JP2013128206A - Visible light communication method and visible light communication system using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an efficient visible light transmission system in which each item of information can be extracted and reproduced, even if the system is configured so that different items of information are transmitted simultaneously to respective aggregations of LED illuminating a plurality of regions.SOLUTION: N transmission side carrier multipliers generate N transmission signals by multiplying N modulation signals output from N modulators, respectively, by any one of N carrier signals orthogonal to each other. N light-emitting element drivers drive light-emitting element assemblies, which are made to correspond with N sub-display regions by grouping a display region into N sub-display regions, so as to emit light in response to N transmission signals output from the N carrier multipliers, respectively.

Description

The present invention relates to a visible light communication method and a visible light communication system using the same.

Convenient data communication using lighting devices installed indoors and outdoors against the background of the rapid spread of lighting devices using LED assemblies such as LEDs (Light Emitting Diodes) Research and development is underway to realize the environment (visible light communication system). As a light source used for optical communication, for example, an LED having lower power consumption and higher luminance than other lighting devices is the most promising candidate.

For example, Patent Document 1 discloses a liquid crystal display device that can transmit an LED aggregate incorporated as a backlight of a liquid crystal display device to the outside of the device by controlling blinking based on a transmission signal.

In patent document 2, it is different for every area | region using the aggregate | assembly of LED integrated as a backlight of one liquid crystal display device, and being divided | segmented for every several area | region on the output display area | region of a display panel. An apparatus configured to transmit information is disclosed.

JP 2004-246274 A JP 2009-2112768 A

Both are technologies for performing visible light communication using an LED incorporated in a display panel of a liquid crystal display device, but the liquid crystal display device described in Patent Document 1 transmits one piece of information across the entire display panel. I could only do it.

Further, in the liquid crystal display device described in Patent Document 2, signals transmitted from each display region of the display panel (a group of LEDs distinguished for each region) in the receiving device can be identified and separated from each other. Therefore, depending on the position of the receiving apparatus, there is a problem that interference occurs and the received signal cannot be reproduced.

That is, in the liquid crystal display device described in Patent Document 2, for example, the display area is divided into four areas, and the LEDs arranged as backlights that illuminate each display area are different for each display area. When the receiving device is close to only one display area (a group of LEDs arranged corresponding to the area), the LEDs arranged in the display area are controlled. Only signals transmitted from a collection of can be received. Therefore, the receiving device can acquire information from the received signal. On the other hand, when the receiving device is close to, for example, two display areas, the receiving apparatus receives different signals simultaneously transmitted from a collection of LEDs respectively disposed in the two display areas, and thus causes interference. Each received signal cannot be demodulated, and there is a problem that information cannot be obtained from either.

As a method for solving the above problem, a method (FDMA, frequency division multiplexing) in which a group of LEDs arranged in each display region uses different transmission frequencies can be easily considered. Since a guard band is required to avoid interference between frequencies, the information transmission speed is significantly reduced. For example, when the number of carriers is 4 and the guard band is 20%, the transmission rate that can be transmitted by the aggregate of LEDs arranged in one display area is frequency division. It becomes about 1/5 of the case without multiplexing.

The same problem is likely to occur when TDMA (time division multiplexing) or CDMA (code division multiplexing) is used.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to divide a display area of a display device into a plurality of areas and incorporate a plurality of built-in backlights of the display device. When the LEDs are grouped in association with such a plurality of areas and different sets of information (ie, different signals) are transmitted from the group of LEDs in each group, the receiving device simultaneously receives different signals. Even so, it is an object of the present invention to provide a visible light communication method and a visible light communication system using the same, which can demodulate each signal without interference.

In order to solve the above-described problem, in the present invention, a transmission apparatus that transmits N pieces of information using signals generated by a plurality of light emitting elements arranged in a display area composed of N display areas of the display apparatus. And a receiving device that receives a signal generated by a light emitting element, the transmitting device inputs N data from N input terminals and N input terminals, respectively. N modulators that respectively modulate N data to be generated to generate N modulated signals, and N carrier signals that are orthogonal to the N modulated signals respectively output from the N modulators N transmission-side carrier multipliers that generate N transmission signals by multiplying each of them, N sub-display areas, and N sub-display areas, respectively. N light emitting element drivers that emit light according to N transmission signals respectively output from the N carrier multipliers, and the receiving apparatus includes N sub-elements. A light receiving element that receives a transmission signal transmitted from each light emitting element assembly associated with each display region and outputs a reception signal corresponding to the received light intensity, and N for the reception signal output from the light receiving element N receiving carrier multipliers that respectively extract N modulated signals modulated for each of N carriers by multiplying any of the carrier signals, and outputs from the N receiving carrier multipliers Visible light comprising N integrating circuits for integrating the N modulated signals respectively, and N demodulators for demodulating each modulated signal integrated by the N integrating circuits Communication system There is provided. With this configuration, even when the display area of the liquid crystal display device is divided into a plurality of pieces and different information is simultaneously transmitted for each group of LEDs that illuminate the plurality of areas, each information is extracted and reproduced. It becomes possible. Further, since multiplexing is performed based on the principle of OFDM, efficient information transmission can be performed with little reduction in information transmission speed. For example, when the number of carriers is 4, the transmission rate that can be transmitted in one display area is about 2/5 of the case without multiplexing by OFDM. This is twice the transmission efficiency compared to the frequency division multiplexing described above.

