JP2008122217A - Road surface state detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a road surface state detector which reduces the effect of environmental light and detects a road surface state from a camera image. <P>SOLUTION: The road surface state detector 1 is equipped with an auxiliary light 10 for irradiating a road surface, an P-polarization receiving device 14 for acquiring P-polarization of the road surface, an S-polarization receiving device 16 for acquiring an S-polarization component, an environmental light component removing part 20 for calculating the respective differences between the P-polarization component and the S-polarization component acquired when the irradiation intensity of the auxiliary light 10 is large and between the P-polarization component and the S-polarization component acquired when the irradiation intensity of the auxiliary light 10 to remove an environmental light component, a polarization degree calculation part 22 for calculating the polarization degrees of the P-polarization component and the S-polarization component from which the environmental light component is removed and a road surface state judging part 24 for judging the state of the road surface on the basis of the polarization degrees. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a road surface state detection device that detects a road surface state.

  Conventionally, as a technique for detecting a road surface state, a technique for embedding a sensor on the road surface and a technique for performing analysis using an image of a camera are known. The former is not practical because it requires a large number of sensors and increases costs. Examples of the latter method include the methods described in Patent Document 1 and Patent Document 2.

  The detection device described in Patent Document 1 is a technique that utilizes the fact that there is a wavelength band in which the absorbance of water is high in the infrared region. Since this method requires an infrared projector and a bandpass filter, the cost increases.

  The road surface state detection device described in Patent Document 2 is a device that detects a road surface state in front of a vehicle at night. This road surface state detection apparatus detects a road surface state as follows. First, the road surface in front of the vehicle is irradiated with a headlight, and the irradiated road surface is imaged. When the intensity of light from the road surface is small, it is determined that there is water on the road surface, that is, a wet state, because the diffuse reflection of light on the road surface is small and the specular reflectance of the road surface is high. When the intensity of light from the road surface is large, the light from the headlight is diffusely reflected on the road surface, and therefore it is determined that the road surface is in a dry state.

  By the way, the road surface condition detection apparatus may receive light such as street lamps other than light emitted by the host vehicle. Therefore, when the intensity of light from the road surface is large, it is conceivable that the road surface is influenced by environmental light such as a street light in addition to the case where the road surface is dry. The road surface state detection apparatus of Patent Literature 2 performs processing using the fact that the specular reflection light on the water surface has a larger vertical polarization component in order to reduce erroneous detection of the road surface state due to environmental light such as a streetlight. . That is, when the light from the road surface is large, the road surface state detection device obtains the vertical polarization component / parallel polarization component of the received light, and when the value is 1, the road surface state detection device determines that the light is in the dry state. When the value of the component / parallel polarization component is larger than 1, it is determined that the state is wet.

As described above, the road surface state detection device described in Patent Document 2 detects the road surface state in consideration of the influence of ambient light.
JP 2003-156430 A JP2004-301708

  However, the road surface state detection apparatus described in Patent Document 2 described above only considers when ambient light is specularly reflected on the road surface and enters the imaging device, and enters the imaging device depending on the position of the light source of ambient light. It does not take into consideration that the degree of polarization of reflected light varies.

  For example, depending on the position of the ambient light source such as a streetlight, the ambient light that is specularly reflected by the water surface does not enter the imaging device, but only the ambient light that is diffusely reflected by the road surface and transmitted from the water to the air enters the imaging device. There is a case. In this case, the apparatus described in Patent Document 2 erroneously determines a wet road surface as a dry state.

  SUMMARY OF THE INVENTION In view of the above background, an object of the present invention is to provide a road surface state detection device capable of reducing the influence of ambient light and detecting a road surface state from a camera image.

  The road surface state detection apparatus of the present invention includes a light that can change the irradiation intensity in at least two stages, a light receiving device that acquires a P-polarized component and an S-polarized component of reflected light from the road surface, and an irradiation intensity of the light A difference acquisition unit for obtaining a difference between the P-polarized component and the S-polarized component acquired when the light intensity is strong, a difference between the P-polarized component and the S-polarized component acquired when the light irradiation intensity is low, A road surface state determination unit that determines a road surface state based on the difference between the S polarization components.

  In this way, by calculating the difference between when the light irradiation intensity is strong and weak for each of the P-polarized component and the S-polarized component of the reflected light from the road surface, the ambient light component contained in the reflected light is reduced, and P The influence of ambient light on the polarization component and the S polarization component can be reduced. And a road surface state can be determined appropriately using the P-polarized light component and the S-polarized light component with reduced influence of ambient light.

