JP2019054400A - Lens and compound eye lens - Google Patents

Abstract

To provide a lens capable of preventing the communicable distance from being reduced.SOLUTION: A lens comprises multiple layers of thin films of refractive index nfor electromagnetic waves of wavelength λ propagating in a medium with refractive index n, which are arranged in layers, in which a part or all of the multiple thin films has almost the same shape as that of the convex lens shape, and n=(n×n). The thin film that has the largest area in the multiple thin films is in contact with the surface on which electromagnetic wave is incident on the surfaces of an obstacle which transmits the electromagnetic wave with a predetermined transmittance, in which the thickness in a direction perpendicular to the plane of the multiple films is an odd multiple of λ/(4×n).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a lens and a compound eye lens.

  In a fifth generation mobile communication system (hereinafter referred to as “5G”), it is considered to develop a base station (hereinafter referred to as “macrocell base station”) having a wide range of radio waves. In addition, in 5G, for areas where people are crowded, it is considered to develop not only macro cell base stations but also base stations with a narrow radio wave reach (hereinafter referred to as “small cell base stations”). . Furthermore, in 5G, an IoT (Internet of things) device having a wireless communication function and various measurement functions is installed in the city, and the load on the small base station is reduced by offloading the traffic of the small base station. Therefore, the installation of a wireless LAN (Local Area Network) access point is being studied. Therefore, in 5G, it is necessary to install not only a micro cell base station and a small cell base station but also a large number of IoT devices and wireless LAN access points. Hereinafter, when devices used for wireless communication such as IoT devices and wireless LAN access points are not distinguished from each other, they are referred to as wireless devices.

  FIG. 19 is a diagram illustrating a usage example of a conventional small cell base station. As shown in FIG. 19, when the small cell base station 801 is installed on the street where the buildings 800 are lined up (for example, the central street of Ginza), the place where the small cell base station is installed is a relatively high place ( For example, 20 [m] from the ground is considered. By installing the small cell base station 801 at a relatively high place on the wall surface of the building 800, a wireless communication service can be provided to a user on the sidewalk. However, when a large number of small cell base stations 801 and wireless devices are installed on the building wall surface, the street scenery may be damaged. Therefore, paying attention to the fact that many buildings 800 are provided with signboards 802 at relatively high places, a small cell base station 801 or a wireless device is located inside the signboard surface of the signboard 802 (hereinafter referred to as “inside the signboard”). It has been proposed to install. In this case, the sign 802 becomes an obstacle that prevents propagation of electromagnetic waves. Therefore, by installing the small cell base station 801 and the wireless device in the signboard, wireless communication in a street where buildings are lined up is possible without deteriorating the scenery. Further, when the small cell base station 801 or the wireless device is installed in the signboard, a power supply cable is already laid on many signboards 802, so that a construction for newly laying the power supply cable is unnecessary. Note that the data received by the small cell base station 801 is transmitted to the entrance base station 803 and transmitted to the base station controller using microwaves, light, or the like. Further, the data is transmitted to an aggregation station 804 such as a communication company via an optical line or the like.

FIG. 20 is a diagram illustrating a usage example of a conventional small cell base station. As a place where the small cell base station is installed, in addition to a street where buildings are lined up, for example, a concourse of a station, an underground shopping center around a station, a department store, or the like can be considered. In such a case, it has been proposed to install a wireless device on the ceiling, pillar, wall or the like. However, in this case as well, the landscape may be damaged. Therefore, as shown in FIG. 20, paying attention to the fact that the lighting device 903 is already installed on the ceiling 900, the pillar 901, the wall 902, etc., the small cell base station and the wireless device 904 are installed inside the casing of the lighting device 903. It has been proposed to do. In the lighting device 903, the globe is an obstacle to electromagnetic waves. Therefore, by installing the small base station and the wireless device 904 inside the lighting device 903, wireless communication at a station concourse or the like is possible without damaging the scenery. Further, since the power supply pipeline is already laid in the lighting device 903, construction for newly laying the power supply pipeline is unnecessary. The data received by the wireless device 904 is transmitted to the network connection point 905, and is transmitted to the network 907 (such as the Internet / Intranet) via the gateway device 906 via Ethernet (registered trademark), an optical fiber, or the like. .
When the wireless apparatus 904 taken up in FIG. 20 is an IoT device, the area indicated by hatching in FIG. 20 (corresponding to the “communicable range” in the small cell base station) is, for example, the IoT device (pyroelectric sensor / infrared ray). If it is a human sensor (such as a sensor or a fish-eye type surveillance camera), it represents a range in which a person in an indoor / indoor / facility situation can be detected. In addition, if the IoT device is a heat detection sensor that grasps a high temperature location from a remote location using infrared rays, or an illuminance sensor that catches flame light with high sensitivity, detection that can catch a fire is detected It can be rephrased as a range. A wireless device 904 equipped with these wireless communication functions can be installed inside the lighting device 903.

  As described above, according to the above-described examination assuming 5G, it is considered that opportunities to install a wireless device inside a signboard or lighting equipment will increase in the future.

Takahiro Tsuchiya, Kazuto Goto, Miki Tsuji, Toshisho Huang, Hideyuki Tsuboi, Satoshi Kurosaki, Atsushi Ota, Masataka Iizuka, "Experimental Evaluation of Wireless Entrance Environment for Street Small Cell Base Station by 75GHz Band Propagation Measurement", Science and Technology IEICE Technical Report RCS2017-74 (2017-06)

  However, when the wireless device is installed in a structure such as a signboard or a lighting device, part of the electromagnetic wave output from the wireless device is reflected by the obstacle. For this reason, the intensity of the electromagnetic wave that passes through the obstacle is reduced due to the generation of the reflected wave, which causes a problem that the communicable distance of the wireless device is shortened.

  In view of the above circumstances, an object of the present invention is to provide a technique capable of suppressing a reduction in a communicable distance.

One aspect of the present invention, a plurality of thin film of refractive index for electromagnetic radiation of wavelength λ having a refractive index propagates the medium is n ₁ is n _c is arranged in a layered shape part or all of the convex lens of said plurality of thin film , N _c = (n ₁ × n ₂ ) ^1/2 , and the thin film having the largest area among the plurality of thin films transmits the electromagnetic wave with a predetermined transmittance. A lens which is in contact with the surface on which the electromagnetic wave is incident among the surfaces of the obstacle to be made and whose thickness in the direction perpendicular to the surface of the plurality of thin films is an odd multiple of λ / (4 × n _c ) It is.

