With my little knowledge of optics I have come across some 'known' designs such as the Double Gauss for example, is there a 'beam compressor'.
My requirements are to reduce an incoming parallel wavefront (source at infinity) to either an outgoing parallel beam (ie afocal), by a factor of around 100 within 10cm or coming to focus at an f-number around 4 or 5.
I have access to Zemax but am currently just searching in the dark worried I might be re-inventing the wheel...