Thermal detectors of uncooled multi-element infrared imaging arrays. I. Thermally insulated elements

The current status of the list of elements of uncooled infrared (IR) imaging arrays based on thermal insulation of their sensors and on accumulation of heat in the element volume during the time necessary for taking one frame is considered. Specific features of operation and the structure of resistive microbolometers and pyroelectric elements are described, as well as typical parameters of these elements. Prospects of improving the parameters of thermally insulated sensors of megapixel arrays are considered. It is noted that the main factor limiting further improvement of the parameters of pixels in IR imaging arrays and increasing the size of the latter is the value of the thermal resistance between the sensor and the substrate. At the modern level of technology development, the thermal resistance has actually reached the limiting value. Another physical principle of operation of IR detectors is required for a further increase in the sensitivity of sensors, a decrease in their response time, and an increase in the size of uncooled megapixel IR arrays; this principle should not include the necessity of thermal insulation of IR detectors. The operation principle based on using pyrotechnical effects will be considered in the second part of the paper.