JP4361911B2 - Visible light communication method and system - Google Patents

Description

  The present invention relates to a communication method using visible light as a communication medium. The information is converted into a scalar quantity or a vector quantity corresponding to a color on the transmission side, and visible light having a wavelength corresponding to this is transmitted to the reception side. The present invention relates to a method of performing photometry on the receiving side and performing inverse conversion from the scalar quantity or vector quantity to information for communication.

  As information transmission systems in conventional information communication systems, AM (amplitude modulation), FM (frequency modulation), PWM (phase modulation), etc. are known for analog transmission.

In digital transmission, the following methods are known.
For example, scalar signal ASK sequences (digital amplitude modulation (amplitude on / off keying ASK)), vector signal QAM (quadrature amplitude modulation: 16QAM, 64QAM, 256QAM) mainly used for fixed wireless communication, mainly between satellite communications Binary phase shift keying (BPSK (Binary PSK): 1 bit (0, π) / phase), vector signal system QPSK (Quadrature Phase shift keying), π / 4 shift QPSK, FSK (Frequency shift keying) of vector signal FSK sequence mainly used for mobile communication: a set of different frequencies (f1, f2) set in advance 1 Bit (0 = f1, 1 = f2)), MSK (minimum shift keying), DMSK (differential MSK (differential minimum shift keying (carrier differential phase modulation))), scalar signal system Time-varying signal TDMA (transmission channel time division multiple access), CDMA (transmission channel code division multiple access), CDMA (transmission channel code division multiple access: OOK (on / off keying) modulation OOK-CDMA system And PPM / CDMA systems using pulse position modulation (PPM)) are known (see, for example, Patent Documents 1 to 7).

JP-A-9-307472 JP 2002-305558 A JP-A-7-131379 JP-A-9-214569 JP 2001-160768 A JP 2000-183984 A JP 2001-86029 A

All of the conventional transmission methods transmit information using a physical quantity obtained by combining time with each of electric quantities such as voltage, current, phase, magnetic flux, and electric charge, or radio wave quantities, or a combination of quantities. It is like that.
That is, as shown in FIG. 5, in the analog transmission system, the change per unit time t of the amplitude (voltage, current) A, the frequency f, or the phase θ of the signal S is the amount of communication. Further, as a method of expressing this as a two-dimensional communication element, there is a method of capturing a spectrum of a radius r, a rotation speed (frequency), and a phase difference (phase speed) as a communication element. In the modulation of each physical quantity, the communication information is temporal in the vector space of the physical quantity formed by the modulation of the electrical quantities of the signal S shown in the figure at any of the radius r and the angular frequency ω (dθ / dt). The change amount is transmitted and identified as a communication elementary amount.
Unlike analog transmission systems that transmit information in response to continuous signal changes, digital transmission systems transmit information in response to changes in the temporal position of the pulse train, but the pulse is the original information signal. It is an analog signal encoded and multiplexed, and it is still transmitted and identified as a communication elementary quantity with the temporal change of the vector space formed by physical quantities of voltage or current, frequency and phase. .

  In addition, as is apparent from the transmission form using an optical fiber cable, the conventional transmission method using light uses light as a communication medium, but the transmitted signal S has a frequency in the visible range. There is no change in the fact that the temporal changes in the physical quantities in the band are used as communication elementary quantities.

  By the way, when an electromagnetic wave (radiation, radiation) having a wavelength of about 380 nm to 780 nm enters a human eye, the person feels light. Physical quantities such as the wavelength and radiation intensity of electromagnetic waves that can be felt by this person can be physically measured. On the other hand, psychological quantities such as the color and brightness of light felt by humans cannot be directly measured. People with normal color recognition can see the same color, recognize it as the same color, and communicate color information. The mechanism for recognizing this color is the information on the light that is input using the eye as a sensor. Are stored as color data in the brain so that the same color can be sensed, and the mapping data and the color recognized by sensing are collated to identify the color.

