As improving manufacturing techniques drive down the expense of imaging detector arrays, the total costs of future thermal imaging systems will become increasingly dominated by the manufacturing costs of the complex lens systems that are necessary for athermalization and achromatization. The concept of wavefront encoding combined with post-detection digital decoding has previously been shown to produce systems that are insensitive to thermal and chromatic defocus in slow imaging systems. In this paper we describe the application of the wavefront coding technique to thermal imaging systems with particular emphasis on the specific difficulties encountered. These difficulties include the use and effects of fast optics (~f/1), wide fields of view and noise amplification in low-contrast thermal images. Modeling results will be presented using diffraction models. We will describe the optimization of the wavefront encoding technique with a specific aim to reduce weight, size, and cost whilst maintaining acceptable imaging performance.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.