US20090310976A1

US20090310976A1 - Illuminative light communication system

Info

Publication number: US20090310976A1
Application number: US12/461,225
Authority: US
Inventors: Masao Nakagawa; Toshihiko Komine; Shinichiro Haruyama; Takaaki Ishigure; Yasuhiro Koike
Original assignee: Nakagawa Laboratories Inc
Current assignee: Nakagawa Laboratories Inc
Priority date: 2002-10-24
Filing date: 2009-08-05
Publication date: 2009-12-17
Also published as: EP1564914A4; WO2004038962A1; US7583901B2; US20090297167A1; US20060056855A1; ATE372614T1; EP1865631A1; DE60336770D1; CN101714898A; EP1855398A1; KR20050071617A; EP1564914A1; KR100970034B1; EP1860801A1; DE60331271D1; EP1564914B1; EP1865631B1; US7929867B2; DE60316178D1; HK1087848A1

Abstract

An light source control unit controls the flashing of a light source and the light amount of a light source according to information to be transmitted. Thus, light, which is modulated according to the information to be transmitted, is emitted from the light source. The light emitted from the light source is made to enter an optical fiber to pass therethrough and enter a light-scattering body which scatters and radiates the modulated light incident from the optical fiber. The scattered light serves as illumination light as it is. Furthermore, if the illumination light is decoded by a decoding unit after being received by a photoreceptor unit of a receiving set, then information carried by the illumination light can be received.

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 Serial No. 2003-323052 filed Sep. 16, 2003, the contents of which are incorporated herein by reference in their entireties.

DISCLOSURE OF THE INVENTION

The present invention aims to provide an illuminative light communication system that allows high-quality communication and increase in a communication rate using a lighting device with an optical fiber.
According to such objective, an illuminative light communication system for transmitting data using illuminative light includes a light source that emits light for lighting, a light source control unit that controls blinking or light intensity of the light source in accordance with data to be transmitted and controls the light source to emit modulated light, an optical fiber that transmits the modulated light emitted from the light source, and a light scatterer that is provided at an end of the optical fiber, scatters the modulated light transmitted through the optical fiber, and emits the scattered, modulated light. The scattered light emitted from the light scatterer is used for lighting and transmission of the data.
The optical fiber and the light scatterer can be made of a plastic material. The optical fiber and the light scatterer can be integrated into one.
The light source that emits an ultraviolet ray or a blue light can be used; and fluorescer can be mixed in the light scatterer to carry out lighting and communication by the fluorescer. Alternatively, multiple light sources that emit different color lights, respectively, can be provided. In this case, the light source control unit can control blinking or light intensity of at least one of the light sources.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram of a first embodiment of the present invention;

FIG. 2 is an explanatory diagram of a first modified example of the first embodiment, according to the present invention;

FIG. 3 is an explanatory diagram of a second modified example of the first embodiment, according to the present invention;

FIG. 4 is an explanatory diagram of a second embodiment, according to the present invention;

FIG. 5 is a schematic block diagram of a modified example of the second embodiment, according to the present invention;

FIG. 6 is a diagram describing an application, according to the present invention;

FIG. 7 is a diagram describing an example of a conventional lighting element using an optical fiber; and

FIG. 8 is a diagram describing an exemplary conventional lighting element using an optical fiber. In the drawing, 401 denotes a light source, and 402 denotes an optical fiber. As shown in FIG. 8, in the conventional lighting element using the optical fiber 402, light emitted from the light source 401 such as a halogen lamp, an LED, or a laser enters an end of the optical fiber 402, which then emits to the outside from the other end. This emitted light is used for lighting.