2. The visible light communication system according to claim 1, wherein the receiving device selects information to be reproduced on the display screen of the receiving device from information of N modulated signals demodulated by the N demodulating units. Selection means may further be included. With this configuration, the user can select information to be reproduced on the display screen of the receiving apparatus by selecting desired information on the display screen of the receiving apparatus.

Furthermore, in the visible light communication system according to claim 1, the receiving device respectively calculates the received signal strengths of the N modulated signals integrated using the N modulated signals respectively integrated by the N integrating circuits. You may further have a received signal detection circuit to detect. With this configuration, various applications using the detection result of the signal strength can be incorporated into the visible light communication system.

Furthermore, in order to solve the above-described problem, in the visible light communication system according to claim 1, the reception device is configured to relatively reduce the received signal strength of the N modulated signals integrated from the received signal detection circuit. It may further include a maximum strength received signal reproducing means for reproducing information of the modulated signal corresponding to the received signal strength having the largest value in the receiving device. With this configuration, the user can select information to be reproduced by bringing the receiving device close to an arbitrary area on the display.

Furthermore, in order to solve the above-described problem, in the visible light communication system according to claim 1, the receiving device has a relative magnitude of the received signal strength of the N modulated signals integrated from the received signal detection circuit. It may further include an action recognition means for recognizing the movement of the receiving apparatus by detecting the change of the above. With this configuration, for example, it is possible to perform a remote control operation with the receiving device.

Furthermore, in order to solve the above-mentioned problem, in the visible light communication system according to claim 1, the transmission device transmits common information using all of the respective light emitting element assemblies respectively associated with the N sub-display areas. Modulated by the common information modulator that modulates the common information carrier multiplier that modulates the modulated common information with the carrier signals of the common information orthogonal to the N carrier signals and the modulator that modulates the common information The receiver further includes N addition synthesizers that respectively add and synthesize the modulation signal of the common information and the modulation signal of N data modulated by the N modulators, and the receiving device multiplies by the carrier signal of the common information The reception side common information carrier multiplier for extracting the common information modulation signal and the common information modulation signal output from the reception side common information carrier multiplier It may further have a common information demodulator for demodulating the modulated signal of common information integration circuit and the common information which are integrated in a common information integrating circuit for integrating to. With this configuration, even when the receiving device is located at a relatively long distance from the liquid crystal display device, the receiving device can acquire information on the common data by demodulating and reproducing the transmission signal of the common data. It becomes possible.

As described above, according to the present invention described above, the visible light communication system according to the present invention divides the display area of the liquid crystal display device into a plurality of pieces, and simultaneously transmits different information for each group of LEDs that illuminate the plurality of areas. Even with this configuration, each information can be extracted and reproduced.

Further, in the present invention, multiplexing is performed based on the principle of OFDM, so that efficient information transmission can be performed with little reduction in information transmission speed. For example, when the number of carriers is 4, the transmission rate that can be transmitted in one display area is about 2/5 of the case without multiplexing by OFDM. This is twice the transmission efficiency compared to the frequency division multiplexing described above.

Further, since each LED assembly 40 is made to emit light with the light emission intensity corresponding to the signal amplitude of each transmission signal without adding each transmission signal in the previous stage of the driver circuit 30, PAPR increase in the OFDM method is adopted. Thus, the dynamic range required for the driver circuit 30 and the LED assembly 40 corresponding to each carrier frequency is kept low. As a result, it is possible to obtain an effect of improving the communication performance by the OFDM system using a small and inexpensive LED drive circuit and LED.

In addition, when the receiving device is set with a menu that allows the user to select information that the user wants to display on the display screen of the receiving device among the information received from the plurality of display areas, the user can display the display screen of the receiving device By selecting desired information above, it is possible to select information to be reproduced on the display screen of the receiving apparatus.

In addition, the reception device is provided with a reception signal detection circuit for detecting the reception signal strength of each carrier frequency component output from the integration circuit, and a setting for reproducing the information of the transmission signal having the highest reception signal strength is provided. In this case, the user can select information to be reproduced by bringing the receiving device close to an arbitrary area on the display.

In addition, when common information to be transmitted is transmitted using all of the light emitting element assemblies respectively associated with the N sub-display areas, the received signal strength of the common information is relatively strong. Even when the receiving device is located at a relatively long distance from the liquid crystal display device, the receiving device can acquire the information of the common data by demodulating and reproducing the transmission signal of the common data.

Furthermore, by monitoring the change in the ratio of the received signal strength of the transmission signal, it is possible to recognize the movement of the receiving device.

The display area | region which consists of sub display area | region # 1 thru | or sub display area | region # 4 of a liquid crystal display device used for the visible light communication system concerning this invention, and a backlight are shown. The outline of the structure of the visible light communication system in the case of transmitting signals of information different from each other using the aggregate of LEDs corresponding to the sub display area # 1 to the sub display area # 4 according to the present invention will be described. 4 Indicates a transmission signal composed of Carrier-OFDM. It is the schematic of the structure of the visible light communication system of this invention in the case of M <N. An example in which a reception signal detection circuit is further provided in the reception apparatus according to the present invention will be described. The display area | region and backlight of a liquid crystal display device used for the visible light communication system concerning the 2nd Embodiment of this invention are shown. The outline of the visible light communication system concerning 2nd Embodiment is shown. 5 Indicates a transmission signal composed of Carrier-OFDM. It shows that the received signal strengths of the transmission signals transmitted from the LED aggregates arranged in the sub display areas # 11 to # 4 are equal. The relative change of the received signal strength of the transmission signal transmitted from the LED assembly arranged in the sub display areas # 11 to # 4 is shown. The relative change of the received signal strength of the transmission signal transmitted from the LED assembly arranged in the sub display areas # 11 to # 4 is shown.

