1、Designation: F1165 10Standard 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 may be performed on anyaircraft transparency in a laboratory or in the field. However,the procedure is limited to a dark environment. Laborat
4、orymeasurements are done in a darkened room and field measure-ments 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 infor-mation only.1.3 This standard may i
5、nvolve hazardous materials, opera-tions, 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
6、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 image formed by
7、 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 image from the
8、primary image as measuredfrom the 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 displa
9、cementof 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. Significance
10、 and Use5.1 With the advent of thick, 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 cu
11、es of hisaltitude, velocity, and approach 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 pri
12、maryimages 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. It may be used for research of1This test method is under the jurisdiction of ASTM Committee F07
13、 onAerospace and Aircraft and is the direct responsibility of Subcommittee F07.08 onTransparent Enclosures and Materials.Current edition approved May 1, 2010. Published June 2010. Originallyapproved in 1988. Last previous edition approved in 2004 as F1165 98 (2004).DOI: 10.1520/F1165-10.2For referen
14、ced 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 that Cause an ApparentAngular Separatio
15、n (u) Between the Primary Image and theSecondary Image1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.multiple imaging, quantifying aircrew complaints, or as thebasis for windscreen specifications.5.3 It should be noted that the basi
16、c multiple imagingcharacteristics of a windscreen are determined 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 i
17、n the selection ofspecification criteria for multiple imaging, 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 characteristi
18、cs.6. Apparatus6.1 Light ArrayThe light array isa7by7matrix 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 rech
19、argable12-V dc gel cell, is also required. A backdrop of nonreflectivematerial (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
20、 a focal length ofabout 50 mm or as is necessary to permit the light array to fillmost of the field of view of the camera. The film should beblack and white.3Digital cameras are an acceptable alternativeto film-based cameras.7. Test Specimen7.1 Position the part to be measured in the installed angle
21、(or installed in the aircraft for a field measurement) such thatthe camera lens is located in the pilots design eye position. Nospecial 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
22、ambientlight that decreases the visibility of the secondary images seenthrough the transparency. If the procedure is performed 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 de
23、sign eye position on the line of sightcorresponding to 0 azimuth, 0 elevation (Fig. 2). The arrayshould be perpendicular (65) to the 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 ens
24、ure that the array is securely attached tothe maintenance stand railing and avoid hitting the nose of theaircraft when moving the 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 ca
25、mera 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 speed 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
26、distance (L) from thesecond primary light image to the sixth primary light image onthe middle row. To ensure accuracy, use a precision measuringdevice, such as a digital caliper.8.8 For each light in the 8 by 10 print, measure the linearseparation (r) of the secondary image from the primary imageusi
27、ng the calipers. Measure from the center of both spots whentaking the measurement.9. Calculation9.1 To obtain the scale factor F, which relates the lineardistances on the photograph to actual angular distances asmeasured from the design eye position, use the equation asfollows:F 5229.2Lmrads/mm (1)9
28、.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 and columns correspond to the location of lights onthe array.10. Precision and Bias10.1 PrecisionAn interlaboratory study4was conductedto deter
29、mine the precision of this test method. Twenty labora-tories (people) measured five different multiple image (MI)photographic 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 should notand did not depend upon the s
30、ize 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 400 has been found satisfactory, also an equivalent may beused.4Supporting data have been filed at ASTM International Headquarters and maybe o
31、btained by requesting Research Report RR: F07 1003.FIG. 2 Schematic Drawing of Component Layout for MeasuringMultiple Imaging Angular DisplacementF1165 102The composite (mean repeatability (Sr) and reproducibility(SR) values:mean Sr= 0.128 mm andmean SR= 0.230 mm.The composite (mean) 95 % limits for
32、 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 the formulas below.Because the 95 % limits are based on the difference between two testresults, the =2 factor was incorporated into the calculation (Pra
33、cticeE177; 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 T
34、est 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 p
35、eople 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 reprodu
36、cibility 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
37、the 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; sec
38、ondary 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 e
39、ye position (7 m). Take the arctan of the resultto get the angle in degrees:R 5 1.960*=2*SR(X1.1)X1.2 Convert the angular separation from degrees tomilliradians by multiplying by 17.45 mrads/.A 5 arctan 0.406/7! 5 3.3 (X1.2)NOTE X1.1If laboratory or field constraints require changing the sizeof the
40、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 X1.3 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 thesix
41、th light of the middle row) by 4 (the number of intervalsbetween 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.A 5 3.3 3 17.45 mrads/ 5 57.6 mrads (X1.3)TABLE 1 Repeatability (Sr) and Reprod
42、ucibility (SR) Values inMillimetresRepeatability (Sr) WithinLabsAReproducibility (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
43、 mm.TABLE 2 95 % Repeatability (r) Limits and 95 % Reproducibility(R) Limits in Millimetres95 % r Limits Within LabsA95 % R Limits BetweenLabsBSample 1 0.316 0.550Sample 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.
44、316 to 0.412 mm.BR ranged from 0.550 to 0.723 mm.F1165 103X2. 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
45、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 should clear the nose of large aircraft topermit field measurements of installed transparencies.X2.2.2 The distance should not be excessively l
46、ong so thatlaboratory measurements can be performed in 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 do
47、ne, 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 determination of the va
48、lidity 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 withdrawn. Your co
49、mments 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 19428-2959,United States.
