1. An optical system comprising a housing with an opening extending in an axial direction and at least one membrane arranged across the opening, defining at the inside of the housing at least one chamber filled with an in general constant amount of a fluid, wherein the membrane comprises an optically active and an optically passive section and at least one actuator to influence a geometry of the optically active section of the membrane by relocation of the fluid, thereby changing the optical characteristics of the optical system wherein the optically active and the optically passive section of the membrane are attached to at least one annular holding frame the annular holding frame separates the membrane into the optically active and optically passive sections, the actuator is interconnected to the annular holding frame to displace the annular holding frame in said axial direction with respect to said housing, the annular holding frame is arranged at a distance to an inner side of the opening said membrane is attached in an elastically stretched manner to said annular holding frame and/or said opening, said actuator comprises a first support and a second support and is adapted to translate a rotational movement of said first support with respect to said second support into an axial displacement of said annular holding frame with respect to said housing.