1、Designation: F 1165 98 (Reapproved 2004)Standard Test Method forMeasuring Angular Displacement of Multiple Images inTransparent Parts1This standard is issued under the fixed designation F 1165; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、 revision, the year 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 measuring the angular separa-tion of secondary images from their respe
3、ctive primary imagesas viewed from the design eye position of an aircraft transpar-ency. Angular separation is measured at 49 points within a 20by 20 field of view. This procedure may be performed on anyaircraft transparency in a laboratory or in the field. However,the procedure is limited to a dark
4、 environment. Laboratorymeasurements are done in a darkened room and field measure-ments are done at night.1.2 The values stated in acceptable metric units are to beregarded as the standard. The values in parentheses are forinformation only.1.3 This standard may involve hazardous materials, opera-ti
5、ons, and equipment. This standard does not purport toaddress all of the safety concerns, associated with its use. It isthe responsibility of the user of this standard to establishappropriate safety and health practices and determine theapplicability of regulatory limitations prior to use.2. Referenc
6、ed Documents2.1 ASTM Standards:2E 177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology (see Fig. 1)3.1 primary imagethe image formed by the rays transmit-ted through the
7、 transparency without being reflected (solidlines).3.2 secondary imagethe image resulting from internalreflections of light rays at the surfaces of the transparency(dashed lines).3.3 angular displacementthe apparent angular separationof the secondary image from the primary image as measuredfrom the
8、design eye position (u).3.4 installed anglethe part attitude as installed in theaircraft; the angle between the surface of the windscreen andthe pilots 0 azimuth, 0 elevation line of sight.4. Summary of Test Method4.1 The procedure for determining the angular displacementof secondary images entails
9、photographing a light array ofknown size and distance from the transparency. The photo-graph is then used to make linear measurements of the imageseparation, which can be converted to angular separation usinga scale factor based on the known geometry.5. Significance and Use5.1 With the advent of thi
10、ck, highly angled aircraft trans-parencies, multiple imaging has been more frequently cited asan optical problem by pilots. Secondary images (of outsidelights), often varying in intensity and displacement across thewindscreen, can give the pilot deceptive optical cues of hisaltitude, velocity, and a
11、pproach angle, increasing his visualworkload. Current specifications for multiple imaging in trans-parencies are vague and not quantitative. Typical specificationsstate “multiple imaging shall not be objectionable.”5.2 The angular separation of the secondary and primaryimages has been shown to relat
12、e to the pilots acceptability ofthe windscreen. This procedure provides a way to quantifyangular separation so a more objective evaluation of thetransparency can be made. It may be used for research ofmultiple imaging, quantifying aircrew complaints, or as thebasis for windscreen specifications.1Thi
13、s 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. 1, 2004. Published October 2004. Originallyapproved in 1988. Last previous edition appro
14、ved in 1998 as F 1165 98.2For 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.FIG. 1 Drawing of Light Ray Paths th
15、at Cause an ApparentAngular Separation (u) Between the Primary Image and theSecondary Image1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.3 It should be noted that the basic multiple imagingcharacteristics of a windscreen are dete
16、rmined early in thedesign phase and are virtually impossible to change after thewindscreen has been manufactured. In fact, a perfectly manu-factured windscreen has some multiple imaging. For a particu-lar windscreen, caution should be taken in the selection ofspecification criteria for multiple imag
17、ing, as the inherentmultiple imaging characteristics may vary significantly de-pending upon windscreen thickness, material, or installationangle. Any tolerances that might be established should allowfor inherent multiple imaging characteristics.6. Apparatus6.1 Light ArrayThe light array isa7by7matri
