Design of a high resolution SLD-OCT and its application

Abstract

OCT is an interferometric technique, relying on interference between a split and later recombined broadband optical field. The axial resolution of an OCT system is determined by the temporal coherence of the light source: light sources with shorter coherence length provide better resolution.

In this project, application of OCT on plant diagnosis is investigated based on the sysmbiosis relationship between orchid plants and the mychorrhizal fungi in the orchid roots. In our studies, we analysed the causes of difference in the OCT images between a fresh root and an ethanol-soaked root. However, further studies are needed to produce a prominent method to investigate the plant health using OCT system.

Besides that, a Time-Domain OCT (TD-OCT) is built using a short-wavelength LED as its light source. The OCT with low wavelength light source gives resolution of about 6.5μm. Due to its insufficient output power, a Xenon lamp OCT is built and a resolution of about 0.6μm is achieved.

Lastly, MATLAB simulation is done to determine an optimum wavelength separation between two SLD or LED sources when combining these sources to achieve wider bandwidth sources. The simulation takes into account both the resolution of the combined source and the sidelobes effects incurred by its non-Gaussian shape.