  The mechanism by which a person recognizes color is different from physically measuring the emission of light, and evaluates light based on psychometric light quantity such as brightness and color of light perceived by a person. The present invention constitutes a new communication method using the psychometric light quantity as an information transmission means and using the psychometric light quantity as the communication elementary quantity instead of the communication elementary quantity formed by the physical quantities.

A colorimetric value obtained by measuring the color difference between hue, brightness, and saturation using the eye as a sensor cannot be expressed as an objective mathematical calculation value. However, in each intercommunication, it is not always necessary to give transmission information complete objectivity. If there is a protocol that can be understood by each other, it is not a necessary and sufficient condition for communication. .
For example, red and blue pedestrian traffic lights may show red or blue signal colors clearly depending on the individual differences in eye sensitivity, and also appear bright red or dark depending on the ambient brightness. It may appear red. Even if everyone who looks at the traffic light can specify the signal color day or night, the colorimetric values will not match. However, changing the signal from red to blue or vice versa means that the viewer can perceive and recognize the change in the color difference of the signal, thereby stopping if it is red and moving if it is blue. Judgment is made. In other words, in the communication of information here, the objective colorimetric value of the signal color is not transmitted from the signal device to the person, but the amount of change in the color difference of the signal color is changed from the signal device to the person by changing the signal color. Therefore, even if it is a psychometric light quantity that is difficult to make the numerical value objective, it is possible to communicate the change amount on the color measurement vector as a communication elementary quantity, and A communication mode combining psychometric light quantity and physical quantities can also be realized.

Therefore, the present invention converts a transmission information into a single or a plurality of groups of colorimetric vectors , and a transmitter having means for emitting visible light having a wavelength associated with the colorimetric vectors ;
It has means for receiving visible light emitted from a transmitter, measuring the color of the received visible light, generating a color measurement vector from the amount of change in color difference, and converting the received color information into reception information associated with the color measurement vector. And a visible light communication method for transmitting information from a transmitter to a receiver using visible light as a communication medium, the same corresponding to the wavelength of visible light for communication between the transmitter and the receiver A colorimetric vector is set, and the amount of spatial or temporal change in the colorimetric vector of visible light is used as a communication element for information transmitted and received between the two devices.

In addition, the visible light communication system of the present invention includes means for converting transmission information into a single or a plurality of groups of colorimetric vectors, and means for emitting visible light having a wavelength associated with the converted colorimetric vectors. A colorimetric vector is generated from a transmitter, means for receiving visible light emitted from the transmitter, means for calculating a colorimetric value of the received visible light, and a color difference change amount of the calculated colorimetric value. And a spatially or temporally generated colorimetric vector associated with the same colorimetric vector corresponding to the wavelength of visible light for communicating with the transmitter. It is characterized by comprising a receiver having means for converting into received information based on the amount of change .

In the communication method and the communication system, a colorimetric scalar quantity can be used as a communication elementary quantity instead of a colorimetric vector. In that case, the transmitter converts the transmission information into the colorimetric scalar amount, the receiver derives the colorimetric scalar amount from the calculation of the colorimetric value, and the inverse conversion from the derived scalar amount to the information is performed. The amount of change over time of the scalar quantity becomes the communication elementary quantity. Also, the conversion of communication information can be performed by associating one unit or a plurality of units of information with a single colorimetric vector amount or scalar amount, or with a plurality of groups of colorimetric vector amounts or scalar amounts. .
In the following, a process for converting information into a colorimetric vector will be described. Processing for conversion to a colorimetric scalar is performed in accordance with this.

