Light receiver, communication device, and communication system

Abstract

To provide a light receiver capable of receiving a wavelength-multiplexed spatial optical signal with sufficient intensity.SOLUTION: A light receiver includes a ball lens, an irradiation position detector that detects the irradiation position of signal light focused by the ball lens, a wavelength separator that wavelength-separates the signal light of multiple wavelengths used for spatial optical communication from the signal light focused by the ball lens, and a light-receiving element group composed of multiple communication light-receiving elements that receive the signal light of multiple wavelengths wavelength-separated by the wavelength separator.SELECTED DRAWING: Figure 21

Description

[Technical field]

[0001] The present disclosure relates to an optical receiver, a communication device, and a communication system. [Background technology]

[0002] In spatial optical communication, wavelength-multiplexed spatial optical signals can be received by attaching wavelength-selective filters to multiple photodiodes. The multiple photodiodes are arranged in a line in a light-collecting range in front of the focal position of the lens. When multiple photodiodes are arranged in this way, the light-receiving area of ​​the photodiode for each wavelength becomes smaller, and the received light intensity of the spatial optical signal decreases.

[0003] Patent Document 1 discloses a space division device for selectively receiving any light beam from a plurality of light sources in optical communication in free space. The device of Patent Document 1 includes a liquid crystal arranged in a planar space. The device of Patent Document 1 is arranged in front of a light receiver. The device of Patent Document 1 selectively receives any light beam from a plurality of light sources by changing the transmittance of the liquid crystal on a pixel-by-pixel basis and switching the introduction of the plurality of light beams incident on the liquid crystal to the light receiver. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-012839 A Summary of the Invention [Problem to be solved by the invention]

[0005] A wavelength-multiplexed spatial optical signal is emitted from a different light source for each wavelength. Therefore, the irradiation position of the signal light focused by the lens shifts for each wavelength. The technique of Patent Document 1 does not correct the shift in the irradiation position of the signal light. Therefore, the technique of Patent Document 1 does not necessarily allow the wavelength-multiplexed spatial optical signal to be received with sufficient intensity.

[0006] An object of the present disclosure is to provide an optical receiver, a communication device, and a communication system capable of receiving a wavelength-multiplexed spatial optical signal with sufficient intensity. [Means for solving the problem]

[0007] An optical receiver according to one embodiment of the present disclosure includes a ball lens, an irradiation position detector that detects the irradiation position of signal light focused by the ball lens, a wavelength separator that wavelength-separates signal light of multiple wavelengths used for spatial optical communication from the signal light focused by the ball lens, and a photodetector group composed of multiple communication photodetectors that receive the signal light of multiple wavelengths wavelength-separated by the wavelength separator. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide an optical receiver, a communication device, and a communication system capable of receiving a wavelength-multiplexed spatial optical signal with sufficient intensity. [Brief description of the drawings]

[0009] [Figure 1] 1 is a block diagram showing an example of a configuration of a communication device according to the present disclosure. [Diagram 2] FIG. 2 is a block diagram showing an example of a configuration of a light receiver according to the present disclosure. [Diagram 3] 1 is a conceptual diagram illustrating an example of incidence of a spatial optical signal into a light receiver in the present disclosure. [Figure 4] FIG. 2 is a conceptual diagram illustrating an example of a configuration of a light receiver according to the present disclosure. [Diagram 5] FIG. 2 is a conceptual diagram illustrating an example of a configuration of a light receiver according to the present disclosure. [Figure 6]FIG. 2 is a conceptual diagram illustrating an example of a configuration of a light receiver according to the present disclosure. [Figure 7] FIG. 2 is a conceptual diagram illustrating an example of a configuration of a wavelength separator in the present disclosure. [Figure 8] FIG. 2 is a conceptual diagram illustrating an example of a configuration of a wavelength separator in the present disclosure. [Figure 9] FIG. 2 is a conceptual diagram illustrating an example of a configuration of a wavelength separator in the present disclosure. [Figure 10] FIG. 2 is a conceptual diagram illustrating an example of a configuration of a light transmitter according to the present disclosure. [Figure 11] 1 is a block diagram showing an example of a configuration of a communication control device according to the present disclosure. [Figure 12] 1 is a conceptual diagram for explaining direction detection of the arrival direction of a spatial optical signal by a communication device in the present disclosure. [Figure 13] FIG. 2 is a conceptual diagram illustrating an example of a configuration of a detector in the present disclosure. [Figure 14] FIG. 1 is a conceptual diagram for explaining an example of communication establishment in the present disclosure. [Figure 15] 11 is a flowchart for explaining an example of communication establishment in the present disclosure. [Figure 16] FIG. 2 is a conceptual diagram illustrating an example of a configuration of an irradiation position detector according to the present disclosure. [Figure 17] FIG. 2 is a conceptual diagram illustrating an example of a configuration of a direction detection circuit according to the present disclosure. [Figure 18] FIG. 2 is a conceptual diagram illustrating an example of a configuration of an irradiation position detector according to the present disclosure. [Figure 19] FIG. 2 is a conceptual diagram illustrating an example of a configuration of a direction detection circuit according to the present disclosure. [Figure 20] 1 is a conceptual diagram for explaining an application example of a communication network configured by a communication device according to the present disclosure. [Figure 21] FIG. 2 is a block diagram showing an example of a configuration of a light receiver according to the present disclosure. [Figure 22] FIG. 2 is a block diagram showing an example of a hardware configuration for executing processing and control in each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments for carrying out the present disclosure will be described with reference to the drawings. In this disclosure, the drawings used in the description of each embodiment relate to one or more embodiments. In addition, the elements included in each drawing may apply to one or more embodiments. The embodiments described below are limited in a manner that is technically preferable for carrying out the present disclosure, but the scope of the disclosure is not limited to the following. In all the drawings used in the description of the following embodiments, the same reference numerals are used for similar parts unless otherwise specified. In the following embodiments, repeated description of similar configurations and operations may be omitted.

[0011] In all the drawings used to explain the following embodiments, the direction of the arrows in the drawings is an example, and does not limit the direction of light or signals. In addition, the lines showing the trajectory of light in the drawings are conceptual, and do not accurately represent the actual traveling direction or state of light. For example, in the drawings, the change in the traveling direction or state 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. In addition, cross sections may not be hatched due to reasons such as illustrating an example of a light path or making the configuration too crowded.

[0012] (First embodiment) First, a receiving device according to the first embodiment will be described with reference to the drawings. The communication device of this embodiment is used for optical space communication in which spatial optical signals propagating through space are transmitted and received. The communication device of this embodiment communicates using spatial optical signals in which light of multiple wavelength bands is multiplexed (wavelength-multiplexed spatial optical signals). The communication device of this embodiment may be used for applications other than optical space communication as long as it is used for transmitting and receiving light propagating through space. Note that the drawings used in the description of this embodiment are conceptual and do not accurately depict the actual structure.

[0013] (composition) FIG. 1 is a block diagram showing an example of a configuration of a communication device 1 according to the present disclosure. The communication device 1 includes a light receiver 10, a light transmitter 15, and a communication control device 16. In the following, the light receiver 10, the light transmitter 15, and the communication control device 16 will each be described individually. In this embodiment, an example is given in which spatial optical communication using a spatial optical signal is performed with another communication device 1 that is a communication target. In addition, in this embodiment, an example is given in which a phase-modulation type spatial light modulator is included in the light transmitter 15.

[0014] [Receiver] Fig. 2 is a block diagram showing an example of the configuration of the optical receiver 10 in the present disclosure. Fig. 3 is a conceptual diagram showing an example of reception of a spatial optical signal by the optical receiver 10 in the present disclosure. Figs. 2 and 3 are conceptual diagrams showing the internal configuration of the optical receiver 10 as seen from a side perspective. The optical receiver 10 has a ball lens 11, an irradiation position detector 12, a wavelength separator 13, and a light receiving element group 14.

[0015] The irradiation position detector 12 includes a plurality of direction detecting light receiving elements used to detect the irradiation position of the signal light. The wavelength separator 13 includes components for wavelength separation of the wavelength-multiplexed signal light. The wavelength separator 13 also includes communication light receiving elements for each wavelength band to be received. FIGS. 2 and 3 show the conceptual positional relationship between the irradiation position detector 12 and the wavelength separator 13. The detailed configurations of the irradiation position detector 12 and the wavelength separator 13 will be described later.

[0016] The spatial light signal S arriving at the receiver 10 L is focused by the ball lens 11. The spatial light signal S L The light (signal light S O The signal light S ) is irradiated onto the irradiation position detector 12. O The irradiation position of the signal light S is detected by the communication control device 16. O Depending on the irradiation position of the signal light S O The spatial optical signal S is guided to the wavelength separator 13 and the light receiving element group 14. LThe spatial light signal S is transmitted to the light transmitter 15, which includes a request to change the transmission direction of the spatial light signal S. L In response to the request to change the transmission direction of the spatial optical signal, the communication target adjusts the transmission direction of the spatial optical signal S. L The signal light S derived from O The signal light S introduced into the wavelength separator 13 is introduced into the wavelength separator 13 through a through hole of the irradiation position detector 12. O The signal light S is separated into each wavelength band. O The light is received by a communication light receiving element assigned to each wavelength band.

