JPS6221012A - Road surface condition sensor - Google Patents

Abstract

PURPOSE:To enable accurate detection of condition of a road surface regardless of changes in the reflectance thereof, by a method wherein the road surface is irradiated with light and the reflected light thereof is received through two polarizing plates with the polarization plane differing by 90 deg. from each other to take the ratio between the outputs thereof. CONSTITUTION:A light emitting element 1 irradiates light to a road surface through a polarization plate 2. A light receiving element 4(6) receives the reflected light from the road surface through a polarization plate 3(5). The three polarization plates are so arranged as to differ in the polarization plane by about 90 deg.C from one another with the plate 2 as reference. The judgement 11-15 on the condition of the road surface is based on the ratio between the resulting outputs of the elements 4 and 6. In this case, in a flat road surface with a grater proportion of diffusive reflection, the output signals of the elements 4 and 6 are almost equal whereas in a rugged road surface with a greater proportion of direct reflection, the output signal of the light receiving element 4 is higher than that of the element 6. Thus, the condition of the road surface can be detected based on the ratio in the output signals of the elements 4 and 6. The ratio of the output signals of closely related to the shape of the road surface but not to the color thereof thereby eliminating misdetection between the ruggedness and uneven color of the road surface.

Description

[Detailed description of the invention] It is something to do.

[Conventional technology]

A road surface condition sensor that detects road surface conditions is necessary, for example, when the suspension of a vehicle is automatically changed depending on the road surface condition.

Conventionally, road surface condition sensors include a light emitting element that irradiates light onto the road surface at a predetermined angle, and a light receiving element that is placed at approximately the same position as the light emitting element and converts reflected light from the road surface into an electrical signal. A system has been proposed that detects the condition of a road surface based on the level of an electrical signal output from a light receiving element. That is, this conventional device detects the condition of the road surface by utilizing the fact that the amount of reflected light incident on the light receiving element is greater on a road surface with unevenness than on a flat road surface.

However, since the conventional device described above detects the condition of the road surface based on the amount of light reflected from the road surface, it has the following problems. In other words, the amount of light reflected from the road surface changes not only depending on the condition of the road surface but also the color (reflectance) of the road surface. There was a problem that it was difficult to distinguish between the two.

[Problem that the invention seeks to solve]

The present invention solves the above-mentioned problems, and its purpose is to make it possible to accurately detect the condition of a road surface even when the reflectance of the road surface changes.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention includes a light emitting element that irradiates light onto a road surface through a first polarizing plate, and a light emitting element that irradiates light from the road surface with a polarization plane of approximately 90° with respect to the first polarizing plate. ° a first light receiving element that receives light through a different second polarizing plate;
a second light-receiving element that receives reflected light from the road surface through a third polarizing plate whose plane of polarization differs by approximately 90'' from the second polarizing plate; and determining means for determining the condition of the road surface based on the ratio of the output of the light receiving element to the output of the light receiving element.

[For production]

On a flat road surface, as shown in Figure 1 (A), the ratio of diffuse reflection is higher than that of regular reflection, and on a road surface with unevenness, as shown in Figure 1 (B), the ratio of diffuse reflection is higher. The proportion of specular reflection is higher than that of . In addition, in the case of specular reflection, the polarization plane of the incident light and the polarization plane of the reflected light match, but in the case of diffuse reflection, the polarization of the reflected light is lost and it becomes natural light.
(For example, even if the incident light is horizontally polarized, vertical polarization may also occur depending on the state of the reflecting surface.) Therefore, the light emitted from the light emitting element 1 is polarized by the first polarizing plate 2, and the reflected light from the road surface is polarized by the second polarizing plate 3 and the second When light is received by the first and second light receiving elements 4.6 through the third polarizing plate 5 whose plane of polarization differs by approximately 90" from the polarizing plate, the first and second light receiving elements 4.6 light receiving element 4,
The output signals of the first light receiving element 4 are almost equal to each other, and the output signal of the first light receiving element 4 is higher than the output signal of the second light receiving element 6 on an uneven road surface with a high proportion of specular reflection.

Therefore, the first. The road surface condition can be detected based on the ratio of the output signals of the second light receiving element 4.6.

Furthermore, the ratio between the output signal of the first light receiving element 4 and the output signal of the second light receiving element 6 is determined by the shape of the road surface and is unrelated to the color of the road surface. There will be no false positives.

〔Example〕

4 is a light receiving element, 5 is a polarized light f
6 is a light receiving element, 7 is a pulse generator, 8 is a driving circuit, 9° is an amplifier, 11 is a multiplexer, 12 is a bandpass filter,
13 is an AD converter, 14 is a memory, and 15 is a microprocessor. The light emitting element 1 and the light receiving element 4.6 are mounted, for example, on a front grill or the like so that the angle with the road surface is about 10'.

