Scientific Instruments > Scientific Optical

The Davidson Lens Diopter Gauge by F. Davidson & Co, London. C. 1900.

Item#: SOI553

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This device is a precision optics gauge to measure lens radius of curvature in order to calculate its focal length. The instrument consists of three short prongs – the middle one is a spring driven micrometer made to measure concave or convex lenses which are about 21mm in diameter or larger. The 2-inch diameter dial, directly reads curvatures from 0 to 20 diopters in 1/4 increment. The readings are than converted to focal length using the simple formula: Focal Length = 2 X Radius of Curvature. Included are a special zero adjusting key; 2 plano convex lenses; box and operating instructions.