1、BRITISH STANDARD BS ISO 9336-3:1994 Implementation of ISO 9336-3:1994 Optics and optical instruments Optical transfer function Application Part 3: Telescopes ICS 37.020.00BSISO 9336-3:1994 This British Standard, having been prepared under the directionof the Consumer Products and Services Sector Boa
2、rd (W/-), was published underthe authority of the Standards Board and comes intoeffect on 15February1995 BSI 12-1999 The following BSI references relate to the work on this standard: Committee reference CPM/17 Draft for comment 91/45536 DC ISBN 0 580 23804 0 Committees responsible for this British S
3、tandard The preparation of this British Standard was entrusted to Technical Committee CPM/17, Fundamental aspects of optical standards, upon which the following bodies were represented: British College of Optometrists Department of Trade and Industry (National Physical Laboratory) Engineering Equipm
4、ent and Materials Users Association Flat Glass Manufacturers Association Ministry of Defence Sira Limited Society of British Aerospace Companies Limited United Kingdom Laser and Electro-optic Association Amendments issued since publication Amd. No. Date CommentsBSISO 9336-3:1994 BSI 12-1999 i Conten
5、ts Page Committees responsible Inside front cover National foreword ii Foreword iii Text of ISO 9336-3 1BSISO 9336-3:1994 ii BSI 12-1999 National foreword This British Standard reproduces verbatim ISO9336-3:1994 and implements it as the UK national standard. This British Standard is published under
6、the direction of the Consumer Products and Services Sector Board whose Technical Committee CPM/17 has the responsibility to: aid enquirers to understand the text; present to the responsible international committee any enquiries on interpretation, or proposals for change, and keep UK interests inform
7、ed; monitor related international and European developments and promulgate them in the UK. NOTEInternational and European Standards, as well as overseas standards, are available from Customer Services, BSI, 389 Chiswick High Road, London W4 4AL. A British Standard does not purport to include all the
8、 necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesiandii, the
9、ISO title page, pagesiitoiv, pages1to8, an inside back cover and abackcover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover.ISO 9336-3:1994(E) ii BSI 12-1999 Contents Page Foreword
10、iii 1 Scope 1 2 Normative references 1 3 Definitions 1 4 General description of test specimen types and the relevance of OTF tests 1 5 Test setup 2 6 Normalization of OTF values 4 7 Test condition 4 8 Specification of the imaging state 4 9 Presentation 4 10 Accuracy of equipment 4 11 Quality assuran
11、ce tests 4 Annex A (informative) Test on components and subassemblies using azimuth scanning systems 8 Annex B (informative) Bibliography Inside back cover Figure 1 Schematic setup: object at infinity, image nominally at infinity 3 Figure 2 Schematic arrangement of an azimuth scanning MTF test syste
12、m 7 Figure A.1 Schematic arrangement for testing retroreflectors and Porro prisms 8 Table 1 5 Table 2 5 Table 3 6 Table 4 6 Descriptors: Optics, optical equipment, telescopes, lenses, image quality indicators, tests, optical tests, optical measurements, resolving power determination.ISO 9336-3:1994(
13、E) BSI 12-1999 iii 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 su
14、bject 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 (
15、IEC) on all matters of electrotechnical standardization. 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 least75% of the member bodies casting a vote. International Stan
16、dard ISO9336-3 was prepared by Technical Committee ISO/TC172, Optics and optical instruments, Subcommittee SC1, Fundamental standards. ISO9336 consists of the following parts, under the general title Optics and optical instruments Optical transfer function Application: Part 1: Interchangeable lenses
17、 for 35 mm still cameras; Part 2: Lenses for office copiers; Part 3: Telescopes. Annex A and Annex B of this part of ISO9336 are for information only.iv blankISO 9336-3:1994(E) BSI 12-1999 1 1 Scope This part of ISO9336 specifies a method of testing telescopes in terms of imaging states aimed at mak
18、ing valid optical transfer function measurements. Information is also given on the testing of some of their components and sub-assemblies. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO9336. At the ti
19、me of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this part of ISO9336 are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. Members of IEC and ISO maintain re