According to one embodiment of the present invention, a plurality of thin films having a refractive index of n _{2 with} respect to an electromagnetic wave having a wavelength λ propagating through a medium having a refractive index of n ₁ are arranged in a layer shape, and a part or all of the plurality of thin films has a convex lens shape. The thin film having the substantially same shape and having the largest area among the plurality of thin films is formed on the surface on the side on which the electromagnetic wave is incident among the surfaces of the obstacle that transmits the electromagnetic wave with a predetermined transmittance. A lens-like member that is in contact with a refractive index with respect to the electromagnetic wave is n ₂ , and is parallel to a surface with which the thin film with the refractive index of n ₂ is in contact with the obstacle, and the refractive index is n ₂ . A thin film-like member in contact with a surface existing on the opposite side of the surface in contact with the thin film, the thickness of the lens-like member in a direction perpendicular to the surface on which the electromagnetic wave is incident, and the electromagnetic wave of the obstacle is incident Thickness in the direction perpendicular to the surface on the side to be In the lens, the total thickness of the film member and the thickness in the direction perpendicular to the surface on which the electromagnetic wave is incident is an odd multiple of λ / (4 × n ₂ ).

One aspect of the present invention is the above-described lens, wherein a distance d _in between the plurality of thin films having substantially the same shape as the convex lens and the first antenna that radiates the electromagnetic wave is the first lens. In the case where the length D of the opening of the antenna and d _in ≧ 2D2 / λ, the shape substantially the same as the shape of the convex lens is the distance between the first antenna and the second antenna that receives the electromagnetic wave. If the d _all, that the sum _{d l} of the thickness of said plurality of thin film having a substantially identical shape to the shape of the convex _{lens, R = (n c -1)} d f, d f = d all - (d _in + d _l ) that is in contact with a spherical surface with a radius of curvature R.

One aspect of the present invention is the above-described lens, wherein a distance d _in between the plurality of thin films having substantially the same shape as the convex lens and the first antenna that radiates the electromagnetic wave is the first lens. In the case where the length D of the antenna opening and d _in <2D ² / λ, the shape that is substantially the same as the shape of the convex lens is a spherical surface with a radius of curvature R that satisfies R = (n _c −1) d _in. It is a shape that touches.

  One embodiment of the present invention is a compound eye lens including a plurality of the above lenses.

  According to the present invention, a communicable distance can be extended.

The figure which shows the specific example of the conventional radio | wireless communications system. The figure which shows the specific sectional drawing of the permeable member 1 of 1st embodiment. The figure which shows the specific structure which looked at the transmissive member 1 of 1st embodiment from the transmission antenna 701 side. The figure explaining the curvature radius R1 in the case where the transmissive member 1 of the first embodiment is sufficiently far from the transmission antenna 701. The figure explaining the curvature radius R2 in case the transmissive member 1 of 1st embodiment exists in the vicinity of the transmission antenna 701. FIG. The figure explaining the principle which the transmissive member 1 of 1st embodiment can suppress a reflected wave. The figure which shows the specific example in case the 1st thin film 11 which contact | connects the obstruction 702 does not contact | connect the circle | round | yen of curvature radius R1. The figure which shows the specific sectional drawing of the permeation | transmission member 2 of 2nd embodiment. The figure which shows the usage example of the permeation | transmission member 2 of 2nd embodiment in the radio | wireless communications system 7 of FIG. The figure of the simulation result which shows the relationship between the curvature radius R2 of the permeation | transmission member 2, and the distance dall of the transmitting antenna 701 and the receiving antenna 703 in FIG. The figure which shows the relationship between horizontal distance din + dL2 of the transmission antenna 701 and the obstruction 702, and the curvature radius R2 of the transmissive member 2. FIG. The figure which shows the specific example in case the 2nd thin film 12 which contact | connects the obstruction 702 does not contact | connect the circle | round | yen of curvature radius R2. The figure which shows the specific example of the structure which looked at the transparent member 1 of the modification from the front. The figure which shows the specific arrangement | positioning of the permeable member 1 in case the some transmissive member 1 contacts the obstruction 702. FIG. The figure which shows the specific example arrangement | positioning of the transmissive member 1 in the case of arranging a plurality of transmissive members 1 of the modification shown in FIG. 13 in the YZ plane. The figure which shows the path | route of the electromagnetic wave which propagates the obstruction 702. The figure which shows the specific example in case the transmissive member 1 or 2 is used in a non-approximation formation system. The figure which shows the path | route of the electromagnetic wave which propagates the obstruction 702a. The figure which shows the usage example of the conventional small cell base station. The figure which shows the usage example of the conventional small cell base station.

(Outline)
FIG. 1 is a diagram illustrating a specific example of a conventional wireless communication system 7. The conventional wireless communication system 7 includes a transmission antenna 701, an obstacle 702, and a reception antenna 703. In FIG. 1, the X axis of the XYZ coordinate system which is an orthogonal coordinate system is an axis parallel to the horizontal direction, and the Y axis is an axis parallel to the vertical direction.

The transmission antenna 701 is provided, for example, in a small cell base station, an IoT device, a wireless LAN access point, or the like. The transmission antenna 701 has an opening diameter D. The transmission antenna 701 exists at a position where the coordinate of its center point is h ₁ with a predetermined position as the coordinate origin. Hereinafter, the presence at such a position is expressed as being at the position of the height h ₁ . The coordinate origin may be, for example, the ground surface.

The obstacle 702 is a member that transmits incident electromagnetic waves with a predetermined transmittance, and is, for example, a signboard surface or a glove of a lighting device. The thickness of the obstacle 702 (i.e., the width of the X-axis direction) is _{d b.} The refractive index of the obstacle 702 with respect to the electromagnetic wave having the wavelength λ is n ₂ .

The reception antenna 703 is provided in, for example, an entrance base station or a network connection point. The receiving antenna 703 is present at a distance d _all away from the transmitting antenna 701 in the X-axis direction. The receiving antenna 703 is present at a height h ₂ that is H 1 away from h _{1 in the} positive Y-axis direction. Note that the difference in the vertical distance between the receiving antenna 703 and the transmitting antenna 701 is sufficiently shorter than the difference in the horizontal distance between the receiving antenna 703 and the transmitting antenna 701. That, H1 satisfies the relation of H1 _{<< d all.}
The transmission antenna 701, the obstacle 702, and the reception antenna 703 are arranged in the order of the transmission antenna 701, the obstacle 702, and the reception antenna 703 in the X-axis direction.

Some of the electromagnetic waves transmitting antenna 701 is radiated, the refractive index is propagated in the direction of the angle theta _a to the outside air of n ₁ with respect to the horizontal direction, transmitted through the obstacle 702. Electromagnetic waves transmitted through the obstacle 702, propagates in the direction of the angle theta _a fresh air in the refractive index n ₁ with respect to the horizontal direction reaches the receiving antenna 703. Note that θ _a satisfies the relationship of tan (θ _a ) = H1 / d _all .

The difference H1 of the vertical distance between the receiving antenna 703 and transmitting antenna 701 is sufficiently shorter than the difference _{d all} the horizontal distance between the receiving antenna 703 and transmitting antenna 701, a H1 _{/ d all} ≒ 0. That, theta _a satisfy the relationship of θ _a ≒ 0. This means that the incident angle of the electromagnetic wave on the obstacle 702 is close to 0 deg, and that the refraction angle of refraction by the electromagnetic wave obstacle 702 can be approximated to zero.

