JP2021157076A - Retroreflective material and object detection method - Google Patents

Abstract

To provide a retroreflective material capable of specifying a direction in which an operator is present.SOLUTION: A retroreflective material controls a wavelength of reflected light using a multilayer film 20 to increase reflectance of light of a desired wavelength in an invisible light region. The retroreflective material has glass beads 10 to be retro-reflected and a multilayer film 20 formed on part of a surface of the glass beads 10. The multilayer film 20 is formed so as to have an increased reflectance of ultraviolet rays or infrared rays, and has 80% or more reflectance of a light beam of a wavelength 800 nm to 1200 nm. Also, the retroreflective material is transparent or translucent.SELECTED DRAWING: Figure 2

Description

The present invention relates to a retroreflective material and an object detection method.

For example, Patent Document 1 describes a retroreflective light reflector that can be worn by an operator, emits laser light toward the worker, and receives the reflected laser light reflected by the light reflector. A position detection device that measures the distance to the light reflector and detects the emission angle of the laser beam to detect the position of the worker, and the worker position detected by the position detection device is a predetermined alarm area. A monitoring system including an alarm device that generates an alarm when the light is inside is disclosed.

Japanese Unexamined Patent Publication No. 2000-182165

An object of the present invention is to provide a retroreflective material capable of specifying the direction in which a worker is present.

The retroreflective material according to the present invention uses an interference film to control the wavelength of the reflected light to increase the reflectance of light having a target wavelength in the invisible light region.

Preferably, it has glass beads that retroreflect and an interference film formed on a part of the surface of the glass beads, and the film interference film is formed so as to have high reflectance of ultraviolet rays or infrared rays. ..

Preferably, the interference film is designed so that the reflectance of light rays having a wavelength of 800 nm to 1200 nm is 80% or more.

Preferably, it is transparent or translucent.

Further, the object detection method according to the present invention includes a step of irradiating a retroreflective material whose reflectance in an invisible region is increased by using an interference film with invisible light or light containing invisible light, and the irradiated light. Among these, it has a step of detecting retroreflected light whose wavelength is controlled by an interference film and a step of determining the presence / absence or displacement of an object based on the detected retroreflected light.

According to the present invention, the direction in which the operator is located can be specified by using the retroreflective.

It is a figure which illustrates the object detection system 1 in this embodiment. It is a figure which illustrates the structure of the retroreflective material 1 in this embodiment. It is a figure which illustrates the structure of the multilayer film 20 vapor-deposited on the glass bead 10. It is a figure explaining the reflection mechanism of the glass bead 10 which formed the multilayer film 20. It is a figure which illustrates the functional structure of the object detection program 50. It is a flowchart explaining the object detection process (S10). It is a figure which illustrates the spectral characteristic of the multilayer film 20 formed on the retroreflective material 1.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the illustrated examples.
FIG. 1 is a diagram illustrating an object detection system 1 according to the present embodiment.
As illustrated in FIG. 1, the object detection system 1 has a work clothes 3 worn by an operator and an object detection device 5 mounted on a work vehicle 4.
The work clothes 3 are clothes to be worn during work work, and include, for example, a jacket 30 having a company name, a worker name, etc. written on the chest, and a retroreflective material 1 attached to the jacket 30. ..
The jacket 30 is, for example, a jacket having a pocket on at least one side, and can be replaced by an off-the-shelf product. The jacket 30 of this example has a company name, a worker name, or the like embroidered or printed on the chest.
The retroreflective material 1 is a glass bead type retroreflective material that is transparent or translucent. The retroreflective material 1 uses an interference film to control the wavelength of the reflected light to increase the reflectance of light having a target wavelength in the invisible light region. The retroreflective material 1 is attached to the whole or at least a part of the cap body 30. The retroreflective material 1 of this example is attached, for example, at a position overlapping the position where the company name, worker name, etc. of the outerwear 30 are described. Since the retroreflective material 1 is transparent or translucent, the company name, worker name, etc. can be visually recognized even if the retroreflective material 1 is attached at a position overlapping the position where the company name, worker name, etc. are described. Although the case where the retroreflective material 1 of this example is attached to the work clothes 3 will be described, it may be attached to a helmet.

