Receiving apparatus, communication apparatus, and communication system

Abstract

Provided is a reception device (1) comprising: a ball lens (11) for condensing optical signals propagating through a space in order to receive optical signals arriving from various directions, using an appropriate number of light-receiving elements (15); a light guide (13) constituted from a plurality of basic units (130) annularly arranged on the periphery of the ball lens (11), the light guide (13) guiding optical signals condensed by the ball lens (11) in a direction substantially perpendicular to the incidence direction of the optical signals; and a plurality of light-receiving elements (15) corresponding respectively to the plurality of basic units (130), the light-receiving elements (15) receiving optical signals emitted from the basic units (130) and outputting a signal derived from the received optical signals.

Description

Technical Field

[0001] The present disclosure relates to a receiving device that receives an optical signal propagating in space, etc.

Background Art

[0002] In free-space optical communication, optical signals (hereinafter also referred to as free-space optical signals) that propagate in space are transmitted and received without using a medium such as an optical fiber. In order to receive a free-space optical signal that spreads and propagates in space, it is preferable to use a lens with as large a diameter as possible. In free-space optical communication, in order to perform high-speed communication, a light-receiving element with a small capacitance is adopted. Such a light-receiving element has a small area of the light-receiving portion. Since there is a limit to the focal length of the lens, it is difficult to guide free-space optical signals arriving from various directions to the small-area light-receiving portion using a large-diameter lens.

[0003] Patent Document 1 discloses an optical receiving device aimed at enabling highly efficient reception with less angular dependence for a wide light-receiving angle. The device of Patent Document 1 includes a spherical lens, an optical fiber bundle, and at least one light-receiving element. The spherical lens condenses light incident from a wide angle onto one end face of the optical fiber bundle. The optical fiber bundle is a bundle structure in which a plurality of optical fibers are assembled. One end face of the optical fiber bundle is a planar light-incident portion. The light-incident portion is provided at the focal distribution position of the spherical lens. At least one light-receiving element is provided at the other end face of the optical fiber bundle. At least one light-receiving element receives the emitted light emitted from the other end face of the optical fiber bundle.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the method of Patent Document 1, the light condensed by the spherical lens is received by an optical fiber bundle composed of a plurality of optical fibers. The angle at which each individual optical fiber can condense light is very limited. Therefore, the incident surface of each individual optical fiber needs to be arranged substantially perpendicular to the spherical lens. As a result, one end face side of the optical fiber bundle becomes larger than the diameter of the spherical lens. For example, even without using optical fibers, if the periphery of the ball lens is surrounded by a strip-shaped sensor array, optical signals arriving from 360-degree azimuths can be received. However, when configured in this way, the number of light receiving elements becomes extremely large.

[0006] An object of the present disclosure is to provide a receiving device or the like that can receive optical signals arriving from various directions using an appropriate number of light receiving elements.

Means for Solving the Problems

[0007] The receiving device according to one aspect of the present disclosure includes a ball lens that condenses an optical signal propagating in space, a light guide that is constituted by a plurality of basic units annularly arranged around the ball lens, and guides the optical signal condensed by the ball lens in a direction substantially perpendicular to the incident direction of the optical signal, and a plurality of light receiving elements that are associated with each of the plurality of basic units, receive the optical signal emitted from the basic unit, and output a signal derived from the received optical signal.

Effects of the Invention

[0008] According to the present disclosure, it becomes possible to provide a receiving device or the like that can receive optical signals arriving from various directions using an appropriate number of light receiving elements.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

Figure 19

Figure 20

Figure 21

Figure 22

Figure 23

Figure 24

Figure 25

Figure 26

Figure 27

Figure 28

Figure 29

Figure 30

Figure 31

Figure 32

Figure 33

Figure 34

Figure 35

Figure 36

Figure 37

Figure 38

Figure 39

Figure 40

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, although the embodiments described below have technically preferable limitations for carrying out the present invention, they do not limit the scope of the invention below. In all the drawings used in the following description of the embodiments, the same reference numerals are given to the same parts unless otherwise specified. Also, in the following embodiments, repeated descriptions of the same configuration and operation may be omitted.

[0011] In all the drawings used in the following description of the embodiments, the directions of the arrows in the drawings are shown as an example and do not limit the directions of light and signals. Also, the lines indicating the trajectories of light in the drawings are conceptual and do not accurately represent the actual traveling directions and states of light. For example, in the drawings, changes in the traveling directions and states of light due to refraction, reflection, diffusion, etc. at the interface between air and a substance may be omitted, or a light beam may be represented by a single line. Also, depending on reasons such as illustrating the optical path or the configuration being complex, hatching may not be applied to the cross-sectional view.

[0012] (First Embodiment) First, the receiving apparatus according to the present embodiment will be described with reference to the drawings. The receiving apparatus of the present embodiment is used for optical space communication that transmits and receives optical signals propagating in space (hereinafter also referred to as spatial optical signals) without using a medium such as an optical fiber. The receiving apparatus of the present embodiment may be used for applications other than optical space communication as long as it is for the purpose of receiving light propagating in space. In the present embodiment, unless otherwise specified, the spatial optical signal is regarded as parallel light because it arrives from a sufficiently distant position. Note that the drawings used in the description of the present embodiment are conceptual and do not accurately depict the actual structure.

[0013] (Configuration) FIGS. 1 to 3 are conceptual diagrams showing an example of the configuration of the receiving apparatus 1 according to the present embodiment. The receiving apparatus 1 includes a ball lens 11, a light guide 13, and a plurality of light receiving elements 15. FIG. 1 is a plan view of the receiving apparatus 1 as viewed from above. FIG. 2 is a side view of the receiving apparatus 1 as viewed from the side. The ball lens 11 and the light guide 13 are fixed to each other by a support (not shown). In the present embodiment, the support for fixing the light guide 13 to the ball lens 11 is omitted.

[0014] The ball lens 11 is a spherical lens. The ball lens 11 is an optical element that condenses the spatial optical signal arriving from the outside. The ball lens 11 is spherical when viewed from any angle. The ball lens 11 condenses the incident spatial optical signal. The light (also referred to as an optical signal) derived from the spatial optical signal condensed by the ball lens 11 is condensed toward the condensing region. Since the ball lens 11 is spherical, it condenses the spatial optical signal arriving from any direction. That is, the ball lens 11 exhibits the same condensing performance for the spatial optical signal arriving from any direction.

[0015] FIG. 3 is a conceptual diagram showing an example of the trajectory of light focused by the ball lens 11. In the example of FIG. 3, it shows how the light irradiated from the light source 110 that emits parallel light toward the ball lens 11 is refracted by the ball lens 11. The light incident on the ball lens 11 is refracted when entering the inside of the ball lens 11. Also, the light traveling inside the ball lens 11 is refracted again when exiting to the outside of the ball lens 11. Most of the light emitted from the ball lens 11 is focused in the focusing region. On the other hand, the light incident from the periphery of the ball lens 11 is emitted in a direction deviating from the focusing region when exiting the ball lens 11.

[0016] For example, the ball lens 11 can be made of materials such as glass, crystal, and resin. When receiving a spatial optical signal in the visible region, materials such as glass, crystal, and resin that transmit / refract light in the visible region can be applied to the ball lens 11. For example, optical glasses such as crown glass and flint glass can be applied to the ball lens 11. For example, crown glass such as BK (Boron Kron) can be applied to the ball lens 11. For example, flint glass such as LaSF (Lanthanum Schwerflint) can be applied to the ball lens 11. For example, the bo For the ball lens 11, quartz glass can be applied. For example, for the ball lens 11, crystals such as sapphire can be applied. For example, for the ball lens 11, transparent resins such as acrylic can be applied. When the spatial light signal is light in the near-infrared region (hereinafter also referred to as near-infrared light), a material that transmits near-infrared light is used for the ball lens 11. For example, when receiving a spatial light signal in the near-infrared region of about 1.5 micrometers (μm), in addition to glass, crystals, resins, etc., materials such as silicon can be applied to the ball lens 11. When the spatial light signal is light in the infrared region (hereinafter also referred to as infrared light), a material that transmits infrared light is used for the ball lens 11. For example, when the spatial light signal is infrared light, materials such as silicon, germanium, and chalcogenide-based materials can be applied to the ball lens 11. As long as the light in the wavelength region of the spatial light signal can be transmitted / refracted, there is no limitation on the material of the ball lens 11. The material of the ball lens 11 may be appropriately selected according to the required refractive index and application.

[0017] The light guide 13 is arranged in the light condensing region of the ball lens 11 so as to surround the periphery of the ball lens 11. The light guide 13 is composed of a plurality of basic units 130. The basic unit 130 has an incident surface facing the ball lens 11 and an exit surface facing the light receiving portion of the light receiving element 15. The incident surface is provided on a part of the side surface of the basic unit 130. The exit surface (also referred to as the exit end) is provided on the end surface of the basic unit 130. The incident surface and the exit surface are formed on surfaces perpendicular to each other.

[0018] Figures 4 to 5 are conceptual diagrams for explaining an example of the basic unit 130 constituting the light guide 13. Figure 4 is a side view of the basic unit 130 as viewed from the side of the ball lens 11. Figure 5 is a cross-sectional view of the basic unit cut along the A-A cutting line in Figure 4. Figures 4 to 5 show an example of the beam spot of the light signal condensed by the ball lens 11 and the path of the light signal traveling inside the basic unit 130.

[0019] The basic unit 130 includes a light guide 133 and a diffraction element 135. The light guide 133 is the main body of the basic unit 130. FIG. 4 illustrates the diffraction element 135 disposed on the second surface side, which is visible through the light guide 133 from the side of the first surface.

[0020] The light guide 133 has a first surface facing the ball lens 11 and a second surface facing the first surface. The light guide 133 has an incident surface 131 and an exit surface 137. The incident surface 131 is provided on a part of the first surface of the light guide 133. The exit surface 137 is provided on a part of the side surface of the light guide 133. The incident surface 131 and the exit surface 137 are formed on surfaces orthogonal to each other.

[0021] The light guide 133 has a narrowed shape from the portion where the incident surface 131 is provided to the portion where the exit surface 137 is provided. In the case of the example in FIG. 4, the portion of the light receiving range (vertical light receiving range) where the incident surface 131 is provided is rectangular. The portion where the exit surface 137 is provided is a trapezoid that tapers from one side of the rectangle of the vertical light receiving range toward the light receiving portion 150 of the light receiving element 15. The shape of the basic unit 130 is not limited to the shape in FIG. 4. For example, the basic unit 130 may be a teardrop shape that tapers from the vertical light receiving range toward the light receiving portion 150. For example, the vertical light receiving range of the basic unit 130 may have a shape other than a rectangle.

[0022] The light guide 133 guides the optical signal that has entered the inside of the light guide 133 from the vertical light receiving range of the first surface toward the exit surface 137. The signal light that has entered the inside of the light guide 133 is reflected by the first surface and the second surface of the light guide 133 and guided to the light receiving portion 150 of the light receiving element 15. The light guide 133 is formed of a material that transmits the signal light. For example, the light guide 133 can be formed of a material such as glass or plastic. Note that as long as the signal light can pass through, there is no limitation on the material of the light guide 133.

[0023] The diffraction element 135 is an element that guides the optical signal entering from the incident surface 131 toward the light-receiving portion 150 of the light-receiving element 15. The diffraction element 135 is a kind of optical path-changing member. The diffraction element 135 has a diffraction surface that diffracts the optical signal incident from the incident surface 131 toward the exit surface 137. The diffraction element 135 is disposed on the second surface facing the first surface on which the incident surface 131 of the light guide 133 is formed. For example, the diffraction element 135 is provided inside the light guide 133. For example, the diffraction element 135 is disposed with its diffraction surface facing the surface facing the incident surface 131 of the light guide 133. The diffraction element 135 diffracts the optical signal that has entered the inside of the light guide 133 from the incident surface 131 toward the exit surface 137 where the light-receiving element 15 is disposed.

[0024] For example, the diffraction element 135 is composed of a reflective diffraction grating having a structure in which a plurality of gratings with a height on the order of micrometers are arranged. For example, the diffraction element 135 is configured by changing the grating pitch so that the total reflection condition is satisfied. For example, the diffraction element 135 diffracts the light so that the optical signal entering from the incident surface 131 of the light guide 133 travels toward the exit surface 137 while satisfying the total reflection condition. For example, the diffraction element 135 can be realized by a blazed diffraction grating or a holographic diffraction grating.

[0025] Each of the plurality of light-receiving elements 15 is associated with each of the plurality of basic units 130 constituting the light guide 13 and is disposed on the exit surface 137 of the light guide 13. The light-receiving element 15 includes a light-receiving portion 150 that receives an optical signal derived from the spatial optical signal to be received. Each individual light-receiving element 15 is disposed with its light-receiving portion 150 facing the exit surface 137 of the light guide 133 of the basic unit 130. The optical signal condensed by the ball lens 11 has its traveling direction changed by the light guide 13 and is received by the light-receiving portion 150 of the light-receiving element 15. The light-receiving surface of each individual light-receiving element 15 includes a region where the light-receiving portion 150 is located (also referred to as the light-receiving region) and a region where the light-receiving portion 150 is not located (also referred to as the insensitive region).

