Optical wireless communication system and optical wireless communication method

Abstract

In this optical wireless communication system having a first optical wireless communication device and a second optical wireless communication device, the first optical wireless communication device comprises a transmitting unit that transmits an optical signal to the second optical wireless communication device through a first polarizing filter, and the second optical wireless communication device comprises a receiving unit that receives the optical signal through a second polarizing filter, a measuring unit that measures the signal strength of the optical signal, and a control unit that changes the orientation of the second polarizing filter or the first polarizing filter so that the signal strength increases.

Description

Technical Field

[0001] The present invention relates to an optical wireless communication system Muji and an optical wireless communication method.

Background Art

[0002] With the depletion of radio frequency resources, an optical wireless communication system that realizes wireless communication in a different way from conventional radio wave-based wireless communication has been studied. An optical wireless communication system is a communication system that performs wireless communication using electromagnetic waves (light) with wavelengths ranging from infrared rays to visible light. According to the optical wireless communication system, it is possible to realize wireless communication that does not interfere with conventional wireless communication that uses a predetermined frequency band. In addition, since light does not transmit through a shielding object such as a building wall in the optical wireless communication system, it has immunity to interference and is also attracting attention from the viewpoint of high security (see, for example, Non-Patent Document 1).

[0003] Hereinafter, the configuration of a general optical wireless communication system when visible light is used for downlink signal transmission will be described. FIG. 11 is a diagram showing an example of the configuration of a general optical wireless communication system. The optical wireless communication system 8 shown in FIG. 11 includes an optical wireless communication device 810 and an optical wireless communication device 820. The optical wireless communication device 810 is a communication device installed, for example, on the ceiling indoors and functions as a radio base station that houses the optical wireless communication device 820. The optical wireless communication device 820 is, for example, a small terminal device and communicates with the optical wireless communication device 810.

[0004] As shown in FIG. 11, the optical wireless communication device 810 includes a light source 811, an infrared light receiving unit 812, and an optical signal processing unit 813. The light source 811 includes, for example, an LED (Light Emitting Diode) and emits visible light VL. Note that the light source 811 may be provided in a general lighting fixture or the like. The light source 811 is connected to the optical signal processing unit 813. The optical signal processing unit 813 can control the light source 811 and change the lighting cycle, lighting intensity, etc. of the visible light VL emitted from the light source 811. The optical signal processing unit 813 converts the desired information to be transmitted to the optical wireless communication device 820 into an optical signal represented by a change in the visible light VL. Thereby, an optical signal (downlink signal) using the visible light VL is transmitted from the optical wireless communication device 810 to the optical wireless communication device 820. Note that the optical signal processing unit 813 may be connected to an upper communication network such as the Internet or an intranet.

[0005] As shown in FIG. 11, the optical wireless communication device 820 includes a visible light receiving unit 821 and an infrared light transmitting unit 822. The visible light receiving unit 821 receives the visible light VL emitted from the light source 811. The visible light receiving unit 821 reads out the optical signal (downlink signal) included in the visible light VL. The optical wireless communication device 820 performs various processes such as reception processing and data conversion on the optical signal read out by the visible light receiving unit 821. Further, infrared light is used for the optical signal (uplink signal) transmitted from the optical wireless communication device 820 to the optical wireless communication device 810. The infrared light transmitting unit 822 transmits an optical signal using infrared light to the optical wireless communication device 810.

[0006] The infrared rays emitted from the infrared transmission unit 822 are received by the infrared light receiving unit 812 of the optical wireless communication device 810. The infrared light receiving unit 812 reads out the optical signal (uplink signal) included in the infrared rays. The infrared light receiving unit 812 is connected to the optical signal processing unit 813. The optical signal processing unit 813 performs various processes such as reception processing and data conversion on the optical signal read out by the infrared light receiving unit 812. Note that the optical signal processing unit 813 may transfer the optical signal on which various processes have been performed to the upper communication network. In this way, a general optical wireless communication system using visible light and infrared rays is realized.

[0007] Note that the optical wireless communication system 8 shown in FIG. 11 is a system configuration assuming that the downlink signal is transmitted using existing lighting equipment such as LED lighting installed indoors, for example. However, an infrared ray may also be used for the transmission of the downlink signal. FIG. 12 is a diagram showing an example of the configuration of an optical wireless communication system that uses infrared rays for both the transmission of the uplink signal and the transmission of the downlink signal. The optical wireless communication system 9 shown in FIG. 12 includes an optical wireless communication device 910 and an optical wireless communication device 920. The optical wireless communication device 910 includes an infrared transmission unit 911, an infrared light receiving unit 912, and an optical signal processing unit 913. The infrared transmission unit 911 is connected to the optical signal processing unit 913. The optical signal processing unit 913 can control the infrared transmission unit 911 and blink the infrared rays emitted from the infrared transmission unit 911. The optical signal processing unit 913 converts the desired information to be transmitted to the optical wireless communication device 920 into an optical signal represented by, for example, the on and off of infrared rays. As a result, an optical signal (downlink signal) using infrared rays is transmitted from the optical wireless communication device 910 to the optical wireless communication device 820.

[0008] As shown in FIG. 12, the optical wireless communication device 920 includes an infrared light receiving unit 921 and an infrared light transmitting unit 922. The infrared light receiving unit 921 receives the infrared light transmitted from the infrared light transmitting unit 911. The infrared light receiving unit 921 reads out the optical signal (downlink signal) included in the infrared light. The optical wireless communication device 920 performs various processes such as reception processing and data conversion on the optical signal read by the infrared light receiving unit 921. Further, infrared light is used for the optical signal (uplink signal) transmitted from the optical wireless communication device 920 to the optical wireless communication device 910, similar to the optical wireless communication system 8 shown in FIG. 11 described above. The configurations of the infrared light transmitting unit 922 and the infrared light receiving unit 912 are the same as the configurations of the infrared light transmitting unit 822 and the infrared light receiving unit 812 shown in FIG. 11 described above.

[0009] The infrared light receiving unit 912 of the optical wireless communication device 910 is connected to an optical signal processing unit 913. The optical signal processing unit 913 performs various processes such as reception processing and data conversion on the optical signal read by the infrared light receiving unit 912. In this way, a general optical wireless communication system using infrared light is realized for both the transmission of the uplink signal and the transmission of the downlink signal.

[0010] Note that the optical wireless communication system 8 illustrated in FIG. 11 is configured to perform wireless communication between an optical wireless communication device 810 which is a wireless base station and an optical wireless communication device 820 which is a wireless communication terminal, and the optical wireless communication system 9 illustrated in FIG. 12 is configured to perform wireless communication between an optical wireless communication device 910 which is a wireless base station and an optical wireless communication device 920 which is a wireless communication terminal, but it is not limited to such a configuration. For example, it may be a communication system for performing wireless communication using visible light, infrared light, etc. between a plurality of optical wireless communication devices having the same configuration, such as a plurality of wireless relay stations in relay wireless. Thus, the optical wireless communication system can have an arbitrary system configuration according to the purpose.

Prior Art Documents

Non-Patent Documents

[0011]

Non-Patent Document 1

[0012] In an optical wireless communication system, the transmission frequency (transmission wavelength and equivalent) of the signal light is defined by the elements used in light sources such as LEDs. Here, when a plurality of optical signals are simultaneously transmitted using a plurality of light sources of the same type installed in close proximity to each other, interference may occur between these optical signals, and the transmission characteristics may deteriorate.

