KR100944024B1 - Light receiving apparatus and visible light communication apparatus - Google Patents

Abstract

An object of the present invention is to perform high-quality data transmission at high speed by using light of a plurality of wavelength bands output from a plurality of light emitting means having different response speeds at the time of light output.

As a solution for this, the data signal to be transmitted is supplied to the modulator 12 of the transmitter 10, and the output of the blue light-excited white LED 14 is modulated by the modulator 12, and the blue LED light and the phosphor Light is output. The blue light after modulation passes through the LED light transmitting color filter 22B and enters the photoelectric converter 24B. On the other hand, the phosphor light after modulation passes through the phosphor light transmitting color filter 22F and is incident on the photoelectric converter 24F. In the photoelectric converters 24B and 24F, incident light is converted into an electrical signal. After the amplification by the amplifiers 26B and 26F, the signal after conversion is emphasized by the equalizers 28B and 28F in response to the response characteristics of the blue light and the response characteristics of the phosphor light, thereby reducing the slowing of the waveform.

Visible light, communication, blue LED light, phosphor light, transmission color filter, photoelectric converter, equalizer

Description

LIGHT RECEIVING APPARATUS AND VISIBLE LIGHT COMMUNICATION APPARATUS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission system for transmitting a signal using visible light. For example, light reception suitable for communication using a white light emitting diode (hereinafter, referred to as a white LED) including light emission of a phosphor. A device and a visible light communication device.

In recent years, the development of white LEDs has been actively conducted, and is being used in various fields such as lighting, vehicle mounting lamps, and liquid crystal backlights. This white LED has characteristics such as a very fast on / off switching response speed compared with, for example, a white light source such as a fluorescent lamp. Accordingly, a visible light communication system has been proposed that has a data transmission function for illumination light of a white LED using white light by the LED as a data transmission medium (see Patent Document 1 below). That is, the light emission intensity of the white LED is modulated in accordance with the transmission data, and the reception side converts the intensity of the light into an electrical signal through a photoelectric converter such as a photo diode (hereinafter referred to as PD) to realize data transmission.

However, the white LED can be mainly classified into three types according to the light emission method, for example, as shown in the following Non-Patent Document 1.

(1) Blue light excitation type white LED: A combination of a blue LED and a phosphor emitting mainly yellow light. The phosphor represented by the YAG (yttrium aluminum garnet) system is arrange | positioned around a blue LED, and it has a structure accommodated in one package. In this system, the surrounding phosphor is excited by the blue light output from the blue LED arranged at the center, and the color (mainly yellow) mainly having a complementary color relation with blue is output from this phosphor. By mixing the yellow fluorescence by this fluorescent substance and the blue light by the said blue LED, white light is pseudo-obtained.

The advantages of such blue-light-excited white LEDs include (1) high energy utilization efficiency and high illumination, and (2) low cost due to simple configuration. . On the other hand, as a disadvantage, the color rendering is bad. Color rendering refers to the characteristic of the way the color of an object is seen by illumination, and the color rendering is good as the color is closer to that seen in natural light.

6A illustrates an example of a blue light excited white LED. As shown in the figure, a blue LED 900 is provided on the main surface of the resin case 902. The driving voltage application terminal (not shown) of the blue LED 900 is connected to the extraction electrodes 904 and 906, respectively. When a driving voltage is applied to these lead electrodes 904 and 906, blue light is output from the blue LED 900, a part of which is incident on the phosphor 908. As a result, the phosphor 908 is excited to output fluorescence. Some blue LEDs have light emission characteristics of various wavelengths, and those having a peak wavelength in the range of 440 to 470 nm are used. The phosphor 908 is used to emit light on the longer wavelength side than the peak wavelength of the blue LED. Then, the phosphor particles 908 are disposed in the radially translucent transparent resin so as not to block the light emitted from the blue LED. 6B shows emission spectrum characteristics of the blue light excited white LED. The part enclosed by the dotted line SA is a blue light part, and the part enclosed by the dotted line SB is a light emission part by fluorescent substance. In this way, the light emitted by the phosphor exists on the longer wavelength side than the peak wavelength of the light emitted by the blue LED.

 (2) The ultraviolet light excitation type white LED is a combination of an ultraviolet LED and phosphors emitting three primary colors of R, G, and B (red, green, and blue). The phosphors emitting three primary colors of R, G, and B are disposed around the ultraviolet light LED, respectively, and are stored in one package. In this system, the surrounding phosphor is excited by the ultraviolet light output from the ultraviolet light LED disposed at the center, and three primary colors of R, G, and B are output from these phosphors, respectively. White light is obtained by mixing these R, G, and B light.

Ultraviolet LEDs have light emission characteristics of various wavelengths, and those having a peak wavelength in the range of 380 to 410 nm are used. The phosphor emits light on the longer wavelength side than the peak wavelength of the ultraviolet LED. In order to sufficiently absorb and excite the light emitted by the ultraviolet LED, a large number of phosphor particles emitting three primary colors of light are disposed in the translucent transparent resin.

An advantage of such ultraviolet-excited white LEDs is that the color rendering properties described above are good. On the other hand, the disadvantages include (1) the energy utilization efficiency is lower than the blue light excitation type white LED, it is difficult to obtain a high illuminance, (2) the ultraviolet light emission because the driving voltage of the LED is high.

