1、raising standards worldwide NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW BSI Standards Publication BS ISO 9335:2012 Optics and photonics Optical transfer function Principles and procedures of measurementBS ISO 9335:2012 BRITISH STANDARD National foreword This British Standa
2、rd is the UK implementation of ISO 9335:2012. It supersedes BS ISO 9335:1995 which is withdrawn.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 secreta
3、ry. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2012. Published by BSI Standards Limited 2012 ISBN 978 0 580 73545 5 ICS 17.180.01 Compliance with a British Standard cann
4、ot confer immunity from legal obligations. This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 October 2012. Amendments issued since publication Date Text affectedBS ISO 9335:2012 ISO 2012 Optics and photonics Optical transfer function Princip
5、les and procedures of measurement Optique et photonique Fonction de transfert optique Principes et procdures de mesure INTERNATIONAL STANDARD ISO 9335 Second edition 2012-10-01 Reference number ISO 9335:2012(E)BS ISO 9335:2012ISO 9335:2012(E) ii ISO 2012 All rights reserved COPYRIGHT PROTECTED DOCUM
6、ENT ISO 2012 All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body
7、in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in SwitzerlandBS ISO 9335:2012ISO 9335:2012(E) ISO 2012 All rights reserved iii Contents Page Foreword iv Introductio
8、n v 1 Scope 1 2 Normative references . 1 3 T erms and definitions . 1 4 Measuring equipment and environment . 1 4.1 General aspects . 1 4.2 Environment . 2 4.3 Measuring equipment . 2 4.4 System components . 3 5 Measurement procedures .10 5.1 General .10 5.2 Setting the measuring conditions .10 5.3
9、Additional considerations of measurement . 11 5.4 Particular measuring conditions .13 6 Corrections to measured data .14 6.1 Normalization .14 6.2 Correction of the frequency scale 14 6.3 Correction of the measured modulation .14 6.4 Auxiliary imaging systems .15 7 Presentation of OTF data 15 7.1 Ge
10、neral .15 7.2 Statement of identification and measuring conditions .15 7.3 Graphical presentation of OTF data .16 7.4 Numerical presentation .17 8 Accuracy checks .17 Annex A (informative) Examples of the presentation of OTF data 19 Bibliography .24BS ISO 9335:2012ISO 9335:2012(E) Foreword ISO (the
11、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
12、 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 electrotechnic
13、al 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 bo
14、dies 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 an
15、y or all such patent rights. ISO 9335 was prepared by Technical Committee ISO/TC 172, Optics and photonics, Subcommittee SC 1, Fundamental standards. This second edition cancels and replaces the first edition (ISO 9335:1995), of which it constitutes a minor revision. It also incorporates the Technic
16、al Corrigendum ISO 9335:1995/Cor.1:2005. iv ISO 2012 All rights reservedBS ISO 9335:2012ISO 9335:2012(E) Introduction The optical transfer function is an important aid to objective evaluation of the image-forming capability of optical, electro-optical and photographic systems. In order that optical
17、transfer function measurements achieved using different measuring principles or obtained from measuring instruments in different laboratories can be compared, it is necessary to ensure equivalence of measurement parameters such as focus setting and spatial frequency range. For this reason, an agreed
18、 terminology has been defined in order for the measurement parameters used in this International Standard to be understood by all users. This International Standard gives guidance for the construction and operation of equipment for optical transfer function measurement. The specifications in this In
19、ternational Standard form the basic requirements of measurement instrumentation and procedures for guaranteeing a defined accuracy of measurement of the optical transfer function. ISO 2012 All rights reserved vBS ISO 9335:2012BS ISO 9335:2012Optics and photonics Optical transfer function Principles
20、and procedures of measurement 1 Scope This International Standard gives general guidance for the construction and use of equipment for measurement of the optical transfer function (OTF) of imaging systems. This International Standard specifies important factors that can influence the measurement of
21、the OTF, and gives general rules for equipment performance requirements and environmental controls. It specifies important precautions that should be taken to ensure accurate measurements and correction factors to be applied to the collected data. The OTF measuring equipment described in this Intern
22、ational Standard is restricted to that which analyses the radiation distribution in the image plane of the optical imaging system under test. Interferometer-based instruments are outside the scope of this International Standard. 2 Normative references The following referenced documents are indispens
23、able 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 9334, Optics and photonics Optical transfer function Definitions and mathematical relationshi
24、ps 3 T erms and definitio ns For the purposes of this document, the terms and definitions given in ISO 9334 apply. 4 Measuring equipment and environment 4.1 General aspects 4.1.1 Measuring conditions Any measured OTF depends on the imaging state (I-state) of the imaging system. Thus, before making m
25、easurements, those parameters which form the I-state of the system shall be identified and the degree to which the I-state depends on those parameters determined. The complete set of parameters that form the I-state shall be set to fixed values. The fixed values represent a particular I-state and ar
26、e called the measuring conditions. 4.1.2 Accuracy of measurement The measuring equipment, and the environment in which it is used, shall allow the prescribed measuring conditions to be set and maintained to a precision which is consistent with the required accuracy of measurement (see ISO 11421, whi
27、ch describes the various parameters which have an impact on the accuracy of measurement). The accuracy of an OTF measurement may be considered as the combination of measurement uncertainties arising from the many separate parameters in the I-state. When a required accuracy of OTF measurement is stat
28、ed, it shall be apportioned among the known contributing parameters such that a tolerance can be set for each parameter of the I-state. Thus, an overall requirement to an accuracy of measurement of 0,05 of the modulation transfer function (MTF) might require, among other factors, a temperature stabi
