Design of an Ultra Precision Diaphragm Flexure Stage for Out-of-Plane Motion Guidance

Abstract

An ultra-precision diaphragm flexure stage was designed and optimized for pure out-of-plane Z-motion guidance with an effort to minimize parasitic lateral and tilt motions. The diaphragm flexure stage will be used to guide an objective lens along the optical axis in a high performance microscope. A concept with cross-linked radial spoke geometry akin to a bicycle wheel was designed to maximize its in-plane to out-of-plane stiffness ratio. The geometry was then optimized using finite element analysis. Several prototypes were manufactured using an abrasive water jet machining center and tested with a reconfigurable test fixture. Sets of two and four diaphragms were tested. Negligible improvement in parasitic motion was observed between the two and four-diaphragm configurations. The experimental results for out-of-plane stiffness matched the finite element result within 0.3%. Negligible hysteresis in vertical motion was observed. Maximum lateral parasitic motion on the order 2 μm was measured over a Z-motion range of 140 μm. The lateral displacement was linear (R2=0.998) and repeatable, and could be an artifact of misalignment of the diaphragms in the test fixture.