Method and system for profiling objects having multiple reflective surfaces using wavelength-tuning phase-shifting interferometry
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United States of America Patent
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Mar 19, 2002
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N/A
app pub date -
Jul 9, 1999
filing date -
Jul 9, 1999
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Abstract
The invention features methods and systems for interferometrically profiling a measurement object having multiple reflective surfaces, e.g., to profile a selected one of the multiple reflective surfaces. The methods and systems involve: positioning the measurement object within an unequal path length interferometer (e.g., a Fizeau interferometer) employing a tunable coherent light source; recording an optical interference image for each of multiple wavelengths of the light source, each image including a superposition of multiple interference patterns produced by pairs of wavefronts reflected from the multiple surfaces of the measurement object and a reference surface; and extracting phases of a selected one of the interference patterns from the recorded images by using a phase-shifting algorithm that is more sensitive (e.g., at least ten times more sensitive) to a wavelength-dependent variation in the recorded images caused by the selected interference pattern than to wavelength-dependent variations in the recorded images caused by the other interference patterns.
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