Japan Lab Pushes LED Wireless Power to 5 Meters for Battery-Free IoT

A Japan research team has extended LED-based optical wireless power to roughly 5 meters indoors, about five times their 2019 reach. The advance came from pairing adaptive optics with AI beam tracking: Professor Tomoyuki Miyamoto's group at the Institute of Science Tokyo combined a tunable liquid lens, an imaging lens, and a stepper-driven reflector steered by a small neural network that reads an RGB-and-IR depth camera (EE Times; Science Tokyo).

The jump puts LED power inside the room, where neither RF nor laser serves cheaply and safely. RF wireless charging handles low-power sensors but loses range and creates electromagnetic interference. Lasers reach tens of meters, but their energy density makes indoor eye-safety compliance a barrier. LEDs sit between: cheap, long-lived, and integrable into ceiling lighting, so a lighting-like module could illuminate a room and power small ceiling devices at the same time (Tokyo Tech).

A retroreflective film at each receiver edge lets the camera spot devices in total darkness, holding delivery stable day and night. The team's earlier 200 mW-class LED work required careful alignment at about 1 meter (ResearchGate); the new adaptive design removes that step. Chinese outlet ITHome reports the lab LED chip pushed 1.53 W of radiant flux, a figure to confirm against the underlying paper before any delivered-power claim is locked in (ITHome).

Miyamoto names indoor sensor networks in factories, farms, and smart buildings as the first use case, with modest per-device power; phones and laptops remain outside the target. What stays unclear is how much usable power actually reaches a receiver at 5 meters, and whether the beam-steering AI holds up outside a controlled lab.