[0017] The ball lens 11 is supported by a support (not shown). The ball lens 11 is a spherical lens. The ball lens 11 is an optical element that focuses a spatial optical signal arriving from the outside. The ball lens 11 is spherical when viewed from an arbitrary angle. The ball lens 11 focuses the incident spatial optical signal. The signal light originating from the spatial optical signal focused by the ball lens 11 is focused toward the focusing area of ​​the ball lens 11. Since the ball lens 11 is spherical, it focuses a spatial optical signal arriving from an arbitrary direction. That is, the ball lens 11 exhibits the same focusing performance for a spatial optical signal arriving from an arbitrary direction. The light that enters the ball lens 11 is refracted when entering the inside of the ball lens 11. In addition, the light that has traveled inside the ball lens 11 is refracted again when it is emitted to the outside of the ball lens 11. Most of the light emitted from the ball lens 11 is focused toward the focusing area.

[0018] For example, ball lens 11 can be made of materials such as glass, crystal, and resin. When receiving a spatial optical signal in the visible region, a material that transmits / refracts light in the visible region can be used for ball lens 11. For example, optical glass such as crown glass and flint glass can be used for ball lens 11. For example, crown glass such as BK (Boron Kron) can be used for ball lens 11. For example, flint glass such as LaSF (Lanthanum Schwerflint) can be used for ball lens 11. For example, quartz glass can be used for ball lens 11. For example, crystal such as sapphire can be used for ball lens 11. For example, transparent resin such as acrylic can be used for ball lens 11.

[0019] When the spatial optical signal is light in the near-infrared region (hereinafter also referred to as near-infrared), a material that transmits near-infrared light is used for the ball lens 11. For example, when receiving a spatial optical signal in the near-infrared region of about 1.5 micrometers (μm), materials such as silicon can be used for the ball lens 11 in addition to glass, crystal, resin, etc. When the spatial optical signal is light in the infrared region (hereinafter also referred to as infrared), a material that transmits infrared light is used for the ball lens 11. For example, when the spatial optical signal is infrared, materials such as silicon, germanium, and chalcogenide can be used for the ball lens 11. There is no limitation on the material of the ball lens 11 as long as it can transmit / refract light in the wavelength region of the spatial optical signal. The material of the ball lens 11 may be appropriately selected according to the required refractive index and application.

[0020] The irradiation position detector 12 is disposed in the light collecting region of the ball lens 11. FIGS. 4 to 6 are conceptual diagrams showing an example of the configuration of the irradiation position detector 12 in the present disclosure. FIG. 4 is a side view of the irradiation position detector 12 seen from a lateral viewpoint. FIG. 5 is a perspective view of the light receiving surface of the irradiation position detector 12 seen from obliquely above. FIG. 6 is a front view of the light receiving surface of the irradiation position detector 12 seen from the viewpoint of the ball lens 11. The irradiation position detector 12 has a substrate 121, a light receiving element 122 for direction detection, and a light guide tube 124. The irradiation position detector 12 has a plurality of light receiving elements 122 for direction detection. In the examples of FIGS. 3 to 5, the irradiation position detector 12 has four light receiving elements 122 for direction detection. The number of the light receiving elements 122 for direction detection is not limited to four.

[0021] The substrate 121 is a substrate used for a printed circuit board. A through hole A is formed in the substrate 121. The opening diameter of the through hole A is formed to match the size of the incident end (the opening end on the left side in FIG. 4) of the light guide tube 124. On the incident surface (the surface on the left side in FIG. 4) of the substrate 121, a plurality of light receiving elements 122 for direction detection are arranged around the through hole A. In the example of FIGS. 4 to 6, four light receiving elements 122 for direction detection are arranged around the through hole A. Note that the substrate 121 may be omitted as long as the positional relationship of the plurality of light receiving elements 122 for direction detection can be maintained and the optical signal collected by the ball lens 11 can be efficiently guided to the wavelength separator 13.

[0022] The direction detection light receiving elements 122 are arranged on the incident surface (the surface on the left side in FIG. 4) of the substrate 121. The direction detection light receiving elements 122 are arranged on the circumference of a circle centered on the through hole A of the substrate 121. The light receiving portion of the direction detection light receiving element 122 is directed toward the ball lens 11. The direction detection light receiving element 122 has sensitivity to light in the wavelength band of the spatial optical signal used for searching for the communication target. For example, the direction detection light receiving element 122 is realized by a photodiode having sensitivity to infrared light. For example, the direction detection light receiving element 122 is realized by an indium gallium arsenide InGaAs-based photodiode. For example, the communication light receiving element is realized by an InGaAs-based photodiode. The direction detection light receiving element 122 only needs to be able to detect the spatial optical signal, so it may be slower than the communication light receiving element. Therefore, the direction detection light receiving element 122 may be realized by a germanium Ge-based or silicon Si-based photodiode. Silicon-based photodiodes are used in the wavelength band from visible light to 1000 nm. On the other hand, InGaAs-based photodiodes are used in the wavelength band from 1300 to 1550 nm. Silicon-based photodiodes and InGaAs-based photodiodes are selected depending on the wavelength of the spatial optical signal used in communication. The spatial optical signal received by the direction detection light receiving element 122 is converted into an electrical signal. The converted electrical signal is output to the communication control device 16. If the communication control device 16 includes an integrator (not shown), the converted electrical signal is supplied to the integrator included in the communication control device 16. The electrical signal supplied to the integrator is integrated to a level that can be detected by the communication control device 16.

[0023] The light guide tube 124 is a cylindrical member having an incident end and an exit end. The incident end (open end on the left side in FIG. 4) is formed to match the size of the opening diameter of the through hole A. The exit end (open end on the right side in FIG. 4) has a smaller opening diameter than the incident end. The opening diameter of the exit end is formed to match the inner diameter of the wavelength separator 13. There are no particular limitations on the material and shape of the light guide tube 124. For example, a reflective surface that reflects the signal light may be formed on the inner surface of the light guide tube 124. For example, a light absorbing material may be disposed on the inner surface of the light guide tube 124 to reduce diffuse reflection of the signal light. Note that if the optical signal collected by the ball lens 11 can be efficiently guided to the wavelength separator 13, the light guide tube 124 may be omitted.

[0024] The wavelength separator 13 separates the wavelength-multiplexed spatial optical signal (signal light) into each wavelength band. The entrance of the wavelength separator 13 is connected to the exit end (the open end on the right side in FIG. 4) of the light guide tube 124. The wavelength separator 13 includes a configuration for separating light into wavelengths. For example, the wavelength separator 13 includes at least one dichroic mirror. For example, the wavelength separator 13 includes at least one convex lens. For example, the wavelength separator 13 includes at least one concave lens. For example, the wavelength separator 13 includes at least one dichroic cross prism.

[0025] The wavelength separator 13 includes a plurality of communication light receiving elements. Each of the plurality of communication light receiving elements is associated with one of the wavelength bands of the wavelength-multiplexed spatial optical signal used for communication. The wavelength-separated signal light is incident on each of the plurality of communication light receiving elements. The communication light receiving element has sensitivity to light in the wavelength band of the spatial optical signal to be communicated. For example, the communication light receiving element is realized by a photodiode having sensitivity to infrared light. For example, the communication light receiving element is realized by an indium gallium arsenide InGaAs-based or silicon-based photodiode. The spatial optical signal received by the communication light receiving element is converted into an electrical signal. The converted electrical signal is output to the communication control device 16.

[0026] FIG. 7 is a conceptual diagram showing an example of reception of signal light S1 derived from a wavelength-multiplexed spatial optical signal. The signal light S1 is multiplexed in two wavelength bands (wavelength λ1, wavelength λ2). FIG. 7 is a cross-sectional view of a portion of an example of the optical receiver 10 (optical receiver 10-1) seen from a side perspective. The optical receiver 10-1 includes a wavelength separator 13-1. The wavelength separator 13-1 includes a dichroic mirror 131, a communication light receiving element 141, and a communication light receiving element 142. The reflecting surface of the dichroic mirror 131 reflects the signal light of wavelength λ1 (first wavelength). The signal light of wavelength λ2 (second wavelength) passes through the dichroic mirror 131. The communication light receiving element 141 (first communication light receiving element) has sensitivity to light of wavelength λ1 (first wavelength). The communication light receiving element 142 (second communication light receiving element) has sensitivity to light of wavelength λ2 (second wavelength).

[0027] 7, the reflecting surface of the dichroic mirror 131 is tilted downward at an angle of 45 degrees with respect to the incident axis of the signal light S1. The communication light receiving element 141 is disposed below the dichroic mirror 131. The light receiving portion of the communication light receiving element 141 is directed toward the reflecting surface of the dichroic mirror 131 disposed above. The signal light of wavelength λ1 reflected by the reflecting surface of the dichroic mirror 131 is received by the communication light receiving element 141.

[0028] The communication light receiving element 142 is disposed after the dichroic mirror 131. The light receiving portion of the communication light receiving element 142 is directed toward the rear surface of the dichroic mirror 131. The signal light of wavelength λ2 that has passed through the dichroic mirror 131 is received by the communication light receiving element 142.

