Overview: Half-Penta prisms also known as Bauernfeind prisms or Semi-pentaprisms are used to
deviate the line of sight by 45° without inverting or reverting the
image. It is widely used in telescopes and also has applications in
projection and imaging system, in microscope tubes, and in geodesy. The Half-penta prism has the geometrical structure of a penta prism
cut in half. The beam is reflected twice in the prism, first with
total internal reflection and a second time on a coated reflecting
surface. The prism requires aluminized and over-coated with Inconel
and black paint for the non-TIR surface to be usable in practice. Combining a Half-Penta Prism with a correspond size Schmidt roof
prism creates a Pechan prism pair. The Pechan prism pair will
invert or revert the image while not deviating the line of sight. General Specifications of Half-penta Prism: | Material | BK7 | | | Dimension Tolerance | ±0.2mm | | Angle Tolerance | <3 arc minutes | | Roof Angle Tolerance | <3 arc sec | | Flatness | λ/4@632.8nm | | Surface Quality | 60/40 scratch and dig | | Clear Aperture | >90% | | Coating | No coating, available |
Standard Products of Half-penta Prism: | PN. | Material | A (mm) | h (mm) | AR Coating | HR Coating | | HPP1212 | N-BK7 | 12.7 | 12.7 | Uncoated | Uncoated | | HPP1616 | N-BK7 | 16.5 | 16.5 | Uncoated | Uncoated | | HPP1820 | N-BK7 | 18.0 | 20 | Uncoated | Uncoated | | HPP1212-450-650-MAL | N-BK7 | 12.7 | 12.7 | AR@450-650nm | Protected Aluminum | | HPP1616-450-650-MAL | N-BK7 | 16.5 | 16.5 | AR@450-650nm | Protected Aluminum | | HPP1820-450-650-MAL | N-BK7 | 18.0 | 20.0 | AR@450-650nm | Protected Aluminum |
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