JP2000346943A - Vehicle-mounted light reflector and system for measuring distance between vehicles - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a vehicle-mounted light reflector that can be easily improved in reflection efficiency for measurement light and can be fitted to an arbitrary site, and a system for measuring distance between vehicles using the vehicle- mounted light reflector. SOLUTION: A light-sensitive resin is applied to a transparent resin substrate 4 capable of transmitting visible light, diffusion light, and parallel light are applied from the side of the surface for applying the light-sensitive resin and the side of the resin substrate 4, respectively, for sensitizing the light-sensitive resin, thus creating a hologram 6 on one surface of the resin substrate 4. The hologram 6 acts similarly as a concave mirror for measurement light for recursive reflection by performing the diffraction reflection of measurement light at an infrared wavelength region being applied from the side of the surface for forming the hologram. Visible light at a wavelength region other than the measurement light passes through a light reflector 2, thus preventing the visual field from being screened or vehicle design from being scarified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-vehicle light reflector for reflecting measurement light from another vehicle in the direction of arrival of the measurement light, and an inter-vehicle distance measurement for transmitting and receiving the measurement light to measure an inter-vehicle distance. About the system.

[0002]

2. Description of the Related Art Conventionally, a device for generating an alarm for avoiding a collision when an abnormal approach to another vehicle or an obstacle or the like and a device for automatically controlling a vehicle speed so that a distance between the vehicle and a preceding vehicle becomes constant. 2. Description of the Related Art There is known an on-vehicle optical distance measuring device that is applied and detects a distance to an object that reflects measurement light by transmitting and receiving measurement light composed of infrared light or the like.

In this type of optical distance measuring apparatus, FIG.
As shown in FIG. 4A, pulsed measurement light is emitted forward (or backward) of the vehicle at regular time intervals, and a reflected wave from a target object existing in the irradiation direction is received.
As shown in (b), the time required for the measurement light to reciprocate with the target object or the phase difference between the transmission and reception signals caused by the measurement light reciprocating with the target object is detected,
The distance from the vehicle to the object is measured based on the detection result (for example, Japanese Patent Laid-Open No. 7-9838).
No. 1).

By the way, even if the target object reflecting the measuring light is at the same distance, the intensity of the reflected light received by the optical distance measuring device becomes higher as the target object has higher reflection efficiency. That is, a target object having a higher reflection efficiency can be measured from a farther distance. This causes a phenomenon that even if there are a plurality of target objects at the same distance, a target object with high reflection efficiency is detected, but a target object with low reflection efficiency is not detected.

[0005] Generally, the brighter and brighter the color of an object, the higher the light reflection efficiency. Therefore, the reflection efficiency of a vehicle varies depending on the color of the vehicle body and the degree of dirt on the vehicle body surface. However, the vehicle is required by law (road transport vehicle law, road transport vehicle security standards) to have a light reflector called a reflector, and is installed in the front or rear of the vehicle in advance. As shown in FIG. 5, the reflector includes a large number of minute triangular pyramid-shaped projections P, and multiple reflection of light is performed at the projections.
Since the light is configured to be retroreflected, the reflection efficiency in the light arrival direction is higher than that of the vehicle itself,
Optical properties such as color are also limited by regulations. In FIG. 5, (a) is a plan view of the reflector,
(B) is the A sectional view.

That is, due to the presence of such a reflector, the reflection efficiency of the vehicle with respect to the measurement light is always kept at a certain level or more without being greatly influenced by the color or surface condition of the vehicle body. I have.

[0007]

However, since the size of the reflector and the portion to be attached to the vehicle body are limited by the above-mentioned regulations and the design of the vehicle, the reflector cannot reflect the measuring light retroreflectively (so-called blind spot). May be present. In other words, despite the fact that the vehicle is at a distance that can be sufficiently detected if the reflector retroreflects the measurement light, the measurement light may not be detected due to the measurement light coming from the blind spot of the reflector. was there. In fact, in the case of two-wheeled vehicles (motorcycles, etc.), it is not mandatory to mount a reflector on the front of the vehicle body. Generally, such a reflector on the front of the vehicle body is not mounted. Very difficult. Further, since the color of the reflector is limited to red or orange, there is also a problem that there is a limit in extending the detection distance.

