JP3465017B2 - Illumination light transmitting device, illumination light receiving device, and phosphor type illumination light communication system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illumination light transmitting device that transmits a signal using illumination light and an illumination light receiving device suitable for receiving the signal.

[0002]

2. Description of the Related Art A white light emitting diode (Light Emit
An illumination using a light emitting diode (LED) is expected to be put into practical use because of its excellent characteristics such as long life, small size, and low power consumption as compared with illumination such as a fluorescent lamp. Since white LED lighting uses LEDs as its light source, it has characteristics that it does not require a residual heat time and has a very high response speed as compared with a fluorescent lamp. Utilizing this characteristic, a system has been proposed in which a white LED illumination has a data transmission function. White L
A data transmission system using ED illumination uses white light from LEDs as a data transmission medium. White L
Data transmission is realized by modulating the light emission intensity of the ED illumination according to the transmission data and detecting the intensity of the light on the receiving side by an optoelectric converter (O / E) such as a photodiode. As described above, the data transmission system using the white LED illumination can not only use the white LED illumination used as illumination for data transmission at the same time, but also can use a general radio transmission technique using radio waves or an optical wireless using infrared rays. Compared to the transmission technology, a large amount of electric power used for lighting can be used for data transmission as well, so that good communication characteristics can be obtained, and it has attracted much attention. In addition, since the lighting is arranged so as not to cast a shadow on the entire room at the stage of designing the lighting, it is possible to transmit data in the entire room without causing the shadow that is often associated with infrared communication. Such high power and abundant arrangement of light sources are often not allowed in infrared light data transmission or wireless data transmission. The common advantage with infrared communication is that it can be used in environments where it is difficult to use radio waves, such as hospitals, trains, airplanes, spacecraft, and pacemaker users, and is not covered by a wireless station license. .

On the other hand, white LEDs are roughly divided into 2
There are different types. One is GaN (gallium nitride)
A YAG (yttrium-aluminum-garnet) -based phosphor is placed around a blue-based LED and is packaged in a single package (phosphor type). In this, blue light is emitted by emitting a blue LED arranged in the center, and white light is obtained by exciting the phosphor to emit light. The other is to obtain white light by putting LEDs corresponding to the three primary colors of red, green, and blue light in one package and emitting light at the same time (three primary color type). As the LED lighting, although the phosphor type can obtain higher brightness, even if it is called white, it has a drawback that it is based on blue light and lacks warmth. On the other hand, 3
You can adjust the primary color type to reddish white, close to green, or close to blue according to your preference, and it is possible to illuminate in colors apart from white. Also, it becomes possible to change the color depending on the time. Furthermore, when considering an illumination light communication system, with a phosphor-type white LED,
Since the two-step process of emitting light from the central LED and then emitting the phosphor is performed, there are three primary colors of white L
Compared with ED, there is a difficulty in high-speed data transmission, and the upper limit of transmission speed is currently about 1 Mbps. However, in the case of transmitting data simultaneously with illumination, the three-primary-color white LED can have a higher transmission speed than the phosphor type. This is because there is no process of exciting the phosphor, and white light is directly illuminated.

[0004]

The data transmission method in which a phosphor and a blue LED are combined and the LED is modulated involves a two-step step of exciting the phosphor after emitting the central blue LED. In addition, there is a drawback that the data transmission speed cannot be increased. In order to increase the speed, it is conceivable to use white illumination light that uses the three primary colors for data transmission. When actually realizing white light in a white LED of three primary colors, three types of L, red, green, and blue, are used.
EDs are used and mixed to obtain white light, but in this case, it is necessary to change the emission power of each of the three LEDs. This is because human luminosity characteristics have wavelength dependence. The human visibility characteristics are shown in FIG. The human eye has the maximum sensitivity at 555 nm, and the visible region is around 400 to 700 nm. Due to these characteristics, it is necessary to change the mixing ratio of the red, green, and blue light emission powers in order to obtain light that seems to be white light to the human eye. For example, in order to obtain white with x = 0.31 and y = 0.33 in the CIE standard chromaticity diagram (see FIG. 3), it is necessary to emit the three primary colors at the ratios shown in Table 1.
In other words, there are several methods for obtaining the same white light, and the luminous efficiency also differs depending on the combination.