18、x of smallincandescent lights (flashlight bulbs) mounted on a metalframe. The separation of the lights is 406.4 mm (16 in.) oncenter making the overall dimensions of the array 2.44 by 2.44m (8 by 8 ft). A suitable power supply, such as a rechargable12-V dc gel cell, is also required. A backdrop of n
19、onreflectivematerial (such as black velvet) should be placed several inchesbehind the array to block out background lights and preventreflections.6.2 Camera/filmNo special camera or modification isneeded for this process. The lens should have a focal length ofabout 50 mm or as is necessary to permit
20、 the light array to fillmost of the field of view of the camera. The film should beblack and white.37. Test Specimen7.1 Position the part to be measured in the installed angle(or installed in the aircraft for a field measurement) such thatthe camera is located in the pilots design eye position. Nosp
21、ecial conditioning other than cleaning is required.8. Procedure8.1 The procedure for taking the multiple image photographshould be performed in a darkened room to reduce ambientlight that decreases the visibility of the secondary images seenthrough the transparency. If the procedure is performed in
22、thefield at night, turn off nearby lights that affect the visibility ofthe secondary images.8.2 Set up the light array so the center light is 7 m (23 ft 65 %) from the design eye position on the line of sightcorresponding to 0 azimuth, 0 elevation (Fig. 2). The arrayshould be perpendicular (65) to t
23、he line of sight. For fieldmeasurements, it may be necessary to attach the array to amaintenance stand to elevate it to the appropriate height. Careshould be taken to ensure that the array is securely attached tothe maintenance stand railing and avoid hitting the nose of theaircraft when moving the
24、elevated array. If wind conditionspresent a hazard, do not attempt to measure.8.3 Turn the array board on.8.4 Place the camera in the design eye position and adjustthe camera such that the array is centered in the field of view;focus the lens on the center light of the array.8.5 Set the camera apert
25、ure to f/16 and the shutter speed toan appropriate setting.8.6 Take the picture(s) and develop 8 by 10 prints or asuitable enlargement.8.7 On the photograph, measure the distance (L) from thesecond light to the sixth light on the middle row. To ensureaccuracy, use a precision measuring device, such
26、as a digitalcaliper.8.8 For each light in the 8 by 10 print, measure the linearseparation (r) of the secondary image from the primary imageusing the calipers. Measure from the center of both spots whentaking the measurement.9. Calculation9.1 To obtain the scale factor F, which relates the lineardist
27、ances on the photograph to actual angular distances asmeasured from the design eye position, use the equation asfollows:F 5229.2Lmrads/mm (1)9.2 Compute the angular separation u for each light of thearray using the equation:u5r 3 F (2)9.3 Enter the angular separation data intoa7by7table sothe rows a
28、nd columns correspond to the location of lights onthe array.10. Precision and Bias10.1 PrecisionAn interlaboratory study4was conductedto determine the precision of this test method. Twenty labora-tories (people) measured five different multiple image (MI)photographic distances plus one scale factor,
29、 ten times each.Tables 1 and 2 and summarize the results.10.1.1 Since the accuracy of the measurements should notand did not depend upon the size of the measured object, it islogical to take a mean of the six samples to derive thecomposite precision values indicative of this method.3Kodak Tri-X ASA
30、400 has been found satisfactory, also an equivalent may beused.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: F07 1003.FIG. 2 Schematic Drawing of Component Layout for MeasuringMultiple Imaging Angular DisplacementF 1165 98 (2
31、004)2The composite (mean repeatability (Sr) and reproducibility(SR) values:mean Sr= 0.128 mm andmean SR= 0.230 mm.The composite (mean) 95 % limits for repeatability (r) and95 % limits for reproducibility (R) values:mean r = 0.353 mm andmean R = 0.636 mm.NOTE 1The 95 % limits were calculated using th
32、e formulas below.Because the 95 % limits are based on the difference between two testresults, the =2 factor was incorporated into the calculation (PracticeE 177; Section 27.3.3).r 5 1.960*=2*Sr(3)where:Sr= repeatability standard deviation andr = 95 % repeatability limit (within laboratories).R 5 1.9
