lens clock
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Lens clock — A lens clock is a mechanical dial caliper that is used to measure dioptric power of a lens. It is a specialized version of a spherometer. A lens clock measures the curvature of a surface, but gives the result in diopters, assuming the lens is… … Wikipedia
Clock of the Long Now — The first prototype, on display at the Science Museum in London. The Clock of the Long Now, also called the 10,000 year clock, is a proposed mechanical clock designed to keep time for 10,000 years. The project to build it is part of the Long Now… … Wikipedia
Lens — The transparent structure inside the eye that focuses light rays onto the retina (the nerve layer that lines the back of the eye, senses light and creates impulses that go through the optic nerve to the brain). The lens was named after the lentil … Medical dictionary
Contact lens — Contacts redirects here. For the software application, see Address book. A pair of contact lenses, positioned with the concave side facing upward … Wikipedia
Dioptre — This article is about the unit of measure in optics. For other uses, see Diopter (disambiguation). A dioptre, or diopter, is a unit of measurement of the optical power of a lens or curved mirror, which is equal to the reciprocal of the focal… … Wikipedia
Vertometer — A vertometer is an ophthalmic bench instrument used to measure dioptric power of a lens. It differs from a lensmeter or lensometer which is a general dispensary tool for opticians to verify spectacle prescriptions at the laboratory. A vertometer … Wikipedia
Optical power — For the power of light, see Radiant flux and Luminous flux. Optical power (also referred to as dioptric power, refractive power, focusing power, or convergence power) is the degree to which a lens, mirror, or other optical system converges or… … Wikipedia
Spherometer — A spherometer is an instrument for the precise measurement of the radius of a sphere. Originally, these instruments were primarily used by opticians to measure the curvature of the surface of a lens.The usual form consists of a fine screw moving… … Wikipedia
Lensmeter — The parameters used by a lensmeter is derived from the prescriptions written by an ophthalmologist or optometrist, being sphere, cylinder, axis, add, and in some cases, prism. The lensmeter is also used to check the accuracy of progressive lenses … Wikipedia
measure — 1. To determine the magnitude or quantity of a substance by comparing it to some accepted standard or by calculation. 2. A specified magnitude of a physical quantity. 3. A graduated instrument used to m. an object or substance. [O.F. mesure, fr.… … Medical dictionary