In the wireless communication system 7, the distance traveled by the electromagnetic wave passing through the obstacle 702 in the obstacle 702 is d _b / cos (θ _a ). In the wireless communication system 7, the distance the electromagnetic wave travels in the obstacle 702 are substantially the same length in the d _b. For simplicity below, particularly unless otherwise specified, a theta _a ≒ 0, in a wireless communication system 7, the distance electromagnetic waves traveling in the obstacle 702 will be described as a d _b.

For example, streets lined with outdoor buildings are examples of scenes where the wireless communication system 7 is used. In this case, the transmission antenna 701 may be installed, for example, inside a billboard on the building wall. In this case, for example, the height difference H1 between the transmission antenna 701 and the reception antenna 703 is 7 m, and the horizontal distance d _all May be 70 m. For example, a station concourse is an example of a usage scene of the wireless communication system 7. The transmission antenna 701 may be installed in a lighting device installed on an indoor wall or pillar. In this case, for example, the height difference H1 between the transmission antenna 701 and the reception antenna 703 (NW connection point or the like) may be 3 m, and the horizontal distance d _all may be 30 m. In these usage scenes, the relationship of 10 ≦ d _all / H1 and the relationship of θ _a <5.71 deg are satisfied. That is, in this case, 1 / cos (θ _a ) is about 1.005 and is substantially the same as 1.

The wireless communication system 7 is not limited to such a system, and the transmission antenna 701, the obstacle 702, and the reception antenna 703 are set so that the transmission antenna 701, the obstacle 702, and the reception antenna 703 satisfy θ _a ≈0. Any wireless communication system may be used as long as the wireless communication systems are arranged in this order.

  In each of the embodiments described below, it is possible to reduce the communicable distance by disposing a transmissive member configured to satisfy a predetermined condition on the obstacle 702 of the conventional wireless communication system shown in FIG. Suppress.

  Hereinafter, the transmissive member of the embodiment will be described with reference to the drawings.

(First embodiment)
FIG. 2 is a diagram illustrating a specific cross-sectional view of the transmission member 1 according to the first embodiment. The transmitting member 1 is in contact with the surface on the transmitting antenna 701 side among the surfaces parallel to the YZ plane of the obstacle 702 in the wireless communication system 7 of FIG. The transmitting member 1 suppresses the reflection of the incident electromagnetic wave on the surface of the obstacle 702 and condenses the incident electromagnetic wave on the receiving antenna 703. Note that the XYZ coordinates in FIG. 2 are the same as the XYZ coordinates in FIG.

The transmissive member 1 includes first thin films 11-1 to 11-5. The first thin film 11-1～5 has a thickness of _{d s1,} the thickness of the total formed by laminating a first film 11-1～5 as will be described later is _{d L1,} the refractive index _{n c} This is a dielectric thin film. Refractive index _{n c} is
n _c = (n ₁ × n ₂ ) ^1/2 (1)
Meet.
The total thickness d _L1 is
d _L1 = m × (λ / 4 × n _c ) (2)
Satisfy the relationship. In this formula (2), m is an odd number (m = 1, 3, 5,...), And λ is the wavelength of the electromagnetic wave incident on the transmissive member 1 in vacuum. The first thin film 11-1～5 Although each have the same thickness _{d s1} and refractive index _{n c,} shape or size is different. The first thin film 11-5 is in contact with the obstacle 702. The surface where the first thin film 11-5 is in contact with the obstacle 702 is a surface perpendicular to the positive X-axis direction (that is, the thickness direction).

  FIG. 3 is a diagram illustrating a specific configuration of the transmissive member 1 according to the first embodiment as viewed from the transmission antenna 701 side. The first thin films 11-1 to 11-5 are circular in the YZ plane, and the first thin film 11-1, the first thin film 11-2, the first thin film 11-3, the first thin film 11-4, The radius is short in the order of the first thin film 11-5.

Returning to the description of FIG. The first thin films 11-1 to 11-5 are the first thin film 11-1, the first thin film 11-2, the first thin film 11-3, the first thin film 11-4, and the first thin film 11-5. Are layered in order. More specifically, the first thin films 11-1 to 11-5 are laminated so as to form substantially the same shape as the convex lens shape. Therefore, the transmissive member 1 functions as a convex lens that collects incident electromagnetic waves. The thickness d _L1 of the X-axis direction of the transmission member 1, a superimposed first thin film 11-1～5 as previously described (stacked) thick, in the example of FIG. 2 d _L1 = D _s1 × 5 is satisfied. Therefore, d _s1 = (m / 5) × (λ / 4 × n _c ) from the previous equation (2). Here, m is an odd number.

  The radius of curvature of the convex lens shape formed by the first thin films 11-1 to 11-5 is the length R1. That is, the sizes of the first thin films 11-1 to 11-5 are adjusted so as to be in contact with the boundary of the circle having the curvature radius R1. The radius of curvature R1 is calculated by a method similar to the method of calculating the length of the radius of curvature of a commercially available lens based on the distances between the transmitting antenna 701, the obstacle 702, and the receiving antenna 703.

Hereinafter, the thin film whose refractive index satisfies the relationship of the formula (1) and whose thickness satisfies the relationship of the formula (2) is referred to as a first thin film 11.
Note that the transmission member 1 does not necessarily include the first thin film 11 of five sheets. If m is an odd number and the total thickness of a plurality of stacked layers is m / 4 times the wavelength within the substance, any number of sheets may be used. It may be.
In addition, the transmissive member 1 of the embodiment is not necessarily configured by the first thin film 11 having the same thickness, and is configured by a plurality of thin films having a refractive index of (n ₁ × n ₂ ) ^1/2. The thickness of the transmissive member 1 (that is, the width in the X-axis direction, d _L1 in FIG. 2) is an odd multiple of ¼ of the in-substance wavelength, and the shape of the transmissive member 1 is substantially the same as that of the convex lens. Any shape may be used as long as it has a shape.
Moreover, the transmissive member 1 may be formed by bonding the first thin film 11 like a seal, or may be formed by bonding the first thin films 11 together with an adhesive.

  FIG. 4 is a diagram illustrating the radius of curvature R1 when the transmissive member 1 of the first embodiment is sufficiently far from the transmission antenna 701. FIG.

In FIG. 4, the arrangement of the transmission antenna 701, the obstacle 702, and the reception antenna 703 is the same as that of the wireless communication system 7 of FIG.
In FIG. 4, the transmissive member 1 is sufficiently far from the transmitting antenna 701. Therefore, the electromagnetic wave radiated from the transmission antenna 701 is approximately a plane wave on the incident surface of the transmissive member 1. For example, if the distance between the transmitting antenna 701 and the transmission member 1 and _{d in, d in satisfy} the relation of _{d in} ≧ 2D ² _λ.