  In the present invention, the means for emitting visible light of a predetermined wavelength provided in the transmitter includes, for example, a white light source, a spectroscope that divides the light source, and a wavelength of visible light to which the transmitted colorimetric vector is adapted. It is possible to generate a spectral spectrum by combining with an attenuator, and use one spectral spectrum as one transmission channel to emit light. Further, another spectral spectrum may be formed in the same manner as another channel, and the spectral spectrum may be used as a plurality of channels. Furthermore, a light source configured so that the wavelength of the output light can be appropriately set and adjusted may be used. A plurality of light emitting diodes having different spectral radiation distributions may be used, and the wavelength of the visible light to be emitted may be adjusted in accordance with the colorimetric vector to be transmitted.

  The color measurement vector is not a physical quantity measurement Fourier space vector by spectroscopy, but a vector of a psychometric color measurement system using an eye as a sensor, that is, a CIE color system (RGB color system, XYZ color system, color mixture chromaticity), USC table Color system space, color vision color display system (psychological perception system Munsell color system color (color hue 104), psychophysical colorimetry system Ostwald color system (24 colors)) ULCS color system (Adams uniform color vision space) , Hunter uniform color vision space) or a color vector displayed in a DIN color system space, or a colorimetric space vector for light source color photometry and object reflection color photometry. From these, the same colorimetric vector for communication between the corresponding transmitter and receiver is selected.

  In the transmitter, the information to be transmitted is associated with the spectral spectrum, and on the arbitrary colorimetric vector space, transmission data is generated with a vector change amount as a communication elementary amount, Visible light can be emitted.

  On the other hand, the stimulator direct reading method and the spectrocolorimetric method are used as means for receiving visible light emitted from the transmitter and measuring the colorimetric value in the receiver. For the stimulus value direct reading method, for example, a sensor that receives visible light and measures tristimulus values or a colorimeter equipped with the sensor, for the colorimetry method, for example, a diffraction grating or a spectroscope and optical power A sensor for measuring a spectral spectrum by combining a measuring instrument and a polychromator, a spectrocolorimeter equipped with a spectroscopic sensor, and the like can be used.

Specifically, the measurement of visible light can be performed by measuring the spectrum distribution S (λ) of the received light using a monochromator or polychromator as described in JIS Z 8724, for example. Then, the tristimulus values X, Y, and Z in the color solid space shown in FIG. 1A are obtained from the spectrum distribution, and are projected onto a plane (x + y + z = 1), and are shown in FIG. The xyz color system 2D plane color coordinates shown are determined.
In the figure, when the white point of the color coordinates (0.333, 0.333) is the center, photometry (x, y) obtained from the spectrum distribution of the color light is represented by a plane vector (x−0.333, y -0.333), when moving to the x, y coordinate axis center, vector change of plane vector F (= x + jy) with 90 ° declination as imaginary number [j], plane phase vector change, rotation including time element The speed vector change can be used as a communication element of transmission information.

  That is, the present invention multiplies the color matching functions x (λ), y (λ), and z (λ) by a constant and a spectrum analysis determined so that the value of y matches the photometric amount for each wavelength. In addition, a sum of wavelengths from about 380 nm to 780 nm, which is a visible light region, is obtained to obtain tristimulus values X, Y, and Z. From the number of tristimulus values X, Y, and Z, chromaticity coordinates x = X / ( X + Y + Z) and y = Y / (X + Y + Z) are obtained, respectively, and the color coordinate values of x and y are moved by (x = 0.333, y = 0.333), and the Y cylindrical axis, plane coordinates (x, A colorimetric vector of y) cylindrical three-dimensional coordinates is obtained. The spatial change amount, the temporal change amount, the change speed, and the acceleration on the colorimetric vector are used as communication elementary amounts.

In this way, a colorimetric vector space for visible light is formed, and the amount of spatial or temporal change in the vector is used as a communication elementary, compared with a conventional information transmission method using a physical quantity as a communication elementary. Therefore, the amount of information transmitted can be dramatically increased, and the transmission efficiency can be dramatically increased. In addition, by using visible light as an information communication medium, various devices and devices having a function of emitting visible light, for example, color light emitting devices such as illumination lamps, light-emitting bulletin boards, video displays, etc. It can be used as a transmitter used for transmission, and the transmission form of information can be expanded in various ways.

