Title:
Illuminative light communication system, lighting device and illuminative light source
Kind Code:
A1


Abstract:
Information received from a wired network terminal on the wall face, or the like, is delivered as a light signal from a light transmitting/receiving section of a light communication unit. A lighting fixture is provided with a light transmitting/receiving section where light is received from the light communication unit in order to acquire information, and a light emitting element emits illumination light modulated according to that information. A terminal can acquire the information by receiving the illumination light at a light transmitting/receiving section. Since communication is performed from the light communication unit to the terminal by irradiating light into the space, a convenient illumination light communication system requiring no communication cable or laying work of optical fibers can be constructed.



Inventors:
Nakagawa, Masao (Kanagawa, JP)
Komine, Toshihiko (Shizuoka, JP)
Haruyama, Shinichiro (Kanagawa, JP)
Application Number:
12/461226
Publication Date:
12/03/2009
Filing Date:
08/05/2009
Assignee:
Nakagawa Laboratories, Inc. (Tokyo, JP)
Primary Class:
International Classes:
G09F9/33; H04B3/54; H04B10/114; H04B10/116
View Patent Images:
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Primary Examiner:
PASCAL, LESLIE C
Attorney, Agent or Firm:
FISHMAN STEWART PLLC (BLOOMFIELD HILLS, MI, US)
Claims:
What is claimed is:

1. An illuminative light communication system, comprising: a plurality of lighting units that emits light for lighting; and an optical communication unit that optically transmits data through the air to the lighting units; wherein the lighting units receive light from the optical communication unit, thereby capturing data, and modulate emitted light in accordance with the data.

2. An illuminative light communication system, comprising: a plurality of lighting units that emits light for lighting; and an optical communication unit that optically transmits data through the air to one or more of the lighting units; wherein the one or more of the lighting units receive light from the optical communication unit, thereby capturing data, and optically transmit the data through the air to another lighting unit; and each lighting unit modulates emitted light in accordance with the data received from the optical communication unit or another lighting unit and transmits the data via the modulated, emitted light.

3. The illuminative light communication system according to either claim 1 or claim 2, wherein the plurality of lighting units is an indoor illumination lamp.

4. The illuminative light communication system according to claim 2, wherein the plurality of lighting units is a street lamp.

5. The illuminative light communication system according to either claim 1 or claim 2, wherein the plurality of lighting units allows optical bidirectional communication through the air with the optical communication unit or another lighting unit.

6. The illuminative light communication system according to claim 5, wherein the plurality of lighting units comprises a light receiving unit that receives light modulated in accordance with data emitted from a terminal device, which receives emitted light and thereby receives data, and allows optical bidirectional communication between the terminal device and the plurality of lighting units.

7. The illuminative light communication system according to either claim 1 or claim 2, wherein the plurality of lighting units uses a semiconductor light emitting device as an illuminative light source.

8. A lighting device, comprising: one or a plurality of illuminative light emitting units that emits light for lighting; an optical transmitting and receiving unit for optically communicating through the air with a light emitting unit provided in a device; and a control unit that controls the illuminative light emitting unit in accordance with data received by the light transmitting and receiving unit, so as to modulate light emitted from the illuminative light emitting unit in accordance with the data, thereby transmitting the data.

9. The lighting device according to claim 8, wherein the optical transmitting and receiving unit is deployed in a plurality of positions in different communication directions; and the control unit controls so that data received by a certain light transmitting and receiving unit can be optically transmitted through the air from another light transmitting and receiving unit to the device.

10. The lighting device according to claim 8, wherein the illuminative light emitting unit lights indoors.

11. The lighting device according to claim 8, wherein the illuminative light emitting unit lights the road.

12. The lighting device according to claim 8, wherein the optical transmitting and receiving unit allows bidirectional optical communication through the air with the device.

13. The lighting device according to claim 12, further comprising a light receiving unit that receives light modulated in accordance with data emitted from a terminal device, which receives light emitted from the light emitting unit, thereby receiving data; wherein bidirectional communication with the terminal device is carried out via light.

14. The lighting device according to claim 8, wherein the illuminative light emitting unit comprises one or a plurality of semiconductor light emitting devices as an illuminative light source.

15. An illuminative light source, comprising: one or a plurality of illuminative light emitting devices that emits light for lighting; an optical transmitting and receiving unit for optically communicating through the air with a light emitting unit provided in another lighting unit; and a control unit that controls the illuminative light emitting device in accordance with data received by the optical transmitting and receiving unit, so as to modulate light emitted by the illuminative light emitting device in accordance with the data, thereby transmitting the data.

