Illumination light communication device

Technical Field

0001The present invention relates to a technology that contributes to illuminative light communication.

Background Art

0002<patcit id="pcit0001" dnum="WO0225842A2"><text>WO 02/25842 A2</text></patcit> relates to smart lighting devices bearing processors and networks comprising smart lighting devices capable of providing illumination and detecting stimuli with sensors and/or sending signals. Sensors and emitters can be removed and added in a modular fashion. Smart lighting devices and smart lighting networks can be used for communication purposes, building automation, systems monitoring and a variety of other functions.

0003An article by <nplcit id="ncit0001" npl-type="s"><text>Komine and Nakagawa, which was a contribution to the 13th IEEE international symposium on personal, indoor and mobile radio communications in September 2002 in PISCATA-WAY, NJ, USA (IEEE, vol. 4, 15 September 2002, p. 1762 - 1766</text></nplcit>) describes an integrated system of white LED visible-light communication and power-line communication. The paper proposes an easy wiring system for optical communication using existing power-line.

0004<patcit id="pcit0002" dnum="DE4137032A1"><text>DE 41 37 032 A1</text></patcit> relates to a device for an optical data communication using a light source emitting light that hits on the transmitting side a retro reflector. An optical modulator is arranged in front of the retro reflector and modulates the reflected light in accordance with data to be transmitted.

0005<patcit id="pcit0003" dnum="JP2001176678A"><text>JP 2001-176678</text></patcit> describes a device, in which detecting means for detecting a power volume to be able to be supplied to an illumination lamp are provided. Further, a switching means is provided for switching between an external power supply and a battery. Also it is disclosed to perform lighting by solar cell electric power for a long time in an emergency, when abnormalities occur in external power supply.

0006In recent years, a radio wave communication system has become available along with portable terminals. Recently, shorter wavelength infrared rays have been widely used due to available frequency depletion. Other than available frequency depletion, radio waves may influence medical devices or various precision equipment. Moreover, there is fear that infrared rays may adversely influence the human body (e.g., eyes). As a result, optical communication is in the spotlight as a safe communication method.

0007Meanwhile, white LEDs are developed owing to the success of development of blue LEDs. The features of white LEDs are: extremely lower power consumption than that of conventional incandescent lamps or fluorescent lamps, small size, and long life. Accordingly, use of white LEDs as a illuminative light source is considered. Another feature of white LEDs is a fast response speed relative to supplied power. Paying attention to these features, a study of electrically controlling blinking or light intensity and thereby transferring a signal has been conducted.

0008A study of integration of such signal transfer using white LED lights with the aforementioned power-line communication system has been conducted. For example, a proposal regarding that study has been disclosed in <nplcit id="ncit0002" npl-type="b"><text>'INTEGRATED SYSTEM OF WHITE LED VISIBLE-LIGHT COMMUNICATION AND POWER-LINE COMMUNICATION written by inventors: T. Komine, Y. Tanaka, and M. Nakagawa, Institute of Electronics, Information, and Communication Engineers Technical Research Report, The Institute of Electronics, Information, and Communication Engineers, March 12, 2002, Vol. 101, No. 726, pp. 99 - 104</text></nplcit>. Since such system utilizes lights, there are no effects on the human body, allowing safe communication. In addition, other applications are expected.

0009The present invention, aims to provide an emergency light including a light source having excellent electric power efficiency and long operating life, a wireless emergency light data transmission system that uses the emergency light as a data transmission source while in an emergency, and an emergency light that is used in the system. Such an object is achieved by an emergency lamp according to claim 1 and wireless emergency lamp data transmission system according to claim 3. Further developments are described in the dependent claims.

0010An emergency light, which is embedded with a battery and turns a light source on while in an emergency without electric power supplied from an external power source, is characterized by the light source made up of LEDs. The feature of LEDs or high electric power efficiency allows suppression of battery consumption. Reduced battery size allows reduction in device size. Moreover, extended operating life as to light emitting time is provided. Moreover, since LEDs have a long operating life, intervals between maintenance such as light source replacement intervals can be extended, which allows reduction in maintenance cost. Furthermore, since LEDs are highly crashproof, an available emergency light that will not be damaged due to a devastating disaster can be provided.

0011The emergency light further includes a storage unit that is stored with data to be transmitted while in an emergency and an optical modulator that controls electric power supplied to the LEDs in accordance with data stored in the storage unit, so as for the LEDs to change light intensity or blink. As described above, since LEDs have an excellent response speed characteristic, modulation based on such data is possible, and light for displaying can be used for data transmission as is. With such structure, the emergency light, which is conventionally used merely for indicating an emergency exit and an emergency staircase, can be used as a data source while in an emergency. At this time, since the light source, which functions as an emergency light, is used as is, it never consumes large electric power as opposed to the case of voice output. As a result, most of electric power consumption is expected to be an amount for only the light source. As a result, there is no need to provide an additional large-capacity battery for transmitting data, thereby allowing the light source to operate as a data source with a battery provided for display.

0012Alternatively, a demodulator may be provided, so as to separate data, which is superimposed on a voltage of an external power source and then transmitted, while being driven by an external power source while not at a time other than in an emergency. Data provided from the modulator is then stored in a storage unit. Such a structure allows distribution of data, which is to be transmitted while in an emergency, to respective emergency lights via the power line while not in an emergency. As a result, data to be transmitted while in an emergency can be easily set and updated.

