The revolution in surface machining, testing and alignment of optical systems open new horizons for lens design. Imaging systems that are generally non axi-symmetric can be made. Freeform optical surfaces can be machined. In this paper we propose a method based on the generalized Sine condition for the design of aplanatic optical systems that are generally made of free form optics. As a proof of concept we present the design of a two mirrors fast aplanatic telescope. We also show the possibility of designing plane symmetric optical systems.