JP2005043240A - Sensor for detecting road surface conditions - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a sensor for detecting a road surface conditions, which can precisely distinguish the road surface conditions. <P>SOLUTION: The sensor for detecting the road surface conditions is composed of a light source 1 having at least an infrared wavelength range; a first analyzer 2 arranged on an optical path through which incident light emitted from the light source 1 is projected onto the road surface 4 and transmitting only polarized light with a first orientation 15 in the incident light; a second analyzer 6 arranged on an optical path of reflection light 5 formed from the incident light 3 which is reflected by either the road surface or either a water film and an ice layer on the road surface, or by both of them, after passing through the first analyzer 2 and which transmits only polarized light with a second orientation 16 perpendicular to the first orientation 15; light-detecting means 10, 11 which individually detect light intensities of two or more specific wavelength values in the polarized light with the second orientation 16; and a signal processing means 14 which processes output signals which are the output from the light-detecting means 10, 11 and based on a plurality of specific wavelength values. The road surface conditions are distinguished, on the basis of relative light intensities among the plurality of specific wavelength values in the polarized light with the second orientation 16. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a road surface state detection sensor that detects a state of wetness or freezing of a road surface.

  In the conventional road surface state detection sensor, for example, as shown in FIG. 2 of Patent Document 1, the projection light in the infrared region emitted from the light source is irradiated onto the road surface, and two specific wavelengths in the reflected light reflected by the road surface are emitted. The light intensity was compared, and the road surface condition was identified by the ratio, that is, the relative light intensity. This is based on the principle that the absorption spectrum ratio of water changes depending on whether the absorption spectrum of water is in a liquid state (water) or a solid state (ice).

  Further, in another conventional road surface state detection sensor, for example, as shown in FIG. 1 of Patent Document 2, the projection light emitted from the light source is once transmitted through the polarizing plate to make only specific polarized light, and then on the road surface. Irradiated and measured the light intensity of the reflected light from the road surface to identify the road surface condition. This is because it utilizes the property that specific polarized light is reflected with a higher light intensity than the road surface state, and the road surface state becomes easier to detect.

Japanese Patent Laid-Open No. 10-73538

JP-A-5-264441

  In the conventional road surface condition detection sensor described above, when the road surface is wet or frozen, a water (or ice) film is formed on the road surface. When light is projected onto the road surface in this state, the water film is transmitted and reflected by the road surface. Not only reflected light but also reflected light reflected on the surface of the water film was generated at the same time. Therefore, on the side of the light receiver, as a result, the reflected light including both is received. Since the light reflected from the surface of the water film is not affected by the absorption of water (or ice), it is a light component that does not contain any signal component from the viewpoint of road surface condition detection. As a result, since the amount of change in the output signal with respect to the change in the road surface state is reduced, there is a problem that the sensitivity to the road surface state detection is lowered.

  The present invention has been made to solve the above-described problems, and can detect a change in an output signal with a higher sensitivity to a change in road surface state, and can identify a road surface state with high accuracy. An object is to obtain a road surface state detection sensor.

  The road surface state detection sensor according to the present invention includes a light source having a wavelength of at least an infrared region, and a polarized light in a first direction in the projection light that is disposed on an optical path from the light emitted from the light source to the road surface. A first analyzer that transmits only light, and reflected light generated by reflecting the projection light after passing through the first analyzer by either one or both of the road surface or a film made of water or ice on the road surface. A second analyzer that is disposed on the optical path and transmits only polarized light in the second direction orthogonal to the first direction, and individually detects the light intensity of at least two or more specific wavelengths in the polarized light in the second direction. Light detection means and signal processing means for processing output signals based on the plurality of specific wavelengths from the light detection means, and based on relative light intensity between the plurality of specific wavelengths in the polarized light in the second direction. Know road conditions It decided to.

