JPH0552857A - Space filter type speed measuring apparatus. - Google Patents

Abstract

PURPOSE:To enable the detection of a speed of an automobile, etc., accurately regardless of water pool on a road surface or the like and a mirror reflection object such as glass piece, etc., in an onboard type speed measuring apparatus. CONSTITUTION:A projector 1 which emits a light beam 6a to a road surface 5 and 2 a photodetector which detects the light beam 6b reflected on the road surface 5 and the surface of a water pool 7. A polarization plate 3 for polarization is arranged on the front of a light emission window and a polarization plate 4 for detecting light is arranged on the front of a light incident window of the photodetector 2. The directions of polarization of both the polarization plates 3 and 4 are orthogonal to each other. An optical type road surface condition sensor 8 is provided near the photodetector 2 to judge condition of the road surface such as water pool. The polarization plates 3 and 4 are made movable along a rail and a guide groove and when any water pool 7 on the road surface 5 causes a mirror reflection, the polarization plates are inserted into an optical path. When the road surface 5 is dry to cause a diffusive reflection, they are retracted from the optical path.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a velocity measuring device using the principle of a spatial filter. For example, this speed measuring device is used as a vehicle-mounted complete non-contact vehicle speed meter or the like.

[0002]

2. Description of the Prior Art FIG. 7 shows the structure of a spatial filter type velocity measuring device (Ohm Electronics "Electronics" 1959).
Monthly issue, pp. 73-76). The spatial filter type velocity measuring device 21 includes a light projector 1 and a light receiver 2 fixed to a holder 22.
The light emitting side of the light projector 1 and the light incident side of the light receiver 2 are attached to the road surface 5 in the vicinity of the front bumper of an automobile or the like.

The projector 1 includes a concave reflecting mirror 23 and a lamp 24.
Also, the aspherical lens 25 is housed in a case 26, and the light emitted from the lamp 24 and the light reflected by the concave reflecting mirror 23 are applied to the road surface 5 through the aspherical lens 25.

Further, the light receiver 2 includes the objective lens 27, the slit 28, the light receiving element 29 and the preamplifier 30 in the case 3
The light reflected by the road surface 5 is converged by the objective lens 27, and the light passing through the slit 28 is imaged on the light receiving element 29.

As shown in FIG. 8, the light receiving element 29 (differential type spatial filter detector) has electrodes 33 and 34 having a comb-shaped structure formed on the surface of a substrate 32, and the surface on the road surface 5 is formed. The pattern is imaged on the light receiving element 29. Further, when the automobile moves, light reflection unevenness moves on the light receiving element 29, and a photocurrent change occurs. At this time, the reflection unevenness (spacing Δ) that was in the grid pitch is caused by the pair of electrodes 33, 3
4 causes a large photocurrent change deviated from each other by a half wavelength, so that only regular reflection unevenness at intervals of Δ occurs in the light receiving element 2.
Taken out by 9.

The road surface contains irregular patterns such as pebbles, sand, and asphalt of various sizes of 1 mm to several cm and tire marks, and uneven reflection (color unevenness, uneven unevenness, etc.). Is formed. The spatial filter type velocity measuring device 21 uses Δ (= approximately 2.3) because of these irregular patterns.
(mm) only the components lined up at regular intervals are the light receiving elements 2
It is taken out by 9, and the fluctuation of the reflected light amount generated thereby is converted into an electric signal and sent to a speedometer main body (not shown). In the speedometer main body, this signal is passed through a bandpass filter, shaped into a waveform, converted into a pulse train, and measured. Since this signal is generated from the reflection unevenness at intervals of Δ, the speed can be obtained by multiplying the count value of pulses corresponding to 1 second by the value Δ.

[0007]

However, in the spatial filter type velocity measuring device having the above structure,
There was a problem when used as an on-road speedometer.

That is, when there is a water pool on the road surface, most of the light emitted from the projector is specularly reflected on the surface of the water pool, and the light reflected by the water pool forms an image on the light receiving element. It was not possible to detect uneven reflection from the road surface, and it was not possible to measure an accurate speed. Especially on rainy days, speed measurement was difficult.

The present invention has been made in view of the drawbacks of the above-mentioned conventional examples, and an object thereof is to accurately control the speed even if there are water pools or specular reflections such as glass fragments on the road surface. An object is to provide a spatial filter type velocity measuring device capable of detecting.

