###### Abstract  
Growing requirements for in situ metrology during manufacturing have led to an increased interest in optical coherence tomography (OCT) configurations of low coherence interferometry (LCI) for industrial domains. This paper investigates the optimisation of spectral domain OCT hardware and signal processing for such implementations. A collation of the underlying theory of OCT configured LCI systems from disparate sources linking the journey of the light reflected from the object surface to the definition of the measurand is presented. This is portrayed in an applicable, comprehensible design framework through its application to profilometry measurements for optimising system performance.  
in-process; metrology for machining; optical coherence tomography 20  
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. Optical coherence tomography (OCT) is a branch of applied LCI developed for operating in non-ideal environments within biomedical science [7]. OCT has been developed for over three decades and demonstrates high data integrity with high spatial resolution even whilst operating within the hostile environment of the human body [8]. OCT configurations have demonstrated straightforward coupling with fibre optics, allowing sensors to be located in situ and at a distance from the readout sensor and electronics, meaning only the chemically inert, extremely compact and robust optical fibre needs to be integrated within the manufacturing process environment. This allows for potential sensor integration into hostile areas in the presence of issues such as high temperatures, electromagnetic interference, corrosive fluids and radioactive activity, whereas current electronic sensors would be prevented from working properly or require extensive shielding. Additionally, the sensors require relatively inexpensive optical components that are readily available making this technology highly accessible. These characteristics make OCT configurations of LCI particularly interesting for in situ measurement where integration using current sensor technology is currently not possible for profilometry.  
Although several review papers have been generated from literature on the developments in OCT systems [8; 9; 10; 11], these focus on its application in the biomedical domain. As a result, areas of the underlying theoretical principles of parameters affecting the captured signal and methods of its processing for such configurations remain largely dispersed and isolated amongst the literature. An in-depth end-to-end demonstration of the theory of operation, from light source to spatial measurement in non-ideal, realistic scenarios with the additional focus for manufacturing regimes, has not yet been completed. As this technology transitions over to greater use in different engineering sectors and applications, a complete practical methodology for its design and application into such environments is required.  
The purpose of this article is to create an optical and data processing design framework for system hardware characteristic selection and signal processing to optimise desired system performance. This is achieved though collation of the underlying theory of spectral domain OCT systems from disparate sources with an application to industrial metrology, linking the journey from the light reflected from the object surface to the definition of the measurand, portraying it in an applicable, comprehensible format through its application to profilometry.