Scanner mirrors and space-born telescope mirrors have one thing in common: every gram counts. Consequently, light-weight structures are typically used. Conventional techniques with back pockets and drilled structures allow for weight reductions of more than 30%. Combining a dedicated design with an additive manufacturing process enables weight reductions of more than 65%.
The team from Fraunhofer IOF uses selective laser melting to manufacture metal mirrors. Due to the lightweight design with stochastic or symmetric structures, a mass reduction of up to 75% has been achieved. Several materials have been qualified, such as AlSi12, AlSi40, and Al6061. Mirrors of 150-mm diameter exhibit high stability and stiffness along with a surface roughness of <1 nm RMS and form a deviation of <150 nm PV after post finishing.