1、BSI Standards PublicationBS ISO 14490-6:2014Optics and photonics Testmethods for telescopic systemsPart 6: Test methods for veiling glare indexBS ISO 14490-6:2014 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of ISO 14490-6:2014. It supersedes BS ISO 14490-6:2005 wh
2、ich is withdrawn.The UK participation in its preparation was entrusted to Technical Committee CPW/172, Optics and Photonics.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a
3、 contract. Users are responsible for its correct application. The British Standards Institution 2014.Published by BSI Standards Limited 2014ISBN 978 0 580 86276 2 ICS 37.020 Compliance with a British Standard cannot confer immunity from legal obligations.This British Standard was published under the
4、 authority of the Standards Policy and Strategy Committee on 30 November 2014.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e d ISO 2014Optics and photonics Test methods for telescopic systems Part 6: Test methods for veiling glare indexOptique et photonique Mthodes dessai p
5、our systmes tlescopiques Partie 6: Mthodes dessai de lindice de lumire parasiteINTERNATIONAL STANDARDISO 14490-6Second edition 2014-10-15Reference number ISO 14490-6:2014(E)BS ISO 14490-6:2014ISO 14490-6:2014(E)ii ISO 2014 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2014All rights reserved.
6、Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at t
7、he address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 14490-6:2014ISO 14490-6:2014(E)Contents PageForeword iv1 Scope . 1
8、2 Normative references 13 Terms and definitions . 14 General considerations 15 Principle 26 Test arrangement . 26.1 General . 26.2 Integrating sphere 36.3 Object-side collimator. 36.4 Test specimen mounting . 46.5 Limiting stop . 46.6 Measurement and evaluation unit . 47 Procedure. 47.1 Adjustment o
9、f the measurement set-up . 47.2 Determination of results . 48 Presentation of results . 59 Repeatability 510 Test report . 5Annex A (informative) Method for determination of the luminance ratio of the black reference surface to the internal surface of the integrating sphere . 6Bibliography 8 ISO ISO
10、 pub-date year All rights reserved iiiBS ISO 14490-6:2014ISO 14490-6:2014(E)ForewordISO (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 t
11、echnical 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 clos
12、ely 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 n
13、eeded 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 pate
14、nt 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
15、 in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barr
16、iers to Trade (TBT) see the following URL: Foreword - Supplementary informationThe committee responsible for this document is ISO/TC 172, Optics and photonics, Subcommittee SC 4, Telescopic systems.This second edition cancels and replaces the first edition (ISO 14490-6:2005), of which it constitutes
17、 a minor revision. ISO 14490 consists of the following parts, under the general title Optics and photonics 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 fo
18、r astronomical telescopes Part 5: Test methods for transmittance Part 6: Test methods for veiling glare index Part 7: Test methods for limit of resolution Part 8: Test methods for night-vision devicesiv ISO ISO pub-date year All rights reservedBS ISO 14490-6:2014Optics and photonics Test methods for
19、 telescopic systems Part 6: Test methods for veiling glare index1 ScopeThis part of ISO 14490 specifies the test methods for the determination of the veiling glare index of telescopic systems and observational telescopic instruments.2 Normative referencesThe following documents, in whole or in part,
20、 are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 9358:1994, Optics and optical instruments Veiling
21、 glare of image forming systems Definitions and methods of measurementISO 14132-1, Optics and photonics Vocabulary for telescopic systems Part 1: General terms and alphabetical indexes of terms in ISO 14132ISO 14490-1:2005, Optics and photonics Test methods for telescopic systems Part 1: Test method
22、s for basic characteristics3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 14132-1 apply.4 General considerationsThe veiling glare test methods are generally described in ISO 9358:1994. ISO 9358:1994 deals with arbitrary optical instruments and contai
23、ns two basic approaches to measuring the veiling glare, namely integral (or black patch) method and analytical (or glare spread function) method.For terrestrial telescopes with which this part of ISO 14490 deals, the black patch method is more adequate while the glare spread function might prove to
24、be better for astronomical telescopes. For the moment, consideration in this part of ISO 14490 is given only to the black patch method. If need of measuring the glare spread function arises, the reference shall be made directly to appropriate clauses of ISO 9358:1994.From the classification given in
25、 ISO 9358:1994, Clause 3, the case where both the object and the image are at infinity will usually apply to telescopic systems. Clauses 6 and 7 give detailed and more specific descriptions of the general test method given in ISO 9358:1994, 4.1 and of test conditions given in ISO 9358:1994, 5.1.INTE
26、RNATIONAL STANDARD ISO 14490-6:2014(E) ISO 2014 All rights reserved 1BS ISO 14490-6:2014ISO 14490-6:2014(E)5 PrincipleThe determination of the veiling glare index, S, is based upon the measurement of the illuminance of the image of a black surface in diffuse scattered white light and the measurement
27、 of the illuminance of the image of the white background.The veiling glare of an optical instrument is determined by the ratio of the illuminance, E1, of the image of a black surface within a white illuminated wide surface to the illuminance, E2, of an image of a totally white surface.SEE=12(1)NOTE
28、In both cases, the white surface ensures a homogenous distribution of the illumination across the whole entrance pupil of the test specimen.6 Test arrangement6.1 GeneralThe measurement set-up consists of an integrating sphere, an object-side collimator, the test specimen mounting, the limiting stop,
29、 the image-side collimator, and the measurement and evaluation unit.See Figures 1 and 2.Key1 black object simulator 6 object-side collimator lens 11 filter2 selectable segments 7 slewing point I 12 image-side collimator lens3 integrating sphere 8 test specimen 13 measuring stop4 baffle 9 slewing poi
