ASTM C1426-99
(Practice)Standard Practices for Verification and Calibration of Polarimeters
Standard Practices for Verification and Calibration of Polarimeters
SCOPE
1.1 Polarimeters of polariscopes used for measuring stress in glass are described in Test Methods F218, C148, and C978. These instruments include a light source and several optical elements (polarizers, optical retarders, filters, and so forth) that require occasional cleaning, realigning, and calibration. The objective of these practices is to describe the calibration and verification procedures required to maintain these instruments in calibration and ensure that the optical setup is within specification for satisfactory measurements.
1.2 It is mandatory throughout these practices that both verification and calibration are carried out by qualified personnel who fully understand the concepts used in measurements of stress retardation and are experienced in the practices of measuring procedures described in Test Methods F218, C148, and C978.
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Designation: C 1426 – 99
Standard Practices for
Verification and Calibration of Polarimeters
This standard is issued under the fixed designation C 1426; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4.1.1 Procedure A: (Verification)—Measure individual
components and their orientation to ensure that the require-
1.1 Polarimeters and polariscopes used for measuring stress
ments of Test Methods F 218, C 148, and C 978 are satisfied.
in glass are described in Test Methods F 218, C 148, and
4.1.2 Procedure B: (Calibration)—Determine the accuracy
C 978. These instruments include a light source and several
of the polarimeter using a calibrated gage or retarder.
optical elements (polarizers, optical retarders, filters, and so
forth) that require occasional cleaning, realigning, and calibra-
5. Auxiliary Component Requirements
tion. The objective of these practices is to describe the
5.1 The following are required to verify and calibrate a
calibration and verification procedures required to maintain
polarimeter:
these instruments in calibration and ensure that the optical
5.1.1 Verification of Components (Procedure A):
setup is within specification for satisfactory measurements.
5.1.1.1 Verification of Polarization Effıciency, a light-
1.2 It is mandatory throughout these practices that both
intensity meter, linear over the range of measured values.
verification and calibration are carried out by qualified person-
5.1.1.2 Verification of Quarter-Wave Plate, a Babinet com-
nel who fully understand the concepts used in measurements of
pensator equipped polarimeter, with a monochromatic light
stress retardation and are experienced in the practices of
source of traceable wavelength.
measuring procedures described inTest Methods F 218, C 148,
5.1.1.3 Reference Polarizer with Known Axis.
and C 978.
5.1.2 Calibration of Polarimeter (Procedure B):
2. Referenced Documents 5.1.2.1 Procedure B requires a gage with a calibrated,
known retardation. The calibrated gage must have sufficient
2.1 ASTM Standards:
retardation to calibrate the instrument within its intended use
C 148 Test Methods for Polariscopic Examination of Glass
range. For example, a polariscope/polarimeter used in Test
Containers
2 Methods C 148 should be calibrated using a gage exhibiting a
C 162 Terminology of Glass and Glass Products
retardation range of from 0 to 227 nm (0 to 10 temper grade).
C 770 Test Method for Measurement of Glass Stress—
2 5.1.2.2 Alternately, a rectangular cross-section specimen
Optical Coefficient
prepared from an SRM glass having a known stress-optical
C 978 Test Method for Photoelastic Determination of Re-
constant, subjected to uniaxial compression in a calibrated
sidual Stress in a Transparent Glass Matrix Using a
testing machine, may be used instead of a calibrated gage with
Polarizing Microscope and Optical Retardation Compen-
2 known retardation.
sation Procedures
F 218 Test Method for Analyzing Stress in Glass
6. Verification and Calibration Procedures
3. Terminology 6.1 Procedure A—Verification and Aligning of Components:
6.1.1 Verification of Polarization Effıciency—Using a light-
3.1 For definitions of terms used in these practices, see
intensity meter, measure the light intensity, with polarizers
Terminology C 162.
crossed (dark field) and then with polarizers parallel, I .
p
4. Principles of Verification and Calibration Procedures Calculate the polarization efficiency, E, as follows:
4.1 Verification and calibration of polarimeters are accom-
~I – I !
p c
E 5 (1)
plished using the following procedures: I
p
The efficiency must satisfy the requirements of the test
method for which the polarimeter is used for.
These practices are under the jurisdiction of ASTM Committee C-14 on Glass
6.1.2 Verification of Position of Axes—Using a reference
and Glass Products and are the direct responsibility of Subcommittee C14.04 on
polarizer, verify that the polarizer, P, is oriented at 45 6 1° to
Physical and Mechanical Properties.
the instrument reference axis. Rotate the analyzer to attain the
Current edition approved May 10, 1999. Publi
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