DETAILED DESCRIPTION OF THE INVENTION

According to this method, since light with a favorable rectilinear progression characteristic is emitted from a point light source or an end of the optical fiber 402, a large amount of light is emitted to a narrow viewing angle. Therefore, when directly looking at an end of the optical fiber 402, it is very bright. In addition, there is a disadvantage that wide-range lighting is impossible. To solve this problem, a diffusing plate is provided at the output end of the optical fiber 402 to diffuse light emitted from that end of the optical fiber 402, thereby widely emitting light, and reducing brightness.
On the other hand, indoor wireless optical communication technologies have been used along with advancement in high-speed communication technologies. More specifically, the infrared LAN has been widely used not only in offices but also homes. However, a transmitter/receiver, which is an access point to the infrared LAN, must be provided on the ceiling. When there is an interference between the access point and a terminal, data communication is typically impossible. Furthermore, it is necessary to control electric power for preventing an adverse influence on the human body such as eyes, and is thus impossible to carry out high-speed and high-quality communication.
To solve such problems, an illuminative light communication system has been considered. The present invention shows a structure for carrying out lighting and communication using an optical fiber.
FIG. 1 is an explanatory diagram of a first embodiment of the present invention. In the drawing, 411 denotes a light source controller, 412 denotes a light source, 413 denotes an optical fiber, 414 denotes a light scatterer, 415 denotes a reflector plate, 421 denotes a receiver, 422 denotes a light receiving unit, and 423 denotes a demodulator. A high-speed response device such as an LED or a laser diode is used as the light source 412, which emits light for lighting.
The light source controller 411 controls blinking or light intensity of the light source 412 in accordance with data to be transmitted. As a result, modulated light is emitted from the light source 412.
The optical fiber 413 sends light emitted by the light source 412 from one end to the other end. A glass fiber and a plastic optical fiber (POF) may be used as the optical fiber 413. According to comparison of these fibers, since the POF is lighter and can have a larger diameter than a glass fiber, optical energy density per POF cross section is lower than that of the glass fiber. As a result, higher power optical energy may be transmitted. In addition, the POF can be easily connected and has more flexibility than the glass fiber.
The light scatterer 414 is provided at an end of the optical fiber 413, and radiates light transmitted through the optical fiber 413. A high-intensity scattering optical transmission polymer may be used as the light scatterer 414. The high-intensity scattering optical transmission polymer may be made of a highly scattering optical transmission (HSOT) polymer having a micron-order of a non-uniform structure in, for example, a photonics polymer, and may be used as a highly effective visible light scatterer for a lighting element. When using the POF as the optical fiber 413, since the light scatterer 414 and the optical fiber 413 are made of plastic, integrating them into one is possible. For example, this integration may be carried out by individually fabricating each of them, or alternatively, by making adjustments to additives and fabrication conditions. The light scatterer 414 may have an arbitrary shape. For example, it may have a hemispherical shape as shown in FIG. 1, to the center of which an end of the optical fiber 413 is connected.
The reflector plate 415 has a mirror surface facing the light scatterer 414, and returns scattered light from the top of the light scatterer 414 into the light scatterer 414 so as to increase the amount of scattered light from the bottom of the light scatterer 414. This reflector plate 415 may be made of another material. Alternatively, it may have a reflecting surface formed by coating or depositing a reflector material upon a reflecting surface. Note that this exemplary structure is assumed to have the hemispherical light scatterer 414 as shown in FIG. 1 to illuminate from a room ceiling. In such a case, since the flat surface of the hemisphere faces the ceiling, and emission of scattered light from this surface is unnecessary, the reflector plate 415 is provided on the flat surface of the light scatterer 414 so as to increase lighting efficiency. However, when it is unnecessary to improve the shape of a lighting element and/or lighting efficiency, a structure without the reflector plate 415 is possible.
The receiver 421 receives the modulated scattered light emitted from the light scatterer 414 via the optical fiber 413 as described above, resulting in reception of the transmitted data. To do this operation, it is made up of a light receiving unit 422 and a demodulator 423. The light receiving unit 422 receives modulated scattered light emitted from the light scatterer 414 via the optical fiber 413, converts it to an electric signal, and then transmits the resulting signal to the demodulator 423. The demodulator 423 demodulates the electric signal corresponding to the intensity of the light received by the light receiving unit 422, and reconstructs the original data. This allows reception of transmitted data.
An exemplary operation of a first embodiment according to the aforementioned the present invention is described. The present invention can be used as a lighting element as is when not transmitting data. In other words, light emitted from the light source 412 enters into and passes through the optical fiber 413, and then enters the light scatterer 414. The light scatterer 414 scatters the incident light from the optical fiber 413, and scatters and radiates it. Note that light emitted from the flat top surface of the hemispheric light scatterer 414 is reflected by the reflector plate 415, entering the light scatterer 414 again, and is then scattered. This light scattered by the light scatterer 414 should be used as illuminative light.