[0013] FIG. 13 is a diagram showing an example of the configuration of an optical wireless communication system that simultaneously transmits a plurality of optical signals using a plurality of light sources of the same type. The optical wireless communication system 8' shown in FIG. 13 has a configuration in which two sets of the optical wireless communication devices 810 and 820 of the optical wireless communication system 8 shown in FIG. 11 described above are installed in close proximity. As shown in FIG. 13, the optical wireless communication device 810-1 and the optical wireless communication device 820-1 form a set of optical wireless communication devices that communicate with each other, and the optical wireless communication device 810-2 and the optical wireless communication device 820-2 form a set of optical wireless communication devices that communicate with each other.

[0014] In an optical wireless communication system 8' in which a plurality of light sources 811 of the same type are installed in proximity to each other as shown in FIG. 13, downstream signals are transmitted from these plurality of light sources 811 to a plurality of optical wireless communication devices 820 respectively. In such a case, there has been a problem that interference may occur between two downstream signals and the transmission characteristics may deteriorate. Also, there has been the same problem not only in the transmission of downstream signals but also in the transmission of upstream signals.

[0015] In view of the above circumstances, an object of the present invention is to provide a technology capable of performing optical wireless communication without causing interference between optical signals even when optical signals are transmitted respectively using a plurality of light sources of the same type.

Means for Solving the Problem

[0016] One aspect of the present invention is an optical wireless communication system having a plurality of first optical wireless communication devices and a plurality of second optical wireless communication devices, and forming communication links for each combination of the first optical wireless communication device and the second optical wireless communication device, wherein the first optical wireless communication device includes a transmission unit that transmits an optical signal to the second optical wireless communication device via a first polarization filter, and the second optical wireless communication device includes a reception unit that receives the optical signal via a second polarization filter, a measurement unit that measures the signal intensity of the optical signal, and a control unit that changes the orientation of the second polarization filter or the first polarization filter so that the signal intensity becomes stronger.

[0017] Also, one aspect of the present invention is an optical wireless communication system having a plurality of first optical wireless communication devices and a plurality of second optical wireless communication devices, and forming communication links for each combination of the first optical wireless communication device and the second optical wireless communication device. The first optical wireless communication device includes a transmission unit that transmits an optical signal including instruction information for designating the orientation of a second polarization filter to the second optical wireless communication device via a first polarization filter. The second optical wireless communication device includes a reception unit that receives the optical signal via the second polarization filter, an acquisition unit that acquires the instruction information from the optical signal, and a control unit that changes the orientation of the second polarization filter so as to be the orientation designated by the instruction information.

[0018] Also, one aspect of the present invention is an optical wireless communication device including a reception unit that receives, via a second polarization filter, an optical signal transmitted from another optical wireless communication device via a first polarization filter, a measurement unit that measures the signal intensity of the optical signal, and a control unit that changes the orientation of the second polarization filter or the first polarization filter so that the signal intensity becomes stronger.

[0019] Also, one aspect of the present invention is an optical wireless communication device including a reception unit that receives, via the second polarization filter, an optical signal including instruction information for designating the orientation of a second polarization filter and transmitted from another wireless communication device via a first polarization filter, an acquisition unit that acquires the instruction information from the optical signal, and a control unit that changes the orientation of the second polarization filter so as to be the orientation designated by the instruction information.

[0020] Also, one aspect of the present invention is an optical wireless communication method by an optical wireless communication system having a plurality of first optical wireless communication devices and a plurality of second optical wireless communication devices, and forming communication links for each combination of the first optical wireless communication device and the second optical wireless communication device, the method comprising: a transmission step in which the first optical wireless communication device transmits an optical signal to the second optical wireless communication device via a first polarization filter; a reception step in which the second optical wireless communication device receives the optical signal via a second polarization filter; a measurement step in which the second optical wireless communication device measures the signal strength of the optical signal; and a control step in which the second optical wireless communication device changes the orientation of the second polarization filter or the first polarization filter so that the signal strength becomes stronger.

[0021] Also, one aspect of the present invention is an optical wireless communication method by an optical wireless communication system having a plurality of first optical wireless communication devices and a plurality of second optical wireless communication devices, and forming communication links for each combination of the first optical wireless communication device and the second optical wireless communication device, the method comprising: a transmission step in which the first optical wireless communication device transmits an optical signal including instruction information specifying the orientation of a second polarization filter to the second optical wireless communication device via a first polarization filter; a reception step in which the second optical wireless communication device receives the optical signal via the second polarization filter; an acquisition step in which the second optical wireless communication device acquires the instruction information from the optical signal; and a control step in which the second optical wireless communication device changes the orientation of the second polarization filter to the orientation specified by the instruction information.

Advantages of the Invention

[0022] According to the present invention, even when optical signals are transmitted using a plurality of light sources of the same type, it is possible to perform optical wireless communication without causing interference between the optical signals.

Brief Description of the Drawings

[0023]

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Embodiments for Carrying Out the Invention

[0024] Hereinafter, the optical wireless communication system Muji and the optical wireless communication method of the present invention will be described with reference to the drawings. The present invention relates to an optical wireless communication system Muji and an optical wireless communication method that realize optical wireless communication using visible light, infrared light, etc. Note that the embodiments described below are merely one form, and the embodiments to which the present invention can be applied are not limited to the embodiments described below.

[0025] <First Embodiment> Hereinafter, the first embodiment of the present invention will be described.

[0026] [Configuration of Optical Wireless Communication System] Hereinafter, the configuration of the optical wireless communication system 1 in the first embodiment will be described. FIG. 1 is a diagram showing the configuration of the optical wireless communication system 1 in the first embodiment of the present invention. As shown in FIG. 1, the optical wireless communication system 1 includes an optical wireless communication device 110-1, an optical wireless communication device 110-2, an optical wireless communication device 120-1, and an optical wireless communication device 120-2.

[0027] In the following description, when it is not necessary to distinguish between the optical wireless communication device 110-1 and the optical wireless communication device 110-2, they may simply be referred to as "optical wireless communication device 110". Also, in the following description, when it is not necessary to distinguish between the optical wireless communication device 120-1 and the optical wireless communication device 120-2, they may simply be referred to as "optical wireless communication device 120".

[0028] The optical wireless communication device 110-1 is a communication device installed, for example, on the ceiling inside a room, and functions as a wireless base station that houses the optical wireless communication device 120-1. Similarly, the optical wireless communication device 110-2 is a communication device installed, for example, on the ceiling inside a room, and functions as a wireless base station that houses the optical wireless communication device 120-2.

[0029] The optical wireless communication device 120-1 is, for example, a small terminal device and communicates with the optical wireless communication device 110-1. Similarly, the optical wireless communication device 120-2 is, for example, a small terminal device and communicates with the optical wireless communication device 110-2.

[0030] As shown in FIG. 1, the optical wireless communication device 110-1 includes a light source 111, an infrared light receiving unit 112, an optical signal processing unit 113, and two polarization filters 115. The light source 111 includes, for example, an LED and emits visible light VL. Note that the light source 111 may be provided in a general lighting fixture or the like. The light source 111 is connected to the optical signal processing unit 113.

[0031] The optical signal processing unit 113 can control the light source 111 and change the lighting cycle, lighting intensity, etc. of the visible light VL emitted from the light source 111. The optical signal processing unit 113 converts the desired information to be transmitted to the optical wireless communication device 120-1 into an optical signal represented by the change in the visible light VL. Thereby, an optical signal (downlink signal) using the visible light VL is transmitted from the optical wireless communication device 110-1 to the optical wireless communication device 120-1.

[0032] The visible light VL emitted from the light source 111 is transmitted through the polarization filter 115. Note that the configuration of the polarization filter 115 will be described later.

