JP2008182446A - Two-way visible-light communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two-way visible-light communication apparatus which uses semiconductor light-emitting devices for both lighting and receiving light and dose not require devices for receiving light. <P>SOLUTION: A timing generator 16 generates and outputs switching signals to switch receiving and transmission at a period where lighting functions due to turning off of a group of light-emitting devices 13 are not impaired, when receiving. When transmitting, a modulator 11 modulates transmission data and transmits it to the group of light-emitting devices 13 through a switching part 12. Then, each semiconductor light-emitting device of the group of light-emitting devices 13 blinks or emits a light, while changing the amount of light, according to the modulated transmission data to transmit the transmission data; meanwhile, when receiving, the group of light-emitting devices 13 does not emit light but will receive the light and outputs signals. The signals are transmitted to a receiver 14 through the switching part 12 and demodulated, and as a result, data transmitted from a communication terminal device 2 is received. Thereby, a plurality of semiconductor light-emitting devices receive light, so that strong signals can be acquired. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for performing communication using illumination light.

  In recent years, illumination using a semiconductor light emitting element such as an LED (Light Emitting Diode) as a light source has been put into practical use, and a technique for transmitting information using the illumination light has been proposed in, for example, Patent Document 1. In order to use as illumination, a certain amount of intense light is required, and information can be transmitted by such intense light. In order to obtain such strong light, the lighting device is provided with a number of semiconductor light emitting elements to emit light.

  However, since the illumination light is only emitted from the illumination device, the communication is only in one direction. In order to realize bidirectional communication, a light receiving element is conventionally provided in a lighting fixture. For example, in Patent Document 2, a visible light or infrared light receiving element is provided separately from the semiconductor light emitting element for illumination.

  On the other hand, for example, Non-Patent Document 1 discloses that a single LED, which is a light emitting element, can be used as a light receiving element. However, the light receiving characteristics of LEDs are inferior to the light receiving characteristics of photodiodes currently widely used as light receiving elements. Therefore, the optical system for condensing light, such as a lens, is provided, and communication can only be performed in a state where transmission and reception are fixed.

  Further, in order to use the light emitting element as a light receiving element as it is, it is necessary to receive light without emitting light. However, when a light emitting element is used as illumination, there is a problem that the function as illumination is lost if the light emitting element is not allowed to emit light.

Japanese Patent No. 3827082 JP 2004-221747 A Kensho Okamoto, “New optical device using ultra-high brightness light emitting diode as light emitting and receiving element”, IEICE, IEICE Technical Report OQE90-7, 1990

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a bidirectional illumination optical communication device that uses a semiconductor light emitting element that performs illumination for light reception as it is, and does not require an element for light reception. It is what.

  The present invention provides a bidirectional illumination light communication apparatus, a light emitting means comprising a plurality of semiconductor light emitting elements that emit illumination light, a modulation means that modulates data to be transmitted to change blinking or light quantity of the light emitting means, A receiving means for receiving data transmitted based on a signal obtained when the light emitting means is not emitting light, transmission of data by light emission of the light emitting means, and no light emission of the light emitting means. And a timing signal generating means for generating a switching signal for switching the transmission and reception of data in a time division manner with respect to the switching means.

  The light emitting means connects a plurality of semiconductor light emitting elements in parallel, or groups several of the plurality of semiconductor light emitting elements as a group, connects the semiconductor light emitting elements in the group in series, and connects each group in parallel. Can be connected and configured. Alternatively, the connection of the plurality of semiconductor light emitting elements can be configured to be switched to a parallel connection or a series connection by a switching signal from the timing signal generation unit.

  The timing signal generating means generates a switching signal for switching transmission / reception of data at a cycle in which flicker does not occur even when the light emitting means is turned off at the time of data reception.

  According to the present invention, the light emitting means composed of a plurality of semiconductor light emitting elements provided for illumination can be used for data transmission and data reception, and data can be transmitted and received only by the light emitting means. It can be carried out. In addition, a single semiconductor light emitting device has a very small output during light reception, but by receiving light using a plurality of semiconductor light emitting devices provided for illumination, an output sufficient for receiving data can be obtained. Can do.

  Furthermore, when data is received, it must be performed in a state in which the light emitting means does not emit light, and illumination cannot be performed by turning off the light emitting means. In the present invention, by switching between transmission and reception at high speed, it appears to the human eye as if it is continuously lit, and thus there is an effect that data can be transmitted and received while performing illumination.

  FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is an illumination device, 11 is a modulation unit, 12 is a switching unit, 13 is a light emitting element group, 14 is a reception unit, 15 is a timing generation unit, 2 is a communication terminal device, 21 is a light receiving unit, and 22 is a reception unit. , 23 is a synchronization unit, 24 is a modulation unit, and 25 is a light emitting unit.

