JPH08247940A - Road surface state detection device - Google Patents

Abstract

PURPOSE: To provide a road surface state detection device for detecting dry, wet, and frozen road surface state even when a vehicle is driving, and further detecting the road surface state in front of the vehicle. CONSTITUTION: A light projecting means 2 is provided with light sources 21 and 22 with different wavelengths and light with a wavelength of λ1 and a wavelength of λ2 is projected toward a road surface in front of a vehicle. A light reception means 3 detects the level of reflection light at each wavelength by light reception elements 33 and 34 via spectroscopes 31 and 32 corresponding to the wavelength of the projected light. The output 33a and 34a of the light reception elements 33 and 34 is converted to digital data by an A/D converter 4 and is supplied to a road surface state-judging means 5. The road surface state judging means 5 is provided with reflection light level data in each kind of road surface state and judges the road surface state by comparing the light reception level of each wavelength, thus outputting a judgment result 5a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road surface condition detecting device for detecting the condition of a road surface (drying, wetting, freezing) based on the light receiving levels of reflected light from the road surface in different wavelength regions.

[0002]

2. Description of the Related Art A technique for detecting a frozen state of a road surface based on a reception level of a reflected wave of a microwave radiated on a road surface at a constant level and a radiation temperature of the road surface, and previous road surface data prior to this detection is particularly known. It is proposed in Japanese Laid-Open Publication No. 55-147378.

Japanese Patent Application Laid-Open No. 59-188545 proposes a device for detecting the temperature of the road surface by detecting infrared rays from the road surface directly under the vehicle to issue a road surface freezing warning.

[0004]

Problems to be Solved by the Invention JP-A-55-1473
The technique proposed in Japanese Patent No. 78 is suitable for detecting the road surface condition at a fixed observation point because it is necessary to take the previous road surface data into consideration when detecting the road surface freezing. Is not suitable for detecting.

The road surface freeze warning device proposed in Japanese Patent Laid-Open No. 59-188545 detects infrared rays from the road surface directly under the vehicle, so that it is possible to detect the road surface temperature that is less affected by sunlight. However, the warning of freezing is only issued based on the road surface temperature, and the fact that the road surface is in a frozen state is not accurately detected.

The present invention has been made to solve the above problems, and an object thereof is to provide a road surface state detecting device capable of detecting a road surface state even while traveling and further detecting a road surface state in front of a vehicle. To do.

[0007]

In order to solve the above-mentioned problems, a road surface state detecting device according to the present invention comprises a light projecting means for projecting lights having different wavelengths, and a light receiving means for receiving reflected light from the road surface. It is characterized in that it comprises a road surface condition judging means for judging the road surface condition by comparing the levels of the reflected lights of the respective wavelengths.

It is desirable to use light in the infrared light to far infrared light region having a wavelength of 0.8 μm to 20 μm. Also,
The light projecting means may project polarized light. Further, the light projecting means may project the modulated light, and the light receiving means may include means for extracting the signal component of the modulated light.

[0009]

2 is a spectrum of light reflected from the road surface. The horizontal axis represents the wavelength of light and the vertical axis represents the reflectance. Characteristic D is a dry road surface (Dry), and characteristic W is a wet road surface (Wate).
r), characteristic I is the spectrum of the reflected light from the frozen road surface (Ice). As shown in FIG. 2, the spectrum of the reflected light differs depending on the condition of the road surface. For example, the ratio of the reflectance (light receiving level) of the wavelength 2.5 μm and the wavelength 3 μm is about 1.1: 0.3 on the frozen road surface, 1.38: 1.0 on the wet road surface, and 1. on the dry road surface. It is 8: 1.2. Therefore, the road surface condition can be detected by comparing the reflected light levels of different wavelengths.

By using light in the infrared light to far infrared light region having a wavelength of 0.8 μm to 20 μm, the light beam for detecting the road surface condition can be seen in front of the vehicle without being noticed by human eyes. High intensity light can be emitted for detection. Further, by projecting polarized light, the influence of ambient light can be reduced, and highly accurate detection can be performed. further,
By adopting a configuration in which modulated light is projected and the light receiving means extracts the signal component of the modulated light, the influence of ambient light (sunlight, street lights, headlights of other vehicles, etc.) is reduced, and high precision is achieved. It becomes possible to detect.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram of a road surface state detecting device according to the present invention. The road surface state detecting device 1 includes a light projecting unit 2, a light receiving unit 3, an A / D converter 4, and a road surface state determining unit 5.

The light projecting means 2 comprises a first light source 21 which emits light of a first wavelength λ1 and a second light source 22 which emits light of a second wavelength λ2. It is configured to project the light generated in 1) toward the road surface.

The light receiving means 3 includes a spectroscope 31 for the first wavelength λ1, a spectroscope 32 for the second wavelength λ2, and each spectroscope 3
The light receiving elements 33 and 34 that detect the light dispersed by the light sources 1 and 32 and generate an electrical output according to the intensity of the light are provided.

Outputs 33a, 34 of the respective light receiving elements 33, 34
The a is converted into corresponding digital data 4a by the A / D converter 4, and is supplied to the road surface state determination means 5. The outputs 33a and 34a of the light receiving elements 33 and 34 may be A / D converted after being amplified by a DC amplifier or the like.

The road surface condition judging means 5 judges the road surface condition by comparing the light receiving levels of the respective wavelengths, and outputs the judgment result 5a of dryness, wetness and freezing. In order to determine the road surface condition, the light receiving level for each wavelength on the various road surfaces or the data of the ratio of the light receiving levels of the two wavelengths is registered in advance.

