Porro Prisms
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Porro Prisms operate on the principle of total internal reflection (TIR). A beam entering perpendicular to the entrance / exit surface is reflected by the two roof surfaces and emerges parallel to itself. For applications in which either the acceptance angle for TIR is exceeded, or the reflecting surfaces cannot be kept sufficiently clean for TIR, a metal or dielectric coating can be applied to the reflecting surfaces.
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RMI Standard Specifications
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| Materials: |
BK7, FS, UVFS, CaF2 |
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Surface Figure:
BK7, UVFS, FS:
CaF2:
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All polished surfaces:
λ/20 at 633 nm
λ/4 at 633 nm
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Surface Quality:
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All polished surfaces:
10-5
60-40
20-10
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| Dimensional Tolerance: |
+ 0.000", – 0.010" |
Angular Deviation:
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180º |
| Bevels: |
0.010" – 0.030" at 45º on input edge; minimum safety bevel on roof edges |
| Clear Aperture: |
Exceeds central 85% of diameter |
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