Extremely aspheric mirrors: prototype development of an innovative manufacturing process based on active optics

摘要

The next generation of focal-plane astronomical instruments requires technological breakthroughs to reduce their systemcomplexity while increasing their scientific performances. Applied to the optical systems, recent studies show that theuse of freeform reflective optics allows competitive compact systems with less optical components. In this context, ourchallenge is to supply an active freeform mirror system, using a combination of different active optics techniques. Theoptical shape will be provided during the fabrication using the mechanical property of metals to plasticize and will becoupled with a specific actuator system to compensate for the residual form errors, during the instrument operationphase. We present in this article the development of an innovative manufacturing process based on cold hydro-formingmethod, with the aim to adapt it for VIS/NIR requirements in terms of optical surface quality. It can operate on thin andflat polished initial substrates. The realization of a first prototype for a 100 mm optical diameter mirror is in progress, tocompare the mechanical behaviours obtained by tests and by Finite Element Analysis (FEA), for different materials.Then, the formed samples will be characterized optically. The opto-mechanical results will allow a fine tuning of FEAparameters to optimize the residual form errors obtained through this process. It concerns the microstructureconsiderations, the springback effects and the work hardening evolutions of the samples, depending on the initialsubstrate properties and the boundary conditions applied. Modeling and tests have started with axi-symmetric sphericaland aspherical shapes and will continue with highly aspherics and freeforms.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.