1、BRITISH STANDARD BS ISO 13653:1996 Optics and optical instruments General optical test methods Measurement of relative irradiance in the image field ICS 11.040.70BS ISO 13653:1996 This British Standard, having been prepared under the directionof the Consumer Products and Services Sector Board, was p
2、ublished under theauthority of the StandardsBoard and comes intoeffect on 15April1997 BSI 12-1998 ISBN 0 580 27214 1 National foreword This British Standard reproduces verbatim ISO13653:1996 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Techn
3、ical Committee CPW/172, Optics and optical instruments, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related
4、 international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI
5、 Standards Catalogue under the section entitled “International Standards Correspondence Index”, or using the “Find” facility of the BSI Standards Electronic Catalogue. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsibl
6、e 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, the ISO title page, pages ii to iv, pages 1 to 12 and a back cover. This standard has been upd
7、ated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover. Amendments issued since publication Amd. No. Date CommentsBS ISO 13653:1996 ii BSI 12-1998 Contents Page Foreword iii Introduction 1 1 Scope 1 2 Quantities, sym
8、bols and units 1 3 Definitions 2 4 Designation 2 5 Description of measurement procedures 2 6 Measurement of relative irradiance 4 7 Measurement of radiant power 6 8 Presentation of results 7 9 Test report 8 10 Examples 9 Figure 1 Arrangement for measurement procedure A1 for relativeirradiancemeasure
9、ment 10 Figure 2 Arrangement for measurement procedure A2 for measuring therelative irradiance of objects with infinite image distance 10 Figure 3 Arrangement for measurement procedureB for measuringtherelativeradiant power 11 Figure 4 Graphic representation of relative irradiance as a function ofim
10、ageheight for different aperture settings for a rotationally symmetric system 11 Figure 5 Curves of equal relative irradiance (50%, 30% and 10%) withcircularimage field 12 Table 1 Quantities, symbols and units 1 Table 2 Symbols for the measurement procedures 2 Table 3 Survey of the application of me
11、asuring procedures and presentationofresults 8 Table 4 Relative irradiance as a function of stop value 9 Descriptors: Optics, optical equipment, tests, optical tests, determination, irradiation, optical measurements.BS ISO 13653:1996 BSI 12-1998 iii Foreword ISO (the International Organization for S
12、tandardization) 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 ri
13、ght 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. Draft Intern
14、ational 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. International Standard ISO13653 was prepared by Technical Committee ISO/TC 172, Optics
15、 and optical instruments, Subcommittee SC1, Fundamental standards.iv blankBS ISO 13653:1996 BSI 12-1998 1 Introduction In every image projected by an optical or electro-optical system, the irradiance varies from the centre to the edge independently of the object structures. It generally decreases, i
16、.e. even an object surface of uniform radiance will be imaged with an irradiance which decreases from the image centre to the edge. In special cases, it can, however, increase. In optical systems which are rotationally symmetric, the variation will not always be rotationally symmetric, for example i
17、f limiting apertures are not rotationally symmetric. 1 Scope This International Standard is applicable to optical imaging systems in the optical spectral region froml = 100nm to l=1m. Theoretical reflections and the comparison with the calculation apply only to optical systems. These need not, howev
18、er, be rotationally symmetric; anamorphic systems, for example, are included. Telescopic systems are also included. The title of this International Standard refers to the relative irradiance in the image field, but this standard is also applicable to determination of the relative radiant power. NOTE
19、For telescopic systems it will be suitable to state only the radiant power; for most imaging systems, the conversion from radiant power to irradiance will be easy. As far as measurements are concerned, this International Standard can also be applied to electro-optical systems. The two methods descri
20、bed differ particularly in the influence of veiling glare. 2 Quantities, symbols and units Table 1 Quantities, symbols and units Quantity Symbol Unit Relative irradiance E rel(w p ) Function for natural fall-off in brightness F nat(w p ) Function for relative pupil surface F p(w p ) Function for vig
21、netting F vig(w p ) Function for relative transmission F T(w p ) Influence function of distortion F ver(w p ) Relative distortion V r % Image coordinates u9 mm v9 mm Object height (onedimensional) h mm Image height (onedimensional) h9 mm Pupil field angle, object-space w p rad, degree Pupil field an
22、gle image-space w9 p9 rad, degree Azimuth of object to be measured F rad, degree Wall thickness of the analysing aperture t mm Diameter of the analysing aperture d mmBSISO 13653:1996 2 BSI 12-1998 3 Definitions For the purposes of this International Standard, the following definitions apply. 3.1 rel
23、ative irradiance quotient of radiant power and surface area NOTE1 When a surface element of the object is imaged, the irradiance in the image is a function of the object-space pupil field angle w p ; of the radiant power which originates from the object element and passes through the lens (and possi
24、bly also through the electro-optical imaging element); of the size of the image surface element which is struck by the radiant power. NOTE 2Radiant power and surface area are functions of the object-space pupil field angle w por of the image position (u9, v9). NOTE 3The relative irradiance is relate
25、d to the axial surface element. 3.2 object-space pupil field angle, w p angle formed by the optical axis and the line joining the centre of the entrance pupil and the object point 3.3 image-space pupil field angle, w9 p9 angle formed by the optical axis and the line joining the centre of the exit pu
26、pil and the image point 4 Designation Two measurement procedures are specified, the first of which has two variants. They will be distinguished by symbols. Table 2 Symbols for the measurement procedures Example: designation of a measurement of relative irradiance according to measurement procedure A
27、1: Measurement of relative irradiance ISO13653A1 5 Description of measurement procedures 5.1 Factors influencing the relative irradiance 5.1.1 General The angular dependence of the relative irradiance is due to several factors which are independent of one another. In the various measurement and calc
