JP2012191498A - Visible light communication device, visible light communication system, and visible light communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably provide transmission and reception of visible light data even when the lighting time of an LED lamp varies with time.SOLUTION: According to an embodiment, a visible light communication device comprises a light-emitting module, a detection module, and a transmission control module. The light-emitting module causes a light-emitting source to emit visible light according to variation with time in power output value. The detection module detects timing at which the power output value exceeds a reference set value. The transmission control module superimposes transmission data on the visible light and transmits the superimposed data according to the timing.

Description

  Embodiments described herein relate generally to a visible light communication apparatus that transmits and receives data using visible light.

  In recent years, the development of visible light communication devices that transmit and receive data by modulating and demodulating visible light has been promoted. As a receiving device of a visible light communication device, there is a receiving device that extracts data from transmitted visible light using an image sensor such as a video camera.

  In such a visible light receiving system using an image sensor, an LED (light emitting diode) illumination lamp (hereinafter sometimes referred to as an LED lamp) or the like is used as a visible light emission source on the visible light transmitter side. In this case, a DC lighting type LED lamp that is continuously lit at a constant intensity is effective.

JP 2008-245231 A

  In the visible light reception system using an image sensor, when the LED lamp is not lit continuously at a constant intensity, the lighting condition of the LED lamp fluctuates with time, so data is reliably obtained from the received visible light. Extraction may not be possible. Specifically, there are a case where the LED lamp is turned on by drive control in which the smoothing process is not performed after the AC power source is rectified, and a case where dimming control is performed to adjust the light amount by a PWM (pulse width modulation) method.

  Therefore, even when the lighting state of the LED lamp fluctuates with time, it is required to reliably transmit / receive visible light data.

  According to the present embodiment, the visible light communication device includes a light emitting unit, a detecting unit, and a transmission control unit. The light emitting means emits visible light corresponding to the temporal change of the power output value from the light emitting source. The detecting means detects a timing at which the power output value exceeds a reference set value. The transmission control means transmits transmission data superimposed on the visible light according to the timing.

The block diagram for demonstrating the structure of the visible light communication system regarding embodiment. The timing chart for demonstrating operation | movement of the visible light transmitter regarding embodiment. The timing chart for demonstrating operation | movement of the visible light transmitter regarding embodiment. The figure for demonstrating the format of the visible light communication data regarding embodiment. The block diagram for demonstrating the structure of the transmission control apparatus regarding embodiment. The block diagram for demonstrating the structure of the visible light receiver regarding embodiment. The timing chart for demonstrating operation | movement of the visible light receiver regarding embodiment. The timing chart for demonstrating operation | movement of the visible light receiver regarding embodiment. The timing chart for demonstrating operation | movement of the visible light receiver regarding embodiment. The flowchart for demonstrating the visible light transmission / reception operation | movement regarding embodiment.

  Embodiments will be described below with reference to the drawings.

[Configuration of visible light communication device]
FIG. 1 is a block diagram for explaining a configuration of a visible light communication (transmission / reception) system according to this embodiment.

  As shown in FIG. 1, the visible light communication system of the present embodiment includes a visible light transmitter that emits visible light 100 and transmits data, and a visible light receiver 20 that receives visible light 100 and receives data. It consists of.

  The visible light transmitter includes an LED lamp 10 as a light source that emits visible light 100, a support member 11 that supports the LED lamp 10, and a transmission controller 12. The LED lamp 10 is an illumination lamp having a dimming function, for example. The transmission control device 12 controls the LED lamp 10 to transmit the transmission data superimposed on the visible light 100. The LED lamp 10 is, for example, a road lamp installed on the road.

  On the other hand, the visible light receiving device 20 receives the visible light 100 emitted from the LED lamp 10 by the video camera 23 and performs a receiving process for demodulating the transmission data (modulated transmission data) superimposed on the visible light 100. . The video camera 23 incorporates an image sensor such as a CCD or a CMOS, and outputs image data to be photographed including the LED lamp 10.

  The visible light receiving device 20 is roughly divided into a controller 21 and a memory 22. The controller 21 is a computer or dedicated hardware that executes image processing software. The memory 22 is a memory for storing an image memory and image processing software described later. The visible light receiving device 20 is mounted on a vehicle traveling on a road, for example, and receives road traffic information and the like distributed by visible light communication.

