|Penta Prism is a five-sided prism
containing two reflecting surfaces at 45 degree to each
other, and two refracting faces perpendicular to the entering
and emerging beams.
The important properties of Penta Prism are:
The image is neither inverted nor reversed, just deviated
With the prism, a constant deviation angle applies to
all rays transmitted by the useful aperture, regardless
of the angles between these rays and the optical axis
(or entrance and exit face normal).
The deviation angle of 90deg is thus independent of the
orientation of the prism, making it especially important
in applications in which the prism orientation cannot
be precisely controlled.
This prism is commonly used in optical tooling, alignment,
rangefinding, surveying, and other instrumental application.
Due to the geometry that total internal reflection cannot
be used, the reflecting surfaces must be coated with a
metallic or dielectric coating.