Welcome to the Special Section on Smart Sensors!

T HE articles contributed to this Special Section on Smart Sensors were inspired by the papers presented at the 2005 IEEE International Symposium on Circuits and Systems (ISCAS). The growing field of " smart sensors " caught our attention and prompted discussion on a Special IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS—I: REGULAR PAPERS issue dedicated to this important topic. Recent research has clearly shown that advanced sensory systems can be fabricated in almost any CMOS process. Such compatibility gives analog and digital designers another boost for developing creative circuit solutions for smart sensory systems. In addition , the neuromorphic engineering field has recently made significant progress and continues to mature, hand in hand with the VLSI technology, providing another venue for advances in smart sensor systems Other advances in technology and engineering have enabled active pixel sensors (APS) in CMOS to compete with charge-coupled devices (CCDs) in imaging quality and to surpass them in smart focal-plane image processing applications. All these developments promote future excitement and growth in the field of smart sensors. The papers in this Special Section on Smart Sensors cover a broad range of topics, such as vision systems and smart CMOS sensors for audio, olfactory, biochemical, and other sensors inspired by biology. The papers also come from four different continents. We are privileged to be the first three women guest editing such a special section; we certainly hope we are not the last. The papers are divided into four main categories of topic: 1) CMOS imagers; 2) neuromorphic sensory systems; 3) bio and biomedical sensors; and finally, 4) other smart sensor topics including capacitive sensors and interface circuits. Each of these areas is discussed next in terms of their importance and integration with the overall field of smart sensors. A smart 3-D imager based on single photon avalanche diode is presented in the paper " A CMOS 3-D Imager Based on SPAD. " The imager is linear and consists of 64 elements, each pixel occupying 38 180 in a high-voltage 0.8-m CMOS process. Each element includes, in addition to the SPAD, a dedicated read circuit for the arrival time estimation of incident light pulses. Results of both, direct and indirect time of flight measurements were presented mapping a range of 2–5 m with precision of cm. Another chip that offers smart processing via adaptive quan-tization is reported in the paper " Adaptive-Quantization Digital Image Sensor for …