  In the road surface condition detection apparatus, the light illuminates a road surface in front of the vehicle, and the road surface state determination unit determines that the road surface is in a wet state when the difference in the P polarization component is substantially larger than the difference in the S polarization component. If the intensity of the P-polarized component and the intensity of the S-polarized component are substantially equal, it may be determined that the road surface is in a dry state.

  In this way, when the road surface in front of the vehicle is irradiated, the light receiving device provided in the vehicle receives diffusely reflected light from the road surface and hardly receives specularly reflected light. Therefore, when there is water on the road surface, the diffusely reflected light on the road surface is transmitted from the water into the air, so that the P-polarized component becomes larger than the S-polarized component. Conversely, when there is no water on the road surface, the P-polarized component and the S-polarized component of the diffusely reflected light are substantially equal. Therefore, the road surface state can be appropriately determined based on the difference between the P-polarized component and the difference between the S-polarized component.

  The road surface condition detection apparatus may include a light control unit that changes the irradiation intensity of the light at a cycle determined based on a traveling speed of the vehicle.

  By determining the period for changing the light irradiation intensity based on the traveling speed of the vehicle in this way, the reflected light when the light irradiation intensity is strong and weak is almost the same position on the road surface regardless of the movement of the vehicle. The road surface condition can be detected appropriately.

  The road surface state detection method according to the present invention includes a step of changing the irradiation intensity of the light that irradiates the road surface in at least two steps, and a P of reflected light from the road surface when the light irradiation intensity is strong and weak, respectively. Obtaining a polarization component and an S polarization component; a P polarization component and an S polarization component obtained when the illumination intensity of the light is high; and a P polarization component and an S polarization component obtained when the illumination intensity of the light is low And a step of determining a road surface state based on the difference between the P polarization component and the difference between the S polarization components.

  With this configuration, similarly to the road surface state detection device of the present invention, the environmental light component contained in the reflected light from the road surface can be reduced, and the road surface state can be appropriately determined. In addition, various configurations of the road surface state detection device of the present invention can be applied to the road surface state detection method of the present invention.

  The program according to the present invention is a program for detecting a road surface state, a light capable of changing an irradiation intensity in at least two stages, and a P-polarized component of light reflected from the road surface irradiated by the light. And a computer having a light receiving device for acquiring S-polarized light components, changing the illumination intensity of the light that irradiates the road surface in at least two stages, and each of the road surface when the illumination intensity of the light is strong and weak A P-polarized component and an S-polarized component of the reflected light from the light, a P-polarized component and an S-polarized component acquired when the light irradiation intensity is high, and a P acquired when the light irradiation intensity is low Based on the step of obtaining the difference between the polarization component and the S polarization component, and the difference between the P polarization component and the difference between the S polarization components, To execute determining a state of the surface.

  With this configuration, similarly to the road surface state detection device of the present invention, the environmental light component contained in the reflected light from the road surface can be reduced, and the road surface state can be appropriately determined. In addition, various configurations of the road surface condition detection device of the present invention can be applied to the program of the present invention.

  According to the present invention, for each of the P-polarized component and S-polarized component of the reflected light from the road surface, the ambient light component contained in the reflected light is reduced by obtaining the difference between when the light irradiation intensity is strong and weak. The road surface condition can be appropriately determined.

  Hereinafter, a road surface state detection device according to an embodiment of the present invention will be described with reference to the drawings. The road surface condition detection device of the present embodiment is used by being mounted on a vehicle.

[First Embodiment]
FIG. 1 is a diagram showing a configuration of a road surface state detection device 1 according to a first embodiment of the present invention. The road surface state detection apparatus 1 includes an auxiliary light 10, an auxiliary light control unit 12 that controls the irradiation intensity of the auxiliary light 10, a P-polarized light receiving device 14 that acquires a P-polarized component of reflected light from the road surface, and an S-polarized component. S-polarized light receiving device 16 for obtaining

  The auxiliary light 10 has two levels of irradiation intensity, strong irradiation and weak irradiation. The irradiation intensity of the auxiliary ride 10 is controlled by the auxiliary light control unit 12. The P-polarized light receiving device 14 includes a P-polarized filter and an imaging device such as a CCD. The S-polarized light receiving device 16 includes an S-polarized filter and an imaging device such as a CCD.

