An optical system having a substantially flat image field is disclosed. The optical system is formed from optical subsystems wherein an input optical subsystem forms an intermediate image which is the object of an output optical system. The intermediate image has a curvature which compensates that from the remaining optical components of the system to result in a substantially flat image for the optical system. Preferably, the optical elements preceding the intermediate image and the optical elements succeeding the intermediate image are separately corrected for odd aberrations. The optical elements preceding the intermediate image and the optical elements succeeding the intermediate image compensate for each other and result in a substantially aberration free flat image for the optical system. The optical system preferably contains an input optical subsystem and an output optical subsystem wherein the input optical subsystem is a catadioptric system and wherein the output optical system is a dioptric system. Most preferably the input optical system is a 1X catadioptric system and the output optical system is an NX dioptric system. The optical systems of the present invention are used for subquarter micron photolithography tools for microelectronic fabrication, such as scanners and steppers.