Hereinafter, the outline of the visible light communication method according to the first embodiment of the present invention and the configuration of the visible light communication system using the same will be described first, and then described together with illustrated examples.

In the visible light communication system according to the first embodiment of the present invention, the LEDs incorporated as the backlight of the display device are grouped into a plurality of regions on the display, and are grouped according to each region. A visible light communication system in which a collection of LEDs transmits a plurality of information. Then, a transmission signal multiplied by a carrier frequency having a frequency relationship of OFDM (Orthogonal Frequency Division Multiplexing) is transmitted to a group of LEDs grouped for each display area. Therefore, the receiving device can separate and extract signals transmitted from the LED aggregates arranged in each display area without interference, and reproduces the information assigned to each LED aggregate. It can be done. Hereinafter, the configuration of a visible light communication method and a visible light communication system using the same according to the first embodiment of the present invention will be described.

The transmission-side device (transmission device 100) used in the visible light communication system according to the present invention is a display device that displays an image, such as a liquid crystal display device, and divides the display area of the display device into a plurality of regions. The apparatus is configured to transmit different information assigned to each LED group by controlling driving of the LED group arranged in each region. In addition, although this invention is demonstrated below taking a liquid crystal display device as an example, if it is an apparatus which displays an image etc. using LED aggregates, such as LED, it will not be limited to a liquid crystal display device.

FIG. 1 shows a display area 100-2 of a liquid crystal display device used in a visible light communication system according to the present invention, for example, divided into four areas consisting of a sub display area # 1 to a sub display area # 4. It is a figure which shows controlling to transmit different information (Data1 thru | or Data4) for every display area with respect to several LED arrange | positioned as the backlight 100-1 which illuminates an area | region. Although FIG. 1 shows a case of illuminating with a direct backlight, that is, with a plurality of LEDs arranged uniformly on a plane facing each sub-display area, other methods, for example, an edge-type backlight are shown. When illuminating with lights, that is, with a plurality of LEDs arranged linearly at the top and bottom or left and right edges for each sub-display area, for example, a plurality of LED aggregates corresponding to each sub-display area should be defined. Is applicable. Hereinafter, when the display area of the transmission device 100 is divided into four areas (sub-display area # 1 to sub-display area # 4), and signals of different information are transmitted using a set of LEDs corresponding to each area. Will be described as an example.

FIG. 2 is a diagram showing an outline of the configuration of the visible light communication system in the case where signals of different information are transmitted using a set of LEDs corresponding to the sub display areas # 1 to # 4. The visible light communication system includes the transmission device 100 and the reception device 300 described above. The transmission device 100 includes four modulators 10 to 13, four carrier multipliers 20 to 23, four driver circuits D1 to D4, and four LED assemblies L1 to L4. On the other hand, the receiving apparatus 300 includes a light receiving element 310, four carrier multipliers 330 to 333, four integrators 340 to 343, and four demodulators 350 to 353. Note that the present embodiment is described in an example in which the display area is divided into four areas, and each includes four modulators, carrier multipliers, driver circuits, LED aggregates, and integrators. However, the number of modulators, carrier multipliers, driver circuits, LED aggregates, integrators, etc. used in the visible light communication method and the visible light communication system using the same is limited to this example. It goes without saying that it is not done.

First, transmission data (Data 1 to Data 4) are input to the corresponding modulators 10 to 13, respectively, and arbitrary modulation (for example, BPSK (Binary Phase Shift Keying) is performed for each transmission data in the corresponding modulators 10 to 13, respectively. , QPSK (Quadrature Phase Shift Keying) and 16QAM (Quadrature Amplitude Modulation) are performed, and modulated signals for each transmission data output from the modulators 10 to 13 are input to corresponding carrier multipliers 20 to 23, respectively. The input modulation signal is multiplied by the carrier sine wave signal in the carrier multipliers 20 to 23. Here, the carrier frequency f1 multiplied by the modulation signal generated for each transmission data. four carrier sinusoidal signal cos corresponding to _{f4 (2πf 1 t) ~cos (} 2πf 4 t) are those having an orthogonal relationship to each other.

Modulated signals (hereinafter referred to as transmission signals) multiplied by the carrier sine wave signals by the multipliers 20 to 23 are input to the corresponding driver circuits 30 to 33, respectively. The driver circuits 30 to 33 are provided for each of the LED assemblies L1 to L4, and are used to drive the LED assemblies L1 to L4. When the corresponding transmission signal is input, the driver circuits D1 to D4 control the amount of current supplied to the LED assemblies L1 to L4 based on the input transmission signal, and emit light according to the signal amplitude of the transmission signal. Each LED aggregate is caused to emit light with intensity. The transmission signals transmitted from the display areas by the light emission of the LED assemblies L1 to L4 are added in space to form 4 Carrier-OFDM shown in FIG.

