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A lens is a transmissive optical device ... In many cases these aberrations can be compensated for to a great extent by using a combination of simple lenses with ...
Prime lens - a photographic lens whose focal length is fixed, as opposed to a zoom lens, or that is the primary lens in a combination lens system. Zoom lenses - variable focal length lenses. Zoom lenses cover a range of focal lengths by utilising movable elements within the barrel of the lens assembly.
Cylindrical lenses are prescribed to correct astigmatism. [2]Cross cylinder, which is a combination of two cylindrical lenses with equal strength and opposite power, is used in subjective refraction to diagnose astigmatism, and assess the strength and axis of the astigmatic power etc. [3]
Several close-up lenses may be used in combination; the optical power of the combination is the sum of the optical powers of the component lenses. For example, a set of lenses of +1, +2, and +4 diopters can be combined to provide a range from +1 to +7 in steps of 1.
In an achromatic lens, two wavelengths are brought into the same focus, here red and blue. An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration. Achromatic lenses are corrected to bring two wavelengths (typically red and blue) into focus on the same plane.
Often one element is a positive lens made of crown glass and the other is a negative lens made of flint glass. This combination produces a better image than a simple lens. Some Trilobites, which are now extinct, had natural doublet lenses in their eyes. [1] Apochromats can also be made as doublets. Doublets can be air-spaced, cemented, or "oiled".
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