[0029] FIG. 8 is a conceptual diagram showing an example of receiving a signal light S2 derived from a wavelength-multiplexed spatial optical signal. The signal light S2 is multiplexed in three wavelength bands (wavelength λ1, wavelength λ2, and wavelength λ3). FIG. 8 is a cross-sectional view of a part of an example of the optical receiver 10 (optical receiver 10-2) seen from a side perspective. The optical receiver 10-2 includes a wavelength separator 13-2. The wavelength separator 13-2 includes a concave lens 130, a dichroic mirror 131, a dichroic mirror 132, a convex lens 135, a convex lens 136, a convex lens 137, a communication light receiving element 141, a communication light receiving element 142, and a communication light receiving element 143. The reflecting surface of the dichroic mirror 131 reflects the signal light of wavelength λ1 (first wavelength). The signal lights of wavelength λ2 (second wavelength) and wavelength λ3 (third wavelength) pass through the dichroic mirror 131. The reflective surface of the dichroic mirror 132 reflects the signal light of wavelength λ2 (second wavelength). The signal light of wavelength λ3 (third wavelength) passes through the dichroic mirror 132. The communication light receiving element 141 (first communication light receiving element) is sensitive to light of wavelength λ1 (first wavelength). The communication light receiving element 142 (second communication light receiving element) is sensitive to light of wavelength λ2 (second wavelength). The communication light receiving element 143 (third communication light receiving element) is sensitive to light of wavelength λ3 (third wavelength).

[0030] 8, concave lens 130 is disposed at the entrance of wavelength separator 13-2. The entrance surface of concave lens 130 faces ball lens 11. Signal light S2 incident on concave lens 130 is emitted from the exit surface. The emitted signal light S2 travels along the optical axis of concave lens 130.

[0031] The dichroic mirror 131 (first dichroic mirror) is disposed after the concave lens 130. The reflecting surface of the dichroic mirror 131 is tilted downward at an angle of 45 degrees with respect to the incident axis of the signal light S2. The reflecting surface of the dichroic mirror 131 reflects the signal light of wavelength λ1. The signal lights of wavelengths λ2 and λ3 are transmitted through the dichroic mirror 131. The convex lens 135 is disposed below the dichroic mirror 131. The incident surface of the convex lens 135 is directed toward the reflecting surface of the dichroic mirror 131 above. The communication light receiving element 141 is disposed below the convex lens 135. The light receiving portion of the communication light receiving element 141 is directed toward the exit surface of the convex lens 135 disposed above. The signal light of wavelength λ 1 reflected by the reflecting surface of the dichroic mirror 131 is condensed by the convex lens 135 and received by the light receiving element 141 for communication.

[0032] The dichroic mirror 132 (second dichroic mirror) is disposed after the dichroic mirror 131. The reflecting surface of the dichroic mirror 132 is tilted downward at an angle of 45 degrees with respect to the incident axis of the signal light S2. The reflecting surface of the dichroic mirror 132 reflects the signal light of wavelength λ2. The signal light of wavelength λ3 passes through the dichroic mirror 132. The convex lens 136 is disposed below the dichroic mirror 132. The incident surface of the convex lens 136 faces the reflecting surface of the dichroic mirror 132 above. The communication light receiving element 142 is disposed below the convex lens 136. The light receiving portion of the communication light receiving element 142 faces the exit surface of the convex lens 136 disposed above. The signal light of wavelength λ2 reflected by the reflecting surface of the dichroic mirror 132 is condensed by the convex lens 136 and received by the light receiving element 142 for communication.

[0033] The convex lens 137 is disposed after the dichroic mirror 132. The incident surface of the convex lens 137 faces the back surface of the dichroic mirror 132. The communication light receiving element 143 is disposed after the convex lens 137. The light receiving portion of the communication light receiving element 143 faces the exit surface of the convex lens 137. The signal light of wavelength λ3 transmitted through the dichroic mirror 132 is collected by the convex lens 137 and received by the communication light receiving element 143.

[0034] Fig. 9 is a conceptual diagram showing an example of reception of signal light S3 derived from a wavelength-multiplexed spatial optical signal. The signal light S3 is multiplexed in three wavelength bands (wavelength λ1, wavelength λ2, and wavelength λ3). Fig. 9 is a cross-sectional view of a portion of an example of the optical receiver 10 (optical receiver 10-3) seen from a side perspective. The optical receiver 10-3 includes a wavelength separator 13-3. The wavelength separator 13-3 includes a concave lens 130, a dichroic cross prism 134, a convex lens 135, a convex lens 136, a convex lens 137, a communication light receiving element 141, a communication light receiving element 142, and a communication light receiving element 143.

[0035] 9, concave lens 130 is disposed at the entrance of wavelength separator 13-3. The entrance surface of concave lens 130 faces ball lens 11. Signal light S3 incident on concave lens 130 is emitted from the exit surface. The emitted signal light S3 travels along the optical axis of concave lens 130.

[0036] The dichroic cross prism 134 is disposed after the concave lens 130. The dichroic cross prism 134 reflects the signal light of wavelength λ1 downward. The dichroic cross prism 134 reflects the signal light of wavelength λ2 upward. The signal light of wavelength λ3 passes through the dichroic cross prism 134.

[0037] The convex lens 135 is disposed below the dichroic cross prism 134. The incident surface of the convex lens 135 faces the dichroic cross prism 134 above. The communication light receiving element 141 is disposed below the convex lens 135. The light receiving portion of the communication light receiving element 141 faces the exit surface of the convex lens 135 disposed above. The signal light of wavelength λ1 reflected downward by the dichroic cross prism 134 is collected by the convex lens 135 and received by the communication light receiving element 141.

[0038] The convex lens 136 is disposed above the dichroic cross prism 134. The incident surface of the convex lens 136 faces the dichroic cross prism 134 below. The communication light receiving element 142 is disposed above the convex lens 136. The light receiving portion of the communication light receiving element 142 faces the exit surface of the convex lens 136 disposed below. The signal light of wavelength λ2 reflected upward by the dichroic cross prism 134 is collected by the convex lens 136 and received by the communication light receiving element 142.

[0039] The convex lens 137 is disposed after the dichroic cross prism 134. The incident surface of the convex lens 137 faces the back surface of the dichroic cross prism 134. The communication light receiving element 143 is disposed after the convex lens 137. The light receiving portion of the communication light receiving element 143 faces the exit surface of the convex lens 137. The signal light of wavelength λ3 transmitted through the dichroic cross prism 134 is collected by the convex lens 137 and received by the communication light receiving element 143.

[0040] [Light transmitter] FIG. 10 is a conceptual diagram showing an example of the configuration of the light sender 15 in the present disclosure. FIG. 10 is a diagram showing the internal configuration of the light sender 15 from a side perspective. FIG. 10 shows an example in which light in the Fraunhofer region is used. The light sender 15 has a light source 151 and a spatial light modulator 153. FIG. 10 conceptually shows the positional relationship between the light source 151 and the spatial light modulator 153. FIG. 10 does not limit the positional relationship between the light source 151 and the spatial light modulator 153.

[0041] Light source 151 includes a plurality of emitters. In the example of FIG. 10, light source 151 includes an emitter that emits light of wavelength λ1, an emitter that emits light of wavelength λ2, and an emitter that emits light of wavelength λ3. The plurality of emitters are arranged inside the housing of light source 151 with their emission surfaces facing obliquely upward. The emission surface of light source 151 is directed toward modulation section 1530 of spatial light modulator 153 arranged above. Each of the plurality of emitters emits emission light in accordance with the control of communication control device 16.

[0042] A collimator is disposed in each of the multiple emitters. The collimator is disposed on an emission surface of the emitter. The collimator converts the emission light emitted from the emitter into parallel light. The parallel light (illumination light) converted by the collimator is irradiated onto the modulation section 1530 of the spatial light modulator 153. For example, each of the multiple emitters is associated with at least one of the multiple modulation regions set in the modulation section 1530 of the spatial light modulator 153. The illumination light derived from the emission light emitted from each of the multiple emitters travels toward the associated modulation region.

[0043] The multiple emitters included in the light source 151 emit laser light in different wavelength bands. The wavelength of the laser light emitted from the emitter is not particularly limited and may be selected according to the application. For example, the emitter emits laser light in a visible or infrared wavelength band. In this embodiment, a silicon-based photodiode for search and an InGaAs-based photodiode for communication are used separately. The silicon-based photodiode has sensitivity around 850 nm. The InGaAs photodiode has sensitivity around 1550 nm. For example, for near infrared rays of 800 to 1000 nm, the laser class can be raised compared to visible light, so that the sensitivity can be improved compared to visible light. For example, for infrared rays of a wavelength band of 1.55 micrometers (μm), a higher output laser light source can be used than for near infrared rays of 800 to 1000 nm. As a laser light source that emits infrared rays in the 1.55 μm wavelength band, an aluminum gallium arsenide phosphide (AlGaAsP) type laser light source or an indium gallium arsenide (InGaAs) type laser light source 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. For example, the emitter may be realized by a surface-emitting element such as a PCSEL (Photonic Crystal Surface Emitting Laser) type laser.