On the other hand, in addition to a reflector incorporated at the time of manufacturing (hereinafter referred to as an incorporated reflector),
By additionally providing a reflector having the same retroreflectivity (hereinafter referred to as a retrofitted reflector), it is conceivable to improve the reflection efficiency of the vehicle as a whole or to compensate for the blind spot of the built-in reflector.

That is, the reflection efficiency of an object is represented by an optical reflection efficiency η1 expressed by a ratio of the intensity of the reflected light to the intensity of the incident light determined by the material and color of the object, and the area projected by the object relative to the total projected area of the incident light. It can be represented by the product η1 × η2 with the area ratio η2 represented by the ratio of the object reflection surface area. Therefore, if the reflection surface area of the portion having high optical reflection efficiency (that is, the reflector portion) is increased within the range of the measurement light projection area, the reflection efficiency of the entire vehicle can be improved.

A retroreflector having a triangular pyramid-shaped projection array like the above-mentioned built-in reflector can be used for such a retrofitted reflector, for example.
"Scotchlite" (trademark) manufactured by Company M is known. However, in a configuration having such a triangular pyramid-shaped projection row,
Even if the reflector is made of a transparent resin, the light is scattered by the prism effect of the protruding portion, and the reflector is only as transparent as so-called frosted glass. And what obstructs the view cannot be stuck on the window glass by law,
In such a retrofitted reflector, there is a problem that the mounting portion is limited. Further, even when such a retrofit reflector is attached to a vehicle body (a part other than the window glass), if the reflector and the vehicle body are different in color, there is a problem that the vehicle design is impaired.

The present invention has been made in order to solve the above problems.
It is an object of the present invention to provide an in-vehicle light reflector that can easily improve the reflection efficiency with respect to measurement light and that can be attached to an arbitrary part, and an inter-vehicle distance measuring system using the in-vehicle light reflector. I do.

[0012]

According to a first aspect of the present invention, there is provided an on-vehicle light reflector for transmitting visible light and transmitting measurement light in a wavelength range different from the visible light. It is characterized by selective retroreflection.

It is to be noted that such an on-vehicle light reflector specifically has an interference having the same effect as a concave mirror on a measurement light on a light-transmitting resin substrate as described in claim 2. It can be configured by stacking holograms on which stripes are recorded. That is, the measurement light incident on the hologram through a point corresponding to the focal point of the concave mirror (hereinafter, simply referred to as the focal point) is reflected by the hologram and condensed at the same focal point, so that it diverges beyond this focal point. The retroreflectivity is obtained for the measurement light irradiated toward the focal point from a region within the divergence angle of the reflected light.

In the vehicle-mounted light reflector of the present invention having the above-described structure, the measuring light applied to the light reflector is not only retroreflected in the irradiation direction but also transmits visible light, so that a window is required. Even if it is mounted on glass, it does not obstruct the field of view, and even if it is mounted on the vehicle body, the surface of the vehicle body can be seen through.

Therefore, the on-vehicle light reflector according to the present invention can be provided at any place including a window glass and a license plate without impairing the view or the vehicle design or violating laws and regulations.
It can be attached, and the reflection efficiency with respect to the measurement light at an arbitrary position of the vehicle can be easily improved.

As a result, by mounting the on-vehicle light reflector of the present invention on a vehicle, it can be reliably and reliably mounted on another vehicle having an on-vehicle optical distance detecting device regardless of the positional relationship. The vehicle can be detected from a long distance. Next, an on-vehicle light reflector according to claim 3 is characterized in that it transmits visible light and selectively absorbs and re-radiates measurement light in a wavelength range different from that of visible light.

