Intrusion Detection: Pyroelectric Sensor Applications

This lecture focuses on intrusion detection systems utilizing pyroelectric detectors. The instructor begins by introducing the concept of intrusion detectors and their reliance on pyroelectric technology. A schematic of a single pyroelectric detector is presented, highlighting the polarization direction of the pyroelectric crystal and the generation of charges due to infrared light. The discussion progresses to inter-digital pyroelectric dual detectors, which are essential for detecting moving objects, such as a person. The instructor explains the role of micro lenses in focusing infrared light emissions from a black body at room temperature onto the detector. The lecture includes a detailed analysis of the detector's circuit, emphasizing the small signal analysis of the system. The instructor describes the configuration of the pyroelectric detectors, their polarization directions, and the resulting current flow to a common load resistance. The analysis concludes with a discussion on measuring the voltage in relation to thermal conductance and light intensity differences between the two cells, providing insights into the operational principles of intrusion detection systems.