METROLOGICAL STYLUS ASSEMBLY

摘要

A metrological instrument usable for scanning a small area (for example 0.5 mm x 0.5 mm) of the surface of a workpiece to detect roughness features has a stylus assembly in which a short (10 mm) lightweight (5 mg) stylus arm (9) is loaded with a hairspring (17) which provides most of the static stylus force (100 mg force). This construction provides a high acceleration for the stylus tip (13), allowing the stylus to track features of an amplitude over 0.1 mu m with data points 1 mu m apart and a stylus traverse speed of at least 5 mm s<-1>. The stylus assembly (7) is supported and driven by a two dimensional traverse unit (5) having two one dimensional stages. Each stage has a balanced compound rectilinear spring mounting using flexure springs arranged to resist gravity through their resistance to bending within the plane of the spring.