[0044] For example, the light source 151 may include a plurality of emitters that emit light in the same wavelength band. For example, the light source 151 is realized by a laser array in which a plurality of emitters are arranged in an array. For example, the laser array has a plurality of emitters arranged in 4 rows x 2 columns. For example, the light source 151 may be a combination of a plurality of emitters that emit illumination light in the same wavelength band and an emitter that emits illumination light in a wavelength band different from the emitters. For example, the light source 151 may be a combination of an emitter that emits laser light in a wavelength band used for communication with a communication target and an emitter that emits laser light in a wavelength band different from the laser light. For example, one of the plurality of emitters that constitute the laser array is used as a search emitter, and the others are used as communication emitters. For example, the search emitter emits light in a wavelength band of 850 nm. In that case, a silicon-based photodiode is used as the search light receiving element. For example, the communication emitter emits light in the wavelength band of 1550 nm. In that case, an InGaAs photodiode is used as the communication light receiving element. If the laser array is configured in this way, a search is performed using the search emitter (850 nm), and when the search is completed, the communication is switched to the communication using the communication emitter (1550 nm).

[0045] The spatial light modulator 153 is a phase modulation type spatial light modulator. The spatial light modulator 153 has a modulation section 1530. The spatial light modulator 153 is disposed diagonally above the light source 151. The modulation section 1530 of the spatial light modulator 153 is directed toward the emission surface of the light source 151. The illumination light irradiated to the modulation section 1530 of the spatial light modulator 153 is modulated according to a pattern (phase image) set in the modulation section 1530. The modulated light modulated by the modulation section 1530 is transmitted as a spatial light signal. The traveling direction of the spatial light signal (modulated light) can be adjusted according to the pattern (phase image) set in the modulation section 1530.

[0046] For example, the spatial light modulator 153 is realized by a spatial light modulator using ferroelectric liquid crystal, homogeneous liquid crystal, vertically aligned liquid crystal, or the like. For example, the spatial light modulator 153 can be realized by LCOS (Liquid Crystal on Silicon). The spatial light modulator 153 may also be realized by MEMS (Micro Electro Mechanical System). In the phase modulation type spatial light modulator 153, the spatial light signal S L By operating the parts used for transmitting light in a sequential manner, it is possible to concentrate energy on the image portion. Therefore, when the phase modulation type spatial light modulator 153 is used, if the output of the emitter included in the light source 151 is the same, the image can be displayed brighter than with other methods.

[0047] At least one modulation area is set in the modulation section 1530 of the spatial light modulator 153. The number of modulation areas set in the modulation section 1530 is set according to the number of emitters included in the light source 151. Each of the multiple modulation areas is associated with one of the multiple emitters included in the light source 151. Each of the multiple modulation areas is irradiated with illumination light derived from the laser light emitted from the associated emitter. However, as long as the illumination light derived from the laser light emitted from the emitter is incident on the modulation surface of the modulation area, the correspondence between the modulation area and the emitter is not particularly limited. In addition, the number of modulation areas set in the modulation section 1530 may be different from the number of emitters included in the light source 151.

[0048] The modulation area is divided into a plurality of areas (also called tiling). A phase image is assigned to each of the plurality of tiles. Each of the plurality of tiles is composed of a plurality of pixels. A phase image corresponding to an image to be projected is set to each of the plurality of tiles. A phase image is tiled to each of the plurality of tiles assigned to the modulation area. For example, a phase image generated in advance is set to each of the plurality of tiles. When illumination light is irradiated to the modulation area with phase images set to the plurality of tiles, modulated light that forms an image corresponding to the phase image of each tile is emitted. The more tiles that are set in the modulation area, the clearer the image that can be displayed, but the resolution decreases when the number of pixels in each tile decreases. Therefore, the size and number of tiles set in the modulation area are set according to the application.

[0049] In each of the multiple modulation regions, a spatial optical signal S L A pattern (also called a phase image) corresponding to the image displayed by the modulation area is set in each of the multiple modulation areas. A pattern (phase image) is set in each of the multiple modulation areas. The illumination light irradiated to each of the multiple modulation areas is modulated according to the pattern (phase image) set in the modulation area. The modulated light modulated in each of the multiple modulation areas is represented as a spatial light signal S L is sent as

[0050] For example, a shield (not shown) may be disposed downstream of the spatial light modulator 153. The shield is a frame that shields unnecessary light components contained in the modulated light and defines the outer edge of the display area of ​​the projected light. For example, the shield is an aperture. In such an aperture, a slit-shaped opening is formed in a portion that passes light (desired light) that forms a desired image. The desired light is first-order diffracted light. The shield passes the desired light and shields unnecessary light components. For example, the shield shields zero-order light contained in the modulated light, unnecessary first-order light that appears at a position point-symmetrical with respect to the desired light with the zero-order light as the center, and ghost images that include second-order or higher-order light. Details of the shield are omitted. For example, a projection lens (not shown) may be disposed downstream of the spatial light modulator 153. If a concave lens is used as the projection lens, the spatial light signal S L The beam diameter can be reduced.

[0051] [Communication Control Device] 11 is a conceptual diagram showing an example of the configuration of the communication control device 16. The communication control device 16 has a direction detection circuit 17 and a communication circuit 18. The direction detection circuit 17 includes a plurality of detectors 170 and a control circuit 177. The communication circuit 18 includes a plurality of signal processing circuits 181 and a communication unit 183.

[0052] Each of the multiple detectors 170 is connected to each of the multiple direction detection light receiving elements 122. The multiple detectors 170 are connected to a control circuit 177. The detector 170 includes an amplifier 171, a detector 173, and a conversion circuit 175. In FIG. 11, the conversion circuit 175 is represented as an ADC (Analog-to-Digital Converter). The multiple detectors 170 may include a filter corresponding to the modulation frequency to be received. The filter cuts off signals derived from ambient light such as sunlight.

[0053] The amplifier 171 is connected to the direction detection light receiving element 122. An electrical signal derived from the signal light received by the direction detection light receiving element 122 is input to the amplifier 171. The amplifier 171 amplifies the input electrical signal at a set amplification factor. For example, if only the AC component of the signal from the direction detection light receiving element 122 is amplified, the influence of sunlight can be eliminated. The amplification factor of the amplifier 171 can be set arbitrarily. The electrical signal amplified by the amplifier 171 is output to the detector 173.

[0054] The signal having the modulation frequency to be received and amplified by the amplifier 171 is input to the detector 173. The detector 173 detects the input signal. An amplifier may be disposed after the detector 173. The signal detected by the detector 173 is supplied to the conversion circuit 175.

[0055] The signal detected by the detector 173 is input to the conversion circuit 175. The conversion circuit 175 converts the input signal (analog signal) into a digital signal. The converted digital signal is output to the control circuit 177.

[0056] The control circuit 177 receives a signal derived from the signal light received by each of the plurality of direction detection light receiving elements 122. The control circuit 177 detects the arrival direction of the spatial optical signal according to the state of reception of the signal light by each of the plurality of direction detection light receiving elements 122.

[0057] FIG. 12 is a conceptual diagram for explaining detection of the direction of arrival of a spatial optical signal by control circuit 177. FIG. 12 is a conceptual diagram of the light receiving surface of irradiation position detector 12 as viewed from the viewpoint of ball lens 11. In FIG. 12, alphabets (A, B, C, D) are added to the end of the reference characters representing the multiple direction detection light receiving elements 122 to distinguish them from one another. FIG. 12 also shows the inner surface of light guide tube 124 and wavelength separator 13. The multiple direction detection light receiving elements 122 are arranged on the circumference of a circle centered on wavelength separator 13. FIG. 12 shows an example of the light collection range of light collected by ball lens 11 as a circle.

[0058] The signal light irradiated within the range of the light-collecting range R1 (dashed line) is received by the direction detection light-receiving element 122-C and the direction detection light-receiving element 122-D. The control circuit 177 sets the transmission direction of the spatial optical signal to the light transmitter 15 according to the reception state of the signal light by the direction detection light-receiving element 122-C and the direction detection light-receiving element 122-D. The signal light irradiated within the range of the light-collecting range R1 (dashed line) is received by the light-receiving element group 14. The control circuit 177 may set the transmission direction of the spatial optical signal, including the reception state of the signal light by the light-receiving element group 14. The control circuit 177 may set the transmission direction of the spatial optical signal according to the intensity of the signal light received by the direction detection light-receiving element 122-C and the direction detection light-receiving element 122-D. When the signal light is irradiated within the range of the light-collecting range R1 (dashed line), the spatial optical signal arrives from the upper left direction as viewed from the viewpoint of the light-receiving surface. Therefore, the control circuit 177 outputs a control signal for directing the transmission direction of the spatial optical signal to the upper left direction to the light transmitter 15. The control circuit 177 controls the transmission direction of the spatial optical signal by changing the pattern (phase image) of the modulation section 1530 of the spatial light modulator 153.