In this manner, when using the light scatterer 414 as a lighting element, the light scatterer 414 is provided at an output end of the optical fiber 413, and light passing through the optical fiber 413 is radiated as scattered light. Therefore, brightness per unit area is lower than that provided through directly illuminating from an end of the optical fiber 413. Accordingly, in direct sight, it is not so bright. In addition, the light scatterer 414 can illuminate a wide area.
Furthermore, in the case of integrating the light scatterer 414 and the optical fiber 413 into one, only the light scatterer 414 needs to be provided indoors, and large devices such as conventional lighting elements are unnecessary. In addition, indoor light sources such as conventional lighting elements are unnecessary as long as light can be transferred via the optical fiber 413 regardless of the position of the light source 412. Accordingly, when used in a place where a problem such as an electrical short circuit may develop, the light source 412 may be used as a lighting element and may be deployed in another room and the optical fiber 413 may be extended thereto. This allows safe lighting without developing problems such as an electric leakage and an electrical short circuit.
When transmitting data, the data to be transmitted is provided to the light source controller 411. The light source controller 411 controls blinking or light intensity of the light source 412 in accordance with the received data to be transmitted, thereby emitting light modulated in accordance with the data to be transmitted from the light source 412. As with the aforementioned case of lighting, modulated light emitted from the light source 412 enters into the optical fiber 413, and passing it through to the light scatterer 414. The light scatterer 414 scatters the incident modulated light from the optical fiber 413 and then emits the resulting scattered light. Even if the light scatterer 414 has scattered light, there is no influence on the frequency of the modulated light as long as that frequency is lower than the optical frequency. As a result, modulated scattered light is emitted from the light scatterer 414.
In addition, since a high-speed response device is used as the light source 412 as described above, the light source controller 411 can control fast blinking and/or light intensity, resulting in change in fast blinking and/or light intensity of modulated scattered light emitted from the light scatterer 414. However, high-speed change in blinking and/or high-speed light intensity is unperceivable to the human eye, and it seems like light illuminates at an almost constant light intensity. As a result, scattered light emitted from the light scatterer 414 can be used as illuminative light as is even when it has been modulated.
When receiving data, the light receiving unit 422 of the receiver 421 should receive the modulated scattered light emitted from the light scatterer 414. Light received by the light receiving unit 422 is converted to an electric signal, and the resulting electric signal is then transmitted to the demodulator 423. Data can then be reconstructed by the demodulator 423 demodulating that signal.
In this way, lighting and data transmission are possible. According to the conventional optical fiber communication, it is difficult to move a receiver because an optical fiber must be extended to the receiver. On the other hand, the present invention allows data reception wherever illuminative light can be received. In addition, since direct connection to the optical fiber is unnecessary, the receiver is movable. For example, it is possible to use a portable terminal together with the receiver 421. In addition, according to the conventional infrared data communication and wireless communication, a specific transmitter besides a lighting element must be provided. On the other hand, the present invention allows lighting and communication by providing the light scatterer 414 as a lighting element, which is typically provided indoors, and extending the optical fiber 413 instead of an electric wire.
In addition, since scattered light is emitted by the light scatterer 414, an expanded illuminative range can be provided, allowing expansion in communicative range. Furthermore, a high electric power ranging from several watts to several tens of watts is needed for lighting. However, since that power can be used for communication, high-speed and high-quality communication is possible.
FIG. 2 is an explanatory diagram of a first modified example of the first embodiment according to the present invention. In the drawing, the same symbols are given to the same parts as those in FIG. 1, and repetitive descriptions thereof are thus omitted. With the aforementioned structure, since communication is possible as long as a receiver 421 can receive illuminative light, the shape of the light scatterer 414 may be arbitrary, and various shapes are available. The first modified example shows a case that a flat-plate light scatterer 414 is used as an example. Note that the structure and operation are the same as those described above except that the shape of the light scatterer 414 is a flat plate.
By using such flat-plate light scatterer 414, incident light to the light scatterer 414 from the optical fiber 413 is scattered in the horizontal direction, and light scattered in the vertical direction is emitted from a flat surface. By using scattered light emitted from the flat surface as illuminative light, the light scatterer 414 can be used as a two-dimensional illuminative light source. This allows provision of a very thin lighting element as thin as the light scatterer 414.
Note that when there is a surface from which emission of scattered light is unnecessary, a reflector plate 415 shown in FIG. 1 or a reflecting surface corresponding to the reflector plate 415 may be formed on that surface. In the exemplary structure shown in FIG. 2, the reflector plate 415 is provided upon the upper surface of the flat-plate light scatterer 414. This reflector plate 415 returns the scattered light emitted from the top of the light scatterer 414 into the light scatterer 414 again, allowing increase in lighting efficiency.