In general, the length r ₀ the radius of curvature of the convex lens for converging the focus of the focal length f ₀ of the electromagnetic wave of a plane wave incident on itself, the refractive index of the outside air is 1, the refractive index of itself as n _0, r ₀ = (N ₀ −1) f ₀ is satisfied.
On the other hand, the transmitting member 1 in FIG. 4 radiates from the transmitting antenna 701 and condenses the electromagnetic wave that is a plane wave incident on the transmitting member 1 on the receiving antenna 703.
Therefore, the radius of curvature R1 of the transmitting member 1 is the focal length is substantially the same in d _f in Figure 4,
R1 = (n _c −1) d _f (3)
It is expressed. Incidentally, _{d f} is the horizontal distance between the transmitting antenna 701 side of the surface of the receiving antenna 703 and the obstacle 702. That, _{d f} is the sum of the _{d out} and _{d b} in FIG. That is, in the situation shown in FIG. 4, when the transmissive member 1 is sufficiently far from the transmitting antenna 701, the above equation (3) for obtaining the radius of curvature is R1 = (n _c −1) (d _out + d _b ) It becomes. D _out is a horizontal distance between the receiving antenna 703 and the surface of the obstacle 702 on the receiving antenna 703 side.

  FIG. 5 is a diagram illustrating the radius of curvature R <b> 2 when the transmissive member 1 of the first embodiment is in the vicinity of the transmission antenna 701.

In FIG. 5, the arrangement of the transmission antenna 701, the obstacle 702, and the reception antenna 703 is the same as that of the wireless communication system 7 of FIG. In FIG. 5, the transmissive member 1 is in the vicinity of the transmission antenna 701. Therefore, the electromagnetic wave radiated from the transmission antenna 701 is approximately a spherical wave on the incident surface of the transmissive member 1. For example, the distance d _in between the transmission antenna 701 and the transmission member 1 satisfies the relationship d _in <2D ² λ.

In FIG. 5, the electromagnetic wave radiated from the point P on the transmission antenna 701 is transmitted through the transmission member 1 to be a plane wave, propagates in the outside air, and reaches the reception antenna 703.
Therefore, a focal length d _in, the curvature radius R1 of the transmitting member 1 in FIG. 4,
R1 = (n _c −1) d _in (4)
Satisfy the relationship.

  In FIG. 5, the electromagnetic wave transmitted through the transmissive member 1 is not collected at one point on the receiving antenna 703. However, the electromagnetic wave that has passed through the transmissive member 1 is converted into a plane wave electromagnetic wave that is not diffused by the diffusing spherical wave electromagnetic wave and is received by the receiving antenna 703. Hereinafter, this case is also referred to as light collection.

  FIG. 6 is a diagram for explaining the principle by which the transmissive member 1 of the first embodiment can suppress the reflected wave.

In FIG. 6, the incident wave L _i 1 and the incident wave L _i 2 are electromagnetic waves that propagate in the outside air in the same phase and are incident on the transmission member 1. The incident wave L _i 1 is reflected at the boundary between the transmission member 1 and the obstacle 702, propagates through the obstacle 702 as a reflected wave L _R 1 and exits to the outside air. The incident wave L _i 2 is reflected at the boundary between the outside air and the transmissive member 1 and propagates in the outside air as a reflected wave L _R 2. Hereinafter, when there is no need to distinguish between the incident wave _{L i} 1 and the reflected wave _{L R} 1, referred to the electromagnetic wave L1. Hereinafter, when the incident wave L _i 2 and the reflected wave L _R 2 are not distinguished, they are referred to as an electromagnetic wave L2.

  In general, electromagnetic waves are reflected at locations where substances having different refractive indexes come into contact. That is, a reflected wave is generated by an electromagnetic wave incident on a place where substances having different refractive indexes are in contact. However, when the phase difference between the reflected waves of the electromagnetic waves reflected at a plurality of locations is an odd multiple of 180 degrees, the reflected waves cancel each other. Therefore, the generation of reflected waves is suppressed.

The transmissive member 1 has a configuration in which a plurality of thin films are stacked, and the total thickness of the stacked thin films has m / 4 (m: odd number) of the in-substance wavelength (that is, λ / n _c ). Therefore, the electromagnetic wave L1 incident on the transmissive member 1 propagates longer than the electromagnetic wave L2 by an odd multiple of a half wavelength before being emitted to the outside as the reflected wave L _R 1. For this reason, the phase of the electromagnetic wave L1 advances more than that of the electromagnetic wave L2 by propagation by an approximately identical phase to an odd multiple of 180 degrees.

Moreover, the transmissive member 1 includes a first thin film 11 having a refractive index of (n ₁ × n ₂ ) ^1/2 . The equation of n _c = (n ₁ × n ₂ ) ^1/2 that the refractive index of the first thin film 11 satisfies is an equation that is generally known as an equation that gives the refractive index of the antireflection film of the optical element. Since the refractive index of the transmissive member 1 satisfies the formula n _c = (n ₁ × n ₂ ) ^1/2 , the phase shift when the electromagnetic wave L1 enters the obstacle 702 from the transmissive member 1 and is reflected, and the electromagnetic wave The phase shift when L2 is incident on the transmitting member 1 from the outside and reflected is substantially the same.

Thus, the transmissive member 1 has a refractive index of (n ₁ × n ₂ ) ^1/2 , and includes a plurality of first thin films 11 stacked in layers, where m is an odd number, and the overall thickness is a substance. since the inner wavelength is of m / 4, cancel each other in the outside air and the reflected wave _{L R} 2 of the reflected wave _{L R} 1 and an electromagnetic wave L2 of the electromagnetic wave L1. Therefore, the transmissive member 1 suppresses the generation of reflected waves.

Further, the transmissive member 1 configured as described above is formed by laminating a plurality of first thin films 11 having a refractive index of (n ₁ × n ₂ ) ^1/2 and m is an odd number. Therefore, the generation of the reflected wave of the electromagnetic wave incident on the obstacle 702 is suppressed, and the electromagnetic wave is condensed on the receiving antenna 703 to extend the communicable distance of the transmitting antenna 701. Can do. In particular, when a small wireless device such as an IoT device is used, the gain is not so large and the communication distance is short, but the communicable distance can be extended by the transmissive member 1 configured in this way.
Furthermore, the transmissive member 1 configured as described above can extend the communicable distance of the transmission antenna 701 only by being installed on the surface of the obstacle 702. Therefore, for example, as compared with a method of increasing the gain of the amplifier corresponding to the expansion of the antenna aperture to be used or the amplification of weak signals, the transmission member 1 of the embodiment has a large apparatus for extending the communicable distance. It is possible to increase the communicable distance while suppressing increase in installation cost and installation cost.