[0026] The light-receiving element 15 receives light in the wavelength range of the spatial optical signal to be received. For example, the light-receiving element 15 has sensitivity to light in the visible region. For example, the light-receiving element 15 has sensitivity to light in the infrared region. The light-receiving element 15 has sensitivity to light with a wavelength in the band of, for example, 1.5 μm (micrometer). Note that the wavelength band of light to which the light-receiving element 15 has sensitivity is not limited to the 1.5-μm band. The wavelength band of light received by the light-receiving element 15 can be arbitrarily set according to the wavelength of the spatial optical signal transmitted from a transmission device (not shown). The wavelength band of light received by the light-receiving element 15 may be set, for example, to the 0.8-μm band, the 1.55-μm band, or the 2.2-μm band. Also, the wavelength band of light received by the light-receiving element 15 may be, for example, in the 0.8 to 1-μm band. A shorter wavelength band is advantageous for optical space communication during rainfall because absorption by moisture in the atmosphere is small. Also, if the light-receiving element 15 is saturated by intense sunlight, the optical signal derived from the spatial optical signal cannot be read. Therefore, a color filter that selectively passes light in the wavelength band of the spatial optical signal may be installed in front of the light-receiving element 15.

[0027] For example, the light-receiving element 15 can be realized by an element such as a photodiode or a phototransistor. For example, the light-receiving element 15 is realized by an avalanche photodiode. The light-receiving element 15 realized by an avalanche photodiode can support high-speed communication. Note that the light-receiving element 15 may be realized by an element other than a photodiode, a phototransistor, or an avalanche photodiode as long as it can convert an optical signal into an electrical signal. In order to improve the communication speed, it is preferable that the light-receiving portion 150 of the light-receiving element 15 be as small as possible. For example, the light-receiving portion 150 of the light-receiving element 15 has a light-receiving surface in the shape of a square with a side length of about 5 mm (millimeter). For example, the light-receiving portion 150 of the light-receiving element 15 has a light-receiving surface in the shape of a circle with a diameter of about 0.1 to 0.3 mm. The size and shape of the light-receiving portion 150 of the light-receiving element 15 may be selected according to the wavelength band of the spatial optical signal, the communication speed, and the like.

[0028] The light-receiving element 15 converts the received optical signal into an electrical signal. The light-receiving element 15 outputs the converted electrical signal to a receiving circuit (not shown). The configuration including the receiving circuit will be described later.

[0029] FIG. 6 is a conceptual diagram showing an example in which the receiving device 1 receives a spatial optical signal. FIG. 6 is a plan view of the receiving device 1 as viewed from above. Since the ball lens 11 is spherical, the receiving device 1 can equally receive spatial optical signals arriving from any direction as long as they are within the range that can be received by the light guide 13. For example, when the plane formed by the light guide 13 is set parallel to the horizontal plane, the receiving device 1 is likely to receive spatial optical signals arriving horizontally from the same height. For example, when the plane formed by the light guide 13 is set perpendicular to the horizontal plane, the receiving device 1 is similarly likely to receive spatial optical signals arriving from any height.

[0030] FIG. 7 is a conceptual diagram for explaining the light-receiving range of the spatial optical signal that can be received by the receiving device 1. FIG. 7 is a plan view of the receiving device 1 as viewed from above. Although part of the light of the spatial optical signal arriving toward the ball lens 11 is blocked by the light guide 13 and the light-receiving element 15, most of it is condensed by the ball lens 11 and received by the light-receiving element 15 via the light guide 13. As shown in FIG. 7, the receiving device 1 can receive spatial optical signals arriving from 360-degree directions within a plane parallel to the plane including the circle formed by the light guide 13.

[0031] As described above, the receiving apparatus of the present embodiment includes a ball lens, a light guide, and a plurality of light receiving elements. The ball lens condenses an optical signal propagating in space. The light guide is composed of a plurality of basic units arranged annularly around the ball lens. The basic unit includes a light guide and a light traveling direction changing member. The light guide includes a first surface including an incident surface on which the optical signal condensed by the ball lens is incident, a second surface facing the first surface, and an output end from which the optical signal incident from the incident surface exits. The light traveling direction changing member is disposed at a position facing the incident surface on the side of the second surface. The light traveling direction changing member changes the traveling direction of the optical signal incident from the incident surface toward the output end. The light traveling direction changing member is a diffraction element that diffracts the optical signal incident from the incident surface toward the output end. The light guide guides the optical signal condensed by the ball lens in a direction substantially perpendicular to the incident direction of the optical signal. The basic unit is arranged to guide the optical signal entering from the incident surface in a direction perpendicular to the surface formed by the arrangement of the plurality of basic units. Each of the plurality of light receiving elements is associated with each of the plurality of basic units. The light receiving element receives the optical signal emitted from the basic unit. The light receiving element has a light receiving portion that receives light in the wavelength region of the optical signal, and is arranged toward the output end of the basic unit. The light receiving element outputs a signal derived from the received optical signal.

[0032] The receiving apparatus of the present embodiment uses a diffraction element included in any one of the plurality of basic units constituting the light guide to guide optical signals arriving from various directions toward the light receiving element associated with that basic unit. According to the receiving apparatus of the present embodiment, optical signals arriving from various directions can be received collectively for each basic unit constituting the light guide, so that the number of light receiving elements can be reduced. Therefore, according to the receiving apparatus of the present embodiment, optical signals arriving from various directions can be received using an appropriate number of light receiving elements.

[0033] (Second Embodiment) Next, a receiver according to the second embodiment will be described with reference to the drawings. The receiver of this embodiment differs from that of the first embodiment in the configuration of the light guide. Note that the drawings used in the description of this embodiment are conceptual and do not accurately depict the actual structure.

[0034] (Configuration) Figs. 8 to 9 are conceptual diagrams showing an example of the configuration of the receiver 2 according to this embodiment. The receiver 2 includes a ball lens 21, a light guide 23, and a plurality of light receiving elements 25. Fig. 8 is a plan view of the receiver 2 as viewed from above. Fig. 9 is a side view of the receiver 2 as viewed from the side. The ball lens 21 and the light guide 23 are fixed in their relative positions by a support (not shown). In this embodiment, the support for fixing the light guide 23 to the ball lens 21 is omitted.

[0035] The ball lens 21 has the same configuration as the ball lens 11 of the first embodiment. The ball lens 21 condenses the spatial optical signal arriving from the outside onto the condensing region of the ball lens 21.

[0036] The light guide 23 is arranged around the ball lens 21 so as to surround the periphery of the ball lens 21 in the condensing region of the ball lens 21. The light guide 23 is composed of a plurality of basic units 230. The basic unit 230 has an incident surface directed toward the ball lens 21 and an exit surface (also referred to as an exit end) directed toward the light receiving portion of the light receiving element 25. The incident surface is provided on a part of the side surface of the basic unit 230. The exit surface is provided on the end surface of the basic unit 230. The incident surface and the exit surface are formed on surfaces orthogonal to each other.

[0037] Figs. 10 to 11 are conceptual diagrams for explaining an example of the basic unit 230 constituting the light guide 23. Fig. 10 is a side view of the basic unit 230 as viewed from the side of the ball lens 21. Fig. 11 is a cross-sectional view of the basic unit 230 cut along the cutting line B-B in Fig. 10. Fig. 11 shows an example of the path of the optical signal traveling inside the basic unit 230.

[0038] The basic unit 230 includes a light guide 233 and a multi-mirror 235. The light guide 233 is the main body of the basic unit 230. FIG. 10 illustrates the multi-mirror 235 disposed on the second surface side that can be seen through the light guide 233 from the side of the first surface.

[0039] The light guide 233 has the same configuration as the light guide 133 of the first embodiment. The light guide 233 has a first surface facing the ball lens 21 and a second surface facing the first surface. The light guide 233 has an incident surface 231 and an exit surface 237. The incident surface 231 is provided on a part of the first surface of the light guide 233. The exit surface 237 is provided on a part of the side surface of the light guide 233. The incident surface 231 and the exit surface 237 are formed on surfaces orthogonal to each other.

[0040] The light guide 233 guides the optical signal that has entered the interior of the light guide 233 from the incident surface 231 on the first surface toward the exit surface 237. The signal light that has entered the interior of the light guide 233 is reflected by the first surface and the second surface of the light guide 233 and is guided to the light receiving portion 250 of the light receiving element 25.

[0041] The multi-mirror 235 is a structure that guides the optical signal that has entered from the incident surface 231 toward the light receiving portion 250 of the light receiving element 25. The multi-mirror 235 is a type of optical path changing member. The multi-mirror 235 has a plurality of reflecting surfaces that reflect the optical signal incident from the incident surface 231 toward the exit surface 237. The multi-mirror 235 has a plurality of arc-shaped reflecting surfaces with a center of curvature in the direction of the exit surface 237. Note that the shape of the reflecting surface of the multi-mirror 235 may be a curve such as a parabola, hyperbola, or ellipse instead of an arc shape. For example, the multi-mirror 235 is disposed with its reflecting surface facing the second surface that faces the first surface on which the incident surface 231 of the light guide 233 is formed. The multi-mirror 235 diffracts the optical signal that has entered the interior of the light guide 233 from the incident surface 231 toward the exit surface 237 where the light receiving element 25 is disposed.

[0042] As shown in FIG. 11, the reflecting surface of the multi-mirror 235 has the shape of a right triangle. A reflecting surface is formed on the inclined surface of the reflecting surface (right triangle) of the multi-mirror 235. The inclined surface forming the reflecting surface of the multi-mirror 235 is set such that the optical signal incident from the incident surface 231 travels toward the emission surface 237. Note that the cross section of the reflecting surface of the multi-mirror 235 may be formed in a curved shape instead of a linear shape. The plurality of reflecting surfaces constituting the multi-mirror 235 are formed such that the height of the vertex on the first surface side gradually decreases from the incident surface 231 toward the emission surface 237. The optical signals reflected by the plurality of reflecting surfaces constituting the multi-mirror 235 travel toward the emission surface 237 of the light guide 233.

[0043] For example, a multi-mirror 235 can be formed by forming an excavation surface by cutting the second surface side of the light guide 233 and providing a reflective layer on the excavation surface. For example, a reflective layer can be formed by depositing a material with high reflectivity such as metal on the excavation surface of the light guide 233. For example, a reflective layer can be formed by depositing metal on the excavation surface of the light guide 233. For example, the multi-mirror 235 may be formed by processing the second surface of the light guide 233 by etching or the like. For example, the multi-mirror 235 may be formed on the second surface of the light guide 233 formed by injection molding or a 3D printer.

[0044] The light receiving element 25 has the same configuration as the light receiving element 15 of the first embodiment. Each of the plurality of light receiving elements 25 is associated with each of the plurality of basic units 230 constituting the light guide 23 and is disposed on the emission surface 237 of the light guide 23. The light receiving element 25 includes a light receiving portion 250 that receives an optical signal derived from the spatial optical signal to be received. Each individual light receiving element 25 is disposed on the emission surface 237 of the light guide 233 of the basic unit 230 with the light receiving portion 250 facing it. The optical signal condensed by the ball lens 21 has its traveling direction changed by the light guide 23 and is received by the light receiving portion 250 of the light receiving element 25.

[0045] The light receiving element 25 converts the received optical signal into an electrical signal. The light receiving element 25 outputs the converted electrical signal to a receiving circuit (not shown). The configuration including the receiving circuit will be described later.

[0046] As described above, the receiving apparatus of the present embodiment includes a ball lens, a light guide, and a plurality of light receiving elements. The ball lens condenses an optical signal propagating in space. The light guide is composed of a plurality of basic units arranged annularly around the ball lens. The basic unit includes a light guide and a light traveling direction changing member. The light guide includes a first surface including an incident surface on which the optical signal condensed by the ball lens is incident, a second surface facing the first surface, and an emission end from which the optical signal incident from the incident surface exits. The light traveling direction changing member is disposed at a position facing the incident surface on the side of the second surface. The light traveling direction changing member changes the traveling direction of the optical signal incident from the incident surface toward the emission end. The light traveling direction changing member is a multi-mirror in which a plurality of reflecting surfaces that reflect the optical signal incident from the incident surface toward the emission end are combined. The light guide guides the optical signal condensed by the ball lens in a direction substantially perpendicular to the incident direction of the optical signal. The basic unit is arranged to guide the optical signal entering from the incident surface in a direction perpendicular to the surface formed by the arrangement of the plurality of basic units. Each of the plurality of light receiving elements is associated with each of the plurality of basic units. The light receiving element receives the optical signal emitted from the basic unit. The light receiving element has a light receiving portion that receives light in the wavelength region of the optical signal, and is arranged toward the emission end of the basic unit. The light receiving element outputs a signal derived from the received optical signal.

[0047] The receiving apparatus of the present embodiment guides optical signals arriving from various directions toward the light receiving element associated with the basic unit by the multi-mirror included in the basic unit constituting the light guide. According to the receiving apparatus of the present embodiment, optical signals arriving from various directions can be received collectively for each basic unit constituting the light guide, so that the number of light receiving elements can be reduced. Therefore, according to the receiving apparatus of the present embodiment, optical signals arriving from various directions can be received using an appropriate number of light receiving elements.

[0048] (Third Embodiment) Next, a receiving device according to the third embodiment will be described with reference to the drawings. The receiving device of this embodiment differs from those of the first and second embodiments in the configuration of the light guide unit. Note that the drawings used in the description of this embodiment are conceptual and do not accurately depict the actual structure.

[0049] (Configuration) Figs. 12 to 14 are conceptual diagrams showing an example of the configuration of the receiving device 3 according to this embodiment. The receiving device 3 includes a ball lens 31, a light guide 33, and a plurality of light receiving elements 35. Fig. 12 is a plan view of the receiving device 3 as viewed from above. Fig. 13 is a side view of the receiving device 3 as viewed from the side. Fig. 14 is a cross-sectional view of the receiving device 3 taken along the cutting line C-C of Fig. 13. The ball lens 31 and the light guide 33 are fixed in their relative positions by a support (not shown). In this embodiment, the support for fixing the light guide 33 to the ball lens 31 is omitted.

