Porro prism is a type of reflection prism which can be used to alter the orientation of an image. Light enters the large face of the prism, then hits on the roof, by total internal reflection twice from the roof, the beam exits again through the large face.
An image traveling through a Porro prism is rotated by 180deg but not inverted.
| Attribute | Specification |
| Material | N-BK7, Fused Silica,etc |
| Dimension Tolerance(mm) | 0 |
| Clear Aperture | >90% |
| Angle Tolerance | 10 arc sec |
| Roof Angle Tolerance | 5 arc sec |
| Flatness@ 633mm | λ/8 |
| Surface Quality | 10/5 |