  Since the road surface state detection sensor according to the present invention is configured as described above, it is easy to remove the specularly reflected light component from the water film generated on the road surface that is unnecessary for the road surface state identification, and the information necessary for the identification. Since reflected light transmitted through a certain water film or ice layer can be detected with a high signal intensity ratio, a road surface state detection sensor capable of highly accurate road surface state identification can be obtained.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a road surface state detection sensor according to Embodiment 1 of the present invention. In FIG. 1, 1 is a light source including at least an infrared region (wavelength: 1.0 to 2.0 μm), 2 is arranged on an optical path from the light source 1 to the road surface, and is a specific polarized light by projection light from the light source 1. The first polarizer (first analyzer) that selects only polarized light (S-polarized light) in the direction (first direction), 3 is the projection light that passes through the first polarizer 2 and reaches the road surface, 4 is the road surface, 5 Is the reflected light from the road surface, 6 is the second polarizer (second analyzer) that selects only the polarized light (P-polarized light) in the second direction orthogonal to the first direction of the reflected light 5, and 7 is the first A dichroic mirror that branches the polarized light transmitted through the two polarizers 6 into wavelength regions including _two specific wavelengths λ ₁ and λ ₂ , and 8 is a narrower first specific wavelength of one reflected light branched by the dichroic mirror 7. The first wavelength filter to be selected as λ ₁ , 9 is the other one separated by the dichroic mirror 7 The second wavelength filters 10 and 11 for selecting the reflected light to the narrower second specific wavelength λ ₂ receive the light transmitted through the first and second wavelength filters 8 and 9, respectively, and convert them into electrical signals. Two photodetectors 12 and 13 are first and second amplifiers for amplifying the output signals of the first and second photodetectors 10 and 11, respectively, and 14 is a comparison of the output signals of the first and second amplifiers 12 and 13. Each comparator is shown.

  Also, in FIGS. 1 to 3, reference numeral 15 denotes projection light 3 transmitted through the first analyzer 2, which is perpendicular to the incident surface, that is, a polarization direction having an oscillation axis in the first direction (S polarization direction), 5a Reflected light from the road surface when the road surface 4 is in a dry state, 17a and 17b are polarization directions of the reflected light from the road surface 4, 17a is the first polarization direction identical to the polarization direction 15, and 17b is the polarization direction 15 Represents the polarization direction in the vertical direction, that is, the second direction. Here, the incident surface is a plane including the normal direction of the incident light and the incident surface, and corresponds to a surface parallel to the paper surface in FIGS.

Further, in FIG. 3, 4a is a water film (or ice layer) formed when the road surface is wet (or frozen), 5b is reflected light reflected from the surface of the water film (or ice layer) 4a, and 5c is water. Reflected light that is transmitted through the film (or ice layer) 4a and reflected by the road surface 4, 18 is the polarization direction of the reflected light 5b from the surface of the water film (or ice layer) 4a, and 19a and 19b are water films (or ice). Layer) 4a, and the two orthogonal polarization directions of the reflected light 5c reflected by the road surface 4 are shown. FIG. 4 is a diagram showing the relationship between the wavelength of the reflected light and the light intensity of the reflected light when the road surface condition is used as a parameter. 4, 20 is the wavelength axis, the 21 ratio of the second specific wavelength lambda ₂ of the light intensity I _.lambda.2 to light intensity I _.lambda.1 of the first specific wavelength lambda ₁ (relative light intensity), 22 the water film on the road surface The reflected light spectrum from the transmitted road surface, 23 is the reflected light spectrum from the road surface that has passed through the ice layer on the road surface, and 24 is the reflected light spectrum when the road surface is dried. Here, the reflected light spectrum of each of 22 and 23 is the road surface The spectrum is normalized at the time of drying. Reference numeral 25 denotes a plurality of specific wavelengths λ ₁ and λ _{2 serving as a} reference in observing the relative change in the reflected light spectrum, and 25a and b denote the first specific wavelength λ ₁ and the second specific wavelength λ ₂ to be measured. Each is shown. The specific wavelength may be 2 or more.