[0050] The ball lens 31 has the same configuration as the ball lens 11 of the first embodiment. The ball lens 31 condenses the spatial optical signal arriving from the outside onto the condensing region of the ball lens 31.

[0051] The light guide 33 is arranged in the light condensing area of the ball lens 31 so as to surround the periphery of the ball lens 31. The light guide 33 is composed of a plurality of basic units 330. The basic unit 330 has a curved shape in which a concave first surface (also called a concave curved surface) and a convex second surface (also called a convex curved surface) face each other, like the tip of a spoon. Both surfaces of the basic unit 330 are reflecting surfaces for reflecting optical signals. The plurality of basic units 330 are arranged with the concave first surface facing the ball lens 31. One end side of the first surface of the basic unit 330 functions as an incident surface, and the other end side of the first surface functions as a light guiding portion. The one end side and the other end side of the first surface of the basic unit 330 are arranged in accordance with the circumferential direction of the ball lens 31. One end side (incident surface) of the first surface of the basic unit 330 faces the ball lens 31. The other end side (light guiding portion) of the first surface of the basic unit 330 is arranged on the back side of the second surface of the adjacent basic unit 330. A light receiving element 35 is arranged on the other end side of the first surface of the basic unit 330. The light receiving element 35 is arranged such that the light receiving surface is substantially perpendicular to the first surface at the end portion of the other end side of the first surface. The plurality of basic units 330 surround the periphery of the ball lens 31 while overlapping with the adjacent basic units 330 like fish scales.

[0052] FIG. 15 is an enlarged view of a part of the cross-sectional view of FIG. 14. FIG. 15 shows an example of the path of the optical signal condensed by the ball lens 31. The optical signal condensed by the ball lens 31 enters the incident surface of the first surface of the basic unit 330. The optical signal incident on the incident surface of the basic unit 330 is reflected between the convex surface of the adjacent basic unit 330 and the reflecting surface of the light guiding portion of the basic unit 330, and travels toward the light receiving portion 350 of the light receiving element 35.

[0053] FIG. 16 is a conceptual diagram showing a part of the light guide 33 as viewed from the side of the ball lens 31. FIG. 16 shows an example in which the light guide 33 is composed of n basic units 330-1 to n (n is a natural number). In FIG. 16, the parts behind the basic units 330-1 to n are shown by broken lines. Behind the basic unit 330-1, the light guide part of the basic unit 330-n is arranged. Behind the basic unit 330-1, the light receiving element 35-n of the basic unit 330-n is arranged. Behind the basic unit 330-2, the light guide part of the basic unit 330-1 is arranged. Behind the basic unit 330-2, the light receiving element 35-1 of the basic unit 330-1 is arranged. Behind the basic unit 330-3, the light guide part of the basic unit 330-2 is arranged. Behind the basic unit 330-3, the light receiving element 35-2 of the basic unit 330-2 is arranged. Behind the basic unit 330-4, the light guide part of the basic unit 330-3 is arranged. Behind the basic unit 330-4, the light receiving element 35-3 of the basic unit 330-3 is arranged.

[0054] FIG. 16 shows the beam spot of the optical signal condensed by the ball lens 31 and the path of the optical signal traveling while being reflected by the reflecting surface of the basic unit 330. In the example of FIG. 16, the optical signal irradiated on the incident surface of the basic unit 330-2 is reflected toward the light receiving element 35-2 at the incident surface. The optical signal reflected toward the light receiving element 35-2 is reflected by the back surface (convex surface) of the basic unit 330-3 and the light guide part of the basic unit 330-2 and travels toward the light receiving part 350-2 of the light receiving element 35-2.

[0055] For example, the basic unit 330 is realized by a material such as glass, plastic, or metal having a mirror surface formed on its surface. The basic unit 330 is not limited to that material as long as it can reflect an optical signal. For example, the range 360 exposed to the outside of the second surface of the basic unit 330 does not have to be a mirror surface in order to prevent diffuse reflection of the spatial optical signal.

[0056] The light receiving element 35 has the same configuration as the light receiving element 15 of the first embodiment. Each of the plurality of light receiving elements 35 is associated with each of the plurality of basic units 330 constituting the light guide 33 and is arranged at the end of the other end side (light guide portion) of the first surface of the light guide 33. The light receiving element 35 includes a light receiving portion 350 that receives an optical signal derived from a spatial optical signal to be received. The light receiving element 35 is arranged such that the light receiving portion 350 is substantially perpendicular to the first surface at the end portion on the other end side of the first surface of the basic unit 330. The optical signal condensed by the ball lens 31 has its traveling direction changed by the light guide 33 and is received by the light receiving portion 350 of the light receiving element 35.

[0057] The light receiving element 35 converts the received optical signal into an electrical signal. The light receiving element 35 outputs the converted electrical signal to a receiving circuit (not shown). The configuration including the receiving circuit will be described later.

[0058] (Modification example) Next, a modification example of the present embodiment will be described with reference to the drawings. In the following modification examples, a plurality of basic units constituting the light guide of the receiving device of the first to second embodiments are arranged like the plurality of basic units constituting the light guide of the receiving device of the present embodiment. That is, in the following modification examples, the light guide directions of the plurality of basic units constituting the light guide of the receiving device of the first to second embodiments are aligned with the circumferential direction of the ball lens. Hereinafter, an example of replacing the light guide 33 of the receiving device 3 of the present embodiment will be described. The description of the ball lens 31 and the light receiving element 35 will be omitted.

[0059] 〔Modification example 1〕 FIGS. 17 to 18 are conceptual diagrams for explaining the configuration of a light guide 33A included in the receiving device of Modification example 1. FIG. 17 is a conceptual diagram of a part of the light guide 33A viewed from the side of the ball lens 31. FIG. 18 is a cross-sectional view taken along the cutting line D-D of FIG. 17. FIGS. 17 to 18 show an example in which the light guide 33A is composed of n basic units 330A-1 to n (n is a natural number). The basic unit 330A has a light guide 333A and a diffraction element 335A. The light guide 333A and the diffraction element 335A are the same as the corresponding configurations of the first embodiment. The basic unit 330A has a structure obtained by laying the basic unit 130 of the first embodiment on its side. In FIG. 17, the parts behind the basic units 330A-1 to n are shown by broken lines.

[0060] The light guide 33A is arranged so as to surround the periphery of the ball lens 31. The light guide 33A is composed of a plurality of basic units 330A-1 to n. Each basic unit 330A has a light guide 333A and a diffraction element 335A. The basic configurations of the light guide 333A and the diffraction element 335A are the same as those of the first embodiment. Different from the first embodiment, the light guide 333A and the diffraction element 335A have a bent shape in accordance with the condensing region of the ball lens 31. The light guide 333A is the main body of the basic unit 330A.

[0061] The light guide 333A has a first surface (concave surface) facing the ball lens 31 and a second surface (convex surface) facing the first surface. An incident surface is formed on a part (incident part) of the first surface of the light guide 333A. The incident part is provided on a part of the first surface of the light guide 333A. The remaining part (light guide part) of the first surface of the light guide 333A is arranged behind the adjacent basic unit 330A. An emission surface (also called an emission end) is provided on a part of the side surface of the light guide 333A. A light receiving element 35A is arranged on the emission surface of the light guide 333A. The light receiving element 35A has the same configuration as the light receiving element 15 of the first embodiment. The light guide part of the light guide 333A is tapered so that the cross-sectional area gradually decreases toward the light receiving element 35A.

[0062] The plurality of basic units 330A are arranged with their concave first surfaces facing the ball lens 31. One end side of the first surface of the basic unit 330A functions as an incident surface. The other end side of the first surface functions as a light guide portion. The one end side and the other end side of the first surface of the basic unit 330A are arranged in alignment with the circumferential direction of the ball lens 31. One end side (incident surface) of the first surface of the basic unit 330A faces the ball lens 31. The emission surface of the basic unit 330A is arranged on the back side of the second surface of the adjacent basic unit 330A. A light receiving element 35A is arranged on a part of the side surface of the basic unit 330A. The light receiving element 35A is arranged on the emission surface of the basic unit 330A such that the light receiving surface is substantially perpendicular to the first surface. The plurality of basic units 330A surround the periphery of the ball lens 31 while overlapping with adjacent basic units 330A.

[0063] Behind the light guide 333A-1 of the basic unit 330A-1, the light guide portion of the light guide 333A-n of the basic unit 330A-n is arranged. Behind the light guide 333A-1 of the basic unit 330A-1, the light receiving element 35A-n of the basic unit 330A-n is arranged. Behind the light guide 333A-2 of the basic unit 330A-2, the light guide portion of the light guide 333A-1 of the basic unit 330A-1 is arranged. Behind the light guide 333A-2 of the basic unit 330A-2, the light receiving element 35A-1 of the basic unit 330A-1 is arranged. Behind the light guide 333A-3 of the basic unit 330A-3, the light guide portion of the light guide 333A-2 of the basic unit 330A-2 is arranged. Behind the light guide 333A-3 of the basic unit 330A-3, the light receiving element 35A-2 of the basic unit 330A-2 is arranged. Behind the light guide 333A-4 of the basic unit 330A-4, the light guide portion of the light guide 333A-3 of the basic unit 330A-3 is arranged. Behind the light guide 333A-4 of the basic unit 330A-4, the light receiving element 35A-3 of the basic unit 330A-3 is arranged.

[0064] Figures 17 to 18 show the beam spot of the optical signal condensed by the ball lens 31 and the path of the optical signal traveling while being reflected by the reflecting surface of the basic unit 330A. In the examples of Figures 17 to 18, the optical signal irradiated on the incident surface of the basic unit 330A-2 is diffracted by the diffraction element 335A-2 facing the incident surface and travels toward the light receiving portion 350A-2 of the light receiving element 35A-2. The optical signal diffracted by the diffraction element 335A-2 is reflected by the first surface and the second surface of the light guiding portion of the basic unit 330A-2 behind the basic unit 330A-3 and travels toward the light receiving portion 350A-2 of the light receiving element 35A-2.

[0065] 〔Modification Example 2〕 Figures 19 to 20 are conceptual diagrams for explaining the configuration of the light guide 33B included in the receiving device of Modification Example 2. Figure 19 is a conceptual diagram of a part of the light guide 33B seen from the side of the ball lens 31. Figure 20 is a cross-sectional view taken along the cutting line E-E of Figure 19. Figures 19 to 20 show an example in which the light guide 33B is composed of n basic units 330B-1 to n (n is a natural number). The basic unit 330B has a light guide 333B and a multi-mirror 335B. The light guide 333B and the multi-mirror 335B are the same as the corresponding configurations of the first embodiment. The basic unit 330B has a structure in which the basic unit 230 of the second embodiment is laid on its side. In Figure 19, the portions behind the basic units 330B-1 to n are shown by broken lines.

[0066] The light guide 333B has a first surface (concave surface) facing the ball lens 31 and a second surface (convex surface) facing the first surface. An incident surface is formed on a part (incident portion) of the first surface of the light guide 333B. The incident portion is provided on a part of the first surface of the light guide 333B. The remaining part (light guiding portion) of the first surface of the light guide 333B is arranged behind the adjacent basic unit 330B. An emission surface is provided on a part of the side surface of the light guide 333B. The light receiving element 35B is arranged on the emission surface of the light guide 333B. The light receiving element 35B has the same configuration as the light receiving element 15 of the first embodiment. The light guiding portion of the light guide 333B is tapered so that the cross-sectional area gradually decreases toward the light receiving element 35B.

[0067] The plurality of basic units 330B are arranged with the concave first surface facing the ball lens 31. One end side of the first surface of the basic unit 330B functions as an incident surface. The other end side of the first surface functions as a light guide portion. The one end side and the other end side of the first surface of the basic unit 330B are arranged in accordance with the circumferential direction of the ball lens 31. One end side (incident surface) of the first surface of the basic unit 330B faces the ball lens 31. The emission surface of the basic unit 330B is arranged on the back side of the second surface of the adjacent basic unit 330B. A light receiving element 35B is arranged on a part of the side surface of the basic unit 330B. The light receiving element 35B is arranged on the emission surface of the basic unit 330B such that the light receiving surface is substantially perpendicular to the first surface. The plurality of basic units 330B surround the periphery of the ball lens 31 while overlapping with adjacent basic units 330B.

[0068] Behind the light guide 333B-1 of the basic unit 330B-1, the light guide portion of the light guide 333B-n of the basic unit 330B-n is arranged. Behind the light guide 333B-1 of the basic unit 330B-1, the light receiving element 35B-n of the basic unit 330B-n is arranged. Behind the light guide 333B-2 of the basic unit 330B-2, the light guide portion of the light guide 333B-1 of the basic unit 330B-1 is arranged. Behind the light guide 333B-2 of the basic unit 330B-2, the light receiving element 35B-1 of the basic unit 330B-1 is arranged. Behind the light guide 333B-3 of the basic unit 330B-3, the light guide portion of the light guide 333B-2 of the basic unit 330B-2 is arranged. Behind the light guide 333B-3 of the basic unit 330B-3, the light receiving element 35B-2 of the basic unit 330B-2 is arranged. Behind the light guide 333B-4 of the basic unit 330B-4, the light guide portion of the light guide 333B-3 of the basic unit 330B-3 is arranged. Behind the light guide 333B-4 of the basic unit 330B-4, the light receiving element 35B-3 of the basic unit 330B-3 is arranged.