An OFDM signal generated by adding each transmission signal in space is received by a light receiving element 310 included in the receiving apparatus 300. The light receiving element 310 is composed of, for example, one PD (Photo Diode). When the light is received, an electrical signal (hereinafter referred to as a reception signal) corresponding to the intensity of the received light is output from the light receiving element 310. The received signal output from the light receiving element 310 is subjected to FFT (Fast Fourier Transform) processing according to the principle of OFDM demodulation. That is, the reception signal output from the light receiving element 310 is input to the carrier multipliers 330 to 333. The carrier multipliers 330 to 333, for example, for the received signal, respectively, a carrier sine wave signal cos (2πf ₁ t), a carrier sine wave signal cos (2πf ₂ t), a carrier sine wave signal cos (2πf ₃ t), And the carrier sine wave signal cos (2πf ₄ t).

In this way, the carrier multipliers 330 to 333 multiply the received signal by the carrier sine wave signal, so that each carrier multiplier 330 to 333 multiplies each carrier multiplier 330 to 333 respectively. A transmission signal corresponding to the wave signal is extracted.

Each transmission signal extracted by the multipliers 330 to 333 is input to the corresponding integrating circuits 350 to 353. In the integration circuits 350 to 353, for each transmission signal extracted from the multipliers 330 to 333 (output signals of the multipliers 330 to 333), an integration operation is performed in the integration interval up to the OFDM symbol length (T) on the time axis. The signal component corresponding to each of the carrier frequencies f1 to f4 is extracted. Each carrier frequency component extracted by the integrators 340 to 343 is input to the corresponding demodulators 350 to 353. When the demodulator 350 to 353 performs arbitrary demodulation processing (BPSK, QPSK, 16QAM) corresponding to each carrier frequency component, a data string corresponding to each transmission signal is restored, and each transmission data ( Information of Data1 to Data4) can be obtained. Although there is a driving method called local dimming as a driving method of the liquid crystal display device, the visible light communication system according to the present invention can be implemented even with the liquid crystal display device of the driving method.

As described above, when the display area of the transmission device 100 is divided into four areas (sub-display area # 1 to sub-display area # 4), and signals of different information are transmitted using a set of LEDs corresponding to each area. Was described as an example. That is, when the number of LED aggregates (the number of driver circuits that respectively drive the LED aggregates) is M and the number of carrier frequencies (the number of different information signals) is N, the number of M and N is The case where they are equal has been described as an example. Next, the visible light communication system when the relationship between M and N is M <N will be described below with reference to FIG.

FIG. 4 is a schematic diagram of the configuration of the visible light communication system in the case of M <N. It is a figure which shows the outline of a structure of a visible light communication system. Transmitting apparatus 100 of the visible light communication system according to the present embodiment basically transmits signals of different information using a collection of LEDs corresponding to sub display area # 1 to sub display area # 4. In this case, the configuration is almost the same as that of the transmission apparatus 100, but the number of driver circuits that drive the LED aggregates, the number of LED aggregates corresponding to the number of driver circuits, the number of transmission data, and the number of transmission data The difference is that the number of corresponding carrier frequencies is different. Another difference is that it further includes an adder / synthesizer that adds and synthesizes the transmission signals generated by the carrier multiplier.

In this example, the number of driver circuits for driving the LED assemblies is two (driver circuits D1 and D2), and the number of LED assemblies is two (LED assemblies L1 and L2). Transmission data includes Data1 to Data5, and carrier sine wave signals of cos (2πf ₁ t) to cos (2πf ₅ t) are prepared. In this example in which five transmission signals are two combined transmission signals, the number of addition synthesizers is three (addition synthesizers 50 to 53).

Transmission data Data1 to Data5 are input to the corresponding modulators 10 to 14, respectively. In the corresponding modulators 10 to 14, arbitrary modulation (for example, BPSK (Binary Phase Shift Keying), QPSK (for each transmission data) is performed. Quadrature Phase Shift Keying and 16QAM (Quadrature Amplitude Modulation) are performed, and the modulation signals for each of the transmission data (Data 1 to Data 5) output from the modulators 10 to 14 are input to the corresponding carrier multipliers 20 to 24, respectively. The input modulation signal is multiplied by a carrier sine wave signal in the carrier multipliers 20 to 24. Here, the modulation signal generated for each transmission data is multiplied. Five carrier sinusoidal signal cos corresponding to the carrier frequency _{f1~f5 (2πf 1 t) ~cos (} 2πf 5 t) has an orthogonal relation to each other.

Multiplier 20 adds and synthesizes the transmission data (Data1) and transmission data (Data2) signals multiplied by carrier sine wave signal cos (2πf ₁ t) or carrier sine wave signal cos (2πf ₁ t), respectively, and transmits the result. A combined transmission signal of data (Data 1) and transmission data (Data 2) is generated. The carrier sinusoidal signal cos (2 [pi] f ₃₎ in the multiplier 21, the transmission data carrier sinusoidal signal cos (2πf ₄ t) or carrier sinusoidal signal cos (2πf ₅ t) is multiplied, respectively (Data3), transmission data Each signal of (Data 4) and transmission data (Data 5) is added and combined to generate a combined transmission signal of transmission data (Data 3), transmission data (Data 4) and transmission data (Data 5).

