JP4950778B2 - COMMUNICATION DEVICE, TRANSMISSION DEVICE, AND RECEPTION DEVICE - Google Patents

Description

  The present invention relates to a communication device, a transmission device, and a reception device that perform communication using light from an LED including a phosphor.

Various light sources are used for general lighting, backlight light sources for displays, and electric display panels. Currently, incandescent bulbs and fluorescent lamps are mainly used as the light source. However, in recent years, white light emitting diodes (hereinafter referred to as white LEDs) have begun to be used because of low power consumption. White LEDs have long life, high-speed response, and high color purity in addition to their low power consumption, and may be widely used as light sources in various fields such as lighting in the future. In particular, lighting fixtures such as incandescent bulbs and fluorescent lamps are highly likely to be replaced with white LEDs in the future in terms of energy consumption efficiency and life cycle environment. Therefore, it can contribute to CO ₂ reduction and can stop the use of mercury used in fluorescent lamps, so it can be expected as an environmentally friendly light source. Even at the present time, it has already begun to be partially used for traffic signal lights and automobile brake lamps.

  As general lighting, white LEDs are already being used for some indoor lights and street lights. Illumination using these white LEDs as a light source can be pulse-driven at such a high speed that it cannot be recognized by human eyes. Utilizing this characteristic, it is possible to transmit data by pulse driving simultaneously with the illumination function, and various proposals have been made as visible light communication devices.

  Data communication using white LED illumination can be used as it is for large-scale power energy used as illumination, so it is efficient and can obtain good communication characteristics. .

  White LEDs can be broadly divided into two types (first type and second type). In the first type, a phosphor that emits yellow color (for example, a YAG phosphor or an oxonitride glass phosphor) is arranged around a GaN (gallium nitride) blue LED, and the blue LED emits light. Thus, blue light is emitted, whereby the phosphor is excited to emit light, and white light is obtained by mixing the blue light and the yellow light of the phosphor.

  In the second type, red, green, and blue LEDs, which are the three primary colors of light, emit light simultaneously, and the three colors are mixed to obtain white.

  The white LED of the first type (that is, phosphor type) has better luminous efficiency that converts electric energy into light energy than the white LED of the second type (that is, RGB type), and high brightness is easily obtained. As the general illumination, the first type (phosphor type) is mainly used.

  The phosphor type white LED can change the color temperature of the white emission color by adjusting the type and amount of the phosphor, and the illumination has a low color temperature such as warm bulb color illumination, It is possible to realize lighting with various color temperatures, such as lighting with vivid color temperature.

  For example, Patent Document 1 proposes a phosphor type illumination light communication system.

FIG. 1 is a block diagram of a phosphor type illumination light communication system disclosed in Patent Document 1. In FIG. In the phosphor type illumination light communication system of FIG. 1, a blue filter 45 is provided in front of the photodetector 43 to remove the yellow emission color due to the phosphor, and only the blue emission color of the blue LED is used for communication.
Japanese Patent No. 3465017

  A single LED can perform optical space communication at a communication speed of, for example, 100 MHz or more due to its high speed. However, the response speed of the phosphor excited by the LED is slower than that of the LED. Therefore, Patent Document 1 describes that the optical space communication speed using the white light of the white LED is about 1 MHz.

  Phosphors used in white LEDs (for example, YAG phosphors and oxynitride glass phosphors) are excited by blue light from blue LEDs, emit yellow light, and the two colors are mixed to produce white. Light is emitted.

  In general, the response speed of a phosphor used in a white LED is not the same as the color development time until the phosphor emits light when excited and the quenching time until the phosphor extinguishes after the excitation light disappears. In contrast, the color development time is short.

  FIG. 2 shows the excited light intensity of a YAG phosphor that is a general phosphor and the light intensity of semiconductor laser light that is excitation light. In FIG. 2, the horizontal axis represents time, and the vertical axis represents light intensity.

  FIG. 3 shows a measurement system for measuring the light intensity of FIG. The measurement system of FIG. 3 includes, for example, a YAG-based phosphor 301 that is an object to be measured, a semiconductor laser 302 for exciting the phosphor 301 that is an object to be measured, a spectrometer 303 that separates the excited light, The streak camera 304 has a high time resolution.

