ISO/DIS 14490-5

Optics and optical instruments -- Test methods for telescopic systems

Optique et instruments d'optique -- Méthodes d'essai pour systèmes téléscopiques

Standards Content (sample)

DRAFT INTERNATIONAL STANDARD ISO/DIS 14490-5
ISO/TC 172/SC 4 Secretariat: GOST R
Voting begins on Voting terminates on
2002-11-07 2003-04-07

INTERNATIONAL ORGANIZATION FOR STANDARDIZATION • МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ • ORGANISATION INTERNATIONALE DE NORMALISATION

Optics and optical instruments — Test methods for
telescopic systems —
Part 5:
Test methods for transmittance

Optique et instruments d'optique — Méthodes d'essai pour systèmes télescopiques —

Partie 5: Méthodes d'essai du facteur de transmission
ICS 37.020

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Conformément aux dispositions de la Résolution du Conseil 15/1993, ce document est

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© International Organization for Standardization, 2002
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ISO/DIS 14490-5
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ii © ISO 2002 — All rights reserved
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ISO/DIS 14490-5
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 ........................................................................................................ 2

5.3 Monochromator or set of filters.............................................................................................................. 2

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

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

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

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

5.8 Integrating sphere ................................................................................................................................... 3

5.9 Radiation detector................................................................................................................................... 3

6 Procedure ................................................................................................................................................ 3

6.1 Preparation of the test assembly............................................................................................................ 3

6.2 Determination of the measuring values ................................................................................................. 4

6.3 Further test methods............................................................................................................................... 4

7 Accuracy of the measurement................................................................................................................ 4

8 Presentation of the results...................................................................................................................... 4

9 Analysis ................................................................................................................................................... 4

9.1 Effective transmittance for photopic vision........................................................................................... 4

1.2 Effective transmittance for scotopic vision............................................................................................ 5

10 Test report ............................................................................................................................................... 5

Annex A (informative) Calibration procedure for the photoreceiver/measuring instrument............................. 6

A.1 Control of proportionality of the photocurrent measured by the instrument to the illuminance

on the light sensitive surface of the photoreceiver ............................................................................... 6

A.2 Checking the independence of readings of the indicating device in relation to the size of the

illuminated surface of the photoreceiver in the case of constant light flux.......................................... 7

Annex B (informative) Trichromatic coefficients and color contribution index................................................. 9

B.1 Trichromatic coefficients ........................................................................................................................ 9

B.2 Values for the colour contribution index................................................................................................ 9

© ISO 2002 — All rights reserved iii
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ISO/DIS 14490-5
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.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. 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.

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.

ISO 14490-5 was prepared by Technical Committee ISO/TC 172, Optics and optical instruments, Subcommittee

SC 4, Telescopic systems.

ISO 14490 consists of the following parts, under the general title Optics and optical instruments — Test methods

for telescopic systems:
¾ Part 1: Test methods for basic characteristics
¾ Part 2: Test methods for binocular systems
¾ Part 3: Test methods for telescopic sights
¾ Part 4: Test methods for astronomical telescopes
¾ Part 5: Test methods for transmittance
¾ Part 6: Test methods for veiling glare index
¾ Part 7: Test methods for limit of resolution
Annexes A and B of this part of ISO 14490 are for information only.
iv © ISO 2002 — All rights reserved
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DRAFT INTERNATIONAL STANDARD ISO/DIS 14490-5
Optics and optical instruments — Test methods for
telescopic systems —
Part 5:
Test methods for transmittance
1 Scope

This part of ISO 14490 specifies the test methods for the determination of the transmittance of telescopic systems

and observational telescopic instruments.
2 Normative references

The following normative documents contain provisions which, through reference in this text, constitute provisions of

this part of ISO 14490. For dated references, subsequent amendments to, or revisions of, any of these publications

do not apply. However, parties to agreements based on this part of ISO 14490 are encouraged to investigate the

possibility of applying the most recent editions of the normative documents indicated below. For undated

references, the latest edition of the normative document referred to applies. Members of IEC and ISO maintain

registers of currently valid International Standards.

ISO 6728:1983, Photography — Camera lenses — Determination of ISO colour contribution index (ISO/CCI)

ISO 10526, CIE standard illuminants for colorimetry
ISO/CIE 10527:1991, CIE standard colorimetric observers

ISO 14132-1: , Optics and optical instruments — Vocabulary for telescopic systems — Part 1: General terms and

alphabetical indexes of terms in ISO 14132

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

basic characteristics
CIE Publ. 18.2:1983, The basis of physical photometry
3 Terms and definitions

For the purposes of this part of ISO 14490 the terms and definitions given in ISO 14132-1 apply.

4 Principle

To determine the spectral transmittance t(l) the flux of radiation in a limited bundle of rays will be measured before

entering F (l) and after passing F (l) through the optical system. The transmittance results from the equation (1):

o p
Fp(l)
t(l) = (1)
Fo(l)
1) To be published.
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ISO/DIS 14490-5

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.
5 Test arrangement
5.1 General

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

filters, a collimator lens, the aperture stop, the specimen mounting, a veiling glare stop, the integrating sphere, the

radiation detector and the measuring and evaluation unit (signal processing).
See figure 1.
1 4 5 7 8 9 10 11 12
2 3 6
5 6
3 7
2 8
1 9
0 10
VD E 12
VDO GS TÜV99

1 — radiation source; 2 — condenser; 3 — monochromator; 4 — selectable diaphragm as field stop; 5 — collimator lens;

6 — aperture stop; 7 — test specimen; 8 — veiling glare stop; 9 — integrating sphere; 10 — detector; 11 — baffle;

12 — measuring and evaluation unit
Figure 1 — Test arrangement (schematic)
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.
2 © ISO 2002 — All rights reserved
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ISO/DIS 14490-5
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 should 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. Auxiliary

systems can be used for beam forming to realize these requirements. These systems shall stay in the ray path

during measuring with and wi
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