A (multidimensional) spherical periscope is a system of two ideal mirrors that
reflect every ray of light emanating from some point back to this point. A spherical periscope
defines a local diffeomorphism of the space of rays through this point, and we describe such
diffeomorphisms. We also solve a similar problem for (multidimensional) reversed periscopes,
the systems of two mirrors that reverse the direction of a parallel beam of light.
Keywords:
periscope, optical reflection, projectively gradient vector field
Citation:
Tabachnikov S., Two Variations on the Periscope Theorem, Regular and Chaotic Dynamics,
2020, Volume 25, Number 1,
pp. 11-17