(3) Three-color emitting white LED: A combination of R, G, and B LEDs. Three types of LEDs, red LED, green LED and blue LED, are stored in one package. In this system, white light is obtained by simultaneously emitting respective LEDs having three primary colors.

Advantages of such a three-color light emitting white LED is that the color rendering is good, as in the ultraviolet light-excited white LED. On the other hand, since the three types of LEDs are mounted in one package, the disadvantage is that they are expensive compared to other methods.

The characteristics of the case where the white LED of each system is used for data transmission are as follows.

(1) In the case of using the blue light excitation type white LED, since the response speed of the light output from the phosphor is low, only a transmission rate of a few Mbps can be obtained at most (see Non-Patent Document 2 below). Fig. 7A shows a transceiver configuration of this type. In the figure, data to be transmitted is input to a modulator 922 of the transmitter 920 to receive a predetermined modulation, and a modulated signal is supplied to a blue light excited white LED 924. Therefore, the output light of the blue light excitation type white LED 924 is modulated by a modulation scheme such as OOK (On-Off Keying) and flashes. The flashing light after modulation is input to the photoelectric converter 932 of the receiver 930 to be converted into an electrical signal, amplified by the amplifier 934 and then input to the demodulator 936, where demodulation of data is performed. Here, when the transmission side is turned on / off at high speed, the waveform is slowed due to the delay of the response speed of the light emitted from the phosphor 908, and the intersymbol interference occurs. That is, as shown in FIG. 7B, the output signal SQ of the photoelectric converter 932 is slowed with respect to the modulation signal SP of the modulator 922. This is a detrimental factor in realizing high-speed transmission using a blue light excitation type white LED.

In order to solve this problem, a method of speeding up by providing an LED light transmitting color filter that transmits only blue light in front of the photoelectric converter and removing a light component having a slow response speed output from the phosphor by the color filter has been proposed ( See Patent Document 1). Fig. 7C shows the configuration of a transceiver in this case. The LED light transmitting color filter 952 is arranged on the light incident side of the photoelectric converter 932 of the receiver 950. The light emitted from the phosphor having a slow response speed in the optical signal is removed by the LED light transmitting color filter 952. Accordingly, only the light of the blue LED 900 is incident on the photoelectric converter 932, and as a result, it is possible to perform data transmission faster than the above configuration. However, even with this method, only a few tens of Mbps can be achieved. In addition, as can be seen from the following non-patent document 3, there is also a point that the transmission quality of data cannot be maintained due to the solid dispersion of the light emission characteristics of the white LED, deterioration with time, and uneven distribution of the color temperature.

(2) In the case of using the ultraviolet light-excited white LED, the transmission rate is about several Mbps for the same reason as in the case of using the blue light-excited white LED. In addition, since the driving voltage of the LED is high, the configuration of the driving circuit is also complicated.

(3) In the case of using a three-color white light emitting LED, there is no phosphor light emitting component compared to the above-described method, and it is also possible to perform data transmission by performing wavelength multiplexing such that each LED carries a different signal, thereby enabling high speed (below). See Patent Document 2). However, the cost is high because a plurality of LEDs are used.

Next, when spatial light transmission is performed through a combination of a diffusion light source such as an LED and a photoelectric converter such as a PD, the amount of light received by the PD is inversely proportional to the square of the distance (for example, Non-Patent Documents 4 to 5 below). Reference). Therefore, a large dynamic range is required at the receiver side in order to secure a range of distances to which information can be transmitted. For example, Infra-red Data Association (IrDA), an infrared communication standard, requires a dynamic range of 100 Hz or more on the receiver side for a transmission distance range of 1 cm to 100 cm (see Patent Documents 3 to 6 below). See chapter 2).

In particular, in the case of performing spatial light transmission using visible light as a data transmission medium as in the present invention, disturbance light such as sunlight or fluorescent lamps is very large. In addition, unlike infrared communication, it is difficult to remove optical disturbance light by the visible light cut filter. Thus, more stringent conditions are placed on the receiver side. In general, to obtain a large dynamic range on the receiver side, use an AGC (Auto Gain Control) circuit for the amplifier (Chapter 7 of Non-Patent Document 6), or prepare a plurality of amplifiers with different gains and adjust the input signal level. Therefore, a means for performing gain switching of the amplifier is employed.

[Patent Document 1] Japanese Patent No. 3465017

[Patent Document 2] Japanese Patent Application Laid-Open No. 2002-290335

[Patent Document 3] Japanese Unexamined Patent Publication No. 10-51387

[Non-Patent Document 1] CMC Publishing, 'Application and Future Prospect of White LED Lighting System Technology'

[Non-Patent Document 2] Theological Bulletin ICD2005-44, Vol. 105, No. 184, 25-30p, 'Starting LED Driver for Visible Light Communication and Evaluation of Response Performance of Visible Light LED'

[Non-Patent Document 3] 2006 Conference on Electronics and Telecommunications Society, "Consideration of Brightness Degradation of White LED"

[Non-Patent Document 4] Demand Company 'Spatial Transmission Optics', Chapter 6

[Non-Patent Document 5] 2005 Society for Electronics and Telecommunications, Conference Society 'Optical Analysis of Reception Characteristics of Parallel Optical Space Transmission System'

[Non-Patent Document 6] Torrix, 'Infrared Communication Technology'

As described above, it is possible to increase the transmission speed by using a three-color white LED, but since the LED itself is expensive, it is difficult to say that this method is suitable in terms of cost and versatility.

