ISO/DIS 14490-5
(Main)Optics and photonics -- Test methods for telescopic systems
Optics and photonics -- Test methods for telescopic systems
Optique et photonique -- Méthodes d'essai pour systèmes télescopiques
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DRAFT INTERNATIONAL STANDARD
ISO/DIS 14490-5
ISO/TC 172/SC 4 Secretariat: DIN
Voting begins on: Voting terminates on:
2020-10-09 2021-01-01
Optics and photonics — Test methods for telescopic
systems —
Part 5:
Test methods for transmittance
Optique et photonique — Méthodes d'essai pour systèmes télescopiques —
Partie 5: Méthodes d'essai du facteur de transmission
ICS: 37.020
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ISO/DIS 14490-5:2020(E)
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ISO/DIS 14490-5:2020(E)
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ISO/DIS 14490-5:2020(E)
Contents Page
Foreword ........................................................................................................................................................................................................................................iv
1 Scope ................................................................................................................................................................................................................................. 1
2 Normative references ...................................................................................................................................................................................... 1
3 Terms and definitions ..................................................................................................................................................................................... 1
4 Principle ........................................................................................................................................................................................................................ 1
5 Test arrangement ................................................................................................................................................................................................. 2
5.1 General ........................................................................................................................................................................................................... 2
5.2 Radiation source and condenser ............................................................................................................................................. 3
5.3 Monochromator or set of filters ............................................................................................................................................... 3
5.4 Collimator .................................................................................................................................................................................................... 3
5.5 Aperture stop ........................................................................................................................................................................................... 4
5.6 Specimen mounting ............................................................................................................................................................................ 4
5.7 Integrating sphere ................................................................................................................................................................................ 4
5.8 Radiation detector ............................................................................................................................................................................... 4
5.9 Selectable diaphragm as field stop ........................................................................................................................................ 5
6 Procedure..................................................................................................................................................................................................................... 5
6.1 Preparation of the test arrangement ................................................................................................................................... 5
6.2 Determination of the measurement values .................................................................................................................... 5
6.3 Further test methods ......................................................................................................................................................................... 5
7 Precision of the measurement ............................................................................................................................................................... 5
8 Presentation of the results ......................................................................................................................................................................... 6
9 Analysis .......................................................................................................................................................................................................................... 6
9.1 Effective transmittance for photopic vision ................................................................................................................... 6
9.2 Effective transmittance for scotopic vision .................................................................................................................... 6
10 Test report ................................................................................................................................................................................................................... 7
Annex A (informative) Calibration procedure for the photoreceiver/measuring instrument ................8
Annex B (informative) Trichromatic coefficients and colour contribution index..............................................11
Bibliography .............................................................................................................................................................................................................................16
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ISO/DIS 14490-5:2020(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
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/ patents).Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.This document was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee
SC 4, Telescopic systems.This third edition cancels and replaces the second edition (ISO 14490-5:2017), which has been
technically revised.The main changes compared to the previous edition are as follows:
— Updates Clause 5 Test arrangements, in particular 5.7. Veiling glare stop was deleted, clarification of
requirements on Integration sphere, addition of 5.9 selectable diaphragmas as field stop;
— Clarification of requirements in Clause 10 Test report;— addition of B.4 CIELUV values;
A list of all parts in the ISO 14490 series can be found on the ISO website.
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.iv © ISO 2020 – All rights reserved
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DRAFT INTERNATIONAL STANDARD ISO/DIS 14490-5:2020(E)
Optics and photonics — Test methods for telescopic
systems —
Part 5:
Test methods for transmittance
1 Scope
This document specifies the test methods for the determination of the transmittance of telescopic
systems and observational telescopic instruments.2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO/CIE 11664-1, Colorimetry — Part 1: CIE standard colorimetric observersISO 11664-2, Colorimetry — Part 2: CIE standard illuminants
ISO 14132-1, Optics and photonics — Vocabulary for telescopic systems — Part 1: General terms and
alphabetical indexes of terms in ISO 14132ISO 14490-1:2005, Optics and optical instruments — Test methods for telescopic systems — Part 1: Test
methods for basic characteristicsCIE 18.2:1983Basis of Physical Photometry (E)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 14132-1 apply.
No terms and definitions are listed in this document.ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/— ISO Online browsing platform: available at https:// www .iso .org/ obp
4 Principle
To determine the spectral transmittance τλ() , the flux of radiation in a limited bundle of rays will be
measured before entering (Φ ()λ ) and after passing (Φ ()λ ) through the optical system.