16. The illuminative light source according to claim 15, wherein the optical transmitting and receiving unit is deployed in a plurality of positions in different communication directions; and the control unit controls so that data received by a certain light transmitting and receiving unit can be optically transmitted through the air from another light transmitting and receiving unit to the another device.

17. The illuminative light source according to claim 15, wherein the optical transmitting and receiving unit is structured to be capable of changing an optical transmission and a reception direction.

18. The illuminative light source according to claim 15, wherein the optical transmitting and receiving unit is deployed in plural; one is used, in the case of the plurality of illuminative light emitting devices being arranged, to allow optical communication through the air with an adjacent illuminative light source, while the other is used to allow optical communication through the air with another illuminative light source provided in another lighting unit.

19. The illuminative light source according to claim 15, wherein the optical transmitting and receiving unit carries out bidirectional optical communication through the air with the another lighting unit.

20. The illuminative light source according to claim 19, further comprising a light receiving unit that receives light modulated in accordance with data emitted from a terminal device, which receives light emitted from the light emitting unit, thereby receiving data; wherein bidirectional optical communication is carried out through the air with the terminal device.

21. The illuminative light source according to claim 15, wherein the illuminative light emitting device is one or a plurality of semiconductor light emitting devices.

Description:

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S patent application Ser. No. 10/532,250 filed Oct. 23, 2003, as International Application No. PCT/JP03/013539, now pending, the contents of which, including specification, claims and drawings, are incorporated herein by reference in their entirety. This application claims priority from Japanese Patent Application Ser. No. 2003-084819 filed Mar. 26, 2003, the contents of which are incorporated herein by reference in their entireties.

BACKGROUND OF THE INVENTION

The present invention aims to provide an illuminative light communication system that does not require electrical work for providing a cable or an optical fiber, and prevents problems such as restriction on bandwidths, radio wave radiation, and superimposition of noise from developing, which is different than power line communication, and a lighting device and an illuminative light source used for such illuminative light communication system.

According to such objective, an illuminative light communication system that carries out communication using illuminative light includes multiple lighting units that emit light for lighting and an optical communication unit that optically transmits data through the air to the lighting units. The lighting units receive light from the optical communication unit, thereby capturing data, and modulate emitted light in accordance with the data. According to such objective, an illuminative light communication system includes multiple lighting units that emit light for lighting; and an optical communication unit that optically transmits data through the air to one or more of the lighting units. The one or more of the lighting units receive light from the optical communication unit, thereby capturing data, and optically transmit the data through the air to another lighting unit. Each lighting unit modulates emitted light in accordance with the data received from the optical communication unit or another lighting unit and transmits the data via the modulated, emitted light.

With such structure, data to be transmitted to the lighting unit that allows communication through modulating illuminative light is transmitted through the air from the optical communication unit or another peripheral lighting unit. When using an optical fiber for optical communication, it is necessary to provide the optical fiber. On the other hand, it is unnecessary when carrying out optical communication via the air. As a result, the illuminative light communication system can be constructed very easily. In addition, different than power line communication, problems such as restriction on bandwidths and radio wave radiation do not develop.

Note that the plurality of lighting units allows optical bi-directional communication through the air with the optical communication unit or another lighting unit. In addition, since the plurality of lighting units includes a light receiving unit that receives light modulated in accordance with data emitted from a terminal device, which receives emitted light and thereby receives data, optical bidirectional communication between the terminal device and the plurality of lighting units is possible. Furthermore, the plurality of lighting units uses a semiconductor light emitting device such as an LED as an illuminative light source. The plurality of lighting units can be an indoor illumination lamp or a street lamp.

A lighting device used for such aforementioned illuminative light communication system includes one or multiple illuminative light emitting units that emits light for lighting, an optical transmitting/receiving unit for optically communicating through the air with a light emitting unit provided in a device, and a control unit that controls the illuminative light emitting unit in accordance with data received by the light transmitting/receiving unit, so as to modulate light emitted from the illuminative light emitting unit in accordance with the data, thereby transmitting the data.

With such structure, since there is no need to provide a cable or an optical fiber as described above, an illuminative light communication system can be constructed through simple electrical work such as replacement of an existing lighting device with a lighting device, according to the present invention.

Note that the optical transmitting/receiving unit is deployed in multiple positions in different communication directions, and data received by a certain light transmitting/receiving unit can be optically transmitted through the air from another light transmitting/receiving unit to the device. As a result, the lighting devices can be deployed freely, and data transmission is possible regardless of the positions of the lighting devices. In addition, the light transmitting/receiving unit allows bi-directional optical communication through the air with another device. Furthermore, since the plurality of lighting units includes a light receiving unit that receives light modulated in accordance with data emitted from a terminal device, which receives emitted light and thereby receives data, optical bidirectional communication among the terminal device and the plurality of lighting units is possible. The plurality of illuminative light emitting units uses a semiconductor light emitting device such as an LED as an illuminative light source. The plurality of lighting units can be an indoor illumination lamp or a street lamp.

