The deviation angle of 90° is thus independent of the orientation of the prism, making it especially important in applications in which the prism orientation cannot be precisely controlled. Due to geometry that total internal reflection cannot be used, the reflecting surfaces must be coated with a metallic or dielectric coating. The standard Penta Prism reflecting surfaces are coated with aluminum or enhanced aluminum. Sometimes, the coated surfaces are with black painting.
Specifications:
| Material: | N-BK7 or other optical glass |
| Dimension Tolerance: | +0.0, -0.2mm |
| Surface quality: | 60-40 S/D |
| Surface flatness: | λ/4 @ 632.8nm |
| Angle Tolerance: | ±30 arc sec(Standard); ±5 arc sec(High Precision) |
| Clear Aperture: | >85% of dimension |
| Bevel: | <0.25mm×45° |
| Coating: | Surfaces S1 & S2 :Single layer MgF2 coating Surfaces S3 & S4: Aluminized and painted black |
Typical Sizes:
| Deminsion:A×h(mm) | Deminsion:Axh(mm) |
| 2.5×2.5 | 2.5×2.5 |
| 7.0×5.0 | 10.0×10.0 |
| 15.0×15.0 | 20.0×20.0 |
Other sizes and shapes are available.