In 1996, after Professor Nikko Nakamura published a blue LED, the red, green and blue LEDs representing the three primary colors were finally in place. Because LED has the characteristics of light weight, low power consumption, high-speed response, etc., the white light composed of RGB three-color LED has been regarded as the next generation light source, and Taiwan, Japan, Korea, America and Europe have joined the ranks of white LED development. At present, white LEDs are mostly used in LCD backlighting modules, traffic lights, and portable electronic backlighting modules.
Traditionally, the use of invisible light for communication transmission, mostly using longer wavelength infrared light, is quite mature in this part, and the matching standards are widely used in the industry. Visible light communication refers to a new generation of wireless communication using high-speed response characteristics of visible light lines such as LEDs. Visible light communication limits the receiving area and is ideal for road guidance, guided tours, intelligent transportation systems for pedestrians (ITS), hospitals, indoor information transmission, etc.
The transmitting end transposes the electrical signal according to the transmitted data, and then converts the light into light by the LED. The receiving end receives the light by using the light receiving component (light sensor), and then converts the light into an electrical signal, and repeats the signal to read the signal. Therefore, the use of visible light to develop a source that is easy for the naked eye to recognize information, is less prone to mechanical malfunction, or has an impact on the human body, no electromagnetic wave damage, and the like.
VLCC (Visible Light Communication Consortiun), established in October 2003, was established as an franchise company at the beginning of its establishment. VLCC carried out various working group activities on the standardization and application of visible optical communication technology. In January, in order to enhance the visibility of visible light communication, 23 member companies including Toshiba and other companies officially launched a working group activity. The specific contents were the review of portable terminals and tags, and the establishment of visible light ID standardization. working team.
Visible light communication is a common communication technology for peripheral devices such as lighting fixtures and billboards. In order to popularize visible light communication, it is necessary to establish standardized specifications that can be applied to various terminal machines. At present, VLCC has formulated two specifications, respectively, Visible optical communication system specification VLCC-STD-001, and visible light ID specification VLCC-STD-003 for low-speed communication visible light ID. The scope of application is a communication system using visible light as a medium, especially when the system is divided into a physical layer and an upper layer of application, the applicable range of the physical layer is specified, including the light-emitting component at the receiving end, the light-receiving component and the light-emitting component at the receiving end. Free space interface.
In terms of wavelength, since visible light is used, the wavelength ranges from 380 nm of blue light to 780 nm of red light. The part of the frequency allocation can change the transmission mode of the original signal, in addition to the application in the visible light communication system, the typical transmission system also has an infrared signal system and the like. In order to prevent the space transmission systems from interfering with each other, the sub-transmission wave frequency of the visible optical communication system is also established.
Visible light communication limits the receiving area and is ideal for road guidance, guided tours, and intelligent road traffic systems for pedestrians. The LED point light source visible light wireless communicator completely eliminates the doubts of the traditional high frequency wireless electromagnetic wave on the interference of the human body and the surrounding electronic machines, and is suitable for application in the field of data transmission such as offices and hospitals.
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