[0069] Figs. 19 to 20 show the beam spot of the optical signal condensed by the ball lens 31 and the path of the optical signal traveling while being reflected by the reflecting surface of the basic unit 330B. In the examples of Figs. 19 to 20, the optical signal irradiated on the incident surface of the basic unit 330B-2 is reflected by the multi-mirror 335B facing the incident surface and travels toward the light-receiving portion 350B-2 of the light-receiving element 35B-2. The optical signal reflected by the multi-mirror 335B is reflected by the first surface and the second surface of the light guide portion of the basic unit 330B-2 behind the basic unit 330B-3 and travels toward the light-receiving portion 350B-2 of the light-receiving element 35B-2.

[0070] As described above, the receiving device of the present embodiment includes a ball lens, a light guide, and a plurality of light-receiving elements. The ball lens condenses the optical signal propagating in space. The light guide is composed of a plurality of basic units arranged annularly around the ball lens. The basic unit includes a concave surface including an incident surface that reflects an optical signal, a convex surface facing the concave surface, and an output end through which the optical signal incident on the incident surface is guided. The plurality of basic units are arranged with the concave surface facing the ball lens so as to guide the optical signal entering from the incident surface in a direction along the circumferential direction of the circle formed by the arrangement of the plurality of basic units. The output end of each of the plurality of basic units is arranged on the side of the convex surface of the adjacent basic unit. The light-receiving element has a light-receiving portion that receives light in the wavelength region of the optical signal. The light-receiving element is arranged with the light-receiving portion facing the output end of the basic unit. The light-receiving element receives the optical signal that is reflected and guided by the concave surface of the associated basic unit and the convex surface of the basic unit adjacent to the associated basic unit. The light-receiving element outputs a signal derived from the received optical signal.

[0071] The receiving device of this embodiment reflects an optical signal incident on the incident surface of the basic unit by the concave curved surface of the basic unit and the convex curved surface of the basic unit adjacent to the basic unit, and guides the light along the circumferential direction of a circle formed by the arrangement of a plurality of basic units. According to the receiving device of this embodiment, in order to guide optical signals arriving from various directions along the circumferential direction of the circle formed by the arrangement of a plurality of basic units, the thickness of the light guide can be reduced. Therefore, according to the receiving device of this embodiment, the light receiving range in the thickness direction of the light guide becomes wider.

[0072] (Fourth Embodiment) Next, the receiving device according to the fourth embodiment will be described with reference to the drawings. The receiving device of this embodiment is different from the first to third embodiments in the configuration of the light guide portion. Note that the drawings used in the description of this embodiment are conceptual and do not accurately depict the actual structure.

[0073] (Configuration) 21 to 22 are conceptual diagrams showing an example of the configuration of the receiving device 4 according to this embodiment. The receiving device 4 includes a ball lens 41, a light guide 43, a plurality of light receiving elements 45, and a light shielding band 46. FIG. 21 is a plan view of the receiving device 4 viewed from above. FIG. 22 is a side view of the receiving device 4 viewed from the side. In FIG. 22, the configuration (the first curved mirror 431 and the second curved mirror 432) hidden by the light shielding band 46 is shown by a broken line. The ball lens 41 and the light guide 43 are fixed in their positional relationship with each other by a support (not shown). In this embodiment, the support for fixing the light guide 43 to the ball lens 41 is omitted.

[0074] The ball lens 41 has the same configuration as the ball lens 11 of the first embodiment. The ball lens 41 condenses the spatial optical signal arriving from the outside onto the condensing region of the ball lens 41.

[0075] The light guide 43 is arranged in the light collecting area of the ball lens 41 so as to surround the periphery of the ball lens 41. The light guide 43 is composed of a plurality of basic units 430. The basic unit 430 is composed of a first curved mirror 431 and a second curved mirror 432.

[0076] The first curved mirror 431 has a concave surface on which a reflecting surface is formed. The concave surface (reflecting surface) of the first curved mirror 431 faces the ball lens 41. Also, a light receiving element 45 is arranged on a part of the concave surface (reflecting surface) of the first curved mirror 431. An optical signal collected by the ball lens 41 is incident on the concave surface (reflecting surface) of the first curved mirror 431. The optical signal incident on the concave surface (reflecting surface) of the first curved mirror 431 is reflected toward the second curved mirror 432.

[0077] For example, the first curved mirror 431 is realized by a material such as glass, plastic, or metal in which a mirror surface is formed on the concave surface. The first curved mirror 431 is not limited to its material as long as it can reflect the optical signal on the concave surface (reflecting surface). On the convex surface facing the concave surface (reflecting surface) of the first curved mirror 431, measures to prevent the irregular reflection of the spatial optical signal coming from the outside, such as measures to prevent the reflection of light or measures to absorb light, may be added. For example, a light absorbing layer may be formed on the convex surface of the first curved mirror 431.

[0078] The second curved mirror 432 has a convex surface on which a reflecting surface is formed. The convex surface (reflecting surface) of the second curved mirror 432 faces the concave surface (reflecting surface) of the first curved mirror 431. Also, the convex surface (reflecting surface) of the second curved mirror 432 faces the light receiving element 45. An optical signal reflected by the concave surface (reflecting surface) of the first curved mirror 431 is incident on the convex surface (reflecting surface) of the second curved mirror 432. The optical signal incident on the convex surface (reflecting surface) of the second curved mirror 432 is reflected toward the light receiving element 45.

[0079] For example, the second curved mirror 432 is realized by a material such as glass, plastic, or metal with a mirror surface formed on its convex surface. The second curved mirror 432 is not limited to a specific material as long as it can reflect an optical signal on its convex surface (reflective surface). On the concave surface facing the convex surface (reflective surface) of the second curved mirror 432, measures to prevent light reflection or to absorb light may be added to prevent the diffuse reflection of the optical signal focused by the ball lens 41. For example, a light-absorbing layer may be formed on the concave surface of the second curved mirror 432.

[0080] The light-shielding band 46 is arranged to cover the peripheries of the first curved mirror 431 and the second curved mirror 432. The light-shielding band 46 prevents the spatial optical signal from entering the ball lens 41 from the positions of the first curved mirror 431 and the second curved mirror 432. It is preferable that measures to prevent light reflection or to absorb light are added to the surface of the light-shielding band 46 to prevent the diffuse reflection of the spatial optical signal. For example, the light-shielding band 46 is realized by a material that easily absorbs light in the wavelength band of the spatial optical signal. The first curved mirror 431, the second curved mirror 432, and the light-shielding band 46 may be arranged with a gap therebetween or may be in close contact. When measures to prevent light reflection or to absorb light are added to the convex surface of the first curved mirror 431 or the concave surface of the second curved mirror 432, the light-shielding band 46 may be omitted.

[0081] Figs. 23 to 24 are conceptual diagrams for explaining an example of a basic unit 430 constituting the light guide 43. Fig. 23 is a plan view of the basic unit 430. Fig. 24 is a cross-sectional view of the basic unit 430 cut along the F-F cutting line in Fig. 23. Figs. 23 to 24 show an example of the path of the optical signal entering the basic unit 430.

[0082] Most of the optical signals focused by the ball lens 41 are incident on the concave surface (reflective surface) of the first curved mirror 431. The optical signals incident on the concave surface (reflective surface) of the first curved mirror 431 are reflected toward the convex surface (reflective surface) of the second curved mirror 432. The optical signals incident on the convex surface (reflective surface) of the second curved mirror 432 are reflected toward the light receiving element 45. Among the optical signals reflected by the convex surface (reflective surface) of the second curved mirror 432, the optical signals incident on the light receiving portion 450 of the light receiving element 45 are received by the light receiving element 45. Note that, among the optical signals focused by the ball lens 41, the optical signals directly incident on the light receiving portion 450 of the light receiving element 45 are received by the light receiving element 45. Also, among the optical signals focused by the ball lens 41, the optical signals incident on the concave surface of the second curved mirror 432 are not received by the light receiving element 45.

[0083] The light receiving element 45 has the same configuration as the light receiving element 15 of the first embodiment. Each of the plurality of light receiving elements 45 is disposed on a part of the concave surface (reflective surface) of the first curved mirror 431 of each of the plurality of basic units 430 constituting the light guide 43. The light receiving element 45 includes a light receiving portion 450 that receives an optical signal derived from a spatial optical signal to be received. The light receiving portions 450 of the individual light receiving elements 45 are directed toward the reflective surface (convex surface) of the second curved mirror 432 of the basic unit 430. The optical signals focused by the ball lens 41 are redirected in their traveling direction by the light guide 43 and received by the light receiving portions 450 of the light receiving elements 45.

[0084] The light receiving element 45 converts the received optical signal into an electrical signal. The light receiving element 45 outputs the converted electrical signal to a receiving circuit (not shown). The configuration including the receiving circuit will be described later.

[0085] (Modification example) Next, a modification example of the present embodiment will be described with reference to the drawings. In the drawings of the following modification examples, the same reference numerals as those in FIGS. 21 to 24 are used for the same configurations as those in FIGS. 21 to 24. For the same configurations as those in FIGS. 21 to 24, the description may be omitted.

[0086] 〔Modification example 3〕 Figs. 25 to 26 are conceptual diagrams for explaining the configuration of the receiving device 4-3 of Modification 3. The receiving device 4 -3 includes a ball lens 41, a light guide 43-3, a plurality of light receiving elements 45, and a light shielding band 46. In this modification, a reflecting surface is formed on the concave surface of the second curved mirror that constitutes the basic unit. The light guide 43-3 is composed of a plurality of basic units 430-3. Fig. 25 is a plan view of the receiving device 4-3 as viewed from above. Fig. 26 is an enlarged view of the basic unit 430-3.

[0087] The light guide 43-3 is arranged in the light condensing region of the ball lens 41 so as to surround the periphery of the ball lens 41. The light guide 43-3 is composed of a plurality of basic units 430-3. The basic unit 430-3 is composed of a first curved mirror 431 and a second curved mirror 432-3.

[0088] The first curved mirror 431 has a concave surface on which a reflecting surface is formed. The concave surface (reflecting surface) of the first curved mirror 431 faces the ball lens 41. Also, a light receiving element 45 is arranged on a part of the concave surface (reflecting surface) of the first curved mirror 431. The light signal condensed by the ball lens 41 is incident on the concave surface (reflecting surface) of the first curved mirror 431. The light signal incident on the concave surface (reflecting surface) of the first curved mirror 431 is reflected toward the second curved mirror 432. On the convex surface of the first curved mirror 431, measures to prevent light reflection or measures to absorb light may be added to prevent specular reflection of the spatial light signal coming from the outside. For example, a light absorbing layer may be formed on the convex surface of the first curved mirror 431.

[0089] The second curved mirror 432-3 has a concave surface on which a reflecting surface is formed. The concave surface (reflecting surface) of the second curved mirror 432-3 faces the concave surface (reflecting surface) of the first curved mirror 431. Also, the concave surface (reflecting surface) of the second curved mirror 432-3 faces the light receiving element 45. An optical signal reflected by the concave surface (reflecting surface) of the first curved mirror 431 is incident on the concave surface (reflecting surface) of the second curved mirror 432-3. The optical signal incident on the concave surface (reflecting surface) of the second curved mirror 432-3 is reflected toward the light receiving element 45. On the convex surface of the second curved mirror 432-3, measures to prevent light reflection or measures to absorb light may be added to prevent specular reflection of the optical signal condensed by the ball lens 41. For example, a light absorbing layer may be formed on the convex surface of the second curved mirror 432-3.

[0090] The light receiving element 45 is disposed on a part of the concave surface (reflecting surface) of the first curved mirror 431 of the basic unit 430-3. The light receiving element 45 includes a light receiving portion 450 that receives an optical signal derived from a spatial optical signal to be received. The light receiving portion 450 faces the reflecting surface (concave surface) of the second curved mirror 432-3 of the basic unit 430-3. For example, the light receiving portion 450 is disposed at the focal point position of the reflecting surface (concave surface) of the second curved mirror.

[0091] The light shielding band 46 is disposed so as to cover the peripheries of the first curved mirror 431 and the second curved mirror 432. The light shielding band 46 prevents the spatial optical signal from entering the ball lens 41 from the positions of the first curved mirror 431 and the second curved mirror 432. When measures to prevent light reflection or measures to absorb light are added to the convex surface of the first curved mirror 431 or the convex surface of the second curved mirror 432, the light shielding band 46 may be omitted.

[0092] In this modification, since the focal point position of the second curved mirror 432-3 is clearly determined, it is easy to determine the design of the curved surfaces of the first curved mirror 431 and the second curved mirror 432-3 and the position where the light receiving element 45 is disposed.

[0093] [Modification 4] Figures 27 to 28 are conceptual diagrams for explaining the configuration of the receiving device 4-4 of Modification 4. The receiving device 4 -4 includes a ball lens 41, a light guide 43-4, a plurality of light receiving elements 45, and a light shielding band 46. In this modification, the second curved mirror 432 is omitted, and the light receiving element 45 is arranged at the position of the second curved mirror 432. The light guide 43-4 is composed of a plurality of basic units 430-4 (first curved mirror 431). FIG. 27 is a plan view of the receiving device 4-4 viewed from above. FIG. 28 is an enlarged view of a part of the basic unit 430-4.

[0094] The light guide 43-4 is arranged in the condensing region of the ball lens 41 so as to surround the periphery of the ball lens 41. The light guide 43-4 is composed of a plurality of basic units 430-4 (first curved mirror 431). The basic unit 430-4 is a single first curved mirror 431.

