Underwater optical wireless communication system

Abstract

This underwater optical wireless communication system (100) comprises: a first communication device (2) that rotates underwater together with a rotating body (1); and a second communication device (3) that wirelessly communicates with the first communication device in a direction intersecting a rotation axis (60) of the rotating body, wherein the first communication device has a first light emitting unit (20) that emits first light (50), and a first information conversion unit (21) that converts, to the first light, state information input from a state information detection unit (4) which detects state information (40) serving as information pertaining to the state of the rotating body, and the second communication device has a second light receiving unit (30) that receives the first light.

Description

Technical Field

[0001] The present invention relates to an underwater optical wireless communication system, and particularly to an underwater optical wireless communication system for transmitting information of a rotating body provided underwater.

Background Art

[0002] Conventionally, an underwater optical wireless communication system for transmitting information of a rotating body provided underwater has been known. Such an underwater wireless communication system is disclosed in, for example, Japanese Patent No. 6380722.

[0003] Japanese Patent No. 6380722 discloses a hydraulic power generation control system including a first detection unit, a first wireless communication unit, and a control device, which transmits the rotation speed of a waterwheel. The first detection unit disclosed in Japanese Patent No. 6380722 detects the rotation speed of the waterwheel based on a gear that rotates in conjunction with the rotation of the waterwheel and a pop-up sensor provided near the gear. Further, the first wireless communication unit is configured to transmit the rotation speed of the waterwheel detected by the first detection unit to the control device by wireless communication using radio waves.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Here, although not disclosed in Patent No. 6380722, there is a need to acquire information about the water turbine (rotating body) itself while it is in operation (rotating). In order to acquire information (state information) about the rotating body itself while it is rotating, it is necessary to install the first detection unit (state information detection unit) and the first wireless communication unit (first communication device) together with the rotating body in the water. However, in the configuration disclosed in Patent No. 6380722, the first communication device uses radio waves for wireless communication. Although not disclosed in Patent No. 6380722, it is generally known that radio waves attenuate greatly in water and are not suitable for communication underwater. Therefore, if the first communication device disclosed in Patent No. 6380722 is installed together with the rotating body in the water in order to acquire state information of the rotating body, there is a problem in that it is difficult to acquire information from the state information detection unit installed together with the rotating body in the water.

[0006] This invention was made to solve the above-mentioned problems, and one of its objectives is to provide an underwater optical wireless communication system that can acquire information about a rotating body rotating underwater by wireless communication using a communication device provided together with the rotating body. [Means for solving the problem]

[0007] This invention 1 The underwater optical wireless communication system in this context is an underwater optical wireless communication system for acquiring the state of a rotating body in water, comprising: a first communication device provided on the rotating body and rotating together with the rotating body; and a second communication device provided spaced apart from the first communication device in a direction intersecting the rotation axis of the rotating body, and performing wireless communication with the first communication device using light, wherein the first communication device includes: a first light-emitting unit that emits first light, which is light used for communication with the second communication device, in a direction intersecting the rotation axis of the rotating body; and an information conversion unit that converts state information input from a state information detection unit that detects state information, which is information about the state of the rotating body, into first light, A casing having a cylindrical shape, housing the first light-emitting part, and rotating together with the rotating body It has, The first light-emitting unit emits first light from the side of the cylindrical housing in a direction intersecting the rotation axis of the rotating body. The second communication device has a second light-receiving unit that receives the first light. [Effects of the Invention]

[0008] This invention 1 In this context, the underwater optical wireless communication system includes a first light-emitting unit that emits a first light, which is light used for communication with a second communication device, and an information conversion unit that converts state information input from a state information detection unit, which detects state information, which is information about the state of a rotating body, into the first light. , a casing having a cylindrical shape, housing the first light-emitting part, and rotating together with the rotating body The system comprises a first communication device having a first light receiving unit and a second communication device having a second light receiving unit that receives the first light. The first light-emitting unit emits first light from the side of the cylindrical housing in a direction intersecting the rotation axis of the rotating body. As a result, the first communication device transmits state information using first light, which attenuates less in water than radio waves. Therefore, wireless communication can be performed between the first communication device and the second communication device even when the first communication device is installed in water together with the rotating body. Consequently, it is possible to provide an underwater optical wireless communication system that can acquire information (state information) of a rotating body rotating in water by wireless communication using the first communication device installed together with the rotating body. Furthermore, the first communication device transmits state information to the second communication device, which is installed in a direction intersecting the rotation axis of the rotating body. Therefore, even when it is difficult to position the second communication device in a direction along the rotation axis of the rotating body so that light from the first communication device can always be received regardless of the rotation angle position of the rotating body, state information can be transmitted from the first communication device to the second communication device. Furthermore, the underwater optical wireless communication system in the second aspect of this invention is an underwater optical wireless communication system for acquiring the state of a rotating body that rotates underwater, comprising: a first communication device provided on the rotating body and rotating together with the rotating body; and a second communication device provided spaced apart from the first communication device in a direction intersecting the rotation axis of the rotating body, and performing optical wireless communication with the first communication device, wherein the first communication device includes a first light-emitting unit that emits first light, which is light used for communication with the second communication device, in a direction intersecting the rotation axis of the rotating body, and the rotating body The device comprises an information conversion unit that converts state information, which is state information, input from a state information detection unit into a first light, and a housing that houses a first light-emitting unit and rotates together with a rotating body. The first light-emitting unit includes a first light source that emits first light, and a light-transmitting unit that transmits the first light emitted from the first light source inside the housing in a direction intersecting the rotation axis of the rotating body. The light-transmitting unit is an optical fiber connected to the first light-emitting unit, and the optical fiber is configured to emit first light from multiple positions on the side surface of the optical fiber. Furthermore, the underwater optical wireless communication system in the third aspect of this invention is an underwater optical wireless communication system for acquiring the state of a rotating body that rotates underwater, comprising: a first communication device provided on the rotating body and rotating together with the rotating body; and a second communication device provided spaced apart from the first communication device in a direction intersecting the rotation axis of the rotating body, and performing wireless communication with the first communication device using light, wherein the first communication device includes a first light-emitting unit that emits first light, which is light used for communication with the second communication device, in a direction intersecting the rotation axis of the rotating body, and a unit that detects state information, which is information about the state of the rotating body. The device comprises an information conversion unit that converts state information input from a state information detection unit into a first light, and a housing that houses a first light-emitting unit and rotates together with the rotating body. The first light-emitting unit includes a first light source that emits the first light, and a light-transmitting unit that transmits the first light emitted from the first light source inside the housing in a direction intersecting the rotation axis of the rotating body. The first light source is configured to emit the first light in a direction along the rotation axis of the rotating body, and the light-transmitting unit is a reflective member provided in the housing at a position opposite the first light source and reflects the first light toward multiple radial directions of the rotating body. Furthermore, the underwater optical wireless communication system in the fourth aspect of this invention is an underwater optical wireless communication system for acquiring the state of a rotating body that rotates underwater, comprising: a first communication device provided on the rotating body and rotating together with the rotating body; and a second communication device provided spaced apart from the first communication device in a direction intersecting the rotation axis of the rotating body, and performing optical wireless communication with the first communication device, wherein the first communication device includes a first light-emitting unit that emits first light, which is light used for communication with the second communication device, in a direction intersecting the rotation axis of the rotating body, and information on the state of the rotating body. The device comprises an information conversion unit that converts state information input from a state information detection unit that detects state information into a first light, and a housing that houses a first light-emitting unit and rotates together with the rotating body. The first light-emitting unit includes a first light source that emits first light, and a light-transmitting unit that transmits the first light emitted from the first light source in a direction intersecting the rotation axis of the rotating body from inside the housing. The light-transmitting unit is connected to the first light source and is also provided inside the housing, and consists of multiple optical fibers provided in multiple radial directions of the rotating body, each for the direction in which the first light is transmitted. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram showing the overall configuration of an underwater optical wireless communication system according to one embodiment. [Figure 2] This is a schematic diagram illustrating a facility in which an underwater optical wireless communication system according to one embodiment is used. [Figure 3] This is a block diagram illustrating the configuration of a first communication device and a second communication device according to one embodiment. [Figure 4]It is a schematic diagram for explaining a configuration in which a first communication device according to an embodiment emits first light in a direction intersecting the rotation axis of a rotating body. [Figure 5] It is a schematic diagram (A) for explaining the structure of an optical fiber according to an embodiment, a schematic diagram (B) for explaining the arrangement of the optical fiber, and a schematic diagram (C) for explaining the emission range of the first light emitted from the optical fiber. [Figure 6] It is a flowchart for explaining a process of transmitting status information from a first communication device to a second communication device according to an embodiment. [Figure 7] It is a flowchart for explaining a process of switching the transmission mode of status information by a first communication device according to an embodiment. [Figure 8] It is a schematic diagram for explaining a configuration in which a first communication device according to a first modification example emits first light in a direction intersecting the rotation axis of a rotating body. [Figure 9] It is a schematic diagram for explaining the emission range of the first item when a reflecting member according to the first modification example reflects the first light. [Figure 10] It is a schematic diagram for explaining a configuration in which a first communication device according to a second modification example emits first light in a direction intersecting the rotation axis of a rotating body. [Figure 11] It is a schematic diagram (A) for explaining the structure of an optical fiber according to the second modification example, a schematic diagram (B) for explaining the arrangement of the optical fiber, and a schematic diagram (C) for explaining the emission range of the first light emitted from the optical fiber. [Figure 12] It is a schematic diagram for explaining the configuration of an underwater optical wireless communication system according to a third modification example.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments embodying the present invention will be described based on the drawings.

