JP2011211364A - Optical communication system, light-emitting device, illumination device, display device, indication device, and optical communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high-speed data communication via a light source comprising a combination of a light emitting diode and a phosphor.SOLUTION: While a light-emitting device 1 emits an illumination light which is obtained by synthesizing a blue light emitted from a blue color light-emitting diode 11 and a yellow light emitted by exciting the phosphor 12 by the blue light, it modulates an electrical signal for driving the blue color light-emitting diode 11 in accordance with a data signal. A reception device 2 receives the synthesized light, converts it to the electrical signal, and demodulates the converted electrical signal to the data signal. The light-emitting device 1 is provided with an encoding circuit 15 to remove a frequency component of the phosphor 12 included in the electrical signal.

Description

  The present invention relates to an optical communication system, a light emitting device, a lighting device, a display device, a marking device, and an optical communication method that perform optical communication using a light source such as a pseudo white LED composed of a single color LED (Light Emitting Diode) and a phosphor. .

  The white LED is roughly classified into a quasi-white LED composed of a combination of a single-color LED and a phosphor in addition to a three primary color white light source using a red LED, a green LED, and a blue LED. In recent years, the characteristics of light sources such as pseudo white LEDs have been greatly improved and the manufacturing cost has been reduced.

  On the other hand, an illumination light communication device that performs data communication using illumination light is disclosed (for example, see Patent Document 1).

JP 2003-318836 A

  A number of devices that perform illumination and communication using the combined light of the three primary color LEDs, such as the illumination light communication device described in Patent Document 1, have been proposed, but as described in Patent Document 1 as well, A light source composed of a combination of a light emitting diode such as a pseudo-white LED and a phosphor is not suitable for data communication by high-speed modulation because the restoration of received data is low due to the slow response speed of the phosphor. It had been.

  The present invention has been made in view of the above circumstances, and an optical communication system, a light emitting device, a lighting device, a display device, and a high-speed data communication using a light source composed of a combination of a light emitting diode and a phosphor, An object is to provide a marking device and an optical communication method.

In order to achieve the above object, an optical communication system according to a first aspect of the present invention includes:
The combined light obtained by combining the light emitted from the light emitting diode and the light of at least one color emitted by exciting the phosphor with the light is emitted, and the light emitting diode is driven according to the data signal A light emitting device that modulates an electrical signal for
A receiver that receives the combined light and converts it into an electrical signal, and demodulates the converted electrical signal into a data signal;
With
A filter is provided that removes the spectral component of the phosphor contained in either the electric signal for driving the light emitting diode or the electric signal converted from the combined light.

In this case, the light emitting device
An encoder that encodes the modulated electrical signal using an mBnB code as the filter;
The receiving device is:
A decoding unit for decoding the electrical signal converted from the combined light;
It is good as well.

In this case, the mBnB code is a biphase code.
It is good as well.

In addition, the receiving device
As the filter,
A high-pass filter that removes components below a predetermined frequency included in the electrical signal converted from the combined light;
It is good as well.

The light emitted from the light emitting diode is blue light, and the light emitted from the phosphor is yellow light.
It is good as well.

The light emitted from the light emitting diode is blue light, and the light emitted from the phosphor is red light and green light.
It is good as well.

The light emitted from the light emitting diode is near ultraviolet light, and the light emitted from the phosphor is red light, green light, and blue light.
It is good as well.

A light emitting device according to a second aspect of the present invention provides:
A light source that emits combined light obtained by combining light emitted from the light emitting diode and at least one color light emitted by exciting the phosphor with the light;
A modulator for modulating an electrical signal for driving the light emitting diode according to a data signal;
An encoding unit that encodes the electrical signal modulated by the modulation unit into an mBnB code;
Is provided.

A lighting device according to a third aspect of the present invention is:
Illumination is performed using the combined light emitted from the light emitting device of the present invention.

A display device according to the fourth aspect of the present invention provides:
A light emitting device of the present invention, a plurality of display units arranged on the display surface,
A control unit that controls the light emission state of the plurality of light emitting devices to display information on the display surface, and inputs the data signal to each light emitting device;
Is provided.

