JP2008283446A - Visible light communication device and visible light communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a visible light communication device which allows extension of a communication distance while securing illuminance. <P>SOLUTION: A control part 13 causes a current having a first value larger than 0 and a current having a second value larger than the first value to flow to a light source 11 in accordance with data accepted by an acceptance part 12, and data are transmitted by visible light emitted from the light source 11. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a visible light communication apparatus and a visible light communication method capable of communicating with visible light.

  In the visible light communication device, a light source such as an LED that can be controlled electrically is turned on and off, and the light source is blinked at high speed to transmit data.

  In recent years, a visible light communication device that performs communication while satisfying the function as a lighting fixture has been proposed or put into practical use. Such a visible light communication device is described in, for example, Japanese Patent Application Laid-Open No. 2007-81703.

  Such a visible light communication device must ensure a certain level of illuminance in order to satisfy the function as a lighting fixture even during data transmission. For this reason, the visible light communication apparatus performs communication while ensuring the lighting time of the light source by using pulse modulation such as four-value PPM modulation.

  FIG. 4 is an explanatory diagram for explaining on / off control of a light source by quaternary PPM modulation.

  The visible light communication apparatus performs 4-level PPM modulation on the data 101 to generate a PPM signal 102. Specifically, in 4-level PPM modulation, data 101 is divided into 2-bit units, and a PPM signal 102 having a position specified according to each 2-bit data as a pulse is generated. For example, a PPM signal 102 “1000” is generated from the data 101 “00”, a PPM signal 102 “0100” is generated from the data 101 “01”, and a PPM signal 102 “0010” is generated from the data 101 “10”. A PPM signal 102 “0001” is generated from the data 101 “11”. The position of the PPM signal 102 “1” is a pulse.

  At the position of the PPM signal 102 “0”, the visible light communication device continuously supplies current to the light source and keeps the light source on. Further, the visible light communication device causes a current to flow through the light source at the position of the PPM signal 102 “1” and causes the light source to blink. Here, the value of the current supplied to the light source at the time of lighting is the same as the value of the peak current of the pulse at the time of blinking.

Thereby, it becomes possible to ensure the lighting time of a light source, and to ensure illumination intensity.
JP 2007-81703 A

  When a high value current flows through a light source continuously, the possibility that the light source will fail increases.

  When communication is performed using pulse modulation as described above, a current having the same value as the peak current of the pulse flows through the light source continuously, and thus the peak current value cannot be made higher than a predetermined value.

  For this reason, the communication distance does not increase beyond a certain value. This is because the communication distance increases as the peak current value increases. This is because the higher the peak current value, the greater the amount of light emitted by the light source, and a light receiving element such as a photodiode that receives the PPM signal reacts when the amount of light of the PPM signal is greater than a certain value.

  In order to increase the communication distance, it is also conceivable to increase the peak current value by increasing the number of pulses to reduce the time during which current is continuously supplied to the light source. However, with this method, it is difficult to ensure the illuminance necessary to satisfy the function as a lighting fixture.

  Accordingly, an object of the present invention is to provide a visible light communication device and a visible light communication method capable of extending a communication distance while ensuring illuminance.

  In order to achieve the above object, a visible light communication device according to the present invention includes a light source that emits visible light, a reception unit that receives data, and a first greater than 0 according to data received by the reception unit. A control unit that sends a current of a value and a current of a second value larger than the first value to the light source and transmits the data with visible light emitted from the light source.

  Further, the visible light communication method of the present invention includes a receiving step for receiving data, a current having a first value greater than 0, and a second value greater than the first value in accordance with the received data. And a control step of transmitting an electric current to a light source that emits visible light and transmitting the data using visible light emitted from the light source.

  According to the present invention, it is possible to increase the communication distance while ensuring illuminance.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of a visible light communication apparatus according to an embodiment of the present invention.

  In FIG. 1, the visible light communication device 1 includes a light source 11, a reception unit 12, and a control unit 13.

