JPH06109865A - Method and apparatus for detecting wet state of road surface - Google Patents

Abstract

PURPOSE:To make it possible to detect the freezing of a road surface and to estimate the freezing of the road surface by excellently detecting the dry state and the wet state of the road surface by the measurement of the reflected light from the road surface, and combining the detection and, e.g. the measurement of outside air temperature. CONSTITUTION:A beam splitter B splits road-surface reflected light R into two directions. A polarizing plate F1 transmits a polarized light component (s), which is orthogonal to the incident plane of one split road-surface reflected light R. A polarizing plate F2 transmits a polarized light component (p), which is in parallel with the incident plane of the other split rord-surface reflected light R. Two photoelectric converter elements N1 and N2 receive the respective polarized light components (s) and (p), which are transmitted through the polarizing plates. A measuring means compares and measures the electric changes of the photoelectric converter elements. These parts are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road surface wetness detecting method and its device, which are expected to be applied to the field of snow and ice disaster prevention.

At present, the freezing of the road surface in cold regions is one of the causes of traffic accidents, and can even become a serious trigger for personal injury.

Since the occurrence of freezing on the road surface requires the presence of water on the road surface, it is possible to detect the road surface freezing by detecting the water content on the road surface and measuring the temperature.

[0004]

2. Description of the Related Art Conventionally, as a method for detecting moisture on the road surface, a method has been proposed in which the electric resistance or the permittivity of the road surface, which changes with the amount of water, is measured.

[0005]

However, in the case of the above proposed structure, since each of the detection electrodes must be installed on the road surface, damage due to a passing vehicle is unavoidable, and in the case of detection by the detection electrodes, local detection is required. Since it will be detected automatically,
For example, if the detection portion of the detection electrode is dry and the surroundings are wet, it is determined that the detection electrode is dry, and there is a problem that a detection error is likely to occur.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve such an inconvenience, and the road surface wetness detecting method according to the first aspect of the present invention uses a beam splitter to convert road surface reflected light into two directions. A polarized component s perpendicular to the incident surface is detected from one of the separated road surface reflected lights by using two polarizing plates, and a polarized component parallel to the incident surface from the other separated road surface reflected light. p is detected, and both polarization components s
It is characterized in that the wet state of the road surface is detected by comparing and measuring the intensity difference of p.

The road surface wetness state detecting device according to the second aspect of the present invention includes at least a beam splitter for splitting the road surface reflected light into two directions and a polarization component s perpendicular to the incident surface of one of the split road surface reflected lights. A polarizing plate that transmits the polarized light component, a polarizing plate that transmits the polarized light component p parallel to the incident surface of the other spectrally reflected light on the road surface, and each polarized light component s that transmits the respective polarizing plate.
It comprises two photoelectric conversion elements for receiving p and a measuring means for comparatively measuring the electrical change of each photoelectric conversion element.

[0008]

The reflected light on the road surface is split into two directions by the beam splitter, the polarization component s perpendicular to the incident surface of the one reflected light on the road surface passes through the polarizing plate, and the other reflected light on the other road surface is incident. The polarization component p parallel to the plane is transmitted through another polarizing plate, and each polarization component sp transmitted through each polarizing plate is received by the photoelectric conversion element, and the measuring means compares the electrical changes of the photoelectric conversion elements. The intensity difference between both polarization components s and p is measured and detected.

In the case of a smooth reflecting surface, the reflectance R _s of the polarized component s perpendicular to the incident surface and the reflectance R _p of the polarized component p parallel to the incident surface are as follows at incident angles other than 0 ° and 90 °. R _s > R
_{At p} , R _s −R _p has a maximum value above the Brewster angle.
The maximum value of R _s -R _{p on} the road surface of concrete or asphalt is smaller than the value on the smooth surface because it diffusely reflects when the surface is dry, and the unevenness of the surface smoothes when wet with water. Increase. That is, when the road surface is dry, the voltage from the photoelectric conversion element that outputs a voltage according to the value of R _s · R _p is approximately the same, but when the road surface gets wet, the reflectance R of the polarization component p is R. _{Since p} is attenuated and the voltage from the photoelectric conversion element that detects this p-polarized light decreases, the reflectance R _s of the polarization component s increases and the voltage from the photoelectric conversion element that detects this s-polarized light increases. It is intended to detect the wet state of the road surface by the intensity difference between the two polarization components s and p.

[0010]

1 to 3 show an embodiment of the apparatus of the present invention, in which B is a beam splitter, in this case 5 mm × 5 mm × 5 mm in a state where two right-angle prisms are bonded together.
Is formed into a cubic shape, and a plano-convex lens G is arranged in front of the light entrance surface of the beam splitter B.
One of the entrance surface to the exit surface is stuck a film-like polarizing plate F ₁ that transmits vertically polarized light components s a (plane perpendicular to the road surface), the main shaft M ₁ and the polarizer F in this case the polarizer F ₁ of ₂ spindles M ₂
Are orthogonal to each other, and a film-like polarizing plate F ₂ that transmits the polarization component p parallel to the incident surface is attached to the other light emitting surface of the beam splitter B.

