Hard-field tomography imaging in secondary contrast

Tomography is now a well-established method for indirect imaging, where physical measurements of a set of path integrals of the target function can be inverted to yield its spatial distribution. Traditionally, using low frequency electrical and/or magnetic fields, Tomography has been applied to imaging of cross sections of the real and imaginary permittivity of objects and at high photon energies (x-rays and gamma-rays)-the object density. The intermediate spectral range, including the visible, infrared and terahertz regions, allows chemically- specific imaging based on resonant absorption, as well as imaging based on the real part of the complex refractive index, e.g. exploiting measurements of the pulse delay and wave-guiding losses introduced by the target function. A common approach based on the simple path-integral description allows to identify the target function in all these cases. Here we review three cases of hard-field Tomography which allow imaging in secondary contrast, i.e. the recalculation of the target function distribution into another parameter which is not directly measured: a) temperature Tomography, b) refractive index Tomography and c) surface deformation Tomography. © 2013 Published under licence by IOP Publishing Ltd.