Furthermore, an illuminative light source includes one or multiple illuminative light emitting devices that emits light for lighting, an optical transmitting/receiving unit for optically communicating through the air with a light emitting unit provided in another lighting unit, and a control unit that controls the illuminative light emitting device in accordance with data received by the optical transmitting/receiving unit, so as to modulate light emitted by the illuminative light emitting device in accordance with the data, thereby transmitting the data.

In this manner, by providing the optical transmitting/receiving unit and the control unit in the illuminative light source, construction of an illuminative light communication system using the existing lighting device, merely with simple electrical work such as replacement of a fluorescent lamp or an electric bulb with an illuminative light source according to the present invention becomes possible.

The optical transmitting/receiving unit is deployed in multiple positions in different communication directions. Data received by a certain light transmitting/receiving unit can be optically transmitted through the air from another light transmitting/receiving unit to another device. In addition, by structuring the optical transmitting/receiving unit so as to be able to change an optical transmission/reception direction, deployment of them on arbitrarily positioned lighting devices becomes possible. Furthermore, as with a lighting device using a fluorescent lamp, the optical transmitting/receiving unit is deployed in plural; one is used, in the case of the plurality of illuminative light emitting devices being arranged, to allow optical communication through the air with an adjacent illuminative light source, while the other is used to allow optical communication through the air with another illuminative light source provided in another lighting unit.

With such an illuminative light source, the optical transmitting/receiving unit can be structured allowing bidirectional optical communication through the air with another lighting unit. Furthermore, since the plurality of lighting units includes a light receiving unit that receives light modulated in accordance with data emitted from a terminal device, which receives emitted light and thereby receives data, optical bidirectional communication among the terminal device and the plurality of lighting units is possible. The illuminative light emitting device may be one or multiple semiconductor light emitting devices such as LEDs. Note that the illuminative light source may be an indoor illumination lamp or an outdoor street lamp.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram of an illuminative light communication system, according to a first embodiment of the present invention;

FIG. 2 is an explanatory diagram of an illuminative light communication system, according to a second embodiment of the present invention;

FIG. 3 is an aerial view of an exemplary lighting element in the illuminative light communication system, according to the second embodiment of the present invention;

FIGS. 4A and 4B each is an explanatory diagram of a first modified example of the illuminative light communication device, according to the second embodiment of the present invention; FIG. 4A is a cross-sectional view; and FIG. 4B is a perspective view;

FIG. 5 is an explanatory diagram of a second modified example of the illuminative light communication system, according to the second embodiment of the present invention;

FIG. 6 is an explanatory diagram of a third modified example of the illuminative light communication system, according to the second embodiment of the present invention;

FIG. 7 is an explanatory diagram of an illuminative light communication system, according to a third embodiment of the present invention;

FIG. 8 is another explanatory diagram of the illuminative light communication system, according to the third embodiment of the present invention;

FIG. 9 is an explanatory diagram describing an exemplary illuminative light source in the illuminative light communication system, according to the third embodiment of the present invention;

FIG. 10 is an explanatory diagram of an illuminative light communication system, according to a fourth embodiment of the present invention;

FIG. 11 is an explanatory diagram describing an exemplary illuminative light source in the illuminative light communication system, according to the fourth embodiment of the present invention; and

FIG. 12 is an explanatory diagram of an illuminative light communication system, according to a fifth embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Lighting elements are provided on a ceiling, or a pole is provided for illuminating light from above so as to prevent shadows across a certain area. There is an advantage for illuminative light communication in that high quality communication is possible because shadowing does not develop and high illuminative electric power is available.

Meanwhile, since lighting elements are provided in high places such as the ceiling as described above, there is a problem that it is difficult to carry out electrical work. For example, in the case of the aforementioned illuminative light communication, data to be transmitted must be sent to the lighting elements through illuminative light communication. A method of providing a cable or an optical fiber for a network may be considered as a method for transmitting data to lighting elements, for example. However, since new electrical work is necessary for providing a cable or an optical fiber, usage of illuminative light communication is not easy and is costly.

As with the present invention, a method of superimposing a signal on an electric wire for lighting and transmitting the resulting data to lighting elements, for example, has been considered as a method not requiring provision of additional cables or optical fibers. However, in the case of transmitting data by superimposing a signal on an electric wire, undesired radio emission may often develop or wireless communication may be interrupted when the frequency of the signal is high. In addition, there is another problem in that signals are easily influenced by motor noise and inverter noise.