  FIG. 2 is a diagram for explaining the P-polarized component and the S-polarized component. As shown in FIG. 2, the P-polarized light component is a wave that vibrates in a plane perpendicular to the reflecting surface (a surface including a normal line standing on the reflecting surface and the traveling direction of light). The S-polarized component is a wave that oscillates in a plane perpendicular to the plane of vibration of P-polarized light.

  Returning to FIG. 1, the road surface condition detection apparatus 1 will be described. The road surface state detection device 1 determines the road surface state based on the P-polarized light component of the reflected light acquired by the P-polarized light receiving device 14 and the S-polarized light component of the reflected light acquired by the S-polarized light receiving device 16. A calculation processing unit 18 is provided.

  The calculation processing unit 18 includes an ambient light component removal unit 20, a polarization degree calculation unit 22, and a road surface state determination unit 24. For each of the P-polarized light component and the S-polarized light component, the ambient light component removing unit 20 reflects reflected light acquired when the irradiation intensity of the auxiliary light 10 is strong, and reflected light acquired when the irradiation intensity of the auxiliary light 10 is weak The component of ambient light is removed by obtaining the difference between the two. The calculation processing unit 18 is connected to the auxiliary light control unit 12 and acquires information on the timing of the intensity of irradiation intensity from the auxiliary light control unit 12. Thereby, the calculation processing unit 18 obtains a difference between the reflected light acquired when the irradiation intensity is high and the reflected light acquired when the irradiation intensity of the auxiliary light 10 is low in synchronization with the intensity of the irradiation intensity. Can do.

  Both the light intensity acquired when the irradiation intensity of the auxiliary light 10 is high and the light intensity acquired when the irradiation intensity is low include an ambient light component. Therefore, the environmental light component can be canceled by taking these differences.

  The polarization degree calculation unit 22 has a function of obtaining the degree of polarization (P polarization component / S polarization component) using the P polarization component and the S polarization component from which the environment light component has been removed by the environment light component removal unit 20.

  The road surface state determination unit 24 has a function of determining the road surface state based on the polarization degree obtained by the polarization degree calculation unit 22. Here, the relationship between the P polarization component and the S polarization component and the road surface state will be described.

  FIG. 3A is a diagram for explaining the P-polarized component and the S-polarized component when the road surface is in a dry state, and FIG. 3B is a diagram for explaining the P-polarized component and the S-polarized component when the road surface is in a wet state. FIG. In the present embodiment, since the auxiliary light 10 irradiates the front of the vehicle, the light entering the light receiving devices 14 and 16 from the road surface in front of the vehicle is diffusely reflected light on the road surface. Therefore, in FIG. 3A and FIG. 3B, only diffuse reflection light is described, and specular reflection light is not described.

  As shown in FIG. 3A, the light emitted from the auxiliary light 10 is diffusely reflected by fine irregularities on the road surface. Since the P-polarized component and the S-polarized component included in the light emitted from the auxiliary light 10 are substantially equal, the P-polarized component and the S-polarized component of the diffusely reflected light are substantially equal when the road surface is dry. Accordingly, the degree of polarization (P-polarized component / S-polarized component) is substantially 1.

  As shown in FIG. 3B, when the road surface is wet, the light from the auxiliary light 10 reaches the road surface through the water on the surface of the road surface and diffusely reflects on the road surface. The diffusely reflected light passes from the water into the air and enters the light receiving devices 14 and 16. In water, the P-polarized component and the S-polarized component of diffusely reflected light are almost equal, but the transmittance from water to the air is higher in the P-polarized component. Therefore, in air, the P-polarized component> the S-polarized component. . Accordingly, the degree of polarization (P-polarized component / S-polarized component) is substantially larger than 1.

  Using the above principle, the road surface state determination unit 24 determines the road surface state based on the degree of polarization. The road surface state determination unit 24 determines that the vehicle is in a wet state when the degree of polarization is substantially larger than 1. When determining whether the degree of polarization is substantially larger than 1, a predetermined threshold is used to determine whether the degree of polarization is greater than (1 + predetermined threshold). If it is determined whether or not the degree of polarization is strictly 1, if the degree of polarization fluctuates due to a cause other than the road surface state, the road surface state may be erroneously detected. In the present embodiment, it is possible to reduce road surface misdetection by determining whether or not a substantial difference exceeding the error range has occurred between the P polarization component and the S polarization component using a predetermined threshold. The predetermined threshold is preferably set according to various conditions.