  In FIG. 2, the quenching time of the YAG phosphor excited by a semiconductor laser pulse having a width of about 5 n (nano) seconds is about 60 nsec. Here, the extinction time represents the time when the intensity becomes 1 / e with respect to the peak light intensity. When the YAG phosphor is used, the extinction time is about 60 ns, so that optical space communication at 16.7 MHz or higher which is the reciprocal of the extinction time cannot be performed. In FIG. 2, the color development time of the YAG phosphor is close to the measurement limit, and is not inferior to the general LED light rise time.

  As described above, the response time of a general YAG phosphor type white LED, that is, the combined time of color development time and quenching time is as long as several tens of nanoseconds. When using a YAG phosphor type white LED, Specifically, high-speed optical space communication at 16.7 MHz or higher cannot be performed.

  In Patent Document 1, in view of the slow response speed of the phosphor, a blue filter 45 is provided in front of the light detector 43 to remove yellow emission color due to the phosphor having a slow response time, thereby increasing the speed of light space. It is to achieve communication.

  However, in the method of Patent Document 1, since the blue filter is used, the light intensity received by the photodetector 43 is reduced by the blue filter 45. This is because the light power of the blue light component of the phosphor type white LED is about 1/3 of the total light power, and if a general silicon-based photodiode is used as the light receiving element for detecting data, it can be detected. The intensity of the emitted blue light will be less than a quarter of the whole. Therefore, the S / N ratio in optical communication is -6 dB worse than when all white light is received.

  Hereinafter, the above-described contents will be described in detail.

  FIG. 4 shows an example of a wavelength spectrum of a general phosphor type white LED in which a YAG phosphor and a GaN blue LED are combined. FIG. 4 shows that the emission peak intensity of the blue light component is higher than that of the yellow light component.

  FIG. 5 shows the wavelength spectrum of the blue light component of the phosphor type white LED, which represents the wavelength spectrum of the light emission of the phosphor type white LED after passing through the blue filter. .

  FIG. 6 shows the wavelength spectrum of the yellow light component of the phosphor type white LED, which represents the wavelength spectrum after the emission of the phosphor type white LED passes through the yellow filter. ing.

  5 and 6, the light intensities of the blue light component and the yellow light component substantially coincide with the integrated values of the respective wavelength spectra, that is, the areas, and when the area ratio is 1, the yellow light component is about It can be seen that the yellow light component is twice as large as the blue light component.

  FIG. 7 is a diagram showing a spectral sensitivity curve of a photodiode which is a general silicon-based light receiving element. Referring to FIG. 7, the sensitivity gradually decreases on the short wavelength side from the absorption peak wavelength of 950 nm of the silicon-based light receiving element.

  By multiplying the spectral sensitivity curve of the photodiode shown in FIG. 7 and the wavelength spectrum of the blue light component of the phosphor type white LED shown in FIG. 5, the calculation of the phosphor type white LED received by the photodiode is calculated. It is possible to determine the intensity of the blue light component.

  FIG. 8 shows the product of the spectral sensitivity curve of the photodiode shown in FIG. 7 and the blue light component of the phosphor type white LED shown in FIG.

  In FIG. 8, the area represented by the spectral sensitivity curve is the received signal intensity of the blue light component of the phosphor type white LED received by the photodiode.

  Further, by multiplying the spectral sensitivity curve of the photodiode shown in FIG. 7 with the wavelength spectrum of the yellow light component of the phosphor type white LED shown in FIG. 6, the phosphor type white LED received by the photodiode is calculated. It is possible to determine the intensity of the yellow light component.

  FIG. 9 shows a product of the spectral sensitivity curve of the photodiode shown in FIG. 7 and the yellow light component of the phosphor type white LED shown in FIG.

  In FIG. 9, the area represented by the spectral sensitivity curve is the received signal intensity of the yellow light component of the phosphor type white LED received by the photodiode.