(Configuration of visible light transmitter)
FIG. 5 is a block diagram for explaining the configuration of the transmission control apparatus 12 of the visible light transmission apparatus according to this embodiment. The transmission control device 12 includes a rectification unit 13, a comparator 15, a delay unit 16, a buffer memory 17, an encoder 18, and an LED control unit 19.

  The rectification unit 13 rectifies the power output of the AC power supply 14 without smoothing, and supplies the rectified unit 13 to the comparator 15 and the LED control unit 19. That is, as shown in FIG. 2, the rectifier 13 supplies a power output waveform 120 in which the current level (I), which is a power output value, fluctuates, to the comparator 15 and the LED controller 19. In the present embodiment, the current level (I) is assumed as the power supply output value.

  The comparator 15 compares the current level I which is the power supply output value of the rectifier 13 with a preset reference level (reference set value) RL, and the timing when the current level I from the rectifier 13 exceeds the reference level RL. The detection signal is output with. The delay unit 16 outputs a start signal 160 to the encoder 18 after a predetermined time has elapsed since the rising edge of the detection signal from the comparator 15.

  The encoder 18 reads data that can be superimposed during one ON period of the power output waveform 120 from the transmission data stored in the buffer memory 17 in response to the start signal 160 and outputs the data to the LED control unit 19 after modulation. The LED control unit 19 superimposes the modulated data 180 on the power output waveform 120 supplied from the rectifying unit 13 and supplies the modulated data 180 to the LED lamp 10 to control driving (see FIG. 3).

(Configuration of visible light receiver)
FIG. 6 is a block diagram for explaining the configuration of the visible light receiving apparatus 20 of the present embodiment.

  The visible light receiving device 20 includes an image input control unit 24, an image memory 25, an attention area setting unit 26, an image output control unit 27, a luminance value calculation unit 28, a background luminance calculation unit 29, and a luminance difference calculation. Part 30 and bit string decoder 31.

  The image input control unit 24 receives the video output from the image sensor 23 of the video camera, converts it into image data, and stores it in the image memory 25 in the order of frames. Here, the image sensor 23 outputs an image of an area specified by the attention area setting unit 26 under the control of the image output control 27.

  The luminance value calculation unit 28 sequentially reads image data from the image memory 25 and calculates a temporal change in the intensity of the visible light signal (visible light on which the data is superimposed). Specifically, the luminance value calculation unit 28 calculates the luminance value of the attention area of the image data read from the image memory 25, and calculates the fluctuation of the luminance value as the calculation result. This luminance value data is time-series data in the frame order input by the image sensor 23.

  The background luminance calculation unit 29 calculates a background luminance variation obtained by removing the data superimposition from the change in the intensity time of the visible light signal calculated by the background luminance calculation unit 28. The luminance difference calculation unit 30 calculates the difference between the intensity time change of the visible light signal and the background luminance time change, and extracts visible light communication data (transmission data superimposed on the visible light). The bit string decoder 31 decodes the extracted visible light communication data and restores the data bit string of the transmission data.

(Visible light transmission / reception operation)
The visible light transmission / reception operation of the present embodiment will be described with reference to the flowchart of FIG.

  In the visible light transmission device of this embodiment, as shown in FIG. 1, the transmission control device 12 controls the LED lamp 10 and visible light communication data in which transmission data is superimposed on the visible light 100 emitted from the LED lamp 10. Send. Here, as shown in FIG. 2, the LED lamp 10 is supplied with power output from the rectifying unit 13 in which the current level (I) that is the power output value varies. That is, the current flowing through the LED lamp 10 changes with time, and consists of a period in which the current value is large and a period in which the current value is small or zero. Such control of the LED lamp 10 includes, for example, dimming control in which lighting on and off is controlled temporally.

  FIG. 4 is a diagram illustrating an example of a format of visible light communication data. As shown in FIG. 4A, transmission data in units of frames is superimposed while the LED lamp 10 is lit. As shown in FIG. 4B, in the frame configuration, the start area (SOF) includes a preamble part (PRE) and a data size part (D-SIZE). The payload includes the main body of transmission data. As shown in FIG. 4C, the transmission data is modulated into a pulse train in the time axis direction in which, for example, a 2-bit code is a horizontal axis.

