And when the image sensor is not capturing images it could still be harvesting energy and be used to charge up a local battery. This could be useful for wireless sensor networking (WSN) nodes and the Internet of Things and potentially for personal devices such as smartphones.
The Columbia team, led by Shree Nayar, Professor of Computer Science at Columbia Engineering, has designed a pixel circuit that not only measures the incident light but also converts that light into electrical power to drive the circuit. The image is black and white and the resolution is 30 pixels by 40 pixels but the technique appears to be readily scalable.
Array of 30 by 40 photodiodes. Since the photodiodes have leads on two of their sides, each one was oriented at 45 degrees so as to achieve a lower pixel pitch. Also seen on the front of the board are the readout transistors and the microcontroller. Source: Columbia University.
Nayar's team has made use of the fact that the key component present in both the image sensor and the solar cell is the silicon photodiode. To date these photodiodes have been optimized independently resulting in a different approach; in the photodiode in a camera pixel is used in a photoconductive mode while in a solar cell it is used in a photovoltaic mode.