  The lighting device 1 includes a light emitting element group 13 for emitting light to illuminate, and a modulation unit 11, a switching unit 12, a receiving unit 14, a timing generation unit 15, and the like.

  The modulation unit 11 modulates transmission data to be transmitted with illumination light. The modulation method may be a method in which the amount of light emitted from the light emitting element group 13 is made as uniform as possible regardless of the transmission data to be transmitted.

  The switching unit 12 switches between transmission and reception, and passes transmission data modulated by the modulation unit 11 to the light emitting element group 13 during transmission, and passes a signal received by the light emitting element group 13 to the receiving unit 14 during reception. A switching signal for switching between transmission and reception is received from the timing generation unit 15.

  The light emitting element group 13 includes a plurality of semiconductor light emitting elements such as LEDs and LDs (Laser Diodes). In this embodiment, the semiconductor light emitting elements are connected in parallel. At the time of transmission, the light is emitted by blinking or changing the amount of light according to the transmission data modulated by the modulation unit 11 and used as illumination light as a whole. Further, at the time of reception, there is no signal for light emission, and the received signal is transmitted to the receiving unit 14. At this time, since the semiconductor light emitting elements are connected in parallel, if signal light (signal light emitted from the communication terminal device 2) is irradiated within a certain range, the light can be received by a plurality of semiconductor light emitting elements. Also grows. In addition, in the case of series connection, reception is not possible unless all semiconductor light emitting elements are irradiated with signal light, but in the case of parallel connection, reception is possible even when signal light is partially irradiated.

  As the LEDs used as the respective semiconductor light-emitting elements constituting the light-emitting element group 13, it is desirable to use LEDs that emit white light or a color close to white in order to emit illumination light. However, the LED has a characteristic that the reception sensitivity is higher as the wavelength is closer to red. Therefore, for example, an element that emits light of RGB three wavelengths is used rather than a light source that irradiates phosphor with blue light and obtains white light, and a light reception signal of red light among the three wavelengths is obtained. Furthermore, the light receiving area may be increased by using a reflective LED or the like.

  The receiving unit 14 demodulates the signal received by the light emitting element group 13 and outputs received data.

  The timing generation unit 15 generates a switching signal for switching transmission and reception in a time division manner. At this time, since the light emitted from the light emitting element group 13 is assumed to be used as illumination, it is necessary to prevent the illumination from being obstructed when the light is turned off at the time of reception, or to prevent people from flickering. Therefore, it is desirable to perform the switching cycle at several kHz or more. Of course, the lighting time and the lighting time do not have to be the same, and the lighting time may be longer during lighting. Conversely, when the illumination is turned off, the reception time may be lengthened, or the reception state may be set while transmission is not being performed.

  The communication terminal device 2 has a function of receiving data transmitted by illumination light from the illumination device 1 and transmitting data by light. As a configuration for that purpose, the communication terminal device 2 includes a light receiving unit 21, a receiving unit 22, a synchronizing unit 23, a modulating unit 24, a light emitting unit 25, and the like.

  The light receiving unit 21 receives illumination light and converts it into an electrical signal. For example, it can be composed of an element such as a photodiode that converts light into an electrical signal. The receiving unit 22 demodulates the signal output from the light receiving unit 21 and receives the original data. In addition, the signal received from the light receiving unit 21 is also passed to the synchronizing unit 23, and the data is received according to the synchronizing signal received from the synchronizing unit 23.

  The synchronization unit 23 detects the transmission timing in the lighting device 1 based on the signal passed from the reception unit 22, and passes the detection result to the reception unit 22 and the modulation unit 24. In particular, since the lighting device 1 switches between transmission and reception as described above, it can be synchronized by paying attention to the fact that the illumination light disappears when the lighting device 1 enters the reception phase.

  The modulation unit 24 modulates data to be transmitted to the lighting device 1 according to the synchronization signal from the synchronization unit 23 and passes the data to the light emitting unit 25. The light emitting unit 25 converts the modulated data passed from the modulation unit 24 into light and transmits the light. As the light emitting unit 25, a light emitting element such as an LED can be used. The emitted light should have a wavelength that can be received as efficiently as possible by the light emitting element group 13 of the illumination device 1. For example, when an RGB light emitting element is used as the semiconductor light emitting element 13, a color close to red may be used.

  In the communication terminal device 1, the light receiving unit 21 and the light emitting unit 25 may be configured by light emitting elements in the same manner as the lighting device 1.

  Next, the operation in one embodiment of the present invention will be described. In the following description, it is assumed that light emitted by the light emitting element group 13 is used as illumination. The timing generation unit 16 generates and outputs a switching signal for switching between reception and transmission in a cycle in which the function as illumination is not impaired by turning off the light emitting element group 13 at the time of reception.