  8 and 9, the intensity ratio of the blue light component and the yellow light component detected when a silicon photodiode is used as the light receiving element is about 1: 3.

  Therefore, in the method of Patent Document 1 using a blue filter using a general silicon-based photodiode as a light receiving element for detecting communication data in visible light communication, the light intensity of the detected blue light component is It becomes less than a quarter of the light intensity of the whole white light, and when converted to the S / N ratio, it is -6 dB worse than receiving the whole white light. For this reason, the method of Patent Document 1 has a problem that good optical communication cannot be performed.

  An object of the present invention is to provide a communication device, a transmission device, and a reception device capable of performing high-speed and good optical communication when communication is performed using light from an LED including a phosphor. .

In order to achieve the above object, an invention according to claim 1 is directed to an LED including a phosphor, a modulation unit that modulates transmission data to form a modulation signal, and a modulation signal from the modulation unit at a certain period. driving means for driving the LED by adding the reference signal with increased drive current of the LED, light receiving means for receiving light from the LED, to detect the reference signal from an output signal from said light receiving means, using the detected the reference signal as a reference of the time axis, from an output signal from said light receiving means is a communication apparatus characterized by comprising a demodulation means for demodulating the modulated signal.

  According to a second aspect of the present invention, in the communication device according to the first aspect, in the LED including the phosphor, a phosphor that emits yellow color is disposed around the blue LED, and the blue light from the blue LED is used. The phosphor is a phosphor type white LED that excites and emits light to obtain white light by mixing the blue light and the yellow light of the phosphor.

  According to a third aspect of the present invention, in the communication device according to the second aspect, the light receiving means is constituted by a single light receiving means that directly receives white light from the LED.

The invention of claim 4 is a communication device according to any one of claims 1 to 3, wherein the demodulating means, before Kimoto in synchronization with the quasi-signal time with a predetermined prescribed The modulation signal is demodulated by comparing the intensity of the output signal from the light receiving means at two intervals with values sampled twice for each bit .

The invention of claim 5, wherein, in the communication apparatus according to any one of claims 1 to 4, wherein the demodulation means, when the output signal from said light receiving means detects said reference signal, It is characterized by using the rising edge of the reference signal as a reference of the time axis.

According to a sixth aspect of the present invention, there is provided an LED including a phosphor, a modulation unit that modulates transmission data into a modulation signal, and driving the LED at a constant period for use in demodulation as a time axis reference. And a driving means for driving the LED by adding a reference signal with an increased current to the modulation signal from the modulation means.

According to a seventh aspect of the present invention, there is provided a light receiving means for receiving light from an LED including a phosphor, and an LED including the phosphor, wherein the LED includes a modulated signal obtained by modulating transmission data at a certain period. when the reference signal with increased drive current is intended to be driven by the added signal, the detecting the reference signal from the output signal from the light receiving means, by using the reference signal detected as the reference time base, And a demodulating means for demodulating the modulated signal from an output signal from the light receiving means.

According to the present invention, on the transmission side, an LED provided with a phosphor, a modulation unit that modulates transmission data into a modulation signal, and a drive current of the LED at a constant period to the modulation signal from the modulation unit Driving means for driving the LED by adding an increased reference signal ,
The receiving side, a receiving means for receiving light from said LED, said detecting said reference signal from an output signal from the light receiving means, by using the reference signal detected as the reference time base, from the light receiving means Since it comprises demodulation means for demodulating the modulation signal from the output signal,
When communication is performed using light from an LED including a phosphor, high-speed and good optical communication can be performed.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  As described above, the rise time and color development time of the excited yellow light are faster than the quenching time. That is, this indicates that the reception rising signal of optical space communication (optical communication) can be received at high speed on the receiving side.

  In the present invention, in order to perform optical spatial communication in illumination using a phosphor type white LED, on the transmission side, a predetermined reference signal (for example, a guide signal pulse) is inserted into the modulation signal every certain period of time. Drive type white LED. On the receiving side, when the light from the phosphor type white LED is received by the light receiving means, the response speed of the phosphor is utilized, and the output signal from the light receiving means is used to quickly increase the predetermined reference signal. The modulated signal is demodulated from the output signal from the light receiving means using this as a reference for the time axis. As a result, since the light intensity is not reduced on the receiving side, the modulated signal from the transmitting side can be demodulated reliably and at high speed without reducing the S / N ratio. Optical space communication can be performed.

