Power via light beam: Japanese system delivers a 16-foot range with infrared LEDs
A research team from the Institute of Science Tokyo has introduced a new system that delivers power to small devices using a focused LED light beam, enabling wireless energy transmission over distances of up 16 feet (5 meters). The technology is primarily intended for IoT devices – networked sensors used in everyday or industrial environments, such as smart thermostats or motion detectors that automatically exchange data. The study was published on November 3 in the journal Optics Express.
The concept is straightforward: a focused LED beam is directed at photovoltaic cells, which convert the light into electrical energy – a potential solution to the growing challenge of powering an ever-increasing number of IoT devices. As these devices proliferate, so do the costs and effort associated with battery replacement and maintenance. Although optical power transmission over distances of several feet already exists, it typically relies on laser beams, which can pose safety risks. Instead, the research team led by Tomoyuki Miyamoto and Mingzhi Zhao chose high-powered infrared LEDs as a safer alternative.
16-foot range through tight beam focus
At the heart of the system is an infrared LED, tightly focused using a two-stage lens setup. A liquid lens dynamically adjusts the focus, while a fixed lens directs the beam onto the photovoltaic cells. According to the study, the LED beam remains precise enough to consistently hit small solar cells at distances beyond 16 feet.
Also works with moving targets – even in the dark
The system is also designed to power moving devices. To achieve this, it combines a two-axis mirror setup with a depth camera. The Intel RealSense D435 detects the small solar cells using standard imaging during the day and retroreflector signals at night. An AI model controls the system, ensuring that the light beam is automatically tracked and focused via the liquid lens. According to the researchers, the setup operates reliably under all lighting conditions – a key requirement for IoT sensors in industrial or remote environments.
Not particularly efficient yet, but with potential
According to the study results, the system operates reliably but is still too inefficient for practical everyday use. In testing, it achieved an efficiency of 56.2%, primarily limited by radiation losses and absorption in the liquid lens. The researchers expect to increase this figure to as much as 80% by optimizing the LED optics, which would make real-world applications far more feasible. In the long term, the technology could be used wherever battery replacement is costly or cabling impractical – particularly in industrial sensor networks, but potentially also in smart home devices or medical measurement equipment.
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