Bena Optics' SiC Aspheric Mirrors

In optical systems, aspheric optical elements can increase the number of free design variables without introducing new aberrations, thereby enhancing imaging quality and reducing the system's size and weight. As a result, aspheric elements are widely used in high-end optoelectronic instruments, such as space and ground-based astronomical telescopes, deep space exploration and Earth observation optics, deep ultraviolet (DUV) and extreme ultraviolet (EUV) lithography optics, and high-performance cameras. Two key performance indicators of astronomical telescope systems are angular resolution (AR) and light collection capability (LCC), both of which are closely related to the system’s aperture. Angular resolution is inversely proportional to the telescope’s diameter, while light collection capability is proportional to the square of the diameter. The larger the aperture, the higher the angular resolution and light collection capability. Therefore, increasing the aperture is crucial for enhancing telescope performance, which explains the high demand for large telescopes in the fields of astronomy and Earth observation.

However, the increasing size of primary mirrors in modern ground-based telescopes and space cameras imposes stringent requirements on mirror materials and full spatial frequency (FSF) shape error control. Thus, breakthroughs are urgently needed in mirror materials and the precise and efficient manufacturing of large aspheric mirrors. Compared to other mirror materials such as ULE® and Zerodur®, silicon carbide (SiC) offers higher specific stiffness and dimensional stability, making it suitable for use in harsh environments. Additionally, the reaction-bonded silicon carbide (RB-SiC) process can produce semi-closed back structures, further enhancing its specific stiffness and dimensional stability. Consequently, large-aperture SiC mirrors, with their superior mechanical and thermal properties, have quickly become the new favorite in the global telescope field.

Bena Optics possesses internationally leading capabilities in processing SiC mirrors. Currently, they can manufacture mirrors with a maximum diameter of 1.2 meters. Utilizing large ring polishing machines, CCOS (Computer Controlled Optical Surfacing) correction, and ultimate finishing techniques such as IBF (Ion Beam Figuring) and MRF (Magnetorheological Finishing), Bena Optics can achieve high RMS (Root Mean Square) surface accuracy of less than λ/180 and ultra-smooth mirror surfaces.