Low coherence interferometry for measurements in non-ideal environments

The ability to robustly measure a components physical dimensions is a critical part of a production process for ensuring adherence to required standards. Developments in industry are driving the requirement for dimensional measurements made within the production environment for providing in-situ monitoring, verification, and control of processes. Low-coherence interferometry (LCI) is a well-established optical method used for obtaining absolute geometric measurements present in many metrology laboratories around the world. However, typical LCI instruments are large and not suited to direct implementation into machining processes, often utilising white light scanning configurations prone to error from external environmental factors and requiring dedicated workstations. Developments in a branch of LCI known as optical coherence tomography (OCT) have demonstrated measurement robustness in non-ideal environments during biomedical applications. Additionally, due to their inexpensive optical components, straightforward coupling with fibre optics, and spectral-domain implementations make OCT configurations of LCI particularly interesting for in-situ absolute distance measurements. However, the use of OCT outside the field of biomedical science is sparse and the integration of such a sensor into an industrial environment for measurement of metallic samples for recovery of form and surface texture has not been studied.

This thesis presents LCI in a lensless, spectral-domain, fully fibre deployed, common path configuration, allowing for single-shot depth-resolved measurements whilst limiting the effect of environmental variations such as temperature, pressure and vibrations on the obtained interferometric signal for the measurement of metallic components in non-ideal environments. [Continues.]