel can be measured in real time by simple measurement using a TV camera, and the contrast between the road surface and wall surface can be measured. The purpose of this study is to propose a new method of measuring brightness in tunnels by image processing that enables evaluation.

[0007]

In order to achieve the above object, the method for measuring the brightness in a tunnel by image processing according to the present invention is attached to a traveling means in the visibility evaluation in the tunnel, and is 30 to 50 meters forward. A television camera adapted to capture an image centering on the road surface, an image processing device for processing the captured image signal from the television camera into a predetermined image signal, and recording and reproducing the captured image signal from the television camera. The traveling means is caused to travel at an appropriate speed by a device including a video tape recorder, a front image is photographed by a television camera, video information photographed by the television camera is taken into the image processing device, and the latter stage of the image processing device is taken. When the image is displayed on the display of a monitor TV at the same time as being captured by a video tape recorder connected to The management device, (1) from the correction coefficient obtained by experiment, performs correction by vignetting characteristics of the aperture value and the camera lens at the time of shooting. (2) The gamma characteristic of the television camera is corrected based on the correction coefficient previously obtained by the experiment. (3) The color temperature correction coefficient of the light source is obtained in advance by experiment, the correction coefficient is selected according to the type of the light source at that time, and the color temperature is corrected according to the type of the illumination light source. (4) Average brightness A [cd /
m ² ] is calculated as the luminance value of the road surface. (5) The field of view is limited to the wall surface, and the average brightness B [c
d / m ² ] is calculated as the brightness value of the wall surface. (6) The dirt condition in the tunnel is evaluated by the road surface brightness A and the wall surface brightness B. (7) The visibility of the road surface is evaluated based on the average brightness ratio B / A. (8) The gist is that the brightness value measured as described above is overlaid on the image as a numerical value and recorded by the image processing apparatus. In addition, an alarm output device that outputs an alarm signal when the processed output B / A deviates from a preset value range is added to the subsequent stage of the image processing device, and when a processed image is recorded on a video tape recorder, When the brightness value of the wall surface is less than or equal to the set value, or when the ratio of the brightness of the wall surface to the brightness of the road surface is less than or equal to the set value, it is desirable to record at the same time when the alarm output is issued.

[0008]

According to the method for measuring the brightness in the tunnel by the image processing described above, it is possible to measure while traveling at a speed of about 80 kilometers per hour, so that it is not necessary to regulate traffic for measurement, and the measurement work can be completed in a short time. Therefore, it does not hinder the running of other vehicles. In addition, since the entire measuring device is mounted on the vehicle and moved, it is possible to perform measurement on the overtaking lane side without an inspection road. Furthermore, since the alarm information is issued in real time, the operator can visually check the condition inside the tunnel at the time of the alarm, and since the brightness value is continuously measured, the brightness change inside the tunnel can be measured finely. You can and do not overlook partially dark areas.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for measuring brightness in a tunnel by image processing according to the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a measuring device used to measure brightness in a tunnel by image processing of the present invention, and FIG. 2 shows a measuring vehicle equipped with the measuring device. In the drawings, reference numeral 1 denotes a television camera which is mounted so as to face the windshield of the measurement vehicle 10 and whose mounting angle is adjusted so as to capture an image centered on a road surface in front of 30 to 50 meters. By using the one having a structure (not shown) mounted, it is possible to capture an image without shake corresponding to the moving speed of the measurement vehicle 10. 2 is a TV camera 1
It is an image processing device for processing the image signal taken from the image signal into a predetermined image signal, and appropriately displays the processed video on the display device 3. Further, 4 is a video tape recorder (image recording device) for recording and reproducing the image signal taken by the television camera 1, and 5 is a processing output from the image processing device 2, that is, an evaluation value of a stain on the wall surface. Alternatively, it is an alarm output device that outputs an alarm S1 or S2, respectively, when the visibility evaluation value deviates from a preset value range. The alarm outputs S1 and S2 are recorded on the video tape recorder 4 in real time together with the processed images, and if necessary, the hard copy device 6 connected to the subsequent stage of the video tape recorder 4 is used.
Allows you to make a hard copy 7. Reference numeral 8 is a monitor television connected to the television camera 1.

