1、Designation: F 1181 96 (Reapproved 2003)Standard Test Method forMeasuring Binocular Disparity in Transparent Parts1This standard is issued under the fixed designation F 1181; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 aircraftw
3、indscreens, 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-te
4、m” 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 apparatu
5、s currently beingused in the measurement of optical angular deviation underMethod F 801.1.4 The values stated in inch-pound units are the preferredunits. The values in parentheses are for information only.1.5 This standard does not purport to address all of thesafety concerns, if any, associated wit
6、h 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:2F 801 Test Method for Measuring Optical Angular Devia-tion of Trans
7、parent Parts3. Terminology3.1 Definitions:3.1.1 angular deviationthe angular displacement of alight ray 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 ofdisplacement increas
8、es 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 d
9、isparity 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 f
10、act 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
11、 of Test Method4.1 Using an optoelectronic system (consisting of a trans-mitter and a receiver) and with the part held in its installedangle, two sets of angular deviation measurements are made atseveral intervals (for example, 2) in both azimuth and eleva-tion. The extent of the area to be measured
12、 is dependent on thetype of part being measured, for example, windscreen, visor,and so forth. The first set of measures is taken from the left eyeposition, the second from the right eye position. The separationbetween the two eye positions is 2.5 in. (6.35 cm), a distanceequivalent to the interpupil
13、lary distance between the humaneyes. The measurements taken from the left eye position aresubtracted from that taken from the right eye position todetermine binocular disparity.5. Significance of Use5.1 Diplopia or doubling of vision occurs when there issufficient binocular disparity present so that
14、 the bounds ofPanums area (the area of single vision) is exceeded. Thiscondition arises whenever one object is significantly closer (orfarther) 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
15、 other object) on a distantwall. Now place your thumb to one side of the image of the1This 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 Oct.
16、 1, 2003. Published October 2003. Originallyapproved in1 988. Last previous edition approved in 1996 as F 1181 96.2For 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 th
17、e standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.clock. Now open both eyes. If you look at the clock, youshould see two thumbs. If you look at your thumb, you shouldsee two clocks.5
18、.2 Complaints from pilots flying aircraft equipped withwide field of view HUDs such as the LANTIRN HUDindicated that they were experiencing discomfort (eye fatigue,headaches, and so forth.) or seeing either two targets or twopippers when using the HUD. Subsequent investigations re-vealed that the pr
19、oblem arose from the fact that the transpar-ency and the HUD significantly changed the optical distancesof the target and the HUD imagery so that binocular disparitywhich exceeded Panums area was induced. Use of this testmethod provides a procedure by which the amount of binoculardisparity being exp
20、erienced by a human operator due to thepresence of a transparent part in his field of view may be easilyand precisely measured.6. Apparatus6.1 Transmitter capable of projecting collimated light raysfrom a suitable target. The transmitter should be firmly fixed tothe floor or other stationary fixture
21、.6.2 Receiver firmly affixed to the floor or a stable platformconsisting of the following components:6.2.1 Displacement Compensation and Imaging Lens witha focal length of 10 in. (254 mm).6.2.2 Optical Beam Splitter to separate the incoming lightinto two orthogonal elements (elevation and azimuth).
