JP2010141393A - Illumination light communication apparatus and illumination light communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an illumination light communication apparatus capable of reducing a change in luminance between a communication and non-communication without causing deterioration in efficiency; and to provide an illumination light communication system. <P>SOLUTION: The illumination light communication apparatus for using an illumination light source and performing communication by lighting on and off the light source based on transmission information has: a transmission signal generating section for generating a transmission signal based on the transmission information and outputting the transmission signal to the light source; and a dummy signal generating section for generating a dummy signal based on the information about the transmission signal from the transmission signal generating section or the transmission signal and for outputting the generated dummy signal to the light source. A transmission signal output period in which a transmission signal is outputted and a dummy signal output period in which a dummy signal is outputted continue to each other. The dummy signal generating section generates a dummy signal so that a mean value of optical output of the light source in communication during the transmission signal output period and the dummy signal output period may be equal to optical output of the light source in non-communication in which communication based on the transmission information is not performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an illumination light communication apparatus and an illumination light communication system, and more particularly, to an illumination light communication apparatus and an illumination light communication system that use a light emitting element such as an LED (light emitting diode) as an illumination light source.

  In recent years, lighting devices using light emitting elements such as LEDs (light emitting diodes) provide original illumination, that is, “light”, and are also used for data communication and the like. However, if the LED is blinked to perform data communication, the light output (luminance) during communication is the light output during non-communication when data is not transmitted, that is, when the light is steadily lit by a constant DC current. Flickering (luminance change) occurs due to a decrease in light output. Therefore, various methods for suppressing such flicker have been studied.

For example, by controlling the current flowing through the LED when the LED is lit during communication to be larger than the current flowing through the LED during non-communication, and making the light output of the LED equal during communication and non-communication, A method for reducing flicker is known (see Patent Document 1).
JP 2008-34988 A

  However, the method described in Patent Document 1 requires a very high light output in order to compensate for a decrease in light output when the LED is turned off during communication only when the LED is turned on during communication. In other words, it is necessary to flow a very large current so that the light output of the LED is saturated, and there is a problem that the efficiency is lowered. Furthermore, as the current flowing through the LED increases, the overshoot that occurs when switching between lighting and extinguishing increases, and there is a problem of further increasing flicker.

  Specifically, this will be described with reference to FIG. FIG. 6 is a diagram illustrating a relationship between a general LED driving current and light output (luminance). As shown in FIG. 6, the relationship between the drive current and the luminance is approximately linear until the luminance is about 80%. However, when the luminance exceeds 80%, the relationship becomes non-linear and the inclination becomes suddenly gentle. For this reason, when the LED is used in a high luminance region, the efficiency is drastically reduced.

  The present invention has been made in view of the above problems, and an illumination light communication apparatus and an illumination light communication system that can reduce a change in luminance between communication and non-communication without causing a decrease in efficiency. The purpose is to provide.

  The above object is achieved by the invention described in any one of 1 to 5 below.

1. In an illumination light communication apparatus that performs communication by using a light source for illumination and turning on and off the light source based on transmission information,
A transmission signal generating unit that generates a transmission signal based on the transmission information and outputs the generated transmission signal to the light source;
A dummy signal generating unit that generates a dummy signal based on the information related to the transmission signal from the transmission signal generating unit or the transmission signal, and outputs the generated dummy signal to the light source,
The transmission signal output period in which the transmission signal is output and the dummy signal output period in which the dummy signal is output are continuous,
The dummy signal generator is
The average value of the light output of the light source during communication through the transmission signal output period and the dummy signal output period is equal to the light output of the light source during non-communication when the communication based on the transmission information is not performed. The dummy light signal is generated as described above.

  2. 2. The illumination light communication apparatus according to 1 above, wherein the dummy signal is a DC signal.

  3. 2. The illumination light communication apparatus according to claim 1, wherein the dummy signal is a pulse signal obtained by inverting the on and off phases of the transmission signal.

  4). 4. The illumination light communication apparatus according to any one of 1 to 3, wherein the light source is a light emitting diode.

5). 5. The illumination light communication apparatus according to any one of 1 to 4,
And a receiver that receives light from the illumination light communication device and receives the transmission information.

  According to the present invention, the dummy signal output period is provided continuously to the transmission signal output period, and the light output of the light source during communication through the transmission signal output period and the dummy signal output period is determined by the dummy signal in the dummy signal output period. Is equal to the light output of the light source during non-communication when communication based on transmission information is not performed.