It is to be noted that such an on-vehicle light reflector is, for example, such that fine particles that absorb and re-emit measurement light are dispersed on a light-transmitting resin substrate. Can be configured. In the on-vehicle light reflector of the present invention configured as described above, since the measurement light applied to the light reflector is absorbed and re-emitted in all directions, it is ensured that the measurement light arrives from any direction. In addition to being able to emit (reflect) light in the direction of its arrival, because it transmits visible light, it does not obstruct the field of view even when mounted on a window glass. I can see

Therefore, the vehicle-mounted light reflector according to the present invention can obtain exactly the same effects as the vehicle-mounted light reflector according to the first and second aspects. Next, in the inter-vehicle distance measuring system according to the fifth aspect, the vehicle is provided with the first to fourth aspects.
The vehicle-mounted light reflector according to any of the above aspects is additionally provided at a portion different from the light reflector required to be mounted according to laws and regulations.

[0019] With this arrangement, when the light reflector is required to be mounted and is installed at a position where the measurement light is irradiated at the same time, the area of the portion having high reflection efficiency with respect to the measurement light is increased. Vehicles equipped with an optical distance measuring device can detect vehicles located farther away, and if they are installed at positions where the required light reflectors are blind spots, Even in such a positional relationship, a portion having high reflection efficiency can be included in the irradiation range of the measurement light, and the vehicle can be reliably detected.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 is a schematic sectional view showing the configuration of a vehicle-mounted light reflector according to a first embodiment.

In-vehicle light reflector (reflector) of this embodiment
2 is provided with a transparent resin substrate 4 that transmits visible light, and an interference fringe that transmits visible light and acts on measurement light in the infrared region in the same manner as a concave mirror is recorded on one surface of the resin substrate 4. Hologram 6 and light reflector 2 on the other surface
An adhesive layer 8 is laminated for adhesively fixing the substrate to a window glass or a vehicle body of a vehicle.

Here, the procedure for manufacturing the on-vehicle light reflector 2 of this embodiment will be described. That is, first, a single resin substrate 4 is formed by forming a transparent resin that transmits visible light into a sheet, and a photosensitive agent (photosensitive resin) that is exposed to infrared light on one surface of the single resin substrate 4 is irradiated. Is applied.
The photosensitizer used has a property that the refractive index (dielectric constant) changes according to the degree of photosensitivity.

As shown in FIG. 2A, the resin substrate 4 coated with the photosensitive agent is diffused uniformly from a point light source from one side (here, the photosensitive agent side). Irradiate light, and at the same time, the other side (here, resin substrate 4
From the side), the photosensitive agent is exposed by irradiating parallel light so as to be incident on the surface of the resin substrate 4 from a perpendicular direction.

Then, interference occurs between the diffused light irradiated from both sides of the substrate and the parallel light, so that interference fringes, that is, a periodic light intensity distribution appears inside the photosensitive agent. The photosensitive agent is exposed. At this time, the distribution of points having the same light intensity in the light intensity distribution, the so-called equiphase surface,
It has an arc shape centered on a point light source of diffused light (hereinafter simply referred to as a diffused light source).

As a result, the refractive index distribution of the photosensitive agent exposed to the interference light having such a light intensity distribution also has an arc-shaped equirefractive index surface centered on the diffused light source.
This works as the hologram 6. For example, photosensitive resin A-
Looking at the refractive index distribution in the A section, as shown in FIG. 2B, the refractive index periodically increases and decreases along the thickness direction of the photosensitive agent.

As described above, the distribution of the refractive index of the photosensitive agent after exposure coincides with the light intensity distribution of the interference light at the time of exposure, and the point where the light intensity distribution is the weakest and the point where the refractive index is the minimum are determined. To accommodate this, the minimum value of the refractive index is generally equal to or slightly greater than the refractive index of the photosensitive agent before exposure. However, the minimum value and the maximum value differ depending on the photosensitive characteristics of the photosensitive agent.

