From lasers to spectrophotometers, reflecting microscope objectives are today finding a wealth of applications: reflecting objectives are widely used in the UV microlithography as well as in FTIR spectrophotometry, as part of the delivery system to focus the beam to precisely controlled spot sizes (e.g., for excimer laser beams - submicron size). Because of achromatism these objectives can be used simultaneously for aligning and viewing the targets. In the 'classical' layout the smaller mirror obstructs the central portion of the incident beam. The current paper describes a new solution to reduce the central obstruction by incorporating refracting components in the objective construction. We will discuss the conditions for aberrations correction and diffraction limitation as a function of both the focal length and aperture. Some examples of reflecting/refracting objectives (RRO) will be presented.
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