[0010]

A first spatial filter type velocity measuring device of the present invention is a projector for irradiating a relative moving object such as a road surface with light, and a light receiver for detecting reflected light from the relative moving object. In a device for measuring velocity using the principle of a spatial filter, a first polarizing element is provided at a light emission position of the light projector, and the light receiver is emitted from the light projector and reflected by the relative moving object. The second polarizing element is disposed at the light incident position of the light receiver such that the polarization direction viewed along the optical path of the light beam incident on the optical axis is orthogonal to the polarizing direction of the first polarizing element. And at least one of the second polarizing element is provided so as to be freely inserted into and removed from the optical path.

A second spatial filter type velocity measuring device of the present invention comprises a light projector for irradiating a relative moving object such as a road surface with light, and a light receiver for detecting reflected light from the relative moving object, In a device for measuring velocity using the principle of a spatial filter, a first polarizing element is arranged at a light emitting position of the light projector, and a light beam is emitted from the light projector, reflected by the relative moving object, and incident on the light receiver. As the polarization direction seen along the optical path of is orthogonal to the polarization direction of the first polarization element, the second polarization element is disposed at the light incident position of the light receiver, and the first and second It is characterized in that the polarization function of at least one of the polarization elements can be electrically adjusted.

[0012]

In the first spatial filter type velocity measuring device of the present invention, when the road surface is mirror-reflected due to water pool or the like, the light emitting position of the light projector and the light incident position of the light receiver have polarization directions which are mutually opposite. Polarizing elements can be inserted so as to be orthogonal to each other.

When the polarizing element is inserted in the optical path, the light (non-polarized light) emitted from the light projector is converted into linearly polarized light by the polarizing element and emitted to the road surface side. Since the surface of the water pool is specularly reflected and the polarization state is preserved, it does not pass through the second polarization element and is not detected by the light receiver. On the other hand, the light rays that have passed through the water pool and reflected on the road surface are in a non-polarized state due to irregular reflection, and some of them pass through the second polarizing element and are detected by the light receiver.

Therefore, even when the road surface is specularly reflected by a water pool or the like, the specular reflection component due to the water pool or the like can be cut, and only the light reflected from the road surface can be detected to accurately measure the speed.

On the other hand, when there is no water pool or the like on the road surface and the light is diffusely reflected, not only the polarizing element is not necessary but also the amount of light received by the light receiver is reduced to prevent accurate measurement from being performed. Can remove at least one of the two polarizing elements from the optical path.

However, when the road surface is diffusely reflected (dry state), accurate speed measurement can be performed with a small amount of light, the power consumption of the light source is reduced, and the life of the light source is kept long. be able to.

Further, in the second spatial filter type velocity measuring device of the present invention, the polarizing elements are provided at the light emitting position of the light emitter and the light incident position of the light receiver, and at least one of the polarizing elements is provided. The polarization function can be adjusted electrically. That is, when the road surface is specularly reflected due to water pools or the like, the polarization function can be generated in the two polarizing elements so that the polarization directions are orthogonal to each other, and when the road surface is dry and diffusely reflected, at least one The polarization function of the two polarizing elements can be eliminated.

Therefore, the device has the same function as that of the first spatial filter type velocity measuring device, and in addition, since there is no mechanical operating portion, the device can be made compact. Furthermore, since it is faster to electrically change the polarization function than to mechanically move the polarizing element, the response speed of the device to the change of the road surface condition can be increased.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic view of one embodiment of the present invention. 1
Is a light projector, and 2 is a light receiver, both of which have the same internal structure as that already described in FIG. A polarizing plate 3 for polarization is arranged in front of the light exit window of the projector 1, and a polarizing plate 4 for analysis is arranged in front of the light entrance window of the light receiver 2. The polarization directions of the plates 3 and 4 are orthogonal to each other.

That is, when tracing the optical paths of the light rays 6a, 6b which are emitted from the light projector 1, reflected by the road surface 5 and incident on the light receiver 2, the polarization direction of one polarizing plate 3 seen from the light rays 6a, 6b. α and the polarization direction β of the other polarizing plate 4 are orthogonal to each other.

For example, as shown in FIG. 1, the polarization direction α of the polarizing plate 3 is parallel to the plane containing the emitted light ray 6a and the reflected light ray 6b (direction parallel to the paper surface of FIG. 1). The polarization direction β of the polarizing plate 4 is oriented in a direction perpendicular to the plane including the emitted light ray 6a and the reflected light ray 6b (direction perpendicular to the paper surface of FIG. 1).

