Abstract:
In the case of performing communication by using illumination light when the illumination is on, switches are turned on, a signal modulated in an optical modulation part in accordance with information is superposed to a power waveform for the illumination with a power distributor and the illumination  16  is driven in a modulated state. When the illumination is off, the switches are turned off, a switch is turned on and a communication part is driven in a modulated state by the optical modulation part. The communication part can be constituted so as to include an infrared light emitting element part to perform infrared communication when the illumination is off. Consequently communication can be performed not only when the of illumination is on but also when the lighting is kept off. The communication device can be constituted of one element integrating the illumination part and the communication part, so that a compact system can be constituted.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    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. 2003-070673 filed Mar. 14, 2003, the contents of which are incorporated herein by reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention aims to provide an illuminative light communication device, which allows communication even without lighting and effectively utilizes infrared light data communication, and a lighting device preferable for such illuminative light communication device. 
         [0003]    According to such objective, the illuminative light communication device includes a lighting unit that emits light for lighting, a modulator that controls blinking or light intensity of the lighting unit in accordance with data, thereby modulating the emitted light, a communicating unit that transmits the data through optical communication other than illuminative light communication, and a switch that changes over respective operations of the modulator and the communicating unit based on whether the lighting unit is on or off. The switch changes over such that the communicating unit can operate while the lighting unit is off. The communicating unit may be structured so as to transmit data through infrared light data communication. 
         [0004]    As described above, in addition to illuminative light communication that is made possible by the lighting unit outputting illuminative light modulated by the modulator, illuminative light communication is carried out while the lighting unit is on, using a conventional communication unit such as infrared light communication unit. On the other hand, without lighting, communication is carried out using a communication unit such as infrared light data communication. This allows continuous communication even without lighting. 
         [0005]    Note that when carrying out infrared light data communication, an infrared light emitting device that can selectively emit infrared light can be included in multiple LED devices in the lighting unit. As a result, it is unnecessary to separately provide another communicating unit to be used without lighting, and an indoor lighting unit that is deployed so as to prevent generation of a shadow can be used for infrared light data communication. This allows reduction in influences of shadowing, and stable infrared light data communication. 
         [0006]    An illuminative light communication device includes a lighting unit that emits light for lighting and a modulator that controls blinking or light intensity of the lighting unit in accordance with data, thereby modulating the emitted light. In response to an on-switching instruction, the modulator modulates in accordance with the data while supplying sufficient electric power for lighting to the lighting unit while in response to an off-switching instruction, the modulator modulates in accordance with the data to allow the lighting unit to blink a number of times necessary for communication. 
         [0007]    This structure allows communication with lighting with sufficient light intensity for lighting, and communication using emitted light only required for the communication when light intensity is unnecessary or without lighting. As a result, users can turn the lighting either on or off, and optical communication is possible even without lighting. 
         [0008]    Furthermore, a lighting device for emitting illuminative light includes an illuminative light emitting device that emits white light for lighting and an infrared light emitting device that emits infrared light for infrared data communication. The illuminative light emitting device can be controlled for modulation to carry out illuminative light communication independently of the infrared light emitting device. This allows illuminative light communication with lighting by illuminative light emitted from the illuminative light emitting device, and infrared light data communication without lighting by infrared light emitted from the infrared light emitting device. As a result, communication is possible even without lighting, although communication could not be carried out through conventional illuminative light communication without lighting. In addition, an additional communicating unit is not needed for infrared light data communication, influences of shadowing can be reduced and stable infrared light data communication can be carried out, thereby increasing the possibility of infrared light data communication. 
