A dach prism is a type of optical prism commonly used in binoculars and other optical devices. It features a roof-like design that allows light to be reflected at specific angles, which helps to invert and revert the image. This design makes the device more compact and easier to handle while maintaining a straight view. Dach prisms are typically made from glass or other transparent materials and are essential in achieving a smaller form factor in devices like binoculars and cameras. They are often found in two main configurations: Porro prisms and roof prisms, each serving a unique purpose in optical systems.