Dimensional Metrology at PTB to Support Optical Fabrication

Dimensional metrology is the enabling technology required not only for ensuring the quality of optical products but also for monitoring/controlling the manufacturing processes.Dimensional metrology of micro and nano structures and form metrology of flat,spherical,aspherical,ruled and free form surfaces are needed.This paper introduced some dimensional metrology research activities at PTB to support optical fabrication.A metrological large range atomic force microscope(AFM) with a capable measurement volume of 25 mm×25 mm×5 mm was introduced for versatile measurements of micro/nano structures.A kind of assembled cantilever probe(ACP) which is applicable for direct and non-destructive sidewall measurements was presented.A true 3D AFM using flared AFM probes was described by specially developed vector approaching probe(VAP) strategy for true 3D measurements of nano structures.Difference deflectometry and traceable multi sensor(TMS) methods applicable for absolute form metrology of flat to moderately curved surfaces were detailed.Finally,the challenges in form metrology are discussed and ultra precision CMMs applicable for form measurements are introduced.