         [0009]    Note that the lighting device can be structured of a red, a blue, and a green light emitting device in line with the infrared light emitting devices. Alternatively, it may be structured of infrared light emitting devices in line with illuminative light emitting devices, which are made up of a blue or an ultraviolet light emitting device and fluorescer provided surrounding the light emitting devices. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a block diagram of an illuminative light communication device, according to a first embodiment of the present invention; 
           [0011]      FIG. 2  is a table describing exemplary operations defined according to respective combinations of an ON and an OFF status of switches  12  through  14 ; 
           [0012]      FIG. 3  is a schematic diagram of an exemplary lighting element, according to the present invention, which is preferable to being used for the illuminative light communication device, according to the present invention; 
           [0013]      FIG. 4  is a diagram describing an application of an exemplary lighting element, according to the present invention, to the illuminative light communication device, according to the present invention; 
           [0014]      FIG. 5  is a schematic diagram of another exemplary lighting element, according to the present invention, which is preferable to being used for the illuminative light communication device, according to the present invention; 
           [0015]      FIG. 6  is a diagram describing another application of an exemplary lighting element, according to the present invention, to the illuminative light communication device, according to the present invention; 
           [0016]      FIG. 7  is a block diagram of an illuminative light communication device, according to a second embodiment of the present invention; and 
           [0017]      FIGS. 8A-8B  each is a diagram of an exemplary structure of a typical white LED;  FIG. 8A  shows an exemplary structure using three color light emitting elements; and  FIG. 8B  shows an exemplary structure using fluorescer. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]      FIG. 8  is a diagram of a configuration of an exemplary typical white LED. In the drawing,  331  and  341  denote LED devices,  332  denotes a red light emitting element,  333  denotes a green light emitting element,  334  denotes a blue light emitting element,  342  denotes a light emitting element, and  343  denotes fluorescer. An exemplary white LED shown in  FIG. 8A  is configured such that the red light emitting element  332 , the green light emitting element  333 , and the blue light emitting element  334  are arranged in the LED device  331 . White light can be seen when red, green, and blue light emitted from respective light emitting elements are mixed. 
         [0019]    In the case of an exemplary white LED shown in  FIG. 8B , a blue or an ultraviolet light emitting element  342  is provided in the LED device  341 , and the fluorescer  343  is provided surrounding the light emitting element  342 . As with a fluorescent lamp, the LED device  341  has the fluorescer  343 , which emits white light when blue light or ultraviolet light emitted from the light emitting element  342  is irradiated on the fluorescer  343 . As a result, white light is emitted. 
         [0020]    Since such single LED device has less light intensity for lighting, an LED array made up of multiple LED devices is typically used. In the following description, the LED array may be referred to as just LED. Such LED array is used for some traffic control signals, rear lamps of an automobile, desk lamps, and foot lights, for example. The features of LEDs are longer life, smaller size, and lower power consumption than those of conventional illuminative light sources such as incandescent lamps and fluorescent lamps. Accordingly use of LEDs as a future illuminative light source is considered. 
         [0021]    In addition, another feature of light emitting elements such as LEDs is a very fast response speed since a preheating time is unnecessary. Paying attention to those features such as a fast response speed and electrical controllability, a study of superimposing a signal on an illuminative LED light and thereby transferring the signal has been conducted. 
         [0022]    Lighting elements are often provided on the ceiling or a wall surface, or a pole is set up to irradiate a certain area from above, thereby preventing generation of a shadow. Typically, wireless communication including optical communication has a problem of shadowing which causes decrease in signal intensity and disturbance in communication behind an object. However, since lighting elements are often provided so as to prevent shadowing as described above, this means that illuminative light communication is possible without development of shadowing. In addition, there is an advantage that high communication quality is ensured using a high electric power for lighting. 
         [0023]    However, use of illuminative light develops a problem that illuminative light communication cannot be carried out without lighting. Lights may be kept on even when unnecessary. However, users may not appreciate keeping lights turned on when unnecessary in view of energy conservation, or lighting may be prohibited at night, for example. There is a problem that communication cannot be carried out without lighting and cannot be carried out when unattended, at night, or while using a projector. 