[0059] The signal light irradiated within the range of the light-collecting range R2 (dotted line) is received by the direction-detecting light-receiving element 122-D. The control circuit 177 sets the transmission direction of the spatial light signal to the light transmitter 15 according to the reception state of the signal light by the direction-detecting light-receiving element 122-D. When the signal light is irradiated within the range of the light-collecting range R2 (dotted line), the spatial light signal arrives from the left direction as viewed from the viewpoint of the light-receiving surface. Therefore, the control circuit 177 outputs a control signal to the light transmitter 15 to change the transmission direction of the spatial light signal to the left. The control circuit 177 controls the transmission direction of the spatial light signal by changing the pattern (phase image) of the modulation section 1530 of the spatial light modulator 153.

[0060] The signal light irradiated within the range of the light collection range R3 (two-dot chain line) is received by the direction detection light receiving element 122-B and the direction detection light receiving element 122-C. The control circuit 177 sets the transmission direction of the spatial optical signal to the light transmitter 15 according to the reception state of the signal light by the direction detection light receiving element 122-B and the direction detection light receiving element 122-C. The control circuit 177 may set the transmission direction of the spatial optical signal according to the intensity of the signal light received by the direction detection light receiving element 122-B and the direction detection light receiving element 122-C. When the signal light is irradiated within the range of the light collection range R3 (two-dot chain line), the spatial optical signal arrives from the upper right direction as viewed from the viewpoint of the light receiving surface. Therefore, the control circuit 177 outputs a control signal to the light transmitter 15 to direct the transmission direction of the spatial optical signal to the upper right direction. The control circuit 177 controls the transmission direction of the spatial light signal by changing the pattern (phase image) of the modulation section 1530 of the spatial light modulator 153.

[0061] When the orientation of the light receiving surface of the optical receiver 10 is changeable, the control circuit 177 may be configured to perform control to change the orientation of the light receiving surface of the optical receiver 10 according to the reception status of the signal light. For example, if the optical receiver 10 is arranged to be movable in the horizontal and vertical planes along a trajectory centered on the ball lens 11, the orientation of the light receiving surface of the optical receiver 10 can be freely changed.

[0062] 13 is a conceptual diagram showing another example of the detector 170 (detector 170-1). The detector 170-1 includes a digital filter 176. The digital filter 176 separates the signal light received by the direction detection light receiving element 122 into each frequency band to be received. In the example of FIG. 13, the digital filter 176 separates a signal S with a modulation frequency f1 from the signal light received by the direction detection light receiving element 122. f1 , a signal S with modulation frequency f f2 , and a signal S with modulation frequency f f3 The number of frequency bands to be received is not limited to three, and may be four or more. By using the detector 170-1, signals of multiple frequency bands can be separated from the signal light received by a single direction detection light receiving element 122.

[0063] Each of the multiple signal processing circuits 181 is connected to one of the multiple communication light receiving elements included in the light receiving element group 14. In the example of Fig. 11, each of the multiple signal processing circuits 181 is connected to one of the communication light receiving elements 141, 142, and 143. The multiple signal processing circuits 181 are connected to a communication unit 183. In Fig. 11, the internal configuration of the signal processing circuit 181 is omitted.

[0064] The signal processing circuit 181 acquires an electrical signal derived from a signal light received by any one of a plurality of communication light receiving elements included in the light receiving element group 14. The signal processing circuit 181 amplifies the acquired electrical signal. The signal processing circuit 181 converts the amplified electrical signal from an analog signal to a digital signal. The signal processing circuit 181 outputs the converted digital signal to the communication unit 183. For example, the signal processing circuit 181 may be provided with a limiting amplifier (not shown) in front of an amplifier (not shown). If a limiting amplifier is provided, a dynamic range can be secured. For example, the signal processing circuit 181 may be provided with a filter (not shown) such as a high-pass filter, a low-pass filter, or a band-pass filter. The high-pass filter or the band-pass filter cuts off a signal derived from ambient light such as sunlight, and selectively passes a signal of a high-frequency component corresponding to the wavelength band of the spatial light signal.

[0065] The communication unit 183 decodes the signal output from the signal processing circuit 181. The communication unit 183 individually decodes the signal for each frequency band included in the spatial optical signal transmitted from the communication target. The communication unit 183 causes the light transmitter 15 to transmit the spatial optical signal for each frequency band in response to the decoded signal for each frequency band. In this way, the communication device 1 of this embodiment can transmit and receive spatial optical signals multiplexed in multiple frequency bands.

[0066] [Communication established] FIG. 14 is a conceptual diagram for explaining the establishment of communication in a communication network including the communication device 1 of this embodiment. FIG. 14 relates to the establishment of communication between the communication device 1A and the communication device 1B. The communication device 1A and the communication device 1B use a spatial optical signal in which three systems of spatial optical signals with different wavelengths are multiplexed. The communication device 1A uses a spatial optical signal S A1 , a spatial optical signal S with wavelength λ A2 , and a spatial optical signal S of wavelength λ A3 The communication device 1B transmits three types of spatial optical signals. B1 , a spatial optical signal S with wavelength λ B2 , and a spatial optical signal S of wavelength λ B3 The communication device 1A and the communication device 1B use spatial optical signals of different wavelengths to establish communication with a communication target independently for each wavelength.

[0067] The example of Fig. 14 shows a state in which communication is established between communication device 1A and communication device 1B using spatial optical signals with wavelength λ1. If communication using one system of spatial optical signals is established as in Fig. 14, an instruction to adjust the transmission direction of the spatial optical signals can be issued to the communication targets for the other two systems with which communication is not established as soon as even a small amount of spatial optical signals are received. Therefore, the time spent establishing communication for the other two systems with which communication is not established is shorter than that for the first system.

[0068] Fig. 15 is a flowchart for explaining an example of communication establishment in the present disclosure. In the explanation following the flowchart in Fig. 15, the explanation will be given with the communication device 1 as the subject of the operation.

[0069] In FIG. 15, first, the communication device 1 scans for a communication target using three types of scan signals (step S11).

[0070] When a scan signal is received from the communication target (Yes in step S12), the communication device 1 transmits one system of scan signals corresponding to the received scan signal to the communication target (step S13). When a scan signal is not received from the communication target (No in step S12), the communication device 1 continues scanning using the three systems of scan signals (step S11).

[0071] After step S13, the communication device 1 establishes one line of communication using one line of scan signals and communication signals (step S14).

[0072] When a scan signal in a different wavelength band with which communication has not been established is received from a communication target (Yes in step S15), the communication device 1 transmits the reception status of the scan signal in the different wavelength band to the communication target (step S16). When a scan signal in the different wavelength band has not been received from a communication target (No in step S15), the communication device 1 waits until it receives a scan signal in the different wavelength band.

[0073] After step S16, the communication device 1 establishes another system of communication (step S17).

[0074] When communication is established in all systems (Yes in step S18), the communication device 1 ends the process according to the flowchart in Fig. 15 and communicates with the communication target using the spatial optical signals of all systems. If communication is not established in all systems (No in step S18), the communication device 1 returns to the process of step S15. In a situation where communication is not established in all systems, the communication device 1 communicates using the spatial optical signals of the systems with which communication is already established.

[0075] (Modification) Next, modified examples of the irradiation position detector 12 included in the optical receiver 10 of this embodiment will be described. Two modified examples will be given below. The first modified example 1 is an example in which a wavelength filter is placed in front of a photodiode sensitive to light in the same wavelength band. The second modified example 2 is an example in which a photodiode sensitive to light in a different wavelength band is used. The following modified examples are merely examples and do not limit the irradiation position detector 12 included in the optical receiver 10 of this embodiment.

[0076] [Variation 1] Modification 1 is an example in which a wavelength filter is placed in front of a photodiode sensitive to light in the same wavelength band. FIG. 16 is a conceptual diagram showing an example (irradiation position detector 12-1) of the irradiation position detector 12 in the present disclosure. FIG. 16 is a front view of the light receiving surface of the irradiation position detector 12-1 as seen from the viewpoint of the ball lens 11. In this modification, light in multiple wavelength bands contained in the spatial light signal is modulated with modulation frequencies different from each other. The spatial light signal is multiplexed with signals in wavelength bands of wavelength λ1, wavelength λ2, and wavelength λ3.

[0077] The irradiation position detector 12-1 has a substrate 121, a light receiving element 122 for direction detection, a wavelength filter 127, and a light guide tube 124. The substrate 121, the light receiving element 122 for direction detection, and the light guide tube 124 will not be described. The irradiation position detector 12 has a plurality of light receiving elements 122 for direction detection. In the example of FIG. 16, the irradiation position detector 12-1 has 12 light receiving elements 122 for direction detection. The number of the light receiving elements 122 for direction detection is not limited to 12. One wavelength filter 127 is disposed on the light receiving surface of each of the plurality of light receiving elements 122 for direction detection. In the example of FIG. 16, four wavelength filters 127-1, four wavelength filters 127-2, and four wavelength filters 127-3 are disposed. The wavelength filters 127 may be disposed according to the wavelength band to be received.

[0078] Wavelength filter 127-1 selectively transmits light of wavelength λ1. Wavelength filter 127-2 selectively transmits light of wavelength λ2. Wavelength filter 127-3 selectively transmits light of wavelength λ3. Wavelengths λ1, λ2, and λ3 are different from one another. The signal light that passes through each of wavelength filters 127-1 to 127-3 is received by direction detection light receiving element 122 arranged in the subsequent stage.

