JPH0217420A - Apparatus for measuring luminance of road - Google Patents

Abstract

PURPOSE:To make it possible to measure the average luminance of a road surface regardless of the changes in width of a lane and configuration of the road by providing a memory part wherein the luminance signals of the lane and its vicinity undergo A/D conversion and the results are stored. CONSTITUTION:A lane judging part 5 distinguishes only a part of a lane 9 inner than a white line 8 that is drawn in the direction of the axis of the lane on the road from other peripheral part 11 based on a digital signal. An operating part 6 receives only the luminance of the lane 9 from the analog signal of a memory part 2 based on the result of the judgement of the lane and computes the average of the luminances. When the threshold value of the white line 8 on the road surface is set at the intermediate value between the luminance of the white line and the luminance of the road surface, the part of the white line becomes a positive value. There are various luminances in the peripheral parts 11. Therefore, the luminances of the parts which are judged as the lane 9 at scanning lines a-c in the lane between front parts A-B of a specified road- surface-luminance measuring device are all taken out of the memory part 2. The average value of the total sum is computed, and the result is displayed on a display part 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a road surface brightness measuring device for measuring road surface brightness.

Conventional technology A method for measuring road surface brightness is defined in the Japanese Industrial Standard JIS "Road Lighting Standard JZ9111 (1988).

Figure 3 shows the method for measuring road surface brightness specified in the Japanese Industrial Standards. The measurement range of road surface brightness is determined to be within the roadway width of 60 m to 160 m in front of the brightness meter 13, and to be measured from a height of 1.5 m at a position one-fourth of the roadway width W. When viewed from a perspective view, it becomes a trapezoid as shown in FIG. Therefore, the road surface brightness measuring device is configured to be able to measure the road surface brightness in such a trapezoidal field of view.

FIG. 5 shows a configuration diagram of a conventional road surface brightness measuring device. This road surface brightness measuring device consists of a first lens 2 that focuses incident light.
0, an aperture mirror 21 provided at the focal point of the first lens 20 and having an aperture shaped like the trapezoid in FIG. , a light receiver 23 for converting the light from the diffuser plate into an electrical signal, an amplifier 24 for amplifying this electrical signal, a measurement value display section 25 for displaying the amplified electrical signal, and an image from the aperture mirror. It consists of a relay lens 17 for sending the image to the finder, and a reflecting mirror 16 located between the relay lens 17.

Conventionally, such a road surface brightness measuring device has been used to measure the average road surface brightness in a certain section, but since the measurement range is necessarily fixed, the following problems have arisen.

(1) In a curved section, the trapezoidal field of view of the aperture does not match the shape of the lane 60 m to 160 m ahead. In such cases, in order to reduce the error as much as possible,
A trapezoidal aperture with a reduced measurement range in the road axis direction was used.

(2) When the width of the roadway is different, it is necessary to prepare an aperture corresponding to the width of the roadway.

(3) As shown in FIG. 5, the aperture mirror 21 measures the light from the trapezoidal aperture, so the light from this part is not reflected to the observer, and the observer 18 sees it through the finder. The measurement range is visible as a black area as shown in FIG. Therefore, it is difficult to confirm whether there is a white line within the measurement range that may cause an error.

Problems to be Solved by the Invention Conventional road surface brightness measurement devices have a fixed measurement range, so if the road width or road & 8 alignment changes, it is difficult to accurately measure the brightness within the lane surrounded by white lines. I couldn't do it.

Means for Solving the Problems The present invention solves the above-mentioned problems, and its technical means includes: a first memory section that stores brightness signals of lanes and their surroundings as analog signals; A
It is equipped with a second memory section that converts it into a digital signal by /D conversion and stores the digital signal, and takes advantage of the fact that white lines drawn on roads have a high reflectance, and uses the digital signal of the second memory section to The purpose of this method is to determine the lane area and extract only the analog signal for that area.

Operation The present invention measures the brightness within a traffic lane by having the above-described configuration.

Embodiment FIG. 1 shows a configuration diagram of the present invention. The present invention comprises an analog signal manual unit 1 that captures luminance signals of lanes and their surroundings, a first memory unit 2 that stores analog signals, an A/D converter 3 that converts analog signals into digital signals, and a digital a second memory section 4 for storing signals; and a lane discrimination section 5 for distinguishing only the part of the lane inside the white line drawn in the direction of the lane axis on the road surface from other peripheral parts based on the digital signal. , comprises an arithmetic unit 6 that captures only the lane brightness from the analog signal in the first memory unit based on the lane discrimination result and calculates the average thereof, and a display unit 7 that displays the average brightness of this lane. There is.