         [0024]    On the other hand, infrared light communication has been widely used, and standardization has been carried out by the infrared data association (IrDA) or the like. There is fear that infrared light communication may adversely influence the human body such as eyes. As a result, it is impossible to carry out high electric power communication. In addition, it is characterized in that it is easily influenced by shadowing, which causes decrease in communication quality due to characteristics of light when an obstruction such as a user exists. From these reasons, an available range is limited, and that communication may not be stably carried out. 
         [0025]    To solve such problems, a communication device with the following structure uses illuminative light and infrared light together and is available even without lighting. 
         [0026]      FIG. 1  is a block diagram of an illuminative light communication device, according to a first embodiment of the present invention. In the drawing,  311  denotes an optical modulator,  312  through  314  denote switches,  315  denotes an electric power divider,  316  denotes a lighting unit,  317  denotes a communicating unit,  321  denotes a data terminal, and  322  denotes a light receiving unit. A light source which emits light for lighting is provided in the lighting unit  316 . Since a semiconductor light emitting element capable of operating at a fast response speed such as a white LED is used as a light source, illuminative light communication is possible by controlling blinking and/or light intensity. In addition, the communicating unit  317  may transmit data using an optical communication method other than illuminative light communication such as infrared light communication. Note that the lighting unit  316  and the communicating unit  317  may be deployed in the same device to be described later. Needless to say, those may be formed separately. 
         [0027]    The optical modulator  311  and the electric power divider  315 , which are used as a modulation means according to the present invention, modulate illuminative light by controlling blinking and/or light intensity of the lighting unit  316  in conformity with data. In this exemplary structure, the optical modulator  311  modulates received data using a predetermined modulation method, superimposes the resulting modulated data on an electric power waveform, and then transmits the resulting superimposed data waveform to the electric power divider  315  via the switch  313  or to the communicating unit  317  via the switch  314 . This allows control of light intensity and on/off control of the lighting unit  316  and the communicating unit  317 . 
         [0028]    The electric power divider  315  mainly supplies electric power to the lighting unit  316 . When an electric power superimposed with modulated data to be transmitted from the optical modulator  311  via the switch  313  is supplied, this electric power is supplied to the lighting unit  316 . 
         [0029]    The switches  312  through  314 , which are switching means of the present invention, are turned on or off in conformity with an external command for turning on or off. The switch  312  allows or prohibits electric power supply to the electric power divider  315 , thereby turning lights on or off. The switch  313  allows or prohibits provision of the modulated data to the electric power divider  315 , thereby allowing or prohibiting transmission of data via illuminative light (illuminative light communication) while the lighting unit  316  is illuminating. The switch  314  allows or prohibits transmission of the modulated data to the communicating unit  317 . Note that either the switch  312  or the switch  313  is turned on or both of them are turned off at the same time. 
         [0030]      FIG. 2  is a table describing exemplary operations defined according to respective combinations of an on and an off status of the switches  312  through  314 . When the switch  312  is on, the switch  313  is off, and the switch  314  is on, the communicating unit  317  carries out communication while the lighting unit  316  is illuminating as shown in  FIG. 2  ( 1 ). Note that in  FIG. 2 , communication by the communicating unit  317  is described as ‘infrared light communication’, but the present invention is not limited to this. When setting of the switches  312  and  313  is the same as that just described, and the switch is off, only lighting is carried out without carrying out communication as shown in  FIG. 2  ( 2 ). In this case, illuminative light is not used for communication. When the switch  312  is off, the switch  313  is on, and the switch  314  is on, as shown in  FIG. 2  ( 3 ), the lighting unit  316  carries out lighting and illuminative light communication, and the communicating unit  317  also carries out data communication. In this configuration, when the switch  314  is off, the lighting unit  316  carries out lighting and illuminative light communication as shown in  FIG. 2  ( 4 ). When both switches  312  and  313  are off, the lighting unit  316  is not used. In this configuration, when the switch  314  is on, the communicating unit  317  carries out data communication as shown in  FIG. 2  ( 5 ). Otherwise, when the switch  314  is off, neither lighting nor communication is carried out as shown in  FIG. 2  ( 6 ). 