On the other hand, in the case of using the blue light excitation type white LED, there is no problem in this cost aspect, and by using the LED light transmitting color filter 952 which blocks the light emission from the phosphor 908 having a slow response speed as described above, Data transfer can be performed. However, the cut-off frequency of a typical blue LED is at most several tens of MHz (see Non-Patent Document 2 above), and the optical signal outputted by performing OOK modulation at a transmission rate exceeding this frequency is also shown in FIG. 7 (B). As described above, a slowdown occurs and inter-symbol interference occurs. Therefore, the upper limit of the data transfer rate is limited and only a transfer rate of several tens of Mbps can be obtained at most. The transmission quality of data is also degraded.

In addition, in the case of data transmission using an ultraviolet light-excited white LED, as in the case of using the blue light-excited white LED, the problem of delay in transmission speed due to delayed response speed of light emission of the phosphor cannot be avoided. There is also a problem that the driving voltage of the external light LED increases.

In addition, a method of accelerating the response speed of light output from the phosphor through improvement of the phosphor material may be considered, but problems such as the fact that the desired illuminance is not obtained or the cost of the phosphor material itself may be raised. In this regard, it would be suitable to be able to perform high-speed data transmission using a general purpose and inexpensive blue light excitation white LED.

On the other hand, it is inevitable that the circuit configuration is complicated by using an AGC circuit or by switching the gain of the amplifier according to the input signal level to obtain a large dynamic range. In addition, when the distance between the transmitter and the receiver is close and the amount of light incident on the PD is large, the signal waveform as shown by the graph SQ in FIG. 7B due to the space charge effect (see Non-Patent Document 7). A wave may be generated at the arrival of, causing interference between codes and hindering the securement of good transmission quality.

[Non-Patent Document 7] Engineering Book, 'Optical Communication Device Engineering'

SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and its object is to perform high-speed data transmission using light of a plurality of wavelength bands output from a plurality of light emitting means having different response speeds at the time of light output. Another purpose is to maintain the quality of data transmission. Another purpose is to obtain a good dynamic range.

According to the optical receiving device of the present invention, a light emitting diode and a phosphor which is excited by a light source of the light emitting diode and emits light are modulated to receive data from a plurality of light emitting means having different response speeds and to perform data transmission. In an optical receiving apparatus for receiving light of a plurality of wavelength bands, the object is achieved by a plurality of filter means for selectively transmitting light of each of the plurality of wavelength bands from the light of the modulated plurality of wavelength bands. .

One of the main aspects is a plurality of photoelectric conversion means for converting each of the light of the plurality of wavelength bands transmitted through the plurality of filter means into an electrical signal for each wavelength band, and each of the electrical signals after conversion by the plurality of photoelectric conversion means. A plurality of equalizing means for performing waveform equalization corresponding to the response speed for each wavelength band, an adding means for making the outputs of the plurality of equalizing means as one addition output, and a discriminating means for discriminating the addition output of the adding means. It characterized by having a.

In another aspect, the plurality of light emitting means emits light of a light emitting diode having a peak wavelength in a range of 440 to 470 nm, and is excited by a light source of the light emitting diode and emits light of a longer wavelength side than the peak wavelength of the light emitting diode. Blue light excitation type white light emitting means which becomes white light by mixing with light emitted from the phosphor.

In another aspect, the plurality of light emitting means may include a plurality of light emitting elements that are excited by a light source of a light emitting diode having a peak wavelength in a range of 380 to 410 nm and emit light having a longer wavelength than the peak wavelength of the light emitting diode. It is an ultraviolet light excitation type white light emitting means which emits white light.

The invention of another optical receiving device is a plurality of modulated to perform data transmission by receiving output from a plurality of light emitting diodes having different response speeds by means of a light emitting diode and a phosphor which is excited by a light source of the light emitting diode and emits light. A light receiving device for receiving light in a wavelength band of the light source, comprising: a plurality of filter means for selectively transmitting the light in the modulated plurality of wavelength bands, and light transmitted through the plurality of filter means for each of the plurality of filter means A plurality of photoelectric conversion means for converting each into an electrical signal, an adding means for making the outputs of the plurality of photoelectric conversion means into one addition output, a discriminating means for discriminating the addition output of the adding means, and one-side photoelectric conversion The signal level of the output of the means is detected, and when it is below a predetermined threshold, the image of the output of the other photoelectric conversion means It is provided with a signal control means for blocking an input of the adding means.

One of the main aspects is that the signal control means controls the signal level detecting means for detecting the signal level of the output of the one photoelectric conversion means and the output of the other photoelectric conversion means in accordance with the detection result of the signal level detecting means. It is characterized by comprising a switch means. In another embodiment, equalizing means is provided for performing waveform equalization to the output of the photoelectric conversion means in response to the response speed at the time of light output by the light emitting means.

One of the other aspects is also an adaptive equalizer in which the equalization means adaptively performs waveform equalization.

The visible light communication apparatus of the present invention uses white light emitting means including a phosphor as a light emitting means as a light source on the transmission side, and receives the light output from the white light emitting means in the light receiving device according to any one of the above.

According to the present invention, high-speed data transmission can be made good transmission quality using a low-cost, high-speed general purpose white LED. In addition, the dynamic range of the receiver can be enlarged, or in other words, the distance range of the data transmission can be expanded. In addition, by adding equalization means, good transmission quality can be obtained.

