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Deck prism. A deck prism, or bullseye, is a prism inserted into the deck of a ship to provide light down below. [1] [2] [3] For centuries, sailing ships used deck prisms to provide a safe source of natural sunlight to illuminate areas below decks. Before electricity, light below a vessel's deck was provided by candles, oil and kerosene lamps ...
where f is the focal length of the lens. To describe combinations of optical components, ray transfer matrices may be multiplied together to obtain an overall RTM for the compound optical system. For the example of free space of length d followed by a lens of focal length f:
Corrective lens. A pair of contact lenses, positioned with the concave side facing upward. A corrective lens is a transmissive optical device that is worn on the eye to improve visual perception. The most common use is to treat refractive errors: myopia, hypermetropia, astigmatism, and presbyopia.
These prisms have the additional function of folding the optical path from the objective lens to the prime focus, reducing the overall length for a given primary focal length. A prismatic star diagonal for an astronomical telescope may consist of a single Porro prism (configured for a single reflection, giving a mirror-reversed image) or an ...
A historic example of a long-eye relief (LER) telescopic sight is the German ZF41 which was used during World War II on Karabiner 98k rifles. An early example of a man-portable sight for low visibility/night use is the Zielgerät (aiming device) 1229 (ZG 1229), also known by its code name Vampir ("vampire").
Single lenses have a variety of applications including photographic lenses, corrective lenses, and magnifying glasses while single mirrors are used in parabolic reflectors and rear-view mirrors. Combining a number of mirrors, prisms, and lenses produces compound optical instruments which have practical uses.