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US 8,275,573 B1Granted
Large-surface defect detection by single-frame spatial-carrier interferometry
AssigneeBruker Nano, Inc.
InventorsJoanna Schmit, Florin Munteanu
Life of this patent
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AssigneeBruker Nano, Inc.
InventorsJoanna Schmit, Florin Munteanu
Estimating the term…
An adaptive algorithm is tailored to fit the local fringe frequency of single-frame spatial-carrier data under analysis. Each set of data points used sequentially by the algorithm is first processed with a Fourier Transform to find the local frequency of the fringes being analyzed. That information is then used to adapt the algorithm to the correct phase step thus calculated, thereby optimizing the efficiency and precision with which the algorithm profiles the local surface area. As a result, defects are identified and measured with precision even when the slope of the surface varies locally to the point where the algorithm without adaptive modification would not be effective to measure them. Once so identified, the defects may be measured again locally with greater accuracy by conventional temporal PSI.
An interferometric method for profiling a sample surface with single-frame irradiance measurements and a predetermined processing algorithm, the method comprising the following steps:
An interferometric method for detecting defects in a sample surface comprising the following steps:
A method of adapting an interferometric processing algorithm to a local fringe frequency of an interferogram, the method comprising the following steps:
Interferometric apparatus for profiling a sample surface with single-frame spatial-carrier irradiance measurements and a predetermined processing algorithm, comprising:
Non-transitory computer readable medium containing computer instructions stored therein for causing a computer processor to acquire an interferogram from a sample surface, calculate a fringe frequency in said interferogram, modify the processing algorithm to obtain an adapted algorithm conforming to the fringe frequency so calculated, and process the interferogram to produce a profile of the sample surface.
Non-transitory computer readable medium containing computer instructions stored therein for causing a computer processor to modify a processing algorithm formulated in terms of equations relating a set of coefficients to a fringe frequency in an interferogram, said computer readable medium being programmed to find values for said set of coefficients that satisfy the equations when the fringe frequency is equal to a local fringe frequency in the interferogram, and to determine a phase with an arctangent function expressed in terms of said values for the set of coefficients and irradiance measurements corresponding to said local fringe frequency.
Dependencies are inferred from the claim text.