JPH08201288A - Detector for state of road surface - Google Patents

Abstract

PURPOSE: To provide the detector for the state of a road surface, which can detect the wet state of the road surface, the coefficient of friction against the road surface and the like in real time with the simple circuit constitution even if the road surface has relatively achromatic color. CONSTITUTION: In an automobile running on a road surface, the following parts are provided. Irradiation means 1 and 2 irradiate the road surface. A reflected- light-quantity detecting means 4 receives the reflected light of the light emitted from the irradiation means 1 and 2 from the road surface, which is irradiated by the irradiation means 1 and 2, and detects the quantity of the reflected light. An irradiating-light-quantity detecting means 3 detects the quantity of the irradiating light from the irradiation means 1 and 2. A reflectivity detecting means 5 detects the specular reflectivity of the road surface based on the ratio with the quantity of the light received with the reflected-light-quantity detecting means 4. A comparing means 6 compares the result of the operation with the predetermined constant. The specular reflectivity is compared with the constant by the comparing means 6. When the reflectivity is larger than the constant, it is discriminated that the road surface is wet in this constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can detect the condition of the road surface of an automobile or the like to detect a warning to the driver and data necessary for a braking operation of an antilock braking system or the like. The present invention relates to a road surface state detecting device.

[0002]

2. Description of the Related Art FIG. 19 is a block diagram of a conventional road surface condition detecting device disclosed in, for example, Japanese Patent Publication No. 5-69011. In the figure, 20 is a photographing means, 21 is an image processing means, 22 is a comparison and determination means, 23 is a road surface state storage means, 2
Reference numeral 4 is a road friction coefficient storage means, and 25 is a friction coefficient selection means.

A conventional road surface condition detecting device attempts to detect the road surface condition in the traveling direction without bringing the detector into contact with the road surface.

The operation will be described. First, the photographing means 2
0 captures the road surface condition in the traveling direction. The video signal obtained from the photographing means 20 is converted into the image processing means 21.
To separate into R, G, B signals. The road surface state storage means 23 stores various road surface states as a distinguishable map in the coordinates formed by the R, G, B signals, and compares them with the R, G, B signals obtained from the image processing means 21. To select the type of road surface. Next, the friction coefficient of the selected road surface is selected from the friction coefficient selecting means 24 in which the friction coefficient of the road surface is stored for each condition of the selected road surface.

[0005]

The conventional road surface condition detecting device detects the kind of road surface by using the information of the color of the road surface, but the road surface is usually achromatic. Also, even if the road surface gets wet, the color of the road surface will only slightly darken, especially,
As for the new asphalt road surface, even if the road surface gets wet, the color hardly changes. Therefore, there is a problem that it is difficult to determine whether or not the road surface is wet.

Further, there is a problem that the result is easily influenced by the color temperature of the photographing condition and the white balance function of the image pickup apparatus.

The present invention has been made to solve the above problems. Even if the road surface is an achromatic color, the wet condition of the road surface, the coefficient of friction of the road surface, etc. can be obtained by a simple circuit structure.
It is an object of the present invention to obtain a road surface condition detecting device that can detect in real time.

[0008]

According to a first aspect of the present invention, there is provided a road surface state detecting device which receives an illumination means for illuminating a road surface and a reflected light from the road surface emitted by the illumination means. Depending on the ratio of the reflected light amount detecting means for detecting the light amount, the irradiation light amount detecting means for detecting the light amount irradiated to the road surface from the illuminating means, and the light amount detected by the irradiated light amount detecting means and the light amount detected by the reflected light amount detecting means. It is composed of a reflectance detecting means for detecting the reflectance of the road surface and a comparing means for comparing the reflectance of the road surface with a predetermined constant.

Further, a road surface state detecting device according to a second aspect of the present invention receives an illumination means for illuminating the road surface and a reflected light from the road surface illuminated by the illumination means, and detects a light quantity of the reflected light. The reflected light amount detecting means and the comparing means for comparing the light amount detected by the reflected light amount detecting means with a predetermined constant.

According to a third aspect of the present invention, in the road surface state detecting device according to the first or second aspect, the constant for comparing with the light amount detected by the reflected light amount detecting means is compared. A plurality of means are provided.

Further, a road surface state detecting device according to a fourth aspect of the present invention is the road surface state detecting device according to any one of the first to third aspects, in which the road surface state is distinguished according to the wet condition of the road surface. The friction coefficient storage means stores therein the friction coefficient corresponding to.