In addition, since light passing through an optical fiber 413 has a rectilinear progression characteristic, sufficient scattering by only a single-plate light scatterer 414 may be impossible. In such cases, multiple-plate light scatterers 414 may be overlapped. This allows increase in scattering angle, and emission of further uniformly scattered light over a wider angle. In addition, a reflector plate may be provided on a surface opposite to a joint surface between the light scatterer 414 and the optical fiber 413 so as to reflect rectilinear propagating light, changing the propagating direction, and thereby sufficiently scattering it. Alternatively, sufficient scattering may also be achieved by using multiple optical fibers from which incident lights hit the light scatterer 414 in multiple directions.
FIG. 3 is an explanatory diagram of a second modified example of the first embodiment according to the present invention. In the drawing, the same symbols are given to the same parts as those in FIG. 1, and repetitive descriptions thereof are thus omitted. 416 denotes a fluorescent material. In the second modified example, ultraviolet rays or a blue LED or a laser diode is used as a light source 412. In addition, a light scatterer 414 is mixed with the fluorescent material 416.
Incident ultraviolet rays or blue light emitted from the light source 412 via an optical fiber 413 hit the light scatterer 414. As with fluorescent lamps, the fluorescent material 416 in the light scatterer 414 is then exited by the incident ultraviolet rays or blue light, resulting in emission of white light. This white light is radiated from the light scatterer 414. The light radiated from the light scatterer 414 may be used as illuminative light for lighting. In addition, control of the light source 412 to blink or to emit a controlled intensity of light in accordance with data to be transmitted allows the light source 412 to emit modulated ultraviolet rays or blue light. As a result, modulated white light is radiated from the light scatterer 414. Reception of that white light by the light receiving unit 422 in the receiver 421 allows data communication.
Note that the light scatterer 414 in this case is not limited to having a hemispheric shape as shown in FIG. 3, and various shapes such as a flat plate as shown in FIG. 2 are available.
FIG. 4 is an explanatory diagram of a second embodiment of the present invention. In the drawing, the same symbols are given to the same parts as those in FIG. 1, and repetitive descriptions thereof are thus omitted. In the second embodiment, multiple optical fibers 413 are connected to a single light scatterer 414, and lights with different wavelengths are sent to the optical fibers 413, respectively. In the exemplary structure shown in FIG. 4, a red, a green, and a blue light source are used as a light source 412, and color lights emitted from the light sources 412 enter into three optical fibers 413, respectively.
The red, the green, and the blue light entered into the respective optical fibers 413 passing therethrough then hit the light scatterer 414. Respective incident color lights that hit the light scatterer 414 scatter and mix with each other, resulting in radiation of white light. Accordingly, when using light emitted from the light scatterer 414 as illuminative light, it can be used as a white light source. Needless to say, besides using it as a white light source, illuminative light with an arbitrary color can be provided by making adjustments to intensity respective color lights.
In the case of data communication, all of or some of those multiple light sources 412 may be controlled to be driven at the same time. In the exemplary structure shown in FIG. 4, only an LED or a laser diode which emits red color light is controlled to be driven and a green and a blue LED or laser diodes are not controlled to be driven. Consequently, only red light is modulated, but other color lights are not. For example, such a structure is effective when the light receiving unit 422 in the receiver 421 has the highest sensitivity to red light or infrared rays.
When some of color lights are modulated as described above, it is desirable that the receiver 421 receives and demodulates those modulated optical components. For example, in the case where red light is modulated by the exemplary structure shown in FIG. 4, data can be reliably received by selectively receiving red light using various well-known methods and then demodulating it by the demodulator 423; wherein those various well-known methods may be one that provides a red light passing filter, one that uses the light receiving unit 422 having high optical sensitivity to red light, or one that divides red light using a prism.
Note that light passing through the multiple optical fibers 413 can be arbitrary and is not limited to the aforementioned red, green or blue light, and that light intensity may be changed as desired. For example, the same color light may be used to increase light intensity. Alternatively, when using the red, the green, and the blue light source 412, as described above, three-color light s may enter into a single optical fiber 413. In addition, color of light to be modulated in transmitting data is not limited to red, and other multiple color lights should be modulated.
In the structure shown in FIG. 4, the light sources 412 may be controlled to be driven individually in accordance with different pieces of data, respectively, allowing transmission of multiple pieces of data. In other words, it is possible to transmit first data using red light, second data using green light, and third data using blue light. By selecting a color of light to be received by the receiver 421, transmitted data can be selectively received based on the selected color.
In addition, besides multiple optical fibers 413 through which illuminative light passes, another optical fiber for data transmission may be provided to transmit data by controlling a light source corresponding to that optical fiber. In this case, use of a white light source allows transmission of data without changing illuminative light color. Alternatively, use of infrared light also allows data transmission.