  The light source 11 emits visible light. The light source 11 is, for example, an LED, an organic EL, or an inorganic EL. The light source 11 is not limited to an LED, an organic EL, or an inorganic EL, and can be changed as appropriate.

  The accepting unit 12 accepts data. For example, the reception unit 12 is connected to a communication network such as a power line communication network, and receives data from the communication network.

  In accordance with the data received by the receiving unit 12, the control unit 13 causes the current of the first value greater than 0 and the current of the second value greater than the first value to flow through the light source 11. The data is transmitted by visible light that emits light.

  Specifically, the control unit 13 includes a modulation unit 13a and a drive unit 13b, and each unit performs the following processing.

  The modulation unit 13a performs pulse modulation on the data received by the reception unit 12 to generate a pulse modulation signal. The pulse modulation is preferably multilevel PPM modulation (multilevel pulse position modulation).

  In response to the pulse modulation signal generated by the modulation unit 13a, the drive unit 13b causes the first value current and the second value current to flow through the light source 11, and the visible light emitted from the light source 11 is transmitted. Send data. Specifically, the driving unit 13b causes the current of the second value to flow to the light source 11 at the position of the pulse peak of the pulse modulation signal, and the first value at a position different from the pulse peak of the pulse modulation signal. Is supplied to the light source 11.

  FIG. 2 is an explanatory diagram for explaining data transmitted by visible light.

  Transmission data 201 indicates data transmitted from the light source 11 when the light source 11 blinks.

  The transmission data 202 indicates data transmitted from the light source 11 when a current having a first value and a second value flows through the light source 11. When the transmission data 202 is transmitted, the light source 11 is not turned off, so that it is possible to ensure illuminance. Further, the drive unit 13b increases the communication distance of the transmission data 202 by setting the second value to be larger than the value of the peak current of the pulse of the transmission data 201 (hereinafter referred to as a predetermined peak current). It can be extended from the communication distance.

  Hereinafter, data transmitted with visible light when pulse modulation is multilevel PPM modulation will be described in more detail. The pulse modulation signal is referred to as a PPM signal.

  Transmission data 301 indicates data transmitted by the drive unit 13b blinking the light source 11 when the pulse modulation is multilevel PPM modulation.

  At this time, at the position of the pulse of the PPM signal, the driving unit 13 b causes the light source 11 to blink by causing a predetermined peak current to flow intermittently through the light source 11. On the other hand, at a position different from the pulse in the PPM signal, the driving unit 13b continuously supplies a current having the same value as the value of the predetermined peak current to the light source 11 to keep the light source 11 on.

  The transmission data 302 indicates data that is transmitted when the drive unit 13b sends a first value and a second value of current to the light source 11 when pulse modulation is multilevel PPM modulation.

  At this time, at the position of the pulse of the PPM signal, the driving unit 13b alternately causes the current of the first value and the current value of the second value to flow through the light source 11, and the amount of visible light emitted by the light source 11 Give strength to. In addition, the driving unit 13b continuously turns on the light source 11 by continuously supplying a current having the first value to the light source 11 at a position different from the pulse in the PPM signal.

  Thereby, when the transmission data 302 is transmitted, at least the second value of current flows through the light source 11, and thus the light source 11 is not turned off. For this reason, it becomes possible to ensure illumination intensity. Even if the second value is increased, the current of the second value does not flow to the light source 11 continuously, so that the possibility that the light source 11 will fail can be reduced. For this reason, the second value can be increased, and the communication distance can be increased.

  Next, the operation will be described.

  When receiving the data, receiving unit 12 outputs the data to modulating unit 13a.

  When receiving the data, the modulation unit 13a performs 4-value PPM modulation on the data to generate a PPM signal. The modulation unit 13a outputs the PPM signal to the drive unit 13b.

  The drive unit 13b causes the current of the second value to flow through the light source 11 at the pulse peak position of the pulse modulation signal, and the first value at a position different from the pulse peak of the pulse modulation signal. A current is passed through the light source 11.

