Optics and photonics -- Test methods for telescopic systems

ISO 14490-5:2017 specifies the test methods for the determination of the transmittance of telescopic systems and observational telescopic instruments.

Optique et photonique -- Méthodes d'essai pour systèmes télescopiques

General Information

Status
Replaced
Publication Date
25-Jul-2017
Withdrawal Date
25-Jul-2017
Current Stage
9599 - Withdrawal of International Standard
Completion Date
26-Jul-2017
Ref Project

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INTERNATIONAL ISO
STANDARD 14490-5
Second edition
2017-08
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
Reference number
ISO 14490-5:2017(E)
ISO 2017
---------------------- Page: 1 ----------------------
ISO 14490-5:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form

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ii © ISO 2017 – All rights reserved
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ISO 14490-5:2017(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 Source of radiation and condenser ........................................................................................................................................ 3

5.3 Monochromator or set of filters ............................................................................................................................................... 3

5.4 Collimator .................................................................................................................................................................................................... 3

5.5 Aperture stop ........................................................................................................................................................................................... 3

5.6 Specimen mounting ............................................................................................................................................................................ 3

5.7 Veiling glare stop ................................................................................................................................................................................... 3

5.8 Integrating sphere ................................................................................................................................................................................ 4

5.9 Radiation detector ............................................................................................................................................................................... 4

6 Procedure..................................................................................................................................................................................................................... 4

6.1 Preparation of the test assembly ............................................................................................................................................. 4

6.2 Determination of the measurement values .................................................................................................................... 4

6.3 Further test methods ......................................................................................................................................................................... 5

7 Precision of the measurement ............................................................................................................................................................... 5

8 Presentation of the results ......................................................................................................................................................................... 5

9 Analysis .......................................................................................................................................................................................................................... 5

9.1 Effective transmittance for photopic vision ................................................................................................................... 5

9.2 Effective transmittance for scotopic vision .................................................................................................................... 6

10 Test report ................................................................................................................................................................................................................... 6

Annex A (informative) Calibration procedure for the photoreceiver/measuring instrument ................7

Annex B (informative) Trichromatic coefficients and colour contribution index..............................................10

Bibliography .............................................................................................................................................................................................................................14

© ISO 2017 – All rights reserved iii
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ISO 14490-5:2017(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.

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 on 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 the following

URL: w w w . i s o .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee

SC 4 Telescopic systems.

This second edition cancels and replaces the first edition (ISO 14490-5:2005), which has been

technically revised. It also incorporates the ISO 14490-5:2005/Amd 1:2015.
The main changes are as follows:
— the normative references has been updated;

— In 5.8, the wording has been changed to “maximum diameter of the aperture stop”;

— Formulae (3) and (4) have been corrected.
A list of all parts in the ISO 14490 series can be found on the ISO website.
iv © ISO 2017 – All rights reserved
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INTERNATIONAL STANDARD ISO 14490-5:2017(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 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 14132

ISO 14490-1:2005, Optics and optical instruments — Test methods for telescopic systems — Part 1: Test

methods for basic characteristics
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 14132-1 apply.

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 http:// 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. The

() ()
0 p
transmittance results from Formula (1):
Φ λ
τλ = (1)
Φ λ

During the spectral measurement, the emergent light of the radiation source will be limited to a small

wavelength band by means of a monochromator or a set of filters.
© ISO 2017 – All rights reserved 1
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ISO 14490-5:2017(E)
5 Test arrangement
5.1 General

The measuring device consists of radiation source (optionally with a condenser), monochromator or

set of filters, collimator lens, aperture stop, specimen mounting, veiling glare stop, integrating sphere,

radiation detector and measuring and evaluation unit (signal processing).
See Figure 1.
Key
1 radiation source 6 aperture stop
2 condenser 7 integrating sphere
3 monochromator 8 detector
4 selectable diaphragm as field stop 9 baffle
5 collimator lens 10 measurement and evaluation unit
Figure 1 — Test arrangement without test specimen (schematic)
Key
1 radiation source 7 test specimen
2 condenser 8 veiling glare stop
3 monochromator 9 integrating sphere
4 selectable diaphragm as field stop 10 detector
5 collimator lens 11 baffle
6 aperture stop 12 measurement and evaluation unit
Figure 2 — Test arrangement with test specimen (schematic)
2 © ISO 2017 – All rights reserved
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ISO 14490-5:2017(E)
5.2 Source of radiation 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.
5.3 Monochromator or set of filters

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 rendition indices are to be calculated.

Instead of a monochromator, a set of filters can be used. They are especially useful with flat-shaped

transmittance 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 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 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 objective lens of the test specimen if possible.

The diameter should be ≤80 % (50 % recommended) of the maximum available aperture 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

measuring 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. In this case, it is recommended to take the entrance pupil as the “maximum available

aperture”.
5.6 Specimen mounting

The mounting of the test specimen shall be designed in a way that the test specimen can be adjusted

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 Veiling glare stop

A veiling glare stop with a diameter that is 1,1 times the diameter of the image of the aperture stop

is located in the image plane of the aperture stop, consequently in the exit pupil of the telescope. The

veiling glare stop shall be dull black on both sides. It shall be designed in a way that the veiling glare

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ISO 14490-5:2017(E)

resulting from the test specimen and upsetting of the measurement result is reduced as far as possible.

It shall further be designed in a way that the necessary radiation for the measurement passes through

unobstructed.
5.8 Integrating sphere

The integrating sphere shall be located near the veiling glare stop to ensure that the light passing

through the veiling glare stop will be completely collected by the integrating sphere. 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 (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 spectra
...

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