The marking device according to the fifth aspect of the present invention is:
The light emitting device of the present invention, a plurality of marking portions arranged on the marking surface,
Controlling the light emission state of a plurality of the light emitting devices, causing the information to be displayed on the marking surface, and inputting the data signal to each of the light emitting devices;
Is provided.

An optical communication method according to a sixth aspect of the present invention includes:
The combined light obtained by combining the light emitted from the light emitting diode and the light of at least one color emitted by exciting the phosphor with the light is emitted, and the light emitting diode is driven according to the data signal A light emitting process for modulating an electrical signal to perform,
Receiving the combined light, converting it into an electrical signal, and demodulating the converted electrical signal into a data signal;
Including
The frequency component of the phosphor included in the electric signal for driving the light emitting diode in the light emitting step is removed using a filter, or the electric signal included in the electric signal converted from the combined light in the receiving step The frequency component of the phosphor is removed using a filter.
It is characterized by that.

  According to the present invention, the frequency component of the phosphor is removed from either an electric signal for driving the light emitting diode or an electric signal corresponding to the received combined light. As a result, the undulation of the envelope of the spectral component of the electrical signal that is the restoration source of the data signal can be removed, so that the restoration performance of the data signal in the receiving apparatus can be improved. As a result, high-speed data communication using a light source composed of a combination of a light emitting diode and a phosphor is possible.

1 is a block diagram showing a configuration of an optical communication system according to a first embodiment of the present invention. FIG. 2A is a graph showing an example of the frequency response of the light source when the blue light emitting diode is blinked without encoding the voltage signal by the encoding circuit. FIG. 2B is a graph for explaining spectral components included in the frequency response. 3A is an example of a signal waveform of a voltage signal before being encoded, and FIG. 3B is an example of a signal waveform of a voltage signal after being encoded by a biphase code. It is a graph which shows the power spectrum of a NRZ code and a biphase code. It is a graph which shows an example of the spectrum component of the pseudo white light radiate | emitted from a light source. It is a block diagram which shows the structure of the optical communication system which concerns on the 2nd Embodiment of this invention. It is a graph which shows an example of the spectrum component of the voltage signal output from a high pass filter. It is a schematic diagram which shows the structure of the optical communication system which concerns on the 3rd Embodiment of this invention.

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

(First embodiment)
First, a first embodiment of the present invention will be described.

  FIG. 1 shows a configuration of an optical communication system 100 according to the present embodiment. As shown in FIG. 1, the optical communication system 100 includes a light emitting device 1 and a receiving device 2.

  The light emitting device 1 is an illuminating device that is installed on, for example, an indoor ceiling and illuminates the room. The light emitting device 1 includes a light source 10. The light source 10 includes a blue light emitting diode 11 and a phosphor 12.

  The blue light emitting diode 11 emits blue light (for example, light having a wavelength of about 450 nm). The phosphor 12 is excited by the blue light emitted from the blue light emitting diode 11, and generates yellow light (for example, light having a wavelength of about 580 nm).

  The blue light emitted from the blue light emitting diode 11 and the yellow light emitted from the phosphor 12 are combined, and pseudo white light is emitted from the light source 10 as the combined light. The light emitting device 1 illuminates the room using the pseudo white light.

  In order to perform this illumination, the light emitting device 1 further includes a drive circuit 13. The drive circuit 13 causes the blue light emitting diode 11 to emit light by causing a drive current to flow through the blue light emitting diode 11 based on a voltage applied from a power supply (not shown). As a result, pseudo white light is emitted from the light source 10.

  The light emitting device 1 further includes a modulation circuit 14 and an encoding unit 15 before the drive circuit 13.

  The modulation circuit 14 receives a voltage signal applied from a power supply (not shown), modulates the voltage signal based on the data signal, and outputs the voltage signal to the encoding circuit 15.

  FIG. 2A shows an example of the frequency response of the light source 10 when the blue light emitting diode 11 is blinked without encoding the voltage signal by the encoding circuit 15 described later. As shown in FIG. 2A, the frequency response envelope has undulations from low to high. This swell causes the data signal to be remarkably deteriorated when the combined signal from the light source 10 is received and the data signal is demodulated.