It is necessary to use laser light having substantially the same wavelength as the measuring light as the diffused light and the parallel light used for producing the hologram. In this embodiment, the wavelength is 800 to 1000.
[Nm] laser light is used. Further, when the resin substrate 4 is large, instead of exposing the entire region with a single light source at once, the resin substrate 4 may be divided into a plurality of regions and the same operation may be performed for each region.

Finally, an adhesive layer 8 made of a transparent adhesive that transmits at least visible light is laminated on the surface of the resin substrate 4 opposite to the hologram forming surface, so that the on-vehicle light reflection of this embodiment is achieved. The vessel 2 is completed. However, the exposed surface of the adhesive layer 8 may be covered with a release paper.

The on-vehicle light reflector 2 of the present embodiment thus constructed is used by being attached to an arbitrary position of a vehicle body, including a window glass and a license plate of the vehicle, and is used for an on-vehicle optical distance measurement. The inter-vehicle distance measurement system is configured together with the device. Note that the measurement light emitted by the optical distance measuring device is set in an infrared region (for example, 850 [nm]) having substantially the same wavelength as the laser light used when producing the hologram. When the measurement light from the optical distance measuring device is incident from the hologram forming surface side of the light reflector 2, the measurement light is diffracted and reflected by the hologram 6 and returns from the light reflector 2 in the incident direction. The reflected wavefront has a concentric spherical shape centered on the position O of the point light source used at the time of fabrication.

That is, the on-vehicle light reflector 2 of this embodiment acts on the measuring light in the same manner as a concave mirror having the point O of the point light source as the focal point, and the divergence angle of the reflected light diverging beyond the focal point. The measurement light in the infrared region irradiated toward the focal point from the region inside is retroreflected, and visible light (400 to
700 [nm]).

As described in detail above, in the on-vehicle light reflector 2 of the present embodiment, the resin substrate 4, the hologram 6, and the adhesive layer 8, which are constituent elements of the light reflector 2, all transmit visible light. Because it has a light-transmitting property, it does not obstruct the view even when it is mounted on the window glass of the vehicle. However, there is no difficulty in reading, or the color of only the attachment part is different.

Therefore, the on-vehicle light reflector 2 of this embodiment is
It can be attached to any part of the vehicle without obstructing the view, damaging the vehicle design, or violating regulations, and can easily improve the reflection efficiency with respect to the measurement light at any part of the vehicle. In other words, the area of a portion having high reflection efficiency can be arbitrarily expanded.

As a result, when the on-vehicle light reflector 2 of this embodiment is mounted on a vehicle, the vehicle and the vehicle provided with the on-vehicle optical distance detecting device are in any positional relationship. However, the detection can be performed reliably and from a longer distance. Also, when a system that originally needs to detect an inter-vehicle distance with a vehicle located behind by an optical distance detection device is configured, the present embodiment is mounted on a front surface of a vehicle (for example, a two-wheeled vehicle) having no reflector on the front surface. If the in-vehicle light reflector 2 is mounted, such vehicle detection can be performed reliably. Second Embodiment Next, a second embodiment will be described.

FIG. 3 is a schematic sectional view showing the structure of a vehicle-mounted light reflector according to the second embodiment. As shown in FIG. 3, the on-vehicle light reflector 12 of this embodiment includes a transparent resin substrate 14 that transmits visible light, and semiconductor fine particles 16 that absorb and re-emit infrared rays are provided on the resin substrate 14. Evenly distributed.

The on-vehicle light reflector 12 is made of a resin substrate 14
It is formed by applying a resin coating obtained by uniformly dispersing the semiconductor fine particles 16 to a binder resin as a raw material of the resin at an arbitrary place of the vehicle and drying the coating. The semiconductor fine particles 16 may include, for example, A in a crystal lattice of ZnO.
“23-K” (Hakusui Chemical Co., Ltd.), which is made into an N-type semiconductor by doping with l ³⁺ , can be suitably used, but is not limited thereto. Any substance that emits light may be used.