(Modification)
FIG. 7 is a diagram illustrating a specific example in a case where the first thin film 11 in contact with the obstacle 702 does not contact a circle with a radius of curvature R1. The transmissive member 1 in FIG. 7 includes a first thin film 11-6 instead of the first thin film 11-1 in the transmissive member 1 in FIG. The refractive index and thickness of the first thin film 11-6 are the same as those of the first thin film 11. The first thin film 11-6 has the same area as or wider than the first thin film 11-4 (see FIGS. 13 and 14 described later). The first thin film 11-6 contacts the obstacle 702 and does not contact the circle having the curvature radius R1. The first thin film 11-6 has the same or larger area as the first thin film 11-4, and has the same refractive index and thickness as the first thin film 11, and has a radius of curvature R1. Any thin film may be used as long as it is not in contact with the circle. For example, the first thin film 11-6 may have a shape that covers the entire surface of the obstacle 702 that it contacts. In this case, since it is not necessary to process the first thin film 11-6 into a shape in contact with the circle having the curvature radius R1, the effect of facilitating the creation of the transmission member 1 is achieved. Further, when the user attaches the transmissive member 1 including the first thin film 11-6 to the obstacle 702, the transmissive member 1 includes the first thin film 11-6, so that the user covers the obstacle 702. What is necessary is just to attach the permeable member 1 to. Therefore, the transmissive member 1 configured as described above has an effect of making it easy for the user to attach the transmissive member 1 to the obstacle 702. The area of the first thin film 11 is an area of a plane parallel to the YZ plane of the first thin film 11.

(Second embodiment)
FIG. 8 is a diagram illustrating a specific cross-sectional view of the transmission member 2 according to the second embodiment. The transmitting member 2 is in contact with a surface parallel to the YZ plane of the obstacle 702 in the wireless communication system 7 of FIG. The transmitting member 2 suppresses the reflection of the incident electromagnetic wave on the incident surface and condenses the incident electromagnetic wave on the receiving antenna 703. The XYZ coordinates in FIG. 8 are the same as the XYZ coordinates in FIG. In the following, the same components as those shown in FIGS.
Further, regarding the two reflected waves L1 and L2 described in FIG. 6, in FIG. 8, the reflected wave on the surface of the third thin film 13 (the previous L1 was the first thin film 11-1). And a reflected wave on the surface of the second thin film 12-5 (corresponding to L2 above).

The transmissive member 2 includes a lenticular member 21 and a third thin film 13. Lenticular member 21 and the third film 13 has a refractive index n _2. The lens-shaped member 21 has a convex lens shape and is in contact with the surface of the obstacle 702 on the transmission antenna 701 side. On the other hand, the third thin film 13 is in contact with the other surface of the obstacle 702 (that is, the surface on the receiving antenna 703 side). The thickness d _L2 of the lens-like member 21 of the transmissive member 2 and the thickness d _s3 of the third thin film 13 are _expressed as d _L2 + d _b + d _s3 = m × (λ / 4 × n ₂ ). The lenticular member 21 includes second thin films 12-1 to 12-5. The second thin films 12-1 to 12-5 have the same thickness d _s2 and refractive index n ₂ , respectively, but are different in shape or size. The second thin films 12-1 to 12-5 are circular in the YZ plane, and the second thin film 12-1, the second thin film 12-2, the second thin film 12-3, the second thin film 12-4, The radius is shorter in the order of the second thin film 12-5. Similar to the first thin film 11, the second thin film 12 is laminated so as to form a shape substantially the same as the convex lens shape. Therefore, the shape of the lens-shaped member 21 is substantially the same as that of the convex lens. The second thin films 12-1 to 12-5 are laminated so as to be in contact with the circle having the curvature radius R2, similarly to the first thin films 11-1 to 11-5. The curvature radius R2 is calculated by the same method as the curvature radius R1.

Hereinafter, a thin film having a refractive index of n ₂ and a thickness of d _s2 is referred to as a second thin film 12.
The transmission member 2 does not necessarily include the five second thin films 12, and the total thickness of all the third thin films 13 and the obstacles 702 is m, where m is an odd number. Any number of second thin films 12 may be provided as long as they are m / 4 times the inner wavelength.
Further, the lens-like member 21 of the embodiment does not necessarily need to be configured by the second thin film 12 having the same thickness. The lens-shaped member 21 may be configured in any way as long as it is configured to satisfy the following three conditions. The first condition, the total thickness of the refractive index of itself as n _2, and its thickness, the thickness of the obstacle 702 having a refractive index n _2, the thickness of the third thin film 13 having a refractive index n ₂ Is a thickness satisfying an odd multiple of 1/4 of the wavelength within the substance. The second condition is that the convex lens has substantially the same shape. The third condition is that the thin film has a refractive index of n ₂ .
Moreover, the transmissive member 2 may be formed by bonding the second thin film 12 like a seal, or may be formed by bonding the second thin films 12 with an adhesive.

The third thin film 13 suppresses generation of a reflected wave that is generated when an electromagnetic wave propagating through the obstacle 702 enters the outside air from the obstacle 702.
The third thin film 13 is a thin film having a refractive index of n ₂ and is in contact with the surface of the obstacle 702 opposite to the surface on which the second thin film 12 is in contact. Note that the surface of the third thin film 13 in contact with the obstacle 702 is a surface perpendicular to the thickness direction. The thickness d _s3 of the third thin film is such that d _L2 + d _b + d _s3 is an odd multiple of λ / (4 × n ₂ ).
That is, the thickness d _s3 of the third thin film is
d _L2 + d _b + d _s3 = λ / (4 × n ₂ ) × m (m: odd number) (5)
Satisfy the relationship. D _L2 is the thickness of the second thin films 12-1 to 12-5 stacked, and satisfies the relationship d _L2 = d _s2 × 5.
Since the thickness d _s3 of the third thin film is an odd multiple of λ / (4 × n ₂ ), generation of reflected waves of electromagnetic waves incident on the outside air from the obstacle 702 is suppressed by the same physical phenomenon as in FIG. Is done.
The third thin film 13 may cover the entire surface of the obstacle 702 with which the third thin film 13 is in contact, or may cover a part thereof.

  Next, the relationship between the radius of curvature R2 of the transmission member 2 of the second embodiment and the horizontal arrangement of the transmission antenna 701, the obstacle 702, and the reception antenna 703 will be described with reference to FIGS.

FIG. 9 is a diagram illustrating a usage example of the transmissive member 2 of the second embodiment in the wireless communication system 7 of FIG. 1. 9, the distance between the transmission member 2 and the transmission antenna 701 is d _in , and d _in satisfies the relationship (d _in ≧ 2D ² / λ. Therefore, the electromagnetic waves radiated from the transmission antenna 701 are transmitted through the transmission member 2. The transmitting member 2 condenses the incident electromagnetic wave on the receiving antenna 703.

Therefore, the radiating member 2 in FIG. 9 has the curvature radius R2 as in the description of FIG. 4 of the first embodiment.
R2 = (n _c −1) d _f (6)
Satisfy the relationship. D _f As described above, the horizontal distance between the transmitting antenna 701 side of the surface of the receiving antenna 703 and the obstacle 702. Therefore, in FIG. _9, d _f = d _{all -} a (d in _{+ d L2),} obtains a curvature radius (6) _{is, R2 = (n c -1)} {d all - (d in + d L2) }. Here, d _all is the horizontal distance between the transmitting antenna 701 and the receiving antenna 703.

