| 摘要 |
Interferometric measurements are carried out in conventional manner to produce a correlogram corresponding to successive scanner steps. An approximation of the actual scan-step size between frames is calculated from multiple-frame intensity data collected around the frame of interest using common irradiance algorithms. The scan-step size so measured is then used in standard PSI, VSI or PSIOTF algorithms, instead of the scanner's nominal phase step. According to one embodiment, the invention utilizes a five-frame PSI algorithm to produce an average scan-step size of four scan steps. According to another embodiment, the phase step between frames is calculated directly utilizing a novel five-frame algorithm that produces an approximation of actual phase step for a given frame, rather than an average value of four steps around the frame. The method requires reduced data processing and can advantageously be applied "on-the fly" as intensity data are acquired during scanning.
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