  A monochromator, a polychromator, a photoelectric colorimeter, or the like can be used as a spectroscope for measuring the spectrum distribution of visible light. Any of an interference type in which the optical path length is variable and a dispersion type using dispersion elements having different refractive indexes may be used. Since the monochromator mechanically rotates the diffraction grating, the analysis processing time is restricted by the rotational speed. Therefore, it is preferable to use a polychromator capable of simultaneously measuring the spectral distribution using a photodiode array for equipment that transmits and processes high-speed and large-capacity information.

  The colorimetric vector is formed not only by the above-described xyz color system chromaticity diagram, but also, for example, by a chromaticity coordinate (x, y) and tristimulus value Y obtained by a photoelectric colorimeter as shown in FIG. A three-dimensional space may be formed, and the space change, time change, speed, and acceleration of the cylindrical space vector may be used as communication elementary quantities. Furthermore, instead of the tristimulus value Y of the luminance value, color rendering (JIS Z 8726) and color temperature (JIS Z 8725) may be used.

The color display method is calculated from the L, a ^* , b ^* , and L, u ^* , v ^* color display methods of JIS Z 8729, and the chroma, hue angle, and tristimulus values described therein. A cylindrical coordinate vector may be configured with the brightness L.
Furthermore, a colorimetric space vector is formed by using various color display methods based on photometric amounts described in known documents (for example, “New Color Science Handbook”, edited by the Japan Color Society, University of Tokyo Press), and the vector Can be used as a communication element.

  Furthermore, the present invention provides a public information communication based on a published color matching function, etc., and a colorimetric evaluation function (e.g., color matching function × spectral solid angle reflectance, color matching function × spectral solid) Confidential information communication is possible by having both the transmitting and receiving sides have (angle transmittance, proportional constant) and photometric means. Since the conventional communication elementary quantity is a physical quantity, the measured communication elementary quantity can be grasped physically, so retroactive calculation can be retroactively performed, but the communication elementary quantity is the quantity in the colorimetric vector space. If so, a high degree of retroactive retroactive processing is required, and the confidentiality of information can be significantly improved. By forming transmission information by mixing dummy colorimetric vectors with colorimetric vectors obtained by converting communication information, it is possible to further improve the confidentiality of confidential information communication.

The colorimetric vector may be regarded as a spectrum of spread spectrum communication, and the present invention may be a spread spectrum communication system formed by multiplying a narrowband transmission spectrum by a code sequence.
In the spread spectrum communication exemplified in the prior art, for example, transmission data is multiplied and transmitted with exclusive OR on the transmission side, and the communication data is generated and transmitted on the reception side. To obtain the original transmission data. That is, in spread spectrum communication, transmission data, which is physical quantities, is modulated by mathematical operations to generate communication data, which is transmitted with radio waves, which are physical quantities, and on the side where it is received, This is a communication processing method in which various amounts of received data are subjected to demodulation processing by inverse calculation to obtain original transmission data.
In the course of this communication process, the modulation process performed on the transmission side is a process for performing a unique function process on the transmission data, and the data demodulation process performed on the reception side is similarly performed on the received data by performing a unique function process. This is a process of converting to transmission data, and it is possible to replace the function processing unique to such modulation / demodulation with a colorimetric function.
A communication method that uses this unique function processing as a colorimetric function is colorimetric spectrum communication, and uses the property that the effect of color measurement is small in the range of light intensity where the colorimetry is constant. If the communication is regarded as a spectrum of spread communication, it is spread to the spectrum of the entire visible light, and under the random light noise, the colorimetric spread spectrum communication with excellent secrecy using the chromaticity coordinate two-dimensional vector is realized. Is possible.

