University of Michigan engineers Euisik Yoon and Sung-Yun Park have developed a nearly microscopic image sensor that doesn`t require an external source of power. Measuring less than a millimeter across, this prototype camera could be placed just about anywhere - it only requires a light source to harvest energy. The technology is detailed in a study recently published in IEEE Xplore.
This isn`t the first self-powered image sensor project, however earlier explorations of the technology had limitations. One previous example involved embedding photovoltaics into a sensor for harvesting the energy to power it, which reduced the amount of light available to produce the image.
When put to the test, the sensor was able to capture 15 images per second
The prototype created by Yoon and Park differs, instead sensing the image and harvesting energy simultaneously without reducing the sensing area. This is made possible by placing a second diode, which acts as a photovoltaic, beneath the photodetector. When exposed to daylight, some photons pass through the initial photodetector diode, where they then reach the second diode and are converted into electricity to power the sensor.
With this arrangement, the sensor`s pixel area is almost fully dedicated to capturing the image while the `waste` photons are grabbed to power the camera. When put to the test, the sensor was able to capture 15 images per second at the quality shown below.
The number of frames that can be captured per second depends on the amount of available light. Full, sunny daylight at 60k lux provided enough power to capture 15 frames per second, though normal daylight at 20k to 30k lux produced enough energy for half that rate at 7.5 frames per second.
Eventually, as IEEE Spectrum notes, the proof-of-concept prototype could be refined to improve its efficiency in lower lighting conditions. The engineers could also choose to embed other components, such as a tiny wireless trans ...
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