The calibration unit of the ESO SOXS telescope which Incident Angle is developing for FINCA at the time of writing this, operates over a wide spectral range from VIS to NIR. In order to achromatize the collimating lenses, the indices of refraction had to be recalculated.
Originally suggested by Maksutov, a Maksutov microscope objective (or eyepiece) is a reverse Gregorian type reflective objective. It has high numerical aperture and has corrected spherical, coma and color aberrations. It requires a field flattener to correct the field curvature, but for on-axis observations, it has a long working distance and short total track.
For prototyping purposes, our company engages in creating different applications with stock optics. This time we focused on a fast MWIR (3-5μm) optics. Available stock optics are severely limited, but we managed to pull off a 50° FFOV diffraction-limited objective. Field would benefit from custom optics, but most prototyping and proof-of-concepts are quite possible with just stock optics.