Traditional and tried-and-tested binoculars have Porro systems. This was the first type of prism to be used in the production of binoculars. They are named after the designer Ignazio Porro. Here two prism segments are used, which correct the image using total internal reflection by deflecting the light path by 180° per segment. At the boundary surfaces of the prisms, the light ray is not broken, but instead reflected at a specific angle of incidence. A typical characteristic which makes Porro binoculars recognisable is the offset eyepieces and objective lenses. Their advantage is that they produce a very three-dimensional visual image.