  To see color, the human visual system combines the response of three types of
cone cells in the retina--a compressive process that discards a significant
amount of spectral information. Here, we present an approach to enhance human
color vision by breaking its inherent binocular redundancy, providing different
spectral content to each eye. We fabricated a set of optical filters that
"splits" the response of the short-wavelength cone between the two eyes in
individuals with typical trichromatic vision, simulating the presence of
approximately four distinct cone types ("tetrachromacy"). Such an increase in
the number of effective cone types can reduce the prevalence of metamers--pairs
of distinct spectra that resolve to the same tristimulus values. This technique
may result in an enhancement of spectral perception, with applications ranging
from camouflage detection and anti-counterfeiting to new types of artwork and
data visualization.