30、nt II 14 radiation detector5 light source 10 limiting stop 15 indicatoraThe measurement and evaluation unit consists of the limiting stop, filter, image-side collimator lens, measuring stop, radiation detector, and indicator.Figure 1 Test arrangement for on-axis measurement (schematic)2 ISO 2014 All
31、 rights reservedBS ISO 14490-6:2014ISO 14490-6:2014(E)Key1 black object simulator 6 object-side collimator lens 11 filter2 selectable segments 7 slewing point I 12 image-side collimator lens3 integrating sphere 8 test specimen 13 measuring stop4 baffle 9 slewing point II 14 radiation detector5 light
32、 source 10 limiting stop 15 indicatoraThe measurement and evaluation unit consists of the limiting stop, filter, image-side collimator lens, measuring stop, radiation detector, and indicator.Figure 2 Test arrangement for off-axis measurement (schematic)6.2 Integrating sphereThe integrating sphere sh
33、ould have a diameter 15 times the diameter of the entrance pupil of the test specimen, but at least 1 m.It has two opposite openings. In the first opening, the collimating lens is inserted. In the second opening, removable circular elements adapted to the interior surface of the sphere are inserted
34、to act as white and black reference surfaces.The white reference surface is composed of a disk that entirely fills the second opening in the sphere. The black reference surface is composed of a disk with an aperture of the desired diameter (i.e. an annulus) that is fitted into the second opening in
35、the sphere. It is followed by a light trap outside the sphere. The luminance of the light trap shall be less than 0,1 % of the luminance of the illuminated interior surface of the sphere.NOTE See Annex A for background information about the black patch method.The interior surface of the sphere and t
36、he annular and circular elements shall be white and opaque. The reflectance across the whole spectral range from 380 nm to 780 nm should be at least 85 %.The light source shall emit a constant radiant flux. The radiant flux shall not change more than 1 % during the measurement of one pair of values.
37、 The light source shall correspond to a black body source with a colour temperature between 2 800 K and 3 200 K.6.3 Object-side collimatorFor the purpose of a collimator, an achromatic lens with a minimum f-number of 10 (i.e. maximum relative aperture 1:10) is appropriate, but the aperture shall exc
38、eed 1,2 times the diameter of the objective lens of the test specimen.The focal length of the collimator and the interior diameter of the sphere shall be identical. All glass-air surfaces need an antireflection coating. ISO 2014 All rights reserved 3BS ISO 14490-6:2014ISO 14490-6:2014(E)The object-s
39、ide collimator is being fixed in the opening so that the collimator with its frame closes the interior of the sphere and the lens is located outside the sphere.6.4 Test specimen mountingThe test specimen mounting shall be constructed in a way that the combination of the test specimen and the measure
40、ment and evaluation unit can be adjusted and held stable and turned around the entrance pupil for off-axis measurements.Additionally, the test specimen mounting shall be constructed in a way that the measurement and evaluation unit can be turned around the exit pupil for off-axis measurements.6.5 Li
41、miting stopIn the plane of the test specimens exit pupil, a limiting stop of 8 mm diameter shall be attached.NOTE 1 This limiting stop prevents light which would not reach the observers eye from entering the radiation detector.NOTE 2 A limiting stop of 8 mm diameter is assumed to match the eyes maxi
42、mum pupil diameter.6.6 Measurement and evaluation unitThe measurement and evaluation unit consists of the limiting stop, the filter, the image-side collimator, the radiation detector, and the indicator.The image-side collimator (achromatic lens with antireflection coatings) images the white or black
43、 reference surface at the surface of the radiation detector.It shall be positioned directly behind the test specimens exit pupil. The clear aperture shall be at least 10 mm.At the image surface in front of the radiation detector, a measuring stop with a diameter of 20 % to 50 % of the diameter of th
44、e image of the black surface is arranged.The filter serves to convert the spectral sensitivity curve of the detector to the photopic response curve of the human eye for the radiation source used.The size and aperture of the radiation detector shall be sufficient to collect all radiation which is tra
45、nsmitted by the measuring stop.7 Procedure7.1 Adjustment of the measurement set-upThoroughly clean the optical surfaces of the collimators and of the test specimen.The size of the black surface corresponds to a 1 object-side field of view; this is valid for test specimens with at least 2 field of vi
46、ew. If the test specimen has a smaller field of view, then the object-side angle of the black surface should correspond to about half the test specimens field of view.Attach the test specimen as closely as possible to the object-side collimator and centre it to the optical axis. This ensures that th
47、e light enters the test specimen with the maximum solid angle.7.2 Determination of resultsFirst, measure the illuminance in the image of the white surface, then measure the illuminance in the image of the black surface.4 ISO 2014 All rights reservedBS ISO 14490-6:2014ISO 14490-6:2014(E)For the deter
48、mination of the veiling glare index of off-axis object points, slew the test specimen around the entrance pupil and slew the measurement and evaluation unit around the exit pupil.For the measurement off-axis, object points of 0,5 and 0,7 of half the field of view shall be chosen.Because the veiling
49、glare index of non-rotationally-symmetric erecting systems (prisms) is not equal at corresponding azimuths, determine the maximum value.8 Presentation of resultsThe veiling glare index, S, is expressed as a percentage.The measurement results shall be presented in tabular and in graphical form, as follows.a) In the presentation in tabular form, the measurements, and the calculated values of the veiling glare index (see Note) shall be given; the values shall be expressed as a percentage to one decimal digit.b) I
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