Driver circuits D1 and D2 are provided for each of the LED assemblies L1 and L24, and are used to drive the LED assemblies L1 and L2. When the combined transmission signals are input from the adder / synthesizers 50 and 52, the driver circuits D1 and D2 control the amount of current supplied to the LED assemblies L1 and L2 based on the input combined transmission signals, The LED aggregates L1 and L2 are caused to emit light with a light emission intensity corresponding to the signal amplitude of the combined transmission signal. Therefore, the LED aggregate L1 can transmit information on Data1 and Data2, and the LED aggregate L2 can transmit information on Data3, Data4, and Data5.

As in the first embodiment, the combined transmission signals output from the LED assemblies L1 and L2 are added in space to become 5 Carrier-OFDM. The OFDM signal generated by adding the transmission signals in space is received by the light receiving element 310 included in the receiving apparatus 300, and thereafter, an assembly of LEDs corresponding to the sub display area # 1 to the sub display area # 4. As in the case of the visible light communication system in the case where signals of different information are transmitted using each, the FFT processing is performed according to the principle of OFDM demodulation, and each information can be extracted and reproduced.

As described above, the receiving device 300 used in the visible light communication system according to the present embodiment can obtain information on each piece of transmission data (Data 1 to Data 5), and thus receives all pieces of information on each piece of transmission data. You may display on the display screen of the apparatus 300. FIG. Alternatively, for example, when the receiving device 300 is set with a menu that allows the user to select information that the user desires to display on the display screen of the receiving device 300 among the information received from the plurality of display areas, the user receives By selecting desired information on the display screen of the device, it is possible to select information to be reproduced on the display screen of the receiving device.

FIG. 5 shows an example in which the receiving apparatus 300 is further provided with a received signal detection circuit (Spectrum Detector) 360 for detecting the received signal strength of each carrier frequency component output from the integrating circuits 350 to 353. The receiving apparatus 300 measures the intensity (reception power) of each of the extracted transmission signals and compares the intensity (reception power) of each transmission signal to reproduce the information of the transmission signal having the highest reception signal intensity. When set, the user can select information to be reproduced by bringing the receiving apparatus close to an arbitrary area on the display. The means for reproducing the information of the transmission signal having the highest received signal strength by comparing the strength (received power) of each transmitted signal may be provided with a circuit for comparing the strength (received power) of each transmitted signal. Processing for comparing the strength (reception power) of each transmission signal may be set by software.

With the above-described configuration, the visible light communication system according to the present invention divides the display area of the liquid crystal display device into a plurality of pieces, and simultaneously transmits different information for each group of LEDs that illuminate the plurality of areas. Even if configured, each information can be extracted and reproduced.

Further, the receiving apparatus 300 is provided with a reception signal detection circuit 360 for detecting the reception signal strength of each carrier frequency component output from the integration circuit 350, and is configured to reproduce the information of the transmission signal having the highest reception signal strength. In this case, the user can select information to be reproduced by bringing the receiving apparatus close to an arbitrary area on the display.

In the invention, since multiplexing is performed based on the principle of OFDM, efficient information transmission can be performed with little reduction in information transmission speed. For example, when the number of carriers is 4, the transmission rate that can be transmitted in one display area is about 2/5 of the case without multiplexing by OFDM. This is twice the transmission efficiency compared to the frequency division multiplexing described above.

Further, since each LED assembly 40 is made to emit light with the light emission intensity corresponding to the signal amplitude of each transmission signal without adding each transmission signal in the previous stage of the driver circuit 30, the PAPR increase in the OFDM method is adopted. Thus, the dynamic range required for the driver circuit 30 and the LED assembly 40 corresponding to each carrier frequency is kept low. As a result, it is possible to obtain an effect of improving the communication performance by the OFDM system using a small and inexpensive LED drive circuit and LED.

FIG. 6 shows a display area of the liquid crystal display device used in the visible light communication system according to the second embodiment of the present invention, for example, divided into four areas consisting of sub display area # 1 to sub display area # 4. And it is a figure which shows controlling different information (Data1 to Data4) and common information (common data) for every display area with respect to LED arrange | positioned as the backlight corresponding to each display area. In this embodiment, not only a direct type backlight but also an edge type backlight can be applied.

In the case of transmitting different information signals using the LED aggregates corresponding to the sub-display areas # 1 to # 4 of the first embodiment, the transmission device 100 includes four display areas. It is divided into (sub-display area # 1 to sub-display area # 4), and signals of different information are transmitted using a set of LEDs corresponding to each area. In the second embodiment, The transmitting apparatus 100 is configured to transmit not only different information signals transmitted by the LED aggregates corresponding to each area, but also information signals transmitted in common in all areas. Yes.