  FIG. 4 is a flowchart showing the operation of the road surface condition detection apparatus 1 according to the present embodiment. The road surface state detection device 1 increases the irradiation intensity of the auxiliary light 10 (S10), and acquires the P-polarized component and the S-polarized component of the reflected light from the road surface in this state (S12). Next, the road surface state detection device 1 weakens the irradiation intensity of the auxiliary light 10 (S14), and acquires the P-polarized component and the S-polarized component of the reflected light from the road surface in this state (S16). The irradiation intensity of the auxiliary light 10 is controlled by the auxiliary light control unit 12.

  Next, the road surface state detection device 1 obtains respective differences between the P-polarized component and the S-polarized component acquired when the irradiation intensity of the auxiliary light 10 is strong, and the P-polarized component and the S-polarized component acquired when the auxiliary light 10 is weak. The difference between the P-polarized components and the difference between the S-polarized components obtained here are components from which the influence of ambient light has been removed. That is, the P-polarized component and the S-polarized component included in the reflected light of the auxiliary light 10 in the absence of ambient light.

  Subsequently, the road surface state detection apparatus 1 obtains the polarization degree of the P-polarized component and the S-polarized component from which the influence of the environmental light is removed. Specifically, the polarization degree calculation unit 22 obtains the degree of polarization (P polarization component / S polarization component) using the difference between the P polarization components and the difference between the S polarization components (S20). The road surface state detection apparatus 1 determines whether the value of the polarization degree is substantially 1 or substantially larger than 1 (S22). The road surface state detection apparatus 1 determines that the road surface is wet when the degree of polarization is substantially greater than 1 (S24), and determines that the road surface is dry when the degree of polarization is substantially 1 (S26). The configuration and operation of the road surface state detection device 1 according to the present embodiment have been described above.

  The road surface condition detection apparatus 1 according to the present embodiment is configured to obtain a P-polarized component and an S-polarized component acquired when the auxiliary light 10 has a high irradiation intensity, and a P-polarized component acquired when the auxiliary light 10 has a low irradiation intensity. By taking each difference from the S-polarized component, the influence of ambient light can be reduced.

  FIGS. 5A and 5B are diagrams for explaining ambient light incident on the light receiving devices 14 and 16. As shown in FIG. 5A, when the ambient light source is located in front of the vehicle equipped with the road surface state detection device, most of the light incident on the light receiving devices 14 and 16 is specularly reflected by the water surface. Since it is light, P polarization component <S polarization component. Conversely, when the ambient light source shown in FIG. 5 (b) is in front of the road surface in front of the vehicle (vehicle side), the specular reflection light on the water surface is not incident on the light receiving devices 14 and 16, Since light diffusely reflected on the road surface and transmitted from water to air enters, P polarization component> S polarization component. As described above, the influence of the ambient light on the degree of polarization varies depending on the position of the light source.

  The road surface condition detection device 1 according to the present embodiment reduces the influence of ambient light by taking the difference of reflected light acquired when the irradiation intensity of the auxiliary light 10 is different, and detects the light irradiated by the auxiliary light 10. Therefore, it is possible to appropriately detect the road surface state regardless of environmental changes.

[Second Embodiment]
FIG. 6 is a diagram illustrating a configuration of the road surface state detection device 2 according to the second embodiment. The road surface condition detection device 2 of the second embodiment has the same basic configuration as that of the first embodiment, but the auxiliary light control unit 12 determines the irradiation intensity of the auxiliary light according to the traveling speed of the vehicle. The point to control is different.

  The road surface state detection device 2 includes a speed sensor 26 that detects the traveling speed of the vehicle. Information on the speed detected by the speed sensor 26 is input to the auxiliary light control unit 12.

  The auxiliary light control unit 12 determines a period (frequency) for changing the irradiation intensity of the auxiliary light 10 based on the vehicle speed information acquired from the speed sensor 26. The auxiliary light control unit 12 adjusts the irradiation intensity in relation to the moving speed of the vehicle so that the reflected light from the same position on the road surface enters the image sensor of the light receiving devices 14 and 16 when the irradiation intensity is strong and weak. Determine the cycle of switching.

  In the road surface condition detection device 2 according to the present embodiment, the auxiliary light control unit 12 determines the period for changing the irradiation intensity of the auxiliary light 10 based on the traveling speed of the vehicle. The reflected light when the intensity is strong and the reflected light when the irradiation intensity is weak can be acquired at substantially the same position, and the road surface state can be detected appropriately.

