A Multiplexed Chemical Sensing CMOS Imager

A miniaturized and multiplexed chemical sensing technology is urgently needed to empower mobile devices, Internet-of-Things (IoTs) and robots for various new applications. Here, we show that a complementary metal-oxide-semiconductor (CMOS) imager can be turned into a multiplexed colorimetric sensing chip by coating micron-scale colorimetric sensing spots on the imager surface. Each sensing spot contains chemical sensing materials and nanoparticles for colorimetric signal enhancement. The sensitivity is spot-size invariant, and high-performance chemical sensing can be achieved on sensing spot as small as ~ 10 µm. This great scalability combined with millions of pixels of a CMOS imager offers a promising platform for highly integrated chemical sensors. Moreover, the chemical CMOS chip can be readily integrated with mobile electronics. As a proof-of-concept, we have built a smartphone accessary based on this chemical CMOS chip for personal health management. We anticipate that this new platform will pave the way for the widespread application of chemical sensing, such as mobile health (mHealth), IoTs, electronic nose, and smart homes.

Fixed Pattern Noise Reduction and Linearity Improvement in Time-Mode CMOS Image Sensors

In the paper, a digital clock stopping technique for gain and offset correction in time-mode analog-to-digital converters (ADCs) has been proposed. The technique is dedicated to imagers with massively parallel image acquisition working in the time mode where compensation of dark signal non-uniformity (DSNU) as well as photo-response non-uniformity (PRNU) is critical. Fixed pattern noise (FPN) reduction has been experimentally validated using 128-pixel CMOS imager. The reduction of the PRNU to about 0.5 LSB has been achieved. Linearity improvement technique has also been proposed, which allows for integral nonlinearity (INL) reduction to about 0.5 LSB. Measurements confirm the proposed approach.