29、lity of the measuring equipment of 1 C and focal plane setting to 5 m. The discussion of instrumental and environmental settings INTERNATIONAL STANDARD ISO 9335:2012(E) ISO 2012 All rights reserved 1BS ISO 9335:2012ISO 9335:2012(E) in the following subclauses relates to tolerances apportioned from t
30、he required OTF measurement accuracy in this manner. 4.2 Environment 4.2.1 General The ambient conditions of the OTF equipment shall be kept sufficiently free from influences that can lead to climatic, mechanical or electromagnetic disturbances. The measuring equipment and the atmosphere in the meas
31、uring room shall be kept free from dust, moisture and smoke. All optical surfaces shall be protected from the incidence of scratches and finger prints. 4.2.2 Temperature and humidity control The temperature shall be kept constant within a stated tolerance and at a suitable value. Humidity shall also
32、 be kept within acceptable limits. Both temperature and humidity shall be recorded. Air turbulence and stratification may affect the measurement and shall be minimized through the use of shielding. 4.2.3 Vibration Vibration shall be kept to a minimum and the use of basement space is recommended if v
33、ibration, caused for example by machinery, cannot otherwise be avoided. The degree of vibration isolation for a given measuring accuracy depends on the characteristics of the vibration, the measuring method, and the spatial frequency range. If the method consists of measuring the line spread functio
34、n, a suitable tolerance might be that the movement of the image and the analyser caused by vibrations should not exceed, for example, 1/20 of the width at half the maximum intensity of the test slit image. 4.2.4 Electromagnetic disturbances For some systems, it can be necessary to monitor power supp
35、ly vibrations and keep these to a tolerable minimum. The influence of external electromagnetic fields and the level of ambient light shall be reduced until they do not affect the measured OTF significantly. 4.3 Measuring equipment 4.3.1 Optical mounts The basis of any measuring equipment shall be a
36、sturdy optical bench or plate, to which mountings for the test target unit, test specimen, image analyser and other auxiliary units can be attached and brought into position, with respect to each other, to the required accuracy. Depending on the imaging systems to be tested, different requirements c
37、an arise regarding the linearity of adjustments and/or the parallelism of equipment slideways. Deviations from ideal linearity and parallelism requirements shall not cause a greater change of the measured MTF than 1/3 of the permitted or specified measurement accuracy. 4.3.2 Defocusing tolerance For
38、 photographic lenses, the defocusing effects caused by bench misalignment result in errors in the measured MTF which increase with rising spatial frequency or with decreasing f-number and reduced wavefront aberration. Table 1 gives the defocusing tolerances of a diffraction-limited lens with circula
39、r pupil and incoherent illumination that leads to a 0,05 MTF change. The wavelength of the light is assumed to be 500 nm. 2 ISO 2012 All rights reservedBS ISO 9335:2012ISO 9335:2012(E) Table 1 Defocusing tolerances Dimensions in micrometres f-number Defocusing tolerance for spatial frequency mm 1 1
40、5 10 20 50 100 1 45 9 4,5 2,3 1,0 0,5 1,4 62 12,5 6,3 3,2 1,4 0,8 2 89 18 9 4,7 2,0 1,1 4 180 36,5 18,8 9,8 4,6 3 8 360 74 39 21,5 12 12,2 16 720 157 86 54 49 468 NOTE For a change of 0,10 in MTF, defocusing tolerances are twice those shown in this table. 4.3.3 Provision of measuring scales The meas
41、uring equipment shall provide adequate means for determining the positions of test target, system or device under test (test specimen), image analyser and auxiliary systems. These include scales, spindles and dial gauges. Furthermore, means shall be provided to monitor, set or determine all other pa
42、rameters that form the I-state of the specimen. 4.4 System components 4.4.1 General The following subclauses give details concerning the measuring arrangement and its basic elements including the test target unit, test specimen, image analyser and auxiliary imaging systems. 4.4.2 Optical benches 4.4
43、.2.1 General Several arrangements of the measuring equipment are possible, but those in 4.4.2.2 to 4.4.2.5 are recommended. 4.4.2.2 Object and image at finite conjugates For tests in which object and image are at finite distances from the test specimen, the configurations shown in Figure 1 or 2 shal
44、l be used. In these arrangements, two of the three basic units (test specimen, test target unit and image analyser) are moved along slideways parallel to one another and perpendicular to the reference axis. Usually, the test specimen is fixed and the other two units moved as shown in Figures 1 and 2
45、. When electro-optical components such as image intensifiers are to be tested, auxiliary imaging systems are used to produce an image of the test pattern at the input of the test specimen. The image at the output of the test specimen is then relayed to the image analyser. The corresponding arrangeme
46、nt is shown in Figure 2. 4.4.2.3 Nominal infinite ob ject conjugate For tests in which the object conjugate is infinite (i.e. the test target is at the principal focus of a collimator), arrangements similar to that shown in Figure 3 shall be used. When off-axis measurements are to be made, the colli
47、mator may be rotated by an angle about an axis passing through the entrance pupil of the test specimen and perpendicular to the reference axis (see Figure 3). Alternatively, the collimator may be fixed and the test specimen and image analyser rotated together about the entrance pupil. In this case,
48、the mounting fixture for the test specimen and the image analyser slideway ISO 2012 All rights reserved 3BS ISO 9335:2012ISO 9335:2012(E) are both rigidly fixed to a rotating baseplate (this arrangement is consequently often referred to as the “rotary table” type). 4.4.2.4 Nominal infinite im age co
49、njugate The same arrangement as described in 4.4.2.3 (see Figure 3) shall be used, with the image analyser and test target unit interchanged. 4.4.2.5 Object and image at nominal infinite conjugat es For systems which are tested with both the object and image at infinite conjugates, arrangements similar to those shown in Figure 4 shall be used. When off-axis measurements are to be made, the object side collimator with the test target unit should be rotated by an angle about an axis passing through the entrance pupil and p
