ISO INTERNATIONAL STANDARD 11455 First edition ANSI Internat Doc Sec 1995-03-15 Raw optical glass Determination of birefringence Verre d'optique brut -- Determination de la biréfringence ISO Reference number ISO 11455:1995(E) ISO11455:1995(E) Foreword IsO (the International Organization for Standardization) is a worldwide federation of national standards bodies (IsO member bodies). The work of preparing International Standards js 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 ctosely 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 avote International Standard ISO 11455 was prepared by Technical Committee ISO/TC 172, Optics and optical instruments, Subcommittee SC 3, Optical materials and components. Annex A of this International Standard is for information only ISO1995 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 the publisher. International Organization for Standardization Case Postale 56 : CH-1211 Geneve 20 : Switzerland Printed in Switzerland ii oISO IS011455:1995(E) Introduction Raw optical glass in buik and preshaped forms may have permanent stress thermal or mechanicai load. These stresses cause anisotropy of the refractive index which causes path differences of the light path in the given object (in centimetres) which are measurable by interference optics. The birefringence, in nanometres per centimetre, is valid for the glass value for the resultant wavefront deformation caused by an anisotropy of the refractive index. i