Wavefront accuracy of mechanically assembled all-cordierite reflective optical system for cryogenic applications.

Although a reflective optical system can theoretically realize ideal optical designs, it is not always the optimal choice compared with a refractive one because of the difficulty in achieving high wavefront accuracy. A promising solution is to build reflective optical systems by mechanically assembling all the optical and structural components made of cordierite, which is a ceramic with a very low thermal expansion coefficient. Interferometric evaluations of an experimental product demonstrated that diffraction-limited performance in the visible wavelength was achieved and maintained even after cooling to 80 K. This new technique may be the most cost-effective method for utilizing reflective optical systems, especially for cryogenic applications.