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Excerpt from Field Guide to Visual and Ophthalmic Optics
Vergence is a concept in ophthalmic optics in which distances are converted to a dioptric power. Vergence is defined as
where d is the absolute distance between an object and a plane of interest, and n is the refractive index of the space. By convention, converging light has a positive vergence and diverging light has a negative vergence. Zero vergence occurs when the object is at infinity. Vergence is in units of diopters for d in meters.
Based on vergence, the lens formula is
where U is the object vergence, φ is power of the lens, and V is image vergence. For a thin lens, the plane of interest for both vergences is at the lens. For thick lenses, the planes of interest are the front and rear principal planes. The magnification is U / V.
|Object Vergence (D)||Distance|