ISO 14490-7:2005

Optics and optical instruments — Test methods for telescopic systems — Part 7: Test methods for limit of resolution

ISO 14490-7:2005 specifies the test methods for the determination of the limit of resolution of telescopic systems and observational telescopic instruments.

Optique et instruments d'optique — Méthodes d'essai pour systèmes télescopiques — Partie 7: Méthodes d'essai pour limite de résolution

General Information

• Status: Withdrawn
• Publication Date: 16-Oct-2005
• Withdrawal Date: 16-Oct-2005
• ICS: 37.020 - Optical equipment
• Technical Committee: ISO/TC 172/SC 4 - Telescopic systems
• Drafting Committee: ISO/TC 172/SC 4 - Telescopic systems
• Current Stage: 9599 - Withdrawal of International Standard
• Completion Date: 14-Nov-2016

Relations

• Revised: ISO 14490-7:2016 - Optics and photonics — Test methods for telescopic systems — Part 7: Test methods for limit of resolution
• Effective Date: 05-Nov-2015

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 14490-7
First edition
2005-10-15

Optics and optical instruments — Test
methods for telescopic systems —
Part 7:
Test methods for limit of resolution
Optique et instruments d'optique — Méthodes d'essai pour systèmes
télescopiques —
Partie 7: Méthodes d'essai pour limite de résolution




Reference number
ISO 14490-7:2005(E)
©
ISO 2005

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ISO 14490-7:2005(E)
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ii © ISO 2005 – All rights reserved

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ISO 14490-7:2005(E)
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
Bibliography .9

© ISO 2005 – All rights reserved iii

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ISO 14490-7:2005(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.
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 photonics, 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:
⎯ Part 1: Test methods for basic characteristics
⎯ Part 2: Test methods for binocular systems
⎯ Part 3: Test methods for telescopic sights
⎯ Part 4: Test methods for astronomical telescopes
⎯ Part 5: Test methods for transmittance
⎯ Part 6: Test methods for veiling glare index
⎯ Part 7: Test methods for limit of resolution

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ISO 14490-7:2005(E)
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
⎯ secondary spectrum (dispersive aberrations);
⎯ distortion;
⎯ vignetting;
⎯ colour matching.
The secondary spectrum of the test specimen can produce colour fringes surrounding observed objects
(especially at high-contrasty 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.

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INTERNATIONAL STANDARD ISO 14490-7:2005(E)

Optics and optical instruments — Test methods for telescopic
systems —
Part 7:
Test methods for limit of resolution
1 Scope
This part of ISO 14490 specifies the test methods for the determination of the limit of resolution of telescopic
systems and observational telescopic instruments.
2 Normative references
The following referenced documents are indispensable for the application 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 14132-1:2002, Optics and optical instruments — 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.
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 centrelines 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 shall be determined with the test arrangement shown in Figure 1.
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ISO 14490-7:2005(E)
The bar-type resolution test target has contrast
ττ−
tr op
K= W 0,9 (1)
ττ+
tr op
where
τ is the transmittance of a translucent part of the resolution test target;
tr
τ is the transmittance of an opaque part of the resolution test target.
op
It shall 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 dimensions of one acceptable design of bar-type resolution test target are given in Annex A.
The resolution test target shall be illuminated uniformly (± 5 %) by means of a light source with a correlated
colour temperature of 5 000 K to 6 000 K, condenser and diffuser for non-dazzling observation conditions. The
illuminance of the resolution test target shall be optimum for observation of its image.
The diameter of the collimator lens shall at least exceed 1,2 times the diameter of the entrance pupil of the
test specimen. The focal length of the collimator lens shall be at least 5 times that of the objective of the test
specimen.
The magnification of the auxiliary telescope shall not reduce the diameter of the exit pupil of the whole system
below 0,8 mm.

Key
1 light source 5 collimator lens
2 condenser 6 test specimen
3 diffuser 7 auxiliary telescope
4 bar-type resolution test target
a
The auxiliary telescope should not be used if the angular limit of resolution behind the eyepiece of the test specimen is
worse than 2' to 3' and the diameter of the exit pupil is below 1 mm.
Figure 1 — Test arrangement for measurement of the limit of resolution (schematic)
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ISO 14490-7:2005(E)
4.3 Preparation and carrying out of measurements
Eliminate all possible stray light and vibration from the test set-up.
Check the cleanliness of the
...