FIG. 7 is a diagram illustrating an outline of a visible light communication system according to the second embodiment. The transmission device 100 of the visible light communication system according to the present embodiment basically uses each of the LED aggregates corresponding to the sub display area # 1 to the sub display area # 4 of the first embodiment. The configuration is almost the same as that of the transmission apparatus 100 in the case of transmitting signals of different information, but the transmission data is greatly different in that it includes not only Data1 to Data4 but also common data. Therefore, in the transmission device 100 used in the visible light communication system according to the second embodiment, the modulator 14 that modulates the common data, and the modulated common data are multiplied by the carrier sine wave signal cos (2πf ₅ t). A carrier multiplier 24, and an addition synthesizer 50 that adds and synthesizes the modulation signal of the common data and any one of the modulation signals Data1 to Data4. Reception apparatus 100 further includes a carrier multiplier 334, an integrator 344, and a demodulator 354 so that a transmission signal of common data can be extracted and demodulated. Hereinafter, the transmission apparatus 100 used in the visible light communication system according to the second embodiment will be described mainly with respect to differences from the first embodiment with reference to FIG.

Similarly to other transmission data (Data 1 to Data 4), the common data is arbitrarily modulated for each transmission data (for example, BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16 QAM (equat quat modulation key equat). The carrier sine wave signal cos (2πf ₅ t) is multiplied by the carrier multiplier 20. Here, the carrier sine wave signal cos (2πf ₅ t) is multiplied by the other four carrier sine wave signals cos (2πf _1). t) to cos (2πf ₄ t).

The modulation signal of the common data (hereinafter referred to as a transmission signal of the common data) multiplied by the carrier sine wave signal cos (2πf ₅ t) by the multiplier 24 is converted into Data1 to Data4 corresponding to each display region in the adder / synthesizer 50, respectively. Are combined with the modulated signals multiplied by the carrier sine wave signal cos (2πf ₁ t) to carrier sine wave signal cos (2πf ₄ t). Therefore, the adder / synthesizers 50 to 53 add and synthesize the common data and the combined transmission signal of the data 1 of the modulation signal of the common data and the modulation signal of the Data 1 and the combined transmission signal of the Data 1 and the modulation signal of the common data and the modulation signal of the Data 2. The common data and the combined transmission signal of Data2, the common data and the combined transmission signal of Data3, and the combined transmission signal of the common data and Data3, and the combined signal of the common data and the modulation signal of Data4 are combined and combined. The common data and the combined transmission signal of Data1 are generated.

The driver circuits D1 to D4 are provided for each of the LED assemblies L1 to L4, and are used to drive the LED assemblies L1 to L4. When the combined transmission signals are input from the adder / synthesizers 50 to 53, the driver circuits D1 to D4 control the amount of current supplied to the LED assemblies L1 to L4 based on the input combined transmission signals, respectively. The LED aggregates L1 to L4 are caused to emit light with a light emission intensity corresponding to the signal amplitude of the combined transmission signal. Accordingly, each of the LED aggregates L1 to L4 can transmit information on any one of Data1 to Data4 and information on common data.

As in the first embodiment, the combined transmission signals output from the LED aggregates L1 to L4 are added in space to form 5 Carrier-OFDM shown in FIG. The OFDM signal generated by adding each transmission signal in space is received by the light receiving element 310 of the receiving apparatus 300, and thereafter, the FFT processing is performed according to the principle of OFDM demodulation as in the first embodiment. Done.

By the way, since the signal of the common data is transmitted from the aggregate of LEDs in the entire display area, the reception intensity of the reception signal corresponding to the common data output from the light receiving element 310 of the receiving device 300 is The signals transmitted from the LED assembly are added and become stronger than the signals of other Data1 to Data4. Therefore, in the visible light communication system according to the present embodiment, the reception device 300 is located at a relatively long distance from the liquid crystal display device by utilizing the relatively strong received signal strength of the common data. However, the receiving apparatus 300 can acquire the information of the common data by demodulating and reproducing the transmission signal of the common data.

Further, when the receiver 300 is located at a relatively short distance of the liquid crystal display device, each display area (LED aggregate) transmitted from the adjacent display area (LED aggregate) in addition to the information of the common data. Different information can be demodulated and reproduced.

Also in the present example, as in the first embodiment, the information that the user wants to display on the display screen of the receiving device 300 is selected from the information received from the plurality of display areas. If a menu that can be set is set, the user can easily select information to be reproduced on the display screen of the receiving apparatus. In addition, the reception apparatus 300 is provided with a reception signal detection circuit 360 for detecting the reception signal strength of each carrier frequency component output from the integration circuits 350 to 354, and reproduces the information of the transmission signal having the highest reception signal strength. When the setting to be performed is provided, the user can select information to be reproduced by bringing the receiving apparatus close to an arbitrary area on the display.

The visible light communication system according to the third embodiment of the present invention uses different LED signals corresponding to the sub-display area # 1 to sub-display area # 4 according to the first embodiment. The carrier frequency components of Data1 to Data4 output from the received signal detection circuit 360 for detecting the received signal strength of each carrier frequency component to the receiver 300. The received signal strength is monitored, and the movement of the receiving terminal is detected from the change in the signal strength ratio of each carrier frequency component.

For example, as shown in FIG. 1, the display area of the transmission device 100 is divided into four areas (sub-display area # 1 to sub-display area # 4), and different information is obtained using an aggregate of LEDs corresponding to each area. In the case of transmitting the above signal, a case where the light receiving element 310 is arranged at one end in the longitudinal direction of the substantially rectangular receiving device 300 will be described as an example.