  Next, the operation of the road surface state detection sensor according to the first embodiment will be described. Light having a wavelength in the infrared region of at least 1.0 to 2.0 μm emitted from the light source 1 is polarized in the first direction by the action of the first polarizer 2, that is, in the direction perpendicular to the incident surface. After only certain polarized light (S-polarized light) is selected, the road surface 4 is irradiated as projection light 3. When the road surface 4 is in a dry state, the projection light 3 is reflected by the road surface 4, and the reflected light 5 a is the first direction that the projection light 3 originally has, that is, polarized light (S-polarized light) in the polarization direction 17 a, and the projection light 3. It becomes a state where polarized light (P-polarized light) in the orthogonal P direction, that is, the polarization direction 17b is mixed.

  On the other hand, when the road surface 4 is in a wet or frozen state, a water film (or ice layer) 4a is formed on the road surface 4, so that a part of the projection light 3 is a water film (or ice layer) 4a. At the same time, the remaining part of the light is transmitted through the surface of the water film (or ice layer) 4a and reflected by the road surface 4. The reflected light 5 b reflected on the surface of the water film (or ice layer) 4 a is only polarized light (S-polarized light) having a polarization direction 18 that is the same first direction as the polarization direction 15 of the projection light 3. In the case of an ice layer, there are some orthogonal components.

  In addition, the reflected light 5c transmitted through the water film (or ice layer) 4a and reflected by the road surface 4 is not only polarized light (S-polarized light) in the polarization direction 19a which is the same first direction as the projection light 3, It also has polarized light (P-polarized light) in the polarization direction 19b in the second direction orthogonal to the projection light 3. Thus, the second analyzer in a state where the reflected light 5b reflected on the surface of the water film (or ice layer) 4a and the reflected light 5c transmitted through the water film (or ice layer) 4a and reflected on the road surface 4 are mixed. 6, but only the polarized light (P-polarized light) in the second polarization direction 19 b orthogonal to the projection light 3 is selected by the action of the second analyzer 6, and then enters the dichroic mirror 7.

  That is, when the road surface 4 is in a dry state, only the polarized light (P-polarized light) in the polarization direction 17b that is the second direction that is a part of the reflected light 5a from the road surface 4 is in a wet (or frozen) state of the road surface. In this case, a part of the reflected light that is incident on the surface of the water film (or ice layer) 4a formed on the road surface, travels through the water film (or ice layer) and is reflected by the road surface 4, that is, the second direction. Only polarized light (P-polarized light) in the polarization direction 19b is selected.

The wavelength regions of the polarized light (P-polarized light) in the polarization directions 17b and 19b, which are the second directions selected by the second analyzer 6, are separated by the action of the dichroic mirror 7, and the first and second wavelength filters 8, 9 are separated. After the wavelength components of the first specific wavelength λ ₁ (25a) and the second specific wavelength λ ₂ (25b) are selected by, respectively, they are received by the first and second photodetectors 10 and 11 for each wavelength individually. The Output signals from the first and second photodetectors 10 and 11 are amplified by the first and second amplifiers 12 and 13, respectively, and then input to the comparator 14. The comparator 14 receives the received light intensity I _λ1 , I _λ2 (I _λ1 : received light intensity at the first specific wavelength λ ₁ , I _{1) at} the first and second specific wavelengths λ ₁ , λ ₂ based on the input output signal from each amplifier. _.lambda.2: identifying second comparing the received light intensity) at a particular wavelength lambda _2, the drying of the road 4 based on the result, the wet, the road surface condition of the freezing and the like.