[0011] Referring to FIGS. 1 to 5, the configuration of an underwater optical wireless communication system 100 according to the present embodiment will be described.

[0012] (Configuration of Underwater Optical Wireless Communication System) The underwater optical wireless communication system 100 shown in FIG. 1 is an underwater optical wireless communication system for acquiring the state of the rotating body 1 that rotates underwater. The rotating body 1 can be, for example, the propeller of a waterwheel, the propeller for propulsion of a ship or other underwater moving body. That is, the underwater optical wireless communication system 100 according to the present embodiment is a system for acquiring the state of the propeller. The state of the propeller includes, for example, the presence or absence of distortion of the rotating body 1, the presence or absence of bubbles (cavitation) generated on the surface of the rotating body 1, and the like.

[0013] As shown in FIG. 1, the underwater optical wireless communication system 100 includes a first communication device 2 and a second communication device 3.

[0014] The first communication device 2 is configured to transmit the state information 40 input from the state information detection unit 4 that detects the state information 40, which is information on the state of the rotating body 1, to the second communication device 3. The first communication device 2 is also configured to receive the control signal 41 transmitted from the second communication device 3. The state information detection unit 4 includes, for example, a strain sensor that detects the strain of the rotating body 1 and / or a camera that captures an image of the rotating body 1. When the state information detection unit 4 is a strain sensor, the state information 40 includes the output value of the strain sensor. When the state information detection unit 4 is a camera, the state information 40 includes the image captured by the camera. When the state information detection unit 4 is a strain sensor and a camera, the state information 40 includes the output value of the strain sensor and the image captured by the camera. Note that the image captured by the camera may be a moving image, a still image, or both a moving image and a still image.

[0015] In the present embodiment, the state information detection unit 4 is provided on the rotating body 1 and rotates together with the rotating body 1. Therefore, when the state information detection unit 4 is a camera, the camera rotates integrally with the rotating body 1 and can capture the rotating propeller blades as if they were stationary. Thereby, the cavitation on the surface of the propeller blades can be clearly captured.

[0016] The second communication device 3 is configured to receive status information 40 transmitted from the first communication device 2. The second communication device 3 is also configured to transmit the received status information 40 to the information processing device 5. Furthermore, the second communication device 3 is configured to transmit control signals 41 received from the information processing device 5 to the first communication device 2. The information processing device 5 is, for example, a PC (Personal Computer).

[0017] In this embodiment, the rotating body 1, the first communication device 2, and the state information detection unit 4 are provided in water. The second communication device 3 may be placed in water or in the atmosphere. The information processing device 5 is generally placed in the atmosphere, but if it is in water, it may be placed in the air space inside a watertight casing. In this embodiment, the second communication device 3 and the information processing device 5 are placed in the atmosphere.

[0018] In this embodiment, the first communication device 2 and the second communication device 3 are wirelessly connected and communicate using light. The first communication device 2 and the status information detection unit 4 are wiredly connected. The second communication device 3 and the information processing device 5 are wirelessly or wiredly connected.

[0019] (Examples of use of underwater optical wireless communication systems) The example shown in Figure 2 illustrates an example of the use of the underwater optical wireless communication system 100 according to this embodiment. Specifically, the underwater optical wireless communication system 100 is configured to acquire state information 40 (see Figure 1) of a propeller (rotating body 1) used in a hydroelectric power generation facility 110. In the example shown in Figure 2, the underwater region 70 is shown with hatching. In the example shown in Figure 2, the region other than the underwater region 70 is the atmospheric region 71.

[0020] As shown in Figure 2, the hydroelectric power generation facility 110 comprises a generator 111, a casing 112, a water storage section 113, a first water channel 114, and a second water channel 115.

[0021] The generator 111 is connected to the rotating body 1. The generator 111 is configured to generate electricity as the rotating body 1 rotates.

[0022] The casing 112 is configured to house the rotating body 1. The casing 112 is also connected to the water reservoir 113 via the first water channel 114.

[0023] The water reservoir 113 is configured to store water for rotating the rotating body 1. The water reservoir 113 is also connected to the casing 112 via the first water channel 114.

[0024] The first waterway 114 is a waterway connecting the reservoir 113 and the casing 112. The first waterway 114 is the waterway through which the water stored in the reservoir 113 flows into the casing 112.

[0025] The second channel 115 is connected to the casing 112. The second channel 115 is a channel for draining water from the casing 112.

[0026] As shown in Figure 2, the first communication device 2 is mounted on the rotating body 1. That is, the first communication device 2 is configured to rotate together with the rotating body 1. The first communication device 2 is powered by a wired power supply (not shown) or by a battery mounted on the rotating body 1 together with the first communication device 2.

[0027] Furthermore, as shown in Figure 2, the second communication device 3 is positioned at a distance from the first communication device 2 in a direction intersecting the rotation axis 60 of the rotating body 1. The second communication device 3 is configured to communicate wirelessly with the first communication device 2 using light. The second communication device 3 is powered by a wired power supply (not shown) or a battery.

[0028] In this embodiment, a light-transmitting section 115a is provided in the second waterway 115 at a position where it intersects with the straight line 61 connecting the first communication device 2 and the second communication device 3, so that the first communication device 2 and the second communication device 3 can communicate wirelessly using light. The light-transmitting section 115a may be, for example, a maintenance hatch or a window provided for communication between the first communication device 2 and the second communication device 3. In other words, the light-transmitting section 115a separates the underwater region 70 from the atmospheric region 71. The light-transmitting section 115a is formed of a light-transmitting material such as acrylic or glass. Note that the straight line 61 is a hypothetical line illustrated for illustrative purposes.

[0029] (First communication device and second communication device) As shown in Figure 3, the first communication device 2 includes a first light-emitting unit 20 and a first information conversion unit 21. In this embodiment, the first communication device 2 also includes a first light-receiving unit 22, a first control unit 23, an information acquisition unit 24, a first storage unit 25, and a housing 26.

[0030] The first light-emitting unit 20 is configured to emit first light 50, which is light used for communication with the second communication device 3, in a direction intersecting the rotation axis 60 (see Figure 2) of the rotating body 1 (see Figure 2). The first light-emitting unit 20 includes a first light source 20a and a light-transmitting unit 20b.

[0031] The first light source 20a is configured to emit first light 50. In this embodiment, the first light source 20a is configured to emit visible light as the first light 50. The first light source 20a is a light-emitting device including, for example, a light-emitting element such as a laser diode.

[0032] The light transmitting unit 20b is configured to transmit the first light 50 emitted from the first light source 20a in a direction intersecting the rotation axis 60 of the rotating body 1. The light transmitting unit 20b is, for example, an optical fiber 20c (see Figure 4). The detailed configuration of the light transmitting unit 20b (optical fiber 20c) and the detailed configuration of how the light transmitting unit 20b transmits the first light 50 in a direction intersecting the rotation axis 60 of the rotating body 1 will be described later. In this specification, "transmitting light" means changing the irradiation direction of the first light 50 between the time the first light 50 emitted from the first light source 20a irradiates the outside of the housing 26.

[0033] The first information conversion unit 21 is configured to convert electrical signals into optical signals. Specifically, the first information conversion unit 21 generates information about a light emission pattern for emitting an optical signal corresponding to an electrical signal using the first light source 20a. In this embodiment, the first information conversion unit 21 is configured to convert state information 40, which is information about the state of the rotating body 1, input from the state information detection unit 4 into a first light 50. That is, the first information conversion unit 21 generates information about a light emission pattern for emitting an optical signal corresponding to an electrical signal based on the state information 40. The first information conversion unit 21 is a functional block that functions when the first control unit 23 executes a predetermined program. The first information conversion unit 21 is also configured to convert an electrical signal converted from an optical signal by the first light receiving unit 22 into information. In this embodiment, the first information conversion unit 21 is configured to convert a second light 51, which will be described later, transmitted from the second communication device 3 and converted into an electrical signal by the first light receiving unit 22, into a control signal 41. Note that the first information conversion unit 21 is an example of an "information conversion unit" within the scope of the claim.

[0034] The first light-receiving unit 22 is configured to receive the second communication light 51 emitted from the second communication device 3. The first light-receiving unit 22 includes a light-receiving element capable of receiving visible light. The first light-receiving unit 22 is also configured to convert the received second light 51 into an electrical signal. The first light-receiving unit 22 includes, for example, a photodiode or a photomultiplier tube.

[0035] The first control unit 23 functions as a control unit that controls each part of the first communication device 2 by executing various programs stored in the first storage unit 25. In this embodiment, the first control unit 23 is configured to control the first communication device 2 to transmit state information 40 by first light 50 based on a control signal 41 transmitted from the second control unit 32, which will be described later. The first control unit 23 is a computer, processor, or circuit that includes a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory), etc.

