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  2. Real image - Wikipedia

    en.wikipedia.org/wiki/Real_image

    As the object approaches the focal point the image approaches infinity, and when the object passes the focal point the image becomes virtual and is not inverted (upright image). The distance is not the same as from the object to the lenses. Real images may also be inspected by a second lens or lens system. This is the mechanism used by ...

  3. Thin lens - Wikipedia

    en.wikipedia.org/wiki/Thin_lens

    Sign convention for Gaussian lens equation Parameter Meaning + Sign - Sign s o: The distance between an object and a lens. Real object Virtual object s i: The distance between an image and a lens. Real image Virtual image f: The focal length of a lens. Converging lens Diverging lens y o: The height of an object from the optical axis. Erect ...

  4. Lens - Wikipedia

    en.wikipedia.org/wiki/Lens

    An extended hemispherical lens is a special type of plano-convex lens, in which the lens's curved surface is a full hemisphere and the lens is much thicker than the radius of curvature. Another extreme case of a thick convex lens is a ball lens, whose shape is completely round. When used in novelty photography it is often called a "lensball".

  5. Focal length - Wikipedia

    en.wikipedia.org/wiki/Focal_length

    For a thin lens in air, the focal length is the distance from the center of the lens to the principal foci (or focal points) of the lens.For a converging lens (for example a convex lens), the focal length is positive and is the distance at which a beam of collimated light will be focused to a single spot.

  6. Lens (geometry) - Wikipedia

    en.wikipedia.org/wiki/Lens_(geometry)

    A lens contained between two circular arcs of radius R, and centers at O 1 and O 2. In 2-dimensional geometry, a lens is a convex region bounded by two circular arcs joined to each other at their endpoints. In order for this shape to be convex, both arcs must bow outwards (convex-convex). This shape can be formed as the intersection of two ...

  7. Photographic lens design - Wikipedia

    en.wikipedia.org/wiki/Photographic_lens_design

    Fisheye lens - an extreme wide-angle lens with a strongly convex front element. Spherical aberration is usually pronounced and sometimes enhanced for special effect. Optically designed as a reverse telephoto to enable the lens to fit into a standard mount as the focal length can be less than the distance from lens mount to focal plane.

  8. Optics - Wikipedia

    en.wikipedia.org/wiki/Optics

    where S 1 is the distance from the object to the lens, θ 2 is the distance from the lens to the image, and f is the focal length of the lens. In the sign convention used here, the object and image distances are positive if the object and image are on opposite sides of the lens. [45]

  9. Least distance of distinct vision - Wikipedia

    en.wikipedia.org/wiki/Least_distance_of_distinct...

    The focal point F and focal length f of a positive (convex) lens, a negative (concave) lens, a concave mirror, and a convex mirror.. In optometry, the least distance of distinct vision (LDDV) or the reference seeing distance (RSD) is the closest someone with "normal" vision (20/20 vision) can comfortably look at something. [1]