         [0031]    For example, in the case of carrying out communication when lighting is needed, data communication by the communicating unit  317  or illuminative light communication by the lighting unit  316  may be carried out by turning the switch  312  on, the switch  313  off, and the switch  314  on as shown in  FIG. 2  ( 1 ), or turning the switch  312  off, the switch  313  on, and the switch  314  either on or off as shown in  FIG. 2  ( 3 ) or  FIG. 2  ( 4 ). On the other hand, when lighting is unnecessary, data communication by the communicating unit  317  is carried out by turning both switches  312  and  313  off, and the switch  314  on as shown in  FIG. 2  ( 5 ). 
         [0032]    As described above, illuminative light communication with lighting is possible, and communication without lighting is also possible. When infrared light communication is used as a communication method for the communicating unit  317  as described above, since infrared light is invisible, a person cannot sense the brightness during communication. Therefore, communication can be carried out even without lighting. 
         [0033]      FIG. 3  is a schematic diagram of an exemplary lighting element, according to the present invention, which is preferable to be used for the illuminative light communication device, according to the present invention.  FIG. 4  is a diagram describing an exemplary application of the lighting element, according to the present invention, to the illuminative light communication device, according to the present invention. In the drawing, the same symbols are given to the same parts as those in  FIG. 8 , and repetitive descriptions thereof are thus omitted.  335  denotes an infrared light emitting element. As shown in  FIG. 8 , needless to say, typical LEDs for lighting emit only visible lights, and do not emit infrared light. Accordingly, in the case of carrying out infrared light communication by the communicating unit  317  as described above, an infrared light LED must be additionally provided as the communicating unit  317 . Needless to say, different LEDs may be used in the lighting unit  316  and the communicating unit  317 . Alternatively, since both LEDs have similar structures, they can be integrated into one. An example of this case is shown in  FIG. 3 . 
         [0034]    In the example shown in  FIG. 3 , the infrared light emitting element  335  is provided in an LED which emits white light by mixing red, green, and blue emitted lights as shown in  FIG. 8A . Even though the infrared light emitting element  335  is provided in this manner, the package size is several millimeters wide and several millimeters high, which is almost the same as that of typical LEDs. 
         [0035]    To use such lighting element in an illuminative light communication device, as shown in  FIG. 4 , the red light emitting element  332 , the green light emitting element  333 , and the blue light emitting element  334  are electrically connected to the electric power divider  315  so as to receive electric power with lighting or modulated electric power during illuminative light communication. In addition, the infrared light emitting element  335  is connected to the optical modulator  311  via the switch  314 , allowing the optical modulator  311  to modulate and drive the infrared light emitting element  335  when the switch  314  is turned on. Furthermore, a shared electrode may be grounded along with the optical modulator  311  and the electric power divider  315 . 
         [0036]    For ordinary lighting, a visible white illuminative light is emitted by mixing three color lights emitted from the red light emitting element  332 , the green light emitting element  333 , and the blue light emitting element  334 . High-speed modulation of this illuminative light allows illuminative light communication. In addition, light emitted from the infrared light emitting element  335  is invisible. However, high-speed modulation of light to be emitted allows wireless communication using invisible infrared light. 
         [0037]    As described above, illuminative light communication by carrying out high-speed modulation of respective lights emitted from the red light emitting element  332 , the green light emitting element  333 , and the blue light emitting element  334 , and infrared light communication by carrying out high-speed modulation of light emitted from the infrared light emitting element  335  can be changed over by changing settings of the switches  312  through  314  as described above. For example, when both lighting and communication are required, the red light emitting element  332 , the green light emitting element  333 , and the blue light emitting element  334  are operated to emit respective lights, and at the same time the emitted lights are modulated at a high speed, thereby transmitting data. As a result, since an optical power needed for lighting may also be used for communication, high-speed and high-quality communication can be carried out. In addition, when lighting is unnecessary but communication is required, communication is carried out by modulating and driving the infrared light emitting element  335  and operating it to emit infrared light. In this case, since infrared light is invisible, communication can be carried out even without lighting. In addition, typically, since people are often absent when lights are off, adverse influences on the human body such as eyes can be decreased. 