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ISO/DIS 14490-5:2020(E)
The spectral transmittance is given by:
Φ λ
τλ()= (1)
Φ λ
During the spectral measurement, the emergent light of the radiation source will be limited to a narrow
wavelength band by means of a monochromator or a set of filters.5 Test arrangement
5.1 General
The test arrangement as given in Figure 1 consists of a radiation source (1) (optionally with a condenser
(2)), a monochromator (3) or a set of filters, a selectable diaphragm as field stop (4), a collimator lens
(5), an aperture stop (6), a test specimen (7) mounting,, an integrating sphere (8), a radiation detector
(9) and a measurement and evaluation unit (signal processing) (11).The monochromator (3) or the set of filters can be omitted if the signal processing unit comprises a
spectral detector.Key
1 radiation source 6 aperture stop
2 Condenser 8 integrating sphere
3 monochromator/set of filters 9 radiation detector
4 selectable diaphragm as field stop 10 baffle
5 collimator lens 11 measurement and evaluation unit
Figure 1 — Test arrangement without test specimen (schematic)
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ISO/DIS 14490-5:2020(E)
Key
1 radiation source 7 test specimen
2 Condenser 8 integrating sphere
3 monochromator/set of filters 9 radiation detector
4 selectable diaphragm as field stop 10 baffle
5 collimator lens 11 measurement and evaluation unit
6 aperture stop
Figure 2 — Test arrangement with test specimen (schematic)
5.2 Radiation source and condenser
The radiation source shall emit a continuous flux of radiation in the specified wavelength range. The
variation of flux during the measurement of a pair of values shall be less than 1 %. The condenser adapts
the radiation source to the optical measurement path. It should be e.g. an achromatic doublet or an off-
axis paraboloidal mirror to avoid introducing too much lateral chromatism into the optical ray path.
5.3 Monochromator or set of filtersThe monochromator or the set of filters can be omitted if the signal processing unit comprises a spectral
detector.Grating or prism monochromators can be used to select the wavelength. The smallest adjustable
wavelength distance shall be less than 2 % of the dominant wavelength of the respective measurement.
The necessary spectral bandwidth depends on the sample. It shall be ensured that a steep alteration of
the transmission curve is detected correctly. Thus, the bandwidth shall be smaller than the distance
in the wavelength, at which the transmittance is changed by 4 %. This condition cannot always be
satisfied because of measuring and energy reasons or because the time/cost effort is not adequate. In
these cases, a maximum bandwidth of 4 % of the wavelength is allowable. A bandwidth of less than 2 %
of the wavelength is necessary if the colour contribution indices are to be calculated.
Instead of a monochromator, a set of narrow-band filters (Full Width Half Maximum < 20 nm) can be
used. They are especially useful with flat-shaped transmission curves. The number of measuring points
shall allow for a definite curve fitting. Measurement with spectral filters can be applied as well if only
single measuring points are required.5.4 Collimator
The collimator may contain a refracting lens or a mirror. The collimator has to be adjusted to the aligned
components in such a way that full and uniform illumination of the following aperture stop is assured.
The focal length of the collimator shall be long enough that in relation to the field stop of the collimator
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ISO/DIS 14490-5:2020(E)
the spot diameter is small enough to pass the image plane of the test specimen and is not obscured by
target marks and internal structures. One-third of the image plane diameter should not be exceeded.
The ray bundle shall be collimated as well as possible within the measurement distance by adjusting
the collimator position. The axial chromatic aberration of a refracting lens shall be less than or equal to
1 % of its focal length in the spectral range used. An off-axis parabolic mirror or an equivalent system
is also suitable as a collimator.5.5 Aperture stop
The aperture stop should be circular and located close to the objective lens of the test specimen if
possible. The diameter should be ≤50 % of the entrance pupil of the test specimen, as well as smaller
than the opening of the integrating sphere. Auxiliary systems can be used for beam forming to realize
these requirements. These systems shall stay in the ray path during the measurement with and without
test specimen.Generally, the smallest possible aperture stop should be used which is compatible with the signal-to-
noise requirements of the detector.Special care should be taken when measuring telescopic systems with variable magnification where at
some magnification settings the entrance pupil can be considerably smaller than the free objective lens
diameter.5.6 Specimen mounting
The mounting of the test specimen shall be designed in a way that the test specimen can be positioned
and aligned and held stable.The test specimen should be oriented in a way such that no obstructions occur in the measurement
beam (e.g. by reticle structures).5.7 Integrating sphere
The distance between aperture stop and integration sphere shall be arranged according to the
requirements of the test specimen. The distance shall not be changed during the measurement with and
without test specimen so that the light always will be completely collected by the integrating sphere.
It is recommended to choose a large distance of e.g. 100 mm between eyepiece and integrating sphere
to avoid the impact of multiple reflections. The position of the integrating sphere should be chosen so
that the diameter of the ray bundle entering the integrating sphere is almost the same as without the
specimen.The integrating sphere has two openings, one for the input of the bundle of rays to be measured and one
for the detector. Both openings shall not be located opposite each other. Direct radiation incident on the
detector is prevented by baffles. The surfaces of the two openings together shall not occupy more than
5 % of the internal surface of the sphere. The diameter of the integrating sphere opening shall exceed
the maximum diameter of the aperture stop (Key 6 in Figure 1) by 5 % to 7 %.The reflectance of the internal coating of the integrating sphere shall be as high as possible and diffuse
across the whole spectral range. The reflectance across the whole spectral range from 380 nm to
780 nm shall be at least 85 %.5.8 Radiation detector
The linearity of the radiation detector shall be better than 0,5 %, including the accompanying signal
processing.4 © ISO 2020 – All rights reserved
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ISO/DIS 14490-5:2020(E)
5.9 Selectable diaphragm as field stop
The diameter should be selected such that the angular extension on the eyepiece side of the test
specimen does not exceed 5 degrees to avoid pupil and reticle vignetting.6 Pro
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