[0036] The information acquisition unit 24 is configured to acquire state information 40 input from the state information detection unit 4. The information acquisition unit 24 is also configured to output the acquired state information 40 to the first control unit 23. The information acquisition unit 24 is, for example, an input / output interface.

[0037] The first storage unit 25 is configured to store various programs executed by the first control unit 23 and state information 40 acquired by the information acquisition unit 24. The first storage unit 25 is, for example, a non-volatile storage device such as an HDD (Hard Disk Drive) or an SSD (Solid State Drive).

[0038] The housing 26 houses the first light-emitting unit 20 and the first light-receiving unit 22 and is configured to rotate together with the rotating body 1 (see Figure 2). In this embodiment, the housing 26 houses the first information conversion unit 21, the first control unit 23, the information acquisition unit 24, and the first storage unit 25 together with the first light-emitting unit 20 and the first light-receiving unit 22, and rotates together with the rotating body 1.

[0039] Furthermore, as shown in Figure 3, the second communication device 3 has a second light receiving unit 30. In this embodiment, the second communication device 3 also includes a second light emitting unit 31, a second control unit 32, a second information conversion unit 33, a communication unit 34, a second storage unit 35, and a housing 36.

[0040] The second light-receiving unit 30 is configured to receive the first light 50. The second light-receiving unit 30 includes a light-receiving element capable of receiving visible light. The second light-receiving unit 30 is also configured to convert the received first light 50 into an electrical signal. The second light-receiving unit 30 includes, for example, a photodiode or a photomultiplier tube.

[0041] The second light-emitting unit 31 is configured to emit a second light 51. In this embodiment, the second light-emitting unit 31 is configured to emit visible light as the second light 51. The second light-emitting unit 31 is a light-emitting device that includes, for example, a light-emitting element such as a laser diode.

[0042] The second control unit 32 functions as a control unit that controls various parts of the second communication device 3 by executing various programs stored in the second storage unit 35. The second control unit 32 is also configured to control the second communication device 3 so that it transmits a control signal 41, which is a signal to control the first communication device 2, to the first control unit 23 using the second optical signal 51. The second control unit 32 is a computer, processor, or circuitry that includes a CPU, ROM, RAM, etc.

[0043] The second information conversion unit 33 is configured to convert the electrical signal converted from the optical signal by the second light receiving unit 30 into information. In this embodiment, the second information conversion unit 33 is configured to convert the first light 50, which is irradiated from the first communication device 2 and received by the second light receiving unit 30, into state information 40. The second information conversion unit 33 is also configured to convert the electrical signal into an optical signal. Specifically, the second information conversion unit 33 generates information about a light emission pattern for emitting an optical signal corresponding to an electrical signal from the second light emitting unit 31. In this embodiment, the second information conversion unit 33 is configured to convert the control signal 41 based on the operation input input from the information processing device 5 into the second light 51. That is, the second information conversion unit 33 generates information about a light emission pattern for emitting an optical signal corresponding to an electrical signal based on the control signal 41. The second information conversion unit 33 is a functional block that functions when the second control unit 32 executes a predetermined program.

[0044] The communication unit 34 is configured to connect the second communication device 3 and the information processing device 5 in a communicative manner. In this embodiment, the communication unit 34 is configured to wirelessly connect the second communication device 3 and the information processing device 5. The communication unit 34 includes, for example, a wireless communication device.

[0045] The second storage unit 35 is configured to store various programs executed by the second control unit 32. The second storage unit 35 is, for example, a non-volatile storage device such as an HDD or an SSD.

[0046] The housing 36 is configured to house the second light receiving unit 30, the second light emitting unit 31, the second control unit 32, the communication unit 34, and the second storage unit 35.

[0047] In this embodiment, the first light-emitting unit 20 (first light source 20a) is configured to emit first light 50, which has a different wavelength band from second light 51, so that the first communication device 2 and the second communication device 3 can communicate bidirectionally at the same time. The second light-emitting unit 31 is configured to emit second light 51, which has a different wavelength band from first light 50. In this specification, "simultaneously" in the statement "simultaneously perform bidirectional communication" means that the first light 50 and the second light 51 are irradiated at the same time. Furthermore, "bidirectional communication" in the statement "simultaneously perform bidirectional communication" means communication from the first communication device 2 to the second communication device 3, and communication from the second communication device 3 to the first communication device 2. In other words, "simultaneously perform bidirectional communication" means that communication from the first communication device 2 to the second communication device 3, and communication from the second communication device 3 to the first communication device 2 are performed while the first light 50 and the second light 51 are irradiated at the same time. Furthermore, having different wavelength bands means that even when the first light 50 and the second light 51 are irradiated simultaneously, there is a difference in wavelength bands sufficient to distinguish between the two lights.

[0048] (Transmission of the first beam of light in a direction intersecting the rotation axis of the rotating body) Next, with reference to Figures 4 and 5, a configuration in which the first light source 20a and the optical fiber 20c transmit the first light 50 in a direction intersecting the rotation axis 60 of the rotating body 1 will be described. In Figure 4, for convenience, the first light 50 and the second light 51 are shown with different hatching to indicate that they have different wavelength bands. In the example shown in Figure 4, the light-transmitting section 115a is not shown, but in reality, a light-transmitting section 115a is provided between the first communication device 2 and the second communication device 3. That is, the rotating body 1, the first communication device 2, and the state information detection unit 4 are located in water, while the second communication device 3 and the information processing device 5 are located in the atmosphere.

[0049] As shown in Figure 4, the housing 26 has a cylindrical shape. In this embodiment, the entire housing 26 is configured to rotate integrally with the rotating body 1. That is, the entire first communication device 2 rotates in the rotational direction around the rotation axis 60 of the rotating body 1.

[0050] Furthermore, as shown in Figure 4, the light transmitting unit 20b is an optical fiber 20c connected to the first light emitting unit 20 (first light source 20a). One end 20d of the optical fiber 20c is connected to the first light source 20a inside the housing 26, and the other end 20e is positioned on the outer circumferential surface 26a of the housing 26.

[0051] As shown in Figure 4, the optical fiber 20c is configured to transmit the first light 50 emitted from the first light source 20a inside the housing 26 in a direction intersecting the rotation axis 60 of the rotating body 1. Specifically, the light transmitting unit 20b (optical fiber 20c) is configured to transmit the first light 50 in multiple radial directions of the rotating body 1. In the example shown in Figure 4, the direction in which the rotation axis 60 of the rotating body 1 extends is defined as the X direction, and the radial direction of the rotating body 1 is defined as the Y direction.

[0052] Furthermore, as shown in Figure 4, the housing 26 includes a light-transmitting portion 26b that transmits light. The light-transmitting portion 26b is formed of a light-transmitting material, such as acrylic or glass. In Figure 4, for convenience, the light-transmitting portion 26b is shown with a dashed line. When the second communication device 3 is positioned diagonally below the first communication device 2, the second light 51 from the second communication device 3 is irradiated onto the first communication device 2 from a diagonally downward direction. Therefore, the bottom surface 26c of the light-transmitting portion 26b is also configured to transmit light. However, when the second light 51 is irradiated from the side surface 26d of the light-transmitting portion 26b, the bottom surface 26c of the light-transmitting portion 26b does not need to transmit light.

[0053] The first light-receiving unit 22 is provided in the light-transmitting unit 26b. This allows the first light-receiving unit 22 to receive the second light 51 emitted from the second communication device 3.

[0054] The second communication device 3 transmits a control signal 41 (see Figure 3) to the first communication device 2 by emitting a second light 51 from the second light-emitting unit 31. The control signal sent from the second communication device 3 to the first communication device 2 is transmitted at any arbitrary timing. Therefore, the first light-receiving unit 22 needs to be able to receive the second light 51 at any arbitrary timing. In other words, the first light-receiving unit 22 is configured to always be able to receive the second light 51.

[0055] Figure 5(A) is a schematic diagram illustrating the configuration in which the optical fiber 20c emits the first light 50. As shown in Figure 5(A), the optical fiber 20c is configured to emit the first light 50 from multiple positions on the side surface 20f of the optical fiber 20c. Specifically, multiple light-emitting sections 20g are provided on the side surface 20f of the optical fiber 20c at mutually different positions. The optical fiber 20c is configured to emit the first light 50 from each of the multiple light-emitting sections 20g provided at mutually different positions. Each of the multiple light-emitting sections 20g emits the first light 50 within a predetermined angular range.

[0056] Furthermore, the optical fiber 20c is configured so that the first light 50 is not emitted from the end portion 20e that is not connected to the first light source 20a, and from the side portion 20f where the light emission portion 20g is not provided. The light emission portion 20g is a region where light does not undergo total internal reflection and is emitted to the outside of the optical fiber 20c. In addition, the side portion 20f of the optical fiber 20c other than the light emission portion 20g is a region where light undergoes total internal reflection and is not emitted to the outside of the optical fiber 20c.