The polarizing plates 3 and 4 are movably provided along rails and guide grooves provided in the casing of the speed measuring device, etc., and the polarizing plates 3 and 4 are slid. It can be inserted into or removed from the optical path.

An optical road surface state sensor 8 capable of discriminating road surface states such as dryness, puddle, wetness, freezing, and snow is provided near the light receiver 2.

FIG. 2 is a schematic view showing an example of the road surface condition sensor 8. This uses Brewster's law that specularly reflected light is almost completely polarized when the angle of incidence on a transparent medium is equal to a certain angle determined by the medium (this is called Brewster angle θ _b ). is there.

The road surface condition sensor 8 is a light projector 1 which is a light source.
The angle between the road surface condition sensor 8 and the road surface condition sensor 8 is twice the Brewster's angle (2θ _b ). A plano-convex lens and a roof prism are attached to the light incident part of the road surface condition sensor 8. The image splitting lens 51 is arranged, and the reflected light beam 6b incident on the road surface state sensor 8 is condensed by the image splitting lens 51 and at the same time the optical path is split into two.

A first light receiving element 54 is provided at the image forming position on one of the divided optical paths, and the first light receiving element 5 is provided.
In front of 4, the first linear polarization element 52 is arranged such that the polarization direction is parallel to the incident surface (the surface including the light rays 6a and 6b).

A second light receiving element 55 is provided at the image forming position on the other optical path, and the second light receiving element 55 is arranged in front of the light receiving element 55 so that the polarization direction is perpendicular to the incident surface. The polarizing element 53 is arranged. In addition, both light receiving elements 5
The outputs of 4, 55 are amplified by amplifiers 56, 57 and then output as voltage signals V1, V2.

Therefore, the road surface reflected light beam 6b incident on the road surface condition sensor 8 is divided into two directions by the image splitting lens 51, and the first light receiving element 54 has only the parallel polarization component passing through the first polarization element 52. The detected signal is output from the amplifier 56 as a signal V1 proportional to the intensity of the parallel polarization component. Similarly, in the second light receiving element 55, the second polarizing element 5
Only the vertically polarized component that has passed 3 is detected, and the amplifier 57
Outputs a signal V2 proportional to the intensity of the vertically polarized component.

Here, when the road surface 5 is dry,
Since the reflected light ray 6b is diffused light, the parallel polarization component and the vertical polarization component are equal, and the output signal is V1≈V2. On the other hand, when the road surface 5 is wet, the reflected light beam 6b
Is reflected specularly, it contains almost no vertically polarized component (Brewster's law), and V2≈0. Therefore,
For example, the output ratio k = V2 / V1 is monitored, and when this value k exceeds a certain threshold value, it is determined to be a dry surface, and when k falls below the threshold value, it is determined to be a wet road surface. Can be made

In this embodiment, the reflected light 6b from the road surface of the emitted light 6a of the light projector 1 is measured, but the speed measuring device and the road surface condition sensor are separately provided, and the road surface condition sensor 8 is provided. A dedicated floodlight may be provided separately.

FIG. 3 shows a block diagram of the control system of this embodiment. The control device 11 determines the signal output from the road surface state sensor 8 installed near the light receiver 2 to detect the presence / absence of a specular reflection object on the road surface 5, and drives the polarizing plates 3 and 4 and the light projecting device 1. The lamp voltage adjusting device 10 for adjusting the light quantity of the lamp 24 therein is controlled according to the road surface condition.

The driving device 9 is for moving the polarizing plates 3 and 4 in parallel, and for inserting the polarizing plates 3 and 4 into the optical path or, conversely, for moving the polarizing plates 3 and 4 out of the optical path. Is. The drive device 9 may use a motor as power, or may use air pressure or electromagnetic force.

In addition to the mode in which the drive device 9 is automatically controlled by the output of the road surface state sensor 8,
You may provide the mode which operates manually.

The lamp voltage adjusting device 10 includes a control device 11
The light amount of the lamp 24 is switched between large and small according to a control signal from.

When the road surface 5 is in a state of being mirror-reflected by the water pool 7 or the like, the road surface condition sensor 8 and the control device 11 detect this, and the driving device 9 inserts the polarizing plates 3 and 4 into the optical path. Lamp voltage adjusting device 10
Thus, the light quantity of the lamp 24 in the projector 1 is increased.