The road surface condition detecting device according to a fifth aspect of the present invention is the road surface condition detecting device according to any one of the first to third aspects, wherein the type of material of the road surface such as soil, asphalt, concrete, etc. is preset. A friction coefficient of the road surface, which is provided, and which selects a road surface type, a road surface friction coefficient corresponding to the road surface type, and a road surface state that is distinguished according to the wetness of the road surface. And storage means.

A road surface condition detecting apparatus according to a sixth aspect of the present invention is the road surface state detecting apparatus according to any one of the first to fifth aspects, wherein the angle of incidence is an angle formed by the illumination means and a normal line of the road surface. The respective angles are set so that the light receiving angle, which is the angle formed by the photodetector and the normal to the road surface, is equal.

A road surface condition detecting device according to a seventh aspect of the present invention is the road surface condition detecting device according to any one of the first to sixth aspects, in which the illuminating means and the reflected light amount detecting means are affected by external light. It should be installed at the bottom of the car so that it does not exist.

[0015]

In the road surface state detecting device according to the first aspect of the present invention, the road surface reflectance obtained from the ratio of the illumination light amount of the illumination light and the light amount of the light reflected by the road surface is compared with a predetermined constant. To do.

Further, in the road surface state detecting device according to the second aspect of the present invention, the quantity of light reflected by the road surface of the illumination light is compared with a predetermined constant.

Further, in the road surface condition detecting apparatus according to claim 3 of the present invention, the reflectance of the road surface obtained from the ratio of the irradiation light amount of the illumination light and the light amount of the reflected light of the illumination light by the road surface, or the illumination light. The amount of light reflected by the road surface of is compared with a plurality of constants.

Further, in the road surface state detecting device according to the fourth aspect of the present invention, the friction coefficient corresponding to the detected road surface condition is output from the friction coefficient storage means.

Further, in the road surface condition detecting apparatus according to the fifth aspect of the present invention, the friction coefficient storage means outputs the friction coefficient according to the selected road surface type and the detected road surface condition.

Further, in the road surface state detecting device according to the sixth aspect of the present invention, the specular light reflected by the road surface of the light emitted from the illumination is incident on the reflected light amount detecting means.

Further, in the road surface state detecting device according to the seventh aspect of the present invention, light other than the illumination light of the illumination is not incident on the reflected light amount detecting means.

[0022]

【Example】

Example 1. FIG. 1 is a diagram showing a road surface state detecting device according to a first embodiment of the present invention. In the figure, 1 is a light source, 2 is a power source for the light source 1, and the light source 1 and the power source 2 constitute a lighting means for illuminating a road surface. Further, 3 is an irradiation light amount detecting means for detecting an irradiation light amount of the illumination from the power supply voltage of the illumination 1, 4 is a reflected light amount detecting means for detecting a reflected light amount on a road surface, and 5 is a light amount emitted from the illumination 1 and the reflected light amount detecting means. Reflectance detecting means for calculating a ratio with the amount of light detected by 4;
Reference numeral 6 is a comparison means for comparing the calculation result by the reflectance detection means with a predetermined constant. In FIG. 2, reference numeral 7 denotes a road surface, which shows the arrangement of the illumination 1, the reflected light amount detection means 4, and the road surface 7.

The road surface state detecting device configured as described above will be described. FIG. 2 is an arrangement relationship diagram of the illumination 1 and the reflected light amount detection means. As shown in the figure, the illumination 1 is installed so as to illuminate the road surface 7, and the light emitted from the illumination 1 is reflected by the road surface 7. The reflected light amount detecting means 4 receives the reflected light of the road surface 7 of the illumination light. The reflected light amount detecting means 4 can be realized, for example, by using a lens 8 that collects the reflected light on the road surface 7 and a light receiving element 9 such as a photodiode or a CCD as shown in FIG.

FIG. 4 is a diagram showing the relationship between the light quantity of the illumination 1 and the voltage value of the power supply 2. The irradiation light amount detection means 3 is the illumination 1
The relationship between the voltage value of the power source 2 and the amount of light is stored in advance.
The irradiation light amount detection means 3 can detect the light amount of the illumination 1 by inputting the voltage of the power supply 2. Further, the relationship diagram between the voltage of the power supply 2 and the light quantity of the illumination 1 shown in FIG. 4 is an example, and the relationship between the light quantity of the illumination and the power supply voltage depends on the type of the lamp used for the illumination 1 (halogen, metal halide lamp, etc.). Although different, if the relationship between the light quantity and the power supply voltage is stored in the irradiation light quantity detection means 3 according to the type of lamp used, the light quantity of the illumination 1 can be detected. The irradiation light amount detecting means 3 uses the detected irradiation light amount as the reflected light detecting means 5
Output to. The reflectance detecting means 5 calculates a ratio between the irradiation light quantity and the light quantity detected by the reflected light quantity detecting means 4. The ratio obtained by the reflectance detecting means 5 is taken as the reflectance of the road surface.