0013Further, a wireless emergency light data transmission system for transmitting data to a terminal using an emergency light, which has a light source turned on while in an emergency without electric power supplied from an external power source, is provided. In the wireless emergency light data transmission system, the emergency light includes a battery, an LED that is used as a light source, a storage unit that is stored with data to be transmitted while in an emergency, and an optical modulator that controls electric power supplied to the LED in accordance with data stored in the storage unit, thereby controlling light intensity or blinking of the LED. The terminal includes a light receiving unit that receives light emitted from the LED in the emergency light and converts it to an electric signal, and a demodulator that demodulates the electric signal output from the light receiving unit, thereby capturing the data. This structure allows optical data transmission from an emergency light to a terminal while in an emergency. Various pieces of data such as escape routes for evacuees, informing destination, or a map and descriptive text data for floors can be displayed on the terminal, which allows smoothly guiding users to evacuate while in an emergency.

Brief Description of the Drawings

0014<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is a block diagram of a broadcast system, according to a first example for understanding the present invention;</li><li><figref idref="f0002">FIG. 2(A)</figref> is a diagram describing an exemplary signal waveform of an electric wire; <figref idref="f0002">FIG. 2(B)</figref> is a partially magnified diagram thereof,</li><li><figref idref="f0003">FIG. 3</figref> is a block diagram of a broadcast system, according to a second example for understanding the present invention;</li><li><figref idref="f0004">FIG. 4(A)</figref> is an explanatory diagram of an electric bulb applicable to the broadcast system, according to the first and second example for understanding the present invention; <figref idref="f0004">FIG. 4(B)</figref> is a diagram describing how to detach the electric bulb;</li><li><figref idref="f0005">FIG. 5</figref> is a diagram describing a first application of the first and second example ;</li><li><figref idref="f0006">FIG. 6</figref> is a diagram describing a second application of the first and second example ;</li><li><figref idref="f0007">FIG. 7</figref>. is a block diagram of an emergency light and a wireless emergency light data communication system, according to an embodiment of the present invention;</li><li><figref idref="f0008">FIG. 8</figref> shows an exemplary LED array used as a light source; FIG. 56(A) shows an appearance of an emergency light when a cover is removed; FIG. 56(B) shows an exemplary LED array to be used; and FIG. 56(C) shows an another example of a pictorial mark formed on the cover;</li><li><figref idref="f0008">FIG. 9</figref> is a block diagram of an emergency light and a wireless emergency light data communication system, according to an embodiment of the present invention;</li></ul>

0015Useful Examples for Understanding the invention

0016Useful examples for understanding the present invention are described forthwith. These examples relate to a broadcast system that optically broadcasts data, and an electric bulb preferable for the same.

0017A power-line communication system has been studied as one of communication systems. The power-line communication system transmits data using a power line, which is provided in a house or a building as a signal transmission medium. The power line is a very popular infrastructure, which basically allows communication among devices connected via the power line. Meanwhile, communication among devices, such as portable terminals, not connected via the power line is impossible. The examples provide a broadcast system, which broadcasts data to many devices not connected via the power line.

0018<figref idref="f0001">FIG. 1</figref> is a block diagram of the broadcast system, according to the first example. In the drawing, 101 denotes a data source, 102 denotes a power-line modulator, 103 denotes a power line, 104 and 105 denote outlets, 106 denotes an LED lighting element, 107 denotes a light reception terminal, 111 denotes an AC-DC converter, 112 denotes a band pass filter, 113 denotes a selector, 114 denotes a superimposing unit, and 115 denotes an LED group. The data source 101 may be constituted by apparatus, such as a TV, a CATV, a radio, and a tuner or a receiver for the CATV, as well as a computer, which are capable of outputting various data. Accordingly, what is broadcast may be various data, such as picture data, music data, sound data, image data, and character data. Moreover, what is broadcast may be a single piece of data or multiple pieces of data; it is assumed here that multiple pieces of data are output.

0019The power-line modulator 102 modulates and multiplexes multiple pieces of data output from the data source 101, superimposes the resulting data on an electric power waveform, and then transmits the resulting superimposed data waveform to the power line 103. Note that ordinary power-line communication systems often include a demodulating means, which allows bi-directional communication; however, such a demodulating means is unnecessary for a broadcast system because the broadcast system allows only unidirectional communication. In addition, according to an exemplary data multiplexing method, frequency division is carried out for multiplexing.

0020Typically, the power line 103 is an electric wire, which is provided indoors or outdoors. An existing electric wire may be used as the power line 103. In addition, the outlets 104 and 105 are fixed to a wall surface in order to receive power from the power line 103. Existing outlets may be used as the outlets 104 and 105. In the exemplary structure shown in <figref idref="f0001">FIG. 1</figref>, the power-line modulator 102 is inserted into the outlet 104, and the LED lighting element 106 is inserted into the outlet 105. Needless to say, the power line 103 and the outlets 104 and 105 may be newly provided. Note that with this exemplary structure, it is assumed that AC electric power used as general commercial electric power is supplied.

0021The LED lighting element 106, which is connected to the power line 103, illuminates in the vicinity thereof. In the case of indoors, for example, it is fixed to the ceiling. Other various lighting elements, such as a spotlight, are available for various applications. In this exemplary structure, the LED lighting element 106 includes the AC-DC converter 111, the band pass filter 112, the selector 113, the superimposing unit 114, and the LED group 115.

