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 or 0.1 μrad as well as stabilities down to tens of picometers per few minutes after locking.
High resolution, high stability alignment mechanisms consist of an adjustment mechanism and a locking device.
Complex monolithic flexure-based mechanisms are designed to align specific degrees of freedom. They are realized by means of spark erosion. The benefits of these mechanisms are no play, no hysteresis, high stiffness, a simplified thermal design, easy to assemble. Using alignment mechanisms a passive system can be maintained.
Locking after alignment is mandatory to guarantee sub-nanometer stability. However, a high accuracy alignment will be disturbed again due to drift during locking if the locking device is not properly designed. Several low-drift locking devices have been designed and developed.
The dedicated alignment mechanisms presented here are based on: (a) the results of an internal ongoing research program on alignment and locking and (b) experience with mechanisms developed at TNO TPD for high precision optical instruments, which are used in e.g. a white light interferometer breadboard (Nulling) and an interferometer with picometer resolution for ESA’s future cornerstone missions “DARWIN” and “GAIA”.