[0079] FIG. 17 is a conceptual diagram showing an example (direction detection circuit 17-1) of the direction detection circuit 17 according to this modification. The direction detection circuit 17-1 includes a detector 170 for each of the plurality of direction detection light receiving elements 122. The signal light of wavelength λ1 that has passed through the wavelength filter 127-1 is received by the direction detection light receiving element 122 arranged in the rear stage. The signal light of wavelength λ2 that has passed through the wavelength filter 127-2 is received by the direction detection light receiving element 122 arranged in the rear stage. The signal light of wavelength λ3 that has passed through the wavelength filter 127-3 is received by the direction detection light receiving element 122 arranged in the rear stage. The plurality of direction detection light receiving elements 122 output an electric signal according to the received signal light to the detector 170 in the rear stage. Each of the plurality of detectors 170 amplifies, detects, and AD converts the input electric signal, and outputs it to the control circuit 177.

[0080] The control circuit 177 receives a signal derived from the signal light received by each of the plurality of direction detection light receiving elements 122. The control circuit 177 detects the arrival direction of the spatial light signal according to the reception state of the signal light by each of the plurality of direction detection light receiving elements 122. The control circuit 177 detects the arrival direction of the spatial light signal for each wavelength of the signal light. The control circuit 177 controls the transmission direction of the spatial light signal for each wavelength by changing the pattern (phase image) of the modulation section 1530 of the spatial light modulator 153.

[0081] [Modification 2] Modification 2 is an example in which photodiodes sensitive to light of different wavelength bands are used. FIG. 18 is a conceptual diagram showing an example (irradiation position detector 12-2) of the irradiation position detector 12 in the present disclosure. FIG. 18 is a front view of the light receiving surface of the irradiation position detector 12-2 as seen from the viewpoint of the ball lens 11. In this modification, light of multiple wavelength bands included in the spatial light signal is modulated with modulation frequencies different from each other. The spatial light signal is multiplexed with signals of wavelength bands of wavelengths λ1, λ2, and λ3. The signal of wavelength λ1 is modulated with modulation frequency f1. The signal of wavelength λ2 is modulated with modulation frequency f2. The signal of wavelength λ3 is modulated with modulation frequency f3.

[0082] The irradiation position detector 12-2 has a substrate 121, a light receiving element for direction detection 122, and a light guide tube 124. The substrate 121 and the light guide tube 124 will not be described. The irradiation position detector 12 has a plurality of light receiving elements for direction detection 122. In the example of FIG. 18, the irradiation position detector 12-2 has four light receiving elements for direction detection 122-1, four light receiving elements for direction detection 122-2, and four light receiving elements for direction detection 122-3. The number of each of the light receiving elements for direction detection 122-1 to 3 is not limited to four. The light receiving element for direction detection 122-1 is sensitive to light of wavelength λ1. The light receiving element for direction detection 122-2 is sensitive to light of wavelength λ2. The light receiving element for direction detection 122-3 is sensitive to light of wavelength λ3.

[0083] 19 is a conceptual diagram showing an example (direction detection circuit 17-2) of the direction detection circuit 17 according to this modification. The direction detection circuit 17-2 includes a detector 170 (detector 170-2A, detector 170-2B, detector 170-2C) for each of the light receiving elements for direction detection 122-1 to 122-3. The detector 170-2A is connected to the light receiving element for direction detection 122-1. The detector 170-2B is connected to the light receiving element for direction detection 122-2. The detector 170-2C is connected to the light receiving element for direction detection 122-3.

[0084] The detector 170-2A includes an amplifier 171, a filter 172A, a detector 173, and a conversion circuit 175. An electric signal derived from the signal light of wavelength λ1 received by the direction detection light receiving element 122-1 is input to the amplifier 171 of the detector 170-2A. The amplifier 171 amplifies the input electric signal by a set amplification factor. The electric signal amplified by the amplifier 171 is output to the filter 172A. An electric signal derived from the signal light of wavelength λ1 is input to the filter 172A. The filter 172A selectively passes the modulation frequency f1 of the signal of wavelength λ1. The signal that has passed through the filter 172A is input to the detector 173. The signal of modulation frequency f1 to be received that has passed through the filter 172A is input to the detector 173. The detector 173 detects the input signal. The signal detected by detector 173 is supplied to conversion circuit 175. The signal detected by detector 173 is input to conversion circuit 175. Conversion circuit 175 converts the input signal (analog signal) into a digital signal. The converted digital signal is output to control circuit 177.

[0085] The detector 170-2B includes an amplifier 171, a filter 172B, a detector 173, and a conversion circuit 175. An electric signal derived from the signal light of wavelength λ2 received by the direction detection light receiving element 122-2 is input to the amplifier 171 of the detector 170-2B. The amplifier 171 amplifies the input electric signal by a set amplification factor. The electric signal amplified by the amplifier 171 is output to the filter 172B. An electric signal derived from the signal light of wavelength λ2 is input to the filter 172B. The filter 172B selectively passes the modulation frequency f2 of the signal of wavelength λ2. The signal that has passed through the filter 172B is input to the detector 173. The signal of modulation frequency f2 to be received that has passed through the filter 172B is input to the detector 173. The detector 173 detects the input signal. The signal detected by detector 173 is supplied to conversion circuit 175. The signal detected by detector 173 is input to conversion circuit 175. Conversion circuit 175 converts the input signal (analog signal) into a digital signal. The converted digital signal is output to control circuit 177.

[0086] The detector 170-2C includes an amplifier 171, a filter 172C, a detector 173, and a conversion circuit 175. The amplifier 171 is connected to the direction detection light receiving element 122-3. An electrical signal derived from the signal light of wavelength λ3 received by the direction detection light receiving element 122-3 is input to the amplifier 171 of the detector 170-2C. The amplifier 171 amplifies the input electrical signal by a set amplification factor. The electrical signal amplified by the amplifier 171 is output to the filter 172C. An electrical signal derived from the signal light of wavelength λ3 is input to the filter 172C. The filter 172C selectively passes the modulation frequency f3 of the signal of wavelength λ3. The signal that has passed through the filter 172C is input to the detector 173. The signal of modulation frequency f3 to be received that has passed through the filter 172C is input to the detector 173. The detector 173 detects the input signal. The signal detected by detector 173 is supplied to conversion circuit 175. The signal detected by detector 173 is input to conversion circuit 175. Conversion circuit 175 converts the input signal (analog signal) into a digital signal. The converted digital signal is output to control circuit 177.

[0087] The control circuit 177 receives signals derived from the signal light received by each of the direction detection light receiving elements 122-1 to 3. The control circuit 177 detects the arrival direction of the spatial light signal according to the reception state of the signal light by each of the direction detection light receiving elements 122-1 to 3. The control circuit 177 detects the arrival direction of the spatial light signal for each wavelength (modulation frequency) of the signal light. The control circuit 177 controls the transmission direction of the spatial light signal for each wavelength (modulation frequency) by changing the pattern (phase image) of the modulation section 1530 of the spatial light modulator 153.

[0088] (Examples) Next, application examples of this embodiment will be described with reference to the drawings. In the following application example, a plurality of communication devices 1 transmit and receive spatial optical signals. Fig. 20 is a conceptual diagram for explaining this application. In this application example, an example of a communication network (communication system) configured with a plurality of communication devices 1 is given on the top of a pole (pole space) such as a utility pole or a streetlight arranged in a city.

[0089] There are few obstacles in the space above the pole. Therefore, the space above the pole is suitable for installing the communication device 1. Also, if the communication device 1 is installed at a similar height, the direction of arrival of the spatial optical signal is limited to the horizontal direction. L A pair of communication devices 1 that transmit and receive spatial optical signals are arranged such that at least one of the communication devices 1 receives the spatial optical signal transmitted from the other communication device 1. A pair of communication devices 1 may be arranged to transmit and receive spatial optical signals to each other. When a communication network of spatial optical signals is formed by multiple communication devices 1, a communication device 1 located in between may be configured to relay a spatial optical signal transmitted from another communication device 1 to another communication device 1.

[0090] According to this application example, communication using spatial optical signals is possible between a plurality of communication devices 1 arranged in the space above a pole. For example, in response to communication between the communication devices 1, communication by wireless communication may be performed between the communication device 1 and a wireless device or base station installed in a car, a house, or the like. For example, the communication device 1 may be connected to the Internet via a communication cable or the like installed on a pole.

[0091] As described above, the communication device of this embodiment includes a light receiver, a light transmitter, and a communication control device. The light receiver includes a ball lens, an irradiation position detector, a wavelength separator, and a light receiving element group. The ball lens is a spherical lens. The irradiation position detector detects the irradiation position of the signal light focused by the ball lens. The wavelength separator wavelength-separates the signal light of multiple wavelengths used for spatial optical communication from the signal light focused by the ball lens. The light receiving element group is composed of multiple communication light receiving elements that receive the signal light of multiple wavelengths wavelength-separated by the wavelength separator. The light transmitter transmits a wavelength-multiplexed spatial optical signal used for spatial optical communication. The communication control device detects the arrival direction of the spatial optical signal according to the irradiation position detected by the irradiation position detector included in the light receiver. The communication control device causes the light transmitter to transmit the spatial optical signal toward the detected arrival direction.