The light (non-polarized light) emitted from the projector 1 is converted into linearly polarized light by the first polarizing plate 3 and emitted to the road surface side. Then, on the surface of the water pool 7, the light beam 6a emitted from the light projector 1 is specularly reflected and the polarization state is preserved.
It does not pass through the second polarizing plate 4 and is not detected by the light receiver 2.
On the other hand, the light ray 6b that has passed through the water pool 7 and is reflected by the road surface 5 is in a non-polarized state due to irregular reflection, and a part thereof passes through the second polarizing element 4 and is detected by the light receiver 2.

Therefore, even when the road surface 5 is specularly reflected by the water pool 7 or the like, the specular reflection component by the water pool 7 or the like can be cut and only the reflected light from the road surface 5 can be imaged on the light receiver 2. At this time, the lamp light quantity is increased to compensate for the light quantity reflected or absorbed by the polarizing plates 3 and 4, so that accurate speed measurement can be performed.

On the other hand, there is no water pool 7 etc. on the road surface 5
In the case of diffuse reflection, not only the polarizing plates 3 and 4 are not necessary, but also the amount of received light is reduced, which prevents accurate measurement on the contrary. In FIG. 1, the light is moved away from the optical path as shown by the dotted line, and the lamp voltage adjusting device 10 reduces the light quantity of the lamp to reduce the light quantity emitted from the projector 1.

Therefore, accurate speed measurement can be performed regardless of whether the road surface is specularly reflected (a state with water pools or the like) or diffusely reflected (a dry state), and the amount of lamp light is required. Can be minimized
The power consumption can be reduced and the lamp life can be extended.

The present embodiment can also be constructed by using a polarizing element other than the above polarizing plate, for example, a polarizing beam splitter or a polarizing plate capable of electrically adjusting the polarization function. It is also possible to use different types of polarizing elements on the polarization side and the analysis side.

FIGS. 4A and 4B show another embodiment of the present invention and its operation. The speed measuring device of this embodiment has almost the same configuration as that of the embodiment of FIG. 1, but the polarizing plates 3 and 4 slide in the embodiment of FIG. 1, whereas the rotating shaft 3a, Polarizing plates 3 and 4 are rotatably supported by 4a. When the road surface 5 is wet, the polarizing plates 3 and 4 are inserted into the optical path as shown in FIG.
When the road surface is dry, the polarizing plates 3 and 4 can be rotated by the driving device to be removed from the optical path as shown in FIG. 4B.

FIGS. 5A and 5B show still another embodiment of the present invention and its operation. In this embodiment, the polarizing plates 3 and 4 are moved in a direction orthogonal to the sliding direction of the polarizing plate in the embodiment of FIG. That is, in the embodiment of FIG. 1, the polarizing plates 3 and 4 are moved to the center between the light projector 1 and the light receiver 2, whereas in this embodiment, they are moved to the rear of the light projector 1 and the light receiver 2.

Next, another embodiment of the present invention will be described. The present embodiment is similar to the embodiment of FIG. 1 in terms of the basic configuration, but polarizing plates 3 and 4 whose polarization function is electrically adjustable are fixed in the optical path. That is, these polarizing plates 3 and 4 have a polarization function when a voltage V ₀ is applied and disappear when the voltage V ₀ is turned off. In addition,
When the voltage V ₀ is applied to the polarizing plates 3 and 4 to generate the polarization function, the polarization directions are arranged so as to be orthogonal to each other.

As the polarizing plates 3 and 4, it is possible to use, for example, elements utilizing various electro-optical effects and properties of liquid crystals and the like.

FIG. 6 shows a block diagram of the control system of this embodiment. The control device 11 discriminates the signal output from the road surface condition sensor 8 installed in the vicinity of the light receiver 2 to detect the presence / absence of a specular reflector on the road surface 5, and adjust the polarizing function of the polarizing plates 3 and 4. The voltage regulator 12 and the lamp 2 in the projector 1
The lamp voltage adjusting device 10 for adjusting the light amount of No. 4 is controlled.

The polarizing plate voltage adjusting device 12 includes a controller 11
When the road surface 5 is specularly reflected by the water pool 7 or the like, the output voltage V ₀ is turned on to cause the polarizing plates 3 and 4 to have a polarization function. On the contrary, when the road surface 5 is dried and diffusely reflected, the output voltage V ₀ is turned off to eliminate the polarization function of the polarizing plates 3 and 4 and make the polarizing plates 3 and 4 optically transparent.

