Periscope (lens)
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.
See also
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