0022The AC-DC converter 111 converts AC electric power supplied from the power line 103 to DC electric power, which is supplied to the LED group 115 to emit light. A conventional AC-DC converter may be used as the AC-DC converter 111. In addition, the AC-DC converter 111 also makes an adjustment to the operating voltage for the LED group 115. Furthermore, it supplies electric power needed for operation of the band pass filter 112. Note that since a modulated data waveform is superimposed on the power line 103 as described above, it is desirable that a smoothing circuit, for example, should be used for preventing development of the data waveform on a DC waveform.

0023The band pass filter 112 is provided for extracting a data signal superimposed on the power line 103. As described above, with this exemplary structure, since individual pieces of data are multiplexed through frequency division, the band pass filter 112, which allows only a specific frequency to pass through, can selectively isolate single data from multiple pieces of data. In the example shown in <figref idref="f0001">FIG. 1</figref>, multiple band pass filters, each allowing a different frequency to pass through, are arranged in parallel. Alternatively, a band pass filter, which is capable of changing frequency bandwidths passed therethrough, may be arranged. Note that a separated data waveform may be biased, trimmed, or amplified.

0024The selector 113 selects one or more out of multiple filters in the band pass filter 112, thereby allowing selection of data to be optically distributed. This selection may be manually made; alternatively, it may be made using another method or by selectively demodulating a transmitted control signal of a specific frequency and then making a selection of a filter based on that control signal. Alternatively, a structure capable of changing frequencies that pass through the band pass filter 112 may be used, and the selector 113 may set a frequency corresponding to data to be distributed to the band pass filter 112. In <figref idref="f0001">FIG. 1</figref>, the selector 113 is provided before the band pass filter 112; alternatively, it may be provided thereafter. In addition, in the case of that structure capable of changing a frequency band that the band pass filter 112 passes, the selector 113 may set a frequency bandwidth for the band pass filter 112 in conformity with a control signal of a specific frequency. Furthermore, when the LED lighting element 106 broadcasts only data of a fixed frequency, the selector 113 is unnecessary, and only the band pass filter 112 that passes signals of a fixed frequency bandwidth should be provided.

0025The superimposing unit 114 superimposes a data signal extracted by the band pass filter 112 on a converted DC electric power waveform, which is provided by the AC-DC converter 111. This allows change in voltage applied to the LED group 115 in conformity with the resulting data signal, and control of light intensity or blinking of the LED group 115. For example, in the case of making the LED group 115 blink, a structure such that electric power from the AC-DC converter 111 is controlled to turn on and off in conformity with a signal from the band pass filter 112 is possible.

0026The LED group 115 is basically an LED light source for lighting, which may be constituted by a great number of white LEDs, for example. Needless to say, a structure with a set of red LEDs, a set of blue LEDs, and a set of green LEDs is possible. Electric power from the superimposing unit 114 is supplied to the LED group 115, which then emits light. Since LEDs have excellent response characteristics, they can output optical data through changing light intensity and/ or blinking in conformity with a data signal. In this case, since high-speed change in light intensity and/ or high-speed blinking is unperceivable to the human eye, LEDs may be used for lighting as they are.

0027The light reception terminal 107 has a light reception means, receives light illuminated from the LED lighting element 106, extracts a data signal therefrom and demodulates it into data. An arbitrary device including a light reception means may be used as the light reception terminal 107, and it may be a variety of apparatus, such as a personal computer, a portable terminal, a cellular phone, an audio device having a light reception means, or a display apparatus such as a television.

0028An exemplary operation of the broadcast system, according to the first example is briefly described forthwith. Various contents to be broadcasted are prepared as the data source 101. For example, in addition to data from a computer, various kinds of data from a TV, a CATV, and a radio are prepared for respective applications.

0029The power-line modulator 102 modulates and multiplexes multiple pieces of data output from the data source 101, superimposes the resulting data on an electric power waveform, and then transmits the resulting superimposed data waveform to the power line 103. <figref idref="f0002">FIG. 2</figref> is a graph describing an exemplary signal waveform of an electric wire. Here, a commercial AC electric power supply (50 Hz/ 60 Hz) is used, and a data signal waveform is superimposed on an electric power waveform. A data signal waveform, which is smaller than an electric power waveform, is superimposed so as to avoid adversely influencing other devices. A magnified view of <figref idref="f0002">FIG. 2(B)</figref> shows an instance of data modulated using a method such as binary phase shift keying (BPSK) and then superimposed on the electric power waveform. Note that an existing electric wire may be used as the power line 103. In addition, receiving electric power from an outlet, separating and using data allows provision of data as with the case of using conventional power-line communication.

0030Electric power and data are transmitted to the LED lighting element 106 from the outlet 105 via the power line 103. The LED lighting element 106 receives from the outlet 105 electric power on which a signal waveform is superimposed. The AC-DC converter 111 rectifies and supplies DC electric power, which is then used to drive the LED group 115, and transmits it to the superimposing unit 114. On the other hand, a filter in the band pass filter 112 selected by the selector 113 passes and outputs only a predetermined frequency component. At this time, that component may be biased, trimmed, or amplified as necessary.

