A simple model of near-field pixel-to-pixel image transfer using
magneto-inductive arrays is presented. The response of N-dimensional
rectangular arrays is first found as an excitation of eigenmodes. This
analytical method involves approximating the effect of sources and detectors,
and replaces the problem of solving large numbers of simultaneous equations
with that of evaluating a sum. Expressions are given for the modal expansion
coefficients, and in the low-loss case it is shown that the coefficient values
depend only on the difference in reciprocal frequency space of the operating
frequency from the resonant frequency of each mode. Analytic expressions are
then derived for quasi-optical quantities such as the spatial frequency
response, point-spread function and resolving power, and their implications for
imaging fidelity and resolution are examined for arrays of different dimension.
The results show clearly that there can be no useful image transfer for in-band
excitation. Out-of-band excitation allows image transfer. Provided the array is
larger than the expected image by at least the size of the point spread
function, the effect of the array boundaries may be ignored and imaging is
determined purely by the properties of the medium. However, there is a tradeoff
between fidelity and throughput, and good imaging performance using thick slabs
depends on careful choice of the operating frequency. The approximate analytic
method is verified by comparison of exact numerical solution.