Periscope (lens)

Scheme of the periscope camera lens with central aperture

The periscope (from ancient Greek περί peri “around, around” and σκοπεῖν skopein “look”) is an early, symmetrical lens (optics) that was developed in 1865 by Hugo Adolf Steinheil . It consists of two unconnected meniscus lenses .

A symmetrical lens structure reduces the aberrations, distortion and coma if the diaphragm lies between the two lenses, as is the case with a periscope.