[0095] The first curved mirror 431 has a concave surface on which a reflecting surface is formed. The concave surface (reflecting surface) of the first curved mirror 431 faces the ball lens 41. An optical signal condensed by the ball lens 41 is incident on the concave surface (reflecting surface) of the first curved mirror 431. The optical signal incident on the concave surface (reflecting surface) of the first curved mirror 431 is reflected toward the light receiving portion 450 of the light receiving element 45. On the convex surface of the first curved mirror 431, measures to prevent light reflection or measures to absorb light may be added to prevent specular reflection of the spatial optical signal coming from the outside. For example, a light absorbing layer may be formed on the convex surface of the first curved mirror 431.

[0096] The light receiving element 45 is arranged with its light receiving surface facing the concave surface (reflective surface) of the first curved mirror 431. The surface facing the light receiving surface of the light receiving element 45 (also referred to as the back surface) is directed towards the ball lens 41. The light receiving portion 450 of the light receiving element 45 is directed towards the concave surface (reflective surface) of the first curved mirror 431. For example, the light receiving portion 450 is arranged at the focal position of the reflective surface (concave surface) of the first curved mirror 431. On the back surface of the light receiving element 45, measures to prevent light reflection may be added to prevent the irregular reflection of the optical signal. For example, a layer that absorbs the optical signal is formed on the back surface of the light receiving element 45. For example, a configuration similar to the light shielding band 46 may be arranged on the back surface of the light receiving element 45 to prevent the optical signal condensed by the ball lens 41 from being irregularly reflected. Such a configuration may have a layer that absorbs light formed on the side surface facing the ball lens 41.

[0097] The light shielding band 46 is arranged to cover the periphery of the first curved mirror 431. The light shielding band 46 prevents the spatial optical signal from entering the ball lens 41 from the position of the first curved mirror 431. If measures to prevent light reflection or measures to absorb light are added to the convex surface of the first curved mirror 431 or the back surface of the light receiving element 45, the light shielding band 46 may be omitted.

[0098] In this modification, the second curved mirror 432 is omitted, and the light receiving element 45 is arranged at the position of the second curved mirror 432. The receiving device 4-4 of this modification can efficiently receive an optical signal while having a simple configuration. Also, in this modification, since the light receiving element 45 only needs to be arranged at the focal position of the first curved mirror 431, the design of the curved surface of the first curved mirror 431 becomes easier.

[0099] As described above, the receiving device of this embodiment includes a ball lens, a light guide, and a plurality of light receiving elements. The ball lens condenses the optical signal propagating in space. The light guide is composed of a plurality of basic units arranged annularly around the ball lens. The basic unit is composed of a first curved mirror including an incident surface that reflects an optical signal, and a second curved mirror whose reflecting surface is directed toward the first curved mirror. A plurality of the first curved mirrors are arranged with their incident surfaces facing the ball lens. Each of the plurality of light receiving elements is associated with each of the plurality of basic units. The light receiving element receives the optical signal emitted from the basic unit. The light receiving element has a light receiving portion that receives light in the wavelength region of the optical signal, and is arranged on the same curved surface as the incident surface of the first curved mirror of the associated basic unit, facing the reflecting surface of the second curved mirror. The light receiving element outputs a signal derived from the received optical signal.

[0100] The receiving device of the present embodiment guides an optical signal arriving from various directions toward a light receiving element arranged on the concave surface of the first curved mirror of the basic unit by the first curved mirror and the second curved mirror that constitute the plurality of basic units that make up the light guide. According to the receiving device of the present embodiment, since optical signals arriving from various directions can be received collectively for each basic unit that constitutes the light guide, the number of light receiving elements can be reduced. Therefore, according to the receiving device of the present embodiment, an appropriate number of light receiving elements can be used to receive optical signals arriving from various directions.

[0101] In one aspect of the present embodiment, the basic unit is composed of a first curved mirror including an incident surface that reflects an optical signal. A plurality of the first curved mirrors are arranged with their incident surfaces facing the ball lens. The light receiving element has a light receiving portion that receives light in the wavelength region of the optical signal, and is arranged facing the reflecting surface of the first curved mirror of the associated basic unit. According to this aspect, by omitting the second curved mirror and arranging the light receiving element in the position of the second curved mirror, an optical signal can be received efficiently with a simple configuration.

[0102] (Fifth Embodiment) Next, the receiving device according to the fifth embodiment will be described with reference to the drawings. The receiving device of the present embodiment has a configuration in which a light guide assist device that assists in guiding an optical signal condensed by a ball lens to a light guide unit is added to the receiving devices of the first to fourth embodiments.

[0103] (Configuration) FIG. 29 is a conceptual diagram showing an example of the configuration of the receiving apparatus 5 according to the present embodiment. The receiving apparatus 5 includes a ball lens 51, a light guide 53, a plurality of light receiving elements (not shown), and a light guide assistor 57. FIG. 29 is a plan view of the receiving apparatus 5 as viewed from above. A side view of the receiving apparatus 5 as viewed from the lateral direction is omitted. The ball lens 51, the light guide 53, and the light guide assistor 57 are fixed in their relative positions by a support (not shown). In the present embodiment, the support for fixing the light guide 53 and the light guide assistor 57 to the ball lens 51 is omitted.

[0104] The ball lens 51 has the same configuration as the ball lens 11 of the first embodiment. The ball lens 51 condenses the spatial optical signal arriving from the outside onto the condensing region of the ball lens 51.

[0105] The light guide assistor 57 has an annular shape. The light guide assistor 57 is disposed between the ball lens 51 and the light guide 53. The light guide assistor 57 is disposed so as to surround the periphery of the ball lens 51. The light guide assistor 57 has an inner surface along the inner diameter and an outer surface along the outer diameter. The optical signal condensed by the ball lens 51 is incident on the inner surface of the light guide assistor 57. The optical signal that has entered the interior of the light guide assistor 57 travels toward the outer surface. The optical signal that has reached the outer surface of the light guide assistor 57 is emitted toward the light guide 53. A configuration example for realizing the light guide assistor 57 will be described later.

[0106] The light guide 53 is any one of the light guides according to the first to fourth embodiments. The light guide 53 is disposed so as to surround the periphery of the light guide assistor 57. The light guide 53 is composed of a plurality of basic units 530. The optical signal emitted from the light guide assistor 57 is incident on the light guide 53. The light guide 53 guides the incident optical signal toward a light receiving element (not shown).

[0107] The light-receiving element (not shown) has the same configuration as the light-receiving element 15 of the first embodiment. Each of the plurality of light-receiving elements is arranged in association with each of the plurality of basic units constituting the light guide 53. The optical signal condensed by the ball lens 51 reaches the light guide 53 via the light guide auxiliary 57. The optical signal reaching the light guide 53 has its traveling direction changed by the light guide 53 and is received by the light-receiving element. The light-receiving element converts the received optical signal into an electrical signal. The light-receiving element outputs the converted electrical signal to a receiving circuit (not shown).

[0108] FIG. 30 is a conceptual diagram showing an example of a configuration (light guide auxiliary 57-1) for realizing the light guide auxiliary 57. The light guide auxiliary 57-1 is composed of a plurality of transparent layers 571 and a plurality of shielding layers 572. The transparent layer 571 is composed of a member having a high transmittance in the wavelength band of the optical signal. For example, the transparent layer 571 can be realized by a material such as glass or plastic. As long as the transmittance is high in the wavelength band of the optical signal, the material of the transparent layer 571 is not limited. The shielding layer 572 is a layered member composed of a member having a high absorption rate in the wavelength band of the optical signal. For example, the shielding layer 572 can be realized by a material such as carbon or plastic. The light guide auxiliary 57-1 has a structure in which the plurality of transparent layers 571 and the plurality of shielding layers 572 are alternately adjacent in the circumferential direction of the ball lens 51.

[0109] Among the optical signals entering from the inner surface of the light guide auxiliary 57-1, the components that do not hit the shielding layer 572 are emitted from the outer surface and enter the light guide 53. Among the optical signals entering from the inner surface of the light guide auxiliary 57-1, the components that hit the shielding layer 572 are absorbed by the shielding layer 572. The optical signal absorbed by the shielding layer 572 is not emitted from the outer surface of the light guide auxiliary 57-1. That is, the shielding layer 572 blocks stray light between the ball lens 51 and the light guide 53. If the thickness of the light guide auxiliary 57-1 is too thick, the amount of optical signal absorbed by the shielding layer 572 increases. Therefore, it is preferable that the thickness of the light guide auxiliary 57-1 be set according to the balance between the effect of blocking stray light and the amount of optical signal absorbed by the shielding layer 572.

[0110] In the configuration of the light guide auxiliary device 57-1 (Fig. 30), a plurality of shielding layers 572 are arranged for each basic unit 530. Therefore, according to the configuration of the light guide auxiliary device 57-1 (Fig. 30), it is possible to prevent the light signal from being received across the light receiving elements corresponding to each of the adjacent basic units 530.

[0111] Fig. 31 is a conceptual diagram showing another example (light guide auxiliary device 57-2) of the configuration for realizing the light guide auxiliary device 57. The light guide auxiliary device 57-2 is composed of a plurality of partition walls 575. The partition walls 575 are arranged along the boundaries of the adjacent basic units 530. For example, the partition walls 575 are composed of members having a high absorption rate in the wavelength band of the light signal.

[0112] Among the light signals entering from the inner surface of the light guide auxiliary device 57-2, the components that do not hit the partition wall 575 are emitted from the outer surface and incident on the light guide device 53. When the light absorption of the partition wall 575 is high, among the light signals entering from the inner surface of the light guide auxiliary device 57-2, the components that hit the partition wall 575 are not emitted from the outer surface.

[0113] In the configuration of the light guide auxiliary device 57-2 (Fig. 31), a partition wall 575 is arranged between the adjacent basic units 530. Therefore, according to the configuration of the light guide auxiliary device 57-2 (Fig. 31), it is possible to prevent the light signal from being received across the light receiving elements corresponding to each of the adjacent basic units 530.

[0114] (Modification example) Next, a modification example of the present embodiment will be described with reference to the drawings. The following modification example is a configuration in which the ball lens and the light guide auxiliary device are in close contact. In the drawings of the following modification example, the same reference numerals as those in Fig. 29 are used for the same configurations as those in Fig. 29.

[0115] 〔Modification example 5〕 FIG. 32 is a conceptual diagram for explaining the configuration of the receiving device 5-5 of Modification 5. The receiving device 5-5 includes a ball lens 51, a light guide 53, a plurality of light receiving elements (not shown), and a light guide assist device 57. The light guide 53 is composed of a plurality of basic units 530. FIG. 32 is a plan view of the receiving device 5-5 viewed from above. Since the components of the receiving device 5-5 are the same as those in the configuration of FIG. 29, detailed description is omitted.

[0116] In the receiving device 5-5, the outer periphery of the ball lens 51 is in close contact with the inner surface of the light guide assist device 57. In the case of the configuration of the receiving device 5-5, it is preferable that the refractive index of the ball lens 51 is the same as the refractive index of a transparent layer (not shown) included in the light guide assist device 57.

[0117] According to the configuration of the receiving device 5-5 (FIG. 32), since the space between the ball lens 51 and the inner surface of the light guide assist device 57 disappears, the optical signal condensed by the ball lens 51 is not reflected by the surface of the light guide assist device 57. That is, according to the configuration of the receiving device 5-5, the optical signal condensed by the ball lens 51 is less likely to escape before reaching the light guide 53. Therefore, according to the configuration of the receiving device 5-5, the optical signal can be received more efficiently.

[0118] As described above, the receiving device of the present embodiment includes a light guide assist device that is disposed between the ball lens and the light guide and guides the optical signal condensed by the ball lens toward the light guide. For example, the light guide assist device is composed of a plurality of shielding layers arranged along the diameter direction of the ball lens and a plurality of transparent layers formed between the layers of the plurality of shielding layers and through which the optical signal passes. For example, the light guide assist device is composed of a plurality of partition walls arranged along the diameter direction of the ball lens. For example, the light guide assist device is disposed in close contact with the ball lens.

[0119] The receiving device of this embodiment guides the optical signal condensed by the ball lens to the light guide device via the light guide auxiliary device. Therefore, according to the receiving device of this embodiment, by more surely guiding the optical signal condensed by the ball lens to the light guide device, light can be received more efficiently.

[0120] (Sixth Embodiment) Next, the receiving device according to the sixth embodiment will be described with reference to the drawings. The receiving device of this embodiment has a configuration in which a receiving circuit for decoding the optical signal received by the light receiving element is added to the receiving devices of the first to fourth embodiments.

[0121] (Configuration) FIG. 33 is a conceptual diagram showing an example of the configuration of the receiving device 6 according to this embodiment. The receiving device 6 includes a ball lens 61, a light guide device 63, a plurality of light receiving elements 65, and a receiving circuit 67. FIG. 33 is a side view of the receiving device 6 viewed from the lateral direction. A plan view of the receiving device 6 viewed from above is omitted. The ball lens 61 and the light guide device 63 are fixed in their relative positions by a support (not shown). In this embodiment, the support for fixing the light guide device 63 to the ball lens 61 is omitted.

[0122] The ball lens 61, the light guide device 63, and the plurality of light receiving elements 65 constitute a light receiving unit 60. The light receiving unit 60 is any one of the receiving devices according to the first to fifth embodiments. FIG. 33 shows, as an example, a configuration in which a receiving circuit 67 is added to the receiving device 1 (corresponding to the light receiving unit 60) of the first embodiment. The description of the configuration of the light receiving unit 60 is omitted.