  When transmission data is transmitted by illumination light using a switching signal from the timing generation unit 16, the modulation unit 11 modulates the transmission data, and the switching unit 12 supplies the modulated transmission data to the light emitting element group 13. Thereby, each semiconductor light emitting element of the light emitting element group 13 emits light by blinking or changing the amount of light according to the modulated transmission data, and transmits the transmission data. The blinking or light amount fluctuation at this time is not perceived by human eyes by performing at high speed. Further, if transmission data is modulated so that the amount of illumination light does not fluctuate, the light emitted by the light emitting element group 13 can be used as substantially uniform illumination light.

  If the illumination light emitted from the light emitting element group 13 is received by the light receiving unit 21 of the communication terminal device 2 and demodulated by the demodulation unit 22, transmission data can be received. In the communication terminal device 2, the synchronization unit 23 detects the transmission / reception switching timing in the lighting device 1 from the signal obtained by receiving the illumination light, and receives data and transmits data according to the detected timing.

  On the other hand, when data is transmitted from the communication terminal device 2 to the lighting device 1, the lighting device 1 is in a receiving state according to the transmission / reception switching timing of the lighting device 1 detected by the synchronization unit 23 by receiving the illumination light. Sometimes, the light emitting unit 25 is driven by the data modulated by the modulating unit 24, and the data is transmitted by light.

  In the illuminating device 1, when data is received, the switching unit 12 performs switching so that a signal from the light emitting element group 13 is passed to the receiving unit 14 by a switching signal from the timing generation unit 16. Light emitted from the light emitting unit 25 of the communication terminal device 2 and modulated by data is received by the light emitting element group 13. At this time, since the light from the communication terminal device 2 is diffused to some extent, it is received by a plurality of semiconductor light emitting elements connected in parallel and converted into an electrical signal by each semiconductor light emitting element. Accordingly, although one semiconductor light emitting element has a small light receiving capability, a larger signal can be obtained by receiving light with a plurality of semiconductor light emitting elements. Note that the magnitude of the signal at the time of reception increases as the number of semiconductor light emitting elements increases.

  The signal output from the light emitting element group 13 is input to the receiving unit 14 and can be demodulated to receive data transmitted from the communication terminal device 2.

  A specific example of communication according to an embodiment of the present invention will be described. FIG. 2 is an explanatory diagram of an example of data transmission / reception. Here, as an example, a PPM (Pulse Position Modulation) method is used as a modulation method, one symbol is configured by 8 slots, and the first 4 slots are used for communication from the lighting device 1 to the communication terminal device 2. The latter four slots are used for communication from the communication terminal device 2 to the lighting device 1. Then, it indicates one of 00, 01, 10, and 11, which is a 2-bit pattern, depending on which of the four slots each has a pulse.

  In the example shown in FIG. 2, when transmitting from the lighting device 1 to the communication terminal device 2, a generally used PPM waveform is inverted and used. That is, the waveform falls at the position where the pulse exists. Thus, by taking a long ON time, a reduction in the amount of illumination light is suppressed as much as possible. Further, in PPM, the ON / OFF time does not change so much depending on the data, so that a stable illumination light quantity can be secured.

  Concerning communication from the communication terminal device 2 to the lighting device 1, the power consumption can be suppressed by shortening the light emission time, contrary to the lighting device 1, so the generally used PPM method is used. Sending data.

  FIG. 3 is an explanatory diagram of an example of a timing detection method in the communication terminal device 2. As shown in FIG. 2, when data is transmitted from the lighting device 1 using the inverted waveform of the PPM method, the latter four slots are always OFF, and any one slot is also OFF for the first four slots. It only becomes. If the lighting device 1 is not transmitting data, the first four slots are all ON.

  Using such characteristics, the synchronization unit 2 of the communication terminal device 2 can detect the transmission / reception switching timing in the lighting device 1. That is, as shown in FIG. 3A, various types of data are transmitted from the lighting device 1, or if no data is transmitted, received signals for one frame (8 slots) are combined, added, or averaged. As shown in FIG. 3B, the first four slots are turned on and the latter four slots are turned off as shown in FIG. If this rising or falling edge is detected, the transmission / reception switching timing in the illumination device 1 can be detected in the communication terminal device 2. Data transmission / reception may be switched in the communication terminal device 2 using the switching timing thus detected.

  In order to detect the switching timing, it is necessary to synthesize, add, or average the illumination light from the lighting device 1 for a plurality of frames. However, if the number of frames is increased, more accurate timing can be detected. can do. In addition, when the lighting device 1 is turned off, data can be transmitted using a general PPM waveform. However, even in this case, if the data is transmitted from the lighting device 1, the switching timing is detected by the same method. Can communicate.

