When the maximum possible clear aperture is required in a folded Newtonian or Cassegrain telescope design, the optical component of choice is an elliptically shaped coated flat mirror.
Elliptical flat mirrors are used to fold and re-direct optical beams. Due to the elliptical geometry of the coated substrate, the aperture of a circular beam can be rotated by 45˚ around the minor axis without truncation.
Manufactured from highly stable optical materials such as Zerodur or ClearCeram-Z, Optical Surfaces talented optical engineers can regularly achieve surface accuracies of better than ʎ/10 peak to valley on elliptical optical flats up to 600mm length (long axis).
The most common coating on optical flats is aluminium which offers reasonable reflectivity in the UV, visible and mid-infrared spectral wavebands. Protected silver coatings provides the highest reflectivity for coated flat mirrors operating in the visible and protected gold is the most efficient coating for infrared applications.
Optical Surfaces has for over 50 years, supplied uncoated optical flats, and coated flat mirrors to renowned astronomy and defence groups worldwide. The company’s thermally stable production environment has made them pre-eminent in applications requiring optical flats and coated flat mirrors. All optical flats from Optical Surfaces come with full quality testing assurance. Optics up to 600mm diameter are provided with a Fizeau interferometric test report, larger flats are quality assured using the Ritchey-Common test procedure.