  The present invention is described in detail below.

  In visible light communication using LEDs, there is an RZ (Return to Zero) method as one of methods for digitally modulating LEDs. Further, the RZ system includes several encoding systems that encode data to be transmitted (for example, binary encoding and Manchester encoding).

  FIG. 10 is a diagram for explaining a method of modulating an LED by binary coding. Referring to FIG. 10, in the method of modulating an LED by binary encoding, the LED is turned off when digital data to be transmitted, that is, the data is “0”, and the LED is turned on when the data is “1”.

  On the other hand, FIG. 11 is a diagram for explaining a method of modulating an LED by Manchester encoding. Referring to FIG. 11, in the LED modulation method by Manchester encoding, when digital data to be transmitted is “0”, the LED is turned off when it is “0”, and when the data is “1”, the LED is turned off. Change from to lighting.

  When considering the modulation of an LED used as illumination, the latter Manchester encoding is considered to be more effective than the former binary encoding.

  The reason is that in the former binary encoding method, the ratio of the time during which the LEDs are lit changes due to the non-uniformity of the ratio of “0” and “1” of the data to be transmitted, causing blinking.

  On the other hand, in the latter Manchester system, the ratio of the time during which the LED is lit is constant regardless of the equality between “0” and “1” of the data to be transmitted. Therefore, the blinking as in the binary encoding does not occur, and the function as the illumination does not occur.

  Therefore, in the optical communication using illumination light, the Manchester system is generally advantageous as a method for modulating a light source such as an LED.

  FIG. 12 shows a drive waveform (drive signal, modulation signal) for driving the phosphor type white LED when the phosphor type white LED is blinked and modulated at high speed by the Manchester method.

  FIG. 13A shows a signal obtained by receiving the communication light (transmission light) of the white LED subjected to the high-speed blinking modulation with the drive signal (modulation signal) of FIG. 12 by a light receiving element (for example, a silicon type photodiode). (Received signal) is shown.

  In the conventional optical space communication method, in order to demodulate the signal received by the light receiving element, it is necessary to set an appropriate threshold voltage. In the example of FIG. 13, the threshold voltage is set as C. By comparing the level of the received signal with the threshold voltage C, as shown in FIG. 13B, the threshold voltage is shown in FIG. Communication data (transmission data, LED drive signal (transmission digital signal)) can be demodulated into a digital signal (demodulation signal). FIG. 14 is a diagram showing an example of a conventional receiving circuit (demodulating circuit). In the example of FIG. 14, the current that flows when communication light enters the light receiving element 4 is converted into a voltage by the current-voltage conversion unit 11, amplified by the amplifier 12, and the voltage from the amplifier 12 and a predetermined threshold voltage C Are compared by the comparator 13, and when the voltage from the amplifier 12 is larger than the threshold voltage C, a digital signal of "1" can be output as a demodulated signal.

  13 (a) and 13 (b), it can be seen that in the conventional Manchester system, demodulation is not possible unless the threshold voltage C is set in the range indicated by D. Even if the threshold voltage C is set within the range indicated by D, the waveform of the demodulated digital signal (demodulated signal) is deformed compared to the waveform of the transmitted digital signal (LED drive signal) in FIG. It can be seen that good demodulation is difficult.

  This indicates that it is difficult to perform good high-speed communication when using the conventional Manchester system in optical space communication using a phosphor type white LED.

  FIG. 15 is a diagram illustrating a configuration example of a communication apparatus according to the present invention. As shown in FIG. 15, the communication device of the present invention modulates the transmission data with the LED 1 equipped with a phosphor in order to realize good high-speed communication in optical space communication using a phosphor type white LED. A modulation means 2 for generating a modulation signal; a drive means 3 for driving the LED 1 by adding a predetermined reference signal to the modulation signal from the modulation means 2; a light receiving means 4 for receiving light from the LED 1; A demodulating means 5 that detects a predetermined reference signal from the output signal from the light receiving means 4 and demodulates the modulation signal from the output signal from the light receiving means 4 using the detected predetermined reference signal as a time axis reference. It is characterized by having.