As described above, there have been no preferred means for transmitting data to lighting elements for illuminative light communication, which has been an obstacle to illuminative light communication. The present invention provides a preferred means for transmitting data to each lighting element.

FIG. 1 is an explanatory diagram of an illuminative light communication system, according to a first embodiment of the present invention. In the drawing, 501 denotes an optical communication device, 502 denotes lighting elements, 503 denotes a terminal device, 511, 522, and 531 denote light transmitting/receiving units, 512 denotes a communication cable, 521 denotes light emitting devices, and 523 denotes light reception devices. In the example shown in FIG. 1, an illuminative light communication system is structured using lighting elements provided for indoor lighting.

The optical communication device 501, which transmits to the lighting elements 502 data that is to be sent by them through illuminative light communication, is provided indoors. The optical communication device 501 is connected to the network, and transmits/receives data via the network. The network is a wired network, which is provided in offices, schools, plants, and homes, and is configured from an optical fiber, a coaxial cable, or a stranded wire, many of which are connected to an external telephone network or the Internet. A terminal of such network is often provided in a wall as shown in FIG. 1. In such case, electrical connection between the wall surface terminal and the optical communication device 501 is made by the communication cable 512.

The optical communication device 501 allows communication via the network as described above, and has the light transmitting/receiving unit 511 allowing optical communication among the lighting elements 502 through the air. According to the present invention, since optical communication is carried out through the air, an optical fiber is unnecessary. Needless to say, it is unnecessary to extend the communication cable 512 to the respective lighting elements 502. Since the lighting elements 502 are provided at a high position such as the ceiling, the optical communication device 501 may be provided at a lower position where the lighting elements 502 carrying out communication cannot be blinded.

The light transmitting/receiving unit 511 includes a light emitting device and a light reception device, emits modulated light through control of the light emitting device to modulate in accordance with data, and transmits data to the lighting elements 502. In this example, it is desirable that lights emitted from the light emitting device may be received by the multiple lighting elements 502. Therefore, light with poor directivity is preferable. Alternatively, it is possible to output to the respective lighting elements 502 emitted lights with high directivity, which allows identification of each lighting element 502.

The light reception device receives light emitted from the light transmitting/receiving units 522 of the lighting elements 502, thereby receiving data transmitted from the lighting elements 502. Note that since illuminative light emitted from the lighting elements 502 is received, it is necessary to separate and capture data from the light emitted from the light transmitting/receiving units 522 of the lighting element 502. When it is unnecessary to receive data from the lighting elements 502, the light reception device is unnecessary.

With such structure, the optical communication device 501 allows communication via the wired communication cable 512 and functions as a gateway, which carries out conversion for optical communication. In addition, through communication with multiple lighting elements 502, it also functions as a base station for wireless (optical) communication. Note that light used by the light transmitting/receiving unit 511 for communication is not limited to visible light, and infrared light is also available.

The lighting elements 502, according to the present invention, are provided on the ceiling, for example, and illuminates indoors by light emitted from the light emitting device. The lighting elements 502 are each provided with light transmitting/receiving units 522 including light emitting devices and light reception devices. According to this embodiment, optical communication with the optical communication device 501 through the air is carried out. The light emitting devices should be formed so as to allow pinpoint reception of light from the light transmitting/receiving unit 511 of the optical communication device 501 by providing a lens system, for example. Needless to say, direction should be appropriately changeable in consideration of light incident direction. The light emitting devices are provided for transmitting data to the optical communication device 501 from the lighting elements 502, and should allow pinpoint transmission of light to the light transmitting/receiving unit 511 of the optical communication device 501. For example, when using laser diodes (LDs), a rectilinear progression characteristic may improve, and identifiability of the optical communication device 501 may be improved by coherent light. These light transmitting/receiving units 522 allow bidirectional data communication among the lighting elements 502 and the optical communication device 501.

The lighting elements 502 are each provided with a controller not shown in the drawing. The light transmitting/receiving units 522 receive and demodulate light, and the resulting demodulated data is transmitted to corresponding controller. The controller controls the light emitting devices 521 to modulate in accordance with received data and emits illuminative light modulated in accordance with that data. This allows illuminative light data transmission from the lighting elements 502 to the terminal device 503.

In the example shown in FIG. 1, the light emitting devices 521 are indicated by o symbols, and the light reception devices 523 indicated by • symbols are provided therebetween. Since the light emitting devices 521, which are used for lighting as described above, emit light modulated in accordance with data, those having a high-speed response characteristic are available. For example, semiconductor light emitting devices such as LEDs and LDs are optimum.