20、gisters of currently valid International Standards. ISO 9334:, Optics and optical instruments Optical transfer function Definitions and mathematical relationships 1) . ISO 9335:, Optics and optical instruments Optical transfer function Principles and procedures of measurement 1) . CIE Publication No
21、. 18.2 (1983), The basis of physical photometry. 3 Definitions For the purposes of this part of ISO9336, the definitions given in ISO9334 apply. 4 General description of test specimen types and the relevance of OTF tests The specimens considered are direct view telescopes which generally give the ob
22、server an enlarged presentation of a distant scene and include many instruments such as theodolite telescopes, hand-held binoculars and vehicle-mounted observation instruments. Some, such as theodolite telescopes, have small fields of view, say 1 in object space, present a flat field with little or
23、no astigmatism and have magnifications of about 20. On the other hand, binoculars and other similar instruments have larger fields of view, say up to 3,5 in object space with a magnification of 10. Such instruments can have significant curvature of field coupled with astigmatism depending on the aim
24、s of the optical designer. For example, curvature of field can be minimized in one section but considerable astigmatism can be left or alternatively the astigmatism can be reduced to a negligibly low level with field curvature of1or2dioptres at the edge of the field. Ideally, instruments would be be
25、st with no astigmatism and no curvature of field coupled with good chromatic correction but frequently compromises as mentioned above must be tolerated. Many optical systems now include roof prisms to give a compact instrument in which case the orientation of the roof edge shall be noted. In use, th
26、e eye is coherently coupled to the telescope, so it may be contended that the only valid test would be one that included the eye: reference is made to the case of cascaded optical systems in the introduction to ISO9334. However, in observer tests using telescopes, improved performance has been obtai
27、ned with instruments with better measured OTF performance in a variety of tests, including contrast sensitivity using sinusoidal grating targets, which confirms the value of OTF tests. OTF tests also enable performance to be compared with that computed by the telescope designer and provide effective
28、 quality assurance tests of production specimens. When considering the details of tests, some features of the eye need to be borne in mind, especially its ability to accommodate for varying object distances and to adjust the working aperture, varying the iris size, according to the ambient illuminat
29、ion. Thus firstly, unlike the photographic lens testing case, refocusing for off-axis tests is necessary. Secondly, the working aperture of the telescope, i.e. the exit pupil diameter, will need to match the receiving eye pupil, which generally has a range of7mm down to3mm diameter, in OTF tests rel
30、evant to the use of the telescope at different ambient illumination levels. 1) To be published.ISO 9336-3:1994(E) 2 BSI 12-1999 5 Test setup 5.1 Arrangement of optical bench The test setup is shown schematically inFigure 1. The separation between the test pattern unit and the collimator is adjusted
31、to give an infinite conjugate for the test. The separation between the image analyser collimator and the image analyser needs to be adjustable by a suitable micrometer, operating on the image analyser focus slideway, to position the image analyser at the image of the test pattern. When the object ge
32、nerator assembly (test pattern unit and collimator) and the image analyser assembly (image analyser collimator and image analyser) are aligned, without the optical system to be tested, the micrometer setting for optimum response of the test system will be the datum. When the optical system to be tes
33、ted is positioned for an on-axis test, refocusing of the image analyser is needed and any change from the datum setting gives a measure of the on-axis dioptre setting of the system being tested. In off-axis tests, a different setting from that for on-axis tests will be found and the new change from
34、the datum will give the dioptre setting for the particular field point and azimuth of the test; the difference from that of the on-axis test gives a measure of the curvature of field. In off-axis tests with an arrangement where the test specimen is retained in a fixed position, the object generator