As shown in FIG. 4, the received light intensity ratio I _λ2 / I _λ1 of the first and second specific wavelengths λ ₁ and λ ₂ strongly depends on the state of the road surface 4. When the light intensity of each road surface state is normalized as _{1 at} the first specific wavelength λ ₁ and further the light intensity in the dry state is normalized to 1 in all wavelength regions, the reflection at the road surface dry state at the second specific wavelength λ ₂ In the reflected light spectrum 22 in the road surface state in which the light spectrum 24 has the maximum light intensity and the water film is formed, I _λ2 / I _λ1 is about ½, and in the reflected light spectrum 23 in the road surface state in which the ice layer is formed, It becomes even smaller.

In short, assuming that I _λ2 / I _λ1 is an identification index, the value of the received light intensity ratio I _λ2 / I _{λ1 is} as follows: a road surface dry ratio is a, a wet ratio is b, and a freezing ratio is c. The relationship is a>b> c. Identification of the road surface state can be realized with higher accuracy than before by the difference in the amount of change in the received light intensity for each specific wavelength.

FIG. 5 shows the experimental results of the road surface state detection sensor of the present embodiment. The projection light 3 is only S-polarized light selected by the first analyzer 2, and the reflected light is selected only by P-polarized light by the second analyzer 6. The light intensity on the vertical axis in the graph is normalized with the light intensity at the time of drying as 1. Water was sprayed on the road surface, and the reflected light spectrum of the reflected light at the time when a certain time had elapsed was measured, and actual measurement data corresponding to each road surface state was obtained. Using the elapsed time after spraying water as a parameter, the reflected light spectrum was measured after 130 seconds, 210 seconds and 510 seconds. Since the road surface freezes about 200 seconds after spraying water, the road surface is wet after 130 seconds, and the road surface is frozen after 210 seconds and 510 seconds. As can be seen from FIG. 5, the light intensity decreases in the order of a wet road surface (after 130 seconds) and a frozen road surface (after 210 and 510 seconds) with respect to a light intensity of 1 when the road surface is dried in a wavelength range of 1450 to 1500 nm. To do. That is, the result of being clearly separated into the light intensity corresponding to each road surface state was obtained. From the above experimental results, the first specific wavelength λ ₁ is preferably a region where each reflected light spectrum is as flat as possible, that is, a wavelength range of 1.1 μm to 1.3 μm, and the second specific wavelength λ ₂ is 1. It has been found that a wavelength range of 4 μm or more and 1.6 μm or less is suitable.

  FIG. 6 shows the result of a comparative experiment performed on the experiment of FIG. The projection light 3 is S-polarized light selected by the first analyzer 2, and the reflected light is selected only as S-polarized light in the same direction as the projection light unlike the above experiment. The light intensity on the vertical axis is normalized assuming that the light intensity during drying is 1. The reflected light spectrum was measured after a certain period of time after water was sprayed on the road surface, and actual measurement data corresponding to each road surface state was obtained. Using the elapsed time after water spray as a parameter, the reflected light spectrum after 140 seconds, 410 seconds and 1010 seconds was measured. After 140 seconds, the road surface is wet, and after 410 seconds and 1010 seconds, the road surface is frozen. As can be easily seen from FIG. 6, when the polarization direction of the projection light and the reflected light is the same direction, the difference in light intensity between the reflected light spectra corresponding to each road surface state is significantly larger than the experimental result of FIG. It became small. The effectiveness of the road surface condition detection sensor according to the present embodiment was verified also from the result of the comparative experiment.

  As described above, in the road surface state detection sensor of the present embodiment, the first analyzer on the projection light side is used in order to use the fact that the shape of the water absorption spectrum in the infrared region is different between liquid (water) and solid (ice). Since the detection optical system is configured to receive only the polarization component orthogonal to the projection light with respect to two specific wavelengths in the infrared wavelength region by orthogonalizing the polarization directions of the reflected light and the second analyzer on the reflected light side, the road surface state is identified. Because it is easy to remove the specularly reflected light component from the water film generated on the road surface that is unnecessary, and the reflected light transmitted through the water film or ice layer, which is information necessary for identification, can be detected with a high signal intensity ratio A road surface state detection sensor capable of highly accurate road surface state identification is obtained.