[0057] Figure 5(B) is a schematic diagram illustrating the arrangement of the optical fiber 20c with respect to the housing 26. As shown in Figure 5(B), the optical fiber 20c is provided wound around the outer circumferential surface 26a of the housing 26 along the rotation axis 60 of the rotating body 1. In this embodiment, the optical fiber 20c is wound around the outer circumferential surface 26a of the housing 26 such that multiple optical emission sections 20g (see Figure 5(A)) are arranged in multiple radial directions of the housing 26. Also, as shown in Figure 5(B), the optical fiber 20c is wound around the housing 26 multiple times. Furthermore, the optical fiber 20c is wound around the housing 26 at an angle from within the radial plane of the housing 26. This makes it possible to make the positions of each of the multiple optical emission sections 20g in the X direction different.

[0058] Each of the light-emitting units 20g is configured to emit the first light 50 within a predetermined angular range in the X direction. In this embodiment, the optical fiber 20c is wound around the housing 26 such that the irradiation ranges 50a of the first light 50 emitted from each of the multiple light-emitting units 20g overlap in the X direction.

[0059] Figure 5(C) is a schematic diagram showing the housing 26 as viewed from the direction of the rotation axis 60 of the rotating body 1 (see Figure 5(B)). As shown in Figure 5(C), the first light 50 (see Figure 5(A)) is emitted from each of the multiple light emitting sections 20g, so that the first light 50 can be emitted in multiple radial directions of the rotating body 1, regardless of the rotational angle position of the rotating body 1.

[0060] Furthermore, as shown in Figure 5(C), in this embodiment, the position and irradiation angle of the first light 50 are set so that the irradiation ranges 50a of the first light 50 emitted from adjacent light emitting units 20g overlap each other. Therefore, in this embodiment, the light transmitting unit 20b (optical fiber 20c) is configured to emit the first light 50 (see Figure 5(A)) transmitted in multiple radial directions of the rotating body 1 over the entire circumference in the rotational direction around the rotation axis 60 of the rotating body 1. In this embodiment, the light transmitting unit 20b is configured to emit the first light 50 over the entire circumference in the rotational direction around the rotation axis 60 of the rotating body 1 using a single component. As a result, no matter what rotational angle position the rotating body 1 (housing 26) is at, the second light receiving unit 30 (see Figure 3) can always receive the first light 50 emitted from one or more light emitting units 20g.

[0061] In this case, if the status information 40 (see Figure 3) is a moving image, the operator may want to view the moving image in real time (sequentially). Therefore, if the status information 40 is a moving image, the first control unit 23 (see Figure 3) is configured to continuously emit the first light 50. In other words, the first control unit 23 is configured to continuously transmit the status information 40, which is a moving image, to the second communication device 3 (see Figure 3).

[0062] Furthermore, if the status information 40 is an output value from a strain sensor or the like, the operator may not need to check the output value in real time (sequentially). For this reason, if the status information 40 is an output value from a strain sensor or the like, the first control unit 23 is configured to emit the first light 50 at predetermined time intervals. The predetermined time interval may be stored in advance in the first storage unit 25 (see Figure 3), or it may be transmitted from the second communication device 3 by a control signal 41 (see Figure 3). Also, the first control unit 23 may be configured to emit the first light 50 continuously even if the status information 40 is an output value from a strain sensor or the like. In other words, the first control unit 23 may be configured to transmit the status information 40, which is an output value from a strain sensor or the like, to the second communication device 3 in real time (sequentially).

[0063] In this embodiment, the first control unit 23 is configured to switch between continuous communication and communication at predetermined intervals based on a control signal 41 input by the operator in the information processing device 5 (see Figure 1) and transmitted to the first communication device 2 via the second communication device 3. The first control unit 23 may also be configured to switch between continuous communication and communication at predetermined intervals depending on the type of state information 40 emitted as the first light 50.

[0064] Next, referring to Figure 6, the process by which the first communication device 2 (see Figure 1) transmits status information 40 (see Figure 1) to the second communication device 3 (see Figure 1) will be described. Note that the process by which the first communication device 2 transmits status information 40 to the second communication device 3, as shown in Figure 6, is performed while the rotating body 1 (see Figure 1) is rotating.

[0065] The process by which the first communication device 2 transmits status information 40 to the second communication device 3 is initiated when an operator inputs an operation to start acquiring status information 40 to the second communication device 3.

[0066] In step 300, the second control unit 32 (see Figure 3) transmits a control signal 41 (see Figure 3) to the first communication device 2 to start acquiring state information 40 by controlling the second light-emitting unit 31 (see Figure 3) to emit the second light 51 (see Figure 3). The second control unit 32 controls the emission of the second light 51 based on the light emission pattern information generated by the second information conversion unit 33 (see Figure 3) based on the control signal 41 to start acquiring state information 40. As a result, the second control unit 32 transmits a control signal 41 to start acquiring state information 40 to the first communication device 2.

[0067] Next, the process moves to the first communication device 2. In step 200, the first light receiving unit 22 (see Figure 3) receives a control signal 41 to start acquiring state information 40 as a second light 51. The first control unit 23 (see Figure 3) receives the control signal 41 to start acquiring state information 40, which has been received by the first light receiving unit 22 and converted into an electrical signal.

[0068] In step 201, the first control unit 23 (see Figure 3) starts acquiring state information 40 from the state information detection unit 4 (see Figure 1).

[0069] In step 202, the first information conversion unit 21 converts the state information 40 into the first light 50 (see Figure 3). Specifically, the first information conversion unit 21 generates information for the light emission pattern in which the first light source 20a (see Figure 3) emits light, with the light signal corresponding to the electrical signal of the state information 40.

[0070] In step 203, the first control unit 23 emits the first light 50 to the second communication device 3 based on the information of the light emission pattern generated based on the state information 40. The processing in steps 202 and 203 continues until a control signal 41 indicating the termination of the acquisition of the state information 40 is transmitted from the second communication device 3.

[0071] Next, the process moves to the second communication device 3. In step 301, the second light receiving unit 30 (see Figure 3) receives the first light 50. The second control unit 32 also acquires the first light 50 received by the second light receiving unit 30 as state information 40.

[0072] In step 302, the second control unit 32 transmits the acquired status information 40 to the information processing device 5 (see Figure 1).

[0073] In step 303, the second control unit 32 determines whether or not there has been an operation input to terminate the acquisition of status information 40. If there is no operation input to terminate the acquisition of status information 40, the process proceeds to step 302. If there has been an operation input to terminate the acquisition of status information 40, the process proceeds to step 304.

[0074] In step 304, the second control unit 32 controls the second light-emitting unit 31 (see Figure 3) to transmit a control signal 41 to the first communication device 2 via the second light 51, indicating the termination of the acquisition of state information 40. The control signal 41 for terminating the acquisition of state information 40 is transmitted to the first communication device 2 as the second light 51 based on the light emission pattern generated by the second information conversion unit 33. After that, processing in the second communication device 3 is completed.

[0075] Next, the process moves to the first communication device 2. In step 204, the first light receiving unit 22 receives a control signal 41 indicating the termination of the acquisition of state information 40 as the second light 51. The first control unit 23 receives the control signal 41 indicating the termination of the acquisition of state information 40, which has been converted into an electrical signal by the first light receiving unit 22.

[0076] In step 205, the first control unit 23 determines whether or not it has received a control signal 41 to terminate the acquisition of state information 40. Specifically, the first control unit 23 determines whether or not the second light 51 received by the first light receiving unit 22 is a control signal 41 to terminate the acquisition of state information 40. If a control signal 41 to terminate the acquisition of state information 40 has not been received, the process proceeds to step 202. If a control signal 41 to terminate the acquisition of state information 40 has been received, the process proceeds to step 206.

[0077] In step 206, the first control unit 23 finishes acquiring the status information 40. After that, the processing in the first communication device 2 ends.

[0078] Next, referring to Figure 7, the process by which the first communication device 2 (see Figure 3) switches the mode of emission of the first light 50 (see Figure 3) will be described. The process by which the first communication device 2 switches the mode of emission of the first light 50 is initiated when the second communication device 3 (see Figure 3) transmits a control signal 41 (see Figure 3) to switch the mode of emission of the first light 50.

[0079] In step 400, the first light receiving unit 22 (see Figure 3) receives the second light 51 (see Figure 3) emitted from the second communication device 3. The first control unit 23 (see Figure 1) acquires the control signal 41 which has been converted into an electrical signal by the first light receiving unit 22.

[0080] In step 401, the first control unit 23 determines whether the control signal 41 is a signal for continuous communication. If the control signal 41 is a signal for continuous communication, the process proceeds to step 402. If the control signal 41 is not a signal for continuous communication, the process proceeds to step 403.

[0081] In step 402, the first control unit 23 switches to a mode in which the first light 50 is emitted continuously. After that, the process ends. If the system is already in a mode in which the first light 50 is emitted continuously, the process in step 402 is skipped.

[0082] If the process proceeds from step 401 to step 403, in step 403, the first control unit 23 switches to a mode in which the first light 50 is emitted at predetermined time intervals. After that, the process ends. If the first light 50 is already in a mode in which it is emitted at predetermined time intervals, the process in step 403 is skipped.

