A 1.2-V reconfigurable resolution CMOS image sensor with energy harvesting capability

In this paper, we propose a low voltage, low power, reconfigurable resolution CMOS image sensor with energy harvesting capability for wireless image sensor networks. Logarithmic type pixel is adopted to provide a wide dynamic range for image capturing. Semi-pixel level single slope analog-to-digital conversion is realized by employing in-pixel transistors as a part of the column comparator. A correlated double sampling (CDS) control transistor is introduced to remove fixed pattern noise (FPN) due to transistor threshold voltage variations. Energy/power scalability is achieved through reconfiguring the spatial resolution of the imager. The photodiode in the proposed pixel can be used as an energy harvesting device to scavenge energy from the ambient light after photo-sensing. The proposed 64 × 66 imager is designed with AMIS CMOS 0.35-μm digital process, and operates at a supply voltage of 1.2 V. It can achieve a dynamic range of 108.6 dB with an energy efficiency of 10.74 nJ/pixel/frame in simulation. A comparison with other reported designs reveals that the proposed imager is one of the most energy efficient imagers of wide dynamic range. Moreover, the energy harvesting capability of the proposed imager could lead to further improved energy efficiency.