[Third Embodiment]
FIG. 7 is a diagram illustrating a configuration of the road surface state detection device 3 according to the third embodiment. The road surface state detection device 3 of the third embodiment has the same basic configuration as the road surface state detection device 1 of the first embodiment, but includes an auxiliary light control unit 12 and a calculation processing unit 18. It is different that it is not connected. In addition to this, in addition to the function described in the first embodiment, the ambient light component removing unit 20 is different in that the period of the irradiation intensity of the auxiliary light 10 is obtained by calculation.

  The ambient light component removing unit 20 of the calculation processing unit 18 assists based on the intensity of either the P-polarized component received by the P-polarized light receiving device 14 or the S-polarized component received by the S-polarized light receiving device 16, or both. The period of the irradiation intensity of the light 10 and the timing at which the irradiation intensity increases and decreases are obtained. The ambient light component removing unit 20 obtains the difference between the P-polarized component and the S-polarized component acquired at the timing when the irradiation intensity is strong and the timing when it is weak.

  As described above, the auxiliary light control unit 12 and the calculation processing unit are configured to obtain the period of the irradiation intensity of the auxiliary light 10 and the timing of the intensity of the irradiation intensity using the intensity of either or both of the P-polarized component and the S-polarized component. Thus, the road surface condition detection device 3 having a configuration independent of the number 18 can be realized.

  In the present embodiment, a configuration has been described in which the period of the irradiation intensity of the auxiliary light 10 and the timing of the intensity of the irradiation light are determined based on the intensity of the P-polarized light component and the S-polarized light component. If the period is known, the timing of the intensity of irradiation intensity may be obtained using the period information. Thereby, the timing of intensity of irradiation intensity can be obtained with high accuracy.

  The road surface state detection device of the present invention has been described in detail with reference to the embodiment, but the present invention is not limited to the above-described embodiment.

  In the above-described embodiment, the example in which the reflected light from the road surface is acquired when the irradiation intensity of the auxiliary light 10 is strong and weak is described. However, the auxiliary light 10 may be turned off when the irradiation intensity is low. . That is, the auxiliary light 10 may be blinked, and reflected light from the road surface may be acquired when the auxiliary light 10 is turned on and off.

  In the above-described embodiment, the example in which the irradiation intensity of the auxiliary light 10 is changed in two levels of strength and weakness has been described. However, based on the obtained reflected light, the irradiation intensity of the auxiliary light 10 is changed in multiple stages. It is good also as judging a road surface state. Thereby, since the data used as the basis of judgment increase, a road surface state can be detected more appropriately.

  In the above-described embodiment, when comparing the P-polarized component and the S-polarized component, the degree of polarization was obtained by comparing the ratio between the two. A method may be used. For example, the light intensity of the P-polarized component and the S-polarized component may be compared by obtaining the difference between them.

  In the above-described embodiment, the example in which the auxiliary light 10 is used to irradiate the road surface has been described. However, a headlight may be used as the light that irradiates the road surface. Moreover, when using a headlight, a headlight may be comprised by several LED and the road surface may be irradiated using some LED.

  In the above-described embodiment, the auxiliary light 10 irradiates the front of the vehicle. However, the light receiving device may be disposed at a position where the lower side of the vehicle is irradiated and the specular reflected light on the water surface can be received. With this configuration, since the specular reflection light of the light can be obtained by the light receiving device, the wet state of the road surface can be detected using the light having a strong specular reflection light. In the case of specularly reflected light on the water surface, the S-polarized component is larger than the P-polarized component, so that the criterion for the degree of polarization is less than 1 as opposed to the above-described embodiment. If it is, it will be determined as a wet state.

  In the above-described embodiment, the example in which the auxiliary light control unit 12 determines the period for switching the intensity of the auxiliary light 10 based on the traveling speed of the vehicle has been described. The period may be determined by another method. For example, the period of ambient light such as street light may be obtained, and the irradiation intensity may be switched at a period shorter than the period of ambient light. At this time, it is preferable to switch the irradiation intensity at a period of 1/2 or less of the period of the ambient light.

  In the above-described embodiment, the imaging range by the light receiving device may be limited to a part in front of the vehicle. Thereby, the influence of the auxiliary light 10 of an oncoming vehicle can be reduced.

  Moreover, you may use the light which emits near-infrared light as a light which irradiates a road surface. By using a light different from the auxiliary light 10, the influence of the auxiliary light 10 of the oncoming vehicle can be reduced.

  In the above-described embodiment, the road surface state detection device 1 and the road surface state detection method using the device have been described, but a program for realizing the device is also included in the scope of the present invention. The program of the present invention is, for example, a program that executes steps executed by the calculation processing unit 18 described in the above embodiment.