Embodiment 2. FIG.
FIG. 7 is a configuration diagram of a road surface state detection sensor according to Embodiment 2 of the present invention. The same reference numerals as those in FIGS. 1 to 3 denote the same or corresponding parts. In FIG. 7, reference numeral 30 denotes a polarization beam splitter (polarization branching unit) that separates reflected light according to the polarization direction, and transmits polarized light (S-polarized light) having a polarization direction 33 that is the same first direction as the projection light 3. Polarized light (P-polarized light) having a polarization direction 34 that is a second direction orthogonal to the projection light 3 is reflected. 31 is transmitted light (S-polarized light) transmitted through the polarizing beam splitter 30, 32 is reflected light (P-polarized light) having a polarization direction 34 that is the second direction reflected by the polarizing beam splitter 30, and 33 is the same as the projection light 3. , 34 is a polarization direction (second direction) orthogonal to the projection light 3, 35 is a third photodetector that receives the transmitted light 31 and converts it into an electrical signal, and 36 is a reflected light 32. , A half mirror 37, a fourth photodetector for receiving one light separated by the half mirror 36, and 38 and 39 amplifying output signals from the third and fourth photodetectors 35 and 37, respectively. The third and fourth amplifiers 40 and 40 are comparators that receive the output signals from the amplifiers 12, 13, 38, and 39, compare the intensities of the output signals, and identify road surface conditions.

  Next, the operation of the road surface state detection sensor according to the second embodiment will be described. Light having a wavelength in the infrared region of at least 1.0 to 2.0 μm generated from the light source 1 is only polarized light (S-polarized light) having a polarization direction 15 which is a first direction set in advance by the action of the first polarizer 2. And the road surface 4 is irradiated as the projection light 3. The reflected light 5 from the road surface 4 is separated by the polarization direction through the polarization beam splitter 30. Specifically, the polarized light (P-polarized light) in the polarization direction 34, which is the second direction orthogonal to the projection light 3, is reflected, while the polarized light (S) in the polarization direction 33, which is the same first direction as the projection light 3, is reflected. (Polarized light) is transmitted. The transmitted light 31 is received by the third photodetector 35, converted into an electrical signal, amplified by the third amplifier 38 and input to the comparator 40.

On the other hand, the reflected light 32 reflected by the polarization beam splitter 30 is further split into two by a half mirror 36. One light is received by a fourth photodetector 37 and converted into an electric signal, and then amplified by a fourth amplifier 39. And input to the comparator 40. The other light branched by the half mirror 36 is separated into each specific wavelength via the dichroic mirror 7, and the first and second wavelength filters 8 and 9 have the first specific wavelength λ ₁ and the second specific wavelength λ _{2 respectively} . After the specific wavelength components are selected, the first and second photodetectors 10 and 11 individually receive light for each specific wavelength. Output signals from the photodetectors 10 and 11 are amplified by the first and second amplifiers 12 and 13, respectively, and then input to the comparator 40. The comparator 40 discriminates road surface conditions such as dryness, wetness, and freezing of the road surface 4 based on the input signals from the amplifiers.

The output signals I _λ1 and I _λ2 of the first and second photodetectors 10 and 11 change according to the dry, wet, frozen state, etc. on the road surface as already described in the first embodiment. To do. Furthermore, the output signals from the third and fourth photodetectors 35 and 37 indicate the polarization characteristics of the reflected light 5 from the road surface 4. Of the reflected light 5, polarized light having the same polarization direction as the projection light 3 ( The output of the third photodetector 35 indicating the light intensity of the S-polarized light is Is, and the output of the fourth photodetector 37 indicating the light intensity of the polarized light (P-polarized light) in the polarization direction orthogonal to the projection light 3 is Ip. Then, the index value Is / (Is + Ip) obtained by standardizing Is with Is + Ip changes according to the surface state of the road surface 4. The output Is is the sum of the light intensities of the polarized light (S-polarized light) in the first polarization direction 19a as well as the polarized light (S-polarized light) in the first polarization direction 18 in FIG. The output Ip corresponds to the light intensity of the polarized light (P-polarized light) in the polarization direction 19b which is the second direction.