  FIG. 2B shows various spectral components included in the frequency response shown in FIG. As shown in FIG. 2B, this frequency response includes a spectral component due to the blue light emitting diode 11 and a spectral component due to the phosphor 12.

  The spectral component due to the blue light emitting diode 11 is flatter than the spectral component due to the phosphor 12 to a higher frequency. On the other hand, the spectral component of the phosphor 12 has a larger amplitude ratio in the lower region than the spectral component of the blue light emitting diode 11. These two spectral components cause undulations in the overall frequency response envelope.

  The encoding circuit 15 is provided to prevent the data signal from being restored due to this swell. The encoding circuit 15 inputs the voltage signal modulated by the modulation circuit 14 as a data signal, and encodes the data signal. For this encoding, a biphase code is used. The biphase code is a code that gives rise and fall to the binary signal to be transmitted at the center of each bit.

  FIG. 3A shows an example of the signal waveform of the voltage signal before encoding, and FIG. 3B shows the signal waveform of the voltage signal after encoding by the biphase code. An example is shown. As shown in FIG. 3B, in this biphase code, a signal indicating “1” changes from low level to high level, and a signal indicating “0” changes from high level to low level. In this way, the voltage signal corresponding to 1 bit is converted into the voltage signal for 2 bits by biphase encoding. The biphase code shown in FIG. 3B is also called a Manchester code.

As shown in FIG. 3A, the voltage signal before encoding is a so-called NRZ (Non Return to Zero) code. FIG. 4 shows power spectra of the voltage signal of the NRZ code and the voltage signal of the biphase code. In the graph shown in FIG. 4, the horizontal axis indicates the reference frequency f / f ₀ , and the vertical axis indicates the normalized power spectrum. As shown in FIG. 4, when comparing the power spectrum of the voltage signal of the NRZ code and the voltage signal of the biphase code, the NRZ code has a maximum DC component of 1.0, whereas the biphase code The direct current component is not included and is 0.0.

  In the present embodiment, in accordance with the modulated and biphase-encoded voltage signal, a transistor provided in the drive circuit 13 (a transistor to which the modulated voltage is input as a base voltage) is turned on and off to emit blue light. The drive current flowing through the diode 11 is modulated, and the blue light emitting diode 11 blinks.

  As the blue light emitting diode 11 blinks, the intensity of yellow light emitted from the phosphor 12 also varies. As a result, the intensity of the pseudo white light that is the combined light thereof varies. The speed of this variation is so high that it is not perceived by humans.

  Returning to FIG. 1, the receiving device 2 is provided in a household electrical appliance or a communication device installed indoors.

  The receiving device 2 includes an optoelectric converter (O / E) 20, a decoding circuit 21, and a demodulation circuit 22. The photoelectric converter 20 has a silicon photodiode (not shown) as a light receiving element, receives the pseudo white light emitted from the light source 10 by the light receiving element, and converts the received pseudo white light into a current signal. The decoding circuit 21 decodes a voltage signal based on the current signal. The demodulation circuit 22 demodulates and outputs a data signal based on the decoded electrical signal.

  Next, the operation of the optical communication system 100 according to the present embodiment will be described.

  When a power switch (not shown) is turned on and a voltage signal modulated by the modulation circuit 14 and encoded by the encoding circuit 15 is applied to the drive circuit 13, the drive circuit 13 emits blue light based on the voltage signal. The diode 11 is driven. When the data signal is not input to the modulation circuit 14, the drive current flowing through the blue light emitting diode 11 is constant, and the light source 10 illuminates the room with a constant light amount.

  When a data signal is input from a host device (not shown), the modulation circuit 14 modulates the voltage applied to the encoding circuit 15 according to the data signal. As a result, a modulated drive current flows through the blue light emitting diode 11, and the intensity of the blue light emitted from the blue light emitting diode 11 is modulated. By this modulation, the intensity of yellow light generated in the phosphor 12 is also modulated, and finally the intensity of pseudo white light is modulated. Since the intensity modulation of the pseudo white light emitted from the light source 10 is so fast that it cannot be perceived by human eyes, the light source 10 can continue to illuminate the room as a white light source.