The light reception devices 523 are used for receiving light from the terminal device 503. They receive and demodulate modulated light emitted from the terminal device 503, and the controller can then capture data transmitted from the terminal device 503. The captured data may be optically transmitted from the light transmitting/receiving units 522 to the optical communication device 501, and then to the network. Those light reception devices 523 allow bidirectional communication among the lighting elements 502 and the terminal device 503. Note that those light reception devices 523 may receive infrared light, other than visible light. In addition, a structure such that an antenna is provided instead of the light reception devices 523 for radio wave data reception from the terminal device 503 is possible. In the case of a broadcast system, the light reception devices 523 are unnecessary.

The terminal device 503 is a data terminal comprising the light transmitting/receiving unit 531. The light transmitting/receiving unit 531 receives and demodulates illuminative light, thereby capturing data. In addition, the light transmitting/receiving unit 531 is controlled to emit light modulated in accordance with data, thereby transmitting data from the terminal device 503 to the lighting elements 502. The terminal device 503 may be provided in an arbitrary position as long as it is illuminated by the lighting elements 502. Accordingly, communication is possible even if the terminal device 503 is movable. In addition, since the lighting elements are typically provided so as to prevent shadows, and illuminative light has large electric power, high quality and high speed communication is possible. Furthermore, illuminative light may be used safely without adversely influencing the human body such as eyes as with infrared rays.

In the aforementioned first embodiment, the optical communication device 501 controls the light transmitting/receiving unit 511 to emit light, thereby optically transmitting data, which has been transmitted from the network, through the air. The respective light transmitting/receiving units 522 of the lighting elements 502 receive light emitted from the light transmitting/receiving unit 511 of the optical communication device 501, thereby receiving data. The respective lighting elements 502 then control the light emitting devices 521 to modulate in accordance with data captured through reception of light by the light transmitting/receiving units 522, and thereby outputting the modulated illuminative light. The terminal device 503 receives and demodulates the modulated illuminative light, and thus the terminal device 503 can receive data.

On the other hand, the light transmitting/receiving unit 531 of the terminal device 503 emits light modulated in accordance with data in the terminal device 503. The light reception devices 523 of the lighting devices 502 then receive that emitted light, thereby receiving that data. The light transmitting/receiving units 522 of the lighting devices 502 then emit light modulated in accordance with that received data, transmitting the data to the optical communication device 501. In the optical communication device 501, the light transmitting/receiving unit 511 receives modulated light from the lighting elements 502 and converts it to electrical signals, transmitting the resulting signals to the network. This allows data transmission from the terminal device 503 to the network.

FIG. 2 is an explanatory diagram of an illuminative light communication device, according to a second embodiment of the present invention. FIG. 3 is a planar view of an exemplary lighting element, according to the second embodiment of the present invention. In the drawings, the same symbols are given to the same parts as those in FIG. 1, and repetitive descriptions thereof are thus omitted. 502-1 through 502-4 denote lighting elements, 541 denotes sockets, and 542 denotes rod-shaped illuminative light sources. The aforementioned first embodiment gives an example where the lighting elements 502 receive modulated light from the optical communication device 501, respectively. On the other hand, the second embodiment shows a case of data transmission among the lighting elements 502-1 through 502-4. In addition, different from the example shown in FIG. 1, the light emitting devices 521 are arranged in the lighting elements 502-1 through 502-4 so as to form the same shape as typically used strip lights. Note that the lighting elements 502-1 through 502-4 are identical lighting elements, which are referred to as lighting elements 502 when they are not being differentiated.

In the second embodiment, as shown in FIG. 3, light transmitting/receiving units 522 are provided on all four sides of the lighting elements 502, and allow communication among the lighting elements 502. In addition, only the light transmitting/receiving units 522 of any one or multiple lighting elements 502 communicate with the optical communication device 501. Other lighting elements 502, which do not communicate directly with the optical communication device 501, transmit/receive data by communicating with another lighting element 502.

In the example shown in FIG. 2, the lighting element 502-1 communicates directly with the optical communication device 501. The lighting elements 502-2 and 502-3 communicate with the lighting element 502-1 to receive/transmit data from/to the optical communication device 501. The lighting element 502-4 communicates with the lighting element 502-2 or 502-3 to receive/transmit data from/to the optical communication device 501. For example, data from the optical communication device 501 is transmitted to the lighting element 502-1, and that transmitted data is then transmitted to the lighting elements 502-2 and 502-3. The data is then transmitted from the lighting element 502-2 or 502-3 to the lighting element 502-4. As a result, the data from the optical communication device 501 is transmitted to the lighting elements 502-1 through 502-4, and the respective lighting elements 502-1 through 502-4 transmit data via illuminative light to the terminal device 503. On the other hand, when the lighting element 502-4 receives modulated light from the terminal device 503, the lighting element 502-4 transmits that data to the lighting element 502-2 or 502-3, the lighting element 502-2 or 502-3 transmits that data to the lighting element 502-1, the lighting element 502-1 transmits that data to the optical communication device 501, and the data is then transmitted to the network.