[0083] (Effects of this embodiment) In this embodiment, the following effects can be obtained.

[0084] In this embodiment, as described above, the underwater optical wireless communication system 100 is an underwater optical wireless communication system for acquiring the state of a rotating body 1 that rotates in water, and comprises a first communication device 2 provided on the rotating body 1 and rotating together with the rotating body 1, and a second communication device 3 provided spaced apart from the first communication device 2 in a direction (Y direction) intersecting the rotation axis 60 of the rotating body 1, and performing wireless communication with the first communication device 2 using light, the first communication device 2 has a first light-emitting unit 20 that emits first light 50, which is light used for communication with the second communication device 3, in a direction intersecting the rotation axis 60 of the rotating body 1, and a first information conversion unit 21 that converts state information 40, which is state information of the state of the rotating body 1, input from a state information detection unit 4 into first light 50, and the second communication device 3 has a second light-receiving unit 30 that receives the first light 50.

[0085] As a result, the first communication device 2 transmits state information 40 using first light 50, which is light that attenuates less in water than radio waves. Therefore, even when the first communication device 2 is installed in water together with the rotating body 1, wireless communication can be performed between the first communication device 2 and the second communication device 3. As a result, an underwater optical wireless communication system 100 can be provided that can acquire information (state information 40) of the rotating body 1 rotating in water by wireless communication using the first communication device 2 installed together with the rotating body 1. Furthermore, the first communication device 2 transmits state information 40 to the second communication device 3, which is installed in a direction intersecting the rotation axis 60 of the rotating body 1. Therefore, even when it is difficult to position the second communication device 3 in a direction along the rotation axis 60 of the rotating body 1 (X direction) so that it can always receive light (first light 50) from the first communication device 2 regardless of the rotational angle position of the rotating body 1, state information 40 can be transmitted from the first communication device 2 to the second communication device 3.

[0086] Furthermore, in the above embodiment, the following additional effects can be obtained by configuring it as follows.

[0087] In other words, in this embodiment, as described above, the first communication device 2 further has a first light receiving unit 22 that receives the second communication light 51 emitted from the second communication device 3, and the second communication device 3 further has a second light emitting unit 31 that emits the second light 51. As a result, by receiving the second light 51 emitted from the second light emitting unit 31 with the first light receiving unit 22, information can be transmitted from the second communication device 3 to the first communication device 2. Consequently, bidirectional communication can be performed between the first communication device 2 and the second communication device 3.

[0088] Furthermore, in this embodiment, as described above, there is a housing 26 that houses the first light-emitting unit 20 and the first light-receiving unit 22 and rotates together with the rotating body 1. The first light-emitting unit 20 includes a first light source 20a that emits first light 50, and a light-transmitting unit 20b that transmits the first light 50 emitted from the first light source 20a inside the housing 26 in a direction intersecting the rotation axis 60 of the rotating body 1. As a result, the first light 50 emitted from the first light source 20a is transmitted by the light-transmitting unit 20b, so that the first light 50 can be emitted in a direction intersecting the rotation axis 60 of the rotating body 1 regardless of the arrangement of the first light source 20a. As a result, the degree of freedom in the arrangement of the first light source 20a can be improved.

[0089] Furthermore, in this embodiment, as described above, the light transmitting unit 20b is configured to transmit the first light 50 in multiple radial directions of the rotating body 1. This makes it possible to suppress the narrowing of the angular range in which the first light 50 illuminates the second communication device 3, compared to a configuration in which the first light 50 is transmitted in only one radial direction (Y direction) of the rotating body 1. In other words, it is possible to shorten the time during which communication between the first communication device 2 and the second communication device 3 is unavailable. As a result, it is possible to suppress the increase in the transmission interval of the status information 40, compared to a configuration in which the first light 50 is transmitted in only one radial direction of the rotating body 1. As a result, even when transmitting status information 40 with a large data capacity, such as a moving image, the time required to transmit the status information 40 can be shortened.

[0090] Furthermore, in this embodiment, as described above, the light transmitting unit 20b is configured to emit the first light 50, which has been transmitted in multiple radial directions (Y direction) of the rotating body 1, over the entire circumference of the rotational direction around the rotation axis 60 of the rotating body 1. This allows the first light 50 to be continuously irradiated from the first communication device 2 to the second communication device 3. Therefore, continuous communication is possible between the first communication device 2 and the second communication device 3, so, for example, moving images acquired sequentially by the state information detection unit 4 can be continuously transmitted from the first communication device 2 to the second communication device 3. As a result, the operator can check the moving images acquired sequentially by the state information detection unit 4 in real time (sequentially).

[0091] Furthermore, in this embodiment, as described above, the light transmitting unit 20b is configured to emit the first light 50 over the entire circumference in the rotational direction around the rotation axis 60 of the rotating body 1 using a single component. This effectively suppresses an increase in the number of components compared to a configuration in which the first light 50 is emitted over the entire circumference in the rotational direction around the rotation axis 60 of the rotating body 1 using multiple components.

[0092] Furthermore, in this embodiment, as described above, the light transmitting unit 20b is an optical fiber 20c connected to the first light emitting unit 20, and the optical fiber 20c is configured to emit the first light 50 from multiple positions on the side surface 20f of the optical fiber 20c. As a result, the first light 50 is emitted from multiple positions on the side surface 20f of the optical fiber 20c, so that the first light 50 can be easily emitted in multiple radial directions (Y direction) of the rotating body 1 using a single optical fiber 20c.

[0093] Furthermore, in this embodiment, as described above, the optical fiber 20c is provided wound around the outer circumferential surface 26a of the housing 26 along the rotation axis 60 of the rotating body 1. As a result, since the optical fiber 20c is wound around the outer circumferential surface 26a of the housing 26, each of the multiple positions (positions of the multiple light emission sections 20g) from which the first light 50 is irradiated from the side surface 20f of the optical fiber 20c can be directed in multiple radial directions (Y direction) of the rotating body 1. Consequently, the first light 50 can be easily emitted over the entire circumference of the rotational direction around the rotation axis 60 of the rotating body 1 using a single optical fiber 20c.

[0094] Furthermore, in this embodiment, as described above, the first communication device 2 further includes a first control unit 23, and the second communication device 3 further includes a second control unit 32. The second control unit 32 is configured to control the second communication device 3 by transmitting a control signal 41, which is a signal to control the first communication device 2, to the first control unit 23 via a second optical signal 51. The first control unit 23 is configured to control the first communication device 2 by transmitting status information 40 via a first optical signal 50 based on the control signal 41 transmitted from the second control unit 32. As a result, the first communication device 2 can be controlled by the control signal 41 transmitted from the second communication device 3 to the first communication device 2. For example, the start and end of the transmission of status information 40 by the first communication device 2 can be easily performed via the second communication device 3. In addition, the transmission interval of the status information 40 transmitted from the first communication device 2 to the second communication device 3 can be easily controlled. As a result, user convenience (usability) can be improved.

[0095] [Differentiation] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than by the description of the embodiments above, and further includes all modifications (exceptions) within the meaning and scope of the claims.

[0096] [First variation] For example, in the above embodiment, an example configuration was shown in which the light transmitting unit 20b (see Figure 3) is an optical fiber 20c (see Figure 5(A)) that emits the first light 50 (see Figure 5(A)) from multiple positions on the side surface 20f (see Figure 5(A)), but the present invention is not limited to this. For example, as in the underwater optical wireless communication system 120 according to the first modified example shown in Figure 8, the light transmitting unit 20b does not have to be an optical fiber 20c that emits the first light 50 from multiple positions on the side surface 20f.

[0097] The underwater optical wireless communication system 120 according to the first modified example differs from the underwater optical wireless communication system 100 according to the above embodiment in that it includes a first communication device 121 instead of the first communication device 2 (see Figure 3). The other configurations of the underwater optical wireless communication system 120 are the same as those of the underwater optical wireless communication system 100 according to the above embodiment.

[0098] The first communication device 121 according to the first modification differs from the first communication device 2 according to the above embodiment in that it includes a housing 122 instead of a housing 26 (see Figure 3), and a light transmitting unit 123 instead of a light transmitting unit 20b. The other configurations of the first communication device 121 are the same as those of the first communication device 2 according to the above embodiment.

[0099] The housing 122 according to the first modification differs from the housing 26 according to the above embodiment in that it houses a light-transmitting unit 123 instead of a light-transmitting unit 20b.

[0100] The light-transmitting unit 123 according to the first modification differs from the light-transmitting unit 20b according to the above embodiment in that it includes a reflective member 123a instead of an optical fiber 20c.

[0101] As shown in Figure 8, in the first modified example, the first light source 20a is configured to emit the first light 50 in the direction (X direction) along the rotation axis 60 of the rotating body 1. In the example shown in Figure 8, the light-transmitting part 115a (see Figure 2) is not shown.