The objects, features, and advantages described herein will become apparent from the following detailed description and the accompanying drawings.

EMBODIMENT OF THE INVENTION Hereinafter, the best form for implementing this invention is demonstrated in detail based on an Example.

[ Example  One]

First, Embodiment 1 of the present invention will be described with reference to FIGS. 1A and 2. In Fig. 1A, the circuit configuration of the main part of this embodiment is shown. In the figure, from the transmitting side, data to be transmitted is input to the modulator 12 of the transmitter 10. On the output side of the modulator 12, the above-mentioned blue light excitation type white LED 14, which is a white light emitting means, is connected. As the modulator 12, an LED driving circuit capable of modulating the output light of the blue light-excited white LED 14 at high speed may be used.

As the blue light excitation type white LED 14, the apparatus described with reference to Fig. 6A is used. The blue light excitation type white LED 14 uses a blue LED as a light source. Some of these blue LEDs 900 have light emission characteristics of various wavelengths, and those having a peak wavelength in the range of 440 to 470 nm are used. The phosphor 908 is used to emit light on the longer wavelength side than the peak wavelength of the blue LED 900. In addition, the particle-shaped phosphor 908 is disposed in the transparent resin having a radial thickness and not to block light emitted from the blue LED.

On the other hand, the receiving side includes a circuit for LED light output from the blue LED of the blue light excitation type white LED 14 and a circuit for fluorescence output from the phosphor. First, from the time of LED light, the photoelectric converter 24B which is a photoelectric conversion means is provided on the light-incidence side via the LED light transmission color filter 22B which is a filter means. The output side of this photoelectric converter 24B is connected to the equalizer or the adaptive equalizer 28B via the amplifier 26B. On the other hand, about the circuit of phosphor light, the photoelectric converter 24F is provided in the light incident side via the phosphor light transmission color filter 22F. The output side of this photoelectric converter 24F is connected to the equalizer 28F via an amplifier 26F.

Among the above parts, the LED light transmitting color filter 22B is a color filter that selectively transmits blue light emitted by the blue LED 900 (see FIG. 6A) in the blue light excitation type white LED 14. On the other hand, the phosphor light transmitting color filter 22F is a color filter for selectively transmitting the light emitted by the phosphor 908 in the blue light excitation-type white LED 14. The photoelectric converters 24B and 24F are photo detectors for converting input light into electrical signals, and the electrical signals after the conversion are amplified by the amplifiers 26B and 26F, respectively. Equalizers 28B and 28F emphasize waveforms by amplifying the high frequencies of the amplified signal.

The output side of the equalizers 28B and 28F is connected to the input side of the adder 30 which is an adder, and the output side of the adder 30 is connected to the discriminator 34 of the demodulator 32 which is a discriminating means. The signal after equalization is added by the adder 30, and further discriminated by the discriminator 34 as a binary signal.

Next, the operation of the present embodiment configured as described above will be described. The data signal to be transmitted is supplied to the modulator 12 of the transmitter 10, and the light output of the blue light excited type white LED 14 is modulated by the OOK method, for example. As described above, the blue light-excited white LED 14 has the configuration shown in FIG. 6A. When the output light of the blue LED 900 is modulated, the output light of the phosphor 908 is also modulated.

The blue LED light and the phosphor light after modulation are incident on the receiver 20. Of the incident light on the receiver 20 side, the blue light output from the blue LED 900 (see FIG. 6 (B) dotted line SA) passes through the LED light transmitting color filter 22B and enters the photoelectric converter 24B. On the other hand, the phosphor light output from the phosphor 908 (see dotted line SB in Fig. 6 (B)) passes through the phosphor light transmitting color filter 22F and is incident on the photoelectric converter 24F. Incident light in the photoelectric converters 24B and 24F is converted into an electrical signal. The signal after conversion is amplified by the amplifiers 26B and 26F, respectively.

2 shows a signal waveform of each part. In the figure, (A) is a data signal waveform on the transmitting side. On the other hand, the converted signal waveform of the blue light by the photoelectric converter 24B is as shown by the dotted line graph SB1 of (B) of the figure. On the other hand, the converted signal waveform of the phosphor light by the photoelectric converter 24F is as shown by the dashed-dotted line graph SF1 of (B) of the figure. In comparison, the graph SF1 is a slowed waveform with respect to the graph SB1. This is because the response speed of the light output from the phosphor 908 is slow as described above.

Thus, in the present embodiment, waveform equalization is performed by the equalizers 28B and 28F. The equalizers 28B and 28F adjust frequency characteristics with respect to the response characteristics of blue light or the response of phosphor light, respectively, and emphasize harmonic components. Therefore, the graphs SB1 and SF1 in (B) of the figure are the same as the graphs SB2 and SF2 shown in (C) of the figure, and the slowing of the waveform is reduced. The signal after equalization is added by the adder 30 and input to the discriminator 34 of the demodulator 32 to perform binarization. Since the slowing of the waveform has been improved, the binarization process can be satisfactorily performed. Therefore, high speed data transfer is possible.

As in the background art described above, in the case of not separating the blue light from the phosphor light, it is equalized in a state in which light having different time responsiveness is added. Therefore, there is a problem that the circuit configuration of the equalizer for performing equalization suitable for performing high-speed data transmission becomes complicated and adjustment is difficult. On the other hand, according to the present embodiment, since the equalizer is configured for each of the blue light and the phosphor light, the simplicity and practicality are improved.

