Photonic Guided-Path Tomography with Fibre Transducers

N. Nurgiyatna, J. Davidson and K. B. Ozanyan School of Electrical and Electronic Engineering,

J. Vaughan and P. Scully

School of Chemical Engineering and Analytical Science,

The University of Manchester, Manchester, M60 1QD, United Kingdom, Email: k.ozanyan@manchester.ac.uk

ABSTRACT

The basic concepts of the recently introduced Guided-Path Tomography (GPT) are reviewed in the light of the possibility to measure the spatial distribution of various fields on near-flat surfaces. As opposed to a previous demonstration of GPT with low-frequency EM fields (down to DC) for temperature imaging, we report here on the extension of GPT into high-frequency EM fields, i.e. Photonic GPT, notably in the visible and near IR where low-cost optoelectronic components are available.

We demonstrate Photonic GPT for imaging of deformation on a near-flat surface utilising specially developed and manufactured Plastic Optical Fibre (POF) sensor elements consisting of a large number of curvature transducers. Each element of length 3m was sensitised to bending by cutting grooves, through the cladding and into the core of the fibre, along a 0.74m middle section of the element. The performance of the individual transducers is optimised to achieve linear response of the light attenuation through the fibre to an appropriate range of bending. Thus, each POF element yields the line integral of light attenuation, analogous to the classical hard-field tomography implementation of x-ray CT. However, Photonic GPT allows imaging on near-flat or curved surfaces because of the high efficiency of wave guiding in the optical domain.

A set of forward-transformed data from 32 line integrals, grouped in 4 projections at 45o, is obtained with a varying number, size and shape of common household objects, deforming a thick foam mat. Images of the deformation on the mat’s surface are reconstructed by an iterative Landweber technique with median filtering. The results show the ability of this embodiment of Photonic GPT to reproduce correctly the position, number and shape of objects, as well as the relative change in deformation as a function of their weight.

Keywords Guided-Path Tomography, plastic optical fibre, deformation imaging