  That is, in the transmission signal output period, a decrease in light output when the light source that is repeatedly turned on / off is extinguished is compensated for by a separately provided dummy signal output period without being compensated for within the transmission signal output period. Thus, for example, by adjusting the dummy signal output period, it is possible to sufficiently compensate for the light output that has decreased in the transmission signal output period without flowing a current that is large enough to saturate the light output of the light source. As a result, it is possible to reduce a change in luminance between communication and non-communication without causing a decrease in efficiency.

Embodiments of an illumination light communication device and an illumination light communication system according to the present invention will be described below with reference to the drawings. In addition, although this invention is demonstrated based on embodiment of illustration, this invention is not limited to this embodiment.
(Embodiment 1)
First, a schematic configuration of the illumination light communication system according to the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram illustrating a schematic configuration of an illumination light communication system 1 according to the first embodiment.

  As shown in FIG. 1, the illumination light communication system 1 includes an illumination light communication device 2, a receiver 3, and the like, and turns on an illumination light source based on transmission information inputted from the outside to the illumination light communication device 2. The communication with the receiver 3 is performed by turning off and turning off (hereinafter also referred to as ON / OFF).

  The illumination light communication apparatus 2 includes a light source drive signal generation unit 201, a transmission signal generation unit 202, a dummy signal generation unit 203, a signal switching unit 205, a light source 206, and the like.

  The light source drive signal generation unit 201 generates a constant DC signal (steady signal) that steadily lights the light source 206 during non-communication when communication based on transmission information input from the outside is not performed.

  The transmission signal generation unit 202 generates a pulsed transmission signal for turning on / off the light source 206 based on transmission information input from the outside.

  The dummy signal generation unit 203 generates a DC dummy signal that turns on the light source 206 based on information related to the transmission signal output from the transmission signal generation unit 202 (for example, ON time / OFF time of the pulse signal, signal level, etc.). To do.

  Here, a transmission signal output period tws described later in which a transmission signal is output by the transmission signal generation unit 202 and a dummy signal output period twd in which a dummy signal is output by the dummy signal generation unit 203 are continuous by the signal switching unit 205. Is set to Then, the dummy signal generation unit 203 uses the average value of the light output of the light source 206 during communication through the transmission signal output period tws and the dummy signal output period twd during non-communication when communication based on transmission information is not performed (non-transmission). A dummy signal is generated so as to be equal to the light output of the light source 206 during the communication period tw). Details of the steady signal, the transmission signal, and the dummy signal will be described later.

  The signal switching unit 205 converts any one of the steady signal, the transmission signal, and the dummy signal input from the light source drive signal generation unit 201, the transmission signal generation unit 202, and the dummy signal generation unit 203, to the transmission signal generation unit 202. The signal is selected by the switching signal from, and output to the light source 206. As for the switching signal, when the transmission information from the outside is not input, the stationary signal is selected, and when the transmission information is input, the transmission signal is first selected and then the dummy signal is selected.

  The light source 206 includes a light emitting element such as an LED (light emitting diode), for example, and provides original illumination, that is, “light”, and performs data communication and the like.

  The receiver 3 includes a photoelectric conversion element such as a photodiode, for example, and receives light from the illumination light communication device 2 to receive transmission information.

  Here, an example of a steady signal, a transmission signal, and a dummy signal will be described with reference to a term chart shown in FIG.

  First, in a non-communication period tw in which transmission information is not input, a steady signal that causes the light output (luminance) of the light source 206 to be, for example, 50% is generated by the light source drive signal generation unit 201 and the signal switching unit 205 is Via the light source 206.

  Next, when transmission information is input at time t1, the transmission signal generation unit 202 generates a pulsed transmission signal for turning on / off the light source 206 based on the input transmission information, and transmits a transmission signal output period tws. Is output to the light source 206 via the signal switching unit 205. Also, information related to the output transmission signal (for example, ON time / OFF time of the pulse signal, signal level, etc.) is output to the dummy signal generation unit 203.

