1、Designation: F2964 12Standard Test Method forDetermining the Uniformity of the Luminance of anElectroluminescent Lamp or Other Diffuse Lighting Device1This standard is issued under the fixed designation F2964; the number immediately following the designation indicates the year oforiginal adoption or
2、, in the case of revision, the year 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 procedures for determining theuniformity of the luminan
3、ce of an electroluminescent (EL)lamp. While written specifically for the purpose of evaluatingEL devices, which are intrinsically very uniform, it can beapplied (judiciously) to the measurement of any diffuse,essentially planar, light source. For specific purposes, it can beapplied to partially asse
4、mbled devices into which the illumi-nation is installed (such as a membrane switch) as a diagnosticfor the performance of the entire device. In such a case it mustbe understood that the results pertain only to the partialassembly and will be modified as the further assembly pro-ceeds.1.2 The method
5、is to take a 2-dimensional set ofmeasurements, sampling the surface of the unit under test withappropriate density. The method is restricted to measuringluminance only, since variations in color will also show asluminance non-uniformity especially in any photoptically cali-brated measuring device.1.
6、3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard 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-
7、priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2F2360 Test Method for Determining Luminance of a Mem-brane Switch Backlit with Diffuse Light SourceF2771 Test Method for Determining the Luminance Cur
8、veof an Electroluminescent Lamp at Ambient Conditions3. Terminology3.1 Definitions:3.1.1 luminance, nmeasure of the brightness or luminousintensity of light, usually expressed in units of candelas persquare metre (cd/m2) or foot lamberts. 1 fL = 3.426 cd/m2.3.1.2 luminance curve, na graphical repres
9、entation of thevariation of luminance with time (implicitly under unvaryingoperating conditions).3.1.3 electroluminescent lamp (EL lamp), nessentially acapacitor structure with phosphor and a dielectric sandwichedbetween electrodes, one of which is transparent to allow lightto escape. Application of
10、 an ac voltage across the electrodesgenerates a charging field within the phosphor, which causes itto emit light.3.1.4 time to half luminance (THL), nthe elapsed operat-ing time over which the luminance of a lamp maintained underconstant power will be reduced to half of its initial value.3.1.5 UUT,
11、nunit under test.4. Significance and Use4.1 Application of an EL lamp (or other diffuse lightingsource) to illuminate a device has a functional purpose andmust meet specifications to satisfy the functional requirementsof the device.4.2 Illumination of the device or application can be affectedby vari
12、ations in the quality, efficiency, and design of the lampand any attendant mounting or shading fixtures.4.3 This test method addresses only the optical and visualappearance of the lamp and not its electrical function.4.4 This test method is non-destructive.4.5 This test method is described for appli
13、cation to theillumination layer in which case the results apply to that layeronly. However, it may be desirable and practical to apply thetest to a further assembly or to a fully assembled device withbuilt in illumination. In such a case, the results refer specifi-cally to the subassembly or the ent
14、ire device respectively.1This test method is under the jurisdiction of ASTM Committee F01 onElectronics and is the direct responsibility of Subcommittee F01.18 on MembraneSwitches.Current edition approved July 1, 2012. Published August 2012. DOI: 10.1520/F2964122For referenced ASTM standards, visit
15、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.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.
