ISO INTERNATIONAL STANDARD 8576 First edition 1996-12-15 Optics and optical instruments - Microscopes -- Reference system of polarized light microscopy Optique et instruments d'optique - Microscopes - Systeme de référenceenmicroscopiedepolarisation ISO Reference number ISO 8576:1996(E) No reproduction or networking permited without license from IHS Not for Resale ISO8576:1996(E) Foreword 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 (lEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are Standard requires approval by at ieast 75 % of the member bodies casting a vote. International Standard ISO 8576 was prepared by Technical Committee ISO/TC172. Opticsand optical instruments, subcommittee SC5 Microscopes and endoscopes. ISO 1996 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 International OrganizationforStandardization CasePostale56·CH-1211Geneve20·Switzerland Printed in Switzerland d without license from IHS Not for Resale ISO 8576:1996(E) INTERNATIONALSTANDARD@ISO Optics and optical instruments - Microscopes - Reference system of polarized light microscopy 1 Scope This International Standard establishes a reference system incorporating all calibrated motions of rotation and polarizing devices, and compensators. 2Principles The optical properties of an anisotropic, non-absorbing crystal of minimum symmetry under constant conditions of pressure, temperature and wavelength are described by a triaxial index ellipsoid. The lengths of the semi-axes are containing the centre of the ellipsoid generally has the 'shape of an ellipse with the axes of length nα and ny'. By definition, the relationship nα ≤ nα ≤ nβ ≤ ny ≤ n is true. ny. NOTE - To emphasize that |ny >|nαl in an object, the subscripts and α are often used instead of ' and α'. The index ellipsoid of uniaxial crystals is a rotation ellipsoid. This is characterized by two principal axes specified by na and ng, where w refers to the ordinary and refers to the extraordinary vibration direction. The latter is the direction of the rotation axis. The following definitions are true: nα = nβ = no ± ny = ng (positive) ny = nβ = no ± nα = ng (negative) i.e. if ng is larger than n the crystal is uniaxial and optically positive; if no is larger than ng the crystal is uniaxial and opticaiy negative. 3 Reference system for rotation directions and displacements (see figure 1) 3.1 General Generally, a positive Cartesian reference coordinate system x, y, z is used as a basis whose z-direction is determined by the privileged direction of light propagation from the lamp towards the observer. Accordingly, in direction, in the mathematically positive sense. This is true for upright and inverted microscopes. 1 Copyright Inter onal Organization for Standardization Not for Resale