  The light source 11 emits visible light with a light amount corresponding to the value of the supplied current, and transmits the data to the light receiving device 2.

  Next, the effect will be described.

  According to the present embodiment, the control unit 13 generates a first value current greater than 0 and a second value current greater than the first value according to the data received by the reception unit 12. The data is transmitted by visible light emitted from the light source 11.

  In this case, a current having a first value larger than 0 and a current having a second value larger than the first value flow to the light source 11 according to the data.

  For this reason, the illuminance can be ensured by the current having the first value. Therefore, the illuminance can be ensured without continuously flowing the current having the second value to the light source 11. Therefore, for example, the communication distance can be extended by causing the current of the second value to flow through the light source 11 intermittently. Therefore, it is possible to increase the communication distance while ensuring illuminance.

  In the present embodiment, the modulation unit 13a generates a pulse modulation signal by pulse-modulating the data received by the reception unit 12. The driving unit 13b causes the current of the second value to flow through the light source 11 at the pulse peak position of the pulse modulation signal generated by the modulation unit 13a, and the current of the first value at a position different from the pulse in the pulse modulation signal. To the light source 11.

  In this case, the second value current flows to the light source 11 at the peak position of the pulse, and the first value current flows to the light source 11 at a position different from the pulse peak.

  For this reason, it becomes possible to ensure illumination intensity with the electric current of the first value. In addition, since the second value current does not continuously flow through the light source 11, the communication distance can be increased by increasing the second value current.

  Furthermore, the smaller the number of pulses, the shorter the time during which the current of the second value flows through the light source 11. Therefore, the smaller the number of pulses, the larger the second value can be, and the communication distance can be increased. Become.

  In this embodiment, the pulse modulation is multilevel PPM modulation.

  In this case, the illuminance can be easily secured.

  In the embodiment described above, the illustrated configuration is merely an example, and the present invention is not limited to the configuration.

It is the block diagram which showed the structure of the visible light communication apparatus of one Example of this invention. It is explanatory drawing for demonstrating the data transmitted with visible light. It is explanatory drawing for demonstrating the data transmitted by visible light when pulse modulation is made into multilevel PPM modulation. It is explanatory drawing for demonstrating on-off control of the light source by 4-value PPM modulation.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Visible light communication apparatus 2 Light receiving apparatus 11 Light source 12 Reception part 13 Control part 13a Modulation part 13b Drive part

Claims (6)

A light source that emits visible light;
A reception unit for receiving data;
According to the data received by the receiving unit, a first value current greater than 0 and a second value current greater than the first value are passed through the light source, and the visible light emitted from the light source A visible light communication device including a control unit that transmits the data by light. The visible light communication device according to claim 1,
The controller is
A modulation unit for pulse-modulating the data received by the reception unit to generate a pulse modulation signal;
The current of the second value is caused to flow through the light source at the position of the pulse peak of the pulse modulation signal generated by the modulation unit, and the first value at a position different from the pulse peak of the pulse modulation signal. Visible light communication device for flowing current of the above to the light source. The visible light communication device according to claim 2,
The visible light communication apparatus, wherein the pulse modulation is multilevel PPM modulation. A reception step for receiving data;
In response to the received data, a current having a first value greater than 0 and a current having a second value greater than the first value are passed through a light source that emits visible light, and the light source emits light. And a control step of transmitting the data with visible light. The visible light communication method according to claim 4,
The control step includes
A modulation step of pulse-modulating the received data to generate a pulse-modulated signal;
The current of the second value is caused to flow through the light source at the position of the pulse peak of the generated pulse modulation signal, and the current of the first value at a position different from the peak among the pulses of the pulse modulation signal. A visible light communication method in which a light is passed through the light source. The visible light communication method according to claim 5,
The visible light communication method, wherein the pulse modulation is multilevel PPM modulation.

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