[0033] Note that the optical signal processing unit 113 may be connected to a higher-level communication network such as the Internet or an intranet.

[0034] As shown in FIG. 1, the optical wireless communication device 120-1 includes a visible light receiving unit 121, an infrared transmitting unit 122, and two polarization filters 125. The visible light receiving unit 121 receives the visible light VL emitted from the light source 111. The visible light receiving unit 121 receives the visible light VL through the polarization filter 125. Note that the configuration of the polarization filter 125 will be described later.

[0035] The visible light receiving unit 121 reads out the optical signal (downlink signal) included in the visible light VL. The optical wireless communication device 120-1 performs various processes such as reception processing and data conversion on the optical signal read by the visible light receiving unit 121. For example, the visible light receiving unit 121 converts the downlink signal from an optical signal into an electrical signal.

[0036] In addition, infrared rays are used for the optical signal (uplink signal) transmitted from the optical wireless communication device 120-1 to the optical wireless communication device 110-1. The desired information transmitted to the optical wireless communication device 110-1 is converted into an optical signal represented by, for example, turning on and off of infrared rays. The infrared ray transmitting unit 122 emits the infrared rays by flashing them, and thereby emits the infrared rays including the optical signal toward the optical wireless communication device 110-1. Thereby, an optical signal (uplink signal) using infrared rays is transmitted from the optical wireless communication device 120-1 to the optical wireless communication device 110-1.

[0037] The infrared ray transmitting unit 122 emits the infrared rays through the polarization filter 125. The configuration of the polarization filter 125 will be described later.

[0038] The infrared rays emitted from the infrared ray transmitting unit 122 through the polarization filter 125 are received by the infrared ray receiving unit 112 of the optical wireless communication device 110-1. The infrared ray receiving unit 112 receives the infrared rays through the polarization filter 115. The configuration of the polarization filter 115 will be described later.

[0039] The infrared ray receiving unit 112 reads out the optical signal (uplink signal) included in the infrared rays. The infrared ray receiving unit 112 is connected to the optical signal processing unit 113. The optical signal processing unit 113 performs various processes such as reception processing and data conversion on the optical signal read by the infrared ray receiving unit 112. Note that the optical signal processing unit 113 may transfer the optical signal on which various processes have been performed to a higher-level communication network. In this way, optical wireless communication using visible light and infrared rays is realized.

[0040] Note that since the configuration of the optical wireless communication device 110-2 is the same as that of the above-described optical wireless communication device 110-1, and the configuration of the optical wireless communication device 120-2 is the same as that of the above-described optical wireless communication device 120-1, the description thereof will be omitted.

[0041] [Configuration of Polarizing Filter] Hereinafter, the configurations of the polarizing filter 115 and the polarizing filter 125 will be described. Note that since the function of the polarizing filter 125 is basically equivalent to that of the polarizing filter 115, the polarizing filter 115 will be described as an example here.

[0042] The polarizing filter 115 is, for example, a film made of polyvinyl alcohol or a derivative thereof, having a thickness of about 0.1 [mm], which is colorless and transparent, and is stretched and fixed 3 to 5 times by utilizing thermoelasticity or swelling elasticity, resulting in a film in which polymer micelles are arranged in a specific direction.

[0043] FIG. 2 is a schematic diagram showing the configuration of the polarizing filter 115 in the first embodiment of the present invention. As described above, the configuration of the polarizing filter 125 is the same as that of the polarizing filter 115. The polarizing filter 115 is a filter that transmits only light having a specific transmission axis, and is, for example, a linear polarizing filter. Note that the polarizing filter 115 may be a filter other than a linear polarizing filter, such as a circular polarizing filter.

[0044] As shown in FIG. 2, the polarizing filter 115 is a linear polarizing filter having a transmission axis that is an axis in the fiber direction and an absorption axis that is an axis in a direction orthogonal to the transmission axis. For example, when light vibrating randomly at 360 degrees passes through the polarizing filter 115, due to the extremely fine slit-like structure of the polarizing filter 115, the wave along the transmission axis is transmitted, and the wave along the absorption axis is absorbed and not transmitted. Also, among the waves vibrating obliquely, the component corresponding to the transmission axis is transmitted, and the component corresponding to the absorption axis is absorbed.

[0045] By installing the polarization filter 115 and the polarization filter 125 in predetermined directions respectively, the light transmitted between the optical wireless communication device 110 and the optical wireless communication device 120 can be blocked or transmitted by the polarization filter on the receiving side.

[0046] FIG. 3 is a diagram for explaining the blocking of light by the polarization filter 115 and the polarization filter 125 in the first embodiment of the present invention. When the polarization filter 115 and the polarization filter 125 are linear polarization filters, the polarization filter 115 and the polarization filter 125 are installed in such a direction that their transmission axes are orthogonal to each other, so that the light is blocked. In FIG. 3, the polarization filter 115 is installed so that its transmission axis is in the vertical direction, and the polarization filter 125 is installed so that its transmission axis is in the horizontal direction, and their transmission axes are orthogonal to each other. Therefore, in FIG. 3, the overlapping range of the polarization filter 115 and the polarization filter 125 is the range that blocks the light.

[0047] FIG. 4 is a diagram for explaining the transmission of light by the polarization filter 115 and the polarization filter 125 in the first embodiment of the present invention. When the polarization filter 115 and the polarization filter 125 are linear polarization filters, the polarization filter 115 and the polarization filter 125 are installed in such a direction that their transmission axes are parallel to each other, so that the light is transmitted. In FIG. 4, the polarization filter 115 is installed so that its transmission axis is in the vertical direction, and the polarization filter 125 is also installed so that its transmission axis is in the vertical direction, and their transmission axes are parallel to each other. Therefore, in FIG. 4, the light is transmitted in all ranges including the overlapping range of the polarization filter 115 and the polarization filter 125.

[0048] The optical wireless communication system 1 according to the first embodiment shown in FIG. 1 utilizes the properties of the polarization filter 115 and the polarization filter 125 as described above, so that even when a plurality of light sources 111 of the same type are brought close to each other and the optical signals are transmitted simultaneously, optical wireless communication can be performed without causing interference between the optical signals transmitted from the respective light sources 111.

[0049] As shown in FIG. 1, the optical wireless communication device 110-1 and the optical wireless communication device 110-2 are each provided with a polarization filter 115 having a transmission axis in a specific direction outside the light source 111 and outside the infrared light receiving unit 112. Further, the optical wireless communication device 120-1 and the optical wireless communication device 120-2 are each provided with a polarization filter 115 having a transmission axis in a specific direction outside the visible light receiving unit 121 and outside the infrared light transmitting unit 122.

[0050] As shown in FIG. 1, when the combination of the optical wireless communication device 110 and the optical wireless communication device 120 is such that the transmission axes of the polarization filter 115 and the polarization filter 125 coincide, optical wireless communication becomes possible. This is because the directions of the transmission axes of the polarization filter 115 and the polarization filter 125 are the same, so the light transmitted through the polarization filter 115 also passes through the polarization filter 125. Similarly, the light transmitted through the polarization filter 125 also passes through the polarization filter 125.

[0051] In FIG. 1, the direction of the transmission axis of the polarization filter 115 of the optical wireless communication device 110-1 coincides with the direction of the transmission axis of the polarization filter 125 of the optical wireless communication device 120-1 (in FIG. 1, the directions of both transmission axes are in the vertical direction). Therefore, the optical wireless communication device 110-1 and the optical wireless communication device 120-1 can perform optical wireless communication. Also, in FIG. 1, the direction of the transmission axis of the polarization filter 115 of the optical wireless communication device 110-2 coincides with the direction of the transmission axis of the polarization filter 125 of the optical wireless communication device 120-2 (in FIG. 1, the directions of both transmission axes are in the horizontal direction). Therefore, the optical wireless communication device 110-2 and the optical wireless communication device 120-2 can perform optical wireless communication.

