ISO/DIS 14490-7

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 14490-7
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 7:
Assessment of the image quality

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

Partie 7: Évaluation de la qualité de l'image
ICS 37.020

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in the English language only.

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 14490-7
Copyright notice

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ii © ISO 2002 — All rights reserved
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ISO/DIS 14490-7
Contents Page

Foreword ............................................................................................................................................................. iv

Introduction.......................................................................................................................................................... v

1 Scope....................................................................................................................................................... 1

2 Normative references.............................................................................................................................. 1

3 Terms and definitions ............................................................................................................................. 1

4 Method of determination of the limit of resolution................................................................................. 1

4.1 General..................................................................................................................................................... 1

4.2 Test equipment........................................................................................................................................ 1

4.3 Preparation and carrying out of measurements .................................................................................... 3

4.4 Determination of results.......................................................................................................................... 3

5 Test report ............................................................................................................................................... 3

Annex A (informative) Dimensions of a bar-type test target for determination of the limit of resolution

of telescopic systems ............................................................................................................................. 4

A.1 Resolution test target layout................................................................................................................... 4

A.2 Layout of groups of resolution test target ............................................................................................. 4

A.3 Dimensions.............................................................................................................................................. 4

A.4 Bar width.................................................................................................................................................. 5

A.5 Number of bars........................................................................................................................................ 5

A.6 Angular distance between centre lines of adjacent bars....................................................................... 6

Bibliography......................................................................................................................................................... 9

© ISO 2002 — All rights reserved iii
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ISO/DIS 14490-7
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 14490-7 was prepared by Technical Committee ISO/TC 172, Optics and optical instruments, Subcommittee

SC 4, Telescopic systems.

SO 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
Annex A of this part of ISO 14490 is for information only.
iv © ISO 2002 — All rights reserved
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ISO/DIS 14490-7
Introduction

There are various characteristics which are relevant for overall image quality of telescopic systems and

observational telescopic instruments. Two important characteristics are the limit of resolution and the optical

transfer function.

The present part of ISO 14490 specifies the test method for the determination of the limit of resolution of telescopic

systems and observational telescopic instruments. Optical transfer function measurement as applied to telescopic

systems is specified in ISO 9336-3 (see bibliography).

Besides the limit of resolution and the optical transfer function further characteristics are relevant for an

assessment of the image quality; the most important of them are:
¾ secondary spectrum (dispersive aberrations);
¾ distortion;
¾ vignetting;
¾ colour matching.

The secondary spectrum of the test specimen can produce colour fringes surrounding observed objects (especially

at high contrast edges) which can look like coloured neon tube light.

The distortion of the perceived image might be of barrel or pincushion type. The pincushion type is considered to

give a more naturalistic impression of the observed object when swivelling the test specimen.

Vignetting can lead to a perceivable intensity degradation from the centre to the edge of the field of view.

Colour matching is the accuracy of the colour rendition of an object observed with the test specimen. Any colour

deviation might be due to the lens material or to coatings.
© ISO 2002 — All rights reserved v
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DRAFT INTERNATIONAL STANDARD ISO/DIS 14490-7
Optics and optical instruments — Test methods for
telescopic systems —
Part 7:
Assessment of the image quality
1 Scope

This part of ISO 14490 specifies the test methods for the determination of the limit of resolution and the

assessment of the image quality 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 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
3 Terms and definitions

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

4 Method of determination of the limit of resolution
4.1 General

The limit of resolution of a telescopic system is the minimum angular distance between centre lines of two adjacent

bright (or dark) bars of the bar-type resolution test target whose direction can be detected when viewing through

the test specimen.
4.2 Test equipment

The limit of resolution of telescopic systems should be determined with the test arrangement shown in figure 1.

The bar-type resolution test target has contrast
1) To be published.
© ISO 2002 — All rights reserved 1
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ISO/DIS 14490-7
t - t
tr op
K = ³ 0,9 (1)
t + t
tr op
where
t is the transmittance of a translucent part of the resolution test target;
t is the transmittance of an opaque part of the resolution test target.
It should be placed at the focal plane of the collimator lens.

For systems that require the limit of resolution to be measured with a focus setting other than infinity, the position of

the resolution test target with respect to the collimator lens shall be adjusted in order to obtain its image at the

specified distance from the test specimen.

The bar-type resolution test target is a glass plate bearing a picture that consists of bright bars having different

widths on a dark background.
The dimensi
...