1、Designation: F 1181 09Standard 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 of last revision.
2、 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, canopie
3、s, 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
4、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 beingus
5、ed in the measurement of optical angular deviation underMethod F 801.1.4 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 standar
6、d 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
7、 Standards:2F 801 Test Method for Measuring Optical Angular Devia-tion of Transparent 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,mill
8、iradians. 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 th
9、at 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 me
10、rge 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
11、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 F 801) and withthe part held in its installed angle, two sets of angular deviationmeasurement
12、s 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
13、 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. Sig
14、nificance 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 A
15、STM Committee F07 onAerospace and Aircraft and is the direct responsibility of Subcommittee F07.08 onTransparent Enclosures and Materials.Current edition approved May 15, 2009. Published June 2009. Originallyapproved in 1988. Last previous edition approved in 2003 as F 1181 96 (2003).2For referenced
16、 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Cons
17、hohocken, PA 19428-2959, United States.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 thumb to one side of the image of theclock. Now
18、open both eyes. If you look at the clock, youshould see two thumbs. If you look at your thumb, you shouldsee two clocks.5.2 Complaints from pilots flying aircraft equipped withwide field of view head up displays (HUDs) such as theLANTIRN HUD indicated that they were experiencing dis-comfort (eye fat
19、igue, headaches, and so forth.) or seeing eithertwo targets or two pippers (aiming symbols on the HUD) whenusing the HUD. Subsequent investigations revealed that theproblem arose from the fact that the aircraft transparency andthe HUD significantly changed the optical distances of thetarget and the
20、HUD imagery so that binocular disparity, whichexceeded Panums area was induced. Use of this test methodprovides a procedure by which the amount of binoculardisparity being experienced by a human operator due to thepresence of a transparent part in his field of view may be easilyand precisely measure
21、d.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.6.2 Receiver firmly affixed to the floor or a stable platformconsisting of the following components:6.2.1 Displacement Compe
22、nsation 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). Thebeam splitter should be positioned to keep both optical pathlengths equal.6.2.3 Two Linear Charge Coupled Devices (CCD or
23、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 orientedvertically (for the measurement of elevation changes). Anappropriate element spacing of the arrays is 0.001 in. (0.02
24、54mm). 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 center diode ofthe band of illuminated diodes on each CCD array.6.2.5 Electronic System that converts the number to bedispl
25、ayed 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 attainment of collimated light.7. Test Specimen7.1 Position the part to be tested in such a manner as toapproximate its
26、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 elevation and azimuth position ofthe part.8.2 Locate and firmly mount the transmitter at a positioncorresponding to the d
27、esign 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) of the design eye position.8.3 Locate and firmly mount the receiver external to the partto be measured and at a distance f
28、rom the transmitter that iscommensurate with the part being measured (sufficient toensure the part being measured will not physically contact thereceiver unit).8.4 Establish a baseline or zero determination without atransparency in the optical path. Record the number as dis-played on the digital rea
29、dout 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. Recordreadings for each point (azimuth, elevation) of the transparencythat is measured. Determine
30、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 as appropri-ate.9. Calculation and Report9.1 Determine the amount of horizontal and vertical bino
31、cu-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 disparity.9.1.1 Determine the amount of disparity present at eachpoint (azimuth, elevation) on the tra
32、nsparent 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 YRdisparity in elevation! (2)9.1.2 Calculate the mean for these disparity readings usingthe Eq 3. This
33、 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(Dy= sum of elevation readings.9.1.3 Calculate the standard deviation for these readingsusing the E
34、q 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)F1181092where:Sx= standard deviation for azimuth,(Dx2= sum of the squares for each reading,(Dx)2= sum of all readings squared,N = number of readings, andN1 = degre
35、es of freedom.9.1.4 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, standard deviation,and max error) with scores given in appropriate specificationsregarding the amount of dispa
36、rity 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 errors due to shape, thickness, and so forth. of the windscreenand manufacturing errors due to the process m
37、aterials 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 subcommittee meeting. The written report was entitled“Angular Deviation Revisited: Results of a Round Robin Test”and
38、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 calculating the binocular disparity.10.2 There are two primary sources of error with thisprocedure: 1) thos
39、e 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 equipment, this section will beconfined to data relating to the precision of the measurementdevice itself.
40、10.3 The round-robin testing accomplished for F 801 used acalibrated wedge to compare results between five measurementdevices located at three laboratories. The overall repeatabilitywas found to be 60.1 milliradians for the 95 % confidencelevel. If the error sources are random then the calculatedrep
41、eatability 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 calculation is 60.14 milliradians.10.4 The overall 95 % confidence level reproducibility ofthe procedure for mea
42、suring 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 disparity calculation is 1.414 times 0.29which is 0.41 milliradians or about 8 %.10.5 There is no bias with this
43、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; binocular vi-sion; diplopia; double visionASTM International takes no position respecting the validity of
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