The next generation of focal-plane astronomical instruments requires technological breakthroughs to reduce their system
complexity while increasing their scientific performances. Applied to the optical systems, recent studies show that the
use of freeform reflective optics allows competitive compact systems with less optical components. In this context, our
challenge is to supply an active freeform mirror system, using a combination of different active optics techniques. The
optical shape will be provided during the fabrication using the mechanical property of metals to plasticize and will be
coupled with a specific actuator system to compensate for the residual form errors, during the instrument operation
phase. We present in this article the development of an innovative manufacturing process based on cold hydro-forming
method, with the aim to adapt it for VIS/NIR requirements in terms of optical surface quality. It can operate on thin and
flat polished initial substrates. The realization of a first prototype for a 100 mm optical diameter mirror is in progress, to
compare 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 FEA
parameters to optimize the residual form errors obtained through this process. It concerns the microstructure
considerations, the springback effects and the work hardening evolutions of the samples, depending on the initial
substrate properties and the boundary conditions applied. Modeling and tests have started with axi-symmetric spherical
and aspherical shapes and will continue with highly aspherics and freeforms.