When Is and Ip during road drying advance normalized so as to have the same value, a ₁ the ratio of the dry the index _value, b ₁ and when _wet, c ₁ and upon _freezing, d ₁ the time snow Then, the relationship of b ₁ > c ₁ > a ₁ or b ₁ > d ₁ > a ₁ is established. When the change in the polarization characteristics (Is / Is + Ip) and the change in the received light intensity ratio I _λ2 / I _λ1 between two specific wavelengths are used in combination, the former mainly identifies the road surface state, and the latter Mainly, the film type on the road surface can be identified with higher accuracy. Therefore, it is possible to identify with higher accuracy by using the above two identification indexes together to identify the road surface state.

  As described above, in the road surface state detection sensor according to the present embodiment, the polarization direction of the projection light is specified, and when the reflected light is received, the polarization direction is separated and further received for each specific wavelength, so that the road surface is wet ( (In the case of freezing or snow), the reflected light from the road surface and the light that enters from the water surface and travels through the water film and reflects from the road surface are separated and detected. Since the road surface state is identified using parameters such as the light intensity ratio, a road surface state detection sensor capable of detecting the road surface state with higher accuracy can be obtained.

Embodiment 3 FIG.
FIG. 8 is a block diagram of a road surface state detection sensor according to Embodiment 3 of the present invention. The same reference numerals as those in FIGS. 1 to 3 and FIG. 7 denote the same or corresponding parts. In FIG. 8, 41 is the scattered light generated from the road surface 4 when the projection light 3 is irradiated onto the road surface 4, 43 is the fifth photodetector for receiving the scattered light 41 from the road surface 4 and converting it into an electrical signal, 44 The fifth amplifier 45 for amplifying the output signal from the fifth photodetector 43 receives the output signals from the amplifiers 12, 13, 38, 39, and 44, and identifies the road surface state by comparing the signal values. A comparator is shown.

  In the road surface state detection sensor according to the third embodiment, in addition to the device configuration shown in the second embodiment, a fifth photodetector 43 that receives scattered light from the road surface 4 and a fifth amplifier 44 that amplifies the output signal are provided. It is characterized in that it is newly provided.

  Next, the operation of the road surface state detection sensor according to the third embodiment will be described. The comparison of the light intensity of two specific wavelengths and the detection of the road surface state using the change in polarization characteristics are as described in the second embodiment.

The scattered light 41 generated from the road surface 4 is received by the fifth photodetector 43, converted into an electrical signal, amplified by the fifth amplifier 44, and then input to the comparator 45. The light intensity of the scattered light 41 strongly depends on the road surface condition. For example, when the road surface 4 is wet, the surface is smoother than when it is dry, so that the light intensity of the scattered light 41 is relatively small. When comparing the light intensity for each road surface state, when each light intensity is a ₂ at the time of drying, b ₂ at the time of wet, c ₂ at the time of freezing, and d ₂ at the time of snow accumulation, d ₂ > a ₂ > c between each light intensity. the relation represented by _2> b ₂ is satisfied, based on these relations, it can be identified with higher precision the road surface condition.

  As described above, the comparison of the received light intensity between the two wavelengths in the reflected light in which only the polarized light having the polarization direction orthogonal to the projected light described in the second embodiment is selected, and the same polarization with respect to the projected light in the reflected light intensity from the road surface. In addition to the comparison of the relative intensity ratio between the polarized light in the direction and the polarized light in the orthogonal direction, a third parameter of the received light intensity change of the scattered light measured by the additional apparatus configuration shown in the present embodiment is By identifying the road surface state using a total of three independent parameters, it is possible to further improve the road surface state identification accuracy.

