1、 BSI BS*5LO 7q 3b24bb9 0338684 3 m .! This British Standard, having been approved by the Instrument Industry Standards Committee, was published under the authority of the Executive Board on 10 September, 1974. British Standards Institution, 1974 ISBN: O 580 08066 8 Copyright Users of British Standar
2、ds are reminded that copyright subsists in all BSI publications. No part of this publication may be reproduced in any form without the prior permission in writing of BSI. This does not preclude the free use, in the course of implementing the standard, of necessary details such as symbols and size, t
3、ype or grade designations. Enquiries should be addressed to the BSI Secretariat. Contract requirements Attention is drawn to the fact that this British Standard does not purport to include all the necessary provisions of a contract. Revision of British. Standards In order to keep abreast of progress
4、 in the industries concerned, British Standards are subject to periodical review. Suggestions for improvements will be recorded and in due course brought to the notice of the committees charged with the revision of the standards to which they refer. British Standards are revised, when necessary, by
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7、bership, which has considerable advantages, will be welcomed, and should be made to Subscriptions Department. Both departments are located at: 101 Pentonville Road, London N1 9ND (Telephone 01-837 8801 ; Telex 23218). The following BSI references relate to the work on this standard: Committee refere
8、nce E/2 Draft for comment 72/32590 DC Co-operating organizations The Instrument Industry Standards Committee, under whose supervision this British Standard was prepared, consists of representatives from the following Government departments and scientific and industrial organizations: British Calibra
9、tion Service HEVAC Association British Electrical and Allied Manufacturers Association *Institute of Measurement and Control British Industriai Measuring and Control Apparatus British Mechanical Engineering Confederation British Nautical Instrument Trade Association British Railways Board British St
10、eel Industry Council of British hlanufacturers of Petroleum Equipment Department of the Environment Electrical Research Association Electricity Supply Industry in England and Wales Electronic Engineering Association Gauge and Tool Makers Association Manufacturers Association *Engineering Equipment U
11、sers Association Institution of Chemical Engineers Institution of Electrical Engineers Institution of Mechanical Engineers Institution of Production Engineers Meteorological Office *Ministry of Defence National Coal Board *National Physical Laboratory (Department of Trade and Industry) *Scientific I
12、nstrument hianufacturers Association %IRA Institute Oil Companies Materials Associafion The Government departments and scientific and industrial organizations marked with an asterisk in the above list, together with the following, were directly represented on the committee entrusted with the prepara
13、tion of this standard: British Bioadcasting Corporation Research Department British Photographic Manufacturers Association Department of Trade and Industry Flat Glass Manufacturers Association Illuminating Engineering Society Institute of Physics Royal hlicroscopical Society University of Reading .
14、-_ 7409-2k-B - BSI BSr5109 74 W Lb24bb 0138685 3 = Amd. No. Date of issue BS 5109 : September 1974 Text affected UDC 001.4 : 681. 7.013 : 535.31 Glossary of Terms used in assessing the performance of optical devices and systems British Standards Institution 2 Park Street London WIA 2BS Telephone O1
15、-629 9000 Telex 266933 - BSI BS*5109 74 W 1624bb 0118bBb BS 5109 : 1974 - 5 Foreword This British Standard Glossary defines terms used in objective techniques of assessing performance of optical devices and systems. These terms do not necessarily apply to devices and systems working with coherent li
16、ght. and through the International Commission for Optics throughout the world. Recently a need has arisen to define terms particularly applicable to objective techniques for assessing the performance of optical devices and systems. The objective techniques referred to include those covered by BS 477
17、9 ?Recommendations for measurement of the optical transfer function of optical devices? and BS 4793 ?Recommendations for specifying the optical performance of lenses for television?, The ground work leading to the preparation of this glossary and of the standards mentioned above was carried out by a
18、n Image Quality Group administered by SIRA Institute. Terms which are commonly understood and terms which are in CIE Publication No. 17, International Lighting Vocabulary (3rd edition 1970), have not in general been included. Certain optical terms will also be found in BS 1019 ?Photographic lenses.