  The above-described communication method is an example, and the number of slots for one symbol and the number of assigned slots in one symbol may be determined at the time of design. For example, a method is possible in which 1 symbol is 12 slots, 8 slots are used for communication from the lighting device 1 to the communication terminal device 2, and 4 slots are used for communication from the communication terminal device 2 to the lighting device 1. In this case, since the time during which the light emitting element group 13 of the lighting device emits light becomes longer, the amount of illumination light can be increased. Of course, the modulation method is not limited to PPM, but a modulation method with little variation in the amount of light as illumination light may be selected.

  FIG. 4 is a block diagram showing a first modification in one embodiment of the present invention. In the configuration example shown in FIG. 1, the semiconductor light emitting elements in the light emitting element group 13 are connected in parallel. When connected in parallel as described above, it is possible to use signals from the respective semiconductor light emitting elements irradiated with light from the communication terminal device 2 when receiving data. However, since it is necessary to supply a driving current to each semiconductor light emitting element connected in parallel when emitting light, the driving current increases. Therefore, in order to reduce the current during light emission, in the modification shown in FIG. 4, several semiconductor light emitting elements are connected in series as a group, and such groups are connected in parallel. The configuration of the communication terminal device 2 may be the same as the configuration shown in FIG.

  In such a configuration, the voltage when driving the light emitting element group 13 to emit light can be increased and the current can be lowered, and the light emitting element group 13 can be driven with a smaller current than the configuration shown in FIG. In addition, since a signal can be output if light is applied to the semiconductor light emitting elements in the group, even when light is applied to a part of the light emitting element group 13, the light can be received and output.

  FIG. 5 is a block diagram showing a second modification of the embodiment of the present invention. This second modification shows a configuration in which the connection of each semiconductor light emitting element of the light emitting element group 13 is switched to a serial connection at the time of transmission and to a parallel connection at the time of reception. FIG. 5 (A) shows the case of switching to a serial connection, and FIG. 5 (B) shows the case of switching to a parallel connection. Although illustration of the communication terminal device 2 is omitted, the configuration may be the same as in FIG.

  When transmitting data from the illuminating device 1, a large amount of electric power is required because the illumination light is emitted. Therefore, as shown in FIG. 5A, switching is performed so that the semiconductor light emitting elements are connected in series. As a result, a high voltage is applied and light emission can be driven with a small current. At the time of reception, in order to efficiently use the signal received and output by each semiconductor light emitting element, switching is performed so that the semiconductor light emitting elements are connected in parallel as shown in FIG. When a plurality of semiconductor light emitting elements are connected in series, only the weakest signal is output from the signals output from the serially connected semiconductor light emitting elements. Can be used.

  The switching between the series connection and the parallel connection can be performed using a switching signal from the timing generation unit 15 used for switching between transmission and reception by the switching unit 12.

  The above-described embodiment and its modifications are merely examples, and it goes without saying that other various modifications are possible without departing from the scope of the present invention.

It is a block diagram which shows one Embodiment of this invention. It is explanatory drawing of an example of transmission / reception of data. It is explanatory drawing of an example of the timing detection method in the communication terminal device. It is a block diagram which shows the 1st modification in one Embodiment of this invention. It is a block diagram which shows the 2nd modification in one Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Illuminating device, 11 ... Modulating part, 12 ... Switching part, 13 ... Light emitting element group, 14 ... Receiving part, 15 ... Timing generation part, 2 ... Communication terminal device, 21 ... Light receiving part, 22 ... Receiving part, 23 ... Synchronization unit, 24... Modulation unit, 25.

Claims (5)

  Light receiving means comprising a plurality of semiconductor light emitting elements for emitting illumination light, modulation means for modulating the data to be transmitted to change the blinking or light quantity of the light emitting means, and light received by the light emitting means not emitting light Receiving means for receiving data sent based on signals obtained from time to time, switching means for switching between transmission of data by light emission of the light emitting means and reception of data performed without causing the light emitting means to emit light, A bidirectional illumination optical communication apparatus comprising timing signal generation means for generating a switching signal for switching transmission / reception of data in a time division manner with respect to the switching means.   The bidirectional illumination light communication apparatus according to claim 1, wherein the light emitting means includes a plurality of the semiconductor light emitting elements connected in parallel.   2. The light emitting device according to claim 1, wherein several of the plurality of semiconductor light emitting elements are grouped, the semiconductor light emitting elements in the group are connected in series, and the groups are connected in parallel. Two-way illumination optical communication device.   2. The bidirectional illumination light communication apparatus according to claim 1, wherein the light emitting unit switches the connection of the plurality of semiconductor light emitting elements to a parallel connection or a series connection by a switching signal from the timing signal generation unit.   The timing signal generation unit generates a switching signal for switching transmission / reception of data at a cycle in which flicker does not occur even when the light emitting unit is turned off at the time of data reception. The bidirectional illumination optical communication device according to Item.

Images