  Next, when the transmission signal output period tws ends at time t2, the dummy signal generation unit 203 generates a dummy signal that can turn on the light source 206 based on the information related to the transmission signal output from the transmission signal generation unit 202. The signal is output to the light source 206 via the signal switching unit 205 in the dummy signal output period twd. At this time, the dummy signal generation unit 203 does not perform communication based on the average value of the light output of the light source 206 during communication through the transmission signal output period tws and the dummy signal output period twd when communication based on transmission information is not performed ( A dummy signal is generated so as to be equal to the optical output 8 (for example, 50%) of the light source 206 in the non-communication period tw).

  Specifically, the dummy signal generation unit 203 adds a signal amount equal to the signal amount (light quantity) decreased when the transmission signal is turned off during the transmission signal output period tws to the steady signal to obtain a dummy signal. For example, as shown in FIG. 2, the signal level in the dummy signal output period twd corresponding to the signal amount decreased in the transmission signal output period tws is set to 30% with respect to the steady signal having the signal level corresponding to the light output of 50%. Then, the level of the dummy signal generated by the dummy signal generation unit 203 becomes a value corresponding to an optical output of 50 + 30 = 80%.

  As described above, in the illumination light communication system 1 according to Embodiment 1 of the present invention, the dummy signal output period twd is provided continuously to the transmission signal output period tws, and the transmission signal is generated by the dummy signal in the dummy signal output period twd. The average value of the light output of the light source 206 during communication through the output period tws and the dummy signal output period twd is the light output of the light source 206 during non-communication (non-communication period tw) when communication based on transmission information is not performed. To be equal.

  That is, in the transmission signal output period tws, the decrease in light output when the light source 206 that repeatedly blinks ON / OFF is OFF is compensated for by the dummy signal output period twd provided separately without compensating for the transmission signal output period tws. I made it. Accordingly, for example, by adjusting the dummy signal output period, the light output decreased in the transmission signal output period tws can be sufficiently obtained without flowing a large current that the light output of the light source 206 is saturated (for example, 80% or more). Can be supplemented. As a result, it is possible to reduce a change in luminance between communication and non-communication without causing a decrease in efficiency.

Further, since the dummy signal is a DC signal, it is not affected by the overshoot that occurs during ON / OFF switching unlike the pulse signal. Thereby, the brightness change between the time of communication and the time of non-communication can further be reduced.
(Embodiment 2)
A schematic configuration of the illumination light communication system according to the second embodiment will be described with reference to FIG. FIG. 3 is a block diagram illustrating a schematic configuration of the illumination light communication system 1 according to the second embodiment.

  As in the case of the first embodiment, the illumination light communication system 1 includes an illumination light communication device 2 and a receiver 3 as shown in FIG.

  The illumination light communication device 2 includes a light source drive signal generation unit 201, a transmission data transfer unit 212, a transmission data delay unit 213, an inverter 214, a signal switching unit 205, a light source 206, and the like. Note that the configurations and operations of the light source drive signal generation unit 201, the signal switching unit 205, and the light source 206 are the same as those in the first embodiment, and a description thereof will be omitted.

  The transmission data transfer unit 212 corresponds to a transmission signal generation unit in the present invention, and serial data (transmission information) input from the outside is transmitted to the light source 206 via the signal switching unit 205 as a transmission signal for turning on / off the light source 206. While outputting sequentially, a transmission signal is output to the transmission data delay part 213. FIG. The transmission data transfer unit 212 is a shift register having a so-called FIFO (First In, First Out) structure, for example, which processes first incoming data first and waits until the first incoming data is finished. is there.

  The transmission data delay unit 213 is, for example, a shift register having a FIFO structure that delays the transmission signal output from the transmission data transfer unit 212 for a predetermined time.

  The inverter 213 is, for example, an inverter that inverts the ON / OFF phase of the transmission signal output from the transmission data delay unit 213 to generate a dummy signal. The transmission data delay unit 213 and the inverter 213 correspond to a dummy signal generation unit in the present invention.

  Here, an example of a steady signal, a transmission signal, and a dummy signal will be described with reference to a term chart shown in FIG.

  First, in a non-communication period tw in which no transmission information is input, a steady signal such that the light output (luminance) of the light source 206 is 40%, for example, is generated by the light source drive signal generation unit 201 and the signal switching unit 205 is set. Via the light source 206.

  Next, when transmission information is input at time t1, the transmission data transfer unit 212 switches the input serial data (transmission information) as a transmission signal for turning on / off the light source 206 in the transmission signal output period tws. The signals are sequentially output to the light source 206 via the unit 205 and the transmission signal is output to the transmission data delay unit 213. At this time, the signal level when the transmission signal is ON is set to a value at which the light output (luminance) of the light source 206 is, for example, 80%.

