The Evolution of a Fast Speed Wide AngleTelescope Design using Freeform AsphericsDavid ShaferDavid Shafer Optical Design15 degree flat field at f/2.0UNITS:MMOPTICAL SYSTEM LAYOUTDES:Shafer85.3Design goals1)15 degree diameter field of view2)f2.03)A flat image4)No obscuration or vignetting5)Convenient image position6)Diffraction limited over field at.50u for a 100 mm aperture diameterStarting pointIn 1980 I discovered anunusual system twotwo spheres,four reflectionsUNITS:MMFOCAL LENGTH 81.94 NA 0.3316DES:Shaferspherical mirrors with equal23but opposite radii and with 4reflections between them.For one particular mirrorspacing and a particularobject/image conjugate pairthe system is corrected for 3rdorder spherical aberration,coma,astigmatism andPetzval.The magnificationhas to be 3.325X for thissolution.