Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1995-02-13
1996-03-26
Turner, Samuel A.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
G01B 902
Patent
active
055025668
ABSTRACT:
A method and apparatus for measuring an absolute profile of a flat using an interferometer system that includes an interferometer adapted to support two flats, a detection system, and a computer adapted to compute the OPD (optical path difference) between surface of the two flats, wherein a first flat A! having a first surface and a second flat B! having a second surface are supported in the interferometer, with the second surface facing the first surface. The interferometer system measures the OPDs between the first and second surfaces for each pixel. The first flat A! then is rotated by a number of predetermined angles relative to its initial position and each time the OPDs are measured. The first flat A! is rotated to its initial position or 180.degree. therefrom. A third flat C! having a third surface is substituted for the second flat. The OPDs between the first and third surfaces are measured. The first flat A! is replaced by the second flat, with the second surface facing the third in an orientation mirror imaged to its original orientation. The interferometer system is operated to measure the OPDs. The computer solves first, second, and third equations to obtain the entire surface topographies of the first, second, and third surface, wherein each equation is expressed as a sum of even--even, even-odd, odd-even, and odd--odd parts so as to effectuate cancellation of terms, permitting solving of the equations for the surface topography.
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Ai Chiayu
Parks Robert E.
Shao Lian-Zhen
Wyant James C.
Hoffman Charles R.
Turner Samuel A.
Wyko Corporation
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