28、ulation procedures, they will be allowed for in different ways. It is therefore important to know the individual influence factors. The provisions of5.1.2 to 5.1.7 are based on the assumption that the object surface is radiant Lambertian and the optical system has a flat entrance pupil. 5.1.2 Natura
29、l fall-off in brightness, F nat =cos 4w p(cos 4law) This cos 4law shall always apply if the pupil boundary is flat and perpendicular to the axis, the aperture of the test specimen small and the detector area a plane perpendicular to the axis. 5.1.3 Relative pupil surface, F p (w p ) Due to pupil abe
30、rrations, the surface of the entrance pupil as an image formed by the aperture stop is a function of the pupil field angle if lens elements are arranged between the object and the aperture stop. The relative surface shall be related to the pupil surface for w p =0. 5.1.4 Vignetting, F vig (w p ) Wit
31、h increasing pupil field angle, rims in front of and behind the aperture stop and other stops can limit (vignette) the aperture. Symbol Measurement procedure A1 measurement of the relative irradiance at finite image distance A2 measurement of the relative irradiance at infinite image distance B meas
32、urement of the relative radiant powerBS ISO 13653:1996 BSI 12-1998 3 5.1.5 Influence of the transmission, F T (w p ) Any change of the incident angle on the surfaces of the optical components (lenses, prisms) can result in a change of the reflectivity. The net transmission can change because the pat
33、hs in glass are a function of the pupil field angle. 5.1.6 Change in size of the image surface element due to distortion At the image scale b9=0 At a finite image scale: 5.1.7 Resulting relative irradiance For the resulting relative irradiance in the image field as a function of the pupil field angl
34、e, the following relationship is valid: E rel (w p ) = cos 4w p F p (w p ) F vig (w p ) F T (w p ) F ver (w p ) The first four factors are related to a change in radiant power, whereas the last value characterizes the variation in size of the image surface element. When making irradiance measurement
35、s, the radiant power shall pass through the optical system in the same direction that is experienced in normal operation because the influence of distortion and veiling glare will change when the direction of beam travel is reversed. 5.2 Classification of the measurement procedures Two different mea
36、surement procedures are generally acceptable: irradiance measurement and radiant power measurement. In the case of imaging systems, the procedure for irradiance measurements will directly take all five factors in the equation in5.1.7 into account, and shall, therefore, be given preference. The proce
37、dure of radiant power measurement will neglect the effect of distortion on the size of the image surface element. If the value is known, it can be taken into account by calculation. In a great number of cases, the factor is, however, to be neglected because the distortion is small (2%). Even for med
38、ium levels of distortion it can, however, assume distinct values. The result of the measurement shall be multiplied by the factor cos 3w pso that the relative irradiance is obtained from the relative radiant power. As compared with the method of irradiance measurement, this procedure offers the adva
39、ntage that the result is generally influenced to a lesser extent by veiling glare. According to this International Standard, telescopic systems shall be measured solely by the method of radiant power measurement. 5.3 Brief description of the irradiance measurement The relative irradiance shall be de
40、termined as a function of the image height. This measurement presupposes that there is a uniformly radiating surface in the object space, which behaves as a Lambertian emitter and as a uniform radiance. It need not, however, be situated in the object surface but can also be arranged directly in fron
41、t of the entrance pupil. A small reference surface with photoelectric detector shall be displaced by a measurable amount in the image plane; the irradiance shall be measured in arbitrary units as a function of the image height h9, and the measured value shall be related to the axial value (procedure
42、A1, seeFigure 1).BSISO 13653:1996 4 BSI 12-1998 In systems with an infinitely great image distance (e.g. projection lenses), the diaphragm can be arranged at the focus of an auxiliary optical system (telescope optics) which is turned to a measurable degree about the exit pupil of the object (procedu
43、reA2, seeFigure 2). The irradiance rated by the radiation detector shall be determined according to the cos 4law. 5.4 Brief description of the radiant power measurement To measure the relative radiant power, the test specimen shall be irradiated with a collimated bundle of rays. The axes of collimat
44、or and test specimen can be swung in relation to one another. In the image space, the passing radiant power shall be measured relative to the axial value as a function of the object-space pupil field angle w pusing an integrating sphere and a photoelectric detector (procedureB, seeFigure 3). 6 Measu
45、rement of relative irradiance 6.1 Description of the measuring set-up 6.1.1 Source of radiation To represent a Lambertian radiation characteristic, it will be advantageous to insert a diffusing screen into the aperture of an integrating sphere according to Figure 1. In the spectral region in which t
46、he specimen is used, the inside surface of the integrating sphere shall be non-selective, and the diffusing screen shall ensure uniform radiance over that part of its surface which is made use of. The source of radiation shall emit radiation into the test specimen at least from the useful range of t
47、he pupil field angle. Within this range, the constancy of the radiance shall be better than 2%. 6.1.2 Test specimen holder The test specimen shall be held so that the front edge of its mount abuts almost directly on the diffusing screen or extends so far to the aperture of the integrating sphere tha
48、t irradiation from the entire useful range of the pupil field angle is ensured. The test specimen holder may be of the rigid type. To measure in different azimuths, test specimens whose mechanical design is not rotationally symmetric shall, however, be rotatable about their own axes. 6.1.3 Measuring
49、 system 6.1.3.1 General The measuring system shall consist of the diaphragm, a filter frame and a radiation detector. It shall be possible to axially displace the measuring system so that it can be adjusted to the respective image plane. To adjust the image point, the system shall be displaceable in the image plane by a measurable amount. An auxiliary device is necessary for focussing. To measure test specimens with an infinitely great image distance, the measuring system shall be arranged in the axial image point of an auxiliary op
