ASTM_F_1181_-_09_2014.pdf

Designation:F118109(Reapproved 2014)Standard Test Method forMeasuring Binocular Disparity in Transparent Parts1This standard is issued under the fixed designation F1181;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 This test method covers the amount of binocular dispar-ity that is induced by transparent parts such as aircraftwindscreens,canopies,HUD combining glasses,visors,orgoggles.This test method may be applied to parts of any size,shape,or thickness,individually or in combination,so as todetermine the contribution of each transparent part to theoverall binocular disparity present in the total“viewing sys-tem”being used by a human operator.1.2 This test method represents one of several techniquesthat are available for measuring binocular disparity,but is theonly technique that yields a quantitative figure of merit that canbe related to operator visual performance.1.3 This test method employs apparatus currently beingused in the measurement of optical angular deviation underMethod F801.1.4 The values stated in inch-pound units are to be regardedas standard.The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.5 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2F801 Test Method for Measuring Optical Angular Deviationof Transparent Parts3.Terminology3.1 Definitions:3.1.1 angular deviationthe angular displacement of a lightray as it passes through a transparent part,expressed as anangular measurement,for example,degree,minutes of arc,milliradians.Since it is an angular measurement,the amount oflinear displacement increases with distance.3.1.2 binocular disparitythe difference between the twoimages on the retina resulting from the lateral separationbetween the two eyes when viewing an object at a fixationpoint or due to the fact that an object is either nearer or fartherthan the fixation point.A certain amount of disparity isbeneficial and natural,leading to the perception of depth.However,when the disparity exceeds the limits for binocularfusion,doubling of vision,eye fatigue,and headaches occur asthe eyes strain to merge the disparate images.3.1.3 diplopiathe doubling of images of an object due tothe fact that the object is either nearer or farther than the pointof fixation or due to the fact that the lines of regard of the eyesdo not intersect at the point of fixation.3.1.4 Panums areathe area on the retina in which theeyes are able to fuse disparate images so that single visionoccurs.4.Summary of Test Method4.1 Using an optoelectronic system(consisting of a trans-mitter and a receiver,described in Test Method F801)and withthe part held in its installed angle,two sets of angular deviationmeasurements are made at several intervals(for example,2)in both azimuth and elevation.The extent of the area to bemeasured is dependent on the type of part being measured,forexample,windscreen,visor,and so forth.The first set ofmeasures is taken from the left eye position,the second fromthe right eye position.The separation between the two eyepositions is 2.5 in.(6.35 cm),a distance equivalent to theinterpupillary distance between the human eyes.The measure-ments taken from the left eye position are subtracted from thattaken from the right eye position to determine binoculardisparity.5.Significance of Use5.1 Diplopia or doubling of vision occurs when there issufficient binocular disparity present so that the bounds ofPanums area(the area of single vision)is exceeded.Thiscondition arises whenever one object is significantly closer(or1This test method 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 Dec.1,2014.Published December 2014.Originallyapproved in 1988.Last previous edition approved in 2009 as F1181 09.DOI:10.1520/F1181-09R14.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 farther)than another so that looking at one will cause the imageof the other to appear double.This can be easily demonstrated:Close one eye and look at a clock(or other object)on a distantwall.Now place your