and Laser Heads for Laser-Interferometer Positioning Systems (1995).
More specifically, conventional polarizing interferometers include a first laser source for providing a first beam having a first frequency and a first linear polarization and a second laser source having a second frequency and a second linear polarization that is orthogonal to the first polarization state. A polarizing interferometer also includes reference and measurement arms as well as a polarizing beam splitter for separating the first and second beams based upon their polarization such that one of the beams is directed to the measurement arm of the interferometer, while the other beam is directed to the reference arm of the interferometer. Upon returning from the measurement and reference arms, the first and second beams are mixed by a polarization analyzer orstudy. Thanks to Dr Philippa Dall and Professor Malcolm Granat who developed the HSC analysis program. This study was funded by Versus Arthritis (Grant number 20874).

All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by Marie Therese McDonald, Sara Cameron, and Elaine Coulter. The first draft of the manuscript was written by Elaine Coulter and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Dr Coulter, Ms McDonald, Dr Siebert and Professor Paul received a research grant from Versus Arthritis (formally Arthritis Research UK) during the conduct of the study. Ms Cameron declares no conflicts of interest.
