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Annex G (informative) Parameters affecting the measurement of wavelength cut
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International Standard ISO 8980-3 | |
Ophthalmic optics — Uncut finished spectacle lenses Part 3: Transmittance specifications and test methods — AMENDMENT 1 Optique ophtalmique — Verres de lunettes finis non détourés — Partie 3: Spécifications relatives au facteur de transmission et méthodes d'essai — AMENDEMENT 1 Reference number ISO 8980-3:2022/Amd 1:2026(en) | Fourth edition AMENDMENT 1 2022-06
© ISO 2026
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© ISO 2026
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ContentsPage
Foreword
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This document was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee SC 7, Ophthalmic optics and instruments, in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 170, Ophthalmic optics,in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
Any feedback or questions on this document should be directed to the user’s national standards body. A complete listing of these bodies can be found at www.iso.org/members.html.
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Scope
Replace the following sentence:
“This document specifies requirements for the transmittance properties of uncut and unmounted finished spectacle lenses, including attenuation of solar radiation.”
by:
"This document specifies requirements and claims for the transmittance properties of uncut and unmounted finished spectacle lenses, including attenuation of solar radiation.”
Clause 3
Add a new term 3.1 as follows:
"3.1
wavelength cut
the lowest wavelength at which the spectral transmittance rises to a specified level
Note 1 to entrysee 6.7.2 for the requirement"
6.7
Add a new paragraph 6.7 as follows:
"6.7 Claimed wavelength cut
6.7.1 General
In cases where it is claimed that a lens has a specific wavelength cut, the relevant requirement(s) in 6.7.2 shall apply.
NOTEFor information, see Annex G.
6.7.2 Wavelength cut
For lenses claimed to have a wavelength cut at a nominated wavelength, the spectral transmittance measured according to 7.2 shall be less than 5,0 % at the nominated wavelength. Spectral transmittance for all wavelengths from 280 nm to 10 nm shorter than the nominated wavelength shall be less than 1,0 %.
Following ultraviolet irradiation as specified in 7.7, the claimed transmittance performance shall continue to be satisfied."
7.2
Delete the following:
“The uncertainties of the test methods determining transmittance values shall be not greater than:
—
2 % absolute, for transmittance >20 %;
—
1 % absolute, for luminous transmittance ≤20 %;
—
10 % relative, for UV transmittance of lenses with luminous transmittance ≤ 20 %.
These measurement uncertainties shall be based on a confidence level of 95 %.
NOTEGuidelines for evaluating uncertainty can be found in ISO/IEC Guide 98-3. Advice on the specific issues in evaluating uncertainty of measurement in lenses can be found in ISO 18526-2:2020, Annex B. The user can refer to operating manuals and other information provided by manufacturers of specific instruments for additional information.”
7.2.1 and 7.2.2
Add the two new paragraphs as follows:
"7.2.1 General
The uncertainties of measurement in determining spectral transmittance values shall not be greater than
—
2,0 % absolute, for spectral transmittance >20 %,
—
1,0 % absolute, for spectral transmittance in the range of ≤20 %, ≥5 %, and
—
0,5 % absolute, for spectral transmittance <5 %.
These measurement uncertainties shall be based on a confidence level of 95 %.
NOTEGuidelines for evaluating uncertainty can be found in ISO/IEC Guide 98-3. Advice on the specific issues in evaluating uncertainty of measurement in lenses can be found in ISO 18526-2:2020, Annex B. The user can refer to operating manuals and other information provided by manufacturers of specific instruments for additional information.
7.2.2 Specific methods for wavelength cut claims
The spectral transmittance shall be measured with a spectrophotometer or other equivalent measurement device that is capable of making spectral transmittance measurements with relative uncertainty less than or equal to 10 % and spectral (wavelength) uncertainty within ±1,0 nm.
NOTEA calibrated holmium oxide or didymium filter can be used for this verification.
The spectral resolution shall be not greater than 1 nm.
The spectrophotometer shall
a)
operate over the wavelength range 280 nm to 780 nm, and
b)
have a spectral bandwidth (full width at half maximum, FWHM) not exceeding 2 nm;
NOTEThe required uncertainties of measurement, especially towards the lower wavelength limit, can be achieved by using a spectrophotometer with a double monochromator and/or a source with low energy in the wavelengths longer than the claimed wavelength cut.
A plano lens of thickness ISO_2__mml_m1
mm shall be used to determine the transmittance. If a thickness outside this range is used, the thickness shall be stated.
mm shall be used to determine the transmittance. If a thickness outside this range is used, the thickness shall be stated.The measurement shall be made at the reference point and with the incident beam normal to the front surface of the lens.
The general methods of evaluating the components of uncertainty are set out in ISO/IEC Guide 98-3.
Annex G provides some informative background to the measurement methodology."
7.3
Replace the heading “7.3.1” by “7.3.1 Principle”.
Replace the heading “7.3.2” by “7.3.2 Calculation of visual attenuation coefficient”.
Clause 8
Replace the first sentence:
“The following information shall be supplied by the manufacturer or supplier on the package of the lens or an accompanying document:”
by:
“The following information shall be supplied by the manufacturer or supplier on the package of the lens, in an accompanying document or in any other available information provided separately.
NOTEAppropriate means of supplying the information can include in hard copy or digital form by means of electronic solutions, such as a QR or data matrix code.”
Replace “d) any claimed absorption or transmittance properties in accordance with 6.6;”
by:
“d) any claimed absorption or transmittance properties in accordance with 6.6 and/or 6.7;"
Add a new Annex G:
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Annex G
(informative)
Parameters affecting the measurement of wavelength cut
G.1General
A number of parameters including the lens geometry and the spectrophotometer configuration can influence the outcome of the measurement. As it is impractical/ not economic to measure every lens configuration in production, the lens geometry specified for wavelength cut ensures that uniform comparative claims are generated. This annex provides background information for the basis of the methodology for this measurement. More detailed information and guidance can be obtained from the referenced documents.
G.2Impact of lens factors
The specified 2 mm thickness is to allow comparison between materials and is used for all transmittance properties. Lens thickness can influence the wavelength cut. Thinner lenses have increased transmittance and decreased cut-off wavelength. For example, measurements of 1,0 mm polycarbonate gave a cut at 382 nm, whilst that of a 2,0 mm thick lens gave a cut at 386 nm. In general, the shift in wavelength cut has been found to be between 3 nm to 5 nm for a 1 mm change in thickness, which can be estimated by measurement or calculation.
G.3Impact of instrument factors
Inter-instrument variability can result from a number of known spectrophotometer characteristics, resulting in differences in transmittance results. Single grating instruments can show apparent transmission at shorter wavelengths due to stray light/radiation that can result in an underestimation of the wavelength cut. Compensation for this in single grating instruments can result in an overestimation or underestimation of the transmittance. Stray light/radiation in some instruments with a diode array can affect the transmittance measurement in a similar way.
At the 5 % spectral transmittance level, instrument bandwidth can result in a shift of cut-off wavelength, e.g. 1 nm when shifting from a 2 nm bandwidth to a 5 nm bandwidth.
For additional information on uncertainties refer to ISO 18526-2:2020, Annex B.
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