[0052] In contrast, in FIG. 1, the direction of the transmission axis of the polarization filter 115 of the optical wireless communication device 110-1 is the vertical direction, and the direction of the transmission axis of the polarization filter 125 of the optical wireless communication device 120-2 is the horizontal direction. The directions of both transmission axes are orthogonal to each other. Therefore, the optical wireless communication device 110-1 and the optical wireless communication device 120-2 cannot perform optical wireless communication. Also, in FIG. 1, the direction of the transmission axis of the polarization filter 115 of the optical wireless communication device 110-2 is the horizontal direction, and the direction of the transmission axis of the polarization filter 125 of the optical wireless communication device 120-1 is the vertical direction. The directions of both transmission axes are orthogonal to each other. Therefore, the optical wireless communication device 110-2 and the optical wireless communication device 120-1 cannot perform optical wireless communication.

[0053] This is because the direction of the transmission axis of the polarization filter 115 and the direction of the transmission axis of the polarization filter 125 are orthogonal, so the light transmitted through the polarization filter 115 does not pass through the polarization filter 125. Similarly, the light transmitted through the polarization filter 125 does not pass through the polarization filter 115.

[0054] By providing such a configuration, according to the optical wireless communication system 1 in the first embodiment, the visible light VL respectively transmitted from a plurality of adjacent light sources 111 and transmitted through the polarization filter 115 or the polarization filter 125 does not interfere with each other on the receiving side. Thereby, the optical wireless communication system 1 can prevent the deterioration of the transmission quality due to interference.

[0055] Specifically, as shown in FIG. 1, the directions of the transmission axes of the polarization filters (the polarization filter 115 and the polarization filter 125) of the optical wireless communication devices that perform optical wireless communication with each other are installed so as to be in the same direction, and the directions of the transmission axes of the polarization filters of the optical wireless communication devices that do not perform optical wireless communication with each other are installed so as to be in different directions (for example, orthogonal directions) from each other. By doing so, it becomes possible to prevent interference between optical signals in a plurality of optical wireless communications.

[0056] As described above, the polarization filters 115 and 125 do not necessarily need to correspond to linearly polarized light, and may be, for example, circularly polarized light or the like. As long as it is an optical wireless communication system capable of simultaneously performing spatial multiplexing transmission by combining polarization filters having different (for example, orthogonal) transmission axes, it is not limited to the configuration of the optical wireless communication system 1 described above.

[0057] Note that the configuration may be such that the polarization filter 115 is provided only in the light source 111 of the optical wireless communication device 110, and the polarization filter 125 is provided only in the visible light light receiving unit 121 of the optical wireless communication device 120. That is, the polarization filters 115 and 125 may be used only for the downlink signal, and the configuration may be such that only the interference between the optical signals in the transmission of the downlink signal is prevented. Conversely, the configuration may be such that the polarization filter 115 is provided only in the infrared light receiving unit 112 of the optical wireless communication device 110 and the polarization filter 125 is provided only in the infrared light transmitting unit 122 of the optical wireless communication device 120. That is, the polarization filters 115 and 125 may be used only for the uplink signal, and the configuration may be such that only the interference between the optical signals in the transmission of the uplink signal is prevented.

[0058] Note that in the optical wireless communication system 1 illustrated in FIG. 1, the optical wireless communication device 110 is configured to include one light source 111 and one infrared light receiving unit 112 each, but may include a plurality of light sources 111 and a plurality of infrared light receiving units 112. For example, one optical wireless communication device 110 may be configured to perform optical wireless communication with both the optical wireless communication devices 120-1 and 120-2 using polarization filters 115 installed in different directions.

[0059] Note that the types and the directions of the transmission axes of the polarization filters 115 provided in the light source 111 and the infrared light receiving unit 112 may be the same or different. Similarly, the types and the directions of the transmission axes of the polarization filters 125 provided in the visible light receiving unit 121 and the infrared light transmitting unit 122 may be the same or different. That is, the same light can pass through between the optical wireless communication devices that perform optical wireless communication with each other (for example, the optical wireless communication device 110-1 and the optical wireless communication device 120-1, and the optical wireless communication device 110-2 and the optical wireless communication device 120-2), and the same light cannot pass through between the optical wireless communication devices that do not perform optical wireless communication with each other (for example, the optical wireless communication device 110-1 and the optical wireless communication device 120-2, and the optical wireless communication device 110-2 and the optical wireless communication device 120-1). As long as such a configuration is provided, the types and the directions of the transmission axes of the polarization filter 115 and the polarization filter 125 can be arbitrarily selected.

[0060] [Correction Processing for the Direction of the Transmission Axis of the Polarization Filter] Hereinafter, the correction processing for the direction of the transmission axis of the polarization filter 125 by the optical wireless communication device 120 in the optical wireless communication system 1 according to the first embodiment will be described.

[0061] When at least one of the optical wireless communication device 110 and the optical wireless communication device 120 is a device that may perform an operation involving rotation or the like, the direction of the transmission axis of the polarization filter changes according to the operation. That is, when the positional relationship between the optical wireless communication device 110 and the optical wireless communication device 120 or the direction of at least one of the optical wireless communication device 110 and the optical wireless communication device 120 changes, a deviation (discrepancy) may occur between the direction of the transmission axis of the polarization filter 115 of the optical wireless communication device 110 and the direction of the transmission axis of the polarization filter 125 of the optical wireless communication device 120. When a deviation occurs in the direction of the transmission axis of the polarization filter between the optical wireless communication device 110 and the optical wireless communication device 120, the optical signal is blocked by the polarization filter of the optical wireless communication device on the receiving side, so that the transmission characteristics deteriorate.

[0062] In the optical wireless communication apparatus 120 of the optical wireless communication system according to the first embodiment, a rotation mechanism for rotating the polarization filter 125 is provided so as to correct the deviation generated between the direction of the transmission axis of the polarization filter 115 of the optical wireless communication apparatus 110 and the direction of the transmission axis of the polarization filter 125 of the optical wireless communication apparatus 120. In the present embodiment, as an example, the case where the above rotation mechanism is provided only in the optical wireless communication apparatus 120 will be described, but the present invention is not limited to this configuration. The above rotation mechanism may be provided in both the optical wireless communication apparatus 110 and the optical wireless communication apparatus 120, or may be provided only in the optical wireless communication apparatus 110.

[0063] FIGS. 5 and 6 are diagrams for explaining the configuration of the rotation mechanism 127 of the polarization filter 125 included in the optical wireless communication apparatus 120 according to the first embodiment of the present invention. FIG. 5 is a side view around the rotation mechanism 127 of the optical wireless communication apparatus 120, and FIG. 6 is a plan view around the rotation mechanism 127 of the optical wireless communication apparatus 120.

[0064] As shown in FIG. 5, the rotation mechanism 127 is provided between the visible light receiving unit 121 and the infrared transmitting unit 122 and the polarization filter 125, respectively. When infrared rays are used for transmitting the downlink signal, the rotation mechanism 127 is provided between an infrared light receiving unit (not shown) and the polarization filter 125. The polarization filter 125 is fixedly installed with respect to the rotation mechanism 127. The rotation mechanism 127 is movably installed with respect to the visible light receiving unit 121 and the infrared transmitting unit 122 (that is, the rotation mechanism 127 can perform a rotation operation).