Although not shown, the object detection device 5 has a light source, a light receiving sensor, and a warning display unit in terms of hardware. The light source irradiates invisible light, and the light receiving sensor detects infrared rays retroreflected by the retroreflective material 1 attached to the worker's work clothes 3. Then, the warning display unit notifies the operator who operates the work vehicle 4 that the worker is within the range where the hook of the work vehicle 4 comes into contact.
The light source is a light irradiator that mainly irradiates light containing infrared rays or ultraviolet rays, that is, invisible light or light containing invisible light. The light source is preferably one that irradiates infrared rays or ultraviolet rays from the viewpoint of not interfering with the work of the operator. The light source of this example irradiates infrared rays. (Hereinafter, the light emitted by the light source may be referred to as infrared rays or simply light.) Further, the light source may be provided in a plurality of directions.
The light receiving sensor is a sensor that detects retroreflected light that is retroreflected by invisible light emitted by a light source. The sensitivity of the light receiving sensor is a sensitivity capable of detecting the reflected light reflected from a predetermined position within the working range of the work vehicle 4. Here, the work vehicle 4 is a work vehicle including an arm such as a hydraulic excavator, a crane car, and a forklift, and the work range of the work vehicle 4 is a bucket, a hook, etc. attached to the tip of the arm. It is within the reach of the nails. In this example, the sensitivity is such that the reflected light reflected from a predetermined position within the reach of the bucket of the hydraulic excavator can be detected. Further, the light receiving sensor may be provided so as to face in a plurality of directions.
The warning display unit is a warning device that notifies the operator of the work vehicle 4 that there is a worker within the work range of the work vehicle 4. In this example, it is notified that there is an operator within the reach of the bucket of the hydraulic excavator.

(Retroreflective material 1)
FIG. 2 is a diagram illustrating the configuration of the retroreflective material 1 in the present embodiment.
As illustrated in FIG. 2, the retroreflective material 1 has a glass bead 10, a multilayer film 20, a fixing layer 60, an adhesive layer 62, and a base material 64. The retroreflective material 1 is transparent or translucent as a whole.
The glass beads 10 are transparent beads having high retroreflective properties. The glass beads 10 are, for example, spherical glass having a refractive index of 1.50 to 2.20, preferably spherical glass having a refractive index of 1.90 to 2.20. The diameter of the glass beads 10 is, for example, 10 μm to 150 μm, preferably 45 μm to 75 μm. The glass beads 10 of this example are glass beads having a refractive index of 1.93 and a diameter of 45 μm to 75 μm. The specific gravity of the glass beads 10 is 4.2 ± 0.1.
Since the glass beads 10 of this example are glass beads having a refractive index of 1.93, light incident from the air is refracted on the surface of the glass beads 10, and the refracted light passes through the inside of the glass beads 10. Focus on its bottom. A part goes out of the glass beads from the bottom surface, but it is reflected at the same angle as the incident angle to the focal point, and the reflected light is refracted again on the surface of the glass beads 10 in the same direction as the incident light. It is emitted from the glass beads 10 in the direction. As described above, the glass beads 10 of this example are glass beads that retroreflect light incident from the air.
Further, the glass beads 10 are fixed to the surface of the base material 64 via the adhesive layer 62 in a state where one-third or more of the diameter is exposed from the fixing layer 60. The glass beads 10 of this example are fixed to the base material 64 with half the diameter exposed.

The multilayer film 20 is an interference film formed on a part of the surface of the glass beads 10. The multilayer film 20 of this example is a film formed by vapor deposition on a part of the surface of the glass beads 10, that is, a so-called vapor deposition film. The multilayer film 20 is laminated with a plurality of layers having a unique refractive index, and at least three or more layers are laminated. The details of the multilayer film 20 will be described later.

The fixing layer 60 is a binder layer that fixes the glass beads 10 to the surface of the base material 64 via the adhesive layer 62.
The adhesive layer 62 is, for example, a polyurethane resin-based adhesive that adheres the fixing layer 60 and the base material 64.

The base material 64 is composed of, for example, a transparent or translucent fiber base material, a nonflammable base material, or a synthetic resin material base material. Specifically, the base material 64 is a cloth, a non-woven fabric, paper, a film, a plastic plate, or the like. The base material 64 is transparent to the extent that the characters, figures, and the like described on the outer shell cap body 30 can be seen through. The thickness of the base material 64 is not particularly limited.