  In the lighting state of the LED lamp 10 as described above, the transmission control device 12 detects the current level I that is the power output value of the rectifying unit 13 (step S1). That is, the comparator 15 compares the current level I of the rectifying unit 13 with the reference level RL, and outputs a detection signal at a timing when the current level I from the rectifying unit 13 exceeds the reference level RL. This detection signal is a signal indicating the timing at which the current level I rises to a level effective for lighting the LED lamp 10. In other words, the detection signal is a signal indicating the rising timing of the pulse waveform of the power supply output from the rectifying unit 13.

  The delay unit 16 outputs a start signal 160 to the encoder 18 after a predetermined time has elapsed from the rising edge of the detection signal from the comparator 15 (step S2). The encoder 18 reads from the transmission data stored in the buffer memory 17 in response to the start signal 160, data that can be superimposed during one ON period (the lighting period of the LED lamp 10) of the power output waveform 120 (step S3). . Here, the buffer memory 17 stores transmission data such as road traffic information distributed by a network from a server (not shown).

  The encoder 18 encodes (modulates) the transmission data into predetermined code data 180 and outputs it to the LED control unit 19 (step S4). As shown in FIG. 3, the LED control unit 19, in the power output waveform 120 supplied from the rectifying unit 13, the LED lamp 10 so as to superimpose the modulated data 130 in the period of the current level exceeding the reference level RL. Is controlled (step S5).

  On the other hand, as shown in FIG. 1, the visible light receiving side of the present embodiment receives visible light 100 emitted from the LED light 10 on the visible light transmitting side, and receives visible light communication data. Here, the video camera 23 and the visible light receiving device 20 are mounted on a vehicle traveling on a road, for example.

  In the visible light receiving device 20, the image input control unit 24 inputs an image output from the image sensor 23 of the video camera (step S11). Here, the image sensor 23 outputs video of the set frame rate and the area (output range) specified by the attention area setting unit 26 under the control of the image output control 27. That is, the image sensor 23 outputs an image in a range including the LED lamp 10 on the visible light transmission side.

  The image input control unit 24 converts the input video into image data and stores it in the image memory 25 in the order of frames (step S12). Next, the luminance value calculation unit 28 sequentially reads the image data from the image memory 25, and calculates luminance value data for a period in which the luminance value exceeds a predetermined value from the variation of the luminance value (step S13). That is, as shown in FIG. 7, the luminance value calculation unit 28 calculates luminance value data for a period indicating a predetermined intensity from a temporal change in the intensity of the visible light signal on which the modulation data 130 is superimposed. This luminance value data is time-series data in the frame order input by the image sensor 23.

  Further, as shown in FIG. 8, the background luminance calculation unit 29 calculates a background luminance variation 120 obtained by removing the superimposed data from the intensity time change of the visible light signal calculated by the background luminance calculation unit 28 (step S <b> 14). ). The luminance difference calculation unit 30 calculates the difference between the intensity time change of the visible light signal and the background luminance time change, and extracts the visible light communication data 140 (transmission data superimposed on the visible light) as shown in FIG. (Step S15). The bit string decoder 31 decodes the extracted visible light communication data 140 and restores the data bit string of the transmission data (step S16).

  As described above, according to the present embodiment, the visible light transmission device detects a change in the power output value (current value) of the LED lamp 10 and transmits transmission data in a period effective for lighting in which the current value exceeds the reference value. The superimposed visible light communication data is transmitted. Therefore, even when the LED lamp 10 is an illumination lamp having a dimming function, for example, the power supply current value changes with time and the effective lighting period is not continuous, the transmission data is superimposed on the visible light 100 and transmitted. It becomes possible.

  Specifically, when the LED lamp 10 is used as, for example, a road lamp installed on a road, transmission data such as road traffic information is transmitted using visible light 100 that is discontinuously emitted from the LED lamp 10. It becomes possible to superimpose and deliver.

