Lens Clock

A lens clock is a mechanical dial indicator 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 as an optical power in diopters, assuming the lens is made of a material with a particular refractive index.

Read more about Lens Clock:  How It Works, Radius of Curvature, Estimating Thickness

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