1、Designation: F1165 15Standard Test Method forMeasuring Angular Displacement of Multiple Images inTransparent Parts1This standard is issued under the fixed designation F1165; 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 () 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 respective primary imagesa
3、s 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 is designed for perfor-mance on any aircraft transparency in a laboratory or in thefield. However, the procedure is limited to a dark environ
4、ment.Laboratory measurements are done in a darkened room andfield measurements are done at night.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.2.1 ExceptionThe values in parentheses are for informa-tion only.1.3 This sta
5、ndard possibly involves hazardous materials,operations, 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
6、 of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology (see Fig. 1)3.1 primary imagethe
7、image formed by the rays transmit-ted through the 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
8、image from the primary image as measuredfrom the design eye position ().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
9、angular displacementof secondary images entails 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
10、. Significance and Use5.1 With the advent of thick, highly angled aircrafttransparencies, multiple imaging has been more frequentlycited as an optical problem by pilots. Secondary images (ofoutside lights), often varying in intensity and displacementacross the windscreen, can give the pilot deceptiv
11、e optical cuesof his altitude, velocity, and approach angle, increasing hisvisual workload. Current specifications for multiple imaging intransparencies are vague and not quantitative. Typical specifi-cations state “multiple imaging shall not be objectionable.”5.2 The angular separation of the secon
12、dary and primaryimages has been shown to relate to the pilots acceptability ofthe windscreen. This procedure provides a way to quantifyangular separation so a more objective evaluation of thetransparency can be made. This procedure is of use for researchof multiple imaging, quantifying aircrew compl
13、aints, or as thebasis for windscreen specifications.5.3 It is of note that the basic multiple imaging character-istics of a windscreen are determined early in the design phaseand are virtually impossible to change after the windscreen hasbeen manufactured. In fact, a perfectly manufactured wind-scre
14、en has some multiple imaging. For a particular windscreen,caution is advised in the selection of specification criteria for1This 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 M
15、aterials.Current edition approved Nov. 1, 2015. Published November 2015. Originallyapproved in 1988. Last previous edition approved in 2010 as F1165 10. DOI:10.1520/F1165-15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For
16、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 States1multiple imaging, as inherent multiple imaging characteristicshave the po
17、tential to vary significantly depending upon wind-screen thickness, material, or installation angle. Any tolerancesthat might be established are advised to allow for inherentmultiple imaging characteristics.6. Apparatus6.1 Light ArrayThe light array isa7by7matrix of smallincandescent lights (flashli
18、ght 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 nonreflectivematerial (such as black ve
19、lvet), placed several inches behindthe array, blocks out background lights and prevents reflec-tions.6.2 Camera/filmNo special camera or modification isneeded for this process. A lens focal length of about 50 mm ispreferred, to permit the light array to fill most of the field ofview of the camera. B
20、lack and white film is preferred.3Digitalcameras are an acceptable alternative to film-based cameras.7. 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 lens is located in the pilots design eye position
21、. Nospecial conditioning other than cleaning is required.8. Procedure8.1 The procedure for taking the multiple image photographis optimally performed in a darkened room to reduce ambientlight that decreases the visibility of the secondary images seenthrough the transparency. If the procedure is perf
22、ormed in 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). Set the arrayperpendicular (65) t
23、o the line of sight. For fieldmeasurements, attach the array to a maintenance stand toelevate it to the appropriate height, if necessary. Ensure that thearray is securely attached to the maintenance stand railing andavoid hitting the nose of the aircraft when moving the elevatedarray. If wind condit
24、ions present a hazard, do not attempt tomeasure.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 aperture to f/16 and the shutter sp
25、eed toan appropriate setting.8.6 Take the picture(s) and produce 8 by 10 prints or asuitable enlargement.8.7 On the photograph, measure the distance (L)inmmfrom the second primary light image to the sixth primary lightimage on the middle row. To ensure accuracy, use a precisionmeasuring device, such
26、 as a digital caliper.8.8 For each light in the 8 by 10 print, measure the linearseparation (r) in mm of the secondary image from the primaryimage using the calipers. Measure from the center of both spotswhen taking the measurement.9. Calculation9.1 To obtain the scale factor F, which relates the li
