# Direct reconstruction of complex refractive index distribution from boundary measurement of intensity and normal derivative of intensity

Varma, Hari M and Vasu, Mohan R and Nandakumaran, AK (2007) Direct reconstruction of complex refractive index distribution from boundary measurement of intensity and normal derivative of intensity. In: Journal of the Optical Society of America A, 24 (10). pp. 3089-3099.

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## Abstract

We present an optical tomographic reconstruction method to recover the complex refractive index distribution from boundary measurements based on intensity, which are the logarithm of intensity and normal derivative of intensity. The method, which is iterative, repeatedly implements the forward propagation equation for light amplitude, the Helmholtz equation, and computes appropriate sensitivity matrices for these measurements. The sensitivity matrices are computed by solving the forward propagation equation for light and its adjoint. The results of numerical experiments show that the data types ln(I) and $\partial I/\partial n$ reconstructed, respectively, the imaginary and the real part of the object refractive index distribution. Moreover, the imaginary part of the refractive index reconstructed from $\partial I/\partial n$ and the real part from ln(I) failed to show the object's inhomogeneity. The value of the propagation constant, k, used in our simulations was 50, and this value resulted in smoothing of the reconstructed inhomogeneities. Thus we have shown that it is possible to reconstruct the complex refractive index distribution directly from the measured intensity without having to first find the light amplitude, as is done in most of the currently available reconstruction algorithms of diffraction tomography.

Item Type: Journal Article Copyright of this article belongs to Optical Society of America. Division of Physical & Mathematical Sciences > Instrumentation and Applied Physics (Formally ISU)Division of Physical & Mathematical Sciences > Mathematics 11 Jul 2008 19 Sep 2010 04:47 http://eprints.iisc.ernet.in/id/eprint/14960