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  2. Lens - Wikipedia

    en.wikipedia.org/wiki/Lens

    A lens with one convex and one concave side is convex-concave or meniscus. Convex-concave lenses are most commonly used in corrective lenses , since the shape minimizes some aberrations. For a biconvex or plano-convex lens in a lower-index medium, a collimated beam of light passing through the lens converges to a spot (a focus ) behind the lens.

  3. Focal length - Wikipedia

    en.wikipedia.org/wiki/Focal_length

    The lens is moved until a sharp image is formed on the screen. In this case ⁠ 1 / u ⁠ is negligible, and the focal length is then given by . Determining the focal length of a concave lens is somewhat more difficult. The focal length of such a lens is defined as the point at which the spreading beams of light meet when they are extended ...

  4. List of lens designs - Wikipedia

    en.wikipedia.org/wiki/List_of_lens_designs

    Simple lenses are lenses consisting of a single element. Lenses in this section may overlap with lens designs in other sections, for example the Wollaston landscape lens is a single element and also a camera lens design. Basic types. Biconcave lens; Biconvex lens; Convex-concave lens; Plano concave lens; Plano convex lens; Meniscus lens; Designs

  5. History of optics - Wikipedia

    en.wikipedia.org/wiki/History_of_optics

    Ibn al-Haytham (Alhacen) wrote about the effects of pinhole, concave lenses, and magnifying glasses in his 11th century Book of Optics (1021 CE). [ 46 ] [ 48 ] [ 49 ] The English friar Roger Bacon , during the 1260s or 1270s, wrote works on optics, partly based on the works of Arab writers, that described the function of corrective lenses for ...

  6. Eyepiece - Wikipedia

    en.wikipedia.org/wiki/Eyepiece

    Modern improvements typically have fields of view of 60°−70°. König design revisions use exotic glass and / or add more lens groups; the most typical adaptation is to add a simple positive, concave-convex lens before the doublet, with the concave face towards the light source and the convex surface facing the doublet.

  7. Crown glass (optics) - Wikipedia

    en.wikipedia.org/wiki/Crown_glass_(optics)

    A concave lens of flint glass is commonly combined with a convex lens of crown glass to produce an achromatic doublet. The dispersions of the glasses partially compensate for each other, producing reduced chromatic aberration compared to a singlet lens with the same focal length.

  8. Corrective lens - Wikipedia

    en.wikipedia.org/wiki/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.

  9. Concave - Wikipedia

    en.wikipedia.org/wiki/Concave

    Concave lens; Concave mirror; Mathematics. Concave function, the negative of a convex function; Concave polygon, a polygon which is not convex; Concave set;

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