When the direction of the front end where the light receiving element 310 of the transmission device 300 is disposed is toward the center point of the display area where the sub display areas # 1 to # 4 are in contact with each other, the light receiving element 310 and each of the sub display areas # 1 to ## 4, the received signal strengths of the transmission signals transmitted from the LED aggregates arranged in the sub display areas # 11 to # 4 are also equal as shown in FIG. 9, for example.

In this state, when the direction of the tip portion where the light receiving element 310 of the transmission device 300 is arranged is changed to the sub display region # 4, the light receiving element 310 of the transmission device 300 is transmitted from the LED aggregate arranged in each display region. Change occurs in the received signal strength of the transmitted signal. Since the distance between the display area # 4 and the light receiving element 310 is relatively short, and the distance between the sub display area # 1 and the light receiving element 310 is relatively long, as shown in FIG. The reception signal intensity of the transmission signal received from the LED arranged in the sub display area # 4 is relatively strong, and the reception signal intensity of the transmission signal received from the LED arranged in the sub display area # 1 is relatively weak.

Further, for example, the direction of the front end portion where the light receiving element 310 of the transmission device 300 is arranged is changed from the center point of the sub display area where the sub display areas # 1 to # 4 touch each other to the sub display area # 2 and the sub display area # 4. When the position is changed, the distance between the sub display areas # 2 and # 4 and the light receiving element 310 is relatively short, and the distance between the sub display areas # 1 and # 3 and the light receiving element 310 is relatively long. Therefore, as shown in FIG. 11, the received signal intensity of the transmission signal received by the light receiving element 310 from the LEDs arranged in the sub display areas # 2 and # 4 is relatively strong, and the sub display areas # 1 and # The reception signal strength of the transmission signal received from the LED arranged at 3 is relatively weak.

As described above, the receiving apparatus 300 receives the signal by monitoring the change in the ratio of the received signal strength of each transmission signal because the change in the ratio of the received signal strength of each transmitted signal is correlated with the movement of the receiving apparatus 300. The movement of the device 300 can be recognized.

The means for monitoring the change in the ratio of the received signal strength of each transmission signal and judging the movement of the receiving apparatus 300 in response to the change separately compares the change in the ratio of the received signal strength of each transmission signal. Accordingly, a circuit for judging the movement of the receiving apparatus 300 may be provided, or a process for monitoring the change in the ratio of the received signal strength of each transmission signal by software and determining the movement of the receiving apparatus 300 according to the change is set. May be.

The visible light communication method and the visible light communication system using the same according to the present embodiment are superimposed on the visible light communication method and the visible light communication system using the visible light communication method according to the first and second embodiments. Therefore, it is possible to use the receiver 300 by monitoring the change in the ratio of the received signal strength of each transmission signal while performing the visible light communication realized by the first and second embodiments. This produces an operational effect that makes it possible to recognize the movement of the camera.

In an environment where bidirectional communication with the liquid crystal display device is possible by wireless, infrared, or visible light communication, the receiving device 300 transmits information to the liquid crystal display device according to the movement of the receiving device 300. Remote control can be performed. For example, a remote control operation of selecting any of the sub display areas # 1 to # 4 using the receiving apparatus 300 will be described as an example. The receiving apparatus 300 is transmitted from each of the sub display areas # 1 to # 4. A change in the ratio of the received signal strength of the transmitted signal is monitored, and when the received signal strength of the transmitted signal transmitted from the sub display area # 1 becomes relatively high, the receiving apparatus 300 selects the sub display area # 1. The remote control operation is realized by setting to determine that it means that, and transmitting a signal indicating selecting the sub display area # 1 to the liquid crystal display device in accordance with the determination.

Realization of the remote control operation can be applied not only to a direct type backlight, but also to an edge type backlight, for example. Further, when the number of LED aggregates (the number of driver circuits that respectively drive the LED aggregates) is M and the number of carrier frequencies (the number of different information signals) is N, the relationship between M and N The present invention can also be applied to a visible light communication system when M <N.

In particular, in the case of an edge-type backlight or in the case of M <N, the association between each sub-display area and the LED assembly is, for example, in accordance with the distance between each sub-display area and the LED assembly. In some cases, it will disappear. In that case, it becomes difficult for the user to select information to be reproduced according to the intensity of light received by the receiving device 300. However, even in such a case, there is a configuration in which the receiving apparatus 300 determines the movement of the receiving apparatus 300 according to the change in the ratio of the received signal strength of each transmission signal, and performs a remote control operation in accordance with such determination. In this case, the user can make a selection by bringing the receiving apparatus close to an arbitrary area on the sub-display.

The visible light communication method according to the embodiment of the present invention and the visible light communication system using the same have been described above, but the present invention is not limited to the above-described embodiment and does not depart from the gist of the present invention. Of course, various changes can be made within the range.