FIG. 10 is a diagram of a simulation result showing the relationship between the radius of curvature R2 of the transmission member 2 and the distance d _all between the transmission antenna 701 and the reception antenna 703 in FIG. In the simulation of FIG. 10, d _all in FIG. 9 satisfies the relationship of 10 ≦ d _all / H1. In FIG. 9, an angle θ _a formed by a straight line connecting the center of the transmission antenna 701 and the center of the reception antenna 703 and the surface of the obstacle 702 satisfies the relationship of θ _a <5.71 deg.
10 is the same as FIG. 9 in that n ₁ = 1.00, n ₂ = 1.50, n _c = 1.22, d _in = 5 cm, d _L1 = 15λ / (4 × n _c ) = 15 × 0. If it is 4 / (4 × 1.22) ≒ 1.23cm, frequency representing the relationship between the radius of curvature R2 and _{d all} of the transmitting member 2 to be focused on the receive antenna 703 electromagnetic waves of 75 GHz. Here, d _in + d _L2 ≈6.7 cm is a fixed value, and the curvature radius R2 in the case where d _all is a value in the range of 0 to 200 m is obtained and shown. In FIG. 10, the entire thickness d _{L2 of} the transmissive member 2 formed by laminating the second thin film 12 is 45λ / (4 × n _c ) = 45 × 0.4 / (4 × 1.22) ≈ It is the result of the simulation set to 3.7 cm. Graph in Figure 10 _shows that a large radius of curvature R2 as _{d all} larger.

FIG. 11 is a diagram illustrating the relationship between the distance d _in + d _{L2 in} the horizontal direction between the transmitting antenna 701 and the obstacle 702 and the radius of curvature R2 of the transmissive member 2. In the simulation of FIG. 11, d _all in FIG. 9 satisfies the relationship of 10 ≦ d _all / H1.
The graph of FIG. 11 shows that an electromagnetic wave having a frequency of 75 GHz is applied to the receiving antenna 703 when n ₁ = 1.00, n ₂ = 1.50, n _c = 1.22, d _all = 200 m in FIG. The relationship between the curvature radius R2 of the condensing member 2 to condense and _dall is represented. Here, a graph of the radius of curvature R2 when d _all = 200 m is a fixed value and d _in + d _L2 is a value within the range of 0 to 40 cm is shown. The radius of curvature R2 is smaller as d _in + d _L2 is larger.

The transmissive member 2 configured in this manner has the same refractive index as that of the obstacle 702, and the second thin film 12− satisfying the relationship that d _L2 + d _b + d _s3 is an odd multiple of λ / (4n ₂ ). Since 1-5 and the 3rd thin film 13 are provided, the intensity | strength of the electromagnetic wave which permeate | transmits the obstruction 702 and is output to external air can be increased compared with the case where the transmissive member 2 is not provided. Further, the transmissive member 2 configured in this manner is formed by laminating a plurality of second thin films 12 so as to form a convex lens shape, m being an odd number, and the total thickness being the in-substance wavelength. Since m / 4 is set, electromagnetic waves can be collected on the receiving antenna 703. In addition, since the transmissive member 2 configured in this manner has the same refractive index as that of the obstacle 702, the transmissive member 2 can be produced using the same material as the obstacle 702, and the effect of facilitating the production of the transmissive member is achieved.
(Modification)

  The transmission member 2 does not necessarily require that all the second thin films 12 be in contact with the circle having the radius of curvature R2. For example, the second thin film 12 that is in contact with the obstacle 702 covers the entire surface of one side of the obstacle 702. And it is not necessary to touch the circle of curvature radius R2.

  FIG. 12 is a diagram showing a specific example when the second thin film 12 in contact with the obstacle 702 is not in contact with the circle having the curvature radius R2. The transmissive member 2 in FIG. 12 includes a second thin film 12-6 instead of the second thin film 12-1 in the transmissive member 2 in FIG. The refractive index and thickness of the second thin film 12-6 are the same as those of the second thin film 12. The second thin film 12-6 contacts the obstacle 702 and does not contact the circle having the curvature radius R2. For example, the second thin film 12-6 may have a shape that covers the entire surface of the obstacle 702 in contact with the transmission member 2. In this case, since it is not necessary to process the second thin film 12-6 into a shape in contact with the circle having the curvature radius R2, the effect of facilitating the creation of the transmissive member 2 is achieved. For the user, attaching the transmissive member 2 including the second thin film 12-6 to the obstacle 702 is different from attaching the transmissive member 2 including the second thin film 12-1 to the obstacle 702. Prior to mounting, the labor of processing the second thin film 12 into a shape in contact with the circle having the curvature radius R2 is reduced. Therefore, the transmissive member 1 configured as described above has an effect of making it easy for the user to attach the transmissive member 2.

  The shape and area of the second thin film 12-6 are the same as or wider than those of the second thin film 12-4, and the shape and area covering part or all of the surface of the obstacle 702 are included. Any shape and area may be used.

  Hereinafter, a modification common to the transmission member 1 of the first embodiment and the transmission member 2 of the second embodiment will be described with reference to FIGS. However, for the sake of simplicity, description will be made assuming that the transmissive member is the transmissive member 1. In addition, the number in parenthesis in FIGS. 13-15 shows that the member represented with the code | symbol may be sufficient. That is, for example, in FIG. 13, the reference numeral 1 (2) indicates that the transmissive member 1 or 2 may be used.

FIG. 13 is a diagram illustrating a specific example of a configuration in which the transmissive member 1 according to the modification is viewed from the front. The first thin film 11 of the transmissive member 1 does not necessarily have to be all circular in the YZ plane, and as shown in this figure, the shape in the YZ plane is a quadrangle, octagon, or the like. It may be non-circular.
As shown in FIG. 7, a part of the first thin film 11 of the transmission member 1 may be the first thin film 11 having an area covering the obstacle 702.

  In the transmissive member 1 of the modified example, only one transmissive member 1 may not necessarily contact the obstacle 702, and a plurality of transmissive members 1 may contact the obstacle 702.

  FIG. 14 is a diagram illustrating a specific arrangement of the transmissive members 1 when the plurality of transmissive members 1 are in contact with the obstacle 702. Hereinafter, a member including a plurality of transmission members 1 according to the embodiment is referred to as a first aggregate member 101. In the first assembly member 101, the transmission members 1 may be arranged so as to circumscribe each other. In this case, the in-plane density of the transmission member 1 in the first assembly member 101 is increased. Therefore, when the irradiation area of the electromagnetic wave to the obstacle 702 is wider than the area of the transmissive member 1, the first aggregate member 101 has an effect of condensing the electromagnetic wave more efficiently than the case where the single transmissive member 1 is used. Play.

  FIG. 15 is a diagram showing a specific arrangement of the transmissive member 1 when a plurality of transmissive members 1 of the modification shown in FIG. 13 are arranged in the YZ plane. Hereinafter, a member including a plurality of the transmissive members 1 according to the modified examples is referred to as a second aggregate member 102. In the second assembly member 102, as shown in the drawing, the transmissive member 1 of the modified example has thin films having a non-circular or circular shape such as a quadrangle or octagon in the YZ plane. A plurality of sheets may be arranged so as to contact each other.