  The photoelectric converter 20 of the receiving device 2 receives the pseudo white light emitted from the light source 10 and outputs a current signal corresponding to the intensity of the received pseudo white light. The decoding circuit 21 decodes the current signal from the biphase code to the NRZ code and outputs it as a voltage signal of the NRZ code. The demodulation circuit 22 demodulates the data signal based on the voltage signal. The data signal demodulated by the demodulation circuit 23 is output to a home appliance or a communication device, and is used for controlling them, for example.

  FIG. 5 shows the spectral components of the pseudo white light emitted from the light source 10. In FIG. 5, the solid line indicates the spectral component of the pseudo white light when the encoding circuit 15 performs biphase encoding, and the broken line indicates the case where the encoding circuit 15 does not perform biphase encoding. The spectral component of pseudo white light is shown.

  As described above, the data signal for 1 bit is converted into the data signal for 2 bits by biphase encoding, and the DC component becomes 0 (see FIG. 3). Therefore, by performing biphase encoding in the encoding circuit 15, as shown in FIG. 5, the spectral component of the pseudo white light includes a component in a low frequency band, that is, a component corresponding to the spectral component by the phosphor 12. Reduced. As a result, the swell included in the envelope of the spectral component of the pseudo white light can be removed, so that it is possible to prevent the data signal demodulated in the receiving circuit 2 from being degraded.

  In the present embodiment, the bi-phase code used for encoding is a Manchester code (dipulse code), but a CMI (Coded Mark Inversion Code) code may be adopted, or a DMI (Differential Mode Inversion Code) code may be used. May be adopted.

  In the present embodiment, the voltage signal is encoded by the biphase code, but the present invention is not limited to this. The voltage signal may be encoded by an mBnB code such as a 3B4B code or a 6B7B code.

  The mBnB code is a code encoded from an m-bit data signal to an n-bit data signal, and m <n. The biphase code is a 1B2B code. These mBnB codes are all effective for removing low frequency components of the original signal.

  The values of m and n can be appropriately determined according to the data transfer speed between the light source 10 and the photoelectric converter 20. The larger the ratio n / m between m and n, the higher the transfer rate required. Conversely, if the spectral component of the phosphor 12 can be sufficiently removed, it can be said that the ratio n / m is preferably as small as possible in consideration of the limit of the transfer capability of the apparatus.

  As described above in detail, according to the present embodiment, the frequency component of the phosphor 12 is removed from the voltage signal for driving the blue light emitting diode 11. As a result, the swell included in the envelope of the spectral component of the voltage signal from which the data signal is restored can be removed, so that the data restoration in the receiving device 2 can be improved. As a result, high-speed data communication using the light source 10 (pseudo white LED) in which the blue light emitting diode 11 and the phosphor 12 are combined becomes possible.

(Second Embodiment)
Next, a second embodiment of the present invention will be described.

  FIG. 6 shows a configuration of the optical communication system 100 according to the present embodiment. As shown in FIG. 6, the optical communication system 100 includes a light emitting device 1 and a receiving device 2.

  As shown in FIG. 6, the light emitting device 1 does not include the encoding circuit 15. As a result, in the light emitting device 1, the voltage signal modulated by the modulation circuit 14 is directly input to the drive circuit 13, the blue light emitting diode 11 is modulated according to the voltage signal, and finally the pseudo white color emitted from the light source 10. The light intensity is modulated.

  In the present embodiment, since the voltage signal for driving the blue light emitting diode 11 is not encoded with the mBnB code, the spectral component of the pseudo white light wavinessed in the envelope as shown by the dotted line in FIG. Will remain.

  In the present embodiment, the receiving device 2 is provided with a high-pass filter 23 instead of the decoding circuit 21. In FIG. 7, the frequency response of the high-pass filter 23 is indicated by a one-dot chain line. The high-pass filter 23 removes components below a predetermined frequency (cutoff frequency) fc included in the current signal converted from the combined light. The cut-off frequency fc is obtained by changing the envelope of the frequency response of the light source 10 when the blue light-emitting diode 11 shown in FIG. It is set to a frequency that is almost the same as the frequency at which the component shifts.