DESCRIPTION OF SYMBOLS 100 Transmission apparatus 100-1 Backlight 100-2 Display area 10 Modulator 20 Transmission side carrier multiplier 300 Transmission apparatus 330 Reception side carrier multiplier 340 Integrator 350 Demodulator 360 Reception signal detection circuit

Claims (14)

Transmitting device for transmitting N pieces of information using signals generated by a plurality of light emitting elements arranged in a display area composed of N sub display areas of the display device, and receiving signals generated by the light emitting elements In a visible light communication system comprising a receiving device,
The transmitter is
N input terminals to which the N data are respectively input;
N modulators for modulating N data respectively input from the N input terminals to generate N modulated signals;
N transmission-side carrier multipliers that generate N transmission signals by multiplying N modulation signals respectively output from the N modulators by N carrier signals orthogonal to each other;
The N sub-display areas;
N light-emitting element drivers that emit light in accordance with N transmission signals respectively output from the N carrier multipliers, each of the light-emitting elements associated with the N sub-display areas; Have
The receiving device is:
A light receiving element that receives a transmission signal transmitted from an assembly of light emitting elements respectively associated with the N sub-display areas, and outputs a reception signal corresponding to the received light intensity;
N reception sides that respectively extract N modulation signals modulated for each of the N carriers by multiplying the reception signal output from the light receiving element by any of the N carrier signals. A carrier multiplier,
N integrating circuits for integrating the N modulated signals output from the N receiving carrier multipliers, respectively,
N demodulators for demodulating each modulation signal integrated by the N integration circuits;
A visible light communication system characterized by comprising: The receiving apparatus further includes information reproduction selecting means for selecting information to be reproduced on the display screen of the receiving apparatus from information of the N modulated signals demodulated by the N demodulating units. The visible light communication system according to claim 1. The reception apparatus further includes a reception signal detection circuit that detects reception signal strengths of the N modulated signals integrated by using the N modulation signals respectively integrated by the N integration circuits. The visible light communication system according to claim 1, wherein the visible light communication system is characterized. The receiving apparatus obtains information on a modulation signal corresponding to a received signal strength having a relatively largest value among received signal strengths of the integrated N modulated signals output from the received signal detection circuit. 4. The visible light communication system according to claim 3, further comprising a maximum intensity received signal reproducing means for reproducing in the receiving device. The operation of recognizing the movement of the receiving apparatus by detecting a change in the relative magnitude of the received signal intensity of the integrated N modulated signals output from the received signal detection circuit. The visible light communication system according to claim 3 or 4, further comprising means. The transmission apparatus includes a common information modulator that modulates common information to be transmitted using all of the aggregates of the light emitting elements respectively associated with the N sub-display areas, and the modulated common information is the N information. A common-side information carrier multiplier that multiplies each carrier signal by a carrier signal of common information orthogonal to each other to generate a transmission signal of the common information, a transmission signal of the common information, and a transmission signal of the N data And N addition synthesizers that respectively add and synthesize
The reception apparatus extracts a modulation signal of the common information by multiplying by the carrier signal of the common information, and a reception side common information carrier multiplier,
A common information integration circuit for integrating the modulation signal of the common information output from the reception side common information carrier multiplier;
A common information demodulator that demodulates the modulation signal of the common information integrated by the common information integration circuit;
The visible light communication system according to claim 1, further comprising: N input terminals to which N pieces of data are respectively input;
N modulators for modulating N data respectively input from the N input terminals to generate N modulated signals;
N transmission-side carrier multipliers that generate N transmission signals by multiplying N modulation signals respectively output from the N modulators by N carrier signals orthogonal to each other;
By grouping the display area into N sub-display areas, a set of light-emitting elements respectively associated with the N sub-display areas is output from the N carrier multipliers. And N light emitting element drivers that emit light according to N transmission signals. The common information to be transmitted using all of the aggregates of the respective light emitting elements respectively associated with the N sub-display areas is multiplied by the common information carrier signal orthogonal to the N carrier signals, and the common information 8. The transmission-side common information carrier multiplier for generating a transmission signal, and N addition synthesizers for adding and combining the transmission signal of the previous common information and the N transmission signals, respectively. The transmitting device according to 1. A light receiving element that receives a transmission signal transmitted from an assembly of light emitting elements respectively associated with the N sub-display areas and outputs a reception signal corresponding to the received light intensity;
N reception sides that respectively extract N modulation signals modulated for each of the N carriers by multiplying the reception signal output from the light receiving element by any of the N carrier signals. A carrier multiplier,
N integration circuits for integrating each of the N modulation signals output from the N reception-side carrier multipliers;
And a N demodulator for demodulating the N modulation signals integrated by the N integration circuits. The receiving apparatus further includes information reproduction selection means for selecting information to be reproduced on the display screen of the receiving apparatus from information of the N modulated signals demodulated by the N demodulators. The receiving device according to claim 9. The reception apparatus further includes a reception signal detection circuit that detects reception signal strengths of the N modulated signals integrated by using the N modulation signals integrated by the N integration circuits. The receiving device according to claim 10. The receiving apparatus obtains information on a modulation signal corresponding to a received signal strength having a relatively largest value among received signal strengths of the integrated N modulated signals output from the received signal detection circuit. 12. The receiving apparatus according to claim 11, further comprising a maximum intensity received signal reproducing means for reproducing the receiving apparatus. The operation of recognizing the movement of the receiving apparatus by detecting a change in the relative magnitude of the received signal intensity of the integrated N modulated signals output from the received signal detection circuit. The receiving device according to claim 11 or 12, further comprising means. A receiving-side common information carrier multiplier that extracts the modulation signal of the common information by multiplying by the carrier signal of the common information;
A common information integration circuit for integrating the modulation signal of the common information output from the reception side common information carrier multiplier;
The receiving apparatus according to claim 9, further comprising: a common information demodulator that demodulates a modulation signal of the common information integrated by the common information integration circuit.

Images