  The exoplanet revolution is well underway. The last decade has seen
order-of-magnitude increases in the number of known planets beyond the Solar
system. Detailed characterization of exoplanetary atmospheres provide the best
means for distinguishing the makeup of their outer layers, and the only hope
for understanding the interplay between initial composition chemistry,
temperature-pressure atmospheric profiles, dynamics and circulation. While
pioneering work on the observational side has produced the first important
detections of atmospheric molecules for the class of transiting exoplanets,
important limitations are still present due to the lack of sys- tematic,
repeated measurements with optimized instrumentation at both visible (VIS) and
near-infrared (NIR) wavelengths. It is thus of fundamental importance to
explore quantitatively possible avenues for improvements. In this paper we
report initial results of a feasibility study for the prototype of a versatile
multi-band imaging system for very high-precision differential photometry that
exploits the choice of specifically selected narrow-band filters and novel
ideas for the execution of simultaneous VIS and NIR measurements. Starting from
the fundamental system requirements driven by the science case at hand, we
describe a set of three opto-mechanical solutions for the instrument prototype:
1) a radial distribution of the optical flux using dichroic filters for the
wavelength separation and narrow-band filters or liquid crystal filters for the
observations; 2) a tree distribution of the optical flux (implying 2 separate
foci), with the same technique used for the beam separation and filtering; 3)
an exotic solution consisting of the study of a complete optical system (i.e. a
brand new telescope) that exploits the chromatic errors of a reflecting surface
for directing the different wavelengths at different foci.
