ASTM_F_2429_-_15.pdf

Designation:F242915Standard Terminology Relating toAerospace Transparent Materials and Enclosures1This standard is issued under the fixed designation F2429;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 These definitions cover generic optical terms whichappear in one of more standards relating to aerospace trans-parent materials and enclosures.1.2 The definitions cover,in most cases,special meaningsused in the transparency industry.No attempt has been made toinclude common meanings of the same terms as used outside ofthe transparency industry.1.3 Definitions included have,in general,been approved asstandard.2.Terminology2.1 Definitions:angular deviationthe angular displacement of a light rayfrom its original path caused by non-parallelism of oppositesurfaces as it passes through a transparent material,which isexpressed in units of angle(degree,minutes of arc,millira-dians)and is a function of the angle of incidence at eachsurface of the material and the index of refraction of thematerial.angular displacementthe angular separation of the second-ary image from the primary image as measured from thedesign eye position of a transparency.binocular disparitythe difference in angular deviation be-tween two light rays passing through a transparency,origi-nating from two eye positions located 2.5 in.apart.birefringencethe separation of a light beam as it penetratesa doubly refracting material into two diverging beamscommonly known as ordinary and extraordinary beams,which have been known to appear in transparencies asrainbowing or the apparent random dispersion of light intoits component colors.crazingthe occurrence of very small,localized,micro-cracksat or under the surface of,but not extending entirely through,a transparent material,which act like tiny mirrors that reflectlight in unwanted directions.design eyethe reference point in aircraft design from whichall visual or optical anthropometrical design considerationsare taken.distortionthe rate of change of angular deviation across thetransparency,usually characterized by grid-line slope,result-ing in the non-linear mapping of objects viewed through thetransparency.grid line slopean optical distortion evaluation parameter thatcompares the slope of a deviated grid line to that of anon-deviated grid line,which is expressed as a ratio such as1 in 8 or 1 in 20(the visual optical quality improves as thesecond number of the ratio gets larger).halationthe scattering of light by the transparency into theviewers line-of-sight reducing the perceived contrast ofexternal objects,also referred to as haze.hazethe percent of transmitted light that is scattered so thatits direction deviates more than a specified angle from thedirection of the incident beam,resulting in the reduction ofcontrast of objects viewed through the transparency.multiple imaging separationthe angular separation of pri-mary and secondary multiple images as measured from thedesign eye position.rainbowingcolored patterns in a transparency produced bythe photo-elastic molecular nature of the material and stressgradients in the transparency in which certain angles andlight polarizations in relation to some windscreen designshave been known to produce localized bands of color in thetransparency,often referred to as birefringence.scratchany marking or tearing of the surface in glass orplastic caused by an abrasive material.secondary imagethe image resulting from internal reflec-tions of light rays at the surfaces of the transparency.transmission coefficientthe ratio of the amount of radiantenergy leaving the last surface of an optical system to theamount of radiant energy incident on the first surface.1This terminology is under the jurisdiction of ASTM Committee F07 onAerospace and Aircraft and is the direct responsibility of Subcommittee F07.08 onTransparent Enclosures and Materials.Current edition approved Nov.1,2015.Published November 2015.Originallyapproved in 2005.Last previous edition approved in 2010 as F2429-05(2010).DOI:10.1520/F2429-15.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 RELATED MATERIALASTM Test Method D1003 for Haze and Luminous Transmittance ofTransparent PlasticsASTM Test Method F1165 for Measuring Angular Displacement ofMultiple Images in Transparent PartsASTM Test Method F1316 for Measuring the Transmissivity of Trans-parent PartsASTM Test Method F2156 for Measuring Optical Distortion in Transpar-ent Parts Using Grid Line SlopeAL-TR-1993-0036,Definitions of Terms Relating to Aircraft Windscreens,Canopies,and Transparencies,Authored by Barbato,Maryann H.,Kama,William N.,Task,Harry L.,Hausmann,MarthaA.,Bridenbaugh,John C.,Logicon Technical Services,Inc.ASTM International ta