The roof prism makes the imaging deviate or deflect to be 90°. In fact, roof prism may regard as a right-angle prism, and the bevel replaced as the 90°whole internal reflection roof. The cleanliness and quality of the surface in the whole internal reflection roof is very importance. Only the ray which plumb the plane of incidence and exit facet can circumvolve 90°, and all the other rays, use the similar way with the common right prism produce the different deflection. The roof prism is applied in the instance, which not only need 90°deflexion but also erection imaging, such as the viewfinder in some instrument.
| ATTRIBUTE | SPECIFICATIONS |
| material | N-BK7 or specified |
| DIAMETER TOLERANCE | +0.2, -0.2mm |
| angle TOLERANCE | +/-1' |
| flatness | λ/4 @632.8nm |
| CLEAR APERTURE | >90% |
| SURFACE QUALITY | 60/40 scratch and dig |
| BEVEL | < 0.2 mm x 45° |
| COATING | With or without AR coating on outside surfaces |