  Here, the LED 1 provided with the phosphor, the modulation means 2 that modulates transmission data to make a modulation signal, and a predetermined reference signal to be used for demodulation are added to the modulation signal from the modulation means 2 and the LED 1 The driving means 3 for driving is configured as a transmission device.

  The light receiving means 4 for receiving light from the LED 1 provided with a phosphor and the LED 1 provided with the phosphor are driven by a signal obtained by adding a predetermined reference signal to a modulation signal obtained by modulating transmission data. When a predetermined reference signal is detected from the output signal from the light receiving means 4 and the detected predetermined reference signal is used as a time axis reference, the modulation signal is detected from the output signal from the light receiving means 4. The demodulating means 5 for demodulating is configured as a receiving device.

  Further, the LED 1 provided with the phosphor is specifically, for example, a phosphor that develops yellow color is arranged around a blue LED, and the phosphor is excited by blue light from the blue LED to emit light, A phosphor type white LED that obtains white light by mixing blue light and yellow light of the phosphor.

  More specifically, the driving unit 3 is configured to drive the LED 1 by inserting a predetermined reference signal (for example, a guide signal pulse) into the modulation signal every certain period.

  More specifically, the demodulating unit 5 compares the strength of the output signal from the light receiving unit 4 at predetermined time intervals in synchronization with the predetermined reference signal. The modulated signal is demodulated.

  More specifically, the demodulating means 5 uses a rising edge of the predetermined reference signal as a time axis reference when detecting a predetermined reference signal from the output signal from the light receiving means 4. Yes.

The light receiving means 4 is constituted by one light receiving means for directly receiving white light from the LED 1.

  FIG. 16 is a diagram showing a more specific configuration example of the communication apparatus of the present invention.

  In FIG. 16, for example, a phosphor type white LED used as illumination light is used for the LED 1, and for example, a silicon-based photodiode is used for the light receiving means 4 as a light receiving element. The demodulator 5 uses the guide signal detector 6 that detects a guide signal as a predetermined reference signal and the guide signal detected by the guide signal detector 6 as a time axis reference from the light receiver 4. And a demodulator 7 for demodulating the modulated signal from the output signal.

  FIG. 17 shows an LED drive signal waveform for white-light modulation of the white LED 1 in the present invention.

  In the present invention, as shown in FIG. 17, a modulation signal to which a predetermined reference signal (guide signal) is added every predetermined fixed period is used as a drive signal. In the example of FIG. 17, a guide signal is obtained by increasing the drive current of the phosphor type white LED 1 every certain period.

  As a method for generating the guide signal, there is a method in which the phosphor type white LED 1 is extinguished for a certain period so that the rising of the reception signal in the light receiving element 4 is clarified. At this time, it is desirable that the period of time during which the light is extinguished is equal to or longer than the quenching time of the phosphor used in the phosphor type white LED 1, and in the case of a general YAG phosphor, the quenching time is about 60 n (nano) seconds.

  In FIG. 18A, the light (light space communication light) from the phosphor type white LED 1 subjected to the high-speed blinking modulation with the drive signal shown in FIG. 17 is received by the light receiving element (for example, a silicon-based photodiode) 4. The waveform of the received signal is shown.

  As shown in FIG. 18 (a), for example, the rise time and color development time of the YAG phosphor used in the phosphor type white LED 1 are much faster than the extinction time. By detecting the rising edge of the signal that exceeds the predetermined threshold voltage E from the received signal shown in (2), it is possible to easily extract a predetermined reference signal (guide signal) serving as a time axis reference.

  The received signal is demodulated in a manner as shown in FIG. 18B using the guide signal extracted in this way as a temporal reference (more precisely, using the rising edge of the guide signal as a temporal reference). This makes it possible to perform good demodulation.

