| 摘要 |
The invention relates to measuring a phase-modulated signal 5. The signal is measured along at least five different steps (P1 - P5) corresponding to preselected phase angles of the carrier wave 4. From the associated sets of measured values, at least three sets of measured values are used to determine at least three measured phase values for the modulated signal [.PHI.i = arctan (Z i/N i) where i is equal to or greater than 3]. The correct phase value is computed based upon the known frequency of the carrier wave. The essence of the invention is the finding that linear combinations of a i Z i and a i N i can be used for the computation of an accurate phase measurement where the factors a i are selected so that the phase error, as a function of the preselected phase steps, has at least three zero positions among the measured phase steps (P1 - P5). As a result, the systemic errors that normally accompany phase measuring are significantly reduced. The invention is particularly suitable for the evaluation of bar pattern images and multiple-bar pattern images.
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