`
`STANDARD
`
`ISO
`
`7944
`
`Second edition
`1998-06-01
`
`Optics and optical instruments —
`Reference wavelengths
`
`Optique et instruments d'optique — Longueurs d'onde de référence
`
`_m\_
`
`—W—
`
`Reference number
`ISO 7944:1998(E)
`
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`ISO 7944:1998(E)
`
`Foreword
`
`ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
`member bodies). The work of preparing International Standards is normally carried out through ISO technical
`committees. Each member body interested in a subject for which a technical committee has been established has
`the right to be represented on that committee. International organizations, governmental and non-governmental, in
`liaison with ISO, also take part
`in the work.
`ISO collaborates closely with the International Electrotechnical
`Commission (IEC) on all matters of electrotechnical standardization.
`
`Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
`Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
`
`International Standard ISO 7944 was prepared by Technical Committee ISO/TC 172, Optics and optical
`instruments.
`
`This second edition cancels and replaces the first edition (ISO 7944:1984), which has been technically revised.
`
`© ISO 1998
`
`All rights reserved. Unless othenNise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
`or mechanical, including photocopying and microfilm, without permission in writing from the publisher.
`International Organization for Standardization
`Case postale 56 0 CH-1211 Genéve 20 0 Switzerland
`Internet
`iso@iso.ch
`Printed in Switzerland
`
`ii
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`INTERNATIONAL STANDARD © ISO
`
`ISO 7944:1998(E)
`
`Optics and optical instruments — Reference wavelengths
`
`1 Scope
`
`This International Standard specifies two reference wavelengths to be used for the characterization of optical
`materials, optical systems and instruments, as well as ophthalmic lenses.
`It defines the associated principal
`refractive indices and principal dispersions, as well as the Abbe numbers with regard to these reference
`wavelengths and principal dispersions.
`
`2 Reference wavelengths, principal dispersions and Abbe numbers
`
`2.1 General
`
`The reference wavelengths are the mercury e-line 546,07 nm (see 2.2) and the helium d-line 587,56 nm (see 2.3).
`
`For non-ophthalmic applications the mercury e—line shall be the reference wavelength.
`
`Other wavelengths which may be used in addition to these reference wavelengths are given in tables 1, 2 and 3.
`
`NOTE
`
`For the future, it is envisaged that only one reference wavelength is to be specified, even for ophthalmic use.
`
`2.2 Mercury e-line 546,07 nm
`
`The associated principal refractive index ne is the refractive index at the green mercury e-line and the associated
`
`principal dispersion is
`
`”F. — no,
`
`where
`
`nF.
`
`nc.
`
`is the refractive index at the blue cadmium F'-|ine;
`
`is the refractive index at the red cadmium C'-line.
`
`The Abbe number Ve with regard to this reference wavelength and this principal dispersion is defined as:
`
`ne—1
`v =—
`e
`
`nF. — no.
`
`2.3 Helium d-line 587,56 nm
`
`The associated principal refractive index ”d is the refractive index at the yellow helium d-line and the associated
`
`principal dispersion is
`
`I'll: - "C.
`
`where
`
`”F
`
`is the refractive index at the blue hydrogen F-line;
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`Iso 7944:1998(E)
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`© ISO
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`”C
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`is the refractive index at the red hydrogen C-line.
`
`The Abbe number Vd with regard to this reference wavelength and this principal dispersion is defined as:
`
`n —1
`
`"F
`
`”c
`
`Table 1 — Reference wavelengths and recommended wavelengths
`in the visible and ultraviolet spectral ranges
`
`Spectral lines
`
`Ultraviolet
`mercury mercury mercury cadmium hydrogen mercury
`i-line
`
`helium cadmium hydrogen
`
`1) This single line of the Hg-triplet should be used.
`
`404,66
`
`435,83
`
`479,99
`
`486,13
`
`546,07
`
`He
`587,56
`
`ca
`643,85
`
`656,27
`
`706,52
`
`546,07
`
`587,56
`
`m He
`Wavelength nm 365,011)
`Reference
`wavelength
`nm
`
`Principal
`refractive
`index
`
`Table 2 — Recommended wavelengths in the infrared spectral range
`
`m mum-Lulu .9
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`2) Mercuryt—line
`
`1) Caesium s—line
`
`Table 3 — Recommended laser wavelengths
`
` wavelength
`
`543,5 nm
`
`nm
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`ISO 7944:1998(E)
`
`© ISO
`
`ICS 17.180.01
`
`Descriptors: optics, optical equipment, ophthalmic equipment, optical tests,
`
`testing conditions, reference data, wavelengths.
`
`Price based on 2 pages
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