[0123] The receiving circuit 67 acquires the signals output from each of the plurality of light receiving elements 65. The receiving circuit 67 amplifies the signals from each of the plurality of light receiving elements 65. The receiving circuit 67 decodes the amplified signals and analyzes the signals from the communication target. For example, the receiving circuit 67 is configured to analyze the signals for each of the plurality of light receiving elements 65 collectively. When analyzing the signals for each of the plurality of light receiving elements 65 collectively, a single-channel receiving device 6 that communicates with a single communication target can be realized. For example, the receiving circuit 67 is configured to analyze the signals individually for each of the plurality of light receiving elements 65. When analyzing the signals individually for each of the plurality of light receiving elements 65, a multi-channel receiving device 6 that communicates with a plurality of communication targets simultaneously can be realized. The signals decoded by the receiving circuit 67 are used for any application. There is no particular limitation on the use of the signals decoded by the receiving circuit 67.

[0124] 〔Receiving Circuit〕 Next, an example of the detailed configuration of the receiving circuit 67 included in the receiving device 6 will be described with reference to the drawings. FIG. 34 is a block diagram showing an example of the configuration of the receiving circuit 67. In the example of FIG. 34, the number of the plurality of light receiving elements 65 is set to M (M is a natural number). Note that FIG. 34 is an example of the configuration of the receiving circuit 67 and does not limit the configuration of the receiving circuit 67.

[0125] The receiving circuit 67 includes a plurality of first processing circuits 671-1 to M, a control circuit 672, a selector 673, and a plurality of second processing circuits 675-1 to N (M and N are natural numbers). The first processing circuit 671 is associated with any one of the plurality of light receiving elements 65-1 to M. The first processing circuit 671 may be configured for each group formed by collectively combining the plurality of light receiving elements 65 included in the plurality of light receiving elements 65-1 to M.

[0126] For example, the first processing circuit 671 includes a high-pass filter (not shown). The high-pass filter acquires the signal from the light receiving element 65. The high-pass filter selectively passes the signal of the high-frequency component corresponding to the wavelength band of the spatial light signal among the acquired signals. The high-pass filter cuts the signal derived from ambient light such as sunlight. For example, instead of the high-pass filter, a band-pass filter that selectively passes the signal of the wavelength band of the spatial light signal may be configured. If the light receiving element 65 is saturated by intense sunlight, the optical signal becomes unreadable. Therefore, a color filter that selectively passes the light of the wavelength band of the spatial light signal may be installed in front of the light receiving portion of the light receiving element 65.

[0127] For example, the first processing circuit 671 includes an amplifier (not shown). The amplifier acquires the signal output from the high-pass filter. The amplifier amplifies the acquired signal. There is no particular limitation on the amplification factor of the signal by the amplifier.

[0128] For example, the first processing circuit 671 includes an output monitor (not shown). The output monitor monitors the output value of the amplifier. The output monitor outputs the signal exceeding a predetermined output value among the signals amplified by the amplifier to the selector 673. Among the signals output to the selector 673, the signal to be received is assigned to any one of the plurality of second processing circuits 675-1 to N according to the control of the control circuit 672. The signal to be received is a spatial light signal from a communication device (not shown) to be communicated with. The signal from the light receiving element 65 that is not used for receiving the spatial light signal is not output to the second processing circuit 675.

[0129] For example, the first processing circuit 671 may include an integrator (not shown) as an output monitor. The integrator acquires the signal output from the high-pass filter. The integrator integrates the acquired signal. The integrator outputs the integrated signal to the control circuit 672. The integrator is arranged to measure the intensity of the spatial light signal received by the light receiving element 65. Since the spatial light signal received in a state where the beam diameter is not narrowed is weaker in intensity than when the beam diameter is narrowed, it is difficult to measure the voltage of the signal amplified only by the amplifier. By using the integrator, for example, the voltage of the signal can be increased to a level where voltage measurement is possible by integrating the signal for a period of several milliseconds to several tens of milliseconds.

[0130] The control circuit 672 acquires the signals output from each of the plurality of first processing circuits 671-1 to M. In other words, the control circuit 672 acquires the signals derived from the optical signals received by each of the plurality of light receiving elements 65-1 to M. For example, the control circuit 672 compares the read values of the signals from the plurality of adjacent light receiving elements 65. The control circuit 672 selects the light receiving element 65 with the maximum signal intensity according to the comparison result. The control circuit 672 controls the selector 673 to assign the signal derived from the selected light receiving element 65 to any one of the plurality of second processing circuits 675-1 to N.

[0131] When the position of the communication target is specified in advance, the process of estimating the arrival direction of the free-space optical signal is not performed, and the signals output from the light-receiving elements 65-1 to M may be output to any of the preset second processing circuits 675. On the other hand, when the position of the communication target is not specified in advance, the second processing circuit 675 of the output destination of the signals output from the light-receiving elements 65-1 to M may be selected. For example, by the control circuit 672 selecting the light-receiving element 65, the arrival direction of the free-space optical signal can be estimated. That is, the control circuit 672 selecting the light-receiving element 65 corresponds to specifying the communication device that is the transmission source of the free-space optical signal. Also, assigning the signal from the light-receiving element 65 selected by the control circuit 672 to any of the plurality of second processing circuits corresponds to associating the specified communication target with the light-receiving element 65 that receives the free-space optical signal from that communication target. That is, the control circuit 672 can specify the communication device that is the transmission source of the optical signal (free-space optical signal) based on the optical signals received by the plurality of light-receiving elements 65-1 to M.

[0132] Signals amplified by the amplifiers included in each of the plurality of first processing circuits 671-1 to M are input to the selector 673. The selector 673 outputs, in accordance with the control of the control circuit 672, the signal that is the reception target among the input signals to any one of the plurality of second processing circuits 675-1 to N. Signals that are not the reception target are not output from the selector 673.

[0133] Signals from any of the plurality of light-receiving elements 65-1 to N, assigned by the control circuit 672, are input to the plurality of second processing circuits 675-1 to N. Each of the plurality of second processing circuits 675-1 to N decodes the input signal. Each of the plurality of second processing circuits 675-1 to N may be configured to perform some signal processing on the decoded signal, or may be configured to output it to an external signal processing device or the like (not shown).

[0134] By selecting, with selector 673, the signal derived from the light-receiving element 65 selected by control circuit 672, one second processing circuit 675 is assigned to one communication target. That is, control circuit 672 assigns the signals derived from the spatial light signals from a plurality of communication targets received by the plurality of light-receiving elements 65-1 to M to any one of the plurality of second processing circuits 675-1 to N. Thereby, receiving device 6 can simultaneously read the signals derived from the spatial light signals from a plurality of communication targets on individual channels. For example, in order to communicate with a plurality of communication targets simultaneously, the spatial light signals from the plurality of communication targets may be read in time division on a single channel. In the method of this embodiment, since the spatial light signals from a plurality of communication targets are simultaneously read on a plurality of channels, the transmission speed is higher than when using a single channel.

[0135] For example, the arrival direction of the spatial light signal may be specified by a primary scan with low accuracy, and a secondary scan with high accuracy may be performed in the specified direction to specify the exact position of the communication target. When it becomes possible to communicate with the communication target, the exact position of the communication target can be determined by the signal exchange with the communication target. Note that when the position of the communication target is specified in advance, the process of specifying the position of the communication target can be omitted.

[0136] As described above, the receiving device of this embodiment includes a ball lens, a light guide, a plurality of light-receiving elements, and a receiving circuit. The ball lens condenses the optical signal propagating in space. The light guide is composed of a plurality of basic units arranged annularly around the ball lens. The light guide guides the optical signal condensed by the ball lens in a direction substantially perpendicular to the incident direction of the optical signal. Each of the plurality of light-receiving elements is associated with each of the plurality of basic units. The light-receiving element receives the optical signal emitted from the basic unit. The light-receiving element outputs a signal derived from the received optical signal. The transmitting device transmits a spatial light signal. The receiving circuit acquires the signals output from the plurality of light-receiving elements. The receiving circuit decodes the acquired signals.

[0137] The receiving device according to this embodiment guides an optical signal arriving from various directions to a light-receiving element associated with a basic unit by any one of a plurality of basic units constituting a light guide. The receiving device according to this embodiment decodes the optical signal received by the light-receiving element. According to the receiving device of this embodiment, optical signals arriving from various directions can be decoded collectively for each basic unit constituting the light guide. Therefore, according to the receiving device of this embodiment, optical signals arriving from various directions can be decoded.

[0138] (Seventh Embodiment) Next, a communication device according to the seventh embodiment will be described with reference to the drawings. The communication device of this embodiment includes a receiving device according to any one of the first to sixth embodiments and a transmitting device that transmits a spatial optical signal corresponding to the received spatial optical signal. Hereinafter, an example of a communication device including a transmitting device including a phase modulation type spatial light modulator will be described. Note that the communication device of this embodiment may include a transmitting device including a light transmitting function that is not a phase modulation type spatial light modulator.

[0139] FIG. 35 is a conceptual diagram showing an example of the configuration of a communication device 700-1 according to this embodiment. The communication device 700-1 includes a receiving device 710, a control device 750, and a transmitting device 770. The receiving device 710 and the transmitting device 770 transmit and receive spatial optical signals to and from an external communication target. Therefore, an aperture or a window for transmitting and receiving spatial optical signals is formed in the communication device 700-1.

[0140] The receiving device 710 is a receiving device according to any one of the first to sixth embodiments. The receiving device 710 may be a receiving device having a configuration combining the first to sixth embodiments. The receiving device 710 receives a spatial optical signal transmitted from a communication target (not shown). The receiving device 710 converts the received spatial optical signal into an electrical signal. The receiving device 710 outputs the converted electrical signal to the control device 750.

[0141] The control device 750 acquires the signal output from the receiving device 710. The control device 750 executes processing according to the acquired signal. There is no particular limitation on the processing executed by the control device 750. The control device 750 outputs a control signal for transmitting an optical signal according to the executed processing to the transmitting device 770. For example, the control device 750 executes processing based on predetermined conditions according to the information included in the signal received by the receiving device 710. For example, the control device 750 executes processing according to the operation input by the user according to the information included in the signal received by the receiving device 710.

[0142] The transmitting device 770 acquires the control signal from the control device 750. The transmitting device 770 projects a spatial optical signal according to the control signal. The spatial optical signal projected from the transmitting device 770 is received by a communication target (not shown). For example, the transmitting device 770 includes a phase modulation type spatial light modulator. Further, the transmitting device 770 may include a light transmitting function that is not a phase modulation type spatial light modulator.

[0143] 〔Transmitting Device〕 FIG. 36 is a conceptual diagram showing an example of the configuration of the transmitting device 770. The transmitting device 770 includes a light source 771, a spatial light modulator 773, a curved mirror 775, and a control unit 777. FIG. 36 is a side view of the internal configuration of the transmitting device 770 viewed from the lateral direction. FIG. 36 is conceptual and does not accurately represent the positional relationship between each component and the traveling direction of light, etc.

[0144] The light source 771 emits laser light in a predetermined wavelength band according to the control of the control unit 777. The wavelength of the laser light emitted from the light source 771 is not particularly limited and may be selected according to the application. For example, the light source 771 emits laser light in the visible or infrared wavelength band. For example, if it is near-infrared light of 800 to 900 nanometers (nm), the laser class can be increased, so the sensitivity can be improved by about one digit compared to other wavelength bands. For example, if it is infrared light in the wavelength band of 1.55 micrometers (μm), a high-power laser light source can be used. As the laser light source for infrared light in the 1.55-μm wavelength band, an aluminum gallium arsenide phosphide (AlGaAsP)-based laser light source, an indium gallium arsenide (InGaAs)-based laser light source, etc. can be used. The longer the wavelength of the laser light, the larger the diffraction angle can be and the higher the energy can be set. The light source 771 includes a lens that expands the laser light according to the size of the modulation region set in the modulation unit 7730 of the spatial light modulator 773. The light source 771 emits the light 702 expanded by the lens. The light 702 emitted from the light source 771 travels toward the modulation unit 7730 of the spatial light modulator 773.

[0145] The spatial light modulator 773 has a modulation unit 7730 irradiated with the light 702. The modulation unit 7730 of the spatial light modulator 773 is irradiated with the light 702 emitted from the light source 771. A modulation region is set in the modulation unit 7730 of the spatial light modulator 773. In the modulation region of the modulation unit 7730, a pattern (also called a phase image) corresponding to the image displayed by the projection light 705 is set according to the control of the control unit 777. The light 702 incident on the modulation unit 7730 of the spatial light modulator 773 is modulated according to the pattern set in the modulation unit 7730 of the spatial light modulator 773. The modulated light 703 modulated by the modulation unit 7730 of the spatial light modulator 773 travels toward the reflection surface 7750 of the curved mirror 775.

[0146] For example, the spatial light modulator 773 can be realized by a spatial light modulator using ferroelectric liquid crystal, homogeneous liquid crystal, vertically aligned liquid crystal, etc. For example, the spatial light modulator 773 can be realized by LCOS (Liquid Crystal on Silicon). Also, the spatial light modulator 773 may be realized by M EMS (Micro Electro Mechanical System). In the phase modulation type spatial light modulator 773, by operating to sequentially switch the location where the projection light 705 is projected, energy can be concentrated on the image portion. Therefore, when using the phase modulation type spatial light modulator 773, if the output of the light source 771 is the same, compared with other methods, an image can be displayed brighter.

[0147] The modulation region of the modulation unit 7730 of the spatial light modulator 773 is divided into a plurality of regions (also called tiling). For example, the modulation region of the modulation unit 7730 is divided into rectangular regions (also called tiles) with a desired aspect ratio. A phase image is assigned to each of the plurality of tiles set in the modulation region of the modulation unit 7730. Each of the plurality of tiles is composed of a plurality of pixels. A phase image corresponding to the projected image is set for each of the plurality of tiles. The phase images set for each of the plurality of tiles may be the same or different.