[0092] The optical receiver of this embodiment separates the wavelengths of the signal light collected by the ball lens. The optical receiver of this embodiment receives the wavelength-separated signal light with one of a plurality of communication light receiving elements. Therefore, the optical receiver of this embodiment can receive the wavelength-multiplexed spatial optical signal with sufficient intensity.

[0093] In one aspect of this embodiment, the light receiving element group is composed of a first light receiving element for communication and a second light receiving element for communication. The first light receiving element for communication is sensitive to light of a first wavelength. The second light receiving element for communication is sensitive to light of a second wavelength. The wavelength separator includes a dichroic mirror. The dichroic mirror reflects the signal light of the first wavelength toward the first light receiving element for communication. The dichroic mirror transmits the signal light of the second wavelength toward the second light receiving element for communication. According to this aspect, the signal light of two wavelengths can be wavelength-separated using one dichroic mirror.

[0094] In one aspect of this embodiment, the light receiving element group is composed of a first communication light receiving element, a second communication light receiving element, and a third communication light receiving element. The first communication light receiving element is sensitive to light of the first wavelength. The second communication light receiving element is sensitive to light of the second wavelength. The third communication light receiving element is sensitive to light of the third wavelength. The wavelength separator includes a first dichroic mirror and a second dichroic mirror. The first dichroic mirror reflects the signal light of the first wavelength toward the first communication light receiving element. The first dichroic mirror transmits the signal light of the second wavelength and the signal light of the third wavelength. The second dichroic mirror reflects the signal light of the second wavelength that has passed through the first dichroic mirror toward the second communication light receiving element. The second dichroic mirror transmits the signal light of the third wavelength that has passed through the first dichroic mirror toward the third communication light receiving element. According to this aspect, signal light of three wavelengths can be separated by using two dichroic mirrors.

[0095] In one aspect of this embodiment, the light receiving element group is composed of a first light receiving element for communication, a second light receiving element for communication, and a third light receiving element for communication. The first light receiving element for communication is sensitive to light of a first wavelength. The second light receiving element for communication is sensitive to light of a second wavelength. The third light receiving element for communication is sensitive to light of a third wavelength. The wavelength separator includes a dichroic cross prism. The dichroic cross prism reflects the signal light of the first wavelength toward the first light receiving element for communication. The dichroic cross prism reflects the signal light of the second wavelength toward the second light receiving element for communication. The dichroic cross prism transmits the signal light of the third wavelength toward the third light receiving element for communication. According to this aspect, the signal light of three wavelengths can be wavelength-separated using one dichroic cross prism.

[0096] In one aspect of this embodiment, the irradiation position detector includes a substrate, a plurality of direction detection light receiving elements, and a light guide tube. The substrate has a light receiving surface facing the ball lens and a back surface opposite the light receiving surface. A through hole is opened in the substrate, penetrating the light receiving surface and the back surface. The plurality of direction detection light receiving elements are arranged around the through hole in the light receiving surface of the substrate, with the light receiving portion facing the ball lens. The light guide tube includes a light receiving surface side opening end connected to the through hole and a back surface side opening end connected to the wavelength separator. According to this aspect, the arrival direction of the spatial optical signal can be detected using the plurality of direction detection light receiving elements arranged around the through hole of the substrate.

[0097] In one aspect of this embodiment, the irradiation position detector has a plurality of direction detection light receiving elements corresponding to a plurality of wavelengths used in spatial optical communication. Wavelength filters that selectively transmit light of the wavelengths to be received are disposed in the light receiving portions of the plurality of direction detection light receiving elements. According to this aspect, the wavelength-multiplexed signal light can be wavelength-separated by using the wavelength filters that transmit the wavelengths to be received.

[0098] In one aspect of this embodiment, the irradiation position detector has a plurality of direction detection light receiving elements corresponding to a plurality of wavelengths used in the spatial optical communication. Each of the plurality of direction detection light receiving elements has sensitivity to light of the corresponding wavelength. According to this aspect, the wavelength-multiplexed signal light can be wavelength-separated by using the plurality of direction detection light receiving elements corresponding to the plurality of wavelengths.

[0099] In one aspect of this embodiment, the receiver includes a plurality of direction detection light receiving elements arranged with their light receiving portions facing the ball lens. The communication control device detects the arrival direction of the spatial optical signal according to the reception state of the signal light by the plurality of direction detection light receiving elements. The communication control device causes the light transmitter to transmit a spatial optical signal including information regarding the reception state of the signal light by the plurality of direction detection light receiving elements toward the detected arrival direction. According to this aspect, the arrival direction of the spatial optical signal detected according to the reception state of the signal light by the plurality of direction detection light receiving elements can be notified to the communication target.

[0100] A communication system according to one aspect of the present embodiment includes a plurality of the communication devices described above. 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 for transmitting and receiving spatial optical signals can be realized.

[0101] Second embodiment Next, a photoreceiver according to a second embodiment will be described with reference to the drawings. The photoreceiver of this embodiment has a simplified configuration of the photoreceiver of the first embodiment.

[0102] 21 is a conceptual diagram showing an example of the configuration of the optical receiver 20 in the present disclosure. The optical receiver 20 includes a ball lens 21, an irradiation position detector 22, a wavelength separator 23, and a light receiving element group 24.

[0103] Ball lens 21 is a spherical lens. Irradiation position detector 22 detects the irradiation position of the signal light focused by ball lens 21. Wavelength separator 23 wavelength-separates signal light of multiple wavelengths used for spatial optical communication from the signal light focused by ball lens 21. Light receiving element group 24 is composed of multiple communication light receiving elements that receive the signal light of multiple wavelengths separated by wavelength separator 23.

[0104] The optical receiver of this embodiment separates the wavelengths of the signal light collected by the ball lens. The optical receiver of this embodiment receives the wavelength-separated signal light with one of a plurality of communication light receiving elements. Therefore, the optical receiver of this embodiment can receive the wavelength-multiplexed spatial optical signal with sufficient intensity.

[0105] (Hardware) Next, a hardware configuration for executing the control and processing in the present disclosure will be described with reference to the drawings. Here, an information processing device 90 (computer) in Fig. 22 is given as an example of such a hardware configuration. The information processing device 90 in Fig. 22 is an example of a configuration for executing the control and processing in the present disclosure, and does not limit the scope of the present disclosure.

[0106] As shown in Fig. 22, an information processing device 90 includes a processor 91, a main storage device 92, an auxiliary storage device 93, an input / output interface 95, and a communication interface 96. In Fig. 22, the interface is abbreviated as I / F (Interface). The processor 91, the main storage device 92, the auxiliary storage device 93, the input / output interface 95, and the communication interface 96 are connected to each other via a bus 98 so as to be able to communicate data with each other. In addition, the processor 91, the main storage 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.

[0107] The processor 91 loads a program (instructions) stored in the auxiliary storage device 93 or the like into the main storage device 92. For example, the program is a software program for executing the control and processing in the present disclosure. The processor 91 executes the program loaded into the main storage device 92. The processor 91 executes the program to execute the control and processing in the present disclosure.

[0108] The main memory device 92 has an area in which a program is loaded. The processor 91 loads a program stored in the auxiliary memory device 93 or the like in the main memory device 92. The main memory device 92 is realized by a volatile memory such as a dynamic random access memory (DRAM). Furthermore, a non-volatile memory such as a magneto resistive random access memory (MRAM) may be configured / added to the main memory device 92.

[0109] 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 the main storage device 92 to store various data and omit the auxiliary storage device 93.

[0110] The input / output interface 95 is an interface for connecting the information processing device 90 to 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 a common interface for connecting to an external device.

[0111] Input devices such as a keyboard, a mouse, and a touch panel may be connected to the information processing device 90 as necessary. These input devices are used to input information and settings. When a touch panel is used as the input device, a screen having the function of the touch panel becomes the interface. The processor 91 and the input devices are connected via an input / output interface 95.

[0112] The information processing device 90 may be equipped with a display device for displaying information. When the display device is equipped, the information processing device 90 is equipped with a display control device (not shown) for controlling the display of the display device. The information processing device 90 and the display device are connected via an input / output interface 95.

[0113] The information processing device 90 may be provided with a drive device. The drive device mediates between the processor 91 and a recording medium (program recording medium) in reading data and programs stored in the recording medium and writing the processing results of the information processing device 90 to the recording medium. The information processing device 90 and the drive device are connected via an input / output interface 95.

[0114] The above is an example of a hardware configuration for enabling the control and processing in the present disclosure. The hardware configuration in FIG. 22 is an example of a hardware configuration for executing the control and processing in the present disclosure, and does not limit the scope of the present disclosure. A program for causing a computer to execute the control and processing in the present disclosure is also included in the scope of the present disclosure.

[0115] A program recording medium on which a program for executing the processing in this embodiment is recorded is also included in the scope of the present invention. For example, the program recording medium is a computer-readable non-transient recording medium. The recording medium can be realized by 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. The recording medium may also be realized by a magnetic recording medium such as a flexible disk or other recording medium.