         [0038]    Needless to say, infrared light communication may also be carried out with lighting, by modulating and driving the infrared light emitting element  335 . In this case, what should be done on a receiver side is to receive only infrared light, and there is no need to deal with multiple wavelengths, allowing provision of a simplified structure. 
         [0039]    Alternatively, communication using both illuminative light and infrared light may be carried out by modulating and driving respective lights from the red light emitting element  332 , the green light emitting element  333 , the blue light emitting element  334 , and also modulating and driving light from the infrared light emitting element  335 . In this case, since all power is available, higher-speed and higher-quality communication than that using the aforementioned methods is possible. 
         [0040]    Note that since the red light emitting element  332 , the green light emitting element  333 , the blue light emitting element  334 , and the infrared light emitting element  335  in the configuration shown in  FIG. 3  may be driven independently, multiple pieces of data can be transmitted at the same time by dividing wavelengths. 
         [0041]      FIG. 5  is a schematic diagram of another exemplary lighting element, according to the present invention, which is preferable to be used for the illuminative light communication device according to the present invention.  FIG. 6  is a diagram describing another application of an exemplary lighting element, according to the present invention, to the illuminative light communication device according to the present invention. In the drawing, the same symbols are given to the same parts as those in  FIG. 8 , and repetitive descriptions thereof are thus omitted.  344  denotes an infrared light emitting element. In the example shown in  FIG. 5 , the infrared light emitting element  344  is provided in the LED device  341  structured as shown in  FIG. 8B . 
         [0042]    To use such a lighting element in the illuminative light communication device, as shown in  FIG. 6 , the light emitting element  342  is electrically connected to the electric power divider  315  and receives electric power with lighting, and receives modulated power during illuminative light communication. In addition, the infrared light emitting element  335  is electrically connected to the optical modulator  311  via the switch  314 , allowing the optical modulator  311  to modulate and drive the infrared light emitting element  335  while the switch  314  is turned on. Furthermore, a shared electrode may be grounded along with the optical modulator  311  and the electric power divider  315 . 
         [0043]    For ordinary lighting, white light is emitted by irradiating the fluorescer  343  with blue light or ultraviolet light emitted from the light emitting element  342 . In this case, illuminative light can be used for communication by carrying out high-speed modulation and driving the light emitting element  342 . In addition, modulation and driving of the infrared light emitting element  344  allow wireless communication using invisible infrared light. 
         [0044]    As with the example shown in  FIG. 3 , when both lighting and communication are required, modulation and driving of the light emitting element  342  are carried out, thereby transmitting data. As a result, since optical power needed for lighting can also be used for communication, high-speed and high-quality communication can be carried out. In addition, when lighting is unnecessary but communication is required, communication is carried out by modulating and driving the infrared light emitting element  335  to emit infrared light. In this case, since infrared light is invisible, communication can be carried out without lighting. In addition, typically, since people are often absent when lights are off, adverse influences on the human body such as eyes can be decreased. 
         [0045]    Needless to say, as with the example shown in  FIG. 3 , with lighting, infrared light communication may be carried out by modulating and driving the infrared light emitting element  344 , or by modulating and driving both the light emitting element  342  and the infrared light emitting element  344 . Note that according to the configuration shown in  FIG. 5 , it is possible to transmit different pieces of data in parallel by driving the light emitting element  342  and the infrared light emitting element  344  individually, however, it is impossible to transmit different pieces of data via a red, a green, and a blue illuminative light wavelength, respectively. 