[ Example 2 ]

Next, Embodiment 2 of the present invention will be described. The same reference numerals are used for the same or corresponding components as those in the above-described first embodiment (the same applies to the third and subsequent embodiments). This embodiment is an example in which the equalizers 28B and 28F of Embodiment 1 described above use an adaptive equalizer for adaptively waveform equalizing an amplified signal. The equalizer of this embodiment has a fixed coefficient (i.e., its characteristic is fixed), but the adaptive equalizer of this embodiment has a variable coefficient and the characteristic changes according to the input waveform. By using such an adaptive equalizer, it is possible to maintain good data transmission quality at all times against changes in the output light characteristics due to the solid dispersion of the light emission characteristics of the blue light-excited white LED 14 and the deterioration over time (see Non-Patent Document 3). Can be. In particular, since phosphors are more likely to deteriorate than LEDs, adaptive deteriorators are suitable. In addition, the blue light excitation type white LED 14 is said to have a color unevenness with respect to the light emission direction (refer the said nonpatent literature 1). Specifically, in the spatial distribution of light, blue is stronger in the center portion, and yellow is strongly changed toward the outside. Even in such a case, according to the present embodiment, a good data transmission quality can always be maintained regardless of the positional relationship (specifically, the incident angle of light) between the blue light excited type white LED 14 and the receiver 20.

[ Example 3 ]

Next, with reference to FIG. 1 (B), Embodiment 3 of the present invention will be described. As shown in the figure, in this embodiment, an ultraviolet light excitation type white LED 44, which is a white light emitting means, is provided in the transmitter 40, and the output light is modulated at high speed by the modulator 12. have. On the other hand, on the receiver 50 side, blue fluorescence transmission color filters 52B, red fluorescence transmission color filters 52R, and green fluorescence transmission color filters 52G are provided as filter means. Of these, the blue fluorescent color filter 52B is a filter that selectively transmits the light emitted by the blue light emitting phosphor among the white light output from the ultraviolet light-excited white LED 44. Similarly, the red fluorescence transmission color filter 52R is a filter for selectively transmitting the light emitted by the red luminescence phosphor among the white light output from the ultraviolet light excitation type white LED 44. The green fluorescence transmissive color filter 52G is a filter for selectively transmitting the light emitted by the green luminescent phosphor among the white light output from the ultraviolet light-excited white LED 44.

On the light output side of each of these filters 52B, 52R, 52G, photoelectric converters 54B, 54R, 54G, which are photoelectric conversion means, are provided, respectively, and the electrical signals after the conversion by these amplifiers are supplied by the amplifiers 56B, 56R, 56G. It is amplified and supplied to equalizers (or adaptive equalizers) 58B, 58R, 58G which are equalization means, respectively. The outputs of the equalizers 58B, 58R, 58G are added by the adder 60 which is an addition means, and are further discriminated by the discriminator 64 of the demodulator 62 which is a discriminating means.

In the present embodiment, since the ultraviolet light excitation type white LED 44 is used, all of the blue, red, and green light constituting the white light are phosphor light. Thus, the phosphor light is extracted with the color filters 52B, 52R, and 52G, respectively, and photoelectric conversion, amplification, and equalization are performed in the same manner as in the above-described embodiment. Also in this embodiment, the equalizers 58B, 58R, and 58G have their frequency characteristics adjusted for the response characteristics of the blue, red, and green phosphor light, respectively, so that harmonic components are emphasized to improve the slowing of the waveform. Therefore, the binarization processing can be performed satisfactorily in the same manner as in the above embodiment, thereby enabling high-speed data transmission.

In addition, the ultraviolet light excitation type white LED 44, which is a light emitting means, is excited by a light source of a light emitting diode having a peak wavelength in the range of 380 to 410 nm, and emits light at a longer wavelength side than the peak wavelength of the light emitting diode. They emit three primary colors of blue, red, and green from a plurality of kinds of phosphors, and white light is emitted by these photosynthesis.

[ Example 4 ]

Next, with reference to FIG. 3 (A), Embodiment 4 of the present invention will be described. This embodiment is an embodiment for the purpose of expanding the dynamic range. The output side of the amplifier 26B of the blue LED light side circuit of the receiver 100 is connected to one input side of the adder 30 which is an adding means and the input side of the signal level detector 102. On the other hand, the output side of the amplifier 26F of the phosphor light side circuit is connected to the input side of the analog switch 104 which is a switch means, and the output side of this analog switch 104 is connected to the other input side of the adder 30. .

The detection output side of the above-described signal level detector 102 is connected to the control terminal of the analog switch 104, and the ON / OFF operation of the analog switch 104 is performed according to the detection result of the signal level detector 102. have. In this way, the signal control means is composed of a signal level detector and an analog switch. The output side of the adder 30 is the same as that of the first embodiment described above.

The signal level detector 102 detects an amplitude level of an input signal and outputs a result. For example, a RSSI (Received Signal Strength Indicator) using a log amplifier, a peak bottom detector, or the like is used. A predetermined threshold is set in advance in the signal level detector 102. When the threshold does not exceed the input signal level, the analog switch 104 is controlled to 'ON' by a control signal, and conversely, the threshold is input signal level. When this is exceeded, the analog switch 104 is controlled to be 'OFF'.

