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Proceedings Paper

British Standard On Surface Flaws
Author(s): Lionel R. Baker; Alan Chapman; Taj Wojtowicz
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Paper Abstract

The existing British standard, BS 4301:1982, relating to cosmetic defects, such as scratches and digs, has proved difficult to apply. Both industry and the Ministry of Defence have stressed the urgent need for a technique which can be readily employed by the majority of optical component manufacturers, is suitable for assessing appearance and functional flaws, and has traceability to national standards. This paper describes a new proposal, under consideration by a BSI committee, which recommends replacing standard scratch artefacts, made by etching a rectangular trough in a glass substrate, by the use of a standard line reference plate used to calibrate a flaw comparator instrument. The problems currently met by industry when using present visibility standards, such as BS 4301:1982 and MIL-0-13830A:1963, will be discussed in relation to the new proposal in which the signifance of a flaw is quantified in terms of a line-equivalent width (LEW) rating. The method of operation of a microscope image comparator, used for calibrating reference flaws in terms of their LEW value, will be described, and results recently obtained by inspecting transmitting and reflecting surfaces, which may be flat or curved, coated or uncoated, will be presented.

Paper Details

Date Published: 20 December 1989
PDF: 11 pages
Proc. SPIE 1164, Surface Characterization and Testing II, (20 December 1989); doi: 10.1117/12.962821
Show Author Affiliations
Lionel R. Baker, Sira Ltd (United Kingdom)
Alan Chapman, Copperstones (United Kingdom)
Taj Wojtowicz, Sira Electro-optics Ltd (United Kingdom)


Published in SPIE Proceedings Vol. 1164:
Surface Characterization and Testing II
John E. Greivenkamp; Matthew Young, Editor(s)

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