When a white illumination light data transmission system is realized using three primary color type white LEDs having such characteristics, since the red, green and blue LEDs have different emission powers, their communication characteristics are different for each wavelength. Will be different. For example, in Table 1, in the case of the lowest combination, the communication quality of data transmitted from the red, green, and blue LEDs has a maximum difference of 10 dB or more in terms of SN ratio.

[0006]

[Table 1] As described above, in an illumination light communication system using LEDs of three primary colors, when white light is generated by the three LEDs and the three colors emit light with the same emission power, the human eye feels white. Absent. Therefore, it is necessary to select the three primary colors so that the three colors have different emission powers and the ratio thereof changes depending on how to select each wavelength. In this case, there will be inequality in the quality of the data transmitted by each LED.

In view of the above problems, it is an object of the present invention to provide an illumination light transmitting device that realizes information distribution suitable for illumination light communication and an illumination light receiving device suitable for signal reception thereof.

[0008]

The illumination light transmitting apparatus of the present invention divides data to be transmitted into three and allocates them to respective wavelengths of three primary colors, and each light emission by the data allocated by the allocator. Lighting LEDs of three primary colors that are modulated at a rate according to the intensity, and each emission intensity of the lighting LED are adjusted
Intensity adjusting means for
Change at a rate according to the emission intensity adjusted by the adjustment means.
Adjusted.

Further, by further comprising control means for controlling to transmit the information in which the rate of modulating the light of the three primary colors is changed when the emission intensity is changed by the intensity adjusting means, the receiving apparatus can control the rate. Even if it is not detected, normal reception can be started immediately after the rate change .

[0010] Further, the illumination light receiving device of the present invention has three primary colors.
Optical-electrical converter that converts each optical signal into an electrical signal
And the electric signal output from the opto-electric converter
A synthesizer that synthesizes with different weights and an output from the synthesizer
A demodulator for demodulating the applied electric signal.

The phosphor type illumination light communication system of the present invention has (1) a blue LED which emits blue light modulated by a signal, and a phosphor which is excited by the blue light from the blue LED. The direct light of the blue LED
An illumination light transmitting device that illuminates white with the light emitted from the phosphor , (2) a blue filter that selectively transmits direct light from the blue LED, and a photodetector that detects light through the blue filter. And an illumination light receiving device having a demodulator that demodulates the electrical signal output from the photodetector.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a diagram showing configurations of an illumination light transmitter and an illumination light receiver according to a first embodiment of the present invention. The illumination light transmitting device includes an assigner 11, a red LED 12a,
White LED 1 having green LED 12b and blue LED 12c
2, the adjusting unit 16 and the control unit 17 are provided. The illumination light receiving device includes a red filter 13a and a green filter 13 respectively.
b, photoelectric converter 1 which receives light through the blue filter 13c
4a, 14b, 14c and a demodulator 15 are provided.

The allocator 11 inputs the original data to be transmitted, and the red LED 12a and the green LED 12 of the white LED 12 are input.
b, the serial data input so as to have a multiplex number according to the light emission power of the blue LED 12c is distributed to three parallel data,
It is assigned to each LED and output at a rate according to each multiplexing number. In the case of the bottom of Table 1, for example, the red LED 12a
For the green LED 12b, 11 for the green LED 12b, and 7 for the blue LED 12c.

The white LED 12 is a red LED 12a and a green L
The ratio of the light emission powers of the ED 12b and the blue LED 12c is adjusted for illumination, and the number of multiplexes corresponding to each light emission power, that is, the rate data is input, and the red LED 12a, the green LED 12b, and the blue are used for each rate data. LED12
c is modulated and emits light.

The opto-electric converters 14a, 14b, 14c are
Red light, green light respectively received through the red filter 13a, green filter 13b and blue filter 13c,
It selectively converts blue light into electrical signals.

The demodulator 15 inputs in parallel electric signals which are modulated at different rates corresponding to red light, green light and blue light, demodulates them respectively and converts them into original serial data.

The adjusting section 16 is a red LED of the white LED 12.
12a, the green LED 12b, and the blue LED 12c are adjusted in emission power to obtain natural white illumination light. It is also possible to leave the white color and produce another color by adjustment. Furthermore, the color of the illumination light can be changed according to the time zone.