The light transmitting/receiving units 522 are used for optical communication among the respective lighting elements 502 through the air. This allows communication from the optical communication device 501 to the respective lighting elements 502 without providing a communication cable or an optical fiber. In addition, with the first embodiment, it can be considered that light intensity for communication among the optical communication device 501 and the lighting elements 502 attenuates if the lighting elements 502 are provided at a distance from the optical communication device 501. On the other hand, with the second embodiment, since the respective lighting elements 502 are provided at almost regular intervals, communication quality does not decrease due to locations of the lighting elements 502. Furthermore, since data is transmitted through communication among the lighting elements 502, even the lighting elements 502 provided within an area visible from the optical communication device 501 may be used for illuminative light communication, which is possible by communicating indirectly with the optical communication device 501 through communication with another lighting element 502.

The light transmitting/receiving units 522 allow bi-directional communication among the lighting elements 502 and among the lighting elements 502 and the optical communication device 501. Note that in the case of unidirectional communication as with a broadcast system, the light transmitting/receiving units 522 may be constituted by either light emitting devices or light reception devices, and light emitting devices and light reception devices of the respective lighting elements 502 for data communication should be provided facing one another.

In the second embodiment, the rod illuminative light sources 542 with the same shape as strip lights as shown in FIG. 3 are used. One or several lines of light emitting devices 521 are arranged in the rod illuminative light sources 542, and light reception devices 523 are provided therebetween. To provide a new lighting element, the shape of illuminative light source is arbitrary and is determined based on illuminative light source and design. However, if an existing lighting element is used, it is desirable that the rod-shaped illuminative light sources 542 with the same shape as strip lights are used. When the rod illuminative light sources 542 are inserted into the fluorescent sockets 541, electric power is supplied to the rod illuminative light sources 542, allowing lighting. In this case, a controller not shown in the drawing is provided in each of the rod illuminative light sources 542. In addition, the light transmitting/receiving units 522 should be provided surrounding the existing lighting elements and be electrically connected to the rod illuminative light sources 542. As a result, the lighting elements, according to the present invention, may be provided using existing lighting elements. Use of existing lighting elements allows illuminative light communication at lower cost than that for replacement with new lighting elements.

Needless to say, the shape of the illuminative light source is not limited to the same rod shape as strip lights and may have a circular shape as with circular fluorescent lamps. Alternatively, an electric bulb-shaped illuminative light source is available, as described later.

FIGS. 4A and 4B each is an explanatory diagram of a first modified example of the illuminative light communication system, according to the second embodiment of the present invention. In the example shown in FIG. 2, the lighting elements are provided on the ceiling. Alternatively, for example, the lighting elements 502 may be embedded in the ceiling as shown in FIGS. 4A and FIG. 4B. In such case, as shown in FIGS. 4A and 4B, for example, the light transmitting/receiving units 522 are provided protruding from the ceiling, allowing optical communication among the lighting elements 502.

FIG. 5 is an explanatory diagram of a second modified example of the illuminative light communication system, according to the second embodiment of the present invention. In the example shown in FIG. 5, the lighting elements 502 are also embedded in the ceiling. When embedding the lighting elements 502 in the ceiling, there is space under the roof exceeding that needed for embedding the lighting elements 502. A structure that utilizes this space under the roof to provide the light transmitting/receiving units 522 under the roof for communication among the lighting elements 502 and among the lighting elements 502 and the optical communication device 501 is possible.

FIG. 6 is an explanatory diagram of a third modified example of the illuminative light communication system, according to the second embodiment of the present invention. The example shown in FIG. 6 shows a case of using suspended shades as the lighting elements 502. In the case of suspended lamps, electric bulbs are often used as the light sources. According to the present invention, electric bulb-shaped illuminative light sources are used. In addition, the light transmitting/receiving units 522 are provided at the upper part of underneath the shades of the lighting elements 502. Needless to say, the positions of the light transmitting/receiving units 522 may be arbitrary as long as communication with other lighting elements 502 and with the optical communication device 501 is possible.