22、Thebeam splitter should be chosen to keep both optical pathlengths equal.6.2.3 Two Linear Charge Coupled Devices (CCD or diode)Arrays, each located at the focal plane of the displacementcompensating lens. One array is oriented horizontally (for themeasurement of azimuthal changes) and the other orie
23、ntedvertically (for the measurement of elevation changes). Anappropriate element spacing of the arrays is 0.001 in. (0.0254mm). Using this element spacing and the 10-in. (254-mm) lens,each diode will represent the equivalent of 0.1 mrad angulardeviation.6.2.4 Electronic System that determines the ce
24、nter diode ofthe band of illuminated diodes on each CCD array.6.2.5 Electronic System that converts the number to bedisplayed on the digital readout.6.3 Transmitter and Receiver Lenses should be of achro-matic construction to reduce the effect of aberrations on themeasurement.6.4 Dioptomer to verify
25、 attainment of collimated light.7. Test Specimen7.1 Position the part to be tested in such a manner as toapproximate its installed configuration. No special condition-ing other than cleaning is required.8. Procedure8.1 Mount the transparent part on a fixture that allowsaccurate determination of the
26、elevation and azimuth position ofthe part.8.2 Locate and firmly mount the transmitter at a positioncorresponding to the design eye position (the cyclopean eyeposition). To obtain the position corresponding to the left(right) eye position, move the transparency 1.25 in. (31.7 mm)to the right (left) o
27、f the design eye position.8.3 Locate and firmly mount the receiver external to the partto be measured and at a distance from the transmitter that iscommensurate with the part being measured. For example, 4.9ft (1.5 m) if the part is an aircraft windscreen.8.4 Establish a baseline or zero determinati
28、on without atransparency in the optical path. Record the number as dis-played on the digital readout under this condition.8.5 Locate the transparency part between the transmitter andreceiver. Take the readings from the left (right) eye positionover area of interest as specified by using activity. Re
29、cordreadings for each point (azimuth, elevation) of the transparencythat is measured. Determine differences between these readingsand readings (8.4) made without the transparency in place.8.6 Repeat 8.5, taking readings with the transmitter locatedand firmly mounted at right (left) eye position or a
30、s appropri-ate.9. Calculation and Report9.1 Determine the amount of horizontal and vertical binocu-lar disparity present in the transparent part by completing thecalculations set forth in paragraphs 9.1.1-9.1.4. Azimuth scoreswill yield horizontal disparity, elevation scores will yieldvertical dispa
31、rity.9.1.1 Determine the amount of disparity present at eachpoint (azimuth, elevation) on the transparent part by subtract-ing the readings from the left eye position from the readingstaken from the right eye positions using the equations asfollows:Dx5 XL2 XRdisparity in azimuth! (1)or Dy5 YL2 YRdis
32、parity in elevation! (2)9.1.2 Calculate the mean for these disparity readings usingthe Eq 3. This yields the average of the disparity readingsfound throughout the part.Dx5 (Dx/NorDy5 (Dy/N (3)where:Dx= mean for azimuth,(Dx= sum of azimuth readings,N = number of readings,Dy= mean for elevation, and(D
33、y= sum of elevation readings.9.1.3 Calculate the standard deviation for these readingsusing the Eq 4 shown below. This yields a measure of thedispersion or variability of the readings obtained from a givenpart.Sx5(Dx22 (Dx!2/NN 2 1(4)where:Sx= standard deviation for azimuth,(Dx2= sum of the squares
34、for each reading,(Dx)2= sum of all readings squared,N = number of readings, andN1 = degrees of freedom.F 1181 96 (2003)29.1.4 Inspect the data to determine the largest absolute valuefor the readings obtained. This is the maximum error for thegiven readings.9.2 Compare the scores obtained (mean, stan
35、dard deviation,and max error) with scores given in appropriate specificationsregarding the amount of disparity allowable in a given trans-parency. For current aircraft transparencies, this value istypically 10 min of arc (3 mrad).NOTE 1This value is composed of 2 components, for example,geometric er
36、rors due to shape, thickness, and so forth. of the windscreenand manufacturing errors due to the process materials tolerances, and soforth.10. Precision and Bias10.1 The data used to develop this section was obtained asthe result of a round-robin test reported at the September 1990F07.08 subcommitte
37、e meeting. The written report was entitled“Angular Deviation Revisited: Results of a Round Robin Test”and is available from ASTM headquarters. This round-robintest was done in support of Test Method F-801 but is applicablehere since the same basic device and procedure is used toobtain the data for c
38、alculating the binocular disparity.10.2 There are two primary sources of error with thisprocedure: 1) those dealing with the measurement device itself,and 2) those dealing with the positioning of the part to bemeasured. Since this procedure only addresses the measure-ment device and not positioning
39、equipment, this section will beconfined to data relating to the precision of the measurementdevice itself.10.3 The round-robin testing accomplished for F801 used acalibrated wedge to compare results between five measurementdevices located at three laboratories. The overall repeatabilitywas found to
40、be 60.1 milliradians for the 95 % confidencelevel. If the error sources are random then the calculatedrepeatability of a number that involves the subtraction of 2measurements would be 1.414 times the repeatability of thesingle number. This implies the repeatability for the binoculardisparity calcula
41、tion is 60.14 milliradians.10.4 The overall 95 % confidence level reproducibility ofthe procedure for measuring angular deviation was found to be60.29 milliradians for a 5.07 milliradian calibrated wedge (orabout 6 %). This implies the 95 % confidence level reproduc-ibility of the binocular disparit
42、y calculation is 1.414 times 0.29which is 0.41 milliradians or about 8 %.10.5 There is no bias with this procedure since the calcula-tion involves subtracting one reading from the other whichremoves any bias from the resulting relative number.11. Keywords11.1 angular deviation; binocular disparity;
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44、he riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision
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46、dmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).F 1181 96 (2003)3