Next, the operation of the present embodiment configured as described above will be described. The operation of the transmitter 10 side is the same as in the first embodiment described above, and blue LED light and phosphor light after modulation based on the data signal are incident on the receiver 100. The operation up to the amplified signal output by the amplifiers 26B and 26F during the operation on the receiver 100 side is also the same as in the first embodiment.

The signal relating to the blue LED light output from the amplifier 26B is input to the signal level detector 102. When the signal level detector 102 determines that the signal level of the blue LED light has exceeded a predetermined threshold, the analog switch 104 is controlled to 'OFF'. Therefore, the adder 30 is supplied with only the signal relating to the blue LED light from the amplifier 26B, which is supplied to the demodulator 32. On the other hand, when the signal level detector 102 determines that the signal level of the blue LED light does not exceed a predetermined threshold, the analog switch 104 is controlled to 'ON'. Therefore, the adder 30 is supplied with the signal relating to the blue LED light from the amplifier 26B and the signal relating to the phosphor light from the amplifier 26F, respectively, and is added to the demodulator 32.

For example, when the distance between the transmitter 10 and the receiver 100 is close and the amount of light of the blue LED light incident on the receiver 100 is large, only the signal of the blue LED light is input to the demodulator 32. In this case, only the blue LED light can sufficiently transmit information. Since no phosphor light is used, the effect due to the slowing of the waveform due to the phosphor light or the effect of the space charge is reduced. On the contrary, when the distance between the transmitter 10 and the receiver 100 is far and the amount of light of the blue LED light incident on the receiver 100 is small, the signals of the blue LED light and the phosphor light are added to the demodulator 32 to be input to the blue LED. Demodulation is performed using not only light but also phosphor light effectively.

Thus, according to this embodiment, by selecting the light used for transmission according to the incident light quantity level of the blue LED light, it is possible to enlarge the dynamic range of the receiver, in other words, to extend the distance range of data transmission.

[ Example 5 ]

Next, referring to Fig. 3B, the second signal control means according to the fifth embodiment of the present invention will be described. As shown in the figure, in this embodiment, in comparison with the above-described embodiment 4, instead of the amplifier 26F on the phosphor light side of the receiver 110 and the analog switch 104, a programmable gain amplifier (PGA) 112 is used. Switch means is connected, and the control signal of the signal level detector 102 described above is input to the control input side of the PGA 112. The PGA 112 has a function capable of adjusting the gain of signal amplification according to the detection result of the signal level detector 102. That is, when the signal level detector 102 determines that the input signal level does not exceed the threshold, the gain of the PGA 112 is controlled to a predetermined value by the control signal, and conversely, when it is determined that the input signal level exceeds the threshold, the PGA The gain of 112 is controlled to be "0". According to the present embodiment, the operation of the amplifier 26F and the analog switch 104 of the fourth embodiment is performed by the PGA 112.

[ Example 6 ]

Next, with reference to Fig. 4A, a sixth embodiment of the present invention will be described. This embodiment combines Embodiment 1 of Fig. 1A and Embodiment 4 of Fig. 3A described above. That is, the output side of the amplifier 26B, which is the circuit on the blue LED light side of the receiver 120, is connected to the input side of the equalizer 28B and the input side of the signal level detector 102, respectively. On the other hand, the output side of the amplifier 26F, which is the circuit on the phosphor light side, is connected to the input side of the analog switch 104, and the output side of the analog switch 104 is connected to the input side of the equalizer 28F. The output side of these equalizers 28B, 28F is connected to the input side of the adder 30, respectively. The output side of the adder 30 is the same as that of the first embodiment described above.

The operation of this embodiment is a combination of Embodiment 1 and Embodiment 4 described above. That is, when the signal level detector 102 determines that the signal level of the blue LED light exceeds a predetermined threshold, the analog switch 104 is controlled to 'OFF'. Therefore, only the signal output from the amplifier 26B is waveform equalized by the equalizer 28B and supplied to the adder 30. On the other hand, when the signal level detector 102 determines that the signal level of the blue LED light does not exceed a predetermined threshold, the analog switch 104 is controlled to 'ON'. Therefore, the signals output from the amplifiers 26B and 26F are waveform equalized by the equalizers 28B and 28F, respectively, and added by the adder 30.

According to this embodiment, the effect by the waveform equalization process of Example 1 and the signal by the signal selection of Example 4 can be obtained. That is, not only can the transmission quality be improved at the time of high speed transmission, but also the dynamic range can be expanded. In addition, when the adaptive equalizer is used as the equalizers 28B and 28F, the combination of the second embodiment and the fourth embodiment is achieved.

[ Example 7 ]

Next, with reference to Fig. 4B, a seventh embodiment of the present invention will be described. As shown in the figure, in the present embodiment, a PGA 112 is connected in place of the amplifier 26F and the analog switch 104 on the phosphor light side of the receiver 130 in comparison with the above-described sixth embodiment. The control signal of the signal level detector 102 described above is input to the control input side of the PGA 112. A combination of the first embodiment of FIG. 1A and the fifth embodiment of FIG. 3B may be considered. The operation of the amplifier 26F and the analog switch 104 of the sixth embodiment is performed by the PGA 112. FIG. Is performed by. Also in this embodiment, an adaptive equalizer may be used as the equalizers 28B and 28F.

