optical browser modem

one device transmits by flashing a large patch of black, white, and gray on its screen. another device receives by pointing its camera at the first screen. each frame is one bit. no network, no bluetooth — only photons crossing a few feet of air.

point the camera at the centre of the transmitting screen from 1–3 feet away · keep the room stable · auto-exposure on most phones will adapt within a second.

116 frames · ~17.4 s per loop · 6.7 fps

• visible light communication is a real protocol family — li-fi, qr codes, infrared remotes, and the throbbing pixel-clock of a row of led signs all carry data through photons.
• no network is involved. the browser uses its display as a transmitter and its camera as a receiver, with the air between them as the channel.
• auto-exposure is the enemy. modern phone cameras average their exposure across the full frame; the longer your message, the more the camera tries to compensate. high-fps phones with manual exposure work best.
• bandwidth is photon-limited. this demo runs about 6.7 fps which is fine for chat-length text. mature li-fi systems push gigabits per second using infrared and dedicated transceivers.