Focimeter calibration set


Set taratura frontifocometro

Focimeter calibration set by IODA s.r.l.

Set taratura frontifocometro

Documentation of IODA’s focimeter calibration set

This report contains the results of the measurements performed on a series of 12 lenses submitted by IODA s.r.l.

The series is made of 5 negative spherical lenses of nominal power −5,−10, −15, −20, −25 dioptres (symbol D), 5 positive spherical lenses of nominal +5, +10, +15, +20, +25 D, 1 cylindrical lens of nominal power Cyl +5 D, and 1 prismatic lens of nominal power 5 prismatic dioptres.

From February 2018 the focimeter set will have also other prismatic lenses, saying nominal power 2, 10, 15, 20 prismatic dioptres.

This is to comply with ISO requirements. In particular ISO 9342-1:2005 specifies requirements for test lenses for the calibration of focimeters that are used for the measurement of spectacle form lenses.

ISO 9342-1:2005 applies to focimeters meeting the requirements of ISO 8598.

The spherical lenses are made of K5 glass, 25 mm in diameter; they are mounted in a plastic frame where the identification mark is engraved.

The cylindrical lens is made of C B23-59 glass, 60×40 mm2 in size; the mark is engraved on the glass. The prismatic lens is made of K5 glass, 26×50 mm2 in size; the mark is engraved on the glass.

The lenses are identified one by one by means of their nominal power in dioptres and their serial number.


The ophthalmic power is obtained from the geometrical and physical characteristics of the lenses.

You can download the verification document of diopter lens power of the set N ° 085, to be displayed as an example (Set calibratio data sheet).
The following symbols are used:

N refractive index of the glass
R1 first radius of curvature (*)
R2 second radius of curvature (*)
T axial thickness of the lens
f focal length of the lens
Á power of the lens (Á = 1/f)
BFL back focal length
© ophthalmic power (© = 1/BFL)

For more details about Focimeter calibration set see the PDF document in the right side of this page.

The technical report of focimeter calibration set has been prepared by the National Institute of Applied Optics in Florence, and it is part of focimeter set.

This document is written according to the international optical rules and each one has a progressive number, every lens of this set is measured, attesting the dioptric value of each lens, its tolerance and the method used for measurement.

The Focimeter calibration set is accompanied by a robust and elegant carrying case.

You may also be interested in Spherocylindrical-power reference lens Link

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