Visible Light Communication
Visible light communication (VLC) is a data communications medium using visible light between 400 THz (780 nm) and 800 THz (375 nm). Visible light is not injurious to vision.
The technology uses fluorescent lamps (ordinary lamps, not special communications devices) to transmit signals at 10 kbit/s, or LEDs for up to 500 Mbit/s. Low rate data transmissions at 1 kilometre (0.6 mi) and 2 kilometres (1.2 mi) were demonstrated. RONJA achieves full Ethernet speed (10 Mbit/s) over the same distance thanks to larger optics and more powerful LEDs.
Specially designed electronic devices generally containing a photodiode receive signals from such light sources, although in some cases a cell phone camera or a digital camera will be sufficient. The image sensor used in these devices is in fact an array of photodiodes (pixels) and in some applications its use may be preferred over a single photodiode. Such a sensor may provide either multi-channel communication (down to 1 pixel = 1 channel) or a spatial awareness of multiple light sources.
VLC can be used as a communications medium for ubiquitous computing, because light-producing devices (such as indoor/outdoor lamps, TVs, traffic signs, commercial displays, car headlights/taillights, etc.) are used everywhere.
Read more about Visible Light Communication: History
Famous quotes containing the words visible and/or light:
“All visible objects, man, are but as pasteboard masks. But in each event—in the living act, the undoubted deed—there, some unknown but still reasoning thing puts forth the mouldings of its features from behind the unreasoning mask. If man will strike, strike through the mask!”
—Herman Melville (1819–1891)
“When you take a light perspective, it’s easier to step back and relax when your child doesn’t walk until fifteen months, . . . is not interested in playing ball, wants to be a cheerleader, doesn’t want to be a cheerleader, has clothes strewn in the bedroom, has difficulty making friends, hates piano lessons, is awkward and shy, reads books while you are driving through the Grand Canyon, gets caught shoplifting, flunks Spanish, has orange and purple hair, or is lesbian or gay.”
—Charlotte Davis Kasl (20th century)