  By appropriately detecting the road surface state using the road surface state detection devices 1 and 2 of the present embodiment, the present invention can be applied to the following applications.

  In the current headlamp control system (AFS), when a car curves, control is performed so that the headlamp is directed in the direction of the curve. At this time, if the road surface is wet, there is a problem that the driver of the host vehicle or the oncoming vehicle becomes dazzled by the reflection of light from the headlamp. By detecting whether the road surface state is a wet state or a dry state by the road surface state detection device 1 in advance, it is possible to control the headlamps so that neither the driver of the own vehicle nor the driver of the oncoming vehicle is dazzled according to the road surface state. Become.

  Further, when the road surface is wet, the friction between the tire and the road surface becomes small and slippery. However, by determining the road surface state, it is possible to perform vehicle control in accordance with the road surface state.

  It is also possible to estimate whether the road surface is frozen by combining external temperature information and the like.

  As described above, according to the present invention, the influence of ambient light is reduced, and the road surface state can be appropriately determined using the P-polarized component and the S-polarized component included in the reflected light from the road surface. In addition, it is useful as a road surface condition detection device mounted on a vehicle or the like.

It is a figure which shows the structure of the road surface state detection apparatus of 1st Embodiment. It is a figure for demonstrating P polarized light and S polarized light. (A) It is a figure for demonstrating the P polarization component and S polarization component when a road surface is a dry state. (B) It is a figure for demonstrating the P polarization component and S polarization component when a road surface is a wet state. It is a flowchart which shows operation | movement of the road surface state detection apparatus of 1st Embodiment. (A) It is a figure which shows the example in which ambient light from the front injects into a light receiving device. (B) It is a figure which shows the example which the environmental light from the road surface near enters into a light-receiving device. It is a figure which shows the structure of the road surface state detection apparatus of 2nd Embodiment. It is a figure which shows the structure of the road surface state detection apparatus of 3rd Embodiment.

Explanation of symbols

1-3 Road surface state detection apparatus 10 Auxiliary light 12 Auxiliary light control unit 14 P-polarized light receiving device 16 S-polarized light receiving device 18 Calculation processing unit 20 Ambient light component removing unit 22 Polarization degree calculating unit 24 Road surface state determining unit 26 Speed sensor

Claims (5)

A light capable of changing the irradiation intensity in at least two stages;
A light receiving device that acquires a P-polarized component and an S-polarized component of light reflected from the road surface;
A difference acquisition unit for obtaining a difference between the P-polarized component and the S-polarized component acquired when the light irradiation intensity is high, and the P-polarized component and the S-polarized component acquired when the light irradiation intensity is weak;
A road surface state determination unit that determines a road surface state based on the difference between the P polarization components and the difference between the S polarization components;
A road surface condition detecting device. The light illuminates the road surface in front of the vehicle,
The road surface state determination unit determines that the road surface is wet when the difference between the P polarization components is substantially larger than the difference between the S polarization components, and the difference between the P polarization components and the difference between the S polarization components is substantially equal. The road surface state detection device according to claim 1, wherein the road surface state is determined to be dry when they are equal.   The road surface state detection device according to claim 1, further comprising a light control unit that changes an irradiation intensity of the light at a cycle determined based on a traveling speed of the vehicle. Changing the illumination intensity of the light that illuminates the road surface in at least two stages;
Obtaining a P-polarized component and an S-polarized component of reflected light from the road surface, respectively, when the illumination intensity of the light is strong and weak;
Obtaining a difference between a P-polarized component and an S-polarized component acquired when the light irradiation intensity is high, and a P-polarized component and an S-polarized component acquired when the light irradiation intensity is weak;
Determining a road surface state based on the difference between the P-polarized component and the difference between the S-polarized components;
A road surface state detection method comprising: A program for detecting a road surface state, which can obtain a light capable of changing an irradiation intensity in at least two stages, and a P-polarized component and an S-polarized component of reflected light from the road surface illuminated by the light. A computer equipped with a light receiving device
Changing the illumination intensity of the light that illuminates the road surface in at least two stages;
Obtaining a P-polarized component and an S-polarized component of reflected light from the road surface, respectively, when the illumination intensity of the light is strong and weak;
Obtaining a difference between a P-polarized component and an S-polarized component acquired when the light irradiation intensity is high, and a P-polarized component and an S-polarized component acquired when the light irradiation intensity is weak;
Determining a road surface state based on the difference between the P-polarized component and the difference between the S-polarized components;
A program that executes

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