Next, referring to the hard copy 7 of the photographed image of FIG. 3, the hard copy 7 of the processed image of FIG. 4, and the data analysis diagram of FIG. 5, the method of measuring the brightness in the tunnel by the image processing using the above apparatus will be described. While explaining. (1) The measurement vehicle 10 is driven at a speed of about 80 kilometers per hour, and the front image is captured by the television camera 1. (See FIG. 3) (2) The video information captured by the television camera 1 is captured by the video tape recorder 4 and at the same time captured by the image processing device 2. (3) A correction process for converting the image signal taken into the image processing device 2 into a brightness value is performed. It is difficult to match the characteristics of the television camera 1 with the human visual sensitivity characteristics,
Perform the following method. (3-1) From the correction coefficient obtained by the experiment in advance, correction is performed by the aperture value at the time of shooting and the peripheral dimming characteristic of the camera lens. (3-2) The gamma characteristic of the television camera 1 is corrected from the correction coefficient previously obtained by the experiment. (3-3) The color temperature correction coefficient of the light source is obtained in advance by experiment, the correction coefficient is selected according to the type of the light source at that time, and the color temperature is corrected according to the type of the illumination light source. The color correction coefficient can be calculated from a luminance meter and image processing results for representative points, by theoretical calculation from the mixture ratio of light sources, and using a color camera to predict the light source from the RGB ratio from the standard reflection surface. Can be used. (4) After the correction processing, conversion is performed and converted into a brightness value. (5) The brightness of the road surface and the wall surface is measured from the processed image, and when the brightness of the wall surface is less than or equal to a set value, the dirt warning output S1 is calculated, and the ratio of the brightness of the wall surface to the brightness of the road surface is instantly calculated.
When the value is less than the set value, the visibility warning output S2 is issued via the warning output device 5. The luminance value is measured, for example, every 1/60 seconds in synchronization with the field signal of the video. (5-1) Average luminance A [cd / in the visual field limited to the road surface
m ² ] is calculated as the luminance value of the road surface. (5-2) The field of view is limited to the background portion of the wall surface, and the average brightness B [cd / m ² ] is calculated and used as the brightness value of the wall surface. (5-3) The dirt condition in the tunnel is determined by the brightness of the road surface and the wall surface. (5-4) The visibility of the road surface is determined by the average brightness ratio B / A. (6) The brightness value measured as described above is displayed as a numerical value on the image by the image processing device 2, and
The video at that time is recorded on the video tape recorder 4, and at the same time, recorded on the alarm output S1 or S2 audio channel. (7) In order to make it easier to understand the luminance distribution on the entire screen, the above-mentioned recording is performed by dividing the luminance value exponentially into several stages and separately color-coding (pseudo-color display [see FIG. 4]) the video tape recorder. You can also record to 4.

The measured value (image processed value [cd / m ² ]) obtained by the above measurement has almost no error compared with the luminance meter value [cd / m ² ] actually measured by the luminance meter as shown in FIG. It turns out that there is no.

Further, FIG. 6 is a graph showing measured values and luminance meter values of a road surface and a wall surface in a tunnel when stationary measurement is performed at a moving distance of 5 meters, and the measurement of the present invention is performed at all points. It can be seen that the measurement value obtained by the method substantially matches the luminance measurement value actually measured by the luminance meter.

Further, FIG. 7 shows the measuring vehicle 10 at 70 K / h.
This is a comparison between the measured value of the road surface when measured while traveling at m / h and the luminance meter value using a luminance meter, and both can obtain substantially equal values. Therefore, it is possible to carry out the measurement in the traveling state while keeping the other front inter-vehicle distance sufficiently (50 meters or more) without stopping the measurement vehicle 10.