[0065] Also, as shown in FIG. 6, the polarization filter rotation mechanism drive unit 126 is provided so as to be in contact with the rotation mechanism 127. The polarization filter rotation mechanism drive unit 126 rotates the rotation mechanism 127 under the control of a polarization filter control unit 124 described later. For example, the polarization filter rotation mechanism drive unit 126 may be configured to rotate by power from a power source (not shown) such as a motor, and the rotation mechanism 127 in contact with the polarization filter rotation mechanism drive unit 126 rotates in the reverse direction in conjunction therewith. As a result, the installation direction of the polarization filter 125 fixedly installed on the rotation mechanism 127 also changes, and the direction of the transmission axis of the polarization filter 125 changes.

[0066] [Configuration of Optical Wireless Communication Device] Hereinafter, the details of the configuration of the optical wireless communication device 120 will be described. FIG. 7 is a block diagram showing the configuration of the optical wireless communication device 120 according to the first embodiment of the present invention. The optical wireless communication device 120 is a small terminal device whose orientation may change due to rotation or the like, for example. The optical wireless communication device 120 functions as a wireless communication terminal accommodated in the opposing optical wireless communication device 110.

[0067] As shown in FIG. 7, the optical wireless communication device 120 includes a visible light light receiving unit 121, an infrared transmitting unit 122, a data processing unit 123, a polarization filter control unit 124, two polarization filters 125, a polarization filter rotation mechanism drive unit 126, and a received optical power measurement unit 128.

[0068] Note that the optical wireless communication device 120 shown in FIG. 7 is assumed to be a terminal device included in an optical wireless communication system that transmits a downlink signal using visible light VL and transmits an uplink signal using infrared light as an example. However, the present invention is not limited to such a configuration. For example, a configuration in which infrared light is used for both the transmission of the downlink signal and the transmission of the uplink signal may also be possible.

[0069] The visible light receiving unit 121 receives the visible light VL transmitted from the opposing optical wireless communication device 110. The visible light receiving unit 121 receives the visible light VL through the polarization filter 125. Note that the configuration of the polarization filter 125 is as described above with reference to FIGS. 2 to 4.

[0070] The visible light receiving unit 121 reads out the optical signal (downlink signal) included in the visible light VL. The visible light receiving unit 121 performs various processes such as reception processing and data conversion on the read optical signal. For example, the visible light receiving unit 121 converts the downlink signal from an optical signal to an electrical signal. The visible light receiving unit 121 is connected to the data processing unit 123. The visible light receiving unit 121 outputs the signal subjected to various processes to the data processing unit 123.

[0071] In addition, infrared rays are used for the optical signal (uplink signal) transmitted from the optical wireless communication device 120 to the optical wireless communication device 110. The electrical signal indicating the desired information to be transmitted to the optical wireless communication device 110 is converted by the infrared transmitting unit 122 into an optical signal represented by, for example, turning on and off of infrared rays. The infrared transmitting unit 122 transmits the infrared rays in a blinking manner, thereby transmitting the infrared rays including the optical signal toward the optical wireless communication device 110. Thereby, an optical signal (uplink signal) using infrared rays is transmitted from the optical wireless communication device 120 to the optical wireless communication device 110.

[0072] The infrared transmitting unit 122 transmits the infrared rays through the polarization filter 125. Note that the configuration of the polarization filter 125 is the same as the configuration of the aforementioned polarization filter 125 described with reference to FIGS. 2 to 4.

[0073] The received optical power measurement unit 128 measures the signal intensity of the visible light VL received by the visible light receiving unit 121. The received optical power measurement unit 128 outputs information indicating the measurement result of the signal intensity to the polarization filter control unit 124.

[0074] The polarization filter control unit 124 acquires information indicating the measurement result of the signal intensity output from the received optical power measurement unit 128. Based on the information indicating the measurement result of the signal intensity, the polarization filter control unit 124 instructs the polarization filter rotation mechanism drive unit 126 to rotate the polarization filter 125 in the direction in which the signal intensity of the visible light VL received by the visible light receiving unit 121 becomes stronger.

[0075] Specifically, for example, the polarization filter control unit 124 rotates the polarization filter 125 by a predetermined angle in a specific direction (for example, clockwise), and compares the signal intensity before rotation and the signal intensity after rotation. As a result of the comparison, if the signal intensity after rotation is stronger than the signal intensity before rotation, or if the signal intensity before rotation is the same as the signal intensity after rotation, the polarization filter control unit 124 rotates the polarization filter 125 by a predetermined angle again in the same direction (for example, clockwise). Also, as a result of the comparison, if the signal intensity before rotation is stronger than the signal intensity after rotation, the polarization filter control unit 124 rotates the polarization filter 125 by a predetermined angle in the reverse direction (for example, counterclockwise).

[0076] By repeating the above-described processing, the polarization filter control unit 124 controls the direction of the transmission axis of the polarization filter 125 so that the signal intensity of the visible light VL received by the visible light receiving unit 121 becomes stronger (or the strongest). By performing the above-described control, as a result, the deviation (deviation) between the direction of the transmission axis of the polarization filter 115 of the optical wireless communication device 110 and the direction of the transmission axis of the polarization filter 125 of the optical wireless communication device 120 is corrected.

[0077] [Operation of Optical Wireless Communication Device] Hereinafter, an example of the operation of the optical wireless communication device 120 will be described. FIG. 8 is a flowchart showing the operation of the optical wireless communication device 120 in the first embodiment of the present invention. The operation of the optical wireless communication device 120 shown in the flowchart of FIG. 8 starts when visible light VL including an optical signal (downlink signal) is transmitted from the optical wireless communication device 110 to the optical wireless communication device 120.

[0078] The visible light receiving unit 121 receives visible light VL including an optical signal (downlink signal) transmitted from the opposing optical wireless communication device 110 (step S01). The received optical power measurement unit 128 measures the signal intensity of the visible light VL received by the visible light receiving unit 121 (step S02). The received optical power measurement unit 128 outputs information indicating the measurement result of the signal intensity to the polarization filter control unit 124.

[0079] The polarization filter control unit 124 acquires information indicating the measurement result of the signal intensity output from the received optical power measurement unit 128. Based on the information indicating the measurement result of the signal intensity, the polarization filter control unit 124 controls the direction of the transmission axis of the polarization filter 125 so that the signal intensity of the visible light VL received by the visible light receiving unit 121 becomes stronger (step S03). Thus, the operation of the optical wireless communication device 120 shown in the flowchart of FIG. 8 ends.

[0080] By having the configuration as described above, even when the optical wireless communication system 1 in the first embodiment transmits optical signals using a plurality of light sources of the same type installed close to each other, optical wireless communication can be performed without causing interference between the optical signals.

[0081] Furthermore, in the optical wireless communication system 1 in the first embodiment, the optical wireless communication device 120 includes a rotation mechanism 127 that changes the direction of the transmission axis of the polarization filter 125. And the polarization filter control unit 124 has a configuration that controls the direction of the transmission axis of the polarization filter 125 so that the signal intensity of the visible light VL received by the visible light receiving unit 121 becomes stronger. By having such a configuration, as a result, the optical wireless communication system 1 can correct the deviation between the direction of the transmission axis of the polarization filter 115 of the optical wireless communication device 110 and the direction of the transmission axis of the polarization filter 125 of the optical wireless communication device 120. Thereby, even when the optical wireless communication device 120a operates with rotation or the like, the optical wireless communication system 1 in the first embodiment can perform optical wireless communication without causing interference between optical signals.