Next, the comparing means 6 compares the reflectance obtained by the reflectance detecting means 5 with a predetermined constant k. 5 and 6 are diagrams showing the relationship between the state of the road surface and the reflected light. In FIG. 6, 10 is water. The surface of the road is uneven so that the friction with the tire of the automobile is large, and a road surface having a flat surface such as a mirror surface is not normally possible. Therefore, if the road surface 7 is dry,
Since the light emitted from the illumination 1 is diffused on the road surface 7 as shown in, the amount of light reflected to the reflected light amount detection means 4 is small. However, when the road surface gets wet, the water 4 covers the unevenness on the road surface as shown in FIG. 6 and reflects the illumination light as a mirror surface. Therefore, the reflectance of the road surface 7 increases as the road surface gets wet. Fig. 7 shows the relationship between the road surface condition and reflectance.
Shown in Since the reflectance increases as the road surface gets wet as described above, it can be determined that the road surface is wet when the reflectance is larger than k. The comparing means 6 compares the reflectance with the constant k, and when the reflectance is larger than k, it is determined that the road surface is wet, and when the reflectance is smaller than k, it is determined that the road surface is not wet.

Example 2. FIG. 8 is a diagram showing a road surface state detecting device according to the second embodiment of the present invention. In the figure, 1,
Nos. 2, 3, and 5 are the same as those in the first embodiment, and the description thereof is omitted.

The road surface state detecting device configured as described above will be described. In the road surface state detecting device of the first embodiment, if the voltage value of the power supply 2 is kept constant, the amount of light emitted from the illumination 1 can also be treated as a constant value. Therefore, when the irradiation light amount is a constant value, the light amount detected by the reflected light amount detection circuit 4 can be directly regarded as the reflectance of the road surface. FIG. 9 is a diagram showing the relationship between the road surface condition and the reflectance. In the figure, the constant k'is a value obtained by multiplying k shown in the first embodiment by the value of the irradiation light amount of the illumination 1 which is constant. The comparison means 6 compares the reflectance with a constant k ′,
When the reflectance is larger than k ′, it is determined that the road surface is wet, and when it is smaller than k ′, the road surface is not wet. With the above configuration, the road surface condition can be detected without providing the irradiation light amount detecting means 3 and the emissivity detecting means 5 shown in the first embodiment.

Example 3. In the road surface state detecting device of the first embodiment, a plurality of constants k to be compared by the comparing means 6 are provided. For example, in the first embodiment, the state of the road surface is determined by comparing the constant k with the reflectance of the road surface. However, as shown in FIG. 10, a plurality of constants k1, k2, k3 are provided.
The condition of the road surface is gradually "dry", "a little wet", "pretty wet", "very wet" from the dry condition to the condition where the water completely covers the road surface. When the reflectance is equal to or higher than k1, it is determined to be “slightly wet”, when the reflectance is equal to or higher than k2, it is determined to be “very wet”, and when the reflectance is equal to or higher than k3, it is determined to be “extremely wet”. By providing a plurality of constants as described above, it is possible not only to determine whether or not the road surface is wet, but also to determine a plurality of steps for each stage.

Further, in the road surface state detecting apparatus of the second embodiment, a plurality of constants k'compared by the comparing means 6 are provided as shown in FIG. 11 such as k1 ', k2' and k3 ', and the reflected light amount detecting means 4 outputs When the output value is k1 'or more, it is judged as "a little wet", when it is k2' or more, it is judged as "pretty wet", and when it is k3 'or more, it is judged as "terribly wet". In the same manner, it goes without saying that not only the condition of the road surface can be determined but also a plurality of conditions can be determined for each stage.

Example 4. FIG. 12 is a diagram showing a road surface state detecting device according to the fourth embodiment of the present invention. In the figure, 1 to 6 are the same as those in FIG. 1, and their explanations are omitted. Reference numeral 11 denotes a road surface coefficient storage unit that stores a friction coefficient corresponding to a road surface state that is distinguished according to a wet condition of the road surface.