  Furthermore, when the colorimetric vector formed for each sector divided by the color difference of the colorimetric solid space is used as transmission data, an exclusive OR sequence corresponding to a plurality of sectors in the solid space is generated, Colorimetric vector spread spectrum that transmits the visible light spectrum obtained by multiplying the generated sequence by transmission data, and multiplies the visible light spectrum received at the receiving side by an exclusive OR number sequence to demodulate the transmitted data Communication is also possible. A three-dimensional space sector may be a two-dimensional sector of chromaticity coordinates, an exclusive OR sequence corresponding to the sector may be generated, and the same processing may be performed.

In addition to the above method, a complementary color relationship can also be used for the communication element of the colorimetric vector.
According to the description of the known document (part 155), the complementary color relationship is obtained by adding two color lights P (x _p , y _p ) and Q (x _q , y _q ) as an additive color mixture, resulting in white W (x _{w 2} , y _w ), the original dichroic light is defined as having a complementary color relationship. Further, since the outer frame on the chromaticity diagram indicates the wavelength, the outer frame wavelengths on the chromaticity diagram that pass through the white W (x _w , y _w ) are called complementary wavelength pairs. On the inner side of the outer frame, coordinate points are configured by a spectrum group having an arbitrary wavelength, and two of these colors can form a complementary color relationship.
As an example of a colorimetric vector communication method using the complementary color relationship unique to these colorimetric vectors, from the Euler's formula [Exp (jθ) = cosθ + jsinθ], If −1) = Exp (jπ), colors having a complementary color relationship can be used as a communication element.
Further, according to the description of the above-mentioned known document, in the chromaticity coordinates, if Y stimulus value is given as ky _p × (x _q −x _w ) and Q as ky _q × (x _w −x _p ), P (x _p , y _p ), Q (x _q , y _q ) are additively mixed to create white W (x _w , y _w ), and the complementary color relationship is positioned. As in the Munsell coordinate vector , It can be used as a communication element. In addition, the afterimage pairs described in the above-mentioned known document (page 157) can also be used as the amount of communication.
Further, a colorimetric phase change obtained by multiplying a colorimetric phase change Exp (j (θ ₁ −θ ₂ )) by a complementary color operator vector Exp (jπ) with respect to two phase angles θ ₁ and θ ₂ capable of an arbitrary color difference. Colorimetric vector change complementary colors obtained by multiplying Exp (jπ + j (θ ₁ −θ ₂ )) by an arbitrary spectrum may be used. If the complementary color operator vector is an arbitrary rotation vector operator Exp (jθ), BPSK, QPSK , Π / 4 shift QPSK, arbitrary θ shift QPSK, FSK, MSK, DMSKDMA, CDMA, OOK, PPM, etc. it can.

A preferred embodiment of the present invention will be described with reference to the drawings.
FIG. 3 is a conceptual diagram of a visible light communication system according to the present invention.
As shown in the figure, this visible light communication system includes a transmitter 1 having a light emitting unit 11 and a receiver 2 having a light receiving unit 21 as constituent elements, and visible light VR emitted from the transmitter 1. As a communication medium, information is transmitted from the transmitter 1 to the receiver 2. Transmission of visible light VR from the transmitter 1 to the receiver 2 is also performed using an optical fiber.

The transmitter 1 corresponds to a colorimetric vector coordinate unit 12, a vector modulation unit 13 that associates a spectral component from a light source with the coordinate unit and converts a transmission information signal into a colorimetric vector, and a converted colorimetric vector. And a spectrum modulation unit 14 that generates visible light having the above-described wavelength, and is configured to emit the synthesized visible light from the light emitting unit 11.
The receiver 2 is measured by a colorimetric vector coordinate unit 22 that is the same as the colorimetric vector coordinate unit 12 of the transmitter 1 and a colorimetric unit 23 that measures a colorimetric value of the visible light VR received by the light receiving unit 21. And a spectrum demodulator 24 for generating a colorimetric vector from the colorimetric vector coordinate unit 22 and a vector demodulator 25 for converting the generated vector into received information. Yes. Note that the information transmitted from the transmitter 1 to the receiver 2 includes all types of data to be digitized such as characters, images, and sounds.