0031The superimposing unit 114 then combines DC electric power waveform, which is provided through conversion by the AC-DC converter 111, and a data signal extracted by the band pass filter 112, and then applies the resulting composite data signal waveform to the LED group 115. Voltage applied to the LED group 115 varies depending on the composite data signal waveform. As a result, light intensity of the LED group 115 changes depending on the data signal waveform, which allows transmission of data.

0032Light emitted from the LED group 115 is received by a light reception device on the light reception terminal 107 side. The light reception terminal 107 can receive data by detecting and demodulating changes in received light intensity. In this manner, of pieces of data provided from the data source 101, one selected by the LED lighting element 106 is transferred along with illuminative light; the light reception terminal 107 then receives that transferred data. In this case, the light reception unit in the light reception terminal 107 may not exactly face the LED lighting element 106 (LED group 115); however, it is possible to capture a data signal as long as a certain degree of illuminative light can be received since communication quality is excellent. This is because the LED illuminative light is used for lighting and apparent transmitted electric power is extremely large. When a signal with a similar signal intensity is transmitted using conventionally available infrared rays, influences on the human body (e.g., eyes) are unavoidable. In this regard, it is advantageous to optically transmit data.

0033Note that: only a single LED lighting element 106 is shown in the drawing; however, if multiple LED lighting elements 106 are arranged at a short distance, this arrangement is resistant to shadowing and can accommodate movement as long as the same data is selected and broadcast. On the other hand, even if an LED lighting element 106 for selecting and broadcasting data exists at a short distance, since light from another LED lighting element attenuates as long as reception is made near an LED lighting element 106, its influence becomes weak. In addition, if a problem of interference with other LED lighting elements develops, data from the data source 101 should be modulated using an interference resistant modulation method, such as on-off keying, return-to-zero (OOK-RZ) or orthogonal frequency division multiplexing (OFDM).

0034In addition, in the exemplary structure shown in <figref idref="f0001">FIG. 1</figref>, the AC-DC converter 111 and the band pass filter 112 are provided in the LED lighting element 106. However, this structure is not limited to this; alternatively, those circuits may be fixed in a light on/off wall switch, and DC electric power with a superimposed data waveform may be supplied between the switch and the LED lighting element 106. In this case, a switch to be used as the selector 113 may be fixed to a wall along with a light on/off switch. Needless to say, arrangement of respective units is not limited to those proposals, and may arbitrarily be made.

0035<figref idref="f0003">FIG. 3</figref> is a block diagram of a broadcast system, according to a second example. In the drawing, the same reference numerals are given to the same parts as those in <figref idref="f0001">FIG. 1</figref>, and repetitive descriptions thereof are thus omitted. 116 denotes a band pass filter, 117 denotes a determination unit, and 118 denotes a selector. In this exemplary structure, an identification code (such as IP, PN code) is assigned to each LED lighting element 106 or each piece of data, and only a specific piece of data is selected based on its own identification code and then broadcast.

0036A power-line modulator 102 divides multiple pieces of data from a data source 101 into packets, adds a header to the top of each packet, carries out time division multiplexing, and superimposes the resulting packets of data on the electric power waveform. The header includes an identification code.

0037The LED lighting element 106 includes the band pass filter 116, the determination unit 117, and the selector 118 as well as an LED group 115 and an AC-DC converter 111. The band pass filter 116 removes AC components from electric power and separates data signal components. In this exemplary structure, all signals of multiple pieces of data pass through the band pass filter 116.

0038The determination unit 117 extracts a header from data signals separated by the band pass filter 116, compares it with a predetermined identification code, and determines whether or not the transmitted data should be optically transmitted. If YES, the selector 118 then selects a data signal and outputs it to a superimposing unit 114. The superimposing unit 114 superimposes a signal passed through the selector 118 on a DC electric power waveform, which is provided through conversion by the AC-DC converter 111, and supplies the resulting superimposed signal to the LED group 115. Subsequently, as with the above-mentioned first example, light intensity or blinking of the LED group 115 is controlled based on a data signal, which allows optical data transmission. In addition, lighting comes from lights emitted by the LED group 115.

0039According to the second example, by assigning an identification code to, for example, each LED lighting element 106, data broadcast by each LED lighting element 106 can be controlled on a transmitter side from which data is transmitted to the power line 103. Moreover, a structure that allows assignment of separate identification codes allows selection of data to be broadcast from each LED lighting element 106. In this case, multiple identification codes may be assigned, and multiple pieces of data may be selected to be optically transmitted.

0040The second example may be structured in different ways as with the above-mentioned first example. In addition, there are the same advantages as those of the above-mentioned first example.

0041In addition to those examples, without selecting data to be broadcast using illuminative light, all data transmitted via the power line 103 may be optically broadcast, and broadcast data may be received and selected on a terminal side.

0042<figref idref="f0004">FIG. 4</figref> is an explanatory diagram of an electric bulb applicable to the broadcast system, according to the first and second example. In the drawing, 121 denotes an electric bulb, 122 denotes a base, and 123 denotes a socket. The bulb shown in <figref idref="f0004">FIG. 4</figref> may be applied as a part of an LED lighting element 106 in the broadcast system, according to each example described above. Typically, a lighting element including an attachable incandescent bulb has been available. As shown in <figref idref="f0004">FIG. 4(B)</figref>, the socket 123 is arranged on the ceiling or the like, and electrical connection can be made by inserting the base 122 of the electric bulb 121 into the socket 123. Here, existing facility in the interconnect portion extending until the power line 103 or the socket 123 is used as is, and as shown in <figref idref="f0004">FIG. 4(A)</figref>, the internal structure of the LED lighting element 106, according to the first or the second example described above, is accommodated in the electric bulb 121. For example, that structure may be accommodated in the base 122 of the electric bulb 121. In addition, differing from conventional point light sources with a filament such as an incandescent bulb, since a great number of LEDs are deployed in the same plane, a circuit can be deployed therebehind.

