  The human's visual system detect intensity images. Quite interesting,
detector systems have shown the existence of different kind of images. Among
them, images obtained by two detectors (detector array or spatially scanning
detector) capturing signals within short window times may reveal a "hidden"
image not contained in either isolated detector: Information on this image
depend on the two detectors simultaneously. In general, they are called
"high-order" images because they may depend on more than two electric fields.
Intensity images depend on the square of magnitude of the light's electric
field. Can the human visual sensory system perceive high-order images as well?
This paper proposes a way to test this idea. A positive answer could give new
insights on the "visual-conscience" machinery, opening a new sensory channel
for humans. Applications could be devised, e.g., head position sensing, privacy
in communications at visual ranges and many others.
