[New technology] Adjusting LED light source can transmit data

Recently, Fujitsu announced a technology that uses RGB LEDs to transfer data to mobile phones and tablets. The technology can be used to illuminate exhibits such as retail merchandise or museums, while also sending data about the merchandise to mobile cameras without being noticed by the human eye.

It is understood that in recent years there have been many messages using LEDs to transmit data, and some companies have also shown that using white LEDs has more RF channels than WIFI. Companies like Byte Light and GE are investigating the use of LEDs to provide indoor positioning data to mobile devices.

But Fujitsu has different ideas in data modulation. Fujitsu uses color modulation techniques to change the composition of red, green, and blue (RGB) in LED light sources. By constantly modifying the color intensity of each color channel, the ID data is encoded and implanted into the light source without changing the visibility characteristics of the light source itself. For example, in a museum, visitors can directly use a cell phone camera to align an artwork illuminated by an LED light source to obtain information about the artwork. Fujitsu said that this method can reduce the appearance area of ​​the object itself, and the data transmission is invisible when the person watches the object.

Fujitsu said the technology is scalable and can even be used to transmit very large object data such as buildings. Moreover, the technology is also very versatile. For example, a performer can go to the stage, and the viewer can download the song he is singing by pointing at the performer with a smartphone. The company said it will commercialize the technology in 2015.

In this regard, the author called Dr. Dong Jianfei, National Key Laboratory of Semiconductor Lighting Innovation, he said: "The implementation of this application is based on the basic principle of visible light communication, using the high switching frequency of LED chips , so that LED lamps flash a unique The identity code of the luminaire is obtained by demodulating the optical signal when the camera or photodiode of the mobile phone receives the flickering light. The mobile phone or other receiving device retrieves the code in the database to obtain the corresponding information. And displayed on the display of a mobile phone or other receiving device, or playing a voice through a microphone."

Dr. Dong Jianfei said that the technology of optical coding can use ordinary white LED chips. In the above Fujitsu technology, if only text information is transmitted, the communication bandwidth does not have to be very high, and a white light chip can be used; if the audio and video is transmitted, the bandwidth needs to be increased accordingly, and three kinds of LED chips can be used, and color shift keying is used. The modulation method can basically increase the communication bandwidth to only three times that of the white light chip.

In the white light chip, the phosphor has a certain low-pass filtering effect due to its glow effect, thus reducing the switching speed of the white LED chip itself. However, in the case of low bandwidth requirements, this effect can be ignored.

Moreover, Fujitsu's technology is similar to QR code and NFC tags in some respects, but the advantage is that no other signal transmitting and receiving devices are needed, and NFC requires it, and requires the mobile phone to support it at the same time. But this technology requires special drive and control devices (because the information needs to be modulated into the PWM dimming signal), and at the same time the cost is high, because of the need for lighting, there is no advantage in energy saving.

Dr. Dong Jianfei believes that for the visible light communication, it is necessary to consider the irreplaceable application scenarios in order to truly take advantage of the technology. It is generally considered that it is not allowed to use wireless signal communication, for example, where information security is high, otherwise There is no big advantage in the competition of technology.