Embodiment 4 FIG.
FIG. 9 is a configuration diagram of a road surface state detection sensor according to Embodiment 4 of the present invention. Those given the same reference numerals as in FIG. 1 are the same or equivalent. In FIG. 9, 50 is the first light source having a single specific wavelength in the infrared region (1.0 to 2.0 μm), 51 is the first light source in the infrared region (1.0 to 2.0 μm) wavelength region. A single-wavelength second light source having a specific wavelength other than one light source 50, 52 is a first projection light from the first light source 50, 53 is a second projection light from the second light source 51, and 54 is a first and second light source. A half mirror for combining the projection lights 52 and 53 is shown. Here, as the single wavelength light source, a light-emitting diode (LED) or a semiconductor laser (LD) having a simple device configuration and extremely light weight is preferable.

  Next, the operation of the road surface state detection sensor according to the fourth embodiment will be described. The operation itself is substantially the same as that of the road surface state detection sensor of the first embodiment.

The first projection light 52 projected from the first light source 50 having a single wavelength whose wavelength is the first specific wavelength λ ₁ in the infrared region (1.0 to 2.0 μm), and the infrared region (1 The second projection light 53 projected from the second light source 51 having a single wavelength having a second specific wavelength λ ₂ that is different from the first specific wavelength λ ₁ but by a half mirror 54. After multiplexing, the first polarizer 2 is transmitted, and only the polarized light in the first direction (S-polarized light) is selected and applied to the road surface 4. The reflected light selected by the second analyzer 6 out of the reflected light 5 from the road surface 4 is further separated into specific wavelength regions by the action of the dichroic mirror 7, and the first and second wavelength filters 8 and 9 respectively. After being selected as the wavelength component of the first specific wavelength λ ₁ (25a) and the second specific wavelength λ ₂ (25b), the first and second photodetectors 10 and 11 individually receive the light. Output signals from the first and second photodetectors 10 and 11 are amplified by the first and second amplifiers 12 and 13, respectively, and input to the comparator 14. The comparator 14 compares the received light intensities of specific two wavelengths λ ₁ and λ ₂ based on the output signals from the input amplifiers, and based on the result, determines the road surface condition such as dry, wet, and frozen of the road surface 4. Identify. Since the details of the identification method are the same as those in the first embodiment, the description is omitted.

  As described above, the present embodiment is characterized in that a single wavelength light source such as an LED or an LD is applied as a plurality of specific wavelength light sources. In other words, by using a semiconductor light source that is small and light by itself, such as an LED or LD, as a light source for road surface irradiation, a highly accurate road surface state detection sensor that is reduced in size and weight as an entire device can be easily obtained. can get.