FIG. 5 is a schematic block diagram of a modified example of the second embodiment according to the present invention. As shown in FIG. 5, for example, when modulating only lights with specific colors, a structure of providing a light scatterer 414 with modulated light from only a light source 412, which is controlled to be driven by a light source controller 411, via the optical fibers 413 and directly providing a light scatterer 414 with lights emitted by light sources 412, which emit lights with other colors, is possible. In this case, since incident color lights are mixed and synthesized at the light scatterer 414, the resulting synthesized lights may be used as illuminative light. Moreover, since a specific color light is modulated, and that optical component thereof is received by a light receiving unit 422 in a receiver 421 and then demodulated by a demodulator 423, data can be reconstructed. FIG. 5 shows an example of modulating red light, but the present invention is not limited to this. Alternatively, blue or green light may be modulated, or two of the three colors may be modulated.
FIG. 6 is a diagram describing an exemplary structure of an application, according to the present invention. In this exemplary structure, data is broadcast to multiple rooms. As described above, according to the present invention, that structure may be used as a lighting element. Therefore, light scatterers 414 are provided on the room ceilings. In the case of illuminative light communication, communication quality decreases due to shadows. When providing the light scatterers 414 on the ceilings as described above, shadows of someone or something are difficult to generate, which allows avoidance of such a shadowing problem.
Meanwhile, multiple light scatterers 414 provided in a room A are exemplified. By providing multiple light scatterers 414, it is possible to further decrease adverse influences by shadows. When providing multiple light scatterers 414, modulated light may be transmitted to the multiple light scatterers 414 from the same light source via optical fibers 413. Therefore, it is unnecessary to provide the light source controller 411 and the light source for each lighting element, thereby considerably reducing cost for installation of transmitters. Needless to say, it is possible to provide a structure of transmitting different pieces of data from the multiple light scatterers 414. In this case, data can be selectively received by selecting illuminative light received by a receiver 421.
Similarly, the light scatterer 414 is also provided in a room B. In this case, modulated light may be transmitted to the room B from the same light source in the room A. As a result, the same data can be broadcast to different rooms. In this case, the light source controller 411 and the light source 412 can be shared by different rooms.
Note that in the aforementioned first and the second embodiment, unidirectional data communication has been described. However, since the optical fibers 413 allows light to pass through bi-directionally, bi-directional data communication is naturally possible. In other words, light emitted from a light source existing outside of the light scatterers 414 is output from an end of the light source 412 via the light scatterers 414 and the optical fibers 413. This structure is used to control a light source existing outside of the light scatterers 414 to be driven to emit modulated light. This modulated light is output from an end of the optical fibers 413 on the light source 412 side. A light separating means such as a half mirror is provided between the light source 412 and the optical fibers 431, light emitted from the end of the optical fibers 413 on the light source 412 side is separated and received, and is then demodulated, resulting in reception of transmitted data. This allows bi-directional data communication. Note that the intensity of incident light to the optical fibers 413 via the light scatterers 414 becomes extremely weak due to scattering by the light scatterers 414. However, improved optical sensitivity and signal identifying technology allows reliable data communication.
According to the present invention as described above, provision of an optical fiber and a light scatterer allows lighting and illuminative light communication. Moreover, it is unnecessary to provide a lighting element and a communication device on a ceiling separately as with prior arts. In addition, illuminative light communication allows high-electric power communication. Therefore, high-speed and high-quality communication is possible. In addition, since a lighting element has large electric power and is typically deployed at a site that is difficult to develop shadows, a shadowing problem with infrared LAN, or a problematic phenomenon that communication is interrupted due to an interference may considerably decrease. Furthermore, light emitted from a light source is output from a light scatterer via an optical fiber. In this case, only light is used without an electric circuit, allowing simplification of a system and prevention of development of problems such as an electrical leakage and an electrical short circuit.

Claims

1. An illuminative light communication system for transmitting data using illuminative light, comprising:

a light source that emits light for lighting;

a light source control unit that controls blinking or light intensity of the light source in accordance with data to be transmitted and controls the light source to emit modulated light;

an optical fiber that transmits the modulated light emitted from the light source; and

a light scatterer that is provided at an end of the optical fiber, scatters the modulated light transmitted through the optical fiber, and emits the scattered, modulated light; wherein the scattered light emitted from the light scatterer is used for lighting and transmission of the data.

2. The illuminative light communication system according to claim 1, wherein the optical fiber and the light scatterer are made of a plastic material.

3. The illuminative light communication system according to claim 1, wherein the optical fiber and the light scatterer are integrated into one.

4. The illuminative light communication system according to claim 1, wherein the light source emits an ultraviolet ray or a blue light; and fluorescer is mixed in the light scatterer.

5. The illuminative light communication system according to claim 1, wherein a plurality of light sources is provided and emits different color lights, respectively.

6. The illuminative light communication system according to claim 5, wherein the light source control unit controls blinking or light intensity of at least one of the light sources.