3868 NTERNATIONAL STANDARD (Tso InTERNATIOnAL ORGANizATION FOR STANDARDizATION MEKIyHAPOIHA OPrAHW3AlMA IO CTAHiaPTW2AiWW.ORGANiSATION INTERNATIONALE DEe NORMALiSATION Metallic and other non-organic coatings - Measurement of coating thicknesses --- Fizeau multiple-beam interferometry method Revetements metalliques et autres revetements non organiques -- Mesurage de I'epaisseur - Methode basee sur le principe de Fizeau d'interferometrie a faisceaux multiples First edition -- 1976-11-01 ISO 3868-1976 (E) UDC 669.058 : 531.715.1 Ref. No. ISO 3868-1976 (E) Descriptors : coatings, metal coatings, dimensional measurement, thickness, optical measurement, interferometers Price based on 4 pages Copyright International Organization for Standardization ed without license from IHS Not for Resale No FOREWORD IsO (the International Organization for Standardization) is a worldwide federation of national standards institutes (ISO Member Bodies). The work of developing International Standards is carried out through iSO Technical Committees. Every Member Body interested in a subject for which a Technical Committee has been set up 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. Draft International Standards adopted by the Technical Committees are circulated to the Member Bodies for approval before their acceptance as International Standards by the Iso Council. International Standard iSO 3868 was drawn up by Technical Committee ISO/TC 107, Metallic and other non-organic coatings, and was circulated to the Member Bodies in July 1975. It has been approved by the Member Bodies of the following countries : Bulgaria Italy South Africa, Rep. of Czechoslovakia Japan Switzerland France Mexico Turkey Germany New Zealand U.S.A. Hungary Poland U.S.S.R. India Portugal Israel Romania The following country Member Body of the expressed disapproval of the document : United Kingdom International Organization for Standardization, 1976 : Printed in Switzerland Copyright International Organization for Standardization Not for Resale Nor ed without license from IHS ISO 3868-1976 (E) INTERNATIONAL STANDARD Metallic and other non-organic coatings -- Measurement of coating thicknesses --- Fizeau multiple-beam interferometry method 1 SCOPE AND FIELD OF APPLICATION 3.4 fringe ines : The dark lines caused by interference of light waves. This International Standard specifies a method for the measurement of the thickness of thin, highly reflective 3.5 hairlines : The part of the filar eyepiece moved by coatings (up to 2 μm) by the use of Fizeau multiple-beam means of the graduated knob to measure fringe line-spacing interferometry. and offset. The method described cannot be applied to vitreous enamel coatings. 3.6 offset : The displacement of a fringe line which occurs when it encounters a vertical variation on the surface of a specimen. 2 PRINCIPLE By completely dissolving a small area of the coating 3.7 spacing : The distance between fringe lines. without attack of its substrate (or by masking before plating), a step is formed from the surface of the coating to 4 EQUIPMENT that of its substrate. The height of this step is measured with a muitiple-beam interferometer. The instrument employs : A monochromatic light beam is reflected back and forth a) a beam of monochromatic light; between the specimen surface and a superimposed trans- parent mirror serving as a planar reference plate, so as to b) optics to direct the light through a specially coated produce a pattern of interference fringes observed through Fizeau plate which comes into contact with the a low-power microscope. The reference plate is tilted specimen at a slight angle and forms an air wedge. An slightly with respect to the surface being inspected, so that interference fringe pattern is produced in the air wedge the fringe pattern is a series of paraliel lines. A step in the and viewed through a