<About the case where θ _a ≈0 cannot be considered>
Hereinafter, _a wireless communication system (hereinafter referred to as a “non-approximate system”) in which the transmission antenna 701, the obstacle 702, and the reception antenna 703 are provided in the same order as the wireless communication system 7 but cannot be regarded as θ _a ≈0 will be described. . In the non-approximation established system, each transmitting member 1 or 2 in the formula (3) to (6), replacing the _{d f} to _{d f / cos (θ a)} , a _{d b d b / cos (θ} a) The following formulas (7) to (10) substituted with:
R1 = (n _c −1) d _f / cos (θ _a ) (7)
R1 = (n _c −1) d _in / cos (θ _a ) (8)
(D _L2 + d _b + d _s3 ) / cos (θ _a ) = λ / (4 × n ₂ ) × m (9)
R2 = (n _c −1) d _f / cos (θ _a ) (10)

An example of a use scene of the non-approximation system is, for example, a rooftop of a building where a transmitting antenna 701 is installed in a billboard on a building wall 10 m from the ground and faces the building across a 30 m wide road (on the ground) 20 m) to a radio communication system in which a receiving antenna 703 is installed. In this case, since the horizontal distance d _all between the two antennas is 30 m and the height difference H1 is 10 m, 10> d _all / H1 (= 3) and 10 ≦ d _all / H1 and θ _a <5.71 deg. And are not satisfied. That is, θ _a ≈0 is not observed.

  Hereinafter, refraction of electromagnetic waves in a non-approximation system will be described.

FIG. 16 is a diagram illustrating a path of an electromagnetic wave propagating through the obstacle 702. FIG. 16 is an enlarged view of the obstacle 702 in FIG. 1 in order to make the path of the electromagnetic wave noticeable.
The electromagnetic wave radiated from the transmission antenna 701 enters the obstacle 702. The electromagnetic wave incident on the obstacle 702 is refracted and propagates through the obstacle 702. At the boundary where the obstacle 702 propagates to the outside air, the light enters the boundary at the incident angle θ _b and propagates in the outside air in the direction of the emission angle θ _a .
U is U = d _b / cos (θ _b ), where U is the distance (hereinafter referred to as “propagation path length”) through which the electromagnetic wave passes through the obstacle 702.

Considering Snell's law, n ₁ × sin (θ _b ) = n ₂ × sin (θ _a )
θ _b = arcsin (n ₁ × sin (θ _a )) / n ₂ (11)
Meet.
Therefore, the propagation path length U is U = d _b / cos {arcsin (n ₁ × sin (θ _a )) / n ₂ } (12)
It is.

Using Equations (11) and (12), the location on the receiving antenna 703 where the electromagnetic wave reaches due to the refraction of the electromagnetic wave by the obstacle 702 and the size thereof are specifically shown. In FIG. 16, the case where d _all = 30 m, H 1 = 10 m, d _b = 8 mm, n ₁ = 1.00 and n ₂ = 1.50 will be considered. First, since d _all = 30 m and H1 = 10 m, tan (θ _a ) = H1 / d _all = 10 / 30≈0.333. In this case, θ _a = 18.43 deg. Since sin (θ _a ) = 0.316, using equation (11),
θ _b = arcsin (n ₁ × sin (θ _a )) / n ₂
= Arcsin (1.00 × 0.316) /1.50
= 18.43 / 1.50
= 12.29 deg
It is.
Therefore, tan (θ _b ) = 0.218, and d _b {tan (θ _a ) −tan (θ _b )} ≈8 × {0.333−0.218} = 0.92 mm. Therefore, since H1 = 10 m, 0.92 mm / 10 m is a very small value of 0.0001 or less.
This indicates that even in a non-approximation system, there is an electromagnetic wave that propagates through substantially the same path as the wireless communication system 7 depending on conditions. Further, this indicates that the transmission member 1 or 2 satisfies the expressions (3) to (10) depending on the conditions even in a non-approximation system.

Incidentally, the propagation of when considering the case without consideration of the refraction by the electromagnetic obstacle 702 shall not be regarded as θ _a ≒ 0 (i.e., if the propagation path length and _{d 2 / cos (θ a)} ), the refractive The difference in path length is as follows. The propagation path length when refraction is not taken into account is d _b / cos (θ _a ) = 8 / 0.989 = 8.09 mm. On the other hand, the propagation path length when considering refraction is d _b / cos (θ _b ) = 8 / 0.949 = 8.19 mm. These differences (hereinafter referred to as “expression dependent path length differences”) are 0.24 mm. The equation-dependent path length difference is about 3% of the propagation path length when refraction is considered, and is a small value compared to the propagation path length when refraction is considered. Further, the formula depends path length difference is a small value as compared to the thickness d _b of the obstacle. This means that the transmissive member 1 or 2 satisfies part or all of the equations (3) to (10) with good accuracy depending on the conditions even in the non-approximation system. The good accuracy means that the transmission member 1 or 2 satisfying part or all of the expressions (3) to (10) is a position where the transmission member 1 or 2 satisfying the expressions (11) and (12) is condensed and It means that light is condensed at a position and range substantially the same as the range.

FIG. 17 is a diagram illustrating a specific example when the transmissive member 1 or 2 is used in a non-approximation system. Components having the same functions as those in FIG. 1 are denoted by the same reference numerals and description thereof is omitted.
In FIG. 17, the X axis of the XYZ coordinate system, which is an orthogonal coordinate system, is an axis parallel to the horizontal direction, and the Y axis is an axis parallel to the vertical direction.

The transmission antenna 701a is, for example, a small cell base station, an IoT device, a wireless LAN access point, or the like installed on an indoor ceiling. The transmission antenna 701a has an opening diameter D. The transmission antenna 701a exists at a position of height h ₃ (that is, Y coordinate is h ₃ ). Existence at the position of height h ₃ means that the Y coordinate of its center point is h ₃ . Transmitting antenna 701 is a Y-axis negative direction, radiating electromagnetic waves in the direction of the angle theta _a with respect to the vertical direction. The angle theta _a is a straight line in the vertical direction and an angle connecting the centers of the transmitting antenna 701a and the receiving antenna 703a.

The obstacle 702a is a member that transmits incident electromagnetic waves with a predetermined transmittance, and is, for example, a ceiling, a signboard surface, or a glove of a lighting device. Obstacles 702a has a thickness (i.e., the width of the Y-axis direction) is _{d b.} Refractive index for electromagnetic radiation of wavelength λ obstacle 702a is _{n 2.}

The reception antenna 703a is, for example, an entrance base station or a network connection point installed on an indoor wall. The receiving antenna 703a is present at a distance d _{all in the} X-axis direction with respect to the transmitting antenna 701a. Receive antenna 703a is present at a height _{h 5} is also separated by H2 in Y-axis negative direction from _{h 3.} Note that H2 does not satisfy the relationship of H2 << _dall . H2 is 5 m, for example, and d _all is 30 m, for example. The height of the indoor ceiling in FIG. 17 is h4, and an obstacle 702a also exists at the height h4.
The transmission antenna 701a, the obstacle 702a, and the reception antenna 703a are arranged in the order of the transmission antenna 701a, the obstacle 702a, and the reception antenna 703a in the negative Y-axis direction.