[0148] A phase image is tiled for each of the plurality of tiles assigned to the modulation region of the modulation unit 7730. For example, a pre-generated phase image is set for each of the plurality of tiles. When the modulation unit 7730 is irradiated with light 702 in a state where phase images are set for the plurality of tiles, modulated light 703 that forms an image corresponding to the phase image of each tile is emitted. The more tiles set in the modulation unit 7730, the clearer the image can be displayed, but if the number of pixels in each tile decreases, the resolution decreases. Therefore, the size and number of tiles set in the modulation region of the modulation unit 7730 are set according to the application.

[0149] The curved mirror 775 is a mirror having a curved reflecting surface 7750. The reflecting surface 7750 of the curved mirror 775 has a curvature corresponding to the projection angle of the projection light 705. The reflecting surface 7750 of the curved mirror 775 may be any curved surface. In the example of FIG. 36, the reflecting surface 7750 of the curved mirror 775 has the shape of the side surface of a cylinder. For example, the reflecting surface 7750 of the curved mirror 775 may be a spherical surface. For example, the reflecting surface 7750 of the curved mirror 775 may be a free-form surface. For example, the reflecting surface 7750 of the curved mirror 775 may not be a single curved surface, but a shape combining a plurality of curved surfaces. For example, the reflecting surface 7750 of the curved mirror 775 may be a shape combining a curved surface and a plane.

[0150] The curved mirror 775 is disposed on the optical path of the modulated light 703 with the reflecting surface 7750 facing the modulation unit 7730 of the spatial light modulator 773. The reflecting surface 7750 of the curved mirror 775 is irradiated with the modulated light 703 modulated by the modulation unit 7730 of the spatial light modulator 773. The light (projection light 705) reflected by the reflecting surface 7750 of the curved mirror 775 is enlarged at a magnification corresponding to the curvature of the reflecting surface 7750 and then projected. In the example of FIG. 33, the projection light 705 is enlarged along the horizontal direction (the direction perpendicular to the plane of FIG. 36) according to the curvature of the irradiation range of the modulated light 703 on the reflecting surface 7750 of the curved mirror 775.

[0151] For example, a shield (not shown) may be disposed between the spatial light modulator 773 and the curved mirror 775. In other words, the shield may be disposed on the optical path of the modulated light 703 modulated by the modulation unit 7730 of the spatial light modulator 773. The shield is a frame that shields unnecessary light components included in the modulated light 703 and defines the outer edge of the display area of the projection light 705. For example, the shield is an aperture in which slit-shaped openings are formed in a portion that allows light forming a desired image to pass through. The shield allows light forming a desired image to pass through and shields unnecessary light components. For example, the shield shields the zero-order light and ghost images included in the modulated light 703. Details of the shield will be omitted from the description. In the example of FIG. 36, the curved mirror 775 is used. However, in the transmission device 770, instead of the curved mirror 775, a projection optical system including a Fourier transform lens, a projection lens, or the like may be provided. Further, the transmission device 770 may be configured to directly project the light modulated by the modulation unit 7730 of the spatial light modulator 773 without using the curved mirror 775 or the projection optical system.

[0152] The control unit 777 controls the light source 771 and the spatial light modulator 773. For example, the control unit 777 is realized by a microcomputer including a processor and a memory. The control unit 777 sets a phase image corresponding to the projected image in the modulation unit 7730 according to the aspect ratio of the tiling set in the modulation unit 7730 of the spatial light modulator 773. For example, the control unit 777 sets a phase image corresponding to an image according to the application, such as image display, communication, distance measurement, etc., in the modulation unit 7730. The phase image of the projected image may be stored in advance in a storage unit (not shown). There is no particular limitation on the shape and size of the projected image.

[0153] The control unit 777 drives the spatial light modulator 773 so that a parameter that determines the difference between the phase of the light 702 irradiated on the modulation unit 7730 of the spatial light modulator 773 and the phase of the modulated light 703 reflected by the modulation unit 7730 changes. For example, the parameter is a value related to optical characteristics such as refractive index and optical path length. For example, the control unit 777 adjusts the refractive index of the modulation unit 7730 by changing the voltage applied to the modulation unit 7730 of the spatial light modulator 773. The phase distribution of the light 702 irradiated on the modulation unit 7730 of the phase modulation type spatial light modulator 773 is modulated according to the optical characteristics of the modulation unit 7730. Note that the driving method of the spatial light modulator 773 by the control unit 777 is determined according to the modulation method of the spatial light modulator 773.

[0154] The control unit 777 drives the light source 771 in a state where the phase image corresponding to the displayed image is set in the modulation unit 7730. As a result, the light 702 emitted from the light source 771 is irradiated onto the modulation unit 7730 of the spatial light modulator 773 in accordance with the timing when the phase image is set in the modulation unit 7730 of the spatial light modulator 773. The light 702 irradiated onto the modulation unit 7730 of the spatial light modulator 773 is modulated in the modulation unit 7730 of the spatial light modulator 773. The modulated light 703 modulated in the modulation unit 7730 of the spatial light modulator 773 is emitted toward the reflecting surface 7750 of the curved mirror 775.

[0155] For example, the curvature of the reflecting surface 7750 of the curved mirror 775 included in the transmission device 770 and the distance between the spatial light modulator 773 and the curved mirror 775 are adjusted to set the projection angle of the projection light 705 to 180 degrees. If two such configured transmission devices 770 are used, the projection angle of the projection light 705 can be set to 360 degrees. Further, if a part of the modulated light 703 is folded back by a plane mirror or the like inside the transmission device 770 so that the projection light 705 is projected in two directions, the projection angle of the projection light 705 can be set to 360 degrees. For example, a configuration is adopted in which the transmission device 770 configured to project projection light in 360-degree directions is combined with the receiving device 2 of the second embodiment. With such a configuration, a communication device that transmits a spatial light signal in 360-degree directions and receives a spatial light signal arriving from 360-degree directions can be realized.

[0156] 〔Communication device〕 FIG. 37 is a conceptual diagram showing an example of the configuration of the communication device 700-1. The communication device 700-1 includes a receiver 7101, a transmitter 7701, and a control device (not shown). In FIG. 40, the receiving circuit and the control device are omitted. The communication device 700-1 has a configuration in which a receiver 7101 and a transmitter 7701 having a cylindrical outer shape are combined.

[0157] The receiver 7101 includes a ball lens 71, a light guide 73, a plurality of light receiving elements 75, a support member 781, a substrate 782, a conducting wire 783, and a color filter 784. The ball lens 71 is sandwiched at its upper and lower portions by a pair of support members 781 arranged vertically. Since the upper and lower portions of the ball lens 71 are not used for transmitting and receiving spatial optical signals, they may be processed into a planar shape so as to be easily sandwiched by the support members 781. The light guide 73 is arranged in accordance with the condensing region of the ball lens 71 so as to receive the spatial optical signal to be received. The light guide 73 is composed of a plurality of basic units 730. A light receiving element 75 is associated with each of the plurality of basic units 730. The plurality of light receiving elements 75 are arranged on the substrate 782. Each of the plurality of light receiving elements 75 is connected to a control device (not shown) or a transmitter 7701 by a conducting wire 783.

[0158] A color filter 784 is arranged on the side surface of the cylindrical receiver 7101. The color filter 784 removes unnecessary light and selectively transmits the spatial optical signal used for communication. A pair of support members 781 are arranged on the upper and lower surfaces of the cylindrical receiver 7101. The pair of support members 781 sandwich the upper and lower portions of the ball lens 71. An annularly formed light guide 73 is arranged on the light emitting side of the ball lens 71. The spatial optical signal incident on the ball lens 71 through the color filter 784 is condensed by the ball lens 71 toward the light guide 73. The optical signal condensed on the light guide 73 is guided by any one of the basic units 730 toward the light receiving portion of the light receiving element 75 associated with that basic unit 730. The optical signal reaching the light receiving portion of the light receiving element 75 is received by that light receiving element 75. The control device (not shown) causes the transmitter 7701 to transmit a spatial optical signal according to the optical signal received by the light guide 73.

[0159] The transmitter 7701 can be realized by the configuration shown in FIG. 36. The transmitter 7701 is housed inside a housing on a cylinder. A slit is formed in the cylindrical housing so as to align with the transmission direction of the spatial optical signal by the transmitter 7701. For example, when the transmitter 7701 can transmit spatial optical signals in all 360-degree directions, a slit that encircles the side surface is formed in the housing of the transmitter 7701 so as to align with the transmission direction of the spatial optical signal.

[0160] 〔Application Example 1〕 Next, Application Example 1 of the communication device 700-1 of the present embodiment will be described with reference to the drawings. FIG. 38 is a conceptual diagram for explaining this application example. In this application example, an example of a communication network (also referred to as a communication system) in which a plurality of communication devices 700-1 are arranged above a pole such as a utility pole or a streetlight (also referred to as the space above the pole) is shown.

[0161] There are few obstacles above poles such as utility poles and streetlights (the space above the pole). Therefore, the space above the pole is suitable for installing the communication device 700-1. Also, if the communication device 700-1 is installed at the same height, the arrival direction of the spatial optical signal is limited to the horizontal direction, so the light-receiving area of the light guide 73 constituting the receiver 7101 can be reduced and the device can be simplified. A pair of communication devices 700-1 that transmit and receive spatial optical signals is arranged such that at least one of the communication devices 700-1 receives the spatial optical signal transmitted from the other communication device 700-1. The pair of communication devices 700-1 may be arranged to transmit and receive spatial optical signals to and from each other. When a communication network of spatial optical signals is configured by a plurality of communication devices 700-1, the communication device 700-1 located in the middle may be arranged to relay the spatial optical signal transmitted from another communication device 700-1 to another communication device 700-1.

[0162] According to this application example, communication using free-space optical signals becomes possible among a plurality of communication devices 700-1 arranged in the space above the columns. For example, in response to communication among the communication devices 700-1 arranged in the space above the columns, communication by wireless communication may be configured between the wireless devices and base stations installed in automobiles, houses, etc. and the communication devices 700-1. For example, the communication devices 700-1 may be configured to be connected to the Internet via communication cables or the like installed on the columns.

[0163] As described above, the communication device, receiving device, transmitting device, and control device of this embodiment are provided. The receiving device includes a ball lens, a light guide, a plurality of light receiving elements, and a receiving circuit. The ball lens condenses the optical signal propagating in the space. The light guide is composed of a plurality of basic units arranged annularly around the ball lens. The light guide guides the optical signal condensed by the ball lens in a direction substantially perpendicular to the incident direction of the optical signal. Each of the plurality of light receiving elements is associated with each of the plurality of basic units. The light receiving element receives the optical signal emitted from the basic unit. The light receiving element outputs a signal derived from the received optical signal. The transmitting device transmits a free-space optical signal. The receiving circuit acquires the signals output from the plurality of light receiving elements. The receiving circuit decodes the acquired signals. The control device acquires a signal based on the free-space optical signal from another communication device received by the receiving device. The control device executes processing according to the acquired signal. The control device causes the transmitting device to transmit a free-space optical signal according to the executed processing.

[0164] The communication device of this embodiment includes a receiving device that guides optical signals arriving from various directions to a light receiving element associated with a basic unit by any one of the plurality of basic units constituting the light guide. According to the communication device of this embodiment, since optical signals arriving from various directions can be received collectively for each basic unit constituting the light guide, the number of light receiving elements can be reduced. Therefore, according to the communication device of this embodiment, optical signals arriving from various directions can be received using an appropriate number of light receiving elements.

[0165] A communication system according to an aspect of this embodiment includes a plurality of the above-described communication devices. In the communication system, the plurality of communication devices are arranged to transmit and receive spatial optical signals to and from each other. According to this aspect, a communication network that transmits and receives spatial optical signals can be realized.

[0166] (Eighth Embodiment) Next, a receiving device according to the eighth embodiment will be described with reference to the drawings. The receiving device of this embodiment has a simplified configuration compared to the receiving devices of the first to sixth embodiments. FIG. 39 is a conceptual diagram showing an example of the configuration of a receiving device 8 according to this embodiment. The receiving device 8 includes a ball lens 81, a light guide 83, and a plurality of light receiving elements 85.

[0167] The ball lens 81 condenses an optical signal propagating in space. The light guide 83 is composed of a plurality of basic units 830 arranged annularly around the ball lens 81. The light guide 83 guides the optical signal condensed by the ball lens 81 in a direction substantially perpendicular to the incident direction of the optical signal. Each of the plurality of light receiving elements 85 is associated with each of the plurality of basic units 830. The light receiving element 85 receives the optical signal emitted from the basic unit 830. The light receiving element 85 outputs a signal derived from the received optical signal.

[0168] As described above, the receiving device of this embodiment guides optical signals arriving from various directions to a light receiving element associated with a basic unit by any one of the plurality of basic units constituting the light guide. According to the receiving device of this embodiment, optical signals arriving from various directions can be received collectively for each basic unit constituting the light guide, so the number of light receiving elements can be reduced. Therefore, according to the receiving device of this embodiment, optical signals arriving from various directions can be received using an appropriate number of light receiving elements.

[0169] (Hardware) Here, regarding the hardware configuration that executes the control and processing according to each embodiment of the present disclosure, the information processing apparatus 90 in FIG. 40 will be taken as an example for explanation. Note that the information processing apparatus 90 in FIG. 40 is a configuration example for executing the control and processing of each embodiment, and does not limit the scope of the present disclosure.

