The term "Smart Sensors", one of the most strategic devices of Micro System Technologies (MST), refers to sensors which contain both sensing and signal processing capabilities with objectives ranging from simple viewing to sophisticated remote sensing, surveillance, search/track, weapon guidance, robotics, perceptronics and intelligence applications. This paper deals specifically with a new class of smart sensors in infrared spectral bands whose development started some years ago, when it was recognized that the rapid advances of "very large scale integration" (VLSI) processor technology and mosaic infrared detector array technology could be combined to develop a new generation of infrared smart sensor systems with much improved performances. Sophisticated signal processing operations have been studied for these new systems by integrating microcomputers and other VLSI signal processors within or next to the sensor arrays on the same focal plane, avoiding computing systems located far away from sensors. Recently, this approach has being upgraded by introducing inside the sensor some of the basic function of living eyes, such as dynamic stare, dishomogenity compensation, spatial and temporal filtering. New objectives and requirements and the relevant microsystems technologies are presented for this type of new infrared smart sensors which has been originally developed by us.