BS-EN-ISO-9342-1998.pdf

BRITISH STANDARD BS EN ISO 9342:1998 Incorporating Amendment No. 1 to BS ISO 9342:1996 (renumbers the BS ISO as BS EN ISO 9342:1998) Optics and optical instruments Test lenses for calibration of focimeters ICS 11.040.70 Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 15 13:08:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN ISO 9342:1998 This British Standard, having been prepared under the direction of the Health and Environment Sector Board, was published under the authority of the Standards Board and comes into effect on 15 December 1996 © BSI 05-1999 The following BSI references relate to the work on this standard: Committee reference CH/78/6 Draft for comment 91/51539 DC ISBN 0 580 26871 3 Committees responsible for this British Standard The preparation of this British Standard was entrusted by Technical Committee CH/78, Ophthalmic optics, to Subcommittee CH/78/6, Ophthalmic instruments, upon which the following bodies were represented: Association of British Dispensing Opticians Association of British Health-care Industries Association of Contact Lens Manufacturers British College of Optometrists British Contact Lens Association British Medical Association British Spectacle Frame Makers Association Consumer Policy Committee of BSI Department of Health Department of Trade and Industry (National Physical Laboratory) Federation of Manufacturing Opticians Federation of Ophthalmic and Dispensing Opticians Flat Glass Manufacturers Association OPTIC (UK) Royal College of Ophthalmologists Amendments issued since publication Amd. No.DateComments 10217October 1998Implements European Standard Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 15 13:08:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN ISO 9342:1998 © BSI 05-1999i Contents Page Committees responsibleInside front cover National forewordii Foreword2 Forewordiii Text of ISO 93421 List of referencesInside back cover Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 15 13:08:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN ISO 9342:1998 ii © BSI 05-1999 National foreword This British Standard is the English language version of EN ISO 9342:1998 published by the European Committee for Standardization (CEN). This British Standard is published under the direction of the Health and Environment Sector Board whose Technical Committee CH/78 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 informed; 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. It has been assumed in the drafting of this British Standard that the execution of its provisions is entrusted to appropriately qualified and experienced people. Although not stated explicitly, the test lenses specified in this standard are intended for use with focimeters conforming to BS ISO 8598:1996. A British Standard does not purport to include all the 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. Cross-reference Publication referred toCorresponding British Standard ISO 7944:1984BS 7017:1988 Specification for reference wavelengths for optics and optical instruments (Identical) Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the EN ISO title page, page 2, the ISO title page, pages ii to iv, pages 1 to 6, an inside back cover and a back cover. 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. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 15 13:08:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN ISO 9342 July 1998 ICS 11.040.70 Descriptors: See ISO document English version Optics and optical instruments Test lenses for calibration of focimeters (ISO 9342:1996) Optique et instruments doptique Verres étalons pour létalonnage des frontofocomètres (ISO 9342:1996) Optik und optische Instrumente Prüfgläser zur Kalibrierung von Scheitelbrechwert-Meßgeräten (ISO 9342:1996) This European Standard was approved by CEN on 22 June 1998. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comité Européen de Normalisation Europäisches Komitee für Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels © 1998 All rights of exploitation in any form and by any means reserved worldwide for CEN national Members Ref. No. EN ISO 9342:1998 E Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 15 13:08:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN ISO 9342:1998 © BSI 05-1999 2 Foreword The text of the International Standard from Technical Committee ISO/TC 172, Optics and optical instruments, of the International Organization for Standardization (ISO) has been taken over as a European Standard by Technical Committee CEN/TC 170, Ophthalmic optics, the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by January 1999, and conflicting national standards shall be withdrawn at the latest by January 1999. According to CEN/CENELEC Internal Regulations, the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Endorsement notice The text of the International Standard ISO 9342:1996 has been approved by CEN as a European Standard without any modification. NOTENormative references to International Standards are listed in Annex ZA (normative). A-deviations are given in Annex ZB (informative). Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 15 13:08:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 15 13:08:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN ISO 9342:1998 ii © BSI 05-1999 Contents Page Forewordiii 1Scope1 2Normative reference1 3Definitions1 4Design requirements and recommendations for test lenses1 5Tolerances2 Annex A (informative) Manufacture of test lenses for focimeters3 Annex ZA (normative) Normative references to international publications with their corresponding European publications5 Annex ZB (informative) A-deviations5 Figure 1 Cylindrical test lens2 Table 1 Design range for the standard test lenses2 Table 2 Tolerances for spherical test lenses2 Table 3 Tolerances for prismatic test lenses2 Table A.1 Production tolerances3 Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 15 13:08:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN ISO 9342:1998 © BSI 05-1999iii 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 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 closely with the International Electrotechnical Commission (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 least 75 % of the member bodies casting a vote. International Standard ISO 9342 was prepared by Technical Committee ISO/TC 172, Optics and optical instruments, Subcommittee SC 7, Ophthalmic optics and instruments. Annex A of this International Standard is for information only. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 15 13:08:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI iv blank Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 15 13:08:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN ISO 9342:1998 © BSI 05-19991 1 Scope This International Standard specifies requirements for test lenses for the calibration of focimeters. NOTE 1It is accepted that other test lenses can also be used with powers within the given range, manufactured to the same standard of accuracy and form, but different back vertex powers. However, only lenses with integer nominal powers, as described in Annex A, can be used for the calibration of digitally-rounding focimeters. 2 Normative reference The following standard contains provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent edition of the standard indicated below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 7944:1984, Optics and optical instruments Reference wavelengths. 3 Definitions For the purposes of this International Standard, the following definitions apply. 3.1 spherical test lenses lenses used for the calibration of the dioptric power measurements by focimeters, in which the power of each lens is expressed as its back vertex power in dioptres (D) 3.2 prismatic test lenses lenses used for the calibration of the prismatic deviation measurements by focimeters, in which the prismatic power of each lens is expressed in centimetres deviation per metre distance (cm/m) NOTE 2The special name for the unit for expressing prismatic power is the “prism dioptre” for which the symbol “%” is used. 3.3 cylindrical test lenses lenses with cylindrical faces which are used to calibrate the axis marker and axis indicator with respect to the adjustment orientation of the rail NOTE 3These lenses are usually specially designed and marked. 3.4 reference wavelength wavelengths specified in ISO 7944 NOTE 4For the purposes of this International Standard, the reference wavelengths are either the green mercury line (2e= 546,07 nm) or the yellow helium line (2d= 587,56 nm). NOTE 5The reference wavelength for which the test lenses are calibrated should be stated. 4 Design requirements and recommendations for test lenses 4.1 General Test lenses shall be made of homogeneous white crown glass with a refractive index nd= 1,523 ± 0,002, or ne= 1,525 ± 0,002 selected to be free of bubbles and striae in an area of 4 mm radius surrounding the centre of the free aperture. NOTE 6Test lenses should have a protective mount, which is designed so that, when the lens is correctly placed on the lens support, the focimeter is not obstructed. 4.2 Spherical test lenses For a complete set of spherical test lenses the following set of back vertex powers is recommended: 25 D, 20 D, 15 D, 10 D, 5 D, + 5 D, + 10 D, + 15 D, + 20 D, + 25 D Spherical test lenses should have a free aperture of at least 15 mm. In order to minimize the influence of spherical aberration, the curvature of the back surface and the centre thickness shall approximately correspond to those of common spectacle lenses. Table 1 gives nominal back surface powers and ranges for centre thickness which will ensure that the lenses are of this form. 4.3 Prismatic test lenses The optical surfaces of prismatic test lenses shall be plano. The number of prismatic test lenses that should be used to adjust or to check a focimeter depends on the measuring range of the instrument. If a test lens is used, it shall meet the requirements of this International Standard. For a complete set, the following set of prismatic deviations is recommended: 2% 5% 10% 15% 20% 4.4 Cylindrical test lenses The test lens shall be a rectangular positive plano cylinder of at least 5 D and shall have the dimensions shown in Figure 1. The cylinder axis shall be parallel to the longer side of the rectangle and shall be marked by a centreline. One of the longer sides shall be marked as the reference side. Licensed Copy: sheffieldun sheffieldun, na, Wed Nov 15 13:08:53 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN ISO 9342:1998 2 © BSI 05-1999 Table 1 Design range for the standard test lenses 5 Tolerances 5.1 Tolerances for spherical test lenses The permissible tolerances for spherical test lenses shall be as given in Table 2. Table 2 Tolerances for spherical test lenses NOTE 7In Annex A, an example is given for the proper design of test lenses which meet the requirements of Table 1 and Table 2 for free apertures of up to 9 mm diameter. 5.2 Tolerances for prismatic test lenses The free aperture of prismatic test lenses shall be at least 15 mm. The tolerances shall not exceed the values given in Table 3. Table 3 Tolerances for prismatic test lenses 5.3 Tolerances for cylindrical test lenses The angular deviation between the cylinder axis and the longer side of the rectangle (see Figure 1) shall not exceed 209 of arc. The displacement of the centreline from the afocal meridian shall not exceed 0,1 mm. These tolerances shall not be additive and allow the angular deviation between the cylinder axis and the centreline to be greater than 209 of arc. Figure 1 Cylindrical test lens Nominal back vertex power, BVP m1 (D) Nominal back surface power, BSP m1 (D) Power range for BSP9 m1 (D) Range for centre thicknessa mm 25 20 15 10 5 + 5 + 10 + 15 + 20 + 25 25 20 15 12 9 5 3 1 0 0 ± 126 26 26 28 28 37 37 57 79 911 NOTESurface power is defined by the equation: surface power = (refractive index 1)/radius of curvature in metres. a The centre thicknesses are requi