In the vehicle-mounted light reflector 12 of the present embodiment thus configured, when the measurement light in the infrared region is irradiated,
This is mixed with the semiconductor fine particles 16 dispersed in the resin substrate 14.
Absorbs and re-emits. At the time of re-emission, the light is emitted in all directions, so that the measurement light is surely emitted (reflected) also in the arrival direction.

That is, the on-vehicle light reflector 12 of this embodiment has a property that the measuring light in the infrared region is reflected in the arrival direction thereof, and the visible light in the other wavelength region is transmitted. Therefore, according to the on-vehicle light reflector 12 of the present embodiment,
The same effect as that of the on-vehicle light reflector 2 of the first embodiment can be obtained.

Further, according to the on-vehicle light reflector 12 of this embodiment, even if the measurement light is from any direction, the light reflector 1 can be used.
As long as the light is irradiated to the light reflector 2, the light is surely reflected in the arrival direction of the measurement light. Can be.

Further, according to the on-vehicle light reflector 12 of the present embodiment, since it is formed by drying and solidifying the paint, it can be reliably provided even in a complicated shape. In this embodiment, the paint is dried and solidified to be formed directly on the vehicle. However, the resin substrate 14 in which the semiconductor fine particles 16 are dispersed is used.
May be formed in a sheet shape in advance similarly to the first embodiment, and this may be bonded to the vehicle.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a vehicle-mounted light reflector according to a first embodiment.

FIG. 2 is an explanatory view showing a method of manufacturing the on-vehicle light reflector of the first embodiment and an operation thereof.

FIG. 3 is a cross-sectional view illustrating a schematic configuration of a vehicle-mounted light reflector according to a second embodiment.

FIG. 4 is an explanatory diagram showing an outline of an inter-vehicle distance measuring system.

FIG. 5 is an explanatory diagram illustrating a configuration and a reflection principle of a conventional reflector.

[Explanation of symbols]

2,12 ... in-vehicle light reflector 4,14 ... resin substrate 6 ... hologram 8 ... adhesive layer 16 ... semiconductor fine particles

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D044 AA31 AA49 AC59 5H180 AA01 CC02 CC03 LL01 LL04 LL09 5J084 AA02 AA05 AB01 AC02 AD01 AD02 BA03 BB01 DA01 EA22

Claims (5)

[Claims] 1. An on-vehicle light reflector attached to a vehicle for reflecting measurement light emitted from another vehicle in the direction of arrival of the measurement light, wherein the light reflector transmits visible light, and An on-vehicle optical reflector, which selectively retroreflects measurement lights in different wavelength ranges. 2. The method according to claim 1, wherein a hologram in which interference fringes having the same effect as the concave mirror on the measurement light is recorded is laminated on a light transmitting resin substrate. The on-vehicle light reflector as described. 3. An on-vehicle light reflector mounted on a vehicle for reflecting measurement light emitted from another vehicle in the direction of arrival of the measurement light, wherein the light reflector transmits visible light, and An on-vehicle light reflector characterized by selectively absorbing and re-radiating measurement light in different wavelength ranges. 4. The on-vehicle light reflector according to claim 3, wherein fine particles that absorb and re-emit the measurement light are dispersed on a light-transmitting resin substrate. 5. A light source for emitting a measuring light and receiving reflected light from a target vehicle existing in a direction of irradiation of the measuring light, and a time difference between a light emitting time and a light receiving time or a phase difference between a light emitting signal and a light receiving signal. An inter-vehicle distance measuring system using an on-vehicle optical distance measuring device for measuring a distance to the target vehicle based on the vehicle, wherein the on-vehicle light reflector according to any one of claims 1 to 4 is mounted on the vehicle. An inter-vehicle distance measurement system, which is additionally provided at a part different from a light reflector which is required to be mounted according to laws and regulations.