An infrared imaging system for imaging infrared radiation from an object onto a detector includes optics configured for producing, with the infrared radiation, transverse ray intercept curves that are substantially straight, sloped lines. A wavefront coding element is configured such that a modulation transfer function of the optics and wavefront coding element, combined, exhibits reduced variation, over a range of spatial frequencies and caused, at least in part, by thermal variation within the imaging system, as compared to a modulation transfer function of the optics alone, without the wavefront coding element. A post processor is configured for generating an improved modulation transfer function, over the range of spatial frequencies, as compared to the modulation transfer function of the optics and the wavefront coding element.