The operation of the road surface condition detecting device constructed as described above will be described. Lighting 1 to comparison means 6
The operation up to this point is the same as that of the first embodiment, and therefore its explanation is omitted. The comparison means 6 determines whether or not the road surface is wet by comparing with the constant k as in the first embodiment. The friction coefficient storage means 11 has a typical friction coefficient μ1 when the road surface is dry and a typical friction coefficient μ2 when the road surface is wet. When the comparison means 6 determines that the road surface is wet, the friction coefficient storage means 11 outputs the friction coefficient μ1 and when the road surface is determined to be dry, the friction coefficient μ2 is output.

Further, in the road surface state detecting device shown in FIG. 12, the comparing means 6 judges whether or not the road surface is wet by comparing the reflectance with the constant k, and the friction coefficient storing means 11 makes the judgment. The coefficient of friction of the road surface was output according to the result, but a plurality of constants k were provided as in the third embodiment, and the state of the road surface was discriminated by the comparing means 6 depending on the degree of wetting, and it was determined whether the state was the road surface state. And friction coefficient storage means 1
In FIG. 1, friction coefficients corresponding to a plurality of road surface states distinguished by the wetness of the road surface are stored in advance, and the friction coefficient of the road surface is output from the friction coefficient storage means 11 according to the determination result by the comparison means 6. As a result, the friction coefficient can be detected according to the degree of wetting of the road surface.

Furthermore, the road surface condition detecting device shown in FIG. 12 in the present embodiment can detect the road surface friction coefficient by providing the road surface condition detecting device shown in FIG. 1 with the friction coefficient storing means 11. I realized a detector,
As shown in FIG. 13, the road surface state detecting device shown in FIG. 8 is also provided with the friction coefficient storing means 11, and in FIG. 13, the comparing means 6 outputs the output of the reflected light amount detecting means 4 as in the second embodiment. When the value is larger than k ′, it is determined that the road surface is wet, the friction coefficient storage means 11 outputs μ1, and when the value is smaller than k ′, it is determined that the road surface is not wet, and the friction coefficient storage means 11 is μ2. It goes without saying that the same effect can be obtained by outputting.

Furthermore, in the road surface condition detecting device shown in FIG. 13, the comparing means 6 has a constant k'as in the third embodiment.
Are provided, and the comparison means 6 distinguishes the condition of the road surface by the degree of wetting to determine whether the condition of the road surface is
The friction coefficient storage means 11 stores in advance friction coefficients according to a plurality of road surface states distinguished by the wetness of the road surface, and the friction coefficient storage means stores the friction coefficient of the road surface according to the determination result by the comparison means 6. By outputting from 11,
The friction coefficient can be detected according to the wetness of the road surface.

Example 5. FIG. 14 is a diagram showing a road surface state detecting device according to the fifth embodiment of the present invention. In the figure, 1
1 to 6 are the same as those in FIG. 1, and the description thereof will be omitted. 15
Is a selecting means for selecting a type of road surface distinguished by a switch or the like with respect to the material of the road surface, and 11 is a friction coefficient corresponding to the type of the road surface selected by the selecting means and the state of the road surface related to the wet condition of the road surface. Is a road surface coefficient storing means.

The operation of the road surface condition detecting device configured as described above will be described. The operations from 1 to 5 are the same as those in the first embodiment, and the description thereof will be omitted. The comparing means determines whether or not the road surface is wet by comparing with the constant k as in the first embodiment. Selection means 15
Is provided with types of road surfaces relating to road surface materials such as asphalt, soil, and concrete. By selecting any of the types of road surfaces, the type of road surface currently running is stored in the friction coefficient storage means 11. Is entered. The friction coefficient storage means 11 is provided with the type of the road surface and a friction coefficient corresponding to whether or not the road surface is wet, and is input from the type of the road surface input from the selection means 15 and the discrimination result by the comparison means 6. The friction coefficient according to the road surface is output.

Further, in the road surface state detecting device shown in FIG. 14, the comparing means 6 determines whether or not the road surface is wet by comparing the reflectance with the constant k, and the friction coefficient storing means 11 stores the above information. The friction coefficient of the road surface was output according to the determination result and the type of the road surface input from the selecting means. However, as in the third embodiment, a plurality of constants k are provided, and the comparing means 6 distinguishes the road surface state by the wet condition. It is determined whether the road surface is in a different state, and the friction coefficient storage means 11 is responsive to the plurality of road surface states distinguished by the wetness of the road surface and the type of the road surface input from the selection means 15. The friction coefficient is stored in advance, and the friction coefficient of the road surface is output from the friction coefficient storage means 11 in accordance with the determination result by the comparison means 6 and the type of the road surface input from the selection means 15. It is possible to detect the friction coefficient according.