For example, the suspended lighting elements 502 are often provided over each customer's seat in a store. The structure shown in FIG. 6 is useful for such application. For example, when opening an internet cafe, broadband communication may be provided merely through optical communication among the lighting elements 502 and among the lighting elements 502 and the optical communication device 501 without providing cables in the store.

FIGS. 7 and 8 are explanatory diagrams of an illuminative light communication system, according to a third embodiment of the present invention. FIG. 9 is a diagram describing an exemplary illuminative light source, according to the third embodiment of the present invention. In the drawing, 551 denotes illuminative light sources, 552 denotes inter-adjacent light source light transmitting/receiving units, and 553 denotes inter-lighting element light transmitting/receiving units. In the aforementioned example shown in FIG. 3, the light transmitting/receiving units 522 must be provided in addition to the illuminative light sources even when using the existing lighting elements. The third embodiment shows an exemplary structure where the illuminative light sources and the light transmitting/receiving units 522 are integrated.

In the example shown in FIG. 9, for example, the shape of the illuminative light sources 551, according to the fifth embodiment of the present invention, is the same rod shape as strip lights as with the example shown in FIG. 3. The illuminative light sources 551 each comprises light emitting devices 521, light reception devices 523, and a controller not shown in the drawing. In addition, the inter-adjacent light source light transmitting/receiving units 552 are provided on the tube and are used for communication between adjacent illuminative light sources 551 when the illuminative light sources 551 are positioned so as to provide multiple fluorescent lamps in parallel. Note that assuming the case of providing three or more of illuminative light sources 551, the inter-adjacent light source light transmitting/receiving units 552 should be provided on both sides of the tube.

In addition, the inter-lighting element light transmitting/receiving units 553 are provided for communicating with illuminative light sources 551 other than the adjacent illuminative light sources 551 and the optical communication device 501. The inter-lighting element light transmitting/receiving units 553 should be formed such that the length and orientation thereof are adjustable to accommodate various lighting elements. Note that in FIG. 9, the inter-lighting element light transmitting/receiving units 553 are provided at both ends; alternatively they may be provided at either end.

Such illuminative light sources 551 are fixed replacing the existing fluorescent lamps of the lighting elements. In this case, the illuminative light sources 551 should be attached directly to the sockets to which fluorescent lamps are inserted. As a result, electric power may be supplied to the illuminative light sources 551 from the sockets of the lighting elements. Illuminative light data transmission is possible by regulating the length and orientation of the inter-lighting element light transmitting/receiving units 553.

The example shown in FIG. 7 shows an application to the first embodiment according to the present invention shown in FIG. 1. In this case, the inter-lighting element light transmitting/receiving units 553 attached to the respective illuminative light sources 551 should face the optical communication device 501. In this case, the inter-lighting element light transmitting/receiving units 553 may be provided in a single illuminative light source 551 of the respective lighting elements, and the inter-adjacent light source light transmitting/receiving units 552 may be used for data communication for the other illuminative light sources.

The example shown in FIG. 8 shows an application to the second embodiment according to the present invention shown in FIG. 234. In this case, the optical communication device 501 communicates with the inter-lighting element light transmitting/receiving units 553 provided in a certain illuminative light source 551 and communicates with the inter-adjacent light source light transmitting/receiving units 552 or the inter-lighting element light transmitting/ receiving units 553 for the other illuminative light sources 551. When at least a single stroke communication route is prepared, illuminative light communication for all illuminative light sources 551 is possible. Needless to say, multiple communication routes may be specified.

Note that FIGS. 7 and 8 show a case of attaching the illuminative light sources 551 to the lighting elements embedded in the ceiling. In such case, it is effective that the inter-lighting element light transmitting/receiving units 553 are provided protruding downward as shown in the drawings. Similarly, according to the lighting elements to which the illuminative light sources 551 are attached, surrounding shades extend below the illuminative light sources 551. In such cases, it is also effective that the inter-lighting element light transmitting/receiving units 553 are provided protruding downward.

FIG. 10 is an explanatory diagram of an illuminative light communication system, according to a fourth embodiment of the present invention. FIG. 11 is a diagram describing an exemplary illuminative light source, according to the fourth embodiment of the present invention. In the fourth embodiment, the light transmitting/receiving units 522 are not provided in the illuminative light sources 551 or in the lighting elements 502, and the light emitting devices 521 and the light reception devices 523 are alternatively used. In this case, the illuminative light sources 551, which comprise the light emitting devices 521 and the light reception devices 523 as shown in FIG. 11, are used and attached to the existing lighting elements, thereby constituting the illuminative light communication system. As can be understood through comparison with the illuminative light sources 551 shown in FIG. 9, the inter-adjacent lighting source light transmitting/receiving units 552 and the inter-lighting element light transmitting/receiving units 553 are not provided in the exemplary illuminative light sources 551 shown in FIG. 11.