[0170] As shown in FIG. 40, the information processing apparatus 90 includes a processor 91, a main memory device 92, an auxiliary storage device 93, an input / output interface 95, and a communication interface 96. In FIG. 40, the interface is abbreviated as I / F (Interface). The processor 91, the main memory device 92, the auxiliary storage device 93, the input / output interface 95, and the communication interface 96 are connected to be able to communicate with each other via a bus 98. Also, the processor 91, the main memory device 92, the auxiliary storage device 93, and the input / output interface 95 are connected to a network such as the Internet or an intranet via the communication interface 96.

[0171] The processor 91 expands the program stored in the auxiliary storage device 93 or the like into the main memory device 92. The processor 91 executes the program expanded in the main memory device 92. In this embodiment, a configuration using the software program installed in the information processing apparatus 90 may be adopted. The processor 91 executes the control and processing according to each embodiment.

[0172] The main memory device 92 has an area where the program is expanded. In the main memory device 92, the program stored in the auxiliary storage device 93 or the like is expanded by the processor 91. The main memory device 92 is realized by a volatile memory such as DRAM (Dynamic Random Access Memory), for example. Also, as the main memory device 92, a non-volatile memory such as MRAM (Magnetoresistive Random Access Memory) may be configured / added.

[0173] The auxiliary storage device 93 stores various data such as programs. The auxiliary storage device 93 is realized by a local disk such as a hard disk or a flash memory. Note that it is also possible to configure to store various data in the main storage device 92 and omit the auxiliary storage device 93.

[0174] The input / output interface 95 is an interface for connecting the information processing device 90 and peripheral devices based on standards and specifications. The communication interface 96 is an interface for connecting to an external system or device through a network such as the Internet or an intranet based on standards and specifications. The input / output interface 95 and the communication interface 96 may be shared as an interface for connecting to external devices.

[0175] Input devices such as a keyboard, a mouse, and a touch panel may be connected to the information processing device 90 as necessary. Those input devices are used for inputting information and settings. Note that when using a touch panel as an input device, the display screen of the display device may also serve as the interface of the input device. Data communication between the processor 91 and the input device may be mediated by the input / output interface 95.

[0176] In addition, the information processing device 90 may be equipped with a display device for displaying information. When equipped with a display device, it is preferable that the information processing device 90 is provided with a display control device (not shown) for controlling the display of the display device. The display device may be connected to the information processing device 90 via the input / output interface 95.

[0177] In addition, the information processing device 90 may be equipped with a drive device. The drive device mediates reading of data and programs from the recording medium and writing of the processing results of the information processing device 90 to the recording medium between the processor 91 and the recording medium (program recording medium). The drive device may be connected to the information processing device 90 via the input / output interface 95.

[0178] The above is an example of a hardware configuration for enabling the control and processing according to each embodiment of the present invention. Note that the hardware configuration in FIG. 40 is an example of a hardware configuration for executing the control and processing according to each embodiment, and does not limit the scope of the present invention. Also, a program for causing a computer to execute the control and processing according to each embodiment is included in the scope of the present invention. Further, a program recording medium recording the program according to each embodiment is included in the scope of the present invention. The recording medium can be realized by, for example, an optical recording medium such as a CD (Compact Disc) or a DVD (Digital Versatile Disc). The recording medium may be realized by a semiconductor recording medium such as a USB (Universal Serial Bus) memory or an SD (Secure Digital) card. Also, the recording medium may be realized by a magnetic recording medium such as a flexible disk or other recording media. When the program executed by the processor is recorded on the recording medium, the recording medium corresponds to a program recording medium.

[0179] The components of each embodiment may be arbitrarily combined. Also, the components of each embodiment may be realized by software or by a circuit.

[0180] Although the present invention has been described with reference to the embodiments above, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art within the scope of the present invention can be made to the configuration and details of the present invention.

[0181] Some or all of the above embodiments may be described as follows in the appended claims, but are not limited thereto. (Appended Claim 1) A ball lens that condenses an optical signal propagating in space, A light guide constituted by a plurality of basic units arranged annularly around the ball lens, for guiding the optical signal condensed by the ball lens in a direction substantially perpendicular to the incident direction of the optical signal, A receiving device comprising: a plurality of light receiving elements each associated with one of the plurality of basic units, receiving the optical signal emitted from the basic unit, and outputting a signal derived from the received optical signal. (Appendix 2) The basic unit is A light guide including a first surface including an incident surface on which the optical signal condensed by the ball lens is incident, a second surface facing the first surface, and an emission end from which the optical signal incident from the incident surface is emitted. A light traveling direction changing member disposed at a position facing the incident surface on the side of the second surface, and changing the traveling direction of the optical signal incident from the incident surface toward the emission end. The light receiving element is The receiving device according to Appendix 1, wherein a light receiving portion that receives light in the wavelength region of the optical signal is disposed toward the emission end of the basic unit. (Appendix 3) The light traveling direction changing member is The receiving device according to Appendix 2, which is a diffraction element disposed at a position facing the incident surface on the side of the second surface, and diffracting the optical signal incident from the incident surface toward the emission end. (Appendix 4) The light traveling direction changing member is The receiving device according to Appendix 2, which is a multi-mirror formed by combining a plurality of reflecting surfaces formed at a position facing the incident surface on the side of the second surface and reflecting the optical signal incident from the incident surface toward the emission end. (Appendix 5) The basic unit is The receiving device according to any one of Appendices 2 to 4, which is disposed so as to guide the optical signal entering from the incident surface in a direction perpendicular to the surface formed by the arrangement of the plurality of basic units. (Appendix 6) The basic unit is Disposed so as to guide the optical signal entering from the incident surface in a direction along the circumferential direction of a circle formed by the arrangement of the plurality of basic units, The emission ends of each of the plurality of basic units are The receiving device according to any one of Appendices 2 to 4, which is disposed on the side of the second surface of the adjacent basic unit. (Appendix 7) The basic unit includes a concave curved surface including an incident surface that reflects the optical signal, a convex curved surface facing the concave curved surface, and an output end through which the optical signal incident on the incident surface is guided, A plurality of the basic units are arranged with the concave curved surface facing the ball lens so as to guide the optical signal entering from the incident surface in a direction along the circumferential direction of a circle formed by the arrangement of the plurality of the basic units. The output end of each of the plurality of the basic units is disposed on the side of the convex curved surface of the adjacent basic unit. The light receiving element has a light receiving portion that receives light in the wavelength region of the optical signal, is disposed with the light receiving portion facing the output end of the basic unit, and receives the optical signal reflected and guided by the concave curved surface of the associated basic unit and the convex curved surface of the basic unit adjacent to the associated basic unit. The receiving device according to Appendix 1. (Appendix 8) The basic unit is composed of a first curved mirror including an incident surface that reflects the optical signal and a second curved mirror with a reflecting surface facing the first curved mirror. A plurality of the first curved mirrors are disposed with the incident surface facing the ball lens. The light receiving element has a light receiving portion that receives light in the wavelength region of the optical signal, and is disposed with the light receiving portion facing the reflecting surface of the second curved mirror on the same curved surface as the incident surface of the first curved mirror of the associated basic unit. The receiving device according to Appendix 1. (Appendix 9) The basic unit is composed of a first curved mirror including an incident surface that reflects the optical signal. A plurality of the first curved mirrors arranged facing the incident surface toward the ball lens, the light receiving element, A receiving device according to Addendum 1, wherein a light receiving unit that receives light in the wavelength region of the optical signal is arranged facing the incident surface of the first curved mirror of the associated basic unit. (Addendum 10) A receiving device according to any one of Addenda 1 to 9, comprising a light guiding auxiliary device that is arranged between the ball lens and the light guide and guides the optical signal condensed by the ball lens toward the light guide. (Addendum 11) The light guiding auxiliary device, a plurality of shielding layers arranged along the diameter direction of the ball lens, and a plurality of transparent layers formed between the plurality of shielding layers and through which the optical signal passes, and is configured by the receiving device according to Addendum 10. (Addendum 12) The light guiding auxiliary device, is configured by a plurality of partition walls arranged along the diameter direction of the ball lens, and is the receiving device according to Addendum 10. (Addendum 13) The light guiding auxiliary device, is arranged in close contact with the ball lens, and is the receiving device according to any one of Addenda 10 to 12. (Addendum 14) A receiving device according to any one of Addenda 1 to 13, comprising a receiving circuit that acquires the signals output from the plurality of light receiving elements and decodes the acquired signals. (Addendum 15) The receiving device according to Addendum 14, a transmitting device that transmits a spatial optical signal, and a control device that acquires a signal based on a spatial optical signal from another communication device received by the receiving device, executes processing according to the acquired signal, and transmits a spatial optical signal according to the executed processing to the transmitting device. A communication device comprising. (Addendum 16) A plurality of the communication devices according to Addendum 15 are provided, the plurality of communication devices, A communication system arranged to transmit and receive spatial optical signals to and from each other.

Explanation of symbols

[0182] 1, 2, 3, 4, 5, 6 Receiving devices 11, 21, 31, 41, 51, 61 Ball lenses 13, 23, 33, 43, 53, 63 Light guides 15, 25, 35, 45, 65 Light-receiving elements 46 Light-shielding band 57 Light-guide assistor 60 Light-receiving section 67 Receiving circuit 130, 230, 330, 430 Basic units 133, 233 Light conductors 135 Diffraction element 235 Multi-mirror 431 First curved mirror 432 Second curved mirror 571 Transparent layer 572 Shielding layer 575 Partition wall 671 First processing circuit 672 Control circuit 673 Selector 675 Second processing circuit 700 Communication device 710 Receiving device 750 Control device 770 Transmitting device 771 Light source 773 Spatial light modulator 775 Curved mirror 781 Support member 782 Substrate 783 Conductive wire 784 Color filter 7101 Receiver 7701 Transmitter

Claims

1. A ball lens that condenses an optical signal propagating in space, A light guide composed of a plurality of basic units arranged annularly around the ball lens, for guiding the optical signal condensed by the ball lens in a direction substantially perpendicular to the incident direction of the optical signal, A plurality of light receiving elements respectively associated with the plurality of basic units, receiving the optical signal emitted from the basic unit, and outputting a signal derived from the received optical signal, The basic unit includes A light guide including a first surface including an incident surface on which the optical signal condensed by the ball lens is incident, a second surface facing the first surface, and an output end from which the optical signal incident from the incident surface exits, An optical propagation direction changing member disposed at a position facing the incident surface on the side of the second surface, for changing the propagation direction of the optical signal incident from the incident surface toward the output end, The light receiving element includes A light receiving unit that receives light in the wavelength region of the optical signal, and a receiving device disposed toward the output end of the basic unit.

2. The optical propagation direction changing member is The receiving device according to claim 1, which is a diffraction element that diffracts the optical signal incident from the incident surface toward the output end.

3. The optical propagation direction changing member is The receiving device according to claim 1, which is a multi-mirror in which a plurality of reflecting surfaces that reflect the optical signal incident from the incident surface toward the output end are combined.

4. A ball lens that condenses an optical signal propagating in space, A light guide composed of a plurality of basic units arranged annularly around the ball lens, for guiding the optical signal condensed by the ball lens in a direction substantially perpendicular to the incident direction of the optical signal, A plurality of light receiving elements, each associated with one of the plurality of basic units, receiving the optical signal emitted from the basic unit and outputting a signal derived from the received optical signal. The basic unit includes a concave curved surface including an incident surface that reflects the optical signal, a convex curved surface facing the concave curved surface, and an output end through which the optical signal incident on the incident surface is guided. The plurality of basic units are arranged with the concave curved surface facing the ball lens so as to guide the optical signal entering from the incident surface in a direction along the circumferential direction of a circle formed by the arrangement of the plurality of basic units. The output end of each of the plurality of basic units is arranged on the side of the convex curved surface of the adjacent basic unit. The light receiving element has a light receiving portion that receives light in the wavelength region of the optical signal, is arranged with the light receiving portion facing the output end of the basic unit, and is a receiving device that receives the optical signal reflected and guided by the concave curved surface of the associated basic unit and the convex curved surface of the basic unit adjacent to the associated basic unit.

5. A ball lens that condenses an optical signal propagating in space, a light guide formed by a plurality of basic units annularly arranged around the ball lens, guiding the optical signal condensed by the ball lens in a direction substantially perpendicular to the incident direction of the optical signal, a plurality of light receiving elements, each associated with one of the plurality of basic units, receiving the optical signal emitted from the basic unit and outputting a signal derived from the received optical signal. The basic unit is composed of a first curved mirror including an incident surface that reflects the optical signal and a second curved mirror with a reflecting surface facing the first curved mirror. The plurality of first curved mirrors are arranged with the incident surface facing the ball lens. The light receiving element A receiving device in which a light receiving unit that receives light in the wavelength region of the optical signal is disposed on the same curved surface as the incident surface of the first curved mirror of the associated basic unit, facing the reflecting surface of the second curved mirror.

6. The receiving device according to any one of claims 1 to 5, further comprising a light guiding auxiliary device disposed between the ball lens and the light guide, and guiding the optical signal condensed by the ball lens toward the light guide.

7. The receiving device according to any one of claims 1 to 6, further comprising a receiving circuit that acquires the signals output from the plurality of light receiving elements and decodes the acquired signals.

8. The receiving device according to claim 7, A transmitting device that transmits a free space optical signal, and a control device that acquires a signal based on a free space optical signal from another communication device received by the receiving device, executes processing according to the acquired signal, and causes the transmitting device to transmit a free space optical signal according to the executed processing.

9. A communication system including a plurality of the communication devices according to claim 8, wherein the plurality of communication devices are arranged to transmit and receive free space optical signals to and from each other.

Images