Enhancing optical measuring systems for manufacturing process control

Modern industries are stressed by the market for a crazy and continuous reduction of time-to-market and an increase of required quality of final products. Manufacturing should evolve in order to satisfy market, by increasing the process complexity and fighting against requirements (in terms of batch sizes and tolerances). Production should be fast and accurate and this implies that measuring systems have to be faster, more flexible and possibly in-line, in order to continuously adjust the process. Optical metrology seems to be the perfect solution for this challenging context. However, optical metrology is characterized by binding physical limitations that reduce accuracy and sometimes applicability. Nevertheless, the exponential increase of computational power helps the evolution and optimization of optical measuring systems by permitting real time corrections and fast post-process. The aim of this work is the development of different correction and numerical methods to enhance optical measuring system capabilities. Confocal microscopy, optical CMM (coordinate measuring systems) and X-ray computed tomography are analysed in different types of applications, ensuring a reduction of measuring process variability and increasing measurement accuracy. Algorithms developed specifically for quantification and minimization of influencing factors are presented and implemented for real time correction and control of manufacturing process. Void pixels in confocal microscopy are studied and managed, thus reducing variability of surface roughness parameters and increasing capabilities of measuring instrument for micro-milling process control. Optical systems are analysed for thread measurements proposing a correction method for inline, fast and reliable evaluation of threads geometry. Finally, surface roughness is taken into account for correction of computed tomography dimensional measurements. Different technologies applied in different fields are joined by the common need of correction for enhancing measuring capabilities