  In FIG. 7, the spectral component of the voltage signal demodulated by the demodulation circuit 13 is shown by a solid line. As shown in FIG. 7, among the frequency components of the voltage signal, the spectral component due to the phosphor 12 is reduced by the high-pass filter 23, and the envelope is flat in a wide band. As a result, it is possible to prevent the restoration of the data signal demodulated by the demodulation circuit 22 from being deteriorated.

  As described above in detail, according to the present embodiment, the spectral component of the phosphor 12 is removed from the voltage signal converted from the received combined light. As a result, the spectral component of the voltage signal from which the data signal is restored can be flattened from the low range to the high range, so that the data signal can be restored in the receiving device 2. As a result, high-speed data communication using the light source 10 formed by combining the blue light emitting diode 11 and the phosphor 12 is possible.

(Third embodiment)
Next, a third embodiment of the present invention will be described.

  As shown in FIG. 8, the optical communication system 100 according to the present embodiment includes a display device 50 and a light receiving device 2. The display device 50 includes a display unit 40 and a control unit 41.

  A large number of light emitting devices 1 are arranged on the display screen of the display unit 40. Each light emitting device 1 constitutes a pixel of this display screen. The circuit configurations of the light emitting device 1 and the receiving device 2 may be those shown in FIG. It may be as shown in FIG.

  The control unit 41 controls the respective light emission states of the light emitting device 1 on the display screen of the display unit 40 to display images and character information on the display screen.

  In addition to this image display, the control unit 41 inputs a data signal to the modulation circuit 14 of the light emitting device 1 and modulates a voltage signal for driving the blue light emitting diode 11.

  The light receiving device 2 detects a fluctuation in the intensity of the received combined light and demodulates the data signal.

  Unlike the first and second embodiments, in the optical communication system 100, the intensity of the combined light discarded from each light-emitting device 1 changes as needed according to the displayed image. However, since the frequency of the intensity change of the combined light of the light emitting device 1 by this image is extremely lower than the frequency of the intensity modulation by data communication, the change in the light intensity due to the image change is removed, and only the data signal is obtained It is fully possible to extract.

  Instead of the display device 50 that displays an image or the like, a plurality of light emitting devices 1 may be provided on the marking surface, and a labeling device that displays a sign, an advertisement, or the like by light emission of the plurality of light emitting devices 1 may be provided. .

  In each of the above embodiments, the light source 10 composed of a combination of the blue light emitting diode 11 and the phosphor 12 is employed, but the present invention is not limited to this. The present invention can be applied to any light source in which the phosphor emits light different from the light emitted from the light emitting diode and the combined light of two or more lights is emitted.

  For example, instead of the light source 10, a blue light emitting diode, a phosphor that is excited by blue light emitted from the blue light emitting diode to generate red light, and a phosphor that is excited by blue light to generate green light are provided. And a light source that emits combined light of blue light, red light, and green light may be used. Such a light source is also called a so-called high color rendering type pseudo white LED. Also in this case, since the blue light emitted from the light emitting diode, the red light emitted from the two phosphors, and the green light become wavy in the envelope of the spectrum component, the present invention is applied. As a result, it is possible to improve the recoverability of the data signal.

  Further, instead of the light source 10, a light emitting diode that emits near ultraviolet light (for example, light having a wavelength of 300 nm to 400 nm), a phosphor that is excited by the near ultraviolet light emitted from the light emitting diode and generates red light, A phosphor that generates green light when excited by near ultraviolet rays and a phosphor that generates green light when excited by near ultraviolet rays, and combines the combined red, green, and blue light emitted from the phosphor. A light source that emits light may be used.

  With this light source, the combined light is emitted, and at the same time, near ultraviolet rays from the light emitting diode are emitted. Therefore, if near ultraviolet rays are modulated, combined light of near ultraviolet rays and red light, green light, and blue light is modulated and output, and if this is received and demodulated by a receiving device, data communication becomes possible. . In this case, in the receiving apparatus, it is necessary to use a light receiving element that is sensitive to light with a wavelength of 300 nm to 400 nm (for example, a silicon photodiode).

  Also in this case, since the near ultraviolet rays emitted from the light emitting diode and the red light, the green light, and the blue light emitted from the three phosphors, undulations occur in the envelope of the spectral component. If is applied, the recoverability of the data signal can be improved.

