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Chicken eyeglasses, also known as chicken specs, chicken goggles, generically as pick guards, and under other names, [2] were small eyeglasses made for chickens intended to prevent feather pecking and cannibalism. They differ from blinders in that they allow the bird to see forward, whereas blinders do not. One variety used rose-colored lenses ...
In some lenses, the curved surfaces are replaced with flat surfaces, with a different angle in each section. Such a lens can be regarded as an array of prisms arranged in a circular fashion with steeper prisms on the edges and a flat or slightly convex center. In the first (and largest) Fresnel lenses, each section was actually a separate prism.
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 ...
Aberrations of the eye. The eye, like any other optical system, suffers from a number of specific optical aberrations. The optical quality of the eye is limited by optical aberrations, diffraction and scatter. [1] Correction of spherocylindrical refractive errors has been possible for nearly two centuries following Airy's development of methods ...
By measuring this zone, the autorefractor can determine when a patient's eye properly focuses an image. The instrument changes its magnification until the image comes into focus. The process is repeated in at least three meridians of the eye and the autorefractor calculates the refraction of the eye, sphere, cylinder and axis.
Viewfinder. In photography, a viewfinder is a small window the photographer looks through to see what a photo will look like before they capture it. [1] Some viewfinders see directly through the lens, whereas others are separate and show an approximation of what the photo will look like. The second type is much simpler to design, but creates a ...