What is "pseudoscope"

Pseudoscope \Pseu"do*scope\, n. [Pseudo- + -scope.] (Opt.) An instrument which exhibits objects with their proper relief reversed; -- an effect opposite to that produced by the stereoscope.
--Wheatstone.

n. (label en optics) An optical instrument that reverses perception of depth.

A pseudoscope is a binocular optical instrument that reverses depth perception. It is used to study human stereoscopic perception. Objects viewed through it appear inside out, for example: a box on a floor would appear as a box shaped hole in the floor.

It typically uses sets of optical prisms, or periscopically arranged mirrors to swap the view of the left eye with that of the right eye.