Next, the configuration of the multilayer film 20 will be described in detail.
FIG. 3 is a diagram illustrating the configuration of the multilayer film 20 deposited on the glass beads 10.
The multilayer film 20 is formed so as to have a high reflectance of ultraviolet rays or infrared rays. The multilayer film 20 of this example is formed by laminating a plurality of layers having a unique refractive index so that the reflectance of ultraviolet rays or infrared rays is higher than the reflectance of visible light. _{The multilayer film 20 contains silicon dioxide (SiO 2} ) as a main component so that the refractive index of light rays having a wavelength of 800 nm to 1200 nm is 50% or more, preferably 80% or more of light rays having a wavelength of 800 nm to 950 nm. A layer with a low refractive index (refractive index of 1.6 or less) (SiO ₂ layer) and a layer with a high refractive index (refractive index of 2.0 or more) containing _{titanium oxide (TiO 2) as a main component.} TiO ₂ layers) are alternately laminated. The multilayer film 20 of this example has a silicon dioxide layer and a titanium oxide layer so that the reflectance of light rays having a wavelength of 800 nm to 950 nm is 80% or more and the reflectance of light rays having a wavelength of 450 nm to 750 nm is 20% or less. The number of layers and the layer thickness are adjusted. As a result, the retroreflective material 1 becomes a reflective material having a higher reflectance in the invisible light region than in the visible light region. The case where the multilayer film 20 of this example has a three-layer structure of the first layer to the third layer will be described as a specific example. The thickness of the multilayer film 20 is 0.07 μm or more and 0.2 μm or less.

Next, the first layer to the third layer of the multilayer film 20 will be described in detail.
The first layer is a thin film that is directly vapor-deposited on the glass beads 10 and has a uniform thickness, and is formed of _{TiO 2} or SiO _2. The first layer of this example is a SiO ₂ layer. By using the SiO ₂ layer as the first layer, _{the affinity with the glass beads 10 whose main component is SiO 2} is good, and the first layer is less likely to be peeled off from the glass beads 10.

The second layer is a thin film formed on the first layer and formed of a compound different from that of the first layer. The second layer is formed by _{the other of SiO 2} or TiO ₂ forming the first layer. In this example, since the first layer is the SiO ₂ layer, the second layer is the TiO ₂ layer.

The third layer is formed on the second layer and is composed of the same main components as the first layer, but is different from the thickness of the first layer. By setting different film thicknesses for the first layer and the third layer, the reflection of light is different. The third layer of this example is _{formed of two} SiO layers and has a thicker film thickness than the first layer. As a result, the period of the waveform of the light incident on the third layer is shorter than that of the first layer. Therefore, the interference action of the light incident on the multilayer film 20 is different depending on whether the third layer has the same thickness as the first layer and the third layer has a thickness different from that of the first layer. That is, the wavelength of the reflected light can be a specific wavelength.

Next, the reflection mechanism of the glass beads 10 forming the multilayer film 20 will be described.
FIG. 4 is a diagram illustrating a reflection mechanism of the glass beads 10 forming the multilayer film 20. FIG. 4A is a diagram for explaining the light incident on the glass beads 10 on which the multilayer film 20 is vapor-deposited, and FIG. 4B is a diagram for explaining the light incident on the multilayer film 20.
As illustrated in FIG. 4A, the glass bead 10 refracts infrared light incident on the glass bead 10 from the air on the surface of the glass bead 10, and the refracted light passes through the inside of the glass bead 10. And focus on the bottom. Then, the light is reflected at the same angle as the incident angle to the focal point, the reflected light is refracted again on the surface of the glass beads 10, and the light is emitted from the glass beads 10 in the same direction as the incident direction. At this time, as illustrated in FIG. 4B, the multilayer film 20 emits light rays having a wavelength of 800 nm to 950 nm rather than light rays having a wavelength of 450 nm to 750 nm due to the interference action of the light reflected by each layer constituting the multilayer film 20. Highly reflected, the glass beads 10 mainly reflect light rays having a wavelength of 800 nm to 950 nm in the same direction as the incident light rays. As a result, the retroreflecting material has a higher reflectance in the invisible light region than in the visible light region with respect to the retroreflected light.