The light reception devices 523 receive light (visible light or infrared light) emitted from the light transmitting/receiving unit 511 of the optical communication device 501, thereby receiving data from the optical communication device 501. Light emitted from the light emitting devices 521 is modulated in accordance with the received data, and the resulting modulated illuminative light is emitted. The terminal device 503 then receives and demodulates the modulated illuminative light, allowing the terminal device 503 to receive data.

On the other hand, in the case of transmitting data from the terminal device 503, the light reception devices 523 in the illuminative light sources 551 receive and demodulate modulated light emitted from the terminal device 503, and then data from the terminal device 503 is transmitted to the illuminative light sources 551. Light emitted from the light emitting devices 521 is modulated in accordance with the received data, and the resulting modulated illuminative light is emitted. If the light transmitting/receiving unit 511 of the optical communication device 501 receives and demodulates the modulated illuminative light, data is transmitted from the terminal device 503 to the optical communication device 501.

In this manner, in the fourth embodiment, both the optical communication device 501 and the terminal device 503 emit light to the illuminative light sources 551, and receive illuminative light emitted from the illuminative light sources 551. This allows use of illuminative light having large electric power and reduction in influences of shadowing since the lighting elements are provided in the ceiling where shadows are difficult to generate, thereby providing favorable communication rather than the case of direct optical communication between the optical communication device 501 and the terminal device 503. Needless to say, it is unnecessary to extend a communication cable or an optical cable to the lighting elements 502.

Note that in the example shown in FIG. 10, dedicated illuminative light sources 551 as shown in FIG. 11 are used. Similarly, the light transmitting/receiving units 522 may not be provided in the lighting elements 502 in the case of using dedicated lighting elements as shown in FIG. 1.

FIG. 12 is an explanatory diagram of an illuminative light communication system, according to a fifth embodiment of the present invention. In the drawing, 561 denotes street lights. Currently, a mercury lamp, a sodium lamp, or a fluorescent lamp is mainly used as the street lights 561 on a road. Alternatively, a semiconductor light emitting device such as an LED may be applied. When a semiconductor light emitting device is used as the illuminative light source of the street lights 561, various pieces of data may be transmitted through illuminative light to moving vehicles and pedestrians. In this case, it is costly to provide a communication cable or an optical cable to transmit data to the respective street lights 561.

According to the present invention, the light transmitting/receiving units 522 are provided in the street lights 561, and optical data communication among the street lights 561 is provided through the air as with the aforementioned second embodiment. This allows data transmission to the respective street lights 561 and illuminative light data transmission by the street lights 561. Such structure is economical since only electrical work for the respective street lights 561 is necessary without providing a communication cable or an optical fiber.

Note that the intervals between the street lights 561, for example, of approximately 30 m on an expressway are longer than in the aforementioned case of indoors. However, optical communication is sufficiently possible. In addition, due to the present topology or structure of the road, the orientation of the light transmitting/receiving units 522 must be regulated so as for those units to face adjacent street lights. This is not very difficult as long as they have typical intervals between adjacent street lights. Furthermore, a problem that the field of vision may be obstructed by mist is expected. However, this is not a significant problem since the intervals are approximately 30 m.

An example of optical communication among the street lights provided on the road is shown as an outdoor network herein, and an application according to the present invention is not limited to this. For example, it is applicable to taxiway lights for air crafts or illumination lamps in event halls.

Several embodiments and modified examples according to the present invention have been described above. In the aforementioned description, data is transmitted from the optical communication device 501 to the lighting elements 502, the illuminative light sources 551, or the street lights 561 (referred to as lighting elements and the like). It is unnecessary for the respective lighting elements and the like to transmit received data as is through illuminative light. For example, a structure such that an address or an ID is attached to a header of data to be transmitted and that the lighting elements and the like select data in accordance with that header and transmit the selected data via illuminative light is possible. In addition, the lighting elements and the like, which function as a relay or a router and are not used for illuminative light data communication, may be provided.

As described above, according to the present invention, when each of lighting elements and illuminative light sources are used for optical communication, data is transmitted thereto through the air. Therefore, electrical work for providing a communication cable or an optical fiber is unnecessary, allowing constituting an illuminative light communication system at low cost. In this case, the system may be structured using existing lighting elements, allowing further reduction in cost. In addition, different from power line communication, optical communication prevents problems such as constraints on bandwidth, radio wave radiation, and superimposition of noise from developing, allowing high-quality data communication.