[0082] In the present embodiment, the optical wireless communication device 120 is configured to include a rotation mechanism that rotates the polarization filter 125 in accordance with the rotation of the own device, in order to cope with the change in the direction of the transmission axis of the polarization filter 125 accompanying the rotation of the own device. However, the present invention is not limited to such a configuration. For example, the optical wireless communication device 120 may be configured to include a rotation mechanism that rotates not only the polarization filter 125 but also a part or all of the own device in accordance with the rotation of the own device.

[0083] Note that the polarization filter control unit 124 may be configured to instruct the polarization filter 115 of the optical wireless communication device 110 to rotate in a direction in which the signal intensity of the visible light VL received by the visible light receiving unit 121 becomes stronger, based on the information indicating the measurement result of the signal intensity. In this case, the polarization filter control unit 124 may transmit the instruction information to the optical wireless communication device 110 using an optical signal (uplink signal), or may transmit the instruction information using a signal in another communication method. In this case, the instruction information may include, for example, information indicating the measurement result of the signal intensity, or information for designating the direction of the transmission axis of the polarization filter 115. Also, in this case, the optical wireless communication device 110 includes a rotation mechanism for changing the direction of the transmission axis of the polarization filter 115.

[0084] Note that the optical wireless communication system 1 may be configured to include a control station (not shown) that collectively executes the rotation control of the polarization filters 125 of the plurality of optical wireless communication devices 120. Also, a configuration may be adopted in which each of the plurality of optical wireless communication devices 120 can recognize the appropriate direction of the transmission axis of the polarization filter by exchanging information regarding such control among the plurality of optical wireless communication devices 120.

[0085] <Second Embodiment> Next, a second embodiment of the present invention will be described. The optical wireless communication system 1 in the above-described first embodiment corrects the deviation (discrepancy) between the direction of the transmission axis of the polarization filter 115 of the optical wireless communication device 110 and the direction of the transmission axis of the polarization filter 125 of the optical wireless communication device 120, which is caused by a change in the positional relationship between the optical wireless communication device 110 and the optical wireless communication device 120, and / or a change in the orientation of at least one of the optical wireless communication device 110 and the optical wireless communication device 120.

[0086] In addition to the case of rotationally controlling the polarization filter to correct such an unintended deviation, there may be a case where the polarization filter is intentionally rotationally controlled. For example, in a case where it is desired to dynamically change the combination of the optical wireless communication device 110 and the optical wireless communication device 120 that communicate with each other according to the occurrence status of communication traffic or the like. In such a case, by dynamically changing the direction of the transmission axis of the polarization filter, the above-described change process can be realized.

[0087] Note that the overall configuration of the optical communication system in the second embodiment is basically the same as the overall configuration of the optical wireless communication system 1 in the first embodiment shown in FIG. 1 above, and thus the description thereof will be omitted.

[0088] [Configuration of Optical Wireless Communication Device] Next, the configuration of the optical wireless communication device 120a of the optical wireless communication system in the second embodiment will be described. FIG. 9 is a block diagram showing the configuration of the optical wireless communication device 120a in the second embodiment of the present invention. The optical wireless communication device 120a is, for example, a small terminal device. The optical wireless communication device 120a functions as a wireless communication terminal housed in the opposing optical wireless communication device 110 (not shown).

[0089] As shown in FIG. 9, the optical wireless communication device 120a includes a visible light light receiving unit 121, an infrared ray transmitting unit 122, a data processing unit 123, a polarization filter control unit 124, two polarization filters 125, and a polarization filter rotation mechanism driving unit 126.

[0090] Note that the optical wireless communication device 120a shown in Fig. 9 is a terminal device of an optical wireless communication system that transmits a downstream signal using visible light VL and an upstream signal using infrared light, similar to the optical wireless communication system 1 in the aforementioned first embodiment. However, it is not limited to such a configuration. For example, a configuration in which infrared light is used for both the transmission of the downstream signal and the transmission of the upstream signal may also be acceptable.

[0091] The visible light receiving unit 121 receives the visible light VL transmitted from the opposing optical wireless communication device 110 (not shown). The visible light receiving unit 121 receives the visible light VL through the polarization filter 125. Since the configuration of the polarization filter 125 is the same as that of the polarization filter 115 shown in Figs. 2 to 4 described above, the description thereof is omitted.

[0092] The visible light receiving unit 121 reads out the optical signal (downstream signal) included in the visible light VL. The visible light receiving unit 121 performs various processes such as reception processing and data conversion on the read optical signal. For example, the visible light receiving unit 121 converts the downstream signal from an optical signal to an electrical signal. The visible light receiving unit 121 is connected to the data processing unit 123. The visible light receiving unit 121 outputs the signal on which various processes have been performed to the data processing unit 123.

[0093] In addition, infrared light is used for the optical signal (upstream signal) transmitted from the optical wireless communication device 120a to the optical wireless communication device 110 (not shown). The desired information transmitted to the optical wireless communication device 110 (not shown) is converted into an optical signal represented by, for example, the on and off of infrared light. The infrared transmitting unit 122 transmits the infrared light by blinking it, thereby sending the infrared light including the optical signal toward the optical wireless communication device 110 (not shown). As a result, an optical signal (upstream signal) using infrared light is transmitted from the optical wireless communication device 120a to the optical wireless communication device 110 (not shown).

[0094] The infrared transmitting unit 122 transmits the infrared light through the polarization filter 125. Since the configuration of the polarization filter 125 is the same as that of the polarization filter 115 shown in Figs. 2 to 4 described above, the description thereof is omitted.

[0095] As shown in FIG. 9, the data processing unit 123 is configured to include an instruction information acquisition unit 1231. The instruction information acquisition unit 1231 reads instruction information from the signal acquired from the visible light light-receiving unit 121. The instruction information acquisition unit 1231 outputs the read instruction information to the polarization filter control unit 124. The instruction information here is information for designating the direction of the transmission axis of the polarization filter 125 provided in the optical wireless communication device 120a. The optical wireless communication device 110 transmits visible light VL including an optical signal (downlink signal) indicating the instruction information to the optical wireless communication device 120a.

[0096] Note that the information indicating the direction of the transmission axis of the polarization filter 125 designated for the optical wireless communication device 120a (that is, the information that is the source of the instruction information) is transmitted, for example, from a higher-level network to the optical wireless communication device 110. For example, the higher-level network dynamically changes the combination of the optical wireless communication device 110 and the optical wireless communication device 120a that communicate with each other according to the traffic generation situation and the like, and thus determines the direction of the transmission axis of the polarization filter 125 designated for each of the optical wireless communication devices 120a.

[0097] Note that the instruction information does not necessarily have to be transmitted from the optical wireless communication device 110 to the optical wireless communication device 120a by an optical signal using visible light VL. For example, the instruction information may be transmitted from the optical wireless communication device 110 or a higher-level network or the like to the optical wireless communication device 120a by communication using a cellular system such as 5G (5th Generation Mobile Communication System), a wireless LAN (Local Area Network), a wired LAN, or any other arbitrary communication method.

[0098] The polarization filter control unit 124 rotates the two polarization filters 125 so that the directions of the transmission axes of the two polarization filters 125 are the directions specified by the instruction information acquired from the instruction information acquisition unit 1231. As a result, it becomes possible to dynamically change the combination of the optical wireless communication device 110 and the optical wireless communication device 120a that communicate with each other.

[0099] Note that since the configuration of the opposing optical wireless communication device 110 (not shown) is basically the same as the configuration of the optical wireless communication device 110 in the first embodiment described above, the description thereof is omitted.