[0102] In the first modified example, the reflective member 123a is provided in the housing 122 at a position facing the first light source 20a. The reflective member 123a is configured to reflect the first light 50 in multiple radial directions (Y direction) of the rotating body 1. Specifically, the reflective member 123a has a conical shape and is configured to reflect the first light 50 in multiple radial directions of the rotating body 1. The reflective member 123a has a conical shape, for example. As a result, the reflective member 123a can emit the first light 50 over the entire circumference of the rotation direction around the rotation axis 60 of the rotating body 1 with just one member. Furthermore, the reflective member 123a is configured to emit the first light 50 over the entire circumference of the rotation direction around the rotation axis 60 of the rotating body 1 for each position in the X direction where the first light 50 is irradiated. The reflective member 123a includes, for example, a prism, a lens, etc.

[0103] Furthermore, the reflective member 123a may have a conical shape other than a cone shape, as long as it is possible to reflect the first light 50 toward multiple radial directions of the rotating body 1. If the reflective member 123a has a conical shape other than a cone shape, it is preferable that the shape of the base of the reflective member 123a is a polygon with many sides. Also, the reflective member 123a may be formed by combining multiple plate-shaped members. In other words, the reflective member 123a may have a shape other than a cone shape, as long as it is possible to reflect the first light 50 toward multiple radial directions of the rotating body 1.

[0104] In the first modified example, the housing 122 includes a light-transmitting portion 122a. The light-transmitting portion 122a is formed of a light-transmitting material, such as acrylic or glass. Because the housing 122 includes the light-transmitting portion 122a, the first light 50 reflected by the reflective member 123a is emitted in a direction intersecting the rotation axis 60 of the rotating body 1. In Figure 8, for convenience, the light-transmitting portion 122a is shown with a dashed line. The bottom surface 122b of the light-transmitting portion 122a does not need to transmit light. The other configurations of the housing 122 are the same as those of the housing 26 in the above embodiment.

[0105] As shown in Figure 8, the reflective member 123a is positioned on the light-transmitting portion 122a such that its vertex 123b faces the first light source 20a.

[0106] Furthermore, the second light 51 emitted from the second communication device 3 passes through the light-transmitting part 122a and is irradiated onto the reflecting member 123a. The second light 51 irradiated onto the reflecting member 123a is reflected in the direction along the rotation axis 60 of the rotating body 1 (X direction). The second light 51 is then irradiated onto the first light-receiving unit 22 via an optical member (not shown). As a result, bidirectional communication can be performed simultaneously in the underwater optical wireless communication system 120 according to the first modified example. Also, in the first modified example, since the second light 51 is reflected by the reflecting member 123a to the first light-receiving unit 22, the first light-receiving unit 22 can always receive the second light 51 regardless of the rotational angle position of the rotating body 1. The first light-receiving unit 22 may be arranged coaxially with the first light source 20a.

[0107] Figure 9 is a schematic diagram showing the illumination range 50a of the first light 50 (see Figure 8) reflected by the reflective member 123a. As shown in Figure 9, in the underwater optical wireless communication system 120 (see Figure 8) according to the second modified example, the illumination range 50a of the first light 50 reflected by the reflective member 123a is emitted over the entire circumference in the rotational direction of the rotating body 1 (see Figure 8). Therefore, in the underwater optical wireless communication system 120 according to the first modified example, the first communication device 2 (see Figure 8) and the second communication device 3 (see Figure 8) can communicate continuously.

[0108] (Effects of the first modified example) The first form of torture can produce the following effects:

[0109] In the first modified example, as described above, the first light source 20a is configured to emit the first light 50 in the direction (X direction) along the rotation axis 60 of the rotating body 1, and the light transmitting unit 123 is a reflective member 123a provided in the housing 122 at a position opposite to the first light source 20a, which reflects the first light 50 toward multiple radial directions (Y direction) of the rotating body 1. Thus, unlike a configuration in which, for example, a first light source 20a is provided for each direction in which the first light 50 is irradiated, by arranging the reflective member 123a at a position opposite to the first light source 20a, the first light 50 can be easily reflected toward multiple radial directions of the rotating body 1 by a single reflective member 123a. As a result, the first light 50 can be easily transmitted toward multiple radial directions of the rotating body 1 while suppressing an increase in the number of parts.

[0110] Furthermore, in the first modified example, as described above, the reflective member 123a has a conical shape and is configured to reflect the first light 50 toward multiple radial directions of the rotating body 1. As a result, because the reflective member 123a has a conical shape, the first light 50 can be easily reflected toward multiple radial directions of the rotating body 1 by positioning the vertex 123b of the reflective member 123a toward the first light source 20a.

[0111] Furthermore, the other effects of the underwater optical wireless communication system 120 according to the first modified example are the same as those of the underwater optical wireless communication system 100 according to the above embodiment.

[0112] [Second variation] Furthermore, although the above embodiment shows an example in which the light transmitting unit 20b is an optical fiber 20c that emits the first light 50 from multiple positions on the side surface 20f, the present invention is not limited to this. For example, as in the underwater optical wireless communication system 130 according to the second modified example shown in Figure 10, the light transmitting unit 20b does not have to be an optical fiber 20c that emits the first light 50 from multiple positions on the side surface 20f. Note that even in the example shown in Figure 10, the light transmitting unit 115a (see Figure 2) is not shown.

[0113] The underwater optical wireless communication system 130 according to the second modification differs from the underwater optical wireless communication system 100 according to the above embodiment in that it includes a first communication device 131 instead of the first communication device 2 (see Figure 3). The other configurations of the underwater optical wireless communication system 130 are the same as those of the underwater optical wireless communication system 100 according to the above embodiment.

[0114] The first communication device 131 differs from the first communication device 2 according to the above embodiment in that it includes an optical distributor 132, an optical transmission unit 133 instead of an optical transmission unit 20b (see Figure 3), a housing 134 instead of a housing 26 (see Figure 4), a plurality of optical fibers 22a, and an optical multiplexer 22b. The other configurations of the first communication device 131 are the same as those of the first communication device 2 according to the above embodiment.

[0115] The housing 134 according to the second modification differs from the housing 26 according to the above embodiment in that it houses a light transmitting unit 133 instead of a light transmitting unit 20b, houses an optical distributor 132, houses a plurality of optical fibers 22a, houses an optical multiplexer 22b, and does not include an optical transmission unit 26b.

[0116] The light-transmitting unit 133 in the second modified example differs from the light-transmitting unit 20b in the above embodiment in that it comprises multiple optical fibers 135 instead of the optical fiber 20c (see Figure 4).

[0117] As shown in Figure 10, the light-transmitting unit 133 in the second modified example is connected to the first light source 20a and is provided inside the housing 134. It consists of multiple optical fibers 135 provided in multiple radial directions of the rotating body 1, one for each direction in which the first light 50 is transmitted. In the second modified example, each of the multiple optical fibers 135 is connected to the first light source 20a via an optical distributor 132.

[0118] The optical distributor 132 is installed between the first light source 20a and the plurality of optical fibers 135. The optical distributor 132 is configured to transmit the first light 50 emitted from the first light source 20a to each of the plurality of optical fibers 135.

[0119] Each of the multiple optical fibers 135 has one end 135a connected to the first light source 20a via an optical distributor 132, and the other end, the output end 135b, is located on the side surface 134a of the housing 134. Therefore, the light transmitting unit 133 in the second modified example can emit the first light 50 emitted from one first light source 20a in multiple radial directions (Y direction) of the rotating body 1 using the multiple optical fibers 135.

[0120] Each of the multiple optical fibers 22a has one end 22c connected to an optical multiplexer 22b, and the other end 22d positioned on the side surface 134a of the housing 134. Each of the multiple optical fibers 22a is configured to direct the second light 51, which is incident from its end 22d, into the first light receiving unit 22 via the optical multiplexer 22b. Furthermore, each of the multiple optical fibers 22a has its end 22d positioned on the side surface 134a of the housing 134 at predetermined angular intervals so that the second light 51 can always be received regardless of the rotational angle position of the rotating body 1. In other words, the multiple optical fibers 22a are arranged in the housing 134 such that the light-receiving ranges of the other end 22d of each of the multiple optical fibers 22a overlap with each other.

[0121] The optical multiplexer 22b is configured to combine multiple second light beams 51 incident from each of the multiple optical fibers 22a into a single second light beam 51. The optical multiplexer 22b is configured to transmit the combined single second light beam 51 to the first light receiving unit 22.

[0122] As shown in Figure 11(A), the optical fiber 135 has an end 135a connected to the first light source 20a via an optical distributor 132. The exit end 135b is configured to irradiate the first light 50 within a predetermined angular range. The exit end 135b is provided with an optical element such as a lens, and a diffuser plate configured to irradiate light within a predetermined angular range is provided thereon. Alternatively, the optical element such as a lens may be integrally provided on the exit end 135b.

[0123] As shown in Figure 11(B), multiple optical fibers 135 (see Figure 11(A)) are provided in the housing 134 such that their exit ends 135b are arranged at predetermined intervals in the circumferential direction of the side surface 134a of the housing 134. The interval at which the exit ends 135b are arranged is determined by the angular range of the first light 50 emitted from the exit ends 135b. In other words, the number of multiple optical fibers 135 is determined by the angular range of the first light 50 emitted from each of the exit ends 135b of the multiple optical fibers 135.