FIG. 4 shows an example of the configuration of the signal processing unit included in the transmitter 1 and the receiver 2.
As shown in FIG. 1A, the transmitter 1 includes a light source unit 15 that emits white light and a spectroscope 16 that splits the light source light, and the vector modulation unit 13 is converted into transmission information by an eigenfunction. An amplifier 14a that amplifies the spectrum of each spectrum by the spectroscope 16 is configured by an encoding processing unit 13a that performs weighting processing and an attenuation controller 13b that associates the weighted information with data for each wavelength. And an attenuator 14b that selectively controls light of each spectrum by the attenuation controller 13b.
Then, the transmission information signal is converted into a colorimetric vector and weighted by an eigenfunction, and visible light corresponding to the spectrum is generated by the spectrum modulation unit 14 and emitted from the light emitting unit 11. is there.
Further, as shown in FIG. 5B, the receiver 2 includes the spectrophotometer 23a and the photoelectric device 23b to extract the spectrum of the visible light VR received and extracts the same code as described above. The colorimetric vector coordinate unit 22 and the spectrum demodulating unit 24 having the conversion processing unit 22a generate a colorimetric vector from the extracted spectrum change amount, and the vector demodulating unit 25 converts the colorimetric vector into reception information. It is.

  In the illustrated form, the spectrum of the visible light region is configured using a white light source. However, the spectrum may be configured using visible light of a specific color such as an LED or a laser beam. Visible light converted from a color scalar can be generated by any suitable means.

It is a figure for demonstrating the process which uses the variation | change_quantity of the colorimetric vector in this invention as a communication elementary quantity. It is a figure for demonstrating the correspondence of the element of communication at the time of utilizing cylindrical three-dimensional space as a colorimetric vector in this invention. 1 is a conceptual diagram of a visible light communication system according to the present invention. (A), (B) is the figure which showed an example of the structure of the signal processing part which a transmitter and a receiver respectively comprise. It is a figure for demonstrating the process of the analog transmission system which used the physical quantity as the communication elementary quantity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmitter, 2 receiver, VR visible light, 11 Light emission part, 12 Vector coordinate part, 13 Vector modulation part, 14 Spectrum modulation part, 21 Light reception part, 22 Vector coordinate part, 23 Color measurement part, 24 Spectrum demodulation part , 25 Vector demodulator

Claims (2)

A transmitter having means for converting transmission information into a single or a plurality of groups of colorimetric vectors and emitting visible light having a wavelength associated with the colorimetric vectors ;
It has means for receiving visible light emitted from a transmitter, measuring the color of the received visible light, generating a color measurement vector from the amount of change in color difference, and converting the received color information into reception information associated with the color measurement vector. In a visible light communication method comprising a receiver and transmitting information from a transmitter to a receiver using visible light as a communication medium,
The same colorimetric vector corresponding to the wavelength of visible light for communication between the transmitter and receiver is set, and the colorimetric vector of visible light is used as a communication element of information transmitted and received between the two units. A visible light communication method characterized by using a spatial or temporal change amount. A transmitter having means for converting transmission information into a single or a plurality of groups of colorimetric vectors, and means for emitting visible light having a wavelength associated with the converted colorimetric vectors ;
Means for receiving visible light emitted from the transmitter, means for calculating a colorimetric value of the received visible light, means for generating a colorimetric vector from the amount of change in the color difference of the calculated colorimetric value, and generation Based on the amount of spatial or temporal change of the generated colorimetric vector associated with the same colorimetric vector corresponding to the wavelength of visible light for communicating with the transmitter. And a visible light communication system comprising a receiver having means for converting into reception information.

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