The control unit 17 controls the white LE by the adjusting unit 16.
Red LED 12a, green LED 12b, blue LED 1 of D12
When the light emission power of 2c is adjusted and changed, it is controlled to transmit information that the rate of modulating the light of the three primary colors is changed. For example, the multiple number of red, green, and blue is 1: 1.
If the ratio of 1: 7 becomes 1: 8: 5 by adjustment, the fact that it becomes 1: 8: 5 is transmitted as information. As a result, the illumination light receiving device can immediately receive the signal of the new rate normally. However, the illumination light receiving device may be configured to constantly detect the rate, detect the change in the rate, and demodulate the signal at the new rate. In this case, the controller 17 is not needed.

Further, as the white illumination light is used, the adjusting portion 16 may be semi-fixed so that the user cannot adjust the color of the illumination light. In this case as well, the control unit 1
You don't need 7.

FIG. 4 is a diagram showing an example of each modulation rate of the three primary color LEDs. Red LED 1 of white LED 12 described above
As an example of different modulation rates of the 2a, the green LED 12b, and the blue LED 12c, as shown in FIG. 4, if it is 2: 8: 4, the amount of information transmitted by each is naturally 2: 8: 4. Since the SN ratios of the LEDs are different, it is possible to achieve the same bit error rate even if the data amount to be allocated is different.

FIG. 5 is a diagram showing an example of each communication quality of the data assigned to the LEDs of the three primary colors. The red LED 12a, the green LED 12b, and the blue LED 12c of the white LED 12 may have the same wavelength multiplex number to change the quality of the data transmitted from each LED. That is, the LED that is responsible for transmission is different depending on the importance of the data to be transmitted. How to map the most important data to green, the second most important to blue, and the least important to red. This will be very effective in (indoor) data transmission systems that will handle multimedia information in which various kinds of information are simultaneously included in the future.

FIG. 6 is a diagram showing a configuration of an illumination light transmitter and an illumination light receiver according to the second embodiment of the present invention. The illumination light transmitter includes red LED 21a and green LED 21.
b, a white LED 21 having a blue LED 21c is provided.
The illumination light receiving device includes photoelectric converters 23a, 23b and 23c and coefficient multipliers 24a and 24 which receive light through a red filter 22a, a green filter 22b and a blue filter 22c, respectively.
b, 24c, an adder 25, and a demodulator 26.

The white LED 21 is a red LED 21a and a green L
The ratio of the light emission powers of the ED 21b and the blue LED 21c is adjusted for illumination, and each emits light simultaneously modulated by the original data input.

The photoelectric converters 23a, 23b and 23c are
Red light, green light respectively received through the red filter 22a, green filter 22b and blue filter 22c,
It selectively converts blue light into electrical signals.

The coefficient units 24a, 24b, 24c multiply the electric signals input from the photoelectric converters 23a, 23b, 23c by a coefficient according to the mixing ratio of each LED of the white LED 21 and output the product.

The adder 25 includes coefficient units 24a, 24b,
The electrical signal weighted by the coefficient, which is input from 24c, is added as it is and output.

The demodulator 26 demodulates the electric signal input from the adder 25 and outputs the original data.

In this case, since multiplexing is not performed, a plurality of L
Although the total data rate cannot be increased by the ED, the transmission power can be added by adding the light emission power of each LED on the receiving side. Further, when the light emission power ratio of the three LEDs is changed, it may be measured by the light receiving unit and the value of the coefficient unit may be automatically changed.

FIG. 7 is a diagram showing the structure of an illumination light transmitting apparatus according to the third embodiment of the present invention. This embodiment is of the above-mentioned phosphor type, and the illumination light transmitting device is based on the substrate 31.
In this structure, the phosphor 33 is arranged around the blue LED 32 placed in the recess.

FIG. 8 is a diagram showing a spectrum of a phosphor type white LED. When stimulated by the light emission of the blue LED 32, light other than blue is emitted by the phosphor 33, and the direct light of the blue LED 32 and the light spectrum of the phosphor 33 are as shown in FIG. Both the direct light of the blue LED 32 and the light emitted by the phosphor 33 are mixed and recognized as white by a human being, so that it can be used for lighting or the like.

FIG. 10 is a diagram showing a configuration of an illumination light communication system including a conventional phosphor type illumination light transmitter and illumination light receiver. White LED 4 by modulator 41
When 2 is modulated by ON-OFF or the like, white light blinks, and the blinking is detected by a photodetector 43 at a remote position,
If demodulated by the demodulator 44, the digital signal can be wirelessly transmitted. If this ON-OFF is performed at low speed, it will be turned on by the phosphor
-OFF waveform does not deteriorate, but at high speed,
As shown in 0, the waveform distortion due to the phosphor becomes significant. FIG. 10 shows an example in which the output waveform of the photodetector is distorted because it is modulated with high-speed data. This distortion leads to data errors.