  Specifically, as shown in FIGS. 18A and 18B, the demodulation is performed by sampling the received signal after a predetermined time T1 with reference to the rising time of the guide signal.

  After that, the received signal is sampled every time T2 which is the unit time of transmission data, which is the reciprocal of the modulation frequency. The time T2 coincides with a half of the modulation speed, and good demodulation is possible by sampling twice for each bit of transmission data.

  Specifically, as shown in FIG. 18A, a value obtained by first sampling the received signal after T1 time after receiving the guide signal (after detecting the rising edge of the guide signal) is set as S1. A value obtained by sampling the received signal after T2 time is S2, and a value obtained by sampling the received signal nth is Sn.

  At this time, in order to demodulate the received signal into received data, when n ≧ 1, the (2n−1) th value S (2n−1) and the (2n) th value S (2n) are compared. , S (2n−1)> S (2n), the nth data of the received data is set to “0”, and if S (2n−1) <S (2n), the nth data of the received data The first data is set to “1”.

  As described above, in the present invention, a predetermined reference signal (guide signal) is used as a time axis reference, and the received signal is synchronized with the guide signal in units of predetermined time S1, S2, S3,. By sampling as described above and demodulating the received data (demodulated signal) in the manner described above, it is possible to easily and satisfactorily demodulate the received data (demodulated signal).

  FIG. 19 is a diagram showing a specific example of the receiving circuit (light receiving means 4, demodulating means 5) of the communication apparatus shown in FIG. In FIG. 19, the same parts as those in FIG. In FIG. 19, the comparator 23 has a function as the guide signal detector 6, and the counters 24 and 25, the sample hold circuits 26 and 27, and the comparator 28 have a function as the demodulator 7. In the example of FIG. 19, the current that flows when communication light enters the light receiving element 4 is converted into a voltage by the current-voltage converter 11, amplified by the amplifier 12, and the voltage from the amplifier 12 and a predetermined threshold voltage E Can be extracted as a predetermined reference signal (guide signal) when the voltage (received signal) from the amplifier 12 becomes larger than the threshold voltage E. Then, the counters 24 and 25 alternately count the time interval T2. The counter 24 initially counts the time T1. Then, after the time T1 has elapsed from a predetermined reference signal (guide signal), the voltage (received signal) from the amplifier 12 is sampled by the sample hold circuits 26 and 27 at every time interval T2 counted alternately by the counters 24 and 25. Each of the signals is sampled, and the comparator 28 compares the outputs S (2n-1) and S (2n) from the sample hold circuits 26 and 27, and outputs a digital signal of "1" or "0" as a demodulated signal. Can do.

  20 is a diagram showing another specific example of the receiving circuit (light receiving means 4, demodulating means 5) of the communication apparatus shown in FIG. 16. In the example of FIG. (CPU) 30 is used. FIG. 21 shows a flowchart of processing of the demodulator 7 using the MPU 30 of FIG. Referring to FIG. 21, upon receiving the guide signal (step S1), the MPU 30 measures the time T1 (step S2), and initializes the sampling count n to “1” (step S3).

  The received signal is sampled to S (2n-1) (step S4). Next, the time T2 is measured (step S5), and the received signal is sampled and set to S (2n) (step S6). Then, S (2n-1) and S (2n) are compared (step S7), and when S (2n-1) is larger than S (2n), the received signal is output as "0" (step S8). , S (2n−1) is smaller than S (2n), the received signal is output as “1” (step S9).

Next, it is determined whether or not the received data has ended (step S10). If the received data has not ended, n is incremented by “1” (step S11), and the time T2 is counted (step S11). S12) Returning to step S4 again, the processes of steps S4 to S10 are repeated. In this way, demodulation processing as shown in FIG. 18 can be performed.

