Roof Prism Binocular Design

Have a sleek and compact design.

Roof prism binocular design.

A roof prism also called a dach prism or dachkanten prism from the german. Dollar for dollar a porro prism design will give better performance for the money especially in medium or low priced binoculars. Due to the path of light passage porro prism binoculars have bulkier wider design than roof prism binocular. Built to last in a harsh environment a roof prism binoculars central portion that connects the 2 tubes is either an open bridge or closed bridge design.

This is why roof prism binoculars have an aligned eyepiece to objective lens construction. Most roof prism binoculars use either the abbe koenig prism named after ernst karl abbe and albert koenig and patented by carl zeiss in 1905 or the schmidt pechan prism invented in 1899 designs to erect the image. These two 90 faces resemble the roof of a building giving this prism type its name. Porro prism binoculars are not obsolete however.

The path of the light is straight thus giving it a more slim design. Dachkante lit roof edge is a reflective optical prism containing a section where two faces meet at a 90 angle. In 1897 moritz hensoldt began marketing roof prism binoculars. Now there are a few variations of the roof prism design.

Reflection from the two 90 faces returns an image that is flipped laterally across the axis where the faces meet. Like binoculars the roof prism design in the spotting scopes results in a more streamlined shape but the porro prism design offers greater depth perception and generally offers a wider field of view. Today roof prisms dominate the top end birding binocular market. The hinge between the two oculars is small presenting a structure like a letter h.

Essentially they all maintain the same basic function to keep light waves entering and exiting the binocular in a straight line. Binoculars using roof prisms may have appeared as early as the 1870s in a design by achille victor emile daubresse. Better porro prisms binoculars are made from a high density glass bak 4.