1、Designation: C1426 14Standard Practices forVerification and Calibration of Polarimeters1This standard is issued under the fixed designation C1426; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number
2、in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 Polarimeters and polariscopes used for measuring stressin glass are described in Test Methods F218, C148, and C978.These instruments include a
3、 light source and several opticalelements (polarizers, optical retarders, filters, and so forth) thatrequire occasional cleaning, realigning, and calibration. Theobjective of these practices is to describe the calibration andverification procedures required to maintain these instrumentsin calibratio
4、n and ensure that the optical setup is withinspecification for satisfactory measurements.1.2 It is mandatory throughout these practices that bothverification and calibration are carried out by qualified person-nel who fully understand the concepts used in measurements ofstress retardation and are ex
5、perienced in the practices ofmeasuring procedures described in Test Methods F218, C148,and C978.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.2. Referenced Documents2.1 ASTM Standards:2C148 Test Methods for Polariscopic Ex
6、amination of GlassContainersC162 Terminology of Glass and Glass ProductsC770 Test Method for Measurement of Glass StressOptical CoefficientC978 Test Method for Photoelastic Determination of Re-sidual Stress in a Transparent Glass Matrix Using aPolarizing Microscope and Optical Retardation Compen-sat
7、ion ProceduresF218 Test Method for Measuring Optical Retardation andAnalyzing Stress in Glass3. Terminology3.1 For definitions of terms used in these practices, seeTerminology C162.4. Principles of Verification and Calibration Procedures4.1 Verification and calibration of polarimeters are accom-plis
8、hed using the following procedures:4.1.1 Procedure A: (Verification)Measure individual com-ponents and their orientation to ensure that the requirements ofTest Methods F218, C148, and C978 are satisfied.4.1.2 Procedure B: (Calibration)Determine the accuracyof the polarimeter using a calibrated gage
9、or retarder.5. Auxiliary Component Requirements5.1 The following are required to verify and calibrate apolarimeter:5.1.1 Verification of Components (Procedure A):5.1.1.1 Verification of Polarization Effciency, a light-intensity meter, linear over the range of measured values.5.1.1.2 Verification of
10、Quarter-Wave Plate, a Babinet com-pensator equipped polarimeter, with a monochromatic lightsource of traceable wavelength.5.1.1.3 Reference Polarizer with Known Axis.5.1.2 Calibration of Polarimeter (Procedure B):5.1.2.1 Procedure B requires a gage with a calibrated,known retardation. The calibrated
11、 gage must have sufficientretardation to calibrate the instrument within its intended userange. For example, a polariscope/polarimeter used in TestMethods C148 should be calibrated using a gage exhibiting aretardation range of from 0 to 227 nm (0 to 10 temper grade).5.1.2.2 Alternately, a rectangula
12、r cross-section specimenprepared from an SRM glass having a known stress-opticalconstant, subjected to uniaxial compression in a calibratedtesting machine, may be used instead of a calibrated gage withknown retardation.6. Verification and Calibration Procedures6.1 Procedure AVerification and Alignin
13、g of Components:6.1.1 Verification of Polarization EffciencyUsing a light-intensity meter, measure the light intensity, with polarizerscrossed, Ic(dark field) and then with polarizers parallel, Ip.Calculate the polarization efficiency, E, as follows:E 5Ip2 Ic!Ip(1)1These practices are under the juri
14、sdiction of ASTM Committee C14 on Glassand Glass Productsand are the direct responsibility of Subcommittee C14.04 onPhysical and Mechanical Properties.Current edition approved May 1, 2014. Published May 2014. Originallyapproved in 1999. Last previous addition approved in 2009 as C142609. DOI:10.1520
15、/C1426-14.2For 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.Copyright ASTM International, 100 Barr Harbor Drive
16、, PO Box C700, West Conshohocken, PA 19428-2959. United States1The efficiency must satisfy the requirements of the testmethod for which the polarimeter is used.6.1.2 Verification of Position of AxesUsing a referencepolarizer, verify that the polarizer, P, is oriented at 45 6 1 tothe instrument refer
17、ence axis. Rotate the analyzer to attain themaximum dark field, and record the analyzer reading to thenearest degree or 0.05 fringe. Repeat this measurement fivetimes and compute the average. This “zero” reading to thenearest degree or 0.05 fringe must be algebraically applied toretardations measure
18、d with this polarimeter.6.1.3 Verification of Quarter-Wave Plate, QUsing a pola-rimeter equipped with a Babinet compensator, measure theretardation of the quarter-wave plate. The retardation must be141 6 5 nm.6.2 Procedure BCalibration of Polarimeter Using a Cali-brated Retarder:6.2.1 Use of a Calib
19、rated GageThe gage must haveuniform and known direction of axes and a calibrated value ofretardation, Rc, in at least one location, marked permanently onthe gage.6.2.1.1 If using a variable-field retarder, place the gage inthe field of view with its axes aligned with the referencedirection of the po
20、larimeter (see Figs. 1 and 2). Rotate theanalyzer clockwise from the zero position until the black fringeis centered over the calibrated gage mark (the objective is tominimize the light intensity at the gage mark) and take areading from the analyzer dial. If using a uniform-fieldretarder, place the
21、gage in the field of view with its tensile axisaligned parallel to the reference direction of the polarimeter. Inthis position, the retarder will appear brightest (maximum lightintensity) and the field will appear darker as the analyzer dialis rotated clockwise. If that does not occur, rotate the re
22、tarder90 in the field of view to bring it into the correct orientation.Rotate the analyzer clockwise from the zero position until theretarder is uniformly at its darkest hue (maximum extinction)and take the reading from the analyzer dial. Convert theanalyzer reading to retardation in nanometers (See
23、 Test Meth-ods F218). Repeat five times and calculate the average retar-dation. The result of the measurement should equal Rcwithin1 % or 10 nm, whichever is greater.NOTE 1The reference direction of your polarimeter may be along adifferent axis than that shown. If the reference direction is unknown,
24、 rotatethe analyzer with the retarder removed from the field of view. When thefield of view is darkest, stop rotating the analyzer and note the location ofthe 45 mark on the analyzer dial. This will identify the reference axis ofthe polarimeter (see 6.1.2).6.2.1.2 The use of strain disks (described
25、in Test MethodsC148) in series at a point 6.4 mm from the disks outercircumferences, tangentially parallel or perpendicular to thepolarimeter reference direction, will give optical retardationsof 22.8, 45.6, 68.4, and so forth, with uncertainties of 64%.Five repeat retardation averages for any selec
26、ted level of disksin series must be within 4 % of these values for a successfulcalibration.6.2.2 Use of an SRM GlassFollowing Procedure C of TestMethod C770, measure the stress-optical constant of an SRMglass having a certified value for this constant.3The ratio of thecertified value of the stress-o
27、ptical constant to the measuredvalue should be used as a corrective factor for measurementswith the polarimeter.7. Report7.1 Report the following in the verification and calibrationreport:7.1.1 Date of verification and calibration,7.1.2 Auxiliary components used,7.1.3 Significant data obtained, and7
28、.1.4 Organization performing the calibration.8. Keywords8.1 calibration; glass; polarimeter3SRM 709 has a stress-optical constant of 1.359 1012Pa1. This SRMproduces retardations from 0 to 136 nm when following Procedure C of Test MethodC770.FIG. 1 Components of the Polarimeter Showing Stress Birefri
29、n-gence OrientationC1426 142ASTM 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 infr
30、ingement 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 standa
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32、ws 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 contacti
33、ng 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).FIG. 2 Orientation of Calibrated Retardation Gage in Procedure BC1426 143
