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We developed a new application on Microsoft Foundation Classes (MFC) to identify correct
transmission spheres (TS) for Spherical Surface Testing (SST). Spherical surfaces are important optical
surfaces, and the wide application and high production rate of spherical surfaces necessitates an accurate
and highly reliable measuring device. A Fizeau Interferometer is an appropriate tool for SST due to its subnanometer
accuracy. It measures the contour of a spherical surface using a common path, which is
insensitive to the surrounding circumstances. The Fizeau Interferometer transmits a wide laser beam,
creating interference fringes from re-converging light from the transmission sphere and the test surface. To
make a successful measurement, the application calculates and determines the appropriate transmission
sphere for the test surface. There are 3 main inputs from the test surfaces that are utilized to determine the
optimal sizes and F-numbers of the transmission spheres: (1) the curvatures (concave or convex), (2) the
Radii of Curvature (ROC), and (3) the aperture sizes. The application will firstly calculate the F-numbers
(i.e. ROC divided by aperture) of the test surface, secondly determine the correct aperture size of a convex
surface, thirdly verify that the ROC of the test surface must be shorter than the reference surface’s ROC of
the transmission sphere, and lastly calculate the percentage of area that the test surface will be measured.
However, the amount of interferometers and transmission spheres should be optimized when measuring
large spherical surfaces to avoid requiring a large amount of interferometers and transmission spheres for
each test surface. Current measuring practices involve tedious and potentially inaccurate calculations. This
smart application eliminates human calculation errors, optimizes the selection of transmission spheres
(including the least number required) and interferometer sizes, and increases efficiency.
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