| A video camera has a self-powered image sensor and runs indefinitely without an external power supply if imaging a well-lit indoor scene. (Image: Computer Vision Laboratory) |
A research team led by Shree K. Nayar, a professor of computer science at Columbia University (New York, NY), has create a video camera with photovoltaic pixels that self-power the camera if it is shooting a well-lit indoor scene (for example, 300 lux, which leads to an estimated 0.77 mW of harvested power). The camera can then produce an image each second, indefinitely.
The team is presenting its work at the International Conference on Computational Photography at Rice University (Houston, TX; April 24 to 26, 2015).1
Nayar, working with Columbia research engineer Daniel Sims and consultant Mikhail Fridberg of ADSP Consulting (Sharon, MA), used off-the-shelf components to fabricate an image sensor with 30 x 40 pixels. In his prototype camera, which is housed in a 3D-printed body, each pixel's photodiode is always operated in the photovoltaic mode.
This video was made using the self-powered camera. (Video: Computer Vision Laboratory)
In an image-capture cycle, the CMOS pixels first capture and read out the image and then spend the rest of the cycle converting ambient light to electrical energy that charges the device's power supply. If the scene brightness changes much, then an adaptive algorithm can speed up or slows down the cycle.
The device itself is far from optimized, say the researchers; in addition, the imaging lens had an effective F-number of 3.5 -- a slow lens. Future versions of the device should have an appreciably higher resolution-framerate product.
The pixel design is very simple, using just two transistors. 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.
Nayar notes that the image sensor could use a rechargeable battery and charge it via its harvesting capability: "But we took an extreme approach to demonstrate that the sensor is indeed truly self-powered and used just a capacitor to store the harvested energy," he says.
The research was funded by the Office of Naval Research.
Source: http://engineering.columbia.edu/columbia-engineer-invents-video-camera-runs-without-battery
REFERENCE:
1. S. K. Nayar, D. C. Sims, and M. Fridberg, "Towards Self-Powered Cameras," Proceeding of the International Conference on Computational Photography (ICCP), pp. 1-10, April 2015.