19、Definitions, methods and accuracy of marking?. associated preferred terms. Most of the terms defined have been in use for many years and have become agreed terminology both nationally Where appropriate, non-preferred terms are shown immediately below, and in a lighter typeface than, the 2 BS 5109 :
20、1974 British Standard Glossary of Terms used in assessing the performance of optical devices and systems Term aberration angular aberration chromatic aberration longitudinal chromatic aberration transverse (lateral) chromatic aberration longitudinal aberration transverse aberration wavefron t aberra
21、tion Definition A defect in the geometrical image-forming properties of an optical system which may remain from the result of compromises which have to be made in the optical design of most lens systems, or from faults in manufacture. A variety of methods is used for specifying the amount of aberrat
22、ion present in a system but each is concerned essentially with the imaging of point sources of monochromatic light in the object field, and with the way in which the rays or waves emitted from each point emerge from the optical system. NOTE. The aberration is expressed as a function of the position
23、of the point of inter.- section of the particular ray (or wave-normal) with the entrance pupil of the optical system. The difference between the direction of a ray emerging from an optical system and the direction in which it would emerge if the system were free from aberration. The variation of ima
24、ge position and monochromatic aberration with wavelength. The change in back focal length with wavelength. The change in position on the image surface of an image point, due to wavelength changes. NOTE. The definitions of the chromatic aberrations define a situation arising from the total effects of
25、 changes of the other defined aberrations with wavelength. The distance from the image plane at which a ray intersects, or most closely approaches, the principal ray of the beam emitted by the point object. The distance between the point of intersection of a ray in the image plane and some origin in
26、 that plane which may, for example, be the ideal image point for an aberration-free system. The distance between the wavefront passing through the exit pupil of the optical system and a spherical surface which is coincident with the wavefront at the centre of the pupil, and whose centre of curvature
27、 coincides with a specified point image. In an ideal optical system the image point would be determined by geometrical optics but in a practical optical system the image point may be chosen to provide the best image. 3 A system which ideally images an infinitely distant target at infinity and theref
28、ore produces neither real nor virtual images. In use the dioptre setting of the eyepiece in such a system may give real or virtual images at distances behind or in front of the eyepiece respectively. Defined by NA = n sin a, where n is the index of refraction of the medium in which the image is form
29、ed (approximately 1, if the image is formed in air) and a is the angle subtended at the axial point of the image by the semi- diameter of the exit pupil of the lens at a given diaphragm setting. That limiting mechanical aperture which restricts the beam of light passing between a point object on the
30、 axis of an optical system and its image. The ratio 1 : A or the fraction 1/A (written in this manner with the first member of the ratio, or the numerator of the fraction, equal to 1) where A is defined by the equation: 1 A=- 2n sin a In this formula, n is the index of refraction of the medium in wh
31、ich the image is formed (approximately 1, if the image is formed in the air) and Q is the angle subtended at the axial point of the image by the semi-diameter of the exit pupil of the lens at a given diaphragm setting. If the ixit pupil is not circular, an equivalent circle having the same area as t
32、he actual exit pupil should be used. For a system having both object and image space in air, the aperture ratio is equal to 2sin a. If the aperture ratio is given without qualifi- cation, its value is that corresponding to the largest indicated diaphragm opening and an infinitely distant object. If
33、the object is at a finite distance, the value of the aperture ratio should be qualified by a statement of the corresponding conjugation. See relative aperture. The maximum aperture of that part of the surface which is used in forming an image in any part of the field. For a photographic objective fo
34、r distant objects, at a given setting of the diaphragm, an opening equivalent to a right section of the largest beam of parallel light from an axial object point that is transmitted by the lens. It is usually circular, or approximately so, and is specified by its diameter. If the section is not circ
35、ular, the effective diameter is the diameter of a circle having equal area. The diameter of the entrance pupil of the lens measured in units of the equivalent focal length. It is written as a fraction of the equivalent focal length, thus f/(numerical value). For an object at an infinite distance the
36、 denominator of the relative aperture and the second number in the aperture ratio are identical if the image is formed in air and its formation obeys the Abb sine condition. (See aperture ratio and f-number.) 4 apparent field of view (afocal systems) area-weighted average resolution axial transmissi
37、on factor axis of best definition best back focal distance best principal focus calibrated focal length calibrated magnification BSI BS*5LO 74 LBII BS 5109 : 1974 The angular size of the field of view in the image space as distinct from the size of the field of view in the object space. In the absen
38、ce of distortion, the following felationship holds: Q tan #) = Mtan 2 where 2 Q is the apparent field angle in the object space, #) is the true field angle in the image space, and M is the angular magnification of the instrument. A single average value for the resolution over the picture format may
39、be determined for any given focal plane as the area-weighted average resolution, or AWAR. To determine the AWAR, the picture format is divided into concentric annular zones whose boundaries are determined from the angles which are midway between successive test angles. For zones which extend beyond
40、the boundaries of the picture format, only the area lying within the format shall be used in determining the weighting ratio. The resolution obtained at any giveii test angle is multiplied by the ratio of the area of the zone for that angle to the total area of the picture format. The AWAR is the su
41、m of these products. To obtain a single value of the resolution for each test angle, the geometric mean of the tangential and radial resolutions shall be used. The ratio (normally expressed as a percentage) of the transmitted radiance to the incident irradiance in an axial beam of light that passes
42、through the lens without any light being obstructed by the aperture stop. This factor may be measured for light of a particular spectral power distribution. That line perpendicular to the plane of best definition which passes through the principal focus. The distance measured from the vertex of the
43、back surface of the lens to the plane of best definition. The point of intersection of the lens axis with the plane of best definition of an extended object at infinity. An adjusted value of the equivalent focal length of a mounted lens in an instrument, so chosen as to distribute the distortion in
44、the manner best suited to the conditions under which the instrument is to be employed. The value of the paraxial magnification of a lens mounted in an instrument so chosen as to distribute the distortion in the manner best suited to conditions under which the lens is to be employed. camera-type lens
45、 test bench A bench designed to hold the lens under test and a carriageway, termed a field slide, perpendicular to the optical axis of that lens. A viewing or analysing system mounted on that carriageway may then be arranged to examine the lens performance at the required field position. chromatic a
46、berration clear aperture colour contribution See under aberration. See under aperture. The effect that the optical system has upon the spectral characteristics of the light flux passing through the system. This property of an optical system is usually specified and measured in terms of Conventional
47、spectral transmittance curves wherein transmittance in percent is plotted against wavelengths in nanometres. 5 BS 5109 : i974 colour correction cosmetic defects beauty defects aesthetic defects diaphragm ghost The correction of longitudinal and lateral chromatic aberrations for two or more wavelengt
48、hs. NOTE. Colour correction may be appropriate for visual, photographic, etc., uses. Those visible imperfections of components and elements of an optical system which do not cause a significant degradation of image quality or environmental stability. A distribution of light in the image plane which
49、is an identifiable image of the diaphragm. diffusion The scattering of light by reflection or transmission in random directions. dioptre dioptre scale dioptre setting distortion radiai distortion radial distortion factor tangential distortion A unit used to express the power of a lens. The power of a lens in dioptres is the reciprocal of its equivalent focal length in metres. A series of markings on a focusing eyepiece arranged so that at zero the instrument is in afocal adjustment and at other positions calibrated dioptre setti
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