[0015]

As described above, according to the method for measuring the brightness in the tunnel by the image processing according to the present invention, (1) it is not necessary to regulate the traffic for the measurement. (2) Since the measurement can be performed while traveling at a speed of about 80 kilometers per hour, the measurement work can be completed in a short time without disturbing the traveling of other vehicles. (3) Since the entire measuring device is mounted on the vehicle and moved, it is possible to perform measurement on the overtaking lane side without an inspection road. (4) Since alarm information is issued in real time during measurement,
Workers can visually check the inside of the tunnel (dirt, etc.) when an alarm is issued. (5) By performing a relative comparison before and after the wall surface cleaning operation, the effect of cleaning can be objectively evaluated. (6) Since the video and the data are recorded on the video tape recorder, the storage and the data totalization processing are easy. (7) Since the brightness value is measured at short intervals (every 1/60 second) in synchronization with the field signal of the image, it is possible to measure the brightness change in the tunnel finely and Never overlook. (8) Since it is possible to measure while moving by mounting the measuring device on the vehicle, one worker can perform the work in a short time, and the measurement work can be greatly saved.
Moreover, the working environment can be greatly improved. (9) It is possible to simultaneously evaluate the stains at any place in the tunnel, such as comparing the brightness values of the upper part (for example, 60 degrees, 90 degrees, etc.) in the tunnel. (10) Comprehensive measurement can be performed by a simple method as compared with the movement measurement by the luminance meter, and the cleaning result of the wall surface can be appropriately evaluated. The advantages after the present invention are extremely large.

[Brief description of drawings]

FIG. 1 is a block diagram of a measuring device used for implementing a method for measuring brightness in a tunnel by image processing according to the present invention.

FIG. 2 is a schematic view of a measurement vehicle equipped with the same brightness measuring device.

FIG. 3 is a hard copy of an image taken in a tunnel.

FIG. 4 is a hard copy diagram of the processed image in FIG.

FIG. 5 is an explanatory diagram for verifying data analysis.

FIG. 6 is a graph showing a measured value and a luminance meter value of a road surface and a wall surface in a tunnel when static measurement is performed at a moving distance of 5 meters.

FIG. 7 is a diagram showing a measured value and a luminance meter value when a measurement vehicle is run and measured.

[Explanation of symbols]

 1 TV camera 2 Image processing device 3 Display device 4 Video tape recorder 5 Alarm output device 6 Hard copy device 7 Hard copy 8 Monitor TV

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-4-347300 (JP, A) JP-A-4-222175 (JP, A) JP-A-4-217600 (JP, A) JP-A-3- 51495 (JP, A)

Claims (2)

[Claims] 1. A television camera, which is attached to a traveling means to take an image centering on a road surface in front of 30 to 50 meters, in the evaluation of dirt condition and visibility in a tunnel. An image processing device that processes a captured image signal into a predetermined image signal and a device that includes a video tape recorder that records and reproduces a captured image signal from a television camera are caused to travel the traveling means at an appropriate speed, and When an image is taken by a TV camera, video information taken by the TV camera is taken into an image processing apparatus, and taken into a video tape recorder connected to the latter stage of the image processing apparatus, at the same time when it is displayed on a monitor TV display, With the image processing device, (1) From the correction coefficient obtained in advance by experiment, the aperture value at the time of shooting and the camera Correction based on the peripheral dimming characteristics of the lens. (2) The gamma characteristic of the television camera is corrected based on the correction coefficient previously obtained by the experiment. (3) The color temperature correction coefficient of the light source is obtained in advance by experiment, the correction coefficient is selected according to the type of the light source at that time, and the color temperature is corrected according to the type of the illumination light source. (4) Average brightness A [cd /
m ² ] is calculated as the luminance value of the road surface. (5) The field of view is limited to the wall surface, and the average brightness B [c
d / m ² ] is calculated as the brightness value of the wall surface. (6) The dirt condition in the tunnel is evaluated by the road surface brightness A and the wall surface brightness B. (7) The visibility in the tunnel is evaluated by the ratio B / A of the average brightness. (8) A method for measuring brightness in a tunnel by image processing, wherein the brightness value measured as described above is overlaid as a numerical value on an image by an image processing apparatus and recorded. 2. The processing output A after the image processing device.
And B or B / A is provided with an alarm output device that outputs an alarm signal when the value deviates from a preset value range, and when the processed image is recorded on the video tape recorder, the brightness value of the wall surface is less than or equal to the set value. Alternatively, when the ratio of the brightness of the wall surface to the brightness of the road surface is equal to or less than a set value, an alarm output is issued and the alarm is recorded at the same time.