The light emitted from the light emitting element 1 is pulse-modulated by the pulse generator 7 and the drive circuit 8, and is irradiated onto the road surface via the polarizing plate 2.
The reflected light from the road surface passes through polarizing plates 3 and 5 to light receiving elements 4.
6. Amplifiers 9 and 10 each have a light receiving element 4.
, 6 are amplified with the same amplification factor and applied to the multiplexer 11.

The following table shows the amplifier 9 when the reflecting surface is in the states (A) to (J).
, 100 output voltages Va, Vb (volts) and their ratio Vb/Va. However, (A) is a case where a concrete piece approximately 20m thick is placed on an asphalt road surface, (B) is a case where a brown rusted steel plate with a thickness of 3n is placed on an asphalt road surface, and (C) is a case where a piece of concrete with a thickness of about 20m is placed on an asphalt road surface. If you place a brown rusted iron pipe with a diameter of 201mm on , (D) is a flat concrete road surface, (E) is a flat asphalt road surface, (F) is a flat gray tile, (G)
is a flat blue sponge, (H) is a flat white paper, (
1) is the case of flat blue rubber, and (J) is the case of flat black rubber.

As can be seen from the table, when the reflective surface is flat, the heat associated with its color (the ratio of signal Va to signal vb, vb/Va, is smaller than when the reflective surface has unevenness. Therefore, by performing the processing shown in the flowchart of FIG. 3 by the microprocessor 15, it becomes possible to detect the state of the road surface without being affected by uneven color of the road surface.

That is, if the microprocessor 15 determines that light is being emitted from the light emitting element 1 based on the output signal of the pulse generator 7 (if the determination result in step S1 is YES), it sends a switching signal to the multiplexer 11. In addition, amplifier 9
, 10 are sequentially applied to the bandpass filter 12, and the signal Va is applied via the AD converter 13.

vb are sequentially read (steps S2, 3). Next J, ),
The microprocessor 15 calculates the ratio V between the signal Va and the signal vb.
b/Va is determined (step S4), and then the ratio Vb/
Va, the value of the signal vb read in step S3, and memory 1
The road surface condition is determined based on the stored contents of step S5), and a suspension control signal corresponding to the determination result is outputted (step S6). In addition, as shown in FIG.
b/Va is stored as a parameter, and for example, the value of the signal vb read in step S3 is
(However, y 3 < v x < V 4 ), and the ratio Vb/Va obtained in step S4 is αX (however, α3<
If αx × α4), microprocessor −5
It is determined that the road surface is a concrete road surface with unevenness.

In the above embodiment, the ratio Vb/Va and the signal v
The road surface condition was detected based on the ratio V
Of course, it is also possible to detect the road surface condition based on b/Va and the signal Va. Furthermore, if the purpose is simply to determine whether there are irregularities on the road surface, the ratio Vb/Va
It is possible to judge whether or not there are irregularities on the road surface by simply comparing this value with an appropriate darkness value.

〔Effect of the invention〕

As explained above, the present invention includes a light emitting element that irradiates light onto a road surface through a first polarizing plate, and a light emitting element that irradiates light onto a road surface through a first polarizing plate, and a light emitting element that directs light reflected from the road surface to a light emitting element whose polarization plane differs by approximately 90 degrees from that of the first polarizing plate. a first light-receiving element that receives light through a second polarizing plate; and a second light-receiving element that receives light reflected from the road surface through a third polarizing plate whose polarization plane is approximately 90″ different from the second polarizing plate. A light receiving element,
Since the apparatus includes a determining means for determining the condition of the road surface based on the ratio of the output of the first light receiving element and the output of the second light receiving element, it is possible to There is also an advantage that the road surface condition can be detected accurately.

[Brief explanation of drawings]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a block diagram of an embodiment of the invention, Fig. 3 is a flowchart showing part of the processing contents of the microprocessor 15, and polarizing plates whose planes differ by approximately 90°. , 4 is a light receiving element, 5 is a polarizing plate whose polarization plane differs from the polarizing plate 3 by approximately 90'', 6 is a light receiving element, 7 is a pulse generator, 8 is a drive circuit, 9°10 is an amplifier, 11 is a multiplexer, 12 is a Band pass filter, 13 is a converter, 14 is a memory, and 15 is a microprocessor. Patent applicant Fujitsu Ten Ltd. (1 other person) Patent attorney Gobe Tamamushi (1 other person) Microprocessor Fig. 3 is a flowchart showing the processing contents of the sensor 15;

Claims (1)

[Scope of Claims] A road surface condition sensor that detects the condition of a road surface, comprising: a light emitting element that irradiates light onto the road surface through a first polarizing plate; and a light emitting element that irradiates light onto the road surface through a first polarizing plate; a first light-receiving element that receives light through a second polarizing plate whose polarization plane differs from that of the plate by approximately 90 degrees; and a third light-receiving element which receives light reflected from the road surface through a second polarizing plate whose polarization plane differs by approximately 90 degrees from the second polarizing plate. a second light-receiving element that receives light through a polarizing plate; and a determining means that determines the condition of the road surface based on a ratio of the output of the first light-receiving element and the output of the second light-receiving element. A road surface condition sensor characterized by: