Researchers have created CMOS image sensor able to simultaneously generate electricity from the sunlight and take pictures.
So far, researchers had CMOS image sensors for digital cameras. They operated in solar battery mode, but its functions operated interchangeably: sensor could either generate electric current, or take pictures or videos. A team of researchers from the University of Michigan has used standard 180 nm CMOS process to create pixels of an innovative design, which allows for energy harvesting from light sources and record a video signal.
The study titled Simultaneous Imaging and Energy Harvesting in CMOS Image Sensor Pixels published in IEEE Electron Device Letters explains that theoretical considerations were already verified in practice: researchers created 100×90 pixels CMOS imaging sensor in 180 nm standard CMOS process, each pixel measuring 5×5 µm for a total sensor area of 660×860 µm. Finished device allows for 30 μW of harvested power at 120,000 lux. The power consumption of CIS (Contact Image Sensor) core at a 0.6 V supply was 3.9 μW at 7.5 frames per seconds and 10.08 μW for 15 fps, respectively, well within the pixel’s energy harvesting budget.
Thus, newly developed sensor has proved to be viable and supports 15 fps under an illumination of 60,000 lux, which is comparable to the illumination on a sunny day, and supports 7,5 fps under an illumination of 20-30 klux.
Developers say that such sensors may be useful for permanently turned on self-contained batteryless cameras – for the solutions in the internet of things, for instance.