Battery Not Included: This Digital Camera Is Powered By Its Image Sensor

In a paper titled, “Towards Self-Powered Cameras,” scientists Shree K. Nayar, Daniel C. Sims and Mikhail Fridberg have proposed a digital camera that does not need a battery to run. Instead, it uses a modified image sensor with photodiodes that not only measure the incident light level (and hence take a picture), but also convert the incident light into electrical energy (as in solar panels). This “eternal camera” can then run forever as long as there is an ample light source to produce the power needed.

This is not a novel idea as such and some have tried in the past to use a small external solar panel situated close to a camera to power the camera’s electronics. This proved both expensive and bulky.

Another solution used only a portion of the image sensor for image acquisition, while the remaining area was used for power generation. Such a sensor architecture, however, requires the sacrifice of valuable real-estate on the sensor plane for non-imaging purposes.

In their work, Shree K. Nayar et al. take a more extreme approach and redesign each pixel of the image sensor:

In our work, we take a more extreme approach. Our goal is to redesign the pixels of the sensor such that they not only measure incident light but can also harvest all the energy needed for the measurements to be read out. In our pixel design, we use a photodiode in the photovoltaic mode rather than the photoconductive mode used in conventional image sensors. This ensures that each pixel consumes zero power to measure light and yet can convert light into electrical energy for powering the readout of the image.

The front of the printed circuit board includes an array of photovoltaic cells, the readout transistors and the microcontroller. The back of the board includes the discrete components of each pixel and the energy harvester. For storage of harvested energy, a supercap is used instead of a battery.

What is a supercapacitor?

Using off-the-shelf discrete components, they used an array of compact photovoltaic cells that are commonly used for solar power generation. The sensor is powered by a supercap, which is charged during the harvesting period of each image capture cycle. A lens with an effective F-number of 3.5 is used to form images on the sensor array.

Self-powered camera: A Fresnel lens with an effective F-number of 3.5 is used to form an image on the pixel array.

For practical uses, this new technology could easily find a home in wearable devices, the Internet of things, personalized medicine, smart environments, sensor networks and scientific imaging. Imagine that your wearable devices and sensor networks never needed a battery change… because one is not included nor needed.