16、 United States15. Interferences5.1 State of AssemblyTests on incomplete assemblies giveresults appropriate to that state of assembly. Specifically, laterapplication of mounting hardware, baffling, or fixtures mayalter the results.5.2 Filling of ApertureFailure to fill the sampling apertureof the pho
17、tometer will bias the results in a way which is notnecessarily predictable.5.3 Age of DeviceSince every system of illuminationchanges characteristics as it ages, it must be recognized that theresults apply to a particular interval in the lifetime of thesystem. Characterization of the aging propertie
18、s may beaddressed in a separate test method. (See for example TestMethod F2771.)5.4 PerpendicularitySince the angular distribution ofemitted light can be altered by any material through which itpasses, it is important that the photometer be held perpendicu-lar to the area to be sampled.5.5 Temperatu
19、reSince the performance of many lightsources can vary with temperature, it is important to allow theUUT to stabilize thermally, if necessary, and then record theambient temperature at which the measurements are made.5.6 PowerSince the performance of many power sourcescan vary with temperature, it is
20、 important to allow the powersupply for the UUT to stabilize thermally, if necessary, andthen record the warm-up time at which the measurements aremade.5.7 Ambient LightStray light sources will be detected bythe photometer and will affect the UUT luminance measure-ment. It is important to measure th
21、e ambient light beforeilluminating the UUT. This ambient light reading should bezero or as close to zero as possible.5.8 Sampling ApertureThe sampling aperture (area of theUUT sample and over which luminance values are averaged bythe measuring instrument) should be large enough to averageover any in
22、trinsic granularity of the UUT. This area should alsobe small enough compared with the overall size of the UUT toallow multiple measurements to be made without the samplingapertures of adjacent measurements overlapping (at least ninemeasurements are recommended). If areas overlap, the indi-vidual sa
23、mples may no longer be considered as independentsamples. The decision to allow individual samples to overlapor to remain physically distinct is one the experimenter mustmake and be conscious of. Use of a preplanned sequence ofmeasurements is recommended. See Fig. 1 for example of asample sequence an
24、d distribution.6. Apparatus6.1 A working or mounting surface to hold and support theUUT and any supporting fixtures, providing electrical access tothe termination region from which the EL lamp illumination isto be powered and visible access to all regions of interest on thelamp at which the luminanc
25、e is to be measured.6.2 A power supply providing appropriate, stable and ad-equate power to drive the illumination device(s) with appro-priate connector(s). This should be specified as dc or ac, withvoltage and power level given, and ideally should be switched.6.3 A calibrated device to measure surf
26、ace luminance (orradiance). This is typically a spot photometer, with a fairlycompact sampling aperture (1-cm diameter at the minimumworking distance). Output should be in foot lamberts (candelaper meter squared).Alternatively, a radiometer may be used, oreven a video photometer, but cognizance must
27、 be maintainedof the output units and calibration. Hereinafter we refer to thisas the photometer.6.4 A means to support the photometer at a fixed distanceand orientation to the emitting surface of the UUT.6.5 A means to move the lamp and photometer relative toeach other with enough travel to allow t
28、he instrument con-trolled and stable visual access to all regions of the UUT. Theapparatus or set up should allow the experimenter to collectdata with sufficient density and knowledge of the location ofthe samples to allow an adequate characterization of the UUT.See Fig. 1 and 5.8.6.6 A means to con
29、trol or exclude stray light and prevent itfrom entering the aperture of the photometer.7. Procedure7.1 This method is similar to that in F2360, Test Method forDetermining Luminance of a Membrane Switch Backlit withNOTE 1A sequence of nine, non-overlapping measurements whichwill reveal side-to-side,
30、center to edge, and top to bottom non-uniformitiesof luminance. The order of sampling is suggested by the numbers. See 5.8.NOTE 2Size for the sampling area (shown here as small rectangles)can be chosen to maximize significance by taking it to be large enough toaverage over any intrinsic granularity
31、of the lamp (such as phosphorcrystal size) and small enough to avoid overlap with its neighbor (and thusremain independent).FIG. 1 Suggested Organization of Sampling Points for UniformityMeasurementF2964 122Diffuse Light Source, which may be used as a working guideto the current method.7.2 Mount UUT
32、 on the working surface with the illuminatedsurface visible.7.3 Attach a switched power source as appropriate to theillumination device set to the design operating point.7.4 Mount the photometer or luminance meter so that theaxis of its field of view is perpendicular to the area of the UUTto be meas