27、neardistances on the photograph to actual angular distances asmeasured from the design eye position, use the equation asfollows:F 5230.4Lmrads/mm (1)9.2 Compute the angular separation for each light of thearray using the equation: 5 r 3 F (2)9.3 Enter the angular separation data intoa7by7table sothe
28、 rows and columns correspond to the location of lights onthe array.10. Precision and Bias10.1 PrecisionAn interlaboratory study4was conducted todetermine the precision of this test method. Twenty laborato-ries (people) measured five different multiple image (MI)3Kodak Tri-X ASA 400 has been found sa
29、tisfactory. An equivalent film is alsopermitted.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: F07 1003.FIG. 1 Drawing of Light Ray Paths that Cause an Apparent Angu-lar Separation () Between the Primary Image and the Secondar
30、yImageFIG. 2 Schematic Drawing of Component Layout for MeasuringMultiple Imaging Angular DisplacementF1165 152photographic distances plus one scale factor, ten times each.Tables 1 and 2 and summarize the results.10.1.1 Since the accuracy of the measurements is notexpected to and in fact did not depe
31、nd upon the size of themeasured object, it is logical to take a mean of the six samplesto derive the composite precision values indicative of thismethod.The composite (mean repeatability (Sr) and reproducibility(SR) values:mean Sr= 0.128 mm andmean SR= 0.230 mm.The composite (mean) 95 % limits for r
32、epeatability (r) and95 % limits for reproducibility (R) values:mean r = 0.353 mm andmean R = 0.636 mm.NOTE 1The 95 % limits were calculated using the formulas below.Because the 95 % limits are based on the difference between two testresults, the=2 factor was incorporated into the calculation (Practi
33、ceE177; Section 27.3.3).r 5 1.960*=2*Sr(3)where:Sr= repeatability standard deviation andr = 95 % repeatability limit (within laboratories).R 5 1.960*=2*SR(4)where:SR= reproducibility standard deviation andR = 95 % reproducibility limit (between laboratories).10.1.2 The final value determined by Test
34、 Method F1165 isangular displacement (in mrads). This final angular valuedepends upon and is relative to the original photographicgeometry and enlargement size; therefore, no general precisionvalue in terms of angular displacement can be calculated orexpressed. The error in the method is due to peop
35、le usingcalipers to make actual physical measurements of separateddots of lights on photographs, not in the calculation of angulardisplacement. The precision values in milliradians for anyspecific implementation of this test can be obtained by substi-tuting the values of repeatability and reproducib
36、ility in 10.1.3into Eq 2 once the scale factor, F, is known.10.1.3 In summary, the statistical analysis (Practices E691and E177) 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
37、 mean 95 % limits for reproducibility (R) was 0.636mm.10.2 BiasThe procedure in this test method has no knownbias because the angular separation of the multiple image isdefined only in terms of the test method.11. Keywords11.1 aircraft transparency; angular displacement; canopy;primary image; second
38、ary image; transparent parts; windscreenAPPENDIXES(Nonmandatory Information)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
39、position (7 m). Take the arctan of the resultto get the angle in degrees:A 5 arctan0.406/7! 5 3.3 (X1.1)X1.2 Convert the angular separation from degrees to milli-radians by multiplying by 17.45 mrads/.A 5 3.3 317.45 mrads/ 5 57.6 mrads (X1.2)NOTE X1.1If laboratory or field constraints require changi
40、ng the sizeof the array or the distance from the array to the design eye 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 th
41、e second to thesixth light of the middle row) by 4 (the number of intervalsbetween these lights).TABLE 1 Repeatability (Sr) and Reproducibility (SR) Values inMillimetresRepeatability (Sr) WithinLabsAReproducibility (SR)Between LabsBSample 1 0.114 0.198Sample 2 0.119 0.226Sample 3 0.122 0.199Sample 4
42、 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 % Reproducibility(R) Limits in Millimetres95 % r Limits Within LabsA95 % R Limits BetweenLabsBSample 1 0.316 0.550Sam
43、ple 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.F1165 153X1.4 Divide the angular separation of the lights, A, by theiraverage linear separation, L/4, to obtain the s
44、cale factor F,inunits of mrads/mm.F 5 AL 4! 5 4AL 5 230.4 mradsmm (X1.3)X2. SELECTION OF ARRAY DISTANCEX2.1 This procedure was developed to permit the evaluationof multiple image parameters both in the laboratory and in thefield. Therefore, the equipment is portable in nature andaccommodates measure
45、ments on a variety of aircraft.X2.2 The selection of7masthedistance from the array tothe design eye location was made considering several factors:X2.2.1 The array is to clear the nose of large aircraft topermit field measurements of installed transparencies.X2.2.2 The distance is advised not to be e
46、xcessively long,so that laboratory measurements can be performed in areasonably sized room.X2.2.3 Shorter distances decrease the accuracy of the resultsbecause of the increased relative effect of lateral displacement.X2.3 If necessary, change the 7 m distance to meet addi-tional requirements. If thi
47、s change is done, the calculations inAppendix X1 must be repeated using 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 determina
48、tion of the validity of any such patent rights, and the 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 with
49、drawn. Your comments are invited either for revision of this standard 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 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 19