As described above, in the multilayer film 20 formed on the glass beads 10 illustrated in FIG. 3, the thickness of each layer constituting the multilayer film 20 is set so that the reflectance of invisible light having a wavelength of 800 nm to 950 nm is 80% or more. Alternatively, the number of times of stacking is selected. Therefore, it is possible to control the wavelength of the light to be retroreflected by the combination of the number of layers and the thickness of each layer constituting the multilayer film 20.

_{In this example, TiO 2} is used as the layer having a high refractive index, _{but Nb 2} O ₅ , Ta ₂ O ₅ , or ZrO ₂ may be used as long as it has a high refractive index. _{Further, in this example, SiO 2} is used as the layer having a low refractive index, but if it has a low refractive index, Al ₂ O ₃ , La ₂ O ₃ , or Mg F ₂ may be used. However, _{the combination of TiO 2} and SiO ₂ is preferable because it has high reflection brightness, is less likely to cause cracks in the layer, and can be realized at low cost. Further, although the first layer is _{formed of SiO 2} , it may be formed of TiO _{2. In} this case, the second layer is formed of _{SiO 2.}

(Object detection device 5)
FIG. 5 is a diagram illustrating the functional configuration of the object detection program 50.
As illustrated in FIG. 5, the object detection program 50 includes an irradiation unit 500, a detection unit 502, a determination unit 504, and a notification unit 506. The object detection program 50 is a computer program installed in the object detection device 5 via a recording medium such as a CD-ROM.

The irradiation unit 500 causes the light source to irradiate invisible light. The irradiation unit 500 irradiates infrared rays when it is a light source that irradiates infrared rays, and irradiates ultraviolet rays when it is a light source that irradiates ultraviolet rays. Further, the irradiation unit 500 may continuously irradiate the light source with infrared rays, or may intermittently irradiate the light source with infrared rays.
The detection unit 502 detects the invisible light retroreflected by the retroreflective material 1 via the light receiving sensor. The detection unit 502 of this example detects infrared rays. The detection unit 502 detects infrared rays received by the light receiving sensor at the timing of irradiation from the light source.

The determination unit 504 determines the displacement of the object and the presence / absence of the object based on the detection result detected by the detection unit 502. A specific example is the case where the determination unit 504 of this example determines the presence or absence of an object. When the detection unit 502 detects the infrared rays retroreflected by the detection unit 502, the determination unit 504 determines that there is an object based on the result of detecting the infrared rays. That is, the worker wearing the work clothes 3 to which the retroreflective material 1 is attached determines that the worker is within the work range in which the bucket of the work vehicle 4 comes into contact. Further, when the determination unit 504 does not detect the infrared rays retroreflected by the detection unit 502, the determination unit 504 determines that there is no object based on the result of not detecting the infrared rays. That is, the worker wearing the work clothes 3 to which the retroreflective material 1 is attached determines that there is no worker within the work range in which the bucket of the work vehicle 4 comes into contact.

The notification unit 506 causes the warning display unit to notify the warning display unit based on the determination result that the determination unit 504 determines that the object exists. For example, when the warning display unit is a monitor, the notification unit 506 displays on the monitor that there is an operator, and when the warning display unit is a lamp, the lamp lights up to indicate that there is an operator and displays a warning. If the part is a speaker, make a voice notification that there is a worker.

FIG. 6 is a flowchart illustrating the object detection process (S10).
In the present process illustrated in FIG. 6, for example, steps 100 to 106 are continuously repeated while the work vehicle 4 is being operated. First, an outline of a series of flows will be described. As illustrated in FIG. 6, the object detection process (S10) includes a step of irradiating the retroreflective material 1 with invisible light (S100) and a step of detecting the retroreflected light of the irradiated invisible light (S102). ), A step of determining the presence or absence of an object based on the detected retroreflected light (S104), and a step of displaying a warning based on the determination result of determining the presence of an object (S106). Hereinafter, a detailed description will be given.

In step 100 (S100), the irradiation unit 500 causes the light source to irradiate infrared rays to the retroreflective material 1 attached to the worker's work clothes 3. That is, the light source irradiates the retroreflective material 1 whose reflectance in the invisible region is increased by using an interference film with invisible light or light containing invisible light.
In step 102 (S102), the detection unit 502 detects the infrared rays retroreflected by the retroreflective material 1 at the timing when the light emitted from the light source is retroreflected. That is, the detection unit 502 detects the retroreflected light whose wavelength is controlled by the interference film among the irradiated light.