[ Example 8 ]

Next, with reference to FIG. 5 (A), Embodiment 8 of the present invention will be described. As shown in the figure, the output side of the phosphor light side amplifier 26F is connected to the signal level detector 142 of the receiver 140. That is, although the signal level of the blue LED light of the amplifier 26B is detected in the fourth embodiment of FIG. 3A described above, in the present embodiment, the signal level of the phosphor light of the amplifier 26F is detected to detect the signal level of the analog switch 104. Control is to be performed. According to the present embodiment, when the signal level detector 142 determines that the signal level of the phosphor light has exceeded a predetermined threshold, the analog switch 104 is controlled to 'OFF'. Therefore, the adder 30 is supplied with only the signal relating to the blue LED light from the amplifier 26B, which is supplied to the demodulator 32. On the other hand, when the signal level detector 142 determines that the signal level of the phosphor light does not exceed a predetermined threshold, the analog switch 104 is controlled to 'ON'. Therefore, the adder 30 is supplied with the signal relating to the blue LED light from the amplifier 26B and the signal relating to the phosphor light from the amplifier 26F, respectively, and is added to the demodulator 32.

[ Example 9 ]

Next, with reference to Fig. 5B, a ninth embodiment of the present invention will be described. This embodiment combines Embodiment 1 of Fig. 1A and Embodiment 8 of Fig. 5A described above. That is, the output side of the amplifier 26B on the blue LED light side of the receiver 150 is connected to the input side of the equalizer 28B. On the other hand, the output side of the amplifier 26F on the phosphor light side is connected to the input side of the analog switch 104 and the signal level detector 142, respectively, and the output side of the analog switch 104 is the input side of the equalizer 28F. Is connected to. The output sides of these equalizers 28B and 28F are connected to the adder input side of the adder 30, respectively. The output side of the adder 30 is the same as that of the first embodiment described above.

The operation of this embodiment is a combination of Embodiment 1 and Embodiment 8 described above. That is, when the signal level detector 142 determines that the signal level of the phosphor light has exceeded a predetermined threshold, the analog switch 104 is controlled to 'OFF'. Therefore, only the signal relating to the blue LED light from the amplifier 26B is equalized by the equalizer 28B, supplied to the adder 30, and further supplied to the demodulator 32. On the other hand, when the signal level detector 142 determines that the signal level of the phosphor light does not exceed a predetermined threshold, the analog switch 104 is controlled to 'ON'. Therefore, the output signals of the amplifiers 26B and 26F are equalized by the equalizers 28B and 28F and supplied to the adder 30. The added signal is then supplied to the demodulator 32. Also in this embodiment, an adaptive equalizer may be used as the equalizers 28B and 28F.

In addition, this invention is not limited to the Example mentioned above, A various change can be added in the range which does not deviate from the summary of this invention. For example, the following is also included.

(1) In the above embodiment, the phosphor 908 excited by the light of the blue LED 900 of the blue light excitation type white LED emits yellow light having a complementary color relationship, but recently, the phosphor light emitting component includes a red component. Some LEDs are also included in the blue light excitation white LED.

(2) As the equalizer or adaptive equalizer described above, any of analog and digital types may be used.

(3) The color filter and the photoelectric converter may be integrated and configured as a color sensor or a light receiving element. Since the light receiving element has a wavelength band of light for photoelectric conversion, by setting this to a desired value, the characteristics as a color filter can be combined.

According to the present invention, since light of a plurality of wavelength bands is extracted from modulated light including phosphor light to perform signal processing, high-speed data transmission is possible. Therefore, it is suitable for visible light communication using a white LED, especially a blue light excitation type white LED.

1 is a circuit block diagram showing the main configuration of an embodiment of the present invention, (A) is a block diagram of Embodiments 1 and 2, and (B) is a block diagram of Embodiment 3. FIG.

Fig. 2 is a graph showing the signal waveforms of the main part in the first embodiment, (A) shows a data signal waveform, (B) shows a signal waveform before equalization, and (C) shows a signal waveform after equalization.

3A is a block diagram of Embodiment 4, and (B) is a block diagram of Embodiment 5. FIG.

4A is a block diagram of Embodiment 6, and (B) is a block diagram of Embodiment 7. FIG.

5A is a block diagram of the eighth embodiment, and (B) is a block diagram of the ninth embodiment.

6A is a diagram showing an example of the configuration of a blue light excitation type white LED, and (B) is a graph showing the emission spectral characteristics thereof.

7A is a circuit block diagram showing an example of the prior art, (B) a graph showing an example of a signal waveform, and (C) is a circuit block diagram showing another example of the prior art.

* Explanation of symbols for main parts of the drawings

10: transmitter

12: modulator

14: Blue light excitation type white LED

20: receiver

22B: LED Light Transmitting Color Filter

22F: phosphor light transmitting color filter

24B: Photoelectric Converters

24B, 24F: Photoelectric Converters

26B, 26F: Amplifier

28B, 28F: Equalizer

30: adder

32: demodulator

34: discriminator

40: transmitter

44: ultraviolet light excitation type white LED

50: receiver

52B: Blue Fluorescent Transmission Color Filter

52G: Green Fluorescent Transmissive Color Filter

52R: Red Fluorescent Transmission Color Filter

54B, 54R, 54G: Photoelectric Converters

56B, 56R, 56G: Amplifiers

58B, 58R, 58G: Equalizer

60: adder

62: demodulator

64: discriminator

100: receiver

102: signal level detector

104: analog switch

110: receiver

112: PGA

120, 130, 140: receiver

142: signal level detector

150: receiver

900: blue LED

902: Resin Case

904, 906: lead-out electrode

908: phosphor

920: transmitter

922 modulator

924 blue light excitation type white LED

930: receiver

932: Photoelectric Converter

934: Amplifier

936: demodulator

950: receiver

952: LED Light Transmitting Color Filter

Claims (15)