  On the other hand, the visible light receiving device detects the luminance fluctuation of the visible light from the LED lamp 10 from the video input to the image sensor 23, so that the transmission data is transmitted from the visible light communication data 130 in a period in which the luminance value is a certain level or more. 140 can be extracted. The visible light receiving device can receive transmission data such as road traffic information distributed from the LED lamp 10 by decoding the transmission data 140.

  Specifically, a vehicle traveling on a road receives the visible light 100 that is discontinuously emitted from the LED lamp 10 that is a road light by mounting the video camera 23 and the visible light receiving device 20. For example, transmission data such as road traffic information can be received.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

10 ... LED lamp, 11 ... support member, 12 ... transmission control device,
13 ... Rectifying unit, 14 ... AC power supply, 15 ... Comparator, 16 ... Delay unit,
17 ... Buffer memory, 18 ... Encoder, 19 ... LED control unit,
20 ... Visible light receiving device, 21 ... Controller, 22 ... Memory,
23 ... Video camera, 24 ... Image input controller, 25 ... Image memory,
26 ... attention area setting unit, 27 ... image output control unit, 28 ... luminance value calculation unit 29 ... background luminance calculation unit, 30 ... luminance difference calculation unit, 31 ... bit string decoder.

Claims (11)

A light emitting means for emitting visible light corresponding to a temporal change in a power output value from a light source;
Detecting means for detecting a timing at which the power output value exceeds a reference set value;
A visible light communication apparatus comprising: a transmission control unit that transmits transmission data superimposed on the visible light according to the timing. The detection means includes
The power supply output value is compared with a reference set value, and a timing after a predetermined delay time from the time when the power supply output value exceeds the reference set value is detected. The visible light communication apparatus described. The transmission control means includes
Modulation means for modulating the transmission data according to the timing;
The visible light communication apparatus according to claim 1, further comprising a control unit that superimposes the transmission data modulated by the modulation unit on the visible light. The detection means includes
4. The visible light communication device according to claim 1, wherein the visible light communication device is configured to detect a rising edge of a pulse waveform of a predetermined level as the power output as the timing. 5. The detection means includes
The visible light communication apparatus according to any one of claims 1 to 4, wherein either one of a current value and a voltage value is used as the power supply output value. The light emitting means includes
LED is used as the light source,
The visible light communication apparatus according to claim 1, further comprising means for controlling lighting of the LED in accordance with a temporal change in the power output level. Image input means for receiving visible light emitted from a light source and converting it into image data, and inputting image data including the light source;
Luminance value calculating means for calculating luminance value data indicating temporal changes in luminance values from the image data;
A visible light communication apparatus comprising: data detection means for detecting data superimposed on the visible light based on the luminance value data. The data detecting means includes
Based on the luminance value data, luminance difference means for calculating a difference between a visible light signal having a luminance value equal to or greater than a predetermined value in the luminance value variation of the visible light and a background signal;
The visible light communication apparatus according to claim 7, further comprising: means for extracting and demodulating data superimposed on the visible light based on the luminance difference value calculated by the luminance difference means. A visible light communication system comprising a visible light transmitting device for transmitting data using visible light and a visible light receiving device for receiving the data,
The visible light transmitter is
A light emitting means for emitting visible light corresponding to a temporal change in a power output value from a light source;
Detecting means for detecting a timing at which the power output value exceeds a reference set value;
Transmission control means for transmitting transmission data superimposed on the visible light according to the timing,
The visible light receiving device is:
Image input means for receiving visible light emitted from a light source and converting it into image data, and inputting image data including the light source;
Luminance value calculating means for calculating luminance value data indicating temporal changes in luminance values from the image data;
A visible light communication system comprising: data detection means for detecting data superimposed on the visible light based on the luminance value data. A process of emitting visible light according to the temporal change of the power output value from the light source;
A process of detecting a timing at which the power output value exceeds a reference set value;
The visible light communication method which performs the process which superimposes transmission data on the said visible light according to the said timing, and transmits. Receiving visible light emitted from a light source, converting it into image data, and inputting image data including the light source;
Processing for calculating luminance value data indicating temporal changes in luminance values from the image data;
A visible light communication method for executing processing for detecting data superimposed on the visible light based on the luminance value data.

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