N ₁ and N ₂ are photoelectric conversion elements. In this case, a photodiode is used, and both polarization components s and p transmitted through the above-mentioned polarizing plates F ₁ and F ₂ are received and the amount of received light is changed. Output the corresponding voltage.

H is a measuring means, which is a photoelectric conversion element N ₁
An amplifier A for amplifying the output voltage from N ₂ , a synchroscope K, and a recorder B are provided, and are configured to compare and measure the voltage changes from the photoelectric conversion elements N ₁ and N ₂ .

Since this embodiment has the above construction, the road surface reflected light R reflects on the road surface U, then enters the beam splitter B through the plano-convex lens G, and is split into two directions by the beam splitter B and split. A polarization component s perpendicular to the incident surface of the one road surface reflected light R is transmitted through the polarizing plate F ₁ and is a polarization component p parallel to the incident surface of the other road surface reflected light R that is spectrally separated.
Is transmitted through the other polarizing plate F _2, the polarizers F ₁ · F ₂ each polarization component s · p transmitted through it is received each photoelectric conversion element N ₁ · N _2, the photoelectric conversion element N ₁ · N ₂ The voltages E ₁ and E ₂ corresponding to the intensity of the polarization component are output, and the respective measuring voltages are compared and measured by the measuring means H.

At this time, when the road surface is wet, the road surface becomes smooth due to the water surface, and when the road surface U is dry, each output voltage E ₁
Since E ₂ has almost the same voltage, E = E ₁ −E ₂ = 0, but when the road surface gets wet, the reflectance R _p of the polarization component _p is attenuated and the photoelectric conversion element for detecting this p-polarized light is obtained. The voltage R from decreases and the reflectance R _s of the polarization component s increases and this s
The voltage from the photoelectric conversion element that detects polarized light rises, and E =
A voltage difference between E _{1 and} E ₂ is generated, and the measuring means H compares and measures the electrical change of the photoelectric conversion elements N ₁ and N ₂ to measure both polarization components s and
The strength difference of p is detected, and the wet state of the road surface is detected by this comparative measurement.

The present invention is not limited to the above embodiment, and in particular, the circuit structure of the measuring means H is appropriately modified and designed.

In the above embodiment, the road surface reflected light R of natural light is used. However, artificial light such as a laser diode, a halogen lamp, and a discharge lamp has a similar tendency to that of natural light, so that modulated light is used. It is also possible to measure independently of natural light.

For example, when a metal halide lamp or the like is used as the light source, in order to remove the influence of ambient light,
It is desirable to use a phase detector so as to synchronize with the blinking of the light source and measure changes in only the voltage component from the metal halide lamp of the voltages from the photoelectric conversion elements N ₁ and N ₂ . .

As the photoelectric conversion element, a photodiode which is the above photovoltaic element is used.
The same applies when a photoconductive element such as an s cell is used.

[0019]

As described above, according to the road surface wetness detecting method and apparatus of the present invention, the dryness and wetness of the road surface can be satisfactorily detected by measuring the road surface reflected light. It is possible to detect the freezing of the road surface and to predict the freezing of the road surface in combination with the above, and in particular the wet condition of the road surface can be detected from above the road surface without contact, so there is no damage such as damage due to passing vehicles. In addition, since it is possible to detect a wide range of wet conditions on the road surface, it is possible to prevent detection errors, and since it does not react with a small amount of wet condition, for example, it reacts when there is a high probability of freezing, thus improving reliability of freezing prediction You can

As described above, the intended purpose can be sufficiently achieved.

[Brief description of drawings]

FIG. 1 is a conceptual explanatory diagram of an optical system according to an embodiment of the present invention.

FIG. 2 is a partial plan view of an essential part of the embodiment of the present invention.

FIG. 3 is a configuration system diagram of an embodiment of the present invention.

[Explanation of symbols]

B beam splitter F ₁ polarizing plate F ₂ polarizing plate N ₁ photoelectric conversion element N ₂ photoelectric conversion element H measuring means R road surface reflected light

Claims (2)

[Claims] 1. A road splitter reflected light is split into two directions by a beam splitter, and two polarizing plates are used to detect a polarized component s perpendicular to the incident surface from one of the split road reflected lights and to split it. A wet condition of the road surface is detected by detecting a polarization component p parallel to the incident surface from the other reflected light on the road surface and comparing and measuring the intensity difference between the polarization components s and p. State detection method. 2. A beam splitter for splitting the road surface reflected light into two directions, a polarizing plate for transmitting a polarization component s perpendicular to the incident surface of one of the split road surface reflected lights, and the other spectrally separated light. A polarizing plate that transmits a polarization component p parallel to the incident surface of the road surface reflected light, two photoelectric conversion elements that receive each polarization component s · p that has passed through each polarization plate, and a photoelectric conversion element of each photoelectric conversion element. A road surface wetness state detection device comprising a measuring means for comparatively measuring electric changes.