  Next, when the transmission signal output period tws ends at time t2, the transmission data delay unit 213 sequentially outputs the transmission signals output from the transmission data transfer unit 212 that have been delayed to the inverter 214. Subsequently, the inverter 213 inverts the ON / OFF phase of the transmission signal output from the transmission data delay unit 213 and outputs it as a dummy signal to the light source 206 via the signal switching unit 205 in the dummy signal output period twd. .

As described above, the signal obtained by inverting the ON / OFF phase w of the transmission signal in the dummy signal output period twd is used as a dummy signal, so that the communication at the time of communication through the transmission signal output period tws and the dummy signal output period twd is performed. The average value of the light output of the light source 206 can be made equal to the light output 8 (for example, 40%) of the light source 206 during non-communication (non-communication period tw) when communication based on transmission information is not performed. As a result, the same effects as those of the first embodiment can be obtained, and the transmission data transfer unit 212 having a simple FIFO structure as the transmission signal generation unit and the transmission data delay having the FIFO structure similarly as the dummy signal generation unit can be obtained. By using the unit 213 and the inverter 214, the circuit configuration of the illumination light communication apparatus 1 can be simplified.
(Embodiment 3)
The configuration of the illumination light communication system 1 according to the third embodiment is substantially the same as that of the second embodiment, and the form of a steady signal during non-communication (non-communication period tw) is different.

  FIG. 5 shows an example of a steady signal, a transmission signal, and a dummy signal. The steady signal according to the present embodiment is a pulse signal for turning on / off the light source 206 as shown in FIG. The form of the transmission signal and the dummy signal is the same as that of the second embodiment, and the average value of the light output of the light source 206 during communication through the transmission signal output period tws and the dummy signal output period twd is the transmission information. It is equal to the average value (for example, 40%) of the light output of the light source 206 at the time of non-communication (non-communication period tw) in which the communication based on is not performed. Even in such a configuration, the same effect as in the case of the first embodiment can be obtained, and the circuit configuration of the illumination optical communication device 1 can be simplified as in the case of the second embodiment.

It is a block diagram which shows schematic structure of the illumination light communication system which concerns on Embodiment 1 of this invention. It is a time chart of the light source drive signal which concerns on Embodiment 1 of this invention, a transmission signal, and a dummy signal. It is a block diagram which shows schematic structure of the illumination light communication system which concerns on Embodiment 2 of this invention. It is a time chart of the light source drive signal which concerns on Embodiment 2 of this invention, a transmission signal, and a dummy signal. It is a time chart by another example of the light source drive signal which concerns on Embodiment 2 of this invention, a transmission signal, and a dummy signal. It is a figure which shows the relationship between the drive current of a light source, and a brightness | luminance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Illumination light communication system 2 Illumination light communication apparatus 201 Light source drive signal generation part 202 Transmission signal generation part 203 Dummy signal generation part 205 Signal switching part 206 Light source 212 Transmission data transfer part 213 Transmission data delay part 214 Inverter 3 Receiver

Claims (5)

In an illumination light communication apparatus that performs communication by using a light source for illumination and turning on and off the light source based on transmission information,
A transmission signal generating unit that generates a transmission signal based on the transmission information and outputs the generated transmission signal to the light source;
A dummy signal generating unit that generates a dummy signal based on the information related to the transmission signal from the transmission signal generating unit or the transmission signal, and outputs the generated dummy signal to the light source,
The transmission signal output period in which the transmission signal is output and the dummy signal output period in which the dummy signal is output are continuous,
The dummy signal generator is
The average value of the light output of the light source during communication through the transmission signal output period and the dummy signal output period is equal to the light output of the light source during non-communication when the communication based on the transmission information is not performed. The dummy light signal is generated as described above. The illumination light communication apparatus according to claim 1, wherein the dummy signal is a DC signal. The illumination light communication apparatus according to claim 1, wherein the dummy signal is a pulse signal obtained by inverting the on and off phases of the transmission signal. The illumination light communication apparatus according to any one of claims 1 to 3, wherein the light source is a light emitting diode. The illumination light communication apparatus according to any one of claims 1 to 4,
And a receiver that receives light from the illumination light communication device and receives the transmission information.

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