[0124] In the second modified example, as shown in Figure 11(C), the output end 135b of each of the multiple optical fibers 135, which is the end opposite to the end 135a (see Figure 11(A)) connected to the first light source 20a (see Figure 11(A)), is configured to emit the first light 50 (see Figure 11(A)) such that the irradiation ranges 50a of the first light 50 overlap with each other.

[0125] The second modification yields the following effects:

[0126] In the second modified example, as described above, the light transmitting unit 133 is connected to the first light source 20a and is also provided inside the housing 134. It consists of multiple optical fibers 135 provided in each of the multiple radial directions (Y direction) of the rotating body 1 for transmitting the first light 50. This differs from the configuration in which a first light source 20a is provided for each direction of irradiation of the first light 50. As a result, the first light 50 can be easily transmitted from a single first light source 20a to multiple radial directions of the rotating body 1 using multiple optical fibers 135. Consequently, the number of parts can be kept from increasing while easily transmitting the first light 50 to multiple radial directions of the rotating body 1.

[0127] Furthermore, in the second modified example, as described above, the output end 135b of each of the multiple optical fibers 135, which is the end opposite to the end 135a connected to the first light source 20a, is configured to emit the first light 50 such that the irradiation ranges 50a of the first light 50 overlap with each other. As a result, the irradiation ranges 50a of the first light 50 overlap with each other due to the output end 135b, making it possible to easily emit the first light 50 over the entire circumference in the rotational direction around the rotation axis 60 of the rotating body 1. Consequently, continuous communication between the first communication device 2 and the second communication device 3 can be easily performed.

[0128] Furthermore, the other effects of the underwater optical wireless communication system 130 according to the second modified example are the same as those of the underwater optical wireless communication system 100 according to the above embodiment.

[0129] [Third variation] Furthermore, while the above embodiment shows an example in which the underwater optical wireless communication system 100 is installed in a hydroelectric power generation facility 110 (see Figure 2), the present invention is not limited thereto. For example, as shown in the third modified underwater optical wireless communication system 140 in Figure 12, it may be configured to transmit state information 40 of a rotating body 1 installed on a ship 6. The third modified underwater optical wireless communication system 140 differs from the above embodiment in that the first communication device 2 is installed on the rotating body 1 installed on the ship 6, and the second communication device 3 is installed on the ship 6. The other configurations are the same as those of the underwater optical wireless communication system 100 in the above embodiment. The rotating body 1 installed on the ship 6 is, for example, a propeller or a screw. The other configurations of the third modified underwater optical wireless communication system 140 are the same as those of the underwater optical wireless communication system 100 in the above embodiment. Furthermore, the same effects as those of the underwater optical wireless communication system 100 in the above embodiment can be obtained with the third modified underwater optical wireless communication system 140.

[0130] [Other variations] Furthermore, while the above embodiment shows an example configuration in which the first communication device 2 is equipped with a first light receiving unit 22 and the second communication device 3 is equipped with a second light emitting unit 31, and the first communication device 2 and the second communication device 3 perform bidirectional communication, the present invention is not limited to this. For example, the first communication device 2 does not need to be equipped with a first light receiving unit 22, and the second communication device 3 does not need to be equipped with a second light emitting unit 31. That is, as long as the first communication device 2 can transmit status information 40 to the second communication device 3 using the first light 50, the first communication device 2 and the second communication device 3 do not need to perform bidirectional communication. However, if the first communication device 2 and the second communication device 3 do not perform bidirectional communication, it becomes difficult for the operator to control the first communication device 2. Therefore, it is preferable that the first communication device 2 is equipped with a first light receiving unit 22 and the second communication device 3 is equipped with a second light emitting unit 31 so that the first communication device 2 and the second communication device 3 can perform bidirectional communication.

[0131] Furthermore, although the above embodiment shows an example in which the wavelength bands of the first light 50 emitted from the first light-emitting unit 20 and the wavelength bands of the second light 51 emitted from the second light-emitting unit 31 are different, the present invention is not limited thereto. The first light 50 emitted from the first light-emitting unit 20 and the second light 51 emitted from the second light-emitting unit 31 may be light with the same wavelength band. In this case, if the first light 50 and the second light 51 are emitted simultaneously, the lights will interfere with each other. Therefore, when the wavelength bands of the first light 50 and the second light 51 are the same, and bidirectional communication is performed between the first communication device 2 and the second communication device 3, the emission of the first light 50 and the emission of the second light 51 should be performed alternately.

[0132] Furthermore, while the above embodiment shows an example in which the light transmitting unit 20b transmits the first light 50 in multiple radial directions of the rotating body 1, the present invention is not limited thereto. For example, the light transmitting unit 20b may be configured to transmit the first light 50 in one radial direction of the rotating body 1. However, if the light transmitting unit 20b is configured to transmit the first light 50 in one radial direction of the rotating body 1, there is a possibility that the second communication device 3 (second light receiving unit 30) may not be able to receive the first light 50 depending on the rotation angle of the rotating body 1. In other words, if the light transmitting unit 20b is configured to transmit the first light 50 in one radial direction of the rotating body 1, it may not be possible to perform continuous communication between the first communication device 2 and the second communication device 3. Therefore, it is preferable that the light transmitting unit 20b is configured to transmit the first light 50 in multiple radial directions of the rotating body 1.

[0133] Furthermore, while the above embodiment shows an example in which the light transmitting unit 20b emits the first light 50 over the entire circumference in the rotational direction around the rotation axis 60 of the rotating body 1, the present invention is not limited to this. For example, the light transmitting unit 20b does not need to emit the first light 50 over the entire circumference in the rotational direction around the rotation axis 60 of the rotating body 1, as long as it emits the first light 50 in multiple radial directions of the rotating body 1. However, if the light transmitting unit 20b is not configured to emit the first light 50 over the entire circumference in the rotational direction around the rotation axis 60 of the rotating body 1, there is a possibility that the second communication device 3 (second light receiving unit 30) may not be able to receive the first light 50 depending on the rotational speed and rotational angle of the rotating body 1. In other words, if the light transmitting unit 20b is not configured to emit the first light 50 over the entire circumference in the rotational direction around the rotation axis 60 of the rotating body 1, it may not be possible to perform continuous communication between the first communication device 2 and the second communication device 3. Therefore, it is preferable that the light transmitting unit 20b is configured to emit the first light 50 over the entire circumference in the rotational direction around the rotation axis 60 of the rotating body 1.

[0134] Furthermore, while the above embodiment shows an example of a configuration in which the first control unit 23 controls the start and end of the transmission of status information 40 to the second communication device 3 based on a control signal 41 transmitted from the second communication device 3, the present invention is not limited thereto. For example, the first control unit 23 may be configured to control the start and end of the transmission of status information 40 to the second communication device 3 based on the rotational speed of the rotating body 1. That is, the first control unit 23 may be configured to start the transmission of status information 40 when the rotational speed of the rotating body 1 exceeds a predetermined speed, and to end the transmission of status information 40 when the rotational speed of the rotating body 1 falls below a predetermined speed. Alternatively, the first control unit 23 may be configured to control the start and end of the transmission of status information 40 based on time.

[0135] Furthermore, in the above embodiment, the first modified example, and the second modified example, the first communication device 2 (121, 131) has separate configurations for emitting the first light 50 and receiving the second light 51, but the present invention is not limited thereto. The configurations for emitting the first light 50 and receiving the second light 51 of the first communication device may be combined in any combination of the configurations of the embodiment, the first modified example, and the second modified example.

[0136] Furthermore, in the above embodiment, for the sake of explanation, the process of acquiring the state information 40 of the present invention and the process of switching the transmission mode of the state information 40 were described using a flow-driven flowchart that processes the processes sequentially according to the processing flow, but the present invention is not limited thereto. In the present invention, the process of acquiring the state information 40 and the process of switching the transmission mode of the state information 40 may be performed by event-driven processing, which executes the processing on an event-by-event basis. In this case, it may be performed as a completely event-driven process, or a combination of event-driven and flow-driven processing may be performed.

[0137] [Aspect] Those skilled in the art will understand that the exemplary embodiments described above are specific examples of the following embodiments.

[0138] (Item 1) An underwater optical wireless communication system for acquiring the state of a rotating body in water, A first communication device is provided on the rotating body and rotates together with the rotating body, The system includes a second communication device which is provided at a distance from the first communication device in a direction intersecting the rotation axis of the rotating body and which communicates wirelessly with the first communication device using light, The first communication device is A first light-emitting unit that emits a first light, which is light used for communication with the second communication device, in a direction intersecting the rotation axis of the rotating body, The system includes an information conversion unit that converts state information, which is information about the state of the rotating body, into the first light, which is input from a state information detection unit. The second communication device is An underwater optical wireless communication system having a second light-receiving unit that receives the first light.

[0139] (Item 2) The first communication device further includes a first light receiving unit that receives a second light for communication emitted from the second communication device. The underwater optical wireless communication system according to item 1, wherein the second communication device further comprises a second light-emitting unit that emits the second light.