Furthermore, the road surface condition detecting device shown in FIG. 14 in the present embodiment can detect the friction coefficient of the road surface by providing the road surface condition detecting device shown in FIG. 12 with selecting means 15. Was realized, but Fig. 15
As shown in FIG. 13, the road surface state detecting device shown in FIG. 13 is also provided with the selecting means 15, and the comparing means 4 in FIG. Depending on whether or not the road surface is wet,
It goes without saying that the friction coefficient storage means 11 can also be realized by outputting the friction coefficient of the road surface according to the determination result and the type of road surface selected by the selection means 15.

Further, in the road surface state detecting device shown in FIG. 15, the comparing means 6 has a constant k'as in the third embodiment.
Are provided, and the comparison means 6 distinguishes the condition of the road surface by the degree of wetting to determine whether the condition of the road surface is
The friction coefficient storage means 11 stores in advance friction coefficients corresponding to a plurality of road surface states distinguished by the wetness of the road surface and the type of road surface input from the selection means 15, and the comparison result by the comparison means 6 By outputting the friction coefficient of the road surface from the friction coefficient storage means 11 in accordance with the type of the road surface selected by the selection means 15, the friction coefficient can be detected according to the wetness of the road surface.

Example 6. FIG. 16 is a diagram showing a road surface state detecting device according to a sixth embodiment of the present invention. In the figure,
1, 3, and 7 are the same as those in FIG. 2, and the description thereof will be omitted.

The operation of the road surface condition detecting device constructed as described above will be described. In the road surface condition detecting device shown in the first to fifth embodiments, the illumination 1 is installed in the vehicle so as to illuminate the road surface 7. The reflected light amount detection means 4 is
The light emitted from the illumination 1 is reflected by the road surface 7, and the reflected light is incident on the vehicle so that it is on the diagonal of the reflected light. That is, in FIG. 16, the illumination 1 and the reflected light amount detection means 4 are installed so that the incident angle θ1 and the reflected angle θ2 are equal.

By installing the illumination 1 and the reflected light amount detecting means 4 in this way, the difference between the case where the road surface is wet and the case where the road surface is not wet in the first embodiment is larger as shown in FIG. Therefore, it becomes easier to determine the road surface condition.

Example 7. FIG. 18 is a diagram showing a road surface state detecting device according to a seventh embodiment of the present invention. In the figure, 1
6 is a car.

In the road surface condition detecting apparatus according to the first to sixth embodiments, the illumination 1 and the reflected light amount detecting means 4 are installed on the bottom of the automobile 16 where external light does not enter. By installing as described above, the reflected light of the road surface can be imaged without being affected by sunlight, lighting other than the lighting 1 installed in the automobile 12, or the like.

[0045]

As described above, according to the road surface condition detecting apparatus of the first aspect of the present invention, it is possible to determine whether or not the road surface is wet even if the road surface is achromatic. A detection device can be obtained.

Further, according to the road surface state detecting device of the second aspect of the present invention, the irradiation light amount detecting means can be omitted.

Further, according to the road surface condition detecting apparatus of the third aspect of the present invention, it is possible to obtain the road surface condition detecting apparatus which can determine the wet condition of the road surface even if the road surface is achromatic.

Further, according to the road surface condition detecting device of the fourth aspect of the present invention, it is possible to obtain the road surface condition detecting device capable of detecting the friction coefficient of the road surface even if the color of the road surface is achromatic.

Further, according to the road surface condition detecting apparatus of the fifth aspect of the present invention, even if there are various kinds of road surfaces,
It is possible to obtain a road surface state detection device that can detect the friction coefficient of the road surface.

Further, according to the road surface condition detecting device of the sixth aspect of the present invention, a more accurate road surface condition detecting device can be obtained.

According to the road surface condition detecting device of the seventh aspect of the present invention, a more accurate road surface condition detecting device can be obtained without being affected by light other than the installed illumination.

[Brief description of drawings]

FIG. 1 is a diagram showing a road surface state detection device according to a first embodiment of the present invention.

FIG. 2 is an arrangement relationship diagram between the illumination 1 and the reflected light amount detection means 4.

FIG. 3 is a diagram showing a configuration of a reflected light amount detection means 4.

FIG. 4 is a diagram showing the relationship between the light quantity of the illumination 1 and the voltage value of the power supply 2.