FIG. 2 shows the spectrum of the light reflected from the road surface,
FIG. 3 is an explanatory diagram showing the measurement conditions of the same spectrum.
The spectrum shown in FIG. 2 is obtained by measuring the reflected light of the light projected at an incident angle of 80 degrees with respect to the road surface. The measuring distance is 10 cm. Light deflected by 90 degrees was used for the measurement.

From the measurement results shown in FIG. 2, it can be seen that the dry road surface has a high reflectance and the frozen road surface has a low reflectance. However, the reflectance also varies depending on the unevenness of the road surface and the incident angle is different. Therefore, it is difficult to determine the road surface condition with high accuracy. Therefore, it was decided to determine the road surface condition by paying attention to the difference in spectrum depending on the road surface condition. For example, a level of 2 to 2.5 μm (reflectance)
Or comparing the level of 4μm wavelength (reflectance) and the level of 3μm wavelength (reflectance), it is 3μm on the frozen road surface.
The level of m is greatly reduced, and the level of the level is small on a road surface wet with water or the like. In this way, by comparing the received light levels of different wavelengths, it is possible to accurately determine the road surface condition.

FIG. 4 is a block diagram of another road surface state detecting device according to the present invention. This road surface condition detection device 10
Is a device for emitting modulated light. The light projecting means 20 includes a modulating means 23, which emits light that is pulse-modulated at a predetermined cycle or intensity-modulated at a predetermined frequency to each light source 21,
Light is emitted from 22.

The light receiving means 30 comprises amplification / detection means 35, 36 for amplifying / detecting the outputs of the respective light receiving elements 33, 34, and filter means 37, 38 for extracting the signal component used for modulation from each detection output. The influence of ambient light can be reduced by adopting a configuration in which the modulation component is extracted via each of the filter means 37, 38.

The light projecting means 2 and 20 project polarized light, and the light receiving means 3 and 30 receive light of a specific polarization angle so as to reduce the influence of ambient light. You can Further, the light receiving means 3 and 30 may be provided with means for detecting the polarization angle of the reflected light to detect the change in the refractive index of the polarized light depending on the road surface state, and to detect the road surface state in more detail. Good.

In each of the embodiments, the light receiving element is provided for each wavelength, but the light projecting means 2 and 20 are the first.
When the wavelengths of and the second wavelength are projected time-divisionally,
The light receiving element, the amplification / detection circuit, and the filter means may be shared by synchronizing the light emission wavelength with the different spectral characteristics.

The light projecting means 2, 20 may project light including various wavelength components without providing a light source for each wavelength. The light receiving means 3 and 30 may be configured to include a device that analyzes the spectrum of reflected light. In this case, spectrum data of reflected light in various road surface conditions as shown in FIG. 2 is registered in advance in the road surface condition determining means 5. Then, the road surface condition is determined by comparing the spectrum of the reflected light with the spectra of various road surface conditions registered in advance.

Further, when the road surface condition detecting device 1 or 10 according to the present invention is mounted on a vehicle, the light projecting means 2 and 20 project light toward a road surface in front of the vehicle (for example, about 20 meters) and receive light. 3 and 30 are configured to receive the reflected light from the road surface, thereby detecting the road surface state in the traveling direction of the vehicle,
It is possible to notify the driving vehicle that the vehicle is frozen.

[0024]

As described above, the road surface state detecting device according to the present invention has a structure for determining the road surface state by comparing the levels of reflected light of respective wavelengths. Therefore, only the road surface state at a fixed observation point is determined. Not only that, the road surface condition can be detected even while the vehicle is traveling. In addition, by projecting light toward the front of the vehicle, the road surface condition in front of the vehicle is detected,
The driver can also be notified of the road surface condition.

Further, by utilizing the light in the infrared light to far-infrared light region having a wavelength of 0.8 μm to 20 μm, the light ray for detecting the road surface condition can be seen in front of the vehicle without being noticed by human eyes. High intensity light can be emitted for detection. Further, by projecting polarized light, the influence of ambient light can be reduced, and highly accurate detection can be performed. further,
By adopting a configuration in which modulated light is projected and the light receiving means extracts the signal component of the modulated light, the influence of ambient light (sunlight, street lights, headlights of other vehicles, etc.) is reduced, and high precision is achieved. It becomes possible to detect.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of a road surface state detecting device according to the present invention.

[Figure 2] Spectrum of light reflected from the road surface

FIG. 3 is an explanatory diagram showing measurement conditions of the spectrum shown in FIG.

FIG. 4 is a block diagram of another road surface state detecting device according to the present invention, a time chart showing a phase difference detecting operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1,10 Road surface state detection device 2,20 Light projecting means 3,30 Light receiving means 4 A / D converter 21,22 Light source 23 Modulating means 31,32 Spectroscope 33,34 Light receiving element 37,38 Filtering means

Claims (4)

[Claims] 1. A light projecting means for projecting light having different wavelengths,
A road surface state detecting device comprising: a light receiving means for receiving the reflected light from the road surface; and a road surface state determining means for judging the road surface state by comparing the levels of the reflected light of each wavelength. 2. Infrared light having a wavelength of 0.8 μm to 20 μm
The light in the far infrared light region is used, wherein
The road surface condition detection device described. 3. The road surface state detecting device according to claim 1, wherein the light projecting means projects polarized light. 4. The road surface condition detecting device according to claim 1, wherein the light projecting means projects the modulated light, and the light receiving means includes means for extracting a signal component of the modulated light.