FIG. 9 shows a firefly according to a third embodiment of the present invention.
It is a diagram illustrating the configuration of an optical element type illumination light communication system.
That provided a blue filter 45 in front of the phosphor type illumination optical communication system in the light detector 43 of this embodiment is different from the conventional. The blue filter 45 blocks light other than blue light. Only the blue color passes and its intensity is detected. The light other than blue has a characteristic that there is a delay caused by the light emission of the phosphor 33, and therefore is the light that causes waveform distortion, and the blue light is the direct light from the blue LED 32.
It is a component that is not easily distorted even at high-speed modulation. If blue light is extracted by the blue filter 45 and detected, high-speed wireless transmission is performed without the influence of the time response distortion due to the phosphor 33. However, although the intensity of the detected light is smaller than that of the light detected as white light, in high-speed transmission, it is more effective to be able to eliminate the influence of distortion.

The present invention is not limited to the above embodiment.

[0035]

As described above, according to the present invention of claim 1, it is possible to perform an effect of illuminating with an arbitrary color and to make the data transmitted at each wavelength have a role. .

Further , according to the present invention according to claim 3,
It is possible to transmit regularly.

[0037] Also, the claimsFourAccording to the present invention according to
Illumination light of optical type As illumination light peculiar to communication system
While taking advantage of the excellent luminous efficiency and simplicity of the device,
It is possible to dramatically improve the transmission speed, which is the weak point of the type.
it can.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an illumination light transmission device and an illumination light reception device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing human visibility characteristics.

FIG. 3 is a diagram showing a CIE standard chromaticity diagram.

FIG. 4 is a diagram showing an example of each modulation rate of a three primary color LED.

FIG. 5 is a diagram showing an example of each communication quality of data assigned to LEDs of three primary colors.

FIG. 6 is a diagram showing configurations of an illumination light transmitting device and an illumination light receiving device according to a second embodiment of the present invention.

FIG. 7 is a diagram showing a structure of an illumination light transmission device according to a third embodiment of the present invention.

FIG. 8 is a diagram showing a spectrum of a phosphor-type white LED.

FIG. 9 is a diagram showing a configuration of a phosphor type illuminated light communication system according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of an illumination light communication system including a conventional phosphor type illumination light transmitter and illumination light receiver.

[Explanation of symbols]

45 blue filter

Continuation of the front page (56) Reference JP-A-1-122220 (JP, A) JP-A-9-98155 (JP, A) JP-A-8-279802 (JP, A) Sakaki Kanehaku et al., Indoor LED lighting Influence of reflected light in optical communication system, IEICE Technical Report, Japan, The Institute of Electronics, Information and Communication Engineers, March 12, 2002, Vol. 101, No. 730, pp. 93-98 (58) Fields investigated (Int.Cl. ⁷ , DB name) H04B 10/00-10/28 H04J 14/00-14/08 H01L 31/0232 JISC file (JOIS)

Claims (4)

(57) [Claims] 1. A allocator that distributes data to be transmitted into three and allocates each wavelength of three primary colors, and illumination of three primary colors that is modulated at a rate according to each emission intensity by the data allocated by the allocator. LED for illumination and intensity adjusting means for adjusting each emission intensity of the LED for illumination, wherein the LED for illumination is modulated at a rate according to the emission intensity adjusted by the intensity adjusting means. Illumination light transmitter. 2. The control device further comprises control means for controlling so as to transmit information having a changed rate for modulating light of the three primary colors when the emission intensity is changed by the intensity adjusting means. Illumination light transmitter described. 3. An opto-electric converter for converting an optical signal of each of the three primary colors into an electric signal, a combiner for combining the electric signals output from the opto-electric converter with different weights, and a combiner. And a demodulator for demodulating the electric signal output from the illumination light receiving device. A blue LED that emits wherein (1) a blue light modulated by the signal, have a phosphor and excited by the blue light from the blue LED, direct light and the phosphor of the blue LED From
An illumination light transmitting device that illuminates white with light, (2) a blue filter that selectively transmits direct light from the blue LED, a photodetector that detects light via the blue filter, and the light detection And a demodulator for demodulating an electric signal output from the lamp, and a phosphor-type illumination light communication system.