33、ured. Ensure that the sampling aperture is filled bythe area to be measured on the UUT. Measure and record theextent and location of the field of view.7.5 Verify the means by which relative motion of the UUTand photometer permits the desired density, locations, andextent of samples (see Fig. 1). Thi
34、s requires that the samplingplan (the number, locations, and sizes of the samples) be wellplanned and understood.7.6 Establish an initial point (location on the UUT) for theset of measurements to be made. Suggested areas are the centerof the UUT (for Method 1) or a particular corner of the UUT.8. Me
35、thod 1 (Preferred)NOTE 1To be used where there is confidence that the stray light effectsare negligible.8.1 Measure the stray light level by taking a photometerreading while the UUT luminous source is not powered. If thisvalue is not zero or very close to it, do not proceed, but takesteps to reduce
36、the stray light present. This may be as simple asreducing the ambient room light or switching the overheadlights off altogether.8.2 Switch on the power and illuminate the UUT.8.3 Measure and record the luminance of the sample area ofthe UUT at the current position.8.4 Move the location of the sampli
37、ng aperture to the nextdesired location for measurement.8.5 Repeat steps 8.2 and 8.3 until the entire UUT has beenmeasured at all desired locations.8.6 Go to 10.1.9. Method 2NOTE 2To be used where there is no confidence that the stray lighteffects are negligible.9.1 Measure the stray light level by
38、taking a photometerreading while the UUT luminous source is not powered. If thisvalue is not zero or very close to it, do not proceed, but takesteps to reduce the stray light present. This may be as simple asreducing the ambient room light or switching the overheadlights off altogether.9.2 Switch on
39、 the power and illuminate the UUT.9.3 Measure and record the luminance of the sample area ofthe UUT at the current position.9.4 The luminance at the point of measurement is taken asthe difference in the powered and unpowered values.9.5 Move the location of the sampling aperture to the nextdesired lo
40、cation for measurement.9.6 Measure and record the luminance of the sample area ofthe UUT at the current position.9.7 Switch off the UUT and allow to settle for 3 min (someillumination sources, especially EL may retain an afterglowonce the power is removed). Measure and record the luminanceof the sam
41、ple area of the UUT at the current position. If thisvalue is not zero or very close to it, do not proceed, but takesteps to reduce the stray light present. If necessary repeat steps9.1 and 9.2.9.8 The luminance at the point of measurement is taken asthe difference in the powered and unpowered values
42、.9.9 Move the location of the sample area to the next insequence and begin from step 9.1 until the entire UUT has beenmeasured at all desired locations.10. Both Methods10.1 After all desired samples have been recorded, returnthe sample area to the initial point and measure and record theluminance at
43、 that location (correcting for unpowered lumi-nance if completing Method 2). Compare to the first measure-ment. If the first and last points are not the same to within thedesired precision, investigate the source of the drift. This mayinclude stray light effects. If a significant effect is found, th
44、emeasurement should be repeated from steps at 7.1, 8.1,or9.1as appropriate.11. Report11.1 Report the following information:11.1.1 State and identification of UUT (assembled or not),11.1.2 Stray light level, and method used,11.1.3 Warm up time for the power supply and settling timeused for the displa
45、y,11.1.4 Luminance measured at each point,11.1.5 Power conditions for the illumination device,11.1.6 Location and size of the sample area or areas,11.1.7 Photometer used, sample settings, calibration status,and the size of the sampling aperture,11.1.8 Ambient temperature, and11.1.9 Date of test.11.2
46、 Uniformity can be characterized a relative luminancedifference between center and edge, from top to bottom, orfrom side to side. A contour plot or other statistical measurescan also be used.12. Precision and Bias12.1 Because of the similarity in procedure, UUT, and datagathering between these metho
47、ds and Test Method F2360, theprecision of this test method is based on an Inter-laboratorystudy of F2360-04, conducted in 2006. It is appropriate toreport precision and bias only where the samples taken areindependent, as is the case in well designed measurementsfollowing Method 1 with no overlap to
48、 the sample areas. In theF2360-04 study, each of six laboratories tested three differenttypes of lamps. A single “test result” represents an individualdetermination. Every laboratory produced twelve test resultsfor each material.F2964 12312.2 RepeatabilityTwo test results obtained within onelaborato
49、ry shall be judged not equivalent if they differ by morethan the “r” value for that material; “r” is the intervalrepresenting the critical difference between two test results forthe same material, obtained by the same operator using thesame equipment on the same day in the same laboratory.12.3 ReproducibilityTwo test results shall be judged notequivalent if they differ by more than the “R” value for thatmaterial; “R” is the interval representing the difference be-tween two test results for the same material, obtained bydifferent operators using different equipmen
