The reflection system for picture-erection is provided between a lens and an eyepiece. At the lens end a first mirror (11) is set at 45 degrees to the incoming rays, and followed by a second mirror (12) reflecting at right-angles to these rays. A third mirror (13) at the eyepiece end reflects parallel to the incoming rays at the second mirror and a fourth (14) reflects parallel to the incoming rays at the lens to the eyepiece. One or more lenses are mounted between the first and fourth mirrors an at right-angles to one of the reflection axes.
