Now, a battery-less video camera that doesn't need charging

Scientists have invented a prototype video camera, that runs without a battery.

The first to be fully self-powered, the camera, created by the research team led by Professor Shree K. Nayar, T.C. Chang at Columbia Engineering, can produce an image each second, indefinitely, of a well-lit indoor scene. The pixel is designed as such that it can not only measure incident light but also convert the incident light into electric power.

Nayar realized that although digital cameras and solar panels have different purposes - one measures light while the other converts light to power - both were constructed from essentially the same components. The photodiode in a camera pixel is used in the photoconductive mode, while in a solar cell it is used in the photovoltaic model.

Working with research engineer Daniel Sims BS'14 and consultant Mikhail Fridberg of ADSP Consulting, he used off-the-shelf components to fabricate an image sensor with 30x40 pixels. In his prototype camera, which is housed in a 3D printed body, each pixel's photodiode is always operated in the photovoltaic mode.

The pixel design is very simple, and uses just two transistors. During each image capture cycle, the pixels are used first to record and read out the image and then to harvest energy and charge the sensor's power supply-the image sensor continuously toggles between image capture and power harvesting modes. When the camera is not used to capture images, it can be used to generate power for other devices, such as a phone or a watch.

The prototype was the first demonstration of a fully self-powered video camera, and they believe the results were a significant step forward in developing an entirely new generation of cameras that can function without being externally powered.

The findings will be presented at the International Conference on Computational Photography at Rice University in Houston.