delete Receiving light from a plurality of wavelength bands modulated to perform data transmission by receiving output from a plurality of means for obtaining light emission having different response speeds by a light emitting diode and a phosphor excited by the light source of the light emitting diode and emitting light; In the optical receiving device, A plurality of filter means for selectively transmitting light of each of the plurality of wavelength bands from the light of the modulated plurality of wavelength bands, The plurality of light emitting means includes light of a light emitting diode having a peak wavelength in a range of 440 to 470 nm, and light emitted from a phosphor that is excited by a light source of the light emitting diode and emits light of a longer wavelength side than the peak wavelength of the light emitting diode. And a blue light excitation type white light emitting means that becomes white light by mixing with the light. Receiving light from a plurality of wavelength bands modulated to perform data transmission by receiving output from a plurality of means for obtaining light emission having different response speeds by a light emitting diode and a phosphor excited by the light source of the light emitting diode and emitting light; In the optical receiving device, A plurality of filter means for selectively transmitting light of each of the plurality of wavelength bands from the light of the modulated plurality of wavelength bands, The plurality of light emitting means is ultraviolet light that is excited by a light source of a light emitting diode having a peak wavelength in the range of 380 to 410 nm and emits white light from a plurality of kinds of phosphors that emit light on a longer wavelength side than the peak wavelength of the light emitting diode. An optical receiving device, characterized in that the excitation type white light emitting means. Receiving light from a plurality of wavelength bands modulated to perform data transmission by receiving output from a plurality of means for obtaining light emission having different response speeds by a light emitting diode and a phosphor excited by the light source of the light emitting diode and emitting light; In the optical receiving device, A plurality of filter means for selectively transmitting the light of each of the plurality of wavelength bands from the light of the modulated plurality of wavelength bands; A plurality of photoelectric conversion means for converting each of the light in the plurality of wavelength bands transmitted through the plurality of filter means into electrical signals for each wavelength band; A plurality of equalization means for performing waveform equalization for each wavelength band after conversion by the plurality of photoelectric conversion means in response to the response speed; Adding means for making outputs of the plurality of equalizing means as one addition output; And discriminating means for discriminating the addition output of the adding means. The method of claim 4, wherein The plurality of light emitting means includes light of a light emitting diode having a peak wavelength in a range of 440 to 470 nm, and light emitted from a phosphor that is excited by a light source of the light emitting diode and emits light of a longer wavelength side than the peak wavelength of the light emitting diode. And a blue light excitation type white light emitting means that becomes white light by mixing with the light. The method of claim 4, wherein The plurality of light emitting means is ultraviolet light that is excited by a light source of a light emitting diode having a peak wavelength in the range of 380 to 410 nm and emits white light from a plurality of kinds of phosphors that emit light on a longer wavelength side than the peak wavelength of the light emitting diode. An optical receiving device, characterized in that the excitation type white light emitting means. The method according to any one of claims 4 to 6, And the equalizing means is an adaptive equalizer for adaptively performing waveform equalization. Receiving light from a plurality of wavelength bands modulated to perform data transmission by receiving output from a plurality of means for obtaining light emission having different response speeds by a light emitting diode and a phosphor excited by the light source of the light emitting diode and emitting light; In the optical receiving device, A plurality of filter means for selectively transmitting the light of the modulated plurality of wavelength bands; A plurality of photoelectric conversion means for converting light transmitted through the plurality of filter means into electrical signals for each of the plurality of filter means; Addition means for making outputs of the plurality of photoelectric conversion means as one addition output; Discriminating means for discriminating the addition output of the adding means, And a signal control means for detecting the signal level of the output of one side photoelectric conversion means and for interrupting the input of the output of the other photoelectric conversion means to said addition means when it is below a predetermined threshold. The method of claim 8, A plurality of equalizing means for equalizing waveforms in response to the response speed at the time of light output by the light emitting means is provided at the rear end of each of the plurality of photoelectric conversion means, respectively. Device. The method of claim 9, And the equalizing means is an adaptive equalizer for adaptively performing waveform equalization. The method of claim 8, The signal control means, Signal level detection means for detecting a signal level of the output of the one-side photoelectric conversion means; And switch means for controlling the output of said other photoelectric conversion means in accordance with the detection result of said signal level detecting means. The method of claim 11, And a plurality of equalizing means for respectively equalizing the waveforms of the outputs of the plurality of photoelectric conversion means in response to the response speed at the time of light output by the light emitting means, respectively. . The method of claim 12, And the equalizing means is an adaptive equalizer for adaptively performing waveform equalization. White light emitting means comprising a phosphor as a light emitting means as a light source on the transmitting side is used, and the light output from the white light emitting means is the light according to any one of claims 2 to 6 and 8 to 13. A visible light communication device, characterized in that receiving by a receiving device. A white light emitting means including a phosphor as a light emitting means as a light source on the transmission side, and the light output from the white light emitting means is received by the light receiving device according to claim 7.

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