Flexure-based alignment mechanisms : design, development and application

For high accuracy alignment of optical components in optical instruments TNO TPD has developed dedicated,monolithic, flexure-based alignment mechanisms, which provide accuracies below 0.1 µm and 0.1 µrad as well asstabilities down to subnanometer stabilty per minute.High resolution, high stability alignment mechanisms consist of an adjustment mechanism and a locking device.Complex monolithic flexure-based mechanisms were designed to align specific degrees of freedom. They are realizedby means of spark erosion. The benefits of these mechanisms are no play, no hysteresis, high stiffness, a simplifiedthermal design and easy assemblage. The overall system can remain a passive system, which yields simplicity.An actuator is used for positioning. Locking after alignment is mandatory to guarantee sub-nanometer stability perminute. A proper design of the locking device is important to minimize drift during locking.The dedicated alignment mechanisms presented here are based on: (a) the results of an internal ongoing researchprogram on alignment and locking and (b) experience with mechanisms developed at TNO TPD for high precisionoptical instruments, which are used in e.g. a white light interferometer breadboard (Nulling) and an interferometer withpicometer resolution for ESA’s future cornerstone missions "DARWIN" and "GAIA".