[0100] [Operation of Optical Wireless Communication Device] Hereinafter, an example of the operation of the optical wireless communication device 120a will be described. FIG. 10 is a flowchart showing the operation of the optical wireless communication device 120a in the second embodiment of the present invention. The operation of the optical wireless communication device 120a shown in the flowchart of FIG. 10 starts when the visible light receiving unit 121 reads out an optical signal (downlink signal) including instruction information included in the visible light VL transmitted from the opposing optical wireless communication device 110 (not shown) and outputs a signal subjected to various processes to the data processing unit 123.

[0101] The instruction information acquisition unit 1231 of the data processing unit 123 reads out the instruction information from the signal acquired from the visible light receiving unit 121 (step S11). Note that the instruction information here is information for specifying the direction of the transmission axis of the polarization filter 125 provided in the optical wireless communication device 120a, as described above. The instruction information acquisition unit 1231 outputs the read instruction information to the polarization filter control unit 124.

[0102] Next, the polarization filter control unit 124 rotationally controls the two polarization filters 125 so that the directions of the transmission axes of the two polarization filters 125 are the directions specified by the instruction information acquired from the instruction information acquisition unit 1231 (step S12). Thus, the operation of the optical wireless communication device 120a shown in the flowchart of FIG. 10 ends.

[0103] By having the configuration as described above, the optical wireless communication system in the second embodiment can perform optical wireless communication without causing interference between optical signals even when transmitting optical signals using a plurality of light sources of the same type, similar to the optical wireless communication system 1 in the aforementioned first embodiment.

[0104] Note that the instruction information indicating the direction of the transmission axis of the specified polarization filter 125, which is transmitted to the optical wireless communication device 120a, may be configured to be shared among the plurality of optical wireless communication devices 110. In this case, since it is possible to control the directions of the transmission axes of the polarization filters 125 not to match between adjacent optical wireless communication devices 120a, it becomes possible to perform optical wireless communication without causing interference between optical signals. In this way, it is possible to adjust the directions of the transmission axes of the polarization filters to be different from each other between communication links formed in proximity.

[0105] Note that a configuration may be adopted in which the configuration of the optical wireless communication system 1 in the aforementioned first embodiment and the configuration of the optical wireless communication system in the second embodiment are combined. That is, the optical wireless communication system may simultaneously perform control to change the direction of the transmission axis of the polarization filter so that the signal intensity of the optical signal transmitted by optical wireless communication becomes stronger while dynamically changing the combination of the optical wireless communication device 110 and the optical wireless communication device 120 (120a) that communicate with each other by transmitting instruction information.

[0106] Note that in the aforementioned first and second embodiments, the case where the direction of the transmission axis of the polarization filter 115 or 125 for transmission and the direction of the transmission axis of the polarization filter 115 or 125 for reception of the optical wireless communication device 110 and the optical wireless communication device 120 are the same has been described, but the configuration is not limited to this and they may be different from each other.

[0107] In the above-described first and second embodiments, an optical wireless communication system using visible light and infrared light has been described. However, the present invention is not limited to this configuration. The present invention can be applied to any optical wireless communication belonging to so-called free-space optical communication (FSO), including, for example, a laser, as long as it is an optical wireless communication system using a polarization filter.

[0108] According to the optical wireless communication system 1 in the first embodiment and the optical wireless communication system in the second embodiment described above, even when optical wireless transmission is performed using the same type of light sources installed in close proximity to each other, it is possible to perform optical wireless communication without causing interference between the respective communication links. As a result, an increase in communication capacity and throughput can be expected.

[0109] Further, in the optical wireless communication system 1 in the first embodiment and the wireless communication system in the second embodiment described above, two opposing optical wireless communication devices each include a polarization filter installed so that the directions of the same transmission axes are aligned, or a polarization filter controlled so that the directions of the same transmission axes are aligned. Thereby, since optical wireless communication can be established only between communication links formed through polarization filters having the same transmission axis direction, the occurrence of interference between communication links can be prevented.

[0110] According to the above-described embodiment, the optical wireless communication system includes a plurality of first optical wireless communication devices and a plurality of second optical wireless communication devices. For example, the optical communication system is the optical wireless communication system 1 in the embodiment, the first optical wireless communication device is the optical wireless communication device 110 in the embodiment, and the second optical wireless communication device is the optical wireless communication device 120a in the embodiment. The optical wireless communication system forms communication links for each combination of the first optical wireless communication device and the second optical wireless communication device.

[0111] The above-described first optical wireless communication device includes a transmission unit. For example, the transmission unit is the light source 111 in the embodiment. The transmission unit transmits an optical signal to the second optical wireless communication device via a first polarization filter. For example, the first polarization filter is the polarization filter 115 in the embodiment, and the optical signal is an optical signal (downlink signal) transmitted using visible light VL in the embodiment. The above-described second optical wireless communication device includes a reception unit, a measurement unit, and a control unit. For example, the reception unit is the visible light receiving unit 121 in the embodiment, the measurement unit is the received optical power measurement unit 128 in the embodiment, and the control unit is the polarization filter control unit 124 in the embodiment. The reception unit receives the optical signal via a second polarization filter. For example, the second polarization filter is the polarization filter 125 in the embodiment. The measurement unit measures the signal strength of the optical signal. The control unit changes the orientation of the second polarization filter or the first polarization filter so that the signal strength becomes stronger. For example, the orientation of the second polarization filter is the orientation of the transmission axis of the polarization filter 125 in the embodiment.

[0112] Also, according to the above-described embodiment, the optical wireless communication system includes a plurality of first optical wireless communication devices and a plurality of second optical wireless communication devices. For example, the first optical wireless communication device is the optical wireless communication device 110 in the embodiment, and the second optical wireless communication device is the optical wireless communication device 120a in the embodiment. The optical wireless communication system forms communication links for each combination of the first optical wireless communication device and the second optical wireless communication device.

[0113] The above-described first optical wireless communication device includes a transmission unit. For example, the transmission unit is the light source 111 in the embodiment. The transmission unit transmits an optical signal including instruction information specifying the orientation of the second polarization filter to the second optical wireless communication device via the first polarization filter. For example, the first polarization filter is the polarization filter 115 in the embodiment, the second polarization filter is the polarization filter 125 in the embodiment, and the optical signal is an optical signal (downlink signal) transmitted using visible light VL in the embodiment. The above-described second optical wireless communication device includes a reception unit, an acquisition unit, and a control unit. For example, the reception unit is the visible light light-receiving unit 121 in the embodiment, the acquisition unit is the instruction information acquisition unit 1231 in the embodiment, and the control unit is the polarization filter control unit 124 in the embodiment. The reception unit receives the optical signal via the second polarization filter. The acquisition unit acquires the instruction information from the optical signal. The control unit changes the orientation of the second polarization filter so as to be the orientation specified by the instruction information. For example, the orientation of the second polarization filter is the orientation of the transmission axis of the polarization filter 125 in the embodiment, and the orientation of the first polarization filter is the orientation of the transmission axis of the polarization filter 115 in the embodiment.

[0114] In addition, in the above optical wireless communication system, the second optical wireless communication device may further include a rotation mechanism. For example, the rotation mechanism is the rotation mechanism 127 in the embodiment. In this case, the rotation mechanism enables the second polarization filter to rotate. The control unit changes the orientation of the second polarization filter using the rotation mechanism.

[0115] In addition, in the above optical wireless communication system, the orientation of the first polarization filter included in one first optical wireless communication device and the orientation of the first polarization filter included in the other first optical wireless communication device may be orthogonal to each other. For example, one first optical wireless communication device is the optical wireless communication device 110-1 in the embodiment, and the other first optical wireless communication device is the optical wireless communication device 110-2 in the embodiment.