35、assembly will be rotated about a point on the reference axis, at or near the entrance pupil of the specimen, through an angle . The image analyser assembly will be rotated about a point on the reference axis, at or near the exit pupil of the specimen, through an angle . 5.2 Collimators The object co
36、llimator shall be a well-corrected achromat with a focal length at least twice that of the objective of the specimen and a working aperture diameter at last10mm greater than the objective of the specimen. For the image analyser collimator, a convenient focal length would be 100mm as this would ensur
37、e that the movement of the image analyser along its focus slideway would be within the range of a readily available (e.g. 25mm) micrometer movement if the curvature of field reached, say,2dioptres. 5.3 Spectral response The spectral response of the test system must match that of an observer using th
38、e specimen in its normal viewing role. This may be achieved by using a specially designed filter combination to give the desired match in conjunction with the source emission and the detector spectral sensitivity (seenotes toTable 2). The most effective position for the filter is after the image ana
39、lysing element as the effect of stray radiation is reduced. However, in good laboratory conditions, it is quite practicable to position the filter within the test pattern unit. 5.4 Spatial frequency range To a large extent, the test specimen will be the controlling influence on spatial frequency ran
40、ges as derived in object space. In image space, the range is limited by the resolution of the eye, and for most applications a range of0to2mrad 1is adequate. The corresponding frequency range in object space will be given by0to2M mrad 1where M is the magnification of the telescope. The spatial frequ
41、ency in object space may be obtained either a) by calculation, using the linear spatial frequency of the test pattern in conjunction with the focal length of the collimator; or b) by measurement of the angular subtense of a number of cycles of the collimated test pattern, followed by the appropriate
42、 calculation to give the spatial frequency. 5.5 Azimuths Tests at two orthogonal azimuths are generally sufficient, i.e. in the radial and tangential sections. A special case is that of systems containing roof prisms where one of the measurements shall be made with the direction of variation of inte
43、nsity of the test pattern normal to the roof edge. 5.6 Preparing the test specimen The exposed optical surfaces shall be clean and the specimen shall have attained the stable temperature of the test laboratory. Unless otherwise specified, focusing eyepieces shall be set to 1,0 dioptres, a value freq
44、uently used for fixed focus instruments. The complete series of specified tests is carried out at this setting.ISO 9336-3:1994(E) BSI 12-1999 3 For tests assessing performance with a reduced exit pupil, uncertainties can arise due to the difficulty of correctly positioning a stop at the exit pupil e
45、specially when making off-axis measurements. This is due to a combination of vignetting, pupil distortion and pupil wander along the reference axis relative to the on-axis pupil position. Consequently, it is preferable to position a stop of the corresponding diameter at the entrance pupil. The size
46、of the stop is given by the product of the desired exit pupil and the magnification of the specimen. 5.7 Auxiliary equipment In addition to fixtures for holding test specimens, some means for aligning the test beam with the input axis of the specimen can be needed particularly for instruments having
47、 large offsets between input and output axes. Mechanical means should be used for this if practical; otherwise, adjustable periscopic beam deviators using a framework and plane mirrors may be employed. Mirrors for this purpose should be flat to /10. Thecombined mirror system shall be such that the w
48、avefront degradation does not significantly affect the accuracy of measurement. Figure 1 Schematic setup: object at infinity, image nominally at infinityISO 9336-3:1994(E) 4 BSI 12-1999 6 Normalization of OTF values The normalization arrangement with equipment which permits the response at zero cycl
49、es to be set to1,0will generally be satisfactory but further checks can be needed. 7 Test condition The testing shall be carried out in accordance with the general principles and procedures given in ISO9335. 8 Specification of the imaging state 8.1 Test specimen Table 1 specifies an imaging state for the test specimen. 8.2 Measuring equipment Table 2 specifies an imaging state for the measuring equipment. 8.3 Measurement Table 3 specifies an imaging state for the measurement. 9 Presentation Table 4 specifies an imag