0043Use of such electric bulb 121 and only replacement of a typical incandescent bulb with the electric bulb 121, according to the first and second example allows use of the electric bulb 121 as an optical data transmission source.

0044Needless to say, variously shaped conventional electric bulbs may be used other than the shape as shown in <figref idref="f0004">FIG. 4</figref>. The shape of the electric bulb 121, according to the first and second example, is not limited to that in <figref idref="f0004">FIG. 4</figref>, and it may be an arbitrary shape. For example, the electric bulb 121 may be structured with a form of linearly arranged LEDs such as a fluorescent lamp.

0045Next, several applications of the broadcast system, according to the first and second example, are described forthwith. <figref idref="f0005">FIG. 5</figref> is a diagram describing a first application, according to the first and second example. In the drawing, 131 denotes LED lighting elements, 132 denotes artworks, and 133 denotes a light reception terminal. <figref idref="f0005">FIG. 5</figref> shows a case of the broadcast system according to the first and second example for understanding the invention, which is used in an art gallery or a museum. In an art gallery or a museum, lighting such as spotlighting is used for each artwork or showpiece (hereafter, referred to as artworks 132) and description thereof. The LED lighting elements 131, according to the first and second example, are used as lighting elements for illuminating the artworks 132. On the other hand, descriptive data for the artworks 132 is superimposed on a power line 103 via which electric power is supplied to the LED lighting elements 131, and the resulting superimposed data is transmitted. In this case, descriptive data for a great number of artworks 132 is superimposed on the power line 103. Each LED lighting element 131, which is provided for each artwork 132, selectively extracts descriptive data for each artwork, and controls light intensity or blinking of illuminative light as described above, optically transmitting the descriptive data.

0046When an appreciator takes out the light reception terminal 133 in front of an artwork 132, light is illuminated to the light reception terminal 133 and changes in the light intensity or blinking are captured and then demodulated, which allow the appreciator to read the descriptive data for the corresponding artwork 132. In addition, when the appreciator moves in front of the next artwork, descriptive data for the next artwork is then transmitted via light for illuminating that artwork. As a result, the appreciator can read the descriptive data for that artwork displayed in the light reception terminal 133.

0047In this manner, descriptive data for each artwork 132 is superimposed on an electric power waveform and then transmitted to the power line 103, and on the other hand, each of the LED lighting elements 131 for illuminating respective artworks selects descriptive data for the corresponding artwork 132 and optically transmits the resulting selected data, which allows provision of lighting to each artwork 132 and also allows an appreciator to read descriptive data for each artwork 132.

0048There may be more than once piece of descriptive data for each artwork. For example, in the case of providing descriptive data for each artwork in multiple languages, the LED lighting elements 131 select multiple pieces of descriptive data for artworks 132 to be illuminated, and optically transmit the selected data. The light reception terminal 133 then separates and demodulates optically transmitted, multiple pieces of descriptive data, selects descriptive data in a language of choice specified by the appreciator, and presents it to the appreciator. Alternatively, a structure such that the same LED lighting element 131 optically transmits multiple pieces of descriptive data for a single artwork 132, such as descriptive data for adults and that for children, is possible. Note that descriptive data is not limited to text data, and may be sound data, image data, or animation data. Alternatively, a combination thereof is also possible.

0049<figref idref="f0006">FIG. 6</figref> is a diagram describing a second application, according to the first and second example. In the drawing, 141 denotes LED lighting elements, 142 and 143 denote seats, and 144 denotes light reception terminals. The second application shows a case of the broadcast system, according to the first and second example, used in an airplane, a train, or a bus. In <figref idref="f0006">FIG. 6</figref>, the LED lighting elements 141 are provided to the respective seats, illuminating them. The LED lighting elements 141 also optically transmit data, which is transmitted via the power line 103. Furthermore, the light reception terminal 144 is provided in the backside of the front seat 142 so that a passenger seated in the seat 143 can see the screen of the light reception terminal 144. The light reception terminal 144 receives light illuminated from an LED lighting element 141, and captures data from the light. A passenger may select and view desired data through manipulation of the light reception terminal 144.

0050In an airplane or a spaceship, in particular, a radio wave must not be used because there may be adverse influences on instruments therein. Meanwhile, light has no effect on instruments as well as the human body. Accordingly, wireless data distribution may be carried out as shown in <figref idref="f0006">FIG. 6</figref>. Note that data may be selected by the light reception terminal 144 in addition to the LED lighting element 141.

0051Note that in an airplane, a train, or a bus, direct current is often used as electric power for lighting. Accordingly, the AC-DC converter 111 in <figref idref="f0001">FIGS. 1</figref> and <figref idref="f0003">3</figref> is unnecessary. For example, in the case of optically transmitting all data transmitted via the power line 103, the band pass filter 112 and the superimposing unit 114 are unnecessary. Data may be optically transmitted by driving the LED group with data waveform superimposed electric power, which is supplied from the power line 103.