The principle of distinguishing only the portion of the road surface within the white line from other surrounding areas will be explained with reference to FIG. FIG. 2 shows the situation of the traffic lane and its surrounding area, which is manually input to the solid-state image sensor 12 through the lens of the camera corresponding to the analog signal input section 1 of FIG. 8 is a white line, 9 is a lane, 10 is a road shoulder, and 11 is a surrounding area.

Further, A indicates the lane position 160 m in front of the road surface brightness measuring device, and B indicates the lane position 60 m in front of the road surface brightness measuring device.

In FIG. 2, representative scanning lines a, b, and c will now be explained. FIG. 2 shows an example of luminance distribution on scanning lines a, b, and c. a'b' c, shows the state after A/D conversion in Fig. 1, and the threshold value
It is binarized depending on whether it is positive or negative.

A white line drawn on a road surface usually has a higher reflectance than the road surface, so its brightness is high.If the threshold value Become. In addition, since there are objects with various luminances in the peripheral area, the sign of the value cannot be uniquely determined for areas other than the road surface on the scanning line ab'c''. , c, and the range of negative values in a (the interval between a positive value and the next positive value) is the standard length (set according to the lane width). ), the section is determined to be a lane.Furthermore, since the scan line b is closer than the scan line a, the lane width seen in a perspective view is longer. , a negative section longer than a is determined to be a lane.Also, in C, a negative section (interval between positive and positive values) that is longer than the length determined as a lane in b is similarly determined to be a lane. Note that the setting of the reference length in a is changed depending on the lane width to be measured.

The above-mentioned scanning lines a, b, and c are taken up for the purpose of explanation.Actually, in each scanning line from 160 m to 60 m ahead shown in Fig. 2, the brightness of the part determined to be a lane is compared to the scanning line 1 in Fig. 1. All data are taken out from the memory unit 2 of , and the average value of the sum is calculated by the calculation unit 6, and then displayed on the display unit 7.

In addition to the above, the following three methods can be considered as methods for distinguishing lanes from surrounding areas.

The second method is to set a reference length for each scanning line, and when indicating a negative value of length longer than that,
How to determine this section as a lane.

The third method is to determine that this section is a lane when the negative value is the longest on the - scanning lines.

The fourth method is when the width of the white line itself is known and the length indicating a positive value is equal to the length on the scanning line corresponding to the width of this white line, the positive value is calculated by considering the influence of the brightness of the white line. A method in which the area up to the next positive value is regarded as a lane.

Further, in this conventional example, a two-dimensional solid-state image sensor is used in the input section, but the present invention is not limited to this, and it is also possible to use a -dimensional (line test) solid-state image sensor.

Although this embodiment shows the road surface brightness measuring device in the range of 60 m to 160 m ahead, the present invention does not limit the measurement range.

Effects of the Invention With the above configuration, the present invention can distinguish between the road surface and its surroundings, and measure the average brightness of the road surface regardless of changes in lane width or road alignment.

[Brief explanation of the drawing]

FIG. 1 shows the luminance meter (1 force diagram,
Figure 2 is an explanatory diagram to explain the principle of distinguishing lanes and their surrounding areas, Figures 3 and 4 are illustrations of the brightness measurement method specified by the Japanese Industrial Standards, and Figure 5 is an illustration of the conventional road surface. FIG. 6, a block diagram of the luminance measuring device, is a diagram showing a trapezoidal field of view as seen from the finder. DESCRIPTION OF SYMBOLS 1... Analog signal input section, 2... First memory section, 3... A/D conversion section, 4... Second memory section, 5
. . . lane discrimination section, 6. calculation section, 7. display section,
8... White line, 9... Lane, 10... Road shoulder, 11...
... Peripheral area, 12... Solid-state image sensor, 13... Luminance meter, 14... Measurement area, 15... Width of measurement versus R road surface, 16... Reflector, 17... Relay lens, 18
... Observer, 19... Subject, 20... Lens,
21...Aperture mirror 22...Diffusion plate, 28
... Light receiver, 24 ... Amplifier, 25 ... Measured value display section, 26 ... Road lighting equipment. Name of agent: Patent attorney Shigetaka Awano

Claims (1)

[Claims] An analog signal input section that takes in brightness signals of the lane and its surroundings, a first memory section that stores the analog signal, an A/D conversion section that converts the analog signal into a digital signal, and a second memory section that stores the digital signal. a memory section, a lane discrimination section that distinguishes only the part of the lane inside the white line drawn in the direction of the lane axis on the road surface from other peripheral parts based on the digital signal, and a first A road surface brightness measurement device that calculates the average road surface brightness within the lane, consisting of an arithmetic section that captures only the brightness of the lane from the analog signal in the memory section and calculates the average, and a display section that displays the average brightness of this lane. .