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SEMI MF1763 Document Information:
Title
TEST METHODS FOR MEASURING CONTRAST OF A LINEAR POLARIZER
Semiconductor Equipment and Materials International
Publication Date:
Jul 1, 2006
Scope:
These test methods are applicable to polarizers that operate in
a transmissive mode at near-normal incidence. Angular or
translative offset of the transmitted beam is acceptable if the
entire transmitted beam power can be measured.
The polarizer size or aperture is not limited by the test
methods, but the operator must appreciate that the contrast is an
average over the beam spot on the polarizer. Contrast measured at
one location on the aperture does not necessarily apply to the
entire aperture.
Three test methods are described. The first method is a direct
contrast measurement that requires a linearly polarized light
source with high contrast, CL. The second
method is a comparison with a linearly polarized light source with
known CL. The third method is an indirect
contrast measurement that can use an unpolarized or polarized light
source of unknown CL.
Direct Contrast Measurement — This is the preferred
method for measuring C of a single polarizer. This method
can be used if CL >> C for the
polarizer to be tested. It is a simple, expedient, and accurate
test method if a highly linear polarized light beam is available at
the required wavelength. The source is normally a polarized laser
beam in combination with a high-contrast prism polarizer. A tunable
broadband source can also be used if a high-contrast polarizer is
available for the wavelength of interest.
Contrast Measurement with Comparison — This method is
used if CL is approximately equal to C
for the polarizer to be tested. The value of CL
must be known to obtain the correct C for the
polarizer.
Indirect Contrast Measurement — This method requires
three polarizers that have similar C. This test method can
be used with any light beam regardless of the contrast of the light
beam. It is the only method that can be used when the available
CL << C for the polarizer to be
tested.
The parties to the test shall agree upon the following
items:
• Test method to be used,
• Light source properties including wavelength, power level, and
degree of collimation, and
• Measurement parameters at the polarizer, including beam size,
location in the aperture, and angle-of-incidence.
NOTICE: This standard does not purport to
address safety issues, if any, associated with its use. It is the
responsibility of the users of this standard to establish
appropriate safety and health practices and determine the
applicability of regulatory or other limitations prior to use.
Purpose
Polarizer contrast is important in polarimetry systems,
ellipsometers, optical modulators, shutters, and target signature
discrimination based on polarized radiation.
These test methods cover measurement of polarizer contrast. A
distinction is made between contrast, which is an intrinsic
polarizer property, and extinction, which is a comparison between
two polarizers. Use of contrast to characterize polarizers is
encouraged because it is an intrinsic property of the polarizer.
Use of extinction to characterize polarizers is discouraged because
it is an average between two polarizers and not specific to either
one.1
These test methods are suitable for use in service evaluation,
manufacturing control, or for research and development purposes.
They are not recommended for use in acceptance testing until their
precision has been evaluated by interlaboratory comparison unless
the parties to the test conduct suitable correlation studies.
1 Leonard, T. A., "Infrared Polarizer Selection,"
Proceedings SPIE 288, 129 (1981).
Keywords:
- contrast
- extinction ratio
- polarization
- polarization ratio
- polarizer
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