0052Two applications of the broadcast system, according to the first and second example, have been shown above. However, the present invention is not limited to those applications, and can be applied to various applications for optically distributing data. For example, it can be used as a distribution system, which distributes to a personal computer on a desk in an ordinary office, and may be used for transmitting data to each process in a factory. In addition, broadcasting a television program or a radio program in a home is also possible, and that program can be viewed in any room using a portable display. In this case, a selector or a tuner may be provided in the LED lighting element, and a broadcasting station may be selected by controlling the selector using a television controller. Moreover, in a sport stadium or an event hall, for example, information of sports or events or information of other halls is superimposed on illuminative light and broadcast, and a portable terminal owned by a spectator receives it and provides that information for the spectator.

0053As described above, according to the first and second example, a great number of pieces of data may be optically distributed using lighting elements as they are. In this case, different from the conventional way, it is unnecessary additionally deploy a transmitter and communication cables. Accordingly, a broadcast system can be constructed at low cost. In addition, there are no adverse effects on the human body, such as eyes, as with infrared rays, and there are no limitations on applications such as a limitation on available radio waves used for airplanes. Therefore, a safe broadcast system can be provided.

0054Next, the present invention is described. The present invention is an application to emergency lights.

0055Of various display apparatus, emergency lights semi-permanently continue to illuminate and are hardly ever switched off once they are switched on. As a provision against accidents such as a fire or a disaster, many emergency lights are deployed in plain view, such as in a building, a theater, a film theater, a hospital, an airport, and a station. The majority of present emergency lights uses a fluorescent lamp as a light source. Since it is expected that external electric power may be turned off when a disaster occurs, an internal battery is used to supply electric power to emergency lights to illuminate while in an emergency. Fluorescent lamps having better electric power efficiency than incandescent bulbs are used for effective utilization of limited electric power. Meanwhile, reduction in maintenance cost using a light source having further excellent electric power efficiency and a long-lived light source has been required. As described above, LEDs have excellent electric power efficiency and a long operating life, but they have not been considered to be used as emergency lights. As merely disclosed in Japanese Patent Application Laid-Open No. <patcit id="pcit0004" dnum="JPHEI919084B"><text>Hei 9-19084</text></patcit>, there is a case that LEDs are used as a secondary light source to display a state of charge, for example. However, LEDs have never been used as a main light source for emergency lights.

0056In addition, ordinary emergency lights deployed in place merely provide visual information of where emergency exits and emergency staircases are located. There is relevant information disclosed in, for example, Japanese Patent Application Laid-Open No. <patcit id="pcit0005" dnum="JPHEI8299475B"><text>Hei 8-299475</text></patcit> in which a voice guiding mechanism is provided and Japanese Patent Application Laid-Open No. <patcit id="pcit0006" dnum="JPHEI867203B"><text>Hei 8-67203</text></patcit> in which radio broadcasting is used. However, large electric power is needed for voice output. Therefore, a large-capacity battery must be embedded for visual indication of the emergency exits, which is the first principle for the emergency lights, and for voice output, thereby developing problems of increase in cost and system size.

0057On the other hand, since LEDs have a high-speed response characteristic and can be modulated at a high speed, use of LEDs for optical data communication has been studied. The idea of using these features and carrying out illumination and communication at the same time has been well-known. However, ordinary lighting elements are switched off when power supply stops due to a disaster. Therefore, those devices cannot be used while in an emergency, and there has been no communication system established assuming an emergency.

0058In order to solve such problems, the present invention shows an application of light emitted from emergency lights for communication.

0059FIG. 55 is a block diagram of an emergency light and a wireless emergency light data communication system, according to an embodiment of the present invention. FIG. 56 is a diagram describing an exemplary LED array used as a light source. In the drawings, 701 denotes an emergency light, 702 denotes a portable terminal, 711 denotes a battery, 712 denotes a switch, 713 denotes an LED array, 714 denotes a modulator/ demodulator, 715 denotes data memory, 716 denotes an optical modulator, 721 denotes a light receiving unit, 722 denotes a demodulator, 723 denotes a display unit, and 731 denotes a cover. The emergency light 701 has the battery 711 as a power source in addition to an external power source, as with typical conventional emergency lights, and the switch 712 to switch a power supply source from the external power source to the battery 711 when power supply from the external power source stops.

0060In the present invention, the LED array 713, instead of a conventional fluorescent light, is used as the illuminative light source. FIG. 56 shows an exemplary shape of the LED array 713. In the example shown in FIG. 56(A), as with typical emergency lights, the LED array 713 is provided in the cover 731 on which a pictorial mark is displayed. When using it in such a manner, the rod-shaped LED array 713 similar to a fluorescent lamp is used, as shown in FIG. 56(B). For example, LED devices should be arranged in one or more rows. In addition, such LED array 713 may be used as a substitute for a DC lighting fluorescent lamp. Accordingly, the emergency light, according to the present invention, may be structured only by replacing a fluorescent light in the conventionally available emergency light with the LED array 713 as shown in FIG. 56(B). In this case, when AC electric power is supplied from a power line, the emergency light should be driven by DC electric power, which is provided through conversion by an AC-DC converter. Moreover, with an emergency light using AC lighting fluorescent light, a DC-AC converter should be embedded in the LED array 713 and used while being driven by the battery 711. Note that use of this such-shaped LED array 713, which can be substituted for a fluorescent lamp, allows provision of the emergency light with the same shape as that of the conventional emergency light in appearance.