Therefore, the spatial filter type velocity measuring device according to the present embodiment has the same function as that shown in FIG. 1 and is compact because it has no mechanical actuation part. Since it is faster to change the polarization function electrically than to move it mechanically, the response speed to changes in road surface conditions is faster.

In the above embodiment, when the road surface is dry, both the polarizing plate on the polarization side and the polarizing plate on the detection side are removed from the optical path, or the polarization function is lost. The polarizing plate may be removed from the optical path, or the polarizing function may be lost.

[0049]

According to the first spatial filter type velocity measuring device of the present invention, when the road surface is specularly reflected due to water pool or the like, the polarization directions are set at the light emitting position of the projector and the light incident position of the light receiver. Since the polarizing elements can be inserted so as to be orthogonal to each other, the specular reflection component due to a pool of water or the like can be cut, and only the reflected light from the road surface can be detected to perform accurate speed measurement.

In addition, when there is no water pool on the road surface and the road surface is diffused and reflected, not only the polarizing element is required but also the light receiving amount of the light receiver is reduced to prevent accurate measurement.
In this case, at least one of the two polarizing elements can be removed from the optical path.

Therefore, whether the road surface is specularly reflected (there is a pool of water or the like) or diffusely reflected (the dry state), accurate speed measurement can be performed, and the amount of emitted light is required. It can be minimized, the power consumption of the light source can be reduced, and the life of the light source can be kept long.

Further, in the second spatial filter type velocity measuring device of the present invention, the polarizing elements are provided at the light emitting position of the projector and the light incident position of the light receiver, and at least one of the polarizing elements is provided. The polarization function can be electrically adjusted, and when the road surface is specularly reflected due to water pools, etc., the polarization directions of the two polarizing elements can be made orthogonal to each other, and the road surface is dry and diffusely reflected. The polarization function of at least one polarization element can be eliminated.

Therefore, the device has the same function as that of the first spatial filter type velocity measuring device, and in addition, the device can be made compact because there is no mechanical operating part, and furthermore, the polarizing plate is mechanically moved. Since it is faster to change the polarization function electrically, the response speed of the device to the change of the road surface condition can be increased.

[Brief description of drawings]

FIG. 1 is a schematic front view showing an embodiment of the present invention.

FIG. 2 is a schematic view of the above road condition sensor.

FIG. 3 is a block diagram showing a control system of the same.

4A and 4B are schematic front views showing another embodiment of the present invention.

5A and 5B are schematic side views showing still another embodiment of the present invention.

FIG. 6 is a block diagram showing a control system of still another embodiment of the present invention.

FIG. 7 is a cross-sectional view showing the structure of a spatial filter type velocity measuring device.

FIG. 8 is a perspective view showing a structure of the above light receiving element.

[Explanation of symbols]

 1 Emitter 2 Light receiver 3,4 Polarizing plate 8 Road surface condition sensor

Claims (2)

[Claims] 1. A device for measuring velocity using the principle of a spatial filter, comprising: a light projector for irradiating a relative moving object such as a road surface with light; and a light receiver for detecting reflected light from the relative moving object. A first polarization element is disposed at the light emission position of the light projector, and the polarization direction seen along the optical path of the light beam emitted from the light projector, reflected by the relative moving object, and incident on the light receiver is the first polarization. A second polarizing element is arranged at the light incident position of the light receiver so as to be orthogonal to the polarization direction of the element, and at least one of the first and second polarizing elements is provided so as to be freely inserted into and removed from the optical path. A spatial filter type velocity measuring device characterized in that 2. An apparatus for measuring velocity using the principle of a spatial filter, comprising: a light projector for irradiating a relative moving object such as a road surface with light; and a light receiver for detecting reflected light from the relative moving object. A first polarization element is disposed at the light emission position of the light projector, and the polarization direction seen along the optical path of the light beam emitted from the light projector, reflected by the relative moving object, and incident on the light receiver is the first polarization. A second polarizing element is arranged at the light incident position of the light receiver so as to be orthogonal to the polarization direction of the element, and the polarization function of at least one of the first and second polarizing elements is electrically adjusted. A spatial filter type velocity measuring device characterized in that it is made possible.