[0116] Also, according to the above-described embodiment, the optical wireless communication device includes a receiving unit, a measuring unit, and a control unit. For example, the receiving unit is the visible light receiving unit 121 in the embodiment, the measuring unit is the received optical power measuring unit 128 in the embodiment, and the control unit is the polarization filter control unit 124 in the embodiment. The receiving unit receives an optical signal transmitted from another optical wireless communication device via a first polarization filter via a second polarization filter. For example, the second polarization filter is the polarization filter 125 in the embodiment. The measuring unit measures the signal strength of the optical signal. The control unit changes the orientation of the second polarization filter or the first polarization filter so that the signal strength becomes stronger. For example, the orientation of the second polarization filter is the orientation of the transmission axis of the polarization filter 125 in the embodiment, and the orientation of the first polarization filter is the orientation of the transmission axis of the polarization filter 115 in the embodiment.

[0117] Also, according to the above-described embodiment, the optical wireless communication device includes a receiving unit, an acquisition unit, and a control unit. For example, the receiving unit is the visible light receiving unit 121 in the embodiment, the acquisition unit is the instruction information acquisition unit 1231 in the embodiment, and the control unit is the polarization filter control unit 124 in the embodiment. The receiving unit receives an optical signal including instruction information specifying the orientation of a second polarization filter, transmitted from another wireless communication device via a first polarization filter, via the second polarization filter. For example, the other wireless communication device is the optical wireless communication device 110 in the embodiment, the first polarization filter is the polarization filter 115 in the embodiment, the second polarization filter is the polarization filter 125 in the embodiment, and the optical signal is an optical signal (downlink signal) transmitted using visible light VL in the embodiment. The acquisition unit acquires the instruction information from the optical signal. The control unit changes the orientation of the second polarization filter so as to be the orientation specified by the instruction information. For example, the orientation of the second polarization filter is the orientation of the transmission axis of the polarization filter 125 in the embodiment.

[0118] A part of the optical wireless communication device 110, a part of the optical wireless communication device 120, and a part of the optical wireless communication device 120a in the above-described embodiment may be realized by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed. Here, the "computer system" shall include hardware such as an OS and peripheral devices. Further, the "computer-readable recording medium" refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or a storage device such as a hard disk built into a computer system.

[0119] Furthermore, the "computer-readable recording medium" may also include something that dynamically holds a program for a short time, like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and something that holds a program for a certain time, like a volatile memory inside a computer system that serves as a server or a client in that case. Also, the above program may be for realizing a part of the aforementioned functions, and may further be realizable in combination with a program already recorded in the computer system for realizing the aforementioned functions, or may be realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0120] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and designs and the like within the scope not departing from the gist of the present invention are also included.

Explanation of Reference Numerals

[0121] 1, 8, 8’, 9… Optical wireless communication system, 110, 110-1, 110-2… Optical wireless communication device, 111… Light source, 112… Infrared light receiving unit, 113… Optical signal processing unit, 115… Polarization filter, 120, 120-1, 120-2, 120a… Optical wireless communication device, 121… Visible light receiving unit, 122… Infrared light transmitting unit, 123… Data processing unit, 124… Polarization filter control unit, 125… Polarization filter, 126… Polarization filter rotation mechanism drive unit, 127… Rotation mechanism, 128… Received optical power measurement unit, 810, 810-1, 810-2… Optical wireless communication device, 811… Light source, 812… Infrared light receiving unit, 813… Optical signal processing unit, 820, 820-1, 820-2… Optical wireless communication device, 821… Visible light receiving unit, 822… Infrared light transmitting unit, 910… Optical wireless communication device, 911… Infrared light transmitting unit, 912… Infrared light receiving unit, 913… Optical signal processing unit, 920… Optical wireless communication device, 921… Infrared light receiving unit, 922… Infrared light transmitting unit, 1231… Instruction information acquisition unit

Claims

1. An optical wireless communication system having a plurality of first optical wireless communication devices and a plurality of second optical wireless communication devices, and forming communication links for each combination of the first optical wireless communication device and the second optical wireless communication device, comprising: The first optical wireless communication device includes: A transmission unit that transmits an optical signal to the second optical wireless communication device via a first polarization filter; A control unit that controls so that the directions of the transmission axes of the second polarization filters provided in a plurality of the second optical wireless communication devices adjacent to each other do not match; And comprising: The second optical wireless communication device includes: A reception unit that receives the optical signal via the second polarization filter; A measurement unit that measures the signal intensity of the optical signal; A control unit that changes the direction of the second polarization filter or the first polarization filter so that the signal intensity becomes stronger; An optical wireless communication system comprising:

2. An optical wireless communication system having a plurality of first optical wireless communication devices and a plurality of second optical wireless communication devices, and forming communication links for each combination of the first optical wireless communication device and the second optical wireless communication device, comprising: The first optical wireless communication device includes: A transmission unit that transmits an optical signal including instruction information for designating the direction of a second polarization filter to the second optical wireless communication device via the first polarization filter, and when a plurality of the second optical wireless communication devices are adjacent to each other, the instruction information designates so that the directions of the second polarization filters of the plurality of the second optical wireless communication devices do not match; And comprising: The second optical wireless communication device includes: A reception unit that receives the optical signal via the second polarization filter; An acquisition unit that acquires the instruction information from the optical signal; A control unit that changes the direction of the second polarization filter so as to be the direction designated by the instruction information; An optical wireless communication system comprising:

3. The second optical wireless communication device further includes: A rotation mechanism that enables the second polarization filter to rotate; And comprising: The control unit changes the direction of the second polarization filter using the rotation mechanism. The optical wireless communication system according to claim 1 or 2.

4. The direction of the first polarization filter provided in one of the first optical wireless communication devices and the direction of the first polarization filter provided in the other first optical wireless communication device are orthogonal to each other. The optical wireless communication system according to claim 1 or 2.

5. An optical wireless communication method by an optical wireless communication system having a plurality of first optical wireless communication devices and a plurality of second optical wireless communication devices, and forming communication links for each combination of the first optical wireless communication device and the second optical wireless communication device, a transmission step in which the first optical wireless communication device transmits an optical signal to the second optical wireless communication device via a first polarization filter; a first control step in which the first optical wireless communication device controls so that the transmission axes of second polarization filters included in a plurality of the second optical wireless communication devices adjacent to each other do not match; a reception step in which the second optical wireless communication device receives the optical signal via the second polarization filter; a measurement step in which the second optical wireless communication device measures the signal intensity of the optical signal; a second control step in which the second optical wireless communication device changes the orientation of the second polarization filter or the first polarization filter so that the signal intensity becomes stronger; An optical wireless communication method having the above steps.

6. An optical wireless communication method by an optical wireless communication system having a plurality of first optical wireless communication devices and a plurality of second optical wireless communication devices, and forming communication links for each combination of the first optical wireless communication device and the second optical wireless communication device, a transmission step in which the first optical wireless communication device transmits an optical signal including instruction information for specifying the orientation of a second polarization filter to the second optical wireless communication device via a first polarization filter, and when a plurality of the second optical wireless communication devices are adjacent to each other, the instruction information is specified so that the orientations of the second polarization filters of the plurality of the second optical wireless communication devices do not match; a reception step in which the second optical wireless communication device receives the optical signal via the second polarization filter; an acquisition step in which the second optical wireless communication device acquires the instruction information from the optical signal; a control step in which the second optical wireless communication device changes the orientation of the second polarization filter to the orientation specified by the instruction information; An optical wireless communication method having the above steps.

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