0061In addition to the structure using the LED array as a substitute for the conventional fluorescent lamp, the LED array 713 may directly display a pictorial mark, which has been put on the cover 731, as shown in FIG. 56(C). In the case of a pictorial mark indicating emergency exits, since the pictorial mark is typically designed in white and green, it can be displayed by arranging white and green LEDs in place. Needless to say, a pictorial mark may be displayed by arranging LEDs in the same manner as a color display apparatus. Note that in such cases, a transparent material should be used as the cover 731.

0062Use of an LED array as a light source for the emergency light 701 in this manner and an advantage of LEDs having low power consumption allows provision of the same lighting time with a small-capacity battery as that by prior art, reduction in size of the battery 711, reduction in size and weight of the emergency light 701, and reduction in cost. On the other hand, if the battery has the same capacity as that of the prior art, the emergency light may be on over a long period of time, allowing an escape guiding display to be displayed for a long time when a disaster occurs. Moreover, a feature of long-lived LEDs allows extension of maintenance intervals, such as replacement of a light source, and decrease in man-hour for maintenance work, resulting in reduction in maintenance cost. Needless to say, it is desirable that maintenance for keeping performance, such as checking stains and battery life, and checking whether lighting is possible against a disaster, should be continued. Furthermore, since LEDs are highly crashproof, it can be expected that a light source will not be damaged and will continue to illuminate even when a devastating disaster occurs.

0063The emergency light 701 according to the present invention shown in <i>FIG. 55</i> further includes the modulator/ demodulator 714, the data memory 715, and the optical modulator 716. A communication method using a power line for supplying electric power from the external power source is used for transmitting data to the emergency light 701. The modulator/ demodulator 714 separates and demodulates modulated data which is superimposed on a voltage from the external power source, and then stores the resulting demodulated data in the data memory 715. For example, data to be transmitted from the emergency light 701 while in an emergency can be transmitted from a computer via a power line. Accordingly, data may be distributed to the emergency light 701 via an external power source while not in an emergency, which allows easy storage of data in the data memory 715. In addition, various pieces of data, such as data stored in the data memory 715 or the status of the emergency light 701, may be modulated and then transmitted via the power line. This allows remote confirmation of rewritten data and remote determination of the operation of the emergency light 701. Note that in the case of not carrying out bi-directional communication, the modulator/ demodulator 714 may be structured to function as a mere demodulator. In the case of data to be transmitted while in an emergency being pre-stored in the data memory 715, the modulator/ demodulator 714 is unnecessary.

0064Data to be transmitted while in an emergency may be stored in the data memory 715. It is desirable that the power consumption of the data memory 715 is minimal. In addition, it is necessary to prevent stored data from being accidentally erased while changing over the power source. For example, rewritable ROM or nonvolatile RAM should be used.

0065Upon detection of an emergency, such as an event of the switch 712 having changed over from the external power source to the battery 711, the optical modulator 716 reads out data to be transmitted while in an emergency from the data memory 715, modulates it, and then superimposes the resulting modulated data on an electric power waveform that is supplied to the LED array 713. This allows control of blinking or light intensity of light emitted from the LED array 713 in accordance with data modulated by the optical modulator 716. This allows optical data communication. Needless to say, even while not in an emergency, data communication is possible by modulating data stored in the data memory 715 and providing the resulting modulated data to the LED array 713. In this case, data may differ from that to be transmitted while in an emergency.

0066The portable terminal 702, which includes the light receiving unit 721, the demodulator 722, and the display unit 723, may be, for example, a PDA with a camera or a cellular phone with a camera. The light receiving unit 721, which may be structured with a camera or a photodiode, receives and converts light emitted from the LED array 713 in the emergency light 701 to an electric signal.

0067The demodulator 722 extracts a modulated data signal from an electric signal transmitted from the light receiving unit 721, demodulates it, and then captures data. The captured data is available for various applications. In this working example, the captured data is displayed on the display unit 723. As a result, data optically transmitted from the emergency light 701 while in an emergency is displayed on the display unit 723. Text and picture data, such as a map regarding emergency exits or escape routes for evacuees on a floor, may be displayed on the display unit 723. Moreover, voice data may be transmitted, and if a speaker is embedded like a cellular phone, voice data can be easily captured.

0068An exemplary operation and an application of the emergency light and the wireless emergency light data communication system, according to the embodiment of the present invention, is described forthwith. Data to be transmitted to the data memory 715 while in an emergency should be pre-stored in the emergency light 701. According to a certain method, power line communication is used for transmitting modulated data, as described above, which is superimposed on an external power source waveform, to the emergency light 701, which then receives and demodulates modulated data transmitted from the external power source, thereby capturing data. Alternatively, data is pre-stored in external ROM, and the external ROM may be fixed, as the data memory 715, to the emergency light 701. For example, a memory card may be fixed thereto.

0069While in an emergency, the optical modulator 716 reads out data from the data memory 715, modulates it, and then superimposes the resulting modulated data on an electric power source waveform to be supplied to the LED array 713. When the electric power on which modulated data is superimposed is supplied to the LED array 713, the LED array 713 then emits light, and light intensity or blinking is controlled allowing optical data transmission.

