ISO 14490-9:2019

INTERNATIONAL ISO
STANDARD 14490-9
First edition
2019-09
Optics and photonics — Test methods
for telescopic systems —
Part 9:
Test methods for field curvature
Reference number
©
ISO 2019
© ISO 2019
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ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Requirements . 1
4.1 General . 1
4.2 Test arrangement . 2
4.3 Preparation and carrying out of measurements . 3
4.4 Determination of results . 4
4.5 Test report . 4
Bibliography . 5
Foreword
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SC 4, Telescopic systems.
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iv © ISO 2019 – All rights reserved

Introduction
As mentioned in ISO 14490-7, there are several characteristics which determine image quality, besides
the limit of resolution. One unmentioned characteristic there is field curvature which can be noted
by the user as a field dependent defocus, which however could be refocused using the test specimen’s
focusing facility.
The intermediate image surface of a telescopic system (except Galilean systems) usually exhibits a
curvature instead of being a plane surface, depending on the optical characteristics of the objective
lens system. In addition, the surface can be split into two separate surfaces, the sagittal and tangential
image surfaces.
This surface, in turn, is being imaged by the eyepiece onto a virtual image surface (looked at by the user)
which also can be split into two separate surfaces. Due to the optical characteristics of the eyepiece,
the slope of the curvature of these surfaces might be different from those of the intermediate image
surfaces.
INTERNATIONAL STANDARD ISO 14490-9:2019(E)
Optics and photonics — Test methods for telescopic
systems —
Part 9:
Test methods for field curvature
1 Scope
This document specifies the test method for the determination of the deviation from a flat image
surface, i.e. the sagittal and tangential field curvature 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 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 defined in ISO 14132-1 and the
following apply.
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