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  2. Contact lens - Wikipedia

    en.wikipedia.org/wiki/Contact_lens

    A pair of contact lenses, positioned with the concave side facing upward. Putting contacts in and taking them out. One-day disposable contact lenses with blue handling tint in blister-pack packaging. Contact lenses, or simply contacts, are thin lenses placed directly on the surface of the eyes. Contact lenses are ocular prosthetic devices used ...

  3. Vertex distance - Wikipedia

    en.wikipedia.org/wiki/Vertex_distance

    Vertex distance. Vertex distance. Vertex distance is the distance between the back surface of a corrective lens, i.e. glasses (spectacles) or contact lenses, and the front of the cornea. Increasing or decreasing the vertex distance changes the optical properties of the system, by moving the focal point forward or backward, effectively changing ...

  4. Astigmatism (optical systems) - Wikipedia

    en.wikipedia.org/wiki/Astigmatism_(optical_systems)

    An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances. The term comes from the Greek α- ( a-) meaning "without" and ...

  5. Achromatic lens - Wikipedia

    en.wikipedia.org/wiki/Achromatic_lens

    Uses an equiconvex crown glass lens (i.e. R 1 > 0 with −R 1 = R 2) and a complementary-curved second flint glass lens (with R 3 = R 2). The back of the flint glass lens is flat ( R 4 = ∞). A Littrow doublet can produce a ghost image between R 2 and R 3 because the lens surfaces of the two lenses have the same radii. Fraunhofer doublet ...

  6. Fresnel lens - Wikipedia

    en.wikipedia.org/wiki/Fresnel_lens

    A Fresnel lens ( / ˈfreɪnɛl, - nəl / FRAY-nel, -⁠nəl; / ˈfrɛnɛl, - əl / FREN-el, -⁠əl; or / freɪˈnɛl / fray-NEL [1]) is a type of composite compact lens which reduces the amount of material required compared to a conventional lens by dividing the lens into a set of concentric annular sections.

  7. Aberrations of the eye - Wikipedia

    en.wikipedia.org/wiki/Aberrations_of_the_eye

    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 ...

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