         [0046]      FIG. 7  is a block diagram of an illuminative light communication device, according to a second embodiment of the present invention. Symbols in the drawing are the same as those in  FIG. 1 . According to the aforementioned first embodiment, communication without lighting is carried out by the communicating unit  317 , which is additionally provided. In the second embodiment, an example where communication is carried out by a lighting unit  316  without a communicating unit  317  without lighting is shown. 
         [0047]    In this exemplary structure, a switch  312  is used for turning lights on or off while a switch  313  is used for changing over between carrying out and not carrying out communication. 
         [0048]    An electric power divider  315  drives the lighting unit  316  in accordance with the statuses of the respective switches  312  and  313 . It carries out optical communication by modulating in accordance with data to be transmitted while supplying electric power sufficient for lighting to the lighting unit  316 . On the other hand, it carries out communication without lighting by modulation-controlling in conformity with data to be transmitted so as to make the lighting unit  316  blink a necessary number of times for communication. 
         [0049]    For example, when the switches  312  and  313  are turned on, illuminative light communication is carried out through modulation while the lighting unit  316  is illuminating. In addition, when the switch  312  is turned off and the switch  313  is turned on, communication is carried out by driving the lighting unit  316  in conformity with a modulation signal from an optical modulator  311 , and making the lighting unit  316  emit for a short time in conformity with data to be transmitted. Short time light emission is unperceivable. Accordingly, even when light is actually emitted, it appears to the human eye as if not illuminating, thereby allowing carrying out communication even when not illuminating. Note that when the switch  312  is turned on and the switch  313  is turned off, ordinary lighting is carried out; otherwise, when both the switches  312  and  313  are turned off, communication is not carried out without lighting. 
         [0050]    In this manner, since without lighting, the lighting unit  316  is controlled not to continuously illuminate, but is allowed to illuminate for a short time in conformity with data, visible light communication can be carried out by the lighting unit  316  while it appears to the human eye as if not illuminating. 
         [0051]    As described above, other than communication through short time light emission, communication by making the lighting unit  316  emit a low intensity of light that allows communication is possible. In this case, without lighting, communication is often possible as long as lighting is not completely prohibited, or illuminating with almost the same intensity as that provided by a safety lamp. 
         [0052]    As described above, the present invention allows provision of an illuminative light communication device capable of carrying out communication even without lighting, and also provision of a lighting element preferable to be used for the illuminative light communication device. 
         [0053]    An illuminating facility may be available around the clock, or otherwise, may not illuminate while unattended, while surrounded by sunlight or while using a projector. An attempt of data transmission using only illuminative light in such a case develops a problem that lighting is required as data is transmitted. The present invention allows communication even without lighting by carrying out infrared light communication without lighting, or by using a low light intensity for short-time communication. 
         [0054]    In addition, in the case of using infrared light communication, provision of a lighting element integrally made up of an illuminative light emitting element and an infrared light emitting element allows infrared light communication without lighting, as described above. Furthermore, lights ranging from visible light to infrared light can be emitted by an integrated element, which allows decrease in device size. In other words, rather than using an independent lighting system and an independent infrared data communication system, a new compact system structured by integrating lighting elements can be provided. From a different point of view, wireless infrared light data communication has been well-known, but it has been structured regardless of lighting. In other words, a transmitter/receiver unit other than a lighting unit is fixed to the ceiling. Therefore, it is often difficult to fix it across a large area of the ceiling, and an adverse influence of shadowing or the like may prevent utilization thereof. However, use of the lighting elements, according to the present invention, allows easy integration of an infrared light data communication system and a lighting system. Since lighting units are typically fixed to a large area of the ceiling or the like, the lighting elements, according to the present invention, can be easily fixed to the large area for data communication. As a result, an adverse influence of shadowing is decreased, and reliable wireless infrared light communication can be provided.