Citation:
Ford HD, Tatam RP. (2017) Passively-coupled, low-coherence interferometric duct profiling with an astigmatism-corrected conical mirror. Optics Express, Volume 25, Issue 8, 2017 pp. 8896-8915
Abstract:
Duct-profiling in test samples up to 25 mm in diameter has been demonstrated
using a passive, low-coherence probe head with a depth resolution of 7.8 μm, incorporating an
optical-fibre-linked conical mirror addressed by a custom-built array of single-mode fibres.
Zemax modelling, and experimental assessment of instrument performance, show that
degradation of focus, resulting from astigmatism introduced by the conical mirror, is
mitigated by the introduction of a novel lens element. This enables a good beam focus to be
achieved at distances of tens of millimetres from the cone axis, not achievable when the cone
is used alone. Incorporation of the additional lens element is shown to provide a four-fold
improvement in lateral imaging resolution, when compared with reflection from the conical
mirror alone.