[0140] (Item 3) The device further comprises a housing that houses the first light-emitting unit and the first light-receiving unit and rotates together with the rotating body, The underwater optical wireless communication system according to item 2, wherein the first light-emitting unit includes a first light source that emits the first light, and a light-transmitting unit that transmits the first light emitted from the first light source inside the housing in a direction intersecting the rotation axis of the rotating body.

[0141] (Item 4) The underwater optical wireless communication system according to item 3, wherein the light transmitting unit is configured to transmit the first light in multiple radial directions of the rotating body.

[0142] (Item 5) The underwater optical wireless communication system according to item 4, wherein the light transmitting unit is configured to emit the first light, which has been transmitted in multiple radial directions toward the rotating body, over the entire circumference in the rotational direction around the rotation axis of the rotating body.

[0143] (Item 6) The underwater optical wireless communication system according to item 5, wherein the light transmitting unit is configured to emit the first light over the entire circumference in the rotational direction around the rotation axis of the rotating body by a single member.

[0144] (Item 7) The light transmitting unit is an optical fiber connected to the first light emitting unit, The underwater optical wireless communication system according to any one of items 3 to 6, wherein the optical fiber is configured to emit the first light from multiple positions on the side surface of the optical fiber.

[0145] (Item 8) The underwater optical wireless communication system according to item 7, wherein the optical fiber is provided wound around the outer surface of the housing along the rotation axis of the rotating body.

[0146] (Item 9) The first light source is configured to emit the first light in a direction along the rotation axis of the rotating body, The underwater optical wireless communication system according to any one of items 3 to 6, wherein the light transmitting unit is provided in the housing at a position opposite to the first light source and is a reflective member that reflects the first light toward multiple radial directions of the rotating body.

[0147] (Item 10) The underwater optical wireless communication system according to item 9, wherein the reflective member has a conical shape and is configured to reflect the first light toward multiple radial directions of the rotating body.

[0148] (Item 11) The underwater optical wireless communication system according to any one of items 3 to 6, wherein the light transmitting unit is connected to the first light source and is provided inside the housing, and is a plurality of optical fibers provided in each of the radial directions of the rotating body for each direction in which the first light is transmitted.

[0149] (Item 12) The underwater optical wireless communication system according to item 11, wherein the exit end of each of the plurality of optical fibers, which is the end opposite to the end connected to the first light source, is configured to emit the first light such that the irradiation ranges of the first light overlap each other.

[0150] (Item 13) The first communication device further comprises a first control unit, The second communication device further comprises a second control unit, The second control unit is configured to control the second communication device by transmitting a control signal, which is a signal for controlling the first communication device, to the first control unit using the second light. The underwater optical wireless communication system according to any one of items 2 to 12, wherein the first control unit is configured to control the first communication device to transmit the state information by the first light based on the control signal transmitted from the second control unit. [Explanation of Symbols]

[0151] 1. Solid of revolution 2, 121, 131 First communication device 3. Second communication device 4. Status Information Detection Unit 20 First light-emitting section 20a 1st light source 20b, 123, 133 Light transmitter 20c optical fiber 21. First Information Conversion Unit (Information Conversion Unit) 22 1st light receiving section 23 First Control Unit 26, 122, 134 cabinets 30 2nd light receiving section 31 Second light-emitting section 32 Second Control Unit 40 Status Information 41 Control signals 50 1st light 51 Second light 60. Axis of Rotation (Axis of rotation of a rotating body) 100, 120, 130, 140 Underwater Optical Wireless Communication System 123a Reflective material 135 Multiple optical fibers 135a Output end

Claims

1. An underwater optical wireless communication system for acquiring the state of a rotating body in water, A first communication device is provided on the rotating body and rotates together with the rotating body, The system includes a second communication device which is provided at a distance from the first communication device in a direction intersecting the rotation axis of the rotating body, and which communicates wirelessly with the first communication device using light, The first communication device is A first light-emitting unit that emits a first light, which is light used for communication with the second communication device, in a direction intersecting the rotation axis of the rotating body, An information conversion unit that converts state information, which is information about the state of the rotating body, into the first light, It has a cylindrical shape, houses the first light-emitting part, and has a housing that rotates together with the rotating body, The first light-emitting unit emits first light from the side surface of the cylindrical housing in a direction intersecting the rotation axis of the rotating body, The second communication device is An underwater optical wireless communication system having a second light-receiving unit that receives the first light.

2. The first communication device further includes a first light receiving unit that receives a second light for communication emitted from the second communication device. The underwater optical wireless communication system according to claim 1, wherein the second communication device further comprises a second light-emitting unit that emits the second light.

3. The housing houses the first light-receiving unit together with the first light-emitting unit, The underwater optical wireless communication system according to claim 2, wherein the first light-emitting unit includes a first light source that emits the first light, and a light-transmitting unit that transmits the first light emitted from the first light source inside the housing in a direction intersecting the rotation axis of the rotating body.

4. The underwater optical wireless communication system according to claim 3, wherein the light transmitting unit is configured to transmit the first light in multiple radial directions of the rotating body.

5. The underwater optical wireless communication system according to claim 4, wherein the light transmitting unit is configured to emit the first light transmitted in multiple radial directions of the rotating body over the entire circumference in the rotational direction around the rotation axis of the rotating body.

6. The underwater optical wireless communication system according to claim 5, wherein the light transmitting unit is configured to emit the first light over the entire circumference in the rotational direction around the rotation axis of the rotating body by a single member.

7. An underwater optical wireless communication system for acquiring the state of a rotating body that rotates underwater, A first communication device is provided on the rotating body and rotates together with the rotating body, The system includes a second communication device which is provided at a distance from the first communication device in a direction intersecting the rotation axis of the rotating body, and which communicates wirelessly with the first communication device using light, The first communication device is A first light-emitting unit that emits a first light, which is light used for communication with the second communication device, in a direction intersecting the rotation axis of the rotating body, An information conversion unit that converts state information, which is information about the state of the rotating body, into the first light, It comprises a housing that houses the first light-emitting unit and rotates together with the rotating body, The first light-emitting unit includes a first light source that emits the first light, and a light-transmitting unit that transmits the first light emitted from the first light source within the housing in a direction intersecting the rotation axis of the rotating body. The light transmitting unit is an optical fiber connected to the first light emitting unit, An underwater optical wireless communication system in which the optical fiber is configured to emit the first light from multiple positions on the side surface of the optical fiber.

8. The underwater optical wireless communication system according to claim 7, wherein the optical fiber is provided wound around the outer surface of the housing along the rotation axis of the rotating body.

9. An underwater optical wireless communication system for acquiring the state of a rotating body that rotates underwater, A first communication device is provided on the rotating body and rotates together with the rotating body, The system includes a second communication device which is provided at a distance from the first communication device in a direction intersecting the rotation axis of the rotating body, and which communicates wirelessly with the first communication device using light, The first communication device is A first light-emitting unit that emits a first light, which is light used for communication with the second communication device, in a direction intersecting the rotation axis of the rotating body, An information conversion unit that converts state information, which is information about the state of the rotating body, into the first light, It comprises a housing that houses the first light-emitting unit and rotates together with the rotating body, The first light-emitting unit includes a first light source that emits the first light, and a light-transmitting unit that transmits the first light emitted from the first light source within the housing in a direction intersecting the rotation axis of the rotating body. The first light source is configured to emit the first light in a direction along the rotation axis of the rotating body, The light transmitting unit is a reflective member provided in the housing at a position opposite to the first light source, which reflects the first light toward multiple radial directions of the rotating body, in an underwater optical wireless communication system.

10. The underwater optical wireless communication system according to claim 9, wherein the reflective member has a conical shape and is configured to reflect the first light toward multiple radial directions of the rotating body.

11. An underwater optical wireless communication system for acquiring the state of a rotating body that rotates underwater, A first communication device is provided on the rotating body and rotates together with the rotating body, The system includes a second communication device which is provided at a distance from the first communication device in a direction intersecting the rotation axis of the rotating body, and which communicates wirelessly with the first communication device using light, The first communication device is A first light-emitting unit that emits a first light, which is light used for communication with the second communication device, in a direction intersecting the rotation axis of the rotating body, An information conversion unit that converts state information, which is information about the state of the rotating body, into the first light, It comprises a housing that houses the first light-emitting unit and rotates together with the rotating body, The first light-emitting unit includes a first light source that emits the first light, and a light-transmitting unit that transmits the first light emitted from the first light source within the housing in a direction intersecting the rotation axis of the rotating body. The light transmitting unit is connected to the first light source and is provided inside the housing, and is a plurality of optical fibers provided in each of the radial directions of the rotating body for each direction in which the first light is transmitted, in an underwater optical wireless communication system.

12. The underwater optical wireless communication system according to claim 11, wherein the exit end of each of the plurality of optical fibers, which is the end opposite to the end connected to the first light source, is configured to emit the first light such that the irradiation ranges of the first light overlap with each other.

13. The first communication device further comprises a first control unit, The second communication device further comprises a second control unit, The second control unit is configured to control the second communication device by transmitting a control signal, which is a signal for controlling the first communication device, to the first control unit using the second light. The underwater optical wireless communication system according to claim 2, wherein the first control unit is configured to control the first communication device to transmit the state information by the first light based on the control signal transmitted from the second control unit.

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