Transmitting antenna 701 is a Y-axis negative direction, the electromagnetic wave radiated in the direction of the angle theta _a to the vertical direction is transmitted through the obstacle 702a. Electromagnetic waves passing through the obstacle 702a is the outside air in the refractive index n ₁ propagates in the direction of the angle theta _a to the vertical, and reaches the receiving antenna 703a. The angle θ _a is, for example, 58.9 deg when H2 is 5 m and d _all is 30 m. In this case, 1 / cos (θ _a ) is substantially the same as 1.941.

  FIG. 18 is a diagram illustrating a path of an electromagnetic wave propagating through the obstacle 702a. In FIG. 18, the obstacle 702 a in FIG. 17 is illustrated in an enlarged manner in order to make the path of electromagnetic waves noticeable.

The electromagnetic wave radiated from the transmission antenna 701a enters the obstacle 702a. The electromagnetic wave incident on the obstacle 702a is refracted and propagates through the obstacle 702a. In the boundary propagating from the obstacle 702a to the outside air, and at an incident angle theta _b to the boundary, propagates in the direction of the emission angle theta _a to the outside air. The emitted electromagnetic wave enters the receiving antenna 703a.

As in FIG. 16, the angle θ _b is
θ _b = arcsin (n ₁ × sin (θ _a )) / n ₂ (13)
Meet. Further, in the same manner as in FIG. 16, _{d b} is
_{d b / cosθ b = d b} / cos {arcsin (n 1 × sinθ a) / n 2} ··· (14)
Meet.
Therefore, in FIGS. 17 and 18, transparent member 1 or 2 is substituted in equation (3), respectively to (6), the _{d f d f / cos {arcsin} (n 1 × sinθ a) / n 2}, the _{d b d b / cos {arcsin} (n 1 × sinθ a) / n 2} substituted expressions (7) satisfies to (10).

Using Expressions (13) and (14), the location on the receiving antenna 703a where the electromagnetic wave reaches due to the refraction of the electromagnetic wave by the obstacle 702a and the size thereof are specifically shown. In Figure _{18, d all = 30m, H2} = 5m, consider the case of _{d b = 8mm, n 1 =} 1.00 and _n 2 = 1.50. First, since d _all = 30 m and H 2 = 5 m, tan (θ _a ) = H 2 / d _all = 5 / 30≈0.166. In this case, θ _a = 9.46 deg. Since sin (θ _a ) = 0.164, using equation (13),
θ _b = arcsin (n ₁ × sin (θ _a )) / n ₂
= Arcsin (1.00 × 0.164) /1.50
= 9.46 / 1.50
= 6.31deg
It is.
Therefore, tan (θ _b ) = 0.111 and d _b {tan (θ _a ) −tan (θ _b )} ≈8 × {0.166−0.111} = 0.44 mm. Therefore, since H2 = 5 m, this means that the deviation of the position where the electromagnetic waves are collected is very small compared to the height difference between the antennas.
This indicates that, even in a non-approximate system, as in FIG. 16, there is an electromagnetic wave that propagates through substantially the same path as the wireless communication system 7 depending on the conditions.

  The transmitting member is an example of a lens. The outside air is an example of a medium. The third thin film 13 is an example of a thin film member. The first collective member 101 and the second collective member 102 are examples of compound eye lenses. The first thin film 11-1 in FIG. 2, the first thin film 11-6 in FIG. 7, and the second thin film 12-1 in FIG. 8 have the largest area among the plurality of thin films. It is an example of the thin film which has. The transmission antenna 701 is an example of a first antenna. The reception antenna 703 is an example of a second antenna.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Transmission member of 1st embodiment, 2 ... Transmission member of 2nd embodiment, 11 ... 1st thin film, 12 ... 2nd thin film, 13 ... 3rd thin film, 21 ... Lens-shaped member, 701 ... Transmitting antenna, 702 ... Obstacle, 703 ... Receiving antenna, 101 ... First assembly member, 102 ... Second assembly member

Claims (5)

Refractive index for electromagnetic radiation of wavelength λ having a refractive index propagates the medium is n ₁ is arranged in a plurality of thin film layered n _c, formed substantially the same shape part or all of the plurality of thin film in the shape of a convex lens And
n _c = (n ₁ × n ₂ ) ^1/2 ,
The thin film having the largest area among the plurality of thin films is in contact with the surface on which the electromagnetic wave is incident among the surfaces of the obstacle that transmits the electromagnetic wave with a predetermined transmittance,
The thickness of the plurality of thin films in the direction perpendicular to the surface is an odd multiple of λ / (4 × n _c );
lens. A plurality of thin films having a refractive index of n _{2 with} respect to an electromagnetic wave having a wavelength λ propagating through a medium having a refractive index of n ₁ are arranged in layers, and a part or all of the plurality of thin films form a shape substantially the same as that of a convex lens. A thin film having the largest area among the plurality of thin films, a lens-like member that is in contact with a surface on which the electromagnetic wave is incident among surfaces having an obstacle that transmits the electromagnetic wave with a predetermined transmittance;
Refractive index is an n ₂ with respect to the electromagnetic wave, among the surfaces of the obstacle has, the refractive index is parallel to the plane on which the thin film is in contact for n _2, opposite to the surface where the refractive index is in contact thin film of n ₂ A thin film member in contact with the surface present on the side;
With
The thickness of the lens-like member in the direction perpendicular to the surface on which the electromagnetic wave is incident, the thickness of the obstacle in the direction perpendicular to the surface on which the electromagnetic wave is incident, and the electromagnetic wave of the thin-film member are incident The total thickness with the thickness in the direction perpendicular to the surface to be
an odd multiple of λ / (4 × n ₂ ),
lens. The distance d _in between the plurality of thin films having substantially the same shape as the convex lens and the first antenna that radiates the electromagnetic wave is the length D of the opening of the first antenna and d _in ≧ 2D ^2. / Λ is substantially the same shape as the shape of the convex lens, the distance between the first antenna and the second antenna that receives the electromagnetic wave is d _all, and the shape is substantially the same as the shape of the convex lens. When the sum of the thicknesses of the plurality of thin films forming d ₁ is d ₁ , it touches a spherical surface with a radius of curvature R that satisfies R = (n _c −1) d _f , d _f = d _all − (d _in + d _l ) Shape,
The lens according to claim 1 or 2. The distance d _in between the plurality of thin films having substantially the same shape as the convex lens and the first antenna that radiates the electromagnetic wave is the length D of the opening of the first antenna and d _in <2D ^2. / Λ, the shape that is substantially the same as the shape of the convex lens is a shape that touches a spherical surface with a radius of curvature R that satisfies R = (n _c −1) d _in .
The lens according to claim 1 or 2. A plurality of lenses according to any one of claims 1 to 4,
Compound eye lens.

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