It is a block diagram of the conventional fluorescent substance type illumination light communication system. It is a figure which shows the light intensity of the semiconductor laser beam which is the excitation light intensity | strength of YAG type | system | group fluorescent substance which is a general fluorescent substance, and excitation light. FIG. 3 is a measurement system diagram for measuring the light intensity in FIG. 2. It is a figure which shows an example of the wavelength spectrum of the general fluorescent substance type white LED which combined YAG type fluorescent substance and GaN type blue LED. It is a figure which shows the wavelength spectrum of the blue light component of fluorescent substance type white LED. It is a figure which shows the wavelength spectrum of the yellow light component of fluorescent substance type white LED. It is a figure which shows the spectral sensitivity curve of the photodiode which is a general silicon-type light receiving element. It is a figure which shows what multiplied the spectral sensitivity curve of the photodiode shown in FIG. 7, and the blue light component of fluorescent substance type white LED shown in FIG. It is the figure which multiplied the spectral sensitivity curve of the photodiode shown in FIG. 7, and the yellow light component of the fluorescent substance type white LED shown in FIG. It is a figure for demonstrating the modulation method of LED by binary encoding. It is a figure for demonstrating the modulation method of LED by Manchester encoding. It is a figure which shows the drive waveform (a drive signal, a modulation signal) which drives fluorescent substance type white LED in the case of carrying out the blinking modulation of fluorescent substance type white LED by the Manchester system at high speed. It is a figure for demonstrating how to demodulate the signal received with the light receiving element in the conventional optical space communication method. It is a figure which shows an example of the conventional receiving circuit (demodulation circuit). It is a figure which shows the structural example of the communication apparatus of this invention. It is a figure which shows the more specific structural example of the communication apparatus of this invention. It is a figure which shows the LED drive signal waveform for carrying out the high-speed blink modulation | alteration of white LED in this invention. It is a figure for demonstrating operation | movement of the communication apparatus of this invention. It is a figure which shows the specific example of the receiving circuit of the communication apparatus shown in FIG. It is a figure which shows the other specific example of the receiving circuit of the communication apparatus shown in FIG. It is a figure which shows the flowchart of a process of the demodulation part using MPU of FIG.

Explanation of symbols

1 LED with phosphor
2 Modulating means 3 Driving means 4 Light receiving means 5 Demodulating means 6 Guide signal detecting section 7 Demodulating section

Claims (7)

An LED including a phosphor, a modulation unit that modulates transmission data to generate a modulation signal, and a reference signal that increases the drive current of the LED at regular intervals to the modulation signal from the modulation unit; driving means for driving a light receiving means for receiving light from the LED, to detect the reference signal from an output signal from said light receiving means, by using the reference signal detected as the reference time axis, the light receiving And a demodulating means for demodulating the modulated signal from an output signal from the means. The communication device according to claim 1, wherein the LED including the phosphor is arranged such that a phosphor that develops yellow color is arranged around a blue LED, and the phosphor is excited by blue light from the blue LED to emit light. A communication device, which is a phosphor-type white LED that obtains white light by mixing blue light and yellow light of a phosphor. 3. The communication apparatus according to claim 2, wherein the light receiving means is constituted by a single light receiving means that directly receives white light from the LED. The communication device according to any one of claims 1 to 3, wherein the demodulating means, before Kimoto in synchronization with the quasi-signal, the output signal from said light receiving means for each predetermined, determined time interval A communication apparatus that demodulates the modulation signal by comparing values obtained by sampling two times for each bit . The communication device according to any one of claims 1 to 4, wherein the demodulation means from the output signal from said light receiving means when detecting the reference signal, the time axis a rising edge of the reference signal A communication device that is used as a reference. An LED including a phosphor, a modulation unit that modulates transmission data to generate a modulation signal, and a reference signal that increases the drive current of the LED for each fixed period to be used for demodulation as a time axis reference; And a driving means for driving the LED in addition to the modulation signal from the transmitter. A light receiving means for receiving light from an LED provided with a phosphor, and a reference signal obtained by increasing the drive current of the LED at regular intervals to a modulation signal obtained by modulating the transmission data of the LED provided with the phosphor. when I and are driven by a signal, wherein detecting the reference signal from the output signal from the light receiving means, by using the reference signal detected as the reference time base, the output signal from said light receiving means, wherein A receiving apparatus comprising: demodulation means for demodulating the modulation signal.

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