0070Moreover, a possessor of the portable terminal 702 can receive data optically transmitted from the emergency light 701 by facing the possessed portable terminal 702 to the emergency light 701 while in an emergency. While in an emergency, people often get lost, and even while evacuating according to emergency lights, they may feel anxious about no information as to how long it takes to evacuate. However, according to the present invention, further detailed various pieces of visual data (or voice data), such as building names, a map of staircases and floors, escape routes for evacuees, and a remaining distance in meters from emergency exits, which the conventional emergency light cannot provide, can be obtained from the emergency light 701. This eases anxiety to a certain extent, allowing more rapid evacuation.

0071Typically, since the portable terminal 702 may often be driven by a battery, it may be effectively used while in an emergency. Accordingly, use of the emergency light, which emits light without an external power source while in an emergency, and the portable terminal 702, which does not need the external power source, together allows smooth escape guidance while in an emergency, in particular, even when the external power source is cut off.

0072Moreover, the emergency light 701, according to the present invention, needs electric power to be supplied to the optical modulator 716 or related units. However, necessary electric power for such electronic circuits to operate is much less than electric power for emitting light. Therefore, even when including such optical data communication capability, reinforcement of the battery 711 for the emergency light 701 is almost unnecessary. Moreover, there is no need to deploy an additional means for significantly suppressing power consumption and transmitting data, as compared to a structure for transmitting radio wave, voice and the like as well as light. For example, in the case of infrared rays, similar power consumption is unavoidable, and an additional transmitter must be provided. In view of reduction in power consumption and simplification of a device, optical data communication using an LED light source is advantageous.

0073Needless to say, the LED array 713 in the emergency light 701 emits light to display guidance to emergency exits and escape routes for evacuees as with the typical emergency light, and is effective for people who do not have the portable terminal 702 while in an emergency. Even when light intensity and/ or blinking is controlled for data communication, such change in light intensity is unperceivable to the human eye. Therefore, the functionality as the emergency light will not be lost. In addition to this, utilization of the features of LEDs provides further enhanced functionality as an emergency light than that of the conventional emergency light.

0074Moreover, data communication by the emergency light 701 is not limited to an emergency. For example, data stored in the data memory 715 may always be optically transmitted. Alternatively, it is possible to transmit information of surrounding shops and news to the portable terminal 702 by pre-storing non-emergency data as well as emergency data in the data memory 715 and changing over between those pieces of data according to whether or not it is an emergency by the optical modulator 716. Once the emergency light 701 is switched on, it is never switched off and is always on day and night. Therefore, a user of the portable terminal 702 can always capture data from the emergency light 701. In addition, since the content of the data memory can be updated as needed through power line communication as described above, real time distribution of data to the portable terminal 702 while not in an emergency is possible.

0075The case of capturing data through power line communication and case of storing data in the data memory 715 in advance have been described above. However, the present invention is not limited to those cases, and various methods for transmitting data to the emergency light 701 are available.

0076FIG. 57 is a block diagram of an emergency light and a wireless emergency light data communication system, according to another embodiment of the seventh aspect of the present invention. In the drawing, 741 denotes an antenna, and 742 denotes a modulator/ demodulator. In the example shown in FIG. 57, the emergency light 701 receives data transmitted from the outside via radio wave and then stores it in the data memory 715. Data received by the antenna 741 is demodulated by the modulator/ demodulator 742, and the resulting demodulated data is then stored in the data memory 715. Such data reception should be carried out while not in an emergency. Since electric power can be supplied from the external power source while in an emergency, such radio wave data reception is possible. Needless to say, in the case of broadcasting data, mere demodulating capability is required to the modulator/ demodulator 742.

0077Furthermore, other than radio waves as shown in FIG. 57, a communication line, such as an optical cable or a communication cable, except for a power line may be utilized to receive data in advance. Note that use of power line communication shown in FIG. 55 develops an advantage that data reception is possible without deploying an antenna or an additional cable.

0078In this manner, according to the present invention, use of LEDs as a light source allows suppression of battery consumption due to high electric power efficiency of LEDs, reduction in device size due to a reduced battery size, and an extended light emitting time. Moreover, since LEDs have a long operating life, maintenance intervals such as light source replacement intervals can be longer, allowing reduction in maintenance cost. Furthermore, since LEDs are highly crashproof, provision of an emergency light that will not be damaged and be available even when a devastating disaster occurs is possible.

0079In addition, since LEDs have excellent response characteristics, they may be used as an optical data transmission source by controlling blinking or light intensity thereof. The emergency light includes a battery, allowing continuous light emission even when the electric power supply is cut off due to a disaster. Various pieces of emergency data, such as positional data for emergency exits and emergency staircases, and data for escape routes for evacuees to the emergency exits, which have been pre-stored, can be transmitted using this emitted light. Since provision of such data transmission capability is not costly and does not consume much electric power as compared to the case of providing an additional radio wave or an additional infrared ray transmission system, the capability of emitting light as an emergency light while in an emergency is not lost.

0080Furthermore, once the emergency light is switched on, it is not switched off semi-permanently and is not influenced by weather and seasons. Therefore, it is generally provided in plain view. Moreover, transmission of not only emergency data, but also general data, such as surrounding advertisements or guidance, is possible. Accordingly, it is expected that the emergency light will be frequently used even while not in an emergency, allowing increase in added value of the emergency light.