33、60*=2*SR(4)where:SR= reproducibility standard deviation andR = 95 % reproducibility limit (between laboratories).10.1.2 The final value determined by Test Method F 1165 isangular displacement (in mrads). This final angular valuedepends upon and is relative to the original photographicgeometry and en
34、largement size; therefore, no precision valuein terms of angular displacement can be calculated or ex-pressed. The error in the method is due to people using calipersto make actual physical measurements of separated dots oflights on photographs, not in the calculation of angulardisplacement.10.1.3 I
35、n summary, the statistical analysis (Practices E 691and E 177) revealed that the methods mean repeatability (Sr)was 0.128 mm and the mean reproducibility (SR) was 0.230mm. The mean 95 % limits for repeatability (r) was 0.353 mmand the mean 95 % limits for reproducibility (R) was 0.636mm.10.2 BiasThe
36、 procedure in this test method has no biasbecause the angular separation of the multiple image is definedonly in terms of the test method.11. Keywords11.1 aircraft transparency; angular displacement; canopy;primary image; secondary image; transparent parts; windscreenAPPENDIXES(Nonmandatory Informat
37、ion)X1. DERIVATION OF EQUATIONSX1.1 The angular separation between the lights of the arraycan be calculated by dividing the actual distance betweenadjacent lights (0.406 m) by the distance of the center lightfrom the design eye position (7 m). Take the arctan of the resultto get the angle in degrees
38、:A 5 arctan 0.406/7! 5 3.3 (X1.1)X1.2 Convert the angular separation from degrees tomilliradians by multiplying by 17.45 mrads/.A 5 3.3 3 17.45 mrads/ 5 57.6 mrads (X1.2)NOTE X1.1If laboratory or field constraints require changing the sizeof the array or the distance from the array to the design eye
39、 position, it isnecessary to recalculate a new value of A using Eq X1.1 and X1.2 andsubstituting in the appropriate values.X1.3 Compute the average linear separation of lights on thephotograph by dividing L (the distance from the second to thesixth light of the middle row) by 4 (the number of interv
40、alsbetween these lights).X1.4 Divide the angular separation of the lights, A, by theiraverage linear separation, L/4, to obtain the scale factor F,inunits of mrads/mm.F 5AL/454AL5229.2Lmrads/mm (X1.3)TABLE 1 Repeatability (Sr) and Reproducibility (SR) Values inMillimetresRepeatability (Sr) WithinLab
41、sAReproducibility (SR)Between LabsBSample 1 0.114 0.198Sample 2 0.119 0.226Sample 3 0.122 0.199Sample 4 0.149 0.253Sample 5 0.128 0.240Scale factor 0.133 0.261Mean 0.128 0.230ASrranged from 0.114 to 0.149 mm.BSRranged from 0.198 to 0.261 mm.TABLE 2 95 % Repeatability (r) Limits and 95 % Reproducibil
42、ity(R) Limits in Millimetres95 % r Limits Within LabsA95 % R Limits BetweenLabsBSample 1 0.316 0.550Sample 2 0.329 0.627Sample 3 0.337 0.550Sample 4 0.412 0.701Sample 5 0.354 0.665Scale factor 0.368 0.723Mean 0.353 0.636Ar ranged from 0.316 to 0.412 mm.BR ranged from 0.550 to 0.723 mm.F 1165 98 (200
43、4)3X2. SELECTION OF ARRAY DISTANCEX2.1 This procedure was developed to permit the evalua-tion of multiple image parameters both in the laboratory and inthe field. Therefore, the equipment is portable in nature andshould accommodate measurements on a variety of aircraft.X2.2 The selection of7masthedi
44、stance from the array tothe design eye location was made considering several factors:X2.2.1 The array should clear the nose of large aircraft topermit field measurements of installed transparencies.X2.2.2 The distance should not be excessively long so thatlaboratory measurements can be performed in
45、a reasonablysized room.X2.2.3 Shorter distances decrease the accuracy of the resultsbecause of the increased relative effect of lateral displacement.X2.3 If necessary, the 7 m distance may be changed to meetadditional requirements. If this is done, the calculations inAppendix X1 must be repeated usi
46、ng the new distance value.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infrin
47、gement 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 of this standard
48、 or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views
49、 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 1165 98 (2004)4