1 is a configuration diagram of a road surface state detection sensor according to a first embodiment. FIG. 6 is a diagram for explaining the operation of the road surface state detection sensor according to the first embodiment. FIG. 6 is a diagram for explaining the operation of the road surface state detection sensor according to the first embodiment. It is a figure which shows the wavelength dependence of the reflected light intensity ratio of a road surface. It is a figure which shows the wavelength dependence of the reflected light intensity of the road surface measured by the road surface state detection sensor by this Embodiment 1. FIG. It is a figure showing the result of the comparison experiment with respect to the experiment shown in FIG. FIG. 6 is a configuration diagram of a road surface state detection sensor according to a second embodiment. FIG. 6 is a configuration diagram of a road surface state detection sensor according to a third embodiment. FIG. 10 is a configuration diagram of a road surface state detection sensor according to a fourth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source, 2 Polarizer (analyzer), 3 Projection light, 4 Road surface, 4a Water film or ice layer, 5a Reflected light, 5b Reflected light reflected from water film (or ice layer) surface, 5c Water film (or ice) Reflected light generated on the road surface, 6 analyzer, 7 dichroic mirror, 8 first wavelength filter, 9 second wavelength filter, 10 first photodetector, 11 second photodetector, 12 first amplifier 13 Second amplifier, 14 Comparator, 15 Polarization direction (first direction) having a vibration axis perpendicular to the incident surface in the polarization direction of the projected light, 16 Second direction, 17a, b Polarization of road surface reflected light Direction, 18 Polarization direction of water film (or ice layer) surface reflected light, 19a, 19b Polarization direction of light transmitted through water film (or ice layer) and generated on road surface, 20 wavelength axis, 21 light intensity ratio, 22 road surface Permeates the water film above The reflected light spectrum from the road surface, 23 the reflected light spectrum from the road surface that has passed through the ice layer on the road surface, 24 the reflected light spectrum when the road surface is dried, 25a a specific wavelength that is a reference for observing the relative change in the transmitted spectrum, 25b Specific wavelength to be measured, 30 Polarization beam splitter (polarization branching means), 31 Transmitted light transmitted through polarization beam splitter, 32 Light reflected by polarization beam splitter, 33 Same polarization direction as projection light (first direction) ), 34 Polarization direction orthogonal to the projected light (second direction), 35 Third photodetector, 36 Half mirror, 37 Fourth photodetector, 38 Third amplifier, 39 Fourth amplifier, 40 Comparator, 41 Scattering Light, 43 fifth light detector, 44 fifth amplifier, 45 comparator, 50 first light source, 51 second light source, 52 first projection light, 53 2 projected light, 54 a half mirror.

Claims (6)

A light source comprising at least wavelengths in the infrared region;
A first analyzer that is disposed on an optical path from the light source to the road surface and transmits only polarized light in a first direction in the projection light;
The projected light after passing through the first analyzer is arranged on the optical path of the reflected light generated by reflecting the road surface or the water or ice film on the road surface, or orthogonal to the first direction. A second analyzer that transmits only polarized light in the second direction,
Light detecting means for individually detecting the light intensity of at least two or more specific wavelengths in the polarized light in the second direction;
Signal processing means for processing an output signal based on the plurality of specific wavelengths from the light detection means, and
A road surface state detection sensor that identifies a road surface state based on relative light intensity between a plurality of specific wavelengths in polarized light in the second direction. A light source comprising at least wavelengths in the infrared region;
A first analyzer that is disposed on an optical path from the light source to the road surface and transmits only polarized light in a first direction in the projection light;
The projection light after passing through the first analyzer is arranged on the optical path of the reflected light generated by reflecting the road surface or one or both of the film made of water or ice on the road surface, and the reflected light is Polarization branching means for branching into polarized light in one direction and polarized light in a second direction orthogonal to the first direction;
A light detecting means for individually detecting the light intensity of the polarized light in the first direction in the reflected light and the light intensity for at least two or more specific wavelengths in the polarized light in the second direction;
Signal processing means for processing each output signal from the light detection means,
The road surface state is identified based on the relative light intensity between the polarized light in the first and second directions in the reflected light and the relative light intensity between a plurality of specific wavelengths in the polarized light in the second direction. Road surface condition detection sensor. Scattered light detection means for detecting the light intensity of scattered light from one or both of the road surface or water or ice film on the road surface generated by the projection light, and the signal processing means is the scattered light. 3. A road surface state detection sensor according to claim 1, wherein the scattered light intensity is also used for identifying the road surface state by processing an output signal from the detection means. The road surface condition detection sensor according to any one of claims 1 to 3, wherein the light source includes a plurality of single wavelength light sources that emit light at different specific wavelengths. 5. The road surface state detection sensor according to claim 1, wherein the polarized light in the first direction is S-polarized light and the polarized light in the second direction is P-polarized light. 6. The first specific wavelength of the plurality of specific wavelengths is 1.1 μm to 1.3 μm, and the second specific wavelength is 1.4 μm to 1.6 μm. The road surface condition detection sensor according to claim 1.

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