FIG. 5 is a diagram showing a relationship between a state of a road surface and reflected light.

FIG. 6 is a diagram showing a relationship between a state of a road surface and reflected light.

FIG. 7 is a diagram showing a relationship between a road surface state and reflectance.

FIG. 8 is a diagram showing a road surface state detecting device according to a second embodiment of the present invention.

FIG. 9 is a diagram showing a relationship between a road surface state and reflectance in Example 2;

FIG. 10 is a diagram showing a relationship between a road surface state and reflectance in Example 3;

FIG. 11 is a diagram showing a relationship between a road surface state and reflectance in Example 3;

FIG. 12 is a diagram showing a road surface state detection device according to a fourth embodiment of the present invention.

FIG. 13 is a diagram showing a road surface state detection device according to a fourth embodiment of the present invention.

FIG. 14 is a diagram showing a road surface state detection device according to a fifth embodiment of the present invention.

FIG. 15 is a diagram showing a road surface state detecting device according to a fifth embodiment of the present invention.

FIG. 16 is a diagram showing a road surface state detecting device according to a sixth embodiment of the present invention.

FIG. 17 is a diagram showing a relationship between the road surface state and the reflectance when the incident angle and the light receiving angle are the same and different.

FIG. 18 is a diagram showing a relationship among an automobile, lighting, and a photodetector.

FIG. 19 is a configuration diagram of a conventional road surface state detecting device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 illumination, 2 power supply, 3 irradiation light amount detecting means, 4 reflected light amount detecting means, 5 reflectance detecting means, 6 comparing means, 7
Road surface, 8 lenses, 9 light receiving element, 10 water, 11
Friction coefficient storage means, 15 selection means, 16 automobiles, 2
0 photographing means, 21 image processing means, 22 comparison judgment means, 23 road surface state storage means, 24 friction coefficient storage means, 25 road surface friction coefficient storage means

Claims (7)

[Claims] 1. A lighting unit for irradiating a road surface, a reflected light amount detecting unit for receiving reflected light from the road surface irradiated by the illuminating unit, and detecting a light amount of the reflected light, and an amount of light irradiated from the illuminating unit. Irradiation light amount detecting means for detecting, the light amount detected by the irradiation light amount detecting means, the reflectance detecting means for detecting the reflectance of the road surface by the ratio of the light amount detected by the reflected light amount detecting means, and the reflectance detection result. It is characterized by comprising a comparison means for comparing with a predetermined constant, and comparing the reflectance of the road surface with the constant by the comparison means, and if it is larger than the constant, it is determined that the road surface is wet. Road condition detector. 2. A lighting unit for irradiating a road surface, a reflected light amount detecting unit for receiving reflected light from the road surface irradiated by the illuminating unit, and detecting a light amount of the reflected light, and a reflected light amount detecting unit for detecting the reflected light amount. And a light quantity detected by the reflected light quantity detecting means is larger than the constant, the road surface condition is characterized by determining that the road surface is wet. Detection device. 3. A plurality of constants for comparing with the light quantity detected by the reflected light quantity detecting means are provided in the comparing means, whereby it is possible to determine a plurality of road surface states according to the wetness of the road surface. Alternatively, the road surface state detecting device according to claim 2. 4. A friction coefficient storage means for storing a friction coefficient corresponding to a state of a road surface which is distinguished according to a wet condition of the road surface is provided, and according to a detected state of the road surface,
The road surface state detecting device according to any one of claims 1 to 3, wherein a friction coefficient is output from the friction coefficient detecting means. 5. Soil, asphalt, concrete, etc.
The type of the road surface is provided in advance, and the driver can select the type of the road surface, and the road surface corresponding to the type of the road surface and the state of the road surface distinguished according to the wet condition of the road surface. A friction coefficient storage unit that stores a friction coefficient, and outputs the friction coefficient from the friction coefficient detection unit according to the type of road surface selected by the selection unit and the degree of wetting of the detected road surface. The road surface state detection device according to any one of claims 1 to 3, which is characterized. 6. The respective units are installed so that an incident angle, which is an angle formed by the illumination means and a normal line of the road surface, and a light receiving angle, which is an angle formed by the photodetector and a normal line of the road surface, are substantially equal to each other. The road surface state detection device according to any one of claims 1 to 5. 7. The road surface condition detection according to claim 1, wherein the illumination means and the reflected light amount detection means are installed at the bottom of the automobile so as not to be affected by external light. apparatus.