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This publication describes a method for measuring and characterizing micron and sub-micron optical beam sizes used for, but not limited to, optical recording of data on various types of optical media.
English (United States)
This text was extracted from a PDF file.
This is the abbreviated version, containing approximately
83% of the total text.
Page 1 of 1
A Method and Apparatus for Measuring Micron and Sub-Micron Beam Sizes
This publication describes a method for measuring and characterizing micron
and sub-micron optical beam sizes used for, but not limited to, optical recording
of data on various types of optical media.
Miscellaneous techniques have been used in the past to measure beams of
this nature. All have depended upon either stepping a target between a detector
and the beam to be measured or spinning a target. In both cases, the accuracy
of the measurement depends upon determining the speed of the target in the
latter case, or the steady positioning of the target in the former case. The
detector signal is representative of the beam size if the velocity or the position of
the target is accurately known.
The subject method uses a displacement signal from a HeNe laser
positioning system to accurately trigger a D/A converter every 5.27 nanometers
of target travel. The D/A converter samples the output of the detector which is
then stored in computer memory. Various computer programs collect, perform
noise reduction and analyze this data.
By utilizing a very accurate XYZ stage, a repeatability of ten nanometers has
been routinely achieved. In addition, diffraction-limited spot sizes of a 780
nanometer laser have been measured through various Z axis positioning, giving
a through focus curve characterization (see figure).
Added spot and beam characteristics can be realized with this method. As
an example, focus a...