In step 104 (S104), when the detection unit 502 detects the infrared rays retroreflected by the detection unit 502, the determination unit 504 determines that there is an object based on the detection result that the infrared rays have been detected. That is, the determination unit 504 determines that there is an operator who wears the work clothes 3 to which the retroreflective material 1 is attached. Then, the object detection process (S10) shifts to the process of S106. Further, when the detection unit 502 does not detect the retroreflected infrared rays, it is determined that there is no object based on the detection result that the infrared rays are not detected. That is, it is determined that no worker wears the work clothes 3 to which the retroreflective material 1 is attached. Then, the object detection process (S10) ends this process.
In step 106 (S106), the notification unit 506 notifies the warning display unit that the worker is within the range of contact with the bucket of the work vehicle 4 based on the determination result that the determination unit 504 determines that the object exists. Let me know.
In this way, it is possible to notify the operator who controls the work vehicle 4 so that the bucket of the work vehicle 4 does not come into contact with the operator.

FIG. 7 is a diagram illustrating the spectral characteristics of the multilayer film 20 formed on the retroreflective material 1.
As illustrated in FIG. 7, among the light reflected by the multilayer film 20 formed on the retroreflective material 1 of the present embodiment, the reflectance of each wavelength was investigated in the wavelength range of 350 nm to 1200 nm. As a result, it was confirmed that the reflectance of light rays was 80% or more in the wavelength range of 800 nm to 950 nm and that the reflectance of light rays was 20% or less in the wavelength range of 450 nm to 750 nm. It was also confirmed that the reflectance of light rays was 80% or more in the wavelength range of 380 nm to 410 nm. That is, it was confirmed that the light retroreflected by the retroreflective material 1 has a higher reflectance in the invisible light region than in the visible light region.
In the retroreflective material 1 of this example, the case where the reflectance in the invisible light region is higher than that in the visible light region has been described from the viewpoint of increasing the transparency, but the transmissivity of the retroreflective material 1 may be reduced. If so, a high reflectance that is substantially equal to or even slightly higher than that of the invisible light region may be provided in the visible region.

As described above, according to the retroreflective material 1 in the present embodiment, since the irradiated light is retroreflected, the direction in which the operator is located can be specified with reference to the irradiated position.
Although the embodiments according to the present invention have been described above, the present invention is not limited to these, and various changes, additions, and the like can be made without departing from the spirit of the invention.

Next, a modification of the above embodiment will be described.
In the modified example, elements having substantially the same function and configuration as those in the above embodiment are designated by the same reference numerals, so that duplicate description will be omitted.
[Modification example]
In the above embodiment, the case where the multilayer film 20 which is an interference film is formed by vapor deposition on a part of the surface of the glass beads 10 has been described, but the present invention is not limited to this, and the fixing layer 60 for fixing the glass beads 10 is not limited thereto. May contain a powdered interference film. Specifically, an interference film having an increased reflectance in an invisible region is formed by vapor deposition on the plate surface, and the formed interference film is finely powdered. The pulverized interference film is dispersed in the fixing resin, and the glass beads 10 are fixed to the base material 64 with the fixing resin in which the interference film is dispersed. As a result, the fixing layer 60 can contain a powdered interference film.

1 Retroreflective material 10 Glass beads 20 Multilayer film 60 Adhesive layer 62 Adhesive layer 64 Base material 5 Object detection device
500 Irradiation unit 502 Detection unit 504 Judgment unit 506 Notification unit

Claims (5)

A retroreflective material that uses an interference film to control the wavelength of reflected light to increase the reflectance of light of the target wavelength in the invisible light region. Retroreflective glass beads and
It has an interference film formed on a part of the surface of the glass beads.
The retroreflective material according to claim 1, wherein the film interference film is formed so as to have a high reflectance of ultraviolet rays or infrared rays. The retroreflective material according to claim 2, wherein the interference film is designed so that the reflectance of light rays having a wavelength of 800 nm to 1200 nm is 80% or more. The retroreflective material according to claim 3, which is transparent or translucent. A step of irradiating a retroreflective material whose reflectance in an invisible region is increased by using an interference film with invisible light or light containing invisible light, and
The step of detecting the retroreflected light whose wavelength is controlled by the interference film among the irradiated light,
An object detection method having a step of determining the presence / absence or displacement of an object based on the detected retroreflected light.

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