Design of a single lens wavefront coded infrared camera

We present the design of a single lens infrared imaging system based on the wavefront coding approach. Spatially invariant PSF with consistent performance over the full field of view ±(4^∘×3^∘) and athermalization (-20^∘C to +60^∘C) is achieved in a compact single lens design by a combination of both lens bending and introduction of a generalized cubic phase on the back surface of the lens. The aberration compensation characteristics of the cubic phase and the generalized cubic phase are analyzed, and it is observed that the generalized cubic phase performs better against quadratic-order aberrations. In the optimization process, we therefore first use the aspheric surface and lens bending to optimize the nominal lens to minimize coma and spherical aberration. A generalized cubic phase mask is then introduced on the back surface of the lens to optimize the lens with respect to defocus and other quadratic order aberrations. The resultant design has nearly invariant MTF over temperature-induced defocus as well as the full field of view of interest. Image simulations are shown with variation in temperature and field angle. Wiener de-convolution with the single on-axis point spread function (PSF) is shown to recover good-quality images over a full field of view for the desired temperature range. The proposed design is feasible to realize with current fabrication methodologies and will be useful for developing lightweight, compact, and low-cost infrared optical imaging systems.