[0116] The components in the present disclosure may be combined in any manner. The components in the present disclosure may be realized by software. The components in the present disclosure may be realized by a circuit.

[0117] Although the present disclosure has been described above with reference to the embodiments, the present disclosure is not limited to the above-mentioned embodiments. Various modifications that can be understood by a person skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure. Furthermore, each embodiment can be appropriately combined with other embodiments.

[0118] A part or all of the above-described embodiments can be described as, but is not limited to, the following supplementary notes. (Appendix 1) A ball lens and an irradiation position detector that detects an irradiation position of the signal light focused by the ball lens; a wavelength separator that separates signal light of a plurality of wavelengths used for free-space optical communication from the signal light collected by the ball lens; a light receiving element group constituted by a plurality of communication light receiving elements that receive the signal light of the plurality of wavelengths separated by the wavelength separator. (Appendix 2) The light receiving element group includes: a first light receiving element for communication having sensitivity to light of a first wavelength; a second communication light receiving element having sensitivity to light of a second wavelength, The wavelength separator comprises: 2. The optical receiver of claim 1, further comprising a dichroic mirror that reflects the signal light of the first wavelength toward the first optical receiver for communication and transmits the signal light of the second wavelength toward the second optical receiver for communication. (Appendix 3) The light receiving element group includes: a first light receiving element for communication having sensitivity to light of a first wavelength; a second light receiving element for communication having sensitivity to light of a second wavelength; a third communication light receiving element having sensitivity to light of a third wavelength, The wavelength separator comprises: a first dichroic mirror that reflects the signal light of the first wavelength toward the first communication light receiving element and transmits the signal light of the second wavelength and the signal light of the third wavelength; a second dichroic mirror that reflects the second wavelength signal light that has passed through the first dichroic mirror toward the second communication light receiving element, and transmits the third wavelength signal light that has passed through the first dichroic mirror toward the third communication light receiving element. (Appendix 4) The light receiving element group includes: a first light receiving element for communication having sensitivity to light of a first wavelength; a second light receiving element for communication having sensitivity to light of a second wavelength; a third communication light receiving element having sensitivity to light of a third wavelength, The wavelength separator comprises: 2. The optical receiver of claim 1, including a dichroic cross prism that reflects the signal light of the first wavelength toward the first optical receiver for communication, reflects the signal light of the second wavelength toward the second optical receiver for communication, and transmits the signal light of the third wavelength toward the third optical receiver for communication. (Appendix 5) The irradiation position detector includes: a substrate having a light receiving surface facing the ball lens and a back surface opposite to the light receiving surface, the substrate having a through hole penetrating the light receiving surface and the back surface; a plurality of direction detection light receiving elements arranged around the through hole on the light receiving surface of the substrate with a light receiving portion facing the ball lens; 2. The optical receiver according to claim 1, further comprising a light guide tube including a light receiving surface side opening end connected to the through hole and a back surface side opening end connected to the wavelength separator. (Appendix 6) The irradiation position detector includes: a plurality of light receiving elements for direction detection each corresponding to a plurality of wavelengths used in the spatial optical communication; 6. The receiver according to claim 5, wherein a wavelength filter that selectively transmits light of a wavelength to be received is disposed in the light receiving portion of each of the plurality of direction detection light receiving elements. (Appendix 7) The irradiation position detector includes: a plurality of light receiving elements for direction detection each corresponding to a plurality of wavelengths used in the spatial optical communication; 6. The receiver according to claim 5, wherein each of the plurality of direction detecting light receiving elements has sensitivity to light of a corresponding wavelength. (Appendix 8) A receiver according to any one of claims 1 to 7; a light transmitter that transmits a wavelength-multiplexed spatial optical signal used in the spatial optical communication; and a communication control device that detects an arrival direction of a spatial optical signal according to an irradiation position detected by the irradiation position detector included in the optical receiver, and causes the optical transmitter to transmit the spatial optical signal toward the detected arrival direction. (Appendix 9) The optical receiver includes: a plurality of direction detection light receiving elements arranged with light receiving portions facing the ball lens; The communication control device includes: Detecting the direction of arrival of the spatial optical signal according to a state of reception of the signal light by the plurality of direction detection light receiving elements; 9. The communication device according to claim 8, wherein the light transmitter is configured to transmit the spatial light signal including information regarding a state in which the signal light is received by the plurality of direction detection light receiving elements toward a detected direction of arrival. (Appendix 10) A plurality of communication devices according to claim 8, A plurality of the communication devices, A communication system arranged to transmit and receive spatial optical signals to and from each other. [Explanation of symbols]

[0119] 1. Communications equipment 10 Receiver 11 Ball Lens 12 Irradiation position detector 13 Wavelength separator 15 Light transmitter 16 Communication control device 17 Direction detection circuit 18 Communication Circuits 121 Substrate 122 Direction detection light receiving element 124 Light guide tube 127 Wavelength Filter 130 Concave Lens 131, 132 Dichroic mirror 134 Dichroic Cross Prism 135, 136, 137 Convex lenses 141, 142, 143 Light receiving element for communication 151 Light source 153 Spatial Light Modulator 170 Detector 171 Amplifier 173 Detector 175 Conversion circuit 176 Digital Filter 177 Control Circuit 181 Signal Processing Circuit 183 Communications Department

Claims

1. A ball lens and an irradiation position detector that detects an irradiation position of the signal light focused by the ball lens; a wavelength separator that separates signal light of a plurality of wavelengths used for free-space optical communication from the signal light collected by the ball lens; a light receiving element group constituted by a plurality of communication light receiving elements that receive the signal light of the plurality of wavelengths separated by the wavelength separator.

2. The light receiving element group includes: a first light receiving element for communication having sensitivity to light of a first wavelength; a second communication light receiving element having sensitivity to light of the second wavelength, The wavelength separator comprises:

2. The optical receiver according to claim 1, further comprising a dichroic mirror that reflects the signal light of the first wavelength toward the first optical receiver for communication and transmits the signal light of the second wavelength toward the second optical receiver for communication.

3. The light receiving element group includes: a first light receiving element for communication having sensitivity to light of a first wavelength; a second light receiving element for communication having sensitivity to light of a second wavelength; a third communication light receiving element having sensitivity to light of a third wavelength, The wavelength separator comprises: a first dichroic mirror that reflects the signal light of the first wavelength toward the first communication light receiving element and transmits the signal light of the second wavelength and the signal light of the third wavelength; a second dichroic mirror that reflects the second wavelength signal light that has passed through the first dichroic mirror toward the second communication light receiving element, and transmits the third wavelength signal light that has passed through the first dichroic mirror toward the third communication light receiving element.

4. The light receiving element group includes: a first light receiving element for communication having sensitivity to light of a first wavelength; a second light receiving element for communication having sensitivity to light of a second wavelength; a third communication light receiving element having sensitivity to light of a third wavelength, The wavelength separator comprises:

2. The optical receiver according to claim 1, further comprising a dichroic cross prism that reflects the signal light of the first wavelength toward the first optical receiving element for communication, reflects the signal light of the second wavelength toward the second optical receiving element for communication, and transmits the signal light of the third wavelength toward the third optical receiving element for communication.

5. The irradiation position detector includes: a substrate having a light receiving surface facing the ball lens and a back surface opposite to the light receiving surface, the substrate having a through hole penetrating the light receiving surface and the back surface; a plurality of direction detection light receiving elements arranged around the through hole on the light receiving surface of the substrate with a light receiving portion facing the ball lens; 2. The optical receiver according to claim 1, further comprising a light guide tube including a light receiving surface side open end connected to the through hole and a rear surface side open end connected to the wavelength separator.

6. The irradiation position detector includes: a plurality of light receiving elements for direction detection each corresponding to a plurality of wavelengths used in the spatial optical communication; 6. The receiver according to claim 5, wherein a wavelength filter that selectively transmits light of a wavelength to be received is disposed in the light receiving portion of each of the plurality of direction detecting light receiving elements.

7. The irradiation position detector includes: a plurality of light receiving elements for direction detection each corresponding to a plurality of wavelengths used in the spatial optical communication; 6. The receiver according to claim 5, wherein each of the plurality of direction detection light receiving elements has sensitivity to light of a corresponding wavelength.

8. A receiver according to any one of claims 1 to 7; a light transmitter that transmits a wavelength-multiplexed spatial optical signal used in the spatial optical communication; and a communication control device that detects an arrival direction of a spatial optical signal according to an irradiation position detected by the irradiation position detector included in the optical receiver, and causes the optical transmitter to transmit the spatial optical signal toward the detected arrival direction.

9. The optical receiver includes: a plurality of direction detection light receiving elements arranged with light receiving portions facing the ball lens; The communication control device includes: Detecting the direction of arrival of the spatial optical signal according to a state of reception of the signal light by the plurality of direction detection light receiving elements; The communication device according to claim 8 , wherein the optical transmitter is caused to transmit the spatial optical signal including information on a reception state of the signal light by the plurality of direction detection light receiving elements toward the detected arrival direction.

10. A communication device according to claim 8, A plurality of the communication devices, A communication system arranged to transmit and receive spatial optical signals to and from each other.

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