  As described above, the present invention can be applied to any light source that emits both the light emitted from the light emitting diode and the light emitted from the phosphor, not limited to the pseudo white LED.

  Note that in the modulation circuit 14, the encoding circuit 15, the decoding circuit 21, and the demodulation circuit 22, the high-pass filter 23 may be configured by an electric circuit or software.

  Such an optical communication system is expected to be used everywhere in the future because of its ubiquitous and environmental impact. For example, this system can be applied to a local area network (LAN) indoors and outdoors. It is also possible to apply this system to road-to-vehicle communication between a traffic light and a vehicle.

  INDUSTRIAL APPLICABILITY The present invention is suitable for optical communication using an illumination device, a display device, a marking device, etc. using a light source that combines a light emitting diode and a phosphor.

DESCRIPTION OF SYMBOLS 1 Light-emitting device 2 Receiver 10 Light source 11 Blue light emitting diode 12 Phosphor 13 Drive circuit 14 Modulating circuit 15 Encoding circuit 20 Photoelectric converter 21 Decoding circuit 22 Demodulating circuit 23 High-pass filter 40 Display unit 41 Control unit 50 Display Apparatus 100 optical communication system

Claims (12)

The combined light obtained by combining the light emitted from the light emitting diode and the light of at least one color emitted by exciting the phosphor with the light is emitted, and the light emitting diode is driven according to the data signal A light emitting device that modulates an electrical signal for
A receiver that receives the combined light and converts it into an electrical signal, and demodulates the converted electrical signal into a data signal;
With
A filter is provided that removes a spectral component of the phosphor contained in one of an electric signal for driving the light emitting diode and an electric signal converted from the combined light;
An optical communication system. The light emitting device
An encoder that encodes the modulated electrical signal using an mBnB code as the filter;
The receiving device is:
A decoding unit for decoding the electrical signal converted from the combined light;
The optical communication system according to claim 1. The mBnB code is a biphase code.
The optical communication system according to claim 2. The receiving device is:
As the filter,
A high-pass filter that removes components below a predetermined frequency included in the electrical signal converted from the combined light;
The optical communication system according to claim 1, wherein the optical communication system is an optical communication system. The light emitted from the light emitting diode is blue light, and the light emitted from the phosphor is yellow light.
The optical communication system according to claim 1, wherein the optical communication system is an optical communication system. The light emitted from the light emitting diode is blue light, and the light emitted from the phosphor is red light and green light.
The optical communication system according to claim 1, wherein the optical communication system is an optical communication system. The light emitted from the light emitting diode is near ultraviolet light, and the light emitted from the phosphor is red light, green light, and blue light.
The optical communication system according to claim 1, wherein the optical communication system is an optical communication system. A light source that emits combined light obtained by combining light emitted from the light emitting diode and at least one color light emitted by exciting the phosphor with the light;
A modulator for modulating an electrical signal for driving the light emitting diode according to a data signal;
An encoding unit that encodes the electrical signal modulated by the modulation unit into an mBnB code;
A light emitting device comprising:   The illuminating device which illuminates using the synthetic light radiate | emitted from the light-emitting device of Claim 8. A light emitting device according to claim 8, wherein a plurality of display units are arranged on the display surface;
A control unit that controls the light emission state of the plurality of light emitting devices to display information on the display surface, and inputs the data signal to each light emitting device;
A display device comprising: A light emitting device according to claim 8, wherein a plurality of marking portions arranged on a marking surface;
Controlling the light emission state of a plurality of the light emitting devices, causing the information to be displayed on the marking surface, and inputting the data signal to each of the light emitting devices;
A marking device comprising: The combined light obtained by combining the light emitted from the light emitting diode and the light of at least one color emitted by exciting the phosphor with the light is emitted, and the light emitting diode is driven according to the data signal A light emitting process for modulating an electrical signal to perform,
Receiving the combined light, converting it into an electrical signal, and demodulating the converted electrical signal into a data signal;
Including
The frequency component of the phosphor included in the electric signal for driving the light emitting diode in the light emitting step is removed using a filter, or the electric signal included in the electric signal converted from the combined light in the receiving step The frequency component of the phosphor is removed using a filter.
An optical communication method characterized by the above.

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