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| Working Group 5.41 |
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Interferometry on Spheres
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Plan-face Interferometer
The density of mercury is to be redetermined in cooperation with the PTB sections
"Density" and
"Mass".
A density standard with a density of about 13600 kg/m3 is required for this purpose.
It is to be realized by determining the volume and mass of a cubic body of about 80 mm edge length
by interferometry and weighing, respectively.
Bild 1: Schematical layout of plan-face interferometer
A plane-face interferometer is set up to determine the volume of cuboid bodies by interferometry.
This interferometer is equipped with a device for the precise adjustment and control of the path
difference, which allows the resulting Fizeau interferences to be evaluated by the method of
phase-stepping interferometry. The two plane faces form a solid etalon into which the cube can
be introduced. For the purpose of measurement, the cube faces to be investigated are adjusted
parallel to the etalon's plane faces. The distances between opposite faces of the cube are obtained
as the difference between the result obtained when measuring the empty etalon and the distances
between the faces of the cube and the plane faces.
The interferometer is also suitable for a fundamental investigation of material measures of length
with plane, parallel measuring faces. In contrast to the conventional interferometric measurement
of gauge blocks, for which an auxiliary plate wrung to the block is required, the two opposite
faces are in this case directly subjected to optical probing. This allows the influence of wringing
to be investigated.
© Physikalisch-Technische Bundesanstalt
Page created: 26-Sep-2006, last update: 26-Feb-2008 10:31 AM,
K. Eggert |
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