  Omni-resonance refers to the broadening of the spectral transmission through
a planar cavity, not by changing the cavity structure, but by judiciously
preconditioning the incident optical field. As such, broadband imaging can be
performed through such a cavity with all the wavelengths simultaneously
resonating. We examine here the spatial resolution of omni-resonant imaging and
find that the spectral linewidth of the cavity resonance determines the spatial
resolution. Surprisingly, the spatial resolution improves at longer wavelengths
because of the negative angular dispersion intrinsic to Fabry-Perot resonances,
in contrast to conventional diffraction-limited optical imaging systems where
the spatial resolution improves at shorter wavelengths. These results are
important for applications ranging from transparent solar windows to nonlinear
resonant image processing.
